Separator and electrochemical element including the same

Abstract

To provide a separator in which the ratio of the peak intensities of a (020)-surface and a (110)-surface of an X-ray diffraction (XRD) analysis graph is in the range of 2.6 to 5.7.SOLUTION: The separator according to an embodiment has an excellent high-temperature stability by satisfying the ratio of the XRD analysis graph peak intensities.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a separator and an electrochemical device including the same.

Background Art

[0002] In an electrochemical device, the separator of a battery is very important for improving the stability, life, and performance of the battery. The main function of the separator is to provide a path for ion movement in the battery and prevent physical contact between the negative electrode and the positive electrode. By improving the characteristics of the separator, a battery with excellent performance can be manufactured.

[0003] To improve the characteristics of the separator used in a battery, a multilayer separator is formed by laminating porous polymers such as polyolefin-based or polypropylene-based polymers, or a separator is developed in which a porous polymer is used as a base material and a coating layer is formed by mixing a binder and inorganic particles. The coating layer mixed with the multilayer separator or the binder can improve various characteristics of the separator compared to a single-layer separator, but the thickness of the separator can increase, and the battery performance may rather decrease due to low permeability, decreased wettability, and decreased impregnation. In order to solve such problems, research has been conducted to manufacture a separator that can improve the battery performance by being sufficiently suitable for the separator of the battery in terms of various characteristics, having a thin thickness, and satisfying mechanical and chemical stability.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] One embodiment provides a separator with excellent heat resistance.

[0006] Another embodiment provides an electrochemical element including the separator.

Means for Solving the Problems

[0007] One embodiment includes the following porous substrate and an inorganic particle layer including inorganic particles on at least one surface of the porous substrate, and provides a separator in which the ratio I of peak intensities represented by the following formula 1 020 / 110 is 2.6 to 5.7. [Formula 1] I 020 / 110 =I(020) / I(110) (In the above formula 1, I(020) and I(110) are peak intensities corresponding to the (020) plane and the (110) plane, respectively, in an X-ray diffraction (XRD) analysis graph.)

[0008] In this specification, the I(020) parameter can refer to a characteristic and / or observable crystal peak (showing a specific intensity) in the (020) plane of XRD analysis, particularly, the peak of the inorganic particles contained in the inorganic particle layer. Further, the I(110) parameter can refer to a characteristic and / or observable crystal peak (showing a specific intensity) in the (110) plane of XRD analysis, particularly, the peak of the polymer contained in the porous substrate.

[0009] Another embodiment provides an electrochemical element including the separator according to the above embodiment.

Advantages of the Invention

[0010] The present disclosure relates to a separator in which the ratio of peak intensities corresponding to the (020) plane and the (110) plane of an X-ray diffraction (XRD) analysis graph is 2.6 to 5.7. The separator according to one embodiment has excellent high-temperature stability by satisfying the above ratio of XRD analysis graph peak intensities.

Brief Description of the Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] The embodiments described in this specification may be modified into various other forms, and the technology according to one embodiment is not limited to the embodiments described below. Further, throughout the specification, when a component is described as "comprising", "including", "containing", or "having", unless otherwise stated to the contrary, it means that it may further include other components rather than excluding other components, and does not exclude elements, materials, or processes not further listed.

[0013] The numerical ranges used in this specification include the lower limit value and the upper limit value, all values within that range, increments logically derived from the form and width of the defined range, all of the limited values and all possible combinations of the upper and lower limits of numerical ranges limited to different forms. As an example, when the content of a composition is limited to 10% to 80% or 20% to 50%, numerical ranges of 10% to 50% or 50% to 80% should also be construed as those described in this specification. Unless otherwise specifically defined in this specification, values outside the numerical ranges that may occur due to experimental error or rounding of values are also included in the defined numerical ranges.

[0014] Hereinafter, unless otherwise specifically defined in this specification, "about" is considered to be a value within 30%, 25%, 20%, 15%, 10%, 5%, 3%, 2%, 1%, or 0.5% of the explicitly stated value.

[0015] Hereinafter, unless otherwise specifically defined in this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0016] Unless otherwise defined herein, the average particle size of the inorganic particles is D 50 means the value.

[0017] Unless otherwise defined herein, when a part such as a layer, film, thin film, region, plate, etc. is "on" or "above" another part, this includes not only the case where it is "immediately above" the other part, but also the case where there are other parts in between.

[0018] Unless otherwise defined herein, "polymer" means a molecule with a relatively high molecular weight, and its structure may include multiple repetitions of units derived from low molecular weight molecules. In one aspect, the polymer can be an alternating copolymer, block copolymer, random copolymer, graft copolymer, gradient copolymer, branched copolymer, crosslinked copolymer, or a copolymer containing all of these (e.g., a polymer containing more than one monomer). In other aspects, the polymer can be a homopolymer (e.g., a polymer containing one monomer).

