Composite separator for lithium secondary battery containing organic polymer adhesive layer, manufacturing method of electrode assembly for lithium secondary battery using same, electrode assembly for lithium secondary battery manufactured therefrom, and lithium secondary battery having same

Abstract

A composite separator for a lithium secondary battery according to one aspect of the present invention comprises an inorganic heat-resistant layer and an organic polymer adhesive layer sequentially provided on at least one surface of a porous organic polymer substrate, wherein organic binder polymer particles included in the organic polymer adhesive layer are a mixture of acrylic polymer particles and vinylidene fluoride-based polymer particles, the average particle diameter (D50) of the acrylic polymer particles is 2500nm or more larger than the average particle diameter (D50) of the vinylidene fluoride-based polymer particles, the average particle diameter (D50) of the acrylic polymer particles is 3000nm or more, the average particle diameter (D50) of the vinylidene fluoride-based polymer particles is 100nm to 500nm, and the weight ratio of the acrylic polymer particles to the vinylidene fluoride-based polymer particles is 3.5:6.5 to 4.5:5.5.

Description

A composite separator for a lithium secondary battery comprising an organic polymer adhesive layer, a method for manufacturing an electrode assembly for a lithium secondary battery using the same, an electrode assembly for a lithium secondary battery manufactured therefrom, and a lithium secondary battery having the same

[0001] The present invention relates to a composite separator for a lithium secondary battery having an inorganic heat-resistant layer and an organic polymer adhesive layer sequentially provided on the surface of a porous organic polymer substrate, a method for manufacturing an electrode assembly for a lithium secondary battery using the same, an electrode assembly for a lithium secondary battery manufactured therefrom, and a lithium secondary battery having the same.

[0002] This application is a priority claim application for Korean Patent Application No. 10-2024-0164497 filed on November 18, 2024, and all contents disclosed in the specification of said application are incorporated into this application by reference.

[0003] Lithium-ion batteries are energy storage devices with high energy density that can be charged and discharged by reversibly converting chemical and electrical energy, typically composed of a cathode, separator, anode, and electrolyte. They are widely used in small electronic devices such as mobile phones and laptops. Recently, in response to environmental issues, high oil prices, and the need for energy efficiency and storage, their applications are rapidly expanding into hybrid electric vehicles (HEVs), plug-in electric vehicles (Plug-in EVs), e-bikes, and energy storage systems (ESS).

[0004] Ensuring safety in the manufacturing and use of such lithium secondary batteries is a critical challenge. In particular, conventional separators made of porous organic polymer substrates exhibit extreme thermal shrinkage behavior under conditions such as high temperatures due to their material properties and manufacturing process characteristics, leading to safety issues such as internal short circuits. Accordingly, to ensure the safety of lithium secondary batteries, a separator has been developed in which an inorganic heat-resistant layer is formed by coating a mixture of inorganic particles and an organic binder polymer that binds the inorganic particles together onto an organic porous polymer substrate.

[0005] In particular, for purposes such as reducing resistance, an inorganic heat-resistant layer is formed by dispersing inorganic particles and organic binder polymer particles in water, a non-solvent, so that the particle shape is maintained, and then coating / drying this onto a porous organic polymer substrate.

[0006] However, when manufacturing an electrode assembly by laminating this type of composite separator with an electrode, the interlayer adhesion between the electrode and the composite separator is insufficient, and they may separate from each other. When the electrode and the separator separate, problems arise where the cell bends or its shape warps due to the expansion / contraction of the electrode during the charging and discharging process. These problems are exacerbated in pouch-type batteries and become more severe when increasing the number of stacks and manufacturing them in a long cell shape. Therefore, a composite separator with a three-layer structure (porous organic polymer substrate / inorganic heat-resistant layer / organic polymer adhesive layer) is proposed to improve adhesion with the electrode by forming a coating layer of organic polymer particles on the surface of the composite separator.

[0007] It is common practice to manufacture separator rolls by winding these three-layer composite separators into a rolled state like toilet paper, and then transport and store them. When manufacturing a battery, they are unwound and fed into the lamination process with the electrode.

[0008] To prevent separator rolls from unraveling during transportation and storage, they must be wound tightly; however, if ambient temperatures rise during transport, the separators may stick together, leading to damage upon unwinding. Additionally, wavy patterns may occur on the wound separators. To resolve these issues, a protective film is laminated onto the surface of the separator as an interlayer during winding to prevent these problems. However, this method places an increased economic burden due to the need for additional equipment and the resulting higher costs.

[0009] Therefore, a composite separator with a three-layer structure (porous organic polymer substrate / inorganic heat-resistant layer / organic polymer adhesive layer) is required, which improves the phenomenon of inter-separator bonding and wave phenomena in the wound state without a protective film, while maintaining good adhesion to the electrode and cell performance.

[0010] The first objective of the present invention is to provide a composite separator for a lithium secondary battery having a composite separator having an inorganic heat-resistant layer and an organic polymer adhesive layer sequentially provided on the surface of a porous organic polymer substrate, wherein the phenomenon of separators bonding to each other and the wavy phenomenon in the wound state are improved even without a protective film, while maintaining good adhesion to the electrode and cell performance.

[0011] In addition, the second objective of the present invention is to provide a method for manufacturing an electrode assembly for a lithium secondary battery having a composite separator for a lithium secondary battery having the aforementioned characteristics, and an electrode assembly for a lithium secondary battery manufactured therefrom.

[0012] In addition, the third objective of the present invention is to provide a lithium secondary battery having an electrode assembly having the aforementioned characteristics.

[0013] Other objects and advantages of the present invention will be understood from the following description. Meanwhile, it will be readily apparent that the objects and advantages of the present invention can be realized by the means or methods described in the claims and combinations thereof.

[0014] A composite separator for a lithium secondary battery according to the first aspect of the present invention is,

[0015] porous organic polymer substrate,

[0016] A porous inorganic heat-resistant layer comprising an organic binder polymer that binds inorganic particles to each other and is coated on at least one surface of the above-mentioned organic polymer substrate.

