Separator for electrochemical device and electrochemical device comprising same

Abstract

A separator for an electrochemical device of the present invention comprises: a porous polymer substrate; and a coating layer disposed on at least one surface of the porous polymer substrate and including inorganic particles, wherein the porous polymer substrate has a porosity of about 50-65 vol%, the porous polymer substrate includes a polymer having a melt index of about 0.0001-0.01 g / 10 min, and the coating layer has a porosity of about 40-70 vol%.

Description

Separator for electrochemical devices and electrochemical devices containing the same

[0001] The present invention claims the benefit of Korean Patent Application No. 10-2024-0120067, filed with the Korean Intellectual Property Office on September 4, 2024, and Korean Patent Application No. 10-2025-0116288, filed with the Korean Intellectual Property Office on August 21, 2025, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a separator for an electrochemical device and an electrochemical device including the same.

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions. Recently, lithium secondary batteries have been widely used due to their high energy density and voltage, long cycle life, and wide range of applications.

[0004] Lithium secondary batteries generate electricity through a chemical reaction in which lithium ions move between the positive and negative electrodes. The lithium ions from the positive electrode move to the negative electrode, charging the battery. The lithium ions from the negative electrode return to the positive electrode, releasing energy and discharging. This requires an electrolyte, which acts as a path for the lithium ions between the positive and negative electrodes, and a separator, which prevents the two electrodes from touching each other. Generally, the four components of a lithium-ion battery are the positive electrode, negative electrode, electrolyte, and separator.

[0005] The present invention provides a separator for an electrochemical device comprising a porous polymer substrate with a high porosity and a coating layer, wherein the porous polymer substrate comprises a polymer with a low melting index (MI), thereby providing a separator for an electrochemical device having low resistance and excellent mechanical strength.

[0006] 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 and including inorganic particles, wherein the porous polymer substrate has a porosity of about 50% by volume or more and 65% by volume or less, the porous polymer substrate includes a polymer having a melt index of about 0.0001 g / 10 min or more and 0.01 g / 10 min or less, and the coating layer has a porosity of about 40% by volume or more and 70% by volume or less.

[0007] In the above porous polymer substrate, the crystallinity of the polymer may be 60% or more and 90% or less.

[0008] In the above porous polymer substrate, the polymer may have a weight average molecular weight of about 1,500,000 g / mol or more and 2,500,000 g / mol or less.

[0009] In the above porous polymer substrate, the polymer may be at least one selected from polyethylene, polypropylene, polybutylene, polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimideamide, nylon, and polytetrafluoroethylene.

[0010] The inorganic particles included in the coating layer may be in a cubic shape.

[0011] The inorganic particles included in the coating layer have an average particle diameter (D 50 ) may be approximately 200 nm or more and 1 μm or less.

[0012] The inorganic particles included in the coating layer are boehmite (γ-AlO(OH)), alumina (Al2O3), 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(Mg1 / 3 Nb 2 / 3 )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).

[0013] The content of the inorganic particles may be about 90 parts by weight or more based on 100 parts by weight of the total weight of the coating layer.

[0014] The above coating layer may further include a binder, and the content of the binder may be about 1 part by weight or more and 10 parts by weight or less based on 100 parts by weight of the total weight of the coating layer.

[0015] The thickness of the above porous polymer substrate may be about 4 μm or more and 20 μm or less.

[0016] The thickness of the above coating layer may be about 0.5 μm or more and 4 μm or less.

[0017] The present invention provides an electrochemical device comprising an anode, a cathode, and a separator for the electrochemical device, wherein the separator for the electrochemical device is interposed between the anode and the cathode.

[0018] The present invention provides a method for manufacturing a separator for an electrochemical device, comprising the steps of: extruding a polymer sheet composition containing a polymer and a diluent (S10); forming and stretching the polymer sheet composition extruded in step (S10) into a sheet shape (S20); extracting the diluent from the polymer sheet stretched in step (S20) to manufacture a porous polymer substrate (S30); heat-setting the porous polymer substrate (S40); and forming a coating layer containing inorganic particles on at least one surface of the porous polymer substrate (S50). In the porous polymer substrate, the melt index of the polymer is about 0.0001 g / 10 min or more and 0.01 g / 10 min or less, and the content of the diluent is about 70 parts by weight or more and 90 parts by weight or less based on 100 parts by weight of the total polymer sheet composition.

[0019] The separator for an electrochemical device according to the present invention includes a porous polymer substrate and a coating layer having a high porosity, so that the resistance of the separator is low, and since the porous polymer substrate includes a polymer having a low melting index, the mechanical strength can be excellent.

[0020] The following drawings attached to this specification illustrate embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0021] Figure 1 is a flow chart 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 will be described in more detail so that a person having ordinary skill in the art to which the present invention pertains can easily practice it; however, this is only an example, and the scope of the rights of the present invention is not limited by the following contents.

[0023] As used herein, the term "comprises" is used to list materials, compositions, devices, and methods useful in the present invention, but is not limited to the listed examples.

[0024] In this specification, the terms "about" and "substantially" are used to mean a range or approximation of a numerical value or degree, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly exploiting the disclosure, which mentions exact or absolute numerical values ​​provided to aid understanding of the present invention.

[0025] In this specification, when it is said that a component is “on”, this does not exclude other components being placed therebetween, unless otherwise specifically stated, but rather means that other components may be placed thereon.

[0026] In this specification, "electrochemical device" may refer to a primary battery, a secondary battery, a supercapacitor, or the like. More specifically, the electrochemical device may be a lithium ion secondary battery, and may be pouch-shaped, cylindrical, square, or coin-shaped, but the specific shape is not limited thereto.

[0027] In this specification, "electrode" refers to both "positive electrode" and "negative electrode," and may mean an electrode active material applied to at least one surface of a conductive material that does not cause a chemical change in an electrochemical device and dried. The types of the material and electrode active material are not limited as long as they can be used in an electrochemical device.

[0028] In this specification, the term "separator" may generally refer to a functional separator having a porous coating layer comprising an inorganic substance and a binder formed on at least one surface of a porous polymer substrate, such as a polyolefin substrate or non-woven fabric. In addition, the separator has porous characteristics including a large number of pores, and acts as a porous ion-conducting barrier that allows ions to pass while blocking electrical contact between the cathode and the anode in an electrochemical device.

[0029] In this specification, the characteristic of having a void or pore means that the object includes a plurality of voids or pores and that the voids or pores are interconnected with each other, thereby allowing a gaseous and / or liquid fluid to pass from one side of the object to the other side.

[0030] In this specification, the term "porous polymer substrate" may refer to a porous membrane having a plurality of pores formed therein, which electrically insulates the positive and negative electrodes to prevent short circuits. For example, when the electrochemical device is a lithium secondary battery, the porous polymer substrate may be an ion-conductive barrier that blocks electrical contact between the positive and negative electrodes while allowing lithium ions to pass through. At least a portion of the pores may form a three-dimensional network that connects 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 of the particles (D 50 )" or “average particle size (D 50)” means the diameter of the particle corresponding to the 50% point of the cumulative number of particles in the cumulative particle size distribution for the particles to be measured. The diameter can be measured using the laser diffraction method. For example, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and the particle size distribution is calculated by measuring the difference in the diffraction pattern according to the particle size when the particles pass through the laser beam. By calculating the particle diameter at the point where it becomes 50% of the cumulative number of particles according to the diameter in the measuring device, the diameter (D) of the particle 50 ) can be measured.

