Cell pouch film, packaging structure containing the same, and method for storing the cell pouch film.

Abstract

This invention relates to a film for cell pouches, a packaging structure containing the same, and a method for storing the cell pouch film. By controlling the moisture content of the cell pouch film, excellent moldability, heat deformation bubble level, and mechanical properties can be achieved.

Description

Technical Field

[0001] This 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.

[0002] [National Research and Development Project that Supported the Invention] [Problem Specific Number] 1415185612 [Problem Number] 20022450 [Department Name] Ministry of Trade, Industry and Energy of Korea [Name of the Agency in Charge of Problem Management (Specialty)] Korea Institute for Advancement of Technology [Research Project Name] Material Parts Package Type (Top Company) [Research Problem Name] Development of Next-generation Secondary Battery Pouch with Adhesive Strength More than Twice as High (60°C) <​​​​​​​​​​​​​​​​​​​​

[0005] [Patent Document 1] Korean Patent Registration No. 10-2042252 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In one embodiment, the present invention aims to provide a cell pouch film that is excellent in moldability, thermal deformation appearance characteristics, and mechanical properties by controlling the moisture content of the cell pouch film, as well as a secondary battery enclosed using the same and a method for manufacturing the same.

[0007] In another aspect, the present invention aims to provide a storage method for maintaining a constant moisture content of a cell pouch film, and a packaging structure used in the distribution process of the cell pouch film. [Means for solving the problem]

[0008] In an exemplary embodiment of the present invention, a cell pouch film is provided which comprises at least an outer layer containing nylon, a barrier layer made of metal, and a sealant layer, wherein the moisture content measured by the following method is 1300 ppm or less.

[0009] [Method for measuring the moisture content of film for cell pouches] Prepare a sample of cell pouch film cut to 60 mm x 40 mm in the longitudinal direction (Machine direction; MD) x transverse direction (TD). Divide this sample into four equal parts of 15 mm x 40 mm in the longitudinal direction (MD) x transverse direction (TD). Place the four divided samples into vials and seal them. Place these sealed vials in a moisture meter (e.g., Metrohm 917 Coulometer) and measure the amount of moisture vaporized from the vial at a temperature of 150°C. This is taken 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.

[0010] Furthermore, in an exemplary embodiment of the present invention, a method for storing cell pouch film is provided, comprising the steps of storing the cell pouch film in an environment with a temperature of 25°C and a relative humidity of 5% or more and less than 25%, so that the saturated moisture content of the cell pouch film becomes 1300 ppm or less.

[0011] Furthermore, in an exemplary embodiment of the present invention, a cell pouch packaging structure including a cell pouch comprises a wound cell pouch film and an inner packaging material surrounding the wound cell pouch film in at least one layer, wherein the water vapor transmission rate (WVTR) of the inner packaging material is 0.1 to 1.0 g / m². 2 * Provides a cell pouch packaging structure.

[0012] Furthermore, in an exemplary embodiment of the present invention, a cell pouch including the aforementioned cell pouch film is provided.

[0013] Furthermore, in an exemplary embodiment of the present invention, a secondary battery enclosed in the aforementioned cell pouch film is provided.

[0014] Furthermore, in an exemplary embodiment of the present invention, a method for manufacturing a secondary battery is provided in which the secondary battery is enclosed with the aforementioned cell pouch film. [Effects of the Invention]

[0015] According to an exemplary embodiment of the present invention, by controlling the moisture content of the film for cell pouches, excellent moldability, heat deformation bubble level, and mechanical properties such as yield strength and heat adhesion strength can be achieved. [Brief explanation of the drawing]

[0016] [Figure 1] This graph shows the change in moisture content of a cell pouch film according to one embodiment of the present invention, in response to temperature, relative humidity, and time. [Figure 2] This is an image showing the thermal deformation evaluation criteria for a film for a cell pouch according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, exemplary realizations of the present disclosure will be described in detail with reference to the accompanying drawings.

[0018] The embodiments of the present invention disclosed in this specification are merely exemplified for the purpose of explanation, and the embodiments of the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described in this specification. The present invention can be subjected to various modifications and can have various forms, so the embodiments are not intended to limit the present invention to a specific disclosed form, but should be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0019] In this specification, when a certain part "includes" a certain component, this means that, unless otherwise specified, it does not exclude other components, but may further include other components.

[0020] Throughout the specification, when a part such as a layer, film, region, plate, etc. is said to be "on" or "above" another part, this includes not only the case where it is directly above the other part, but also the case where there is another part in between. Throughout the specification, terms such as first, second, etc. can be used to describe various components, but the components should not be limited by these terms. The terms are used only for the purpose of distinguishing one component from another.

[0021] The "cell" in this specification means a battery, and can be used in the broadest sense including all various batteries such as secondary batteries such as lithium-ion batteries and lithium polymer batteries, and portable storage batteries.

[0022] In this specification, "cell pouch" refers to a device in which cell components such as anodes, cathodes, and separators are impregnated with an electrolyte and housed within it. It is used in the broadest sense to include all devices in which a laminated film structure, taking into consideration gas barrier properties, flexibility, electrolyte resistance, and heat adhesion, is processed into a bag or box shape to house the cell components.

[0023] In this specification, "barrier properties" refer to the ability to block water vapor from entering the battery from the outside.

