Separator for electrochemical elements and electrochemical elements equipped therewith

Abstract

The present invention relates to a separator for an electrochemical element having excellent compression resistance and an electrochemical element including the separator. The separator for an electrochemical device includes a polymer layer located on at least one surface of a porous polymer substrate, the polymer layer including a binder polymer having a crosslinked structure having a structure represented by the following Formula 1: JPEG2024504325000012.jpg64170For the above Chemical Formula 1, please refer to the above content.

Description

[Technical Field]

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

[0002] This application claims priority based on Korean Patent Application No. 10-2021-0127572, filed on 27 September 2021, and all content disclosed in the specification and drawings of said application is incorporated herein. [Background technology]

[0003] In recent years, interest in energy storage technologies has been steadily increasing. As applications expand to include mobile phones, video cameras, laptops, and even electric vehicles, the need for higher energy density batteries used as power sources for these electronic devices is growing. Rechargeable batteries are the type of battery that best meets these needs, and research into them is currently being actively pursued.

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

[0005] However, during the lamination of separators and electrodes for the manufacture of secondary batteries, the separator can be locally compressed due to heat and pressure. Furthermore, the volume expansion that occurs during charge-discharge cycles can also locally compress the separator. This raises concerns about the deterioration of the separator's physical properties, such as its voltage resistance characteristics.

[0006] In particular, in recent years, there has been an increasing trend to use silicon or other materials instead of graphite in the negative electrode to increase the energy density of secondary batteries. However, because these materials are hard, there is a possibility that problems associated with separator compression will increase even further.

[0007] For this reason, there is currently a very high demand for separators with excellent compression resistance. [Overview of the project] [Problems that the invention aims to solve]

[0008] Therefore, the problem that the present invention aims to solve is to provide an electrochemical element separator with excellent compression resistance and an electrochemical element equipped therewith. [Means for solving the problem]

[0009] To solve the aforementioned problems, according to one aspect of the present invention, a separator for an electrochemical element in the following form is provided.

[0010] The first aspect is, A porous polymer substrate and A polymer layer comprising a binder polymer having a crosslinked structure, located on at least one surface of the porous polymer substrate, Includes, The present invention relates to a separator for electrochemical elements, characterized in that the aforementioned cross-linked binder polymer contains the structure of the following chemical formula 1. [ka] In the above chemical formula 1, R1 and R2 are, independently, substituted or unsubstituted C1-C 10 Alkylene group, substituted or unsubstituted C3-C 10 The cycloalkylene group, and substituted or unsubstituted C6-C 20 It is one of the arylene groups selected from among the following: The aforementioned n is between 1 and 200.

[0011] The second embodiment is an electrochemical element separator according to the first embodiment, wherein the crosslinked binder polymer may include a crosslinked product of a boron-containing compound and a hydroxyl group-containing binder polymer.

[0012] Aspect 3 is the separator for an electrochemical element according to Aspect 2, wherein the boron-containing compound may contain borax, boric acid, lithium borate, potassium borate, or two or more of these.

[0013] Aspect 4 is the separator for an electrochemical element according to Aspect 2 or Aspect 3, wherein the hydroxy group-containing binder polymer may contain poly(vinyl alcohol), poly(ethylene glycol), or all of these.

[0014] Aspect 5 is the separator for an electrochemical element according to any one of Aspects 2 to 4, wherein the weight ratio of the boron-containing compound to the hydroxy group-containing binder polymer may be 30:70 to 70:30.

[0015] Aspect 6 is the separator for an electrochemical element according to any one of Aspects 1 to 5, wherein the crosslinked binder polymer may contain the structure of Chemical Formula 2 below.

Chemical formula

[0016] Aspect 7 is the separator for an electrochemical element according to any one of Aspects 1 to 6, wherein the thickness reduction rate of the separator for an electrochemical element may be 4% or less.

[0017] To solve the above problems, according to one aspect of the present invention, an electrochemical element of the following aspect is provided.

[0018] Aspect 8 is including 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 element characterized in that the separator is an electrochemical element separator described in any one of the first to seventh embodiments. [Effects of the Invention]

[0019] An electrochemical element separator according to one embodiment of the present invention can have excellent compression resistance by containing a binder polymer with a crosslinked structure having the structure of chemical formula 1. [Modes for carrying out the invention]

[0020] Preferred embodiments of the present invention will now be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and in the claims should not be interpreted in a manner limited to their usual or dictionary meanings, but rather in a manner corresponding to the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best describe the invention.

