Film for discharging gas, method for manufacturing same, and secondary battery comprising same

Abstract

A film for discharging gas of the present invention comprises an active layer and a support layer from the surface side in contact with the inside of a secondary battery, wherein the active layer contains polydimethylsiloxane, the ratio of the forward transmittance of gas generated inside the secondary battery to the reverse transmittance of air is about 2 or more under the conditions of a relative pressure value of about 15 psi or 50 psi, the forward direction is a direction from the inside of the secondary battery to the outside of the secondary battery, and the reverse direction is a direction from the outside of the secondary battery to the inside of the secondary battery.

Description

Gas exhaust film, method of manufacturing the same, and secondary battery including the same

[0001] The present invention relates to a film for gas discharge, a method for manufacturing the same, and a secondary battery including the same. The present application claims the benefit of priority based on Korean Patent Application No. 2024-0141185 filed October 16, 2024 and Korean Patent Application No. 2025-0140182 filed September 26, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of the specification.

[0002] Swelling occurs in secondary batteries due to abnormal operating conditions such as decomposition of the electrolyte, internal short circuits, overcharging exceeding the allowed current and voltage, exposure to high temperatures, or deformation caused by drops or external impacts. If the amount of gas generated continues to increase (continuous swelling), it can lead to ignition or explosion of the battery. Recently, as the operating environments of secondary batteries have become harsher and their capacities have increased, there is a growing need to more effectively control issues of reduced stability caused by internal gas generation.

[0003] For example, Korean Published Patent Application No. 2015-0034498 proposes a battery that ensures quality and stability by forming a venting hole in a pouch case to discharge gas inside the pouch, and covering the venting hole with a venting cover that opens when the gas pressure inside the case reaches a reference value, thereby maintaining the sealability of the pouch-type battery under normal conditions while enabling rapid venting in accident situations.

[0004] The present invention provides a gas discharge film that can continuously and non-destructively discharge gas generated inside a secondary battery under both high and low pressure conditions, while effectively blocking the inflow of external moisture and atmosphere (air) into the secondary battery, and has excellent resistance to electrolyte.

[0005] The present invention simplifies the process and improves price competitiveness by implementing the film with a simple structure and / or material.

[0006] The present invention provides a secondary battery with further improved stability and lifespan by including the film in at least a portion of the secondary battery.

[0007] One aspect of the present invention relates to a gas discharge film having different gas permeability characteristics on both sides to discharge gas generated inside a secondary battery to the outside and prevent external air and water vapor from permeating into the secondary battery, wherein the film comprises an active layer and a support layer from the side in contact with the inside of the secondary battery, the active layer comprises polydimethylsiloxane, and under conditions of a relative pressure value of about 15 psi or about 50 psi, the ratio of the forward permeability of gas generated inside the secondary battery to the reverse permeability of air is about 2 or more, the forward direction is a direction from the inside of the secondary battery to the outside of the secondary battery, and the reverse direction is a direction from the outside of the secondary battery to the inside of the secondary battery.

[0008] In one embodiment, the active layer may be derived from a polydimethylsiloxane precursor and a curing agent.

[0009] In one embodiment, the weight ratio of the polydimethylsiloxane precursor to the curing agent in the active layer may be about 1 to 10.

[0010] In one embodiment, the active layer may comprise one or more selected from polyimide, polytetrafluoroethylene, polypropylene, fluorinated polymers, and combinations thereof.

[0011] In one embodiment, the ratio of the thickness of the support layer to the thickness of the active layer may be about 0.85 or less.

[0012] In one embodiment, the active layer may have a thickness of about 120 μm or more and 1000 μm or less.

[0013] In one embodiment, the support layer may include a porous support and a polymer coating layer on at least one surface of the porous support.

[0014] In one embodiment, the porous support may be in the form of a nonwoven fabric, a woven fabric, or a mesh in which polymer fibers are irregularly intertwined.

[0015] In one embodiment, the polymer coating layer may include one or more selected from polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethyl chloride, polyvinylidene fluoride, and combinations thereof.

[0016] In one embodiment, the support layer has a tensile strength of about 0.1 kgf / mm 2 Up to 10 kgf / mm 2 It can be.

[0017] In one embodiment, the thickness of the support layer may be less than about 140 μm.

[0018] In one embodiment, the thickness of the film may be about 200 μm to 1000 μm.

[0019] In one embodiment, the film may have an active layer and a support layer adjacent to each other.

[0020] Another aspect of the present invention relates to a secondary battery comprising at least a portion of the film, wherein gas generated inside the secondary battery is non-destructively discharged to the outside through the film.

[0021] Another aspect of the present invention relates to a method for manufacturing a film having different gas permeability characteristics on both sides to discharge gas generated inside a secondary battery to the outside and prevent external air and water vapor from permeating into the secondary battery, comprising the step (step S1) of applying a composition for forming an active layer on a support layer, wherein the film has a ratio of the forward permeability of gas generated inside the secondary battery to the reverse permeability of air under conditions of a relative pressure value of about 15 psi or about 50 psi, wherein the forward direction is a direction from inside the secondary battery to outside the secondary battery, and the reverse direction is a direction from outside the secondary battery to inside the secondary battery.

[0022] In one embodiment, the above S1 step can be performed at a speed of about 100 rpm to 900 rpm.

[0023] In one embodiment, the S1 step can be performed for about 1 second to 100 seconds.

[0024] In one embodiment, the composition for forming the active layer may include a polydimethylsiloxane precursor and a curing agent.

[0025] In one embodiment, the weight ratio of the polydimethylsiloxane precursor to the curing agent in the composition for forming the active layer may be about 1 to 10.

[0026] In one embodiment, the composition for forming the active layer may include one or more selected from polyimide, polytetrafluoroethylene, polypropylene, fluorinated polymers, and combinations thereof.

[0027] The present invention can provide a gas discharge film that can continuously and non-destructively discharge gas generated inside a secondary battery under both high-pressure and low-pressure conditions, while effectively blocking the inflow of external moisture and atmosphere (air) into the secondary battery, and has excellent resistance to electrolyte.

[0028] The present invention can simplify the process and improve price competitiveness by implementing the gas exhaust film with a relatively simple structure and / or material.

[0029] The present invention can also provide a secondary battery with further improved stability and lifespan by including the gas discharge film in at least a part of the secondary battery.

[0030] The following drawings attached to this specification illustrate embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0031] Figures 1 and 2 each show a film structure according to an example of the present invention.

[0032] FIGS. 3, FIGS. 4(a) and FIGS. 4(b) are schematic diagrams of a cylindrical secondary battery according to an example of the present invention.

[0033] FIGS. 5(a) to 5(c) are schematic diagrams of a prismatic secondary battery according to an example of the present invention.

[0034] FIGS. 6(a) and FIGS. 6(b) are schematic diagrams of a pouch-type case according to an example of the present invention.

[0035] FIG. 7 is a flowchart illustrating a film manufacturing method according to an example of the present invention.

[0036] FIG. 8 is a digital microscope (DM) image showing the results of the electrolyte resistance evaluation of the films according to Examples 4 to 8 of the present invention.

[0037] FIG. 9 is a digital microscope (DM) image observing the results of the electrolyte resistance evaluation of films according to Examples 1 to 3 of the present invention.

[0038] In parts of the attached drawings, corresponding components are given the same reference numerals. Those skilled in the art understand that the drawings are intended to illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to aid in understanding various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated compared to others. Additionally, elements of known technology that are useful or essential in commercially viable embodiments may often be omitted so as not to hinder the spirit of the various embodiments of the present invention.

