Separator and electrochemical device comprising the same

Abstract

To provide a separator having pore diameters (D10, D50, D90) satisfying all of 180 nm≤D10≤350 nm, 380 nm≤D50≤650 nm, and 670 nm≤D90≤1000 nm.SOLUTION: A separator according to one embodiment has improved heat resistance by satisfying the predetermined pore diameter ranges, and a battery comprising the separator may have improved performance.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In an electrochemical element, 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] In order to improve the characteristics of the separator used in a battery, a multilayer separator is formed by laminating a porous polymer such as a polyolefin-based or polypropylene-based polymer, 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 a multilayer separator or a binder can improve various characteristics of the separator compared to a single-layer separator, but the thickness of the separator can increase, and the performance of the battery 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 performance of the battery 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 and adhesion.

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

Means for Solving the Problems

[0007] One embodiment provides a separator that satisfies all of the ranges of pore diameters (D10, D50, D90) of the following Formulas 1 to 3. 180 nm ≤ D10 ≤ 350 nm (Formula 1) 380 nm ≤ D50 ≤ 650 nm (Formula 2) 670 nm ≤ D90 ≤ 1000 nm (Formula 3)

[0008] Another embodiment provides an electrochemical element including the separator according to the one embodiment.

Effects of the Invention

[0009] The present disclosure relates to a separator that satisfies a range of a predetermined pore diameter. The separator according to one embodiment can improve the heat resistance of the separator and the performance of a battery including the same by satisfying the range of the predetermined pore diameter.

Modes for Carrying Out the Invention

[0010] 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 (comprising, including, containing)”, “including”, “containing”, or “having (having)”, it means that other components can be further included, rather than excluding other components, unless otherwise stated to the contrary, and does not exclude elements, materials, or processes not further listed.

[0011] The numerical ranges used in this specification include the lower limit value and the upper limit value, all values within that range, increments logically derivable from the form and width of the defined range, all of the limited values among them, and all possible combinations of the upper and lower limits of numerical ranges limited to different forms from each other. 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 interpreted as being described in this specification. Unless otherwise specifically defined in this specification, values outside the numerical ranges that may occur due to experimental errors or rounding of values are also included in the defined numerical ranges.

[0012] 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.

[0013] Hereinafter, unless otherwise specifically defined in this specification, "(meth)acryl" means acrylic and / or methacrylic.

[0014] Unless otherwise defined in this specification, the average particle diameter of the inorganic particles is D 50 means the value.

[0015] Unless otherwise defined in this specification, 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 is another part in between.

[0016] Unless otherwise defined herein, "polymer" means a molecule of relatively high molecular weight, the structure of which may include multiple repetitions of units derived from low molecular weight molecules. In one aspect, the polymer can be an alternating copolymer, a block copolymer, a random copolymer, a graft copolymer, a gradient copolymer, a branched copolymer, a crosslinked copolymer, or a copolymer that includes all of these (e.g., a polymer that includes more than one monomer). In other aspects, the polymer may be a homopolymer (e.g., a polymer that includes one type of monomer).

[0017] One embodiment provides a separator having high heat resistance and excellent adhesion between a porous substrate and an inorganic particle layer. Specifically, the separator according to one embodiment is characterized in that the pore diameters (diameters) D10, D50, and D90 all satisfy 180 nm ≤ D10 ≤ 350 nm, 380 nm ≤ D50 ≤ 650 nm, and 670 nm ≤ D90 ≤ 1000 nm. By satisfying the range of the predetermined pore diameters, the heat resistance of the separator according to one embodiment is improved, and during charging and discharging of a battery including the separator, 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.

[0018] The above effect is an effect due to the pore diameters (D10, D50, D90) of the separator all satisfying the predetermined range, and is not an effect affected only by a component of the separator or a specific element during the manufacturing process of the separator. As confirmed from one embodiment, the range of the pore diameters of the separator can be realized by various means including various factors such as the average particle diameter or weight ratio of the inorganic substance, the solid content of the slurry, and the coating speed, and there is no limitation on how the range of the pore diameters of the separator is realized.

[0019] Therefore, regardless of the manufacturing conditions of the separator, i.e., 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 the porous substrate, regardless of the electrolyte of the battery, and when the separator includes an inorganic particle layer, regardless of the average particle size, distribution, or combination of the inorganic substances contained in the inorganic particle layer, when the pore diameter range of the separator of the above-described embodiment is satisfied, the separator has excellent heat resistance, and the characteristics (life characteristics, charge / discharge characteristics, etc.) of the battery manufactured using the same are excellent.

