Pouch-type battery case and molding device thereof, and pouch-type secondary battery

Abstract

To provide a pouch-type battery case and a molding device thereof, and a pouch-type secondary battery, which can prevent interference between a die edge and an electrode tab.SOLUTION: A pouch-type battery case according to an embodiment of the present invention includes a cup portion that houses an electrode assembly formed by stacking electrodes and separators, and a plurality of die edges that connect a wall of the cup portion and sides extending from the wall, and at least one of the die edges includes a first region that is rounded with a first radius of curvature and a second region that is rounded with a second radius of curvature smaller than the first radius of curvature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0129025, filed October 6, 2020, and Korean Patent Application No. 10-2021-0074479, filed June 8, 2021, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a pouch-type battery case, a molding device therefor, and a pouch-type secondary battery, and more particularly to a pouch-type battery case, a molding device therefor, and a pouch-type secondary battery that can prevent interference between a die edge and an electrode tab. [Background technology]

[0003] Common types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. These secondary batteries are used not only in small products such as digital cameras, DVD players, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also in large products that require high output, such as electric vehicles and hybrid vehicles, as well as in power storage devices that store surplus generated power and renewable energy, and as backup power storage devices.

[0004] To manufacture such a secondary battery, first, an electrode active material slurry is applied to a positive electrode current collector and a negative electrode current collector to form a positive electrode and a negative electrode, which are then stacked on both sides of a separator to form an electrode assembly of a predetermined shape, which is then housed in a battery case, filled with an electrolyte, and sealed.

[0005] Secondary batteries are classified into pouch types and can types depending on the material of the case that houses the electrode assembly. Pouch types house the electrode assembly in a pouch made of a flexible polymer material, while can types house the electrode assembly in a case made of metal or plastic.

[0006] The pouch, which is the case of a pouch-type secondary battery, is manufactured by pressing a flexible pouch film to form a cup portion. Once the cup portion is formed, an electrode assembly is placed in the receiving space of the cup portion and the sides are sealed to manufacture the secondary battery.

[0007] Drawing during press processing involves inserting a pouch film into a forming device such as a press and applying pressure to the pouch film with a punch to stretch it. The pouch film is composed of multiple layers, the inner moisture barrier layer of which is made of metal. However, if the formability of the moisture barrier layer is improved to make the cup wall nearly vertical and improve the radius of curvature of the cup edge, there is a problem in that the die edge presses against the electrode tab, causing interference between the die edge and the electrode tab. Prior art documents include Korean Patent Publication No. 2017-0124882. Summary of the Invention [Problem to be solved by the invention]

[0008] The problem to be solved by the present invention is to provide a pouch-type battery case and molding apparatus therefor, and a pouch-type secondary battery, which can prevent interference between the die edge and the electrode tab.

[0009] The objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned above will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0010] In order to solve the above problems, a pouch-type battery case according to an embodiment of the present invention includes a cup portion that houses an electrode assembly formed by stacking electrodes and a separator, and a plurality of die edges that connect the wall of the cup portion to sides extending from the wall, and at least one of the die edges includes a first region that is rounded with a first radius of curvature and a second region that is rounded with a second radius of curvature that is smaller than the first radius of curvature.

[0011] The first radius of curvature may be 1.7 mm to 2.7 mm. The second radius of curvature may be 1.2 mm or less. The second radius of curvature may be 0.7 mm or less.

[0012] The pouch film may also be produced by molding a pouch film, the pouch film including: a sealant layer made from a first polymer and formed as an innermost layer; a surface protective layer made from a second polymer and formed as an outermost layer; and a moisture barrier layer laminated between the surface protective layer and the sealant layer, the moisture barrier layer being made of an aluminum alloy thin film having a thickness of 50 to 80 μm and a crystal grain size of 10 to 13 μm, and the sealant layer being 60 to 100 μm in thickness.

[0013] The depth of the cup portion may be 7 mm when one cup portion is formed, and 6.5 mm when two cup portions are formed. Also, the first region may be formed on each of the two opposing die edges.

[0014] Also, a plurality of the first regions may be formed on one die edge. Also, the second region may be formed between a plurality of the first regions.

[0015] A pouch-type secondary battery according to an embodiment of the present invention for solving the above problems includes an electrode assembly formed by stacking electrodes and a separator, and a battery case including a cup portion that houses the electrode assembly therein, wherein the battery case includes a plurality of die edges that connect a wall of the cup portion and a side extending from the wall, and at least one of the die edges includes a first region that is rounded with a first radius of curvature and a second region that is rounded with a second radius of curvature that is smaller than the first radius of curvature.

[0016] The area of ​​the electrode assembly is 15,000 mm 2 ~100,000mm 2 may be. Also, an electrode tab protruding from one side of the electrode assembly may be placed on the first region.

[0017] In order to solve the above problems, a battery case molding device according to an embodiment of the present invention includes a die having an upper surface on which a pouch film is placed and at least one molding space recessed inward from the upper surface, and a punch disposed above the molding space and descending to insert and mold the pouch film into the molding space, wherein the die includes a plurality of pressure edges connecting the molding space and the upper surface, and at least one of the pressure edges includes a third region rounded with a third radius of curvature and a fourth region rounded with a fourth radius of curvature smaller than the third radius of curvature.

[0018] The third radius of curvature may be 1.5 mm to 2.5 mm. The fourth radius of curvature may be 1 mm or less.

[0019] To solve the above problems, a pouch-type secondary battery according to an embodiment of the present invention includes an electrode assembly formed by stacking electrodes and a separator, and a battery case including a cup portion that accommodates the electrode assembly therein, wherein the battery case includes a plurality of die edges that connect a wall of the cup portion and a side extending from the wall, and at least one of the die edges includes a first region that corresponds to an electrode tab protruding from one side of the electrode assembly and is recessed inward.

[0020] Also, the at least one die edge may further include a second region connected to the first region and formed in a slightly recessed shape inward from the first region.

[0021] The first region may be rounded with a first radius of curvature, and the second region may be rounded with a second radius of curvature that is smaller than the first radius of curvature. Further details of the invention are included in the detailed description and drawings. [Effects of the Invention]

[0022] The embodiments of the present invention have at least the following advantages. The first region of the die edge where the electrode tab is placed is rounded with a relatively large first radius of curvature, and the second region where the electrode tab is not placed is rounded with a relatively small second radius of curvature. This makes the wall of the cup portion nearly vertical, and prevents interference between the die edge and the electrode tab even if the radius of curvature of the die edge of the cup portion is reduced.

