KR20240075723A - Gas permeable film, pouch case and secondary battery comprising the same - Google Patents

Abstract

The gas permeable film of the present invention includes a first polymer layer, a second polymer layer, and a third polymer layer disposed between the first polymer layer and the second polymer layer, and the third polymer layer is made of polypropylene and polytetra. It is characterized in that fluoroethylene is contained in a weight ratio of 9:1 to 1:9. The gas permeable film has excellent gas permeability, so when applied to a secondary battery, it can effectively discharge gas generated inside the secondary battery.

Description

Gas permeable film, pouch exterior material containing the same, and secondary battery {GAS PERMEABLE FILM, POUCH CASE AND SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a gas permeable film, and more specifically, to a secondary battery in which the gas permeable film is applied to a pouch exterior material or lead tab film to improve the gas permeability of the secondary battery.

Secondary batteries are widely used as a power source for mobile devices such as mobile phones, laptops, and camcorders. In particular, the use of lithium secondary batteries is rapidly increasing due to the advantages of high operating voltage and high energy density per unit weight.

These lithium secondary batteries mainly use lithium-based oxide as a positive electrode active material and carbon material as a negative electrode active material, and are generally classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries depending on the type of electrolyte used. Depending on the external shape of the battery, it is classified into cylindrical, prismatic, and pouch-type secondary batteries. Typically, in terms of battery shape, there is high demand for prismatic secondary batteries and pouch-shaped secondary batteries that can be applied to products such as mobile phones due to their thin thickness.

Among them, interest is focused on pouch-type secondary batteries, which are particularly suitable for manufacturing lightweight, thin cells because they have no restrictions on shape and size, are easy to assemble through heat fusion, and are easy to expel gas or liquid when abnormal behavior occurs. It is becoming.

On the other hand, secondary batteries are charged and discharged by repeating the process of inserting and desorbing lithium ions from the lithium metal oxide of the positive electrode to the graphite electrode of the negative electrode. There are various problems that threaten the safety of secondary batteries, such as electrolyte decomposition and thermal runaway phenomenon.

In particular, as the energy density of secondary batteries increases, the electrolyte and electrode active material react electrochemically due to repeated charging and discharging, and the amount of gas generated as a result increases. This gas generation is significantly shortening the lifespan of secondary batteries, and this problem is expected to worsen in the future.

On the other hand, when moisture penetrates into the secondary battery, the moisture may react with the electrolyte of the secondary battery, resulting in reduced performance of the secondary battery and gas generation. Therefore, it is necessary to control moisture penetrating into the secondary battery.

However, there is insufficient research on extracting the gas generated inside the secondary battery to the outside and simultaneously minimizing moisture penetrating into the secondary battery from the outside.

The purpose of the present invention is to provide a film with an improved gas exhaust function to solve the above problems.

Another object of the present invention is to provide a secondary battery with an improved function of discharging internal gas by applying the gas-permeable film as a lead film of a secondary battery.

Another object of the present invention is to apply the film to an exterior material pouch for secondary batteries to provide a pouch exterior material that has good durability based on excellent adhesive strength, has an excellent effect in preventing external moisture infiltration, and has an improved function of discharging internal gas. The purpose is to

In order to achieve the above object, the gas permeable film according to the present invention includes a first polymer layer, a second polymer layer, and a third polymer layer disposed between the first polymer layer and the second polymer layer, 3 The polymer layer is characterized by containing polypropylene and polytetrafluoroethylene in a weight ratio of 9:1 to 1:9.

In one embodiment, the first polymer layer and the second polymer layer each independently contain a polyolefin-based polymer.

In one embodiment, the second polymer layer includes a modified polyolefin-based resin.

In one embodiment, the third polymer layer is characterized in that polypropylene and polytetrafluoroethylene are included in a weight ratio of 8:2 to 2:8.

In one embodiment, the first polymer layer has a thickness of 40 to 200 ㎛.

In one embodiment, the second polymer layer has a thickness of 40 to 200 ㎛.

In one embodiment, the third polymer layer has a thickness of 40 to 600 ㎛.

In one embodiment, a secondary battery according to the present invention includes an electrode assembly; A pouch exterior material that accommodates the electrode assembly; an electrode lead electrically connected to the electrode assembly; and a gas-permeable film adhered to at least one surface of the electrode lead, wherein the film is the gas-permeable film described above.

In one embodiment, the gas permeable film of the secondary battery according to the present invention is characterized in that the second polymer layer includes a polypropylene acrylic acid copolymer.

In one embodiment, the pouch exterior material according to the present invention is a pouch exterior material that accommodates an electrode assembly; wherein the pouch exterior material has a structure in which a metal layer and a polymer layer are laminated, the pouch exterior material has one or more holes, and , wherein the one or more holes are sealed with the gas-permeable film described above.

In one embodiment, the pouch exterior material is characterized in that the outer layer and the inner layer are the polymer layer, and the deep portion interposed between the outer layer and the inner layer is the metal layer.

In one embodiment, the outer layer of the pouch exterior material includes at least one selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, polycarbonate, and nylon. It is characterized by:

In one embodiment, the deep portion of the pouch exterior material includes at least one selected from the group consisting of aluminum, copper, nickel, iron, carbon, chromium, manganese, and alloys containing two or more of these. Pouch exterior material.

In one embodiment, the inner layer portion of the pouch exterior material is characterized in that it includes at least one selected from the group consisting of polypropylene, acid-modified polypropylene, random polypropylene, and ethylene propylene copolymer.

In one embodiment, the pouch exterior material includes an electrode assembly stored in the pouch exterior material having an electrode lead electrically connected to the electrode assembly, the electrode lead being drawn out to the outside of the pouch exterior material, and the electrode lead being connected to the outside of the pouch exterior material. A gas collecting part is formed between the area drawn out and the electrode assembly, and a hole is formed in the pouch exterior material area corresponding to the gas collecting part.