[0032] In this specification, “melting index (MI)” or “melt flow index” is a measure of the fluidity of a polymer material or the ease of flow of a polymer melt, and refers to the flow rate when a polymer melt is extruded at a specific temperature and pressure. This melting index may be affected by the molecular weight of the polymer, etc., and if the molecular weight of the polymer is high, the melting index of the polymer may be low. For example, the melting index of the polymer may be measured at a temperature of 190°C and a load of 21.6 kg according to ASTM D 1238.

[0033] In this specification, “cubic shape” means that the particle has a cubic shape, for example, a rectangular parallelepiped shape. For example, in the case of boehmite, which is a type of inorganic particle, the particle may have an amorphous, spherical, plate-like or cubic shape, and among them, the cubic shape of boehmite may have a particle shape that has a three-dimensional rectangular parallelepiped shape when observed with a scanning electron microscope.

[0034] In this specification, “porosity” means the ratio of the volume occupied by pores to the total volume in a certain structure, and uses volume % as its unit, and can be used interchangeably with terms such as porosity, porosity, and porosity. In the present invention, the measurement of the porosity is not particularly limited, and for example, it can be measured according to the BET (Brunauer-Emmett-Teller) measurement method using nitrogen gas or the mercury penetration method (Hg porosimeter) and ASTM D-2873. Alternatively, the true density of the membrane can be calculated from the density (apparent density) of the membrane and the composition ratio of the materials included in the membrane and the density of each component, and the porosity of the porous polymer, coating layer, or membrane can be calculated from the difference between the apparent density and the true density.

[0035] In this specification, the “crystallinity” of a polymer means the proportion of the portion arranged in a crystalline state among the whole polymer or material, and uses % as its unit, and can be used interchangeably with terms such as crystallinity, crystallinity, etc. In the present invention, the measurement of the crystallinity is not particularly limited, and according to an embodiment of the present invention, for example, it can be measured by X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), or density measurement and related ASTM or ISO standards. For example, the crystallinity can be measured by X-ray diffraction (XRD).

[0036] In this specification, the "MD direction" (Machine Direction) means a direction parallel to the direction in which the polymer sheet is transported in the stretching process and the direction in which the porous polymer substrate is transported within the manufacturing system for a separator for an electrochemical device, for example, a longitudinal direction. The "TD direction" (Transverse Direction) means a direction perpendicular to the direction in which the polymer sheet is transported, for example, a traverse direction. Therefore, the MD direction and the TD direction are perpendicular to each other.

[0037]

[0038] Among the components of an electrochemical device, a separator may include a polymer substrate having a porous structure located between the anode and cathode. The separator isolates the anode and cathode, preventing electrical short-circuiting between the two electrodes while simultaneously allowing electrolyte and ions to pass through. Although the separator itself does not participate in the electrochemical reaction, its physical properties, such as wettability with respect to the electrolyte, porosity, and thermal shrinkage, may affect the performance and safety of the electrochemical device.

[0039] Therefore, to enhance the physical properties of such membranes, various methods have been attempted, such as adding a coating layer to a porous polymer substrate and adding various substances to the coating layer to improve the properties of the coating layer. For example, inorganic substances may be added to the coating layer to enhance the mechanical strength of the membrane, or inorganic substances or hydrates may be added to the coating layer to enhance the flame retardancy and heat resistance of the polymer substrate.

[0040] Within the above coating layer, inorganic particles can be linked 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 including the polymer binder and inorganic particles serves to prevent thermal shrinkage of the separator while also assisting the movement of lithium ions through the separator.

[0041] Meanwhile, if the porous polymer substrate and coating layer used in the electrochemical device separator have low porosity, there is a problem that the resistance of the electrochemical device separator may increase, which may deteriorate the performance of the electrochemical device including it. Accordingly, research is being conducted on methods to lower the resistance of the electrochemical device separator and simultaneously increase the output by increasing the porosity of the porous polymer substrate and coating layer. However, the electrochemical device separator including the porous polymer substrate with high porosity has a disadvantage in that it has poor mechanical strength and is vulnerable to external pressure, such as electrode expansion due to the lamination process and cell operation. Therefore, the electrochemical device including the electrochemical device separator that is vulnerable to such external pressure has a problem in that the stability during long-term operation is poor.

[0042] For example, a separator for an electrochemical device including a porous polymer substrate with a high porosity may have low electrical resistance, but may have poor mechanical strength, such as compression resistance, due to the high porosity. Therefore, a conventional separator for an electrochemical device including a porous polymer substrate with such a high porosity may have a problem in that the pores present in the porous polymer substrate are closed due to the pressure generated during the lamination process. As a result, in the electrochemical device separator that has undergone lamination, the porosity of the porous polymer substrate may decrease, which may cause a problem in that the resistance of the separator increases. In addition, when the electrochemical device is operated, the electrode included in the electrochemical device may expand, which may apply pressure to the separator for the electrochemical device. This pressure may cause deformation of the separator for the electrochemical device, resulting in a problem in that the stability of the electrochemical device is reduced.

[0043] Considering these points, the present invention provides a separator for an electrochemical device and a manufacturing method thereof, which includes a porous polymer substrate and a coating layer with a high porosity, has low resistance of the separator, and also has excellent mechanical strength by controlling the melting index of the polymer used in the substrate.

[0044]

[0045] Hereinafter, the present invention will be described in more detail with reference to the attached drawings.

[0046]

[0047] According to one embodiment of the present invention, the separator for the electrochemical device includes a porous polymer substrate and a coating layer disposed on at least one surface of the porous polymer substrate and including inorganic particles, the porosity of the porous polymer substrate is about 50% by volume or more and 65% by volume or less, the porous polymer substrate includes a polymer having a melt index (MI) of about 0.0001 g / 10 min or more and 0.01 g / 10 min or less, and the porosity of the coating layer is about 40% by volume or more and 70% by volume or less.

[0048]

[0049] The above-described separator for an electrochemical device may be a membrane having a coating layer including the inorganic particles disposed on one or both sides of a porous polymer substrate. The porosity of the porous polymer substrate is about 50% by volume or more and 65% by volume. For example, the porosity of the porous polymer substrate may be about 50% by volume or more, about 51% by volume or more, about 52% by volume or more, about 53% by volume or more, about 54% by volume or more, or about 55% by volume or more, and may also be about 65% by volume or less, about 64% by volume or less, about 63% by volume or less, about 62% by volume or less, about 61% by volume or less, about 60% by volume or less, about 59% by volume or less, about 58% by volume or less, about 57% by volume or less, about 56% by volume or less, or about 55% by volume or less. When the porosity of the porous polymer substrate satisfies the above range, since a sufficient volume of pores exists in the porous polymer substrate, lithium ions can smoothly move through the pores, and accordingly, the mechanical strength and compression resistance of the separator for an electrochemical device can be maintained at appropriate values, while also maintaining low resistance. Furthermore, due to the high porosity of the porous polymer substrate, the output of the electrochemical device including the separator for an electrochemical device can also be high.

