Battery case molding device, molding method, and battery case

Abstract

To solve the above problem, one embodiment of the present invention provides a battery case molding device including: 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 upper surface of the die includes at least one die inclined surface.

Description

[Technical field]

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0129026 filed on October 6, 2020, and Korean Patent Application No. 10-2021-0131992 filed on October 5, 2021, and all contents disclosed in the documents of said Korean patent applications are incorporated as part of this specification.

[0002] The present invention relates to a battery case molding device, a molding method, and a battery case, and more particularly to a battery case molding device and molding method for molding a pouch film to form a cup portion so that the outer wall of the cup portion formed on the folding section side that integrally connects a first case and a second case is nearly vertical. [Background technology]

[0003] Generally, types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, lithium-ion polymer batteries, etc. These 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, as well as in power storage devices and backup power storage devices that store surplus power or new renewable energy.

[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 placed in a battery case, and the case is sealed after injection of an electrolyte.

[0005] Secondary batteries are classified into pouch type and can type depending on the material of the case that contains the electrode assembly. The pouch type contains the electrode assembly in a pouch made of a ductile polymer material that does not have a uniform shape.

[0006] A pouch, which is a case of a pouch-type secondary battery, is manufactured by pressing a flexible pouch film to form a cup portion, and then, 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 a secondary battery.

[0007] Among such press processes, drawing is performed by inserting a pouch film into a forming device such as a press and applying pressure to the pouch film with a punch to stretch the pouch film. However, since there is a clearance between the inner wall of the forming space of the die and the outer wall of the punch, the outer wall of the cup part in the pouch-type battery case is formed with a slope. Therefore, there is a problem that the space between the outer wall of the cup part and the electrode assembly increases. In particular, if the outer wall of the cup part formed on the folding part side that integrally connects the first case and the second case of the battery case has a slope, the outer wall of the cup part may be deformed in a later degassing process, and the punch edge on the folding part side may protrude outward and become high, resulting in an edge high phenomenon. This edge high phenomenon increases unnecessary thickness of the secondary battery and reduces the energy density per volume. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Publication No. 2018-0055427 Summary of the Invention [Problem to be solved by the invention]

[0009] The problem that the present invention aims to solve is to provide a battery case molding device, a molding method, and a battery case that, when molding a pouch film to form a cup portion, molds the outer wall of the cup portion formed on the folding section side that connects the first case and the second case together so that it is nearly vertical.

[0010] The object of the present invention is not limited to the above-mentioned object, 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]

[0011] 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 recessed inward from the upper surface, and a punch disposed above the molding space and descending to insert the pouch film into the molding space to mold it, the upper surface of the die including at least one die inclined surface.

[0012] The die inclined surface may have an inclination in the direction in which the punch descends.

[0013] The molding space may be formed by recessing the die inward from the die inclined surface.

[0014] Also, the die inclined surface may include a first die inclined surface and a second die inclined surface, and the first die inclined surface and the second die inclined surface may be formed symmetrically to each other.

[0015] In addition, the first die inclined surface and the second die inclined surface may have a downward inclination as they become closer to each other.

[0016] The molding space may include a first molding space recessed from the first die inclined surface to the inside of the die, and a second molding space recessed from the second die inclined surface to the inside of the die.

[0017] The die may further include a partition formed between the first molding space and the second molding space.

[0018] In addition, the partition may be formed so that its thickness increases toward its lower portion, and an inner wall of the molding space formed by the partition may have an inclination.

[0019] The punch may be formed with a groove, into which the partition is inserted, at a position corresponding to the partition.

[0020] Moreover, the punch can include a first forming portion that inserts the pouch film into the first forming space, and a second forming portion that inserts the pouch film into the second forming space.

[0021] The upper surface of the die may further include a horizontal die surface that extends from at least one end of the inclined die surface and is perpendicular to a direction in which the punch descends.

[0022] Further, the punch may have a forming portion that comes into direct contact with the pouch film having the same inclination as the die inclined surface.

[0023] The apparatus may further include a stripper that is disposed above the die and moves down to pinch the pouch film and contact the die to fix the pouch film.

[0024] The stripper may further include at least one stripper inclined surface having a lower surface that abuts against the die inclined surface and has the same inclination as the die inclined surface.

[0025] To solve the above problems, a battery case molding method according to an embodiment of the present invention may include the steps of placing a pouch film on an upper surface of a die, a punch disposed above a molding space recessed inward from the upper surface of the die, descending in a direction inclined relative to at least a portion of the upper surface, and the punch inserting the pouch film into the molding space to form a cup portion in the pouch film.

[0026] In the step of lowering the punch, the upper surface of the die may include at least one die inclined surface.

[0027] To solve the above problems, a battery case according to an embodiment of the present invention includes a cup portion formed in at least one of a first case or a second case, in which an outer wall is formed along an edge of one surface of a bottom to provide an accommodation space for an electrode assembly, and a folding portion folded at one side of the cup portion to integrally connect the first case and the second case, wherein the outer wall includes a first outer wall formed on the edge of one surface of the bottom toward the folding portion, a second outer wall formed on an opposite side of the first outer wall, a third outer wall formed to connect the first outer wall and the second outer wall, and a fourth outer wall formed on the opposite side of the third outer wall, and an inner inclination angle between the first outer wall and the bottom may be 90° to 95°.

[0028] Also, an inner inclination angle between the second outer wall and the bottom may be greater than an inner inclination angle between the first outer wall and the bottom.

[0029] Also, an inner inclination angle between the second outer wall and the bottom may be at least 10° larger than an inner inclination angle between the first outer wall and the bottom.

[0030] Further details of the invention are contained in the detailed description and the drawings. Effect of the Invention

[0031] According to the embodiment of the present invention, at least the following effects are obtained.

[0032] The inclination angle from the bottom of the outer wall of the cup portion formed on the folding portion side can be further reduced to be closer to vertical, so that the electrode assembly can be positioned very close to the outer wall of the cup portion, thereby reducing unnecessary volume of the cup portion.

[0033] In addition, even if the internal pressure of the cup portion is reduced during the degassing process, the outer wall or bottom of the cup portion is prevented from being deformed, and the edge-high phenomenon can be prevented from occurring.

[0034] Also, the size of the bat ears can be reduced, and the problem of the bat ears being conspicuous can be prevented.

