Separator and electrochemical device including the same

Abstract

The invention relates to a diaphragm of which the pore diameters (D10, D50 and D90) respectively meet the requirements that D10 is more than or equal to 180nm and less than or equal to 350nm, D50 is more than or equal to 380nm and less than or equal to 650nm, and D90 is more than or equal to 670nm and less than or equal to 1000nm. The separator according to one embodiment of the present invention satisfies the prescribed pore diameter range, thereby improving the heat resistance of the separator, and improving the performance of a battery including the separator.

Description

Technical Field

[0001] The present invention relates to a separator and an electrochemical device including the separator. 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. Therefore, a battery with excellent performance can be manufactured by improving the characteristics of the separator.

[0003] To improve the characteristics of the separator for a battery, a multi-layer separator formed by laminating porous polymers such as polyolefins or polypropylenes, or a separator formed by using a porous polymer as a substrate and mixing adhesives and inorganic particles, etc. to form a coating is being developed. Compared with a single-layer separator, the multi-layer separator or the coating mixed with adhesives, etc. can improve various characteristics of the separator, but the thickness of the separator may increase, and due to reduced low permeability, wettability, and impregnation, the performance of the battery may instead be reduced. To solve the above problems, research is being conducted to manufacture a separator whose various characteristics are sufficient for the separator of a battery, and which is thin while also satisfying mechanical stability and chemical stability, thereby improving the performance of the battery. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] An object of a specific embodiment is to provide a separator having excellent heat resistance and adhesiveness.

[0006] Another object of a specific embodiment is to provide an electrochemical device including the separator.

[0007] (II) Technical Solutions

[0008] A specific embodiment provides a separator that satisfies the pore size (D10, D50, D90) ranges of the following Formula 1 to Formula 3.

[0009] 180 nm ≤ D10 ≤ 350 nm (Formula 1)

[0010] 380 nm ≤ D50 ≤ 650 nm (Formula 2)

[0011] 670 nm ≤ D90 ≤ 1000 nm (Formula 3)

[0012] Another specific embodiment provides an electrochemical device including the separator according to the above specific embodiment.

[0013] (III) Advantageous Effects

[0014] The present invention relates to a separator that satisfies a specified pore diameter range. The separator according to a specific embodiment satisfies the above-specified pore diameter range, thereby improving the heat resistance of the separator and the performance of a battery including the separator. Detailed Description

[0015] The embodiments described in this specification can be modified into various other embodiments, and thus the technology according to a specific embodiment is not limited to the embodiments described below. Further, throughout the specification, unless otherwise specifically stated to the contrary, the description of "comprising" or "including (comprising, including, containing)", "having", "containing" or "having (having)" a certain component means that other components can also be included, rather than excluding other components, and does not exclude elements, materials or processes not further listed.

[0016] The numerical ranges used in this specification include the lower limit value and the upper limit value and all values within that range, increments logically derived from the form and width of the defined range, all values defined therein, and all possible combinations of the upper and lower limits of numerical ranges defined in different forms from each other. As an example, when the composition content is defined as 10% to 80% or 20% to 50%, the numerical ranges of 10% to 50% or 50% to 80% should be interpreted as also being described in this specification. In this specification, unless otherwise specifically defined, values outside the numerical range that may occur due to experimental error or rounding of values are also included in the defined numerical range.

[0017] Hereinafter, unless otherwise specifically defined in this specification, "about" may mean a value within 30%, 25%, 20%, 15%, 10%, 5%, 3%, 2%, 1% or 0.5% of the specified value.

[0018] Hereinafter, unless otherwise specifically defined in this specification, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid.

[0019] In this specification, unless otherwise specified, the average particle size of the inorganic particles refers to the D50 value.

[0020] In this specification, unless otherwise specified, when describing that a part such as a layer, film, thin film, region, plate, etc. is "on" or "above" another part, this includes not only the case of being "directly" "on" another part, but also the case of having other parts in between.

[0021] In this specification, unless otherwise specified, "polymer" refers to 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 embodiment, the polymer may 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 containing all of these copolymers (e.g., a polymer containing more than one monomer). In another embodiment, the polymer may be a homopolymer (e.g., a polymer containing one monomer).

[0022] A specific 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 a specific embodiment is characterized in that the pore sizes (diameters) D10, D50, and D90 all satisfy 180 nm ≤ D10 ≤ 350 nm, 380 nm ≤ D50 ≤ 650 nm, and 670 nm ≤ D90 ≤ 1000 nm. The separator according to a specific embodiment satisfies the specified pore size range, thereby improving the heat resistance of the separator. In a battery including the separator, lithium ions can move uniformly during charge and discharge. At the same time, it is first recognized that the problem of side reactions caused by moisture can be effectively suppressed, and thus the separator is developed.

[0023] The above effects are due to the fact that the pore diameters (D10, D50, D90) of the separator all satisfy the above-specified range, rather than being affected only by any specific element in the components of the separator or the manufacturing process of the separator. As confirmed in one embodiment, the pore size range of the separator can be achieved in various ways including various factors such as the average particle size or weight ratio of the inorganic substance, the solid content of the slurry, the coating speed, etc. Therefore, there is no limitation on how to achieve the pore diameter range of the separator.

