Separation membrane for electrochemical device and electrochemical device including said separation membrane

Abstract

The present invention provides a separator for an electrochemical device, the separator comprising a polymeric porous support and an inorganic composite porous layer formed on at least one surface of the porous support, the inorganic composite porous layer comprising a binder polymer and an inorganic filler, the content of the inorganic filler being 30 to 200 parts by weight based on 100 parts by weight of the binder polymer, the binder polymer comprising a non-crystalline polymer having a glass transition temperature (Tg) of 180°C or more, and the separator for an electrochemical device having a dielectric breakdown voltage of 2 kV or more. The separator for an electrochemical device according to the present invention has improved voltage resistance characteristics of an electrochemical device, exhibits a high dielectric breakdown voltage, and reduces the rate of short circuit occurrence (hi-pot failure rate) even under high voltage conditions.

Description

[Technical Field]

[0001] The present invention relates to a separator for an electrochemical device and an electrochemical device including the separator.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0011666, filed on January 26, 2022, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings thereof. [Background technology]

[0003] Recently, interest in energy storage technology has been growing. As its application fields expand to include mobile phones, camcorders, laptops, and even electric vehicles, research and development efforts in electrochemical devices are becoming increasingly focused. Among these, interest has been focused on the development of secondary batteries, which are energy storage devices that can be charged and discharged based on electrochemical principles. Furthermore, in the development of such batteries, research and development related to new electrode and battery designs has been conducted recently to improve capacity density and specific energy.

[0004] Lithium-ion secondary batteries, in particular, are batteries that can be used repeatedly because lithium ions store and generate electricity by moving back and forth between the positive and negative electrodes. Lithium-ion secondary batteries are characterized by high voltage and energy density, a long cycle life, excellent storage properties, and high output, which has led to a wide range of applications, including portable IT devices, electric vehicle batteries, and energy storage systems (ESS). The widespread use of electric vehicles is a key factor in the growth of secondary batteries and is the main driving force behind the secondary battery market.

[0005] The four main components of such a secondary battery are a positive electrode, a negative electrode, an electrolyte, and a separator. Among these, the separator separates the two electrodes (positive and negative electrodes) in the secondary battery to prevent electrical short circuits caused by physical contact, and provides ion conductivity by providing a path through which ions can move between the electrodes via the electrolyte held in micropores.

[0006] Such separation membranes are made of microporous polymer film materials having the above-mentioned functions, and polyolefin separation membranes are particularly widely used. Representative polyolefin separation membranes include polyethylene (PE)-based and polypropylene (PP)-based polymer materials.

[0007] However, polyolefin-based separators have the problem of shrinking or melting at high temperatures, resulting in poor heat resistance. To address this issue, a widely used method is to improve heat resistance by coating the surface of the separator with inorganic particles and a binder polymer. However, when a battery is heated to high temperatures due to internal or external stimuli, the separator shrinks or melts, potentially causing contact between the positive and negative electrodes and resulting in a short circuit. Therefore, there is a need to improve the safety of batteries.

[0008] In addition, there is a strong demand for thinner separators to increase the energy density of batteries, but thinner separators may contain insufficient insulating material, resulting in reduced insulating properties or reduced mechanical strength. Therefore, there is a need for separators that have both excellent insulating properties and high mechanical strength. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a separator for an electrochemical device that has excellent insulating properties and a reduced incidence of short circuits, and an electrochemical device including the separator.

[0010] Another object of the present invention is to provide a method for manufacturing a separator for an electrochemical device using an immersion phase separation method, which has excellent insulating properties and a reduced incidence of short circuits.

[0011] It will be readily apparent that other objects and advantages of the present invention can be achieved by the means or methods recited in the claims and combinations thereof. [Means for solving the problem]

[0012] The present inventors have found that the above-mentioned problems can be solved by the following separator for an electrochemical device, an electrochemical device including the separator, and a method for manufacturing the electrochemical device.

