Method for manufacturing pouch film, pouch film, and pouch-type battery case comprising same

Abstract

The present invention relates to: a method for manufacturing a pouch film by which a pouch film can be manufactured having excellent high-temperature heat seal strength and insulation resistance by controlling the input amount and dispersion degree of a polyolefin-based elastomer, and by adjusting the length of a mixing unit of an extruder to easily control the dispersion degree and average particle diameter of the polyolefin-based elastomer; and a pouch film having improved chemical resistance and high-temperature stability by including a pre-determined content of polyolefin-based elastomer having an average particle diameter within a specific range.

Description

Method for manufacturing pouch film, pouch film, pouch-type battery case including same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0194084, filed December 28, 2023, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

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

[0006]

[0007] Secondary batteries can be repeatedly charged and discharged, and can be classified into cylindrical secondary batteries, square secondary batteries, and pouch-type secondary batteries depending on their structure and manufacturing method. Among these, pouch-type secondary batteries include a battery body (e.g., electrodes, separator, and / or electrolyte) and a pouch film that covers the battery body. Because of their relatively simple structure and relatively large capacity per unit volume, they are widely used in energy storage devices such as automobile batteries.

[0008] A method of enclosing a battery body with a pouch film generally involves bringing the innermost layers of the pouch films (e.g., sealant layers) into contact with each other, then applying heat and pressure to the innermost layers to thermally bond them together to form a seal, thereby sealing the battery body. In this way, a battery body sealed with a pouch film may not be substantially exposed to the external environment.

[0009] Meanwhile, to prevent the battery body from being exposed to the external environment, the pouch film is required to have excellent sealing properties, and in particular, excellent sealing properties are required to be maintained under various environmental conditions. This is because exposure of the battery body to the external environment may result in problems such as a decline in the function of the pouch-type secondary battery or an explosion.

[0010] Here, the sealability and retention characteristics of the pouch film can be evaluated by the sealing strength of the pouch film. Sealing strength is an indicator of the superiority of the thermal bonding strength at the sealing portion of the pouch film. If the sealing strength of the pouch film is excellent, the sealability of the pouch film can generally be considered excellent.

[0011] Meanwhile, conventional pouch films have struggled to ensure sufficient thermal bonding strength at the sealing portion, and research into improving this strength has been limited. Conventional pouch films have struggled to ensure sufficient sealing strength, and venting of the thermally bonded sealing portion frequently occurs. Therefore, research is underway to develop pouch films with enhanced chemical resistance and high-temperature stability, and particularly superior thermal bonding strength and insulation resistance at high temperatures.

[0012]

[0013] The problem to be solved by the present invention is to provide a method for manufacturing a pouch film having excellent high-temperature thermal bonding strength and insulation resistance, a pouch film, and a pouch-type secondary battery case including the same.

[0014]

[0015] The present invention provides a method for manufacturing a pouch film, a pouch film, and a pouch-type battery case including the same.

[0016] (1) The present invention provides a method for manufacturing a pouch film, comprising the steps of (S1) supplying a polyolefin resin and a polyolefin elastomer to an extruder to produce a sealant layer, (S2) bonding the sealant layer to one surface of a barrier layer including aluminum, and (S3) bonding an outer layer to the other surface of the barrier layer, wherein the polyolefin elastomer is supplied in an amount of 7 wt% or more and 30 wt% or less relative to the total resin of the sealant layer, and the extruder includes a mixing section, wherein the length of the mixing section is 6% or more and 10% or less relative to the total length of the extruder.

[0017] (2) The present invention provides a method for manufacturing a pouch film, wherein in the above (1), the step (S1) includes a step of dispersing the polyolefin elastomer in the polyolefin resin by the mixing unit.

[0018] (3) The present invention provides a method for manufacturing a pouch film, wherein, in the above (2), the average particle diameter of the polyolefin elastomer dispersed in the polyolefin resin is 30 nm or more and 150 nm or less.

[0019] (4) The present invention provides a method for manufacturing a pouch film, wherein the step (S2) is performed by an extrusion lamination method in any one of the above (1) to (3).

[0020] (5) The present invention provides a method for manufacturing a pouch film, further comprising an extrusion bonding coating layer containing a polyolefin resin between the barrier layer and the sealant layer in the above (4).

[0021] (6) The present invention provides a method for manufacturing a pouch film, wherein in any one of the above (1) to (5), the polyolefin-based resin comprises at least one selected from the group consisting of a copolymer derived from a monomer derived from polyethylene, polypropylene, polybutylene, ethylene and / or propylene and an alpha-olefin-derived monomer, or a mixture thereof.

[0022] (7) The present invention provides a method for manufacturing a pouch film, wherein, in any one of the above (1) to (6), the polyolefin-based elastomer is supplied in an amount of 10 wt% or more and 20 wt% or less relative to the total resin of the sealant layer.

[0023] (8) The present invention provides a pouch film comprising: a sequentially laminated outer layer; a barrier layer comprising aluminum; and an inner layer, wherein the inner layer comprises a first sealant layer disposed on the barrier layer, and a second sealant layer disposed on the first sealant layer, wherein the first sealant layer and the second sealant layer each independently comprise a matrix resin; and a domain resin contained in the matrix resin, wherein the content of the domain resin in the second sealant layer is 10 wt% or more and 20 wt% or less relative to the total resin of the second sealant layer, and wherein the average particle diameter of the domain resin in the second sealant layer is 30 nm or more and 150 nm or less.

