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

Abstract

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

Description

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

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

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0065882, filed May 21, 2024, the entire contents of which are incorporated herein by reference.

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

[0004] The fundamental requirements for separators in lithium secondary batteries are to electrically isolate the positive and negative electrodes, while simultaneously enhancing ionic conductivity by enhancing the permeability of ions, such as lithium ions, through high porosity. While these separators themselves do not participate in the electrochemical reactions of secondary batteries, their physical properties, such as wettability to electrolytes, porosity, and thermal shrinkage, significantly impact the performance and safety of the battery.

[0005] However, membranes using porous polymer substrates have the risk of internal short-circuiting due to shrinkage of the membrane at high temperatures, and the risk of ignition due to melting of the polymer membrane substrate during thermal runaway. Accordingly, to compensate for the shortcomings of porous polymer substrates, methods have been proposed that include adding a porous coating layer to one or both sides of the porous polymer substrate and adding inorganic particles and a binder to the porous coating layer that can compensate for the shortcomings of the porous polymer substrate.

[0006] Meanwhile, the binder included in the porous coating layer can be distinguished into a particulate binder and a soluble binder depending on whether it dissolves in a solvent. In the case of a soluble binder, when applying a slurry for forming a porous coating layer to the surface of a porous substrate, there is a concern that the soluble binder may flow into the surface through the pores of the porous substrate, thereby clogging the pores of the porous substrate. To improve this phenomenon, a technology using a particulate binder has been proposed. However, during the pressurizing process of laminating the negative electrode, the positive electrode, and the separator between the negative and positive electrodes and applying heat and pressure, the particulate binder in the porous coating layer may lose its shape or become a film. At this time, the binder may block the pores within the porous coating layer or the pores of the porous polymer substrate, resulting in a problem of reduced porosity and wettability of the separator with respect to the electrolyte. Therefore, there is a need for a method for manufacturing a separator having excellent adhesive strength and excellent ionic conductivity and wettability to an electrolyte using a particle-type binder as a binder, and a separator manufactured thereby.

[0007] The present invention was developed to solve the above-described technical problem, and specifically, the purpose is to provide a method for manufacturing a separator having excellent wettability to an electrolyte even when a particle-type binder is included in a porous coating layer, a separator manufactured therefrom, and a lithium secondary battery including the same.

[0008] Another object of the present invention is to provide a lithium secondary battery having excellent wettability and air permeability by introducing pores of various sizes.

[0009] To achieve this purpose, according to one aspect of the present invention, a negative electrode, a method for manufacturing the negative electrode, and a lithium secondary battery including the same are provided.

[0010] According to a first embodiment, a method for manufacturing a separator is provided, comprising the steps of (S10) preparing a slurry composition for coating a membrane including pore-inducing particles; inorganic particles; a particulate binder and a solvent; (S20) applying the slurry composition for coating a membrane on at least one surface of a porous polymer substrate to form a porous coating layer; (S30) removing at least a portion of the pore-inducing particles of the porous coating layer with an etchant; and (S40) drying the porous coating layer from which at least a portion of the pore-inducing particles have been removed.

[0011] According to a second embodiment, in the first embodiment, the pore-inducing particles may be a material that reacts with the etching solution.

[0012] According to a third embodiment, in any one of the first to second embodiments, the pore-inducing particles may include silica (SiO2), titania (TiO2), zirconia (ZrO2), or two or more thereof.

[0013] According to a fourth embodiment, in any one of the first to third embodiments, the etchant may include hydrogen fluoride, sodium hydroxide, potassium hydroxide, nitric acid, hydrogen peroxide, carbonic acid, or two or more thereof.

[0014] According to a fifth embodiment, in any one of the first to fourth embodiments, in the step (S10), the content of the pore-inducing particles in the slurry composition for membrane coating may be 20 to 90 parts by weight based on 100 parts by weight of the inorganic particles.

[0015] According to the sixth embodiment, in any one of the first to fifth embodiments, the D of the pore-inducing particles 50 may be between 20 nm and 500 nm.

[0016] According to a seventh embodiment, in any one of the first to sixth embodiments, the particulate binder may be an acrylic particulate binder, a fluorine-based particulate binder, or a combination thereof.

[0017] According to the eighth embodiment, in any one of the first to seventh embodiments, the glass transition temperature (Tg) of the particulate binder may be 40°C to 80°C.

[0018] According to the ninth embodiment, in any one of the first to eighth embodiments, D of the particle-type binder 50 may be 150 nm to 1 μm.

[0019] According to a tenth embodiment, in any one of the first to ninth embodiments, the porous polymer substrate may include polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, or two or more thereof.

[0020] According to the eleventh embodiment, in any one of the first to tenth embodiments, in step (S20), after applying the membrane coating layer slurry composition on at least one surface of the porous polymer substrate (S21), a step of drying the solvent in the slurry composition may be further included.

[0021] According to the 12th embodiment, in any one of the 11th embodiments, after step (S21), the method may further include a step (S22) of pressurizing the separation membrane under conditions of a pressure of 0.5 MPa to 20 MPa and a temperature of 20°C to 85°C for 1 second to 60 seconds.

[0022] According to the 13th embodiment, in any one of the first to twelfth embodiments, after step (S40), the method may further include a step (S41) of pressurizing the separation membrane under conditions of a pressure of 0.5 MPa to 20 MPa and a temperature of 20°C to 85°C for 1 second to 60 seconds.

[0023] According to a 14th embodiment, a separation membrane manufactured by the method of manufacturing a separation membrane according to any one of the 1st to 13th embodiments is provided, comprising: a porous polymer substrate; and a porous coating layer positioned on at least one surface of the porous polymer substrate and including inorganic particles and a particle-type binder; wherein the porous coating layer includes pores formed by removing at least a portion of pore-inducing particles by an etchant.

[0024] According to the 15th embodiment, in the 14th embodiment, the porosity of the separation membrane may be 10 to 50 volume%.

