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 on October 6, 2020 and Korean Patent Application No. 10-2021-0074479 filed on 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 and a molding apparatus thereof, and a pouch-type secondary battery, and more particularly to a pouch-type battery case and a molding apparatus thereof, which can prevent interference between a die edge and an electrode tab, and a pouch-type secondary battery. [Background technology]

[0003] Generally, types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. Such secondary batteries are used not only in small products such as digital cameras, P-DVDs, MP3Ps, 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, power storage devices that store surplus generated power and renewable energy, and backup power storage devices.

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

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

[0006] The pouch, which is the case of the pouch-type secondary battery, is manufactured by pressing a flexible pouch film to form a cup portion. After 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] The drawing during the press process is performed by inserting the pouch film into a forming device such as a press device, applying pressure to the pouch film with a punch, and stretching the pouch film. The pouch film is composed of multiple layers, and the moisture barrier layer located in the middle is made of metal. However, if the formability of the moisture barrier layer is improved to make the wall of the cup part nearly vertical and improve the curvature radius of the edge of the cup part, there is a problem that the die edge presses 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] An object of the present invention is to provide a pouch-type battery case and a molding apparatus therefor, and a pouch-type secondary battery, which are capable of preventing interference between the die edge and the electrode tab.

[0009] The object of the present invention is not limited to the above-mentioned objects, and other objects not mentioned herein 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 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.

[0011] The first radius of curvature may be between 1.7 mm and 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 be produced by molding, and the pouch film may include a sealant layer produced from a first polymer and formed as an innermost layer, a surface protective layer produced 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 die edges facing each other.

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

[0015] In order 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 separators, 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 smaller than the first radius of curvature.

[0016] The area of ​​the electrode assembly is 15,000 mm 2 ~100000mm 2 may be also possible. In addition, 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 apparatus 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 formed by recessing inward from the upper surface, and a punch arranged above the molding space and descending to insert the pouch film into the molding space to mold it, wherein the die includes a plurality of pressure edges connecting the molding space and the upper surface to each other, 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 between 1.5 mm and 2.5 mm. The fourth radius of curvature may be 1 mm or less.

[0019] 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 connecting 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 inwardly.

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

[0021] Also, 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 smaller than the first radius of curvature. Further details of the invention are included in the detailed description and the drawings. Effect of the Invention

[0022] The embodiments of the present invention have at least the following advantages. A first region of the die edge on which the electrode tab is placed is rounded with a relatively large first radius of curvature, and a second region on which the electrode tab is not placed is rounded with a relatively small second radius of curvature. This makes it possible to prevent interference between the die edge and the electrode tab even if the wall of the cup portion becomes closer to vertical and 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 description of the drawings]

[0024] [Figure 1] FIG. 1 is an assembly diagram of a secondary battery according to an embodiment of the present invention. [Diagram 2]FIG. 2 is a cross-sectional view of a pouch film according to one embodiment of the present invention. [Diagram 3] 1 is a graph showing the iron and silicon contents of aluminum alloys having alloy number AA8079 and aluminum alloys having 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 having alloy number AA8079 and alloy number AA8021. [Diagram 5] 1 shows enlarged SEM images of crystal grains of aluminum alloys having alloy numbers AA8079 and AA8021. [Figure 6] FIG. 2 is an enlarged schematic diagram 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 one embodiment of the present invention. [Figure 8] 4 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 and electrode tabs of a die edge in accordance with an embodiment of the present invention. [Figure 10] FIG. 4 is a schematic diagram showing an enlarged view of a second region of the die edge of the cup portion and an electrode tab in accordance with an embodiment of the present invention. [Figure 11] 1 is a schematic diagram of a molding apparatus 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. 4 is a partial perspective view of a secondary battery according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The advantages and features of the present invention, as well as the 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 embodiments are provided merely 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 only defined 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 in this specification may be used as meanings commonly understood by those having ordinary skill in the art to which the present invention belongs. 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 describing the 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 phrase. The words "comprises" and / or "comprising" used in the specification do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will 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 the formability can be improved when the pouch film 135 is molded to manufacture the pouch-type battery case 13.

