Separator and electrochemical device including the same

Abstract

The present invention relates to a separator and an electrochemical device comprising the same. According to one aspect of the present invention, there is provided a separator comprising: a porous substrate; the separator includes a porous substrate, and an inorganic particle layer formed on at least one surface of the porous substrate and including a binder and inorganic particles, the separator having a Gurley air permeability of 10-250 sec / 100 ml, a puncture strength of 0.3 N / [mu] m or more, and a tensile strength in a machine direction and a width direction of 1500 kgf / cm2 or more. The hot shrinkage rate in the machine direction and the width direction measured after standing at 130 DEG C for 60 minutes is 5% or less, and the saturated moisture content measured by the Karl Fischer method is 350-1000 ppm.

Description

Technical Field

[0001] The present invention relates to a separator and an electrochemical device comprising the separator. Background Art

[0002] In recent years, as the demand for environmentally friendly energy has increased, electrochemical devices have been studied in various fields such as electronic devices such as mobile phones and computers and electric vehicles.

[0003] In order to achieve high capacity / high power characteristics of electrochemical devices, the direction of thinning the thickness of the insulating separator sandwiched between the positive electrode and the negative electrode is being studied, but when the thickness of the separator becomes thinner, there is a problem of reduced mechanical strength and / or heat resistance. When the mechanical strength and / or heat resistance decreases, the possibility of safety problems occurring during the manufacturing process and use of the battery increases. As an example, due to damage or deformation of the separator caused by the increase in temperature inside the battery, a short circuit between the electrodes may occur, and the risk of overheating or fire of the battery may increase.

[0004] Therefore, it is necessary to develop a separator having a thin thickness and improved mechanical strength and heat resistance as described above. In addition, at the same time, in order to increase capacity and power, it is necessary to develop a separator having high transmittance. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] According to one aspect of the present invention, it is possible to provide a separator having excellent heat resistance and adhesiveness even in a thin thickness and an electrochemical device including the separator.

[0007] According to another aspect of the present invention, a separator having improved mechanical strength and permeability even at a thin thickness and an electrochemical device including the separator can be provided.

[0008] According to another aspect of the present invention, an electrochemical device having excellent resistance characteristics and thermal safety can be provided.

[0009] The diaphragm of the present invention can be widely used in electric vehicles, battery charging stations, other green technology fields such as solar power generation and wind power generation using batteries. In addition, the diaphragm of the present invention can be used in eco-friendly electric vehicles, hybrid vehicles, etc. that prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0010] (II) Technical solution

[0011] The diaphragm according to the present invention comprises: a porous substrate; and an inorganic particle layer, wherein the inorganic particle layer is formed on at least one side of the porous substrate and comprises a binder and inorganic particles, and the diaphragm has a Gurley air permeability of 10-250 seconds / 100 milliliters (cc), a puncture strength of 0.3N / μm or more, and a tensile strength of 1500kgf / cm in the mechanical direction and the width direction. 2 In the above, the heat shrinkage in the machine direction and the width direction measured after standing at 130° C. for 60 minutes was 5% or less, and the saturated moisture content measured by the Karl Fischer method was 350-1000 ppm.

[0012] In a specific embodiment, the Gurley air permeability may be 90-230 seconds / 100 milliliters, and the saturated moisture content may be 450-1000 ppm.

[0013] In a specific embodiment, the average thickness of the porous substrate may be 5-15 μm, and the ratio of the average thickness of the porous substrate to the average thickness of the separator may be greater than 0.7.

[0014] In a specific embodiment, the total thickness of the inorganic particle layer formed on the porous substrate may be 3.2 μm or less.

[0015] In a specific embodiment, the adhesive may include a polyacrylamide-based resin.

[0016] In a specific embodiment, the polyacrylamide-based resin may be a copolymer including a unit derived from a (meth)acrylamide-based monomer and a unit derived from a comonomer.

[0017] In a specific embodiment, the polyacrylamide-based resin may include a structural unit derived from a (meth)acrylamide-based monomer and a structural unit derived from a (meth)acrylic acid-based monomer containing a hydroxyl group.

[0018] In a specific embodiment, the weight average molecular weight of the polyacrylamide-based resin may be 100,000-2,000,000 g / mol.

[0019] In a specific embodiment, the adhesive may further include any one or two or more water-based polymers selected from polyvinyl alcohol, polyvinylidene fluoride, carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyethylene glycol, polyacrylonitrile, polyvinyl pyrrolidone and copolymers thereof.

[0020] In a specific embodiment, the content of the water-based polymer may be 0.1-30 wt % of the total content of the adhesive.

[0021] In a specific embodiment, the BET specific surface area of ​​the inorganic particles can be 3-7 m 2 / g.

[0022] In a specific embodiment, the average particle size (D50) of the inorganic particles may be 0.5-1.5 μm.

[0023] In a specific embodiment, the inorganic particles may include any one or two or more selected from metal hydroxides, metal oxides, metal nitrides and metal carbides.

[0024] In a specific embodiment, the weight ratio of the inorganic particles to the binder in the inorganic particle layer may be 50:50 to 99.9:0.1.

[0025] In a specific embodiment, the inorganic particle layer can be formed into 0.5-10g / m 2 .

[0026] In addition, the present invention provides an electrochemical device including the separator as described above.

[0027] (III) Beneficial effects

[0028] The separator according to the present invention may have excellent heat resistance and adhesiveness even at a thin thickness.

[0029] In addition, the separator according to the present invention can have excellent mechanical strength and permeability even in a thin thickness.

[0030] In addition, the present invention can provide an electrochemical device including the separator according to a specific embodiment to have excellent resistance characteristics and thermal safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 : is a diagram showing a schematic structure of a diaphragm according to an embodiment.

[0032] Description of reference numerals:

[0033] 100: diaphragm; 10: porous substrate; 20: inorganic particle layer. DETAILED DESCRIPTION

[0034] The present invention is described in detail below, but this is merely exemplary, and the present invention is not limited to the specific embodiments described exemplarily.

[0035] In addition, unless otherwise specifically stated herein, singular forms used in the specification and the claims may also include plural forms.

[0036] In addition, the numerical range used in this specification includes the lower limit value and the upper limit value and all values ​​within the range, the 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 the numerical range defined in different forms. In this specification, unless otherwise specifically defined, values ​​outside the numerical range that may be generated due to experimental errors or rounding of values ​​are also included in the defined numerical range.

[0037] Furthermore, throughout the specification, unless otherwise specifically described to the contrary, “comprising” or “including” a certain component means that other components may also be included, rather than excluding other components.