[0020] In one embodiment, specifically, the pore diameter of the separator can satisfy all of the following formulas 1-1 to 3-1.

[0021] 200 nm ≤ D10 ≤ 350 nm (Formula 1-1) 400 nm ≤ D50 ≤ 650 nm (Formula 2-1) 700 nm ≤ D90 ≤ 950 nm (Formula 3-1).

[0022] Alternatively, the pore diameter of the separator may satisfy 220 nm ≤ D10 ≤ 330 nm, 230 nm ≤ D10 ≤ 330 nm, 230 nm ≤ D10 ≤ 320 nm, or 230 nm ≤ D10 ≤ 310 nm. Alternatively, the pore diameter of the separator may satisfy 400 nm ≤ D50 ≤ 630 nm, 400 nm ≤ D50 ≤ 620 nm, 400 nm ≤ D50 ≤ 610 nm, 400 nm ≤ D50 ≤ 600 nm, 410 nm ≤ D50 ≤ 590 nm, 450 nm ≤ D50 ≤ 600 nm, or 470 nm ≤ D50 ≤ 590 nm. Alternatively, the pore diameter of the separator may satisfy 710 nm ≤ D90 ≤ 950 nm, 720 nm ≤ D90 ≤ 940 nm, 730 nm ≤ D90 ≤ 930 nm, 740 nm ≤ D90 ≤ 930 nm, 750 nm ≤ D90 ≤ 920 nm, or 760 nm ≤ D90 ≤ 920 nm.

[0023] In one embodiment, the method for measuring the pore diameter is not necessarily limited to the measurement method described in this specification, and it is also possible to use a known method or any other method.

[0024] According to one embodiment, the pore diameter may be measured by a pore analysis method including the following steps. (S1) A step of impregnating the separator with a liquid grease and then taking it out and drying it; (S2) A step of staining the dried separator; (S3) A step of using a FIB / SEM (Focused ion beam-scanning electron microscope) apparatus to cut the cross-section of the separator at a predetermined interval and then obtaining a SEM image of the cross-section; (S4) A step of creating a three-dimensional separator image using the SEM image of the cross-section.

[0025] In one embodiment, after the step (S2), it may further include a step (S2-A) of forming a coating layer containing a transition metal on the surface of the stained separator, and the transition metal may include platinum (Pt), cobalt (Co), iron (Fe), nickel (Ni), palladium (Pd), ruthenium (Ru), titanium (Ti), vanadium (V), chromium (Cr), silver (Ag), cadmium (Cd), or oxides thereof.

[0026] In one embodiment, the step (S3) may include a step (S3-A) of forming a platinum (Pt) film on a predetermined region on the surface of the separator, a step (S3-B) of etching an outer region of the predetermined region where the platinum film is formed into a trench pattern, and a step (S3-C) of using a FIB / SEM (Focused ion beam-scanning electron microscope) apparatus to cut the cross-section of the separator at a predetermined interval and then obtaining a SEM image of the cross-section.

[0027] In one embodiment, after the step (S4), it may further include a step (S5) of selectively separating a ceramic inorganic particle image from the three-dimensional separator image to obtain a three-dimensional ceramic coating layer shape structure image.

[0028] In one embodiment, after the step (S5), it can further include a step (S6) of analyzing the pore size distribution of the pores in the ceramic coating layer from the three-dimensional ceramic coating layer shape structure image.

[0029] In one embodiment, the liquid oil and fat may be vegetable oil, animal oil, processed oil, waste oil, or a combination thereof.

[0030] The pore diameter described in this specification may mean the pore diameter of the inorganic particle layer.

[0031] In one embodiment, the separator may include a porous substrate and an inorganic particle layer including inorganic particles on at least one surface of the porous substrate. When the inorganic particle layer is formed on the porous substrate, the inorganic particle layer may be formed only on any one surface of the porous substrate or on both surfaces.

[0032] In one embodiment, the type of the inorganic particles included in the inorganic particle layer is not particularly limited as long as the inorganic particles are known to be electrochemically stable. For example, it may include any one or more of boehmite, BaSO4, CeO2, MgO, CaO, ZnO, Al2O3, TiO2, BaTiO3, HfO2, SrTiO3, SnO2, NiO, ZrO2, Y2O3, and / or SiC.

[0033] In one embodiment, the average particle size (D50) of the inorganic particles can be appropriately selected according to experimental conditions and purposes as long as the range of the average pore diameter of the separator according to one embodiment can be satisfied, and is not necessarily limited to a specific range. For example, the average particle size 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 1.0 μm.

