Pouch film, and pouch exterior material and secondary battery comprising same

Abstract

The present invention comprises: an outer layer; a barrier layer; and sealant layers, the outer layer, barrier layer, and sealant layers being sequentially laminated, wherein the sealant layers include a polyolefin-based resin and a polyolefin-based elastomer. In the case of the sealant layers, an area ratio can be specified on the basis of the melting temperature by differential scanning calorimetry (DSC) to find an optimal sealing temperature condition between the melting start temperature and melting end temperature of the sealant layers and thereby facilitate thermal fusion between the sealant layers and achieve a sealing shape that is complete. Therefore, the present invention may have the effects of improving adhesiveness, insulation, and bendability.

Description

Pouch film, pouch outer material including the same, and secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0193081, filed December 27, 2023, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to a pouch film, a pouch outer material including the same, and a secondary battery.

[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 making the sealant layers of the pouch film (e.g., sealant layers) come into contact with each other, and then applying heat and pressure to the sealant layers in contact to thermally bond them together to form a sealing portion, 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 had difficulty securing sufficient heat bonding strength at the sealing portion, and research on improving the heat bonding strength at the sealing portion has also been insufficient. In addition, conventional pouch films have had difficulty securing sufficient sealing strength, and the heat-bonded sealing portion frequently has problems with venting. In particular, the area where heat and pressure are applied to the sealing portion is where polyolefin-based resins, such as polypropylene resins, melt and heat bond, but the polypropylene-based resins in the pressure-applied portion are pushed out to the surrounding area where pressure is not applied, which naturally increases the thickness, and the pressurization and heating of the sealing portion are not evenly applied. In addition, when heat is transferred to the surrounding area, although fluidity is generated due to the transferred heat, there is a problem of forming an incomplete sealing shape due to insufficient heat energy. Accordingly, in order to solve such problems, research is being conducted to manufacture a pouch film in which the polypropylene resin of the sealing portion has sufficient fluidity to facilitate heat fusion between contact surfaces, has a complete sealing portion shape, and thereby has improved insulation, adhesiveness, and banding properties.

[0012]

[0013] The problem to be solved by the present invention is to provide a pouch film having excellent levels of adhesiveness, insulation, and banding properties by easily achieving heat fusion between sealant layers to realize a complete sealing shape.

[0014] In addition, an object of the present invention is to provide a pouch outer material including the pouch film.

[0015] In addition, an object of the present invention is to provide a secondary battery including the pouch outer material.

[0016]

[0017] The present invention provides a pouch film, a pouch outer material including the same, and a secondary battery.

[0018] (1) The present invention provides a pouch film comprising a sequentially laminated outer layer; a barrier layer; and a sealant layer, wherein the sealant layer comprises a polyolefin-based resin; and a polyolefin-based elastomer, wherein the sealant layer has a melting temperature (Tm) of 130°C or more and 160°C or less measured under a temperature increasing condition of 10°C / min using differential scanning calorimetry (DSC), and satisfies the following condition 1.

[0019] [Condition 1]

[0020] In the graph derived through the above differential scanning calorimetry method, the ratio of the area (area A) below the reference point 140 ℃ to the sum of the area (area B) above the reference point 140 ℃ (area A / (area A+area B)) of the area below the reference point 140 ℃ is 40% or more and less than 85%.

[0021] (2) The present invention provides a pouch film in the above (1), wherein the polyolefin resin includes at least one material selected from the group consisting of homo polypropylene (Homo-PP), random polypropylene copolymer (Random-PP), and block polypropylene copolymer (Block-PP).

[0022] (3) The present invention provides a pouch film in which the content of the polyolefin-based elastomer in (1) or (2) is 10 wt% or more and 50 wt% or less relative to the total resin of the sealant layer.

[0023] (4) The present invention provides a pouch film in which the polyolefin-based elastomer 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 elastomer resin, an ethylene-octene copolymer (EOR)-based elastomer resin, a propylene-butene copolymer (PBR)-based elastomer resin, a propylene-hexene copolymer (PHR)-based elastomer resin, a propylene-octene copolymer (POR)-based elastomer resin, an LLDPE-based elastomer resin, and a thermoplastic polyurethane (TPU) elastomer resin.