[0017] The above-mentioned porous inorganic heat-resistant layer is coated on the outer surface and comprises an organic polymer adhesive layer containing organic binder polymer particles, and

[0018] The organic binder polymer particles included in the above organic polymer adhesive layer are a mixture of acrylic polymer particles and vinylidene fluoride polymer particles, and

[0019] Average particle size (D) of the above acrylic polymer particles 50 ) is the average particle size (D) of the vinylidene fluoride-based polymer particles above. 50 It is more than 2500 nm larger than ) and

[0020] Average particle size (D) of the above acrylic polymer particles 50 ) is 3000 nm or larger, and the average particle size (D) of the vinylidene fluoride-based polymer particles is 50 ) is 100 to 500 nm, and

[0021] The weight ratio of the above acrylic polymer particles to vinylidene fluoride polymer particles is 3.5:6.5 to 4.5:5.5.

[0022] The second aspect of the present invention is, in the first aspect,

[0023] The above acrylic polymer particles are (meth)acrylate 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 decyl, (meth)acrylate hydroxymethyl, (meth)acrylate hydroxyethyl, (meth)acrylate ethylene glycol, di(meth)acrylate ethylene glycol, di(meth)acrylate propylene glycol, tri(meth)acrylate trimethylolpropane, It may be composed of a polymer derived from one or more monomers selected from the group consisting of tetra(meth)acrylate pentaerythritol, hexa(meth)acrylate dipentaerythritol, (meth)acrylate allyl, and di(meth)acrylate ethylene.

[0024] A third aspect of the present invention is, in the first or second aspect,

[0025] The above vinylidene fluoride-based polymer particles may be composed of vinylidene fluoride-hexafluoropropylene copolymer.

[0026] A fourth aspect of the present invention is, in any one of the first to third aspects, the average particle size (D) of the acrylic polymer particles. 50 ) can be 4000 to 8000 nm, and more specifically, 5500 to 6500 nm.

[0027] The fifth aspect of the present invention is, in any one of the first to fourth aspects

[0028] Average particle size (D) of the vinylidene fluoride-based polymer particles above 50 ) can be 100 to 300 nm.

[0029] The sixth aspect of the present invention is, in any one of the first to fifth aspects,

[0030] The Tg (glass transition temperature) of the above acrylic polymer particles is 40 to 70 °C, and the Tm (melting point) of the above vinylidene fluoride polymer particles may be 130 °C or higher.

[0031] The seventh aspect of the present invention is, in any one of the first to sixth aspects,

[0032] The organic binder polymer included in the above porous inorganic heat-resistant layer may include an acrylic polymer.

[0033] The eighth aspect of the present invention is, in any one of the first to seventh aspects,

[0034] Average particle size (D) of the above inorganic particles 50 ) can be 100 to 800 nm, and more specifically, 300 to 600 nm.

[0035] The ninth aspect of the present invention is, in any one of the first to eighth aspects,

[0036] The above inorganic particles may be 70 to 99 weight percent based on the total weight of the inorganic heat-resistant layer.

[0037] The tenth aspect of the present invention relates to a method for manufacturing an electrode assembly for a lithium secondary battery, wherein

[0038] A step of preparing and winding a composite separator for a lithium secondary battery according to any one of the first to ninth aspects to manufacture a separator roll;

[0039] Step of disassembling the above-mentioned membrane roll; and

[0040] The above-mentioned deconstructed separator is interposed between the anode and the cathode, and an electrode assembly is prepared by heating and pressurizing.

[0041] The eleventh aspect of the present invention relates to an electrode assembly for a lithium secondary battery manufactured according to the tenth aspect.

[0042] The 12th aspect of the present invention relates to a lithium secondary battery having an electrode assembly for a lithium secondary battery according to the 11th aspect.

[0043] The composite separation membrane according to the present invention sequentially comprises an inorganic heat-resistant layer and an organic polymer adhesive layer on at least one surface of a porous organic polymer substrate, and the average particle size and content ratio of acrylic polymer particles and vinylidene fluoride polymer particles included in the organic polymer adhesive layer are each simultaneously controlled to a predetermined range.

[0044] Accordingly, when manufacturing the separator roll, phenomena such as interlocking or swells between separators in the wound state are improved even without a protective film, and when the separator roll is unwound to manufacture an electrode assembly, the adhesion with the electrode is good and cell performance can be maintained.

[0045] The attached drawings illustrate preferred embodiments of the invention and explain the principles of the invention together with the detailed description, but the scope of the invention is not limited thereto. Meanwhile, the shapes, sizes, scales, or proportions of elements in the drawings included in this specification may be exaggerated to emphasize clearer explanations.

[0046] FIG. 1 is a cross-sectional view schematically illustrating a cross-section of a lithium secondary battery having a composite separator according to one embodiment of the present invention.

[0047] FIG. 2 is an enlarged view of the “A” portion of the first porous inorganic heat-resistant layer (3a) and the first organic polymer adhesive layer (5a) of FIG. 1.

[0048] Terms or words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. Accordingly, the embodiments described in this specification and the configurations illustrated in the drawings are merely one preferred embodiment of the invention and do not represent all of the technical spirit of the invention; therefore, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0049] <Definition>

[0050] Throughout this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0051] In this specification, the average particle size (D50) is measured using a Malvern Mastersizer 3000 particle size analyzer. Specifically, the organic binder polymer particles are a dispersion obtained by diluting the organic binder polymer particles in a dispersion medium, and the average particle size (D50) is measured using the particle size analyzer. 50 Measures ). Meanwhile, the average particle size of inorganic particles (D 50 ) is obtained by adding inorganic particles and a dispersant to a dispersion medium and then sonifying, and then using the particle size analyzer to determine the average particle size (D 50 Measures ). D 50 It refers to the particle size at the 50% point of the cumulative distribution of particle numbers according to particle size.

