Separator for electrochemical element, and electrochemical element with the same

Abstract

To provide a separator for an electrochemical element, which is excellent in compressive resistance, and the electrochemical element with the same.SOLUTION: The present invention relates to a separator for an electrochemical element, which is excellent in compressive resistance, and the electrochemical element with the same. The separator for the electrochemical element includes a polymer layer which is positioned on at least one surface of a porus polymer-based material and which includes a binder polymer having a cross-linked structure including a structure expressed by the following chemical formula 1.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a separator for an electrochemical element and an electrochemical element including the separator.

[0002] This application claims priority based on Korean Patent Application No. 10-2021-0127572, filed on September 27, 2021, and the entire contents disclosed in the specification and drawings of that application are incorporated herein by reference. [Background technology]

[0003] In recent years, interest in energy storage technology has been growing. As the range of applications for energy storage technology expands to include mobile phones, video cameras, laptops, and even electric vehicles, there is a growing need for higher energy density batteries used as power sources for these electronic devices. Secondary batteries are the type of battery that can best meet this need, and research into them is currently being actively conducted.

[0004] Such a secondary battery generally includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a non-aqueous electrolyte solution containing an electrolyte salt and an organic solvent, and a separator sandwiched between the positive electrode and the negative electrode to electrically insulate them.

[0005] However, when laminating a separator and electrodes to manufacture a secondary battery, the separator may be locally compressed due to heat and pressure. Furthermore, the separator may also be locally compressed due to volume expansion that occurs with charge-discharge cycles. This may result in deterioration of the separator's physical properties, such as its voltage resistance.

[0006] In particular, in recent years, there has been an increase in the use of silicon instead of graphite in the negative electrode in order to increase the energy density of secondary batteries. However, these materials have a high hardness, which could further increase the problems associated with separator compression.

[0007] For this reason, there is currently a great need for separators with excellent compression resistance. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide a separator for an electrochemical element having excellent compression resistance, and an electrochemical element including the separator. [Means for solving the problem]

[0009] In order to solve the above problems, according to one aspect of the present invention, there is provided a separator for an electrochemical element having the following features.

[0010] The first aspect is a porous polymer substrate; a polymer layer located on at least one surface of the porous polymer substrate and including a binder polymer having a crosslinked structure; Including, The crosslinked binder polymer relates to a separator for an electrochemical device, characterized by having a structure represented by the following Chemical Formula 1: [ka] In the above chemical formula 1, The R1 and R2 each independently represent a substituted or unsubstituted C1 to C 10 Alkylene group, substituted or unsubstituted C3-C 10 and substituted or unsubstituted C6-C 20 and The n is 1 to 200.

[0011] In a second aspect, in the separator for an electrochemical element according to the first aspect, the binder polymer having a crosslinked structure may include a crosslinked product of a boron-containing compound and a hydroxy group-containing binder polymer.

[0012] A third aspect is the separator for an electrochemical element according to the second aspect, wherein the boron-containing compound may include borax, boric acid, lithium borate, potassium borate, or two or more of these.

[0013] A fourth aspect is the separator for an electrochemical element according to the second or third aspect, The hydroxy-containing binder polymer may include poly(vinyl alcohol), poly(ethylene glycol), or all of these.

[0014] In a fifth aspect, in the separator for an electrochemical element according to any one of the second to fourth aspects, a weight ratio of the boron-containing compound to the hydroxy group-containing binder polymer may be 30:70 to 70:30.

[0015] According to a sixth aspect, in the separator for an electrochemical element according to any one of the first to fifth aspects, the binder polymer having a crosslinked structure may include a structure represented by the following Chemical Formula 2: [ka] In the above chemical formula 2, m is 1 to 200.

[0016] According to a seventh aspect, in the separator for an electrochemical device according to any one of the first to sixth aspects, a thickness reduction rate of the separator for an electrochemical device may be 4% or less.

[0017] In order to solve the above problems, according to one aspect of the present invention, there is provided an electrochemical device having the following configuration.

