Separator and electrochemical element including the same

Abstract

To provide a separator and an electrochemical element having the separator.SOLUTION: The separator according to one aspect of the present disclosure includes: a porous base material; and an inorganic particle layer formed on at least one surface of the porous base material, the layer containing a binder and inorganic particles. The separator has a peak which appears in the range of 1082.5-1086.5 cm-1 in a spectrum measured by Fourier transformation infrared spectroscopy (FT-IR), and a saturated moisture content measured by the Karl-Fischer method is in the range of 350-1000 ppm.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Recently, with the increasing demand for environmentally friendly energy, research has been conducted on electrochemical elements in various fields, including electronic devices such as mobile phones and PCs, as well as electric vehicles.

[0003] Research is being conducted to make the insulating separator interposed between the positive and negative electrodes thinner in order to achieve the high capacity / high output characteristics of electrochemical devices, but when the separator is made thinner, there is a problem that the mechanical strength and / or heat resistance is reduced. When the mechanical strength and / or heat resistance is reduced, the possibility of safety issues occurring during the manufacturing process and use of the battery increases. For example, a short circuit between the electrodes may occur due to damage or deformation of the separator caused by an increase in temperature inside the battery, which may increase the risk of the battery overheating or fire.

[0004] Therefore, there is a need to develop a separator that has a small thickness and has improved mechanical strength and heat resistance as described above. In addition, there is a need to develop a separator that has high permeability in order to improve capacity and output. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Korean Patent Publication No. 2016-0109669 (September 21, 2016) Summary of the Invention [Problem to be solved by the invention]

[0006] According to one aspect of the present disclosure, it is possible to provide a separator that has excellent heat resistance and adhesiveness even when it is thin, and an electrochemical device including the separator.

[0007] According to another aspect of the present disclosure, it is possible to provide a separator having improved mechanical strength and permeability even with a small thickness, and an electrochemical device including the same.

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

[0009] The separator of the present disclosure can be widely applied in green technology fields such as electric vehicles, battery charging stations, and other battery-based solar power generation and wind power generation, etc. In addition, the separator of the present disclosure can be used in eco-friendly electric vehicles, hybrid vehicles, etc., which prevent climate change by suppressing air pollution and greenhouse gas emissions. [Means for solving the problem]

[0010] The separator according to the present disclosure includes a porous substrate and an inorganic particle layer formed on at least one surface of the porous substrate and containing a binder and inorganic particles. -1 The saturated water content measured by the Karl Fischer method is 350 to 1000 ppm.

[0011] In one embodiment, the saturated water content may be 450 to 1000 ppm.

[0012] In one embodiment, the average thickness of the porous substrate may be 5 to 15 μm, and the ratio of the average thickness of the porous substrate to the average thickness of the separator may be 0.7 or more.

[0013] In one embodiment, the total thickness of the inorganic particle layer formed on the porous substrate may be 3.2 μm or less.

[0014] In one embodiment, the binder may include a polyacrylamide resin.

[0015] In one embodiment, the polyacrylamide resin may be a copolymer containing units derived from a (meth)acrylamide monomer and units derived from a comonomer.

[0016] In one embodiment, the polyacrylamide resin may contain structural units derived from a (meth)acrylamide monomer and structural units derived from a (meth)acrylic monomer containing a hydroxy group.

[0017] In one embodiment, the polyacrylamide resin may have a weight average molecular weight of 100,000 to 2,000,000 g / mol.

[0018] In one embodiment, the binder may further include any one or more additional binders selected from the group consisting of polyvinyl alcohol, polyvinylidene fluoride, carboxymethyl cellulose, styrene butadiene rubber, polyacrylic acid, polyethylene glycol, polyacrylonitrile, polyvinylpyrrolidone, and copolymers thereof.

[0019] In one embodiment, the content of the additional binder may be 0.1 to 30% by weight of the total content of the binder.

[0020] In one embodiment, the inorganic particles have a BET specific surface area of ​​3 to 7 m 2 / g.

[0021] In one embodiment, the inorganic particles may have an average particle size (D50) of 0.5 to 1.5 μm.

[0022] In one embodiment, the inorganic particles may include any one or more selected from the group consisting of metal hydroxides, metal oxides, metal nitrides, and metal carbides.

[0023] In one embodiment, the separator may have a thermal shrinkage of 5% or less in the machine direction and transverse direction measured after being left at 130° C. for 60 minutes.

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

[0025] In one embodiment, the inorganic particle layer has a density of 0.5 to 10 g / m 2 It may be formed of.

[0026] The present disclosure also provides an electrochemical device including a separator as described above. Effect of the Invention

[0027] The separator according to the present disclosure can have excellent heat resistance and adhesiveness even at a small thickness.

[0028] Furthermore, the separator according to the present disclosure can have excellent mechanical strength and permeability even with a small thickness.

[0029] Furthermore, the present disclosure can provide an electrochemical device having excellent resistance characteristics and thermal safety by including a separator according to one embodiment. [Brief description of the drawings]

[0030] [Figure 1] 1 is an FT-IR spectrum measured for the separator according to Example 1. [Diagram 2] 4 is an FT-IR spectrum measured for the separator according to Comparative Example 2. [Diagram 3] 4 is an FT-IR spectrum measured for the separator according to Comparative Example 3. [Figure 4] 4 is an FT-IR spectrum measured for the separator according to Comparative Example 4. [Diagram 5] FIG. 2 is an enlarged view of a portion of the FT-IR spectra measured for the separators of Example 1 and Comparative Examples 2 to 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The present disclosure will now be described in detail, but this is by way of example only and is not intended to be limiting of the present disclosure to the specific embodiments illustratively described.