[0024] (5) The present invention provides a pouch film in which the ratio of area A / (area A + area B) of condition 1 is 50% or more and 80% or less in any one of the above (1) to (4).

[0025] (6) The present invention provides a pouch film in any one of the above (1) to (5), wherein the sealant layer has a melting temperature (Tm) of 130°C or more and 150°C or less, measured under a temperature increasing condition of 10°C / min using a differential scanning calorimetry method.

[0026] (7) The present invention provides a pouch film in any one of the above (1) to (6), wherein the outer layer includes at least one material selected from the group consisting of nylon and polyethylene terephthalate.

[0027] (8) The present invention provides a pouch film according to any one of the above (1) to (7), wherein the barrier layer comprises at least one selected from the group consisting of aluminum, stainless steel, copper, titanium, and alloys thereof.

[0028] (9) The present invention provides a pouch film having an insulation resistance of 50 GΩ or more according to the following measurement method when the pouch film is sealed at a temperature of 165°C or more and 185°C or less, for 2 seconds or more and 4 seconds or less, and under a pressure of 0.1 Mpa or more and 0.3 Mpa or less to form a pouch outer shell, in any one of the above (1) to (8).

[0029] [measurement method]

[0030] A pouch film sample was formed into a 30 mm x 40 mm x 5 mm, 2 ml of electrolyte was injected, a lead tab was inserted, and a dummy cell was manufactured through side sealing and tab sealing. After that, the dummy cell was left for 24 hours, and the resistance when a voltage of 1,000 V was applied was measured.

[0031] (10) The present invention provides a pouch outer material including a pouch film according to any one of (1) to (9).

[0032] (11) The present invention provides a pouch outer material in the above (10), wherein the pouch outer material is formed by sealing at a temperature of 165°C or more and 185°C or less, for 2 seconds or more and 4 seconds or less, and at a pressure of 0.1 MPa or more and 0.3 MPa or less.

[0033] (12) The present invention provides a secondary battery including a pouch outer case according to (10) or (11).

[0034]

[0035] The pouch film of the present invention can easily achieve thermal fusion between sealant layers by finding the optimal sealing temperature condition between the melting start temperature and the melting end temperature of the sealant layer, thereby realizing a complete sealing shape, and thereby can have the effect of improving adhesiveness, insulation, and banding properties.

[0036]

[0037] Figure 1 shows an example of a DSC graph according to condition 1 of the present invention.

[0038] Figure 2 is a schematic diagram showing the process of heat-melting sealant layers and then recrystallization.

[0039] Figure 3 shows a complete sealing shape and an incomplete or irregular sealing shape.

[0040]

[0041] 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.

[0042] 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.

[0043] 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.

[0044] In this specification, “perfect sealing shape” means, with reference to FIG. 3, a case where the shape of the thermal bonding periphery formed by the sealant layers contacting each other during the thermal bonding process is a gentle, smooth curve, and “incomplete sealing shape” means a case where a boundary line is visible between the sealant layers or the shape of the thermal bonding periphery is not a gentle curve but includes an angular or sharp protrusion shape.

[0045]

[0046] pouch film

[0047] The present invention provides a pouch film comprising an outer layer, a barrier layer, and a sealant layer laminated sequentially, wherein the sealant layer comprises a polyolefin resin and a polyolefin elastomer, and wherein the sealant layer has a melting temperature (Tm) of 130°C or more and 160°C or less measured under a temperature increasing condition of 10°C / min using differential scanning calorimetry (DSC), and satisfies the following condition 1.

[0048] [Condition 1]

[0049] In the graph derived through the above differential scanning calorimetry method, the ratio of the area (area A) below the reference point 140 ℃ to the sum of the area (area B) above the reference point 140 ℃ (area A / (area A+area B)) of the area below the reference point 140 ℃ is 40% or more and less than 85%.

[0050] The inventor of the present invention has conducted research to find the optimal sealing conditions between the melting start temperature and the melting end temperature of the sealant layer, and has found that when analyzing the cross-section of the sealing portion according to a certain area ratio and sealing temperature change that can be calculated by dividing the region around a certain reference point in the graph derived through the differential scanning calorimetry method, the characteristics such as sealing properties, insulation properties, and bending properties are affected. Accordingly, the present invention can provide a pouch film having a complete sealing shape of the sealing portion and excellent sealing properties, adhesiveness, insulation properties, and bending properties by specifying the melting temperature (Tm) at the DSC endothermic peak and the region ratio centered around the reference point (temperature) in the graph derived from DSC based on the optimal sealing conditions.