[0018] The eighth aspect is a positive electrode, a negative electrode, and a separator sandwiched between the positive electrode and the negative electrode; The present invention relates to an electrochemical device, wherein the separator is the separator for an electrochemical device according to any one of the first to seventh aspects. [Effects of the Invention]

[0019] The separator for an electrochemical device according to an embodiment of the present invention may have excellent compression resistance by including a binder polymer having a crosslinked structure having the structure of Chemical Formula 1. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in the specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as having meanings and concepts corresponding to the technical ideas of the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best explain the invention.

[0021] Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can be substituted therefor at the time of this application.

[0022] A separator for an electrochemical element according to one aspect of the present invention comprises: a porous polymer substrate; a polymer layer located on at least one surface of the porous polymer substrate and including a binder polymer having a crosslinked structure; Including, The crosslinked binder polymer is characterized by having a structure represented by the following Chemical Formula 1: [ka] In the above chemical formula 1, The R1 and R2 each independently represent a substituted or unsubstituted C1 to C 10Alkylene group, substituted or unsubstituted C3-C 10 and substituted or unsubstituted C6-C 20 and The n is 1 to 200.

[0023] The porous polymer substrate can be any material that can be used as a separator for an electrochemical device. Such a porous polymer substrate is a thin film containing a polymer material. Non-limiting examples of the polymer material include at least one polymer resin, such as polyolefin resin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene. The porous polymer substrate can be a nonwoven fabric or porous polymer film formed from the polymer material, or a laminate of two or more of these materials. Specifically, the porous polymer substrate can be any one of the following a) to e):

[0024] a) a porous film formed by melting and extruding a polymer resin; b) a multilayer film in which two or more porous films of a) are laminated; c) a nonwoven web produced by accumulating filaments obtained by melting / spinning a polymer resin; d) a multilayer film in which two or more layers of the nonwoven fabric web of c) are laminated; e) A porous membrane having a multilayer structure containing two or more of the above a) to d).

[0025] In one embodiment of the present invention, the thickness of the porous polymer substrate may be 5 μm to 50 μm. Although the thickness of the porous polymer substrate is not particularly limited to the above range, when the thickness is within the above range, it is possible to ensure energy density while preventing the problem of the separator being easily damaged during use of the battery.

[0026] Meanwhile, the pore size and porosity of the pores present in the porous polymer substrate are not particularly limited either, but may be 0.01 μm to 50 μm and 10% to 95%, respectively.

[0027] In the present invention, the porosity and pore size of the porous polymer substrate can be measured by a BET 6-point method using a scanning electron microscope (SEM) image, a mercury porosimeter, a capillary flow porometer, or a pore size distribution analyzer (Belsorp-II mini, manufactured by Bell Japan Co., Ltd.) in accordance with a nitrogen gas adsorption flow method. In this case, it is more preferable to use a capillary flow pore size distribution analyzer.

[0028] The polymer layer is disposed on at least one surface of the porous polymer substrate. For example, the polymer layer may be disposed on one or both surfaces of the porous polymer substrate. The polymer layer includes a crosslinked binder polymer having the structure of Formula 1.

[0029] When laminating a separator and an electrode to manufacture an electrochemical device with the separator and electrode stacked together, the separator may be locally compressed due to the heat and pressure applied during the lamination process. For example, the separator may be locally compressed due to the heat and pressure applied when laminating the separator and electrode under conditions of approximately 7.8 MPa and 70°C for 10 seconds. Furthermore, the separator may also be locally compressed due to volume expansion that occurs during charge-discharge cycles.

[0030] If the thickness reduction rate of the separator for electrochemical elements is 10% or more, the pores of the separator may shrink, which may result in a decrease in the output and life characteristics of the battery, and / or an increased risk of short-circuiting of the electrodes.

[0031] The separator for an electrochemical device according to one embodiment of the present invention includes the binder polymer having a crosslinked structure, which has excellent elasticity, and thus may have improved compression resistance.

[0032] For example, the thickness reduction rate of the separator for an electrochemical device may be 4% or less. In particular, the thickness reduction rate of the separator for an electrochemical device under lamination temperature and pressure conditions may be 4% or less. The lamination temperature and pressure conditions may be, for example, 7.8 MPa and 70°C for 10 seconds. When the thickness reduction rate of the separator for an electrochemical device satisfies the above range, damage to the separator is minimized, and the performance of the electrochemical device is likely to be further improved.

