Method for manufacturing separator, separator manufactured thereby, and lithium secondary battery including same

Abstract

The present disclosure provides a method for manufacturing a separator, the method comprising the steps of: (S10) preparing a separator coating slurry composition comprising pore inducing particles, inorganic particles, a particulate binder, and a solvent; (S20) applying the separator coating slurry composition to at least one surface of the porous polymer substrate to form a porous coating; (S30) removing at least some of the pore-inducing particles of the porous coating by an etching solution; and (S40) drying the porous coating from which at least some of the pore-inducing particles have been removed.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method for manufacturing a separator, a separator manufactured thereby, and a lithium secondary battery including the same.

[0002] This application is based on and claims priority to Korean Patent Application No. 10-2024-0065882, filed on May 21, 2024, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. BACKGROUND

[0003] Non-aqueous secondary batteries including lithium secondary batteries are widely used as power sources for portable electronic devices such as laptop computers, mobile phones, digital cameras or camcorders, and electric vehicles.

[0004] One component of a lithium secondary battery, a separator, is essentially required to separate and electrically insulate a cathode from an anode, and to increase the permeability of ions (e.g., lithium ions) based on high porosity, so as to increase the ionic conductivity. The separator does not participate in the electrochemical reaction of the secondary battery, but greatly affects the performance and safety of the secondary battery due to the physical properties of the secondary battery such as electrolyte wettability, porosity, or thermal shrinkage.

[0005] However, the separator using a porous polymer substrate shrinks at high temperatures, causing internal short-circuiting, and in the case of thermal runaway, the polymer separator substrate melts, thereby increasing the risk of fire. Accordingly, a method of overcoming the disadvantages of the porous polymer substrate by adding a porous coating including inorganic particles for overcoming the disadvantages of the porous polymer substrate and a binder to one or both surfaces of the porous polymer substrate has been proposed.

[0006] Meanwhile, the binder included in the porous coating can be classified into a particulate-type binder and a soluble binder depending on whether the binder is dissolved in a solvent. In the case of the soluble binder, when a slurry for forming the porous coating is applied to the surface of the porous substrate, the soluble binder can flow to the surface through the pores of the porous substrate, causing the pores of the porous substrate to be clogged. In order to prevent this problem, the use of a particulate-type binder has been proposed. However, the particulate-type binder in the porous coating can lose its shape or form a film during the process of stacking the anode, the cathode, and the separator between the anode and the cathode and applying heat and pressure. In this case, the binder can clog the pores inside the porous coating or the pores of the porous polymer substrate, resulting in low porosity and poor electrolyte wettability of the separator. Accordingly, there is a need for a method of manufacturing a separator having strong adhesion strength, high ionic conductivity, and good electrolyte wettability by using a particulate-type binder as a binder, and a separator manufactured thereby. SUMMARY

[0007] Technical Problem

[0008] The present disclosure aims to solve the above technical problem, and in particular, the present disclosure relates to a method of manufacturing a separator having good electrolyte wettability in the presence of a particulate type binder in a porous coating, a separator manufactured thereby, and a lithium secondary battery including the same.

[0009] The present disclosure also relates to providing a lithium secondary battery having high wettability and permeability by introducing pores of various sizes.

[0010] Technical Solution

[0011] To achieve the above object, according to one aspect of the present disclosure, there is provided a separator, a method for manufacturing a separator, and a lithium secondary battery including the same of the following embodiments.

[0012] According to a first embodiment, there is provided a method for manufacturing a separator, the method including the steps of: (S10) preparing a separator coating slurry composition including pore-inducing particles, inorganic particles, a particulate type binder, and a solvent; (S20) applying the separator coating slurry composition to at least one surface of a porous polymeric substrate to form a porous coating; (S30) removing at least some of the pore-inducing particles of the porous coating by an etching solution; and (S40) drying the porous coating from which at least some of the pore-inducing particles have been removed.

[0013] According to a second embodiment, in the first embodiment, the pore-inducing particles can be a material that reacts with the etching solution.

[0014] According to a third embodiment, in any one of the first and second embodiments, the pore-inducing particles can include silicon dioxide (SiO2), titanium dioxide (TiO2), zirconium oxide (ZrO2), or two or more of them.

[0015] According to a fourth embodiment, in any one of the first to third embodiments, the etching solution can include hydrogen fluoride, sodium hydroxide, potassium hydroxide, nitric acid, hydrogen peroxide, carbonic acid, or two or more of them.

[0016] According to a fifth embodiment, in any one of the first to fourth embodiments, in the step (S10), the amount of the pore-inducing particles in the separator coating slurry composition can be 20 to 90 parts by weight, based on 100 parts by weight of the inorganic particles.

[0017] According to a sixth embodiment, in any one of the first through fifth embodiments, the D 50 may be 20 nm to 500 nm.

[0018] According to a seventh embodiment, in any one of the first through sixth embodiments, the particulate binder can include an acrylic particulate binder, a fluorine-based particulate binder, or a combination thereof.

[0019] According to an eighth embodiment, in any one of the first through seventh embodiments, a glass transition temperature (Tg) of the particulate binder can be 40℃ to 80℃.

[0020] According to a ninth embodiment, in any one of the first through eighth embodiments, the D 50 may be 150 nm to 1 µm.

[0021] According to a tenth embodiment, in any one of the first through ninth embodiments, the porous polymer substrate can include polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, or two or more thereof.

[0022] According to an eleventh embodiment, in any one of the first through tenth embodiments, the step (S20) can further include a step (S21) of drying a solvent in the separator coating slurry composition after the separator coating slurry composition is applied to at least one surface of the porous polymer substrate.

[0023] According to a twelfth embodiment, in the eleventh embodiment, the method for manufacturing a separator can further include, after the step (S21), a step (S22) of applying a pressure of 0.5 MPa to 20 MPa to the separator for 1 second to 60 seconds under a temperature condition of 20℃ to 85℃.

[0024] According to a thirteenth embodiment, in any one of the first through twelfth embodiments, the method for manufacturing a separator can further include, after the step (S40), a step (S41) of applying a pressure of 0.5 MPa to 20 MPa to the separator for 1 second to 60 seconds under a temperature condition of 20℃ to 85℃.

[0025] According to a fourteenth embodiment, there is provided a separator manufactured by the method for manufacturing a separator defined in any one of the first to thirteenth embodiments, the separator including a porous polymer substrate and a porous coating layer present on at least one surface of the porous polymer substrate, the porous coating layer including inorganic particles and a particulate binder, wherein the porous coating layer includes pores formed by removing at least some of the pore-inducing particles by an etching solution.