[0051] The above melting temperature (Tm) can be measured by differential scanning calorimetry (DSC). That is, the raw material used in the sealant layer is a polymer, and the melting temperature of the polymer can generally be measured through DSC. DSC is a method for analyzing the physical and chemical properties of a sample from temperature and heat change data obtained from the energy supplied to a sample and a reference furnace. It measures the difference in energy input as a function of temperature while changing the temperatures of the sample and reference. Quantitative information can be obtained from the position, shape, and number of peaks analyzed in this way. When the temperature is increased at a constant rate, after the glass transition temperature (Tg) appears, heat is absorbed at a specific temperature and another peak occurs, and the corresponding temperature is called the melting temperature (Tm).

[0052] The sealant layer may be a sealant layer of the secondary battery outer pouch film. That is, the sealant layer may be in direct contact with the battery main body (e.g., electrode, separator, and / or electrolyte). To this end, the sealant layer includes a polyolefin-based resin as a matrix resin and a polyolefin-based elastomer as a domain resin.

[0053] In addition, the sealant layer may have a melting temperature (Tm) of 130°C or more and 160°C or less, measured under a temperature increasing condition of 10°C / min using Differential Scanning Calorimetry (DSC). For example, the melting temperature may be 130°C or more, 131°C or more, 133°C or more, 135°C or more, 137°C or more, 139°C or more, 140°C or more, 160°C or less, 157°C or less, 155°C or less, 153°C or less, 151°C or less, or 150°C or less, and specifically, the melting temperature may be 130°C or more and 150°C or less. Here, the melting temperature may be controlled depending on the type or form of the polyolefin resin included in the sealant layer. At the same time, in the graph derived through the differential scanning calorimetry method, the ratio of the area (area A) below the reference point 140°C to the sum of the area (area B) above the reference point 140°C and the area (area A) below the reference point 140°C (area A / (area A + area B)) may be 40% or more and less than 85%. For example, the area ratio may be 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, less than 85%, or 80% or less.

[0054] Fig. 1 illustrates an example of a DSC graph according to condition 1 of the present invention. Referring to Fig. 1, the DSC graph of the sealant layer can be divided into regions A and B based on 140°C. Here, the reference point of 140°C refers to the minimum temperature at which heat bonding is possible during the process of heat bonding sealant layers together to manufacture a pouch outer material from a pouch film. Specifically, heat bonding does not occur at a temperature lower than 140°C, and heat bonding occurs from a temperature higher than 140°C. In addition, the area ratio can be adjusted depending on the type and content of the polyolefin-based elastomer included in the sealant layer.

[0055] When the melting temperature of the sealant layer falls within the above range, and at the same time, the larger the ratio of the A area / (A area + B area), specifically, when it is 40% or more, the sealant layer can have sufficient fluidity at a low sealing temperature, and heat sealing between contact surfaces (between sealant layers) can be facilitated. Since it can have sufficient fluidity, a sufficient mixing process can proceed, and recrystallization can begin after a sufficient mixing process has proceeded. Accordingly, a complete sealing shape can be realized, and thereby excellent levels of sealing properties, adhesive properties, banding properties, and insulating properties can be achieved.

[0056] On the other hand, if the melting temperature of the sealant layer is outside the above range, and at the same time, the ratio of the A area / (A area + B area) is smaller, specifically, less than 40%, the fluidity of the sealant layer at low temperatures is insufficient, and the mixing process of the sealant layer for heat sealing is not smooth. Accordingly, an imperfect sealing shape may be realized, and sealing properties, adhesive properties, banding properties, and insulation properties may be reduced.

[0057] Fig. 2 is a schematic diagram showing the process from heat-fusion of sealant layers to recrystallization during the sealing process. Referring to Fig. 2, Figure 1 shows the process of applying heat and pressure after contacting sealant layers (PP layers), and Figure 2 shows the process of mixing between contact surfaces due to the generation of fluidity in the sealant layers. Accordingly, when the melting temperature and condition 1 are satisfied, sufficient mixing occurs and recrystallization proceeds thereafter, so that excellent sealing properties, insulation properties, and bending properties can be achieved. On the other hand, when the melting temperature and condition 1 are not satisfied, the fluidity of the sealant layers is weak, so that recrystallization proceeds before sufficient mixing occurs, resulting in an incomplete sealing shape, and deterioration of sealing properties, insulation properties, and bending properties.