[0024] (9) The present invention provides a pouch film in which, in the above (8), the average particle diameter of the domain resin in the second sealant layer is 50 nm or more and 125 nm or less.

[0025] (10) The present invention provides a pouch film according to (8) or (9), wherein the matrix resin includes a polyolefin resin.

[0026] (11) The present invention provides a pouch film in which the domain resin comprises at least one material selected from the group consisting of an ethylene-propylene copolymer (EPR)-based elastomer resin, an ethylene-butene copolymer (EBR)-based elastomer resin, an ethylene-hexene copolymer (EHR)-based polyolefin elastomer resin, an ethylene-octene copolymer (EOR)-based polyolefin elastomer resin, a propylene-butene copolymer (PBR)-based polyolefin elastomer resin, a propylene-hexene copolymer (PHR)-based polyolefin elastomer resin, a propylene-octene copolymer (POR)-based polyolefin elastomer resin, an LLDPE-based elastomer resin, and a thermoplastic polyurethane (TPU) elastomer resin.

[0027] (12) The present invention provides a pouch film according to any one of the above (8) to (11), wherein the outer layer comprises polyethylene terephthalate.

[0028] (13) The present invention provides a pouch film having a thermal bonding strength of 130 N / 15 mm or more under the following condition 1 in any one of the above (8) to (12), and a thermal bonding strength reduction rate according to the following formula 1 of 35% or less.

[0029] [Condition 1]

[0030] After thermally bonding the pouch film with the sealant layers under the conditions of 200 ℃, 0.2 Mpa, and 2 sec, the specimens were cut to a width of 15 mm to manufacture the specimens, and the specimens were fixed between two jigs of a tensile tester (UTM) under room temperature conditions (initial jig gap (30 mm)), and the peel strength was measured at a peel angle of 180° at a peel speed of 50 mm / min.

[0031]

[0032] [Formula 1]

[0033] Thermal bonding strength reduction rate = 100 - (thermal bonding strength at room temperature / thermal bonding strength at 60 ℃) x 100

[0034] In equation 1,

[0035] The thermal bonding strength at the above room temperature is the peel strength measured under the above condition 1,

[0036] The thermal bonding strength at 60°C above is the peel strength measured at a peeling angle of 180° at a peeling speed of 50 mm / min after thermally bonding the sealant layers of the pouch film under the conditions of 200°C, 0.2 Mpa, and 2 sec, cutting the pouch film into a 15 mm wide specimen, fixing the specimen between two jigs of a tensile tester (UTM) under a temperature condition of 60°C (initial jig gap (30 mm)).

[0037] (14) The present invention provides a pouch-type secondary battery case including a pouch film according to any one of the above (8) to (13).

[0038]

[0039] The pouch film manufacturing method of the present invention can manufacture a pouch film having excellent high-temperature heat-sealing strength and insulation resistance by controlling the amount and degree of dispersion of a polyolefin-based elastomer.

[0040] The present invention relates to a method for manufacturing a foam film, which can simply control the dispersion and average particle size of a polyolefin elastomer by adjusting the length of a mixing section of an extruder.

[0041] The pouch film of the present invention can have the effect of improving chemical resistance and high-temperature stability by including a polyolefin-based elastomer having an average particle diameter of a specific range in a certain amount.

[0042]

[0043] Figure 1 (a) is a schematic diagram of an extruder used in manufacturing a pouch film according to an example, and (b) is a schematic diagram of an extruder used in manufacturing a pouch film according to a comparative example.

[0044] Figure 2 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Example 1 of the present invention.

[0045] Figure 3 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Example 2 of the present invention.

[0046] Figure 4 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Example 3 of the present invention.

[0047] Figure 5 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Comparative Example 1 of the present invention.

[0048] Figure 6 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Comparative Example 2 of the present invention.

[0049] Figure 7 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Comparative Example 5 of the present invention.

[0050]

[0051] Hereinafter, the present invention will be described in more detail to facilitate understanding. The terms and words used in this specification and claims should not be interpreted based on their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0052] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0053] In this specification, it should be understood that the terms “include,” “comprising,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0054]

[0055] Pouch film manufacturing method

[0056] The present invention provides a method for manufacturing a pouch film, comprising the steps of (S1) supplying a polyolefin resin and a polyolefin elastomer to an extruder to produce a sealant layer, (S2) bonding the sealant layer to one surface of a barrier layer including aluminum, and (S3) bonding an outer layer to the other surface of the barrier layer, wherein the polyolefin elastomer is supplied in an amount of 7 wt% or more and 30 wt% or less relative to the total resin of the sealant layer, and the extruder includes a mixing section, wherein the length of the mixing section is 6% or more and 10% or less relative to the total length of the extruder.

[0057] The method for manufacturing a pouch film of the present invention comprises a step (S1) of supplying a polyolefin-based resin and a polyolefin-based elastomer to an extruder to manufacture a sealant layer. The sealant layer may be the innermost layer of the pouch film for external use in a secondary battery. That is, the sealant layer may be in direct contact with a battery main body (e.g., an electrode, a separator, and / or an electrolyte). Therefore, the sealant layer must have excellent electrolyte resistance and excellent insulation. To this end, the sealant layer may include at least a polyolefin-based resin.

