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

Abstract

The present invention relates to a method for manufacturing a secondary battery pouch case, a secondary battery pouch film, and a secondary battery pouch case. Specifically, the invention relates to a method for manufacturing a secondary battery pouch case and a secondary battery pouch film that, during the process of manufacturing a pouch case by molding a pouch film, can measure the elongation rate through the color of the outer layer of the pouch film without separate sampling, and determine whether elongation has occurred at a dangerous level just before cracking or at a defective level where cracking occurs.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a secondary battery pouch case, a secondary battery pouch film, and a secondary battery pouch case. Specifically, the invention relates to a method for manufacturing a secondary battery pouch case, a secondary battery pouch film, and a secondary battery pouch case that, during the process of manufacturing a pouch by molding a pouch film, can measure the elongation rate through the color of the outer layer of the pouch film without separate sampling, and determine whether elongation has occurred at a dangerous level just before cracking or at a defective level where cracking occurs. Background Technology

[0002] Secondary batteries, capable of repeated charging and discharging, can be classified into cylindrical, prismatic, and pouch-type secondary batteries depending on their structure or manufacturing method. While cylindrical and prismatic batteries, which primarily use metal cans as exterior materials, have traditionally dominated the market, these structures have the disadvantage of restricting the design of electronic products using them as power sources due to their fixed shapes, and there have been difficulties in reducing their volume. Consequently, active development of pouch-type secondary batteries is currently underway.

[0003] A pouch-type secondary battery generally has a structure in which an electrode assembly having an alternating arrangement of electrodes and separators is housed within a sheet-shaped pouch film (or pouch outer material). More specifically, it is broadly divided into a lower case having a cup portion (or housing portion) and an upper case covering it, and the electrode assembly housed in the cup portion is formed by stacking a positive electrode, a negative electrode, and a separator. An electrode tab is drawn out from each electrode, and a tape is attached to the electrode tab in the portion that overlaps with the sealing portion.

[0004] Unlike cylindrical batteries, pouch-type secondary batteries with this structure have the advantage of being relatively easy to deform and capable of realizing a secondary battery of the same capacity with a smaller volume and mass; however, since a soft pouch case is used as a container, there is a problem of weak mechanical strength.

[0005] In particular, pouch cases equipped with a cup portion formed by molding a sheet-type pouch film inevitably undergo elongation during the manufacturing process, and if excessive elongation occurs, they are exposed to the risk of microscopic cracks or fractures. If cracks or fractures occur in the pouch case, which serves as an outer casing, the electrolyte may leak or react with oxygen, leading to a decrease in battery performance and a failure to guarantee safety.

[0006] Therefore, to solve these problems, conventional methods involved sampling the molded pouch case, extracting the portion presumed to have undergone critical elongation, measuring the elongation rate by determining the thickness using a microscope, and then detecting pouch defects by verifying whether elongation had occurred to the extent that it could cause cracking or fracture.

[0007] However, this method has limitations in detecting all defective pouch cases because it requires random sampling for defect detection, and there is a problem that the defect detection rate and efficiency are significantly lower because sampling must be done separately.

[0008] Ultimately, conventional methods cannot sufficiently guarantee the safety of the battery and require improvement due to the low productivity of the entire process. In other words, there is a need to develop a secondary battery pouch case manufacturing method, a secondary battery pouch film, and a secondary battery pouch case that can more easily identify and detect whether cracks or fractures have occurred due to stretching after the forming of the pouch film, or whether stretching has reached a dangerous level just before such occurrence. The problem to be solved

[0009] The present invention has been devised to solve the above-mentioned problems, and the objective of the present invention is to provide a method for manufacturing a secondary battery pouch case, a secondary battery pouch film, and a secondary battery pouch case, which, during the process of manufacturing a pouch case by forming a pouch film, can measure the elongation rate through the color of the outer layer of the pouch film without separate sampling and determine whether elongation has occurred at a dangerous level just before cracking or at a defective level where cracking occurs. means of solving the problem

[0010] A method for manufacturing a secondary battery pouch case according to the present invention comprises the steps of: laminating a metal layer on top of an inner layer and laminating an outer layer containing colored dye particles on top of the metal layer to produce a pouch film; forming the pouch film into a three-dimensional shape so that an electrode assembly can be accommodated inside; and measuring the elongation rate of the pouch film through the color of the outer layer.

