Separator for electrochemical device and electrochemical device comprising same

Abstract

The present invention relates to a separator for an electrochemical device, wherein an aerogel layer containing cellulose nanofibers is provided on a coating layer containing inorganic particles. The separator for an electrochemical device includes a cellulose nanofiber aerogel having high porosity and excellent mechanical strength compared to conventional coating layers made of inorganic materials, and has high mechanical strength, such as high puncture strength, and low resistance.

Description

Separator for electrochemical devices and electrochemical devices containing the same

[0001] This invention claims the benefit of Korean Patent Application No. 10-2024-0122182, filed with the Korean Intellectual Property Office on September 9, 2024, and Korean Patent Application No. 10-2025-0110017, filed with the Korean Intellectual Property Office on August 8, 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] Among the components of these electrochemical devices, the 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.

[0005] 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.

[0006] 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.

[0007] 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 smoothly pass through the separator due to the relatively low porosity of the coating layer, which may increase the resistance of the separator. To solve this problem, a method of coating a thin coating layer on the polymer substrate and simultaneously placing an aerogel layer with a high porosity on the coating layer is being attempted. In this case, there is an advantage in that the thickness of the coating layer is reduced, thereby lowering the resistance of the separator. However, the most commonly used silica aerogel has the problem of being environmentally undesirable due to the toxicity generated during the synthesis of silica.

[0008] Accordingly, there is a need to develop a novel separator for electrochemical devices that includes an aerogel layer that is non-toxic and environmentally friendly while being disposed on the coating layer to lower the resistance of the separator.

[0009] The present invention aims to provide a separator for an electrochemical device having low resistance and excellent mechanical strength, by including an aerogel layer having a high porosity, and wherein the aerogel layer includes cellulose nanofiber (CNF) aerogel.

[0010] In order to solve the above-described problem, the present invention provides a separator for an electrochemical device, comprising a porous polymer substrate, a coating layer disposed on at least one surface of the porous polymer substrate and including inorganic particles, and an aerogel layer disposed on the coating layer and including cellulose nanofiber aerogel, wherein the average pore diameter of the aerogel layer is 50 nm or more and 200 nm or less.

[0011] The porosity of the above aerogel layer may be 80% by volume or more and 99% by volume or less.

[0012] The content of the cellulose nanofiber aerogel may be 90 parts by weight or more and 99 parts by weight or less based on 100 parts by weight of the total weight of the aerogel layer.

[0013] The thickness of the above aerogel layer may be 0.5 μm or more and 2 μm or less.

[0014] The thickness of the above coating layer may be 0.3 μm or more and 1.2 μm or less.

[0015] The porosity of the above coating layer may be 40% by volume or more and 70% by volume or less.

[0016] The average diameter of the above cellulose nanofibers may be 5 nm or more and 50 nm or less.

[0017] The aspect ratio of the above cellulose nanofibers may be 1:50 or more and 1:200 or less.

[0018] The content of the inorganic particles may be 80 parts by weight or more and 95 parts by weight or less based on 100 parts by weight of the total weight of the coating layer.

[0019] The above inorganic particles have an average diameter (D 50 ) may be 200 nm or more and 800 nm or less.

[0020] 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.

[0021] The separator for an electrochemical device according to the present invention has a cellulose nanofiber aerogel layer having an average pore diameter of 50 to 200 nm disposed on a coating layer, so that the separator has low resistance and excellent mechanical strength, and further has the advantage of being environmentally friendly by using cellulose nanofibers instead of toxic silica.

[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 in which a porous coating layer containing an inorganic substance and a binder is formed on at least one surface of a porous polymer substrate such as a polyolefin substrate or a non-woven fabric, but in this specification, it may refer to a separator in which a coating layer containing an inorganic substance is formed on at least one surface of the porous polymer substrate, and an aerogel layer containing cellulose nanofiber aerogel is formed on the coating layer. In addition, the separator has a porous characteristic including a large number of pores, and serves 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.

[0029] In this specification, the characteristic of having pores means that the object includes a plurality of pores or pores, and the pores or pores are interconnected with each other, thereby allowing gaseous and / or liquid fluids 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, "average diameter (D 50 )" means the diameter at the 50% point of the cumulative distribution of the number of particles according to the diameter. The diameter can be measured using a laser diffraction method. Specifically, 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 the cumulative distribution of the number of particles according to the diameter in the measuring device becomes 50%, the diameter (D) of the particle 50 ) can be measured.

[0032] In this specification, “average pore diameter” means the average value of the pore diameter in a material having multiple pores, such as a porous polymer substrate, a coating layer, or an aerogel layer. The average pore diameter can be calculated using image processing software (such as Sigma Scan Pro 5.0) by utilizing a scanning electron microscopy (SEM) image. Alternatively, the capillary flow porosimetry method can be used to obtain a permeation curve of a 1 / 2 dry sample and a permeation curve of a wet sample, and the size corresponding to the intersection of these two curves can be used as the average pore diameter.

