Method of manufacturing separator for secondary battery, separator obtained therefrom, and secondary battery comprising the same

Abstract

The present disclosure relates to a separator for a secondary battery, including: a porous polymer substrate; a first coating layer disposed on one surface of the porous polymer substrate and including a plurality of inorganic particles and a first binder polymer; a second coating layer disposed on the other surface of the porous polymer substrate and including a plurality of inorganic particles and the first binder polymer; and a third coating layer disposed between the porous polymer substrate and the first coating layer, and / or between the porous polymer substrate and the second coating layer, and including a second binder polymer, wherein the second binder polymer includes a non-wetting polymer. The present disclosure also relates to a method of manufacturing the separator and a secondary battery including the separator. Since the separator includes a non-wetting polymer, a deviation in physical properties between the coated one surface and the other surface of the separator can be minimized.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2020-0128921, filed in Korea on October 6, 2020.

[0002] This disclosure relates to a method for manufacturing a separator for a secondary battery, the separator obtained therefrom, and a secondary battery including said separator. Background Technology

[0003] Energy storage technology has recently received increasing attention. Efforts to develop electrochemical devices are increasingly being realized, as applications of energy storage technology have expanded to power mobile phones, cameras, and laptops, and even electric vehicles. In this context, electrochemical devices have garnered the most attention. Among these electrochemical devices, the development of rechargeable secondary batteries has been a focus. Recently, active research has been conducted on designing novel electrodes and batteries to improve capacity density and specific energy in the development of these batteries.

[0004] Such secondary batteries typically include a positive electrode containing positive active material, a negative electrode containing negative active material, a non-aqueous electrolyte containing electrolyte salt and organic solvent, and a separator inserted between the positive and negative electrodes to electrically insulate the two electrodes.

[0005] Polyolefin-based porous substrates commonly used as separators for secondary batteries exhibit severe thermal shrinkage behavior at temperatures of 100°C or higher due to their material properties and characteristics during their manufacturing process, including orientation, which can lead to short circuits between the positive and negative electrodes.

[0006] To address the aforementioned safety issues of secondary batteries, a separator with a porous coating formed by applying a slurry containing inorganic particles and a binder polymer to at least one surface of a porous polymer substrate has been proposed. Recently, separators with porous coatings on both surfaces of a porous polymer substrate have been frequently used in automotive batteries.

[0007] Generally, porous coatings can be formed on both surfaces of a porous polymer substrate via a dip coating process. This dip coating process involves immersing the porous polymer substrate in a slurry comprising inorganic particles and a binder polymer to simultaneously form the porous coating. However, this dip coating process is limited in terms of operating speed and is difficult to completely interrupt from the outside, thus having technical limitations such as changes in solids content due to continuous evaporation of the solvent in the immersion system during the process. Therefore, sequential coating processes have recently been used more frequently because they demonstrate better coating processability and productivity.

[0008] Sequential coating is a process in which a slurry comprising inorganic particles and a binder polymer is applied to one surface of a porous polymer substrate, and then the same slurry is applied to another surface of the same substrate. However, when using this sequential coating process, there is a discrepancy in the physical properties between the coated surfaces, and this discrepancy significantly affects the processability of battery assembly. This is because when the slurry is applied to another surface of the porous polymer substrate, the binder polymer in the slurry applied to one surface is not in a dry state. Consequently, the binder polymer penetrates into the pores of the porous polymer substrate, resulting in a reduction in the absolute amount of binder polymer required for that surface.

[0009] In these cases, there is an urgent need for a technique that can minimize the deviation of physical properties between one surface of the separator and another when the separator is coated sequentially. Summary of the Invention

[0010] Technical issues

[0011] This disclosure is designed to address problems in the related art, and therefore relates to providing a method for manufacturing a separator for a secondary battery, which minimizes the amount of binder polymer penetrating into the pores of the porous polymer substrate when a slurry comprising inorganic particles and a binder polymer is coated onto a porous polymer substrate by a sequential coating process, and thus minimizes the deviation of physical properties between one surface and the other surface of the separator while providing excellent thermal safety; the separator obtained by this method; and a secondary battery comprising the separator.

[0012] Technical solution

[0013] In one aspect of this disclosure, a separator for a secondary battery is provided according to any of the following embodiments.

[0014] According to a first embodiment, a separator for a secondary battery is provided, comprising:

[0015] Porous polymer substrate;

[0016] A first coating is disposed on one surface of the porous polymer substrate and includes a plurality of inorganic particles and a first adhesive polymer.

[0017] A second coating disposed on another surface of the porous polymer substrate and comprising a plurality of inorganic particles and the first adhesive polymer; and

[0018] A third coating, comprising a second adhesive polymer, is disposed between the porous polymer substrate and the first coating, and / or between the porous polymer substrate and the second coating.

[0019] The second adhesive polymer includes a non-wetting polymer.

[0020] According to the second embodiment, a separator for a secondary battery as defined in the first embodiment is provided.

[0021] The content of the third coating is from 0.066 parts by weight to 0.166 parts by weight of 100 parts by weight of the first coating or the second coating.

[0022] According to the third embodiment, a separator for a secondary battery as defined in the first or second embodiment is provided.

[0023] The non-wetting polymers mentioned therein include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA), ethylene tetrafluoroethylene (ETFE), or two or more thereof.

[0024] According to the fourth embodiment, a separator for a secondary battery as defined in any of the first to third embodiments is provided.

[0025] The second adhesive polymer further includes a third adhesive polymer, and the third adhesive polymer is an adhesive polymer.

[0026] According to the fifth embodiment, a separator for a secondary battery as defined in the fourth embodiment is provided.

[0027] The third adhesive polymer includes styrene-butadiene rubber (SBR), acrylic copolymer, polyacrylic acid (PAA), polyacrylate, carboxymethyl cellulose (CMC), polyvinyl alcohol, or two or more thereof.

[0028] According to the sixth embodiment, a separator for a secondary battery as defined in any of the first to fifth embodiments is provided.

[0029] The first adhesive polymer includes polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co-chlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetatebutyrate, and cellulose acetate propionate. Propionate, cyanoethyl pullullan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullullan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, or two or more thereof.

[0030] In another aspect of this disclosure, a method for manufacturing a separator for a secondary battery is provided according to any of the following embodiments.

[0031] According to a seventh embodiment, a method for manufacturing a separator for a lithium secondary battery is provided, comprising the following steps:

[0032] (S1) Prepare a porous polymer substrate;

[0033] (S2) A coating solution comprising a second adhesive polymer is applied to at least one surface of the porous polymer substrate and then dried to obtain a primary separator.