[0039] Terms and words used in this specification and claims shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0040] Therefore, it should be understood that the configurations of the embodiments described in this specification are merely one embodiment of the present invention and do not represent all of the technical ideas of the present invention, and that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0041] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0042] In this specification, when a part is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Thus, for example, a composition comprising compound A may include compounds other than A. However, the term “comprising” also encompasses, in a more restrictive sense as a specific embodiment thereof, “essentially / essentially composed of” and “composed of,” so, for example, a “composition comprising compound A” may also be (essentially / essentially) composed of compound A.

[0043] In connection with this, terms such as “comprising” or “having,” as described in this specification, are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0044] In this specification, when any member is described as being located “on” another arbitrary member, this includes not only cases where such member is in contact with another member, but also cases where another member or material exists between the two members.

[0045] Where in this specification a quantity, concentration, or other value or parameter is given as an enumeration of a range, a preferred range, a preferred upper limit, and a preferred lower limit, it should be understood that any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the range is disclosed separately, specifically discloses all ranges that may be formed. Where a range of numerical values ​​is mentioned in this specification, unless otherwise stated, for example, without limiting terms such as greater than or less than, the range is intended to include its endpoint value and all integers and fractions within that range. The scope of the invention is not intended to be limited to the specific value mentioned when defining the range.

[0046] Among the physical properties mentioned in this specification, if the measured temperature affects the property, the property is measured at room temperature unless specifically otherwise specified. The term "room temperature" refers to a natural temperature that has not been heated or cooled, and may mean, for example, any temperature within the range of about 10°C to 30°C, about 23°C, or about 25°C. Furthermore, unless specifically otherwise specified, the unit of temperature in this specification is °C.

[0047] As used herein, “about,” “approximately,” and “substantially” are used to mean a range of figures or degrees or approximations thereof, taking into account inherent manufacturing and material tolerances (e.g., ±5%).

[0048] In addition, among the physical properties mentioned in this specification, if the measured pressure affects the physical property, unless otherwise specifically defined, the physical property is measured at normal pressure, that is, atmospheric pressure (about 1 atmosphere).

[0049] Conventional secondary batteries have a problem in that a venting section is installed to vent gases generated inside the battery, but the battery cannot be reused after the venting cover of the venting section is vented, and they do not include other alternative elements to prevent accidents in the event that the venting cover is not properly vented due to unexpected reasons in an accident situation, and they do not consider issues such as the ingress of external moisture or air through the venting cover.

[0050] The first aspect of the present invention relates to a gas discharge film having different gas permeability characteristics on both sides, which discharges gas generated inside a secondary battery to the outside and prevents external air and water vapor from passing into the secondary battery.

[0051] In this specification, "inside of a secondary battery" may refer to a space in which an electrode assembly and an electrolyte are located, bounded by a case containing an electrode assembly and an electrolyte, and "outside of a secondary battery" may refer to a space other than the inside, bounded by the case. The case may be a cylindrical can / cap assembly constituting a cylindrical secondary battery, a prismatic can / base plate constituting a prismatic secondary battery, or a pouch constituting a pouch-type secondary battery, etc.

[0052] Referring to FIG. 1, a gas discharge film (100) (hereinafter referred to as the film) according to one embodiment of the present invention may include, for example, a support layer (10) which is a surface in contact with the outside of the secondary battery and an active layer (20) which is a surface in contact with the inside of the secondary battery when installed in a secondary battery. Accordingly, the active layer (20) may be directly exposed to the electrolyte inside the secondary battery and / or vapor derived therefrom, and the support layer (10) may be directly exposed to moisture and / or air (atmosphere) outside the secondary battery.

[0053] The active layer (20) may include polydimethylsiloxane in one example. The active layer (20) may include, for example, about 80 weight percent or more of polydimethylsiloxane. In another example, the active layer may include about 85 weight percent or more, 90 weight percent or more, 95 weight percent or more, 99 weight percent or more, 99 weight percent or more, 99.9 weight percent or more, or about 100 weight percent or less of polydimethylsiloxane.

[0054] The active layer (20) may be derived, for example, from a polydimethylsiloxane precursor and a curing agent. In the present invention, the polydimethylsiloxane precursor may refer, for example, to a PDMA A substance. In this specification, "the active layer is derived from a polydimethylsiloxane precursor and a curing agent" may mean that the active layer (20) is derived from a composition for forming an active layer that includes a polydimethylsiloxane precursor and a curing agent. The active layer (20) of the present invention may include a PDMS kit B having a structure in which PDMS strands are clustered together through curing, for example, as a layer in which the polydimethylsiloxane precursor and the curing agent are cured by other elements (e.g., light or heat). The curing agent may be, for example, dimethyl, methylhydrogen siloxane.

[0055] The active layer (20) may, for example, have a weight ratio of the polydimethylsiloxane precursor to the curing agent of about 1 to 10. The active layer (20) may, for example, be a layer derived from a composition for forming an active layer in which the weight ratio of the polydimethylsiloxane precursor to the curing agent of about 1 to 10. In another example, the active layer (20) may have a weight ratio of the polydimethylsiloxane precursor to the curing agent of about 1.5 or more, 2 or more, 2.5 or more, 3 or more, 3.5 or more, 4 or more, or 4.5 or more, or about 9.5 or less, 9 or less, 8.5 or less, 8 or less, 7.5 or less, 7 or less, 6.5 or less, 6 or less, or 5.5 or less.

[0056] In another example, the active layer (20) may comprise one or more selected from polyimide, polytetrafluoroethylene, polypropylene, fluorinated polymers, and combinations thereof. The active layer (20) may comprise, for example, one or more selected from polyimide, polytetrafluoroethylene, polypropylene, fluorinated polymers, and combinations thereof in an amount of about 80 weight% or more. In another example, the active layer (20) may comprise one or more selected from polyimide, polytetrafluoroethylene, polypropylene, fluorinated polymers, and combinations thereof in an amount of about 85 weight% or more, 90 weight% or more, 95 weight% or more, 99 weight% or more, 99 weight% or more, 99.9 weight% or more, or 99.99 weight% or more, or about 100 weight% or less.

[0057] The film of the present invention, by ensuring that the active layer (20) is formed with the above-mentioned material and weight ratio, can effectively block the inflow of external moisture and atmosphere (air) into the secondary battery while continuously and non-destructively discharging gas generated inside the secondary battery under both high-pressure and low-pressure conditions through a simple structure and / or material, and can have excellent resistance to electrolyte. Furthermore, this effect can be further enhanced by controlling the thickness of the active layer (20) as follows. In this specification, "high-pressure condition" refers to a pressure condition where there is a significant risk of causing ignition or explosion due to damage to at least a part of the secondary battery case, and may, for example, mean a pressure exceeding about 20 psi, about 50 psi, or about 100 psi. "Low-pressure condition" may refer to a range of about 20 psi or less, where there is a relatively low risk of damage to the case while exceeding atmospheric pressure, which allows gas generated inside the secondary battery to be discharged to the outside.

[0058] A film (100) according to one embodiment of the present invention may, for example, have a ratio of the forward permeability of gas generated inside a secondary battery to the reverse permeability of air at a relative pressure value of about 15 psi or about 50 psi, such that the ratio is about 2 or more. In another example, the film (100) may, at a relative pressure value of about 15 psi or about 50 psi, have a ratio of the forward permeability of gas generated inside a secondary battery to the reverse permeability of air such that the ratio is about 2.5 or more, 3 or more, 3.5 or more, 4 or more, 4.5 or more, 4.5 or more, 5 or more, 5.5 or more, 6 or more, 6.5 or more, 7 or more, 7.5 or more, 8 or more, 8.5 or more, 9 or more, or 9.5 or more, or about 20 or less, 18 or less, 16 or less, or 14 or less. In this specification, "forward direction" refers to the direction from inside the secondary battery to outside the secondary battery, and "reverse direction" refers to the direction from outside the secondary battery to inside the secondary battery.