[0024] In this specification, "formability" refers to the maximum molding depth when a sample of cell pouch film has been cut and molded, and the depth is measured. If all 10 samples do not break at a given depth, then an even deeper depth is applied. If even one break occurs at that depth, the depth immediately preceding the break is considered the maximum molding depth, and this is referred to as the formability. In the case of medium or large secondary batteries, a maximum molding depth of 16 mm or more is considered to indicate excellent formability.

[0025] In this specification, the moisture content or moisture rate of a cell pouch film can be determined, for example, by cutting the cell pouch film to a certain length, dividing it into four equal parts, placing them in a sealed vial, and then placing this sealed vial in a moisture measuring device (e.g., Metrohm 917 Coulometer) and measuring the amount of moisture vaporized from the sealed vial under constant temperature and gas flow conditions (in ppm). Such a moisture measuring device and moisture measuring method are well known to those skilled in the art.

[0026] In this specification, saturated moisture content or saturated moisture content refers to the level at which, when a cell pouch film is stored in a room with a constant temperature and relative humidity, the moisture content or moisture content of the cell pouch film converges to a certain level without increasing further after a certain period of time.

[0027] In this specification, thermal deformation refers to the process in which, during the heat sealing process of a cell pouch containing a certain amount of moisture, moisture in the nylon film vaporizes and manifests as bubbles.

[0028] In this specification, the evaluation of thermal deformability, thermal deformability appearance characteristics, or thermal deformability bubble characteristics (level) is an evaluation that confirms whether or not bubbles are generated in the pouch due to thermal bonding.

[0029] In this specification, "relative humidity (RH)" refers to the percentage (%) of the amount of water vapor currently present in the air relative to the saturation vapor pressure that a given volume of air can hold.

[0030] In this specification, mechanical properties mean at least yield strength and / or thermal bonding strength.

[0031] The embodiments will be described. The inventors of the present invention have discovered that the moisture content or moisture ratio (hereinafter referred to as "moisture ratio") of a film for cell pouches not only affects the moldability of the film, but also affects mechanical properties such as the level of heat-deformed bubbles (heat-deformed appearance characteristics), heat-bonding strength, and yield strength. As a result of diligent research, they have arrived at the present invention.

[0032] In other words, as can be seen from the experimental examples described later, the higher the moisture content of the cell pouch film, the greater the moldability. However, this may decrease the level of heat-deformed bubbles and mechanical properties such as heat adhesion strength and yield strength. Therefore, in order to maintain excellent moldability while ensuring excellent heat-deformed bubble levels and mechanical properties, it is necessary to control the moisture content of the cell pouch film.

[0033] In this regard, the film for cell pouches consists of a barrier layer, an inner sealant layer, and an outer layer. This outer layer contains at least nylon and may be composed of, for example, polyethylene terephthalate film and nylon film.

[0034] In cell pouch films, the components and thicknesses of the barrier layer, sealant layer, and outer layer, as well as the thickness and components of the adhesive layers between the barrier layer and sealant layer, and between the barrier layer and outer layer, can vary. However, the influence of other variables on the overall moisture content of the cell pouch film is small, and it is considered that the nylon film, in particular, has a significant impact on the overall moisture content of the cell pouch film.

[0035] The following describes a film for cell pouches, a storage method for controlling the moisture content of the cell pouch film to a certain level, and a packaging structure for maintaining the moisture content of the cell pouch film at a desired level during the distribution process.

[0036] Cell pouch film In an exemplary embodiment of the present invention, a cell pouch film is provided which comprises at least an outer layer containing nylon, a barrier layer made of metal, and a sealant layer, wherein the moisture content measured by the following method is 1300 ppm or less.

[0037] [Method for measuring the moisture content of film for cell pouches] Prepare a sample of cell pouch film cut to 60 mm x 40 mm in the longitudinal direction (Machine direction; MD) x transverse direction (TD). Divide this sample into four equal parts of 15 mm x 40 mm in the longitudinal direction (MD) x transverse direction (TD). Place the four divided samples into vials and seal them. Place these sealed vials in a moisture meter (e.g., Metrohm 917 Coulometer) and measure the amount of moisture vaporized from the vial at a temperature of 150°C. This is taken 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.

[0038] In one embodiment, if the moisture content of the cell pouch film exceeds 1300 ppm, the level of thermal deformation bubbles increases, leading to appearance defects and potentially reducing mechanical properties such as thermal bonding strength and yield strength.

[0039] In one embodiment, the lower limit of the moisture content of the cell pouch film may be at least 300 ppm or more from the viewpoint of moldability.

[0040] In the exemplary embodiment, the moisture content of the cell pouch film may be 1300 ppm or less, 1250 ppm or less, 1200 ppm or less, 1150 ppm or less, 1100 ppm or less, 1050 ppm or less, 1000 ppm or less, 950 ppm or less, 900 ppm or less, 850 ppm or less, 800 ppm or less, 750 ppm or less, 700 ppm or less, 650 ppm or less, 600 ppm or less, 550 ppm or less, 500 ppm or less, 450 ppm or less, 400 ppm or less, or 350 ppm or less. Alternatively, it may be 300 ppm or more, 350 ppm or more, 400 ppm or more, 450 ppm or more, 500 ppm or more, 550 ppm or more, 600 ppm or more, 650 ppm or more, 700 ppm or more, 750 ppm or more, 800 ppm or more, 850 ppm or more, 900 ppm or more, 950 ppm or more, 1000 ppm or more, 1050 ppm or more, 1100 ppm or more, 1150 ppm or more, 1200 ppm or more, or 1250 ppm or more.

