Composition for forming coating layer of separator for electrochemical device, separator for electrochemical device using same, and electrochemical device comprising same

Abstract

Disclosed is a composition for forming a coating layer of a separator for an electrochemical device, the composition comprising a polymer binder and inorganic particles, wherein the polymer binder includes a copolymer including i) a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or a repeating unit derived from these two monomers, and ii) a repeating unit derived from an acrylic monomer having an amide group, the copolymer has a weight average molecular weight of 10,000 to 500,000, the inorganic particles include an aluminum hydroxide oxide, and the inorganic particles have an average particle diameter D50 of 0.33 to 1.5 μm.

Description

Composition for forming a coating layer of an electrochemical device separator, a separator for an electrochemical device using the same, and an electrochemical device including the same

[0001] The present invention relates to a composition for forming a coating layer of an electrochemical device separator, a separator for an electrochemical device using the same, and an electrochemical device including the same.

[0002] This application is a priority claim application for Korean Patent Application No. 10-2024-0166978 filed on November 21, 2024, and all contents disclosed in the specification of said application are incorporated into this application by reference.

[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] Among the components of such an electrochemical device, the separator may comprise a polymer substrate having a porous structure located between the anode and the cathode. The separator isolates the anode and the cathode to prevent an electrical short circuit between the two electrodes, while simultaneously allowing the electrolyte and ions to pass through. Although the separator itself does not participate in electrochemical reactions, its physical properties, such as wettability to the electrolyte, porosity, and thermal shrinkage rate, can affect the performance and safety of the electrochemical device.

[0005] Therefore, to enhance the physical properties of such separation membranes, various methods are being attempted to improve the properties of the coating layer by adding a coating layer to a porous polymer substrate and adding various materials to the coating layer. For example, inorganic materials may be added to the coating layer to improve the mechanical strength of the separation membrane, or inorganic materials or hydrates may be added to the coating layer to improve the flame retardancy and heat resistance of the polymer substrate.

[0006] Within the coating layer, inorganic particles can be connected to other inorganic particles by a polymer binder to form an interstitial volume, and lithium ions can move through the interstitial volume. That is, the coating layer containing a polymer binder and inorganic particles serves to prevent thermal shrinkage of the separator while simultaneously facilitating the movement of lithium ions through the separator.

[0007] When forming the coating layer, inorganic particles must be uniformly distributed to minimize defects such as protrusions on the surface of the coating layer or uncoated areas, and excellent coating properties can be achieved to ensure the heat resistance of the separator. Furthermore, when forming the coating layer, the polymer binder can provide sufficient adhesion between inorganic materials and between inorganic materials and the porous polymer substrate, thereby sufficiently suppressing dry thermal shrinkage and / or wet thermal shrinkage of the porous polymer substrate at high temperatures.

[0008] Accordingly, there is a need to develop a coating layer for electrochemical device separators that improves the dispersibility of inorganic particles during coating layer formation to minimize coating defects, sufficiently suppresses dry thermal shrinkage and / or wet thermal shrinkage of porous polymer substrates at high temperatures, and possesses good air permeability and resistance.

[0009] A technical problem according to one aspect of the present invention is to provide a composition for forming a coating layer of an electrochemical device separator that improves the dispersibility of inorganic particles during coating layer formation to minimize coating defects, sufficiently suppresses dry thermal shrinkage and / or wet thermal shrinkage of a porous polymer substrate at high temperatures, and has good air permeability and resistance.

[0010] A technical problem according to another aspect of the present invention is to provide a separator for an electrochemical device having good air permeability and resistance, which minimizes coating defects and sufficiently suppresses dry thermal shrinkage and / or wet thermal shrinkage of a porous polymer substrate at high temperatures, and an electrochemical device equipped with the same.

[0011] A composition for forming a coating layer of an electrochemical device separator according to the first aspect of the present invention is,

[0012] It includes a polymer binder and inorganic particles,

[0013] The above polymer binder 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

[0014] The weight-average molecular weight of the copolymer is 10,000 to 500,000, and

[0015] The above inorganic particles contain aluminum hydroxide, and

[0016] The average particle size D50 of the above inorganic particles is 0.33 to 1.5 μm.

[0017] The second aspect of the present invention is, in the first aspect,

[0018] The molar ratio of the above i) (meth)acrylic acid monomer, (meth)acrylic acid salt monomer, or repeating unit derived from both of these monomers and ii) repeating unit derived from the acrylic monomer having the amide group is 1:1 to 19.

[0019] A third aspect of the present invention is, in the first aspect or the second aspect

[0020] The above (meth)acrylate monomer is one or more selected from the group consisting of sodium (meth)acrylate, potassium (meth)acrylate, lithium (meth)acrylate, and ammonium (meth)acrylate.

[0021] The fourth aspect of the present invention is, in any one of the first to third aspects,

[0022] The above acrylic monomer having an amide group is 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 is one or more selected from the group consisting of N-methoxyethyl (meth)acrylamide and N-butoxymethyl (meth)acrylamide.

[0023] The fifth aspect of the present invention is, in any one of the first to fourth aspects,

[0024] The copolymer further comprises iii) repeating units derived from acrylic monomers having hydroxyl groups.

[0025] The sixth aspect of the present invention is, in the fifth aspect,

[0026] The above-mentioned acrylic monomer having a hydroxyl group is one or more selected from the group consisting of hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate.

[0027] The seventh aspect of the present invention is, in any one of the first to sixth aspects,

[0028] The weight-average molecular weight of the copolymer is 50,000 to 150,000.

[0029] The eighth aspect of the present invention is, in any one of the first to seventh aspects,

[0030] The above aluminum hydroxide is cubic boehmite.

