Separator for electrochemical device and electrochemical device comprising same

Abstract

The present invention relates to a separator for an electrochemical device, the separator comprising an inorganic heat-resistant coating layer, wherein the coating layer comprises both cubic boehmite and platelet-shaped boehmite as inorganic particles, thereby improving the stability of the separator while achieving low resistance.

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. 2025-0006684 filed with the Korean Intellectual Property Office on January 16, 2025 and Korean Patent Application No. 2025-0188464 filed on December 2, 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] Among the components of an electrochemical device, the separator comprises a porous polymer substrate with a porous structure located between the anode and the cathode. It serves to isolate the anode and cathode, prevent electrical short circuits between the two electrodes, and allow the passage of electrolytes and ions. Although the separator itself does not participate in electrochemical reactions, its physical properties, such as electrolyte impregnation, degree of porosity, and thermal shrinkage rate, can affect the performance and safety of the electrochemical device.

[0005] Accordingly, various methods are being attempted to modify the physical properties of a coating layer by adding a coating layer to a porous polymer substrate to enhance the physical properties of the separation membrane, and by 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 porous polymer substrate.

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

[0007] On the other hand, while inorganic particles can improve the mechanical strength and heat resistance of separators for electrochemical devices, depending on the shape of the particles, the spacing between them may become too narrow, resulting in a failure to form an appropriate gap. If an appropriate gap is not formed between the particles, it hinders the movement of ions within the electrochemical device, which can increase the resistance of the separator. Consequently, this may lead to a problem where the performance of the electrochemical device containing such particles deteriorates. Conversely, depending on the shape of the inorganic particles added to the coating layer, the resistance of the separator can be lowered; however, this may result in poor mechanical strength and heat resistance, leading to a problem where the stability of the electrochemical device is compromised.

[0008] Therefore, there is a need to develop separators for electrochemical devices that have low resistance and excellent stability by controlling the shape and type of added inorganic particles.

[0009] 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.

[0010] A technical problem according to another aspect of the present invention, together with the technical problem according to the aforementioned aspect, is to provide a separator for an electrochemical device having low resistance and excellent mechanical strength and heat resistance, and an electrochemical device including the same.

[0011] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0012] According to one aspect of the present invention, a separator for an electrochemical device of the following embodiments is provided.

[0013] The separator for an electrochemical device according to the first embodiment is,

[0014] porous polymer substrate; and

[0015] A coating layer disposed on at least one surface of the above-mentioned porous polymer substrate and comprising inorganic particles and a binder, and

[0016] The above inorganic particles contain cubic boehmite and plate-shaped boehmite in a weight ratio of 1:1 to 4:1.

[0017] According to the second embodiment, in the first embodiment,

[0018] Average particle size (D) of the above cubic boehmite 50 ) can be 0.5 μm to 0.7 μm.

[0019] According to the third embodiment, in the first embodiment or the second embodiment,

[0020] The aspect ratio of the above plate-shaped boehmite can be 2 to 10.

[0021] According to the fourth embodiment, in any one of the first to third embodiments,

[0022] The average long side of the above plate-shaped boehmite may be 0.7 μm to 0.9 μm.

[0023] According to the fifth embodiment, in any one of the first to fourth embodiments,

[0024] The packing density of the above coating layer is 0.9 g / cm³ 3 Up to 1.3 g / cm³ 3It could be.

[0025] According to the 6th embodiment, in any one of the 1st to 5th embodiments,

[0026] The above binder may comprise a non-crosslinked copolymer comprising i) repeating units derived from an acrylic monomer having a hydroxyl group, ii) repeating units derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and iii) repeating units derived from an acrylic monomer having an amide group.

[0027] According to the seventh embodiment, in any one of the first to sixth embodiments,

[0028] The above binder may include a non-crosslinked 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.

[0029] According to the eighth embodiment, in any one of the first to seventh embodiments,

[0030] The above (meth)acrylate monomer may include sodium (meth)acrylate, potassium (meth)acrylate, lithium (meth)acrylate, ammonium (meth)acrylate, or a mixture of two or more of these.

[0031] According to the ninth embodiment, in any one of the first to eighth embodiments,

[0032] 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 may include N-methoxyethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, or a mixture of two or more of these.

[0033] According to the 10th embodiment, in any one of the 1st to 9th embodiments,

[0034] The alkyl group of the above hydroxyalkyl acrylate monomer may have 2 to 4 carbon atoms.

[0035] According to the 11th embodiment, in any one of the 1st to 10th embodiments,

[0036] The thickness of the coating layer formed on one surface of the porous polymer substrate may be 0.5 μm to 4 μm.

[0037] According to the 12th embodiment, in any one of the 1st to 11th embodiments,

[0038] The above coating layer is,

[0039] A first coating layer comprising the above-mentioned cubic boehmite and a first binder; and

[0040] It may include a second coating layer disposed on the first coating layer and comprising the plate-shaped boehmite and the second binder.

[0041] According to the 13th embodiment, in any one of the 1st to 12th embodiments,

[0042] The thickness ratio of the first coating layer and the second coating layer may be 1:0.5 to 1:1.5.

