Separator for electrochemical device, and electrochemical device comprising same

Abstract

The present invention relates to a separator for an electrochemical device, the separator having a coating layer comprising a dispersant that comprises i) repeating units derived from a (meth)acrylic acid monomer, a (meth) acrylate salt monomer, or both, and ii) repeating units derived from an acrylic monomer having an amide group. Specifically, by specifying the molar ratio and molecular weight of the repeating units of the dispersant, the present invention improves the dispersibility of inorganic particles in the coating layer and consequently achieves the effects of reducing the electrical resistance of the separator while improving the thermal shrinkage rate.

Description

Separator for an electrochemical device and an electrochemical device including the same

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

[0002] The present application claims priority based on Korean Patent Application No. 10-2025-0006016 filed with the Korean Intellectual Property Office on January 15, 2025 and Korean Patent Application No. 10-2025-0154946 filed on October 23, 2025, and all contents disclosed in the specifications of said applications are incorporated into the present application.

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions; recently, lithium-ion batteries, which offer high energy density and voltage, long cycle life, and applicability to various fields, are widely used.

[0004] A lithium secondary battery may comprise an electrode assembly made of a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, and may be manufactured by housing the electrode assembly together with an electrolyte in a case. The separator may comprise a porous coating layer comprising a polymer binder and inorganic particles on at least one surface of a porous substrate. The inorganic particles may be connected to other inorganic particles by the polymer binder to form an interstitial volume, and lithium ions may move through the interstitial volume. In addition to fixing the inorganic particles, the polymer binder may impart adhesion to the coating layer, and the coating layer may adhere to the porous substrate and the electrode, respectively.

[0005] Meanwhile, when heat is generated during the operation of an electrochemical device, the separator may shrink, causing electrical short circuits between electrodes or a decrease in adhesion to the electrodes. Therefore, there is an increasing trend of using novel and complex polymer binders in coating layers formed on porous substrates to improve the thermal shrinkage rate of the separator. However, the use of such polymer binders has resulted in a problem of reduced dispersibility of inorganic particles within the coating slurry. Due to this reduced dispersibility, the air permeability and resistance of the separator with the coating layer deteriorate, leading to a decrease in the output and cycle characteristics of the electrochemical device. Consequently, there was a need to develop a dispersant that improves dispersibility during coating layer formation while simultaneously not hindering the thermal shrinkage rate of the separator.

[0006] A technical problem according to one aspect of the present invention is to provide a separator for an electrochemical device in which the dry thermal shrinkage rate and the wet thermal shrinkage rate at high temperatures are simultaneously improved, and an electrochemical device equipped with the same.

[0007] According to one aspect of the present invention, the purpose is to provide a separator for an electrochemical device having a lower electrical resistance in which inorganic particles are uniformly dispersed within a coating layer, and an electrochemical device equipped with the same.

[0008] According to one aspect of the present invention, a separator for an electrochemical device of the following embodiments is provided.

[0009] The separator for an electrochemical device according to the first embodiment is,

[0010] porous substrate and

[0011] A coating layer disposed on at least one surface of the above-mentioned porous substrate and comprising inorganic particles and a binder polymer, and

[0012] The above-mentioned dispersant comprises a copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and ii) a repeating unit derived from an acrylic monomer having an amide group, and

[0013] The molar ratio of the above i) repeating unit derived from the (meth)acrylic acid monomer, the (meth)acrylic acid salt monomer, or both of these monomers, and ii) repeating unit derived from the acrylic monomer having an amide group is 2:8 to 8:2, and

[0014] The weight-average molecular weight of the above dispersant is 30,000 g / mol to 250,000 g / mol, and

[0015] The electrical resistance of the above separator is set to be 0.6 Ω or less.

[0016] According to the second embodiment, in the first embodiment,

[0017] Based on 100 parts by weight of the above inorganic particles, the content of the dispersant may be 0.1 to 2 parts by weight.

[0018] According to the third embodiment, in the first embodiment or the second embodiment,

[0019] The air permeability of the above membrane may be 80 s / 100 cc or less.

[0020] According to the fourth embodiment, in any one of the first to third embodiments,

[0021] The electrical resistance of the above separator may be 0.55 Ω or less.

[0022] According to the fifth embodiment, in any one of the first to fourth embodiments,

[0023] The glass transition temperature (Tg) of the above dispersant may be 90 to 180°C.

[0024] According to the 6th embodiment, in any one of the 1st to 5th embodiments,

[0025] The weight ratio of the binder and the dispersant may be 5:1 to 15:1.

[0026] According to the seventh embodiment, in any one of the first to sixth embodiments,

[0027] The above binder may comprise a non-crosslinked copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iii) a repeating unit derived from an acrylic monomer having a hydroxyl group.

[0028] According to the eighth embodiment, in any one of the first to seventh embodiments,

[0029] The above binder may include i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iv) a copolymer comprising a silane monomer, a monomer having a silanol group, or a repeating unit derived from both of these monomers.

[0030] According to the ninth embodiment, in any one of the first to eighth embodiments,

[0031] The weight-average molecular weight of the binder may be 100,000 g / mol to 200,000 g / mol.

[0032] According to the 10th embodiment, in any one of the 1st to 9th embodiments,

[0033] The glass transition temperature (Tg) of the above binder may be 100 to 200°C.

[0034] According to the 11th embodiment, in any one of the 1st to 10th embodiments,

[0035] The above binder may include a copolymer composed of repeating units derived from a hydroxyalkyl acrylate monomer, repeating units derived from a (meth)acrylic acid monomer, and repeating units derived from an acrylic monomer having an amide group.

[0036] According to the 12th embodiment, in any one of the 1st to 11th embodiments,

[0037] Average particle size (D of the above inorganic particles) 50 ) can be 400 nm to 600 nm.

[0038] According to the 13th embodiment, in any one of the 1st to 12th embodiments,

[0039] Based on 100 parts by weight of the coating layer, the content of the inorganic particles may be 80 to 95 parts by weight.

[0040] According to the 14th embodiment, in any one of the 1st to 13th embodiments,

[0041] The thickness of the coating layer may be 0.5 μm to 2 μm.

[0042]

[0043] According to another aspect of the present invention, an electrochemical device according to the following embodiment may be provided.

[0044] The electrochemical device according to the 15th embodiment is,

[0045] It comprises an anode, a cathode, and a separator for an electrochemical device according to any one of the first to fourth embodiments, and

[0046] The separator for the electrochemical device may be interposed between the anode and the cathode.

[0047] The coating layer in a separator for an electrochemical device according to the present invention comprises inorganic particles, a binder, and a dispersant. In this case, the dispersant comprises i) repeating units derived from (meth)acrylic acid monomers, (meth)acrylic acid salt monomers, or both of these monomers, and ii) repeating units derived from acrylic monomers having amide groups in a specific molar ratio range. Additionally, the inorganic particles and the dispersant are included in a specific content range. Through this, an excellent effect of lowering the electrical resistance of the separator can be achieved by improving the dispersibility of solid components within the coating layer.

[0048] In addition, the separator for an electrochemical device according to the present invention has the advantage of improving the thermal shrinkage characteristics of the separator by providing such a coating layer, thereby significantly improving the thermal shrinkage rate, especially at high temperatures, in both dry and wet states, but the effects of the present invention are not limited thereto.

[0049] Hereinafter, each component of the present invention is described in more detail so that a person skilled in the art to which the present invention pertains can easily implement it; however, this is merely an example, and the scope of the rights of the present invention is not limited by the following.

[0050] In the present specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0051] In this specification, when a component is described as being disposed on "one side," this means that, unless specifically stated otherwise, other components may be disposed therein, not excluding the placement of other components in between.

[0052] In this specification, "electrochemical device" may mean a primary battery, a secondary battery, or a supercapacitor, etc. More specifically, the electrochemical device may be a lithium-ion secondary battery and may be pouch-type, cylindrical-type, prismatic-type, or coin-type, but the specific shape is not limited thereto.

[0053] In this specification, "electrode" collectively refers to "anode" and "cathode," and may mean a material having conductivity without causing chemical changes in an electrochemical device, on which an electrode active material is coated and dried. The types of the material and the electrode active material are not limited, as long as they can be used in an electrochemical device.

[0054] In this specification, "separator" may generally refer to a functional separator in which a porous coating layer comprising inorganic particles and a binder is formed on at least one surface of a porous substrate, such as a polyolefin substrate or a nonwoven fabric. Additionally, the separator has porous characteristics containing a plurality of pores and acts as a porous ion-conducting barrier that blocks electrical contact between a cathode and an anode in an electrochemical device while allowing ions to pass through.

[0055] In this specification, the characteristic of having porosity or pores means that a gaseous and / or liquid fluid can pass from one side to the other side of the object through a structure in which the object includes a plurality of voids or pores and said voids or pores are interconnected.