[0038] In this specification, when a layer, film, region, plate or the like is described as being “on” or “over” another part, this includes not only the case of being “directly” “on” another part but also the case of having other parts in between.

[0039] In this specification, "average particle size" refers to "D50", and "D50" refers to the particle size of inorganic particles corresponding to a cumulative fraction of 50% based on volume. The average particle size can be obtained from the particle size distribution results of sampling the inorganic particles as the measurement object according to ISO 13320-1 standard and analyzing them using S3500 of MICROTRAC. In addition, "D90" refers to the particle size of particles corresponding to a cumulative fraction of 90% based on volume, and "D10" refers to the particle size of inorganic particles corresponding to a cumulative fraction of 10% based on volume. D90 and D10 can be obtained by the same method as D50.

[0040] The present invention provides a diaphragm 100, comprising: a porous substrate 10; and an inorganic particle layer 20, wherein the inorganic particle layer 20 is formed on at least one side of the porous substrate 10 and comprises an adhesive and inorganic particles, wherein the diaphragm has a Gurley air permeability of 10-250 seconds / 100 milliliters, a puncture strength of 0.3 N / μm or more, and a tensile strength of 1500 kgf / cm in a mechanical direction and a width direction. 2 In the above, the heat shrinkage in the machine direction and the width direction measured after standing at 130° C. for 60 minutes was 5% or less, and the saturated moisture content measured by the Karl Fischer method was 350-1000 ppm.

[0041] In the past, when a separator is manufactured with a very thin thickness, it is impossible to provide a separator that satisfies all the physical properties as described above. However, as a result of repeated studies by the inventors of the present invention, it has been confirmed that by simultaneously achieving the above-mentioned ranges of Gurley air permeability, puncture strength, tensile strength, and saturated water content, a separator having excellent heat resistance and adhesion as well as excellent mechanical strength and permeability can be provided even at a thin thickness.

[0042] In addition, the electrochemical device according to a specific embodiment includes a separator that satisfies the physical properties as described above, and thus can have excellent resistance characteristics and thermal safety at the same time. Specifically, the electrochemical device according to a specific embodiment can exhibit a significantly low discharge resistance after 600 cycles, thereby having improved charge and discharge performance.

[0043] In addition, when the rate of increase of the moisture content of the diaphragm is large, the moisture content remaining in the battery will increase even after being assembled into a battery, and this increase in moisture content may become a reason for reducing the capacity of the battery, such as causing the decomposition of the electrolyte. In the past, in order to reduce the moisture content in the battery, it was necessary to use expensive packaging materials such as aluminum. On the other hand, the diaphragm according to the present invention simultaneously satisfies the above-mentioned physical properties including the saturated moisture content, so that it can have the advantage of a small rate of increase of moisture content due to storage. Therefore, the present invention can provide a battery as follows, which has excellent performance even if a polyethylene material packaging material is used instead of an aluminum material due to the low moisture content remaining in the battery. That is, according to the present invention, it has the advantage of improving the performance of the battery while reducing the price of the battery.

[0044] As a specific embodiment, for the separator, even if the average thickness of the porous substrate is less than 15 μm, and the thickness of the porous substrate is more than 0.7 times the total thickness of the separator, that is, it has a very thin inorganic particle layer, it can also have excellent mechanical properties, electrical properties and thermal properties described later. The manufacture of the separator having the above-mentioned properties can be achieved by adjusting the thickness of each layer selected from the separator, the size of the inorganic particles, the type of binder, the surface area of ​​the inorganic particles, and the saturated water content of the separator. However, as long as it can be achieved, the method is not particularly limited.

[0045] That is, in the past, when a separator is manufactured with a very thin thickness as described above, it is impossible to provide a separator that satisfies all the physical properties as described above. However, as a result of repeated studies by the inventors of the present invention, it has been confirmed that by simultaneously achieving the above-mentioned ranges of Gurley air permeability, puncture strength, tensile strength, and saturated water content, a separator having excellent heat resistance and adhesion as well as excellent mechanical strength and permeability even at a thin thickness can be provided.

[0046] As a specific embodiment, the separator having the saturated moisture content and the physical properties as described above can be manufactured by using inorganic particles having a specific specific surface area. For example, the BET specific surface area of ​​the inorganic particles included in the separator according to a specific embodiment can be 3 m 2 / g or more, 4m 2 / g or more, 7m 2 / g or less, 6m 2 / g or below or between the above values, specifically 3-7m 2 / g or 4-6m 2 / g.

[0047] As a specific embodiment, the diaphragm having the physical properties as described above can be manufactured by adjusting the thickness ratio of the porous substrate and the inorganic particle layer contained therein to a specific value. For example, the ratio of the average thickness of the porous substrate to the average thickness of the diaphragm can be 0.7 or more, 0.75 or more, 0.77 or more, 0.99 or less, 0.9 or less, 0.85 or less, or a value between the above values, specifically 0.7 to 0.99, 0.75 to 0.9, or 0.77 to 0.85.

[0048] As a specific embodiment, the diaphragm having the physical properties as described above can be manufactured by using a specific resin as the binder contained therein. For example, the binder can include a polyacrylamide-based resin, specifically, for example, a polyacrylamide-based resin including a structural unit derived from a (meth)acrylamide-based monomer and a structural unit derived from a (meth)acrylic acid-based monomer containing a hydroxyl group.

[0049] According to a specific embodiment, the diaphragm having the physical properties as described above can be manufactured by using the above-mentioned polyacrylamide-based resin and a specific water-based polymer as a binder. For example, the specific water-based polymer can be selected from polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP) and any one or more of their copolymers.

[0050] In a specific embodiment, the adhesive may have a glass transition temperature of 0°C to 200°C, 0°C to 150°C, 30°C to 200°C, 30°C to 150°C, or 50°C to 150°C.

[0051] According to another specific embodiment, the diaphragm having the physical properties as described above can be manufactured by using the above-mentioned polyacrylamide-based resin as an adhesive and using a porous substrate having a surface containing polar functional groups. Non-limiting examples of the polar functional groups can include carboxyl, aldehyde, hydroxyl, etc., but are not particularly limited. According to one example, the polar functional groups can be introduced by hydrophilic surface treatment, and according to one example, the hydrophilic surface treatment can be carried out by including one or more of corona discharge treatment and plasma discharge treatment.

[0052] Hereinafter, the separator will be described in more detail.