[0021] Therefore, the embodiments described herein and the configurations shown in the drawings represent only one of the most preferred embodiments of the present invention and do not represent the entire technical concept of the present invention. It should be understood that there are various equivalents and modifications that can be substituted for these at the time of filing this application.

[0022] One aspect of the present invention is an electrochemical element separator, A porous polymer substrate and A polymer layer comprising a binder polymer having a crosslinked structure, located on at least one surface of the porous polymer substrate, Includes, The aforementioned crosslinked binder polymer is characterized by containing the structure of the following chemical formula 1. [ka] In the above chemical formula 1, R1 and R2 are, independently, substituted or unsubstituted C1-C 10Alkylene group, substituted or unsubstituted C3-C 10 The cycloalkylene group, and substituted or unsubstituted C6-C 20 It is one of the arylene groups selected from among the following: The aforementioned n is between 1 and 200.

[0023] The porous polymer substrate can be any material that is normally usable as a separator material for electrochemical elements, without any particular limitations. Such a porous polymer substrate is a thin film containing a polymer material, and non-limiting examples of the polymer material include at least one of the following polymer resins: polyolefin resin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, etc. The porous polymer substrate can be a nonwoven fabric or a porous polymer film formed from the polymer material, or a laminate of two or more of these. Specifically, the porous polymer substrate may 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 together, c) Nonwoven web manufactured by assembling filaments obtained by melting / spinning polymer resins. d) A multilayer film in which two or more layers of the nonwoven fabric web described in c) are laminated, e) A porous film with 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. The thickness of the porous polymer substrate is not particularly limited to the range described above, but when the thickness is within the range described above, it is possible to ensure energy density while preventing the problem of the separator being easily damaged during battery use.

[0026] On the other hand, the pore diameter and porosity of the pores present in the porous polymer substrate are also not particularly limited, 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 the BET 6-point method using nitrogen gas adsorption flow, with a scanning electron microscope (SEM) image, a mercury porosimeter, a capillary flow porometer, or a porosimetry analyzer (Belsorp-II mini manufactured by Nippon Bell Co., Ltd.). In this case, it is even more preferable to use a capillary flow porometer.

[0028] The polymer layer is located on at least one surface of the porous polymer substrate. For example, the polymer layer may be located on one or both surfaces of the porous polymer substrate. The polymer layer contains a binder polymer having a crosslinked structure with the structure of chemical formula 1.

[0029] When manufacturing an electrochemical element in which a separator and an electrode are laminated together, the heat and pressure applied during the lamination process can cause localized compression of the separator. For example, when laminating the separator and electrode together under conditions of approximately 7.8 MPa and 70°C for 10 seconds, the heat and pressure applied can cause localized compression of the separator. Furthermore, the volume expansion that occurs during charge-discharge cycles can also cause localized compression of the separator.

[0030] If the thickness reduction rate of the separator for electrochemical elements exceeds 10%, there is a possibility that the battery's output and life characteristics may decrease due to the shrinkage of the separator's pores, and / or the risk of electrode short circuits may increase.

[0031] A separator for an electrochemical element according to one embodiment of the present invention contains a binder polymer with a crosslinked structure having excellent elasticity, and thus its compressive resistance can be improved.

[0032] For example, the thickness reduction rate of the separator for the electrochemical element may be 4% or less. In particular, the thickness reduction rate of the separator for the electrochemical element under the 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 the electrochemical element meets the above range, damage to the separator is minimized, making it easier to further improve the performance of the electrochemical element.

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

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

[0035] The thickness reduction rate of the separator = (Thickness of the separator at the time of initial manufacture - Thickness of the separator after compression) / (Thickness of the separator at the time of initial manufacture)

[0036] In this specification, substituted or unsubstituted C1-C 10 The alkylene group refers to 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 a halogen atom, a hydroxyl group, -SH, a nitro group, [ka] A cyano group, a substituted or unsubstituted amino group (-NH2, -NH(R’), -N(R’’)(R’’’), where R’, R’’, and R’’’ are each independently a C1-C 10 alkyl group), an amidino group, hydrazine, a hydrazone group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, a C1-C 20 alkyl group, a C1-C 20 halogenated alkyl group, a C1-C 20 alkenyl group, a C1-C 20 alkynyl group, a C1-C 20 heteroalkyl group, a C6-C 20 aryl group, a C6-C 20 arylalkyl group, a C6-C 20 heteroaryl group, or a C6-C 20 heteroarylalkyl group may be substituted.

