Method for manufacturing a separation membrane with a polymer adhesive layer, a separation membrane with a polymer adhesive layer formed by the method, and an electrochemical device including the same

Abstract

The present disclosure discloses a method for producing a separation membrane with a polymer adhesive layer, comprising: (S1) preparing an aqueous polymer slurry containing a particulate binder polymer having a Tg of 20°C or higher and a particle size D50 of 300 to 800 nm, a wetting agent, and a particulate acrylic binder polymer having a Tg of -10°C or lower and a particle size D50 of 100 to 200 nm; and (S2) coating the aqueous polymer slurry onto at least one surface of a porous polyolefin-based porous membrane and drying the coating.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a separator having a polymer adhesive layer, a separator with a polymer adhesive layer formed by the manufacturing method, and an electrochemical device including the separator.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0137451, filed on October 24, 2022, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings thereof. [Background technology]

[0003] Electrochemical devices such as lithium secondary batteries are typically composed of a positive electrode, a separator, a negative electrode, and an electrolyte. They are high-energy density energy storage devices that can be charged and discharged by reversibly converting chemical energy and electrical energy, and are widely used in small electronic devices such as mobile phones and notebook PCs. In recent years, in response to environmental issues, high oil prices, and the need for energy efficiency and storage, their application in hybrid electric vehicles (HEVs), plug-in electric vehicles (Plug-in EVs), electric bicycles (e-bikes), and energy storage systems (ESSs) has been rapidly increasing.

[0004] In such electrochemical devices, a polyolefin porous membrane is usually used as the separation membrane.

[0005] To improve the adhesion of polyolefin-based porous membranes to electrodes, a separator with a polymer adhesive layer has been developed, in which an adhesive layer of binder polymer particles is formed on the surface of the porous membrane. The particulate binder polymer adhesive layer is useful for minimizing increases in the resistance of the separator and minimizing decreases in the breathability of the polyolefin-based porous membrane.

[0006] The binder polymer particle coating layer is formed by dispersing the binder polymer particles in an aqueous solvent such as ethanol or water, adding a wetting agent such as a surfactant, coating the aqueous slurry on one or both sides of the polyolefin porous membrane, and then drying the coating. The wetting agent facilitates coating of the aqueous slurry on the hydrophobic polyolefin porous membrane.

[0007] However, wetting agents have the problem that they penetrate into the pores of the polyolefin-based porous membrane during the coating and drying process of the aqueous slurry to form the coating layer, thereby increasing the resistance and decreasing the air permeability. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a method for manufacturing a separator membrane with a polymer adhesive layer that has good resistance and air permeability even when a wetting agent is used to improve coating properties when forming an adhesive layer of polymer particles on a polyolefin porous membrane.

[0009] Another object of the present invention is to provide a separation membrane with a polymer adhesive layer having the above-mentioned properties.

[0010] Another object of the present invention is to provide an electrochemical device including a separator with a polymer adhesive layer having the above-mentioned properties.

[0011] Other objects and advantages of the present invention will become apparent from the following description, and can be realized by the means and combinations thereof set forth in the claims. [Means for solving the problem]

[0012] A first aspect of the present invention for achieving the above object relates to a method for producing a separation membrane with a polymer adhesive layer, (S1) preparing an aqueous polymer slurry containing a particulate binder polymer having a Tg of 20°C or higher and a particle size D50 of 300 to 800 nm, a wetting agent, and a particulate acrylic binder polymer having a Tg of -10°C or lower and a particle size D50 of 100 to 200 nm; (S2) coating the aqueous polymer slurry onto at least one surface of a porous polyolefin-based membrane and drying the coating.

[0013] A second aspect of the present invention is the first aspect, wherein the particle size D50 of the particulate binder polymer:the particle size D50 of the particulate acrylic binder polymer is 2:1 to 6:1.

[0014] A third aspect of the present invention is the first or second aspect, wherein the particle size D50 of the particulate binder polymer is 300 to 600 nm, and the particle size D50 of the particulate acrylic binder polymer is 100 to 150 nm.