[0023] The effects of the present invention are not limited to the above-mentioned examples, and various other effects are included within the present specification. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is an assembly diagram of a secondary battery according to an embodiment of the present invention; [Figure 2]1 is a cross-sectional view of a pouch film according to one embodiment of the present invention. [Figure 3] 1 is a graph showing the iron and silicon contents of aluminum alloys with alloy number AA8079 and aluminum alloys with alloy number AA8021. [Figure 4] 1 is a graph showing the variation of tensile strength, elongation, and grain size as a function of iron content for aluminum alloys with alloy number AA8079 and aluminum alloy number AA8021. [Figure 5] 1 shows enlarged SEM images of crystal grains of an aluminum alloy with alloy number AA8079 and an aluminum alloy with alloy number AA8021. [Figure 6] FIG. 10 is an enlarged schematic view of a die edge and an electrode tab according to a comparative example of the present invention. [Figure 7] FIG. 2 is a partial plan view of a battery case according to an embodiment of the present invention. [Figure 8] 3 is a partial plan view showing an electrode assembly inserted into a cup portion of a battery case according to an embodiment of the present invention; FIG. [Figure 9] FIG. 2 is a schematic diagram of an enlarged view of a first region of a die edge and an electrode tab according to an embodiment of the present invention. [Figure 10] 4 is a schematic enlarged view of a second region of the die edge of the cup portion and an electrode tab according to an embodiment of the present invention. FIG. [Figure 11] 1 is a schematic diagram of a molding device according to an embodiment of the present invention. [Figure 12] FIG. 2 is a partial enlarged view of a die according to an embodiment of the present invention. [Figure 13] FIG. 10 is a partial perspective view of a secondary battery according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The advantages and features of the present invention, as well as methods for achieving them, will become apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be realized in various different forms. The present embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully convey the scope of the invention to those skilled in the art to which the present invention pertains. The present invention is defined solely by the claims. The same reference numerals refer to the same elements throughout the specification.

[0026] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in the sense commonly understood by those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless clearly defined otherwise.

[0027] The terms used in this specification are for the purpose of describing embodiments and are not intended to limit the present invention. In this specification, the singular form includes the plural form unless otherwise specified in the wording. The words "comprises" and / or "comprising" used in this specification do not exclude the presence or addition of one or more other elements in addition to the elements mentioned.

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is an assembly diagram of a secondary battery 1 according to one embodiment of the present invention.

[0029] According to one embodiment of the present invention, the tensile strength and elongation of the pouch film 135 are improved, thereby increasing toughness and improving formability when molding the pouch film 135 to manufacture a pouch-type battery case 13.

[0030] To this end, pouch film 135 according to one embodiment of the present invention includes sealant layer 1351 (shown in FIG. 2) made of a first polymer and formed as an innermost layer, surface protective layer 1353 (shown in FIG. 2) made of a second polymer and formed as an outermost layer, and moisture (or gas) barrier layer 1352 (shown in FIG. 2) laminated between surface protective layer 1353 and sealant layer 1351. Moisture barrier layer 1352 may be made of an aluminum alloy thin film having a thickness of 50 to 80 μm and a grain size of 10 to 13 μm, and sealant layer 1351 may be 60 to 100 μm thick. In particular, moisture barrier layer 1352 preferably has a thickness of 55 to 65 μm, and sealant layer 1351 preferably has a thickness of 75 to 85 μm.

[0031] The electrode assembly 10 is formed by alternately stacking electrodes and separators. First, a slurry containing an electrode active material, a binder, and a plasticizer is applied to a positive electrode current collector and a negative electrode current collector to form electrodes such as a positive electrode and a negative electrode. Then, a separator is stacked between the electrodes to form the electrode assembly 10. The electrode assembly 10 is inserted into a battery case 13, and the case is sealed after electrolyte is injected.

[0032] The electrode assembly 10 has an area of ​​15,000 mm 2 ~100,000mm 2 In particular, the overall width of the electrode assembly 10 may be 60 mm or more. Furthermore, the electrode assembly 10 may have a thickness of 6 mm to 20 mm in the stacking direction. Therefore, the electrode assembly 10 according to one embodiment of the present invention can provide a larger battery capacity than a typical small battery.

[0033] Specifically, the electrode assembly 10 includes two types of electrodes, a positive electrode and a negative electrode, and a separator interposed between the electrodes to insulate them from each other. Examples of such electrode assemblies 10 include stack, jelly roll, and stack-and-fold types. The two types of electrodes, i.e., the positive electrode and the negative electrode, are each constructed by applying an active material slurry to a metal foil or metal mesh electrode collector containing aluminum and copper. The active material slurry can typically be formed by stirring a granular active material, a conductive material, and the like, in a solvent. The solvent is removed in a subsequent process.

[0034] As shown in FIG. 1, the electrode assembly 10 includes electrode tabs 11. The electrode tabs 11 are connected to the positive and negative electrodes of the electrode assembly 10, respectively, and protrude from the electrode assembly 10 to provide a path for electrons to move between the inside and outside of the electrode assembly 10. The electrode current collector of the electrode assembly 10 includes a portion coated with an electrode active material and an end portion, i.e., a plain portion, where the electrode active material is not coated. The electrode tabs 11 may be formed by cutting the plain portion or by connecting a separate conductive member to the plain portion by ultrasonic welding or the like. The electrode tabs 11 may protrude in different directions from the electrode assembly 10 as shown in FIG. 1, but are not limited thereto and may protrude in various directions, such as protruding side by side in the same direction from one side.

[0035] An electrode lead 12 that supplies electricity to the outside of the secondary battery 1 is connected to the electrode tab 11 of the electrode assembly 10 by spot welding or the like. A portion of the electrode lead 12 is surrounded by an insulating portion 14. The insulating portion 14 is located only on a side 134 of the battery case 13 where the first case 131 and the second case 132 are heat-sealed, and adheres the electrode lead 12 to the battery case 13. The insulating portion 14 prevents electricity generated from the electrode assembly 10 from flowing to the battery case 13 through the electrode lead 12, thereby maintaining the seal of the battery case 13. Therefore, the insulating portion 14 is made of a non-conductive material that does not conduct electricity well. Typically, the insulating portion 14 is made of insulating tape, which is easy to adhere to the electrode lead 12 and is relatively thin, but is not limited thereto and various materials may be used as long as they can insulate the electrode lead 12.

[0036] The electrode lead 12 has one end connected to the electrode tab 11 and the other end protruding out of the battery case 13. That is, the electrode lead 12 includes a positive electrode lead 121 having one end connected to the positive electrode tab 111 and extending in the direction in which the positive electrode tab 111 protrudes, and a negative electrode lead 122 having one end connected to the negative electrode tab 112 and extending in the direction in which the negative electrode tab 112 protrudes. Meanwhile, as shown in FIG. 1 , the other ends of both the positive electrode lead 121 and the negative electrode lead 122 protrude out of the battery case 13. This allows electricity generated inside the electrode assembly 10 to be supplied to the outside. In addition, because the positive electrode tab 111 and the negative electrode tab 112 protrude in various directions, the positive electrode lead 121 and the negative electrode lead 122 can also extend in various directions.

[0037] The positive electrode lead 121 and the negative electrode lead 122 may be made of different materials. That is, the positive electrode lead 121 may be made of the same aluminum (Al) material as the positive electrode current collector, and the negative electrode lead 122 may be made of the same copper (Cu) material as the negative electrode current collector, or a copper material coated with nickel (Ni). A portion of the electrode lead 12 protruding outside the battery case 13 serves as a terminal portion and is electrically connected to an external terminal.

[0038] The battery case 13 is a pouch manufactured by molding a pouch film 135 made of a flexible material, which houses the electrode assembly 10 therein. Hereinafter, the battery case 13 will be described as a pouch. When the flexible pouch film 135 is drawn using a punch 22 (shown in FIG. 11 ) or the like, a portion of the flexible pouch film 135 is stretched to form a cup portion 133 including a bag-shaped storage space 1331, thereby manufacturing the battery case 13.

