Pouch, molding device for the pouch, and method for manufacturing secondary battery including the pouch

Abstract

The pouch forming apparatus of the present invention includes a first mounting part and a second mounting part connected to each other, and when an electrode assembly is loaded, the first mounting part and the second mounting part are folded to cover the upper and lower sides of the electrode assembly, and the pouch is sealed in a state where sealing parts of the first mounting part and the second mounting part are in contact with each other. The pouch forming apparatus includes a lower mold having a first groove recessed from an upper surface to a certain depth and a second groove further recessed from a bottom surface of the first groove; and a flat surface on one side that enters the first groove. an upper mold having a protrusion protruding from the flat portion and entering the second groove; and when the upper mold and the lower mold are pressed together with a pouch sheet placed between them, the first and second mounting portions are formed at the portion pressed by the flat portion, and the protrusion connects the first and second mounting portions at the portion pressed by the protrusion, and when an electrode assembly is mounted, a sidewall portion is formed that forms a surface parallel to a side surface of the electrode assembly.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0078759, filed on June 26, 2020, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a pouch for a secondary battery, a molding device for forming the pouch, and a method for manufacturing a secondary battery including the pouch. More specifically, the present invention relates to a molding device for forming a pouch that can accommodate an electrode assembly having a greater thickness by forming a side wall portion within a moldable range of a pouch sheet, a pouch manufactured by the molding device, and a method for manufacturing a secondary battery including the pouch. [Background technology]

[0003] Demand for highly efficient secondary batteries is rapidly increasing in the fields of mobile devices and electric vehicles, etc. Among such secondary batteries, lithium secondary batteries, which have high energy density and can maintain a relatively high voltage, and have a low self-discharge rate, have been commercialized and widely used, and research and development to improve their performance is being actively conducted.

[0004] A secondary battery has a structure in which an electrode assembly and an electrolyte are housed in a case such as a can, pouch, etc. The electrode assembly has a structure in which a positive electrode, a separator, and a negative electrode are repeatedly stacked, and can generally be classified into a winding type in which the positive electrode, the separator, and the negative electrode are stacked and rolled up and housed in a case, and a stack type in which the positive electrode, the separator, and the negative electrode are cut to a certain size and then stacked.

[0005] The wound electrode assembly is suitable for cylindrical batteries because of its spirally wound structure, but is disadvantageous in terms of space utilization in square or pouch type batteries. Conversely, the stacked electrode assembly can be easily made into a square shape that fits the case because the size can be adjusted when cutting the electrodes and separator, but it has the disadvantages of being relatively complex to manufacture and relatively vulnerable to external impact. In order to combine the advantages of the wound and stacked types, a stack and folding method has been developed. The stack and folding method is manufactured by placing a C-type bicell (a bicell with a stacked structure of positive electrode / separator / negative electrode / separator / positive electrode) and an A-type bicell (a bicell with a stacked structure of negative electrode / separator / positive electrode / separator / negative electrode) on a folding separator and folding the bicell.

[0006] The electrode assemblies manufactured in the above-mentioned various ways are then mounted in a case such as a can or a pouch.

[0007] Among these, pouches are manufactured by laminating a metal layer of aluminum material and a resin layer of polymeric material, and when provided in sheet form, they are processed into a fixed shape using a molding device.

[0008] That is, referring to FIG. 1a showing an electrode assembly mounted in a conventional pouch and FIG. 1b showing cross sections of the conventional pouch in an open and closed state, the pouch 2 in which the hexahedral electrode assembly 1 is mounted includes a second mounting part 4 on which the lower surface of the electrode assembly 1 is mounted and a first mounting part 3 covering the upper surface of the electrode assembly 1, and when the electrode assembly 1 is mounted in an open state, the first mounting part 3 and the second mounting part 4 are folded so as to cover the upper and lower surfaces of the electrode assembly 1, and are in a closed state.

[0009] When closed, the sealing parts 3b, 4b of the first seating part 3 and the second seating part 4 come into contact with each other, and in this contact state, heat and pressure are applied to seal the pouch 2. At this time, the grooves 3a, 4a of the first seating part 3 and the second seating part 4 are provided to have a depth that allows the electrode assembly 1 to be mounted thereon.

