Separator for electrochemical device and electrochemical device including the same

Abstract

The present invention provides a separator for an electrochemical device, comprising: a porous polymer substrate; and a porous coating layer formed on at least one surface of the porous polymer substrate, the porous coating layer comprising first metal-organic framework (MOF) particles modified with polyimide, second metal-organic framework particles, and a polymer binder, wherein at least one of the first metal-organic framework particles and the second metal-organic framework particles comprises zirconium and has an amine group introduced therein.

Description

[Technical Field]

[0001] This application claims priority based on Korean Patent Application No. 10-2023-0048993, filed with the Korean Intellectual Property Office on April 13, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a separator for an electrochemical device and an electrochemical device including the separator. [Background technology]

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions, and in recent years, lithium secondary batteries have been widely used due to their high energy density, high voltage, long cycle life, and applicability in various fields. A lithium secondary battery may include an electrode assembly made of a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and may be manufactured by housing the electrode assembly together with an electrolyte in a case.

[0004] During storage or operation of lithium secondary batteries, abnormal operation due to internal short circuits, overcharging, or exposure to temperatures higher than the operating temperature can cause the electrolyte in the battery to decompose, potentially generating gas. Gas generated within the battery can increase the battery's internal resistance and shorten its lifespan. If a large amount of gas is generated, it can cause deformation of the battery case or internal structure, potentially leading to battery fire or explosion. Therefore, research is being conducted into methods to reduce the amount of gas generated or the expansion of battery volume due to gas. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a separator for an electrochemical device capable of adsorbing gases generated in the electrochemical device, and an electrochemical device including the separator. [Means for solving the problem]

[0006] One aspect of the present invention provides a separator for an electrochemical device, comprising: a porous polymer substrate; and a porous coating layer formed on at least one surface of the porous polymer substrate, the porous coating layer comprising first metal-organic framework (MOF) particles modified with polyimide, second metal-organic framework particles, and a polymer binder, wherein at least one of the first metal-organic framework particles and the second metal-organic framework particles comprises zirconium (Zr) and has an amine group introduced therein.

[0007] The first metal-organic framework particles and the second metal-organic framework particles each have an average particle size (D 50 ) can be 300 nm or more and 10 μm or less.

[0008] The first metal-organic framework particles and the second metal-organic framework particles may each have an average pore diameter of more than 5 nm and less than 200 nm.

[0009] The first metal-organic framework particles and the second metal-organic framework particles each have a pore volume per unit mass of 0.2 cm 3 / g or more 1.0cm 3 / g or less.

[0010] The first metal-organic framework particles and the second metal-organic framework particles can be independently selected from the group consisting of UiO-66-NH2, UiO-67-NH2, NU-1002-NH2, and MOF-808-NH2.

[0011] The first metal-organic framework particles and the second metal-organic framework particles may be contained in a weight ratio of 35:65 to 45:55.

[0012] The metal-organic framework particles and the polymer binder may be contained in a weight ratio of 80:20 to 95:5.

[0013] Another aspect of the present invention provides an electrochemical device including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the separator is a separator for another electrochemical device.

[0014] The electrochemical device may be a lithium secondary battery. [Effects of the Invention]

[0015] The separator for an electrochemical device according to the present invention can prevent the performance of the electrochemical device from being deteriorated by gases such as carbon dioxide generated by decomposition of the electrolyte solution by adsorbing the gases in the coating layer. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, each component of the present invention will be described in more detail so that a person having ordinary skill in the art to which the present invention pertains can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited by the following content.

[0017] As used herein, the term "comprising" is used to list materials, compositions, devices, and methods useful in the present invention, without limiting the examples listed.

[0018] As used in this specification, the terms "about" and "substantially" are used to mean a range of values ​​or degrees, or a similar range, taking into consideration inherent manufacturing and material tolerances, and are provided to aid in the understanding of the present invention and to prevent infringers from unfairly exploiting the disclosure in which exact or absolute values ​​are mentioned.

[0019] As used herein, "electrochemical device" may refer to a primary battery, a secondary battery, a supercapacitor, and the like.

[0020] One embodiment of the present invention provides a separator for an electrochemical device, comprising a porous polymer substrate, first metal-organic framework (MOF) particles modified with polyimide, second metal-organic framework particles, and a polymer binder, and a porous coating layer formed on at least one surface of the porous polymer substrate, wherein at least one of the first and second metal-organic framework particles comprises zirconium (Zr) and has an amine group introduced therein.

[0021] The porous polymer substrate may be a porous membrane having a plurality of pores formed therein, which electrically insulates the positive and negative electrodes to prevent short circuits. For example, when the electrochemical device is a lithium secondary battery, the porous polymer substrate may be an ion-conductive barrier that blocks electrical contact between the positive and negative electrodes while allowing lithium ions to pass through. At least some of the pores may form a three-dimensional network that connects the surface and interior of the porous polymer substrate, allowing fluid to pass through the porous polymer substrate through the pores.