[0033] The thickness reduction rate of the separator for an electrochemical device can be calculated by measuring the thickness of the separator after compressing it under conditions of, for example, 7.8 MPa and 70° C. for 10 seconds.

[0034] The thickness reduction rate of the separator for an electrochemical element can be calculated by the following formula.

[0035] Separator thickness reduction rate = (separator thickness at initial manufacture - separator thickness after compression) / (separator thickness at initial manufacture)

[0036] In the present specification, substituted or unsubstituted C1 to C 10 The alkylene group in the above means a substituted or unsubstituted, linear or branched, saturated divalent hydrocarbon moiety having 1 to 10 carbon atoms, and such an alkylene group may be a substituted or unsubstituted C1 to C6 alkylene group, or a substituted or unsubstituted C1 to C3 alkylene group. For example, one or more hydrogen atoms contained in the alkylene group may be replaced by a halogen atom, a hydroxy group, -SH, a nitro group, [ka] a cyano group, a substituted or unsubstituted amino group (-NH, -NH(R'), -N(R'')(R'''), where R', R'', and R''' are independently C1 to C 10 alkyl group), amidino group, hydrazine, hydrazone group, carboxyl group, sulfonic acid group, phosphate group, C1-C 20 Alkyl groups, C1-C 20 Halogenated alkyl groups, C1-C 20 Alkenyl groups, C1-C 20 Alkynyl groups, C1-C 20 Heteroalkyl groups of C6-C 20 Aryl groups, C6-C 20 Aryl alkyl groups, C6-C 20 or a heteroaryl group of C6 to C 20 may be substituted by a heteroarylalkyl group of the formula:

[0037] Substituted or unsubstituted C3-C 30 The cycloalkylene group in the above means a substituted or unsubstituted divalent monocyclic ring system having 3 to 30 carbon atoms, and such a cycloalkylene group is a substituted or unsubstituted C3 to C 15 Cycloalkylene groups, substituted or unsubstituted C3-C 12 or a substituted or unsubstituted C3 to C6 cycloalkylene group. For example, one or more hydrogen atoms contained in the cycloalkylene group can be substituted with the same substituents as in the alkylene group.

[0038] Substituted or unsubstituted C6-C 30 An arylene group, used alone or in combination, means a substituted or unsubstituted divalent carbocyclic aromatic system having 6 to 30 carbon atoms containing one or more rings, which rings may be attached together in a pendant manner or may be fused. The arylene group may be a substituted or unsubstituted C6 to C 18 or a substituted or unsubstituted C6-C 15The aryl group may be an arylene group such as phenyl, naphthyl, or biphenyl, and may include, for example, one or more hydrogen atoms contained in the aryl group may be substituted with the same substituents as in the alkylene group.

[0039] In one embodiment of the present invention, the binder polymer having a cross-linked structure may have the structure of Formula 1. For example, the binder polymer having a cross-linked structure may consist solely of the structure of Formula 1.

[0040] In one embodiment of the present invention, the crosslinked binder polymer may include a product obtained by crosslinking a boron-containing compound with a hydroxyl-containing binder polymer. The crosslinked binder polymer may have a structure formed by crosslinking a hydroxyl group of the boron-containing compound with a hydroxyl group of the hydroxyl-containing binder polymer. For example, the boron-containing compound may be dissolved in an aqueous solvent to form borate ions, and the hydroxyl groups of the borate ions may form hydrogen bonds with the hydroxyl groups of the hydroxyl-containing binder polymer, thereby crosslinking the binder polymer.

[0041] In one embodiment of the present invention, the boron-containing compound may include borax, boric acid, lithium borate, potassium borate, or two or more of these. When the boron-containing compound is borax, it is easier to form a binder polymer with a crosslinked structure.

[0042] In this specification, the borax refers to the compound Na2B4O7. The borax can have the following structure:

[0043] [ka]

[0044] The borax is dissolved in an aqueous solvent to form hydroxide ions (OH -) and boric acid, which can react with the aqueous solvent to form borate ions. The hydroxyl groups of the borate ions can react with the hydroxyl groups of the hydroxyl-containing binder polymer to form the crosslinked binder polymer.