[0026] According to a fifteenth embodiment, in the fourteenth embodiment, the porosity of the separator can be 10% to 50% by volume.

[0027] According to a sixteenth embodiment, there is provided a lithium secondary battery including: a positive electrode; a negative electrode; an electrolyte solution; and a separator interposed between the positive electrode and the negative electrode, wherein the separator is the separator defined in any one of the fourteenth and fifteenth embodiments.

[0028] Advantageous Effects

[0029] The separator according to the embodiments of the present disclosure includes a particulate binder in a porous coating layer, but has pores at positions where pore-inducing particles have been removed, resulting in higher porosity than conventional separators using a particulate binder, thereby achieving good electrolyte wettability of the separator.

[0030] Due to the pores of various sizes in the porous coating layer, the separator according to the embodiments of the present disclosure has good electrolyte wettability and high permeability. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1a is an image of the separator of Example 1 after the wettability test.

[0032] Figure 1b is an image of the separator of Comparative Example 1 after the wettability test.

[0033] Figure 2a shows a scanning electron microscope (SEM) image of a surface of the separator of Example 1 and IAM program-assisted masking images of inorganic particles, pores, acrylic particulate binder, and fluorine-based particulate binder.

[0034] Figure 2b shows a SEM image of a surface of the separator of Comparative Example 1 and IAM program-assisted masking images of inorganic particles, pores, acrylic particulate binder, and fluorine-based particulate binder. DETAILED DESCRIPTION

[0035] The terms or words used in the specification and appended claims should not be construed as limited to their general or dictionary meanings, but should be interpreted based on their meanings and concepts corresponding to the technical aspects of this disclosure, based on the principle that the inventors are permitted to properly define terms for the best interpretation.

[0036] The terminology used herein is for describing exemplary embodiments of this disclosure and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms include the plural forms.

[0037] <Definition>

[0038] The terms “comprising,” “including,” and “having” are used in this specification to specify the presence of the said element, but do not exclude the presence or addition of one or more other elements unless the context clearly indicates otherwise.

[0039] In this specification, D50 refers to the particle size at the 50% point of the cumulative particle size distribution. That is, D 50 This refers to the particle size at the 50% point of the cumulative particle size distribution. Furthermore, D... 10 This refers to the particle size at the 10% point of the cumulative particle size distribution, and D 90 It refers to the particle size at the 90% point of the cumulative particle size distribution.

[0040] Particle size can be measured using the laser diffraction method. Specifically, the particle size distribution is calculated by dispersing the powder to be measured in a dispersion medium, feeding it into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500), and measuring the difference in the diffraction pattern as a function of particle size as the particles pass through the laser beam. 10 D 50 and D 90 The particle size can be measured by calculating the particle size at the 10%, 50%, and 90% points of the cumulative particle size distribution in the measuring instrument.

[0041] In this specification, certain terms are provided for ease of description but are not intended to limit this disclosure. The terms “left,” “right,” “up,” and “down” as used herein may indicate direction in the referenced figures and should not be limiting. These terms include the listed words, their derivatives, and words with similar meanings.

[0042] <Methods for manufacturing partitions>

[0043] This disclosure provides a method for manufacturing a separator for an electrochemical device.

[0044] According to one aspect of this disclosure, the method for manufacturing a separator includes the following steps: (S10) preparing a separator coating slurry composition comprising pore-inducing particles, inorganic particles, particulate binder, and solvent; (S20) applying the separator coating slurry composition to at least one surface of a porous polymer substrate to form a porous coating; (S30) removing at least some of the pore-inducing particles from the porous coating by an etching solution; and (S40) drying the porous coating from which at least some of the pore-inducing particles have been removed.

[0045] The following sections will describe in detail each step of the method used to manufacture the partition.

[0046] The method begins with step (S10): preparing a separator coating slurry composition comprising pore-inducing particles, inorganic particles, particulate binder and solvent.

[0047] In embodiments of this disclosure, the pore-inducing particles are materials contained in the separator coating slurry composition and can be removed by reacting with an etching solution after they have been applied to the porous polymer substrate.

[0048] In embodiments of this disclosure, the pore-inducing particles have the property of being dissolved by the etching solution described below, and may comprise organic particles and / or ceramic particles. The pore-inducing particles may include ceramic particles. The ceramic particles are not limited to a specific type and may comprise any material that can be dissolved and removed by the etching solution. For example, the ceramic particles may include silicon dioxide (SiO2), titanium dioxide (TiO2), zirconium oxide (ZrO2), or two or more of these. A chemical reaction, such as a wet etching reaction between the solid pore-inducing particles and the liquid etching solution, can produce ionic products, which can be removed by washing. The empty spaces left after removal can be provided as pores.

[0049] In embodiments of this disclosure, the etching solution may include hydrogen fluoride, sodium hydroxide, potassium hydroxide, nitric acid, hydrogen peroxide, carbonic acid, or two or more of these. In this case, the etching rate may vary depending on the type and combination of the etching solution.

[0050] For example, in embodiments of this disclosure, where silicon dioxide (SiO2) is used as pore-inducing particles and hydrogen fluoride (HF) is used as an etching solution, a reaction represented by the following formula 1 can be carried out.

[0051] SiO2(s)+6HF(aq)→H2SiF6(aq)+2H2O(l) … Formula (1)

[0052] For example, in an embodiment of this disclosure, where silicon dioxide (SiO2) is used as pore-inducing particles and sodium hydroxide (NaOH) is used as an etching solution, a reaction represented by the following formula 2 can be carried out when heated.

[0053] SiO2(s)+2 NaOH(aq)→Na2SiO3(aq)+H2O(l) … Formula (2)

[0054] In embodiments of this disclosure, based on 100 parts by weight of inorganic particles, the amount of pore-inducing particles in the separator coating slurry composition can be from 20 to 90 parts by weight, or from 30 to 80 parts by weight. When the amount of pore-inducing particles falls within the above range, the manufactured separator can have good thermal properties, high porosity, and high ionic conductivity. Furthermore, when the amount of pore-inducing particles falls within the above range, the inorganic particles in the porous coating can hold the mechanical framework structure together, and when subjected to external pressure such as external forces, the structure of the porous coating can not collapse and can retain the pores generated by the pore-inducing particles.