[0043] According to the 14th embodiment, in any one of the 1st to 13th embodiments,

[0044] Based on 100 parts by weight of the coating layer, the content of the inorganic particles may be 80 to 95 parts by weight.

[0045]

[0046] According to another aspect of the present invention, an electrochemical device according to the following embodiment may be provided.

[0047] The electrochemical device according to the 15th embodiment is,

[0048] It comprises an anode, a cathode, and a separator for an electrochemical device according to any one of the first to fourth embodiments, and

[0049] The separator for the electrochemical device may be interposed between the anode and the cathode.

[0050] A separator for an electrochemical device according to one embodiment of the present invention has the advantage of being able to lower the resistance of the separator by including cubic boehmite as an inorganic particle of the heat-resistant coating layer. At the same time, the separator has the advantage of being able to further improve the mechanical strength and heat resistance of the separator by including plate-shaped boehmite as an inorganic particle of the heat-resistant coating layer.

[0051] In particular, a separator for an electrochemical device according to one embodiment of the present invention may exhibit the advantage of further improving the heat resistance of the coating layer by including a non-crosslinked copolymer comprising repeating units derived from acrylic monomers having hydroxyl groups as a binder, along with boehmite containing hydroxyl groups (-OH) as an inorganic particle of the coating layer. Specifically, the hydroxyl groups of the copolymer form intermolecular forces, such as hydrogen bonds, with the hydroxyl groups of the boehmite, thereby not only improving the heat resistance of the coating layer but also improving the bonding between inorganic particles and / or between the porous polymer substrate and the coating layer and / or between the separator and the electrode. Accordingly, the separator for an electrochemical device according to one embodiment of 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; however, the effects of the present invention are not limited thereto.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] In this specification, the term "aspect ratio" is used to denote the ratio of the long side to the short side of a plate-shaped inorganic particle. The aspect ratio is defined as [length of the long side] / [length of the remaining side (short side) perpendicular to the long side direction] on the flat plane of the plate-shaped inorganic particle.

[0062] In this specification, the term "packing density" can be calculated based on the weight per unit volume of the coating layer. The unit of the packing density is g / cm³ 3 am.

[0063] In this specification, the term "non-crosslinked copolymer" refers to 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.

[0064] In this specification, the term "repeating unit derived from a ~ monomer" refers to a repeating unit included in a copolymer formed by the polymerization of a ~ monomer.

[0065] 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.

[0066] In this specification, "acrylic monomer" means a monomer comprising an acrylate structure within the 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.

[0067]

[0068] The present invention will be described in more detail below.

[0069] According to one aspect of the present invention, a separator for an electrochemical device is provided.

[0070] A separator for an electrochemical device according to one aspect of the present invention is,

[0071] porous polymer substrate; and

[0072] A coating layer disposed on at least one surface of the above-mentioned porous polymer substrate and comprising inorganic particles and a binder, and

[0073] The above inorganic particles contain cubic type boehmite and plate type boehmite in a weight ratio of 1:1 to 4:1.

[0074]

[0075] [Coating layer]

[0076] inorganic particles

[0077] As described above, a separation membrane according to one aspect of the present invention comprises boehmite (AlO(OH)) containing hydroxyl groups (-OH) in its structure as an inorganic particle of the coating layer. Specifically, it comprises cubic boehmite and plate-shaped boehmite.

[0078] In one embodiment of the present invention, the cubic boehmite may refer to a polyhedral boehmite having one or more faces. For example, the term "cubic" may include polyhedra such as cubes and rectangular prisms, and cases where one face of the polyhedron is deformed in an irregular manner. Due to its unique three-dimensional structure, the cubic boehmite can ensure sufficient spacing between inorganic particles. As sufficient spacing between inorganic particles is ensured, lithium ions can move smoothly within the separator, thereby exhibiting the advantage of maintaining low resistance of the separator. Furthermore, an electrochemical device to which a separator having low resistance is applied may exhibit the advantage of improved output performance, but the mechanism of the present invention is not limited thereto.

[0079] In one embodiment of the present invention, the plate-shaped boehmite may refer to boehmite having a shape having at least one long side and one short side. The plate-shaped boehmite may include an amorphous side. Additionally, the thickness of the plate-shaped boehmite may be smaller than the long side or the short side. Due to the widely spread particle shape of the plate-shaped boehmite, thermal stress can be evenly distributed within the inorganic particles. Accordingly, when the plate-shaped boehmite is applied to the coating layer of the separator, it can exhibit an effective advantage in preventing the separator from shrinking or expanding in specific areas due to heat. Furthermore, the plate-shaped boehmite may be arranged in the plane direction of the coating layer and / or stacked to be thinly and uniformly distributed within the coating layer. Through this, when the plate-shaped boehmite is applied as an inorganic particle to the coating layer, it may exhibit an advantage in improving the mechanical strength of the separator, but the mechanism of the present invention is not limited thereto.

[0080] According to one embodiment of the present invention, when the coating layer comprises only cubic boehmite as inorganic particles, it may be advantageous in terms of lowering the resistance of the electrochemical device to which it is applied, but a problem may arise in which the mechanical properties of the separator are degraded due to low stress caused by its unique three-dimensional structure.

