Composition for forming coating layer and method for manufacturing separator for electrochemical device by using same

Abstract

The present invention relates to: a composition for forming a coating layer used in the manufacture of a separator for an electrochemical device; and a method for manufacturing a separator for an electrochemical device by using same. The composition for forming a coating layer has excellent dispersibility by including polyacrylic acid (PAA) having a weight-average molecular weight of 200,000-500,000 g / mol, and, accordingly, a thin film coating layer can be manufactured through the method for manufacturing a separator for an electrochemical device.

Description

Composition for forming a coating layer and method for manufacturing a separator for an electrochemical device using the same

[0001] The present invention claims the benefit of the filing dates of Korean Patent Application No. 10-2024-0128230 filed with the Korean Intellectual Property Office on September 23, 2024 and Korean Patent Application No. 10-2025-0117575 filed with the Korean Intellectual Property Office on August 22, 2025, the entire contents of which are incorporated into the present invention.

[0002] The present invention relates to a composition for forming a coating layer and a method for manufacturing a separator for an electrochemical device using the same.

[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] Lithium-ion batteries generate electricity through a chemical reaction in which lithium ions move between the cathode and the anode. As lithium ions move from the cathode to the anode, the battery is charged, and as lithium ions return from the anode to the cathode, energy is released, causing the battery to discharge. At this stage, an electrolyte is required to act as a pathway for lithium ions between the cathode and the anode, and a separator is required to prevent the cathode and the anode from coming into contact with each other. Generally, the four components of a lithium-ion battery refer to these: the cathode, the anode, the electrolyte, and the separator.

[0005] The present invention provides a coating layer forming composition for forming a coating layer provided on one side of a porous polymer substrate for a separator for an electrochemical device, wherein the coating layer forming composition comprises polyacrylic acid (PAA) having a weight average molecular weight of 200,000 g / mol or more and 500,000 g / mol or less as a dispersant, thereby enabling the formation of a thin film of the coating layer.

[0006] In addition, the present invention provides a method for manufacturing a separator for an electrochemical device that can form a coating layer with a thickness of 1.3 μm or less using the above-described composition for forming a coating layer.

[0007] To solve the above problems, the present invention provides a composition for forming a coating layer comprising inorganic particles, a binder, a solvent, and a dispersant, wherein the dispersant comprises polyacrylic acid (PAA) having a weight average molecular weight of about 200,000 g / mol or more and 500,000 g / mol or less, and the content of the dispersant is about 1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the total weight of the inorganic particles.

[0008] The above-mentioned composition for forming a coating layer may have a viscosity of about 5 cp or more and 30 cp or less, measured at a temperature of 25°C and a shear rate of 10 rpm.

[0009] Average particle size (D of the solid content of the above coating layer forming composition) 50 ) may be approximately 1 μm or more and 1.5 μm or less.

[0010] The above-mentioned composition for forming a coating layer may have a solid content of about 30% by weight or more and 35% by weight or less.

[0011] The content of the above inorganic particles may be about 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 solids of the composition for forming the coating layer.

[0012] The content of the binder may be about 0.5 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the total weight of the solids of the composition for forming the coating layer.

[0013] The present invention provides a method for manufacturing a separator for an electrochemical device, comprising the steps of applying a coating layer-forming composition to at least one surface of a porous polymer substrate and drying the coating layer-forming composition to form a coating layer, wherein the step of applying the coating layer-forming composition involves applying the coating layer-forming composition at a speed of about 3 mpm or more and 10 mpm or less.

[0014] In the step of applying the composition for forming the coating layer, the porous polymer substrate may be driven at a speed of about 10 mpm or more and 50 mpm or less.

[0015] The step of forming the coating layer may involve drying the composition for forming the coating layer at a temperature of about 50°C or higher and 70°C or lower.

[0016] The method may further include a step of preparing the composition before the step of applying the composition for forming the coating layer.

[0017] The present invention provides a separator for an electrochemical device comprising a porous polymer substrate and a coating layer disposed on at least one surface of the porous polymer substrate, wherein the coating layer comprises inorganic particles, a binder, and a dispersant, wherein the dispersant comprises polyacrylic acid (PAA) having a weight average molecular weight of about 200,000 g / mol or more and 500,000 g / mol or less, the content of the dispersant is about 1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the total weight of the inorganic particles, and the thickness of the coating layer is about 1.3 μm or less.

[0018] The composition for forming a coating layer according to the present invention includes polyacrylic acid (PAA) having a weight average molecular weight of about 200,000 g / mol or more and 500,000 g / mol or less as a dispersant, thereby having the effect of enabling the formation of a thin film coating layer.

[0019] In addition, the method for manufacturing a separator for an electrochemical device according to the present invention has the advantage that, by coating the coating layer forming composition onto a porous polymer substrate at a speed of about 3 mpm or more and 10 mpm or less, it is possible to manufacture a separator for an electrochemical device having a coating layer having a thickness of 1.3 μm or less on at least one surface of the porous polymer substrate.

[0020] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0021] FIG. 1 is a flowchart showing a method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention.

[0022] 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.

[0023] In this specification, the term “comprising” is used when listing materials, compositions, devices, and methods useful to the present invention, and is not limited to the examples listed.

[0024] In this specification, the terms “about” and “substantially” are used to mean a range of numerical or degree or an approximation thereof, taking into account inherent manufacturing and material tolerances, and are used to prevent an infringer from unfairly exploiting the disclosure in which precise or absolute figures provided to aid in understanding the invention are mentioned.

[0025] In this specification, when a component is described as being "on" one component, this means that, unless specifically stated otherwise, other components may be placed in between, without excluding the placement of other components.

[0026] In this specification, "electrochemical device" may refer to a primary battery, a secondary battery, or a supercapacitor, etc. For example, the electrochemical device may be a lithium-ion secondary battery and may be pouch-type, cylindrical-type, prismatic-type, or coin-type depending on its form, but the shape of the lithium-ion secondary battery is not limited thereto.

[0027] 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.

[0028] 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.

[0029] In this specification, the characteristic of having porosity or pores means that a gaseous and / or liquid fluid can pass from one side of the object to the other side by means of a structure comprising a plurality of voids or pores and said voids or pores connected to one another.

[0030] 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.

