Film and battery pouch comprising same

Abstract

The present invention can provide a film with excellent durability against an electrolyte, capable of effectively blocking the inflow of external moisture and atmosphere (air) into a battery while continuously and non-destructively discharging gas, generated inside the battery, under a low pressure condition as well as a high pressure condition. The present invention can provide a battery pouch capable of further improving the stability and lifespan of the battery by comprising the film in at least a portion thereof.

Description

Film and battery pouch containing the same

[0001] The present invention relates to a film and a battery pouch including the same.

[0002] Pouch-type batteries are attracting much attention because they have high energy density per unit weight, are inexpensive, are easily deformed, and can be stacked with high integration.

[0003] Because these pouch-type batteries use flexible outer packaging materials, improving safety is one of the main research tasks. Specifically, lithium secondary batteries can experience swelling due to abnormal operating conditions such as electrolyte decomposition, internal short circuits, overcharge exceeding the allowable current and voltage, high temperature exposure, and deformation due to dropping or external impact. If the amount of gas generated continues to increase (continuous swelling occurs), the deformation of the pouch can cause damage to the exterior of the battery pouch (hole formation), which can lead to fire or explosion.

[0004] Therefore, there is a need to introduce a device that can discharge the gas generated inside the battery to the outside. For example, Patent Document 1 discloses a battery in which a venting hole for discharging the gas inside the pouch is formed in the pouch case, and a venting cover that opens when the gas pressure inside the case reaches a reference value covers the venting hole, thereby maintaining the sealing property of the pouch-type battery under normal circumstances while enabling rapid venting in an accident situation, thereby ensuring quality and stability. However, the battery according to Patent Document 1 cannot be reused after the venting cover is vented, and does not include any other alternative elements that can prevent an accident if the venting cover is not properly vented for an unexpected reason in an accident situation. In addition, it is problematic in that it does not consider issues such as the inflow of external moisture or air through the venting cover.

[0005] [Prior Art Literature]

[0006] [Patent Document]

[0007] (Patent Document 1) Republic of Korea Patent Publication No. 2015-0034498

[0008] The present invention has one object to provide a film that can continuously and non-destructively discharge gases generated inside a secondary battery under both high-pressure and low-pressure conditions, while effectively blocking external moisture and air from entering the secondary battery, and having excellent durability against electrolyte.

[0009] Another object of the present invention is to provide a battery pouch that can further improve the stability and lifespan of a secondary battery by including at least a portion of the film.

[0010] One aspect of the present invention may relate to a film having different gas permeability characteristics on both sides so as to discharge gas generated inside a secondary battery to the outside and prevent external air and water vapor from penetrating into the inside of the secondary battery, the film including a protective layer, an active layer, and a support layer from the side in contact with the inside of the secondary battery, wherein the protective layer includes amorphous perfluorinated polymers and has resistance to a secondary battery electrolyte, and under a relative pressure of 20 psi, the ratio of the forward permeability of gas generated inside the secondary battery to the reverse permeability of air is 20 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.

[0011] In one embodiment, the film of the present invention may have a forward permeability of gas generated inside the secondary battery of 5 GPU or more under a relative pressure of 20 psi, a forward permeability of gas generated inside the secondary battery of 10 GPU or more under a relative pressure of 40 psi, or a forward permeability of gas generated inside the secondary battery of 15 GPU or more under a relative pressure of 50 psi.

[0012] In one embodiment, the film of the present invention may have a reverse air permeability of 0.1 GPU or less at a relative pressure of 15 psi, a reverse air permeability of 0.5 GPU or less at a relative pressure of 20 psi, or a reverse air permeability of 1 GPU or less at a relative pressure of 60 psi.

[0013] In one embodiment, the protective layer may further include at least one selected from the group consisting of polyimide, Nafion, and polydimethylsiloxane.

[0014] In one embodiment, the protective layer may have a contact angle of 30° or more with respect to the secondary battery electrolyte.

[0015] In one embodiment, the active layer can absorb gas generated inside the secondary battery and transmit it to the outside.

[0016] In one embodiment, the active layer may include a cross-linked structure of a compound comprising cellulose and two or more carboxylic acids.

[0017] In one embodiment, the cross-linked structure of the compound comprising cellulose and two or more carboxylic acids may be represented by the following chemical formula 1:

[0018] [Chemical Formula 1]

[0019]

[0020] In the above chemical formula 1, R1 to R4 are the same as or different from each other, and are each independently hydrogen; deuterium; a hydroxyl group; a substituted or unsubstituted alkyl group; or a substituted or unsubstituted alkoxy group, and Y1 is a direct bond; a substituted or unsubstituted alkylene group; a substituted or unsubstituted alkenylene group; or a substituted or unsubstituted arylene group, or a direct bond; a substituted or unsubstituted alkylene group; a substituted or unsubstituted alkenylene group; And a combination of substituents selected from the group consisting of substituted or unsubstituted arylene groups, r1 is an integer from 1 to 10, and when r1 is 2 or more, R1s are the same as or different from each other, r2 is an integer from 1 to 7, and when r2 is 2 or more, R2s are the same as or different from each other, r3 is an integer from 1 to 9, and when r3 is 2 or more, R3s are the same as or different from each other, r4 is an integer from 1 to 8, and when r4 is 2 or more, R4s may be the same as or different from each other.