[0034] (S3) A slurry comprising inorganic particles, a first binder polymer, and a solvent for the first binder polymer is sequentially applied to one surface and another surface of the primary separator; and

[0035] (S4) The product of drying step (S3),

[0036] The second adhesive polymer comprises a non-wetting polymer that is impermeable to solvents used in the first adhesive polymer.

[0037] According to the eighth embodiment, a method for manufacturing a separator for a secondary battery as defined in the seventh embodiment is provided.

[0038] The coating solution is at a concentration of 0.01 g / m 2 Up to 0.015g / m 2 The amount of load.

[0039] According to the ninth embodiment, a method for manufacturing a separator for a secondary battery, as defined in the seventh or eighth embodiment, is provided.

[0040] The non-wetting polymers mentioned therein include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA), ethylene tetrafluoroethylene (ETFE), or two or more thereof.

[0041] According to the tenth embodiment, a method for manufacturing a separator for a secondary battery as defined in any of the seventh to ninth embodiments is provided.

[0042] The coating solution further comprises a third adhesive polymer, and the third adhesive polymer is an adhesive polymer.

[0043] According to the eleventh embodiment, a method for manufacturing a separator for a secondary battery as defined in the tenth embodiment is provided.

[0044] The third adhesive polymer includes styrene-butadiene rubber (SBR), acrylic copolymer, polyacrylic acid (PAA), polyacrylate, carboxymethyl cellulose (CMC), polyvinyl alcohol, or two or more thereof.

[0045] According to the twelfth embodiment, a method for manufacturing a separator for a secondary battery as defined in any of the seventh to eleventh embodiments is provided.

[0046] The coating in step (S2) includes spraying the coating solution, in gaseous or microdroplet form, onto at least one surface of the porous polymer substrate.

[0047] According to the thirteenth embodiment, a method for manufacturing a separator for a secondary battery as defined in any of the seventh to twelfth embodiments is provided.

[0048] The first adhesive polymer includes polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co-chlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetatebutyrate, and cellulose acetate propionate. Propionate, cyanoethyl pullullan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullullan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, or two or more thereof.

[0049] According to the fourteenth embodiment, a method for manufacturing a separator for a secondary battery as defined in any of the seventh to thirteenth embodiments is provided.

[0050] The slurry is sequentially applied to one and another surface of the primary partition using a gravure roller coating process, a rod coating process, a slot die coating process, a doctor blade coating process, or two or more of these processes.

[0051] In another aspect of this disclosure, a lithium secondary battery according to the following embodiments is provided.

[0052] According to the fifteenth embodiment, a secondary battery is provided, including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the separator is a separator for a secondary battery as defined in any of the first to sixth embodiments.

[0053] Beneficial effects

[0054] A separator for a secondary battery according to an embodiment of the present disclosure includes a third coating disposed between a porous polymer substrate and a first coating, and / or between a porous polymer substrate and a second coating, and including a non-wetting polymer, thereby minimizing the amount of the first adhesive polymer penetrating into the pores of the porous polymer substrate, thereby minimizing the deviation of physical properties between one surface and the other surface of the separator.

[0055] In addition, the separator for secondary batteries according to embodiments of this disclosure may use a controlled amount of a third coating to prevent non-wetting polymer from penetrating into the pores of the porous polymer substrate and to minimize the deviation of physical properties between one surface and the other surface of the separator.

[0056] A method for manufacturing a separator for a secondary battery according to embodiments of this disclosure includes coating a coating solution containing a non-wetting polymer that is impermeable to a solvent for a first binder polymer onto at least one surface of a porous polymer substrate. Therefore, even when a slurry comprising inorganic particles and a first binder polymer is sequentially coated onto one and another surface of the porous polymer substrate, the amount of the first binder polymer penetrating into the pores of the porous polymer substrate can be minimized, thereby providing excellent coating processability and productivity, and minimizing deviations in physical properties between one and another surface of the finished separator.

[0057] Furthermore, in the method for manufacturing a separator for a secondary battery according to an embodiment of the present disclosure, the loading of the coating solution can be controlled to prevent non-wetting polymers from penetrating into the pores of the porous polymer substrate and to minimize the deviation of physical properties between one surface and the other surface of the separator. Attached Figure Description

[0058] The accompanying drawings illustrate preferred embodiments of the present disclosure and, together with the following disclosure, are used to provide a further understanding of the technical features of the present disclosure; therefore, the present disclosure should not be construed as limited to the drawings.

[0059] Figure 1This is a flowchart illustrating a method for manufacturing a separator for a secondary battery according to an embodiment of the present disclosure.

[0060] Figure 2 The diagram illustrates a system for sequentially coating a slurry comprising inorganic particles and a first binder polymer in a method for manufacturing a separator for a secondary battery according to an embodiment of the present disclosure.

[0061] Figure 3 This is a schematic diagram illustrating a separator for a secondary battery according to an embodiment of the present disclosure. Detailed Implementation

[0062] In the following description, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terminology used in the specification and appended claims should not be construed as limited to its common or dictionary meaning, but should be interpreted based on its meaning and concept in relation to the technical aspects of the present disclosure, on the basis of allowing the inventors to appropriately define the terminology for the best interpretation.

[0063] Therefore, the descriptions presented herein are merely preferred examples for illustrative purposes and are not intended to limit the scope of this disclosure. It should be understood that other equivalents and modifications may be made thereto without departing from the scope of this disclosure.

[0064] According to relevant technologies, in order to improve coating processability and productivity, the separator is obtained by coating a slurry comprising inorganic particles and binder polymers onto one surface of a porous polymer substrate, then sequentially coating the slurry onto another surface of the porous polymer substrate, and then drying it.

[0065] However, this sequential coating process leads to a reduction in the amount of binder polymer ultimately present on one surface of the porous polymer substrate. This is because, when the slurry is applied to one surface of the porous polymer substrate and then to the other, the binder polymer in the slurry applied to one surface seeps into the pores of the porous polymer substrate. Therefore, there is a deviation in the physical properties between one surface and the other surface of the finished separator.

[0066] In these cases, the inventors of this disclosure have developed a method for manufacturing a separator in which a slurry comprising inorganic particles and a binder polymer is sequentially coated on one surface and another surface of a porous polymer substrate, while preventing the binder polymer in the slurry from penetrating into the pores of the porous polymer substrate, thereby minimizing the deviation of physical properties between one surface and the other surface of the finished separator, and the separator obtained by this method. The present invention is based on this.