[0031] The ninth aspect of the present invention is, in any one of the first to eighth aspects,

[0032] The average particle size D50 of the above inorganic particles is 0.35 to 0.6 μm.

[0033] The tenth aspect of the present invention is, in any one of the first to ninth aspects,

[0034] The average particle size D90 of the above inorganic particles is 1.5 μm or less.

[0035] The eleventh aspect of the present invention is, in any one of the first to ten aspects,

[0036] The average particle size D50 of the above inorganic particles is 0.35 to 0.6 μm, and the average particle size D90 of the above inorganic particles is 1.0 μm or less.

[0037] The 12th aspect of the present invention relates to a separator for an electrochemical device, wherein

[0038] porous polymer substrate; and

[0039] A coating layer disposed on at least one surface of the above-mentioned porous polymer substrate and comprising a polymer binder and inorganic particles, and

[0040] The above polymer binder 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

[0041] The weight-average molecular weight of the copolymer is 10,000 to 500,000, and

[0042] The above inorganic particles contain aluminum hydroxide, and

[0043] The present invention provides a separator for an electrochemical device having an average particle size D50 of the inorganic particles of the above-mentioned material of 0.33 to 1.5 μm.

[0044] The 13th aspect of the present invention is, in the 12th aspect,

[0045] The molar ratio of the above i) (meth)acrylic acid monomer, (meth)acrylic acid salt monomer, or repeating unit derived from both of these monomers and ii) repeating unit derived from the acrylic monomer having the amide group is 1:1 to 19.

[0046] The 14th aspect of the present invention is, in the 12th or 13th aspect,

[0047] The weight-average molecular weight of the copolymer is 50,000 to 150,000.

[0048] The 15th aspect of the present invention is, in any one of the 12th to 14th aspects,

[0049] The average particle size D50 of the above inorganic particles is 0.35 to 0.6 μm.

[0050] The 16th aspect of the present invention is, in any one of the 12th to 15th aspects,

[0051] The average particle size D90 of the above inorganic particles is 1.5 μm or less.

[0052] The 17th aspect of the present invention is, in any one of the 12th to 16th aspects,

[0053] The average particle size D50 of the above inorganic particles is 0.35 to 0.6 μm, and the average particle size D90 of the above inorganic particles is 1.0 μm or less.

[0054] The 18th aspect of the present invention is, in any one of the 12th to 17th aspects,

[0055] The packing density of the above coating layer is 1.45 g / (m²) 2 It is less than *㎛.

[0056] The 19th aspect of the present invention is, in any one of the 12th to 18th aspects,

[0057] The peel strength of the above separator is 100 gf / 15mm or more.

[0058] The 20th aspect of the present invention is, in any one of the 12th to 19th aspects,

[0059] The thermal shrinkage rate of the above separator at 135°C is 10% or less.

[0060] The 21st aspect of the present invention relates to an electrochemical device, wherein

[0061] An electrochemical device is provided comprising: an anode; a cathode; and a separator for an electrochemical device interposed between the anode and the cathode, wherein any one of the 12th to 20th sides.

[0062] A composition for forming a coating layer according to one embodiment of the present invention uses a copolymer of a predetermined component and controls its weight-average molecular weight to improve the dispersibility of inorganic particles and minimize coating defects. Furthermore, a polymer binder containing a copolymer of the predetermined component can sufficiently impart adhesion between inorganic particles and between inorganic particles and a porous polymer substrate, thereby sufficiently suppressing dry thermal shrinkage and / or wet thermal shrinkage of the porous polymer substrate at high temperatures. In particular, this effect can be further manifested when the average particle size D90 of the inorganic particles is controlled to a predetermined range.

[0063] In addition, the composition for forming a coating layer according to one embodiment of the present invention comprises aluminum hydroxide as an inorganic particle, and has good air permeability and resistance by controlling the average particle size D50 to a predetermined range.

[0064] FIG. 1 is a schematic diagram of a separator for an electrochemical device according to one embodiment of the present invention.

[0065] 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.

[0066] 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.

[0067] 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, without excluding other components from being disposed in between.

[0068] 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.

[0069] 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.

[0070] In this specification, "separator" generally refers 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 polymer 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.

[0071] 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.

[0072] In this specification, "porous polymer 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 polymer 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 polymer substrate, and a fluid may pass through the porous polymer substrate through the pores.

[0073] In this specification, "particle diameter (D50)" or "particle diameter (D90)" refers to the diameter of a particle corresponding to the 50% and 90% points, respectively, of the volume-cumulative particle diameter distribution for the particle to be measured. The particle diameter can be measured using a 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 measure the difference in diffraction patterns according to particle size as the particles pass through a laser beam, thereby calculating the particle size distribution. By calculating the particle diameter at the point that is 50% of the cumulative particle number distribution according to diameter in the measuring device, the average particle diameter (D50) can be measured, and by calculating the particle diameter at the point that is 90% of the cumulative particle number distribution according to diameter in the measuring device, the average particle diameter (D90) can be measured.

[0074] In this specification, "repeating unit derived from ~ monomer" refers to a repeating unit included in a copolymer formed by polymerizing a ~ monomer.

[0075] 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.

[0076] In this specification, "acrylic monomer" refers to a monomer comprising an acrylate structure within the molecule, except for the following hydroxyalkyl acrylates. 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 above 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 above-described chemical formula structure (CH2=CHCOOB) and may have additional functional groups attached to the carbon double bond.

[0077] In this specification, "Wet state" may mean a state in which the separator is impregnated with at least a portion of the electrolyte, and "Dry state" may mean a dry state in which the separator is not impregnated by the electrolyte.

