Pouch-type secondary battery case forming device and forming method using the same

Abstract

The present invention relates to a forming apparatus for a pouch-type secondary battery case and a forming method using the same, and more particularly to a forming apparatus for a pouch-type secondary battery case, the apparatus including: a die having a forming groove formed therein; a punch that moves up and down above the die to come into close contact with the inner surface of the forming groove; and a pouch sheet fixing part that moves up and down above the die to fix an edge of a pouch sheet, the punch having a plurality of air flow paths for injecting external air in the direction of the forming groove or for sucking air. The present invention also relates to a manufacturing method using the same.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0086154, filed July 13, 2022, and all contents disclosed in the Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a forming apparatus for a pouch-type secondary battery case and a forming method using the same, and more particularly to a forming apparatus for a pouch-type secondary battery case that can check for defects in a pouch sheet and prevent cracks from occurring in a housing groove during a process of changing the direction of air movement using a punch having an air flow path, and a forming method using the same. [Background technology]

[0003] Recently, due to air pollution and energy depletion caused by the use of fossil fuels, there has been an increasing demand for secondary batteries that can store electrical energy produced by the development of alternative energy sources. Rechargeable secondary batteries are used in mobile devices, electric vehicles, hybrid electric vehicles, etc., and are closely related to everyday life.

[0004] These secondary batteries are classified into can-type battery cells, in which a cell assembly in which electrodes and separators are alternately stacked is housed in a metal can, and pouch-type battery cells, in which a cell assembly is housed in a pouch. Pouch-type battery cells are attracting much attention due to their low manufacturing cost, light weight, and easy shape modification, and their usage is gradually increasing.

[0005] A pouch-type secondary battery cell is manufactured through a process in which a pouch sheet (also known as an "aluminum laminate sheet") is formed to form a receiving groove, a cell assembly is placed in the receiving groove, and then the periphery of the receiving groove is sealed.

[0006] Meanwhile, cracks or pinholes may occur during the manufacturing process of the pouch sheet, or various foreign substances such as metal particles or dust may adhere to the pouch sheet during storage or transportation of the pouch sheet.

[0007] As described above, when a pouch-type battery cell is manufactured using a sheet with cracks or pinholes or a sheet with foreign matter attached thereto, moisture or air may penetrate into the battery cell, or the foreign matter may have a significant impact on safety and quality.

[0008] Furthermore, the pouch sheet for secondary batteries is subjected to a forming process by being pressed by a punch into a mold in which a storage portion is formed, which can cause cracks and wrinkles in the storage portion of the pouch sheet.

[0009] In this regard, Patent Document 1 (FIG. 1) discloses a technique for forming a pouch film 10 by providing an air injection unit 31 in an upper press 30 and injecting air toward the upper surface of the pouch film 10 to adhere a portion of the pouch film 10 to the inner surface of a forming groove 21, and then connecting the air injection unit 31 of the upper press 30 to the forming groove 21. However, a drawback of this technique is that the air must be injected at a fairly high pressure to adhere the pouch film to the forming groove by air injection.

[0010] Furthermore, Patent Document 1 does not at all recognize the problems caused by defects or contamination of the pouch sheet itself. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Korean Patent Publication No. 10-2018-0134133 Summary of the Invention [Problem to be solved by the invention]

[0012] In order to solve the above problems, an object of the present invention is to provide a forming apparatus for a pouch-type secondary battery case that can form a pouch sheet without injecting air at high pressure, and a forming method using the same.

[0013] Another object of the present invention is to provide a forming device for a pouch-type secondary battery case that can form a pouch sheet while detecting defects such as cracks and pinholes in the pouch sheet, and a forming method using the same.

[0014] Another object of the present invention is to provide a forming device for a pouch-type secondary battery case, which can minimize the occurrence of cracks in the storage grooves of a pouch sheet and thereby improve the accuracy of the formed storage grooves, and a forming method using the same. [Means for solving the problem]

[0015] To achieve the above object, the forming apparatus for a pouch-type secondary battery case according to the present invention includes a die (100) having a forming groove (110) formed therein, a punch (200) that moves up and down above the die (100) to closely contact the inner surface of the forming groove (110), and a pouch sheet fixing part (400) that moves up and down above the die (100) to fix the edge of a pouch sheet (S), and the punch (200) is characterized by having a plurality of air flow paths (210) for injecting external air toward the forming groove (110) or for sucking air.