[0021] In one embodiment, R1 to R4 may be the same as or different from each other, and each may independently be a substituted or unsubstituted methyl group.

[0022] In one embodiment, the support layer has a tensile strength of 0.1 to 10 kgf / mm. 2 It could be.

[0023] In one embodiment, the support layer may comprise a porous support.

[0024] 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.

[0025] In one embodiment, the support layer may include a polymer coating layer on at least one surface of the porous support.

[0026] In one embodiment, the polymer coating layer may include at least one selected from the group consisting of polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethyl chloride, polyvinylidene fluoride, and combinations thereof.

[0027] In one embodiment, the film of the present invention may include a gutter layer on at least one side of the support layer.

[0028] In one embodiment, the film of the present invention may include a gutter layer on both sides of the support layer.

[0029] In one embodiment, each of the gutter layers can independently comprise polydimethylsiloxane.

[0030] In one embodiment, the outermost layer of the film in contact with the outside air may have a water contact angle of 80° to 120°.

[0031] Another aspect of the present invention may relate to a battery pouch comprising at least a portion of the film, wherein gas generated inside a secondary battery is non-destructively discharged to the outside through the film.

[0032] The present invention provides a film capable of continuously and non-destructively discharging gases generated within a battery, both under high and low pressure conditions, while effectively blocking the inflow of external moisture and air into the battery, and exhibiting excellent durability against electrolyte. The present invention can provide a battery pouch that further enhances the stability and lifespan of the battery by including at least a portion of the film.

[0033] Figure 1 illustrates an exemplary structure of a film according to the present invention.

[0034] Figure 2 illustrates another exemplary structure of a film according to the present invention.

[0035] Figure 3 illustrates another exemplary structure of a film according to the present invention.

[0036] Fig. 4 illustrates an exemplary structure of a support layer of the present invention.

[0037] Figure 5 is an image showing the results of electrolyte durability evaluation on the protective layer surface of examples and comparative examples.

[0038] Figure 6 is an image of the depth-direction structure of a film according to the present invention observed using a CLSM (Confocal Laser Scanning Microscope).

[0039] Figure 7 is an image showing the results of evaluating the water contact angle of the outermost layer of the film of the examples and comparative examples.

[0040] 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.

[0041] Accordingly, the configuration of the embodiments described in this specification is only one of the most preferred embodiments of the present invention and does not represent all of the technical ideas of the present invention, so it should be understood that various equivalents and modified examples that can replace them may exist at the time of filing this application.

[0042] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0043] When a part in this specification is said to “comprise” a certain component, this does not exclude other components unless specifically stated to the contrary, but rather means that other components may be included. Thus, for example, a composition comprising compound A may include compounds other than A. However, the term “comprise” also encompasses, as a specific embodiment thereof, the more restrictive meanings of “consisting essentially / essentially of” and “consisting of,” so that, for example, “a composition comprising compound A” may also consist (essentially / essentially) of compound A.

[0044] In this connection, it should be understood that terms such as “have” or “have” as used herein are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0045] When it is said in this specification that any element is located “on” another element, this includes not only cases where such element is in contact with the other element, but also cases where another element or material exists between the two elements.

[0046] Where an amount, concentration, or other value or parameter is given herein as a range, a preferred range, or an enumeration of an upper preferred value and a lower preferred value, this should be understood to specifically disclose any range that can be formed by any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the range is separately disclosed. Where a range of numerical values ​​is recited herein, unless otherwise stated, e.g., there is no limiting term such as greater than, less than, etc., the range is intended to include the endpoint values ​​and all integers and fractions within the range. The scope of the present invention is not intended to be limited to the specific values ​​recited when defining a range.

[0047] Among the properties mentioned in this specification, if the measurement temperature affects the property, the property is measured at room temperature unless otherwise specified. The term "room temperature" refers to the natural temperature without heating or cooling, and may mean, for example, any temperature within the range of about 10°C to 30°C, or about 23°C or about 25°C. In addition, unless otherwise specified, the unit of temperature in this specification is ℃.

[0048] In addition, among the properties mentioned in this specification, if the measurement pressure affects the property, the property is measured at normal pressure, i.e., atmospheric pressure (approximately 1 atm), unless otherwise specified.

[0049] One aspect of the present invention relates to a film having different gas permeability characteristics on both sides so as to discharge gas generated inside a secondary battery to the outside and prevent external air and water vapor from penetrating into the inside of the secondary battery, the film including a protective layer, an active layer, and a support layer from the side in contact with the inside of the secondary battery, wherein the protective layer includes amorphous perfluorinated polymers and has resistance to a secondary battery electrolyte, and under a relative pressure of 20 psi, the ratio of the forward permeability of gas generated inside the secondary battery to the reverse permeability of air is 20 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.

