Separator for electrochemical device and electrochemical device comprising same

Abstract

The present invention relates to a separator for an electrochemical device, the separator comprising: a porous polymer substrate; and a plurality of coating layers which are formed on at least one surface of the porous polymer substrate so as to be spaced apart from each other and comprise aramid, wherein the coating layers extend parallel to the TD direction of the porous polymer substrate.

Description

Separator for an electrochemical device and an electrochemical device including the same

[0001] The present invention claims the benefit of the filing dates of Korean Patent Application No. 10-2024-0130683 filed with the Korean Intellectual Property Office on September 26, 2024 and Korean Patent Application No. 10-2025-0136773 filed with the Korean Intellectual Property Office on September 23, 2025, the entire contents of which are incorporated into the present invention.

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

[0003]

[0004] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions; recently, lithium-ion batteries, which offer high energy density and voltage, long cycle life, and applicability to various fields, are widely used.

[0005] A lithium secondary battery may comprise an electrode assembly made of a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, and may be manufactured by housing the electrode assembly together with an electrolyte in a case. The separator may comprise a coating layer comprising a polymer binder and inorganic particles on at least one surface of a porous polymer substrate. The inorganic particles may be connected to other inorganic particles by the polymer binder to form an interstitial volume, and lithium ions may move through said interstitial volume. In addition to fixing the inorganic particles, the polymer binder may impart adhesive force to the coating layer, and the coating layer may be adhered to the porous polymer substrate and the electrode, respectively.

[0006]

[0007] The present invention aims to provide a separator for an electrochemical device having excellent mechanical strength and improved air permeability and resistance, comprising a plurality of coating layers including aramid, and an electrochemical device including the same.

[0008]

[0009] One aspect of the present invention provides a separator for an electrochemical device comprising a porous polymer substrate and a plurality of coating layers formed spaced apart from each other on at least one surface of the porous polymer substrate, the coating layers comprising inorganic particles, a polymer binder, and an aramid, wherein the coating layers extend parallel to the TD direction of the porous polymer substrate.

[0010] The coating layer may be formed on both sides of the porous polymer substrate.

[0011] The above porous polymer substrate may include a dry film.

[0012] The coverage of the above plurality of coating layers may be 30% or more and 80% or less.

[0013] The width of the coating layer may be 100 μm or more and 500 μm or less.

[0014] The thickness of the coating layer may be 0.5 μm or more and 4 μm or less.

[0015] The aramid may be included in an amount of 1% or more and 10% or less with respect to the total weight of the coating layer.

[0016] The polymer binder may be one or more selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polyvinylidene fluoride-trichloroethylene.

[0017] One aspect of the present invention provides an electrochemical device comprising an anode, a cathode, and a separator disposed between the anode and the cathode, wherein the separator is a separator for an electrochemical device according to the one aspect.

[0018] The above electrochemical device may be a lithium secondary battery.

[0019]

[0020] The separator for an electrochemical device according to the present invention has excellent mechanical strength and provides improved air permeability and resistance characteristics.

[0021]

[0022] FIG. 1 is a plan view of a separator for an electrochemical device according to one embodiment of the present invention.

[0023] FIG. 2 is a cross-sectional view of a separator for an electrochemical device according to one embodiment of the present invention.

[0024] FIG. 3 is a cross-sectional view of a separator for an electrochemical device according to one embodiment of the present invention.

[0025]

[0026] Hereinafter, each component of the present invention is described in more detail so that a person skilled in the art to which the present invention pertains can easily implement it; however, this is merely an example, and the scope of the rights of the present invention is not limited by the following.

[0027] The term “comprising” as used herein is used when listing materials, compositions, devices, and methods useful to the present invention, and is not limited to the examples listed.

[0028] As used herein, “about” and “substantially” are used to mean a range of numerical values ​​or degrees or approximations thereof, taking into account inherent manufacturing and material tolerances, and are used to prevent an infringer from unfairly exploiting the disclosure in which precise or absolute figures provided to aid in understanding the invention are mentioned.

[0029] As used in this specification, the term “electrochemical device” may refer to primary batteries, secondary batteries, supercapacitors, etc.

[0030] As used in this specification, “coverage” may refer to the ratio of the total area of ​​the plurality of coating layers to the area of ​​one side of the porous polymer substrate when the plurality of coating layers are formed on only one side of the porous polymer substrate, and may refer to the ratio of the total area of ​​the plurality of coating layers to the total surface area of ​​the porous polymer substrate when the plurality of coating layers are formed on both sides of the porous polymer substrate.

[0031]

[0032] Although the present invention has been described below by specific examples and embodiments, the present invention is not limited thereto and may include a combination of one or more of the specific examples and embodiments by those skilled in the art to which the present invention belongs, and various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below.

[0033]

[0034] Films contained in a porous polymer substrate can be classified into dry films and wet films depending on the formation method. Dry films are manufactured by melting a polymer resin to form a primary film, followed by stretching and heat setting. During the stretching process, a film having a lamellar structure mixed with crystalline and amorphous materials is formed, and pores oriented in a linear direction on the crystal plane may be formed. In the case of wet films, a polymer resin is mixed with wax and extruded to form a film, which is then stretched, and the wax is melted to form pores. Due to the differences in the manufacturing methods described above, dry films have the advantage of having excellent ion conductivity and low electrical resistance because the pore curvature is minimal. Nevertheless, dry films have had limitations in use because their mechanical strength is low due to the mechanical stretching process, making them vulnerable to external impact. To overcome these limitations, a method of coating the surface of the dry film with a material capable of supplementing mechanical strength can be considered. However, when a coating layer containing a crosslinking material is formed over the entire surface of the dry film, there was a limitation in that the advantages of the dry film could not be fully utilized, such as resistance increasing due to pore shielding.

