Electrode-integrated separator for lithium secondary battery and method for producing same

Abstract

The present invention relates to an electrode-integrated separator for a lithium secondary battery and a method for manufacturing the same. According to the present invention, an electrode-integrated separator for a lithium secondary battery that can minimize the occurrence of defects and exhibit excellent insulating properties and a method for manufacturing the same are provided.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0109885, filed August 22, 2023, Korean Patent Application No. 10-2023-0109887, filed August 22, 2023, and Korean Patent Application No. 10-2024-0110508, filed August 19, 2024, and all contents disclosed in the documents of these Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to an electrode-integrated separator for a lithium secondary battery and a method for producing the same. [Background technology]

[0003] As the functionality of mobile phones, laptops, tablet computers, mobile batteries, electric vehicles, personal mobility devices, etc. increases, the demand for secondary batteries used as their driving power sources is steadily increasing. In particular, lithium secondary batteries, which have a high operating voltage and a high energy density per unit weight, are the most widely used.

[0004] Lithium secondary batteries generally have a structure in which a chargeable and dischargeable electrode assembly consisting of a positive electrode, a separator, and a negative electrode is mounted in a battery case. The positive and negative electrodes are fabricated by coating one or both sides of a metal current collector with a slurry containing an electrode active material, followed by drying and rolling.

[0005] The separator is one of the important factors that determine the lifespan of a secondary battery and electrically insulates the positive and negative electrodes. Separators are required to have ion permeability and mechanical strength to allow the electrolyte to pass through smoothly. As the range of applications for high-energy lithium secondary batteries expands, the safety of separators at high temperatures is also becoming increasingly important.

[0006] Typically, separators made of a substrate and an inorganic coating layer have poor adhesion to electrodes due to their material properties, which can lead to partial lifting or wrinkles at the interface between the electrode and separator. Furthermore, polyolefins, which are commonly used as the substrate, have poor thermal stability, such as melting at high temperatures.

[0007] To address these issues, a method has been proposed in which the substrate is removed and a separator is constructed solely from an inorganic coating film. However, such separators still have insufficient adhesion to the electrodes and significantly poor insulation, making them vulnerable to internal short circuits when used in electrochemical devices. Such separators have a fatal drawback: their low tensile strength and elongation make them prone to tearing, which can lead to micro-short circuits within the electrode assembly. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides an electrode-integrated separator for a lithium secondary battery that minimizes the occurrence of defects and exhibits excellent insulating properties.

[0009] The present invention also provides a method for producing the electrode-integrated separator for a lithium secondary battery. [Means for solving the problem]

[0010] According to one embodiment of the present invention, a porous layer laminated on an electrode substrate, the porous layer comprises a polymeric binder and inorganic fine particles dispersed on the polymeric binder; The inorganic fine particles include two or more types of inorganic fine particles having different green densities measured under the same pressure condition. An electrode-integrated separator for a lithium secondary battery is provided.

[0011] According to another embodiment of the present invention, applying a slurry containing a polymeric binder, inorganic fine particles, and a solvent onto an electrode substrate to form a porous layer; The inorganic fine particles include two or more types of inorganic fine particles having different green densities measured under the same pressure condition. A method for manufacturing the electrode-integrated separator for a lithium secondary battery is provided.

[0012] According to another embodiment of the present invention, there is provided a lithium secondary battery including the electrode-integrated separator for a lithium secondary battery.

[0013] Hereinafter, the electrode-integrated separator for a lithium secondary battery according to an embodiment of the present invention and a method for manufacturing the same will be described in more detail.

[0014] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the invention, based on the principle that the inventor can appropriately define the concept of the term in order to best explain his or her invention.

[0015] Unless otherwise defined herein, all technical and scientific terms have the same meaning as commonly understood by those of ordinary skill in the art to which this invention belongs. The terms used in describing the present invention are merely for the purpose of effectively describing specific specific examples and are not intended to limit the present invention.

[0016] As used herein, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates to the contrary.

[0017] As used herein, the meaning of "comprising" is to specify certain properties, regions, integers, steps, operations, elements and / or components and does not exclude the presence or addition of other certain properties, regions, integers, steps, operations, elements, components and / or groups.

[0018] The present invention can be modified in various ways and can have various forms, so that specific embodiments are exemplified and described in detail below, but it should be understood that this is not intended to limit the present invention to the specific disclosed embodiments, and that the present invention includes any modifications, equivalents, or alternatives falling within the spirit and technical scope of the present invention.

[0019] In this specification, when the positional relationship of two parts is described using, for example, "above," "on top," "below," or "to the side," unless the expressions "directly" or "immediately" are used, one or more other parts may be located between the two parts.

[0020] In this specification, when a temporal relationship is described using, for example, "after," "following," "next," or "before," the terms "directly" or "immediately" are not used, and therefore non-consecutive cases may also be included.

[0021] As used herein, the term "at least one" should be understood to include all possible combinations of one or more of the associated items.

[0022] As used herein, the term "green density" refers to the density (g / cm) of a green pellet made by filling a mold with a specific amount of inorganic particles and applying pressure. 3 ) means

[0023] In this specification, terms including ordinal numbers, such as "first" and "second," are used to distinguish one component from another, and are not limited by the ordinal number. For example, within the scope of the present invention, a first component may be designated as a second component, and similarly, a second component may be designated as a first component.

[0024] In this specification, "one surface of the porous layer facing the electrode substrate" means the surface of the porous layer opposite to the surface in contact with the electrode substrate. That is, the porous layer has one surface in contact with the electrode substrate and another surface facing the electrode substrate.

[0025] According to one embodiment of the present invention, a porous layer laminated on an electrode substrate, the porous layer comprises a polymeric binder and inorganic fine particles dispersed on the polymeric binder; The inorganic fine particles include two or more types of inorganic fine particles having different green densities measured under the same pressure condition. An electrode-integrated separator for a lithium secondary battery is provided.

