Separator and lithium secondary battery including the same

Abstract

To provide a separator and a lithium secondary battery including the same.SOLUTION: One aspect of the disclosure provides a separator and a lithium secondary battery including the same. The separator comprises a porous substrate and an adhesive layer. The adhesive layer is placed on at least one surface of the porous substrate, and contains a binder and anisotropic particles. The adhesive layer contains 1.2 pts.wt. or more of the anisotropic particles with respect to 100 pts.wt. of the binder. The anisotropic particles have an aspect ratio of 4 to 1,000 and include one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150°C or higher. Advantageously, the separator has excellent adhesion to an electrode.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a separator and a lithium secondary battery including the same.

Background Art

[0002] Recently, in line with the trend of high capacity and high output of secondary batteries, the need for improving the characteristics of separators for the electrical safety of secondary batteries during high strength, high permeability, thermal stability, and charge and discharge of separators has been further increasing. As an example, high mechanical strength is required to improve the safety during the battery manufacturing process and use, and high permeability and high thermal stability are required to improve the capacity and output.

[0003] In addition, if the adhesion between the separator for a secondary battery and the electrode is insufficient, the separator and the electrode are separated during the cell assembly process, and distortion, deformation, etc. of the electrode assembly occur. That is, when the adhesion between the separator and the electrode is insufficient as described above, a misalignment problem occurs between the electrode and the separator in the jelly roll during cell stacking. When driving a stack cell battery in which misalignment has occurred as described above, a short circuit occurs between the electrodes due to the generation of local resistance due to misalignment or physical damage due to continuous use, and there are safety problems such as fire.

[0004] Therefore, improving the adhesion between the separator and the electrode is an issue that must be improved for the safety of the battery.

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to one aspect of the present disclosure, a separator having excellent adhesion to an electrode and a lithium secondary battery including the same can be provided.

[0006] According to another aspect of the present disclosure, there can be provided a separator capable of effectively suppressing a blocking phenomenon in which an adhesive layer is transferred to the opposite surface and peeled off during winding of the separator, and a lithium secondary battery including the same.

[0007] According to another aspect of the present disclosure, there can be provided a lithium secondary battery having excellent life characteristics.

[0008] According to another aspect of the present disclosure, there can be provided a separator having significantly improved adhesiveness to an electrode within a specific temperature range.

[0009] According to another aspect of the present disclosure, there can be provided a separator and a lithium secondary battery including the same, in which an adhesive force to an electrode is exhibited within a specific temperature range, and a blocking phenomenon is effectively suppressed at a temperature lower than the specific temperature range. For example, the separator according to an embodiment of the present disclosure can effectively suppress the occurrence of blocking between the adhesive layers of the separator at a temperature lower than 150°C, while the adhesive force is exhibited at a temperature of 150°C or higher.

[0010] The separator and the lithium secondary battery including the same according to the present disclosure are widely applicable in the fields of green technologies such as electric vehicles, battery charging stations, and other uses of batteries for solar power generation and wind power generation. Further, the separator and the lithium secondary battery including the same according to the present disclosure can be used in eco-friendly electric vehicles, hybrid vehicles, etc., which suppress air pollution and greenhouse gas emissions to prevent climate change.

Means for Solving the Problems

[0011] One embodiment of the present disclosure relates to a separator for an electrochemical element such as a lithium secondary battery.

[0012] Other embodiments of the present disclosure relate to a secondary battery including a separator according to one embodiment. The secondary battery can be a lithium secondary battery including the separator of the present disclosure.

[0013] The separator according to the present disclosure includes a porous substrate and an adhesive layer located on at least one surface of the porous substrate and containing a binder and anisotropic particles. The adhesive layer contains 1.2 parts by weight or more of anisotropic particles with respect to 100 parts by weight of the binder. The anisotropic particles include any one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150°C or higher. The aspect ratio of the anisotropic particles is 4 to 1,000.

[0014] In the present disclosure, the binder and the anisotropic particles can be distinguished on the surface of the material and can be different from each other. For example, it can be the case where the binder is an organic material such as a polymer and the anisotropic particles are inorganic particles. Alternatively, the binder can be an organic material such as a polymer and the anisotropic particles can be organic particles. Here, the binder and the anisotropic organic particles can have different respective organic materials, polymers, or shapes. For example, the polymer material for the binder may have an aspect ratio less than 4 and be smaller than that of the anisotropic organic particles, or may have a lower glass transition temperature (for example, 50°C or more lower), and the shapes may be different from each other. For example, while the anisotropic organic particles are fibrous polymers, the binder can be spherical or amorphous polymer particles rather than in fibrous form.

[0015] In one embodiment, the anisotropic particles can have an aspect ratio of 4 to 200.

[0016] In one embodiment, the anisotropic particles can have an average length in the long axis direction of 10 nm to 5,000 nm and an average length in the short axis direction of 1 nm to 500 nm.

[0017] In one embodiment, the first inorganic particles can include any one or more selected from the group consisting of metal hydroxides, metal oxides, metal nitrides, and metal carbides.

[0018] In one embodiment, the organic particles can include any one or two or more copolymers selected from the group consisting of styrene-based polymers, acrylic-based polymers, and cellulose-based polymers.

[0019] In one embodiment, the adhesive layer can include 1.2 to 20 parts by weight of anisotropic particles with respect to 100 parts by weight of the binder.

[0020] In one embodiment, the adhesive layer can include 1.2 to 10 parts by weight of anisotropic particles with respect to 100 parts by weight of the binder.

[0021] In one embodiment, the binder can have a glass transition temperature in the range of 30°C to 120°C.

[0022] In one embodiment, the binder can be a particulate binder.

[0023] In one embodiment, the particulate binder can have an average particle size of 0.01 μm to 5 μm.

[0024] In one embodiment, the binder can include any one or more selected from the group consisting of acrylic-based polymers, fluorine-based polymers, ester-based polymers, amide-based polymers, imide-based polymers, styrene-based polymers, vinyl alcohol-based polymers, vinyl pyrrolidone-based polymers, and cellulose-based polymers.

[0025] In one embodiment, the total thickness of the adhesive layer can be 0.1 μm to 10 μm. In other embodiments, the total thickness of the adhesive layer can be 0.5 μm to 5 μm, or 1.0 μm to 2.5 μm, or 1.0 μm to 2.0 μm.

[0026] The "total thickness" means the total thickness of all the adhesive layers present on or above the porous substrate. For example, when an adhesive layer is formed only on one side of the porous substrate, the "total thickness" is the thickness of this single adhesive layer. Also, when adhesive layers are formed on both sides of the porous substrate, the "total thickness" is the total thickness of the adhesive layers.

[0027] In one embodiment, the separator is laminated such that the adhesive layer of the separator faces the positive electrode, and after being pressure-bonded at 80 °C and 10 kgf / cm 2 for 30 seconds with a heat press machine, the adhesive strength measured according to ASTM D903 can be 0.5 gf / cm or more.

[0028] In one embodiment, the separator can further include an inorganic particle layer formed between the porous substrate and any one of the adhesive layers. That is, in this case, the adhesive layer is disposed on at least one surface (not directly on) of the porous substrate. Unless otherwise defined in the present disclosure, the term "on" means that a portion such as a layer, film, thin film, region, or plate is "on" another portion, which means that another portion (film, layer, or further corresponding portion) can be further included therebetween. Therefore, when the adhesive layer is on at least one surface of the porous substrate, an intermediate layer, for example, an inorganic particle layer, can be included between the porous substrate and the adhesive layer.