[0039] The battery case 13 accommodates and seals the electrode assembly 10 such that a portion of the electrode lead 12 is exposed. As shown in FIG. 1, the battery case 13 includes a first case 131 and a second case 132. The first case 131 is formed with a cup portion 133 and is provided with an accommodation space 1331 that can accommodate the electrode assembly 10, and the second case 132 covers the accommodation space 1331 from above to prevent the electrode assembly 10 from falling out of the battery case 13. The first case 131 and the second case 132 may be manufactured with one side connected to each other as shown in FIG. 1, but are not limited thereto and may be manufactured in various ways, such as being separated from each other and separately manufactured.

[0040] When forming the cup portions 133 in the pouch film 135, only one cup portion 133 may be formed in one pouch film 135, but is not limited thereto, and two cup portions 133 may be formed adjacent to each other by draw molding in one pouch film 135. Then, as shown in Fig. 1, the cup portions 133 are formed in the first case 131 and the second case 132, respectively. In this case, the cup portions 133 formed in the first case 131 and the second case 132 may have the same depth D, but is not limited thereto, and the depths D may be different from each other.

[0041] In one embodiment of the present invention, the depth D of the cup portion 133 may be 3 mm or more, particularly 6.5 mm or more. Therefore, the cup portion 133 according to one embodiment of the present invention can accommodate an electrode assembly 10 having a larger electrode capacity than a general small battery.

[0042] After the electrode assembly 10 is accommodated in the accommodation space 1331 defined in the cup portion 133 of the first case 131, the battery case 13 can be folded around the bridge 136 formed between the two cup portions 133 of the battery case 13 so that the two cup portions 133 face each other. The cup portion 133 of the second case 132 then accommodates the electrode assembly 10 from above. Therefore, because two cup portions 133 accommodate one electrode assembly 10, it is possible to accommodate an electrode assembly 10 that is thicker than when there is only one cup portion 133. Furthermore, because the first case 131 and the second case 132 are integrally connected by folding the battery case 13, the number of sides 134 to be sealed during a subsequent sealing process can be reduced. This can improve the process speed and reduce the number of sealing processes.

[0043] Meanwhile, the battery case 13 may include a cup portion 133 having an accommodation space 1331 for accommodating the electrode assembly 10, and a degassing portion 137 formed on the side of the cup portion 133 and discharging gas generated inside the cup portion 133 through a vent hole. When the electrode assembly 10 is accommodated in the cup portion 133 of the battery case 13 and an electrolyte is injected, an activation process is performed, generating gas inside the battery case 13, and a degassing process is performed to discharge the gas to the outside.

[0044] After the electrode lead 12 is connected to the electrode tab 11 of the electrode assembly 10 and an insulating portion 14 is formed on a portion of the electrode lead 12, the electrode assembly 10 is accommodated in the accommodation space 1331 defined in the cup portion 133 of the first case 131, and the second case 132 covers the space from above. An electrolyte is then injected into the interior, and the sides 134 extending outward from the cup portions 133 of the first case 131 and the second case 132 are sealed. The electrolyte transports lithium ions generated by an electrochemical reaction at the electrodes during charging and discharging of the secondary battery 1. The electrolyte may include a non-aqueous organic electrolyte solution, which is a mixture of lithium salt and high-purity organic solvents, or a polymer using a polymer electrolyte. The electrolyte may also include a sulfide-based, oxide-based, or polymer-based solid electrolyte, which may be flexible enough to be easily deformed by external force. This method allows the pouch-type secondary battery 1 to be manufactured.

[0045] FIG. 2 is a cross-sectional view of a pouch film 135 according to one embodiment of the present invention. The pouch, which is the battery case 13 of the pouch-type secondary battery 1 according to one embodiment of the present invention, is manufactured by drawing a pouch film 135. That is, the pouch film 135 is stretched using a punch 22 or the like to form a cup portion 133. According to one embodiment of the present invention, the pouch film 135 includes a sealant layer 1351, a moisture barrier layer 1352, and a surface protection layer 1353, as shown in FIG. 2, and may further include a drawing assistance layer 1354, if necessary.

[0046] The sealant layer 1351 is made of a first polymer and is formed as the innermost layer, allowing direct contact with the electrode assembly 10. Here, the innermost layer refers to the layer located most closely to the moisture barrier layer 1352 when facing the electrode assembly 10. The battery case 13 is manufactured by drawing the laminated pouch film 135 using a punch 22 or the like, stretching a portion of the film to form a cup portion 133 including a bag-shaped receiving space 1331. The electrode assembly 10 is then placed in the receiving space 1331, and an electrolyte is then injected. The first case 131 and the second case 132 are then brought into contact with each other and thermocompressed to the sides 134, thereby adhering the sealant layers 1351 to each other and sealing the pouch. In this case, the sealant layer 1351 must be insulating because it comes into direct contact with the electrode assembly 10, and corrosion-resistant because it also comes into contact with the electrolyte. Furthermore, it must have high sealing properties because it must completely seal the interior and prevent material transfer between the interior and exterior. That is, the sides 134 where the sealant layers 1351 are bonded together must have excellent thermal adhesive strength. Generally, the first polymer used to form the sealant layer 1351 may be one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. In particular, polyolefin resins such as polypropylene (PP) or polyethylene (PE) are commonly used. Polypropylene (PP) has excellent mechanical properties such as tensile strength, rigidity, surface hardness, abrasion resistance, and heat resistance, and excellent chemical properties such as corrosion resistance, and is therefore mainly used to manufacture the sealant layer 1351. Furthermore, it may be made of unstretched polypropylene (Cated Polypropylene), acid-modified polypropylene, or polypropylene-butylene-ethylene terpolymer.Here, the acid-modified polypropylene may be MAH PP (Maleic Anhydride Polypropylene). Also, the sealant layer 1351 may have a single film structure made of any one material, or a composite film structure formed by layers of two or more materials.

[0047] According to one embodiment of the present invention, the thickness of the sealant layer 1351 may be 60 to 100 μm, and particularly 75 to 85 μm. If the thickness of the sealant layer is thinner than 60 μm, problems may occur, such as internal rupture during sealing, reducing seal durability. Conversely, if the thickness of the sealant layer is thicker than 100 μm, the overall thickness of the pouch may be excessively thick, which may result in reduced formability or a reduced energy density per volume of the secondary battery. If the thickness of the sealant layer 1351 is small, the dielectric breakdown voltage of the pouch film 135 may be reduced, resulting in reduced insulation. Therefore, when a pouch film 135 with poor insulation properties is used to manufacture a battery, the defective rate may be high.

[0048] The moisture barrier layer 1352 is laminated between the surface protective layer 1353 and the sealant layer 1351 to ensure the mechanical strength of the pouch, block the ingress and egress of gas or moisture outside the secondary battery 1, and prevent electrolyte leakage. The moisture barrier layer 1352 may be made of an aluminum alloy thin film. The aluminum alloy thin film can ensure a certain level of mechanical strength while being lightweight, and can ensure the electrochemical properties of the electrode assembly 10 and the electrolyte, as well as heat dissipation.

[0049] More specifically, the aluminum alloy thin film according to one embodiment of the present invention may have a grain size of 10 to 13 μm, preferably 10.5 to 12.5 μm, and more preferably 11 to 12 μm. When the grain size of the aluminum alloy thin film satisfies this range, the forming depth can be increased without generating pinholes or cracks during cup forming.

