Separator for electrochemical device and electrochemical device including the same

Abstract

The present invention provides a separator for an electrochemical device, the separator comprising a porous substrate and a porous coating layer formed on at least one side of the substrate, the porous coating layer comprising a binder resin, inorganic particles, and an ionic dispersant, the inorganic particles having a Mohs hardness (mhs) of 3 or less and a dispersibility of 3 g / cm 3 The separator for an electrochemical element according to the present invention comprises plate-like particles a having the following density, wherein the plate-like particles a comprise kaolin. The separator for an electrochemical element according to the present invention can be made thinner and lighter, and can have improved thermal shrinkage properties and prevent damage to the separator due to pressure.

Description

[Technical Field]

[0001] This application claims priority to Korean Patent Application No. 10-2021-0109732, filed on August 19, 2021.

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

[0003] Recently, interest in energy storage technology has been increasing. As its application fields expand to include mobile phones, camcorders, laptops, and even electric vehicles, efforts toward the research and development of electrochemical devices have been gradually realized. Electrochemical devices are the field that has attracted the most attention from this perspective, and among them, the development of rechargeable secondary batteries and lithium secondary batteries with high energy density has been the focus of attention. Recently, ensuring safety in the development of such secondary batteries has been a major focus.

[0004] Currently produced lithium secondary batteries use porous substrates made of polyolefin polymer resins as separator substrates to prevent short circuits between the positive and negative electrodes. However, these porous substrates have the problem of shrinking or melting at high temperatures, resulting in poor heat resistance. Therefore, when the battery is heated to a high temperature due to internal or external stimuli, the separator shrinks or melts, increasing the likelihood of the positive and negative electrodes coming into contact with each other and short-circuiting. This can lead to a sudden release of electrical energy, which can cause the battery to explode or catch fire.

[0005] Therefore, to solve the above-mentioned problems, a method of improving heat resistance by forming a porous coating layer containing a mixture of inorganic particles and a binder polymer on at least one surface of a porous polymer substrate has been widely used.

[0006] Metal oxides or hydroxides such as alumina and boehmite are widely used as inorganic particles. However, these inorganic particles may be compressed by pressing against the porous substrate during the battery assembly process, which may damage the pore structure of the porous substrate. In particular, if the inorganic particles have high hardness, damage due to localized pressure on the porous substrate may be severe. Therefore, it is necessary to prevent damage to the separator due to pressure.

[0007] In addition, the polyolefin-based porous polymer substrate commonly used as the separator exhibits extreme thermal shrinkage at temperatures above 150°C due to its material properties and manufacturing process characteristics, including stretching, which can cause short circuits between the positive and negative electrodes. For this reason, it is necessary to prevent the separator from shrinking at high temperatures. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide a separator for an electrochemical device, which can achieve a reduction in thickness and weight, improve thermal shrinkage characteristics, and prevent damage to the separator due to pressure, and an electrochemical device including the separator. It will be readily understood that other objects and advantages of the present invention can be achieved by the means or methods set forth in the claims, and combinations thereof. [Means for solving the problem]

[0009] The present inventors have found that the above-mentioned problems can be solved by the following separator for an electrochemical device and an electrochemical device including the same.

[0010] The first embodiment is A separator for an electrochemical device The separator includes a porous substrate and a porous coating layer formed on at least one side of the substrate, the porous coating layer includes a binder resin, inorganic particles, and an ionic dispersant; The inorganic particles have a Mohs hardness (mohs) of 3 or less and a hardness of 3 g / cm 3 Plate-like particles a having a density of: The separator for an electrochemical element is characterized in that the plate-like particles a contain kaolin.

[0011] The second embodiment is the same as the first embodiment, The present invention relates to a separator for an electrochemical element, wherein the ionic dispersant is an anionic surfactant.

[0012] The third embodiment is the same as the first embodiment, The separator for an electrochemical device is characterized in that the ionic dispersant is ammonium polymethacrylate, ammonium polyacrylate, sodium polymethacrylate, or sodium polyacrylate.

[0013] The fourth embodiment is the same as the first to third embodiments. The present invention relates to a separator for electrochemical elements, characterized in that the kaolin contains hydroxyl groups on the surface thereof.