[0056] In this specification, "porous substrate" may refer to a porous membrane having a plurality of pores formed therein, which electrically insulates the positive electrode and the negative electrode to prevent a short circuit. For example, if the electrochemical device is a lithium secondary battery, the porous substrate may be an ion-conducting barrier that blocks electrical contact between the positive electrode and the negative electrode while allowing lithium ions to pass through. At least some of the pores may form a three-dimensional network communicating the surface and the interior of the porous substrate, and a fluid may pass through the porous substrate through the pores.

[0057] In this specification, "average particle size (D 50 "" refers to the diameter of the particle corresponding to the 50% point of the cumulative volume in the cumulative particle size distribution for the particle being measured. The particle size can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) to calculate the particle size distribution by measuring the difference in diffraction patterns according to particle size as the particles pass through the laser beam. By calculating the particle diameter at the point that is 50% of the cumulative distribution of the number of particles according to diameter in the measuring device, the average particle size (D 50 ) can be measured.

[0058] In this specification, "non-crosslinked copolymer" means a copolymer that melts transparently when water is added to a concentration of 10% and stirred for 30 minutes after the copolymer has been left in an oven at 100°C for 30 minutes.

[0059] In this specification, "repeating unit derived from ~ monomer" refers to a repeating unit included in a copolymer formed by polymerizing a ~ monomer.

[0060] In this specification, "(meth)acrylic acid monomer" encompasses both acrylic acid monomers and methacrylic acid monomers. Additionally, "(meth)acrylic acid salt monomer" encompasses both acrylic acid salt monomers and methacrylic acid salt monomers.

[0061] In this specification, "acrylic monomer" means a monomer comprising an acrylate structure within a molecule. For example, the acrylic monomer may be represented by a chemical formula such as CH2=CHCOOB, where B is hydrogen, nitrogen, oxygen, or a substituted or unsubstituted hydrocarbon group having 1 to 10 carbon atoms. In the chemical formula, B may be hydrolyzed by water or steam to have one or more hydroxyl groups. Furthermore, the acrylic monomer is not limited to the chemical formula structure (CH2=CHCOOB) described above, and may have additional functional groups attached to the carbon double bond.

[0062]

[0063] The present invention will be described in more detail below.

[0064] According to one aspect of the present invention, a separator for an electrochemical device is provided.

[0065] A separator for an electrochemical device according to one aspect of the present invention is,

[0066] It includes a porous substrate; and a coating layer disposed on at least one surface of the porous substrate and comprising inorganic particles, a binder, and a dispersant.

[0067] Here, the dispersant comprises a copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and ii) a repeating unit derived from an acrylic monomer having an amide group.

[0068] In one embodiment of the present invention, the copolymer may be a copolymer in which the monomer is copolymerized in the form of a random copolymer, a graft copolymer, or a block copolymer, and specifically, the copolymer may be a random copolymer, but the form of the present invention is not limited thereto.

[0069] According to one embodiment of the present invention, when a copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and ii) a repeating unit derived from an acrylic monomer having an amide group is used as a dispersant for a coating layer, the shape deformation of the dispersant is minimal when forming the coating layer, and the compatibility with inorganic particles and solvation with the solvent of the coating layer slurry are appropriately exhibited, thereby providing an effect of uniformly dispersing inorganic particles within the coating layer. For example, the (meth)acrylic acid monomer or the (meth)acrylic acid salt monomer contains a negatively charged carboxylic acid within its structure, which can generate a repulsive force between solid components within the slurry for forming the coating layer. This prevents the aggregation of inorganic particles and binders within the slurry, thereby providing an excellent effect of improving the dispersibility of solid components. In addition, the acrylic monomer having the above amide group has excellent ability to form hydrogen bonds in a slurry for forming a coating layer, particularly in an aqueous slurry, due to the amide group, and thus has excellent water solubility, and thereby has an excellent effect of improving the dispersibility of inorganic particles in the slurry.

[0070] In this regard, in particular, the molar ratio of the above-mentioned dispersant to the i) repeating unit derived from the (meth)acrylic acid monomer, (meth)acrylic acid salt monomer, or both of these monomers, and ii) repeating unit derived from the acrylic monomer having an amide group is set to be 2:8 to 8:2.

[0071] In one embodiment of the present invention, the molar ratio of i) repeating units derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and ii) repeating units derived from an acrylic monomer having an amide group may be, for example, 2:8 to 8:2, 2:8 to 7:3, 2:8 to 6:4, 2:8 to 5:5, 2:8 to 4:6, 2:8 to 3:7, or 2:8 to 2.5:7.5. When the molar ratio of the repeating units is within the ranges described above, it may exhibit an advantageous effect for achieving low electrical resistance of the separator or / or an improved thermal shrinkage rate, but the effects of the present invention are not limited thereto. For example, if the (meth)acrylic acid monomer, (meth)acrylic acid salt monomer, or repeating units derived from both monomers are included in greater quantities than the range described above, the dispersant may become excessively negatively charged, which may lead to a problem of reduced dispersion efficiency. Additionally, if the repeating units derived from the acrylic monomer having the amide group are included in greater quantities, excessive hydrogen bonding may be formed, causing inorganic particles to aggregate, which may lead to a problem of reduced dispersibility of solids in the slurry, but the present invention is not limited thereto.

[0072] In addition, to improve the dispersibility of the inorganic particles and binder and to maintain a small particle size of the slurry for forming a coating layer, the dispersant comprises a weight-average molecular weight of 30,000 g / mol to 250,000 g / mol.

[0073] In one embodiment of the present invention, the dispersant may include a weight-average molecular weight (Mw) of, for example, 30,000 g / mol to 250,000 g / mol. Specifically, the weight-average molecular weight of the dispersant may be, for example, 50,000 g / mol to 200,000 g / mol, 50,000 g / mol to 175,000 g / mol, 50,000 g / mol to 150,000 g / mol, 100,000 g / mol to 200,000 g / mol, or 125,000 g / mol to 150,000 g / mol. When the weight-average molecular weight of the above-described dispersant is within the range described above, the particle size of the slurry for forming the coating layer is kept small to facilitate the realization of a thin film coating layer, and the dispersibility of solid components within the coating layer is improved to provide an effect that is advantageous for realizing a low electrical resistance of the separation membrane, but the effects of the present invention are not limited thereto.

[0074] In this specification, the weight-average molecular weight may be a value measured using gel permeation chromatography (GPC: PL GPC220, Agilent Technologies). For example, the weight-average molecular weight may be a value measured using an Agilent High Temperature RI detector under conditions of a PL Olexis (Polymer Laboratories) column (column temperature 160°C) using TCB (Trichlorobenzene) as the solvent, a sample concentration of 1.0 mg / mL, a flow rate of 1.0 mL / min, and an injection volume of 200 µL (corrected as a cubic function, reference: Polystyrene).

[0075] A separator according to one aspect of the present invention comprises the coating layer described above and has an electrical resistance of 0.6 Ω or less.

[0076] In one embodiment of the present invention, the electrical resistance of the separator may specifically be 0.6 Ω or less, 0.60 Ω or less, 0.58 Ω or less, or 0.55 Ω or less. More specifically, the electrical resistance of the separator may be, for example, 0.3 Ω to 0.6 Ω, 0.4 Ω to 0.55 Ω, 0.50 Ω to 0.55 Ω, 0.51 Ω to 0.55 Ω, 0.51 Ω to 0.54 Ω, 0.51 Ω to 0.53 Ω, or 0.51 Ω to 0.52 Ω. While the electrical resistance of the separator within the above-described range may exhibit advantageous effects in terms of significantly improving the performance of an electrochemical device to which it is applied, the effects of the present invention are not limited thereto.

[0077] In this specification, the electrical resistance of the separator may be represented by a value measured, for example, in the following manner. A coin cell is fabricated by interposing the separator to be measured between SUS materials and injecting an electrolyte, and the electrical resistance is measured according to the EIS method. Here, for the electrical resistance measurement, the EIS frequency is set to a range of 100,000 to 10,000 Hz, and the electrolyte may, for example, use a composition in which LiPF6 is dissolved at a molar concentration in a mixed non-aqueous solvent of carbonate (EC):ethyl methyl carbonate (EMC) = 3:7 v / v. According to one embodiment of the present invention, in order to include a large amount of inorganic particles within the coating layer and to improve the dispersibility of the inorganic particles, the content of the dispersant may be 0.1 to 2 parts by weight based on 100 parts by weight of the inorganic particles.

[0078] In one embodiment of the present invention, the content of the dispersant may be, for example, 0.1 to 2 parts by weight, 0.2 to 1.8 parts by weight, 0.3 to 1.6 parts by weight, 0.4 to 1.5 parts by weight, 0.5 to 1.2 parts by weight, 0.5 to 1 part by weight, 0.5 to 1.0 parts by weight, 0.5 to 0.8 parts by weight, or 0.5 to 0.6 parts by weight, based on 100 parts by weight of the inorganic particles. When the content of the dispersant is within the range described above, it may exhibit an advantageous effect in terms of lowering the electrical resistance of the membrane by achieving the air permeability of the membrane within an appropriate range, but the effects of the present invention are not limited thereto.