[0050] Such an aluminum alloy thin film may contain one or more metal elements other than aluminum, such as iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), and zinc (Zn).

[0051] Furthermore, according to one embodiment of the present invention, the thickness of the moisture barrier layer 1352 may be 50 μm to 80 μm, and particularly 55 μm to 65 μm. Conventionally, the moisture barrier layer was thinner than 50 μm, resulting in poor formability. Therefore, when the pouch film 135 was draw-molded to form a deep cup, there was a limit to how close the cup wall could be to being perpendicular, and there was also a limit to how small the curvature radius of the cup edge could be. Furthermore, there was also a problem with weak puncture strength, which made the internal electrode assembly susceptible to damage when the battery case received external impact.

[0052] Conversely, if the thickness of the moisture barrier layer is greater than about 80 μm, not only will manufacturing costs increase, but the overall thickness of the secondary battery will become too thick, resulting in a decrease in the volumetric energy density of the secondary battery.If the thickness of the sealant layer is reduced to less than 60 μm in order to reduce the overall thickness of the secondary battery, the durability of the seal will decrease.

[0053] However, if the thickness of the aluminum alloy thin film is simply increased, the forming depth can be increased, but pinholes and cracks may occur in the aluminum alloy thin film after forming, resulting in problems with sealing durability.

[0054] Therefore, after extensive research, the inventors discovered that by using an aluminum alloy thin film with a specific crystal grain size as the material for the moisture barrier layer and controlling the thickness of the moisture barrier layer and sealant layer within a specific range, it is possible to form a deep cup portion while maintaining excellent sealing durability, and thus completed the present invention.

[0055] Specifically, the moisture barrier layer 1352 according to the present invention includes an aluminum alloy thin film having a grain size of 10 μm to 13 μm, preferably 10.5 to 12.5 μm, and more preferably 11 to 12 μm. When the grain size of the aluminum alloy thin film satisfies this range, the forming depth can be increased without the occurrence of pinholes or cracks during cup forming. If the grain size of the aluminum alloy thin film exceeds 13 μm, the strength of the aluminum alloy thin film decreases and it becomes difficult to distribute internal stress during stretching, increasing the occurrence of cracks and pinholes. If the grain size is less than 10 μm, the flexibility of the aluminum alloy thin film decreases, limiting the improvement of formability.

[0056] Meanwhile, the grain size varies depending on the composition of the aluminum alloy thin film and the processing method of the aluminum alloy thin film, and can be measured by observing a cross section of the aluminum alloy thin film in the thickness direction using a scanning electron microscope (SEM). Specifically, in the present invention, an SEM image of the cross section of the aluminum alloy thin film in the thickness direction was obtained using a scanning electron microscope, and the maximum diameters of a predetermined number of grains among the grains observed in the SEM image were measured, and the average value of these was evaluated as the grain size.

[0057] The surface protective layer 1353 is made of a second polymer and is formed as the outermost layer. It protects the secondary battery 1 from external friction and impact while electrically insulating the electrode assembly 10 from the outside. Here, the outermost layer refers to the layer located most recently in the opposite direction from the moisture barrier layer 1352 toward the electrode assembly 10. The second polymer used to form the surface protective layer 1353 may be one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. In particular, it is preferable to use a polymer such as polyethylene terephthalate (PET), which is primarily abrasion-resistant and heat-resistant. The surface protective layer 1353 may have a single film structure made of any one material or a composite film structure formed by layers of two or more materials.

[0058] According to one embodiment of the present invention, the thickness of the surface protective layer 1353 may be 5 μm to 25 μm, and particularly 7 μm to 12 μm. If the thickness of the surface protective layer is thinner than 5 μm, there may be a problem of reduced external insulation. Conversely, if the thickness of the surface protective layer is thicker than 25 μm, the overall thickness of the pouch increases, which may actually reduce the volume-specific energy density of the secondary battery.

[0059] On the other hand, PET is inexpensive, durable, and has excellent electrical insulation properties, but it also has poor adhesion to aluminum, which is often used for the moisture barrier layer 1352, and their behavior when stretched by applying stress may differ. Therefore, if the surface protective layer 1353 and the moisture barrier layer 1352 are directly bonded, the surface protective layer 1353 and the moisture barrier layer 1352 may peel off during draw forming. This can cause the moisture barrier layer 1352 to be stretched unevenly, resulting in a problem of reduced formability.

[0060] According to one embodiment of the present invention, the battery case 13 may further include a stretching assist layer 1354 made of a third polymer and laminated between the surface protective layer 1353 and the moisture barrier layer 1352. The stretching assist layer 1354 is laminated between the surface protective layer 1353 and the moisture barrier layer 1352 and can prevent peeling between the surface protective layer 1353 and the moisture barrier layer 1352 when they are stretched. The third polymer from which the stretching assist layer 1354 is made may be one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon (registered trademark), and glass fiber. In particular, nylon resin can be mainly used as the third polymer because nylon resin easily adheres to polyethylene terephthalate (PET) of the surface protective layer 1353 and behaves similarly when stretched to the aluminum alloy of the moisture barrier layer 1352. The stretching assist layer 1354 may have a single film structure made of any one material, or a composite film structure formed by layers of two or more materials.

[0061] Conventionally, the moisture barrier layer has a thickness of approximately 40 μm, and the stretching auxiliary layer has a relatively thin thickness of approximately 15 μm. That is, the thickness ratio of the stretching auxiliary layer to the moisture barrier layer is 1:2.67, which means that the thickness ratio of the moisture barrier layer is relatively high. As described above, according to one embodiment of the present invention, the moisture barrier layer 1352 has a thickness of approximately 50 to 80 μm, particularly 55 to 65 μm, thereby improving the formability of the moisture barrier layer 1352. To improve the formability of the stretching auxiliary layer 1354, the stretching auxiliary layer 1354 may have a thickness of 20 to 50 μm, preferably 25 to 38 μm. If the stretching auxiliary layer is thinner than 20 μm, it cannot keep up with the improved formability of the moisture barrier layer and may be damaged during stretching. Conversely, if the stretching auxiliary layer is thicker than 50 μm, the overall thickness of the pouch increases, which may increase the volume of the secondary battery and reduce the energy density. In particular, according to one embodiment of the present invention, the thickness ratio of the stretching assisting layer 1354 to the moisture barrier layer 1352 may be less than 1:2.5. That is, the thickness ratio of the stretching assisting layer 1354 can be increased more than conventionally. However, if the thickness of the stretching assisting layer 1354 is too thick, the overall thickness of the pouch will increase, so to avoid an excessive thickness, the thickness ratio may be greater than 1:1.5. That is, the thickness ratio may be 1:1.5 to 1:2.5.

[0062] FIG. 3 is a graph showing the iron and silicon contents of aluminum alloys with alloy number AA8079 and aluminum alloys with alloy number AA8021. As described above, the aluminum alloy thin film that forms the moisture barrier layer 1352 may have a grain size of 10 to 13 μm, preferably 10.5 to 12.5 μm, and more preferably 11 to 12 μm.

[0063] The iron (Fe) content of the aluminum alloy thin film may be 1.2 wt% to 1.7 wt%, preferably 1.3 wt% to 1.7 wt%, and more preferably 1.3 wt% to 1.45 wt%. If the iron (Fe) content in the aluminum alloy thin film is less than 1.2 wt%, the strength of the aluminum alloy thin film will decrease, and cracks and pinholes may occur during forming. If the iron (Fe) content exceeds 1.7 wt%, the flexibility of the aluminum alloy thin film will decrease, and there will be a limit to the improvement of formability.