[0058] In addition, the polyolefin-based resin may include, for example, a polyolefin derived from an olefin or a derivative thereof, a copolymer thereof, or a blend comprising at least one of the foregoing. For example, the polyolefin-based resin may include at least one selected from the group consisting of polyethylene, polypropylene, polybutylene, a copolymer derived from a monomer derived from ethylene and / or propylene and a monomer derived from an alpha-olefin, or a blend thereof.

[0059] In addition, the sealant layer includes a polyolefin-based elastomer in addition to the polyolefin-based resin. The polyolefin-based elastomer can modify the surface of the sealant layer and change the mechanical strength and chemical properties of the sealant layer. The polyolefin-based elastomer can function as a domain resin within the sealant layer.

[0060] According to one embodiment of the present invention, the polyolefin-based elastomer is supplied to the extruder in an amount of 7 wt% or more and 30 wt% or less relative to the total resin of the sealant layer. For example, the polyolefin-based elastomer may be supplied to the extruder in an amount of 7 wt% or more, 8 wt% or more, 9 wt% or more, 10 wt% or more, 11 wt% or more, 12 wt% or more, 13 wt% or more, 14 wt% or more, 30 wt% or less, 27 wt% or less, 25 wt% or less, 23 wt% or less, 21 wt% or less, 20 wt% or less, 19 wt% or less, 18 wt% or less, 17 wt% or less, 16 wt% or less, or 15 wt% or less relative to the total resin of the sealant layer. Specifically, the polyolefin-based elastomer may be supplied in an amount of 10 wt% or more and 20 wt% or less. The content of polyolefin and polyolefin-based elastomer as materials supplied to the extruder during the manufacture of the above sealant layer is an important factor in changing the mechanical and chemical properties. If the amount of polyolefin-based elastomer supplied is outside the lower limit of the above numerical range, the thermal bonding strength and insulation resistance characteristics at high temperatures may deteriorate. In addition, if the amount of polyolefin-based elastomer supplied is outside the upper limit of the above numerical range, the thermal bonding strength may be improved, but the insulation resistance characteristics may be significantly deteriorated.

[0061] According to one embodiment of the present invention, the extruder includes a mixing section, and the length of the mixing section may be 6% or more and 10% or less of the total length of the extruder. In addition, the step (S1) may include a step of dispersing the polyolefin elastomer within the polyolefin resin by the mixing section.

[0062] Referring to Fig. 1, (a) of Fig. 1 schematically illustrates an extruder used in manufacturing a pouch film according to an embodiment, and (b) of Fig. 1 schematically illustrates an extruder used in manufacturing a pouch film according to a comparative example. In (a) of Fig. 1, it can be seen that the length of the mixing section is shorter than in (b) of Fig. 1. The extruder may include a supply section (10), a melting section (20), a mixing section (30), and a metering section (40). A method for manufacturing a sealant through the extruder is as follows. First, the polyolefin-based resin and the polyolefin-based elastomer are supplied to the supply section (10). Here, the average particle diameter of the supplied polyolefin-based elastomer may be 2 mm to 3 mm. Thereafter, a melting process of the polyolefin-based resin and the polyolefin-based elastomer supplied from the melting section (20) is performed. A screw rod is arranged in the above melting unit (20) so that a mixing process of the polyolefin-based resin and the polyolefin-based elastomer can be performed. The polyolefin-based resin and the polyolefin-based elastomer can be transferred to a mixing unit after passing through the melting unit (20). The mixing unit can perform a secondary mixing process so that the polyolefin-based elastomer in the polyolefin-based resin can be dispersed as a domain resin. In particular, since the degree of dispersion and the average particle size modify the surface of a sealant layer to be manufactured later and affect the mechanical and chemical properties, it is important to control the length ratio of the mixing unit so that the polyolefin-based elastomer in the polyolefin-based resin has a desired degree of dispersion and a desired average particle size.

[0063] The length of the above mixing section (30) may be 6% or more and 10% or less of the entire length of the extruder. Specifically, the length of the above mixing section may be 6.0% or more, 6.3% or more, 6.5% or more, 6.7% or more, 6.9% or more, 7.0% or more, 7.2% or more, 7.4% or more, 7.5% or more, 7.7% or more, 7.9% or more, 8.0% or more, 10.0% or less, 9.7% or less, 9.5% or less, 9.3% or less, 9.2% or less, 9.0% or less, 8.7% or less, 8.5% or less, 8.3% or less, 8.1% or less, 8.0% or less, 7.9% or less, 7.7% or less, 7.5% or less of the entire length of the extruder. If the length ratio of the above mixing section is outside the upper limit of the above numerical range, the polyolefin elastomer may be excessively dispersed, the average particle size may be too small, the degree of surface modification of the manufactured sealant layer may be minimal, and the chemical resistance characteristics may be deteriorated. In addition, if the length ratio of the above mixing section is outside the upper limit of the above numerical range, the polyolefin elastomer may not be smoothly dispersed, which may correspond to a level that is inferior in thermal bonding strength.

