Separator and manufacturing method thereof

Abstract

One aspect of the present invention provides a separator that includes a porous support and a hydrophilic polymer applied to a surface of the porous support from a solution containing the hydrophilic polymer and a solvent, and that satisfies the following formula, and a method for producing the same. <expression> 0.015≦(C×D) / (A×B)≦0.65 In the above formula, A is the thickness (μm) of the porous support, B is the air permeability (Gurley, sec / 100 ml) of the porous support, C is the porosity (volume %) of the porous support, and D is the content (weight %) of the hydrophilic polymer in the solution.

Description

[Technical Field]

[0001] The present invention relates to a separator and a method for manufacturing the same, and more particularly to a separator for a lithium secondary battery having improved impregnation properties with an electrolyte solution and a method for manufacturing the same. [Background technology]

[0002] Lithium secondary batteries are widely used as power sources for various electrical products that require compactness and light weight, such as smartphones, laptops, and tablet PCs. As their application fields expand to include smart grids and medium- to large-sized batteries for electric vehicles, there is a demand for the development of lithium secondary batteries with large capacity, long life, and high stability.

[0003] As a means to achieve this goal, research and development is being actively conducted on separators with micropores that separate the positive and negative electrodes to prevent internal shorts and facilitate the movement of lithium ions during charging and discharging. In particular, microporous separators made of polyolefins such as polyethylene are advantageous in forming pores through thermally induced phase separation, are economical, and easily satisfy the physical properties required for separators.

[0004] Polyolefin-based separators, which have been widely used in the past, have problems with poor heat resistance and mechanical strength. To address these issues, a technology has been proposed in which a heat-resistant layer containing ceramic particles is coated on the surface of the separator. However, heat-resistant layers pose significant technical challenges related to air permeability and electrical conductivity (resistance), which are factors that critically affect separator performance. Forming a heat-resistant layer containing ceramic particles on the surface of a porous substrate improves the separator's heat resistance, but the ceramic particles contained in the heat-resistant layer block the pores in the porous substrate, reducing the separator's air permeability. This significantly reduces the ion transport pathways between the positive and negative electrodes, resulting in significant degradation of the charge and discharge performance of secondary batteries. Furthermore, when the heat-resistant layer is continuously exposed to the electrolyte inside the battery, the ceramic particles can partially and continuously detach from the porous substrate, gradually reducing the separator's heat resistance.

[0005] A lithium secondary battery has a structure in which an electrode assembly is formed by interposing a porous separator between a positive electrode and a negative electrode, each of which has an active material applied to an electrode current collector, and a non-aqueous electrolyte containing a lithium salt is impregnated into the electrode assembly.

[0006] Lithium secondary batteries are manufactured by fabricating an electrode assembly consisting of alternately stacked positive and negative electrodes with a separator between them, inserting the electrode assembly into a battery case consisting of a can or pouch of a certain size and shape, and finally injecting an electrolyte. The electrolyte penetrates between the positive and negative electrodes and the separator due to capillary force. However, due to the characteristics of the materials, the positive and negative electrodes and the separator are hydrophobic, while the electrolyte is hydrophilic. Therefore, improving the impregnation and wettability of the electrodes and separator with the electrolyte requires considerable time and strict process conditions. This limits the ability to balance and improve the electrolyte impregnation and process productivity.

[0007] To improve the electrolyte impregnation, methods such as injecting the electrolyte at a high temperature or injecting the electrolyte under pressure or vacuum have been used, but these methods have problems such as deformation of the electrode assembly and electrolyte due to heat, which can cause internal short circuits, etc. Furthermore, because this process is performed after the electrode assembly and the electrolyte are housed in a battery case, the electrode assembly can be impregnated with the electrolyte non-uniformly, and in particular, in the case of a jelly-roll type electrode assembly, non-uniform impregnation occurs between the center and outer portions of the winding, which can shorten the battery life. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a separator that can achieve a balance between electrolyte impregnation and process productivity, and a manufacturing method thereof. [Means for solving the problem]

[0009] One aspect of the present invention provides a separator that includes a porous support and a hydrophilic polymer that is applied to the surface of the porous support using a solution containing the hydrophilic polymer and a solvent, and satisfies the following formula: <expression> 0.015≦(C×D) / (A×B)≦0.65 In the above formula, A is the thickness (μm) of the porous support, B is the air permeability (Gurley, sec / 100 ml) of the porous support, C is the porosity (volume %) of the porous support, and D is the content (weight %) of the hydrophilic polymer in the solution.