[0067] In one aspect of this disclosure, a method for manufacturing a separator for a secondary battery is provided, comprising the following steps:

[0068] (S1) Prepare a porous polymer substrate;

[0069] (S2) A coating solution comprising a second adhesive polymer is applied to at least one surface of the porous polymer substrate and then dried to obtain a primary separator.

[0070] (S3) A slurry comprising inorganic particles, a first binder polymer, and a solvent for the first binder polymer is sequentially applied to one surface and another surface of the primary separator; and

[0071] (S4) The product of drying step (S3),

[0072] The second adhesive polymer comprises a non-wetting polymer that is impermeable to solvents used in the first adhesive polymer.

[0073] Figure 1 This is a flowchart illustrating a method for manufacturing a separator for a secondary battery according to an embodiment of the present disclosure.

[0074] The method for manufacturing a separator for a secondary battery according to this disclosure will be explained in detail below.

[0075] First, a porous polymer substrate is prepared (S1). Any material can be used for the porous polymer substrate without particular limitation, as long as it can be conventionally used as a separator material for secondary batteries. The porous polymer substrate is a thin film comprising a polymer material, and non-limiting examples of such polymer material include at least one selected from polymer resins such as polyolefin resins, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, and polyethylene naphthalate. The porous polymer substrate may comprise a nonwoven web or porous polymer film formed from these polymer materials, or laminates of two or more layers thereof. Specifically, the porous polymer substrate may be any of the following a) to e):

[0076] a) A porous membrane formed by melting and extruding a polymer resin;

[0077] b) Multilayer membranes formed by stacking two or more porous membranes of a);

[0078] c) Nonwoven webs formed by integrating filaments obtained from melted and spun polymer resins;

[0079] d) Multilayer films formed by stacking two or more layers of nonwoven webs from c); and

[0080] e) A porous composite membrane having a multilayer structure including two or more of a) to d).

[0081] Porous polymer substrates can be obtained by forming pores from the aforementioned materials using conventional processes known to those skilled in the art, such as wet processes using solvents, diluents, or pore-forming agents, or orientation-based dry processes, in order to ensure excellent air permeability and porosity.

[0082] Next, a coating solution comprising a second adhesive polymer is applied to at least one surface of a porous polymer substrate, followed by drying to obtain a primary separator (S2). The coating solution may be applied to only one surface of the porous polymer substrate, or it may be applied to both surfaces of the porous polymer substrate.

[0083] The second adhesive polymer includes a non-wetting polymer that is impermeable to the solvent used in the first adhesive polymer.

[0084] According to this disclosure, "non-wetting polymer" means a polymer that is impermeable to the first adhesive polymer in a slurry comprising inorganic particles, a first adhesive polymer, and a solvent for the first adhesive polymer. The portion of the coating solution comprising the non-wetting polymer in the primary separator where it is coated and dried exhibits the lowest affinity for the spread of the solvent for the first adhesive polymer. For example, the solvent for the first adhesive polymer may form spherical droplets with a contact angle of 90° or greater at the portion of the coating solution comprising the non-wetting polymer in the primary separator where it is coated and dried. The contact angle corresponds to the angle between the solvent-vapor interface of the first adhesive polymer and the solvent-primary separator when the primary separator and the solvent for the first adhesive polymer are present in a vapor environment.

[0085] Because the non-wetting polymer is impermeable to the solvent used for the first adhesive polymer, the first adhesive polymer dissolved in the solvent cannot pass through the surface of the primary separator on which the coating solution, including the non-wetting polymer, is applied and dried. Therefore, the first adhesive polymer is prevented from penetrating into the pores of the porous polymer substrate. As a result, the deviation in physical properties between one surface and the other surface of the finished separator can be minimized.

[0086] According to embodiments of this disclosure, the non-wetting polymer may be impermeable to aqueous solvents. When the non-wetting polymer is impermeable to aqueous solvents, a slurry comprising a first binder polymer dissolved or dispersed in the aqueous solvent cannot pass through the surface of a primary separator on which a coating solution comprising the non-wetting polymer is coated and dried. Therefore, the first binder polymer in the slurry can be prevented from penetrating into the pores of the porous polymer substrate.

[0087] According to another embodiment of this disclosure, the non-wetting polymer may be impermeable to organic solvents. When the non-wetting polymer is impermeable to organic solvents, a slurry comprising a first binder polymer dissolved or dispersed in the organic solvent cannot pass through the surface of a primary separator on which a coating solution comprising the non-wetting polymer is coated and dried. Therefore, the first binder polymer in the slurry can be prevented from penetrating into the pores of the porous polymer substrate.

[0088] According to embodiments of this disclosure, the non-wetting polymer may include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA), ethylenetetrafluoroethylene (ETFE), or two or more of these. Non-wetting polymers do not include polyvinylidene fluoride (PVDF).

[0089] According to embodiments of this disclosure, the non-wetting polymer can be used in amounts of 90% to 99.9% by weight, or 92% to 98% by weight, based on 100% by weight of the coating solution. When the non-wetting polymer is used in the coating solution within the above-defined range, it can facilitate the prevention of the first binder polymer in the slurry from penetrating through the primary separator surface where the coating solution containing the non-wetting polymer is coated and dried.

[0090] According to embodiments of this disclosure, the coating solution may further include a third adhesive polymer, and the third adhesive polymer may be an adhesive polymer.

[0091] Third binder polymers can be used to complement non-wetting polymers with low adhesion. There are no particular limitations on the third binder polymer, as long as it can be mixed with the non-wetting polymer to form a coating solution.

[0092] According to embodiments of this disclosure, the third adhesive polymer may include styrene-butadiene rubber (SBR), acrylic copolymer, polyacrylic acid (PAA), polyacrylate, carboxymethyl cellulose (CMC), polyvinyl alcohol, or two or more thereof.

[0093] Acrylic copolymers may include, but are not limited to, ethyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(dimethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, or two or more thereof.

[0094] According to embodiments of this disclosure, the content of the third adhesive polymer can be from 0.1% to 5% by weight, or from 1% to 2% by weight, based on 100% by weight of the coating solution. When the content of the third adhesive polymer meets the above-defined range, it is more readily available that, while supplementing the low adhesion of the non-wetting polymer, the non-wetting polymer can be present in the coating solution in an amount sufficient to prevent the first adhesive polymer in the slurry from penetrating into the pores of the porous polymer substrate.