[0034] Alternatively, the inorganic particles may be used by mixing one, two, three or more kinds of inorganic particles having different average particle sizes. 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 average particle size of the second inorganic particles is 0.55 μm to 1.0 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 a 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 mixed and used. For example, the inorganic particles may include 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.

[0035] In one embodiment, when using inorganic particles having two different average particle diameters, their weight ratio is not particularly limited. 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 in 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 in the above weight ratio. Here, the first inorganic particles and the second inorganic particles may be the same inorganic particles as each other, or different inorganic particles from each other.

[0036] In one embodiment, the inorganic particle layer may further include a binder. The binder may be appropriately selected according to the target situation from binders known to ordinary technicians in the technical field disclosed in the present application. In one embodiment, the binder may include a polymer. For example, it may include 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 include an acrylamide-based polymer. Or, for example, the binder may include 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. As long as the inorganic particles formed on the surface of the porous base material layer of the secondary battery separator are used as the binder of the inorganic particle layer in which the pores are formed by being connected to each other by the binder, there is no limitation.

[0037] In one embodiment, the content of the binder can 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 to 20.0 parts by weight, 0.1 to 15.0 parts by weight, 1.0 to 10.0 parts by weight, 1.0 to 5.0 parts by weight, or about 4.0 parts by weight based on 100 parts by weight of the inorganic particles.

[0038] 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 150,000 g / mol. However, this is only an example, and it may be appropriately selected according to the experimental conditions as long as the range of the surface roughness of the separator according to the present application can be satisfied. The weight average molecular weight may be measured by gel permeation chromatography (GPC). Specifically, the measurement of the weight average molecular weight is performed using GPC (manufactured by Tosoh Corporation, EcoSEC HLC-8320 GPC Refractive Index detector). The GPC column is Tskgel guard PWx, two TSKgel GMPWxl, and TSKgel G2500PWxl (7.8×300 mm). The developing solvent is an aqueous solution of 0.1 M NaNO3, the standard is polyethylene glycol, and the analysis may be performed at 40°C with a flow rate of 1 mL / min.

[0039] In one embodiment, the dispersant may be appropriately selected from known dispersants and is not necessarily limited to a specific dispersant. For example, acrylate polymers, urethane polymers, silicone polymers, modified acrylate polymers, etc. may be used. Specifically, for example, BYK-151, BYK-154, DISPERBYK, BYK-420, BYK-E 420, BYK 300 series, BYK-017, etc. may be used.

[0040] In one embodiment, the content of the dispersant 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 dispersant may be 0.01 parts by weight to 10.0 parts by weight, 0.1 parts by weight to 5.0 parts by weight, 0.1 parts by weight to 3.0 parts by weight, or 0.1 parts by weight to 2.0 parts by weight with respect to 100 parts by weight of the inorganic particles.

[0041] 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 use 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 (registered trademark), and / or polytetrafluoroethylene, and any two or more of these may be used.

[0042] In one embodiment, the thickness of the porous substrate is not particularly limited and may be, for example, 1 μm to 100 μm, 1 μm to 50 μm, 1 μm to 30 μm, 5 μm to 20 μm, or about 9 μm.

[0043] In one embodiment, the thickness of the inorganic particle layer that can be formed on either 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. 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 5.0 μm, or about 3.0 μm.

[0044] In one embodiment, after the separator is left at 150 °C for 60 minutes, the shrinkage rates in the machine direction (MD) and the transverse direction (TD) may all be 5.0% or less, where the lower limit may be 0.5%. 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, when the separator includes the inorganic particle layer, the change amount of the air permeability before and after coating the inorganic particle layer may be 10 s / 100 cc to 100 s / 100 cc, 10 s / 100 cc to 70 s / 100 cc, 20 s / 100 cc to 60 s / 100 cc, 20 s / 100 cc to 50 s / 100 cc, or 20 s / 100 cc to 40 s / 100 cc. The air permeability is the air permeability (Gurley permeability) measured according to ASTM D726.

[0046] In one embodiment, the moisture content of the separator after aging at 80 °C for 12 hours may be 300 ppm to 700 ppm, 300 ppm to 650 ppm, 350 ppm to 650 ppm, or 400 ppm to 600 ppm.

[0047] In one embodiment, the peel strength between the porous substrate and the inorganic particle layer measured according to ASTM D903 may be 30 gf / 15 mm or more, 50 gf / 15 mm or more, 60 gf / 15 mm or more, or 80 gf / 15 mm or more. Here, the upper limit may be 200 gf / 15 mm or less, 180 gf / 15 mm or less, 150 gf / 15 mm or less, 130 gf / 15 mm or less, or 110 gf / 15 mm or less.