[0029] In one embodiment, the inorganic particle layer can contain 0.1 to 20 parts by weight of a binder resin with respect to 100 parts by weight of the second inorganic particles. In one embodiment, the second inorganic particles can be a mixture of two or more types of inorganic particles having different average particle diameters, such as 1, 2, 3, or more types. Such a mixture can exhibit a mono-, di-, tri-, or multi-modal particle size distribution. Such a mono-, di-, tri-, or multi-modal particle size distribution can preferably be observed from a mixture of inorganic particles before being added to the coating slurry, that is, in terms of particle size, it can be one using two or more types of inorganic particles. For example, the "second inorganic particles" can be a mixture of inorganic particles having an average particle diameter of 0.05 μm to 0.5 μm, 0.10 μm to 0.54 μm, 0.10 μm to 0.50 μm, 0.20 μm to 0.40 μm, 0.30 μm to 0.40 μm, or about 0.30 μm, and inorganic particles having a size greater than 0.5 μm and less than or equal to 2 μm, 0.55 μm to 1.0 μm, 0.60 μm to 0.90 μm, 0.60 μm to 0.80 μm, 0.70 μm to 0.80 μm, or about 0.70 μm. For example, the second inorganic particles can be a mixture of inorganic particles having an average particle diameter of 0.3 μm and inorganic particles having an average particle diameter of 0.7 μm.

[0030] The present disclosure also provides a lithium secondary battery including a positive electrode, a negative electrode, a separator as described above interposed between the positive electrode and the negative electrode, and an electrolyte.

[0031] The present disclosure also provides a method for manufacturing a separator for an electrochemical element. For example, it provides a method for manufacturing a separator for an electrochemical element such as a lithium secondary battery.

[0032] The method for manufacturing a separator of the present disclosure is (a) providing a porous substrate, (a-1) applying a coating solution for forming an adhesive layer containing a binder and anisotropic particles to at least one surface of the porous substrate, and drying to form the adhesive layer, (a-2) thereby obtaining a separator, or (a-i) Coating a slurry for forming an inorganic particle layer containing second inorganic particles and a binder resin on at least one surface of a porous substrate, and drying to form the inorganic particle layer; (a-ii) Coating a coating solution for forming an adhesive layer containing a binder and anisotropic particles on the inorganic particle layer, and drying to form the adhesive layer; (a-iii) thereby obtaining a separator; including, in the above (a-i) and (a-ii), the adhesive layer contains 1.2 parts by weight or more of anisotropic particles with respect to 100 parts by weight of the binder, and the anisotropic particles have an aspect ratio of 4 to 1,000 and can include one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150°C or higher.

Advantages of the Invention

[0033] The separator according to the present disclosure can have the merit of excellent adhesiveness to the electrode.

[0034] In addition, the present disclosure can provide a separator with improved blocking phenomenon occurring during winding of the separator.

[0035] In addition, the present disclosure can provide a lithium secondary battery having excellent life characteristics by including a separator according to an embodiment.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0037] The embodiments described in this specification can be modified into various other forms, and the technology according to one embodiment is not limited to the embodiments described below. Also, the embodiments of one embodiment are provided to more fully explain the present disclosure to those with average knowledge in the relevant technical field.

[0038] Also, the singular forms used in the specification and the appended claims can be intended to include the plural forms as well, unless otherwise specifically stated in the context.

[0039] Also, the numerical ranges used in this specification include the lower limit value and the upper limit value, all values within that range, increments logically derived from the form and width of the defined range, among which all possible combinations of all limited values and the upper and lower limits of different numerically defined ranges are included. In this specification, unless otherwise specified, values outside the numerical range that may occur due to experimental error or rounding of values are also included in the defined numerical range.

[0040] Furthermore, throughout the specification, stating that a certain component "includes" means that it can further include other components, rather than excluding other components, unless there is a specific statement to the contrary.

[0041] In this specification, when a part such as a layer, film, region, plate, etc. is "on" or "above" another part, this includes not only the case where it is "immediately above" the other part, but also the case where there are further other parts in between.

[0042] Terms such as first, second, etc. used in this specification can be used to describe various components, but the components should not be limited by the terms. The terms are only used for the purpose of distinguishing one component from another.

[0043] In this specification, the average particle size means D50, and D50 means the particle size of particles corresponding to 50% in terms of the cumulative fraction based on volume. The average particle size can be derived from the results of the particle size distribution obtained by sampling a sample in accordance with the ISO 13320-1 standard for the particles to be measured and analyzing it using S3500 manufactured by MICROTRAC.

[0044] In this specification, the glass-transition temperature (Tg) means the temperature range in which glass transition occurs, and means the value measured using a dilatometer (DMT) or a differential scanning calorimeter (DSC).

[0045] In this specification, "Anisotropic Particles" means particles in which the length in the major axis direction and the length in the minor axis direction are different from each other. For example, it means particles having an aspect ratio of 4 or more and 4 to 1000. In this specification, particles not defined as "anisotropic particles" mean those having an aspect ratio of less than 4, 3 or less, 2 or less, and are distinguished from the said anisotropic particles. For example, in this specification, the "first inorganic particles" and "organic particles having a glass transition temperature of 150°C or higher" contained in the adhesive layer are "anisotropic" particles, and in addition, the "particle binder" contained in the adhesive layer and the "second inorganic particles" contained in the inorganic particle layer are particles distinguished from anisotropic particles, and when having an aspect ratio, the aspect ratio can be less than 4, 3 or less, 2 or less.

[0046] In this specification, the aspect ratio means the value obtained by dividing the average length in the major axis direction by the average length in the minor axis direction. The length in the major axis direction means the longest length of the particle, and the average length in the minor axis direction means the longest length in the direction perpendicular to the major axis.

[0047] In this specification, the average length in the major axis direction and the average length in the minor axis direction can be obtained from the average of the values measured by arbitrarily selecting 20 particles each from 5 images measured with a transmission electron microscope (TEM, JEOL Ltd, JEM-2100F).

[0048] The present disclosure includes a porous substrate and an adhesive layer located on at least one surface of the porous substrate and containing a binder and anisotropic particles. The adhesive layer contains 1.2 parts by weight or more of anisotropic particles with respect to 100 parts by weight of the binder. The anisotropic particles include any one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150°C or higher. The aspect ratio of the anisotropic particles is 4 to 1,000, and a separator is provided.

[0049] When the adhesive layer contains anisotropic particles having specific composition and physical properties (for example, an aspect ratio of 4 to 1,000 and a glass transition temperature of 150°C or higher) as described above, a separator excellent in adhesiveness to an electrode can be provided. Further, by including the anisotropic particles, the separator can effectively suppress the blocking phenomenon in which the adhesive layer is transferred to the opposite surface and peeled off during winding of the separator. Further, a lithium secondary battery according to an embodiment can have excellent electrical characteristics and safety by including the above-described separator.

[0050] According to one embodiment, a coating liquid for forming an adhesive layer containing a binder and anisotropic particles can be applied to at least one surface of a porous substrate or an inorganic particle layer and dried to form an adhesive layer. Here, the separator according to one embodiment can prevent the coffee-ring phenomenon in which the binder accumulates at the periphery of the coating region while the coating liquid for forming the adhesive layer containing anisotropic particles having an aspect ratio of 4 to 1000 evaporates. Such a coffee-ring phenomenon can cause the binder to be unevenly distributed and reduce the adhesiveness between the separator and the electrode. The separator according to one embodiment includes the anisotropic particles, effectively preventing the coffee-ring phenomenon, and having the merit of excellent adhesiveness to the electrode because the binder contained in the adhesive layer is uniformly distributed throughout the adhesive layer.

[0051] Further, the separator according to one embodiment includes anisotropic particles containing any one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150°C or higher, thereby effectively suppressing the blocking phenomenon in which the adhesive layer transfers to the opposite surface and peels off during winding of the separator.

[0052] In one embodiment, the anisotropic particles mean particles having an anisotropic particle shape, and the aspect ratio can be 4 or more, 5 or more, 10 or more, 20 or more, 1000 or less, 750 or less, 500 or less, 200 or less, or a value between the above numerical values. For example, the aspect ratio of the anisotropic particles can be 4 to 1000, 5 to 750, 10 to 500, 4 to 200, or 20 to 200. When the anisotropic particles have an aspect ratio within the above range, the binder contained in the adhesive layer is uniformly distributed throughout the adhesive layer, so that the effect of excellent adhesiveness between the separator and the electrode can be achieved.