[0053] In a specific embodiment, the Gurley permeability of the diaphragm can be less than 250 seconds / 100 ml, less than 230 seconds / 100 ml, less than 200 seconds / 100 ml, less than 180 seconds / 100 ml, more than 10 seconds / 100 ml, more than 50 seconds / 100 ml, more than 90 seconds / 100 ml, more than 100 seconds / 100 ml, or a value between the above values. Specifically, the Gurley permeability can be 10-250 seconds / 100 ml, 50-200 seconds / 100 ml, 90-230 seconds / 100 ml, or 100-180 seconds / 100 ml. By satisfying the Gurley permeability in the above range, excellent ionic conductivity can be obtained, and due to the low internal resistance of the electrochemical device, the charge and discharge characteristics of the electrochemical device can be improved.

[0054] In a specific embodiment, the puncture strength of the diaphragm can be 0.3 N / μm or more, 0.32 N / μm or more, 0.35 N / μm or more, 1.0 N / μm or less, 0.8 N / μm or less, 0.5 N / μm or less, or a value between the above values. Specifically, the puncture strength can be 0.3-1.0 N / μm, 0.32-0.8 N / μm, or 0.35-0.5 N / μm.

[0055] In a specific embodiment, the tensile strength of the separator in the machine direction (machine direction, MD) may be 1500-2500 kgf / cm 2 or 1500-2000kgf / cm 2 .

[0056] In a specific embodiment, the tensile strength of the separator in the width direction (transverse direction, TD) may be 1500 kgf / cm 2 Above, 1600kgf / cm 2 Above, 1700kgf / cm 2 Above, 2500kgf / cm 2 Below, 2000kgf / cm 2 Specifically, the tensile strength in the width direction may be 1500-2500 kgf / cm 2 、1600-2000kgf / cm 2 or 1700-2000kgf / cm 2 .

[0057] By satisfying the above-mentioned ranges of puncture strength and tensile strength, the electrochemical device has excellent resistance to external stress generated during the manufacture of the electrochemical device and dendrites generated during the charge and discharge of the electrochemical device, thereby ensuring the safety of the electrochemical device.

[0058] The separator according to one embodiment may have excellent heat resistance even at a thin thickness. In one embodiment, the heat shrinkage in the mechanical direction and the width direction measured after the separator is placed at 130° C. for 60 minutes may be 5% or less, 4% or less, 3% or less, 2% or less, or 1.5% or less.

[0059] In a specific embodiment, the saturated moisture content is measured after being placed in a thermostat set at 40°C and 90% relative humidity for 24 hours, and the saturated moisture content may be 350 ppm or more, 450 ppm or more, 500 ppm or more, 550 ppm or more, 600 ppm or more, 1000 ppm or less, 900 ppm or less, 800 ppm or less, 750 ppm or less, or a value between the above values. Specifically, the saturated moisture content may be 350-1000 ppm, 450-1000 ppm, 500-900 ppm, 550-800 ppm, or 600-750 ppm.

[0060] In a specific embodiment, the average thickness of the porous substrate is 5-15 μm, and the ratio of the average thickness of the porous substrate to the average thickness of the separator can be 0.7 or more. The separator according to a specific embodiment can also achieve the above-mentioned range of Gurley air permeability, puncture strength, tensile strength and saturated moisture content at the same time even under the above-mentioned range of thickness conditions. Therefore, the filmization of the secondary battery separator can be achieved, so that it is suitable for application in high-capacity / high-power batteries.

[0061] In a specific embodiment, the average thickness of the porous substrate may be 5 μm or more, 8 μm or more, 15 μm or less, 12 μm or less, or a value between the above values, but is not necessarily limited thereto. Specifically, the average thickness of the porous substrate may be 5-15 μm or 8-12 μm.

[0062] In a specific embodiment, the ratio of the average thickness of the porous substrate to the average thickness of the separator can be 0.7 or more, 0.75 or more, 0.77 or more, 0.99 or less, 0.9 or less, 0.85 or less, or a value between the above values. Specifically, the ratio of the average thickness of the porous substrate to the average thickness of the separator can be 0.7 to 0.99, 0.75 to 0.9, or 0.77 to 0.85.

[0063] In a specific embodiment, the average thickness of the separator can be 7 μm or more, 10 μm or more, 12 μm or more, 20 μm or less, 15 μm or less, or a value between the above values, but is not necessarily limited thereto. Specifically, the average thickness of the separator can be 7-20 μm, 10-15 μm, or 12-15 μm.

[0064] In a specific embodiment, the inorganic particle layer can be coated on one side or both sides of the porous substrate. When the inorganic particle layer is coated on both sides of the porous substrate, the thickness of the inorganic particle layer coated on one side and the other side can be the same or different.

[0065] In a specific embodiment, the total thickness of the inorganic particle layer formed on the porous substrate may be 4 μm or less, 3.5 μm or less, 1 μm or more, 1.5 μm or more, or a value between the above values, but is not necessarily limited thereto. Specifically, the total thickness of the inorganic particle layer may be 3.2 μm or less. More specifically, the total thickness of the inorganic particle layer may be 1-4 μm, 1.5-3.5 μm, 1-3.2 μm, or 1.5-3.2 μm.

[0066] In a specific embodiment, the adhesive may include a polyacrylamide-based resin.

[0067] In a specific embodiment, the polyacrylamide-based resin can be polyacrylamide or a copolymer comprising polyacrylamide. In a specific embodiment, the copolymer can be a block copolymer or a random copolymer, but the copolymer described in the present invention refers to a random copolymer formed by mixing and polymerizing two or more monomers.

[0068] In a specific embodiment, the polyacrylamide-based resin may be a copolymer comprising a unit derived from a (meth)acrylamide-based monomer and a unit derived from a comonomer. Specifically, the polyacrylamide-based resin may comprise a structural unit derived from a (meth)acrylamide-based monomer and a structural unit derived from a (meth)acrylic acid-based monomer containing a hydroxyl group.

[0069] The separator according to one embodiment includes the copolymer instead of the homopolymer derived from the acrylamide-based monomer, thereby further improving mechanical strength, air permeability, heat resistance and adhesion. In addition, the electrochemical device includes the separator, thereby having more excellent resistance characteristics and thermal safety.

[0070] The unit derived from the (meth)acrylamide-based monomer of the polyacrylamide-based resin may be represented by Chemical Formula 1 below.

[0071] [Chemical formula 1]

[0072]

[0073] In the Chemical Formula 1, R1 may be hydrogen or a C1 to C6 alkyl group.

[0074] The unit derived from the (meth)acrylic acid-based monomer containing a hydroxyl group of the polyacrylamide-based resin may be represented by Chemical Formula 2 below.