[0055] In embodiments of this disclosure, when the pore-inducing particles function as pores forming a septum without disrupting the structure of the porous coating, the size D of the pore-inducing particles is... 50 Not limited to a specific scope.

[0056] In embodiments of this disclosure, the size D of the pore-inducing particles can be appropriately selected within a desired range. 50 To control the hole size.

[0057] In embodiments of this disclosure, the D of the pore-induced particles 50 It can be 20nm to 500nm, or 50nm to 200nm. When the pore-induced particle's D... 50 When falling within the above range, the pore-inducing particles can be uniformly spread in the separator coating slurry composition, and the manufactured separator can have optimal porosity.

[0058] In embodiments of this disclosure, the size of the pores formed by the pore-inducing particles can be substantially equal to the size of the pore-inducing particles. That is, based on 100 vol% of pore-inducing particles, the size of the pores induced by the pore-inducing particles can be in the range of 80 vol% to 120 vol%, 90 vol% to 110 vol%, 95 vol% to 105 vol%, or 98 vol% to 102 vol%. In other words, when using pore-inducing particles, the pore size in the partition can be controlled.

[0059] In embodiments of this disclosure, the porous coating preferably has a uniform pore size so that the separator has a uniform ionic conductivity throughout the entire surface. Therefore, for this purpose, the pore-inducing particles included in the porous coating preferably have both a uniform particle size and the aforementioned average particle size. Furthermore, when the pore-inducing particles have a non-uniform particle size, the porous coating may tend to have low thickness uniformity.

[0060] In embodiments of this disclosure, the pore-induced particles preferably have a monomodal particle size distribution. In this specification, a monomodal particle size distribution can be defined as a distribution with a standard deviation in the range of 1% or greater and less than 40%, preferably 1% or greater and 35% or less, when analyzed using a particle size analyzer (Dynamic Light Scattering: DLS, Nicomp 380). A bimodal or multimodal particle size distribution can be a distribution with a standard deviation of 40% or greater when the particle size and its distribution are determined using a particle size analyzer. When the standard deviation is 40% or greater, two or more particle size peaks can be observed.

[0061] In specific embodiments of this disclosure, the inorganic particles are not limited to specific types and may include any electrochemically stable particles. That is, the inorganic particles used in this disclosure are not limited to a specific type and may include any type of inorganic particles in which oxidation and / or reduction reactions do not occur within the operating voltage range of the applied electrochemical device (e.g., 0 to 5 V for Li / Li+). In particular, when inorganic particles with a high dielectric constant are used as inorganic particles, they can contribute to an increased degree of dissociation of the electrolyte salt (e.g., lithium salt) in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte solution.

[0062] For the reasons stated above, inorganic particles preferably include high dielectric constant inorganic particles with a dielectric constant of 5 or greater, preferably 10 or greater. Non-limiting examples of inorganic particles with a dielectric constant of 5 or greater include BaTiO3, Pb(Zr,Ti)O3(PZT), and Pb... 1-x La x Zr 1-y Ti yO3 (PLZT, 0 < x < 1, 0 < y < 1), Pb(Mg 1 / 3 Nb 2 / 3 )O3 - PbTiO3 (PMN - PT), hafnium dioxide (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, TiO2, or a mixture thereof.

[0063] In addition, the inorganic particles may include inorganic particles having the ability to transport lithium ions, that is, inorganic particles containing lithium but not storing lithium and having the function of moving lithium ions. Non - limiting examples of inorganic particles having the ability to transport lithium ions include: lithium phosphate (Li3PO4); lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3); lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3); (LiAlTiP) x O y - based glass (0 < x < 4, 0 < y < 13), such as 14Li2O - 9Al2O3 - 38TiO2 - 39P2O5; lithium lanthanum titanate (Li x La y TiO 3, 0 < x < 2, 0 < y < 3); lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), such as Li 3.25 Ge 0.25 P 0.75 S4; lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), such as Li3N; SiS2 - based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), such as Li3PO4 - Li2S - SiS2; P2S5 - based glass (Li x P y S z,0 < x < 3, 0 < y < 3, 0 < z < 7), such as LiI-Li2S-P2S5; or mixtures thereof.

[0064] In embodiments of this disclosure, in a porous coating, inorganic particles are stacked in contact with each other and held together by a particulate binder to form an interstitial volume between the inorganic particles, and the interstitial volume between the inorganic particles becomes the voids that form pores.

[0065] In other words, particulate adhesives can bind inorganic particles together to make them stick together, and connect and hold inorganic particles together. In addition, the pores in the porous coating can be formed by the voids created by the interstitial volume between inorganic particles, and can be the space defined by inorganic particles that are substantially in close contact with each other in a closely packed or densely packed structure.

[0066] In embodiments of this disclosure, the porous coating structure may not collapse when the partition is subjected to external pressure because the inorganic particles remain together.

[0067] In embodiments of this disclosure, the porous coating may include both an interstitial volume defined by inorganic particles and pores formed by pore removal-induced particles, wherein the inorganic particles are substantially in close contact with each other through a structure of close or dense packing of inorganic particles.

[0068] Furthermore, the average particle size of the inorganic particles is not limited to a specific range, but is preferably in the range of 0.1 μm to 1.5 μm to form a coating with uniform thickness and optimal porosity. When the average particle size of the inorganic particles is less than 0.1 μm, dispersion may be reduced, and when the average particle size of the inorganic particles is greater than 1.5 μm, an inorganic coating with a larger thickness may be formed.

[0069] In embodiments of this disclosure, the content of inorganic particles may be 50% by weight or more, based on the total solids content of 100% of the separator coating slurry composition, for example, in the range of 50% by weight to 97% by weight, or in the range of 50% by weight to 95% by weight, or in the range of 50% by weight to 90% by weight.

[0070] In embodiments of this disclosure, the particulate adhesive may have the property of retaining its original particulate shape without changing its shape when dispersed in a solvent. Specifically, the particulate adhesive may refer to an adhesive that exists in a particulate state in an aqueous solvent. More specifically, the particulate adhesive may refer to a type of adhesive that has low solubility in an aqueous solvent and is dispersed in a particulate phase within the aqueous solvent.

[0071] In embodiments of this disclosure, the particulate adhesive may include acrylic particulate adhesive, fluoropolymer particulate adhesive, or a combination thereof.