[0035] The effects of the present invention are not limited to the above-mentioned examples, and various other effects are included in the present specification. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is an assembly diagram of a secondary battery 1 according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of a pouch film 135 according to one embodiment of the present invention. [Diagram 3] FIG. 1 is a perspective view of a conventional battery case molding apparatus 4. [Figure 4] FIG. 1 is a schematic diagram of a conventional battery case molding apparatus 4. [Diagram 5] FIG. 13 is a schematic diagram showing a conventional punch 43 descending. [Figure 6] 13 is a partially enlarged view of a punch edge 3334 of a conventional cup portion 333. FIG. [Figure 7] FIG. 13 is a partial enlarged view of a folding portion 339 of a conventional secondary battery 3. [Figure 8] FIG. 1 is a schematic diagram showing a conventional secondary battery 3 from above. [Figure 9]1 is a flowchart showing a method for manufacturing a battery case 13 by performing press working on a pouch film 135 according to one embodiment of the present invention. [Figure 10] FIG. 1 is a perspective view of a battery case molding apparatus 2 according to one embodiment of the present invention. [Figure 11] FIG. 1 is a schematic diagram of a battery case molding apparatus 2 according to one embodiment of the present invention. [Figure 12] FIG. 2 is a schematic diagram showing a state in which the stripper 22 according to the embodiment of the present invention has been lowered. [Figure 13] FIG. 2 is a schematic diagram showing a state in which a punch 23 according to an embodiment of the present invention has been lowered. [Figure 14] 1 is a partially enlarged view of a punch edge 1334 of a cup portion 133 according to one embodiment of the present invention. [Figure 15] 2 is a partial enlarged view of a folding portion 139 of the secondary battery 1 according to one embodiment of the present invention. FIG. [Figure 16] FIG. 1 is a schematic diagram showing a secondary battery 1 according to one embodiment of the present invention from above. [Figure 17] FIG. 2 is a perspective view of a battery case molding device 2a according to another embodiment of the present invention. [Figure 18] FIG. 2 is a schematic diagram of a battery case molding apparatus 2a according to another embodiment of the present invention. [Figure 19] FIG. 13 is a schematic view showing a state in which a stripper 22a according to another embodiment of the present invention is lowered. [Figure 20] FIG. 11 is a schematic diagram showing a state in which a punch 23a according to another embodiment of the present invention is lowered. [Figure 21] 13 is a partially enlarged view of a punch edge 1334a of a cup portion 133a according to another embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] 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 present embodiments are provided solely to complete the disclosure of the present invention and to fully inform those skilled in the art of the present invention of the scope of the invention, and the present invention is only defined by the scope of the claims. The same reference numerals refer to the same elements throughout the specification.

[0038] 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 knowledge in the technical field to which the present invention belongs. In addition, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless specifically defined.

[0039] The terms used in this specification are for the purpose of 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 context. As used in this specification, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other elements in addition to the elements mentioned.

[0040] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0041] FIG. 1 is an assembly diagram of a secondary battery 1 according to one embodiment of the present invention.

[0042] 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 collector and a negative electrode 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.

[0043] 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. Such electrode assemblies 10 include stack type, jelly roll type, stack and folding type, etc. 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 an electrode collector in the form of a metal foil or metal mesh containing aluminum and copper. The slurry may be typically formed by stirring a granular active material, an auxiliary conductor, a binder, a plasticizer, etc., in a state where a solvent is added. The solvent is removed in a subsequent process.

[0044] As shown in FIG. 1, the electrode assembly 10 includes an electrode tab 11. The electrode tab 11 is connected to the positive and negative electrodes of the electrode assembly 10, and protrudes 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 tab 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 be formed to protrude in various directions, such as protruding in the same direction from one side.

[0045] 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 where the first case 131 and the second case 132 of the battery case 13 are heat-sealed, and bonds 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 sealing of the battery case 13. Therefore, the insulating part 14 is made of a non-conductor having non-conductivity that does not allow electricity to pass through well. Generally, the insulating part 14 is often made of insulating tape that is easy to attach to the electrode lead 12 and has a relatively thin thickness, but is not limited thereto and can be made of various materials as long as it can insulate the electrode lead 12.

[0046] 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, the positive electrode lead 121 and the negative electrode lead 122 each have the other end protruding out of the battery case 13 as shown in FIG. 1. This allows electricity generated inside the electrode assembly 10 to 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.

[0047] 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.

[0048] The battery case 13 is a pouch made of a flexible material that houses the electrode assembly 10 therein. In the following, the battery case 13 will be described as a pouch. When a flexible pouch film 135 is drawn using a punch 23 (shown in FIG. 10 ) 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 producing the battery case 13.

[0049] The battery case 13 receives the electrode assembly 10 and is sealed so 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 has a cup portion 133 formed therein to provide a receiving space 1331 capable of receiving the electrode assembly 10, and the second case 132 covers the receiving 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.

[0050] 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 drawn adjacent to each other in one pouch film 135. Then, as shown in FIG. 1, the first case 131 and the second case 132 are each formed with a cup portion 133. At this time, 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 may have different depths D. 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 two cup parts 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 part 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.

[0051] Meanwhile, the battery case 13 may include a cup part 133 having an accommodation space 1331 for accommodating the electrode assembly 10, and a gas vent part 137 formed on a side of the cup part 133 to discharge gas generated inside the cup part 133 through a gas vent hole H. When the electrode assembly 10 is accommodated in the cup part 133 of the battery case 13, an electrolyte is injected, and an activation process is performed, gas is generated inside the battery case 13. In order to discharge the gas to the outside, a gas vent hole is punched in the gas vent part 137, a gas vent process is performed, and then the gas vent part 137 can be sealed and cut to remove it.

[0052] 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 an 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 extending outward from 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 during charging and discharging of the secondary battery 1, 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. In this manner, the pouch-type secondary battery 1 may be manufactured.

[0053] FIG. 2 is a cross-sectional view of a pouch film 135 according to one embodiment of the present invention.

[0054] 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 and forming a pouch film 135. That is, the pouch film 135 is stretched by a punch 23 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.

[0055] The sealant layer 1351 is made of a first polymer and is formed as an innermost layer, so that it can be in direct contact with the electrode assembly 10. Here, the innermost layer refers to a layer located at the very end when facing the direction in which the electrode assembly 10 is located 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 23 or the like, and a part of the pouch film 135 is stretched to form a cup portion 133 including a bag-shaped receiving space 1331. When the electrode assembly 10 is received inside the receiving 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 subjected to thermocompression bonding, so that the sealant layers 1351 are bonded to each other, thereby sealing the battery case 13. At this time, the sealant layer 1351 should have insulating properties since it is in direct contact with the electrode assembly 10, and should have corrosion resistance since it is in contact with the electrolyte. In addition, since it must completely seal the inside and block the movement of materials between the inside and the outside, it should have high sealing properties. That is, the side 134 where the sealant layers 1351 are bonded together should 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) is mainly used to manufacture the sealant layer 1351 because it has excellent mechanical properties such as tensile strength, rigidity, surface hardness, abrasion resistance, and heat resistance, and excellent chemical properties such as corrosion resistance.Furthermore, it may be made of cated polypropylene, acid modified polypropylene, or a terpolymer of polypropylene-butylene-ethylene. 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 forming layers of two or more materials.