[0031] In this specification, the “average diameter (D) of the particle 50 The average diameter refers to the diameter of the particle corresponding to the 50% point of the cumulative volume distribution of the particle being measured. The above average diameter can be measured using the laser diffraction method. For example, 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., Mastersizer 3000) 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 diameter of the particle (D) 50 ) can be measured.

[0032] In this specification, "average particle size (D 50 (average particle size) refers to the average particle size of solids contained in a slurry, such as a composition for forming a coating layer. For example, the average particle size of solids in a composition for forming a coating layer refers to the average distribution of all particle sizes contained in the composition for forming a coating layer, such as inorganic particles, binders, and dispersants, and can be measured by the same method as the average diameter of the particles.

[0033]

[0034] Among the components of 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.

[0035] 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.

[0036] 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. The coating layer containing the polymer binder and inorganic particles serves to prevent thermal shrinkage of the separator while simultaneously facilitating the movement of lithium ions through the separator.

[0037] Meanwhile, when a thick coating layer is placed on the porous polymer substrate to improve the thermal shrinkage problem of the separator, lithium ions may not be able to pass smoothly through the separator due to the coating layer having a relatively lower porosity compared to the porous polymer substrate, which may consequently increase the resistance of the separator. Furthermore, when the coating layer is thick, the volume of the electrode and electrode active material within the limited electrochemical device is inevitably reduced, and consequently, there is also the problem of a lower energy density of the electrochemical device. Accordingly, there is a growing demand for thin coating layers that minimize the thermal shrinkage problem of the porous polymer substrate. As a means to devise a separator for an electrochemical device equipped with such a coating layer, research is actively being conducted on a coating layer-forming composition capable of forming a thin film and a method for forming a coating layer using the same. For example, to manufacture such a coating layer thin film, the dispersibility of the coating layer-forming composition must be excellent.

[0038] Considering these points, the present invention provides a novel composition for forming a coating layer capable of forming a thin film coating layer, and a method for manufacturing a separator for an electrochemical device using the same.

[0039]

[0040] The present invention will be described in more detail below.

[0041] A separator for an electrochemical device according to one embodiment of the present invention comprises a porous polymer substrate and a coating layer provided on at least one surface of the porous polymer substrate, the coating layer comprising a polymer binder and inorganic particles.

[0042] The present invention provides a composition for forming a coating layer for manufacturing a coating layer of a separator for an electrochemical device comprising a porous polymer substrate and a coating layer. The separator for an electrochemical device may have a coating layer manufactured from the composition for forming a coating layer disposed on one or both sides of the porous polymer substrate.

[0043] According to one embodiment of the present invention, the composition for forming a coating layer comprises inorganic particles, a binder, a solvent, and a dispersant, wherein the dispersant comprises polyacrylic acid (PAA) having a weight average molecular weight of about 200,000 g / mol or more and 500,000 g / mol or less, and the content of the dispersant is about 1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the total weight of the inorganic particles.

[0044]

[0045] The above-described composition for forming a coating layer includes polyacrylic acid (PAA) having a weight-average molecular weight of about 200,000 g / mol or more and 500,000 g / mol or less as a dispersant, so that the dispersant can be effectively adsorbed onto the surface of inorganic particles. For example, the weight-average molecular weight of the polyacrylic acid may be about 200,000 g / mol or more, about 250,000 g / mol or more, about 300,000 g / mol or more, or about 350,000 g / mol or more, and may also be about 500,000 g / mol or less, about 450,000 g / mol or less, about 400,000 g / mol or less, or about 350,000 g / mol or less. When the weight-average molecular weight of the polyacrylic acid satisfies the above range, the dispersant, which has a long linear length due to the high molecular weight, can be adsorbed over a large amount of inorganic particles. Therefore, due to steric hindrance, electrostatic repulsion may be high between a large number of inorganic particles adsorbed with the aforementioned dispersant, and a coating layer-forming composition with reduced aggregation between inorganic particles may exhibit excellent dispersion stability. Consequently, when the coating layer-forming composition with excellent dispersion stability is applied at a relatively low coating rate, it may be possible to form a thin film coating layer. If the weight-average molecular weight of the polyacrylic acid dispersant is maintained within the above range, the dispersion effect and dispersion stability of the coating layer-forming composition may be excellent, and a thin film of the coating layer can be easily formed. Furthermore, the viscosity of the coating layer-forming composition may be sufficiently low, and accordingly, it is possible to form a coating layer using a coating layer-forming composition with high dispersion stability.

[0046]

[0047] In addition, the polyacrylic acid dispersant can increase the dispersion stability of the coating layer forming composition by adsorbing to inorganic particles in a negatively charged state within the coating layer forming composition, and accordingly, the coating layer forming composition may be advantageous for forming a thin film of the coating layer compared to a dispersant having the same weight average molecular weight.

[0048]

[0049] The content of the dispersant may be about 1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the total weight of the inorganic particles. For example, the content of the dispersant may be about 1 part by weight or more, about 1.5 parts by weight or more, about 2 parts by weight or more, or about 2.5 parts by weight or more based on 100 parts by weight of the total weight of the inorganic particles, and may also be about 5 parts by weight or less, about 4.5 parts by weight or less, about 4 parts by weight or less, about 3.5 parts by weight or less, or about 3 parts by weight or less. When the content of the dispersant satisfies the above range, the dispersant is sufficiently present in the composition for forming a coating layer, so that the dispersant can be adsorbed over a large amount of inorganic particles as described above, and accordingly, the dispersion stability of the composition for forming a coating layer may be excellent. When the content of the dispersant satisfies the above range, the dispersant is sufficiently supplied within the composition for forming a coating layer to prevent increased aggregation between inorganic particles, and accordingly, the dispersion stability of the composition for forming a coating layer can be excellent. In addition, when the content of the dispersant satisfies the above range, increased aggregation between dispersants that may occur due to an excessive amount of dispersant can be prevented, and accordingly, the viscosity of the composition for forming a coating layer can be maintained sufficiently low.

