Pouch-type secondary battery

Abstract

To provide a pouch-type secondary battery in which, even when a side is folded, the side and a cup part are not bonded to each other, and retention force of the side is increased to maintain a folded state.SOLUTION: A pouch-type secondary battery according to an embodiment of the present invention for solving the above problem includes: an electrode assembly in which electrodes and separators are stacked; and a pouch-type battery case comprising a cup part configured to accommodate the electrode assembly therein. The pouch-type battery case includes a side extendedly formed outside the cup part. The side includes: a sealing part disposed at a relatively outside and is sealed; and a non-sealing part disposed at a relatively inside and is not sealed. The side is not bonded to the cup part and is folded at the non-sealing part.SELECTED DRAWING: Figure 24

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0104225 filed on August 19, 2020, and Korean Patent Application No. 10-2021-0074474 filed on June 8, 2021, and all the contents disclosed in the documents of the Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a pouch-type secondary battery, and more particularly, to a pouch-type secondary battery in which, even when the side is folded, the side and the cup portion are not adhered to each other, the storage power of the side is increased, and the folded state is maintained.

Background Art

[0003] Generally, types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. Such secondary batteries are used not only in small products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also in large products that require high power such as electric vehicles and hybrid vehicles, as well as power storage devices for storing surplus generated power and new renewable energy and backup power storage devices.

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

[0005] Secondary batteries can be classified into pouch type and can type, etc., according to 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. Also, the can type houses the electrode assembly in a case made of a material such as metal or plastic.

[0006] The pouch, which is the case of the pouch type secondary battery, is manufactured by subjecting a flexible pouch film to press working to form a cup portion. Also, when the cup portion is formed, the electrode assembly is housed in the accommodation space of the cup portion, and the sides are sealed to manufacture the secondary battery.

[0007] Among such press working, drawing forming 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 a plurality of layers, and among them, the moisture barrier layer located inside is made of metal. However, conventionally, the metal of such a moisture barrier layer had a large crystal grain size in the aluminum alloy, and the thickness of the moisture barrier layer was formed thin. Therefore, when the sides were folded to reduce the energy density per volume, the sides were not fixed and unfolded at a predetermined angle. For this reason, when a tape was attached to the sides separately, there was a problem that the total thickness of the secondary battery increased due to the thickness of the tape itself. Also, after the process of folding the sides, an additional process of attaching a tape was required, which increased the number of processes and also had a problem of reducing the manufacturing yield of the secondary battery.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The problem to be solved by the present invention is to provide a pouch-type secondary battery in which even when the side is folded, the side and the cup portion are not adhered to each other, the storage power of the side is increased, and the folded state is maintained.

[0010] The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

Means for Solving the Problems

[0011] A pouch-type secondary battery according to an embodiment of the present invention for solving the above problems includes an electrode assembly formed by laminating electrodes and separators, and a pouch-type battery case in which a cup portion for accommodating the electrode assembly therein is formed. The pouch-type battery case includes a side extending outside the cup portion. The side includes a sealing portion that is relatively located outside and sealed, and an unsealed portion that is relatively located inside and not sealed. The side is not adhered to the cup portion and is folded at the unsealed portion.

[0012] Further, the side can be folded while contacting the outer wall of the cup portion.

[0013] Further, the side can be folded at an angle of 85° to 95°.

[0014] Further, the side can include a first folding portion folded at a position closer to the relatively outer end portion and a second folding portion folded at a position closer to the cup portion.

[0015] Further, the first folding portion can be located at the sealing portion, and the second folding portion can be located at the unsealed portion.

[0016] Further, the side can be folded at an angle of 170° to 180° with respect to the first folding portion.

[0017] Further, the side can be folded at an angle of 85° to 95° with respect to the second folding portion.

[0018] Further, the side can be folded at an angle of 88° to 92° with respect to the second folding portion.

[0019] Further, the pouch-type battery case is manufactured by molding a pouch film. The pouch film includes a sealant layer formed as the innermost layer and manufactured from a first polymer, a surface protection layer formed as the outermost layer and manufactured from a second polymer, and a moisture barrier layer laminated between the surface protection 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 crystal grain size of 10 to 13 μm, and the sealant layer can have a thickness of 60 to 100 μm.

[0020] Further, the aluminum alloy thin film can be alloy number AA8021.

[0021] Further, the aluminum alloy thin film can contain 1.3 wt% to 1.7 wt% of iron and 0.2 wt% or less of silicon.

[0022] Further, the moisture barrier layer can have a thickness of 55 to 65 μm, and the sealant layer can have a thickness of 75 to 85 μm.

[0023] Further, it can further include a stretching auxiliary layer manufactured from a third polymer and laminated between the surface protection layer and the moisture barrier layer.

[0024] Further, the stretching auxiliary layer can have a thickness of 20 to 50 μm.

[0025] In addition, the area of the electrode assembly can be 15000 mm 2 ~ 100000 mm 2 .

[0026] Other specific matters of the present invention are included in the detailed description and the drawings. [Effect of the Invention]

[0027] According to the embodiments of the present invention, there are at least the following effects.

[0028] Even when the side is folded, the side is not adhered to the cup portion, and the storage force of the side is increased, so that the folded state can be maintained.

[0029] In addition, when the side is folded toward the cup portion, the folding can be maintained at an angle of 85° to 95°, preferably 88° to 92°, thereby reducing the wasted volume of the secondary battery.

[0030] The effects according to the present invention are not limited to the contents exemplified above, and more various effects are included in this specification. [Brief Description of the Drawings]

[0031]

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Embodiments for Carrying Out the Invention

[0032] The advantages and features of the present invention, and the method for achieving them, will become clear by referring to the embodiments described in detail hereinafter together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be realized in various different forms. Further, the present embodiment is provided to complete the disclosure of the present invention and to fully inform those having ordinary knowledge in the technical field to which the present invention pertains of the scope of the invention, and the present invention is only defined by the scope of the claims. The same reference numerals throughout the specification refer to the same components.

[0033] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification can be used in the meaning commonly understood by those having ordinary knowledge in the technical field to which the present invention pertains. Also, terms defined in commonly used dictionaries are not ideally or excessively interpreted unless specifically defined otherwise.

[0034] The terms used in this specification are for explaining the embodiments and do not limit the present invention. In this specification, the singular form includes the plural form unless specifically mentioned in a clause. The “comprises” and / or “comprising” used in the specification do not exclude the presence or addition of one or more other components in addition to the mentioned components.

[0035] Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

[0036] FIG. 1 is an assembly view of a secondary battery 1 according to an embodiment of the present invention.

[0037] According to an embodiment of the present invention, by improving the tensile strength and elongation rate of the pouch film 135, the toughness increases, and when the pouch film 135 is formed to manufacture the pouch-type battery case 13, the formability can be improved.

[0038] For this purpose, the pouch film 135 according to an embodiment of the present invention is made of a first polymer and has a sealant layer 1351 (shown in FIG. 2) formed on the innermost layer, a surface protection layer 1353 (shown in FIG. 2) made of a second polymer and formed on the outermost layer, and a moisture (or gas) barrier layer 1352 (shown in FIG. 2) laminated between the surface protection layer 1353 and the sealant layer 1351. 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 can have a thickness of 60 to 100 μm. In particular, it is preferable that the moisture barrier layer 1352 has a thickness of 55 to 65 μm and the sealant layer 1351 has a thickness of 75 to 85 μm.

[0039] The electrode assembly 10 is formed by alternately laminating electrodes 101 (shown in FIG. 8) and separators 102 (shown in FIG. 8). First, a slurry obtained by mixing 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, a separator 102 is laminated between the electrodes 101 to form the electrode assembly 10. After inserting the electrode assembly 10 into the battery case 13 and injecting an electrolyte, it is sealed.

[0040] The electrode assembly 10 can have an area obtained by multiplying the total length and the total width of 15000 mm 2 ~100000 mm 2 In particular, the total width of the electrode assembly 10 can be 60 mm or more. Also, the electrode assembly 10 can have a thickness of 6 mm to 20 mm in the lamination direction. Therefore, the electrode assembly 10 according to an embodiment of the present invention can provide a larger battery capacity compared to a general small-sized battery.

[0041] 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 electrode assemblies 10 include a stack type, a jelly roll type, a stack and folding type, and the like. The two types of electrodes 101, that is, 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 a metal mesh containing aluminum and copper. The active material slurry can usually be formed by stirring a granular active material, a conductive material, etc. in a state where a solvent is added. The solvent is removed in a subsequent process.

[0042] As shown in FIG. 1, the electrode assembly 10 includes an electrode tab 11. The electrode tab 11 is connected to the positive electrode and the negative electrode of the electrode assembly 10 respectively, protrudes from the electrode assembly 10 to the outside, and forms a path through which electrons can move between the inside and the outside of the electrode assembly 10. The electrode current collector of the electrode assembly 10 is composed of a portion coated with the electrode active material and an end portion not coated with the electrode active material, that is, a plain portion. Further, the electrode tab 11 can be formed by cutting the plain portion, or can be formed by connecting another conductive member to the plain portion by ultrasonic welding or the like. As shown in FIG. 1, such an electrode tab 11 can protrude in different directions of the electrode assembly 10, but is not limited thereto, and can also be formed to protrude in various directions, such as protruding side by side in the same direction from one side.

[0043] An electrode lead for supplying electricity to the outside of the secondary battery 1 is connected to the electrode tab 11 of the electrode assembly 10 by spot welding or the like. A part of the electrode lead 12 is surrounded by an insulating portion 14 around it. The insulating portion 14 is located only at the side 134 where the first case 131 and the second case 132 of the battery case 13 are heat-sealed, and adheres the electrode lead 12 to the battery case 13. Also, it prevents the 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, such an insulating portion 14 is manufactured from a non-conductive insulator having poor electrical conductivity. Generally, as the insulating portion 14, an insulating tape that is easy to adhere to the electrode lead 12 and has a relatively thin thickness is often used, but it is not limited to this, and various members can be used as long as they can insulate the electrode lead 12.

[0044] One end of the electrode lead 12 is connected to the electrode tab 11, and the other end protrudes outside the battery case 13, respectively. 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. On the other hand, as shown in FIG. 1, the other ends of both the positive electrode lead 121 and the negative electrode lead 122 protrude outside the battery case 13. Thereby, the electricity generated inside the electrode assembly 10 can be supplied to the outside. Also, since the positive electrode tab 111 and the negative electrode tab 112 protrude in various directions respectively, the positive electrode lead 121 and the negative electrode lead 122 can also extend in various directions respectively.

[0045] 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.

[0046] The battery case 13 is a pouch manufactured by molding a pouch film 135 made of a flexible material, which houses the electrode assembly 10 therein. Hereinafter, the battery case 13 will be described as a pouch. When the flexible pouch film 135 is drawn and molded 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.

[0047] The battery case 13 accommodates and seals the electrode assembly 10 such that a portion of the electrode lead 12 is exposed. As shown in FIG. 1, the battery case 13 includes a first case 131 and a second case 132. The first case 131 is formed with a cup portion 133 to provide 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 to prevent the electrode assembly 10 from falling out of the battery case 13. The first case 131 and the second case 132 may be manufactured with one side connected to each other as shown in FIG. 1, but the present invention is not limited thereto and may be manufactured in various ways, such as being separated and individually manufactured.

[0048] When forming the cup portion 133 in the pouch film 135, although only one cup portion 133 may be formed in one pouch film 135, it is not limited thereto, and two cup portions 133 can also be drawn and formed adjacent to each other in one pouch film 135. As a result, as shown in FIG. 1, cup portions 133 are formed in the first case 131 and the second case 132, respectively. At this time, the respective cup portions 133 formed in the first case 131 and the second case 132 can have the same depth D as each other, but are not limited thereto, and can also have different depths D from each other.

[0049] In the case of one embodiment of the present invention, the depth D of the cup portion 133 can 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.

[0050] After accommodating the electrode assembly 10 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 so that the two cup portions 133 face each other. As a result, the cup portion 133 of the second case 132 also accommodates the electrode assembly 10 from above. Therefore, since the two cup portions 133 accommodate one electrode assembly 10, an electrode assembly 10 that is thicker than when there is one cup portion 133 can also be accommodated. Further, by folding the battery case 13, the first case 131 and the second case 132 are integrally connected to each other. Therefore, hereinafter, when performing the sealing process, the number of sides 134 to be sealed can be reduced. Therefore, the process speed can be improved, and the number of sealing processes can also be reduced.

[0051] On one hand, the battery case 13 can include a cup portion 133 provided with a housing space 1331 for housing the electrode assembly 10, and a degassing portion 137 formed on a side portion of the cup portion 133 for discharging gas generated inside the cup portion 133 through a degassing hole H. After the electrode assembly 10 is housed in the cup portion 133 of the battery case 13 and electrolyte is injected, when an activation process is performed, gas is generated inside the battery case 13, and a degassing process is performed to discharge such gas to the outside. A detailed description of the degassing portion 137 will be given later.

[0052] When an 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 housed in the housing 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 therein, and the sides 134 formed to extend outside the cup portions 133 of the first case 131 and the second case 132 are sealed. The electrolyte is for moving lithium ions generated by the electrochemical reaction of the electrode 101 during charging and discharging of the secondary battery 1, and can include a non-aqueous organic electrolyte which is a mixture of a lithium salt and high-purity organic solvents or a polymer using a polymer electrolyte. Further, the electrolyte can also include a sulfide-based, oxide-based or polymer-based solid electrolyte, and such a solid electrolyte can also have flexibility to be easily deformed by an external force. In such a manner, the pouch-type secondary battery 1 can be manufactured.

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

[0054] 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, it is manufactured by stretching the pouch film 135 with a punch 22 or the like to form a cup portion 133. According to an embodiment of the present invention, such a 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 needed.

[0055] The sealant layer 1351 is made of a first polymer and is formed on the innermost layer so that it can be in direct contact with the electrode assembly 10. Here, the innermost layer means the layer that is located last when moving in the direction in which the electrode assembly 10 is located with respect to the moisture barrier layer 1352. When the pouch film 135 having the above-described laminated structure is drawn and formed using a punch 22 or the like, the battery case 13 is manufactured while a part thereof is stretched to form a cup portion 133 including a bag-shaped accommodation space 1331. Then, when the electrode assembly 10 is accommodated inside such an accommodation space 1331, an electrolyte is injected. Thereafter, when the first case 131 and the second case 132 are brought into contact with each other so as to face each other and thermocompression bonding is performed on the side 134, the sealant layers 1351 are adhered to each other, thereby sealing the pouch. At this time, since the sealant layer 1351 is in direct contact with the electrode assembly 10, it needs to have insulation properties, and since it also comes into contact with the electrolyte, it needs to have corrosion resistance. In addition, since the inside needs to be completely sealed to block the movement of substances between the inside and the outside, it needs to have high sealing properties. That is, the side 134 where the sealant layers 1351 are adhered to each other needs to have excellent thermoadhesive strength. Generally, the first polymer for manufacturing such a sealant layer 1351 can be composed of one or more substances selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon (registered trademark), and glass fiber. In particular, polyolefin resins such as polypropylene (PP) or polyethylene (PE) are mainly used. Polypropylene (PP) is mainly used for manufacturing the sealant layer 1351 because it is excellent in mechanical properties such as tensile strength, rigidity, surface hardness, abrasion resistance, and heat resistance, and chemical properties such as corrosion resistance. Furthermore, it can also be composed of cast polypropylene or acid modified polypropylene or a polypropylene-butylene-ethylene terpolymer.Here, the acid-treated polypropylene can be MAH PP (maleic anhydride polypropylene). Further, the sealant layer 1351 can have a single film structure composed of any one substance, or can have a composite film structure formed by two or more substances each forming a layer.