[0048] By satisfying the pore diameter of the separator according to one embodiment within the range of the predetermined average pore diameter, the thermal shrinkage rate can be low, and the water content can be set at the most appropriate level for realizing the performance of the separator and the performance of the battery. As a result, the charge and discharge performance and life characteristics of the battery are excellently realized. If the pore diameter range of the separator is not satisfied, the water content of the separator is high, and during charge and discharge of the battery, a decrease in performance may occur due to side reactions caused by water, or the heat resistance of the separator may be low, or the battery resistance may be high, and the thermal stability and battery performance may not be fully realized.

[0049] When the separator according to one embodiment includes an inorganic particle layer, it may be manufactured from the steps of preparing a composition for forming an inorganic particle layer containing inorganic particles, and applying (or coating) the composition for forming an inorganic particle layer on at least one surface of the porous substrate and then drying to form the 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.

[0050] 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.

[0051] 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, 20 wt% to 50 wt%, 20 wt% to 40 wt%, 25 wt% to 35 wt%, or 30 wt% to 35 wt%.

[0052] 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. For example, roll coating, spin coating, dip coating, bar coating, die coating, slit coating, or inkjet printing may be used.

[0053] In one embodiment, the drying may be performed by drying with warm air, hot air, 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. 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.

[0054] As described above, the pore size range 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.

[0055] Another embodiment provides an electrochemical element including the separator according to the above embodiment, and the electrochemical element can be a secondary battery or a lithium secondary battery.

[0056] Hereinafter, the components of the secondary battery according to the present disclosure will be further described.

[0057] [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.

[0058] (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 or stainless steel surface-treated with silver. The positive electrode current collector is not limited thereto, and may be, for example, 10 μm to 50 μm.

[0059] (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.

[0060] 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).

[0061] The positive electrode active material may further include a coating element or a doping element. For example, an element 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.

[0062] 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.

[0063] 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.

[0064] In some embodiments, the cathode 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).

[0065] (Method for manufacturing the cathode) For example, the cathode active material may be mixed in a solvent to produce a cathode slurry. After coating the cathode slurry on a cathode current collector, it may be dried and rolled to produce a cathode 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 cathode mixture layer may further include a binder, and optionally, may further include a conductive material, a thickener, etc.

[0066] (Cathode solvent) Non-limiting examples of the solvent used in the production of the cathode mixture include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0067] (Cathode binder) The binder may include polyvinylidene fluoride (PVDF), polyvinylidene 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 cathode binder.

[0068] (Cathode conductive material) The conductive material may be added to enhance the conductivity of the cathode active material 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, but is not limited thereto.

[0069] (Cathode thickener / dispersant) Optionally, the cathode active material may further include a thickener and / or a dispersant, etc. In one embodiment, the cathode active material may include a thickener such as carboxymethyl cellulose (CMC).

[0070] [Anode] The anode may include an anode current collector and an anode active material layer disposed on at least one surface of the anode current collector.

[0071] (Anode 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, but may be, for example, 10 to 50 μm.

[0072] (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 composites, and carbon fibers, lithium metal, lithium alloys, silicon (Si)-containing substances, or tin (Sn)-containing substances may be used.

[0073] Examples of the amorphous carbon include hard carbon, soft carbon, coke, mesocarbon microbeads (MCMB), and mesophase pitch-based carbon fibers (MPCF).

[0074] Examples of the crystalline carbon include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, and graphitized MPCF.

[0075] Examples of the lithium metal include pure lithium metal and 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.

[0076] Examples of the elements included in the lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.

[0077] 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.

[0078] (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 may 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.

[0079] 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.

[0080] (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.

[0081] (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.

[0082] In some embodiments, as the negative electrode binder, a styrene-butadiene rubber (SBR) - based binder, carboxymethyl cellulose (CMC), polyacrylic acid - based binder, poly(3,4 - ethylenedioxythiophene) (PEDOT) - based binder, etc. may be used.

[0083] [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.

[0084] [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.

[0085] (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 - wherein, as the anion (X - ) of the lithium salt, 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 - etc. can be mentioned.

[0086] The organic solvent may include an organic compound that has sufficient solubility in the lithium salt and the additive and has 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.

[0087] (Additive) The non-aqueous electrolyte may further contain an additive. The additive may include, for example, a cyclic carbonate compound, a fluorine-substituted carbonate compound, a sultone compound, a cyclic sulfate compound, a cyclic sulfite compound, a phosphate compound, and a borate compound. The cyclic carbonate compound may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and the like. The fluorine-substituted cyclic carbonate compound may include fluoroethylene carbonate (FEC), and the like. The sultone compound may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, and the like. The cyclic sulfate compound may include 1,2-ethylene sulfate, 1,2-propylene sulfate, and the like. The cyclic sulfite compound may include ethylene sulfite, butylene sulfite, and the like. The phosphate compound may include lithium difluoro bis-oxalato phosphate, lithium difluoro phosphate, and the like. The borate compound may include lithium bis(oxalate)borate, and the like.

