Separator for electrochemical device and electrochemical device comprising same

Abstract

The present invention relates to a separator for an electrochemical device, the separator comprising a coating layer including a non-crosslinked copolymer as a binder, wherein the non-crosslinked copolymer includes i) repeating units derived from an acrylic monomer having a hydroxyl group, ii) repeating units derived from a (meth)acrylic acid monomer, a (meth)acrylate monomer, or both monomers, and iii) repeating units derived from an acrylic monomer having an amide group. The copolymer includes i) repeating units derived from an acrylic monomer having a hydroxyl group and ii) repeating units derived from a (meth)acrylic acid monomer, a (meth)acrylate monomer, or both monomers in a molar ratio of 1: 0.1-1, thereby improving a heat shrinkage rate in both dry and wet states.

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] This application is a priority claim application for Korean Patent Application No. 10-2024-0129374 filed on September 24, 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] Meanwhile, the poly(meth)acrylic acid binder, the polyacrylamide binder having an amide group, or the copolymer binder of (meth)acrylic acid and acrylamide used as the polymer binder have excellent heat resistance, and thus have the advantage of effectively reducing the thermal shrinkage problem of the porous polymer substrate when used together with the inorganic particles. However, the adhesive strength of the binder is low at room temperature or high temperature, and as the temperature rises, the adhesive strength of the binder weakens. Consequently, there was a problem in that the dry thermal shrinkage rate and / or wet thermal shrinkage rate of the separator for an electrochemical device containing the binder in the coating layer decreased at high temperatures.

[0008] 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.

[0009] A separator for an electrochemical device according to the first aspect of the present invention is,

[0010] porous polymer substrate; and

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

[0012] 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, and

[0013] The molar ratio of the above i) repeating unit derived from an acrylic monomer having a hydroxyl group and the above ii) repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers is 1:0.1 to 1.

[0014] The second aspect of the present invention is, in the first aspect,

[0015] The copolymer comprises 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, ii) repeating units derived from an acrylic monomer having an amide group, and iii) repeating units derived from an acrylic monomer having an amide group.

[0016] A third aspect of the present invention is, in the first aspect or the second aspect

[0017] The copolymer is composed of repeating units derived from hydroxyalkyl acrylate monomers, repeating units derived from (meth)acrylic acid monomers, and repeating units derived from acrylic monomers having amide groups.

[0018] The fourth aspect of the present invention is, in the third aspect,

[0019] The alkyl group of the above hydroxyalkyl acrylate monomer has 2 to 4 carbon atoms.

[0020] The fifth aspect of the present invention is, in any one of the first to fourth aspects,

[0021] The molar ratio of the above i) repeating unit derived from an acrylic monomer having a hydroxyl group and the above iii) repeating unit derived from an acrylic monomer having an amide group is 1:1 to 2.

[0022] The sixth aspect of the present invention is, in any one of the first to fifth aspects,

[0023] The molar ratio of the above i) repeating unit derived from an acrylic monomer having a hydroxyl group and the above iii) repeating unit derived from an acrylic monomer having an amide group is 1:1.2 to 1.6.

[0024] The seventh aspect of the present invention is, in any one of the first to sixth aspects,

[0025] 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.

[0026] The eighth aspect of the present invention is, in any one of the first to seventh aspects,

[0027] 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.

[0028] The ninth aspect of the present invention is, in any one of the first to eighth aspects,

[0029] 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.

[0030] The tenth aspect of the present invention is, in any one of the first to ninth aspects,

[0031] The content of the binder is 3 parts by weight or more and 12 parts by weight or less, based on 100 parts by weight of the total weight of the coating layer.

[0032] The eleventh aspect of the present invention is, in any one of the first to ten aspects,

[0033] The above copolymer has a weight average molecular weight of 100,000 g / mol or more and 200,000 g / mol or less.

[0034] The 12th aspect of the present invention is, in any one of the 1st to 11th aspects,

[0035] The content of the above inorganic particles is 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 coating layer.

[0036] The 13th aspect of the present invention is, in any one of the 1st to 12th aspects,

[0037] The thickness of the coating layer is 0.5 μm or more and 2 μm or less.