[0015] In a fourth aspect of the present invention, in any one of the first to third aspects, the particulate acrylic binder polymer has a Tg of −20° C. or lower.

[0016] In a fifth aspect of the present invention, in any one of the first to fourth aspects, the weight ratio of the particulate binder polymer to the particulate acrylic binder polymer is 95:5 to 97:3.

[0017] A sixth aspect of the present invention is directed to any one of the first to fifth aspects, wherein the content of the wetting agent is 1 to 30 wt % based on the total weight of the particulate binder polymer and the particulate acrylic binder polymer.

[0018] A seventh aspect of the present invention is the method according to any one of the first to sixth aspects, wherein the particulate binder polymer is an acrylic binder polymer, a polyvinylidene fluoride binder polymer, or a mixture thereof.

[0019] In an eighth aspect of the present invention, in any one of the first to seventh aspects, the polyvinylidene fluoride-based binder polymer is a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride and another polymerizable monomer, or a mixture of two or more of these.

[0020] A ninth aspect of the present invention is related to any one of the first to eighth aspects, wherein the particulate acrylic binder polymer comprises an acrylic polymer containing an alkyl (meth)acrylate repeating unit having an alkyl group having 1 to 18 carbon atoms.

[0021] A tenth aspect of the present invention is related to any one of the first to ninth aspects, wherein the particulate binder polymer is a polyvinylidene fluoride-based binder polymer, and the particulate acrylic binder polymer is an acrylic polymer including an alkyl (meth)acrylate repeating unit having an alkyl group having 1 to 18 carbon atoms.

[0022] Aspect 11 of the present invention is related to any one of aspects 1 to 10, wherein the wetting agent is at least one selected from the group consisting of a fluorine-based surfactant, a siloxane-based surfactant, and a hydrocarbon-based surfactant.

[0023] In a twelfth aspect of the present invention, in any one of the first to eleventh aspects, the dispersion medium of the aqueous polymer slurry is water.

[0024] A thirteenth aspect of the present invention relates to a separation membrane with a polymer adhesive layer, The porous polymer substrate includes a polymer adhesive layer formed on at least one surface of the polymer substrate, the polymer adhesive layer includes a particulate binder polymer, a non-particulate binder polymer, and a wetting agent; The particulate binder polymer has a Tg of 20°C or higher and an average particle size of 300 to 800 nm, The non-particulate binder polymer is an acrylic binder polymer having a Tg of −10° C. or lower.

[0025] A fourteenth aspect of the present invention relates to an electrochemical device comprising a negative electrode, a positive electrode, and a separator interposed between the negative electrode and the positive electrode, The separation membrane is a separation membrane with a polymer adhesive layer described on page 13.

[0026] In a fifteenth aspect of the present invention, in the fourteenth aspect, the electrochemical device is a lithium secondary battery. [Effects of the Invention]

[0027] According to the method for manufacturing a separator with a polymer adhesive layer of the present invention, a particulate acrylic binder polymer having a low Tg loses its particulate form in the slurry and transforms into a film-like shape, and migrates to the polyolefin porous membrane during the drying process of the slurry, thereby improving the phenomenon of wetting agent penetrating into the pores of the porous membrane. As a result, even when a wetting agent is used to improve coating properties when forming an adhesive layer of particulate binder particles on a polyolefin porous membrane, a separator with low resistance and good air permeability can be manufactured.

[0028] The particulate binder polymer in the polymer adhesive layer improves the adhesive strength of the polyolefin-based porous film to the electrode.

[0029] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, explain the principles of the present invention, so the scope of the present invention should not be interpreted as being limited thereto. Note that the shape, size, scale, ratio, etc. of elements in the drawings attached to this specification may be exaggerated to emphasize a clearer description. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is an SEM photograph of the surface of a separation membrane with a polymer adhesive layer according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] The terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts corresponding to the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of terms in order to best explain the invention. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferable embodiment of the present invention, and do not represent the entire technical idea of ​​the present invention, and therefore, there may be various equivalents and modifications that can be substituted for them at the time of filing this application.

