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KR-102961113-B1 - CELL POUCH FILM, PACKAGING STRUCTURE INLCUDING THE SAME AND METHOD FOR STORING THE CELL POUCH FILM

KR102961113B1KR 102961113 B1KR102961113 B1KR 102961113B1KR-102961113-B1

Abstract

The present specification relates to a film for a cell pouch, a packaging structure including the same, and a method for storing the film for the cell pouch. According to the present invention, by controlling the moisture content of the film for the cell pouch, it is possible to achieve excellent moldability, a level of thermal deformation bubbles, and mechanical properties.

Inventors

  • 김유한
  • 김희훈
  • 송녹정
  • 송문규
  • 신성철
  • 한희식

Assignees

  • 율촌화학 주식회사

Dates

Publication Date
20260507
Application Date
20240607

Claims (10)

  1. A film for a cell pouch comprising at least an outer layer including a nylon film, a barrier layer made of metal, and a sealant layer, The moisture content of the film measured as follows is 300 ppm to 1300 ppm, and The moldability of the above film is 16 mm or more, and A film for a cell pouch having a thermal deformation bubble level of 1 or less: [Method for Measuring Moisture Content of Films for Cell Pouches] Prepare a sample of cell pouch film cut to 60 mm × 40 mm in the machine direction (MD) × transverse direction (TD). Divide this sample into four equal parts of 15 mm × 40 mm in the MD × TD direction. Place the four-part sample into a vial and seal it. Insert this sealed vial into a moisture measuring device, measure the moisture content vaporizing from the vial at a temperature of 150°C, and verify this as the moisture content of the cell pouch film. The measurement conditions are a temperature of 150°C and a gas flow rate of 50 mL/min; [Method for Measuring Thermal Deformation Bubble Levels in Cell Pouch Films] After heat sealing the film for the cell pouch at a heat sealing temperature of 220℃, a heat sealing pressure of 0.2 MPa, and a heat sealing time of 1.6 seconds, the level of heat-deformed bubbles was checked visually or with a loupe; [Evaluation Criteria for Thermal Deformation Bubble Levels in Cell Pouch Films] Level 1: No bubbles formed, Level 2: Not easily visible to the naked eye but confirmable with a loupe, with fine dots on the sealing line/outside. Level 3: Fine air bubbles on the front of the sealing area, Level 4: Large bubbles on the front of the sealing area.
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  3. In paragraph 1, A film for a cell pouch, wherein the outer layer is composed of a polyethylene terephthalate (PET) film and a nylon film, the barrier layer is composed of aluminum, and the sealant layer comprises a polypropylene layer.
  4. In paragraph 3, A film for a cell pouch, wherein the yield strength of the film is 120 N/15 mm to 150 N/15 mm, and the yield strength is measured using a Universal Testing Machine (UTM) under conditions of a test speed of 50 mm/min and a grip distance of 50 mm.
  5. In paragraph 3, A film for a cell pouch, wherein the heat sealing strength of the film for the cell pouch is 128 N/15 mm to 140 N/15 mm, and the heat sealing strength is measured using a Universal Testing Machine (UTM) under conditions of a test speed of 50 mm/min and a grip distance of 50 mm.
  6. In paragraph 3, A film for a cell pouch, wherein the moldability of the above film is 16 mm to 19 mm.
  7. As a method of storing film for cell pouches, The method includes the step of storing a film for a cell pouch in an environment with a temperature of 25℃ and a relative humidity of 5% or more and less than 25% so that the saturated moisture content of the film measured as follows becomes 300 ppm to 1300 ppm; The moldability of the above film is 16 mm or more, and A storage method for a film for a cell pouch, wherein the thermal deformation bubble level of the above film is 1 level or less: [Method for Measuring Saturated Moisture Content of Cell Pouch Films] Prepare a sample of cell pouch film cut to 60 mm × 40 mm in the machine direction (MD) × transverse direction (TD). Divide this sample into four equal parts of 15 mm × 40 mm in the MD × TD direction. Place the four-part sample into a vial and seal it. Insert this sealed vial into a moisture measuring device, measure the moisture content vaporizing from the vial at a temperature of 150°C, and verify this as the moisture content of the cell pouch film. The measurement conditions are a temperature of 150°C and a gas flow rate of 50 mL/min; [Method for Measuring Thermal Deformation Bubble Levels in Cell Pouch Films] After heat sealing the film for the cell pouch at a heat sealing temperature of 220℃, a heat sealing pressure of 0.2 MPa, and a heat sealing time of 1.6 seconds, the level of heat-deformed bubbles was checked visually or with a loupe; [Evaluation Criteria for Thermal Deformation Bubble Levels in Cell Pouch Films] Level 1: No bubbles formed, Level 2: Not easily visible to the naked eye but confirmable with a loupe, with fine dots on the sealing line/outside. Level 3: Fine air bubbles on the front of the sealing area, Level 4: Large bubbles on the front of the sealing area.
  8. In a cell pouch packaging structure including a cell pouch, A film for a cell pouch according to any one of claims 1 and 3 to 6 wound; and It includes an inner packaging material that surrounds the wound film for the cell pouch at least one layer, and The above inner packaging material is a cell pouch packaging structure having a water vapor transmission rate (WVTR) of 0.1 g/m2*day to 1.0 g/m2*day.
  9. A secondary battery enclosed in a film for a cell pouch according to any one of paragraphs 1 and 3 through 6.
  10. A method for manufacturing a secondary battery by externaling the secondary battery with a film for a cell pouch according to any one of claims 1 and 3 to 6.