[0030] For this purpose, the pouch film 135 according to one embodiment of the present invention includes a sealant layer 1351 (shown in FIG. 2) made of a first polymer and formed as an innermost layer, a surface protective layer 1353 (shown in FIG. 2) made of a second polymer and formed as an outermost layer, and a moisture (or gas) barrier layer 1352 (shown in FIG. 2) laminated between the surface protective layer 1353 and the sealant layer 1351, and the moisture barrier layer 1352 may be 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 1351 may be made of a thickness of 60 to 100 μm. In particular, it is preferable that the moisture barrier layer 1352 is 55 to 65 μm thick, and the sealant layer 1351 is 75 to 85 μm thick.

[0031] The electrode assembly 10 is formed by alternately stacking electrodes and separators. First, a slurry of an electrode active material, a binder, and a plasticizer is applied to a positive electrode current collector and a negative electrode current collector to manufacture 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 ~100000mm 2 In particular, the electrode assembly 10 may have a total width of 60 mm or more. Also, 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 the electrodes from each other. Examples of such an electrode assembly 10 include a stack type, a jelly roll type, and a stack and folding type. The two types of electrodes, i.e., the positive electrode and the negative electrode, are each structured such that an active material slurry is applied to a metal foil or metal mesh-like electrode collector containing aluminum and copper. The active material slurry can be formed by stirring a granular active material, a conductive material, and the like in a state where a solvent is added. The solvent is removed in a subsequent process.

[0034] The electrode assembly 10 includes an electrode tab 11 as shown in FIG. 1. The electrode tab 11 is connected to the positive and negative electrodes of the electrode assembly 10, protruding from the electrode assembly 10 to the outside, and serves as 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 tab 11 may be formed by cutting the plain portion or by connecting another 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 be formed to protrude in various directions, such as protruding in the same direction from one side.

[0035] An electrode lead 12 for supplying 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 part 14. The insulating part 14 is located at 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 part 14 prevents electricity generated from the electrode assembly 10 from flowing to the battery case 13 through the electrode lead 12, and maintains the seal of the battery case 13. Therefore, the insulating part 14 is made of a non-conductive material that does not conduct electricity well. Generally, the insulating part 14 is often made of an insulating tape that is easy to attach to the electrode lead 12 and has a relatively thin thickness, but is not limited thereto, and various materials may be used as long as they can insulate the electrode lead 12.

[0036] One end of the electrode lead 12 is connected to the electrode tab 11, and the other end protrudes outside 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, the other ends of both the positive electrode lead 121 and the negative electrode lead 122 protrude outside the battery case 13 as shown in FIG. 1. As a result, electricity generated inside the electrode assembly 10 can be supplied to the outside. In addition, since the positive electrode tab 111 and the negative electrode tab 112 are formed to 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 forming 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 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 the electrode assembly 10 and is sealed such that a portion of the electrode lead 12 is exposed. The battery case 13 includes a first case 131 and a second case 132, as shown in FIG. 1. The first case 131 is formed with a cup portion 133 and is provided with an accommodation space 1331 in which the electrode assembly 10 can be accommodated, and the second case 132 covers the accommodation space 1331 from above so that the electrode assembly 10 does not fall 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 variously manufactured, such as being separated from each other and separately manufactured.

[0040] When forming the cup portion 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 in one pouch film 135 by draw molding. Then, as shown in Fig. 1, the cup portion 133 is formed in each of the first case 131 and the second case 132. 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 the 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 provided 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 in the battery case 13 so that the two cup portions 133 face each other. Then, the cup portion 133 of the second case 132 accommodates the electrode assembly 10 from above as well. Therefore, since the 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. In addition, since the first case 131 and the second case 132 are integrally connected to each other by folding the battery case 13, the number of sides 134 to be sealed in a later sealing process can be reduced. Therefore, the process speed can be improved and the number of sealing processes can be reduced.