[0011] The step of measuring the elongation rate may include the step of extracting color data of the outer layer, the step of inputting the color data into a data table in which color and elongation rate correspond, and the step of outputting the elongation rate value of the pouch film corresponding to the input color data.

[0012] After the step of measuring the elongation rate, the step of determining a molding defect is further included, and the step of determining a molding defect can determine that the pouch film is defective if its elongation rate is 40% or more.

[0013] The step of manufacturing an outer layer is further included prior to the step of manufacturing a pouch film, and the step of manufacturing the outer layer may form the outer layer by laminating polyethylene terephthalate containing a colored dye on top of nylon.

[0014] The step of manufacturing the outer layer can manufacture the outer layer with a thickness of 12㎛ to 30㎛.

[0015] In the stage of manufacturing the pouch film, the inner layer can be formed from polypropylene.

[0016] In the stage of manufacturing the pouch film, the metal layer can be formed from aluminum.

[0017] The secondary battery pouch film according to the present invention comprises an inner layer, a metal layer laminated on top of the inner layer, and an outer layer laminated on top of the metal layer and mixed with colored dye particles.

[0018] When forming the pouch film, the elongation rate of the outer layer can be measured through the color of the outer layer.

[0019] When the outer layer becomes brighter than the reference color during the molding of the pouch film, it may be determined that it has reached a dangerous elongation.

[0020] The reference color may be the color of the outer layer when the elongation rate reaches 40%.

[0021] The outer layer is formed by laminating polyethylene terephthalate on top of nylon, and the polyethylene terephthalate may contain colored dye particles.

[0022] The metal layer can be formed of aluminum, and the inner layer can be formed of polypropylene.

[0023] A secondary battery pouch case according to the present invention comprises a lower case having a cup portion formed in an indented shape and an upper case covering the upper part of the lower case from above, wherein the lower case and the upper case are manufactured by forming a pouch film, and the pouch film comprises an inner layer, a metal layer laminated on top of the inner layer, and an outer layer laminated on top of the metal layer and containing colored dye or pigment particles.

[0024] The cup portion is formed to have one bottom surface and four sides, wherein the bottom surface and sides may have different colors in the edge areas and the central areas of each side.

[0025] The bottom and side surfaces may have edge areas that are brighter than the central area.

[0026] For the bottom and side surfaces, the concentration of colored dyes or pigments may be distributed lower in the edge areas of each surface than in the central area. Effects of the invention

[0027] The method for manufacturing a secondary battery pouch case according to the present invention comprises the steps of: laminating a metal layer on top of an inner layer and laminating an outer layer containing colored dye particles on top of the metal layer to produce a pouch film; molding the pouch film into a three-dimensional shape so that an electrode assembly can be accommodated inside; and measuring the elongation rate of the pouch film through the color of the outer layer. Accordingly, in the process of molding the pouch film to produce a pouch case, the elongation rate can be measured through the color of the outer layer of the pouch film without separate sampling, and it can be determined whether elongation has occurred at a dangerous level just before cracking or at a defective level where cracking occurs. Brief explanation of the drawing

[0028] FIG. 1 is a perspective view illustrating a typical secondary battery pouch case. FIG. 2 is a flowchart illustrating 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 embodiments 1 and 2 of the present invention before stretching occurs. FIG. 4 is a cross-sectional view showing the cross-section of a pouch film after stretching has occurred according to embodiments 1 and 2 of the present invention. FIG. 5 is a perspective view illustrating a secondary battery pouch case according to Example 3 of the present invention. Specific details for implementing the invention

[0029] Hereinafter, preferred embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited or restricted by the following embodiments.

