Method for manufacturing pouch case of secondary battery, pouch film of secondary battery and pouch case of secondary battery

Abstract

To provide a method for manufacturing a pouch case of a secondary battery, a pouch film of a secondary battery, and a pouch case of a secondary battery, where, during a process of manufacturing a pouch case by forming a pouch film, an elongation rate can be measured by the color of an outer layer of the pouch film without separate sampling, and it can be determined whether elongation has occurred which causes a critical level in which a crack is about to occur or a defective level in which a crack is occurring.SOLUTION: A method for manufacturing a pouch case of a secondary battery according to the present invention includes: stacking a metal layer above an inner layer and stacking an outer layer, which includes colored dye particles, above the metal layer, thereby producing a pouch film; forming the pouch film into a three-dimensional shape so that an electrode assembly may be accommodated therein; and measuring an elongation rate of the pouch film through color of the outer layer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0158223 filed on November 23, 2020, and Korean Patent Application No. 10-2021-0143257 filed on October 26, 2021, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a method for manufacturing a pouch case for a secondary battery, a pouch film for a secondary battery, and a pouch case for a secondary battery, and more particularly, to a method for manufacturing a pouch case for a secondary battery, which is capable of determining whether stretching has occurred to a dangerous level just before cracking or to a defective level at which cracking will occur by measuring the stretch rate via the color of the outer layer of the pouch film without separate sampling during the process of forming the pouch film to manufacture a pouch, a pouch film for a secondary battery, and a pouch case for a secondary battery. [Background technology]

[0003] Secondary batteries that can be repeatedly charged and discharged can be classified into cylindrical secondary batteries, prismatic secondary batteries, pouch-type secondary batteries, etc. depending on their structure or manufacturing method. Existing secondary battery casings have mainly been cylindrical or prismatic batteries that use metal cans. However, batteries with such structures have drawbacks, such as limited design of electronic products using them as power sources due to their fixed shape, and difficulty in reducing their volume. Therefore, active development of pouch-type secondary batteries is underway.

[0004] A pouch-type secondary battery generally has a structure in which an electrode assembly having electrodes and separators alternately arranged inside a sheet-like pouch film (or pouch outer material) is housed. More specifically, it is roughly divided into a lower case having a cup portion (or container portion) and an upper case covering the lower case. The electrode assembly housed in the cup portion is made up of a positive electrode, a negative electrode, and a separator stacked together. Electrode tabs are pulled out from each electrode, and tape is attached to the electrode tabs where they overlap with the sealing portion.

[0005] Unlike cylindrical batteries, pouch-type secondary batteries with this structure have the advantage that they are relatively easy to deform and can realize a secondary battery with the same capacity with a smaller volume and mass. However, they have the problem of weak mechanical strength because they use a soft pouch case as a container.

[0006] In particular, a pouch case having a cup portion formed from a sheet-type pouch film inevitably undergoes stretching during the manufacturing process, and excessive stretching can lead to the risk of fine cracks or breakage. If a crack or break occurs in the pouch case, which serves as an exterior material, the electrolyte may leak or react with oxygen, resulting in a decrease in battery performance and an inability to ensure safety.

[0007] Therefore, in order to solve this problem, a conventional method involves sampling a molded pouch case, extracting a portion where dangerous stretching is suspected to have occurred, measuring the stretching rate by measuring the thickness using a microscope, and then determining whether the pouch has been stretched to a degree that could cause a risk of cracking or breaking, thereby detecting a defective pouch.

[0008] However, this method requires optional sampling for defect detection, which limits its ability to detect all defective pouch cases. In addition, since separate sampling and measurement are required, there are problems in that the defect detection rate and efficiency are significantly reduced.

