Film and battery pouch containing same

Abstract

The present invention can provide a film that can continuously and non-destructively release gas generated inside a battery not only under high-pressure conditions but also under low-pressure conditions, while effectively blocking the inflow of external moisture and the atmosphere (air) into the battery, and that has excellent durability against the electrolyte. The present invention can provide a battery pouch that, by at least partially containing the film, can further improve the stability and lifespan of the battery.

Description

[Technical Field]

[0001] This application is a national phase application of International Application PCT / KR2024 / 008309, filed on June 17, 2024, and claims priority to Korean Patent Application No. 10-2023-0130975, filed on September 27, 2023, the entire text of which is incorporated herein by reference.

[0002] The present invention relates to a film and a battery pouch containing the same. [Background technology]

[0003] Pouch-type batteries have attracted much attention because they have a high energy density per unit weight, are inexpensive, are easily deformable, and can be stacked with a high degree of integration.

[0004] Because pouch-type batteries use flexible exterior materials, improving their safety is one of the major research topics. Specifically, lithium secondary batteries can swell due to abnormal battery operation, such as decomposition of the electrolyte, internal short circuit, overcharging exceeding the allowable current and voltage, exposure to high temperatures, or deformation due to being dropped or external impact. If the amount of gas generated continues to increase (continuous swelling), deformation of the pouch can cause damage to the exterior of the battery pouch (holes), which can lead to fire or explosion.

[0005] Therefore, a device capable of venting gas generated inside such batteries to the outside is necessary. For example, Patent Document 1 discloses a battery in which a vent hole for venting gas inside the pouch is formed in the pouch case, and a vent cover that opens when the gas pressure inside the case reaches a predetermined value covers the vent hole, thereby maintaining the hermeticity of the pouch-type battery under normal circumstances while enabling quick venting in the event of an accident, thereby ensuring quality and stability. However, the battery disclosed in Patent Document 1 cannot be reused after the vent cover is vented, and does not include any alternative elements to prevent an accident if the vent cover does not vent properly for unexpected reasons in an accident. It also fails to consider issues such as the intrusion of external moisture or air through the vent cover, which are problematic. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Republic of Korea Patent Publication No. 2015-0034498 Summary of the Invention [Problem to be solved by the invention]

[0007] One object of the present invention is to provide a film that can continuously and non-destructively discharge gas generated inside a secondary battery under high-pressure conditions as well as low-pressure conditions, while effectively blocking the inflow of external moisture and atmospheric air into the secondary battery, and that has excellent durability against electrolyte.

[0008] Another object of the present invention is to provide a battery pouch that contains the film at least in part, thereby further improving the stability and lifespan of a secondary battery. [Means for solving the problem]

[0009] One aspect of the present invention is a film having different gas permeability characteristics on both sides so as to exhaust gas generated inside a secondary battery to the outside and prevent external air and water vapor from permeating into the inside of the secondary battery, and the film has a protective layer, an active layer, and a support layer on the side that contacts the inside of the secondary battery. In order the protective layer includes an amorphous perfluorinated polymer and is resistant to the electrolyte of the secondary battery, and at 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 being from the inside of the secondary battery to the outside of the secondary battery, and the reverse direction being from the outside of the secondary battery to the inside of the secondary battery.

[0010] In one embodiment, the film of the present invention may have a forward permeability of 5 GPU or more for gas generated inside a secondary battery at a relative pressure of 20 psi, a forward permeability of 10 GPU or more for gas generated inside a secondary battery at a relative pressure of 40 psi, or a forward permeability of 15 GPU or more for gas generated inside a secondary battery at a relative pressure of 50 psi.

[0011] 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.

[0012] In one embodiment, the protective layer may further include at least one selected from the group consisting of polyimide, naphtha, and polydimethylsiloxane.

[0013] In an embodiment, the protective layer may have a contact angle of 30° or more with respect to an electrolyte of a secondary battery.

[0014] In one embodiment, the active layer may absorb gas generated inside the secondary battery and transfer the gas to the outside.