[0026] As a result of continuous research by the present inventors, it has been confirmed that an electrode-integrated separator for a lithium secondary battery that satisfies the above characteristics can minimize the occurrence of defects and exhibit excellent insulating properties.

[0027] In particular, the porous layer contains two or more types of inorganic fine particles having different green densities, which gives the porous layer a dense pore structure and high pore tortuosity. Such a porous layer minimizes the occurrence of defects and exhibits low resistance and high ionic conductivity. Furthermore, the porous layer allows a uniform potential to be formed in the electrode-integrated separator for lithium secondary batteries, thereby enabling the development of excellent insulating properties.

[0028] The electrode-integrated separator for a lithium secondary battery includes a porous layer laminated on an electrode substrate.

[0029] The electrode substrate may be an electrode substrate for a negative electrode or a positive electrode.

[0030] According to one embodiment, the electrode substrate includes an electrode active material layer laminated on an electrode current collector layer, and the porous layer is laminated on the electrode active material layer.

[0031] The electrode current collector layer may be made of any electrode current collector known in the art to which the present invention pertains as having conductivity without inducing chemical changes in lithium secondary batteries. For example, the electrode current collector may be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like.

[0032] Preferably, the electrode current collector may have a thickness of 3 μm to 500 μm. The electrode current collector may have a surface with fine irregularities to enhance adhesion to the electrode material. The electrode current collector may have various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0033] The electrode active material layer includes an electrode material composition that is a mixture of an electrode active material, a conductive material, and a binder.

[0034] The conductive material can be used to provide electronic conductivity to the electrode.

[0035] The conductive material can be any material that has electronic conductivity and does not cause chemical changes in the lithium secondary battery. Non-limiting examples of the conductive material include carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; graphite, such as natural graphite and artificial graphite; metal powder or metal fiber, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. The conductive material may be a mixture of one or more of the above-mentioned materials.

[0036] The content of the conductive material may be adjusted within a range that exhibits an appropriate level of conductivity without causing a decrease in the capacity of the lithium secondary battery, and preferably, the content of the conductive material may be 1 wt % to 10 wt %, or 1 wt % to 5 wt %, based on the total weight of the electrode material composition.

[0037] The binder is used to make the electrode material composition adhere well to the electrode current collector.

[0038] Non-limiting examples of the binder include polyvinyl alcohol, polyacrylate, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon resin, etc. The binder may be one of the above-mentioned examples or a mixture of two or more of them.

[0039] The content of the binder may be adjusted within a range that exhibits an appropriate level of adhesiveness without causing a decrease in the capacity of the lithium secondary battery, and preferably, the content of the binder may be 1 wt % to 10 wt %, or 1 wt % to 5 wt %, based on the total weight of the electrode material composition.

[0040] When the electrode substrate is a positive electrode, any material capable of reversibly inserting and extracting lithium ions can be used as the positive electrode active material without any particular limitation.

[0041] For example, the positive electrode active material may be a composite oxide or phosphate containing lithium and one of cobalt, manganese, nickel, iron, or a combination thereof.

[0042] As another example, the positive electrode active material may be a compound represented by any one of the following chemical formulas: Li a A 1-b R b D2(0.90≦a≦1.8, 0≦b≦0.5);Li a E 1-b R b O 2-c D c (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05);LiE 2-b R b O 4-c D c (0≦b≦0.5, 0≦c≦0.05);Li a Ni 1-b-c Co b R c D d (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d≦2);Li a Ni 1-b-c Co b R c O 2-d Z d (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d<2);Li a Ni 1-b-c Co b R c O 2-d Z2(0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d<2);Li a Ni 1-b-c Mn b R c D d (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d≦2);Li a Ni 1-b-c Mn b R c O 2-d Z d (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d<2);Li a Ni 1-b-c Mn b R c O 2-d Z2(0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d<2);Li a Nib E c G d O2(0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1.);Li a Ni b Co c Mn d G e O2(0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0.001≦e≦0.1);Li a NiG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a CoG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a MnG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn2G b O4(0.90≦a≦1.8, 0.001≦b≦0.1);QO2;QS2;LiQS2;V2O5;LiV2O5;LiTO2;LiNiVO4;Li (3-f) J2(PO4)3(0≦f≦2);Li (3-f) Fe2(PO4)3(0≦f≦2); and LiFePO4.

[0043] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; Z is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; T is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0044] The cathode active material may have a coating layer on its surface, or may be a mixture of the cathode active material and a cathode active material having a coating layer. The coating element contained in the coating layer may be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof.

[0045] According to one embodiment, the positive electrode active material may be included in an amount of 80 wt % to 95 wt % based on the total weight of the electrode material composition, and preferably, the positive electrode active material may be included in an amount of 82 wt % to 95 wt %, 82 wt % to 93 wt %, 85 wt % to 93 wt %, or 85 wt % to 90 wt % based on the total weight of the electrode material composition.

[0046] When the electrode substrate is a negative electrode portion, the negative electrode active material may include a material capable of reversibly intercalating and deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0047] Examples of the material capable of reversibly intercalating and deintercalating lithium ions include carbonaceous materials such as crystalline carbon, amorphous carbon, and mixtures thereof. Specifically, the carbonaceous material may be natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitches, mesophase pitch-based carbon fiber, carbon microbeads, petroleum or coal tar pitch-derived cokes, soft carbon, and hard carbon.

[0048] The alloy of the lithium metal may be an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Sn, Bi, Ga, and Cd.

[0049] The substance capable of doping and undoping lithium may be Si, Si-C composite, SiOx (0 < x < 2), Si-Q alloy (where Q is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof; provided that Si is excluded), Sn, SnO2, Sn-R alloy (where R is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof; provided that Sn is excluded), etc. And as the substance capable of doping and undoping lithium, at least one of the above examples and SiO2 can be mixed and used. Q and R may be Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, etc.

[0050] And the transition metal oxide may be vanadium oxide, lithium vanadium oxide, lithium titanium oxide, etc.