[0056] The moisture barrier layer 1352 is laminated between the surface protection layer 1353 and the sealant layer 1351 to ensure the mechanical strength of the pouch, block the ingress and egress of gas or moisture from the secondary battery 1, and prevent electrolyte leakage. The moisture barrier layer 1352 is made of metal, and may be made of metal including an aluminum alloy. Aluminum 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, and heat dissipation, etc. The aluminum alloy may include various materials. For example, the aluminum alloy may include one or more selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), and zinc (Zn). In this case, when the moisture barrier layer 1352 is made of a material containing iron, the mechanical strength is improved, and when the moisture barrier layer 1352 is made of a material containing aluminum, the flexibility is improved, so that the moisture barrier layer 1352 may be used in consideration of the respective characteristics.

[0057] The surface protective layer 1353 is made of a second polymer and is formed as the outermost layer to protect 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 at the very end when facing 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 forming 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) having mainly wear resistance and heat resistance. 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] On the other hand, PET is inexpensive, has excellent durability, and has excellent electrical insulation, but has poor adhesion to aluminum, which is often used as the moisture barrier layer 1352, and their behaviors when stretched by applying stress are different. Therefore, if the surface protection layer 1353 and the moisture barrier layer 1352 are directly bonded to each other, they may peel off from each other during drawing. This can cause a problem that the moisture barrier layer 1352 is not uniformly stretched, decreasing formability.

[0059] According to an embodiment of the present invention, the battery case 13 may further include a stretching assist layer (not shown) made of a third polymer and laminated between the surface protective layer 1353 and the moisture barrier layer 1352. The stretching assist layer is laminated between the surface protective layer 1353 and the moisture barrier layer 1352, and prevents the surface protective layer 1353 and the moisture barrier layer 1352 from peeling off when they are stretched. The third polymer from which such a stretching assist layer 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, it is preferable to mainly use nylon resin 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. The stretching auxiliary layer may have a single film structure made of any one material, or a composite film structure formed by layers of two or more materials.

[0060] FIG. 3 is a perspective view of a conventional battery case molding apparatus 4, and FIG.

[0061] As shown in Figures 3 and 4, a conventional battery case molding apparatus 4 includes a die 41 on whose upper surface 412 a pouch film 135 is placed and which includes a molding space 411 formed by recessing inward from the upper surface 412, a stripper 42 which is arranged above the die 41 and which, when lowered, abuts against the die 41 while sandwiching the pouch film 135 to fix the pouch film 135, and a punch 43 which is arranged above the molding space 411 and at the center of the stripper 42 and which descends to insert the pouch film 135 into the molding space 411 to mold it.

[0062] First, as shown in Fig. 4, the flexible pouch film 135 is placed on the upper surface 412 of the die 41. At this time, the pouch film 135 is placed on the upper surface 412 of the die 41 so that the molding space 411 is located in an area where the cup portion 333 will be formed later. Conventionally, the upper surface 412 of the die 41 is formed horizontally with the ground surface. Therefore, the pouch film 135 is also placed on the upper surface 412 of the die 41 horizontally with the ground surface.

[0063] FIG. 5 is a schematic diagram showing a conventional punch 43 in a state where it has been lowered.

[0064] 5, the stripper 42 is disposed above the die 41, and descends when the pouch film 135 is placed on the upper surface 412 of the die 41. Then, the stripper 42 sandwiches the pouch film 135 and comes into contact with the die 41, pressing the pouch film 135 from above to fix it in place.

[0065] The punch 43 descends with a constant pressure and speed to apply pressure to the upper surface of the pouch film 135 placed on the die 41, thereby stretching the pouch film 135. As a result, a cup portion 333 is formed in the pouch film 135, and the pouch-type battery case 33 can be manufactured.

[0066] The punch 43 corresponds in shape and size to the molding space 411 of the die 41. Here, the corresponding shape means that the punch 43 has a shape identical or similar to that of the molding space 411 of the die 41, and when the pouch film 135 is stretched later to form the cup portion 333, the cup portion 333 is formed in a shape identical or similar to that of the punch 43 and the molding space 411 of the die 41. And the corresponding size means that the punch 43 is inserted into the molding space 411 of the die 41 together with the pouch film 135 and stretches the pouch film 135, so that the punch 43 is minutely smaller than the molding space 411 of the die 41 by as much as the clearance CL.

[0067] The clearance CL refers to the horizontal distance between the inner wall 414 of the molding space 411 of the die 41 and the outer wall 3333 of the punch 43. In reality, there is a minute size difference between the molding space 411 of the die 41 and the punch 43, which is as small as the clearance CL. If the clearance CL is too small, the distance between the inner wall 414 of the molding space 411 and the outer wall 432 of the punch 43 becomes too small. Then, the pouch film 135 may not be able to be inserted into the molding space 411, or friction may be too large, causing damage to the pouch film 135.

[0068] Conventionally, the lower surface 422 of the stripper 42 and the forming portion 431 of the punch 43 were both formed horizontally with the ground surface. Therefore, when the pouch film 135 was formed to form the cup portion 333, the bottom portion 3332 of the cup portion 333 was also formed horizontally with the ground surface.

[0069] FIG. 6 is a partially enlarged view of a punch edge 3334 of a conventional cup portion 333. As shown in FIG.

[0070] In the battery case 33, the edges of the cup portion 333 include various kinds of edges such as punch edges 3334, die edges, thickness edges, etc. Among them, the punch edges 3334 are formed corresponding to the edges of the punch 43, and connect the multiple outer walls 3333 surrounding the periphery of the cup portion 333 to the bottom portion 3332.

[0071] The clearance CL, which is the horizontal distance between the inner wall 414 of the forming space 411 of the die 41 and the outer wall 432 of the punch 43, can be expressed as the horizontal distance between the upper end of the outer wall 3333 of the cup portion 333 in the battery case 33 and the boundary point between the punch edge 3334 and the outer wall 3333 of the cup portion 333. However, as described above, the larger the clearance CL, the larger the inclination angle C of the outer wall 3333 of the cup portion 333 from the bottom 3332 in the pouch-type battery case 33, and there is a problem that the space between the outer wall 3333 of the cup portion 333 and the electrode assembly 10 increases. In fact, even if the clearance CL is minimized, there has been a limit in forming the outer wall 3333 of the cup portion 333 close to vertical, with the inclination angle C from the bottom 3332 being 95° or less.

[0072] FIG. 7 is a partial enlarged view of a folding portion 339 of the conventional secondary battery 3, and FIG. 8 is a schematic view showing the conventional secondary battery 3 from above.