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

[0044] When 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 part of the electrode lead 12, the electrode assembly 10 is accommodated in the accommodation space 1331 provided in the cup portion 133 of the first case 131, and the second case 132 covers the space from above. Then, an electrolyte is injected into the interior, and the side 134 formed by extending outside the cup portion 133 of the first case 131 and the second case 132 is sealed. The electrolyte is for moving lithium ions generated by an electrochemical reaction of the electrodes when the secondary battery 1 is charged and discharged, and may include a non-aqueous organic electrolyte solution that is a mixture of lithium salt and high-purity organic solvents, or a polymer using a polymer electrolyte. Furthermore, the electrolyte may include a sulfide-based, oxide-based, or polymer-based solid electrolyte, and such a solid electrolyte may have flexibility that is easily deformed by an external force. The pouch-type secondary battery 1 can be manufactured by this method.

[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 an embodiment of the present invention, is manufactured by drawing a pouch film 135. That is, the pouch film 135 is stretched by a punch 22 or the like to form a cup portion 133. According to an 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 as necessary.

[0046] The sealant layer 1351 is made of a first polymer and is formed as an innermost layer, and can be in direct contact with the electrode assembly 10. Here, the innermost layer refers to a layer located at the very end in the direction toward the electrode assembly 10 based on the moisture barrier layer 1352. The battery case 13 is manufactured by drawing the pouch film 135 having the laminated structure as described above using a punch 22 or the like, and a part of the pouch film 135 is stretched to form a cup portion 133 including a bag-shaped storage space 1331. When the electrode assembly 10 is stored inside the storage space 1331, an electrolyte is injected. Thereafter, the first case 131 and the second case 132 are brought into contact with each other so as to face each other, and the sides 134 are thermocompressed, and the sealant layers 1351 are bonded to each other to seal the pouch. In this case, the sealant layer 1351 must have insulating properties since it is in direct contact with the electrode assembly 10, and must have corrosion resistance since it is in contact with the electrolyte. In addition, the sealant layer 1351 must have high sealing properties since it must completely seal the inside and block material transfer between the inside and the outside. That is, the side 134 where the sealant layers 1351 are bonded together must have excellent thermal adhesive strength. In general, the first polymer for manufacturing 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 mainly 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 catered 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 an embodiment of the present invention, the thickness of the sealant layer 1351 may be 60 to 100 μm, and may be 75 to 85 μm. If the thickness of the sealant layer is less than 60 μm, there may be a problem that the seal durability is reduced, such as the inside being destroyed during sealing. On the other hand, if the thickness of the sealant layer is greater than 100 μm, the overall thickness of the pouch becomes excessively thick, and the moldability may be reduced or the energy density relative to the volume of the secondary battery may be reduced. If the thickness of the sealant layer 1351 is small, the dielectric breakdown voltage of the pouch film 135 may be reduced, and the insulation may be reduced, and the defective rate may be high when a battery is manufactured using a pouch film 135 with poor insulation.

[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, is light in weight, and can ensure the complementation of electrochemical properties of the electrode assembly 10 and the electrolyte, heat dissipation, etc.

[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 the above range, the forming depth can be increased without generating pinholes or cracks during the forming of a cup.

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

[0051] Also, according to one embodiment of the present invention, the moisture barrier layer 1352 may have a thickness of 50 μm to 80 μm, and in particular, 55 μm to 65 μm. Conventionally, the moisture barrier layer was thinner than 50 μm, resulting in poor formability. When the pouch film 135 was draw-formed to increase the depth of the cup, there was a limit to how close the cup wall could be to a vertical shape, and there was also a limit to how much the curvature radius of the edge of the cup could be reduced. In addition, there was also a problem that the internal electrode assembly was easily damaged when the battery case received an external impact due to its weak puncture strength.

[0052] Conversely, if the thickness of the moisture barrier layer is thicker than about 80 μm, not only will the manufacturing cost increase, but the thickness of the entire secondary battery will become excessively thick, resulting in a problem of a decrease in the volume-specific 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 thickness of the entire secondary battery, a problem of a decrease in seal durability will occur.