[0032] Also, as used in the specification and the appended claims, the singular forms "a," "an," and "the" can be intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0033] In addition, the numerical ranges used herein include lower and upper limits, and all values ​​within the range, increments logically derived from the form and width of the ranges defined, and all values ​​limited therein, and all possible combinations of upper and lower limits of numerical ranges limited in different forms from each other. Unless otherwise specified herein, values ​​outside the numerical ranges that may occur due to experimental error or rounding of values ​​are included in the numerical ranges defined.

[0034] Furthermore, throughout the specification, the term "comprising" an element means that it may further include other elements, but not excluding other elements, unless specifically stated to the contrary.

[0035] As used herein, when a layer, film, region, plate, or other part is referred to as being "on" or "on top of" another part, this includes not only when it is "directly on" the other part, but also when there are other parts in between.

[0036] In this specification, "average particle size" refers to "D50", and "D50" refers to the particle size of inorganic particles that corresponds to 50% of the total volume fraction. The average particle size can be derived from the particle size distribution of inorganic particles to be measured, which are collected according to the ISO 13320-1 standard and analyzed using a Microtrac S3500. "D90" refers to the particle size of particles that correspond to 90% of the total volume fraction, and "D10" refers to the particle size of inorganic particles that correspond to 10% of the total volume fraction. D90 and D10 can be derived in the same manner as D50.

[0037] The present disclosure provides a porous substrate and an inorganic particle layer formed on at least one surface of the porous substrate, the inorganic particle layer including a binder and inorganic particles, the inorganic particle layer having a wavelength of 1082.5 to 1086.5 cm in a spectrum measured by Fourier transform infrared spectroscopy (FT-IR). -1 The present invention provides a separator having a peak (hereinafter referred to as the first peak) appearing in the range of 350 to 1000 ppm of saturated moisture content as measured by the Karl Fischer method.

[0038] According to one embodiment, in the FT-IR spectrum, -1 A separator having a peak in this range and a saturated moisture content of 350 to 1000 ppm can provide a separator that is excellent in heat resistance and adhesiveness even with a thin thickness, and also has excellent permeability.

[0039] In addition, the electrochemical device according to one embodiment may have both excellent resistance characteristics and thermal safety by including a separator that simultaneously satisfies a first peak in a specific range in an FT-IR spectrum and a saturated water content in a specific range. Specifically, the electrochemical device according to one embodiment may have a significantly low discharge resistance after 600 cycles and may have improved charge / discharge performance.

[0040] On the other hand, if the increase rate of the moisture content of the separator is large, the moisture content remaining in the battery will be high even after assembly into the battery, and such an increase in the moisture content may cause the electrolyte to decompose, which may result in a decrease in the capacity of the battery. Conventionally, in order to reduce the moisture content in the battery, it was necessary to use an expensive packaging material such as aluminum. On the other hand, the separator according to the present disclosure has the advantage of having a small increase rate in the moisture content due to storage by simultaneously satisfying a first peak in a specific range that appears in the FT-IR spectrum and a saturated moisture content in a specific range. As a result, the present disclosure can provide a battery with excellent performance even if the moisture content remaining in the battery is low and a packaging material made of polyethylene material is used instead of aluminum material. In other words, the present disclosure has the advantage of improving the performance of the battery and reducing the cost of the battery.

[0041] In one embodiment, the separator has a very thin inorganic particle layer, in which the average thickness of the porous substrate is 15 μm or less and the thickness of the porous substrate is 0.7 times or more the total thickness of the separator, and yet has excellent mechanical properties, electrical properties, and thermal properties, as described below. The production of a separator having the above properties can be achieved by adjusting any one or more selected from the thickness of each layer of the separator, the size of the inorganic particles, the type of binder, the type of binder used, the surface properties of the porous substrate, the surface area of ​​the inorganic particles, and the saturated moisture content of the separator, but the means are not particularly limited as long as this can be achieved.

[0042] In one embodiment, a separator having a first peak in a specific range in an FT-IR spectrum and a saturated water content in a specific range can be manufactured using inorganic particles having a specific specific surface area. For example, a separator according to one embodiment includes inorganic particles having a BET specific surface area of ​​3 m 2 / g or more, 4m 2 / g or more, 7m 2 / g or less, 6m 2 / g or less or a value between the above values, specifically, 3 to 7m 2 / g or 4~6m 2 / g.

[0043] In one embodiment, the separator as described above can be manufactured by adjusting the thickness ratio of the porous substrate contained therein to a specific value. For example, 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, 0.7 to 0.99, 0.75 to 0.9, or 0.77 to 0.85.

[0044] In one embodiment, the separator as described above may be manufactured by using a binder contained therein as a specific resin. For example, the binder may include a polyacrylamide-based resin, and may be preferably a polyacrylamide-based resin including a structural unit derived from a (meth)acrylamide-based monomer and a structural unit derived from a (meth)acryl-based monomer containing a hydroxyl group.

[0045] According to one embodiment, the separator as described above may be manufactured by using a specific additional binder together with the polyacrylamide resin as a binder. For example, the specific additional binder may be any one or more selected from the group consisting of polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and copolymers thereof.

[0046] According to another embodiment, the separator as described above may be manufactured by using the polyacrylamide resin as a binder and a porous substrate having a polar functional group on the surface. Non-limiting examples of the polar functional group include, but are not limited to, a carboxyl group, an aldehyde group, and a hydroxyl group. According to one example, the polar functional group may be introduced by a hydrophilic surface treatment, and according to one example, the hydrophilic surface treatment may include one or more of a corona discharge treatment and a plasma discharge treatment.

[0047] The separator having the first peak in a specific range in the FT-IR spectrum and the saturated water content in a specific range as described above may be obtained by adjusting any one or a combination of two or more selected from the thickness and thickness ratio of each layer of the separator, the size of the inorganic particles, the type of binder, the type of binder used, the surface characteristics of the porous substrate, and the surface area of ​​the inorganic particles. However, as long as the separator can satisfy the first peak in the FT-IR spectrum and the saturated water content in a specific range, it is within the scope of the present disclosure, and the means for achieving this is not particularly limited.

