Separation membrane for electrochemical elements, and electrochemical elements containing 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 13 April 2023, and the entire contents of the said Korean application are incorporated herein by reference.

[0002] The present invention relates to a separation membrane for an electrochemical element, and an electrochemical element containing the same. [Background technology]

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions. In recent years, lithium-ion batteries, which have high energy density and voltage, long cycle life, and can be used in various fields, have become widely used. A lithium-ion battery may include an electrode assembly made of a positive electrode, a negative electrode, and a separator membrane placed between the positive and negative electrodes, and the electrode assembly may be manufactured by housing it in a case together with an electrolyte.

[0004] During storage or operation, abnormal operation of lithium secondary batteries due to internal short circuits, overcharging, or exposure to temperatures higher than the operating temperature can cause the electrolyte inside the battery to decompose, potentially generating gas. This gas can increase the battery's internal resistance, potentially shortening 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 ignition or explosion. Therefore, research is being conducted on methods to reduce the amount of gas generated or the expansion of battery volume due to gas. [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a separation membrane for an electrochemical element that can adsorb gases generated within the electrochemical element, and an electrochemical element containing the same. [Means for solving the problem]

[0006] One aspect of the present invention provides a separation membrane for an electrochemical element, 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 contains zirconium (Zr) and has an amine group introduced thereinto.

[0007] Each of the first metal-organic framework particles and the second metal-organic framework particles may have an average particle diameter (D 50 ) of 300 nm or more and 10 μm or less, as measured by particle size distribution (PSD) analysis.

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

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

[0010] The first metal-organic framework particles and the second metal-organic framework particles may be each 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 element comprising a positive electrode, a negative electrode, and a separation membrane disposed between the positive electrode and the negative electrode, wherein the separation membrane is a separation membrane for another electrochemical element in the one aspect.

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

[0015] The separation membrane for electrochemical elements according to the present invention can prevent performance degradation of electrochemical elements due to gases by adsorbing gases such as carbon dioxide generated by the decomposition of the electrolyte with the coating layer. [Modes for carrying out the invention]

[0016] The following describes in more detail each component of the present invention so that it can be easily implemented by a person with ordinary skill in the art to which the present invention belongs. However, this is merely an example, and the scope of the rights of the present invention is not limited to the following.

[0017] As used herein, the term "including" is used to enumerate materials, compositions, apparatus, and methods useful for the present invention, and is not limited to such enumerated examples.

[0018] As used herein, “about” and “substantially” are used to mean a range of numerical values ​​or degrees, or something close to it, taking into account inherent manufacturing and material tolerances, and are provided to aid in understanding the invention and to prevent infringers from unfairly exploiting disclosures that refer to precise or absolute numerical values.

[0019] As used herein, "electrochemical elements" may refer to primary batteries, secondary batteries, supercapacitors, and the like.

[0020] One specific example of the present invention provides a separation membrane for an electrochemical element, comprising a porous polymer substrate, a first metal-organic framework (MOF) particle modified with polyimide, a second metal-organic framework particle, and a polymer binder, wherein the membrane includes a porous coating layer formed on at least one surface of the porous polymer substrate, and at least one of the first and second metal-organic framework particles contains zirconium (Zr) and has an amine group introduced into it.

[0021] The porous polymer substrate is a porous membrane with multiple pores formed therein, which can electrically insulate the positive and negative electrodes to prevent short circuits. For example, if the electrochemical element is a lithium secondary battery, the porous polymer substrate can be an ion-conducting barrier that blocks electrical contact between the positive and negative electrodes while allowing lithium ions to pass through. At least some of the pores can form a three-dimensional network connecting the surface and interior of the porous polymer substrate, allowing fluids to pass through the porous polymer substrate via the pores.

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

[0023] The porous polymer substrate may have a single-layer or multi-layer structure. The porous polymer substrate can provide a shutdown function in the event of a high-temperature runaway of the battery by including two or more polymer resin layers with different melting points (Tm). 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 that order. The polyethylene layer can shut down the pores and prevent thermal runaway of the battery by melting when the battery temperature rises above a predetermined temperature.