[0010] A pouch having such a structure is manufactured by processing a flat pouch sheet. That is, referring to Fig. 1c showing a cross section of a conventional pouch forming apparatus, the conventional pouch forming apparatus includes an upper mold 7 and a lower mold 6, and the lower mold 6 has two grooves 6a and 6b on both sides, and the space between the two grooves 6a and 6b is partitioned by a protrusion 6c.

[0011] The upper die 7, which rises and falls on the lower die 6, has two cores 7 that can enter the grooves 6a and 6b of the lower die 6, and has a shape in which a hole 7a is formed between the cores 7 so that the protrusion 6c of the lower die 6 can enter.

[0012] Therefore, when the upper die 7 descends with the pouch sheet resting on the lower die 6 and pressurizes the pouch sheet, it is shaped into a pouch 2 as shown in FIG. 1b according to the shapes of the grooves 6a, 6b and protrusions 6c of the lower die 6.

[0013] The pouch 2 is folded along a folding point (C) in the middle to accommodate the electrode assembly 1 therein. The folding point (C) is the folding portion 5 in FIG. 1a.

[0014] Meanwhile, as described above, the pouch 2 has a structure in which a metal layer and a resin layer are laminated. Therefore, when molding is performed between the upper mold 7 and the lower mold 6, there is a limit to the elongation of the metal layer, and the size of the portion (d) where elongation is performed cannot be increased, so the distance (t) between the groove 3a and the sealing portion 3b of the first seating part and the distance between the groove 4a and the sealing portion 4b of the second seating part must be limited.

[0015] Therefore, due to the molding conditions of the pouch, the thickness of the electrode assembly 1 mounted in the pouch is also limited. Due to such constraints, pouch-type secondary batteries with larger capacity have been provided in a form in which the area is increased without increasing the thickness of the electrode assembly.

[0016] However, as the need for high-capacity secondary batteries gradually increases, a pouch capable of mounting a thicker electrode assembly and a molding apparatus capable of manufacturing the pouch are required. Summary of the Invention [Problem to be solved by the invention]

[0017] The present invention has as its main object to provide a pouch capable of mounting a thicker electrode assembly in response to the gradually increasing demand for high-capacity secondary batteries, a molding device capable of manufacturing the pouch, and a method for manufacturing a secondary battery including the pouch. [Means for solving the problem]

[0018] In order to achieve the above object, the present invention provides a pouch, a molding apparatus capable of manufacturing the pouch, and a method for manufacturing a secondary battery including the pouch.

[0019] The pouch forming apparatus according to the present invention includes a first mounting part and a second mounting part connected to each other, and when an electrode assembly is mounted, the first mounting part and the second mounting part are folded to cover upper and lower sides of the electrode assembly, and a sealing part of the first mounting part and the second mounting part are abutted against each other to produce a sealed pouch. The pouch forming apparatus includes a lower mold having a first groove recessed from an upper surface to a certain depth and a second groove further recessed from a bottom surface of the first groove; an upper mold having a flat portion and a protrusion that enters the second groove protruding from the flat portion; and when the upper mold and the lower mold are pressed together with a pouch sheet placed between them, a first mounting portion and a second mounting portion are formed at a portion pressed by the flat portion, and a sidewall portion that connects the first mounting portion and the second mounting portion and forms a surface parallel to a side surface of the electrode assembly when the electrode assembly is mounted is formed at a portion pressed by the protrusion.

[0020] The pouch is constructed by laminating a metal layer of aluminum material and a resin layer of polymeric material, and the protruding height of the protruding portion from the flat portion is determined by the extension rate of the metal layer.

[0021] The second groove is located at the center of the first groove, and the protrusion is located at the center of the flat portion.

[0022] The corners of the upper mold that enter the first groove and the corners of the protrusion are rounded with a predetermined curvature, and the corners of the lower mold in which the first groove is formed are rounded with a predetermined curvature.

[0023] Further, the pouch provided in the present invention includes a first seating part and a second seating part connected to each other, and when an electrode assembly is loaded, the first seating part and the second seating part are folded to cover the upper and lower sides of the electrode assembly and are sealed in a state where the sealing parts of the first seating part and the second seating part are abutted against each other, the pouch includes a first seating part covering either the upper or lower side of the electrode assembly, a second seating part covering the other of the upper or lower side of the electrode assembly and having one side connected to one side of the first seating part, and a side wall part having one side connected to one side of the first seating part and the other side connected to the second seating part, and the side wall part may be folded at each of the first seating part and the second seating part, and may be formed in a flat plane shape on both the inner side and the outer side of the pouch. In this case, the side wall part may be folded so as to be perpendicular to the first seating part and the second seating part.

