Pouch-type battery case and pouch-type secondary battery

Abstract

To solve the above problems, a pouch-type battery case according to an embodiment of the present invention includes a first case and a second case each formed with a cup portion for accommodating an electrode assembly formed by stacking electrodes and a separator, and a bridge formed between the two cup portions, the bridge having a thickness of 2 mm or less.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0104223 filed on August 19, 2020, and Korean Patent Application No. 10-2021-0074469 filed on June 8, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a pouch-type battery case and a pouch-type secondary battery, and more particularly to a pouch-type battery case and a pouch-type secondary battery that can increase the energy density per volume when manufacturing a secondary battery, have a beautiful appearance, and improve marketability. [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 generated power and 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 housed in a battery case, an electrolyte is injected, and the battery case is sealed.

[0005] Secondary batteries are divided 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] Among such press processes, drawing is performed by inserting a pouch film into a forming device such as a press device and applying pressure to the pouch film with a punch to stretch the pouch film. The pouch film is formed of multiple layers, of which the moisture barrier layer located inside is made of metal. However, in the past, the metal of such moisture barrier layer was an aluminum alloy with a large crystal grain size, and the moisture barrier layer was thin, which caused a problem of reduced formability. Therefore, when forming a cup part in the pouch film, there was a limit to improving the thickness of the bridge and the width of the folding part while forming the depth of the cup part deep. In addition, there was a limit to reducing the size of the butt ear, and the energy density relative to the volume of the secondary battery was also reduced. Furthermore, there was a limit to manufacturing a sharp shape overall, which caused the secondary battery to have a poor appearance and reduced marketability. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Registration No. 6022956 Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide a pouch-type battery case and a pouch-type secondary battery that can increase the energy density per volume when manufacturing a secondary battery, have a beautiful appearance, and improve marketability.

[0010] The object of the present invention is not limited to the above-mentioned objects, and other objects not mentioned can 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 pouch-type battery case according to an embodiment of the present invention includes a first case and a second case each having a cup portion for accommodating an electrode assembly formed by stacking electrodes and a separator, and a bridge formed between the two cup portions, the bridge having a thickness of 2 mm or less.

[0012] The bridge may also have a thickness of 1.4 mm or less.

[0013] Also, the thickness of the bridge may be 1 / 200 to 1 / 30 of the width of the electrode assembly.

[0014] Also, the bridge may be rounded with a curvature radius of 1 mm or less.

[0015] Also, the bridge may be rounded with a curvature radius of 0.7 mm or less.

[0016] Also, the thickness of the bridge may be the distance between two bridge perpendicular lines that pass through the boundary points of the bridge and the outer wall on the bridge side and are perpendicular to the bottom.

[0017] The cup portion may include a plurality of punch edges respectively connecting a bottom portion and a plurality of outer walls surrounding a periphery, and at least one of the punch edges may be rounded.

[0018] The radius of curvature of the punch edge may be 1 / 20 to 1 / 6 of the depth of the cup portion.

[0019] In addition, among the plurality of punch edges, a bridge-side punch edge that connects an outer wall of the bridge side toward the bridge side and the bottom portion may be formed by rounding.

[0020] Also, the cup portion may further include a thickness edge connecting two adjacent outer walls to each other, and the thickness edge may be connected to two adjacent punch edges to form a corner.

[0021] At least one of the corners may be rounded, and a radius of curvature of the corners may be equal to or greater than a radius of curvature of at least one of the punch edge and the thickness edge.

[0022] Also, the cup portion may further include a plurality of die edges connecting the outer wall to a side or a degassing portion.

[0023] The radius of curvature of the die edge may be 1 / 20 to 1 / 6 of the depth of the cup portion.

[0024] Also, at least one of the die edges may be rounded with a curvature radius of 1 mm or less.

[0025] Also, at least one of the die edges may be rounded with a curvature radius of 0.7 mm or less.

[0026] In addition, the vertical distance between a die edge vertical line that passes through the boundary point between the die edge and the outer wall on the die edge side and is perpendicular to the bottom, and an edge vertical line that passes through the boundary point between the punch edge on the die edge side and the outer wall on the die edge side and is perpendicular to the bottom, can be 0.5 mm or less.

[0027] The cup portion may have a depth of 6.5 mm or more.

[0028] The outer wall of the cup portion may have an inclination angle of 90° to 95° from the bottom of the cup portion.

[0029] Also, the pouch film may be produced by molding, and the pouch film may include a sealant layer made of a first polymer and formed as an innermost layer, a surface protective layer made of 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 formed 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.

[0030] The aluminum alloy thin film may be alloy number AA8021.

[0031] The aluminum alloy thin film may contain 1.3 wt % to 1.7 wt % iron and 0.2 wt % or less silicon.

[0032] The moisture barrier layer may have a thickness of 55 to 65 μm, and the sealant layer may have a thickness of 75 to 85 μm.

[0033] The film may further include an orientation-assist layer made of a third polymer and laminated between the surface protection layer and the moisture barrier layer.

[0034] The stretching auxiliary layer may have a thickness of 20 to 50 μm.

[0035] In order to solve the above problems, a pouch-type battery case according to an embodiment of the present invention includes a first case and a second case each formed with a cup portion for accommodating an electrode assembly formed by stacking electrodes and a separator, and a bridge formed between the two cup portions, and the bridge may have a thickness of 1 / 30 or less of a width of the electrode assembly.

[0036] 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 pouch-type battery case formed with a cup portion that accommodates the electrode assembly therein, the pouch-type battery case including a first case and a second case each having the cup portion formed therein, and a folding portion that connects the first case and the second case together, and the folding portion may have a width of 1 mm to 3.2 mm.

[0037] The area of ​​the electrode assembly is 15,000 mm 2 It can be more than that.

[0038] The folding portion may have a width of 1 mm to 1.6 mm.

[0039] Also, the folding portion may be formed to include a groove recessed inwardly.

[0040] The battery case may further include a pair of protrusions protruding outwardly with the groove between them, and the distance between the innermost part of the groove and the outermost part of the protrusions may be 0.8 mm or less.

[0041] In addition, the battery case may be manufactured by molding a pouch film, and the pouch film may include a sealant layer made of a first polymer and formed as an innermost layer, a surface protective layer made of 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 formed 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.

[0042] The aluminum alloy thin film may be alloy number AA8021.

[0043] The moisture barrier layer may have a thickness of 55 to 65 μm, and the sealant layer may have a thickness of 75 to 85 μm.

[0044] The present invention also provides a pouch-type secondary battery including the pouch-type battery case.

[0045] Further details of the invention are included in the detailed description and the drawings. Effect of the Invention

[0046] According to the embodiment of the present invention, at least the following advantages are obtained.

[0047] By improving the formability of the pouch film, the thickness of the bridge can be made thinner, so the width of the folding portion can be reduced, and the energy density per volume of the secondary battery can be increased.

[0048] Also, the size of the battery cell can be reduced, and the energy density per volume of the secondary battery can be increased.

[0049] Furthermore, the pouch-type battery case and pouch-type secondary battery can be manufactured with an overall sharp shape, the appearance of the secondary battery is beautiful, and the merchantability can be improved.

[0050] 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]

[0051] [Figure 1] FIG. 1 is an assembly diagram of a secondary battery 1 according to one embodiment of the present invention. [Diagram 2] FIG. 1 is a cross-sectional view of a pouch film 135 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 change in tensile strength, elongation, and grain size depending on the iron content of an aluminum alloy having an alloy number AA8079 and an aluminum alloy having an alloy number AA8021. [Diagram 5] 1 is an SEM photograph showing enlarged crystal grains of an aluminum alloy having alloy number AA8079 and an aluminum alloy having alloy number AA8021. [Figure 6] FIG. 1 is a schematic diagram of a molding apparatus 2 according to one embodiment of the present invention. [Figure 7] FIG. 13 is an enlarged schematic view of a conventional cup portion 333 and a bridge 336. [Figure 8] FIG. 1 is a schematic diagram of an enlarged view of cup portion 133 and bridge 136 according to one embodiment of the present invention. [Figure 9] FIG. 2 is a schematic diagram showing an enlarged view of the cup portion 133 and the degassing portion 137 according to an embodiment of the present invention. [Figure 10] 1 is a schematic top view illustrating an electrode assembly 10 housed in a cup portion 133 according to an embodiment of the present invention. [Figure 11] FIG. 3 is a schematic diagram showing a conventional corner 364. [Figure 12] FIG. 1 is a schematic diagram illustrating a corner 164 according to one embodiment of the present invention. [Figure 13] 2 is a schematic diagram showing a state in which a battery case 13 according to an embodiment of the present invention is folded. FIG. [Figure 14] FIG. 2 is a schematic diagram showing a state in which a battery case 13 according to an embodiment of the present invention is folded. [Figure 15] FIG. 13 is an enlarged view of a groove 1391 formed in a battery case 13 according to one embodiment of the present invention. [Figure 16] FIG. 16 is a schematic diagram showing an enlarged view of a cup portion 133 and a die edge 1621 according to another embodiment of the present invention. [Figure 17] 11 is a schematic diagram showing a state in which a battery case 13a according to another embodiment of the present invention is folded. FIG. [Figure 18] FIG. 11 is a schematic diagram showing a battery case 13a according to another embodiment of the present invention in a folded state. [Figure 19] FIG. 13 is an enlarged view of a groove 1391a formed in a battery case 13 according to another embodiment of the present invention. [Figure 20] 13 is a schematic diagram showing a conventional battery case 33 from above before a degassing portion 337 is cut off. FIG. [Figure 21] 1 is a schematic diagram showing a state of a battery case 13 according to an embodiment of the present invention before a degassing portion 137 is cut from above. FIG. [Figure 22] FIG. 4 is a block diagram of an inspection device 4 according to an embodiment of the present invention. [Diagram 23] 1 is a schematic diagram showing a state in which the degassing portion 137 of the battery case 13 according to one embodiment of the present invention has been cut off and the manufacture of the secondary battery 1 has been completed. FIG. [Figure 24] FIG. 13 is a schematic side view showing a conventional side 334 folded. [Diagram 25] FIG. 13 is a schematic diagram showing a conventional side 334 folded from above. [Figure 26] FIG. 13 is a schematic side view of a side 134 folded according to an embodiment of the present invention. [Figure 27] FIG. 1 is a schematic diagram of a battery module 5 according to one embodiment of the present invention. [Figure 28]FIG. 1 is an enlarged front view showing a state in which a conventional secondary battery 3 is housed in a housing 51 of a battery module 5. [Figure 29] FIG. 1 is an enlarged side view showing a state in which a conventional secondary battery 3 is housed in a housing 51 of a battery module 5. [Diagram 30] 1 is an enlarged front view showing a secondary battery 1 according to an embodiment of the present invention housed in a housing 51 of a battery module 5. FIG. [Diagram 31] 1 is an enlarged side view showing a secondary battery 1 according to an embodiment of the present invention housed in a housing 51 of a battery module 5. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] The advantages and features of the present invention, as well as the methods for achieving them, will become clear from the detailed description of the embodiments below 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. Furthermore, the present embodiments are provided to fully disclose the present invention and fully inform those skilled in the art of the present invention of the scope of the invention, and the present invention is defined only by the claims. The same reference symbols refer to the same elements throughout the specification.

[0053] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in the sense that a person having ordinary knowledge in the technical field to which the present invention belongs can commonly understand. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless they are clearly and specifically defined.

[0054] The terms used in the present specification are for the purpose of describing the embodiments and are not intended to limit the present invention. In the present 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 elements in addition to the elements mentioned.

[0055] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0056] FIG. 1 is an assembly diagram of a secondary battery 1 according to one embodiment of the present invention.

[0057] 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.

[0058] For this purpose, the pouch film 135 according to an 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 is formed 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 formed as 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.

[0059] The electrode assembly 10 is formed by alternately stacking electrodes 101 (shown in FIG. 8) and separators 102 (shown in FIG. 8). First, a slurry containing a mixture 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 101 such as a positive electrode and a negative electrode. Then, separators 102 are stacked between the electrodes 101 to form the electrode assembly 10. The electrode assembly 10 is inserted into a battery case 13, an electrolyte is injected, and the case is sealed.

[0060] The electrode assembly 10 has an area of ​​15,000 mm, calculated by multiplying the total length and the total width. 2 ~100000mm 2 In particular, the overall width of the electrode assembly 10 may be 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.

[0061] Specifically, the electrode assembly 10 includes two types of electrodes 101, a positive electrode and a negative electrode, and a separator 102 interposed between the electrodes 101 to insulate the electrodes 101 from each other. Such an electrode assembly 10 may be of a stack type, a jelly roll type, a stack and folding type, etc. The two types of electrodes 101, i.e., the positive electrode and the negative electrode, each have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper. The active material slurry may be formed by stirring a granular active material, a conductive material, etc., in a state in which a solvent is added. The solvent is removed in a subsequent process.

[0062] 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 is composed of a portion coated with an electrode active material and an end portion not coated with the electrode active material, i.e., a plain portion. 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.

[0063] 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. In addition, a portion of the electrode lead 12 is surrounded by an insulating part 14. The insulating part 14 is located only on 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. In addition, 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 through which electricity does not easily pass. Generally, the insulating part 14 is often made of insulating tape which is easy to attach to the electrode lead 12 and has a relatively thin thickness, but is not limited thereto and various materials can be used as long as they can insulate the electrode lead 12.

[0064] 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.

[0065] 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). In addition, 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.

[0066] The battery case 13 is a pouch manufactured by forming a pouch film 135 having 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 and formed using a punch 22 (shown in FIG. 6) 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.

[0067] 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 manufactured in various ways, such as being separated from each other and separately manufactured.

[0068] 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. Thus, as shown in Fig. 1, the cup portions 133 are formed in the first case 131 and the second case 132, respectively. In this case, the cup portions 133 formed in the first case 131 and the second case 132 may have the same depth D, but is not limited thereto, and may have different depths D.

[0069] 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.

[0070] 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. As a result, 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 during the subsequent sealing process can be reduced. Therefore, the process speed can be improved and the number of sealing processes can be reduced.

[0071] Meanwhile, the battery case 13 may include a cup part 133 having an accommodation space 1331 for accommodating the electrode assembly 10, and a degassing part 137 formed on a side of the cup part 133 and discharging gas generated within the cup part 133 through a degassing hole H. When the electrode assembly 10 is accommodated in the cup part 133 of the battery case 13 and an activation process is performed after injecting an electrolyte, gas is generated within the battery case 13, and a degassing process is performed to discharge the gas to the outside. A detailed description of the degassing part 137 will be given later.

[0072] 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 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 electrode 101 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. By this method, the pouch-type secondary battery 1 may be manufactured.

[0073] FIG. 2 is a cross-sectional view of a pouch film 135 according to one embodiment of the present invention.

[0074] 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 and forming 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.

[0075] 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 means a layer located last 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 22 or the like, whereby 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 heat compression bonding, so that the sealant layers 1351 are bonded to each other, thereby sealing 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) is mainly used for manufacturing the sealant layer 1351 because of its excellent mechanical properties such as tensile strength, rigidity, surface hardness, abrasion resistance, and heat resistance, and its excellent chemical properties such as corrosion resistance. In addition, it may be made of cated polypropylene, acid modified polypropylene, or polypropylene-butylene-ethylene terpolymer.Here, the acid-treated 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.

[0076] According to an embodiment of the present invention, the thickness of the sealant layer 1351 may be 60 to 100 μm, and in particular, 75 to 85 μm. If the thickness of the sealant layer 1351 is thinner than 60 μm, there may be a problem of reduced seal durability, such as internal destruction during sealing. Also, if the thickness of the sealant layer 1351 is thicker than 100 μm, the overall thickness of the pouch may be excessively thick, which may result in reduced moldability or reduced energy density relative to the volume of the secondary battery 1. If the thickness of the sealant layer 1351 is small, the dielectric breakdown voltage of the pouch film 135 may be reduced, resulting in reduced insulation, and if a battery is manufactured using a pouch film 135 with reduced insulation, the defective rate may be high.

[0077] 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 exterior of 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.

[0078] More specifically, the aluminum alloy thin film according to the 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 cup forming.

[0079] 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).