The gas permeable film according to the present invention has excellent physical properties as a gas permeable material and has excellent durability due to excellent adhesion between the films constituting the gas permeable film. In addition, when the gas-permeable film according to the present invention is applied to a hole formed in the exterior material of a secondary battery pouch, it has excellent adhesion to the exterior material of the pouch and can effectively prevent penetration of external moisture, or when applied to the lead film for a secondary battery, the secondary battery Gas generated inside the battery can be smoothly discharged to the outside.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention along with the contents of the above-described invention. Therefore, the present invention is limited to the matters described in such drawings. It should not be interpreted in a limited way.
1 is a cross-sectional view of a gas-permeable film according to an embodiment of the present invention.
Figure 2 is a perspective view of an electrode assembly according to an embodiment of the present invention.
Figure 3 is a cross-sectional view of an electrode assembly and a pouch exterior material according to an embodiment of the present invention.
Figure 4 is an enlarged cross-sectional view of the electrode lead portion of the pouch exterior material according to an embodiment of the present invention.
Figure 5 is an enlarged cross-sectional view of the electrode lead portion of the pouch exterior material according to an embodiment of the present invention, showing a case where the gas discharge path is opened toward the upper pouch.
Figure 6 is an enlarged cross-sectional view of the electrode lead portion of the pouch exterior material according to an embodiment of the present invention, showing another example when the gas discharge path is open to the upper and lower pouch sides.
Figure 7 is a cross-sectional view of the pouch exterior material according to an embodiment of the present invention, showing a case in which a hole is formed.
Figure 8 is an enlarged cross-sectional view of a portion where a hole is formed in the pouch exterior material according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. Terms or words used in this specification and claims should not be construed as limited to their common or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it is.

Accordingly, the embodiments described in this specification and the configurations described in the drawings are only one of the most preferred embodiments of the present invention, and do not represent the entire technical idea of the present invention, so at the time of filing this application, various alternatives are available to replace them. It should be understood that equivalents and variations may exist.

The terminology used herein is for describing embodiments and is not intended to limit the invention. As used herein, singular forms also include plural forms, unless specifically stated otherwise in the context. As used in the specification, “comprises” and/or “comprising” does not exclude the presence or addition of one or more other elements in addition to the mentioned elements.

In this specification, when it is said that a part includes a certain component, this does not mean that other components are excluded, but that it may further include other components, unless specifically stated to the contrary.

The description of “A and/or B” herein means A, or B, or A and B.

In this specification, “%” means weight percent unless explicitly stated otherwise.

According to one aspect of the present invention, a gas permeable film is provided including a first polymer layer, a second polymer layer, and a third polymer layer located between the first polymer layer and the second polymer layer.

Here, the third polymer layer includes polypropylene (PP) and polytetrafluoroethylene (PTFE), and the weight ratio of the two polymer materials may be 9:1 to 1:9, preferably 8. :2 or less, 7:3 or less, or 6:4 or less, and 2:8 or more or 3:7 or more. By containing polytetrafluoroethylene in the above range, the film according to the present invention can block moisture while effectively discharging gas, and can improve adhesion between films. If either polypropylene or polytetrafluoroethylene is extremely small or large, or only one of them is present, for example, if polypropylene is extremely large, the gas permeation performance becomes significantly poor, resulting in the problem of not being able to prevent the swelling phenomenon. If there is an extremely large amount of polytetrafluoroethylene, the adhesion between films cannot be maintained, and there is a risk that durability will be significantly poor. Accordingly, it may be desirable to mix polypropylene and polytetrafluoroethylene in the above range.

When the third polymer layer is exposed to the outside, for example, when it becomes a surface that adheres to an electrode lead or a surface that is fused to a pouch, the content of polytetrafluoroethylene must be sufficiently increased because it affects the adhesive performance. I can't. However, in the present invention, since the third polymer layer is located between the first polymer layer and the second polymer layer, it is not exposed to the outside, so a relatively excessive amount of polytetrafluoroethylene can be included. In this case, gas Emission performance may be even better.

Polypropylene is a material with good moldability and excellent dimensional stability. In addition, it is lightweight and has good chemical resistance, bending fatigue resistance, and heat resistance, so it is used in various housings, exterior materials, films, etc. However, because polypropylene is moisture permeable, the moisture blocking effect is insufficient when only polypropylene is used as the polymer layer. Meanwhile, polytetrafluoroethylene is a material with good moisture barrier properties and particularly excellent gas permeability, but has low adhesiveness.

In the present invention, the third polymer layer includes polypropylene and polytetrafluoroethylene as a mixture, and can exhibit both the excellent mechanical properties and adhesiveness of polypropylene and the moisture blocking effect of polytetrafluoroethylene, and the gas according to the present invention. The gas permeability of the permeable film can be further improved.

Figure 1 is a cross-sectional view of a gas permeable film 10 according to an embodiment of the present invention. The third polymer layer 13 is located between the first polymer layer 11 and the second polymer layer 12.

In one embodiment of the present invention, the first polymer layer and the second polymer layer may each independently include a polyolefin-based polymer, and the first polymer layer is polypropylene (PP) or polyethylene terephthalate. , PET), polyethylenenaphtalate (PEN), polybutyleneterephthalate (PBT), polybutylenenaphtalate (PBN), and polyimide (PI). It may include more.

Specifically, the polypropylene resin may include propylene polymer (homopolypropylene), propylene copolymer (PP co-polymer), propylene terpolymer (PP ter-polymer), etc. In addition, the propylene copolymer (PP co-polymer) may include a propylene-ethylene block copolymer, etc., and the propylene terpolymer (PP ter-polymer) may include a propylene-ethylene-butylene block copolymer, etc. You can.

When the first polymer layer includes polypropylene, the water resistance of the film manufactured according to the present invention can be improved because polypropylene is a hydrophobic material. In addition, because the melting point of polypropylene is high, the film according to the present invention has excellent heat resistance and can improve the sealing effect. Additionally, physical properties such as adhesion and mechanical strength of the film according to the present invention may be improved.