[0019] One embodiment provides a separator with high heat resistance and capable of realizing excellent battery performance. Specifically, the separator according to one embodiment includes an inorganic particle layer containing inorganic particles on at least one surface of a porous substrate. As a result of X-ray diffraction (XRD) analysis of the separator, the ratio I 020 / 110 of the peak intensity I(020) corresponding to the (020) plane to the peak intensity I(110) corresponding to the (110) plane, represented by the following formula 1 in the graph, is 2.6 to 5.7. The separator according to one embodiment improves the heat resistance of the separator by satisfying the ratio of the peak intensities, and when the battery including this is charged and discharged, lithium ions can move uniformly, and it was devised by first recognizing that the problem of side reactions caused by moisture can be effectively suppressed.

[0020] [Formula 1] I020 / 110 =I(020) / I(110)

[0021] The above effect is due to the ratio I of the peak intensities of the separator satisfying 2.6 to 5.7, and is not an effect that affects only certain elements during the manufacturing process of the components of the separator or the separator. As confirmed from one embodiment, the ratio I of the peak intensities of the separator 020 / 110 can be realized by various means including various factors such as the average particle size or weight ratio of the inorganic substance, the thickness of the inorganic particle layer and the porous substrate, and there is no limitation on how the ratio of the peak intensities of the separator is realized. Specifically, for example, the ratio of the peak intensities may vary depending on the temperature and pressure during the process of manufacturing the inorganic particles, and may also vary depending on the commercial products or forms of the inorganic particles. Also, the elongation rate, copolymerization rate, and commercial products in the manufacturing step of the porous substrate may also vary 020 / 110

[0022] Therefore, regardless of the manufacturing conditions of the separator, that is, the content and type of the binder, dispersant, and lubricant, the solid content of the slurry, the rotation speed and / or bead size in the slurry manufacturing step, the use or non-use of a smoothing bar, the drying temperature, regardless of what the porous substrate is, regardless of what the electrolyte of the battery is, and when the separator includes an inorganic particle layer, regardless of what the average particle size, distribution, or combination of the inorganic substances contained in the inorganic particle layer is, when the ratio of the peak intensities of the separator of the above one embodiment is satisfied, the separator has excellent heat resistance, and the characteristics (life characteristics, charge and discharge characteristics, etc.) of the battery manufactured using this are excellent

[0023] In one embodiment, the peak corresponding to the (020) plane may be the peak of the inorganic particles contained in the inorganic particle layer, and / or the peak corresponding to the (110) plane may be the peak of the porous substrate

[0024] ​In one embodiment, the peak of the (020) plane may be a peak represented by 2θ = 14.5° ± 0.5°, 2θ = 14.5° ± 0.4°, 2θ = 14.5° ± 0.3°, 2θ = 14.5° ± 0.2°, 2θ = 14.5° ± 0.1°, or 2θ = 14.5°.

[0025] In one embodiment, the peak of the (110) plane may be a peak represented by 2θ = 21.6° ± 0.5°, 2θ = 21.6° ± 0.4°, 2θ = 21.6° ± 0.3°, 2θ = 21.6° ± 0.2°, 2θ = 21.6° ± 0.1°, or 2θ = 21.6°.

[0026] In one embodiment, the inorganic particles and their respective characteristic peaks displayed on the plane of the XRD measurement can be one or more selected from the group consisting of the following.

[0027] AlO(OH) (boehmite) peak: 2θ = 14.5° ± 0.5°, (020) plane, BaSO4 (Barite) peak: 2θ 22.8° ± 0.5°, (111) plane, CeO2 (Cerium Dioxide) peak: 2θ 28.55° ± 0.5°, (111) plane, MgO (Magnesium Oxide) peak: 2θ 42.8° ± 0.5°, (200) plane, CaO (Calcium Oxide) peak: 2θ 37.4° ± 0.5°, (200) plane, ZnO (Zinc Oxide) peak: 2θ 36.25° ± 0.5°, (101) plane, Al2O3 (Aluminium Oxide) peak: 2θ 25.6° ± 0.5°, (012) plane, TiO2 (Titanium Dioxide) - Anatase phase peak: 2θ 25.3° ± 0.5°, (101) plane - Rutile phase peak: 2θ 27.4° ± 0.5°, (110) plane, BaTiO3 (Barium Titanate) peak: 2θ 31.5° ± 0.5°, (101) plane (depending on the polymorphic phase), HfO2 (Hafnium Dioxide) peak: 2θ 28.3° ± 0.5°, (111) plane (monoclinic phase), SrTiO3 (Strontium Titanate) peak: 2θ 32.4° ± 0.5°, (110) plane, SnO2 (Tin Dioxide) peak: 2θ 29.8° ± 0.5°, (110) plane, NiO (Nickel Oxide) peak: 2θ 43.3° ± 0.5°, (200) plane, ZrO2 (Zirconium Dioxide) - Monoclinic phase peak: 2θ 27.8° ± 0.5°, (-111) plane, - Tetragonal phase peak: 2θ 29.8° ± 0.5°, (101) plane, Y2O3 (Yttrium Oxide) peak: 2θ 29.2° ± 0.5°, (222) plane (cubic phase), and SiC (Silicon Carbide) - 4H polytype peak: 2θ 35.7° ± 0.5°, (004) plane;

[0028] In one embodiment, the polymer of the porous substrate and each characteristic peak displayed on the plane of the XRD measurement can be one or more selected from the group consisting of the following.