[0050] In this specification, "inside the secondary battery" may mean a space where the electrode assembly and electrolyte are located, with the case containing the electrode assembly and electrolyte as the boundary, and "outside the secondary battery" may mean a space other than the inside, with the case as the boundary. The case may be a cylindrical can, a square can, a pouch, or the like, and more specifically, may be a pouch.

[0051] The amorphous perfluorinated polymer may be, for example, at least one selected from the group consisting of poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) and polytetrafluoroethylene.

[0052] The amorphous perfluoropolymer may have a molar weight, for example, within the range of 100 to 1000 g / mol. In other examples, the amorphous perfluoropolymer may have a molar weight of at least 150 g / mol, at least 200 g / mol, at least 250 g / mol, or at least 300 g / mol, or at most 900 g / mol, at most 800 g / mol, at most 700 g / mol, at most 600 g / mol, at most 500 g / mol, or at most 400 g / mol.

[0053] The film of the present invention may include, for example, a protective layer, an active layer, and / or a support layer from the side in contact with the interior of the secondary battery. Each of the layers may be formed by directly contacting adjacent layers or indirectly contacting them via another layer.

[0054] The film of the present invention can have resistance to a secondary battery electrolyte, for example, if the protective layer includes an amorphous perfluorinated polymer.

[0055] In this specification, “the film is resistant to the secondary battery electrolyte” may mean that the surface of the film that comes into contact with the interior of the secondary battery does not dissolve and does not absorb or transmit the electrolyte and / or vapor derived therefrom even when initially exposed or exposed for a considerable period of time.

[0056] The film of the present invention may have, for example, a ratio of the forward permeability of gas generated inside the secondary battery to the reverse permeability of air under a relative pressure of 20 psi of 20 or more. In another example, the film of the present invention may have a ratio of the forward permeability of gas generated inside the secondary battery to the reverse permeability of air under a relative pressure of 20 psi of 25 or more, 30 or more, or 35 or more, or 100 or less, 90 or less, or 80 or less.

[0057] The film of the present invention may have a forward permeability of gas generated inside a secondary battery of 5 GPU or more, for example, under a relative pressure of 20 psi. In the present specification, the gas permeability characteristics may be measured by a method according to the following evaluation example. In the present specification, the relative pressure value may mean a pressure value based on atmospheric pressure of 0 psi. In another example, the film of the present invention may have a forward permeability of gas generated inside a secondary battery of 6 GPU or more, 7 GPU or more, 15 GPU or less, 10 GPU or less, 9 GPU or less, or 8 GPU or less, under a relative pressure of 20 psi.

[0058] The film of the present invention may, for example, have a forward permeability of gas generated inside a secondary battery of 10 GPU or more under a relative pressure of 40 psi. In another example, the film of the present invention may have a forward permeability of gas generated inside a secondary battery of 11 GPU or more, 12 GPU or more, 13 GPU or more, 14 GPU or more, or 15 GPU or more, or 20 GPU or less, 19 GPU or less, 18 GPU or less, 17 GPU or less, or 16 GPU or less under a relative pressure of 40 psi.

[0059] The film of the present invention may, for example, have a forward permeability of gas generated inside a secondary battery of 15 GPU or more under a relative pressure of 50 psi. In another example, the film of the present invention may have a forward permeability of gas generated inside a secondary battery of 16 GPU or more, 17 GPU or more, or 18 GPU or more, or 25 GPU or less, 24 GPU or less, 23 GPU or less, 22 GPU or less, 21 GPU or less, or 20 GPU or less under a relative pressure of 50 psi.

[0060] The film of the present invention may have a reverse air permeability of 0.1 GPU or less, for example, under a relative pressure of 15 psi.

[0061] The film of the present invention may, for example, have a reverse air permeability of 0.5 GPU or less at a relative pressure of 20 psi. In other examples, the film of the present invention may have a reverse air permeability of 0.4 GPU or less, 0.3 GPU or less, or 0.2 GPU or less at a relative pressure of 20 psi.

[0062] The film of the present invention may have, for example, a reverse air permeability of 1 GPU or less at a relative pressure of 60 psi. In other examples, the film of the present invention may have a reverse air permeability of 0.9 GPU or less, 0.8 GPU or less, or 0.7 GPU or less at a relative pressure of 60 psi.

[0063] The present invention provides a film that can continuously and non-destructively discharge gases generated inside a secondary battery under high pressure conditions exceeding 20 psi as well as low pressure conditions below 20 psi, while effectively blocking external moisture and air (air) from entering the battery, and has excellent durability against electrolyte. In the present invention, the high pressure condition means a pressure condition in which there is a significant risk that at least a portion of the secondary battery case will be damaged, resulting in ignition or explosion, and may mean, for example, a pressure exceeding 20 psi, 50 psi, or 100 psi. The low pressure condition may mean a range of 20 psi or less that is above atmospheric pressure at which gases generated inside the secondary battery can be discharged to the outside, but has a relatively low risk of the case being damaged.