[0010] In one embodiment, the thickness of the porous support may be 1 to 30 μm. In one embodiment, the porosity of the porous support may be 40 to 70% by volume. In one embodiment, the porous support may comprise one selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and combinations of two or more thereof.

[0011] In one embodiment, the hydrophilic polymer may be one selected from the group consisting of ethylene vinyl alcohol, polyvinyl alcohol, polyacrylic acid, polyoxyethylene-polyoxypropylene block copolymer, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl acetal, polyvinyl butyral, cellulose derivatives, glycerol, and combinations of two or more thereof. In one embodiment, the content of the hydrophilic polymer in the solution may be 0.05 to 3% by weight.

[0012] In one embodiment, the solvent is water, NMP (N-Methyl-2-pyrrolidone), acetone, DMF (N,N-dimethylformamide), DMSO (Dimethyl sulfoxide), CHP (Cyclohexyl-pyrrolidinone), N12P (N-dodecyl-pyrrolidone), benzyl benzoate, N8P (N-Octyl-pyrrolidone), DMEU (dimethyl-imidazolidinone), cyclohexanone, DMA (dimethylacetamide), NMF (N-Methyl Formamide), bromobenzene, chloroform, chlorobenzene, benzonitrile, quinoline, benzyl ether, ethanol, isopropyl alcohol, methanol, butanol, 2-ethoxyethanol, 2-butoxyethanol, 2-methoxypropanol, THF (tetrahydrofuran), ethylene glycol, pyridine, N-vinylpyrrolidone, methyl ethyl ketone, alpha-terpineol, formic acid, ethyl acetate, acrylonitrile, and combinations of two or more thereof.

[0013] In one embodiment, the length change rate in the machine direction (MD) of the electrolyte solution added dropwise to the surface of the separator may be 80% or more from immediately after the addition of the electrolyte solution to the surface of the separator until 3 minutes have elapsed. In one embodiment, the length change rate in the transverse direction (TD) of the electrolyte solution added dropwise to the surface of the separator may be 80% or more from immediately after the addition of the electrolyte solution to the surface of the separator until 3 minutes have elapsed.

[0014] Another aspect of the present invention provides a method for producing a separator, the method including: (a) preparing a porous support; and (b) preparing a solution containing a hydrophilic polymer and a solvent, and applying the solution to a surface of the porous support. [Effects of the Invention]

[0015] In one aspect of the present invention, a separator is provided by applying a hydrophilic polymer to a hydrophobic polyolefin-based separator to impart hydrophilicity, and by deriving and combining the thickness, air permeability, porosity, and concentration of the solution containing the hydrophilic polymer of the porous support constituting the separator as variables that optimize and achieve a predetermined level of electrolyte impregnation, the productivity of the process for applying the hydrophilic polymer, the hydrophilicity of the separator, and the resulting electrolyte impregnation can be balanced.

[0016] It should be understood that the effects of the present invention are not limited to the effects described above, but include all effects that can be inferred from the configuration of the invention described in the detailed description of the present invention or the claims. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0018] Throughout the specification, when a part is said to be "connected" to another part, this includes not only "directly connected" but also "indirectly connected" through an intervening member. Furthermore, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further comprise other components, unless otherwise specified.

[0019] A separator according to one aspect of the present invention may include a porous support and a hydrophilic polymer applied to a surface of the porous support using a solution containing a hydrophilic polymer and a solvent, and may satisfy the following formula: <expression> 0.015≦(C×D) / (A×B)≦0.65 In the above formula, A is the thickness (μm) of the porous support, B is the air permeability (Gurley, sec / 100 ml) of the porous support, C is the porosity (volume %) of the porous support, and D is the content (weight %) of the hydrophilic polymer in the solution.

[0020] The porous support is hydrophobic, but can be made hydrophilic by applying a certain amount of the hydrophilic polymer to the porous support. In this case, the thickness (A), air permeability (B), and porosity (C) of the porous support, and the concentration of the solution containing the hydrophilic polymer, i.e., the content (D) of the hydrophilic polymer in the solution, are derived as variables for optimizing and achieving the required electrolyte impregnation, and these variables are combined to achieve a balanced productivity of the process for applying the hydrophilic polymer, the hydrophilicity of the separator, and the resulting electrolyte impregnation.