[0064] The aluminum alloy thin film may have a silicon (Si) content of 0.2 wt% or less, preferably 0.05 to 0.2 wt%, and more preferably 0.1 to 0.2 wt%. If the silicon content exceeds 0.2 wt%, formability may be reduced.

[0065] Specifically, the aluminum alloy thin film according to the present invention may be an aluminum alloy with alloy number AA8021. In contrast, conventional battery pouches have primarily used aluminum alloy thin films with alloy number AA8079. When the aluminum alloy contains a large amount of iron, the mechanical strength is improved, and when the aluminum alloy contains a small amount of iron, the flexibility is improved.

[0066] As shown in Figure 3, alloy number AA8079 contains 0.6 wt% to 1.2 wt% iron and 0.3 wt% or less silicon. The aluminum alloy with alloy number AA8079 contains a relatively small amount of iron, and when used to manufacture moisture barrier layer 1352, flexibility can be improved, but strength can be reduced, limiting formability.

[0067] In contrast, alloy number AA8021 may contain 1.2 wt% to 1.7 wt%, particularly 1.3 wt% to 1.7 wt%, of iron, and 0.2 wt% or less of silicon, as shown in Figure 3. When the moisture barrier layer 1352 is manufactured using such an aluminum alloy with alloy number AA8021, the tensile strength, elongation rate, and puncture strength can be improved due to the relatively high iron content.

[0068] Meanwhile, the relationship between tensile strength and elongation when a tensile force is applied to a material can be graphed. In this graph, the vertical axis represents tensile strength and the horizontal axis represents elongation. The area under the graph represents the toughness of the material. Toughness refers to the degree to which a material is resistant to fracture, and the higher the toughness, the more the material can be stretched before breaking.

[0069] Therefore, when the moisture barrier layer 1352 is manufactured using the aluminum alloy of alloy number AA8021, the tensile strength and elongation are improved, which increases toughness and improves formability.

[0070] FIG. 4 is a graph showing the changes in tensile strength (Rm), elongation, and grain size depending on the iron content of aluminum alloys with alloy numbers AA8079 and AA8021, and FIG. 5 is an enlarged SEM image of the grains of aluminum alloys with alloy numbers AA8079 and AA8021.

[0071] As shown in Figure 4, the tensile strength, elongation, and grain size of aluminum alloys change depending on the iron content. Specifically, since the tensile strength and elongation are proportional to the iron content, the tensile strength and elongation increase as the iron content increases. On the other hand, since the grain size is inversely proportional to the iron content, the grain size decreases as the iron content increases.

[0072] Alloy No. AA8079 has a relatively large crystal grain size of 13 μm to 21 μm, which results in less internal stress being dispersed during stretching and more pinholes, resulting in a problem of reduced formability of the battery case 13.

[0073] Alloy No. AA8021 has a relatively small crystal grain size of 10 μm to 13 μm, which allows for more dispersion of internal stress during stretching, reducing pinholes and improving the formability of the battery case 13.

[0074] Meanwhile, the pouch film 135 according to the present invention may have a total thickness of 160 μm to 200 μm, preferably 180 μm to 200 μm. When the thickness of the pouch film 135 satisfies this range, it is possible to increase the molding depth while minimizing the reduction in the battery accommodating space and the deterioration in sealing durability due to an increase in the pouch thickness.

[0075] The pouch film 135 according to the present invention includes an aluminum alloy thin film having a specific thickness and crystal grain size, and thus has excellent tensile strength and elongation. Specifically, the pouch film 135 according to the present invention, after being cut into a size of 15 mm x 80 mm and pulled at a pulling rate of 50 mm / min, has a tensile strength of 200 N / 15 mm to 300 N / 15 mm, preferably 210 N / 15 mm to 270 N / 15 mm, and more preferably 220 N / 15 mm to 250 N / 15 mm, and an elongation of 120% to 150%, preferably 120% to 140%, and more preferably 120% to 130%. Thus, the pouch film laminate according to the present invention has high tensile strength and elongation, which increases toughness and reduces the occurrence of cracks even when the molding depth is large during cup molding.

[0076] Furthermore, the pouch film laminate according to the present invention includes an aluminum alloy thin film having a specific thickness and crystal grain size, and has excellent puncture strength. Specifically, the pouch film laminate according to the present invention may have a puncture strength of 30 N or more. Figure 6 is an enlarged schematic view of a die edge 138 and an electrode tab 11 according to a comparative example of the present invention.

[0077] The cup portion 133 includes various edges, specifically a punch edge 139 formed corresponding to the pressure edge 221 of the punch 22, and a die edge 138 formed corresponding to the pressure edge 213 of the die 21. The punch edge 139 connects the bottom 1332 to a plurality of walls 1333 surrounding the periphery of the cup portion 133, and the die edge 138 connects the walls 1333 to the sides 134. If the pressure edge of the die is not rounded, the pressure edge of the die will be sharp, which will cause stress to concentrate on the die edge of the cup portion when forming the pouch film 135, potentially resulting in cracks.

[0078] To solve this problem, the pressurizing edge 213 of the die 21 is rounded, so that the die edge 338 of the cup portion 333 is rounded as shown in FIG. 6, and the stress concentrated on the die edge 338 can be dispersed to some extent.

[0079] However, when the cup portion is formed to a depth greater than a certain depth, and the radius of curvature of the die edge of the cup portion is made small (for example, 2 mm or less), cracks may still occur in the pouch film 135. For example, the certain depth may be about 7 mm when one cup portion 133 is formed, and about 6.5 mm when two cup portions 133 are formed.

[0080] In this specification, when the die edge 138, 338 is formed to be rounded, it means that the curved surface is formed to have a curvature. Such a curved surface may have a constant curvature overall, but is not limited thereto and may have a non-constant curvature overall.

[0081] Therefore, according to one embodiment of the present invention, the thickness of the sealant layer 1351 may be 60 to 100 μm, particularly 75 to 85 μm, and the thickness of the moisture barrier layer 1352 may be 50 to 80 μm, particularly 55 to 65 μm, and the moisture barrier layer 1352 may be made of an aluminum alloy thin film with a grain size of 10 to 13 μm.

[0082] This improves the formability of the moisture barrier layer 1352, so that, as shown in FIG. 6, when the pouch film 135 is draw-molded, the depth of the cup portion 333 can be formed to be greater than a certain depth, while the wall 3333 of the cup portion 333 becomes nearly vertical, and the radius of curvature R3 of the edges 338, 339 of the cup portion 333 can also be reduced.

[0083] Alternatively, according to another embodiment of the present invention, when the pouch film 135 is draw-molded, the depth of the cup portion 333 is formed to be equal to or less than the specific depth, so that the wall 3333 of the cup portion 333 becomes closer to vertical, and the radius of curvature R3 of the edges 338, 339 of the cup portion 333 can also be reduced.