[0029] At 2θ, the polyethylene peak can appear at 21° to 24°, specifically, it can appear at 21.6° ± 0.5° on the (110) plane.

[0030] At 2θ, the polypropylene peak can appear at 14° ± 0.5° to 14.5° ± 0.5°, or at 2θ of 21.6° ± 0.5° on the (110) plane. Specifically, the polyethylene peak can appear at 2θ of 21.6° ± 0.5° on the plane (110).

[0031] In one embodiment, the ratio I of the peak intensity 020 / 110 is 2.7 to 5.7, 2.8 to 5.7, 4.5 to 5.3, 4.5 to 5.1, 4.7 to 5.1, 2.7 to 5.1, 2.6 to 3.0, or 4.0 to 5.7, 2.7 to 3.0, or 4.5 to 5.3, 2.8, or 4.5 to 5.1, 2.6 to 3.0, or 4.5 to 5.1.

[0032] In one embodiment, the inorganic particle layer may be formed on at least one surface of the porous substrate. For example, the inorganic particle layer may be formed on one surface of the porous substrate or on both surfaces.

[0033] In one embodiment, the type of the inorganic particles contained in the inorganic particle layer is not particularly limited as long as they are inorganic particles known to be electrochemically stable. For example, it may contain any one or more of boehmite, CeO2, MgO, CaO, ZnO, Al2O3, TiO2, BaTiO3, HfO2, SrTiO3, SnO2, NiO, ZrO2, Y2O3, and / or SiC. Specifically, for example, the inorganic particles may include boehmite.

[0034] In one embodiment, the average particle diameter (D 50 ) of the inorganic particles may be appropriately selected according to experimental conditions and purposes as long as the ratio of the peak intensity of the separator according to one embodiment is satisfied, and is not necessarily limited to a specific range. For example, the average particle diameter of the inorganic particles may be 0.01 μm to 10.0 μm. Or it may be 0.01 μm to 5.0 μm, 0.1 μm to 10.0 μm, 0.1 μm to 5.0 μm, 0.1 μm to 3.0 μm, 0.1 μm to 2.0 μm, or 0.1 μm to 1.5 μm.

[0035] Alternatively, as the inorganic particles, inorganic particles having different average particle sizes may be used alone or in combination of two, three, or more types. For example, the first inorganic particles having an average particle size of 0.10 μm to 0.54 μm, 0.10 μm to 0.50 μm, 0.20 μm to 0.40 μm, 0.30 μm to 0.40 μm, or about 0.35 μm, the second inorganic particles having an average particle size of 0.55 μm to 2.0 μm, 0.55 μm to 1.5 μm, 0.55 μm to 1.2 μm, 0.60 μm to 0.90 μm, 0.60 μm to 0.80 μm, 0.70 μm to 0.80 μm, or about 0.75 μm, and any one or more of the third inorganic particles having an average particle size of 0.01 μm to 3.0 μm, 0.1 μm to 2.0 μm, or 0.1 μm to 1.0 μm may be used in combination. For example, the inorganic particles may contain only the first inorganic particles, or may contain the first inorganic particles and the second inorganic particles, or may include the first inorganic particles and the third inorganic particles. Here, the first inorganic particles, the second inorganic particles, and the third inorganic particles may be the same inorganic particles as each other, or may be different inorganic particles from each other.

[0036] In one embodiment, when using inorganic particles having two different average particle sizes, the weight ratio thereof is not particularly limited, and for example, they may be mixed at 20:80 to 80:20, 30:70 to 70:30, 50:50 to 80:20, 70:30, or 50:50. For example, the inorganic particles may include the first inorganic particles and the second inorganic particles at a weight ratio of 20:80 to 80:20, 30:70 to 70:30, 50:50 to 80:20, 30:70, 50:50, or 70:30. However, this is only an example, and the inorganic particles do not necessarily have to be mixed at the above weight ratio. Here, the first inorganic particles and the second inorganic particles may be the same inorganic particles as each other, or may be different inorganic particles from each other.

[0037] In one embodiment, the inorganic particle layer may further contain a binder. The binder may be appropriately selected according to the intended purpose and situation from binders known to those of ordinary skill in the technical field disclosed in the present application. In one embodiment, the binder may contain a polymer, for example, it may contain any one or more selected from the group consisting of ester-based polymers, amide-based polymers, imide-based polymers, acrylic-based polymers, acrylamide-based polymers, vinyl alcohol-based polymers, fluorine-based polymers, and / or vinyl pyrrolidone-based polymers. In one embodiment, the binder may contain an acrylamide-based polymer. Alternatively, for example, the binder may contain a polymer produced from any one or more of (meth)acrylamide-based monomers, (meth)acrylic monomers containing a hydroxy group, and / or polyfunctional (meth)acrylamide-based monomers. There is no limitation as long as the inorganic particles formed on the surface of the porous base material layer of the secondary battery separator are used as a binder for the inorganic particle layer in which the pores are formed by being connected to each other by the binder.