[0038] The 14th aspect of the present invention relates to an electrochemical device, and,

[0039] A positive electrode; a negative electrode; and a separator for an electrochemical device according to any one of the first to thirteenth aspects, comprising

[0040] The above-described separator for the electrochemical device provides an electrochemical device that is interposed between the anode and the cathode.

[0041] A separator for an electrochemical device according to the present invention comprises a non-crosslinked copolymer as a binder used in a coating layer together with inorganic particles, wherein the non-crosslinked copolymer comprises 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. Furthermore, the i) repeating units derived from an acrylic monomer having a hydroxyl group and the ii) repeating units derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers are included in a specific molar ratio range. Accordingly, the copolymer can bond sufficiently strongly to the surface of the porous polymer substrate, the electrode surface, and especially the surface of the inorganic particles through intermolecular forces such as hydrogen bonding with the inorganic particles and the porous polymer substrate by means of component i) of the above content range even at high temperatures, and sufficiently ensure not only heat resistance but also compatibility with the inorganic particles by means of component ii) of the above content range. This copolymer can also be dissolved in an aqueous solvent to enable solution coating.

[0042] Consequently, the separator for an electrochemical device according to the present invention, in which the above copolymer binder is included in the coating layer, has an improved thermal shrinkage rate, particularly at high temperatures, in both dry and wet conditions.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] In this specification, "the diameter of the particle (D 50 )" or “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 to be measured. The above 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.

[0052] In this specification, “non-crosslinked copolymer” means a copolymer that melts transparently when water is added to a concentration of 10% and stirred for 30 minutes after the copolymer has been left in an oven at 100°C for 30 minutes.

[0053] In this specification, “repeating unit derived from ~ monomer” refers to a repeating unit included in a copolymer formed by polymerizing a ~ monomer.

[0054] 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.

[0055] 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.

[0056]

[0057] The present invention will be described in more detail below.

[0058] The present invention provides a separator for an electrochemical device.

[0059] According to one embodiment of the present invention, a separator for an electrochemical device comprises a porous polymer substrate; and

[0060] A coating layer disposed on at least one surface of the above-mentioned porous polymer substrate and comprising inorganic particles and a binder, and

[0061] 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, and

[0062] The molar ratio of the above i) repeating unit derived from an acrylic monomer having a hydroxyl group and the above ii) repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers is 1:0.1 to 1.

[0063] 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.

[0064] The above copolymer is a non-crosslinked copolymer. If the copolymer is a crosslinked copolymer, the molecular chains become denser, increasing brittleness, which makes it difficult to achieve a sufficient adhesion area with inorganic particles. Additionally, since the hydroxyl groups of the repeating units derived from acrylic monomers having the hydroxyl groups of i) are lost due to the crosslinking reaction, the bonding strength with inorganic particles is reduced, thereby lowering the wet heat shrinkage rate. Therefore, the above copolymer maintains a non-crosslinked copolymer even after the separator manufacturing process and the battery assembly process. According to the present invention, the non-crosslinked copolymer can be prepared as a water-soluble solution-type binder that dissolves in water-based solvents such as water. Since the binder has a solution-type form, it can adhere to inorganic particles and porous polymer substrates over a wider surface area within the coating layer, thus having the advantage of effectively lowering the heat shrinkage rate of the separator compared to a particulate binder.

[0065] A binder comprising a polyacrylic acid binder or, ii) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers, and in particular, iii) a repeating unit derived from an acrylic monomer having an amide group, has the advantage of being able to lower the thermal shrinkage rate of the separator in the dry state because the binder itself undergoes little deformation at high temperatures due to its high glass transition temperature. However, a copolymer containing only the above-mentioned components ii) and iii) had the problem that it was difficult to improve the thermal shrinkage rate in the wet state because the binding strength with inorganic materials was poor in the wet state. 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. However, since polyacrylic acid has poor binding strength with inorganic particles, there is a problem that it is difficult to improve the thermal shrinkage problem of the separator in the wet state 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 their binding strength with inorganic particles is poor—similar to that of polyacrylic acid—there is a problem in that it is difficult to improve the thermal shrinkage of the separator in a wet state when applied to a coating layer as a binder, either alone or in a copolymer form with acrylic acid monomers.