[0009] Ultimately, the conventional method cannot sufficiently ensure the safety of the battery and has low productivity throughout the process, and therefore, improvements are required. That is, there is a need to develop a method for manufacturing a secondary battery pouch case, a secondary battery pouch film, and a secondary battery pouch case that can more easily determine and detect whether cracks or breaks due to stretching have occurred after the pouch film is formed, or whether stretching has reached a dangerous level immediately before such occurrence. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been devised to solve the above problems, and an object of the present invention is to provide a method for manufacturing a pouch case for a secondary battery, a pouch film for a secondary battery, and a pouch case for a secondary battery, which are capable of measuring the elongation rate through the color of the outer layer of the pouch film without separate sampling during the process of forming a pouch film to manufacture a pouch case, and determining whether elongation has occurred to a dangerous level just before cracking or to a defective level where cracks will occur. [Means for solving the problem]

[0011] A method for manufacturing a secondary battery pouch case according to the present invention includes the steps of: laminating a metal layer on top of an inner layer; laminating an outer layer containing colored dye particles on top of the metal layer to form a pouch film; forming the pouch film into a three-dimensional shape so that an electrode assembly can be housed therein; and measuring the elongation rate of the pouch film based on the color of the outer layer.

[0012] The step of measuring the stretch rate may include the steps of extracting color data of the outer layer, inputting the color data into a data table in which the color and the stretch rate are associated, and outputting a value of the stretch rate of the pouch film corresponding to the input color data.

[0013] The method may further include a step of determining whether a molding defect occurs after the step of measuring the stretch rate, and in the step of determining whether a molding defect occurs, if the stretch rate of the pouch film is 40% or more, the pouch film may be determined to be defective.

[0014] The method may further include a step of manufacturing an outer layer before the step of manufacturing the pouch film, and the step of manufacturing the outer layer may include laminating polyethylene terephthalate containing a colored dye on top of nylon to form the outer layer.

[0015] In the step of manufacturing the outer layer, the thickness of the outer layer can be manufactured to be 12 μm to 30 μm.

[0016] In fabricating the pouch film, the inner layer can be made of polypropylene.

[0017] In the step of manufacturing the pouch film, the metal layer can be formed of aluminum.

[0018] The secondary battery pouch film according to the present invention comprises an inner layer, a metal layer laminated on the inner layer, and an outer layer laminated on the metal layer and containing colored dye particles.

[0019] When the pouch film is formed, the stretching rate of the outer layer can be measured based on the color of the outer layer.

[0020] When the outer layer becomes lighter than the reference color during the formation of the pouch film, it can be determined that the critical stretch has been reached.

[0021] The reference color may be the color of the outer layer when the stretching ratio reaches 40%.

[0022] The outer layer is formed by laminating polyethylene terephthalate on top of nylon, and the polyethylene terephthalate may contain colored dye particles.

[0023] The metal layer may be formed of aluminum and the inner layer may be formed of polypropylene.

[0024] The secondary battery pouch case according to the present invention includes a lower case having a concave cup-shaped portion and an upper case covering the upper part of the lower case from above. The lower case and the upper case are manufactured by molding a pouch film. The pouch film is composed of an inner layer, a metal layer laminated on the upper part of the inner layer, and an outer layer laminated on the upper part of the metal layer and containing colored dye or pigment particles.

[0025] The cup portion may be formed to have one bottom and four side surfaces, and the bottom and side surfaces may be formed so that the peripheral and central regions of each surface have different colors.

[0026] The bottom and side surfaces may be formed such that the peripheral areas of each surface are brighter than the central area.

[0027] The bottom and side surfaces may be distributed with a lower concentration of colored dye or pigment in the peripheral regions of each surface than in the central region. [Effects of the Invention]

[0028] A method for manufacturing a secondary battery pouch case according to the present invention includes the steps of: laminating a metal layer on an inner layer, laminating an outer layer containing colored dye particles on the metal layer to form a pouch film; molding the pouch film into a three-dimensional shape so that an electrode assembly can be housed therein; and measuring the elongation rate of the pouch film through the color of the outer layer. Thus, during the process of molding the pouch film and manufacturing the pouch case, the elongation rate can be measured through the color of the outer layer of the pouch film without any additional sampling, and it can be determined whether elongation has reached a dangerous level just before cracking or a defective level at which cracks will occur. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a perspective view showing a typical secondary battery pouch case. [Figure 2] 3 is a flowchart showing a method for manufacturing a secondary battery pouch case according to the first embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view showing the cross section of the pouch film according to Examples 1 and 2 of the present invention before stretching occurs. [Figure 4] FIG. 2 is a cross-sectional view showing a cross section of the pouch film according to Examples 1 and 2 of the present invention after stretching has occurred. [Figure 5] FIG. 10 is a perspective view showing a secondary battery pouch case according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030]

[0030] The present invention will now be described in detail with reference to the accompanying drawings, in order to enable those skilled in the art to easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the following embodiments.