[0052] The term "particle" of an organic polymer, such as acrylic polymer particles and vinylidene fluoride polymer particles in this specification, means that the organic binder polymer within the coating layer formed by adding the organic binder polymer in a particle shape to a dispersion medium for the formation of a porous inorganic heat-resistant layer or an organic polymer adhesive layer, and then coating and drying it, maintains the particle shape in which it was added. In particular, the "particle" may be a particle with an aspect ratio of "1 to 2." In this specification, the term "non-particle" means that the organic binder polymer in a particle shape is added to a solvent for the formation of a porous inorganic heat-resistant layer or an organic polymer adhesive layer and dissolves in the solvent, thereby losing its particle shape, or is added to a dispersion medium and, even if it does not dissolve, loses its particle shape and deforms into a film-like form during the drying process when forming the coating layer.

[0053]

[0054] FIG. 1 schematically illustrates a cross-section of a composite separator and a lithium secondary battery equipped with the same according to a specific embodiment of the present invention. For convenience of explanation, the negative electrode (20) and the positive electrode (30) in FIG. 1 are shown as being spaced apart from the composite separator (10), but in an actual lithium secondary battery, the negative electrode (20), the composite separator (10), and the positive electrode (30) are in close contact with each other. Additionally, the composite separator (10) of FIG. 1 is illustrated in an embodiment in which an inorganic heat-resistant layer (3) and an organic polymer adhesive layer (5) are formed on both sides of a porous organic polymer substrate (1), respectively, with a first inorganic heat-resistant layer (3a) and a second inorganic heat-resistant layer (3b) and a first organic polymer adhesive layer (5a) and a second organic polymer adhesive layer (5b). However, it is also possible to form only the first inorganic heat-resistant layer (3a) and the first organic polymer adhesive layer (5a) facing the cathode (20) without forming the second inorganic heat-resistant layer (3b) and the second organic polymer adhesive layer (5b) facing the cathode (20), or conversely, to form only the second inorganic heat-resistant layer (3b) and the second organic polymer adhesive layer (5b) facing the anode (30) without forming the first inorganic heat-resistant layer (3a) and the first organic polymer adhesive layer (5a) facing the cathode (20).

[0055] Referring to FIG. 1, a composite separator (10) according to one embodiment of the present invention is coated on both sides of an organic polymer substrate (1) and comprises a first porous inorganic heat-resistant layer (3a) and a first porous inorganic heat-resistant layer (3a), which is a porous inorganic heat-resistant layer (3) containing inorganic particles and an organic binder polymer that binds the inorganic particles together. Additionally, it comprises a first organic polymer adhesive layer (5a) and a second organic polymer adhesive layer (5b), which are coated on the outer surfaces of the first porous inorganic heat-resistant layer (3a) and the first porous inorganic heat-resistant layer (3a), respectively, and each contain organic binder polymer particles.

[0056] The first organic polymer adhesive layer (5a) faces the negative electrode (20), and the second organic polymer adhesive layer (5b) faces the positive electrode (30).

[0057] The organic binder polymer particles included in the organic polymer adhesive layer (5a, 5b) are a mixture of acrylic polymer particles and vinylidene fluoride polymer particles. Since the organic polymer adhesive layer (5a, 5b) is an "organic polymer" adhesive layer as the term implies, it does not contain inorganic particles.

[0058] The mixture of acrylic polymer particles and vinylidene fluoride polymer particles included in the organic polymer adhesive layer (5) maintains good adhesion of the composite separator to the anode and cathode. In addition, it also performs the function of ensuring that the inorganic particles included in the porous inorganic heat-resistant layer (3) are well fixed without detaching.

[0059] In addition, as described below, the average particle size (D) of the acrylic polymer particles and vinylidene fluoride polymer particles included in the organic polymer adhesive layer (5) 50 The content ratio and the ) are each controlled simultaneously within a predetermined range. Accordingly, when manufacturing the separator roll, the phenomenon of the separators sticking together or swelling in the wound state without a protective film is improved, and when the separator roll is unwound to manufacture an electrode assembly, the adhesion with the electrode is good and cell performance can be maintained.

[0060] Hereinafter, each component constituting the composite separator of the present invention and the lithium secondary battery equipped with the same will be described in more detail.

[0061] porous organic polymer substrate

[0062] According to a specific embodiment of the present invention, the porous organic polymer substrate (1) can provide a path for the movement of lithium ions while electrically insulating the negative electrode and the positive electrode to prevent short circuits, and can be used without special limitations as long as it is capable of being used as an organic polymer separator substrate for a lithium secondary battery. As such a separator substrate, for example, a porous organic polymer film or an organic polymer nonwoven fabric comprising one or more of the following polymer resins may be used: polyolefins such as polyethylene and polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene.

[0063] In the present invention, the thickness of the organic polymer substrate may be 3 μm to 50 μm. Although the range of the organic polymer substrate is not specifically limited to the aforementioned range, if the thickness is excessively thin compared to the aforementioned lower limit, the mechanical properties may deteriorate, and the separator may be easily damaged during battery use. Meanwhile, the pore size and porosity present in the organic polymer substrate are also not specifically limited, but may be 0.01 μm to 50 μm and 10 vol% to 95 vol%, respectively.

[0064] porous inorganic heat-resistant layer

[0065] As is well known, the porous inorganic heat-resistant layer (3a, 3b) comprises a plurality of inorganic particles and an organic binder polymer that binds the inorganic particles together. By coating the organic polymer substrate (1) with the porous inorganic heat-resistant layer (3a, 3b) containing inorganic particles in this way, the heat resistance and mechanical properties of the composite separation membrane (10) are improved.