[0095] According to embodiments of this disclosure, the coating solution may be a solution comprising a non-wetting polymer dissolved in an organic solvent. When the coating solution is a solution, the organic solvent may include N-methyl-2-pyrrolidone (NMP) or the like.

[0096] According to another embodiment of this disclosure, the coating solution may be a suspension.

[0097] According to another embodiment of this disclosure, the coating solution can be a suppository. When the coating solution is an emulsion, it includes a dispersion medium and can be obtained by adding a gaseous monomer of a non-wetting polymer to a continuous phase in which a surfactant is dissolved. Here, the dispersion medium can be water or the like.

[0098] Surfactants may include ammonium perfluorocarboxylate, ammonium perfluorocaprylate, ammonium perfluorooctanoate, or two or more of these.

[0099] Surfactants can be used in amounts of 0.02% to 2% by weight, or 0.5% to 1% by weight, based on 100% by weight of the coating solution. When surfactants are used within the above-defined ranges, it is easier to impart sufficient emulsion stability to the coating solution.

[0100] The coating solution can be prepared at 40°C to 80°C for 1 to 12 hours.

[0101] According to embodiments of this disclosure, the coating solution can be 0.01 g / m 2 Up to 0.015g / m 2 or 0.012g / m 2 Up to 0.014 g / m 2 The amount of coating solution loaded. When the loading amount of the coating solution meets the above-defined range, it can prevent the first adhesive polymer from penetrating into the pores of the porous polymer substrate and promote the prevention of non-wetting polymers from penetrating into the pores of the porous polymer substrate.

[0102] In addition, when the loading of the coating solution meets the above-defined range, it can help prevent non-wetting polymers from penetrating into the pores of the porous polymer substrate and thus improve the air permeability of the finished separator.

[0103] The coating solution can be applied to at least one surface of a porous polymer substrate using conventional methods known to those skilled in the art. The method of applying the coating solution to at least one surface of the porous polymer substrate can be a conventional method known to those skilled in the art.

[0104] According to embodiments of this disclosure, the coating in step (S2) may include spraying a coating solution in gaseous or microdroplet form onto at least one surface of a porous polymer substrate. Specifically, the coating solution may be applied to at least one surface of the porous polymer substrate using a sprayer coating process. When the coating solution is sprayed and applied in gaseous or microdroplet form, it can be coated across the entire porous polymer substrate to a relatively small thickness. Therefore, it is beneficial to prevent non-wetting polymers in the coating solution from penetrating into the pores of the porous polymer substrate.

[0105] The coating solution applied to at least one surface of a porous polymer substrate can be dried using conventional methods known to those skilled in the art. According to embodiments of this disclosure, drying can be carried out at 40°C to 90°C, or 65°C to 75°C, for 10 minutes to 1 hour, or 30 minutes to 50 minutes.

[0106] According to embodiments of this disclosure, drying may further include the step of allowing the coating solution to air dry at room temperature for one day or longer.

[0107] Then, a slurry comprising inorganic particles, a first binder polymer, and a solvent for the first binder polymer is sequentially applied to one surface and another surface of the primary separator (S3).

[0108] There are no particular restrictions on the inorganic particles used, as long as they are electrochemically stable. That is, there are no particular restrictions on the inorganic particles that can be used in this paper, as long as they are within the operating voltage range of the applicable electrochemical device (e.g., based on Li / Li).+ It should not cause oxidation and / or reduction in the range of 0-5V.

[0109] According to embodiments of this disclosure, the inorganic particles can be high-dielectric-constant inorganic particles having a dielectric constant of 5 or greater, or 10 or greater, inorganic particles with lithium-ion transport capability, or combinations thereof. Non-limiting examples of inorganic particles having a dielectric constant of 5 or greater may include, alone or in combination, BaTiO3, BaSO4, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT, where 0 < x < 1, 0 < y < 1), Pb(Mg) 1 / 3 Nb 2 / 3 Hafnium oxide (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, Y2O3, SiO2, Al2O3, γ-AlOOH, Al(OH)3, SiC, TiO2, or similar. However, the scope of this disclosure is not limited thereto.

[0110] According to embodiments of this disclosure, while there are no particular limitations on the particle size of the inorganic particles in the porous coating, the inorganic particles may have a particle size of about 0.01 μm to 10 μm, or about 0.05 μm to 1.0 μm. When the size of the inorganic particles meets the above-defined range, the inorganic particles are more likely to maintain dispersibility to facilitate control of the physical properties of the separator used in secondary batteries. In addition, mechanical properties can be improved. Furthermore, it is less likely that internal short circuits will occur during battery charging / discharging due to excessively large pore sizes.

[0111] The term "average particle diameter of inorganic particles" refers to D 50 Particle diameter, and "D" 50 "Particle diameter" refers to the particle diameter at the 50th percentile of the cumulative distribution of particle numbers, depending on the particle diameter. Particle diameter can be determined using a laser diffraction method. Specifically, the powder to be analyzed is dispersed in a dispersion medium and introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500). The difference in the diffraction pattern, depending on the particle size, is then measured as the particles pass through the laser beam, and the particle size distribution is calculated. The particle diameter at the 50th percentile of the cumulative distribution of particle numbers, depending on the particle diameter, is then calculated to determine D. 50 .

[0112] According to embodiments of this disclosure, the first adhesive polymer may include polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co-chlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Propionate, cyanoethyl pullullan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullullan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, or two or more thereof. However, the scope of this disclosure is not limited thereto.

[0113] According to embodiments of this disclosure, the weight ratio of inorganic particles to the first adhesive polymer can be 20:80 to 99.9:0.1, 50:50 to 99.5:0.5, or 70:30-80:20. When the weight ratio of inorganic particles to the first adhesive polymer meets the above-defined ranges, it is easier to ensure sufficient adhesion between inorganic particles while also ensuring adequate open spaces formed between them.

[0114] Depending on the specific type of the first adhesive polymer, the solvent used for the first adhesive polymer may act as a solvent capable of dissolving the first adhesive polymer, or as a dispersion medium that cannot dissolve the first adhesive polymer but can disperse it.

[0115] According to embodiments of this disclosure, the solvent used for the first adhesive polymer can be an aqueous solvent. For example, the solvent used for the first adhesive polymer can be water. When the solvent used for the first adhesive polymer is an aqueous solvent, the non-wetting polymer is impermeable to the aqueous solvent.

[0116] According to another embodiment of this disclosure, the solvent used for the first adhesive polymer can be an organic solvent. For example, the solvent used for the first adhesive polymer can be acetone, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, or two or more of these. When the solvent used for the first adhesive polymer is an organic solvent, the non-wetting polymer is impermeable to the organic solvent.