[0024] 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 preparation step, whether a smoothing bar is used, what the drying temperature is, what the porous substrate is, what the electrolyte of the battery is, and how the average particle size or distribution or combination of the inorganic substances contained in the inorganic particle layer is if the separator includes an inorganic particle layer, when the pore diameter range of the separator according to the above specific embodiment is satisfied, the separator has excellent heat resistance, and the characteristics (life characteristics, charge and discharge characteristics, etc.) of the battery manufactured using the separator are excellent.

[0025] In one embodiment, the pore diameters of the separator may specifically all satisfy the following formulas 1-1 to 3-1.

[0026] 200 nm ≤ D10 ≤ 350 nm (Equation 1-1)

[0027] 400 nm ≤ D50 ≤ 650 nm (Equation 2-1)

[0028] 700 nm ≤ D90 ≤ 950 nm (Equation 3-1)

[0029] Alternatively, the pore diameter of the diaphragm 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 diaphragm 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 diaphragm 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.

[0030] In one embodiment, the method for measuring the pore diameter is not necessarily limited to the measurement methods described in this specification, and known methods or any other methods may also be used.

[0031] According to one embodiment, the pore diameter can be measured by a pore analysis method including the following steps: (S1) immersing the diaphragm in liquid-phase grease, taking it out, and drying; (S2) dyeing the dried diaphragm; (S3) cutting the cross-section of the diaphragm at a prescribed interval using a Focused ion beam-scanning electron microscope (FIB / SEM) device to obtain a cross-section SEM image; and (S4) producing a three-dimensional diaphragm image using the cross-section SEM image.

[0032] In one embodiment, after the step (S2), a step (S2-A) of forming a coating containing a transition metal on the surface of the dyed diaphragm may be further included, 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 their oxides.

[0033] In one embodiment, the step (S3) may include the following steps: (S3-A) forming a platinum (Pt) film in a prescribed region on the surface of the diaphragm; (S3-B) etching an outer region of the prescribed region where the platinum film is formed in a trench pattern; and (S3-C) obtaining a cross-sectional SEM image by cutting the cross-section of the diaphragm at prescribed intervals using a focused ion beam scanning electron microscope (FIB / SEM) device.

[0034] In one embodiment, after the step (S4), it may further include the step (S5) of selectively separating the ceramic inorganic particle image from the three-dimensional diaphragm image to obtain a three-dimensional ceramic coating shape structure image.

[0035] In one embodiment, after the step (S5), it may further include the step (S6) of analyzing the size distribution of the pores in the ceramic coating in the three-dimensional ceramic coating shape structure image.

[0036] In one embodiment, the liquid-phase grease may be vegetable grease, animal grease, processed grease, waste oil, or a combination thereof.

[0037] The pore size described in this specification may refer to the pore size of the inorganic particle layer.

[0038] In one embodiment, the diaphragm may include a porous substrate and an inorganic particle layer containing 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 either one surface or both surfaces of the porous substrate.

[0039] In one embodiment, the type of the inorganic particles contained in the inorganic particle layer is not particularly limited as long as they are known to be electrochemically stable inorganic particles. For example, they may be inorganic particles containing any one or more of boehmite, BaSO4, CeO2, MgO, CaO, ZnO, Al2O3, TiO2, BaTiO3, HfO2, SrTiO3, SnO2, NiO, ZrO2, Y2O3, and / or SiC.

[0040] In one embodiment, the average particle size (D50) of the inorganic particles may be appropriately selected according to experimental conditions and purposes as long as it can satisfy the average pore diameter range of the diaphragm according to a specific embodiment, and is not limited to a specific range. For example, the average particle size of the inorganic particles may be from 0.01 μm to 10.0 μm. Or, it may be from 0.01 μm to 5.0 μm, from 0.1 μm to 10.0 μm, from 0.1 μm to 5.0 μm, from 0.1 μm to 3.0 μm, or from 0.1 μm to 1.0 μm.

[0041] Alternatively, the inorganic particles may be a mixture of one, two, three or more inorganic particles having different average particle sizes from each other. 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 may be used in combination; the second inorganic particles having an average particle size of 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 may be used in combination; 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 include the first inorganic particles and the second inorganic particles, or may include the first inorganic particles and the third inorganic particles. At this time, 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.

[0042] In one embodiment, when using two inorganic particles having different average particle sizes from each other, their weight ratio is not particularly limited. However, for example, they may be mixed in a ratio of 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 merely an example, and thus the inorganic particles do not necessarily have to be mixed in the above weight ratios. At this time, 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.

[0043] In one embodiment, the inorganic particle layer may further comprise an adhesive. Regarding the adhesive, those skilled in the art can appropriately select known adhesives according to the purpose and circumstances. In one embodiment, the adhesive may comprise a polymer, for example, it may comprise any one or more selected from 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 adhesive may comprise an acrylamide-based polymer. Alternatively, for example, the adhesive may comprise a polymer prepared from any one or more monomers selected from (meth)acrylamide-based monomers, (meth)acrylic acid-based monomers containing a hydroxyl group, and / or polyfunctional (meth)acrylamide-based monomers, and the adhesive is not limited as long as it is used as an adhesive for forming an inorganic particle layer that connects inorganic particles formed on the surface of the porous substrate layer of the secondary battery separator to form pores.