[0037] The substituted or unsubstituted C3-C 30 cycloalkylene group means a substituted or unsubstituted divalent monocyclic system having 3 to 30 carbon atoms. Such a cycloalkylene group may be a substituted or unsubstituted C3-C 15 cycloalkylene group, a substituted or unsubstituted C3-C 12 [[ID=3)]]cycloalkylene group, or a substituted or unsubstituted C3-C6 cycloalkylene group. For example, one or more hydrogen atoms contained in the cycloalkylene group can be substituted by the same substituents as in the case of the alkylene group. <r

[0038] The substituted or unsubstituted C6-C 30 arylene group means a substituted or unsubstituted divalent carbocyclic aromatic system having 6 to 30 carbon atoms, which contains one or more rings and can be attached or fused together by a pendant method. The arylene group may be a substituted or unsubstituted C6-C 18 arylene group, or a substituted or unsubstituted C6-C 15The aryl group may also be an arylene group, and may include a phenyl group, a naphthyl group, a biphenyl group, and the like. For example, one or more hydrogen atoms in the aryl group can be substituted with substituents similar to those in the alkylene group.

[0039] In one embodiment of the present invention, the crosslinked binder polymer may have the structure of chemical formula 1. For example, the crosslinked binder polymer may consist solely of the structure of chemical formula 1.

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

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

[0042] In this specification, the term "borax" refers to the compound Na2B4O7. The borax may have the following structure.

[0043] [ka]

[0044] The borax mentioned above is dissolved in a water-soluble solvent and reacts with hydroxide ions (OH -This process generates boric acid, which can react with a water-soluble solvent to form borate ions. The hydroxyl groups of these borate ions react with the hydroxyl groups of the hydroxyl group-containing binder polymer to form the aforementioned crosslinked binder polymer.

[0045] In one embodiment of the present invention, the hydroxyl group-containing binder polymer may contain a hydroxyl group at its terminal end. When a hydroxyl group is present at the terminal end of the hydroxyl group-containing binder polymer, the reaction between the hydroxyl group of the boron-containing compound and the hydroxyl group of the hydroxyl 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 that has excellent adhesive strength or excellent heat resistance.

[0047] Furthermore, 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 of these. In particular, poly(vinyl alcohol) has excellent heat resistance and can be used even more favorably as a hydroxyl group-containing binder polymer.

[0049] In one embodiment of the present invention, the weight ratio of the boron-containing compound to the hydroxyl group-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 group-containing binder polymer satisfies the above range, the compressive resistance of the separator for electrochemical elements containing the crosslinked binder polymer can be further improved.

[0050] In one embodiment of the present invention, the crosslinked binder polymer can have a degree of crosslinking of 10% to 90% or 30% to 70%. When the crosslinked binder polymer satisfies the aforementioned degree of crosslinking, the compressive resistance of the separator for electrochemical elements containing the crosslinked binder polymer can be further improved, and such a degree of crosslinking is easily achievable.

[0051] The degree of crosslinking can be determined by measuring the weight (Wd) of the manufactured separator after vacuum drying at 60°C for 12 hours, and then measuring the weight again (Ww) after supporting it in distilled water for another hour, according to the following formula.

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

[0053] In one embodiment of the present invention, the crosslinked binder polymer may include the structure of the following chemical formula 2. [ka] In the chemical formula 2 above, m is between 1 and 200.

[0054] For example, a binder polymer having a crosslinked structure including the structure of chemical formula 2 may include a crosslinking product resulting from the reaction of poly(vinyl alcohol) and borax.

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

[0056] In one embodiment of the present invention, the crosslinked binder polymer may have the structure of chemical formula 2. The crosslinked binder polymer may consist of the structure of 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 satisfies the above range, it is possible to further improve the compressive resistance while ensuring high and low stability of the separator for the electrochemical element including the polymer layer. Furthermore, it is possible to further improve the compressive resistance of the separator while preventing deterioration of physical properties such as resistance and air permeability time.

[0058] An electrochemical element separator according to one embodiment of the present invention can be manufactured by the following manufacturing method, but is not limited thereto.