[0038] In one embodiment, the content of the binder may be appropriately adjusted according to the situation and purpose within a range that satisfies the range of the average pore diameter of the separator. For example, the content of the binder may be 0.1 part by weight to 20.0 parts by weight, 0.1 part by weight to 15.0 parts by weight, 1.0 part by weight to 10.0 parts by weight, 1.0 part by weight to 5.0 parts by weight, or about 3.0 parts by weight with respect to 100 parts by weight of the inorganic particles.

[0039] In one embodiment, the binder (or the polymer contained in the binder) may have a weight average molecular weight (Mw) of 50,000 g / mol to 2,000,000 g / mol, 50,000 g / mol to 1,000,000 g / mol, 50,000 g / mol to 500,000 g / mol, 50,000 g / mol to 300,000 g / mol, 100,000 g / mol to 300,000 g / mol, or about 280,000 g / mol. However, this is only an example, and it may be appropriately selected according to experimental conditions as long as the ratio of the peak intensity of the separator according to the present application can be satisfied. The weight average molecular weight may be measured by gel permeation chromatography (GPC).

[0040] In one embodiment, the porous substrate is not particularly limited as long as it is commonly used in the art. For example, it may be a woven fabric, a non-woven fabric, or a porous film. Specifically, the porous substrate may be made of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ether ketone, polyaryl ether ketone, polyether imide, polyamide imide, polybenzimidazole, polyether sulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon, and / or polytetrafluoroethylene, or any two or more of these may be used.

[0041] In one embodiment, the thickness of the porous substrate is not particularly limited. For example, it may be 1 μm to 100 μm, 1 μm to 50 μm, 1 μm to 30 μm, 5 μm to 20 μm, or about 9 μm or 11 μm.

[0042] In one embodiment, the thickness of the inorganic particle layer that can be formed on one surface of the porous substrate may be, for example, 0.1 μm to 10.0 μm, 0.1 μm to 5.0 μm, 0.5 μm to 3.0 μm, 1.0 μm to 3.0 μm, or about 1.5 μm, 2.0 μm, or 3.0 μm. When the inorganic particle layer is formed on both surfaces of the porous substrate, the thickness may be 0.2 μm to 15.0 μm, 0.3 μm to 10.0 μm, 1.0 μm to 8.0 μm, 2.0 μm to 6.0 μm, or about 3.0 μm, 4.0 μm, or 6.0 μm.

[0043] In one embodiment, after being left at 130°C for 60 minutes, the shrinkage rates in the machine direction (MD) and the transverse direction (TD) of the separator may both be 5.0% or less, where the lower limit may be 0.5% or 0. Specifically, the shrinkage rate may be 0.5% to 5.0%, 1.0% to 4.0%, or 1.0% to 3.0%.

[0044] In one embodiment, after being left at 150°C for 60 minutes, the shrinkage rates in the machine direction (MD) and the transverse direction (TD) of the separator can both be 5.0% or less, where the lower limit may be 0.5% or 0. Specifically, the shrinkage rate may be 0.5% to 5.0%, 1.0% to 4.0%, or 1.0% to 3.0%.

[0045] In one embodiment, the porous substrate included in the separator may have an air permeability (Gurley permeability) measured according to ASTM D726 of 10 s / 100 cc to 300 s / 100 cc, 50 s / 100 cc to 200 s / 100 cc, 60 s / 100 cc to 160 s / 100 cc, or 70 s / 100 cc to 150 s / 100 cc, but it is not particularly limited as long as the ratio of the peak strength of the separator according to one embodiment is achieved.

[0046] In one embodiment, the separator has a water content of 1000 ppm or less. Here, the water content may be a value obtained by measuring the amount of water generated while heating a test piece at 150°C in accordance with the Karl Fischer titration method using a water content measuring device (Metrohm, 917 Coulometer) after collecting 0.3 g of the separator.

[0047] The separator according to one embodiment has a ratio I of peak intensities in the XRD analysis graph 020 / 110 satisfying 2.6 to 5.7, and thus has excellent heat resistance and can have the most preferable water content for realizing battery performance. As a result, the charge / discharge performance and life characteristics of the battery can be excellently realized. When the ratio of peak intensities of the separator is not satisfied, the water content of the separator is high, and during charging and discharging of the battery, performance degradation may occur due to problems of side reactions caused by water, or the heat resistance of the separator is low or the battery resistance is low, and there is a possibility that thermal stability and battery performance are not sufficiently realized.

[0048] The separator according to one embodiment may be manufactured from the steps of preparing a composition for forming an inorganic particle layer containing inorganic particles, and after applying (or coating) the composition for forming an inorganic particle layer on at least one surface of a porous substrate, drying to form an inorganic particle layer. Further, in one embodiment, before the step of forming the inorganic particle layer, a step of surface-treating the porous substrate may be further included. The surface treatment may be performed by introducing polar groups onto the surface by corona discharge treatment.

[0049] In one embodiment, the solvent used in the composition for forming the inorganic particle layer is not particularly limited, and when the composition contains a binder, a solvent that easily dissolves or disperses the binder may be selected. For example, water, acetone, ethanol, tetrahydrofuran, methylene chloride, chloroform, cyclohexane, dimethylformamide, and / or N-methyl-2-pyrrolidone may be used.