[0032] A method for producing a separation membrane with a polymer adhesive layer according to a first aspect of the present invention includes: (S1) preparing an aqueous polymer slurry containing a particulate binder polymer having a Tg of 20°C or higher and a particle size D50 of 300 to 800 nm, a wetting agent, and a particulate acrylic binder polymer having a Tg of -10°C or lower and a particle size D50 of 100 to 200 nm; (S2) coating the aqueous polymer slurry onto at least one surface of a porous polyolefin-based membrane and drying the coating.

[0033] In the present invention, a particulate binder polymer and a particulate acrylic binder polymer refer to a polymer that is added in particulate form to an aqueous dispersion medium during preparation of an aqueous polymer slurry, and are distinguished from a "non-particulate" binder polymer, which refers to a polymer that is dissolved in a solvent or, even if not dissolved in a solvent, loses its particulate form and is transformed into a film-like form during the drying process during the formation of a polymer adhesive layer. That is, in the present invention, "particulate" refers to a polymer that maintains substantially the same shape as the added particles, and the shape is typically, but not limited to, circular particles.

[0034] First, an aqueous polymer slurry is prepared (S1), which contains a particulate binder polymer having a Tg of 20°C or higher and a particle size D50 of 300 to 800 nm, a wetting agent, and a particulate acrylic binder polymer having a Tg of -10°C or lower and a particle size D50 of 100 to 200 nm.

[0035] The particulate binder polymer improves adhesion to the electrode and maintains its particulate shape within the formed polymer adhesive layer. The particulate binder polymer has a Tg of 20°C or higher, more specifically, a Tg of 30°C or higher. If the Tg is lower than 20°C, the particulate shape may be lost during coating and drying of the slurry. The particulate binder polymer also has a particle size D50 of 300 to 800 nm. If the particle size D50 is less than 300 nm, the difference between the particle size D50 of the particulate acrylic binder polymer is not significant, resulting in poor separation, which may result in reduced adhesion to the electrode and reduced breathability. If the particle size D50 exceeds 800 nm, an uneven coating layer may be formed, resulting in poor adhesion between the electrode and the separator. In this regard, the particle size D50 of the particulate binder polymer is preferably 300 to 600 nm, more preferably 400 to 600 nm.

[0036] The particulate binder polymer may be, but is not limited to, an acrylic binder polymer, a polyvinylidene fluoride binder polymer, or a mixture thereof.

[0037] As the polyvinylidene fluoride-based binder polymer, a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride and another polymerizable monomer, or a mixture of two or more of these may be used.

[0038] Examples of the vinylidene fluoride and other polymerizable monomers include, but are not limited to, one or more selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorofluoroethylene, 1,2-difluoroethylene, perfluoro(methyl vinyl) ether, perfluoro(ethyl vinyl) ether, perfluoro(propyl vinyl) ether, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole), trichloroethylene, and vinyl fluoride. In particular, the fluoropolymer may be a copolymer of vinylidene fluoride and hexafluoropropylene. The content of vinylidene fluoride and other polymerizable monomers may be, but is not limited to, 1 to 20 wt % of the copolymer.

[0039] When an acrylic binder polymer is used as the particulate binder polymer, it may be, but is not limited to, an acrylic polymer containing a repeating unit of alkyl (meth)acrylate having an alkyl group having 1 to 18 carbon atoms. More specifically, the acrylic binder polymer may be a polymer containing a repeating unit of a carboxylic acid ester, and preferably a (meth)acrylic acid ester. Specific examples of such (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, n-amyl (meth)acrylate, i-amyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, and (meth)acrylate. Examples include decyl acrylate, hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, ethylene glycol (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, ethylene di(meth)acrylate, etc., and the copolymer may be one or more selected from these. Among these, the copolymer may be one or more selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and methyl (meth)acrylate is particularly preferred.

[0040] The wetting agent is added to improve the coating property by making the aqueous slurry having the above-mentioned composition easily wet the hydrophobic polyolefin-based porous membrane. As such a wetting agent, a known wetting agent can be used, for example, a fluorine-based surfactant, a siloxane-based surfactant, or a hydrocarbon-based surfactant, and it is preferable to use a fluorine-based surfactant, but it is not limited thereto.

