Pouch film laminate and pouch-type secondary battery

Abstract

The present invention provides a pouch film laminate in which a base layer, a gas barrier layer, and a sealant layer are laminated in this order, wherein the base layer contains a polyamide-based film, and the ratio (H / A) of the height (W / g) (H) of the melting peak of the polyamide-based film obtained by differential scanning calorimetry (DSC) to the melting enthalpy (W sec / g) (A) of the polyamide-based film is 0.03 sec -1 The above relates to the pouch film laminate.

Description

[Technical Field]

[0001] Cross-Citation of Related Applications This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0090095 filed on July 11, 2023 and Korean Patent Application No. 10-2024-0084073 filed on June 26, 2024, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] Technical Field The present invention relates to a pouch film laminate and a pouch-type secondary battery, and more particularly to a pouch film laminate and a pouch-type secondary battery in which poor appearance of the pouch that can occur at high sealing temperatures is improved. [Background technology]

[0003] Generally, types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, lithium-ion polymer batteries, etc. Such secondary batteries are used not only in small products such as digital cameras, DVD players, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also in large products that require high output such as electric vehicles and hybrid vehicles, as well as in power storage devices and backup power storage devices that store surplus generated power and new renewable energy.

[0004] To manufacture such a secondary battery, first, an electrode active material slurry is applied to a positive electrode current collector and a negative electrode current collector to form a positive electrode and a negative electrode, which are then stacked on both sides of a separator to form an electrode assembly of a predetermined shape, and then the electrode assembly is placed in a battery case, an electrolyte is injected, and the battery case is sealed.

[0005] Secondary batteries are classified into pouch types and can types depending on the material of the case that houses the electrode assembly. Pouch types house the electrode assembly in a pouch made of flexible polymer material, while can types house the electrode assembly in a case made of metal or plastic.

[0006] The pouch, which is the case of a pouch-type secondary battery, is manufactured by pressing a flexible pouch film laminate to form a cup portion. Once the cup portion is formed, the electrode assembly is placed in the receiving space inside the cup portion, and the seal portion is sealed to manufacture the secondary battery.

[0007] Generally, a pouch film laminate is formed of multiple layers, with a polymer film such as polyethylene terephthalate laminated on one side of a metal gas barrier layer and a sealant layer laminated on the other side.

[0008] Increasing the thickness of the gas barrier layer to improve the moldability of pouches for secondary batteries has traditionally resulted in a problem of slower heat transfer to the sealant layer when sealing the pouch. This slows down the melting of the sealant layer, reducing the pouch's seal strength. To ensure sufficient seal strength, however, it has been necessary to increase the sealing temperature and apply more heat to the seal. However, if the sealing temperature is raised above 220°C, the base layer melts, resulting in poor pouch appearance.

[0009] Therefore, there is a need for the development of a pouch film laminate in which deformation of the base layer is suppressed even when sealing is performed at a sealing temperature of 220°C or higher, thereby improving the appearance of the pouch. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention is intended to solve the above-mentioned problems, and provides a pouch film laminate and a pouch-type secondary battery in which the base layer contains a polyamide film with a narrow melting peak obtained by a differential scanning calorimeter, thereby suppressing deformation of the pouch appearance even when sealed at a temperature of 220°C or higher, and ensuring sealability and productivity. [Means for solving the problem]

[0011] According to one embodiment, the present invention provides a pouch film laminate in which a base layer, a gas barrier layer, and a sealant layer are laminated in this order, wherein the base layer includes a polyamide-based film, and the ratio (H / A) of the height (W / g) (H) of the melting peak of the polyamide-based film obtained by differential scanning calorimetry (DSC) to the melting enthalpy (W·sec / g) (A) of the polyamide-based film is 0.03 sec -1 More than 0.04 seconds, preferably 0.04 seconds -1 The pouch film laminate is provided as described above.

[0012] The polyamide film may have a full width at half maximum of a melting peak of 5.0°C or less, preferably 4.5°C or less, and more preferably 4.0°C or less.

[0013] The lower limit of the relative moisture content index of the polyamide film represented by the following formula 1 is 11,500 ppm g / cm 2 , preferably 13,000 ppm g / cm 2 , more preferably 14,000 ppm g / cm 2 The upper limit is 21,500 ppm g / cm 2 , preferably 21,000 ppm g / cm 2 , more preferably 20,000 ppm g / cm 2 may be.

[0014] [Formula 1] Relative moisture content index (ppm g / cm 2) = [(moisture content of pouch) × (density of pouch)] × [(thickness of second base layer) / (total thickness of pouch film laminate)]

[0015] The polyamide film may contain at least one selected from the group consisting of nylon 6, nylon 6,6, nylon MXD6 (polyxylylene adipamide), nylon 4, nylon 4,6, and nylon 4,10, and preferably contains nylon 6.

[0016] Meanwhile, the substrate layer may have a two-layer structure in which a first substrate layer and a second substrate layer are laminated in order, and the second substrate layer may include the polyamide-based film.

[0017] Here, the thickness of the first base layer may be 5 μm to 30 μm, preferably 5 μm to 25 μm, and more preferably 7 μm to 20 μm.

[0018] The thickness of the second base layer may be 5 μm to 30 μm, preferably 7 μm to 29 μm, and more preferably 10 μm to 27 μm.

[0019] The first base layer may include a polyester film.

[0020] The gas barrier layer may contain one or more materials selected from the group consisting of aluminum, copper, and stainless steel.

[0021] The thickness of the gas barrier layer may be 20 μm to 100 μm, preferably 30 μm to 90 μm, and more preferably 35 μm to 85 μm.

[0022] The thickness of the sealant layer may be 30 μm to 130 μm, preferably 40 μm to 120 μm, and more preferably 60 μm to 100 μm.