[0056] According to an embodiment of the present invention, the thickness of the sealant layer 1351 can be 60 to 100 μm, and in particular, can be 75 to 85 μm. When the thickness of the sealant layer 1351 is less than 60 μm, there may be a problem that the seal durability decreases, such as internal destruction during sealing. Further, when the thickness of the sealant layer 1351 is greater than 100 μm, the thickness of the entire pouch becomes excessively thick, so that the moldability may decrease or the energy density with respect to the volume of the secondary battery 1 may decrease. When the thickness of the sealant layer 1351 is small, the breakdown voltage of the pouch film 135 may become low and the insulation property may decrease. When a battery is manufactured using the pouch film 135 with a decreased insulation property, the defect rate may increase.

[0057] 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 entry and exit of gas or moisture outside the secondary battery 1, and prevent electrolyte leakage. The moisture barrier layer 1352 can be manufactured from an aluminum alloy thin film. The aluminum alloy thin film can ensure mechanical strength above a predetermined level, is light in weight, and can ensure complementarity to the electrochemical properties of the electrode assembly 10 and the electrolyte, heat dissipation, etc.

[0058] More specifically, the aluminum alloy thin film according to an embodiment of the present invention can have a crystal grain size of 10 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 the occurrence of pinholes or cracks during cup forming.

[0059] Such aluminum alloy thin films can contain one or more selected from the group consisting of metal elements other than aluminum, such as iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), and zinc (Zn).

[0060] Conventionally, the moisture barrier layer had a thickness of approximately 30 to 50 μm, particularly 40 μm, thereby reducing the formability. Therefore, even when the pouch film is drawn and formed, as the depth D' of the cup portion 333 (shown in FIG. 7) increases, there is a limit to forming the outer wall 338 (shown in FIG. 7) of the cup portion 333 close to vertical, and there is also a limit to reducing the radius of curvature of the edge 36 (shown in FIG. 7) of the cup portion 333. In addition, there was also a problem that the puncture strength was weak, and when the battery case was subjected to an external impact, the internal electrode assembly was easily damaged.

[0061] To solve this problem, when the thickness of the moisture barrier layer 1352 is increased to be greater than approximately 80 μm, not only does the manufacturing cost increase, but also the overall thickness of the pouch becomes excessively thick, resulting in a problem that the energy density with respect to the volume of the secondary battery 1 decreases. When the thickness of the sealant layer 1351 is decreased to be less than 60 μm in order to reduce the overall thickness of the pouch, there is a problem that the seal durability decreases as described above.

[0062] According to an embodiment of the present invention, to improve this, such a moisture barrier layer 1352 can have a thickness of 50 μm to 80 μm, and in particular, can be 55 μm to 65 μm. Therefore, the formability of the moisture barrier layer 1352 is improved. When the pouch film 135 is drawn and formed, the depth D of the cup portion 133 can be formed deeper, the outer wall 138 of the cup portion 133 can be made closer to vertical, and the radius of curvature R2 of the edge 16 (shown in FIG. 8) of the cup portion 133 can also be reduced. As a result, since the volume of the accommodation space 1331 increases, the volume of the electrode assembly 10 accommodated therein can also increase, and the energy efficiency with respect to the volume of the secondary battery 1 can also increase. Also, without significantly increasing the manufacturing cost, without reducing the thickness of the sealant layer 1351 and without significantly increasing the overall thickness of the pouch, the seal durability can be prevented from decreasing.

[0063] In addition, since the puncture strength of the pouch film 135 is improved, even if it is subjected to a large external pressure or pierced by a sharp object and damaged, the internal electrode assembly 10 can be more effectively protected. Here, excellent puncture strength means that the strength when punching a hole in the pouch film 135 is high.

[0064] However, when simply increasing the thickness of the aluminum alloy thin film, although the forming depth can be increased, pinholes and cracks are generated in the aluminum alloy thin film after forming, and problems occur in the seal durability.

[0065] Therefore, as a result of intensive research by the present inventors, when an aluminum alloy thin film having a specific crystal grain size is applied as the material of the gas barrier layer and the thicknesses of the gas barrier layer and the sealant layer are controlled within a specific range, it has been found that the cup portion can be formed deeper and excellent seal durability can be maintained, and the present invention has been completed.

[0066] 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 the occurrence of 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, it is difficult to disperse internal stress during stretching, and the occurrence of cracks and pinholes increases. When the crystal grain size is less than 10 μm, the flexibility of the aluminum alloy thin film decreases, and there is a limit to the improvement of formability.

[0067] On the other hand, the crystal 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 in the thickness direction of the aluminum alloy thin film with a scanning electron microscope (SEM). Specifically, in the present invention, using a scanning electron microscope, a cross-sectional SEM image in the thickness direction of the aluminum alloy thin film is obtained, and after measuring the maximum diameter of a preset number of crystal grains observed in the SEM image, these average values are evaluated as the crystal grain size.

[0068] The surface protective layer 1353 is made of a second polymer and is formed on the outermost layer to protect the secondary battery 1 from friction and collision with the outside, while electrically insulating the electrode assembly 10 from the outside. Here, the outermost layer means the last layer when moving in the direction opposite to the direction in which the electrode assembly 10 is located, based on the moisture barrier layer 1352. The second polymer for manufacturing such a surface protective layer 1353 can be one or more substances selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon (registered trademark), and glass fiber. In particular, it is preferable to use a polymer such as polyethylene terephthalate (PET) which mainly has abrasion resistance and heat resistance. Also, the surface protective layer 1353 can have a single film structure composed of any one substance, or a composite film structure in which two or more substances are formed into layers respectively.

[0069] According to an embodiment of the present invention, the thickness of such a surface protective layer 1353 can be 5 μm to 25 μm, and in particular, can be 7 μm to 12 μm. When the thickness of the surface protective layer 1353 is thinner than 5 μm, there may be a problem that the external insulation property deteriorates. Conversely, when the thickness of the surface protective layer 1353 is thicker than 25 μm, since the thickness of the entire pouch becomes thick, conversely, the energy density with respect to the volume of the secondary battery 1 may decrease.

[0070] On the other hand, PET is inexpensive, has excellent durability, and excellent electrical insulation, but also has weak adhesion to aluminum which is often used as the moisture barrier layer 1352, and the behaviors when stress is applied and stretched may also be different from each other. Therefore, when the surface protective layer 1353 and the moisture barrier layer 1352 are directly adhered, the surface protective layer 1353 and the moisture barrier layer 1352 may peel off during the drawing process. Therefore, a problem may occur that the moisture barrier layer 1352 is not uniformly stretched and the formability deteriorates.

[0071] According to an embodiment of the present invention, the battery case 13 is manufactured from a third polymer and may further include a stretching auxiliary layer 1354 laminated between the surface protection layer 1353 and the moisture barrier layer 1352. The stretching auxiliary layer 1354 is laminated between the surface protection layer 1353 and the moisture barrier layer 1352 and can prevent peeling when the surface protection layer 1353 and the moisture barrier layer 1352 are stretched. The third polymer for manufacturing such a stretching auxiliary layer 1354 can be one or more substances selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon (registered trademark), and glass fiber. In particular, the nylon resin is easily adhered to the polyethylene terephthalate (PET) of the surface protection layer 1353 and has a behavior similar to that of the aluminum alloy of the moisture barrier layer 1352 when stretched. Therefore, mainly nylon resin can be used as the third polymer. Also, the stretching auxiliary layer 1354 can have a single film structure composed of any one substance or a composite film structure formed by two or more substances forming layers respectively.

[0072] Conventionally, the moisture barrier layer had a thickness of approximately 40 μm, and accordingly, the stretching auxiliary layer had a relatively thin thickness of approximately 15 μm. That is, the ratio of the thickness of the stretching auxiliary layer to the moisture barrier layer was 1:2.67, and the ratio of the thickness of the moisture barrier layer was relatively high. However, as described above, according to one embodiment of the present invention, since the moisture barrier layer 1352 has a thickness of approximately 50 to 80 μm, particularly 55 μm to 65 μm, the formability of the moisture barrier layer 1352 is improved. At this time, in order to also improve the formability of the stretching auxiliary layer 1354, the stretching auxiliary layer 1354 can have a thickness of 20 μm to 50 μm, and particularly preferably has a thickness of 25 μm to 38 μm. When it is thinner than 20 μm, the stretching auxiliary layer 1354 may not be able to cope with the improved formability of the moisture barrier layer 1352 and may be damaged during stretching. Conversely, when it is thicker than 50 μm, since the thickness of the entire pouch increases, the volume of the secondary battery 1 may increase and the energy density may decrease. Particularly, according to one embodiment of the present invention, the ratio of the thickness of the stretching auxiliary layer 1354 to the moisture barrier layer 1352 can be smaller than 1:2.5. That is, the ratio of the thickness of the stretching auxiliary layer 1354 can be increased more than before. However, when the thickness of the stretching auxiliary layer 1354 becomes excessively thick, since the thickness of the entire pouch becomes thick, in order not to become an excessive thickness, the ratio of the thickness can be larger than 1:1.5. That is, the ratio of the thickness can be 1:1.5 to 1:2.5.

[0073] Figure 3 is a graph showing the iron and silicon contents of the aluminum alloy of alloy number AA8079 and the aluminum alloy of alloy number AA8021.

[0074] As described above, the aluminum alloy thin film forming the moisture barrier layer 1352 can have a crystal grain size of 10 to 13 μm, preferably 10.5 to 12.5 μm, and more preferably 11 to 12 μm.

[0075] In addition, the iron (Fe) content of the aluminum alloy thin film can be 1.2 wt% to 1.7 wt%, preferably 1.3 wt% to 1.7 wt%, and more preferably 1.3 wt% to 1.45 wt%. When the iron (Fe) content in the aluminum alloy thin film is less than 1.2 wt%, the strength of the aluminum alloy thin film decreases, and cracks and pinholes may occur during forming. When it exceeds 1.7 wt%, the flexibility of the aluminum alloy thin film decreases, and there is a limit to the improvement of formability.

[0076] In addition, the silicon (Si) content of the aluminum alloy thin film can be 0.2 wt% or less, preferably 0.05 to 0.2 wt%, and more preferably 0.1 to 0.2 wt%. When the silicon content exceeds 0.2 wt%, the formability may decrease.

[0077] Specifically, the aluminum alloy thin film according to the present invention can be an aluminum alloy of alloy number AA8021.

[0078] On the other hand, in the conventionally used battery pouch, an aluminum alloy thin film of alloy number AA8079 has been mainly used. When the aluminum alloy contains a large amount of iron, the mechanical strength is improved. When the iron content is low, the flexibility is improved.

[0079] As shown in FIG. 3, alloy number AA8079 contains 0.6 wt% to 1.2 wt% of iron and 0.3 wt% or less of silicon. In the case of the aluminum alloy of alloy number AA8079, since the iron content is relatively low, when the moisture barrier layer 1352 is manufactured using this, the flexibility can be improved, but the strength decreases, and there may be a limit to the formability.

[0080] On the one hand, as shown in FIG. 3, alloy number AA8021 can contain 1.2 wt% to 1.7 wt%, particularly 1.3 wt% to 1.7 wt% of iron, and silicon can be contained at 0.2 wt% or less. When manufacturing the moisture barrier layer 1352 with such an aluminum alloy of alloy number AA8021, since it contains relatively more iron, the tensile strength, elongation rate, and puncture strength can be improved.

[0081] On the other hand, when a tensile force is applied to a certain material, the relationship between the tensile strength and the elongation rate can be shown in a graph. At this time, if the vertical axis of the graph is the tensile strength and the horizontal axis is the elongation rate, the area under the graph is the toughness of the material. Toughness indicates the strength of the material's resistance to fracture, and the higher the toughness, the more the material can be stretched without breaking.

[0082] Therefore, when manufacturing the moisture barrier layer 1352 with the aluminum alloy of alloy number AA8021, since the tensile strength and the elongation rate are improved, the toughness increases and the formability can be enhanced.

[0083] FIG. 4 is a graph showing the changes in the tensile strength (Rm), elongation rate, and crystal grain size according to the iron content of the aluminum alloy of alloy number AA8079 and the aluminum alloy of alloy number AA8021, and FIG. 5 is an enlarged SEM photograph of the crystal grains of the aluminum alloy of alloy number AA8079 and the aluminum alloy of alloy number AA8021.

[0084] As shown in FIG. 4, according to the iron content of the aluminum alloy, the tensile strength, elongation rate, and crystal grain size change. Specifically, since the tensile strength and the elongation rate are proportional to the iron content, the higher the iron content, the higher the tensile strength and the elongation rate. On the other hand, since the crystal grain size is inversely proportional to the iron content, the higher the iron content, the smaller the crystal grain size.

[0085] Alloy number AA8079 has a relatively large crystal grain size of 13 μm to 21 μm. Therefore, when it is stretched, the dispersion of internal stress is not sufficient, and the number of pinholes increases, resulting in a problem of reduced formability of the battery case 13.

[0086] Alloy number AA8021 has a relatively small crystal grain size of 10 μm to 13 μm. Therefore, when it is stretched, more internal stress is dispersed, so the number of pinholes decreases, and the formability of the battery case 13 can be improved.

[0087] The pouch-type battery case 13 manufactured by forming the pouch film 135 having such a moisture barrier layer 1352 has improved formability, can form the depth D of the cup portion 133 deeper, the outer wall 138 of the cup portion 133 also becomes closer to vertical, and the radius of curvature of the edge 16 of the cup portion 133 can also be reduced, and a larger and thicker electrode assembly 10 can also be accommodated. Therefore, the secondary battery 1 manufactured with such a battery case 13 can increase the energy efficiency with respect to the volume.

[0088] On the other hand, the pouch film 135 according to the present invention can have an overall thickness of 160 μm to 200 μm, preferably 180 μm to 200 μm. When the thickness of the pouch film 135 satisfies the above range, it can minimize the reduction of the battery accommodation space due to the increase in the thickness of the pouch, the decrease in seal durability, etc., and can increase the forming depth.

[0089] The pouch film 135 according to the present invention includes an aluminum alloy thin film having a specific thickness and crystal grain size, and thus has excellent tensile strength and elongation. Specifically, after the pouch film 135 according to the present invention is cut into a size of 15 mm × 80 mm, the tensile strength measured while pulling at a tensile speed of 50 mm / min is 200 N / 15 mm to 300 N / 15 mm, preferably 210 N / 15 mm to 270 N / 15 mm, more preferably 220 N / 15 mm to 250 N / 15 mm, and the elongation is 120% to 150%, preferably 120% to 140%, and more preferably 120% to 130%. Thus, the pouch film laminate according to the present invention has high tensile strength and elongation, thereby increasing toughness and reducing crack generation even when the forming depth is large during cup forming.

[0090] Further, the pouch film laminate according to the present invention includes an aluminum alloy thin film having a specific thickness and crystal grain size, and thus has excellent punching strength. Specifically, the pouch film laminate according to the present invention can have a punching strength of 30 N or more.