[0064] The supply amount of the polyolefin-based elastomer and the length ratio of the mixing section are not independent conditions or elements, but are in an organically linked relationship that must be satisfied in order to control the dispersion and average particle size of the polyolefin-based elastomer in the polyolefin-based resin. That is, the present invention satisfies all of the above conditions in order to control the dispersion and average particle size of the polyolefin-based elastomer in the polyolefin-based resin, and the sealant layer manufactured therefrom and the pouch film including the same can have high chemical resistance and high-temperature stability.

[0065] According to one embodiment of the present invention, the average particle diameter of the polyolefin elastomer dispersed in the polyolefin resin may be 30 nm or more and 150 nm or less. As described above, the average particle diameter of the polyolefin elastomer initially supplied to the supply unit (10) may be 2 mm to 3 mm. As the mixing and dispersion process proceeds in the mixing unit after passing through the melting unit (20), the polyolefin elastomer may be dispersed in the polyolefin resin with an average particle diameter of 30 nm or more and 150 nm or less.

[0066] Specifically, the average particle diameter of the polyolefin elastomer dispersed in the polyolefin resin is 30 nm or more, 31 nm or more, 33 nm or more, 35 nm or more, 37 nm or more, 39 nm or more, 40 nm or more, 42 nm or more, 45 nm or more, 47 nm or more, 49 nm or more, 50 nm or more, 51 nm or more, 53 nm or more, 55 nm or more, 57 nm or more, 59 nm or more, 60 nm or more, 61 nm or more, 63 nm or more, 65 nm or more, 67 nm or more, 69 nm or more, 70 nm or more, 71 nm or more, 150 nm or less, 149 nm or less, 147 nm or less, 145 nm or less, 143 nm or less, 141 nm or less, 140 nm or less, 137 nm or less, 135 nm or less, 133 nm or less, 131 nm or less, 130 nm or less, 127 nm or less, 125 nm or less, 123 nm or less, 120 nm or less, 117 nm or less, 115 nm or less, 113 nm or less, 110 nm or less, 107 nm or less, 105 nm or less, 103 nm or less, 100 nm or less, 98 nm or less, 95 nm or less, 93 nm or less, 91 nm or less, 90 nm or less. When the average particle diameter of the polyolefin-based elastomer satisfies the above numerical range, the chemical resistance of the pouch film can be improved, and the heat-sealing strength at high temperatures can be improved. The above average particle diameter can be calculated by the arithmetic mean method based on the major axis of each domain resin based on a photograph measured through a TEM (transmission electron microscope).Specifically, FIG. 2 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Example 1 of the present invention, FIG. 3 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Example 2 of the present invention, FIG. 4 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Example 3 of the present invention, FIG. 5 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Comparative Example 1 of the present invention, FIG. 6 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Comparative Example 2 of the present invention, and FIG. 7 is a TEM photograph of the surface of the sealant layer (CPP layer) in the pouch film of Comparative Example 5 of the present invention. The average particle diameter of each domain resin can be calculated by the arithmetic mean method based on the major diameter of the domain resin shown in the TEM photographs.

[0067] The method for manufacturing a pouch film of the present invention includes a step (S2) of adhering the sealant layer to one surface of a barrier layer containing aluminum and a step (S3) of adhering an outer layer to the other surface of the barrier layer.

[0068] According to one embodiment of the present invention, the step (S2) may be performed using an extrusion lamination method. For example, the method of laminating the sealant layer to the barrier layer may be performed using an extrusion lamination (hereinafter abbreviated as EC) method and a solvent-dry lamination (hereinafter abbreviated as SDL) method.

[0069] The above solvent dry lamination method is a method of bonding a barrier layer (metal layer) on a polypropylene (PP) layer using a solvent-based adhesive and drying the solvent-based adhesive, so that the sealant layer manufactured thereby is made of a polypropylene (PP) layer.

[0070] The above extrusion lamination method is a method of extruding a polyolefin resin, preferably a polypropylene resin, when adhering a polypropylene-based resin layer, preferably a non-stretched polypropylene (CPP) film, which is mainly used in the sealant layer, to a barrier layer (metal layer). As a result, the sealant layer is composed of an extrusion lamination coating (abbreviated as EC) layer (mainly an extruded polypropylene layer) and a polypropylene (PP) layer resin, preferably a non-stretched polypropylene (CPP) layer, underneath it (on the inner side based on the pouch film). Here, the extrusion lamination coating layer may be a layer that assists in the adhesion of the barrier layer and the non-stretched polypropylene (CPP) layer, while further enhancing its function as an inner layer, and the non-stretched polypropylene (CPP) layer may be a layer that constitutes the innermost inner layer of the pouch film, and may be a layer that performs the function of preventing leakage of a secondary battery, particularly a non-aqueous electrolyte, while sealing.

[0071] In the case of the method for manufacturing the pouch film of the present invention, a pouch film having improved chemical resistance, excellent electrolyte peel strength, and excellent insulation resistance can be provided by manufacturing it using an extrusion lamination method.