[0023] Furthermore, a pouch-type secondary battery according to another embodiment of the present invention may include a pouch-type battery case manufactured by molding any of the above-described pouch film laminates, and an electrode assembly housed in the pouch-type battery case. [Effects of the Invention]

[0024] The pouch film laminate according to the present invention includes a polyamide-based film with a narrow melting peak in the base layer, and thus can suppress deformation of the base layer even when the sealing temperature is increased to 220°C or higher, thereby improving the appearance defects of the pouch-type secondary battery.

[0025] Furthermore, in the pouch film laminate according to the present invention, deformation of the base layer is suppressed even when the sealing temperature is raised to 220° C. or higher during sealing, so that the sealant layer can be melted by applying sufficient heat, thereby increasing the seal strength when sealing the pouch film laminate and shortening the sealing time, thereby ensuring productivity. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a cross-sectional view showing the structure of a pouch film laminate according to one embodiment of the present invention. [Figure 2] FIG. 4 is a cross-sectional view showing the structure of a pouch film laminate according to another embodiment of the present invention. [Figure 3] 1 is an exploded view of a pouch-type secondary battery according to the present invention; [Figure 4] 1 is a graph showing the results of DSC evaluation performed in Experimental Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0027] The advantages and features of the present invention, as well as methods for achieving them, will become more apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be realized in various different forms. The present embodiments are provided merely to complete the disclosure of the present invention and to enable those skilled in the art to fully understand the scope of the invention. The present invention is defined only by the claims. The same reference numerals refer to the same elements throughout the specification.

[0028] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that the inventor can appropriately define the concept of the term in order to best explain his or her invention.

[0029] The terms used in this specification are for the purpose of describing embodiments and are not intended to limit the present invention. In this specification, the singular includes the plural unless otherwise specified. As used in this specification, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other elements in addition to the elements being mentioned.

[0030] The present invention will be described in more detail below.

[0031] The present inventors have developed a pouch film laminate with a base layer having a melting peak height (W / g) (H) ratio (H / A) of 0.03 sec. -1 The inventors have found that when the pouch film contains the polyamide-based film described above, deformation of the base layer can be suppressed even when the pouch film is sealed at a temperature of 220°C or higher, and high sealing strength and a shortened sealing time can be ensured, leading to the completion of the present invention.

[0032] Pouch film laminate The pouch film laminate according to the present invention is a pouch film laminate in which a base layer, a gas barrier layer, and a sealant layer are laminated in this order, and the base layer contains a polyamide-based film, and in a melting peak of the polyamide-based film obtained by a differential scanning calorimeter (DSC), the ratio (H / A) of the peak height (W / g) (H) to the melting enthalpy (W sec / g) (A) of the polyamide-based film is 0.03 sec -1 Specifically, the pouch film laminate according to the present invention may be a pouch film laminate.

[0033] Hereinafter, the pouch film laminate according to the present invention and each layer contained in the pouch film laminate will be described in detail with reference to FIG.

[0034] FIG. 1 is a cross-sectional view of a pouch film laminate 100 according to the present invention.

[0035] 1, the pouch film laminate 100 includes a base layer 110, a gas barrier layer 120, and a sealant layer 130. In the pouch film laminate 100, the base layer 110, the gas barrier layer 120, and the sealant layer 130 may be laminated in this order.

[0036] (1) Base material layer According to one embodiment of the present invention, the substrate layer 110 is formed as the outermost layer of the pouch film laminate 100 to protect the secondary battery from external friction and impact. The substrate layer 110 is made of a polymer and can electrically insulate the electrode assembly from the outside.

[0037] The base layer 110 may include a polyamide-based film. For example, the polyamide-based film may include at least one selected from the group consisting of nylon 6, nylon 6,6, nylon MXD6 (polyxylene adipamide), nylon 4, nylon 4,6, and nylon 4,10, but is not limited thereto. The polyamide-based film preferably includes nylon 6, which has the advantage of improving the formability of the pouch due to the excellent stretchability of nylon 6.

[0038] Differential scanning calorimetry (DSC) is a method for analyzing the physical and chemical properties of a sample material by measuring the difference in heat flow between a sample material and a reference material as a function of temperature when the material is heated or cooled at a specific temperature. The area of ​​the melting peak in a graph obtained from a differential scanning calorimeter is defined as the area between the horizontal axis of the graph and the peak, and is expressed in units of W·°C / g. The melting enthalpy of the sample material (unit: W·sec / g) can be measured by dividing the peak area by the heating rate (unit: °C / min) of the DSC instrument. The peak height (W / g) is defined as the maximum value of the melting peak and represents the amount of crystals in the sample material that melt at the peak temperature. The full width at half maximum (°C) of the peak is defined as the width of the peak at half the peak height and represents the melting temperature distribution of the crystals in the sample material.

[0039] In the melting peak of the polyamide-based film obtained by a differential scanning calorimeter (DSC), the ratio (H / A) of the height (W / g) (H) of the peak to the melting enthalpy (W·sec / g) (A) of the polyamide-based film is 0.03 sec -1 More than 0.04 seconds, preferably 0.04 seconds -1 It may be more than that.

[0040] The melting enthalpy of the polyamide film means the amount of crystals contained in the polyamide film, so the larger the melting enthalpy, the larger the amount of crystals contained in the polyamide film. Also, the higher the melting peak height of the polyamide film, the larger the amount of crystals that melt at the peak temperature. Therefore, the present invention aims to make the ratio of the melting peak height to the melting enthalpy of the polyamide film 0.03 sec -1 By adjusting as above, the amount of crystals that melt at the peak temperature is increased, and a polyamide film whose melting initiation temperature is adjusted to 215°C is used.

[0041] Specifically, when the above range is satisfied, the melting peak of the polyamide-based film measured by a differential scanning calorimeter has a relatively narrow width and a high height. For the same melting enthalpy, the higher the melting peak height of a polyamide-based film, the more densely the crystals are formed. Conversely, for the same melting enthalpy, the lower the melting peak height of a polyamide-based film, the more sparsely the crystals are formed, and the more crystals melt at a temperature lower than the peak temperature.