[0080] Conventionally, the moisture barrier layer has a thickness of about 30 to 50 μm, particularly 40 μm, which reduces formability. Therefore, even if the pouch film is drawn, as the depth D' of the cup portion 333 (shown in FIG. 7) increases, there is a limit to how far the outer wall 338 (shown in FIG. 7) of the cup portion 333 can be formed nearly vertically, and there is also a limit to how far the curvature radius of the edge 36 (shown in FIG. 7) of the cup portion 333 can be reduced. In addition, there is a problem that the puncture strength is weak, and when the battery case receives an impact from the outside, the internal electrode assembly is easily damaged.

[0081] If the thickness of moisture barrier layer 1352 is increased to more than approximately 80 μm in order to solve this problem, not only will the manufacturing cost increase, but the overall thickness of the pouch will become excessively thick, resulting in a problem of a decrease in the energy density relative to the volume of secondary battery 1. If the thickness of sealant layer 1351 is reduced to less than 60 μm in order to reduce the overall thickness of the pouch, as described above, there will be a problem of a decrease in seal durability.

[0082] According to an embodiment of the present invention, this can be improved and the thickness of the moisture barrier layer 1352 can be 50 μm to 80 μm, and particularly 55 μm to 65 μm. Therefore, the formability of the moisture barrier layer 1352 is improved, and when the pouch film 135 is drawn, the depth D of the cup part 133 can be formed deep, the outer wall 138 of the cup part 133 can be made nearly vertical, and the curvature radius R2 of the edge 16 (shown in FIG. 8) of the cup part 133 can be reduced. As a result, the volume of the accommodation space 1331 increases, so the volume of the electrode assembly 10 accommodated therein can also be increased, and the energy efficiency relative to the volume of the secondary battery 1 can also be increased. In addition, the manufacturing cost does not increase significantly, the thickness of the sealant layer 1351 does not decrease, the thickness of the entire pouch does not increase significantly, and the seal durability does not decrease.

[0083] In addition, since the puncture strength of the pouch film 135 is improved, the internal electrode assembly 10 can be more effectively protected even if it is subjected to a large external pressure or is pierced by a sharp object and broken. Here, excellent puncture strength means that the strength when a hole is punched in the pouch film 135 is high.

[0084] However, if the thickness of the aluminum alloy thin film is simply increased, the forming depth can be increased, but pinholes and cracks may occur in the aluminum alloy thin film after forming, resulting in problems with seal durability.

[0085] Therefore, as a result of extensive research, the inventors have found that when an aluminum alloy thin film having a specific crystal grain size is used as the material for the gas barrier layer, and the thicknesses of the gas barrier layer and the sealant layer are controlled within specific ranges, it is possible to form a deep cup portion while maintaining excellent seal durability, and have thus completed the present invention.

[0086] Specifically, the gas 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 becomes 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.

[0087] 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 cross-sectional SEM image 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.

[0088] The surface protection 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 last when facing the opposite direction to the direction in which the electrode assembly 10 is located, based on the moisture barrier layer 1352. The second polymer for forming the surface protection layer 1353 may be one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, 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 wear resistance and heat resistance. Also, the surface protective layer 1353 may have a single film structure made of any one material, or may have a composite film structure in which two or more materials are formed into layers.

[0089] According to one embodiment of the present invention, the thickness of the surface protective layer 1353 may be 5 μm to 25 μm, and in particular, 7 μm to 12 μm. If the thickness of the surface protective layer 1353 is thinner than 5 μm, there may be a problem of reduced external insulation. Conversely, if the thickness of the surface protective layer 1353 is thicker than 25 μm, the overall thickness of the pouch becomes thick, and the energy density relative to the volume of the secondary battery 1 may instead decrease.

[0090] 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 may differ from each other. Therefore, if the surface protection layer 1353 and the moisture barrier layer 1352 are directly bonded to each other, the surface protection layer 1353 and the moisture barrier layer 1352 may peel off during drawing. Therefore, the moisture barrier layer 1352 may not be stretched uniformly, which may cause a problem of reduced formability.

[0091] 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. In addition, the stretching auxiliary layer 1354 can have a single film structure made of any one material, or a composite film structure formed by layers of two or more materials.

[0092] Conventionally, the moisture barrier layer has a thickness of about 40 μm, and accordingly, the stretching auxiliary layer has a thickness of about 15 μm, which is considerably thin. 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 as well, the stretching auxiliary layer 1354 may have a thickness of 20 μm to 50 μm, particularly preferably 25 to 38 μm. If the stretching auxiliary layer 1354 is thinner than 20 μm, it cannot respond to the improved formability of the moisture barrier layer 1352, and may be damaged during stretching. Conversely, if it is thicker than 50 μm, the overall thickness of the pouch becomes thick, which may increase the volume of the secondary battery 1 and reduce the energy density. 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 may be increased more than in the past. However, if the thickness of the stretching assist layer 1354 becomes excessively thick, the overall thickness of the pouch becomes 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.

[0093] 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.

[0094] As described above, the aluminum alloy thin film constituting 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.

[0095] The content of iron (Fe) in 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 content of iron (Fe) in the aluminum alloy thin film is less than 1.2wt%, the strength of the aluminum alloy thin film may decrease, causing cracks and pinholes during forming, and if it exceeds 1.7wt%, the flexibility of the aluminum alloy thin film may decrease, limiting the improvement of formability.

[0096] 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.

[0097] Specifically, the aluminum alloy thin film according to the present invention may be an aluminum alloy having alloy number AA8021.

[0098] On the other hand, conventional battery pouches mainly use aluminum alloy thin film with alloy number AA8079. When the aluminum alloy contains a large amount of iron, the mechanical strength is improved, and when the iron content is small, the flexibility is improved.

[0099] 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 this, the flexibility can be improved, but the strength can be reduced and there can be a limit to the formability.

[0100] Meanwhile, 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.

[0101] Meanwhile, the relationship between tensile strength and elongation when a tensile force is applied to a material 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 resistance of a material to destruction, and the higher the toughness, the more the material can be stretched before it breaks.

[0102] Therefore, when the moisture barrier layer 1352 is manufactured using the aluminum alloy of alloy number AA8021, the tensile strength and elongation are improved, so that the toughness is increased and the formability is improved.

[0103] FIG. 4 is a graph showing the change in tensile strength (Rm), elongation, and grain size depending on the iron content of aluminum alloys having alloy numbers AA8079 and AA8021, and FIG. 5 is a SEM photograph showing enlarged grains of aluminum alloys having alloy numbers AA8079 and AA8021.

[0104] As shown in Figure 4, the tensile strength, elongation, and grain size change depending on the iron content of the aluminum alloy. Specifically, the tensile strength and elongation are proportional to the iron content, so as the iron content increases, the tensile strength and elongation also increase. Meanwhile, the grain size is inversely proportional to the iron content, so as the iron content increases, the grain size decreases.

[0105] Alloy No. AA8079 has a relatively large crystal grain size of 13 μm to 21 μm, and therefore, when stretched, internal stress is not sufficiently dispersed, resulting in an increase in pinholes, which causes a problem of reduced formability of the battery case 13.

[0106] Alloy No. AA8021 has a relatively small crystal grain size of 10 μm to 13 μm, and therefore, the internal stress is more dispersed during stretching, resulting in fewer pinholes and improved formability of the battery case 13.

[0107] The pouch-type battery case 13 manufactured by molding the pouch film 135 having such a moisture barrier layer 1352 has improved moldability, the depth D of the cup part 133 can be formed deeper, the outer wall 138 of the cup part 133 becomes nearly vertical, the radius of curvature of the edge 16 of the cup part 133 can be reduced, and a larger and thicker electrode assembly 10 can be accommodated. Therefore, the secondary battery 1 manufactured in such a battery case 13 can have increased energy efficiency per volume.

[0108] 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, the reduction in the battery accommodating space and the deterioration of the seal durability due to the increase in the pouch thickness can be minimized, and the molding depth can be increased.

[0109] The pouch film 135 according to the present invention is excellent in tensile strength and elongation by including an aluminum alloy thin film having a specific thickness and crystal grain size. Specifically, the pouch film 135 according to the present invention has 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%, and even more preferably 120% to 130%. Thus, the pouch film laminate according to the present invention has high tensile strength and elongation, which increases toughness and reduces the occurrence of cracks even when the molding depth is large during cup molding.

[0110] In addition, the pouch film laminate according to the present invention has excellent puncture strength by including an aluminum alloy thin film having a specific thickness and crystal grain size. Specifically, the pouch film laminate according to the present invention may have a puncture strength of 30 N or more.

[0111] FIG. 6 is a schematic diagram of a molding apparatus 2 according to one embodiment of the present invention.

[0112] 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 a punch 22 that is disposed above the die 21 and descends to form the pouch film 135. The die 21 also includes a forming section 211 formed by being recessed inward from the upper surface, and the punch 22 forms a cup section 133 by inserting the pouch film 135 into the forming section 211 and drawing the pouch film 135.

[0113] According to an embodiment of the present invention, when the pouch film 135 is formed using the forming device 2, as shown in Fig. 6, two forming parts 211 are formed adjacent to each other in the die 21, and a partition wall 212 may be formed between the two forming parts 211. When the punch 22 is inserted into both of the two forming parts 211 and draws and forms the pouch film 135, two cup parts 133 are formed in the first case 131 and the second case 132, one each, corresponding to the two forming parts 211, and a bridge 136 may also be formed between the two cup parts 133 corresponding to the partition wall 212.

[0114] The bridge 136 may be a reference portion when folding the battery case 13 in the future. When the secondary battery 1 is manufactured, the bridge 136 may form a folding portion 139 (shown in FIG. 14) 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 the subsequent 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 139 is smaller, the space 17 (shown in FIG. 8) between the outer wall 138 (shown in FIG. 8) of the cup portion 133 and the electrode assembly 10 is also reduced, so that the overall volume of the secondary battery 1 may be reduced and the energy density per volume may be increased.

[0115] The width of the folding portion 139 is proportional to the thickness t (shown in FIG. 8) of the bridge 136, and since the bridge 136 is formed corresponding to the partition wall 212, the thickness t of the bridge 136 is proportional to the thickness of the partition wall 212. Therefore, when forming the pouch film 135, it is preferable to minimize the thickness t of the bridge 136, and therefore it is preferable to minimize the thickness of the partition wall 212 as well. However, if the partition wall 212 is formed too high while being thin, the partition wall 212 may be damaged during the drawing process. In particular, in the conventional die, a bottom portion is present, and in such a case, when the punch 22 forms the pouch film 135, there is a problem that the gas existing in the space between the pouch film 135 and the forming portion 211 is not discharged. Therefore, recently, by removing the bottom portion from such a die, the gas existing in the space between the pouch film 135 and the forming portion 211 can be easily discharged, but there is a problem that the height of the partition wall 212 is formed too high. 6, a reinforcing portion 2121 having a thickness greater than that of the partition wall 212 may be formed below 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 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.

[0116] FIG. 7 is an enlarged schematic view of a conventional cup portion 333 and a bridge 336.

[0117] As described above, conventionally, when manufacturing a moisture barrier layer, aluminum alloys of alloy number AA30XX series have been often used. Also, the moisture barrier layer has a thickness of about 30 to 50 μm, especially 40 μm, and the stretching auxiliary layer has a considerably thin thickness of about 15 μm. Therefore, the pouch film does not have excellent formability, and even if a battery case and a secondary battery are manufactured, the depth D' of the cup part 333 is not deep, and there is a limit to manufacturing a sharp shape overall.

[0118] Specifically, conventionally, there is a limit to how much the radius of curvature of the edge 36 of the cup portion 333 can be reduced.

[0119] The edge 36 of the cup portion 333 includes a punch edge 361 formed to correspond to the edge 221 of the punch 22 (shown in FIG. 6) and a die edge 362 (shown in FIG. 11) formed to correspond to the edge 213 of the die 21 (shown in FIG. 6).

[0120] The punch edge 361 connects the plurality of outer walls 338 surrounding the periphery of the cup portion 333 to the bottom portion 3332. However, if the edge 221 of the punch 22 is not rounded, the edge 221 of the punch 22 becomes sharp, and therefore, when the pouch film 135 is formed, stress is concentrated on the punch edge 361 of the cup portion 333, and cracks are likely to occur. In addition, the die edge 362 connects the plurality of outer walls 338 to the side 134 or the degassing portion 137. However, if the edge 213 of the die 21 is not rounded, the edge of the die 21 becomes sharp, and therefore, when the pouch film 135 is formed, stress is concentrated on the die edge 362 of the cup portion 333, and cracks are likely to occur. Here, being rounded means forming a curved surface to have a curvature, and such a curved surface may have only a predetermined curvature, but is not limited thereto, and may have an inconstant curvature. In this specification, when the punch edge 161, the die edge 162, the bridge 136, etc. are rounded and formed with a specific curvature, this means not only that they have the specific curvature as a whole, but also that they have the specific curvature only in at least a portion.

[0121] In order to solve the above problem, as shown in Fig. 7, the edge 221 of the punch 22 and the edge 213 of the die 21 are rounded to form the punch edge 361 and the die edge 362 of the cup part 333. This makes it possible to disperse the stress concentrated on the punch edge 361 and the die edge 362 of the cup part 333 to some extent.

[0122] However, even if the punch edge 361 and the die edge 362 of the cup portion 333 are formed by rounding, the depth D' of the cup portion 333 is limited to be 2 to 5 times, and particularly 2 to 3.25 times, the ratio of the radii of curvature of the edges 361, 362.

[0123] Therefore, in order to form the depth D' of the cup portion 333 to a certain extent, the radius of curvature R2' of the punch edge 361 and the radius of curvature of the die edge 362 must be made sufficiently large. If the depth D' of the cup portion 333 is too deep compared to the radii of curvature of the punch edge 361 and the die edge 362, cracks will occur in the punch edge 361 and the die edge 362.

[0124] Therefore, in the past, there was a problem in that it was not possible to form the depth D' of the cup portion 333 sufficiently deep (e.g., 6.5 mm or more) while forming the radius of curvature R2' of the punch edge 361 of the cup portion 333 and the radius of curvature of the die edge 362 to a predetermined value (e.g., 2 mm) or less.

[0125] In addition, when two cup portions 133 are formed, the partition wall 212 must be present in the die 21 in order to form the bridge 136. However, conventionally, the formability of a pouch film is not excellent, and there is a limit to how thin the bridge 336 can be formed. That is, if the partition wall 212 is also formed to a predetermined thickness or less in order to form the bridge 336 to a predetermined thickness or less, the partition wall 212 is formed sharply, which causes a problem of cracks occurring in the bridge 336.

[0126] In order to solve this problem, as shown in Fig. 7, the partition 212 is rounded to form the bridge 336. This makes it possible to disperse stress concentrated on the bridge 336 to some extent. In particular, when the radius of curvature R1' of the bridge 336 is constant, the radius of curvature R1' corresponds to half the thickness t' of the bridge 336. For example, when the radius of curvature R1' of the bridge 336 is formed to be approximately 1 mm, the thickness t' of the bridge 336 is formed to be approximately 2 mm.

[0127] However, even if the bridge 336 is rounded, if the radius of curvature R1' of the bridge 336 is small, there is a problem that cracks occur in the bridge 336 when the depth D' of the cup portion 333 is formed to a certain depth. Therefore, in the past, there was a problem that it was not possible to form the thickness t' of the bridge 336 to a predetermined value (e.g., 2 mm) or less while forming the cup portion 333 to a predetermined depth D' (e.g., 6.5 mm) or more.

[0128] Furthermore, the size of the clearance CL' was also quite large, and there was a limit to forming the outer wall 338 of the cup part 333 nearly vertically. The clearance CL refers to the vertical distance between the inner wall of the forming part 211 of the die 21 and the outer wall of the punch 22. In fact, there is a minute difference in size between the forming part 211 of the die 21 and the punch 22 by the clearance CL. If the clearance CL is excessively small, the distance between the inner wall of the forming part 211 and the outer wall of the punch 22 becomes excessively small. As a result, the pouch film 135 cannot be inserted into the forming part 211 or friction occurs so much that the pouch film 135 may be damaged. On the other hand, if the clearance CL is excessively large, the inclination angle of the outer wall 338 of the cup part 333 becomes large, and there is a problem that the space 37 between the outer wall 338 of the cup part 333 and the electrode assembly 10 increases. Therefore, when forming the pouch film 135, it is necessary to set the clearance CL to an appropriate size.