[0050] In one embodiment, the composition for forming the inorganic particle layer may be a slurry, and the solid content of the slurry may be, for example, 10 wt% to 50 wt%, 10 wt% to 40 wt%, 15 wt% to 30 wt%, 20 wt% to 33 wt%, or about 25 wt%.

[0051] In one embodiment, the method of applying or coating the composition for forming the inorganic particle layer on the porous substrate is not particularly limited, and for example, roll coating, spin coating, dip coating, bar coating, die coating, slit coating, or inkjet printing may be used.

[0052] In one embodiment, the drying may be performed by hot air, warm air, drying with low humidity air, vacuum drying, or irradiation methods such as far-infrared rays or electron beams. Since the drying temperature is not particularly limited, it may be appropriately adjusted according to the experimental environment and purpose, and for example, it may be 30°C to 120°C, 30°C to 100°C, 50°C to 80°C, 50°C to 70°C, or about 60°C. The drying time is not particularly limited, but it may be 30 seconds to 300 seconds, 60 seconds to 300 seconds, 100 seconds to 300 seconds, 150 seconds to 250 seconds, or about 180 seconds.

[0053] As described above, the ratio of the peak intensity of the separator according to one embodiment can be realized by various means, and can also be adjusted by the size of the inorganic particles, the degree of distribution of the inorganic particles, the type and content of the binder, the solid content of the slurry, the manufacturing conditions of the slurry, the viscosity of the slurry, the drying conditions (temperature, speed), the coating speed, the flattening means using a smoothing bar, etc.

[0054] Another embodiment provides an electrochemical element including the separator according to the above embodiment, and the electrochemical element may be a secondary battery or a lithium secondary battery.

[0055] Hereinafter, the components of the secondary battery according to the present disclosure will be further described.

[0056] [Positive electrode] The positive electrode may include a positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the positive electrode current collector.

[0057] (Positive electrode current collector) The positive electrode current collector may include stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive electrode current collector may include carbon, nickel, titanium, aluminum surface-treated with silver, or stainless steel. The positive electrode current collector is not limited thereto, and may be, for example, 10 μm to 50 μm.

[0058] (Positive electrode material) The positive electrode mixture layer may include a positive electrode active material. The positive electrode active material may include a compound capable of reversibly intercalating and deintercalating lithium ions.

[0059] According to an exemplary embodiment, any conventionally used positive electrode active material can be used without limitation. For example, the positive electrode active material may include a lithium-nickel metal oxide. The lithium-nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0060] The positive electrode active material may further include a coating element or a doping element. For example, an element that is substantially the same as or similar to the above-described auxiliary element may be used as the coating element or the doping element. For example, one or more of the above-described elements may be used alone or in combination as the coating element or the doping element.

[0061] The positive electrode active material may include a nickel-cobalt-manganese (NCM) based lithium oxide. In this case, an NCM based lithium oxide with an increased nickel content may be used.

[0062] Among the NCM-based lithium oxides, the content of Ni (for example, the molar fraction of nickel among the total moles of nickel, cobalt, and manganese) may be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the content of Ni may be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0063] In some embodiments, the positive electrode active material may include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate-based (LFP) active material (for example, LiFePO4).

[0064] (Method for manufacturing the positive electrode) For example, the positive electrode active material may be mixed in a solvent to produce a positive electrode slurry. After coating the positive electrode slurry on a positive electrode current collector, it may be dried and rolled to produce a positive electrode mixture layer. The coating process may be performed by methods such as gravure coating, slot die coating, simultaneous multilayer die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc., and is not limited thereto. The positive electrode mixture layer may further include a binder, and optionally, may further include a conductive material, a thickener, etc.

[0065] (Positive electrode solvent) Non-limiting examples of the solvent used for manufacturing the positive electrode mixture include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0066] (Positive electrode binder) The binder may include polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polymethylmethacrylate, acrylonitrile butadiene rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. In one embodiment, a PVDF-based binder may be used as the positive electrode binder.

[0067] (Positive electrode conductive material) The conductive material may be added to enhance the conductivity of the positive electrode mixture layer and / or the mobility of lithium ions or electrons. For example, the conductive material may include carbon-based conductive materials such as graphite, carbon black, acetylene black, ketjen black, graphene, carbon nanotubes, VGCF (vapor-grown carbon fiber), carbon fibers, and / or metal-based conductive materials including perovskite substances such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc., but is not limited thereto.

[0068] (Positive electrode thickener / dispersant) Optionally, the positive electrode mixture may further include a thickener and / or a dispersant, etc. In one embodiment, the positive electrode mixture may include a thickener such as carboxymethyl cellulose (CMC).

[0069] [Negative electrode] The negative electrode may include a negative electrode current collector and a negative electrode mixture layer disposed on at least one surface of the negative electrode current collector.

[0070] (Negative electrode current collector) Non-limiting examples of the negative electrode current collector include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, and a polymer substrate coated with a conductive metal. The negative electrode current collector is not limited thereto, and may be, for example, 10 to 50 μm.

[0071] (Negative electrode material) The negative electrode binder layer may contain a negative electrode active material. As the negative electrode active material, a material capable of adsorbing and desorbing lithium ions may be used. For example, as the negative electrode active material, carbon-based materials such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, lithium metal, lithium alloy, silicon (Si)-containing substance, or tin (Sn)-containing substance may be used.