[0013] The first embodiment is A separator for an electrochemical element, The separation membrane comprises a polymer porous support and an inorganic composite porous layer formed on at least one surface of the porous support, the inorganic composite porous layer contains a binder polymer and an inorganic filler, the binder polymer comprises an amorphous polymer having a glass transition temperature (Tg) of 180°C or higher, The content of the inorganic filler is 30 to 200 parts by weight based on 100 parts by weight of the binder polymer, The present invention relates to a separator for electrochemical devices, wherein the separator has a dielectric breakdown voltage of 2 kV or more.

[0014] The second embodiment is the first embodiment, The present invention relates to a separator for electrochemical elements, wherein the separator has a breakdown voltage of 2 kV or more and 6 kV or less.

[0015] The third embodiment is the first or second embodiment, The present invention relates to a separator for electrochemical elements, wherein the separator has a dielectric breakdown strength of 4.5 kV / milliinch or more.

[0016] The fourth embodiment is any one of the first to third embodiments, The present invention relates to a separator for an electrochemical element, wherein the separator has a total thickness of 5 μm to 20 μm.

[0017] The fifth embodiment is any one of the first to fourth embodiments, The present invention relates to a separator for electrochemical elements, wherein the amorphous polymer having a glass transition temperature (Tg) of 180°C or higher comprises polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polyphenylsulfone (PPSU), polyethersulfone (PES), polysulfone (PSU), or two or more of these.

[0018] The sixth embodiment is any one of the first to fifth embodiments, The present invention relates to a separator for an electrochemical element, wherein the binder polymer is made of a non-crystalline polymer having a glass transition temperature (Tg) of 180°C or higher.

[0019] The seventh embodiment is any one of the first to sixth embodiments, The separator for an electrochemical device comprises an inorganic filler content of 40 to 185 parts by weight based on 100 parts by weight of the binder polymer.

[0020] The eighth embodiment is any one of the first to seventh embodiments, The separator for an electrochemical element is characterized in that the inorganic filler has an average particle size of 20 nm to 700 nm.

[0021] A ninth embodiment relates to an electrochemical device including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the separator is a separator for an electrochemical device according to any one of the first to eighth embodiments.

[0022] The tenth embodiment is the ninth embodiment, The electrochemical device is a lithium secondary battery.

[0023] The eleventh embodiment is a method for manufacturing a separator for an electrochemical device according to any one of the first to eighth embodiments, (S1) preparing a polymeric porous support; (S2) applying a slurry containing an amorphous polymer having a glass transition temperature (Tg) of 180°C or higher, an inorganic filler, and a solvent to at least one surface of the polymeric porous support; (S3) immersing the polymer porous support coated with the slurry in a composition containing a non-solvent for the amorphous polymer, and drying the composition to form an inorganic composite porous layer.

[0024] The twelfth embodiment is the eleventh embodiment, The present invention relates to a method for producing a separator for an electrochemical element, wherein the non-solvent comprises water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, tripropylene glycol, acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, isopropyl alcohol, or two or more of these. [Effects of the Invention]

[0025] The separator for an electrochemical device according to an embodiment of the present invention has excellent heat resistance and mechanical strength, as well as a high breakdown voltage and a low incidence of short circuits.

[0026] The drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further understand the technical ideas of the present invention as well as the contents of the invention, and therefore the present invention should not be interpreted as being limited to only the matters depicted in the drawings. Meanwhile, the shape, size, scale, or ratio of elements in the drawings attached to this specification may be exaggerated to emphasize a clearer description. [Brief explanation of the drawings]

[0027] [Figure 1] 10 is a cross-sectional SEM image of the separation membrane according to Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention will be described in detail below. The terms and words used in the specification and claims should not be interpreted as being limited to their ordinary and dictionary meanings, but should be interpreted as having meanings and concepts that correspond to the technical concept of the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best explain the invention.