[0022] The porous polymer substrate may be made of a material that is physically and chemically stable with respect to the organic solvent electrolyte. For example, the porous polymer substrate may include, but is not limited to, polyolefins such as polyethylene, polypropylene, and polybutylene; polyvinyl chloride; polyethylene terephthalate; polycycloolefin; polyethersulfone; polyamide; polyimide; polyimideamide; nylon; polytetrafluoroethylene; and copolymers or mixtures thereof. Preferably, a polyolefin-based resin may be used. Polyolefin-based resins can be processed to a relatively thin thickness and are easy to apply a coating slurry to, making them suitable for manufacturing electrochemical devices with higher energy densities.

[0023] The porous polymer substrate may have a single-layer or multi-layer structure. The porous polymer substrate may include two or more polymer resin layers with different melting points (Tm), thereby providing a shutdown function during high-temperature runaway of the battery. For example, the porous polymer substrate may include a polypropylene layer with a relatively high melting point and a polyethylene layer with a relatively low melting point. Preferably, the porous polymer substrate may have a three-layer structure in which polypropylene, polyethylene, and polypropylene are laminated in this order. The polyethylene layer melts when the temperature of the battery rises above a predetermined temperature, thereby shutting down the pores and preventing thermal runaway of the battery.

[0024] The thickness of the porous polymer substrate may be from 1 μm to 100 μm. Specifically, the thickness of the porous polymer substrate may be from 10 μm to 90 μm, from 20 μm to 80 μm, from 30 μm to 70 μm, or from 40 μm to 60 μm. Preferably, the thickness of the polymer substrate may be from 1 μm to 30 μm. More preferably, the thickness of the polymer substrate may be from 5 μm to 15 μm, or from 8 μm to 13 μm. By adjusting the thickness of the porous polymer substrate within the above range, the volume of the electrochemical device can be minimized and the amount of active material contained in the electrochemical device can be increased while maintaining electrical insulation between the positive and negative electrodes.

[0025] The porous polymer substrate may include pores with an average diameter of 0.01 μm to 1 μm. Specifically, the size of the pores in the porous polymer substrate may be 0.01 μm to 0.09 μm, 0.02 μm to 0.08 μm, 0.03 μm to 0.07 μm, or 0.04 μm to 0.06 μm. Preferably, the size of the pores may be 0.02 μm to 0.06 μm. By adjusting the pore size of the porous polymer substrate within the above ranges, the air permeability and ionic conductivity of the entire separator membrane can be adjusted.

[0026] The porous polymer substrate may have an air permeability of 10s / 100cc to 100s / 100cc. Specifically, the air permeability of the porous polymer substrate may be 10s / 100cc to 90s / 100cc, 20s / 100cc to 80s / 100cc, 30s / 100cc to 70s / 100cc, or 40s / 100cc to 60s / 100cc. Preferably, the air permeability of the porous polymer substrate may be 50s / 100cc to 70s / 100cc. When the air permeability of the porous polymer substrate is within the above range, the air permeability of the resulting separator can be provided within a range suitable for ensuring the output and cycle characteristics of an electrochemical device.

[0027] The air permeability (s / 100cc) refers to the time (seconds) required for 100cc of air to pass through a porous polymer substrate or separator with a given area under a certain pressure. The air permeability can be measured using a Gurley densometer in accordance with ASTM D 726-58, ASTM D726-94, or JIS-P8117. For example, a Gurley 4110N device was used to measure air at a pressure of 0.304 kPa or 1.215 kN / m. 2 100cc of air under pressure of 1 square inch (or 6.54cm) of water 2 For example, using an Asahi Seiko EG01-55-1MR instrument, the time it takes for 100 cc of air to pass through a 1 sq. inch sample at room temperature under a constant pressure of 4.8 inches of water can be measured.

[0028] The porous polymer substrate may have a porosity of 10 vol% to 60 vol%. Specifically, the porosity of the porous polymer substrate may be 15 vol% to 55 vol%, 20 vol% to 50 vol%, 25 vol% to 45 vol%, or 30 vol% to 40 vol%. Preferably, the porosity of the porous polymer substrate may be 30 vol% to 50 vol%. When the porosity of the porous polymer substrate is within the above range, the ionic conductivity of the resulting separator can be provided within a range suitable for ensuring the output and cycle characteristics of an electrochemical device.

[0029] The porosity refers to the ratio of the volume of pores to the total volume of a porous polymer substrate. The porosity can be measured by methods known in the art, such as the Brunauer-Emmett-Teller (BET) method using nitrogen gas adsorption, capillary flow porosimetry, or water or mercury penetration.

[0030] The porous coating layer may be formed on at least one surface of the porous polymer substrate and may include metal-organic framework particles and a polymer binder. The metal-organic framework particles may refer to a single type of metal-organic framework or particles formed by aggregation of one or more types of metal-organic frameworks to form regular or irregular particles.