[0066] In contrast, the copolymer according to the present invention, which further comprises i) repeating units derived from acrylic monomers having hydroxyl groups, wherein 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 monomers is 1:0.1 to 1, contains a sufficient amount of hydroxyl groups. Therefore, even at high temperatures where an electrolyte is present, it can strongly bond to the surface of a porous polymer substrate or the surface of an inorganic particle through intermolecular forces such as hydrogen bonding with inorganic particles and a porous polymer substrate, and can also bond to the electrode surface. Consequently, the separator for an electrochemical device according to the present invention, in which the copolymer binder is included in the coating layer, has an improved thermal shrinkage rate at high temperatures in both dry and wet states.

[0067] The copolymer may be composed 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, iii) repeating units derived from an acrylic monomer having an amide group, and iii) repeating units derived from an acrylic monomer having an amide group. Additionally, the copolymer may be 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.

[0068] The molar ratio of the above i) repeating unit derived from an acrylic monomer having a hydroxyl group and the above ii) repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both monomers may specifically 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 the above i) repeating unit derived from an acrylic monomer having a hydroxyl group and the above ii) repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both monomers may be 1:0.3 to 0.8.

[0069] When 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 within the copolymer satisfies the above range, the component i) having hydroxyl groups can be sufficiently included in the copolymer, so the copolymer binder can have excellent adhesion to inorganic particles and porous polymer substrates in high temperature and wet conditions. Accordingly, the separator for an electrochemical device according to the present invention, which includes the above binder in the coating layer, can 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 polymer substrates in dry conditions can also be excellent, so the separator for an electrochemical device can also have a low thermal shrinkage rate in dry conditions. If the value of the component i) is lower than the above range, the thermal shrinkage rate of the separator in wet conditions increases. In addition, if the content of component i) is higher than the above range, the content of component ii) is relatively reduced, and the thermal shrinkage rate of the membrane in the dry state increases.

[0070] Meanwhile, according to one embodiment of the present invention, the molar ratio of i) a repeating unit derived from an acrylic monomer having a hydroxyl group and iii) a repeating unit derived from an acrylic monomer having an amide group may be 1:1 to 2. Specifically, the molar ratio of the hydroxyalkyl acrylate monomer and the acrylamide monomer may be 1:1 or higher, 1:1.1 or higher, 1:1.2 or higher, 1:1.3 or higher, 1:1.4 or higher, or 1:1.5 or higher, and may also be 1:2 or lower, 1:1.9 or lower, 1:1.8 or lower, 1:1.7 or lower, or 1:1.6 or lower, and in particular, may be 1:1.2 to 1.6. When the ratio of monomers in the copolymer satisfies the above range, the component ii) with excellent heat resistance and, in particular, the component iii) 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 the component i) with excellent adhesion in the 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 separator for the electrochemical device of the present invention includes a binder in which the ratio of monomers in the copolymer satisfies the above range, the thermal shrinkage rate in the dry state as well as in the high temperature wet state can be evenly lowered.

[0071] According to one embodiment of the present invention, the alkyl group of the acrylic monomer having a 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.

[0072] According to one embodiment of the present invention, the (meth)acrylate salt 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.

[0073] According to one embodiment of the present invention, the 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 be one or more selected from the group consisting of N-methoxyethyl (meth)acrylamide and N-butoxymethyl (meth)acrylamide. When the copolymer includes an acrylic monomer having the amide group, the heat resistance of the binder in the dry state may be superior, and accordingly, a separator for an electrochemical device containing the binder in the coating layer may have a low thermal shrinkage rate in the dry state.

[0074] According to one embodiment of the present invention, the content of the binder may be 3 parts by weight or more and 12 parts by weight or less based on 100 parts by weight of the total weight of the coating layer. Specifically, the content of the binder in the coating layer 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 total weight 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 in the coating layer satisfies the above range, the binder is sufficiently present in the coating layer, so the separator for an electrochemical device in which the coating layer is disposed on one surface of a porous polymer substrate may have excellent adhesion to the electrode. In addition, 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. Therefore, the separator for an electrochemical device equipped with the coating layer may have low resistance.