[0072] In embodiments of this disclosure, when the granular adhesive comprises an acrylic granular adhesive and a fluoropolymer granular adhesive, the weight ratio of the acrylic granular adhesive to the fluoropolymer granular adhesive can be 1:99 to 99:1, 10:90 to 90:10, or 20:80 to 80:20. When the weight ratio of the acrylic granular adhesive to the fluoropolymer granular adhesive falls within the above ranges, the adhesion strength of the separator under wetting conditions (wet adhesion strength) and the adhesion strength of the separator under dry conditions (dry adhesion strength) can be improved.

[0073] In embodiments of this disclosure, the acrylic granular adhesive may include, for example, an acrylic homopolymer (i.e., a polymer composed of a single acrylic monomer) or a copolymer of an acrylic monomer with another monomer. For example, the acrylic granular adhesive may include poly(methyl methacrylate), poly(ethyl hexyl acrylate), poly(butyl acrylate), poly(acrylonitrile), copolymers of ethyl hexyl acrylate and methyl methacrylate, copolymers of butyl acrylate and methyl methacrylate, 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 mixtures of two or more thereof.

[0074] In embodiments of this disclosure, fluoropolymer particulate adhesives may include, for example, poly(vinylidene fluoride) homopolymers or copolymers of PVDF with another monomer. For instance, fluoropolymer particulate adhesives may include copolymers of repeating units derived from PVDF and repeating units derived from at least one of trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), trichloroethylene (TrCE), trichlorofluoroethylene (TCFE), chlorotrifluoroethylene (CTFE), polymethyl methacrylate (PMMA), and polyvinylacetate (PVAc), or mixtures of two or more of these.

[0075] In embodiments of this disclosure, the glass transition temperature (Tg) of the particulate adhesive can be from 40°C to 80°C, or from 50°C to 70°C. The glass transition temperature (Tg) can, for example, refer to a value measured by dynamic mechanical analysis (DMA) or differential scanning calorimetry (DSC) (TA Instrument). For instance, the glass transition temperature can refer to a value measured according to the DMA method specified in ASTM D4065. When the particulate adhesive has the aforementioned glass transition temperature, the particulate adhesive can form a film by causing structural collapse under predetermined temperature and pressure conditions during the manufacture of the separator.

[0076] In embodiments of this disclosure, the D of the particulate adhesive 50 The size can be from 150 nm to 1 μm, or from 200 nm to 800 nm. When the size of the particulate adhesive falls within the above range, the adhesion strength and porosity of the separator can be improved.

[0077] In embodiments of this disclosure, the amount of particulate binder in the separator coating slurry composition can be from 20 parts by weight to 80 parts by weight, based on 100 parts by weight of inorganic particles. When the amount of particulate binder falls within the above range, the adhesion strength of the manufactured electrode can be improved.

[0078] In embodiments of this disclosure, the particulate adhesive may, for example, have a single-phase particulate structure or a multi-phase particulate structure, such as a core-shell or a core-first-shell-second-shell.

[0079] In embodiments of this disclosure, the particulate adhesive may have, for example, spherical, elliptical, oval, plate-like, or irregular particle shapes.

[0080] In embodiments of this disclosure, when preparing the separator coating slurry composition, the solvent may comprise water or an aqueous solvent containing water. Furthermore, when there are limitations on drying rate and temperature, methanol, ethanol, or isopropanol, which have a lower boiling point than water, can be used as a co-solvent.

[0081] Subsequently, in step (S20), the separator coating slurry composition is applied to at least one surface of the porous polymer substrate to form a porous coating.

[0082] In embodiments of this disclosure, a porous polymer substrate refers to a substrate having pores internally and acting as a porous ion-conducting barrier to prevent electrical contact between the negative and positive electrodes while allowing ions to pass through. The pores are interconnected, allowing gas or liquid to pass from one side of the substrate to the other.

[0083] The material of the porous polymer substrate can include organic or inorganic materials with electrical insulating properties. In particular, from the perspective of the substrate's shut-off function, thermoplastic resin is a preferred material. Here, the shut-off function refers to the ability of the thermoplastic resin to melt and close the pores of the porous substrate to stop ion migration, thereby preventing thermal runaway of the battery when its temperature rises. The thermoplastic resin may preferably include those with a melting point of less than 200°C.

[0084] In particular, in embodiments of this disclosure, the porous polymer substrate is not limited to a specific type and may include any material that will not cause a physical / chemical reaction with the components of the etching solution due to chemical resistance. Depending on the type of etching solution used, the porous polymer substrate may include, for example, polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, or two or more of the above.

[0085] In this disclosure, the thickness of the porous polymer substrate is preferably 3 μm to 15 μm, or 5 μm to 15 μm. When the thickness is below the above values, the conductive barrier function is insufficient, and conversely, when the thickness is above the above range (i.e., too thick), the resistance of the separator may increase too much.

[0086] In embodiments of this disclosure, the weight-average molecular weight of the porous substrate can be from 100,000 to 5,000,000. When the weight-average molecular weight is less than 100,000, it may be difficult to ensure sufficient mechanical properties. Furthermore, when the weight-average molecular weight is greater than 5,000,000, the shut-off properties may not function properly, or formation may become difficult. Additionally, the puncture strength of the porous polymer substrate can be 300 gf or greater to improve production yield. The puncture strength of the porous substrate refers to the maximum puncture load (gf) measured by a puncture test using a Kato tech KES-G5 handheld compression tester under conditions of a needle tip curvature radius of 0.5 mm and a puncture speed of 4 mm / s.

[0087] In embodiments of this disclosure, the porous polymer substrate can typically have a pore size of 10 nm to 200 nm.

[0088] In embodiments of this disclosure, the porosity of the separator can be from about 30% to 80% by volume. Simultaneously, the permeability of the separator can be in the range of about 50 seconds / 100cc or higher and about 250 seconds / 100cc or lower, or in the range of 50 seconds / 100cc or higher and 150 seconds / 100cc or lower.

[0089] Porosity or pore size can be measured using a BELSORP (BET device) from BEL JAPAN with an adsorbed gas (e.g., nitrogen) or by mercury intrusion porosimetry or capillary flow porosimetry. Specifically, in embodiments of this disclosure, the pore size of the porous coating can be measured by capillary flow porosimetry. Capillary flow porosimetry is a method for measuring the minimum pore size in the thickness direction. Therefore, in order to measure the pore size of the porous coating alone by capillary flow porosimetry, the porous coating can be separated from the porous substrate, and the separated porous coating can be wrapped with a nonwoven fabric to support it, and in this case, the pore size of the nonwoven fabric can be much larger than the pore size of the coating.