[0075] [Chemical formula 2]

[0076]

[0077] In the chemical formula 2, R2 is hydrogen or a C1 to C6 alkyl group. In addition, L1 may be a C1 to C6 linear or branched alkylene group.

[0078] In the polyacrylamide-based resin according to a specific embodiment, the content of the (meth)acrylamide-based monomer may be 65-98 mol%, 70-97 mol%, or 75-95 mol%. The content of the (meth)acrylic acid-based monomer containing a hydroxyl group may be 2-35 mol%, 3-30 mol%, or 5-25 mol%. When the polyacrylamide-based resin is prepared within the above content range, sufficient adhesive strength can be obtained, and more significant effects can be obtained in terms of high-temperature shrinkage.

[0079] In a specific embodiment, the polyethylene glycol-converted weight average molecular weight of the polyacrylamide-based resin measured by gel permeation chromatography can be 100000 g / mol or more, 200000 g / mol or more, 2000000 g / mol or less, 1000000 g / mol or less, 500000 g / mol or less, or a value between the above values. Specifically, the weight average molecular weight of the polyacrylamide-based resin can be 100000-2000000 g / mol, 200000-1000000 g / mol, or 200000-500000 g / mol. According to a specific embodiment, when the weight average molecular weight of the polyacrylamide-based resin meets the above range, heat resistance and adhesion can be further improved.

[0080] The viscosity of the aqueous solution containing the polyacrylamide-based resin with a solid content of 10% by weight may be 3000 cps or less, 2500 cps or less, 2000 cps or less, or 1500 cps or less, but is not limited thereto. When mixed with inorganic particles within the above range to prepare a coating slurry, the viscosity of the slurry can be further reduced, and the coating property can be further improved, so it may be preferred.

[0081] As long as the polyacrylamide-based resin according to the above specific embodiment can be provided, the preparation method is not particularly limited, but in a specific embodiment, the polyacrylamide-based resin can be prepared by various well-known polymerization methods such as emulsion polymerization, suspension polymerization, bulk polymerization, solution polymerization, etc.

[0082] In a specific embodiment, the polyacrylamide-based resin may be obtained by copolymerizing a mixture including the monomer components described above and a polymerization initiator.

[0083] In a specific embodiment, as long as the copolymer can be obtained, the type of the polymerization initiator is not particularly limited, but in a specific embodiment, the polymerization initiator can be an azo initiator, a peroxide-based initiator, or a persulfate-based polymerization initiator such as potassium persulfate, sodium persulfate, and ammonium persulfate.

[0084] According to a specific embodiment, the polyacrylamide-based resin can be obtained by heating to 50-90° C. or 60-80° C., adding a polymerization initiator, and performing a polymerization reaction.

[0085] In a specific embodiment, after the polymerization reaction is completed, the temperature may be lowered to normal temperature (20±5° C.) and an alkaline solution or the like may be added to prepare an aqueous polyacrylamide-based resin solution adjusted to a neutral state.

[0086] In a specific embodiment, the adhesive may further include any one or more water-based polymers selected from polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinyl pyrrolidone (PVP) and their copolymers.

[0087] In the separator according to a specific embodiment, by using the water-based polymer and the polyacrylamide-based resin as a binder, the mechanical strength, air permeability, heat resistance and adhesion can be further improved. In addition, the improvement of the physical properties as described above can be achieved without pre-treatment such as corona discharge treatment of the porous substrate, so there is an advantage in that time and material costs can be reduced in terms of process.

[0088] In a specific embodiment, the content of the water-based polymer can be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 30% by weight or less, 20% by weight or less, 15% by weight or less, or a value between the above values, of the total content of the adhesive. Specifically, the content of the water-based polymer can be 0.1-30% by weight, 1-20% by weight, or 5-15% by weight, but is not necessarily limited thereto.

[0089] In a specific embodiment, the degree of saponification of the water-based polymer may be 80-95 mol %, specifically 85-90 mol %, but is not particularly limited thereto.

[0090] In a specific embodiment, the weight average molecular weight of the water-based polymer may be 10,000-100,000 g / mol, specifically 30,000-70,000 g / mol, but is not particularly limited thereto.

[0091] In a specific embodiment, the porous substrate may be a polyolefin-based porous substrate such as polyethylene, polypropylene and copolymers thereof, but is not limited thereto, and all porous substrates known as porous substrates for separators of electrochemical devices may be used. In a specific embodiment, the porous substrate may be made into a film or a sheet, but is not particularly limited.

[0092] In a specific embodiment, the porosity of the porous substrate may be 20-60%, specifically 30-60%, but is not limited thereto.

[0093] In a specific embodiment, the inorganic particle layer may include an adhesive and inorganic particles, and the inorganic particle layer may be a porous inorganic particle layer, wherein the inorganic particles are connected and fixed by the adhesive to form pores. In a specific embodiment, the inorganic particle layer may be disposed on at least one side of a porous substrate, and based on the entire surface of the porous substrate, the inorganic particle layer may occupy an area fraction of more than 60%, more than 70%, more than 80% or more than 90%, preferably, the inorganic particle layer may be formed on 100% of the area of ​​the porous substrate.

[0094] In a specific embodiment, as long as it is an inorganic particle used in the present technical field, the inorganic particle is not limited. As a non-limiting example, the inorganic particle may include any one or more selected from metal hydroxides, metal oxides, metal nitrides and metal carbides. For example, the inorganic particle may include any one or more selected from magnesium oxide (MgO), magnesium hydroxide (Mg (OH) 2), aluminum oxide (Al2O3), boehmite (γ-AlO (OH)), aluminum hydroxide (Al (OH) 3), silicon dioxide (SiO2), silicon carbide (SiC), calcium oxide (CaO), titanium dioxide (TiO2), strontium titanate (SrTiO3), zinc oxide (ZnO), yttrium oxide (Y2O3), zirconium oxide (ZrO2), tin oxide (SnO2) and cerium oxide (CeO2). From the viewpoint of battery stability, the inorganic particles may be, for example, any one or two or more metal hydroxide particles selected from boehmite, aluminum hydroxide (Al(OH) 3 ) and magnesium hydroxide (Mg(OH) 2 ).

[0095] In a specific embodiment, the shape of the inorganic particles is not limited and may be spherical, elliptical, needle-shaped, or the like.

[0096] In a specific embodiment, the BET specific surface area of ​​the inorganic particles can be 3m 2 / g or more, 4m 2 / g or more, 7m 2 / g or less, 6m 2 / g or a value between the above values. Specifically, the BET specific surface area of ​​the inorganic particles can be 3-7m 2 / g or 4-6m 2 In the present invention, when the specific surface area meets the above range, a separator that simultaneously meets the physical properties to be achieved by the present invention can be provided. At this time, the BET specific surface area of ​​the inorganic particles can be measured by the ASTM C1069 method.