[0058]

[0059] Meanwhile, the pouch film may be used to seal a battery main body (e.g., electrodes, separator, and / or electrolyte). For example, the battery main body may be sealed by bringing the sealant layers of two different pouch films into contact with each other and then thermally bonding them to form a sealing portion. As another example, the battery main body may be sealed by folding a single pouch film in half so that the sealant layers of the two pouch films come into contact with each other and then thermally bonding the sealant layers that come into contact with each other to form a sealing portion.

[0060] The pouch film including the sealing portion formed by thermal bonding of the sealant layer can exhibit excellent sealing properties derived from the excellent sealing strength of the sealant layer. 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.

[0061] According to one embodiment of the present invention, 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.

[0062] Specifically, the polyolefin-based resin may include one or more materials selected from the group consisting of homo-polypropylene (Homo-PP), random polypropylene copolymer (Random-PP), and block polypropylene copolymer (Block-PP). The melting temperature according to the differential scanning calorimetry measurement may be affected by the type of polyolefin-based resin included in the sealant layer. More specifically, the polyolefin-based resin may be a random polypropylene copolymer (Random-PP) or a block polypropylene copolymer (Block-PP).

[0063]

[0064] 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.

[0065] According to one embodiment of the present invention, the polyolefin-based elastomer may include 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 elastomer resin, an ethylene-octene copolymer (EOR)-based elastomer resin, a propylene-butene copolymer (PBR)-based elastomer resin, a propylene-hexene copolymer (PHR)-based elastomer resin, a propylene-octene copolymer (POR)-based elastomer resin, an LLDPE-based elastomer resin, and a thermoplastic polyurethane (TPU) elastomer resin.

[0066] In addition, according to one embodiment of the present invention, the content of the polyolefin-based elastomer may be 10 wt% or more and 50% or less based on the total resin of the sealant layer. For example, the content of the polyolefin-based elastomer may be 10 wt% or more, 15 wt% or more, 20 wt% or more, 25 wt% or more, 30 wt% or more, 35 wt% or more, 40 wt% or more, 50 wt% or less, or 45 wt% or less based on the total resin of the sealant layer. When the content of the polyolefin-based elastomer satisfies the above range, the area ratio on the graph derived from the DSC measurement can be adjusted, and thereby a pouch film having a complete sealing shape and excellent levels of sealing, insulating, and banding properties can be obtained.

[0067]

[0068] According to one embodiment of the present invention, the sealant layer may be composed of a laminate of two or more layers in order to diversify 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 adhesion between the barrier layer and the second sealant layer, while further 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 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, located underneath the first sealant layer (inner side based on the pouch film).

[0069] 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.

[0070] 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, may be a non-stretched polypropylene-based resin.

[0071]

[0072] According to one embodiment of the present invention, a pouch film is provided, wherein the outer layer comprises at least one material selected from the group consisting of nylon and polyethylene terephthalate.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] According to one embodiment of the present invention, a pouch film is provided in which the barrier layer comprises at least one selected from the group consisting of aluminum, stainless steel, copper, titanium, and alloys thereof.

[0077] 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.

[0078] 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.

[0079] 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.

[0080]

[0081] According to one embodiment of the present invention, when the pouch film is sealed at a temperature of 165°C or more and 185°C or less, for 2 seconds or more and 4 seconds or less, at a pressure of 0.1 MPa or more and 0.3 MPa or less to form a pouch outer material, the pouch film has an insulation resistance of 50 GΩ or more according to the following measurement method.

[0082] [measurement method]

[0083] A pouch film sample was formed into a 30 mm x 40 mm x 5 mm, 2 ml of electrolyte was injected, a lead tab was inserted, and a dummy cell was manufactured through side sealing and tab sealing. After that, the dummy cell was left for 24 hours, and the resistance when a voltage of 1,000 V was applied was measured.