[0031] The metal-organic framework particles may be identical to one another, except that they may include first metal-organic framework particles at least partially surface-modified with polyimide and second metal-organic framework particles that are not surface-modified. Alternatively, the metal-organic framework particles may include two or more different types of metal-organic framework particles, one of which may have a surface modified with polyimide, and the particle may be referred to as a first metal-organic framework particle.

[0032] The metal-organic framework particles may include one or more metal ions or metals, including zirconium, and one or more organic ligands, including a ligand having an amine group. At least one of the organic ligands may include one or more amine groups and may be coordinated to the metal ions or metals, thereby exposing one or more amine groups on the surface of the metal-organic framework particles. For example, at least one of the first metal-organic framework particles and the second metal-organic framework particles may include zirconium and have amine groups introduced therein. Preferably, both the first metal-organic framework particles and the second metal-organic framework particles may include zirconium, and an organic ligand including an amine group may be coordinated to the zirconium.

[0033] While the physical properties of metal-organic frameworks vary depending on the type of functional group introduced, metal-organic frameworks incorporating amine groups may exhibit the best gas adsorption properties. For example, metal-organic frameworks incorporating amine groups have larger specific surface areas and pore diameters than metal-organic frameworks incorporating carboxyl, sulfonic acid, or hydroxyl groups, and may therefore exhibit superior carbon dioxide adsorption capabilities. Furthermore, metal-organic framework particles incorporating amine groups exhibit superior carbon dioxide adsorption capabilities compared to metal-organic framework particles without amine groups, due to the amine groups acting primarily as Lewis bases. Metal-organic frameworks incorporating amine groups may exhibit more stable carbon dioxide adsorption capabilities in both the presence and absence of water than metal-organic frameworks incorporating polar or hydrophobic functional groups. For example, metal-organic frameworks incorporating amine groups may exhibit more stable carbon dioxide adsorption capabilities than metal-organic frameworks incorporating naphthyl, nitro, or methoxy groups by forming hydrogen bonds with water or carbon dioxide via the amine groups.

[0034] The first metal-organic framework particles are surface-modified with polyimide. The first metal-organic framework particles may be metal-organic framework particles having amine groups, preferably having one or more amine groups exposed on the particle surface. The polyimide-modified first metal-organic framework particles may be formed by using at least a portion of the amine groups in an imidization reaction to form a polyimide, or may include particles in which a polyimide is introduced via a portion of the metal-organic framework other than the amine group. The polyimide-modified first metal-organic framework may have one or more amine groups exposed on the surface. The polyimide-modified first metal-organic framework particles have superior dispersibility and stability in a coating slurry for forming a porous coating layer compared to unmodified particles. A coating slurry containing the polyimide-modified first metal-organic framework particles may have a slower rate of precipitate formation and sedimentation. The porous coating layer produced from the coating slurry has a higher packing density per unit thickness, thereby providing improved adsorption capacity for gases generated in an electrochemical device.

[0035] The first metal-organic framework particles and the second metal-organic framework particles may each have an average particle size (D50) of 300 nm to 10 μm, as determined by particle size distribution analysis (PSD). Specifically, the average particle size of each particle may be 300 nm to 5000 nm, 400 nm to 2000 nm, or 500 nm to 1000 nm. By adjusting the average particle size of the metal-organic framework particles within the above range, the specific surface area of ​​the porous coating layer is maximized, allowing the production of a separation membrane with excellent gas adsorption capacity. The average particle size of the first metal-organic framework particles modified with polyimide may be larger than the average particle size of the second metal-organic framework particles. Specifically, the second metal-organic framework particles may have an average particle size of 300 nm or more and 1000 nm or less, and the first metal-organic framework particles may have an average particle size in the range of 300 nm or more and 10 μm or less, which is larger than the average particle size of the second metal-organic framework particles.

[0036] In the particle size distribution analysis, the average particle size of the metal-organic framework particles can be obtained from the separation velocity distribution of the particles after dispersing the particles in a dispersion medium. For example, after dispersing one or more particles in the dispersion medium, the light transmittance of the settling particles is measured at regular intervals, and the particle migration velocity obtained from the transmittance profile and the absorbance of the particles relative to the maximum absorbance obtained by converting the transmittance to absorbance can be used to obtain the average particle size.

[0037] The first metal-organic framework particles and the second metal-organic framework particles may each have an average pore diameter of more than 5 nm and less than 200 nm. Specifically, the average pore diameter formed in each particle may be more than 5 nm and less than 190 nm, more than 30 nm and less than 180 nm, more than 50 nm and less than 170 nm, more than 60 nm and less than 160 nm, more than 70 nm and less than 150 nm, more than 80 nm and less than 140 nm, more than 90 nm and less than 130 nm, or more than 100 nm and less than 120 nm. By adjusting the pore diameter of the metal-organic framework particles within the above range, the specific surface area of ​​the porous coating layer can be maximized, allowing the production of a separation membrane with excellent gas adsorption capacity. The average pore diameter of the polyimide-modified first metal-organic framework particles may be smaller than the average pore diameter of the second metal-organic framework. Specifically, the average pore diameter of the second metal-organic framework particles may be 35 nm or more and less than 200 nm, and the average pore diameter of the first metal-organic framework particles may be smaller than the average pore diameter of the second metal-organic framework particles by a range of 5 nm or more and less than 200 nm. The average pore diameter of the first metal-organic framework particles may be 5 nm or more and less than 50 nm, preferably 7 nm or more and less than 30 nm.