[0053] In one embodiment, as long as the anisotropic particles satisfy the aspect ratio within the above-mentioned range, the specific shape is not particularly limited. Non-limitingly, the shape of the anisotropic particles can be selected from rod-like, columnar, wire-like, fibrous, plate-like, etc. Further, when the anisotropic particles are selected from anisotropic first inorganic particles, all of the above shapes are selectable. Also, when the anisotropic particles are selected from organic particles, they can be made of a material and / or shape different from the binder of the adhesive layer. For example, the anisotropic organic particles can be a polymer material having a glass transition temperature higher than that of the binder of the adhesive layer and / or a fibrous polymer.

[0054] In one embodiment, the anisotropic particles can have an average length in the major axis direction of 10 nm or more, 20 nm or more, 30 nm or more, 5000 nm or less, 2000 nm or less, 1000 nm or less, or a value between these numerical values. For example, the average length of the anisotropic particles in the major axis direction can be 10 nm to 5000 nm, 20 nm to 2000 nm, or 30 nm to 1000 nm, but is not particularly limited as long as the aspect ratio within the above-mentioned range is satisfied.

[0055] In one embodiment, the anisotropic particles can have an average length in the minor axis direction of 1 nm or more, 2 nm or more, 500 nm or less, 200 nm or less, 100 nm or less, or a value between these numerical values. For example, the average length of the anisotropic particles in the minor axis direction can be 1 nm to 500 nm, 1 nm to 200 nm, or 2 nm to 100 nm, but is not particularly limited as long as the aspect ratio within the above-mentioned range is satisfied.

[0056] In one embodiment, the anisotropic particles can include any one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150°C or higher.

[0057] The first inorganic particles that can be used as the anisotropic particles can have an average length in the major axis direction of 10 nm to 5000 nm, 10 nm to 2000 nm, 10 nm to 1000 nm, 20 nm to 500 nm, or 20 nm to 200 nm, and an average length in the minor axis direction of 1 nm to 500 nm, 1 nm to 200 nm, 1 nm to 100 nm, 1 nm to 50 nm, or 2 nm to 20 nm, but is not limited thereto as long as it does not deviate from the scope of the present disclosure.

[0058] The organic particles that can be used as the anisotropic particles and have a glass transition temperature of 150°C or higher can have an average length in the major axis direction of 10 nm to 5000 nm, 10 nm to 2000 nm, 10 nm to 1000 nm, 20 nm to 1000 nm, or 100 nm to 1000 nm, and an average length in the minor axis direction of 1 nm to 500 nm, 1 nm to 200 nm, 1 nm to 100 nm, 1 nm to 50 nm, or 1 nm to 20 nm, but is not limited thereto as long as it does not deviate from the scope of the present disclosure.

[0059] In one embodiment, the first inorganic particles are not limited as long as they are inorganic particles used in the technical field. As non-limiting examples, the first inorganic particles can 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 are 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 ), barium titanate (BaTiO 3 ), zinc oxide (ZnO), yttrium oxide (Y 2 O 3 ), zirconium oxide (ZrO 2 ), tin oxide (SnO 2) and cerium oxide (CeO 2 ) can include any one or two or more selected from the group consisting of. From the viewpoints of adhesion to the electrode and anti-blocking properties, etc., the first inorganic particles are boehmite, aluminum hydroxide (Al(OH) 3 ) and magnesium hydroxide (Mg(OH) 2 ) can be any one or two or more metal hydroxide particles selected from the group consisting of, but can be replaced with inorganic particles of other materials as long as it does not deviate from the scope of the present disclosure.

[0060] In one embodiment, the organic particles are polymer particles used in the art and can have a glass transition temperature of 150°C or higher.

[0061] In one embodiment, the organic particles can include any one or two or more copolymers selected from the group consisting of styrene-based polymers, acrylic-based polymers, and cellulose-based polymers, but can be replaced with organic particles of other materials as long as it does not deviate from the scope of the present disclosure. For example, the styrene-based polymer can be any one or more selected from polystyrene, poly(alpha-methylstyrene), poly(bromostyrene), etc. The acrylic-based polymer can be any one or more selected from polyacrylamide, polymethacrylate, polyethyl acrylate, polyacrylate, polybutyl acrylate, and acrylic acid-methacrylic acid copolymer, etc. Also, as the cellulose-based polymer, any one or more selected from cellulose, carboxymethyl cellulose, cellulose acetate propionate, cellulose acetate, and cellulose acetate butyrate, etc. can be used.

[0062] In one embodiment, the adhesive layer can contain 1.2 parts by weight or more of anisotropic particles with respect to 100 parts by weight of the binder. When the anisotropic particles and the binder satisfying the composition ratio are included, not only the adhesiveness to the electrode but also the effect of suppressing the blocking phenomenon can be excellently realized. Specifically, the adhesive layer can contain 1.2 to 20 parts by weight or 1.5 to 20 parts by weight of anisotropic particles with respect to 100 parts by weight of the binder.

[0063] In one embodiment, the adhesive layer can contain 1.2 to 10 parts by weight, 1.5 to 10 parts by weight, or 1.5 to 8 parts by weight of anisotropic particles with respect to 100 parts by weight of the binder. When the above range is satisfied, the adhesiveness between the separator and the electrode can be realized more excellently.

[0064] In one embodiment, the binder contained in the adhesive layer imparts an adhesive force between the adhesive layer and the electrode and can have a glass transition temperature in the range of 30°C to 120°C. The binder can have a glass transition temperature in the range of 50°C to 120°C or 60°C to 110°C.

[0065] In one embodiment, the binder contained in the adhesive layer can have one or more glass transition temperatures within the above range. For example, it can have two or more glass transition temperatures.

[0066] In one embodiment, the binder can be a particulate binder, and the specific shape of the particles is not particularly limited. For example, the particulate binder can have a spherical, elliptical, plate-like, or irregular particle form.

[0067] In one embodiment, the particulate binder may have an average particle size of 0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 5 μm or less, 1 μm or less, 0.7 μm or less, 0.5 μm or less, or a value between the numerical values. For example, the particulate binder may have an average particle size of 0.01 μm to 5 μm, 0.01 μm to 1 μm, 0.05 μm to 0.7 μm, or 0.1 μm to 0.5 μm.

[0068] In one embodiment, the binder may include any one or more selected from the group consisting of acrylic polymers, fluorine polymers, ester polymers, amide polymers, imide polymers, styrene polymers, vinyl alcohol polymers, vinyl pyrrolidone polymers, and cellulose polymers. For example, the binder may include an acrylic polymer, a styrene polymer, a fluorine polymer, or a copolymer of two or more of these. As a non-limiting example, the binder may be any one or two or more copolymers selected from the group consisting of acrylonitrile polymers, styrene polymers, and (meth)acrylamide polymers.

[0069] In one embodiment of the binder, the acrylic polymer can be any one or more selected from polyacrylonitrile, poly(meth)acrylamide, polymethacrylate, polyethyl acrylate, polyacrylate, polybutyl acrylate, and acrylic acid-methacrylic acid copolymer. The fluorine-based polymer can be any one or more selected from polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, hexafluoropropylene, polyfluoride-hexafluoropropylene, and polychlorotrifluoroethylene. The ester-based polymer can be any one or more selected from polyethylene terephthalate, polyethylene naphthalate [polyethylene naphthalate (PEN)], etc. The amide-based polymer can be any one or more selected from polyamide-6, polyamide-66, etc. The imide-based polymer can be any one or more selected from polyimide, polyetherimide, polyesterimide, etc. The styrene-based polymer can be any one or more selected from polystyrene, polyalpha methylstyrene, and polybromostyrene. The vinyl alcohol-based polymer can be any one or more selected from polyvinyl alcohol, polyvinyl acetate, and polyvinyl acetate-polyvinyl alcohol copolymer. The vinyl pyrrolidone-based polymer can be any one or more selected from polyvinyl pyrrolidone and copolymers containing vinyl pyrrolidone. Further, as the cellulose-based polymer, it can be any one or more selected from carboxymethyl cellulose, cellulose acetate propionate, cellulose acetate, and cellulose acetate butyrate, and can be replaced with a binder of other materials as long as it does not deviate from the scope of the present disclosure.