[0129] The bridge 336 is formed corresponding to the partition wall 212 of the die 21, and the punch edge 361 is formed corresponding to the edge 221 of the punch 22. Therefore, the clearance CL′ which is the vertical distance between the inner wall of the molding portion 211 of the die 21 and the outer wall of the punch 22 can be expressed as the vertical distance between the bridge 336 and the punch edge 361 in the battery case 33.

[0130] Specifically, as shown in FIG. 7, the bridge vertical line V1' and the edge vertical line V2' are illustrated as imaginary lines. The bridge vertical line V1' is a virtual vertical line that passes through a boundary point P1' between the bridge 336 and the outer wall 338 on the bridge 336 side, and is perpendicular to the bottom 3332. The edge vertical line V2' is a virtual vertical line that passes through a boundary point P2' between the punch edge 361 on the bridge 336 side and the outer wall 338 on the bridge 336 side, and is perpendicular to the bottom 3332. Such a bridge vertical line V1' corresponds to the inner wall of the molding portion 211 of the die 21, particularly the inner wall of the partition wall 212, and the edge vertical line V2' corresponds to the outer wall of the punch 22. Therefore, the vertical distance between the bridge vertical line V1' and the edge vertical line V2' is the clearance CL' indicated by the battery case 33.

[0131] However, conventionally, when the clearance CL is reduced to 0.5 mm or less, there is a possibility that a problem occurs in that the pouch film 135 is prone to cracking when the depth D' of the cup portion 333 is formed to a certain degree.

[0132] As described above, conventionally, there is a limit to how much the clearance CL' can be made smaller and the depth D' of the cup portion 333 can be made deeper, so when the cup portion 333 is molded to a predetermined depth D' (e.g., 6.5 mm) or more, the outer wall 338 of the cup portion 333 is formed with an inclination angle of more than 95° from the bottom portion 3332. In other words, there is a limit to how much the outer wall 338 of the cup portion 333 can be molded nearly vertically with an inclination angle of 95° or less.

[0133] Meanwhile, since there is a limit to improving the radius of curvature R2' of the edge of the cup portion 333, there is a problem that the volume of the electrode assembly 10 housed in the cup portion 333 is reduced. Specifically, as shown in Fig. 7, in the conventional technology, since the radius of curvature R2' of the punch edge 361 of the cup portion 333 is large, when the electrode assembly 10 is positioned excessively close to the outer wall 338 of the cup portion 333, the electrode 101 of the electrode assembly 10 is damaged by the punch edge 361 of the cup portion 333. That is, one end of the electrode 101 including a metal is positioned on the punch edge 361 of the cup portion 333, and one end of the electrode 101 is deformed in correspondence with the punch edge 361 of the cup portion 333, resulting in damage.

[0134] In order to solve this problem, the electrode assembly 10 has been housed in the cup part 333 so as to be spaced apart from the outer wall 338 of the cup part 333 to some extent. First, the vertical distance g' from the edge vertical line V2' is 0.75 mm, particularly 0.5 mm, and a reference vertical line V3' perpendicular to the bottom part 3332 is imaginarily drawn, and then, as shown in FIG. 7, the electrode assembly 10 is housed so that one end of the electrode 101 is located outside the reference vertical line V3'. As a result, the electrode 101 is spaced apart from the outer wall 338 of the cup part 333 to some extent, so that the electrode 101 can be prevented from being damaged. However, in this case, the space 37 between the outer wall 338 of the cup part 333 and the electrode assembly 10 increases, and the ratio of the volume of the electrode assembly 10 to the volume of the cup part 333 decreases, resulting in a problem of a decrease in the energy density relative to the volume of the secondary battery 3. In addition, the volume of the wasted space inside the cup portion 333 becomes large, and there is a problem that the electrode assembly 10 moves inside the cup portion 333 before the sides are sealed.

[0135] In the electrode assembly 10, the electrodes 101 have high rigidity and are not easily deformed by external forces, whereas the separators 102 have high flexibility and are easily deformed by external forces. However, when adjacent electrodes 101 come into direct contact with each other, a short circuit occurs. To prevent this, the separators 102 are formed larger than the electrodes 101. When the electrode assembly 10 is formed, the separators 102 are formed with peripheral portions 1021 that protrude outward from the electrodes 101. However, in the past, the electrode assembly 10 was stored with a certain distance from the outer wall 338 of the cup part 333, and the peripheral portions 1021 of the separators 102 were all wrinkled or folded in a disorderly manner, exposing the electrodes 101 to the outside, which increased the possibility of a short circuit.

[0136] Thus, conventional pouch films have poor moldability, and there has been a limit to improving the thickness t' of the bridge 336, the depth D' of the cup portion 333, the radius of curvature R2' of the edge 361 of the cup portion 333, and the clearance CL'. In addition, the ratio of the volume of the electrode assembly 10 to the volume of the cup portion 333 is small, and the wasted volume in the secondary battery 3 is large, so the energy density per volume is also low. Furthermore, the outer wall 338 of the cup portion 333 is not formed nearly vertically, and the radius of curvature R2 of the edge 361 of the cup portion 333 is also large, so there is a limit to manufacturing a sharp shape overall, and therefore there is a problem that the appearance of the secondary battery 3 is not beautiful and the marketability is reduced.

[0137] FIG. 8 is a schematic view of an enlarged view of the cup portion 133 and the bridge 136 according to one embodiment of the present invention, and FIG. 9 is a schematic view of an enlarged view of the cup portion 133 and the degassing portion 137 according to one embodiment of the present invention.

[0138] According to one embodiment of the present invention, the formability of the pouch film 135 is improved, so that the thickness t of the bridge 136 can be made thinner, and the radius of curvature R2 and the clearance CL of the edge 16 of the cup portion 133 can be made smaller, thereby increasing the volume of the electrode assembly 10. As a result, the wasted volume of the secondary battery 1 can be reduced, and the energy density per volume can be increased. In addition, the pouch-type battery case 13 and the pouch-type secondary battery 1 can be manufactured into an overall sharp shape, so that the appearance of the secondary battery 1 is excellent and the merchantability can be improved.

[0139] To this end, the pouch-type battery case 13 according to an embodiment of the present invention is formed with a cup portion 133 for accommodating therein an electrode assembly 10 formed by stacking electrodes 101 and separators 102, and the cup portion 133 includes a plurality of punch edges 161 each connecting a plurality of outer walls 138 surrounding the periphery and a bottom portion 1332, at least one of the punch edges 161 may be rounded with a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. If the curvature radius R2 of the punch edge 161 is less than 1 / 20 of the depth D of the cup portion 133, stress may be excessively concentrated on the punch edge 161, causing cracks, and if the curvature radius R2 of the punch edge 161 is greater than 1 / 6 of the depth D of the cup portion 133, the cup portion 133 may not be formed sharply, resulting in a decrease in energy density.

[0140] Specifically, at least one of the punch edges 161 may be rounded with a curvature radius of 1 mm or less, particularly 0.7 mm or less.

[0141] Also, the electrode assembly 10 includes a first case 131 and a second case 132 in which the cup portions 133 are respectively formed, and a bridge 136 formed between the two cup portions 133, and the bridge 136 may have a thickness of 1 / 200 to 1 / 30 of the width of the electrode assembly 10. If the thickness t of the bridge 136 is less than 1 / 200 of the width of the electrode assembly 10, stress may be excessively concentrated on the bridge 136, causing cracks, and if the thickness t is more than 1 / 30 of the width of the electrode assembly 10, the bridge 136 may not be formed sharply, causing a decrease in energy density.

[0142] In particular, the bridge 136 can have a thickness of 2 mm or less, particularly 1.4 mm or less.

[0143] In addition, among the plurality of punch edges 161, a punch edge 1611 on the bridge 136 side connecting the outer wall 1381 on the bridge 136 side and the bottom portion 1332 toward the bridge 136 side may be rounded to have a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, the punch edge 1611 may be rounded to have a curvature radius of 1 mm or less, particularly 0.7 mm or less.

[0144] In addition, the vertical distance between a bridge vertical line V1, which passes through a boundary point P1 between the bridge 136 and the outer wall 1381 on the bridge 136 side and is perpendicular to the bottom 1332, and an edge vertical line V2, which passes through a boundary point P2 between the punch edge 1611 on the bridge 136 side and the outer wall 1381 on the bridge 136 side and is perpendicular to the bottom 1332, can be 0.5 mm or less, particularly 0.35 mm or less.

[0145] The cup portion 133 is formed by forming a flexible pouch film 135 using a punch 22 or the like. The cup portion 133 is surrounded by a plurality of outer walls 138 and a bottom portion 1332, and a space formed by the outer walls 138 and the bottom portion 1332 serves as a storage space 1331 for storing the electrode assembly 10.

[0146] The outer wall 138 of the cup portion 133 surrounds the periphery of the cup portion 133 to define the shape of the cup portion 133. A plurality of outer walls 138 are formed around the periphery of the cup portion 133, and are also formed on the bridge 136 side, the degassing portion 137 side described below, and the electrode lead 12 side. The upper end of each of the outer walls 138 faces the open portion of the cup portion 133, and the lower end faces the bottom 1332.

[0147] Meanwhile, as described above, the edge 16 of the cup portion 133 includes a punch edge 161 formed corresponding to the edge 221 of the punch 22, and a die edge 162 formed corresponding to the edge 213 (shown in FIG. 6) of the die 21. The side 134 and the degassing portion 137 are formed outward from the upper end of the outer wall 138, and the die edge 162 connects the upper end of the outer wall 138 to the side 134 or the degassing portion 137, respectively. In addition, the punch edge 161 connects the lower end of the outer wall 138 to the bottom portion 1332, respectively.

[0148] Since the cup portion 133 has a plurality of outer walls 138, the edges 16 of the cup portion 133 are also formed in a plurality of numbers, equal to the number of the outer walls 138. That is, when the cup portion 133 is formed in a quadrangle, the cup portion 133 has four outer walls 138, and therefore, four punch edges 161 and four die edges 162 are also formed. In addition, according to an embodiment of the present invention, at least one of the punch edges 161 of the cup portion 133 may be rounded with a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup portion 133 due to improved formability of the pouch film 135. Specifically, at least one of the punch edges 161 may be rounded with a curvature radius of 1 mm or less, particularly 0.7 mm or less.

[0149] In particular, according to an embodiment of the present invention, two cup parts 133 are formed in one pouch film 135, and a bridge 136 is also formed between the two cup parts 133. As a result, as shown in Fig. 8, among the plurality of punch edges 161, a punch edge 1611 on the bridge 136 side connecting an outer wall 1381 on the bridge 136 side and the bottom part 1332 toward the bridge 136 side may be rounded with a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup part 133. Specifically, the punch edge 1611 on the bridge 136 side may be rounded with a curvature radius of 1 mm or less, particularly 0.7 mm or less.

[0150] 9, among the punch edges 161, a punch edge 1612 on the die edge 162 side connecting an outer wall 1382 on the die edge 162 side facing the die edge 162 side formed on the degassing unit 137 or the electrode lead 12 and the bottom portion 1332 may also be rounded and formed with a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. If the curvature radius of the die edge 162 is smaller than 1 / 20 of the depth D of the cup portion 133, stress may be excessively concentrated on the die edge 162, causing cracks, and if the curvature radius of the die edge 162 is larger than 1 / 6 of the depth D of the cup portion 133, the upper end of the cup portion 133 may not be formed sharply, causing a decrease in energy density.

[0151] Specifically, the punch edge 1612 on the die edge 162 side may also be rounded with a curvature radius of 1 mm or less, particularly 0.7 mm or less. In this case, it is preferable that the gradient is continuous at boundary points P2 and P4 between the punch edge 161 and the outer wall 138.

[0152] For this reason, the edge 221 of the punch 22 can also be rounded with a predetermined radius of curvature. Here, the radius of curvature of the edge 221 of the punch 22 can be a numerical value obtained by subtracting the thickness of the pouch film 135 itself from the radius of curvature R2 of the punch edge 161. For example, when the thickness of the pouch film 135 is 0.2 mm, and the radius of curvature of the edge 221 of the punch 22 is 0.5 mm or less, the radius of curvature R2 of the punch edge 161 is 0.7 mm or less.

[0153] According to one embodiment of the present invention, due to the improved formability of the pouch film 135, even if the depth D of the cup portion 133 is formed to a certain extent, when the punch 22 draws the pouch film 135, it is possible to prevent cracks from occurring in the punch edge 161 of the cup portion 133. For example, even if the depth D is formed to 7 mm or more when one cup portion 133 is formed, or 6.5 mm or more when two cup portions 133 are formed, or even if the depth D is formed to 10 mm or more, cracks can be prevented from occurring in the punch edge 161 of the cup portion 133.

[0154] Here, the depth D of the cup portion 133 where the above-mentioned cracks may occur is determined based on the remaining rate of the aluminum alloy of the moisture barrier layer 1352. If the remaining rate is 60% or more, it is determined to be a good product, and if the remaining rate is less than 60%, it is determined to be a bad product. The remaining rate means the ratio of the remaining amount of the aluminum alloy of the moisture barrier layer 1352 after molding to the remaining amount before molding at a specific point of the pouch film 135. In fact, if the remaining rate is less than 60%, cracks frequently occur at the specific point when the cup portion 133 is drawn into the pouch film 135, but if the remaining rate is 60% or more, no cracks occur.

[0155] Conventionally, when the depth D' of the cup portion 333 is formed to be 5 times, particularly 3.25 times, the radius of curvature R2' of the punch edge 361 or the radius of curvature of the die edge 362, the survival rate is relatively low and cracks occur frequently. Hereinafter, "prone to cracks" means that the survival rate is relatively low and cracks occur frequently.

[0156] Meanwhile, the outer wall 138 has an upper end facing the opening of the cup part 133, and the side 134 and the degassing part 137 extend to the outside of the cup part 133. In this case, as shown in FIG. 9, the cup part 133 may further include a plurality of die edges 162 connecting the upper end of the outer wall 138 to the side 134 or the degassing part 137, respectively. In addition, at least one die edge 162 may also be rounded to have a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup part 133. Specifically, at least one die edge 162 may be rounded to have a curvature radius of 1 mm or less, particularly 0.7 mm or less. For this purpose, the edge 213 of the die 21 may also be rounded to have a predetermined curvature radius. Here, the curvature radius of the edge 213 of the die 21 may be a value obtained by subtracting the thickness of the pouch film 135 itself from the curvature radius of the die edge 162. For example, if the thickness of the pouch film 135 is 0.2 mm, the radius of curvature of the die edge 162 is 0.7 mm or less, while the radius of curvature of the edge 213 of the die 21 is 0.5 mm or less.

[0157] In particular, as described above, two cup portions 133 may be formed in one pouch film 135, and a bridge 136 may also be formed between the two cup portions 133. That is, the pouch-type battery case 13 according to an embodiment of the present invention includes a first case 131 and a second case 132 each having a cup portion 133 formed therein, the cup portion 133 housing an electrode assembly 10 formed by stacking an electrode 101 and a separator 102, and a bridge 136 formed between the two cup portions 133. Since the bridge 136 is also formed corresponding to the partition wall 212 of the die 21, the bridge 136 may be one type of a plurality of die edges 162.

[0158] Therefore, according to one embodiment of the present invention, the formability of the pouch film 135 is improved, so that the thickness t of the bridge 136 can be 1 / 200 to 1 / 30 of the width EW (see FIG. 10) of the electrode assembly 10. Specifically, the thickness t of the bridge 136 can be formed to be 2 mm or less, particularly 1.4 mm or less.

[0159] Here, the thickness t of the bridge 136 is preferably the distance between two boundary points P1 between the bridge 136 and the outer wall 1381 on the bridge 136 side, as shown in Fig. 8. Specifically, it is preferably the distance between two bridge perpendicular lines V1 that pass through the boundary points P1 between the bridge 136 and the outer wall 1381 on the bridge 136 side, and are perpendicular to the bottom 1332. Therefore, when the bridge 136 has a predetermined radius of curvature, the radius of curvature of the bridge 136 can correspond to half the thickness t. That is, the radius of curvature of the bridge 136 can be 1 mm or less, particularly 0.7 mm or less.