[0091] FIG. 6 is a schematic diagram of a forming apparatus 2 according to an embodiment of the present invention.

[0092] A forming apparatus 2 for forming the pouch film 135 according to an embodiment of the present invention includes a die 21 on which the pouch film 135 is placed on the upper surface, and a punch 22 disposed above the die 21 and descending to form the pouch film 135. Further, the die 21 includes a forming portion 211 formed to be recessed inward from the upper surface, and the punch 22 forms the cup portion 133 by performing drawing forming while inserting the pouch film 135 into the forming portion 211.

[0093] According to an embodiment of the present invention, when forming the pouch film 135 using such a forming device 2, as shown in FIG. 6, two forming parts 211 are formed in the die 21 so as to be adjacent to each other, and a partition wall 212 can be formed between the two forming parts 211. When the pouch film 135 is drawn and formed while the punch 22 is inserted into both of the two forming parts 211, corresponding to the two forming parts 211, a total of two cup parts 133, one each, are formed in the first case 131 and the second case 132, and a bridge 136 can also be formed between such two cup parts 133 corresponding to the partition wall 212.

[0094] The bridge 136 can be a reference part when folding the battery case 13 hereinafter. When the manufacturing of the secondary battery 1 is completed, the bridge 136 can form a folding part 139 (shown in FIG. 14) on one side of the secondary battery 1. Such a folding part 139 connects the first case 131 and the second case 132 integrally with each other, so that when the sealing process is performed hereinafter, the number of sides 134 to be sealed can be reduced. Therefore, the process speed can be improved and the number of sealing processes can also be reduced. At this time, the smaller the width of the folding part 139, the smaller the space 17 (shown in FIG. 8) between the outer wall 138 (shown in FIG. 8) of the cup part 133 and the electrode assembly 10, so that the overall volume of the secondary battery 1 decreases and the energy density with respect to the volume can increase.

[0095] The width of such a folding portion 139 is proportional to the thickness t of the bridge 136 (shown in FIG. 8). 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. For this purpose, it is also preferable to minimize the thickness of the partition wall 212. However, if the partition wall 212 is formed with an excessive height in a state where the thickness is thin, the partition wall 212 may be damaged during the drawing process. In particular, conventionally, there was a bottom portion in the die. In such a case, when the punch 22 forms the pouch film 135, there was a problem that the gas existing in the space between the pouch film 135 and the forming portion 211 was not discharged. Therefore, recently, by removing the bottom portion of such a die, the gas existing in the space between the pouch film 135 and the forming portion 211 is easily discharged, but there is a problem that the height of the partition wall 212 is formed excessively high. Therefore, according to an embodiment of the present invention, as shown in FIG. 6, a reinforcing portion 2121 thicker than the thickness of the partition wall 212 can be formed at the lower portion of the partition wall 212. The reinforcing portion 2121 can be formed below the depth D of the 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 can be determined experimentally according to 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.

[0096] FIG. 7 is an enlarged schematic view of a conventional cup portion 333 and a bridge 336.

[0097] As described above, conventionally, when manufacturing a moisture barrier layer, an aluminum alloy of alloy number AA30XX series was often used. Further, the moisture barrier layer had a thickness of approximately 30 to 50 μm, particularly 40 μm, and the stretching auxiliary layer had a considerably thin thickness of approximately 15 μm. Therefore, the formability of the pouch film was not excellent, and even when manufacturing a battery case and a secondary battery, the depth D' of the cup portion 333 was not deep, and there was a limit to manufacturing an overall sharp shape.

[0098] Specifically, conventionally, there has been a limit to reducing the radius of curvature of the edge 36 of the cup portion 333.

[0099] The edge 36 of the cup portion 333 includes a punch edge 361 formed corresponding to the edge 221 of the punch 22 (shown in FIG. 6) and a die edge 362 (shown in FIG. 11) formed corresponding to the edge 213 of the die 21 (shown in FIG. 6).

[0100] The punch edge 361 connects the plurality of outer walls 338 surrounding the periphery of the cup portion 333 and the bottom 3332 respectively. However, if the edge 221 of the punch 22 is not rounded, the edge 221 of the punch 22 becomes sharp, so when forming the pouch film 135, stress concentrates on the punch edge 361 of the cup portion 333, and there is a problem that cracks are likely to occur. Also, the die edge 362 connects the plurality of outer walls 338 and the side 134 or the degassing portion 137 respectively. However, if the edge 213 of the die 21 is not rounded, the edge of the die 21 becomes sharp, so when forming the pouch film 135, stress also concentrates on the die edge 362 of the cup portion 333, and there is a problem that cracks are likely to occur. Here, being rounded means forming a curved surface so as to have a curvature, and such a curved surface can have only a predetermined curvature, but is not limited thereto and may have a non-constant curvature. In this specification, when the punch edge 161, the die edge 162, the bridge 136, etc. are formed by being rounded with a specific curvature, it means not only having only the specific curvature as a whole, but also including having the specific curvature at least in part.

[0101] To solve the above problems, as shown in FIG. 7, the edge 221 of the punch 22 and the edge 213 of the die 21 are rounded, so that the punch edge 361 and the die edge 362 of the cup portion 333 are formed by being rounded. Thereby, the stress concentrated on the punch edge 361 and the die edge 362 of the cup portion 333 could be dispersed to some extent.

[0102] However, even if the punch edge 361 and the die edge 362 of the cup portion 333 are formed with rounding, the depth D' of the cup portion 333 has a limit that can be produced within 2 to 5 times, particularly 2 to 3.25 times, the ratio of the radii of curvature of the respective edges 361, 362.

[0103] Therefore, in order to form the depth D' of the cup portion 333 to a certain depth, it is necessary to form the radius of curvature R2' of the punch edge 361 and the radius of curvature of the die edge 362 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 occurred in the punch edge 361 and the die edge 362.

[0104] Therefore, conventionally, there has been a problem that it is impossible to form the radius of curvature R2' of the punch edge 361 and the radius of curvature of the die edge 362 of the cup portion 333 to a predetermined value (for example, 2 mm) or less while forming the depth D' of the cup portion 333 sufficiently deep (for example, 6.5 mm or more).

[0105] Further, when two cup portions 133 are formed, in order for the bridge 136 to be formed, it is necessary for the die 21 to have a partition wall 212. However, conventionally, the formability of the pouch film is not excellent, and there is a limit to forming the thickness of such a bridge 336 thin. That is, if the partition wall 212 is also formed to a thickness equal to or less than a predetermined thickness in order to form the bridge 336 to a thickness equal to or less than a predetermined thickness, the partition wall 212 is formed sharply, resulting in a problem that cracks occur in the bridge 336.

[0106] To solve such problems, as shown in FIG. 7, the partition wall 212 was rounded to form the bridge 336 by rounding. As a result, the stress concentrated on the bridge 336 could be dispersed 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 of the thickness t' of the bridge 336. For example, when the radius of curvature R1' of the bridge 336 is formed to be close to about 1 mm, the thickness t' of the bridge 336 is formed to be close to about 2 mm.

[0107] However, even if the bridge 336 is formed by rounding, when the radius of curvature R1' of the bridge 336 is formed to be small, there is a problem that cracks occur in the bridge 336 when the depth D' of the cup portion 333 is formed to be relatively deep to some extent. Therefore, conventionally, there has been a problem that while the cup portion 333 is formed to a predetermined depth D' (for example, 6.5 mm) or more, the thickness t' of the bridge 336 cannot be formed to a predetermined value (for example, 2 mm) or less.

[0108] Furthermore, the size of the clearance CL' is also quite large, and there is a limit to forming the outer wall 338 of the cup portion 333 close to vertical. The clearance CL refers to the vertical distance between the inner wall of the forming portion 211 of the die 21 and the outer wall of the punch 22. In fact, there is a fine size difference between the forming portion 211 of the die 21 and the punch 22 by only the clearance CL. When such a clearance CL is excessively small, the distance between the inner wall of the forming portion 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 portion 211, or excessive friction occurs and the pouch film 135 may be damaged. Conversely, when the clearance CL is excessively large, the inclination angle of the outer wall 338 of the cup portion 333 becomes large, and there is a problem that the space 37 between the outer wall 338 of the cup portion 333 and the electrode assembly 10 increases. Therefore, when forming the pouch film 135, it is necessary to set an appropriate size of the clearance CL.

[0109] 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 perpendicular distance between the inner wall of the molded portion 211 of the die 21 and the outer wall of the punch 22, can be shown as the perpendicular distance between the bridge 336 and the punch edge 361 in the battery case 33.

[0110] Specifically, as shown in FIG. 7, a bridge vertical line V1' and an edge vertical line V2' are virtually illustrated. The bridge vertical line V1' passes through the boundary point P1' between the bridge 336 and the outer wall 338 on the bridge 336 side, and is a virtual vertical line perpendicular to the bottom 3332. Also, the edge vertical line V2' passes through the 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 a virtual vertical line perpendicular to the bottom 3332. Such a bridge vertical line V1' corresponds to the inner wall of the molded 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 perpendicular distance between the bridge vertical line V1' and the edge vertical line V2' is the clearance CL' shown in the battery case 33.

[0111] However, conventionally, when such a clearance CL is reduced to 0.5 mm or less, there is a possibility that cracks may easily occur in the pouch film 135 when the depth D' of the cup portion 333 is molded to a certain depth.

[0112] As described above, conventionally, there is a limit to making the clearance CL' smaller and molding the depth D' of the cup portion 333 deeper. Therefore, when the cup portion 333 is molded to a depth D' (for example, 6.5 mm) or more, the outer wall 338 of the cup portion 333 is formed with an inclination angle greater than 95° from the bottom 3332. That is, there is also a limit to molding the outer wall 338 of the cup portion 333 to be closer to vertical with an inclination angle of 95° or less.

[0113] On the one hand, since there is a limit to improving the radius of curvature R2' of the edge of the cup portion 333, there is also a problem that the volume of the electrode assembly 10 housed in the cup portion 333 becomes small. Specifically, as shown in FIG. 7, conventionally, since the radius of curvature R2' of the punch edge 361 of the cup portion 333 is large, when the electrode assembly 10 is located too close to the outer wall 338 of the cup portion 333, there is a problem that 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 containing metal is located on the punch edge 361 of the cup portion 333, and there is a problem that one end of the electrode 101 is damaged while being deformed corresponding to the punch edge 361 of the cup portion 333.

[0114] In order to solve such a problem, conventionally, when the electrode assembly 10 is housed in the cup portion 333, the electrode assembly 10 is housed at a certain distance from the outer wall 338 of the cup portion 333. First, after 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 3332 is virtually illustrated, 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, since the electrode 101 is separated from the outer wall 338 of the cup portion 333 to a certain extent, the electrode 101 can be prevented from being damaged. However, in such a case, the space 37 between the outer wall 338 of the cup portion 333 and the electrode assembly 10 increases, and the ratio of the volume of the electrode assembly 10 to the volume of the cup portion 333 becomes small, so there is a problem that the energy density with respect to the volume of the secondary battery 3 decreases. In addition, the volume of the useless space inside the cup portion 333 becomes large, and there is also a problem that the electrode assembly 10 moves inside the cup portion 333 before sealing the side.

[0115] In the electrode assembly 10, the electrode 101 has high rigidity and is not easily deformed by an external force, while the separator 102 has high flexibility and is easily deformed by an external force. However, if adjacent electrodes 101 come into direct contact, a short circuit will occur. Therefore, to prevent this, the separator 102 is formed larger than the electrode 101. Thus, when the electrode assembly 10 is formed, peripheral portions 1021 where the separator 102 protrudes outside the electrode 101 are formed together. Conventionally, however, since the electrode assembly 10 was stored at a certain distance from the outer wall 338 of the cup portion 333, all such peripheral portions 1021 of the separator 102 were wrinkled or folded disorderly, and there was also a high possibility of a short circuit due to the exposure of the electrode 101 to the outside.

[0116] As described above, conventionally, the formability of the pouch film was not excellent, and there were limitations in 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'. Also, the ratio of the volume of the electrode assembly 10 to the volume of the cup portion 333 was small, and there was a large amount of wasted volume in the secondary battery 3, so the energy density with respect to the volume was also decreased. Furthermore, since the outer wall 338 of the cup portion 333 was not formed close to being vertical and the radius of curvature R2 of the edge 361 of the cup portion 133 was large, there were limitations in manufacturing the overall shape into a sharp shape. Therefore, there was a problem that the appearance of the secondary battery 3 was not beautiful and the marketability was also decreased.

[0117] FIG. 8 is an enlarged schematic view of the cup portion 133 and the bridge 136 according to an embodiment of the present invention, and FIG. 9 is an enlarged schematic view of the cup portion 133 and the degassing portion 137 according to an embodiment of the present invention.

[0118] According to one embodiment of the present invention, by improving the formability of the pouch film 135, the thickness t of the bridge 136 can be made thinner, the radius of curvature R2 of the edge 16 of the cup portion 133 and the clearance CL can be made smaller, and the volume of the electrode assembly 10 can be increased. Therefore, since the wasted volume in the secondary battery 1 is also reduced, the energy density with respect to the volume can be increased. In addition, the pouch-type battery case 13 and the pouch-type secondary battery 1 can be manufactured in an overall sharp shape, the appearance of the secondary battery 1 is excellent, and the marketability can be improved.

[0119] For this purpose, a pouch-type battery case 13 according to one embodiment of the present invention is formed with a cup portion 133 that houses an electrode assembly 10 formed by laminating an electrode 101 and a separator 102 therein. The cup portion 133 includes a plurality of outer walls 138 surrounding the periphery and a plurality of punch edges 161 connecting to the bottom 1332 respectively. At least one of the punch edges 161 can be formed by rounding with a radius of curvature of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. When the radius of curvature R2 of the punch edge 161 is smaller than 1 / 20 of the depth D of the cup portion 133, stress may be excessively concentrated on the punch edge 161 and cracks may occur. When the radius of curvature R2 of the punch edge 161 is larger than 1 / 6 of the depth D of the cup portion 133, the cup portion 133 may not be formed sharply, so the energy density may decrease.

[0120] Specifically, at least one of the punch edges 161 can be formed by rounding with a radius of curvature of 1 mm or less, particularly 0.7 mm or less.

[0121] Further, it 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. The bridge 136 can have a thickness of 1 / 200 to 1 / 30 of the width of the electrode assembly 10. When 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 and cracks may occur. When the thickness is greater than 1 / 30 of the width of the electrode assembly 10, the bridge 136 may not be formed sharply, so the energy density may decrease.

[0122] Specifically, the bridge 136 can have a thickness of 2 mm or less, particularly 1.4 mm or less.

[0123] Also, among the plurality of punch edges 161, the outer wall 1381 on the bridge 136 side facing the bridge 136 and the punch edge 1611 on the bridge 136 side connecting the bottom 1332 to each other can be formed by rounding with a radius of curvature of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, the punch edge 1611 can be formed by rounding with a radius of curvature of 1 mm or less, particularly 0.7 mm or less.

[0124] Also, the vertical distance between the bridge vertical line V1 passing through the boundary point P1 between the bridge 136 and the outer wall 1381 on the bridge 136 side and perpendicular to the bottom 1332, and the edge vertical line V2 passing through the 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.