[0072] According to one embodiment of the present invention, when the sealant layer includes the extrusion bonding coating layer formed by the extrusion lamination method described above and the non-stretched polypropylene layer, the ratio of the thickness of the non-stretched polypropylene layer to the sum of the thickness of the extrusion bonding coating layer and the thickness of the non-stretched polypropylene layer may be 1:0.5 to 0.99, 1:0.55 to 0.90, 1:0.57 to 0.79, or 1:0.60 to 0.72. Here, when the thickness ratio satisfies the numerical range described above, the adhesive strength with the barrier layer can be sufficiently secured, and further, the thermal bonding strength and insulation resistance characteristics of the sealant layer can be further improved.

[0073] Meanwhile, the extrusion bonding coating layer may contain a polyolefin-based elastomer resin in an amount of 15 wt% to 25 wt% based on the total resin, and the average particle diameter of the polyolefin-based elastomer resin may be 80 nm to 85 nm. In the method for manufacturing the pouch film of the present invention, by controlling the dispersion and average particle diameter of the elastomer in the non-stretched polypropylene layer while maintaining the dispersion and average particle diameter of the elastomer in the extrusion bonding coating layer constant, chemical resistance and high-temperature retention can be improved.

[0074]

[0075] pouch film

[0076] Hereinafter, the pouch film of the present invention will be described. Common portions with those described in the manufacturing method of the pouch film described above will be omitted.

[0077] The present invention provides a pouch film comprising: a sequentially laminated outer layer; a barrier layer comprising aluminum; and an inner layer, wherein the inner layer comprises a first sealant layer disposed on the barrier layer, and a second sealant layer disposed on the first sealant layer, wherein the first sealant layer and the second sealant layer each independently comprise a matrix resin; and a domain resin contained in the matrix resin, wherein the content of the domain resin in the second sealant layer is 10 wt% or more and 20 wt% or less relative to the total resin of the second sealant layer, and wherein the average particle diameter of the domain resin in the second sealant layer is 30 nm or more and 150 nm or less.

[0078] According to one embodiment of the present invention, the inner layer may be composed of a laminate of two or more layers in terms of diversifying functions. As a specific example, the inner 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 adhesion between the barrier layer and the second sealant layer, while further enhancing the function as an inner layer, and the second sealant layer may be a layer that constitutes the innermost inner layer of the pouch film laminate, and may be a layer that simultaneously seals and prevents leakage of a secondary battery, particularly a non-aqueous electrolyte. As described above, 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 a non-stretched polypropylene (CPP) layer, disposed under the first sealant layer (inner side based on the pouch film).

[0079] According to one embodiment of the present invention, a pouch film is provided in which the average particle diameter of the domain resin in the second sealant layer is 50 nm or more and 125 nm or less. As described above, the pouch film of the present invention includes a matrix resin including a polyolefin-based resin and a domain resin including a polyolefin-based elastomer resin, and the content of the domain resin satisfies the numerical range, and the average particle diameter of the domain resin satisfies the numerical range, thereby having excellent heat bonding strength and insulation resistance characteristics, high chemical resistance characteristics, and high temperature stability.

[0080] According to one embodiment of the present invention, a pouch film is provided in which the matrix resin comprises a polyolefin-based resin. Specifically, the matrix resin may be a polypropylene-based resin, and more specifically, a non-stretched polypropylene-based resin.

[0081] According to one embodiment of the present invention, a pouch film is provided, wherein the domain resin includes at least one material selected from the group consisting of an ethylene-propylene copolymer (EPR)-based elastomer resin, an ethylene-butene copolymer (EBR)-based elastomer resin, an ethylene-hexene copolymer (EHR)-based polyolefin elastomer resin, an ethylene-octene copolymer (EOR)-based polyolefin elastomer resin, a propylene-butene copolymer (PBR)-based polyolefin elastomer resin, a propylene-hexene copolymer (PHR)-based polyolefin elastomer resin, a propylene-octene copolymer (POR)-based polyolefin elastomer resin, an LLDPE-based elastomer resin, and a thermoplastic polyurethane (TPU) elastomer resin. Specifically, to improve the chemical resistance and high temperature safety of the sealant film, a polypropylene-based elastomer resin is more appropriate, and thus, the domain resin may include a polyolefin-based elastomer resin.

[0082] The outer layer may be the outermost layer of the pouch film and may include a heat-resistant resin layer having a melting point higher than the heat-bonding temperature of the sealant layer. The heat-resistant resin layer may include any one selected from the group consisting of polyamide, polyester, polyolefin, copolymers thereof, and blends thereof. Here, the outer layer may have a single-layer or multi-layer structure including at least one of the aforementioned materials.

[0083] The outer layer may have an appropriate thickness within a range that can secure sufficient mechanical strength and sufficient formability as an exterior material. For example, the thickness of the outer layer may be 15 μm or more, 20 μm or more, 25 μm or more, 35 μm or more, 140 μm or less, 110 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 50 μm or less, or 40 μm or less. When the above range is satisfied, the insulation breakdown voltage can be maintained at a high level.