[0079] In one embodiment of the present invention, the (meth)acrylate salt monomer may be one or more selected from the group consisting of, for example, sodium (meth)acrylate, potassium (meth)acrylate, lithium (meth)acrylate, ammonium (meth)acrylate, or a mixture of two or more of these, but the present invention is not limited thereto.

[0080] In one embodiment of the present invention, the acrylic monomer having an amide group is, for example, acrylamide, methylacrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, N,N-di(t-butyl)(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, NN-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-ethylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide. It may include N-methoxyethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, or a mixture of two or more of these, but the present invention is not limited thereto.

[0081] In one embodiment of the present invention, the dispersant may include a glass transition temperature (Tg) of, for example, 90 to 180°C. Specifically, the glass transition temperature of the dispersant may be, for example, 100 to 180°C, 120 to 170°C, 125 to 160°C, 129 to 155°C, 130 to 155°C, 140 to 153°C, 141 to 153°C, or 151 to 154°C. When the glass transition temperature of the dispersant is within the range described above, it is advantageous to maintain a small particle size of the slurry for forming a coating layer to facilitate the realization of a thin film coating layer, and to improve the dispersibility of solid components within the coating layer to facilitate the realization of low electrical resistance of the separation membrane; however, the effects of the present invention are not limited thereto.

[0082] In this specification, the glass transition temperature of the polymer may be a value measured, for example, using a Differential Scanning Calorimetry (DSC) instrument. The method of measuring the glass transition temperature using the DSC instrument may follow conventional methods, and for example, it may be measured according to the user manual using the TA Instrument DSC 2920 instrument.

[0083] In one embodiment of the present invention, the weight ratio of the binder and the dispersant in the coating layer may be, for example, 5:1 to 15:1. Specifically, the weight ratio of the binder and the dispersant may be, for example, a weight ratio of 7:1 to 15:1, a weight ratio of 9:1 to 15:1, a weight ratio of 10:1 to 15:1, or a weight ratio of 12:1 to 15:1. When the weight ratio of the binder and the dispersant is within the ranges described above, effects such as the adhesive strength and heat shrinkage rate of the binder can be fully exhibited, and at the same time, the effect of improving the dispersibility of the dispersant can be excellent, but the present invention is not limited thereto.

[0084] In one embodiment of the present invention, the binder may be used without limitation as long as it is capable of binding inorganic particles included in the coating layer and / or imparting adhesion between the coating layer and the porous substrate. For example, the binder may be one that can be conventionally used in a separation membrane coating layer and may include, but is not limited to, an acrylic binder, a fluorine binder, or a hybrid binder thereof. For example, the acrylic binder may be one or more selected from the group consisting of polyacrylic acid, polyacrylamide, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, ethylhexyl acrylate, methyl methacrylate, styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and copolymers comprising one or more of these. For example, the fluorine-based binder may be one or more selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polyvinylidene fluoride-trichloroethylene.

[0085] According to one embodiment of the present invention, in order to improve the heat resistance of the coating layer by the binder and increase the compatibility between the dispersant and the binder, the binder may comprise, for example, a copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and ii) a repeating unit derived from an acrylic monomer having an amide group.

[0086] In one embodiment of the present invention, the binder may comprise a non-crosslinked copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iii) a repeating unit derived from an acrylic monomer having a hydroxyl group.

[0087] In one embodiment of the present invention, the copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iii) a repeating unit derived from an acrylic monomer having a hydroxyl group, may include a "non-crosslinked copolymer." If the copolymer is a crosslinked copolymer, the molecular chains become dense and brittle, making it difficult to achieve a sufficient adhesion area with inorganic particles. Additionally, since the hydroxyl group of the repeating unit derived from the acrylic monomer having a hydroxyl group in iii) is lost due to the crosslinking reaction, the binding strength with inorganic particles is reduced, which may result in a problem of reduced wet heat shrinkage rate. Therefore, when the copolymer is included as a binder, it may be desirable to maintain a non-crosslinked copolymer even after the separator manufacturing process and the battery assembly process, but the present invention is not limited thereto. According to one embodiment of the present invention, when a non-crosslinked copolymer is included as a binder, it may be preferable to use a water-soluble solution-type binder that is soluble in an aqueous solvent such as water. Since the binder has a solution-type form, it can adhere to inorganic particles and porous substrates over a wider surface area within the coating layer, thereby having the advantage of effectively lowering the thermal shrinkage rate of the separation membrane compared to a particulate binder, but the present invention is not limited thereto.

[0088] In one embodiment of the present invention, the binder also comprises i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and ii) a repeating unit derived from an acrylic monomer having an amide group. Since the shape deformation of the binder itself is minimal at high temperatures due to the high glass transition temperature, the advantage of being able to lower the thermal shrinkage rate of the separator in the dry state can be achieved. However, a copolymer comprising only the components i) and ii) may exhibit a problem in that it is difficult to improve the thermal shrinkage rate in the wet state because the binding strength with inorganic particles in the wet state is poor. Specifically, for example, when polyacrylic acid is included as a binder, polyacrylic acid has hydrophilic properties and a high glass transition temperature, so it has the advantage of not causing swelling due to the electrolyte. However, since polyacrylic acid has poor binding strength with inorganic particles, there is a problem in that it is difficult to improve the thermal shrinkage problem of the separator in the wet state when applied to the coating layer alone. Meanwhile, in the case of a polymer of an acrylic monomer having an amide group, such as polyacrylamide, it has the advantage of high rigidity and a high glass transition temperature, resulting in minimal deformation at high temperatures. However, since it also has poor binding strength with inorganic particles like polyacrylic acid, when applied to a coating layer as a binder, either alone or in a copolymer form with an acrylic acid monomer, it may present a problem in that it is difficult to improve the thermal shrinkage problem of the separator in a wet state. In contrast, if the above binder includes a copolymer that further comprises a repeating unit derived from an acrylic monomer having a hydroxyl group in addition to i) and ii) components, the copolymer contains a sufficient amount of hydroxyl groups, so it can strongly bond with the surface of the porous substrate and / or the surface of the inorganic particles through intermolecular history such as hydrogen bonding with the inorganic particles and the porous substrate even at high temperatures where the electrolyte is present, and can also bond to the electrode surface.Accordingly, when the binder comprises the aforementioned ternary copolymer, the separator having the coating layer may exhibit the advantage of improved thermal shrinkage rate at high temperatures in both dry and wet states, but the mechanism of the present invention is not limited thereto.

[0089] In one embodiment of the present invention, the binder may comprise a non-crosslinked copolymer composed of i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iii) a repeating unit derived from an acrylic monomer having a hydroxyl group. Additionally, the binder may comprise a non-crosslinked copolymer composed of a repeating unit derived from a (meth)acrylic acid monomer, a repeating unit derived from an acrylic monomer having an amide group, and a repeating unit derived from a hydroxyalkyl acrylate monomer, but the present invention is not limited thereto.

[0090] In one embodiment of the present invention, where the binder comprises a non-crosslinked copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iii) a repeating unit derived from an acrylic monomer having a hydroxyl group, the molar ratio of the repeating unit derived from the acrylic monomer having a hydroxyl group iii) and the repeating unit derived from the (meth)acrylic acid monomer, the (meth)acrylic acid salt monomer, or both monomers may be, for example, 1:0.1 or more, 1:0.2 or more, 1:0.3 or more, or 1:0.4 or more, and furthermore, 1:1 or less, 1:0.9 or less, 1:0.8 or less, 1:0.7 or less, 1:0.6 or less, or 1: It may be 0.5 or less. In particular, the molar ratio of iii) repeating units derived from acrylic monomers having hydroxyl groups and i) repeating units derived from (meth)acrylic acid monomers, (meth)acrylic acid salt monomers, or both of these monomers may be 1:0.3 to 0.8. When the molar ratio of the repeating units satisfies the above range, the component iii) having hydroxyl groups can be sufficiently included in the copolymer, so the copolymer binder may have excellent adhesion to inorganic particles and porous polymer substrates in high temperature and wet conditions. Accordingly, a separator containing the binder in the coating layer may have a low thermal shrinkage rate in high temperature and wet conditions. In addition, since the component i) is also sufficiently included in the copolymer to impart heat resistance and increase compatibility with inorganic particles, the adhesion to inorganic particles and porous substrates in dry conditions may also be excellent, so the separator for electrochemical devices may also have a low thermal shrinkage rate in dry conditions, but the present invention is not limited thereto.

