Pouch film, pouch-type secondary battery case including same, and secondary battery

Abstract

The present invention relates to a pouch film comprising a sealant layer, a barrier layer, a second outer layer, and a first outer layer sequentially laminated, and a coating layer provided on an outer surface of the first outer layer, wherein the coating layer has a thickness of 0.01 μm to 1.0 μm, and the sealant layer includes a lubricant A having a low melting point and a lubricant B having a high melting point, and a friction coefficient of the sealant layer is controlled, thereby having high moldability so that a desired R value at a corner portion can be obtained when a secondary battery case is molded.

Description

Pouch film, pouch-type secondary battery case including the same, and secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0197928 filed on December 27, 2024, and all contents disclosed in said Korean patent application are incorporated herein as part of this specification.

[0003]

[0004] Technology field

[0005] The present invention relates to a pouch film and a pouch-type secondary battery case including the same.

[0006]

[0007] Secondary batteries are capable of repeated charging and discharging and can be classified into cylindrical, prismatic, and pouch-type secondary batteries depending on their structure and manufacturing method. Among these, pouch-type secondary batteries are a form in which an electrode assembly (cell) is embedded in a pouch made of a metal laminate sheet; they are widely used in energy storage devices such as automotive batteries due to their relatively simple structure and relatively high capacity per unit volume. The pouch, which serves as the case for the pouch-type secondary battery, is manufactured by performing press processing on a flexible pouch film to form a cup portion. Once the cup portion is formed, the electrode assembly is housed in the receiving space of the cup portion, and the sealing portion is sealed to manufacture the secondary battery. In this way, the battery body, sealed by the pouch film, can be substantially protected from external exposure.

[0008] Meanwhile, to prevent the battery body from being exposed to the external environment, the pouch film is required to possess excellent sealing properties; in particular, it is required to maintain sealing performance under various environmental conditions. This is because if the battery body is exposed to the external environment, problems such as degradation of the pouch-type secondary battery's function or explosion may occur.

[0009] Here, the sealing performance and retention characteristics of the pouch film can be evaluated by the sealing strength of the pouch film. Sealing strength is an indicator representing the excellence of the thermal sealing strength at the sealing portion of the pouch film; if the sealing strength of the pouch film is excellent, the sealing performance of the pouch film can generally be considered excellent.

[0010] Meanwhile, the molding process of a secondary battery pouch film includes a step of packaging the battery body (electrode assembly) by placing it inside the pouch film. To improve the efficiency of the process of inserting the battery body (electrode assembly), the pouch film must be manufactured accurately in the desired design during the molding process. However, lubricants are often added to improve the slipperiness of the pouch film surface to enhance moldability; this slippery surface prevents the pouch film from being accurately fixed during molding, which can lead to problems such as failing to achieve the desired edge design or the desired radius of curvature values ​​for each corner.

[0011] (Patent Document 1) KR 10-2024-0000780 A

[0012]

[0013] The problem to be solved by the present invention is to provide a pouch film and a pouch-type secondary battery case including the same, wherein the R-value of the corner portion can be accurately maintained by adjusting the friction coefficient of the outer layer of the pouch film and the friction coefficient of the sealant layer, respectively, through surface characteristic modification, in order to improve the distortion of the R-value of the corner portion that occurs during the molding process of a secondary battery pouch film.

[0014]

[0015] The present invention provides a pouch film and a pouch-type secondary battery case including the same.

[0016] (1) The present invention provides a pouch film comprising a sealant layer, a barrier layer, a second outer layer and a first outer layer sequentially laminated, and a coating layer on the outer surface of the first outer layer, wherein the thickness of the coating layer is 0.01 μm or more and 1.0 μm or less, and the sealant layer comprises a lubricant A having a melting point of 70 °C or more and 125 °C or less and a lubricant B having a melting point of 125 °C or more and 150 °C or less, wherein the coefficient of dynamic friction of the sealant layer measured according to the measurement method below is 0.15 or more and 0.4 or less.

[0017] [measurement method]

[0018] After preparing the film of the first outer layer by cutting it into Sample 1 (TD 120 mm x MD 250 mm) and Sample 2 (TD 65 mm x MD 135 mm), fix Sample 1 to the belt portion of the friction coefficient measuring instrument with the surface to be friction facing upward. Then, prepare a 200 g jig for measuring the friction coefficient (jig size: MD 70 mm x TD 63 mm) and fix Sample 2 to the jig with the surface to be measured facing downward. After placing Sample 2 so that the surfaces to be measured make contact, secure it to the fixing part of the jig with a fishing line so that the belt moves to measure the friction coefficient. The speed is 100 mm / min. The measurement distance is 100 m, and the dynamic friction coefficient is checked at this time.

[0019] (2) The present invention provides a pouch film in which the weight ratio of lubricant A and lubricant B in (1) is 1:1 or higher and 9 or lower.

[0020] (3) The present invention provides a pouch film in which, in (1) or (2), the sealant layer comprises the lubricant A and lubricant B in a total content of 0.01% by weight or more and 0.5% by weight or less.

[0021] (4) The present invention provides a pouch film in which, in any one of (1) to (3), the coating layer comprises an acrylic resin.

[0022] (5) The present invention provides a pouch film in which, in any one of (1) to (4), the coating layer comprises one or more polymers polymerized from one or more monomers selected from the group consisting of acrylate monomers, methacrylate monomers, acrylate monomers containing hydroxyl groups, and styrene monomers.

