Separator and lithium secondary battery comprising same

Abstract

According to one aspect of the present disclosure, provided are a separator and a lithium secondary battery comprising the same, the separator comprising: a porous substrate; and an adhesive layer that is positioned on at least one surface of the porous substrate and contains a binder and anisotropic particles, the adhesive layer containing 1.2 parts by weight or more of the anisotropic particles with respect to 100 parts by weight of the binder, the anisotropic particles include any one or more selected from a group consisting of first inorganic particles and organic particles having a glass transition temperature of 150 DEG C or more, and the aspect ratio of the anisotropic particles is 4 to 1000. The separator of the present disclosure may have an advantage of excellent adhesion to an electrode.

Description

Technical Field

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

[0002] Recently, with the trend of high capacity and high output of secondary batteries, the requirements for the high strength, high transmittance, thermal stability and electrical safety of secondary batteries during charging and discharging of the separators are increasing. For example, high mechanical strength is required to improve the safety of the battery during manufacturing and use, and high transmittance and high thermal stability are required to increase the capacity and output.

[0003] Moreover, if the secondary battery separator lacks adhesion to the electrode, the separator and the electrode may separate during the battery assembly process, causing the electrode assembly to twist, deform, etc. That is, when there is a lack of adhesion between the separator and the electrode as above, there will be misalignment between the electrode and the separator in the jelly roll during cell stacking. When driving the stacked cells that are not aligned as above, local resistance may occur due to misalignment, or physical damage that occurs with continued use may cause short circuits between electrodes, causing safety issues such as fire.

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

[0005] Technical issues

[0006] According to one aspect of the present disclosure, a separator having excellent adhesion to an electrode and a lithium secondary battery including the separator may be provided.

[0007] According to another aspect of the present disclosure, a separator capable of effectively suppressing a sticking phenomenon in which an adhesive layer is transferred to an opposite surface and detached when the separator is wound, and a lithium secondary battery including the separator may be provided.

[0008] According to another invention of the present disclosure, a lithium secondary battery having excellent life characteristics can be provided.

[0009] According to another aspect of the present disclosure, a separator having significantly improved adhesion to an electrode within a specific temperature range may be provided.

[0010] According to another aspect of the present disclosure, a separator that exhibits adhesion to an electrode within a specific temperature range and effectively suppresses adhesion at a temperature below the specific temperature range and a lithium secondary battery including the separator can be provided. For example, the separator according to one embodiment of the present disclosure exhibits adhesion at a temperature above 150°C, and adhesion between adhesive layers of the separator can be effectively suppressed at a temperature below 150°C.

[0011] The diaphragm disclosed herein and the lithium secondary battery including the diaphragm can be widely used in electric vehicles, battery charging stations and other green technology fields such as solar power generation and wind power generation using batteries. In addition, the diaphragm disclosed herein and the lithium secondary battery including the diaphragm can be used in eco-friendly electric vehicles, hybrid vehicles, etc. that prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0012] Technical Solution

[0013] One embodiment of the present disclosure relates to a separator for an electrochemical element such as a lithium secondary battery.

[0014] Another embodiment of the present disclosure is directed to a secondary battery including the separator according to one embodiment. The secondary battery may be a lithium secondary battery including the separator of the present disclosure.

[0015] According to the present disclosure, the diaphragm includes: a porous substrate; and an adhesive layer, which is located on at least one side of the porous substrate and contains an adhesive and anisotropic particles, wherein the adhesive layer contains 1.2 parts by weight or more of anisotropic particles relative to 100 parts by weight of the adhesive, and the anisotropic particles include any one or more selected from a first inorganic particle and an organic particle with a glass transition temperature of 150° C. or more, and the aspect ratio of the anisotropic particles is 4 to 1000.

[0016] In the present disclosure, the binder and the anisotropic particles may be different in material and may be different from each other. For example, the binder may be an organic material such as a polymer, and the anisotropic particles may be inorganic particles. Alternatively, the binder may be an organic material such as a polymer, and the anisotropic particles may be organic particles, wherein the organic materials, polymers, or shapes of the binder and the anisotropic organic particles may be different. For example, compared with the anisotropic organic particles, the polymer material used for the binder may have an aspect ratio of less than 4, or a lower glass transition temperature (for example, more than 50°C lower), or may have a different shape. For example, the anisotropic organic particles may be a polymer in the form of fibers, while the binder may be spherical or amorphous polymer particles rather than fibers.

[0017] In one embodiment, the anisotropic particles may have an aspect ratio of 4 to 200.

[0018] In one embodiment, the average length of the anisotropic particles in the long axis direction may be 10 nm to 5000 nm, and the average length in the short axis direction may be 1 nm to 500 nm.

[0019] In one embodiment, the first inorganic particles may include any one or more selected from the group consisting of metal hydroxides, metal oxides, metal nitrides, and metal carbides.

[0020] In one embodiment, the organic particles may include any one selected from the group consisting of styrene polymers, acrylic polymers, and cellulose polymers, or a copolymer of two or more thereof.

[0021] In one embodiment, the adhesive layer may include 1.2 parts by weight to 20 parts by weight of the anisotropic particles relative to 100 parts by weight of the adhesive.

[0022] In one embodiment, the adhesive layer may include 1.2 parts by weight to 10 parts by weight of the anisotropic particles relative to 100 parts by weight of the adhesive.

[0023] In one embodiment, the adhesive may have a glass transition temperature in a range of 30°C to 120°C.

[0024] In one embodiment, the binder may be a particle-type binder.

[0025] In one embodiment, the particle-type adhesive may have an average particle size of 0.01 μm to 5 μm.

[0026] 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.

[0027] In one embodiment, the total thickness of the adhesive layer may be 0.1 μm to 10 μm. In another embodiment, the total thickness of the adhesive layer may be 0.5 μm to 5 μm, or 1.0 μm to 2.5 μm, or 1.0 μm to 2.0 μm.

[0028] The "total thickness" refers to the total thickness of all adhesive layers present on or on the porous substrate. For example, when an adhesive layer is formed on only one side of the porous substrate, the "total thickness" is the thickness of the one adhesive layer. In addition, when adhesive layers are formed on both sides of the porous substrate, the "total thickness" is the total thickness of each adhesive layer.

[0029] In one embodiment, the separator is stacked on the positive electrode with the adhesive layer of the separator facing the positive electrode and heated by a hot press at 80° C. and 10 kgf / cm 2 The adhesive force of the separator measured according to ASTM D903 after press-fitting for 30 seconds may be 0.5 gf / cm or more.

[0030] In one embodiment, the diaphragm may also include an inorganic particle layer formed between the porous substrate and any adhesive layer. That is, in this case, the adhesive layer is disposed on at least one side of the porous substrate (not directly on it). In the present disclosure, unless otherwise defined, the term "on..." means that a layer, film, film, region, or plate, etc., is "on" other parts, which means that other parts (films, layers, or additional corresponding parts) may also be included in the middle of them. Therefore, in the case where the adhesive layer is located on at least one side of the porous substrate, an intermediate layer, such as an inorganic particle layer, may be included between the porous substrate and the adhesive layer.

