Gas discharge membrane, secondary battery casing, secondary battery, gas discharge membrane fabrication method and secondary battery casing fabrication method

Abstract

The invention relates to a gas discharge film of very good gas discharge performance and capable of being efficiently fabricated. The gas discharge film of the invention is constructed to cover the opening formed in the outer material of the secondary cell and to discharge the internal gas of the outer material, and the gas discharge film may consist of a heat-bonded adhesive layer with a through hole formed therein; and a permeable layer laminated onto one surface of the adhesive layer to cover the through hole and having higher gas permeability than the adhesive layer, wherein the permeable layer may have a thickness equal to or greater than the adhesive layer.

Description

Gas discharge film, secondary battery case, secondary battery, gas discharge film manufacturing method, and secondary battery case manufacturing method

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0146958, filed October 30, 2023, and Korean Patent Application No. 10-2024-0148831, filed October 28, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a gas discharge film for discharging internal gas of a secondary battery, a secondary battery case including such a gas discharge film, a secondary battery including such a secondary battery case, and the like.

[0005] Batteries that store electrical energy can generally be divided into primary and secondary batteries. Primary batteries are disposable, consumable batteries, whereas secondary batteries are rechargeable batteries manufactured using materials capable of repeatable oxidation and reduction processes between current and a substance. In other words, when current causes a reduction reaction in a material, the battery is charged, and when an oxidation reaction occurs in the material, the battery is discharged. This repeated charging and discharging process generates electricity.

[0006] Secondary batteries can be classified into cylindrical cells, pouch cells, and prismatic cells based on their shape. Among them, pouch cells can be manufactured by housing an electrode assembly in which a positive electrode, a negative electrode, a separator, etc. are laminated inside a pouch, and sealing the outer part of the pouch.

[0007] Meanwhile, an electrolyte may be accommodated inside the pouch of the pouch cell together with an electrode assembly. At this time, residual moisture in the electrolyte or moisture that has penetrated from the outside may react with the lithium salt inside the pouch of the pouch cell to generate HF (hydrogen fluoride), and gases such as carbon dioxide, carbon monoxide, ethylene, and methane may be generated due to the decomposition of the electrolyte. In addition, depending on the material of the positive electrode included in the electrode assembly of the pouch cell, additional hydrogen and HF may be generated, which may cause overheating due to overcharging and internal short circuit during the charging and discharging process. As a result, a large amount of gas may be generated inside the pouch. This gas may increase the pressure inside the pouch, and the increased pressure may cause a swelling phenomenon in which the pouch swells or a venting phenomenon in which a portion of the pouch bursts. The pouch cell may include a structure capable of discharging gas inside the pouch to the outside to prevent the venting phenomenon.

[0008] An example of a structure capable of discharging gas from within a pouch to the outside is a structure that forms a hole in the pouch and discharges the gas through a gas discharge film. Conventional pouch cells containing gas discharge films have suffered from reduced gas discharge performance due to adhesive materials clogging the holes during the manufacturing process.

[0009] In addition, conventional gas discharge films are attached to the pouch by thermal fusion using a semi-permeable membrane, but there was a problem that the holes formed in the pouch were blocked due to excessive fusion when attaching such gas discharge films.

[0010] The object of the present invention is to provide a gas-releasing film having excellent gas-releasing performance and capable of preventing over-fusion when attached to a pouch, a secondary battery case including the gas-releasing film, and a secondary battery including the secondary battery case.

[0011] A gas discharge film according to the present invention covers an opening formed in an outer casing of a secondary battery and discharges internal gas of the outer casing, the gas discharge film comprising: an adhesive layer having adhesiveness due to heat and having a through hole formed therein; and a permeable layer laminated to one surface of the adhesive layer to cover the through hole and having a higher gas permeability than the adhesive layer; and the permeable layer may have the same thickness as the adhesive layer or may be formed thicker than the adhesive layer.

[0012] The thickness of the above-mentioned transmission layer and the thickness of the above-mentioned adhesive layer may be 10 μm to 100 μm.

[0013] The above adhesive layer may be composed of any one of PE, PP, and PPA, and the above permeable layer may be composed of PTFE.

[0014] A secondary battery case according to the present invention comprises: an outer material having an opening formed therein, wherein the outer material is provided to accommodate an electrode assembly therein; and a gas discharge film covering the opening formed in the outer material and discharging internal gas of the outer material; wherein the gas discharge film comprises: an adhesive layer having adhesiveness due to heat and having a through hole formed therein; and a permeable layer laminated to one surface of the adhesive layer and having a gas permeability higher than that of the adhesive layer; wherein the permeable layer may have the same thickness as the adhesive layer or may be formed thicker than the adhesive layer.

[0015] The above through hole and the above opening overlap each other, and the diameter of the through hole may be larger than the diameter of the opening.

[0016] The center of the above through hole and the center of the above opening may coincide with each other.

[0017] The diameter of the above opening may be from 1 mm to 7 mm.

[0018] The adhesive layer of the above gas discharge film can be adhered to the inner or outer surface of the outer material.

[0019] The above outer material is composed of a laminate sheet including a resin layer, and the adhesive layer of the gas discharge film is composed of any one of PE, PP, and PPA, and can be heat-sealed to the resin layer of the laminate sheet.

[0020] A secondary battery according to the present invention comprises: an electrode assembly; an outer case having an opening formed therein, which accommodates the electrode assembly; and a gas discharge film covering the opening formed in the outer case and which discharges internal gas of the outer case, wherein the gas discharge film comprises an adhesive layer having adhesiveness due to heat and having a through hole formed therein; and a permeable layer laminated to one surface of the adhesive layer and having a gas permeability higher than that of the adhesive layer, wherein the permeable layer may have the same thickness as the adhesive layer or may be formed thicker than the adhesive layer.

[0021] The above outer material includes a cup portion provided to accommodate the electrode assembly; a sealing portion forming the outermost part of the outer material and sealing the interior; and a terrace portion forming the periphery of the cup portion and positioned between the cup portion and the sealing portion, and the opening can be formed in the terrace portion.

[0022] The above outer material includes a cup portion provided to accommodate the electrode assembly, and the opening can be formed on a peripheral surface of the cup portion.