[0088] Hereinafter, examples and experimental examples will be specifically illustrated and described below. However, the examples and experimental examples described later are illustrative of a part of one embodiment, and the technology described in this specification should not be construed as being limited thereto.

[0089] <Experimental Method> 1. Measurement of average pore diameter (D10, D50, D90) After cutting the manufactured separator into a size of approximately 3 cm × 2 cm, a small amount of butter was placed in a vial, heated to a liquid state at 60 °C, impregnated, then placed in a vacuum oven, left for about 60 minutes at 60 °C under vacuum conditions, taken out, wiped off the excess butter attached to the outside of the separator, and dried at room temperature for 30 minutes or more. Next, the separator was placed in a chamber with an OsO4 gas atmosphere and the butter region was stained for 18 hours.

[0090] After attaching the stained separator to a stub for SEM (Scanning electron microscope) analysis, the surface of the separator was coated with a Pt coater (50 mA, 60 sec). After placing the coated separator in a FIB / SEM (Focused ion beam-scanning electron microscope) equipped with continuous cutting and imaging capabilities, Pt evaporation was performed on the surface of the separator in regions of 10 μm × 10 μm × 2 μm each under the conditions of 30 kV, 0.4 - 0.9 nA, and Rectangle pattern to form a Pt film. Next, after cutting the cross-section at intervals of 10 nm, a SEM image of the cross-section was obtained (software: Auto Slice An View, Thermo Fisher Scientific TM ). The obtained image was processed with image processing software (Avizo, Thermo Fisher Scientific TM) was connected to create a three-dimensional image of the separator. Inorganic particles were selectively separated from the three-dimensional image obtained using the software GeoDict of Math2Market GmbH to create the three-dimensional shape structure of the separator. Next, the pores in the inorganic particle layer were evaluated using the Identify Pore function of GeoDict. Here, the critical value was set to 25% to classify overlapping pores, and pores adjacent to the boundary surface of the three-dimensional structure were excluded from the evaluation to selectively evaluate only the pores in the inorganic particle layer. The pore diameter was evaluated after converting it to the Volume-Equivalent Diameter.

[0091] 2. Measurement of Thermal Shrinkage Rate The thermal shrinkage rate was measured as follows in accordance with ASTM D1204. The manufactured separator was cut into a square shape with sides of 10 cm, and lattice points were marked at 2 cm intervals. Here, one side of the square was the transverse direction (TD), and the other side was the machine direction (MD). The test piece was placed in the center, and seven sheets of paper were placed on top and bottom of the test piece, and the four sides of the paper were wrapped with tape. The test piece wrapped in paper was left in a hot air drying oven at a temperature of 150 °C for 60 minutes. Then, the test piece was taken out, and the separator was observed with a camera, and the shrinkage rate in the machine direction (MD) of the following Mathematical Formula 1 and the shrinkage rate in the transverse direction (TD) of the following Mathematical Formula 2 were calculated.

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

[0093] [Mathematical Formula 2] Shrinkage rate in the transverse direction (TD) (%) = (Length in the transverse direction before heating - Length in the transverse direction after heating) × 100 / Length in the transverse direction before heating

[0094] 3. Measurement of Air Permeability Using a densometer (Toyoseiki Ltd.), in accordance with ASTM D726 standard, the air permeability (Gurley permeability) of the separator before and after coating was measured respectively, and the change value was measured. The air permeability was recorded in seconds, which is the time taken for 100 cc of air to pass through an area of 1 square inch of the separator.

[0095] 4. Measurement of Peel Strength Using a tensile testing device (3343) from INSTRON GmbH, the peel strength between the porous substrate and the inorganic particle layer was measured by the 180-degree peel test method (ASTM D903).

[0096] 5. Measurement of Moisture Content The moisture content of the separator was measured by utilizing the Karl Fischer method. Specifically, using a Karl Fischer Titrator (Metrohm Inc.), the moisture content was measured using the weight of the moisture generated when heating 0.3 g of the separator sample at 150 °C.

[0097] 6. Measurement of Battery Resistance After aging and degassing the battery, it was buffered up to 4.2 V, and the initial resistance of the battery was measured by the J-pulse method.