[0016] In addition, in the pouch-type secondary battery case forming apparatus according to the present invention, the air flow path (210) includes a first air flow path (211) located near the edge of the punch (200) and a second air flow path (212) located inside the first air flow path (211).

[0017] In addition, in the pouch-type secondary battery case forming apparatus according to the present invention, the first air flow path (211) is positioned in an inclined state so as to face the die edge portion (120) of the forming groove (110).

[0018] In addition, the pouch-type secondary battery case forming apparatus according to the present invention is characterized in that it further comprises an air pipe (300) connected to the air flow path (210) on one side and extending to the outside of the punch (200) on the other side.

[0019] In addition, in the pouch-type secondary battery case forming apparatus according to the present invention, the air pipeline (300) is equipped with at least one of a pressure meter and a flow meter.

[0020] In addition, in the pouch-type secondary battery case forming apparatus according to the present invention, the air duct (300) includes a first air duct (310) connected to the first air flow path (211) and a second air duct (320) connected to the second air flow path (212).

[0021] In addition, in the pouch-type secondary battery case forming apparatus according to the present invention, the first air pipeline (310) and the second air pipeline (320) are each provided with an on-off valve for controlling the movement of air.

[0022] The present invention also provides a method for forming a pouch sheet using the above-mentioned pouch-type secondary battery case forming apparatus, comprising: a first step of seating the pouch sheet (S) on top of a die (100) having a forming groove (110) formed therein; a second step of fixing the edge of the pouch sheet (S); a third step of lowering a punch (200) to a predetermined height from the top surface of the pouch sheet (S) and then reducing the pressure of the air flow path (210) of the punch (200) to suck in and remove foreign matter from the pouch sheet (S); a fourth step of pressing the punch (200) tightly against the top surface of the pouch sheet (S) and then reducing the pressure of the air flow path (210); and a fifth step of lowering the punch (200) while maintaining the reduced pressure state of the air flow path (210) to pressurize it against the inner surface of the forming groove (110).

[0023] In addition, in the method for forming a pouch sheet according to the present invention, the third step is characterized in that air is injected through a first air flow path (211) located near the edge of the punch (200) and the pressure in a second air flow path (212) located inside the first air flow path (211) is reduced.

[0024] In addition, in the method for forming a pouch sheet according to the present invention, the fourth step further includes a step of maintaining a reduced pressure state for a predetermined time and checking for cracks or pinholes in the pouch sheet (S).

[0025] In the method for forming a pouch sheet according to the present invention, the presence or absence of cracks or pinholes is confirmed by a change in pressure or a change in flow rate.

[0026] In addition, the method for forming a pouch sheet according to the present invention further comprises a sixth step of injecting air into the forming groove (110) through an air passage (210) after bringing the punch (200) into close contact with the inner surface of the forming groove (110).

[0027] In addition, in the method for forming a pouch sheet according to the present invention, the sixth step is characterized in that the air injection pressure or flow rate through the first air flow path (211) located near the edge of the punch (200) is maintained higher than the air injection pressure or flow rate through the second air flow path (212) located inside the first air flow path (211). [Effects of the Invention]

[0028] As described above, the pouch-type secondary battery case forming apparatus and forming method using the same according to the present invention have the advantage of improving process efficiency because it is possible to check in advance whether or not there are cracks or pinholes in the pouch sheet by closely contacting the punch having an air flow path formed therein with the pouch sheet and then maintaining a reduced pressure state for a certain period of time and checking changes in pressure and flow rate.

[0029] In addition, the pouch-type secondary battery case forming apparatus and forming method using the same according to the present invention have the advantage that cracks can be prevented during the forming process and a more uniform housing groove can be formed by controlling the direction of air movement using the air flow path provided in the punch. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a cross-sectional view of a forming device according to the prior art. [Figure 2] 1 is a cross-sectional view of a forming apparatus for a pouch-type secondary battery case according to a first preferred embodiment of the present invention. [Figure 3] 3 is a plan view of the forming apparatus of FIG. 2 cut along line AA. [Figure 4] FIG. 4 is a cross-sectional view of a forming apparatus for a pouch-type secondary battery case according to a second preferred embodiment of the present invention. [Figure 5] FIG. 10 is a cross-sectional view of a forming apparatus for a pouch-type secondary battery case according to a third preferred embodiment of the present invention. [Figure 6]3 is a flowchart illustrating a forming method using the forming apparatus according to the first preferred embodiment of the present invention. [Figure 7] 10 is a flowchart illustrating a forming method using a forming apparatus according to a third preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of an embodiment of the present invention that will enable a person skilled in the art to easily carry out the present invention. However, in describing the operation principle of the preferred embodiment of the present invention in detail, detailed description of related well-known functions or configurations will be omitted if it is determined that such detailed description may unnecessarily obscure the gist of the present invention.