[0023] A method for manufacturing a gas discharge film according to the present invention may include a punching step of forming a plurality of through holes in an adhesive layer having adhesiveness by heat; a laminating step of laminating the adhesive layer to a permeable layer having a higher gas permeability than the adhesive layer and having the same thickness as the adhesive layer or being formed thicker than the adhesive layer; and a cutting step of cutting the permeable layer and the adhesive layer into unit films having a predetermined size, each unit film having the through holes.

[0024] In the above punching step, the plurality of through holes can be formed to have a constant interval from each other in the length direction and width direction of the adhesive layer.

[0025] In the above cutting step, the transparent layer and the adhesive layer can be cut at regular intervals in the length direction and width direction of the adhesive layer.

[0026] A method for manufacturing a secondary battery case according to the present invention may include a molding step of molding a cup portion for accommodating an electrode assembly into an outer material; a punching step of forming an opening in the outer material in which the cup portion is molded; a laminating step of manufacturing a gas discharge film by laminating a permeable layer having a higher gas permeability than the adhesive layer and having a thickness equal to or thicker than the adhesive layer to an adhesive layer having adhesiveness due to heat and having a through hole formed therein; and an attaching step of attaching the gas discharge film to the outer material so as to cover the opening.

[0027] The above attachment step may include a step of attaching the gas discharge film to the exterior material by pressurizing the gas discharge film and the exterior material with a high-temperature sealing device.

[0028] In the above attachment step, the sealing device can pressurize the entire area of ​​the gas discharge film.

[0029] In the above attachment step, the sealing device can apply heat and pressure to both sides of the gas discharge film and the outer covering material.

[0030] The above punching step may include a step of forming the opening in the periphery of the cup portion formed in the outer material.

[0031] The above punching step may include a step of forming the opening in the circumferential surface of the cup portion formed in the outer material.

[0032] The gas discharge film according to the present invention covers an opening formed in an outer casing of a secondary battery and is a gas discharge film that discharges internal gas of the outer casing. The gas discharge film has adhesiveness due to heat and may include an adhesive layer having a through hole formed therein and a permeable layer laminated to one side of the adhesive layer to cover the through hole and having a higher gas permeability than the adhesive layer. In this case, the permeable layer may have the same thickness as the adhesive layer or may be formed to be thicker than the adhesive layer.

[0033] In this case, the thickness of the adhesive layer that is thermally bonded to the outer material of the secondary battery is formed relatively thin, which has the advantageous effect of preventing the outer material and the adhesive layer from being over-bonded and blocking the opening formed in the outer material.

[0034] In addition, the opening formed in the outer material is covered only by the gas permeable layer, and the adhesive layer does not cover the opening, which has the advantageous effect of effectively discharging the internal gas of the secondary battery.

[0035] Figure 1 is a perspective view showing a gas discharge film according to the present invention attached to a secondary battery.

[0036] Figure 2 is a cross-sectional view illustrating the structure of a gas discharge film according to the present invention.

[0037] FIG. 3 is a drawing for explaining how a gas discharge film according to the present invention covers an opening of a secondary battery case.

[0038] Figure 4 is a perspective view schematically illustrating an example of a secondary battery according to the present invention.

[0039] Figure 5 is a perspective view schematically illustrating another example of a secondary battery according to the present invention.

[0040] Figure 6 is a flowchart schematically illustrating a method for manufacturing a gas discharge film according to the present invention.

[0041] Figure 7 is a perspective view schematically illustrating a state in which an adhesive layer and a permeable layer are combined in a method for manufacturing a gas discharge film according to the present invention.

[0042] Figure 8 is a perspective view for explaining the process of cutting the adhesive layer and the permeable layer in the method for manufacturing a gas discharge film according to the present invention.

[0043] Figure 9 is a flowchart schematically illustrating a method for manufacturing a secondary battery case according to the present invention.

[0044] Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited or restricted by the following examples.

[0045] In order to clearly explain the present invention, a detailed description of a part that is irrelevant to the description or a related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and when adding reference signs to components of each drawing in this specification, the same or similar reference signs are attached to the same or similar components throughout the specification.

[0046] In addition, terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0047]

[0048] Gas discharge film

[0049] Fig. 1 is a perspective view illustrating a gas discharge film according to the present invention attached to a secondary battery. Fig. 2 is a cross-sectional view illustrating the structure of a gas discharge film according to the present invention. Fig. 3 is a drawing illustrating a gas discharge film according to the present invention covering an opening of a secondary battery case.

[0050] Referring to FIGS. 1 to 3, a gas discharge film (200) according to the present invention covers an opening (101) formed in an outer casing (100) of a secondary battery (10), and is a gas discharge film (200) that discharges internal gas of the outer casing (100). The gas discharge film (200) has adhesiveness due to heat, has a through hole (221) formed therein, and may include a permeable layer (210) that is laminated to one surface of the adhesive layer (220) to cover the through hole (221) and has a higher gas permeability than the adhesive layer (220). Here, the permeable layer (210) may have the same thickness as the adhesive layer (220) or may be formed thicker than the adhesive layer (220).

[0051] Here, the adhesive layer (220) can be bonded to the outer covering (100) of the secondary battery (10) by a heat-fusion method. In the gas discharge film (200), the thickness of the adhesive layer (220) that is bonded to the outer covering (100) is formed relatively thin, which has the advantageous effect of preventing the outer covering (100) and the adhesive layer (220) from being excessively bonded and blocking the opening (101) formed in the outer covering (100).

[0052] The thickness (d1) of the transmission layer (210) and the thickness (d2) of the adhesive layer (220) can be formed in various ways. For example, the thickness (d1) of the transmission layer (210) and the thickness (d2) of the adhesive layer (220) can each have a value between 10 μm and 100 μm. In this case, the thickness (d1) of the transmission layer (210) can be thicker than the thickness (d2) of the adhesive layer (220).