[0051] Preferably, the negative electrode active material may contain one or more compounds selected from the group consisting of carbonaceous materials and silicon compounds. Here, the carbonaceous material is one or more substances selected from the group consisting of natural graphite, artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch, mesophase pitch-based carbon fiber, carbon microspheres, petroleum or coal-based coke, softened carbon, and hardened carbon, as exemplified above. And the silicon compound is a compound containing Si exemplified above, that is, Si, Si-C composite, SiO x (0 < x < 2), the Si-Q alloy, mixtures thereof, or mixtures of at least one of these with SiO2 may also be used.

[0052] According to one embodiment, the negative electrode active material may be contained in an amount of 85% to 98% by weight based on the total weight of the electrode material composition. Preferably, the content of the negative electrode active material is 85% to 97% by weight, or 87% to 97% by weight, or 87% to 95% by weight, or 90% to 95% by weight based on the total weight of the negative electrode material.

[0053] According to one embodiment, the thickness of the electrode active material layer is preferably adjusted in the range of 5 μm to 500 μm, or 5 μm to 450 μm, or 10 μm to 450 μm for the manifestation of appropriate performance.

[0054] On the other hand, the electrode integrated separator for the lithium secondary battery includes a porous layer laminated on the electrode substrate. Preferably, the porous layer is laminated on the electrode current collector layer of the electrode substrate.

[0055] According to one embodiment, the porous layer contains a polymer binder and inorganic fine particles dispersed on the polymer binder.

[0056] The polymer binder may be gelled when impregnated with a liquid electrolyte, thereby exhibiting a high degree of swelling. The electrolyte injected after assembly of the lithium secondary battery permeates the polymer binder, and the polymer binder, which holds the absorbed electrolyte, has electrolyte ion conduction capability. Therefore, the polymer binder has a solubility index of 15 to 45 MPa. 1 / 2 A polymer in which

[0057] As an example, the polymer binder may be one or more compounds selected from the group consisting of polyvinylidene fluoride, poly(vinylidene fluoride-co-trichloroethylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-tetrafluoroethylene), poly(vinylidene fluoride-co-hexafluoropropylene), spandex, butyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, and polyvinyl acetate.

[0058] As another example, the binder may further include, in addition to the exemplary compounds, one or more compounds selected from the group consisting of polyimide, polyetherimide, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene-butadiene rubber, and fluororubber.

[0059] The inorganic fine particles form micropores due to empty spaces between the particles, maintain their physical shape at high temperatures, and are electrochemically stable.

[0060] According to one embodiment, the inorganic fine particles may include two or more types of inorganic fine particles having different green densities measured under the same pressure condition, or may consist of two types of inorganic fine particles having different green densities measured under the same pressure condition.

[0061] The green density of the inorganic fine particles is the density of a green pellet made by filling a mold with a specific amount of inorganic particles and applying pressure, and may vary depending on the material, shape, size, or porosity of the inorganic fine particles.

[0062] The porous layer contains two or more types of inorganic fine particles with different green densities, which gives the porous layer a dense pore structure and high pore tortuosity. This porous layer minimizes defects and exhibits low resistance and high ionic conductivity. Furthermore, the porous layer allows a uniform potential to be formed in the electrode-integrated separator for lithium secondary batteries, thereby enabling the development of excellent insulating properties.

[0063] According to one embodiment, the inorganic fine particles have a density of 1 ton / cm 2 Measured under a pressure of 1.2 g / cm 3 or 1.5g / cm 3 and a first inorganic fine particle having a green density of 1 ton / cm. 2 Measured under a pressure of 0.7 g / cm 3 or 1.1 g / cm 3 and second inorganic fine particles having a green density of

[0064] Here, the size of the mold used to form the powder compact of the first and second inorganic fine particles and the amount of each inorganic fine particle are the same. For example, a cylindrical mold with a diameter of 16 mm is filled with 1 g of any inorganic fine particles, and the powder compact is formed at a density of 1 ton / cm. 2When a green pellet is produced by applying a pressure of 1000 kJ / cm 2 to the first and second inorganic fine particles, the green pellet density can be preferably within the above range.

[0065] Specifically, the first inorganic fine particles have a density of 1.20 g / cm 3 or more than 1.21g / cm 3 or more, or 1.22 g / cm 3 or more than 1.23g / cm 3 or more than 1.24g / cm 3 or more, or 1.25g / cm 3 or more, or 1.26g / cm 3 or more, or 1.27 g / cm 3 or more, or 1.28g / cm 3 or more, or 1.29 g / cm 3 or more, or 1.30 g / cm 3 or more, or 1.31 g / cm 3 or more, or 1.32 g / cm 3 or more, or 1.33 g / cm 3 or more, or 1.34 g / cm 3 or more, or 1.35g / cm 3 and 1.50 g / cm 3 or less than 1.49g / cm 3 or less than 1.48g / cm 3 or less than 1.47g / cm 3 or less than 1.46g / cm 3 The second inorganic fine particles may have a green density of 0.70 g / cm or less. 3 or more than 0.71 g / cm 3 or more than 0.72 g / cm 3 or more than 0.73g / cm 3 or more than 0.74g / cm 3 or more than 0.75g / cm 3 or more than 0.76g / cm 3 or more than 0.77g / cm 3 or more than 0.78g / cm 3 or more than 0.79g / cm 3or more than 0.80g / cm 3 and 1.10 g / cm 3 or less than 1.09g / cm 3 or less than 1.08g / cm 3 or less than 1.07g / cm 3 or less than 1.06g / cm 3 or less than 1.05g / cm 3 or less than 1.04g / cm 3 or less than 1.03g / cm 3 or less than 1.02g / cm 3 or less than 1.01g / cm 3 or less than 1.00g / cm 3 The green density may be as follows:

[0066] Preferably, the first inorganic fine particles have a density of 1.20 g / cm 3 or 1.50 g / cm 3 , or 1.21 g / cm 3 or 1.50 g / cm 3 , or 1.22 g / cm 3 or 1.50 g / cm 3 , or 1.23 g / cm 3 or 1.50 g / cm 3 , or 1.24 g / cm 3 or 1.50 g / cm 3 , or 1.25g / cm 3 or 1.50 g / cm 3 , or 1.25g / cm 3 or 1.49 g / cm 3 , or 1.25g / cm 3 or 1.48g / cm 3 , or 1.26 g / cm 3 or 1.48g / cm 3 , or 1.27 g / cm 3 or 1.48g / cm 3 , or 1.28g / cm 3 or 1.48g / cm 3 , or 1.29 g / cm 3 or 1.48g / cm 3 , or 1.30 g / cm3 or 1.48g / cm 3 , or 1.30 g / cm 3 or 1.47 g / cm 3 , or 1.30 g / cm 3 or 1.46 g / cm 3 , or 1.31 g / cm 3 or 1.46 g / cm 3 , or 1.32 g / cm 3 or 1.46 g / cm 3 , or 1.33 g / cm 3 or 1.46 g / cm 3 , or 1.34 g / cm 3 or 1.46 g / cm 3 , or 1.35g / cm 3 or 1.46 g / cm 3 The second inorganic fine particles may have a green density of 0.70 g / cm. 3 or 1.10 g / cm 3 , or 0.71 g / cm 3 or 1.10 g / cm 3 , or 0.72 g / cm 3 or 1.10 g / cm 3 , or 0.73 g / cm 3 or 1.10 g / cm 3 , or 0.74 g / cm 3 or 1.10 g / cm 3 , or 0.75g / cm 3 or 1.10 g / cm 3 , or 0.75g / cm 3 or 1.09 g / cm 3 , or 0.75g / cm 3 or 1.08g / cm 3 , or 0.75g / cm 3 or 1.07 g / cm 3 , or 0.75g / cm 3 or 1.06g / cm 3 , or 0.75g / cm 3 or 1.05g / cm 3 , or 0.76 g / cm 3 or 1.05g / cm 3, or 0.77 g / cm 3 or 1.05g / cm 3 , or 0.78 g / cm 3 or 1.05g / cm 3 , or 0.79 g / cm 3 or 1.05g / cm 3 , or 0.80 g / cm 3 or 1.05g / cm 3 , or 0.80 g / cm 3 or 1.04g / cm 3 , or 0.80 g / cm 3 or 1.03g / cm 3 , or 0.80 g / cm 3 or 1.02 g / cm 3 , or 0.80 g / cm 3 or 1.01g / cm 3 , or 0.80 g / cm 3 or 1.00 g / cm 3 The powder may have a green density of 0.1 to 1.0.

[0067] In order to provide the porous layer with a dense pore structure and high pore tortuosity, the porous layer preferably contains first and second inorganic fine particles that satisfy the green density range.

[0068] However, if the green density of the first and second inorganic fine particles is outside the above range, a dense pore structure may not be formed in the porous layer, which may result in non-uniform potential in the electrode-integrated separator for lithium secondary batteries.Furthermore, if the green density of the first and second inorganic fine particles does not satisfy the above range, an appropriate level of tortuosity may not be achieved, which may increase the possibility of defects occurring in the porous layer and increase resistance.

[0069] According to one embodiment, the difference in green density between the first and second inorganic microparticles may be 0.20 or more, alternatively 0.21 or more, alternatively 0.22 or more, alternatively 0.23 or more, alternatively 0.24 or more, alternatively 0.25 or more, alternatively 0.26 or more, alternatively 0.27 or more, alternatively 0.28 or more, alternatively 0.29 or more, alternatively 0.30 or more, alternatively 0.31 or more, alternatively 0.32 or more, alternatively 0.33 or more, alternatively 0.34 or more, alternatively 0.35 or more; and 0.80 or less, alternatively 0.79 or less, alternatively 0.78 or less, alternatively 0.77 or less, alternatively 0.76 or less, alternatively 0.75 or less, alternatively 0.74 or less, alternatively 0.73 or less, alternatively 0.72 or less, alternatively 0.71 or less, alternatively 0.70 or less, alternatively 0.69 or less, alternatively 0.68 or less, alternatively 0.67 or less, alternatively 0.66 or less, or alternatively 0.65 or less.

[0070] In order to impart a dense pore structure and high pore tortuosity to the porous layer, it is preferable that the difference in green density between the first and second inorganic fine particles is 0.20 or more, alternatively 0.21 or more, alternatively 0.22 or more, alternatively 0.23 or more, alternatively 0.24 or more, alternatively 0.25 or more, alternatively 0.26 or more, alternatively 0.27 or more, alternatively 0.28 or more, alternatively 0.29 or more, alternatively 0.30 or more, alternatively 0.31 or more, alternatively 0.32 or more, alternatively 0.33 or more, alternatively 0.34 or more, or alternatively 0.35 or more.

[0071] However, if the difference in green density between the first and second inorganic fine particles is too large, a dense pore structure may not be formed in the porous layer, and an appropriate level of tortuosity may not be achieved. Therefore, it is preferable that the difference in green density between the first and second inorganic fine particles be 0.80 or less, alternatively 0.79 or less, alternatively 0.78 or less, alternatively 0.77 or less, alternatively 0.76 or less, alternatively 0.75 or less, alternatively 0.74 or less, alternatively 0.73 or less, alternatively 0.72 or less, alternatively 0.71 or less, alternatively 0.70 or less, alternatively 0.69 or less, alternatively 0.68 or less, alternatively 0.67 or less, alternatively 0.66 or less, or alternatively 0.65 or less.