[0024] Each of the first and second mounting parts has a sealing part extending from the remaining sides except for the side connected by the side wall part, and when the electrode assembly is mounted and folded, the sealing part of the first and second mounting parts are sealed.

[0025] The length of the sealing portion of the first mounting part and the sealing portion of the second mounting part extending from the first mounting part and the second mounting part is determined according to the length of the side wall part so that the sealing portion of the first mounting part and the sealing portion of the second mounting part are sealed when the first mounting part and the second mounting part are folded to be parallel to each other.

[0026] A corner where the first mounting portion and the side wall portion are connected and a corner where the second mounting portion and the side wall portion are connected may have a step portion having a concave shape.

[0027] Furthermore, the present invention further provides a method for manufacturing a secondary battery including a pouch having the above-mentioned structure.

[0028] A method for manufacturing a secondary battery according to the present invention is a method for manufacturing a pouch including a first seating part and a second seating part connected to each other, the pouch being folded to cover upper and lower sides of the electrode assembly when an electrode assembly is mounted thereon and sealed in a state in which sealing parts of the first seating part and the second seating part are in contact with each other, and an electrode assembly is contained in the pouch together with an electrolyte, the method comprising: forming a pouch (S10); and sealing the formed pouch with the electrode assembly and the electrolyte contained therein and sealing the sealing part of the pouch (S20). The pouch forming step (S10) includes a step (S11) of placing a pouch sheet on a lower mold having a first groove recessed from an upper surface to a certain depth and a second groove further recessed from a bottom surface of the first groove; a step (S12) of pressing and forming the pouch sheet with an upper mold having a flat portion formed on one side that enters the first groove and a protrusion that enters the second groove protruding from the flat portion; and a step (S13) of folding the molded pouch sheet to form first and second mounting portions facing each other and side wall portions connecting the first and second mounting portions.

[0029] In this case, the side wall portion is formed so that both the inner and outer side surfaces have a flat planar shape.

[0030] In the step of folding the formed pouch sheet (S13), the side wall portion is folded so as to be perpendicular to the first and second seating portions. Effect of the Invention

[0031] The pouch of the present invention having the above-mentioned configuration has a flat side wall portion connecting the first mounting portion and the second mounting portion, and an electrode assembly having a larger thickness can be mounted therein by adjusting the length of the side wall portion.

[0032] That is, in conventional pouches, the extension of the metal layer is limited, and the thickness of the electrode assembly that can be mounted is also limited. However, in the pouch of the present invention, the side wall portion has a flat surface that does not extend between the upper and lower molds, and therefore, by adjusting the length of the flat surface, it is possible to mount a thicker electrode assembly.

[0033] Furthermore, the corners of the upper and lower dies are rounded, which can reduce the occurrence of deformation caused by the pouch sheet being pierced or pushed. [Brief description of the drawings]

[0034] [Figure 1a] FIG. 13 is a perspective view showing an electrode assembly mounted in a conventional pouch. [Figure 1b] 1A and 1B are cross-sectional views showing a conventional pouch in an open state and a closed (folded) state. [Figure 1c] FIG. 1 is a cross-sectional view showing a cross section of a conventional pouch forming apparatus. [Diagram 2] 1 is a cross-sectional view showing a cross section of a pouch forming apparatus according to an embodiment of the present invention. [Diagram 3] 3 is a cross-sectional view showing an electrode assembly being mounted in a pouch manufactured by the pouch forming apparatus of FIG. 2. FIG. [Figure 4] 1 is a cross-sectional view showing a conventional pouch with an electrode assembly mounted thereon and a cross-sectional view showing a thicker electrode assembly mounted thereon in the pouch of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which: FIG. 1 is a block diagram of a semiconductor device according to an embodiment of the present invention;

[0036] In order to clearly describe the present invention, parts that are not relevant to the description will be omitted, and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0037] Furthermore, the terms and words used in this specification and the claims should not be interpreted limited to their ordinary and dictionary meanings, but should be interpreted in a way that is consistent with the technical ideas of the present invention, based on the principle that the inventor himself / herself can appropriately define the concepts of terms in order to explain the invention in the best possible manner.

