Separation membrane for electrochemical elements, and electrochemical elements containing the same

Abstract

The separator for an electrochemical device includes a porous polymer substrate and a porous coating layer formed on at least one surface of the porous polymer substrate. The porous coating layer includes inorganic particles and a polymer binder. The inorganic particles have a polymer coating layer containing amine groups formed on their surfaces, and at least a portion of the polymer binder is crosslinked with the polymer containing amine groups.

Description

[Technical Field]

[0001] This application claims priority based on Korean Patent Application No. 10-2023-0038901, filed with the Korean Intellectual Property Office on March 24, 2023, the contents of which are entirely incorporated herein by reference. The present invention relates to a separation membrane for an electrochemical element and an electrochemical element containing the same. [Background technology]

[0002] 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.

[0003] A lithium secondary 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 together with an electrolyte in a case.

[0004] On the other hand, in order to improve the performance and safety of secondary batteries employing electrochemical elements, improvements have been made to the characteristics of the positive electrode, negative electrode, electrolyte, and separation membrane. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention provides a separation membrane for an electrochemical element in which the rate of dimensional change is reduced in a high-temperature wet state, a method for manufacturing the same, and an electrochemical element including the separation membrane for the electrochemical element.

[0006] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0007] 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, wherein the porous coating layer comprises inorganic particles and a polymer binder, the inorganic particles having a polymer coating layer containing amine groups formed on their surface, and at least a portion of the polymer binder being crosslinked with the polymer containing the amine groups.

[0008] According to one embodiment of the present invention, the polymer containing the amine group is dopamine or a derivative thereof.

[0009] According to one embodiment of the present invention, the thickness of the polymer coating layer is approximately 2 nm to 20 nm.

[0010] According to one embodiment of the present invention, the polymer binder comprises one or more selected from the group consisting of dextrin, polyetheretherketone, polyethersulfone, and polyacrylamide.

[0011] According to one embodiment of the present invention, the polymer binder comprises a (co)polymer of monomers selected from the group consisting of acrylate, acrylic acid, maleic acid, itaconic acid, methacrylic acid, and carboxyethyl acrylate.

[0012] According to one embodiment of the present invention, approximately 60% to 80% by weight of the polymer binder is crosslinked with the polymer containing the amine group.

[0013] According to one embodiment of the present invention, the loading amount of the porous coating layer per unit area of ​​the porous polymer substrate is approximately 5.5 g / m². 2 ~8g / m 2 That is the case.

[0014] According to one embodiment of the present invention, the porous coating layer contains the inorganic particles in an amount of about 90% to 95% by weight relative to the total weight of the porous coating layer.

[0015] According to one embodiment of the present invention, the porous coating layer further comprises a second polymer coating layer formed on the surface thereof, wherein the second polymer coating layer comprises a polymer containing the amine group.

[0016] According to one embodiment of the present invention, at least a portion of the polymer containing the amine group in the second polymer coating layer is crosslinked with the polymer binder in the porous coating layer.

[0017] According to one embodiment of the present invention, the second polymer coating layer further comprises dextrin.

[0018] According to another embodiment of the present invention, an electrochemical element is provided, 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 an electrochemical element relating to one side.

[0019] The electrochemical element may be a lithium secondary battery. [Effects of the Invention]

[0020] A separation membrane for an electrochemical element according to one embodiment of the present invention provides improved dimensional stability in a wet state impregnated with an electrolyte. For example, the separation membrane has a thermal shrinkage rate of less than 10% in the TD direction under high temperature conditions of approximately 130°C or higher, thereby preventing electrode exposure due to thermal shrinkage of the separation membrane. [Brief explanation of the drawing]

[0021] [Figure 1a] This image shows the separation membrane according to Example 1, inserted into a pouch together with the electrolyte, stored in a convection oven at 135°C for 30 minutes, and then removed to confirm its external shape. [Figure 1b] This image shows the separation membrane according to Comparative Example 1, which was placed in a pouch together with the electrolyte solution and stored in a convection oven at 135°C for 30 minutes, after which its external shape was examined.

[0022] Those skilled in the art will understand that these drawings are intended to show elements simply and clearly, and are not necessarily drawn to scale. For example, to aid in understanding the various embodiments, the dimensions of some elements shown in the drawings may be exaggerated compared to others. Also, elements of the prior art that are useful or essential in commercially viable embodiments may often be omitted so as not to detract from the spirit of the various embodiments of the invention. [Modes for carrying out the invention]

[0023] The following describes in more detail each component of the present invention so that a person with ordinary skill in the art to which the present invention belongs can easily implement it. However, this is merely an example, and the scope of the rights of the present invention is not limited to the following.

[0024] 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.

[0025] In this specification, the singular form includes the plural form unless otherwise specified in the text.

[0026] In this specification, "A and / or B" means "A and B, or A or B."

[0027] In this specification, when we say that a component is "placed on top of" another component, this means that, unless otherwise stated, other components may be placed in between, rather than excluding the possibility of other components being placed in between.

[0028] In this specification, "%" means weight percent unless otherwise explicitly indicated.

[0029] 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 used to prevent infringers from unfairly exploiting disclosures that refer to precise or absolute numerical values ​​provided to aid in understanding the invention.

[0030] As used herein, "electrochemical elements" refers to primary batteries, secondary batteries, supercapacitors, and the like.