[0091] In one embodiment of the present invention, when the binder comprises a non-crosslinked copolymer consisting of i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iii) a repeating unit derived from an acrylic monomer having a hydroxyl group, the molar ratio of the repeating unit derived from the acrylic monomer having a hydroxyl group and the repeating unit derived from the acrylic monomer having an amide group may be, for example, 1:1 to 2. Specifically, the molar ratio of the repeating unit derived from the hydroxyalkyl acrylate monomer and the repeating unit derived from the acrylamide monomer may be 1:1 or higher, 1:1.1 or higher, 1:1.2 or higher, 1:1.3 or higher, 1:1.4 or higher, or 1:1.5 or higher, and may also be 1:2 or lower, 1:1.9 or lower, 1:1.8 or lower, 1:1.7 or lower, or 1:1.6 or lower, and in particular, may be 1:1.2 to 1.6. When the ratio of monomers in the copolymer satisfies the above range, the component ii) with excellent heat resistance can be sufficiently included in the copolymer, so the separator for the electrochemical device may have a low thermal shrinkage rate in the dry state. In addition, since component iii) which has excellent adhesion in a wet state can also be sufficiently included in the copolymer, the separator for the electrochemical device may also have a low thermal shrinkage rate in high temperature and wet state. That is, if the coating layer includes a binder in which the ratio of monomers in the copolymer satisfies the above range, the thermal shrinkage rate in a high temperature wet state as well as in a dry state may be lowered more evenly, but the present invention is not limited thereto.

[0092] According to one embodiment of the present invention, the acrylic monomer having a hydroxyl group may include an alkyl acrylic monomer having a hydroxyl group. In this case, the alkyl group may have, for example, 2 to 4 carbon atoms, but is not limited thereto. More specifically, the acrylic monomer having a hydroxyl group may be, for example, hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, or a mixture of two or more of these. When the copolymer includes the monomer described above as a hydroxyalkyl acrylate, the number of carbon atoms in the alkyl group bonded to the hydroxyl group is not large, so a large number of hydroxyl groups may be included per unit volume of the monomer, and accordingly, a large number of hydroxyl groups may be included per unit volume of the copolymer. Accordingly, since the copolymer binder may have excellent adhesion to inorganic particles and porous polymer substrates at high temperatures and in wet conditions, a separator for an electrochemical device containing the binder in a coating layer may have a low thermal shrinkage rate at high temperatures and in wet conditions, but the present invention is not limited thereto.

[0093] In another embodiment of the present invention, the binder may comprise i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iv) a copolymer comprising a silane monomer, a monomer having a silanol group, or a repeating unit derived from both of these monomers.

[0094] In this specification, the term "silane monomer" refers to a monomer having a hydrolyzable silane group, specifically a silane monomer having at least one alkoxy group bonded to a silicon atom. For example, the silane monomer may be represented by a chemical formula such as CH2=CHSi(OA)3, wherein A is a hydrocarbyl group containing 1 to 8 carbon atoms. During the polymerization process, the silane monomer may be hydrolyzed by water or steam, so that the alkoxy group is substituted with a silanol group. Additionally, the term "monomer having a silanol group" refers to a monomer having a silanol group in a side chain.

[0095] In another embodiment of the present invention, the above iv) component can be strongly bonded to the surface of the porous substrate or the surface of the inorganic particle through intermolecular forces such as hydrogen bonding with the inorganic particle and the porous substrate, and can also be bonded to the electrode surface. Consequently, the separator for an electrochemical device according to the present invention, in which the copolymer binder is included in the coating layer, can exhibit the advantage of particularly improved high-temperature thermal shrinkage rate in both dry and wet states, but the present invention is not limited thereto.

[0096] Specifically, when the above-mentioned silane monomer is applied to an aqueous solvent such as water to form a coating layer, it contains silanol groups, and thus possesses silanol groups similar to monomers having silanol groups. A copolymer having silanol groups can strongly bond to the surface of a porous substrate, the surface of an inorganic particle, or the surface of an electrode through intermolecular forces such as hydrogen bonding. Consequently, a separator containing the above-mentioned copolymer binder in the coating layer can have a low thermal shrinkage rate in both dry and wet states, but the present invention is not limited thereto.

[0097] In another embodiment of the present invention, when the binder comprises i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iv) a copolymer comprising a silane monomer, a monomer having a silanol group, or a repeating unit derived from both of these monomers, the binder may be a solution-type binder. Since the binder has a solution-type form, it can adhere to inorganic particles and a porous substrate over a wider surface area within the coating layer, thereby having the advantage of effectively lowering the thermal shrinkage rate of the separator compared to a particle-type binder. In this case, the silanol group of the silane monomer having a silanol group or the silanol group of the monomer having a silanol group can bond to the surface of the porous substrate, the surface of the inorganic particle, or the surface of the electrode through intermolecular forces such as hydrogen bonding by hydrolysis.

[0098] Meanwhile, silicon-containing silicon acrylate monomers do not contain silane groups or silanol groups, unlike the silane monomers mentioned above. Therefore, even if the silicon acrylate monomer is copolymerized with an acrylic monomer and an acrylamide monomer, such copolymers cannot interact strongly with the surface of inorganic particles and porous substrates. Consequently, copolymer binders containing the silicon acrylate monomer, acrylic monomer, and acrylamide monomer may have poor heat resistance in a wet state.

[0099] In one embodiment of the present invention, when the binder comprises a copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iv) a repeating unit derived from a silane monomer, a monomer having a silanol group, or both monomers, the molar ratio of i) the repeating unit derived from the (meth)acrylic acid monomer, the (meth)acrylic acid salt monomer, or both monomers, and iv) the repeating unit derived from the silane monomer, the monomer having a silanol group, or both monomers may be 1:0.01 or more and 1:0.1 or less. Specifically, the molar ratio of the above i) (meth)acrylic acid monomer, (meth)acrylic acid salt monomer, or repeating unit derived from both monomers and the above iv) silane monomer, monomer having a silanol group, or repeating unit derived from both monomers may be 1:0.01 or more, 1:0.02 or more, 1:0.03 or more, 1:0.04 or more, or 1:0.05 or more, and may also be 1:0.1 or less, 1:0.09 or less, 1:0.08 or less, 1:0.07 or less, 1:0.06 or less, 1:0.05 or less, 1:0.04 or less, or 1:0.03 or less. When the content of each monomer included in the copolymer satisfies the above range, the above iv) silane-based monomer, monomer having a silanol group, or repeating unit derived from both of these monomers can be sufficiently included in the copolymer, so the interaction between the copolymer and the inorganic particles can be excellent. Accordingly, the copolymer binder can have excellent adhesion to the inorganic particles and the porous polymer substrate. Accordingly, a separator for an electrochemical device containing the copolymer binder in the coating layer can have a low thermal shrinkage rate at high temperatures and in wet conditions.

[0100] In one embodiment of the present invention, when the binder comprises a copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iv) a repeating unit derived from a silane monomer, a monomer having a silanol group, or both monomers, the molar ratio of i) the (meth)acrylic acid monomer, the (meth)acrylic acid salt monomer, or both monomers having a repeating unit derived from both monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iv) a repeating unit derived from a silane monomer, a monomer having a silanol group, or both monomers having a repeating unit derived from both monomers may be, for example, 1: 3 or more and 5 or less: 0.01 or more and 0.1 or less. When the content of each monomer included in the copolymer satisfies the above range, i) (meth)acrylic acid monomer, (meth)acrylic acid salt monomer, or repeating units derived from both monomers and ii) repeating units derived from acrylic monomers having amide groups, which are effective for improving adhesion in a dry state, and iv) silane monomers, monomers having silanol groups, or repeating units derived from both monomers, which are effective for improving adhesion in a wet state, are present in balance so that improvement in heat shrinkage rate in both dry and wet states can be achieved, but the effects of the present invention are not limited thereto.

[0101] In one embodiment of the present invention, the binder may comprise a weight average molecular weight (Mw) of, for example, 100,000 g / mol to 200,000 g / mol. Specifically, the weight average molecular weight of the binder may be 100,000 g / mol or more, 110,000 g / mol or more, 120,000 g / mol or more, 130,000 g / mol or more, 140,000 g / mol or more, or 150,000 g / mol or more, and may also be 200,000 g / mol or less, 190,000 g / mol or less, 180,000 g / mol or less, 170,000 g / mol or less, 160,000 g / mol or less, or 150,000 g / mol or less. When the weight-average molecular weight of the binder satisfies the above range, the binder may have a sufficient length to effectively prevent the problem of the inorganic particles detaching from the porous substrate by being attached together to the inorganic particles and the porous substrate. Accordingly, a separator for an electrochemical device in which a coating layer containing the binder is disposed on one side of a porous substrate has the advantage of having a low thermal shrinkage rate in dry and wet conditions, but the present invention is not limited thereto.

[0102] In one embodiment of the present invention, the glass transition temperature (Tg) of the binder may be, for example, 100 to 200°C. Specifically, the glass transition temperature of the binder may be, for example, 120 to 180°C, 140 to 160°C, 150 to 155°C, or 155 to 160°C. When the glass transition temperature of the binder is within the range described above, it may have an advantageous effect in reducing the swelling phenomenon caused by the electrolyte and improving not only the dry thermal shrinkage rate but also the wet thermal shrinkage rate of the coating layer, but the present invention is not limited thereto.

[0103] In one embodiment of the present invention, the inorganic particles may be used without limitation as long as they can be included in the coating layer to improve the heat resistance of the separator. The inorganic particles may be, for example, within the operating voltage range of an electrochemical device (e.g., Li / Li + Oxidation and / or reduction reactions may not occur at a standard of 0 V to 5 V. Specifically, the inorganic particles are BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT, 0 <x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3 It may be one or more selected from the group consisting of )O3-PbTiO3(PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, Al(OH)3, TiO2, boehmite, aluminum peroxide, zinc-tin hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4) and antimony pentoxide (Sb2O5). Among these, boehmite, alumina, or a mixture thereof may be particularly selected.