[0084] The pouch film of the present invention has a specific melting temperature, and at the same time, when a specific condition 1 is satisfied, when the pouch film is sealed under the sealing conditions to form a pouch outer material, it can have considerably excellent insulation resistance characteristics. The sealing conditions may be, among sealing temperature conditions, 165 ℃ or higher, 170 ℃ or higher, 175 ℃ or higher, 185 ℃ or lower, or 180 ℃ or lower, and the sealing time conditions may be 2.1 seconds or lower, 2.0 seconds or lower, 1.9 seconds or lower, or 1.8 seconds or lower. In addition, the sealing pressure may be 0.1 MPa or higher, or 0.2 MPa or higher, and further, 0.3 MPa or lower, or 0.2 MPa or lower. For example, the higher the melting temperature (Tm) of the sealant layer and the higher the A area ratio, the better the insulation resistance characteristics and sealing shape can be formed when sealing under high sealing temperature conditions. By controlling the sealing temperature, time, and pressure in this way, a complete sealing shape can be realized when the sealant layers in the pouch film of the present invention are thermally bonded together, and thereby a pouch outer material having excellent insulation resistance, thermal bonding strength, and banding properties can be obtained.

[0085]

[0086] Pouch outer material

[0087] The present invention provides a pouch outer material including a pouch film according to the present invention described above.

[0088] In addition, according to one embodiment of the present invention, the pouch outer case is formed by sealing at a temperature of 165°C or more and 185°C or less, for 2 seconds or more and 4 seconds or less, and at a pressure of 0.1 MPa or more and 0.3 MPa or less. The sealing conditions may be, for example, a sealing temperature condition of 165°C or more, 170°C or more, 175°C or more, 185°C or less, or 180°C or less, and a sealing time condition may be 2.1 seconds or less, 2.0 seconds or less, 1.9 seconds or less, or 1.8 seconds or less. In addition, the sealing pressure may be 0.1 MPa or more, or 0.2 MPa or more, and further, 0.3 MPa or less, or 0.2 MPa or less.

[0089]

[0090] secondary batteries

[0091] The present invention provides a secondary battery including a pouch outer case according to the present invention described above.

[0092] The secondary battery of the present invention includes a pouch casing including the battery body and the pouch film, and the battery body is sealed by the pouch casing. 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] The above pouch and material may have excellent sealing strength characteristics. Therefore, the battery body sealed by the pouch and material may not be exposed to the external environment.

[0097]

[0098] 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.

[0099]

[0100] Examples and Comparative Examples

[0101] Example 1

[0102] 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 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 a polypropylene extrusion coating (EC) layer (thickness 30㎛) and a non-stretched polypropylene film (CPP) (thickness 50㎛) using an extrusion lamination method, wherein the extrusion coating (EC) layer includes a random polypropylene copolymer (Random-PP), the non-stretched polypropylene film (CPP) includes a random polypropylene copolymer (Random-PP), and the sealant layer includes 10 to 20 wt% of an ethylene-propylene copolymer (EPR)-based elastomer resin. A pouch film having the melting temperature and A area ratio described in Table 1 below was manufactured. At this time, the melting temperature was measured for the sealant layer of the manufactured pouch film using differential scanning calorimetry, and the A area ratio was calculated as the ratio of the area (A area) below the reference point 140 ℃ to the sum of the area (A area) below the reference point 140 ℃ and the area (B area) above the reference point 140 ℃ in the graph derived through the differential scanning calorimetry (A area / (A area + B area)). Thereafter, the manufactured pouch film was subjected to a sealing process under the respective temperature conditions described in Table 1 at 0.2 MPa and 3 sec to manufacture a pouch outer material, and then the sealing shape evaluation, insulation evaluation, and bending evaluation were performed according to the experimental example below.

[0103]