[0031] As used herein, "wet state" means a state in which the separation membrane is impregnated with at least a portion of the electrolyte.

[0032] The separation membrane may include a porous coating layer containing a polymer binder and inorganic particles on at least one surface of a porous substrate. The inorganic particles are linked together by the polymer binder to form interstitial volumes, through which lithium ions can move. In addition to fixing the inorganic particles, the polymer binder can provide adhesion to the porous coating layer, which can then adhere to the porous substrate and the electrodes, respectively.

[0033] A porous coating layer containing a polymer binder and inorganic particles can prevent thermal shrinkage of the porous polymer substrate, and the separation membrane containing the porous coating layer exhibits excellent dimensional stability in a dry state without electrolyte. However, in a wet state where the separation membrane is impregnated with electrolyte, the polymer binder is swollen by the electrolyte, or the separation membrane is exposed to temperatures of approximately 130°C or higher due to the operation of the lithium secondary battery containing the separation membrane, reducing the adhesive strength of the polymer binder. In such a high-temperature wet state, the adhesive strength of the porous coating layer decreases, and the separation membrane shrinks significantly. In particular, cylindrical batteries, in which the electrode assembly is wound up and inserted into a case while tension is applied to the electrode assembly, require relatively less adhesive strength between the electrode and the separation membrane compared to pouch-type batteries. Therefore, the polymer binder content is low, and there is a problem of further reduced dimensional stability in the wet state.

[0034] In order to prevent such problems, the present invention provides a separation membrane that ensures dimensional stability under high temperature and wet conditions while maintaining a relatively low content of polymer binder in the porous coating layer.

[0035] One embodiment 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, wherein the porous coating layer comprises inorganic particles and a polymer binder, the inorganic particles having a polymer coating layer containing amine groups formed on their surface, and at least a portion of the polymer binder being crosslinked with the polymer containing the amine groups.

[0036] According to one embodiment of the present invention, the porous polymer substrate is a porous membrane having a plurality of pores formed therein, which electrically insulates the positive electrode and the negative electrode to prevent short circuits. For example, when the electrochemical element is a lithium secondary battery, the porous polymer substrate is an ion-conducting barrier that blocks electrical contact between the positive electrode and the negative electrode while allowing lithium ions to pass through. At least a portion of the pores can form a three-dimensional network that connects the surface and the interior of the porous polymer substrate, allowing fluids to pass through the porous polymer substrate via the pores.

[0037] According to one embodiment of the present invention, the porous polymer substrate uses a material that is physically and chemically stable with respect to an electrolyte, which is an organic solvent. For example, the porous polymer substrate includes, but is not limited to, resins such as polyethylene, polypropylene, and polybutylene (polyolefins), polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimidoamide, nylon, polytetrafluoroethylene, and copolymers or mixtures thereof. For example, 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.

[0038] According to one embodiment of the present invention, the porous polymer substrate has a single-layer or multi-layer structure. The porous polymer substrate includes two or more polymer resin layers with different melting points (Tm) to provide a shutdown function in the event of a high-temperature runaway of the battery. For example, the porous polymer substrate includes a polypropylene layer with a relatively high melting point and a polyethylene layer with a relatively low melting point. Alternatively, the porous polymer substrate may have a three-layer structure in which polypropylene, polyethylene, and polypropylene are laminated in that order. The polyethylene layer melts as the battery temperature rises above a predetermined temperature, thereby shutting down the pores and preventing thermal runaway of the battery.

[0039] According to one embodiment of the present invention, the thickness of the porous polymer substrate is approximately 1 μm to 100 μm. For example, the thickness of the porous polymer substrate may be approximately 10 μm to 90 μm, approximately 20 μm to 80 μm, approximately 30 μm to 70 μm, or approximately 40 μm to 60 μm. Alternatively, the thickness of the polymer substrate may be approximately 1 μm to 30 μm. For example, the thickness of the polymer substrate may be approximately 5 μm to 15 μm, or approximately 8 μm to 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, thereby increasing the amount of active material contained in the electrochemical element.

[0040] According to one embodiment of the present invention, the porous polymer substrate contains pores with an average diameter of approximately 0.01 μm to 1 μm. For example, the size of the pores contained in the porous polymer substrate may be approximately 0.01 μm to 0.09 μm, approximately 0.02 μm to 0.08 μm, approximately 0.03 μm to 0.07 μm, or approximately 0.04 μm to 0.06 μm. Alternatively, the size of the pores may be approximately 0.02 μm to 0.06 μm. By adjusting the pore size of the porous polymer substrate within the above range, the air permeability and ionic conductivity of the entire separation membrane produced can be adjusted.

[0041] According to one embodiment of the present invention, the porous polymer substrate has an air permeability of about 10 s / 100 cc to 100 s / 100 cc. For example, the air permeability of the porous polymer substrate may be about 10 s / 100 cc to 90 s / 100 cc, about 20 s / 100 cc to 80 s / 100 cc, about 30 s / 100 cc to 70 s / 100 cc, or about 40 s / 100 cc to 60 s / 100 cc. Alternatively, the air permeability of the porous polymer substrate may be about 50 s / 100 cc to 70 s / 100 cc. 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.

[0042] According to one embodiment of the present invention, the 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. The air permeability can be measured using an air permeability tester (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.