[0098] 7. Measurement of Thickness Thickness of the separator: After stacking 10 separators, at 5 arbitrary points in the width direction, the thickness was measured using a thickness gauge 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.

[0099] 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 gauge manufactured by Mitutoyo, then deriving the average thickness of the 10-layer porous film, and further dividing by 10 to obtain the average thickness of a single porous substrate.

[0100] Thickness of the inorganic particle layer: Derived by calculation as the value obtained by subtracting the average thickness of the single porous film from the overall average thickness of the single separator determined by the above method.

[0101] <Example 1> Manufacture of the separator Boehmite with average particle sizes (D50) of 0.35 μm and 0.75 μm respectively was added to distilled water at a weight ratio of 7:3. To the weight of the boehmite, 1 wt% of a dispersant (BYK-154) and 4 wt% of a polyacrylamide-based binder were added, and the mixture was stirred with a ball mill to produce a slurry with a solid content of 32 wt%.

[0102] A polyethylene porous film with a thickness of 9 μm (porosity: 40%, Gurley permeability: 160 s / 100 cc, tensile strength MD: 2240 kgf / cm 2 , TD: 1860 kgf / cm 2 ) was subjected to corona discharge treatment on both sides (power density: 2 W / mm, speed: about 3 - 5 mpm (meter per minute)) to introduce surface polar groups. Subsequently, the slurry produced above was coated on both sides of the surface-treated porous film, and then left standing at room temperature for 10 minutes. Thereafter, it was dried in a dryer at 65 °C for 3 minutes to form inorganic particle layers with a thickness of 1.5 μm each, and then aged at 80 °C for 12 hours.

[0103] Manufacture of the battery 94 wt% of LiCoO2 as the positive electrode active material, 2.5 wt% of polyvinylidene fluoride as the binder, 3.5 wt% of carbon black as the conductive material were added to NMP (N-methyl-2-pyrrolidone) as the solvent and stirred to produce a uniform positive electrode slurry. The slurry was coated, dried and crimped onto an aluminum foil with a thickness of 30 μm to produce a positive electrode plate with a thickness of 150 μm.

[0104] As a negative electrode active material, 95% by weight of artificial graphite, 3% by weight of an acrylic latex (Acrylic latex, solid content 20% by weight) with a Tg of -52°C as a binder, and 2% by weight of CMC (Carboxymethyl cellulose) as a thickener were added to water as a solvent and stirred to produce a uniform negative electrode slurry. The slurry was coated on a copper foil with a thickness of 20 μm, dried, and pressed to produce a negative electrode plate with a thickness of 150 μm.

[0105] A pouch-type battery was assembled in a stacking manner using the separator manufactured as described above between the positive electrode and the negative electrode manufactured as described above, and an electrolyte in which 1 M of lithium hexafluorophosphate (LiPF6) was dissolved in ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) = 3:5:2 (volume ratio) was injected to produce a lithium secondary battery with a capacity of 2 Ah.

[0106] <Example 2> A battery was manufactured in the same manner as in Example 1, except that inorganic particles with average particle diameters (D50) of 0.35 μm and 0.75 μm, respectively, were used in a weight ratio of 1:1 in the manufacture of the separator of Example 1.

[0107] <Example 3> A battery was manufactured in the same manner as in Example 1, except that inorganic particles with average particle diameters (D50) of 0.35 μm and 0.75 μm, respectively, were used in a weight ratio of 3:7 in the manufacture of the separator of Example 1.

[0108] <Example 4> A battery was manufactured in the same manner as in Example 1, except that inorganic particles with an average particle diameter (D50) of 0.4 μm were used in the manufacture of the separator of Example 1.

[0109] <Comparative Example 1> Manufacture of separator To distilled water, boehmite with an average particle size (D50) of 0.2 μm and 2 wt% of a dispersant (BYK-154) based on the weight of the boehmite were added, and after stirring with a bead mill (200 rpm, 10 minutes), 4 wt% of a polyacrylamide-based binder based on the weight of the boehmite was added, followed by further stirring with a ball mill to produce a slurry with a solid content of 45 wt%.

[0110] A polyethylene porous film with a thickness of 9 μm (porosity: 40%, Gurley permeability: 160 s / 100 cc, tensile strength MD: 2240 kgf / cm 2 , TD: 1860 kgf / cm 2 ) was subjected to corona discharge treatment on both sides (power density: 2 W / mm, speed: about 3 - 5 mpm (meter per minute)) to introduce surface polar groups. Next, the slurry produced above was coated on both sides of the surface-treated porous film, and then left standing at room temperature for 10 minutes. Thereafter, it was dried in a dryer at 45 °C for 10 minutes to form an inorganic particle layer with a thickness of 1.5 μm each, and then aged at 100 °C for 12 hours.