[0021] The value of (C×D) / (A×B) according to the above formula is 0.015 to 0.65, preferably 0.02 to 0.6, and more preferably 0.02 to 0.4. If the value of (C×D) / (A×B) according to the above formula is less than 0.015, the required hydrophilicity and the resulting electrolyte impregnation ability cannot be imparted to the porous support, whereas if it exceeds 0.65, a portion of the hydrophilic polymer may close the pores of the porous support, increasing resistance and degrading the electrochemical properties of the battery.

[0022] The thickness of the porous support is 1 to 30 μm, preferably 3 to 25 μm, and more preferably 5 to 20 μm. If the thickness of the porous support is less than 1 μm, the mechanical properties and heat resistance of the separator may be reduced, while if it exceeds 30 μm, the resistance increases, which not only reduces the electrochemical properties of the battery but also reduces the productivity of the process required to introduce the hydrophilic polymer into the porous support.

[0023] The porous support has an air permeability (Gurley) of 40 to 300 seconds / 100 ml, preferably 50 to 200 seconds / 100 ml. If the air permeability of the porous support is less than 40 seconds / 100 ml, the mechanical properties and heat resistance of the separator may be reduced, while if it exceeds 300 seconds / 100 ml, the resistance increases, which not only reduces the electrochemical properties of the battery but also reduces the productivity of the process required to introduce the hydrophilic polymer into the porous support.

[0024] The porosity of the porous support is 40 to 70 vol%, preferably 45 to 70 vol%, and more preferably 50 to 60 vol%. Generally, the porosity of polyolefin-based porous separators for lithium secondary batteries is about 30 to 50 vol%, preferably about 30 to 40 vol%. Increasing the porosity of the porous support can increase the surface and / or internal pore area to which the hydrophilic polymer can be applied. The larger the area coated with the hydrophilic polymer, the more improved the electrolyte impregnation. If the porosity of the porous support is less than 40 vol%, the resistance increases, degrading the electrochemical characteristics of the battery and reducing the productivity of the process required to incorporate the hydrophilic polymer into the porous support. If the porosity exceeds 70 vol%, the mechanical properties and heat resistance of the separator may be reduced.

[0025] The porous support may include one selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and combinations of two or more thereof, and preferably includes a polyolefin resin such as polyethylene or polypropylene, and more preferably includes polyethylene, but is not limited thereto.

[0026] The hydrophilic polymer is applied to the surface of the porous support and the surfaces of the pores formed inside and / or outside the porous support through the solution, thereby imparting hydrophilicity to the porous support. The content of the hydrophilic polymer in the solution is 0.05 to 3 wt %, preferably 0.1 to 2 wt %, and more preferably 0.5 to 2 wt %. If the content of the hydrophilic polymer in the solution is less than 0.05 wt %, the required hydrophilicity and resulting electrolyte impregnation properties cannot be imparted to the porous support. If the content exceeds 3 wt %, a portion of the hydrophilic polymer may block the pores of the porous support, increasing resistance and degrading the electrochemical properties of the battery.

[0027] The hydrophilic polymer may be one selected from the group consisting of ethylene vinyl alcohol, polyvinyl alcohol, polyacrylic acid, polyoxyethylene-polyoxypropylene block copolymer, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl acetal, polyvinyl butyral, cellulose derivatives, glycerol, and combinations of two or more thereof, preferably ethylene vinyl alcohol, polyvinyl alcohol, and / or polyacrylic acid, and more preferably ethylene vinyl alcohol, but is not limited thereto. The ethylene vinyl alcohol has an ethylene unit content of 10 to 60 mol%, preferably 20 to 50 mol%, and more preferably 25 to 40 mol%.

[0028] The solution may further contain a solvent for appropriately dissolving the hydrophilic polymer, such as water, N-Methyl-2-pyrrolidone (NMP), acetone, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), cyclohexylpyrrolidinone (CHP), N-dodecylpyrrolidone (N12P), benzyl benzoate, N-octylpyrrolidone (N8P), dimethylimidazolidinone (DMEU), cyclohexanone, dimethylacetamide (DMA), or N-Methyl-2-pyrrolidone (NMF). The solvent may be one selected from the group consisting of ethylene vinyl alcohol (EVA), bromobenzene, chloroform, chlorobenzene, benzonitrile, quinoline, benzyl ether, ethanol, isopropyl alcohol, methanol, butanol, 2-ethoxyethanol, 2-butoxyethanol, 2-methoxypropanol, tetrahydrofuran (THF), ethylene glycol, pyridine, N-vinylpyrrolidone, methyl ethyl ketone, alpha-terpineol, formic acid, ethyl acetate, acrylonitrile, phenol, and combinations of two or more thereof. The solvent may be preferably DMSO and / or isopropyl alcohol. More preferably, when the hydrophilic polymer is ethylene vinyl alcohol, the solvent may be DMSO, which has excellent selective and specific solubility for ethylene vinyl alcohol and excellent impregnation ability for the porous support. The concentration of DMSO in the solvent may be substantially about 100%, but is not limited thereto.