Description

Cell pouch film, packaging structure including the same, and method for storing the cell pouch film The present specification discloses a film for a cell pouch, a packaging structure including the same, and a method for storing the film for the cell pouch. Pouch-type batteries, generally used in electric vehicles and the like, have the advantage of being easy to change shape and having a high energy density compared to cylindrical or prismatic batteries. As an outer casing that encloses the battery's electrode group and electrolyte, these cell pouches must satisfy required characteristics such as interlayer adhesion between metal thin films and polymers, thermal fusion strength, electrolyte resistance, airtightness, moisture permeability, and moldability. Korean Registered Patent Publication No. 10-2042252 discloses a battery cell comprising a metal plate for blocking moisture penetration. However, conventional films for cell pouches suffer from problems such as poor formability, poor mechanical properties like yield strength or heat seal strength, or poor appearance due to bubble formation caused by thermal deformation. Therefore, there is a need to develop a film for cell pouches that satisfies all requirements regarding formability, thermal deformation appearance characteristics, and mechanical properties. FIG. 1 is a graph showing the change in moisture content according to temperature, relative humidity, and time of a film for a cell pouch according to one embodiment of the present invention. Figure 2 is an image showing the thermal deformation evaluation criteria of a film for a cell pouch according to one embodiment of the present invention. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings. The embodiments of the present invention disclosed in the text are illustrative for illustrative purposes only, and the embodiments of the present invention may be implemented in various forms and should not be interpreted as being limited to the embodiments described in the text. As the present invention is capable of various modifications and may take various forms, the embodiments are not intended to limit the present invention to a specific disclosed form and should be understood to include all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. In this specification, when a part is described as “comprising” a certain component, it means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Throughout the specification, when a part such as a layer, film, region, plate, etc. is described as being “on” or “above” another part, this may include not only cases where it is immediately above another part, but also cases where there is another part in between. Throughout the specification, terms such as “first,” “second,” etc., may be used to describe various components, but the components should not be limited by these terms. The terms are used solely for the purpose of distinguishing one component from another. In this specification, the term “cell” means a battery and may have the broadest meaning, including all types of batteries such as secondary batteries like lithium-ion batteries and lithium-polymer batteries, or portable storage batteries. In this specification, the term “cell pouch” has the broadest meaning and includes all devices in which cell components, such as an anode, a cathode, and a separator, are impregnated with an electrolyte and housed therein, and which are processed into a pouch or box shape using a laminated film structure that takes into account gas barrier properties, flexibility, electrolyte resistance, and heat sealability to house said cell components. In this specification, “barrier performance” refers to the ability to block water vapor from the outside of the battery. In this specification, “formability” refers to the depth measured after forming a specimen of a film for a cell pouch. If all 10 specimens do not break at that depth, a deeper depth is applied. If even one specimen breaks, the depth immediately preceding that breakage is referred to as the maximum forming depth and is called formability. For medium to large secondary batteries, formability can be considered excellent when the maximum forming depth is particularly 16 mm or more. In this specification, the moisture content or moisture ratio of a film for a cell pouch can be determined, for example, by cutting a film for a cell pouch into a certain length, dividing it into four equal parts, placing it in a sealed vial, placing the sealed vial into a moisture meter (e.g., Metrohm 917 Coulometer), and measuring the moisture vaporized from the sealed vial under certain temperature and gas flow conditions (unit ppm). Such moisture meter and moisture measurement method are well known to a person skilled in the art. In this speci