[0059] In one embodiment of the present invention, the film (100) may, for example, have a ratio of the thickness of the support layer (10) to the thickness of the active layer (20) of about 0.85 or less. In other examples, the ratio of the thickness of the support layer to the thickness of the active layer (20) may be about 0.8 or less, 0.75 or less, 0.7 or less, 0.65 or less, 0.6 or less, 0.55 or less, or 0.5 or less, or about 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, or 0.7 or more. The present invention provides a film having excellent resistance to electrolyte, which can effectively block the inflow of external moisture and atmosphere (air) into the secondary battery while continuously and non-destructively discharging gas generated inside the secondary battery under high pressure conditions as well as low pressure conditions, through a film formed by combining an active layer (20) having the aforementioned features and a support layer (10) described below in a ratio of predetermined thickness.

[0060] The above active layer (20) may, for example, have a thickness of about 120 μm or more and 1000 μm or less. In this specification, “thickness” may be the average thickness between thicknesses measured at any location, the maximum thickness and / or the minimum thickness. In another example, the above active layer (20) has a thickness of about 125 μm or more, 130 μm or more, 135 μm or more, 140 μm or more, 145 μm or more, 150 μm or more, 155 μm or more, 160 μm or more, 165 μm or more, 170 μm or more, 175 μm or more, 180 μm or more, 185 μm or more, 190 μm or more, 195 μm or more, 200 μm or more, 205 μm or more, or 210 μm or more, or about 950 μm or less, 900 μm or less, 850 μm or less, 800 μm or less, 750 μm or less, 700 μm or less, 650 μm or less, 600 μm or less, 550 μm or less, 500 μm or less, 450 It may be µm or less, 400 µm or less, 350 µm or less, 300 µm or less, 250 µm or less, 200 µm or less, or 150 µm or less. In the present invention, the thickness of the active layer (20) may be controlled by the application and / or curing method of the active layer forming composition described later.

[0061] The film (100) of the present invention can further improve its resistance to an electrolyte by controlling the ratio of the thickness between the active layer (20) and the support layer (10) and / or the thickness of the active layer (20) as described above. In this specification, "the film has resistance to a secondary battery electrolyte" may mean that the side of the film (100) in contact with the inside of the secondary battery does not dissolve, and does not absorb or transmit the electrolyte and / or vapor derived therefrom, even when exposed to the electrolyte and / or vapor derived therefrom for an initial or significant period of time.

[0062] The active layer (20) can also absorb, for example, gas generated inside the secondary battery and transfer it outward. The gas may include, for example, gas generated when a Solid Electrolyte Interphase (SEI) film is formed during the secondary battery formation process, and / or abnormal gas generated due to the decomposition of the electrolyte, excessive moisture content of the secondary battery, short circuit, overcharging and / or over-discharging. The composition of the gas may vary slightly depending on the combination of the electrolyte, electrolyte solvent, positive active material, negative active material, and binder used in the secondary battery, but it may exhibit similar properties in that CO2 is the main component in the case of normal use. The gas may be, for example, H2; O2; CO; CO2; and / or hydrocarbon gases such as CH4, C2H2, C2H4, C2H6, C3H6, C3H8, etc. It may include a combination thereof, and the ratio of CO2 gas to the total amount of gas generated may be about 50% or more. As the film (100) of the present invention includes an active layer (20) having the features described below, it can transmit gas generated inside the secondary battery in a forward direction (from the inside of the film to the outside) through a solution-diffusion mechanism. Referring to FIG. 2, the support layer (10) of the gas discharge film (100) according to another embodiment of the present invention may include, for example, a porous support (101) and a polymer coating layer (102) on at least one surface of the porous support.

[0063] The porous support (101) may be, for example, in the form of a nonwoven fabric, a woven fabric, or a mesh in which polymer fibers are irregularly intertwined. The polymer may be, for example, PP (Polypropylene), PMMA (Poly(methyl methacrylate)), PE (Polyethylene) or PET (Polyethylene terephthalate), PES (Polyether sulfone), but is not limited thereto.

[0064] The porosity of the porous support (101) may be about 10% to 90%, but is not limited thereto. The porosity may be measured by the Archimedes principle. In other examples, the porosity of the porous support may be about 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, or 80% or more, or about 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less.

[0065] The polymer coating layer (102) may include, for example, one or more selected from polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethylchloride, polyvinylidene fluoride, and combinations thereof. According to one embodiment, the polymer coating layer (102) may be polysulfone in terms of reinforcing support or gas permeability or selectivity.

[0066] The thickness of the support layer (10) may, for example, be less than about 140 μm. In other examples, the thickness of the support layer may be about 60 μm or more, 70 μm or more, 80 μm or more, or 90 μm or more, or less than about 130 μm, less than 120 μm, or less than 110 μm.

[0067] The above support layer (10) has, for example, a tensile strength of about 0.1 kgf / mm 2 Up to 10 kgf / mm 2 It may be. The above tensile strength may be measured in the manner according to the evaluation example described below.

[0068] The above support layer (10) may, for example, have a water contact angle of about 80° to 120°. In this specification, "water contact angle of the support layer" may refer to the water contact angle of the surface of the support layer (10) that is in contact with external air. In other examples, the water contact angle of the support layer (10) may be about 85° or more, 90° or more, or 95° or more, or about 115° or less, 110° or less, or 105° or less.

[0069] The present invention includes a support layer (10) as described above, thereby maintaining the shape of the film and providing the desired mechanical strength, while also possessing the asymmetric gas permeability and electrolyte resistance characteristic of the film of the present invention through combination with the aforementioned active layer (20). These characteristics can be expressed more effectively by controlling the configuration described below.

[0070] A film (100) according to one embodiment of the present invention may have a thickness of, for example, about 200 μm to 1000 μm. In another example, the film (100) of the present invention may have a thickness of about 220 μm or more, 240 μm or more, 260 μm or more, 280 μm or more, or 300 μm or more, or about 900 μm or less, 800 μm or less, 700 μm or less, 600 μm or less, 500 μm or less, 450 μm or less, 400 μm or less, 350 μm or less, 300 μm or less, or 250 μm or less.

[0071] A film (100) according to one embodiment of the present invention may be configured such that, for example, an active layer (20) and a support layer (10) are adjacent. In this specification, "the active layer (20) and the support layer (10) are adjacent" means that the active layer (20) and the support layer (20) are directly laminated without any separate layer interposed between them. From the perspective of improving processability and productivity through the simplification of the structure, a film (100) according to one embodiment of the present invention may be configured to include only the support layer (10) and the active layer (20). Through such a simple structure, the present invention can provide a film (100) that can continuously and non-destructively discharge gas generated inside the secondary battery under high pressure conditions as well as low pressure conditions, while effectively blocking the inflow of external moisture and atmosphere (air) into the secondary battery, and has excellent resistance to the electrolyte.

[0072] A second aspect of the present invention relates to a secondary battery comprising, in at least a portion, a gas discharge film (100) according to one embodiment of the present invention, wherein gas generated inside the secondary battery is non-destructively discharged to the outside through the film (100).

[0073] The details regarding the first aspect of the present invention may be applied in the same way to the details regarding the second aspect unless specifically described otherwise.

[0074] Conventionally, venting systems have been introduced to solve the problem of increased gas generation due to abnormal operation of the battery, which can lead to ignition or explosion. A venting system is a device that allows internal gas to be discharged to the outside when, for example, the internal pressure of a secondary battery reaches a certain level. However, it is difficult to reuse the secondary battery after venting, and there has been a lack of safety enhancement systems that can be considered as an alternative when such a venting system fails to operate properly for unexpected reasons. However, according to the present invention, by including or installing a gas discharge film (100) as described above in at least a part of the secondary battery, the gas generated inside the battery can be discharged continuously and non-destructively under low pressure conditions as well as high pressure conditions, thereby further improving the lifespan, resistance, and stability of the battery. Furthermore, by applying this film (100) to the battery in combination with a conventional venting system, the above effects can be further enhanced.