[0033] In this specification, “aspect ratio” refers to the ratio of the diameter and length of a fiber, such as a cellulose nanofiber, in a fibrous material whose diameter and length can be measured. Specifically, the diameter, length, and aspect ratio of the fiber can be measured using a scanning electron microscope, and the aspect ratio refers to the average of the aspect ratios measured for any 20 fibers measured using the scanning electron microscope.

[0034] In this specification, the "average diameter" and "average length" of cellulose nanofibers can be obtained by conventional measuring methods in the relevant technical field. For example, the average diameter of the cellulose nanofibers can be calculated by taking the longest straight-line distance connecting any two points on the cross-section of the fiber as the diameter, and taking about 10 fibers as a sample through a scanning electron microscope (SEM), and taking the arithmetic mean of the diameters of these fibers. The average length of the cellulose nanofibers can be calculated by taking about 10 fibers as a sample and taking the arithmetic mean of the fiber lengths.

[0035]

[0036] Hereinafter, the present invention will be described in more detail.

[0037]

[0038] The present invention provides a separator for an electrochemical device.

[0039] According to one embodiment of the present invention, the separator for an electrochemical device is characterized by including a porous polymer substrate, a coating layer disposed on at least one surface of the porous polymer substrate and including inorganic particles, and an aerogel layer disposed on the coating layer and including cellulose nanofiber aerogel, wherein the average pore diameter of the aerogel layer is 50 nm or more and 200 nm or less. The separator for an electrochemical device may be one in which the coating layer is disposed on one surface or both surfaces of the porous polymer substrate, and when the coating layer is disposed on both surfaces of the porous polymer substrate, the aerogel layer may be disposed on at least one or more coating layers.

[0040]

[0041] A coating layer having a relatively low porosity compared to a porous polymer substrate can impede the movement of lithium ions through the separator, thereby increasing the resistance of the separator for an electrochemical device including the coating layer. Therefore, in order to lower the resistance of the separator, it is necessary to reduce the thickness of the coating layer; however, simply using a thin coating layer makes it difficult to improve the thermal shrinkage problem of the separator. Therefore, the separator for an electrochemical device of the present invention has the advantage of having a low thermal shrinkage rate of the separator and a low resistance rate of the separator by using a relatively thin coating layer and disposing an aerogel layer having a high porosity on the coating layer. Specifically, since the cellulose nanofibers have excellent mechanical strength and heat resistance, the separator for an electrochemical device in which the aerogel layer is disposed on the coating layer can have excellent mechanical strength, such as puncture strength, and can also have low thermal shrinkage rate. Furthermore, since the aerogel layer including the cellulose nanofiber aerogel has a high porosity, the separator for an electrochemical device of the present invention can also have a lower resistance rate than a conventional separator in which only a coating layer is disposed. In addition, the cellulose nanofiber aerogel of the electrochemical device separator is non-toxic and environmentally friendly because it is manufactured from cellulose nanofibers manufactured from polymers extracted from tree resources.

[0042]

[0043] The average pore diameter of the aerogel layer may be 50 nm or more and 200 nm or less. Specifically, the average pore diameter of the aerogel layer may be 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, or 100 nm or more, and may also be 200 nm or less, 180 nm or less, 160 nm or less, 140 nm or less, 120 nm or less, or 100 nm or less. When the average pore diameter of the aerogel layer satisfies the above range, since the pore size of the aerogel layer is large, the electrolyte and lithium ions can easily move through the pores. Therefore, the resistance of the separator for an electrochemical device of the present invention including the aerogel layer may be low, and the electrolyte impregnation property may also be excellent. Meanwhile, when the average pore diameter of the aerogel layer exceeds the above range, the mechanical strength of the aerogel layer may deteriorate due to the excessively large pore diameter, and thus the mechanical strength, such as puncture strength, of the separator for an electrochemical device including the aerogel layer may also deteriorate. In addition, when the average pore diameter of the aerogel layer is less than the above range, lithium ions may not be able to smoothly pass through the aerogel layer due to the excessively small pore diameter, and the separator for an electrochemical device including the aerogel layer may have high resistance.

[0044]

[0045] According to one embodiment of the present invention, the aerogel layer may not include inorganic particles. Preferably, the aerogel layer may include cellulose nanofibers, a binder, and a dispersant. When inorganic particles are added to the aerogel layer slurry containing the cellulose nanofibers, the dispersibility of the aerogel layer slurry may be reduced due to the low compatibility of the inorganic particles. Accordingly, the manufactured aerogel layer may have an unstable aerogel network formed due to the irregular change in the electrolyte ion path caused by the inorganic particles, resulting in an uneven microstructure of the aerogel layer. Accordingly, even if the porosity and pore diameter of the aerogel layer are the same as those of the aerogel layer of the present invention, the resistance of the separator may be high. In addition, due to the unstable aerogel network, the heat resistance of the separator may be poor, and the puncture strength of the separator may be poor. On the other hand, the aerogel layer of the present invention including cellulose nanofibers, a binder, and a dispersant has a stable aerogel network, and thus has low resistance and excellent heat resistance and puncture strength.