[0050]

[0051] According to one embodiment of the present invention, the composition for forming a coating layer may have a viscosity of about 5 cp or more and 30 cp or less when measured at a temperature of 25°C and a shear rate of 10 rpm. For example, the composition for forming a coating layer may have a viscosity of about 5 cp or more, about 10 cp or more, about 11 cp or more, about 12 cp or more, about 13 cp or more, about 14 cp or more, or about 15 cp or more when measured at a temperature of 25°C and a shear rate of 10 rpm, and may also have a viscosity of about 30 cp or less, about 25 cp or less, about 20 cp or less, or about 15 cp or less. The composition for forming a coating layer is a non-Newtonian fluid and exhibits dilatant flow in which shear stress increases as the shear rate increases, and accordingly, the viscosity may differ depending on the temperature and shear rate. As the viscosity of the above-described coating layer-forming composition, measured at a temperature of 25°C and a shear rate of 10 rpm, satisfies the above range, the composition may have good flowability at 25°C, which is the temperature at which the coating layer-forming composition is applied. Therefore, the above-described coating layer-forming composition may be advantageous for applying a coating layer evenly and thinly on a porous polymer substrate. In addition, when the viscosity of the coating layer-forming composition satisfies the above range, drying of the coating layer-forming composition is easy, which can shorten the manufacturing process of a separator for an electrochemical device, and accordingly, the economic efficiency of the process may be excellent.

[0052]

[0053] According to one embodiment of the present invention, the average particle size (D) of the solid content of the composition for forming a coating layer 50The particle size of the solid component of the coating layer forming composition may be approximately 1 μm or more and 1.5 μm or less. For example, the average particle size of the solid component of the coating layer forming composition may be approximately 1 μm or more, approximately 1.1 μm or more, approximately 1.2 μm or more, approximately 1.3 μm or more, or approximately 1.4 μm or more, and may also be approximately 1.5 μm or less, approximately 1.4 μm or less, or approximately 1.3 μm or less. When the average particle size of the solid component of the coating layer forming composition satisfies the above range, the average specific surface area of ​​particles such as inorganic particles, binders, and dispersants within the coating layer forming composition may also be high, and accordingly, inter-particle interactions increase, so the dispersion stability of the coating layer forming composition may be excellent. Therefore, the coating layer forming composition may have excellent workability for coating, and it may be easy to form a uniform and thin coating layer during the coating process. In addition, if the average particle size satisfies the above range, the sedimentation of particles can be effectively prevented compared to cases where the particle size is excessively large.

[0054]

[0055] According to one embodiment of the present invention, the composition for forming a coating layer may have a solid content of about 30% by weight or more and about 35% by weight or less. For example, the composition for forming a coating layer may have a solid content of about 30% by weight or more, about 31% by weight or more, or about 32% by weight or more, and may also have a solid content of about 35% by weight or less, about 34% by weight or less, or about 33% by weight or less. When the solid content of the composition for forming a coating layer satisfies the above range, the viscosity of the composition for forming a coating layer may satisfy the above-described range, making it easy to form a thin film of the coating layer. In addition, as described above, drying of the composition for forming a coating layer is easy, which can shorten the manufacturing process of a separator for an electrochemical device, and accordingly, the economic efficiency of the process may be excellent.

[0056]

[0057] According to one embodiment of the present invention, the composition for forming a coating layer may have a solvent content of about 60% by weight or more and 80% by weight or less. When the solvent content satisfies the above range, the composition for forming a coating layer may have a viscosity within the above-described range, which may be advantageous for forming a thin film of the coating layer. In addition, drying of the composition for forming a coating layer is easy, which can shorten the manufacturing process of a separator for an electrochemical device, and accordingly, the economic efficiency of the process may be excellent. Meanwhile, the solvent may be an aqueous solvent, and the aqueous solvent may be one or more selected from polar solvents such as water, methanol, ethanol, ethylene glycol, diethylene glycol, and glycerol. When using an aqueous solvent, there is the advantage of being environmentally friendly, and at the same time, there is the advantage of being able to simplify the equipment compared to when using an organic solvent.

[0058]

[0059] According to one embodiment of the present invention, the content of the inorganic particles may be about 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 solids of the composition for forming the coating layer. For example, the content of the inorganic particles may be about 80 parts by weight or more, about 85 parts by weight or more, about 90 parts by weight or more, or about 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 about 99 parts by weight or less, about 98 parts by weight or less, about 97 parts by weight or less, about 96 parts by weight or less, about 95 parts by weight or less, about 94 parts by weight or less, about 93 parts by weight or less, about 92 parts by weight or less, about 91 parts by weight or less, or about 90 parts by weight or less. When the content of inorganic particles satisfies the above range, the coating layer prepared from the composition for forming the coating layer can sufficiently contain inorganic particles, so the problem of thermal shrinkage of the porous polymer substrate in the separator for an electrochemical device can be minimized.

[0060]

[0061] According to one embodiment of the present invention, the inorganic particles are alumina (Al2O3), boehmite (AlO(OH)), BaTiO3, Pb(Zr,Ti)O3 (PZT), and 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 The inorganic particles may be one or more selected from O3-PbTiO3 (PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, SiC, Al(OH)3, TiO2, aluminum peroxide, zinc-tin hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), and antimony pentoxide (Sb2O5), and for example, the inorganic particles may be alumina. The inorganic particles may be within the operating voltage range of the electrochemical device (e.g., Li / Li + Oxidation and / or reduction reactions may not occur at a standard of 0 V to 5 V. When a composition for forming a coating layer and a coating layer formed therefrom include the inorganic particles described above, the problem of thermal shrinkage of a separator for an electrochemical device can be effectively improved due to the high heat resistance of the inorganic particles described above.

[0062]

[0063] According to one embodiment of the present invention, the content of the binder may be about 0.5 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the total weight of the solids of the composition for forming the coating layer. For example, the content of the binder may be about 0.5 parts by weight or more, about 1 part by weight or more, about 1.5 parts by weight or more, or about 2 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 about 10 parts by weight or less, about 9 parts by weight or less, about 8 parts by weight or less, about 7 parts by weight or less, about 6 parts by weight or less, or about 5 parts by weight or less. When the content of the binder satisfies the above range, the interstitial volume formed by connecting the inorganic particles to each other by the binder can be effectively increased, and as a result, the porosity of the finally formed coating layer can be high. In addition, since the inorganic particles are fixed by the binder, the porosity of the coating layer can be stably maintained even when the electrochemical device is operated for a long period. Furthermore, the adhesion between the coating layer and the electrode can also be improved by the binder.