[0024] The thickness of the porous polymer substrate may be between 1 μm and 100 μm. Specifically, the thickness of the porous polymer substrate may be between 10 μm and 90 μm, between 20 μm and 80 μm, between 30 μm and 70 μm, or between 40 μm and 60 μm. Preferably, the thickness of the polymer substrate may be between 1 μm and 30 μm. More preferably, the thickness of the polymer substrate may be between 5 μm and 15 μm, or between 8 μm and 13 μm. By adjusting the thickness of the porous polymer substrate within the above range, it is possible to minimize the volume of the electrochemical element while electrically insulating the positive and negative electrodes, and to increase the amount of active material contained in the electrochemical element.

[0025] The porous polymer substrate may contain pores with an average diameter of 0.01 μm or more and 1 μm or less. Specifically, the size of the pores contained in the porous polymer substrate may be 0.01 μm or more and 0.09 μm or less, 0.02 μm or more and 0.08 μm or less, 0.03 μm or more and 0.07 μm or less, or 0.04 μm or more and 0.06 μm or less. Preferably, the size of the pores may be 0.02 μm or more and 0.06 μm or less. By adjusting the pore size of the porous polymer substrate within the above range, the permeability and ionic conductivity of the entire separation membrane produced can be adjusted.

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

[0027] The aforementioned air permeability (s / 100cc) refers to the time (in seconds) it takes for 100cc of air to pass through a porous polymer substrate or separation membrane of a predetermined area under constant pressure. This air permeability can be measured using a Gurley densometer in accordance with ASTM D 726-58, ASTM D726-94, or JIS-P8117. For example, using a Gurley 4110N instrument, with air at a pressure of 0.304 kPa or 1.215 kN / m³ 2 Under the pressure of water, 100cc of air will fill 1 square inch (or 6.54cm) 2 The time it takes for a sample to pass through can be measured. For example, using the EG01-55-1MR instrument from Asahi Seiko, the time it takes for 100cc of air to pass through a 1 square inch sample can be measured at room temperature and under constant pressure in 4.8 inches of water.

[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 manufactured separation membrane can be provided within a range suitable for ensuring the output and cycle characteristics of the electrochemical element.

[0029] The porosity refers to the ratio of the volume of pores to the total volume of the porous polymer substrate. The porosity can be measured by methods known in the art. For example, it can be measured by the Brunauer-Emmett-Teller (BET) method utilizing nitrogen gas adsorption, the capillary flow porometer, or the water or mercury osmosis method.

[0030] The porous coating layer is formed on at least one surface of the porous polymer substrate and may contain metal-organic skeleton particles and a polymer binder. The metal-organic skeleton particles may mean one or more single-type metal-organic skeletons aggregated to form shaped or amorphous particles.

[0031] The metal-organic skeleton particles are identical to each other, however, they may include first metal-organic skeleton particles whose surface is modified with polyimide and second metal-organic skeleton particles whose surface is not modified. Alternatively, the metal-organic skeleton particles may include two or more different metal-organic skeleton particles, the surface of any one of these particles may be modified with polyimide, and such particles may be referred to as first metal-organic skeleton particles.

[0032] The metal-organic skeleton particles may comprise one or more metal ions or metals, including zirconium, and one or more organic ligands, each having an amine group. At least one of the organic ligands may contain one or more amine groups and may coordinate to the metal ions or metals, exposing one or more amine groups on the surface of the metal-organic skeleton particles. For example, at least one of the first metal-organic skeleton particles and the second metal-organic skeleton particles may contain zirconium and have an amine group introduced into it. Preferably, both the first metal-organic skeleton particles and the second metal-organic skeleton particles may contain zirconium, and the organic ligand containing an amine group may coordinate to the zirconium.

[0033] The physical properties of a metal-organic skeleton can vary depending on the type of functional group introduced, but properties related to gas adsorption may be best in metal-organic skeletons with amine groups. For example, metal-organic skeletons with amine groups may have a larger specific surface area and pore diameter and superior carbon dioxide adsorption capacity compared to metal-organic skeletons with carboxyl, sulfonic acid, or hydroxyl groups. Furthermore, metal-organic skeleton particles with amine groups exhibit superior carbon dioxide adsorption capacity compared to metal-organic skeleton particles without amine groups, as the amine groups act primarily on Lewis bases. Metal-organic skeletons with amine groups can provide stable carbon dioxide adsorption capacity under both water-present and water-absent conditions compared to metal-organic skeletons with polar or hydrophobic functional groups. For example, metal-organic skeletons with amine groups can form hydrogen bonds with water or carbon dioxide via the amine groups, providing stable carbon dioxide adsorption capacity compared to metal-organic skeletons with naphthyl, nitro, or methoxy groups.

