Pouch folding device for secondary battery and secondary battery

Abstract

The present invention relates to a pouch folding device for a secondary battery and a secondary battery. The pouch folding device for a secondary battery according to the present invention is a pouch folding device for a secondary battery that folds a pouch including a main body in which an electrode assembly is accommodated and a sealing part formed along an edge of the main body, and includes a side folding part that side-folds the sealing part of the pouch toward the main body, and a corner folding part including a corner folding roller that pressurizes a corner portion of the side-folded sealing part to corner-fold the pouch toward the main body, the corner folding roller including a flat surface and an inclined surface formed on a pressing surface, and when pressing, the inclined surface of the corner folding roller is located at a position closer to the main body than the flat surface.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0025558 filed on February 25, 2022 and Korean Patent Application No. 10-2023-0023905 filed on February 22, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated by reference into this specification.

[0002] The present invention relates to a pouch folding device for a secondary battery and a secondary battery. [Background technology]

[0003] Unlike primary batteries, secondary batteries can be recharged, and due to their potential for miniaturization and large capacity, they have been the subject of much research and development in recent years. With technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source is growing rapidly.

[0004] Secondary batteries are classified into coin type batteries, cylindrical type batteries, square type batteries, and pouch type batteries according to the shape of the battery case. In secondary batteries, the electrode assembly installed inside the battery case is a power generating element capable of charging and discharging, which is made of a laminated structure of electrodes and separators.

[0005] Electrode assemblies can be roughly classified into a jelly-roll type in which a separator is interposed between a positive electrode and a negative electrode that are sheet-type electrodes coated with an active material and wound up; a stack type in which unit cells, each having at least one electrode and at least one separator, are stacked in order; and a stack / folding type in which a unit cell is wound up with a long separating film.

[0006] In manufacturing a secondary battery, a process of folding corners of a pouch containing an electrode assembly is performed. In the process of folding corners of the pouch, a problem occurs in insulation quality when the pouch is pressed with a tool.

[0007] More specifically, the pouch has a cup portion, which is a main body in which the electrode assembly is housed, and a sealing portion formed along the edge of the cup portion, where the sealing portion is flat, and the cup portion, which houses the electrode assembly, is not flat but has a three-dimensional shape that is convex with respect to the sealing portion.

[0008] In order to fold the pouch many times, the tool needs to be attached in the direction of the cup part, but if the cup part is pressed with a flat tool as an unsealed part, it will be damaged, and there will be a risk to the insulation quality. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of one aspect of the present invention is to provide a pouch folding device for a secondary battery, and a secondary battery, which can ensure insulation quality when folding a pouch. [Means for solving the problem]

[0010] A pouch folding device for a secondary battery according to an embodiment of the present invention is a pouch folding device for a secondary battery that folds a pouch including a main body in which an electrode assembly is accommodated and a sealing part formed along an edge of the main body, the pouch including a side folding part that side-folds the sealing part of the pouch toward the main body, and a corner folding part including a corner folding roller that pressurizes a corner portion of the side-folded sealing part to corner-fold the pouch toward the main body, the corner folding roller including a flat surface and an inclined surface formed on a pressing surface, and the inclined surface of the corner folding roller may be located closer to the main body than the flat surface when pressing.

[0011] Meanwhile, the secondary battery according to the embodiment of the present invention may be a secondary battery manufactured by the pouch folding apparatus for a secondary battery according to the embodiment of the present invention. Effect of the Invention

[0012] According to the present invention, a corner of a pouch is folded using a corner folding roller having an inclined surface, thereby preventing insulation quality risks from occurring in a pouch portion that is not flat due to the electrode assembly being housed therein. That is, the flat surface of the corner folding roller having a constant diameter presses the sealing area of ​​the flat pouch, and the inclined surface presses the non-sealing area of ​​the pouch that is not flat due to the electrode assembly being housed therein, thereby preventing damage to the non-sealing area of ​​the pouch and ensuring insulation quality. [Brief description of the drawings]