[0035]

[0036] Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a plan view of a separator for an electrochemical device according to an embodiment of the present invention.

[0037]

[0038] One embodiment of the present invention provides a separator for an electrochemical device comprising a porous polymer substrate (10) and a plurality of coating layers (20) formed spaced apart from at least one surface of the porous polymer substrate (10) and comprising inorganic particles, a polymer binder, and aramid, wherein the coating layers (20) extend parallel to the TD direction of the porous polymer substrate (10).

[0039] The porous polymer substrate (10) may be a porous membrane having a plurality of pores formed therein, which electrically insulates the positive electrode and the negative electrode to prevent a short circuit. For example, if the electrochemical device is a lithium secondary battery, the porous polymer substrate (10) may be an ion-conducting barrier that blocks electrical contact between the positive electrode and the negative electrode while allowing lithium ions to pass through. At least some of the pores may form a three-dimensional network connecting the surface and the interior of the porous polymer substrate (10), and a fluid may pass through the porous polymer substrate (10) through the pores.

[0040] The porous polymer substrate (10) above may be a material that is physically and chemically stable with respect to an electrolyte, which is an organic solvent. For example, the porous polymer substrate (10) may include a resin such as polyolefins including polyethylene, polypropylene and polybutylene, polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyamideimide, nylon, polytetrafluoroethylene, and copolymers or mixtures thereof, but is not limited thereto. Preferably, a polyolefin resin may be used. Polyolefin resins are suitable for manufacturing electrochemical devices with higher energy density because they can be processed to a relatively thin thickness and are easy to apply a coating slurry to.

[0041] The thickness of the porous polymer substrate (10) may be 1 μm or more and 100 μm or less. Specifically, the thickness of the porous polymer substrate (10) may be 10 μm or more and 90 μm or less, 20 μm or more and 80 μm or less, 30 μm or more and 70 μm or less, or 40 μm or more and 60 μm or less. Preferably, the thickness of the porous polymer substrate (10) may be 1 μm or more and 30 μm or less. More preferably, the thickness of the porous polymer substrate (10) may be 5 μm or more and 15 μm or less, or 8 μm or more and 13 μm or less. By controlling the thickness of the porous polymer substrate (10) within the above-described range, the volume of the electrochemical device can be minimized while electrically insulating the anode and the cathode, thereby increasing the amount of active material included in the electrochemical device.

[0042] The porous polymer substrate (10) may include pores with 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 (10) may be 0.01 μm or more and 0.09 μm or less, 0.02 μm or more and 0.08 μm or less, 0.03 μm or more and 0.07 μm or less, or 0.04 μm or more and 0.06 μm or less. Preferably, the size of the pores may be 0.02 μm or more and 0.06 μm or less. By controlling the pore size of the porous polymer substrate (10) within the above-described range, the air permeability and ion conductivity of the entire separation membrane being manufactured can be controlled.

[0043] The porous polymer substrate (10) may have a porosity of 10 vol% or more and 60 vol% or less. Specifically, the porosity of the porous polymer substrate (10) may be 15 vol% or more and 55 vol% or less, 20 vol% or more and 50 vol% or less, 25 vol% or more and 45 vol% or less, or 30 vol% or more and 40 vol% or less. Preferably, the porosity of the porous polymer substrate (10) may be 30 vol% or more and 50 vol% or less. When the porosity of the porous polymer substrate (10) is within the range described above, the ion conductivity of the manufactured separator may be provided within a range suitable for securing the output and cycle characteristics of the electrochemical device.

[0044] The above porosity refers to the ratio of the volume of pores to the total volume of the porous polymer substrate (10). The above porosity can be measured by methods known in the art. For example, it can be measured by the BET (Brunauer Emmett Teller) measurement method using nitrogen gas adsorption, the capillary flow porometer, or the water or mercury infiltration method.

[0045] The porous polymer substrate (10) may include a dry film. The dry film may include pores with low curvature, have excellent ion conductivity, and have low electrical resistance. Specifically, the porous polymer substrate (10) may include a dry film uniaxially stretched in the MD direction or a dry film biaxially stretched in the MD direction and the TD direction. Preferably, the porous polymer substrate (10) may include a dry film biaxially stretched in the MD direction and the TD direction. Generally, for the biaxially stretched dry film, it is more effective to perform stretching in the TD direction after shrinking the width of the substrate through stretching in the MD direction, compared to the reverse order.

[0046] The above dry film may be imparted tensile strength in the MD direction during the stretching process in the MD direction, which typically corresponds to the roll direction, but its strength in the TD direction may be relatively inferior. This may be the case even for a dry film that is sequentially stretched in the TD direction following stretching in the MD direction. This may be attributed to the fact that the lamellar structure is oriented in the MD direction during the stretching process in the MD direction, making it difficult for the same effect to occur redundantly during the stretching process in the TD direction.

[0047] The mechanical strength of the porous polymer substrate (10) can be improved by forming a coating layer (20) according to one embodiment of the present invention, which will be described later, by extending it parallel to the TD direction of the porous polymer substrate (10).