[0023] (6) The present invention provides a pouch film in which, in any one of (1) to (5), the lubricant A comprises one or more substances selected from the group consisting of erucamide, oleamide, stearamide and behenamide.

[0024] (7) The present invention provides a pouch film in which, in any one of (1) to (6), the lubricant B comprises one or more substances selected from the group consisting of ethylene bisoleamide and ethylene bissteramide.

[0025] (8) The present invention provides a pouch film in which, in any one of (1) to (7), the surface kinetic friction coefficient of the first outer layer measured according to the measurement method below is 0.20 or higher and 0.40 or lower.

[0026] [measurement method]

[0027] After preparing the film of the first outer layer by cutting it into Sample 1 (TD 120 mm x MD 250 mm) and Sample 2 (TD 65 mm x MD 135 mm), fix Sample 1 to the belt portion of the friction coefficient measuring instrument with the surface to be friction facing upward. Then, prepare a 200 g jig for measuring the friction coefficient (jig size: MD 70 mm x TD 63 mm) and fix Sample 2 to the jig with the surface to be measured facing downward. After placing Sample 2 so that the surfaces to be measured make contact, secure it to the fixing part of the jig with a fishing line so that the belt moves to measure the friction coefficient. The speed is 100 mm / min. The measurement distance is 100 m, and the dynamic friction coefficient is checked at this time.

[0028] (9) The present invention provides a pouch film in which, in any one of (1) to (8), the coating layer is formed in an inline process of the first outer layer.

[0029] (10) The present invention provides a pouch film in which, in any one of (1) to (9), the first outer layer comprises one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon and glass fiber.

[0030] (11) The present invention provides a pouch film in which, in any one of (1) to (10), the thickness of the first outer layer is 5 μm or more and 40 μm or less.

[0031] (12) The present invention provides a pouch-type battery case comprising a pouch film according to any one of (1) to (11).

[0032] (13) The present invention provides a secondary battery comprising: an electrode assembly formed by stacking a positive electrode, a separator, and a negative electrode; and a pouch-type battery case according to (12) that accommodates the electrode assembly.

[0033]

[0034] The pouch film of the present invention can have excellent moldability because the R value of the corner portion can be maintained within a specific range during molding by surface modification of the outer layer and the sealant layer.

[0035]

[0036] FIG. 1 is a schematic diagram showing the composition of a pouch film according to Example 1 of the present invention.

[0037]

[0038] Hereinafter, the present invention will be described in more detail to aid in understanding the invention. In this case, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0039] The terms used in this specification are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0040] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0041] In the present specification, when each layer of a secondary battery pouch is included, it is not necessarily composed only of that layer, but may include additional layers.

[0042] In this specification, being formed on a specific layer includes not only being formed directly on the layer but also being formed after interposing an additional layer.

[0043] In this specification, the extrusion lamination coating (EC) layer refers to an extruded layer of a resin, such as a polyolefin resin, preferably a polypropylene resin, extruded for bonding with a barrier layer as a part of the sealant layer. The extrusion lamination coating (EC) layer of the sealant layer is located on the barrier layer side with respect to the following polypropylene resin layer.

[0044] In this specification, the polypropylene (PP) layer of the sealant layer serves as a core resin layer forming the sealant layer and performs a sealing function, and may consist of one or more layers made of polypropylene-based resin. It is contrasted with the aforementioned extrusion bonding coating (EC) layer for bonding with the barrier layer and is located on the inner side of the pouch film (i.e., the side opposite the barrier layer) relative to the aforementioned extrusion bonding coating (EC) layer.

[0045] In this specification, the R value refers to the radius of curvature of each corner of the receiving space capable of accommodating the electrode assembly in the molding fixation of the pouch film. In other words, the R value indicates how rounded the corners are. A smaller R value signifies sharper corners, while a larger R value signifies corners with softer, gentler curves.

[0046]

[0047] Pouch film

[0048] The present invention provides a pouch film comprising a sealant layer, a barrier layer, a second outer layer, and a first outer layer sequentially laminated, wherein the outer surface of the first outer layer comprises a coating layer, the thickness of the coating layer being 0.01 μm or more and 1.0 μm or less, the sealant layer comprising a lubricant A having a melting point of 70 °C or more and 125 °C or less and a lubricant B having a melting point of 125 °C or more and 150 °C or less, and the friction coefficient of the sealant layer being 0.15 or more and 0.4 or less.

[0049] The outer layer contained in the pouch film serves to block contact with the outside and seal the electrode assembly housed inside, and thus requires excellent processability and moldability. These processability and moldability are influenced by mechanical properties, particularly the mechanical properties of the outer layer. The inventors of the present invention have confirmed that in the case of conventional pouch films, errors occur in the molding depth and radius of curvature (R value) at each corner of the receiving space capable of accommodating the electrode assembly during the molding process, making it difficult to accommodate an electrode assembly of the desired size; consequently, this can have an adverse effect on the quality of the pouch film product. Furthermore, the inventors of the present invention have confirmed that the processability can be influenced by the properties of the outer layer positioned at the outermost edge of the pouch film and the properties of the sealant layer located at the innermost edge. To solve the above problems, research was conducted to control the friction coefficient of the outer layer and the friction coefficient of the sealant layer within a specific range.