[0059] A method for manufacturing an electrochemical element separator according to one embodiment of the present invention is: The steps include coating at least one surface of a porous polymer substrate with a first coating solution containing a hydroxyl group-containing binder polymer and drying it, The steps include coating the upper surface of a porous polymer substrate coated with the hydroxyl group-containing binder polymer with a second coating solution containing a boron-containing compound and drying it, It can include...

[0060] The following describes a method for manufacturing an electrochemical element separator according to one embodiment of the present invention, focusing on its essential aspects.

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

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

[0063] For details regarding the hydroxyl group-containing binder polymer, please refer to the information provided above.

[0064] The first coating solution may contain a hydroxyl group-containing binder polymer dissolved or dispersed in a water-soluble solvent. If the first coating solution 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 solution may be 5 to 20% by weight or 5 to 15% by weight, based on 100% by weight of the first coating solution. When the content of the hydroxyl group-containing binder polymer satisfies the above range, the coating with the first coating solution becomes easier, and the hydroxyl group-containing binder polymer is more easily dissolved by the first coating solution.

[0066] There are no limitations on the method of coating the first coating solution onto at least one surface of the porous polymer substrate, and methods such as dip coating, die coating, roll coating, comma coating, doctor blade coating, reverse roll coating, and direct roll coating can be used.

[0067] The drying described above can be carried out by methods known in the industry and can be performed in batch or continuous manner using an oven or heated chamber within a temperature range that takes into account the vapor pressure of the solvent used.

[0068] In one embodiment of the present invention, the drying can be carried out at a temperature of 40°C to 100°C. When drying is carried out within the aforementioned range, it is easier to prevent the first coating liquid from remaining undried and to prevent the porous polymer substrate from being distorted by high temperatures.

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

[0070] For information regarding the boron-containing compounds mentioned above, please refer to the details provided previously.

[0071] The second coating solution may be a boron-containing compound dissolved in a water-soluble solvent. If the second coating solution 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 solution may be 5 to 20% by weight or 5 to 15% by weight, based on 100% by weight of the second coating solution. When the content of the boron-containing compound satisfies the above range, the coating of the second coating solution becomes easier, and the boron-containing compound is more easily dissolved by the second coating solution.

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

[0074] There are no limitations on the method of coating the upper surface of the porous polymer substrate coated with the hydroxyl group-containing binder polymer with the second coating solution. Methods such as dip coating, die coating, roll coating, comma coating, doctor blade coating, reverse roll coating, and direct roll coating can be used.

[0075] The drying described above can be carried out by methods known in the industry and can be performed in batch or continuous manner using an oven or heated chamber within a temperature range that takes into account the vapor pressure of the solvent used.

[0076] In one embodiment of the present invention, the drying can be carried out at a temperature of 40°C to 100°C. When drying is carried out within the aforementioned range, it is easier to prevent the first coating liquid from remaining undried and to prevent the porous polymer substrate from being distorted by high temperatures.

[0077] An electrochemical element can be manufactured by sandwiching the above-mentioned separator for electrochemical elements between the positive and negative electrodes.

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

[0079] In particular, the electrochemical element 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 electrodes to be used with the separator for electrochemical elements of the present invention are not particularly limited and can be manufactured in a form in which an electrode active material layer comprising an electrode active material, a conductive material, and a binder is bonded to a current collector, according to common methods well known in the art.

[0081] Among the electrode active materials, non-limiting examples of positive electrode active materials include layered compounds such as lithium cobalt composite oxide (LiCoO2) and lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-xLithium manganese oxides such as O4 (where x = 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O5, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented as O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01~0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxides represented as O2 (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 in the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc. are examples, but the invention is not limited to these.

[0082] Non-restrictive examples of negative electrode active materials include conventional negative electrode active materials that have been used for the negative electrodes of electrochemical elements, and in particular, lithium adsorbent materials such as lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, graphite, or other carbon compounds can be used.

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

[0084] In one embodiment of the present invention, the conductive material used in the negative electrode and positive electrode can typically be added in an amount of 1% to 30% by weight based on the total weight of each active material layer. Such conductive materials are not particularly limited as long as they do not induce chemical changes in the battery and are conductive. For example, graphite such as natural graphite or artificial graphite, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride, aluminum, and nickel powder, conductive whiskers such as zinc oxide and 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 assists in the bonding of the active material to a conductive material and to the current collector, and can usually be added in an amount of 1% to 30% by weight based on the total weight of each active material layer. Examples of such binders include polyvinylidene fluoride (PVdF), polyacrylic acid (PAA), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, 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 element includes an electrolyte, and the electrolyte may include an organic solvent and a lithium salt. An organic solid electrolyte or an inorganic solid electrolyte can be used as the electrolyte.