[0160] For this reason, the upper surface of the partition wall 212 of the molding part 211 may also be rounded with a predetermined radius of curvature. In this case, it is preferable that the gradient is continuous at the boundary point P1 between the bridge 136 and the outer wall 1381 on the bridge 136 side. Here, the radius of curvature of the upper surface of the partition wall 212 of the molding part 211 may be a value obtained by subtracting the thickness of the pouch film 135 itself from the radius of curvature of the bridge 136. For example, when the thickness of the pouch film 135 is 0.2 mm, and the radius of curvature of the upper surface of the partition wall 212 is 0.5 mm or less, the radius of curvature of the bridge 136 is 0.7 mm or less.

[0161] According to an embodiment of the present invention, by improving the formability of the pouch film 135, even if the depth D of the cup portion 133 is formed to be relatively deep and the radius of curvature of the edge 213 of the die 21 is reduced and the thickness of the partition wall 212 is formed to be thin, it is possible to prevent cracks from occurring in the die edge 162 and the bridge 136. The bridge 136 may have a sector-shaped cross section, and the more the outer wall 138 of the cup portion 133 is formed to be closer to vertical, the more the cross section may be closer to a semicircle.

[0162] Here, even if the depth D of the cup portion 133 is molded to 3 mm or more, particularly 6.5 mm or more, and even more particularly 10 mm or more, based on the case where two cup portions 133 are molded, it is possible to prevent cracks from occurring in the bridge 136.

[0163] Furthermore, by improving the formability of the pouch film 135, the clearance CL can be reduced to 0.5 mm or less, and all of the outer walls 138 can be formed nearly vertical. For example, as shown in Fig. 8, among the outer walls 138, the outer wall 1381 on the bridge 136 side can be formed nearly vertical. That is, the clearance CL, which is the vertical distance between a bridge vertical line V1 passing through a boundary point P1 between the bridge 136 and the outer wall 1381 on the bridge 136 side and perpendicular to the bottom 1332, and an edge vertical line V2 passing through a boundary point P2 between the punch edge 1611 on the bridge 136 side and the outer wall 1381 on the bridge 136 side and perpendicular to the bottom 1332, can be 0.5 mm or less, particularly 0.35 mm or less.

[0164] 9, the outer wall 1382 on the die edge 162 side among the outer walls 138 may also be formed nearly vertically. That is, a clearance CL, which is a vertical distance between a die edge vertical line V4 passing through a boundary point P3 between the die edge 162 and the outer wall 1382 on the die edge 162 side and perpendicular to the bottom 1332, and an edge vertical line V2 passing through a boundary point P4 between the punch edge 1612 on the die edge 162 side and the outer wall 1382 on the die edge 162 side and perpendicular to the bottom 1332, may be 0.5 mm or less, particularly 0.35 mm or less.

[0165] As a result, even if the depth D of the cup portion 133 is formed to be 3 mm or more, particularly 6.5 mm or more, or even 10 mm or more, based on the case where two cup portions 133 are formed, the outer wall 138 of the cup portion 133 can be formed nearly vertically with an inclination angle of 90° to 95° from the bottom portion 1332, or even with an inclination of 90° to 93°, thereby preventing the occurrence of cracks in the battery case 13. In addition, the space 17 between the outer wall 138 of the cup portion 133 and the electrode assembly 10 is also reduced, and therefore the energy density per volume of the secondary battery 1 can be increased.

[0166] On the other hand, the radius of curvature R2 of the punch edge 161 of the cup portion 133 can be further reduced, and even if the electrode assembly 10 is positioned very close to the outer wall 138 of the cup portion 133, the electrode 101 of the electrode assembly 10 can be prevented from being damaged.

[0167] To this end, a manufacturing method of a pouch-type secondary battery 1 according to one embodiment of the present invention may include the steps of: laminating an electrode 101 and a separator 102 to form an electrode assembly 10; forming a pouch film 135 to form a cup portion 133 to manufacture a pouch-type battery case 13; accommodating the electrode assembly 10 in an accommodating space 1331 of the cup portion 133; and sealing a side 134 formed extending outward from the cup portion 133 to manufacture a pouch-type secondary battery 1.

[0168] In particular, in the step of housing the electrode assembly 10, a difference between a width CW of the cup portion 133 and a width EW of the electrode assembly 10 may be 2.5 mm or less, particularly 1.7 mm or less. Here, the width EW of the electrode assembly 10 may refer to the width of the electrode 101. That is, a peripheral portion 1021 of the separator 102 protruding from the electrode 101 may be excluded from the calculation of the width EW.

[0169] In addition, the electrode assembly 10 can be stored so that at least one end of the electrode 101 passes through the boundary point P2 between the punch edge 161 and the outer wall 138 and is located at a vertical distance g of 0.75 mm, particularly 0.5 mm or less, from an edge vertical line V2 perpendicular to the bottom 1332.

[0170] Specifically, as shown in Figs. 8 and 9, an imaginary edge vertical line V2 is illustrated, which passes through the boundary point P2 between the punch edge 161 and the outer wall 138 and is perpendicular to the bottom 1332. The electrode assembly 10 is accommodated such that at least one end of the electrode 101 is located at a vertical distance g of 0.75 mm or less, particularly 0.5 mm or less, from the edge vertical line V2. More specifically, a reference vertical line V3 is illustrated imaginarily, which is perpendicular to the bottom 1332 and has a vertical distance g of 0.75 mm, particularly 0.5 mm, from the edge vertical line V2. At this time, since the radius of curvature R2 of the punch edge 161 can be particularly 0.7 mm or less, the reference vertical line V3 can also pass through the center of curvature C of the punch edge 161. The electrode assembly 10 is accommodated such that one end of the electrode 101 is located between the edge vertical line V2 and the reference vertical line V3. This can be confirmed by disassembling the secondary battery 1 itself, but is not limited thereto, and can also be confirmed by various methods without disassembling the secondary battery 1, such as CT (Computerized Tomography), MRI (Magnetic Resonance Imaging), X-Ray, etc. As a result, damage to the electrode 101 can be prevented, and the ratio of the volume of the electrode assembly 10 to the volume of the cup part 133 can be increased, thereby improving the energy efficiency per volume. In addition, since the wasted volume inside the cup part 133 is reduced, the electrode assembly 10 can be prevented from moving inside the cup part 133.

[0171] Furthermore, the electrode assembly 10 can be stored so as to be positioned very close to the outer wall 138 of the cup portion 133, and the separator 102 can be prevented from being wrinkled or folded randomly. As shown in Fig. 8, the peripheral portion 1021 of the separator 102 protruding outward from the electrode 101 can be folded in the opposite direction to the bottom portion 1332 based on one end of the electrode 101.

[0172] The electrode assembly 10 is formed by stacking the electrodes 101 and the separators 102, and the electrodes 101 and the separators 102 may each be formed in a plurality of layers. When the battery case 13 includes a first case 131 and a second case 132, and the bridge 136 of the battery case 13 is folded to accommodate the upper portion of the electrode assembly 10 in the cup portion 133, the separator 102 accommodated in the cup portion 133 of the first case 131 may have the peripheral portion 1021 folded toward the second case 132, and the separator 102 accommodated in the cup portion 133 of the second case 132 may have the peripheral portion 1021 folded toward the first case 131. As a result, the peripheral portion 1021 of the separator 102 is aligned and folded to provide an orderly state. In addition, the separator 102 covers the electrodes 101 so that they are not exposed to the outside, and therefore, a short circuit can be prevented from occurring.

[0173] More specifically, before the electrode assembly 10 is accommodated in the cup portion 133, the width of the separator 102 may be wider than the width CW of the cup portion 133. Therefore, during the process of accommodating the electrode assembly 10 in the cup portion 133, the peripheral portion 1021 of the separator 102 may be in contact with the inner circumference of the cup portion 133 and folded in a predetermined direction.

[0174] The difference between the width CW of the cup portion 133 and the width EW of the electrode assembly 10 may be very small, such as 2.5 mm or less, and particularly 1.7 mm or less. Therefore, in the process of inserting the electrode assembly 10 into the cup portion 133, a process may be required to easily fold the peripheral portion 1021 of the separator 102.

[0175] Therefore, the step of accommodating the electrode assembly 10 in the accommodating space 1331 of the cup part 133 may include a process of pressing the electrode assembly 10 into the cup part 133. As a result, compared to the conventional method of placing the electrode assembly 10 in a cup part, the difference between the width CW of the cup part 133 and the width EW of the electrode assembly 10 can be kept small, and the separator 102 can be folded in a predetermined direction, so that the electrode assembly 10 can be easily and reliably accommodated in the accommodating space 1331 of the cup part 133.

[0176] In addition, the step of accommodating the electrode assembly 10 in the receiving space 1331 of the cup part 133 may further include a process of folding each corner (vertex) of the plurality of separators 102 in the electrode assembly 10 by heat and pressure before pressing the electrode assembly 10 into the cup part 133. This process may be performed by folding each corner (vertex) of the plurality of separators 102 so that they are gathered at the center of the stacking direction of the electrode assembly 10 using a separate sealing tool.

[0177] That is, the electrode assembly 10 can be inserted into the cup portion 133 with the four corners of the separator 102 aligned in advance. This allows the electrode assembly 10 to be smoothly inserted into the receiving space 1331 of the cup portion 133. As described above, according to an embodiment of the present invention, the formability of the pouch film 135 is improved, so that the thickness t of the bridge 136 can be made thinner, and the curvature radius R2 and the clearance CL of the edge 16 of the cup portion 133 can be made smaller, thereby increasing the volume of the electrode assembly 10. Therefore, the wasted volume of the secondary battery 1 can be reduced, and the energy density per volume can be increased. In addition, the pouch-type battery case 13 and the pouch-type secondary battery 1 can be manufactured into a sharp shape overall, so that the appearance of the secondary battery 1 is beautiful and the merchantability can be improved.

[0178] FIG. 10 is a schematic top view showing the electrode assembly 10 housed in the cup portion 133 according to an embodiment of the present invention.

[0179] According to an embodiment of the present invention, as described above, the radius of curvature R2 of the punch edge 161 of the cup portion 133 can be further reduced, and the electrode assembly 10 is stored so that one end of the electrode 101 is located between the edge perpendicular line V2 and the reference perpendicular line V3. This makes it possible to prevent the electrode 101 of the electrode assembly 10 from being damaged even if the electrode assembly 10 is located very close to the outer wall 138 of the cup portion 133.

[0180] The edge perpendicular line V2 and the reference perpendicular line V3 may also be illustrated on the punch edge 1611 on the bridge 136 side, and may also be illustrated on the punch edge 1612 on the die edge 162 side. The perpendicular distance g between such edge perpendicular line V2 and the reference perpendicular line V3 may be 0.75 mm, particularly 0.5 mm.

[0181] In addition, when two cup portions 133 are formed in the battery case 13, a bridge 136 is present, and therefore a bridge vertical line V1 can be illustrated on one side of the cup portion 133 and a die edge vertical line V4 on the other side. The vertical distance CL between the bridge vertical line V1 and the edge vertical line V2 can be 0.5 mm or less, particularly 0.35 mm or less, and the vertical distance CL between the die edge vertical line V4 and the edge vertical line V2 can also be 0.5 mm or less, particularly 0.35 mm or less.

[0182] However, if only one cup portion 133 is formed in the battery case 13, no bridge exists. However, since a die edge 162 is formed on both sides of the cup portion 133, a die edge perpendicular line V4 can be illustrated on both sides of the cup portion 133.

[0183] When two cup portions 133 are formed in the battery case 13, the width CW of the cup portion 133 can be regarded as the vertical distance from the bridge vertical line V1 to the die edge vertical line V4. However, when only one cup portion 133 is formed, the width CW of the cup portion 133 can also be regarded as the vertical distance between the two die edge vertical lines V4.

[0184] Both the bridge vertical line V1 and the die edge vertical line V4 pass through the upper end of the outer wall 138 of the cup portion 133. Therefore, according to one embodiment of the present invention, the width CW of the cup portion 133 may be the vertical distance between the upper ends of the outer walls 138 on both sides of the cup portion 133. The difference between the width CW of the cup portion 133 and the width EW of the electrode assembly 10 may be 2.5 mm or less, particularly 1.7 mm or less. Also, as described above, the width EW of the electrode assembly 10 may be 60 mm or more.

[0185] In the battery case 13, the width CW of the cup portion 133 can be derived by measuring the vertical distance between the upper ends of the outer walls 138 on both sides of the cup portion 133. In the secondary battery 1, the width CW of the cup portion 133 can be derived by grasping the position between the upper ends of the outer walls 138 on both sides from the outside of the cup portion 133 using a laser displacement sensor or the like and calculating the distance between the two positions. In this case, when a laser displacement sensor or the like moves from the side 134 toward the die edge 162 and the outer wall 138 while irradiating a laser from the outside of the cup portion 133 and detects a point where the displacement changes suddenly, the point can be recognized as the upper end of the outer wall 138. The above describes a method for measuring the width CW of the cup portion as an example, and the scope of the present invention does not necessarily include only the above measurement method. The width CW of the cup portion can be any width CW of the cup portion as defined in the present invention as long as it falls within the scope of the claims and the spirit of the present invention.

[0186] FIG. 11 is a schematic diagram illustrating a conventional corner 364, and FIG. 12 is a schematic diagram illustrating a corner 164 according to one embodiment of the present invention.

[0187] 12, the edge 16 of the cup portion 133 includes not only the punch edge 161 and the die edge 162, but also a thickness edge 163 connecting two adjacent outer walls 138 of the cup portion 133 to each other. The thickness edge 163 is formed in the thickness direction of the cup portion 133, and is formed while the pouch film 135 is stretched between a corner of the forming portion 211 of the die 21 and a corner of the punch 22 when the pouch film 135 is stretched. In addition, at least one of the thickness edges 163 may be formed by rounding.

[0188] The thickness edge 163 may have a radius of curvature equal to or different from the radius of curvature R2 of two adjacent punch edges 161, i.e., the first punch edge 1613 and the second punch edge 1614. For example, as described above, at least one of the punch edges 161 may be rounded to a radius of curvature of 1 mm or less, particularly 0.7 mm or less, and at least one of the thickness edges 163 may be rounded to a radius of curvature of 0.5 mm to 5 mm, particularly 0.5 mm to 2 mm. Conventionally, when the thickness edge 363 is rounded to a radius of curvature of 5 mm or less, particularly 2 mm or less, there is a problem that stress is concentrated in the thickness edge 363 of the cup portion 333, and cracks are likely to occur. However, according to one embodiment of the present invention, even if the depth D of the cup portion 133 is formed to be relatively deep, it is possible to prevent cracks from occurring in the thickness edge 163 of the cup portion 133. In this case, one of the first punch edge 1613 and the second punch edge 1614 may be a punch edge 1611 on the bridge 136 side, and the other may be a punch edge (not shown) on the electrode lead 12 side. Alternatively, one of the two may be a punch edge 1612 on the die edge 162 side, and the other may be a punch edge (not shown) on the electrode lead 12 side.

[0189] As shown in Fig. 12, the thick edge 163 is connected to two adjacent punch edges 161, i.e., a first punch edge 1613 and a second punch edge 1614, to form a corner 164. Conventionally, as shown in Fig. 11, a plurality of edges 221 of a punch 22 are all rounded with the same radius of curvature, and accordingly, corners (not shown) of the punch 22 are naturally rounded with the same radius of curvature. Therefore, when the pouch film 135 is formed by using such a punch 22 and the pouch film 135 is stretched, the corner 364 is also naturally rounded with the same radius of curvature as the punch edge 361.

[0190] However, when the pouch film 135 is stretched, there is a problem that stress is concentrated at the corner 364. In particular, since the corner 364 is formed by the contact of three edges 36, it is stretched more than the punch edge 361 or the thickness edge 363, and therefore stress is concentrated more at the corner 364 than at the punch edge 361 or the thickness edge 363. As a result, the pouch film 135 is stretched excessively, and a whitening phenomenon occurs in which a specific portion turns white just before a crack occurs, which ultimately causes a problem that cracks are likely to occur.