[0043] According to one embodiment of the present invention, the porous polymer substrate has a porosity of about 10 vol% to 60 vol%. For example, the porosity of the porous polymer substrate may be about 15 vol% to 55 vol%, about 20 vol% to 50 vol%, about 25 vol% to 45 vol%, or about 30 vol% to 40 vol%. Alternatively, the porosity of the porous polymer substrate may be about 30 vol% to 50 vol%. When the porosity of the porous polymer substrate is within the above range, the ionic conductivity of the separation membrane produced can be provided within a range suitable for ensuring the output and cycle characteristics of the electrochemical element.

[0044] According to one embodiment of the present invention, the porosity refers to the volume ratio 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.

[0045] According to one embodiment of the present invention, the porous coating layer is formed on at least one surface of the porous polymer substrate and comprises inorganic particles and a polymer binder.

[0046] According to one embodiment of the present invention, the porous coating layer is formed by coating at least one surface of a porous polymer substrate with a coating slurry containing inorganic particles, a polymer binder, and a dispersion medium. For example, the separation membrane can be manufactured by applying the coating slurry to at least one surface of a porous polymer substrate, and then drying it to remove the dispersion medium. The porous coating layer contains interstitial volumes in which the inorganic particles are linked by the polymer binder, allowing lithium ions to pass through while adhering to the porous polymer substrate and preventing thermal shrinkage of the porous polymer substrate.

[0047] According to one embodiment of the present invention, the coating slurry contains a dispersion medium to dissolve or disperse at least a portion of the polymer binder and disperse inorganic particles. The coating slurry is used in which the polymer binder and inorganic particles are uniformly dispersed by adjusting the type and content of the dispersion medium. For example, the dispersion medium is one selected from the group consisting of water, ethanol, acetone, isopropyl alcohol (IPA), dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), acetonitrile, and combinations thereof. Using the above-mentioned types of dispersion medium, a porous coating layer in which inorganic particles are uniformly dispersed can be formed.

[0048] According to one embodiment of the present invention, the coating slurry has a viscosity of about 100 cps to 1,000 cps. For example, the viscosity of the coating slurry may be about 200 cps to 900 cps, about 300 cps to 800 cps, about 400 cps to 700 cps, or about 500 cps to 600 cps. Alternatively, the viscosity of the coating slurry may be about 300 cps to 800 cps. By adjusting the viscosity of the coating slurry within the above range, a porous coating layer can be formed by continuous application to a porous polymer substrate.

[0049] According to one embodiment of the present invention, the coating slurry further contains additives such as dispersants, surfactants, defoamers, and flame retardants to improve dispersibility and flame retardancy, and to improve 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.

[0050] According to one embodiment of the present invention, the additive is contained in an amount of about 0% to 5% by weight, based on the total weight of the coating slurry. For example, the content of the additive may be about 0.01% to 4% by weight, about 0.1% to 3% by weight, or about 1% to 2% by weight. Alternatively, the content of the additive may be about 3% to 5% by weight. By adjusting the content of the additive within the above range, uniform dispersion and stability of the inorganic particles contained in the coating slurry can be achieved.

[0051] According to one embodiment of the present invention, the dispersion medium contained in the coating slurry is removed by drying or heating after the formation of the porous coating layer. For example, the porous coating layer contains the dispersion medium at a concentration of about 5 ppm or less. Alternatively, the porous coating layer may consist of an acrylic polymer binder, a copolymer binder, and inorganic particles. In the process of removing the dispersion medium, a plurality of pores are formed on the surface and inside the porous coating layer. These pores include interstitial volumes formed between the inorganic particles and have a structure that allows fluid to pass through by forming a three-dimensional network.

[0052] According to one embodiment of the present invention, the thickness of the porous coating layer is approximately 0.1 μm to 10 μm. For example, the thickness of the porous coating layer may be approximately 0.5 μm to 9.5 μm, approximately 1.0 μm to 9.0 μm, approximately 1.5 μm to 8.5 μm, approximately 2.0 μm to 8.0 μm, approximately 2.5 μm to 7.5 μm, approximately 3.0 μm to 7.0 μm, approximately 3.5 μm to 6.5 μm, approximately 4.0 μm to 6.0 μm, or approximately 4.5 μm to 5.5 μm. Alternatively, the thickness of the porous coating layer may be approximately 0.5 μm to 5 μm. Alternatively, the thickness of the porous coating layer may be approximately 0.5 μm to 2 μm. 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.

[0053] According to an embodiment of the present invention, the porous coating layer includes inorganic particles having a polymer coating layer containing an amine group formed on the surface and a polymer binder, and at least a part of the polymer binder is crosslinked with the polymer containing the amine group. For example, the polymer binder may include two or more different types of polymer binders, and one or more of them can be crosslinked with the polymer containing the amine group. The polymer binder that crosslinks with the polymer containing the amine group forms a physical bond or a chemical bond with the polymer containing the amine group. Alternatively, the polymer binder that crosslinks with the polymer containing the amine group can be thermally crosslinked through the amine group. The polymer binder is bound to one or more inorganic particles through crosslinking with the coating layer of the inorganic particles to form an interstitial volume. The polymer binder forms and maintains a stronger bond with the inorganic particles having the coating layer than with the inorganic particles without the coating layer, and the porous coating layer containing the polymer binder can exhibit a reduced thermal shrinkage rate in a high-temperature wet state.