[0125] The cup portion 133 is formed by molding a flexible pouch film 135 using a punch 22 or the like. Such a cup portion 133 is surrounded by a plurality of outer walls 138 and a bottom 1332, and the space formed by such an outer wall 138 and a bottom 1332 serves as an accommodation space 1331 for accommodating the electrode assembly 10.

[0126] The outer wall 138 of the cup portion 133 surrounds the periphery of the cup portion 133 and embodies the shape of the cup portion 133. The outer wall 138 is formed in plurality around the periphery of the cup portion 133, is also formed on the side of the bridge 136, is also formed on the side of the degassing portion 137 described below, and is also formed on the side of the electrode lead 12. Such an outer wall 138 has an upper end facing the open portion of the cup portion 133 and a lower end facing the bottom 1332.

[0127] On the other hand, 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. Also, the punch edge 161 connects the lower end of the outer wall 138 to the bottom 1332, respectively.

[0128] Since a plurality of outer walls 138 of the cup portion 133 are formed, a plurality of edges 16 of the cup portion 133 are also formed in the same number as the number of outer walls 138. That is, when the cup portion 133 is formed in a quadrangular shape, four outer walls 138 of the cup portion 133 are formed, so four punch edges 161 and four die edges 162 are also formed. Also, according to an embodiment of the present invention, by improving the formability of the pouch film 135, at least one of the punch edges 161 of the cup portion 133 can be formed by rounding 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 can be formed by rounding with a curvature radius of 1 mm or less, particularly 0.7 mm or less.

[0129] In particular, according to one embodiment of the present invention, two cup portions 133 are formed on one pouch film 135, and a bridge 136 is also formed between the two cup portions 133. As a result, as shown in FIG. 8, among the plurality of punch edges 161, the outer wall 1381 on the bridge 136 side facing the bridge 136 and the punch edge 1611 on the bridge 136 side connecting the bottom 1332 to each other can be formed by rounding with a radius of curvature of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, the punch edge 1611 on the bridge 136 side can be formed by rounding with a radius of curvature of 1 mm or less, particularly 0.7 mm or less.

[0130] Also, as shown in FIG. 9, among the plurality of punch edges 161, the outer wall 1382 on the die edge 162 side facing the die edge 162 formed in the degassing portion 137 or the electrode lead 12 and the punch edge 1612 on the die edge 162 side connecting the bottom 1332 to each other can also be formed by rounding with a radius of curvature of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. When the radius of curvature 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 and cracks may occur. When the radius of curvature 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 is not formed sharply, so the energy density may decrease.

[0131] Specifically, the punch edge 1612 on the die edge 162 side can also be formed by rounding with a radius of curvature of 1 mm or less, particularly 0.7 mm or less. At this time, it is preferable that the gradient is continuous at the boundary points P2 and P4 between the punch edge 161 and the outer wall 138.

[0132] For this purpose, the edge 221 of the punch 22 can also be subjected to rounding processing 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, when 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.

[0133] 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 to a certain extent, when such a punch 22 draws and forms the pouch film 135, it is possible to prevent cracks from occurring at the punch edge 161 of the cup portion 133. For example, based on the case of forming one cup portion 133, 7 mm or more, based on the case of forming two cup portions 133, 6.5 mm or more, and even when formed to 10 mm or more, cracks can be prevented from occurring at the punch edge 161 of the cup portion 133.

[0134] Here, the depth D of the cup portion 133 at which the above-mentioned cracks can occur is determined to be a good product when the residual ratio of the aluminum alloy in the moisture barrier layer 1352 is 60% or more, and a defective product when the residual ratio is less than 60%. The residual ratio means the ratio of the residual amount after forming to the residual amount before forming of the aluminum alloy in the moisture barrier layer 1352 at a specific point of the pouch film 135. In fact, when the residual ratio is less than 60%, when the cup portion 133 is drawn and formed on the pouch film 135, the frequency of crack generation is high at a specific point, but when the residual ratio is 60% or more, cracks do not occur.

[0135] Conventionally, when the depth D' of the cup portion 333 was formed to be more than 5 times, particularly more than 3.25 times the radius of curvature R2' of the punch edge 361 or the radius of curvature of the die edge 362, the residual ratio was relatively low and the frequency of crack generation was high. Hereinafter, "prone to crack" means that the residual ratio is relatively low and the frequency of crack generation is high.

[0136] On one hand, the upper end of the outer wall 138 faces the opening of the cup portion 133, and the side 134 and the degassing portion 137 extend outside the cup portion 133. At this time, as shown in FIG. 9, the cup portion 133 can further include a plurality of die edges 162 that connect the upper end of the outer wall 138 to the side 134 or the degassing portion 137, respectively. Also, at least one die edge 162 can also be formed by being rounded with a radius of curvature of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, at least one die edge 162 can be formed by being rounded with a radius of curvature of 1 mm or less, particularly 0.7 mm or less. For this reason, the edge 213 of the die 21 can also be subjected to a rounding process with a predetermined radius of curvature. Here, the radius of curvature of the edge 213 of the die 21 can be a numerical value obtained by subtracting the thickness of the pouch film 135 itself from the radius of curvature of the die edge 162. For example, when 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 when the radius of curvature of the edge 213 of the die 21 is 0.5 mm or less.

[0137] In particular, as described above, two cup portions 133 can also be formed in one pouch film 135, and a bridge 136 is also 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 in which cup portions 133 for accommodating the electrode assembly 10 formed by laminating the electrodes 101 and the separator 102 are respectively formed, 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 can be one type of the plurality of die edges 162.

[0138] Therefore, according to an embodiment of the present invention, by improving the formability of the pouch film 135, the thickness t of the bridge 136 can be in the range of 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.

[0139] Here, as shown in FIG. 8, the thickness t of the bridge 136 is preferably the distance between two boundary points P1 of the bridge 136 and the outer wall 1381 on the bridge 136 side. Specifically, it is preferably the distance between two bridge vertical lines V1 passing through the boundary points P1 of the bridge 136 and the outer wall 1381 on the bridge 136 side and 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 of 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.

[0140] For this purpose, rounding processing can also be performed on the upper surface of the partition wall 212 of the forming portion 211 with a predetermined radius of curvature. At this time, 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 forming portion 211 can 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, when 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.

[0141] According to an embodiment of the present invention, by improving the formability of the pouch film 135, the depth D of the cup portion 133 can be formed to be relatively deep to a certain extent. Even if the radius of curvature of the edge 213 of such a die 21 decreases and the thickness of the partition wall 212 is formed to be thin, cracks can be prevented from occurring in the die edge 162 and the bridge 136. Such a bridge 136 can have a sector-shaped cross-section, and the closer the outer wall 138 of the cup portion 133 is formed vertically, the closer the cross-section can be to a semi-circular shape.

[0142] Here, even if the depth D of the cup portion 133 is formed to be 3 mm or more, particularly 6.5 mm or more, and further 10 mm or more, based on the case of forming two cup portions 133, cracks can be prevented from occurring in the bridge 136.

[0143] Furthermore, by improving the formability of the pouch film 135, the clearance CL can be reduced to 0.5 mm or less, and a plurality of outer walls 138 can all be formed to be close to vertical. For example, as shown in FIG. 8, among the plurality of outer walls 138, the outer wall 1381 on the bridge 136 side can be formed to be close to vertical. That is, the clearance CL, which is the vertical distance between the bridge vertical line V1 passing through the boundary point P1 between the bridge 136 and the outer wall 1381 on the bridge 136 side and perpendicular to the bottom 1332, and the edge vertical line V2 passing through the 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.

[0144] Also, as shown in FIG. 9, the outer wall 1382 on the die edge 162 side among the plurality of outer walls 138 can also be formed to be close to vertical. That is, a clearance CL, which is the perpendicular distance between a die edge perpendicular line V4 passing through the 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 perpendicular line V2 passing through the 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, can be 0.5 mm or less, particularly 0.35 mm or less.

[0145] 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, and further 10 mm or more based on the case of forming two cup portions 133, the outer wall 138 of the cup portion 133 can have an inclination with an inclination angle of 90° to 95° from the bottom 1332, and further, can be formed to be close to vertical so as to have an inclination of 90° to 93°, thereby preventing cracks from occurring in the battery case 13. Also, since the space 17 between the outer wall 138 of the cup portion 133 and the electrode assembly 10 is reduced, the energy density with respect to the volume of the secondary battery 1 can also be increased.

[0146] 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 located very close to the outer wall 138 of the cup portion 133, it is possible to prevent the electrodes 101 of the electrode assembly 10 from being damaged.

[0147] Therefore, a method for manufacturing the pouch-type secondary battery 1 according to an embodiment of the present invention can include a step of laminating the electrodes 101 and the separator 102 to form the electrode assembly 10, a step of manufacturing the pouch-type battery case 13 by forming the pouch film 135 to form the cup portion 133, a step of housing the electrode assembly 10 in the accommodation space 1331 of the cup portion 133, and a step of sealing the side 134 extended outside the cup portion 133 to manufacture the pouch-type secondary battery 1.

[0148] In particular, in the step of housing the electrode assembly 10, the difference between the width CW of the cup portion 133 and the width EW of the electrode assembly 10 can be 2.5 mm or less, particularly 1.7 mm or less. Here, the width EW of the electrode assembly 10 can mean the width of the electrode 101. That is, the peripheral portion 1021 protruding from the electrode 101 in the separator 102 can be excluded from the calculation of the width EW.

[0149] Also, 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 the electrode assembly 10 can be housed such that the vertical distance g is 0.75 mm or less, particularly 0.5 mm or less, from the edge vertical line V2 perpendicular to the bottom 1332.

[0150] Specifically, as shown in FIGS. 8 and 9, an edge vertical line V2 that passes through the boundary point P2 between the punch edge 161 and the outer wall 138 and is perpendicular to the bottom 1332 is virtually illustrated. Further, the electrode assembly 10 is housed such that at least one end of the electrode 101 is located from the edge vertical line V2 at a vertical distance g of 0.75 mm or less, particularly 0.5 mm or less. More specifically, a reference vertical line V3 that 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 is virtually illustrated. 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. Further, the electrode assembly 10 is housed 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), and X-Ray. Thereby, it is possible to prevent 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 with respect to the volume can also be increased. Further, since the wasted volume inside the cup portion 133 is reduced, it is possible to prevent the electrode assembly 10 from moving inside the cup portion 133.

[0151] Furthermore, the electrode assembly 10 can be housed very close to the outer wall 138 of the cup portion 133, and the separator 102 can be prevented from being wrinkled or folded disorderly. As shown in FIG. 8, the peripheral portion 1021 where the separator 102 protrudes outside the electrode 101 can be folded in the direction opposite to the bottom 1332 with respect to one end of the electrode 101.

[0152] The electrode assembly 10 is formed by laminating the electrodes 101 and the separators 102, and a plurality of such electrodes 101 and separators 102 can be formed respectively. The battery case 13 includes a first case 131 and a second case 132. When the bridge 136 of the battery case 13 is folded and the upper part of the electrode assembly 10 is also housed in the cup part 133, the separator 102 housed in the cup part 133 of the first case 131 has its peripheral part 1021 folded toward the second case 132, and the separator 102 housed in the cup part 133 of the second case 132 can have its peripheral part 1021 folded toward the first case 131. Thereby, the peripheral parts 1021 of the separators 102 can be aligned and folded to have order. Also, since the separator 102 covers the electrodes 101 so that they are not exposed to the outside, it is possible to prevent the occurrence of a short circuit.

[0153] More specifically, in a state before the electrode assembly 10 is housed in the cup part 133, the width of the separator 102 can be wider than the width CW of the cup part 133. Therefore, in the process of housing the electrode assembly 10 in the cup part 133, the peripheral part 1021 of the separator 102 can be folded in a predetermined direction in contact with the inner circumference of the cup part 133.

[0154] The difference between the width CW of the cup part 133 and the width EW of the electrode assembly 10 can be very small, 2.5 mm or less, particularly 1.7 mm or less. Therefore, in the process of housing the electrode assembly 10 in the cup part 133, a process may be required for the peripheral part 1021 of the separator 102 to be easily folded.

[0155] Therefore, the step of accommodating the electrode assembly 10 in the accommodation space 1331 of the cup portion 133 may include the process of pressurizing the electrode assembly 10 inside the cup portion 133. Thereby, compared with the conventional method of placing the electrode assembly 10 on the cup portion, the difference between the width CW of the cup portion 133 and the width EW of the electrode assembly 10 is maintained small, and the separator 102 is folded in a predetermined direction, so that the electrode assembly 10 can be easily and reliably accommodated in the accommodation space 1331 of the cup portion 133.

[0156] Also, the step of accommodating the electrode assembly 10 in the accommodation space 1331 of the cup portion 133 may further include the process of folding each corner (vertex) of the plurality of separators 102 in the electrode assembly 10 with heat and pressure before pressurizing the electrode assembly 10 inside the cup portion 133. The process can be carried out using another sealing tool to fold each corner (vertex) of the plurality of separators 102 so as to gather at the central portion with respect to the stacking direction of the electrode assembly 10.

[0157] That is, with the four corners of the separator 102 pre-aligned, the electrode assembly 10 can be inserted inside the cup portion 133. Thereby, the electrode assembly 10 can be smoothly inserted into the accommodation space 1331 of the cup portion 133. Thus, according to an embodiment of the present invention, by improving the formability of the pouch film 135, the thickness t of the bridge 136 can be made thinner, the radius of curvature R2 of the edge 16 of the cup portion 133 and the clearance CL can be made smaller, and the volume of the electrode assembly 10 can be increased. Therefore, since the wasted volume in the secondary battery 1 is also reduced, the energy density with respect to the volume can be increased. In addition, the pouch-type battery case 13 and the pouch-type secondary battery 1 can be manufactured in an overall sharp shape, the appearance of the secondary battery 1 is beautiful, and the commerciality can also be improved.

[0158] FIG. 10 is a schematic top view showing a state in which the electrode assembly 10 is accommodated in the cup portion 133 according to an embodiment of the present invention.

[0159] According to one 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 housed so that one end of the electrode 101 is located between the edge vertical line V2 and the reference vertical line V3. Thereby, even when the electrode assembly 10 is located very close to the outer wall 138 of the cup portion 133, it is possible to prevent the electrode 101 of the electrode assembly 10 from being damaged.

[0160] The edge vertical line V2 and the reference vertical line V3 can also be shown on the punch edge 1611 on the bridge 136 side and can also be shown on the punch edge 1612 on the die edge 162 side. The vertical distance g between such an edge vertical line V2 and a reference vertical line V3 can be 0.75 mm, particularly 0.5 mm.

[0161] Further, when two cup portions 133 are formed in the battery case 13, since the bridge 136 exists, a bridge vertical line V1 can be shown on one side of the cup portion 133 and a die edge vertical line V4 can be shown on the other side. The vertical distance CL between such a bridge vertical line V1 and an 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.

[0162] However, when only one cup portion 133 is formed in the battery case 13, there is no bridge. However, since die edges 162 are formed on both sides of the cup portion 133, die edge vertical lines V4 can be shown on both sides of the cup portion 133, respectively.

[0163] 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.

[0164] Both the bridge vertical line V1 and the die edge vertical line V4 pass through the upper ends of the outer walls 138 of the cup portion 133. Therefore, according to one embodiment of the present invention, the width CW of the cup portion 133 can 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 can be 2.5 mm or less, particularly 1.7 mm or less. Also, as described above, the width EW of the electrode assembly 10 can be 60 mm or more.