[0050]

[0051] The porous polymer substrate includes a polymer having a melt index of about 0.0001 g / 10 min or more and 0.01 g / 10 min or less. For example, the polymer may have a melt index of about 0.0001 g / 10 min or more, about 0.0005 g / 10 min or more, about 0.001 g / 10 min or more, or about 0.005 g / 10 min or more, and may also have a melt index of about 0.01 g / 10 min or less, about 0.005 g / 10 min or less, about 0.001 g / 10 min or less, or about 0.0005 g / 10 min or less. When the melt index of the polymer satisfies the above range, the weight average molecular weight and density of the polymer may be high, and accordingly, the porous polymer substrate including the polymer may have excellent mechanical strength such as compression resistance.

[0052]

[0053] The separator for an electrochemical device of the present invention comprises a porous polymer substrate manufactured from a polymer having a low melt index, high density, and excellent mechanical strength. Therefore, even when pressure is applied during the lamination process, the problem of pore closure within the substrate can be minimized, and the resistance increase rate of the separator can also be low. In addition, as described above, the porous polymer substrate of the present invention has excellent mechanical strength, such as compression resistance, so the problem of pore closure within the substrate during operation of the electrochemical device can also be minimized, and an electrochemical device including the separator for an electrochemical device has the advantage of high long-term operation stability. In addition, the high compression resistance can also lead to a high breakdown voltage of the separator. For example, attempts have been made to improve the compression resistance of a porous polymer substrate by manufacturing a polymer having a low melt index in the past. However, the low processability of the polymer has made it difficult to maintain a high porosity of the substrate. However, in the case of the present invention, the task of manufacturing a substrate having a porosity of approximately 50 to 65 vol% was achieved through the manufacturing method of a porous polymer substrate described below, while using a polymer with a low melting index. Therefore, the present invention achieves both the effect of improving the compression resistance of the substrate, which was previously a trade-off, and the effect of reducing the resistance of the separator due to the high porosity.

[0054]

[0055] The porosity of the coating layer is about 40% by volume or more and 70% by volume or less. For example, the porosity of the coating layer may be about 40% by volume or more, about 45% by volume or more, about 50% by volume or more, about 55% by volume or more, or about 60% by volume or more, and may also be about 70% by volume or less, about 65% by volume or less, about 60% by volume or less, about 55% by volume or less, or about 50% by volume or less. When the porosity of the coating layer satisfies the above range, since a sufficient volume of pores exists in the coating layer, lithium ions can smoothly move through the pores, and accordingly, the resistance of the separator for an electrochemical device can be low while maintaining appropriate mechanical strength. Furthermore, the output of an electrochemical device including the separator for an electrochemical device can also be high.

[0056]

[0057] In summary, the electrochemical device separator of the present invention can exhibit low resistance and high output due to the high porosity of both the porous polymer substrate and the coating layer. Furthermore, the electrochemical device separator can exhibit excellent stability due to its high mechanical strength, such as compression resistance, due to the porous polymer substrate comprising a high melting index polymer.

[0058]

[0059] According to one embodiment of the present invention, the crystallinity of the polymer in the porous polymer substrate may be about 60% or more and 90% or less. For example, the crystallinity of the polymer may be about 60% or more, about 65% or more, about 70% or more, about 75% or more, or about 80% or more, and may also be about 90% or less, about 85% or less, about 80% or less, or about 75% or less. When the crystallinity of the polymer satisfies the above range, the durability of the porous polymer substrate is excellent, so that the problem of pores in the substrate being closed due to the lamination process or the expansion of the electrode can be minimized, and thus the stability of the separator can be excellent when the electrochemical device is operated, and stable performance can be maintained even during long-term operation.

[0060]

[0061] According to one embodiment of the present invention, the polymer may have a weight average molecular weight of about 1,500,000 g / mol or more and 2,500,000 g / mol or less. For example, the polymer may have a weight average molecular weight of about 1,500,000 g / mol or more, 1,800,000 g / mol or more, or about 2,000,000 g / mol or more, and may also have a weight average molecular weight of about 2,500,000 g / mol or less, about 2,000,000 g / mol or less, or about 1,800,000 g / mol or less. When the weight average molecular weight of the polymer satisfies the above range, since the fluidity of the polymer is low, the melt index of the polymer may satisfy the above-described range. Therefore, since the porous polymer substrate including the polymer has excellent mechanical strength such as compression resistance, the stability of the separator for an electrochemical device including the porous polymer substrate can also be excellent.

[0062]

[0063] According to one embodiment of the present invention, the polymer may be at least one selected from polyethylene, polypropylene, polybutylene, polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimideamide, nylon, and polytetrafluoroethylene, and for example, the polymer may be polyethylene. Since the above-listed polymers are physically and chemically stable with respect to an organic solvent, such as an electrolyte, a porous polymer substrate including the same has the advantage of being suitable for use in a separator for an electrochemical device. For example, when the porous polymer substrate includes polyethylene, the stability of the separator for an electrochemical device may also be excellent due to the high chemical / electrochemical stability of the polyethylene. Furthermore, since the polyethylene has excellent ionic conductivity, a separator for an electrochemical device including the same may have low resistance.

[0064]

[0065] According to one embodiment of the present invention, the inorganic particles may be in a cubic shape. In the case of a conventional coating layer including amorphous inorganic particles, the porosity of the coating layer may be low because the inorganic particles in the coating layer are densely packed. In contrast, when the inorganic particles are in a cubic shape, a sufficient gap can be secured between the inorganic particles due to the three-dimensional structure unique to the cubic shape, and thus the porosity of the coating layer can satisfy the above range. In addition, when the shape of the inorganic particles is in a cubic shape, unlike when amorphous inorganic particles are used, it is easy to determine the physical properties of the particles, such as the volume or specific surface area, and thus there is an advantage in that it is easy to control the porosity of the coating layer by adjusting the volume or content of the inorganic particles.

[0066]

[0067] According to one embodiment of the present invention, the inorganic particles have an average particle diameter (D 50) may be about 200 nm or more and 1 μm or less. For example, the inorganic particles may have an average diameter of about 200 nm or more, about 300 nm or more, about 400 nm or more, or about 500 nm or more, and may also have a diameter of about 1 μm or less, about 900 nm or less, about 800 nm or less, about 700 nm or less, about 600 nm or less, or about 500 nm or less. When the average diameter of the inorganic particles satisfies the above range, a sufficient gap may exist between the inorganic particles packed in the coating layer, and thus the porosity of the coating layer may be high as in the above-described range. Furthermore, when the average diameter of the inorganic particles satisfies the above range, the dispersibility of the inorganic particles may be excellent in the coating layer slurry prepared for manufacturing the coating layer, and the thickness of the coating layer manufactured therefrom may also be thin.