[0025] According to a 16th embodiment, a lithium secondary battery is provided, comprising: a positive electrode; a negative electrode; an electrolyte; and a separator interposed between the positive electrode and the negative electrode, wherein the separator is a separator according to any one of the 14th to 15th embodiments.

[0026]

[0027] According to one embodiment of the present invention, a separator has a higher porosity than a separator using a conventional particle-type binder because pores are formed in a location where pore-inducing particles have been removed even if a particle-type binder is included in the porous coating layer, and thus the separator can have excellent wettability with respect to an electrolyte.

[0028] A separator according to one embodiment of the present invention may have excellent wettability and air permeability for an electrolyte by introducing pores of various sizes into a porous coating layer.

[0029] Figure 1a is a photograph showing a wettability test performed on the separator of Example 1.

[0030] Figure 1b is a photograph showing a wettability test performed on the separator of Comparative Example 1.

[0031] Figure 2a is an SEM image of the surface of the membrane of Example 1 and an image of the inorganic particles, pores, acrylic particle-type binder, and fluorine particle-type binder masked using an IAM program, respectively.

[0032] Figure 2b is an SEM image of the surface of the membrane of Comparative Example 1 and an image in which the inorganic particles, pores, acrylic particle-type binder, and fluorine particle-type binder are each masked using an IAM program.

[0033] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0034] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0035] Justice

[0036] Throughout this specification, when it is said that a part "includes" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0037] D in the original specification 50 D means the particle size at the 50% point of the cumulative distribution of particle numbers according to particle size. That is, D 50 refers to the particle size at the 50% point of the cumulative distribution of particle numbers according to particle size. In addition, D 10 D means the particle size at the 10% point of the cumulative distribution of particle numbers according to particle size. 90 refers to the particle size at the 90% point of the cumulative distribution of particle numbers according to particle size.

[0038] The above particle size can be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium, and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), and the difference in diffraction pattern according to particle size is measured when the particles pass through the laser beam to calculate the particle size distribution. By calculating the particle diameters at points where the number of particles is 10%, 50%, and 90% of the cumulative distribution according to particle size in the measuring device, D is calculated, respectively. 10 , D 50 and D 90 can be measured.

[0039] Certain terminology used in the following detailed description of the invention is for convenience only and is not intended to be limiting. The words "left," "right," "upper," and "lower" may indicate direction in the drawings to which reference is made and should not be construed as limiting. These terms include the words listed above, their derivatives, and words of similar meaning.

[0040]

[0041] <Method for manufacturing a separation membrane>

[0042] The present invention provides a method for manufacturing a separator for an electrochemical device.

[0043] According to one aspect of the present invention, a method for manufacturing a separation membrane of the present invention comprises the steps of (S10) preparing a slurry composition for separation membrane coating comprising pore-inducing particles; inorganic particles; a particulate binder and a solvent; (S20) applying the slurry composition for separation membrane coating onto at least one surface of a porous polymer substrate to form a porous coating layer; (S30) removing at least a portion of the pore-inducing particles of the porous coating layer with an etchant; and (S40) drying the porous coating layer from which at least a portion of the pore-inducing particles have been removed.

[0044] Below, we will examine the membrane manufacturing method in detail step by step.

[0045] First, a slurry composition for membrane coating is prepared, including (S10) pore-inducing particles; inorganic particles; a particle-shaped binder and a solvent.

[0046] In one embodiment of the present invention, the pore-inducing particles may be a material that can be included in a slurry composition for membrane coating, applied onto a porous polymer substrate, and then removed by reacting with an etchant.

[0047] In one embodiment of the present invention, the pore-inducing particles have a property of being dissolved in an etchant described below, and may be organic particles and / or ceramic particles. The pore-inducing particles may be ceramic particles. The ceramic particles are not particularly limited as long as they are dissolved and removed in an etchant, but may include, for example, silica (SiO2), titania (TiO2), zirconia (ZrO2), or two or more thereof. The solid-state pore-inducing particles may chemically react with a liquid-state etchant, for example, through a wet etching reaction, to generate an ionic product, and by removing the product through washing, an empty space may be provided as pores after the product is removed.

[0048] In one embodiment of the present invention, the etchant may include hydrogen fluoride, sodium hydroxide, potassium hydroxide, nitric acid, hydrogen peroxide, carbonic acid, or two or more thereof. In this case, the etching rate may vary depending on the type and combination of the etchant.

[0049]

[0050] For example, in one embodiment of the present invention, when silica (SiO2) is used as the pore-inducing particle and hydrogen fluoride (HF) is used as the etchant, a reaction as shown in Equation 1 below may proceed.

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

[0052]

[0053] For example, in one embodiment of the present invention, when silica (SiO2) is used as the pore-inducing particle and sodium hydroxide (NaOH) is used as the etchant and this is performed with heating, a reaction as shown in Equation 2 below may occur.

[0054] SiO2(s) + 2 NaOH(aq) → Na2SiO3(aq) + H2O(l) … Equation (2)

[0055]

[0056] In one embodiment of the present invention, the content of the pore-inducing particles in the slurry composition for membrane coating may be 20 to 90 parts by weight, or 30 to 80 parts by weight, based on 100 parts by weight of the inorganic particles. When the content of the pore-inducing particles satisfies the above-described range, the manufactured membrane may have excellent thermal properties, high porosity, and excellent ionic conductivity. In addition, when the content of the pore-inducing particles satisfies the above-described range, the inorganic particles in the porous coating layer maintain a mechanical skeletal structure with each other, so that the structure of the porous coating layer does not collapse even when subjected to external pressure such as pressurization, and the pores by the pore-inducing particles can be maintained.

[0057] In one embodiment of the present invention, the size (D) of the pore-inducing particles 50 ) has no limitations as long as it can perform the role of pores of the separation membrane without destroying the structure of the porous coating layer.