[0041] In the exemplary embodiment, the moisture content of the cell pouch film may preferably be 1200 ppm or less, 1100 ppm or less, or 1000 ppm or less, for example, 300 to 1200 ppm, more preferably 300 to 1000 ppm. Alternatively, it may be 350 to 950 ppm, or 400 to 900 ppm, or 450 to 850 ppm, or 500 to 800 ppm, or 550 to 750 ppm, or 600 to 700 ppm.

[0042] The lower the moisture content in the cell pouch film, the greater the yield strength, the lower the toughness, and the less deformation tends to occur. In particular, if the moisture content of the cell pouch film is below the lower limit, the amount of deformation will decrease and moldability may be reduced. On the other hand, if the moisture content of the cell pouch film exceeds the upper limit, poor thermal deformation and air bubble defects may occur during sealing, and the mechanical properties such as thermal adhesion strength and yield strength may also decrease.

[0043] Although the layer structure of the cell pouch film and the material and composition of each layer may vary, the inventors have found that the resulting moisture content of the cell pouch film is an indicator that can be used to check the moldability of the cell pouch and whether or not there are defects in appearance or bubbles during heat bonding. Therefore, by controlling the moisture content of the cell pouch film, it is possible to easily control the moldability of the cell pouch and whether or not there are defects in appearance or bubbles during heat bonding. The moisture content of the cell pouch film is mainly affected by the moisture content of the outer nylon layer (film).

[0044] In one exemplary embodiment, the yield strength of the cell pouch film may be 120N / 15mm to 150N / 15mm or 130N / 15mm to 150N / 15mm.

[0045] The aforementioned yield strength or yield stress refers to the boundary point at which the force measured when a force is applied to an object transitions from tensile strength or tensile strength to elastic deformation and then to plastic deformation. A sample elongates in proportion to an increase in load, but beyond the elastic limit, it begins to elongate independently of the load; this is called the yield point. In this invention, the upper limit yield point at which the sample begins to elongate has been selected.

[0046] More specifically, the yield strength of the film may be 120N / 15mm or more, 121N / 15mm or more, 122N / 15mm or more, 123N / 15mm or more, 124N / 15mm or more, 125N / 15mm or more, 126N / 15mm or more, 127N / 15mm or more, 128N / 15mm or more, 129N / 15mm or more, 130N / 15mm or more, 131N / 15mm or more, 132N / 15mm or more, 133N / 15mm or more, 134N / 15mm or more, 135N / 15mm or more, and 150N The dimensions may be 15mm or less, 149N / 15mm or less, 148N / 15mm or less, 147N / 15mm or less, 146N / 15mm or less, 145N / 15mm or less, 144N / 15mm or less, 143N / 15mm or less, 142N / 15mm or less, 141N / 15mm or less, 140N / 15mm or less, 139N / 15mm or less, 138N / 15mm or less, 137N / 15mm or less, 136N / 15mm or less, 135N / 15mm or less, or 134N / 15mm or less, but are not limited to these. More specifically, the yield strength of the film may be 130 N / 15 mm or more, 131 N / 15 mm or more, 132 N / 15 mm or more, 132.84 N / 15 mm or more, 133 N / 15 mm or more, 134 N / 15 mm or more, 135 N / 15 mm or more, and 150 N / 15 mm or less, 149 N / 15 mm or less, 148 N / 15 mm or less, 147 N / 15 mm or less, 146 N / 15 mm or less. The following are also acceptable, but are not limited to: 145N / 15mm or less, 144N / 15mm or less, 143N / 15mm or less, 142.94N / 1N / 15mm or less, 142N / 15mm or less, 141N / 15mm or less, 140N / 15mm or less, 139N / 15mm or less, 138N / 15mm or less, 137N / 15mm or less, 136N / 15mm or less, and 135N / 15mm or less.

[0047] In one embodiment, the yield strength of the film can be measured using a UTM (Universal Testing Machine) tester under conditions of a test speed of 50 mm / min and a grip distance of 50 mm. More specifically, the measurement temperature for the yield strength may be 50°C or higher, 100°C or higher, 150°C or higher, 200°C or higher, or 300°C or lower, 250°C or lower, or 200°C or lower, but is not limited to these.

[0048] In one embodiment, the heat-bonding strength of the cell pouch film may be 128N / 15mm or more, 129N / 15mm or more, 130N / 15mm or more, 131N / 15mm or more, 132N / 15mm or more, 133N / 15mm or more, 134N / 15mm or more, 140N / 15mm or less, 139N / 15mm or less, 138N / 15mm or less, 137N / 15mm or less, 136N / 15mm or less, 135N / 15mm or less, or 134N / 15mm or less, but is not limited to these.

[0049] In one embodiment, the moldability of the cell pouch film may preferably exceed 15 mm, and in the case of medium or large secondary batteries, it is particularly preferable to be 16 mm or more. There is no upper limit to the moldability of the film.

[0050] In one embodiment, the moldability of the film is 16 to 19 mm. More specifically, the moldability of the film may be greater than 15 mm, 15.2 mm or more, 15.4 mm or more, 15.6 mm or more, 15.8 mm or more, 16 mm or more, 16.2 mm or more, 16.4 mm or more, 16.6 mm or more, 16.8 mm or more, 17 mm or more, and may be 19 mm or less, 18.8 mm or less, 18.6 mm or less, 18.4 mm or less, 18.2 mm or less, 18 mm or less, 17.8 mm or less, 17.6 mm or less, 17.4 mm or less, 17.2 mm or less, and 17 mm or less, but is not limited to these.