[0053] In particular, the thickness (d1) of the transmission layer (210) may be 60 μm to 100 μm, and the thickness (d2) of the adhesive layer (220) may be 50 μm to 100 μm. Here, the thickness (d1) of the transmission layer (210) may be the same as or thicker than the thickness (d2) of the adhesive layer (220). For example, when the thickness (d1) of the transmission layer (210) is 60 μm, the thickness (d2) of the adhesive layer (220) may be 50 μm, and when the thickness (d1) of the transmission layer (210) is 100 μm, the thickness (d2) of the adhesive layer (220) may be 100 μm.

[0054] When the thickness (d1) of the permeable layer (210) is 60 μm or less, the thickness (d1) of the permeable layer (210) becomes relatively thin, so that the electrolyte contained inside the outer material (100) may pass through the permeable layer (210) and leak to the outside.

[0055] In addition, when the thickness (d1) of the permeable layer (210) is 1000 μm or more, the thickness (d1) of the permeable layer (210) becomes thicker, and the gas permeability of the internal gas of the outer material (100) passing through the permeable layer (210) may decrease. Therefore, it is appropriate for the thickness (d1) of the permeable layer (210) to be formed to be 60 μm to 100 μm.

[0056] When the thickness (d2) of the adhesive layer (220) is 50 μm or less, the adhesive layer (220) may be formed thinly, which may lower the bonding strength between the adhesive layer (220) and the exterior material (100). In addition, when the thickness (d2) of the adhesive layer (220) is 100 μm or more, the adhesive layer (220) may be excessively fused to the exterior material (100), which may block the opening (101) formed in the exterior material (100) or damage the exterior material (100). Therefore, it is appropriate that the thickness (d2) of the adhesive layer (220) be formed to be 50 μm to 100 μm.

[0057] Meanwhile, the transparent layer (210) and the adhesive layer (220) can be combined in various ways. For example, the transparent layer (210) and the adhesive layer (220) can be thermally bonded while overlapping each other after each of the surfaces is treated with plasma.

[0058] The permeable layer (210) of the gas discharge film (200) may be provided to cover the opening (101) of the outer material (100). In addition, an adhesive layer (220) may be placed between the outer material (100) and the permeable layer (210) to adhere the outer material (100) and the permeable layer (210).

[0059] The adhesive layer (220) of the gas discharge film (200) may include a material having adhesiveness due to heat. Materials having adhesiveness due to heat include polyethylene (PE), polypropylene (PP), polypropylene-graft-maleic anhydride (PPA), etc. Accordingly, the adhesive layer (220) may include at least one of PE, PP, and PPA.

[0060] In addition, as an example of a configuration for improving gas discharge performance, a through hole (221) may be formed in the adhesive layer (220) of the gas discharge film (200). Since the through hole (221) overlaps with the opening (101) formed in the outer material (100), the gas inside the outer material (100) may pass through the opening (101) and the through hole (221) and then pass through the permeable layer (210) to be discharged to the outside.

[0061] Meanwhile, the permeable layer (210) of the gas discharge film (200) according to the present invention may have a cross-section of an approximately rectangular shape. This is merely an example, and the permeable layer (210) may have a cross-section of a different shape.

[0062] The permeable layer (210) of the gas discharge film (200) is attached to the outer material (100) so as to cover the opening (101) formed in the outer material (100), and can allow the internal gas of the outer material (100) to pass through. Specifically, the gas generated inside the outer material (100) can pass through the opening (101) and then be discharged to the outside of the outer material (100) through the permeable layer (210).

[0063] The permeable layer (210) of the gas discharge film (200) may have higher gas permeability than the outer material (100). In addition, the permeable layer (210) may include a material that allows gas to be discharged but does not allow liquid to pass through. For example, the permeable layer (210) of the gas discharge film (200) may include a fluorine-based resin.

[0064] Specifically, the permeable layer (210) may be made of PTFE (Polytetrafluoroethylene) material. In this case, the electrolyte provided inside the outer material (100) cannot pass through the permeable layer (210), but the gas generated inside the outer material (100) can pass through the permeable layer (210).

[0065] In Fig. 3, the adhesive layer (220) and the through hole (221) are depicted as circular, but this is merely an example. That is, the adhesive layer (220) may be arranged in a different shape for bonding the transparent layer (210) and the outer material (100). In addition, the through hole (221) may also be formed in a different shape.

[0066] Meanwhile, the gas discharge film (200) is bonded to the outer case (100) of the secondary battery (10) by a heat-fusion method, and a part of the adhesive layer (220) melted by heat may not block the opening (101) of the outer case (100). Specifically, the diameter (t2) of the through hole (221) between the adhesive layers (220) is larger than the diameter (t1) of the opening (101) formed in the outer case (100), so even if a part of the adhesive layer (220) melts by heat, it may flow down to the upper region of the opening (101) and solidify again in the upper region of the opening (101).

[0067] Accordingly, even when the gas discharge film (200) and the outer covering material (100) are heat-sealed, the opening (101) of the outer covering material (100) is not blocked, so the internal gas of the outer covering material (100) can be discharged more efficiently.

[0068]

[0069] Secondary battery case

[0070] FIG. 1 illustrates an example of a secondary battery (10) according to the present invention, and also illustrates a secondary battery case containing an electrode assembly and an electrolyte therein.

[0071] Referring to FIG. 1, a secondary battery case according to the present invention may include an outer material (100) having an opening (101) formed therein to accommodate an electrode assembly therein, and a gas discharge film (200) that covers the opening (101) formed in the outer material (100) and discharges internal gas of the outer material (100). That is, the secondary battery case may have a structure in which a gas discharge film (200) is combined with an outer material (100) having an opening (101) formed therein.

[0072] The gas discharge film (200) has adhesiveness by heat and includes an adhesive layer (220) in which a through hole (221) is formed and a permeable layer (210) that is laminated to one side of the adhesive layer (220) and has a higher gas permeability than the adhesive layer (220). The permeable layer (210) may have the same thickness as the adhesive layer (220) or may be formed thicker than the adhesive layer (220).

[0073] In this case, the opening (101) formed in the outer material (100) is covered only by the gas permeable layer (210), and the adhesive layer (220) does not cover the opening (101), which has the advantageous effect of effectively discharging the internal gas of the housing (100).