[0034] The surface of the first metal-organic skeleton particles is modified with polyimide. The first metal-organic skeleton particles may be metal-organic skeleton particles having amine groups, preferably with one or more amine groups exposed on the surface of the particles. The polyimide-modified first metal-organic skeleton particles may include those in which polyimide is formed by using at least a portion of the amine groups in an imidation reaction, or in which polyimide is introduced in the metal-organic skeleton via other parts that are not amine groups. The polyimide-modified first metal-organic skeleton may have one or more amine groups exposed on its surface. The polyimide-modified first metal-organic skeleton particles have better dispersibility and stability in coating slurries forming a porous coating layer compared to unmodified particles. Coating slurries containing the polyimide-modified first metal-organic skeleton particles may have slower precipitate formation and settling rates. The porous coating layer produced by the aforementioned coating slurry has a higher packing density per unit thickness, thereby providing improved adsorption capacity for gases generated within the electrochemical element.

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

[0036] In the aforementioned particle size distribution analysis, the average particle size can be obtained from the separation velocity distribution of the particles after they have been dispersed in a dispersion medium. For example, after dispersing one or more particles in the dispersion medium, the average particle size can be obtained by measuring the light transmittance of the settling particles at regular intervals, using the particle migration velocity obtained from the transmittance profile and the absorbance of the particle relative to the maximum absorbance obtained by converting the transmittance to absorbance.

[0037] The first metal-organic skeleton particles and the second metal-organic skeleton particles may each have an average pore diameter greater than 5 nm and less than 200 nm. Specifically, the average pore diameters formed in each particle may be greater than 5 nm and less than 190 nm, greater than 30 nm and less than 180 nm, greater than 50 nm and less than 170 nm, greater than 60 nm and less than 160 nm, greater than 70 nm and less than 150 nm, greater than 80 nm and less than 140 nm, greater than 90 nm and less than 130 nm, or greater than 100 nm and less than 120 nm. By adjusting the pore diameter of the metal-organic skeleton particles within the above range, the specific surface area of ​​the porous coating layer can be maximized, and a separation membrane with excellent gas adsorption capacity can be manufactured. The average pore diameter of the first metal-organic skeleton particles modified with polyimide may be smaller than the average pore diameter of the second metal-organic skeleton. Specifically, the average pore diameter of the second metal-organic skeleton particles may be 35 nm or more and less than 200 nm, and the average pore diameter of the first metal-organic skeleton particles may be in the range of 5 nm or more and less than 200 nm, and may be smaller than the average pore diameter of the second metal-organic skeleton particles. The average pore diameter of the first metal-organic skeleton 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 skeleton particles may be a value measured during the process of calculating the BET model using a BET-specific surface area analyzer. The first metal-organic skeleton particles and the second metal-organic skeleton particles each have a pore volume per unit mass of 0.2 cm³. 3 / g or more and 1.0 cm 3 / g or less. Specifically, each particle may have 0.3 cm 3 / g or more and 0.9 cm 3 / g or less, or 0.5 cm 3 / g or more and 0.8 cm 3 / g or less of pores. By adjusting the pore volume of the metal-organic framework particles within the above-mentioned range, the specific surface area of the porous coating layer is maximized, and a separation membrane excellent in gas adsorption performance can be produced. 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 in the second metal-organic framework particles is 0.8 cm 3 / g or more and 1.0 cm 3 / g or less, and the pore volume of the first metal-organic framework particles is 0.2 cm 3 / g or more and 1.0 cm 3 / g or less, and may be smaller than the pore volume of the second metal-organic framework particles. The average pore diameter of the first metal-organic framework particles may be 0.2 cm 3 / g or more and 0.5 cm 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 be each independently 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 be each independently 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 exposed on the surface even after modification, and the second metal-organic framework particles may be UiO-66-NH2.

[0041] The porous coating layer may contain first metal-organic skeleton particles modified with polyimide and second metal-organic skeleton 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 skeleton particles and second metal-organic skeleton particles in a weight ratio of 35:65 to 40:60. The first metal-organic skeleton can improve the dispersibility of the coating slurry and increase the packing density of the porous coating layer, while the second metal-organic skeleton can increase the specific surface area of ​​the porous coating layer. When all first metal-organic skeleton particles and second metal-organic skeleton particles are included in the weight ratios described above, a separation membrane can be obtained in which a porous coating layer with high packing density and high specific surface area can be formed simultaneously. When the first metal-organic skeleton particles are included in a larger proportion than described above, the specific surface area of ​​the porous coating layer decreases, and the amount of gas adsorbed by the separation membrane decreases.