[0097] In a specific embodiment, the average particle size (D50) of the inorganic particles can be 0.5 μm or more, 0.6 μm or more, 1.5 μm or less, 1.0 μm or less, or a value between the above values. Specifically, the D50 of the inorganic particles can be 0.5-1.5 μm or 0.6-1.0 μm, but it can be changed as long as it does not depart from the scope of the present invention.

[0098] In a specific embodiment, the average particle size (D10) of the inorganic particles may be 0.2 μm to 0.7 μm, 0.25 μm to 0.7 μm, 0.3 μm to 0.7 μm, 0.35 μm to 0.7 μm, or 0.35 μm to 0.6 μm, but is not necessarily limited thereto.

[0099] In a specific embodiment, the average particle size (D90) of the inorganic particles may be 1.3 μm to 3.0 μm, 1.3 μm to 2.5 μm, 1.3 μm to 2.2 μm, 1.5 μm to 2.5 μm or 1.5 μm to 2.2 μm, but is not necessarily limited thereto.

[0100] In a specific embodiment, the weight ratio of the inorganic particles to the binder of the inorganic particle layer may be 50:50 to 99.9:0.1, 60:40 to 98:2, or 80:20 to 98:2, but is not particularly limited thereto.

[0101] In a specific embodiment, the inorganic particle layer can be formed into 0.5-10g / m 2 , specifically it can be formed into 1-5g / m 2 , more specifically, it can be formed into 2.5-4g / m 2 , but is not particularly limited thereto.

[0102] Hereinafter, the method for producing the separator of the present invention will be described.

[0103] The method for manufacturing a separator satisfying the above physical properties may include: a first step of preparing a coating slurry containing a binder and inorganic particles; and a second step of coating the coating slurry on at least one side of a porous substrate to form an inorganic particle layer.

[0104] The descriptions of the porous substrate, the inorganic particle layer, the inorganic particles, and the binder are the same as those described above, and thus the detailed descriptions are omitted.

[0105] In the first step, the method for preparing the coating slurry can apply all conventional methods known in the technical field without restriction, and there is no particular limitation, but according to a non-limiting example, the inorganic particles can be dispersed by stirring to prepare the slurry, and a ball mill can also be used to disperse the aggregated inorganic particles.

[0106] The coating slurry may include inorganic particles, a binder and a solvent. The solvent may be water, ethanol, methanol, propanol and other lower alcohols, dimethylformamide, acetone, tetrahydrofuran, ether, dichloromethane, N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone, hexane, cyclohexane and other solvents or mixtures thereof, but is not necessarily limited thereto.

[0107] In a specific embodiment, the solid content of the coating slurry is not particularly limited, but can be, for example, 1-50 wt %, 5-30 wt % or 10-30 wt %, but is not limited thereto.

[0108] In a specific embodiment, the coating slurry may contain 50-99.9 wt % of inorganic particles and 0.1-50 wt % of binder based on the total weight of the solid matter. Specifically, it may contain 60-98 wt % of inorganic particles and 2-40 wt % of binder. More specifically, it may contain 80-98 wt % of inorganic particles and 2-20 wt % of binder, but it is not limited thereto.

[0109] In the second step, the method for applying the coating slurry can be applied without limitation to all conventional methods known in the art, and according to non-limiting examples, roller coating, spin coating, dip coating, rod coating, die coating, slot coating, inkjet printing and a combination thereof can be applied. The coated slurry can be dried to form an inorganic particle layer. The drying for forming the inorganic particle layer is not particularly limited, but can be dried at less than 100° C. or at 30-60° C.

[0110] In a specific embodiment, after the drying for forming the inorganic particle layer is performed, the process of aging the porous substrate formed with the inorganic particle layer may not be further included. The aging can be performed at 50-150°C or 60-120°C, and the aging time can be 2-24 hours or 10-20 hours. More specifically, the aging can be performed at a temperature range of 70-120°C for 10-15 hours. According to a specific embodiment, even if the aging process is not performed, a diaphragm that satisfies the physical properties as described above can be manufactured at the same time, so it has the advantage of reducing time and material costs in terms of process.

[0111] The present invention can provide an electrochemical device, the electrochemical device comprising a separator according to one of the above-mentioned specific embodiments. The electrochemical device comprises the separator as described above, so that the resistance can be reduced, thereby having significantly excellent life characteristics, and having excellent thermal stability at high temperatures.

[0112] The electrochemical device may be any known energy storage device, and is not particularly limited, but as a non-limiting example, a lithium secondary battery may be cited. The lithium secondary battery is well known, and its structure is also well known, so it is not described in detail in the present invention.

[0113] A lithium secondary battery according to one embodiment may include the separator between a positive electrode and a negative electrode. At this time, the positive electrode and the negative electrode may be used without limitation as long as they are positive electrodes and negative electrodes generally used for lithium secondary batteries.

[0114] Generally, when the separator according to one embodiment is used for a battery, a conventional manufacturing method is followed by providing a negative electrode, a separator, and a positive electrode and assembling and injecting an electrolyte, and thus it is not further described in detail herein.

[0115] The embodiments of the present invention are further described below with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are only used to illustrate the present invention, and are not used to limit the scope of rights. Various changes and modifications can be made to the embodiments within the scope of the scope and technical ideas of the present invention, which is obvious to those skilled in the art, and it is also natural that such variations and modifications also belong to the scope of rights.

[0116] First, a method for measuring the physical properties of a separator and a method for evaluating the characteristics of a secondary battery are described.

[0117] [Average thickness of separator and porous substrate (μm)]

[0118] The average thickness of the separator is obtained by the following method: The separator is stacked into 10 layers, and then the thickness is measured at 5 points in the width direction using a thickness gauge produced by Mitutoyo. The average thickness of the 10-layer separator is obtained by dividing by 5, and then the average thickness of the single-layer separator is obtained by dividing by 10.

[0119] The average thickness of the porous substrate is obtained by the following method. Before the inorganic particle layer is formed, only the porous substrate without the inorganic particle layer is stacked into 10 layers, and then the thickness is measured at any 5 points in the width direction using a thickness measuring instrument of Mitutoyo Co., Ltd., and then the average thickness of the 10 layers of the porous substrate is obtained by dividing by 5, and then the average thickness of the porous substrate is obtained by dividing by 10. After the inorganic particle layer is formed, all methods known in the art are applied without restriction to make the inorganic particle layer fall off and fully dry, and then the average thickness of the porous substrate with the inorganic particle layer falling off is obtained by the above method.