[0078] The present invention will be described in more detail below.

[0079] The present invention provides a composition for forming a coating layer of an electrochemical device separator.

[0080] According to one embodiment of the present invention, a composition for forming a coating layer of an electrochemical device separator is,

[0081] It includes a polymer binder and inorganic particles,

[0082] The above polymer binder 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

[0083] The weight-average molecular weight of the copolymer is 10,000 to 500,000, and

[0084] The above inorganic particles contain aluminum hydroxide, and

[0085] The average particle size D50 of the above inorganic particles is 0.33 to 1.5 μm.

[0086] The copolymer may be one 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.

[0087] The above copolymer may be a non-crosslinked copolymer. When the copolymer is a non-crosslinked copolymer, it can have a sufficient adhesion area with inorganic particles. In the case of a non-crosslinked copolymer, it can be manufactured as a water-soluble solution-type binder that dissolves in aqueous solvents such as water. Since the binder has a solution-type form, it can adhere to inorganic particles and porous polymer substrates with a wider surface area within the coating layer, thus having the advantage of effectively lowering the thermal shrinkage rate of the separator compared to a particle-type binder. Here, "non-crosslinked copolymer" may refer to a copolymer that dissolves transparently when the copolymer is left in an oven at 100°C for 60 minutes, water is added to a concentration of 10%, and the mixture is stirred for 24 hours.

[0088] A copolymer binder comprising i) (meth)acrylic acid monomers, (meth)acrylic acid salt monomers, or repeating units derived from both monomers, and in particular ii) repeating units derived from acrylic monomers having amide groups, has the advantage of being able to lower the thermal shrinkage rate of the separator at high temperatures due to the low deformation of the binder itself at high temperatures caused by a high glass transition temperature. Specifically, for example, in the case of polyacrylic acid, it has hydrophilic properties and a high glass transition temperature, so it has the advantage of not causing swelling due to the electrolyte. On the other hand, in the case of a polymer of acrylic monomers having amide groups, such as polyacrylamide, it has high rigidity and a high glass transition temperature, so it has the advantage of having low deformation at high temperatures. In this regard, the molar ratio of 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 the amide group may be 1:1 to 19, and more specifically, 1:1 to 8.

[0089] The copolymer may be composed 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.

[0090] The (meth)acrylate monomer may be one or more selected from the group consisting of sodium (meth)acrylate, potassium (meth)acrylate, lithium (meth)acrylate, and ammonium (meth)acrylate.

[0091] Acrylic monomers having an amide group include 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 be one or more selected from the group consisting of N-methoxyethyl (meth)acrylamide and N-butoxymethyl (meth)acrylamide.

[0092] The copolymer may further comprise iii) repeating units derived from an acrylic monomer having a hydroxyl group. Specifically, the molar ratio of the repeating unit derived from the acrylic monomer having a hydroxyl group to the repeating unit derived from i) (meth)acrylic acid monomer, (meth)acrylic acid salt monomer, or both of these monomers may be 1:0.1 or more, 1:0.2 or more, 1:0.3 or more, or 1:0.4 or more, and may also be 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 1:0.5 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.

[0093] Meanwhile, according to one embodiment of the present invention, the molar ratio of the iii) repeating unit derived from an acrylic monomer having a hydroxyl group and the ii) repeating unit derived from an acrylic monomer having an amide group may be 1:1 to 2. Specifically, the molar ratio of the repeating unit derived from an acrylic monomer having a hydroxyl group and the ii) repeating unit derived from an acrylic monomer having an amide group 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. The alkyl group of the acrylic monomer having the hydroxyl group may have 2 to 4 carbon atoms, but is not limited thereto. More specifically, it may be one or more selected from the group consisting of hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate. When the copolymer comprises the monomer described above as a hydroxyalkyl acrylate, the number of carbon atoms of the alkyl group bonded to the hydroxyl group is not large, so a large number of hydroxyl groups may be contained per unit volume of the monomer, and accordingly, a large number of hydroxyl groups may be contained per unit volume of the copolymer. Therefore, since the copolymer binder may have excellent adhesion to inorganic particles and porous polymer substrates in high temperature and wet conditions, the separator for an electrochemical device containing the binder in the coating layer may have a low thermal shrinkage rate in high temperature and wet conditions.

[0094] The weight-average molecular weight of the copolymer is 10,000 to 500,000.

[0095] Specifically, the weight-average molecular weight (Mw) of the copolymer may be 10,000 or more and 400,000 or less, 10,000 or more and 300,000 or less, 10,000 or more and 250,000 or less, 10,000 or more and 240,000 or less, 10,000 or more and 230,000 or less, 10,000 or more and 220,000 or less, 10,000 or more and 210,000 or less, 10,000 or more and 200,000 or less, or 50,000 or more and 150,000 or less. If the above-described range is exceeded, the dispersibility of inorganic particles within the coating layer decreases, and the particle size D90 of the composition for forming the coating layer increases, which may cause coating defects such as the occurrence of protrusions during coating, and may increase air permeability and resistance. If the above-mentioned range is not met, peel strength and heat resistance properties may be reduced. In this regard, the weight-average molecular weight of the copolymer may be 50,000 to 150,000.

[0096] In the present specification, the weight-average molecular weight (Mw) can be measured by gel permeation chromatography (GPC: gel permeation chromatography, PL GPC220, Agilent Technologies), and the measurement conditions can be set as follows.