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

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

[0044] The aforementioned acrylic polymer binder is (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, It may contain 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 as repeating units.

[0045] For example, the acrylic polymer binder may contain 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 binder. For example, the fluorine-based polymer binder may be one or more 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 specifically, it may be a copolymer containing polyvinylidene fluoride.

[0047] The polymer binder may be particulate. For example, the polymer binder may be spherical or elliptical, but is not limited to these. 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 lithium ion migration path and the adhesion of the porous coating layer to the porous substrate.

[0048] The metal-organic skeleton particles and the polymer binder may be present in a weight ratio of 80:20 to 95:5. The metal-organic skeleton particles include all of the first and second metal-organic skeleton particles, and the weight ratio of the metal-organic skeleton particles to the polymer binder may be 85:15, 90:10, or 95:5. By adjusting the content of the metal-organic skeleton particles and polymer binder within the above range, adhesion of the porous coating layer to the porous polymer substrate and thermal shrinkage of the porous polymer substrate can be reduced.

[0049] The packing density of the porous coating layer is 1 g / cm³. 3 More than 1.04g / cm 3 The following is possible: By adjusting the packing density of the porous coating layer within the range described above, a separation film 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 containing the first metal-organic skeleton particles, the second metal-organic skeleton particles, a polymer binder, and a dispersion medium. For example, the separation membrane may be manufactured by applying the coating slurry to at least one surface of the porous polymer substrate, and then drying it to remove the dispersion medium. The porous coating layer may have a porous structure, containing the first metal-organic skeleton particles, the second metal-organic skeleton particles, or an interstitial volume in which the first metal-organic skeleton particles and the second metal-organic skeleton particles are linked by the polymer binder. The porous coating layer can be bonded to the porous polymer substrate to allow lithium ions to pass through and to prevent thermal shrinkage of the porous polymer substrate.

[0051] The coating slurry contains a dispersion medium that dissolves or disperses at least a portion of the polymer binder, thereby dispersing the first metal-organic skeleton particles and the second metal-organic skeleton particles. By adjusting the type and content of the dispersion medium, the coating slurry can be used in which the metal-organic skeleton particles are uniformly dispersed. The first metal-organic skeleton particles can exhibit excellent dispersibility in the coating slurry by polyimide modification. For example, the dispersion medium may 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-described type of dispersion medium, a porous coating layer in which the first metal-organic skeleton particles and the second metal-organic skeleton 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 manufacture separation films by continuous coating onto porous polymer substrates, and productivity cannot be ensured.

[0053] The coating slurry can be further enriched with additives such as dispersants, surfactants, defoamers, flame retardants, and wetting agents to improve its dispersibility and flame retardancy, and to enhance the uniformity of the porous coating layer formed. For example, the dispersant may contain one or more 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. By using the above-mentioned types of dispersants, the stability of the coating slurry can be improved, and the uniformity of the porous coating layer formed by the coating slurry can be ensured.

[0054] The additive may be present in an amount of 0% to 5% by weight based on the total weight of the coating slurry. Specifically, the content of the additive may be 0.01% to 4% by weight, 0.1% to 3% by weight, or 1% to 2% by weight. Preferably, the content of the additive may be 3% to 5% by weight or more. By adjusting the content of the additive within the above range, uniform dispersion and stability of the first metal-organic skeleton particles and the second metal-organic skeleton particles contained 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 formation of the porous coating layer. For example, the porous coating layer may contain the dispersion medium at a concentration of 5 ppm or less. Preferably, the porous coating layer may consist of first metal-organic skeleton particles, second metal-organic skeleton particles, and a polymer binder. During the process of removing the dispersion medium, a plurality of pores may be formed on the surface and inside the porous coating layer. These pores may include the first metal-organic skeleton particles, the second metal-organic skeleton particles, or interstitial volumes formed between the first and second metal-organic skeleton particles, forming a three-dimensional network that can have a structure through which fluids can pass.

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

[0057] The separation membrane for the electrochemical element may have an air permeability of 50 s / 100 cc to 150 s / 100 cc. Specifically, the air permeability of the separation membrane 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 separation membrane may be 50 s / 100 cc to 80 s / 100 cc. When the air permeability of the separation membrane is within the above range, the output, stability, and cycle characteristics of the electrochemical element can be ensured.