[0090] As used herein, the term "permeability" refers to the time it takes for 100 cc of air to pass through an object (here, a separator or porous polymer substrate), and its unit is indicated by seconds per 100 cc. Permeability can be used interchangeably with air permeability and is typically expressed as a Gelley value. In specific embodiments of this disclosure, permeability can be measured according to JIS P8117. Furthermore, the permeability P1 of air measured in an object having a thickness T1 can be converted to the permeability P2 of an object with a thickness of 20 μm using the equation: P2 = (P1 × 20) / T1.

[0091] In embodiments of this disclosure, the porous coating can be applied to a thickness of 1.0 μm to 5.0 μm. When the thickness falls within this range, the adhesion strength relative to the electrode can be improved, thereby increasing the cell strength of the battery. Conversely, a thickness of 5.0 μm or less is advantageous in terms of the battery's cycle characteristics and resistance characteristics. When the inorganic coating is present on both surfaces of the porous polymer substrate, the thickness of the porous coating refers to a measurement of the porous coating present on either surface of the porous polymer substrate.

[0092] Common coating methods using Meyer bars, die coaters, reverse roller coaters, or gravure coaters can be used to apply slurry compositions for diaphragm coating.

[0093] Subsequently, (S30) at least some of the pore-inducing particles of the porous coating are removed by an etching solution. Step S30 can be performed by dipping a porous polymer substrate with a porous coating in an etching solution or by spraying an etching solution onto the porous coating. In this case, as shown in Formula 1 or Formula 2 above, the pore-inducing particles react with the etching solution to generate ionic material and separate from the separator, and the voids formed due to the dissolution and removal of the pore-inducing particles are provided as pores of the separator. Subsequently, the separator can be washed to remove the reactant solution of the pore-inducing particles and the etching solution. In this case, the washing solution may include an aqueous solvent containing water and / or ethanol.

[0094] In embodiments of this disclosure, pores can be formed at the locations of pore-inducing particles within the porous coating. For example, pores can be formed at the locations of the pore-inducing particles after the pore-inducing particles have been removed by an etching solution when the pore-inducing particles come into contact with inorganic particles and / or pore-inducing particles.

[0095] In this case, pores formed by the interstitial volume of inorganic particles are formed through contact between inorganic particles as described above, while pores formed by removing pore-inducing particles are produced by removing pore-inducing particles at the location in contact with inorganic particles and / or particulate adhesives, and thus they can be distinguished by scanning electron microscope (SEM) images.

[0096] Subsequently, step (S40) is performed, in which the porous coating from which at least some of the pore-inducing particles has been removed is dried. The drying rate and temperature can vary depending on the solvent used. For example, the drying time can be from 10 minutes to 10 hours, and the drying temperature can be in the range of 30°C to 100°C. The drying method is not limited to a specific one and can be any method for removing the washing solution from the separator, and suitable methods may include, for example, any one of convection drying, hot air drying, blow-drying, or natural drying, or a combination of two or more of these. In embodiments of this disclosure, drying can be performed by vacuum drying under reduced pressure.

[0097] In embodiments of this disclosure, step S20 may further include: step (S21) drying the solvent in the separator coating slurry composition after applying the separator coating slurry composition to at least one surface of the porous polymer substrate. In this case, the drying process may include preliminary drying after the formation of the porous coating and secondary drying after the removal of pore-inducing particles. The drying time for each drying may be from 10 minutes to 10 hours, and the drying temperature may be in the range of 30°C to 100°C. The drying method is not limited to a particular one and may include any method for removing the washing solution from the separator, and suitable methods may include, for example, any one of convection drying, hot air drying, blow drying, or natural drying, or a combination of two or more of them. In embodiments of this disclosure, drying may be performed by vacuum drying under reduced pressure.

[0098] In embodiments of this disclosure, when the method further includes drying the solvent in the separator coating slurry composition after applying the separator coating slurry composition to at least one surface of the porous polymer substrate, the method may also include a process of applying pressure to the separator after the drying process.

[0099] That is, in the embodiments of this disclosure, after step S21, the method may further include: step (S22), applying a pressure of 0.5 MPa to 20 MPa to the partition at a temperature of 20°C to 85°C for 1 second to 60 seconds. Specifically, step S22 may be performed at a pressure of 0.5 MPa to 20 MPa, 1 MPa to 10 MPa, or 2 MPa to 8 MPa and a temperature of 20°C to 85°C, 25°C to 80°C, or 25°C to 70°C. In this case, the particulate binder in the porous coating can form a film in the state where the pore-inducing particles are not removed. Subsequently, when at least some of the pore-inducing particles of the porous coating are removed by an etching solution, pores with a shape similar to the pore-inducing particles can be formed, which can be used to control the shape of the pores. That is, in this case, the particle size distribution of the pore-inducing particles and the pore size distribution may be similar.

[0100] In embodiments of this disclosure, the drying process may not be performed immediately after the separator coating slurry composition is applied to at least one surface of the porous polymer substrate, and may further include a process of applying pressure to the separator after at least some of the pore-inducing particles are removed and the porous coating is dried.

[0101] That is, in the embodiments of this disclosure, after step S40, the method may further include: step (S41) applying a pressure of 0.5 MPa to 20 MPa to the partition at a temperature of 20°C to 85°C for 1 second to 60 seconds. Specifically, step S41 may be performed at a pressure of 0.5 MPa to 20 MPa, 1 MPa to 10 MPa, or 2 MPa to 8 MPa and a temperature of 20°C to 85°C, 25°C to 80°C, or 25°C to 70°C. In this case, the process for manufacturing the partition can be simplified by omitting the drying step (S21).

[0102] <Partition>

[0103] This disclosure provides a separator for an electrochemical device.

[0104] Specifically, the separator includes a porous polymer substrate and a porous coating present on at least one surface of the porous polymer substrate, the porous coating including inorganic particles and particulate binder, wherein the porous coating includes pores formed by removing at least some pore-inducing particles by an etching solution.

[0105] Porous coatings can include pores inside the surface and pores on the surface, and some pores can be formed by removing pore-induced particles with an etching solution.

[0106] In embodiments of this disclosure, pores formed by removal with an etching solution can be formed at the contact points between pore-inducing particles and inorganic particles or particulate adhesive polymers.