[0014] The fifth embodiment is any one of the first to fourth embodiments, The present invention relates to a separator for an electrochemical element, characterized in that the kaolin is contained in an amount of 50% by weight or more relative to 100% by weight of inorganic particles.

[0015] The sixth embodiment is any one of the first to fifth embodiments, The present invention relates to a separator for an electrochemical element, characterized in that the ionic dispersant is contained in an amount of 0.3 to 5% by weight relative to 100% by weight of inorganic particles.

[0016] The seventh embodiment is any one of the first to fifth embodiments, the aspect ratio of the plate-like particles a is 5 to 30, The aspect ratio relates to a separation membrane whose aspect ratio is defined as [length in the major axis direction] / [width in the direction perpendicular to the major axis direction].

[0017] The eighth embodiment is any one of the first to fifth embodiments, a ratio of the packing density of the porous coating layer to the density of the plate-like particles is 0.45 to 0.8; The packing density is defined as the weight per unit volume of the porous coating layer.

[0018] The ninth embodiment relates to an electrochemical element including 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 according to any one of the first to eighth embodiments.

[0019] The tenth embodiment is the same as the ninth embodiment, The electrochemical device is a lithium secondary battery. [Effects of the Invention]

[0020] The separator for an electrochemical device according to the present invention can exhibit improved heat shrinkage resistance by suppressing shrinkage due to high temperatures, and can also exhibit improved compression resistance by suppressing deformation due to pressure applied during the battery assembly process. [Brief explanation of the drawings]

[0021] The drawings attached to this specification illustrate preferred embodiments of the present invention and serve to facilitate a better understanding of the technical concept of the present invention together with the contents of the invention described above, and therefore the present invention should not be interpreted as being limited to only the matters shown in those drawings. Meanwhile, the shape, size, scale, or ratio of elements in the drawings included in this specification may be exaggerated to emphasize a clearer description.

[0022] [Figure 1] FIG. 1 is a schematic diagram showing the mechanism of action when kaolin 1, which is a plate-like particle, and an ionic dispersant 2 are used in a separation membrane according to one embodiment of the present invention. [Figure 2] 1 is an SEM image of a cross section of the separation membrane of Example 1. [Figure 3] 1 is an SEM image of a cross section of the separation membrane of Comparative Example 1. [Figure 4] 1 is an SEM image of a cross section of the separation membrane of Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be described in detail below. The terms and words used in the specification and claims should not be interpreted as being limited to their ordinary and dictionary meanings, but should be interpreted in a meaning and concept that is consistent with the technical idea of the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to best describe the invention.

[0024] Throughout this specification, when a part "comprises" a certain element, this does not mean that it excludes other elements, but that it can further include other elements, unless otherwise specified.

[0025] Furthermore, the terms "about" and "approximately" used throughout this specification mean a numerical value or a value close to the numerical value when manufacturing and material tolerances inherent in the stated meaning are given, and are used to prevent unscrupulous infringers from unfairly taking advantage of the disclosure in which exact or absolute numerical values are stated to aid in the understanding of this specification.

[0026] Throughout this specification, the phrase "A and / or B" means "A or B or both."

[0027] The present invention relates to a separator for an electrochemical device.

[0028] In the present invention, the electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction and includes all devices that perform electrochemical reactions, and specific examples thereof include all types of primary batteries, secondary batteries, fuel cells, solar cells, and capacitors such as supercapacitors. In particular, among the secondary batteries, lithium secondary batteries, including lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, and lithium ion polymer secondary batteries, are preferred.

[0029] In the present invention, the separator may include a porous substrate and a porous coating layer formed on at least one side of the substrate.

[0030] The porous substrate refers to a substrate having a plurality of pores formed therein, which act as a porous ion-conducting barrier that allows ions to pass through while blocking electrical contact between the negative and positive electrodes. These pores have an interconnected structure, allowing gas or liquid to pass from one side of the substrate to the other. To provide a shutdown function, a porous polymer film containing a thermoplastic resin can be used as the porous substrate. Here, the shutdown function refers to the function of preventing thermal runaway of the battery by blocking ion migration when the battery temperature rises by dissolving the thermoplastic resin and closing the pores of the porous substrate. Non-limiting examples of the thermoplastic resin include polyolefin resins such as polyethylene, polypropylene, polybutylene, and polypentene. From the perspective of the shutdown function, the thermoplastic resin preferably has a melting point of less than 200°C.