[0087] Examples of suitable organic solvents 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, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 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 readily soluble in the organic solvent, for example, 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, and imides can be used.

[0089] Furthermore, to improve charge-discharge characteristics, flame retardancy, etc., the electrolyte may be further enriched with, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. In some cases, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene may be further added to provide non-flammability, and carbon dioxide may be further added to improve high-temperature storage characteristics.

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

[0091] Examples of suitable inorganic solid electrolytes include lithium nitrides, halides, and sulfates such as Li3N, LiI, Li5NI2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, and Li3PO4-Li2S-SiS2.

[0092] The injection of the electrolyte can be carried out at an appropriate stage during the battery manufacturing process, depending on the manufacturing process and required physical properties of the final product. That is, it can be carried out before battery assembly or at the final stage of battery assembly.

[0093] In one embodiment of the present invention, the process of applying the electrochemical element separator to a battery includes, in addition to the usual winding process, lamination (stack) and folding processes of the separator and electrode.

[0094] In one embodiment of the present invention, the separator for the electrochemical element may be sandwiched between the positive and negative electrodes of the electrochemical element, or, when a plurality of cells or electrodes are assembled to form an electrode assembly, it may be sandwiched between adjacent cells or electrodes. The electrode assembly can 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 of 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 give a more complete explanation of the present invention to a person of average knowledge in the art.

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

[0097] A borax aqueous solution was prepared by adding 5% by weight of borax and 95% by weight of water to a second tank. The polyethylene coated with poly(vinyl alcohol) was immersed in the second tank. This was then dried at 80°C.

[0098] This resulted in obtaining a separator for electrochemical elements containing a binder polymer with a crosslinked structure formed by the reaction of poly(vinyl alcohol) and borax.

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

[0100] Comparative Example 1 Polyethylene (JGP) with a thickness of 11 μm was used as a separator for electrochemical elements without any treatment.

[0101] Comparative Example 2 A binder polymer solution was prepared by dissolving 5 parts by weight of particulate butyl acrylate (manufactured by Zeon Corporation) as a binder polymer in water as a solvent. 95 parts by weight of inorganic particles Al2O3 (average particle size: 500 nm) were then added to this solution. Finally, the inorganic particles were crushed and dispersed using a ball mill method over a total of 12 hours to produce a slurry for forming an organic-inorganic composite porous layer.

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

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

[0104] The thickness reduction rate of the separator was measured after compressing the separator in a hot press (manufactured by QMESYS, South Korea) at 70°C and 7.8 MPa for 10 seconds. To ensure uniform pressure distribution, a polyethylene terephthalate (PET) film was placed between the separator and the hot press.

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

[0106] [Table 1]

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

Claims

1. A porous polymer substrate and A polymer layer comprising a binder polymer having a crosslinked structure, located on at least one surface of the porous polymer substrate, Includes, The aforementioned crosslinked binder polymer is a separator for an electrochemical element, comprising the structure of the following chemical formula 1. The aforementioned crosslinked binder polymer includes a crosslinked product of a boron-containing compound and a hydroxyl group-containing binder polymer. The boron-containing compound is borax, boric acid, lithium borate, potassium borate, or two or more of these. The hydroxyl group-containing binder polymer is poly(vinyl alcohol), poly(ethylene glycol), or all of these. The weight ratio of the boron-containing compound to the hydroxyl group-containing binder polymer is 30:70 to 70:

30. Separators for electrochemical elements with a thickness reduction rate of 4% or less: 【Chemistry 1】 In the above chemical formula 1, The aforementioned R １ and R ２ These are, independently, substituted or unsubstituted C. １ ~C １０ alkylene group, substituted or unsubstituted C ３ ~C １０ The cycloalkylene group and substituted or unsubstituted C ６ ~C ２０ It is one of the arylene groups selected from among the following: The aforementioned n is between 1 and 200.

2. The binder polymer of the crosslinked structure comprises the structure of the following chemical formula 2, wherein the separator for the electrochemical element according to claim 1: 【Chemistry 2】 In the above chemical formula 2, m is between 1 and 200.

3. It includes a positive electrode, a negative electrode, and a separator sandwiched between the positive electrode and the negative electrode. An electrochemical element in which the separator is the separator for electrochemical elements described in claim 1 or 2.

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