[0068]

[0069] According to one embodiment of the present invention, the inorganic particles are boehmite (γ-AlO(OH)), alumina (Al2O3), and BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT, 0 <x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3)O3-PbTiO3(PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, 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 boehmite. The inorganic particles may be selected from the operating voltage range of the electrochemical device (e.g., Li / Li + It may be that no oxidation and / or reduction reaction occurs at a voltage range of 0 V to 5 V as a reference. For example, when the coating layer includes the boehmite as an inorganic particle, the heat shrinkage problem of the separator for electrochemical devices can be effectively improved due to the high heat resistance of the boehmite. In addition, due to the low density of the boehmite, there is an advantage in that the coating layer and the separator can be made lighter. Furthermore, when the coating layer includes the cubic boehmite as described above, the heat shrinkage problem of the separator can be effectively improved, and at the same time, the resistance of the separator can be lowered due to the high porosity of the coating layer.

[0070]

[0071] According to one embodiment of the present invention, the content of the inorganic particles may be about 90 parts by weight or more based on 100 parts by weight of the total weight of the coating layer. For example, the content of the inorganic particles may be about 90 parts by weight or more, about 91 parts by weight or more, about 92 parts by weight or more, about 93 parts by weight or more, or about 94 parts by weight or more based on 100 parts by weight of the total weight of 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, or about 95 parts by weight or less. When the content of the inorganic particles in the coating layer satisfies the above range, the inorganic particles having excellent heat resistance are sufficiently included in the coating layer, so that the heat shrinkage problem can be minimized in a separator for an electrochemical device in which the coating layer is provided on at least one surface of a porous polymer substrate.

[0072]

[0073] According to one embodiment of the present invention, the coating layer further includes a binder, and the content of the binder may be about 1 part by weight or more and 10 parts by weight or less based on 100 parts by weight of the total weight of the coating layer. For example, the content of the binder may be about 1 part by weight or more, about 2 parts by weight or more, about 3 parts by weight or more, about 4 parts by weight or more, or about 5 parts by weight or more based on 100 parts by weight of the total weight of 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 coating layer includes the binder in the above content range, the interstitial volume formed by connecting the inorganic particles to each other by the binder may effectively increase, and thus the porosity of the coating layer may 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 of time. Furthermore, the adhesive strength between the coating layer and the electrode can also be improved by the binder.

[0074]

[0075] According to one embodiment of the present invention, the binder is polyacrylic acid, polyacrylamide, 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 propionate), cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxymethylcellulose, acrylonitrile-styrene butadiene copolymer, polyimide, and styrene-butadiene rubber.

[0076]

[0077] According to one embodiment of the present invention, the thickness of the porous polymer substrate may be about 4 μm or more and 20 μm or less. For example, the thickness of the porous polymer substrate may be about 4 μm or more, about 6 μm or more, about 8 μm or more, about 10 μm or more, or about 12 μm or more, and may also be about 20 μm or less, about 18 μm or less, about 16 μm or less, about 14 μm or less, about 12 μm or less, about 10 μm or less, about 8 μm or less, about 6 μm or less, or about 5 μm or less. When the thickness of the porous polymer substrate satisfies the above range, the thickness of a separator for an electrochemical device including the porous polymer substrate is not excessively increased, so that the resistance of the separator may be low. In addition, since the thickness of the porous polymer substrate is not excessively thin, the mechanical strength of the separator may also be excellent. Furthermore, a separator for an electrochemical device including a porous polymer substrate satisfying the above thickness range can electrically insulate the positive and negative electrodes while minimizing the volume of the electrochemical device, thereby increasing the amount of active material included in the electrochemical device.

[0078]

[0079] According to one embodiment of the present invention, the thickness of the coating layer may be about 0.5 μm or more and 4 μm or less. For example, the thickness of the coating layer may be about 0.5 μm or more, about 1 μm or more, about 1.5 μm or more, about 2 μm or more, or about 2.5 μm or more, and may also be about 4 μm or less, about 3.5 μm or less, about 3 μm or less, about 2.5 μm or less, about 2 μm or less, about 1.5 μm or less, or about 1 μm or less. When the thickness of the coating layer satisfies the above range, the insulation and thermal stability of a separator for an electrochemical device including the same can be effectively improved, and at the same time, the overall thickness of the separator can also be reduced. Therefore, the amount of an active material included in an electrochemical device can be relatively increased, and thus the energy density of the electrochemical device can also be increased.

[0080]

[0081] According to one embodiment of the present invention, the thickness of the separator for an electrochemical device may be about 7 μm or more and 25 μm or less. For example, the thickness of the separator for an electrochemical device may be about 7 μm or more, about 9 μm or more, about 11 μm or more, about 13 μm or more, or about 15 μm or more, and may also be about 25 μm or less, about 23 μm or less, about 21 μm or less, about 19 μm or less, about 17 μm or less, about 15 μm or less, or about 13 μm or less. When the thickness of the separator for an electrochemical device satisfies the above range, the separator can electrically insulate the positive and negative electrodes, and at the same time, the volume of the separator for an electrochemical device can be minimized. Therefore, the amount of the active material included in the electrochemical device can relatively increase, and thus the energy density of the electrochemical device can also increase.

[0082]

[0083] 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, about 0.04 μm or more, about 0.05 μm or more, or about 0.1 μm or more, and may also be about 1 μm or less, about 0.5 μm or less, about 0.1 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 ionic conductivity of the entire manufactured membrane can be controlled.

[0084]

[0085] The porous polymer substrate may have a permeability of about 10 s / 100cc or more and 100 s / 100cc or less. For example, the 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, or about 70 s / 100cc or less. For example, the 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 within the above-described range, 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. The air permeability (s / 100cc) refers to the time (seconds) it takes for 100cc of air to pass through a porous polymer substrate or separator of a predetermined area under a constant pressure. The air permeability can be measured using a Gurley densometer according to ASTM D 726-58, ASTM D726-94 or JIS-P8117. For example, using a 4110N device from Gurley, air at a pressure of 0.304 kPa or a pressure of 1.215 kN / m 2 100 cc of air under the pressure of water occupies 1 square inch (or 6.54 cm 2 ) can be used to measure the time it takes for 100 cc of air to pass through a 1-square-inch sample under a constant pressure of 4.8 inches of water at room temperature. For example, using the Asahi Seiko EG01-55-1MR equipment, the time it takes for 100 cc of air to pass through a 1-square-inch sample can be measured.

[0086]

[0087] The present invention provides a method for manufacturing a separator for an electrochemical device.

[0088] A method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention may be a method for manufacturing the separator for an electrochemical device, and accordingly, any content overlapping with the description of the separator for an electrochemical device will be omitted.