[0117] According to embodiments of this disclosure, in addition to inorganic particles and a first binder polymer, the slurry may further include a dispersant.

[0118] According to embodiments of this disclosure, the dispersant may include carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polymethyl methacrylate (PMAA), cyano resin, or two or more of these.

[0119] According to embodiments of this disclosure, the dispersant may be used in amounts of 0.1 to 2 parts by weight, or 0.5 to 1.5 parts by weight, based on 100 parts by weight of inorganic particles.

[0120] According to embodiments of this disclosure, a slurry can be prepared by dissolving or dispersing a first binder polymer in a solvent for the first binder polymer, adding inorganic particles thereto, and dispersing them. The inorganic particles can be added after being pre-crushed to a predetermined average particle diameter. Alternatively, the inorganic particles can be added to a solution comprising the first binder polymer dissolved therein, followed by crushing and dispersion, while controlling them to have a predetermined average particle diameter using a ball milling process or the like.

[0121] According to this disclosure, step (S3) involves applying slurry to one surface of the primary partition plate and then sequentially applying slurry to the other surface of the primary partition plate. That is, step (S3) includes the following steps: applying slurry to one surface of the primary partition plate; and applying slurry to the other surface of the primary partition plate. When the slurry is applied to the other surface of the primary partition plate, the slurry applied to one surface of the primary partition plate is not yet dry. In other words, the slurry is applied to the other surface of the primary partition plate before the slurry applied to one surface of the primary partition plate dries.

[0122] Figure 2 An embodiment of a system for sequentially coating a slurry comprising inorganic particles and a first binder polymer is illustrated in a method for manufacturing a separator for a secondary battery according to an embodiment of the present disclosure.

[0123] Reference Figure 2 The coating system 100 includes: a feed roller 110 configured to supply a primary separator 200; a first coating unit 120 configured to apply slurry to one surface A of the primary separator 200; a second coating unit 130 configured to apply slurry to another surface B of the primary separator 200; a rotating roller 140 configured to transport the primary separator 200 by friction while in contact with either surface A or surface B of the primary separator 200 mentioned above; and a dryer 150 configured to dry the primary separator 200 coated on both sides.

[0124] According to embodiments of this disclosure, the method of sequentially coating the slurry on one surface and another surface of the primary partition in step (S3) may include gravure roller coating process, bar coating process, slot die coating process, doctor blade coating process, or two or more of these.

[0125] According to embodiments of this disclosure, phase separation may be performed in step (S3). A phase separation process refers to a process for forming a porous structure by means of phase separation phenomena known to those skilled in the art. For example, a phase separation process may be performed by steam-induced phase separation or impregnation phase separation.

[0126] First, we will explain vapor-induced phase separation.

[0127] Vapor-induced phase separation refers to phase separation that occurs when a separator is exposed to an atmosphere of a non-solvent used for the first adhesive polymer. Here, the non-solvent can be introduced in a gaseous state. There are no particular limitations on the non-solvent, as long as it does not dissolve the first adhesive polymer but is partially compatible with the solvent used for the first adhesive polymer. For example, the non-solvent can be water, methanol, ethanol, isopropanol, butanol, or two or more of these. Vapor-induced phase separation can be carried out at a relative humidity of 15% to 80% or 30% to 50% at a temperature of 15°C to 70°C or 20°C to 50°C.

[0128] Next, we will explain the separation of the impregnated phase.

[0129] A primary separator coated with a slurry is immersed in a coagulant solution comprising a non-solvent-based binder polymer. During this immersion, the slurry coated on the primary separator transforms into a porous structure as the first binder polymer cures. The resulting product is then washed with water to remove the coagulant solution and subsequently dried. In the impregnation phase separation, the non-solvent can be used in an amount of 60% by weight or greater of a 100% by weight coagulant solution to form a high-quality pore structure and improve productivity.

[0130] After that, the product from step (S3) is dried (S4). In step (S3), while the slurry coated on one surface of the primary separator is not yet dry, the slurry is coated on the other surface of the primary separator. After the slurry is coated on the other surface of the primary separator, the slurry coated on one surface of the primary separator and the slurry coated on the other surface of the primary separator are dried simultaneously in step (S4).

[0131] According to embodiments of this disclosure, drying can be performed using a drying process for manufacturing conventional partitions. For example, drying can be performed at 30°C to 100°C, or 40°C to 70°C. Alternatively, drying can be performed using air for 3 to 45 seconds, or 5 to 40 seconds. When the drying time meets the above-defined ranges, it is easier to remove residual solvents or dispersion media without adversely affecting productivity.

[0132] When using the method for manufacturing a separator for a secondary battery according to this disclosure, at least one surface of the porous polymer substrate is coated with a coating solution comprising a non-wetting polymer impermeable to a solvent for a first binder polymer. Therefore, even when a slurry comprising inorganic particles and the first binder polymer is sequentially coated on one and another surface of a primary separator coated with the coating solution, the amount of the first binder polymer penetrating into the porous polymer surface can be minimized. Thus, deviations in physical properties between one and another surface of the finished separator can be minimized while providing excellent slurry coating processability and separator productivity.

[0133] In another aspect of this disclosure, a separator for a secondary battery is provided, comprising:

[0134] Porous polymer substrate;

[0135] A first coating is disposed on one surface of the porous polymer substrate and includes a plurality of inorganic particles and a first adhesive polymer.

[0136] A second coating disposed on another surface of the porous polymer substrate and comprising a plurality of inorganic particles and the first adhesive polymer; and

[0137] A third coating, comprising a second adhesive polymer, is disposed between the porous polymer substrate and the first coating, and / or between the porous polymer substrate and the second coating.

[0138] The second adhesive polymer includes a non-wetting polymer.

[0139] Figure 3 This is a schematic diagram illustrating a separator for a secondary battery according to an embodiment of the present disclosure.

[0140] Reference Figure 3 The separator 1 for secondary batteries includes a porous polymer substrate 10.

[0141] Refer to the above description of the porous polymer substrate 10.

[0142] According to embodiments of this disclosure, the porous polymer substrate 10 may have a thickness of 5 μm to 50 μm. The thickness of the porous polymer substrate is not limited to the range defined above. However, when the thickness is within the range defined above, it is easier to prevent the separator from being easily damaged during battery use and to ensure energy density. Meanwhile, although there are no particular limitations on the pore size and porosity of the porous polymer substrate, the porosity and pore size may be from 0.01 μm to 50 μm and 10% to 95%, respectively.