[0053] However, if only the thickness of the aluminum alloy thin film is 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, as a result of extensive research, the inventors discovered that by using an aluminum alloy thin film having a specific crystal grain size as the material for the moisture barrier layer and controlling the thicknesses of the moisture barrier layer and sealant layer within a specific range, it is possible to form the cup portion deeply and maintain excellent sealing durability, thereby completing the present invention.

[0055] Specifically, the moisture barrier layer 1352 according to the present invention includes an aluminum alloy thin film having a crystal grain size of 10 μm to 13 μm, preferably 10.5 to 12.5 μm, and more preferably 11 to 12 μm. When the crystal grain size of the aluminum alloy thin film satisfies the above range, the forming depth can be increased without generating pinholes or cracks during cup forming. When the crystal grain size of the aluminum alloy thin film exceeds 13 μm, the strength of the aluminum alloy thin film decreases and it is difficult to disperse internal stress during stretching, increasing the occurrence of cracks and pinholes. When the crystal 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 with a scanning electron microscope (SEM). Specifically, in the present invention, a SEM image of a cross section of the aluminum alloy thin film in the thickness direction is obtained using a scanning electron microscope, and the maximum diameters of a predetermined number of grains among the grains observed in the SEM image are measured, and the average value thereof is evaluated as the grain size.

[0057] The surface protective layer 1353 is made of a second polymer and is formed as the outermost layer, and electrically insulates the electrode assembly 10 from the outside while protecting the secondary battery 1 from external friction and impact. Here, the outermost layer refers to the layer located last in the opposite direction to the direction in which the electrode assembly 10 is located with respect to the moisture barrier layer 1352. The second polymer for manufacturing 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 mainly 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 forming 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 less than 5 μm, there may be a problem that the external insulation property is reduced. Conversely, if the thickness of the surface protective layer is greater than 25 μm, the thickness of the entire pouch becomes large, and the energy density relative to the volume of the secondary battery may be reduced.

[0059] On the other hand, PET is inexpensive, has excellent durability, and has excellent electrical insulation properties, but has poor adhesion to aluminum, which is often used as the moisture barrier layer 1352, and their behaviors when stretched by applying stress may differ from each other. Therefore, if the surface protective layer 1353 and the moisture barrier layer 1352 are directly bonded to each other, the surface protective layer 1353 and the moisture barrier layer 1352 may peel off during draw forming. This may cause a problem that the moisture barrier layer 1352 is not uniformly stretched, resulting in a decrease in formability.

[0060] According to an 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 the surface protective layer 1353 and the moisture barrier layer 1352 from peeling off 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, and glass fiber. In particular, nylon resin can be mainly used as the third polymer since 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. And, the stretching auxiliary 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 about 40 μm, and the stretching auxiliary layer has a relatively thin thickness of about 15 μm. That is, the thickness ratio of the stretching auxiliary layer to the moisture barrier layer is 1:2.67, and the thickness ratio of the moisture barrier layer is considerably high. However, as described above, according to one embodiment of the present invention, the moisture barrier layer 1352 has a thickness of about 50 to 80 μm, particularly 55 to 65 μm, so that the formability of the moisture barrier layer 1352 is improved. At this time, in order to improve the formability of the stretching auxiliary layer 1354, the stretching auxiliary layer 1354 may have a thickness of 20 μm to 50 μm, and particularly preferably has a thickness of 25 μm to 38 μm. If it is thinner than 20 μm, the stretching auxiliary layer cannot keep up with the improved formability of the moisture barrier layer and may be broken during stretching. On the other hand, if it is thicker than 50 μm, the thickness of the entire pouch becomes thick, so that the volume of the secondary battery increases and the energy density may decrease. In particular, according to one embodiment of the present invention, the thickness ratio of the stretching assist layer 1354 to the moisture barrier layer 1352 may be less than 1:2.5. That is, the thickness ratio of the stretching assist layer 1354 can be further increased compared to the conventional case. However, if the thickness of the stretching assist layer 1354 becomes too thick, the thickness of the entire pouch will become too thick, so in order to avoid the 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 having alloy number AA8079 and aluminum alloys having alloy number AA8021. As described above, the aluminum alloy thin film forming 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 1.2wt% to 1.7wt%, preferably 1.3wt% to 1.7wt%, and more preferably 1.3wt% to 1.45wt%. If the iron (Fe) content in the aluminum alloy thin film is less than 1.2wt%, the strength of the aluminum alloy thin film decreases, and cracks and pinholes may occur during forming, while if it exceeds 1.7wt%, the flexibility of the aluminum alloy thin film decreases, and there is 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%, the formability may decrease.