[0066] The inorganic particles constituting the porous inorganic heat-resistant layers (3a, 3b) exist in a state of substantially adhering to each other, forming an interstitial volume between the inorganic particles, and this interstitial volume forms an empty space, thereby having a microporous structure. At this time, an organic binder polymer is interposed between the inorganic particles to bind them together, and the inorganic particles also serve as a kind of spacer that can maintain the physical shape of the porous inorganic heat-resistant layers (3a, 3b). Since the inorganic particles generally have the characteristic that their physical properties do not change even at high temperatures of 200 °C or higher, the composite separator (10) has excellent heat resistance due to the porous inorganic heat-resistant layers (3a, 3b). In the present invention, the porous inorganic heat-resistant layers (3a, 3b) may each have a thickness ranging from 1 μm to 50 μm, or from 1 μm to 30 μm, or from 1 μm to 5 μm.

[0067] The inorganic particles included in the porous inorganic heat-resistant layers (3a, 3b) are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles 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, using inorganic particles capable of transporting lithium ions can improve performance by increasing the ion conductivity within the electrochemical device. Additionally, using inorganic particles with a high dielectric constant can improve the ion conductivity of the electrolyte by contributing to an increase in the dissociation degree of electrolyte salts, such as lithium salts, within the liquid electrolyte. For the reasons mentioned above, the inorganic particles may include high dielectric constant inorganic particles with a dielectric constant of 5 or more, or 10 or more, inorganic particles capable of transporting lithium ions, or mixtures thereof. Non-limiting examples of inorganic particles with a dielectric constant of 5 or more include BaTiO3, Pb(Zr,Ti)O3 (PZT), and Pb 1-x La x Zr 1-y Ti y O3(PLZT, where, 0 < x < 1, 0 < y < 1), Pb(Mg 1 / 3 Nb 2 / 3 O3-PbTiO3 (PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, alumina (Al2O3), boehmite, SiC, TiO2, etc., can be used individually or in a mixture of two or more types. Furthermore, when the aforementioned high-dielectric constant inorganic particles are mixed with inorganic particles having lithium ion transport capabilities, their synergistic effects can be doubled. Non-limiting examples of inorganic particles having lithium ion transport capabilities include lithium phosphate (Li3PO4) and lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Lix Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), such as (LiAlTiP) 14Li2O-9Al2O3-38TiO2-39P2O5 x O y Series glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (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, etc. x Ge y P z S w Lithium nitrides such as , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), Li3N, etc. (Li x N y , 0 < x < 4, 0 < y < 2), SiS2-based glass such as Li3PO4-Li2S-SiS2 (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5 series glass such as LiI-Li2S-P2S5 (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7) or mixtures thereof, etc.

[0068] Average particle size of inorganic particles (D 50 ) is not particularly limited, but, for example, can be 100 to 1000 nm, specifically 100 to 800 nm, and more specifically 300 to 600 nm.

[0069] As an organic binder polymer included in the porous inorganic heat-resistant layer (3a, 3b) and binding inorganic particles together, both particulate and non-particulate organic binder polymers can be used.

[0070] Organic binder polymer non-particles include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cyanoethylpullulan, Examples include cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose. These may be used individually or in combination of two or more of them, but are not limited thereto.The formation of the first porous inorganic heat-resistant layer (3a) and the second porous inorganic heat-resistant layer (3b) using organic binder polymer non-particles can be achieved by dispersing inorganic particles in a solvent such as acetone, then adding and dissolving an organic binder in the solvent to produce a slurry, and then coating the slurry onto a porous organic polymer substrate (1) using methods such as gravure coating or bar coating.

[0071] In the porous inorganic heat-resistant layer (3a, 3b), using organic binder polymer particles as the organic binder polymer that binds the inorganic particles together is preferred in terms of reducing the resistance of the inorganic heat-resistant layer. That is, since the organic binder polymer particles maintain their particle shape within the coating layer, they hardly penetrate into the pores of the porous organic polymer substrate, thereby contributing to improving the pore clogging phenomenon of the organic polymer substrate.

[0072] As organic binder polymer particles, known organic binder polymer particles used in organic polymer adhesive layers can be used, for example, acrylic polymer particles.

[0073] The acrylic polymer is, more specifically, a polymer comprising carboxylic acid esters as repeating units, preferably a polymer of (meth)acrylic acid esters. 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, decyl (meth)acrylate, hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, ethylene glycol (meth)acrylate, di(meth)acrylate ethylene glycol, di(meth)acrylate propylene glycol. Examples include tri(meth)acrylate trimethylolpropane, tetra(meth)acrylate pentaerythritol, hexa(meth)acrylate dipentaerythritol, allyl (meth)acrylate, ethylene di(meth)acrylate, etc., and one or more selected from these may be used. Among these, in particular, one or more selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate may be used. The acrylic polymer particles may have a glass transition temperature (Tg) of 30 °C or higher, but are not limited thereto. When the Tg of the acrylic polymer is lower than room temperature, it may be used as an organic binder polymer non-particle.

[0074] As organic binder polymer particles, a vinylidene fluoride-based polymer may be included independently or together with the aforementioned acrylic polymer. The vinylidene fluoride-based polymer may be a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride with other polymerizable monomers, or a mixture of two or more of these. Examples of 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(methylvinyl)ether, perfluoro(ethylvinyl)ether, perfluoro(propylvinyl)ether, perfluoro(1,3-dioxol), perfluoro(2,2-dimethyl-1,3-dioxol), and trichloroethylene. In particular, the vinylidene fluoride-based polymer may be a copolymer of vinylidene fluoride and hexafluoropropylene. The content of vinylidene fluoride and other polymerizable monomers may be 1 to 20 weight percent of the copolymer, but is not limited thereto.

[0075] Average particle size of organic binder polymer particles (D 50 ) is not particularly limited, but can be, for example, 50 to 1000 nm, more specifically 100 to 500 nm.

[0076] In the porous inorganic heat-resistant layer (3a, 3b), the content ratio of inorganic particles and organic binder polymer is determined by considering the thickness, pore size, and porosity of the inorganic heat-resistant layer to be finally manufactured, and the inorganic particles may be included in a range of 70% to 99% by weight relative to 100% by weight of the inorganic heat-resistant layer based on weight ratio.