[0072] Examples of the amorphous carbon include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), and mesophase pitch-based carbon fiber (MPCF).

[0073] Examples of the crystalline carbon include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, and graphitized MPCF.

[0074] Examples of the lithium metal include pure lithium metal or lithium metal with a protective layer formed for suppressing dendrite growth. In one embodiment, a lithium metal-containing layer vapor-deposited or coated on the negative electrode current collector may be used as the negative electrode active material layer. In one embodiment, a lithium thin film layer may be used as the negative electrode active material layer.

[0075] Examples of the elements contained in the lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.

[0076] The silicon-containing substance can provide increased capacity characteristics. The silicon-containing substance may include Si, SiO x (0 < x < 2), metal-doped SiO x (0 < x < 2), and may include silicon-carbon composites, etc. The metal may include lithium and / or magnesium, and metal-doped SiO x (0 < x < 2) may include metal silicates.

[0077] (Method for manufacturing the negative electrode) For example, the negative electrode active material may be mixed in a solvent to produce a negative electrode slurry. After coating / vapor-depositing the negative electrode slurry on a negative electrode current collector, it can be dried and rolled to produce a negative electrode mixture layer. The coating process may be performed by methods such as gravure coating, slot die coating, simultaneous multilayer die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc., and is not limited thereto. The negative electrode mixture layer may further include a binder, and optionally, may further include a conductive material, a thickening agent, etc.

[0078] In some embodiments, the negative electrode may include a negative electrode active material layer in the form of lithium metal formed by a vapor deposition / coating process.

[0079] (Negative electrode solvent) Non-limiting examples of the solvent for the negative electrode mixture include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, t-butanol, etc.

[0080] (Negative electrode binder / conductive material / thickening agent) As the binder, conductive material, and thickening agent, the above-mentioned substances that can be used during the manufacture of the positive electrode may be used.

[0081] In some embodiments, as the negative electrode binder, a styrene-butadiene rubber (SBR)-based binder, carboxymethyl cellulose (CMC), a polyacrylic acid-based binder, a poly(3,4-ethylenedioxythiophene) (PEDOT)-based binder, or the like may be used.

[0082] [Electrode assembly] According to an exemplary embodiment, a positive electrode, a negative electrode, and a separator may be repeatedly arranged to form an electrode assembly. In some embodiments, the electrode assembly may be of a winding type, a stacking type, a z-folding type, or a stack-folding type.

[0083] [Electrolyte] The electrode assembly may be housed in a case together with an electrolyte to define a lithium secondary battery. According to an exemplary embodiment, a non-aqueous electrolyte may be used as the electrolyte.

[0084] (Lithium salt / Organic solvent) The non-aqueous electrolyte contains a lithium salt as an electrolyte and an organic solvent. The lithium salt is represented by, for example, Li+X−. Examples of the anion (X−) of the lithium salt include F−, Cl−, Br−, I−, NO3−, N(CN)2−, BF4−, ClO4−, PF6−, (CF3)2PF4−, (CF3)3PF3−, (CF3)4PF2−, (CF3)5PF−, (CF3)6P−, CF3SO3−, CF3CF2SO3−, (CF3SO2)2N−, (FSO2)2N−, CF3CF2(CF3)2CO−, (CF3SO2)2CH−, (SF5)3C−, (CF3SO2)3C−, CF3(CF2)7SO3−, CF3CO2−, CH3CO2−, SCN−, and (CF3CF2SO2)2N−.

[0085] The organic solvent may include an organic compound having sufficient solubility in the lithium salt and the additive and having no reactivity in the battery. As the organic solvent, for example, it may include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, and aprotic solvents.As the organic solvent, for example, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, vinylene carbonate, methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), fluoroethyl acetate (FEA), difluoroethyl acetate (DFEA), trifluoroethyl acetate (TFEA), dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF) and 2-methyltetrahydrofuran, ethanol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma-butyrolactone, and propylene sulfite may be used. These may be used alone or in combination of two or more.

[0086] (Additive) The non-aqueous electrolyte can further contain an additive. The additive may include, for example, cyclic carbonate compounds, fluorine-substituted carbonate compounds, sultone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, and borate compounds. The cyclic carbonate compounds may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), etc. The fluorine-substituted cyclic carbonate compounds may include fluoroethylene carbonate (FEC), etc. The sultone compounds may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc. The cyclic sulfate compounds may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc. The cyclic sulfite compounds may include ethylene sulfite, butylene sulfite, etc. The phosphate compounds may include lithium difluoro bis-oxalato phosphate, lithium difluoro phosphate, etc. The borate compounds may include lithium bis(oxalate)borate, etc.

[0087] Hereinafter, examples and experimental examples will be specifically illustrated and described below. However, the examples and experimental examples described below illustrate a part of one embodiment, and it should not be construed that the technology described in this specification is limited thereto.

[0088] <Experimental Method> 1. X-ray diffraction (XRD) analysis The XRD analysis conditions are as follows.