[0064]

[0065] According to one embodiment of the present invention, the binder comprises polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, poly(ethylene-co-vinyl acetate), polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cyanoethylpullulan. It may be one or more selected from cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxymethylcellulose, acrylonitrile-styrene butadiene copolymer, polyimide, and styrene-butadiene rubber. When a composition for forming a coating layer and a coating layer formed therefrom include the binder described above, the separator for an electrochemical device may have excellent adhesion to the electrode due to the high adhesive strength of the binder described above.

[0066]

[0067] The present invention provides a method for manufacturing a separator for an electrochemical device.

[0068] The method for manufacturing a separator for an electrochemical device described above utilizes the composition for forming a coating layer, and, for example, includes the step of forming a coating layer on at least one surface of a porous polymer substrate using the composition for forming a coating layer. In the method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention, details that overlap with the description of the composition for forming a coating layer are omitted.

[0069]

[0070] The present invention will be described in more detail with reference to FIG. 1.

[0071]

[0072] A method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention comprises the step (S20) of applying a coating layer forming composition to at least one surface of a porous polymer substrate and the step (S30) of drying the coating layer forming composition to form a coating layer, wherein the step of applying the coating layer forming composition (S20) may involve applying the coating layer forming composition at a speed of about 3 mpm or more and 10 mpm or less.

[0073]

[0074] According to one embodiment of the present invention, the method for manufacturing a separator for an electrochemical device may further include the step (S10) of preparing a composition for forming a coating layer. The step (S10) of preparing the composition for forming a coating layer may involve preparing inorganic particles, a binder, a dispersant, and a surfactant. The prepared inorganic particles, binder, dispersant, and surfactant may be added to, for example, ultrapure distilled water (DIW) in a certain weight ratio, and then the inorganic particles are crushed and dispersed to prepare the composition for forming a coating layer.

[0075]

[0076] The step of applying the composition (S20) is a step of applying the composition for forming a coating layer to at least one surface of a porous polymer substrate, and may be a step of applying the composition for forming a coating layer using various methods such as bar coating, dip coating, die coating, roll coating, comma coating, or a combination thereof. For example, the step of applying the composition for forming a coating layer (S20) may be a step of applying the composition for forming a coating layer to at least one surface of a porous polymer substrate through bar coating at a speed of about 3 mpm (meter per minute) or more and 10 mpm or less. For example, the step (S20) of applying the coating layer forming composition may be to apply the coating layer forming composition onto a porous polymer substrate at a speed of about 3 mpm or more, 4 mpm or more, 5 mpm or more, or 6 mpm or more, and may also be to apply the coating layer forming composition onto a porous polymer substrate at a speed of about 10 mpm or less, about 9 mpm or less, about 8 mpm or less, about 7 mpm or less, about 6 mpm or less, about 5 mpm or less, or about 4 mpm or less. Since the coating layer forming composition has shear thickening properties, depending on the application speed of the coating layer forming composition, it may be possible to form a thin film, or it may be difficult to form the coating layer itself. In accordance with the present invention, by applying the coating layer forming composition to one surface of a porous polymer substrate at the above speed, the coating layer forming composition having shear thickening properties can be smoothly applied to one surface of the porous polymer substrate, thereby enabling the formation of a uniform and thin coating film. When the application speed of the coating layer forming composition is within the above range, a thin coating layer can be easily formed while maintaining process economic efficiency.In addition, when the application speed of the coating layer forming composition is within the above range, a coating layer of uniform thickness can be applied by means of the shear-thickening properties of the coating layer forming composition while maintaining the thickness of the coating layer at a thin level.

[0077]

[0078] According to one embodiment of the present invention, the step (S20) of applying the composition for forming a coating layer may be to apply the composition for forming a coating layer at a temperature of about 20°C or higher and 30°C or lower. For example, the step (S20) of applying the composition may be to apply the composition for forming a coating layer at a temperature of about 20°C or higher, 22.5°C or higher, or about 25°C or higher, and may also be to apply the composition for forming a coating layer at a temperature of about 30°C or lower, about 27.5°C or lower, or about 25°C or lower. When the composition for forming a coating layer is applied within the above temperature range, the viscosity at the time of application of the composition for forming a coating layer may satisfy the above-described range, and accordingly, the flowability of the composition for forming a coating layer is improved, making it easy to form a uniform and thin film coating layer.

[0079]

[0080] According to one embodiment of the present invention, in the step (S20) of applying the composition for forming the coating layer, the porous polymer substrate may be driven at a speed of about 10 mpm or more and about 50 mpm or less. For example, the driving speed of the porous polymer substrate may be about 10 mpm or more, about 20 mpm or more, or about 30 mpm or more, and may also be about 50 mpm or less, about 40 mpm or less, or about 30 mpm or less. When the porous polymer substrate is driven at the above speed, the productivity of the porous polymer substrate may be increased compared to when the driving speed is excessively slow. In addition, when the porous polymer substrate is driven at the above speed, the coating layer may be applied evenly and thinly to one or both sides of the porous polymer substrate compared to when the driving speed is excessively fast.

[0081]

[0082] The step (S30) of forming a coating layer by drying the composition for forming the coating layer may be a step of forming a coating layer on at least one surface of a porous polymer substrate by drying the composition for forming the coating layer applied through the step (S20) of applying the composition, thereby forming a coating layer on at least one surface of the porous polymer substrate. The drying in the step (S30) of forming the coating layer may involve removing the solvent present in the composition for forming the coating layer to form a thin film of the coating layer containing inorganic particles, a binder, a dispersant, etc.

[0083]

[0084] According to one embodiment of the present invention, the step (S30) of forming the coating layer may involve drying the composition for forming the coating layer at a temperature of approximately 50°C or higher and 70°C or lower. For example, the drying temperature may be approximately 50°C or higher, approximately 55°C or higher, or approximately 60°C or higher, and may also be approximately 70°C or lower, approximately 65°C or lower, or approximately 60°C or lower. When the drying temperature of the step (S30) of forming the coating layer satisfies the above range, the solvent is sufficiently removed so that the coating layer can be formed while fixed to one surface of the porous polymer substrate. In addition, since the heat applied to the composition for forming the coating layer is relatively low, there is an advantage that the materials included in the coating layer, such as inorganic particles, binders, and dispersants, as well as the porous polymer substrate, undergo minimal deformation due to heat.