[0013] [Figure 1] 11 is a plan view illustrating an example of a process in which an electrode assembly is accommodated in a pouch before the pouch is folded. FIG. [Diagram 2] 5A to 5C are front views illustrating a process in which a pouch is side-folded through a side folding unit in the pouch folding device for a secondary battery according to an embodiment of the present invention. [Diagram 3] 4 is a perspective view illustrating a state in which a pouch is side-folded by a pouch folding device for a secondary battery according to an embodiment of the present invention. FIG. [Figure 4] 4 is a perspective view showing a corner folding unit in the pouch folding device for a secondary battery according to an embodiment of the present invention; FIG. [Diagram 5] 2 is a perspective view showing a folding roller and a roller moving unit in a pouch folding device for a secondary battery according to an embodiment of the present invention; FIG. [Figure 6] FIG. 2 is a front view showing a corner folding roller in the pouch folding device for secondary batteries according to an embodiment of the present invention. [Figure 7] FIG. 2 is a perspective view of a main part illustrating a corner-folding concept in a pouch folding device for a secondary battery according to an embodiment of the present invention. [Figure 8] 1 is a perspective view of a main part of a pouch that has been corner-folded in a pouch folding device for a secondary battery according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The object, particular advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings. In this specification, when referring to components in each drawing, it should be noted that the same components are numbered as much as possible even if they are displayed on different drawings. In addition, the present invention can be realized in various different forms and is not limited to the embodiments described herein. In addition, in describing the present invention, detailed descriptions of related known technologies that may obscure the gist of the present invention will be omitted.

[0015] FIG. 1 is a plan view illustrating an example of a process of placing an electrode assembly in a pouch before folding the pouch, FIG. 2 is a front view illustrating a process of side folding a pouch through a side folding section in a pouch folding device for a secondary battery according to an embodiment of the present invention, FIG. 3 is a perspective view illustrating a state in which a pouch has been side folded through a pouch folding device for a secondary battery according to an embodiment of the present invention, and FIG. 4 is a perspective view illustrating a corner folding section in a pouch folding device for a secondary battery according to an embodiment of the present invention.

[0016] 1 to 4, a pouch folding device for a secondary battery according to an embodiment of the present invention is a pouch folding device for a secondary battery that folds a pouch 10 including a body 12 in which an electrode assembly 20 is accommodated and a sealing part 13, and includes a side folding part SR that side-folds the sealing part 13 of the pouch 10 toward the body 12, and a corner folding part CR including a corner folding roller 110 that pressurizes a corner portion 14 of the side-folded sealing part 13 to corner-fold the pouch 10 toward the body 12.

[0017] More specifically, referring to Fig. 1, a secondary battery 1 applicable to a pouch folding device for a secondary battery according to an embodiment of the present invention includes an electrode assembly 20 and a pouch 10 that accommodates the electrode assembly 20 in an internal accommodation portion 11. The secondary battery 1 may further include an electrode lead 30 connected to the electrode assembly 20 and extending to the outside of the pouch 10. The electrode lead 30 may extend in a length direction of the secondary battery 1. Here, the length direction of the secondary battery 1 may be, for example, a Y-axis direction with reference to Fig. 1.

[0018] The pouch 10 includes a body 12 in which an electrode assembly 20 is housed, and a sealing portion 13 formed along an edge of the body 12 .

[0019] Here, the sealing portion 13 is formed in a flat shape, and the body 12 is formed in a three-dimensional shape that is convex with respect to the sealing portion 13 to accommodate the electrode assembly 20 .

[0020] The electrode assembly 20 may be formed by alternately stacking electrodes and separators. The electrode assembly 20 is a power generating element capable of charging and discharging.

[0021] The electrodes include a positive electrode and a negative electrode, and the electrode assembly 20 may be formed by alternately stacking a positive electrode, a separator, and a negative electrode, where the separator separates and electrically insulates the positive electrode and the negative electrode.

[0022] The positive electrode can include a positive electrode current collector and a positive electrode active material laminated on the positive electrode current collector.

[0023] The positive electrode current collector may be made of an aluminum foil.

[0024] The positive electrode active material may be lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, or a compound or mixture containing at least one of these.

[0025] The negative electrode can include a negative electrode current collector and a negative electrode active material laminated on the negative electrode current collector.

[0026] The negative electrode current collector may be, for example, a foil made of copper (Cu).

[0027] The negative electrode active material can be a compound or mixture that includes a graphite-based material.