[0041] The particulate acrylic binder polymer has a Tg of -10°C or lower. The particulate acrylic binder polymer's low Tg allows it to lose its particulate form in the slurry or during the drying process of the slurry. The added particulates are disintegrated and transformed into a film-like form, migrating toward the polyolefin porous membrane during the drying process of the slurry, thereby reducing the penetration of the wetting agent into the pores of the porous membrane. This allows for the production of a separator membrane with low resistance and good breathability, even when a wetting agent is used to improve coating properties when forming an adhesive layer of particulate binder particles on the polyolefin porous membrane. Specifically, the alkyl groups of the acrylic binder polymer interact with the hydrogen groups of the polyolefin porous membrane to migrate toward the polyolefin porous membrane during the drying process of the slurry. The wetting agent then surrounds the acrylic binder polymer, thereby interacting with the alkyl groups of the acrylic binder polymer and reducing the amount of wetting agent penetrating into the pores of the polyolefin porous membrane.

[0042] If the Tg of the particulate acrylic binder polymer exceeds -10°C, it will maintain its particulate shape and may not be able to perform the aforementioned functions. Therefore, a Tg of -20°C or less is preferable. The particle size D50 is 100-200 nm. If it is less than 100 nm, the acrylic binder polymer may penetrate into the pores of the polyolefin porous membrane during coating layer formation, which may result in problems with the wetting agent not being able to penetrate into the raw film. Furthermore, if the particle size D50 of the particulate acrylic binder polymer exceeds 200 nm, the difference in particle size D50 between the particulate binder polymer and the acrylic binder polymer may be too small to allow for smooth separation, resulting in reduced adhesion to the electrode and reduced breathability. In this respect, specifically, the particle size D50 of the particulate acrylic binder polymer is 100 to 180 nm, more specifically 100 to 150 nm, and the particle size D50 of the particulate binder polymer:particle size D50 of the particulate acrylic binder polymer may be specifically 2:1 to 6:1, more specifically 2.5:1 to 5:1.

[0043] The particulate acrylic binder polymer may be, but is not limited to, an acrylic polymer containing an alkyl (meth)acrylate repeating unit having an alkyl group having 1 to 18 carbon atoms. More specifically, the acrylic binder polymer may be a polymer containing a carboxylic acid ester as a repeating unit, and preferably a (meth)acrylic acid ester. Specific examples of such (meth)acrylic acid esters include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, n-amyl (meth)acrylate, i-amyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, and methyl (meth)acrylate. Examples of the acrylate include decyl (meth)acrylate, hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, ethylene glycol (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, and ethylene di(meth)acrylate, and the acrylate may be one or more selected from these. Among these, the acrylate may be one or more selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and methyl (meth)acrylate is particularly preferred.

[0044] In one embodiment of the present invention, the particulate binder polymer may be a polyvinylidene fluoride-based binder polymer, and the particulate acrylic binder polymer may be an acrylic polymer containing an alkyl (meth)acrylate repeating unit having an alkyl group having 1 to 18 carbon atoms.

[0045] Considering the adhesive strength with the electrode and the resistance and air permeability of the separator, the weight ratio of the particulate binder polymer to the particulate acrylic binder polymer may be, but is not limited to, 95:5 to 97:3. Also, the content of the wetting agent may be 1 to 30 wt% based on the total weight of the particulate binder polymer and the particulate acrylic binder polymer.

[0046] In addition to the above-mentioned components, the aqueous polymer slurry may of course further contain a thickener or the like within the range that does not impair the object of the present invention.

[0047] In one embodiment of the present invention, the aqueous dispersion medium of the aqueous polymer slurry may contain at least one of water and an alcohol having 1 to 5 carbon atoms. For example, the aqueous dispersion medium may contain a mixture of water and isopropyl alcohol. By using an aqueous dispersion medium in the production method, the binder particles are not dissolved in the dispersion medium, but are dispersed in the aqueous dispersion medium and do not flow into the pores of the polyolefin porous membrane. In particular, using water as the aqueous dispersion medium is economical because it does not require explosion-proof equipment.