[0051] When measuring the depth of a sample cut from cell pouch film after molding, if all 10 samples do not break at that depth, a deeper depth is applied. If even one break occurs at that depth, the depth immediately preceding the break is considered the maximum depth, and the moldability is measured at that depth.

[0052] In one embodiment, the outer layer comprises at least nylon and may further comprise polyethylene terephthalate (PET). It may also further comprise at least one resin selected from the group consisting of polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polyhydroxyaldehyde (PHA), polylactic acid (PLA), thermoplastic starch (TPS), polyvinyl alcohol (PVA), polycaprolactam (PCL), polyethylene (PE), polypropylene (PP), ethylene vinyl acetate (EVA), ethylene vinyl alcohol (EVOH), and polyvinylidene chloride (PVDC). The outer layer is required to have properties such as heat resistance, pinhole resistance, chemical resistance, abrasion resistance, moldability, and insulation. The outer layer may be composed of multiple layers.

[0053] As described above, in one embodiment, the outer layer preferably contains nylon and may preferably consist of a PET (polyethylene terephthalate) layer and a nylon layer. In one embodiment, the thickness of the PET (polyethylene terephthalate) layer may be 12 to 25 μm, and the thickness of the nylon layer may be 3 to 30 μm.

[0054] In one exemplary implementation, the nylon layer (film) may have a moisture content of 4,000 to 10,000 ppm, a moisture content of 300 to 900 μg, or the ratio of the moisture content of nylon to the total weight of the cell pouch film may be 70 to 87%.

[0055] The aforementioned nylon has the property of absorbing moisture. When nylon absorbs moisture, its strength and modulus of elasticity decrease compared to when it is dry, while its toughness increases. Conversely, when nylon is dry, its strength and modulus of elasticity increase, but its toughness decreases. From the viewpoint of thermal bonding strength, the strength and modulus of elasticity of the base material must be high, so it is necessary to manage the moisture content to prevent the outer layer of nylon from absorbing moisture and to improve thermal bonding strength. The moisture content of the nylon affects the overall moisture content of the cell pouch film, and this moisture content may affect not only thermal bonding strength but also yield strength, appearance characteristics such as heat-deformed bubbles, and moldability.

[0056] In the exemplary embodiment, the moisture content of the nylon layer (film) is 10,000 ppm or less, 9,900 ppm or less, 9,800 ppm or less, 9,700 ppm or less, 9,600 ppm or less, 9,500 ppm or less, 9,400 ppm or less, 9,300 ppm or less, 9,200 ppm or less, 9,100 ppm or less, 9,000 ppm or less, 8,900 ppm or less, 8,800 ppm or less. Below, 8700ppm or less, 8600ppm or less, 8500ppm or less, 8400ppm or less, 8300ppm or less, 8200ppm or less, 8100ppm or less, 8000ppm or less Lower, 7900ppm or less, 7800ppm or less, 7700ppm or less, 7600ppm or less, 7500ppm or less, 7400ppm or less, 7300ppm or less, 7200ppm or less , 7100ppm or less, 7000ppm or less, 6900ppm or less, 6800ppm or less, 6700ppm or less, 6600ppm or less, 6500ppm or less, 6400ppm or less , 6300ppm or less, 6200ppm or less, 6100ppm or less, 6000ppm or less, 5900ppm or less, 5800ppm or less, 5700ppm or less, 5600ppm or less It may be 5500 ppm or less, 5400 ppm or less, 5300 ppm or less, 5200 ppm or less, 5100 ppm or less, 5000 ppm or less, 4900 ppm or less, 4800 ppm or less, 4700 ppm or less, 4600 ppm or less, 4500 ppm or less, 4400 ppm or less, 4300 ppm or less, 4200 ppm or less, or 4100 ppm or less.Alternatively, 4000 ppm or more, 4100 ppm or more, 4200 ppm or more, 4300 ppm or more, 4400 ppm or more, 4500 ppm or more, 4600 ppm or more, 4700 ppm or more, 4800 ppm or more, 4900 ppm or more, 5000 ppm or more, 5100 ppm or more, 5200 ppm or more, 5300 ppm or more, 5400 ppm or more, 5500 ppm or more, 5600 ppm or more, 5700 ppm or more, 5800 ppm or more, 5900 ppm or more, 6000 ppm or more, 6100 ppm or more, 6200 ppm or more, 6300 ppm or more, 6400 ppm or more, 6500 ppm or more, 6600 ppm or more, 6700 ppm or more, 6800 ppm or more, 6900 ppm or more, 70 It may be 00 ppm or more, 7100 ppm or more, 7200 ppm or more, 7300 ppm or more, 7400 ppm or more, 7500 ppm or more, 7600 ppm or more, 7700 ppm or more, 7800 ppm or more, 7900 ppm or more, 8000 ppm or more, 8100 ppm or more, 8200 ppm or more, 8300 ppm or more, 8400 ppm or more, 8500 ppm or more, 8600 ppm or more, 8700 ppm or more, 8800 ppm or more, 8900 ppm or more, 9000 ppm or more, 9100 ppm or more, 9200 ppm or more, 9300 ppm or more, 9400 ppm or more, 9500 ppm or more, 9600 ppm or more, 9700 ppm or more, 9800 ppm or more, or 9900 ppm or more.