[0089] X-ray source anode: Cu Generator voltage: 45 kV, tube current: 40 mA Scan 2θ range: 10~80° Step size: 0.02626° Time per Scan: 100 s

[0090] 2. Measurement of air permeability Using a densometer (Toyoseiki Ltd.), in accordance with ASTM D726 standard, the air permeability (Gurley permeability) of the porous substrate was measured, and the time taken for 100 cc of air to pass through an area of 1 square inch of the separator was recorded in seconds.

[0091] 3. Measurement of thermal shrinkage rate After cutting the manufactured separator into a square shape with a side length of 10 cm, the sample was placed in the middle, and 5 sheets of paper were placed on top and bottom of the sample, and the four sides of the paper were wrapped with tape. The sample wrapped in paper was left in a hot air drying oven at a temperature of 130 °C for 60 minutes. Then, the sample was taken out and the separator was measured with a camera, and the machine direction (MD) shrinkage rate of the following Mathematical Formula 1 was calculated. If it was less than 5%, it was evaluated as OK; if it was 5% or more, it was evaluated as NG.

[0092] [Mathematical Formula 1] Machine direction (MD) shrinkage rate (%) = (Length in the machine direction before heating - Length in the machine direction after heating) × 100 / Length in the machine direction before heating

[0093] 4. Measurement of moisture content After collecting 0.3 g of the manufactured separator, using a moisture measuring device (Metrohm, 917 Coulometer), the amount of moisture generated while heating the test piece at 150°C was measured according to the Karl Fischer moisture measurement method. If the measured moisture content was less than 1000 ppm, it was evaluated as OK; if it was 1000 ppm or more, it was evaluated as NG.

[0094] 5. Measurement of weight-average molecular weight The measurement of the weight-average molecular weight was carried out using GPC (manufactured by Tosoh, EcoSEC HLC-8320GPC Reflective Index detector). The GPC column was Tskgel guard PWx, two TSKgel GMPWxl, and TSKgel G2500PWxl (7.8×300 mm). The eluent was 0.1 M aqueous NaNO3 solution. The standard was polyethylene glycol, and the analysis was performed at 40°C with a flow rate of 1 mL / min.

[0095] 6. Measurement of thickness Thickness of the separator: After stacking 10 separators, the thickness was measured at 5 arbitrary points in the width direction using a thickness measuring instrument manufactured by Mitutoyo. Then, the average thickness of the 10-layer separator was derived, and further divided by 10 to obtain the overall average thickness of a single separator.

[0096] Thickness of the porous substrate: The average thickness of the porous substrate was obtained by stacking only 10 porous substrates, measuring the thickness at 5 arbitrary points in the width direction using a thickness measuring instrument manufactured by Mitutoyo, then deriving the average thickness of the 10-layer porous substrate, and further dividing by 10 to obtain the average thickness of a single porous substrate.

[0097] Thickness of the inorganic particle layer: It was calculated and derived by subtracting the average thickness of a single porous substrate from the overall average thickness of a single separator obtained by the above method.

[0098] <Example 1> After replacing the 1.0 L flask with nitrogen, 64.7 g of acrylamide, 10.4 g of 2-hydroxyethyl acrylate, 0.008 g of N-methylenebisacrylamide, and 676 g of distilled water were added, and then the temperature was raised to 70 °C. Thereafter, 0.200 g of potassium persulfate was added to the flask as a polymerization initiator, and then a polymerization reaction was carried out. After the reaction, after 15 hours, it was opened to the air to stop the polymerization reaction. After the temperature was lowered to room temperature, a 1 M sodium hydroxide solution was added to adjust the pH to 7, and an aqueous binder solution with a solid content of 10% by weight was produced. Here, the viscosity of the aqueous solution was 1000 cps, and the weight average molecular weight was about 280,000 g / mol.

[0099] Average particle size (D 50 ) of 15 g of boehmite particles (A) with a diameter of 400 nm and average particle size (D 50 ) of 35 g of boehmite particles (B) with a diameter of 700 nm were placed in 50 g of distilled water containing 0.35 g of ammonium polycarboxylate and stirred for 2 hours to prepare a mixed solution. 100 g of the mixed solution and 100 g of zirconium balls were added to zirconium balls, and using a planetary mixer, after milling at 150 rpm for 5 minutes, filtration was performed using a mesh filter to prepare an inorganic slurry. Here, as a measurement result using a particle size measuring instrument of the LDS (Laser diffraction spectrometry) method, D 50 was 0.4 μm.

[0100] 7.73 g of the binder produced above and 45 g of additional water were added to 50 g of the inorganic slurry, and then stirred for 30 minutes to produce a coating solution with a solid content of 25% by weight.

[0101] As a porous substrate, a polyethylene substrate with a thickness of 9 μm (Gurley permeability: 126 s / 100 cc) was corona-treated under the condition of 0.6 A. Using a wire bar, the prepared coating solution was used to form an inorganic particle layer on both sides of the porous substrate at a speed of 5 m / min, dried while passing through a hot air dryer at 40 °C, and wound up in a roll form to manufacture a separator. After drying, the coating thicknesses were 1.5 μm respectively.

[0102] <Examples 2 to 6> The average particle diameters (D 50 ) of inorganic particles A and B, the weight ratio of inorganic particles, the thickness of the inorganic particle layer, the thickness of the porous substrate, and the Gurley permeability of the porous substrate were the same as those in Table 1 below. A separator was manufactured in the same manner as in Example 1 except for this.