[0029] Throughout this specification, when a part "comprises" another component, it does not mean excluding the other component, but may further include the other component, unless otherwise specified.

[0030] Furthermore, the term "about" used throughout this specification is used to mean a numerical value or a approximation of a numerical value when given the inherent manufacturing and material tolerances, and is used to prevent unscrupulous infringers from unfairly exploiting the contents of the disclosure in which precise or absolute numerical values ​​are mentioned to aid in the understanding of this application.

[0031] Throughout this specification, the phrase "A and / or B" means "A, B, or both."

[0032] The separator for an electrochemical device according to one embodiment of the present invention comprises: The porous support includes a polymeric porous support and an inorganic composite porous layer formed on at least one surface of the porous support, the inorganic composite porous layer contains a binder polymer and an inorganic filler, the binder polymer comprises an amorphous polymer having a glass transition temperature (Tg) of 180°C or higher, The content of the inorganic filler is 30 to 200 parts by weight based on 100 parts by weight of the binder polymer, The separator has a breakdown voltage of 2 kV or more.

[0033] The separator according to an embodiment of the present invention exhibits a high breakdown voltage due to improved withstand voltage characteristics of a battery chemical device. Furthermore, the separator according to an embodiment of the present invention can prevent overdetection of defective separators during a Hi-Pot test, thereby improving test yield. Because the Hi-Pot test is also related to the thickness of the separator, the thin-film separator proposed in the present invention has the advantage of preventing overdetection of defective thin-film separators.

[0034] The separator according to one embodiment of the present invention has a breakdown voltage of 2 kV or more. If the breakdown voltage is less than 2 kV, the breakdown voltage will be similar to the physical properties of the polymeric porous support, resulting in an increased hipot failure rate and poor voltage resistance. For example, the breakdown voltage may be 2 kV to 6 kV, or 3 kV to 6 kV.

[0035] In the present invention, the dielectric breakdown voltage refers to the maximum voltage that an insulator can withstand, and when a voltage is applied to the insulator and gradually increased, the voltage at which the insulator loses its insulating properties and its conductivity increases at a high voltage exceeding a certain value.

[0036] The breakdown voltage can be measured by placing an insulator between metal plates and passing a direct current through the insulator under a predetermined voltage increase. For example, the breakdown voltage can be measured using an AC / DC / IR high-pot tester. The test object is placed between an aluminum jig and a copper jig, and the DC conditions are set to a current of 0.5 mA and a voltage increase of 100 V / s (up to 6 kV). The measurement is completed when a short circuit occurs as the voltage increases, and the voltage at that point can be defined as the breakdown voltage.

[0037] According to one embodiment of the present invention, the separator may have a dielectric breakdown strength of 4.5 kV / milliinch or more. Preferably, the dielectric breakdown strength may be in the range of 4.5 to 7 kV / milliinch or 4.8 to 7 kV / milliinch. When the dielectric breakdown strength satisfies the above range, it is advantageous in improving the hipot yield.

[0038] In the present invention, the dielectric breakdown strength can be calculated by dividing the dielectric breakdown voltage by the thickness of the sample, that is, by dividing the dielectric breakdown voltage by the thickness of the separator.

[0039] The thickness of the separator according to an embodiment of the present invention is not particularly limited, but may be in the range of 5 μm to 20 μm, and preferably in the range of 8 to 20 μm or 10 to 18 μm, in order to exhibit improved insulating properties and heat resistance stability.

[0040] According to an embodiment of the present invention, the polymeric porous support is not limited as long as it has a pore structure, and may be a porous polymer substrate, specifically, a porous polymer film substrate or a porous polymer nonwoven fabric substrate.

[0041] The porous polymer film substrate may be a porous polymer film containing a polyolefin such as polyethylene or polypropylene, and such a polyolefin porous polymer film substrate exhibits a shutdown function at a temperature of, for example, 80 to 130°C.