[0085]

[0086] The step (S30) of forming the coating layer may involve drying the composition for forming the coating layer for a period of about 10 seconds or more and about 10 minutes or less. For example, the drying time of the step (S30) of forming the coating layer may be about 10 seconds or more, about 30 seconds or more, about 1 minute or more, about 2 minutes or more, about 3 minutes or more, or about 4 minutes or more, and may also be about 10 minutes or less, about 5 minutes or less, about 3 minutes or less, about 2 minutes or less, about 1 minute or less, or about 30 seconds or less. When the drying temperature and time of the step (S30) of forming the coating layer satisfy the above ranges, the solvent can be sufficiently removed, and at the same time, there is an advantage that the particles included in the coating layer, such as inorganic particles, binders, and dispersants, undergo minimal deformation due to heat.

[0087]

[0088] The present invention provides a separator for an electrochemical device.

[0089] The above-described separator for an electrochemical device may be manufactured from the composition for forming a coating layer described above, or may be manufactured through the method for manufacturing a separator for an electrochemical device described above. In the description of the separator for an electrochemical device according to one embodiment of the present invention, details that overlap with the description of the composition for forming a coating layer and the method for manufacturing a separator for an electrochemical device are omitted.

[0090]

[0091] According to one embodiment of the present invention, the separator for an electrochemical device comprises a porous polymer substrate and a coating layer disposed on at least one surface of the porous polymer substrate, wherein the coating layer comprises inorganic particles, a binder, and a dispersant, wherein the dispersant comprises polyacrylic acid (PAA) having a weight average molecular weight of 200,000 g / mol or more and 500,000 g / mol or less, and the content of the dispersant is 1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the total weight of the inorganic particles, and the thickness of the coating layer may be 1.3 μm or less.

[0092]

[0093] According to one embodiment of the present invention, the coating layer comprises inorganic particles, a binder, and a dispersant, wherein the dispersant comprises polyacrylic acid (PAA) having a weight average molecular weight of about 200,000 g / mol or more and 500,000 g / mol or less, the content of the dispersant is about 1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the total weight of the inorganic particles, and the thickness of the coating layer may be about 1.3 μm or less. The separator for the electrochemical device may be a thin film having a thickness of about 1.3 μm or less, as the coating layer comprises a polyacrylic acid dispersant having a weight average molecular weight of about 200,000 g / mol or more and 500,000 g / mol or less in a range of about 1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the total weight of the inorganic particles.

[0094]

[0095] For example, the thickness of the coating layer may be about 0.5 μm or more, about 0.6 μm or more, about 0.7 μm or more, about 0.8 μm or more, about 0.9 μm or more, or about 1 μm or more, and may also be about 1.3 μm or less, about 1.2 μm or less, about 1.1 μm or less, about 1 μm or less, about 0.9 μm or less, or about 0.8 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.

[0096]

[0097] According to one embodiment of the present invention, the porosity of the coating layer may be about 30 volume% or more and 60 volume% or less. For example, the porosity of the coating layer may be about 30 volume% or more, about 35 volume% or more, about 40 volume% or more, or about 45 volume% or more, and may also be about 60 volume% or less, about 55 volume% or less, about 50 volume% or less, or about 45 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, such as puncture strength.

[0098]

[0099] According to one embodiment of the present invention, the inorganic particles have an average diameter (D 50 The diameter may be approximately 300 nm or more and 800 nm or less. For example, the inorganic particles may have an average diameter of approximately 300 nm or more, approximately 400 nm or more, or approximately 500 nm or more, and may also have an average diameter of approximately 800 nm or less, approximately 700 nm or less, approximately 600 nm or less, or approximately 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 and air permeability of the coating layer may be excellent. Therefore, since lithium ions can move smoothly through the coating layer, the resistance of the separator for an electrochemical device equipped with the coating layer may be low. Furthermore, when the diameter of the inorganic particles satisfies the above range, the dispersibility of the inorganic particles within the composition for forming the coating layer may be excellent, and the thickness of the coating layer produced therefrom may also be thin.

[0100]

[0101] 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.

[0102]

[0103] 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. According to one embodiment, 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.

[0104]

[0105] 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 substrate may include a polypropylene layer with a relatively high melting point and a polyethylene layer with a relatively low melting point. According to one embodiment, the porous polymer substrate may have a three-layer structure stacked 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.

[0106]

[0107] According to one embodiment of the present invention, the thickness of the porous polymer substrate may be about 6 μm or more and about 15 μm or less. For example, the thickness of the porous polymer substrate may be about 6 μm or more, about 8 μm or more, or about 10 μm or more, and may also be about 15 μm or less, about 13 μm or less, about 11 μm or less, or about 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.

[0108]

[0109] According to one embodiment of the present invention, the porous polymer substrate may include pores having an average diameter of about 0.01 μm or more and 1 μm or less. For example, the size of the pores included in the porous polymer substrate may be about 0.01 μm or more, about 0.02 μm or more, about 0.03 μm or more, or about 0.04 μm or more, and may also be about 1 μm or less, about 0.09 μm or less, about 0.08 μm or less, about 0.07 μm or less, or about 0.06 μm or less. According to one embodiment, the size of the pores may be about 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 being manufactured can be controlled.

[0110]

[0111] The porous polymer substrate may have an air permeability of about 10 s / 100cc or more and 100 s / 100cc or less. For example, the air permeability of the porous polymer substrate may be about 10 s / 100cc or more, about 20 s / 100cc or more, about 30 s / 100cc or more, about 40 s / 100cc or more, or about 50 s / 100cc or more, and may also be about 100 s / 100cc or less, about 90 s / 100cc or less, about 80 s / 100cc or less, about 70 s / 100cc or less, about 60 s / 100cc or less, or about 50 s / 100cc or less. According to one embodiment, the air permeability of the porous polymer substrate may be about 50 s / 100cc or more and 70 s / 100cc or less. When the air permeability of the porous polymer substrate is in the range described above, the air permeability of the manufactured separator can be provided in a range suitable for securing the output and cycle characteristics of the electrochemical device.