[0031] In order to clearly explain the present invention, detailed descriptions of parts that are not relevant to the explanation or related known technologies that may unnecessarily obscure the gist of the present invention will be omitted, and in adding reference symbols to components in each drawing in this specification, the same or similar reference symbols will be used for the same or similar components throughout the specification.

[0032] Furthermore, the terms and words used in the description of the present invention and the claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that an inventor can appropriately define the concept of a term in order to best describe his or her invention.

[0033] Example 1 Fig. 2 is a flowchart showing a method for manufacturing a secondary battery pouch case according to Example 1 of the present invention. Fig. 3 is a cross-sectional view showing a cross-section of a pouch film according to Example 1 of the present invention before stretching occurs. Fig. 4 is a cross-sectional view showing a cross-section of a pouch film according to Example 1 of the present invention after stretching occurs.

[0034] Referring to FIG. 2, the method for manufacturing a secondary battery pouch case according to Example 1 of the present invention includes a step of preparing a pouch film (S10), a step of forming the pouch film (S20), and a step of measuring the elongation rate of the pouch film (S30).

[0035] First, the step of manufacturing the pouch film (S10) will be described in detail. As shown in Fig. 3, the pouch film 100 is formed into a multi-layer structure in which a plurality of layers are stacked, and a metal layer 120 is stacked on top of an inner layer 110, and an outer layer 130 is stacked on top of the metal layer 120.

[0036] The inner layer 110 is the innermost layer of the pouch film 100. It has chemical resistance to the electrolyte and thermal adhesiveness, and serves as a sealant. It is typically made of a polyolefin resin, preferably polypropylene (PP). The metal layer 120 is interposed between the inner layer 110 and the outer layer 130. It maintains the mechanical strength of the pouch film 100 and acts as a barrier against moisture and oxygen. The metal layer 120 may be made of an alloy of iron (Fe), carbon (C), chromium (Cr), and manganese (Mn), an alloy of iron (Fe), carbon (C), chromium (Cr), and nickel (Ni), or the like, preferably aluminum (Al). The outer layer 130 is the outermost layer of the pouch film 100. It protects the battery from external impact and comes into direct contact with the hardware, so it must be insulating and heat-resistant. The material and manufacturing method of the outer layer 130 will be described in detail below.

[0037] The method for manufacturing a secondary battery pouch case according to the first embodiment of the present invention may include a step (S9) of manufacturing an outer layer prior to the step (S10) of manufacturing a pouch film. The material of the outer layer 130 may include a single layer of one material selected from polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), nylon, low-density polyethylene (LDPE), and high-density polyethylene (HDPE), or a composite layer of two or more materials. In the step (S9) of manufacturing the outer layer according to the first embodiment of the present invention, the outer layer 130 may be formed by laminating polyethylene terephthalate (PET) containing a colored dye on top of a transparent nylon film.

[0038] Here, the dye includes both organic dyes and inorganic dyes, and is not particularly limited, as long as it can be contained in the outer layer as a colored dye, and preferably, it can be any dye that can be mixed with or attached to polyethylene terephthalate (PET). In addition, it goes without saying that not only dyes but also pigments can be used.

[0039] The overall thickness of the pouch film 100 is typically 40 to 120 μm, with the inner layer 110 being 10 to 40 μm, the metal layer 120 being 20 to 100 μm, and the outer layer 130 preferably being manufactured to a thickness of 12 μm to 30 μm.

[0040] After the pouch film is manufactured (S10), it can be molded into a three-dimensional shape so that an electrode assembly can be housed inside the pouch film 100 (S20). A pouch-type secondary battery can be broadly divided into a pouch case 1 and an electrode assembly housed inside the pouch case 1. As shown in FIG. 1, the pouch case 1 is divided into a lower case having a cup-shaped portion for housing the electrode assembly and an upper case covering the lower case. The pouch film 100, which is laminated in a multilayer structure, undergoes a process of forming a cup-shaped portion using a molding device. After fixing the area other than the cup-shaped portion of the pouch film 100, a press punch presses the cup-shaped portion, and as the pouch film 100 stretches, the pouch case 1 is formed with a cup-shaped portion corresponding to the punch. In this case, stretching occurs mainly at the corners of the pouch case 1, including the area surrounding the cup-shaped portion of the pouch case 1, and cracks or breakage mainly occur.