[0046]

[0047] According to one embodiment of the present invention, the porosity of the aerogel layer may be 80% by volume or more and 99% by volume or less. Specifically, the porosity of the aerogel layer may be 80% by volume or more, 82% by volume or more, 84% by volume or more, 86% by volume or more, 88% by volume or more, or 90% by volume or more, and may also be 99% by volume or less, 97% by volume or less, 95% by volume or less, 93% by volume or less, 91% by volume or less, or 89% by volume or less. When the porosity of the aerogel layer satisfies the above range, pores having an average pore diameter satisfying the above-described range are sufficiently present in the aerogel layer, so that lithium ions can smoothly move through the aerogel layer. Therefore, a separator for an electrochemical device including the aerogel layer may have low resistance.

[0048]

[0049] According to one embodiment of the present invention, the content of the cellulose nanofiber aerogel may be 90 parts by weight or more and 99 parts by weight or less based on 100 parts by weight of the total weight of the aerogel layer. Specifically, the content of the cellulose nanofiber aerogel may be 90 parts by weight or more, 91 parts by weight or more, 92 parts by weight or more, 93 parts by weight or more, or 94 parts by weight or more, and may also be 99 parts by weight or less, 98 parts by weight or less, 97 parts by weight or less, or 96 parts by weight or less based on 100 parts by weight of the total weight of the aerogel layer. When the content of the cellulose nanofiber aerogel in the aerogel layer satisfies the above range, the mechanical strength of the aerogel layer containing sufficiently the cellulose nanofiber aerogel having high mechanical strength may also be excellent. Furthermore, the heat resistance of the separator may also be excellent due to the aerogel layer. Therefore, the separator for an electrochemical device having the above aerogel layer has the advantage of being excellent in both mechanical strength, such as puncture strength, and heat resistance.

[0050]

[0051] According to one embodiment of the present invention, the aerogel layer may further include a binder, and the content of the binder may be 0.5 parts by weight or more and 8 parts by weight or less based on 100 parts by weight of the total weight of the aerogel layer. Preferably, the aerogel layer may be composed of cellulose nanofibers, a binder, and a dispersant. Specifically, the content of the binder may be 0.5 parts by weight or more, 1.5 parts by weight or more, 2.5 parts by weight or more, 3.5 parts by weight or more, or 4.5 parts by weight or more based on 100 parts by weight of the total weight of the aerogel layer, and may also be 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, or 5 parts by weight or less. When the content of the binder in the aerogel layer satisfies the above range, the adhesion between the aerogel layer and the coating layer on the porous polymer substrate, and between the aerogel layer and the electrode can be improved, and accordingly, the problem of the aerogel layer being detached during long-term operation of the electrochemical device can be minimized.

[0052]

[0053] According to one embodiment of the present invention, the binder is selected from the group consisting of polyacrylic acid, 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, It may be at least one selected from the group consisting of cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene butadiene copolymer, polyimide, and styrene-butadiene rubber. When the aerogel layer includes the binder, the adhesive strength between the aerogel layer and the electrode can be improved, and thus the problem of the aerogel layer being detached during long-term operation of the electrochemical device can be minimized.

[0054]

[0055] According to one embodiment of the present invention, the thickness of the aerogel layer may be 0.5 μm or more and 2 μm or less. Specifically, the thickness of the aerogel layer may be 0.5 μm or more, 0.75 μm or more, 1 μm or more, 1.25 μm or more, or 1.5 μm or more, and may also be 2 μm or less, 1.75 μm or less, 1.5 μm or less, 1.25 μm or less, or 1 μm or less. When the thickness of the aerogel layer satisfies the above range, since lithium ions can easily pass through the aerogel layer having a thin thickness, the resistance of the separator may be low. In addition, since the overall thickness of the separator for an electrochemical device may also be thin, an electrochemical device including the separator for an electrochemical device may have a high energy density. Meanwhile, compared to cases where the thickness of the aerogel layer is excessively thin, the separator for an electrochemical device in which the aerogel layer is disposed can have excellent mechanical strength while also minimizing the problem of thermal shrinkage.