[0084] According to one embodiment of the present invention, a pouch film is provided, wherein the outer layer comprises polyethylene terephthalate. Specifically, the outer layer may be formed of a laminated film of nylon and polyethylene terephthalate (PET). In this case, the thinner the PET film, and the thicker the nylon film, the more advantageous the formability. However, the thinner the PET film may be in terms of insulation breakdown voltage. From this point of view, for example, the thickness of the nylon layer may be 10 ㎛ or more, 12 ㎛ or more, 15 ㎛ or more, 20 ㎛ or more, 40 ㎛ or less, 35 ㎛ or less, or 30 ㎛ or less, and the thickness of the PET layer may be 5 ㎛ or more, 8 ㎛ or more, 10 ㎛ or more, 30 ㎛ or less, 25 ㎛ or less, or 20 ㎛ or less.

[0085] The barrier layer may be an intermediate layer of the pouch film (e.g., a layer positioned between the outer layer and the sealant layer) and may serve to prevent the intrusion of gas and / or moisture. The barrier layer may include, but is not particularly limited to, at least one selected from the group consisting of aluminum, stainless steel, copper, titanium, and alloys thereof, and preferably may include aluminum.

[0086] The above barrier layer may have an appropriate thickness within a range that can effectively prevent the intrusion of the aforementioned gas and / or moisture while ensuring sufficient formability. For example, the thickness of the barrier layer may be 20 ㎛ or more, 30 ㎛ or more, 40 ㎛ or more, 50 ㎛ or more, 55 ㎛ or more, 60 ㎛ or more, 150 ㎛ or less, 140 ㎛ or less, 130 ㎛ or less, 125 ㎛ or less, 120 ㎛ or less, 110 ㎛ or less, 100 ㎛ or less, or 90 ㎛ or less.

[0087] The sealant layer may be the innermost layer of the pouch film. That is, the sealant layer may be in direct contact with the battery main body (e.g., electrode, separator, and / or electrolyte). Therefore, the sealant layer must have excellent electrolyte resistance and excellent insulation. The thickness of the sealant layer may be, for example, 20 ㎛ or more, 30 ㎛ or more, 40 ㎛ or more, 50 ㎛ or more, 80 ㎛ or less, 70 ㎛ or less, or 60 ㎛ or less, and when the above numerical range is satisfied, excellent electrolyte resistance and insulation may be achieved.

[0088]

[0089] According to one embodiment of the present invention, the thermal bonding strength under the following condition 1 may be 130 N / 15 mm or more, and the thermal bonding strength reduction rate according to the following equation 1 may be 35% or less.

[0090] [Condition 1]

[0091] After thermally bonding the pouch film with the sealant layers under the conditions of 200 ℃, 0.2 Mpa, and 2 sec, the specimens were cut to a width of 15 mm to manufacture specimens, and the specimens were fixed between two jigs of a tensile tester (UTM) under room temperature conditions (initial jig gap (30 mm), and then the peel strength was measured at a peel angle of 180° at a peel speed of 50 mm / min.

[0092] [Formula 1]

[0093] Thermal bonding strength reduction rate = 100 - (thermal bonding strength at room temperature / thermal bonding strength at 60 ℃) x 100

[0094] In equation 1,

[0095] The thermal bonding strength at the above room temperature is the peel strength measured under the above condition 1,

[0096] The thermal bonding strength at 60°C above is the peel strength measured at a peeling angle of 180° at a peeling speed of 50 mm / min after thermally bonding the sealant layers of the pouch film under the conditions of 200°C, 0.2 Mpa, and 2 sec, cutting the pouch film into a 15 mm wide specimen, fixing the specimen between two jigs of a tensile tester (UTM) under a temperature condition of 60°C (initial jig gap (30 mm)).

[0097] Here, the thermal bonding strength according to the above condition 1 refers to the thermal bonding strength (sealing strength) under room temperature conditions, and the thermal bonding strength reduction rate according to equation 1 refers to the thermal bonding strength (sealing strength) at approximately 60°C, which is a temperature range increased by heat generation during operation of the secondary battery. Specifically, the higher the thermal bonding strength according to the above condition 1, the better the sealing strength of the pouch film itself is, and the lower the thermal bonding strength reduction rate according to equation 1, the better the high-temperature stability and reliability of the thermal bonding strength at high temperatures can be judged.

[0098] In the case of the pouch of the present invention, the thermal bonding strength at room temperature may be 130 N / 15mm or more, 131 N / 15mm or more, 132 N / 15mm or more, 134 N / 15mm or more, or 136 N / 15mm or more, and the thermal bonding strength reduction rate according to Equation 1 may be 35% or less, 33% or less, 32% or less, 30% or less, 29% or less, 27% or less, 25% or less, 23% or less, 21% or less, 20% or less, 19% or less, or 18% or less.

[0099]

[0100] The present invention can provide a pouch-type secondary battery case including the pouch film according to the present invention.

[0101]

[0102] secondary battery

[0103] The secondary battery of the present invention includes a pouch-type secondary battery case including the battery body and the pouch film, and the 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, and an electrolyte.

[0104] The above lithium secondary battery positive electrode can be used without limitation as long as it is one that is commonly used as a positive electrode of a lithium secondary battery. For example, the above lithium secondary battery positive electrode can be LiCoO2, LiMnO2, LiFeO2, Li(Ni x Mn y Co z )O2(X+Y+Z=1), LiNiCoAlO2, etc. may be included as positive active materials.

[0105] 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 commonly used as electrolytes and organic solvents for lithium secondary batteries, respectively.