[0041] In the method for manufacturing a secondary battery pouch case according to the first embodiment of the present invention, the elongation rate of the pouch film 100 can be measured (S30) based on the color of the outer layer 130 of the pouch film 100. The measurement of the elongation rate of the pouch film 100 based on the color (S30) will be described in detail below with reference to FIG.

[0042] As discussed above, the outer layer 130 is formed by laminating polyethylene terephthalate (PET) containing colored dye particles 131 on top of transparent nylon, and before stretching, the pouch film 100, when viewed from the outside, has the color density of the dye particles 131 of the outer layer 130. However, when stretching occurs during the molding of the pouch film 100, the concentration of the dye particles 131 in the stretched region (B) becomes lower than that in the non-stretched region (A), as shown in FIG. 4. As a result, the color density of the outer layer 130 in the stretched region (B) becomes lighter, and at the same time, the color of the metal layer 120 laminated underneath the outer layer 130 blends in, changing the color of the pouch film 100 in the stretched region (B). In particular, when the metal layer 120 is made of light-colored aluminum (Al), the color of the colored dye particles 131 becomes lighter as the metal layer 120 is stretched, and the light color of the aluminum (Al) is mixed in, so that the color of the stretched portion (B) of the pouch film 100 becomes lighter than that of the non-stretched portion (A). This makes it possible to measure the stretch rate (S30) based on the color of the outer layer 130 of the pouch film 100.

[0043] As described above, the method for manufacturing a secondary battery pouch case according to the first embodiment of the present invention measures the elongation rate through the color of the outer layer 130 of the pouch film 100 without any additional sampling, and can determine whether the elongation has reached a dangerous level just before cracking or a defective level where cracks will occur. Furthermore, although the number of defective inspection targets and the defective determination rate are increased, the time and cost required for the process can be significantly reduced, thereby improving productivity and ensuring product quality and cost competitiveness.

[0044] Next, the step of measuring the stretch ratio (S30) will be described in detail. The step of measuring the stretch ratio (S30) may include the steps of extracting color data of the outer layer 130, inputting the color data into a data table in which the color and the stretch ratio are associated, and outputting the value of the stretch ratio of the pouch film corresponding to the input color data.

[0045] First, considering the step of extracting color data of the outer layer 130, the color of the outer layer 130 can be extracted through an input means and a processor. For example, the color of the outer layer 130 of the pouch film 100 is recognized through an input means such as a camera module including a lens, image, or color detection sensor, and a processor operatively coupled to the sensor identifies the color and then extracts it as data.

[0046] The extracted color data is then input into a previously stored data table in which colors and stretch rates are associated. In this case, the data table in which colors and stretch rates are associated refers to a table in which data is stored on the color change of the pouch film 100 depending on the degree of stretching, based on the initial color of the pouch film 100 having color dye particles 131 of a preset concentration contained in the outer layer 130. For example, the data may be stored by setting a concentration ratio of a specific color dye contained in the PET layer, stretching the pouch film 100 including the outer layer 130 manufactured according to the set value, and then converting the color change into data for each stretch rate range, thereby correlating the color of the pouch film 100 with the stretch rate.

[0047] When the extracted color data is input into the data table, the previously stored color data corresponding to the input color data is selected, and the corresponding value of the elongation rate of the pouch film 100 is output. Therefore, compared to the conventional method of sampling the pouch case, extracting the stretched portion, and then determining the thickness using a microscope, the elongation rate can be measured using only the color data using the previously stored data table, which significantly reduces the time required for the defect detection step, and the elongation rate can be measured only by vision inspection without separate sampling, making it easier to detect defects in all the pouch cases being molded.

[0048] The step of determining whether a molding defect exists (S40) is further included after the step of measuring the stretch rate of the pouch film (S30). In the step of determining whether a molding defect exists (S40), if the stretch rate of the pouch film 100 is 40% or more, it can be determined to be defective. This is because, in the case of a pouch film 100 in which the metal layer 120 is made of aluminum, if stretching of 40% occurs, the possibility of cracking or breaking significantly increases. By determining this as a dangerous level of stretching and determining it as defective, pouch cases that are at risk of cracking or breaking can be preemptively removed even if cracks or breaks do not occur, ensuring the safety of the battery and significantly reducing the time required for determining whether a pouch film is defective.