[0065] Specifically, the aluminum alloy thin film according to the present invention may be an aluminum alloy having alloy number AA8021. In contrast, conventional battery pouches are made of aluminum alloy thin film, mainly 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] Alloy number AA8079 contains 0.6 wt% to 1.2 wt% iron and 0.3 wt% or less silicon, as shown in Fig. 3. In the case of an aluminum alloy with alloy number AA8079, the iron content is relatively small, and when the moisture barrier layer 1352 is manufactured using the alloy, the flexibility can be improved, but the strength can be reduced, limiting the formability.

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

[0068] Meanwhile, when a tensile force is applied to a material, the relationship between tensile strength and elongation can be shown in a graph. In this case, the vertical axis of the graph represents tensile strength, and the horizontal axis represents elongation. The area under the graph represents the toughness of the material. Toughness indicates the degree of resistance to breakage of a material, and the higher the toughness, the more the material can be stretched before it breaks.

[0069] Therefore, when the moisture barrier layer 1352 is manufactured using an aluminum alloy having alloy number AA8021, the tensile strength and elongation are improved, and therefore the toughness is increased and the formability can be improved.

[0070] FIG. 4 is a graph showing the change in tensile strength (Rm), elongation, and grain size as a function of iron content for aluminum alloys having alloy numbers AA8079 and AA8021, and FIG. 5 is a SEM image showing enlarged grains for aluminum alloys having alloy numbers AA8079 and AA8021.

[0071] As shown in Figure 4, the tensile strength, elongation, and grain size of an aluminum alloy 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 leads to a problem that the internal stress is less dispersed during stretching and pinholes increase, resulting in a decrease in the formability of the battery case 13.

[0073] Alloy No. AA8021 has a relatively small crystal grain size of 10 μm to 13 μm, and therefore, the internal stress can be dispersed more during stretching, resulting in fewer pinholes and improved 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 the above range, it is possible to increase the molding depth while minimizing the reduction in the battery accommodation space and the deterioration of the sealing durability due to the 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 is excellent in tensile strength and elongation. Specifically, the pouch film 135 according to the present invention may have a tensile strength of 200N / 15mm to 300N / 15mm, preferably 210N / 15mm to 270N / 15mm, more preferably 220N / 15mm to 250N / 15mm, measured while being pulled at a pulling speed of 50mm / min after being cut into a size of 15mm x 80mm, and an elongation of 120% to 150%, preferably 120% to 140%, more preferably 120% to 130%. Thus, the pouch film laminate according to the present invention has high tensile strength and elongation, thereby increasing toughness, and cracks are less likely to occur even when the molding depth is large during molding of a cup.

[0076] In addition, 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. Fig. 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 a plurality of walls 1333 surrounding the periphery of the cup portion 133 to the bottom portion 1332, and the die edge 138 connects a plurality of walls 1333 to the side 134. If the pressure edge of the die is not rounded, the pressure edge of the die becomes sharp, and there is a problem that stress is concentrated on the die edge of the cup portion when the pouch film 135 is formed, and cracks are likely to occur.

[0078] To solve this problem, by rounding the pressure edge 213 of the die 21, the die edge 338 of the cup portion 333 is formed in a rounded shape, 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 of a specific depth or more, when 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 specific 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, the die edge 138, 338 being formed to be rounded means that a curved surface is formed to have a curvature, and such a curved surface may have a constant curvature overall, but is not limited thereto, and may have a curvature that is not constant overall.