[0075] The above secondary battery may include, for example, an electrode assembly, an electrolyte, and / or a case containing the same, and may further include any known components known to be introduced into the secondary battery without special limitation, provided that such inclusion does not impede the purpose of the present invention.

[0076] The above secondary battery may be, for example, a cylindrical secondary battery, a prismatic secondary battery, and / or a pouch-type secondary battery.

[0077] Hereinafter, examples of applying the above-mentioned gas discharge film to a cylindrical secondary battery will be described with reference to FIG. 3, FIG. 4(a) and FIG. 4(b).

[0078] The cylindrical secondary battery (30) of the present invention may include, for example, an electrode assembly (301), a cylindrical can (302) in which the electrode assembly is housed, and / or a cap assembly (303) that seals the open end of the cylindrical can (302). The cylindrical can (302) may include, for example, a bottom surface of the can and / or a side surface of the can. The bottom surface of the can may, for example, mean the opposite side facing the open end of the can where the cap assembly (303) is mounted. A cylindrical secondary battery (30) according to one embodiment of the present invention may be manufactured by housing the electrode assembly (301) in the cylindrical can (302), injecting an electrolyte into the cylindrical can (302), and then mounting and sealing the cap assembly (303) on the open top surface of the cylindrical can (302). At this time, the cap assembly (303) may be electrically connected to the electrode assembly through an electrode tab (e.g., a positive electrode tab) extending from the electrode assembly (301), or it may be implemented as a cap assembly tab-less structure. The tab-less structure may be, for example, a structure in which each of the positive and negative electrodes included in the electrode assembly (301) includes a non-broad portion, and each of the non-broad portions is electrically connected to an electrode terminal.

[0079] The above-described cylindrical secondary battery (30) may include a hole (H) in one or more of, for example, the bottom portion of the can, the side portion of the can, and / or the cap assembly (303) of the cylindrical can. In one example, the cylindrical secondary battery (30) includes a cylindrical can (302) in which an electrode assembly is received and a cap assembly (303) mounted on the top of the cylindrical can, and includes a hole (H) in a part of the cap assembly (303), and the hole (H) may be covered by the aforementioned gas discharge film (100). The hole (H) may or may not serve as, for example, an electrolyte injection port. If the electrolyte injection port is used as the hole (H), the processability may be improved because the step of forming the hole is not required.

[0080] According to one embodiment, the structure of the cap assembly (303) and the position of the hole are described with reference to FIG. 4(a) and FIG. 4(b), but this is merely an example and the present invention is not limited thereto.

[0081] A cylindrical secondary battery (30) equipped with a cap assembly (303) may have a structure such as that shown in FIG. 4(a), for example. The cap assembly (303) may include, for example, a top cap (3031), a safety vent (3032), and / or a CID filter (3033). The top cap (3031) may, for example, form a positive terminal in a protruding shape and have one or more exhaust ports (not shown) perforated therein. A safety vent (3032), for example, may be located at the bottom of the top cap. The CID filter (3033) may, for example, have a portion of its upper surface connected to the safety vent (3032) and a portion of its lower surface connected to the electrode of the electrode assembly (301). When gas is generated from the electrode assembly (301) due to causes such as overcharging or high temperature and the internal pressure increases, the shape of the safety vent (3032) may be reversed and protrude upward, allowing the gas to be exhausted. At this time, the CID filter (3033) also moves upward, and the notch (N) region is broken, so that the flow of current can be cut off. This can prevent or suppress additional overcharging and explosion of the battery.

[0082] The cap assembly (303) may further include, for example, a gasket (3034) that provides airtightness and insulation between the top cap (3031) and the battery can (302), and the top cap (3031) may be pressed onto a beading portion (3021) formed on the cylindrical can (302) and secured by a crimping portion (3022). The top cap (3031) is a component made of a conductive metal material and can cover the top opening of the cylindrical can (302). The top cap (3031) may be electrically connected to the positive electrode (e.g., positive tab, 304) of the electrode assembly (301) and may be electrically insulated from the cylindrical can (302) through the gasket. Thus, the top cap (3031) can function as a positive terminal of the cylindrical secondary battery (30). The top cap (3031) may have a protrusion formed by protruding upward at its center, and the protrusion may come into contact with an external power source to allow current to be applied from the external power source. In such a cap assembly (303), the hole (H) may be formed, for example, in a part of the safety vent (3032), and may be formed in the area marked H as in FIG. 4(a) in one example, but is not limited thereto and may be formed in an area excluding the notch.

[0083] A cylindrical secondary battery (30) equipped with a cap assembly (303) may have a structure such as that shown in FIG. 4(b), for example. The cap assembly (303) may include, for example, a top plate (3035). The top plate (3035) may be a conductive member that functions as a positive terminal for connection with an external power source and may be electrically connected to an external power source. The top plate (3035) may be electrically connected to a current collector plate (3036) placed at the positive end, for example, to transmit current to the outside. In one example, a tapless structure can be realized and the manufacturing process simplified by implementing a direct connection with the top plate (3035) through a disc-shaped or ring-shaped current collector plate placed at the end of the electrode assembly, without separately drawing out a positive tab from the electrode assembly (301). The current collector plate (3036) may have a known structure. The current collector plate (3036) may be made of, for example, a conductive metal material and may be electrically connected to a top plate (3035) located on the upper side. Accordingly, the current collector plate (3036) enables a stable electrical connection with the top plate without a tap structure, and can ensure structural simplicity and electrical reliability of the positive terminal. The cap assembly (303) may further include, for example, a spacer (3037) located between the cap plate (3035) and the electrode assembly (301). The height of the spacer may correspond to the distance between the cap plate (3035) and the electrode assembly (301). The spacer (3037) may, for example, prevent or suppress the electrode assembly (301) from moving or shaking within the cylindrical can (302).The above cap assembly (303) may also further include a gasket (3034) that provides airtightness and insulation between, for example, the top plate (3035) and the cylindrical can (302), and the structure for mounting the cap assembly to the battery can, such as the crimping portion (3022) or the beading portion (3021), may be applied in the same manner as the content of FIG. 4(a), but may also be replaced with a known structure as long as it does not impede the purpose of the present invention. In such a cap assembly (303), the hole (H) may be formed in, for example, a part of the top plate (3035), and in one example, may be formed in the area marked as H as in FIG. 4(b), but is not limited thereto, and may be formed in an area excluding the notch portion.

[0084] The above cap assembly (303) may have various structures depending on the type of cylindrical secondary battery (30), and may have a positive electrode, a negative electrode, or no pole. Depending on the structure of the cap assembly (303), the position of the hole (H) may vary, but the position of the hole (H) may not be particularly limited as long as it penetrates to connect the inside and outside of the cylindrical secondary battery so as to ensure the smooth function of the cap assembly (303).

[0085] In another example, the cylindrical secondary battery (30) includes a cylindrical can (302) in which an electrode assembly is received and a cap assembly (303) mounted on the top of the cylindrical can, and includes a hole (H) in a part of the cylindrical can (302), and the hole may be covered by the aforementioned gas discharge film (100). The hole (H) may be included, for example, in a part of either the bottom surface or the side surface of the cylindrical can (302), and considering workability, the hole (H) may be formed in the bottom surface of the can without curvature.

[0086] The diameter of the hole (H) may be, for example, about 0.1 mm to 100 mm. In other examples, the diameter of the hole (H) may be about 0.5 mm or more or 1 mm or more, or 50 mm or less, 40 mm or less, 30 mm or less, 20 mm or less, 10 mm or less, 5 mm or less, 2 mm or less, or 1 mm or less, but is not particularly limited as long as it is possible to provide a secondary battery with excellent stability without electrolyte leakage while having an excellent gas discharge effect due to the application of a gas discharge film.