[0104] Example 2

[0105] An outer layer, a barrier layer, and a sealant layer are laminated, and the outer layer uses 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, and the barrier layer uses aluminum (thickness 60㎛), and the sealant layer (thickness 80㎛) is manufactured so that an extrusion coating (EC) layer is formed through a coextrusion method, wherein the extrusion coating (EC) layer includes a first extrusion coating layer in contact with the barrier layer and a second extrusion coating layer located on the lower surface of the first extrusion coating layer, and the first extrusion coating layer includes a block polypropylene copolymer (Block-PP), and the second extrusion coating layer includes a random polypropylene copolymer (Random-PP), and the sealant layer includes an ethylene-propylene copolymer (EPR)-based elastomer resin at 30 wt% to 40 wt%, and has a melting temperature and a temperature as described in Table 1 below. A pouch film having an area ratio of A was manufactured. At this time, the melting temperature was measured for the sealant layer of the manufactured pouch film using differential scanning calorimetry, and the area ratio of A was calculated as the ratio of the area (area A) below the reference point of 140 ℃ to the sum of the area (area B) below the reference point of 140 ℃ and the area (area B) above the reference point of 140 ℃ in the graph derived through the differential scanning calorimetry (area A / (area A + area B)). Thereafter, the manufactured pouch film was subjected to a sealing process at 0.2 MPa and 3 sec and the respective temperature conditions described in Table 1 to manufacture a pouch outer material, and then the sealing shape evaluation, insulation evaluation, and bending evaluation were performed according to the experimental examples below.

[0106]

[0107] Example 3

[0108] In the above Example 1, except that the extrusion coating (EC) layer includes a random polypropylene copolymer (Random-PP), the non-stretched polypropylene film (CPP) includes a random polypropylene copolymer (Random-PP), and the sealant layer includes 20 wt% to 30 wt% of an ethylene-propylene copolymer (EPR)-based elastomer resin, pouch films and pouch outer materials having the melting temperatures and A area ratios described in Table 1 were manufactured in the same manner as in Example 1, and then the sealing shape evaluation, insulation evaluation, and banding evaluation were performed according to the experimental examples below.

[0109] Example 4

[0110] In the above Example 1, except that the extrusion coating (EC) layer includes a random polypropylene copolymer (Random-PP), the non-stretched polypropylene film (CPP) includes a random polypropylene copolymer (Random-PP), and the sealant layer includes 30 wt% to 40 wt% of an ethylene-propylene copolymer (EPR)-based elastomer resin, pouch films and pouch outer materials having the melting temperatures and A area ratios described in Table 1 were manufactured in the same manner as in Example 1, and then the sealing shape evaluation, insulation evaluation, and banding evaluation were performed according to the experimental examples below.

[0111]

[0112] Example 5

[0113] In the above Example 2, the first extrusion coating layer includes a block polypropylene copolymer (Block-PP), the second extrusion coating layer includes a random polypropylene copolymer (Random-PP), and the sealant layer includes 40 to 50 wt% of an ethylene-propylene copolymer (EPR)-based elastomer resin. However, the same procedure as Example 1, which has the melting temperature and A area ratio described in Table 1 below, was performed to manufacture a pouch film and a pouch outer material, and then the sealing shape evaluation, insulation evaluation, and banding evaluation were performed according to the experimental examples below.

[0114]

[0115] Comparative Example 1

[0116] In the above Example 1, the extrusion coating (EC) layer includes a random polypropylene copolymer (Random-PP), the non-stretched polypropylene film (CPP) includes a block polypropylene copolymer (Block-PP), and the sealant layer includes an ethylene-propylene copolymer (EPR)-based elastomer resin in an amount of 5 wt% to less than 10 wt%, and the same procedure as in Example 1 was followed to manufacture pouch films and pouch outer materials having the melting temperatures and A area ratios described in Table 1 below. Then, the sealing shape evaluation, insulation evaluation, and banding evaluation were performed according to the experimental examples below.

[0117]

[0118] Comparative Example 2

[0119] In the above Example 1, except that the extrusion coating (EC) layer includes a block polypropylene copolymer (Block-PP), the non-stretched polypropylene film (CPP) includes a random polypropylene copolymer (Random-PP), and the sealant layer includes more than 50 wt% of an ethylene-propylene copolymer (EPR)-based elastomer resin, pouch films and pouch outer materials having the melting temperatures and A area ratios described in Table 1 below were manufactured in the same manner as in Example 1, and then the sealing shape evaluation, insulation evaluation, and banding evaluation were performed according to the experimental examples below.

[0120]

[0121] Comparative Example 3

[0122] In the above Example 1, except that the extrusion coating (EC) layer includes a random polypropylene copolymer (Random-PP), the non-stretched polypropylene film (CPP) includes a polypropylene terpolymer (Ter-PP), and the sealant layer includes an ethylene-propylene copolymer (EPR)-based elastomer resin in an amount of more than 40 wt% to 50 wt%, the same procedure as in Example 1 was performed to manufacture pouch films and pouch outer materials having the melting temperatures and A area ratios described in Table 1 below, and then the sealing shape evaluation, insulation evaluation, and banding evaluation were performed according to the experimental examples below.