[0032] Furthermore, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when a part is said to be connected to another part, this includes not only a direct connection but also an indirect connection via another element therebetween. Furthermore, unless otherwise specified, "including a certain element" does not mean that other elements are excluded, but that other elements may also be included.

[0033] Hereinafter, a forming apparatus for a pouch-type secondary battery case and a forming method using the same according to the present invention will be described with reference to the accompanying drawings.

[0034] FIG. 2 is a cross-sectional view of a forming apparatus for a pouch-type secondary battery case according to a first preferred embodiment of the present invention, and FIG. 3 is a plan view of the forming apparatus of FIG. 2 cut along line AA.

[0035] As shown in FIGS. 2 and 3, the mold device according to the first preferred embodiment of the present invention includes a die 100, a punch 200, an air duct 300, and a pouch sheet fixing portion 400.

[0036] First, the die 100 has a forming groove 110 having a shape corresponding to the receiving groove for receiving the electrode assembly, and a die edge portion 120 having a predetermined radius of curvature is located along the corner where the bottom surface of the forming groove 110 intersects with the vertical surface.

[0037] The punch 200, which has the same shape as the outer shape of the forming groove 110, operates to move up and down above the die 100. Therefore, after the pouch sheet S is positioned between the die 100 and the punch 200, the punch 200 is lowered to be in close contact with the inner surface of the forming groove 110, and a receiving groove is formed in the pouch sheet S.

[0038] Meanwhile, a plurality of air flow paths 210 are formed in the punch 200. More specifically, the air flow paths 210 may consist of a first air flow path 211 and a second air flow path 212 positioned perpendicular to the bottom surface of the forming groove 110. Here, the first air flow path 211 is positioned near the edge of the punch 200, while the second air flow path 212 is positioned inside the first air flow path 211.

[0039] The first air flow path 211 and the second air flow path 212 are passages through which air moves, and external air flowing in through the air duct 300 is sprayed toward the forming groove 110, or conversely, downward air flows in and is then discharged through the air duct 300.

[0040] By utilizing the first air flow path 211 and the second air flow path 212, foreign matter on the top of the pouch sheet S can be removed, and the presence or absence of cracks or pinholes in the pouch sheet S can be checked, and further, the bottom, side and bent portions of the receiving groove of the pouch sheet S can be made into smooth flat or curved surfaces. This will be described in detail later.

[0041] Although the drawings show ten first air passages 211 and four second air passages 212, this is merely an example and any number of changes are possible.

[0042] Next, we will explain the air duct 300. As described above, the air duct 300 is used to supply air to the air flow path 210, more specifically to the first air flow path 211 and the second air flow path 212, and to discharge the air taken into the first air flow path 211 and the second air flow path 212 to the outside.

[0043] Therefore, one side of the air duct 300 is connected to the punch 200, while the other side extends outside the punch 200, so that the air duct 300 can communicate with the first air flow path 211 and the second air flow path 212.

[0044] Here, air pipeline 300 has a three-way shape, one of which is connected to punch 200, and the remaining two are connected to first vacuum pump P1 and first compressor C1. A first valve V1 and a second valve V2 for controlling the air flow direction are provided near first vacuum pump P1 and first compressor C1, respectively. Furthermore, air pipeline 300 is preferably further provided with at least one of a flow meter (not shown) and a pressure gauge (not shown) so that the flow rate and pressure of air passing through air pipeline 300 can be checked.

[0045] For example, a flow meter and a pressure meter may be installed between the first pressure reducing pump P1 and the first valve V1, and between the first compressor C1 and the second valve V2, but there is no particular limitation as long as they are located at locations where the air flow rate and air pressure can be measured.