[0097] - Column: PL Olexis (Polymer Laboratories)

[0098] - Solvent: TCB (Trichlorobenzene)

[0099] - Flow rate: 1.0 ml / min

[0100] - Sample concentration: 1.0 mg / ml

[0101] - Injection volume: 200 µl

[0102] - Column temperature: 160 ℃

[0103] - Detector: Agilent High Temperature RI detector

[0104] - Standard: Polystyrene (corrected by a cubic function)

[0105] According to one aspect of the present invention, the inorganic particles of the composition for forming a coating layer include aluminum hydroxide. Unlike alumina, which is an aluminum oxide, aluminum hydroxide does not cause an excessive increase in packing density when forming a coating layer, thereby maintaining good air permeability and resistance characteristics of the coating layer.

[0106] Specifically, aluminum hydroxide (AlO(OH)) may include boehmite (γ-AlO(OH)) and diaspore (α-AlO(OH)). According to one embodiment of the present invention, by including aluminum hydroxide in the inorganic particles, good dispersibility within the coating layer can be achieved, while air permeability and resistance characteristics can be improved. According to one embodiment of the present invention, the inorganic particles may be cubic boehmite. As described above, by selecting cubic boehmite as the boehmite, the structural stability of the coating layer can be contributed to and resistance improvement can be achieved.

[0107] According to one embodiment of the present invention, the aluminum hydroxide may be, in particular, cubic boehmite. Cubic boehmite can form a coating layer with a lower packing density compared to using alumina (Al2O3) with the same particle size, thereby maintaining good air permeability and resistance characteristics of the coating layer.

[0108] According to one embodiment of the present invention, the particle size D50 of the inorganic particles is 0.33 to 1.5 μm. If the particle size D50 of the inorganic particles is 0.33 μm or less, the size of the inorganic particles is small, causing the packing density of the coating layer to increase excessively, thereby degrading air permeability and resistance characteristics. If the particle size D50 of the inorganic particles exceeds 1.5 μm, the coating performance is reduced, and coating defects occur.

[0109] Specifically, the D50 of the inorganic particles may be 0.35 μm or more and 1.4 μm or less, 0.4 μm or more and 1.3 μm or less, 0.4 μm or more and 1.2 μm or less, 0.4 μm or more and 1.1 μm or less, 0.4 μm or more and 1.0 μm or less, 0.4 μm or more and 0.9 μm or less, 0.4 μm or more and 0.8 μm or less, 0.4 μm or more and 0.7 μm or less, or 0.35 μm or more and 0.6 μm or less. By controlling the D50 of the inorganic particles within the above-described range, it is possible to secure coating properties while simultaneously improving the air permeability and resistance of the separation membrane.

[0110] According to one embodiment of the present invention, the particle size D90 of the inorganic particles of the coating layer forming composition may be 1.5 μm or less, or 1.0 μm or less. Specifically, the particle size D90 of the inorganic particles of the coating layer forming composition may be 0.5 μm or more and 1.5 μm or less, 0.6 μm or more and 1.5 μm or less, or 0.7 μm or more and 1.5 μm or less. By controlling the particle size D90 of the coating layer forming composition within the above-described range, the occurrence of membrane protrusions can be suppressed, thereby minimizing coating defects.

[0111] In the aforementioned aspect, the average particle size D50 of the inorganic particles is 0.35 to 0.6 μm, and the average particle size D90 of the inorganic particles may be 1.0 μm or less.

[0112] According to one embodiment of the present invention, the content of the inorganic particles may be 80 parts by weight or more and 99 parts by weight or less, based on 100 parts by weight of the total weight of the inorganic particles and the polymer binder. Specifically, the content of the inorganic particles may be 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, or 95 parts by weight or more, based on 100 parts by weight of the total weight of the inorganic particles and the polymer binder of the composition for forming the coating layer, and may also be 99 parts by weight or less, 98 parts by weight or less, 97 parts by weight or less, 96 parts by weight or less, 95 parts by weight or less, 94 parts by weight or less, 93 parts by weight or less, 92 parts by weight or less, 91 parts by weight or less, or 90 parts by weight or less. When the content of the inorganic particles satisfies the above range, the inorganic particles can be sufficiently included in the coating layer, so the problem of thermal shrinkage of the porous polymer substrate in the separator for an electrochemical device can be minimized.

[0113] FIG. 1 is a schematic diagram of a separator for an electrochemical device according to one embodiment of the present invention. One embodiment of the present invention comprises a porous polymer substrate (110); and a coating layer (130) disposed on at least one surface of the porous polymer substrate and comprising a polymer binder and inorganic particles.

[0114] The above polymer binder 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

[0115] The weight-average molecular weight of the copolymer is 10,000 to 500,000, and

[0116] The above inorganic particles contain aluminum hydroxide, and

[0117] The average particle size D50 of the above inorganic particles is 0.33 to 1.5 μm.

[0118] As the components of the copolymer included in the coating layer of the separator for electrochemical devices, and the average particle sizes D50 and D90 of the inorganic particles have been described above, a redundant explanation will be omitted.

[0119] According to one embodiment of the present invention, the porous polymer substrate (110) may be manufactured using a polyolefin-based resin as a base resin. Examples of polyolefin-based resins include polyethylene, polypropylene, polypentene, etc., and may include one or more of these. A porous membrane, i.e., having a plurality of pores, manufactured using such a polyolefin-based resin as a base resin, can provide a shutdown function at an appropriate temperature.

[0120] According to one embodiment of the present invention, the weight-average molecular weight of the polyolefin resin may be 500,000 or more and 1,500,000 or less. By controlling the weight-average molecular weight of the polyolefin resin within the above-described range, the compression resistance of the separator can be improved. Furthermore, when using a mixture of different types of polyolefin resins or forming a separator with a multilayer structure made of different types of polyolefin resins, the weight-average molecular weight of the polyolefin resin can be calculated by adding the weight-average molecular weights according to the content ratio of each polyolefin resin.