[0106] The above-mentioned negative electrode for a lithium secondary battery may be used without limitation as long as it is one that is commonly used as a negative electrode for a lithium secondary battery. For example, the above-mentioned negative electrode for a lithium secondary battery may include a negative electrode active material such as a carbon-based active material or a silicon-based active material.

[0107] The above pouch-type secondary battery case may have excellent sealing strength characteristics. Accordingly, the problem of the battery body sealed by the pouch-type secondary battery case being exposed to the external environment may not occur.

[0108]

[0109] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0110]

[0111] Examples and Comparative Examples

[0112] The pouch films of the examples and comparative examples are laminated with an outer layer, a barrier layer, and a sealant layer. The outer layer is a laminated film of a polyethylene terephthalate (PET) film (thickness 12㎛) as the outermost layer and a nylon (Ny) film (thickness 25㎛) as the inner layer, aluminum is used for the barrier layer (thickness 60㎛), and the sealant layer (thickness 80㎛) is formed as a polypropylene extrusion coating (EC) layer (thickness 30㎛) and a non-stretched polypropylene film (CPP) (thickness 50㎛). Here, the sealant layer was manufactured by the following method. Polypropylene resin and polypropylene elastomer were fed into the supply section (10) of the extruder. The mixing and dispersion process was performed by adjusting the length ratio of the mixing section in the extruder, and the polypropylene elastomer content and the length ratio of the mixing section for each example and comparative example are shown in Table 1 below.

[0113]

[0114] ClassificationExample 1Example 2Example 3Comparative Example 1Comparative Example 2Comparative Example 3Comparative Example 4Comparative Example 5Comparative Example 6Polypropylene elastomer dosage (wt%)EC layer (average particle size)20% (80-82nm)CPP layer10%15%30%5%50%5%10%30%50%Polypropylene elastomer average particle size (nm)CPP layer55nm71nm98nm11nm>15013nm65nm142nm>150Mixing section length ratio (%)(Mixing section length / Total length of extruder) ⅹ 1007.4%7.4%7.4%7.4%7.4%4.7%4.7%4.7%Heat bonding strength (0.2 Mpa, 2 sec, RT) (N / 15mm)131136134115124110121145134Thermal bonding strength (0.2Mpa, 2 sec, 60℃) (N / 15mm)10710391877083977552Thermal bonding strength reduction rate (%)18.324.232.124.343.524.519.848.361.2Insulation resistance (1000V)Number of failures / 10EA1EA(OK)0EA(OK)1EA(OK)10EA(NG)8EA(NG)10EA(NG)6EA(NG)2EA(OK)10EA(NG)

[0115] *Insulation resistance: OK - number of Fails is 1 or less, NG - number of Fails is 2 or more.

[0116]

[0117] Experimental Example 1 - Thermal Bonding Strength

[0118] The pouch films manufactured in the examples and comparative examples were folded in half under the conditions of 200 ℃, 0.2 Mpa, and 2 sec, pressed to a CPP residual rate of 70%, and cut to a width of 15 mm to manufacture samples. Under temperature conditions of room temperature and 60 ℃, respectively, the interfaces of the CPP and CPP of the manufactured samples were fixed to the initial jig gap (30 mm), and then separated by 180° at a peeling speed of 50 mm / min to measure the thermal bonding strength between the two layers. The thermal bonding strength was evaluated using an AGS-1kNX model (UTM) manufactured by SHIMADZU, Japan.

[0119]

[0120] Experimental Example 2 - Insulation Resistance

[0121] The pouch samples of the above examples and comparative examples were molded into 30 mm x 40 mm x 5 mm, and then dummy cells were manufactured through side sealing and tab sealing based on 2 ml of electrolyte. The number of samples was 10 per sample, and after manufacturing the dummy cells, the insulation resistance was measured when a voltage of 1 kV was applied after 24 hours under storage conditions at 60 degrees. At this time, when the insulation resistance of the pouch was 100 MΩ or less when the voltage was applied, it was judged as NG.

[0122]

[0123] Referring to Table 1 above, it can be confirmed that the pouch film manufactured according to the manufacturing method of the present invention has excellent insulation resistance characteristics while maintaining excellent thermal bonding strength and thermal bonding strength reduction rate characteristics.

[0124] On the other hand, in the case of the comparative example that does not satisfy the length ratio of the mixing section and / or the content and average particle diameter of the polyolefin elastomer of the manufacturing method according to the present invention, the thermal bonding strength and the thermal bonding strength reduction rate are inferior, and even if the thermal bonding strength and the thermal bonding strength reduction rate are at the same level, it can be confirmed that the insulation resistance characteristics are at a significantly inferior level. That is, in the case of the comparative example, it can be confirmed that it is difficult to maintain the thermal bonding strength, the thermal bonding strength reduction rate, and the insulation resistance characteristics all at excellent levels.

[0125] 10: Supply Department

[0126] 20: Melting zone

[0127] 30: Mixing section

[0128] 40: Weighing section

[0129] 10-1: Feed section of a conventional extruder

[0130] 20-1: Melting section of a conventional extruder

[0131] 30-1: Mixing section of a conventional extruder

[0132] 40-1: Metering section of a conventional extruder

[0133]

[0134] Acknowledgement

[0135] The present invention is a result of the following task support.