[0087] The hole (H) may be covered, for example, by a gas exhaust film (100). For example, the gas exhaust film (100) may be attached to or installed on a cylindrical secondary battery to cover the hole (H). The diameter of the gas exhaust film (100) may be, for example, larger than the diameter of the hole (H). The gas exhaust film (100) may be attached to or installed on the cylindrical secondary battery by, for example, laser welding or thermal fusion.

[0088] The cylindrical secondary battery (30) of the present invention may also include, without limitation, components included in a known cylindrical secondary battery (30) as long as they do not impede the purpose of the present invention.

[0089] The cylindrical secondary battery of the present invention can improve the stability and lifespan characteristics of the battery by, for example, through the structure described above, continuously and non-destructively discharging gas generated inside the secondary battery under both high-pressure and low-pressure conditions, while effectively blocking the inflow of external moisture and atmosphere (air) into the secondary battery.

[0090] Hereinafter, examples of applying the above-mentioned gas exhaust film to a prismatic secondary battery will be described with reference to FIGS. 5(a) to 5(c).

[0091] The prismatic secondary battery (40) of the present invention may include, for example, an electrode assembly, a prismatic can (401) in which the electrode assembly is received, and / or a base plate (402) mounted on the top of the prismatic can.

[0092] The above-described rectangular can (401) may include, for example, a can bottom portion (4011) and / or a can side portion (4012), and the top of the rectangular can may be open. For example, a base plate (402) may be mounted on the top of the rectangular can (401). The base plate (402) may be mounted, for example, after the electrolyte injection or before the electrolyte injection. The rectangular secondary battery (40) may be sealed by the base plate (402).

[0093] One or more of the can bottom portion (4011), can side portion (4012), and / or base plate (402) of the above-described prismatic secondary battery (40) may include, for example, a hole (H). In one example, the prismatic secondary battery (40) includes a prismatic can (401) in which an electrode assembly is accommodated as in FIG. 5(a) and a base plate (402) mounted on the top of the prismatic can, and a hole (H) is included in a part of the base plate, and the hole may be covered by the aforementioned gas discharge film (100). The hole (H) may be, for example, an electrolyte injection port (4021), or it may be a hole (H) that is not an electrolyte injection port. If an electrolyte injection port is used as the hole (H), the processability may be further improved because there is no need to go through the step of forming a separate hole. In another example, the prismatic secondary battery (40) includes a prismatic can (401) in which an electrode assembly is accommodated as in FIG. 5(b) or FIG. 5(c), and a base plate (402) mounted on the top of the prismatic can, and includes a hole (H) in a part of either the bottom surface (4011) or the side surface (4012) of the prismatic can, and the hole may be covered by the aforementioned gas discharge film (100).

[0094] The diameter of the hole (H) may be, for example, about 0.1 mm to 100 mm. In other examples, the diameter of the hole (H) may be about 0.5 mm or more or 1 mm or more, or 50 mm or less, 40 mm or less, 30 mm or less, 20 mm or less, 10 mm or less, 5 mm or less, 2 mm or less, or 1 mm or less, but is not particularly limited as long as it is possible to provide a secondary battery with excellent stability without electrolyte leakage while having an excellent gas discharge effect due to the application of a gas discharge film.

[0095] The hole (H) may be covered, for example, by a gas exhaust film (100). That is, the gas exhaust film (100) may be attached to or installed on the prismatic secondary battery to cover the hole (H). The diameter of the gas exhaust film (100) may be, for example, larger than the diameter of the hole (H). The gas exhaust film (100) may be attached to or installed on the prismatic secondary battery by, for example, laser welding or thermal fusion.

[0096] The base plate (402) may further include an electrode terminal (4022) connected to, for example, an electrode tab (e.g., a negative electrode tab) of an electrode assembly. The location of the electrode terminal (4022) may, for example, be the central part of the base plate, but is not limited thereto. The electrode terminal may, for example, be protruding. Additionally, between the protruding electrode terminal (4022) and the base plate (402), an insulating member (4023) may be interposed for electrical insulation with respect to the base plate (402), which acts as an electrode terminal itself and is, for example, connected to another electrode (e.g., a positive electrode) of the electrode assembly.

[0097] The prismatic secondary battery (40) of the present invention may also include, without limitation, components included in known prismatic secondary batteries, as long as they do not impede the purpose of the present invention.

[0098] The prismatic secondary battery of the present invention, for example through the aforementioned structure, can continuously and non-destructively discharge gas generated inside the secondary battery under both high-pressure and low-pressure conditions, while effectively blocking the inflow of external moisture and atmosphere (air) into the secondary battery, thereby improving the stability and lifespan characteristics of the battery.

[0099] Hereinafter, examples of applying the above-mentioned gas discharge film to a pouch-type secondary battery will be described with reference to FIG. 6(a) and FIG. 6(b).

[0100] The pouch-type secondary battery (50) of the present invention may include, for example, an electrode assembly and a pouch-type case (501). The pouch-type case (501) may include, for example, a main body portion (5011) and / or a sealing portion (5012). The main body portion (5011) may refer to, for example, a film area in which an electrode assembly is housed, and the sealing portion (5012) may refer to, for example, a film area that seals the edge of the main body portion to block the inside of the battery from the outside. The sealing portion (5012) may refer to, for example, an edge portion of the pouch-type case, and may refer to a film area that is sealed by joining and / or fusing together within the pouch-type case. The sealing portion (5012) may extend along the edge from, for example, the main body portion (5011).

[0101] One or more of the main body portion (5011) and / or sealing portion (5012) of the above pouch-type case (501) may include, for example, a hole (H). In one example, the pouch-type secondary battery (50) includes a pouch-type case (501) in which an electrode assembly is received, and the pouch-type case includes a main body portion (5011) and a sealing portion (5012), and a hole (H) is included in a part of the main body portion (5011), and the hole may be covered by the aforementioned gas discharge film (100). In another example, the pouch-type secondary battery (50) includes a pouch-type case (501) in which an electrode assembly is received, and the pouch-type case includes a main body portion (5011) and a sealing portion (5012), and a hole (H) is included in a part of the sealing portion (5012), and the hole may be covered by the aforementioned gas discharge film (100). Here, the sealing portion (5012) may include, for example, an area (5013) that overlaps with the protrusion of the electrode lead, and a hole (H) may be formed in one area of ​​the sealing portion excluding the area (5013) that overlaps with the protrusion of the electrode lead for the purpose of improving the film application effect, but is not limited thereto.

[0102] The diameter of the hole (H) may be, for example, about 0.1 mm to 100 mm. In other examples, the diameter of the hole (H) may be about 0.5 mm or more or 1 mm or more, or 50 mm or less, 40 mm or less, 30 mm or less, 20 mm or less, 10 mm or less, 5 mm or less, 2 mm or less, or 1 mm or less, but is not particularly limited as long as it is possible to provide a secondary battery with excellent stability without electrolyte leakage while having an excellent gas discharge effect due to the application of a gas discharge film.

[0103] The hole (H) may be covered, for example, by a gas discharge film (100). That is, the gas discharge film (100) may be attached to or installed on a pouch-type secondary battery to cover the hole (H). The diameter of the gas discharge film (100) may be, for example, larger than the diameter of the hole (H). The gas discharge film (100) may be attached to or installed on the pouch-type secondary battery by, for example, laser welding or thermal fusion.

[0104] The above pouch-type case (501) may be manufactured, for example, by molding a pouch film laminate. In this case, the pouch film laminate may have a structure in which a substrate layer, a gas barrier layer, and / or a sealant layer are sequentially laminated, but is not limited thereto, and any known pouch film laminate may be used.