[0121] According to one embodiment of the present invention, the porous polymer substrate (110) may be manufactured by a method (wet method) in which a polyolefin-based resin is mixed with a plasticizer (diluent) at a high temperature to form a single phase, the polymer material and the plasticizer are separated during the cooling process, the plasticizer is extracted to form pores, and then stretched and heat-set.

[0122] According to one embodiment of the present invention, the average size of the pores and the maximum size of the pores of the porous polymer substrate (110) can be easily manufactured by a person skilled in the art to meet the scope of the present invention by adjusting the mixing ratio of the plasticizer, the stretching ratio, and the heat-setting treatment temperature.

[0123] According to one embodiment of the present invention, the thickness of the porous polymer substrate (110) may be 8 μm or more and 15 μm or less. Specifically, the thickness of the porous polymer substrate (110) may be 8 μm or more and 14 μm or less, 8 μm or more and 13 μm or less, 8 μm or more and 12 μm or less, 8 μm or more and 11 μm or less, or 9 μm or more and 11 μm or less, and preferably 10 μm. By controlling the thickness of the porous polymer substrate within the above-described range, the energy density of the battery can be improved.

[0124] According to one embodiment of the present invention, the thickness of the porous polymer substrate can be measured by a contact measurement method using a thickness gauge (Mitutoyo, VL-50S-B).

[0125] According to one embodiment of the present invention, the coating layer (130) is provided on at least one surface of the porous polymer substrate (110). As described above, by including the coating layer (130) disposed on at least one surface of the porous polymer substrate (110) in the electrochemical device separator (100), the heat resistance of the separator is improved, mechanical properties are improved, and the separator shrinks at high temperatures, thereby preventing the occurrence of an electrical short circuit in the electrode.

[0126] According to one embodiment of the present invention, the coating layer (130) comprises a polymer binder and inorganic particles. As described above, by the coating layer (130) comprising the polymer binder and the inorganic particles, the heat resistance of the separator is improved, mechanical properties are improved, the separator shrinks at high temperatures to prevent electrical short circuits in the electrodes, and pores can be formed within the coating layer.

[0127] According to one embodiment of the present invention, the coating layer (130) may be formed by inorganic particles being bound by polymer binder particles and accumulated within the coating layer. The pores within the coating layer may originate from interstitial volumes, which are empty spaces between the inorganic particles.

[0128] According to one embodiment of the present invention, the coating layer (130) may include a plurality of pores. Specifically, the coating layer may be a porous coating layer. More specifically, the coating layer may be a porous coating layer that includes a plurality of pores inside. As described above, by including a plurality of pores in the coating layer, it is possible to physically block the negative electrode and the positive electrode while allowing lithium ions to pass through and current to flow.

[0129] According to one embodiment of the present invention, the thickness of the coating layer (130) may be 2 μm or less. Specifically, the thickness of the coating layer (130) may be 0.5 μm or more and 2 μm or less, or 1 μm or more and 2 μm or less. If the thickness falls below the above-described range, the heat resistance of the coating layer may decrease and the adhesive strength may be reduced, and if the thickness exceeds the above-described range, the air permeability and resistance may increase, and the thickness of the entire separator may increase, which may have a negative effect on battery assembly.

[0130] In one embodiment of the present invention, the thickness of the coating layer (130), etc., can be measured by applying a contact-type thickness gauge. For example, the contact-type thickness gauge may use the VL-50S-B from Mitutoyo.

[0131] According to one embodiment of the present invention, the packing density of the coating layer (130) is 1.45 g / (m²) 2 It may be less than *㎛). Specifically, the packing density of the coating layer (130) is 1 g / (m²) 2 *㎛) or more 1.45 g / (m 2 *㎛) less than, 1 g / (m2 *㎛) or more 1.4 g / (m 2 *㎛) or less, 1.1 g / (m 2 *㎛) or more 1.3 g / (m 2 *㎛) or less or 1.2 g / (m 2 *㎛) or more 1.3 g / (m 2 It may be less than or equal to *㎛. If it exceeds the above-described range, the coating properties may be reduced, and at the same time, the air permeability and resistance of the separator may be degraded; if it falls below the above-described range, the peel strength and heat resistance may be reduced.

[0132] According to one embodiment of the present invention, the packing density of the coating layer (130) is a specific area (m² 2 It can refer to how much material is contained within a specific thickness (㎛). For example, at the same area and thickness, if the material is heavier, the packing density increases, and if it is lighter, it decreases.

[0133] According to one embodiment of the present invention, the peel strength of the separator may be 100 gf / 15mm or more. Specifically, the peel strength of the separator may be 100 gf / 15mm or more and 200 gf / 15mm or less, 100 gf / 15mm or more and 200 gf / 15mm or less, or 110 gf / 15mm or more and 200 gf / 15mm or less. If the peel strength of the separator falls short of the above-described range, it may be due to the low weight-average molecular weight of the polymer binder in the coating layer.

[0134] At this time, the peel strength refers to the force required to peel off the coating layer and the porous polymer substrate by applying an adhesive tape to the surface of the coating layer of a separator measuring 15 mm X 70 mm, mounting the end of the separator on a UTM device (LLOYD Instrument LF Plus), and applying a force at 180° at a measurement speed of 300 mm / min.

[0135] According to one embodiment of the present invention, the thermal shrinkage rate of the separator at 135°C may be 10% or less. If it exceeds the above-described range, the heat resistance properties may be reduced.