[0107] In embodiments of this disclosure, the porous coating may have pores or vacancy formed by the contact between inorganic particles and particulate binder, or a portion of the porous coating may have pores or vacancy formed by inducing particles through etching pores.

[0108] The porous coating has pores formed by removing at least some pore-inducing particles with an etching solution, and in this case, the etching solution does not remove inorganic particles, but only removes pore-inducing particles to create pores, resulting in a higher pore ratio and a higher inorganic particle ratio than a porous coating that does not contain pore-inducing particles.

[0109] In embodiments of this disclosure, the porosity of the separator can be from 10% to 50% by volume. The porosity of the separator can be determined by the pore size of the porous polymer substrate and the pore size of the porous coating.

[0110] In this disclosure, the electrochemical device includes any device involving an electrochemical reaction, and specific examples include any type of primary battery, secondary battery, fuel cell unit, solar cell unit, or capacitor, such as a supercapacitor device. In this disclosure, the electrochemical device may preferably include a secondary battery, and more preferably a lithium-ion secondary battery.

[0111] Lithium-ion secondary batteries

[0112] This disclosure provides a lithium-ion secondary battery.

[0113] The lithium-ion secondary battery disclosed herein includes a positive electrode; a negative electrode; an electrolyte solution; and a separator inserted between the positive electrode and the negative electrode, wherein the separator comprises a separator manufactured by the method described above for manufacturing a separator.

[0114] In embodiments of this disclosure, a positive electrode can be manufactured by coating a positive electrode composition comprising a positive electrode active material, a binder, a conductive material, and a solvent onto a positive electrode current collector.

[0115] The positive electrode active material may include any positive electrode active material commonly used in the positive electrode of an electrochemical device. For example, the positive electrode active material may include lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or lithium composite oxides thereof.

[0116] In this case, based on the total weight of the solid content of the cathode composition, the content of the cathode active material can be from 80 wt% to 99 wt%, preferably from 85 wt% to 98 wt%. When the amount of cathode active material falls within the above range, improved capacity characteristics can be provided.

[0117] The positive electrode current collector is not limited to a specific current collector and can include any material that is conductive without causing a chemical change in the corresponding battery. For example, the positive electrode current collector can include stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treated with carbon, nickel, titanium, or silver.

[0118] Adhesives are used to help hold the active and conductive materials together and bond them to the current collector, and are typically added in amounts from 1% to 30% by weight based on the total solid weight of the cathode composition. Examples of adhesives may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, or various copolymers.

[0119] Conductive materials can typically be added in amounts ranging from 1% to 30% by weight based on the total solid weight of the positive electrode composition.

[0120] Conductive materials are not limited to a specific type and can include any material that is conductive without causing chemical changes in the corresponding battery. Conductive materials can include, for example, graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lampblack, or pyrolytic black; conductive fibers such as carbon fibers or metal fibers; fluorocarbons; metal powders such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide whiskers or potassium titanate whiskers; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives. Specific examples of commercially available conductive materials include acetylene black from Chevron Chemical Company or Denka Singapore Private Limited, products from Gulf Oil Company, Ketjen black, EC series (from Armak Company), Vulcan XC-72 (from Cabot Company), and Super P (Timcal).

[0121] In addition, if desired, the positive electrode active material layer may optionally also include a dispersant.

[0122] The dispersant is not limited to a specific type and can include any dispersant for the positive electrode, and, for example, aqueous dispersants or organic dispersants can be selectively used as needed. Preferably, the dispersant may include any of the following: cellulose-based compounds, polyepoxides, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetal, polyvinyl ether, polyvinyl sulfonic acid, polyvinyl chloride (PVC), polyvinylidene fluoride, chitosan, starch, amylose, polyacrylamide, poly-N-isopropylacrylamide, poly-N,N-dimethylacrylamide, polyethyleneimine, polyoxyethylene, poly(2-methoxyethoxyethylene), poly(acrylamide-co-diallyldimethylammonium chloride), acrylonitrile / butadiene / styrene (ABS) polymers, acrylonitrile / styrene / acrylate (ASA) polymers, mixtures of acrylonitrile / styrene / acrylate (ASA) polymers and propylene carbonate, styrene / acrylonitrile (SAN) copolymers, methyl methacrylate / acrylonitrile / butadiene / styrene (MABS) polymers, styrene-butadiene rubber, nitrile rubber, and fluororubber, or mixtures of two or more thereof. Hydrogenated nitrile rubber (H-NBR) may be used. When the positive electrode active material layer also includes a dispersant, the dispersion of the components (especially conductive materials) of the positive electrode active material layer can be improved, but is not limited to this.

[0123] Furthermore, the solvent may include any solvent commonly used in the relevant technical field, and may include, for example, any one of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, or a mixture of two or more of them. Considering the coating thickness and production yield of the slurry, a sufficient amount of solvent is used to dissolve or disperse the positive electrode active material, conductive material, and binder, and the viscosity is varied to achieve high thickness uniformity in subsequent coating processes to manufacture the positive electrode.

[0124] The negative electrode according to this disclosure can be manufactured by coating a negative electrode composition comprising a negative electrode active material, a binder, a conductive material, and a solvent onto a negative electrode current collector. Furthermore, if desired, the negative electrode composition may optionally also include a dispersant.

[0125] The negative electrode active material may include compounds capable of reversibly inserting and deintercalating lithium. Preferably, the negative electrode may also include a negative electrode active material exhibiting high capacity characteristics, such as silicon-based negative electrode active materials; carbon-based negative electrode active materials; and metal composite oxides, such as Li. x Fe2O3 (0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me'y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2 and 3 elements in the periodic table, halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8); lithium metal; lithium alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4 and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxides; or lithium titanium oxides. The silicon-based negative electrode active material may include at least one selected from the group consisting of: Si, SiO x (0.1 < x < 5), Si-metal alloy, silicon oxide particles doped with metal or chemically bonded with metal (such as Mg(SiO x , 0.1 < x < 5) and Si-SiO x alloy (0.1 < x < 5)). The carbon-based negative electrode active material may include at least one selected from the group consisting of: natural graphite, artificial graphite, amorphous hard carbon, low-crystallinity soft carbon, carbon black, acetylene black, Ketjen black, Super P, graphene, and fibrous carbon.