[0028] The separator is made of an insulating material and electrically insulates the positive electrode from the negative electrode. The separator may be made of a polyolefin resin film such as polyethylene or polypropylene having microporosity.

[0029] 2 and 3, the side folding portion SR can side fold the sealing portion 13 of the pouch 10 towards the main body 12.

[0030] The side folding parts SR may fold the sealing parts 13 located on both sides of the pouch 10 toward the main body 12. Here, the side folding parts SR may side-fold the sealing parts 13 located on both sides of the pouch 10 toward the main body 12 in the width direction of the pouch 10. Here, the width direction of the pouch 10 may be a lateral direction with respect to the length direction of the pouch 10 in which the electrode lead 30 connected to the electrode assembly 20 extends. That is, the width direction of the pouch 10 may be an X-axis direction with reference to FIG. 3. Also, the width direction of the pouch 10 may be the same direction as the width direction of the secondary battery 1.

[0031] Additionally, the side folding portions SR can fold both sides of the sealing portion 13 of the pouch 10 at right angles.

[0032] The side folding unit SR may be, for example, a side folding roller. Here, both sides of the sealing unit 13 of the pouch 10 may be pressed and folded through the side folding roller. However, in the pouch folding device for secondary batteries according to the embodiment of the present invention, the side folding unit SR is not necessarily limited to the side folding roller, and various folding tools may be used, for example, a plurality of folding blocks may be alternately pressed against the sealing unit 13 of the pouch 10 to fold it.

[0033] Fig. 5 is a perspective view showing a folding roller and a roller moving part in a pouch folding device for a secondary battery according to an embodiment of the present invention, Fig. 6 is a front view showing a corner folding roller in the pouch folding device for a secondary battery according to an embodiment of the present invention, Fig. 7 is a perspective view of a main part showing the concept of corner folding in the pouch folding device for a secondary battery according to an embodiment of the present invention, and Fig. 8 is a perspective view of a main part showing a pouch corner-folded in the pouch folding device for a secondary battery according to an embodiment of the present invention.

[0034] 4 to 8, the corner folding unit CR may include a corner folding roller 110 that presses the corner portion 14 at the side-folded sealing portion 13 and folds the corner toward the main body 12.

[0035] 4 and 5, the corner folding unit CR moves the corner folding roller 110 from the outer edge of the pouch 10 toward the center, and performs corner folding so that the corner portion 14 of the side-folded sealing unit 13 comes into close contact with the outer surface of the pouch 10. In addition, the corner folding unit CR can perform corner folding of the sealing unit 13 by moving the corner folding roller 110 in the X-axis direction, which is the width direction of the pouch 10, after the pouch 10 is positioned parallel to the XY plane.

[0036] 6 and 7, the corner folding roller 110 may include a flat surface 112 and an inclined surface 111 formed on the pressing surface 113. Here, the inclined surface 111 may be formed at an end of the corner folding roller 110. That is, the outer peripheral surface portion of the corner folding roller 110 that pressurizes the pouch 10 may include the flat surface 112 formed with a constant diameter and the inclined surface 111 formed so that the diameter becomes smaller toward the end. In addition, in the corner folding roller 110, the inclined surface 111 may be located at a position closer to the main body 12 than the flat surface 112 during pressing.

[0037] Here, when the corner portion 14 of the sealing part 13 side-folded by the corner folding roller 110 is pressed, the inclined surface 111 can be located at a portion of the corner portion 14 that is folded to contact the main body 12. More specifically, the flat surface 112 presses the first portion 14a at the corner portion 14 of the pouch 10, and the inclined surface 111 presses the second portion 14b at the corner portion 14 of the pouch 10, thereby folding the corner portion 14 of the pouch 10. That is, the corner folding section CR pressurizes the corner portion 14 of the sealing section 13, and during corner folding, a first portion 14a pressed against the flat surface 112 of the corner folding roller 110 at the corner portion 14 is folded so as to contact the portion 13a located in the longitudinal direction of the pouch 10 at the sealing section 13, and a second portion 14b pressed against the inclined surface 111 of the corner folding roller 110 at the corner portion 14 can be folded so as to contact the main body 12.