[0143] According to this disclosure, the porosity and average pore size 10 of the porous polymer substrate 10 can be determined from scanning electron microscope (SEM) images, by using a mercury porosimeter or capillary flow porometer, or by using a porosimetry analyzer (Belsorp-II mini, Bell Japan Inc.) based on the BET 6-point method of nitrogen adsorption flow.

[0144] Reference Figure 3 The separator 1 for secondary batteries includes a first coating 20 containing a plurality of inorganic particles and a first binder polymer on one surface of a porous polymer substrate 10.

[0145] In addition, the separator 1 for the secondary battery includes a second coating 20' containing a plurality of inorganic particles and a first adhesive polymer on another surface of the porous polymer substrate 10.

[0146] The first coating 20 and the second coating 20' each comprise a plurality of inorganic particles (not shown) and a first adhesive polymer (not shown), wherein the inorganic particles are attached to each other by the first adhesive polymer so that they can maintain their bonded state (that is, the first adhesive polymer connects and fixes the inorganic particles to each other). Furthermore, the inorganic particles and the porous polymer substrate 10 and / or the third coating described below can be held together by the first adhesive polymer.

[0147] The first coating 20 and the second coating 20' each prevent the porous polymer substrate 10 from exhibiting severe thermal shrinkage behavior by means of inorganic particles, thereby providing a separator with improved safety.

[0148] Since the separator 1 for secondary batteries according to this disclosure includes a first coating 20 on one surface of a porous polymer substrate and a second coating 20' on the other surface of the porous polymer substrate, the safety of the separator can be further improved compared with a separator that includes a porous coating containing inorganic particles and binder polymer only on one surface of the separator.

[0149] Refer to the above description of the inorganic particles and the first binder polymer.

[0150] According to embodiments of the present disclosure, in the first coating 20 and / or the second coating 20', inorganic particles can be bonded to each other by a first adhesive polymer, while they stack up and contact each other, thereby forming an interstitial volume between the inorganic particles, and the interstitial volume between the inorganic particles becomes an empty space to form a pore.

[0151] According to embodiments of this disclosure, the first coating 20 and / or the second coating 20' may have a thickness of 1 μm to 50 μm, 2 μm to 30 μm, or 2 μm to 20 μm.

[0152] According to embodiments of this disclosure, the first coating 20 and / or the second coating 20' may have an average pore size of 0.001 μm to 10 μm, or 0.001 μm to 1 μm.

[0153] According to embodiments of this disclosure, the first coating 20 and / or the second coating 20' may have a porosity of 5% to 95%, 10% to 95%, 20% to 90%, or 30% to 80%. The porosity corresponds to a value obtained by subtracting, from the volume calculated based on the thickness, width, and length of the first coating 20 and / or the second coating 20', the volume expressed as a percentage of the weight and density of each component in the first coating 20 and / or the second coating 20'.

[0154] According to this disclosure, the porosity and average pore size of the first coating 20 and / or the second coating 20' can be determined from scanning electron microscope (SEM) images, by using a mercury porosimeter or capillary flow porometer, or by using a porosimetry analyzer (Belsorp-II mini, Bell Japan Inc.) based on the BET 6-point method of nitrogen adsorption flow.

[0155] Reference Figure 3 According to embodiments of the present disclosure, the separator 1 for a secondary battery may include a third coating 30 between the porous polymer substrate 10 and the first coating 20.

[0156] According to another embodiment of this disclosure, the separator 1 for a secondary battery may include a third coating 30 between the porous polymer substrate 10 and the second coating 20'.

[0157] According to another embodiment of this disclosure, the separator 1 for a secondary battery may include a third coating 30 between the porous polymer substrate 10 and the first coating 20, and between the porous polymer substrate 10 and the second coating 20'. When the third coating 30 is disposed on both surfaces of the porous polymer substrate 10, i.e. between the porous polymer substrate 10 and the first coating 20, and between the porous polymer substrate 10 and the second coating 20', it can more effectively prevent the first adhesive polymer of the first coating 20 and the second coating 20' from penetrating into the pores of the porous polymer substrate 10.

[0158] exist Figure 3 In this process, the third coating 30 is disposed between the porous polymer substrate 10 and the first coating 20. However, the third coating may be disposed between the porous polymer substrate 10 and the first coating 20 and / or between the porous polymer substrate 10 and the second coating 20', as long as it is disposed between the initially formed coating comprising a plurality of inorganic particles and the first binder polymer and the porous polymer substrate.

[0159] The third coating 30 comprises a non-wetting polymer. Refer to the above description of the non-wetting polymer. Because the third coating 30 comprises a non-wetting polymer, the first adhesive polymer in at least one of the first coating 20 and the second coating 20' is prevented from penetrating into the pores of the porous polymer substrate 10.

[0160] According to embodiments of this disclosure, the second adhesive polymer may further include a third adhesive polymer, and the third adhesive polymer may be an adhesive polymer. The third adhesive polymer is used to maintain the third coating 30 in a bonded state to at least one of the first coating 20 and the second coating 20' and / or the porous polymer substrate 10. Non-wetting polymers can exhibit significantly poor adhesion. Therefore, the third adhesive polymer promotes the bonding of the third coating 30 to at least one of the first coating 20 and the second coating 20' and / or the porous polymer substrate 10.

[0161] Refer to the above description regarding the type and content of the third adhesive polymer.

[0162] According to embodiments of this disclosure, the content of the third coating 30 can be from 0.066 parts by weight to 0.166 parts by weight, or from 0.1 parts by weight to 0.166 parts by weight, based on 100 parts by weight of the first coating or the second coating. When the content of the third coating 30 meets the above-defined range, it is possible to more easily prevent the non-wetting polymer in the third coating 30 from penetrating into the pores of the porous polymer substrate while also preventing the first adhesive polymer from penetrating into the pores of the porous polymer substrate.

[0163] In addition, when the content of the third coating 30 meets the above-defined range, it is easier to prevent the non-wetting polymer in the third coating 30 from penetrating into the pores of the porous polymer substrate and further improve the air permeability of the finished partition.

[0164] According to embodiments of this disclosure, the third coating 30 may have a thickness of 0.01 μm to 0.1 μm, or 0.05 μm to 0.1 μm. When the thickness of the third coating 30 meets the above-defined range, it is possible to prevent the non-wetting polymer from penetrating into the pores of the porous polymer substrate 10, while also preventing the first adhesive polymer in at least one of the first coating 20 and the second coating 20' from penetrating into the pores of the porous polymer substrate 10.