[0048]

[0049] The coating layer (20) may include aramid. The aramid is a material with excellent heat resistance, having a melting point of 400°C or higher, and excellent mechanical properties, having high tensile strength and elastic modulus. The aramid may be para-aramid, meta-aramid, or a mixture thereof. Preferably, the aramid may be para-aramid. Para-aramid has excellent tensile strength, elastic modulus, and heat resistance, and meta-aramid has excellent flame retardancy, so the desired properties can be imparted to the coating layer (20) by appropriately selecting or mixing them. As the coating layer (20) includes aramid, heat resistance and mechanical strength are imparted to the porous polymer substrate (10), thereby preventing short circuits between electrodes even if external impact or thermal runaway occurs.

[0050] A plurality of coating layers (20) including the inorganic particles, polymer binder, and aramid may be formed spaced apart from each other on at least one surface of the porous polymer substrate (10). For example, FIG. 2 is a cross-sectional view showing that coating layers (20) are formed spaced apart from each other on one surface of the porous polymer substrate (10) in a separator for an electrochemical device according to one embodiment of the present invention. If the entire surface of the porous polymer substrate (10) is covered with the coating layers (20), the pores of the porous polymer substrate (10) are shielded, which may reduce air permeability and increase resistance. By forming the plurality of coating layers (20) spaced apart from each other, the pores of the porous polymer substrate (10) are not shielded, and the mobility of lithium ions can be improved during electrolyte impregnation. Meanwhile, forming the coating layers (20) by forming a stripe pattern as in FIG. 1 may also be advantageous in terms of simplifying the process.

[0051]

[0052] The coating layer (20) may be extended parallel to the TD direction of the porous polymer substrate (10). For example, as shown in FIG. 1, the coating layer (20) may be extended parallel to the MD and TD directions of the porous polymer substrate (10), respectively. As described above, the porous polymer substrate (10) may have tensile strength and thermal shrinkage rate in the TD direction. For example, by forming the coating layer (20) by extending it parallel to the TD direction as shown in FIG. 1, the mechanical strength and heat resistance of the coating layer (20) containing aramid can be imparted to the porous polymer substrate (10), thereby maximizing the effect of preventing shrinkage in the TD direction. For example, by forming the coating layer (20) spaced apart in the MD direction as shown in FIG. 1, the decrease in air permeability and increase in resistance due to the use of aramid can be prevented.

[0053] The coating layer (20) may be formed on both sides of the porous polymer substrate (10). Preferably, the coating layer (20) may be formed symmetrically on both sides of the porous polymer substrate (10). For example, the coating layer (20) may be formed symmetrically on both sides with respect to the porous polymer substrate (10) as shown in FIG. 3. As described above, when the coating layer (20) is formed on both sides of the porous polymer substrate (10), the mechanical properties and heat resistance of the porous polymer substrate (10) are improved, and the pores of the porous polymer substrate (10) are not completely blocked, thereby preventing an increase in air permeability and resistance.

[0054]

[0055] The coating layer (20) may be formed by coating a coating slurry comprising inorganic particles, a polymer binder, aramid, and a dispersion medium onto at least one surface of the porous polymer substrate (10). The dispersion medium may be one selected from the group consisting of water, ethanol, acetone, isopropyl alcohol (IPA), dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), hexafluoroisopropanol (HFIP), acetonitrile, and combinations thereof. Preferably, the dispersion medium may be one selected from the group consisting of dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), hexafluoroisopropanol (HFIP), acetonitrile, and combinations thereof. Using the above-described type of dispersion medium, a coating layer (20) in which inorganic particles and aramid are uniformly dispersed can be formed.

[0056] The width (W) of the coating layer (20) may be 100 μm or more and 500 μm or less. Specifically, the width (W) of the coating layer (20) may be 150 μm or more and 500 μm or less, 200 μm or more and 500 μm or less, 100 μm or more and 450 μm or less, 150 μm or more and 450 μm or less, or 200 μm or more and 450 μm or less. If the width (W) is smaller than the above-described range, sufficient mechanical strength is not imparted to the porous polymer substrate (10), and the puncture strength and tensile strength of the separation membrane may be inferior. If the width (W) is larger than the above-described range, the air permeability and resistance of the separation membrane may increase. By adjusting the width (W) of the coating layer (20) within the above-described range, mechanical strength can be imparted to the porous polymer substrate (10), and an increase in the air permeability and resistance of the separation membrane can be prevented.

[0057] The coating layer (20) may form a pattern in which the same shape is repeated, but is not limited thereto. For example, referring to FIG. 1, the coating layer (20) may be formed with a constant width (W) and spacing (D), but this is for convenience in the process and is not limited thereto. Preferably, the coating layer (20) satisfies the coverage described below within the aforementioned width (W) range, and when extended parallel to the TD direction, it has excellent mechanical properties and prevents an increase in air permeability and resistance.

[0058]

[0059] The thickness of the coating layer (20) may be 0.5 μm or more and 4 μm or less. Specifically, the thickness of the coating layer may be 0.5 μm or more and 4 μm or less, 0.5 μm or more and 2 μm or less, or 0.5 μm or more and 1 μm or less. By controlling the thickness of the coating layer (20) within the above-described range, the mechanical strength of the porous polymer substrate (10) can be supplemented, and the thickness of the entire separator can be kept thin, thereby enabling the realization of an electrochemical device with high energy density.