[0072] Preferably, the difference in green density between the first and second inorganic fine particles is 0.20 to 0.80, alternatively 0.21 to 0.80, alternatively 0.22 to 0.80, alternatively 0.23 to 0.80, alternatively 0.24 to 0.80, alternatively 0.25 to 0.80, alternatively 0.25 to 0.79, alternatively 0.25 to 0.78, alternatively 0.25 to 0.77, alternatively 0.25 to 0.76, alternatively 0.25 to 0.75, alternatively 0.26 to 0.75, alternatively 0.27 to 0.75, alternatively 0.28 to 0.75, alternatively 0.29 to 0.79. Alternatively, it may be 0.30 to 0.75, alternatively 0.30 to 0.74, alternatively 0.30 to 0.73, alternatively 0.30 to 0.72, alternatively 0.30 to 0.71, alternatively 0.30 to 0.70, alternatively 0.31 to 0.70, alternatively 0.32 to 0.70, alternatively 0.33 to 0.70, alternatively 0.34 to 0.70, alternatively 0.35 to 0.70, alternatively 0.35 to 0.69, alternatively 0.35 to 0.68, alternatively 0.35 to 0.67, alternatively 0.35 to 0.66, alternatively 0.35 to 0.65.

[0073] According to one embodiment, the first inorganic fine particles are 40 m by nitrogen adsorption / desorption. 2 / g or 80m 2 / g Brunauer-Emmett-Teller (BET) specific surface area of ​​90 m 2 / g or 120m 2 The surface area of ​​the substrate may be a Brunauer-Emmett-Teller (BET) specific surface area of ​​1000 nm / g.

[0074] Specifically, the first inorganic fine particles are 40 m by nitrogen adsorption / desorption. 2 / g or more, or 41m 2 / g or more, or 42m 2 / g or more, or 43m 2 / g or more, or 44m 2 / g or more, or 45m 2 / g or more; and 80m 2 / g or less, or 79m 2 / g or less, or 78m2 / g or less, or 77m 2 / g or less, or 76m 2 / g or less, or 75m 2 / g or less, or 74m 2 / g or less, or 73m 2 / g or less, or 72m 2 / g or less, or 71m 2 / g or less, or 70m 2 The second inorganic fine particles may have a Brunauer-Emmett-Teller (BET) specific surface area of ​​90 m / g or less by nitrogen adsorption / desorption. 2 / g or more, or 91m 2 / g or more, or 92m 2 / g or more, or 93m 2 / g or more, or 94m 2 / g or more, or 95m 2 / g or more; and 120m 2 / g or less, or 119m 2 / g or less, or 118m 2 The specific surface area may be a Brunauer-Emmett-Teller (BET) specific surface area of ​​1 / g or less.

[0075] In order to provide the porous layer with a dense pore structure and high pore tortuosity, the porous layer preferably includes first and second inorganic fine particles having a BET specific surface area within the above range. However, if the BET specific surface areas of the first and second inorganic fine particles are outside the above range, the porous layer may not have a dense pore structure and may not have an appropriate level of tortuosity.

[0076] Preferably, the first inorganic fine particles are 40 m by nitrogen adsorption / desorption. 2 / g or 80m 2 / g, or 41m 2 / g or 80m 2 / g, or 42m 2 / g or 80m 2 / g, or 42m 2 / g or 79m 2 / g, or 42m 2 / g or 78m 2 / g, or 42m 2 / g or 77m 2 / g, or 42m 2 / g or 76m 2 / g, or 42m 2 / g or 75m 2 / g, or 43m 2 / g or 75m 2 / g, or 44m 2 / g or 75m 2 / g, or 45m 2 / g or 75m 2 / g, or 45m 2 / g or 74m 2 / g, or 45m 2 / g or 73m 2 / g, or 45m 2 / g or 72m 2 / g, or 45m 2 / g or 71m 2 / g, or 45m 2 / g or 70m 2 The second inorganic fine particles may have a BET specific surface area of ​​90m / g by nitrogen adsorption / desorption. 2 / g or 120m 2 / g, or 91m 2 / g or 120m 2 / g, or 92m 2 / g or 120m 2 / g, or 93m 2 / g or 120m 2 / g, or 94m 2 / g or 120m 2 / g, or 95m 2 / g or 120m 2 / g, or 95m 2 / g or 119m 2 / g, or 95m 2 / g or 118m 2 / g.

[0077] The first inorganic fine particles have a density of 1 ton / cm 2Measured under a pressure of 1.2 g / cm 3 or 1.5g / cm 3 Green density and nitrogen adsorption / desorption 2 / g or 80m 2 The second inorganic fine particles may have a Brunauer-Emmett-Teller (BET) specific surface area of ​​1 ton / cm. 2 Measured under a pressure of 0.7 g / cm 3 or 1.1 g / cm 3 Green density and nitrogen adsorption / desorption 2 / g or 120m 2 The surface area may have a Brunauer-Emmett-Teller (BET) specific surface area of ​​0.01 mm / g.

[0078] According to one embodiment, the first inorganic microparticles may have a primary particle diameter of 40 nm to 70 nm, or 45 nm to 70 nm, or 45 nm to 65 nm; and the second inorganic microparticles may have a primary particle diameter of 10 nm to 35 nm, or 15 nm to 35 nm, or 20 nm to 35 nm.

[0079] The first inorganic fine particles may have a secondary particle diameter of 250 nm to 550 nm, or 260 nm to 550 nm, or 260 nm to 540 nm, or 270 nm to 540 nm, or 270 nm to 530 nm; and the second inorganic fine particles may have a secondary particle diameter of 50 nm to 230 nm, or 60 nm to 230 nm, or 70 nm to 230 nm, or 70 nm to 220 nm, or 70 nm to 210 nm, or 70 nm to 200 nm, or 80 nm to 200 nm, or 90 nm to 200 nm, or 100 nm to 200 nm, or 100 nm to 190 nm, or 100 nm to 180 nm.

[0080] In order to ensure appropriate dispersion and pore size of the inorganic fine particles in the porous layer and to prevent the porous layer from becoming excessively thick, the porous layer preferably includes first and second inorganic fine particles that satisfy the primary particle diameter range and the secondary particle diameter range.

[0081] The particle size of the inorganic fine particles can be confirmed through a scanning electron microscope (SEM) or transmission electron microscope (TEM) image taken of a cross section of the porous layer.