[0050] Accordingly, to solve the above problem, the inventors formed a coating layer on the outer surface of the outer layer, controlled the friction coefficient and chemical properties of the outer layer through the coating layer, and added a lubricant to the sealant layer to control the friction coefficient of the surface of the sealant layer, thereby developing a pouch film capable of achieving a desired molding depth and radius of curvature.

[0051]

[0052] The pouch film of the present invention may have a structure in which a sealant layer, a barrier layer, a second outer layer, and a first outer layer are sequentially laminated, and includes a coating layer on at least one surface including the outer surface of the first outer layer. FIG. 1 shows the configuration of a pouch film according to Example 1 of the present invention, in which a coating layer is disposed on the outer surface of the first outer layer. By including a coating layer on the outer surface of the first outer layer, the pouch film of the present invention may enable fine molding that controls the desired depth and radius of curvature of the corners by adjusting the coefficient of friction of the outer layer surface.

[0053] In addition, the thickness of the coating layer of the present invention may be 0.01 μm or more and 1.0 μm or less. For example, the thickness of the coating layer may be 0.01 μm or more, 0.03 μm or more, 0.07 μm or more, 0.10 μm or more, 0.15 μm or more, 0.20 μm or more, 0.25 μm or more, 0.30 μm or more, 0.35 μm or more, 0.40 μm or more, 0.45 μm or more, 0.50 μm or more, 0.55 μm or more, 0.60 μm or more, 0.65 μm or more, 1.00 μm or less, 0.95 μm or less, 0.90 μm or less, 0.85 μm or less, 0.80 μm or less, 0.75 μm or less, and 0.70 μm or less. If the thickness of the coating layer exceeds the upper limit of the above range, it becomes difficult to control the friction coefficient to a desired level due to the excessive thickness of the coating layer, and a problem may arise in which the formability of the pouch film is reduced as the radius of curvature of each corner of the receiving space of the electrode assembly increases. In addition, if the thickness of the coating layer exceeds the lower limit of the above range, defects may occur on the surface of the outer layer, and a problem of reduced durability may arise.

[0054] According to one embodiment of the present invention, a pouch film is provided in which the coating layer comprises an acrylic resin. Specifically, the coating layer may comprise one or more polymers polymerized from one or more monomers selected from the group consisting of acrylate monomers, methacrylate monomers, acrylate monomers containing hydroxyl groups, and styrene monomers.

[0055] For example, the acrylate monomer may comprise one or more monomers selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, decyl acrylate, dodecyl acrylate, myristyl acrylate, palmityl acrylate, and stearyl acrylate.

[0056] For example, the hydroxyl group-containing acrylate monomer may comprise one or more monomers selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate, and 4-hydroxybutyl acrylate.

[0057] For example, the styrene monomer may comprise one or more monomers selected from the group consisting of styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, divinylbenzene, chlorostyrene, bromostyrene, nitrostyrene, ethoxystyrene, and hydroxystyrene.

[0058] For example, the methacrylate monomer may comprise one or more monomers selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate, benzyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, lauryl methacrylate, and fluoroalkyl methacrylate.

[0059] In addition to the materials described above, the coating layer may further include a cationic emulsifier, a nonionic emulsifier, an initiator, a pH adjuster, water, etc.

[0060] When the coating layer of the present invention comprises the acrylic resin described above, it exhibits excellent wear resistance, mechanical strength, and chemical resistance, thereby effectively preventing thermal deformation of the outer layer in high-temperature environments and controlling the friction coefficient characteristics of the outer layer to maintain excellent moldability.

[0061] According to one embodiment of the present invention, the coating layer may be formed within an in-line process of the first outer layer. An in-line process refers to a process that is included within a specific manufacturing process and proceeds continuously, while an outline process refers to a process that proceeds through a separate process after the manufacturing process.

[0062] Here, the coating layer may be formed as one step in the process of manufacturing the first outer layer. Specifically, the coating layer may be formed by coating the surface of the polyethylene terephthalate (PET) with the acrylic resin before fabricating the polyethylene terephthalate into a sheet by stretching the polyethylene terephthalate in the MD and TD directions, after the polyethylene terephthalate has undergone a pretreatment process as the material for the first outer layer.

[0063] In this way, when the coating layer is formed in an in-line process, the outer film and the coating layer are stretched together according to physical deformation, thereby strengthening adhesion and bonding strength, and improving moldability by uniformly distributing stress. Furthermore, it is possible to apply a uniform coating to the outer layer with a thin thickness, such as the thickness of the coating layer of the present invention.

[0064] On the other hand, when the above coating layer is formed by an outline process, the coating layer is added to the film after stretching, which may result in reduced formability due to stress imbalance between the film and the coating layer, reduced flexibility, and the formation of a relatively thick coating layer compared to an inline process.

[0065] In addition, the sealant layer of the pouch film of the present invention comprises lubricant A, having a melting point of 70°C or higher and 125°C or lower, and lubricant B, having a melting point of 125°C or higher and 150°C or lower. The lubricant can facilitate the molding of the pouch film by imparting slipperiness to the surface of the sealant film and the surface of the outer layer film during the molding or winding process, thereby controlling friction characteristics and preventing adhesion with the mold.

[0066] The lubricant included in the sealant layer of the pouch film of the present invention can be classified into lubricant A, which has a melting point of 70°C or higher and 125°C or lower, and lubricant B, which has a melting point of 125°C or higher and 150°C or lower. Lubricant A is a lubricant having a low melting point, and lubricant B is a lubricant having a high melting point. Lubricant A can improve the slip properties of the sealant layer surface, lower the coefficient of friction, increase the efficiency of the molding process, and minimize fine irregularities by being uniformly distributed on the surface. Additionally, lubricant B can maintain slip properties in a high-temperature environment, prevent thermal deformation, and maintain long-term slip properties by acting slowly on the film surface due to its low solubility.