[0048] The separator will now be described in more detail.

[0049] In one embodiment, the first peak has a wavelength of 1082.5 to 1086.5 cm -1 Specifically, the peak has a maximum intensity in the range of 1083 to 1086.5 cm -1 or 1083.5~1086cm -1 It may be a peak having a maximum intensity in the range of

[0050] In one embodiment, the separator has a peak at 1140 to 1160 cm in an FT-IR spectrum. -1 The second peak may further have a second peak appearing in the range of 1145 to 1155 cm. The second peak is a peak having a maximum intensity in the above range, specifically, 1145 to 1155 cm. -1 It may be a peak having a maximum intensity in the range of

[0051] In one embodiment, the separator has a peak at 2910 to 2930 cm in an FT-IR spectrum. -1 The third peak may further have a third peak appearing in the range of 2915 to 2925 cm. The third peak is a peak having a maximum intensity in the above range, specifically, 2915 to 2925 cm. -1 range or 2915~2920cm -1 It may be a peak having a maximum intensity in the range of

[0052] In one embodiment, the separator has a peak intensity of 3090 to 3100 cm in an FT-IR spectrum. -1 The fourth peak may further have a fourth peak appearing in the range of 3092 to 3098 cm. The fourth peak is a peak having a maximum intensity in the above range, specifically, 3092 to 3098 cm. -1 It may be a peak having a maximum intensity in the range of

[0053] In one embodiment, the separator has a peak intensity of 3270 to 3295 cm in an FT-IR spectrum. -1 The fifth peak may further have a fifth peak appearing in the range of 3275 to 3290 cm. The fifth peak is a peak having a maximum intensity in the above range, specifically, 3275 to 3290 cm. -1 or 3275~3285cm -1 It may be a peak having a maximum intensity in the range of

[0054] In one embodiment, the FT-IR spectrum of the separator may be measured using an FT-IR device equipped with a mercury cadmium telluride (MCT) detector, specifically, 4000 to 675 cm -1 Within 4cm -1 The measurement may be performed in transmission mode, with 5 to 200 scans at a resolution of 100 nm.

[0055] In one embodiment, the Gurley permeability of the separator may be 250sec / 100cc or less, 230sec / 100cc or less, 200sec / 100cc or less, 180sec / 100cc or less, 10sec / 100cc or more, 50sec / 100cc or more, 90sec / 100cc or more, 100sec / 100cc or more, or a value between the above values. Specifically, the Gurley permeability may be 10 to 250sec / 100cc, 50 to 200sec / 100cc, 90 to 230sec / 100cc, or 100 to 180sec / 100cc. By satisfying the Gurley permeability in the above range, the separator may have excellent ion conductivity, and the charge / discharge characteristics of the electrochemical element may be improved due to the low internal resistance of the electrochemical element.

[0056] In one embodiment, the separator may have a puncture strength of 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 numerical values. Specifically, the puncture strength may be 0.3 to 1.0 N / μm, 0.32 to 0.8 N / μm, or 0.35 N / μm to 0.5 N / μm.

[0057] In one embodiment, the separator has a tensile strength in the machine direction (MD) of 1500 to 2500 kgf / cm 2 or 1500~2000kgf / cm 2 may be also possible.

[0058] In one embodiment, the separator has a tensile strength in the transverse direction (TD) of 1500 kgf / cm 2 More than 1600kgf / cm 2 More than 1700kgf / cm 2 More than 2500kgf / cm 2 Below 2000kgf / cm 2 The tensile strength in the width direction may be 1500 to 2500 kgf / cm or less or may be a value between the above values. 2 , 1600~2000kgf / cm 2 or 1700~2000kgf / cm 2 may be also possible.

[0059] 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 to dendrites generated during charging and discharging of the electrochemical device, thereby ensuring the safety of the electrochemical device.

[0060] In one embodiment, the saturated water content is measured after leaving the sample in a thermo-hygrostat set at 40° C. and a relative humidity of 90% for 24 hours, and 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 water content may be 350 to 1000 ppm, 450 to 1000 ppm, 500 to 900 ppm, 550 to 800 ppm, or 600 to 750 ppm.

[0061] In one embodiment, the average thickness t 1 is 5 to 15 μm, and the average thickness of the porous substrate and the average thickness of the separator t 2 Ratio to t 1 / t 2 may be 0.7 or more. The separator according to one embodiment can simultaneously achieve the above-mentioned ranges of Gurley permeability, puncture strength, tensile strength, and saturated water content even under the above-mentioned ranges of thickness conditions. This allows the separator for secondary batteries to be thin, making it suitable for application to high-capacity / high-power batteries.

[0062] In one embodiment, the average thickness of the porous substrate is not necessarily limited thereto, but may be 5 μm or more, 8 μm or more, 15 μm or less, 12 μm or less, or a value between the above numerical values. Specifically, the average thickness of the porous substrate may be 5 to 15 μm or 8 to 12 μm.

[0063] In one embodiment, the ratio of the average thickness of the porous substrate to the average thickness of the separator may 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 numerical values. Specifically, the ratio of the average thickness of the porous substrate to the average thickness of the separator may be 0.7 to 0.99, 0.75 to 0.9, or 0.77 to 0.85.

[0064] In one embodiment, the average thickness of the separator may be, but is not necessarily limited to, 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 numerical values. Specifically, the average thickness of the separator may be 7 to 20 μm, 10 to 15 μm, or 12 to 15 μm.

[0065] In one embodiment, the inorganic particle layer may be coated on one or both sides of the porous substrate. When the inorganic particle layer is coated on both sides of the porous substrate, the thicknesses of the inorganic particle layers coated on one side and the other side may be the same or different.