[0038] The average pore diameter of the metal-organic framework particles may be a value measured during the process of calculating a BET model using a BET-specific surface area analyzer. The first metal-organic framework particles and the second metal-organic framework particles each have a pore volume per unit mass of 0.2 cm or less. 3 / g or more 1.0cm 3 Specifically, each particle may be 0.3 cm 3 / g or more 0.9cm 3 / g or less, or 0.5cm 3 / g or more 0.8cm 3 / g or less. By adjusting the pore volume of the metal-organic framework particles within the above range, the specific surface area of ​​the porous coating layer is maximized, allowing the production of a separation membrane with excellent gas adsorption capacity. The first metal-organic framework particles modified with polyimide may have a smaller pore volume per unit mass than the second metal-organic framework particles. Specifically, the pore volume of the second metal-organic framework particles is 0.8 cm or less. 3 / g or more 1.0cm 3 / g or less, and the pore volume of the first metal-organic framework particles can be 0.2 cm 3 / g or more 1.0cm 3 The average pore diameter of the first metal-organic framework particles may be less than or equal to 0.2 cm / g and less than or equal to 0.2 cm / g. 3 / g or more 0.5cm 3 / g or less.

[0039] The pore volume per unit mass of the metal-organic framework particles can be measured by a method known in the art, similar to the porosity measurement described above.

[0040] The first metal-organic framework particles and the second metal-organic framework particles may each independently be selected from the group consisting of UiO-66, UiO-67, NU-1002, and MOF-808. Specifically, the first metal-organic framework particles and the second metal-organic framework particles may each independently be selected from the group consisting of UiO-66-NH2, UiO-67-NH2, NU-1002-NH2, and MOF-808-NH2. For example, the first metal-organic framework particles may be UiO-66-NH2 modified with polyimide, with one or more amine groups still exposed on the surface after modification, and the second metal-organic framework particles may be UiO-66-NH2.

[0041] The porous coating layer may contain first metal-organic framework particles modified with polyimide and second metal-organic framework particles not modified with polyimide in a weight ratio of 35:65 to 45:55. Preferably, the porous coating layer may contain first metal-organic framework particles and second metal-organic framework particles in a weight ratio of 35:65 to 40:60. The first metal-organic framework improves the dispersibility of the coating slurry, thereby increasing the packing density of the porous coating layer, and the second metal-organic framework improves the specific surface area of ​​the porous coating layer. When the first metal-organic framework particles and the second metal-organic framework particles are all contained in the above weight ratio, a separation membrane having a porous coating layer with high packing density and high specific surface area can be obtained. When the first metal-organic framework particles are contained in a ratio greater than the above ratio, the specific surface area of ​​the porous coating layer decreases, thereby reducing the gas adsorption capacity of the separation membrane.

[0042] The polymer binder can bind the first metal-organic framework particles, the second metal-organic framework particles, or the first metal-organic framework particles and the second metal-organic framework particles contained in the porous coating layer, thereby imparting adhesive strength to the porous coating layer.

[0043] The polymer binder may include an acrylic polymer binder, a fluorine-based polymer binder, or a combination thereof.

[0044] The acrylic polymer binder may be selected from the group consisting of (meth)acrylic acid, (meth)acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-ethylhexyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, n-ethylhexyl methacrylate, The copolymer may contain, as a repeating unit, one or more monomers selected from the group consisting of 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, (meth)acrylonitrile butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, n-oxyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, and tetradecyl (meth)acrylate.

[0045] For example, the acrylic polymer binder may include one or more selected from the group consisting of polyacrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, ethylhexyl acrylate, methyl methacrylate, styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber.

[0046] The fluorine-based polymer binder may be a polyvinylidene fluoride-based polymer binder. For example, the fluorine-based polymer binder may be at least one selected from the group consisting of polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-trichloroethylene (PVDF-TCE), and polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE), and more particularly, may be a copolymer containing polyvinylidene fluoride.

[0047] The polymer binder may be particulate. For example, the polymer binder may be spherical or ellipsoidal, but is not limited thereto. The polymer binder may have an average particle size (D50) of 100 nm to 500 nm. Specifically, the polymer binder may have an average particle size (D50) of 150 nm to 450 nm, 200 nm to 400 nm, or 250 nm to 350 nm. Preferably, the polymer binder may be spherical particles with an average particle size (D50) of 200 nm to 400 nm. By adjusting the particle size of the polymer binder particles within the above range, it is possible to simultaneously ensure the migration path of lithium ions and the adhesion of the porous coating layer to the porous substrate.