[0111] Manufacture of battery A battery was manufactured in the same manner as in Example 1 above.

[0112] <Comparative Example 2> Manufacture of separator To distilled water, 0.7 wt% of a dispersant (BYK-154) based on the weight of boehmite was added, and then boehmite with an average particle size (D50) of 1.6 μm and 4 wt% of a polyacrylamide-based binder based on the weight of the boehmite were added, followed by stirring with a ball mill to produce a slurry with a solid content of 32 wt%.

[0113] A polyethylene porous film with a thickness of 9 μm (porosity: 40%, Gurley permeability: 160 s / 100 cc, tensile strength MD: 2240 kgf / cm 2 , TD: 1860 kgf / cm 2Both sides of ) were subjected to corona discharge treatment (power density: 2 W / mm, speed: approximately 3 - 5 mpm (meter per minute)) to introduce surface polar groups. Subsequently, the produced slurry was coated on both sides of the surface-treated porous film, and then left standing at room temperature for 10 minutes. Next, it was dried in a dryer at 45°C for 10 minutes to form inorganic particle layers with a thickness of 2.2 μm each, and then aged at 80°C for 12 hours.

[0114] Manufacture of battery A battery was manufactured in the same manner as in Example 1.

[0115] <Comparative Example 3> To distilled water, a dispersant (BYK - 154) at 1.5 wt% based on the weight of boehmite and boehmite with an average particle size (D50) of 0.3 μm were added, and after bead mill stirring (200 rpm, 10 minutes), a polyacrylamide-based binder at 4 wt% based on the weight of the boehmite was added, and then further ball mill stirred to produce a slurry with a solid content of 32 wt%.

[0116] Both sides of a 9 - μm thick polyethylene porous film (porosity: 40%, Gurley permeability: 160 s / 100 cc, tensile strength MD: 2240 kgf / cm 2 , TD: 1860 kgf / cm 2 ) were subjected to corona discharge treatment (power density: 2 W / mm, speed: approximately 3 - 5 mpm (meter per minute)) to introduce surface polar groups. Subsequently, the produced slurry was coated on both sides of the surface-treated porous film, and then left standing at room temperature for 10 minutes. Next, it was dried in a dryer at 45°C for 10 minutes to form inorganic particle layers with a thickness of 1.5 μm each, and then aged at 100°C for 12 hours.

[0117] Manufacture of battery A battery was manufactured in the same manner as in Example 1.

[0118] <Comparative Example 4> To distilled water, a dispersant (BYK-154) at 0.7 wt% based on the weight of boehmite and boehmite with average particle sizes (D50) of 0.5 μm and 1.3 μm respectively were added at a weight ratio of 1:1, and after bead mill stirring (200 rpm, 10 minutes), a polyacrylamide-based binder at 4 wt% based on the weight of the boehmite was added, followed by further ball mill stirring to produce a slurry with a solid content of 32 wt%.

[0119] A polyethylene porous film with a thickness of 9 μm (porosity: 40%, Gurley permeability: 160 s / 100 cc, tensile strength MD: 2240 kgf / cm 2 , TD: 1860 kgf / cm 2 ) was subjected to corona discharge treatment on both sides (power density: 2 W / mm, speed: about 3 - 5 mpm (meter per minute)) to introduce surface polar groups. Next, the slurry produced above was coated on both sides of the surface-treated porous film, and then left standing at room temperature for 10 minutes. Then, it was dried in a dryer at 45 °C for 10 minutes to form an inorganic particle layer with a thickness of 1.5 μm each, and then aged at 100 °C for 12 hours.

[0120] Manufacture of the battery A battery was manufactured in the same manner as in Example 1 above.

[0121] <Comparative Example 5> To distilled water, a dispersant (BYK-154) at 0.7 wt% based on the weight of boehmite and boehmite with average particle sizes (D50) of 0.2 μm and 0.5 μm respectively were added at a weight ratio of 2:8, and after bead mill stirring (200 rpm, 10 minutes), a polyacrylamide-based binder at 4 wt% based on the weight of the boehmite was added, followed by further ball mill stirring to produce a slurry with a solid content of 32 wt%.