[0042] Therefore, when the ratio (H / A) of the peak height (H) to the melting enthalpy (A) of the polyamide-based film satisfies the above range, the crystals contained in the polyamide-based film are formed relatively densely, resulting in a high melting initiation temperature. Therefore, when the substrate layer contains moisture at a predetermined level or higher, the amount of melted crystals during sealing at 220°C is relatively small, resulting in minimal deformation of the substrate layer even when the moisture evaporates. As a result, the problem of deformation of the substrate layer due to bubbles can be alleviated, preventing damage to the seal and improving the durability and lifespan of pouch-type secondary batteries.

[0043] Meanwhile, the ratio (H / A) of the peak height (H) to the melting enthalpy (A) of the polyamide film can be adjusted by the cooling / heat treatment conditions and stretching ratio during the polyamide film production process. Specifically, the longer the cooling time, the higher the heat treatment temperature, and the longer the heat treatment time during polyamide film production, the more uniformly sized the polyamide film can be formed. Furthermore, when the stretching ratios in the machine direction (MD) and the transverse direction (TD) of a polyamide film are similar, the film is more likely to have uniformly sized crystals. Here, the more uniform the size of the crystals contained in a polyamide film, the less variation there is in the melting temperature of the crystals, and the greater the amount of crystals that melt at the peak temperature relative to the total amount of crystals, resulting in a larger ratio (H / A).

[0044] On the other hand, in the melting peak of the polyamide-based film obtained by differential scanning calorimetry (DSC), the ratio (H / A) of the peak height (W / g) (H) to the melting enthalpy (W·sec / g) (A) of the polyamide-based film and the ratio of the area of ​​the melting peak in a specific temperature range including the melting onset temperature to the area of ​​the entire melting peak may be independent of each other or may have different trends. For example, when the ratio (H / A) of the peak height (W / g) (H) to the melting enthalpy (W·sec / g) (A) of the polyamide-based film is 0.03 sec -1 or more, the ratio (H / A) of the height of the peak (W / g) (H) to the melting enthalpy (W sec / g) (A) of the polyamide film is 0.03 sec -1 In the cases below, the ratio of the area of ​​the melting peak at 210°C to 220°C to the area of ​​the entire melting peak may be relatively smaller or larger, or may be the same.

[0045] Even if the ratio of the area of ​​the melting peak at 210 ° C. to the area of ​​the entire melting peak is relatively larger, the ratio (H / A) of the height (W / g) (H) of the peak to the melting enthalpy (W sec / g) (A) of the polyamide film is 0.03 sec -1When the melting peak area is 210°C to 220°C or more, deformation of the base layer can be prevented when sealing at a temperature of 220°C or more. On the other hand, even if the ratio of the area of ​​the melting peak at 210°C to 220°C to the area of ​​the entire melting peak is relatively small, the ratio (H / A) of the height (W / g) (H) of the peak to the melting enthalpy (W sec / g) (A) of the polyamide film is 0.03 sec -1 If it is less than this, it may be difficult to prevent deformation of the base layer when sealing at a temperature of 220°C or higher.

[0046] The polyamide film may have a melting peak full width at half maximum of 5.0°C or less, preferably 4.5°C or less, and more preferably 4.0°C or less. For polyamide films with the same melting enthalpy, the smaller the melting peak full width at half maximum, the denser the crystals contained in the polyamide film, and thus the less the amount of crystals that melt at temperatures below the peak temperature. Therefore, when the full width at half maximum falls within the above range, even if the substrate layer contains moisture at a predetermined level or more, the amount of crystals that melt when sealed at 220°C is relatively small, resulting in less deformation of the substrate layer even when the moisture evaporates.

[0047] On the other hand, the lower limit of the relative moisture content index of the polyamide film represented by the following formula 1 is 11,500 ppm g / cm 2 , preferably 13,000 ppm g / cm 2 , more preferably 14,000 ppm g / cm 2 The upper limit is 21,500 ppm g / cm 2 , preferably 21,000 ppm g / cm 2 , more preferably 20,000 ppm g / cm 2 may be.

[0048] [Formula 1] Relative moisture content index (unit: ppm g / cm 2 ) = [(moisture content of pouch) × (density of pouch)] × [(thickness of second base layer) / (total thickness of pouch film laminate)]

[0049] In the pouch film laminate according to the present invention, the relative moisture content index of the polyamide film is 11,500 ppm g / cm 2 4. If the thickness is 100 μm or more, deformation of the substrate layer does not occur when sealing at temperatures of 220° C. or higher.

[0050] Specifically, the relative moisture content index is 11,500 ppm g / cm 2 If the relative moisture content index of the polyamide film is less than 21,500 ppm g / cm, problems such as breakage and cracks may occur when forming the pouch film laminate. 2 If it is larger, the toughness of the polyamide film is reduced, and the formability of the pouch for the secondary battery is reduced.

[0051] As a result, the lower limit of the relative moisture content index of the polyamide film is 11,500 ppm g / cm 2 and the upper limit is 21,500 ppm g / cm 2 In this case, the toughness of the substrate layer is improved, which prevents breakage or cracks from occurring during molding of the pouch film laminate, thereby improving the moldability of the pouch for the secondary battery.

[0052] The base layer 110 may include a polyester film having abrasion resistance and heat resistance. For example, the polyester film may include at least one selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, but is not limited thereto.

[0053] The thickness of the base material layer 110 may be 5 μm to 100 μm, preferably 7 μm to 70 μm, and more preferably 15 μm to 60 μm. When the thickness of the base material layer 110 satisfies the above range, the external insulation is excellent, and the overall thickness of the pouch is not large, resulting in an excellent volumetric energy density of the secondary battery.

[0054] The substrate layer 110 according to the present invention may have a single film structure made of any one material, or a composite film structure formed by layers of two or more materials.

[0055] FIG. 2 is a cross-sectional view showing the structure of a pouch film laminate according to another embodiment of the present invention.