In addition, in one embodiment of the present invention, the second polymer layer is poly(propylene-co-acrylic acid), polyphthalamide (PPA), polypropylene (PP), or polyethylene. In the group consisting of polyyehyleneterephthalate (PET), polyethylenenaphthalate (PEN), polybutyleneterephthalate (PBT), polybutylenenaphtalate (PBN), and polyimide (PI) It may include one or more selected types.

When the second polymer layer includes polypropylene, the water resistance of the film manufactured according to the present invention can be improved because polypropylene is a hydrophobic material. In addition, because the melting point of polypropylene is high, the film according to the present invention has excellent heat resistance and can improve the sealing effect. Additionally, physical properties such as adhesion and mechanical strength of the film according to the present invention may be improved. In particular, when the second polymer layer includes a polypropylene acrylic acid copolymer, the adhesion of the film according to the present invention can be improved. For example, when the second polymer layer is a polypropylene acrylic acid copolymer, the adhesion of the film with the electrode lead can be improved. Adhesion becomes excellent.

In one embodiment according to the present invention, the thickness of the first polymer layer is 40 to 200 ㎛, 40 to 80 ㎛, or 80 to 200 ㎛. Since the thickness of the first polymer layer falls within the above range, the film according to the present invention is lightweight and has excellent mechanical properties and heat resistance.

In one embodiment according to the present invention, the thickness of the second polymer layer is 40 to 200 ㎛, 40 to 80 ㎛, or 80 to 200 ㎛. Since the thickness of the first polymer layer falls within the above range, the film according to the present invention is lightweight and has excellent mechanical properties and heat resistance.

In one embodiment according to the present invention, the third polymer layer has a thickness of 40 to 600 ㎛, 40 to 120 ㎛, or 120 to 600 ㎛. If the thickness of the first polymer layer falls within the above range, the film according to the present invention has sufficient gas permeability.

According to one aspect of the present invention, an electrode assembly; A pouch exterior material that accommodates the electrode assembly; an electrode lead electrically connected to the electrode assembly; and a gas-permeable film according to the present invention described above, which is adhered to at least one surface of the electrode lead.

In general, a secondary battery consists of an electrode assembly consisting of a positive electrode, a negative electrode, and a separator located between them, an electrolyte that transfers lithium ions through the separator, a pouch that stores them, and an electrode lead that allows the passage of current out of the pouch. do.

The electrode lead is electrically connected to the positive electrode (or the positive electrode uncoated area or the positive electrode tab drawn from the positive electrode) and/or the negative electrode (or the negative electrode uncoated area or the negative electrode tab drawn from the negative electrode) of the electrode assembly and is used as the positive terminal or negative electrode terminal. It will happen.

Here, the lead film is attached to the electrode lead to prevent short circuits in the electrode lead and serves to seal the electrode lead and the exterior material. When the gas-permeable film according to the present invention is applied as a lead film, gas generated inside the pouch can be effectively discharged while maintaining sealing properties. Gas may be discharged by penetrating the first, second, and third polymer layers of the gas-permeable film. When the gas-permeable film according to the present invention is applied to the electrode lead, the gas will be discharged in the horizontal direction. In this case, the amount of gas moving through the third polymer layer may be the largest.

The lead film may be formed on the upper and lower surfaces of the electrode lead, and may be formed to cover both sides, including the upper and lower surfaces, so as to cover even the side surfaces of the electrode lead.

Additionally, the other side of the lead film that faces the electrode lead may face the exterior material. Furthermore, the lead film may be bonded to the pouch exterior material through an adhesive, or may be heat-sealed to the pouch exterior material through heat fusion.

Figure 2 shows that the gas permeable film according to the present invention is attached to the electrode lead 120 electrically connected to the electrode assembly 100 according to one embodiment of the present invention as the lead film 110. In addition, Figure 3 is a cross-sectional view showing a secondary battery according to an embodiment of the present invention. The pouch exterior material includes an upper pouch (220a) and a lower pouch (220b), and the upper pouch (220a) and lower pouch (220b) The electrode assembly 100 and the electrolyte (not shown) are accommodated in the internal space 300 formed by . In addition, the upper pouch 220a and the lower pouch 220b have a sealing portion formed on the terrace portion 230 on the outer peripheral surface to seal the internal space, and these sealing portions are bonded (sealed) to each other using a method such as heat fusion.

This pouch exterior material protects internal components such as the electrode assembly 100 and the electrolyte, and is composed of a metal layer such as an aluminum thin film to supplement the electrochemical properties of the electrode assembly 100 and the electrolyte and increase heat dissipation. do. And, this metal layer is interposed between polymer layers formed of an insulating material to ensure insulation. However, gas may be generated internally due to the reaction between the electrode assembly 100 and the electrolyte, and the metal layer and polymer layer used as the existing pouch exterior material have poor gas permeability, so the pouch exterior material may expand or explode. Therefore, the gas generated inside the pouch exterior material must be efficiently discharged to the outside.

Accordingly, by applying the gas-permeable film as described above as a lead film on the electrode lead, when the internal pressure increases due to the gas generated internally, the gas is discharged in a horizontal direction relative to the film through the lead film, which is a gas-permeable film, or the electrode As a portion of the interface between the lead and the lead film is opened, a gas discharge path is formed, and the gas may be transmitted and discharged through the gas-permeable film (lead film) in a direction perpendicular to the film.

Although not specifically shown in the drawings, as shown in FIG. 5 or 6, a film may be further included so that a portion of the interface between the electrode lead and the lead film can be opened. The additional film may be a path forming film, and the path forming film is disposed between the electrode lead and the lead film in the area where the lead film and the electrode lead are bonded, excluding the outermost part in the electrode lead protruding direction. It can be. This path forming film may function to weaken the adhesive force between the electrode lead and the lead film so that the lead film portion can be opened when the internal pressure of the pouch increases. At this time, among the areas where the lead film and the electrode lead are bonded, the outermost portion in the electrode lead protruding direction may be about 10% to 60% of the bonded area.