[0123]

[0124] Experimental Example 1 - Evaluation of Sealing Shape

[0125] Under the same conditions of time 3 sec / pressure 0.2 MPa, samples were prepared by cutting them into 5 mm wide after thermal bonding according to temperature conditions as shown in Table 1. Afterwards, the shape of the sealant layer was observed through epoxy molding so that the cross-section of the sealing part was visible using an optical device (optical microscope DM2700M, manufactured by Leica Microsystems).

[0126] OK: The shape of the heat-sealing periphery is a gentle, smooth curve.

[0127] NG: A shape in which a boundary line is visible between the sealant layers, or the shape of the area surrounding the thermal bonding is not a gentle curve but includes an angular or sharp protrusion shape.

[0128]

[0129] Experimental Example 2 - Insulation Evaluation

[0130] The above-mentioned manufactured pouch film sample was molded into 30 mm x 40 mm x 5 mm, 2 ml of electrolyte was injected, a lead tab was inserted, and a dummy cell was manufactured through side sealing and tab sealing. Thereafter, the dummy cell was left for 24 hours, and the resistance when a voltage of 1,000 V was applied was measured.

[0131] A: 100 GΩ or more

[0132] B: 50 GΩ or more and less than 100 GΩ

[0133] C: 25 GΩ or more and less than 50 GΩ

[0134] D: 10 GΩ or more and less than 25 GΩ

[0135] E: Less than 10 GΩ

[0136]

[0137] Experimental Example 3 - Banding Evaluation

[0138] A specimen manufactured in the same manner as the sample of Experimental Example 2 above was prepared. After the specimen was left at room temperature for 24 hours, a voltage of 500 V was applied to select a sample with an insulation property of 1 GΩ or higher. One side of the heat-bonded surface without a lead tab was repeatedly folded and unfolded, and the number of times one side was repeatedly bent was measured until the insulation property became 1 GΩ or lower.

[0139] A: More than 50 times

[0140] B: 30 times or more but less than 50 times

[0141] C: 10 or more times but less than 30 times​

[0142] D: 5 or more times but less than 10 times

[0143] E: Less than 5 times

[0144]

[0145] Classification PP Main Peak (Tm) A area / A+B area Sealing temperature: 165℃ Sealing temperature: 175℃ Sealing temperature: 185℃ Sealing shape Insulation Bending Sealing shape Insulation Bending Sealing shape Insulation Bending Example 1 (EC) 14540~50% OKBAOKBAOKBA Example 2 (Co-E) 14250~60% OKBAOKBAOKBA Example 3 (EC) 14260~70% OKBAOKBAOKBA Example 4 (EC) 13570% or more OKBAOKBAOKBA Example 5 (Co-E) 15950~60% OKBEOKABOKAB Comparative Example 1 (EC) 16040% or less NGBENGBDOKAD Comparative Example 2 (EC) 16240~50% NGBEOKACOKAC Comparative Example 3(EC)13085% or moreOKCBOKDBOKDB

[0146] Referring to Table 1 above, it can be confirmed that in the cases of Examples 1 to 5 that satisfy the melting temperature range of the present invention and the A area ratio as in Condition 1, the sealing shape exhibits a perfect sealing shape and exhibits excellent insulation and banding properties. The perfect sealing shape refers to a case where the shape of the thermal bonding periphery formed by the sealant layers contacting each other is a gentle and smooth curve, as shown in the OK photograph with reference to Fig. 1.

[0147] On the other hand, in the case of Comparative Examples 1 to 3, where any one of the above-mentioned melting temperature range and A area ratio is not satisfied, it can be confirmed that the sealing shape, insulation, and banding properties are at inferior levels. In particular, in the case of Comparative Example 1, where the A area ratio is less than 40%, the sealing shape is incomplete, and this can be confirmed by referring to FIG. 1 that the shape of the periphery of the thermal bonding is not a gentle curve but includes an angular or sharp protrusion shape, as shown in the NG photograph. In addition, in the case of Comparative Example 2, it can be confirmed that the banding property characteristic is at a very inferior level because the melting temperature range is not satisfied. In addition, as in Comparative Example 3, when the A area ratio exceeds the upper limit of the range, the sealing shape can be in a perfect form, but in addition, it can be confirmed that the insulating property characteristic is at a significantly inferior level.