[0058] In one embodiment of the present invention, the size (D) of the pore-inducing particles 50 ) can control the pore size by appropriately selecting it within the desired range.

[0059] In one embodiment of the present invention, the D of the pore-inducing particles 50The pore-inducing particles may be 20 nm to 500 nm, or 50 nm to 200 nm. When the pore-inducing particles satisfy the above-described range, the dispersibility within the slurry composition for membrane coating is excellent, and the porosity of the manufactured membrane may be appropriate.

[0060] In one embodiment of the present invention, the size of the pores generated by the pore-inducing particles may be substantially the same as the pore-inducing particles. That is, the size of the pores induced by the pore-inducing particles may be within a range of 80% to 120% by volume, within a range of 90% to 110% by volume, within a range of 95% to 105% by volume, or within a range of 98% to 102% by volume, based on 100% by volume of the pore-inducing particles. In other words, when the pore-inducing particles are used, the size of the pores in the separation membrane can be controlled.

[0061] In one embodiment of the present invention, the porous coating layer preferably has uniform pore sizes so that the separator has uniform ionic conductivity across its entire surface. Accordingly, it is preferable that the pore-inducing particles included in the porous coating layer have uniform sizes, and at the same time, it is preferable that the pore-inducing particles have the above-described average particle diameter. Furthermore, the more uneven the sizes of the pore-inducing particles are, the more difficult it is to ensure uniform thickness of the porous coating layer.

[0062] In one embodiment of the present invention, the pore-inducing particles preferably have a monomodal particle size distribution. In the present specification, monomodal can be defined as a standard deviation within a range of 1% to less than 40%, preferably 1% to 35%, when analyzed using a particle size analyzer (Dynamic Light Scattering: DLS, Nicomp 380). Bimodal or multimodal may be a case where the standard deviation is 40% or more when confirming the size and distribution of particles using the particle size analyzer. When the standard deviation is 40% or more, two or more particle size peaks may appear.

[0063]

[0064] In a specific embodiment of the present invention, the inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention are not particularly limited as long as they do not undergo oxidation and / or reduction reactions within the operating voltage range of the applied electrochemical device (e.g., 0 to 5 V based on Li / Li+). In particular, when inorganic particles having a high dielectric constant are used as the inorganic particles, they can contribute to increasing the degree of dissociation of electrolyte salts, such as lithium salts, in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte.

[0065] For the reasons mentioned above, it is preferable that the inorganic particles include high-k inorganic particles having a dielectric constant of 5 or more, preferably 10 or more. Non-limiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT, 0 <x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3)O3-PbTiO3(PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC and TiO2 or mixtures thereof.

[0066] In addition, as the inorganic particles, inorganic particles having lithium ion transfer capability, i.e., inorganic particles containing lithium elements but having the function of transferring lithium ions without storing lithium, can be used. Non-limiting examples of inorganic particles having lithium ion transfer capability include lithium phosphate (Li3PO4), lithium titanium phosphate (LixTiy(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), 14Li2O-9Al2O3-38TiO2-39P2O5, etc. (LiAlTiP) x O y Series Glass (0 <x < 4, 0 < y < 13), 리튬란탄티타네이트(Li x La y TiO3, 0 < x < 2, 0 < y < 3), Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate (Li) such as S4 x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li 3 N ), etc. x N y , 0 < x <4, 0 < y < 2), SiS2 series glasses such as Li3PO4-Li2S-SiS2 (Li x Si y S z, 0 < x < 3, 0 <y < 2, 0 < z < 4), LiI-Li2S-P2S5등과 같은 P2S5계열 글래스(Li x P y S z , 0 < x < 3, 0< y < 3, 0 < z < 7) or mixtures thereof.

[0067] In one embodiment of the present invention, in the porous coating layer, inorganic particles are filled and in contact with each other and are bound to each other by the particle-shaped binder, thereby forming an interstitial volume between the inorganic particles, and the interstitial volume between the inorganic particles becomes an empty space to form pores.

[0068] That is, the particle-type binder can attach the inorganic particles to each other so that they can remain bound to each other, for example, the particle-type binder can connect and fix the inorganic particles together. In addition, the pores of the porous coating layer are pores formed by the interstitial volume between the inorganic particles becoming empty spaces, and these can be spaces defined by the inorganic particles actually meeting in a closely packed or densely packed structure by the inorganic particles.

[0069] In one embodiment of the present invention, the porous coating layer may not collapse in structure even when the separator is subjected to external pressure due to the bonding structure of the inorganic particles.

[0070] In one embodiment of the present invention, the porous coating layer of the present invention may have a mixed interstitial volume defined by inorganic particles substantially interfacing with the filling structure of the inorganic particles and pores formed by the removal of pore-inducing particles.

[0071] In addition, the average particle size of the inorganic particles is not particularly limited, but is preferably in the range of 0.1 µm to 1.5 µm for the formation of a coating layer of uniform thickness and an appropriate porosity. If it is less than 0.1 µm, dispersibility may be reduced, and if it exceeds 1.5 µm, the thickness of the formed inorganic coating layer may increase.

[0072] In one embodiment of the present invention, the inorganic particles may be included in an amount of 50 wt% or more relative to a total solid content of 100 wt% of the slurry composition for membrane coating, for example, in a range of 50 to 97 wt%, or 50 to 95 wt%, or 50 to 90 wt%.

[0073]

[0074] In one embodiment of the present invention, the particulate binder may have a property of maintaining its original particle shape without deformation even when dispersed in a solvent. Specifically, the particulate binder may mean that it exists in a particle state in an aqueous solvent. Specifically, the particulate binder may mean that it has low solubility in an aqueous solvent and thus has a form that is dispersed in the aqueous solvent in a particle form.

[0075] In one embodiment of the present invention, the particulate binder may be an acrylic particulate binder, a fluorine-based particulate binder, or a combination thereof.