[0165] 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. Also, in the secondary battery 1, it can be derived by using a laser displacement sensor or the like to grasp the positions between the upper ends of the outer walls 138 on both sides from the outside of the cup portion 133 and calculating the distance between the two positions. At this time, 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 senses a point where the displacement changes rapidly, the point can be recognized as the upper end of the outer wall 138. The method for measuring the width CW of the cup portion is described as an example above, and not necessarily only the case limited to the measurement method belongs to the scope of the present invention. The width CW of the cup portion can be the width CW of the cup portion as meant in the present invention as long as it corresponds to the description of the claims and the gist of the present invention.

[0166] FIG. 11 is a schematic view showing a conventional corner 364, and FIG. 12 is a schematic view showing a corner 164 according to an embodiment of the present invention.

[0167] 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 that connects two adjacent outer walls 138 of the cup portion 133 to each other as shown in FIG. 12. The thickness edge 163 is formed in the thickness direction of the cup portion 133 and is formed while being stretched between the corner of the forming portion 211 of the die 21 and the corner of the punch 22 when the pouch film 135 is stretched. Also, at least one of the thickness edges 163 can be formed with rounding.

[0168] Such a thickness edge 163 may have the same radius of curvature as the radii of curvature R2 of two adjacent punch edges 161, that is, the first punch edge 1613 and the second punch edge 1614, or may be formed to be different. For example, as described above, at least one of the punch edges 161 can be formed with rounding having a radius of curvature of 1 mm or less, particularly 0.7 mm or less, and at least one of the thickness edges 163 can be formed with rounding having 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 formed with rounding having a radius of curvature of 5 mm or less, particularly 2 mm or less, there has been a problem that stress also concentrates on the thickness edge 363 of the cup portion 333 and cracks are likely to occur. However, according to an 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. At this time, one of the first punch edge 1613 and the second punch edge 1614 may be the punch edge 1611 on the bridge 136 side, and the other may be a punch edge (not shown) on the electrode lead 12 side. Or, one of the two may be the 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.

[0169] As shown in FIG. 12, the thickness edge 163 is connected to two punch edges 161 adjacent to each other, that is, the first punch edge 1613 and the second punch edge 1614, to form a corner 164. Conventionally, as shown in FIG. 11, rounding processing is performed on a plurality of edges 221 of the punch 22 with the same radius of curvature. Accordingly, rounding processing is also naturally performed on the corner (not shown) of the punch 22 with the same radius of curvature. Therefore, when the pouch film 135 is formed by 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.

[0170] However, when the pouch film 135 is stretched, there is a problem that stress concentrates on the corner 364. In particular, since the corner 364 is formed by three edges 36 in contact with each other, it is stretched more than the punch edge 361 or the thickness edge 363, and more stress concentrates than the punch edge 361 or the thickness edge 363. Therefore, the stretching of the pouch film 135 becomes excessive, and a whitening phenomenon occurs in which a specific portion changes to white immediately before a crack occurs. Eventually, there is a problem that cracks are likely to occur.

[0171] Therefore, according to an embodiment of the present invention, as shown in FIG. 12, at least one of the corners 164 is also formed by rounding, and such a corner 164 can have a radius of curvature equal to or greater than at least one of the punch edge 161 and the thickness edge 163.

[0172] Specifically, according to one embodiment of the present invention, the corner 164 can have a varying radius of curvature inside. That is, the radius of curvature of the central portion 1641 of the corner 164 can be different from the radius of curvature of the peripheral portion 1642 of the corner 164. In particular, the radius of curvature of the central portion 1641 of the corner 164 can be larger than the radius of curvature of the peripheral portion 1642 of the corner 164. For example, 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, it can be the same as the radius of curvature of at least one of the punch edge 161 and the thickness edge 163. On the other hand, since the central portion 1641 of the corner 164 is relatively spaced from the first punch edge 1613, the second punch edge 1614, and the thickness edge 163, it can be larger than the radius of curvature of at least one of the punch edge 161 and the thickness edge 163. That is, the corner 164 can have a radius of curvature that is equal to or greater than the radius of curvature of at least one of the punch edge 161 and the thickness edge 163.

[0173] Therefore, the radius of curvature of the corner 164 can gradually increase from the peripheral portion 1642 of the corner 164 to the central portion 1641 of the corner 164. Also, as described above, since the corner 164 has a non-constant and varying radius of curvature inside, the central portion 1641 of the corner 164 can have an aspherical shape rather than an exact spherical shape.

[0174] Corner 164 is different from punch edge 161. Not only the radius of curvature but also the range formed by cup portion 133 needs to be clearly set. When the range in which corner 164 is formed by cup portion 133 is excessively narrow, there is still a problem that the stretching of pouch film 135 is excessive and whitening phenomenon or cracks occur. On the other hand, when the range in which corner 164 is formed by cup portion 133 is excessively wide, conversely, the space 17 between outer wall 138 of cup portion 133 and electrode assembly 10 decreases, so the energy density with respect to the volume of secondary battery 1 can be increased. Therefore, according to one embodiment of the present invention, as shown in FIG. 12, corner 164 can be formed within 2 mm to 3.5 mm in the length direction lc of cup portion 133 from thickness edge 163, within 2 mm to 3.5 mm in the width direction wc of cup portion 133 from thickness edge 163, and within 2 mm to 3.5 mm in the thickness direction dc of cup portion 133 from punch edge 161. Also, the range in which such corner 164 is formed can gradually become wider as the depth D of cup portion 133 is deeper.

[0175] By forming corner 164 of cup portion 133 as described above, the stress concentrated by corner 164 can be dispersed, and the problems of whitening phenomenon and crack generation can be prevented.

[0176] FIG. 13 is a schematic view showing a state of folding battery case 13 according to one embodiment of the present invention, and FIG. 14 is a schematic view showing a state of battery case 13 folded according to one embodiment of the present invention.

[0177] When two cup portions 133 are formed in the pouch film 135, cup portions 133 are formed in the first case 131 and the second case 132 of the battery case 13, respectively. After that, after the electrode assembly 10 is housed in the accommodation space 1331 provided in the cup portion 133 of the first case 131, as shown in FIG. 13, the bridge 136 formed between the two cup portions 133 in the battery case 13 is folded so that the two cup portions 133 face each other. When such a bridge 136 is folded, a folding portion 139 is formed on one side of the secondary battery 1. Further, by injecting an electrolyte therein and sealing the sides 134 extending outside the cup portions 133 of the first case 131 and the second case 132, as shown in FIG. 14, the pouch-type secondary battery 1 can be manufactured.

[0178] The pouch-type secondary battery 1 according to an embodiment of the present invention manufactured in this way includes an electrode assembly 10 formed by laminating an electrode 101 and a separator 102, and a pouch-type battery case 13 in which a cup portion 133 for housing the electrode assembly 10 therein is formed. The cup portion 133 can include a plurality of outer walls 138 surrounding the periphery and a plurality of punch edges 161 connecting the bottom portions 1332, respectively. At least one of the punch edges 161 can be formed by being rounded with a radius of curvature of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, at least one of the punch edges 161 can be formed by being rounded with a radius of curvature of 1 mm or less, particularly 0.7 mm or less.

[0179] The difference between the width CW of the cup portion 133 and the width EW of the electrode assembly 10 can be 2.5 mm or less, particularly 1.7 mm or less. Further, at least one end of at least one of the electrodes 101 of the electrode assembly 10 can pass through the boundary point P2 between the punch edge 161 and the outer wall 138 and be located at a perpendicular distance g of 0.75 mm or less, particularly 0.5 mm or less, from the edge perpendicular line V2 perpendicular to the bottom portion 1332. Further, the battery case 13 can include a first case 131 and a second case 132 in which the cup portion 133 is formed on at least one side, and a folding portion 139 that integrally connects the first case 131 and the second case 132.

[0180] When the battery case 13 is folded to manufacture the secondary battery 1, the bridge 136 becomes the folding portion 139. Thus, in the secondary battery 1, the folding portion 139 integrally connects the first case 131 and the second case 132. Further, the punch edge 1611 on the bridge 136 side becomes the punch edge 1611 on the folding portion 139 side, and the outer wall 1381 on the bridge 136 side becomes the outer wall 1381 on the folding portion 139 side.

[0181] As a result, among the plurality of punch edges 161, the punch edge 1611 on the folding portion 139 side that connects the outer wall 1381 on the folding portion 139 side facing the folding portion 139 side and the bottom portion 1332 to each other can be formed by being rounded with a radius of curvature 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 can be formed by being rounded with a radius of curvature of 1 mm or less, particularly 0.7 mm or less. Further, at least one end of at least one of the electrodes 101 of the electrode assembly 10 can pass through the boundary point P2 between the punch edge 161 and the outer wall 138, the perpendicular distance g from the edge perpendicular line V2 perpendicular to the bottom portion 1332 can be 0.75 mm, particularly 0.5 mm, and it can be located between the edge perpendicular line V2 and a reference perpendicular line V3 perpendicular to the bottom portion 1332. As described above, such a reference perpendicular line V3 can pass through the center of curvature C of the punch edge 161.

[0182] FIG. 15 is an enlarged view of a groove 1391 formed in a battery case 13 according to an embodiment of the present invention.

[0183] According to an embodiment of the present invention, in order to manufacture the secondary battery 1 as described above, when the battery case 13 is folded, the bridge 136 can be in the form of a folding portion 139. Specifically, when the battery case 13 is folded, the rounded shape of the bridge 136 also extends to some extent, but the trace of the bridge 136 remains in the secondary battery 1, and such a trace can become the folding portion 139. Therefore, the bridge 136 and the folding portion 139 of the battery case 13 can correspond to each other.

[0184] For example, when the rounded shape of the bridge 136 does not completely extend to a plane, the folding portion 139 is formed to include a groove 1391 recessed inside the secondary battery 1 as shown in FIG. 15. In such a case, since the folding portion 139 has a smaller curvature than the bridge 136, it can have a larger radius of curvature.

[0185] Since the bridge 136 is a curved surface and the outer wall 1381 on the bridge 136 side has a planar shape, the amount of deformation of each is different. Therefore, when the battery case 13 is folded, the outer wall 1381 on the bridge 136 side deforms relatively more, while the bridge 136 deforms relatively less only to the extent that the rounded shape extends to some extent. As a result, when the battery case 13 is folded, as shown in FIG. 15, the increase and decrease in the amount of change in gradient are converted around the boundary point P1. That is, the boundary point P1 becomes an inflection point respectively. Therefore, the folding portion 139 can be formed by a curved surface between the two boundary points P1, that is, the two inflection points.

[0186] In addition, when the rounded shape of the bridge 136 does not fully extend in the plane, the two boundary points P1, that is, the portions corresponding to the two inflection points, can protrude outward to form protrusions. That is, a pair of protrusions protruding outward with the folding portion 139, more specifically, with the groove 1391 therebetween, can be formed.

[0187] Alternatively, even when the rounded shape of the bridge 136 fully extends in the plane, the boundary points P1 between the bridge 136 and the outer wall 1381 on the bridge 136 side respectively form two lines (not shown) in the secondary battery 1, and the folding portion 139 is formed in the plane between such two lines.

[0188] The folding portion 139 can also be visually confirmed from the appearance of the secondary battery 1. Also, as described above, since the thickness t of the bridge 136 is preferably the distance between the two boundary points P1 of the bridge 136 and the outer wall 1381 on the bridge 136 side, 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 does not fully extend in the plane, the width FW of the folding portion 139 is the distance between the two boundary points P1, that is, the two inflection points. Alternatively, when the rounded shape of the bridge 136 fully extends in the plane, the folding portion 139 is the distance between the two boundary points P1, that is, the distance between the two lines.

[0189] The width FW of the folding portion 139 does not exceed the length of the bridge 136 and can be 1 mm to 3.2 mm, particularly 1 mm to 1.6 mm. As described above, the width FW of such a folding portion 139 can be measured directly using a ruler, but can also be measured using a loupe, or can be measured using a 3D camera or a laser 2D line sensor, etc., and is not limited, and can be measured by various methods.

[0190] Conventionally, the thickness t' of the bridge 336 was formed thick, and the width of the folding portion 339 was also formed large. Accordingly, the space 37 between the outer wall 338 of the cup portion 333 and the electrode assembly 10 was also formed large. However, according to an embodiment of the present invention, since the width FW of the folding portion 139 can be reduced, the space 17 between the outer wall 138 of the cup portion 133 and the electrode assembly 10 can also be reduced. Thereby, the energy density with respect to the volume of the secondary battery 1 can be increased.

[0191] Also, conventionally, since the formability of the pouch film was low, the protruding portion protruded largely outward. However, according to an embodiment of the present invention, the protruding portion can protrude relatively small, and the flatness of the folding portion 139 or the outer wall 1381 on the folding portion 139 side can be improved.

[0192] Specifically, the distance p between the innermost part of the groove 1391 and the outermost part of the protruding portion can be defined as flatness. In the case of a conventional battery case, the flatness was 1 mm or more and was formed up to 1.5 mm. On the other hand, according to an embodiment of the present invention, the flatness p can be formed to be 0.8 mm or less, preferably 0.3 mm or less. Thereby, the energy density with respect to the volume of the secondary battery 1 can be further increased.

[0193] FIG. 16 is an enlarged schematic view of the cup portion 133 and the die edge 1621 according to another embodiment of the present invention.

[0194] According to an embodiment of the present invention, two molding portions 211 are formed on the die 21 so as to be adjacent to each other, and a partition wall 212 can be formed between the two molding portions 211. Therefore, when the pouch film 135 is molded, two cup portions 133 are formed in one pouch film 135, and a bridge 136 is also formed between the two cup portions 133. That is, one cup portion 133 is formed in each of the first case 131 and the second case 132.

[0195] However, according to another embodiment of the present invention, only one forming portion 211 is formed on the die 21 and there is no partition wall. Therefore, when the pouch film 135 is formed, one cup portion 133 is formed in one pouch film 135 and there is no bridge either. That is, the cup portion 133 is formed only in the first case 131.

[0196] According to another embodiment of the present invention, at least one of the punch edges 161a of the cup portion 133 can be formed by rounding with a radius of curvature of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, at least one of the punch edges 161a of the cup portion 133 can be formed by rounding with a radius of curvature of 1 mm or less, particularly 0.7 mm or less. Thereby, the formability of the pouch film 135 is improved, and even when the depth D of the cup portion 133 is formed to be relatively deep, for example, 3 mm or more, particularly 7 mm or more, and further 10 mm or more, when forming one cup portion 133, it is possible to prevent cracks from occurring in the punch edge 161a of the cup portion 133.

[0197] In particular, according to another embodiment of the present invention, as shown in FIG. 16, among the plurality of punch edges 161a, the outer wall 1381a on the second case 132a side facing the second case 132a side and the punch edge 1611a on the second case 132a side connecting the bottom portion 1332 to each other can be formed by rounding with a radius of curvature 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 can be formed by rounding with a radius of curvature of 1 mm or less, particularly 0.7 mm or less.

[0198] Also, the punch edge 1612 on the die edge 162 side can be formed by rounding with 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 can also be formed by rounding with a radius of curvature of 1 mm or less, particularly 0.7 mm or less. At this time, it is preferable that the gradient is continuous at the boundary point P2 between the punch edge 161a and the outer wall 138.