[0042] In this case, the porous polymer film may be formed from a polyolefin polymer such as polyethylene (high density polyethylene, linear low density polyethylene, low density polyethylene, ultra-molecular weight polyethylene), polypropylene, polybutylene, polypentene, or a mixture of two or more of these polymers, or a derivative thereof.

[0043] Representative examples of commercially available polyolefin porous polymer films that can be used as such polymer porous supports include, but are not limited to, wet-type polyethylene systems (Asahi Kasei E-Materials, Toray, SK IEE Technology, Shanghai Energy, Sinoma, Entek), dry-type polypropylene systems (Shenzhen Senior, Cangzhou Mingzhu), and dry-type polypropylene / polyethylene multilayer structures (Polypore, Ube).

[0044] The porous polymer film substrate may be manufactured by molding various polymers such as polyesters in addition to polyolefins into a film. The porous polymer film substrate may be formed into a structure in which two or more film layers are laminated, and each film layer may be formed from the above-mentioned polymers such as polyolefins and polyesters alone or a mixture of two or more of them.

[0045] In addition, the porous polymer film substrate and the porous nonwoven fabric substrate may be formed from a polymer such as polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, etc., either alone or in combination.

[0046] The thickness of the polymeric porous support is not particularly limited, but may be 1 μm or more, 3 μm or more, 15 μm or less, or 10 μm or less. When the thickness of the polymeric porous support satisfies this range, the problem of the support acting as a resistance layer can be improved while maintaining mechanical properties.

[0047] The pore size and porosity of the polymeric porous support are not particularly limited, but the porosity may be in the range of 10 to 95%, and the pore size (diameter) may be 0.1 to 50 μm. When the pore size and porosity satisfy these ranges, the problem of acting as a resistance layer can be prevented and mechanical properties can be maintained. In addition, the polymeric porous support may be in the form of a fiber or membrane.

[0048] The inorganic composite porous layer is located on one surface of the polymeric porous support and includes a binder polymer and an inorganic filler.

[0049] In addition, the inorganic composite porous layer is one of the constituent layers of the separator, and serves as an isolation layer to prevent short circuits between the positive and negative electrodes, while also preventing the polymer porous support from directly contacting lithium metal.

[0050] The porosity of the inorganic composite porous layer may be, but is not limited to, in the range of 5 to 95%. The thickness of the inorganic composite porous layer may be 1 μm or more, 3 μm or more, 15 μm or less, or 10 μm or less. When the thickness of the inorganic composite porous layer satisfies this range, heat resistance is improved, short circuit occurrence is suppressed, a thinner separator can be achieved, and insulating properties are excellent.

[0051] In the inorganic composite porous layer, inorganic fillers are filled and bound together by the binder polymer while in contact with each other, forming interstitial volumes between the inorganic fillers, which then become void spaces and form pores. That is, the binder polymer adheres the inorganic fillers together to maintain their bound state, for example, the binder polymer connects and fixes the inorganic fillers together. Furthermore, the pores in the inorganic composite porous layer are void spaces formed by the interstitial volumes between the inorganic fillers, which are spaces limited by the inorganic fillers that are substantially in contact with each other in a packed structure (closed packed or densely packed) by the inorganic fillers.

[0052] The inorganic filler serves to form micropores by forming spaces between the inorganic fillers and also serves as a kind of spacer that allows the physical shape to be maintained. Generally, the inorganic filler has the property that its physical properties do not change even at high temperatures of 200°C or higher, so the formed organic / inorganic composite porous film has excellent heat resistance.

[0053] Therefore, in a lithium secondary battery including the separator, even if the polymer porous support ruptures inside the battery under severe conditions due to internal or external factors such as high temperature, overcharging, or external impact, the inorganic composite porous layer can prevent the two electrodes from being completely short-circuited. Even if a short circuit does occur, the expansion of the short-circuited area can be suppressed, thereby improving the safety of the battery.