[0031] In one embodiment, the inorganic particle layer may include 0.1 to 20 parts by weight of a binder resin relative to 100 parts by weight of the second inorganic particles. As an embodiment, the second inorganic particles may be a mixture of one, two, three or more inorganic particles with different average particle sizes. This mixture may exhibit a unimodal, bimodal, trimodal or multimodal particle size distribution. This unimodal, bimodal, trimodal or multimodal particle size distribution may preferably be observed in a mixture of inorganic particles before being added to the coating slurry, that is, more than two inorganic particles may be used in terms of particle size. For example, the "second inorganic particles" may be a mixture of inorganic particles having an average particle size 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 an average particle size greater than 0.5 μm and less than 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 may be a mixture of inorganic particles having an average particle size of 0.3 μm and inorganic particles having an average particle size of 0.7 μm.

[0032] Furthermore, the present disclosure provides a lithium secondary battery including: a positive electrode; a negative electrode; the separator as described above disposed between the positive electrode and the negative electrode; and an electrolyte.

[0033] Furthermore, the present disclosure provides a method for manufacturing a separator for an electrochemical device, for example, a method for manufacturing a separator for an electrochemical device such as a lithium secondary battery.

[0034] The method for manufacturing the diaphragm disclosed in the present invention comprises: step (a), providing a porous substrate; and

[0035] Step (a-1), coating a coating solution for forming an adhesive layer comprising an adhesive and anisotropic particles on at least one side of a porous substrate and drying the coating solution to form an adhesive layer; and

[0036] Step (a-2), thereby obtaining a separator,

[0037] or,

[0038] Step (ai), coating a slurry for forming an inorganic particle layer comprising second inorganic particles and a binder resin on at least one side of a porous substrate and drying the slurry to form an inorganic particle layer; and

[0039] Step (a-ii), coating a coating solution for forming an adhesive layer comprising a binder and anisotropic particles on the inorganic particle layer and drying the coating solution to form an adhesive layer; and

[0040] Step (a-iii), thereby obtaining a membrane,

[0041] In step (a-1) and step (a-ii), the adhesive layer contains 1.2 parts by weight or more of anisotropic particles relative to 100 parts by weight of the adhesive, the anisotropic particles having an aspect ratio of 4 to 1000 and containing one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150°C or above.

[0042] Effects of the Invention

[0043] The separator according to the present disclosure may have an advantage of excellent adhesion with an electrode.

[0044] Furthermore, the present disclosure can provide a separator in which a sticking phenomenon occurring when the separator is wound is improved.

[0045] Also, the present disclosure may provide a lithium secondary battery having excellent lifespan characteristics due to including the separator according to one embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a diagram showing a scanning electron microscope (SEM) image of the surface of the diaphragm manufactured according to Comparative Example 1;

[0047] Figure 2 FIG. 4 is a diagram showing a scanning electron microscope (SEM) image of a surface of a diaphragm according to one embodiment. DETAILED DESCRIPTION

[0048] The embodiments described in this specification can be modified into various other modes, and the technology according to one embodiment is not limited to the embodiments described below. Moreover, the embodiments of one embodiment are provided to more completely explain the present disclosure to ordinary technicians in the technical field.

[0049] Furthermore, singular forms used in the specification and the appended claims may be intended to include plural forms as well, unless the context clearly indicates otherwise.

[0050] Moreover, the numerical range used in this specification includes the lower limit, the upper limit, and all values ​​within the range, increments derived from the form and amplitude of the defined range logic, all values ​​of the double definition, and all possible combinations of the upper and lower limits of the numerical range defined in different forms. Unless otherwise specifically defined in this specification, values ​​outside the numerical range that may occur due to experimental errors or numerical rounding are also included in the defined numerical range.

[0051] Furthermore, throughout the specification, unless otherwise stated, “comprising” a certain constituent element does not mean excluding other constituent elements, but indicates that other constituent elements may also be included.

[0052] When it is described in this specification that a layer, film, region, plate or the like is “on” or “over” another part, this includes not only the case where it is “directly on” the other part, but also the case where there are other parts in between.

[0053] The terms "first", "second" and the like used in this specification can be used to describe various components, but the components should not be limited by these terms. The terms are only used to distinguish one component from other components.

[0054] In this specification, the average particle size refers to "D50", which is the particle size of particles with a cumulative fraction of 50% on a volume basis. The average particle size can be derived from the particle size distribution results obtained by taking a sample from the particles to be measured according to ISO 13320-1 and analyzing it using S3500 of MICROTRAC.

[0055] In the present specification, the glass-transition temperature (Tg) refers to the temperature range in which the glass transition occurs, and refers to the value measured by a dilatometer (DMT) or a differential scanning calorimeter (DSC).

[0056] In this specification, "anisotropic particles" refer to particles whose lengths in the major axis direction and the minor axis direction are different from each other. For example, it refers to particles with an aspect ratio of 4 or more and 4 to 1000. In this specification, particles not defined as "anisotropic particles" refer to particles with an aspect ratio of less than 4, less than 3, and less than 2, which are different from the anisotropic particles. For example, in this specification, the "first inorganic particles" and "organic particles with a glass transition temperature of 150°C or more" contained in the bonding layer are "anisotropic" particles. In addition, the "granular adhesive" contained in the bonding layer and the "second inorganic particles" contained in the inorganic particle layer are particles different from the anisotropic particles. In the case of having an aspect ratio, the aspect ratio can be less than 4, less than 3, or less than 2.

[0057] In this specification, the aspect ratio refers to the value of the average length in the major axis direction divided by the average length in the minor axis direction. The length in the major axis direction refers to the longest length of the particle, and the average length in the minor axis direction refers to the longest length in the direction perpendicular to the major axis.

[0058] In the present 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 values ​​measured by arbitrarily selecting 20 particles from 5 images measured with a transmission electron microscope (TEM, JEOL Ltd, JEM-2100F).

[0059] The present disclosure provides a diaphragm, comprising: a porous substrate; and an adhesive layer, which is located on at least one side of the porous substrate and comprises an adhesive and anisotropic particles, wherein the adhesive layer comprises 1.2 parts by weight or more of anisotropic particles relative to 100 parts by weight of the adhesive, wherein the anisotropic particles comprise at least one selected from a first inorganic particle and an organic particle having a glass transition temperature of 150° C. or higher, and an aspect ratio of the anisotropic particles is 4 to 1000.

[0060] The adhesive layer includes anisotropic particles having the above-mentioned specific composition and physical properties (for example, an aspect ratio of 4 to 1000 and a glass transition temperature of 150° C. or above), thereby providing a separator having excellent adhesion to the electrode. Moreover, the separator includes the anisotropic particles, thereby effectively suppressing the adhesion phenomenon of detachment as the adhesive layer is transferred to the opposite surface when the separator is wound. Moreover, the lithium secondary battery according to one embodiment includes the above-mentioned separator, and thus can have excellent electrical characteristics and safety.

[0061] According to one embodiment, a coating liquid for forming an adhesive layer containing an adhesive and anisotropic particles may be applied to at least one side of a porous substrate or an inorganic particle layer and dried to form an adhesive layer. In this case, a diaphragm according to one embodiment contains anisotropic particles with an aspect ratio of 4 to 1000, thereby preventing a coffee ring phenomenon in which the adhesive is accumulated at the edge of the coating area as the applied coating liquid for forming an adhesive layer evaporates. This coffee ring phenomenon may be the cause of a decrease in the adhesion between the diaphragm and the electrode due to uneven distribution of the adhesive. A diaphragm according to one embodiment contains the anisotropic particles, thereby effectively preventing the coffee ring phenomenon so that the adhesive contained in the adhesive layer is evenly distributed throughout the adhesive layer, and thus has the advantage of excellent adhesion to the electrode.