[0075] According to one embodiment of the present invention, the copolymer may have a weight-average molecular weight of 100,000 g / mol or more and 200,000 g / mol or less. Specifically, the weight-average molecular weight of the copolymer 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 copolymer satisfies the above range, the copolymer may have a sufficient length to effectively prevent the problem of the inorganic particles detaching from the porous polymer substrate by being attached together to the inorganic particles and the porous polymer substrate. Accordingly, a separator for an electrochemical device in which a coating layer containing the copolymer is disposed on one side of a porous polymer substrate may have excellent adhesion at room temperature and high temperature, and consequently, may have a low thermal shrinkage rate at high temperature.

[0076] 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 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 total weight of the solids 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.

[0077] According to one embodiment of the invention, the inorganic particles are within the operating voltage range of an electrochemical element (e.g., Li / Li). + Oxidation and / or reduction reactions may not occur at a standard of 0 V to 5 V. Specifically, the inorganic particles are BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT, 0 <x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3It may be one or more selected from the group consisting of )O3-PbTiO3(PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, Al(OH)3, TiO2, boehmite, aluminum peroxide, zinc-tin hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4) and antimony pentoxide (Sb2O5).

[0078] According to one embodiment of the present invention, the inorganic particle has a diameter (D 50 The diameter may be 200 nm or more and 1 μm or less. Specifically, the inorganic particles may have a diameter of 200 nm or more, 300 nm or more, 400 nm or more, or 500 nm or more, and may also have a diameter of 1 μm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, or 500 nm or less. When the diameter of the inorganic particles satisfies the above range, there may be sufficient spacing between the inorganic particles packed within the coating layer, and accordingly, the porosity of the coating layer may be high, and the resistance of the separator may be low.

[0079] According to one embodiment of the present invention, the thickness of the coating layer may be 0.5 μm or more and 2 μm or less. Specifically, the thickness of the coating layer may be 0.5 μm or more, 0.8 μm or more, 1.1 μm or more, or 1.4 μm or more, and may also be 2 μm or less, 1.8 μm or less, 1.6 μm or less, 1.4 μm or less, or 1.2 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 has the advantage of having low resistance. Furthermore, since the total thickness of the separator for the electrochemical device including the coating layer may also be low, the electrochemical device including the separator for the electrochemical device may contain a relatively large amount of electrode active material, and accordingly, the energy density of the electrochemical device may also be high.

[0080] According to one embodiment of the present invention, the porosity of the coating layer may be 30 volume% or more and 50 volume% or less. Specifically, the porosity of the coating layer may be 30 volume% or more, 35 volume% or more, or 40 volume% or more, and may also be 50 volume% or less, 45 volume% or less, or 40 volume% or less. When the porosity of the coating layer satisfies the above range, sufficient pores may exist in the coating layer, allowing lithium ions to move smoothly through the pores, and accordingly, the resistance of the separator for an electrochemical device may be low. In addition, 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.

[0081] According to one embodiment of the present invention, the porous polymer substrate may be 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, when 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 film, and a fluid may pass through the porous polymer substrate through the pores.

[0082] The porous polymer substrate described above may be a material that is physically and chemically stable with respect to an electrolyte, which is an organic solvent. For example, the porous polymer 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, polyimideamide, 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 composition for forming a coating layer.

[0083] The porous polymer substrate may have a single-layer or multi-layer structure. The porous polymer substrate may include two or more polymer resin layers with different melting points (Tm) to provide a shutdown function during high-temperature runaway of the battery. For example, the porous polymer film may include a polypropylene layer with a relatively high melting point and a polyethylene layer with a relatively low melting point. Preferably, the porous polymer 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.

[0084] According to one embodiment of the present invention, the thickness of the porous polymer substrate may be 6 μm or more and 15 μm or less. Specifically, the thickness of the porous polymer film may be 6 μm or more, 8 μm or more, or 10 μm or more, and may also be 15 μm or less, 13 μm or less, 11 μm or less, or 9 μm or less. By controlling the thickness of the porous polymer 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.

[0085] According to one embodiment of the present invention, the porous polymer substrate has an average diameter (D 50It may include pores having a diameter of 0.01 μm or more and 1 μm or less. Specifically, the average diameter of the pores included in the porous polymer substrate may be 0.01 μm or more, 0.02 μm or more, 0.03 μm or more, or 0.04 μm or more, and may also be 1 μm or less, 0.09 μm or less, 0.08 μm or less, 0.07 μm or less, or 0.06 μm or less. Preferably, the pore size may be 0.02 μm or more and 0.06 μm or less. By controlling the pore size of the porous polymer substrate within the above-described range, the air permeability and ion conductivity of the entire separation membrane can be controlled.