[0073] Meanwhile, when the secondary battery 3 is subjected to a gas release process, the gas is discharged from the inside of the battery case 33 to the outside, and the internal pressure of the cup part 333 is reduced. Therefore, in the past, as the internal pressure of the cup part 333 is reduced, the volume of the space between the outer wall 3333 of the cup part 333 and the electrode assembly 10 is also reduced, and the outer wall 3333 or the bottom part 3332 of the cup part 333 may be deformed. In particular, as shown in FIG. 7, the outer wall 3333 on the folding part 339 side of the secondary battery 3 is depressed inward, and the punch edge 3334 on the folding part 339 side of the cup part 333 protrudes outward and becomes high, which is called an edge high phenomenon. This edge high phenomenon increases the unnecessary thickness of the secondary battery 3, and there is a problem that the energy density relative to the volume is reduced. In addition, there is a problem that the outer wall 3333 on the folding part 339 side of the cup part 333 is deformed, and therefore the appearance of the secondary battery 3 is not beautiful and the marketability is reduced.

[0074] Furthermore, as shown in FIG. 8, the edge-high phenomenon causes the size of the butt ears 35 to increase and the shape becomes conspicuous. The butt ears 35 are visibly protruding outward from both ends of the folding portion 339. When the butt ears 35 are formed to be large, the unnecessary volume of the secondary battery 3 increases, and an error occurs between the design value and the actual value of the shape and size of the secondary battery 3. Therefore, when the secondary battery 3 is assembled into a battery module (not shown), it is not easy to assemble the secondary battery 3, and the size of the secondary battery 3 must be designed small from the beginning in consideration of the butt ears 35. In addition, the volume of the secondary battery 3 increases, and the energy density per volume decreases. Furthermore, when the secondary battery 3 is housed in the housing (not shown) of the battery module, the butt ears 35 cause a large distance between the housing and the folding portion 339, and the cooling efficiency of the secondary battery 3 decreases.

[0075] FIG. 9 is a flowchart showing a method for manufacturing a battery case 13 by performing press working on a pouch film 135 according to one embodiment of the present invention.

[0076] According to an embodiment of the present invention, the inclination angle of the outer wall 1333 of the cup part 133 from the bottom 1332 can be further reduced to be nearly vertical, and therefore the electrode assembly 10 can be positioned very close to the outer wall 1333 of the cup part 133, thereby reducing unnecessary volume of the cup part 133. In addition, even if the internal pressure of the cup part 133 is reduced during the degassing process, the outer wall 1333 or the bottom 1332 of the cup part 133 is prevented from being deformed, thereby preventing the edge-high phenomenon from occurring. In addition, the size of the butt ears 15 can be reduced, preventing the problem of the shape of the butt ears 15 being noticeable. To this end, a battery case molding method according to one embodiment of the present invention includes a step (S901) of placing a pouch film 135 on the upper surface of a die 21, a step (S903) of a punch 23 arranged above a molding space 211 recessed inward from the upper surface of the die 21, and a step (S904) of the punch 23 inserting the pouch film 135 into the molding space 211 to form a cup portion 133 in the pouch film 135.

[0077] The contents of each step in the flowchart shown in FIG. 9 will be described below with reference to FIGS.

[0078] FIG. 10 is a perspective view of a battery case molding apparatus 2 according to one embodiment of the present invention, and FIG. 11 is a schematic diagram of the battery case molding apparatus 2 according to one embodiment of the present invention.

[0079] 10 and 11, a battery case molding apparatus 2 according to an embodiment of the present invention includes a die 21 having a pouch film 135 placed on an upper surface thereof and including a molding space 211 formed by recessing inward from the upper surface thereof, and a punch 23 disposed above the molding space 211 and descending to insert the pouch film 135 into the molding space 211 to mold it, the upper surface of the die 21 including at least one die inclined surface 212. In addition, the battery case molding apparatus 2 may further include a stripper 22 disposed above the die 21 and descending to contact the die 21 with the pouch film 135 sandwiched therebetween to fix the pouch film 135.

[0080] The die 21 has a flexible pouch film 135 placed on its upper surface. At this time, the pouch film 135 is placed so that the forming space 211 is located in an area where the cup portion 133 is formed. The upper surface of the die 21 includes at least one die inclined surface 212 having an inclination in the direction in which the punch 23 descends. The upper surface of the die 21 may further include a die horizontal surface 213 extending from at least one end of the die inclined surface 212 and perpendicular to the direction in which the punch 23 descends. The die horizontal surface 213 may be perpendicular to the direction in which the punch 23 descends or horizontal to the ground surface. Therefore, after the pouch film 135 is formed, a portion of the pouch film 135 placed on the die horizontal surface 213 may be formed horizontal to the ground surface without inclination. In order to easily fix the pouch film 135 later, a lattice pattern or fine irregularities may be formed on the upper surface of the die 21.

[0081] According to an embodiment of the present invention, one pouch film 135 may be drawn to have two cup portions 133 adjacent to each other. That is, the first case 131 and the second case 132 may each have the cup portion 133. For this purpose, as shown in FIG. 10 and FIG. 11, the die inclined surface 212 includes a first die inclined surface 2121 and a second die inclined surface 2122, and the first die inclined surface 2121 and the second die inclined surface 2122 may be formed symmetrically to each other. Here, being formed symmetrically means that a line formed at a point where the first die inclined surface 2121 and the second die inclined surface 2122 contact each other becomes a central axis, and the first die inclined surface 2121 and the second die inclined surface 2122 are formed symmetrically with respect to the central axis. In addition, the first die inclined surface 2121 and the second die inclined surface 2122 have a downward inclination as they become closer to each other, so that the die 21 may be formed in a shape concave downward.

[0082] The die 21 includes at least one forming space 211 recessed inward from the upper surface of the die 21. The forming space 211 corresponds in shape and size to the outer surface of the cup portion 133 to be formed later. Here, the corresponding shape means that when the punch 23 stretches the pouch film 135 to form the cup portion 133 later, the cup portion 133 is formed in the same or similar shape as the punch 23 and the forming space 211 of the die 21. Therefore, when the cross section of the cup portion 133 has a rectangular shape, the cross section of the forming space 211 may also have a rectangular shape, and when the cross section of the cup portion 133 has a circular shape, the cross section of the forming space 211 may also have a circular shape. And, the corresponding size means that the punch 23 and the pouch film 135 are inserted together into the forming space 211 of the die 21 when the punch 23 stretches the pouch film 135, so that the shape of the cup portion 133 is minutely smaller than the forming space 211 of the die 21. The forming space 211 is formed in a direction parallel to the downward movement of the punch 23. Therefore, when the punch 23 inserted inside the forming space 211 continues to move downward in the same direction, it moves along the forming space 211, and the pouch film 135 is formed in the direction in which the punch 23 moves.

[0083] According to an embodiment of the present invention, the molding space 211 is recessed from the die inclined surface 212 to the inside of the die 21, and includes a first molding space 2111 recessed from a first die inclined surface 2121 to the inside of the die 21, and a second molding space 2112 recessed from a second die inclined surface 2122 to the inside of the die 21. The die 21 further includes a partition wall 215 formed between the first molding space 2111 and the second molding space 2112. When the pouch film 135 is formed, a bridge 136 corresponding to the partition wall 215 is formed in the battery case 13.