[0062] Furthermore, the separator according to one embodiment includes at least one anisotropic particle selected from the first inorganic particle and the organic particle having a glass transition temperature of 150° C. or higher, so that the sticking phenomenon in which the adhesive layer is transferred to the opposite surface and detached when the separator is wound can be effectively suppressed.

[0063] In one embodiment, the anisotropic particles refer to particles having anisotropic shapes, and the aspect ratio may 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 values. For example, the aspect ratio of the anisotropic particles may be 4 to 1000, 5 to 750, 10 to 500, 4 to 200, or 20 to 200. In the case where the anisotropic particles have an aspect ratio in the above range, the binder contained in the bonding layer is uniformly distributed throughout the bonding layer, so that the effect of excellent bonding between the separator and the electrode can be achieved.

[0064] In one embodiment, as long as the aspect ratio meets the above range, the anisotropic particles are not particularly limited to a specific shape. In a non-limiting manner, the shape of the anisotropic particles can be selected from rods, columns, filaments, fibers, plates, etc. Further, in the case where the anisotropic particles are selected from anisotropic first inorganic particles, all of the above shapes can be selected. Moreover, in the case where the anisotropic particles are selected from organic particles, they can be a material and / or shape different from the adhesive of the adhesive layer. For example, the anisotropic organic particles can be a polymer material having a higher glass transition temperature than the adhesive of the adhesive layer and / or a fiber-shaped polymer.

[0065] In one embodiment, the average length of the long axis direction of the anisotropic particles may be 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 the above values. For example, the average length of the long axis direction of the anisotropic particles may be 10 nm to 5000 nm, 20 nm to 2000 nm, or 30 nm to 1000 nm, but the aspect ratio is not particularly limited thereto as long as it satisfies the above range.

[0066] In one embodiment, the average length of the short axis direction of the anisotropic particles can be 1 nm or more, 2 nm or more, 500 nm or less, 200 nm or less, 100 nm or less, or a value between the above values. For example, the average length of the short axis direction of the anisotropic particles can be 1 nm to 500 nm, 1 nm to 200 nm, or 2 nm to 100 nm, but is not particularly limited thereto as long as the aspect ratio satisfies the above range.

[0067] In one embodiment, the anisotropic particles may include at least one selected from first inorganic particles and organic particles having a glass transition temperature of 150° C. or higher.

[0068] The first inorganic particles that can be used as the anisotropic particles may have an average length in the long 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 short 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 are not limited thereto as long as they do not depart from the scope of the present disclosure.

[0069] The average length of the organic particles having a glass transition temperature of 150° C. or above that can be used as the anisotropic particles may be 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 in the long axis direction, and the average length of the organic particles having a glass transition temperature of 100° C. or above in the short axis direction may be 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 are not limited thereto as long as they do not depart from the scope of the present disclosure.

[0070] In one embodiment, the first inorganic particles are not limited as long as they are inorganic particles used in the technical field. As a non-limiting example, the first 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 first inorganic particles may include magnesium oxide (MgO), magnesium hydroxide (Mg(OH) 2), aluminum oxide (Al 2 O 3 ), boehmite (γ-AlO(OH)), aluminum hydroxide (Al(OH) 3 ), silicon dioxide (SiO 2 ), silicon carbide (SiC), calcium oxide (CaO), titanium dioxide (TiO 2 ), SrTiO 3 ), barium titanate (BaTiO 3 )、ZnO、Yttrium Oxide (Y 2 O 3 )、ZrO 2 ), tin oxide (SnO 2 ) and cerium oxide (CeO 2 ) is any one or more of the group consisting of. From the viewpoint of adhesion and anti-blocking properties between the electrode, the first inorganic particle may be selected from boehmite, aluminum hydroxide (Al(OH) 3 ) and magnesium hydroxide (Mg(OH) 2 ), but may be replaced by inorganic particles of other materials as long as it does not depart from the scope of the present disclosure.

[0071] In one embodiment, the organic particles are polymer particles used in the technical field and may have a glass transition temperature of more than 150°C.

[0072] In one embodiment, the organic particles may include any one or more copolymers selected from the group consisting of styrene polymers, acrylic polymers and cellulose polymers, but may be replaced with organic particles of other materials as long as they do not depart from the scope of the present disclosure. For example, the styrene polymer may be any one or more selected from polystyrene, poly-α-methylstyrene and polybromostyrene. The acrylic polymer may be any one or more selected from polyacrylamide, polymethacrylate, polyethyl acrylate, polyacrylate, polybutyl acrylate and acrylic acid-methacrylic acid copolymer. Moreover, the cellulose polymer may be any one or more selected from cellulose, carboxymethyl cellulose, cellulose acetate propionate, cellulose acetate and cellulose acetate butyrate.

[0073] In one embodiment, the adhesive layer may contain 1.2 parts by weight or more of anisotropic particles relative to 100 parts by weight of the adhesive. In the case of containing anisotropic particles and an adhesive satisfying the composition ratio, a better adhesion between the electrode and the effect of suppressing adhesion can be achieved. Specifically, the adhesive layer may contain 1.2 to 20 parts by weight or 1.5 to 20 parts by weight of anisotropic particles relative to 100 parts by weight of the adhesive.

[0074] In one embodiment, the adhesive layer may 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 relative to 100 parts by weight of the adhesive. When the above range is met, better adhesion between the separator and the electrode can be achieved.

[0075] In one embodiment, the binder included in the adhesive layer provides adhesion between the adhesive layer and the electrode and may have a glass transition temperature in the range of 30° C. to 120° C. The binder may have a glass transition temperature in the range of 50° C. to 120° C. or 60° C. to 110° C.

[0076] In one embodiment, the binder included in the adhesive layer may have one or more glass transition temperatures within the above range, for example, may have two or more glass transition temperatures.

[0077] In one embodiment, the adhesive may be a particle-type adhesive, and the specific shape of the particles is not particularly limited. For example, the particle-type adhesive may have a spherical, elliptical, plate-shaped or irregular particle morphology.

[0078] In one embodiment, the average particle size of the particle-type adhesive may be 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 above values. For example, the average particle size of the particle-type adhesive may be 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.

[0079] In one embodiment, the adhesive 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 adhesive may include acrylic polymers, styrene polymers, fluorine polymers or copolymers of two or more thereof. As a non-limiting example, the adhesive may be any one or copolymers of two or more of the group consisting of acrylonitrile polymers, styrene polymers and (meth) acrylamide polymers.

[0080] In one embodiment of the adhesive, the acrylic polymer may be any one or more selected from polyacrylonitrile, poly(methyl)acrylamide, polymethyl acrylate, polyethyl acrylate, polyacrylate, polybutyl acrylate and acrylic acid-methacrylic acid copolymer. The fluorine polymer may be any one or more selected from polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, hexafluoropropylene, polyfluoro-hexafluoropropylene and polychlorotrifluoroethylene. The ester polymer may be any one or more selected from polyethylene terephthalate, polyethylene naphthalate (PEN), etc. The amide polymer may be any one or more selected from polyamide-6, polyamide-66, etc. The imide polymer may be any one or more selected from polyimide, polyetherimide, polyesterimide, etc. The styrene polymer may be any one or more selected from polystyrene, poly-alpha-methylstyrene and polybromostyrene. The vinyl alcohol polymer may be any one or more selected from polyvinyl alcohol, polyvinyl acetate, and polyvinyl acetate-polyvinyl alcohol copolymers, etc. The vinyl pyrrolidone polymer may be any one or more selected from polyvinyl pyrrolidone and copolymers containing vinyl pyrrolidone, etc. Moreover, the cellulose polymer may be any one or more selected from carboxymethyl cellulose, cellulose acetate propionate, cellulose acetate, and cellulose acetate butyrate, etc., and may be replaced with adhesives of other materials as long as they do not depart from the scope of the present disclosure.