[0070] The adhesive layer can be positioned so as to be the outermost layer of the separator in order to improve the adhesive force with the electrode.

[0071] In one embodiment, the adhesive layer can be coated on one or both surfaces of the porous substrate or on one or both surfaces of the inorganic particle layer described below. When the adhesive layer is coated on both surfaces of the porous substrate (or inorganic particle layer), the thicknesses of the adhesive layers coated on one surface and the other surface can be the same as or different from each other. Although not particularly limited, in one embodiment, the total thickness of the adhesive layer formed on the porous substrate (or inorganic particle layer) can be 0.1 μm to 10 μm. For example, the thickness of the adhesive layer can be 0.1 to 5 μm or 0.5 to 2.5 μm. The thickness is measured by measuring the thickness at any five points with a thickness measuring instrument manufactured by Mitutoyo Corporation and then dividing by 5 to measure the average thickness.

[0072] According to one embodiment, the separator has an excellent adhesiveness to the electrode because the binder and the anisotropic particles satisfy the composition ratio within the above range and the anisotropic particles satisfy the above conditions. For example, the separator is laminated so that the adhesive layer of the separator faces the positive electrode, and after being pressure-bonded at 80 °C and 10 kgf / cm 2 for 30 seconds with a heat press machine, the adhesive strength measured according to ASTM D903 can be 0.4 gf / cm or more. Specifically, the adhesive strength measured according to ASTM D903 can be measured by peeling at 180° using a UTM equipment manufactured by INSTRON. Also, any normal positive electrode used in a lithium secondary battery can be used without limitation as the positive electrode used for measuring the adhesive strength. As an example of the positive electrode, with respect to the total weight of the positive electrode active material, LiCoO 294% by weight, 2.5% by weight of polyvinylidene fluoride as a binder, 3.5% by weight of carbon black as a conductive agent, and added to NMP (N-methyl-2-pyrrolidone) as a solvent and stirred to produce a uniform positive electrode slurry, and the produced positive electrode slurry is coated, dried and crimped on an aluminum foil with a thickness of 30 μm to produce a positive electrode with a total thickness of 150 μm. However, it can be replaced with other components as long as it does not deviate from the scope of the present disclosure. The thickness is measured at any 5 points with a thickness measuring instrument manufactured by Mitutoyo, and then divided by 5 to measure the average thickness.

[0073] Preferably, the separator has an adhesive force measured by the above method of 0.5 gf / cm or more, 0.55 gf / cm or more, 0.6 gf / cm or more, 0.65 gf / cm or more, 2.0 gf / cm or less, 1.5 gf / cm or less, 1.0 gf / cm or less, or a value between the above numerical values. For example, the separator has an adhesive force measured by the above method of 0.5 gf / cm to 2.0 gf / cm, 0.55 gf / cm to 2.0 gf / cm, 0.6 gf / cm to 1.5 gf / cm, or 0.65 gf / cm to 1.0 gf / cm.

[0074] The separator according to one embodiment satisfies the composition ratio of the binder and the anisotropic particles within the above range, and the anisotropic particles satisfy the above conditions, so that when the separator is wound, the blocking phenomenon in which the adhesive layer is transferred to the opposite surface and peeled off can be effectively suppressed. For example, the two separators according to one embodiment are arranged so that the adhesive layers face each other, and after being crimped at a temperature of 50 °C and a pressure of 15 kgf / cm 2 for 1 hour and peeled at 180° according to ASTM D903, the phenomenon that the adhesive layers are adhered to each other and partially or entirely peeled off does not occur, and the adhesive layers can be separated as they are.

[0075] In one embodiment, the separator may further include an inorganic particle layer formed between the porous base material and any one of the adhesive layers. By further including the inorganic particle layer, the separator can have the advantages of excellent adhesiveness and blocking resistance to the electrode, as well as excellent heat resistance. The adhesive layer is for improving the adhesive force with the electrode and can be positioned so as to be the outermost layer in the separator. For example, the separator can have a structure laminated in the order of adhesive layer / porous base material / adhesive layer, adhesive layer / inorganic particle layer / porous base material / inorganic particle layer / adhesive layer, or adhesive layer / porous base material / inorganic particle layer / adhesive layer.

[0076] In one embodiment, the inorganic particle layer can include second inorganic particles and a binder resin, and can be a porous inorganic particle layer in which the second inorganic particles are connected and fixed by the binder resin to form pores.

[0077] In one embodiment, the inorganic particle layer can be formed on one or both surfaces of the porous base material to 90% or more of the total area of each surface. Specifically, it can be 95% or more, and more specifically, it can be formed to 100% of the total area of each surface of the porous base material except when fine defects occur. In the inorganic particle layer, the inorganic particles can be adjacent to each other and pores can be formed between the inorganic particles.

[0078] The second inorganic particles contained in the inorganic particle layer are not limited as long as they are inorganic particles used in the technical field. As a non-limiting example, the second inorganic particles can include any one or more selected from the group consisting of metal hydroxides, metal oxides, metal nitrides, and metal carbides. For example, the second inorganic particles are 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 (TiO2 ) Strontium titanate (SrTiO 3 ), barium titanate (BaTiO 3 ), zinc oxide (ZnO), yttrium oxide (Y 2 O 3 ), zirconium oxide (ZrO 2 ), tin oxide (SnO 2 ), and cerium oxide (CeO 2 ), and may include any one or two or more selected from the group consisting of. From the viewpoint of battery safety and the like, the second inorganic particles are boehmite, aluminum hydroxide (Al(OH) 3 ), and magnesium hydroxide (Mg(OH) 2 ), and may be any one or two or more metal hydroxide particles selected from the group consisting of, but may be replaced with inorganic particles of other materials as long as it does not deviate from the scope of the present disclosure.

[0079] In one embodiment, the form of the second inorganic particles is not limited and can be spherical, elliptical, needle-like, etc.

[0080] In one embodiment, the inorganic particle layer can contain 0.1 to 20 parts by weight, 1 to 15 parts by weight, 1 to 10 parts by weight, or 1 to 5 parts by weight of a binder resin with respect to 100 parts by weight of the second inorganic particles, but is not necessarily limited thereto.

[0081] In one embodiment, the adhesive layer can be formed on one or both sides of a porous substrate or an inorganic particle layer formed on a porous substrate, and can be formed to 60% or more of the total area of each side. Specifically, the adhesive layer can be formed to 80% or more, 90% or more, 95% or more, and more specifically 100% of the total area of each side of the porous substrate or the inorganic particle layer, except when minute defects occur. However, in particular, it is not limited thereto as long as it does not deviate from the scope of the present disclosure.

[0082] In one embodiment, the second inorganic particles have an average particle size (D 50) can be 2 μm or less, 1 μm or less, 0.01 μm or more, 0.05 μm or more, or a value between the above numerical values, specifically, it can be 0.01 μm to 2 μm or 0.05 μm to 1 μm. When the average particle size of the second inorganic particles satisfies the above range, excellent adhesiveness to the electrode, blocking resistance, and heat resistance can be realized.

[0083] In one embodiment, when the second inorganic particles are a combination of two or more types of second inorganic particles having different average particle sizes (D 50 ), they can be combined with the above-described anisotropic particles and / or binders to realize more excellent adhesiveness to the electrode, blocking resistance, and heat resistance.

[0084] Taking the combination of two types of second inorganic particles having different average particle sizes as an example, it can be a combination of inorganic particles having an average particle size of 0.05 μm to 0.5 μm and inorganic particles having an average particle size of more than 0.5 μm and 2 μm or less. Specifically, the second inorganic particles according to one embodiment can be a combination of inorganic particles having an average particle size of 0.1 μm to 0.4 μm and inorganic particles having an average particle size of 0.6 μm to 1 μm.