[0056]

[0057] According to one embodiment of the present invention, the thickness of the coating layer may be 0.3 μm or more and 1.2 μm or less. Specifically, the thickness of the coating layer may be 0.3 μm or more, 0.5 μm or more, or 0.7 μm or more, and further may be 1.2 μm or less, 1 μm or less, 0.8 μm or less, or 0.6 μm or less. When the thickness of the coating layer satisfies the above range, the resistance of the separator may be low due to the low thickness of the coating layer. In addition, since an aerogel layer having high mechanical strength and high porosity can be relatively sufficiently included within a limited separator size, a separator for an electrochemical device including the same may have excellent mechanical strength, such as puncture strength, and may have low resistance of the separator.

[0058]

[0059] According to one embodiment of the present invention, the porosity of the coating layer may be 40% by volume or more and 70% by volume or less. Specifically, the porosity of the coating layer may be 40% by volume or more, 50% by volume or more, or 60% by volume or more, and may also be 70% by volume or less, 60% by volume or less, or 50% by volume or less. When the porosity of the coating layer satisfies the above range, since sufficient pores may exist in the coating layer, lithium ions may smoothly move through the pores, and thus the resistance of the separator for an electrochemical device may be low. In addition, the separator for an electrochemical device of the present invention may have excellent mechanical strength, such as puncture strength, compared to a case where the porosity of the coating layer is excessively high and there are excessively many pores in the coating layer.

[0060]

[0061] According to one embodiment of the present invention, the average pore diameter of the coating layer may be 40 nm or more and 100 nm or less. Specifically, the average pore diameter of the coating layer may be 40 nm or more, 50 nm or more, or 60 nm or more, and may also be 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, or 60 nm or less. When the average pore diameter of the coating layer satisfies the above range, lithium ions can smoothly move through the pores of the coating layer, so that the resistance of the separator for an electrochemical device including the same can be low. In addition, compared to when the average pore diameter of the coating layer is excessively large, the mechanical strength of the coating layer is also excellent, so that the puncture strength of the separator for an electrochemical device can also be excellent.

[0062]

[0063] According to one embodiment of the present invention, the average diameter of the cellulose nanofibers may be 5 nm or more and 50 nm or less. Specifically, the average diameter of the cellulose nanofibers may be 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, or 25 nm or more, and further may be 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, or 30 nm or less. When the average diameter of the cellulose nanofibers satisfies the above range, the surface area of ​​the cellulose nanofibers is high, so that the adhesive strength of the aerogel layer may be improved. Accordingly, the separator for an electrochemical device having the aerogel layer may have excellent adhesive strength to the electrode. In addition, since the volume of the cellulose nanofibers satisfying the above average diameter range is not excessively large, the thickness of the aerogel layer including the cellulose nanofibers may also be thin. Accordingly, since the thickness of the separator for an electrochemical device equipped with the aerogel layer can also be thin, the energy density of the electrochemical device including the separator for an electrochemical device can also be high.

[0064]

[0065] According to one embodiment of the present invention, the average length of the cellulose nanofibers may be 1 μm or more and 10 μm or less. Specifically, the average length of the cellulose nanofibers may be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more, and may also be 10 μm or less, 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, 5 μm or less, or 4 μm or less. When the average length of the cellulose nanofibers satisfies the above range, the surface area of ​​the cellulose nanofibers may be high, and thus the adhesive strength of the aerogel layer may also be improved. Therefore, the separator for an electrochemical device having the aerogel layer may have excellent adhesive strength to an electrode.

[0066]

[0067] According to one embodiment of the present invention, the aspect ratio of the cellulose nanofibers may be 1:50 or more and 1:200 or less. Specifically, the aspect ratio of the cellulose nanofibers may be 1:50 or more, 1:60 or more, 1:70 or more, 1:80 or more, 1:90 or more, or 1:100 or more, and may also be 1:200 or less, 1:180 or less, 1:160 or less, 1:140 or less, 1:120 or less, or 1:100 or less. When the aspect ratio of the cellulose nanofibers satisfies the above range, the adhesiveness of the cellulose nanofibers may be excellent, and the mechanical strength may also be excellent. If the aspect ratio of the cellulose nanofibers is excessively small, the adhesiveness of the aerogel layer may deteriorate, and conversely, if the aspect ratio is excessively large, the breaking strength of the fibers may deteriorate, weakening the mechanical strength of the aerogel layer. In addition, if the aspect ratio of the cellulose nanofibers satisfies the above range, the problem of excessive aggregation of the cellulose nanofibers can be prevented, and further, the problem of reduced air permeability due to pore blocking of the aerogel layer can be prevented.

[0068]

[0069] According to one embodiment of the present invention, the content of the inorganic particles may be 80 parts by weight or more and 95 parts by weight or less based on 100 parts by weight of the total weight of the coating layer. Specifically, the content of the inorganic particles may be 80 parts by weight or more, 85 parts by weight or more, or 90 parts by weight or more, and may also be 95 parts by weight or less, 90 parts by weight or less, or 85 parts by weight or less based on 100 parts by weight of the total weight of the coating layer. When the content of the inorganic particles in the coating layer satisfies the above range, the inorganic particles are sufficiently included in the coating layer, so that the heat shrinkage problem of the porous polymer substrate can be effectively reduced.