[0104] In one embodiment of the present invention, the inorganic particles may be inorganic particles having lithium ion transfer capability, that is, inorganic particles containing lithium elements but having the function of transporting lithium ions without storing lithium. Non-limiting examples of inorganic particles having lithium ion transfer capability include lithium phosphate (Li3PO4) and lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z(PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), such as (LiAlTiP) 14Li2O-9Al2O3-38TiO2-39P2O5 x O y Series glass (0 <x < 4, 0 < y < 13), 리튬란탄티타네이트(Li x La y TiO3, 0 < x <2, 0 <y <3), Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate (Li) such as S4, etc. x Ge y P z S w Lithium nitrides such as , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), Li3N, etc. (Li x N y , 0 < x < 4, 0 < y < 2), SiS2 series glass such as Li3PO4-Li2S-SiS2 (Li x Si y S z , 0 < x < 3, 0 <y < 2, 0 < z < 4), LiI-Li2S-P2S5등과 같은 P2S5계열 glass(Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7) or mixtures thereof, etc.

[0105] In one embodiment of the present invention, the inorganic particles may be flame-retardant inorganic particles capable of imparting flame-retardant properties to the separator or preventing a rapid rise in temperature inside the electrochemical device. Non-limiting examples of flame-retardant inorganic particles include Sb2O3, Sb2O4, Sb2O5, SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, Zn2SnO4, ZnSnO3, ZnSn(OH)6, ZrO2, Y2O3, SiO2, Al2O3, AlOOH, Al(OH)3, SiC, TiO2, H3BO3, HBO2, and mixtures thereof.

[0106] In one embodiment of the present invention, the inorganic particles may specifically include boehmite, alumina, or a mixture thereof, but the present invention is not limited thereto. When the inorganic particles include boehmite, alumina, or a mixture thereof, the heat resistance of the separation membrane may be further improved through interaction with the binder, but the present invention is not limited thereto.

[0107] According to one embodiment of the present invention, the inorganic particles have an average particle size (D 50 The particle size may be 200 nm or larger and 1 μm or smaller. Specifically, the inorganic particle may have an average particle size of 200 nm or larger, 300 nm or larger, 400 nm or larger, or 500 nm or larger, and may also have an average particle size of 1 μm or smaller, 900 nm or smaller, 800 nm or smaller, 700 nm or smaller, 600 nm or smaller, or 550 nm or smaller. When the average particle size of the inorganic particle satisfies the above range, there may be sufficient spacing between the inorganic particles packed within the coating layer, and accordingly, the porosity of the coating layer may be high, which may have an advantageous effect in terms of reducing the resistance of the separator, but the present invention is not limited thereto.

[0108] According to one embodiment of the present invention, the porosity of the coating layer may be, for example, 30 volume% or more and 50 volume% or less. Specifically, the porosity of the coating layer may be 30 volume% or more, 35 volume% or more, or 40 volume% or more, and may also be 50 volume% or less, 45 volume% or less, or 40 volume% or less. When the porosity of the coating layer satisfies the above range, sufficient pores may exist in the coating layer, allowing lithium ions to move smoothly through the pores, and accordingly, the resistance of the separator for an electrochemical device may be low. Furthermore, compared to the case where the porosity of the coating layer is excessively high and there are excessively many pores within the coating layer, the separator for an electrochemical device according to the present invention may have excellent mechanical strength, but the present invention is not limited thereto.

[0109] In one embodiment of the present invention, the content of the inorganic particles based on 100 parts by weight of the coating layer may be, for example, 80 to 95 parts by weight. Specifically, based on 100 parts by weight of the solid content of the coating layer, the content of the inorganic particles may be 80 to 95 parts by weight, 85 to 93 parts by weight, or 90 to 92 parts by weight. When the content of the inorganic particles satisfies the above range, the inorganic particles may be sufficiently included in the coating layer, thereby minimizing the problem of thermal shrinkage of the porous polymer substrate in the separator for an electrochemical device, but the present invention is not limited thereto.

[0110] According to one embodiment of the present invention, the thickness of the coating layer may be, for example, 0.5 μm to 2 μm. Specifically, the thickness of the coating layer may be 0.5 μm or more, 0.7 μm or more, 0.9 μm or more, or 1.0 μm or more, and may also be 2 μm or less, 1.8 μm or less, 1.6 μm or less, or 1.5 μm or less. When the thickness of the coating layer satisfies the above range, lithium ions can pass through the coating layer more smoothly due to the low coating layer thickness, and accordingly, the separator for the electrochemical device may exhibit the advantage of low resistance. Furthermore, since the total thickness of the separator for the electrochemical device including the coating layer may also be low, the electrochemical device including the separator for the electrochemical device may contain a relatively large amount of electrode active material, and accordingly, the energy density of the electrochemical device may also be high, but the present invention is not limited thereto.

[0111] In a separator according to one aspect of the present invention, the porous substrate may be a porous membrane having a plurality of pores formed therein, and may be intended to electrically insulate the positive electrode and the negative electrode to prevent a short circuit. For example, when the electrochemical device is a lithium secondary battery, the porous substrate may be an ion-conducting barrier that blocks electrical contact between the positive electrode and the negative electrode while allowing lithium ions to pass through. At least some of the pores may form a three-dimensional network communicating the surface and the interior of the porous substrate, and a fluid may pass through the porous substrate through the pores.

[0112] In one embodiment of the present invention, the porous substrate may be a material that is physically and chemically stable with respect to an electrolyte, which is an organic solvent. For example, the porous substrate may include, but is not limited to, resins such as polyolefins including polyethylene, polypropylene, and polybutylene, polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyamideimide, nylon, polytetrafluoroethylene, and copolymers or mixtures thereof. Preferably, a polyolefin resin may be used. Polyolefin resins are suitable for manufacturing electrochemical devices with higher energy density because they can be processed to a relatively thin thickness and facilitate the application of a coating slurry.

[0113] In one embodiment of the present invention, the porous substrate may have a single-layer or multi-layer structure. The porous substrate may include two or more polymer resin layers having different melting points (Tm) to provide a shutdown function during high-temperature runaway of the battery. For example, the porous substrate may include a polypropylene layer with a relatively high melting point and a polyethylene layer with a relatively low melting point. Preferably, the porous substrate may have a three-layer structure laminated in the order of polypropylene, polyethylene, and polypropylene. The polyethylene layer may prevent thermal runaway of the battery by shutting down the pores as it melts as the temperature of the battery rises above a predetermined temperature.

[0114] In one embodiment of the present invention, the thickness of the porous substrate may be, for example, 1 μm or more and 100 μm or less. Specifically, the thickness of the porous substrate may be 10 μm or more and 90 μm or less, 20 μm or more and 80 μm or less, 30 μm or more and 70 μm or less, or 40 μm or more and 60 μm or less. Preferably, the thickness of the porous substrate may be 1 μm or more and 30 μm or less. More preferably, the thickness of the porous substrate may be 5 μm or more and 15 μm or less, or 8 μm or more and 13 μm or less. By controlling the thickness of the porous substrate within the above-described range, the volume of the electrochemical device can be minimized while electrically insulating the anode and the cathode, thereby increasing the amount of active material included in the electrochemical device, but the present invention is not limited thereto.

[0115] In one embodiment of the present invention, the porous substrate may include pores having an average diameter of 0.01 μm or more and 1 μm or less. Specifically, the size of the pores included in the porous substrate may be 0.01 μm or more and 0.09 μm or less, 0.02 μm or more and 0.08 μm or less, 0.03 μm or more and 0.07 μm or less, or 0.04 μm or more and 0.06 μm or less. Preferably, the size of the pores may be 0.02 μm or more and 0.06 μm or less. By controlling the pore size of the porous substrate within the above-described range, the air permeability and ion conductivity of the entire separation membrane being manufactured can be controlled, but the present invention is not limited thereto.

[0116] In one embodiment of the present invention, the porous substrate may have an air permeability of 10 s / 100cc or more and 100 s / 100cc or less. Specifically, the air permeability of the porous substrate may be 10 s / 100cc or more and 90 s / 100cc or less, 20 s / 100cc or more and 85 s / 100cc or less, 30 s / 100cc or more and 80 s / 100cc or less, 40 s / 100cc or more and 80 s / 100cc or less, 50 s / 100cc or more and 70 s / 100cc or less, 60 s / 100cc or more and 78 s / 100cc or less, 65 s / 100cc or more and 78 s / 100cc or less, 70 s / 100cc or more and 78 s / 100cc or less, or 75 s / 100cc or more and 78 s / 100cc or less. When the air permeability of the porous substrate is within the range described above, the air permeability of the manufactured separator can be provided within a range suitable for securing the output and cycle characteristics of the electrochemical device, but the present invention is not limited thereto.