[0086] The porous polymer 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 polymer substrate may be 10 s / 100cc or more, 20 s / 100cc or more, 30 s / 100cc or more, 40 s / 100cc or more, or 50 s / 100cc or more, and may also be 100 s / 100cc or less, 90 s / 100cc or less, 80 s / 100cc or less, 70 s / 100cc or less, 60 s / 100cc or less, or 50 s / 100cc or less. Preferably, the air permeability of the porous polymer substrate may be 50 s / 100cc or more and 70 s / 100cc or less. When the air permeability of the porous polymer 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.

[0087] The above air permeability (s / 100cc) refers to the time (in seconds) required for 100cc of air to pass through a porous polymer substrate or membrane of a predetermined area under constant pressure. The above air permeability may be measured using a Gurley densometer in accordance with ASTM D726-58, 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 Seiko 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.

[0088] The porous polymer substrate may have a porosity of 10 volume% or more and 70 volume% or less. Specifically, the porosity of the porous polymer substrate may be 10 volume% or more, 20 volume% or more, 30 volume% or more, or 40 volume% or more, and may also be 70 volume% or less, 60 volume% or less, or 50 volume% or less. Preferably, the porosity of the porous polymer substrate may be 40 volume% or more and 60 volume% or less. When the porosity of the porous polymer substrate is within the range described above, the ionic conductivity of the manufactured separator may be provided within a range suitable for securing the output and cycle characteristics of the electrochemical device.

[0089] The above-described porosity refers to the ratio of the volume of pores to the total volume of each, in the coating layer and the porous polymer substrate. The porosity can be measured by methods known in the art. For example, it can 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.

[0090] The present invention provides an electrochemical device.

[0091] The above electrochemical device may include the separator for the electrochemical device described above.

[0092] According to one embodiment of the present invention, the electrochemical device comprises an anode, a cathode, and a separator for the electrochemical device, and the separator for the electrochemical device may be 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.

[0093] 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.

[0094] 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 problem of thermal shrinkage of the separator can be minimized even when the electrochemical device is operated for a long period of time.

[0095] 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.

[0096] 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), 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, Bi2O4및 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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).

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105]

[0106] Examples and Comparative Examples.

[0107] Preparation of the binder

[0108] Copolymer binders were prepared with different types and contents of monomers as shown in Table 1 below.

[0109] <Preparation Example 1>

[0110] A copolymer binder was prepared containing hydroxyethyl acrylate (HA), acrylic acid (AA), and acrylamide (AM) monomers in a molar ratio of 1:0.4:1.6.

[0111] <Preparation Example 2>

[0112] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that 2-hydroxypropyl acrylate (HA) was used instead of hydroxyethyl acrylate.

[0113] <Preparation Example 3>

[0114] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that hydroxyethyl methacrylate (HA) was used instead of hydroxyethyl acrylate.

[0115] <Preparation Example 4>

[0116] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that 2-hydroxypropyl methacrylate (HA) was used instead of hydroxyethyl acrylate.

[0117] <Preparation Example 5>

[0118] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared such that the molar ratio of the monomers in the copolymer satisfies 1:0.8:1.6.

[0119] <Preparation Example 6>

[0120] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared such that the molar ratio of the monomers in the copolymer satisfies 1:0.4:1.2.

[0121] <Preparation Example 7>

[0122] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared such that the molar ratio of the monomers in the copolymer satisfies 1:0.3:1.3.

[0123] <Preparation Example 8>

[0124] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared such that the molar ratio of the monomers in the copolymer satisfies 1:0.1:1.3.

[0125] <Preparation Example 9>

[0126] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared such that the molar ratio of the monomer in the copolymer satisfies 1:1:1.3.

[0127]

[0128] <Comparative Preparation Example 1>

[0129] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared without using the hydroxyethyl acrylate monomer in Preparation Example 1.

[0130] <Comparative Preparation Example 2>

[0131] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared without using the acrylic acid monomer in Preparation Example 1.

[0132] <Comparative Preparation Example 3>

[0133] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared such that the molar ratio of the monomers in Preparation Example 1 was 1:2.4:1.6.