[0056] 2, when the substrate layer 110 according to the present invention has a composite membrane structure, it may have a two-layer structure in which a first substrate layer 112 and a second substrate layer 114 are sequentially laminated. In the composite membrane structure, an adhesive layer may be disposed between each layer. For example, when the substrate layer 110 according to the present invention includes an adhesive layer, it may have a structure in which the first substrate layer 112, a first adhesive layer (not shown), and a second substrate layer 114 are sequentially laminated. Additionally, the substrate layer 110 may further include a second adhesive layer (not shown) disposed between the second substrate layer 114 and the gas barrier layer 120.

[0057] The first base material layer 112, the second base material layer 114, the first adhesive layer, and the second adhesive layer may be made of materials with different materials and / or physical properties. Interfaces may exist between each layer of the base material layer 110, including the first base material layer 112, the second base material layer 114, the first adhesive layer, and the second adhesive layer. This means that each layer is a different layer and can be formed separately.

[0058] 1) First base layer The first base material layer 112 may be a layer disposed on the outermost layer of the pouch film laminate 100. In that case, the first base material layer 112 plays a role in preventing the penetration of moisture from the outside of the pouch.

[0059] The first base material layer 112 may contain at least one selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon (registered trademark), and glass fiber.

[0060] The first base layer 112 preferably includes the above-mentioned polyester-based film. Specific examples of the polyester-based film are as described above, and therefore detailed description thereof will be omitted.

[0061] Here, the thickness of the first base material layer 112 may be 5 μm to 30 μm, preferably 5 μm to 25 μm, and more preferably 7 μm to 20 μm. When the thickness of the first base material layer 112 satisfies the above numerical range, the insulation properties and formability of the pouch can be ensured while effectively suppressing the penetration of moisture into the inside of the pouch film laminate. In addition, since the overall thickness of the pouch film is not large, the volumetric energy density of the secondary battery can be increased.

[0062] 2) Second base material layer The second base material layer 114 may be a layer disposed between the first base material layer 112 and the gas barrier layer 120. In this case, the second base material layer 114 plays a role in improving the formability of the pouch.

[0063] The second base layer 114 may include the above-mentioned polyamide-based film. Specific examples and characteristics of the polyamide-based film are as described above, and therefore detailed description thereof will be omitted.

[0064] The thickness of the second base layer may be 5 μm to 30 μm, preferably 7 μm to 29 μm, and more preferably 10 μm to 27 μm. When the thickness satisfies the above range, the second base layer is not too thin, ensuring pouch formability, preventing a decrease in the volumetric energy density of the secondary battery due to an excessively thick pouch film laminate, and enabling the second base layer to be formed to a uniform thickness.

[0065] 3) First adhesive layer The first adhesive layer (not shown) may be a layer disposed between the first substrate layer 112 and the second substrate layer 114. In this case, the first adhesive layer serves to bond the first substrate layer 112 and the second substrate layer 114 together.

[0066] The first adhesive layer may contain at least one selected from the group consisting of urethane-based, epoxy-based, and acrylic-based polymers, but is not limited thereto. The first adhesive layer preferably contains a urethane-based polymer, in which case the first adhesive layer can adhere to the first base layer 112 and the second base layer 114 and can be easily shaped and cut.

[0067] The thickness of the first adhesive layer may be 1 μm to 10 μm, preferably 2 μm to 8 μm, and more preferably 2 μm to 5 μm. When the thickness of the first adhesive layer satisfies the above numerical range, sufficient adhesion between the first base material layer 112 and the second base material layer 114 is ensured, while preventing a decrease in the volumetric energy density of the secondary battery due to an excessive increase in the thickness of the pouch film laminate.

[0068] 4)Second adhesive layer The second adhesive layer (not shown) may be a layer disposed between the second base material layer 114 and the gas barrier layer 120. In this case, the second adhesive layer serves to bond the second base material layer 114 and the gas barrier layer 120 together.

[0069] The second adhesive layer may contain at least one selected from the group consisting of urethane-based, epoxy-based, and acrylic-based polymers, but is not limited thereto. The second adhesive layer preferably contains a urethane-based polymer, in which case the second adhesive layer can adhere to the second base layer 114 and the gas barrier layer 120, and is easy to form and cut.

[0070] The thickness of the second adhesive layer may be 1 μm to 10 μm, preferably 2 μm to 8 μm, and more preferably 2 μm to 5 μm. When the thickness of the second adhesive layer satisfies the above numerical range, sufficient adhesion between the second base material layer 114 and the gas barrier layer 120 is ensured, while preventing a decrease in the volumetric energy density of the secondary battery due to an excessive increase in the thickness of the pouch film laminate.

[0071] (2) Gas barrier layer The gas barrier layer 120 is laminated between the base material layer 110 and the sealant layer 130 to ensure the mechanical strength of the pouch, block the entry and exit of gases and moisture from outside the secondary battery, and prevent leakage of electrolyte from inside the pouch-type battery case.

[0072] The gas barrier layer 120 may be formed of a metal, such as, but not limited to, a thin metal film containing one or more metals selected from the group consisting of aluminum (Al), copper (Cu), stainless steel (SUS), nickel (Ni), titanium (Ti), and invar.

[0073] According to one embodiment of the present invention, the gas barrier layer 120 may be formed of an aluminum alloy thin film. Forming the gas barrier layer 120 using an aluminum alloy thin film can ensure a predetermined level of mechanical strength, a light weight, and the electrochemical properties of the electrode assembly and electrolyte can be complemented, and heat dissipation can be ensured. The aluminum alloy thin film may contain elements other than aluminum (Al). For example, the aluminum alloy thin film may contain one or more elements selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0074] As another example, the gas barrier layer 120 may be formed of a stainless steel thin film. Specifically, the gas barrier layer 120 can be manufactured by molding and / or processing a stainless steel thin film. A gas barrier layer 120 formed of stainless steel has relatively low thermal conductivity, which is effective in preventing or delaying heat diffusion to other cells during thermal runaway. Furthermore, its relatively high toughness can suppress the occurrence of cracks in the pouch during use of the pouch-type battery. The stainless steel may contain elements other than iron (Fe), such as one or more selected from the group consisting of copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0075] The thickness of the gas barrier layer 120 may be 20 μm to 100 μm, preferably 30 μm to 90 μm, and more preferably 35 μm to 85 μm. When the thickness is within the above range, the present invention does not cause the problem of deformation of the base layer even when the sealing temperature is increased so that heat is transmitted to the sealant layer, and therefore, it is possible to use a gas barrier layer that is thicker than conventional gas barrier layers, thereby improving moldability and gas barrier performance during molding of the cup portion.