[0081] In addition, if the coating layer comprises only plate-shaped boehmite as inorganic particles, it may be advantageous in terms of thermal shrinkage rate and mechanical strength of the applied membrane; however, since the plate-shaped boehmite particles are closely packed and sufficient space is not secured between the inorganic particles, a problem may arise in which the resistance of the membrane increases.

[0082] Accordingly, a separator according to one aspect of the present invention has the advantage of preventing adhesion between the cubic boehmite and the plate-shaped boehmite by including both as inorganic particles of the coating layer, thereby maintaining an appropriate space between the inorganic particles. Through this, an electrochemical device to which a separator equipped with a coating layer including both the cubic boehmite and the plate-shaped boehmite is applied has the advantage of maintaining low resistance while being advantageous in terms of heat resistance and mechanical strength, but the mechanism of the present invention is not limited thereto.

[0083] According to one embodiment of the present invention, the average particle size (D of the cubic boehmite) 50 ) may be, for example, 200 nm to 1 μm. Specifically, the average particle size (D) of the cubic boehmite is 50 ) may be 0.5 μm to 0.7 μm. More specifically, the average particle size (D) of the cubic boehmite is 50 The particle size may be 0.5 μm or more and 0.7 μm or less, 0.55 μm or more and 0.6 μm or less, 0.6 μm or more and 0.65 μm or less, 0.65 μm or more and 0.7 μm or less, 0.5 μm or more and 0.54 μm or less, 0.5 μm or more and 0.58 μm or less, 0.5 μm or more and 0.62 μm or less, or 0.5 μm or more and 0.68 μm or less. When the average particle size of the cubic boehmite satisfies the aforementioned range, sufficient spacing exists between the cubic boehmites within the coating layer, which can have a favorable effect in lowering the resistance of the separator for the electrochemical device including the coating layer. In addition, excellent dispersibility may be present in the coating layer slurry prepared for manufacturing the coating layer, but the present invention is not limited thereto.

[0084] In one embodiment of the present invention, the aspect ratio of the plate-shaped boehmite may be, for example, 2 to 10. Specifically, the aspect ratio of the plate-shaped boehmite may be 2 or more and 10 or less, 3 or more and 7 or less, 3 or more and 6 or less, 4 or more and 7 or less, or 5 or more and 8 or less. When the aspect ratio of the plate-shaped boehmite satisfies the aforementioned range, the coating layer can be formed broadly and uniformly on the porous polymer substrate. Furthermore, while the present invention may exhibit advantageous effects in effectively reducing thermal shrinkage of the separator for the electrochemical device at high temperatures and maintaining air permeability appropriately, the present invention is not limited thereto.

[0085] In one embodiment of the present invention, the average long side of the plate-shaped boehmite may be, for example, 0.7 μm to 0.9 μm. Specifically, the average long side of the plate-shaped boehmite may be 0.7 μm or more and 0.9 μm or less, 0.8 μm or more and 0.82 μm or less, 0.8 μm or more and 0.84 μm or less, 0.8 μm or more and 0.86 μm or less, 0.8 μm or more and 0.88 μm or less, 0.82 μm or more and 0.84 μm or less, 0.84 μm or more and 0.86 μm or less, 0.86 μm or more and 0.88 μm or less, 0.88 μm or more and 0.9 μm or less, 0.83 μm or more and 0.86 μm or less, or 0.83 μm or more and 0.89 μm or less. When the average long side of the above-described plate-shaped boehmite is within the range described above, it may exhibit an advantageous effect in terms of maintaining the packing density of the coating layer appropriately to maintain excellent air permeability of the separator and improving the thermal stability of the separator, but the present invention is not limited thereto.

[0086] According to one embodiment of the present invention, the thickness of the plate-shaped boehmite may be, for example, 0.01 μm to 0.1 μm. Specifically, it may be 0.01 μm or more and 0.1 μm or less, 0.01 μm or more and 0.05 μm or less, 0.01 μm or more and 0.09 μm or less, 0.02 μm or more and 0.06 μm or less, 0.02 μm or more and 0.1 μm or less, 0.03 μm or more and 0.07 μm or less, 0.04 μm or more and 0.08 μm or less, or 0.05 μm or more and 0.09 μm or less.

[0087] According to one aspect of the present invention, the coating layer comprises the cubic boehmite and the plate-shaped boehmite in a weight ratio of 1:1 to 4:1.

[0088] According to one embodiment of the present invention, the weight ratio of the cubic boehmite and the plate-shaped boehmite may be, for example, (cubic boehmite:plate-shaped boehmite) 1:1 to 4:1, 1:1 to 3:1, 1:1 to 2:1, 2:1 to 3:1, 2:1 to 4:1, 3:1 to 4:1, 1.5:1 to 4:1, 2.5:1 to 3:1, 2.5:1 to 3.5:1, 2.5:1 to 4:1, or 3.5:1 to 4:1. When the weight ratio of the cubic boehmite and the plate-shaped boehmite satisfies the aforementioned range, the cubic boehmite appropriately prevents adhesion between the plate-shaped boehmites, thereby maintaining a low resistance of the separator for the electrochemical device, while being advantageous in terms of heat resistance and mechanical strength.