[0064] The protective layer may further comprise, for example, at least one selected from the group consisting of polyimide, Nafion, and polydimethylsiloxane. When the protective layer further comprises at least one selected from the group consisting of polyimide, Nafion, and polydimethylsiloxane, the weight ratio between the at least one selected from the group consisting of polyimide, Nafion, and polydimethylsiloxane and the amorphous perfluoropolymer may be, for example, in the range of 0.1 to 20, and in other examples, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or less, 18 or less, 16 or less, 14 or less, 12 or less, 10 or less, or 6 or less. The protective layer of the present invention further includes at least one selected from the group consisting of polyimide, Nafion, and polydimethylsiloxane, thereby further improving gas permeability characteristics and further controlling defects such as pinholes.

[0065] The protective layer may have, for example, a contact angle of 30° or more with respect to a secondary battery electrolyte. In the present specification, “contact angle with respect to a secondary battery electrolyte” may mean an initial contact angle and / or a contact angle after exposure to the electrolyte for a certain period of time. The electrolyte contact angle may be measured in a manner according to an evaluation example described below. In other examples, the protective layer may have a contact angle with respect to a secondary battery electrolyte of 35° or more, 40° or more, or 45° or more, or 80° or less, 75° or less, 70° or less, 65° or less, 60° or less, or 55° or less.

[0066] The thickness of the protective layer may be, for example, 10 μm or less. In other examples, the thickness of the protective layer may be, but is not limited to, 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less, or 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more. In the present specification, “thickness of layer A” may mean the thickness of layer A itself, and, for example, when layer A overlaps with another layer, may mean the thickness measured including the portion where layer A overlaps with the other layer. In the present specification, “thickness” may be an average thickness, a maximum thickness, and / or a minimum thickness among thicknesses measured at any position.

[0067] The film of the present invention can further improve the electrolyte durability of the film by including the protective layer as described above in the innermost layer of the film. In this specification, "innermost layer of the film" may refer to the surface of each layer of the film that comes into contact with the interior of the secondary battery.

[0068] The film of the present invention may include, for example, an active layer. The active layer may be formed, for example, on a surface opposite to the surface of the protective layer that comes into contact with the interior of the secondary battery.

[0069] The active layer can, for example, absorb gases generated inside the secondary battery and transmit them to the outside. The gases may include, for example, gases generated when a SEI (Solid Electrolyte Interphase) film is formed during the secondary battery formation process and / or abnormally generated gases generated due to decomposition of the electrolyte, excessive moisture content of the secondary battery, short circuit, overcharge and / or overdischarge. The specific composition of the gases may differ somewhat depending on the combination of the electrolyte, electrolyte solvent, positive electrode active material, negative electrode active material, binder, etc. used in the secondary battery, but may exhibit similar properties in that CO2 is usually the main component. The gases may include, for example, H2; O2; CO; CO2; and / or hydrocarbon gases such as CH4, C2H2, C2H4, C2H6, C3H6, C3H8; and combinations thereof, and the proportion of CO2 gas with respect to the total gas generation may be 50% or more. The film of the present invention includes an active layer having the characteristics described below, and thus can transmit gas generated inside a secondary battery in a positive direction (from the inside of the film to the outside) through a solution-diffusion mechanism.

[0070] The above active layer may include, for example, a cross-linked structure of a compound comprising cellulose and two or more carboxylic acids. The present invention can more effectively perform the above function by maintaining a constant space between cellulose polymer chains in the active layer, thereby improving the packing density and arrangement of the polymer.

[0071] The cross-linked structure of the compound comprising the above cellulose and two or more carboxylic acids can be represented, for example, by the following chemical formula 1.

[0072] [Chemical Formula 1]

[0073]

[0074] In the above chemical formula 1, R1 to R4 may be the same or different, and may each independently be hydrogen; deuterium; a hydroxyl group; a substituted or unsubstituted alkyl group; or a substituted or unsubstituted alkoxy group, and Y1 may be a direct bond; a substituted or unsubstituted alkylene group; a substituted or unsubstituted alkenylene group; or a substituted or unsubstituted arylene group, or a direct bond; a substituted or unsubstituted alkylene group; a substituted or unsubstituted alkenylene group; And it may be a combination of substituents selected from the group consisting of substituted or unsubstituted arylene groups, r1 may be an integer of 1 to 10, and when r1 is 2 or more, R1 may be the same as or different from each other, r2 may be an integer of 1 to 7, and when r2 is 2 or more, R2 may be the same as or different from each other, r3 may be an integer of 1 to 9, and when r3 is 2 or more, R3 may be the same as or different from each other, r4 may be an integer of 1 to 8, and when r4 is 2 or more, R4 may be the same as or different from each other. From the viewpoint of achieving the purpose of discharging gas generated inside the secondary battery to the outside while preventing external air and / or water vapor from penetrating into the secondary battery, it may be preferable that R1 to R4 are each independently a substituted or unsubstituted methyl group.

[0075] The thickness of the active layer may be, for example, 10 μm or less. In other examples, the thickness of the active layer may be, but is not limited to, 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less, or 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more.