[0136] According to one embodiment of the present invention, the thermal shrinkage rate of the separator at 180°C may be 10% or less. If it exceeds the above-described range, the heat resistance properties may be reduced.

[0137] According to one embodiment of the present invention, the method may include the steps of: forming a porous polymer substrate; applying a slurry composition for forming a coating layer comprising a polymer binder and inorganic particles to at least one surface of the porous polymer substrate to form a coating layer; and drying the coated separation membrane. The porous polymer substrate, polymer binder, inorganic particles, and coating layer are as described above.

[0138] According to one embodiment of the present invention, the method of coating the slurry composition for forming the coating layer onto the porous polymer substrate may use conventional coating methods, and various methods such as bar coating, dip coating, die coating, roll coating, comma coating, or a combination thereof may be used.

[0139] One embodiment of the present invention provides an electrochemical device comprising: an anode; a cathode; and the aforementioned separator interposed between the anode and the cathode. In the 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] In one embodiment of the present invention, the electrochemical element 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. In this specification, the secondary battery is capable of charging and discharging and refers to a lithium secondary battery, a nickel-cadmium battery, a nickel-hydrogen battery, etc. The lithium secondary battery uses lithium ions as an ion conductor, and examples include a non-aqueous electrolyte secondary battery containing a liquid electrolyte, an all-solid-state battery containing a solid electrolyte, a lithium polymer battery containing a gel polymer electrolyte, and a lithium metal battery using lithium metal as a negative electrode, but are not limited thereto.

[0141] According to one embodiment of the present invention, the positive electrode comprises 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 LiMn1-xM xIt may include 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; and one or more of Fe2(MoO4)3.

[0142] According to one embodiment of the present invention, the cathode comprises 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 comprises, as the cathode active material, carbon such as lithium metal oxide, non-graphitizable carbon, or graphite-based carbon; LixFe2O3 (0≤x≤1), Li x WO2(0≤x≤1), Sn x 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 포함할 수 있다.

[0143] 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.

[0144] 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.

[0145] 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-cotrichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, 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.

[0146] 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).

[0147] 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.

[0148] According to one embodiment of the present invention, 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 may be provided. 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.

[0149] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0150]

[0151] <Example 1>

[0152] Manufacturing of porous polymer substrates

[0153] A polyethylene resin (weight-average molecular weight 1 million) was extruded, and a porous polymer substrate (total thickness about 10 μm, porosity 55%, air permeability 60 s / 100cc, ER 0.45 ohm) was prepared by a wet method.

[0154] Formation of a coating layer

[0155] Cubic boehmite powder (KB-05S, KC Co.) was prepared as an inorganic particle. Poly(acrylic acid-co-acrylamide) with a weight-average molecular weight (Mw) of 150,000 (molar ratio of acrylic acid to acrylamide = 1:4) was prepared as a polymer binder, sodium carboxymethyl cellulose (CMC-Na) (SG-L02, GL Chem Co.) was prepared as a dispersant, and a polysiloxane-based material was prepared as a wetting agent.

[0156] The above-prepared inorganic particles, polymer binder, dispersant, and wetting agent were added to water in a weight ratio of 93:6:0.5:0.5 and stirred to prepare a slurry composition for forming a coating layer having a solid content of 35% and a viscosity of 50 cPs.

[0157] At this time, the particle size D50 of the slurry composition for forming the coating layer was 0.399 μm, and D90 was 0.742 μm.

[0158] The slurry composition for forming the coating layer was applied to both sides of the porous polymer substrate using a doctor blade in a bar coating method, and dried with a heat gun at 50°C to form a coating layer with a thickness of 1.5 μm on each side.

[0159]

[0160] <Example 2>

[0161] In the above Example 1, a separation membrane was prepared in the same manner as in Example 1, except that the weight-average molecular weight (Mw) of the polymer binder was 50,000, and the particle size D50 of the slurry composition for forming the coating layer was 0.366 μm and D90 was 0.792 μm.

[0162]

[0163] <Example 3>

[0164] In the above Example 1, a separation membrane was prepared in the same manner as in Example 1, except that the type of polymer binder was changed to the copolymer and particle size listed in Table 1.

[0165]

[0166] <Comparative Example 1>

[0167] In the above Example 1, a separation membrane was prepared in the same manner as in Example 1, except that the weight-average molecular weight (Mw) of the polymer binder was 600,000, and the particle size D50 of the slurry composition for forming the coating layer was 12.2 μm and D90 was 161 μm.

[0168]

[0169] <Comparative Example 2>

[0170] In the above Example 1, a separation membrane was prepared in the same manner as in Example 1, except that the weight-average molecular weight (Mw) of the polymer binder was 5,000, and the particle size D50 of the slurry composition for forming the coating layer was 0.341 μm and D90 was 0.752 μm.

[0171]

[0172] <Comparative Example 3>

[0173] In the above Example 1, a separation membrane was prepared in the same manner as in Example 1, except that the inorganic particles were cubic boehmite (KB-03S, KC Co.) powder with a particle size D50 of 0.3 μm.

[0174]

[0175] <Comparative Example 4>

[0176] In the above Example 1, a separation membrane was prepared in the same manner as in Example 1, except that the inorganic particles were alumina powder (Alumina, P172LSB, Alteo) with a particle size D50 of 0.5 μm.

[0177]

[0178] Manufacture of Electrochemical Devices

[0179] Electrochemical devices were each manufactured using the separator membranes for electrochemical devices of the above examples and comparative examples.