[0084] Meanwhile, 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 139 (shown in FIG. 16) on one side of the secondary battery 1. Since the folding portion 139 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. At this time, as the width of the folding portion 139 is smaller, the space between the outer wall 1333 of the cup portion 133 and the electrode assembly 10 is also reduced, so that the total volume of the secondary battery 1 may be reduced and the energy density per volume may be increased.

[0085] The width of the folding portion 139 is proportional to the thickness of the bridge 136, and since the bridge 136 is formed corresponding to the partition wall 215, the thickness of the bridge 136 is proportional to the thickness of the partition wall 215. Therefore, when forming the pouch film 135, it is preferable to minimize the thickness of the bridge 136, and therefore it is preferable to minimize the thickness of the partition wall 215 as well. However, if the partition wall 215 is formed too high while being thin, the partition wall 215 may be damaged during drawing. In particular, in the past, the die 21 had a bottom, and in this case, when the punch 23 forms the pouch film 135, there was a problem that the gas existing between the pouch film 135 and the forming space 211 could not be discharged. Therefore, in recent years, by removing the bottom from the die 21, the gas existing between the pouch film 135 and the forming space 211 can be easily discharged, but there was a problem that the height of the partition wall 215 was formed too high. 11, the partition 215 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 215 may have a substantially triangular shape, and the inner wall 214 of the molding space 211 formed in the partition 215 may have a slope. The exact slope of the inner wall 214 of the molding space 211 formed in the partition 215 may be determined experimentally depending on the thickness of the upper part of the partition 215, the material of the partition 215, the pressure of the punch 23, and the depth of the cup portion 133 to be formed.

[0086] However, without being limited thereto, the upper part of the partition wall 215 may maintain a minimized thickness, and a reinforcing part (not shown) thicker than the thickness of the partition wall 215 may be formed at the lower part of the partition wall 215. The reinforcing part may be formed below the depth of the cup part 133 formed in the battery case 13, and at a position where the partition wall 215 will not be damaged. The exact position of the reinforcing part may be determined experimentally depending on the thickness of the upper part of the partition wall 215, the material of the partition wall 215, the pressure of the punch 23, and the depth of the cup part 133 to be formed. This increases the strength of the partition wall 215, and prevents the partition wall 215 from being damaged during drawing.

[0087] The stripper 22 is disposed above the die 21, and descends when the pouch film 135 is placed on the upper surface of the die 21. Then, the stripper 22 comes into contact with the die 21, sandwiching the pouch film 135, and presses the pouch film 135 from above to fix it. Here, "sandwiching and contacting" does not mean that the two come into direct contact, but that the two come into indirect contact via the pouch film 135. Later, when the punch 23 forms the pouch film 135, the stripper 22 presses the pouch film 135 evenly, and uniformly distributes the stretching force applied to the pouch film 135.

[0088] The lower surface of the stripper 22 comes into contact with the upper surface of the pouch film 135 when fixing the pouch film 135. Therefore, the lower surface of the stripper 22 can have a shape corresponding to that of the upper surface of the die 21. That is, since the upper surface of the die 21 includes at least one die inclined surface 212 and a die horizontal surface 213 extending from at least one end of the die inclined surface 212, the lower surface of the stripper 22 correspondingly includes at least one stripper inclined surface 222 abutting against the die inclined surface 212 and having the same inclination as the die inclined surface 212, and a stripper horizontal surface 223 abutting against the die horizontal surface 213 and extending from at least one end of the stripper inclined surface 222.

[0089] The lower surface of such a stripper 22 comes into contact with the upper surface of the pouch film 135 when fixing the pouch film 135. In order to easily fix the pouch film 135 later, the lower surface of such a stripper 22 may be formed with a lattice pattern or fine irregularities.

[0090] According to an embodiment of the present invention, the die inclined surface 212 includes a first die inclined surface 2121 and a second die inclined surface 2122 that are formed symmetrically to each other. Accordingly, the stripper inclined surface 222 also includes a first stripper inclined surface 2221 and a second stripper inclined surface 2222. The first stripper inclined surface 2221 abuts against the first die inclined surface 2121 with the pouch film 135 interposed therebetween, and the second stripper inclined surface 2222 abuts against the second die inclined surface 2122 with the pouch film 135 interposed therebetween. For this reason, the first stripper inclined surface 2221 may have the same inclination as the first die inclined surface 2121, and the second stripper inclined surface 2222 may have the same inclination as the second die inclined surface 2122. The first stripper inclined surface 2221 and the second stripper inclined surface 2222 are also formed symmetrically to each other and may have a downward inclination toward the center.

[0091] The punch 23 is disposed above the forming space 211 of the die 21, and descends to insert the pouch film 135 into the forming space 211 to form it. The punch 23 descends at a constant pressure and speed. Then, while being inserted into the forming space 211 of the punch 23, the forming part 231 of the punch 23 directly contacts the upper surface of the pouch film 135 placed on the die 21 and applies pressure to stretch the pouch film 135. As a result, the cup part 133 is formed in the pouch film 135, and a pouch can be manufactured. A through part 221 is formed at the approximate center of the stripper 22. The punch 23 penetrates the stripper 22 through the through part 221 and moves up and down. When the punch 23 moves up and down, the inner wall of the through part 221 guides the punch 23, so that the through part 221 corresponds in shape and size to the punch 23. Here, the corresponding shape means that the through-hole 221 has the same or similar shape as the punch 23, and the punch 23 can easily move up and down through the through-hole 221. The corresponding size means that the size of the through-hole 221 is slightly larger than the size of the punch 23. If the size of the through-hole 221 is the same as or smaller than the size of the punch 23, the punch 23 may not be able to move up and down through the through-hole 221, or the punch 23 may not be able to move up and down easily due to friction with the inner wall of the through-hole 221. Conversely, if the size of the through-hole 221 is too large, the inner wall of the through-hole 221 may not be able to guide the punch 23, and the punch 23 may come off from its fixed position. Therefore, it is preferable that the size of the through-hole 221 has an appropriate size that allows the punch 23 to be inserted into the through-hole 221 and easily move up and down, but does not come off from its fixed position. In fact, the size of the through-hole 221 can be determined experimentally according to the size and shape of the cup portion 133 to be formed.