[0038] The present invention provides a pouch, a molding apparatus for manufacturing the pouch, and a method for manufacturing a secondary battery including the pouch. Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0039] (First embodiment) The present invention provides a pouch forming apparatus as a first embodiment. The pouch forming apparatus according to the present invention includes a first mounting part 11 and a second mounting part 12 connected to each other, and is configured to manufacture a pouch 10 in which, when an electrode assembly 1 is mounted, the first mounting part 11 and the second mounting part 12 are folded to cover the upper and lower sides of the electrode assembly 1, and the sealing parts 11a, 12a of the first mounting part 11 and the second mounting part 12 are abutted against each other and sealed.

[0040] 2 is a cross-sectional view of a pouch forming apparatus according to an embodiment of the present invention. As shown in FIG. 2, the forming apparatus of the present invention includes a lower mold 20 and an upper mold 30.

[0041] The lower mold 20 has a flat lower surface, a first groove 21 is formed in the upper surface to a certain depth, and a second groove 22 is formed in the bottom surface of the first groove 21.

[0042] Based on the second groove 22, the first mounting portion 11 of the pouch 10 is formed on one side of the first groove 21, and the second mounting portion 12 is formed on the other side of the first groove 21. The side wall portion 13 of the pouch 10 is formed in the portion where the second groove 22 is located. Therefore, the area of ​​the first groove 21 is determined depending on the size (area) of the first mounting portion 11 and the second mounting portion 12 of the pouch 10 to be manufactured. Similarly, the area of ​​the second groove 22 is determined depending on the size of the side wall portion 13 connecting the first mounting portion 11 and the second mounting portion 12.

[0043] However, the depth of the first groove 21 and the depth of the second groove 22 can be determined by the elongation rate of the metal layer included in the pouch 10. That is, since the pouch sheet formed into the pouch 10 is configured by laminating a metal layer of an aluminum material and a resin layer of a polymeric material, in order to prevent damage to the metal layer, the depth of the first groove 21 and the second groove 22 (the height at which the flat portion enters and the protruding height of the protruding portion from the flat portion) is determined by the elongation rate of the metal layer.

[0044] Furthermore, the upper mold 30 has a structure in which a flat portion 31 is formed on one side that enters the first groove 21 of the lower mold 20, and a protruding portion 32 that enters the second groove 22 protrudes further from the flat portion 31. Although only the flat portion 31 and the protruding portion 32 that enter the first groove 21 and the second groove 22 are shown in Fig. 2, the flat portion 31 and the protruding portion 32 may be integrally formed and may further include a sliding device connected to be movable up and down, and a portion (not shown) that presses the sealing portions 11a and 12a of the pouch.

[0045] Therefore, when a flat pouch sheet is placed between the upper mold 30 and the lower mold 20, the upper mold 30 descends onto the lower mold 20 (or the lower mold rises onto the upper mold) and the pouch sheet is pressed between the upper mold 30 and the lower mold 20.

[0046] When the upper mold 30 and the lower mold 20 are separated after the pressing, a first mounting portion 11 and a second mounting portion 12 are formed in the portion of the pouch sheet where the flat portion 31 is pressed, and a side wall portion 13 is formed that connects the first mounting portion 11 and the second mounting portion 12 in the portion where the protrusion 32 is pressed, and forms a surface parallel to the side of the electrode assembly 1 when the electrode assembly 1 is mounted.

[0047] At this time, the corners of the upper die 30 entering the first groove 21 and the corners of the protrusion 32 are rounded with a predetermined curvature, and the corners of the lower die 20 in which the first groove 21 is formed are also rounded with a predetermined curvature. This is to prevent damage to the pouch sheet that may occur during compression if pressure is concentrated at the corners. This curvature can also be determined by the elongation rate of the metal layer of the pouch sheet.

[0048] Second embodiment The present invention provides, as a second embodiment, a pouch that can be manufactured by the pouch forming apparatus according to the first embodiment.