[0044] In one embodiment, the content of the adhesive can be appropriately adjusted according to the circumstances and purpose within the range that satisfies the average pore diameter range of the separator. For example, relative to 100 parts by weight of the inorganic particles, the content of the adhesive 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 4.0 parts by weight.

[0045] In one embodiment, the weight-average molecular weight (Mw) of the binder (or the polymer contained in the binder) can be 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 merely an example and can be appropriately selected according to the experimental conditions that can satisfy the surface roughness range of the separator according to the present application. The weight-average molecular weight can be measured by gel permeation chromatography (GPC). Specifically, the measurement of the weight-average molecular weight can utilize GPC (EcoSEC HLC-8320 GPC refractive index detector of Tosoh Corporation), the GPC column uses Tskgel guard PWx, 2 TSKgel GMPWxl, and TSKgel G2500PWxl (7.8×300 mm), the eluent uses 0.1 M aqueous NaNO3 solution, the standard is polyethylene glycol, and the analysis can be carried out at 40 °C with a flow rate of 1 mL / minute.

[0046] In one embodiment, the dispersant can be appropriately selected and used from known dispersants and does not have to be limited to a specific dispersant. For example, acrylate-based polymers, urethane-based polymers, silicone-based polymers, modified acrylate-based polymers, etc. can be used. Specifically, for example, BYK-151, BYK-154, DISPERBYK, BYK-420, BYK-E 420, BYK 300 series, BYK-017, etc. can be used.

[0047] In one embodiment, the content of the dispersant can be appropriately adjusted according to circumstances and purposes within the range that satisfies the average pore diameter range of the separator. For example, relative to 100 parts by weight of the inorganic particles, the content of the dispersant can be 0.01 part by weight to 10.0 parts by weight, 0.1 part by weight to 5.0 parts by weight, 0.1 part by weight to 3.0 parts by weight, or 0.1 part by weight to 2.0 parts by weight.

[0048] In one embodiment, the porous substrate is not limited as long as it is a porous substrate commonly used in the art. For example, it can be a woven fabric, a non-woven fabric, or a porous membrane. Specifically, the porous substrate can be made of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ether ketone, polyarylether ketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cycloolefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon and / or polytetrafluoroethylene, and any two or more of them can be used.

[0049] In one embodiment, the thickness of the porous substrate is not particularly limited. For example, it can 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.

[0050] In one embodiment, the thickness of the inorganic particle layer that can be formed on either side of the porous substrate can 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. If the inorganic particle layer is formed on both sides of the porous substrate, its thickness can 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.

[0051] In one embodiment, the shrinkage rates in the machine direction (MD) and the transverse direction (TD) of the separator after being placed at 150 °C for 60 minutes can both be 5.0% or less, and at this time, the lower limit can be 0.5%. Specifically, the shrinkage rate can be 0.5% to 5.0%, 1.0% to 4.0%, or 1.0% to 3.0%.

[0052] In one embodiment, when the separator contains the inorganic particle layer, the change in air permeability before and after coating the inorganic particle layer can be 10 seconds / 100 mL to 100 seconds / 100 mL, 10 seconds / 100 mL to 70 seconds / 100 mL, 20 seconds / 100 mL to 60 seconds / 100 mL, 20 seconds / 100 mL to 50 seconds / 100 mL, or 20 seconds / 100 mL to 40 seconds / 100 mL. The air permeability is the air permeability (Gurley air permeability) measured according to ASTM D726.

[0053] In one embodiment, the moisture content of the separator after aging at 80 °C for 12 hours can be 300 ppm to 700 ppm, 300 ppm to 650 ppm, 350 ppm to 650 ppm, or 400 ppm to 600 ppm.

[0054] In one embodiment, the peel strength between the porous substrate and the inorganic particle layer measured according to ASTM D903 can 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. At this time, the upper limit can 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.

[0055] The pore diameter size of the separator according to one embodiment satisfies the above-specified average pore diameter range, so that the thermal shrinkage rate is low and the moisture content can be at a level most suitable for achieving separator performance and battery performance. Thereby, excellent charge and discharge performance and life characteristics of the battery are achieved. If the pore diameter range of the separator is not satisfied, the moisture content of the separator is high, so that performance degradation may occur due to side reaction problems caused by moisture during charge and discharge of the battery, or thermal stability and battery performance may not be fully achieved due to low heat resistance of the separator or high battery resistance.

[0056] When the separator according to one embodiment includes an inorganic particle layer, it can be prepared by the following steps: preparing a composition for forming an inorganic particle layer containing inorganic particles; and coating (or applying) the composition for forming an inorganic particle layer on at least one surface of the porous substrate and then drying to form an inorganic particle layer. In addition, 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 can be performed by introducing polar groups to the surface through corona discharge treatment.

[0057] In one embodiment, the solvent used in the composition for forming the inorganic particle layer is not particularly limited. When the composition contains a binder, a solvent that is easily soluble or dispersible in the binder can be selected. For example, water, acetone, ethanol, tetrahydrofuran, dichloromethane, trifluoromethane, cyclohexane, dimethylformamide, and / or N-methyl-2-pyrrolidone can be used.

[0058] In one embodiment, the composition for forming the inorganic particle layer can be a slurry, and the solid content of the slurry can be, for example, 20 wt% to 50 wt%, 20 wt% to 40 wt%, 25 wt% to 35 wt%, or 30 wt% to 35 wt%.