[0077] A porous inorganic heat-resistant layer (3a, 3b) using organic binder polymer particles can be manufactured by dispersing inorganic particles in an aqueous dispersion medium, then introducing and dispersing organic binder polymer particles into the aqueous dispersion medium to prepare a slurry, and then coating and drying the slurry on a porous organic polymer substrate (1) by methods such as bar coating or gravure coating. The aqueous dispersion medium may include one or more of water and alcohols having 1 to 5 carbon atoms. By using an aqueous dispersion medium, the particles of the organic binder polymer are not dissolved in the dispersion medium but are dispersed within the aqueous dispersion medium while maintaining their particle shape, and the particle shape is maintained even after coating and drying the slurry on a porous organic polymer substrate (1).

[0078] Organic polymer adhesive layer

[0079] The organic polymer adhesive layer (5a, 5b) coated on the outer surface of the porous inorganic heat-resistant layer (3a, 3b) comprises organic binder polymer particles, and the organic binder polymer particles included in the organic polymer adhesive layer (5a, 5b) are a mixture of acrylic polymer particles and vinylidene fluoride polymer particles.

[0080] FIG. 2 is an enlarged view of the “A” portion of the first porous inorganic heat-resistant layer (3a) and the first organic polymer adhesive layer (5a) of FIG. 1.

[0081] Referring to FIG. 2, a first organic polymer adhesive layer (5a) is positioned on a first porous inorganic heat-resistant layer (3a), and acrylic polymer particles (7) and vinylidene fluoride polymer particles (9) are mixed and positioned thereon.

[0082] In the first organic polymer adhesive layer (5a), the average particle size (D) of the acrylic polymer particles (7) 50 ) is the average particle size (D) of the vinylidene fluoride-based polymer particles (9). 50 The average particle size (D) of the acrylic polymer particles (7) is at least 2500 nm larger than ) 50) is 3000 nm or larger, and the average particle size (D) of the vinylidene fluoride-based polymer particles (9) 50 ) is 100 to 500 nm.

[0083] The acrylic polymer particles (7) have an average particle size (D 50 The average particle size (D) of the vinylidene fluoride-based polymer particles (9) 50 It is at least 2500 nm larger than ) to form a predetermined empty space between the acrylic polymer particles (7), and accordingly performs the function of improving the phenomenon of the separators bonding to each other or the rippling phenomenon in the wound state without a protective film when manufacturing the separator roll. The vinylidene fluoride polymer particles (9) particularly contribute to improving the adhesion between the two electrodes and the composite separator when the composite separator is interposed between the two electrodes and laminated through heat and pressure to manufacture an electrode assembly. The average particle size (D) of the acrylic polymer particles (7) 50 ) and the average particle size (D) of vinylidene fluoride-based polymer particles (9) 50 If the difference is less than 2500 nm, the improvement of the binding phenomenon and swell phenomenon between the membranes is insufficient. In this regard, specifically, the acrylic polymer particles (7) have an average particle size (D 50 The average particle size (D) of the vinylidene fluoride-based polymer particles (9) 50 It can be 3000 nm or larger than ), more specifically 4500 nm or larger.

[0084] In addition, the average particle size (D of the acrylic polymer particles (7) 50 ) is 3000 nm or larger, and specifically can be 5000 nm or larger. The average particle size (D) of the vinylidene fluoride-based polymer particles (9) 50 ) is 100 to 500 nm. The average particle size (D) of the acrylic polymer particles (7) 50If ) is less than 3000 nm, binding and swell phenomena between the membranes may occur. In this regard, the average particle size (D) of the acrylic polymer particles (7) 50 ) can be 4000 to 8000 nm, more specifically 5000 to 7000 nm, and even more specifically 5500 nm to 6500 nm. In addition, the average particle size (D) of the vinylidene fluoride-based polymer particles (9) 50 If ) is less than 100 nm, the dense structure resulting from the excessively small particle size may lead to excessively high adhesion to the electrode, and if it exceeds 500 nm, there is a risk of binding occurring between the separators. In this regard, the average particle size (D) of vinylidene fluoride-based polymer particles 50 More specifically, ) can be 100 to 300 nm.

[0085] Meanwhile, the weight ratio of acrylic polymer particles (7):vinylidene fluoride polymer particles (9) is 3.5:6.5 to 4.5:5.5. If the weight ratio of acrylic polymer particles (7):vinylidene fluoride polymer particles (9) is less than 3.5:6.5, the content of vinylidene fluoride polymer particles becomes excessively high, and as the porosity of the composite separator decreases, a problem arises in which cell performance is degraded. If the weight ratio of acrylic polymer particles (7):vinylidene fluoride polymer particles (9) exceeds 4.5:5.5, the content of vinylidene fluoride polymer particles becomes excessively low, and a problem arises in which the adhesion strength of the composite separator to the electrode decreases.

[0086] Thus, according to the present invention, the average particle size (D) of the acrylic polymer particles (7) and vinylidene fluoride polymer particles (9) included in the organic polymer adhesive layer (5) 50The content ratio and the ) are each controlled simultaneously within a predetermined range. Accordingly, when manufacturing the separator roll, the phenomenon of the separators sticking together or swelling in the wound state without a protective film is improved, and when the separator roll is unwound to manufacture an electrode assembly, the adhesion with the electrode is good and cell performance can be maintained.

[0087] The acrylic polymer particles (7) may be, for example, a polymer containing carboxylic acid esters as repeating units, preferably a polymer of (meth)acrylic acid esters. 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, decyl (meth)acrylate, hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, ethylene glycol (meth)acrylate, di(meth)acrylate ethylene glycol, di(meth)acrylate propylene glycol. Examples include tri(meth)acrylate trimethylolpropane, tetra(meth)acrylate pentaerythritol, hexa(meth)acrylate dipentaerythritol, allyl (meth)acrylate, ethylene di(meth)acrylate, etc., and one or more selected from these may be used. Among these, in particular, one or more selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate may be used. The acrylic polymer particles (7) may have a glass transition temperature (Tg) of 40 °C or higher, more specifically 40 to 70 °C, and even more specifically 55 to 65 °C, but are not limited thereto.