[0029] The length change rate in the machine direction (MD) from immediately after the addition of the electrolyte droplets to the point where 3 minutes have elapsed is 80% or more, preferably 90% or more, and more preferably 95% or more. When the longest length in the machine direction (MD) immediately after the addition of the electrolyte droplets to the surface of the separator is MD1 and the longest length in the machine direction (MD) 3 minutes after the addition is MD2, the length change rate can be calculated by the following formula 1. <Expression 1> Length change rate in the machine direction (MD) (%) = (MD2-MD1) / (MD1) x 100

[0030] The length change rate in the transverse direction (TD) from immediately after the addition of the electrolyte droplets to the separator surface until 3 minutes has elapsed is 80% or more, preferably 90% or more, and more preferably 95% or more. When the longest length in the transverse direction (TD) immediately after the addition of the electrolyte droplets to the separator surface is TD1 and the longest length in the transverse direction (TD) 3 minutes after the addition is TD2, the length change rate can be calculated by the following equation 2. <Expression 2> Transverse (TD) length change rate (%) = (TD2-TD1) / (TD1) x 100

[0031] The electrolyte may be one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and a combination of two or more thereof, and preferably may be, but is not limited to, propylene carbonate (PC).

[0032] When the electrolyte is propylene carbonate (PC), if the length change rate in the machine direction (MD) and the transverse direction (TD) is less than 80%, it can be evaluated that the required electrolyte impregnation property cannot be achieved.

[0033] The ratio of the length change rate of the electrolyte droplets in the machine direction (MD) to the length change rate of the electrolyte droplets in the transverse direction (TD) may be greater than 1.0. That is, the length change rate of the electrolyte droplets in the machine direction (MD) may be greater than the length change rate of the electrolyte droplets in the transverse direction (TD). Furthermore, the ratio of the length change rate of the electrolyte droplets in the machine direction (MD) to the length change rate of the electrolyte droplets in the transverse direction (TD) is 1.1 or less, preferably 1.05 or less, and more preferably 1.03 or less. If the ratio of the length change rate of the electrolyte droplets in the machine direction (MD) to the length change rate of the electrolyte droplets in the transverse direction (TD) exceeds 1.1, the impregnation of the separator with the electrolyte may be non-uniform depending on the direction, which may result in a deterioration in the electrochemical properties of the battery.

[0034] The separator can be manufactured by a method including the steps of: (a) preparing a porous support; and (b) preparing a solution containing a hydrophilic polymer and a solvent, and applying the solution to the surface of the porous support.

[0035] The properties, types, effects, etc. of the porous support, the hydrophilic polymer, and the solvent are as described above.

[0036] In step (b), a solution containing the hydrophilic polymer and the solvent is prepared and then applied to the surface of the porous support by dipping, spraying, rolling, bar application, or a combination of two or more thereof, preferably by dipping, i.e., impregnation or immersion, but not limited thereto.

[0037] The time required for applying the solution can be adjusted depending on the thickness, air permeability, porosity, and concentration of the porous support, within the range of about 0.5 minutes to 48 hours, preferably about 0.5 to 10 minutes, and more preferably about 1 to 5 minutes. If the application time is less than 0.5 minutes, the required hydrophilicity cannot be imparted, and if it exceeds 48 hours, the productivity of the process for imparting hydrophilicity may be significantly reduced.

[0038] In addition, after step (b), the method may further include a step (c) of treating and washing the porous support with a solvent such as ethanol, water, or methylene chloride, followed by drying. The solvent used for washing is preferably ethanol, taking into consideration the external appearance of the separator and the time required for drying, but is not limited thereto. That is, when the solvent is ethanol, the time required for the subsequent drying can be shortened, defects formed on the surface of the dried separator can be minimized, and appropriate external appearance can be ensured.