[0067] According to one embodiment of the present invention, the weight ratio of lubricant A and lubricant B may be 1:1 or higher and 9:0 or lower. For example, the weight ratio of lubricant A and lubricant B may be 1:1.0 or higher, 1.5 or higher, 2.0 or higher, 2.3 or higher, 2.5 or higher, 3.0 or higher, 3.5 or higher, 4.0 or higher, 4.5 or higher, 9.0 or lower, 8.5 or lower, 8.0 or lower, 7.5 or lower, 7.0 or lower, 6.5 or lower, 6.0 or lower, 5.5 or lower, and 5.0 or lower. Depending on the melting point, the time taken to emerge to the surface after being included in the sealant layer varies, and accordingly, the coefficient of friction of the surface of the manufactured sealant layer may vary. Accordingly, the ratio of a lubricant having a low melting point and a lubricant having a high melting point included in the sealant layer may be an important factor. Accordingly, when the weight ratio of lubricant A and lubricant B satisfies the above ratio, the surface friction coefficient of the sealant layer can be optimally controlled, and the R value and molding depth can be finely molded according to the desired purpose, thereby improving the moldability of the pouch film.

[0068] According to one embodiment of the present invention, the sealant layer may contain the lubricant A and lubricant B in a total content of 0.01 weight% or more and 0.5 weight% or less. For example, the total content of lubricant A and lubricant B included in the sealant layer is 0.01 wt% or more, 0.03 wt% or more, 0.05 wt% or more, 0.07 wt% or more, 0.09 wt% or more, 0.10 wt% or more, 0.11 wt% or more, 0.13 wt% or more, 0.15 wt% or more, 0.17 wt% or more, 0.19 wt% or more, 0.20 wt% or more, 0.21 wt% or more, 0.23 wt% or more, 0.25 wt% or more, 0.50 wt% or less, 0.49 wt% or less, 0.47 wt% or less, 0.45 wt% or less, 0.43 wt% or less, 0.41 wt% or less, 0.40 wt% or less, 0.39 wt% or less, 0.37 wt% or less, 0.35 wt% or less, The amount may be 0.33 wt% or less, 0.31 wt% or less, 0.30 wt% or less, 0.29 wt% or less, or 0.27 wt% or less. If the above lubricant is added in excess, moldability is improved, but sealing strength decreases, and it causes poor winding condition and changes in physical properties over time, i.e., changes over time. In addition, since the degree of migration of additives such as lubricants varies depending on conditions such as temperature, pressure, and time, the physical properties of the pouch cannot be maintained uniformly. Furthermore, if migration occurs excessively, it can cause foreign matter issues during the process stage, which becomes a factor that can undermine the reliability of the product. On the other hand, if additives such as lubricants are added in small amounts, the sealing strength is good, but moldability may decrease. That is, when the above lubricant is included within the above range, the physical properties of the pouch film can be maintained uniformly, thereby improving moldability during the process stage and enhancing the product finish.

[0069] According to one embodiment of the present invention, the lubricant A may comprise one or more substances selected from the group consisting of erucamide, oleamide, stearamide, and behenamide. Additionally, the lubricant B may comprise one or more substances selected from the group consisting of ethylene bisoleamide (EBO) and ethylene bissteramide.

[0070] According to one embodiment of the present invention, the surface friction coefficient of the sealant layer may be 0.15 or higher and 0.40 or lower, and, for example, the friction coefficient of the sealant layer may be 0.15 or higher, 0.16 or higher, 0.17 or higher, 0.18 or higher, 0.19 or higher, 0.20 or higher, 0.21 or higher, 0.22 or higher, 0.23 or higher, 0.24 or higher, 0.25 or higher, 0.40 or lower, 0.39 or lower, 0.38 or lower, 0.37 or lower, 0.36 or lower, 0.35 or lower, 0.34 or lower, 0.33 or lower, 0.32 or lower, 0.31 or lower, 0.30 or lower, 0.29 or lower, 0.28 or lower, 0.27 or lower, and 0.26 or lower.

[0071] In addition, the surface friction coefficient of the first outer layer may be 0.20 or higher and 0.40 or lower, and, for example, may be 0.20 or higher, 0.21 or higher, 0.22 or higher, 0.23 or higher, 0.24 or higher, 0.25 or higher, 0.26 or higher, 0.27 or higher, 0.28 or higher, 0.29 or higher, 0.30 or higher, 0.40 or lower, 0.39 or lower, 0.38 or lower, 0.37 or lower, 0.36 or lower, 0.35 or lower, 0.34 or lower, 0.33 or lower, 0.32 or lower, and 0.31 or lower.

[0072] Here, the surface friction coefficient was measured in the MD direction of the first outer layer and sealant layer of the pouch film at a measurement speed of 200 mm / min using a friction coefficient measuring instrument (Labsink FPT-F1 (Friction Tester)).

[0073] If the friction coefficients of the sealant layer and the first outer layer satisfy the above range, the desired R value can be achieved during the molding process, and consequently, the formability of the pouch film can be improved. However, if the friction coefficient of the sealant layer falls outside the upper limit of the above range, the desired R value can be reached during the molding process, but it may be difficult to achieve the desired maximum moldable deformation length. Furthermore, if the friction coefficient of the sealant layer falls outside the lower limit of the above range, the surface of the sealant layer is slippery, and it is difficult to obtain the desired R value during the molding process.