[0059] In one embodiment, the method of coating or applying 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 can be used.

[0060] In one embodiment, the drying can be carried out by drying with warm air, hot air, low-humidity air, vacuum drying, irradiation methods such as far-infrared rays or electron rays, etc. The drying temperature is not particularly limited, and thus can be appropriately adjusted according to the experimental environment or purpose. For example, it can be 30°C to 120°C, 30°C to 100°C, 50°C to 80°C, 50°C to 70°C, or about 65°C. The drying time is not particularly limited, but can 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.

[0061] As described above, the pore diameter range of the separator according to one embodiment can be achieved in various ways, and thus can 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 preparation conditions of the slurry, the viscosity of the slurry, the drying conditions (temperature, speed), the coating speed, the flattening method using a smoothing bar, etc.

[0062] Another specific embodiment provides an electrochemical device including the separator according to one embodiment, and the electrochemical device can be a secondary battery or a lithium secondary battery.

[0063] Hereinafter, the components of the secondary battery according to the present invention will be further described.

[0064] [Positive electrode]

[0065] The positive electrode may include a positive electrode current collector and a positive electrode mixture layer provided on at least one surface of the positive electrode current collector.

[0066] (Positive electrode current collector)

[0067] The positive electrode current collector may contain stainless steel, nickel, aluminum, titanium, or their alloys. The positive electrode current collector may also contain aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. The thickness of the positive electrode current collector is not limited thereto, but for example, it can be 10 μm to 50 μm.

[0068] (Positive electrode material)

[0069] The positive electrode mixture layer may contain a positive electrode active material. The positive electrode active material may contain a compound capable of reversibly inserting and extracting lithium ions.

[0070] According to an exemplary embodiment, any previously used positive electrode active material can be used without limitation. For example, the positive electrode active material can include a lithium-nickel metal oxide. The lithium-nickel metal oxide can further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0071] The positive electrode active material can further include a coating element or a doping element. For example, an element that is substantially the same as or similar to the above auxiliary element can be used as the coating element or the doping element. For example, a single element or a combination of two or more of the above elements can be used as the coating element or the doping element.

[0072] The positive electrode active material can include a nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, an NCM-based lithium oxide with an increased nickel content can be used.

[0073] The Ni content in the NCM-based lithium oxide (e.g., the mole fraction of nickel in the total moles of nickel, cobalt, and manganese) can be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the content of Ni can 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.

[0074] In some embodiments, the positive electrode active material can further 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 (LFP)-based active material (e.g., LiFePO4).

[0075] (Method for manufacturing a positive electrode)

[0076] For example, a positive electrode slurry can be prepared by mixing the positive electrode active material in a solvent. The positive electrode slurry can be coated on a positive electrode current collector and then dried and calendered to manufacture a positive electrode mixture layer. The coating process can be performed by methods such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc., and is not limited thereto. The positive electrode mixture layer can further include a binder and can optionally further include a conductive material, a thickener, etc.

[0077] (Positive electrode solvent)

[0078] Non-limiting examples of the solvent for preparing the positive electrode mixture include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0079] (Positive electrode binder)

[0080] The binder may include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (poly(vinylidene fluoride-co-hexafluoropropylene)), polyacrylonitrile, polymethyl methacrylate, nitrile 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.

[0081] (Positive electrode conductive material)

[0082] The conductive material may be added to improve 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, vapor-grown carbon fiber (VGCF), carbon fiber, etc. and / or metal-based conductive materials including perovskite substances such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc., but is not limited thereto.

[0083] (Positive electrode thickener / dispersant)

[0084] The positive electrode mixture may further include a thickener and / or a dispersant, etc. as needed. As one embodiment, the positive electrode mixture may include a thickener such as carboxymethyl cellulose (CMC).

[0085] [Negative electrode]

[0086] The negative electrode may include a negative electrode current collector and a negative electrode mixture layer provided on at least one surface of the negative electrode current collector.

[0087] (Negative electrode current collector)

[0088] Non-limiting examples of the negative electrode current collector include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and the like. The thickness of the negative electrode current collector is not limited thereto, but may be, for example, 10-50 μm.

[0089] (Negative electrode material)

[0090] The negative electrode mixture layer may contain a negative electrode active material. As the negative electrode active material, a material capable of inserting and extracting 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.

[0091] Examples of the amorphous carbon include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), and the like.

[0092] Examples of the crystalline carbon include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, and graphitized MPCF.

[0093] The lithium metal may be pure lithium metal or lithium metal formed with a protective layer for suppressing dendrite growth or the like. In one embodiment, a layer containing lithium metal 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 also be used as the negative electrode active material layer.

[0094] Elements contained in the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, and indium.

[0095] The silicon-containing substance may provide further increased capacity characteristics. The silicon-containing substance may include Si, SiO x (0 < x < 2), metal-doped SiO x (0 < x < 2), silicon-carbon composites, and the like. The metal may include lithium and / or magnesium, and metal-doped SiO x (0 < x < 2) may include metal silicate.

[0096] (Method for manufacturing negative electrode)

[0097] For example, the negative electrode paste can be prepared by mixing the negative electrode active material in a solvent. The negative electrode paste can be coated / deposited on the negative electrode current collector and then dried and calendered to prepare the negative electrode mixture layer. The coating process can be carried out by methods such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, rod coating, casting, etc., and is not limited thereto. The negative electrode mixture layer can further contain a binder and can optionally further contain a conductive material, a thickener, etc.