[0038] Here, the flat surface 112 folds the first portion 14a at the corner portion 14, pressurizing the sealing area of ​​the flat pouch 10, and the inclined surface 111 folds the second portion 14b at the corner portion 14, accommodating the electrode assembly 20, and pressurizing the non-sealing area of ​​the non-flat pouch 10. Here, the sealing area of ​​the pouch 10 that is pressed may be a portion of the sealing portion 13 that extends in the length direction of the secondary battery 1, and the non-sealing area of ​​the pouch 10 may be a portion of the body 12 of the pouch 10. Here, the portion of the body 12 of the pouch 10 that is pressed by the inclined surface 111 of the corner folding roller 110 may be, for example, a terrace portion. Here, the terrace portion may be a portion of the body 12 that is not in contact with the electrode assembly 20. That is, it may be a portion of the pouch 10 located in the empty space between the end of the electrode assembly 20 in the receiving portion 11 of the pouch 10 and the sealing portion 13 of the pouch 10. Here, the terrace portion may form a slope.

[0039] In addition, the corner folding roller 110 may have an inclined surface 111 located on a side adjacent to the main body 12 with respect to the flat surface 112 when pressing the corner portion 14 of the sealing part 13 of the side-folded pouch 10. Here, the inclined surface 111 of the corner folding roller 110 may be formed with an inclination such that the width of the end portion becomes narrower toward the tip of the end portion. Here, the inclination angle α of the inclined surface 111 may be formed, for example, in a range of 20 to 50°. Here, the inclination angle α of the inclined surface 111 may be the inclination angle of the inclined surface 111 with respect to a virtual extension line extending from the flat surface 112.

[0040] Therefore, the inclination angle α of the inclined surface 111 is formed to be 20° or more, and the effect on the insulation quality can be significantly improved. That is, when a flat cylindrical pressure roller without the inclined surface 111 presses a terrace portion, which is a non-sealed area of ​​the pouch 10 that is not flat and contains the electrode assembly 20, the corner portion of the pressure roller may damage the non-sealed area of ​​the pouch 10, thereby degrading the insulation quality. However, in the pouch folding device for a secondary battery according to the embodiment of the present invention, the inclination angle α of the corner folding roller 110 of the inclined surface 111 is formed to be 20° or more, and when pressing the corner portion 14 of the sealing part 13 of the pouch 10, the corner folding roller 110 can press the terrace portion, which is a non-sealed area of ​​the pouch 10 that is not flat, without damaging it, thereby preventing the non-sealed area of ​​the pouch 10 from being damaged and ensuring the insulation quality.

[0041] Also, the inclination angle α of the inclined surface 111 is formed to be 50° or less, which has the effect of adjusting the degree of pouch folding to a desired shape. That is, when the inclination angle α of the inclined surface 111 is 50° or more, the effect on folding may be significantly small. As a result, when the inclination angle α of the inclined surface 111 is 50° or more, the inclined surface 111 cannot pressurize the non-sealed area of ​​the pouch 10 that is not flat, or the pressing force is significantly reduced, so that folding of the corner portion 14 of the sealing part 13 of the pouch 10 cannot be performed sufficiently, and the non-sealed area of ​​the pouch 10 that is not flat may be damaged by the corner between the inclined surface 111 and the flat surface 112, which may deteriorate the insulation quality.

[0042] Meanwhile, the length L2 of the flat surface 112 may be, for example, 2 mm or more. As a result, the length L2 of the flat surface 112 in the corner folding roller 110 is formed to be 2 mm or more, and corner folding of the sealing portion 13 of the side-folded pouch 10 is possible.

[0043] Meanwhile, for example, in the corner folding roller 110, the orthogonal projection length L1 of the inclined surface 111 can be formed to be longer than the length L2 of the flat surface 112. Note that in the corner folding roller 110, the orthogonal projection length L1 of the inclined surface 111 can be formed to be 400% or less of the length L2 of the flat surface 112.

[0044] Meanwhile, the corner folding roller 110 may further include a roller shaft 114. The roller shaft 114 may be configured as a rotation axis of the corner folding roller 110.

[0045] Meanwhile, corner folding of the sealing portion 13 of the pouch 10 using the corner folding roller 110 may be performed, for example, at room temperature, but the method of implementing the pouch folding device for secondary batteries according to an embodiment of the present invention is not necessarily limited thereto.