[0049] Example 2 Fig. 3 is a cross-sectional view showing a cross section of the pouch film according to Example 2 of the present invention before stretching occurs, and Fig. 4 is a cross-sectional view showing a cross section of the pouch film according to Example 2 of the present invention after stretching occurs.

[0050] The second embodiment of the present invention differs from the first embodiment in that the second embodiment of the present invention relates to a pouch film 100 used in the method for manufacturing a secondary battery pouch case of the first embodiment.

[0051] The content common to Example 1 will be omitted as much as possible, and differences will be mainly described for Example 2. In other words, if content not described in Example 2 is necessary, it is obvious that it can be regarded as the content of Example 1.

[0052] Referring to FIG. 3, a secondary battery pouch film 100 according to a second embodiment of the present invention includes an inner layer 110, a metal layer 120, and an outer layer .

[0053] A metal layer 120 is laminated on the inner layer 110, and an outer layer 130 containing colored dye particles 131 is formed on the metal layer 120 to form the pouch film 100. The metal layer 120 may be made of aluminum (AL), and the inner layer 110 may be made of polypropylene (PP). The outer layer 130 may be formed by laminating polyethylene terephthalate (PET) on top of nylon, and the colored dye particles 131 may be contained in the polyethylene terephthalate (PET).

[0054] In particular, the outer layer 130 may be manufactured so that the elongation rate can be measured through the color of the outer layer 130 when the pouch film 100 is formed. Specifically, when the pouch film 100 is formed, if the color becomes lighter than a reference color, it can be determined that the critical elongation has been reached, and the reference color may be, for example, the color of the outer layer 130 when the elongation rate reaches 40%.

[0055] The pouch film 100 according to Example 2 of the present invention can be measured for elongation rate through the color of the outer layer 130 of the pouch film 100 without separate sampling, and it can be determined whether elongation has reached a dangerous level just before cracking or a defective level where cracking will occur.

[0056] Example 3 FIG. 5 is a perspective view showing a secondary battery pouch case according to a third embodiment of the present invention.

[0057] The third embodiment of the present invention differs from the first embodiment in that it relates to the manufacturing method of the secondary battery pouch case of the first and second embodiments, and the secondary battery pouch case manufactured using the pouch film.

[0058] The content common to Examples 1 and 2 will be omitted as much as possible, and differences will be mainly described for Example 3. In other words, if content not described in Example 3 is necessary, it is obvious that it can be regarded as the content of Examples 1 and 2.

[0059] 5, a secondary battery pouch case 1 according to Example 3 of the present invention includes a lower case 10 having a concave cup portion 11 and an upper case 20 covering the upper portion of the lower case 10 from above, and the lower case 10 and the upper case 20 are manufactured by molding a pouch film. The pouch film is composed of an inner layer, a metal layer laminated on the inner layer, and an outer layer laminated on the metal layer and containing colored dye or pigment particles. Here, the pouch film refers to the pouch film of Example 2 described above, and the inner layer, metal layer, and outer layer may be understood to be the same as those of Example 2.

[0060] As a result, when the pouch case 1 according to Example 3 of the present invention is stretched and molded, the color change can be observed through a vision inspection, and the stretched portion and the degree of stretching can be confirmed, making it easy to determine whether stretching to a dangerous level or a defective level that would cause cracks has occurred.

[0061] Here, the concave shape of the cup portion 11 means the concave shape when viewed from the upper case 20 toward the lower case 10, and when viewed from the opposite direction to the concave direction, it may have an outward protruding shape.

[0062] Meanwhile, the cup portion 11 is formed to have one bottom surface 11a and four side surfaces 11b, and the bottom surface 11a and the side surfaces 11b may be formed so that the peripheral region and the central region of each surface have different colors. That is, the peripheral region may be the region (B) where stretching has occurred, and the central region may be the region (A) where stretching has not occurred. In this way, the degree of stretching of the pouch case 1 according to the present invention can be determined by checking the external color of the peripheral region where stretching mainly occurs. Meanwhile, the colors of the peripheral region and the central region may not be clearly distinguished from each other at a specific boundary, and may be formed so that the color gradually becomes lighter or darker from the peripheral region to the central region.