[0054] The inorganic filler is not particularly limited as long as it is electrochemically stable. That is, the inorganic filler that can be used in the present invention is a filler that can be used in the range of the operating voltage of the battery to be applied (for example, Li / Li + There are no particular limitations on the inorganic filler, as long as it does not undergo oxidation and / or reduction reactions at a voltage of 0 to 5 V relative to the reference voltage. Examples of such inorganic fillers include alumina (Al2O3), fumed alumina, aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), boehmite (AlOOH), or a mixture of two or more of these. Specifically, alumina (Al2O3) may be used.

[0055] The inorganic filler preferably has an average particle size (D50) of 20 nm to 700 nm to form an inorganic composite porous layer with a uniform thickness and an appropriate porosity. Specifically, it may be in the range of 100 nm to 500 nm. When the inorganic filler has an average particle size (D50) within this range, the dispersion of the inorganic composite porous layer slurry is maintained, making it easy to control the physical properties of the separator. This prevents problems such as a decrease in mechanical properties due to an excessive increase in separator thickness or an internal short circuit during battery charge and discharge due to excessive pore size. In addition, the increased packing density contributes to the thermal shrinkage rate, and a particle size within this range exhibits excellent heat resistance.

[0056] In the present invention, the average particle size (D50) of the inorganic filler is defined as the particle size at 50% of the particle size distribution. In the present invention, the average particle size (D50) of the inorganic filler can be measured by observation using an electron microscope such as a scanning electron microscope (SEM) or a field emission scanning electron microscope (FE-SEM), or by laser diffraction. When measuring by laser diffraction, more specifically, the inorganic filler is dispersed in a dispersion medium, introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT3000), and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W. The average particle size (D50) at 50% of the particle size distribution measured by the analyzer can then be calculated.

[0057] The inorganic filler may be a primary particle, which is a single particle, or a secondary particle formed from an aggregate of primary particles.

[0058] The content of the inorganic filler is 30 to 200 parts by weight per 100 parts by weight of the binder polymer. Specifically, the content of the inorganic filler may be 30 parts by weight or more, 40 parts by weight or more, 200 parts by weight or less, or 185 parts by weight or less per 100 parts by weight of the binder polymer. When the content of the inorganic filler is within this range, not only can heat resistance be improved, but also problems of reduced pore size and porosity in the inorganic composite porous layer formed due to an excessive binder polymer content can be prevented. Also, problems of reduced adhesion between inorganic materials due to a low binder polymer content, resulting in poor peel resistance of the inorganic composite porous layer, can be resolved.

[0059] The binder polymer includes an amorphous polymer having a glass transition temperature (Tg) of 180°C or higher. Specifically, the first binder polymer may be an amorphous polymer having a glass transition temperature (Tg) of 180°C to 350°C. For example, the amorphous binder polymer may be, but is not limited to, polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polyphenylsulfone (PPSU), polyethersulfone (PES), polysulfone (PSU), or a mixture of two or more thereof. Specifically, the glass transition temperatures of the amorphous binder polymers are approximately 250 to 340°C for polyimide, approximately 280 to 290°C for polyamideimide, approximately 217°C for polyetherimide, approximately 222°C for polyphenylsulfone, approximately 230°C for polyethersulfone, and approximately 185°C for polysulfone.

[0060] According to an embodiment of the present invention, the binder polymer may be an amorphous polymer having a glass transition temperature (Tg) of 180° C. or higher.

[0061] According to one embodiment of the present invention, a method for producing a separation membrane includes: (S1) preparing a polymeric porous support; (S2) applying a slurry containing an amorphous polymer having a glass transition temperature (Tg) of 180°C or higher, an inorganic filler, and a solvent to at least one surface of the polymeric porous support; (S3) The method may include a step of immersing the polymeric porous support coated with the slurry in a composition containing a non-solvent for the amorphous polymer, and drying the composition to form an inorganic composite porous layer.