[0046] Meanwhile, in the folding device for a pouch 10 for a secondary battery according to an embodiment of the present invention, the corner folding unit CR may further include a roller moving unit 120 , a lower support unit 130 , an upper support unit 140 , and a support frame 150 .

[0047] The corner folding rollers 110 are attached to the roller moving unit 120, and the roller moving unit 120 can move the corner folding rollers 110. The roller moving unit 120 can move the corner folding rollers 110 from the outer edge of the pouch 10 toward the center along the X-axis direction.

[0048] The lower support part 130 can support the lower part of the pouch 10 during corner folding. The lower support part 130 is made up of a plurality of blocks and can support the lower end of the body 12 of the pouch 10.

[0049] The upper support part 140 may support an upper part of the pouch 10 during corner folding. The upper support part 140 may be located on the opposite side between the corner folding roller 110 and the pouch 10 when the pouch 10 is pressed by the corner folding roller 110. Thus, when the pouch 10 is pressed by the corner folding roller 110, the upper support part 140 supports the pouch 10, and the folding operation may be easily performed.

[0050] The support frame 150 can support each device of the corner folding section CR.

[0051] 5 and 6, the pouch folding device for a secondary battery according to the embodiment of the present invention configured as described above folds the corner portion 14 of the pouch 10 using the corner folding roller 110 having the inclined surface 111 formed thereon, thereby preventing insulation quality risks from occurring in the portion of the pouch 10 that is not flat due to the electrode assembly 20 being accommodated therein. That is, the flat surface 112 having a constant diameter in the corner folding roller 110 presses the sealing area of ​​the flat pouch 10, and the inclined surface 111 presses the non-sealing area of ​​the pouch 10 that is not flat due to the electrode assembly 20 being accommodated therein, thereby preventing damage to the non-sealing area of ​​the pouch 10 and ensuring insulation quality.

[0052] Meanwhile, referring to Figs. 1, 7 and 8, a secondary battery 1 can be manufactured using a pouch folding apparatus for a secondary battery according to an embodiment of the present invention.

[0053] That is, the secondary battery according to the embodiment of the present invention is the secondary battery 1 manufactured through the pouch folding apparatus for a secondary battery according to the embodiment of the present invention described above.

[0054] The secondary battery 1 is provided in a state where a corner portion 14 at a sealing portion 13 of the pouch 10 is corner-folded toward the main body.

[0055] The folded corner portion 14 includes a first portion 14a that is pressed and folded against a flat surface 112 of a corner folding roller 110, and a second portion 14b that is pressed and folded against an inclined surface 111 of the corner folding roller 110.

[0056] The first portion 14a forms a flat portion, and the second portion 14b forms an inclined portion that is inclined with respect to the first portion 14a.

[0057] The second portion 14b may be formed to be inclined at an angle of 20 to 50 degrees with respect to an imaginary extension line of the first portion 14a.

[0058] <Production Example> A pouch folding device for a secondary battery was manufactured, which folds a pouch including a body in which an electrode assembly is housed and a sealing portion formed along an edge of the body.

[0059] The pouch folding device for the secondary battery was manufactured to include a corner folding unit that pressurizes the corner portion of the side-folded sealing unit to fold the corner toward the main body.

[0060] The corner folding section was composed of a corner folding roller including a flat surface and an inclined surface formed on the pressing surface.

[0061] The corner folding roller was manufactured in such a shape that the inclined surface could be positioned on the side adjacent to the body of the pouch when pressure was applied.

[0062] 6, the corner folding roller has a flat surface 112 with a length L2 of 2 mm, and an orthogonal projection length L1 of an inclined surface 111 with a length of 3.5 m. The inclination angle α of the inclined surface 111 is 25°.

[0063] <Comparative Example> A pouch folding device for a secondary battery was manufactured in the same manner as in the manufacturing example, except that the pressing surfaces of the corner folding rollers were all formed to be flat surfaces.

[0064] <Experimental Example> In the secondary batteries manufactured using the pouch folding apparatus for secondary batteries according to the examples and comparative examples, the IR (resistance) failure rate and the IV (voltage) failure rate of the corner folding portion of the pouch were measured based on 100 MOhm.

[0065] Here, the secondary battery in the pouch, in which the width of the sealing part was 2 mm, was corner-folded.