[0074] In addition, the adhesive layer (220) can be bonded to the outer covering (100) of the secondary battery (10) by a heat-fusion method. In the gas discharge film (200), the thickness of the adhesive layer (220) that is bonded to the outer covering (100) is formed relatively thin, which has the advantageous effect of preventing the outer covering (100) and the adhesive layer (220) from being excessively bonded and blocking the opening (101) formed in the outer covering (100).

[0075] Meanwhile, the through hole (221) and the opening (101) overlap each other, and the diameter (t2) of the through hole (221) may be larger than the diameter (t1) of the opening (101). Here, the area of ​​the through hole (221) may be formed to be wider than the area of ​​the opening (101).

[0076] Specifically, the center of the through hole (221) and the center of the opening (101) coincide with each other, and the entire area of ​​the opening (101) can be included within the through hole (221). In particular, the diameter (t2) of the through hole (221) can be approximately 0 to 4 mm larger than the diameter (t1) of the opening (101).

[0077] If the diameter (t2) of the through hole (221) is smaller than the diameter (t1) of the opening (101), a portion of the opening (101) may be blocked by the adhesive layer (220), which may lower the gas discharge efficiency. In addition, if the diameter (t2) of the through hole (221) is excessively larger than the diameter (t1) of the opening (101), the adhesive strength of the adhesive layer (220) may be reduced.

[0078] Therefore, the diameter (t2) of the through hole (221) must be formed appropriately, and when the diameter (t2) of the through hole (221) is approximately 0 to 4 mm larger than the diameter (t1) of the opening (101), the gas discharge efficiency can be improved and the adhesive strength of the adhesive layer (220) can be maintained at a high level.

[0079] For example, when the diameter (t1) of the circular opening (101) is approximately 4.5 mm or more and 5.5 mm or less, the diameter (t2) of the circular through hole (221) may be approximately 6.5 mm or more and 7.5 mm or less. In addition, when the diameter (t1) of the circular opening (101) is approximately 5 mm, the diameter (t2) of the circular through hole (221) may be approximately 5 mm or more and 9 mm or less.

[0080] In addition, the diameter (t1) of the opening (101) may have a value of 1 mm or more and 7 mm or less. At this time, the diameter (t2) of the through hole (221) may be approximately 0 to 4 mm larger than the diameter (t1) of the opening (101). That is, the diameter (t2) of the through hole (221) may have a value of 1 mm or more and 11 mm or less.

[0081] The outer material (100) is composed of a laminate sheet including a resin layer, and the adhesive layer (220) of the gas discharge film (200) may be composed of any one of PE, PP, and PPA. At this time, the adhesive layer (220) may be heat-sealed to the resin layer of the laminate sheet.

[0082] Specifically, the outer layer (100) may include an inner layer, a metal layer, and an outer layer, and the inner layer may have sealing properties due to heat and pressure. After the outer layer (100) accommodates the electrode assembly therein, the inner layer may be sealed by heat and pressure. The metal layer may mainly be made of Al, STS, etc. In addition, the outer layer may have insulating properties.

[0083] The inner layer capable of sealing the outer material (100) through sealing may be formed of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. In particular, a polyolefin resin such as polypropylene (PP) or polyethylene (PE) may be mainly used.

[0084] Meanwhile, the adhesive layer (220) of the gas discharge film (200) can be adhered to the inner or outer surface of the outer material (100). That is, the gas discharge film (200) can be accommodated inside the outer material (100) or exposed to the outside of the outer material (100). When the gas discharge film (200) is arranged on the inner surface of the outer material (100), gas generated inside the outer material (100) can pass through the opening (101) after permeating the permeable layer (210) and then be discharged to the outside of the outer material (100).

[0085] Preferably, considering moisture penetration and ease of manufacturing, etc., the gas discharge film (200) may be disposed on the outer surface of the outer material (100). Specifically, the gas discharge film (200) may be disposed on the terrace portion (120) of the outer material (100). That is, the opening (101) of the outer material (100) may be formed on the terrace portion (120). As described above, the terrace portion (120) of the outer material (100) forms the periphery of the cup portion (110) and may be disposed between the cup portion (110) and the sealing portion (130).

[0086] Since the facing surfaces of the sealing portion (130) of the outer material (100) are sealed with a seal, the gas discharge performance may decrease when the gas discharge film (200) is placed on the sealing portion (130). Therefore, in order to prevent the gas discharge performance of the gas discharge film (200) from decreasing, the gas discharge film (200) may be placed on the terrace portion (120). In addition, the gas discharge film (200) may be placed spaced apart from the electrode assembly, so that the internal gas of the outer material (100) may be discharged to the outside through the opening (101) more efficiently.

[0087]

[0088] secondary battery

[0089] FIG. 1 illustrates a secondary battery according to one embodiment of the present invention.

[0090] Referring to FIG. 1, a secondary battery (10) according to one embodiment of the present invention may include an electrode assembly, an outer case (100) that accommodates the electrode assembly and has an opening (101) formed therein, and a gas discharge film (200) that covers the opening (101) formed in the outer case (100) and discharges internal gas of the outer case (100). At this time, the gas discharge film (200) has adhesiveness due to heat, includes an adhesive layer (220) in which a through hole (221) is formed, and a permeable layer (210) that is laminated to one surface of the adhesive layer (220) and has a higher gas permeability than the adhesive layer (220). The permeable layer (210) may have the same thickness as the adhesive layer (220) or may be formed thicker than the adhesive layer (220).

[0091] In this case, the opening (101) formed in the outer material (100) is covered only by the gas permeable layer (210), and the adhesive layer (220) does not cover the opening (101), which has the advantageous effect of effectively discharging the internal gas of the secondary battery (10).

[0092] In addition, the adhesive layer (220) can be bonded to the outer covering (100) of the secondary battery (10) by a heat-fusion method. In the gas discharge film (200), the thickness of the adhesive layer (220) that is bonded to the outer covering (100) is formed relatively thin, which has the advantageous effect of preventing the outer covering (100) and the adhesive layer (220) from being excessively bonded and blocking the opening (101) formed in the outer covering (100).

[0093] A secondary battery (10) may include an electrode assembly (not shown), an outer case (100), and a gas discharge film (200). This secondary battery (10) may refer to a secondary battery including an outer case (100) whose shape can be changed among various types of secondary batteries capable of being charged and discharged. That is, the outer case (100) may be a pouch-shaped outer case composed of a laminate sheet.