[0031] The thickness of the porous substrate is not particularly limited, but is preferably 1 to 100 μm, more preferably 5 to 50 μm, or 5 to 30 μm. The pores present in the porous substrate are also not particularly limited, but are preferably 10 to 95% or 35 to 65%.

[0032] The porous coating layer may be formed on at least one side of the substrate and may include a binder resin, inorganic particles, and an ionic dispersant.

[0033] In the present invention, the porous coating layer has a structure in which the inorganic particles are filled and in contact with each other and bound to each other by the binder resin, thereby forming interstitial volumes between the inorganic particles, and the interstitial volumes between the inorganic particles become empty spaces to form pores. Specifically, in the present invention, the weight ratio of inorganic particles to binder resin in the porous coating layer may be 97:3 to 55:45.

[0034] In the present invention, the binder resin is not particularly limited as long as it can provide binding strength between inorganic particles and between the porous coating layer and the electrode. For example, the binder resin may be polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co-chlorotrifluoroethylene, or the like. ethylene), poly(methyl) methacrylate, polyethyl (meth)acrylate, poly n-propyl (meth)acrylate, polyisopropyl (meth)acrylate, poly n-butyl (meth)acrylate, poly t-butyl (meth)acrylate, poly sec-butyl (meth)acrylate, polypentyl (meth)acrylate, poly 2-ethylbutyl poly(meth)acrylate, poly 2-ethylhexyl (meth)acrylate, poly n-octyl (meth)acrylate, polyisooctyl (meth)acrylate, polyisononyl (meth)acrylate, polylauryl (meth)acrylate, polytetradecyl (meth)acrylate, poly N-vinylpyrrolidinone, polyacrylonitrile, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate acetate), cellulose acetate butyrate, cellulose acetate propionateThe polymer may be one or a mixture of two or more selected from the group consisting of acrylonitrile-styrene-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, and polyimide.

[0035] The binder resin may be a particulate binder polymer resin. For example, it may be an acrylic copolymer, a styrene-butadiene rubber, or a mixture of two or more thereof. The acrylic copolymer may include a copolymer of ethylhexyl acrylate and methyl methacrylate, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, a copolymer of butyl acrylate and methyl methacrylate, or a mixture of two or more thereof.

[0036] In the present invention, the inorganic particles may include plate-like particles a.

[0037] According to one embodiment of the present invention, the plate-like particles a have a Mohs hardness (MOHS) of about 3 or less and a density of about 3 g / cm 3 Preferably, the Mohs hardness is about 2.3 to 2.7 and the density is about 2.5 to 2.8 g / cm 3By including the plate-like particles a having the Mohs hardness and density described above, the separator can be formed with a lighter weight and thinner thickness than conventional separators, and exhibits high packing density and excellent heat resistance and safety. In addition, the separator can be resistant to deformation due to pressure applied during the battery assembly process, thereby exhibiting excellent compression resistance.

[0038] In the above, the aspect ratio of the plate-like particles a is 5 to 100, preferably 5 to 30, and the aspect ratio is defined as [length in the major axis direction] / [width in the direction perpendicular to the major axis direction]. If the aspect ratio is greater than the above range, the path along which lithium ions move becomes longer, which can increase the resistance of the separator. In addition, the plate-like particles a may be aligned or stacked in a direction parallel to the porous coating layer (plane direction).

[0039] According to one embodiment of the present invention, the plate-like particles a may include kaolin.

[0040] Kaolin has the chemical composition Al2O3·2SiO2·2H2O and is available in three varieties: ordinary kaolin, metakaolin, and calcined kaolin. Kaolin in this specification refers to ordinary kaolin, which contains hydroxyl groups (-OH groups) on its surface.