[0015] In one embodiment, the active layer comprises a polymeric polymer containing cellulose and two or more carboxylic acids. base The compound may include a cross-linked structure comprising:

[0016] In one embodiment, the cellulose and two or more carboxylic acids base The cross-linked structure of the compound containing the formula (I) can be represented by the following formula (I):

[0017] [ka]

[0018] In the above Chemical Formula 1, R1 to R4 are the same or different and each independently represent hydrogen, deuterium, a hydroxy group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group, and Y1 represents a direct bond, a substituted or unsubstituted alkylene group, or a substituted or unsubstituted alkenylene group. ; a substituted or unsubstituted arylene group; or A combination of substituents selected from the group consisting of substituted or unsubstituted alkylene groups; substituted or unsubstituted alkenylene groups; and substituted or unsubstituted arylene groups, wherein r1 is an integer from 1 to 10, and when r1 is 2 or greater, R1s may be the same or different from each other; r2 is an integer from 1 to 7, and when r2 is 2 or greater, R2s may be the same or different from each other; r3 is an integer from 1 to 9, and when r3 is 2 or greater, R3s may be the same or different from each other; and r4 is an integer from 1 to 8, and when r4 is 2 or greater, R4s may be the same or different from each other.

[0019] In one embodiment, R1 to R4 may be the same or different and may each independently be a substituted or unsubstituted methyl group.

[0020] In one embodiment, the support layer has a tensile strength of 0.1 to 10 kgf / mm 2 It could be.

[0021] In one embodiment, the support layer may include a porous support.

[0022] 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 randomly entangled.

[0023] In one embodiment, the support layer may include a polymer coating layer on at least one surface of a porous support.

[0024] In one embodiment, the polymer coating layer is made of polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethyl Chloroacrylate , polyvinylidene fluoride, and combinations thereof.

[0025] In one embodiment, the film of the present invention may include a gutter layer on at least one side of the support layer.

[0026] In one embodiment, the film of the present invention may include gutter layers on both sides of the support layer.

[0027] In one embodiment, the gutter layers may each independently include polydimethylsiloxane.

[0028] 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°.

[0029] Another aspect of the present invention may relate to a pouch for a battery that includes the film as at least a portion thereof, and through which gas generated inside a secondary battery is non-destructively discharged to the outside. [Effects of the Invention]

[0030] The present invention can provide a film that can continuously and non-destructively exhaust gas generated inside a battery not only under high-pressure conditions but also under low-pressure conditions, while effectively blocking the inflow of external moisture and atmospheric air into the battery, and that has excellent durability against the electrolyte. The present invention can provide a battery pouch that further improves the stability and lifespan of the battery by at least partially including the film. [Brief explanation of the drawings]

[0031] [Figure 1]1 illustrates an exemplary structure of a film according to the present invention. [Figure 2] 1 illustrates another exemplary structure of a film according to the present invention. [Figure 3] 1 illustrates yet another exemplary structure of a film according to the present invention. [Figure 4] 1 illustrates an exemplary structure of a support layer of the present invention. [Figure 5] 1 is an image showing the results of evaluation of the durability of the electrolyte solution on the protective layer surfaces of Examples and Comparative Examples. [Figure 6] 1 is an image of the depth structure of a film according to the present invention observed using a CLSM (Confocal Laser Scanning Microscope). [Figure 7] 1 is an image showing the results of evaluation of the water contact angle of the outermost layer of the film of an example and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0032] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to best explain his or her invention.

[0033] Therefore, it should be understood that the configuration of the embodiment described in this specification is merely one of the most preferred embodiments of the present invention and does not represent the entire technical idea of ​​the present invention, and that at the time of this application, there may be various equivalents and modifications that can be substituted for them.

[0034] In this specification, the singular expression includes the plural expression unless the context clearly indicates otherwise.

[0035] As used herein, when a moiety "comprises" a certain component, this means that it may further contain other components, rather than excluding other components, unless otherwise specified. Thus, for example, a composition containing compound A may contain compounds other than A. However, the term "comprise" also encompasses the more restrictive meanings of "consisting essentially of" and "consisted of," as specific embodiments thereof; for example, a "composition comprising compound A" may also consist (essentially of) compound A.

[0036] In this regard, as used herein, terms such as "comprises" or "having" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the possibility of the presence or addition of one or more different features, numbers, steps, components, or combinations thereof.

[0037] In this specification, when a member is said to be located "on" another member, this includes not only when such member is in contact with the other member, but also when there is another member or substance between the two members.

[0038] When an amount, concentration, or other value or parameter is given herein by listing a range, a preferred range, or a preferred upper and lower limit, it should be understood that this specifically discloses all ranges that may 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 otherwise disclosed. When a range of numerical values ​​is recited herein, unless otherwise stated, and unless limited by terms such as greater than, less than, etc., the range is intended to include the endpoints and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values ​​recited when defining a range.