[0094] The electrode assembly of a secondary battery (10) may include a positive electrode, a negative electrode, and a separator. Here, the separator may be placed between the positive electrode and the negative electrode to physically separate them. The electrode assembly may be in the form of a stacked positive electrode, negative electrode, and separator, or in the form of a jelly-roll in which the positive electrode, negative electrode, and separator are wound.

[0095] The secondary battery (10) may include an electrode lead. The electrode lead may be electrically connected to the electrode assembly and may be arranged to protrude outside the outer case (100). The secondary battery (10) may provide electrical energy to the outside by the electrode lead protruding outside the outer case (100). Accordingly, the electrode lead may be a conductor.

[0096] The lead film may cover the electrode lead so that the outer material (100) and the electrode lead are insulated from each other. Specifically, the lead film may be placed on both sides of the electrode lead to cover the electrode lead. The lead films may be configured as a pair and placed on each side of the electrode lead.

[0097] The outer material (100) may include a cup portion (110) provided to accommodate an electrode assembly, a sealing portion (130) forming the outermost shell of the outer material (100) and sealing the interior, and a terrace portion (120) forming the periphery of the cup portion (110) and positioned between the cup portion (110) and the sealing portion (130).

[0098] Here, the cup portion (110) of the outer material (100) may refer to a portion where a space capable of accommodating an electrode assembly is formed by forming a pouch film. The sealing portion (130) may refer to a portion that forms the outermost shell of the outer material (100) and is sealed by heat and pressure. In addition, the terrace portion (120) forms the periphery of the cup portion (110) and may be arranged between the cup portion (110) and the sealing portion (130). Specifically, a portion sealed by sealing around the cup portion (110) excluding the cup portion (110) may be the sealing portion (130), and the other portion may be the terrace portion (120).

[0099] The sealing portion (130) may include a portion from which the electrode lead protrudes. The portion of the sealing portion (130) from which the electrode lead protrudes may be sealed with the lead film. Additionally, the portion of the sealing portion (130) from which the electrode lead does not protrude may be sealed with the facing outer materials (100).

[0100] Meanwhile, as the secondary battery (10) is repeatedly charged and discharged, gas may be generated, which may increase the pressure inside the outer case (100). If the pressure inside the outer case (100) increases excessively, a venting phenomenon may occur, causing the secondary battery (10) to lose its function.

[0101] Specifically, an electrolyte may be accommodated together with an electrode assembly inside the outer case (100) of the secondary battery (10). At this time, residual moisture of the electrolyte inside the outer case (100) of the secondary battery (10) or moisture that has penetrated from the outside may react with a lithium salt to generate HF, and gases such as carbon dioxide, carbon monoxide, ethylene, and methane may be generated due to decomposition of the electrolyte. In addition, depending on the material of the positive electrode included in the electrode assembly of the secondary battery (10), hydrogen and HF may be additionally generated, which may cause overheating due to overcharging and internal short circuit during the charging and discharging process. Accordingly, a large amount of gas may be generated inside the outer case (100). The pressure inside the outer case increases due to such gas, and the increased pressure may cause a swelling phenomenon in which the outer case (100) swells or a venting phenomenon in which a portion of the outer case (100) bursts.

[0102] The secondary battery (10) according to the present invention may include a structure capable of discharging gas inside the outer case (100) to the outside of the outer case (100) to prevent a venting phenomenon from occurring.

[0103] As an example of a configuration that can discharge gas inside an outer casing (100) to the outside of the outer casing (100), an opening (101) may be formed in a portion of the outer casing (100) of a secondary battery (10). In addition, the secondary battery (10) may include a gas discharge film (200) that is placed in a portion of the outer casing (100) where the opening (101) is formed.

[0104] Referring to Fig. 1, the opening (101) formed in the outer material (100) may have a generally circular cross-section. This is merely an example, and the opening (101) may be formed in a different shape. In addition, a plurality of openings (101) may be formed in the outer material (100).

[0105] Meanwhile, Fig. 4 is a perspective view schematically illustrating another embodiment of a secondary battery according to the present invention. The secondary battery illustrated in Fig. 4 may differ from the secondary battery illustrated in Fig. 1 in the arrangement of the gas discharge film.

[0106] Referring to 4, the gas discharge film (200) of the secondary battery (10) may be placed on the cup portion (110) of the outer case (100). In this regard, the outer case (100) may include a cup portion (110) formed in a concave shape for placing the electrode assembly. The cup portion (110) may include a surface on which the electrode assembly is placed and a peripheral surface that is folded at the surface to form a border. Here, the gas discharge film (200) may be placed on the peripheral surface that forms the border of the cup portion (110).

[0107] In this regard, when a plurality of secondary batteries (10) are arranged for manufacturing a battery module, the secondary batteries (10) may be stacked in parallel. At this time, the plurality of secondary batteries (10) may be arranged in a state where one surface of the cup portion (110) is in contact with each other. Specifically, the surface where adjacent secondary batteries (10) are in contact with each other may be the surface having the widest area in the cup portion (110) on which the electrode assembly is placed. Therefore, when the gas discharge film (200) is arranged on the surface of the cup portion (110) on which the electrode assembly is placed, the gas discharge efficiency may be reduced. That is, since the secondary battery (10) according to the present invention has the gas discharge film (200) arranged on the peripheral surface of the cup portion (110), more efficient gas discharge is possible even when the secondary batteries (10) are stacked for manufacturing a battery module.

[0108] Meanwhile, the secondary battery (10) illustrated in FIG. 4 may include a plurality of gas discharge films (200). Here, the gas discharge films (200) may be respectively positioned at different locations on the circumference of the cup portion (110). Since the secondary battery (10) includes a plurality of gas discharge films (200), gas within the outer packaging material (100) can be efficiently discharged.

[0109] Fig. 5 is a perspective view schematically illustrating another embodiment of a secondary battery according to the present invention. The secondary battery illustrated in Fig. 5 may have a different shape of the outer packaging material from the secondary batteries illustrated in Figs. 1 and 4.