[0074] According to one embodiment of the present invention, the pouch film of the present invention comprises an inner sealant layer, an outer layer, and a barrier layer containing aluminum between the inner sealant layer and the outer layer. Additionally, as previously described, the outer layer comprises a first outer layer and a second outer layer.

[0075] The outer layer may be the outermost layer of the pouch film for the exterior of the lithium secondary battery, and the outer layer may have an appropriate thickness within a range that ensures sufficient mechanical strength and sufficient moldability as an exterior material. For example, the thickness of the outer layer may be 15㎛ or more, 20㎛ or more, 25㎛ or more, 27㎛ or more, 35㎛ or more, 37㎛ or more, 70㎛ or less, 50㎛ or less, or 40㎛ or less. When the above range is satisfied, the dielectric breakdown voltage may be maintained at a high level.

[0076] The above outer layer comprises a first outer layer and a second outer layer, and the first outer layer may comprise one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber.

[0077] In addition, the second outer layer, which is a heat-resistant resin layer having a melting point greater than the heat sealing temperature of the sealant layer, may comprise one or more compounds selected from the group consisting of polyamide compounds, polyester compounds, polyolefin compounds, and polyacrylic compounds.

[0078] According to one embodiment of the present invention, the outer layer may be composed of a laminated film of a first outer layer (polyethylene terephthalate) and a second outer layer (nylon). In this case, the thinner the thickness of the first outer layer and the thicker the thickness of the second outer layer, the more advantageous it is for moldability. However, the thinner the thickness of the first outer layer, the more disadvantageous it may be in terms of dielectric breakdown voltage. In this regard, exemplarily, the thickness of the first outer layer may be 5 μm or more, 7 μm or more, 9 μm or more, 10 μm or more, 11 μm or more, 12 μm or more, 40 μm or less, 39 μm or less, 37 μm or less, 35 μm or less, 33 μm or less, 31 μm or less, 30 μm or less, 29 μm or more, 27 μm or more, 25 μm or less, 23 μm or more, 20 μm or less, 17 μm or less, and 15 μm or less. When the first outer layer satisfies the thickness range, the coating layer described above can effectively prevent external contamination while maintaining an excellent level of molding.

[0079] In addition, the thickness of the second outer layer may be 10 μm or more, 12 μm or more, 15 μm or more, 17 μm or more, 20 μm or more, 40 μm or less, 37 μm or less, 35 μm or less, 30 μm or less, 27 μm or less, or 25 μm or less.

[0080] According to one embodiment of the present invention, the sealant layer may be the innermost layer of the pouch film for the exterior of the lithium secondary battery. That is, the sealant layer may come into direct contact with the battery body (e.g., electrode, separator, and / or electrolyte). Accordingly, the sealant layer must have excellent electrolyte resistance and excellent insulation properties. To this end, the sealant layer may include at least a polyolefin resin. The polyolefin resin has excellent electrolyte resistance and excellent insulation properties, and accordingly, the sealant layer containing the polyolefin resin may also have excellent electrolyte resistance and excellent insulation properties derived from the polyolefin resin.

[0081] The above polyolefin resin may include, for example, a polyolefin derived from an olefin or its derivative, a copolymer thereof, or a blend comprising at least one of these. For example, the above polyolefin resin may include one or more selected from the group consisting of polyethylene, polypropylene, polybutylene, copolymers derived from monomers derived from ethylene and / or propylene and monomers derived from alpha-olefins, or blends thereof.

[0082] The thickness of the sealant layer may, for example, be 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, or 60 μm or less, and if the above numerical range is satisfied, it may have excellent resistance to electrolytes and insulation properties.

[0083] According to one embodiment of the present invention, the sealant layer may be composed of two or more layers to diversify its functions. As a specific example, the sealant layer may include a first sealant layer disposed on the barrier layer and a second sealant layer disposed on the first sealant layer. Here, the first sealant layer may be a layer that assists in the adhesion between the barrier layer and the second sealant layer while simultaneously enhancing the function as a sealant layer, and the second sealant layer may be a layer that constitutes the innermost sealant layer of the pouch film and performs the function of sealing while simultaneously preventing leakage of a secondary battery, particularly a non-aqueous electrolyte. The first sealant layer may be an extrusion lamination coating (EC) layer (mainly an extruded polypropylene layer), and the second sealant layer may be a polypropylene (PP) layer resin, preferably an unoriented polypropylene (CPP) layer, located below the first sealant layer (inner side relative to the pouch film). In this case, for example, the thickness of the unoriented polypropylene (CPP) layer of the sealant layer may be, for example, 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, 80 μm or less, 70 μm or less, or 60 μm or less, and the thickness of the polypropylene (PP) layer of the sealant layer may be, for example, 0 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, 60 μm or less, 50 μm or less, or 40 μm or less.

[0084] In addition, according to one embodiment of the present invention, the polypropylene (PP) layer of the sealant layer may contain various additives (rubber, elastomer, lubricant, etc.) depending on the required physical properties.