[0088] The vinylidene fluoride-based polymer particles (9) may be a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride with other polymerizable monomers, or a mixture of two or more of these. One or more of the vinylidene fluoride and other polymerizable monomers selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorofluoroethylene, 1,2-difluoroethylene, perfluoro(methylvinyl)ether, perfluoro(ethylvinyl)ether, perfluoro(propylvinyl)ether, perfluoro(1,3-dioxol), perfluoro(2,2-dimethyl-1,3-dioxol), and trichloroethylene may be included, but are not limited thereto. In particular, the vinylidene fluoride-based polymer may be a copolymer of vinylidene fluoride and hexafluoropropylene. The content of vinylidene fluoride and other polymerizable monomers may be 1 to 20 weight percent of the copolymer, but is not limited thereto. Vinylidene fluoride-based polymer particles (9) may have a melting point (Tm) of 130 °C or higher.

[0089] The organic polymer adhesive layer (5) can be manufactured by preparing a slurry by dispersing acrylic polymer particles (7) and vinylidene fluoride polymer particles (9) in an aqueous dispersion medium, and then coating and drying the slurry on a porous inorganic heat-resistant layer (3) by methods such as bar coating or gravure coating. The aqueous dispersion medium may include one or more of water and alcohols having 1 to 5 carbon atoms. By using an aqueous dispersion medium, the particles of the organic binder polymer are not dissolved in the dispersion medium but are dispersed within the aqueous dispersion medium while maintaining their particle shape, and the particle shape is maintained even after coating and drying the slurry on a porous organic polymer substrate (1).

[0090] The coating amount of the first organic polymer adhesive layer (5a) and the second organic polymer adhesive layer (5b) is 0.1 to 30 g / m² each. 2 It may be, specifically 0.2 to 10 g / m² 2It may be, and more specifically, 0.5 to 5 g / m 2 It could be.

[0091] The organic polymer adhesive layer (5a, 5b) may include other polymer particles or polymer non-particles in addition to acrylic polymer particles and vinylidene fluoride polymer particles as needed, and may include other additives such as dispersants.

[0092] For example, the organic polymer adhesive layer (5a, 5b) may include a compound having ethylene oxide repeating units and a double bond at the end as a dispersant. The compound having ethylene oxide repeating units and a double bond at the end included in the first organic polymer adhesive layer (5a) ensures that the organic polymer particles are well dispersed when hydrophobic organic polymer particles are dispersed in an aqueous dispersion medium such as water to form the first organic polymer adhesive layer (5a), and is presumed to participate in a reaction in which it is reduced during the activation process of the battery after electrolyte injection to form a negative electrode film (SEI), thereby improving wet adhesion more effectively. In addition, by including the compound having ethylene oxide repeating units and a double bond at the end in the first organic polymer adhesive layer (5a), the content of the electrolyte additive for forming the negative electrode film (SEI) can be relatively reduced, so the viscosity of the electrolyte can be lowered, and thus the ionic conductivity of the electrolyte can be improved. The compound having these ethylene oxide repeating units and having a double bond at the end may be one or more selected from the group consisting of poly(ethylene glycol) methyl ether methacrylate, poly(propylene glycol) dimethacrylate, poly(ethylene glycol) methyl ether acrylate, poly(ethylene glycol) diacrylate, and poly(ethylene glycol) dimethacrylate. The weight ratio of the organic polymer particles included in the first organic polymer adhesive layer (5a) to the compound having ethylene oxide repeating units and a double bond at the end may be 99:1 to 90:10 when considering the aforementioned effects.

[0093] cathode and anode

[0094] In a specific embodiment according to the present invention, the lithium secondary battery can be manufactured according to conventional methods known in the art. According to an embodiment according to the present invention, an electrode assembly can be manufactured by laminating the aforementioned composite separator (10) between the negative electrode (20) and the positive electrode (30).

[0095] That is, the composite separator (10) manufactured by the above-described method is wound to form a separator roll.

[0096] The separator roll can be stored for a specified period as needed, and when manufacturing the electrode assembly, the separator roll is removed and introduced into the lamination process with the electrode.

[0097] That is, an electrode assembly is manufactured by interposing a separator between the cathode (20) and the anode (30) and applying heat and pressure. In one embodiment of the present invention, the lamination process may be performed by a roll press device comprising a pair of pressure rollers. That is, the cathode, the separator, and the anode are sequentially laminated, placed between the pressure rollers, and heat and pressurized to achieve interlayer bonding. Through the heat and pressure process, the acrylic polymer particles (7) among the organic polymer particles constituting the organic polymer adhesive layer (5a) of the composite separator (10) lose their particulate form and are flattened, and accordingly, the vinylidene fluoride polymer particles (9) come into sufficient contact with the electrode, thereby sufficiently improving the adhesion strength with the electrode. In this regard, the temperature during heat and pressure may be 5 to 10 °C or higher than the Tg of the acrylic polymer particles (7), but is not limited thereto.

[0098] In one embodiment of the present invention, the electrode is not particularly limited and can be manufactured in a form in which the electrode active material is adhered to the electrode current collector according to conventional methods known in the art. Among the electrode active materials, non-limiting examples of the positive electrode active material include conventional positive electrode active materials that can be used in the positive electrode of a conventional lithium secondary battery, and in particular, lithium intercalation materials such as lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or composite oxides formed by a combination thereof are preferred. Non-limiting examples of the negative electrode active material include conventional negative electrode active materials that can be used in the negative electrode of a conventional lithium secondary battery, and in particular, lithium intercalation materials such as lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, graphite, or other carbons are preferred. Non-limiting examples of positive current collectors include foils made of aluminum, nickel, or combinations thereof, and non-limiting examples of negative current collectors include foils made of copper, gold, nickel, or copper alloys or combinations thereof.