[0082] The first inorganic fine particles have a density of 1 ton / cm 2 Measured under a pressure of 1.2 g / cm 3 or 1.5g / cm 3 and a secondary particle diameter of 250 nm to 550 nm. 2 Measured under a pressure of 0.7 g / cm 3 or 1.1 g / cm 3 and a secondary particle diameter of 50 nm to 230 nm.

[0083] The first inorganic fine particles have a density of 1 ton / cm 2 Measured under a pressure of 1.2 g / cm 3 or 1.5g / cm 3 Green density, nitrogen adsorption / desorption 40m 2 / g or 80m 2 The second inorganic fine particles may have a Brunauer-Emmett-Teller (BET) specific surface area of ​​1 ton / cm and a secondary particle diameter of 250 nm to 550 nm. 2 Measured under a pressure of 0.7 g / cm 3 or 1.1 g / cm 3 Green density, nitrogen adsorption / desorption 90m 2 / g or 120m 2 / g and a secondary particle diameter of 50 nm to 230 nm.

[0084] According to one embodiment, the inorganic fine particles may have a particle shape selected from the group consisting of acicular particles, angular particles, dendritic particles, fibrous particles, flaky particles, granular particles, irregular particles, nodular particles, and spheroidal particles.

[0085] Preferably, the first inorganic fine particles and the second inorganic fine particles may have different particle shapes.

[0086] For example, the first inorganic fine particles may be angular particles, and the second inorganic fine particles may be acicular particles. For another example, the first inorganic fine particles may be irregular particles, and the second inorganic fine particles may be fibrous particles.

[0087] However, since the green density of the inorganic fine particles may vary depending on the material, shape, size, or porosity of the inorganic fine particles, the shapes of the first inorganic fine particles and the second inorganic fine particles do not necessarily need to be different.

[0088] According to an embodiment, the inorganic fine particles may include the first inorganic fine particles and the second inorganic fine particles in a weight ratio of 1:1 to 100:1.

[0089] Specifically, the inorganic fine particles may include the first inorganic fine particles and the second inorganic fine particles in a weight ratio of 1:1 to 100:1, alternatively 1.5:1 to 100:1, alternatively 1.5:1 to 80:1, alternatively 2:1 to 80:1, alternatively 2:1 to 60:1, alternatively 2:1 to 40:1, or alternatively 2:1 to 20:1.

[0090] In order to provide the porous layer with a dense pore structure and high pore tortuosity, the inorganic fine particles preferably include the first inorganic fine particles and the second inorganic fine particles in the weight ratio range.

[0091] However, if the weight ratio of the first and second inorganic fine particles is outside the above range, a dense pore structure may not be formed in the porous layer, and an appropriate level of tortuosity may not be achieved.

[0092] According to one embodiment, the inorganic fine particles preferably do not undergo oxidation and / or reduction reactions within the operating voltage range of the secondary battery (e.g., 0 to 5 V based on Li / Li+). The inorganic fine particles preferably have high electrolyte ion transfer ability. The inorganic fine particles preferably have as low a density as possible so that they can be well dispersed within the polymer binder. Furthermore, the inorganic fine particles preferably have a high dielectric constant so that they can contribute to increasing the degree of dissociation of the electrolyte salt within the electrolyte.

[0093] Preferably, the inorganic fine particles may be one or more types selected from the group consisting of inorganic particles having a dielectric constant of 1 or more, inorganic particles having piezoelectricity, and inorganic particles having lithium ion transport ability.

[0094] For example, inorganic particles such as SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite (AlO(OH)), Al(OH)3, TiO2, and SiC have a dielectric constant of 1 or more and can be preferably used as the inorganic fine particles.

[0095] As another example, the piezoelectric inorganic particles are non-conductors at normal pressure, but when a certain pressure is applied, they become conductive due to a change in their internal structure. The piezoelectric inorganic particles have a high dielectric constant of 100 or more. When a certain pressure is applied to the piezoelectric inorganic particles to stretch or compress them, charges are generated, causing one side to become positively (+) charged and the other side to become negatively (-) charged, resulting in a potential difference between the two sides. Due to the characteristics of the piezoelectric inorganic particles, when an internal short circuit occurs in the electrodes of a secondary battery due to an external impact, direct contact between the positive and negative electrodes can be prevented, resulting in a gradual decrease in voltage and improved safety. Examples of the piezoelectric inorganic particles include BaTiO3, Pb(Zr,Ti)O3 (PZT), and Pb 1-x La x Zr 1-y Ti y O3(PLZT), Pb(Mg 1 / 3 Nb 2 / 3 Inorganic particles such as )O3-PbTiO3 (PMN-PT) and HfO2 can be preferably applied.

[0096] As another example, the inorganic particles having lithium ion transport ability refer to inorganic particles containing lithium element and having the function of transporting lithium ions without storing lithium. The inorganic particles having lithium ion transport ability can improve the conductivity of lithium ions in a battery. Examples of such inorganic particles include Li3PO4, Li x Ti y (PO4)3(0 <x<2、0<y<3)、Li x Al y Ti z (PO4)3(0 <x<2、0<y<1、0<z<3)、(LiAlTiP) x O y (0 <x<4、0<y<13)、Li x La y TiO3(0 <x<2、0<y<3)、Li x Ge y P z S w (0 <x<4、0<y<1、0<z<1、0<w<5)、Li x N y(0 < x < 4, 0 < y < 2), Li x Si y S z (0 < x < 3, 0 < y < 2, 0 < z < 4), and Li x P y S z Examples include inorganic particles such as (0 < x < 3, 0 < y < 3, 0 < z < 7).