[0136] [Project ID] 1415185612

[0137] [Assignment Number] 20022450

[0138] Ministry of Trade, Industry and Energy

[0139] [Name of Project Management (Specialist) Institution] Korea Institute of Industrial Technology Planning and Evaluation

[0140] [Research Project Name] Material and Components Technology Development (Leeum Company)

[0141] [Research Project Name] Development of a Next-Generation Secondary Battery Pouch Capable of Delivering More Than Double the Highest Adhesive Strength (60°C)

[0142] [Contribution rate] 1 / 1

[0143] [Name of Project Performing Organization] Yulchon Chemical Co., Ltd.

[0144] [Research Period] January 1, 2023 - December 31, 2023

Claims

1. A step (S1) of manufacturing a sealant layer by supplying a polyolefin resin and a polyolefin elastomer to an extruder; Step (S2) of bonding the sealant layer to one surface of the barrier layer including aluminum; and Including a step (S3) of bonding an outer layer to the other surface of the above barrier layer, The above polyolefin elastomer is supplied in an amount of 7 wt% to 30 wt% based on the total resin of the sealant layer, A method for manufacturing a pouch film, wherein the extruder includes a mixing section, and the length of the mixing section is 6% or more and 10% or less of the total length of the extruder.

2. In claim 1, A method for manufacturing a pouch film, wherein the step (S1) includes a step of dispersing the polyolefin-based elastomer within the polyolefin-based resin by the mixing unit.

3. In claim 2, A method for manufacturing a pouch film, wherein the average particle diameter of the polyolefin elastomer dispersed in the polyolefin resin is 30 nm or more and 150 nm or less.

4. In claim 1, A method for manufacturing a pouch film, wherein the above step (S2) is performed by an extrusion lamination method.

5. In claim 4, A method for manufacturing a pouch film further comprising an extrusion bonding coating layer containing a polyolefin resin between the barrier layer and the sealant layer.

6. In claim 1, A method for manufacturing a pouch film, wherein the polyolefin resin comprises at least one selected from the group consisting of polyethylene, polypropylene, polybutylene, a copolymer derived from a monomer derived from ethylene and / or propylene and a monomer derived from alpha-olefin, or a mixture thereof.

7. In claim 1, A method for manufacturing a pouch film, wherein the polyolefin-based elastomer is supplied in an amount of 10 wt% to 20 wt% based on the total resin of the sealant layer.

8. A sequentially laminated outer layer; a barrier layer including aluminum; and an inner layer, The inner layer includes a first sealant layer disposed on the barrier layer, and a second sealant layer disposed on the first sealant layer, The first sealant layer and the second sealant layer each independently include a matrix resin; and a domain resin included in the matrix resin, The content of the domain resin in the second sealant layer is 10 wt% or more and 20 wt% or less relative to the total resin of the second sealant layer, A pouch film, wherein the average particle diameter of the domain resin in the second sealant layer is 30 nm or more and 150 nm or less.

9. In claim 8, A pouch film, wherein the average particle size of the domain resin in the second sealant layer is 50 nm or more and 125 nm or less.

10. In claim 8, A pouch film wherein the matrix resin comprises a polyolefin-based resin.

11. In claim 8, A pouch film wherein the domain resin includes at least one material selected from the group consisting of an ethylene-propylene copolymer (EPR)-based elastomer resin, an ethylene-butene copolymer (EBR)-based elastomer resin, an ethylene-hexene copolymer (EHR)-based polyolefin elastomer resin, an ethylene-octene copolymer (EOR)-based polyolefin elastomer resin, a propylene-butene copolymer (PBR)-based polyolefin elastomer resin, a propylene-hexene copolymer (PHR)-based polyolefin elastomer resin, a propylene-octene copolymer (POR)-based polyolefin elastomer resin, an LLDPE-based elastomer resin, and a thermoplastic polyurethane (TPU) elastomer resin.

12. In claim 8, A pouch film wherein the outer layer comprises polyethylene terephthalate.

13. In claim 8, A pouch film having a thermal bonding strength of 130 N / 15 mm or more under the following condition 1 and a thermal bonding strength reduction rate of 35% or less according to the following formula 1: [Condition 1] The pouch film was heat-bonded between the sealant layers under the conditions of 200°C, 0.2 MPa, and 2 sec, and then cut to a width of 15 mm to produce a specimen. The specimen was then fixed between two jigs of a tensile tester (UTM) at room temperature (initial jig gap (30 mm)), and the peel strength was measured at a peel angle of 180° at a peel speed of 50 mm / min. [Formula 1] Thermal bonding strength reduction rate = 100 - (thermal bonding strength at room temperature / thermal bonding strength at 60 ℃) x 100 In equation 1, The thermal bonding strength at the above room temperature is the peel strength measured under the above condition 1, The thermal bonding strength at 60°C above is the peel strength measured at a peel angle of 180° at a peel speed of 50 mm / min after thermally bonding the sealant layers of the pouch film under the conditions of 200°C, 0.2 MPa, and 2 sec, cutting the pouch film to a width of 15 mm, and then fixing the specimen between two jigs of a tensile tester (UTM) under a temperature condition of 60°C (initial jig gap (30 mm)).

14. A pouch-type secondary battery case comprising a pouch film according to claim 8.

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