[0046] On the other hand, the decompression pump is used to create a negative pressure in the air flow path, and is not necessarily limited to a decompression pump, but can be modified as much as necessary as long as it can perform the same function.Furthermore, the compressor is used to supply air to the air flow path, and is not necessarily limited to a compressor, but can be modified as long as it can perform the same function.

[0047] The pouch sheet fixing part 400 is for fixing the edge of the pouch sheet S while moving up and down above the die 100. Although not shown in the drawings, the pouch sheet fixing part 400 may further be provided with a lifting means.

[0048] 4 is a cross-sectional view of a pouch-type secondary battery case forming apparatus according to a second preferred embodiment of the present invention. Referring to FIG. 4, only the shape of the air flow path 210 is different, and the remaining configuration is the same as that of the first embodiment described above. Therefore, only the different configuration will be described.

[0049] The air flow path 210 of the forming device according to the second embodiment of the present invention is composed of a first air flow path 211 and a second air flow path 212, which are inclined so that the air flows toward the die edge portion 120, and therefore the opening of the first air flow path 211 is located near the die edge portion 120.

[0050] In this way, when the air sprayed from the first air flow path 211 is directed toward the die edge portion 120, not only does it become easier to form the curved portion of the pouch sheet S, which is relatively difficult to form, but it can also be guided to form a smooth curved surface.

[0051] FIG. 5 is a cross-sectional view of a pouch-type secondary battery case forming apparatus according to a third preferred embodiment of the present invention.

[0052] Referring to FIG. 5, only the configuration of the air flow path 210 and the air pipeline 300 is different, and the remaining configuration is the same as that of the first embodiment described above, so only the different configuration will be described.

[0053] In the case of the forming apparatus according to the third embodiment of the present invention, the air flow path 210 is composed of a first air flow path 211 and a second air flow path 212, but as in the second embodiment, the air is inclined so that it flows toward the die edge portion 120, and therefore the opening of the first air flow path 211 is located near the die edge portion 120.

[0054] Meanwhile, the air pipeline 300 is composed of a first air pipeline 310 connected to the first air flow path 211 and a second air pipeline 320 connected to the second air flow path 212. The first air pipeline 310 is provided with a first decompression pump P1 and a first compressor C1, and the second air pipeline 320 is provided with a second decompression pump P2 and a second compressor C2, so that the air supplied to or discharged from these air pipelines can be individually controlled. Of course, the first air pipeline 310 may be equipped with a third valve V3 and a fourth valve V4, and the second air pipeline 320 may be equipped with a fifth valve V5 and a sixth valve V6.

[0055] Also, similar to the first embodiment, each of the first air pipeline 310 and the second air pipeline 320 may be provided with one or more of a flow meter (not shown) and a pressure gauge (not shown) so that the flow rate and pressure of the air passing through these pipelines can be checked individually.

[0056] In this way, when the first air duct 310 and the second air duct 320 are provided in a state separated from each other so that air can be supplied to and discharged from the first air flow path 211 and the second air flow path 212, respectively, foreign matter on the pouch sheet S can be more easily removed. This will be described in more detail later.

[0057] FIG. 6 is a flowchart illustrating a forming method using a forming apparatus according to a first preferred embodiment of the present invention.

[0058] The forming method using the forming apparatus according to the first embodiment includes a first step of seating the pouch sheet S on top of the die 100 in which the forming groove 110 is formed; a second step of fixing the edge of the pouch sheet S; a third step of lowering the punch 200 to a predetermined height based on the top surface of the seated pouch sheet S, and then reducing the pressure of the air flow path of the punch 200 to suck in and remove foreign matter on the top surface of the pouch sheet S; a fourth step of pressing the punch 200 against the top surface of the pouch sheet S, and then reducing the pressure of the air flow path; a fifth step of lowering the punch 200 while maintaining the reduced pressure state of the air flow path to pressurize it against the inner surface of the forming groove 110; and a sixth step of spraying air through the air flow path in the direction of the forming groove 110.

[0059] Specifically, the first step is to position the pouch sheet S cut to a predetermined size above the die 100, and the second step is to lower the pouch sheet fixing part 400 to firmly press and fix the edge of the pouch sheet S so that the pouch sheet S remains fixed even when the punch 200 moves into the forming groove 110.