[0039] Hereinafter, examples of the present invention will be described in detail. Example 1-1 A porous support with a thickness of 9 μm, an air permeability of 50 s / 100 ml (Gurley), and a porosity of 60% by volume was prepared. Ethylene vinyl alcohol (EVOH, Kuraray, EVAL, PE-32 mol%) was added to a dimethyl sulfoxide (DMSO) solvent and stirred at 80°C for 1 hour to produce a solution with an ethylene vinyl alcohol content of 0.5 wt%.

[0040] The porous support was immersed in the solution for 30 seconds, and then excess solution remaining on both sides of the porous support was removed using a silicone blade.The porous support was then immersed in ethanol for 60 seconds to wash it, and then placed in an oven preheated to 60°C and dried for 1 minute to produce a separator.

[0041] Example 1-2 A separator was manufactured in the same manner as in Example 1-1, except that the content of ethylene vinyl alcohol in the solution was changed to 0.75 wt %.

[0042] Examples 1-3 A separator was manufactured in the same manner as in Example 1-1, except that the content of ethylene vinyl alcohol in the solution was changed to 1 wt %.

[0043] Examples 1-4 A separator was manufactured in the same manner as in Example 1-1, except that the content of ethylene vinyl alcohol in the solution was changed to 3 wt %.

[0044] Comparative Example 1-1 A separator was manufactured in the same manner as in Example 1-1, except that the content of ethylene vinyl alcohol in the solution was changed to 5 wt %. The manufacturing conditions of the separators according to the examples and comparative examples are shown in Table 1 below. - Thickness (μm): The thickness of the porous support was measured using a micro thickness measuring instrument. Air permeability (Gurley, seconds / 100 ml): Using Asahi Seiko's Gurley Densometer EGO2-5 model, the time it takes for 100 ml of air to pass through the porous support at a measurement pressure of 0.025 MPa was measured. Porosity (%): The porosity of the porous support was measured using a capillary porometer manufactured by PMI Corporation in accordance with ASTM F316-03.

[0045] [Table 1]

[0046] Experimental Example 1 The electrolyte impregnation of the separators prepared in the examples and comparative examples was measured as follows: Propylene carbonate (PC) solution was used as the electrolyte, and 2 μL of the propylene carbonate solution was dropped onto the surface of the separator. Immediately after the drop, the droplet sizes (MD1, TD1) and the droplet sizes (MD2, TD2) of the dispersed droplets after 3 minutes were measured along the machine direction (MD) and the cross direction (TD). The results are shown in Table 2 below.

[0047] [Table 2]

[0048] Referring to Table 2, both the Examples and Comparative Examples were evaluated to have good electrolyte impregnation properties. However, in the case of the separator according to Comparative Example 1-1, the excessive amount of EVOH impregnated and coated blocked the pores of the separator, resulting in reduced air permeability and ionic conductivity.

[0049] Example 2-1 A porous support with a thickness of 20 μm, an air permeability of 180 s / 100 ml (Gurley), and a porosity of 50% by volume was prepared. Ethylene vinyl alcohol (EVOH, Kuraray, EVAL, PE-32 mol%) was added to a dimethyl sulfoxide (DMSO) solvent and stirred at 80°C for 1 hour to produce a solution with an ethylene vinyl alcohol content of 1.5 wt%.

[0050] The porous support was immersed in the solution for 30 seconds, and then excess solution remaining on both sides of the porous support was removed using a silicone blade.The porous support was then immersed in ethanol for 60 seconds to wash it, and then placed in an oven preheated to 60°C and dried for 1 minute to produce a separator.

[0051] Example 2-2 A separator was manufactured in the same manner as in Example 2-1, except that the content of ethylene vinyl alcohol in the solution was changed to 2 wt %.

[0052] Example 2-3 A separator was manufactured in the same manner as in Example 2-1, except that the porous support was immersed in the solution for 1 minute.

[0053] Examples 2-4 A separator was manufactured in the same manner as in Example 2-2, except that the porous support was immersed in the solution for 1 minute.

[0054] Comparative Example 2-1 A separator was manufactured in the same manner as in Example 2-1, except that the content of ethylene vinyl alcohol in the solution was changed to 1 wt %.

[0055] Comparative Example 2-2 A separator was manufactured in the same manner as in Comparative Example 2-1, except that the porous support was immersed in the solution for 3 minutes.

[0056] Comparative Example 2-3 A separator was manufactured in the same manner as in Comparative Example 2-1, except that the porous support was immersed in the solution for 5 minutes.