[0048] Meanwhile, in one embodiment of the present invention, the aqueous polymer slurry is preferably controlled so that the solids concentration, excluding the dispersion medium, is in the range of 3 wt% to 50 wt%. Adjusting the solids concentration, the average particle size and content ratio of the added binder particles, etc., within the above-mentioned ranges is advantageous for obtaining a separator having a polymer adhesive layer of the present invention.

[0049] Next, the prepared aqueous polymer slurry is coated on at least one surface of a porous polyolefin-based membrane and dried (S2).

[0050] In one embodiment of the present invention, the coating method may be dip coating, die coating, roll coating, comma coating, or a combination thereof.

[0051] According to a specific embodiment of the present invention, the polyolefin-based porous membrane can electrically insulate the negative electrode and the positive electrode to prevent short circuits and provide a path for lithium ion migration, and any polyolefin porous membrane that can be used as a separator substrate for an electrochemical device can be used without any particular limitation. Examples of such porous membrane substrates include polyethylene, polypropylene, and mixtures or laminates thereof.

[0052] In the present invention, the thickness of the polyolefin-based porous membrane may be 3 μm to 50 μm. The thickness of the polyolefin-based porous membrane is not particularly limited to the above range, but if the thickness is thinner than the above lower limit, the mechanical properties may be reduced and the separator may be easily damaged during use of the battery. Meanwhile, the size and porosity of the pores present in the polyolefin-based porous membrane are also not particularly limited, but may be 0.01 μm to 50 μm and 10 vol% to 95 vol%, respectively.

[0053] During the drying process of the coated aqueous polymer slurry, the particulate acrylic binder polymer loses its particulate shape, transforms into a film-like form, and migrates toward the polyolefin porous membrane. This prevents the wetting agent from penetrating the pores of the porous membrane. Meanwhile, the particulate binder polymer maintains its particulate shape even after drying and is primarily located on the surface of the adhesive layer, improving its adhesive strength to the electrode.

[0054] The separation membrane with a polymer adhesive layer manufactured by this method is The porous polymer substrate includes a polymer adhesive layer formed on at least one surface of the polymer substrate, the polymer adhesive layer includes a particulate binder polymer, a non-particulate binder polymer, and a wetting agent; The particulate binder polymer has a Tg of 20°C or higher and an average particle size of 300 to 800 nm, The non-particulate binder polymer is a polyacrylic binder polymer having a Tg of −10° C. or less.

[0055] In one aspect of the present invention, the thickness of the formed polymer adhesive layer may be, but is not limited to, 0.5 to 3 μm based on the thickness formed on either side of the polyolefin porous membrane.

[0056] The separator with a polymer adhesive layer described above can be applied to an electrochemical device. The electrochemical device may include an anode and a cathode, with the separator with a polymer adhesive layer interposed between the anode and the cathode. The electrochemical device includes all devices that perform electrochemical reactions, including all types of primary batteries, secondary batteries, fuel cells, solar cells, and capacitors. Among the secondary batteries, lithium ion secondary batteries, including lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, and lithium ion polymer secondary batteries, are particularly preferred.

[0057] In a specific embodiment of the present invention, the electrochemical device may be fabricated by a conventional method known in the art, and may be constructed by interposing the separator with the polymer adhesive layer between the positive electrode and the negative electrode.

[0058] That is, the separator with the polymer adhesive layer prepared by the above method is interposed between the anode and cathode and fabricated into an electrode assembly by a lamination process in which heat and / or pressure are applied to bond them. In one embodiment of the present invention, the lamination process may be performed using a roll press device including a pair of pressure rollers. That is, the anode, separator, and cathode may be sequentially stacked and then inserted between the pressure rollers to achieve interlayer bonding. In this case, the lamination process may be performed using a hot rolling method.

[0059] The electrode assembly, in which the negative electrode, separator, and positive electrode are stacked, is placed in a battery case, and an electrolyte is then injected into the battery case to manufacture the electrochemical device.