[0045] In an embodiment of the present invention, the hydroxy group-containing binder polymer may have a hydroxy group at its terminal. When the hydroxy group-containing binder polymer has a hydroxy group at its terminal, the reaction between the hydroxy group of the boron-containing compound and the hydroxy group of the hydroxy group-containing binder polymer is more likely to occur.

[0046] In one embodiment of the present invention, the hydroxyl group-containing binder polymer may be a binder polymer having excellent adhesive strength or excellent heat resistance.

[0047] In one embodiment of the present invention, the hydroxyl group-containing binder polymer may be a water-soluble binder polymer.

[0048] In one embodiment of the present invention, the hydroxyl group-containing binder polymer may include poly(vinyl alcohol), poly(ethylene glycol), or two or more thereof. In particular, poly(vinyl alcohol) has excellent heat resistance and is therefore more suitable for use as the hydroxyl group-containing binder polymer.

[0049] In one embodiment of the present invention, the weight ratio of the boron-containing compound to the hydroxyl-containing binder polymer may be 30:70 to 70:30, or 40:60 to 60:40, or 45:55 to 55:45. When the weight ratio of the boron-containing compound to the hydroxyl-containing binder polymer satisfies the above range, the compression resistance of the separator for electrochemical devices containing the crosslinked binder polymer can be further improved.

[0050] In one embodiment of the present invention, the binder polymer having a crosslinked structure may have a crosslinking degree of 10% to 90%, or 30% to 70%. When the binder polymer having a crosslinked structure satisfies the above-mentioned crosslinking degree, the compression resistance of the separator for an electrochemical device including the binder polymer having a crosslinked structure can be further improved, and it is easy to achieve such a crosslinking degree.

[0051] The crosslinking degree can be measured by measuring the weight (Wd) of the prepared separator after vacuum drying at 60°C for 12 hours, and then re-measuring the weight (Ww) after further soaking in distilled water for 1 hour, according to the following equation:

[0052] Crosslinking degree (%) = (Ww - Wd) / Wd × 100

[0053] In one embodiment of the present invention, the binder polymer having a crosslinked structure may have a structure represented by the following Formula 2: [ka] In the above chemical formula 2, m is 1 to 200.

[0054] For example, the binder polymer having a crosslinked structure including the structure of Formula 2 may include a crosslinked product obtained by reacting poly(vinyl alcohol) with borax.

[0055] The reaction mechanism between poly(vinyl alcohol) and borax is as follows: [ka]

[0056] In one embodiment of the present invention, the binder polymer having a cross-linked structure may have a structure represented by Chemical Formula 2. The binder polymer having a cross-linked structure may be composed of a structure represented by Chemical Formula 2.

[0057] In one embodiment of the present invention, the thickness of the polymer layer may be 1 μm to 16 μm, or 4 μm to 12 μm. When the thickness of the polymer layer is within the above range, the separator for an electrochemical device including the polymer layer can have improved compression resistance while maintaining high and low stability. Furthermore, the separator can have improved compression resistance while preventing deterioration of physical properties such as resistance and air permeability time.

[0058] The separator for an electrochemical device according to one embodiment of the present invention can be produced by the following production method, but is not limited thereto.

[0059] According to one embodiment of the present invention, a method for producing a separator for an electrochemical element includes the steps of: A step of coating at least one surface of a porous polymer substrate with a first coating liquid containing a hydroxyl group-containing binder polymer and drying the first coating liquid; a step of coating a second coating liquid containing a boron-containing compound on the upper surface of the porous polymer substrate coated with the hydroxyl group-containing binder polymer, and drying the second coating liquid; may include:

[0060] Hereinafter, a method for producing a separator for an electrochemical element according to one embodiment of the present invention will be described, focusing on its essential parts.

[0061] First, a first coating liquid containing a hydroxyl group-containing binder polymer is coated on at least one surface of a porous polymer substrate and then dried.