[0054] According to an embodiment of the present invention, electrochemically stable inorganic particles are used. The inorganic particles are not particularly limited as long as no oxidation reaction and / or reduction reaction occurs within the operating voltage range of the electrochemical device (e.g., 0 to 5V based on Li / Li + reference). For example, when using inorganic particles with a high dielectric constant as the inorganic particles, it contributes to an increase in the dissociation degree of electrolyte salts in the liquid electrolyte, such as lithium salts, and improves the ionic conductivity of the electrolyte solution. For the reasons described above, it is preferable that the inorganic particles include high dielectric constant inorganic particles having a dielectric constant of 5 or more, preferably 10 or more. Non-limiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT, 0 < x < 1, 0 < y < 1), Pb(Mg 1 / 3 Nb 2 / 3)There are O3-PbTiO3 (PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, Al(OH)3, SiC, AlOOH, TiO2, or mixtures thereof, etc.

[0055] In addition, as the inorganic particles, inorganic particles having lithium ion transfer ability, that is, inorganic particles containing lithium element but having the function of moving lithium ions without storing lithium can be used. Non-limiting examples of inorganic particles having lithium ion transfer ability include 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 -based glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), Li 3.25 Ge 0.25 P 0.75 S4, etc., such as 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-based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5-based glass (Li x P y S z, (0 < x < 3, 0 < y < 3, 0 < z < 7), or a mixture thereof, etc.

[0056] Further, as the inorganic particles, inorganic particles having flame retardancy can be used, which can impart flame retardant properties to the separation membrane or prevent the temperature inside the electrochemical device from rising rapidly. Non-limiting examples of the flame-retardant inorganic particles include Sb2O3, Sb2O4, Sb2O5, SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, Zn2SnO4, ZnSnO3, ZnSn(OH)6, ZrO2, Y2O3, SiO2, Al2O3, AlOOH, Al(OH)3, SiC, TiO2, H3BO3, HBO2, and mixtures thereof.

[0057] According to one embodiment of the present invention, the average particle size (D50) of the inorganic particles is about 50 nm or more and 5,000 nm or less. For example, the average particle size (D50) of the inorganic particles can be about 100 nm or more and 4,500 nm or less, about 200 nm or more and 4,000 nm or less, about 300 nm or more and 3,000 nm or less, about 400 nm or more and 2,000 nm or less, or about 500 nm or more and 1,000 nm or less. Alternatively, the average particle size of the inorganic particles can be about 200 nm or more and 500 nm or less. When the average particle size of the inorganic particles is less than about 50 nm, as the specific surface area increases, a polymer binder for bonding between the inorganic particles is further required, which is disadvantageous in terms of electrical resistance. When the average particle size of the inorganic particles exceeds about 5,000 nm, the uniformity of the coating layer surface decreases, and damage to the porous polymer substrate or electrode during lamination may occur.

[0058] According to one embodiment of the present invention, the aspect ratio of the inorganic particles is about 1 to 2. For example, the aspect ratio of the inorganic particles may be about 1.1 to 1.9, about 1.2 to 1.8, about 1.3 to 1.7, or about 1.4 to 1.6. By adjusting the aspect ratio of the inorganic particles within the above range, the movement of the polymer binder through the voids between the inorganic particles is facilitated, and a porous coating layer containing interstitial volumes that allow lithium ions to move can be formed.

[0059] According to one embodiment of the present invention, the BET specific surface area of ​​the inorganic particles is approximately 5 m². 2 / g or more 25m 2 It is less than / g. For example, the BET specific surface area of ​​the inorganic particles is approximately 6 m². 2 / g or more 24m 2 / g or less, about 7m 2 / g or more 23m 2 / g or less, about 8m 2 / g or more 22m 2 / g or less, about 9m 2 / g or more 21m 2 / g or less, about 10m 2 / g or more 20m 2 / g or less, approximately 11m 2 / g or more 19m 2 / g or less, about 12m 2 / g or more 18m 2 / g or less, approximately 13m 2 / g or more 17m 2 / g or less, or approximately 14m 2 / g or more 26m 2 It may be less than / g. By adjusting the BET specific surface area of ​​the inorganic particles within the range described above, the movement of the polymer binder through the voids between the inorganic particles can be controlled.

[0060] According to one embodiment of the present invention, the density of the inorganic particles is approximately 3 g / cm³. 3 More than 9g / cm 3 The following applies: For example, the density of the inorganic particles is approximately 3.5 g / cm³. 3 More than 8.5g / cm3 Below, about 4g / cm 3 More than 8g / cm 3 Below, about 4.5g / cm 3 More than 7.5g / cm 3 Below, about 5g / cm 3 More than 7g / cm 3 The following, or approximately 5.5 g / cm³ 3 More than 6.5g / cm 3 It may be as follows: Or, the density of the inorganic particles is about 3 g / cm³. 3 More than 4.5g / cm 3 The following is possible: By adjusting the density of the inorganic particles within the range described above, uniform dispersion of inorganic particles within the porous coating layer can be achieved, and thermal shrinkage of the porous polymer substrate can be reduced.