[0085] Additionally, the barrier layer may be an intermediate layer of the pouch film for the exterior of the lithium secondary battery (e.g., a layer disposed between the outer layer and the sealant layer) and may serve to prevent the intrusion of gas and / or moisture. Although the type of the barrier layer is not particularly limited, it may include at least one selected from the group consisting of aluminum, stainless steel, copper, titanium, and alloys thereof, and specifically, may include aluminum.

[0086] The barrier layer may have an appropriate thickness within a range that effectively prevents the intrusion of the aforementioned gas and / or moisture while ensuring sufficient moldability. For example, the thickness of the barrier layer may be 40 μm or more, 50 μm or more, 55 μm or more, 60 μm or more, 150 μm or less, 140 μm or less, 130 μm or less, 125 μm or less, 120 μm or less, 115 μm or less, 110 μm or less, 105 μm or less, 100 μm or less, 95 μm or less, 90 μm or less, 85 μm or less, or 80 μm or less.

[0087] According to one embodiment of the present invention, the maximum moldable deformation length of the pouch film of the present invention may be 8 mm or more and 17 mm or less. For example, the maximum deformation length may be 8.0 mm or more, 8.5 mm or more, 9.0 mm or more, 9.5 mm or more, 10.0 mm or more, 10.5 mm or more, 11.0 mm or more, 11.5 mm or more, 12 mm or more, 12.5 mm or more, 13.0 mm or more, 13.5 mm or more, 14.0 mm or more, 14.5 mm or more, 15.0 mm or more, 17 mm or less, 16.5 mm or less, and 16 mm or less. The maximum forming length refers to the maximum height of the space in which an electrode assembly can be accommodated within the pouch film, and the present invention can achieve an accurate deformation length by reducing recovery force, while simultaneously achieving a maximum deformation length compared to conventional pouch films. If the maximum deformation length satisfies the above range, more electrode assemblies can be accommodated, which can have an excellent level in terms of electrical capacitance.

[0088]

[0089] Pouch-type secondary battery case and secondary battery

[0090] The secondary battery of the present invention comprises a pouch-type secondary battery case including the electrode assembly (battery body) and the pouch film laminate, wherein the electrode assembly (battery body) is sealed by the pouch-type secondary battery case. For example, the secondary battery may be a lithium secondary battery, and in this case, the battery body may include a negative electrode for a lithium secondary battery, a positive electrode for a lithium secondary battery, a separator, a current collector, and an electrolyte.

[0091] The above-mentioned cathode for a lithium secondary battery may be used without limitation as long as it is commonly used as a cathode for a lithium secondary battery. For example, the above-mentioned cathode for a lithium secondary battery may be LiCoO2, LiMnO2, LiFePO4, Li(Ni x Mny Co z It may include positive active materials such as )O2(X+Y+Z=1), LiNiCoAlO2, etc.

[0092] The above electrolyte may include a lithium salt and a non-aqueous organic solvent. Here, the lithium salt and the non-aqueous organic solvent may be used without limitation as long as they are those commonly used as electrolytes and organic solvents for lithium secondary batteries, respectively.

[0093] The above-mentioned negative electrode for a lithium secondary battery may be used without limitation as long as it is one that is conventionally used as a negative electrode for a lithium secondary battery. For example, the above-mentioned negative electrode for a lithium secondary battery may include negative electrode active materials such as carbon-based active materials and silicon-based active materials.

[0094] The above pouch-type secondary battery case can have excellent sealing strength characteristics. Therefore, the problem of the battery body sealed by the above pouch-type secondary battery case being exposed to the external environment may not occur.

[0095]

[0096] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0097]

[0098] Example 1

[0099] A pouch film was manufactured by laminating an outer layer, a barrier layer, and a sealant layer, wherein the outer layer is a laminated film of an outermost polyethylene terephthalate (PET) film (first outer layer, thickness 12 μm) and an inner nylon (Ny) film (second outer layer, thickness 25 μm), the barrier layer is aluminum (thickness 60 μm), and the sealant layer (thickness 80 μm) is manufactured by using an extrusion lamination method to include a polypropylene extrusion coating (EC) layer (thickness 30 μm) and an unoriented polypropylene film (CPP) (thickness 50 μm). During the manufacture of the polyethylene terephthalate film, an acrylic resin composition was coated on the outer surface of the polyethylene terephthalate film in an inline process to form a coating layer. Here, the acrylic resin composition used was a composition comprising 0.5 wt% cationic emulsifier, 0.3 wt% nonionic emulsifier, 18 wt% acrylate monomer, 5 wt% methacrylate monomer, 10 wt% styrene monomer, 2 wt% functional monomer, 0.8 wt% hydroxyl group-containing acrylate monomer, 0.025 wt% initiator, 0.5 wt% pH adjuster, and 62.875 wt% water.

[0100] After forming the coating layer, a stretching process (approximately 12 times) was performed. The coating raw materials used in the coating layer formation process and the thickness of the coating layer are shown in Table 1 below. In addition, lubricant A (Erucamide) and lubricant B (EBO) were added to the unoriented polypropylene film (CPP) in a ratio of 6:4 to produce 0.4 wt% based on CPP. The friction coefficients of the manufactured sealant layer and the first outer layer are shown in Table 1. Here, the surface friction coefficient was measured using a friction coefficient measuring instrument (Labsink FPT-F1 (Friction Tester)), and two samples (Sample 1 and Sample 2) were prepared for each of the first outer layer or the sealant layer. After preparing Sample 1 (TD 120mm x MD 250mm) and Sample 2 (TD 65mm x MD 120mm) by cutting them, the film of the first outer layer is prepared by cutting Sample 1 (TD 120mm x MD 250mm) and Sample 2 (TD 65mm x MD 135mm) respectively. Then, Sample 1 is fixed to the belt portion of the friction coefficient measuring instrument with the surface to be friction facing upward. Next, a 200g jig for measuring the friction coefficient is prepared (jig size: MD 70mm x TD 63mm), and Sample 2 is fixed to the jig with the surface to be measured facing downward. After placing Sample 2 so that the surfaces to be measured are in contact, it is secured to the fixing part of the jig with a fishing line, and the friction coefficient is measured as the belt moves. The speed is 100 mm / min. The measurement distance is 100 m, and the dynamic friction coefficient is checked at this time.