[0103] <Comparative Examples 1 to 3> The average particle diameters (D 50 ) of inorganic particles A and B, the weight ratio of inorganic particles, the thickness of the inorganic particle layer, the thickness of the porous substrate, and the Gurley permeability of the porous substrate were the same as those in Table 1 below. A separator was manufactured in the same manner as in Example 1 except for this.

[0104]

Table 1

[0105] As a result of XRD measurement of the separators manufactured in the above Examples and Comparative Examples, the intensities (I(020), I(110)) of the peaks corresponding to the (020) plane and the (110) plane and the ratio I 020 / 110 thereof, and the results of measuring the thermal shrinkage rate and the moisture content of the separator are summarized in Table 2 below.

[0106]

Table 2

[0107] In the results of the XRD, the peak corresponding to the (020) plane is the peak of boehmite which is the inorganic particles contained in the inorganic particle layer, and the peak corresponding to the (110) plane is the peak of polyethylene which is the porous substrate. The ratio I of the intensities of the two peaks 020 / 110 The separators of the examples where 020 / 110 is 2.6 to 5.7 all satisfied that the thermal shrinkage rate at 130 °C was less than 5%, and were superior in high-temperature stability compared with the comparative examples. Further, as a result of evaluating the thermal shrinkage rate by raising the temperature to 150 °C using the separators of Example 1, Example 2, and Comparative Examples 1 to 3, both Example 1 and Example 2 still satisfied that the thermal shrinkage rate was less than 5%, while in Comparative Examples 1 to 3, it was confirmed that the thermal shrinkage rate was 5% or more for all of them.

[0108] Also, in the case of the separators of the examples, the water content was less than 1000 ppm for all of them, while the separator of Comparative Example 4 had a high water content of 1000 ppm or more. Therefore, it is expected that the battery performance will be deteriorated due to side reactions caused by water during battery charge and discharge.

[0109] As described above, one embodiment has been described in detail by way of examples and experimental examples. However, the scope of one embodiment is not limited to specific examples, and must be construed according to the appended claims.

Claims

1. A porous substrate and an inorganic particle layer including inorganic particles on at least one surface of the porous substrate, The peak intensity ratio I represented by the following formula 1 ０２０／１１０ is 2.6 to 5.

7. [Formula 1] I ０２０／１１０ =I(020) / I(110) In the above formula 1, I(020) and I(110) are the peak intensities corresponding to the (020) plane and the (110) plane, respectively, in an X-ray diffraction (XRD) analysis graph.

2. The separator according to claim 1 , wherein the peak corresponding to the (020) plane is a peak of inorganic particles contained in the inorganic particle layer.

3. The separator according to claim 1 , wherein the peak corresponding to the (110) plane is a peak of a porous substrate.

4. 2. The separator according to claim 1, wherein the peak of the (020) plane is a peak expressed by 2θ=14.5°±0.5°.

5. 2. The separator according to claim 1, wherein the peak of the (110) plane is a peak expressed by 2θ=21.6°±0.5°.

6. I ０２０／１１０ The separator according to claim 1, wherein the molecular weight is 2.8 to 5.

7.

7. The separator according to claim 1 , wherein the inorganic particle layer further comprises a binder.

8. 8. The separator according to claim 7, wherein the binder comprises at least one selected from the group consisting of ester-based polymers, amide-based polymers, imide-based polymers, acrylic-based polymers, acrylamide-based polymers, vinyl alcohol-based polymers, fluorine-based polymers, and vinylpyrrolidone-based polymers.

9. The separator according to claim 7, wherein the binder is contained in an amount of 0.1 to 20.0 parts by weight based on 100 parts by weight of the inorganic particles.

10. The inorganic particles have an average particle size (D ５０ 2. The separator according to claim 1, comprising inorganic particles having a particle size of 0.1 μm to 10.0 μm.

11. The inorganic particles have different average particle sizes (D ５０ 2. The separator of claim 1, comprising one or more inorganic particles having a molecular weight of 1.2 or more.

12. The inorganic particles have an average particle size (D ５０ 12. The separator according to claim 11, wherein the inorganic particles having a particle size of 0.10 μm to 0.54 μm and the inorganic particles having a particle size of 0.55 μm to 1.5 μm are mixed.

13. The separator according to claim 1, wherein the inorganic particle layer has a thickness of 0.1 μm to 10.0 μm.

14. The separator according to claim 1 , wherein the separator has a machine direction (MD) shrinkage rate of 5.0% or less after being left at 130° C. for 60 minutes.

15. The separator according to claim 1, wherein the porous substrate has a thickness of 1 μm to 50 μm.

16. 2. The separator according to claim 1, wherein the porous substrate has a Gurley permeability according to ASTM D726 of 50 s / 100 cc to 200 s / 100 cc.

17. The separator according to claim 1 , wherein the inorganic particles are boehmite.

18. An electrochemical element comprising the separator according to any one of claims 1 to 17.

19. The electrochemical device according to claim 18 , wherein the electrochemical device is a secondary battery.

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