[0117] According to one embodiment of the present invention, a separator having the coating layer described above may have an air permeability of, for example, 80 s / 100 cc or less. Specifically, the air permeability of the separator may be, for example, 10 to 80 s / 100 cc, 30 to 80 s / 100 cc, 50 to 80 s / 100 cc, 70 to 80 s / 100 cc, 75 to 80 s / 100 cc, 75 to 79 s / 100 cc, 75 to 78 s / 100 cc, 75 to 76 s / 100 cc, or 74 to 75 s / 100 cc, but the present invention is not limited thereto.

[0118] In this specification, the air permeability (s / 100cc) of the porous substrate and the separator refers to the time (in seconds) required for 100cc of air to pass through a porous substrate or separator of a predetermined area under constant pressure. The air permeability may be measured using a Gurley densometer in accordance with ASTM D 726-58, ASTM D726-94, or JIS-P8117. For example, using a Gurley 4110N instrument, air at a pressure of 0.304 kPa or 1.215 kN / m 2 100cc of air under water pressure is 1 square inch (or 6.54 cm²) 2 The time it takes for ) to pass through a sample can be measured. For example, using the Asahi Seico EG01-55-1MR instrument, the time it takes for 100cc of air to pass through a 1 square inch sample under a constant pressure of 4.8 inches of water at room temperature can be measured.

[0119] In one embodiment of the present invention, the porous substrate may have a porosity of, for example, 10 vol% or more and 60 vol% or less. Specifically, the porosity of the porous substrate may be 15 vol% or more and 55 vol% or less, 20 vol% or more and 50 vol% or less, 25 vol% or more and 45 vol% or less, or 30 vol% or more and 40 vol% or less. Preferably, the porosity of the porous substrate may be 30 vol% or more and 55 vol% or less. When the porosity of the porous substrate is within the range described above, the ion conductivity of the manufactured separator may be provided within a range suitable for securing the output and cycle characteristics of the electrochemical device, but the present invention is not limited thereto.

[0120] In this specification, the porosity refers to the ratio of the volume of pores to the total volume of the porous substrate. The porosity may be measured by methods known in the art. For example, it may be measured by the BET (Brunauer Emmett Teller) measurement method using the adsorption of nitrogen gas, the capillary flow porometer, or the water or mercury infiltration method.

[0121] According to one embodiment of the present invention, the coating layer may be formed using a slurry for forming a coating layer.

[0122] According to one embodiment of the present invention, the slurry for forming the coating layer comprises the inorganic particles, binder, and dispersant described above as solids, and may include a dispersion solvent as a dispersion medium for dispersing them.

[0123] In one embodiment of the present invention, the slurry for forming a coating layer may include a dispersion medium to dissolve or disperse at least a portion of the binder and to disperse inorganic particles. It is preferable to use a slurry for forming a coating layer in which the binder and inorganic particles are uniformly dispersed by adjusting the type and content of the dispersion medium. For example, the dispersion medium may include water, ethanol, acetone, isopropyl alcohol (IPA), dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), acetonitrile, or a mixture of two or more of these, but the present invention is not limited thereto. A coating layer in which inorganic particles are uniformly dispersed may be formed using the types of dispersion media described above, but the present invention is not limited thereto.

[0124] In one embodiment of the present invention, the slurry for forming a coating layer may exhibit a negative charge by including i) a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or a repeating unit derived from both monomers within the structure of the dispersant as described above. For example, the zeta potential of the slurry for forming a coating layer may be -40 mV or less. Specifically, the zeta potential of the coating layer may be -55 mV or more and -40 mV or less, or -51 mV or more and -42 mV or less. When the zeta potential of the slurry for forming a coating layer is within the range described above, sufficient repulsion between inorganic particles is achieved to prevent aggregation of the slurry, thereby exhibiting the advantages of lowering the electrical resistance of the formed coating layer and improving the thermal shrinkage rate; however, the present invention is not limited thereto.

[0125] In this specification, the "zeta potential" of the slurry for forming the coating layer may be a measurement of the surface charge of the solid components, including inorganic particles, a binder, and a dispersant, included in the coating layer. The measurement of the zeta potential may be performed in a solvent in which the solid components are dispersed. Specifically, the zeta potential may be a value measured using a dynamic light scattering device (Zetasizer Lab, Malvern Panalytical) at room temperature after diluting a slurry containing inorganic particles, a binder, a dispersant, and other additives (wetting agents, thickeners, etc.) in water to a concentration of 0.1 to 1.0 weight%.

[0126] In one embodiment of the present invention, the slurry for forming the coating layer has a particle size (D 90 ) may be, for example, 0.65 μm or less. Specifically, the particle size (D) of the slurry for forming the coating layer is 90The particle size of the slurry for forming the coating layer may be 0.60 μm or less or 0.56 μm or less. When the particle size of the slurry for forming the coating layer is within the range described above, a thin coating layer can be formed with a uniform thickness, and accordingly, the air permeability of the separator can be lowered and the energy density of the electrochemical device can be increased, but the present invention is not limited thereto.

[0127] According to one embodiment of the present invention, the dispersion medium included in the slurry for forming the coating layer may be removed by drying or heating after the formation of the coating layer. For example, the coating layer may contain the dispersion medium at a concentration of 5 ppm or less. Preferably, the porous coating layer may be composed of inorganic particles, a binder, and a dispersant. During the process of removing the dispersion medium, a plurality of pores may be formed on the surface and inside the coating layer. The pores may include an interstitial volume formed by adjacent inorganic particles being connected by the polymer binder, and may have a structure that allows fluid to pass through by forming a three-dimensional network.

[0128] According to one embodiment of the present invention, a method for manufacturing a separator for an electrochemical device may be provided, comprising the steps of: forming a coating layer by coating at least one surface of a porous substrate with a slurry for forming a coating layer comprising the binder, inorganic particles, a dispersant, and a dispersion medium; and manufacturing a separator by drying the coating layer to remove the dispersion medium. Any content overlapping with that described in the description of the separator for an electrochemical device is replaced by the preceding description.

[0129] In one embodiment of the present invention, the step of forming the coating layer involves coating at least one surface of a porous substrate with a coating slurry comprising a polymer binder, inorganic particles, a dispersant, and a dispersion medium. For example, the coating may be formed by a method such as a bar coater, wire bar coater, roll coater, spray coater, spin coater, inkjet coater, screen coater, reverse coater, gravure coater, knife coater, slot die coater, hot melt coater, comma coater, direct metering coater, etc., but is not limited thereto. Preferably, the step of forming the coating layer may involve coating a cross-section of the porous substrate or simultaneously coating both sides using a bar coater or a slot die coater with the coating slurry.

[0130] In one embodiment of the present invention, the step of forming the coating layer may further include the step of corona discharge treatment of at least one surface of the porous substrate. After the corona discharge treatment step, the slurry for forming the coating layer may be coated onto the surface-treated surface of the porous substrate. The step of corona discharge treatment of at least one surface of the porous substrate prevents a decrease in the bonding strength between the surface of the porous substrate and the surface of the coating layer at high temperatures, and prevents a decrease in the bonding strength between the surface of the porous substrate and the surface of the coating layer due to the electrolyte.

[0131] In one embodiment of the present invention, the corona discharge treatment may be performed by treating at least one surface of the porous substrate with a voltage of 0.1 kV or more and 10 kV or less in air. Specifically, the corona discharge treatment may be performed by treating with a voltage of 0.2 kV or more and 9 kV or less, 0.3 kV or more and 8 kV or less, 0.4 kV or more and 7 kV or less, 0.5 kV or more and 6 kV or less, 0.6 kV or more and 5 kV or less, 0.7 kV or more and 4 kV or less, 0.8 kV or more and 3 kV or less, 0.9 kV or more and 2 kV or less, or 1.0 kV or more and 2 kV or less in air. Preferably, the corona discharge treatment may be performed with a voltage of 1.8 kV in air. By adjusting the applied voltage of the corona discharge treatment within the above-described range, appropriate waterway functional groups can be formed on the surface of the porous substrate, and damage to the surface of the porous substrate can be prevented.

[0132] In one embodiment of the present invention, the step of removing the dispersion medium to manufacture a separation membrane may involve drying or heating the coating layer to evaporate the dispersion medium contained in the coating layer. The dispersion medium removal step may be performed at a temperature that allows only the dispersion medium contained in the coating layer to evaporate without deforming the polymer binder contained in the coating layer. For example, the dispersion medium removal step may involve heating the coating layer to a predetermined temperature, provided that the surface temperature of the coating layer does not exceed 60°C. When heating the coating layer under these conditions, thermal energy may first be used to heat the dispersion medium to cause a phase change, and may not be used to deform the polymer binder.

[0133] A separator according to one aspect of the present invention may, for example, have a wet heat shrinkage rate of 10% or less, 9% or less, specifically 0% to 10%, 1% to 9%, 2% to 8%, 3% to 7%, 4% to 6%, or 4% to 5%, but the present invention is not limited thereto. The heat shrinkage rate of the separator in at least one of MD (machine direction) and TD (transverse direction) may be within the above-described range, and preferably, the heat shrinkage rate measured in both MD and TD directions is implemented within the above-described range, thereby demonstrating the excellent effects of the present invention.