[0101]

[0102] Examples 2 to 6

[0103] A pouch film was manufactured in the same manner as Example 1 above, except that the thickness of the coating layer, the coating method, the ratio of lubricant A and lubricant B, and the total lubricant content were different as described in Table 1 below.

[0104]

[0105] Comparative Examples 1 to 7

[0106] A pouch film was manufactured in the same manner as Example 1 above, except that the thickness of the coating layer, the coating method, the ratio of lubricant A and lubricant B, and the total lubricant content were different as described in Table 1 below.

[0107]

[0108] Experimental Example 1 - R-value evaluation

[0109] For the pouch films prepared in the above examples and comparative examples, a specimen was prepared with dimensions of MD 240 mm X TD 266 mm, and molding was performed using a 1-Cup molding machine with an R value of 4. The cup portion was molded to a size of 155 mm X 85 mm, and the pressure was set to 0.3 MPa. After molding, the R value was measured using a 3D shape analyzer (non-contact, Micro-vu EXCEL 501UC). Specifically, the corner portion of the cup sample was cut and fixed using double-sided tape. The optical focus of the 3D shape analyzer (non-contact, Micro-vu EXCEL 501UC) was aligned with the measurement area of ​​the sample, and a measurement range was set to perform scanning. The scan data was output in a 3D format including the height change of the corner portion, imported into software, and the radius of curvature of the corner portion was calculated. Specifically, the corner portion cross-section was selected in the software, the cross-sectional curve was extracted, and a circular fitting was performed on the curve to record the radius of the circle as the R value. The above measurement was repeated 3 to 5 times to derive the average value of the R value. When the R value was measured, it was evaluated as A if it was 1.0 or higher and 2.0 or lower, B if it was greater than 2.0 and 2.5 or lower, and C if it was greater than 2.6 and 4.0 or lower. The lower the R value, the more the desired corner portion of the cup can be realized after molding.

[0110]

[0111] Experimental Example 2 - Moldability Evaluation

[0112] For the pouch films prepared in the above examples and comparative examples, specimens were prepared with dimensions of MD 240 mm X TD 266 mm, and molding was performed using a 1 Cup molding machine with an R value of 4. The cup portion was molded to a size of 155 mm X 85 mm, and the pressure was set to 0.3 MPa. The moldability of the pouch films in the above examples and comparative examples was evaluated at a depth of 12 mm. Molding was repeated 10 times at each depth, and it was judged as NG if it broke even once, and OK if it succeeded in molding all 10 times.

[0113]

[0114] Classification Sealant Layer 1 Outer Layer Friction Coefficient R Value ** Molding 12mm Lubricant A: Lubricant B Weight Ratio Total Lubricant Content Coating Type Coating Thickness (㎛) Coating Method Sealant Layer * 1st outer layer *Example 13: 70.33 wt% acrylic 0.03 inline coating BCAOK Example 23: 70.33 wt% acrylic 0.8 inline coating BCAOK Example 33: 70.33 wt% acrylic 0.3 inline coating BCAOK Example 44: 60.33 wt% acrylic 0.07 inline coating BCAOK Example 55: 50.33 wt% acrylic 0.07 inline coating BCAOK Example 63: 70.5 wt% acrylic 0.07 inline coating BCAOK Comparative Example 13: 70.33 wt% none inline coating BBQOK Comparative Example 23: 70.33 wt% acrylic 1.5 inline coating BCAN.G Comparative Example 33: 70.33 wt% acrylic 1.1 post-treatment Coating BCAN.G Comparative Example 43: 70.33 wt% Acrylic 2.5 Post-treatment Coating BCAN.G Comparative Example 53: 70.33 wt% Acrylic 5 Post-treatment Coating BCAN.G Comparative Example 6 None None Acrylic 0.07 In-line Coating CCAN,G Comparative Example 7 10: 00.33 Wt% Acrylic 0.07 In-line Coating ACCOK Comparative Example 80: 100.33 Wt% Acrylic 0.07 In-line Coating BCBN.G* Coefficient of Friction - A: 0.1 or more, less than 0.15, B: 0.15 or more, 0.20 or less, C: 0.20 or more, 0.40 or less** R-value - A: 1.0 or more, 2.0 or less, B: 2.0 or more, 2.5 or less, C: 2.6 or more, 4.0 or less

[0115] Referring to Table 1 above, in the case of an example in which the sealant layer includes a lubricant having a low melting point and a lubricant having a high melting point, and at the same time, a coating layer is formed on the first outer layer and the thickness of the coating layer satisfies the scope of the present invention, both the R value and moldability were excellent. On the other hand, in the case of Comparative Example 1, which does not include a coating layer, and Comparative Examples 2 to 5, which include a coating layer but fall outside the thickness range of the coating layer of the present invention, it can be confirmed that although the R value is low, the moldability is significantly reduced, making actual commercialization difficult. Furthermore, in the case of Comparative Example 6, which does not include a lubricant, and Comparative Examples 7 and 8, which do not include both lubricants A and B, it can be confirmed that both the R value and moldability are inferior.