[0058] Another specific example of the present invention provides an electrochemical element comprising a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode, wherein the separation membrane is the separation membrane for the electrochemical element of the above-described embodiment. The electrochemical element can be manufactured by inserting the electrode assembly, which comprises the positive electrode, the negative electrode, and the separation membrane interposed between the positive electrode and the negative electrode, into a case or pouch and sealing it. Before sealing the case or pouch, the electrode assembly can be impregnated with an electrolyte by pouring in the electrolyte. The shape of the case or pouch is not limited. For example, the electrochemical element may be a cylindrical, rectangular, coin-type, or pouch-type lithium secondary battery.

[0059] The positive electrode and the negative electrode may be configured by coating at least one surface of each current collector with an electrode active material, which is then applied and dried. The current collector can be made of a conductive material that does not cause chemical changes to the electrochemical element. For example, the positive electrode current collector may be made of aluminum, nickel, titanium, calcined carbon, stainless steel, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., but is not limited thereto. For example, the negative electrode current collector may be made of copper, nickel, titanium, calcined carbon, stainless steel, or copper or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., but is not limited thereto. The current collector can be in various forms such as a thin metal sheet, 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 comprising a positive electrode active material, a conductive material, and a binder resin. The positive electrode active material is a layered compound such as lithium manganese composite oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented as O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3); chemical formula LiMn 1-x M xa lithium manganese composite oxide represented by O2 (wherein M is Co, Ni, Fe, Cr, Zn or Ta, and x is 0.01 to 0.1), or Li2Mn3MO8 (wherein M is Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of Li in the chemical formula is substituted with alkaline earth metal ions; a disulfide compound; and may comprise one or a mixture of two or more selected from the group consisting of Fe2(MoO4)3.

[0061] The negative electrode comprises a negative electrode current collector and a negative electrode active material layer comprising a negative electrode active material, a conductive material and a binder resin provided on at least one surface of the current collector. The negative electrode comprises, as the negative electrode active material, carbon such as lithium metal oxide, non-graphitizable 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) and other metal composite oxides; lithium metal; lithium alloys; tin-based alloys; 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 comprise 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 whiskers, conductive metal oxides, carbon nanotubes, activated carbon, and polyphenylene derivatives, or a mixture of two or more conductive materials among the foregoing. The carbon nanotube has a cylindrical shape with a nanoscale diameter formed by a graphite sheet, and sp 2The carbon nanotube has a bonding structure and exhibits conductive or semiconductor properties depending on the angle and structure in which the graphite surface is wound. 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, it may be one 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, or a mixture of two or more conductive materials from this group.

[0063] As the binder resin, a binder resin commonly used for electrodes of electrochemical elements can be used. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples include, but are not limited to, acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methylcellulose.

[0064] The aforementioned electrolyte is A + B - A salt with a structure like this, + is Li + na + , K+ It contains alkali metal cations such as, or ions consisting of combinations thereof, B - PF6 - BF4 - Cl - , Br - , I - ClO4 - AsF6 - CH3CO2 - CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - Salts containing anions such as these, or ions consisting of combinations thereof, may be dissolved or dissociated in organic solvents 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 mixtures thereof.

[0065] The electrochemical element including the electrode assembly may be a lithium secondary battery. The battery can 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, and electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs) that are powered by electric motors; electric motorcycles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0066] Another specific example of the present invention provides a method for manufacturing a separation membrane for an electrochemical element, which includes the step of forming a porous coating layer on at least one surface of a porous polymer substrate, comprising a first metal-organic skeleton particle modified with polyimide, a second metal-organic skeleton particle, and a polymer binder. Any content that overlaps with the description of the separation membrane for the electrochemical element described above will be replaced by the description of the above specific example.

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

[0068] The step of forming the porous coating layer may further include a step of corona-discharging at least one surface of the porous polymer substrate before applying the coating slurry to the porous polymer substrate. The step of corona-discharging at least one surface of the porous polymer substrate can prevent a decrease in the bonding strength between the surface of the porous polymer substrate and the surface of the coating layer at high temperatures, and can prevent a decrease in the bonding strength between the surface of the polymer substrate and the surface of the coating layer due to electrolytes.