[0076] In one embodiment of the present invention, when the particulate binder includes an acrylic particulate binder and a fluorine-based particulate binder, the weight ratio of the acrylic particulate binder and the fluorine-based particulate binder may be 1:99 to 99:1, 10:90 to 90:10, or 20:80 to 80:20. When the weight ratio of the acrylic particulate binder and the fluorine-based particulate binder satisfies the above-described range, the adhesive strength of the separator in a state of being immersed in an electrolyte (wet adhesive strength) and the adhesive strength of the separator in a dry state (dry adhesive strength) may be excellent.

[0077] In one embodiment of the present invention, the acrylic particle-type binder may include, for example, an acrylic homopolymer polymerized only with an acrylic monomer, or may include a copolymer of an acrylic monomer and another monomer. For example, the acrylic particle-type binder is poly(methylmethacrylate), poly(ethylexyl acrylate), poly(butylacrylate), poly(acrylonitrile), a copolymer of ethylhexyl acrylate and methyl methacrylate, a copolymer of butylacrylate and methyl methacrylate, an ethyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, an ethyl acrylate-acrylic acid-2-(dimethylamino)ethyl acrylate copolymer, an ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, It may include an ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer or a mixture of two or more thereof.

[0078] In one embodiment of the present invention, the fluorine-based particle-type binder may include, for example, a polyvinylidene fluoride (PVDF) homopolymer, or a copolymer of vinylidene fluoride and another monomer. For example, the fluorine-based particle-type binder may include a copolymer of a repeating unit derived from vinylidene fluoride and one or two or more derived repeating units selected from trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), trichloroethylene (TrCE), trichlorofluoroethylene (TCFE), chlorotrifuloroethylene (CTFE), polymethylmethacrylate (PMMA), and polyvinylacetate (PVAc), or a mixture of two or more thereof.

[0079]

[0080] In one embodiment of the present invention, the glass transition temperature (Tg) of the particulate binder may be 40°C to 80°C, or 50°C to 70°C. The glass transition temperature (Tg) may represent a value measured by, for example, a dynamic mechanical analysis (DMA) or DSC (TA Instrument) equipment. For example, the glass transition temperature may represent a value measured according to the DMA method specified in ASTM D4065. When the particulate binder has the above-described glass transition temperature, the binder in the form of particles may collapse under certain temperature and pressure conditions during the manufacture of the separation membrane, thereby forming a film.

[0081] In one embodiment of the present invention, D of the particle-shaped binder 50 The size of the particle-shaped binder may be 150 nm to 1 μm or 200 nm to 800 nm. When the size of the particle-shaped binder satisfies the above-described range, the adhesion and porosity of the membrane may be better.

[0082] In one embodiment of the present invention, the content of the particulate binder in the slurry composition for membrane coating may be 20 to 80 parts by weight based on 100 parts by weight of inorganic particles. When the content of the particulate binder satisfies the above-described range, the adhesive strength of the manufactured electrode may be better.

[0083]

[0084] In one embodiment of the present invention, the particulate binder may have a particle structure of, for example, a single-phase or a multi-phase such as core-shell, core-first shell-second shell, etc.

[0085] In one embodiment of the present invention, the particulate binder may have a particle shape of, for example, a spherical, oval, plate-shaped or irregular shape.

[0086] In one embodiment of the present invention, when preparing a slurry composition for membrane coating, the solvent may be water or an aqueous solvent containing water. Furthermore, when drying speed and temperature are limited, a co-solvent such as methanol, ethanol, or isopropyl alcohol, which have a boiling point lower than water, may be used.

[0087]

[0088] Thereafter, (S20) the slurry composition for membrane coating is applied on at least one surface of a porous polymer substrate to form a porous coating layer.

[0089] In one embodiment of the present invention, the porous polymer substrate refers to a substrate having a plurality of pores formed therein, which serve as a porous ion-conducting barrier that allows ions to pass while blocking electrical contact between the cathode and the anode. The pores are structured to be interconnected, allowing gas or liquid to pass from one side of the substrate to the other.

[0090] The material constituting this porous polymer substrate can be any organic or inorganic material with electrical insulation properties. In particular, from the perspective of imparting a shutdown function to the substrate, it is preferable to use a thermoplastic resin as the substrate material. Here, the shutdown function refers to the function of preventing thermal runaway of the battery by blocking the movement of ions by melting the thermoplastic resin and closing the pores of the porous substrate when the battery temperature rises. Suitable thermoplastic resins include those with a melting point below 200°C.

[0091] In particular, in one embodiment of the present invention, the porous polymer substrate is not limited in type as long as it does not cause a physical / chemical reaction with the etchant component due to chemical resistance. Depending on the type of etchant used, the porous polymer substrate may include, for example, polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, or two or more thereof.

[0092] In the present invention, the porous polymer substrate preferably has a thickness of 3 μm to 15 μm or 5 μm to 15 μm. If the thickness falls short of the above values, the conductive barrier function is insufficient, whereas if the thickness exceeds the above range (i.e., is too thick), the resistance of the separator may excessively increase.

[0093] In one embodiment of the present invention, the weight average molecular weight of the porous substrate may be 100,000 to 5,000,000. If the weight average molecular weight is less than 100,000, it may be difficult to secure sufficient mechanical properties. In addition, if it exceeds 5,000,000, the shutdown characteristics may deteriorate or molding may become difficult. In addition, the puncture strength of the porous polymer substrate may be 300 gf or more from the viewpoint of improving the manufacturing yield. The puncture strength of the porous substrate refers to the maximum puncture load (gf) measured by performing a puncture test under the conditions of a needle tip radius of 0.5 mm and a puncture speed of 4 mm / sec using a Kato tech KES-G5 handy compression tester.

[0094] In one embodiment of the present invention, the porous polymer substrate may have a pore diameter of generally 10 nm to 200 nm.