[0098] In some embodiments, the negative electrode may further include a negative electrode active material layer in the form of lithium metal formed by a deposition / coating process.

[0099] (Negative electrode solvent)

[0100] As non-limiting examples of the solvent for the negative electrode mixture, water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, and tert-butanol can be cited.

[0101] (Negative electrode binder / conductive material / thickener)

[0102] The binder, conductive material, and thickener can be the above substances that can be used in the manufacture of the positive electrode.

[0103] In some embodiments, the negative electrode binder can use a styrene-butadiene rubber (SBR)-based binder, carboxymethyl cellulose (CMC), a polyacrylic acid-based binder, a poly(3,4-ethylenedioxythiophene) (PEDOT)-based binder, etc.

[0104] [Electrode assembly]

[0105] According to an exemplary embodiment, the electrode assembly can be formed by repeatedly arranging the positive electrode, negative electrode, and separator. In some embodiments, the electrode assembly can be of a winding type, a stacking type, a z-folding type, or a stack-folding type.

[0106] [Electrolyte]

[0107] The electrode assembly is housed in a case together with the electrolyte, whereby a lithium secondary battery can be defined. According to an exemplary embodiment, the electrolyte can use a non-aqueous electrolyte.

[0108] (Lithium salt / organic solvent)

[0109] The non-aqueous electrolyte contains a lithium salt as an electrolyte and an organic solvent. The lithium salt is, for example, composed of Li+ X - represents that as the anion (X - ) of the lithium salt, examples 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 - etc.

[0110] The organic solvent may include an organic compound that has sufficient solubility for the lithium salt and the additive and is non-reactive in the battery. The organic solvent may include, for example, at least one of a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, and an aprotic solvent. 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), ethyl fluoroacetate (FEA), ethyl difluoroacetate (DFEA), ethyl trifluoroacetate (TFEA), dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), 2-methyltetrahydrofuran, ethyl alcohol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, diethoxyethane, sulfolane, γ-butyrolactone, and propylene sulfite may be used. These may be used alone or in combination of two or more.

[0111] (Additive)

[0112] The non-aqueous electrolyte may further contain an additive. The additive may include, for example, a cyclic carbonate-based compound, a fluorine-substituted carbonate-based compound, a sultone-based compound, a cyclic sulfate-based compound, a cyclic sulfite-based compound, a phosphate-based compound, and a borate-based compound. The cyclic carbonate-based compound may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), etc. The fluorine-substituted carbonate-based compound may include fluoroethylene carbonate (FEC), etc. The sultone-based compound may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc. The cyclic sulfate-based compound may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc. The cyclic sulfite-based compound may include ethylenesulfite, butylene sulfite, etc. The phosphate-based compound may include lithium difluoro bis-oxalato phosphate, lithium difluorophosphate, etc. The borate-based compound may include lithium bis(oxalate)borate, etc.

[0113] Hereinafter, examples and experimental examples will be specifically illustrated for explanation. However, the following examples and experimental examples are only used to illustrate a part of a specific implementation, and the technology described in this specification should not be construed as being limited thereto.

[0114] <Experimental Method>

[0115] 1. Measurement of average pore size (D10, D50, D90)

[0116] After cutting the prepared separator into a size of about 3 cm × 2 cm, it is immersed in a liquid phase prepared by adding a small amount of butter to a vial and heating to 60 °C, and then placed in a vacuum oven and left for about 60 minutes at 60 °C under vacuum conditions and then taken out. Excess butter adhering to the outside of the separator is wiped off, and then dried at room temperature for more than 30 minutes. Then, the separator is placed in a chamber with an OsO4 gas atmosphere, and the butter area is stained for 18 hours.

[0117] Attach the dyed separator to a sample stage (stub) for Scanning electron microscope (SEM) analysis, and then coat the surface of the separator with a Pt Coater (50 mA, 60 seconds). Place the coated separator in a Focused ion beam scanning electron microscope (FIB / SEM) device capable of continuous cutting and imaging, and then perform Pt deposition on the surface of the separator in a 10 μm × 10 μm × 2 μm area under the conditions of 30 kV, 0.4 - 0.9 nA, and a Rectangle pattern to form a Pt film. Then, obtain a cross-sectional SEM image after cutting the cross-section at 10 nm intervals (software: Auto Slice And View, Thermo Fisher Scientific TM (Thermo Fisher Scientific TM ). Connect the obtained images to image processing software (Avizo, Thermo Fisher Scientific TM ) to produce a three-dimensional image of the separator. Use the software GeoDict from Math2Market GmbH to selectively separate inorganic particles from the obtained three-dimensional image to produce a three-dimensional shape structure of the separator. Then, use the Identify Pore function of GeoDict to evaluate the pores in the inorganic particle layer. At this time, to distinguish overlapping pores, set the threshold to 25%, and to only selectively evaluate the pores in the inorganic particle layer, exclude the pores adjacent to the boundary surface of the three-dimensional structure during evaluation. The diameter of the pores is converted to the Volume-Equivalent Diameter for evaluation.