[0060] In one embodiment of the present invention, the electrode is not particularly limited, and an electrode active material may be prepared by a conventional method known to those skilled in the art in the form of being attached to an electrode current collector. Among the electrode active materials, non-limiting examples of the positive electrode active material include conventional positive electrode active materials used in the positive electrodes of electrochemical devices, particularly lithium intercalation materials such as lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or composite oxides formed by combinations thereof. Non-limiting examples of the negative electrode active material include conventional negative electrode active materials used in the negative electrodes of electrochemical devices, particularly lithium intercalation materials such as lithium metal or lithium alloys, carbon, petroleum coke, activated carbon, graphite, or other carbonaceous materials. Non-limiting examples of positive electrode current collectors include foils made of aluminum, nickel, or a combination thereof, and non-limiting examples of negative electrode current collectors include foils made of copper, gold, nickel, or a copper alloy, or a combination thereof.

[0061] The electrolyte that can be used in the present invention is A + B - A salt having the structure: + Li + , Na + , K. + or a combination thereof, - PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 -Examples of the salts containing anions such as those listed above or ions consisting of a combination thereof are dissolved or dissociated in an organic solvent consisting of propylene carbonate (PC), ethylene carbonate (EC), diethylene carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), γ-butyrolactone, or a mixture thereof, but are not limited thereto.

[0062] The electrolyte injection may be performed at an appropriate stage during the battery manufacturing process depending on the manufacturing process and desired properties of the final product. That is, it may be applied before battery assembly or at the final stage of battery assembly. In addition to the conventional winding process, the process of applying the electrode assembly of the present invention to a battery may include lamination (stack) and folding processes of the separator and electrodes.

[0063] The present invention will be described in detail below with reference to examples. However, the examples according to the present invention can be modified in various other forms, and the scope of the present invention is not limited to the following examples. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0064] Example 1 A particulate binder polymer [D50: 400 nm, copolymer of VDF and HFP polymerized in a molar ratio of 95:5, Tg: 40°C], a particulate acrylic binder polymer [D50: 150 nm, copolymer of ethyl acrylate and methyl methacrylate, Tg: -20°C], and a wetting agent (fluorine-based surfactant) were added to water in the weight amounts shown in Table 1 below and dispersed to prepare an aqueous polymer slurry.

[0065] Next, a porous membrane made of polyethylene (air permeability 80 sec / 100 ml, resistance 0.4 Ω, thickness 10 μm) was prepared, and the slurry was applied to both sides of the surface of the porous membrane by bar coating using a doctor blade. The resulting mixture was dried with hot air at 60°C using a heat gun, thereby producing a separator membrane having a polymer adhesive layer with a thickness of 1 μm on one side.

[0066] Example 2 A separation membrane was manufactured in the same manner as in Example 1, except that an aqueous polymer slurry was used instead of the composition shown in Table 1 below.

[0067] Comparative Example 1 A separator was prepared in the same manner as in Example 1, except that no wetting agent was added.

[0068] Comparative Example 2 A separator was prepared in the same manner as in Example 1, except that the particulate acrylic binder polymer was not added.

[0069] Comparative Example 3 A separator was manufactured in the same manner as in Example 1, except that the particle size D50 of the particulate binder polymer was changed to 200 nm. [Table 1] In Table 1, the wettability and peelability (PEEL) were evaluated as follows.

[0070] Wettability: When the slurry is coated onto the porous membrane, no bubbles are generated and the slurry is evenly applied to the surface of the porous membrane.

[0071] Wettability △: When the porous membrane is coated with the slurry, uncoated areas are generated in the middle of the coating layer, causing uneven distribution of the liquid.

[0072] Wettability ×: When the slurry is coated onto the porous membrane, the slurry is not applied to the surface of the porous membrane at all, resulting in uneven distribution of the liquid.

[0073] Peelability ×: The porous film and the polymer adhesive layer were not bonded, and peeled off even with a small force.

[0074] Measurement of average particle size D50 D50 can be defined as the particle size at 50% of the particle size distribution, and was measured using the laser diffraction method.