[0063] The bottom surface 11 a and the side surface 11 b may be formed so that the peripheral regions of each surface are brighter than the central region. This is because, if the metal layer is formed of light-colored aluminum, the color of the colored dye particles becomes lighter as the stretching occurs, and the light color of the aluminum is mixed in, so that the peripheral regions of each surface where stretching has occurred are brighter than the central region where stretching has not occurred.

[0064] However, this is not necessarily limited to this, and the peripheral region of each side may be formed darker than the central region as needed. That is, the peripheral region of each side of the bottom surface 11a and the side surface 11b may have a lower concentration of colored dye or pigment distributed therein than the central region, and the relative brightness and darkness of the peripheral region and the central region of the pouch case 1 may vary depending on the hue of the metal layer of the pouch film and the hue of the colored dye.

[0065] Although the present invention has been described above using limited embodiments and drawings, the present invention is not limited thereto, and various implementations within the technical spirit of the present invention and the scope of the claims set forth below can be realized by a person having ordinary skill in the art to which the present invention pertains. [Explanation of symbols]

[0066] 1 pouch case 10 Lower Case 20 Upper case 11 Cup section 11a Bottom 11b Side 100 pouch film 110 Inner layer 120 metal layer 130 outer layer 131 Dye particles A: Area where no stretching has occurred B: Area where stretching occurred S9 Outer layer manufacturing stage S10 Pouch film production stage S20 Pouch film forming stage S30 Pouch film elongation rate measurement stage S40 Pouch defect judgment stage

Claims

1. inner layer; a metal layer laminated on top of the inner layer; and The outer layer is laminated on the metal layer and contains colored dye particles. The outer layer is formed by: A secondary battery pouch film in which the concentration of dye particles in the stretched region (B) is lower than that in the region (A) where stretching has not occurred, resulting in a lighter hue concentration of the outer layer in the stretched region (B), and at the same time, the hue of the metal layer laminated underneath the outer layer is mixed, changing the hue of the stretched region (B).

2. The secondary battery pouch film according to claim 1, wherein the outer layer allows measurement of the elongation rate through the color of the outer layer when forming the pouch film.

3. The secondary battery pouch film according to claim 1 or 2, wherein it can be determined that the outer layer has reached a critical stretching point when the outer layer becomes brighter than a reference color during the formation of the pouch film.

4. The secondary battery pouch film according to claim 3 , wherein the reference color is the color of the outer layer when the stretching ratio reaches 40%.

5. The outer layer is The secondary battery pouch film according to any one of claims 1 to 4, characterized in that it is formed by laminating polyethylene terephthalate on top of nylon, and the polyethylene terephthalate contains colored dye particles.

6. The secondary battery pouch film according to any one of claims 1 to 5, wherein the metal layer is made of aluminum, and the inner layer is made of polypropylene.

7. a lower case having a concave cup portion formed therein; and an upper case covering an upper portion of the lower case from above; The lower case and the upper case are manufactured by molding a pouch film, The pouch film is inner layer; a metal layer laminated on top of the inner layer; and an outer layer laminated on the metal layer and containing colored dye or pigment particles; The outer layer is formed by: A secondary battery pouch case in which the concentration of dye particles in the stretched area (B) is lower than that in the area (A) where stretching has not occurred, resulting in a lighter hue concentration of the outer layer in the stretched area (B), and at the same time, the hue of the metal layer laminated underneath the outer layer is mixed, changing the hue of the stretched area (B).

8. The cup portion is It is formed to have one bottom surface and four side surfaces, The bottom surface and the side surface are The secondary battery pouch case according to claim 7, wherein the peripheral and central regions of each side are formed to have different colors.

9. The bottom surface and the side surface are The secondary battery pouch case according to claim 8, wherein the peripheral areas of each side are formed brighter than the central area.

10. The bottom surface and the side surface are 10. The secondary battery pouch case according to claim 8, wherein the peripheral region of each side has a lower concentration of colored dye or pigment than the central region.

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