[0118] 2. Measurement of Thermal Shrinkage Rate

[0119] The thermal shrinkage rate is measured based on ASTM D1204 as follows. Cut the prepared separator into a square with a side length of 10 cm, and mark grid points at 2 cm intervals. At this time, one side of the square is the width direction (Transverse Direction, TD), and the other side is the machine direction (Longitudinal Direction, MD). Place the specimen at the center, place 7 sheets of paper above and below the specimen, and wrap the four sides of the paper with tape. Place the specimen wrapped with paper in a hot air drying oven at a temperature of 150 °C for 60 minutes. Then, take out the specimen, observe the separator with a camera, and calculate the shrinkage rate in the machine direction (MD) of the following Mathematical Formula 1 and the shrinkage rate in the width direction (TD) of the following Mathematical Formula 2.

[0120] [Mathematical Formula 1]

[0121] 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

[0122] [Equation 2]

[0123] Transverse Direction (TD) shrinkage rate (%) = (Length in the transverse direction before heating - Length in the transverse direction after heating) × 100 / Length in the transverse direction before heating

[0124] 3. Measurement of air permeability

[0125] Using a densometer (Toyoseiki Ltd.), the air permeability ( Gurley air permeability) of the separator before and after coating was measured according to ASTM D726 standard, and the change value was measured. The air permeability is the time in seconds required for 100 milliliters (cc) of air to pass through a separator with an area of 1 square inch.

[0126] 4. Measurement of peel strength

[0127] Using a tensile measurement device (3343) of INSTRON GmbH, the peel strength between the porous substrate and the inorganic particle layer was measured by the 180-degree peel test (ASTM D903).

[0128] 5. Measurement of moisture content

[0129] The moisture content of the separator was measured using 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 0.3 g of the separator sample was heated to 150 °C.

[0130] 6. Measurement of battery resistance

[0131] After the battery was aged and degassed, it was charged to 4.2 V, and the initial resistance of the battery was measured by the J-pulse method.

[0132] 7. Measurement of thickness

[0133] Thickness of the separator: The separator was stacked into 10 layers, and then the thickness was measured at any 5 points in the width direction using a thickness gauge of Mitutoyo Corporation. Then, the average thickness of the 10-layer separator was obtained and divided by 10 to obtain the overall average thickness of a single-layer separator.

[0134] Thickness of the porous membrane: For the average thickness of the porous membrane, stack the porous membranes into 10 layers only, then measure the thickness at any 5 points in the width direction using a thickness gauge from Mitutoyo Corporation, then obtain the average thickness of the 10-layer porous membrane, and divide it by 10 to obtain the average thickness of a single-layer porous substrate.

[0135] Thickness of the inorganic particle layer: The thickness of the inorganic particle layer is obtained by calculating the value obtained by subtracting the average thickness of the single-layer porous membrane from the overall average thickness of the single-layer separator obtained by the above method.

[0136] <Example 1>

[0137] Manufacture of the separator

[0138] Add boehmite with average particle sizes (D50) of 0.35 μm and 0.75 μm respectively in distilled water at a weight ratio of 7:3, and add 1 wt% of a dispersant (BYK-154) and 4 wt% of a polyacrylamide-based binder relative to the weight of the boehmite, and stir using a ball mill to prepare a slurry with a solids content of 32 wt%.

[0139] Perform corona discharge treatment (power density: 2 W / mm, speed: approximately 3 - 5 meters per minute (mpm)) on both sides of a polyethylene porous membrane with a thickness of 9 μm (porosity: 40%, Gurley permeability: 160 seconds / 100 mL, MD tensile strength: 2240 kgf / cm 2 , TD tensile strength: 1860 kgf / cm 2 ) to introduce surface polar groups. Then, coat the prepared slurry on both sides of the surface-treated porous membrane, and then let it stand at room temperature for 10 minutes. After that, dry it in a dryer at 65 °C for 3 minutes to form an inorganic particle layer with a thickness of 1.5 μm respectively, and then age it at 80 °C for 12 hours.

[0140] Manufacture of the battery

[0141] Add 94 wt% of LiCoO2 as the positive electrode active material, 2.5 wt% of polyvinylidene fluoride as the binder, and 3.5 wt% of carbon-black as the conductive material to N-methyl-2-pyrrolidone (NMP) as the solvent and stir to prepare a uniform positive electrode slurry. Coat the slurry on an aluminum foil with a thickness of 30 μm, and perform drying and calendering to manufacture a positive electrode plate with a thickness of 150 μm.

[0142] 95 wt% of artificial graphite as the negative electrode active material, 3 wt% of acrylic latex with a Tg of -52°C as the binder (solid content: 20 wt%), and 2 wt% of carboxymethyl cellulose (CMC) as the thickener were added to water as the solvent and stirred to prepare a homogeneous negative electrode slurry. The slurry was coated on a copper foil with a thickness of 20 μm, dried, and calendered to produce a negative electrode plate with a thickness of 150 μm.

[0143] The separator prepared as described above was used between the positive electrode and the negative electrode thus obtained, and a pouch-type battery was assembled in a stacked manner, and an electrolyte solution 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 manufacture a lithium secondary battery with a capacity of 2 Ah.

[0144] <Example 2>

[0145] A battery was manufactured by the same method as in Example 1, except that in the manufacture of the separator of Example 1, inorganic particles with average particle diameters (D50) of 0.35 μm and 0.75 μm were used at a weight ratio of 1:1.