[0060] The above inorganic particles may be electrochemically stable. The above inorganic particles may be used within the operating voltage range of the electrochemical device (e.g., Li / Li). + There are no particular limitations as long as oxidation and / or reduction reactions do not occur at a voltage of 0 to 5V. In particular, when using inorganic particles with a high dielectric constant, the ionic conductivity of the electrolyte can be improved by contributing to an increase in the degree of dissociation of electrolyte salts, such as lithium salts, within the liquid electrolyte. For the reasons mentioned above, it is preferable that the inorganic particles comprise high dielectric constant inorganic particles having a dielectric constant of 5 or more, preferably 10 or more. Non-limiting examples of inorganic particles with a dielectric constant of 5 or more include BaTiO3, Pb(Zr,Ti)O3 (PZT), and Pb 1-x La x Zr 1-y Ti y O3(PLZT, 0 <x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3 There are O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, Al(OH)3, SiC, AlOOH, TiO2, or mixtures thereof.

[0061] In addition, as inorganic particles, inorganic particles having lithium ion transport capability may be used; that is, inorganic particles containing lithium elements that do not store lithium but have the function of transporting lithium ions. Non-limiting examples of inorganic particles having lithium ion transport capability include lithium phosphate (Li3PO4) and lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z(PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), such as (LiAlTiP) 14Li2O-9Al2O3-38TiO2-39P2O5 x O y Series glass (0 <x < 4, 0 < y < 13), 리튬란탄티타네이트(Li x La y TiO3, 0 < x <2, 0 <y <3), Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate (Li) such as S4, etc. x Ge y P z S w Lithium nitrides such as , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), Li3N, etc. (Li x N y , 0 < x < 4, 0 < y < 2), SiS2 series glass such as Li3PO4-Li2S-SiS2 (Li x Si y S z , 0 < x < 3, 0 <y < 2, 0 < z < 4), LiI-Li2S-P2S5등과 같은 P2S5계열 glass(Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7) or mixtures thereof, etc.

[0062] In addition, as inorganic particles, flame-retardant inorganic particles can be used to impart flame-retardant properties to the separator or to prevent a rapid rise in temperature inside the electrochemical device. Non-limiting examples of flame-retardant inorganic particles include Sb2O3, Sb2O4, Sb2O5, SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, Zn2SnO4, ZnSnO3, ZnSn(OH)6, ZrO2, Y2O3, SiO2, Al2O3, AlOOH, Al(OH)3, SiC, TiO2, H3BO3, HBO2, and mixtures thereof.

[0063] The average particle size (D50) of the above inorganic particles may be 50 nm or more and 5,000 nm or less. Specifically, the average particle size (D50) of the above inorganic particles may be 100 nm or more and 4,500 nm or less, 200 nm or more and 4,000 nm or less, 300 nm or more and 3,000 nm or less, 400 nm or more and 2,000 nm or less, or 500 nm or more and 1,000 nm or less. If the average particle size of the inorganic particles is less than 50 nm, additional polymer binder is required for bonding between inorganic particles as the specific surface area increases, which is disadvantageous in terms of electrical resistance. If the average particle size of the inorganic particles exceeds 5,000 nm, the uniformity of the surface of the coating layer (20) is reduced, and damage to the porous polymer substrate (10) or electrode may occur during lamination.

[0064] The coating layer (20) may have a content of the inorganic particles of 80 to 95 weight% relative to the total weight of the coating layer (20). Specifically, for 100 weight% of the coating layer (20), the content of the inorganic particles may be 80 weight% or more and 95 weight% or less, 81 weight% or more and 94 weight% or less, 82 weight% or more and 93 weight% or less, 83 weight% or more and 92 weight% or less, 84 weight% or more and 91 weight% or less, 85 weight% or more and 90 weight% or less, 86 weight% or more and 89 weight% or less, or 87 weight% or more and 88 weight% or less. Preferably, for 100 weight% of the coating layer (20), the content of the inorganic particles may be 85 weight% or more and 95 weight% or less, or 90 weight% or more and 95 weight% or less. A coating layer (20) satisfying the above-described range can be bonded to the porous polymer substrate (10) to minimize thermal shrinkage of the porous polymer substrate (10).

[0065] The polymer binder may bind inorganic particles contained in the coating layer (20) and impart adhesive force to the coating layer (20). The polymer binder may include an acrylic binder, a fluorine binder, or a hybrid binder thereof, but is not limited thereto. Preferably, the polymer binder may be a fluorine binder. For example, the acrylic binder may be one or more selected from the group consisting of polyacrylic acid, polyacrylamide, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, ethylhexyl acrylate, methyl methacrylate, styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and copolymers comprising one or more of these. For example, the fluorine-based binder may be one or more selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polyvinylidene fluoride-trichloroethylene. By using the polymer binder of the type described above, the aramid can be well fixed and uniformly dispersed within the coating layer (20), and at the same time, the adhesion to the electrode can be improved. In terms of miscibility with the aramid, it may be preferable to use the polymer binder as a fluorine-based binder.