[0061] According to one embodiment of the present invention, the inorganic particles have a coating layer formed on their surface that includes a polymer containing amine groups. For example, the inorganic particles and the coating layer can form a core-shell structure. Alternatively, the inorganic particles may be spherical, and the coating layer may completely enclose the inorganic particles with a certain thickness.

[0062] According to one embodiment of the present invention, the polymer containing the amine group contains both a catechol group and an amine group. For example, the polymer containing the amine group may be one or more selected from dopamine and its derivatives. The polymer containing the amine group may be physically or chemically bonded to the inorganic particles via the catechol group to form a coating layer, exposing one or more amine groups on the surface of the coating layer. For example, the inorganic particles may contain one or more hydroxyl groups on their surface, or be surface-treated to have hydroxyl groups, and the polymer containing the amine group may form a coating layer through hydrogen bonding with the hydroxyl groups via the catechol group, exposing the amine group on the surface of the coating layer. The method of bonding the polymer containing the amine group to the inorganic particles is not limited thereto.

[0063] According to one embodiment of the present invention, the thickness of the coating layer formed on the surface of the inorganic particles is approximately 2 nm to 20 nm. For example, the thickness of the coating layer formed on the surface of the inorganic particles may be approximately 2 nm to 18 nm, approximately 4 nm to 16 nm, approximately 6 nm to 14 nm, or approximately 8 nm to 12 nm. Alternatively, the thickness of the coating layer may be approximately 2 nm to 5 nm. By adjusting the thickness of the coating layer within the above range, it is possible to prevent the coating layer from detaching from the inorganic particles under the operating conditions of the electrochemical element, and to form crosslinks with the polymer binder to reduce the thermal shrinkage of the separation film.

[0064] According to one embodiment of the present invention, the polymer binder crosslinks with the polymer containing the amine group and comprises one or more selected from the group consisting of dextrin, polyetheretherketone (PEEK), polyethersulfone (PES), and polyacrylamide (PAAm). The polymer binder is crosslinked with the polymer containing the amine group via a carboxyl group. Alternatively, the polymer containing the amine group is dopamine, and the polymer binder forms hydrogen bonds with the hydroxyl group of dopamine via the amine group. The polymer binder has a high glass transition temperature (Tg) or decomposition temperature (Td), which imparts dimensional stability to the separation membrane at high temperatures, and at the same time forms bonds with the coating layer to prevent deformation of the porous coating layer.

[0065] According to one embodiment of the present invention, the polymer binder crosslinks with the polymer containing the amine group and comprises a monomer (co)polymer selected from the group consisting of acrylate, acrylic acid, maleic acid, itaconic acid, methacrylic acid, and carboxyethyl acrylate. The (co)polymer may contain a carboxyl group and can be crosslinked by forming an amide bond with the amine group exposed on the surface of the coating layer. The polymer binder can form a stable bond with one or more inorganic particles to form interstitial volume and at the same time prevent deformation of the porous coating layer.

[0066] According to one embodiment of the present invention, the polymer binder further comprises a fluorine-based polymer binder in addition to one that can crosslink with the polymer containing the amine group. For example, the fluorine-based polymer binder may be a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride and another copolymerizable monomer, or a mixture thereof.

[0067] According to one embodiment of the present invention, the polymer binder contains, based on the total weight of the polymer binder, a polymer that can crosslink with the polymer containing the amine group in an amount of about 60% to 80% by weight. For example, about 66% to 75% by weight of the polymer binder can be crosslinked with the polymer containing the amine group, i.e., with the coating layer formed on the surface of the inorganic particles. By adjusting the content of the polymer binder that is crosslinked with the inorganic particles on which the coating layer is formed within the range described above, it is possible to form a porous coating layer that does not deform in a high-temperature wet state while allowing lithium ions to pass through.

[0068] According to one embodiment of the present invention, the porous coating layer contains inorganic particles in an amount of about 90% to 95% by weight relative to the total weight of the porous coating layer. For example, the porous coating layer may contain inorganic particles in an amount of about 90% to 95% by weight, about 91% to 92% by weight, or about 93% to 94% by weight. Alternatively, the porous coating layer may contain inorganic particles in an amount of about 92% to 94% by weight. By adjusting the content of inorganic particles within the above ranges, a separation membrane having mechanical strength and thermal properties suitable for cylindrical batteries can be manufactured.

[0069] According to one embodiment of the present invention, the loading amount of the porous coating layer per unit area of ​​the porous polymer substrate in the separation membrane is approximately 5.5 g / m². 2 More than 8.0g / m 2 The following applies: For example, the loading amount for a porous coating layer is approximately 5.7 g / m². 2 More than 7.8g / m 2Below, approximately 5.9g / m 2 More than 7.6g / m 2 Below, approximately 6.1g / m 2 More than 7.4g / m 2 Below, about 6.3g / m 2 More than 7.2g / m 2 Below, about 6.5g / m 2 More than 7.0g / m 2 The following, or approximately 6.7 g / m 2 More than 6.8g / m 2 The following may be true: Alternatively, the loading amount of the porous coating layer may be approximately 5.6 g / m². 2 More than 6.5g / m 2 The following is possible: By adjusting the loading amount of the porous coating layer within the range described above, the durability of the separation membrane against the electrolyte can be ensured, and thermal shrinkage in a high-temperature wet state can be reduced.