[0062] When the inorganic filler is applied to the inorganic composite porous layer, the slurry may be prepared by dissolving the amorphous polymer in a solvent (which may be a dispersion medium for the inorganic filler), adding the inorganic filler, and dispersing the mixture. The inorganic filler may be added in a state of being crushed to an appropriate size, or the inorganic filler may be added to the amorphous polymer solution and then crushed and dispersed using a ball mill or the like.

[0063] The solvent may have a solubility index similar to that of the binder polymer and a low boiling point, which facilitates uniform mixing and subsequent solvent removal.

[0064] Examples of such solvents include one compound or a mixture of two or more compounds selected from acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, methanol, ethanol, isopropyl alcohol, and water.

[0065] In this case, the solvent may function as a solvent for dissolving the binder polymer or a dispersion medium for dispersing the binder polymer, depending on the type of the binder polymer to be mixed.

[0066] According to one embodiment of the present invention, methods for coating the slurry onto a polymeric porous support include a pre-metering method and a post-metering method. The pre-metering method is a method in which a coating amount is determined in advance and applied, such as slot die coating and gravure coating. The post-metering method is a method in which a sufficient amount of the coating solution, i.e., the slurry, is applied to the polymeric porous support, and then a predetermined amount is scraped out, such as bar coating. Another method is direct-metering coating, which combines the pre-metering and post-metering methods.

[0067] The slurry can be applied by any of the methods described above, and the polymeric porous support to which the slurry has been applied can be immersed in a composition containing a non-solvent to cause phase separation and form an inorganic composite porous layer.

[0068] According to one embodiment of the present invention, the non-solvent may be an aqueous solvent or a mixture of an aqueous solvent and an oil-based solvent. For example, the non-solvent may include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, tripropylene glycol, acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, isopropyl alcohol, or two or more thereof. Specifically, the non-solvent may be a mixture of water and N-methyl-2-pyrrolidone, or a mixture of water and dimethylacetamide.

[0069] An electrochemical device according to an embodiment of the present invention includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and the separator is the separator according to the embodiment of the present invention described above.

[0070] The electrode to be used with the separator of the present invention is not particularly limited, and may be prepared by binding an electrode active material to an electrode current collector by a conventional method well known in the art.

[0071] Non-limiting examples of the positive electrode active material among the electrode active materials include common positive electrode active materials used in the positive electrodes of conventional lithium secondary batteries, and particularly preferred are lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a lithium composite oxide made by combining these.

[0072] Non-limiting examples of the negative electrode active material include conventional negative electrode active materials used in the negative electrodes of conventional lithium secondary batteries, and particularly preferred are lithium metal or lithium alloys, carbon, petroleum coke, activated carbon, graphite, or other carbon-based lithium-absorbing materials.

[0073] Non-limiting examples of positive electrode current collectors include foils made of aluminum, nickel, or a combination thereof, and non-limiting examples of negative electrode current collectors include foils made of copper, gold, nickel, or a copper alloy, or a combination thereof.

[0074] The electrolyte used in the electrochemical element according to one embodiment of the present invention is + B - and A + Li + , Na + , K. + or a combination thereof, - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - or a combination thereof, dissolved or dissociated in an organic solvent such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), γ-butyrolactone, or a mixture thereof, but is not limited thereto.

[0075] The electrolyte may be injected at an appropriate stage in the battery manufacturing process depending on the manufacturing process and desired physical properties of the final product, i.e., before battery assembly or at the final stage of battery assembly.

[0076] The present invention also provides a battery module including a battery having an electrode assembly as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include, but are not limited to, power tools driven by an electric motor, electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters, electric golf carts, and power storage systems. [Example]

[0077] The present invention will be described in detail below with reference to specific examples. However, the examples according to the present invention can be modified into many other forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0078] Separation membranes of the examples and comparative examples were prepared in the following manner.