[0076] (3) Sealant layer The sealant layer 130 is intended to completely seal the interior of the pouch-type battery case by thermally bonding the seal portions together when the pouch-type battery case housing the electrode assembly inside is sealed, and therefore may be formed of a material with excellent thermal bonding strength.

[0077] The sealant layer 130 may be formed of a material having insulating properties, corrosion resistance, and sealing properties. Specifically, since the sealant layer 130 is in direct contact with the electrode assembly and / or electrolyte inside the pouch-type battery case, it may be formed of a material having insulating properties and corrosion resistance. Furthermore, since the sealant layer 130 must completely seal the interior of the pouch-type battery case to prevent the transfer of substances between the inside and outside, it may be formed of a material having high sealing properties (e.g., excellent thermal adhesive strength). To ensure such insulating properties, corrosion resistance, and sealing properties, the sealant layer 130 may be formed of a polymer material.

[0078] The sealant layer 130 may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon (registered trademark), and is preferably made of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be cast polypropylene (CPP), acid-modified polypropylene (PPa), polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer.

[0079] The thickness of the sealant layer 130 may be 30 μm to 130 μm, preferably 40 μm to 120 μm, and more preferably 60 μm to 100 μm. When the thickness of the sealant layer satisfies the above range, it is possible to ensure the formability of the pouch film laminate while ensuring the seal strength of the sealed portion.

[0080] Meanwhile, the sealant layer 130 according to the present invention may have a composite film structure formed by layers of two or more materials. For example, the sealant layer 130 may have a multi-layer structure. An adhesive layer and / or a skin layer may be disposed between each layer of the sealant layer 130 having a composite film structure. The adhesive layer and / or the skin layer have thermal adhesive properties and serve to support the adhesion between each layer of the sealant layer 130. For example, the adhesive layer and / or the skin layer may include, but is not limited to, a polypropylene-based resin. The adhesive layer and / or the skin layer may also be disposed between the sealant layer 130 and the gas barrier layer 120.

[0081] Specifically, the sealant layer 130 according to the present invention may include a first sealant layer 132 and a second sealant layer 134. As one example, the sealant layer 130 may be composed of the first sealant layer 132 and the second sealant layer 134. As another example, the sealant layer 130 may further include a third sealant layer and / or a fourth sealant layer in addition to the first sealant layer 132 and the second sealant layer 134. Each layer of the sealant layer 130, including the first sealant layer 132 and the second sealant layer 134, may be made of materials with different materials and / or physical properties. An interface may exist between each layer included in the sealant layer 130. This means that each layer is a different layer and can be formed separately.

[0082] The pouch film laminate of the present invention as described above can be produced by a method known in the art for producing a pouch film laminate. For example, the pouch film laminate of the present invention can be produced by a method in which the base layer 110 is attached to the upper surface of the gas barrier layer 120 using an adhesive, and the sealant layer 130 is formed on the lower surface of the gas barrier layer 120 using coextrusion or an adhesive layer, or by methods such as dry lamination or sandwich lamination. However, the method for producing the pouch film laminate is not limited to these.

[0083] The pouch film laminate according to the present invention may have a total thickness of 120 μm to 250 μm, preferably 140 μm to 230 μm, and more preferably 150 μm to 215 μm. When the thickness of the pouch film laminate satisfies the above range, it is possible to minimize the reduction in battery accommodating space and the deterioration of sealing durability due to an increase in the thickness of the pouch laminate, and to increase the molding depth.

[0084] Pouch-type secondary battery Next, the pouch-type secondary battery according to the present invention will be described.

[0085] FIG. 3 is an exploded view of a pouch-type secondary battery 200 according to the present invention.

[0086] 3, a pouch-type secondary battery 200 according to the present invention may include a pouch-type battery case 210 manufactured by molding the above-described pouch film laminate, and an electrode assembly 260 housed in the pouch-type battery case 210. Specifically, the pouch-type secondary battery 200 according to the present invention may include the pouch-type battery case 210, the electrode assembly 260, an electrode lead 280, an insulating part 290, and an electrolyte (not shown).

[0087] Hereinafter, each component of the pouch-type secondary battery of the present invention will be described in more detail with reference to FIG.

[0088] (1) Pouch-type battery case The pouch-type battery case 210 can be manufactured by molding the pouch film laminate of the present invention as described above. The pouch-type battery case 210 can house the electrode assembly 260 inside. The detailed structure and properties of the pouch film laminate have been described above, so a detailed description thereof will be omitted.

[0089] The pouch film laminate may be drawn and stretched using a punch or the like to manufacture the pouch-type battery case 210. As a result, the pouch-type battery case 210 may include a cup portion 222 and a receiving portion 224. The receiving portion 224 is a portion that receives the electrode assembly, and may refer to a receiving space formed in a pocket shape inside the cup portion 222 by forming the cup portion 222.

[0090] According to an embodiment of the present invention, the pouch-type battery case 210 may include a first case 220 and a second case 230, as shown in Fig. 3. The first case 220 may include a receiving portion 224 that can receive the electrode assembly 260, and the second case 230 may cover the receiving portion 224 from above to prevent the electrode assembly 260 from falling out of the battery case 210. The first case 220 and the second case 230 may be manufactured with one side connected to each other as shown in Fig. 3, but the present invention is not limited thereto and may be manufactured in various ways, such as being separated from each other and separately manufactured.