[0081] In order to improve the adhesion between the electrode and the separator, the adhesive layer may be located on the outermost layer.

[0082] In one embodiment, the adhesive layer may be coated on one or both sides of a porous substrate or on one or both sides of the inorganic particle layer described below. When the porous substrate (or inorganic particle layer) is coated on the adhesive layer, the thickness of the adhesive layer coated on one side and the other side may be the same or different. Although there is no particular limitation, in one embodiment, the total thickness of the adhesive layer formed on the porous substrate (or inorganic particle layer) may be 0.1 μm to 10 μm. For example, the thickness of the adhesive layer may be 0.1 μm to 5 μm or 0.5 μm to 2.5 μm. The thickness is measured at any 5 points using a thickness gauge from Mitutoyo and then divided by 5 to determine the average thickness as the thickness.

[0083] According to one embodiment, the binder and the anisotropic particles of the separator satisfy the composition ratio within the above range and the anisotropic particles satisfy the above conditions, so the adhesion between the separator and the electrode is excellent. For example, the separator is stacked on the positive electrode with the adhesive layer of the separator facing the positive electrode and pressed with a hot press at 80°C and 10 kgf / cm 2 The adhesion of the separator measured according to ASTM D903 after 30 seconds of pressing can be 0.4 gf / cm or more. The adhesion measured according to ASTM D903 can be measured by peeling 180° using the UTM equipment of INSTRON. Moreover, the positive electrode used in measuring the adhesion can be used without restriction as long as it is a common positive electrode for lithium secondary batteries. As an example of the positive electrode, 94 wt% of LiCoO 2 , 2.5 wt% polyvinylidene fluoride as a fusion agent, 3.5 wt% carbon black as a conductive agent, N-methyl-2-pyrrolidone (NMP) as a solvent and stirred to prepare a uniform positive electrode slurry, and the prepared positive electrode slurry is coated on an aluminum foil with a thickness of 30 μm and dried and pressed to produce a positive electrode with a total thickness of 150 μm, but other components can be replaced as long as they do not depart from the scope of the present disclosure. The thickness is measured at any 5 points using a thickness meter from Mitutoyo Company and then divided by 5 to determine the average thickness as the thickness.

[0084] Preferably, the adhesive force of the separator measured by the above method can be 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 values. For example, the adhesive force of the separator measured by the above method can be 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.

[0085] According to an embodiment of the separator, the adhesive and the anisotropic particles satisfy the composition ratio within the above range and the anisotropic particles satisfy the above conditions, so that the adhesion phenomenon that the adhesive layer is transferred to the opposite surface and detached when the separator is wound can be effectively suppressed. For example, for the separator, two separators according to an embodiment are arranged so that the adhesive layers face each other and are heated at a temperature of 50°C and 15kgf / cm 2 After 1 hour of pressure lamination, when peeled 180° according to ASTM D903, the adhesive layers are adhered to each other, so that the adhesive layers are not partially or entirely peeled off, and the adhesive layers can be separated intactly.

[0086] In one embodiment, the diaphragm may further include an inorganic particle layer formed between the porous substrate and any adhesive layer. The diaphragm also includes an inorganic particle layer, so it not only has adhesion and anti-adhesion properties with the electrode, but also has the advantage of excellent heat resistance. The adhesive layer is used to enhance the adhesion with the electrode and may be located at the outermost layer of the diaphragm. For example, the diaphragm may have a structure stacked in the order of adhesive layer / porous substrate / adhesive layer, adhesive layer / inorganic particle layer / porous substrate / inorganic particle layer / adhesive layer or adhesive layer / porous substrate / inorganic particle layer / adhesive layer.

[0087] In one embodiment, the inorganic particle layer may include second inorganic particles and a binder resin, and may be a porous inorganic particle layer in which the second inorganic particles are connected and fixed by the binder resin to form pores.

[0088] In one embodiment, for one or both sides of the porous substrate, the inorganic particle layer may be formed on more than 90% of the total area of ​​each side, specifically more than 95%, and more specifically, 100% of the total area of ​​each side of the porous substrate except for the case where micro defects occur. The inorganic particle layer may be a layer in which a plurality of inorganic particles are adjacent to each other to form pores between the plurality of inorganic particles.

[0089] 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 may 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 may include magnesium oxide (MgO), magnesium hydroxide (Mg(OH) 2 ), aluminum oxide (Al 2 O 3 ), boehmite (γ-AlO(OH)), aluminum hydroxide (Al(OH) 3 ), silicon dioxide (SiO 2 ), silicon carbide (SiC), calcium oxide (CaO), titanium dioxide (TiO 2 ), SrTiO 3 ), barium titanate (BaTiO 3 )、ZnO、Yttrium Oxide (Y 2 O 3 )、ZrO 2 ), tin oxide (SnO 2 ) and cerium oxide (CeO 2 ) or any one or more of the group consisting of. From the perspective of battery stability, the second inorganic particle may be selected from boehmite, aluminum hydroxide (Al(OH) 3 ) and magnesium hydroxide (Mg(OH) 2 ), but may be replaced by inorganic particles of other materials as long as it does not depart from the scope of the present disclosure.

[0090] In one embodiment, the morphology of the second inorganic particles is not limited, and may be spherical, elliptical, needle-shaped, or the like.

[0091] In one embodiment, the inorganic particle layer may contain 0.1 to 20 parts by weight of a binder resin relative to 100 parts by weight of the second inorganic particles, may contain 1 to 15 parts by weight, 1 to 10 parts by weight, or 1 to 5 parts by weight, but is not necessarily limited thereto.

[0092] In one embodiment, the adhesive layer may be formed on one or both sides of the porous substrate or the inorganic particle layer formed on the porous substrate, and may be formed on more than 60% of the total area of ​​each side. Specifically, the adhesive layer may be formed on more than 80%, more than 90%, or more than 95% of the total area of ​​each side of the porous substrate or the inorganic particle layer. More specifically, the adhesive layer may be formed on 100% of the total area of ​​each side of the porous substrate or the inorganic particle layer except for the case where micro defects occur, but it is not limited thereto as long as it does not depart from the scope of the present disclosure.

[0093] In one embodiment, the average particle size (D50) of the second inorganic particles may 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 values, specifically, 0.01 μm to 2 μm or 0.05 μm to 1 μm. When the average particle size of the second inorganic particles meets the above range, excellent adhesion, anti-adhesion and heat resistance with the electrode can be achieved.

[0094] In one embodiment, when a combination of two or more second inorganic particles having different average particle sizes (D50) is used in the second inorganic particles, they are combined with the anisotropic particles and / or adhesive as described above, thereby achieving better adhesion, anti-adhesion and heat resistance with the electrode.

[0095] If the two second inorganic particles with different average particle sizes are used as an example, they can be a combination of inorganic particles with an average particle size of 0.05 μm to 0.5 μm and inorganic particles with an average particle size greater than 0.5 μm and less than 2 μm. Specifically, the second inorganic particles according to one embodiment can be a combination of inorganic particles with an average particle size of 0.1 μm to 0.4 μm and inorganic particles with an average particle size of 0.6 μm to 1 μm.