[0191] Therefore, according to one embodiment of the present invention, as shown in FIG. 12, at least one of the corners 164 is also formed by rounding, and such corner 164 may have a radius of curvature greater than or equal to the radius of curvature of at least one of the punch edge 161 and the thickness edge 163.

[0192] Specifically, according to an embodiment of the present invention, the radius of curvature of the corner 164 may vary inside. That is, the radius of curvature of the center 1641 of the corner 164 may be different from the radius of curvature of the peripheral portion 1642 of the corner 164. In particular, the radius of curvature of the center 1641 of the corner 164 may be greater than the radius of curvature of the peripheral portion 1642 of the corner 164. For example, the radius of curvature of the peripheral portion 1642 of the corner 164 may be equal to the radius of curvature of at least one of the punch edge 161 and the thickness edge 163 since the peripheral portion 1642 of the corner 164 is relatively adjacent to the first punch edge 1613, the second punch edge 1614, and the thickness edge 163. Meanwhile, the radius of curvature of the center 1641 of the corner 164 may be greater than the radius of curvature of at least one of the punch edge 161 and the thickness edge 163 since the central portion 1641 of the corner 164 is relatively distant from the first punch edge 1613, the second punch edge 1614, and the thickness edge 163. That is, the corner 164 may have a radius of curvature equal to or greater than the radius of curvature of at least one of the punch edge 161 and the thickness edge 163 .

[0193] Therefore, the radius of curvature of the corner 164 may gradually increase from the peripheral portion 1642 of the corner 164 to the center portion 1641 of the corner 164. Also, as described above, since the radius of curvature of the corner 164 is not constant but varies inside, the center portion 1641 of the corner 164 may have an aspherical shape rather than an exact sphere.

[0194] Unlike the punch edge 161, the corner 164 needs to be clearly set not only in the radius of curvature but also in the area formed by the cup portion 133. If the area formed by the corner 164 by the cup portion 133 is too narrow, the pouch film 135 is still stretched excessively, and there is a problem of whitening or cracks occurring. On the other hand, if the area formed by the corner 164 by the cup portion 133 is too wide, the space 17 between the outer wall 138 of the cup portion 133 and the electrode assembly 10 is reduced, so that the energy density per volume of the secondary battery 1 can be increased. Therefore, according to an embodiment of the present invention, as shown in FIG. 12, the corner 164 may be formed within 2 mm to 3.5 mm from the thickness edge 163 in the length direction lc of the cup portion 133, 2 mm to 3.5 mm from the thickness edge 163 in the width direction wc of the cup portion 133, and 2 mm to 3.5 mm from the punch edge 161 in the thickness direction dc of the cup portion 133. In addition, the area in which the corner 164 is formed may become gradually wider as the depth D of the cup portion 133 becomes deeper.

[0195] Since the corners 164 of the cup portion 133 are formed as described above, the stress concentrated at the corners 164 can be dispersed, and the problems of whitening and cracking can be prevented.

[0196] FIG. 13 is a schematic diagram showing a state in which the battery case 13 according to one embodiment of the present invention is folded, and FIG. 14 is a schematic diagram showing a state in which the battery case 13 according to one embodiment of the present invention is folded.

[0197] When the two cup parts 133 are formed in the pouch film 135, the first case 131 and the second case 132 of the battery case 13 each have a cup part 133. Then, the electrode assembly 10 is accommodated in the accommodation space 1331 provided in the cup part 133 of the first case 131, and then, as shown in Fig. 13, the bridge 136 formed between the two cup parts 133 in the battery case 13 is folded so that the two cup parts 133 face each other. The bridge 136 is folded to form a folding part 139 on one side of the secondary battery 1. Then, an electrolyte is injected inside, and the side 134 extended outward from the cup parts 133 of the first case 131 and the second case 132 is sealed, thereby manufacturing the pouch-type secondary battery 1 as shown in Fig. 14.

[0198] The pouch-type secondary battery 1 according to an embodiment of the present invention thus manufactured includes an electrode assembly 10 formed by stacking an electrode 101 and a separator 102, and a pouch-type battery case 13 having a cup portion 133 formed therein for accommodating the electrode assembly 10, and the cup portion 133 may include a plurality of punch edges 161 each connecting a plurality of outer walls 138 surrounding the periphery and a bottom portion 1332. At least one of the punch edges 161 may be rounded with a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, at least one of the punch edges 161 may be rounded with a curvature radius of 1 mm or less, particularly 0.7 mm or less.

[0199] A difference between a width CW of the cup portion 133 and a width EW of the electrode assembly 10 may be 2.5 mm or less, particularly 1.7 mm or less. In addition, the electrode assembly 10 may be such that at least one end of the electrode 101 is positioned at a vertical distance g of 0.75 mm, particularly 0.5 mm or less from an edge vertical line V2 that passes through a boundary point P2 between the punch edge 161 and the outer wall 138 and is perpendicular to the bottom 1332. In addition, the battery case 13 may include a first case 131 and a second case 132 having a cup portion 133 formed on at least one side thereof, and a folding portion 139 that integrally connects the first case 131 and the second case 132.

[0200] When the battery case 13 is folded to manufacture the secondary battery 1, the bridge 136 becomes the folding section 139, and therefore the folding section 139 integrally connects the first case 131 and the second case 132 in the secondary battery 1. In addition, the punch edge 1611 on the bridge 136 side becomes the punch edge 1611 on the folding section 139 side, and the outer wall 1381 on the bridge 136 side becomes the outer wall 1381 on the folding section 139 side.

[0201] Accordingly, among the plurality of punch edges 161, a punch edge 1611 on the folding portion 139 side connecting the outer wall 1381 on the folding portion 139 side and the bottom portion 1332 toward the folding portion 139 side may be rounded with a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, the punch edge 1611 on the folding portion 139 side may be rounded with a curvature radius of 1 mm or less, particularly 0.7 mm or less. In addition, the electrode assembly 10 may be such that at least one end of the electrode 101 passes through a boundary point P2 between the punch edge 161 and the outer wall 138 and is perpendicular to the bottom portion 1332, and is located between an edge perpendicular line V2 perpendicular to the bottom portion 1332 and a reference perpendicular line V3 perpendicular to the bottom portion 1332, the reference perpendicular line V3 having a vertical distance g of 0.75 mm, particularly 0.5 mm, from the edge perpendicular line V2. As described above, such a reference vertical line V3 may pass through the center of curvature C of the punch edge 161.

[0202] FIG. 15 is an enlarged view of a groove 1391 formed in a battery case 13 according to one embodiment of the present invention.

[0203] According to an embodiment of the present invention, when the battery case 13 is folded to manufacture the secondary battery 1 as described above, the bridge 136 may take the form of the folding portion 139. Specifically, when the battery case 13 is folded, the rounded shape of the bridge 136 is also stretched to some extent, and a trace of the bridge 136 remains on the secondary battery 1, and this trace may become the folding portion 139. Therefore, the bridge 136 and the folding portion 139 of the battery case 13 may correspond to each other.

[0204] For example, if the rounded shape of the bridge 136 does not completely extend in a plane, the folding portion 139 is formed to include a groove 1391 recessed into the inside of the secondary battery 1, as shown in Fig. 15. In such a case, the folding portion 139 has a smaller curvature than the bridge 136, and therefore can have a larger radius of curvature.

[0205] Since the bridge 136 has a curved surface and the outer wall 1381 on the bridge 136 side has a flat shape, the deformation amounts are different between them. Therefore, when the battery case 13 is folded, the outer wall 1381 on the bridge 136 side is deformed relatively more, but the bridge 136 is deformed relatively less to the extent that the rounded shape is stretched to a certain extent. As a result, when the battery case 13 is folded, as shown in FIG. 15, the increase and decrease of the change amount of the gradient is converted around the boundary point P1. That is, the boundary point P1 becomes an inflection point. Therefore, the folding portion 139 can be formed by the two boundary points P1, i.e., the curved surface between the two inflection points.

[0206] In addition, when the rounded shape of the bridge 136 is not completely extended on a plane, the two boundary points P1, i.e., the portions corresponding to the two inflection points, may protrude outward to form protrusions. That is, the protrusions may be formed as a pair protruding outward across the folding portion 139, more specifically, the groove 1391.

[0207] Alternatively, even if the rounded shape of the bridge 136 is completely extended on a plane, the boundary point P1 between the bridge 136 and the outer wall 1381 on the bridge 136 side each forms two lines (not shown) on the secondary battery 1, and the folding portion 139 is formed on the plane between these two lines.

[0208] The folding portion 139 can be visually confirmed from the exterior of the secondary battery 1. As described above, the thickness t of the bridge 136 is preferably the distance between the two boundary points P1 between the bridge 136 and the outer wall 1381 on the bridge 136 side, and therefore the width FW of the folding portion 139 is the distance between the two boundary points P1. When the rounded shape of the bridge 136 is no longer completely stretched on a plane, the width FW of the folding portion 139 is the distance between the two boundary points P1, i.e., the two inflection points. Alternatively, when the rounded shape of the bridge 136 is completely stretched on a plane, the width FW of the folding portion 139 is the distance between the two boundary points P1, i.e., the two lines.

[0209] The width FW of the folding portion 139 does not exceed the length of the bridge 136 and may be 1 mm to 3.2 mm, particularly 1 mm to 1.6 mm. As described above, the width FW of the folding portion 139 may be measured directly using a ruler, or may be measured using a magnifying glass, or may be measured using a 3D camera or a laser 2D line sensor, and may be measured in various ways without limitation.

[0210] Conventionally, the thickness t' of the bridge 336 is large and the width of the folding portion 339 is large, and therefore the space 37 between the outer wall 338 of the cup portion 333 and the electrode assembly 10 is also large. However, according to an embodiment of the present invention, the width FW of the folding portion 139 can be reduced, and therefore the space 17 between the outer wall 138 of the cup portion 133 and the electrode assembly 10 can also be reduced. As a result, the energy density per volume of the secondary battery 1 can be increased.

[0211] In addition, in the conventional pouch film, the protrusions protrude significantly outward due to the poor formability of the pouch film. However, according to one embodiment of the present invention, the protrusions can protrude relatively small, and the flatness of the folding part 139 or the outer wall 1381 on the folding part 139 side can be improved.

[0212] Specifically, the distance p between the innermost part of the groove 1391 and the outermost part of the protrusion can be defined as the flatness. In the case of a conventional battery case, the flatness is 1 mm or more, and can be as high as 1.5 mm. Meanwhile, according to an embodiment of the present invention, the flatness p can be 0.8 mm or less, and preferably 0.3 mm or less. This can further increase the energy density relative to the volume of the secondary battery 1.

[0213] FIG. 16 is a schematic diagram of an enlarged view of a cup portion 133 and a die edge 1621 according to another embodiment of the present invention.

[0214] According to an embodiment of the present invention, two forming parts 211 are formed adjacent to each other in the die 21, and a partition wall 212 may be formed between the two forming parts 211. Therefore, when the pouch film 135 is formed, two cup parts 133 are formed in one pouch film 135, and a bridge 136 is also formed between the two cup parts 133. That is, one cup part 133 is formed in each of the first case 131 and the second case 132.

[0215] However, according to another embodiment of the present invention, only one molding portion 211 is formed in the die 21, and no partition is present. Therefore, when the pouch film 135 is molded, one cup portion 133 is formed in one pouch film 135, and no bridge is present. That is, the cup portion 133 is formed only in the first case 131.

[0216] According to another embodiment of the present invention, at least one punch edge 161a of the cup portion 133 may be rounded with a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, at least one punch edge 161a of the cup portion 133 may be rounded with a curvature radius of 1 mm or less, particularly 0.7 mm or less. This improves the formability of the pouch film 135, and prevents cracks from occurring in the punch edge 161a of the cup portion 133 even if the depth D of the cup portion 133 is formed to a certain degree, 3 mm or more, particularly 7 mm or more, and even 10 mm or more based on the case where one cup portion 133 is formed.

[0217] In particular, according to another embodiment of the present invention, as shown in Fig. 16, among the plurality of punch edges 161a, a punch edge 1611a on the second case 132a side connecting an outer wall 1381a on the second case 132a side facing the second case 132a side and the bottom portion 1332 may be rounded with a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, the punch edge 1611a on the second case 132a side may be rounded with a curvature radius of 1 mm or less, particularly 0.7 mm or less.

[0218] In addition, the punch edge 1612 on the die edge 162 side may also be rounded to a radius of curvature of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, the punch edge 1612 on the die edge 162 side may also be rounded to a radius of curvature of 1 mm or less, particularly 0.7 mm or less. In this case, it is preferable that the gradient is continuous at a boundary point P2 between the punch edge 161a and the outer wall 138.

[0219] Hereinafter, with regard to other embodiments of the present invention, the description of the contents overlapping with the embodiment of the present invention will be omitted, however, this is for the convenience of explanation and not for the purpose of limiting the scope of the rights.

[0220] FIG. 17 is a schematic diagram showing a state in which a battery case 13a according to another embodiment of the present invention is folded, and FIG. 18 is a schematic diagram showing a state in which a battery case 13a according to another embodiment of the present invention is folded.

[0221] The upper end of the outer wall 138 faces the opening of the cup part 133, and the second case 132a, the side 134, and the degassing part 137 extend outside the cup part 133. In this case, the die edge 162 connecting the upper end of the outer wall 138 to the second case 132a, the side 134, or the degassing part 137 may also be rounded with a curvature radius of 1 / 20 to 1 / 6 of the depth D of the cup part 133. Specifically, the die edge 162 may be rounded with a curvature radius of 1 mm or less, particularly 0.7 mm or less.

[0222] That is, according to another embodiment of the present invention, as shown in Fig. 17, there is no bridge in the battery case 13a, and the die edge 1621 connects the cup portion 133 of the first case 131 and the second case 132a to each other. For this purpose, the edge 213 of the die 21 may be rounded with a curvature radius obtained by subtracting the thickness of the pouch film 135 from the die edge 162. For example, if the thickness of the pouch film 135 is 0.2 mm, the edge 213 of the die 21 may be rounded with a curvature radius of 0.8 mm or less, particularly 0.5 mm or less.

[0223] Furthermore, the clearance CL may be reduced to 0.5 mm or less, so that the outer wall 138a of the cup portion 133 is nearly vertical. For example, as shown in Fig. 16, the clearance CL, which is the vertical distance between a die edge vertical line V4 that passes through a boundary point P1 between the die edge 1621 and the outer wall 1381a on the second case 132a side and is perpendicular to the bottom 1332, and an edge vertical line V2 that passes through a boundary point P2 between the punch edge 1611a on the second case 132a side and the outer wall 1381a on the second case 132a side and is perpendicular to the bottom 1332, may be 0.5 mm or less, particularly 0.35 mm or less.

[0224] In addition, the electrode assembly 10 can be stored so that one end of the electrode 101 is located between the edge perpendicular line V2 and a reference perpendicular line V3 that is perpendicular to the bottom 1332 and has a vertical distance of 0.75 mm, particularly 0.5 mm, from the edge perpendicular line V2.

[0225] As a result, according to another embodiment of the present invention, the formability of the pouch film 135 is improved, and even if the depth D of the cup portion 133 is formed to a certain extent, for example, to be about 3 mm or more, particularly 7 mm or more, or even 10 mm or more, based on the formation of one cup portion 133, it is possible to prevent cracks from occurring in the punch edge 161a and the die edge 162 of the cup portion 133. In addition, the outer wall 138 of the cup portion 133 can be formed nearly vertically with an inclination angle of 90° to 95°, particularly 90° to 93°, from the bottom 1332, thereby preventing the electrode 101 from being damaged, and the ratio of the volume of the electrode assembly 10 to the volume of the cup portion 133 can be further increased, and the energy efficiency per volume can also be improved.

[0226] FIG. 19 is an enlarged view of a groove 1391a formed in a battery case 13a according to another embodiment of the present invention.

[0227] According to another embodiment of the present invention, when the battery case 13a is folded to manufacture the secondary battery 1a, the die edge 1621 on the second case 132a side becomes the folded portion 139a. Specifically, when the battery case 13 is folded, the rounded shape of the die edge 1621 is also stretched, and a trace of the die edge 1621 remains on the secondary battery 1a, and this trace becomes the folded portion 139a. Therefore, the die edge 1621 on the second case 132a side of the battery case 13a and the folded portion 139a correspond to each other.