[0134] In this specification, the wet heat shrinkage rate can be calculated using the following formula by, for example, preparing a separator to be measured as a specimen of size 5 cm x 5 cm, inserting each into an aluminum pouch of size 7 cm x 10 cm, injecting 1 g of electrolyte, sealing the pouch, storing it in a convection oven at 140°C for 30 minutes, removing the separator, and measuring the ratio of the reduced length of the specimen to the length of the original specimen. At this time, the electrolyte may be used to include, for example, 2 wt% vinylene carbonate (VC) and the lithium salt LiPF61 M as additives to a solvent mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a weight ratio of 3 / 7.

[0135] [(Initial specimen length - Length after storage at @140℃ / 0.5h) / (Initial specimen length)] X 100 (%)

[0136]

[0137] According to another aspect of the present invention, an electrochemical device comprising the above-described separator is provided.

[0138] An electrochemical device according to another aspect of the present invention comprises an anode, a cathode, and a separator, wherein the separator has a structure interposed between the anode and the cathode.

[0139] In an electrochemical device according to one embodiment of the present invention, details that overlap with the description of the separator for the electrochemical device are omitted.

[0140] The above-mentioned electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept that encompasses primary batteries and secondary batteries. The above-mentioned secondary batteries are capable of charging and discharging and refer to lithium secondary batteries, nickel-cadmium batteries, nickel-hydrogen batteries, etc. The above-mentioned lithium secondary batteries use lithium ions as ion conductors, and examples include, but are not limited to, non-aqueous electrolyte secondary batteries containing a liquid electrolyte, all-solid-state batteries containing a solid electrolyte, lithium polymer batteries containing a gel polymer electrolyte, and lithium metal batteries using lithium metal as the negative electrode.

[0141] As the above-described electrochemical device includes the separator for the electrochemical device of the present invention, the adhesion between the separator for the electrochemical device and the electrode can be excellent, and accordingly, there is an advantage that the decrease in safety due to the detachment of the separator can be minimized even when the electrochemical device is operated for a long period of time.

[0142] According to one embodiment of the present invention, the electrochemical device may be manufactured by inserting an electrode assembly, for example, comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, into a battery case and sealing it. Before sealing the battery case, an electrolyte may be injected to impregnate the electrode assembly with the electrolyte. The shape of the battery case is not limited and may be, for example, cylindrical, prismatic, coin-shaped, or pouch-shaped.

[0143] According to one embodiment of the present invention, the positive electrode may comprise a positive electrode current collector and a positive electrode active material layer comprising a positive electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The positive electrode active material is a layered compound such as a lithium manganese complex oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 ~ 0.3); chemical formula LiMn 1-x M x It may comprise a lithium manganese complex oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the Li of the chemical formula is substituted with alkaline earth metal ions; a disulfide compound; or a mixture of two or more of Fe2(MoO4)3.

[0144] According to one embodiment of the present invention, the cathode may comprise a cathode current collector and a cathode active material layer comprising a cathode active material, a conductive material, and a binder resin on at least one surface of the current collector. The cathode may comprise carbon such as lithium metal oxide, non-graphitizable carbon, or graphite-based carbon as the cathode active material; Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Snx Me 1-x Me y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, and 3 elements of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물 중 선택된 1종 또는 2종 이상의 혼합물을 포함하는 것일 수 있다.

[0145] According to one embodiment of the present invention, the conductive material may be, for example, any one selected from the group consisting of graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whiskers, conductive metal oxide, activated carbon, and polyphenylene derivative, or a mixture of two or more of these conductive materials. More specifically, it may be one selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more of these conductive materials.

[0146] According to one embodiment of the present invention, the current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used.

[0147] According to one embodiment of the present invention, the binder resin may be a polymer commonly used in the industry for electrodes. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples include acetatepropionate), cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, but are not limited thereto.

[0148] According to one embodiment of the present invention, the anode slurry for manufacturing the anode active material layer may include a dispersant, and the dispersant may be a pyrrolidone-based compound. Specifically, it may be N-methylpyrrolidone (N-methylpyrrolidone, ADC-01, LG Chem).

[0149] According to one embodiment of the present invention, the electrochemical element may further include an electrolyte, and the electrolyte is A + B - As a salt with a structure like that, A + is Li + , Na + , K + It may include alkali metal cations such as or ions composed of a combination thereof. In addition, B - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - A salt comprising an anion such as or a combination thereof may be dissolved or dissociated in an organic solvent comprising propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone, or a mixture thereof, but is not limited thereto.

[0150] One embodiment of the present invention may provide a battery module comprising a battery including the electrochemical element as a unit cell, a battery pack comprising the battery module, and a device comprising the battery pack as a power source. Specific examples of the device include, but are not limited to, a power tool that moves by receiving power from a battery motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle including an electric bicycle (E-bike) or an electric scooter (E-scooter); an electric golf cart; and a power storage system.

[0151] According to one embodiment of the present invention, the electrochemical device may form a cylindrical secondary battery by interposing a separator for the electrochemical device between the positive electrode and the negative electrode. In this case, the separator, the positive electrode, and the negative electrode may be stacked in the form of an electrode assembly having a separator / positive electrode / separator / negative electrode structure or a positive electrode / separator / negative electrode / separator structure and then wound. The positions of the positive electrode and the negative electrode may be interchanged. The electrode assembly stacked as described above may be inserted into a cylindrical can after being bound to a winding core and crimped to be manufactured into a cylindrical secondary battery.

[0152]

[0153] The present invention will be explained in more detail below through specific embodiments and experimental examples. The following embodiments and experimental examples are intended to illustrate the present invention, and the present invention is not limited by the following embodiments and experimental examples.

[0154] Example 1

[0155] Preparation of a slurry for forming a coating layer

[0156] Average particle size (D) of inorganic particles 50 Boehmite (AlOOH) with a molecular weight of 500 nm was prepared. A copolymer was prepared containing repeating units derived from acrylic acid (AA), acrylamide (AM), and hydroxyethyl acrylate (HEA) monomers in a molar ratio of 0.4:1.6:1 (AA:AM:HEA) as a binder (weight-average molecular weight: 150,000 g / mol, Tg: 155 ℃).

[0157] As a dispersant, a copolymer (weight-average molecular weight: 150,000 g / mol) was prepared by polymerizing acrylic acid (AA) and acrylamide (AM) in a molar ratio of 2:8.

[0158] Sodium carboxymethyl cellulose (CMC-Na) (SG-L02, GL Chem) was prepared as a thickening agent.

[0159] Next, the inorganic particles, binder, dispersant, and thickener prepared above were added to distilled water at room temperature (25℃) in a weight ratio of 92:6:0.5:1.5 and stirred with a shaker for 120 minutes to prepare a coating slurry (solid content: 30%).

[0160]

[0161] Preparation of porous substrate

[0162] As the porous substrate, a polyethylene film with a porosity of 55 vol% and a thickness of 10 μm was used.

[0163]

[0164] Manufacturing of separation membranes

[0165] A slurry for forming a coating layer was applied to both sides of the porous substrate prepared above using a doctor blade in a bar coating method, and dried with a heat gun at 50°C to produce a separation membrane with a coating layer formed on both sides of the porous substrate.

[0166]

[0167] Example 2

[0168] A separation membrane was prepared in the same manner as in Example 1, except that the weight-average molecular weight of the dispersant was changed to 50,000 g / mol when preparing the slurry for forming the coating layer.

[0169]

[0170] Example 3

[0171] A separation membrane was prepared in the same manner as in Example 1, except that the molar ratio of acrylic acid and acrylamide-derived units in the dispersant was changed to 4:6 when preparing the slurry for forming the coating layer.

[0172]

[0173] Example 4

[0174] A separation membrane was prepared in the same manner as in Example 1, except that the molar ratio of acrylic acid and acrylamide-derived units of the dispersant was changed to 6:4 when preparing the slurry for forming the coating layer.

[0175]

[0176] Example 5

[0177] A separation membrane was prepared in the same manner as in Example 1, except that the weight ratio of inorganic particles, binder, dispersant, and thickener was changed to 90.5:7.5:0.5:1.5 when preparing the slurry for forming the coating layer.

[0178]

[0179] Comparative Example 1

[0180] A separation membrane was prepared in the same manner as in Example 1, except that the weight-average molecular weight of the dispersant was changed to 25,000 g / mol when preparing the slurry for forming the coating layer.

[0181]

[0182] Comparative Example 2

[0183] A separation membrane was prepared in the same manner as in Example 1, except that the weight-average molecular weight of the dispersant was changed to 300,000 g / mol when preparing the slurry for forming the coating layer.

[0184]

[0185] Comparative Example 3

[0186] A separation membrane was prepared in the same manner as in Example 1, except that the molar ratio of acrylic acid and acrylamide-derived units in the dispersant was changed to 1:9 when preparing the slurry for forming the coating layer.