[0066] In one embodiment, the total thickness of the inorganic particle layer formed on the porous substrate may be, but is not necessarily limited to, 4 μm or less, 3.5 μm or less, 1 μm or more, 1.5 μm or more, or a value between the above numerical values. Preferably, the total thickness of the inorganic particle layer may be 3.2 μm or less. Specifically, the total thickness of the inorganic particle layer may be 1 to 4 μm, 1.5 to 3.5 μm, 1 to 3.2 μm, or 1.5 to 3.2 μm.

[0067] In one embodiment, the binder may include a polyacrylamide resin.

[0068] In one embodiment, the polyacrylamide resin may be polyacrylamide or a copolymer containing the same. In one embodiment, the copolymer may be a block copolymer or a random copolymer, but the copolymer described in one embodiment of the present disclosure is a random copolymer obtained by mixing and polymerizing two or more monomers together.

[0069] In one embodiment, the polyacrylamide resin may be a copolymer containing a unit derived from a (meth)acrylamide monomer and a unit derived from a comonomer. Preferably, the polyacrylamide resin may contain a structural unit derived from a (meth)acrylamide monomer and a structural unit derived from a (meth)acrylic monomer containing a hydroxyl group.

[0070] According to an embodiment, the separator includes the copolymer instead of a homopolymer derived from an acrylamide monomer, and thus mechanical strength, gas permeability, heat resistance, and adhesiveness can be further improved. In addition, an electrochemical device including the separator can have better resistance characteristics and thermal safety.

[0071] The unit derived from the (meth)acrylamide monomer of the polyacrylamide resin may be represented by the following Chemical Formula 1.

[0072] [ka]

[0073] In the above formula 1, R 1 may be hydrogen or a C1 to C6 alkyl group.

[0074] The unit derived from the (meth)acrylic monomer containing a hydroxy group of the polyacrylamide resin can be represented by the following Chemical Formula 2.

[0075] [ka]

[0076] In the above formula 2, R 2 is hydrogen or a C1 to C6 alkyl group. 1is a C1 to C6 linear or branched alkylene group, specifically a C1 to C3 alkylene group, and more specifically can be ethylene.

[0077] In one embodiment of the polyacrylamide resin, the (meth)acrylamide monomer may be contained in an amount of 65 to 98 mol%, 70 to 97 mol%, or 75 to 95 mol%. The (meth)acrylic monomer containing a hydroxyl group may be contained in an amount of 2 to 35 mol%, 3 to 30 mol%, or 5 to 25 mol%. When the polyacrylamide resin is produced within the above content ranges, sufficient adhesive strength can be obtained, and a more significant effect can be obtained in terms of high temperature shrinkage rate.

[0078] In one embodiment, the polyacrylamide resin may have a weight average molecular weight in terms of polyethylene glycol measured by gel permeation chromatography of 100,000 g / mol or more, 200,000 g / mol or more, 2,000,000 g / mol or less, 1,000,000 g / mol or less, 500,000 g / mol or less, or a value between the above values. Specifically, the polyacrylamide resin may have a weight average molecular weight of 100,000 to 2,000,000 g / mol, 200,000 to 1,000,000 g / mol, or 200,000 to 500,000 g / mol. According to one embodiment, when the weight average molecular weight of the polyacrylamide resin satisfies the above range, the heat resistance and adhesiveness can be further improved.

[0079] In one embodiment, the binder may further include any one or more additional binders selected from the group consisting of polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and copolymers thereof.

[0080] In one embodiment, the separator may further improve mechanical strength, gas permeability, heat resistance, and adhesiveness by using the additional binder together with the polyacrylamide resin as a binder. In addition, the improvement in physical properties as described above may be achieved without pretreatment such as corona discharge treatment of the porous substrate, which has the advantage of reducing time and material costs in terms of processing.

[0081] In one embodiment, the content of the additional binder may 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 of the total binder content, or a value between the above values. Specifically, the content of the additional binder may be 0.1 to 30% by weight, 1 to 20% by weight, or 5 to 15% by weight, but is not necessarily limited thereto.

[0082] In one embodiment, when the additional binder is polyvinyl alcohol, the degree of saponification may be 80 to 95 mol %, specifically 85 to 90 mol %, but is not particularly limited thereto.

[0083] In one embodiment, the weight average molecular weight of the additional binder may be 10,000 to 100,000 g / mol, specifically, 30,000 to 70,000 g / mol, but is not particularly limited thereto.

[0084] The separator according to one embodiment can have excellent heat resistance even at a small thickness. In one embodiment, the separator has a heat shrinkage rate in the machine direction and the width direction measured after being left at 130° C. for 60 minutes of 5% or less, preferably 4% or less, more preferably 3% or less, 2% or less, or 1.5% or less.

[0085] In one embodiment, the porous substrate may be a polyolefin-based porous substrate such as polyethylene, polypropylene, or a copolymer thereof, but is not limited thereto, and any porous substrate known as a porous substrate for a separator of an electrochemical device may be used. In one embodiment, the porous substrate may be manufactured as a film or sheet, but is not particularly limited thereto.

[0086] In one embodiment, the porous substrate may have a porosity of 20 to 60%, specifically 30 to 60%, but is not limited thereto.

[0087] In one embodiment, the inorganic particle layer may include a binder and inorganic particles, or may be a porous inorganic particle layer in which inorganic particles are linked and fixed by the binder to form pores. In one embodiment, the inorganic particle layer is provided on at least one surface of the porous substrate, and may occupy an area fraction of 60% or more, 70% or more, 80% or more, or 90% or more of the entire surface of the porous substrate, and preferably, the inorganic particle layer may be formed on 100% of the area of ​​the porous substrate.