Specifically, referring to FIG. 4 , a gas permeable film 210 may be disposed as a lead film 110 on the electrode lead 120 on the upper pouch 220a and lower pouch 220b.

When the pressure inside the battery increases due to the gas generated internally, as shown in FIG. 5, a portion of the interface between the electrode lead 120 and the lead film 110, that is, the first polymer layer of the gas permeable film 210 The interface between (11) and the electrode lead 120 may be opened to form a gas discharge path 320, and as shown in FIG. 6, the gas permeable film 210 on both the upper and lower pouch sides may be opened to form a gas discharge path 320. ) may be formed, and the gas may pass through the gas permeable film 210 through the gas discharge path 320 and be discharged to the outside, thereby lowering the internal pressure of the battery.

According to one embodiment of the present invention, the second polymer layer in the gas permeable film according to the present invention adhered to the electrode lead is characterized by comprising a polypropylene acrylic acid copolymer. Since the electrode lead is made of a metal material, the adhesion to the metal can be improved by including polypropylene acrylic acid copolymer in the second polymer layer of the film according to the present invention. Therefore, when the gas-permeable film is adhered to the electrode lead, it is preferable to adhere the second polymer layer so that it faces the electrode lead.

The polypropylene acrylic acid copolymer of the second polymer layer can be manufactured by treating the polypropylene layer with maleic anhydride.

According to one embodiment of the present invention, in the gas permeable film according to the present invention adhered to the electrode lead, the thickness of the first polymer layer is 80 to 200 μm, 80 to 180 μm, 80 to 160 μm, and 100 to 200 μm. , it is preferably 120 to 200 μm, 100 to 180 μm, or 120 to 160 μm. When the gas-permeable film according to the present invention is applied as a lead film attached to an electrode lead, the gas generated inside the pouch penetrates the film in the horizontal direction and is discharged to the outside. Therefore, when the thickness of the film applied as the lead film falls within the above range, appropriate horizontal gas permeability can be achieved and electrolyte sealing properties can be maintained.

According to one embodiment of the present invention, in the gas permeable film according to the present invention adhered to the electrode lead, the thickness of the second polymer layer is 80 to 200 μm, 80 to 180 μm, 80 to 160 μm, and 100 to 200 μm. , it is preferably 120 to 200 μm, 100 to 180 μm, or 120 to 160 μm. When the gas-permeable film according to the present invention is applied as a lead film attached to an electrode lead, the gas generated inside the pouch penetrates the film in the horizontal direction and is discharged to the outside. Therefore, when the thickness of the gas permeable film applied as the lead film falls within the above range, appropriate horizontal gas permeability can be achieved and electrolyte sealing properties, etc. can be maintained.

According to one embodiment of the present invention, in the gas permeable film according to the present invention adhered to the electrode lead, the thickness of the third polymer layer is 120 to 600 ㎛, 150 to 600 ㎛, 200 to 600 ㎛, 250 to 600 ㎛ , 120 to 550 μm, 120 to 500 μm, 120 to 450 μm, 150 to 550 μm, 200 to 500 μm, 250 to 450 μm, or 300 to 400 μm. When the gas-permeable film according to the present invention is applied as a lead film attached to an electrode lead, the gas generated inside the pouch penetrates the gas-permeable film in the horizontal direction and is discharged to the outside. Therefore, when the thickness of the gas permeable film applied as the lead film falls within the above range, appropriate horizontal gas permeability can be achieved and electrolyte sealing properties, etc. can be maintained.

According to one embodiment of the present invention, the metal conductor used as an electrode lead is copper (Cu), aluminum (Al), nickel (Ni), iron (Fe), carbon (C), chromium (Cr), and manganese (Mn). ) and an alloy containing two or more of these, but is not limited thereto, and any material that can be electrically connected to the electrode tab can be used without particular limitation. The metal conductor may include aluminum, optionally silicon, boron, germanium, arsenic, antimony, copper, magnesium, manganese, zinc, lithium, iron, chromium, vanadium, titanium, bismuth, potassium, tin, lead. It may be an alloy containing an element selected from the group consisting of zirconium, nickel, cobalt, and combinations thereof.

The metal conductor can be selected considering mechanical strength and flexibility. In addition, aluminum is preferably used for the anode, and copper, nickel, or a nickel-plated metal is preferably used for the cathode, but is not limited to this. In addition, the metal conductor may have a thickness of 0.1 mm to 1.0 mm and a width of 1 mm to 200 mm, but is not limited thereto and may have a standard determined according to the purpose of the secondary battery being manufactured.

According to one aspect of the present invention, a pouch exterior material for storing an electrode assembly, wherein the pouch exterior material has a structure in which a metal layer and a polymer layer are laminated, the pouch exterior material has one or more holes, and the one or more holes. A pouch exterior material is provided, wherein the hole is sealed with the gas-permeable film according to the present invention described above.

Since the portion of the pouch exterior material where the metal layer and polymer layer are laminated has low gas permeability, it is difficult to discharge gas generated inside the pouch from the portion where the metal layer and polymer layer are laminated. Therefore, after the metal layer and the polymer layer are stacked and one or more holes are formed vertically penetrating the same position of each layer, the one or more holes are sealed with the gas-permeable film according to the present invention described above, so that the electrolyte solution While maintaining the role of the pouch exterior material that prevents escape and protects the internal electrode assembly, gas can be smoothly discharged through the gas-permeable film portion according to the present invention. Specifically, since the first polymer layer, the second polymer layer, and the third polymer layer of the gas-permeable film according to the present invention have excellent gas permeability, the gas generated inside the pouch exterior material flows through the gas-permeable film according to the present invention in the vertical direction. It can penetrate and be discharged to the outside.