[0091] According to another embodiment of the present invention, when forming cup portions in a pouch film laminate, two symmetrical cup portions 222, 232 may be adjacent to one another by drawing molding. In this case, the first case 220 and the second case 230 may be formed with the cup portions 222, 232, respectively, as shown in FIG. 3 . The electrode assembly 260 may be accommodated in the accommodation portion 224 provided in the cup portion 222 of the first case 220, and then the bridge portion 240 formed between the two cup portions 222, 232 may be folded so that the two cup portions 222, 232 face each other. In this case, the cup portion 232 of the second case 230 can accommodate the electrode assembly 260 from above. Therefore, since two cup portions 222, 232 accommodate one electrode assembly 260, a thicker electrode assembly 260 can be accommodated than when there is only one cup portion 222. In addition, since one edge is formed on the secondary battery 200 by folding the pouch-type battery case 210, the number of edges to be sealed in a subsequent sealing process can be reduced, thereby improving the processing speed of the pouch-type secondary battery 200 and reducing the number of sealing processes.

[0092] The pouch-type battery case 210 may be sealed with the electrode assembly 260 housed therein so that a portion of the electrode lead 280, i.e., a terminal portion, described below, is exposed. Specifically, after the electrode lead 280 is connected to the electrode tab 270 of the electrode assembly 260 and an insulating portion 290 is formed on a portion of the electrode lead 280, the electrode assembly 260 may be housed in a housing portion 224 provided in the cup portion 222 of the first case 220, and the housing portion 224 may be covered from above by the second case 230. Next, an electrolyte may be injected into the housing portion 224, and the seal portion 250 formed on the edges of the first case 220 and the second case 230 may be sealed.

[0093] The sealing portion 250 serves to seal the accommodating portion 224. Specifically, the sealing portion 250 may be formed along the edge of the accommodating portion 224 to seal the accommodating portion 224. The temperature at which the sealing portion 250 is sealed may be 180°C to 250°C, specifically 200°C to 250°C, and more specifically 210°C to 240°C. When the sealing temperature is within the above range, the pouch-type battery case 210 can ensure sufficient seal strength through thermal bonding.

[0094] (2) Electrode assembly The electrode assembly 260 may be inserted into the pouch-type battery case 210, and after the electrolyte is injected, the pouch-type battery case 210 may be sealed.

[0095] The electrode assembly 260 may be formed by sequentially stacking a positive electrode, a separator, and a negative electrode. Specifically, the electrode assembly 260 may include two types of electrodes, a positive electrode and a negative electrode, and a separator interposed between the electrodes to insulate the electrodes from each other.

[0096] The positive electrode and the negative electrode may have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or a metal mesh containing aluminum and copper, respectively. The slurry may be formed by stirring a granular active material, an auxiliary conductor, a binder, a conductive material, etc., in a solvent. The solvent may be removed in a subsequent process.

[0097] A slurry containing an electrode active material, a binder, and / or a conductive material is applied to a positive electrode current collector and a negative electrode current collector to form a positive electrode and a negative electrode, which are then stacked on both sides of a separator to form a predetermined shape of the electrode assembly 260. Types of the electrode assembly 260 include, but are not limited to, a stack type, a jelly roll type, and a stack-and-fold type.

[0098] The electrode assembly 260 may include an electrode tab 270 .

[0099] The electrode tabs 270 are connected to the positive and negative electrodes of the electrode assembly 260, respectively, and protrude from the electrode assembly 260 to serve as paths for electrons to move between the inside and outside of the electrode assembly 260. The electrode current collector included in the electrode assembly 260 may be composed of a portion coated with an electrode active material and an end portion, i.e., a plain portion, where the electrode active material is not coated. The electrode tabs 270 may be formed by cutting the plain portion or by connecting a separate conductive member to the plain portion by ultrasonic welding or the like. As shown in FIG. 3 , the electrode tabs 270 may protrude in different directions from the electrode assembly 260, but are not limited thereto. They may be formed to protrude in various directions, such as protruding in parallel from one side in the same direction.

[0100] (3) Electrode lead The electrode lead 280 can supply electricity to the outside of the secondary battery 200. The electrode lead 280 may be connected to the electrode tab 270 of the electrode assembly 260 by spot welding or the like.

[0101] An electrode lead 280 may be connected to the electrode assembly 260 and may protrude to the outside of the pouch-type battery case 210 via the seal portion 250. Specifically, one end of the electrode lead 280 may be connected to the electrode assembly 260, particularly to the electrode tab 270, and the other end of the electrode lead 280 may protrude to the outside of the pouch-type battery case 210.

[0102] The electrode lead 280 may include a positive electrode lead 282 having one end connected to the positive electrode tab 272 and extending in the direction in which the positive electrode tab 272 protrudes, and a negative electrode lead 284 having one end connected to the negative electrode tab 274 and extending in the direction in which the negative electrode tab 274 protrudes. The other ends of the positive electrode lead 282 and the negative electrode lead 284 may protrude to the outside of the battery case 210. This allows electricity generated inside the electrode assembly 260 to be supplied to the outside. Furthermore, since the positive electrode tab 272 and the negative electrode tab 274 protrude in different directions, the positive electrode lead 282 and the negative electrode lead 284 may also extend in different directions. The positive electrode lead 282 and the negative electrode lead 284 may be made of different materials. That is, the positive electrode lead 282 may be made of aluminum (Al), the same material as the positive electrode current collector, and the negative electrode lead 284 may be made of copper (Cu) or nickel (Ni)-coated copper, the same material as the negative electrode current collector. The portion of the electrode lead 280 that protrudes outside the battery case 210 may serve as a terminal portion and be electrically connected to an external terminal.

[0103] (4) Insulation section The insulating portion 290 prevents electricity generated from the electrode assembly 260 from flowing to the battery case 210 via the electrode lead 280, thereby maintaining the sealing of the battery case 210. To this end, the insulating portion 290 may be formed of an insulator that is electrically non-conductive and does not easily pass electricity. Generally, insulating tape or film that is easy to attach to the electrode lead 280 and has a relatively thin thickness is often used as the insulating portion 290, but the insulating portion 290 is not limited thereto, and any material that can insulate the electrode lead 280 may be used.