[0060] Here, it is preferable that the inner vertical surface of the pouch sheet fixing portion 400 is located on the same vertical extension line as the vertical wall surface forming the forming groove 110 of the die 100 .

[0061] The third step is to remove various foreign objects that have landed on or adhered to the pouch sheet S during the manufacturing or transportation process. That is, the punch 200 is lowered so that the distance from the upper surface of the pouch sheet S is no more than a few centimeters, preferably no more than 2 cm, and then air is sucked in near the upper surface of the pouch sheet S to remove the foreign objects. Here, the first valve V1 of the air pipe 300 connected to the first decompression pump P1 is open, while the second valve V2 of the air pipe 300 connected to the first compressor C1 is closed.

[0062] The fourth step is to check for cracks or pinholes that occurred during the manufacturing or transportation process of the pouch sheet S. Specifically, the punch 200 is lowered so that the top surface of the pouch sheet S is in close contact with the bottom surface of the punch 200, and then the first valve V1 of the air pipe 300 connected to the first decompression pump P1 is opened, and the second valve V2 of the air pipe 300 connected to the first compressor C1 is closed.

[0063] Here, when there are no cracks or pinholes in the pouch sheet S, the suction pressure or air flow rate of the air pipeline 300 connected to the first decompression pump P1 does not change. Conversely, when there are cracks or pinholes, the suction pressure or air flow rate changes, so it is possible to determine whether or not there are cracks or pinholes.

[0064] The fifth step is to bring the punch 200 into close contact with the inner surface of the forming groove 110 to form the storage groove in the pouch sheet S. Here, the second valve V2 of the air pipe 300 connected to the first compressor C1 is closed, and the first valve V1 of the air pipe 300 connected to the first decompression pump P1 is opened so that the pouch sheet S can be formed in close contact with the punch 200.

[0065] The sixth step is a kind of forming finishing step, in which air is sprayed in the direction of the forming groove 110. Although the storage groove is formed in the pouch sheet S by the fifth step of bringing the outer surface of the punch 200 into close contact with the inner surface of the forming groove 110, it may occur that a part of the storage groove does not have a smooth surface. However, when the step of spraying air in the direction of the forming groove 110 is performed, the surface of the storage groove can be finished to be smooth by the pressure of the air spray.

[0066] Meanwhile, the forming method using the forming apparatus according to the second embodiment of the present invention is similar to the forming method using the forming apparatus according to the first embodiment described above. However, the forming apparatus according to the second embodiment has an advantage in that the opening of the first air flow path 211 is located near the die edge portion 120, and therefore the curved surface of the bent portion of the pouch sheet S, which is relatively fragile during forming, can be smoothly finished.

[0067] FIG. 7 is a flowchart illustrating a forming method using a forming apparatus according to a third preferred embodiment of the present invention.

[0068] As with the forming method according to the first embodiment described above, the first step of seating the pouch sheet S on top of the die 100 in which the forming groove 110 is formed, and the second step of fixing the edge of the pouch sheet S are the same.

[0069] However, in the third stage, the punch 200 is lowered to a predetermined height based on the upper surface of the seated pouch sheet S, and then air is supplied to the first air flow path 211 of the punch 200, and the second air flow path 212 is made negative pressure, i.e., the pressure is reduced, to suck in and remove foreign matter on the upper surface of the pouch sheet S.

[0070] That is, the fourth valve V4 of the first air line 310 connected to the first compressor C1 is open, but the third valve V3 is closed. Also, the fifth valve V5 of the second air line 320 connected to the second pressure-reducing pump P2 is open. Of course, the sixth valve V6 of the second air line 320 connected to the second compressor C2 is closed.

[0071] Therefore, when foreign matter on the pouch sheet S is far away from the opening of the second air flow path 212, it can be difficult to suck it in. However, by injecting air through the first air flow path 211 provided along the edge of the punch 200 and sucking it in through the second air flow path 212, the foreign matter can be effectively sucked in through the second air flow path 212, which is an advantage.

[0072] The fourth step of depressurizing the air flow path 210 after the punch 200 is pressed against the upper surface of the pouch sheet S, the fifth step of lowering the punch 200 while maintaining the reduced pressure state of the air flow path 210 to press it against the inner surface of the forming groove 110, and the sixth step of spraying air through the air flow path 210 in the direction of the forming groove 110 are also substantially the same as the forming method according to the first embodiment described above.