[0030] In order to clearly explain the present invention, detailed descriptions of related prior art that are irrelevant to the explanation or that may unnecessarily obscure the essence of the invention have been omitted. Furthermore, when assigning reference numerals to the components of each drawing in this specification, identical or similar reference numerals are assigned to identical or similar components throughout the entire specification.

[0031] Furthermore, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0033] Example 1

[0034] FIG. 2 is a flowchart illustrating a method for manufacturing a secondary battery pouch case according to Example 1 of the present invention. FIG. 3 is a cross-sectional view illustrating a cross-section of a pouch film before stretching occurs according to Example 1 of the present invention. FIG. 4 is a cross-sectional view illustrating a cross-section of a pouch film after stretching occurs according to Example 1 of the present invention.

[0035] Referring to FIG. 2, a method for manufacturing a secondary battery pouch case according to Example 1 of the present invention includes the steps of producing a pouch film (S10), forming a pouch film (S20), and measuring the elongation rate of the pouch film (S30).

[0036] First, the step (S10) of manufacturing the pouch film is described in detail. As shown in FIG. 3, the pouch film (100) is formed as a multilayer film structure in which a plurality of layers are laminated, and a metal layer (120) is laminated on top of an inner layer (110), and an outer layer (130) is laminated on top of the metal layer (120).

[0037] The inner layer (110) is a layer located at the innermost side of the pouch film (100) and serves as a sealing material with chemical resistance to electrolyte and heat sealability. It is mainly formed from a polyolefin-based resin, and preferably can be formed from polypropylene (PP). The metal layer (120) is a layer interposed between the inner layer (110) and the outer layer (130), and serves as a layer that maintains the mechanical strength of the pouch film (100) and acts as a barrier against moisture and oxygen. The metal layer (120) can be formed from an alloy of iron (Fe), carbon (C), chromium (Cr), and manganese (Mn), an alloy of iron (Fe), carbon (C), chromium (Cr), and nickel (Ni), and preferably can be formed from aluminum (Al). The outer layer (130) is a layer formed on the outermost side of the pouch film (100) and serves to protect the battery from external shocks. Since it comes into direct contact with hardware, insulation and heat resistance are required. The material and manufacturing method of the outer layer (130) will be described in detail below.

[0038] The method for manufacturing a secondary battery pouch case according to Example 1 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 or two or more composite layers selected from polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), nylon, low-density polyethylene (LDPE), and high-density polyethylene (HDPE). The step (S9) of manufacturing an outer layer according to Example 1 of the present invention may form the outer layer (130) by laminating polyethylene terephthalate (PET) containing a colored dye onto a transparent nylon film.

[0039] Here, the term "dyes" includes both organic and inorganic dyes without any specific limitations; any colored dye capable of being incorporated into the outer layer is sufficient, and preferably, any dye capable of being mixed into or attached to polyethylene terephthalate (PET) is acceptable without restriction. Furthermore, it goes without saying that this applies not only to dyes but also to pigments.

[0040] The total thickness of the pouch film (100) is typically 40 to 120 μm, the inner layer (110) may be 10 to 40 μm, the metal layer (120) may be 20 to 100 μm, and the outer layer (130) may preferably be manufactured with a thickness of 12 μm to 30 μm.

[0041] After producing the pouch film (S10), it can be molded into a three-dimensional shape so that an electrode assembly can be accommodated inside the pouch film (100) (S20). A pouch-type secondary battery can be broadly divided into a pouch case (1) and an electrode assembly accommodated inside the pouch case (1). As shown in FIG. 1, the pouch case (1) is divided into a lower case with a cup portion formed to accommodate the electrode assembly and an upper case covering it. The pouch film (100), which is laminated in a multilayer structure, undergoes a process of forming the cup portion by a molding device. After fixing the area of ​​the pouch film (100) other than the cup portion, a press punch presses the cup portion, and as the pouch film (100) is stretched, a pouch case (1) is formed with a cup portion in a shape corresponding to the punch. In this case, stretching mainly occurs at the corner portions of the pouch case (1), including the edge portion of the cup portion of the pouch case (1), and cracks or fractures mainly occur.