[0084] Specifically, the wall 3333 of the cup portion 333 may be formed nearly vertically with an inclination angle of 90° to 95°, preferably 90° to 93°, from the bottom 3332. Also, at least one of the edges 338, 339 of the cup portion 333 may be rounded with a radius of curvature of 1 / 20 to 1 / 6 of the depth of the cup portion 333. Specifically, even if at least one of the edges 338, 339 of the cup portion 133 is rounded with a radius of curvature R3 of 1 mm or less, particularly 0.7 mm or less, it is possible to prevent cracks from occurring.

[0085] By manufacturing the battery case 13 as described above, the volume of the receiving space 1331 increases, and therefore the volume of the electrode assembly 10 housed therein can also be increased, thereby improving the energy efficiency relative to volume of the secondary battery 1. Furthermore, the manufacturing cost does not increase significantly, and even if the thickness of the sealant layer 1351 is not reduced, the overall thickness of the pouch does not increase significantly, and seal durability does not decrease. In addition, the pouch-type battery case 13 and the pouch-type secondary battery 1 can have an overall sharp shape, which improves the appearance of the secondary battery 1 and its merchantability.

[0086] However, as the wall 3333 of the cup portion 333 becomes closer to vertical and the radius of curvature of the edges 338, 339 of the cup portion 333 decreases, interference may occur between the die edge 338 and the electrode tab 11, as shown in FIG. 6 . Specifically, the electrode tabs 11 protrude from the electrodes stacked in the electrode assembly 10, and thus may be formed in a number equal to the number of electrodes in the electrode assembly 10. The plurality of electrode tabs 11 are then stacked and connected to one another and then placed on the side 134. In this case, the electrode tabs 11 are placed from the die edge 338 to the side 134. However, as the radius of curvature R3 of the die edge 338 decreases, the die edge 338 may be further recessed into the cup portion 333, which may reduce the flexibility of the die edge 338. As a result, the distance between the die edge 338 and the electrode tab 11 also decreases, and the die edge 338 presses against the electrode tab 11, which may result in interference between the die edge 338 and the electrode tab 11. In particular, the greater the number of electrode tabs 11, the thicker the electrode tabs 11 are stacked, and the narrower the space between the wall 3333 of the cup portion 333 and the electrode tabs 11. Therefore, the die edge 338 presses the electrode tabs 11 more, which may cause problems such as an insufficient power supply and even breakage of the electrode tabs 11.

[0087] FIG. 7 is a partial plan view of a battery case 13 according to one embodiment of the present invention, and FIG. 8 is a partial plan view showing an electrode assembly 10 inserted into a cup portion 133 of a battery case 13 according to one embodiment of the present invention.

[0088] According to an embodiment of the present invention, the formability of the pouch film 135 is improved, making the wall 1333 of the cup portion 133 closer to vertical, and even if the curvature radii R1 and R2 of the die edge 138 of the cup portion 133 are reduced, interference between the die edge 138 and the electrode tab 11 can be prevented.

[0089] To this end, the pouch-type battery case 13 according to an embodiment of the present invention includes a cup portion 133 that houses an electrode assembly 10 formed by stacking electrodes and separators, and a plurality of die edges 138 that connect the wall 1333 of the cup portion 133 to the side 134 extending from the wall 1333, and at least one of the die edges 138 includes a first region 1381 that is rounded with a first radius of curvature R1 (shown in FIG. 9) and a second region 1382 that is rounded with a second radius of curvature R2 (shown in FIG. 10) that is smaller than the first radius of curvature R1.

[0090] Furthermore, a pouch-type secondary battery 1 according to one embodiment of the present invention includes an electrode assembly 10 formed by stacking electrodes and separators, and a battery case 13 including a cup portion 133 that accommodates the electrode assembly 10 therein, and the battery case 13 includes a plurality of die edges 138 that connect a wall 1333 of the cup portion 133 to a side 134 extending from the wall 1333, and at least one of the die edges 138 includes a first region 1381 that is rounded with a first curvature radius R1 and a second region 1382 that is rounded with a second curvature radius R2 that is smaller than the first curvature radius R1.

[0091] As described above, the battery case 13 includes a plurality of walls 1333 surrounding the periphery of the cup portion 133 and a side 134 extending from the walls 1333. The die edges 138 connect the walls 1333 to the sides 134, respectively. According to one embodiment of the present invention, at least one die edge 138 is rounded with two different radii of curvature R1 and R2. That is, as shown in FIG. 7 , at least one die edge 138 includes a first region 1381 rounded with a first radius of curvature R1 and a second region 1382 rounded with a second radius of curvature R2 smaller than the first radius of curvature R1.

[0092] Here, the first curvature radius R1 may be 1.7 mm to 2.7 mm, and the second curvature radius R2 may be 1.2 mm or less, preferably 0.7 mm or less. That is, the first curvature radius R1 may be 1.5 to 4 times the second curvature radius R2.

[0093] 7 and 8, the first region 1381 is a region where the electrode tab 11 protruding from one side of the electrode assembly 10 is placed. In contrast, the second region 1382 is a region where the electrode tab 11 is not placed. Therefore, the first region 1381 is rounded with a relatively large first radius of curvature R1, and the second region 1382 is rounded with a relatively small second radius of curvature R2.

[0094] The length of the first region 1381 may correspond to the width of the electrode tab 11 so that the electrode tab 11 can be stably placed. Here, "corresponding" means that the length of the first region 1381 is the same as or slightly larger than the width of the electrode tab 11. If the length of the first region 1381 is smaller than the width of the electrode tab 11, the electrode tab 11 cannot be stably placed on the die edge 138.

[0095] Meanwhile, the die edges 138 are formed along the periphery of the walls 1333 of the cup part 133, and therefore, a plurality of die edges 138 are formed in the number equal to the number of walls 1333. For example, as shown in Fig. 7, if the cup part 133 has a rectangular shape, four die edges 138 may be formed. However, the number of die edges 138 is not limited thereto, and may vary depending on the number of walls 1333 of the cup part 133.

[0096] When the electrode tabs 11 protrude in different directions from the electrode assembly 10, the first regions 1381 on which the electrode tabs 11 are placed may also be formed on different die edges 138. For example, as shown in FIG. 7, one first region 1381 may be formed on each of two opposing die edges 138. In this case, the first region 1381 may be located approximately at the center of the die edge 138, and second regions 1382 may be formed on both sides of the first region 1381. However, without being limited thereto, when the electrode tabs 11 protrude in the same direction from one side of the electrode assembly 10, a plurality of first regions 1381 may be formed on one die edge 138. In this case, the second region 1382 may be formed between the plurality of first regions 1381.

[0097] Meanwhile, since the first region 1381 and the second region 1382 are rounded with different curvature radii R1 and R2, a step may be formed between the first region 1381 and the second region 1382.

[0098] However, without being limited thereto, a connecting region may be formed to connect the first region 1381 and the second region 1382 so as to prevent a step from being formed. Such a connecting region may also be formed to be rounded, and the radius of curvature may continuously change from the first radius of curvature R1 to the second radius of curvature R2 as it extends from the first region 1381 to the second region 1382. This allows the first region 1381 and the second region 1382 to be continuously connected without forming a step.

[0099] FIG. 9 is an enlarged schematic view of the first region 1381 and electrode tab 11 of the die edge 138 of one embodiment of the present invention, and FIG. 10 is an enlarged schematic view of the second region 1382 and electrode tab 11 of the die edge 138 of the cup portion 133 of one embodiment of the present invention.