[0062] The porous polymer substrate can be used as described above, and can be manufactured from the above-mentioned materials by forming pores using a conventional method known in the art, for example, a wet method using a solvent, a diluent, or a pore-forming agent, or a dry method using a stretching method, in order to ensure excellent breathability and porosity.

[0063] For the hydroxyl group-containing binder polymer, please refer to the above description.

[0064] The first coating liquid may be a liquid in which a hydroxyl group-containing binder polymer is dissolved or dispersed in a water-soluble solvent. When the first coating liquid contains a water-soluble solvent, it is environmentally friendly.

[0065] In one embodiment of the present invention, the content of the hydroxyl group-containing binder polymer in the first coating liquid may be 5 to 20 wt % or 5 to 15 wt % based on 100 wt % of the first coating liquid. When the content of the hydroxyl group-containing binder polymer satisfies the above range, coating of the first coating liquid is more easily performed, and the hydroxyl group-containing binder polymer is more easily dissolved in the first coating liquid.

[0066] The method for coating at least one surface of the porous polymer substrate with the first coating liquid is not limited, and methods such as dip coating, die coating, roll coating, comma coating, doctor blade coating, reverse roll coating, and direct roll coating may be used.

[0067] The drying can be carried out by a method known in the art, and can be carried out in a batch or continuous manner using an oven or a heated chamber at a temperature range taking into account the vapor pressure of the solvent used.

[0068] In one embodiment of the present invention, the drying may be performed at a temperature of 40° C. to 100° C. When the drying is performed within the above range, it is easy to prevent the first coating liquid from being left undried in some areas, and it is easy to prevent the porous polymer substrate from being distorted due to high temperatures.

[0069] Thereafter, a second coating liquid containing a boron-containing compound is coated on the upper surface of the porous polymer substrate coated with the hydroxyl group-containing binder polymer, and then dried.

[0070] For the boron-containing compound, please refer to the above description.

[0071] The second coating liquid may be a liquid in which a boron-containing compound is dissolved in a water-soluble solvent. When the second coating liquid contains a water-soluble solvent, it is environmentally friendly.

[0072] In one embodiment of the present invention, the content of the boron-containing compound in the second coating liquid may be 5 to 20 wt % or 5 to 15 wt % based on 100 wt % of the second coating liquid. When the content of the boron-containing compound satisfies the above range, coating of the second coating liquid is more easily performed, and the boron-containing compound is more easily dissolved in the second coating liquid.

[0073] In one embodiment of the present invention, the pH of the second coating liquid may be 8 to 10. For example, the pH of the second coating liquid can be adjusted to the above-mentioned range by adding sodium bicarbonate or the like to the second coating liquid. When the pH of the second coating liquid satisfies the above-mentioned range, the boron-containing compound easily forms borate ions, and therefore the crosslinking reaction between the boron-containing compound and the hydroxyl group-containing binder polymer occurs more easily.

[0074] There is no limitation on the method for coating the second coating liquid onto the upper surface of the porous polymer substrate coated with the hydroxyl group-containing binder polymer, and methods such as dip coating, die coating, roll coating, comma coating, doctor blade coating, reverse roll coating, and direct roll coating may be used.

[0075] The drying can be carried out by a method known in the art, and can be carried out in a batch or continuous manner using an oven or a heated chamber at a temperature range taking into account the vapor pressure of the solvent used.

[0076] In one embodiment of the present invention, the drying may be performed at a temperature of 40° C. to 100° C. When the drying is performed within the above range, it is easy to prevent the first coating liquid from being left undried in some areas, and it is easy to prevent the porous polymer substrate from being distorted due to high temperatures.

[0077] An electrochemical element can be produced by sandwiching the above separator for an electrochemical element between a positive electrode and a negative electrode.

[0078] The electrochemical device of the present invention encompasses all devices that perform electrochemical reactions, and specific examples include all types of primary and secondary batteries, fuel cells, solar cells, and capacitors such as supercapacitor devices.

[0079] In particular, the electrochemical device may be a lithium secondary battery, such as a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0080] The electrode to be used together with the separator for an electrochemical element of the present invention is not particularly limited, and may be prepared in a form in which an electrode active material layer containing an electrode active material, a conductive material, and a binder is bound to a current collector according to a conventional method well known in the art.