[0041] The metakaolin is calcined at a temperature of about 500°C or higher to remove most of the hydroxyl groups on its surface, and the calcined kaolin is calcined at a temperature of about 900°C or higher to remove all of the hydroxyl groups on its surface. However, in the present invention, kaolin containing hydroxyl groups on its surface is preferred, and metakaolin and / or calcined kaolin are not preferred.

[0042] In particular, the present invention achieves the effect of suppressing shrinkage due to high temperatures and deformation due to pressure by combining plate-like general kaolin with an ionic dispersant, which will be described later. This is because when kaolin, which has hydroxyl groups (-OH groups) on its surface, is used in combination with an ionic dispersant, the plate-like kaolin is aligned in the plane direction, so that damage to the porous substrate by the kaolin does not occur even when pressure is applied.

[0043] However, when metakaolin or calcined kaolin that has been calcined at high temperatures is used together with an ionic dispersant, the charge characteristics of the particles change, preventing the metakaolin or calcined kaolin from aligning in the plane, thereby failing to achieve the desired effect of the present invention. Furthermore, even when metal oxides such as alumina or boehmite are used as inorganic particles commonly used in the art, the inorganic particles are compressed against the porous substrate by the pressure applied during the battery assembly process, damaging the pore structure of the porous substrate or deforming the separator due to the pressure, thereby failing to achieve the desired effect of the present invention.

[0044] In addition, when general kaolin and an ionic dispersant (described later) are used together in the present invention, a high packing density can be exhibited in the porous coating layer. In particular, in the present invention, a density of about 3 g / cm 3 Preferably, the density is about 2.5 to 2.8 g / cm 3 Although it contains kaolin, which is a plate-like particle, it has a density of about 1.1 to 1.5 g / cm 3 or about 1.1 to 1.3 g / cm 3 In the present invention, the packing density can be calculated as the weight per unit volume of the porous coating layer.

[0045] In the present invention, the effects of suppressing shrinkage due to high temperatures and deformation due to pressure can be determined by the degree of in-plane alignment of the plate-like particles. The degree of in-plane alignment of the plate-like particles tends to increase in proportion to the ratio of the packing density of the porous coating layer to the density of the plate-like particles ([packing density] / [density]). Generally, when high-density particles are contained in a porous coating layer, the packing density tends to be high due to the high density. Therefore, the in-plane alignment of the plate-like particles cannot be determined solely from the packing density of the porous coating layer; the intrinsic density of the plate-like particles must be taken into consideration. In the present invention, even when kaolin particles, which are particles with a relatively low density, are contained, the kaolin particles can be aligned in-plane, thereby exhibiting a high packing density. In such a case, the [packing density] / [density] ratio may be 0.45 to 0.80, preferably 0.46 or more. This allows the formation of a separator that is lighter and thinner than conventional separators, and exhibits a high packing density and excellent heat resistance. When the plate-like particles have an aspect ratio outside the above-mentioned aspect ratio range, the ratio of [packing density] / [density] may be greater than the above-mentioned range, and in this case, the path along which lithium ions travel may become longer, which may increase the resistance of the separator.

[0046] According to one embodiment of the present invention, the plate-like particles a may be included in an amount of 30 wt % or more or 50 wt % or more based on 100 wt % of the inorganic particles in order to improve the heat resistance of the separator.

[0047] In the present invention, the inorganic particles may include particles other than particle a, and the inorganic particles other than particle a are not particularly limited as long as they are electrochemically stable. For example, the inorganic particles other than particle a are not particularly limited as long as they do not undergo oxidation and / or reduction reactions within the operating voltage range of the applied electrochemical device (e.g., 0 to 5 V based on Li / Li+). Non-limiting examples include ZrO2, BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti yO3(PLZT), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO 2、 AlOOH, Al(OH)3, SiC, or a mixture thereof, etc. On the other hand, in addition to this, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y -system glass (glass) (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), SiS2-system glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5-system glass (Li × P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), or can further contain two or more of these inorganic particles 。

[0048] According to one embodiment of the present invention, the ionic dispersant is added to disperse inorganic particles and prevent aggregation of solids during the formation of a porous coating layer. In particular, the use of an ionic dispersant in the present invention allows the plate-like particles a contained in the porous coating layer to be aligned in the plane direction. This can suppress shrinkage due to high temperatures and deformation due to pressure. In the present invention, the plane direction alignment means that the broad surfaces of the plate-like particles a are aligned in a direction approximately parallel to the plane of the porous substrate.