[0048] The metal-organic framework particles and the polymer binder may be included in a weight ratio of 80:20 to 95:5. The metal-organic framework particles include both first and second metal-organic framework particles, and the weight ratio of the metal-organic framework particles to the polymer binder may be 85:15, 90:10, or 95:5. By adjusting the contents of the metal-organic framework particles and the polymer binder within the above ranges, it is possible to improve the adhesion of the porous coating layer to the porous polymer substrate and reduce thermal shrinkage of the porous polymer substrate.

[0049] The packing density of the porous coating layer is 1 g / cm 3 More than 1.04g / cm 3 By adjusting the packing density of the porous coating layer within the above range, a separator exhibiting stable cycle characteristics in terms of air permeability and resistance can be obtained.

[0050] The porous coating layer may be formed by coating one surface of the porous polymer substrate with a coating slurry including the first metal-organic framework particles, the second metal-organic framework particles, a polymer binder, and a dispersion medium. For example, the separator may be fabricated by applying the coating slurry to at least one surface of the porous polymer substrate and then drying the coating slurry to remove the dispersion medium. The porous coating layer may have a porous structure including interstitial volumes in which the first metal-organic framework particles, the second metal-organic framework particles, or the first and second metal-organic framework particles are connected by the polymer binder. The porous coating layer is adhered to the porous polymer substrate to allow lithium ions to pass through and may prevent thermal shrinkage of the porous polymer substrate.

[0051] The coating slurry includes a dispersion medium that dissolves or disperses at least a portion of the polymer binder, thereby dispersing the first metal-organic framework particles and the second metal-organic framework particles. The coating slurry can be used in which the metal-organic framework particles are uniformly dispersed by adjusting the type and content of the dispersion medium. The first metal-organic framework particles can exhibit excellent dispersibility in the coating slurry due to polyimide modification. For example, the dispersion medium can be one selected from the group consisting of water, ethanol, acetone, isopropyl alcohol (IPA), dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), acetonitrile, and combinations thereof. Using the above-mentioned dispersion medium, a porous coating layer in which the first metal-organic framework particles and the second metal-organic framework particles are uniformly dispersed can be formed.

[0052] The coating slurry may have a viscosity of 20 cps or more and less than 100 cps. Specifically, the viscosity of the coating slurry may be 30 cps or more and 90 cps or less, or 40 cps or more and 80 cps or less. Preferably, the viscosity of the coating slurry may be 25 cps or more and 40 cps or less. If the viscosity of the coating slurry is 100 cps or more, it becomes difficult to produce a separation membrane by continuously applying the coating slurry to a porous polymer substrate, and productivity cannot be ensured.

[0053] The coating slurry may further contain additives such as a dispersant, a surfactant, an antifoaming agent, a flame retardant, or a wetting agent to improve dispersibility and flame retardancy and to improve the uniformity of the porous coating layer formed. For example, the dispersant may include at least one selected from the group consisting of oil-soluble polyamines, oil-soluble amine compounds, fatty acids, fatty alcohols, sorbitan fatty acid esters, tannic acid, and pyrogallic acid. The use of the above-mentioned types of dispersants may improve the stability of the coating slurry and ensure the uniformity of the porous coating layer formed from the coating slurry.

[0054] The additive may be included in an amount of 0 to 5 wt % based on the total weight of the coating slurry. Specifically, the content of the additive may be 0.01 to 4 wt %, 0.1 to 3 wt %, or 1 to 2 wt %. Preferably, the content of the additive may be 3 to 5 wt %. By adjusting the content of the additive within the above range, uniform dispersion and stability of the first metal-organic framework particles and the second metal-organic framework particles in the coating slurry can be achieved.

[0055] The dispersion medium contained in the coating slurry can be removed by drying or heating after the porous coating layer is formed. For example, the porous coating layer can contain 5 ppm or less of the dispersion medium. Preferably, the porous coating layer can be composed of first metal-organic framework particles, second metal-organic framework particles, and a polymer binder. During the process of removing the dispersion medium, a plurality of pores can be formed on the surface and inside of the porous coating layer. The pores can include interstitial volumes formed between the first metal-organic framework particles, the second metal-organic framework particles, or the first and second metal-organic framework particles, forming a three-dimensional network and having a structure that allows fluid to pass through.

[0056] The thickness of the porous coating layer may be from 1 μm to 15 μm. Specifically, the thickness of the porous coating layer may be from 2 μm to 14 μm, from 3 μm to 13 μm, from 4 μm to 12 μm, from 5 μm to 11 μm, from 6 μm to 10 μm, or from 7 μm to 9 μm. Preferably, the thickness of the porous coating layer may be from 1 μm to 5 μm. By adjusting the thickness of the porous coating layer within the above range, shrinkage of the porous polymer substrate can be minimized and stable adhesion to the porous polymer substrate can be achieved.