[0089] In one embodiment of the present invention, the packing density of the coating layer is, for example, 0.9 g / cm³ 3 Up to 1.3 g / cm³ 3 It may be. Specifically, the packing density of the coating layer is 0.9 g / cm³ 3 Above 1.3 g / cm³ 3 Below, 1 g / cm³ 3 Above 1.3 g / cm³ 3Below, 1.0 g / cm³ 3 Above 1.3 g / cm³ 3 Below, 1.1 g / cm³ 3 Above 1.3 g / cm³ 3 Below, 1.1 g / cm³ 3 Above 1.2 g / cm³ 3 Below, 1.1 g / cm³ 3 Above 1.25 g / cm² 3 Less than or equal to 1.2 g / cm³ 3 Above 1.3 g / cm³ 3 It may be less than or equal to the above. When the packing density satisfies the aforementioned range, a separator can be formed with a light and thin thickness, and excellent heat resistance can be exhibited by displaying an appropriate packing density, but the present invention is not limited thereto.

[0090] In one embodiment of the present invention, the thickness of the coating layer formed on one surface of the porous polymer substrate may be, for example, 0.5 μm to 4 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 4 μm or less, 3.5 μm or less, 3 μm or less, 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 having low resistance. Furthermore, since the total thickness of the separator for an electrochemical device including the coating layer may also be low, the electrochemical device including the separator for an 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.

[0091] In one embodiment of the present invention, the coating layer may further include boehmite of other shapes in addition to the cubic boehmite and plate-shaped boehmite described above.

[0092] In another embodiment of the present invention, the coating layer may further include other types of inorganic particles in addition to the cubic boehmite and plate-like boehmite described above. The inorganic particles that may further be included in the coating layer are within the operating voltage range of the electrochemical device (e.g., Li / Li). + Other inorganic particles that do not undergo oxidation and / or reduction reactions at 0 V to 5 V (based on reference), e.g., 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 )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, aluminum peroxide, zinc-tin hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), antimony pentoxide (Sb2O5), lithium phosphate (Li3PO4), 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(Lix 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), etc. may be further used to the extent that it does not impede the purpose of the present invention.

[0093] In one embodiment of the present invention, the content of the inorganic particles within the coating layer may be, for example, 80 parts by weight or more and 99 parts by weight or less based on 100 parts by weight of the coating layer. 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 solid content of 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 may be sufficiently included in the coating layer, thereby minimizing the thermal shrinkage problem of the polymer substrate in the composite separator for an electrochemical device, but the present invention is not limited thereto. At this time, the cubic boehmite and plate-shaped boehmite may be 50% or more by weight, 60% or more by weight, 70% or more by weight, 80% or more by weight, 90% or more by weight of the total inorganic particles, and may be 100% by weight.

[0094]

[0095] bookbinder

[0096] In one embodiment of the present invention, the coating layer comprises a binder to bind inorganic particles together and / or to provide adhesion between the porous substrate and the coating layer and / or to provide adhesion between the separator and the electrode.

[0097] In one embodiment of the present invention, the binder may be used without limitation as long as it is usable in the coating layer of the separator. For example, the binder may be one that is typically usable in the coating layer of the separator 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.

[0098] In one embodiment of the present invention, in order to further improve the heat resistance of the separation membrane by the binder, the binder may comprise, for example, i) repeating units derived from an acrylic monomer having a hydroxyl group, ii) repeating units derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and iii) repeating units derived from an acrylic monomer having an amide group.

[0099] In one embodiment of the present invention, the copolymer included as the binder 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.

[0100] In one embodiment of the present invention, if the copolymer included as the binder 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 the hydroxyl group of i) 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.

[0101] In one embodiment of the present invention, when the binder comprises polyacrylic acid or a copolymer comprising ii) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and iii) a repeating unit derived from an acrylic monomer having an amide group, the high glass transition temperature of the copolymer results in minimal deformation of the binder itself at high temperatures, thereby providing the advantage of lowering the thermal shrinkage rate of the separator in the dry state. However, a copolymer comprising only components ii) and iii) may exhibit a problem in that it is difficult to improve the thermal shrinkage rate in the wet state due to poor binding strength with inorganic particles in the wet state. Specifically, for example, when polyacrylic acid is included as the binder, polyacrylic acid has hydrophilic properties and a high glass transition temperature, so there is an advantage that swelling caused by the electrolyte does not occur. 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 issue of the separator in wet conditions when applied to the coating layer alone. On the other hand, polymers of acrylic monomers containing amide groups, such as polyacrylamide, have 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, it may present a problem in that it is difficult to improve the thermal shrinkage issue of the separator in wet conditions when applied to the coating layer alone or as a binder in a copolymer form with acrylic acid monomers.In contrast, if the binder comprises a copolymer that further includes i) a repeating unit derived from an acrylic monomer having a hydroxyl group in addition to components ii) and iii), the copolymer contains a sufficient amount of hydroxyl groups, so that even at high temperatures where an electrolyte is present, it can strongly bond with the surface of the porous substrate and / or the surface of the inorganic particles through intermolecular histories such as hydrogen bonding with the inorganic particles and the porous substrate, and can also bond to the electrode surface, thereby exhibiting the advantage of being able to bond to the electrode surface. Accordingly, if the binder comprises the aforementioned ternary copolymer, the separator having the coating layer can 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.