[0199] Hereinafter, regarding other embodiments of the present invention, descriptions of the contents overlapping with one embodiment of the present invention will be omitted. However, this is for convenience of explanation and not for limiting the scope of rights.

[0200] FIG. 17 is a schematic view showing a state of folding the battery case 13a according to another embodiment of the present invention, and FIG. 18 is a schematic view showing a state of the battery case 13a folded according to another embodiment of the present invention.

[0201] The upper end of the outer wall 138 faces the opening of the cup portion 133, and the second case 132a, the side 134, and the degassing portion 137 extend outside the cup portion 133. At this time, the die edge 162 connecting the upper end of the outer wall 138 to the second case 132a, the side 134, or the degassing portion 137 can also be formed by rounding with a radius of curvature of 1 / 20 to 1 / 6 of the depth D of the cup portion 133. Specifically, the die edge 162 can be formed by rounding with a radius of curvature of 1 mm or less, particularly 0.7 mm or less.

[0202] 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 can be rounded with a radius of curvature 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 can be rounded with a radius of curvature of 0.8 mm or less, particularly 0.5 mm or less.

[0203] Furthermore, the clearance CL can be reduced to 0.5 mm or less so that the outer wall 138a of the cup portion 133 is formed near vertically. For example, as shown in FIG. 16, passing through the boundary point P1 between the die edge 1621 and the outer wall 1381a on the second case 132a side, the die edge vertical line V4 perpendicular to the bottom 1332, passing through the 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 the edge vertical line V2 perpendicular to the bottom 1332, the clearance CL, which is the vertical distance therebetween, can be 0.5 mm or less, particularly 0.35 mm or less.

[0204] Also, the electrode assembly 10 can be housed such that one end of the electrode 101 is located between the edge vertical line V2 and the reference vertical line V3 perpendicular to the bottom 1332 with a vertical distance of 0.75 mm, particularly 0.5 mm, from the edge vertical line V2.

[0205] Accordingly, 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 be approximately 3 mm or more, particularly 7 mm or more, and further 10 mm or more, based on the standard of forming one cup portion 133 with a certain depth, cracking of the punch edge 161a and die edge 162 of the cup portion 133 can be prevented. Further, the outer wall 138 of the cup portion 133 can be formed vertically close to having an inclination with an inclination angle of 90° to 95°, particularly between 90° and 93° from the bottom 1332, preventing the electrode 101 from being damaged, and further increasing the ratio of the volume of the electrode assembly 10 to the volume of the cup portion 133, and increasing the energy efficiency with respect to the volume.

[0206] FIG. 19 is an enlarged view of the groove 1391a formed in the battery case 13a according to another embodiment of the present invention.

[0207] 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 folding portion 139a. Specifically, when the battery case 13 is folded, the rounded shape of the die edge 1621 also extends, but the trace of the die edge 1621 remains on the secondary battery 1a, and such a trace becomes the folding portion 139a. Therefore, the die edge 1621 on the second case 132a side of the battery case 13a and the folding portion 139a correspond to each other.

[0208] For example, when the rounded shape of the die edge 1621 does not completely extend to a plane, the folding portion 139a is formed to include a groove 1391a recessed inside the secondary battery 1a as shown in FIG. 19. In such a case, since the folding portion 139a has a smaller curvature than the die edge 1621, it can have a larger radius of curvature.

[0209] Since the die edge 1621 has a curved surface and the outer wall 1381a on the die edge 1621 side has a planar shape, their amounts of deformation are different from each other. Therefore, when the battery case 13 is folded, the outer wall 1381a on the die edge 1621 side deforms relatively more, while the die edge 1621 deforms relatively less, only to the extent that its rounded shape extends to a certain degree. As a result, when the battery case 13 is folded, as shown in FIG. 19, the increase and decrease in the amount of change in the gradient are converted around the boundary point P1. That is, the boundary points P1 each become an inflection point. Therefore, the folding portion 139a is formed by the curved surface between the two boundary points P1, that is, the two inflection points.

[0210] Alternatively, even if the rounded shape of the die edge 1621 extends completely flat, two lines (not shown) are formed on the secondary battery 1a respectively by 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, and the folding portion 139a is formed by the plane between such two lines.

[0211] The width FW of such a folding portion 139 does not exceed the length of the die edge 1621 and can be 1 mm to 3.2 mm, particularly 1 mm to 1.6 mm.

[0212] FIG. 20 is a schematic view showing from above the state before cutting the degassing portion 337 of the conventional battery case 33.

[0213] The bridge 136 of the battery case 13 is folded to form a folding portion 139 on one side of the secondary battery 1, and such a folding portion 139 integrally connects the first case 131 and the second case 132. However, the battery case 13 is formed by drawing a pouch film 135. At this time, not only the cup portion 133 is limited and stretched, but also the peripheral side 134 of the cup portion 133 is stretched finely as a whole. Therefore, when the bridge 136 is folded, the finely stretched portions of the side 134 accumulate and protrude outward from a part of both ends of the folding portion 139 and become visibly apparent. This is referred to as Bat ear (35 or 15).

[0214] The size of the Bat 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 larger 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 Bat ear 35 also increases. However, conventionally, there has been 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 Bat ear 35 was formed to be quite large, and there was also a limit to reducing it.

[0215] When the size of such a Bat ear 35 is formed to be large, the wasted volume of the secondary battery 3 further increases, resulting in 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), the assembly is not easy, and there has been a problem that the size of the secondary battery 3 has to be designed small from the beginning considering such a Bat ear 35. Also, in order to increase the volume of the secondary battery 3, there is also a problem that the energy density with respect to the volume decreases.

[0216] On the one hand, as described above, the pouch-type battery case 13 according to an embodiment of the present invention includes a cup portion 133 provided with a housing space 1331 for housing the electrode assembly 10, and a degassing portion 137 formed on one side of the cup portion 133 for discharging gas generated inside the cup portion 133 through the degassing hole H.

[0217] Also, in the process of sealing the side 134, a formation process and a degassing process can be performed. Specifically, after the electrode assembly 10 is housed in the cup portion 133, in the battery case 13, the corner portion 1371 included in the degassing portion 137 can be opened, and the remaining sides 134 can be sealed. When an opening is formed by opening the corner portion 1371 of the battery case 13, an electrolytic solution is injected into the battery case 13 through the opening.

[0218] After injecting the electrolytic solution into the battery case 13, the degassing portion 137 is first sealed to form a temporary sealing portion 1340. Thereafter, since the degassing portion 137 is secondarily sealed to form a sealing portion 1341, the temporary sealing portion 1340 is preferably formed at a position close to the corner portion 1371 in the degassing portion 137.

[0219] Thereafter, a formation process can be performed. The formation process (formation process) is a process of finally completing charging so that the secondary battery 1 can supply power. Since the formation process is performed after forming the temporary sealing portion 1340 and completely sealing the battery case 13, the charging rate is high, gas is discharged quickly, and the manufacture of the secondary battery 1 can be completed within a specified process time.

[0220] When the activation process is completed, gas is generated inside the battery case 13. Therefore, a degassing hole H is drilled in the degassing portion 137 of the battery case 13. Through such a degassing hole H, the gas is discharged from the inside of the battery case 13 to the outside. At this time, as the gas is easily discharged, the injected electrolyte may leak through the degassing hole H. To prevent this, the degassing hole H is preferably drilled at a position close to the temporary sealing portion 1340. When the degassing hole H is drilled, a degassing process is performed to discharge the gas to the outside of the battery case 13.

[0221] When the degassing hole H is drilled, the inside of the battery case 13 is also opened, and the internal electrolyte can leak to the outside. Therefore, the boundary between the cup portion 133 and the degassing portion 137 is secondarily sealed to form a sealing portion 1341. At this time, the sealing portion 1341 is preferably formed between the cup portion 133 and the degassing hole H, and particularly, at a position close to the cup portion 133.

[0222] While performing the activation process and the degassing process in this way, it is necessary to drill the degassing hole H and perform primary sealing and secondary sealing. Furthermore, when mass-producing the secondary battery 1, it is necessary to collectively manage the specifications and quality of the secondary battery 1. For this purpose, the battery case 13 or the secondary battery 1 can be inspected using the inspection device 4 (shown in FIG. 22) including the vision sensor 41.

[0223] Conventionally, there has been a limit to manufacturing the battery case 33 and the secondary battery 3 in an overall sharp shape. Therefore, when the battery case 33 is photographed with a vision sensor, large errors in the size and position of each configuration occurred.

[0224] Specifically, hereinafter, when the manufacturing of the secondary battery 1 is completed, the electrode leads 12 of a plurality of 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 plurality of secondary batteries 1 must all be constant. However, conventionally, since the electrode 101 is arranged at a certain distance from the outer wall 338 of the cup portion 333, the electrode assembly 10 may move inside the cup portion 333 before sealing the side 134. Therefore, when mass-producing the secondary battery 3, even if the volumes of the cup portion 333 and the electrode assembly 10 are all constant, the positions of the electrode assemblies 10 are slightly different from each other, and the positions of the electrode leads 12 are also slightly different from each other. Therefore, it is necessary to accurately measure the positions of such electrode leads 12 using the inspection device 4.

[0225] In addition, in order to drill the degassing hole H at an accurate position and size and perform the primary sealing and secondary sealing at accurate positions and sizes, it is necessary to accurately measure the position of the degassing portion 137. In addition, in order to efficiently manage the overall quality of the plurality of secondary batteries 1, it is necessary to accurately measure the positions of various components of the battery case 13 or the secondary battery 1, such as the side 134, the folding portion 139, and the insulating portion 14 protruding from the battery case 13, and furthermore, the width between the cup portions 133.

[0226] In order to measure the positions of the above components, it is necessary to set a specific reference line and measure the vertical distance from the reference line to the component to be measured. For example, when the electrode assembly 10 moves inside the cup portion 333, generally, based on what is shown in FIG. 20, it often moves in the left-right direction, that is, in the direction toward the folding portion 339 and the degassing portion 337. 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 in order to measure the vertical distance to the left or right corner, it is necessary to set a reference parallel to the left or right corner.

[0227] However, conventionally, since the outer wall 338 of the cup portion 333 is not formed close to being vertical and the radius of curvature R2' of the punch edge 361 of the cup portion 333 is also large, when the vision sensor 41 captures an image of the battery case 33, in the image, as shown in FIG. 20, the punch edge 361 of the cup portion 333 is not clearly shown. Therefore, the position of the configuration cannot be measured based on the punch edge 361 of the cup portion 333, and it is set based on the butt ear 35 close to the punch edge 361, or the user directly manually sets it based on the punch edge 361 of the cup portion 333.

[0228] However, since the butt ear 35 is formed by folding the bridge 136 in a state where the peripheral side 134 of the cup portion 133 is also overall finely stretched, the size of the butt ear 35 is slightly different for each of the plurality of secondary batteries 1. As a result, even when the position of the configuration is measured by the vision sensor, since the size of the reference butt ear 35 is different, the deviation of the position of the configuration becomes large between the secondary batteries 3, and there is also a problem that quality control is difficult.

[0229] In particular, even when the vision sensor captures an image of the battery case 33 and measures the position of the electrode lead 12, the position of the electrode lead 12 is slightly different, and when connecting the electrode leads 12 to manufacture the battery module 5, there is a problem that the connection is not easy. Also, when stacking the plurality of secondary batteries 1 in order or aligning them in a row to manufacture the battery module 5, the position of the cup portion 333 is not accurate, and there is also a problem that the alignment degree of the plurality of secondary batteries 1 decreases.

[0230] Also, when manufacturing the battery module 5 by housing the secondary battery 3 in another housing 51 (shown in FIG. 27), since the deviation of the measured value is large, when designing the housing 51, the design tolerance is set unnecessarily large, and there is also a problem that the energy density with respect to the volume of the battery module 5 decreases.

[0231] FIG. 21 is a schematic view showing from above the state before cutting the degassing portion 137 of the battery case 13 according to an embodiment of the present invention, and FIG. 22 is a block diagram of the inspection apparatus 4 according to an embodiment of the present invention.

[0232] According to an embodiment of the present invention, as illustrated in FIG. 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. As a result, the size of the butt ear 15 can also be further reduced. Therefore, the secondary battery 1 can be easily assembled into the battery module 5, and the wasted volume of the secondary battery 1 can be reduced, so that the energy density with respect to the volume can also be increased.

[0233] Also, according to an embodiment of the present invention, as illustrated in FIG. 21, since the punch edge 1611 of the cup portion 133 is clearly shown in the video of the battery case 13, the inspection apparatus 4 can automatically set the punch edge 161 of the cup portion 133 to the reference line ST. Based on the punch edge 161 of the cup portion 133, the distances to various components of the battery case 13 or the secondary battery 1 can be accurately measured. Furthermore, the width CW between the cup portions 133 can also be accurately measured. As a result, the positions of the components of the battery case 13 or the secondary battery 1 can be accurately measured, the error of the measured value can be reduced, and the deviation between the secondary batteries 1 can also be reduced.

[0234] For this purpose, an inspection apparatus 4 for a battery case 13 or a secondary battery 1 according to an 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, a video analysis unit 422 that analyzes the image and detects the outline corresponding to the punch edge 161 of the cup portion 133 in which the accommodation space 1331 for accommodating the electrode assembly 10 is provided in the battery case 13, 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.

[0235] Also, an inspection method for a battery case 13 or a secondary battery 1 according to an embodiment of the present invention using such an inspection apparatus 4 includes a step in which the vision sensor 41 photographs the battery case 13 and acquires an image of the battery case 13 or the secondary battery 1, a step in which the outline extraction unit 421 extracts an outline of the configuration of the battery case 13 or the secondary battery 1 from the image, a step in which the video analysis unit 422 analyzes the image and detects the outline corresponding to the punch edge 161 of the cup portion 133 in which the accommodation space 1331 for accommodating the electrode assembly 10 is provided in the battery case 13, a step in which the reference line setting unit 423 sets the outline corresponding to the punch edge 161 as a reference line ST, and a step in which the distance calculation unit 424 calculates the distance from the reference line ST to the configuration.

[0236] Specifically, as shown in FIG. 22, the inspection apparatus 4 includes a vision sensor 41 and a control unit 42. These components can be connected to each other via a bus (not shown) for communication. All components included in the control unit 42 can be connected to the bus via at least one interface or adapter, or directly connected to the bus. The bus can also be connected to other subsystems in addition to the above-described components. Such a bus includes a memory bus, a memory controller, a peripheral bus, and a local bus.

[0237] The vision sensor 41 captures a specific area and acquires an image by receiving an image signal for the specific area. For this purpose, generally, the vision sensor 41 includes an imaging device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor) image sensor. In particular, the vision sensor 41 according to an embodiment of the present invention can capture the battery case 13 after the bridge 136 of the battery case 13 is folded, and acquire an image of each component of the battery case 13 or the secondary battery 1. Here, the components include the cup portion 133, the degassing portion 137, the electrode lead 12, the battery ear 15, the side 134, the folding portion 139, and the insulating portion 14 described above. Thereafter, the manufacture of the secondary battery 1 is completed by cutting the degassing portion 137. Therefore, if the vision sensor 41 captures the battery case 13 before cutting the degassing portion 137, an image of the battery case 13 and the electrode lead 12 can be acquired, and if the vision sensor 41 captures the battery case 13 after cutting the degassing portion 137, an image of the secondary battery 1 can be acquired.