[0069] The corona discharge treatment may involve treating at least one surface of the porous polymer substrate with a voltage of 0.1kV to 10kV in air. Specifically, the corona discharge treatment may be performed with a voltage of 0.2kV to 9kV, 0.3kV to 8kV, 0.4kV to 7kV, 0.5kV to 6kV, 0.6kV to 5kV, 0.7kV to 4kV, 0.8kV to 3kV, 0.9kV to 2kV, or 1.0kV to 2kV in air. Preferably, the corona discharge treatment may be performed with a voltage of 1.8kV in air. By adjusting the applied voltage of the corona discharge treatment within the range described above, an appropriate number of functional groups can be formed on the surface of the polymer substrate, preventing damage to the surface of the polymer substrate.

[0070] The step of forming the porous coating layer may include applying the coating slurry to a porous polymer substrate to form a coating. For example, the coating can be formed by methods such as 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, but is not limited to these. Preferably, the step of forming the porous coating layer may involve simultaneously coating both sides of the porous polymer substrate with the coating slurry using a bar coater or 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 dispersion medium contained in the coating layer. The removal of the dispersion medium may be carried out at a temperature that allows only the dispersion medium contained in the coating layer to evaporate without deforming the polymer binder contained in the coating layer. For example, the removal of the dispersion medium may involve heating the coating layer to a predetermined temperature, but ensuring that the temperature of the coating layer surface does not exceed 60°C. When heating the coating layer under the above conditions, the thermal energy may be used first to heat the dispersion medium and cause a phase change, and not to deform the polymer binder.

[0072] The present invention will be described in more detail below with reference to specific examples and experimental cases. The following examples and experimental cases are for illustrative purposes only, and the present invention is not limited to the following examples and experimental cases.

[0073] Example 1 Preparation of coating slurry As metal-organic skeleton particles, UiO-66-NH2 (average particle size (D50): 1 μm, average pore diameter: 7 nm, pore volume: 0.8 cm³) 3 We used ( / g). The amine groups on the surface of the metal-organic skeleton were reacted with the anhydride of polyimide to prepare polyimide-modified first metal-organic skeleton particles.

[0074] At room temperature (25°C), 100 mL of distilled water is mixed with: acrylic polymer binder (Toyo Ink Co., Ltd., CSB130, solids content 40%, average particle size (D50) 177 nm): carboxymethylcellulose (Jielchem ​​Co., Ltd., SG-L02): wetting agent. The agent was added in a weight ratio of 8:5:1, and 12g of polyimide-modified primary metal-organic skeleton particles and 18g of polyimide-unmodified secondary metal-organic skeleton particles were added (the weight ratio of (primary metal-organic skeleton + secondary metal-organic skeleton):polymer binder was 95:5). The mixture was stirred in a shaker for 60 minutes to produce a coating slurry.

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

[0076] Manufacturing of separation membranes A polyethylene film was coated on both sides with the coating slurry using a bar coater to form a coating layer with a thickness of 3 μm for each layer.

[0077] A separation membrane with a total thickness of 15 μm was produced by repeating the process of removing the dispersion medium by applying low-temperature air to a polyethylene film on which a coating layer had been formed, five times.

[0078] Example 2 The separation membrane was manufactured in the same manner as in Example 1, except that 10.5 g of first metal-organic skeleton particles and 19.5 g of second metal-organic skeleton particles were added during the production of the coating slurry.

[0079] Comparative Example 1 The separation membrane was manufactured in the same manner as in Example 1, except that 18 g of first metal-organic skeleton particles and 12 g of second metal-organic skeleton particles were added during the production of the coating slurry.

[0080] Comparative Example 2 The separation membrane was manufactured in the same manner as in Example 1, except that 9 g of first metal-organic skeleton particles and 21 g of second metal-organic skeleton particles were added during the production of the coating slurry.

[0081] Comparative Example 3 The separation membrane was manufactured in the same manner as in Example 1, except that 6 g of first metal-organic skeleton particles and 24 g of second metal-organic skeleton particles were added during the production of the coating slurry.

[0082] Comparative Example 4 The separation membrane was manufactured in the same manner as in Example 1, except that 30 g of only the second metal-organic skeleton particles were added during the production of the coating slurry, without using the first metal-organic skeleton particles.

[0083] Comparative Example 5 During the production of the coating slurry, without using first metal-organic skeleton particles and second metal-organic skeleton particles, alumina (Sumitomo, AES11, average particle size (D50) 500 nm, density 4 g / cm³) is used. 3 The separation membrane was manufactured in the same manner as in Example 1, except that 30 g of particles were added.