[0049] In the present invention, any ionic dispersant can be used without limitation as long as it can align the plate-like particles a in the plane direction.

[0050] In the present invention, when the plate-like particles a contain kaolin, an anionic surfactant can be used as the ionic dispersant.

[0051] Figure 1 is a schematic diagram showing the mechanism of action when kaolin 1, which is a plate-like particle, and an ionic dispersant 2 are used. For example, the mechanism of action when an anionic surfactant is used as the ionic dispersant will be explained.

[0052] The surface area of kaolin is almost negatively charged (δ - ), and the edge part is almost positively charged (δ + ) Therefore, without an anionic surfactant, the negative charges on the kaolin surface and the positive charges on the edges interact, preventing alignment in the plane direction. However, when kaolin and an anionic surfactant are used together, the anionic surfactant interacts with the positive charges on the edges of the kaolin, causing the anionic surfactant to be adsorbed to the edges of the kaolin surface. This increases the overall negative charge on the kaolin surface, suppressing the interaction between the negative charges on the kaolin surface and the positive charges on the edges, resulting in alignment of the kaolin in the plane direction.

[0053] Compared to other kaolins such as metakaolin and calcined kaolin, or other plate-like metal hydroxides such as aluminum hydroxide and magnesium hydroxide, ordinary kaolin, which is a plate-like particle, has a larger difference in charge between the surface and edge, allowing it to exhibit relatively excellent planar alignment when used with ionic dispersants. This can be expressed as a relatively higher [packing density] / [density] ratio.

[0054] The anionic surfactant refers to a surfactant containing an anionic functional group as an ionic or ionizable group. For example, the anionic functional group contained in the anionic surfactant is -CO2 - , PO4 3- , -SO3 - , -OSO3 - , -HPO3 - , -PO3 2- , -HPO2 - , -PO2 2- , -PO - or a combination of two or more of these.

[0055] In one embodiment of the present invention, the anionic surfactant may include at least one metal salt containing the anionic functional group. Examples of the metal salt include sodium salts, potassium salts, ammonium salts, and magnesium salts, and the surfactant may include one or more of these. However, the surfactant is not particularly limited thereto. For example, the anionic surfactant may include a sodium salt, potassium salt, ammonium salt, or magnesium salt of a carboxylic acid, or a combination of two or more of these. Specific examples include ammonium polymethacrylate, ammonium polyacrylate, sodium polymethacrylate, and sodium polyacrylate, and the surfactant may include two or more of these. However, the surfactant is not particularly limited thereto.

[0056] The ionic dispersant may be contained in an amount of 0.3 to 5% by weight, or 0.5 to 3% by weight, relative to 100% by weight of the inorganic particles, in order to align the plate-like particles a in the plane direction.

[0057] Meanwhile, in the present invention, the separator may further include other additives such as a flame retardant as necessary, in addition to the binder resin, inorganic particles, and ionic dispersant described above as components of the porous coating layer.

[0058] A separator according to an embodiment of the present invention may be manufactured by preparing a composition for forming a porous coating layer, the composition including inorganic particles, a binder resin, and an ionic dispersant, applying the composition to at least one surface of a porous substrate, and drying the composition.

[0059] First, the composition for forming a porous coating layer can be prepared by dissolving a binder resin in a solvent to prepare a polymer solution, and then adding inorganic particles to the polymer solution and dispersing the resulting solution. The inorganic particles can be added in a pre-crushed state to have a predetermined average particle size. Alternatively, the inorganic particles can be added to the solvent, and then crushed and dispersed to have a predetermined particle size using a ball mill or the like to prepare a dispersion. In one embodiment of the present invention, the solids concentration, excluding the solvent, in the dispersion is preferably controlled to be in the range of 20 wt% to 70 wt%.