[0165] A separator for a secondary battery according to an embodiment of the present disclosure includes a third coating 30 containing a non-wetting polymer on at least one surface of a porous polymer substrate, thereby preventing the first adhesive polymer in at least one of the first and second coatings from penetrating into the pores of the porous polymer substrate. Therefore, the first adhesive can be present in sufficient quantity not only on one surface of the separator but also on the other surface, thus minimizing the deviation in physical properties between the two surfaces of the separator.

[0166] In a separator for a secondary battery according to an embodiment of the present disclosure, a first adhesive polymer is present in sufficient quantity not only on one surface but also on the other surface, thereby minimizing the deviation in adhesion of the electrodes between the two surfaces.

[0167] In addition, since the first adhesive polymer is present in sufficient quantity not only on one surface but also on the other, it prevents inorganic particles from detaching from the porous polymer substrate on both surfaces. Therefore, adhesion to the electrodes can be ensured on both surfaces of the separator.

[0168] A separator for a secondary battery can be inserted between the positive and negative terminals to obtain a secondary battery.

[0169] The secondary battery according to this disclosure preferably includes a lithium secondary battery. Specific examples of lithium secondary batteries include lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries, or the like.

[0170] There are no particular limitations on the electrodes used in combination with the separator according to this disclosure, and they can be obtained by incorporating the electrode active material into the electrode current collector by methods generally known in the art.

[0171] When the secondary battery is a lithium secondary battery, non-limiting examples of positive electrode active materials include conventional positive electrode active materials that can be used as positive electrodes in conventional electrochemical devices. In particular, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or lithium composite oxides comprising combinations thereof are preferred.

[0172] When the secondary battery is a lithium secondary battery, non-limiting examples of negative electrode active materials include conventional negative electrode active materials that can be used as negative electrodes in conventional electrochemical devices. In particular, materials such as lithium metal or lithium alloys that intercalate lithium, carbon, petroleum coke, activated carbon, graphite, or other carbonaceous materials are preferred.

[0173] Non-limiting examples of positive current collectors include foils made of aluminum, nickel, or combinations thereof, while non-limiting examples of negative current collectors include foils made of copper, gold, nickel, copper alloys, or combinations thereof.

[0174] When the secondary battery is a lithium secondary battery, the electrolyte that can be used in the lithium secondary battery according to this disclosure is having A + B - Salts of structure, in which A + Including, for example, Li + Na + K + alkali metal cations such as B, or combinations thereof, - Including PF6 - BF4 - Cl - ,Br - I - ClO4 - AsF6 - CH3CO2 - CF3SO3 - N(CF3SO2)2 - C(CF2SO2)3 - Anions such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma-butyrolactone (γ-butyrolactone), or combinations thereof, are present in organic solvents, including but not limited to these.

[0175] Depending on the manufacturing process of the final product and the desired properties of the final product, electrolyte injection can be performed at an appropriate step during the process used to manufacture the battery. That is, electrolyte injection can be performed before battery assembly or as a final step in battery assembly.

[0176] According to embodiments of this disclosure, in addition to conventional processes, i.e., winding, separators for secondary batteries can also be applied to batteries by laminating, stacking, and folding separators with electrodes.

[0177] According to embodiments of this disclosure, a separator for a secondary battery can be inserted between the positive and negative electrodes. When an electrode assembly is formed by assembling multiple cells or electrodes, the separator can be inserted between adjacent cells or electrodes. The electrode assembly can have various structures, such as simple stacked type, jelly roll type, stacked folded type, laminated stacked type, or similar.

[0178] The embodiments will then be described in more detail so that this disclosure can be readily understood. However, the following embodiments may be embodied in many different forms and should not be construed as limited to the exemplary implementations set forth herein. Rather, these exemplary implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0179] Example 1

[0180] First, 97 parts by weight of polytetrafluoroethylene (PTFE) (available from DuPont Co.'s Teflon) TM A coating solution was prepared by mixing an aqueous dispersion of 1 part by weight of a surfactant (5% by weight of ethanol and 95% by weight of water) and 2 parts by weight of an acrylic copolymer (zeonPX-LP17).

[0181] Next, 0.014 g / m 2 The coating solution was sprayed onto both surfaces of a porous polyethylene substrate (available from SEMOORPCo., thickness: 9 μm) to obtain primary separators, which were then dried at 70°C for 30 minutes to remove water. The primary separators were then allowed to air dry at room temperature for 1 day.

[0182] Then, 78 parts by weight of Al2O3 (available from Sumitomo, average particle diameter: 500 nm) as inorganic particles, 21 parts by weight of polyvinylidene fluoride (PVDF) (Solvay Co.) as the first binder polymer, and 1 part by weight of cyano resin (available from Shin-Etsu Co.) as a dispersant were mixed with 100 parts by weight of acetone to prepare a slurry, which was then coated onto one surface of a primary separator using a rod coater (loading: 7.5 g / m²). 2 ).

[0183] After that, before the slurry applied to one surface dries, it is applied to the other surface of the primary separator (load: 7.5 g / m²). 2 The separator is then dried at 50°C for 5 minutes at 50% relative humidity to obtain a separator for secondary batteries.

[0184] Example 2

[0185] The separator was obtained in the same manner as in Example 1, except that: 1.48 g / m 2 The coating solution prepared according to Example 1 was coated onto a surface of a porous polyethylene substrate (available from SEMOORP Co., thickness: 9 μm) using a rod coater. The slurry was prepared by mixing 78 parts by weight of Al2O3 (available from Sumitomo, average particle diameter: 500 nm) as inorganic particles, 21 parts by weight of polyvinylidene fluoride (PVDF) (Solvay Co.) as a first binder polymer, and 1 part by weight of cyano resin (available from Shin-Etsu Co.) as a dispersant with 100 parts by weight of acetone.

[0186] Comparative Example 1

[0187] First, 78 parts by weight of Al2O3 (available from Sumitomo, average particle diameter: 500 nm) as inorganic particles, 21 parts by weight of polyvinylidene fluoride (PVDF) (Solvay Co.) as the first binder polymer, and 1 part by weight of cyano resin (available from Shin-Etsu Co.) as a dispersant were mixed with 100 parts by weight of acetone to prepare a slurry. Then, the slurry was coated onto one surface of a porous polyethylene substrate (available from SEMOORPCo., thickness: 9 μm) using a rod coater (loading: 7.5 g / m²). 2 ).