[0049] Fig. 3 is a cross-sectional view showing the placement of an electrode assembly 1 in a pouch 10 manufactured by the pouch forming apparatus of Fig. 2. Referring to the figure, the pouch 10 provided in this embodiment includes a first mounting part 11 and a second mounting part 12 connected to each other, and when the electrode assembly 1 is placed therein, the first mounting part 11 and the second mounting part 12 are folded to cover the upper and lower sides of the electrode assembly 1, and the sealing parts 11a, 12a of the first mounting part 11 and the second mounting part 12 are abutted against each other to perform sealing.

[0050] In this case, the first mounting portion 11 covers either the upper or lower portion of the electrode assembly 1 , and the second mounting portion 12 covers the other of the upper or lower portion of the electrode assembly 1 .

[0051] The first mounting portion 11 and the second mounting portion 12 are connected to each other via a side wall portion 13, one side of which is connected to one side of the first mounting portion 11 and the other side of which is connected to the second mounting portion 12.

[0052] The side wall portion 13 may be folded perpendicularly to the first seating portion 11 and the second seating portion 12, so that the inner and outer surfaces of the pouch 10 are all formed into a flat plane.

[0053] That is, in the conventional structure, a folding point (C) is formed at the connecting point between the first mounting part 3 and the second mounting part 4, and the pouch has a portion that protrudes outward, so that a flat surface is not formed, but in the structure of the present invention, the first mounting part 11 and the second mounting part 12 are folded at both ends of the side wall part 13, so that such a folding point (C) is eliminated and the inner and outer surfaces of the pouch 10 can all be flat and planar. Therefore, the pouch 10 of the present invention can have a neater appearance than the conventional structure.

[0054] It should be noted that the term "vertical" used in this invention does not mean only an exact right angle, but rather means a state in which an angle is approximately adjacent to a right angle when a bend occurs between two components.

[0055] Referring to FIG. 4, when a pouch is formed using the pouch forming device according to the present invention, a pouch capable of accommodating a significantly thicker electrode assembly than the conventional pouch can be produced, and as the thickness of the electrode assembly increases, the side wall portion 13 becomes more perpendicular to the first mounting portion 11 and the second mounting portion 12.

[0056] Therefore, the pouch of the present invention has a significantly vertical shape compared to the conventional pouch. Therefore, the word "vertical" is used to express such a state, but the word "vertical" in this specification should not be interpreted as meaning only a 90 degree right angle.

[0057] For example, when the side wall portion is folded at the first mounting portion or the second mounting portion, even if it is folded at 80 degrees or 100 degrees depending on the increased thickness of the electrode assembly, it should be considered to be in the vertically folded category to be considered a pouch according to the present invention.

[0058] In addition, in the present invention, the side wall portion having a shape as a "flat plane" does not mean only a completely flat surface state in which the radius of curvature is infinite and the curvature is zero at all points, but should be understood to mean that there are no overall folded points or bent shapes as compared to conventional technologies.

[0059] In addition, since the pouch is made by laminating thin metal layers and resin layers and has flexibility, it can easily deform due to external forces. Therefore, even if it is manufactured without bending or folding overall, even if it has some wrinkles or slight bends, it should be considered to be within the category of a "flat surface."

[0060] Furthermore, similar to the conventional structure, the first mounting portion 11 and the second mounting portion 12 are formed by extending sealing portions 11a, 12a from the remaining sides except for the side connected by the side wall portion 13, and when the electrode assembly 1 is mounted and folded, the sealing portion 11a of the first mounting portion 11 and the sealing portion 12a of the second mounting portion 12 are joined in abutting contact with each other and sealed.

[0061] At this time, the sealing parts 11a and 12a are configured to have a sufficient length to be bonded to each other by the length of the side wall part 13. That is, the length of the sealing part 11a of the first seating part and the sealing part 12a of the second seating part extending from each of the first seating part 11 and the second seating part 12 is determined according to the length of the side wall part 13 so that the sealing part 11a of the first seating part and the sealing part 12a of the second seating part are sealed when the first seating part 11 and the second seating part 12 are folded in parallel.