[0126] The negative electrode current collector is not limited to a specific type and may include any material having high conductivity without causing chemical changes in the battery, and for example, may include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or copper or stainless steel surface-treated with carbon, nickel, titanium or silver, or aluminum cadmium alloy. In addition, the thickness of the negative electrode current collector can generally be 3 μm to 500 μm, and in the same manner as the positive electrode current collector, the negative electrode current collector can have a micro-textured surface to increase the bonding strength of the negative electrode active material. The negative electrode current collector can appear in different forms, such as film, sheet, foil, mesh, porous body, foam or non-woven fabric.

[0127] The conductive material, binder, solvent or dispersant contained in the negative electrode composition is not limited to a specific one and may include any one commonly used in the electrode composition, and for example, may include the above conductive material, binder, solvent or dispersant in the positive electrode composition.

[0128] In addition, the lithium secondary battery may further include an electrolyte solution. The electrolyte solution may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte for manufacturing a lithium secondary battery, but is not limited thereto.

[0129] Specifically, the electrolyte solution may include organic solvents and lithium salts.

[0130] Organic solvents are not limited to a specific type and can include any organic solvent that acts as a medium for the movement of ions involved in the electrochemical reactions used in the battery. Specifically, organic solvents can include: ester solvents, such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; ether solvents, such as dibutyl ether or tetrahydrofuran; ketone solvents, such as cyclohexanone; aromatic hydrocarbon solvents, such as benzene or fluorobenzene; carbonate solvents, such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), or propylene carbonate (PC); alcohol solvents, such as ethanol or isopropanol; and nitriles, such as R-CN. (R is a C2 to C20 straight-chain hydrocarbon, branched hydrocarbon, or cyclic hydrocarbon, and may include exocyclic double bonds or ether bonds); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane; or sulfolane. Preferably, a carbonate-based solvent is used, more preferably a mixture of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant, and low-viscosity straight-chain carbonate-based compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) that helps improve the charge / discharge performance of the battery. In this case, when the cyclic carbonate and straight-chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte solution can exhibit high performance.

[0131] Lithium salts are not limited to a specific type and can include any compound capable of providing lithium ions for use in lithium secondary batteries. Specifically, lithium salts may include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of lithium salts can range from 0.1 M to 2.0 M. When the concentration of lithium salts falls within the above range, the electrolyte solution can have optimal conductivity and viscosity, resulting in high performance of the electrolyte solution and efficient movement of lithium ions.

[0132] In addition to the components described above, the electrolyte solution may also include, for example, at least one type of additive: halogenated olefin carbonate-based compounds, such as ethylene difluorocarbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether, triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolides, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol, or aluminum trichloride, to improve battery life characteristics, prevent battery capacity decay, and improve battery discharge capacity. In this case, the additive content may be from 0.1 parts by weight to 5 parts by weight based on the total weight of 100 parts by weight of the electrolyte solution.

[0133] The present disclosure will be described in more detail below by way of examples, but the following examples are intended to illustrate the present disclosure by way of example and the scope of the present disclosure is not limited thereto.

[0134] <Example 1>

[0135] Alumina (Al2O3, D) will be used as inorganic particles. 50 : 450nm, Sumitomo) and silica (SiO2, D) as pore-inducing particles 50 Add 100nm) to water at room temperature and stir evenly, and add acrylic granular binder (polyacrylate, Tg: 40℃, D: 100nm) at a 1:1 weight ratio. 50 (400nm) and fluorinated particulate adhesives (PVDF, Tg: 40℃, D 50 A separator coating slurry composition was prepared using particles with a density of 400 nm. The solid content of the separator coating slurry composition was 35% by weight. Furthermore, the weight ratio of inorganic particles: acrylic particulate binder: fluorine-based particulate binder: pore-inducing particles was 85:5:5:5.

[0136] The separator coating slurry composition was applied to both surfaces of a polyethylene substrate (thickness: 12 μm, porosity: 70 vol%) using a doctor blade, followed by solvent drying to form a porous coating. After drying, the porous coating had a thickness of approximately 5.0 μm on one side.

[0137] Subsequently, the separator with the porous coating was immersed in hydrogen fluoride (concentration: 35%) as an etching solution for 10 minutes to remove pore-induced particles (SiO2), and ethanol was added for washing. After washing, it was dried at 60°C for 2 hours to produce a separator with a thickness of approximately 22 μm.

[0138] <Comparative Example 1>

[0139] Alumina (Al2O3, D) will be used as inorganic particles. 50 Add 450nm, Sumitomo) to water at room temperature and stir evenly, and add acrylic granular binder (polyacrylate, Tg: 40℃, D) at a 1:1 weight ratio. 50 (400nm) and fluorinated particulate adhesives (PVDF, Tg: 40℃, D 50 A separator coating slurry composition was prepared by means of inorganic particles (400 nm). The solid content of the separator coating slurry composition was 35% by weight. In addition, the weight ratio of inorganic particles: acrylic particulate adhesive: fluorine-based particulate adhesive was 90:5:5.

[0140] The separator coating slurry composition was applied to both surfaces of a polyethylene substrate (thickness: 12 μm, porosity: 70 vol%) using a doctor blade, followed by solvent drying to form a porous coating. After drying, the porous coating had a thickness of approximately 5.0 μm on one side.

[0141] <Experimental Example>

[0142] <Experimental Example 1: Evaluation of the wettability of separators>

[0143] LiCoO2 (as the positive electrode active material), carbon black (as the conductive material), and polyvinylidene fluoride (PVdF) (as the binder) were added to N-methylpyrrolidone (NMP) (as the solvent) in a weight ratio of 96:2:2 to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a sheet aluminum current collector and dried to prepare a sample with a capacitance of 4.0 mAh / cm³. 2 The final positive charge of the positive electrode.

[0144] The separators from Example 1 and Comparative Example 1 were placed on the prepared positive electrodes, and transparent PET films were stacked on the separators. The laminates were then subjected to a pressure of 6.5 MPa for 1 second at 70°C to generate a laminate. Subsequently, 1 M LiPF6 was dissolved in an organic solvent (EC:DEC = 1:1 (v:v)) to prepare a non-aqueous electrolyte solution, and the laminate was filled with this electrolyte solution for wettability testing. Imaging was then performed on the transparent PET side, and the ratio of the wetted area to the total area was calculated. The results are shown below. Figure 1a and Figure 1b middle.