[0076] The film of the present invention may also include, for example, a support layer.

[0077] The above support layer has, for example, a tensile strength of 0.1 to 10 kgf / mm.2 The film of the present invention can have excellent mechanical strength as the support layer has the tensile strength as described above.

[0078] The support layer may include, for example, a porous support. The porous support 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, but is not limited to, PP (Polypropylene), PMMA (Poly(methyl metacrylate)), PE (Polyethylene), PET (Polyethylene terephthalate), PES (Polyether sulfone), etc.

[0079] The thickness of the porous support may be, for example, 50 to 150 μm, but is not limited thereto. In other examples, the thickness of the porous support may be 60 μm or more, 70 μm or more, 80 μm or more, or 90 μm or more, or 140 μm or less, 130 μm or less, 120 μm or less, 110 μm or less, or 100 μm or less.

[0080] The porosity of the porous support may be, but is not limited to, 10 to 90%. The porosity can be measured by Archimedes' principle. In other examples, the porosity of the porous support may be 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, or 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less.

[0081] The support layer may, for example, include a polymer coating layer on at least one surface of the porous support. The polymer coating layer may be formed on one surface of the porous support or on both surfaces.

[0082] The polymer coating layer may include, for example, at least one selected from the group consisting of polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethyl chloride, polyvinylidene fluoride, and / or combinations thereof.

[0083] The thickness of the support layer may be, for example, 1 to 1000 μm.

[0084] The present invention can maintain the shape of the film and have the desired mechanical strength by including a support layer as described above, while not lowering the overall gas permeability characteristics of the film.

[0085] The film of the present invention may, for example, include a gutter layer on at least one side of the support layer. From the perspective of maintaining the shape of the film, it may be preferable to include a gutter layer between the active layer and the support layer, and from the perspective of maintaining the shape of the film and blocking external air or water vapor, it may be more preferable to include a gutter layer on both sides of the support layer.

[0086] The above gutter layers may, for example, each independently comprise polydimethylsiloxane. The polydimethylsiloxane may be comprised in an amount of 90 wt% or more, 95 wt% or more, 99 wt% or more, or 100 wt% based on the dry weight of the gutter layer.

[0087] The thickness of the above gutter layer may be, for example, 10 μm or less. When the gutter layer is formed on both sides of the support layer, the thickness of the gutter layer may refer to the thickness of each gutter layer or the sum of the thicknesses of each gutter layer.

[0088] The outermost layer of the film in contact with the outside air may have, for example, a water contact angle of 80° to 120°. The water contact angle of the outermost layer of the film may be measured according to the evaluation example described below. In other examples, the water contact angle of the outermost layer of the film may be 85° or more, 90° or more, or 95° or more, or 115° or less, 110° or less, or 105° or less. By controlling the water contact angle of the outermost layer of the film as described above, the present invention can more effectively block external moisture and / or air without hindering the discharge of internally generated gases.

[0089] In the present invention, each of the aforementioned layers, for example, the protective layer, the active layer, the support layer, and / or the gutter layer, may or may not overlap with an adjacent layer. In one example, at least a portion of the protective layer may or may not overlap with the active layer. In another example, at least a portion of the gutter layer may or may not overlap with the support layer or the active layer.

[0090] Another aspect of the present invention relates to a battery pouch comprising at least a portion of a film, wherein gas generated inside a secondary battery is non-destructively discharged to the outside through the film.

[0091] The aforementioned matters regarding the film can be equally applied to the invention regarding the battery pouch of the present invention, unless specifically stated otherwise.

[0092] Conventionally, venting systems have been introduced to address the problem of increased gas generation due to abnormal battery operation, which can lead to fire or explosion. Venting systems are devices that allow internal gas to escape to the outside when the internal pressure of a secondary battery reaches a certain level. However, after venting, it is difficult to reuse the secondary battery, and in cases where the venting system fails to function properly for unexpected reasons, an alternative safety-enhancing system has been insufficient. However, according to the present invention, by including the film described above in at least a portion of a battery pouch, the gas generated inside the battery can be continuously and non-destructively discharged under both high-pressure and low-pressure conditions, thereby further improving the lifespan, durability, and stability of the battery. Furthermore, when applied to a battery in combination with an existing venting system, such a film can further enhance these effects.

[0093] Another aspect of the present invention relates to a secondary battery, comprising a battery pouch and an electrode assembly and an electrolyte within the battery pouch.

[0094] The matters relating to the above film and / or battery pouch can be equally applied to the matters relating to the secondary battery of the present invention unless specifically stated otherwise.

[0095] The electrode assembly may include, for example, an anode, a cathode, and / or a separator. Any known electrode assembly may be used as the electrode assembly. The electrode assembly may be, for example, a jelly-roll type, a stack type, and / or a stack / folding type, but is not limited thereto.