[0180] 1) Manufacture of the anode

[0181] Cathode active material (LiNi 0.8 Mn 0.1 Co 0.1 O2), a conductive material (carbon black), a dispersant (N-methylpyrrolidone, ADC-01, LG Chem), and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for an anode active material layer with a concentration of 50 wt% of the components excluding water. Next, the slurry was applied to the surface of an aluminum thin film (thickness 10 μm) and dried to manufacture an anode having an anode active material layer (thickness 120 μm).

[0182] 2) Preparation of the cathode

[0183] Graphite (a blend of natural graphite and artificial graphite), a conductive material (carbon black), a dispersant (Polyvinylpyrrolidone, Junsei, Japan), and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a negative electrode active material layer with a concentration of 50 wt% of the components excluding water. Next, the slurry was applied to the surface of a copper thin film (thickness 10 μm) and dried to manufacture a negative electrode having a negative electrode active material layer (thickness 120 μm).

[0184] 3) Lamination Process

[0185] An electrochemical device was obtained by interposing the separator of the above example and comparative example between the above-manufactured cathode and anode, stacking them, and performing a lamination process. The lamination process was performed using a hot press for 1 second under conditions of 60°C and 6.5 MPa.

[0186]

[0187] <Experimental Example>

[0188] Measurement of the weight-average molecular weight of a copolymer

[0189] The weight-average molecular weight (Mw) was measured by gel permeation chromatography (GPC: gel permeation chromatography, PL GPC220, Agilent Technologies) under the following conditions.

[0190] - Column: PL Olexis (Polymer Laboratories)

[0191] - Solvent: TCB (Trichlorobenzene)

[0192] - Flow rate: 1.0 ml / min

[0193] - Sample concentration: 1.0 mg / ml

[0194] - Injection volume: 200 µl

[0195] - Column temperature: 160 ℃

[0196] - Detector: Agilent High Temperature RI detector

[0197] - Standard: Polystyrene (corrected by a cubic function)

[0198]

[0199] Particle size (D50, D90) measurement

[0200] For the compositions for forming the coating layer of the above examples and comparative examples, the difference in diffraction patterns according to particle size was measured by introducing them into a laser diffraction particle size measuring device (Microtrac S3500) as the particles passed through the laser beam, and the particle sizes D50 and D90 were measured at the points where the cumulative distribution of the number of particles was 50% and 90%.

[0201]

[0202] Peel strength measurement

[0203] For the separator membranes of the above examples and comparative examples, a 15 mm x 70 mm specimen of the separator membrane was prepared to measure the peel strength. After attaching an adhesive tape to the surface of the coating layer of the prepared separator membrane, the end of the separator membrane was mounted on a UTM device (LLOYD Instrument LF Plus). The force required to peel off the coating layer and the porous polymer substrate was measured by applying force at a UTM device angle of 180° and a measurement speed of 300 mm / min.

[0204]

[0205] Measurement of thermal shrinkage rate at 135 ℃

[0206] The separator membranes of the above examples and comparative examples were cut to a size of 5 cm x 5 cm to prepare a sample. The sample was placed on a polyethylene terephthalate release liner, placed in an aluminum pouch, filled with 2 g of electrolyte, sealed, and then left in an oven at 135°C for 1 hour. After removing the sample, the transverse and longitudinal dimensions were measured, and the shrinkage rate (%) in the transverse direction (MD) and longitudinal direction (TD) was measured.

[0207]

[0208] Measurement of thermal shrinkage rate at 180 ℃

[0209] A sample was prepared by cutting the separator membrane of the above example and comparative example into a size of 8 cm x 8 cm. A square measuring 5 cm x 5 cm was drawn on the surface of the sample, placed between paper or alumina powder, and left in an oven at 180°C for 1 hour. After removing the sample, the dimensions of the side of the drawn square were measured, and the shrinkage rate (%) in the transverse direction (MD) and the longitudinal direction (TD) was measured.

[0210]

[0211] Measuring the number of membrane protrusions

[0212] For the separation membranes of the above examples and comparative examples, observe the unit area (m²) using an optical microscope. 2The number of protrusions with a diameter of 1.0 μm or more was measured.

[0213]

[0214] Air permeability measurement

[0215] For the separators of the above examples and comparative examples, air permeability was measured using a Gurley densometer (Gurley, 4110N) with 100 cc of air having a diameter of 28.6 mm and an area of ​​645 mm 2 The time (s) taken to pass through the membrane was measured.

[0216]

[0217] Resistance measurement

[0218] For the separators of the above examples and comparative examples, the resistance was measured by the alternating current method at 25°C using Electrochemical Impedance Spectroscopy (EIS) with a 1M LiPF6 ethylene carbonate / ethyl methyl carbonate (weight ratio 3:7) electrolyte, as the resistance value when the separator was cut and placed in a 2032 coin cell and impregnated with an electrolyte.

[0219]

[0220] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Polymer Binder Type Poly(acrylic acid-co-acrylamide) Poly(acrylic acid-co-acrylamide) Poly(acrylic acid-co-acrylamide-co-hydroxyethylacryate) Poly(acrylic acid-co-acrylamide) Poly(acrylic acid-co-acrylamide) Poly(acrylic acid-co-acrylamide) Poly(acrylic acid-co-acrylamide) Weight Average Molecular Weight (g / mol) 150,000 50,000 150,000 600,000 5,000 150,000 150,000 Composition Particle size (㎛) D500 0.39 90.36 60.46 112.20 34 10.19 70.41 2D900 0.74 20.79 20.98 41 610.75 20.56 40.77 6 Coating layer packing density (g / (m²) 2 *㎛))1.21 1.25 1.33 1.30 1.15 1.58 1.76 Peel Strength (gf / 15mm) 190 114 23 117 227 128 84 135 ℃ Wet MD / TD Thermal Shrinkage Rate (%) 5 / 36 / 34 / 25 / 317 / 133 / 37 / 4180 ℃ Dry MD / TD Thermal Shrinkage Rate (%) 3 / 23 / 22 / 35 / 346 / 40 3 / 21 / 2 Number of Separator Protrusions (ea / m 2 )000133000 Air Permeability (s / 100cc)11510313419480167145 Resistance (Ohm)0.640.500.620.950.470.770.81