[0039] In the present specification, when a physical property is affected by the temperature at which it is measured, that property is measured at room temperature unless otherwise specified. The term "room temperature" refers to a natural temperature that is not heated or cooled, and may refer to, for example, any temperature within the range of about 10°C to 30°C, or a temperature of about 23°C or about 25°C. Unless otherwise specified, the unit of temperature in the present specification is °C.

[0040] Furthermore, among the physical properties mentioned in this specification, when the measurement pressure affects the corresponding physical property, unless otherwise specified, the physical property is measured at normal pressure, i.e., atmospheric pressure (approximately 1 atmosphere).

[0041] One aspect of the present invention is a film having different gas permeability characteristics on both sides so as to exhaust gas generated inside a secondary battery to the outside and prevent external air and water vapor from permeating into the inside of the secondary battery, and the film has a protective layer, an active layer, and a support layer on the side that contacts the inside of the secondary battery. In order the protective layer comprises an amorphous perfluorinated polymer and is resistant to the electrolyte of the secondary battery, and at 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 being from the inside of the secondary battery to the outside of the secondary battery, and the reverse direction being from the outside of the secondary battery to the inside of the secondary battery.

[0042] In this specification, the "interior of the secondary battery" may refer to the space in which the electrode assembly and the electrolyte are located, with the case containing the electrode assembly and the electrolyte as the boundary, and the "exterior of the secondary battery" may refer to the space other than the interior of the case as the boundary. The case may be a cylindrical can, a rectangular can, a pouch, or the like, and more specifically, may be a pouch.

[0043] The amorphous perfluorinated polymer may be, for example, one or more selected from the group consisting of poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) and polytetrafluoroethylene.

[0044] The amorphous perfluorinated polymer may have a molecular weight in the range of, for example, 100 to 1000 g / mol. In other examples, the amorphous perfluorinated polymer may have a molecular weight of 150 g / mol or more, 200 g / mol or more, 250 g / mol or more, or 300 g / mol or more, or 900 g / mol or less, 800 g / mol or less, 700 g / mol or less, 600 g / mol or less, 500 g / mol or less, or 400 g / mol or less.

[0045] The film of the present invention may be, for example, a film having a protective layer, an active layer, and / or a support layer on the side that contacts the inside of a secondary battery. In order The layers may be formed so that adjacent layers are in direct contact with each other or indirectly in contact with each other via another layer.

[0046] In the film of the present invention, for example, the protective layer contains an amorphous perfluorinated polymer and can be resistant to the electrolyte of a secondary battery.

[0047] In this specification, "the film is resistant to the electrolyte of the secondary battery" may mean that the surface of the film that comes into contact with the inside of the secondary battery does not dissolve, absorbs, or does not allow the electrolyte and / or vapor derived therefrom to pass through, even when initially exposed or exposed for a considerable period of time.

[0048] For 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 at a relative pressure of 20 psi of at least 20. In other examples, 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 at a relative pressure of 20 psi of at least 25, at least 30, or at least 35, or may have a ratio of at most 100, at most 90, or at most 80.

[0049] The film of the present invention may have a forward permeability of 5 GPU or more for gas generated inside a secondary battery, for example, at a relative pressure of 20 psi. Herein, gas permeability characteristics may be measured using the method described in the following evaluation examples. Herein, the relative pressure value may refer to a pressure value relative to atmospheric pressure of 0 psi. In other examples, the film of the present invention may have a forward permeability of 6 GPU or more or 7 GPU or more for gas generated inside a secondary battery, or 15 GPU or less, 10 GPU or less, 9 GPU or less, or 8 GPU or less, at a relative pressure of 20 psi.

[0050] The film of the present invention may have a forward permeability of gas generated inside a secondary battery of 10 GPU or more at a relative pressure of 40 psi, for example. In other examples, 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 at a relative pressure of 40 psi, or 20 GPU or less, 19 GPU or less, 18 GPU or less, 17 GPU or less, or 16 GPU or less.

[0051] The film of the present invention may have a forward permeability of gas generated inside a secondary battery of 15 GPU or more at a relative pressure of 50 psi, for example. In other examples, 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 at a relative pressure of 50 psi, 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.