[0057] In the exemplary embodiment, the moisture content of the nylon layer (film) may be 300 μg or more, 350 μg or more, 400 μg or more, 450 μg or more, 500 μg or more, 550 μg or more, 600 μg or more, 650 μg or more, 700 μg or more, 800 μg or more, or 850 μg or more. Alternatively, it may be 900 μg or less, 850 μg or less, 800 μg or less, 750 μg or less, 700 μg or less, 650 μg or less, 600 μg or less, 550 μg or less, 500 μg or less, 450 μg or less, 400 μg or less, or 350 μg or less.

[0058] In the exemplary embodiment, the ratio of the moisture content of the nylon layer in the outer layer to the total weight of the cell pouch film may be 70 to 87%.

[0059] In exemplary embodiments, the moisture content of the nylon layer of the outer layer relative to the total weight of the cell pouch film may be 70% or more, 71% or more, 72% or more, 73% or more, 74% or more, 75% or more, 76% or more, 77% or more, 78% or more, 79% or more, 80% or more, 81% or more, 82% or more, 83% or more, 84% or more, 85% or more, or 86% or more. Alternatively, it may be 87% or less, 86% or less, 85% or less, 84% or less, 83% or less, 82% or less, 81% or less, 80% or less, 79% or less, 78% or less, 77% or less, 76% or less, 75% or less, 74% or less, 73% or less, 72% or less, or 71% or less.

[0060] In one embodiment, the metal constituting the barrier layer, specifically the metal thin film or metal vapor-deposited layer, may be at least one selected from the group consisting of aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), tin (Sn), zinc (Zn), indium (In), and tungsten (W) (a single metal or a mixture of single metals), or at least two alloys selected from these. In one embodiment, the metal of the barrier layer is aluminum or an alloy thereof. The barrier layer is required to have barrier properties against water vapor and other gases, as well as properties such as formability. Furthermore, the barrier layer may be surface-treated with phosphoric acid or chromium for corrosion resistance.

[0061] In one embodiment, the cell pouch film may further include an adhesive layer formed on the other side of the barrier layer and a sealant layer formed on the other side of the adhesive layer.

[0062] In one embodiment, the sealant layer comprises at least one polyolefin resin selected from the group consisting of polypropylene, low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, polybutene, and ethylene / propylene copolymer. The sealant layer is required to have properties such as heat resistance, cold resistance, thermal adhesion, and moldability, as well as electrolyte resistance and insulation resistance, since it is a layer that comes into contact with the electrolyte. The sealant layer may be composed of multiple layers.

[0063] In one embodiment, both sides of the barrier layer are surface-treated. In one embodiment, the surface-treated layer may be a surface-treated layer of phosphoric acid or chromium, zirconium, cerium, lanthanum, etc., to provide corrosion resistance to the metal.

[0064] In one embodiment, the adhesive layer may include at least one of epoxy adhesives, polyurethane adhesives, phenolic resin adhesives, polyester adhesives, and polyolefin adhesives. In one example, the thickness of the inner adhesive layer and the outer adhesive layer may each be 0.5 to 10 μm.

[0065] In one embodiment, the thickness of the barrier layer may be 5 to 100 μm. If the thickness of the barrier layer is less than 5 μm, it is not easy to realize it as a cell pouch for a secondary battery, and if the thickness of the barrier layer exceeds 100 μm, the battery capacity may decrease significantly in the bending test of the cell pouch.

[0066] In one embodiment, the thickness of the outer layer may be 5 to 50 μm.

[0067] In one embodiment, the thickness of the sealant layer may be 5 to 100 μm.

[0068] In one embodiment, an extruded resin layer may be further formed between the inner adhesive layer and the sealant layer. The extruded resin layer may improve the flexibility, adhesion, and insulation properties of the pouch. In one example, the extruded resin layer may contain an olefin resin such as a polypropylene resin.

[0069] In another embodiment, the inner layer of the cell pouch film may be constructed using the extruded resin layer and the sealant layer without the inner adhesive layer. If there is no inner adhesive layer as described above, the extruded resin layer may perform the role of the inner adhesive layer.

[0070] In one embodiment, the thickness of the extruded resin layer may be 5 to 80 μm.

[0071] Method for adjusting the initial moisture content of cell pouch film In one exemplary implementation, the film for the cell pouch may be dried after the initial manufacturing process under conditions that allow moisture to escape, in order to maintain its moisture content. More specifically, these conditions include, for example, a temperature of 40 to 100°C, a relative humidity (RH) of 15% or less, and a drying time of 10 hours or more.

[0072] Thereafter, in order to maintain the moisture content of the film, it may be stored using the storage method described later, or managed at a temperature below the dew point.

[0073] Storage method for cell pouch film In another exemplary embodiment of the present invention, a storage method is provided for adjusting the storage conditions of the cell pouch film, particularly at least one of relative humidity and temperature, so that the saturated moisture content of the cell pouch film is 1300 ppm or less.

[0074] In one embodiment, among the storage conditions for the cell pouch film, it is preferable to store it in an environment where the relative humidity is 5% or more and less than 25%, preferably 5% or more and 22% or less.

[0075] More specifically, the relative humidity may be 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, 15% or more, 16% or more, 17% or more, 18% or more, 19% or more, 20% or more, or 21% or more. Alternatively, it may be less than 25%, 24% or less, 23% or less, 22% or less, 21% or less, 20% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, or 6% or less, but is not limited to these.