[0110] Referring to FIG. 5, the secondary battery (10') may include an outer covering (100') that surrounds the electrode assembly. That is, the outer covering (100') of the secondary battery (10') may be arranged to surround the side of the electrode assembly and may be combined with caps (300) that are arranged at both ends of the electrode assembly. Here, the outer covering (100') and the cap (300) may be combined through sealing or the like.

[0111] Specifically, the outer material (100') covering the side of the electrode assembly may be joined at one end and the other end by a seal or the like. In addition, one end and the other end of the electrode assembly that are not covered by the outer material (100') may be covered by a cap (300).

[0112] Referring to FIG. 5, the gas discharge film (200) may be disposed on one surface of the outer material (100'). Specifically, the gas discharge film (200) may be disposed on the outer surface of the outer material (100'). The gas discharge film (200) may be disposed on both the inner and outer surfaces of the outer material (100'). Preferably, the gas discharge film (200) may be disposed on the outer surface of the outer material (100') in consideration of gas discharge efficiency and ease of manufacturing. Accordingly, gas generated inside the outer material (100') and the cap (300) can be efficiently discharged to the outside.

[0113] The fact that the adhesive layer (220) of the gas discharge film (200) includes a through hole (221) having a larger area than the hole formed in the outer material (100') is the same as in the case of the secondary battery (10) illustrated in FIGS. 1 and 4.

[0114] The shape of the secondary battery (10') illustrated in FIG. 5 is merely an example. The position at which the outer casing (100') is arranged and the number of outer casings (100') may vary within the scope that can achieve the effects of the present invention. Although not described in detail in the present invention, the secondary battery (10') may further include a gas removal member formed in the cap (300).

[0115]

[0116] Gas discharge film manufacturing method

[0117] The method for manufacturing a gas-emitting film according to the present invention may refer to a method for manufacturing a unit film (1300) that is combined with an outer material (100) so as to discharge gas inside the outer material (100). That is, the unit film (1300) manufactured by the method for manufacturing a gas-emitting film can be used in the manufacture of a secondary battery (10). In addition, the unit film (1300) combined with the outer material (100) through a process such as sealing can become a gas-emitting film (200).

[0118] Figure 6 is a flowchart schematically illustrating a method for manufacturing a gas-emitting film according to the present invention. Figure 7 is a perspective view schematically illustrating a state in which an adhesive layer and a permeable layer are laminated in a method for manufacturing a gas-emitting film according to the present invention. Figure 8 is a perspective view illustrating a process of cutting an adhesive layer and a permeable layer in a method for manufacturing a gas-emitting film according to the present invention.

[0119] Referring to FIGS. 6 to 8, a method for manufacturing a gas discharge film according to the present invention may include a punching step (S11) of forming a plurality of through holes (221) in an adhesive layer (1100) having adhesiveness by heat, a laminating step (S12) of laminating an adhesive layer (220) to a permeable layer (1200) having a higher gas permeability than the adhesive layer (1100) and having the same thickness as the adhesive layer (1100) or being formed thicker than the adhesive layer (1100), and a cutting step (S13) of cutting the permeable layer (1200) and the adhesive layer (1100) into unit films having a preset size, each unit film having a through hole (221).

[0120] In this case, the opening (101) formed in the outer material (100) is covered only by the gas permeable layer (210), and the adhesive layer (220) does not cover the opening (101), so the gas discharge film (200) manufactured by the above manufacturing method has the advantageous effect of being able to effectively discharge the internal gas of the secondary battery (10).

[0121] In addition, the adhesive layer (220) can be bonded to the outer case (100) of the secondary battery (10) by a heat-fusion method. In the gas discharge film (200), the thickness of the adhesive layer (220) that is bonded to the outer case (100) is formed relatively thin, so that when the gas discharge film (200) is bonded to the outer case (100), there is an advantageous effect of preventing the outer case (100) and the adhesive layer (220) from being excessively bonded and blocking the opening (101) formed in the outer case (100).

[0122] In the punching step (S11), a plurality of through holes (221) can be formed in an adhesive layer (1100) having adhesiveness due to heat. At this time, the through holes (221) can have a shape that penetrates from one surface of the adhesive layer (1100) to the other surface, and can have a cross-section that is approximately circular. However, the cross-sectional shape of the through holes (221) can vary.

[0123] In the punching step (S11), a plurality of through holes (221) can be formed at a constant interval with respect to the length direction and width direction of the adhesive layer (1100). Therefore, unit films (1300) of the same size can be efficiently manufactured through the cutting step (S13) described later.

[0124] Referring to FIG. 7, in the bonding step (S12), the adhesive layer (1100) may be bonded to a permeable layer (1200) having a higher gas permeability than the adhesive layer (1100). Here, the adhesive layer (1100) may have a through hole (221) perforated therein. In addition, the overall shape of the adhesive layer (1100) may be approximately similar to the overall shape of the permeable layer (1200). Accordingly, the permeable layer (1200) may be arranged to cover the adhesive layer (1100).

[0125] Referring to FIG. 8, in the cutting step (S13), the adhesive layer (1100) laminated with the transparent layer (1200) can be cut into unit films (1300) having a preset size. Here, the adhesive layer (1100) laminated with the transparent layer (1200) can be cut so that each unit film (1300) has a through hole (221).

[0126] Meanwhile, in the cutting step (S13), the adhesive layer (1100) combined with the transparent layer (1200) can be cut at regular intervals in the longitudinal and width directions of the adhesive layer (1100). Accordingly, each unit film (1300) can have the same shape while including a through hole (221). That is, unit films (1300) of the same size can be efficiently manufactured through the cutting step (S13).

[0127] That is, the gas discharge film manufacturing method according to the present invention can manufacture multiple unit films (1300) having the same shape through a single cycle. Therefore, the efficiency and economic feasibility of the manufacturing process can be improved.

[0128]

[0129] Secondary battery case manufacturing method

[0130] Figure 9 is a flowchart schematically illustrating a method for manufacturing a secondary battery case according to the present invention.