[0066]

[0067] The coating layer (20) may contain 1% or more and 10% or less of the aramid with respect to the total weight of the coating layer (20). Specifically, the coating layer (20) may contain the aramid in an amount of 1 wt% or more and 10 wt% or less, 1 wt% or more and 8 wt% or less, 1 wt% or more and 6 wt% or less, 1 wt% or more and 5 wt% or less, 2 wt% or more and 10 wt% or less, 2 wt% or more and 8 wt% or less, 2 wt% or more and 6 wt% or less, 2 wt% or more and 5 wt% or less, 3 wt% or more and 10 wt% or less, 3 wt% or more and 8 wt% or less, 3 wt% or more and 6 wt% or less, 3 wt% or more and 5 wt% or less, 4 wt% or more and 10 wt% or less, 4 wt% or more and 8 wt% or less, 4 wt% or more and 6 wt% or less, or 4 wt% or more and 5 wt% or less, based on the total weight of the coating layer (20). If the aramid is contained in a smaller amount than the above-described range, the heat resistance and mechanical strength of the porous polymer substrate (10) may be degraded. If aramid is included in a larger amount than the above-described range, dispersibility within the coating slurry may be reduced, and precipitation may occur. Additionally, if aramid is included in a larger amount than the above-described range, the porous properties of the coating layer (20) may be reduced, and the air permeability and resistance of the separation membrane may increase. By controlling the content of the aramid within the above-described range, the increase in the air permeability and resistance of the separation membrane can be prevented.

[0068] The coverage of the plurality of coating layers (20) may be 30% or more and 80% or less. The coverage can be adjusted by controlling the spacing (D) between the coating layers (20) while determining the width (W) of the coating layers (20). If the coverage is lower than the range described above, mechanical properties such as puncture strength and tensile strength of the separation membrane may be inferior. If the coverage is higher than the range described above, pores of the porous polymer substrate (10) are not secured, and the air permeability and resistance of the separation membrane may increase. By controlling the coverage of the plurality of coating layers (20) within the range described above, mechanical properties can be imparted to the porous polymer substrate (10), and the increase in air permeability and resistance of the separation membrane can be prevented.

[0069]

[0070] The separator for the electrochemical device described above may further include an adhesive layer formed on the porous polymer substrate (10), the coating layer (20), or a combination thereof. The adhesive layer may provide adhesion to the electrode of the separator. The adhesive layer may include an acrylic binder, a fluorine binder, or a combination thereof, but is not limited thereto. The adhesive layer may include a particulate binder, a solution binder, or a combination thereof, but is not limited thereto. By further forming the adhesive layer, the adhesion between the separator and the electrode can be improved during the lamination process of the electrochemical device, and the adhesion can be maintained even if the coating layer (20) is wetted by the electrolyte.

[0071] The separator for the electrochemical device described above may have an air permeability of 80 s / 100cc or more and 125 s / 100cc or less. Specifically, the air permeability of the separator for the electrochemical device may be 90 s / 100cc or more and 125 s / 100cc or less, or 95 s / 100cc or more and 125 s / 100cc or less. When the separator for the electrochemical device is within the range described above, the output, stability, and cycle characteristics of the electrochemical device can be secured.

[0072] The above air permeability (s / 100cc) refers to the time (in seconds) required for 100cc of air to pass through a porous polymer substrate (10) or a separator with a predetermined area under constant pressure. The above air permeability may be measured using a Gurley densometer according to ASTM D 726-58, ASTM D726-94, or JIS-P8117. For example, using a Gurley 4110N instrument, air at a pressure of 0.304 kPa or 1.215 kN / m 2 100cc of air under water pressure is 1 square inch (or 6.54 cm²) 2 The time it takes for ) to pass through a sample can be measured. For example, using the Asahi Seico EG01-55-1MR instrument, the time it takes for 100cc of air to pass through a 1 square inch sample under a constant pressure of 4.8 inches of water at room temperature can be measured.

[0073] The separator for the electrochemical device described above may have an electrical resistance of 0.60 Ohm or less. Specifically, the electrical resistance of the separator for the electrochemical device may be 0.45 Ohm or more and 0.60 Ohm or less, 0.50 Ohm or more and 0.60 Ohm or less, 0.45 Ohm or more and 0.60 Ohm or less, or 0.50 Ohm or more and 0.60 Ohm or less. When the electrical resistance of the separator for the electrochemical device is within the range described above, the output of the electrochemical device is excellent and cycle characteristics can be secured.

[0074] The puncture strength of the separator for the electrochemical device may be 400 gf or more. Specifically, the puncture strength of the separator for the electrochemical device may be 420 gf or more, 450 gf or more, 480 gf or more, 500 gf or more, 700 gf or less, 600 gf or less, or 550 gf or less. The puncture strength refers to the resistance of the separator to penetration by an external object. The puncture strength can be tested, for example, by penetrating the separator vertically at a predetermined speed with a needle or pin having a predetermined diameter, and measuring the force applied when the separator is penetrated using ASTM D5748-95 or ASTM D4649.

[0075]

[0076] One embodiment of the present invention provides a method for manufacturing a separator for an electrochemical device, comprising the steps of: forming a plurality of coating layers spaced apart from each other by coating at least one surface of a porous polymer substrate with a coating slurry comprising inorganic particles, a polymer binder, aramid, and a dispersion medium; and manufacturing a separator by drying the coating layers to remove the dispersion medium. Any content overlapping with that described in the description of the separator for an electrochemical device is replaced by the description of the preceding embodiment.