[0075] Measurement of Tg Using DSC, Tg of a 25 mg sample was measured under conditions of a nitrogen atmosphere, room temperature to 300°C, and a heating rate of 10°C / min.

[0076] Peel Measurement The separators obtained in each example and comparative example were attached to double-sided tape to prepare specimens. The size of the specimens was 1.5 cm x 6 cm.

[0077] Each specimen was left at room temperature for 1 hour and then the adhesive strength was measured by peeling at an angle of 180° using a tensile tester (UTM (universal testing machine)).

Claims

1. (S1) preparing an aqueous polymer slurry containing a particulate binder polymer having a Tg of 20°C or higher and a particle size D50 of 300 to 800 nm, a wetting agent, and a particulate acrylic binder polymer having a Tg of -10°C or lower and a particle size D50 of 100 to 200 nm; (S2) coating the aqueous polymer slurry onto at least one surface of a porous polyolefin-based porous membrane and drying it; A method for producing a separation membrane with a polymer adhesive layer, comprising:

2. the particle size D50 of the particulate binder polymer:the particle size D50 of the particulate acrylic binder polymer is 2:1 to 6:1; A method for producing the separation membrane with a polymer adhesive layer according to claim 1.

3. The particle size D50 of the particulate binder polymer is 300 to 600 nm, and the particle size D50 of the particulate acrylic binder polymer is 100 to 150 nm. A method for producing the separation membrane with a polymer adhesive layer according to claim 1.

4. the particulate acrylic binder polymer has a Tg of −20° C. or less; A method for producing the separation membrane with a polymer adhesive layer according to claim 1.

5. the weight ratio of the particulate binder polymer to the particulate acrylic binder polymer is 95:5 to 97:3; A method for producing the separation membrane with a polymer adhesive layer according to claim 1.

6. The content of the wetting agent is 1 to 30 wt % based on the total weight of the particulate binder polymer and the particulate acrylic binder polymer. A method for producing the separation membrane with a polymer adhesive layer according to claim 1.

7. the particulate binder polymer is an acrylic binder polymer, a polyvinylidene fluoride binder polymer, or a mixture thereof; A method for producing the separation membrane with a polymer adhesive layer according to claim 1.

8. The polyvinylidene fluoride-based binder polymer is a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride and another polymerizable monomer, or a mixture of two or more of these. A method for producing the separation membrane with a polymer adhesive layer according to claim 7.

9. the particulate acrylic binder polymer is an acrylic polymer containing an alkyl (meth)acrylate repeating unit having an alkyl group having 1 to 18 carbon atoms; A method for producing the separation membrane with a polymer adhesive layer according to claim 1.

10. the particulate binder polymer is a polyvinylidene fluoride-based binder polymer, and the particulate acrylic binder polymer is an acrylic polymer containing an alkyl (meth)acrylate repeating unit having an alkyl group having 1 to 18 carbon atoms; A method for producing the separation membrane with a polymer adhesive layer according to claim 1.

11. The wetting agent is at least one selected from the group consisting of a fluorine-based surfactant, a siloxane-based surfactant, and a hydrocarbon-based surfactant. A method for producing the separation membrane with a polymer adhesive layer according to claim 1.

12. The dispersion medium of the aqueous polymer slurry is water. A method for producing the separation membrane with a polymer adhesive layer according to claim 1.

13. The porous polymer substrate includes a polymer adhesive layer formed on at least one surface of the polymer substrate, the polymer adhesive layer comprises a particulate binder polymer, a non-particulate binder polymer, and a wetting agent; the particulate binder polymer has a Tg of 20°C or higher and an average particle size of 300 to 800 nm; The non-particulate binder polymer is an acrylic binder polymer having a Tg of −10° C. or less.

14. An electrochemical device comprising a negative electrode, a positive electrode, and a separator interposed between the negative electrode and the positive electrode, An electrochemical device, wherein the separation membrane is the separation membrane with a polymer adhesive layer according to claim 13 .

15. 15. The electrochemical device according to claim 14, wherein the electrochemical device is a lithium secondary battery.

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