[0131] Referring to FIG. 9, a method for manufacturing a secondary battery case according to the present invention may include a molding step (S21) of molding a cup portion (110) for accommodating an electrode assembly in an outer material (100), a punching step (S22) of forming an opening (101) in an outer material (100) in which a cup portion (110) is molded, a laminating step (S23) of manufacturing a gas discharge film (200) by laminating an adhesive layer (220) having adhesiveness due to heat and having a through hole (221) formed therein, and a permeable layer (210) having a gas permeability higher than that of the adhesive layer (220) and having the same thickness as or thicker than the adhesive layer (220), and an attachment step (S24) of attaching the gas discharge film (200) to the outer material (100) to cover the opening (101).

[0132] In this case, the opening (101) formed in the outer material (100) is covered only by the gas permeable layer (210), and the adhesive layer (220) does not cover the opening (101), so the secondary battery case manufactured by the above manufacturing method has the advantageous effect of being able to effectively discharge internal gas through the gas discharge film (200).

[0133] In addition, the adhesive layer (220) can be bonded to the outer case (100) of the secondary battery (10) by a heat-fusion method. In the gas discharge film (200), the thickness of the adhesive layer (220) that is bonded to the outer case (100) is formed relatively thin, so that when the gas discharge film (200) is bonded to the outer case (100), there is an advantageous effect of preventing the outer case (100) and the adhesive layer (220) from being excessively bonded and blocking the opening (101) formed in the outer case (100).

[0134] The secondary battery case according to the present invention is described as an example in which a space for accommodating an electrode assembly is formed by molding. In other words, the secondary battery case may refer to an outer material of a pouch-type secondary battery. Accordingly, in the molding step (S21) of the secondary battery case manufacturing method, a cup portion (110) may be molded onto a pouch film. For example, a punch of a molding device may pressurize the pouch film to mold the cup portion (110).

[0135] After the forming step (S21), a punching step (S22) may be performed. In the punching step (S22), an opening (101) may be formed in the pouch film in which the cup portion (110) is formed. Here, the method for forming the opening (101) may vary. The opening (101) may have a shape that penetrates from one side of the pouch film to the other side, and may have a cross-section that is approximately circular. However, the cross-sectional shape of the opening (101) may vary.

[0136] Depending on the shape of the secondary battery case manufactured in the punching step (S22), the position at which the opening (101) is formed may vary. For example, the opening (101) may be formed at the periphery of the cup portion (110) formed on the pouch film, or may be formed on the peripheral surface of the cup portion (110) formed on the pouch film.

[0137] After the punching step (S22), a laminating step (S23) may be performed. In the laminating step (S23), a gas discharge film (200) may be manufactured by laminating an adhesive layer (220) having a through hole (221) formed therein and a gas-permeable layer (210). That is, the gas discharge film (200) manufactured through the laminating step (S23) may include an adhesive layer (220) and a gas-permeable layer (210).

[0138] In the bonding step (S23), the transparent layer (210) and the adhesive layer (220) can be bonded in various ways. For example, the transparent layer (210) and the adhesive layer (220) can be thermally bonded while overlapping each other after each has undergone surface treatment with plasma.

[0139] In the method for manufacturing a secondary battery case according to the present invention, an example in which a bonding step (S23) is performed after a punching step (S22) is described (see Fig. 9). However, the order of the punching step (S22) and the bonding step (S23) may be reversed.

[0140] Meanwhile, in the method for manufacturing a secondary battery case according to the present invention, the area of ​​the through hole (221) can be formed to be wider than the area of ​​the opening (101). Therefore, the phenomenon of the adhesive layer (220) blocking the opening (101) during the manufacturing process can be prevented.

[0141] After the bonding step (S23), an attachment step (S24) may be performed. In the attachment step (S24), a gas discharge film (200) may be attached to a portion of the pouch film where an opening (101) is formed. That is, the opening (101) may be covered by the gas discharge film (200).

[0142] For example, in the attachment step (S24), the gas discharge film (200) may be attached to the pouch film by heat. Specifically, the attachment step (S24) may be a step of attaching the gas discharge film (200) to the exterior material (100) by pressurizing the gas discharge film (200) and the exterior material (100) with a high-temperature sealing device.

[0143] That is, the gas discharge film (200) can be attached to the pouch film through the sealing of the sealing device. A portion of the adhesive layer (220) is melted by heat to have adhesiveness, and the gas discharge film (200) can be attached to the pouch film by the adhesiveness of the adhesive layer (220).

[0144] Meanwhile, in the attachment step (S24), the sealing device described above can pressurize the entire area of ​​the gas discharge film (200).

[0145] Conventionally, the adhesive layer (220) was arranged to cover the opening (101). In this case, when the sealing device applies heat to the entire area of ​​the gas discharge film (200), a portion of the adhesive layer (220) covering the opening (101) may melt due to the heat. In other words, a portion of the adhesive layer (220) melted by the heat may block the opening (101) or cause defects on the outer surface of the opening (101). Therefore, conventionally, the sealing device could only apply heat to a portion corresponding to the shape of the opening (101). As a result, high accuracy was required in the attachment process, which increased the possibility of defects occurring.

[0146] On the other hand, in the method for manufacturing a secondary battery case according to the present invention, a through hole (221) is formed in the adhesive layer (220), and the area of ​​the through hole (221) may be larger than the area of ​​the opening (101). That is, since there is no portion of the adhesive layer (220) that covers the opening (101), even if the sealing device seals the entire area of ​​the gas discharge film (200), the possibility of defects occurring can be significantly reduced. Accordingly, the efficiency of the process can be improved.

[0147] Additionally, in the attachment step (S24), the sealing device described above can apply heat and pressure to both sides of the gas discharge film (200) and the outer material (100).

[0148] In the past, the adhesive layer (220) was arranged to cover the opening (101). In this case, when the sealing device applied heat to the pouch film, the heat could be directly applied to the adhesive layer (220) covering the opening (101) through the opening (101). Therefore, there is a high possibility that a defect in the process may occur, such as a part of the adhesive layer (220) melting due to the heat, and a part of the melted adhesive layer (220) blocking the opening (101). In addition, the sealing device may apply heat only to the gas discharge film (200), so the adhesive strength of the gas discharge film (200) may be weak.