[0077] The step of forming the coating layer involves coating at least one surface of a porous polymer substrate with a coating slurry comprising inorganic particles, a polymer binder, aramid, and a dispersion medium, while maintaining a gap. For example, the coating may be formed by methods such as a bar coater, wire bar coater, roll coater, spray coater, spin coater, inkjet coater, screen coater, reverse coater, gravure coater, knife coater, slot die coater, hot melt coater, comma coater, direct metering coater, etc., but is not limited thereto. For example, the coating may be formed by masking the porous polymer substrate and then coating the coating slurry. Alternatively, for example, the coating may be formed by adjusting the gap of the coater and the coating speed to apply the coating slurry with a gap. Preferably, the step of forming the coating layer may involve using a bar coater to apply the coating slurry with a gap on one or both sides of the porous polymer substrate by adjusting the gap of the bar and the coating speed to form a pattern.

[0078] The step of forming the coating layer may further include the step of corona discharge treatment of at least one surface of the porous polymer substrate. After the corona discharge treatment step, the coating slurry may be coated onto the porous polymer substrate. The step of corona discharge treatment of at least one surface of the porous polymer substrate prevents a decrease in the bonding strength between the surface of the porous polymer substrate and the surface of the coating layer at high temperatures, and prevents a decrease in the bonding strength between the surface of the porous polymer substrate and the surface of the coating layer due to the electrolyte.

[0079] The corona discharge treatment may involve treating at least one surface of the porous polymer substrate with a voltage of 0.1 kV or more and 10 kV or less in air. Specifically, the corona discharge treatment may involve treating with a voltage of 0.2 kV or more and 9 kV or less, 0.3 kV or more and 8 kV or less, 0.4 kV or more and 7 kV or less, 0.5 kV or more and 6 kV or less, 0.6 kV or more and 5 kV or less, 0.7 kV or more and 4 kV or less, 0.8 kV or more and 3 kV or less, 0.9 kV or more and 2 kV or less, or 1.0 kV or more and 2 kV or less in air. Preferably, the corona discharge treatment may involve treating with a voltage of 1.8 kV in air. By adjusting the applied voltage of the corona discharge treatment within the above-described range, appropriate functional groups can be formed on the surface of the porous polymer substrate, and damage to the surface of the porous polymer substrate can be prevented.

[0080] The step of manufacturing a separation membrane by removing the dispersion medium may involve drying or heating the coating layer to evaporate the dispersion medium contained within the coating layer. The dispersion medium removal step may be performed at a temperature that allows only the dispersion medium contained within the coating layer to evaporate without deforming the polymer binder contained within the coating layer. For example, the dispersion medium removal step may involve heating the coating layer to a predetermined temperature, provided that the surface temperature of the coating layer does not exceed 60°C. When heating the coating layer under these conditions, thermal energy may first be used to heat the dispersion medium to cause a phase change, and may not be used to deform the polymer binder.

[0081] The method for manufacturing the above-described separator for an electrochemical device may further include the step of forming an adhesive layer by applying an adhesive layer forming slurry to the surface of the coating layer and drying it.

[0082]

[0083] One embodiment of the present invention provides an electrochemical device comprising an anode, a cathode, and a separator interposed between the anode and the cathode, wherein the separator is a separator for the electrochemical device of the aforementioned embodiment. The electrochemical device may be manufactured by inserting an electrode assembly comprising an anode, a cathode, and a separator interposed between the anode and the cathode into a case or pouch and sealing it. Before sealing the case or pouch, an electrolyte may be injected to impregnate the electrode assembly with the electrolyte. The shape of the case or pouch is not limited. For example, the electrochemical device may be a cylindrical, prismatic, coin-type, or pouch-type lithium secondary battery.

[0084] The anode and the cathode may each have an electrode active material applied and dried to at least one surface of a current collector. The current collector may be made of a material that is conductive without causing chemical changes in the electrochemical device. For example, the current collector for the anode may be aluminum, nickel, titanium, calcined carbon, stainless steel; or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., but is not limited thereto. For example, the current collector for the cathode may be copper, nickel, titanium, calcined carbon, stainless steel; or copper or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., but is not limited thereto. The current collector may be in various forms such as a metal sheet, film, foil, net, porous body, foam, etc.

[0085] The above-described positive electrode comprises a positive current collector and a positive active material layer comprising a positive active material, a conductive material, and a binder resin on at least one surface of the current collector. The positive active material is a layered compound such as a lithium manganese complex oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 ~ 0.3); chemical formula LiMn 1-x M x It may include a lithium manganese complex oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the Li of the chemical formula is substituted with alkaline earth metal ions; a disulfide compound; and one or more of Fe2(MoO4)3.

[0086] The above-mentioned cathode comprises a cathode current collector and a cathode active material layer comprising a cathode active material, a conductive material, and a binder resin on at least one surface of the current collector. The above-mentioned cathode comprises, as the cathode active material, carbon such as lithium metal oxide, non-graphitizable carbon, or graphite-based carbon; LixFe2O3 (0≤x≤1), Li x WO2(0≤x≤1), Si, SiO x (0 <x<2), SiC, Si 합금 등의 실리콘계 재료; Sn x Me 1-x Me y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, and 3 elements of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 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 포함할 수 있다.

[0087] The conductive material may be any one selected from the group consisting of graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whiskers, conductive metal oxide, carbon nanotubes, activated carbon, and polyphenylene derivatives, or a mixture of two or more of these conductive materials. More specifically, it may be one selected from the group consisting of natural graphite, artificial graphite, acetylene black, channel black, furnace black, lamp black, thermal black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more of these conductive materials.

[0088] As the above binder resin, a binder resin commonly used in the electrodes of electrochemical devices can be used. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples include acetatepropionate), cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, but are not limited thereto.