[0112]

[0113] 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 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 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.

[0114]

[0115] The porous polymer substrate may have a porosity of about 10 volume% or more and about 70 volume% or less. For example, the porosity of the porous polymer substrate may be about 10 volume% or more, about 20 volume% or more, about 30 volume% or more, or about 40 volume% or more, and may also be about 70 volume% or less, about 60 volume% or less, or about 50 volume% or less. According to one embodiment, the porosity of the porous polymer substrate may be about 40 volume% or more and about 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.

[0116]

[0117] 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.

[0118]

[0119] The present invention provides an electrochemical device.

[0120] The above electrochemical device may include the separator for the electrochemical device described above.

[0121] 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 composition for forming a coating layer, the method for manufacturing the separator for the electrochemical device, and the separator for the electrochemical device are omitted.

[0122]

[0123] 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.

[0124]

[0125] As the above-described electrochemical device includes the separator for the electrochemical device of the present invention, lithium ions can move smoothly through the separator for the electrochemical device due to the low thickness of the coating layer, thus having the advantage of low resistance and excellent output.

[0126]

[0127] 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 LiNi1-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.

[0128]

[0129] 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.

[0130]

[0131] According to one embodiment of the present invention, the conductive material may be, for example, any one selected from 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. According to one embodiment, it may be one selected from 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.

[0132]

[0133] 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.

[0134]

[0135] 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.

[0136]

[0137] 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).

[0138] 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.

[0139]

[0140] 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.

[0141]

[0142] Hereinafter, the present invention will be described in detail with reference to examples. 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.

[0143]

[0144] Examples and Comparative Examples.

[0145] Preparation of a composition for forming a coating layer

[0146] <Preparation Example 1>

[0147] Inorganic particles of alumina (AES11, Sumitomo, particle diameter (D 50) 500 nm), as a binder, a particulate acrylic binder (CSB140, Toyo Co.), as a dispersant, a polyacrylic acid (CK-702, Lubrizol Co.) with a weight average molecular weight of 345,000 g / mol, and a surfactant (BYK348, BYK Co.) were prepared. The prepared inorganic particles, binder, dispersant, and surfactant were added to 231.6 g of ultrapure distilled water (DIW) in a weight ratio of 95.6:2.5:1:0.9, and then the inorganic particles were crushed and dispersed to prepare a composition for forming a coating layer (solid content 30 wt%). The viscosity of the above coating layer-forming composition measured at a temperature of 25°C and a shear rate of 10 rpm (viscosity measuring equipment: LV model viscometer (using UL Adapter), Brookfield) was 13.2 cp, and the average particle size of the solids of the above coating layer-forming composition (D 50 ) was 1.43 μm.

[0148] <Preparation Example 2>

[0149] A coating layer-forming composition was prepared in the same manner as in Preparation Example 1, except that in Preparation Example 1, the prepared inorganic particles, binder, dispersant, and surfactant were added to 230 g of ultrapure distilled water (DIW) in a weight ratio of 95.1:2.5:1.5:0.9, and then the inorganic particles were crushed and dispersed to prepare a coating layer-forming composition (solid content 30 wt%). The viscosity of the coating layer-forming composition measured at a temperature of 25°C and a shear rate of 10 rpm was 13.8 cp, and the average particle size (D) of the solid content of the coating layer-forming composition 50 ) was 1.44 μm.

[0150] <Preparation Example 3>

[0151] A coating layer-forming composition (solid content 30 wt%) was prepared using the same method as in Preparation Example 1, except that in Preparation Example 1 above, the prepared inorganic particles, binder, dispersant, and surfactant were added to 228.5 g of ultrapure distilled water (DIW) in a weight ratio of 94.6:2.5:2:0.9, and then the inorganic particles were crushed and dispersed to prepare the coating layer-forming composition. The viscosity of the coating layer-forming composition measured at a temperature of 25°C and a shear rate of 10 rpm was 13.8 cp, and the average particle size of the solid content of the coating layer-forming composition (D 50 ) was 1.43 μm.

[0152] <Comparative Preparation Example 1>

[0153] A coating layer-forming composition (solid content 30 wt%) was prepared using the same method as in Preparation Example 1, except that in Preparation Example 1, the prepared inorganic particles, binder, dispersant, and surfactant were added to 233.1 g of ultrapure distilled water (DIW) in a weight ratio of 96.1:2.5:0.5:0.9, and then the inorganic particles were crushed and dispersed to prepare the coating layer-forming composition. The viscosity of the coating layer-forming composition measured at a temperature of 25°C and a shear rate of 10 rpm was 12.6 cp, and the average particle size (D) of the solid content of the coating layer-forming composition 50 ) was 1.41 μm.

[0154] <Comparative Preparation Example 2>

[0155] A coating layer-forming composition was prepared in the same manner as in Example 1, except that in Preparation Example 1 above, the prepared inorganic particles, binder, dispersant, and surfactant were added to 219.3 g of ultrapure distilled water (DIW) in a weight ratio of 91.6:2.5:5:0.9, and then the inorganic particles were crushed and dispersed to prepare a coating layer-forming composition (solid content 30 wt%). The viscosity of the coating layer-forming composition measured at a temperature of 25°C and a shear rate of 10 rpm was 30.6 cp, and the average particle size (D) of the solid content of the coating layer-forming composition 50 ) was 1.59 μm.

[0156] <Comparative Preparation Example 3>

[0157] A coating layer forming composition (solid content 30 wt%) was prepared using the same method as in Preparation Example 1, except that in Preparation Example 1 above, polyacrylic acid (CK732, Lubrizol) with a weight-average molecular weight of 6,000 g / mol was prepared as the dispersant, and the prepared inorganic particles, binder, dispersant, and surfactant were added to 233.6 g of ultrapure distilled water (DIW) in a weight ratio of 95.6:2.5:1:0.9, and then the inorganic particles were crushed and dispersed to prepare the coating layer forming composition. The viscosity of the coating layer forming composition measured at a temperature of 25°C and a shear rate of 10 rpm was 12.0 cp, and the average particle size of the solids of the coating layer forming composition (D 50 ) was 1.87 μm.