[0052] The film of the present invention may have a reverse air permeability of 0.1 GPU or less under a relative pressure of 15 psi, for example.

[0053] The film of the present invention may have a reverse air permeability of 0.5 GPU or less at a relative pressure of 20 psi, for example. 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.

[0054] The film of the present invention may have a reverse air permeability of 1 GPU or less, for example, 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.

[0055] The present invention provides a film that is highly durable against electrolyte and can effectively block the inflow of external moisture and atmospheric air into the battery while continuously and non-destructively venting gas generated inside the secondary battery not only under high-pressure conditions exceeding 20 psi but also under low-pressure conditions below 20 psi. In the present invention, high-pressure conditions refer to pressure conditions under which there is a significant risk of at least a portion of the secondary battery case being damaged, resulting in fire or explosion, and may refer to pressures above 20 psi, 50 psi, or 100 psi. Low-pressure conditions refer to pressures above atmospheric pressure that allow gas generated inside the secondary battery to be vented to the outside, but below 20 psi, under which there is a relatively low risk of the case being damaged.

[0056] The protective layer may further include at least one selected from the group consisting of polyimide, Napion, and polydimethylsiloxane. When the protective layer further includes at least one selected from the group consisting of polyimide, Napion, and polydimethylsiloxane, the weight ratio of the at least one selected from the group consisting of polyimide, Napion, and polydimethylsiloxane to the amorphous perfluorinated polymer may be, for example, within the range of 0.1 to 20, and may be, for example, 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 more, or 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 may further contain at least one selected from the group consisting of polyimide, naphion, and polydimethylsiloxane, thereby further improving the gas permeability properties and further suppressing defects such as pinholes.

[0057] The protective layer may have a contact angle of 30° or more with respect to the electrolyte of the secondary battery. In this specification, the term "contact angle with respect to the electrolyte of the secondary battery" may refer to the initial contact angle and / or the contact angle after exposure to the electrolyte for a certain period of time. The contact angle with the electrolyte may be measured using a method according to the evaluation examples described below. In other examples, the protective layer may have a contact angle with respect to the electrolyte of the secondary battery 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.

[0058] The thickness of the protective layer may be, for example, 10 μm or less. Other examples of the thickness of the protective layer include, but are 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 more, or 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more. In this specification, the "thickness of layer A" may refer to the thickness of layer A itself. For example, when layer A overlaps with another layer, it may refer to the thickness measured including the overlapping portion of layer A. In this specification, the "thickness" may refer to the average thickness, maximum thickness, and / or minimum thickness among thicknesses measured at any position.

[0059] The film of the present invention can further improve the durability of the film against the electrolyte by including the protective layer as described above in the innermost layer of the film. In this specification, the "innermost layer of the film" may refer to the surface of each layer of the film that comes into contact with the inside of the secondary battery.

[0060] The film of the present invention may include, for example, an active layer, which may be formed on the surface of the protective layer opposite to the surface that contacts the inside of the secondary battery.

[0061] The active layer can absorb and transfer gas generated within the secondary battery to the outside. The gas can include, for example, gas generated during the formation of a solid electrolyte interphase (SEI) layer and / or abnormal gas generated due to decomposition of the electrolyte, excessive water content in the secondary battery, short circuit, overcharge, and / or overdischarge. The specific composition of the gas may vary depending on the combination of the electrolyte, electrolyte solvent, positive electrode active material, negative electrode active material, and binder used in the secondary battery. However, the gas typically exhibits similar properties in that CO2 is the main component. The gas can include, for example, H2; O2; CO; CO2; and / or hydrocarbon gases such as CH4, C2H2, C2H4, C2H6, C3H6, and C3H8; and combinations thereof. The proportion of CO2 gas relative to the total gas generation can be 50% or more. The film of the present invention includes an active layer having the characteristics described below, which allows gas generated inside the secondary battery to permeate in the forward direction (from the inside to the outside of the film) through a solution-diffusion mechanism.

[0062] The active layer may be, for example, a polymeric material containing cellulose and two or more carboxylic acids. base The present invention can more effectively exert the above function by maintaining a constant space between the cellulose polymer chains in the active layer and improving the packing density and arrangement of the polymers.