[0089] Referring to FIG. 1, according to one embodiment of the present invention, the method for manufacturing a separator for an electrochemical device includes a step (S10) of extruding a polymer sheet composition including a polymer and a diluent, a step (S20) of forming and stretching the polymer sheet composition extruded in the step (S10) into a sheet shape, a step (S30) of extracting the diluent from the polymer sheet stretched in the step (S20) to manufacture a porous polymer substrate, a step (S40) of heat-setting the porous polymer substrate, and a step (S50) of forming a coating layer including inorganic particles on at least one surface of the porous polymer substrate, wherein the melting index of the polymer is about 0.0001 g / 10 min or more and 0.01 g / 10 min or less, and the content of the diluent is about 70 wt% or more and 90 wt% or less based on 100 parts by weight of the total polymer sheet composition.

[0090]

[0091] The method for manufacturing the above-described separator for an electrochemical device includes a method for manufacturing the porous polymer substrate using a polymer having a low melting index and excellent mechanical strength, thereby having the advantage of being able to manufacture a separator having excellent compression resistance and low resistance as described above.

[0092]

[0093] According to one embodiment of the present invention, the step (S10) may be a step of introducing a polymer and a diluent into an extruder, melt-mixing them, and extruding them to manufacture a composition for forming a polymer sheet in which the diluent is dispersed between the polymers. The step (S20) may be a step of stretching a polymer sheet formed by forming the polymer sheet composition extruded in the step (S10) into a sheet shape, wherein the diluent may be dispersed and present between the polymers in the polymer sheet. The diluent may be an aliphatic hydrocarbon solvent such as liquid paraffin, paraffin oil, mineral oil, or paraffin wax; a vegetable oil such as soybean oil, sunflower oil, rapeseed oil, palm oil, coconut oil, corn oil, grape seed oil, cottonseed oil, or the like; or a plasticizer such as dialkyl phthalate.

[0094]

[0095] In the method for manufacturing the separator for the electrochemical device, the content of the diluent is about 70 parts by weight or more and 90 parts by weight or less based on 100 parts by weight of the total polymer sheet composition. The total weight of the polymer sheet composition refers to the combined weight of the polymer and the diluent. For example, the content of the diluent may be about 70 parts by weight or more, about 75 parts by weight or more, or about 80 parts by weight or more, and may also be about 90 parts by weight or less, about 85 parts by weight or less, or about 80 parts by weight or less. When the content of the diluent satisfies the above range, a sufficient amount of a diluent such as paraffin oil may be included in the polymer sheet composition, and thus, the porous polymer substrate from which the diluent is removed through the step (S30) may have a high porosity. Therefore, in the present invention, even when using the polymer having a low melt index and thus poor processability, it is possible to manufacture a porous polymer substrate having a high porosity compared to conventional polymers, thereby lowering the resistance of the membrane. When the content of the diluent satisfies the above range, the porosity of the final porous polymer substrate can be maintained within an appropriate range, and thus the resistance of the membrane can also be maintained within an appropriate range and low. In addition, the durability of the porous polymer substrate can be maintained, so that the porous polymer substrate can be stably manufactured.

[0096]

[0097] According to one embodiment of the present invention, the step (S20) may be a step of stretching the polymer sheet in the MD direction and the TD direction, and the stretching ratio in the MD direction may be about 6 or more and 10 or less, and the stretching ratio in the TD direction may be about 8 or more and 20 or less. For example, the stretching ratio in the MD direction may be about 6 or more, about 7 or more, or about 8 or more, and further may be about 10 or less, about 9 or less, or about 8 or less. In addition, the stretching ratio in the TD direction may be about 8 or more, about 9 or more, about 10 or more, about 11 or more, or about 12 or more, and further may be about 20 or less, about 18 or less, about 16 or less, about 14 or less, or about 12 or less. In addition to the content of the diluent in the polymer sheet composition, when the elongation in the MD direction and the TD direction satisfies the above range, the porosity of the porous polymer substrate can be high within the above range despite using the polymer having a low melting index and poor processability.

[0098]

[0099] According to one embodiment of the present invention, the stretching temperature in the MD direction and the TD direction in the step (S20) may be about 100°C or more and 120°C or less. For example, the stretching temperature in the MD direction and the TD direction in the step (S20) may be about 100°C or more, about 105°C or more, or about 110°C or more, and may also be about 120°C or less, about 115°C or less, or about 110°C or less. When the stretching temperature range satisfies the above range, the polymer sheet can be effectively stretched to improve the porosity of the substrate, while preventing the substrate from being damaged by high temperatures. Therefore, it can be easy to manufacture a porous polymer substrate with excellent durability and porosity.

[0100]

[0101] The step (S30) above may be a step of manufacturing a porous polymer substrate by extracting the diluent from the polymer sheet stretched in the step (S20). For example, the step (S30) may include a step of extracting the diluent from the polymer sheet using a solvent and then drying the polymer sheet. Any solvent that is used to extract the diluent in the relevant technical field may be used regardless of its type. For example, the solvent may be methyl ethyl ketone, methylene chloride, hexane, etc., which have high extraction efficiency and fast drying. In addition, the extraction of the diluent may be performed using an immersion method, a solvent spray method, an ultrasonic method, etc., individually or in combination.

[0102]

[0103] The above step (S40) is a step of heat-setting the porous polymer substrate, and through the heat-setting process, residual stress within the polymer sheet that is to be shrunk after stretching can be removed, and the porous polymer substrate that has undergone the heat-setting process can have a low heat shrinkage rate when applied to a separator for an electrochemical device.

[0104]

[0105] According to one embodiment of the present invention, the heat setting temperature of the step (S40) may be about 129°C or more and 135°C or less. For example, the heat setting temperature of the step (S40) may be about 129°C or more, about 130°C or more, about 131°C or more, or about 132°C or more, and may also be about 135°C or less, about 134°C or less, or about 133°C or less. When the heat setting temperature satisfies the above range, only the residual stress can be effectively removed without thermal damage to the porous polymer substrate, thereby producing a porous polymer substrate having excellent heat resistance and high porosity. In summary, when the content of the diluent, the elongation in the MD and TD directions, and the heat setting temperature satisfies the above-described ranges, it is easy to control the porosity of the porous polymer substrate within the above-described range even when using the polymer having a low melt index and poor processability. As a result, a separator for an electrochemical device including the porous polymer substrate can have relatively low resistance and excellent compression resistance.

[0106]

[0107] The step (S50) above is a step of forming a coating layer containing inorganic particles on at least one surface of the porous polymer substrate, and the heat resistance of the separator can be improved by the coating layer. The step (S50) may be forming a coating layer on one or both surfaces of the porous polymer substrate using a composition for forming a coating layer containing inorganic particles. The method of forming the coating layer is not particularly limited to any one method, and a conventional method known in the art can be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, bar coating, or a mixture thereof can be used.

[0108]

[0109] According to one embodiment of the present invention, the composition for forming the coating layer may include inorganic particles having a cubic shape, and the average diameter (D) of the inorganic particles 50 ) may be 200 nm or more and 1 μm or less. When a coating layer is formed on at least one surface of a porous polymer substrate using a composition for forming a coating layer including the above-described inorganic particles, a separator in which a coating layer having a porosity in the above-described range is disposed on at least one surface of the substrate can be easily manufactured, and thus both the resistance and heat resistance of the separator can be improved.