[0102] According to one embodiment of the present invention, when the binder comprises a copolymer that further includes i) a repeating unit derived from an acrylic monomer having a hydroxyl group in addition to the components ii) and iii), the i) repeating unit derived from an acrylic monomer having a hydroxyl group contains a hydroxyl group, so it can exhibit the advantage of increasing the bonding strength through intermolecular forces such as hydrogen bonding with cubic boehmite, plate-shaped boehmite, and porous polymer substrate even at high temperatures where an electrolyte is present.

[0103] In 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.

[0104] 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.

[0105] 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.

[0106] In one embodiment of the present invention, where the binder comprises a non-crosslinked copolymer comprising i) a repeating unit derived from an acrylic monomer having a hydroxyl group, ii) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both monomers, and iii) a repeating unit derived from an acrylic monomer having an amide group, the molar ratio of the i) repeating unit derived from an acrylic monomer having a hydroxyl group and the ii) repeating unit derived from a (meth)acrylic acid monomer, a (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 i) repeating units derived from acrylic monomers having hydroxyl groups and ii) 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 i) 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 ii) 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.

[0107] In one embodiment of the present invention, when the binder comprises a non-crosslinked copolymer consisting of i) repeating units derived from an acrylic monomer having a hydroxyl group, ii) repeating units derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and iii) repeating units derived from an acrylic monomer having an amide group, the molar ratio of i) repeating units derived from an acrylic monomer having a hydroxyl group and iii) repeating units derived from an 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 iii) 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.

[0108] 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.

[0109] 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).

[0110] 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.

[0111] 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.

[0112] In one embodiment of the present invention, the binder may be included in an amount of, for example, 1 to 20 parts by weight based on 100 parts by weight of the coating layer. Specifically, the binder may be 1 part by weight or more and 20 parts by weight or less, 2 parts by weight or more and 15 parts by weight or less, 3 parts by weight or more and 12 parts by weight or less, 5 parts by weight or more and 6 parts by weight or less, 5 parts by weight or more and 7 parts by weight or less, 5 parts by weight or more and 8 parts by weight or less, 5 parts by weight or more and 9 parts by weight or less, 7 parts by weight or more and 9 parts by weight or less, or 8 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the solid content of the coating layer. Specifically, the content of the binder may be 3 parts by weight or more, 4 parts by weight or more, or 5 parts by weight or more based on 100 parts by weight of the solid content of the coating layer, and may also be 10 parts by weight or less, 9 parts by weight or less, or 8 parts by weight or less. When the content of the binder is within the range described above, the binder is sufficiently present within the coating layer, so the adhesion between the porous substrate and the coating layer and / or the adhesion between the separator and the electrode may be excellent, but the present invention is not limited thereto. Furthermore, since the binder is sufficiently present, the interstitial volume formed by the inorganic particles being connected to each other by the binder may also increase, and accordingly, the porosity of the coating layer may be high. This may result in a lower resistance of the separator having the coating layer, but the present invention is not limited thereto.

[0113] In one embodiment of the present invention, the porosity of the coating layer may be, for example, 30 vol% or more and 50 vol% or less. Specifically, the porosity of the coating layer may be 30 vol% or more, 35 vol% or more, or 40 vol% or more, and may also be 50 vol% or less, 45 vol% or less, or 40 vol% 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.

[0114] In this specification, the porosity of the coating layer refers to the ratio of the volume of pores to the total volume of the coating layer. 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.

[0115] In one embodiment of the present invention, the coating layer may be composed of a multilayer in which the shapes of the inorganic particles of the upper and lower layers are mixed differently from each other.

[0116] In one embodiment of the present invention, the coating layer may comprise a first coating layer disposed on at least one surface of the porous polymer substrate and comprising the cubic boehmite and a first binder, and a second coating layer disposed on the first coating layer and comprising the plate-like boehmite and a second binder.

[0117] In another embodiment of the present invention, the coating layer may comprise a first coating layer disposed on at least one surface of the porous polymer substrate and comprising the plate-shaped boehmite and a first binder, and a second coating layer disposed on the first coating layer and comprising the cubic boehmite and a second binder.

[0118] In one embodiment of the present invention, when the coating layer is composed of multiple layers, it may be more preferable for the first coating layer to include cubic boehmite and the second coating layer to include plate-like boehmite in order to improve the adhesion between the porous polymer substrate and the first coating layer and to lower the resistance of the separation membrane, but the present invention is not limited thereto.