[0100] As described above, the first region 1381 on which the electrode tab 11 is placed is rounded with a relatively large first radius of curvature R1. Such a first radius of curvature R1 may be 1.7 mm to 2.7 mm. Therefore, as shown in Fig. 9, the die edge 138 does not press the electrode tab 11, and therefore interference between the die edge 138 and the electrode tab 11 can be prevented in the first region 1381 where the electrode tab 11 is placed.

[0101] In contrast, the second region 1382 on which the electrode tab 11 is not placed is rounded with a relatively small second radius of curvature R2, which may be 1.2 mm or less, and preferably 0.7 mm or less.

[0102] Therefore, as shown in FIG. 10, the energy efficiency relative to volume of the secondary battery 1 can be increased, and the pouch-type battery case 13 and the pouch-type secondary battery 1 can be manufactured into a sharp overall shape, which results in an excellent appearance of the secondary battery 1 and improved marketability.

[0103] FIG. 11 is a schematic diagram of a molding apparatus 2 according to one embodiment of the present invention. A molding device 2 for forming a pouch film 135 according to one embodiment of the present invention includes a die 21 on whose upper surface the pouch film 135 is placed and which includes at least one molding space 211 recessed inward from the upper surface, and a punch 22 which is positioned above the molding space 211 and descends to insert the pouch film 135 into the molding space 211 to form it, the die 21 including a plurality of pressure edges 213 connecting the molding space 211 and the upper surface to each other, and at least one of the pressure edges 213 includes a third region 2131 (shown in FIG. 12) formed by being rounded with a third radius of curvature, and a fourth region 2132 (shown in FIG. 12) formed by being rounded with a fourth radius of curvature smaller than the third radius of curvature.

[0104] When forming the pouch film 135 using such a forming apparatus 2, only one cup portion 133 may be formed as described above, but the present invention is not limited thereto and two cup portions 133 may be draw-formed adjacent to each other. To this end, as shown in FIG. 6 , two forming spaces 211 may be formed adjacent to each other in the die 21, and a partition wall 212 may be formed between the two forming spaces 211. When the punch 22 is inserted into both forming spaces 211 to draw-form the pouch film 135, one cup portion is formed in each of the first case 131 and the second case 132 corresponding to each of the two forming spaces 211, for a total of two cup portions 133. A bridge 136 may also be formed between the two cup portions 133 corresponding to the partition wall 212.

[0105] The bridge 136 may serve as a reference when folding the battery case 13 later. After the secondary battery 1 is manufactured, the bridge 136 may form a folding portion (not shown) on one side of the secondary battery 1. This folding portion integrally connects the first case 131 and the second case 132 to each other, thereby reducing the number of sides 134 to be sealed during a subsequent sealing process. This improves the process speed and reduces the number of sealing processes. In this case, as the width of the folding portion becomes smaller, the space between the wall 1333 of the cup portion 133 and the electrode assembly 10 also becomes smaller, thereby reducing the overall volume of the secondary battery 1 and increasing the energy density per volume.

[0106] The width of such a folding portion is proportional to the thickness of the bridge 136, and since the bridge 136 is formed corresponding to the partition wall 212, the thickness of the bridge 136 is proportional to the thickness of the partition wall 212. Therefore, when forming the pouch film 135, it is preferable to minimize the thickness of the bridge 136, and therefore it is also preferable to minimize the thickness of the partition wall 212.

[0107] However, if the partition wall 212 is formed too high while being thin, the partition wall 212 may be damaged during the draw-forming process. In particular, in the conventional die 21, a bottom was provided, which caused a problem that gas present in the space between the pouch film 135 and the forming space 211 could not be discharged when the punch 22 formed the pouch film 135.

[0108] Therefore, in recent years, by removing the bottom from such a die 21, the gas existing in the space between the pouch film 135 and the molding space 211 can be easily discharged, but there has been a problem in that the height of the partition wall 212 is formed excessively high.

[0109] 11 , the upper portion of the partition wall 212 may maintain a minimized thickness, and the lower portion of the partition wall 212 may be formed with a reinforcing portion 2121 that is thicker than the thickness of the partition wall 212. The reinforcing portion 2121 may be formed below the depth D of the cup portion 133 formed in the battery case 13, and may be formed at a position that will not damage the partition wall 212. The exact position of the reinforcing portion 2121 may be determined experimentally depending on the thickness of the partition wall 212, the material of the partition wall 212, the pressure of the punch 22, and the depth D of the cup portion 133 to be formed.

[0110] However, without being limited thereto, the partition wall 212 may be formed so that its thickness gradually increases toward the bottom. That is, at least a portion of the cross section of the partition wall 212 may have an approximately triangular shape, and the inner wall 214 of the forming space 211 formed in the partition wall 212 may have a slope. The exact slope of the inner wall 214 of the forming space 211 formed in the partition wall 212 may be determined experimentally depending on the thickness of the upper part of the partition wall 212, the material of the partition wall 212, the pressure of the punch 22, and the depth of the cup portion 133 to be formed. This increases the strength of the partition wall 212, making it possible to prevent the partition wall 212 from being damaged during the draw forming process.

[0111] FIG. 12 is a partially enlarged view of the die 21 according to one embodiment of the present invention. According to an embodiment of the present invention, at least one die edge 138 of the pouch-type battery case 13 includes a first region 1381 formed by rounding with a first radius of curvature R1, and a second region 1382 formed by rounding with a second radius of curvature R2 smaller than the first radius of curvature R1.

[0112] In order to manufacture such a battery case 13, the die 21 according to an embodiment of the present invention includes a plurality of pressure edges 213 that connect the upper surface and the molding space 211 to each other, and at least one pressure edge 213 includes a third region 2131 that is rounded with a third radius of curvature and a fourth region 2132 that is rounded with a fourth radius of curvature that is smaller than the third radius of curvature.

[0113] A pouch film 135 is placed on the upper surface of the die 21, particularly covering the molding space 211, and a punch 22 arranged above the molding space 211 is lowered to insert and mold the pouch film 135 into the molding space 211. This forms a cup portion 133, and the pouch-type battery case 13 is manufactured. At this time, die edges 138 of the pouch-type battery case 13 are formed corresponding to the multiple pressurizing edges 213 of the die 21.

[0114] The third region 2131 of the pressure edge 213 corresponds to the first region 1381 of the battery case 13. Here, the third radius of curvature of the third region 2131 may be a numerical value obtained by subtracting the thickness of the pouch film 135 itself from the first radius of curvature R1 of the first region 1381. For example, if the thickness of the pouch film 135 is 0.2 mm, the first radius of curvature R1 of the first region 1381 may be 1.7 mm to 2.7 mm, and therefore the third radius of curvature of the third region 2131 may be 1.5 mm to 2.5 mm.

[0115] Additionally, the fourth region 2132 of the pressure edge 213 corresponds to the second region 1382 of the battery case 13. Here, the fourth radius of curvature of the second region 2132 may be a numerical value obtained by subtracting the thickness of the pouch film 135 itself from the second radius of curvature R2 of the second region 1382. For example, the second radius of curvature R2 of the second region 1382 may be 1.2 mm or less, preferably 0.7 mm or less, and therefore the fourth radius of curvature of the fourth region 2132 may be 1 mm or less, preferably 0.5 mm or less.