[0076] In one embodiment, the storage temperature among the storage conditions for the cell pouch film includes storage at a temperature of 25°C. More specifically, the storage temperature may be 15°C or higher, 16°C or higher, 17°C or higher, 18°C ​​or higher, 19°C or higher, 20°C or higher, 21°C or higher, 22°C or higher, 23°C or higher, 24°C or higher, 25°C or higher, or 35°C or lower, 34°C or lower, 33°C or lower, 32°C or lower, 31°C or lower, 30°C or lower, 29°C or lower, 28°C or lower, 27°C or lower, 26°C or lower, or 25°C or lower, but is not limited to these.

[0077] In one embodiment, the storage method for the cell pouch film allows for adjusting the storage time to change the moisture content level, for example, up to 48 hours. Beyond 48 hours, even if the storage time is further extended, the moisture content level of the cell pouch film remains constant (i.e., reaches a saturation level).

[0078] More specifically, the storage time may be more than 0 minutes, 5 minutes or more, 10 minutes or more, 20 minutes or more, 30 minutes or more, 1 hour or more, 2 hours or more, 8 hours or more, 12 hours or more, 16 hours or more, 20 hours or more, 24 hours or more, 28 hours or more, 32 hours or more, 36 hours or more, 40 hours or more, 44 hours or more, or 48 hours or more. Alternatively, it may be 6 months or less, 1 month or less, 1 week or less, 144 hours or less, 120 hours or less, 96 hours or less, 72 hours or less, 60 hours or less, 56 hours or less, 52 hours or less, 48 ​​hours or less, 44 hours or less, 40 hours or less, 36 hours or less, 32 hours or less, 28 hours or less, 24 hours or less, 20 hours or less, 16 hours or less, 12 hours or less, 8 hours or less, 2 hours or less, 1 hour or less, 30 minutes or less, 20 minutes or less, 10 minutes or less, or 5 minutes or less, but is not limited to these.

[0079] According to one embodiment of the present invention, as described above, by adjusting the temperature and relative humidity, the saturated moisture content of the cell pouch film can be preferably maintained at 1300 ppm or less even after long-term storage. This results in excellent moldability, thermal deformation appearance characteristics, and mechanical properties such as yield strength and thermal adhesion strength.

[0080] Cell pouch A cell pouch film according to one embodiment of the present invention is suitable for cell pouch applications because it has excellent moldability, thermal deformation appearance characteristics, and mechanical properties such as yield strength and thermal adhesion strength.

[0081] In another exemplary embodiment of the present invention, a cell pouch is provided that includes the aforementioned cell pouch film.

[0082] Moisture-proof packaging method for cell pouches A cell pouch according to one embodiment of the present invention may be packaged and distributed in moisture-proof packaging.

[0083] In one exemplary embodiment, the cell pouch packaging structure may include a cylindrical tube 10, a cell pouch 50 wrapped around it, and an inner packaging material 80 surrounding the cell pouch 50 in at least one layer. It may further include an outer packaging material 180 surrounding the inner packaging material 80.

[0084] In one exemplary implementation, the inner packaging material is a moisture-proof packaging material, and its water vapor transmission rate (WVTR) is 0.1 to 1.0 g / m². 2 *May also be a day. The inner packaging material may include vacuum metallized cast polypropylene (VACP) or an aluminum bag (Al bag). The aluminum bag may include sequentially laminated nylon, aluminum, and linear low-density polyethylene (LLDPE).

[0085] In one exemplary implementation, the cylindrical tube may include polypropylene (PP).

[0086] In one exemplary implementation, the outer packaging material may consist of a sheet of expanded polystyrene, be wrapped around the inner packaging material, and at its ends, be attached to the inner end of the outer packaging material via tape at the end of the outer packaging material.

[0087] Secondary battery and method for manufacturing the same In another exemplary embodiment of the present invention, a secondary battery enclosed in the aforementioned cell pouch film is provided.

[0088] In one exemplary implementation, the secondary battery may be a medium-sized or large-sized secondary battery for a battery-powered vehicle or energy storage device.

[0089] In another exemplary embodiment of the present invention, a method for manufacturing a secondary battery is provided, comprising the step of enclosing the secondary battery with the aforementioned cell pouch film.

[0090] The present invention will be described in detail below, with reference to preferred embodiments, so that it can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in a variety of different forms and is not limited to the embodiments described below.

[0091] [Experiment 1] <Manufacturing Example 1> Manufacturing of film for cell pouches A 60 μm barrier layer made of aluminum foil metal fabric was formed, and then adhesive layers were provided on both sides of the barrier layer. Next, a 41-42 μm outer layer (nylon: 25 μm; PET: 12 μm; adhesive: 4-5 μm) containing polyethylene terephthalate (PET) and nylon was formed on one side of the adhesive layer, and an 80 μm sealant layer was formed by laminating an unoriented polypropylene film to the other side of the adhesive layer. Then, the film for cell pouches was dried for 10 hours at a temperature of 70°C and a relative humidity of 10% (RH). The manufactured cell pouch film was packaged in an aluminum bag at a temperature below the dew point, and the moisture content was controlled.

[0092] <Test 1> Adjustment and measurement of moisture content of cell pouch film The aluminum bag was removed from the cell pouch film manufactured as described above, and the moisture content of the cell pouch film was adjusted by changing the relative humidity from less than 2% to 50% at 25°C, and the moisture content of each film was measured.