The location of the hole formed in the pouch exterior material is not limited, but, for example, may be formed at a location that does not directly contact the electrode assembly stored in the pouch exterior material.

Figure 7 is a cross-sectional view of an electrode assembly and a pouch exterior material according to an embodiment of the present invention. When the electrode lead 120 electrically connected to the electrode assembly 100 is drawn out of the pouch exterior material 200, the area where the electrode lead 120 is drawn out of the pouch exterior material 200 and the electrode assembly 100 A gas collection unit 310 may be formed between them. Here, one or more holes may be formed in the area of the pouch exterior material corresponding to the gas collection unit 310, and the formed holes may be sealed by the gas-permeable film 210 according to the present invention. At this time, the area of the pouch exterior material corresponding to the gas collection unit 310 may not be in direct contact with the electrode assembly. Therefore, when the gas permeable film 210 according to the present invention is located in the area of the pouch exterior material corresponding to the gas collection portion 310, the gas permeable film 210 may not be in direct contact with the electrode assembly 100. .

Here, sealing may be performed through heat fusion, but is not necessarily limited thereto and may be performed using various methods commonly used for sealing. As the lead film 110, the gas permeable film according to the present invention may be used, but a conventionally widely used lead film may also be used.

In one embodiment of the present invention, when the gas permeable film according to the present invention is applied to the pouch exterior material, the lead film attached to the electrode lead electrically connected to the electrode assembly stored in the pouch exterior material is the gas permeable film according to the present invention. It may be a film, but a lead film generally used in the secondary battery technology field may also be used. For example, the lead film 110 may include polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, polyimide, or two or more thereof.

In one embodiment of the present invention, the gas permeable film may be located on the inner layer of the pouch exterior material. Specifically, one or more holes may be formed in the pouch exterior material, a gas permeable film may be placed on the inner layer of the pouch exterior material, and then the hole may be sealed.

In one embodiment of the present invention, the gas-permeable film may be located on the outer layer of the pouch exterior material. Specifically, one or more holes may be formed in the pouch exterior material, a gas permeable film may be placed on the outer layer of the pouch exterior material, and then the hole may be sealed. Here, sealing may be performed through heat fusion, but is not necessarily limited thereto and may be performed using various methods commonly used for sealing.

In one embodiment of the present invention, the size (diameter) of the hole formed in the pouch exterior material may be 0.5 mm to 20 mm, 1 mm to 10 mm, or 3 mm to 7 mm. If the size of the hole satisfies the above range, when the gas-permeable film according to the present invention seals the hole, gas generated within the pouch can be sufficiently discharged.

In one embodiment of the present invention, the hole formed in the pouch exterior material may be formed in a circular, triangular, square, or polygonal shape. However, the shape of the hole is not limited to this and can be formed in any shape that can be selected by a person skilled in the art.

Figure 8 shows a cross section of the pouch exterior material according to one embodiment. The pouch exterior material is a stack of a metal layer and a polymer layer. The deep layer 223 is a metal layer, and the inner layer 221 and the outer layer 222 are a polymer layer. Here, the laminated metal layer and the polymer layer have holes formed at the same location in each layer, and the holes are sealed with the gas-permeable film 210 according to the present invention. A pouch exterior material made of only a conventional metal layer and a polymer layer without the gas-permeable film 210 according to the present invention may have low gas permeability. However, the pouch exterior material according to the present invention includes a gas-permeable film 210 with excellent gas permeability, so the pouch exterior material can smoothly discharge gas.

According to one embodiment of the present invention, in the gas permeable film according to the present invention in which the one or more holes are sealed, the thickness of the first polymer layer is 40 to 80㎛, 40 to 70㎛, 40 to 60㎛, 50 to 80㎛. It is preferably 80 ㎛, 60 to 80 ㎛, 55 to 75 ㎛ or 50 to 70 ㎛. When the gas-permeable film according to the present invention is applied to the pouch exterior material, the gas generated inside the pouch permeates the film in the vertical direction and is discharged to the outside. Therefore, when the thickness of the film applied to the pouch exterior material falls within the above range, appropriate vertical gas permeability can be achieved and mechanical strength and electrolyte sealing properties can be maintained.

According to one embodiment of the present invention, in the gas permeable film according to the present invention in which the one or more holes are sealed, the thickness of the second polymer layer is 40 to 80㎛, 40 to 70㎛, 40 to 60㎛, 50 to 80㎛. It is preferably 80 μm, 60 to 80 μm, 55 to 75 μm, or 50 to 70 μm. When the gas-permeable film according to the present invention is applied to the pouch exterior material, the gas generated inside the pouch permeates the film in the vertical direction and is discharged to the outside. Therefore, when the thickness of the film applied to the pouch exterior material falls within the above range, appropriate vertical gas permeability can be achieved and mechanical strength and electrolyte sealing properties can be maintained.

According to one embodiment of the present invention, in the film according to the present invention in which the one or more holes are sealed, the thickness of the third polymer layer is 40 to 120 μm, 40 to 100 μm, 40 to 80 μm, and 60 to 120 μm. , it is preferably 80 to 120 μm, 50 to 110 μm, or 60 to 100 μm. When the film according to the present invention is applied to the pouch exterior material, the gas generated inside the pouch penetrates the film in the vertical direction and is discharged to the outside. Therefore, when the thickness of the film applied to the pouch exterior material falls within the above range, appropriate vertical gas permeability can be achieved and mechanical strength and electrolyte sealing properties can be maintained.

According to one embodiment of the present invention, the laminated metal layer and polymer layer of the pouch exterior material are characterized in that the outer layer and the inner layer are polymer layers, and the metal layer is located in the deep portion sandwiched between the outer layer and the inner layer. That is, the outer layer and inner layer of the pouch exterior material may be a polymer layer, and the deep layer interposed between the outer layer and the inner layer may be a metal layer.