[0099] electrolytes

[0100] A lithium secondary battery is manufactured by loading an electrode assembly, in which a negative electrode, a separator, and a positive electrode are stacked and assembled, into a battery case, injecting an electrolyte, and undergoing an activation process. The electrolyte that can be used in the present invention is A + B - As a salt with a structure similar to that of, A + is Li + , Na + , K + It includes alkali metal cations such as or ions composed of combinations thereof, and B - PF6 - , BF4 - , Cl - , Br - , I- , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , NCF3SO2)2 - , CCF2SO2)3 - Salts containing anions such as those or combinations thereof are dissolved or dissociated in organic solvents composed of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma-butyrolactone (γ-butyrolactone), or mixtures thereof, but are not limited thereto. In addition, if VC (vinylene carbonate), which is involved in the cathode film formation reaction, is included as an additive, it may be more advantageous for improving wet adhesion to the cathode.

[0101] The injection of the electrolyte can be performed at an appropriate stage during the battery manufacturing process, depending on the manufacturing process and required physical properties of the final product. That is, it can be applied before battery assembly or at the final stage of battery assembly. In addition to the general winding process, the electrode assembly of the present invention can also be applied as a battery through lamination (stacking) and folding processes of the bonded separator and electrode.

[0102] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0103]

[0104] Example 1

[0105] [Manufacturing of Composite Membranes]

[0106] A composite separation membrane (10) of Fig. 1 was manufactured.

[0107] Inorganic particles (Al2O3, D 50 An emulsion containing 96 parts by weight of an inorganic polymer (500 nm), 3 parts by weight of acrylic polymer particles (CSB-130, Toyo Ink, Tg: -30 °C), and 1 part by weight of sodium carboxymethyl cellulose was added to water to achieve a solid content of 35 wt%, and then zirconia beads with a particle size of 0.7 mm, equal to the amount of inorganic particles, were added and milled in a bead mill for 2 hours to prepare a slurry. This slurry was bar-coated onto both sides of a porous organic polymer separation membrane substrate made of polyethylene (porosity 45%, thickness 9 μm) and dried to form a first inorganic heat-resistant layer and a second inorganic heat-resistant layer with a thickness of 1.5 μm on both sides.

[0108] Next, PVdF-HFP copolymer particles (weight-average molecular weight 500,000, HFP content 10%, Tm 148 °C) and poly(ethylene glycol)methyl ether acrylate (#730270, Sigma-Aldrich) were added to water to achieve a total solid content concentration of 10 wt%, and the mixture was stirred at 1000 rpm for 10 minutes. An equal amount of zirconia beads with a particle size of 0.7 mm was added to the mixture, and a slurry was prepared by milling with a paint shaker for 2 hours. Then, an acrylic polymer particle (Tg: 60 °C) emulsion was further added and stirred at 500 rpm for 10 minutes to prepare an aqueous dispersion of organic binder polymer particles for forming an organic polymer adhesive layer. The weight ratio of PVdF-HFP copolymer particles:dispersant (poly(ethylene glycol)methyl ether acrylate):acrylic polymer particles in the dispersion of organic binder particles is 6:1:4.

[0109] This organic binder particle dispersion was bar-coated onto a separator formed with the first inorganic heat-resistant layer and the second inorganic heat-resistant layer, and dried to form an organic polymer adhesive layer on each side. The coating amount of the organic polymer adhesive layer was 0.7 g / m² based on the weight of the coating layer formed on the first inorganic heat-resistant layer. 2 It was, and the coating amount of the coating layer formed on the second inorganic heat-resistant layer was also the same.

[0110] The composite separator produced in this way was wound onto a rod to produce a separator roll, and stored for 14 days.

[0111] [Manufacturing of Lithium Secondary Batteries]

[0112] LiNi 0.8 Co 0.1 Mn 0.1 O2, PVdF, and carbon black were mixed in a weight ratio of 97.0:1.5:1.5 and dispersed in 2-methyl-2-pyrrolidone to prepare an anode slurry, which was then coated onto an aluminum current collector and dried and rolled to produce an anode.

[0113] A cathode slurry was prepared by mixing graphite, SBR, and CMC in a weight ratio of 89.2:10:0.8 and dispersing it in distilled water, and the slurry was coated onto a copper current collector, followed by drying and rolling to produce a cathode.

[0114] After removing the above separator roll, a monocell specimen was fabricated by laminating it with a porous polyethylene separator fabric, interposing it between the anode and the cathode, and laminating it using a hot press. The size of the specimen was 37 mm x 59 mm.

[0115] After loading the above specimen into a pouch-type case, a secondary battery was manufactured by injecting 0.5g of electrolyte (ethylene carbonate: ethylmethyl carbonate = 7:3 (volume ratio), LiPF6 1M, VC (vinylene carbonate) 2wt%).

[0116] Example 2

[0117] The procedure was carried out in the same manner as Example 1, except that the average particle size of the acrylic polymer contained in the acrylic polymer particle (Tg: 60 °C) emulsion was changed as shown in Table 1 below.

[0118] Comparative Examples 1-4

[0119] The procedure was carried out in the same manner as Example 1, except that the content ratio of acrylic polymer particles and vinylidene fluoride polymer particles was changed as shown in Table 1.

[0120]

[0121] [Dry Adhesion Measurement]

[0122] The dry adhesion between the cathode and the separator was evaluated using each specimen prepared above, and the results are summarized in Table 1 below.

[0123] The negative electrode prepared for manufacturing a lithium secondary battery was cut to a size of 20 mm x 100 mm. The separator prepared in the examples and comparative examples was cut to a size of 20 mm x 100 mm. The prepared separator and negative electrode were overlapped, placed between 100 μm PET films, and bonded using a flatbed press. At this time, the conditions of the flatbed press were heated and pressurized at 60°C and a pressure of 1000 kgf for 5 seconds. The bonded separator and negative electrode were attached to a slide glass using double-sided tape. The separator bonded to the negative electrode was peeled off at a 180° angle using a UTM and measured.