[0120] [Coating amount (g / m 2 )]

[0121] The coating amount is obtained by measuring the per unit area (m2) of the diaphragm before and after coating. 2 Specifically, the substrate before coating was first cut into pieces with a width and length of 10 cm, weighed and multiplied by 100 to convert to m 2 Then, the coated diaphragm was cut into the same size, weighed and multiplied by 100 to convert to m 2 The weight of the substrate is subtracted from the converted value (g / m 2 ) to obtain the coating weight of a single coating.

[0122] [Weight average molecular weight (g / mol)]

[0123] In the measurement of the weight-average molecular weight, GPC (EcoSEC HLC-8320 GPC differential refractometer (Refractive Index detector) of Tosoh Corporation) was used, Tskgel Guard PWx, 2 TSKgel GMPWxl and TSKgel G2500PWxl (7.8×300 mm) were used as GPC columns, 0.1 M NaNO3 aqueous solution was used as the developing solvent, polyethylene glycol was used as the standard, and the analysis was performed at a flow rate of 1 mL / min at 40°C.

[0124] [Gurley air permeability (seconds / 100 ml)]

[0125] The measurement was performed using a Densometer manufactured by Toyoseiki Co., Ltd. in accordance with ASTM D726. The time required for 100 ml of air to pass through a membrane having an area of ​​1 square inch was recorded in seconds and compared.

[0126] [Puncture strength (N / μm)]

[0127] The puncture strength was measured by installing a pin tip with a diameter of 1.0 mm and a radius of curvature of 0.5 mm in a universal test machine (UTM) 3345 from INSTRON and pressing the diaphragm at a speed of 120 mm / min. At this time, the puncture strength was calculated by dividing the load (N) at the time of diaphragm rupture by the thickness (μm) of the diaphragm.

[0128] [Tensile strength (kgf / cm 2 )]

[0129] For the tensile strength, according to ASTM D882, the separator was stretched in the transverse direction and the machine direction at a speed of 100 mm / min using a universal testing machine (UTM) 3345 of Instron, and the strength at which the separator was broken was measured as the tensile strength.

[0130] [Heat shrinkage rate (%)]

[0131] Cut the diaphragm into a square with a side length of 10 cm and mark the width direction (TD) and machine direction (MD). Place the sample in the center, place 5 sheets of paper on the top and bottom of the sample, and wrap the four sides of the paper with tape. Place the paper-wrapped sample in a hot air drying oven at 130°C for 60 minutes. Then, take out the sample, measure the diaphragm with a camera, and calculate the heat shrinkage in the machine direction (MD) and the heat shrinkage in the width direction (TD) using the following formula.

[0132] MD heat shrinkage rate (%) = (MD length before heating - MD length after heating) / MD length before heating × 100

[0133] TD heat shrinkage rate (%) = (TD length before heating - TD length after heating) / TD length before heating × 100

[0134] [Saturated moisture content (ppm)]

[0135] The Karl Fischer method was used to measure the saturated moisture content of the diaphragm. The measuring equipment was a Karl Fischer titrator from Metrohm, Switzerland. The measuring conditions were: the diaphragm sample weight was set to 0.3 g, the oven temperature was set to 150° C., and the measuring time was set to 600 seconds.

[0136] Specifically, the manufactured separator was placed in a thermo-hygrostat set at 40° C. and a relative humidity of 90% for 24 hours, and then the saturated moisture content was measured under the conditions described above.

[0137] [Adhesion]

[0138] The diaphragm was cut into a size of 50 mm in width × 50 mm in length and placed so that the inorganic particle layer faced upward. Black drawing paper (20 mm in width × 150 mm in length × 0.25 mm in thickness) with a dynamic friction coefficient of 0.15 was placed on the diaphragm and a specified pressure (200 g / cm 2 ), then forcibly remove the black drawing paper from the side, confirm the degree of inorganic matter adhering to the surface, and judge it as A / B / C / D / F according to the following grade (Grade) based on the degree of adhesion.

[0139] A: No adhesion occurs

[0140] B: A small amount of inorganic matter adheres

[0141] C to F are the levels of adhesion of the adhesive and the inorganic matter together, and the closer to F, the more severe the adhesion.

[0142] [Battery resistance characteristics]

[0143] Each battery manufactured according to the embodiment and the comparative example was charged and discharged at a constant current and constant voltage (CCCV) of 4.2V using a charge / discharge cycler. Specifically, at 25°C, each battery was charged at a constant current of 0.5C rate until the voltage reached 4.2V, and constant voltage charged while maintaining 4.2V until the current reached 0.01C. Next, the battery was discharged at a constant current of 0.5C until the voltage reached 3.0V, and the cycle was repeated 600 times. When the residual capacity (state of charge, SoC) at the 600th charge and discharge cycle was 60%, the direct current internal resistance (DC-IR) during discharge was measured using the J-Pulse method to obtain the resistance value.

[0144] At this time, based on the resistance value of Example 1, if the resistance increase of each battery manufactured according to the example and the comparative example is less than 5%, it is marked as "low", if the resistance increase of each battery is more than 5%, it is marked as "medium", and if the resistance increase of each battery is more than 10%, it is marked as "high".

[0145] <Preparation Example 1>

[0146] After nitrogen replacement of a 1.0L flask, 932mmol of acrylamide and 89mmol of 2-hydroxyethyl methacrylate monomer components and 700g of distilled water were added to the flask, and then the temperature was raised to 75°C. Then, 0.789mmol of ammonium persulfate was further added to the flask as a polymerization initiator to obtain a mixture, and the flask was sealed to carry out a polymerization reaction of the mixture. After the polymerization reaction was carried out for 12 hours, the sealed flask was opened to the atmosphere, the temperature was lowered to room temperature, and a 1M sodium hydroxide solution was added to adjust the pH to 7, thereby preparing an aqueous solution of a polyacrylamide-based resin. At this time, the weight average molecular weight of the prepared polyacrylamide-based resin was 300000g / mol.

[0147] <Preparation Example 2>

[0148] The polyacrylamide-based resin aqueous solution was prepared by the same method as in Preparation Example 1, except that 1055 mmol of acrylamide was used alone as a monomer component. At this time, the weight average molecular weight of the prepared polyacrylamide-based resin was 280,000 g / mol.