[0119] In one embodiment of the present invention, the combined thickness of the first coating layer and the second coating layer may be, for example, 0.5 μm to 4 μm. Specifically, the combined thickness of the first coating layer and the second coating layer may be 0.5 μm or more, 0.7 μm or more, 0.9 μm or more, 1.0 μm or more, and may also be 4 μm or less, 3.5 μm or less, 3 μm or less, 2 μm or less, 1.8 μm or less, 1.6 μm or less, or 1.5 μm or less.

[0120] In one embodiment of the present invention, the thickness ratio of the first coating layer and the second coating layer may be, for example, 1:0.5 to 1:1.5, specifically 1:0.8 to 1:1.2. Specifically, the thickness ratio may be 1:0.8 to 1:1.1, 1:0.8 to 1:1, 1:0.8 to 1:0.9, 1:0.9 to 1:1.2, or 1:1 to 1:1.2. When the thickness ratio satisfies the aforementioned range, ions in the first coating layer can move smoothly, which may provide an advantageous effect in terms of lowering the resistance of the separator membrane including the first coating layer, and the heat resistance of the second coating layer can be sufficiently secured, which may be advantageous in terms of thermal shrinkage. Through this, the separator membrane may have improved heat resistance and, at the same time, excellent resistance due to the smooth movement of ions, but the present invention is not limited thereto.

[0121] In one embodiment of the present invention, the packing density of the second coating layer is 0.7 g / cm³ 3 Above 1.3 g / cm³ 3 It may be less than or equal to. Specifically, the packing density of the second coating layer is 0.7 g / cm³. 3 Above 1.3 g / cm³ 3 Below, 0.8 g / cm³ 3 Above 1.2 g / cm³ 3 Below, 0.9 g / cm³ 3 Above 1.2 g / cm³ 3 Below, 0.9 g / cm³ 3 Above 1.1 g / cm³ 3 Below, 0.9 g / cm³ 3 Above 1 g / cm³ 3 Below, 0.9 g / cm³ 3 Above 1.0 g / cm³ 3 Less than or equal to 0.9 g / cm³ 3 Above 0.95 g / cm³ 3The following may apply. Regarding the packing density of the second coating layer, it may be the same as that implied by the packing density of the coating layer described above. When the packing density of the second coating layer satisfies the aforementioned range, the second coating layer is disposed on the first coating layer at an appropriate density. Accordingly, the shrinkage problem of the separator can be effectively improved and the resistance of the separator can be lowered, but the present invention is not limited thereto.

[0122] In one embodiment of the present invention, the first binder and the second binder may be the same as or different from the binder described above.

[0123] In one embodiment of the present invention, the first binder and the second binder may each independently comprise a non-crosslinked copolymer comprising i) a repeating unit derived from an acrylic monomer having a hydroxyl group, ii) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and iii) a repeating unit derived from an acrylic monomer having an amide group.

[0124] In one embodiment of the present invention, the first binder and the second binder may each independently comprise a non-crosslinked copolymer composed of a repeating unit derived from a hydroxyalkyl acrylate monomer, a repeating unit derived from a (meth)acrylic acid monomer, and a repeating unit derived from an acrylic monomer having an amide group.

[0125] According to one embodiment of the present invention, the coating layer may be formed using a slurry for forming a coating layer.

[0126] According to one embodiment of the present invention, the slurry for forming the coating layer comprises the inorganic particles and binder described above as solids, and may include a dispersion solvent as a dispersion medium for dissolving or dispersing them.

[0127] 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.

[0128] In one embodiment of the present invention, at least one surface of a porous substrate may be coated with a coating slurry comprising a binder, inorganic particles, and a dispersion medium to form the coating layer. 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 coating layer may be formed by 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, but the present invention is not limited thereto.

[0129] According to one embodiment of the present invention, the separator for an electrochemical device may further include an electrode adhesive layer on the outermost upper surface of the coating layer. The electrode adhesive layer may include a binder for the electrode adhesive layer. The binder for the electrode adhesive layer may include, for example, a fluorine-based binder and an acrylic binder to improve adhesion to the electrode. Specifically, the binder for the electrode adhesive layer may include PVDF-HFP, which is a fluorine-based binder. By including a fluorine-based binder and an acrylic binder, the electrode adhesive layer can stably maintain adhesion to the electrode of the separator for the electrochemical device in both a dry state without an electrolyte and a wet state impregnated with an electrolyte. For example, the electrode adhesive layer may include the fluorine-based binder and the acrylic binder in a weight ratio of 4:6 to 6:4. The thickness of the electrode adhesive layer is formed to be smaller than the thickness of the coating layer, thereby providing electrode adhesion while minimizing the reduction in air permeability of the separator for the electrochemical device, but the present invention is not limited thereto.

[0130]

[0131] porous polymer substrate

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] In this specification, the air permeability (s / 100cc) of the membrane refers to the time (in seconds) required for 100cc of air to pass through a porous substrate or membrane 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.

[0139] 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 50 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.

[0140] In this specification, the porosity of the porous substrate refers to the ratio of the volume of pores to the total volume of the coating layer. 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 nitrogen gas adsorption, the capillary flow porometer, or the water or mercury infiltration method.