[0096] The positive electrode may include, for example, a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector may be, for example, a thin plate made of aluminum, stainless steel, or nickel. In addition, the positive electrode current collector may be, for example, a porous body such as a mesh or mesh-shaped body, or may be coated with an oxidation-resistant metal or alloy film to prevent oxidation. The positive electrode active material layer may include a known positive electrode active material, a binder, and / or a conductive material. The positive electrode active material may be, for example, a compound capable of reversible intercalation and deintercalation of lithium, such as a lithium-transition metal composite oxide including at least one transition metal composed of nickel, cobalt, manganese, and aluminum, and lithium, but is not limited thereto. The binder may be, for example, at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, and fluororubber, but is not limited thereto. The conductive material may be, for example, at least one selected from the group consisting of graphite, carbon black, carbon nanotubes, metal powder, and conductive oxide, but is not limited thereto.

[0097] The negative electrode may include, for example, a negative electrode current collector and a negative electrode active material layer. As the negative electrode current collector, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. In addition, similar to the positive electrode current collector, the bonding strength of the negative electrode active material may be strengthened by forming fine unevenness on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc. The negative electrode active material layer may include a known negative electrode active material, a binder, and / or a conductive material. The negative electrode active material may be, for example, a silicon-based or carbon-based negative electrode active material. The silicon-based negative electrode active material may be, for example, at least one selected from the group consisting of SiOx (0≤x<2) particles, Si-C composites, and Si-Y alloys (wherein Y is an element selected from the group consisting of 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, for example, at least one selected from the group consisting of artificial graphite, natural graphite, and graphitized mesocarbon microbeads, 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 above aqueous binder is soluble in an aqueous solvent such as water, and may be at least one selected from the group consisting of polyvinyl alcohol, polyacrylic acid, polyethylene glycol, polyacrylonitrile, polyacrylamide, carboxymethylcellulose, and combinations thereof, but is not limited thereto.The above rubber-based binder does not dissolve well in an aqueous solvent such as water, but can be smoothly dispersed in an aqueous solvent, and may be at least one selected from the group consisting of 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 negative electrode active material layer may be at least one selected from the group consisting of graphite, carbon black, carbon nanotubes, metal powder, conductive oxide, and combinations thereof, but is not limited thereto.

[0098] The above separator has the function of physically separating the electrodes, and can be used without any special restrictions as long as it is used as a general separator, and in particular, it is preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity. The separator may be made of a porous, non-conductive or insulating material, and may be an independent member or a coating layer added to the positive electrode and / or negative electrode. The separator may be a membrane formed of, for example, a polyolefin polymer such as polyethylene, such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, polypropylene, polybutylene, and polypropylene pentene, either singly or as a mixed polymer.

[0099] The above electrolyte may include an organic solvent and a lithium salt. The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions related to the electrochemical reaction of the battery can move. Specific examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethanol and isopropyl alcohol; R-CN (R is C2~C 20 Examples thereof include nitriles such as straight-chain, branched or cyclic hydrocarbon groups, which may include double-bonded aromatic rings or ether bonds; amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolane. As the lithium salt, any compound capable of providing lithium ions used in a battery may be used without particular limitation. Specific examples of the lithium salt include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2).2　 , LiN(CF3SO2) 2, LiCl, LiI, or LiB(C2O4) 2　 Examples thereof may be given. The concentration of the lithium salt may be within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte may exhibit excellent electrolyte performance due to having appropriate conductivity and viscosity, thereby effectively transporting lithium ions.

[0100] The secondary battery of the present invention may further include, for example, a venting system. The venting system is a system that irreversibly discharges abnormally generated internal gas from the battery, and any known venting system may be applied without particular limitation.

[0101] Hereinafter, the present invention will be described in detail by way of examples to specifically illustrate the disclosure of the present invention and its intended functions and effects, as described above. However, these examples may be modified in various ways, and the scope of this specification is not construed as being limited to these examples. It is emphasized that these examples are provided to represent the present invention and to provide a more concrete explanation to those skilled in the art.

[0102] Example 1

[0103] A film having a structure as shown in Fig. 3 was manufactured in which a protective layer (20), an active layer (10), a first gutter layer (401), a support layer (30), and a second gutter layer (402) were sequentially formed.

[0104] The support layer (30) was manufactured by casting a polymer coating layer solution to a thickness of 50 μm on a nonwoven fabric (porous support, 301) made of polyester material having a thickness of 95 μm to 100 μm to form a polymer coating layer (302), and then placing the cast nonwoven fabric in water. At this time, the polymer coating layer solution was obtained by adding polysulfone solids 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 polysulfone solids in the solution was 18 wt%.

[0105] Next, a second gutter layer (402) was formed on one surface of the support layer (30). The second gutter layer (402) was prepared by applying a gutter layer forming composition formed by mixing Isopar G solvent and PDMS (Dow Corning, Sylgard 184) onto the porous support (301) of the support layer (30) and then drying in a 90°C oven for 5 minutes. At this time, PDMS was included in an amount of 3 wt% with respect to the gutter layer forming composition.