[0070]

[0071] According to one embodiment of the present invention, the inorganic particles have an average diameter (D 50 ) may be 200 nm or more and 800 nm or less. Specifically, the inorganic particles may have an average diameter of 200 nm or more, 300 nm or more, or 400 nm or more, and may also have a diameter of 800 nm or less, 700 nm or less, 600 nm or less, or 500 nm or less. When the diameter of the inorganic particles satisfies the above range, a sufficient gap may exist between the inorganic particles packed in the coating layer, and thus the porosity and air permeability of the coating layer may be excellent. Accordingly, since lithium ions may move smoothly through the coating layer, the resistance of the separator for an electrochemical device provided 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 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.

[0072]

[0073] According to one embodiment of the present invention, the inorganic particles have an operating voltage range of the electrochemical device (e.g., Li / Li + It may be that no oxidation and / or reduction reaction occurs at 0 V to 5 V as a reference. Specifically, the inorganic particles are BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT, 0 <x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3)O3-PbTiO3(PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, Al(OH)3, TiO2, aluminum peroxide, zinc tin hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), and antimony pentoxide (Sb2O5).

[0074]

[0075] According to one embodiment of the present invention, the coating layer may further include a binder. The above binder is polyacrylic acid, 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, It may be at least one selected from the group consisting of cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene butadiene copolymer, polyimide, and styrene-butadiene rubber.

[0076]

[0077] According to one embodiment of the present invention, the porous polymer substrate may be a porous film 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 film, and a fluid may pass through the porous polymer substrate through the pores.

[0078]

[0079] The porous polymer substrate may use a material that is physically and chemically stable with respect to the organic solvent electrolyte. For example, the porous polymer substrate may include, but is not limited to, a resin such as a polyolefin-based resin such as polyethylene, polypropylene, and polybutylene, polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimideamide, nylon, polytetrafluoroethylene, and copolymers or mixtures thereof. A polyolefin-based resin is preferably used. A polyolefin-based resin is suitable for manufacturing an electrochemical device with a higher energy density because it can be processed into a relatively thin thickness and the application of a coating slurry is easy.

[0080]

[0081] 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 having different melting points (Tm), thereby providing a shutdown function in the event of a high-temperature runaway of the battery. For example, the porous polymer film may include a polypropylene layer having a relatively high melting point and a polyethylene layer having a relatively low melting point. Preferably, the porous polymer substrate may have a three-layer structure in which polypropylene, polyethylene, and polypropylene are laminated in that order. The polyethylene layer melts when the temperature of the battery rises above a predetermined temperature, thereby shutting down the pores, thereby preventing thermal runaway of the battery.

[0082]

[0083] According to one embodiment of the present invention, the thickness of the porous polymer substrate may be 4 μm or more and 15 μm or less. Specifically, the thickness of the porous polymer film may be 4 μm or more, 6 μm or more, 8 μm or more, or 10 μm or more, and may also be 15 μm or less, 13 μm or less, 11 μm or less, 9 μm or less, or 7 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 positive and negative electrodes, thereby increasing the amount of active material included in the electrochemical device.

[0084]

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

[0086]

[0087] The porous polymer substrate may have a permeability of 10 s / 100cc or more and 100 s / 100cc or less. Specifically, the permeability of the porous polymer substrate may be 10 s / 100cc or more, 20 s / 100cc or more, 30 s / 100cc or more, 40 s / 100cc or more, or 50 s / 100cc or more, and may also be 100 s / 100cc or less, 90 s / 100cc or less, 80 s / 100cc or less, or 70 s / 100cc or less. Preferably, the permeability of the porous polymer substrate may be 50 s / 100cc or more and 70 s / 100cc or less. When the air permeability of the porous polymer substrate is within the 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.

[0088]

[0089] The above air permeability (s / 100cc) means the time (in seconds) it takes for 100cc of air to pass through a porous polymer substrate or membrane of a predetermined area under a constant pressure. The above air permeability can be measured using an air permeability tester (Gurley densometer) according to ASTM D726-58, ASTM D726-94 or JIS-P8117. For example, using Gurley's 4110N equipment, air at a pressure of 0.304kPa or 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 EG01-55-1MR equipment from Asahi Seiko, the time it takes for 100 cc of air to pass through a 1-square-inch sample can be measured.

[0090]

[0091] The porous polymer substrate may have a porosity of 10% by volume or more and 70% by volume or less. Specifically, the porous polymer substrate may have a porosity of 10% by volume or more, 20% by volume or more, 30% by volume or more, or 40% by volume or more, and may also have a porosity of 70% by volume or less, 60% by volume or less, or 50% by volume or less. Preferably, the porosity of the porous polymer substrate may be 40% by volume or more and 60% by volume or less. When the porosity of the porous polymer substrate is within the above-described range, the ionic conductivity of the manufactured separator can be provided within a range suitable for securing the output and cycle characteristics of the electrochemical device.