[0238] The control unit 42 receives the video signal acquired by the vision sensor 41, and determines the positions of the components of the battery case 13 or the secondary battery 1 from the video signal. Such a control unit 42 includes an outline extraction unit 421, a video analysis unit 422, a reference line setting unit 423, and a distance calculation unit 424. As the control unit 42, it is preferable to use a CPU (Central Processing Unit), an MCU (Micro Controller Unit), a DSP (Digital Signal Processor), etc., but it is not limited thereto, and various logical operation processors can be used.

[0239] The outline extraction unit 421 extracts the outlines of the components of the battery case 13 or the secondary battery 1 from the video received from the vision sensor 41. At this time, the outline extraction unit 421 can extract the outlines of all the components shown in the video, but is not limited thereto, and an ROI (Region Of Interest) can be set in a part of the video, and only the outlines of the components shown within the ROI can be extracted. To extract the outline, first, information regarding the pixels of the image is extracted, and a generally used gradient formula can be used for this purpose. The extracted pixel information shows the outlines of the battery case 13 and the electrode lead 12.

[0240] 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 portion 133 can be further reduced, the outer wall 138 of the cup portion 133 can be formed closer to being vertical, and the gradient of the pixel information corresponding to the punch edge 161 of the cup portion 133 in the video 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 portion 133 can be clearly extracted.

[0241] The image analysis unit 422 analyzes the said image to detect the outline corresponding to the punch edge 161 of the cup part 133 from the battery case 13. For this purpose, the image analysis unit 422 can match the reference outline information of the punch edge 161 of the cup part 133 stored in advance with the information of the said extracted outline to detect the outline corresponding to the punch edge 161 of the cup part 133. At this time, the image analysis unit 422 can match the said two pieces of information by using the Template Matching technique.

[0242] The reference line setting unit 423 can set the outline corresponding to the punch edge 161 as the reference line ST. Since the cup part 133 includes a plurality of punch edges 161, a plurality of outlines corresponding to the punch edge 161 are also extracted. At this time, in order to accurately measure the position of each component of the battery case 13 or the secondary battery 1, the reference line setting unit 423 preferably 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. Also, as described above, since it is necessary to measure the vertical distance from the reference line ST for the position of the component, 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.

[0243] For example, in order to punch the degassing hole H and perform primary and secondary sealing, the inspection device 4 needs to measure the position of the degassing part 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 part 137 and parallel to the corner 1371 included in the degassing part 137, among the plurality of punch edges 161 as the reference line ST.

[0244] Also, for example, in order to inspect whether the positions of all the electrode leads 12 are constant, it is necessary for the inspection device 4 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 on the electrode lead 12 side corresponding to the punching edge 1611 on the folding part 139 side, which is close to the electrode lead 12 and parallel to the corner on the left or right side of the electrode lead 12, among the plurality of punching edges 161.

[0245] Furthermore, in order to measure the width between the cup parts 133, the reference line setting unit 423 can also set, as the reference line ST, any one of the outlines of two punching edges 161 corresponding to the width boundary of the cup part 133 among the plurality of punching edges 161.

[0246] That is, the reference line setting unit 423 is not limited as long as it can accurately measure the positions of the respective components of the battery case 13 or the secondary battery 1, and can set various outlines as the reference line ST.

[0247] 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 said video. For example, when the outline corresponding to the punching 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 the corner included in the degassing part 137. Or, when the outline corresponding to the punching edge 1611 on the folding part 139 side is set as the reference line ST, the distance calculation unit 424 can also calculate the distance from the reference line ST to the corner on one side of the electrode lead 12, and can also calculate the distance to the outline corresponding to the punching edge 1612 on the die edge 162 side.

[0248] The distance calculation unit 424 can use information regarding the relationship between the number of pixels of a pre-stored image and the actual distance. That is, in the said image, the distance calculation unit 424 counts, in terms of the number of pixels, the distance from the reference line ST to each component, and then can calculate the actual distance corresponding to the counted number of pixels by using the information regarding the relationship between the number of pixels of a pre-stored image and the actual distance.

[0249] The inspection device 4 can further include a storage unit 44. The storage unit 44 stores a program for processing and controlling the operation of the inspection device 4, various data generated during the execution of each program, received signals, etc. In particular, reference information regarding the battery case 13 can be stored so that the image analysis unit 422 can detect an outline corresponding to the punch edge 1611 of the cup portion 133. Here, the reference information regarding the battery case 13 can include reference outline information regarding the punch edge 1611 of the cup portion 133, reference information regarding the distance to the configuration of the battery case 13 or the secondary battery 1, etc. This can be directly stored in the storage unit 44 by the user, or the inspection device 4 can also generate and store the said reference information through repeated learning. Also, the storage unit 44 can store information regarding the relationship between the number of pixels of an 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. Furthermore, inspection result information of the battery case 13 to be inspected can also be stored. Such a storage unit 44 can be built into the inspection device 4, or can also 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 is a NAND flash memory which is small in volume, light in weight, and resistant to external impacts, and the volatile memory device can be a DDR SDRAM.

[0250] The control unit 42 can 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 can compare the reference information regarding the battery case 13 stored in the storage unit 44 with the inspection result information of the battery case 13 to be inspected. Also, when the inspection result information is within the error range of the reference information, the battery case 13 is determined to be normal. However, when the inspection result information deviates from the error range of the reference information, the battery case 13 is determined to be defective.

[0251] On the other hand, the inspection device 4 can further include a display unit 43 that receives and displays a video signal. The display unit 43 receives the video signal and displays it to the user. Further, when the outline extraction unit 421 extracts the outline of the battery case 13, the outline can be displayed on the video and the user can also confirm it via the display unit 43. Various methods such as LCD (Liquid Crystal Display), OLED (Organic Liquid Crystal Display), CRT (Cathode Ray Tube), and PDP (Plasma Display Panel) can be used for the display unit 43. Also, the display unit 43 is connected to the bus via a video interface, and the data transmission between the display unit 43 and the bus can be controlled by a graphic controller.

[0252] When the defect determination unit 425 determines that the battery case 13 is defective, the inspection device 4 can further include an alarm unit 45 that generates an alarm. When generating an alarm, it is preferable that the alarm is generated auditorily or visually, such as the lighting of a lamp or a warning sound, so that the user can intuitively know.

[0253] Each component of the above-described vision sensor 41, control unit 42, storage unit 44, and display unit 43 can be implemented by software such as tasks, classes, subroutines, processes, objects, execution threads, programs, etc. in a predetermined area on a memory, or by hardware such as an FPGA (field-programmable gate array) or ASIC (application-specific integrated circuit), and can also be composed of a combination of the software and the hardware. The components can be included in a computer-readable storage medium, and a part of them can be distributed and dispersed among a plurality of computers.

[0254] Also, each block can represent a module, segment, or part of code that includes one or more executable instructions for performing a specific logical function. Also, in some alternative embodiments, the functions referred to in the block can occur deviating from the procedure. For example, two blocks shown continuously can actually be performed substantially simultaneously, and the blocks can sometimes be performed in reverse order according to the corresponding functions.

[0255] When the inspection device 4 according to an embodiment of the present invention is used, since the punch edge 1611 of the cup portion 133 is clearly shown, the inspection device 4 can automatically set the punch edge 161 of the cup portion 133 to the reference line ST, and the distances 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 manufacture of the secondary battery 1 is completed, the sizes and positions of the cup portion 133, the electrode lead 12, the but ear 15, the side 134, the folding portion 139, and the insulating portion 14, etc. can be accurately grasped. Thereby, it is also possible to easily determine whether the secondary battery 1 is defective, and even when the secondary battery 1 is mass-produced, these standards and qualities can be efficiently managed collectively.

[0256] In particular, the position of the electrode lead 12 can be accurately measured, and it can be connected when easily connecting the electrode lead 12 in order to manufacture the battery module 5. Also, the position of the cup portion 333 can be accurately measured, and when stacking the plurality of secondary batteries 1 in order or aligning them in a row to manufacture the battery module 5, the alignment degree of the plurality of secondary batteries 1 can also be improved.

[0257] FIG. 23 is a schematic view showing a state in which the degassing portion 137 of the battery case 13 according to an embodiment of the present invention is cut to complete the manufacture of the secondary battery 1.

[0258] After the battery case 13 is secondarily sealed to form the sealing portion 1341, a cutting line CT is set outside the sealing portion 1341 to cut the degassing portion 137. Thereby, as shown in FIG. 23, the length of the degassing portion 137 becomes short, and the volume of the secondary battery 1 can be reduced. Through the process as described above, the manufacture of the pouch-type secondary battery 1 is completed.

[0259] On the other hand, among the plurality of sides 134, the electrode lead 12 is not formed to protrude on the side 134 remaining after cutting the degassing portion 137. However, if the side 134 is left as it is after being sealed, the overall volume of the secondary battery 1 increases. Therefore, in order to reduce the energy density with respect to the volume, it is preferable to fold the side 134.

[0260] On the other hand, as shown in FIG. 23, the side 134 can include a sealing portion 1341 and an unsealed portion 1342. The sealing portion 1341 is located relatively outside and is a sealed region, and the unsealed portion 1342 is located relatively inside and is an unsealed region.

[0261] Specifically, when the battery case 13 is secondarily sealed to form the sealing portion 1341, the sealing portion 1341 can be formed at a certain distance from the cup portion 133 instead of being immediately connected thereto. When sealing the side 134, it is necessary to apply heat and pressure to the side 134 using another sealing tool (not shown). However, when sealing the side 134 with such a sealing tool in a state where it is in close contact with the cup portion 133, the sealant layer 1351 located inside the side 134 may be partially melted and leak toward the electrode assembly 10, which may contaminate the electrode assembly 10. In addition, the heat of the sealing tool may be transmitted to the electrode assembly 10, which may damage the electrode assembly 10. Therefore, it is preferable to seal the side 134 with the sealing tool separated from the cup portion 133 to some extent. As a result, the portion sealed by the sealing tool becomes the sealing portion 1341, and the portion that is not sealed with the sealing tool separated from the cup portion 133 becomes the unsealed portion 1342.

[0262] FIG. 24 is a schematic view showing a state in which a conventional side 334 is folded from the side, and FIG. 25 is a schematic view showing a state in which a conventional side 334 is folded from the top.

[0263] Conventionally, when the side 334 was folded, there was a problem that the side 334 was not fixed and was unfolded at a predetermined angle. Specifically, as described above, the pouch film 135 is formed by laminating a sealant layer 1351, a moisture barrier layer 1352, a stretching auxiliary layer 1354, and a surface protection layer 1353. Among these, since the sealant layer 1351 contains a first polymer, particularly polypropylene (PP), it has high flexibility and elastic force. 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 a metal, particularly an aluminum alloy, when the side 334 is folded, it exceeds the limit of elastic deformation, and the storage force to maintain the folded state is large.

[0264] However, the conventional pouch film had a moisture barrier layer with a thickness of approximately 30 to 50 μm and a sealant layer with a thickness of approximately 60 to 100 μm. That is, the thickness of the moisture barrier layer was formed to be considerably thinner than the thickness of the sealant layer. Therefore, the restoring force was greater than the storage force, side 334 was not fixed, and it was unfolded at a predetermined angle. As a result, there was a problem that the useless volume of the secondary battery 3 increased due to side 334.

[0265] To solve this, as shown in FIGS. 24 and 25, a tape 38 was separately attached to side 334. In particular, the tape 38 was attached to both the outer surface of the bottom 3332 of the cup portion 333 and side 334, whereby side 334 could be fixed to the cup portion 333 and prevented from being unfolded. However, in such a case, as shown in FIG. 24, there was a problem that the overall thickness of the secondary battery 3 increased due to the thickness of the tape 38 itself. Also, after the process of folding side 334, an additional process of attaching tape 38 was required, and such a process took a lot of time, increased the number of processes, and there was also a problem of reducing the manufacturing yield of the secondary battery 3.

[0266] On the one hand, 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 portion 133 decreases. Conventionally, the electrode assembly 10 was arranged at a certain distance from the outer wall 338 of the cup portion 333. Therefore, since the internal pressure of the cup portion 333 decreases and the volume of the space 37 between the outer wall 338 of the cup portion 333 and the electrode assembly 10 also decreases, the outer wall 338 or the bottom 3332 of the cup portion 333 may be deformed. In particular, as shown in FIG. 24, the outer wall 338 on the folding portion side of the secondary battery 3 is recessed inward, and the punch edge 361 on the folding portion 339 side of the cup portion 333 protrudes outward and the height increases, so that an Edge High phenomenon may occur. Due to such an Edge High phenomenon, there has been a problem that the useless thickness of the secondary battery 3 increases and the energy density with respect to the volume decreases. In addition, since the outer wall 338 on the folding portion 339 side of the cup portion 333 is deformed, the appearance of the secondary battery 3 is not beautiful, and there is also a problem that the commerciality decreases. Furthermore, due to the Edge High phenomenon, there has also been a problem that the size of the battery tab 15 further increases and the shape is emphasized.

[0267] FIG. 26 is a schematic view showing a state in which the side 134 is folded according to an embodiment of the present invention from the side.

[0268] According to an embodiment of the present invention, since the moisture barrier layer 1352 of the pouch film 135 has a thickness of 50 to 70 μm and the sealant layer 1351 has a thickness of 70 to 100 μm, the thickness of the moisture barrier layer 1352 is thicker than before. Therefore, when the side 134 is folded, the storage force is further increased, so that it is not necessary to attach another tape 38, and it is possible to prevent the side 134 from being unfolded again.

[0269] For this purpose, a secondary battery 1 according to an embodiment of the present invention includes an electrode assembly 10 formed by laminating an electrode 101 and a separator 102, and a pouch-type battery case 13 in which a cup portion 133 for accommodating the electrode assembly 10 therein is formed. The pouch-type battery case 13 includes a side 134 extending outward from the outside of the cup portion 133. The side 134 includes a sealing portion 1344 that is relatively positioned on the outside and sealed, and an unsealed portion 1345 that is relatively positioned on the inside and not sealed. The side 134 is not adhered to the cup portion 133 and is folded at the unsealed portion 1345.

[0270] That is, as shown in FIG. 26, after the side 134 is folded toward the cup portion 133 in the secondary battery 1, the side 134 is not adhered to the cup portion 133 and can maintain the folded state without being unfolded. At this time, the side 134 can be folded at an angle of 85° to 95°, particularly at an angle of 88° to 92°. Further, the side 134 is folded at a position adjacent to the cup portion 133, and the side 134 can contact the outer wall 138 of the cup portion 133. In particular, as described above, the side 134 can include a sealing portion 1341 that is relatively disposed on the outside and sealed and an unsealed portion 1342 that is relatively disposed on the inside and not sealed. Further, when the side 134 is folded, it is preferable that the unsealed portion 1342 closer to the cup portion 133 is folded. Thereby, the wasted volume of the secondary battery 1 can be further reduced. However, even in such a case, the side 134 and the cup portion 133 are not adhered to each other, and the storage force of the side 134 is increased to maintain the folded state.

[0271] 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 forming one cup portion 133. As described above, it is because not only the cup portion 133 is intensively stretched, but also the peripheral side 134 of the cup portion 133 is stretched finely as a whole. However, if the width of the side 134 is longer than the depth D of such a cup portion 133, when the side 134 is folded only once, the outer end portion 1343 of the side 134 may protrude outside the bottom portion 1332 of the cup portion 133.