[0096] 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 thickness of the inorganic particle layer coated on one side and the other side may be the same or different. It is not particularly limited, but in one embodiment, the total thickness of the inorganic particle layer formed on the porous substrate may 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 values. In a specific embodiment, the total thickness of the inorganic particle layer may be 0.1 μm to 15 μm, 0.5 μm to 10 μm, or 1 μm to 5 μm. The thickness is measured at any 5 points using a thickness meter from Mitutoyo and then divided by 5 to determine the average thickness as the thickness.

[0097] The binder resin contained in the inorganic particle layer can be used to connect and fix the second inorganic particles, the inorganic particle layer and the porous substrate, and / or the inorganic particle layer and 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 include 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.

[0098] The ester polymer may be any one or more selected from polyethylene terephthalate, polyethylene naphthalate (PEN), etc. The amide polymer may be any one or more selected from polyamide-6, polyamide-66, etc. The imide polymer may be any one or more selected from polyimide, polyetherimide, polyesterimide, etc. The acrylic polymer may be any one or more selected from polyacrylamide, polymethyl acrylate, polyethyl acrylate, polyacrylate, polybutyl acrylate, acrylic acid-methacrylic acid copolymer, etc. The styrene polymer may be any one or more selected from polystyrene, poly-alpha-methyl styrene, polybromostyrene, etc. The vinyl alcohol polymer may be any one or more selected from polyvinyl alcohol, polyvinyl acetate, polyvinyl acetate-polyvinyl alcohol copolymer, etc. The vinyl pyrrolidone polymer may be any one or more selected from polyvinyl pyrrolidone and copolymers containing vinyl pyrrolidone, etc. Furthermore, the cellulose polymer may be any one or more selected from carboxymethyl cellulose, cellulose acetate propionate, cellulose acetate, cellulose acetate butyrate, etc. The fluorine polymer may be any one or more selected from polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, hexafluoropropylene, polyfluoro-hexafluoropropylene, polychlorotrifluoroethylene, etc.

[0099] In one embodiment, from the perspective of achieving better heat resistance, the polymer resin may be a polyacrylamide resin.

[0100] In one embodiment, the porous substrate may be a porous polymer film, sheet, nonwoven fabric, woven fabric, etc. made of polymer and used as a separator, or may include a porous substrate having a laminated structure in which two or more layers are laminated.

[0101] In one embodiment, the porous substrate may be a polyolefin porous substrate such as polyethylene, polypropylene, or copolymers thereof, but is not limited thereto. Any known porous substrate may be used as a porous substrate for a lithium secondary battery separator.

[0102] In one embodiment, the porosity of the porous substrate may be 20% to 60%, specifically 30% to 60%, but is not limited thereto.

[0103] In one embodiment, the thickness of the porous substrate may be 1 μm to 25 μm, 3 μm to 20 μm or 5 μm to 15 μm, but is not necessarily limited thereto. The thickness is measured at 5 points using a thickness meter from Mitutoyo Company and then divided by 5 to determine the average thickness as the thickness.

[0104] In one embodiment, the average thickness of the separator may be 1 μm to 40 μm, 5 μm to 30 μm, or 10 μm to 20 μm, but is not necessarily limited thereto. After the separator is stacked into 10 layers, the thickness is measured at any 5 points in the width direction using a thickness meter of Mitutoyo Company, and then the thickness is divided by 5 to derive the average thickness of the 10 layers of separators, and then divided by 10 to obtain the overall average thickness of a single separator, thereby deriving the average thickness of the separator.

[0105] The following describes a method for producing the separator of the present disclosure.

[0106] According to one embodiment, a method for manufacturing a diaphragm includes: coating a coating liquid for forming an adhesive layer containing an adhesive and anisotropic particles on at least one side of a porous substrate and drying the coating liquid to form an adhesive layer, wherein the adhesive layer contains 1.2 parts by weight or more of anisotropic particles relative to 100 parts by weight of the adhesive, and the anisotropic particles include any one or more selected from a first inorganic particle and an organic particle having a glass transition temperature of 150° C. or more, and the aspect ratio of the anisotropic particles can be 4 to 1000.

[0107] According to another embodiment, a method for manufacturing a diaphragm 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 side of a porous substrate and drying to form an inorganic particle layer; and a step of applying a coating liquid for forming an adhesive layer containing a binder and anisotropic particles on the upper part of the inorganic particle layer and drying to form an adhesive layer, wherein the adhesive layer contains 1.2 parts by weight or more of anisotropic particles relative to 100 parts by weight of the binder, and the anisotropic particles include at least one selected from the first inorganic particles and organic particles having a glass transition temperature of 150° C. or more, and the aspect ratio of the anisotropic particles may be 4 to 1000. For ease of description, the manufacturing method is described based on a diaphragm having an inorganic particle layer and an adhesive layer.

[0108] The descriptions of the separator, porous substrate, inorganic particle layer, adhesive layer, first inorganic particles, second inorganic particles, adhesive, anisotropic particles, and binder resin are the same as those described above, and thus detailed descriptions will be omitted.

[0109] The method for preparing the slurry for forming the inorganic particle layer can be used without restriction by conventional methods known in the technical field. Although there is no particular limitation, according to a non-limiting example, the slurry can be prepared by stirring and dispersing the second inorganic particles and the binder resin, or a ball mill can be used to disperse the agglomerated second inorganic particles.

[0110] The slurry for forming the inorganic particle layer includes second inorganic particles, a binder resin and a dispersion medium. The dispersion medium can be water, ethanol, methanol, propanol and other lower alcohols, dimethylformamide, acetone, tetrahydrofuran, ether, methyl chloride, DMF, N-methyl-2-pyrrolidone, hexane, cyclohexane and other dispersion media or their mixtures, but is not necessarily limited to these.

[0111] In one embodiment, the solid content of the slurry for forming the inorganic particle layer is not particularly limited, but may be, for example, 1 wt % to 50 wt %, 5 wt % to 40 wt %, or 10 wt % to 35 wt %.

[0112] In one embodiment, the slurry for forming the inorganic particle layer may contain 80% to 99% by weight of the second inorganic particles and 1% to 20% by weight of the binder resin based on the total weight of the solid component. Specifically, based on the total weight of the solid component, the slurry may contain 85% to 99% by weight, 90% to 99% by weight, or 95% to 99% by weight of the second inorganic particles. Specifically, based on the total weight of the solid component, the slurry may contain 1% to 15% by weight, 1% to 10% by weight, or 1% to 5% by weight of the binder resin.

[0113] The method for coating the slurry for forming the inorganic particle layer can be any conventional method known in the art without limitation. According to a non-limiting example, roller coating, spin coating, dip coating, rod coating, pattern coating, slit coating, inkjet printing or a combination thereof can be used. The applied slurry can be dried to form an inorganic particle layer. The drying for forming the inorganic particle layer is not particularly limited, but can be dried at less than 100° C. or at 30° C. to 60° C.

[0114] Next, the method for preparing the coating liquid for forming the adhesive layer can also adopt all conventional methods known in the technical field without restriction. Although there is no special limitation, according to a non-limiting example, the coating liquid can be prepared by stirring and dispersing the anisotropic particles and the adhesive, or a ball mill can be used to disperse the agglomerated anisotropic particles and the adhesive.