[0066] [Table 1]

[0067] As shown in Table 1, the IR defect rate in the comparative example was 8.2%, while the IR defect rate in the manufacturing example was 1.7%, a significant decrease. Also, the IR defect rate in the comparative example was 3.45%, while the IR defect rate in the manufacturing example was 0.0%, a significant decrease. Therefore, it can be seen that the insulation defect rate was significantly reduced in the manufacturing example compared to the comparative example.

[0068] Although the present invention has been described in detail with reference to specific examples, these are for the purpose of specifically explaining the present invention, and the present invention is not limited thereto. It can be said that various implementations are possible within the technical concept of the present invention by those having ordinary skill in the art.

[0069] Moreover, the specific scope of protection of the invention will be clarified by the appended claims. [Explanation of symbols]

[0070] 1 Secondary battery 10 pouches 11 Storage section 12 Main unit 13 Sealing section 14 Corner part 14a Part 1 14b Part 2 20 Electrode assembly 30 Electrode Lead 110 Corner folding roller 111 Slope 112 Flat surface 113 Pressurized Surface 114 Roller shaft 120 Roller moving part 130 Lower support part 140 Upper support part 150 Support Frame SR side folding part CR Corner folding section

Claims

1. A pouch folding device for a secondary battery, which folds a pouch including a body in which an electrode assembly is accommodated and a sealing part formed along an edge of the body, a side folding section for side folding the sealing section of the pouch toward the main body; a corner folding unit including a corner folding roller that presses a corner portion of the side-folded sealing unit to perform corner folding toward the main body, The corner folding roller includes a flat surface and an inclined surface formed on a pressing surface, a corner folding roller that, when pressed, causes the inclined surface to be positioned closer to the main body than the flat surface of the corner folding roller;

2. The pouch folding device for a secondary battery according to claim 1 , wherein the side folding units fold the sealing units located on both sides of the pouch toward the main body.

3. The side folding units fold the sealing units located on both sides of the pouch in a width direction of the pouch toward the main body, 3. The pouch folding device for a secondary battery according to claim 2, wherein a width direction of the pouch is a lateral direction with respect to a length direction of the pouch in which an electrode lead connected to the electrode assembly extends.

4. 4. The pouch folding device for a secondary battery according to claim 3, wherein the corner folding unit moves the corner folding roller from an outer edge of the pouch toward a center portion of the pouch, which is the main body direction, to bring the corner portion of the side-folded sealing unit into close contact with an outer surface of the pouch.

5. When the corner folding unit performs corner folding while pressing the corner portion, 5. The pouch folding device for a secondary battery according to claim 4, wherein a first portion of the pouch at the corner portion that is pressed against the flat surface of the corner folding roller is folded to contact a portion of the pouch located in a longitudinal direction of the pouch at the sealing part, and a second portion of the pouch at the corner portion that is pressed against the inclined surface of the corner folding roller is folded to contact the main body.

6. The pouch folding device for secondary batteries according to claim 1 , wherein the inclined surface is located at an end of the corner folding roller.

7. The pouch folding device for secondary batteries according to claim 6 , wherein the inclined surface of the corner folding roller is formed with an inclination such that the width of the end portion becomes narrower toward the tip.

8. 8. The pouch folding device for a secondary battery according to claim 7, wherein the inclined surface has an inclination angle of 20 to 50 degrees.

9. The corner folding portion is The pouch folding device for a secondary battery according to claim 1 , further comprising a roller moving unit to which the corner folding rollers are attached and which moves the corner folding rollers.

10. The corner folding portion is The pouch folding device for a secondary battery according to claim 1 , further comprising a lower support part that supports a lower part of the pouch during corner folding.

11. The corner folding portion is The pouch folding device for a secondary battery according to claim 1 , further comprising an upper support part that supports an upper part of the pouch during corner folding.

12. A secondary battery manufactured by the pouch folding apparatus for secondary batteries according to any one of claims 1 to 11.

13. the secondary battery is provided in a state where the corner portion of the sealing portion of the pouch is corner-folded toward the main body, the folded corner portion includes a first portion folded by pressing against the flat surface of the corner folding roller and a second portion folded by pressing against the inclined surface of the corner folding roller; The secondary battery of claim 12, wherein the second portion is inclined at an angle of 20 to 50 degrees with respect to an extension line of the first portion.

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