[0081] Thus, according to one embodiment of the present invention, the sealant layer 1351 may have a thickness of 60 to 100 μm, particularly 75 to 85 μm, and the moisture barrier layer 1352 may have a thickness of 50 to 80 μm, particularly 55 to 65 μm, and the moisture barrier layer 1352 may be made of an aluminum alloy thin film having 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 closer to 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 storage space 1331 increases, so that the volume of the electrode assembly 10 stored therein can also be increased, and the energy efficiency relative to the volume of the secondary battery 1 can also be increased. 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 the seal durability does not decrease. In addition, the pouch-type battery case 13 and the pouch-type secondary battery 1 can have a sharp shape overall, so that the appearance of the secondary battery 1 is excellent and the merchantability can be improved.

[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 tab 11 protrudes from the electrodes stacked in the electrode assembly 10, and may be formed in a number equal to the number of electrodes in the electrode assembly 10. Then, the electrode tab 11 is stacked and connected to each other and then placed on the side 134. At this time, the electrode tab 11 is placed from the die edge 338 to the side 134. As the radius of curvature R3 of the die edge 338 decreases, the die edge 338 may be further recessed into the inside of the cup portion 333, and the flexibility of the die edge 338 may decrease. Then, the distance between the die edge 338 and the electrode tab 11 also decreases, and the die edge 338 presses the electrode tab 11, and interference may occur between the die edge 338 and the electrode tab 11. In particular, as the number of electrode tabs 11 increases, the thickness at which the electrode tabs 11 are stacked increases, and the space between the wall 3333 of the cup portion 333 and the electrode tabs 11 becomes narrower. Therefore, the die edge 338 presses the electrode tabs 11 further, 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 so that the wall 1333 of the cup portion 133 becomes closer to vertical, and even if the curvature radii R1, 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 a wall 1333 of the cup portion 133 and a side 134 extending from the wall 1333 to each other, 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 houses 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 and a side 134 extending from the wall 1333 to each other, and at least one of the die edges 138 includes a first region 1381 formed by being rounded with a first radius of curvature R1, and a second region 1382 formed by being rounded with a second radius of curvature R2 smaller than the first radius of curvature 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 wall 1333. The die edge 138 connects the plurality of walls 1333 to the side 134. According to an 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 thus the number of die edges 138 is equal to the number of the 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, without being limited thereto, the number of die edges 138 may vary according to the number of the 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 in different die edges 138. For example, as shown in FIG. 7, the first regions 1381 may be formed in each of two die edges 138 facing each other. In this case, the first regions 1381 may be located in the approximate center of the die edge 138, and the second regions 1382 may be formed on both sides of the first regions 1381. However, without being limited thereto, when the electrode tabs 11 protrude in the same direction from one side of the electrode assembly 10, the first regions 1381 may be formed in multiple numbers in one die edge 138. In this case, the second regions 1382 may be formed between the multiple first regions 1381.

[0097] Meanwhile, since the first region 1381 and the second region 1382 are rounded with different radii of curvature 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 change continuously 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. As a result, the first region 1381 and the second region 1382 may be continuously connected without forming a step.

[0099] FIG. 9 is an enlarged schematic diagram of a 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 diagram of a 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, since the die edge 138 does not press the electrode tab 11, it is possible to prevent interference between the die edge 138 and the electrode tab 11 in the first region 1381 on which 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. Such second radius of curvature R2 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 an overall sharp shape, resulting 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 arranged 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 which connect 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) which is rounded with a third radius of curvature, and a fourth region 2132 (shown in FIG. 12) which is 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 device 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 formed adjacent to each other by draw forming. For this purpose, 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 of the two forming spaces 211 to draw forming 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, i.e., two cup portions 133 in total, and a bridge 136 may also be formed between the two cup portions 133 corresponding to the partition wall 212.

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

[0106] The width of such a folded portion is proportional to the thickness of the bridge 136, and since the bridge 136 is formed corresponding to the partition 212, the thickness of the bridge 136 is proportional to the thickness of the partition 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 212.