[0105] The above substrate layer is formed on the outermost layer of a pouch film laminate to protect the secondary battery from friction and collision with the outside, and is made of a polymer to electrically insulate the electrode assembly from the outside. The above substrate layer may be composed of one or more materials selected from, for example, polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber. According to one embodiment, the substrate layer may be composed of polyethylene terephthalate (PET), nylon, or a combination thereof having wear resistance and heat resistance. The above substrate layer may have a single film structure composed of any one material or a composite film structure formed by two or more materials forming separate layers. The thickness of the above substrate layer may be about 5 μm to 50 μm, but is not limited thereto.

[0106] The gas barrier layer is laminated between the substrate layer and the sealant layer to secure the mechanical strength of the pouch, block the entry and exit of gases or moisture from outside the secondary battery, and prevent electrolyte leakage from inside the pouch-type case. The gas barrier layer may include, for example, a metal, and may be formed as an aluminum alloy thin film according to one embodiment. When the gas barrier layer is formed using an aluminum alloy thin film, it is possible to secure mechanical strength above a certain level while maintaining a light weight, and to ensure complementary electrochemical properties of the electrode assembly and electrolyte, as well as heat dissipation. The aluminum alloy thin film may include one or more metal elements other than aluminum, selected from, for example, iron, copper, chromium, manganese, nickel, magnesium, silicon, and zinc. The thickness of the gas barrier layer may be approximately 40 μm to 100 μm, but is not limited thereto.

[0107] The sealant layer is intended to completely seal the inside of a pouch-type case by mutually thermally bonding at the sealing portion when the pouch-type case (505) containing an electrode assembly on the inside is sealed. To this end, the sealant layer may be formed from a material having excellent thermal bonding strength. The sealant layer may be formed from a material having insulating properties, corrosion resistance, and sealing properties. For example, since the sealant layer comes into direct contact with the electrode assembly and / or electrolyte on the inside of the pouch-type case, it may be formed from a material having insulating properties and corrosion resistance. In addition, since the sealant layer must completely seal the inside of the pouch-type case to block material transfer between the inside and the outside, it may be formed from a material having high sealing properties (e.g., excellent thermal bonding strength). To ensure such insulating properties, corrosion resistance, and sealing properties, the sealant layer may be formed from a polymer material. For example, the sealant layer may be composed of one or more materials selected from polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber, and according to one embodiment, the sealant layer may be composed of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be composed of unoriented polypropylene (Cast Polypropylene, CPP), acid-modified polypropylene (Acid Modified Polypropylene, PPa), polypropylene-ethylene copolymer and / or polypropylene-butylene-ethylene terpolymer. The thickness of the sealant layer may be, for example, about 30 μm to 130 μm, but is not limited thereto.

[0108] The pouch-type secondary battery (50) of the present invention may also include, without limitation, components included in a known pouch-type secondary battery (50) as long as they do not impede the purpose of the present invention.

[0109] Any known electrode assembly may be applied as the electrode assembly. The electrode assembly may, for example, include at least one unit cell or be a multi-stack cell. The multi-stack cell may, for example, refer to a cell having a stacked structure in which a structure in which a separator is interposed between an anode and a cathode is repeated three or more times. The unit cell may, for example, be a monocell or a bicell. The monocell refers to a unit cell in which the types of electrodes located on both sides are different in a structure in which one or more anodes and one or more cathodes are stacked with a separator interposed therebetween, and the bicell refers to a unit cell in which the types of electrodes located on both sides are the same in a structure in which one or more anodes and one or more cathodes are stacked with a separator interposed therebetween. The unit cell or the multi-stack cell may each include, for example, an anode, a cathode, and / or a separator. The electrode assembly may also include, for example, electrode tabs (e.g., positive tabs and / or negative tabs) for drawing current outward, and the electrode tabs may be electrically connected to the positive or negative electrode, respectively, and may be structured to protrude in one direction from the electrode assembly. The electrode tabs thus protruding may be connected to the positive lead and / or negative lead, respectively, to enable electrical connection with an external circuit. The electrode leads may be structured to penetrate or extend through the sealing portion and / or terrace portion of the pouch-type case, protruding outward from the pouch-type case. In this way, the electrode leads can form an electrical path between the internal electrode assembly and the external circuit. The electrode assembly may also have a structure such as, for example, a wound type, a stacked type, a stack-and-folding type, or a lamination / stacked type, but is not limited thereto.

[0110] The above-mentioned positive electrode may include, for example, a positive current collector and a positive active material layer formed on at least one surface of the positive current collector. For example, a thin sheet made of aluminum, stainless steel, or nickel may be used as the positive current collector. Additionally, for example, a porous body such as a network or mesh shape may be used as the positive current collector, or a material coated with an oxidation-resistant metal or alloy film may be used to prevent oxidation. In some cases, the positive current collector may be omitted. The positive active material layer may include a known positive active material, a binder, and / or a conductive material. The positive active material may be, for example, a compound capable of reversible intercalation and deintercalation of lithium, such as a lithium transition metal composite oxide containing lithium and at least one transition metal composed of nickel, cobalt, manganese, and aluminum, but is not limited thereto. The binder may be, for example, at least one selected from polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose, starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, and fluororubber, but is not limited thereto. The conductive material may be, for example, one or more selected from graphite, carbon black, carbon nanotubes, metal powder, and conductive oxide, but is not limited thereto. The anode active material layer may also include other known additives as long as they do not impede the purpose of the present invention.

[0111] The above-mentioned cathode may include, for example, a cathode current collector and a cathode active material layer. As the cathode current collector, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, a copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or an aluminum-cadmium alloy may be used. In addition, similar to the anode current collector, fine irregularities may be formed on the surface to strengthen the bonding strength of the cathode active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or nonwoven fabric. In some cases, the above-mentioned cathode current collector may be omitted. The above-mentioned cathode active material layer may include a known cathode active material, a binder, and / or a conductive material. The above-mentioned cathode active material may be, for example, a silicon-based or carbon-based cathode active material. The silicon-based negative electrode active material may be at least one selected from, for example, SiOx (0≤x<2) particles, Si-C composites, and Si-Y alloys (wherein Y is an element selected from alkali metals, alkaline earth metals, transition metals, Group 13 elements, Group 14 elements, rare earth elements, and combinations thereof). The carbon-based negative electrode active material may be at least one selected from, for example, artificial graphite, natural graphite, amorphous carbon, and graphitized mesocarbon micro beads, but is not limited thereto. The binder included in the negative electrode active material layer may be, for example, an aqueous binder or a rubber-based binder. The aqueous binder may be at least one selected from polyvinyl alcohol, polyacrylic acid, polyethylene glycol, polyacrylonitrile, polyacrylamide, carboxymethylcellulose, and combinations thereof, as it is soluble in an aqueous solvent such as water, but is not limited thereto.The above rubber-based binder is not easily soluble in aqueous solvents such as water but is capable of smooth dispersion in aqueous solvents, and may be at least one selected from, for example, styrene-butadiene rubber, hydrogenated nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof, but is not limited thereto. The conductive material included in the above cathode active material layer may be, for example, one or more selected from graphite, carbon black, carbon nanotubes, metal powder, conductive oxide, and combinations thereof, but is not limited thereto.

[0112] The above-mentioned separator has the function of physically separating the electrodes and can be used without special limitations as long as it is used as a conventional separator; for example, a material having low resistance to ion movement of the electrolyte and excellent electrolyte wettability may be used. The above-mentioned separator may be made of a porous, non-conductive, or insulating material, and may be an independent component or a coating layer added to the anode and / or cathode. The above-mentioned separator may be a membrane formed from polyolefin-based polymers such as polyethylene (e.g., high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene), polypropylene, polybutylene, polyylpentene, etc., either individually or in a mixture thereof.

[0113] The above secondary battery may also further include known components, such as an electrolyte, for example.