[0042] The method for manufacturing a secondary battery pouch case according to Example 1 of the present invention can measure the elongation rate (S30) of the pouch film (100) through the color of the outer layer (130) of the pouch film (100). The measurement of the elongation rate (S30) of the pouch film (100) through color will be explained in detail below with reference to FIG. 4.

[0043] As previously described, the outer layer (130) is formed by laminating polyethylene terephthalate (PET) containing colored dye particles (131) on top of transparent nylon, and the pouch film (100) before stretching occurs has the color intensity of the dye particles (131) of the outer layer (130) when viewed from the outside. However, when stretching occurs due to the molding of the pouch film (100), as shown in FIG. 4, the concentration of dye particles (131) in the stretched area (B) becomes lower compared to the area where stretching does not occur (A), and as a result, the color intensity of the outer layer (130) in the stretched area (B) becomes lighter, and at the same time, the color of the metal layer (120) laminated on the bottom of the outer layer (130) is mixed, causing the color of the pouch film (100) in the stretched area (B) to change. In particular, when the metal layer (120) is formed of aluminum (Al) that has a bright color, as elongation occurs, the color of the colored dye particles (131) becomes lighter and the bright color of the aluminum (Al) is mixed, so that the color of the pouch film (100) in the area (B) where elongation occurs becomes brighter compared to the area (A) where elongation does not occur. Thus, the elongation rate (S30) can be measured through the color of the outer layer (130) of the pouch film (100).

[0044] As such, the method for manufacturing a secondary battery pouch case according to Example 1 of the present invention can measure the elongation rate through the color of the outer layer (130) of the pouch film (100) without separate sampling, and determine whether elongation has occurred at a dangerous level just before cracking or at a defective level where cracking occurs. In addition, while increasing the number of defect inspection targets and the defect judgment rate, the time and cost required for the process can be significantly reduced, thereby improving productivity and securing product quality and price competitiveness.

[0045] Next, the step (S30) of measuring the elongation rate is described in detail. The step (S30) of measuring the elongation rate may include the step of extracting color data of the outer layer (130), the step of inputting the color data into a data table in which the color and the elongation rate correspond, and the step of outputting the elongation rate value of the pouch film corresponding to the input color data.

[0046] First, regarding 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, an image, or a color detection sensor, and a processor operatively coupled with the sensor identifies the color and extracts it as data.

[0047] After that, the extracted color data is input into a data table in which the color and elongation rate correspond. The data table in which the color and elongation rate correspond refers to a table in which the color change of the pouch film (100) according to the degree of elongation occurs is stored as data based on the initial color of the pouch film (100) in which colored dye particles (131) of a preset concentration are included in the outer layer (130). For example, it may be a table in which the color and elongation rate of the pouch film (100) are correlated by setting the concentration ratio of a specific colored dye contained in the PET layer, stretching the pouch film (100) containing the outer layer (130) produced according to the preset value, and then converting the color change into data for each elongation rate range.

[0048] When color data extracted from the data table is entered, the stored color data corresponding to the entered color data is selected, and the elongation rate value of the pouch film (100) corresponding thereto is output. Therefore, compared to the conventional method of sampling the pouch case, extracting the area where elongation occurs, and determining the thickness with a microscope, the elongation rate can be measured using only the color data by utilizing the stored data table, so the time required for the defect detection step can be drastically reduced, and the elongation rate can be measured by vision inspection alone without separate sampling, making it easier to perform defect detection work on all of the molded pouch cases.