[0095] In one embodiment of the present invention, the separation membrane may have a porosity of about 30% to 80% by volume. Meanwhile, the separation membrane may have a permeability within a range of about 50 sec / 100cc to about 250 sec / 100cc, or 50 sec / 100cc to 150 sec / 100cc.

[0096] The above porosity or pore size can be measured using BELSORP (BET equipment) of BEL JAPAN using an adsorbed gas such as nitrogen, or can be measured by a method such as mercury intrusion porosimetry or capillary flow porosimetry. Specifically, in one embodiment of the present invention, the pore size of the porous coating layer can be measured by a capillary flow porosimetry method. The capillary flow porosimetry method is a method in which the diameter of the smallest pore in the thickness direction is measured. Therefore, in order to measure the pore size of only the porous coating layer by the capillary flow porosimetry method, the porous coating layer must be separated from the porous substrate and wrapped in a non-woven fabric capable of supporting the separated porous coating layer, and the pore size of the non-woven fabric must be much larger than the pore size of the coating layer.

[0097] The term 'permeability' used in this specification means the time it takes for 100 cc of air to permeate a permeability measurement target such as a membrane or a porous polymer substrate, and the unit thereof can be second / 100 cc, can be used interchangeably with permeability, and is typically expressed as a Gurely value, etc. In a specific embodiment of the present invention, the permeability can be measured in accordance with JIS P8117. In addition, the air permeability P1 measured in an object having a thickness T1 can be converted into the permeability P2 when the thickness of the object is 20 µm by the formula: P2=(P1X20) / T1.

[0098] In one embodiment of the present invention, the porous coating layer may be coated to have a thickness of 1.0 μm to 5.0 μm. Within the above numerical range, the adhesion to the electrode is excellent, and as a result, the cell strength of the battery is increased. Meanwhile, if the thickness is 5.0 μm or less, it is advantageous in terms of cycle characteristics and resistance characteristics of the battery. When the inorganic coating layer is disposed on both sides of the porous polymer substrate, the thickness of the porous coating layer refers to a value measured for the porous coating layer disposed on either side of the porous polymer substrate.

[0099] The above slurry composition for membrane coating can be applied using a conventional coating method such as a Meyer bar, die coater, reverse roll coater, or gravure coater.

[0100]

[0101] Thereafter, (S30) at least a portion of the pore-inducing particles of the porous coating layer are removed using an etchant. This can be performed by dipping the porous polymer substrate on which the porous coating layer is formed into an etchant or spraying the etchant onto the porous coating layer. In this case, as in Equation 1 or Equation 2 described above, the pore-inducing particles react with the etchant to generate an ionic substance that is separated from the separator, and the empty space formed as a result of the pore-inducing particles being dissolved and removed serves as the pores of the separator. Thereafter, the separator can be washed to remove the solution in which the pore-inducing particles and the etchant reacted. At this time, an aqueous solvent containing water and / or ethanol can be used as the washing solution.

[0102] In one embodiment of the present invention, pores may be formed at locations where pore-inducing particles exist within the porous coating layer. For example, when pore-inducing particles are in contact with inorganic particles and / or pore-inducing particles, pores may be formed at locations where the pore-inducing particles are located when the pore-inducing particles are removed by an etching solution.

[0103] At this time, the pores formed by the interstitial volume of the conventional inorganic particles are formed by the inorganic particles coming into contact with each other as described above, whereas the pores formed by the removal of the pore-inducing particles are created by the removal of the pore-inducing particles at the position where they come into contact with the inorganic particles and / or the particle-shaped binder, and thus can be distinguished by SEM images, etc.

[0104]

[0105] Thereafter (S40), the porous coating layer from which at least some of the pore-inducing particles have been removed is dried. The drying speed and temperature may vary depending on the solvent used. For example, the drying time may be performed for 10 minutes to 10 hours, and the drying temperature may be performed in the range of 30°C to 100°C. The drying is not limited to a specific method as long as the washing solution can be removed from the separator, and for example, one or a combination of two or more of convection drying, hot air drying, blowing drying, and natural drying may be applied. In one embodiment of the present invention, the drying may be performed by vacuum drying under reduced pressure.

[0106]

[0107] In one embodiment of the present invention, step (S20) may further include a step of drying the solvent in the slurry composition after applying the membrane coating layer slurry composition on at least one surface of the porous polymer substrate (S21). In this case, the drying process may include primary drying after forming the porous coating layer, and secondary drying after the pore-inducing particles are removed. The drying time may be performed for 10 minutes to 10 hours, and the drying temperature may be performed in the range of 30°C to 100°C. The drying is not limited to a specific method as long as the washing solution can be removed from the membrane, and for example, a suitable method such as one or a combination of two or more of convection drying, hot air drying, air blowing drying, and natural drying may be applied. In one embodiment of the present invention, the drying may be performed by vacuum drying under reduced pressure.

[0108]

[0109] In one embodiment of the present invention, when the step of drying the solvent in the slurry composition after applying the membrane coating layer slurry composition on at least one surface of the porous polymer substrate is further included, a step of pressurizing the membrane after the drying step may be further included.

[0110] That is, in one embodiment of the present invention, after step (S21), step (S22) may further include a step of pressurizing the membrane under conditions of a pressure of 0.5 MPa to 20 MPa and a temperature of 20°C to 85°C for 1 second to 60 seconds. Specifically, the pressurization may be performed under conditions of 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 porous coating layer particle-type binder may be film-formed without the pore-inducing particles being removed. Thereafter, when at least a portion of the pore-inducing particles of the porous coating layer is removed with an etchant, the pores may be formed similarly to the shape of the pore-inducing particles, which may be useful for controlling 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.

[0111]

[0112] In one embodiment of the present invention, after applying the membrane coating layer slurry composition onto at least one surface of the porous polymer substrate, a drying process may not be performed immediately, but a process of drying the porous coating layer after at least some of the pore-inducing particles are removed, and then pressurizing the membrane may be further included.