[0116] The pressing edge 213 of the die 21 corresponds to the die edge 138 of the battery case 13, and the molding space 211 of the die 21 corresponds to the cup portion 133 of the battery case 13. Therefore, since the pressing edge 213 is also formed along the periphery of the molding space 211, if the molding space 211 has a rectangular shape, four pressing edges 213 can be formed.

[0117] The third regions 2131 may also be formed on different pressing edges 213. For example, one third region 2131 may be formed on each of two opposing pressing edges 213. In this case, the third region 2131 may be located approximately at the center of the pressing edge 213, and the fourth regions 2132 may be formed on both sides of the third region 2131. However, without being limited thereto, a plurality of third regions 2131 may be formed on one die edge 138, and the fourth region 2132 may be formed between the third regions 2131.

[0118] Meanwhile, since the third region 2131 and the fourth region 2132 are rounded with different radii of curvature, a step may be formed between the third region 2131 and the fourth region 2132. However, without being limited thereto, a connecting region may be formed connecting the third region 2131 and the fourth region 2132 so that a step is not formed. This connecting region is also rounded, and the radius of curvature may continuously change from the third radius of curvature to the fourth radius of curvature as it extends from the third region 2131 to the fourth region 2132. As a result, the third region 2131 and the fourth region 2132 may be continuously connected without forming a step.

[0119] FIG. 13 is a partial perspective view of a secondary battery 1 according to another embodiment of the present invention. At least one die edge 138 included in the battery case 13 according to this embodiment corresponds to the electrode tab 11 (see FIG. 1) and may include a first region 1381 that is recessed inward. The at least one die edge 138 may further include a second region 1382 that is connected to the first region 1381 and is recessed less inward than the first region 1381.

[0120] More specifically, when the secondary battery 1 is viewed from the outside, the first region 1381 can recess more inward than the second region 1382, i.e., deeper toward the side 134. Therefore, no step or edge that interferes with the electrode tab 11 is formed in the width direction of the electrode tab 11, i.e., in the length direction of the die edge 138.

[0121] That is, when the electrode assembly 10 is housed in the battery case 13, even if the electrode tab 11 does not correspond exactly to the first region 1381 and is partially displaced toward the second region 1382, the electrode tab 11 does not interfere with the second region 1382. For example, even if the length of the first region 1381 is shorter than the width of the electrode tab 11, the electrode tab 11 does not interfere with the second region 1382.

[0122] Furthermore, since the first region 1381 is formed in a concave shape, the electrode tab 11 is not excessively pressed by the first region 1381 . This has the advantage that even if the width of the electrode tab 11 of the electrode assembly 10 changes, there is no need to change the molding device.

[0123] Also in this embodiment, the first region 1381 and the second region 1382 may be rounded with different radii of curvature. That is, the first radius of curvature R1 of the first region 1381 may be larger than the second radius of curvature R2 of the second region 1382.

[0124] Those skilled in the art will understand that the present invention can be embodied in other specific forms without changing the technical spirit or essential characteristics thereof. Therefore, it should be understood that the above-described embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims set forth below rather than the above detailed description, and various embodiments derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention. [Explanation of symbols]

[0125] 1: Secondary battery 2: Molding equipment 10: Electrode assembly 11: Electrode tab 12: Electrode lead 13: Battery case 14: Insulation section 21: Die 22: Punch 111: Positive electrode tab 112: Negative electrode tab 121: Positive lead 122: Negative electrode lead 131: First Case 132: Second Case 133: Cup part 134: Side 135: Pouch film 136: Bridge 137: Degassing section 138: Die Edge 139: Punch Edge 211: Molding space 212: Bulkhead 213: Pressurizing edge of die 221: Pressurizing edge of punch 1331: Containment Space 1332: Bottom 1333: Wall 1351: Sealant layer 1352: Moisture barrier layer 1353: Surface protective layer 1354: Stretched auxiliary layer 1381:First area 1382:Second area 2121: Reinforcement 2131: Third area 2132: 4th area

Claims

1. a cup portion that accommodates an electrode assembly formed by stacking electrodes and separators; a plurality of die edges connecting the wall of the cup portion and the sides extending from the wall to each other; At least one of the die edges comprises: a first region formed by being rounded with a first radius of curvature; a second region formed by being rounded with a second radius of curvature smaller than the first radius of curvature, the first region is a region where an electrode tab protruding from one side of the electrode assembly is placed, The pouch-type battery case has an inclination angle between the wall of the cup portion and the bottom of the cup portion of 90° to 95°.

2. The first radius of curvature is 2. The pouch-shaped battery case according to claim 1, which has a thickness of 1.7 mm to 2.7 mm.

3. The second radius of curvature is 3. The pouch-type battery case according to claim 1, wherein the thickness is 1.2 mm or less.

4. The second radius of curvature is The pouch-type battery case according to claim 1 , wherein the thickness is 0.7 mm or less.

5. It is manufactured by molding pouch film, The pouch film is a sealant layer made from a first polymer and formed as an innermost layer; a surface protection layer made from a second polymer and formed as an outermost layer; a moisture barrier layer laminated between the surface protection layer and the sealant layer, The moisture barrier layer is an aluminum alloy thin film having a thickness of 50 to 80 μm and a grain size of 10 to 13 μm; The sealant layer is 5. The pouch-type battery case according to claim 1, wherein the thickness is 60 to 100 μm.

6. The depth of the cup portion is The pouch-type battery case according to claim 1 , wherein the thickness is 7 mm when one cup portion is formed, and 6.5 mm when two cup portions are formed.

7. The first region is The pouch-type battery case according to claim 1 , wherein one of the plurality of die edges is formed on each of the two die edges facing each other.

8. The first region is The pouch-type battery case according to claim 1 , wherein a plurality of the die edges are formed on one die edge.

9. The second region is The pouch-type battery case according to claim 8 , wherein the first region is formed between a plurality of the first regions.

10. an electrode assembly formed by stacking electrodes and separators; a battery case including a cup portion that accommodates the electrode assembly therein, The battery case is a plurality of die edges connecting the walls of the cup portion and the sides extending from the walls to each other; At least one of the die edges comprises: a first region formed by being rounded with a first radius of curvature; a second region formed by being rounded with a second radius of curvature smaller than the first radius of curvature, the first region is a region where an electrode tab protruding from one side of the electrode assembly is placed, The pouch-type secondary battery has an inclination angle between the wall of the cup portion and the bottom of the cup portion of 90° to 95°.

11. The area of ​​the electrode assembly is 15,000 mm ２ ~100,000 mm ２ The pouch-type secondary battery according to claim 10,

12. A battery case molding apparatus for manufacturing the pouch-shaped battery case according to claim 1, a die having an upper surface on which a pouch film is placed and including at least one molding space recessed inward from the upper surface; a punch disposed above the forming space and descending to insert the pouch film into the forming space and form it; The die is a plurality of pressure edges connecting the molding space and the upper surface to each other; At least one of the pressure edges comprises: a third region formed by being rounded with a third radius of curvature; a fourth region formed by being rounded with a fourth radius of curvature smaller than the third radius of curvature, The third region corresponds to the first region.

13. The third radius of curvature is The battery case molding apparatus according to claim 12, wherein the thickness is 1.5 mm to 2.5 mm.

14. The fourth radius of curvature is The battery case molding device according to claim 12 or 13, wherein the thickness is 1 mm or less.

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