[0116]

[0117] Acknowledgement

[0118]

[0119] [Project ID] 2410004468

[0120] [Assignment No.] 20022450

[0121] [Ministry Name] Ministry of Trade, Industry and Energy

[0122] [Project Management (Specialized) Agency Name] Korea Institute of Industrial Technology Planning and Evaluation

[0123] [Research Project Name] Development of Materials and Components Technology (Leading Company)

[0124] [Project Title] Development of Next-Generation Secondary Battery Pouch Capable of Achieving More Than Twice the High Adhesion Strength (60℃)

[0125] [Contribution Rate] 1 / 1

[0126] [Name of Project Performing Organization] Yulchon Chemical Co., Ltd.

[0127] [Research Period] 2024-01-01 ~ 2024-12-31

[0128]

[0129] Acknowledgement 2

[0130] [Project ID] 2410013070

[0131] [Assignment No.] 20022450

[0132] [Ministry Name] Ministry of Trade, Industry and Energy

[0133] [Project Management (Specialized) Agency Name] Korea Institute of Industrial Technology Planning and Evaluation

[0134] [Research Project Name] Development of Materials and Components Technology (Leading Company)

[0135] [Project Title] Development of Next-Generation Secondary Battery Pouch Capable of Achieving More Than Twice the High Adhesion Strength (60℃)

[0136] [Contribution Rate*] 1 / 1

[0137] [Name of Project Performing Organization] Yulchon Chemical Co., Ltd.

[0138] [Research Period] 2025-01-01 ~ 2025-12-31

Claims

1. Includes a sealant layer, a barrier layer, a second outer layer, and a first outer layer stacked sequentially, The outer surface of the first outer layer includes a coating layer, The thickness of the coating layer is 0.01 μm or more and 1.0 μm or less, and The sealant layer comprises lubricant A having a melting point of 70°C or higher and 125°C or lower, and lubricant B having a melting point of 125°C or higher and 150°C or lower, and A pouch film having a dynamic friction coefficient of the sealant layer measured according to the measurement method below, which is 0.15 or higher and 0.4 or lower. [measurement method] After preparing the film of the first outer layer by cutting it into Sample 1 (TD 120 mm x MD 250 mm) and Sample 2 (TD 65 mm x MD 135 mm), fix Sample 1 to the belt portion of the friction coefficient measuring instrument with the surface to be friction facing upward. Then, prepare a 200 g jig for measuring the friction coefficient (jig size: MD 70 mm x TD 63 mm) and fix Sample 2 to the jig with the surface to be measured facing downward. After placing Sample 2 so that the surfaces to be measured make contact, secure it to the fixing part of the jig with a fishing line so that the belt moves to measure the friction coefficient. The speed is 100 mm / min. The measurement distance is 100 m, and the dynamic friction coefficient is checked at this time.

2. In Claim 1, A pouch film in which the weight ratio of the above lubricant A and lubricant B is 1:1 or greater and 9 or less.

3. In Claim 1, A pouch film in which the sealant layer comprises the lubricant A and lubricant B in a total content of 0.01% by weight or more and 0.5% by weight or less.

4. In Claim 1, The above coating layer is a pouch film comprising an acrylic resin.

5. In Claim 1, The above coating layer comprises one or more polymers polymerized from one or more monomers selected from the group consisting of acrylate monomers, methacrylate monomers, acrylate monomers containing hydroxyl groups, and styrene monomers.

6. In Claim 1, A pouch film wherein the above-mentioned lubricant A comprises one or more substances selected from the group consisting of erucamide, oleamide, stearamide, and behenamide.

7. In Claim 1, A pouch film in which the above lubricant B comprises one or more substances selected from the group consisting of ethylene bisoleamide and ethylene bissteramide.

8. In Claim 1, A pouch film having a surface kinetic friction coefficient of the first outer layer measured according to the measurement method below, which is 0.20 or higher and 0.40 or lower. [measurement method] After preparing the film of the first outer layer by cutting it into Sample 1 (TD 120 mm x MD 250 mm) and Sample 2 (TD 65 mm x MD 135 mm), fix Sample 1 to the belt portion of the friction coefficient measuring instrument with the surface to be friction facing upward. Then, prepare a 200 g jig for measuring the friction coefficient (jig size: MD 70 mm x TD 63 mm) and fix Sample 2 to the jig with the surface to be measured facing downward. After placing Sample 2 so that the surfaces to be measured make contact, secure it to the fixing part of the jig with a fishing line so that the belt moves to measure the friction coefficient. The speed is 100 mm / min. The measurement distance is 100 m, and the dynamic friction coefficient is checked at this time.

9. In Claim 1, The above coating layer is a pouch film formed within an in-line process of a first outer layer.

10. In Claim 1, A pouch film comprising one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber.

11. In Claim 1, A pouch film having a thickness of 5 μm or more and 40 μm or less of the first outer layer.

12. A pouch-type battery case comprising a pouch film according to claim 1.

13. An electrode assembly formed by stacking an anode, a separator, and a cathode; and A secondary battery comprising a pouch-type battery case according to claim 12 that accommodates the electrode assembly.

Images