[0113] That is, in one embodiment of the present invention, after step (S40), the step (S41) may further include a step of pressurizing the separation membrane under conditions of a pressure of 0.5 MPa to 20 MPa and a temperature of 20°C to 85°C for 1 second to 60 seconds. Specifically, the pressurization may be performed under conditions of 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 manufacturing process of the separation membrane can be simplified as the drying step of (S21) is omitted.

[0114]

[0115] <Separator>

[0116] The present invention provides a separator for an electrochemical device.

[0117] Specifically, the separator comprises a porous polymer substrate; a porous coating layer positioned on at least one surface of the porous polymer substrate and including inorganic particles and a particle-type binder, wherein the porous coating layer is characterized in that it includes pores formed by removing at least a portion of pore-inducing particles by an etchant.

[0118] The porous coating layer includes a plurality of pores on the inside and the surface, and some of the pores may be formed by pore-inducing particles being removed by an etchant.

[0119] In one embodiment of the present invention, the pores formed by removal by the etchant may be formed at a location where the pore-inducing particles come into contact with inorganic particles or particle-type binder polymers.

[0120] In one embodiment of the present invention, the porous coating layer may be formed by inorganic particles and particle-type binder being in contact with each other, or a portion of the porous coating layer may have pores, i.e., vacancies, formed by etching of pore-inducing particles.

[0121] The porous coating layer has at least a portion of the pore-inducing particles removed by the etchant, and at this time, the inorganic particles are not removed by the etchant, and only the pore-inducing particles are removed to create pores. Therefore, the ratio of pores and the ratio of inorganic particles can be higher compared to a porous coating layer that does not include pore-inducing particles.

[0122] In one embodiment of the present invention, the porosity of the separator may be 10 to 50 volume%. The porosity of the separator may be determined by the pore size of the porous polymer substrate and the pore size of the porous coating layer.

[0123] In the present invention, the electrochemical device includes all devices that undergo an electrochemical reaction, and specific examples thereof include capacitors such as all types of primary batteries, secondary batteries, fuel cells, solar cells, or supercapacitor devices. In the present invention, the electrochemical device may preferably be a secondary battery, and more preferably, a lithium-ion secondary battery.

[0124]

[0125] Lithium-ion secondary battery

[0126] The present invention provides a lithium ion secondary battery.

[0127] The lithium ion secondary battery of the present invention comprises a positive electrode; a negative electrode; an electrolyte; and a separator interposed between the positive electrode and the negative electrode, wherein the separator comprises a separator manufactured by the above-described method for manufacturing a separator.

[0128] In one embodiment of the present invention, the positive electrode can be manufactured by coating a composition for forming a positive electrode including a positive electrode active material, a binder, a conductive agent, a solvent, etc. on a positive electrode current collector.

[0129] The above-mentioned cathode active material may be a conventional cathode active material that can be used in the cathode of a conventional electrochemical device. For example, the above-mentioned cathode active material may be lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a lithium composite oxide comprising these.

[0130] At this time, the positive electrode active material may be included in an amount of 80 to 99 wt%, preferably 85 to 98 wt%, based on the total solid content of the composition for forming the positive electrode. When the content of the positive electrode active material satisfies the above-described range, excellent capacity characteristics can be exhibited.

[0131] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause chemical changes in the battery. For example, the positive electrode current collector may be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0132] The above binder is a component that assists in the bonding of the active material and the conductive material and the bonding to the current collector, and can typically be added in an amount of 1 to 30 wt% based on the total solid weight of the composition for forming the positive electrode. Examples of such binders 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, various copolymers, etc.

[0133] The above-mentioned conductive agent can typically be added in an amount of 1 wt% to 30 wt% based on the total solid weight of the composition for forming the anode.

[0134] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include: graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as fluorinated carbon, aluminum, and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. Specific examples of commercially available conductive agents include acetylene black series (Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company), Ketjenblack, EC series (Armak Company), Vulcan XC-72 (Cabot Company), and Super P (Timcal).

[0135] In addition, the positive electrode active material layer may optionally further include a dispersant as needed.

[0136] The above dispersant can be used without any special restrictions as long as it is used as a dispersant of the anode, and for example, an aqueous dispersant or an organic dispersant can be selectively used as needed. Preferably, the dispersant is a cellulose compound, polyalkylene oxide, polyvinyl alcohol, polyvinyl pyrrolidone, 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) polymer, acrylonitrile / styrene / acrylate ester (ASA) polymer, a mixture of acrylonitrile / styrene / acrylate ester (ASA) polymer and propylene carbonate, styrene / acrylonitrile (SAN) Examples thereof include copolymers, methyl methacrylate / acrylonitrile / butadiene / styrene (MABS) polymers, styrene butadiene rubber, nitrile butadiene rubber, and fluoroelastomers, and any one or a mixture of two or more thereof may be used. Hydrogenated nitrile butadiene rubber (H-NBR) may be used. When the positive electrode active material layer further includes a dispersant, the dispersibility of the components of the positive electrode active material layer, particularly the conductive material, may be increased, but is not limited thereto.

[0137] In addition, the solvent may be a solvent generally used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these may be used alone or as a mixture of two or more. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0138]

[0139] The negative electrode according to the present invention can be manufactured by coating a negative electrode forming composition including the above-described negative electrode active material, binder, conductive agent, solvent, etc. on a negative electrode current collector. In addition, the negative electrode forming composition may optionally further include a dispersant as needed.