[0124] [Measurement of Average Particle Size of Organic Binder Polymer Particles]

[0125] The average particle size (D) of the organic binder polymer particles, obtained by diluting the organic binder polymer particles in a dispersion medium, using a Malvern Mastersizer 3000 particle size analyzer 50 ) was measured.

[0126] [Measurement of Average Particle Size of Inorganic Particles]

[0127] After adding inorganic particles and a dispersant to a dispersion medium and performing sonification, the average particle size (D) is measured using a Malvern Mastersizer 3000 particle size analyzer. 50 ) was measured.

[0128] [Measurement of Tg of Organic Binder Polymer Particles]

[0129] The Tg of the organic binder polymer particles was measured by the following method:

[0130] Using a DSC (TA instruments), the temperature was increased from 25°C to 500°C at a rate of 5°C / min, maintained for 30 minutes, and then lowered back to 25°C at a rate of 5°C / min. The Tg was measured using the graph obtained from this.

[0131] [Measurement of Tm of Organic Binder Polymer Particles]

[0132] The Tm of the organic binder polymer particles was measured as follows:

[0133] Using a DSC (TA instruments), the temperature was increased from 25°C to 500°C at a rate of 5°C / min, maintained for 30 minutes, and then lowered back to 25°C at a rate of 5°C / min. Tm was measured using the graph obtained from this.

[0134] [Measurement of swells]

[0135] The degree of swell phenomenon was measured for the separator rolls according to the following criteria:

[0136] After flattening the separator of the roll by 3 m, the degree of swell generation was measured.

[0137]

[0138] [Explanation of the symbol]

[0139] 1: Porous organic polymer substrate

[0140] 3a: First porous inorganic heat-resistant layer, 3b: Second porous inorganic heat-resistant layer

[0141] 5a: First organic polymer adhesive layer, 5b: Second organic polymer adhesive layer

[0142] 7: Acrylic polymer particles, 9: Vinylidene fluoride polymer particles

[0143] 10: Composite membrane

[0144] 20: Cathode

[0145] 30: Anode

Claims

1. Porous organic polymer substrate, A porous inorganic heat-resistant layer comprising an organic binder polymer that binds inorganic particles to each other and is coated on at least one surface of the above-mentioned organic polymer substrate. The above-mentioned porous inorganic heat-resistant layer is coated on the outer surface and comprises an organic polymer adhesive layer containing organic binder polymer particles, and The organic binder polymer particles included in the above organic polymer adhesive layer are a mixture of acrylic polymer particles and vinylidene fluoride polymer particles, and Average particle size (D) of the above acrylic polymer particles 50 ) is the average particle size (D) of the vinylidene fluoride-based polymer particles above. 50 It is more than 2500 nm larger than ) and Average particle size (D) of the above acrylic polymer particles 50 ) is 3000 nm or larger, and the average particle size (D) of the vinylidene fluoride-based polymer particles is 50 ) is 100 to 500 nm, and The weight ratio of the above acrylic polymer particles to vinylidene fluoride polymer particles is 3.5:6.5 to 4.5:5.5, Composite separator for lithium secondary batteries.

2. In Paragraph 1, The above acrylic polymer particles are (meth)acrylate 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 decyl, (meth)acrylate hydroxymethyl, (meth)acrylate hydroxyethyl, (meth)acrylate ethylene glycol, di(meth)acrylate ethylene glycol, di(meth)acrylate propylene glycol, tri(meth)acrylate trimethylolpropane, A composite separator for a lithium secondary battery, characterized by being a polymer derived from one or more monomers selected from the group consisting of tetra(meth)acrylate pentaerythritol, hexa(meth)acrylate dipentaerythritol, (meth)acrylate allyl, and di(meth)acrylate ethylene.

3. In Paragraph 1, A composite separator for a lithium secondary battery, characterized in that the vinylidene fluoride-based polymer particles are composed of a vinylidene fluoride-hexafluoropropylene copolymer.

4. In Paragraph 1, Average particle size (D) of the above acrylic polymer particles 50 A composite separator for a lithium secondary battery characterized by having a thickness of 4000 to 8000 nm.

5. In Paragraph 1, Average particle size (D) of the above acrylic polymer particles 50 A composite separator for a lithium secondary battery characterized by having a thickness of 5500 to 6500 nm.

6. In Paragraph 1, Average particle size (D) of the vinylidene fluoride-based polymer particles above 50 A composite separator for a lithium secondary battery characterized by having a thickness of 100 to 300 nm.

7. In Paragraph 1, A composite separator for a lithium secondary battery, characterized in that the Tg of the acrylic polymer particles is 40 to 70 °C and the Tm of the vinylidene fluoride polymer particles is 130 °C or higher.

8. In Paragraph 1, A composite separator for a lithium secondary battery, characterized in that the organic binder polymer included in the porous inorganic heat-resistant layer includes an acrylic polymer.

9. In Paragraph 1, Average particle size (D) of the above inorganic particles 50 A composite separator for a lithium secondary battery, having a thickness of 100 to 800 nm.

10. In Paragraph 1, Average particle size (D) of the above inorganic particles 50 A composite separator for a lithium secondary battery, having a thickness of 300 to 600 nm.

11. In Paragraph 1, A composite separator for a lithium secondary battery, characterized in that the above-mentioned inorganic particles constitute 70 to 99 weight percent based on the total weight of the inorganic heat-resistant layer.

12. A step of preparing and winding a composite separator for a lithium secondary battery according to any one of claims 1 to 11 to manufacture a separator roll; Step of disassembling the above-mentioned membrane roll; and A method for manufacturing an electrode assembly for a lithium secondary battery, comprising the step of preparing an electrode assembly by interposing the above-mentioned separator between the positive electrode and the negative electrode and heating and pressurizing.

13. Electrode assembly for a lithium secondary battery manufactured in accordance with Paragraph 12.

14. A lithium secondary battery having the electrode assembly of claim 13.

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