[0115] The coating liquid for forming an adhesive layer contains an adhesive, anisotropic particles and a solvent. The solvent may be any dispersion medium that can be used to prepare a slurry for forming an inorganic particle layer, and specifically, may be distilled water.

[0116] In one embodiment, the solid content of the adhesive layer forming coating liquid is not particularly limited, but may be, for example, 1 wt % to 20 wt %, 2 wt % to 15 wt %, or 5 wt % to 10 wt %.

[0117] In one embodiment, the coating liquid for forming the adhesive layer may contain 80% to 98.8% by weight of the adhesive and 1.2% to 20% by weight of the anisotropic particles based on the total weight of the solid components. Specifically, based on the total weight of the solid components, the coating liquid may contain 85% to 98.8% by weight, 90% to 98.5% by weight, or 92.5% to 98.5% by weight of the adhesive. Specifically, based on the total weight of the solid components, the coating liquid may contain 1.2% to 10% by weight, 1.5% to 10% by weight, or 1.5% to 7.5% by weight of the adhesive.

[0118] The method for applying the coating liquid for forming the adhesive layer can be any conventional method known in the art without limitation, and specifically, a method for applying a slurry for forming an inorganic particle layer can be adopted. The applied coating liquid can be dried to form an adhesive layer. The drying for forming the adhesive layer is not particularly limited, but can be dried at 100° C. or below or at 30° C. to 60° C.

[0119] One embodiment of the present disclosure provides a lithium secondary battery, which includes: a positive electrode, a negative electrode, the above-mentioned separator disposed between the positive electrode and the negative electrode, and an electrolyte. In this case, the positive electrode, the negative electrode, and the electrolyte can be used without restriction as long as they are commonly used in lithium secondary batteries. According to one embodiment, a lithium secondary battery can be provided, which includes the above-mentioned separator, so that the adhesion and anti-adhesion properties between the positive electrode or the negative electrode and the separator are excellent, and the life characteristics of the battery are improved. In detail, by improving the adhesion phenomenon and the coffee ring phenomenon, the electrode and the separator are firmly bonded, and unnecessary space such as bubbles can be prevented from being generated between the electrode and the separator. Therefore, the problem of reduced battery life due to unnecessary space can be suppressed, so the lithium secondary battery using the separator according to one embodiment can have significantly improved life characteristics.

[0120] The positive electrode and the negative electrode can be manufactured by mixing a solvent with the positive electrode active material and the negative electrode active material, and mixing a binder, a conductive material, a dispersant, etc. as needed and stirring to prepare a mixture, which is then applied to a current collector made of a metal material, dried, and then pressed together.

[0121] Any active material commonly used for the positive electrode of a secondary battery can be used as the positive electrode active material. For example, lithium metal oxide particles including any one or two 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.

[0122] Any active material commonly used for the negative electrode of a secondary battery can be used as the negative electrode active material. The negative electrode active material of a lithium secondary battery can be a material that can be embedded with lithium. As an example, the negative electrode active material can be selected from lithium (metallic lithium), easily graphitized carbon, difficultly graphitized carbon, graphite, silicon, tin (Sn) alloy, silicon (Si) alloy, tin (Sn) oxide, silicon (Si) oxide, titanium (Ti) oxide, nickel (Ni) oxide, iron oxide (FeO) and lithium titanium oxide (LiTiO 2 , Li 4 Ti 5 O 12 ) of the negative electrode active material group.

[0123] A general conductive carbon material may be used as the conductive material without particular limitation.

[0124] The non-aqueous electrolyte comprises a lithium salt as an electrolyte and an organic solvent. The lithium salt can be any lithium salt conventionally used in the electrolyte for lithium secondary batteries, which can be represented by Li + X - .

[0125] As the negative ion of the lithium salt, 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 PF2 - ,(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 more of the above, without particular limitation.

[0126] 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, methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, cyclopentane, γ-butyrolactone and tetrahydrofuran can be used.

[0127] The nonaqueous electrolyte may be injected into an electrode assembly consisting of a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.

[0128] The outer shape of the lithium secondary battery is not particularly limited, but may be selected from a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0129] The embodiments of the present disclosure are further described below in conjunction with specific experimental examples. The embodiments and comparative examples included in the experimental examples are only examples of the present disclosure and do not limit the scope of the attached claims, and various changes and modifications can be made to the embodiments within the scope and technical spirit of the present disclosure. It is obvious to those skilled in the art, and these deformations and modifications naturally fall within the scope of the attached claims.

[0130] First, the physical property evaluation method is described.

[0131] [Average particle size]

[0132] The average particle size was derived from the particle size distribution results of a sample collected from the particles to be measured in accordance with ISO 13320-1 and analyzed using S3500 of MICROTRAC Corporation.

[0133] [Glass-transition temperature (Tg)]

[0134] The glass transition temperature was measured using a differential scanning calorimeter (DSC), manufactured by Mettler Toledo and model DSC1.

[0135] Determination method: Prepare a 5-10 mg test piece according to the size of the DSC Pan, put the test piece into a container and press it with a crimping press. Place the prepared sample and reference (Reference), select the temperature range, heating rate and reactive gas (Reactive gas) for analysis. Tg is the midpoint of the baseline movement, that is, the midpoint of the baseline defined by the start and end points of the heat capacity change.

[0136] The measurement conditions are as follows:

[0137] Temperature range: -100℃~250℃

[0138] Reactive gas: N 2

[0139] Heating / cooling speed: 10℃ / min

[0140] [Aspect ratio of anisotropic particles]

[0141] The aspect ratio is the value obtained by dividing the average length in the major axis direction by the average length in the minor axis direction. The average length in the major axis direction is the longest length of the particle, and the average length in the minor axis direction is the longest length in a direction perpendicular to the major axis.

[0142] The average length in the major axis direction and the average length in the minor axis direction were determined by randomly selecting 20 particles from each of five images measured by a transmission electron microscope (TEM, JEOL Ltd, JEM-2100F) and measuring them and taking the average values.

[0143] [Determination of molecular weight]

[0144] The weight average molecular weight was measured using GPC (Tosoh EcoSEC HLC-8320GPC Reflective Index detector). TSKgel guard PWxl, two TSKgel GMPWxl and TSKgelG2500PWxl (7.8×300 mm) were connected to form a GPC column. The solvent used was 0.1 M NaNO 3 The aqueous solution was analyzed at 40°C and a flow rate of 1 mL / min using PEG / PEO as the standard substance.

[0145] 1) Gel permeation chromatography (GPC) sample processing

[0146] (1) Sample pretreatment: Use the provided samples directly

[0147] (2) Sample dissolution state: Completely dissolved

[0148] (3) Filter the sample solution: 0.45 μm nylon filter

[0149] 2) Gel permeation chromatography (GPC) analysis instrument conditions

[0150] (1) Analytical instrument: Tosoh EcoSEC HLC-8320GPC

[0151] (2) Detector: RI detector

[0152] (3) Developing solvent: 0.1M NaNO 3

[0153] (4) Column (maker, model no.): TSKgel guard PWxl + 2x TSKgelGMPWxl + TSKgel G2500PWxl (7.8 x 300 mm)

[0154] (5) Temperature: 40°C

[0155] (6) Flow rate: 1.0 mL / min

[0156] (7) Injection volume: 100 μL, 10 mg / mL

[0157] (8) Standard substances: PEG / PEO

[0158] [Porosity]

[0159] A sample of 10 cm x 10 cm was cut out and the porosity of the separator was calculated using the following formula.