[0097] Preferably, the inorganic fine particles are SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, AlO(OH), Al(OH)3, TiO2, SiC, BaTiO3, Pb(Zr, Ti)O3, Pb 1-x La x Zr 1-y Ti y O3, Pb(Mg 1 / 3 Nb 2 / 3 )O3 - PbTiO3, HfO2, Li3PO4, Li x Ti y (PO4)3 (0 < x < 2, 0 < y < 3), Li x Al y Ti z (PO4)3 (0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y (0 < x < 4, 0 < y < 13), Li x La y TiO3 (0 < x < 2, 0 < y < 3), Li x Ge y P z S w (0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), Li x N y (0 < x < 4, 0 < y < 2), Li x Si y S z (0 < x < 3, 0 < y < 2, 0 < z < 4), and Li x P y S z It may be one or more selected from the group consisting of (0 < x < 3, 0 < y < 3, 0 < z < 7).

[0098] According to one embodiment, the inorganic microparticles include the first inorganic microparticles and the second inorganic microparticles having different green densities measured under the same pressure condition; the first and second inorganic microparticles may have different particle morphologies and may be made of the same type of components.

[0099] According to one embodiment, the porous layer may include 1 to 90 wt % of the polymer binder and 10 to 99 wt % of the inorganic fine particles, or 1 to 40 wt % of the polymer binder and 60 to 99 wt % of the inorganic fine particles, or 2 to 30 wt % of the polymer binder and 70 to 98 wt % of the inorganic fine particles.

[0100] The inorganic fine particles are preferably contained in an amount of 10 wt % or more to provide the porous layer with appropriate porosity and insulating properties. However, if the inorganic fine particles are contained in an excessive amount, the mechanical properties of the porous layer may be reduced due to weakened adhesive strength. Therefore, the inorganic fine particles are preferably contained in an amount of 99 wt % or less.

[0101] According to one embodiment, the thickness of the porous layer is preferably adjusted in the range of 10 μm to 100 μm, or 10 μm to 80 μm, or 10 μm to 50 μm to exhibit suitable performance.

[0102] Meanwhile, according to one embodiment, the second inorganic fine particles may occupy a larger volume than the first inorganic fine particles within a region of 20% of the total thickness of the porous layer from one surface of the porous layer facing the electrode substrate.

[0103] The second inorganic microparticles occupy a larger volume than the first inorganic microparticles within a region that accounts for 20% of the total thickness of the porous layer from the side of the porous layer facing the electrode substrate, thereby enabling the porous layer to have a uniform surface. Furthermore, the uniform surface of the porous layer reduces the size of pores on the surface due to the microparticle effect, enabling the porous layer to exhibit high insulating properties. Furthermore, the phenomenon of lithium ions migrating in a locally tilted manner on the surface of the porous layer during operation of a lithium secondary battery including the porous layer can be prevented.

[0104] For example, within a region of 20% of the total thickness of the porous layer from one side of the porous layer facing the electrode substrate, the first inorganic microparticles may occupy a volume of 50% or less of the second inorganic microparticles (based on 100% volume).

[0105] In order to achieve the above-mentioned effects, it is preferable that the volume of the first inorganic microparticles in the region of the porous layer is 50% or less, alternatively 45% or less, alternatively 40% or less, alternatively 35% or less, alternatively 30% or less, alternatively 25% or less, alternatively 20% or less, or alternatively 15% or less of the volume of the second inorganic microparticles.

[0106] However, if the volume occupied by the first inorganic fine particles in the region is too small, the tortuosity of the pores in the region may not be adequate. Therefore, it is preferable that the first inorganic fine particles occupy 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, or 7% or more of the volume of the second inorganic fine particles (based on 100% volume) in the region of the porous layer.

[0107] Specifically, within a 20% region of the total thickness of the porous layer from one side of the porous layer facing the electrode substrate, the first inorganic fine particles may occupy a volume of 50% or less, or 1 to 50%, or 1 to 45%, or 1 to 40%, or 2 to 40%, or 3 to 40%, or 3 to 35%, or 3 to 30%, or 4 to 30%, or 5 to 30%, or 5 to 25%, or 5 to 20%, or 5 to 15%, or 6 to 15%, or 7 to 15% of the volume of the second inorganic fine particles (100%).

[0108] Furthermore, within a 20%, 15%, 10%, or 5% region of the total thickness of the porous layer from one side of the porous layer facing the electrode substrate, the first inorganic fine particles may occupy a volume of 50% or less, or 1 to 50%, or 1 to 45%, or 1 to 40%, or 2 to 40%, or 3 to 40%, or 3 to 35%, or 3 to 30%, or 4 to 30%, or 5 to 30%, or 5 to 25%, or 5 to 20%, or 5 to 15%, or 6 to 15%, or 7 to 15% of the volume of the second inorganic fine particles.

[0109] According to one embodiment, it is preferable that the second inorganic microparticles occupy a smaller volume than the first inorganic microparticles in a region from one surface of the porous layer facing the electrode substrate to a point between 20% and 70% of the total thickness of the porous layer.

[0110] If the second inorganic microparticles occupy a larger volume than the first inorganic microparticles in the region from 20% to 70% of the total thickness of the porous layer, the pore size may decrease in this region, resulting in a decrease in ionic conductivity (i.e., an increase in resistance). Therefore, it is preferable that the first inorganic microparticles occupy a relatively larger volume in this region of the porous layer to reduce the resistance of the porous layer.

[0111] Specifically, in a region from the 20% point to the 70% point of the total thickness of the porous layer from one side of the porous layer facing the electrode substrate, the first inorganic fine particles may occupy a volume of 120% or more, or 120 to 2000%, or 120 to 1500%, or 130 to 1500%, or 130 to 1000%, or 130 to 500%, or 130 to 250% of the second inorganic fine particles (based on 100% volume).

[0112] In addition, in a region from one side of the porous layer facing the electrode substrate to 5% to 100%, or 10% to 100%, or 15% to 100%, or 20% to 100%, or 20% to 90%, or 20% to 80%, or 20% to 70% of the total thickness of the porous layer, the first inorganic fine particles may occupy a volume of 120% or more, or 120 to 2000%, or 120 to 1500%, or 130 to 1500%, or 130 to 1000%, or 130 to 500%, or 130 to 250% of the second inorganic fine particles (based on 100% volume).