[0088] In one embodiment, the inorganic particles are not limited as long as they are inorganic particles used in the art. As a non-limiting example, the inorganic particles may include any one or more selected from the group consisting of metal hydroxides, metal oxides, metal nitrides, and metal carbides. For example, the inorganic particles may include magnesium oxide (MgO), magnesium hydroxide (Mg(OH) 2 ), Alumina (Al 2 O 3 ), boehmite (γ-AlO(OH)), aluminum hydroxide (Al(OH) 3 ), silica (SiO 2 ), silicon carbide (SiC), calcium oxide (CaO), titanium dioxide (TiO 2 ), strontium titanate (SrTiO 3 ), zinc oxide (ZnO), yttrium oxide (Y 2 O 3 ), zirconium oxide (ZrO 2 ), tin oxide (SnO 2 ) and cerium oxide (CeO 2 From the viewpoint of battery stability, the inorganic particles may preferably include, for example, boehmite, aluminum hydroxide (Al(OH) 3 ) and magnesium hydroxide (Mg(OH) 2 ) may be any one or more metal hydroxide particles selected from the group consisting of:

[0089] In one embodiment, the shape of the inorganic particles is not limited and may be spherical, elliptical, acicular, or the like.

[0090] In one embodiment, the inorganic particles have a BET specific surface area of ​​3 m 2 / g or more, 4m 2 / g or more, 7m 2 / g or less, 6m 2 / g or less or a value between the above values. Specifically, the BET specific surface area of ​​the inorganic particles is 3 to 7 m 2 / g or 4~6m 2 / g. When the specific surface area is within the above range, the present disclosure can provide a separator that simultaneously satisfies the physical properties that the present disclosure aims to achieve. Here, the BET specific surface area of ​​the inorganic particles may be measured in accordance with the ASTM C1069 method.

[0091] In one embodiment, the inorganic particles may have an average particle size (D50) of 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 inorganic particles may have a D50 of 0.5 to 1.5 μm or 0.6 to 1.0 μm, but this can be changed without departing from the scope of the present disclosure.

[0092] In one embodiment, the inorganic particle layer may have a weight ratio of inorganic particles to binder of 50:50 to 99.9:0.1, 60:40 to 98:2, or 80:20 to 98:2, but is not particularly limited thereto.

[0093] In one embodiment, the inorganic particle layer has a density of 0.5 to 10 g / m 2 , specifically 1 to 5 g / m 2 , more specifically 2.5 to 4 g / m 2 However, the present invention is not particularly limited thereto.

[0094] A method for producing the separator of the present disclosure will now be described.

[0095] A method for producing a separator that simultaneously satisfies the above-mentioned physical properties may include a first step of producing a coating slurry containing a binder and inorganic particles, and a second step of applying the coating slurry to at least one surface of a porous substrate to form an inorganic particle layer.

[0096] The porous substrate, inorganic particle layer, inorganic particles, and binder are as described above, and detailed description thereof will be omitted.

[0097] The method for preparing the coating slurry in the first step may be any method known in the art without any limitation, and is not particularly limited. According to a non-limiting example, the inorganic particles may be dispersed by stirring to prepare a slurry, or the aggregated inorganic particles may be dispersed using a ball mill.

[0098] The coating slurry includes inorganic particles, a binder, and a solvent, and the solvent may be, but is not limited to, water, lower alcohols such as ethanol, methanol, and propanol, dimethylformamide, acetone, tetrahydrofuran, diethyl ether, methylene chloride, DMF, N-methyl-2-pyrrolidone, hexane, and cyclohexane, or a mixture thereof.

[0099] In one embodiment, the solid content of the coating slurry is not particularly limited, and may be, for example, 1 to 50% by weight, 5 to 30% by weight, or 10 to 30% by weight, but is not limited thereto.

[0100] In one embodiment, the coating slurry may contain, based on the total weight of the solid content, 50 to 99.9 wt % of inorganic particles and 0.1 to 50 wt % of binder, specifically, 60 to 98 wt % of inorganic particles and 2 to 40 wt % of binder, more specifically, 80 to 98 wt % of inorganic particles and 2 to 20 wt % of binder, but is not limited thereto.

[0101] The method of applying the coating slurry in the second step may be any method known in the art without limitation, and non-limiting examples include roll coating, spin coating, dip coating, bar coating, die coating, slit coating, inkjet printing, and combinations thereof. The applied slurry may be dried to form an inorganic particle layer. The drying for forming the inorganic particle layer is not particularly limited, and may be performed at 100°C or less, or at 30 to 60°C.

[0102] In a specific embodiment, the method may not further include a step of aging the porous substrate on which the inorganic particle layer is formed after drying for forming the inorganic particle layer. The aging may be performed at 50 to 150°C or 60 to 120°C, and the aging time may be 2 to 24 hours or 10 to 20 hours. More specifically, the aging may be performed at a temperature range of 70 to 120°C for 10 to 15 hours. According to one embodiment, a separator that simultaneously satisfies the above-mentioned physical properties can be produced without performing the aging step, which has the advantage of reducing time and material costs in terms of the process.

[0103] The present disclosure provides an electrochemical element including a separator according to one of the above-mentioned embodiments. The electrochemical element includes the separator as described above, and thus has reduced electrical resistance, significantly excellent life characteristics, and excellent thermal stability at high temperatures.

[0104] The electrochemical device may be any known energy storage device, and is not particularly limited thereto, but a non-limiting example thereof is a lithium secondary battery. The lithium secondary battery is known and its configuration is also well known, so it will not be described in detail in this disclosure.

[0105] The lithium secondary battery according to one embodiment may include the above-mentioned separator between the positive electrode and the negative electrode. Here, the positive electrode and the negative electrode can be any electrode that is generally used in lithium secondary batteries without any restrictions.

[0106] The separator according to one embodiment is generally manufactured in a battery by a typical method of assembling a negative electrode, a separator, and a positive electrode, and then injecting an electrolyte, when used in a battery. Therefore, the separator will not be described in further detail here.