[0106] In addition, a first gutter layer (401) was formed on the other side of the support layer (30). The first gutter layer (401) was manufactured by applying a composition for forming a gutter layer by mixing Isopar G solvent and PDMS (Dow Corning, Sylgard 184) onto the polymer coating layer (302) of the support layer (30) and then drying it in a 90°C oven for 5 minutes.

[0107] The active layer (10) was prepared by applying a composition for preparing an active layer formed by mixing distilled water, methyl cellulose, and maleic acid onto the first gutter layer (401) and then drying the composition in a 90°C oven for 5 minutes. At this time, the composition for preparing an active layer contained 1.5 wt% of methyl cellulose and 0.5 wt% of maleic acid. The thickness of the formed active layer (10) was 1 μm or less.

[0108] The protective layer (20) was formed by mixing Isopar G solvent, poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) (SIGMA-ALDRICH, hyflon, 340.12 g / mol), and PDMS (Dow Corning, Sylgard 184). The protective layer was formed by applying a composition for forming a protective layer to one surface of the active layer (10) on which the first gutter layer (401) was not formed, and then drying in a 90°C oven for 5 minutes. At this time, the composition for forming a protective layer contained 0.5 wt% of poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) and 3 wt% of PDMS.

[0109] Example 2.

[0110] A film was manufactured in the same manner as in Example 1, except that a composition for forming a protective layer was formed by mixing Isopar G solvent and poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) (SIGMA-ALDRICH, hyflon, 340.12 g / mol), and that poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) was included in an amount of 0.5 wt% based on the composition for forming a protective layer.

[0111] Comparative Example 1.

[0112] A film was manufactured in the same manner as in Example 1, except that a composition for forming a protective layer was formed by mixing Isopar G solvent and PDMS (Dow Corning, Sylgard 184), and that PDMS was included in an amount of 3 wt% based on the composition for forming a protective layer.

[0113] Comparative Example 2.

[0114] A film was manufactured in the same manner as in Comparative Example 1, except that the second gutter layer (402) was not formed on the porous support (301) of the support layer (30).

[0115] Evaluation Example 1. Gas Permeation Characteristics

[0116] The gas permeation characteristics of the film were measured using the Constant-Pressure, Variable-Volume Method, and after the permeation was stabilized (after 2 hours or more), the permeation was quantified using a Gas Flowmeter. More specifically, the film was attached to a Pressure Cell (Filter holder type), and the gas was applied at a constant pressure to measure the flow rate of gas passing through the film. At this time, the temperature was set to room temperature, and the forward CO2 gas permeation characteristics and reverse air gas permeation characteristics were measured while varying the pressure.

[0117]

[0118] Evaluation Example 2. Electrolyte Durability

[0119] The electrolyte durability of the protective layer surface was measured according to ASTM D5946. Specifically, 5 to 8 μL of electrolyte (EMC) was dropped onto the protective layer of the films of Example 2 and Comparative Example 1, and the contact angle was measured using an OCA series optical contact angle measurement and contour analysis system. This was performed 10 times for each sample, and measurements were taken every 25 mm.

[0120] As a result, it was confirmed that the contact angle measured 10 times for the protective layer of the Example 2 film showed a value between 47.5° and 53.3°, and the contact angle measured 10 times for the protective layer of the Comparative Example 1 film showed a value between 20.1° and 21.8°. That is, in the case of the Example 2 film having a protective layer formed from poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) (SIGMA-ALDRICH, hyflon), the contact angle was large and the phenomenon of electrolyte impregnation was not observed even after 2 hours or more, whereas in the case of the Comparative Example 1 film having a protective layer formed from PDMS, the contact angle was small and the electrolyte was impregnated (Fig. 5).

[0121] Evaluation Example 3. Film Structure

[0122] The depth-direction (Z-axis) structure of the film was observed using a CLSM (Confocal Laser Scanning Microscope). The CLSM measurement conditions were as follows.

[0123] - Device: Olympus, OLS5100,

[0124] - Light source: Laser 405nm, ~0.95 mW

[0125] - Magnification: 50x

[0126] - Scan speed: 0.1~1 um / s

[0127] As a result, the protective layer, active layer, and first gutter layer were confirmed sequentially, but it was confirmed that at least a portion of each of the protective layer and the first gutter layer was impregnated into the active layer (Fig. 6).

[0128] Evaluation Example 4. Water contact angle of the outermost layer of the film

[0129] The water contact angle of the outermost layer of the film was measured according to ASTM D5946. Specifically, 5 to 8 μL of water was dropped onto the outermost layer of each of the films of Example 1 and Comparative Example 2 (the porous support portion of the support layer in Example 1, and the second gutter layer portion in Comparative Example 2), and the contact angle was then measured using an optical contact angle measurement and contour analysis system of the OCA series. This was performed 10 times for each sample, and measurements were taken every 25 mm.

[0130] As a result, it was confirmed that the contact angle measured 10 times for the outermost layer of the film of Example 1 had a value between 97.0° and 101.5°, and the contact angle measured 10 times for the outermost layer of the film of Comparative Example 2 had a value between 75.0° and 76.9°. In other words, it was confirmed that the film of Example 1 had superior durability against water compared to the film of Comparative Example 2 (Fig. 7).