[0092]

[0093] The porosity described above refers to the volume ratio of pores to the total volume of the aerogel layer, coating layer, and porous polymer substrate, respectively. 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, capillary flow porosimetry, and water or mercury infiltration method.

[0094]

[0095] The present invention provides an electrochemical device.

[0096] The above electrochemical device may include the above-described separator for the electrochemical device.

[0097] 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. 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.

[0098]

[0099] 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.

[0100]

[0101] Since the electrochemical device includes the electrochemical device separator of the present invention described above, lithium ions can move smoothly through the electrochemical device separator due to the high porosity of the aerogel layer, and thus has the advantages of low resistance and excellent output. In addition, since the electrochemical device separator including the aerogel layer has excellent mechanical strength, such as puncture strength, and heat resistance, the electrochemical device including the electrochemical device separator also has the advantage of excellent stability.

[0102]

[0103] 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 M xA 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.

[0104]

[0105] 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.

[0106]

[0107] 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.

[0108]

[0109] 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.

[0110]

[0111] 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.

[0112]

[0113] 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).

[0114]

[0115] 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 as 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.

[0116]

[0117] 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. Specific 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.

[0118]

[0119] 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 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.

[0120]

[0121] Examples and comparative examples.

[0122] Manufacturing of separators for electrochemical devices

[0123] <Example 1>

[0124] Polyethylene resin was extruded and a porous polymer substrate (thickness 11 μm) was manufactured using a wet method.

[0125] Alumina powder as 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 87.5:0.3:12.2, and the inorganic particles were crushed and dispersed to prepare a coating layer slurry.

[0126] The coating layer slurry was applied to one surface of the porous polymer substrate by bar coating using a doctor blade and dried with air at 50°C using a heat gun to form a coating layer on one surface of the porous polymer substrate. At this time, the porosity of the coating layer was 40% by volume, and the thickness of the coating layer was 1 μm.

[0127] A cellulose nanofiber hydrogel composed of cellulose nanofibers (average diameter: 30 nm, average length: 3 μm, aspect ratio: 1:100) was prepared. An aerogel layer slurry containing 95 parts by weight of the cellulose nanofiber hydrogel, 3 parts by weight of the binder, and 2 parts by weight of the dispersant was rapidly cooled with liquid nitrogen and then freeze-dried to prepare a solid aerogel. The solid aerogel was coated on one surface of the coating layer to form an aerogel layer (cellulose nanofiber aerogel content: 95 wt%). At this time, the porosity of the aerogel layer was 85% by volume, the average pore diameter was 100 nm, and the thickness of the aerogel layer was 1 μm.

[0128] <Example 2>

[0129] In the above Example 1, a polyethylene porous polymer substrate having a thickness of 10 μm was used, and a coating layer having a thickness of 1 μm was formed on both sides of the porous polymer substrate using the coating layer slurry, and an aerogel layer having a thickness of 1 μm was formed on one side of the coating layer, except that a separator for an electrochemical device was manufactured in the same manner as in the above Example 1.

[0130] <Example 3>

[0131] In the above Example 1, a polyethylene porous polymer substrate having a thickness of 10 μm was used, and a coating layer having a thickness of 0.5 μm was formed on both sides of the porous polymer substrate using the coating layer slurry, and an aerogel layer having a thickness of 1.5 μm was formed on one side of the coating layer, except that a separator for an electrochemical device was manufactured in the same manner as in the above Example 1.

[0132] <Example 4>

[0133] In the above Example 3, a separator for an electrochemical device was manufactured in the same manner as in the above Example 3, except that the aerogel layer was formed on both sides of the coating layer with a thickness of 1.5 μm.

[0134] <Example 5>

[0135] 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 an aerogel layer having a porosity of 83% by volume and an average pore diameter of 80 nm was formed on one side of the coating layer to a thickness of 1 μm.

[0136] <Comparative Example 1>

[0137] In the above Example 1, a separator for an electrochemical device was manufactured in the same manner as in Example 1, except that a 1.5 μm thick coating layer was formed on one side of a porous polymer substrate using the coating layer slurry, and the aerogel layer was not coated on one side of the coating layer.

[0138] <Comparative Example 2>

[0139] In the above Example 2, a separator for an electrochemical device was manufactured in the same manner as in Example 2, except that the coating layer slurry was used on both sides of the porous polymer substrate to form a coating layer having a porosity of 40% by volume and a thickness of 1.5 μm, and the aerogel layer was not coated.