[0093] As mentioned above, a sample was prepared by cutting a cell pouch film into a 60mm x 40mm sheet in the longitudinal direction (Machine direction; MD) x transverse direction (TD). This sample was then divided into four equal parts of 15mm x 40mm in the longitudinal direction (MD) x transverse direction (TD). The samples were placed in vials and sealed. The amount of water vaporized from these sealed vials was measured at a temperature of 150°C using a Karl Fischer moisture analyzer (Metrohm 917 Coulometer). The measurement conditions were a sample temperature of 150°C and a gas flow rate of 50 mL / min. After measurement, the moisture content of the sample was confirmed.

[0094] Table 1 and Figure 1 show the changes in moisture content in response to changes in time and relative humidity conditions at 25°C.

[0095] [Table 1]

[0096] As can be seen from Table 1 and Figure 1, the moisture content of the cell pouch film changes in response to changes in relative humidity and time. However, under all relative humidity conditions, the change in moisture content stops after approximately 8 hours, 24 hours, or at least 48 hours, and reaches a saturation level.

[0097] The moisture content of each example and comparative example is shown in Tables 2 and 3 below.

[0098] <Test 2> Measurement of yield strength of cell pouch film The yield strength of each cell pouch film was measured. More specifically, samples were prepared by cutting the cell pouch film to 150 mm x 15 mm in the longitudinal direction (Machine direction; MD) x transverse direction (TD). The yield strength of the samples was measured using a UTM (Universal Testing Machine, manufacturer: INSTRON) in accordance with ASTM D638, under conditions of a test speed of 50 mm / min and a grip distance of 50 mm. The yield strength of the samples was determined by measuring the transition point from elastic deformation to plastic deformation.

[0099] The yield strengths of each example and comparative example are shown in Tables 2 and 3 below.

[0100] <Test 3> Evaluation of the heat adhesion strength of cell pouch film The thermal bonding strength of each cell pouch film was evaluated. More specifically, samples were prepared by cutting the cell pouch film. The cut samples were folded in the width direction (TD). The thermal bonding conditions were 1.6 seconds, 0.2 MPa, and 200°C using a seal bar. Samples were prepared by cutting the prepared thermal bonding samples with a 15 mm cutter to a length (MD) x width (TD) of 200 mm x 100 mm. The thermal bonding strength of the samples was measured using a UTM (Universal Testing Machine, manufacturer: INSTRON) at a test speed of 50 mm / min and a grip distance of 50 mm. The samples were left at room temperature for 3 minutes before measurement. The maximum point of seal strength was defined as the maximum strength at the time of seal strength measurement.

[0101] The thermal bonding strength of each example and comparative example is shown in Tables 2 and 3 below.

[0102] <Test 4> Evaluation of the thermal deformability of film for cell pouches The thermal deformation properties of each cell pouch film produced were evaluated. More specifically, the bubbles formed in the cell pouch films were evaluated based on the following criteria. As mentioned above, thermal deformation refers to the phenomenon in the cell pouch manufacturing process where, when a pouch containing a certain amount of moisture is heat-bonded, the moisture in the nylon film vaporizes and manifests as bubbles. The evaluation of thermal deformation properties is an evaluation to confirm whether or not bubbles are generated in the pouch due to heat bonding. The evaluation process for thermal deformation properties is as follows.

[0103] [Evaluation of thermal deformation] (1) Cut the cell pouch film to 200 mm wide and 100 mm long to prepare the sample. (2) Fold it in half lengthwise, so that it is 200mm wide and 50mm long. (3) Heat seal in the lateral direction. The heat bonding temperature is 220°C, the heat bonding pressure is 0.2 MPa, and the heat bonding time is 1.6 seconds. (4) After heat sealing, check the thermal deformability visually or with a magnifying glass.

[0104] Figure 2 is an image showing the criteria for evaluating the thermal deformability of a cell pouch film according to one embodiment of the present invention. Level 1: No bubbles formed (OK) Level 2: Not clearly visible to the naked eye, but can be confirmed with a magnifying glass; tiny dots exist on the seal line / outside (OK) Level 3: Tiny air bubbles are present across the entire surface of the seal (NG) Level 4: Large air bubbles are present across the entire surface of the seal (NG)

[0105] The results are shown in Tables 2 and 3 below.

[0106] <Test 5> Evaluation of the moldability of film for cell pouches The moldability of each cell pouch film produced was evaluated. More specifically, samples measuring 240 mm x 266 mm were taken from the winding roll in both the longitudinal (MD) and widthwise (TD) directions. The collected samples were molded into rectangular shapes (190 mm horizontally, 90 mm vertically) (molding was evaluated using a chromium-coated high-moldability evaluation device with 1 cup. R values ​​varied, but the reference R value for the corners was 4). The molding pressure was fixed at 0.5 MPa. When molding and then measuring the depth, if all 10 samples did not break at that depth, a deeper depth was applied. If even one break occurred at that depth, the depth immediately preceding the break was considered the maximum depth, and this was defined as the moldability. The results are shown in Tables 2 and 3 below.

[0107] <Test Results>

[0108] [Table 2]

[0109] [Table 3]

[0110] As can be seen from Tables 2 and 3, the cell pouch film of the example exhibits excellent mechanical properties in terms of yield strength and heat adhesion strength, as well as excellent moldability and heat deformation bubble level characteristics.

[0111] [Experiment 2] Cell pouch films were manufactured in the same manner as in Experiment 1. The saturated moisture content (ppm) of the cell pouch film, the moisture content (ppm) of the nylon layer alone, the moisture content (μg) of the nylon layer alone, and the moisture content (%) of the nylon layer relative to the entire cell pouch film were measured along with the level of heat-deformable bubbles.