[0085] In one embodiment, the inorganic particle layer can 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 can be the same or different from each other. Although not particularly limited, in one embodiment, the total thickness of the inorganic particle layer formed on the porous substrate can be 0.1 μm or more, 0.5 μm or more, 1 μm or more, 15 μm or less, 10 μm or less, 5 μm or less, or a value between the above numerical values. In a specific embodiment, the total thickness of the inorganic particle layer can be 0.1 to 15 μm, 0.5 to 10 μm, or 1 to 5 μm. The thickness is measured by measuring the thickness at any 5 points with a thickness measuring instrument manufactured by Mitutoyo Corporation and then dividing by 5 to measure the average thickness.

[0086] The binder resin contained in the inorganic particle layer can connect and fix the second inorganic particles, the inorganic particle layer to the porous substrate and / or the inorganic particle layer to the adhesive layer. The binder resin can be used without limitation as long as it is an organic binder resin used in the technical field. As an example, the binder resin can contain any one or more polymers selected from the group consisting of ester polymers, amide polymers, imide polymers, acrylic polymers, styrene polymers, vinyl alcohol polymers, vinyl pyrrolidone polymers, cellulose polymers, and fluorine polymers.

[0087] The ester-based polymer can be any one or more selected from polyethylene terephthalate, polyethylene naphthalate (PEN), etc. The amide-based polymer can be any one or more selected from polyamide-6, polyamide-66, etc. The imide-based polymer can be any one or more selected from polyimide, polyetherimide, polyesterimide, etc. The acrylic-based polymer can be any one or more selected from polyacrylamide, polymethacrylate, polyethyl acrylate, polyacrylate, polybutyl acrylate, and acrylate-methacrylate copolymer, etc. The styrene-based polymer can be any one or more selected from polystyrene, polyalpha-methylstyrene, polybromostyrene, etc. The vinyl alcohol-based polymer can be any one or more selected from polyvinyl alcohol, polyvinyl acetate, and polyvinyl acetate-polyvinyl alcohol copolymer, etc. The vinyl pyrrolidone-based polymer can be any one or more selected from polyvinyl pyrrolidone and copolymers containing vinyl pyrrolidone, etc. Also, as the cellulose-based polymer, it can be any one or more selected from carboxymethyl cellulose, cellulose acetate propionate, cellulose acetate, and cellulose acetate butyrate, etc. The fluorine-based polymer can be any one or more selected from polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, hexafluoropropylene, polyfluoride-hexafluoropropylene, and polychlorotrifluoroethylene, etc.

[0088] In one embodiment, the polymer resin can be a polyacrylamide-based resin in terms of being able to more excellently achieve heat resistance.

[0089] In one embodiment, the porous substrate can be variously used, such as a porous polymer film, sheet, nonwoven fabric, woven fabric, etc. made of a polymer used as a separator, and a porous substrate having a laminated structure in which two or more of the above layers are laminated can also be included.

[0090] In one embodiment, the porous substrate can 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 lithium secondary batteries can be used.

[0091] In one embodiment, the porosity of the porous substrate can be 20 to 60%, specifically 30 to 60%, but is not limited thereto.

[0092] In one embodiment, the thickness of the porous substrate can be 1 to 25 μm, 3 to 20 μm, or 5 to 15 μm, but is not necessarily limited thereto. The thickness is measured at five arbitrary points with a thickness measuring instrument manufactured by Mitutoyo, and then divided by 5 to measure the average thickness.

[0093] In one embodiment, the average thickness of the separator can be 1 to 40 μm, 5 to 30 μm, or 10 to 20 μm, but is not necessarily limited thereto. The average thickness of the separator is measured at five arbitrary points in the TD direction with a thickness measuring instrument manufactured by Mitutoyo after stacking 10 separators, and then divided by 5 to derive the average thickness of the 10-layer separator, and further divided by 10 to derive the average thickness of the entire single separator.

[0094] Hereinafter, a method for manufacturing the separator of the present disclosure will be described.

[0095] The manufacturing method of a separator according to an embodiment includes a step of applying a coating liquid for forming an adhesive layer containing a binder and anisotropic particles on at least one surface of a porous substrate, and drying to form the adhesive layer. The adhesive layer contains 1.2 parts by weight or more of anisotropic particles with respect to 100 parts by weight of the binder. The anisotropic particles include any one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150°C or higher. The aspect ratio of the anisotropic particles can be 4 to 1,000.

[0096] The manufacturing method of a separator according to another embodiment includes a step of applying a slurry for forming an inorganic particle layer containing second inorganic particles and a binder resin on at least one surface of a porous substrate, and drying to form the inorganic particle layer, and a step of applying a coating liquid for forming an adhesive layer containing a binder and anisotropic particles on top of the inorganic particle layer, and drying to form the adhesive layer. The adhesive layer contains 1.2 parts by weight or more of anisotropic particles with respect to 100 parts by weight of the binder. The anisotropic particles include any one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150°C or higher. The aspect ratio of the anisotropic particles can be 4 to 1,000. For convenience, the manufacturing method will be described based on the separator on which the inorganic particle layer and the adhesive layer are formed.

[0097] Since the descriptions of the separator, porous substrate, inorganic particle layer, adhesive layer, first inorganic particles, second inorganic particles, binder, anisotropic particles, and binder resin are as described above, specific descriptions are omitted.

[0098] The method for manufacturing the slurry for forming the inorganic particle layer can apply all ordinary methods known in the art without limitation. Without particular limitation, by way of non-limiting example, the second inorganic particles and the binder resin can be stirred and dispersed to manufacture the slurry, and the aggregated second inorganic particles can also be dispersed using a ball mill.

[0099] The slurry for forming the inorganic particle layer contains second inorganic particles, a binder resin, and a dispersion medium. The dispersion medium can be water, lower alcohols such as ethanol, methanol, and propanol, dimethylformamide, acetone, tetrahydrofuran, diethyl ether, methylene chloride, DMF, N-methyl-2-pyrrolidone, hexane, cyclohexane, or a mixture thereof, but is not necessarily limited thereto.

[0100] In one embodiment, the solid content of the slurry for forming the inorganic particle layer is not particularly limited, but can be, for example, 1 to 50% by weight, 5 to 40% by weight, or 10 to 35% by weight.

[0101] In one embodiment, the slurry for forming the inorganic particle layer can contain 80 to 99% by weight of second inorganic particles and 1 to 20% by weight of a binder resin based on the total weight of the solid content. Specifically, the second inorganic particles can be contained in the slurry at 85 to 99% by weight, 90 to 99% by weight, or 95 to 99% by weight based on the total weight of the solid content. Specifically, the binder resin can be contained in the slurry at 1 to 15% by weight, 1 to 10% by weight, or 1 to 5% by weight based on the total weight of the solid content.

[0102] As a method for applying the slurry for forming the inorganic particle layer, all ordinary methods known in the art can be applied without limitation. By way of non-limiting example, roll coating, spin coating, dip coating, bar coating, die coating, slit coating, inkjet printing, and combinations thereof can be applied. The applied slurry can be dried and formed as an inorganic particle layer. The drying for forming the inorganic particle layer is not particularly limited, but can be performed at 100°C or lower, or at 30 to 60°C.

[0103] Next, the method for producing the coating liquid for forming the adhesive layer can similarly apply without limitation all ordinary methods known in the art. Without particular limitation, by way of non-limiting example, anisotropic particles and a binder can be stirred and dispersed to produce the coating liquid, and an agglomerated anisotropic particles and a binder can also be dispersed using a ball mill.

[0104] The coating liquid for forming the adhesive layer contains a binder, anisotropic particles, and a solvent, and the solvent can be any one of the dispersion media that can be used in the production of the slurry for forming the inorganic particle layer. Specifically, it can be distilled water.

[0105] In one embodiment, the solid content of the coating liquid for forming the adhesive layer is not particularly limited, but for example, it can be 1 to 20 wt%, 2 to 15 wt%, or 5 to 10 wt%.