[0070] According to one embodiment of the present invention, the separation membrane further comprises a second polymer coating layer formed on the surface of the porous coating layer. For example, the second polymer coating layer may contain a polymer containing an amine group. Alternatively, the polymer containing an amine group in the second polymer coating layer may contain both a catechol group and an amine group. For example, the polymer containing an amine group may be one or more selected from dopamine and its derivatives.

[0071] According to one embodiment of the present invention, the second polymer coating layer is formed by applying a polymer solution containing amine groups to the surface of a separation membrane comprising a porous polymer substrate and a porous coating layer, and then drying it. For example, a separation membrane can be obtained by immersing the separation membrane in a polymer solution containing amine groups to form the second polymer coating layer containing the polymer.

[0072] For example, the polymer containing the amine group may be dopamine, and a separation membrane containing a porous polymer substrate and a porous coating layer can be immersed in a dopamine solution to obtain a separation membrane in which a second polymer coating layer containing polydopamine is formed. The immersion time may be about 40 to 48 hours, and the loading amount of polydopamine contained in the second polymer coating layer is about 0.0005 g / m². 2 More than 0.01g / m 2 The following is possible: By adjusting the amount of polydopamine contained in the second polymer coating layer within the range described above, the thermal shrinkage rate of the wet state of the separation membrane can be reduced even under high-temperature conditions.

[0073] According to one embodiment of the present invention, at least a portion of the polymer containing amine groups in the second polymer coating layer is crosslinked with the polymer binder in the porous coating layer. For example, the polymer binder contained in the porous coating layer can be thermally crosslinked via the amine groups. The crosslinking can be performed by applying the polymer solution containing the amine groups to the surface of the porous coating layer and then drying it, or by performing a separate heat treatment after drying. The porous coating layer and the second polymer coating layer can form and maintain a stronger bond through crosslinking between the polymers, and the separation membrane in which the bond is formed can exhibit a further reduced thermal shrinkage rate in a high-temperature wet state.

[0074] According to one embodiment of the present invention, the second polymer coating layer further comprises dextrin. The dextrin imparts durability to the second polymer coating layer and improves the dimensional stability of the separation membrane including the second polymer coating layer. The dextrin uniformly disperses the polymer containing the amine group, and maintains dimensional stability even when electrodes, which are arranged to adhere to or adjacent to the separation membrane, contract or expand and external forces are applied. Alternatively, the dextrin may be cyclodextrin, for example, one or more selected from the group consisting of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0075] According to one embodiment of the present invention, the second polymer coating layer contains the polymer containing the amine group and the dextrin in a weight ratio of about 1:500 to 1:1000. For example, the second polymer coating layer may contain polydopamine and dextrin in a weight ratio of about 1:600 ​​to 1:900, or about 1:700 to 1:800. By adjusting the content of polydopamine and dextrin within the above range, it is possible to simultaneously achieve uniform dispersion of polydopamine contained in the porous coating layer and a reduction in the thermal shrinkage rate of the wet state of the separation membrane at high temperatures.

[0076] According to one embodiment of the present invention, the separation membrane for the electrochemical element has an air permeability of approximately 50 s / 100 cc to approximately 150 s / 100 cc. For example, the air permeability of the separation membrane may be approximately 60 s / 100 cc to 140 s / 100 cc, approximately 70 s / 100 cc to 130 s / 100 cc, approximately 80 s / 100 cc to 120 s / 100 cc, or approximately 90 s / 100 cc to 110 s / 100 cc. Alternatively, the air permeability of the separation membrane may be approximately 100 s / 100 cc to 120 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.

[0077] According to one embodiment of the present invention, the thermal shrinkage rate of the separation membrane for the electrochemical element is less than about 10%. For example, the thermal shrinkage rate of the separation membrane in a wet state is less than about 10%. For example, the thermal shrinkage rate in a wet state is the dimensional change rate based on the separation membrane being exposed to about 135°C for about 30 minutes while impregnated in an electrolyte.

[0078] According to one embodiment of the present invention, when a cell is manufactured using the separation membrane for the electrochemical element, the cell has an electrical resistance of approximately 0.5 Ohm to 1.5 Ohm. For example, the electrical resistance of the cell may be approximately 0.6 Ohm to 1.4 Ohm, approximately 0.7 Ohm to 1.3 Ohm, approximately 0.8 Ohm to 1.2 Ohm, or approximately 0.9 Ohm to 1.1 Ohm. Alternatively, the electrical resistance of the cell may be approximately 0.6 Ohm to 0.8 Ohm.

[0079] Another embodiment of the present invention provides an electrochemical element comprising a positive electrode, a negative electrode, and a separation membrane interposed between the positive and negative electrodes, wherein the separation membrane is the separation membrane for the electrochemical element described above. The electrochemical element can be manufactured by inserting the electrode assembly, comprising the positive electrode, the negative electrode, and the separation membrane interposed between the positive and negative electrodes, 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, prismatic, coin-type, or pouch-type lithium secondary battery.

[0080] According to one embodiment of the present invention, the positive electrode and the negative electrode are coated with an electrode active material applied to and dried on at least one surface of their respective current collectors. The current collector can be made of a material that is conductive without causing a chemical change 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 body, or foam.