[0057] The separator for an electrochemical device may have an air permeability of 50 s / 100 cc to 150 s / 100 cc. Specifically, the air permeability of the separator may be 60 s / 100 cc to 140 s / 100 cc, 70 s / 100 cc to 130 s / 100 cc, 80 s / 100 cc to 120 s / 100 cc, or 90 s / 100 cc to 110 s / 100 cc. Preferably, the air permeability of the separator may be 50 s / 100 cc to 80 s / 100 cc. When the air permeability of the separator is within the above range, the output, stability, and cycle characteristics of the electrochemical device can be ensured.

[0058] Another embodiment of the present invention provides 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 the separator for an electrochemical device of any of the above-described embodiments. The electrochemical device can be manufactured by inserting an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode into a case or pouch and sealing the case or pouch. Before sealing the case or pouch, an electrolyte can be injected to impregnate the electrode assembly with the electrolyte. The shape of the case or pouch is not limited. For example, the electrochemical device can be a cylindrical, prismatic, coin, or pouch-shaped lithium secondary battery.

[0059] The positive electrode and the negative electrode may be formed by coating at least one surface of a current collector with an electrode active material, which is then dried. The current collector may be a conductive material that does not cause chemical changes in the electrochemical device. For example, the positive electrode current collector may be, but is not limited to, aluminum, nickel, titanium, calcined carbon, stainless steel, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. For example, the negative electrode current collector may be, but is not limited to, copper, nickel, titanium, calcined carbon, stainless steel, or copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. The current collector may be in various forms, such as a thin metal plate, film, foil, net, porous material, or foam.

[0060] The positive electrode comprises a positive electrode current collector and a positive electrode active material layer on at least one surface of the current collector, the positive electrode active material layer including a positive electrode active material, a conductive material, and a binder resin. The positive electrode active material may be a layered compound such as lithium manganese composite oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; 1+x Mn 2-x Lithium manganese oxides such as LiMnO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3) 1-x M xO2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1), or a lithium manganese composite oxide represented by Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion; a disulfide compound; and may contain one or a mixture of two or more of Fe2(MoO4)3.

[0061] The negative electrode includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. As the negative electrode active material, the negative electrode includes carbon such as lithium metal oxide, graphitized carbon, and graphite-based carbon; LixFe2O3 (0 ≤ x ≤ 1), Li x WO2 (0 ≤ x ≤ 1), Si, SiO x (0 < x < 2), silicon-based materials such as SiC and Si alloys; Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8), etc. metal composite oxides; lithium metal; lithium alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO,PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; and may contain one or a mixture of two or more selected from titanium oxides.

[0062] The conductive material may be any one selected from the group consisting of graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whisker, conductive metal oxide, carbon nanotube, activated carbon, and polyphenylene derivative, or a mixture of two or more of these conductive materials. The carbon nanotube has a cylinder shape with a nanosize diameter of a graphite sheet and sp 2Carbon nanotubes have a bonding structure and exhibit conductive or semiconductive properties depending on the angle and structure of the graphite plane winding. Carbon nanotubes can be classified into single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs) depending on the number of bonds forming the wall, and these carbon nanotubes can be appropriately selected depending on the application of the dispersion. More specifically, the conductive material may be one or a mixture of two or more conductive materials selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide.

[0063] As the binder resin, a binder resin that is usually used for electrodes of electrochemical elements can be used. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples of suitable cellulose acetates include, but are not limited to, cyanoethyl acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, and carboxyl methyl cellulose.

[0064] The electrolyte is A + B - A salt having the structure: + 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 salt containing an anion such as the above, or an ion consisting of a combination thereof, can be dissolved or dissociated in an organic solvent consisting of 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), gamma butyrolactone, or a mixture thereof.

[0065] The electrochemical device including the electrode assembly may be a lithium secondary battery. The battery may be used as a unit cell, a battery module including the unit cell, a battery pack including the battery module, or a device including the battery pack as a power source. Examples of such devices include, but are not limited to, small devices such as computers, mobile phones, and power tools; electric vehicles powered by electric motors, including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheelers, including electric bicycles (E-bikes) and electric scooters; electric golf carts; and energy storage systems.

[0066] Another embodiment of the present invention provides a method for manufacturing a separator for an electrochemical device, the method comprising forming a porous coating layer on at least one surface of a porous polymer substrate, the porous coating layer including first polyimide-modified metal-organic framework particles, second metal-organic framework particles, and a polymer binder. Any overlapping content with that described above for the separator for an electrochemical device will be superseded by the description of the previous embodiment.

[0067] The step of forming the porous coating layer may include preparing a coating slurry including first metal-organic framework particles, second metal-organic framework particles, a polymer binder, and a dispersion medium, applying the coating slurry to the porous polymer substrate, and drying the coating slurry.

[0068] The step of forming the porous coating layer may further include a step of corona-discharge-treating at least one surface of the porous polymer substrate before applying the coating slurry to the porous polymer substrate. The corona-discharge-treating at least one surface of the porous polymer substrate may prevent a decrease in the adhesive strength between the surface of the porous polymer substrate and the surface of the coating layer at high temperatures and may prevent an electrolyte from causing a decrease in the adhesive strength between the surface of the polymer substrate and the surface of the coating layer.