[0063] the cellulose and two or more carboxylic acids base The cross-linked structure of the compound containing the formula (I) can be represented by, for example, the following chemical formula 1:

[0064] [ka]

[0065] In Chemical Formula 1, R1 to R4 may be the same or different and each independently represent hydrogen, deuterium, a hydroxy group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group, and Y1 represents a direct bond, a substituted or unsubstituted alkylene group, or a substituted or unsubstituted alkenylene group. ; a substituted or unsubstituted arylene group; or The secondary battery may be a combination of substituents selected from the group consisting of substituted or unsubstituted alkylene groups, substituted or unsubstituted alkenylene groups, and substituted or unsubstituted arylene groups, wherein r1 is an integer from 1 to 10, and when r1 is 2 or greater, R1s may be the same or different from each other, r2 is an integer from 1 to 7, and when r2 is 2 or greater, R2s may be the same or different from each other, r3 is an integer from 1 to 9, and when r3 is 2 or greater, R3s may be the same or different from each other, and r4 is an integer from 1 to 8, and when r4 is 2 or greater, R4s may be the same or different from each other. From the viewpoint of achieving the objective 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 is preferable that R1 to R4 are each independently a substituted or unsubstituted methyl group.

[0066] The thickness of the active layer may be, for example, 10 μm or less, other examples include 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, but is not limited thereto.

[0067] The films of the present invention can also include, for example, a support layer.

[0068] The support layer has a tensile strength of, for example, 0.1 to 10 kgf / mm 2 When the support layer has the above-mentioned tensile strength, the film of the present invention can have excellent mechanical strength.

[0069] The support layer may include, for example, a porous support, which may be, for example, a nonwoven fabric in which polymer fibers are randomly entangled. Is it The polymer may be, for example, but is not limited to, PP (Polypropylene), PMMA (Poly(methyl metacrylate)), PE (Polyethylene), PET (Polyethylene terephthalate), PES (Polyether sulfone), etc.

[0070] The thickness of the porous support may be, for example, but not limited to, 50 to 150 μm, and may be, in other examples, 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.

[0071] The porosity of the porous support may be, but is not limited to, 10 to 90%. The porosity can be measured according to 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 more, or 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less.

[0072] The support layer may include, for example, a polymer coating layer formed on at least one surface of the porous support. The polymer coating layer may be formed on one or both surfaces of the porous support.

[0073] The polymer coating layer may be made of, for example, polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethyl Chloroacrylate , polyvinylidene fluoride, and / or combinations thereof.

[0074] The thickness of the support layer may be, for example, 1 to 1000 μm.

[0075] The present invention includes the support layer as described above, which allows the film to maintain its shape and have the desired mechanical strength without deteriorating the overall gas permeability of the film.

[0076] The film of the present invention may include, for example, a gutter layer on at least one side of the support layer. From the viewpoint 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 viewpoint 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.

[0077] The gutter layers may each independently comprise polydimethylsiloxane, for example, in an amount of 90% by weight or more, 95% by weight or more, 99% by weight or more, or 100% by weight based on the dry weight of the gutter layer.

[0078] The thickness of the 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 total thickness of each gutter layer.

[0079] The outermost layer of the film, which comes into contact with external air, may have a water contact angle of, for example, 80° to 120°. The water contact angle of the outermost layer of the film may be measured by the evaluation examples 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 inhibiting the release of internally generated gas.

[0080] In the present invention, each of the aforementioned layers, such as the protective layer, active layer, support layer, and / or gutter layer, may or may not overlap with the 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.

[0081] Another aspect of the present invention relates to a pouch for a battery, which includes a film at least in part, and through which gas generated inside the secondary battery is non-destructively discharged to the outside.

[0082] The matters relating to the film described above can be similarly applied to the invention relating to the battery pouch of the present invention unless otherwise stated.

[0083] Conventionally, vent systems have been introduced to address the problem of increased gas generation due to abnormal battery operation, leading to fire or explosion. Vent systems are devices that release internal gas to the outside when the internal pressure of a secondary battery reaches a certain level. However, after venting, the secondary battery is difficult to reuse. Furthermore, if the vent system malfunctions due to an unexpected reason, there is a lack of a stability enhancement system that can be considered as an alternative. However, according to the present invention, by including the above-described film in at least a portion of a battery pouch, gas generated within the battery can be continuously and non-destructively released under both high-pressure and low-pressure conditions, thereby further improving the life, durability, and stability of the battery. Furthermore, by applying this film to a battery in combination with an existing vent system, these effects can be further enhanced.