[0081] Among the electrode active materials, non-limiting examples of the positive electrode active material include layered compounds such as lithium cobalt composite oxide (LiCoO2) and lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; 1+x Mn 2-xO4 (where x = 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O5, LiV3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by the formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3); 2-x M x Examples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by the formula LiMnO2 (where M=Co, Ni, Fe, Cr, Zn, or Ta, and x=0.01 to 0.1) or Li2Mn3MO5 (where M=Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li is substituted with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3.

[0082] Non-limiting examples of the negative electrode active material include conventional negative electrode active materials that have been used for negative electrodes of electrochemical devices, and in particular, lithium adsorbent materials such as lithium metal or lithium alloys, carbon, petroleum coke, activated carbon, graphite, or other carbons.

[0083] Non-limiting examples of positive electrode current collectors include foils made of aluminum, nickel, or a combination thereof, and non-limiting examples of negative electrode current collectors include foils made of copper, gold, nickel, or a copper alloy, or a combination thereof.

[0084] In one embodiment of the present invention, the conductive material used in the negative electrode and the positive electrode may be added in an amount of 1 wt % to 30 wt % based on the total weight of each active material layer. Such a conductive material is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity. For example, graphite such as natural graphite or artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black, conductive fibers such as carbon fiber or metal fiber, metal powders such as carbon fluoride, aluminum, or nickel powder, conductive whiskers such as zinc oxide or potassium titanate, conductive metal oxides such as titanium oxide, and conductive materials such as polyphenylene derivatives can be used.

[0085] In one embodiment of the present invention, the binder used in the negative electrode and positive electrode is a component that aids in bonding between the active material and the conductive material, etc., and to the current collector, and is typically added in an amount of 1 to 30 wt % based on the total weight of each active material layer. Examples of such binders include polyvinylidene fluoride (PVdF), polyacrylic acid (PAA), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.

[0086] In one embodiment of the present invention, the electrochemical device includes an electrolyte solution, and the electrolyte solution may include an organic solvent and a lithium salt. The electrolyte solution may be an organic solid electrolyte or an inorganic solid electrolyte.

[0087] Examples of the organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran (franc), 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0088] The lithium salt is a substance that is easily dissolved in the organic solvent, such as LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenylborate, imide, etc. can be used.

[0089] Furthermore, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. may be added to the electrolyte solution to improve charge / discharge characteristics, flame retardancy, etc. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart non-flammability, and carbon dioxide may be further added to improve high-temperature storage characteristics.

[0090] Examples of the organic solid electrolyte that can be used include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociative groups.

[0091] As the inorganic solid electrolyte, for example, nitrides, halides, and sulfates of Li such as LiN, LiI, LiNI, LiN-LiI-LiOH, LiSiO, LiSiO-LiI-LiOH, LiSiS, LiSiO, LiSiO-LiI-LiOH, and LiPO-LiS-SiS can be used.

[0092] The electrolyte injection may be performed at any stage during the battery manufacturing process depending on the manufacturing process and required properties of the final product, i.e., before the battery is assembled or at the final stage of the battery assembly.

[0093] In one embodiment of the present invention, the process of applying the separator for an electrochemical device to a battery may include a lamination (stack) and folding process of the separator and electrodes in addition to the conventional winding process.

[0094] In one embodiment of the present invention, the separator for an electrochemical device may be sandwiched between a positive electrode and a negative electrode of an electrochemical device, or may be sandwiched between adjacent cells or electrodes when a plurality of cells or electrodes are assembled to form an electrode assembly. The electrode assembly may have various structures, such as a simple stack type, a jelly-roll type, a stack-folding type, or a lamination-stack type.

[0095] The present invention will be described in more detail below with reference to examples to aid in understanding the present invention. However, the examples according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the following examples. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0096] Example 1 5 wt% poly(vinyl alcohol) (Sigma-Aldrich) and 95 wt% water were placed in a first water tank to dissolve the poly(vinyl alcohol). An 11 μm-thick polyethylene (JGP) was prepared as a porous polymer substrate and immersed in the first water tank to coat the polyethylene with poly(vinyl alcohol). The polyethylene was then dried at 80°C.