[0160] Porosity = {1-[M / (100*T*ρ)]}×100

[0161] Where, T = fabric thickness (cm)

[0162] M = sample weight (g)

[0163] ρ = Density of fabric resin (g / cm 3 )

[0164] [Evaluation of Adhesion to Positive Electrode]

[0165] Based on the total weight of the positive electrode active material, 94 wt% of LiCoO 2 , 2.5 wt% polyvinylidene fluoride as a flux, and 3.5 wt% carbon black as a conductive agent were added to N-methyl-2-pyrrolidone (NMP) as a solvent and stirred to prepare a uniform positive electrode slurry. The prepared slurry was coated on an aluminum foil with a thickness of 30 μm and dried and pressed to manufacture a positive electrode with a total thickness of 150 μm.

[0166] The separators of the examples and comparative examples were placed on the prepared positive electrode with the adhesive layer facing the positive electrode, and heated by a hot press at 80° C. and 10 kgf / cm 2 After 30 seconds of heat and pressure lamination, the adhesion (gf / cm) between the separator and the electrode was measured by peeling 180° using UTM equipment from INSTRON according to ASTM D903.

[0167] [Evaluate whether the coffee ring phenomenon has improved]

[0168] Whether the coffee ring phenomenon is improved was evaluated by scanning electron microscope (SEM) images of the separators of the examples and comparative examples. If ring-shaped stains were observed in the SEM images, it was considered that the coffee ring had occurred. If the occurrence of the coffee ring was confirmed in the SEM images, it was rated as "NG", and if the occurrence of the coffee ring was not confirmed, it was rated as "OK".

[0169] [Evaluation of Anti-blocking Properties]

[0170] The results were evaluated by placing two separators including an adhesive layer so that the adhesive layers face each other and subjecting the separators to a temperature of 50° C. and a pressure of 15 kgf / cm 2 After 1 hour of pressure lamination according to ASTM D903, the adhesive layers are bonded to each other and partially or completely peeled off. Even if partial peeling occurs, it is considered to be adhesion, and if no peeling occurs but the adhesive layers are separated in their original state, it is considered that no adhesion occurs. Whether adhesion occurs is confirmed by scanning electron microscope (SEM) images. If adhesion is confirmed in the SEM image, it is rated as "NG", and if adhesion is not confirmed, it is rated as "OK".

[0171] [Evaluation of battery life characteristics]

[0172] First, a battery was manufactured as follows in order to evaluate the life characteristics of the battery.

[0173] Manufacturing the positive electrode

[0174] 92 wt% LiNi as the positive electrode active material x Co y Mn z O 2 (x=0.4-0.8, y=0.1-0.3, z=0.1-0.3), 4 wt% of carbon black as a conductive material, and 4 wt% of polyvinylidene fluoride (PVdF) as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent and stirred to prepare a uniform positive electrode slurry. The positive electrode slurry was applied to an aluminum (Al) film with a thickness of 30 μm and dried and pressed to manufacture a positive electrode with a total thickness of 150 μm.

[0175] Making the negative electrode

[0176] 96 wt % of graphite carbon as a negative electrode active material, 3 wt % of carbon black as a conductive material, and 1 wt % of PVdF as a binder were added to NMP as a solvent and stirred to prepare a uniform negative electrode slurry. The negative electrode slurry was applied to a copper (Cu) film with a thickness of 20 μm, dried, and pressed to produce a negative electrode with a total thickness of 150 μm.

[0177] Making batteries

[0178] The separator of the embodiment or comparative example was placed between the positive electrode and the negative electrode, and then rolled and placed in an aluminum pack. Then, 1M lithium hexafluorophosphate (LiPF6) was dissolved in a solution containing ethylene carbonate and diethyl carbonate in a volume ratio of 1:1. 6 ) electrolyte and then sealed to produce a secondary battery with a capacity of 2Ah.

[0179] Next, the secondary battery manufactured above was charged and discharged for 600 cycles using a charge / discharge cycler and the discharge capacity in each cycle was measured. Specifically, the battery was charged to 4.2V at a constant current of 1C at 25°C and kept at a constant voltage of 4.2V until the current reached 0.01C, and then discharged to 2.5V at a constant current of 1C as one cycle. The cycle point when the discharge capacity dropped to less than 80% of the first cycle was taken as the cycle life and is shown in Table 1.

[0180] <Example 1>

[0181] Preparation of inorganic particle layer

[0182] Boehmite particles (Nabaltec, Inc.) having an average particle size (D50) of 300 nm were used as inorganic particles. 200SM) and boehmite particles (Nabaltec, 70 parts by weight of B60) 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 prepare a slurry for forming an inorganic particle layer.

[0183] The slurry for forming an inorganic particle layer was bar coated on both sides of a polyethylene porous film (porosity 41%, average thickness: 9 μm) and then fully dried at 40° C. to form an inorganic particle layer with an average thickness of 1.5 μm on both sides of the porous substrate.

[0184] Fabrication of adhesive layer

[0185] 100 parts by weight of acrylic particles with an average particle size (D50) of 500 nm and a glass transition temperature of 60°C as an adhesive and 7.1 parts by weight of cellulose nanofibers (cellulose nanofiber; Hansol, Duracle A) with a glass transition temperature of 200°C as anisotropic particles were dispersed in distilled water so that the fixed component concentration reached 7.5% by weight and then mixed to prepare a coating liquid for forming an adhesive layer. The acrylic particles used here are copolymers made of acrylonitrile, styrene and methacrylamide, and the average length of the cellulose nanofibers in the long axis direction is 350 nm, the average length in the short axis direction is 5 nm, and the glass transition temperature is 200°C.

[0186] After spray coating the adhesive layer-forming coating solution on each surface of the inorganic particle layer formed on both sides of the porous substrate, the adhesive layer having an average thickness of 0.75 μm was formed on both surfaces of the inorganic particle layer at 40° C. Finally, a separator stacked in the order of adhesive layer / inorganic particle layer / porous substrate / inorganic particle layer / adhesive layer was manufactured.

[0187] <Example 2>

[0188] A separator was produced in the same manner as in Example 1 except that cellulose acetate nanofibers having an average length of 350 nm in the major axis direction, an average length of 5 nm in the minor axis direction, and a glass transition temperature of 150° C. were used as anisotropic particles.

[0189] <Example 3>

[0190] A separator was produced in the same manner as in Example 1 except that cellulose nanofibers having an average length of 100 nm in the major axis direction, an average length of 5 nm in the minor axis direction and a glass transition temperature of 200° C. were used as anisotropic particles.

[0191] <Example 4>

[0192] A separator was produced in the same manner as in Example 1 except that cellulose nanofibers having an average length of 1000 nm in the major axis direction, an average length of 5 nm in the minor axis direction and a glass transition temperature of 200° C. were used as anisotropic particles.

[0193] <Example 5>

[0194] A separator was produced in the same manner as in Example 1 except that 7.1 parts by weight of boehmite particles having an average length of 40 nm in the long axis direction and an average length of 8 nm in the short axis direction were used as anisotropic particles. The boehmite particles used here were produced 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 stirred at 120° C. for 24 hours to react.

[0195] <Example 6>

[0196] 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.

[0197] <Example 7>

[0198] 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.

[0199] <Example 8>

[0200] 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.

[0201] <Example 9>

[0202] A separator was produced in the same manner as in Example 1 except that the inorganic particle layer was not formed on both surfaces of the polyethylene porous film.