[0069] The corona discharge treatment may be performed by treating at least one surface of the porous polymer substrate in air at a voltage of 0.1 kV to 10 kV. Specifically, the corona discharge treatment may be performed in air at a voltage of 0.2 kV to 9 kV, 0.3 kV to 8 kV, 0.4 kV to 7 kV, 0.5 kV to 6 kV, 0.6 kV to 5 kV, 0.7 kV to 4 kV, 0.8 kV to 3 kV, 0.9 kV to 2 kV, or 1.0 kV to 2 kV. Preferably, the corona discharge treatment is performed in air at a voltage of 1.8 kV. Adjusting the applied voltage of the corona discharge treatment within the above range allows for the formation of an appropriate number of functional groups on the surface of the polymer substrate and prevents damage to the surface of the polymer substrate.

[0070] The step of forming the porous coating layer may include applying the coating slurry to the porous polymer substrate. For example, the coating may be formed using a method such as, but not limited to, a bar coater, wire bar coater, roll coater, spray coater, spin coater, inkjet coater, screen coater, reverse coater, gravure coater, knife coater, slot die coater, hot melt coater, comma coater, or direct metering coater. Preferably, the step of forming the porous coating layer may involve simultaneously coating the coating slurry on both sides of the porous polymer substrate using a bar coater or a slot die coater.

[0071] The step of forming the porous coating layer may involve applying the coating slurry to a porous polymer substrate and then drying or heating the coating layer to evaporate the dispersant contained in the coating layer. The dispersant may be removed at a temperature that allows only the dispersant contained in the coating layer to evaporate without deforming the polymer binder contained in the coating layer. For example, the dispersant may be removed by heating the coating layer to a predetermined temperature, but the temperature of the coating layer surface may not exceed 60°C. When heating the coating layer under these conditions, the thermal energy may be used primarily to heat the dispersant to cause a phase change, but not to deform the polymer binder.

[0072] The present invention will be described in more detail below with reference to specific examples and experimental examples. The following examples and experimental examples are provided to illustrate the present invention, and the present invention is not limited by the following examples and experimental examples.

[0073] Example 1 Coating slurry preparation Metal-organic framework particles were prepared using UiO-66-NH2 (average particle size (D50): 1 μm, average pore diameter: 7 nm, pore volume: 0.8 cm). 3 The amine groups on the surface of the metal-organic framework were reacted with an anhydride of polyimide to prepare first metal-organic framework particles modified with polyimide.

[0074] In 100 mL of distilled water at room temperature (25°C), an acrylic polymer binder (Toyo Ink, CSB130, solid content 40%, average particle size (D50) 177 nm), carboxymethyl cellulose (Delchem, SG-L02), and a wetting agent were added. The mixture was then charged with a weight ratio of 8:5:1, followed by 12 g of polyimide-modified first metal-organic framework particles and 18 g of polyimide-unmodified second metal-organic framework particles (the weight ratio of (first metal-organic framework + second metal-organic framework):polymer binder was 95:5). The mixture was stirred for 60 minutes using a shaker to prepare a coating slurry.

[0075] Preparation of porous polymer substrates As a porous polymer substrate, (MI: 0.2 g / 10 min, T m The temperature was 135°C, the porosity was 45%, and the average pore size was 45 nm. A polyethylene film having a size of 20 cm x 30 cm and a thickness of 9 μm was used.

[0076] Separation membrane manufacturing The coating slurry was coated on both sides of a polyethylene film using a bar coater to form coating layers each having a thickness of 3 μm.

[0077] The process of applying low-temperature air to the polyethylene film on which the coating layer was formed to remove the dispersion medium was repeated five times to produce a separator with a total thickness of 15 μm.

[0078] Example 2 A separator was prepared in the same manner as in Example 1, except that 10.5 g of the first metal-organic framework particles and 19.5 g of the second metal-organic framework particles were added when preparing the coating slurry.

[0079] Comparative Example 1 A separation membrane was prepared in the same manner as in Example 1, except that 18 g of the first metal-organic framework particles and 12 g of the second metal-organic framework particles were added when preparing the coating slurry.

[0080] Comparative Example 2 A separator was prepared in the same manner as in Example 1, except that 9 g of the first metal-organic framework particles and 21 g of the second metal-organic framework particles were added when preparing the coating slurry.

[0081] Comparative Example 3 A separator was prepared in the same manner as in Example 1, except that 6 g of the first metal-organic framework particles and 24 g of the second metal-organic framework particles were added when preparing the coating slurry.

[0082] Comparative Example 4 A separator was prepared in the same manner as in Example 1, except that the first metal-organic framework particles were not used and only 30 g of the second metal-organic framework particles were added during the preparation of the coating slurry.

[0083] Comparative Example 5 In the preparation of the coating slurry, the first metal-organic framework particles and the second metal-organic framework particles were not used, and alumina (Sumitomo, AES11, average particle size (D50) 500 nm, density 4 g / cm) was used. 3 A separation membrane was prepared in the same manner as in Example 1, except that 30 g of PEG-100 particles were added.