[0092] In addition, the punch 23 corresponds in shape and size to the molding space 211 of the die 21. Here, the corresponding shape means that the punch 23 has the same or similar shape as the molding space 211 of the die 21, and when the pouch film 135 is stretched later to form the cup portion 133, the cup portion 133 is formed in the same or similar shape as the punch 23 and the molding space 211 of the die 21. Therefore, when the punch 23 has a rectangular shape, the molding space 211 of the die 21 also has a rectangular shape, and the cup portion 133 is also formed in a rectangular shape, and when the punch 23 has a circular shape, the molding space 211 of the die 21 also has a circular shape, and the cup portion 133 can also be formed in a circular shape. And, the corresponding size means that the punch 23 is inserted into the forming space 211 of the die 21 together with the pouch film 135 to stretch the pouch film 135, and therefore the punch 23 is minutely smaller than the forming space 211 of the die 21 by the thickness of the pouch film 135.

[0093] According to an embodiment of the present invention, as described above, the molding space 211 of the die 21 includes the first molding space 2111 and the second molding space 2112, and the die 21 further includes the partition wall 215 formed between the first molding space 2111 and the second molding space 2112. Therefore, in order for the punch 23 to correspond to the shape of such a die 21, the molding part 231 of the punch 23 includes a first molding part 2311 that inserts the pouch film 135 into the first molding space 2111 and a second molding part 2312 that inserts the pouch film 135 into the second molding space 2112. And, between the first molding part 2311 and the second molding part 2312, a groove into which the partition wall 215 is inserted is formed at a position corresponding to the partition wall 215 of the die 21.

[0094] FIG. 12 is a schematic diagram showing a state in which the stripper 22 according to one embodiment of the present invention has been lowered.

[0095] When the pouch film 135 is placed on the upper surface of the die 21 (S901), the stripper 22 descends as shown in Fig. 12 (S902). Then, when the lower surface of the stripper 22 comes into contact with the upper surface of the pouch film 135, the stripper 22 and the die 21 come into contact with each other with the pouch film 135 sandwiched between them. Then, the stripper 22 presses the pouch film 135 from above to fix it in place. This causes the pouch film 135 to be pressed evenly, and the stretching force applied to the pouch film 135 when the cup portion 133 is formed later is uniformly distributed.

[0096] At this time, the stripper inclined surface 222 and the die inclined surface 212 come into contact with each other with the pouch film 135 sandwiched therebetween, and the stripper horizontal surface 223 and the die horizontal surface 213 come into contact with each other with the pouch film 135 sandwiched therebetween. Therefore, as shown in Fig. 12, the pouch film 135 in the region where the stripper inclined surface 222 and the die inclined surface 212 come into contact with each other is formed with an inclination, and the pouch film 135 in the region where the stripper horizontal surface 223 and the die horizontal surface 213 come into contact with each other is formed horizontally without an inclination.

[0097] Particularly, according to an embodiment of the present invention, the die inclined surface 212 includes a first die inclined surface 2121 and a second die inclined surface 2122 that are formed symmetrically to each other. The first die inclined surface 2121 and the second die inclined surface 2122 may have a downward inclination as they are closer to each other. Therefore, as shown in FIG 12, the pouch film 135 in the region where the stripper inclined surface 222 and the die inclined surface 212 abut against each other may have both sides symmetrical to each other and have a downward inclination as they are closer to the center.

[0098] FIG. 13 is a schematic diagram showing a state in which the punch 23 according to one embodiment of the present invention has been lowered.

[0099] When the stripper 22 fixes the pouch film 135, the punch 23 descends in a direction inclined relative to the upper surface of the die 21, particularly the die inclined surface 212, as shown in Fig. 13 (S903). Then, the punch 23 is inserted into the molding space 211 together with the pouch film 135, and stretches the pouch film 135 (S903). As a result, the pouch film 135 is molded to form the cup portion 133 (S904). Thereafter, the punch 23 and the stripper 22 rise again, and the pouch film 135 with the cup portion 133 formed thereon is taken out, thereby manufacturing the pouch-type battery case 13 according to one embodiment of the present invention.

[0100] As described above, the forming part 231 of the punch 23 directly contacts the upper surface of the pouch film 135 placed on the die 21 and applies pressure to stretch the pouch film 135. Then, when the pouch film 135 is molded to form the cup portion 133, the bottom portion 1332 of the cup portion 133 is formed into a shape corresponding to the forming part 231 of the punch 23. At this time, the forming part 231 of the punch 23 may also be formed with an inclination, and in particular, may have an inclination of the same inclination angle as the die inclined surface 212. Therefore, when the pouch film 135 is molded to manufacture the battery case 13, the bottom portion 1332 of the cup portion 133 of the battery case 13 may be formed parallel to each other by having an inclination of the same inclination angle as the pouch film 135 in the region where the stripper inclined surface 222 and the die inclined surface 212 abut against each other. However, without being limited thereto, the forming portion 231 of the punch 23 may have an inclination angle different from that of the die inclined surface 212. In such a case, the bottom 1332 of the cup portion 133 of the battery case 13 may also be formed to have an inclination angle different from that of the pouch film 135 in the region where the stripper inclined surface 222 and the die inclined surface 212 abut against each other.

[0101] According to an embodiment of the present invention, the die inclined surface 212 includes the first die inclined surface 2121 and the second die inclined surface 2122, so that the forming part 231 of the punch 23 also includes the first forming part 2311 and the second forming part 2312. The first forming part 2311 of the punch 23 is inserted into the first forming space 2111 of the die 21 to stretch the pouch film 135. Then, the cup part 133 can be formed in the first case 131. At this time, the bottom part 1332 of the cup part 133 formed in the first case 131 can be formed parallel to each other by having the same inclination angle as the pouch film 135 in the region where the first die inclined surface 2121 and the first stripper inclined surface 2221 abut against each other. Then, the second forming part 2312 of the punch 23 is inserted into the second forming space 2112 of the die 21 to stretch the pouch film 135. Then, the cup portion 133 can be formed in the second case 132. At this time, the bottom 1332 of the cup portion 133 formed in the second case 132 can be formed parallel to each other by having the same inclination angle as the pouch film 135 in the region where the second die inclined surface 2122 and the second stripper inclined surface 2222 abut against each other.

[0102] Therefore, when the pouch film 135 is molded to manufacture the battery case 13, the bottoms 1332 of the cup portions 133 formed in the first case 131 and the second case 132, respectively, are also formed symmetrically to each other and may have a downward slope toward the center.

[0103] Meanwhile, when the punch 23 descends and is inserted into the molding space 211 of the die 21, the partition 215 of the die 21 can be inserted into the groove formed between the first molding portion 2311 and the second molding portion 2312 of the punch 23. As a result, when the pouch film 135 is formed, a bridge 136 corresponding to the partition 215 of the die 21 can be formed in the battery case 13. Such a bridge 136 is formed corresponding to the partition 215 of the die 21, and the punch edge 1334 is formed corresponding to the edge of the punch 23. Then, between the inner wall 214 of the molding space 211 of the die 21 and the outer wall 232 of the punch 23, there is a clearance CL which is the horizontal distance between them. Therefore, as shown in FIG. 13, such clearance CL can be shown as the horizontal distance between the bridge 136 and the punch edge 1334 in the battery case 13, and the outer wall 1333 of the cup portion 133 is formed to have an inclination due to the clearance CL.