[0149] <Example 1>

[0150] Preparation of coating slurry

[0151] Based on the total weight of the solids, 96.5 wt% of boehmite (D10: 0.45 μm, D50: 0.71 μm, D90: 1.57 μm, BET specific surface area: 5 m 2 / g) as inorganic particles, 3.0 wt % of the polyacrylamide-based resin of Preparation Example 1, and 0.5 wt % of polyvinyl alcohol (degree of saponification: 88 mol %, Mw: 50000 g / mol) as a binder were added to water, and then stirred to prepare a coating slurry with a solid concentration of 28 wt %.

[0152] Diaphragm manufacturing

[0153] As the porous substrate, a polyethylene porous film with an average thickness of 10 μm (porosity: 42%, Gurley air permeability: 128 sec / 100 ml, MD tensile strength: 2317 kgf / cm 2 , TD tensile strength: 2514kgf / cm 2 The prepared coating slurry was coated on both sides of the porous substrate and then dried to manufacture a separator having an inorganic particle layer with an average thickness of 1.35 μm formed on both sides of the porous substrate. The physical properties of the separator are shown in Table 1 below.

[0154] Manufacturing of secondary batteries

[0155] 94 wt% of LiCoO2 as a positive electrode active material, 2.5 wt% of polyvinylidene fluoride as a binder, and 3.5 wt% of carbon black as a conductive agent are added to N-methyl-2-pyrrolidone (NMP) as a solvent and stirred to prepare a uniform positive electrode slurry. The prepared slurry is coated on an aluminum foil with a thickness of 30 μm and dried and rolled to manufacture a positive electrode with a total thickness of 150 μm. 95 wt% of artificial graphite as a negative electrode active material, 3 wt% of acrylic latex with a Tg of -52°C as a binder, and 2 wt% of carboxymethyl cellulose (CMC) as a thickener are added to water as a solvent and stirred to prepare a uniform negative electrode slurry. The prepared slurry is coated on a copper foil with a thickness of 20 μm and dried and rolled to manufacture a negative electrode with a total thickness of 150 μm. The soft-pack battery is assembled by stacking the manufactured separator between the positive electrode and the negative electrode, and then the assembled battery is thermally fused at 80 ° C and 1 MPa using a hot press to fuse the positive electrode, the negative electrode and the separator to each other. Then, an electrolyte is injected, wherein the electrolyte is an electrolyte in which 1M lithium hexafluorophosphate (LiPF6) is dissolved in a solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 30:50:20, and then sealed to manufacture a secondary battery with a capacity of 2Ah. The resistance characteristics of the secondary battery are shown in Table 1 below.

[0156] <Example 2>

[0157] The separator and the secondary battery were manufactured by the same method as in Example 1, except that 3.5 wt % of the polyacrylamide-based resin of Preparation Example 1 was used as a binder instead of polyvinyl alcohol, and a porous substrate pretreated by the following method was used. The characteristics of the separator and the secondary battery are shown in Table 1 below.

[0158] The pretreated porous substrate was prepared by placing a polyethylene porous membrane (porosity: 42%, Gurley air permeability: 128 sec / 100 ml, MD tensile strength: 2317 kgf / cm 2 , TD tensile strength: 2514kgf / cm 2 ) is produced by performing corona discharge treatment on both sides. At this time, the power density of the corona discharge treatment is set to 2W / mm and the speed is set to 3-20 meters per minute (mpm).

[0159] <Example 3>

[0160] A separator and a secondary battery were manufactured by the same method as in Example 1, except that the same kinds of components as those contained in the coating slurry were used, but the contents were changed to 96.8 wt % of boehmite, 3.0 wt % of the polyacrylamide-based resin of Preparation Example 1, 0.2 wt % of polyvinyl alcohol, and the porous substrate was changed to a polyethylene porous film having an average thickness of 10 μm (porosity: 42%, Gurley air permeability: 109 sec / 100 ml, MD tensile strength: 2055 kgf / cm 2 , TD tensile strength: 2177kgf / cm 2 ). The characteristics of the separator and the secondary battery are shown in Table 1 below.

[0161] <Example 4>

[0162] The separator and the secondary battery were manufactured by the same method as in Example 2, except that a polyethylene porous film having an average thickness of 10 μm (porosity: 42%, Gurley air permeability: 109 sec / 100 ml, MD tensile strength: 2055 kgf / cm 2 , TD tensile strength: 2177kgf / cm 2 ) was subjected to corona discharge treatment and used as a porous substrate. The characteristics of the separator and the secondary battery are shown in Table 1 below.

[0163] <Example 5>

[0164] The separator and the secondary battery were manufactured by the same method as in Example 1, except that boehmite (D10: 0.56 μm, D50: 0.85 μm, D90: 1.93 μm, BET specific surface area: 4 m 2 The properties of the separator and the secondary battery are shown in Table 1 below.

[0165] <Example 6>

[0166] The separator and the secondary battery were manufactured by the same method as in Example 1, except that boehmite (D10: 0.38 μm, D50: 0.67 μm, D90: 1.52 μm, BET specific surface area: 6 m 2 The properties of the separator and the secondary battery are shown in Table 1 below.

[0167] <Example 7>

[0168] A separator and a secondary battery were manufactured by the same method as in Example 1, except that the polyacrylamide-based resin of Preparation Example 2 was used instead of the polyacrylamide-based resin of Preparation Example 1. The characteristics of the separator and the secondary battery are shown in Table 1 below.

[0169] <Comparative Example 1>

[0170] The separator and the secondary battery were manufactured by the same method as in Example 1, except that 93.0 wt % of boehmite (D10: 0.45 μm, D50: 0.71 μm, D90: 1.57 μm, BET specific surface area: 5 m 2 / g) as inorganic particles and 7.0 wt % of a water-dispersible acrylic resin (glass transition temperature of -42°C) with a latex content of 20 wt % as a binder were added to water and stirred to prepare a coating slurry with a solid concentration of 28 wt %, which was used instead of the coating slurry prepared in Example 1. The characteristics of the separator and the secondary battery are shown in Table 2 below.

[0171] <Comparative Example 2>

[0172] The separator and the secondary battery were manufactured by the same method as in Example 2, except that when the separator was manufactured in Example 2, a polyethylene porous film with an average thickness of 9 μm (porosity: 40%, Gurley air permeability: 152 sec / 100 ml, MD tensile strength: 2242 kgf / cm 2 , TD tensile strength: 1864kgf / cm 2 ) were formed on both sides of the separator with an average thickness of 2 μm. The characteristics of the separator and the secondary battery are shown in Table 2 below.