[0084] Experimental example: Confirming the physical properties of separation membranes The physical properties of the separation membranes produced in the examples and comparative examples were confirmed and are shown in Table 1 below.

[0085] Measurement of settling velocity of precipitates in coating slurries

[0086] The settling speed of the precipitate was measured for the coating slurries produced in the process of producing the separation membranes of the Examples and Comparative Examples. The better the dispersibility of the metal-organic framework particles contained in the coating slurry, the slower the settling speed of the precipitate.

[0087] The sedimentation rate of the coating slurry was measured using a LUMiSizer Dispersion & Particle Size Analyzer (LUM GmbH). The coating slurry was dispensed into the tube of the device, and a maximum centrifugal force of 2,300 g was applied to accelerate the sedimentation or creaming of the material within the tube. Near-infrared light was continuously transmitted through the entire tube, and a transmission profile was obtained. The sedimentation rate of the precipitate was calculated from the profile. The results are shown in Table 1 below.

[0088] BET surface area measurement The adsorption isotherm of the coating layer of each separation membrane was measured up to 1 bar using a BET-specific surface area analyzer (BEL, Microtrac) at -196°C, and the BET surface area was calculated from the measured N adsorption isotherm using the Brunauer-Emmett-Teller (BET) model.

[0089] Measurement of CO2 adsorption amount of inorganic particles Using the BET-specific surface area analyzer at 25°C, carbon dioxide with a purity of 99.99% was passed through the inorganic particles before preparing the coating slurry for each separation membrane, and an adsorption isotherm was measured to determine the amount of carbon dioxide adsorbed relative to the weight of the inorganic particles.

[0090] How to obtain CO2 gas volume data The lithium manganese composite oxide, conductive material (Denka black), and binder (PVdF) were weighed out to a weight ratio of 95:2.5:2.5, and then mixed in N-methylpyrrolidone (NMP) to prepare a cathode active material slurry. The cathode active material slurry was coated on a 20 μm thick aluminum foil to a thickness of 200 μm, and then rolled and dried to prepare a cathode.

[0091] A 200 μm thick Li metal plate was used as the negative electrode, and the positive electrode and negative electrode were stacked with the separator of the example or comparative example sandwiched between them, and then inserted into an aluminum pouch.

[0092] 1 g of electrolyte solution containing 3 mol of vinylene carbonate (VC), 1.5 mol of propane sultone (PS), 1 mol of ethylene sulfate (ESa), and 1 mol of lithium salt LiPF6 as additives in a solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) mixed at a weight ratio of 3 / 7 was injected into the aluminum pouch, and the pouch was sealed to fabricate a cell.

[0093] The fabricated cell was charged and discharged once at 0.1 C in a voltage range of 3.0 V to 4.4 V in a chamber at 25° C., and then charged and discharged at 1.0 C 300 times.

[0094] After 300 cycles, the cell was pierced to collect the gas inside the cell, and the amount of carbon dioxide contained in the gas was quantified using a flame ionization detector (FID) and a thermal conductivity detector (TCD).

[0095] [Table 1]

Claims

1. a porous polymer substrate, and a porous coating layer formed on at least one surface of the porous polymer substrate, the porous coating layer comprising first polyimide-modified metal-organic framework (MOF) particles, second metal-organic framework particles, and a polymer binder; Including, At least one of the first metal-organic framework particles and the second metal-organic framework particles contains zirconium and has an amine group introduced therein.

2. The first metal-organic framework particles and the second metal-organic framework particles each have an average particle size (D ５０ 2. The separator for an electrochemical element according to claim 1, wherein the thickness of the first electrode is 300 nm or more and 10 μm or less.

3. 2. The separator for an electrochemical device according to claim 1, wherein the first metal-organic framework particles and the second metal-organic framework particles each have an average pore diameter of more than 5 nm and less than 200 nm.

4. The first metal-organic framework particles and the second metal-organic framework particles each have a pore volume per unit mass of 0.2 cm ３ / g or more 1.0cm ３ The separator for electrochemical elements according to claim 1, wherein the surface roughness is 0.1 μm or less.

5. The first metal-organic framework particles and the second metal-organic framework particles are each independently UiO-66-NH ２ , UiO-67-NH ２ , NU-1002-NH ２ , and MOF-808-NH ２ 2. The separator for an electrochemical element according to claim 1, selected from the group consisting of:

6. 2. The separator for an electrochemical device according to claim 1, wherein the first metal-organic framework particles and the second metal-organic framework particles are contained in a weight ratio of 35:65 to 45:

55.

7. 2. The separator for an electrochemical device according to claim 1, wherein the metal-organic framework particles and the polymer binder are contained in a weight ratio of 80:20 to 95:

5.

8. An electrochemical device comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, An electrochemical element, wherein the separation membrane is the separation membrane for electrochemical elements according to any one of claims 1 to 7.

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