[0114] The above electrolyte may include an organic solvent and a lithium salt. The above organic solvent may be used without special limitations as long as it can serve as a medium through which ions related to the electrochemical reaction of the battery can move. Examples of the above organic solvents include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); arcor-based solvents such as ethanol and isopropyl alcohol; R-CN (R is C2~C 20Examples may include nitriles such as linear, branched, or cyclic hydrocarbon groups (which may include double aromatic rings or ether bonds); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolanes; or sulfolanes. As for the lithium salt, any compound capable of providing lithium ions used in a battery may be used without special limitations. Examples of the lithium salt include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, and LiN(CF3SO2). 2, Examples include LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt may be in the range of about 0.1 M to 2.0 M. When the concentration of the lithium salt according to one embodiment falls within the above range, the electrolyte can exhibit excellent electrolyte performance as it has appropriate conductivity and viscosity, thereby enabling effective transport of lithium ions.

[0115] A third aspect of the present invention may be a method for manufacturing a gas discharge film (100) having different gas permeability characteristics on both sides to discharge gas generated inside a secondary battery to the outside and not allow external air and water vapor to pass into the secondary battery, wherein the film has a ratio of the forward permeability of gas generated inside the secondary battery to the reverse permeability of air at a relative pressure of about 15 psi or about 50 psi, the forward direction is a direction from inside the secondary battery to outside the secondary battery, and the reverse direction is a direction from outside the secondary battery to inside the secondary battery.

[0116] Matters relating to the first and / or second aspects of the present invention may be applied in the same way to the third aspect unless specifically described otherwise.

[0117] Referring to FIG. 7, the method for manufacturing a gas exhaust film (100) of the present invention may include, for example, a step of manufacturing a support layer (10) (step S0) and a step of applying a composition for forming an active layer on the support layer (10) (step S1).

[0118] The above S1 step can be performed by methods such as spin coating, slot-die coating, gravure coating, microgravure coating, dip coating, blade coating, bar coating, slit coating, or inkjet coating.

[0119] In one example, the above S1 step may be performed by a spin coating method, but any coating method capable of precise coating thickness control may be used without limitation. The above S1 step may be performed, for example, at a speed of about 100 rpm to 900 rpm. The above speed may refer to the spin rate of the spin coater. In other examples, the above S1 step may be performed at a speed of about 150 rpm or more, 200 rpm or more, 250 rpm or more, 300 rpm or more, 350 rpm or more, 400 rpm or more, or 450 rpm or more, or at a speed of about 850 rpm or less, 800 rpm or less, 750 rpm or less, 700 rpm or less, 650 rpm or less, 600 rpm or less, or 550 rpm or less.

[0120] The above S1 step may be performed, for example, for about 1 second to 100 seconds. In other examples, the above S1 step may be performed for about 5 seconds or more, 10 seconds or more, 15 seconds or more, 20 seconds or more, 25 seconds or more, or 30 seconds or more, or for about 90 seconds or less, 80 seconds or less, 70 seconds or less, 60 seconds or less, 50 seconds or less, 40 seconds or less, 30 seconds or less, 20 seconds or less, or 10 seconds or less.

[0121] The present invention can form an active layer (20) with a thickness within the aforementioned range by performing step S1 at the above speed and / or for the above time, and as a result, can provide a gas discharge film (100) having excellent resistance to electrolyte and asymmetric gas permeability characteristics.

[0122] The above composition for forming the active layer may include, for example, a polydimethylsiloxane precursor and a curing agent. The weight ratio of the polydimethylsiloxane precursor to the curing agent may be, for example, about 1 to 10.

[0123] The film manufacturing method of the present invention may further include, for example, a step (step S2) of drying a coated composition for forming an active layer to form an active layer (20).

[0124] The above S2 step can be performed, for example, at a temperature of about 70°C to 110°C. The above S2 step can be performed, for example, by an oven.

[0125] The above S2 step may be performed for, for example, about 12 hours or more. In other examples, the above S2 step may be performed for about 30 hours or less or 24 hours or less.

[0126] The present invention can form an active layer (20) with a thickness within the aforementioned range by performing step S2 for the above-mentioned temperature and / or time, and as a result, can provide a gas discharge film (100) having excellent resistance to electrolyte and asymmetric gas permeability characteristics.

[0127] The above S0 step may include, for example, a step of preparing a porous support (101) and / or a step of forming a polymer coating layer (102) on at least one surface of the porous support. The step of forming a polymer coating layer (102) on at least one surface of the porous support (101) may include, for example, a step of applying the polymer coating layer (102) on at least one surface of the porous support (101) and / or a step of drying. The application may be performed, for example, by a spin coater.

[0128] Hereinafter, the present invention is described in detail with reference to examples to explain the disclosure of the present invention as described above and the intended operation and effect of the present invention. However, the examples may be modified in various different forms, and the scope of this specification is not to be interpreted as being limited only to these examples. It is emphasized that the examples are provided to explain the present invention to those skilled in the art. In the following examples, films having different characteristics were manufactured by varying the rotation speed and time of a spin coater that applies an active layer forming composition onto a polymer coating layer (101) of a support layer (10).

[0129] Example 1.

[0130] A film having a structure as shown in FIG. 1, in which a support layer (10) and an active layer (20) are sequentially formed, was manufactured.

[0131] The support layer (10) was prepared by casting a polymer coating layer solution onto a nonwoven fabric made of polyester material (porous support, 101) to form a polymer coating layer (102), and immersing the cast nonwoven fabric in water, with a thickness of 100 μm. At this time, the polymer coating layer solution was obtained by adding a polysulfone solid to a DMF (N, N-dimethylformamide) solution and dissolving it at 80°C to 85°C for 12 hours or more, and the content of the polysulfone solid in the solution was 18% by weight.

[0132] Next, an active layer (20) was formed on one surface of the support layer (10). The active layer (20) was prepared by applying a composition for forming an active layer, in which a PDMS precursor (Sylgard 184, Dow chemical) and a curing agent (Sylgard 184, Dow chemical) were mixed in a weight ratio of 5:1, onto the polymer coating layer (101) of the support layer (10), and then drying it in a 90°C oven for more than 12 hours. At this time, the application was performed at a speed of 500 rpm for 10 seconds, thereby obtaining an active layer (20) with a thickness of approximately 214.7 μm.

[0133] The thickness of the final obtained film (100) was approximately 314.7 μm.

[0134] Example 2.

[0135] A film (100) was manufactured in the same manner as in Example 1, except that when applying the composition for forming the active layer onto the polymer coating layer, the active layer (20) having a thickness of about 150.3 μm was applied at a speed of 500 rpm for 20 seconds. The thickness of the finally obtained film (100) was about 250.3 μm.

[0136] Example 3.

[0137] A film (100) was manufactured in the same manner as in Example 1, except that when applying the composition for forming the active layer onto the polymer coating layer, the active layer (20) having a thickness of about 127.5 μm was applied at a speed of 500 rpm for 30 seconds. The thickness of the finally obtained film (100) was about 227.5 μm.

[0138] Example 4.

[0139] A film (100) was manufactured in the same manner as in Example 1, except that when applying the composition for forming the active layer onto the polymer coating layer, an active layer (20) having a thickness of about 116.6 μm was obtained by applying it at a speed of 1000 rpm for 10 seconds. The thickness of the finally obtained film (100) was about 226.6 μm.

[0140] Example 5.

[0141] A film (100) was manufactured in the same manner as in Example 1, except that when applying the composition for forming the active layer onto the polymer coating layer, the active layer (20) having a thickness of about 94.2 μm was applied at a speed of 1000 rpm for 20 seconds. The thickness of the finally obtained film (100) was about 194.2 μm.

[0142] Example 6.

[0143] A film (100) was manufactured in the same manner as in Example 1, except that when applying the composition for forming the active layer onto the polymer coating layer, the active layer (20) having a thickness of about 88.0 μm was applied at a speed of 1000 rpm for 30 seconds. The thickness of the finally obtained film (100) was about 188.0 μm.

[0144] Example 7.