[0188] After that, before the slurry applied to one surface dries, it is applied to the other surface of the primary separator (load: 7.5 g / m²). 2 The separator is then dried at 50°C for 5 minutes at 50% relative humidity to obtain a separator for secondary batteries.

[0189] Test Example: Determination of the physical properties of the two surfaces of the partition

[0190] According to Examples 1 and 2 and Comparative Example 1, the thickness of the two surfaces of each separator, air permeability, peel strength, and adhesion to the electrode (laminar pressure) were measured. The results are shown in Table 1 below.

[0191] (1) Determination of air permeability on the two surfaces of the partition

[0192] The air permeability of both surfaces of the partition was determined by a method as defined in ASTM D726-94. Here, the air permeability value was measured as 100 mL of air passing through 1 in inch of each partition according to Examples 1 and 2 and Comparative Example 1 under a pressure of 12.2 in water column.2 The time (in seconds) required for the cross-section to be infiltrated is the air infiltration time.

[0193] (2) Determination of peel strength between the two surfaces of the partition

[0194] The peel strength of the two surfaces of the partition was determined by fixing each partition according to Examples 1 and 2 and Comparative Example 1 to a glass plate using double-sided tape, firmly attaching the tape (a transparent tape available from 3M Co.) to each of the first coating on one surface and the second coating on the other surface of the exposed partition, and then measuring the force (gf / 15mm) required to detach the tape using a tensile strength tester.

[0195] (3) Determination of the adhesion (laminar pressure) of the electrodes on the two surfaces of the separator.

[0196] The adhesion of the two surfaces of the separator to the electrode was determined by setting one surface and the other surface of each separator according to Examples 1 and 2 and Comparative Example 1 so that they could face the electrode, passing the resulting structure through a press at a temperature of 60°C and a pressure of 6.5 MPa, and then measuring the peel force required to separate the electrode from the separator.

[0197] The electrode is prepared as follows.

[0198] First, natural graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), and conductive material agents were introduced into water at a weight ratio of 90:2.5:2.5:5 to obtain the negative electrode slurry. Next, the negative electrode slurry was mixed with water at a concentration of 5 mg / cm³. 2 The loading was coated onto a copper (Cu) foil (20 μm thick) and then dried. The resulting structure was then pressed at 90 °C and 8.5 MPa and cut into 60 mm (length) × 25 mm (width) dimensions to obtain the negative electrode.

[0199] [Table 1]

[0200]

[0201]

[0202] As can be seen from Table 1, compared with Comparative Example 1, each separator according to Examples 1 and 2 showed significantly smaller deviations in terms of peel strength between one surface of the separator and adhesion to the electrode.

[0203] Specifically, it can be seen that, compared with Example 2, the separator according to Example 1 exhibits significantly smaller deviations in terms of peel strength between one surface of the separator and adhesion to the electrode. It can also be seen that the separator according to Example 1 exhibits the highest air permeability.

[0204] On the other hand, it can be seen that the separator according to Comparative Example 1 shows a significantly large deviation in terms of peel strength between one surface of the separator and adhesion to the electrode.

Claims

1. A separator for a secondary battery, comprising: Porous polymer substrate; A first coating is disposed on one surface of the porous polymer substrate and includes a plurality of inorganic particles and a first adhesive polymer. A second coating disposed on another surface of the porous polymer substrate and comprising the plurality of inorganic particles and the first adhesive polymer; and A third coating, comprising a second adhesive polymer, is disposed between the porous polymer substrate and the first coating, and / or between the porous polymer substrate and the second coating. The second adhesive polymer comprises a non-wetting polymer that is impermeable to solvents used in the first adhesive polymer, and The content of the third coating is from 0.066 parts by weight to 0.166 parts by weight of 100 parts by weight of the first coating or the second coating.

2. The separator for a secondary battery according to claim 1, wherein the non-wetting polymer comprises polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA), ethylene tetrafluoroethylene (ETFE), or two or more thereof.

3. The separator for a secondary battery according to claim 1, wherein the second adhesive polymer further comprises a third adhesive polymer, and the third adhesive polymer is an adhesive polymer.

4. The separator for a secondary battery according to claim 3, wherein the third adhesive polymer comprises styrene-butadiene rubber (SBR), acrylic copolymer, polyacrylic acid (PAA), polyacrylate, carboxymethyl cellulose (CMC), polyvinyl alcohol, or two or more thereof.

5. The separator for a secondary battery according to claim 1, wherein the first adhesive polymer comprises polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co-trifluorochloroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, or two or more thereof.

6. A method for manufacturing a separator for a secondary battery, comprising the following steps: (S1) Prepare a porous polymer substrate; (S2) A coating solution comprising a second adhesive polymer is applied to at least one surface of the porous polymer substrate and then dried to obtain a primary separator. (S3) A slurry comprising inorganic particles, a first binder polymer, and a solvent for the first binder polymer is sequentially applied to one surface and another surface of the primary separator; and (S4) The product of drying step (S3), The second adhesive polymer comprises a non-wetting polymer that is impermeable to solvents used in the first adhesive polymer, and The coating solution is at a concentration of 0.01 g / m 2 Up to 0.015g / m 2 The amount of load.

7. The method of manufacturing a separator for a secondary battery according to claim 6, wherein the non-wetting polymer comprises polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA), ethylene tetrafluoroethylene (ETFE), or two or more thereof.

8. The method of manufacturing a separator for a secondary battery according to claim 6, wherein the coating solution further comprises a third adhesive polymer, and the third adhesive polymer is an adhesive polymer.

9. The method of manufacturing a separator for a secondary battery according to claim 8, wherein the third adhesive polymer comprises styrene-butadiene rubber (SBR), acrylic copolymer, polyacrylic acid (PAA), polyacrylate, carboxymethyl cellulose (CMC), polyvinyl alcohol, or two or more thereof.

10. The method of manufacturing a separator for a secondary battery according to claim 6, wherein the coating in step (S2) comprises spraying the coating solution in gaseous or microdroplet form onto at least one surface of the porous polymer substrate.

11. The method of manufacturing a separator for a secondary battery according to claim 6, wherein the first adhesive polymer comprises polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co-trifluorochloroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, or two or more thereof.

12. The method of manufacturing a separator for a secondary battery according to claim 6, wherein the slurry is sequentially coated on one surface and another surface of the primary separator by a gravure roller coating process, a rod coating process, a slot die coating process, a doctor blade coating process, or two or more thereof.

13. A secondary battery comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the separator is a separator for a secondary battery as defined in any one of claims 1 to 5.

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