[0104] The insulating portion 290 may be arranged to surround the outer peripheral surface of the electrode lead 280. Specifically, at least a portion of the electrode lead 280 may be surrounded by the insulating portion 290. In this case, the insulating portion 290 may be arranged between the electrode lead 280 and the pouch-type battery case 210. The insulating portion 290 is located in a limited area of ​​the seal portion 250 where the first case 220 and the second case 230 of the pouch-type battery case 210 are heat-sealed, and can bond the electrode lead 280 to the battery case 210.

[0105] (5) Electrolyte The pouch-type secondary battery 200 according to the present invention may further include an electrolyte (not shown) injected into the pouch-type battery case 210. The electrolyte is used to transport lithium ions generated by an electrochemical reaction of the electrodes during charge / discharge of the secondary battery 200, and may include a non-aqueous organic electrolytic solution that is a mixture of a lithium salt and an organic solvent, or a polymer using a polymer electrolyte. The electrolyte may also include a sulfide-based, oxide-based, or polymer-based solid electrolyte, and such a solid electrolyte has flexibility that makes it easily deformed by an external force.

[0106] The present invention will be described in more detail below with reference to specific examples. However, the following examples are merely illustrative to aid in understanding the present invention and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications can be made within the scope and technical concept of the present description, and it is obvious that such changes and modifications are included in the scope of the appended claims. [Example]

[0107] Example 1 A 25 μm-thick nylon 6 film A, a 12 μm-thick second adhesive film, and a 12 μm-thick polyethylene terephthalate (PET) film, each having the thermal properties shown in Table 1 below, were sequentially laminated on one side of a 60 μm-thick aluminum (Al) alloy thin film using a dry lamination method with a urethane adhesive to form a substrate layer. The urethane adhesive was applied so that the adhesive layer was 3 μm thick. Next, a 40 μm-thick acid-modified polypropylene (PPa) film and a 40 μm-thick polypropylene (PP) film were co-extruded on the other side of the aluminum alloy thin film to form an 80 μm-thick sealant layer, thereby producing a pouch film laminate.

[0108] Example 2 A 25 μm-thick nylon 6 film B, a 12 μm-thick second adhesive film, and a 12 μm-thick polyethylene terephthalate (PET) film, each having the thermal properties shown in Table 1 below, were sequentially laminated on one side of a 60 μm-thick aluminum (Al) alloy thin film using a dry lamination method with a urethane adhesive to form a substrate layer. The urethane adhesive was applied so that the adhesive layer was 3 μm thick. Next, a 30 μm-thick acid-modified polypropylene (PPa) film, a 30 μm-thick cast polypropylene (CPP) film, and a 20 μm-thick polypropylene (PP) film were co-extruded on the other side of the aluminum alloy thin film to form an 80 μm-thick sealant layer, thereby producing a pouch film laminate.

[0109] Comparative Example 1 A 25 μm-thick nylon 6 film C, a 12 μm-thick second adhesive film, and a 12 μm-thick polyethylene terephthalate (PET) film, each having the thermal properties shown in Table 1 below, were sequentially laminated on one side of a 60 μm-thick aluminum (Al) alloy thin film using a dry lamination method with a urethane adhesive to form a substrate layer. The urethane adhesive was applied so that the adhesive layer was 3 μm thick. Next, a 30 μm-thick acid-modified polypropylene (PPa) film and a 50 μm-thick cast polypropylene (CPP) film were co-extruded on the other side of the aluminum alloy thin film to form an 80 μm-thick sealant layer, thereby producing a pouch film laminate.

[0110] Comparative Example 2 A 25 μm-thick nylon 6 film D, a 12 μm-thick second adhesive film, and a 12 μm-thick polyethylene terephthalate (PET) film, each having the thermal properties shown in Table 1 below, were sequentially laminated on one side of a 60 μm-thick aluminum (Al) alloy thin film using a dry lamination method with a urethane adhesive to form a substrate layer. The urethane adhesive was applied so that the adhesive layer was 3 μm thick. Next, a 30 μm-thick polypropylene (PP) film and a 50 μm-thick polypropylene film were co-extruded on the other side of the aluminum alloy thin film to form an 80 μm-thick sealant layer, thereby producing a pouch film laminate.

[0111] Comparative Example 3 A 15 μm-thick nylon 6 film E, a 12 μm-thick second adhesive film, and a 12 μm-thick polyethylene terephthalate (PET) film, each having the thermal properties shown in Table 1 below, were sequentially laminated on one side of a 40 μm-thick aluminum (Al) alloy thin film using a dry lamination method with a urethane adhesive to form a substrate layer. The urethane adhesive was applied so that the adhesive layer was 3 μm thick. Next, an 80 μm-thick cast polypropylene (CPP) film was co-extruded on the other side of the aluminum alloy thin film to form an 80 μm-thick sealant layer, thereby producing a pouch film laminate.

[0112] Comparative Example 4 A 15 μm-thick nylon 6 film F, a 12 μm-thick second adhesive film, and a 12 μm-thick polyethylene terephthalate (PET) film, each having the thermal properties shown in Table 1 below, were sequentially laminated on one side of a 40 μm-thick aluminum (Al) alloy thin film using a dry lamination method with a urethane adhesive to form a substrate layer. The urethane adhesive was applied so that the adhesive layer was 3 μm thick. Next, an 80 μm-thick cast polypropylene (CPP) film was co-extruded on the other side of the aluminum alloy thin film to form an 80 μm-thick sealant layer, thereby producing a pouch film laminate.

[0113] Experimental Example 1 - Measurement of thermal properties of nylon film The pouch film laminates of Examples 1 and 2 and Comparative Examples 1 to 4 prepared as described above were loaded into a differential scanning calorimetry (DSC, TA, DSC250) and heated to 280°C at a heating rate of 10°C / min to check the thermal properties of the pouch film laminates. The thermal properties of the nylon 6 films in Examples 1 and 2 and Comparative Examples 1 to 4 were measured from the melting peak of the nylon 6 film, which appeared in the DSC temperature range of 200°C to 230°C. The results are shown in Table 1 below and Figure 4.