[0084] Yet another aspect of the present invention relates to a secondary battery including a battery pouch, and an electrode assembly and an electrolyte solution contained within the battery pouch.

[0085] Unless otherwise specified, the matters relating to the film and / or battery pouch can be similarly applied to the matters relating to the secondary battery of the present invention.

[0086] The electrode assembly may include, for example, a positive electrode, a negative electrode, and / or a separator. Any known electrode assembly may be used. The electrode assembly may be, for example, a jelly-roll type, a stack type, and / or a stack / holding type, but is not limited thereto.

[0087] 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. The positive electrode current collector may also be, for example, a porous material such as a net or mesh, 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 containing lithium and at least one transition metal selected from nickel, cobalt, manganese, and aluminum, but is not limited thereto. The binder may be, for example, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, Poly The conductive material may be, but is not limited to, at least one selected from the group consisting of tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, and fluororubber. The conductive material may be, but is not limited to, at least one selected from the group consisting of graphite, carbon black, carbon nanotubes, metal powder, and conductive oxide.

[0088] The negative electrode may include, for example, a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector may be made of, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or an aluminum-cadmium alloy. Similarly to the positive electrode current collector, the surface may be formed with fine irregularities to strengthen the binding strength of the negative electrode active material. The negative electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric. 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 (where 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 contained in the negative electrode active material layer may be, for example, an aqueous binder or a rubber-based binder. The aqueous binder may be soluble in an aqueous solvent such as water and may be, for example, at least one selected from the group consisting of polyvinyl alcohol, polyacrylic acid, polyethylene glycol, polyacrylonitrile, polyacrylamide, carboxymethyl cellulose, and combinations thereof, but is not limited thereto. The rubber-based binder is one that does not dissolve well in an aqueous solvent such as water but can be smoothly dispersed in an aqueous solvent, and may be, for example, 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 contained in the negative electrode active material layer may be, for example, at least one selected from the group consisting of graphite, carbon black, carbon nanotubes, metal powder, conductive oxides, and combinations thereof, but is not limited thereto.

[0089] The separator functions to physically separate the electrodes and can be any material commonly used for separators. It is particularly preferable that the separator has low resistance to ion migration in the electrolyte and excellent humidifying ability for the electrolyte. The separator may be made of a porous, non-conductive, or insulating material and may be an independent member or a coating layer attached to the positive electrode and / or negative electrode. The separator may be made of a polyolefin polymer, such as polyethylene (e.g., high-density polyethylene, linear low-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene), polypropylene, polybutylene, or polypentene, either alone or in combination.

[0090] The electrolyte may include an organic solvent and a lithium salt. The organic solvent may be any organic solvent that can act as a medium for the movement of ions involved in the electrochemical reaction of the battery. Specific examples of the organic solvent include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether and tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; carbonate-based solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethanol and isopropyl alcohol; and R-CN (where R is C2 to C4). 20Examples of suitable lithium salts include nitriles such as nitriles (which are linear, branched, or cyclic hydrocarbon groups and may contain a double bond, aromatic ring, or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolanes. Any compound capable of providing lithium ions for use in batteries can be used without any particular limitations. Specific examples of suitable lithium salts include LiPF, LiClO, LiAsF, LiBF, LiSbF, LiAlO, LiAlCl, LiCF, SO, LiCF, SO, LiN(C, F, SO), LiN(C, F, SO), LiN(CF, SO), LiCl, LiI, and LiB(C, O). The concentration of the lithium salt may be in the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte solution has appropriate conductivity and viscosity, and therefore exhibits excellent electrolyte performance, allowing lithium ions to migrate effectively.

[0091] The secondary battery of the present invention may further include, for example, a vent system, which irreversibly releases gas abnormally generated inside the battery, and any known vent system may be used without any particular limitation.

[0092] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the disclosed contents of the present invention as described above and the intended actions and effects of the present invention. However, the examples may be modified into several different forms, and the scope of the present specification should not be construed as being limited to the examples. It should be emphasized that the examples are provided to represent the present invention and to more specifically explain it to those skilled in the art. [Example]

[0093] A film having the structure shown in FIG. 3, 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, was produced.