[0106] In one embodiment, the coating liquid for forming the adhesive layer can contain 80 to 98.8 wt% of a binder and 1.2 to 20 wt% of anisotropic particles based on the total weight of the solid content. Specifically, the binder can be contained in the coating liquid at 85 to 98.8 wt%, 90 to 98.5 wt%, or 92.5 to 98.5 wt% based on the total weight of the solid content. Specifically, the binder can be contained in the coating liquid at 1.2 to 10 wt%, 1.5 to 10 wt%, or 1.5 to 7.5 wt% based on the total weight of the solid content.

[0107] As the method for applying the coating liquid for forming the adhesive layer, all ordinary methods known in the art can be applied without limitation. Specifically, the method for applying the slurry for forming the inorganic particle layer can be applied. The applied coating liquid can be dried and formed as an adhesive layer. The drying for forming the adhesive layer is not particularly limited, but it can be dried at 100°C or lower, or at 30 to 60°C.

[0108] One embodiment of the present disclosure provides a lithium secondary battery including a positive electrode, a negative electrode, the separator described above interposed between the positive electrode and the negative electrode, and an electrolyte. Here, the positive electrode, negative electrode, and electrolyte can be used without limitation as long as they are those usually used in lithium secondary batteries. According to one embodiment, by including a separator as described above, it is possible to provide a lithium secondary battery excellent in adhesion and blocking resistance between the positive electrode or negative electrode and the separator, and having improved battery life characteristics. Specifically, the blocking phenomenon and the coffee-ring phenomenon can be improved, the electrode and the separator are strongly adhered, and the generation of unnecessary spaces such as bubbles between the electrode and the separator can be prevented. Thereby, the problem of the battery life being reduced due to unnecessary spaces can be suppressed, and a lithium secondary battery to which a separator according to one embodiment is applied can have significantly improved life characteristics.

[0109] The positive electrode and the negative electrode can be manufactured by mixing and stirring a positive electrode active material and a negative electrode active material with a solvent, and optionally a binder, a conductive material, a dispersant, etc. to produce a mixture, then applying this to a current collector of a metal material, drying, and then pressing.

[0110] The positive electrode active material can be any active material usually used for the positive electrode of a secondary battery. For example, lithium metal oxide particles containing one or more metals selected from the group consisting of Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, B, and combinations thereof can be used.

[0111] The negative electrode active material can be any active material usually used for the negative electrode of a secondary battery. The negative electrode active material of a lithium secondary battery can be a material capable of lithium intercalation. As an example, the negative electrode active material is lithium (metallic lithium), graphitizable carbon, non-graphitizable carbon, graphite, silicon, Sn alloy, Si alloy, Sn oxide, Si oxide, Ti oxide, Ni oxide, Fe oxide (FeO), and lithium-titanate (LiTiO 2 、Li4 Ti 5 O 12 It can be one or more substances selected from the negative electrode active material group of ().

[0112] As the conductive material, ordinary conductive carbon materials can be used without particular limitation.

[0113] The non-aqueous electrolyte contains a lithium salt as an electrolyte and an organic solvent. The lithium salt can be used without limitation, such as those commonly used in electrolytes for lithium secondary batteries. Li + X - It can be represented by.

[0114] The anion of the lithium salt is not particularly limited, and includes F - , Cl - , Br - , I - , NO 3 - , N(CN) 2 - , BF 4 - , ClO 4 - , PF 6 - , (CF 3 ) 2 PF 4 - , (CF 3 ) 3 PF 3 - , (CF 3 ) 4 PF 2 - , (CF 3 ) 5 PF - , (CF 3 ) 6 P - , CF 3 SO 3 - , CF 3 CF 2 SO 3 - , (CF 3 SO 2 ) 2 N- , (FSO 2 ) 2 N - , CF 3 CF 2 (CF 3 ) 2 CO - , (CF 3 SO 2 ) 2 CH - , (SF 5 ) 3 C - , (CF 3 SO 2 ) 3 C - , CF 3 (CF 2 ) 7 SO 3 - , CF 3 CO 2 - , CH 3 CO 2 - , SCN - and (CF 3 CF 2 SO 2 ) 2 N - Any one or two or more thereof can be used.

[0115] As the organic solvent, any one or a mixture of two or more selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma-butyrolactone, and tetrahydrofuran can be used.

[0116] The non-aqueous electrolyte can be injected into an electrode structure including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

[0117] The outer shape of the lithium secondary battery is not particularly limited, but can be selected from a cylindrical shape using a can, a square shape, a pouch type, a coin type, etc.

[0118] Hereinafter, with reference to specific experimental examples, the embodiments of the present disclosure will be further described. The examples and comparative examples included in the experimental examples are 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 examples are possible within the scope of the present disclosure and the scope of the technical idea, and it is natural that such deformations and modifications belong to the scope of the appended claims.

[0119] First, the physical property evaluation method will be described.

[0120] [Average particle size] The average particle size was derived from the particle size distribution results analyzed using S3500 manufactured by MICROTRAC after sampling the particles to be measured according to the ISO 13320-1 standard.

[0121] [Glass-transition temperature (Tg)] The glass-transition temperature was measured using a differential scanning calorimeter (DSC). The manufacturing company was Mettler Toledo, and the model was DSC1.

[0122] The measurement method was as follows: A test piece of 5-10 mg was prepared according to the pan size of the DSC, placed in a container, and pressed with a crimper press. The prepared sample and a reference sample were placed, and analysis was performed by selecting the temperature range, heating rate, and reactive gas. Tg was defined as the midpoint of the baseline shift, that is, the midpoint of the baseline where the change in heat capacity starts and ends.

[0123] The measurement conditions are as follows.

[0124] Temperature range: -100 to 250 °C Reactive gas: N 2 Heating / cooling rate: 10 °C / min

[0125] [Aspect ratio of anisotropic particles] The aspect ratio means the value obtained by dividing the average length in the major axis direction by the average length in the minor axis direction. The length in the major axis direction means the longest length of the particle, and the average length in the minor axis direction means the longest length in the direction perpendicular to the major axis.

[0126] The average length in the major axis direction and the average length in the minor axis direction were obtained from the average of the values measured by arbitrarily selecting 20 particles from each of 5 images measured with a transmission electron microscope (TEM, JEOL Ltd, JEM-2100F).

[0127] [Measurement of molecular weight] The measurement of the weight-average molecular weight was carried out using GPC (manufactured by Tosoh, EcoSEC HLC-8320 GPC Reflective Index detector). The GPC column was used by connecting TSKgel guard PWxl, two TSKgel GMPWxl, and TSKgel G2500PWxl (7.8×300 mm). The solvent used was 0.1 M NaNO 3 aqueous solution, and PEG / PEO was used as the standard substance. Analysis was performed at 40 °C with a flow rate of 1 mL / min.

[0128] 1) GPC (Gel permeation chromatograph) sample treatment (1) Sample pretreatment: Use the provided sample as it is (2) Sample dissolution state: Completely dissolved (3) Sample solution filtration: 0.45 μm nylon filter

[0129] 2) Conditions of GPC (Gel permeation chromatograph) analyzer (1) Analyzer: EcoSEC HLC-8320 GPC manufactured by Tosoh (2) Detector: RI-detector (3) Developing solvent: 0.1M NaNO 3 (4) Column (maker, model no.): Tskgel guard PWxl + 2 x TSKgel GMPWxl + TSKgel G2500PWxl (7.8×300mm) (5) Temperature: 40°C (6) Flow rate: 1.0 mL / min (7) Injection volume: 100 μl, 10 mg / mL (8) Standard substance: PEG / PEO

[0130] [Porosity] The porosity of the separator was calculated from the following mathematical formula by cutting a 10 cm × 10 cm sample.