[0122] A polyethylene porous film with a thickness of 9 μm (porosity: 40%, Gurley permeability: 160 s / 100 cc, tensile strength MD: 2240 kgf / cm 2 , TD: 1860 kgf / cm 2Both sides of ) were subjected to corona discharge treatment (power density: 2 W / mm, speed: about 3 - 5 mpm (meter per minute)) to introduce surface polar groups. Next, the manufactured slurry was applied onto both surfaces of the surface-treated porous film, and then left standing at room temperature for 10 minutes. Next, it was dried in a dryer at 45°C for 10 minutes to form inorganic particle layers each with a thickness of 1.5 μm, and then aged at 100°C for 12 hours.

[0123] Manufacture of battery A battery was manufactured in the same manner as in Example 1 above.

[0124] The average pore diameters (D10, D50, D90) and physical properties of the separators manufactured in the above Examples and Comparative Examples, and the resistance of the batteries were measured, and the results are shown in Tables 1 and 2 below.

[0125]

Table 1

[0126]

Table 2

[0127] As can be confirmed from Tables 1 and 2 above, for the separators of the Examples that all satisfy the range of the average pore diameter of the separator being D10 200 nm - 350 nm, D50 400 nm - 650 nm, and D90 700 nm - 950 nm, the thermal stability is significantly superior to that of the Comparative Examples, the adhesion of the inorganic particle layer to the porous base material is excellent, and the stability is high. On the other hand, if any one of the ranges of the average pore diameter of the separator is not satisfied, the moisture content is excessively high at 700 ppm or more, and during charging and discharging of the battery, the battery resistance increases due to side reactions caused by moisture (Comparative Examples 1, 5), or the thermal stability of the separator significantly decreases (Comparative Example 2), or the adhesion between the porous base material and the inorganic particle layer is not sufficient, making it difficult to achieve the stability of battery performance (Comparative Examples 1 - 5).

[0128] Although the above has been described in detail with reference to examples and experimental examples for one embodiment, the scope of one embodiment is not limited to specific examples and must be construed by the appended claims.

Claims

1. A porous substrate and an inorganic particle layer comprising inorganic particles on at least one surface of the porous substrate, A separator that satisfies all of the following equations 1 to 3, when the pore diameters D10, D50, and D90 are D10, D50, and D90, respectively. 180nm≦D10≦350nm (Formula 1) 380nm≦D50≦650nm (Formula 2) 670nm≦D90≦1000nm (Formula 3)

2. The separator according to claim 1, wherein the pore diameter of the separator satisfies all of the following formulas 1-1 to 3-1. 200nm≦D10≦350nm (Formula 1-1) 400nm≦D50≦650nm (Formula 2-1) 700nm≦D90≦950nm (Formula 3-1)

3. The inorganic particles are boehmite, BaSO ４ , CeO ２ , MgO, CaO, ZnO, Al ２ O ３ , TiO ２ , BaTiO ３ , HfO ２ , SrTiO ３ , SnO ２ , NiO, ZrO ２ , Y ２ O ３ and the separator according to claim 1, comprising one or more selected from the group consisting of SiC.

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

5. The separator according to claim 4, wherein the binder comprises one or more selected from the group consisting of ester polymers, amide polymers, imide polymers, acrylic polymers, acrylamide polymers, vinyl alcohol polymers, fluorine polymers, and vinylpyrrolidone polymers.

6. The separator according to claim 1, wherein the inorganic particles include inorganic particles having an average particle size (D50) of 0.1 μm to 10.0 μm.

7. The separator according to claim 1, wherein the inorganic particles include one or more inorganic particles having different average particle sizes (D50).

8. The separator according to claim 7, wherein the inorganic particles are a mixture of inorganic particles having an average particle size (D50) of 0.10 μm to 0.54 μm and inorganic particles having an average particle size (D50) of 0.55 μm to 1.0 μm.

9. The separator according to claim 1, wherein the thickness of the inorganic particle layer is 0.1 μm to 10.0 μm.

10. The separator according to claim 1, wherein, after being left at 150°C for 60 minutes, the shrinkage rate in the mechanical direction (MD) and the width direction (TD) is 5.0% or less in all directions.

11. The separator according to claim 1, wherein the peeling force between the porous substrate and the inorganic particle layer, as measured in accordance with ASTM D903, is 50 gf / 15 mm or more.

12. The separator according to claim 1, wherein the thickness of the porous substrate is 1 μm to 50 μm.

13. A porous substrate and an inorganic particle layer comprising inorganic particles on at least one surface of the porous substrate, An electrochemical element including a separator that satisfies all of the following equations 1 to 3, when the pore diameters of the separator are D10, D50, and D90, respectively. 180nm≦D10≦350nm (Formula 1) 380nm≦D50≦650nm (Formula 2) 670nm≦D90≦1000nm (Formula 3)

14. The electrochemical element according to claim 13, wherein the electrochemical element is a secondary battery.