[0158] <Comparative Preparation Example 4>

[0159] A coating layer forming composition (solid content 30 wt%) was prepared using the same method as in Preparation Example 1, except that in Preparation Example 1, polyacrylic acid with a weight-average molecular weight of 600,000 g / mol was prepared as the dispersant, and the prepared inorganic particles, binder, dispersant, and surfactant were added to 215.2 g of ultrapure distilled water (DIW) in a weight ratio of 95.6:2.5:1:0.9, and then the inorganic particles were crushed and dispersed to prepare the coating layer forming composition. The viscosity of the coating layer forming composition measured at a temperature of 25°C and a shear rate of 10 rpm was 57.6 cp, and the average particle size of the solids of the coating layer forming composition (D 50 ) was 1.95 μm.

[0160]

[0161] Manufacturing of separators for electrochemical devices

[0162] A polyethylene film (thickness 8.4 μm, air permeability 62 s / 100cc) was prepared as a porous polymer substrate.

[0163] The porous polymer substrate was driven at a speed of 30 mpm, and the coating layer forming composition of the above manufacturing example and comparative manufacturing example was applied to one surface of the moving porous polymer substrate by a bar coating method. Specifically, the application of the coating layer forming composition was performed by a bar coating method using a doctor blade at a temperature of 25°C, and the coating layer forming composition was applied by varying the coating speed of the doctor blade to 1 mpm, 3 mpm, 5 mpm, 7 mpm, 10 mpm, and 20 mpm, respectively. Subsequently, the coated coating layer forming composition was dried for 1 minute with a 70°C airflow using a heat gun to form a coating layer on one surface of the porous polymer substrate, thereby completing the separator for an electrochemical device.

[0164]

[0165] The properties of the composition for forming a coating layer and the separator for an electrochemical device are described in Table 1 below. The weight % below is based on the weight of the solid content of the composition for forming a coating layer.

[0166]

[0167] Composition for Forming a Coating Layer Preparation Example 1 Preparation Example 2 Preparation Example 3 Comparative Preparation Example 1 Comparative Preparation Example 2 Comparative Preparation Example 3 Comparative Preparation Example 4 Inorganic Particle Content (Weight%) 95.6 95.1 94.6 96.1 91.6 95.6 95.6 Binder Content (Weight%) 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Dispersant Content (Weight%) 11.5 20.5 511 Dispersant Content / Inorganic Particle Content (%) 1.1 1.6 2.1 0.5 5.5 1.1 1.1 Dispersant Molecular Weight (g / mol) 3 45,000 3 45,000 3 45,000 3 45,000 3 45,000 6,000 600,000 Viscosity @ 25℃, 10 rpm (cp) 13.2 13.8 13.8 12.6 30.6 125 7.6 Average particle size (μm) 1.4 3 1.4 4 1.4 3 1.4 11.5 9 1.8 7 1.9 Thickness of coating layer according to coating speed (μm) Composition for forming coating layer Preparation Example 1 Preparation Example 2 Preparation Example 3 Comparative Preparation Example 1 Comparative Preparation Example 2 Comparative Preparation Example 3 Comparative Preparation Example 4 Coating speed 1 mpm Coating impossible Coating impossible Coating impossible Coating impossible 2.1 4 1.8 12.1 53 mpm 1.1 20.9 40.8 13.0 22.1 6 1.8 22.2 25 mpm 1.1 7 1.0 50.8 43.0 42.1 7 1.8 42.1 67 mpm1.241.150.953.262.391.822.1810 mpm1.281.271.083.142.281.852.3320 mpm1.681.751.783.052.141.912.34

[0168]

[0169] As shown in Table 1 above, when the coating layer forming compositions of Preparation Examples 1 to 3, which contain polyacrylic acid (PAA) with a weight average molecular weight of 345,000 g / mol (200,000 g / mol or more and 500,000 g / mol or less) as a dispersant in an amount of 1.1% to 2.1% by weight based on 100 parts by weight of inorganic particles, are applied at a speed of 3 mpm to 10 mpm, it can be confirmed that a thin coating film with a thickness of 1.3 μm or less is formed. In addition, in the case of the coating layer forming composition of Preparation Example 3, it can be confirmed that an ultrathin coating layer with a thickness of 0.81 μm is formed at an application speed of 3 mpm. From this, it can be confirmed that the method for manufacturing a separator for an electrochemical device using the coating layer forming composition of the present invention enables the formation of a thin coating layer.

[0170]

[0171] Meanwhile, it can be confirmed that even when using the coating layer forming compositions of Preparation Examples 1 to 3, it is impossible to form a coating layer when the application speed is 1 mpm, or when the application speed is 20 mpm, the thickness of the coating layer exceeds 1.6 μm. In addition, when using the coating layer forming composition of Comparative Preparation Example 1, in which the content of the dispersant in the coating layer forming composition is 0.5%, it can be confirmed that a thick coating layer with a thickness of 3.02 μm to 3.26 μm is formed at an application speed of 3 mpm to 10 mpm, which is the same as Preparation Examples 1 to 3.

[0172]

[0173] Furthermore, when using the coating layer forming compositions of Comparative Preparation Example 3 and Comparative Preparation Example 4, in which the weight average molecular weight of the dispersant is 6,000 g / mol and 600,000 g / mol, respectively, it can be confirmed that relatively thick coating layers with a maximum thickness of 1.91 μm and 2.34 μm, respectively, were formed, even though the application speed was the same as that of Preparation Examples 1 to 3.

[0174]

[0175] Experimental Example

[0176] (1) Measurement of membrane resistance

[0177] Coin cells were prepared by interposing between SUS materials each of the following: a separator for an electrochemical device prepared by applying the coating layer-forming composition of Preparation Example 3 at a speed of 3 mpm, 5 mpm, or 7 mpm, respectively (Examples 1 to 3); a separator for an electrochemical device prepared by applying the coating layer-forming composition of Preparation Example 3 at a speed of 20 mpm (Comparative Example 1); a separator for an electrochemical device prepared by applying the coating layer-forming composition of Comparative Preparation Example 3 at a speed of 3 mpm, 5 mpm, or 7 mpm, respectively (Comparative Examples 2 to 4); and a separator for an electrochemical device prepared by applying the coating layer-forming composition of Comparative Preparation Example 4 at a speed of 3 mpm, 5 mpm, or 7 mpm, respectively (Comparative Examples 5 to 7). An electrolyte containing 1M LiPF6 and mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:2 was injected into the coin cell. To measure the resistance of the above coin cells, the resistance was measured using the VMP3 of BioLogic Science Instrument at 25°C under conditions of an amplitude of 10 mV and a scan range of 0.1 Hz to 1 MHz through electrochemical impedance spectroscopic analysis. The results are shown in Tables 2 and 3 below.