[0131] Porosity = {1 - [M / (100 × T × ρ)]} × 100 Here, T = thickness of the original sheet (cm) M = weight of the sample (g) ρ = density of the original sheet resin (g / cm 3 ) [Adhesion evaluation with electrode] With respect to the total weight of the positive electrode active material, 94 wt% of LiCoO 2 2.5 wt% of polyvinylidene fluoride as a binder, 3.5 wt% of carbon black as a conductive agent were added to NMP (N-methyl-2-pyrrolidone) as a solvent, and stirred to produce a uniform positive electrode slurry. The produced slurry was coated, dried and crimped on an aluminum foil with a thickness of 30 μm to produce a positive electrode with a total thickness of 150 μm.

[0132] Place the separator adhesive layers of the examples and comparative examples on the manufactured positive electrode so that they face each other, and use a heat press machine to press-bond them at 80 °C and 10 kgf / cm 2 for 30 seconds under the heat and pressure of. Then, according to ASTM D903, peel at 180° using a UTM equipment manufactured by INSTRON to measure the adhesive force (gf / cm) between the separator and the electrode.

[0133] [Evaluation of the Feasibility of Improving the Coffee Ring Phenomenon] Evaluate whether the coffee ring phenomenon is improved through the scanning electron microscope (SEM) images of the separators of the examples and comparative examples. If a ring-shaped stain is observed from the SEM image, it is considered that coffee ring occurs. When the occurrence of coffee ring is confirmed in the SEM image, it is evaluated as "NG", and when the occurrence of coffee ring is not confirmed, it is evaluated as "OK".

[0134] [Evaluation of Blocking Resistance] Place two separators including the adhesive layer so that the adhesive layers face each other, and use a heat press machine to press-bond them at a temperature of 50 °C and a pressure of 15 kgf / cm 2 for 1 hour. Then, according to ASTM D903, evaluate whether the phenomenon that the adhesive layers adhere to each other and part or all of them peel off occurs when peeling at 180°. If peeling occurs even in part, it is considered that blocking has occurred, and if the peeling phenomenon does not occur and the adhesive layers are separated as they are, it is considered that blocking does not occur. The occurrence of blocking was confirmed from the scanning electron microscope (SEM) image. When the occurrence of blocking was confirmed in the SEM image, it was evaluated as "NG", and when the occurrence of blocking was not confirmed, it was evaluated as "OK".

[0135] [Evaluation of the Life Characteristics of the Battery] First, in order to evaluate the life characteristics of the battery, the battery was manufactured as follows.

[0136] Manufacture of the Positive Electrode As the positive electrode active material, LiNi x Co y Mn zO 2 (x = 0.4 to 0.8, y = 0.1 to 0.3, z = 0.1 to 0.3) 92% by weight, 4% by weight of carbon black as the conductive material, and 4% by weight of polyvinylidene fluoride (PVdF) as the binder were added to N-methyl-2-pyrrolidone (NMP) as the solvent, and stirred to produce a uniform positive electrode slurry. The positive electrode slurry was applied to an aluminum (Al) thin film with a thickness of 30 μm, dried and crimped to produce a positive electrode with a total thickness of 150 μm.

[0137] Manufacture of negative electrode 96% by weight of graphite carbon as the negative electrode active material, 3% by weight of carbon black as the conductive material, and 1% by weight of PVdF as the binder were added to NMP as the solvent, and stirred to produce a uniform negative electrode slurry. The negative electrode slurry was applied to a copper (Cu) thin film with a thickness of 20 μm, dried and crimped to produce a negative electrode with a total thickness of 150 μm.

[0138] Manufacture of battery What was obtained by disposing the separator of the example or comparative example between the positive electrode and the negative electrode was wound up and put into an aluminum pack. Then, an electrolyte in which 1 M of lithium hexafluorophosphate (LiPF 6 ) was dissolved in a solution containing ethylene carbonate and diethyl carbonate in a volume ratio of 1:1 was injected, and then sealed to manufacture a secondary battery with a capacity of 2 Ah.

[0139] Next, the secondary battery manufactured above was subjected to charge / discharge cycles 600 times using a charge / discharge cycle device, and the discharge capacity at each cycle was measured. Specifically, the battery was charged at a constant current of 1C to 4.2V at 25°C, and then charged at a constant voltage until the current reached 0.01C while maintaining 4.2V, and then discharged at a constant current of 1C to 2.5V. This was defined as one cycle. The cycle point at which the discharge capacity decreased to less than 80% of the discharge capacity in the first cycle was defined as the cycle life and shown in Table 1.

[0140] <Example 1> Manufacture of inorganic particle layer As the inorganic particles, 30 parts by weight of boehmite particles (manufactured by Nabaltec, ACTILOX (registered trademark) 200SM) with an average particle diameter (D 50 ) of 300 nm, 70 parts by weight of boehmite particles (manufactured by Nabaltec, ACTILOX (registered trademark) B60) with an average particle diameter (D 50 ) of 700 nm, and 3 parts by weight of polyacrylamide (weight average molecular weight: 300,000 g / mol) as a binder resin were added to distilled water so that the solid content concentration became 25% by weight, and then stirred to produce a slurry for forming an inorganic particle layer.

[0141] The slurry for forming the inorganic particle layer was bar-coated on both sides of a polyethylene porous film (porosity 41%, average thickness: 9 μm), and then dried sufficiently at 40°C to form an inorganic particle layer with an average thickness of 1.5 μm on each side of the porous substrate.

[0142] Manufacture of adhesive layer As a binder, 100 parts by weight of acrylic particles with an average particle diameter (D 50 ) of 500 nm and a glass transition temperature of 60°C, and 7.1 parts by weight of cellulose nanofibers (manufactured by Hansol, Duracle A) with a glass transition temperature of 200°C as anisotropic particles were dispersed in distilled water so that the solid content concentration became 7.5% by weight, and then mixed to produce a coating liquid for forming an adhesive layer. The acrylic particles used at this time were a copolymer produced from acrylonitrile, styrene, and methacrylamide. The cellulose nanofibers had an average length in the long axis direction of 350 nm, an average length in the short axis direction of 5 nm, and a glass transition temperature of 200°C.

[0143] After spray coating and applying the coating liquid for forming the adhesive layer on each surface of the inorganic particle layers formed on both sides of the porous substrate, it was sufficiently dried at 40 °C, and adhesive layers were formed on both surfaces of the inorganic particle layers with an average thickness of 0.75 μm each. Finally, a separator laminated in the order of adhesive layer / inorganic particle layer / porous substrate / inorganic particle layer / adhesive layer was manufactured.

[0144] <Example 2> A separator was manufactured in the same manner as in Example 1, except that cellulose acetate nanofibers having an average length in the major axis direction of 350 nm, an average length in the minor axis direction of 5 nm, and a glass transition temperature of 150 °C were used as the anisotropic particles.

[0145] <Example 3> A separator was manufactured in the same manner as in Example 1, except that cellulose nanofibers having an average length in the major axis direction of 100 nm, an average length in the minor axis direction of 5 nm, and a glass transition temperature of 200 °C were used as the anisotropic particles.

[0146] <Example 4> A separator was manufactured in the same manner as in Example 1, except that cellulose nanofibers having an average length in the major axis direction of 1000 nm, an average length in the minor axis direction of 5 nm, and a glass transition temperature of 200 °C were used as the anisotropic particles.

[0147] <Example 5> A separator was manufactured in the same manner as in Example 1, except that 7.1 parts by weight of boehmite particles having an average length in the major axis direction of 40 nm and an average length in the minor axis direction of 8 nm were used as the anisotropic particles. The boehmite particles used at this time were manufactured by the following method. First, Al(NO 3 ) 3 ·9H 2 O was dispersed in water to prepare an aluminum precursor solution. Next, acetic acid was added to the aluminum precursor solution to adjust the pH to 3.3, and then the reaction was carried out with stirring at 120 °C for 24 hours.

[0148] <Example 6> A separator was manufactured in the same manner as in Example 5, except that 1.5 parts by weight of boehmite particles were used as the anisotropic particles.

[0149] <Example 7> A separator was manufactured in the same manner as in Example 5, except that 15 parts by weight of boehmite particles were used as the anisotropic particles.

[0150] <Example 8> A separator was manufactured in the same manner as in Example 5, except that 20 parts by weight of boehmite particles were used as the anisotropic particles.