[0140] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Preferably, the negative electrode is a silicon-based negative electrode active material, a carbon-based negative electrode active material, or Li that exhibits high-capacity characteristics. 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, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물; 리튬 티타늄 산화물 등의 음극 활물질을 더 사용할 수 있다. 상기 규소계 음극 활물질은 음극 활물질은 Si, SiOx(0.1<x<5), Si-금속 합금, Mg와 같은 금속이 도핑 또는 화학 결합된 실리콘 산화물 입자(SiOx, 0.1<x<5) 및 Si와 SiOx(0.1<x<5)의 합금으로 이루어진 군에서 선택된 하나 이상을 포함할 수 있다. 상기 탄소계 음극 활물질은 천연 흑연, 인조 흑연, 비정질 하드카본(hard carbon), 저결정질 소프트카본(soft carbon), 카본 블랙, 아세틸렌 블랙, 케첸 블랙, 수퍼 P, 그래핀 (graphene), 및 섬유상 탄소로 이루어진 군으로부터 선택되는 하나 이상을 포함할 수 있다.

[0141] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0142] The conductive material, binder, solvent or dispersant included in the above-described composition for forming the cathode may be applied without any special limitation as long as it is generally usable in a composition for forming an electrode. For example, the conductive material, binder, solvent or dispersant described in the above-described composition for forming the anode may be applied.

[0143]

[0144] In addition, the lithium secondary battery may further include an electrolyte. The electrolyte may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery.

[0145] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0146] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0147] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0148] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total weight of the electrolyte.

[0149]

[0150] Hereinafter, the present invention will be described in more detail through examples, but the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited to these examples.

[0151]

[0152] <Example 1>

[0153] Aluminum oxide (Al2O3, D) as inorganic particles 50 : 450 nm, Sumitomo Corporation), silica (SiO2, D) as pore-inducing particles 50 : 100 nm) was added to water at room temperature and stirred uniformly, and then an acrylic particle-type binder (polyacrylate, Tg: 40℃, D 50 : 400 nm) and fluorine-based particle-type binder (PVDF, Tg: 40℃, D 50 : 400 nm) was added at a weight ratio of 1:1 to prepare a slurry composition for membrane coating. The solid content of the slurry composition was 35 wt%. In addition, the weight ratio of the inorganic particles:acrylic particle-type binder:fluorine particle-type binder:pore-inducing particles was 85:5:5:5.

[0154] The above membrane coating slurry composition was applied to both sides of a polyethylene substrate (thickness: 12 μm, porosity: 70% by volume) using a doctor blade, and the solvent was then dried to form a porous coating layer. After drying, the porous coating layer had a thickness of approximately 5.0 μm per side.

[0155] Afterwards, the membrane with the porous coating layer formed was immersed in hydrogen fluoride (concentration: 35%) as an etchant for 10 minutes to remove the pore-inducing particles (SiO2), and then washed in ethanol. After washing, it was immersed in water for 2 hours at 60 o A separation membrane with a thickness of approximately 22 μm was manufactured by drying at a temperature of C.

[0156]

[0157] <Comparative Example 1>

[0158] Aluminum oxide (Al2O3, D) as inorganic particles 50 : 450 nm, Sumitomo Corporation) was added to water at room temperature and stirred uniformly, and then an acrylic particle-type binder (polyacrylate, Tg: 40℃, D 50 : 400 nm) and fluorine-based particle-type binder (PVDF, Tg: 40℃, D 50 : 400 nm) was added at a weight ratio of 1:1 to prepare a slurry composition for membrane coating. The solid content of the slurry composition was 35 wt%. In addition, the weight ratio of the inorganic particles:acrylic particle-type binder:fluorine particle-type binder was 90:5:5.

[0159] The above membrane coating slurry composition was applied to both sides of a polyethylene substrate (thickness: 12 μm, porosity: 70% by volume) using a doctor blade, and the solvent was then dried to form a porous coating layer. After drying, the porous coating layer had a thickness of approximately 5.0 μm per side.

[0160]

[0161] <Experimental Example>

[0162] <Experimental Example 1: Evaluation of the wettability of the membrane>

[0163] A slurry of positive electrode active material was prepared by adding LiCoO2 as a positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder to N-methylpyrrolidone (NMP) as a solvent at a weight ratio of 96:2:2. The positive electrode active material slurry was coated on a sheet-shaped aluminum current collector and dried to obtain a final positive electrode loading of 4.0 mAh / cm. 2 The polarity was prepared to make this happen.

[0164] The separators of Example 1 and Comparative Example 1 were each laminated on the above-manufactured anode, and a transparent PET film was laminated on the separator, and a laminate was manufactured by pressing at a temperature of 70°C and a pressure of 6.5 MPa for 1 second. After that, a non-aqueous electrolyte was manufactured by dissolving LiPF6 in an organic solvent (EC:DEC = 1:1 (v:v)) to a concentration of 1 M, and then the laminate was immersed in the electrolyte to perform a wettability test. After that, a photograph was taken from the transparent PET side, and the impregnated area relative to the total area was calculated and shown in Figs. 1a and 1b.

[0165] According to Fig. 1a, the separator of Example 1 was impregnated all the way to the center, but according to Fig. 1b, in the case of Comparative Example 1, only the periphery of the separator was impregnated, confirming that the impregnated area was 50% of the total area. That is, it was confirmed that at least a portion of the pore-inducing particles of the separator of Example 1 were removed by the etchant, thereby increasing the wettability of the separator.

[0166]

[0167] <Experimental Example 2: Surface Analysis of the Membrane>

[0168] The surfaces of the membranes of Example 1 and Comparative Example 1 were measured using a scanning electron microscope (SEM, Hitachi). The measured surface of the membranes was analyzed by distinguishing the shapes of the particles using the IAM (Image Analysis Management, LG Energy Solution) program, thereby distinguishing the inorganic particles, pores, acrylic particle-type binder, and fluorine particle-type binder on the surface. Then, each area was masked, and the areas occupied by the inorganic particles, pores, acrylic particle-type binder, and fluorine particle-type binder on the surface, respectively, are shown in Figs. 2a and 2b. At this time, red represents pores, dark green represents acrylic particle-type binder, light green represents fluorine particle-type binder, and gray represents inorganic particles.