[0107] However, if the partition wall 212 is formed too tall while being thin, the partition wall 212 may be damaged during the draw molding process. In particular, in the conventional case where the die 21 has a bottom, there is a problem that gas existing in the space between the pouch film 135 and the molding space 211 cannot be discharged when the punch 22 forms 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 212 is formed excessively high.

[0109] 11, an upper portion of the partition wall 212 may maintain a minimized thickness, and a reinforcing portion 2121 having a thickness greater than that of the partition wall 212 may be formed at a lower portion of the partition wall 212. The reinforcing portion 2121 may be formed below a depth D of a cup portion 133 formed in the battery case 13, and may be formed at a position where the partition wall 212 is not damaged. 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 lower part. That is, at least a portion of the cross section of the partition wall 212 may have a substantially triangular shape, and the inner wall 214 of the molding space 211 formed in the partition wall 212 may have a slope. The exact slope of the inner wall 214 of the molding 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, and prevents 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 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.

[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 connecting the upper surface and the molding space 211 to each other, and at least one of the pressure edges 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 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 produces a pouch-type battery case 13. 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] Moreover, 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 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, since the second radius of curvature R2 of the second region 1382 may be 1.2 mm or less, preferably 0.7 mm or less, 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, the third regions 2131 may be formed on each of two opposing pressing edges 213. In this case, the third region 2131 may be located at a substantially central portion 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. Such a connecting region is also rounded, and as it extends from the third region 2131 to the fourth region 2132, the radius of curvature may change continuously from the third radius of curvature to the fourth radius of curvature at a constant rate. 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 the present embodiment corresponds to the electrode tab 11 (see FIG. 1) and may include a first region 1381 recessed inward. The at least one die edge 138 may further include a second region 1382 connected to the first region 1381 and 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, even if the electrode tab 11 does not correspond exactly to the first region 1381 and is partially displaced toward the second region 1382 when the electrode assembly 10 is housed in the battery case 13, 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] 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] A person having ordinary skill in the art to which the present invention pertains can understand that the present invention can be implemented in other specific forms without changing the technical idea or essential features of the present invention. 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 below rather than the above detailed description, and various embodiments derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in 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 lead 131: First Case 132: Case 2 133: Cup section 134: Side 135: Pouch film 136: Bridge 137: Deaeration section 138: Die Edge 139: Punch Edge 211: Molding space 212: Bulkhead 213: Pressing edge of die 221: Pressing 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 for accommodating an electrode assembly formed by stacking electrodes and separators; a plurality of die edges connecting the walls of the cup portion and the sides extending from the walls; 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 The pouch-type battery case according to claim 1, which is 1.7 mm to 2.7 mm.

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

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

5. It is manufactured by forming a pouch film, The pouch film is a sealant layer formed as an innermost layer and made from a first polymer; a surface protective layer formed as an outermost layer from a second polymer; a moisture barrier layer laminated between the surface protective layer and the sealant layer, The moisture barrier layer is The aluminum alloy thin film has a thickness of 50 to 80 μm and a grain size of 10 to 13 μm. The sealant layer is The pouch-type battery case according to any one of claims 1 to 4, having a thickness of 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 first and second die edges is formed on each of the two die edges that face 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 of the die edges.

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 interconnecting a wall of the cup portion and a side extending from the wall; 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, A pouch-type secondary battery, wherein an inclination angle between the wall of the cup portion and the bottom of the cup portion is 90° to 95°.

11. The area of ​​the electrode assembly is 15000 mm ２ ~100,000mm ２ The pouch-type secondary battery according to claim 10 ,

12. A battery case molding apparatus for manufacturing the pouch-type battery case according to claim 1, 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; A punch is disposed above the forming space and moves down to insert the pouch film into the forming space to form the pouch film; The die includes: a plurality of pressurizing edges connecting the molding space and the upper surface to each other; At least one of the pressing edges comprises: a third region formed by being rounded with a third radius of curvature; a fourth region formed to be 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 apparatus according to claim 12 or 13, wherein the thickness is 1 mm or less.

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