[0149] On the other hand, in the method for manufacturing a secondary battery case according to the present invention, a through hole (221) is formed in the adhesive layer (220), and the area of ​​the through hole (221) may be larger than the area of ​​the opening (101). That is, there is no portion of the adhesive layer (220) that covers the opening (101). Therefore, even if the sealing device applies heat to the pouch film, the possibility of the melted adhesive layer (220) moving to the position where the opening (101) is formed may be reduced. In other words, the possibility of defects occurring during the process may be significantly reduced. Accordingly, the efficiency of the process may be improved.

[0150]

[0151] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and various embodiments are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

[0152]

[0153] [Explanation of symbols]

[0154] 10, 10': Secondary battery 100, 100': Outer material

[0155] 101: Opening 110: Cup

[0156] 120: Terrace section 130: Ceiling section

[0157] 200: Gas discharge film 210: Permeable layer

[0158] 220: Adhesive layer 221: Through hole

[0159] 300: Cap 1100: Adhesive layer

[0160] 1200: Transmittance layer 1300: Unit film

Claims

1. A gas discharge film that covers an opening formed in the outer shell of a secondary battery and discharges internal gas of the outer shell. An adhesive layer having adhesiveness due to heat and having through holes formed therein; and A permeable layer is laminated to one side of the adhesive layer to cover the through hole and has a higher gas permeability than the adhesive layer. A gas discharge film in which the above-mentioned permeable layer has the same thickness as the above-mentioned adhesive layer or is formed thicker than the above-mentioned adhesive layer.

2. In claim 1, A gas discharge film having a thickness of the above-mentioned permeable layer and a thickness of the above-mentioned adhesive layer of 10 μm to 100 μm.

3. In claim 1, The above adhesive layer is composed of any one of PE, PP and PPA materials, The above-mentioned permeable layer is a gas discharge film composed of PTFE material.

4. An outer material having an opening formed therein and configured to accommodate an electrode assembly therein; and It includes a gas discharge film that covers the opening formed in the above outer material and discharges internal gas of the above outer material, The above gas discharge film, An adhesive layer having adhesiveness due to heat and having through holes formed therein; and A permeable layer is bonded to one side of the adhesive layer and has a higher gas permeability than the adhesive layer, A secondary battery case in which the above-mentioned transparent layer has the same thickness as the above-mentioned adhesive layer or is formed thicker than the above-mentioned adhesive layer.

5. In claim 4, A secondary battery case in which the above through hole and the above opening overlap each other, and the diameter of the above through hole is larger than the diameter of the above opening.

6. In claim 4, A secondary battery case in which the center of the above through hole and the center of the above opening are coincident with each other.

7. In claim 6, A secondary battery case wherein the diameter of the above opening is 1 mm to 7 mm.

8. In claim 4, A secondary battery case in which the adhesive layer of the above gas discharge film is adhered to the inner or outer surface of the above outer material.

9. In claim 5, The above exterior material is composed of a laminate sheet including a resin layer, A secondary battery case in which the adhesive layer of the above gas discharge film is made of any one of PE, PP and PPA and is heat-sealed to the resin layer of the above laminate sheet.

10. Electrode assembly; An outer material that accommodates the electrode assembly and has an opening formed therein; and It includes a gas discharge film that covers the opening formed in the above outer material and discharges internal gas of the above outer material, The above gas discharge film, An adhesive layer having adhesiveness due to heat and having through holes formed therein; and A permeable layer is bonded to one side of the adhesive layer and has a higher gas permeability than the adhesive layer, A secondary battery in which the above-mentioned transparent layer has the same thickness as the above-mentioned adhesive layer or is formed thicker than the above-mentioned adhesive layer.

11. In claim 10, The above exterior material is, A cup portion provided to accommodate the above electrode assembly; A sealing portion that forms the outermost layer of the above-mentioned exterior material and seals the interior; and It forms the periphery of the cup portion and includes a terrace portion arranged between the cup portion and the sealing portion, The above opening is a secondary battery formed in the above terrace portion.

12. In claim 10, The above outer material includes a cup portion provided to accommodate the electrode assembly, The above opening is a secondary battery formed on the circumference of the cup portion.

13. A punching step of forming a plurality of through holes in an adhesive layer having adhesiveness due to heat; A laminating step of laminating the adhesive layer to a permeable layer having a gas permeability higher than that of the adhesive layer and having the same thickness as or thicker than that of the adhesive layer; and A method for manufacturing a gas discharge film, comprising a cutting step of cutting the above-mentioned permeable layer and the above-mentioned adhesive layer into unit films having a predetermined size, each unit film having the through hole.

14. In claim 13, A method for manufacturing a gas discharge film, wherein in the above punching step, the plurality of through holes are formed to have a constant interval from each other in the length direction and width direction of the adhesive layer.

15. In claim 13, A method for manufacturing a gas discharge film, wherein in the above cutting step, the permeable layer and the adhesive layer are cut at regular intervals in the length direction and width direction of the adhesive layer.

16. A molding step of molding a cup portion that accommodates an electrode assembly into an outer material; A punching step of forming an opening in the outer material in which the cup portion is formed; A laminating step for manufacturing a gas discharge film by laminating a permeable layer having a higher gas permeability than the adhesive layer and having the same thickness as or thicker than the adhesive layer to an adhesive layer having heat-induced adhesiveness and having through holes formed therein; and A method for manufacturing a secondary battery case, comprising an attachment step of attaching the gas discharge film to the outer material to cover the opening.

17. In claim 16, The above attachment step is, A method for manufacturing a secondary battery case, comprising a step of pressurizing the gas discharge film and the outer covering material with a high-temperature sealing device to attach the gas discharge film to the outer covering material.

18. In claim 17, A method for manufacturing a secondary battery case, wherein in the above attachment step, the sealing device pressurizes the entire area of ​​the gas discharge film.

19. In claim 17, A method for manufacturing a secondary battery case, wherein in the above attachment step, the sealing device applies heat and pressure to both sides of the gas discharge film and the outer material.

20. In claim 16, The above punching step is, A method for manufacturing a secondary battery case, comprising the step of forming an opening in the periphery of a cup portion formed in the outer material.

21. In claim 16, The above punching step is, A method for manufacturing a secondary battery case, comprising the step of forming an opening on the circumferential surface of a cup portion formed on the outer material.

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