[0173] <Comparative Example 3>

[0174] The separator and the secondary battery were manufactured by the same method as in Example 2, except that boehmite (D10: 0.16 μm, D50: 0.31 μm, D90: 0.75 μm, BET specific surface area: 20 m 2 The characteristics of the separator and the secondary battery are shown in Table 2 below.

[0175] <Comparative Example 4>

[0176] The separator and the secondary battery were manufactured by the same method as in Example 2, except that boehmite (D10: 0.79 μm, D50: 1.64 μm, D90: 2.85 μm, BET specific surface area: 2.5 m 2The characteristics of the separator and the secondary battery are shown in Table 2 below.

[0177] <Comparative Example 5>

[0178] The separator and the secondary battery were manufactured by the same method as in Example 2, except that boehmite (D10: 0.31 μm, D50: 0.58 μm, D90: 1.28 μm, BET specific surface area: 8 m 2 The characteristics of the separator and the secondary battery are shown in Table 2 below.

[0179] [Table 1]

[0180]

[0181] [Table 2]

[0182]

[0183] Referring to Table 1 and Table 2, it is confirmed that compared with the comparative example, the separators of Examples 1 to 7 have a heat shrinkage rate of 5% or less even at a thin thickness, and thus have excellent heat resistance, and no adhesion occurs in the adhesion test, and thus have excellent adhesion. In addition, it is confirmed that the discharge resistance of the battery using the separator after 600 cycles is low.

[0184] In particular, it was confirmed that the polyacrylamide-based resins prepared by further including a (meth)acrylic acid-based monomer containing a hydroxyl group in addition to the (meth)acrylamide-based monomer were used as binders in Examples 1 to 6, and therefore had more excellent heat resistance than that of Example 7 in which the (meth)acrylamide-based monomer was used alone.

[0185] In addition, Example 1 further contains polyvinyl alcohol as a binder, and therefore has more excellent heat resistance than Example 2 even without pre-treating the porous substrate.

[0186] On the other hand, in the separator of Comparative Example 1, the result of using an acrylic resin as a binder confirmed that the heat resistance and adhesive force were significantly reduced at a thin thickness. In addition, it was confirmed that the discharge resistance of the battery using this separator after 600 cycles was significantly higher than that of Example 1.

[0187] In addition, in the separator of Comparative Example 2, the t1 / t2 value is less than 0.75, which does not meet the range of saturated moisture content to be achieved by the present invention. Therefore, it is confirmed that the discharge resistance of the battery using this separator after 600 cycles is significantly higher than that of Example 1.

[0188] In addition, in the separator of Comparative Example 3, a separator having a BET specific surface area of ​​20 m2 / g of inorganic particles, the saturated moisture content range to be achieved by the present invention was not satisfied, and therefore it was confirmed that the discharge resistance of the battery using this separator after 600 cycles was higher than that of Example 1.

[0189] In addition, in the separator of Comparative Example 4, a separator having a BET specific surface area of ​​2.5 m 2 The results of the inorganic particles of 100 g / cm2 do not satisfy the range of saturated moisture content to be achieved by the present invention, so it is confirmed that the heat resistance and adhesion are significantly reduced at a thin thickness. In addition, it is confirmed that the discharge resistance of the battery using the separator after 600 cycles is significantly higher than that of Example 1.

[0190] In addition, in the separator of Comparative Example 5, a separator having a BET specific surface area of ​​8 m 2 / g of inorganic particles, the saturated moisture content range to be achieved by the present invention was not satisfied, and therefore it was confirmed that the discharge resistance of the battery using this separator after 600 cycles was higher than that of Example 1.

[0191] The above-described contents are merely examples of applying the principles of the present invention, and other configurations may be further included without departing from the scope of the present invention.

Claims

1. A diaphragm, comprising: Porous substrates; as well as an inorganic particle layer, the inorganic particle layer being formed on at least one side of the porous substrate and comprising a binder and inorganic particles, The diaphragm has a Gurley air permeability of 10-250 seconds / 100 ml, a puncture strength of more than 0.3N / μm, and a tensile strength of 1500kgf / cm in the mechanical direction and the width direction. 2 In the above, the heat shrinkage in the machine direction and the width direction measured after standing at 130° C. for 60 minutes was 5% or less, and the saturated moisture content measured by the Karl Fischer method was 350-1000 ppm.

2. The diaphragm according to claim 1, wherein The Gurley air permeability is 90-230 seconds / 100 milliliters, and the saturated moisture content is 450-1000 ppm.

3. The diaphragm according to claim 1, wherein The average thickness of the porous substrate is 5-15 μm, and the ratio of the average thickness of the porous substrate to the average thickness of the separator is greater than 0.

7.

4. The diaphragm according to claim 1, wherein The total thickness of the inorganic particle layer formed on the porous substrate is 3.2 μm or less.

5. The diaphragm according to claim 1, wherein The adhesive includes a polyacrylamide-based resin.

6. The diaphragm according to claim 5, wherein The polyacrylamide-based resin is a copolymer including units derived from a (meth)acrylamide-based monomer.

7. The diaphragm according to claim 6, wherein: The polyacrylamide-based resin includes a structural unit derived from a (meth)acrylamide-based monomer and a structural unit derived from a (meth)acrylic acid-based monomer containing a hydroxyl group.

8. The diaphragm according to claim 5, wherein The weight average molecular weight of the polyacrylamide-based resin is 100,000-2,000,000 g / mol.

9. The diaphragm according to claim 5, wherein: The adhesive further comprises any one or two or more water-based polymers selected from polyvinyl alcohol, polyvinylidene fluoride, carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyethylene glycol, polyacrylonitrile, polyvinyl pyrrolidone and copolymers thereof.

10. The diaphragm according to claim 9, wherein The content of the water-based polymer is 0.1-30 wt % of the total content of the adhesive.

11. The diaphragm according to claim 1, wherein The BET specific surface area of ​​the inorganic particles is 3-7 m 2 / g.

12. The diaphragm according to claim 1, wherein The average particle size D50 of the inorganic particles is 0.5-1.5 μm.

13. The diaphragm according to claim 1, wherein The inorganic particles include any one or two or more selected from the group consisting of metal hydroxides, metal oxides, metal nitrides and metal carbides.

14. The diaphragm according to claim 1, wherein The weight ratio of the inorganic particles to the binder in the inorganic particle layer is 50:50 to 99.9:0.

1.

15. The diaphragm according to claim 1, wherein The inorganic particle layer is formed to have a particle size of 0.5-10 g / m 2 .

16. An electrochemical device comprising the separator according to any one of claims 1 to 15.

17. The electrochemical device according to claim 16, wherein: The electrochemical device is a secondary battery.

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