[0104] FIG. 14 is a partial enlarged view of the punch edge 1334 of the cup portion 133 according to one embodiment of the present invention.

[0105] 14, even if the outer wall 1333 of the cup part 133 itself is formed to have an incline, according to an embodiment of the present invention, the bottom 1332 of the cup part 133 is also formed to have an incline. Therefore, the inclination angle a of the outer wall 1333 of the cup part 133 from the bottom 1332 is further reduced to be approximately vertical with an inclination angle a between about 90° and 95°, or even between 90° and 93°.

[0106] FIG. 15 is a partial enlarged view of a folding portion 139 of the secondary battery 1 according to one embodiment of the present invention.

[0107] According to an embodiment of the present invention, the inclination angle a of the outer wall 1333 of the cup part 133 from the bottom 1332 may be formed nearly vertically. Then, the electrode assembly 10 may be positioned very close to the outer wall 1333 of the cup part 133, thereby reducing unnecessary volume of the cup part 133. Therefore, even if the internal pressure of the cup part 133 is reduced by performing a degassing process, deformation of the outer wall 1333 or the bottom 1332 of the cup part 133 may be prevented. That is, as shown in FIG. 15, the edge-high phenomenon may be prevented from occurring, and therefore the energy density per volume may not be reduced.

[0108] FIG. 16 is a schematic diagram showing a secondary battery 1 according to one embodiment of the present invention from above.

[0109] As described above, the butt ears 15 are visibly protruding outward from both ends of the folding portion 139 in the secondary battery 1. Specifically, the battery case 13 is formed by drawing the pouch film 135, and at this time, not only the cup portion 133 is stretched in a limited manner, but the peripheral sides 134 of the cup portion 133 are also finely stretched as a whole. Therefore, when the bridge 136 is folded, the finely stretched parts of the sides 134 are accumulated and visibly protrude outward from both ends of the folding portion 139. This is called the butt ears 15.

[0110] According to one embodiment of the present invention, the edge-high phenomenon can be prevented, so the size of the butt ear 15 can be reduced, and the problem of the shape of the butt ear 15 being conspicuous can also be prevented. Therefore, the secondary battery 1 can be easily assembled into a battery module, and the unnecessary volume of the secondary battery 1 can be reduced, so the energy density per volume can be increased. In addition, when the secondary battery 1 is housed in the housing of the battery module, the size of the butt ear 15 is reduced, and the gap between the housing and the folding part 139 is reduced, so the cooling efficiency of the secondary battery 1 can also be increased.

[0111] FIG. 17 is a perspective view of a battery case molding apparatus 2a according to another embodiment of the present invention, and FIG. 18 is a schematic view of the battery case molding apparatus 2a according to another embodiment of the present invention.

[0112] According to one embodiment of the present invention, two cup portions 133 may be formed adjacent to each other in one pouch film 135, and the cup portions 133 may be formed in each of the first case 131 and the second case 132. However, according to another embodiment of the present invention, only one cup portion 133 may be formed in one pouch film 135, and the cup portion 133 may be formed only in the first case 131. For this, as shown in FIG. 17, the upper surface of the die 21a may include only one die inclined surface 212a having an inclination inclined toward the descending direction of the punch 23a. The upper surface of the die 21a may further include a plurality of die horizontal surfaces 213a extending from both ends of the die inclined surface 212a and perpendicular to the descending direction of the punch 23a.

[0113] Since the upper surface of the die 21a includes only one die inclined surface 212a, the die 21a may include only one molding space 211a formed by recessing inward from the upper surface of the die 21a. Therefore, according to another embodiment of the present invention, the die 21a does not include a partition wall, and a bridge may not be formed in the battery case 13a manufactured by molding the pouch film 135.

[0114] The stripper 22a contacts the upper surface of the pouch film 135 when the lower surface thereof fixes the pouch film 135. Therefore, according to another embodiment of the present invention, the stripper 22a also includes only one stripper inclined surface 222a having the same inclination as the inclined surface of the die 21a, and may further include a plurality of stripper horizontal surfaces 223a that abut against the horizontal surface of the die 21a and extend from both ends of the stripper inclined surface 222a.

[0115] According to another embodiment of the present invention, since the die 21a includes only one forming space 211a, the punch 23a may also include only one forming portion 231a that inserts the pouch film 135 into the forming space 211a. And, since the die 21a does not include a partition wall, the punch 23a may also not be formed with a groove into which such a partition wall is inserted.

[0116] FIG. 19 is a schematic diagram showing a state in which a stripper 22a according to another embodiment of the present invention has been lowered.

[0117] When the pouch film 135 is placed on the upper surface of the die 21a (S901), the stripper 22 descends (S902) as shown in Fig. 19. Then, when the lower surface of the stripper 22 comes into contact with the upper surface of the pouch film 135, the stripper 22 and the die 21 come into contact with each other with the pouch film 135 sandwiched between them. Then, the stripper 22 presses the pouch film 135 from above to fix it in place.

[0118] According to another embodiment of the present invention, the die 21a includes only one die inclined surface 212a and the stripper 22a includes only one stripper inclined surface 222a, so that only one inclined region of the pouch film 135 can be formed. And, the die 21a includes a plurality of die horizontal surfaces 213a and the stripper 22a includes a plurality of stripper horizontal surfaces 223a, so that a plurality of horizontal regions of the pouch film 135 can be formed.

[0119] FIG. 20 is a schematic diagram showing a state in which a punch 23a according to another embodiment of the present invention has been lowered.

[0120] When the stripper 22a fixes the pouch film 135, the punch 23a descends in a direction inclined relative to the upper surface of the die 21a, particularly the die inclined surface 212a, as shown in Fig. 20 (S903). Then, the punch 23a is inserted into the molding space 211a together with the pouch film 135, and stretches the pouch film 135 (S903). As a result, the pouch film 135 is molded to form the cup portion 133a (S904). Thereafter, the punch 23a and the stripper 22a rise again, and the pouch film 135 with the cup portion 133a formed therein is taken out, thereby manufacturing the pouch-type battery case 13a according to one embodiment of the present invention.

[0121] According to another embodiment of the present invention, the forming portion 231a of the punch 23a is inserted into the forming space 211a of the die 21a and the pouch film 135 is stretched to form a cup portion 133a in the first case 131, but no cup portion is formed in the second case 132.

[0122] FIG. 21 is a partial enlarged view of a punch edge 1334a of a cup portion 133a according to another embodiment of the present invention.

[0123] 21, even if the outer wall 1333a of the cup portion 133a itself is formed with an incline, according to another embodiment of the present invention, the bottom 1332a of the cup portion 133a is also formed with an incline. Therefore, the inclination angle b of the outer wall 1333a of the cup portion 133a from the bottom 1332a is further reduced, and the outer wall 1333a can be formed close to vertical with an inclination angle b of about 90° to 95°, or even 90° to 93°.