[0114] [Table 1]

[0115] Referring to Table 1 above, for nylon films A and B included in Examples 1 and 2, the ratio (H / A) of the peak height (W / g) (H) to the melting enthalpy (W sec / g) (A) was 0.03 sec -1 The nylon films C, D, E, and F included in Comparative Examples 1 to 4 had a ratio (H / A) of the peak height (W / g) (H) to the melting enthalpy (W sec / g) (A) of 0.03 sec -1 It can be seen from Table 1 above that the ratio (Y / X) of the area of ​​the melting peak at 210°C to 220°C (Y) to the area of ​​the entire melting peak (X) for nylon film A in Example 1 is smaller than that for nylon films C, D, and E in Comparative Examples 1 to 3, but larger than that for nylon film F in Comparative Example 4. That is, it can be seen that the ratio (H / A) of the peak height (W / g) (H) to the melting enthalpy (W sec / g) (A) according to the present invention has an independent relationship with the ratio (Y / X) of the area of ​​the melting peak at 210°C to 220°C (Y) to the area of ​​the entire melting peak (X).

[0116] Experimental example 2 - Presence or absence of external deformation of the seal part The moisture content per unit weight of the pouch film laminate manufactured in Examples 1 and 2 and Comparative Examples 1 to 4 was changed by adjusting the moisture content in the chamber in which the pouch film laminate was stored. After that, when the relative moisture content index of the second substrate layer according to the following formula 1 was 6,000 ppm g / cm 2 , 9,000 ppm·g / cm 2 , 11,500 ppm·g / cm 2 , 14,000 ppm·g / cm 2 Five pouch film laminates having the above structure were prepared for each of Examples 1 and 2 and Comparative Examples 1 to 4.

[0117] [Formula 1] Relative moisture content index = [(moisture content of pouch) x (density of pouch)] x [(thickness of second substrate layer) / (total thickness of pouch film laminate)]

[0118] Next, each pouch film laminate was cut to a size of 266 mm wide and 200 mm long, and then folded in half so that the sealant layers were in contact to make a size of 133 mm wide and 200 mm long. The edge of the long side (200 mm) was then sealed under the following conditions to produce each pouch-type battery case.

[0119] -Sealing conditions: sealing bar area 200mm x 8mm, sealing was performed for 1.6 seconds at 220°C.

[0120] Next, each sealed pouch-type battery case was visually inspected to see if any bubbles had formed in the second base material layer located at the seal portion, causing deformation of the seal portion. The results are shown in Table 2 below. ○ The seal area has been deformed due to the generation of air bubbles. × No air bubbles are generated and the seal is not deformed

[0121] [Table 2]

[0122] According to Table 2, the ratio of the melting peak height to the melting enthalpy of the polyamide film is 0.03 sec -1 In Examples 1 and 2 described above, unlike Comparative Examples 1 to 4, when sealed at a temperature of 220°C, the relative moisture content index was 11,500 ppm g / cm 2 Even in the above cases, it can be confirmed that no bubbles are generated in the second base material layer and no deformation occurs in the appearance of the sealed portion. [Explanation of symbols]

[0123] 100 Pouch film laminate 110 Base material layer 112 1st base layer 114 Second base layer 120 Gas barrier layer 130 Sealant Layer 200 Pouch-type secondary battery 210 Pouch-type case 220 Case 1 222 Cup section 224 Storage Unit 230 Case 2 232 Cup section 240 Bridge section 250 Seal part 260 Electrode assembly 270 Electrode Tab 272 Positive electrode tab 274 Negative electrode tab 280 Electrode Lead 282 Positive lead 284 Negative lead 290 Insulation

Claims

1. A pouch film laminate in which a base layer, a gas barrier layer, and a sealant layer are laminated in this order, the substrate layer includes a polyamide-based film, In the melting peak of the polyamide-based film obtained by a differential scanning calorimeter (DSC), the ratio (H / A) of the height (W / g) (H) of the melting peak to the melting enthalpy (W sec / g) (A) of the polyamide-based film is 0.03 sec. －１ This is the pouch film laminate.

2. The pouch film laminate according to claim 1, wherein the polyamide film has a full width at half maximum of a melting peak of 5.0°C or less.

3. The lower limit of the relative moisture content index of the polyamide film represented by the following formula 1 is 11,500 ppm g / cm ２ and [Equation 1] Relative moisture content index (ppm g / cm ２ ) = [(moisture content of pouch) × (density of pouch)] × [(thickness of second base layer) / (total thickness of pouch film laminate)] The pouch film laminate according to claim 1,

4. The pouch film laminate according to claim 1, wherein the polyamide-based film comprises at least one selected from the group consisting of nylon 6, nylon 6,6, nylon MXD6 (polyxylylene adipamide), nylon 4, nylon 4,6, and nylon 4,10.

5. the substrate layer has a two-layer structure in which a first substrate layer and a second substrate layer are laminated in order, The pouch film laminate according to claim 1 , wherein the second base layer includes the polyamide-based film.

6. The pouch film laminate according to claim 5, wherein the second base layer has a thickness of 5 μm to 30 μm.

7. The pouch film laminate according to claim 5, wherein the thickness of the first base layer is 5 μm to 30 μm.

8. The pouch film laminate according to claim 5 , wherein the first base layer comprises a polyester film.

9. The pouch film laminate according to claim 1 , wherein the gas barrier layer comprises at least one material selected from the group consisting of aluminum, copper, and stainless steel.

10. 2. The pouch film laminate according to claim 1, wherein the gas barrier layer has a thickness of 20 μm to 100 μm.

11. 2. The pouch film laminate according to claim 1, wherein the sealant layer has a thickness of 30 μm to 130 μm.

12. A pouch-type battery case manufactured by molding the pouch film laminate according to any one of claims 1 to 11; and an electrode assembly housed in the pouch-type battery case.

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