[0141]

[0142] [Electrochemical Device]

[0143] According to another aspect of the present invention, an electrochemical device comprising the above-described separator is provided.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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).

[0155] 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.

[0156] 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.

[0157] 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.

[0158]

[0159] 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.

[0160]

[0161] Example 1

[0162] Manufacturing of separators for electrochemical devices

[0163] Cubic boehmite (average particle size (D)) in distilled water at room temperature (25℃) 50 ): 500 nm, KC kB-05S), plate-like boehmite (average long side: 750 nm, aspect ratio: 2.0, density: 3.00 g / cm³) 3 A coating slurry was prepared by adding ) in a weight ratio of 1:1, adding a non-crosslinked copolymer (weight average molecular weight: 150,000 g / mol, Tg: 155 ℃, no crosslinking formed after high-temperature storage at 80℃) containing repeating units derived from hydroxyethyl acrylate (HEA), acrylic acid (AA), and acrylamide (AM) in a molar ratio of 1:0.4:0.6 (HEA:AA:AM) as a binder in a weight ratio of inorganic particles:binder = 93:6, and stirring with a shaker for 120 minutes.

[0164] A polyethylene film with a thickness of 10 μm (porosity 55 vol%) was used as the porous polymer substrate.

[0165] The coating slurry was applied to both sides of a prepared porous polymer substrate 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 each side of the porous substrate.

[0166] Based on the single-sided coating layer, the thickness of each coating layer is 1.5 μm, and the packing density is 1.2 g / cm³. 3 The total thickness of the separator, which had coating layers on both sides, was 13 μm.

[0167]

[0168] Example 2

[0169] A separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that the plate-type boehmite was changed to one with an aspect ratio of 5.0 and cubic-type boehmite and plate-type boehmite were added in a weight ratio of 4:1.

[0170]

[0171] Example 3

[0172] Cubic boehmite (average particle size (D)) in distilled water at room temperature (25℃) 50 A first coating slurry was prepared by adding a non-crosslinked copolymer (weight average molecular weight: 150,000 g / mol, Tg: 155 ℃, no crosslinking formed after high-temperature storage at 80 ℃) containing repeating units derived from hydroxyethyl acrylate (HEA), acrylic acid (AA), and acrylamide (AM) in a molar ratio of 1:0.4:0.6 (HEA:AA:AM) in a weight ratio of 93:6 and stirring with a shaker for 120 minutes.

[0173] A second coating slurry was prepared by adding plate-shaped boehmite (average long side: 750 nm, aspect ratio: 3.0) and a non-crosslinked copolymer (weight average molecular weight: 150,000 g / mol, Tg: 155 °C, no crosslinking formed after high-temperature storage at 80 °C) containing repeating units derived from hydroxyethyl acrylate (HEA), acrylic acid (AA), and acrylamide (AM) in a molar ratio of 1:0.4:0.6 (HEA:AA:AM) to distilled water at room temperature (25 °C) in a weight ratio of 93:6 and stirring with a shaker for 120 minutes.

[0174] The first coating slurry is applied to both sides of a prepared porous polymer substrate (PE film, 10 μm, 55 vol%) by a bar coating method using a doctor blade, and dried with a heat gun at 50°C to form a first coating layer (packing density 1.2 g / cm³). 3 After forming the first coating layer, the second coating slurry is applied to the surface of the first coating layer by a bar coating method, and dried with a heat gun using air at 50°C to form a second coating layer (packing density 0.9 g / cm³ 3 ) was formed. The combined thickness of the formed first coating layer and second coating layer was 1.5 μm, and the thickness ratio of the first coating layer and the second coating layer was 1:1.

[0175]

[0176] Comparative Example 1

[0177] A separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that cubic boehmite and plate-shaped boehmite were added in a weight ratio of 5:1.

[0178]

[0179] Comparative Example 2

[0180] A separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that the plate-shaped boehmite was changed to one with an average long side length of 1 μm.

[0181]

[0182] Comparative Example 3

[0183] A separator for an electrochemical device was manufactured in the same manner as in Example 3 above, except that the plate-shaped boehmite was changed to one with an aspect ratio of 11 to form the second coating layer.

[0184]

[0185] Experimental Example 1: Measurement of membrane resistance

[0186] The resistance of the separator membranes according to Examples 1 to 3 and Comparative Examples 1 to 3 was measured as follows.

[0187] Coin cells were manufactured by interposing the separators for electrochemical devices of the above examples and comparative examples between SUS materials. An electrolyte containing 1M LiPF6 and mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 was injected into the coin cells. To measure the resistance of the coin cells, the resistance was measured through electrochemical impedance spectroscopic analysis at 25°C under conditions of Amplitude 10 mV and Scan range 0.1 Hz to 1 MHz, and the results are shown in Tables 1 and 2 below.

[0188]

[0189] Experimental Example 2: Measurement of thermal shrinkage rate of a separator

[0190] The dry state thermal shrinkage rate and wet state thermal shrinkage rate of the separator membranes according to Examples 1 to 3 and Comparative Examples 1 to 3 were measured as follows.