[0146] <Example 3>

[0147] A battery was manufactured by the same method as in Example 1, except that in the manufacture of the separator of Example 1, inorganic particles with average particle diameters (D50) of 0.35 μm and 0.75 μm were used at a weight ratio of 3:7.

[0148] <Example 4>

[0149] A battery was manufactured by the same method as in Example 1, except that in the manufacture of the separator of Example 1, inorganic particles with an average particle diameter (D50) of 0.4 μm were used.

[0150] <Comparative Example 1>

[0151] Manufacture of the separator

[0152] Boehmite with an average particle diameter (D50) of 0.2 μm and 2 wt% of a dispersant (BYK-154) relative to the weight of the boehmite were added to distilled water and stirred with a bead mill (200 rpm, 10 minutes), and then 4 wt% of a polyacrylamide-based binder relative to the weight of the boehmite was added and further stirred with a ball mill to prepare a slurry with a solid content of 45 wt%.

[0153] A polyethylene porous membrane with a thickness of 9 μm (porosity: 40%, Gurley air permeability: 160 seconds / 100 ml, MD tensile strength: 2240 kgf / cm 2 , TD tensile strength: 1860 kgf / cm 2 ) was subjected to corona discharge treatment on both sides (power density: 2 W / mm, speed: about 3 - 5 meters per minute (mpm)) to introduce surface polar groups. Then, the prepared slurry was coated on both sides of the surface-treated porous membrane, and then left standing at room temperature for 10 minutes. After that, it was dried in a dryer at 45°C for 10 minutes to form inorganic particle layers with a thickness of 1.5 μm respectively, and then aged at 100°C for 12 hours.

[0154] Manufacture of the battery

[0155] The battery was manufactured by the same method as in Example 1.

[0156] <Comparative Example 2>

[0157] Manufacture of the separator

[0158] 0.7 wt% of a dispersant (BYK-154) relative to the weight of boehmite was added to distilled water, and then boehmite with an average particle size (D50) of 1.6 μm and 4 wt% of a polyacrylamide-based binder relative to the weight of the boehmite were added and stirred with a ball mill to prepare a slurry with a solids content of 32 wt%.

[0159] A polyethylene porous membrane with a thickness of 9 μm (porosity: 40%, Gurley air permeability: 160 seconds / 100 ml, MD tensile strength: 2240 kgf / cm 2 , TD tensile strength: 1860 kgf / cm 2 ) was subjected to corona discharge treatment on both sides (power density: 2 W / mm, speed: about 3 - 5 meters per minute (mpm)) to introduce surface polar groups. Then, the prepared slurry was coated on both sides of the surface-treated porous membrane, and then left standing at room temperature for 10 minutes. After that, it was dried in a dryer at 45°C for 10 minutes to form inorganic particle layers with a thickness of 2.2 μm respectively, and then aged at 80°C for 12 hours.

[0160] Manufacture of the battery

[0161] The battery was manufactured by the same method as in Example 1.

[0162] <Comparative Example 3>

[0163] 1.5 wt% of a dispersant (BYK-154) relative to the weight of boehmite and boehmite with an average particle size (D50) of 0.3 μm were added to distilled water and stirred using a bead mill (200 rpm, 10 minutes). Then, 4 wt% of a polyacrylamide-based binder relative to the weight of the boehmite was added and further stirred using a ball mill to prepare a slurry with a solids content of 32 wt%.

[0164] The two sides of a polyethylene porous membrane with a thickness of 9 μm (porosity: 40%, Gurley air permeability: 160 seconds / 100 ml, MD tensile strength: 2240 kgf / cm 2 , TD tensile strength: 1860 kgf / cm 2 ) were subjected to corona discharge treatment (power density: 2 W / mm, speed: approximately 3 - 5 meters per minute (mpm)) to introduce surface polar groups. Subsequently, the prepared slurry was coated on both sides of the surface-treated porous membrane and then left standing at room temperature for 10 minutes. After that, it was dried in a dryer at 45°C for 10 minutes to form inorganic particle layers with a thickness of 1.5 μm respectively, and then aged at 100°C for 12 hours.

[0165] Manufacture of the battery

[0166] The battery was manufactured by the same method as in Example 1.

[0167] <Comparative Example 4>

[0168] 0.7 wt% of a dispersant (BYK-154) relative to the weight of boehmite and boehmite with average particle sizes (D50) of 0.5 μm and 1.3 μm in a weight ratio of 1:1 were added to distilled water and stirred using a bead mill (200 rpm, 10 minutes). Then, 4 wt% of a polyacrylamide-based binder relative to the weight of the boehmite was added and further stirred using a ball mill to prepare a slurry with a solids content of 32 wt%.

[0169] The two sides of a polyethylene porous membrane with a thickness of 9 μm (porosity: 40%, Gurley air permeability: 160 seconds / 100 ml, MD tensile strength: 2240 kgf / cm 2 , TD tensile strength: 1860 kgf / cm 2 ) were subjected to corona discharge treatment (power density: 2 W / mm, speed: approximately 3 - 5 meters per minute (mpm)) to introduce surface polar groups. Subsequently, the prepared slurry was coated on both sides of the surface-treated porous membrane and then left standing at room temperature for 10 minutes. After that, it was dried in a dryer at 45°C for 10 minutes to form inorganic particle layers with a thickness of 1.5 μm respectively, and then aged at 100°C for 12 hours.