[0062] Meanwhile, a step portion 14 may be formed to have a concave shape at a corner where the first seating portion 11 and the side wall portion 13 are connected and at a corner between the second seating portion 12 and the side wall portion 13. When the resin layer laminated on the metal layer is a thermosetting resin during molding in the molding device, the step portion 14 may be formed by bending the first seating portion 11 and the second seating portion 12 away from the point where the resin layer is pressed by the protrusion 32 and the second groove 22 when the resin layer is hardened at the point. Therefore, if the resin layer of the pouch sheet is thermoplastic rather than thermosetting, the step portion 14 may not be formed.

[0063] The pouch 10 of the present invention having the above-mentioned configuration has a side wall portion 13 connecting the first mounting portion 11 and the second mounting portion 12, and an electrode assembly 1 having a larger thickness can be mounted therein by adjusting the length of the side wall portion 13.

[0064] As shown in FIG. 4, which shows a cross section of a conventional pouch with an electrode assembly mounted thereon and a cross section of a pouch of the present invention with a thicker electrode assembly mounted thereon, in the conventional pouch 2, the extension of the metal layer is limited, and the thickness of the electrode assembly 1 that can be mounted thereon is also limited. However, in the pouch 10 of the present invention, the side wall portion 13 has a plane that is not extended between the upper mold 30 and the lower mold 20, and therefore a thicker electrode assembly can be mounted thereon by adjusting the length of the plane.

[0065] Third embodiment The present invention provides, as a third embodiment, a method for manufacturing a secondary battery including the pouch according to the second embodiment.

[0066] The method for manufacturing a secondary battery according to this embodiment includes a pouch forming step (S10) of forming a pouch, and a sealing step (S20) of incorporating an electrode assembly and an electrolyte in the formed pouch and sealing a sealing portion of the pouch.

[0067] In this case, the pouch forming step (S10) includes a step (S11) of placing a pouch sheet on a lower mold 20 having a first groove 21 recessed from an upper surface to a certain depth and a second groove 22 further recessed from a bottom surface of the first groove 21, and a step (S12) of pressing and forming the pouch sheet with an upper mold 30 having a flat portion 31 formed on one side that enters the first groove 21 and a protruding portion 32 that enters the second groove 22 protruding from the flat portion 31. In this case, when the pouch sheet is pressed and formed, the portion formed as the side wall is formed so that both the inner side and the outer side have flat planar shapes.

[0068] The method further includes a step of folding the formed pouch (S13). In this step, the pouch sheet is folded so that a first seating portion 11 and a second seating portion 12 facing each other and a side wall portion 13 connecting the first seating portion 11 and the second seating portion 12 are formed.

[0069] At this time, in the step of folding the formed pouch sheet (S13), the side wall portion 13 is folded so as to be perpendicular to the first seating portion 11 and the second seating portion 12, respectively.

[0070] When the electrode assembly 1 and the electrolyte are placed in the pouch, a sealing step (S20) is performed by applying heat and pressure to the sealing portion of the pouch.

[0071] Although the present invention has been described above using limited embodiments and figures, the present invention is not limited thereto, and various implementations of the present invention are possible within the technical spirit of the present invention and the equivalent scope of the claims described below by a person having ordinary skill in the art to which the present invention pertains. [Explanation of symbols]

[0072] 1 Electrode assembly 10 pouches 11 First landing section 12 Second landing section 20 Lower mold 21 First groove 22 Second groove 30 Upper mold 31 Plane part 32 Protrusion

Claims

1. A pouch forming device for manufacturing a pouch comprising a first mounting portion and a second mounting portion connected to each other via a side wall portion, a step portion formed in a concave shape at a corner where the first mounting portion and the side wall portion are connected and at a corner of the second mounting portion and the side wall portion, and a flat sealing portion connected to the first mounting portion and the second mounting portion respectively on the opposite side of the step portion, the first mounting portion and the second mounting portion being recessed further than the sealing portion, and when an electrode assembly is loaded, the flat sealing portions are folded to cover the upper and lower sides of the electrode assembly and are sealed in abutting state, a lower mold having a first groove recessed from an upper surface to a certain depth and a second groove recessed from a bottom surface of the first groove; an upper mold having a flat surface formed on one side thereof that enters the first groove and a protruding portion that enters the second groove protruding from the flat surface; a pouch forming apparatus comprising: a pouch sheet forming section for forming a pouch sheet between the upper mold and the lower mold, the upper mold and the lower mold are pressed together to form the first mounting portion and the second mounting portion at a portion pressed by the flat portion, the first mounting portion and the second mounting portion are connected at a portion pressed by the protruding portion, and a side wall portion is formed to form a surface parallel to a side surface of the electrode assembly when the electrode assembly is mounted.