The outer layer may include one or more selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, polycarbonate, and nylon, and may be a single layer or multilayer. It can be composed of . However, it is not limited to this, and any material commonly used in the technology field for pouch exterior materials can be used.

The deep portion may include one or more selected from the group consisting of aluminum, copper, nickel, iron, carbon, chromium, manganese, and alloys containing two or more of these, and may be composed of a single layer or multiple layers. . However, it is not limited to this, and any material commonly used in the technology field for pouch exterior materials can be used.

The inner layer may include one or more selected from the group consisting of polypropylene, acid-modified polypropylene, random polypropylene, and ethylene propylene copolymer, and may be composed of a single layer or multiple layers. However, it is not limited to this, and any material commonly used in the technology field for pouch exterior materials can be used.

Hereinafter, the present invention will be further described in detail through examples. However, the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited to these only.

1. Gas permeable film applied as a lead film

Example 1-1

(1) Production of gas permeable film

Polypropylene with a thickness of 40 ㎛ as the first polymer layer, polypropylene acrylic acid copolymer with a thickness of 100 ㎛ as the second polymer layer, and polypropylene and polytetrafluoroethylene with a thickness of 60 ㎛ as the third polymer layer in a ratio of 3:7. A mixture mixed in weight ratio was prepared.

Afterwards, the first polymer layer, the third polymer layer, and the second polymer layer were sequentially laminated and then heat-sealed to produce a gas-permeable film.

(2) Manufacturing of pouch exterior material

A polyethylene terephthalate (PET) film with a width of 266 mm, a length of 50 m, and a thickness of 60 ㎛ is placed on one side of an aluminum alloy thin film measuring 266 mm in width, a height of 50 m, and a thickness of 60 ㎛, and a polyethylene terephthalate (PET) film of 266 mm in width, 50 m in height, and 12 ㎛ thick, and a film of 266 mm in width, 50 m in height, and 25 ㎛ thickness. A nylon film was laminated, and a polypropylene film with a width of 266 mm, a length of 50 m, and a thickness of 80 ㎛ was laminated on the other side to prepare a pouch film laminate with a polyethylene terephthalate/nylon/aluminum alloy thin film/polypropylene film structure.

Here, the polyethylene terephthalate film and nylon film are the base layer, the aluminum alloy thin film is the gas barrier layer, and the polypropylene film is the sealant layer.

The pouch film laminate was molded to manufacture a pouch-type case including a storage portion and a sealing portion.

(3) Manufacturing of secondary batteries

An electrode assembly was manufactured by assembling the cathode, anode, and porous polyethylene separator using a stacking method and then lamination. Afterwards, an electrode lead was coupled to the electrode assembly.

An electrolyte was prepared by dissolving LiPF ₆ to 1.0M in a solvent (EC:EMC:DMC = 3:3:4 volume ratio). The electrode assembly was stored in the pouch-type case with the tip of the electrode lead pulled out, and the electrolyte was injected.

The gas-permeable film prepared above was laminated as a lead film on the upper surface of the electrode lead.

Thereafter, the sealing portion of the pouch-type case was sealed for 2 seconds under the conditions of a seal bar area of 200 mm × 10 mm, 220°C, and 0.27 MPa, and then left at 60°C for 4 hours to manufacture a pouch-type secondary battery. At this time, the part of the sealing part where the lead film is formed has a structure in which lower case / lead film / electrode lead / gas discharge part / lead film / upper case are sequentially stacked.

Example 1-2

A gas-permeable film was prepared in the same manner as in Example 1-1, except that a mixture containing polypropylene and polytetrafluoroethylene at a weight ratio of 5:5 was used in the third polymer layer, and a pouch-type secondary film was prepared in the same manner. A battery was manufactured.

Example 1-3

A gas-permeable film was prepared in the same manner as in Example 1-1, except that a mixture containing polypropylene and polytetrafluoroethylene at a weight ratio of 7:3 was used in the third polymer layer, and a pouch-type secondary film was prepared in the same manner. A battery was manufactured.

Example 1-4

A gas permeable film was manufactured in the same manner as Example 1-3, except that polypropylene was used as the second polymer layer instead of polypropylene acrylic acid copolymer.

Comparative Example 1-1

Polypropylene with a thickness of 40 ㎛ was prepared as the first polymer layer, polypropylene acrylic acid copolymer with a thickness of 100 ㎛ as the second polymer layer, and polypropylene with a thickness of 60 ㎛ as the third polymer layer. Afterwards, the first polymer layer, the third polymer layer, and the second polymer layer were laminated and then heat-sealed to produce a gas-permeable film.

Thereafter, the pouch exterior material and secondary battery were manufactured in the same manner as Example 1-1.

Comparative Example 1-2

A gas permeable film, pouch exterior material, and secondary battery were manufactured in the same manner as Example 1-1 except that a polytetrafluoroethylene film alone was used as the third polymer layer.

Comparative Example 1-3

A gas permeable film, pouch exterior material, and secondary battery were manufactured in the same manner as Example 1-1, except that the first and second polymer layers were not formed and the third polymer layer was formed at a thickness of 200 ㎛. did.

2. Gas permeable film placed on the pouch exterior material

Example 2-1

(1) Production of gas permeable film

A gas permeable film was manufactured in the same manner as Example 1-1, except that polypropylene was used as the second polymer layer instead of polypropylene acrylic acid copolymer.

(2) Manufacturing of pouch exterior material

On one side of the aluminum alloy thin film measuring 266 mm wide, 50 m long, and 60 ㎛ thick, a polyethylene terephthalate (PET) film 266 mm wide, 50 m long, and 12 ㎛ thick, and a polyethylene terephthalate (PET) film 266 mm wide, 50 m long, and 25 ㎛ thick. A nylon film was laminated, and a polypropylene film with a width of 266 mm, a length of 50 m, and a thickness of 80 ㎛ was laminated on the other side to prepare a pouch film laminate with a polyethylene terephthalate/nylon/aluminum alloy thin film/polypropylene film structure.