[0097] A borax solution was prepared by adding 5% by weight of borax and 95% by weight of water to a second water bath. The polyethylene coated with polyvinyl alcohol was immersed in the second water bath and dried at 80°C.

[0098] As a result, a separator for an electrochemical element was obtained, which contained a binder polymer having a crosslinked structure formed by reaction between poly(vinyl alcohol) and borax.

[0099] In the separator for an electrochemical device, the polymer layer was formed to a thickness of 1.5 μm on each side of the polyethylene porous polymer substrate, and the total thickness of the finally manufactured separator was 14 μm.

[0100] Comparative Example 1 A polyethylene (JGP) sheet with a thickness of 11 μm was used as a separator for the electrochemical element without any treatment.

[0101] Comparative Example 2 Five parts by weight of particulate butyl acrylate (manufactured by Zeon Corporation) as a binder polymer was dissolved in water as a solvent to prepare a binder polymer solution, to which 95 parts by weight of Al2O3 (average particle size: 500 nm) as inorganic particles was added, and the inorganic particles were then crushed and dispersed using a ball mill method for a total of 12 hours to prepare a slurry for forming an organic-inorganic composite porous layer.

[0102] The organic-inorganic composite porous layer-forming slurry was coated on both sides of a polyethylene (JGP) sheet having a thickness of 11 μm and dried to produce a separator for an electrochemical element.

[0103] Evaluation example: Measurement of separator thickness reduction rate The thickness reduction rates of the separators produced in Example 1 and Comparative Examples 1 and 2 were measured and are shown in Table 1 below.

[0104] The thickness reduction rate of the separator was measured after compressing the separator for 10 seconds under conditions of 70°C and 7.8 MPa in a hot press (manufactured by QMESYS Co., Ltd., Korea). At this time, a polyethylene terephthalate (PET) film was sandwiched between the separator and the hot press to apply pressure uniformly.

[0105] The thickness reduction rate of the separator was calculated using the following formula. Separator thickness reduction rate = (separator thickness at initial manufacture - separator thickness after compression) / (separator thickness at initial manufacture)

[0106] [Table 1]

[0107] As is clear from Table 1 above, it was confirmed that the separator produced in Example 1 had superior compression resistance compared to the separators produced in Comparative Examples 1 and 2.

Claims

1. a porous polymer substrate; a polymer layer located on at least one surface of the porous polymer substrate and including a binder polymer having a crosslinked structure; Including, The crosslinked binder polymer is a separator for an electrochemical device having a structure represented by the following Chemical Formula 1: 【Chemistry 1】 In the above chemical formula 1, The R １ and R ２ are each independently a substituted or unsubstituted C １ ~C １０ an alkylene group of the formula ３ ~C １０ and substituted or unsubstituted C ６ ~C ２０ and The n is 1 to 200.

2. 2. The separator for an electrochemical device according to claim 1, wherein the binder polymer having a crosslinked structure comprises a crosslinked product of a boron-containing compound and a hydroxyl group-containing binder polymer.

3. 3. The separator for an electrochemical element according to claim 2, wherein the boron-containing compound comprises borax, boric acid, lithium borate, potassium borate, or two or more of these.

4. 3. The separator for an electrochemical element according to claim 2, wherein the hydroxyl group-containing binder polymer comprises poly(vinyl alcohol), poly(ethylene glycol), or all of them.

5. 3. The separator for an electrochemical element according to claim 2, wherein a weight ratio of the boron-containing compound to the hydroxy group-containing binder polymer is 30:70 to 70:

30.

6. 2. The separator for an electrochemical device according to claim 1, wherein the binder polymer having a crosslinked structure has a structure represented by the following Formula 2: 【Chemistry 2】 In the above chemical formula 2, m is 1 to 200.

7. 2. The separator for an electrochemical element according to claim 1, wherein the thickness reduction rate of the separator for an electrochemical element is 4% or less.

8. a positive electrode, a negative electrode, and a separator sandwiched between the positive electrode and the negative electrode; An electrochemical element, wherein the separator is the separator for an electrochemical element according to claim 1 .

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