[0060] Non-limiting examples of the solvent used here include one compound or a mixture of two or more compounds selected from acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, methyl ethyl ketone, cyclohexane, methanol, ethanol, isopropyl alcohol, propanol, and water.

[0061] The method for coating the porous substrate with the composition for forming a porous coating layer is not particularly limited, but slot coating or dip coating is preferably used. Slot coating is a method in which a composition supplied through a slot die is applied to the front surface of a substrate, and the thickness of the coating layer can be controlled depending on the flow rate supplied from a metering pump. Dip coating is a method in which a substrate is immersed in a tank containing the composition to coat it. The thickness of the coating layer can be controlled depending on the concentration of the composition and the speed at which the substrate is removed from the tank. For more accurate control of the coating thickness, the substrate can be post-weighed using a Mayer bar or the like after immersion.

[0062] The porous substrate coated with the composition for forming a porous coating layer is dried in a dryer such as an oven to form an inorganic coating layer on the surface of the porous substrate. The porous coating layer may be formed on at least one side or both sides of the porous substrate.

[0063] The thickness of the separator according to the present invention is not particularly limited, but may be in the range of 5 to 50 μm, preferably in the range of 5 to 20 μm or 10 to 16 μm, in which case the separator can exhibit improved insulating properties and heat resistance stability.

[0064] The electrochemical device according to the present invention includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and the separator is the separator according to one embodiment of the present invention described above.

[0065] The electrode to be used with the separator of the present invention is not particularly limited, and can be prepared by a conventional method known in the art in the form of an electrode active material bound to an electrode current collector.

[0066] Among the electrode active materials, non-limiting examples of the positive electrode active material include common positive electrode active materials that can be used for the positive electrode of conventional lithium secondary batteries, and in particular, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a lithium composite oxide that is a combination thereof.

[0067] Non-limiting examples of the negative electrode active material include common negative electrode active materials that can be used in the negative electrodes of conventional lithium secondary batteries, and particularly preferred are lithium metal or lithium alloys, and lithium-absorbing materials such as carbon, petroleum coke, activated carbon, graphite, or other carbons.

[0068] Non-limiting examples of positive current collectors include foils made of aluminum, nickel, or combinations thereof, and non-limiting examples of negative current collectors include foils made of copper, gold, nickel, or copper alloys, or combinations thereof.

[0069] The electrolyte that can be used in the electrochemical element of the present invention is + B - A salt having the structure: + Li + , Na + , K. + or a combination thereof, - PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , (CF2SO2)3 -or a salt containing an anion such as, or a combination thereof, dissolved or dissociated in an organic solvent such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (γ-butyrolactone), or a mixture thereof.

[0070] The electrolyte injection can be performed at an appropriate stage during the battery manufacturing process depending on the manufacturing process and required properties of the final product, i.e., before battery assembly or at the final stage of battery assembly.

[0071] The present invention also provides a battery module including a battery having an electrode assembly as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include, but are not limited to, power tools powered by an electric motor, electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters, electric golf carts, and power storage systems.

[0072] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the present invention. However, the examples according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art. [Example]

[0073] Separation membranes of the examples and comparative examples were manufactured by the following method.

[0074] Example 1 1) A porous polyethylene film (thickness 9 μm, porosity 45%) was prepared as a porous polymer substrate.

[0075] 2) Next, 20 g of plate-shaped kaolin (aspect ratio 20), 0.3 g of an ionic dispersant (ammonium polyacrylate), and 20 g of 0.5 mm zirconia beads were added to 30 g of a 95:5 mixture of water and ethanol, and the mixture was stirred for 2 hours using a paint shaker to prepare an inorganic dispersion.

[0076] 3) Next, 1 g of a 40% solids acrylic binder (TRD202A, manufactured by JSR Corporation) and 10 g of a 40% water-dispersed acrylic particle binder (APEC AP-0821, particle size 350 nm) were added to the inorganic dispersion and shaken to prepare a coating slurry.

[0077] 4) The coating slurry was filtered through a 200 mesh and coated onto one side of a polyethylene porous film using a bar coater, then dried in a dryer. The opposite side was coated again under the same conditions to produce a double-coated separator.

[0078] The results are shown in Table 2.