2. The pouch is constructed by laminating a metal layer of an aluminum material and a resin layer of a polymeric material, The pouch forming apparatus according to claim 1 , wherein a protruding height of the protruding portion from the flat portion is determined by an elongation rate of the metal layer.

3. The pouch forming apparatus according to claim 1 or 2, wherein the second groove is located at a center of the first groove, and the protrusion is located at a center of the flat portion.

4. The pouch forming apparatus according to claim 3 , wherein a corner of the upper mold that enters the first groove and a corner of the protruding portion are rounded with a predetermined curvature.

5. 4. The pouch forming apparatus according to claim 3, wherein corners of the upper and lower dies in which the first groove is formed are rounded with a predetermined curvature.

6. A pouch comprising a first mounting portion and a second mounting portion connected to each other via a side wall portion, a step portion formed in a concave shape at a corner where the first mounting portion and the side wall portion are connected and at a corner of the second mounting portion and the side wall portion, and flat sealing portions connected to the first mounting portion and the second mounting portion respectively on the opposite side of the step portion, the first mounting portion and the second mounting portion being recessed relative to the sealing portions, and when an electrode assembly is mounted, the flat sealing portions are folded to cover the upper and lower sides of the electrode assembly and are sealed in abutting state, the first seating portion covering either an upper portion or a lower portion of the electrode assembly; a second mounting part covering the other of the upper and lower parts of the electrode assembly and having one side connected to one side of the first mounting part; a side wall portion having one side connected to one side of the first mounting portion and another side connected to the second mounting portion; The side wall portion is folded at each of the first and second mounting portions, and both inner and outer surfaces of the pouch are formed into a flat planar shape.

7. The pouch according to claim 6, wherein the side wall portion can be folded so as to be perpendicular to the first and second mounting portions.

8. Each of the first and second mounting parts is formed by extending a sealing part from an edge other than an edge connected to the side wall part, The pouch according to claim 6 or 7, wherein the sealing portion of the first seating portion and the sealing portion of the second seating portion are sealed when the electrode assembly is mounted and folded.

9. 9. The pouch according to claim 8, wherein the sealing portion of the first mounting part and the sealing portion of the second mounting part have lengths extending from the first mounting part and the second mounting part determined according to a length of a side wall part such that the sealing portion of the first mounting part and the sealing portion of the second mounting part are sealed when the first mounting part and the second mounting part are folded in parallel.

10. A method for manufacturing a secondary battery comprising a pouch including a first mounting portion and a second mounting portion connected to each other via a side wall portion, a step portion formed in a concave shape at a corner where the first mounting portion and the side wall portion are connected and at a corner of the second mounting portion and the side wall portion, and a sealing portion connected to the first mounting portion and the second mounting portion respectively on the opposite side of the step portion, the first mounting portion and the second mounting portion being recessed further than the sealing portion, and when an electrode assembly is mounted, the flat sealing portions are folded to cover the upper and lower sides of the electrode assembly and sealed in abutting state, and an electrode assembly is incorporated into the pouch together with an electrolyte, The method includes a pouch forming step (S10) of forming a pouch, and a sealing step (S20) of sealing a sealing portion of the pouch by incorporating an electrode assembly and an electrolyte in the formed pouch, The pouch forming step (S10) includes: A step of placing a pouch sheet on a lower mold having a first groove recessed to a certain depth from an upper surface and a second groove recessed from a bottom surface of the first groove (S11); A step of pressing and molding the pouch sheet with an upper mold having a flat portion formed on one side that enters the first groove and a protrusion that enters the second groove protruding from the flat portion (S12); and folding (S13) a pouch sheet shaped to form the first and second mounting portions facing each other and a side wall portion connecting the first and second mounting portions.

11. The method of claim 10, wherein the sidewall portion is formed so that both inner and outer side surfaces are flat and planar.

12. The method of claim 11, wherein in the step of folding the formed pouch sheet (S13), the side wall portion is folded so as to be perpendicular to the first mounting portion and the second mounting portion.

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