[0110]

[0111] The present invention provides an electrochemical device.

[0112] According to one embodiment of the present invention, the electrochemical device includes 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. The electrochemical device may further include an electrolyte and a battery case and a cap assembly. In the electrochemical device according to one embodiment of the present invention, any description overlapping with the description of the separator for the electrochemical device will be omitted.

[0113]

[0114] The above electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept encompassing primary batteries and secondary batteries. The secondary battery can be charged and discharged, and refers to a lithium secondary battery, a nickel-cadmium battery, a nickel-hydrogen battery, etc. The lithium secondary battery uses lithium ions as an ion conductor, and examples thereof include, but are not limited to, a non-aqueous electrolyte secondary battery including a liquid electrolyte, an all-solid-state battery including a solid electrolyte, a lithium polymer battery including a gel polymer electrolyte, and a lithium metal battery using lithium metal as an anode.

[0115]

[0116] The above electrochemical device includes the electrochemical device separator of the present invention as described above, so that even if the electrode expands due to long-term operation of the electrochemical device, the electrochemical device can be stably operated due to the electrochemical device separator having excellent compression resistance. In addition, since lithium ions can smoothly move through the electrochemical device separator due to the high porosity of the electrochemical device separator, the electrochemical device has the advantage of excellent output. In addition, since the electrochemical device separator has excellent compression resistance and can maintain a high porosity even during long-term operation, lithium can smoothly move during charge and discharge of the electrochemical device, so that the electrochemical device has the advantage of maintaining a sufficient amount of capacity even after repeated charging and discharging.

[0117]

[0118] According to one embodiment of the present invention, the positive electrode may have a positive electrode current collector and a positive electrode active material layer including a positive electrode active material, a conductive material, and a binder resin on at least one surface of the positive electrode current collector. The positive electrode active material may be a layered compound such as lithium manganese 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; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; 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 to 0.3); chemical formula LiMn 1-x Mx A lithium manganese composite oxide represented by O2 (wherein, M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (wherein, M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of Li in the chemical formula is replaced by an alkaline earth metal ion; a disulfide compound; or a mixture of two or more of Fe2(MoO4)3.

[0119]

[0120] According to one embodiment of the present invention, the negative electrode may have a negative electrode current collector and a negative electrode active material layer including a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The negative electrode may include carbon such as lithium metal oxide, non-graphitizable carbon, and graphite carbon as the negative electrode 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, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물 중 선택된 1종 또는 2종 이상의 혼합물을 포함하는 것일 수 있다.

[0121]

[0122] According to one embodiment of the present invention, the conductive material may be, for example, one selected from the group consisting of graphite, carbon black, carbon fibers or metal fibers, metal powders, conductive whiskers, conductive metal oxides, activated carbon, and polyphenylene derivatives, or a mixture of two or more conductive materials thereof. More specifically, the conductive material 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, summer black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more conductive materials thereof.

[0123]

[0124] 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. can be used.

[0125]

[0126] According to one embodiment of the present invention, the binder resin may be a polymer commonly used in electrodes in the art. 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, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples thereof include, but are not limited to, cellulose acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose.

[0127]

[0128] According to one embodiment of the present invention, the positive electrode slurry for manufacturing the positive electrode active material layer may include a dispersant, and the dispersant may be a pyrrolidone-based compound. Specifically, it may be N-methylpyrrolidone (ADC-01, LG Chemical).

[0129]

[0130] According to one embodiment of the present invention, the electrochemical device may further include an electrolyte, and the electrolyte may be A + B - As a salt with the same structure, A + is Li + , Na + , K + It may include an ion composed of an alkali metal cation such as B or a combination thereof. In addition, B - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - The salt containing an anion such as or a combination thereof may be dissolved or dissociated in an organic solvent consisting of 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), ethyl methyl carbonate (EMC), gamma butyrolactone or a mixture thereof, but is not limited thereto.

[0131]

[0132] One embodiment of the present invention may provide a battery module including a battery including the electrochemical element as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Examples of the device include, but are not limited to, a power tool that is powered by an electric 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) and an electric scooter (E-scooter); an electric golf cart; and a power storage system.

[0133]

[0134] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not construed as being limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0135]

[0136] Examples and Comparative Examples

[0137] Manufacturing of separators for electrochemical devices

[0138] <Example 1>

[0139] A polymer sheet composition comprising polyethylene (weight average molecular weight 2,000,000 g / mol, melt index 0.001 g / 10 min) as a polymer and liquid paraffin as a diluent in a weight ratio of 20:80 was introduced into an extruder (Korea EM, φ32 twin-screw extruder L / D=56) and melt-extruded to obtain an extruded polymer sheet composition. Subsequently, the extruded polymer sheet composition was passed through a T-die, and then a sheet-shaped polymer sheet was manufactured using a cold casting device.

[0140] Next, the polymer sheet was stretched using a tender-type sequential stretching machine under the conditions of an MD stretch ratio of 8, a TD stretch ratio of 12, and a stretching temperature of 110°C. Subsequently, liquid paraffin was removed from the stretched polymer sheet using methylene chloride, thereby producing a porous polymer substrate having formed pores. A coating solution for heat fixation (thermal initiator: 10 wt% dicumyl peroxide, flame retardant: 15 wt% diphenyl(vinyl)phosphine oxide, solvent: ethanol) was applied to one surface of the polymer substrate, and heat fixation of the polymer sheet was performed at 133°C, thereby producing a final porous polymer substrate (thickness of about 10 μm, porosity of 55 vol%).

[0141] Boehmite powder in cubic shape with inorganic particles (particle diameter (D 50 ) 500 nm) were prepared. Polyacrylic acid (K-702, Lubrizol) was prepared as a binder, and sodium carboxymethyl cellulose (CMC-Na) (SG-L02, GL Chem) was prepared as a dispersant. The prepared inorganic particles, binder, and dispersant were added to water at a weight ratio of 95:3:2, and then the inorganic particles were crushed and dispersed to prepare a coating layer slurry.

[0142] The coating layer slurry was applied to both sides of the porous polymer substrate using a doctor blade by bar coating and dried with air at 50°C using a heat gun to form a coating layer on both sides of the porous polymer substrate. At this time, the porosity of the coating layers was 50% by volume, and the thickness of the coating layers was 2 μm. The thickness of the finally manufactured separator was 14 μm.

[0143] <Example 2>

[0144] In the above Example 1, a separator for an electrochemical device was manufactured in the same manner as in the above Example 1, except that a porous polymer substrate (thickness of about 10 μm, porosity of 55% by volume) was manufactured using a polyethylene resin (weight average molecular weight of 1,800,000 g / mol, melt index of 0.005 g / 10 min).

[0145] <Example 3>

[0146] In the above Example 1, a separator for an electrochemical device was manufactured in the same manner as in the above Example 1, except that a porous polymer substrate (thickness of about 10 μm, porosity of 60% by volume) was manufactured using the polyethylene resin (weight average molecular weight of 2,000,000 g / mol, melt index of 0.001 g / 10 min).