[0187]

[0188] Comparative Example 4

[0189] A separation membrane was prepared in the same manner as in Example 1, except that polyacrylic acid (PA) was used as a dispersant when preparing the slurry for forming the coating layer.

[0190]

[0191] Comparative Example 5

[0192] A separation membrane was manufactured in the same manner as in Example 1, except that inorganic particles, a binder, a dispersant, and a thickener were added in a weight ratio of 90.5:6:2:1.5 when preparing the slurry for forming the coating layer.

[0193]

[0194] Experimental Example.

[0195] Particle size (D90) and zeta potential of the slurry for forming the coating layer

[0196] Particle size (D) of the slurry for forming a coating layer according to the above examples and comparative examples 90 The zeta potential of the coating layer forming slurry was measured using a particle size analyzer (Mastersizer 3000, Malvern) utilizing laser diffraction. In addition, the zeta potential of the coating layer forming slurry was measured using a dynamic light scattering instrument (Zetasizer Lab, Malvern Panalytical).

[0197]

[0198] Thickness of the coating layer

[0199] The thickness of each side of the manufactured coating layer was measured using a thickness gauge (Mitutoyo).

[0200]

[0201] Membrane air permeability measurement

[0202] Air permeability was measured using a Gurley densometer (Gurley, 4110N) for 100 cc of air with a diameter of 28.6 mm and an area of ​​645 mm² 2 The time taken to pass through the separation membrane was measured.

[0203]

[0204] Measurement of electrical resistance of the separator

[0205] A coin cell was fabricated by interposing a separator between SUS materials and injecting an electrolyte, and the electrical resistance (ER) was measured using the EIS method. At this time, the frequency was set to a range of 100,000 to 10,000 Hz. The electrolyte was prepared by dissolving LiPF6 at a concentration of 1 molar in a non-aqueous solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a 3:7 ratio.

[0206]

[0207] Measurement of Wet Heat Shrinkage Rate of Separator

[0208] The separators of the above examples and comparative examples were prepared as specimens measuring 5 cm x 5 cm and each was inserted into an aluminum pouch measuring 7 cm x 10 cm. 1 g of the following electrolyte was injected into the pouch, and the pouch was sealed.

[0209] The above electrolyte was used to contain 2 wt% vinylene carbonate (VC) and lithium salt LiPF61 M as additives to a solvent mixed with ethylene carbonate (EC) / ethylmethyl carbonate (EMC) in a weight ratio of 3 / 7.

[0210] After storing the sealed pouch in a 140℃ convection oven for 30 minutes, the separator was removed, and the thermal shrinkage rates in the MD direction and TD direction were calculated according to [(length of the initial specimen - length after storage at @140℃ / 0.5h) / (length of the initial specimen)] X 100 (%).

[0211]

[0212] Example 1 Example 2 Example 3 Example 4 Example 5 Dispersant AA:AM Molar Ratio 2:8 2:8 4:6 6:42:8 Molecular Weight (g / mol) 150,000 50,000 150,000 150,000 150,000 150,000 Tg of Dispersant (°C) 153 153 14 11 29 153 Inorganic Particles:Polymer Binder:Dispersant Content:Other Additives 92:6:0.5:1.5 92:6:0.5:1.5 92:6:0.5:1.5 92:6:0.5:1.5 90.5:7.5:0.5:1.5 Zeta Potential (mV) of Coating Layer Forming Slurry -5 1 -42 -46 -47 -43 Particle Size (㎛, ) of Coating Layer Forming Slurry D50)0.47 0.56 0.49 0.51 0.48 Coating layer thickness (㎛) 1.5 / 1.5 1.5 / 1.5 1.5 / 1.5 1.5 / 1.5 1.5 / 1.5 Separator air permeability (sec / 100cc) 75 79 78 76 76 Separator wet heat shrinkage rate (MD(%) / TD(%)) 6 / 49 / 78 / 67 / 58 / 7 Separator electrical resistance (Ω) 0.51 0.55 0.54 0.53 0.53

[0213] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Dispersant AA:AM Molar Ratio 2:8 2:8 1:9 10:02:8 Molecular Weight (g / mol) 25,000 300,000 150,000 150,000 150,000 150,000 Tg of Dispersant (°C) 153 153 159 105 153 Inorganic Particles:Polymer Binder:Dispersant Content:Other Additives 92:6:0.5:1.5 92:6:0.5:1.5 92:6:0.5:1.5 92:6:0.5:1.5 90.5:6:2:1.5 Zeta Potential (mV) of Coating Layer Forming Slurry -35 -41 -37 -44 -34 Particle Size (㎛, ) of Coating Layer Forming Slurry D50)0.67 0.8 4 0.65 0.9 1 0.71 Coating layer thickness (㎛) 1.5 / 1.5 1.5 / 1.5 1.5 / 1.5 1.5 / 1.5 1.5 / 1.5 Separator air permeability (sec / 100cc) 8 0 9 3 8 1 8 5 83 Separator wet heat shrinkage rate (MD(%) / TD(%)) 1 6 / 10 1 3 / 11 1 2 / 10 1 6 / 13 1 1 / 10 Separator electrical resistance (Ω) 0.6 0 0.68 0.65 0.63 0.64

[0214] As shown in Tables 1 and 2 above, it was confirmed that when the dispersant included in the coating layer comprises a copolymer comprising i) repeating units derived from (meth)acrylic acid monomers, (meth)acrylic acid salt monomers, or both of these monomers, and ii) repeating units derived from acrylic monomers having amide groups, and the molar ratio of i) repeating units derived from (meth)acrylic acid monomers, (meth)acrylic acid salt monomers, or both of these monomers, and ii) repeating units derived from acrylic monomers having amide groups is 2:8 to 8:2, and the dispersant is included in an amount of 0.1 to 2 parts by weight based on 100 parts by weight of inorganic particles, the particle size of the slurry for forming the coating layer is formed small, and thereby the dispersion form of the solid components within the coating layer can be formed uniformly. In particular, it is preferable that the weight-average molecular weight of the dispersant be in the range of 30,000 g / mol to 250,000 g / mol, and it was confirmed that the separation membrane equipped with a coating layer according to one embodiment of the present invention is desirable in terms of air permeability and electrical resistance, and the wet heat shrinkage rate is also significantly improved.

Claims

A separator for an electrochemical device comprising a porous substrate and a coating layer disposed on at least one surface of the porous substrate, The above coating layer comprises inorganic particles, a binder, and a dispersant, and The above-mentioned dispersant comprises a copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and ii) a repeating unit derived from an acrylic monomer having an amide group, and The molar ratio of the above i) repeating unit derived from the (meth)acrylic acid monomer, the (meth)acrylic acid salt monomer, or both of these monomers, and ii) repeating unit derived from the acrylic monomer having an amide group is 2:8 to 8:2, and The weight-average molecular weight of the above dispersant is 30,000 g / mol to 250,000 g / mol, and A separator for an electrochemical device having an electrical resistance of 0.6 Ω or less. In claim 1, A separator for an electrochemical device, wherein the content of the dispersant is 0.1 to 2 parts by weight based on 100 parts by weight of the inorganic particles. In claim 1, A separator for an electrochemical device having an air permeability of 80 s / 100 cc or less. In claim 1, A separator for an electrochemical device having an electrical resistance of 0.55 Ω or less. In claim 1, A separator for an electrochemical device having a glass transition temperature (Tg) of the above-mentioned dispersant of 90 to 180°C. In claim 1, A separator for an electrochemical device, wherein the weight ratio of the binder and the dispersant is 5:1 to 15:

1. In claim 1, The above binder comprises a non-crosslinked copolymer comprising i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iii) a repeating unit derived from an acrylic monomer having a hydroxyl group, for a separator for an electrochemical device. In claim 1, The above binder comprises i) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, ii) a repeating unit derived from an acrylic monomer having an amide group, and iv) a copolymer comprising a silane monomer, a monomer having a silanol group, or a repeating unit derived from both of these monomers, for a separator for an electrochemical device. In claim 1, A separator for an electrochemical device, wherein the weight-average molecular weight of the binder is 100,000 g / mol to 200,000 g / mol. In claim 1, A separator for an electrochemical device, wherein the glass transition temperature (Tg) of the binder is 100 to 200°C. In claim 1, The above binder comprises a copolymer consisting of repeating units derived from a hydroxyalkyl acrylate monomer, repeating units derived from a (meth)acrylic acid monomer, and repeating units derived from an acrylic monomer having an amide group, for use as a separator for an electrochemical device. In claim 1, Average particle size (D of the above inorganic particles) 50 ) is a separator for an electrochemical device having a thickness of 400 nm to 600 nm. In claim 1, A separator for an electrochemical device, wherein the content of the inorganic particles is 80 to 95 parts by weight based on 100 parts by weight of the coating layer. In claim 1, A separator for an electrochemical device, wherein the thickness of the coating layer is 0.5 μm to 2 μm. Comprising an anode, a cathode, and a separator for an electrochemical device according to any one of claims 1 to 14, The above electrochemical device is an electrochemical device in which the separator is interposed between the anode and the cathode.