[0094] The support layer 30 was manufactured by casting a polymer coating solution to a thickness of 50 μm on a polyester nonwoven fabric (porous support 301) having a thickness of 95 μm to 100 μm to form a polymer coating layer 302, and then immersing the cast nonwoven fabric in water. The polymer coating solution was obtained by dissolving polysulfone solids in a DMF (N,N-dimethylformamide) solution at 80°C to 85°C for 12 hours or more, and the polysulfone solid content in the solution was 18 wt%.

[0095] Next, a second gutter layer 402 was formed on one surface of the support layer 30. The second gutter layer 402 was manufactured by coating a gutter layer-forming composition, which was made by mixing Isopar G solvent and PDMS (Sylgard 184, Dow Corning), on the porous support 301 of the support layer 30 and then drying it in an oven at 90°C for 5 minutes. At this time, the PDMS content was 3 wt % of the gutter layer-forming composition.

[0096] Next, a first gutter layer 401 was formed on the other side of the support layer 30. The first gutter layer 401 was manufactured by coating a gutter layer-forming composition, which was made by mixing Isopar G solvent and PDMS (Sylgard 184, Dow Corning), on the polymer coating layer 302 of the support layer 30, and then drying it in an oven at 90°C for 5 minutes.

[0097] The active layer 10 was fabricated by coating a composition for forming an active layer, which was made by mixing distilled water, methyl cellulose, and maleic acid, on the first gutter layer 401 and then drying it in an oven at 90°C for 5 minutes. At this time, the active layer composition 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.

[0098] The protective layer 20 was fabricated by applying a protective layer-forming composition prepared by mixing Isopar G solvent with 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) to the surface of the active layer 10 where the first gutter layer 401 was not formed, and then drying in an oven at 90°C for 5 minutes. The protective layer-forming composition contained 0.5 wt% poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) and 3 wt% PDMS. [Example]

[0099] A protective layer-forming composition was prepared by mixing Isopar G solvent with poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) (Sigma-Aldrich, hyflon, 340.12 g / mol). A film was prepared in the same manner as in Example 1, except that the content of poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) in the protective layer-forming composition was 0.5 wt %.

[0100] Comparative Example 1 A film was prepared in the same manner as in Example 1, except that the composition for forming the protective layer was prepared by mixing Isopar G solvent and PDMS (Dow Corning, Sylgard 184) so ​​that the PDMS content was 3 wt % of the composition for forming the protective layer.

[0101] Comparative Example 2 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.

[0102] Evaluation example 1: Gas permeability properties The gas permeability of the film was measured using the constant-pressure, variable-volume method. After the permeability stabilized (after flowing for more than 2 hours), the permeability was quantified using a gas flow meter. More specifically, the film was fastened to a pressure cell (filter holder type) and gas was applied at a constant pressure to measure the flow rate of gas that permeated the film. The temperature was kept at room temperature, and the forward CO2 gas permeability and reverse air gas permeability were measured while changing the pressure.

[0103] [Table 1]

[0104] Evaluation example 2: Electrolyte durability The electrolyte durability of the protective layer surface was measured in accordance with 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, with measurements taken every 25 mm.

[0105] As a result, the contact angle measured 10 times for the protective layer of the film of Example 2 was between 47.5° and 53.3°, while the contact angle measured 10 times for the protective layer of the film of Comparative Example 1 was between 20.1° and 21.8°. That is, the film of Example 2, which had a protective layer formed from poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole) (Sigma-Aldrich, hyflon), had a large contact angle and showed no sign of electrolyte penetration even after more than two hours, whereas the film of Comparative Example 1, which had a protective layer formed from PDMS, had a small contact angle and was able to be impregnated with the electrolyte (Figure 5).

[0106] Evaluation example 3: Film structure The structure of the film in the depth direction (Z axis) was observed using a CLSM (Confocal Laser Scanning Microscope) under the following measurement conditions:

[0107] -Equipment: Olympus,OLS5100,

[0108] -Light source: Laser 405nm, ~0.95mW

[0109] -Magnification: 50x

[0110] -Scanning speed: 0.1~1um / s

[0111] As a result, the protective layer, active layer, and first gutter layer were confirmed in sequence, and 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 (Figure 6).

[0112] Evaluation Example 4: Water contact angle of the outermost layer of the film 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 film 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 measured using an OCA series optical contact angle measurement and contour analysis system. This was performed 10 times for each sample, with measurements taken every 25 mm.