[0147] <Example 4>

[0148] In the above Example 1, a separator for an electrochemical device was manufactured in the same manner as in the above Example 1, except that the porosity of each coating layer was 60% by volume.

[0149] <Comparative Example 1>

[0150] In the above Example 1, a separator for an electrochemical device was manufactured in the same manner as in the above Example 1, except that a porous polymer substrate (thickness of about 10 μm, porosity of 55% by volume) was manufactured using a polyethylene resin (weight average molecular weight of 1,500,000 g / mol, melt index of 0.02 g / 10 min).

[0151] <Comparative Example 2>

[0152] After manufacturing a porous polymer substrate in the same manner as in Comparative Example 1 above, an amorphous alumina powder (particle diameter (D)) was prepared as inorganic particles. 50 ) 500 nm) were prepared. Polyacrylic acid (K-702, Lubrizol) was prepared as a binder, and sodium carboxymethyl cellulose (CMC-Na) (SG-L02, GL Chem) was prepared as a dispersant. The prepared inorganic particles, binder, and dispersant were added to water at a weight ratio of 95:3:2, and then the inorganic particles were crushed and dispersed to prepare a coating layer slurry.

[0153] The coating layer slurry was applied to both sides of the porous polymer substrate using a doctor blade by bar coating and dried with air at 50°C using a heat gun to form a coating layer on both sides of the porous polymer substrate. At this time, the porosity of the coating layers was 35% by volume, and the thickness of the coating layers was 2 μm. The thickness of the finally manufactured separator was 14 μm.

[0154] <Comparative Example 3>

[0155] In the above Example 1, a separator for an electrochemical device was manufactured in the same manner as in the above Example 1, except that a porous polymer substrate (thickness of about 10 μm, porosity of 40% by volume) was manufactured using a polyethylene resin (weight average molecular weight of 1,000,000 g / mol, melt index of 0.1 g / 10 min).

[0156] Comparative Example 4

[0157] In the above Example 1, a separator for an electrochemical device was manufactured in the same manner as in the above Example 1, except that the polyethylene and the liquid paraffin were fed into an extruder at a weight ratio of 40:60 to manufacture a porous polymer substrate when manufacturing the polymer sheet composition.

[0158]

[0159] Experimental example

[0160] (1) Measurement of individual resistance of the separator

[0161] Coin cells were manufactured by sandwiching the electrochemical device separators of the above examples and comparative examples between SUS. An electrolyte containing 1 M LiPF6 and a mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:2 was injected into the coin cells. In order to measure the resistance of the coin cells, the resistance was measured through electrochemical impedance spectroscopy using VMP3 from BioLogic Science Instrument at 25°C under the conditions of an amplitude of 10 mV and a scan range of 0.1 Hz to 1 MHz, and the results are shown in Tables 1 and 2 below.

[0162]

[0163] ClassificationExample 1Example 2Example 3Example 4Porous polymer substrate Melt index (g / 10 min) 0.001 0.005 0.001 0.001 Polymer crystallinity (%) 8 3 8 0 7 5 8 3 Weight average molecular weight (g / mol) 2 million 1.8 million 2 million 2 million Porosity (volume %) 5 5 5 6 0 5 5 Thickness (μm) 1 0 1 0 1 0 Coating layer Inorganic particle Cubic boehmite Cubic boehmite Cubic boehmite Cubic boehmite Inorganic particle size (nm) 5 0 0 5 0 0 5 0 Porosity (volume %) 5 0 5 0 5 0 6 0 Cross-sectional thickness (μm) 2 2 2 2 Separator thickness (μm) 1 4 1 4 1 4 1 4 Electrical resistance (Ω) 0.4 0.4 0.3 0.3

[0164]

[0165] ClassificationComparative Example 1Comparative Example 2Comparative Example 3Comparative Example 4Porous polymer substrate Melt index (g / 10 min) 0.02 0.02 0.1 0.00 1Polymer crystallinity (%) 70 70 55 80Weight average molecular weight (g / mol) 1.5 million 1.5 million 1 million 2 millionPorosity (volume %) 55 55 40 40Thickness (μm) 10 10 10 10 Coating layerInorganic particleCubic boehmiteAmorphous aluminaCubic boehmiteCubic boehmiteInorganic particle size (nm) 50 0 50 0 50 0 500Porosity (volume %) 50 3 55 0 50Cross-section thickness (μm) 2 2 22Separator thickness (μm) 1 4 1 4 1 4 1 4 Electrical resistance (Ω) 0.5 0.8 0.7 0.8

[0166]

[0167] As shown in Tables 1 and 2 above, the electrochemical device separator of the example has high porosity of both the porous polymer substrate and the coating layer, and thus it can be confirmed that the resistance of the separator is lower than that of the comparative example. Specifically, unlike the separator of the example whose coating layer includes cubic boehmite, the separator of Comparative Example 2 has a low porosity of the coating layer because the coating layer includes amorphous alumina, and thus it can be confirmed that the resistance of the separator is high despite the high porosity of the porous polymer substrate. In addition, the separator of Comparative Example 3 has a low porosity of the porous polymer substrate at 40% by volume despite the high porosity of the coating layer, and thus it can be confirmed that the resistance of the separator is as high as that of Comparative Example 2. In addition, in Comparative Example 4, which used a polymer with a low melting index, but added 60 wt% of the diluent content during the production of the polymer sheet composition, unlike the method for producing a separator for an electrochemical device of the present invention, it was confirmed that the porosity of the substrate was low at 40 vol%, resulting in high resistance of the separator.

[0168]

[0169] (2) Evaluation of the compression characteristics of the membrane

[0170] Measurement of thickness and resistance change after lamination

[0171] For the electrochemical device separators of the above examples and comparative examples, Haze PET / separator / Haze PET were laminated in that order, and lamination was performed using a hot press device under the conditions of 60°C / 6.5MPa / 1sec. The thickness of the separator after lamination was measured, and the resistance was measured in the same manner as the resistance measurement method for the individual separator, and the thickness reduction rate and resistance increase rate before and after lamination were evaluated, and are shown in Table 3.

[0172]

[0173] Classification Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Thickness reduction rate (%) 35551015205 Resistance increase rate (%) 57771015255

[0174]

[0175] As shown in Table 3 above, the electrochemical device separator of the above example has excellent mechanical strength since the porous polymer substrate includes a polymer with a low melting index, so it can be confirmed that there is little deformation in shape, such as thickness, even when pressure is applied to the separator due to lamination. Accordingly, the electrochemical device separator of the above example can have pores that remain intact even after lamination, and the porous polymer substrate maintains a high porosity, so it can be confirmed that the resistance increase rate is significantly lower than that of the comparative example. In contrast, the electrochemical device separator of the comparative example has a porous polymer substrate including a polymer with a high melting index, so it can be confirmed that the thickness is significantly reduced by lamination, and thus the pores are closed, so the resistance is significantly increased.