[0057] Comparative Example 2-4 A separator was manufactured in the same manner as in Comparative Example 2-1, except that the porous support was immersed in the solution for 10 minutes. The manufacturing conditions of the separators according to the examples and comparative examples are shown in Table 3 below.

[0058] [Table 3]

[0059] Experimental Example 2 The electrolyte impregnation of the separators prepared in the examples and comparative examples was measured in the same manner as in Experimental Example 1, and the results are shown in Table 4 below.

[0060] [Table 4]

[0061] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention may be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not limiting. For example, each component described as a single component may be implemented in a distributed form, and similarly, each component described as a distributed component may be implemented in a combined form.

[0062] The scope of the present invention is defined by the following claims, and it should be understood that all modifications and variations derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.

Claims

1. a porous support; A separator comprising a hydrophilic polymer and a hydrophilic polymer applied to a surface of the porous support using a solution containing a hydrophilic polymer and a solvent, Satisfy the following formula, The length change rate in the machine direction (MD) from immediately after the electrolytic solution droplets are added to the surface of the separator until 3 minutes have elapsed is 80% or more, The length change rate in the transverse direction (TD) of the separator is 80% or more from immediately after the electrolytic solution droplets are added to the surface of the separator until 3 minutes have elapsed. Separator. <Formula> 0.015≦(C×D) / (A×B)≦0.65 In the above formula, A is the thickness of the porous support (μm), B is the air permeability of the porous support (Gurley, sec / 100 ml); C is the porosity (vol %) of the porous support; D is the content (wt %) of the hydrophilic polymer in the solution.

2. The separator according to claim 1, wherein the porous support has a thickness of 1 to 30 μm.

3. 2. The separator according to claim 1, wherein the porosity of the porous support is 40 to 70% by volume.

4. 2. The separator according to claim 1, wherein the porous support comprises one selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and combinations of two or more thereof.

5. 2. The separator according to claim 1, wherein the hydrophilic polymer is one selected from the group consisting of ethylene vinyl alcohol, polyvinyl alcohol, polyacrylic acid, polyoxyethylene-polyoxypropylene block copolymer, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl acetal, polyvinyl butyral, cellulose derivatives, glycerol, and combinations of two or more thereof.

6. 2. The separator according to claim 1, wherein the content of the hydrophilic polymer in the solution is 0.05 to 3% by weight.

7. The solvent may be water, NMP (N-Methyl-2-pyrrolidone), acetone, DMF (N,N-dimethylformamide), DMSO (Dimethyl sulfoxide), CHP (Cyclohexyl-pyrrolidone), N12P (N-dodecyl-pyrrolidone), benzyl benzoate, N8P (N-Octyl-pyrrolidone), DMEU (dimethyl-imidazolidinone), cyclohexanone, DMA (dimethylacetamide), NMF (N-Methyl 2. The separator according to claim 1, wherein the solvent is one selected from the group consisting of: benzophenone, benzotriazole, benzophenone-1, benzotriazole, benzotriazole-2, benzotriazole-3, benzotriazole-4, benzotriazole-5, benzotriazole-6, benzotriazole-7, benzotriazole-8, benzotriazole-9, benzotriazole-10, benzotriazole-11, benzotriazole-12, benzotriazole-13, benzotriazole-14, benzotriazole-15, benzotriazole-16, benzotriazole-17, benzotriazole-18, benzotriazole-19, benzotriazole-20, benzotriazole-21, benzotriazole-22, benzotriazole-23, benzotriazole-24, benzotriazole-25, benzotriazole-26, benzotriazole-27, benzotriazole-28, benzotriazole-29, benzotriazole-30, benzotriazole-31, benzotriazole-32, benzotriazole-33, benzotriazole-34, benzotriazole-35, benzotriazole-36, benzotriazole-37, benzotriazole-38, benzotriazole-39, benzotriazole-40, benzotriazole-41, benzotriazole-42, benzotriazole-43, benzotriazole-44, benzotriazole-45, benzotriazole-46, benzotriazole-47, benzotriazole-48, benzotriazole-49, benzotriazole-51, benzotriazole-52, benzotriazole-53, benzotriazole-54, benzotriazole-55, benzotriazole-55, benzotriazole-55, benzotriazole-55, benzotriazole-55, benzotriazole-56, benzotriazole-57, benzo

8. A method for producing the separator according to any one of claims 1 to 7, comprising the steps of: (a) providing a porous support; (b) preparing a solution containing a hydrophilic polymer and a solvent, and applying the solution to the surface of the porous support.

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