[0145] A film (100) was manufactured in the same manner as in Example 1, except that when applying the composition for forming the active layer onto the polymer coating layer, the active layer (20) having a thickness of about 76.4 μm was applied at a speed of 1500 rpm for 10 seconds. The thickness of the finally obtained film (100) was about 176.4 μm.

[0146] Example 8.

[0147] A film (100) was manufactured in the same manner as in Example 1, except that when applying the composition for forming the active layer onto the polymer coating layer, the active layer (20) having a thickness of about 63.7 μm was applied at a speed of 2000 rpm for 10 seconds. The thickness of the finally obtained film (100) was about 163.7 μm.

[0148] Evaluation Example 1. Gas Permeability Characteristics

[0149] The gas permeability characteristics of the film were measured using the Constant-Pressure, Variable-Volume Method, and after the permeability stabilized (after more than 2 hours had passed), the permeability was quantified using a Gas Flowmeter. For example, the film was attached to a Pressure Cell (Filter holder Type), and gas was applied at a constant pressure to measure the flow rate of the gas passing through the film. At this time, the temperature was set to room temperature, and the forward CO2 gas permeability and reverse air gas permeability were measured under pressures of 50 psi or 15 psi.

[0150] The results measured under 50 psi pressure are shown in Table 1 below, and the results measured under 15 psi pressure are shown in Table 2 below.

[0151] Classification Forward CO2 Gas Permeability (GPU) Reverse Air Gas Permeability (GPU) Selectivity Example 1 10.6 1.1 9.6 Example 2 14.2 1.4 10.1 Example 3 18.3 1.5 12.2 Example 4 19.1 1.6 11.9 Example 5 25.6 2.2 11.6 Example 6 29.7 2.4 12.4 Example 7 28.9 2.6 11.1 Example 8 38.2 3.5 10.9

[0152] Classification Forward CO2 Gas Permeability (GPU) Reverse Air Gas Permeability (GPU) Selectivity Example 1 30.3 10 Example 2 4.1 0.4 10.25 Example 3 5.3 0.5 10.6 Example 4 5.5 0.5 11 Example 5 7.5 0.6 12.5 Example 6 8.4 0.7 12 Example 7 8.3 0.8 10.3 75 Example 8 10.1 110.1

[0153] (In Tables 1 and 2, 'selectivity' is the ratio of forward CO2 gas permeability to reverse air gas permeability.)

[0154] As shown in Tables 1 and 2, it can be seen that the selectivity of the gas exhaust film (100) manufactured according to the embodiment of the present invention is 8 or higher in all of Examples 1-8.

[0155] Evaluation Example 2. Electrolyte Resistance

[0156] Electrolyte resistance was evaluated by visually observing or microscopically (DM) the film for swelling.

[0157] For example, when an electrolyte (EMC) was dropped onto the active layer of a film, in the case of films 1 to 3, as shown in FIG. 8, the electrolyte did not permeate the film but remained on the surface and then vaporized, whereas in the case of films 4 to 8, which are relatively thinner than those 1 to 3, as shown in FIG. 9, the electrolyte penetrated the film and the film was perforated. In addition, in films 4 to 8, the thinner the film, the faster the penetration rate of the electrolyte.

[0158] Evaluation Example 3. Tensile strength of the supporting layer

[0159] For a support layer measuring 100 mm * 10 mm, measurements were taken 5 times using a UTM at a speed of 100 mm / min, and the average was taken as the tensile strength of the support layer. As a result, in Examples 1-8, the support layer of the film was 2 kgf / mm 2 It was confirmed that it has a tensile strength.

[0160] Although the foregoing has been described with reference to the embodiments of the present disclosure, a person skilled in the art or having ordinary knowledge in the art will understand that various modifications and changes can be made to the various embodiments of the present disclosure without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

Claims

1. A gas discharge film having different gas permeability characteristics on both sides to discharge gas generated inside a secondary battery to the outside and prevent external air and water vapor from passing into the secondary battery, It includes an active layer and a support layer from the side facing the interior of the secondary battery, The above active layer comprises polydimethylsiloxane, and A gas discharge film, wherein, under conditions of a relative pressure value of approximately 15 psi or approximately 50 psi, the ratio of the forward permeability of gas generated inside a secondary battery to the reverse permeability of air is approximately 2 or greater, wherein the forward direction is the direction from inside the secondary battery to outside the secondary battery, and the reverse direction is the direction from outside the secondary battery to inside the secondary battery.

2. In Paragraph 1, The above active layer is a gas-releasing film derived from a polydimethylsiloxane precursor and a curing agent.

3. In Paragraph 2, The above active layer is a gas-releasing film in which the weight ratio of the polydimethylsiloxane precursor to the curing agent is about 1 to 10.

4. In Paragraph 1, A gas-releasing film comprising one or more types selected from polyimide, polytetrafluoroethylene, polypropylene, fluorinated polymers, and combinations thereof, wherein the active layer is 5. In Paragraph 1, A gas-releasing film in which the ratio of the thickness of the support layer to the thickness of the active layer is about 0.85 or less.

6. In Paragraph 1, The above active layer is a gas-releasing film having a thickness of about 120 μm or more and 1000 μm or less.

7. In Paragraph 1, A gas exhaust film comprising a support layer including a porous support and a polymer coating layer on at least one surface of the porous support.

8. In Paragraph 7, The above porous support is a gas-releasing film in the form of a nonwoven fabric, woven fabric, or mesh in which polymer fibers are irregularly intertwined.

9. In Paragraph 7, A gas-releasing film comprising one or more selected from polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethyl chloride, polyvinylidene fluoride, and combinations thereof.

10. In Paragraph 1, The above support layer has a tensile strength of approximately 0.1 kgf / mm 2 Up to 10 kgf / mm 2 Phosphorus, gas emission film.

11. In Paragraph 1, The above support layer is a gas exhaust film having a thickness of about 140 μm or less.

12. In Paragraph 1, A gas exhaust film having a thickness of about 200 μm to 1000 μm.

13. In Paragraph 1, The above gas exhaust film is a gas exhaust film having an active layer and a support layer adjacent to each other.

14. A secondary battery comprising at least a portion of the gas discharge film of claim 1, wherein gas generated inside the secondary battery is non-destructively discharged to the outside through the gas discharge film.

15. A method for manufacturing a gas discharge film having different gas permeability characteristics on both sides to discharge gas generated inside a secondary battery to the outside and prevent external air and water vapor from permeating into the secondary battery, wherein The method includes the step (step S1) of applying a composition for forming an active layer onto a support layer, and A method for manufacturing a gas exhaust film, wherein, under conditions of a relative pressure value of approximately 15 psi or 50 psi, the ratio of the forward permeability of gas generated inside a secondary battery to the reverse permeability of air is approximately 2 or more, the forward direction is a direction from inside the secondary battery to outside the secondary battery, and the reverse direction is a direction from outside the secondary battery to inside the secondary battery.

16. In Paragraph 15, A method for manufacturing a gas discharge film, wherein the above S1 step is performed at a speed of about 100 rpm to 900 rpm.

17. In Paragraph 15, A method for manufacturing a gas-releasing film, wherein the above S1 step is performed for about 1 second to 100 seconds.

18. In Paragraph 15, A method for manufacturing a gas-releasing film, wherein the above-mentioned active layer forming composition comprises a polydimethylsiloxane precursor and a curing agent.

19. In Paragraph 18, A method for manufacturing a gas-releasing film, wherein the above-mentioned composition for forming an active layer has a weight ratio of polydimethylsiloxane precursor to curing agent of about 1 to 10.

20. In Paragraph 15, A method for manufacturing a gas-releasing film, wherein the above-mentioned active layer forming composition comprises one or more selected from polyimide, polytetrafluoroethylene, polypropylene, fluorinated polymers, and combinations thereof.

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