[0148]

[0149] Acknowledgement

[0150] The present invention is a result of the following task support.

[0151] [Project ID] 1415185612

[0152] [Assignment Number] 20022450

[0153] Ministry of Trade, Industry and Energy

[0154] [Name of Project Management (Specialist) Institution] Korea Institute of Industrial Technology Planning and Evaluation

[0155] [Research Project Name] Material and Components Technology Development (Leeum Company)

[0156] [Research Project Name] Development of a Next-Generation Secondary Battery Pouch Capable of Delivering More Than Double the Highest Adhesive Strength (60°C)

[0157] [Contribution rate] 1 / 1

[0158] [Name of Project Performing Organization] Yulchon Chemical Co., Ltd.

[0159] [Research Period] January 1, 2023 - December 31, 2023

Claims

1. Containing a sequentially laminated outer layer; a barrier layer; and a sealant layer, The above sealant layer comprises a polyolefin resin; and a polyolefin elastomer; The above sealant layer has a melting temperature (Tm) of 130 ℃ or more and 160 ℃ or less as measured under a temperature increasing condition of 10 ℃ / min using differential scanning calorimetry (DSC). A pouch film satisfying the following condition 1: [Condition 1] In the graph derived through the above differential scanning calorimetry method, the ratio of the area (area A) below the reference point 140℃ to the sum of the area (area B) above the reference point 140℃ (area A / (area A + area B)) of the area below the reference point 140℃ is 40% or more and less than 85%.

2. In claim 1, A pouch film wherein the polyolefin resin comprises at least one material selected from the group consisting of homo-polypropylene (Homo-PP), random polypropylene copolymer (Random-PP), and block polypropylene copolymer (Block-PP).

3. In claim 1, A pouch film wherein the content of the polyolefin elastomer is 10 wt% to 50 wt% based on the total resin of the sealant layer.

4. In claim 1, A pouch film comprising at least one material selected from the group consisting of an ethylene-propylene copolymer (EPR) elastomer resin, an ethylene-butene copolymer (EBR) elastomer resin, an ethylene-hexene copolymer (EHR) elastomer resin, an ethylene-octene copolymer (EOR) elastomer resin, a propylene-butene copolymer (PBR) elastomer resin, a propylene-hexene copolymer (PHR) elastomer resin, a propylene-octene copolymer (POR) elastomer resin, an LLDPE-based elastomer resin, and a thermoplastic polyurethane (TPU) elastomer resin.

5. In claim 1, A pouch film in which the ratio of area A / (area A + area B) of condition 1 above is 50% or more and 80% or less.

6. In claim 1, A pouch film having a melting temperature (Tm) of 130°C or more and 150°C or less of the sealant layer as measured under a temperature increasing condition of 10°C / min using a differential scanning calorimetry method.

7. In claim 1, A pouch film wherein the outer layer comprises at least one material selected from the group consisting of nylon and polyethylene terephthalate.

8. In claim 1, A pouch film wherein the barrier layer comprises at least one selected from the group consisting of aluminum, stainless steel, copper, titanium, and alloys thereof.

9. In claim 1, The above pouch film, when sealed at a temperature of 165°C or higher and 185°C or lower, for 2 seconds or longer and 4 seconds or shorter, with a pressure of 0.1 MPa or higher and 0.3 MPa or lower to form a pouch outer shell, has an insulation resistance of 50 GΩ or higher according to the following measurement method. [measurement method] A pouch outer film sample was molded to 30 mm x 40 mm x 5 mm, 2 ml of electrolyte was injected, a lead tab was inserted, and a dummy cell was manufactured through side sealing and tab sealing. After that, the dummy cell was left for 24 hours, and the resistance when a voltage of 1000 V was applied was measured.

10. A pouch outer material comprising a pouch film according to claim 1.

11. In claim 10, The above pouch outer material is a pouch outer material formed by sealing at a temperature of 165°C or higher and 185°C or lower, for 2 seconds or longer and 4 seconds or shorter, and at a pressure of 0.1 MPa or higher and 0.3 MPa or lower.

12. A secondary battery comprising a pouch outer case according to claim 10.

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