[0176]

[0177] Manufacturing of electrochemical devices

[0178] Electrochemical devices were manufactured using the electrochemical device separators of the above examples and comparative examples.

[0179] 1) Manufacturing of the anode

[0180] Cathode active material (LiNi) 0.8 Mn 0.1 Co 0.1 O2), a conductive agent (carbon black), a dispersant (N-methylpyrrolidone, ADC-01, LG Chemical), and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a cathode active material layer with a concentration of 50 wt% of the remaining components excluding water. Next, the slurry was applied to the surface of an aluminum thin film (thickness 10 μm) and dried to manufacture a cathode having a cathode active material layer (thickness 120 μm).

[0181] 2) Manufacturing of cathode

[0182] Graphite (natural graphite and artificial graphite blend), conductive agent (carbon black), dispersant (polyvinylpyrrolidone, Junsei, Japan), and binder resin (PVDF-HFP and PVDF blend) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for an anode active material layer with a concentration of 50 wt% of the remaining components excluding water. Next, the slurry was applied to the surface of a copper thin film (thickness 10 μm) and dried to manufacture an anode having an anode active material layer (thickness 120 μm).

[0183] 3) Lamination process

[0184] The separators of the examples and comparative examples were interposed between the manufactured cathodes and anodes, and a lamination process was performed to obtain an electrode assembly. The lamination process was performed using a hot press at 60°C and 6.5 MPa for 1 second.

[0185] 4) Electrolyte injection process

[0186] After the electrode assembly that went through the above lamination process was loaded into a battery case, an EC / DMC electrolyte containing 1 M concentration of LiPF6 was injected to manufacture an electrochemical device.

[0187]

[0188] (3) Initial resistance evaluation of electrochemical devices

[0189] The electrochemical devices of the above examples and comparative examples were left for 3 hours each, and 0.33 C charge / 0.33 C discharge was repeated 5 times using a charger / discharger from PNE solution in the voltage range of 3.0 V to 4.2 V. Then, the resistance was measured through electrochemical impedance spectroscopy results using VMP3 from BioLogic Science Instrument at 25 °C under the conditions of Amplitude 10 mV and Scan range 0.1 Hz to 1 MHz. Accordingly, the initial resistance of the electrochemical devices was evaluated.

[0190]

[0191] (4) High-rate evaluation of electrochemical devices

[0192] For the electrochemical devices of the above examples and comparative examples, the following cycles were sequentially performed in the voltage range from 3.0 V to 4.2 V using a charger / discharger from PNE solution: 0.2 C charge / 0.2 C discharge 5 times, 0.33 C charge / 0.33 C discharge 5 times, 0.5 C charge / 0.5 C discharge 5 times, 1 C charge / 1 C discharge 5 times, 2 C charge / 2 C discharge 5 times, and 3 C charge / 3 C discharge 5 times, and the capacity retention rate for each C rate was confirmed. The capacity retention rate was calculated as the ratio of the 3 C discharge capacity to the 0.33 C discharge capacity. Accordingly, the capacity retention rate was evaluated.

[0193]

[0194] The initial resistance and capacity retention rates are shown in Table 4 below.

[0195]

[0196] Classification Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Initial Resistance (Ω) 1.2 1.2 1.11 11.3 1.7 1.6 1.6 Capacity Retention Rate (%) 70 70 73 73 6 54 55 0 70

[0197]

[0198] As shown in Table 4 above, it can be confirmed that the electrochemical device separator of the embodiment has a low initial resistance due to the high porosity of the porous polymer substrate and the coating layer. In contrast, the electrochemical device of the comparative example including the electrochemical device separator with a low porosity has a high initial resistance due to a bottleneck phenomenon occurring in the process of lithium ions passing through the separator. In addition, since the electrochemical device of the embodiment includes a porous polymer substrate with excellent compression resistance, it can be confirmed that the electrochemical device separator can maintain a high porosity even after charge and discharge, and thus, the capacity retention rate is high.

[0199]

[0200] Although the present disclosure has been described above with reference to embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that various modifications and changes to the various embodiments of the present disclosure may be made 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 defined by the claims.

Claims

1. Porous polymer substrate; and A coating layer is disposed on at least one surface of the porous polymer substrate and includes inorganic particles, The porosity of the above porous polymer substrate is 50% by volume or more and 65% by volume or less, The above porous polymer substrate includes a polymer having a melting index of 0.0001 g / 10 min or more and 0.01 g / 10 min or less, A separator for an electrochemical device, wherein the porosity of the coating layer is 40% by volume or more and 70% by volume or less.

2. In paragraph 1, A separator for an electrochemical device, wherein the crystallinity of the polymer in the porous polymer substrate is 60% or more and 90% or less.

3. In paragraph 1, A separator for an electrochemical device, wherein in the porous polymer substrate, the polymer has a weight average molecular weight of 1,500,000 g / mol or more and 2,500,000 g / mol or less.

4. In paragraph 1, A separator for an electrochemical device, wherein in the porous polymer substrate, the polymer is at least one selected from polyethylene, polypropylene, polybutylene, polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimideamide, nylon, and polytetrafluoroethylene.

5. In paragraph 1, A separator for an electrochemical device, wherein the inorganic particles included in the coating layer are in a cubic shape.

6. In paragraph 1, The inorganic particles included in the coating layer have an average particle diameter (D 50 ) A separator for an electrochemical device having a thickness of 200 nm or more and 1 μm or less.

7. In paragraph 1, The inorganic particles included in the coating layer are boehmite (γ-AlO(OH)), alumina (Al2O3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT, 0 <x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3(PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, 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).

8. In paragraph 1, A separator for an electrochemical device, wherein the content of the inorganic particles is 90 parts by weight or more based on 100 parts by weight of the total weight of the coating layer.

9. In paragraph 1, The above coating layer further includes a binder, A separator for an electrochemical device, wherein the content of the binder is 1 part by weight or more and 10 parts by weight or less based on 100 parts by weight of the total weight of the coating layer.

10. In paragraph 1, A separator for an electrochemical device, wherein the thickness of the porous polymer substrate is 4 μm or more and 20 μm or less.

11. In paragraph 1, A separator for an electrochemical device, wherein the thickness of the coating layer is 0.5 μm or more and 4 μm or less.

12. Containing a positive electrode; a negative electrode; and a separator for an electrochemical device according to paragraph 1, An electrochemical device wherein the separator for the electrochemical device is interposed between the anode and the cathode.

13. A step of extruding a polymer sheet composition comprising a polymer and a diluent; A step of forming and stretching an extruded polymer sheet composition into a sheet shape; A step of manufacturing a porous polymer substrate by extracting the diluent from the stretched polymer sheet; A step of heat-fixing the above porous polymer substrate; and A step of forming a coating layer including inorganic particles on at least one surface of the porous polymer substrate; In the above porous polymer substrate, the melting index of the polymer is 0.0001 g / 10 min or more and 0.01 g / 10 min or less, A method for manufacturing a separator for an electrochemical device, wherein the content of the diluent is 70 parts by weight or more and 90 parts by weight or less based on 100 parts by weight of the total polymer sheet composition.

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