[0131] Evaluation Example 5. Tensile strength of support layer

[0132] The tensile strength of the support layers used in the examples and comparative examples was measured using a UTM at a speed of 100 mm / min for support layers of 100 mm x 10 mm in size, and was measured for a total of 5 support layers. As a result, each support layer had a tensile strength of 1.5 to 2.5 kgf / mm. 2 It was confirmed that it has a tensile strength of .

[0133] [Explanation of symbols]

[0134] 10: Active layer

[0135] 20: Protective layer

[0136] 30: Supporters

[0137] 301: Porous support

[0138] 302: Polymer coating layer

[0139] 40: Gutter layer

[0140] 401: 1st gutter floor

[0141] 402: Second gutter layer

Claims

1. A film with different gas permeability characteristics on both sides to discharge gases generated inside the secondary battery to the outside and prevent external air and water vapor from penetrating into the secondary battery. It includes a protective layer, an active layer, and a support layer from the side in contact with the inside of the secondary battery, The above protective layer has resistance to secondary battery electrolytes including amorphous perfluorinated polymers, A film in which, under a relative pressure of 20 psi, the ratio of the forward permeability of gas generated inside a secondary battery to the reverse permeability of air is 20 or more, the forward direction being a direction from the inside of the secondary battery to the outside of the secondary battery, and the reverse direction being a direction from the outside of the secondary battery to the inside of the secondary battery.

2. A film in which, in the first paragraph, the forward permeability of gas generated inside the secondary battery is 5 GPU or more under a relative pressure of 20 psi, the forward permeability of gas generated inside the secondary battery is 10 GPU or more under a relative pressure of 40 psi, or the forward permeability of gas generated inside the secondary battery is 15 GPU or more under a relative pressure of 50 psi.

3. A film according to claim 1, wherein the reverse air permeability is 0.1 GPU or less under a relative pressure of 15 psi, the reverse air permeability is 0.5 GPU or less under a relative pressure of 20 psi, or the reverse air permeability is 1 GPU or less under a relative pressure of 60 psi.

4. In the first paragraph, the protective layer is a film further comprising at least one selected from the group consisting of polyimide, Nafion, and polydimethylsiloxane.

5. In the first paragraph, the protective layer is a film having a contact angle of 30° or more with respect to a secondary battery electrolyte.

6. In the first paragraph, the active layer is a film that absorbs gas generated inside the secondary battery and transmits it to the outside.

7. In the first paragraph, the active layer is a film comprising a cross-linked structure of a compound including cellulose and two or more carboxylic acids.

8. In the 7th paragraph, a film having a cross-linked structure of the compound comprising cellulose and two or more carboxylic acids represented by the following chemical formula 1. [Chemical Formula 1] In the above chemical formula 1, R1 to R4 are the same as or different from each other, and are each independently hydrogen; deuterium; a hydroxyl group; a substituted or unsubstituted alkyl group; or a substituted or unsubstituted alkoxy group, and Y1 is a direct bond; a substituted or unsubstituted alkylene group; a substituted or unsubstituted alkenylene group; or a substituted or unsubstituted arylene group, or a direct bond; a substituted or unsubstituted alkylene group; a substituted or unsubstituted alkenylene group; And a combination of substituents selected from the group consisting of substituted or unsubstituted arylene groups, r1 is an integer from 1 to 10, and when r1 is 2 or more, R1s are the same as or different from each other, r2 is an integer from 1 to 7, and when r2 is 2 or more, R2s are the same as or different from each other, r3 is an integer from 1 to 9, and when r3 is 2 or more, R3s are the same as or different from each other, r4 is an integer from 1 to 8, and when r4 is 2 or more, R4s are the same as or different from each other.

9. A film in claim 8, wherein R1 to R4 are the same as or different from each other and are each independently a substituted or unsubstituted methyl group.

10. In the first paragraph, the support layer has a tensile strength of 0.1 to 10 kgf / mm. 2 In, film.

11. A film according to claim 1, wherein the support layer comprises a porous support.

12. In paragraph 11, The above porous support is a film in the form of a non-woven fabric, a woven fabric, or a mesh in which polymer fibers are irregularly intertwined.

13. A film according to claim 11, wherein the support layer comprises a polymer coating layer on at least one surface of the porous support.

14. A film according to claim 13, wherein the polymer coating layer comprises at least one selected from the group consisting of polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethyl chloride, polyvinylidene fluoride, and combinations thereof.

15. A film comprising a gutter layer on at least one side of the support layer according to claim 1.

16. A film comprising a gutter layer on both sides of the support layer according to claim 1.

17. A film according to claim 15 or 16, wherein each of the gutter layers independently comprises polydimethylsiloxane.

18. A film in accordance with claim 1, wherein the outermost layer of the film in contact with external air has a water contact angle of 80° to 120°.

19. A pouch for a battery, which includes at least a portion of the film of clause 1, and through which gas generated inside the secondary battery is non-destructively discharged to the outside.

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