[0228] For example, if the rounded shape of the die edge 1621 does not completely extend in a plane, the folding portion 139a is formed to include a groove 1391a recessed into the inside of the secondary battery 1a, as shown in Fig. 19. In this case, the folding portion 139a has a smaller curvature than the die edge 1621, and therefore may have a larger radius of curvature.

[0229] Since the die edge 1621 has a curved surface and the outer wall 1381a on the die edge 1621 side has a flat shape, the deformation amounts are different between them. Therefore, when the battery case 13 is folded, the outer wall 1381a on the die edge 1621 side is deformed relatively more, but the die edge 1621 is deformed relatively less to the extent that the rounded shape is stretched to a certain extent. As a result, when the battery case 13 is folded, as shown in FIG. 19, the increase and decrease of the change amount of the gradient is converted around the boundary point P1. That is, the boundary point P1 becomes an inflection point. Therefore, the folding portion 139a is formed by the curved surface between the two boundary points P1, i.e., the two inflection points.

[0230] Alternatively, even if the rounded shape of the die edge 1621 is completely extended on a plane, the boundary point P1 between the die edge 1621 and the outer wall 1381 on the second case 132a side and the boundary point between the die edge 1621 and the second case 132a form two lines (not shown) on the secondary battery 1a, and the folding portion 139a is formed on the plane between these two lines.

[0231] The width FW of such a folding portion 139 does not exceed the length of the die edge 1621 and may be 1 mm to 3.2 mm, particularly 1 mm to 1.6 mm.

[0232] FIG. 20 is a schematic diagram showing a conventional battery case 33 from above before the degassing portion 337 is cut off.

[0233] The bridge 136 of the battery case 13 is folded to form a folding part 139 on one side of the secondary battery 1, and this folding part 139 integrally connects the first case 131 and the second case 132. However, the battery case 13 is formed by drawing the pouch film 135, and in this case, not only the cup part 133 is stretched in a limited manner, but the sides 134 surrounding the cup part 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 part 139. This is called a bat ear (35 or 15).

[0234] The size of the butt ear 35 varies depending on the thickness t' of the bridge 336, the clearance CL', the radius of curvature R2' of the punch edge 361 of the cup portion 333, and the depth D' of the cup portion 333. That is, the thicker the thickness t' of the bridge 336, the larger the clearance CL', and the larger the radius of curvature R2' of the punch edge 361 of the cup portion 333, the larger the size of the butt ear 35. However, in the past, there was a limit to improving the thickness t' of the bridge 336, the radius of curvature R2' of the punch edge 361 of the cup portion 333, and the clearance CL'. Therefore, as shown in FIG. 20, the size of the butt ear 35 was formed to be quite large, and there was also a limit to reducing it.

[0235] When the size of such a butt ear 35 is made large, the wasted volume of the secondary battery 3 increases, causing an error between the design value and the actual value of the shape and size of the secondary battery 3. Therefore, when assembling the secondary battery 3 into the battery module 5 (shown in FIG. 27), it is not easy to assemble the secondary battery 3, and there is a problem that the size of the secondary battery 3 must be designed small from the beginning in consideration of such butt ear 35. In addition, there is a problem that the energy density per volume decreases as the volume of the secondary battery 3 increases.

[0236] Meanwhile, as described above, the pouch-type battery case 13 according to one embodiment of the present invention includes a cup portion 133 having an accommodating space 1331 for accommodating an electrode assembly 10, and a degassing portion 137 formed on one side of the cup portion 133 and discharging gas generated inside the cup portion 133 through a degassing hole H.

[0237] In addition, a formation process and a degassing process may be performed in the process of sealing the side 134. Specifically, after the electrode assembly 10 is housed in the cup portion 133, the corner portion 1371 included in the degassing portion 137 of the battery case 13 may be opened, and the remaining side 134 may be sealed. When the corner portion 1371 of the battery case 13 is opened to form an opening, an electrolyte is injected into the battery case 13 through the opening.

[0238] After injecting an electrolyte into the battery case 13, the degassing part 137 is primarily sealed to form a temporary sealing part 1340. Thereafter, the degassing part 137 is secondarily sealed to form a sealing part 1341, so that the temporary sealing part 1340 is preferably formed at a position adjacent to a corner part 1371 of the degassing part 137.

[0239] Then, an activation process may be performed. The activation process (formation process) is a process for finally completing charging so that the secondary battery 1 can supply power. The activation process is performed after forming the temporary sealing part 1340 and completely sealing the battery case 13, so that the charging rate is high, gas is quickly discharged, and the manufacture of the secondary battery 1 can be completed within a set process time.

[0240] When the activation process is completed, gas is generated inside the battery case 13. Therefore, degassing holes H are drilled in the degassing part 137 of the battery case 13. Gas is discharged from the inside of the battery case 13 to the outside through the degassing holes H. At this time, as the gas is easily discharged, the injected electrolyte may leak through the degassing holes H. To prevent this, it is preferable that the degassing holes H are drilled at a position close to the temporary sealing part 1340. After the degassing holes H are drilled, a degassing process is performed to discharge the gas to the outside of the battery case 13.

[0241] When the degassing hole H is drilled, the inside of the battery case 13 is opened again, and the electrolyte inside can leak out. Therefore, the boundary between the cup part 133 and the degassing part 137 is secondarily sealed to form a sealing part 1341. In this case, the sealing part 1341 is formed between the cup part 133 and the degassing hole H, and it is particularly preferable to form the sealing part 1341 at a position close to the cup part 133.

[0242] In this way, it is necessary to drill the degassing holes H and perform the primary and secondary sealing while performing the activation and degassing processes. Furthermore, when the secondary batteries 1 are mass-produced, it is necessary to centrally manage the specifications and quality of the secondary batteries 1. For this reason, the battery case 13 or the secondary battery 1 can be inspected using an inspection device 4 (shown in FIG. 22) including a vision sensor 41.

[0243] Conventionally, there has been a limit to how well the battery case 33 and secondary battery 3 can be manufactured to have a sharp overall shape. Therefore, when the battery case 33 is photographed with a vision sensor, there is a large error in the size and position of each component.

[0244] Specifically, after the secondary battery 1 is manufactured, the electrode leads 12 of the secondary batteries 1 can be connected to each other to manufacture a battery module 5 (shown in FIG. 27). For this purpose, the positions of the electrode leads 12 formed on the secondary batteries 1 must all be uniform. However, in the past, the electrode 101 was disposed at a certain distance from the outer wall 338 of the cup part 333, and therefore the electrode assembly 10 could move inside the cup part 333 before the side 134 was sealed. Therefore, when the secondary batteries 3 are mass-produced, even if the volumes of the cup part 333 and the electrode assembly 10 are all uniform, the positions of the electrode assemblies 10 differ slightly, and the positions of the electrode leads 12 also differ slightly. For this reason, it is necessary to accurately measure the positions of the electrode leads 12 using the inspection device 4.

[0245] In addition, in order to drill the degassing holes H at the correct position and size and to perform the primary sealing and secondary sealing at the correct position and size, it is necessary to accurately measure the position of the degassing portion 137. In addition, in order to efficiently manage the overall quality of a plurality of secondary batteries 1, it is necessary to accurately measure the positions of various components of the battery case 13 or secondary battery 1, such as the sides 134, the folding portion 139, and the insulating portion 14 protruding from the battery case 13, and even the width between the cup portions 133.

[0246] In order to measure the position of the structure, it is necessary to set a specific reference line and measure the vertical distance from the reference line to the structure to be measured. For example, when the electrode assembly 10 moves inside the cup portion 333, it generally moves in the left and right directions, i.e., toward the folding portion 339 and the degassing portion 337, based on the reference shown in FIG. 20. Therefore, in order to measure the position of the electrode lead 12, it is necessary to measure the position of the left or right corner of the electrode lead 12, and it is necessary to set a reference parallel to the left or right corner in order to measure the vertical distance to the left or right corner.

[0247] However, conventionally, the outer wall 338 of the cup portion 333 is not formed nearly vertically, and the radius of curvature R2' of the punch edge 361 of the cup portion 333 is also large, so when the battery case 33 is photographed by the vision sensor 41, the punch edge 361 of the cup portion 333 is not clearly shown in the image, as shown in Fig. 20. Therefore, it is not possible to measure the position of the above-mentioned configuration using the punch edge 361 of the cup portion 333 as a reference, and the butt ear 35 close to the punch edge 361 is set as a reference, or the punch edge 361 of the cup portion 333 is directly and manually set as a reference by the user.

[0248] However, because the butt ear 35 is formed by folding the bridge 136 while the peripheral side 134 of the cup portion 133 is also finely stretched overall, the size of the butt ear 35 varies slightly for each of the multiple secondary batteries 1. As a result, even if the position of the above components is measured using a vision sensor, the size of the reference butt ear 35 differs, so there is a large deviation in the position of the components between the secondary batteries 3, making quality control difficult.

[0249] In particular, even if the positions of the electrode leads 12 are measured by photographing the battery case 33 with a vision sensor, the positions of the electrode leads 12 vary slightly, making it difficult to connect the electrode leads 12 to manufacture a battery module 5. In addition, when stacking a plurality of secondary batteries 1 in order or aligning them in a row to manufacture a battery module 5, the position of the cup portion 333 is not accurate, resulting in a problem of poor alignment of the plurality of secondary batteries 1.

[0250] Furthermore, when manufacturing a battery module 5 by housing the secondary batteries 3 in a separate housing 51 (shown in FIG. 27), there is a problem in that the deviation in the measurement values ​​is large, so that the design tolerances are set unnecessarily large when designing the housing 51, resulting in a decrease in the energy density relative to the volume of the battery module 5.

[0251] FIG. 21 is a schematic diagram showing a state of a battery case 13 according to an embodiment of the present invention before the degassing portion 137 is cut, as viewed from above, and FIG. 22 is a block diagram of an inspection device 4 according to an embodiment of the present invention.

[0252] 21, by improving the formability of the pouch film 135, the thickness t of the bridge 136 can be made thinner, and the radius of curvature R2 and the clearance CL of the punch edge 1611 of the cup portion 133 can be made smaller, thereby reducing the size of the butt ear 15. Therefore, the secondary battery 1 can be easily assembled into the battery module 5, and the energy density per volume can be increased because the wasted volume of the secondary battery 1 is reduced.

[0253] 21, according to an embodiment of the present invention, the punch edge 1611 of the cup portion 133 is clearly shown in the image of the battery case 13, so that the inspection device 4 can automatically set the punch edge 161 of the cup portion 133 as the reference line ST, and can accurately measure the distance to various components of the battery case 13 or the secondary battery 1 based on the punch edge 161 of the cup portion 133, and can also accurately measure the width CW between the cup portions 133. As a result, the positions of the components of the battery case 13 or the secondary battery 1 can be accurately measured, reducing measurement errors and deviations between the secondary batteries 1.

[0254] To this end, the inspection device 4 for the battery case 13 or the secondary battery 1 according to one embodiment of the present invention includes a vision sensor 41 that photographs the battery case 13 and acquires an image of the battery case 13 or the secondary battery 1, an outline extraction unit 421 that extracts an outline of the configuration of the battery case 13 or the secondary battery 1 from the image, an image analysis unit 422 that analyzes the image and detects the outline corresponding to the punch edge 161 of the cup portion 133 in which an accommodating space 1331 for accommodating the electrode assembly 10 in the battery case 13 is provided, a reference line setting unit 423 that sets the outline corresponding to the punch edge 161 as a reference line ST, and a distance calculation unit 424 that calculates the distance from the reference line ST to the configuration.

[0255] In addition, a method for inspecting a battery case 13 or a secondary battery 1 according to an embodiment of the present invention using such an inspection device 4 includes a step in which a vision sensor 41 photographs the battery case 13 to obtain an image of the battery case 13 or the secondary battery 1, a step in which an outline extraction unit 421 extracts an outline of a configuration of the battery case 13 or the secondary battery 1 from the image, a step in which an image analysis unit 422 analyzes the image and detects the outline corresponding to a punch edge 161 of a cup portion 133 in which an accommodating space 1331 for accommodating an electrode assembly 10 is provided in the battery case 13, a step in which a reference line setting unit 423 sets the outline corresponding to the punch edge 161 as a reference line ST, and a step in which a distance calculation unit 424 calculates a distance from the reference line ST to the configuration.

[0256] Specifically, the inspection device 4 includes a vision sensor 41 and a control unit 42, as shown in FIG. 22. These components can be connected to each other and communicate with each other via a bus (not shown). All components included in the control unit 42 can be connected to the bus via at least one interface or adapter, or can be directly connected to the bus. The bus can also be connected to other subsystems in addition to the above-mentioned components. Such buses include a memory bus, a memory controller, a peripheral bus, and a local bus.

[0257] The vision sensor 41 captures an image by photographing a specific area and receiving an image signal for the specific area. For this purpose, the vision sensor 41 generally includes an imaging element such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) image sensor. In particular, the vision sensor 41 according to an embodiment of the present invention can capture an image of each component of the battery case 13 or the secondary battery 1 by photographing the battery case 13 after the bridge 136 of the battery case 13 is folded. Here, the components include the cup portion 133, the degassing portion 137, the electrode lead 12, the butt ear 15, the side 134, the folding portion 139, and the insulating portion 14 described above. Then, the degassing portion 137 is cut to complete the manufacture of the secondary battery 1. Therefore, when the vision sensor 41 photographs the battery case 13 before cutting the degassing portion 137, it can obtain images of the battery case 13 and the electrode leads 12, etc., and when the vision sensor 41 photographs the battery case 13 after cutting the degassing portion 137, it can obtain an image of the secondary battery 1.

[0258] The control unit 42 receives the image signal acquired by the vision sensor 41, and grasps the position of each component of the battery case 13 or the secondary battery 1 from the image signal. The control unit 42 includes an outline extraction unit 421, an image analysis unit 422, a reference line setting unit 423, and a distance calculation unit 424. It is preferable to use a CPU (Central Processing Unit), an MCU (Micro Controller Unit), or a DSP (Digital Signal Processor) as the control unit 42, but is not limited thereto, and various logical operation processors can be used.

[0259] The outline extraction unit 421 extracts the outline of each component of the battery case 13 or the secondary battery 1 from the image received from the vision sensor 41. In this case, the outline extraction unit 421 may extract the outline of all components shown in the image, but is not limited thereto, and may also set a region of interest (ROI) in a portion of the image and extract only the outline of the components shown within the ROI. To extract the outline, information about the pixels of the image is first extracted, and a commonly used gradient formula may be used for this purpose. The outline of the battery case 13 and the electrode lead 12 is shown by the extracted pixel information.

[0260] According to an embodiment of the present invention, the radius of curvature R2 and the clearance CL of the punch edge 161 of the cup part 133 can be made smaller, the outer wall 138 of the cup part 133 can be made nearly vertical, and the gradient of pixel information corresponding to the punch edge 161 of the cup part 133 in the image is large. Therefore, since the boundary between the outline and the background is clear, the outline corresponding to the punch edge 161 of the cup part 133 can be clearly extracted.

[0261] The image analysis unit 422 analyzes the image to detect an outline corresponding to the punch edge 161 of the cup part 133 from the battery case 13. To this end, the image analysis unit 422 can detect the outline corresponding to the punch edge 161 of the cup part 133 by matching pre-stored reference outline information of the punch edge 161 of the cup part 133 with the extracted outline information. At this time, the image analysis unit 422 can match the two pieces of information using a template matching technique.

[0262] The reference line setting unit 423 can set the outline corresponding to the punch edge 161 as the reference line ST. Since the cup portion 133 includes a plurality of punch edges 161, a plurality of outlines corresponding to the punch edges 161 are extracted. At this time, in order to accurately measure the position of each component of the battery case 13 or the secondary battery 1, it is preferable that the reference line setting unit 423 sets the outline corresponding to the punch edge 161 closest to the component to be measured among the plurality of punch edges 161 as the reference line ST. In addition, as described above, since the position of the component needs to be measured by measuring the vertical distance from the reference line ST, the reference line setting unit 423 can set the outline corresponding to the punch edge 161 parallel to the corner of the component to be measured among the plurality of punch edges 161 as the reference line ST.