[0089] The above electrolyte is A + B - As a salt with a structure like that, A + is Li + , Na +, K + It includes alkali metal cations such as or ions composed of combinations thereof, and B - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - A salt comprising an anion such as or a combination thereof may be dissolved or dissociated in an organic solvent comprising propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone, or a mixture thereof, but is not limited thereto.

[0090] The electrochemical device comprising the above electrode assembly may be a lithium secondary battery. The battery may be used as a unit cell, a battery module comprising the unit cell, a battery pack comprising the battery module, or a device comprising the battery pack as a power source. Examples of such devices include small devices such as computers, mobile phones, and power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs) that are powered by an electric motor; electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; and medium-to-large devices such as power storage systems, but are not limited thereto.

[0091]

[0092] The present invention will be explained in more detail below through specific embodiments and experimental examples. The following embodiments and experimental examples are intended to illustrate the present invention, and the present invention is not limited by the following embodiments and experimental examples.

[0093]

[0094] Example 1

[0095] Preparation of porous polymer substrate

[0096] Polypropylene resin was dispersed and then extruded using a T-die. After extrusion, it was formed into a sheet using a cooling casting roll. The molded product was subjected to biaxial stretching by MD stretching followed by TD stretching using a tenter-type sequential stretching machine. Specifically, it was stretched using a roller at 110°C with an MD direction stretching ratio of 2.7 times. Subsequently, it was stretched at 110°C in the TD direction to 150% of the initial input width.

[0097] The stretched sheet was washed with methylene chloride and dried, then immersed in acetone for a second wash and dried. Finally, it was heat-set in an oven at 127°C to prepare a porous polypropylene substrate (MI: 0.8 g / 10 min, porosity: 40%, average pore size: 40 nm, thickness: 10 µm).

[0098]

[0099] Preparation of coating slurry

[0100] A coating slurry was prepared by adding Al2O3 (particle size: 400 nm), PVDF (source: Thermo Scientific Chemicals), and para-aramid (source: Sigma Aldrich) in a weight ratio of 95:0.8:4.2 using NMP as a dispersion medium, and then stirring with a shaker for 60 minutes.

[0101]

[0102] Manufacturing of separation membranes

[0103] The coating slurry was applied to one surface of a prepared substrate using a bar coating method to form a pattern extending parallel to the TD direction. Specifically, the width and coverage of the coating layer were controlled by adjusting the bar gap and coating speed. The width of the coating layer was approximately 320 μm, and the pattern was formed with spacing such that the coverage was 30%. A separator with a patterned coating layer was manufactured by drying with a heat gun at 50°C.

[0104]

[0105] Example 2

[0106] A separator was manufactured in the same manner as in Example 1, except that a pattern was formed such that the width of the coating layer was approximately 420 μm and the coverage was 50%.

[0107]

[0108] Example 3

[0109] A separator was manufactured in the same manner as in Example 1, except that a pattern was formed on both sides of the substrate prepared in Example 1 such that the width of the coating layer was approximately 320 μm and the coverage was 30%.

[0110]

[0111] Example 4

[0112] A separator was manufactured in the same manner as in Example 3, except that a pattern was formed on both sides of the substrate prepared in Example 3 such that the width of the coating layer was approximately 320 μm and the coverage was 50%.

[0113]

[0114] Example 5

[0115] A separator was manufactured in the same manner as in Example 3, except that a pattern was formed on both sides of the substrate prepared in Example 3 such that the width of the coating layer was approximately 320 μm and the coverage was 80%.

[0116]

[0117] Example 6

[0118] A separator was manufactured in the same manner as in Example 3, except that a pattern was formed on both sides of the substrate prepared in Example 3 such that the width of the coating layer was about 250 μm and the coverage was 50%.

[0119]

[0120] Comparative Example 1

[0121] A separator was prepared in the same manner as in Example 1, except that a coating layer was not formed on the substrate prepared in Example 1.

[0122]

[0123] Comparative Example 2

[0124] A separator was manufactured in the same manner as in Example 1, except that a full coating was applied to one surface of a substrate prepared without forming a pattern in Example 1 to achieve 100% coverage.

[0125]

[0126] Comparative Example 3

[0127] A separator was manufactured in the same manner as in Example 1, except that a pattern was formed to extend parallel to the MD direction in Example 1.

[0128]

[0129] Comparative Example 4

[0130] A separator was manufactured in the same manner as in Example 4, except that a pattern was formed to extend parallel to the MD direction in Example 4.

[0131]

[0132] Comparative Example 5

[0133] In the above Example 1, polyethylene resin was extruded onto a porous polymer substrate and prepared by a wet method (MI: 0.2 g / 10 min, T m A separator was prepared in the same manner as in Example 1 above, except that a polyethylene substrate with a thickness of 10 μm was used, having a temperature of 135°C, a porosity of 45%, and an average pore size of 45 nm.

[0134]

[0135] Comparative Example 6

[0136] In the above Example 4, polyethylene resin was extruded onto a porous polymer substrate and prepared by a wet method (MI: 0.2 g / 10 min, T m A separator was prepared in the same manner as in Example 4 above, except that a polyethylene substrate with a thickness of 10 μm and a porosity of 135°C, 45%, and average pore size of 45 nm was used.

[0137]

[0138] Comparative Example 7

[0139] A separation membrane was prepared in the same manner as in Example 4, except that Al2O3, PVDF, and aramid were added in a weight ratio of 85:1:14.