[0151] <Example 9> A separator was manufactured in the same manner as in Example 1, except that inorganic particle layers were not formed on both sides of the polyethylene porous film in Example 1.

[0152] That is, after the coating liquid for forming the adhesive layer was spray-coated on both sides of the porous base material and applied, it was sufficiently dried at 40 °C, and adhesive layers with an average thickness of 0.75 μm were formed on both surfaces of the porous base material, respectively. Finally, a separator laminated in the order of adhesive layer / porous base material / adhesive layer was manufactured.

[0153] <Comparative Example 1> A separator was manufactured in the same manner as in Example 1, except that anisotropic particles were not added during the production of the coating liquid for forming the adhesive layer.

[0154] <Comparative Example 2> A separator was manufactured in the same manner as in Example 1, except that acrylic particles having an average length in the long axis direction of 450 nm, an average length in the short axis direction of 10 nm, and a glass transition temperature of 140 °C were used as the anisotropic particles.

[0155] <Comparative Example 3> A separator was manufactured in the same manner as in Example 1, except that cellulose acetate nanofibers with an average length in the major axis direction of 350 nm, an average length in the minor axis direction of 10 nm, and a glass transition temperature of 140 °C were used as the anisotropic particles.

[0156] <Comparative Example 4> A separator was manufactured in the same manner as in Example 1, except that 100 parts by weight of boehmite particles with an average length in the major axis direction of 800 nm and an average length in the minor axis direction of 300 nm were used as the anisotropic particles.

[0157] <Comparative Example 5> A separator was manufactured in the same manner as in Example 5, except that 1 part by weight of boehmite particles was used as the anisotropic particles.

[0158]

Table 1

[0159] Referring to Table 1 above, the separators of Examples 1 to 9 showed improvement in the coffee ring phenomenon where the binder accumulates at the periphery of the coating area while the coating liquid for forming the adhesive layer evaporates, compared to the separators of the comparative examples. Also, during winding of the separator, the blocking phenomenon where the adhesive layer transfers to the opposite side and peels off was improved.

[0160] On the other hand, for the separator of Comparative Example 1 which does not contain anisotropic particles according to one embodiment, the coffee ring phenomenon and the blocking phenomenon occurred. Also, for the separators of Comparative Examples 2 and 3 which contain organic particles with a glass transition temperature of less than 150 °C as anisotropic particles, the blocking phenomenon occurred. For the separator of Comparative Example 4 which contains anisotropic particles with an aspect ratio of less than 4, the coffee ring phenomenon and the blocking phenomenon occurred. Also, for the separator of Comparative Example 5 which contains less than 1.2 parts by weight of anisotropic particles with respect to 100 parts by weight of the binder, it was confirmed that the coffee ring phenomenon and the blocking phenomenon occurred.

[0161] Specifically, FIG. 1 is a diagram showing an SEM image of the surface of the separator manufactured in Comparative Example 1, and FIG. 2 is a diagram showing an SEM image of the surface of the separator manufactured in Example 5. Referring to these, in the separator of Comparative Example 1 that does not contain anisotropic particles in the adhesive layer, coffee-ring-shaped stains were clearly observed on the surface, but in the separator of Example 5 that contains anisotropic particles in the adhesive layer, the coffee-ring phenomenon was improved on the surface. Further, in the case of the separators of Comparative Examples 2 to 5, coffee-ring-shaped stains as observed from FIG. 1 were clearly observed, and in the case of the separators manufactured in the remaining examples other than Example 5, the coffee-ring phenomenon was improved on the surface of the separator as in Example 5.

[0162] That is, the separator of the present disclosure contains 1.2 parts by weight or more based on 100 parts by weight of the binder, contains any one or more selected from the first inorganic particles and organic particles having a glass transition temperature of 150° C. or higher, and has an aspect ratio of 4 to 1,000. By using anisotropic particles, it has the merits of improving the coffee-ring phenomenon, having excellent adhesiveness to the electrode, and having excellent antiblocking properties.

[0163] The content described above is merely an exemplification applying the principle of the present disclosure, and other configurations can be further included without departing from the scope of the present disclosure.

Claims

1. A porous substrate; an adhesive layer located on at least one surface of the porous substrate, the adhesive layer including a binder and anisotropic particles; The adhesive layer contains 1.2 parts by weight or more of anisotropic particles based on 100 parts by weight of a binder, The anisotropic particles include at least one selected from the group consisting of first inorganic particles and organic particles having a glass transition temperature of 150° C. or higher, and the anisotropic particles have an aspect ratio of 4 to 1,000.

2. The separator according to claim 1 , wherein the anisotropic particles have an aspect ratio of 4 to 200.

3. 2. The separator according to claim 1, wherein the anisotropic particles have an average length in the major axis direction of 10 nm to 5000 nm and an average length in the minor axis direction of 1 nm to 500 nm.

4. The separator according to claim 1 , wherein the first inorganic particles include at least one selected from the group consisting of a metal hydroxide, a metal oxide, a metal nitride, and a metal carbide.

5. 2. The separator according to claim 1, wherein the organic particles contain one or more copolymers selected from the group consisting of styrene-based polymers, acrylic-based polymers, and cellulose-based polymers.

6. 2. The separator according to claim 1, wherein the adhesive layer contains 1.2 to 20 parts by weight of anisotropic particles per 100 parts by weight of the binder.

7. 2. The separator according to claim 1, wherein the adhesive layer contains 1.2 to 10 parts by weight of anisotropic particles per 100 parts by weight of the binder.

8. The separator of claim 1 , wherein the binder has a glass transition temperature in the range of 30° C. to 120° C.

9. The separator of claim 1 , wherein the binder is a particulate binder.

10. The separator according to claim 9, wherein the particulate binder has an average particle size of 0.01 μm to 5 μm.

11. 2. The separator according to claim 1, wherein the binder comprises at least one selected from the group consisting of an acrylic polymer, a fluorine-based polymer, an ester-based polymer, an amide-based polymer, an imide-based polymer, a styrene-based polymer, a vinyl alcohol-based polymer, a vinylpyrrolidone-based polymer, and a cellulose-based polymer.

12. The separator of claim 1 , wherein the adhesive layer has a total thickness of 0.1 μm to 10 μm.

13. The separator was laminated on the positive electrode so that the adhesive layer of the separator faced the positive electrode, and the laminate was heated at 80° C. and 10 kgf / cm ２ 2. The separator according to claim 1, wherein the adhesive strength measured in accordance with ASTM D903 after being pressed at 1000 V for 30 seconds is 0.5 gf / cm or more.

14. The separator according to claim 1 , further comprising an inorganic particle layer formed between the porous substrate and any one of the adhesive layers.

15. The separator according to claim 14, wherein the inorganic particle layer contains 0.1 to 20 parts by weight of a binder resin per 100 parts by weight of the second inorganic particles.

16. A lithium secondary battery comprising: a positive electrode; a negative electrode; the separator according to any one of claims 1 to 15 interposed between the positive electrode and the negative electrode; and an electrolyte.

17. (a) providing a porous substrate; (a-1) applying a coating solution for forming an adhesive layer containing a binder and anisotropic particles to at least one surface of a porous substrate, and drying the coating solution to form an adhesive layer; (a-2) thereby obtaining a separator; or (a-i) applying a slurry for forming an inorganic particle layer, the slurry including second inorganic particles and a binder resin, to at least one surface of a porous substrate, and drying the slurry to form an inorganic particle layer; (a-ii) applying a coating solution for forming an adhesive layer containing a binder and anisotropic particles onto the inorganic particle layer, and drying the solution to form an adhesive layer; (a-iii) thereby obtaining a separator; and in (a-1) and (a-ii), the adhesive layer contains 1.2 parts by weight or more of anisotropic particles relative to 100 parts by weight of the binder, the anisotropic particles having an aspect ratio of 4 to 1,000, and containing one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150° C. or higher.

18. The method for producing a separator according to claim 17 , wherein the electrochemical device is a lithium secondary battery.

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