[0084] Experimental example: Confirmation of 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 the settling velocity of precipitates in coated slurries

[0086] The sedimentation rate of precipitates was confirmed in the coating slurries produced during the separation membrane manufacturing process of the examples and comparative examples. The better the dispersibility of the metal-organic skeleton particles contained in the coating slurry, the slower the sedimentation rate of the precipitates.

[0087] The sedimentation velocity of the precipitate in the coating slurry was confirmed using a LUMiSizer Dispersion & Particle Size Analyzer (LUM GmbH) instrument. The coating slurry was dispensed into a tube of the instrument, and a centrifugal force of up to 2,300 G was applied to accelerate the sedimentation or creaming of the substance in the tube. After obtaining a transmission profile while continuously transmitting near-infrared light throughout the tube, the sedimentation velocity 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 to 1 bar using a BET specific surface area analyzer (BEL, Microtrac) at -196°C. The BET surface area was then calculated from the measured N2 adsorption isotherms using the Brunauer-Emmett-Teller model (BET).

[0089] Measurement of CO2 adsorption amount by inorganic particles At 25°C, using the BET specific surface area analyzer, 99.99% pure carbon dioxide was permeated through inorganic particles before the production of the coating slurry for each separation membrane, and the adsorption isotherm curve was measured to determine the amount of carbon dioxide adsorbed relative to the weight of the inorganic particles.

[0090] Method for obtaining CO2 gas volume data A lithium manganese-based composite oxide, conductive material (Denka black), and binder (PVdF) were weighed in a weight ratio of 95:2.5:2.5, then placed in N-methylpyrrolidone (NMP) and mixed to produce a cathode active material slurry. This slurry was then coated onto a 20 μm thick aluminum foil to a thickness of 200 μm, followed by rolling and drying to produce a cathode.

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

[0092] A cell was manufactured by injecting 1 g of an 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 into an aluminum pouch containing a solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) in a weight ratio of 3 / 7, and then sealing the pouch.

[0093] The manufactured cells were charged and discharged once at 0.1C in a 25°C chamber in the voltage range of 3.0V to 4.4V, and then the 1.0C charging and 1.0C discharging cycle was repeated 300 times.

[0094] After 300 cycles, the cells were pierced to collect the gas inside, 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. Porous polymer substrate, and A porous coating layer formed on at least one surface of the porous polymer substrate, comprising a first metal-organic framework (MOF) particle modified with polyimide, a second metal-organic framework particle, and a polymer binder, Includes, The first metal-organic skeleton particles and the second metal-organic skeleton particles are contained in a weight ratio of 35:65 to 45:

55. A separation membrane for an electrochemical element, wherein at least one of the first metal-organic skeleton particles and the second metal-organic skeleton particles contains zirconium and has an amine group introduced into it.

2. The first metal-organic skeleton particles and the second metal-organic skeleton particles are each measured by particle size distribution analysis (PSD) and have an average particle size (D ５０ The separation membrane for an electrochemical element according to claim 1, wherein the thickness is 300 nm or more and 10 μm or less.

3. The separation membrane for an electrochemical element according to claim 1, wherein the first metal-organic skeleton particles and the second metal-organic skeleton particles each have an average pore diameter greater than 5 nm and less than 200 nm.

4. The first metal-organic skeleton particles and the second metal-organic skeleton particles each have a pore volume of 0.2 cm³ per unit mass. ３ / g or more 1.0cm ３ A separation membrane for an electrochemical element according to claim 1, wherein the amount is less than or equal to / g.

5. The first metal-organic skeleton particle and the second metal-organic skeleton particle are independent of each other, UiO-66-NH ２ , UiO-67-NH ２ , NU-1002-NH ２ , and MOF-808-NH ２ A separation membrane for an electrochemical element according to claim 1, selected from the group consisting of the following.

6. The separation membrane for an electrochemical element according to claim 1, wherein the total of the first metal-organic skeleton particles and the second metal-organic skeleton particles and the polymer binder are contained in a weight ratio of 80:20 to 95:

5.

7. An electrochemical element comprising a positive electrode, a negative electrode, and a separation membrane disposed between the positive electrode and the negative electrode, The separation membrane is an electrochemical element according to any one of claims 1 to 6.

Images