[0134] <Comparative Preparation Example 4>

[0135] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared such that the molar ratio of the monomers satisfied 1:2.4:4.0.

[0136] <Comparative Preparation Example 5>

[0137] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared such that the molar ratio of the monomers satisfied 1: 2.4: 0.4.

[0138] <Comparative Manufacturing Example 6>.

[0139] A copolymer binder was prepared in the same manner as in Preparation Example 1, except that the copolymer was prepared such that the molar ratio of the monomers satisfied 1: 1.2: 0.4.

[0140]

[0141] The weight-average molecular weight of Table 1 was measured using GPC.

[0142]

[0143] Manufacturing of separators for electrochemical devices

[0144] <Example 1>

[0145] A polyethylene film (thickness 10 μm, air permeability 54 s / 100cc) was prepared as a porous polymer substrate.

[0146] Boehmite powder as inorganic particles (particle diameter (D 50): 500 nm) was prepared. As a binder, the binder of Preparation Example 1 above was prepared, as a thickener, sodium carboxymethyl cellulose (CMC-Na) (SG-L02, GL Chem Co.) was prepared, and as a dispersant, a maleic acid-based dispersant was prepared. The prepared inorganic particles, binder, thickener, and dispersant were added to water in a weight ratio of 86:6:1:1, and then the inorganic particles were crushed and dispersed to prepare a composition for forming a coating layer.

[0147] A separator for an electrochemical device was manufactured by applying the composition for forming the coating layer to one surface of the porous polymer substrate using a doctor blade in a bar coating method and drying it with a heat gun at 50°C to form a coating layer on one surface of the porous polymer substrate.

[0148] At this time, based on a total weight of 100 parts by weight of the coating layer, the content of the binder was 6 parts by weight and the content of the inorganic particles was 90 parts by weight. In addition, the porosity of the coating layer was 40 volume% and the thickness of the coating layer was 1.5 μm.

[0149] <Examples 2 to 9 and Comparative Examples 1 to 6>

[0150] In the above Example 1, the separator membranes for electrochemical devices of Examples 2 to 9 and Comparative Examples 1 to 6 were prepared by using the binders of Preparation Examples 2 to 9 and Comparative Examples 1 to 6 instead of the binder of Preparation Example 1.

[0151] <Example 10>

[0152] Alumina powder instead of boehmite powder as inorganic particles (particle diameter (D 50 A separator for an electrochemical device was prepared in the same manner as in Example 1, except that 500 nm was used.

[0153] The physical properties of the separators for electrochemical devices of the aforementioned examples and comparative examples are shown in Tables 2 and 3 below, respectively.

[0154]

[0155] Experimental Example

[0156] (1) Check the wet shrinkage rate of the membrane

[0157] The separators of the above examples and comparative examples were prepared as specimens measuring 5 cm × 5 cm and each was inserted into an aluminum pouch measuring 7 cm × 10 cm. 1 g of the following electrolyte was injected into the pouch, and the pouch was sealed.

[0158] As the above electrolyte, a solvent was used in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a weight ratio of 3 / 7, and 2 wt% vinylene carbonate (VC) and the lithium salt LiPF61 M were added as additives. After storing the sealed pouch in a 140°C 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°C / 0.5h) / (length of the initial specimen)] × 100 (%). The experimental results are shown in Tables 2 and 3 below.

[0159] (2) Check the dry shrinkage rate of the separator

[0160] The separator membranes of the above examples and comparative examples were prepared as specimens measuring 5 cm × 5 cm, stored in a 180°C convection oven for 30 minutes, and then removed. The thermal shrinkage rates in the MD direction and TD direction were calculated, respectively, according to [(length of the initial specimen - length after storage at @180°C / 0.5h) / (length of the initial specimen)] × 100 (%). The experimental results are shown in Tables 2 and 3 below.

[0161] (3) Check whether the copolymer in the coating layer is cross-linked

[0162] After leaving the copolymer in an oven at 100°C for 30 minutes, water was added to achieve a concentration of 10%, and the mixture was stirred for 30 minutes to check if it melted transparently, thereby confirming whether crosslinking had occurred.

[0163] All copolymers used in the examples / comparative examples were confirmed to be non-crosslinked copolymers.