[0049] After the step (S30) of measuring the elongation rate of the pouch film, the method further includes a step (S40) of determining a molding defect. In the step (S40) of determining a molding defect, if the elongation 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 formed of aluminum, if 40% elongation occurs, the likelihood of cracking or breaking increases significantly. Therefore, by determining this as a dangerous level of elongation and judging it as defective, the pouch case with a risk of cracking or breaking can be preemptively removed even if cracking or breaking has not occurred, thereby ensuring the safety of the battery and significantly reducing the time required for defect determination.

[0051] Example 2

[0052] FIG. 3 is a cross-sectional view showing a cross-section of a pouch film according to Example 2 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 2 of the present invention after stretching occurs.

[0053] In Example 2 of the present invention, there is a difference from Example 1 in that the invention relates to a pouch film (100) used in the method for manufacturing a secondary battery pouch case of Example 1.

[0054] Content common to Example 1 will be omitted as much as possible, and Example 2 will be described focusing on the differences. That is, it is obvious that if content not explained in Example 2 is necessary, it can be considered as content of Example 1.

[0055] Referring to FIG. 3, a secondary battery pouch film (100) according to Example 2 of the present invention comprises an inner layer (110), a metal layer (120), and an outer layer (130).

[0056] A metal layer (120) is laminated on top of an inner layer (110), and an outer layer (130) mixed with colored dye particles (131) is formed on top of the metal layer (120) to constitute a pouch film (100). The metal layer (120) may be formed of aluminum (AL), and the inner layer (110) may be formed of polypropylene (PP). The outer layer (130) is formed by laminating polyethylene terephthalate (PET) on top of nylon, and the polyethylene terephthalate (PET) may contain colored dye particles (131).

[0057] In particular, the outer layer (130) can 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, it can be determined that dangerous elongation has been reached if it becomes brighter than the reference color, and the reference color may be, for example, the color of the outer layer (130) when the elongation rate reaches 40%.

[0058] The pouch film (100) according to Example 2 of the present invention can measure the elongation rate through the color of the outer layer (130) of the pouch film (100) without separate sampling, and determine whether elongation has occurred at a dangerous level just before cracking or at a defective level where cracking occurs.

[0060] Example 3

[0061] FIG. 5 is a perspective view illustrating a secondary battery pouch case according to Example 3 of the present invention.

[0062] Example 3 of the present invention differs from Example 1 in that it relates to a secondary battery pouch case manufactured by the secondary battery pouch case manufacturing method and pouch film of Examples 1 and 2.

[0063] Content common to Examples 1 and 2 will be omitted as much as possible, and Example 3 will be described focusing on the differences. That is, it is obvious that if content not explained in Example 3 is needed, it can be considered as content from Examples 1 and 2.

[0064] Referring to FIG. 5, a secondary battery pouch case (1) according to Embodiment 3 of the present invention comprises a lower case (10) having a cup portion (11) formed in an indented shape and an upper case (20) covering the upper part of the lower case (10) from above, and the lower case (10) and the upper case (20) are manufactured by forming a pouch film. In addition, the pouch film consists of an inner layer, a metal layer laminated on top of the inner layer, and an outer layer laminated on top of the metal layer and containing colored dye or pigment particles. Here, the pouch film refers to the pouch film of Embodiment 2 described above, and the inner layer, metal layer, and outer layer can be understood as being the same as those of Embodiment 2.

[0065] Thus, in the pouch case (1) according to Embodiment 3 of the present invention, when the pouch case (1) is stretched and molded, a color change can be observed through vision inspection, and by checking the stretched area and the degree of stretching, it is easy to determine whether stretching has occurred at a dangerous level or a defective level where cracks occur.

[0066] Here, the indented shape of the cup portion (11) refers to an indented shape when viewed from the upper case (20) toward the lower case (10), and may also be a shape that protrudes outward when viewed from the opposite direction of the indentation.