[0169] Fig. 2a is a SEM image of the surface of the membrane of Example 1 and an image in which the inorganic particles, pores, acrylic particle-type binder, and fluorine particle-type binder are each masked using an IAM program. According to Fig. 2a, the surface area ratio of pores:acrylic particle-type binder:fluorine particle-type binder:inorganic material was confirmed to be 6.5:45.5:30.5:17.6.

[0170] Figure 2b is a SEM image of the surface of the membrane of Comparative Example 1 and an image in which the inorganic particles, pores, acrylic particle-type binder, and fluorine particle-type binder are each masked using an IAM program. According to Figure 2b, the surface area ratio of pores:acrylic particle-type binder:fluorine particle-type binder:inorganic material was confirmed to be 2.5:55.7:34.6:7.2.

[0171] It was confirmed that the separation membrane of Example 1 above had at least a portion of the pore-inducing particles removed by the etchant, and thus the ratio of pores and inorganic substances on the surface increased compared to Comparative Example 1.

[0172]

[0173] <Experimental Example 3: Measurement of air permeability>

[0174] The air permeability of the membranes of Example 1 and Comparative Example 1 was measured. Specifically, the air permeability time of each Example and Comparative Example was measured using an air permeability measuring device (Manufacturer: Asahi Seiko, Model: EG01-55-1MR) as the time (sec) required for 100 ml of air to pass through the membrane. A total of three points were measured, one point each on the left / middle / right of the sample, and the average was recorded.

[0175] As a result, the air permeability of the separation membrane of Example 1 was 70 sec / 100cc, and the air permeability of the separation membrane of Comparative Example 1 was 60 sec / 100cc. That is, the air permeability time of the separation membrane of Example 1 was shorter than that of Comparative Example 1, confirming that the air permeability of the separation membrane of Example 1 was superior.

[0176]

[0177] <Other measurement methods>

[0178] Glass transition temperature measurement

[0179] The glass transition temperature was measured by differential scanning calorimetry (DSC). The measurement of the glass transition temperature by the differential scanning calorimetry was performed using a Discovery DSC 250 from TA Instruments and the amount of heat was measured while changing the temperature in the range of -80℃ to 300℃. Specifically, the temperature of the sample to be measured was changed at a rate of 10℃ / min in the order of 1st heating -> 1st cooling -> 2nd heating from 25℃ (start) -> 250℃ (1st heating) -> -80℃ (1st cooling) -> 300℃.

Claims

1. (S10) A step of preparing a slurry composition for membrane coating comprising pore-inducing particles; inorganic particles; a particle-shaped binder and a solvent; (S20) A step of forming a porous coating layer by applying the slurry composition for the above membrane coating onto at least one surface of a porous polymer substrate; (S30) a step of removing at least a portion of the pore-inducing particles of the porous coating layer using an etchant; and (S40) A method for manufacturing a separation membrane, comprising the step of drying the porous coating layer from which at least some of the pore-inducing particles have been removed.

2. In claim 1, A method for manufacturing a separation membrane, characterized in that the pore-inducing particles are a substance that reacts with the etching solution.

3. In claim 1, A method for manufacturing a separation membrane, characterized in that the pore-inducing particles include silica (SiO2), titania (TiO2), zirconia (ZrO2), or two or more thereof.

4. In claim 1, A method for manufacturing a separation membrane, characterized in that the etchant comprises hydrogen fluoride, sodium hydroxide, potassium hydroxide, nitric acid, hydrogen peroxide, carbonic acid, or two or more thereof.

5. In claim 1, A method for manufacturing a separation membrane, characterized in that, in the step (S10), the content of the pore-inducing particles in the slurry composition for separation membrane coating is 20 to 90 parts by weight based on 100 parts by weight of inorganic particles.

6. In claim 1, D of the above pore-inducing particles 50 A method for manufacturing a separation membrane, characterized in that the separation membrane has a thickness of 20 nm to 500 nm.

7. In claim 1, A method for manufacturing a separation membrane, characterized in that the above particle-type binder is an acrylic particle-type binder, a fluorine particle-type binder, or a combination thereof.

8. In claim 1, A method for manufacturing a separation membrane, characterized in that the glass transition temperature (Tg) of the above particle-type binder is 40°C to 80°C.

9. In claim 1, D of the above particle-type binder 50 A method for manufacturing a separation membrane, characterized in that the separation membrane has a thickness of 150 nm to 1 μm.

10. In claim 1, A method for manufacturing a separation membrane, characterized in that the porous polymer substrate comprises polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, or two or more thereof.

11. In claim 1, (S20) A method for manufacturing a separation membrane, characterized in that it further comprises a step of drying a solvent in the slurry composition after applying the separation membrane coating layer slurry composition on at least one surface of a porous polymer substrate in step (S21).

12. In claim 11, A method for manufacturing a separation membrane, characterized in that after step (S21), the method further comprises the step of pressurizing the separation membrane under conditions of a pressure of 0.5 MPa to 20 MPa and a temperature of 20°C to 85°C for 1 second to 60 seconds.

13. In claim 1, A method for manufacturing a separation membrane, characterized in that after step (S40), the method further comprises the step of pressurizing the separation membrane under conditions of a pressure of 0.5 MPa to 20 MPa and a temperature of 20°C to 85°C for 1 second to 60 seconds.

14. A separation membrane manufactured by the method for manufacturing the separation membrane of claim 1, porous polymer substrate; and A porous coating layer located on at least one surface of the porous polymer substrate, comprising inorganic particles and a particle-type binder; A separation membrane characterized in that the porous coating layer includes pores formed by removing at least a portion of pore-inducing particles by an etchant.

15. In claim 14, A separation membrane characterized in that the porosity of the above separation membrane is 10 to 50% by volume.

16. Anode; cathode; electrolyte; and a separator interposed between the anode and cathode, A lithium secondary battery characterized in that the above separator is a separator according to claim 14.

Images