Here, the polyethylene terephthalate film and nylon film are the base layer, the aluminum alloy thin film is the gas barrier layer, and the polypropylene film is the sealant layer.

The pouch film laminate was molded to manufacture a pouch exterior material including a receiving portion and a sealing portion.

Afterwards, a hole with a diameter of 5 mm was punched in the area of the receiving part adjacent to the sealing part to form a through hole, and the previously prepared gas permeable film was placed on the punched hole toward the inner layer and heat treated. A pouch exterior material was manufactured by heat fusion on the pouch film laminate and sealing the hole formed in the pouch film laminate.

At this time, the pouch exterior material was manufactured in a shape that allows a gas collecting portion to be formed between the electrode assembly and the area where the electrode lead is drawn out to the pouch exterior material when the electrode assembly connected to the electrode lead is stored, and the hole corresponds to the gas collecting portion. It was punched to be located on the pouch exterior material of the area.

(3) Manufacturing of secondary batteries

An electrode assembly was manufactured by assembling the cathode, anode, and porous polyethylene separator using a stacking method and then lamination. Afterwards, an electrode lead was coupled to the electrode assembly.

An electrolyte was prepared by dissolving LiPF ₆ to 1.0M in a solvent (EC:EMC:DMC = 3:3:4 volume ratio). The electrode assembly was stored in the pouch-type case with the tip of the electrode lead pulled out, and the electrolyte was injected.

Thereafter, the sealing portion of the pouch-type case was sealed for 2 seconds under the conditions of a seal bar area of 200 mm × 10 mm, 220°C, and 0.27 MPa, and then left at 60°C for 4 hours to manufacture a pouch-type secondary battery. At this time, the part of the sealing part where the lead film is formed has a structure in which lower case / lead film / electrode lead / gas discharge part / lead film / upper case are sequentially stacked.

Example 2-2

A gas-permeable film was prepared in the same manner as in Example 2-1, except that a mixture containing polypropylene and polytetrafluoroethylene in a weight ratio of 5:5 was used in the third polymer layer, and a pouch-type secondary film was prepared in the same manner. A battery was manufactured.

Example 2-3

A gas-permeable film was prepared in the same manner as in Example 2-1, except that a mixture containing polypropylene and polytetrafluoroethylene at a weight ratio of 7:3 was used in the third polymer layer, and a pouch-type secondary film was prepared in the same manner. A battery was manufactured.

Comparative Example 2-1

Polypropylene with a thickness of 40 ㎛ was prepared as the first polymer layer, polypropylene acrylic acid copolymer with a thickness of 100 ㎛ as the second polymer layer, and polypropylene with a thickness of 60 ㎛ as the third polymer layer. Afterwards, the first polymer layer, the third polymer layer, and the second polymer layer were laminated and heat-sealed to produce a gas-permeable film, and a pouch-type secondary battery was manufactured in the same manner.

Comparative Example 2-2

A gas-permeable film and a pouch-type secondary battery were manufactured in the same manner as Comparative Example 2-1, except that a polytetrafluoroethylene film alone was used as the third polymer layer.

Comparative Example 2-3

A gas permeable film and a pouch-type secondary battery were manufactured in the same manner as Example 2-1, except that the first and second polymer layers were not formed and the third polymer layer was formed at a thickness of 200 ㎛. .

Experimental Example 1: Evaluation of adhesion of gas permeable film

For the pouch-type secondary batteries manufactured in Examples and Comparative Examples, the adhesion between the pouch film and the gas-permeable film and the adhesion between the laminated films within the gas-permeable film were evaluated. For set No. 1, the adhesion with the electrode lead was evaluated. was further evaluated

Specifically, CO ₂ gas was generated inside the pouch exterior material and then stored in a 60°C chamber for 5 days. After that, the electrode lead is broken by bending a part 10 mm apart from one edge of the sealing part, and both ends of the lead assembly are joined to the lower jig and upper jig of the UTM, respectively, and then 30 mm in the 180° direction at a speed of 50 mm/min. The average value (kgf/15mm) of the flat section of the adhesive strength graph measured when pulled was calculated. The results are shown in Tables 1 and 2 below.

Experimental Example 2: Evaluation of gas discharge rate

Using ITS's pressure-resistant equipment, CO2 was injected into the pouch-type secondary battery to increase the pressure inside the pouch until the pressure difference between the inside and outside of the pouch reached 1.0 to 2.5 bar, and then placed in a 60°C chamber for 1 to 2 days. Saved. During the storage period, the decrease in pressure inside the pouch was confirmed, and the gas discharge rate was calculated based on the flow rate and pressure decrease values, and are shown in Tables 1 and 2 below.

gas permeable film Gas discharge speed
(ccmm/m ² day) Adhesion (kgf/15mm) 1st floor 2nd floor 3rd floor 1st - 3rd floor 2nd - 3rd floor 1st layer - pouch Second layer - electrode leads Example 1-1 PP PPa PP+PTFE(3:7) 279 1.1 1.0 12.3 7.7 Example 1-2 PP PPa PP+PTFE(5:5) 160 0.8 0.9 12.7 7.3 Example 1-3 PP PPa PP+PTFE(7:3) 124 0.9 1.1 13.1 8.7 Example 1-4 PP PP PP+PTFE(7:3) 121 0.9 1.0 12.8 0.1 Comparative Example 1-1 PP PPa PP(100%) 92 0.9 1.0 11.5 7.0 Comparative Example 1-2 PP PPa PTFE (100%) - < 0.1 < 0.1 - - Comparative Example 1-3 X X PP+PTFE(3:7) 290 - - 3.3 < 0.1

gas permeable film Gas discharge speed
(ccmm/m ² day) Adhesion (kgf/15mm) 1st floor 2nd floor 3rd floor 1st - 3rd floor 2nd - 3rd floor Film (first layer)-pouch adhesion Example 2-1 PP PP PP+PTFE(3:7) 281 0.9 0.9 12.3 Example 2-2 PP PP PP+PTFE(5:5) 158 1.2 1.0 11.7 Example 2-3 PP PP PP+PTFE(7:3) 113 0.9 1.0 13.9 Comparative Example 2-1 PP PPa PP(100%) 96 1.0 0.9 11.5 Comparative Example 2-2 PP PPa PTFE (100%) - < 0.1 < 0.1 - Comparative Example 2-3 - - PP+PTFE(3:7) 290 3.2