[0079] Example 2 and Comparative Examples 1 to 4

[0080] Separation membranes were manufactured in the same manner as in Example 1, except that the types of inorganic substances and dispersants were changed as shown in Table 1 below. The results are shown in Table 2.

[0081] [Table 1]

[0082] [Table 2]

[0083] As can be seen from Table 2, when Examples 1 and 2 are compared with Comparative Examples 1 to 4, the thicknesses of the produced separation membranes are equal or similar. However, since Comparative Examples 1 to 4 are more subject to deformation due to pressure than Examples 1 and 2, it was confirmed that there was a large difference between the thickness of the separation membrane after compression and the thickness of the produced separation membrane.

[0084] It can also be seen that Examples 1 and 2 exhibit higher packing densities than Comparative Examples 1 to 3. Incidentally, Comparative Example 4 exhibits a higher packing density than Example 1, but this is due to the presence of alumina particles with high density, and it can be seen that the ratio of [packing density] / [density] is relatively low.

[0085] Furthermore, when the air permeability of the separators was measured before compression, Examples 1 and 2 showed even higher air permeability, but after compression, Comparative Examples 1 to 4 showed even higher air permeability than the Examples, confirming that the air permeability of Comparative Examples 1 to 4 decreased due to compression.

[0086] In addition, it was confirmed that the separators produced in Examples 1 and 2 had smaller heat shrinkage rates in the MD and TD directions than those produced in Comparative Examples 1 to 4.

[0087] Evaluation of separation membrane properties The physical properties of the separation membranes produced in the examples and comparative examples were evaluated by the following methods.

[0088] (1) Thickness The thickness of the separation membrane was measured using a thickness measuring device (Mitutoyo Corporation, VL-50S-B).

[0089] (2) Measurement of air permeability Measurements were taken using a Gurley air permeability meter in accordance with JIS P-8117. The diameter was 28.6 mm and the area was 645 mm. 2 The time it took for 100cc of air to pass through was measured.

[0090] (3) Evaluation method for heat shrinkage The separator membrane was cut into a 5x5cm piece and stored in a convection oven at 135°C for 30 minutes, and then the length changes in the MD and TD directions were measured. Heat shrinkage rate (%) = {(dimension before shrinkage - dimension after shrinkage) / dimension before shrinkage} x 100

[0091] (4) Sample production of compressed separation membrane A 10x10cm piece of release PET cut into pieces was laminated on top and bottom of a 5x5cm piece of separator. The release side of the release PET was in contact with the separator. The separator laminated with PET was hot pressed at 70°C and 5MPa for 10 seconds to produce a compressed separator sample.

Claims

1. A separator for an electrochemical device The separator includes a porous substrate and a porous coating layer formed on at least one side of the substrate, the porous coating layer includes a binder resin, inorganic particles, and an ionic dispersant; The inorganic particles have a Mohs hardness (mohs) of 3 or less and a surface roughness of 3 g / cm ３ Plate-like particles a having a density of: The plate-like particles a contain kaolin, A separator for an electrochemical device, wherein the ionic dispersant is ammonium polymethacrylate, ammonium polyacrylate, sodium polymethacrylate, or sodium polyacrylate.

2. 2. The separator for an electrochemical element according to claim 1, wherein the kaolin contains hydroxyl groups on the surface thereof.

3. 2. The separator for an electrochemical device according to claim 1, wherein the kaolin is present in an amount of 50% by weight or more relative to 100% by weight of the inorganic particles.

4. 2. The separator for an electrochemical device according to claim 1, wherein the ionic dispersant is contained in an amount of 0.3 to 5% by weight based on 100% by weight of the inorganic particles.

5. the aspect ratio of the plate-like particles a is 5 to 30, 2. The separator for electrochemical elements according to claim 1, wherein the aspect ratio is defined as [length in the major axis direction] / [width in the direction perpendicular to the major axis direction].

6. a ratio of the packing density of the porous coating layer to the density of the plate-like particles is 0.45 to 0.8; 2. The separator for an electrochemical device according to claim 1, wherein the packing density is defined as a weight per unit volume of the porous coating layer.

7. 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 according to any one of claims 1 to 6.

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

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