[0140] <Comparative Example 3>

[0141] In the above Example 2, a separator for an electrochemical device was manufactured in the same manner as in the above Example 2, except that the aerogel layer, instead of the coating layer, was coated on both sides of the porous polymer substrate and the coating layer was not formed. At this time, the thickness of each aerogel layer was 1.5 μm.

[0142] Comparative Example 4

[0143] 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 an aerogel layer having an average pore diameter of 35 nm and a porosity of 85% by volume was formed on one side of the coating layer.

[0144] Comparative Example 5

[0145] 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 an aerogel layer having an average pore diameter of 600 nm and a porosity of 85% by volume was formed on one side of the coating layer.

[0146] <Reference Example 1>

[0147] In the above Example 1, when forming the aerogel layer, 75 parts by weight of the cellulose nanofiber hydrogel, 15 parts by weight of the inorganic particles used in the preparation of the coating layer, 9 parts by weight of the binder, and 1 part by weight of the dispersant were mixed to prepare an aerogel layer slurry, which was rapidly cooled with liquid nitrogen and then freeze-dried to prepare a solid aerogel. A separator for an electrochemical device was prepared in the same manner as in Example 1, except that the solid aerogel was coated on one surface of the coating layer to form an aerogel layer (cellulose nanofiber aerogel content: 75 wt%).

[0148]

[0149] <Measurement of resistance of the separator>

[0150] 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 analysis using a 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. The results are shown in Tables 1 to 3 below.

[0151]

[0152] <Checking the wet shrinkage rate of the membrane>

[0153] The separators of the above examples and comparative examples were prepared as 5 cm × 5 cm sized specimens and each was inserted into an aluminum pouch sized 7 cm × 10 cm. 1 g of the following electrolyte was injected into the pouch, and the pouch was sealed.

[0154] The electrolyte used was a solvent containing ethylene carbonate (EC) / ethyl methyl carbonate (EMC) in a weight ratio of 3 / 7, 2 wt% of vinylene carbonate (VC) as an additive, and lithium salt LiPF61 M. The sealed pouch was stored in a 135°C convection oven for 30 minutes, and the separator was taken out. The thermal shrinkage in the MD and TD directions was calculated according to [(length of initial specimen - length after storage @135°C / 0.5 h) / (length of initial specimen)] × 100 (%). The results are shown in Tables 1 to 3 below.

[0155]

[0156] <Measurement of the puncture strength of the membrane>

[0157] The maximum load values ​​when the separators for electrochemical devices of the above examples and comparative examples were pierced at a speed of 120 mm / min using a needle with a diameter of 1 mm (0.5 mmR) for the separators manufactured according to each example and comparative example are measured and shown in Table 1 below. The test was performed 5 times on each separator using an Instron testing machine according to ASTM D5748-95 and ASTM D4649, and the testing machine calculated the average value. The results are shown in Tables 1 to 3 below.

[0158]

[0159] Example 1 Example 2 Example 3 Example 4 Example 5 Porous polymer substrate Porosity (volume %) 50 50 50 50 50 50 Thickness (μm) 11 10 10 10 11 Coating layer Cross-section / double-sided Cross-section Double-sided Double-sided Double-sided Cross-section Porosity (volume %) 40 40 40 40 40 Thickness (μm) 11 / 10.5 / 0.5 0.5 / 0.5 Aerogel layer Cross-section / double-sided Cross-section Cross-section Double-sided Cross-section Porosity (volume %) 8 5 8 5 8 5 8 3 Average pore diameter (nm) 100 100 100 100 80 Thickness (μm) 11 1.5 1.5 / 1.5 Membrane thickness (μm) 12.8 12.9 12.4 14.1 13.3 Electrical resistance (Ω)0.530.50.410.430.55Puncture strength(gf)543558594597548Wet state heat shrinkage@135℃ / 0.5h (MD(%) / TD(%))11 / 1010 / 85 / 36 / 38 / 5

[0160]

[0161] Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 Comparison Example 5 Porous polymer substrate Porosity (volume %) 50 50 50 50 50 50 Thickness (μm) 11 10 10 11 11 Coating layer Cross-section / double-sided Cross-section Double-sided Cross-section Porosity (volume %) 40 40-40 40 Thickness (μm) 1.5 1.5 / 1.5-11 Aerogel layer Cross-section / double-sided--double-sided Cross-section Porosity (volume %)--8 5 8 5 8 5 Average pore diameter (nm)--10 0 3 5 6 0 Thickness (μm)--1.5 / 1.5 1 1 Separator thickness (μm) 12.3 12.5 13.5 12.1 1 3.2 Electrical resistance (Ω) 0.8 2 0.7 8 0.6 6 0.8 5 0.8 7 Perforation Strength (gf) 493455555503512 Wet state heat shrinkage @ 135℃ / 0.5h (MD (%) / TD (%)) 13 / 812 / 59 / 422 / 1426 / 13

[0162]