[0178]

[0179] (2) Measurement of wet shrinkage rate of the membrane

[0180] The separators for electrochemical devices of Examples 1 to 3 and Comparative Examples 1 to 7 were prepared as specimens measuring 5 cm x 5 cm and each was inserted into an aluminum pouch measuring 7 cm x 10 cm. 1 g of the following electrolyte 1 was injected into the pouch, and the pouch was sealed. After storing the sealed pouch in a 135°C convection oven for 1 hour, 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 135°C / 1h) / (length of the initial specimen)] x 100 (%).

[0181] The above electrolyte was used in a solvent mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a weight ratio of 3 / 7, containing 3 mol of vinylene carbonate (VC), 1.5 mol of propanesulfone (PS), 1 mol of ethylene sulfate (ESa), and 61 mol of the lithium salt LiPF6 as additives. The results are shown in Tables 2 and 3 below.

[0182]

[0183] Classification Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Coating Layer Composition for Forming Coating Layer Preparation Example 3 Preparation Example 3 Preparation Example 3 Preparation Example 3 Comparative Preparation Example 3 Coating Speed ​​(mpm) 35 7 20 3 Thickness (μm) 0.8 10.8 40.9 5 1.7 8 1.8 2 Electrical Resistance (Ω) 0.6 20.6 10.6 30.8 40.8 8 Thermal Shrinkage Rate in Wet Condition @ 135℃ / 1h (MD(%) / TD(%)) 8 / 9 7 / 7 8 / 95 / 65 / 5

[0184]

[0185] Classification Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Coating Layer Comparative Composition for Forming Coating Layer Preparation Example 3 Comparative Preparation Example 3 Comparative Preparation Example 4 Comparative Preparation Example 4 Comparative Preparation Example 4 Coating Speed ​​(mpm) 57357 Thickness (μm) 1.841.822.222.162.18 Electrical Resistance (Ω) 0.890.880.970.960.96 Wet Condition Thermal Shrinkage Rate @135℃ / 1h (MD(%) / TD(%)) 5 / 55 / 54 / 43 / 43 / 4

[0186]

[0187] As shown in Tables 2 and 3 above, the electrochemical device separator of the example manufactured using the coating layer forming composition and separator manufacturing method of the present invention includes a thin film coating layer with a thickness of 0.81 μm to 0.95 μm, and thus it can be confirmed that it has a lower electrical resistance compared to the comparative example which includes a thicker coating layer. Specifically, the electrical resistance of Examples 1 to 3 was 0.61 Ω to 0.63 Ω, whereas that of the comparative examples was 0.84 Ω to 0.97 Ω.

[0188]

[0189] In addition, in the case of Examples 1 to 3 above, the thickness of the thin film coating layer is 0.81 μm to 0.95 μm, which is a thickness sufficient to reduce the thermal shrinkage problem of the porous polymer substrate, so it can be confirmed that the thermal shrinkage rate of the separator is sufficiently low even compared to the comparative example with a thicker coating layer.

[0190]

[0191] Although the foregoing has been described with reference to the embodiments of the present disclosure, a person skilled in the art or having ordinary knowledge in the art will understand that various modifications and changes can be made to the various embodiments of the present disclosure without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

Claims

1. Includes inorganic particles, a binder, a solvent, and a dispersant, and The above dispersant comprises polyacrylic acid (PAA) having a weight average molecular weight of 200,000 g / mol or more and 500,000 g / mol or less, and A composition for forming a coating layer, wherein the content of the dispersant is 1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the total weight of the inorganic particles.

2. In Paragraph 1, The above coating layer forming composition is a coating layer forming composition having a viscosity of 5 cp or more and 30 cp or less, measured at a temperature of 25°C and a shear rate of 10 rpm.

3. In Paragraph 1, Average particle size (D of the solid content of the above coating layer forming composition) 50 A composition for forming a coating layer, wherein ) is 1 μm or more and 1.5 μm or less.

4. In Paragraph 1, A composition for forming a coating layer having a solid content of 30% by weight or more and 35% by weight or less.

5. In Paragraph 1, A coating layer forming composition in which 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 solid content of the coating layer forming composition.

6. In Paragraph 1, A coating layer forming composition wherein the content of the binder is 0.5 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the total weight of the solids of the coating layer forming composition.

7. A step of applying a composition for forming a coating layer according to claim 1 to at least one surface of a porous polymer substrate; and The method includes the step of forming a coating layer by drying the above-mentioned composition for forming a coating layer, and A method for manufacturing a separator for an electrochemical device, wherein the step of applying the above-mentioned coating layer forming composition involves applying the above-mentioned coating layer forming composition at a speed of 3 mpm or more and 10 mpm or less.

8. In Paragraph 7, A method for manufacturing a separator for an electrochemical device, wherein in the step of applying the composition for forming the coating layer, the porous polymer substrate is driven at a speed of 10 mpm or more and 50 mpm or less.

9. In Paragraph 7, A method for manufacturing a separator for an electrochemical device, wherein the step of forming the coating layer is to dry the composition for forming the coating layer at a temperature of 50°C or higher and 70°C or lower.

10. In Paragraph 7, A method for manufacturing a separator for an electrochemical device, comprising the step of preparing a composition for forming a coating layer before the step of applying the composition for forming a coating layer.

11. Porous polymer substrate; and It includes a coating layer disposed on at least one surface of the above-mentioned porous polymer substrate, and The above coating layer comprises inorganic particles, a binder, and a dispersant, and The above dispersant comprises polyacrylic acid (PAA) having a weight average molecular weight of 200,000 g / mol or more and 500,000 g / mol or less, and The content of the above dispersant is 1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the total weight of the above inorganic particles, and A separator for an electrochemical device having a coating layer thickness of 1.3 μm or less.

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