[0112] The moisture content (ppm), moisture content (μg), and moisture content (%) of the nylon (Ny) layer (film) alone, as well as the moisture content of the nylon (Ny) layer (film) relative to the total weight of the cell pouch film, were measured using only the nylon (Ny) layer (film) used as the outer layer of the cell pouch film, after being stored under the same temperature and relative humidity conditions as the cell pouch film.

[0113] In Table 4 below, the moisture content of the cell pouch film is the moisture content at the point when the increase in moisture content stops and it begins to reach a saturated state. The moisture content (ppm), moisture content (μg), and moisture content (%) of the nylon (Ny) film relative to the total weight of the cell pouch film were measured when the nylon (Ny) layer (film) was stored alone under the same conditions as when the moisture content was measured.

[0114] The method for measuring the moisture content or moisture rate is the same as the method for measuring the moisture content or moisture rate of the cell pouch film described above. Specifically, a sample was prepared by cutting a dry nylon (Ny) film to 60 mm x 40 mm in the longitudinal direction (Machine direction; MD) x transverse direction (TD). This sample was divided into four equal parts of 15 mm x 40 mm in the longitudinal direction (MD) x transverse direction (TD). The sample was placed in a vial and sealed. The amount of moisture vaporized from this sealed vial was measured using a Karl Fischer moisture analyzer (Metrohm 917 Coulometer) at a temperature of 150°C to determine the moisture content. The measurement conditions were a sample temperature of 150°C and a gas flow rate of 50 mL / min. After measurement, the moisture content or moisture rate of the sample was confirmed.

[0115] The heat-deformable bubble level test was conducted in the same manner as in Experiment 1.

[0116] The results are shown in Table 4 below.

[0117] [Table 4]

[0118] As can be seen from the above experiment, there is a correlation between the moisture content of the cell pouch film, the moisture content (ppm) of the nylon layer (film) alone, the moisture content (μg) of the nylon layer (film) alone, and the moisture content of the nylon layer (film) relative to the total weight of the cell pouch film (%). In other words, when the moisture content of the nylon layer (film) exceeds 10,000 ppm, or the moisture content exceeds 900 μg, or when the ratio of the moisture content of the nylon layer to the total weight of the cell pouch film exceeds 87%, the moisture content of the cell pouch film also exceeds 1,300 ppm, which results in defects in the foaming level.

[0119] Although exemplary embodiments of the present invention have been described above in relation to the preferred embodiments described above, various modifications or variations can be made without departing from the spirit and scope of the invention. Therefore, the appended claims are intended to encompass such modifications or variations insofar as they fall within the spirit of the invention. [Industrial applicability]

[0120] The cell pouch film of an exemplary embodiment of the present invention is suitable for cell pouch applications because it has excellent moldability, thermal deformation appearance characteristics, and mechanical properties such as yield strength and thermal adhesion strength. Such cell pouches can be usefully used as outer casings for secondary batteries, particularly medium or large secondary batteries.

Claims

1. A cell pouch film comprising at least an outer layer containing a nylon film, a barrier layer made of metal, and a sealant layer, Cell pouch film having a moisture content of 1300 ppm or less, as measured by the method described below. [Method for measuring the moisture content of film for cell pouches] Prepare a sample of cell pouch film cut to 60 mm x 40 mm in the length direction (machine direction; MD) x width direction (transverse direction; TD). Divide this sample into four equal parts of 15 mm x 40 mm in the length direction (MD) x width direction (TD). Place the four divided samples into vials and seal them. Place these sealed vials in a moisture meter and measure the amount of water vaporized from the vials at a temperature of 150°C. This is taken 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.

2. The cell pouch film according to claim 1, wherein the moisture content of the cell pouch film is 300 to 1300 ppm.

3. The cell pouch film according to claim 2, wherein the outer layer consists of a polyethylene terephthalate (PET) film and a nylon film, the barrier layer consists of aluminum, and the sealant layer includes a polypropylene layer.

4. The cell pouch film according to claim 3, wherein the yield strength of the cell pouch film is 120 N / 15 mm to 150 N / 15 mm, and the yield strength is measured using a UTM (Universal Testing Machine) tester under the conditions of a test speed of 50 mm / min and a grip distance of 50 mm.

5. The cell pouch film according to claim 3, wherein the heat bonding strength of the cell pouch film is 128 N / 15 mm to 140 N / 15 mm, and the heat bonding strength is measured using a UTM (Universal Testing Machine) tester under the conditions of a test speed of 50 mm / min and a grip distance of 50 mm.

6. The cell pouch film according to claim 3, wherein the moldability of the film is 16 to 19 mm.

7. A method for storing film for cell pouches, A method for storing cell pouch film, comprising the steps of storing the cell pouch film in an environment with a temperature of 25°C and a relative humidity of 5% or more and less than 25%, so that the saturated moisture content of the cell pouch film is 1300 ppm or less.

8. Cell pouch packaging structure including cell pouch, A cell pouch film according to any one of claims 1 to 6 that has been wound up, The device includes an inner packaging material that surrounds the wound-up cell pouch film with at least one layer, The water vapor transmission rate (WVTR) of the inner packaging material is 0.1 to 1.0 g / m². ２ *A cell pouch packaging structure.

9. A secondary battery enclosed in a cell pouch film according to any one of claims 1 to 6.

10. A method for manufacturing a secondary battery, comprising enclosing the secondary battery with a cell pouch film according to any one of claims 1 to 6.

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