[0113] As a result, it was confirmed that the contact angle measured 10 times on the outermost layer of the film of Example 1 was between 97.0° and 101.5°, while the contact angle measured 10 times on the outermost layer of the film of Comparative Example 2 was between 75.0° and 76.9°. In other words, it was found that the film of Example 1 had better water durability than the film of Comparative Example 2 (Figure 7).

[0114] Evaluation Example 5: Tensile strength of support layer 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 a total of five support layers measuring 100 mm x 10 mm. As a result, each support layer had a tensile strength of 1.5 to 2.5 kgf / mm. 2 It was confirmed that the tensile strength of the film was 100%. [Explanation of symbols]

[0115] 10:Active layer 20:Protective layer 30:Support layer 301: Porous support 302: Polymer coating layer 40: Gutter layer 401: First gutter layer 402: Second gutter layer

Claims

1. A film having different gas permeability properties on both sides so as to discharge gas generated inside the secondary battery to the outside and prevent external air and water vapor from permeating into the inside of the secondary battery, The secondary battery includes, from the surface side that contacts the inside of the secondary battery, a protective layer, an active layer, and a support layer, the protective layer comprises amorphous perfluorinated polymers and is resistant to the electrolyte of the secondary battery; A film in which, under a condition of a relative pressure value 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 being the direction from the inside of the secondary battery to the outside of the secondary battery, and the reverse direction being the direction from the outside of the secondary battery to the inside of the secondary battery.

2. 2. The film according to claim 1, wherein the forward permeability of gas generated inside the secondary battery is 5 GPU or more at a relative pressure of 20 psi, the forward permeability of gas generated inside the secondary battery is 10 GPU or more at a relative pressure of 40 psi, or the forward permeability of gas generated inside the secondary battery is 15 GPU or more at a relative pressure of 50 psi.

3. 2. The film of claim 1, wherein the reverse air permeability is 0.1 GPU or less at a relative pressure of 15 psi, 0.5 GPU or less at a relative pressure of 20 psi, or 1 GPU or less at a relative pressure of 60 psi.

4. The film of claim 1 , wherein the protective layer further comprises at least one selected from the group consisting of polyimide, napion, and polydimethylsiloxane.

5. The film according to claim 1 , wherein the protective layer has a contact angle of 30° or more with respect to an electrolyte solution of a secondary battery.

6. The film according to claim 1 , wherein the active layer absorbs gas generated inside the secondary battery and transfers the gas to the outside.

7. The film of claim 1 , wherein the active layer comprises a cross-linked structure of a compound comprising cellulose and two or more carboxylic acids.

8. The film according to claim 7 , wherein the crosslinked structure of the compound containing cellulose and two or more carboxylic acids is represented by the following chemical formula 1: 【Chemistry 1】 In Formula 1, R to R are the same or different and each independently represent hydrogen, deuterium, a hydroxyl group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group; Y 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 combination of substituents selected from the group consisting of a direct bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group, and a substituted or unsubstituted arylene group; r is an integer from 1 to 10; when r is 2 or greater, R are the same or different; r is an integer from 1 to 7; when r is 2 or greater, R are the same or different; r is an integer from 1 to 9; when r is 2 or greater, R are the same or different; and r is an integer from 1 to 8; when r is 2 or greater, R are the same or different.

9. 9. The film according to claim 8, wherein R1 to R4 are the same or different and each independently represent a substituted or unsubstituted methyl group.

10. The support layer has a tensile strength of 0.1 to 10 kgf / mm ２ 2. The film of claim 1 , wherein:

11. The film of claim 1 , wherein the support layer comprises a porous support.

12. The film according to claim 11, wherein the porous support is in the form of a nonwoven fabric, a woven fabric, or a mesh in which polymer fibers are randomly entangled.

13. The film of claim 11 , wherein the support layer comprises a polymeric coating layer on at least one side of a porous support.

14. 14. The film of claim 13, wherein the polymeric coating layer comprises one or more selected from the group consisting of polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethylchloride, polyvinylidene fluoride, and combinations thereof.

15. The film of claim 1 , including a gutter layer on at least one side of the support layer.

16. The film of claim 1 , including a gutter layer on each side of the support layer.

17. 17. The film of claim 15 or claim 16, wherein the gutter layers each independently comprise polydimethylsiloxane.

18. 2. The film according to claim 1, wherein the outermost layer of the film in contact with the outside air has a water contact angle of 80° to 120°.

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

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