[0272] Therefore, when two cup portions 133 are formed in the pouch film 135, as shown in FIG. 26, a double side folding (DSF) method of folding the side 134 twice can be used. 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 at a position relatively closer to the outer end portion 1343, and the second folding portion 1345 is a portion folded at a position relatively closer to the cup portion 133. Therefore, after the side 134 is folded once based on the first folding portion 1344, the side 134 can be folded a second time based on the second folding portion 1345. At this time, the first folding portion 1344 can be located at the sealing portion 1341 on the side 134, and the second folding portion 1345 can be located at the unsealed portion 1342 on the side 134. Also, the side 134 can be folded at an angle of 170° to 180°, particularly 180°, at the first folding portion 1344. Also, it can be folded at an angle of 85° to 95°, particularly 88° to 92°, at the second folding portion 1345. Thereby, it is possible to prevent the outer end portion 1343 of the side 134 from protruding outside the bottom portion 1332 of the cup portion 133.

[0273] On the one hand, according to an embodiment of the present invention, since the electrode assembly 10 can be located very close to the outer wall 138 of the cup portion 133, the wasted volume of the cup portion 133 is reduced. Therefore, even when the internal pressure of the cup portion 133 is reduced by performing a degassing process, deformation of the outer wall 138 or the bottom 1332 of the cup portion 133 can be prevented. That is, as shown in FIG. 26, since the edge high phenomenon can be prevented, the energy density with respect to the volume can be prevented from decreasing.

[0274] FIG. 27 is a schematic view of a battery module 5 according to an embodiment of the present invention.

[0275] Medium and large-sized electronic devices such as automobiles need to have a large output, so a large number of secondary batteries 1 are required. In order to easily move and install such secondary batteries 1, a battery module 5 can be manufactured. When a plurality of secondary batteries 1 are installed in such a battery module 5, electricity can be stably supplied to the outside.

[0276] On the other hand, since electricity is produced in the electrode assembly 10 of the secondary battery 1, a chemical reaction between the electrode 101 and the electrolytic solution occurs, and heat is generated in such a process. However, if the ambient temperature rises excessively due to heat, there are problems such as malfunction in the circuit of the electrical device in which the secondary battery 1 is installed or shortening of the life of the electrical device. Therefore, the battery module 5 includes a cooling system for cooling the secondary battery 1. The cooling system mainly includes methods such as a water-cooled type cooled by cooling water and an air-cooled type cooled by air. Among these, the water-cooled cooling system has higher cooling efficiency than the air-cooled cooling system and is more widely used.

[0277] The cooling system includes a cooling plate that directly cools the secondary battery 1, and another flow path is formed inside such a cooling plate so that cooling water can flow. Also, the thinner and longer the flow path is, the wider the surface area becomes and the cooling efficiency can be increased.

[0278] To manufacture the battery module 5, first, a plurality of secondary batteries 1 are manufactured, and then such secondary batteries 1 are connected to each other and housed in the housing 51. At this time, the secondary batteries 1 can be aligned in a row and stacked. As shown in FIG. 27, when the secondary battery 1 is housed in the housing 51, the longer side surface of the secondary battery 1 faces downward, and a cooling plate (not shown) can be formed on the lower surface of the housing 51. Therefore, by cooling the cooling plate from the longer side surface of the secondary battery 1, the cooling efficiency can be increased.

[0279] On the other hand, on one side of the secondary battery 1, a folding portion 139 formed by folding the bridge 136 is formed, and on the other side, a side 134 which is a region where the degassing portion 137 is cut and remains is formed. However, if the cooling plate cools from the side surface on which the side 134 is formed among the plurality of surfaces of the secondary battery 1, the distance between the cooling plate and the electrode assembly 10 becomes long due to the side 134, so the cooling efficiency may decrease. Therefore, it is preferable that the cooling plate cools from the side surface on which the folding portion 139 is formed among the longer side surfaces of the secondary battery 1. For this purpose, when the secondary battery 1 is housed in the housing 51, it can be housed so that the folding portion 139 faces the cooling plate, that is, downward.

[0280] FIG. 28 is an enlarged front view showing a state in which the conventional secondary battery 3 is housed in the housing 51 of the battery module 5, and FIG. 29 is an enlarged side view showing a state in which the conventional secondary battery 3 is housed in the housing 51 of the battery module 5.

[0281] As described above, conventionally, there has been a limit to reducing the size of the battery tab 35. In particular, there has been a limit to reducing the size of the battery tab 35 to a predetermined value (for example, 1.5 mm) or less while forming the depth D' of the cup portion 333 sufficiently deep (for example, 6.5 mm or more).

[0282] Conventionally, the angle θ' formed by the folding portion 339 and the inner corner portion 35a of the bat ear 35 was formed to be 151 degrees or less.

[0283] Here, the angle θ' can mean the 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 portion 35a of the bat ear 35. In particular, the first line L1 and the second line L2 can be determined by video analysis. As an example, the first line L1 and the second line L2 can be extracted by connecting a number of edge points confirmed within the ROI (Region of Interest) with a vision device. Therefore, even when the inner corner portion 35a of the folding portion 339 or the bat ear 35 is partially warped or bent, the first line L1 and the second line L2 can be clearly defined. Since such video analysis is a well-known technique, detailed description thereof will be omitted.

[0284] Therefore, as shown in FIG. 28, when the secondary battery 3 is housed in the housing 51, the bat ear 35 is separated from between the housing 51 and the folding portion 339 by a large distance d' (for example, more than 1.5 mm). Therefore, such a distance d' may interfere with the cooling of the cooling plate and reduce the cooling efficiency. To solve this problem, a heat transfer substance 52 is injected into the space between the cooling plate and the folding portion 339 of the secondary battery 1 so that the cooling plate cools the folding portion 139 via the heat transfer substance 52. For example, the heat transfer substance 52 can be thermal grease.

[0285] However, when the bat ear 15 is large, a large amount of such heat transfer substance 52 has to be injected, resulting in an increase in cost. Also, since the distance d' between the cooling plate and the folding portion 139 is large, there is still a problem of low cooling efficiency.

[0286] In addition, when the degassing process is performed through the degassing hole H, the internal pressure of the battery case 33 decreases, and as shown in FIG. 29, the folding portion 339 of the battery case 33 adheres to the electrode assembly 10. However, conventionally, there is a limit to reducing the clearance CL', and the width of the folding portion 339 is also formed large. Therefore, a large space 37 is formed between the outer wall 338 of the cup portion 333 and the electrode assembly 10, resulting in a problem that the energy density with respect to the volume of the secondary battery 3 decreases. Furthermore, since the distance by which the electrode assembly 10 is separated from the thermal grease 52 also increases, there is also a problem that the cooling efficiency becomes lower.

[0287] FIG. 30 is an enlarged front view showing a state in which the secondary battery 1 according to an embodiment of the present invention is housed in the housing 51 of the battery module 5, and FIG. 31 is an enlarged side view showing a state in which the secondary battery 1 according to an embodiment of the present invention is housed in the housing 51 of the battery module 5.

[0288] The pouch-type secondary battery 1 according to an embodiment of the present invention includes an electrode assembly 10 formed by laminating an electrode 101 and a separator 102, and a pouch-type battery case 13 in which a cup portion 133 for housing the electrode assembly 10 therein is formed. The battery case 13 includes a first case 131 and a second case 132 in which the cup portion 133 is formed on at least one side, a folding portion 139 that integrally connects the first case 131 and the second case 132, and a butt ear 15 that protrudes outward at a part of both ends of the folding portion 139. The length D of the butt ear 15 is 1.5 mm or less.

[0289] In addition, the angle θ formed by the folding portion 139 and the inner corner portion 15a of the butt ear 15 can be formed to be greater than 151 degrees. Also, the angle θ can be 180 degrees or less. Also, if the angle θ is 180 degrees, it may mean a state where the butt ear 15 does not exist.

[0290] Here, the angle θ may mean the angle formed by a virtual first line L1 corresponding to the folding portion 139 and a virtual second line L2 corresponding to the inner corner portion 15a of the earpiece 15. Regarding the first line L1 and the second line L2, the above-described content is incorporated. Further, the 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 laminating 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. The battery case 13 includes a first case 131 and a second case 132 in which the cup portions 133 are respectively formed, a folding portion 139 that integrally connects the first case 131 and the second case 132, and earpieces 15 that protrude outward at a part of both ends of the folding portion 139. The earpiece 15 has a length D of 1.5 mm or less.

[0291] As described above, the earpiece 15 is formed by folding the bridge 136 and protruding outward at a part of both ends of the folding portion 139. According to an embodiment of the present invention, the length of such an earpiece 15 can be 1.5 mm or less, particularly 1 mm or less. The length of such an earpiece 15 can be the length measured from the outer wall 1381 on the folding portion 139 side to the outermost end of the earpiece 15. At this time, as described above, the outer wall 1381 on the folding portion 139 side can have an inclination with a clearance CL such that the inclination angle is between 90° and 95° from the bottom 1332. Considering this, as an example of measuring the earpiece, the length of the earpiece 15 can be the length measured from the most outwardly protruding portion of the outer wall 1381 on the folding portion 139 side to the outermost end of the earpiece 15.

[0292] The length of the earpiece 15 can be measured by directly contacting the secondary battery 1 using a ruler or calipers, etc., or can also be measured in a non-contact manner using a laser displacement sensor or a vision sensor, etc.

[0293] The above describes, by way of example, a method for measuring the length of the bat ear, and not all cases necessarily limited to the above measurement method belong to the scope of the present invention. The length of the bat ear can be any length that conforms to the description of the claims and the gist of the present invention and can be considered as the length of the bat ear as meant by the present invention.

[0294] According to an embodiment of the present invention, 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 of the punch edge 1611 of the cup portion 133 and the clearance CL can be made smaller.

[0295] Thereby, while forming the depth D of the cup portion 133 to be 3 mm or more, particularly 6.5 mm or more, the length D of the bat 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. Thereby, the thickness of the heat transfer material 52 inside the housing 51 can be made 1.5 mm or less, and the injection amount of the thermal grease 52 can be further reduced, thereby reducing costs, and the cooling efficiency can also be increased.

[0296] Also, as shown in FIG. 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 with respect to the volume of the secondary battery 1 can be increased. Also, since the distance by which the electrode assembly 10 is separated from the thermal grease 52 is reduced, the cooling efficiency can be further increased.

[0297] Those with ordinary knowledge in the technical field to which the present invention pertains can understand that the present invention can be implemented in other specific forms without changing its technical idea and essential features. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims described later rather than the above detailed description, and various embodiments derived from the meaning and scope of the claims and the equivalent concept thereof should be construed as being included in the scope of the present invention.

Explanation of Reference Numerals

[0298] 1 Secondary battery 2 Molding device 3 Conventional secondary battery 4 Inspection device 5 Battery module 10 Electrode assembly 11 Electrode tab 12 Electrode lead 13 Battery case 14 Insulating part 15 Bat ear 16 Edge 17 Space 21 Die 22 Punch 33 Conventional battery case 35 Conventional bat ear 36 Conventional edge 37 Conventional space 38 Conventional tape 41 Vision sensor 42 Control unit 43 Display unit 44 Storage unit 45 Alarm unit 51 Housing 52 Thermal grease 101 Electrode 102 Separator 111 Positive electrode tab 112 Negative electrode tab 121 Positive electrode lead 122 Negative electrode lead 131 Case 1 132 Case 2 133 Cup part 134 Side 135 Pouch film 136 Bridge 137 Degassing part 138 Outer wall 139 Folding part 161 Punch edge 162 Die edge 163 Thickness edge 164 Corner 211 Forming part 212 Partition 213 Edge of die 221 Edge of punch 333 Conventional cup part 334 Conventional side 336 Conventional bridge 337 Conventional degassing part 338 Conventional outer wall 339 Conventional folding part 361 Conventional punch edge 362 Conventional die edge 421 Outline extraction part 422 Image analysis part 423 Reference line setting part 424 Distance calculation part 425 Defect judgment part 1021 Peripheral part 1331 Accommodation space 1332 Bottom 1333 Outer wall 1340 Temporary sealing part 1341 Sealing part 1342 Unsealed part 1343 Outer end 1344 First folding part 1345 Second folding part 1351 Sealant layer 1352 Moisture barrier layer 1353 Surface protection layer 1354 Extension auxiliary layer 1371 Corner 1381 Outer wall on the bridge side 1382 Outer wall on the degassing section side 1391 Groove 1611 Punch edge on the bridge side 1612 Punch edge on the degassing section side 1613 First punch edge 1614 Second punch edge

Claims

1. An electrode assembly formed by laminating an electrode and a separator, and a pouch-type battery case having a cup portion formed therein for accommodating the electrode assembly, wherein the pouch-type battery case includes a side portion extending outward from the outside of the cup portion, and the side portion includes a sealing portion that is relatively located on the outside and is sealed, and an unsealed portion that is relatively located on the inside and is not sealed, wherein the side portion is not adhered to the cup portion and is folded at an angle of 85° to 95° at the unsealed portion, a pouch-type secondary battery.

2. The side portion is folded while contacting the outer wall of the cup portion, the pouch-type secondary battery according to Claim 1.

3. The side portion includes a first folding portion folded at a position relatively closer to the outer end portion, and a second folding portion folded at a position relatively closer to the cup portion, the pouch-type secondary battery according to Claim 1 or 2.

4. The first folding portion is located in the sealing portion, and the second folding portion is located in the unsealed portion, the pouch-type secondary battery according to Claim 3.

5. The side portion is folded at an angle of 170° to 180° based on the first folding portion, the pouch-type secondary battery according to Claim 3 or 4.

6. The side portion is folded at an angle of 85° to 95° based on the second folding portion, the pouch-type secondary battery according to any one of Claims 3 to 5.

7. The side portion is folded at an angle of 88° to 92° based on the second folding portion, the pouch-type secondary battery according to Claim 6.

8. The pouch-type battery case is manufactured by forming a pouch film, wherein the pouch film is manufactured from a first polymer and has a sealant layer formed as the innermost layer, is manufactured from a second polymer and has a surface protection layer formed as the outermost layer, and includes a moisture barrier layer laminated between the surface protection layer and the sealant layer, wherein the sealant layer has a thickness of 60 to 100 μm, the pouch-type secondary battery according to any one of Claims 1 to 7.

9. The moisture barrier layer has a thickness of 50 to 80 μm, the pouch-type secondary battery according to Claim 8.

10. The moisture barrier layer The pouch-type secondary battery according to claim 8, formed of an aluminum alloy thin film having a crystal grain size of 10 to 13 μm.

11. The aluminum alloy thin film The pouch-type secondary battery according to claim 10, which is alloy number AA8021.

12. The aluminum alloy thin film The pouch-type secondary battery according to claim 10, which contains 1.3 wt% to 1.7 wt% of iron and 0.2 wt% or less of silicon.

13. The moisture barrier layer has a thickness of 55 to 65 μm, The sealant layer The pouch-type secondary battery according to claim 8, which has a thickness of 75 to 85 μm.

14. The pouch-type secondary battery according to claim 8, further comprising a stretching auxiliary layer made of a third polymer and laminated between the surface protection layer and the moisture barrier layer.

15. The stretching auxiliary layer The pouch-type secondary battery according to claim 14, which has a thickness of 20 to 50 μm.

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