[0067] Meanwhile, the cup portion (11) is formed to have one bottom surface (11a) and four sides (11b), and the bottom surface (11a) and the sides (11b) may have different colors in the edge area and the central area of ​​each surface. That is, the edge area may be the area (B) where elongation occurs, and the central area may be the area (A) where elongation does not occur. In this way, the degree of elongation can be determined by checking the exterior color of the edge area where elongation mainly occurs in the pouch case (1) according to the present invention. Meanwhile, the colors of the edge area and the central area may not be clearly distinguished by a specific location as a boundary, and the color may be formed to gradually become lighter or darker as one moves from the edge area to the central area.

[0068] In addition, the bottom surface (11a) and the side surface (11b) may be formed such that the edge area of ​​each surface is brighter than the central area. This is because when the metal layer is formed of bright-colored aluminum, as elongation occurs, the color of the colored dye particles becomes lighter and the bright color of the aluminum is mixed, so that the edge area of ​​each surface, where elongation occurs, is formed to be brighter than the central area, where elongation does not occur.

[0069] However, it is not necessarily limited to this, and the edge areas of each side may be formed darker than the central area as needed. That is, the bottom surface (11a) and the side surface (11b) may have a lower concentration of colored dye or pigment distributed in the edge areas of each side than in the central area, and the relative brightness between the edge areas and the central area of ​​the pouch case (1) may vary depending on the color of the metal layer of the pouch film and the color of the colored dye.

[0070] Although the present invention has been described above by limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs. Explanation of the symbols

[0071] 1: Pouch case 10: Lower case 20: Upper case 11: Cup 11a: Bottom surface 11b: Side 100: Pouch film 110: Inner layer 120: Metal layer 130: Outer layer 131: Dye particles A: Area where elongation did not occur B: Area where elongation occurred S9: Outer layer manufacturing step S10: Pouch film production step S20: Pouch film forming step S30: Pouch film elongation measurement step S40: Pouch defect determination stage

Claims

Claim 1 A secondary battery pouch film comprising: an inner layer; a metal layer laminated on top of the inner layer; and an outer layer laminated on top of the metal layer and mixed with colored dye particles, wherein the change in elongation rate of the outer layer is measured through a change in color, and when the color of the outer layer becomes brighter than a reference color, it can be determined that dangerous elongation has been reached. Claim 2 In claim 1, the outer layer comprises nylon and polyethylene terephthalate, and the polyethylene terephthalate comprises colored dye particles, in a secondary battery pouch film. Claim 3 In claim 1, the metal layer is a secondary battery pouch film comprising aluminum. Claim 4 In claim 1, the inner layer is a secondary battery pouch film comprising polypropylene. Claim 5 In claim 1, the outer layer is a secondary battery pouch film having a thickness of 12㎛ to 30㎛. Claim 6 In claim 1, the color change of the outer layer is a secondary battery pouch film that changes according to the concentration of colored dye particles. Claim 7 A secondary battery pouch film according to claim 1, wherein the above risk elongation is when the elongation rate is 40% or more, and the above standard color is the color of the outer layer when the elongation rate is 40%. Claim 8 A secondary battery pouch case comprising a secondary battery pouch film as described in claim 1. Claim 9 In claim 8, the pouch case comprises a case having a cup portion formed in an indented shape, and the case comprises the pouch film, a secondary battery pouch case. Claim 10 A secondary battery pouch case according to claim 9, wherein the cup portion is formed to have one bottom surface and four sides, and the bottom surface and the sides are characterized in that the colors of the edge area and the central area of ​​each side are formed differently from each other. Claim 11 A secondary battery pouch case according to claim 10, wherein the bottom surface and the side surface are characterized in that the edge area of ​​each surface is formed to be brighter than the central area. Claim 12 A secondary battery pouch case according to claim 10, wherein the bottom surface and the side surface are characterized in that the edge area of ​​each surface has a lower concentration of colored dye or pigment than the central area. Claim 13 A secondary battery comprising a secondary battery pouch case as described in paragraph 8.

Images