[0081] According to an embodiment of the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The positive electrode active material includes layered compounds such as lithium manganese composite oxides (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x O4 (where x is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3), Ni-site type lithium nickel oxide represented by; chemical formula LiMn 1-x M x O2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1), or lithium manganese composite oxide represented by Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a part of Li in the chemical formula is substituted with an alkaline earth metal ion; disulfide compound; one or a mixture of two or more of Fe2(MoO4)3 may be included.

[0082] According to an embodiment of the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The negative electrode uses, as the negative electrode active material, carbon such as lithium metal oxide, graphitized carbon, graphite-based carbon; LixFe2O3 (0 ≦ x ≦ 1), Li x WO2 (0 ≦ x ≦ 1), silicon-based materials such as Si, SiO x (0 < x < 2), SiC, Si alloy; Sn x Me 1-x Me’ y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8), etc. metal composite oxides; lithium metal; lithium alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; may contain one or a mixture of two or more selected from titanium oxides.

[0083] According to one embodiment of the present invention, the conductive material is any one selected from the group consisting of graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whisker, conductive metal oxide, carbon nanotube, activated carbon, and polyphenylene derivative, or a mixture of two or more of these conductive materials. The carbon nanotube has a cylinder shape with a nanosize diameter of a graphite sheet and has a sp 2 bonding structure, and exhibits conductor or semiconductor characteristics depending on the angle and structure of the winding of the graphite sheet. Carbon nanotubes can be classified into single-walled carbon nanotubes (SWCNT, single-walled carbon nanotube), double-walled carbon nanotubes (DWCNT, double-walled carbon nanotube), and multi-walled carbon nanotubes (MWCNT, multi-walled carbon nanotube) according to the number of bonded walls forming the wall, and these carbon nanotubes can be appropriately selected according to the use of the dispersion liquid. For example, the conductive material 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 of these conductive materials.

[0084] According to one embodiment of the present invention, the binder resin can be one that is commonly used for electrodes of electrochemical elements. Non-limiting examples of such binder resins include polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate copolymer, 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.

[0085] According to one embodiment of the present invention, the electrolyte is A + B- A salt with a structure like this, + is Li + kaNa + , 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 those listed above, or ions consisting of combinations thereof, are 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 (γ-butyrolactone), or mixtures thereof.

[0086] For example, the electrolyte may contain a solvent in which the weight ratio of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) is 3 / 7, or a solvent in which the weight ratio of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) is 20 / 5 / 75, thereby maximizing the dimensional stability of the separation membrane according to the above example.

[0087] According to one embodiment of the present invention, the electrochemical element including the electrode assembly is a lithium secondary battery. Furthermore, the separation membrane for the electrochemical element including the electrode assembly according to the present invention can be similarly applied to a sodium secondary battery manufactured using sodium ions as the positive electrode active material.

[0088] Furthermore, unlike the lithium secondary battery described above, the lithium secondary battery according to another embodiment of the present invention may be an all-solid-state battery.

[0089] The battery can be used as a unit cell, and can be used as a battery module including the unit cell, a battery pack including the battery module, or a device including the battery pack as a power source. Examples of such devices include, but are not limited to, small devices such as computers, mobile phones, and power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs) that are powered by electric motors; electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and medium to large devices such as power storage systems.

[0090] The present invention will be described in more detail below with reference to examples and experimental examples. The following examples and comparative experimental examples are for illustrative purposes only, and the examples of the present invention can be modified into various different forms, and the present invention is not limited to the following examples and experimental examples.

[0091] Example 1 [Preparation of inorganic particles on which a coating layer has been formed] 30 g of Al2O3 (particle size: 400 nm) and 2 g of dopamine (a polymer containing an amine group) were mixed in 1000 mL of a basic aqueous solution (Tris buffer, pH 8.5). After storage at 20°C for 4 hours, the mixture was repeatedly ultrasonically washed with secondary distilled water and completely dried at 50°C to obtain inorganic particles with a polydopamine coating layer (thickness: 2 nm) formed on them.

[0092] [Preparation of coating slurry] At room temperature (25°C), 1.5 g of polyacrylate as a polymer binder, 30 g of inorganic particles on which the polydopamine coating layer was formed, and 0.2 g of Si-based surfactant as an additive were added to 50 mL of water and stirred in a shaker for 60 minutes to produce a coating slurry in which the polymer binder and inorganic particles were dispersed.

[0093] [Preparation of porous polymer substrate] As a porous polymer substrate, (MI: 0.2g / 10min, T m A polyethylene film with a thickness of 9 μm was used, with a temperature of 135°C, porosity of 45%, and average pore size of 45 nm.

[0094] [Manufacturing of separation membranes] A polyethylene film is coated on both sides with the coating slurry using a bar coater, with each coating having a thickness of 2 μm and a loading amount of 6.3 g / m². 2 A coating layer was formed.

[0095] A polyethylene film with a coating layer was subjected to a low-temperature airflow of 50°C, and the process of removing the dispersion medium was repeated five times. The film was then dried at 100°C for 10 minutes to crosslink polydopamine and polyacrylic acid, producing a separation membrane with a total thickness of 13 μm.

[0096] Example 2 Polymaleic acid is used as the polymer binder, and the loading amount of the porous coating layer is 6.0 g / m². 2The separation membrane was manufactured using the same method as in Example 1, except that the following was done.