[0107] The following describes the embodiments of the present disclosure further with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are merely illustrative of the present disclosure and do not limit the scope of the appended claims. It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope of the scope and technical ideas of the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended claims.

[0108] First, a method for measuring the physical properties of the separator and a method for evaluating the characteristics of the secondary battery will be described.

[0109] [FT-IR spectrum measurement] The separator was cut into a size of 1 cm x 1 cm to prepare a measurement sample, and the measurement was performed under the following conditions using an FT-IR device (Nicolet iN10 Infrared Microscope, manufactured by Thermo Scientific) equipped with an MCT (mercury cadmium telluride) detector.

[0110] -resolution:4cm -1 -scans:16 -range 4000~675cm -1 - Measurement points per sample: 15 points (10μm intervals) * 15 points (10μm intervals) mapping 3 positions

[0111] [Average thickness of separator and porous substrate (μm)] After stacking the separators 10 times, the thickness was measured at 5 random points in the width direction using a Mitutoyo thickness gauge, and then divided by 5 to obtain the average thickness of the 10 separators, and then divided by 10 to obtain the average thickness of the entire single separator.

[0112] The average thickness of the porous substrate was determined by stacking 10 layers of the porous substrate only, measuring the thickness at any 5 points in the width direction with a Mitutoyo thickness meter, adding up the total thickness, and dividing by 5 to obtain the average thickness of the 10-layer porous substrate, and then dividing by 10 to obtain the average thickness of the porous substrate. After the inorganic particle layer was formed, the inorganic particle layer was detached and sufficiently dried, and the average thickness of the porous substrate from which the inorganic particle layer was detached was determined by the above-mentioned method.

[0113] [Gurley permeability (sec / 100cc)] Measurements were performed using a Densometer manufactured by Toyoseiki Co., Ltd. in accordance with the ASTM D726 standard. The time it took for 100 cc of air to pass through a 1 square inch area of ​​the separator was recorded in seconds and compared.

[0114] [Punching strength (N / μm)] The puncture strength was measured by attaching a pin tip with a diameter of 1.0 mm and a curvature radius of 0.5 mm to an INSTRON Universal Test Machine (UTM) 3345 and pressing the separator at a speed of 120 mm / min. The puncture strength was calculated by dividing the load (N) at which the separator broke by the thickness (μm) of the separator.

[0115] [Tensile strength (kgf / cm 2 )] The tensile strength was measured at room temperature (25°C) in accordance with ASTM D882, using an INSTRON Universal Test Machine (UTM) 3345, in which the separator was pulled in both the transverse and machine directions at a speed of 100 mm / min, and the strength at which the separator broke was measured.

[0116] [Heat shrinkage rate (%)] The separator is cut into a square shape with each side being 10 cm long, and the transverse direction (TD) and machine direction (MD) are marked. The sample is placed in the center, and five sheets of paper are placed above and below the sample, and the four sides of the paper are wrapped with tape. The paper-wrapped test piece is left in a hot air drying oven at 130°C for 60 minutes. The sample is then removed, the separator is measured with a camera, and the thermal shrinkage in the machine direction (MD) and the transverse direction (TD) are calculated using the following formula.

[0117] MD heat shrinkage rate (%) = [(MD length before heating - MD length after heating) / MD length before heating] x 100 TD heat shrinkage rate (%) = [(TD length before heating - TD length after heating) / TD length before heating] x 100

[0118] [Saturated water content (ppm)] The Karl Fischer method was used to measure the saturated moisture content of the separator. The measurement equipment used was a Karl Fischer titration device manufactured by Metrohm. The measurement conditions were: separator sample weight 0.3 g, oven temperature 150 °C, and measurement time 600 seconds.

[0119] Specifically, the prepared separator was left in a thermohygrostat set at 40° C. and a relative humidity of 90% for 24 hours, and then the saturated moisture content was measured under the same conditions.

[0120] [Adhesive strength] The separator is cut to a size of 50 mm wide x 50 mm long, and placed so that the inorganic particle layer is on top. A piece of black construction paper (20 mm wide x 150 mm long x 0.25 mm thick) with a dynamic friction coefficient of 0.15 is placed on top of it, and a predetermined pressure (200 g / cm) is applied using a press device. 2 ) is applied, the black drawing paper is forcefully removed sideways to check the level of inorganic matter on the surface, and depending on the level of matter, it is classified into grades A / B / C / D / E / F according to the following.

[0121] A: Nothing attached B: A small amount of inorganic matter is attached C to F are levels where both binder and inorganic matter are present, and the level F is the more severe.

[0122] [Battery resistance characteristics] Each battery manufactured according to the examples and comparative examples was charged at 4.2V CCCV (Constant Current-Constant Voltage) using a charge / discharge cycle device, and then discharged. Specifically, each battery was charged at a constant current of 0.5C rate at 25°C until the voltage reached 4.2V, and then charged at a constant voltage of 0.01C while maintaining 4.2V. Then, during discharge, a cycle of discharging at a constant current of 0.5C until the voltage reached 3.0V was repeated 600 times. When the remaining capacity (State of charge; SoC) at the 600th charge / discharge cycle was 60%, DC-IR (Direct Current Internal Resistance) was measured during discharge using the J-Pulse method to derive the resistance value.

[0123] Here, based on the resistance value of Example 1, if the increase in resistance of each battery manufactured according to the Examples and Comparative Examples was less than 5%, it was indicated as "low", if it was 5% or more, it was indicated as "medium", and if it was 10% or more, it was indicated as "high".

[0124] <Example 1> Coating Slurry Production Based on the total weight of the solid content, boehmite (D10: 0.45 μm, D50: 0.71 μm, D90: 1.57 μm, BET specific surface area: 5 m) was used as inorganic particles. 296.5% by weight of ethylenediaminetetraacetate (100,000 g / g) and 3.0% by weight of polyacrylamide resin (Mw=300,000 g / mol, acrylamide and 2-hydroxyethyl methacrylate 90 mol %:10 mol %) as a binder, and 0.5% by weight of polyvinyl alcohol (saponification degree 88 mol %, Mw: 50,000 g / mol) were added to water and stirred to produce a coating slurry with a solid concentration of 28% by weight.