[0164]

[0165]

[0166] As shown in Tables 2 and 3 above, it can be confirmed that the separator for an electrochemical device of Comparative Example 1, which contains a copolymer binder of an acrylic monomer and an acrylamide monomer, has a low adhesion between the coating layer and the porous polymer substrate, and thus has a significantly high thermal shrinkage rate in the wet state. In addition, it can be confirmed that the separator for an electrochemical device of Comparative Example 2, which contains a copolymer binder of a hydroxyalkyl acrylate monomer and an acrylamide monomer, also has a high thermal shrinkage rate in the wet state.

[0167] In contrast, in the electrochemical device separator of the example, as a coating layer comprising a copolymer binder of a hydroxyalkyl acrylate monomer, an acrylic monomer, and an acrylamide monomer is disposed on both sides of a porous polymer substrate, it can be confirmed that the thermal shrinkage rate in both the dry and wet states is uniformly low. In particular, in the case of examples using hydroxyethyl acrylate or 2-hydroxypropyl acrylate as the hydroxyalkyl acrylate monomer, it can be confirmed that the thermal shrinkage rate of the separator is even lower.

[0168] In addition, even in Comparative Examples 3 to 6, where a copolymer binder of hydroxyalkyl acrylate monomer, acrylic monomer, and acrylamide monomer was used but the molar ratio of the hydroxyalkyl acrylate monomer and acrylic monomer in the copolymer was outside the scope of the present invention, it can be confirmed that the wet shrinkage rate of the separator is significantly high as a result of the reduced adhesive strength of the binder due to the low content of the hydroxyalkyl acrylate monomer in the copolymer.

[0169] From this, it can be confirmed that the separator for an electrochemical device according to the present invention achieves the effect of lowering both the thermal shrinkage rate in the dry state and the thermal shrinkage rate in the wet state through the copolymer binder described above.

Claims

1. 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 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, and A separator for an electrochemical device, wherein the molar ratio of i) a repeating unit derived from an acrylic monomer having a hydroxyl group and ii) a repeating unit derived from a (meth)acrylic acid monomer, a (meth)acrylic acid salt monomer, or both of these monomers is 1:0.1 to 1.

2. In Paragraph 1, The above copolymer is a separator for an electrochemical device composed 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, iii) repeating units derived from an acrylic monomer having an amide group, and iii) repeating units derived from an acrylic monomer having an amide group.

3. In Paragraph 1, The above copolymer is a separator for an electrochemical device 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.

4. In Paragraph 3, A separator for an electrochemical device in which the alkyl of the above hydroxyalkyl acrylate monomer has 2 to 4 carbon atoms.

5. In Paragraph 1, A separator for an electrochemical device, wherein the molar ratio of the above i) repeating unit derived from an acrylic monomer having a hydroxyl group and the above iii) repeating unit derived from an acrylic monomer having an amide group is 1:1 to 2.

6. In Paragraph 5, A separator for an electrochemical device, wherein the molar ratio of i) a repeating unit derived from an acrylic monomer having a hydroxyl group and iii) a repeating unit derived from an acrylic monomer having an amide group is 1:1.2 to 1.

6.

7. In Paragraph 1, A separator for an electrochemical device, 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.

8. In Paragraph 1, 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, for use as a separator in an electrochemical device.

9. 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 separator for an electrochemical device, comprising one or more selected from the group consisting of N-methoxyethyl (meth)acrylamide and N-butoxymethyl (meth)acrylamide.

10. In Paragraph 1, A separator for an electrochemical device, wherein the content of the binder is 3 parts by weight or more and 12 parts by weight or less based on 100 parts by weight of the total weight of the coating layer.

11. In Paragraph 1, The above copolymer is a separator for an electrochemical device having a weight average molecular weight of 100,000 g / mol or more and 200,000 g / mol or less.

12. In Paragraph 1, A separator for an electrochemical device, wherein the content of the above-mentioned inorganic particles is 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 coating layer.

13. In Paragraph 1, A separator for an electrochemical device having a coating layer thickness of 0.5 μm or more and 2 μm or less.

14. A positive electrode; a negative electrode; and a separator for an electrochemical device according to any one of claims 1 to 13, comprising The above electrochemical device is an electrochemical device in which a separator is interposed between the anode and the cathode.

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