[0263] For example, in order to drill the degassing hole H and perform the primary sealing and secondary sealing, the inspection device 4 needs to measure the position of the degassing unit 137. In such a case, the reference line setting unit 423 can set the outline corresponding to the punch edge 1612 on the die edge 162 side, which is close to the degassing unit 137 and parallel to the corner 1371 included in the degassing unit 137, among the multiple punch edges 161, as the reference line ST.

[0264] Also, for example, in order to inspect whether the positions of all the electrode leads 12 are constant, the inspection device 4 needs to measure the positions of the electrode leads 12. In such a case, the reference line setting unit 423 can also set, as the reference line ST, the outline of the electrode lead 12 side corresponding to the punch edge 1611 on the folding portion 139 side, which is close to the electrode lead 12 and parallel to the left or right corner of the electrode lead 12, among the multiple punch edges 161.

[0265] Furthermore, in order to measure the width between the cup portions 133, the reference line setting unit 423 can set the outline of any one of the outlines of two punch edges 161 that correspond to the boundary of the width of the cup portions 133 among the multiple punch edges 161 as the reference line ST.

[0266] That is, as long as the reference line setting unit 423 can accurately measure the position of each component of the battery case 13 or the secondary battery 1, it can set various outlines for the reference line ST without any limitations.

[0267] The distance calculation unit 424 calculates the distance from the reference line ST to each component of the battery case 13 or the secondary battery 1 in the image. For example, when an outline corresponding to the punch edge 1612 on the die edge 162 side is set as the reference line ST, the distance calculation unit 424 can calculate the distance from the reference line ST to a corner included in the degassing unit 137. Or, when an outline corresponding to the punch edge 1611 on the folding unit 139 side is set as the reference line ST, the distance calculation unit 424 can calculate the distance from the reference line ST to a corner on one side of the electrode lead 12, or can calculate the distance to the outline corresponding to the punch edge 1612 on the die edge 162 side.

[0268] The distance calculation unit 424 can use pre-stored information on the relationship between the number of pixels of the image and the actual distance. That is, the distance calculation unit 424 can count the distance from the reference line ST to each of the components in the image in terms of the number of pixels, and then calculate the actual distance corresponding to the counted number of pixels using pre-stored information on the relationship between the number of pixels of the image and the actual distance.

[0269] The inspection device 4 may further include a storage unit 44. The storage unit 44 stores programs for processing and controlling the operation of the inspection device 4, and various data generated during the execution of each program or received signals. In particular, reference information on the battery case 13 may be stored so that the image analysis unit 422 detects an outline corresponding to the punch edge 1611 of the cup part 133. Here, the reference information on the battery case 13 may include reference outline information on the punch edge 1611 of the cup part 133 and reference information on the distance to the components of the battery case 13 or the secondary battery 1. This may be directly stored in the storage unit 44 by a user, or the inspection device 4 may generate and store the reference information through repeated learning. In addition, the storage unit 44 may store information on the relationship between the number of pixels of the image and the actual distance so that the distance calculation unit 424 can calculate the actual distance from the reference line ST to each component. In addition, the storage unit 44 may store inspection result information of the battery case 13 to be inspected. The storage unit 44 may be built in the inspection device 4, or may be provided as a separate storage server. The storage unit 44 includes a non-volatile memory device and a volatile memory device. The non-volatile memory device can be a NAND flash memory that is small in volume, lightweight, and resistant to external shocks, and the volatile memory device can be a DDR SDRAM.

[0270] The control unit 42 may further include a defect determination unit 425 that determines whether the battery case 13 to be inspected is defective. Such a defect determination unit 425 may compare reference information on the battery case 13 stored in the storage unit 44 with inspection result information of the battery case 13 to be inspected. Furthermore, if the inspection result information is within the error range of the reference information, the battery case 13 is determined to be normal. However, if the inspection result information deviates from the error range of the reference information, the battery case 13 is determined to be defective.

[0271] Meanwhile, the inspection device 4 may further include a display unit 43 that receives an image signal and displays it. The display unit 43 receives the image signal and displays it to a user. Furthermore, when the outline extraction unit 421 extracts the outline of the battery case 13, the outline is displayed on the image so that the user can check it through the display unit 43. The display unit 43 may use various methods such as a liquid crystal display (LCD), an organic liquid crystal display (OLED), a cathode ray tube (CRT), a plasma display panel (PDP), etc. Also, the display unit 43 is connected to a bus via a video interface, and data transmission between the display unit 43 and the bus may be controlled by a graphic controller.

[0272] The inspection device 4 may further include an alarm unit 45 that generates an alarm when the defect determination unit 425 determines that the battery case 13 is defective. When an alarm is generated, it is preferable that the alarm is generated audibly or visually, such as by lighting a lamp or by an alarm sound, so that the user can intuitively know the alarm.

[0273] The above-mentioned components of the vision sensor 41, the control unit 42, the storage unit 44, and the display unit 43 can be realized by software such as a task, class, subroutine, process, object, execution thread, or program executed in a predetermined area on the memory, or by hardware such as an FPGA (field-programmable gate array) or an ASIC (application-specific integrated circuit), or can be a combination of the above software and hardware. The above components can be included in a computer-readable storage medium, or can be distributed in parts across multiple computers.

[0274] Also, each block may represent a module, segment, or portion of code that includes one or more executable instructions for performing a particular logical function. Also, in some alternative implementations, the functions described in the blocks may occur out of sequence. For example, two blocks shown in succession may in fact be performed substantially simultaneously, or the blocks may sometimes be performed in reverse order depending on the functions involved.

[0275] When the inspection device 4 according to the embodiment of the present invention is used, the punch edge 1611 of the cup portion 133 is clearly displayed, so that the inspection device 4 can automatically set the punch edge 161 of the cup portion 133 to the reference line ST, and the distance to each component of the battery case 13 can be accurately measured based on the punch edge 1611 of the cup portion 133. For example, the size and position of the degassing portion 137 can be measured, and even after the production of the secondary battery 1 is completed, the size and position of the cup portion 133, the electrode lead 12, the butt ear 15, the side 134, the folding portion 139, the insulating portion 14, etc. can be accurately grasped. This makes it easy to determine whether the secondary battery 1 is defective, and even if the secondary batteries 1 are mass-produced, the specifications and quality of the batteries can be efficiently and collectively managed.

[0276] In particular, the positions of the electrode leads 12 can be accurately measured, and the electrode leads 12 can be easily connected when manufacturing the battery module 5. In addition, the position of the cup portion 333 can be accurately measured, and the alignment of the multiple secondary batteries 1 can be improved when stacking the multiple secondary batteries 1 in order or aligning them in a row to manufacture the battery module 5.

[0277] FIG. 23 is a schematic diagram showing a state in which the degassing portion 137 of the battery case 13 according to one embodiment of the present invention has been cut to complete the manufacture of the secondary battery 1. As shown in FIG.

[0278] After the battery case 13 is secondarily sealed to form the sealing part 1341, a cutting line CT is set on the outside of the sealing part 1341 to cut the degassing part 137. As a result, as shown in Fig. 23, the length of the degassing part 137 is shortened, and the volume of the secondary battery 1 can be reduced. Through the above process, the manufacture of the pouch-type secondary battery 1 is completed.

[0279] Meanwhile, the side 134 remaining after the degassing portion 137 is cut does not have the electrode lead 12 protruding from it among the multiple sides 134. However, if the side 134 is left as it is after being sealed, the overall volume of the secondary battery 1 increases. Therefore, it is preferable to fold the side 134 in order to reduce the energy density relative to the volume.

[0280] Meanwhile, side 134 may include a sealed portion 1341 and an unsealed portion 1342, as shown in Fig. 23. Sealed portion 1341 is a relatively outer area that is sealed, and unsealed portion 1342 is a relatively inner area that is not sealed.

[0281] Specifically, when the battery case 13 is secondarily sealed to form the sealing part 1341, the sealing part 1341 may be formed to be separated to a certain extent from the cup part 133, rather than being directly connected thereto. When sealing the side 134, it is necessary to apply heat and pressure to the side 134 using a separate sealing tool (not shown). However, when the side 134 is sealed with the sealing tool in close contact with the cup part 133, the sealant layer 1351 located inside the side 134 may be partially melted and leak toward the electrode assembly 10, thereby contaminating the electrode assembly 10. In addition, the heat of the sealing tool may be transferred to the electrode assembly 10, damaging the electrode assembly 10. Therefore, it is preferable to seal the side 134 with the sealing tool separated to a certain extent from the cup part 133. As a result, the part sealed by the sealing tool becomes the sealed part 1341, and the part not sealed because the sealing tool is separated from the cup part 133 becomes the unsealed part 1342.

[0282] FIG. 24 is a schematic diagram showing a conventional side panel 334 after folding, as viewed from the side, and FIG. 25 is a schematic diagram showing a conventional side panel 334 after folding, as viewed from above.

[0283] Conventionally, when the side 334 is folded, the side 334 is not fixed and is unfolded again at a predetermined angle. Specifically, as described above, the pouch film 135 is formed by laminating the sealant layer 1351, the moisture barrier layer 1352, the stretching auxiliary layer 1354, and the surface protection layer 1353. Among them, the sealant layer 1351 contains a first polymer, particularly polypropylene (PP), and therefore has high flexibility and elasticity. Therefore, when the side 134 is folded, the restoring force to return to the original state is large. On the other hand, since the moisture barrier layer 1352 is made of metal, particularly aluminum alloy, when the side 334 is folded, the restoring force to maintain the folded state exceeds the limit of elastic deformation and is large.

[0284] However, in the conventional pouch film, the moisture barrier layer has a thickness of about 30 to 50 μm, and the sealant layer has a thickness of about 60 to 100 μm. That is, the moisture barrier layer is formed to be considerably thinner than the sealant layer. Therefore, the restoring force is greater than the preserving force, and the side 334 is not fixed and is unfolded again at a predetermined angle. Therefore, there is a problem that the side 334 increases the volume of the secondary battery 3 unnecessarily.

[0285] To solve this problem, a separate tape 38 is attached to the side 334 as shown in Figures 24 and 25. In particular, the tape 38 is attached to both the outer surface of the bottom 3332 of the cup part 333 and the side 334, thereby fixing the side 334 to the cup part 333 and preventing it from being unfolded. However, in this case, as shown in Figure 24, there is a problem that the overall thickness of the secondary battery 3 increases due to the thickness of the tape 38 itself. In addition, an additional process of attaching the tape 38 is required after the process of folding the side 334, which takes a lot of time and increases the number of processes, resulting in a problem of reducing the manufacturing yield of the secondary battery 3.

[0286] Meanwhile, when the degassing process is performed, gas is discharged from the inside of the battery case 13 to the outside, and the internal pressure of the cup part 133 is reduced. Conventionally, the electrode assembly 10 is disposed at a certain distance from the outer wall 338 of the cup part 333. Therefore, as the internal pressure of the cup part 333 is reduced, the volume of the space 37 between the outer wall 338 of the cup part 333 and the electrode assembly 10 is also reduced, and the outer wall 338 or the bottom part 3332 of the cup part 333 may be deformed. In particular, as shown in FIG. 24, an edge high phenomenon may occur in which the outer wall 338 on the folding part side of the secondary battery 3 is recessed inward and the punch edge 361 on the folding part 339 side of the cup part 333 protrudes outward and becomes high. This edge high phenomenon increases the unnecessary thickness of the secondary battery 3, resulting in a problem of a decrease in energy density relative to the volume. In addition, the outer wall 338 on the folding part 339 side of the cup part 333 is deformed, which causes a problem that the appearance of the secondary battery 3 is not beautiful and the marketability is reduced. Furthermore, there is also a problem that the size of the butt ear 15 is further increased due to the edge-high phenomenon, which emphasizes the shape.

[0287] FIG. 26 is a schematic side view of the side 134 folded according to one embodiment of the present invention.

[0288] According to one embodiment of the present invention, the pouch film 135 has a moisture barrier layer 1352 having a thickness of 50 to 70 μm and the sealant layer 1351 having a thickness of 70 to 100 μm, so that the moisture barrier layer 1352 is thicker than in the past. Therefore, when the side 134 is folded, the preservative strength is increased, so there is no need to attach a separate tape 38, and the side 134 can be prevented from being unfolded again.

[0289] To this end, a secondary battery 1 according to one embodiment of the present invention includes an electrode assembly 10 formed by stacking an electrode 101 and a separator 102, and a pouch-type battery case 13 formed with a cup portion 133 for accommodating the electrode assembly 10 therein, the pouch-type battery case 13 including a side 134 extended outward from the cup portion 133, the side 134 including a sealing portion 1344 located relatively outwardly and sealed, and an unsealed portion 1345 located relatively inwardly and not sealed, and is not attached to the cup portion 133 and is folded at the unsealed portion 1345.

[0290] That is, as shown in FIG. 26, after the side 134 of the secondary battery 1 is folded toward the cup part 133, the side 134 may not be attached to the cup part 133 and may maintain the folded state and not be unfolded. In this case, the side 134 may be folded at an angle of 85° to 95°, particularly at an angle of 88° to 92°. Also, the side 134 may be folded at a position adjacent to the cup part 133, and the side 134 may contact the outer wall 138 of the cup part 133. In particular, as described above, the side 134 may include a sealing part 1341 that is disposed relatively outward and sealed, and an unsealed part 1342 that is disposed relatively inward and not sealed. Also, when the side 134 is folded, it is preferable that the unsealed part 1342 that is relatively closer to the cup part 133 is folded. This can further reduce the wasted volume of the secondary battery 1. However, even in this case, the side 134 and the cup part 133 are not adhered to each other, and the retention force of the side 134 increases to maintain the folded state.

[0291] When two cup portions 133 are formed in the pouch film 135, the depth D of the cup portion 133 can be made shallower than when one cup portion 133 is formed. As described above, this is because not only the cup portion 133 is stretched in a concentrated manner, but the peripheral side 134 of the cup portion 133 is also finely stretched overall. However, if the width of the side 134 is longer than the depth D of the cup portion 133, the outer end 1343 of the side 134 may protrude outward beyond the bottom 1332 of the cup portion 133 when the side 134 is folded only once.

[0292] Therefore, when two cup portions 133 are formed in the pouch film 135, a double side folding (DSF) method can be used in which the side 134 is folded twice as shown in Fig. 26. Specifically, the side 134 can include a first folding portion 1344 and a second folding portion 1345. The first folding portion 1344 is a portion folded relatively closer to the outer end portion 1343, and the second folding portion 1345 is a portion folded relatively closer to the cup portion 133. Therefore, the side 134 can be primarily folded based on the first folding portion 1344, and then the side 134 can be secondarily folded based on the second folding portion 1345. In this case, the first folding part 1344 may be located at the sealed part 1341 of the side 134, and the second folding part 1345 may be located at the unsealed part 1342 of the side 134. Also, the side 134 may be folded at an angle of 170° to 180°, particularly at an angle of 180°, at the first folding part 1344. Also, the side 134 may be folded at an angle of 85° to 95°, particularly at an angle of 88° to 92°, at the second folding part 1345. This prevents the outer end 1343 of the side 134 from protruding outward beyond the bottom 1332 of the cup part 133.

[0293] Meanwhile, according to an embodiment of the present invention, the electrode assembly 10 can be positioned very close to the outer wall 138 of the cup part 133, thereby reducing the wasted volume of the cup part 133. Therefore, even if the internal pressure of the cup part 133 is reduced by performing a degassing process, the outer wall 138 or the bottom part 1332 of the cup part 133 can be prevented from being deformed. That is, as shown in Fig. 26, the edge-high phenomenon can be prevented from occurring, and therefore the energy density relative to the volume can be prevented from decreasing.

[0294] FIG. 27 is a schematic diagram of a battery module 5 according to one embodiment of the present invention.

[0295] Medium to large electronic devices such as automobiles require large output, and therefore require a large number of secondary batteries 1. A battery module 5 can be manufactured to easily move and install such secondary batteries 1. When multiple secondary batteries 1 are installed in such a battery module 5, electricity can be stably supplied to the outside.