[0140]

[0141] Comparative Example 8

[0142] A separator was manufactured in the same manner as in Example 4, except that a pattern was formed on both sides of the substrate prepared in Example 4 such that the width of the coating layer was approximately 820 μm and the coverage was 50%.

[0143]

[0144] Experimental Example. Confirmation of membrane properties

[0145] Air permeability measurement

[0146] Using a Gurley densometer (Gurley, 4110N), 100 cc of air with a diameter of 28.6 mm and an area of ​​645 mm 2 The time taken to pass through the membrane was measured.

[0147]

[0148] Electrical resistance measurement

[0149] Coin cells were manufactured by interposing the separators of the examples and comparative examples, respectively, between SUS. An electrolyte containing 1M LiPF6 and mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:2 was injected into the coin cells. To measure the resistance of the coin cells, the resistance was measured using the results of electrochemical impedance spectroscopic analysis with a VMP3 from BioLogic Science Instrument at 25°C under conditions of Amplitude 10 mV and Scan range 0.1 Hz to 1 MHz.

[0150]

[0151] Thermal shrinkage rate @ 180℃ / 1h measurement

[0152] The separator membranes of the examples and comparative examples were placed in an oven maintained at 180°C for 1 hour, then removed, and the thermal shrinkage rate was measured by measuring the rate of change in length in the MD direction and TD direction before and after being placed in the oven.

[0153]

[0154] Measurement of puncture strength

[0155] The maximum load value when the individual membranes of the 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) was measured using ASTM D5748-95. This was performed 5 times for each membrane, and the average value was calculated using an Instron testing machine.

[0156]

[0157] Tensile strength measurement

[0158] The separator membranes of the examples and comparative examples were prepared in pieces 15 cm in the MD direction and 2.5 cm in the TD direction, and the tensile strength was measured at 50 mm / sec using a UTM.

[0159]

[0160] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Single-sided / Double-sided Single-sided Double-sided Double-sided Double-sided Coating Layer Width (㎛) 3 20 4 20 3 20 3 20 3 20 250 Coverage (%) 3 0 50 3 0 50 8 0 50 Air Permeability (s / 100cc) 9 7 10 29 8 10 21 0 5 1 21 Electrical Resistance (Ohm) 0.5 4 0.5 0 0.5 2 0.5 3 0.5 7 0.5 4 Thermal Shrinkage @180℃ / 1h (% MD / TD) 1 / 1 2 / 3 4 / 4 1 / 1 1 / 2 1 / 3 Perforation Strength (gf) 4 5 6 5 10 4 8 0 5 18 49 8 43 2 Tensile Strength (kgf / cm²) 2 )(MD / TD)1725 / 12011831 / 15281684 / 10312135 / 20992100 / 20011698 / 1028

[0161]

[0162] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Single-sided / Double-sided Single-sided Single-sided Double-sided Single-sided Double-sided Double-sided Coating Layer Width (㎛)--3 20 3 20 3 20 3 20 3 20 8 20 Coverage (%) 0 1 0 0 3 0 5 3 0 5 5 5 5 5 0 Air Permeability (s / 100cc) 9 8 1 9 1 1 6 7 1 8 0 2 6 7 2 4 9 2 1 2 1 8 2 Electrical Resistance (Ohm) 0.5 8 0.7 2 0.6 5 0.6 7 0.8 7 0.8 5 0.8 4 0.7 8 Thermal Shrinkage @ 180℃ / 1h (% MD / TD) 3 / 43 / 35 / 55 / 43 / 43 / 36 / 107 / 8 Drilling Strength (gf) 175320212240476512158142 Tensile Strength (kgf / cm²) 2 )(MD / TD)1435 / 10211527 / 12851488 / 13571589 / 12882047 / 18222095 / 18441875 / 15481672 / 1495

[0163]

[0164] [Explanation of the symbol]

[0165] 10: Porous polymer substrate

[0166] 20: Coating layer

[0167] L: Width of porous polymer substrate

[0168] W: Coating layer width

[0169] D: Coating layer spacing

Claims

1. Porous polymer substrate; and A plurality of coating layers are formed spaced apart from each other on at least one surface of the porous polymer substrate and include inorganic particles, a polymer binder, and aramid. A separator for an electrochemical device, wherein the coating layer extends parallel to the TD direction of the porous polymer substrate.

2. In Paragraph 1, The above coating layer is formed on both sides of the porous polymer substrate, forming a separator for an electrochemical device.

3. In Paragraph 1, The above porous polymer substrate is a separator for an electrochemical device comprising a dry film.

4. In Paragraph 1, A separator for an electrochemical device, wherein the coverage of the plurality of coating layers is 30% or more and 80% or less.

5. In Paragraph 1, A separator for an electrochemical device, wherein the width of the coating layer is 100 μm or more and 500 μm or less.

6. 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.

7. In Paragraph 1, A separator for an electrochemical device comprising 1% by weight or more and 10% by weight or less of the aramid based on the total weight of the coating layer.

8. In Paragraph 1, The above polymer binder is one or more selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polyvinylidene fluoride-trichloroethylene, a separator for an electrochemical device.

9. An electrochemical device comprising an anode, a cathode, and a separator disposed between the anode and the cathode, wherein The above separator is an electrochemical device, wherein the separator is a separator for an electrochemical device according to any one of claims 1 to 8.

10. In Paragraph 9, The above electrochemical device is an electrochemical device that is a lithium secondary battery.

Images