[0191] (1) Dry state heat shrinkage rate

[0192] The separator membranes of the above examples and comparative examples were prepared as specimens of size 5 cm X 5 cm and stored in a convection oven at 180 ℃ for 30 minutes, after which the separator membranes were 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 @180℃ / 0.5h) / (length of the initial specimen)] × 100 (%).

[0193] The experimental results are shown in Tables 1 and 2 below.

[0194]

[0195] (2) Wet condition heat shrinkage rate

[0196] The separators of the above examples and comparative examples were prepared as specimens measuring 5 cm x 5 cm, inserted into aluminum pouches measuring 7 cm x 10 cm, and sealed.

[0197] 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.

[0198] 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 (%).

[0199] The experimental results are shown in Tables 1 and 2 below.

[0200] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Coating layer structure Single layer Single layer Single layer Single layer Cubic boehmite Average particle size (㎛) 0.5 0.5 0.5 0.5 Plate-shaped boehmite Average long side (㎛) 0.7 5 0.7 5 0.7 5 1.0 Plate-shaped boehmite Aspect ratio 2533 Weight ratio (Cubic:Plate-shaped) 1:14:15:11:1 Packing density of coating layer (g / cm²) 3 )1.1 1.0 0.9 0.9 Separator Resistance (Ω) 0.5 10.4 9 0.5 5 0.5 4 Dry Shrinkage (MD(%) / TD(%)) 5 / 4 7 / 5 10 / 5 31 / 1 8 Wet Shrinkage (MD(%) / TD(%)) 8 / 5 9 / 7 13 / 8 45 / 2 4

[0201] Example 3 Comparative Example 3 Coating Layer Structure Multilayer Structure 1st Coating Layer: Cubic Type 2nd Coating Layer: Plate Type Multilayer Structure 1st Coating Layer: Cubic Type 2nd Coating Layer: Plate Type Cubic Type Boehmite Average Particle Size (㎛) 0.5 0.5 Plate Type Boehmite Average Long Side (㎛) 0.75 0.75 Plate Type Boehmite Aspect Ratio 3 1 1 Weight Ratio (Cubic Type: Plate Type) 1:1 1:1 Packing Density of 1st Coating Layer (g / cm²) 3 )1.21.2 Packing density of the second coating layer (g / cm²) 3 )0.9 0.7 Separator Resistance (Ω) 0.5 0 0.6 1 Dry Shrinkage (MD(%) / TD(%)) 4 / 3 2 4 / 1 4 Wet Shrinkage (MD(%) / TD(%)) 8 / 6 3 4 / 1 1 1

[0202] Through this, it was confirmed that a separator having a coating layer comprising cubic boehmite and plate-shaped boehmite in a weight ratio of 1:1 to 4:1 according to one embodiment of the present invention achieves the effect of maintaining low electrical resistance while having low thermal shrinkage rates in both dry and wet states.

Claims

porous polymer substrate; and A coating layer disposed on at least one surface of the above-mentioned porous polymer substrate and comprising inorganic particles and a binder, and The above inorganic particles comprise cubic boehmite and plate-shaped boehmite in a weight ratio of 1:1 to 4:1, forming a separator for an electrochemical device. In claim 1, Average particle size (D) of the above cubic boehmite 50 A separator for an electrochemical device, having a thickness of 0.5 μm to 0.7 μm. In claim 1, A separator for an electrochemical device, wherein the aspect ratio of the above plate-shaped boehmite is 2 to 10. In claim 1, A separator for an electrochemical device, wherein the average long side of the above plate-shaped boehmite is 0.7 μm to 0.9 μm. In claim 1, The packing density of the above coating layer is 0.9 g / cm³ 3 Up to 1.3 g / cm³ 3 Phosphorus, separator for electrochemical devices. In claim 1, The above binder comprises a non-crosslinked copolymer comprising i) repeating units derived from an acrylic monomer having a hydroxyl group, ii) repeating units derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and iii) repeating units derived from an acrylic monomer having an amide group, for a separator for an electrochemical device. In claim 1, The above binder comprises a non-crosslinked 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 6, The above (meth)acrylate salt monomer comprises sodium (meth)acrylate, potassium (meth)acrylate, lithium (meth)acrylate, ammonium (meth)acrylate, or a mixture of two or more of these, for a separator for an electrochemical device. In claim 6, 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 separator for an electrochemical device comprising N-methoxyethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, or a mixture of two or more of these. In claim 7, A composite separator for an electrochemical device, wherein the alkyl group of the above hydroxyalkyl acrylate monomer has 2 to 4 carbon atoms. In claim 1, A separator for an electrochemical device, wherein the thickness of a coating layer formed on one surface of the above porous polymer substrate is 0.5 μm to 4 μm. In claim 1, The above coating layer is, A first coating layer comprising the above-mentioned cubic boehmite and a first binder; and A separator for an electrochemical device, comprising a second coating layer disposed on the first coating layer and comprising the plate-shaped boehmite and a second binder. In claim 12, A separator for an electrochemical device, wherein the thickness ratio of the first coating layer and the second coating layer is 1:0.5 to 1:1.

5. In claim 12, 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. 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.