[0170] Manufacture of battery

[0171] The battery is manufactured by the same method as in Example 1.

[0172] <Comparative Example 5>

[0173] 0.7 wt% of a dispersant (BYK-154) based on the weight of boehmite and boehmite with average particle sizes (D50) of 0.2 μm and 0.5 μm in a weight ratio of 2:8 are added to distilled water and stirred with a bead mill (200 rpm, 10 minutes). Then, 4 wt% of a polyacrylamide-based binder based on the weight of the boehmite is added and further stirred with a ball mill to prepare a slurry with a solids content of 32 wt%.

[0174] Corona discharge treatment (power density: 2 W / mm, speed: about 3 - 5 meters per minute (mpm)) is performed on both sides of a polyethylene porous membrane with a thickness of 9 μm (porosity: 40%, Gurley air permeability: 160 seconds / 100 ml, MD tensile strength: 2240 kgf / cm 2 , TD tensile strength: 1860 kgf / cm 2 ) to introduce surface polar groups. Then, the prepared slurry is coated on both sides of the surface-treated porous membrane and left to stand at room temperature for 10 minutes. After that, it is dried in a dryer at 45°C for 10 minutes to form an inorganic particle layer with a thickness of 1.5 μm respectively, and then aged at 100°C for 12 hours.

[0175] Manufacture of battery

[0176] The battery is manufactured by the same method as in Example 1.

[0177] The average pore sizes (D10, D50, D90) and physical properties of the separators prepared in the examples and comparative examples and the resistance of the batteries are measured, and the results are shown in Tables 1 and 2 below.

[0178] [Table 1]

[0179]

[0180] [Table 2]

[0181]

[0182] It can be confirmed from Table 1 and Table 2 that, compared with the comparative examples, the diaphragms of the examples where the average pore sizes of the diaphragms all meet the ranges of D10 being 200 nm to 350 nm, D50 being 400 nm to 650 nm, and D90 being 700 nm to 950 nm are significantly superior in thermal stability, and the adhesion of the inorganic particle layer to the porous substrate is excellent, thus having high stability. In addition, when any of the average pore size ranges of the diaphragm is not satisfied, the moisture content is too high, exceeding 700 ppm, resulting in an increase in battery resistance due to side reactions caused by moisture during battery charge and discharge (Comparative Example 1, Comparative Example 5), or a significant decrease in the thermal stability of the diaphragm (Comparative Example 2), or insufficient adhesion between the porous substrate and the inorganic particle layer, thus making it difficult to achieve the stability of battery performance (Comparative Examples 1 to 5).

[0183] As described above, a specific implementation has been detailed through examples and experimental examples, but the scope of a specific implementation is not limited to specific examples and should be interpreted according to the claims.

Claims

1. A diaphragm, when the pore sizes D10 diameter, D50 diameter and D90 diameter of the diaphragm are set to D10, D50 and D90 respectively, the following formulas 1 to 3 are satisfied: 180nm≤D10≤350nm(Formula 1) 380nm≤D50≤650nm(Formula 2) 670nm≤D90≤1000nm (Formula 3).

2. The diaphragm according to claim 1, wherein The pore sizes of the diaphragm all satisfy 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 diaphragm according to claim 1, wherein The separator includes a porous substrate and an inorganic particle layer including inorganic particles on at least one side of the porous substrate.

4. The diaphragm according to claim 3, wherein: The inorganic particles include one or more selected from boehmite, BaSO4, CeO2, MgO, CaO, ZnO, Al2O3, TiO2, BaTiO3, HfO2, SrTiO3, SnO2, NiO, ZrO2, Y2O3 and SiC.

5. The diaphragm according to claim 3, wherein: The inorganic particle layer further includes a binder.

6. The diaphragm according to claim 5, wherein: The adhesive includes at least one selected from the group consisting of an ester-based polymer, an amide-based polymer, an imide-based polymer, an acrylic-based polymer, an acrylamide-based polymer, a vinyl alcohol-based polymer, a fluorine-based polymer, and a vinyl pyrrolidone-based polymer.

7. The diaphragm according to claim 3, wherein: The inorganic particles include inorganic particles having an average particle diameter (D50) of 0.1 μm to 10.0 μm.

8. The diaphragm according to claim 3, wherein: The inorganic particles include one or more inorganic particles having average particle diameters (D50) different from each other.

9. The diaphragm according to claim 8, wherein: The inorganic particles are formed by mixing 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.

10. The diaphragm according to claim 3, wherein The inorganic particle layer has a thickness of 0.1 μm to 10.0 μm.

11. The diaphragm according to claim 1, wherein The separator has shrinkage rates of 5.0% or less in both a machine direction (MD) and a width direction (TD) after being left at 150° C. for 60 minutes.

12. The diaphragm according to claim 3, wherein: The peeling force between the porous substrate and the inorganic particle layer measured according to ASTM D903 is 50 gf / 15 mm or more.

13. The diaphragm according to claim 3, wherein: The porous substrate has a thickness of 1 μm to 50 μm.

14. An electrochemical device comprising the separator according to any one of claims 1 to 13.

15. The electrochemical device according to claim 14, wherein: The electrochemical device is a secondary battery.

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