[0073] When using the forming apparatus according to the third embodiment, the first compressor C1 and the first vacuum pump P1 are used to supply air to or reduce the pressure in the first air pipeline 310, and the second compressor C2 and the second vacuum pump P2 are used to supply air to or reduce the pressure in the second air pipeline 320.

[0074] On the other hand, since the first air duct 310 and the second air duct 320 receive air from the first compressor C1 and the second compressor C2, which are driven independently, it is easier to supply relatively high-pressure air toward the curved surface of the bent portion of the pouch sheet S, which is fragile in forming.

[0075] Although the present invention has been described above with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications and variations within the scope of the present invention may be made based on the above teachings. [Explanation of symbols]

[0076] 100 Dies 110 Forming groove 120 Die edge part 200 punches 210 Air flow path 211 First air flow path 212 Second air flow path 220 Punch edge part 300 Air Pipe 310 First Air Pipe 320 Second Air Pipe 400 Pouch sheet fixing part S Pouch Sheet S1 bent part P1 First pressure reducing pump P2 Second pressure reducing pump C1 First Compressor C2 Second Compressor V1 First valve V2 Second valve V3 3rd valve V4 4th valve

Claims

1. a die in which a forming groove is formed; a punch that moves up and down above the die and comes into close contact with the inner surface of the forming groove; a pouch sheet fixing portion that moves up and down above the die and fixes an edge portion of the pouch sheet; the punch has a plurality of air passages for injecting external air toward the forming groove or for sucking air; the air flow path includes a first air flow path located near an edge of the punch and a second air flow path located inside the first air flow path, a forming apparatus for a pouch-type secondary battery case, wherein the first air flow path is positioned in a state of being inclined toward a die edge portion of the forming groove;

2. The pouch-type secondary battery case forming apparatus according to claim 1 , further comprising an air pipe line, one side of which is connected to the air flow path and the other side of which extends to the outside of the punch.

3. The pouch-type secondary battery case forming apparatus according to claim 2 , wherein the air pipeline is provided with at least one of a pressure meter and a flow meter.

4. 3. The pouch-type secondary battery case forming apparatus according to claim 2, wherein the air duct includes a first air duct connected to the first air flow path and a second air duct connected to the second air flow path.

5. The pouch-type secondary battery case forming apparatus according to claim 4 , wherein the first air pipeline and the second air pipeline each include an on-off valve for controlling the movement of air.

6. A method for forming a pouch sheet using a pouch-type secondary battery case forming device, comprising: The forming device is a die in which a forming groove is formed; a punch that moves up and down above the die and comes into close contact with the inner surface of the forming groove; a pouch sheet fixing portion that moves up and down above the die and fixes an edge portion of the pouch sheet; the punch has a plurality of air passages for injecting external air toward the forming groove or for sucking air; The method comprises: A first step of seating a pouch sheet on top of a die in which a forming groove is formed; A second step of fixing the edge of the pouch sheet using the pouch sheet fixing portion; a third step of lowering the punch (200) to a predetermined height from the upper surface of the pouch sheet, and then reducing the pressure of the air flow path of the punch (200) to suck in and remove foreign matter from the pouch sheet; a fourth step of decompressing the air flow path after the punch is tightly attached to the upper surface of the pouch sheet; and a fifth step of lowering the punch while maintaining the reduced pressure state of the air flow path to bring the punch into close contact with the inner surface of the forming groove.

7. 7. The method of claim 6, wherein the third step includes injecting air through a first air flow path located near an edge of the punch and reducing pressure in a second air flow path located inside the first air flow path.

8. The method of claim 6, wherein the fourth step further comprises the step of maintaining the reduced pressure for a predetermined period of time and checking for cracks or pinholes in the pouch sheet.

9. The method for forming a pouch sheet according to claim 8, wherein the presence or absence of cracks or pinholes is confirmed by a change in pressure or a change in flow rate.

10. The method for forming a pouch sheet according to claim 6, further comprising a sixth step of injecting air in the direction of the forming groove through an air passage after the punch is brought into close contact with the inner surface of the forming groove.

11. 11. The method for forming a pouch sheet according to claim 10, wherein the sixth step maintains an air injection pressure or flow rate through a first air flow path located near the edge of the punch higher than an air injection pressure or flow rate through a second air flow path located inside the first air flow path.

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