[0163] Classification Reference Example 1 Porous polymer substrate Porosity (volume %) 50 Thickness (μm) 11 Coating layer cross-section / double-sided cross-section Porosity (volume %) 40 Thickness (μm) 1 Aerogel layer cross-section / double-sided cross-section Porosity (volume %) 80 Average pore diameter (nm) 80 Thickness (μm) 1 Separator thickness (μm) 13.1 Electrical resistance (Ω) 0.92 Puncture strength (gf) 478 Wet state thermal shrinkage @ 135℃ / 0.5h (MD (%) / TD (%)) 46 / 32

[0164]

[0165] As shown in Tables 1 and 2 above, the electrochemical device separators of Examples 1 to 5, in which an aerogel layer is formed on a coating layer including an inorganic material, have electrical resistances that are up to twice as low as those of the comparative examples, and also have excellent mechanical strengths such as puncture strength. Furthermore, the separators of the examples including cellulose nanofiber aerogels with excellent heat resistance have wet state thermal shrinkage rates that are up to twice as low as those of the comparative examples. Meanwhile, the electrochemical device separator of Example 4, in which both the coating layer and the aerogel layer are double-coated, has significantly lower electrical resistance despite the fact that the separator is thicker than that of the comparative examples.

[0166]

[0167] In addition, in the case of the electrochemical device separators of Comparative Examples 4 and 5 in which the average pore diameter of the aerogel layer is beyond 50 to 200 nm, it can be confirmed that the electrical resistance, puncture strength, and thermal shrinkage of the separator are inferior to those of the examples, even though the porosity of the aerogel layer is not different from that of the present invention. Specifically, in the case of Comparative Example 5 in which the average pore diameter of the aerogel layer exceeds 200 nm, the puncture strength was inferior even though the thickness of the electrochemical device separator was thicker than that of Example 1. In addition, in the case of Comparative Example 4 in which the average pore diameter of the aerogel layer is small, less than 50 nm, the electrical resistance was significantly high even though the thickness of the electrochemical device separator was thinner than that of Example 1.

[0168]

[0169] Meanwhile, in the case of Reference Example 1, where the aerogel layer further includes inorganic particles, the microstructure within the aerogel layer becomes non-uniform due to the inorganic particles, preventing the electrolyte from smoothly passing through the aerogel layer, and thus the resistance of the separator is found to be inferior to that of the Examples. In addition, the aerogel network within the aerogel layer is found to be unstable, and thus the heat resistance and puncture strength of the separator are inferior to that of the Examples.

[0170]

[0171] In summary, through the above experimental examples, it can be confirmed that the present invention includes an aerogel layer containing a coating layer and cellulose nanofiber aerogel on a porous polymer substrate, and that the average pore diameter of the aerogel layer satisfies 50 to 200 nm, so that the electrical resistance and thermal shrinkage of the separator are low, while also having excellent mechanical strength.

Claims

1. Porous polymer substrate; A coating layer disposed on at least one surface of the above-mentioned porous polymer substrate and comprising inorganic particles; and The above coating layer comprises an aerogel layer disposed thereon and comprising a cellulose nanofiber aerogel, and A separator for an electrochemical device having an average pore diameter of the aerogel layer of the above-mentioned aerogel layer of 50 nm or more and 200 nm or less.

2. In Paragraph 1, A separator for an electrochemical device having a porosity of 80 volume% or more and 99 volume% or less of the aerogel layer.

3. In paragraph 1, A separator for an electrochemical device, wherein the content of the cellulose nanofiber aerogel is 90 parts by weight or more and 99 parts by weight or less, based on a total weight of 100 parts by weight of the aerogel layer.

4. In paragraph 1, A separator for an electrochemical device having a thickness of 0.5 μm or more and 2 μm or less of the aerogel layer.

5. In paragraph 1, A separator for an electrochemical device having a coating layer thickness of 0.3 μm or more and 1.2 μm or less.

6. In paragraph 1, A separator for an electrochemical device having a porosity of 40 volume% or more and 70 volume% or less of the coating layer.

7. In Paragraph 1, A separator for an electrochemical device having an average diameter of cellulose nanofibers of 5 nm or more and 50 nm or less.

8. In paragraph 1, A separator for an electrochemical device having an aspect ratio of cellulose nanofibers of 1:50 or more and 1:200 or less.

9. In paragraph 1, A separator for an electrochemical device, wherein the content of the inorganic particles is 80 parts by weight or more and 95 parts by weight or less, based on a total weight of 100 parts by weight of the coating layer.

10. In paragraph 1, The above inorganic particles have an average diameter (D 50 A separator for an electrochemical device having a thickness of 200 nm or more and 800 nm or less.

11. A positive electrode; a negative electrode; and a separator for an electrochemical device according to any one of claims 1 to 10, The above electrochemical device is an electrochemical device in which a separator is interposed between the anode and the cathode.