[0097] Example 3 Dextrin is used as the polymer binder, and the loading amount of the porous coating layer is 6.4 g / m². 2 The separation membrane was manufactured using the same method as in Example 1, except for the following:

[0098] Example 4 PAAm was used as the polymer binder, and the loading amount of the porous coating layer was 5.7 g / m². 2 The separation membrane was manufactured using the same method as in Example 1, except for the following:

[0099] Example 5 The separation membrane was manufactured using the same method as in Example 1, except that dextrin and PVdF-HFP were used as polymer binders in a weight ratio of 3:1.

[0100] Example 6 At room temperature (25°C), dopamine at a concentration of 2 mg / mL and dextrin at a concentration of 50 mg / mL were added to a 20 mM basic buffer (Tris-HCl buffer) in a Petri dish. However, the amount of added ingredients was adjusted so that the final ratio of dopamine to dextrin was 1:1000. Then, the lid of the Petri dish was partially opened to prepare a dopamine and dextrin solution with a dissolved oxygen content of 9 ppm and a pH of 8.

[0101] The separation membrane prepared in Example 1 was immersed in the solution for 48 hours, and then dried at 60°C for 12 hours to produce a separation membrane with a second polymer coating layer having a thickness of 0.5 μm.

[0102] Comparative Example 1 In the separation membrane for the electrochemical element of Example 1, the separation membrane was manufactured using the same method as in Example 1, except that the amount of inorganic particles (30 g) and dopamine (0.5 g) (coating layer thickness 1 nm) was adjusted during the production of the coating slurry.

[0103] Comparative Example 2 In the separation membrane for the electrochemical element of Example 1, the separation membrane was manufactured using the same method as in Example 1, except that polyurethane was used as the polymer binder.

[0104] Comparative Example 3 In the separation membrane for the electrochemical element of Example 1, the separation membrane was manufactured using the same method as in Example 1, except that inorganic particles on which the coating layer was not formed were used.

[0105] Comparative Example 4 In the separation membrane for the electrochemical element of Example 2, the separation membrane was manufactured using the same method as in Example 2, except that inorganic particles on which the coating layer was not formed were used.

[0106] Comparative Example 5 In the separation membrane for the electrochemical element of Example 2, the separation membrane was manufactured in the same manner as in Comparative Example 2, except that inorganic particles on which the coating layer was not formed were used.

[0107] Comparative Example 6 In the separation membrane for the electrochemical element of Example 5, the separation membrane was manufactured in the same manner as in Example 5, except that dextrin and PVdF-HFP were used as the polymer binder in a 1:1 weight ratio.

[0108] Experimental example: Confirmation of physical properties of separation membranes The physical properties of the separation membranes produced according to the examples and comparative examples are shown in Tables 1 and 2, respectively.

[0109] [Confirmation of improved thermal shrinkage rate in wet conditions] Separation membranes for the examples and comparative examples were prepared as 5cm x 5cm test pieces and inserted into 7cm x 10cm aluminum pouches. 1g of electrolyte was injected into each pouch, and the pouches were sealed.

[0110] The electrolyte used was a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a weight ratio of 3 / 7, with the additives 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.

[0111] The sealed pouch was placed in a convection oven at 135°C for 30 minutes, then the pouch was disassembled to obtain a separation membrane, and the thermal shrinkage rate in the TD direction was calculated according to [(length of the initial specimen - length after storage at 135°C / 0.5h) / (length of the initial specimen)] × 100 (%).

[0112] [Table 1]

[0113] [Table 2]

Claims

1. The material comprises a porous polymer substrate and a porous coating layer formed on at least one surface of the porous polymer substrate. The porous coating layer comprises inorganic particles and a polymer binder. The inorganic particles are formed by having a polymer coating layer containing amine groups formed on the surface of the inorganic particles. At least a portion of the polymer binder is crosslinked with the polymer containing the amine group, The polymer containing the amine group is dopamine or a derivative thereof. The thickness of the polymer coating layer is 2 nm to 20 nm. Based on the total weight of the polymer binder, the polymer crosslinked with the polymer containing the amine group is present in an amount of 60% to 80% by weight. Separation membrane for electrochemical devices.

2. The polymer binder is, The separation membrane for an electrochemical element according to claim 1, comprising one or more selected from the group consisting of dextrin and polyacrylamide.

3. The polymer binder is, The separation membrane for an electrochemical element according to claim 1, comprising a (co)polymer of monomers selected from the group consisting of acrylate, acrylic acid, maleic acid, itaconic acid, methacrylic acid, and carboxyethyl acrylate.

4. The loading amount of the porous coating layer per unit area of ​​the porous polymer substrate is 5.5 g / m². ２ ~8g / m ２ The separation membrane for an electrochemical element according to claim 1.

5. The porous coating layer is The separation membrane for an electrochemical element according to claim 1, wherein the inorganic particles are contained in an amount of 90% to 95% by weight relative to the total weight of the porous coating layer.

6. The material further comprises a second polymer coating layer formed on the surface of the porous coating layer, The second polymer coating layer is Contains polydopamine, The separation membrane for an electrochemical element according to claim 1, wherein the loading amount of polydopamine contained in the second polymer coating layer is 0.0005 g / m² or more and 0.01 g / m² or less.

7. The separation membrane for an electrochemical element according to claim 6, wherein the second polymer coating layer further contains dextrin.

8. 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 7.

Images