[0079] Example 1 Polyetherimide (PEI, weight-average molecular weight: 128,000) was dissolved in N-methyl-2-pyrrolidone (NMP) as an organic solvent, and Al2O3 with an average particle size of 100 nm was dispersed as an inorganic filler to prepare a slurry. The inorganic filler was 40 parts by weight per 100 parts by weight of polyetherimide.

[0080] The prepared slurry was applied to one side of a polyethylene porous support (thickness 9 μm, porosity 45%), and then placed in a coagulation bath containing water for the NIPS process, followed by drying.

[0081] <Examples 2 to 5 and Comparative Examples 1 to 4> Separator membranes were manufactured in the same manner as in Example 1, except that the contents of the binder polymer and inorganic filler were changed as shown in Table 1 below.

[0082] [Table 1]

[0083] <Evaluation of separation membrane properties> The physical properties of the separators prepared in the Examples and Comparative Examples were evaluated by the following methods.

[0084] (1) Thickness of the separation membrane The thickness of the separation membrane was measured using a thickness gauge (Mitutoyo Corporation, VL-50S-B).

[0085] (2) Measurement of breakdown voltage The voltage was measured using an AC / DC / IR high-pot tester. The object to be measured was placed between an aluminum jig and a copper jig, and the DC conditions were set to a current of 0.5 mA and a voltage increase of 100 V / s (up to 6 kV). The voltage at which a short circuit occurred as the voltage increased was measured as the breakdown voltage.

Claims

1. A separator for an electrochemical element, the separation membrane is composed of only a polymer porous support and an inorganic composite porous layer formed on at least one surface of the porous support; the inorganic composite porous layer contains a binder polymer and an inorganic filler, the binder polymer comprises an amorphous polymer having a glass transition temperature (Tg) of 180°C or higher, The content of the inorganic filler is 30 to 200 parts by weight based on 100 parts by weight of the binder polymer; The separation membrane has a breakdown voltage of 2 kV or more, the amorphous polymer comprises polyetherimide (PEI); The separator for electrochemical devices has a total thickness of 5 μm to 14 μm and a dielectric breakdown strength of 4.5 kV / milliinch or more.

2. 2. The separator for an electrochemical element according to claim 1, wherein the separator has a breakdown voltage of 2 kV or more and 6 kV or less.

3. 2. The separator for an electrochemical device according to claim 1, wherein the binder polymer is made of a non-crystalline polymer having a glass transition temperature (Tg) of 180°C or higher.

4. 2. The separator for an electrochemical device according to claim 1, wherein the content of the inorganic filler is 40 to 185 parts by weight based on 100 parts by weight of the binder polymer.

5. 2. The separator for an electrochemical device according to claim 1, wherein the inorganic filler has an average particle size of 20 nm to 700 nm.

6. An electrochemical element comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the separator is the separator for electrochemical elements according to any one of claims 1 to 5.

7. 7. The electrochemical device according to claim 6, wherein the electrochemical device is a lithium secondary battery.

8. A method for producing the separator for an electrochemical element according to claim 1, (S1) preparing a polymeric porous support; (S2) applying a slurry containing an amorphous polymer having a glass transition temperature (Tg) of 180°C or more, an inorganic filler, and a solvent to at least one surface of the polymeric porous support; (S3) immersing the polymeric porous support coated with the slurry in a composition containing a non-solvent for the amorphous polymer and drying the composition to form an inorganic composite porous layer; the amorphous polymer comprises polyetherimide (PEI); The method for producing a separator for an electrochemical device, wherein the separator has a total thickness of 5 μm to 14 μm and a dielectric breakdown strength of 4.5 kV / milliinch or more.

9. 9. The method for producing a separator for an electrochemical element according to claim 8, wherein the non-solvent comprises water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, tripropylene glycol, acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, isopropyl alcohol, or two or more thereof.

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