[0203] That is, the coating liquid for forming the adhesive layer was applied to both sides of the porous substrate by spray coating and then fully dried at 40°C to form an adhesive layer with an average thickness of 0.75 μm on both surfaces of the polyethylene porous film. Finally, a separator laminated in the order of adhesive layer / porous substrate / adhesive layer was manufactured.

[0204] <Comparative Example 1>

[0205] A separator was produced in the same manner as in Example 1 except that the anisotropic particles were not added when the adhesive layer-forming coating liquid was prepared.

[0206] <Comparative Example 2>

[0207] A separator was produced in the same manner as in Example 1 except that acrylic particles having an average length of 450 nm in the major axis direction, an average length of 10 nm in the minor axis direction, and a glass transition temperature of 140° C. were used as anisotropic particles.

[0208] <Comparative Example 3>

[0209] A separator was produced in the same manner as in Example 1 except that cellulose acetate nanofibers having an average length of 350 nm in the major axis direction, an average length of 10 nm in the minor axis direction, and a glass transition temperature of 140° C. were used as anisotropic particles.

[0210] <Comparative Example 4>

[0211] A separator was produced in the same manner as in Example 1 except that 100 parts by weight of boehmite particles having an average length of 800 nm in the major axis direction and an average length of 300 nm in the minor axis direction were used as the anisotropic particles.

[0212] <Comparative Example 5>

[0213] A separator was manufactured in the same manner as in Example 5 except that 1 part by weight of boehmite particles were used as the anisotropic particles.

[0214] [Table 1]

[0215]

[0216] Referring to Table 1, compared with the diaphragm of the comparative example, the diaphragms of Examples 1 to 9 have improved coffee ring phenomenon in which the adhesive accumulates to the edge of the coating area as the coating liquid used to form the applied adhesive layer evaporates, and the adhesion phenomenon in which the adhesive layer is transferred to the opposite side and detached when the diaphragm is wound is also improved.

[0217] On the contrary, the separator of Comparative Example 1 not including the anisotropic particles according to one embodiment had a coffee ring phenomenon and a blocking phenomenon. Moreover, the separators of Comparative Examples 2 and 3 including organic particles having a glass transition temperature of less than 150° C. as anisotropic particles had a blocking phenomenon, and the separator of Comparative Example 4 including anisotropic particles having an aspect ratio of less than 4 had a coffee ring phenomenon and a blocking phenomenon. Furthermore, it was confirmed that the separator of Comparative Example 5 including less than 1.2 parts by weight of anisotropic particles relative to 100 parts by weight of the binder had a coffee ring phenomenon and a blocking phenomenon.

[0218] Specifically, Figure 1 is a diagram showing a SEM image of the surface of the diaphragm manufactured in Comparative Example 1, Figure 21 is a diagram showing an SEM image of the surface of the diaphragm manufactured in Example 5. Referring to the accompanying figure, coffee ring-shaped stains are clearly observed on the surface of the diaphragm of Comparative Example 1 in which the adhesive layer does not contain anisotropic particles, while the coffee ring phenomenon on the surface of the diaphragm of Example 5 in which the adhesive layer contains anisotropic particles is improved. In addition, the diaphragms of Comparative Examples 2 to 5 are clearly observed. Figure 1 The same coffee ring-shaped stains observed in the embodiment 1 and 2 were observed in the embodiment 2. In the embodiment 3, the coffee ring phenomenon on the surface of the membrane was improved as in the embodiment 5.

[0219] In summary, the diaphragm disclosed in the present invention uses 1.2 parts by weight or more of an anisotropic particle with an aspect ratio of 4 to 1000 selected from any one of a first inorganic particle and an organic particle with a glass transition temperature of 150° C. or higher relative to 100 parts by weight of a binder. Therefore, the coffee ring phenomenon is improved, and the diaphragm has the advantages of excellent adhesion to the electrode and excellent anti-adhesion properties.

[0220] The above-described contents are merely examples of the application of the principles of the present disclosure, and other configurations may be included without departing from the scope of the present disclosure.

Claims

1. A diaphragm for an electrochemical element, comprising: Porous substrate; as well as an adhesive layer, which is located on at least one side of the porous substrate and comprises an adhesive and anisotropic particles, The adhesive layer contains 1.2 parts by weight or more of anisotropic particles relative to 100 parts by weight of the adhesive. The anisotropic particles include at least one selected from first inorganic particles and organic particles having a glass transition temperature of 150° C. or higher, and an aspect ratio of the anisotropic particles is 4 to 1000. 2 . The separator according to claim 1 , wherein the anisotropic particles have an aspect ratio of 4 to 200. 3 . 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 metal hydroxides, metal oxides, metal nitrides, and metal carbides. 5 . The separator according to claim 1 , wherein the organic particles include any one selected from the group consisting of styrene polymers, acrylic polymers, and cellulose polymers, or a copolymer of two or more thereof. 6 . The separator according to claim 1 , wherein the adhesive layer comprises 1.2 parts by weight to 20 parts by weight of anisotropic particles relative to 100 parts by weight of the binder. 7 . The separator according to claim 1 , the adhesive layer comprises 1.2 parts by weight to 10 parts by weight of anisotropic particles relative to 100 parts by weight of the binder. 8 . The separator according to claim 1 , the binder having a glass transition temperature in the range of 30° C. to 120° C. 9 . The separator according to claim 1 , wherein the binder is a particle-type binder. 10 . The separator according to claim 9 , wherein the particle-type binder has an average particle diameter of 0.01 μm to 5 μm. 11 . The separator according to claim 1 , wherein the binder comprises at least one 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. 12 . The separator according to claim 1 , wherein the adhesive layer has a total thickness of 0.1 μm to 10 μm.

13. The separator according to claim 1, which is laminated on a positive electrode with its adhesive layer facing the positive electrode and is pressed with a hot press at 80°C and 10 kgf / cm 2 The adhesive force of the separator measured according to ASTM D903 after press-fitting 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 , the inorganic particle layer comprises 0.1 parts by weight to 20 parts by weight of a binder resin relative to 100 parts by weight of the second inorganic particles.

16. A lithium secondary battery comprising: positive electrode; negative electrode; The separator according to any one of claims 1 to 15, which is formed between the positive electrode and the negative electrode; as well as Electrolytes.

17. A method for manufacturing a diaphragm for an electrochemical element, comprising: Step (a), providing a porous substrate; as well as Step (a-1), coating a coating solution for forming an adhesive layer comprising an adhesive and anisotropic particles on at least one side of a porous substrate and drying the coating solution to form an adhesive layer; as well as Step (a-2), thereby obtaining a separator; or Step (ai), coating a slurry for forming an inorganic particle layer comprising second inorganic particles and a binder resin on at least one side of a porous substrate and drying the slurry to form an inorganic particle layer; Step (a-ii), coating a coating solution for forming an adhesive layer comprising a binder and anisotropic particles on the inorganic particle layer and drying the coating solution to form an adhesive layer; as well as Step (a-iii), thereby obtaining a membrane, In step (a-1) and step (a-ii), the adhesive layer contains 1.2 parts by weight or more of anisotropic particles relative to 100 parts by weight of the adhesive, the anisotropic particles having an aspect ratio of 4 to 1000 and containing one or more selected from first inorganic particles and organic particles having a glass transition temperature of 150°C or above. 18 . The method for producing a separator according to claim 17 , wherein the electrochemical element is a lithium secondary battery.

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