[0125] Separator manufacturing As a porous substrate, a polyethylene porous film having an average thickness of 10 μm (porosity: 42%, Gurley permeability: 128 sec / 100 cc, MD tensile strength: 2,317 kgf / cm 2 TD tensile strength: 2,514kgf / cm 2 ) was used. The prepared coating slurry was coated on both sides of the porous substrate and then dried to prepare a separator having an inorganic particle layer with an average thickness of 1.35 μm formed on each side of the porous substrate. The physical properties of the separator are summarized in Table 1 below, and the FT-IR spectrum measurement results of the separator are shown in Table 3, FIG. 1, and FIG. 5.

[0126] Secondary battery manufacturing As a positive electrode active material, LiCoO 2A uniform positive electrode slurry was prepared by adding 94 wt% of the above, 2.5 wt% of polyvinylidene fluoride as a fusing agent, 3.5 wt% of carbon black as a conductive agent, and NMP (N-methyl-2-pyrrolidone) as a solvent and stirring. The slurry was coated on an aluminum foil with a thickness of 30 μm, dried and pressed to prepare a positive electrode with a total thickness of 150 μm. A uniform negative electrode slurry was prepared by adding 95 wt% of artificial graphite as a negative electrode active material, 3 wt% of acrylic latex with a Tg of -52°C as a fusing agent, and 2 wt% of CMC (Carboxymethyl cellulose) as a thickener to water as a solvent and stirring. The prepared negative electrode slurry was coated on a copper foil having a thickness of 20 μm, dried and pressed to prepare a negative electrode having a total thickness of 150 μm. The prepared separator was stacked between the positive electrode and the negative electrode to assemble a pouch-type battery, and the assembled battery was heat-sealed at 80° C. and 1 MPa in a heat press to fuse the positive electrode, negative electrode and separator together. Then, 1 M lithium hexafluorophosphate (LiPF 6 The electrolyte in which 1,2-dimethylformamide (D) was dissolved was injected into the battery, which was then sealed to prepare a secondary battery with a capacity of 2 Ah. The resistance characteristics of the secondary battery are summarized in Table 1 below.

[0127] <Example 2> The same procedure as in Example 1 was carried out, except that polyvinyl alcohol was not used as the binder, but 3.5% by weight of a polyacrylamide-based resin was used, and a porous substrate pretreated in the following manner was used. The pretreated porous substrate was a polyethylene porous film (porosity: 42%, Gurley permeability: 128 sec / 100 cc, MD tensile strength: 2,317 kgf / cm) having an average thickness of 10 μm. 2 TD tensile strength: 2,514kgf / cm 2The corona discharge treatment was performed at a power density of 2 W / mm and a speed of 3 to 20 mpm (meter per minute).

[0128] The properties of the prepared separator and secondary battery are summarized in Tables 1 and 3 below.

[0129] <Example 3> In Example 1, when preparing the coating slurry, boehmite (D10: 0.56 μm, D50: 0.85 μm, D90: 1.93 μm, BET specific surface area: 4 m) was used as inorganic particles. 2 A separator and a secondary battery were manufactured in the same manner as in Example 1, except that a 100% cellulose acetate solution was used. The properties of the separator and the secondary battery are summarized in Tables 1 and 3 below.

[0130] <Example 4> In Example 1, when preparing the coating slurry, boehmite (D10: 0.38 μm, D50: 0.67 μm, D90: 1.52 μm, BET specific surface area: 6 m) was used as inorganic particles. 2 A separator and a secondary battery were manufactured in the same manner as in Example 1, except that a 100% cellulose acetate solution was used. The properties of the separator and the secondary battery are summarized in Tables 1 and 3 below.

[0131] <Example 5> A separator and a secondary battery were manufactured in the same manner as in Example 1, except that polyacrylamide having a weight average molecular weight of 200,000 g / mol was used instead of the polyacrylamide resin in Example 1. The characteristics of the separator and the secondary battery are summarized in Tables 1 and 3 below.

[0132] <Comparative Example 1> When manufacturing the separator in Example 2, a polyethylene porous film having an average thickness of 9 μm (porosity: 40%, Gurley permeability: 152 sec / 100 cc, MD tensile strength: 2,242 kgf / cm 2 TD tensile strength: 1,864kgf / cm2 A separator and a secondary battery were manufactured in the same manner as in Example 2, except that inorganic particle layers were formed on both sides of the separator (1) with an average thickness of 2 μm. The properties of the separator and the secondary battery are summarized in Tables 2 and 3 below.

[0133] <Comparative Example 2> In Example 2, when preparing the coating slurry, boehmite (D10: 0.16 μm, D50: 0.31 μm, D90: 0.75 μm, BET specific surface area: 20 m) was used as the inorganic particles. 2 A separator and a secondary battery were manufactured in the same manner as in Example 2, except that a 100% cellulose acetate solution was used. The properties of the separator and the secondary battery are shown in Tables 2 and 3, and in FIG. 2 and FIG. 5.

[0134] <Comparative Example 3> In Example 2, when preparing the coating slurry, boehmite (D10: 0.79 μm, D50: 1.64 μm, D90: 2.85 μm, BET specific surface area: 2.5 m) was used as inorganic particles. 2 A separator and a secondary battery were manufactured in the same manner as in Example 2, except that a 100% cellulose acetate solution was used. The properties of the separator and the secondary battery are shown in Tables 2 and 3, and in FIG. 3 and FIG. 5.