[0221] According to Table 1 above, Examples 1 and 2 have good coating properties and no protrusions, good air permeability and resistance characteristics, and excellent peel strength of the coating layer and Drt / Wet thermal shrinkage rate at high temperatures. In contrast, Comparative Example 1 has a very large weight-average molecular weight of the polymer binder and large particle sizes D50 and D90 of the inorganic particles, which results in reduced coating properties, coating defects, and inferior air permeability and resistance.

[0222] Comparative Example 2 shows that the peel strength and heat resistance are inferior because the weight-average molecular weight of the polymer binder is small.

[0223] Comparative Example 3 shows that the particle size D50 of the inorganic particles is small, which increases the packing density of the coating layer, and consequently, the air permeability and resistance of the separator membrane are inferior.

[0224] Comparative Example 4 shows that when alumina of the same size is used instead of cubic boehmite for the inorganic particles, the packing density increases, and as a result, the air permeability and resistance of the separator membrane are inferior.

[0225] [Explanation of the symbol]

[0226] 100: Separator for electrochemical devices

[0227] 110: Porous polymer substrate

[0228] 130: Coating layer

Claims

1. Includes a polymer binder and inorganic particles, The above polymer binder 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 weight-average molecular weight of the copolymer is 10,000 to 500,000, and The above inorganic particles contain aluminum hydroxide, and A composition for forming a coating layer of an electrochemical device separator, wherein the average particle size D50 of the inorganic particles is 0.33 to 1.5 μm.

2. In Paragraph 1, A composition for forming a coating layer of an electrochemical device separator, wherein the molar ratio of 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 1:1 to 19.

3. In Paragraph 1, A composition for forming a coating layer of an electrochemical device separator, wherein the above (meth)acrylate salt monomer is one or more selected from the group consisting of sodium (meth)acrylate, potassium (meth)acrylate, lithium (meth)acrylate, and ammonium (meth)acrylate.

4. In Paragraph 1, The above acrylic monomer having an amide group is 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, A composition for forming a coating layer of an electrochemical device separator, comprising one or more selected from the group consisting of N-methoxyethyl (meth)acrylamide and N-butoxymethyl (meth)acrylamide.

5. In Paragraph 1, A composition for forming a coating layer of an electrochemical device separator, wherein the copolymer further comprises iii) a repeating unit derived from an acrylic monomer having a hydroxyl group.

6. In Paragraph 5, A composition for forming a coating layer of an electrochemical device separator, wherein the above-mentioned acrylic monomer having a hydroxyl group is one or more selected from the group consisting of hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate.

7. In Paragraph 1, A composition for forming a coating layer of an electrochemical device separator, wherein the weight-average molecular weight of the copolymer is 50,000 to 150,000.

8. In Paragraph 1, A composition for forming a coating layer of an electrochemical device separator, wherein the above aluminum hydroxide is cubic boehmite.

9. In Paragraph 1, A composition for forming a coating layer of an electrochemical device separator, wherein the average particle size D50 of the inorganic particles is 0.35 to 0.6 μm.

10. In Paragraph 1, A composition for forming a coating layer of an electrochemical device separator, wherein the average particle size D90 of the above-mentioned inorganic particles is 1.5 μm or less.

11. In Paragraph 1, A composition for forming a coating layer of an electrochemical device separator, wherein the average particle size D50 of the inorganic particles is 0.35 to 0.6 μm and the average particle size D90 of the inorganic particles is 1.0 μm or less.

12. Porous polymer substrate; and A coating layer disposed on at least one surface of the above-mentioned porous polymer substrate and comprising a polymer binder and inorganic particles, and The above polymer binder 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 weight-average molecular weight of the copolymer is 10,000 to 500,000, and The above inorganic particles contain aluminum hydroxide, and A separator for an electrochemical device, wherein the average particle size D50 of the above inorganic particles is 0.33 to 1.5 μm.

13. In Paragraph 12, A separator for an electrochemical device, wherein the molar ratio of 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 1:1 to 19.

14. In Paragraph 12, A separator for an electrochemical device having a weight-average molecular weight of the copolymer of the above-mentioned form, ranging from 50,000 to 150,000.

15. In Paragraph 12, A separator for an electrochemical device having an average particle size D50 of the above inorganic particles of 0.35 to 0.6 μm.

16. In Paragraph 12, A separator for an electrochemical device having an average particle size D90 of the above inorganic particles of 1.5 μm or less.

17. In Paragraph 12, A separator for an electrochemical device, wherein the average particle size D50 of the inorganic particles is 0.35 to 0.6 μm and the average particle size D90 of the inorganic particles is 1.0 μm or less.

18. In Paragraph 12, The packing density of the above coating layer is 1.45 g / (m²) 2 Separator for electrochemical devices with a size of less than *㎛.

19. In Paragraph 12, A separator for an electrochemical device having a peel strength of 100 gf / 15 mm or more.

20. In Paragraph 12, A separator for an electrochemical device having a thermal shrinkage rate of 10% or less at 135°C.

21. An electrochemical device comprising: an anode; a cathode; and a separator for an electrochemical device according to any one of claims 12 to 20 interposed between the anode and the cathode.

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