Referring to Table 1, the gas permeable films of Examples 1-1 to 1-4 according to an embodiment of the present invention are placed on electrode leads to maintain adhesion between films at an excellent level and also maintain adhesion with the pouch exterior material. It can be confirmed that it can be maintained excellently, and gas emission performance can also be confirmed to be excellent. However, in Examples 1-4, the adhesion with the electrode lead was measured to be low, and in this case, when the interface between the lead film and the electrode lead is opened and the gas discharge path is formed, the internal pressure is slightly higher, and the lead film at the outer end is damaged. It can be seen that there may be a problem of a venting phenomenon occurring when the electrode lead fails to maintain adhesion and completely peels off. Through this, it can be confirmed that it is more preferable to apply a modified polyolefin-based polymer as the second layer, as can be seen from the results of Examples 1-1 to 1-3.

Meanwhile, in the case of Comparative Example 1-2, in which only PTFE was applied as the third layer, it was difficult to form the gas-permeable film itself due to problems with adhesion, so the adhesion with the electrode lead and the pouch exterior material could not be measured, and thus the gas discharge performance could not be confirmed. There wasn't. In addition, Comparative Example 1-1 is a case where only PP was used without mixing PTFE in the third layer. In this case, the adhesive strength was similar to the Examples, but it could be confirmed that the gas discharge performance was very poor compared to the Examples. Furthermore, in the case of Comparative Example 1-3, in which a film was formed by mixing PP and PTFE in a single layer, it was possible to form the film itself, but the adhesion between the pouch exterior material and the electrode lead was poor, so the problem was that it completely peeled off and vented the moment it was opened. Since this occurs, it can be confirmed that durability is very low.

The gas permeable film formed in the hole portion of the pouch exterior material in Table 2 also showed results that were not significantly different from the results in Table 1. In the Examples, the adhesion between films was excellent and the gas emission performance was also excellent compared to the Comparative Examples, but Comparative Examples 2-1 to 2-3 had poor emission performance or adhesion for the same reason as Comparative Examples 1-1 to 1-3. It has been confirmed.

As described above, although the present invention has been described with limited embodiments and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following will be understood by those skilled in the art. Of course, various modifications and variations are possible within the scope of equivalency of the patent claims described in .

10: Gas permeable film
11: first polymer layer
12: second polymer layer
13: Third polymer layer
100: Electrode assembly
110: lead film
120: electrode lead
200: Pouch exterior material
210: Gas permeable film
220a: upper pouch
220b: lower pouch
221: Inner layer part
222: outer layer
223: Deep
230: Terrace part
300: Internal space
310: gas collection unit
320: Gas exhaust path

Claims (15)

It includes a first polymer layer, a second polymer layer, and a third polymer layer disposed between the first polymer layer and the second polymer layer,
The third polymer layer is a gas permeable film characterized in that it contains polypropylene and polytetrafluoroethylene in a weight ratio of 9:1 to 1:9.
According to paragraph 1,
A gas permeable film, wherein the first polymer layer and the second polymer layer each independently contain a polyolefin-based polymer.
According to paragraph 1,
The second polymer layer is a gas-permeable film, characterized in that it contains a modified polyolefin-based resin.
According to paragraph 1,
The third polymer layer is a gas permeable film characterized in that polypropylene and polytetrafluoroethylene are included in a weight ratio of 8:2 to 2:8.
According to paragraph 1,
A gas permeable film, characterized in that the thickness of the first polymer layer is 40 to 200 ㎛.
According to paragraph 1,
A gas permeable film, characterized in that the thickness of the second polymer layer is 40 to 200 ㎛.
According to paragraph 1,
A gas permeable film, characterized in that the thickness of the third polymer layer is 40 to 600 ㎛.
electrode assembly; A pouch exterior material that accommodates the electrode assembly; an electrode lead electrically connected to the electrode assembly; And a secondary battery comprising the gas-permeable film of claim 1 adhered to at least one surface of the electrode lead.
According to clause 8,
The gas permeable film is a secondary battery, wherein the second polymer layer includes a polypropylene acrylic acid copolymer.
In the pouch exterior material for storing the electrode assembly,
The pouch exterior material has a structure in which a metal layer and a polymer layer are stacked,
The pouch exterior material has one or more holes, and the one or more holes are sealed with the gas-permeable film of claim 1.
According to clause 10,
The pouch exterior material has an outer layer and an inner layer made of the polymer layer,
A pouch exterior material, characterized in that the deep portion sandwiched between the outer layer portion and the inner layer portion is the metal layer.
According to clause 10,
The outer layer portion includes at least one member selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, polycarbonate, and nylon. A pouch exterior material.
According to clause 10,
The pouch exterior material, wherein the deep portion includes at least one selected from the group consisting of aluminum, copper, nickel, iron, carbon, chromium, manganese, and alloys containing two or more of these.
According to clause 10,
The pouch exterior material, wherein the inner layer includes at least one selected from the group consisting of polypropylene, acid-modified polypropylene, random polypropylene, and ethylene propylene copolymer.
According to clause 10,
The received electrode assembly has an electrode lead electrically connected to the electrode assembly,
The electrode lead is drawn out of the pouch exterior material,
A gas collection portion is formed between an area where the electrode lead is drawn out of the pouch exterior material and the electrode assembly,
A pouch exterior material, characterized in that the hole is formed in an area of the pouch exterior material corresponding to the gas collection portion.

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