[0135] <Comparative Example 4> In Example 2, when preparing the coating slurry, boehmite (D10: 0.31 μm, D50: 0.58 μm, D90: 1.28 μm, BET specific surface area: 8 m) was used as the inorganic particles. 2 A separator and a secondary battery were manufactured in the same manner as in Example 2, except that a 100% cellulose acetate solution was used. The properties of the separator and the secondary battery are shown in Tables 2 and 3, and in FIGS. 4 and 5.

[0136] [Table 1]

[0137] [Table 2]

[0138] [Table 3]

[0139] Referring to Tables 1 and 2, the separators of Examples 1 to 5 have excellent heat resistance with a thermal shrinkage rate of 5% or less even at a thin thickness, and have excellent adhesion with no defects in the adhesion test, compared to the comparative example. It was also confirmed that the discharge resistance of the battery using these separators after 600 cycles was low.

[0140] Specifically, referring to Table 3, in the FT-IR spectrum, -1 In the case of the separators of the examples, which have a peak in the above range and a saturated moisture content of 350 to 1000 ppm, the separators were excellent in all respects of heat resistance, adhesion, and battery resistance characteristics, unlike Comparative Examples 2 to 4 which do not have a peak in the above range and a saturated moisture content of 350 to 1000 ppm, and Comparative Example 1 which does not have a saturated moisture content in the above range.

[0141] In particular, Examples 1 to 4 use polyacrylamide resins prepared by further including a hydroxyl group-containing (meth)acrylate monomer in addition to a (meth)acrylamide monomer as a binder, and therefore are found to have better heat resistance than Example 5, which uses a (meth)acrylamide monomer alone.

[0142] In addition, it was confirmed that Example 1, which further contained polyvinyl alcohol as a binder, had better heat resistance than Example 2, even though the porous substrate was not pretreated.

[0143] On the other hand, the separator of Comparative Example 1 has the above t 1 / t 2Since the value is less than 0.75, the saturated water content range that the present disclosure aims to achieve cannot be met, and therefore, it was confirmed that the discharge resistance after 600 cycles of the battery to which this was applied was significantly higher than that of the examples.

[0144] The separator of Comparative Example 2 has a BET specific surface area of ​​20 m 2 / g, it was confirmed that the specific range of peaks and the specific range of saturated water content that appear in the FT-IR spectrum that the present disclosure aims to achieve could not be met, and therefore the discharge resistance after 600 cycles of the battery using this was higher than that of the examples.

[0145] The separator of Comparative Example 3 has a BET specific surface area of ​​2.5 m 2 / g, it was confirmed that the specific range of peaks and the specific range of saturated moisture content that appear in the FT-IR spectrum that the present disclosure aims to achieve could not be met, and therefore the heat resistance and adhesive strength at a thin thickness were significantly reduced. In addition, it was confirmed that the discharge resistance after 600 cycles of the battery using this was significantly higher than that of the examples.

[0146] The separator of Comparative Example 4 has a BET specific surface area of ​​8 m 2 / g, it was confirmed that the specific range of peaks and the specific range of saturated water content that appear in the FT-IR spectrum that the present disclosure aims to achieve could not be met, and therefore the discharge resistance after 600 cycles of the battery using this was higher than that of the examples.

[0147] What has been described above is merely illustrative of the application of the principles of the present disclosure and other arrangements may be included without departing from the scope of the present disclosure.

Claims

1. A porous substrate; an inorganic particle layer formed on at least one surface of the porous substrate and including a binder and inorganic particles; In the spectrum by Fourier transform infrared spectroscopy (FT-IR), －１ and the saturated water content measured by the Karl Fischer method is 350 to 1000 ppm.

2. 2. The separator according to claim 1, wherein the saturated moisture content is 450 to 1000 ppm.

3. 2. The separator according to claim 1, wherein the average thickness of the porous substrate is 5 to 15 μm, and the ratio of the average thickness of the porous substrate to the average thickness of the separator is 0.7 or more.

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

5. The separator according to claim 1 , wherein the binder comprises a polyacrylamide resin.

6. The separator according to claim 5 , wherein the polyacrylamide resin is a copolymer containing a unit derived from a (meth)acrylamide monomer and a unit derived from a comonomer.

7. The separator according to claim 6 , wherein the polyacrylamide resin contains a structural unit derived from a (meth)acrylamide monomer and a structural unit derived from a (meth)acrylic monomer containing a hydroxy group.

8. The separator according to claim 5, wherein the polyacrylamide resin has a weight average molecular weight of 100,000 to 2,000,000 g / mol.

9. 6. The separator according to claim 5, wherein the binder further comprises one or more additional binders selected from the group consisting of polyvinyl alcohol, polyvinylidene fluoride, carboxymethyl cellulose, styrene butadiene rubber, polyacrylic acid, polyethylene glycol, polyacrylonitrile, polyvinylpyrrolidone, and copolymers thereof.

10. The separator according to claim 9, wherein the content of the additional binder is 0.1 to 30% by weight of the total content of the binder.

11. The inorganic particles have a BET specific surface area of ​​3 to 7 m ２ The separator of claim 1 , wherein the molecular weight is 1 / g.

12. The separator according to claim 1, wherein the inorganic particles have an average particle size (D50) of 0.5 to 1.5 μm.

13. The separator according to claim 1 , wherein the inorganic particles include at least one selected from the group consisting of metal hydroxides, metal oxides, metal nitrides, and metal carbides.

14. 2. The separator according to claim 1, wherein the separator has a heat shrinkage of 5% or less in the machine direction and width direction measured after being left at 130°C for 60 minutes.

15. 2. The separator according to claim 1, wherein the inorganic particle layer has a weight ratio of inorganic particles to binder of 50:50 to 99.9:0.

1.

16. The inorganic particle layer has a density of 0.5 to 10 g / m ２ The separator of claim 1 formed of

17. An electrochemical element comprising the separator according to any one of claims 1 to 16.

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