[0145] according to Figure 1a In Example 1, the partition was completely wetted to the core, but according to Figure 1b In Comparative Example 1, only the outer area of ​​the partition was wetted, and the wetted area was 50% of the total area. That is, it was confirmed that the partition of Example 1 had enhanced wettability by removing at least some pore-induced particles with the etching solution.

[0146] <Experimental Example 2: Surface analysis of separators>

[0147] The surfaces of the separators in Example 1 and Comparative Example 1 were measured using a scanning electron microscope (SEM, Hitachi). The measured separator surfaces were analyzed using an IAM (Image Analysis Management, LG New Energy) program to determine particle shape in order to identify inorganic particles, pores, acrylic granular adhesives, and fluorine-based granular adhesives, and then masked. Figure 2a and 2b The diagram shows the areas occupied by inorganic particles, pores, acrylic granular adhesive, and fluoropolymer granular adhesive on the surface, respectively. In this case, pores are represented in red, acrylic granular adhesive in dark green, fluoropolymer granular adhesive in light green, and inorganic particles in gray.

[0148] Figure 2a These are SEM images of the surface of the partition in Example 1 and IAM-assisted masking images of inorganic particles, pores, acrylic granular adhesive, and fluoropolymer granular adhesive. According to... Figure 2a The surface area ratio of pores: acrylic granular adhesive: fluorine-based granular adhesive: inorganic material was confirmed to be 6.5:45.5:30.5:17.6.

[0149] Figure 2b This is a SEM image of the surface of the partition in Comparative Example 1, and IAM-assisted masking images of inorganic particles, pores, acrylic granular adhesive, and fluoropolymer granular adhesive. According to... Figure 2b The surface area ratio of pores: acrylic granular adhesive: fluorine-based granular adhesive: inorganic material was confirmed to be 2.5: 55.7: 34.6: 7.2.

[0150] It was confirmed that at least some pore-induced particles were removed by etching solution, and the partition of Example 1 had a higher porosity and a higher inorganic material ratio on the surface compared to Comparative Example 1.

[0151] <Experimental Example 3: Measurement of permeability>

[0152] The permeability of the partitions in Example 1 and Comparative Example 1 was measured. Specifically, the air permeation time of each example and comparative example was determined by measuring the time (in seconds) it took for 100 ml of air to pass through the partition using a permeability measuring instrument (manufacturer: Asahi Seiko, model: EG01-55-1MR). Measurements were taken at three points on the sample (i.e., left point / middle point / right point), and the average value was recorded.

[0153] As a result, the permeation rate of the partition in Example 1 was 70 seconds / 100cc, while the permeation rate of the partition in Comparative Example 1 was 60 seconds / 100cc. That is, it was confirmed that the air permeation time of the partition in Example 1 was shorter than that of Comparative Example 1, and that the partition in Example 1 had a higher permeation rate.

[0154] <Other measurement methods>

[0155] <Measurement of glass transition temperature>

[0156] The glass transition temperature was measured using differential scanning calorimetry (DSC). The DSC measurement of the glass transition temperature was performed using a Discovery DSC 250 from TA Instruments, measuring the heat generated by the temperature change over a range of -80°C to 300°C. Specifically, the sample was subjected to a temperature change at a rate of 10°C / min, following the sequence of first heating → first cooling → second heating: 25°C (start) → 250°C (first heating) → -80°C (first cooling) → 300°C.

Claims

1. A method for manufacturing a partition, the method comprising the following steps: (S10) Prepare a separator coating slurry composition comprising pore-inducing particles, inorganic particles, particulate binder and solvent; (S20) The separator coating slurry composition is applied to at least one surface of a porous polymer substrate to form a porous coating; (S30) Remove at least some of the pore-inducing particles of the porous coating by an etching solution; and (S40) Dry the porous coating from which at least some of the pore-inducing particles have been removed.

2. The method for manufacturing a partition according to claim 1, The pore-inducing particles are materials that react with the etching solution.

3. The method for manufacturing a partition according to claim 1, The pore-inducing particles include silicon dioxide (SiO2), titanium dioxide (TiO2), zirconium oxide (ZrO2), or two or more of them.

4. The method for manufacturing a partition according to claim 1, The etching solution includes hydrogen fluoride, sodium hydroxide, potassium hydroxide, nitric acid, hydrogen peroxide, carbonic acid, or two or more of these.

5. The method for manufacturing a partition according to claim 1, In step (S10), based on 100 parts by weight of the inorganic particles, the amount of the pore-inducing particles in the partition coating slurry composition is 20 to 90 parts by weight.

6. The method for manufacturing a partition according to claim 1, The D of the pore-induced particles 50 The range is from 20nm to 500nm.

7. The method for manufacturing a partition according to claim 1, The granular adhesives mentioned above include acrylic granular adhesives, fluoropolymer granular adhesives, or combinations thereof.

8. The method for manufacturing a partition according to claim 1, The glass transition temperature (Tg) of the particulate adhesive is 40°C to 80°C.

9. The method for manufacturing a partition according to claim 1, The D of the granular adhesive 50 The range is from 150 nm to 1 μm.

10. The method for manufacturing a partition according to claim 1, The porous polymer substrate includes polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, or two or more thereof.

11. The method for manufacturing a partition according to claim 1, Step (S20) further includes: Step (S21): After applying the separator coating slurry composition to at least one surface of the porous polymer substrate, the solvent in the separator coating slurry composition is dried.

12. The method for manufacturing a partition according to claim 11, further comprising, after step (S21): Step (S22) involves applying a pressure of 0.5 MPa to 20 MPa to the partition at a temperature of 20°C to 85°C for 1 to 60 seconds.

13. The method for manufacturing a partition according to claim 1, further comprising, after step (S40): Step (S41) involves applying a pressure of 0.5 MPa to 20 MPa to the partition at a temperature of 20°C to 85°C for 1 to 60 seconds.

14. A partition manufactured by the method for manufacturing a partition as defined in claim 1, the partition comprising: The porous polymer substrate; and The porous coating present on at least one surface of the porous polymer substrate, the porous coating comprising the inorganic particles and the particulate binder, The porous coating comprises pores formed by removing at least some of the pore-inducing particles through the etching solution.

15. The partition according to claim 14, The porosity of the partition is 10% to 50% by volume.

16. A lithium secondary battery, comprising: Positive electrode; negative electrode; electrolyte solution; and a separator inserted between the positive electrode and the negative electrode. The partition is the partition defined in claim 14.

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