[0296] Meanwhile, as electricity is produced in the electrode assembly 10 of the secondary battery 1, a chemical reaction occurs between the electrodes 101 and the electrolyte, generating heat in the process. However, if the surrounding temperature rises excessively due to the heat, there is a problem that the circuit of the electrical device in which the secondary battery 1 is installed may malfunction or the life of the electrical device may be shortened. Therefore, the battery module 5 includes a cooling system for cooling the secondary battery 1. Cooling systems are broadly divided into a water-cooling type that uses cooling water for cooling and an air-cooling type that uses air for cooling. Of these, the water-cooling type cooling system has a higher cooling efficiency than the air-cooling type cooling system and is therefore more widely used.

[0297] The cooling system includes a cooling plate that directly cools the secondary battery 1, and a separate flow path is formed inside the cooling plate to allow the coolant to flow. In addition, the thinner and longer the flow path is, the larger the surface area is, and the greater the cooling efficiency can be.

[0298] To manufacture the battery module 5, first, a plurality of secondary batteries 1 are manufactured, and then the secondary batteries 1 are connected to each other and housed in a housing 51. At this time, the secondary batteries 1 may be aligned in a row and stacked. As shown in Fig. 27, when the secondary batteries 1 are housed in the housing 51, the longer side of the secondary batteries 1 faces downward, and a cooling plate (not shown) may be formed on the lower surface of the housing 51. Therefore, the cooling plate cools the longer side of the secondary batteries 1, thereby increasing the cooling efficiency.

[0299] Meanwhile, a folding part 139 formed by folding the bridge 136 is formed on one side of the secondary battery 1, and a side 134 is formed on the other side, which is an area remaining after the degassing part 137 is cut off. However, if the cooling plate cools the side where the side 134 is formed among the multiple sides of the secondary battery 1, the cooling efficiency may decrease because the side 134 increases the distance between the cooling plate and the electrode assembly 10. Therefore, it is preferable that the cooling plate cools the side where the folding part 139 is formed among the long sides of the secondary battery 1. For this reason, when the secondary battery 1 is stored in the housing 51, the folding part 139 may be stored in a direction toward the cooling plate, i.e., downward.

[0300] FIG. 28 is an enlarged front view showing a conventional secondary battery 3 housed in a housing 51 of a battery module 5, and FIG. 29 is an enlarged side view showing a conventional secondary battery 3 housed in a housing 51 of a battery module 5.

[0301] As described above, conventionally, there has been a limit to reducing the size of the butt ear 35. In particular, there has been a limit to reducing the size of the butt ear 35 to a predetermined value (e.g., 1.5 mm) or less while forming the depth D' of the cup portion 333 sufficiently deep (e.g., 6.5 mm or more).

[0302] Furthermore, conventionally, the angle θ′ between the folding portion 339 and the inner corner 35a of the butt ear 35 is set to 151 degrees or less.

[0303] Here, the angle θ′ may refer to an angle formed by a virtual first line L1 corresponding to the folding portion 339 and a virtual second line L2 corresponding to the inner corner 35a of the butt ear 35. In particular, the first line L1 and the second line L2 may be determined by image analysis. As an example, the first line L1 and the second line L2 may be extracted by connecting a number of edge points identified within a region of interest (ROI) by a vision device. Therefore, even if the folding portion 339 or the inner corner 35a of the butt ear 35 is partially warped or bent, the first line L1 and the second line L2 may be clearly defined. Such image analysis is a well-known technique, and a detailed description thereof will be omitted.

[0304] 28, when the secondary battery 3 is housed in the housing 51, the butt ear 35 separates the housing 51 and the folding part 339 by a large distance d' (for example, more than 1.5 mm). This distance d' may hinder the cooling of the cooling plate, resulting in a decrease in cooling efficiency. To solve this problem, a heat transfer material 52 is injected into the space between the cooling plate and the folding part 339 of the secondary battery 1, so that the cooling plate cools the folding part 139 through the heat transfer material 52. For example, the heat transfer material 52 may be thermal grease.

[0305] However, if the butt ear 15 is large, a large amount of the heat transfer material 52 must be injected, which increases the cost, and the cooling efficiency remains low because the distance d' between the cooling plate and the folding portion 139 is large.

[0306] Also, when a degassing process is performed through the degassing hole H, the internal pressure of the battery case 33 is reduced, and the folding part 339 of the battery case 33 is in close contact with the electrode assembly 10, as shown in FIG. 29. However, in the past, there was a limit to how much the clearance CL' could be reduced, and the width of the folding part 339 was also large. Therefore, the space 37 between the outer wall 338 of the cup part 333 and the electrode assembly 10 is large, which causes a problem of a reduction in the energy density relative to the volume of the secondary battery 3. Furthermore, the distance between the electrode assembly 10 and the thermal grease 52 is also increased, which causes a problem of a lower cooling efficiency.

[0307] Figure 30 is an enlarged front view showing a secondary battery 1 according to one embodiment of the present invention housed in a housing 51 of a battery module 5, and Figure 31 is an enlarged side view showing a secondary battery 1 according to one embodiment of the present invention housed in a housing 51 of a battery module 5.

[0308] A pouch-type secondary battery 1 according to one embodiment of the present invention includes an electrode assembly 10 formed by stacking an electrode 101 and a separator 102, and a pouch-type battery case 13 formed with a cup portion 133 for accommodating the electrode assembly 10 therein, the battery case 13 including a first case 131 and a second case 132 with the cup portion 133 formed on at least one of them, a folding portion 139 that integrally connects the first case 131 and the second case 132, and butt ears 15 formed to protrude outward from portions of both ends of the folding portion 139, the butt ears 15 having a length D of 1.5 mm or less.

[0309] In addition, the angle θ between the folding portion 139 and the inner corner 15a of the butt ear 15 may be greater than 151 degrees. Also, the angle θ may be less than 180 degrees. If the angle θ is 180 degrees, it may indicate that the butt ear 15 does not exist.

[0310] Here, the angle θ may refer to an angle formed by a virtual first line L1 corresponding to the folding portion 139 and a virtual second line L2 corresponding to an inner corner 15a of the butt ear 15. The first line L1 and the second line L2 are described above by reference. In addition, a battery module 5 according to an embodiment of the present invention includes a pouch-type secondary battery 1 in which an electrode assembly 10 formed by stacking an electrode 101 and a separator 102 is housed inside a cup portion 133 formed in a pouch-type battery case 13, and a housing 51 in which the secondary battery 1 is housed, and the battery case 13 includes a first case 131 and a second case 132 in which the cup portion 133 is formed, a folding portion 139 that integrally connects the first case 131 and the second case 132, and butt ears 15 formed to protrude outward from both ends of the folding portion 139, and the butt ears 15 have a length D of 1.5 mm or less.

[0311] As described above, the butt ear 15 is formed by folding the bridge 136 and protruding outward from a part of both ends of the folding portion 139. According to an embodiment of the present invention, the length of the butt ear 15 may be 1.5 mm or less, particularly 1 mm or less. The length of the butt ear 15 may be measured from the outer wall 1381 on the folding portion 139 side to the outermost end of the butt ear 15. In this case, as described above, the outer wall 1381 on the folding portion 139 side may have an inclination angle of 90° to 95° from the bottom 1332 due to the clearance CL. In consideration of this, as an example of the measurement of the butt ear, the length of the butt ear 15 may be measured from the outermost protruding part of the outer wall 1381 on the folding portion 139 side to the outermost end of the butt ear 15.

[0312] The length of the butt ear 15 can be measured by directly contacting the secondary battery 1 using a ruler or calipers, or can be measured in a non-contact manner using a laser displacement sensor or a vision sensor.

[0313] The above is an example of a method for measuring the length of the bat ear, and the scope of the present invention is not necessarily limited to the above-mentioned measurement method. Any bat ear length that falls within the scope of the present invention may be the bat ear length as defined in the claims.

[0314] According to one embodiment of the present invention, the formability of the pouch film 135 is improved, so that the thickness t of the bridge 136 can be made thinner, and the radius of curvature R2 and the clearance CL of the punch edge 1611 of the cup portion 133 can be made smaller.

[0315] As a result, the depth D of the cup portion 133 can be formed to 3 mm or more, particularly 6.5 mm or more, while the length D of the butt ear 15 can be further reduced to 1.5 mm or less, particularly 1 mm or less. Therefore, as shown in Fig. 30, the distance d between the housing 51 and the folding portion 139 can be narrowed to 1.5 mm or less. As a result, the thickness of the heat transfer material 52 inside the housing 51 can be 1.5 mm or less, and the amount of thermal grease 52 injected can be further reduced, thereby reducing costs and increasing cooling efficiency.

[0316] 31, the clearance CL can be made smaller, and the width FW of the folding portion 139 can also be made smaller. Therefore, the space 17 between the outer wall 138 of the cup portion 133 and the electrode assembly 10 is reduced, and the energy density per volume of the secondary battery 1 can be increased. In addition, the distance between the electrode assembly 10 and the thermal grease 52 is reduced, and thus the cooling efficiency can be improved.

[0317] Those skilled in the art will understand that the present invention may be embodied in other specific forms without changing the technical concept 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 set forth below rather than the above detailed description, and various embodiments derived from the meaning and scope of the claims or their equivalents should be interpreted as being included in the scope of the present invention. [Explanation of symbols]

[0318] 1 Secondary battery 2 Molding equipment 3. Conventional secondary batteries 4. Inspection Equipment 5 Battery Module 10 Electrode assembly 11 Electrode tab 12 Electrode Lead 13 Battery case 14 Insulation 15 Bad Year 16 Edge 17 Space 21 Die 22 Punch 33 Conventional battery case 35 Traditional Bat Ear 36 Traditional Edge 37 Traditional Space 38 Conventional Tape 41 Vision Sensor 42 Control section 43 Display section 44 Storage area 45 Alarm section 51 Housing 52 Thermal grease 101 Electrode 102 Separator 111 Positive tab 112 Negative electrode tab 121 Positive lead 122 Negative lead 131 Case 1 132 Case 2 133 Cup section 134 Side 135 Pouch Film 136 Bridge 137 Degassing Department 138 Exterior Wall 139 Folding Section 161 Punch Edge 162 Die Edge 163 Thickness Edge 164 Corners 211 Molding section 212 Bulkhead 213 Die Edge 221 Punch Edge 333 Conventional cup section 334 Conventional Side 336 Traditional Bridge 337 Conventional degassing section 338 Conventional exterior wall 339 Conventional folding section 361 Conventional punch edge 362 Conventional die edge 421 Outline Extraction 422 Video Analysis Department 423 Reference Line Setting Unit 424 Distance calculation section 425 Defective Judgment Department 1021 Periphery 1331 Containment Space 1332 Bottom 1333 Exterior wall 1340 Temporary Sealing Section 1341 Sealing part 1342 Unsealed part 1343 Outer edge 1344 First Folding Section 1345 2nd Folding Section 1351 Sealant Layer 1352 Moisture barrier layer 1353 Surface protective layer 1354 Stretched auxiliary layer 1371 Corner 1381 Bridge side exterior wall 1382 Outer wall of the degassing section 1391 Groove 1611 Bridge side punch edge 1612 Punch edge on the degassing side 1613 First punch edge 1614 2nd punch edge

Claims

1. a first case and a second case each having a cup portion for accommodating an electrode assembly formed by stacking electrodes and a separator; a bridge formed between the two cup portions; The bridge has a thickness of 2 mm or less; the thickness of the bridge is the distance between two bridge perpendicular lines that pass through the boundary points of the bridge and the outer wall on the bridge side and are perpendicular to the bottom, and is 1 / 200 to 1 / 30 of the width of the electrode assembly; The cup portion has a depth of 6.5 mm or more, The cup portion includes a plurality of punch edges each connecting a bottom portion and a plurality of outer walls surrounding the periphery, the punch edges being formed by rounding, The radius of curvature of the punch edge is 1 / 20 to 1 / 6 of the depth of the cup portion, The cup portion further includes a plurality of die edges formed by rounding, the die edges connecting the outer wall and the side or degassing portion, The radius of curvature of the die edge is 1 / 20 to 1 / 6 of the depth of the cup portion, A vertical distance between a die edge vertical line passing through a boundary point between the die edge and the outer wall on the die edge side and perpendicular to the bottom, and an edge vertical line passing through a boundary point between the punch edge on the die edge side and the outer wall on the die edge side and perpendicular to the bottom is 0.5 mm or less; It is manufactured by forming a pouch film, The pouch film is a sealant layer formed as an innermost layer and made of a first polymer; a surface protective layer formed as an outermost layer using a second polymer; a moisture barrier layer laminated between the surface protective layer and the sealant layer, The moisture barrier layer is formed of an aluminum alloy thin film having a thickness of 50 to 80 μm and a grain size of 10 to 13 μm; The sealant layer has a thickness of 60 to 100 μm; The pouch-type battery case, wherein the surface protective layer has a thickness of 5 μm to 25 μm.

2. The bridge is 2. The pouch-type battery case according to claim 1, having a thickness of 1.4 mm or less.

3. The bridge is 3. The pouch-type battery case according to claim 1, which is formed by rounding with a radius of curvature of 1 mm or less.

4. The bridge is 4. The pouch-type battery case according to claim 1, which is formed by rounding with a curvature radius of 0.7 mm or less.

5. The cup portion is Further comprising a thickness edge connecting two adjacent outer walls to each other, The thickness edge is The pouch-type battery case according to claim 1 , wherein two adjacent punch edges are connected to each other to form a corner.

6. The corner is At least one of them is formed by rounding, The pouch-type battery case according to claim 5 , wherein the radius of curvature is equal to or greater than the radius of curvature of at least one of the punch edge and the thickness edge.

7. The die edge is 7. The pouch-type battery case according to claim 1, wherein at least one of the pouches is rounded with a curvature radius of 1 mm or less.

8. The die edge is 8. The pouch-type battery case according to claim 1, wherein at least one of the pouches is rounded with a radius of curvature of 0.7 mm or less.

9. The outer wall of the cup portion is 9. The pouch-type battery case according to claim 1, wherein the bottom of the cup portion is inclined at an angle of 90° to 95°.

10. The aluminum alloy thin film is 10. The pouch-type battery case according to claim 1, wherein the alloy is alloy number AA8021.

11. The aluminum alloy thin film is 11. The pouch-type battery case according to claim 1, containing 1.3 wt % to 1.7 wt % iron and 0.2 wt % or less silicon.

12. The moisture barrier layer is The thickness is 55 to 65 μm, The sealant layer comprises: The pouch-type battery case according to any one of claims 1 to 11, having a thickness of 75 to 85 µm.

13. The pouch-type battery case according to claim 1 , further comprising an extension assist layer made of a third polymer and laminated between the surface protection layer and the moisture barrier layer.

14. The stretching auxiliary layer is The pouch-type battery case according to claim 13, having a thickness of 20 to 50 μm.

15. a first case and a second case each having a cup portion for accommodating an electrode assembly formed by stacking electrodes and a separator; a bridge formed between the two cup portions; the bridge has a thickness of 1 / 200 to 1 / 30 of the width of the electrode assembly; The thickness of the bridge is the distance between two bridge perpendicular lines that pass through the boundary points of the bridge and the outer wall on the bridge side and are perpendicular to the bottom, The cup portion has a depth of 6.5 mm or more, The cup portion includes a plurality of punch edges each connecting a bottom portion and a plurality of outer walls surrounding the periphery, the punch edges being formed by rounding, The radius of curvature of the punch edge is 1 / 20 to 1 / 6 of the depth of the cup portion, The cup portion further includes a plurality of die edges formed by rounding, the die edges connecting the outer wall and the side or degassing portion, The radius of curvature of the die edge is 1 / 20 to 1 / 6 of the depth of the cup portion, A vertical distance between a die edge vertical line passing through a boundary point between the die edge and the outer wall on the die edge side and perpendicular to the bottom, and an edge vertical line passing through a boundary point between the punch edge on the die edge side and the outer wall on the die edge side and perpendicular to the bottom is 0.5 mm or less; It is manufactured by forming a pouch film, The pouch film is a sealant layer formed as an innermost layer and made of a first polymer; a surface protective layer formed as an outermost layer using a second polymer; a moisture barrier layer laminated between the surface protective layer and the sealant layer, The moisture barrier layer is formed of an aluminum alloy thin film having a thickness of 50 to 80 μm and a grain size of 10 to 13 μm; The sealant layer has a thickness of 60 to 100 μm; The pouch-type battery case, wherein the surface protective layer has a thickness of 5 μm to 25 μm.

Images