[0124] Meanwhile, referring to Figures 1, 14 and 16, a battery case according to an embodiment of the present invention includes a cup portion 133 formed in at least one of a first case 131 or a second case 132, an outer wall 1333 formed along an edge of one side of a bottom portion 1332, and a accommodating space for an electrode assembly, and a folding portion 139 folded on one side of the cup portion 133 to integrally connect the first case 131 and the second case 132.

[0125] The outer wall 1333 includes a first outer wall formed on the folding portion 139 side of an edge of one side of the bottom portion 1332, a second outer wall formed on the opposite side of the first outer wall, a third outer wall formed to connect the first outer wall and the second outer wall, and a fourth outer wall formed on the opposite side of the third outer wall, and an inner inclination angle a between the first outer wall and the bottom portion 1332 may be formed to be 90° to 95°.

[0126] Here, when the pouch forming device includes the partition 215, the folding portion 139 is formed as a bridge corresponding to the partition 215, and the bridge may be a reference portion when folding the battery case 13 later. That is, when the manufacturing of the secondary battery 1 is completed, the bridge may form the folding portion 139 on one side of the secondary battery 1, and therefore, it can be understood that the first outer wall is formed on the bridge side of the edge of one surface of the bottom 1332.

[0127] However, when the cup portion 133a is formed in only one of the first case 131 or the second case 132, there is no separate bridge, and in this case, it can be understood that the first outer wall is formed on the folding portion side of the edge of one side of the bottom.

[0128] As a result, the inclination angle a from the bottom 1332 of the first outer wall, which is the outer wall of the cup portion 133 formed on the folding portion 139 side, can be further reduced and formed nearly vertically, and therefore the electrode assembly can be positioned very close to the outer wall of the cup portion, thereby reducing unnecessary volume of the cup portion.

[0129] Meanwhile, an inner inclination angle between the second outer wall and the bottom 1332 may be formed to be larger than an inner inclination angle a between the first outer wall and the bottom 1332 .

[0130] In addition, an inner inclination angle between the second outer wall and the bottom portion 1332 may be formed to be at least 10° larger than an inner inclination angle a between the first outer wall and the bottom portion 1332 .

[0131] Those skilled in the art will understand that the present invention can be embodied in other specific forms without changing the technical idea or essential features of the present invention. Therefore, the above-described embodiments are illustrative in all respects and should not be construed as 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]

[0132] 1: Secondary battery 2: Molding equipment 10: Electrode assembly 11: Electrode tab 12: Electrode lead 13: Battery case 14: Insulation section 15: Bad Year 21: Die 22: Stripper 23: 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: Gas vent 139: Folding section 211: Molding space 212: Die inclined surface 213: Die horizontal surface 214:Inner wall 215: Bulkhead 221: Penetration 222: Stripper inclined surface 223: Stripper horizontal surface 231: Molding section 232: Exterior wall 333 Cup section 339 Folding Section 411 Molding space 412 Top surface 414 Interior wall 422 Bottom surface 431 Molding section 432 Exterior Wall 1331: Containment Space 1332: Bottom 1333: Exterior wall 1334: Punch Edge 1351: Sealant layer 1352: Moisture barrier layer 1353: Surface protective layer 2111: 1st molding space 2112:Second molding space 2121: First die inclined surface 2122: Second die inclined surface 2151: Reinforcement 2221: First stripper inclined surface 2222: Second stripper inclined surface 2311: 1st molding section 2312:Second molding section

Claims

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: the upper surface includes at least one die ramp; Further comprising a stripper disposed above the die, lowering to pinch the pouch film and contact the die to fix the pouch film; When the punch forms the pouch film, the stripper evenly presses against the pouch film to evenly distribute the stretching force applied to the pouch film.

2. The die inclined surface is The battery case molding device according to claim 1 , wherein the punch has an inclination inclined in a descending direction.

3. The molding space is The battery case molding apparatus according to claim 1 , wherein a recess is formed from the die inclined surface toward an inside of the die.

4. The die inclined surface is a first die ramp and a second die ramp, The first die inclined surface and the second die inclined surface are The battery case molding apparatus according to any one of claims 1 to 3, which are formed symmetrically to each other.

5. The first die inclined surface and the second die inclined surface are The battery case molding device according to claim 4 , wherein the adjacent moldings have a downward inclination.

6. The molding space is a first molding space formed by recessing the first die inclined surface toward the inside of the die; The battery case molding apparatus according to claim 5 , further comprising: a second molding space recessed from the second die inclined surface toward an inner side of the die.

7. The die includes: The battery case molding device according to claim 6 , further comprising a partition wall formed between the first molding space and the second molding space.

8. 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: the upper surface includes at least one die ramp; The die inclined surface is a first die ramp and a second die ramp, The first die inclined surface and the second die inclined surface are are formed symmetrically to each other, The first die inclined surface and the second die inclined surface are The closer they are to each other, the more downwardly they slope. The molding space is a first molding space formed by recessing the first die inclined surface toward the inside of the die; a second molding space recessed from the second die inclined surface to an inner side of the die, The die includes: The molded article further includes a partition wall formed between the first molding space and the second molding space, The partition wall is formed to have a thickness that increases toward the bottom.

4. A battery case molding apparatus, comprising: a molding space formed by the partition wall, the molding space having an inner wall that is inclined;

9. The punch is The battery case molding device according to claim 7 or 8, wherein a groove into which the partition is inserted is formed at a position corresponding to the partition.

10. The punch is A first molding section that inserts the pouch film into the first molding space; The battery case molding device according to any one of claims 6 to 9, further comprising: a second molding section that inserts the pouch film into the second molding space.

11. 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: the upper surface includes at least one die ramp; The die includes: the upper surface further includes a horizontal die surface extending from at least one end of the inclined die surface and perpendicular to a direction in which the punch descends.

12. The punch is The battery case molding apparatus according to any one of claims 1 to 11, wherein a molding portion that directly contacts the pouch film has the same inclination as the die inclined surface.

13. 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: the upper surface includes at least one die ramp; Further comprising a stripper disposed above the die, lowering to pinch the pouch film and contact the die to fix the pouch film; The stripper includes: a lower surface of the battery case molding apparatus including at least one stripper sloped surface abutting the die sloped surface and having the same slope as the die sloped surface.

14. A battery case molding method for molding a battery case by the battery case molding apparatus according to any one of claims 1 to 13, comprising the steps of: placing the pouch film on the top surface of the die; a step in which the punch disposed above the forming space formed by recessing inward from the upper surface of the die is lowered in a direction inclined with respect to at least a part of the upper surface; and a step of the punch inserting the pouch film into the molding space to form a cup portion in the pouch film.

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