[0113] The volume ratio of the inorganic fine particles can be obtained by analyzing a cross-sectional SEM image of the porous layer, for example, by quantitatively quantifying the contrast ratio difference of each particle through rule-based computational vision analysis of the cross-sectional SEM image of the porous layer.

[0114] Meanwhile, according to another embodiment of the present invention, applying a slurry containing a polymeric binder, inorganic fine particles, and a solvent onto an electrode substrate to form a porous layer; The inorganic fine particles include two or more types of inorganic fine particles having different green densities measured under the same pressure condition. A method for manufacturing the electrode-integrated separator for a lithium secondary battery is provided.

[0115] The electrode-integrated separator for a lithium secondary battery may be provided by the manufacturing method.

[0116] In the step of forming the porous layer, the polymer binder, the inorganic fine particles, and the electrode substrate may be the same as those described above.

[0117] According to one embodiment, the slurry containing the polymer binder, inorganic fine particles, and solvent is obtained by first preparing a dispersion in which two or more types of inorganic fine particles having different green densities are dispersed in the solvent, and then mixing the polymer binder into the dispersion.

[0118] According to one embodiment, the solvent contained in the slurry is preferably a solvent that exhibits a solubility of 1 wt % or more, 2.5 wt % or more, 5 wt % or more, 7.5 wt % or more, or 10 wt % or more in the polymer binder at room temperature (25°C).

[0119] Preferably, the solvent may be one or more selected from the group consisting of methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone, dibutyl ether, tetrahydrofuran, cyclohexanone, benzene, fluorobenzene, N-methyl-2-pyrrolidone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, dimethylformamide, 1,3-dioxolane, and sulfolane.

[0120] According to one embodiment, the slurry preferably has a solids content of 30% to 80% by weight.

[0121] If the solid content of the slurry is too high, the viscosity may increase, preventing the slurry from penetrating into the pore regions of the electrode active material layer, which may reduce the interfacial adhesion between the electrode substrate and the porous layer. However, if the solid content of the slurry is too low, pinholes may occur during coating of the slurry, and the drying efficiency of the slurry coating may decrease.

[0122] Specifically, the solids content of the slurry may be 30% by weight or more; and 80% by weight or less, alternatively 70% by weight or less, alternatively 60% by weight or less. Preferably, the solids content of the slurry may be 30% to 80% by weight, alternatively 30% to 70% by weight, alternatively 30% to 60% by weight.

[0123] The slurry containing the polymer binder, the inorganic fine particles, and the solvent is coated on the electrode substrate, preferably on the electrode active material layer.

[0124] The slurry may be coated by any conventional method known in the art, such as spin coating, dip coating, die coating, roll coating, comma coating, gravure coating, bar coating, curtain coating, screen printing, inkjet printing, doctor blade, or a combination thereof.

[0125] In the slurry coating step, the thickness of the coating layer formed on the electrode substrate may be adjusted in consideration of the composition of the slurry and the thickness of the porous layer to be finally formed.

[0126] According to an embodiment, the step of forming the porous layer may be performed by evaporating the solvent from the slurry coated on the electrode substrate.

[0127] Preferably, the step of forming the porous layer can be performed at a temperature of 80° C. to 130° C. or 80° C. to 120° C. If the temperature does not satisfy this range, the drying efficiency may decrease or the morphology of the electrode substrate or the porous layer may change, causing defects.

[0128] According to one embodiment, the porous layer formed by the method may contain 1 to 90 wt % of the polymer binder and 10 to 99 wt % of the inorganic fine particles. The inorganic fine particles are preferably contained in an amount of 10 wt % or more to provide the porous layer with appropriate porosity and insulating properties. However, if the inorganic fine particles are contained in an excessive amount, the mechanical properties of the porous layer may be reduced due to weakened adhesive strength. Therefore, the inorganic fine particles are preferably contained in an amount of 99 wt % or less.

[0129] According to another embodiment of the present invention, there is provided a lithium secondary battery including the above-described electrode-integrated separator for a lithium secondary battery.

[0130] For example, the lithium secondary battery may include an electrode assembly including a counter electrode disposed on a porous layer of the electrode, an electrolyte impregnated in the electrode assembly, and a battery case that hermetically houses the electrode assembly and the electrolyte.

[0131] The lithium secondary battery includes the electrode assembly described above, and thus exhibits excellent durability and stable performance.

[0132] The lithium secondary battery may have various shapes such as a prismatic shape, a cylindrical shape, a pouch shape, and the like.

[0133] The lithium secondary battery can be used as an energy supply source with improved performance and safety in the fields of portable electronic devices such as mobile phones, laptops, tablet computers, mobile batteries, and digital cameras, and in the field of transportation such as electric vehicles, electric motorcycles, and personal mobility devices.

[0134] According to one embodiment, the electrolyte may be any electrolyte known in the art to which the present invention pertains that is applicable to lithium secondary batteries, without any particular limitation. For example, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc.

[0135] Specifically, the electrolyte may include a non-aqueous organic solvent and a lithium salt.

[0136] The non-aqueous organic solvent may be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0137] Specifically, the non-aqueous organic solvent may be an ester-based solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether-based solvent such as dibutyl ether or tetrahydrofuran; a ketone-based solvent such as cyclohexanone; an aromatic hydrocarbon-based solvent such as benzene or fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), or propylene carbonate (propylene carbonate). Examples of suitable solvents include carbonate solvents such as ethylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a hydrocarbon group having 2 to 20 carbon atoms and having a linear, branched, or cyclic structure, which may contain a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolane.

[0138] Among the above examples, carbonate-based solvents are preferably used as the non-aqueous organic solvent.

[0139] In particular, in consideration of the charge / discharge performance of the battery and compatibility with the sacrificial cathode material, a mixture of a cyclic carbonate (e.g., ethylene carbonate, propylene carbonate) having high ionic conductivity and a high dielectric constant and a linear carbonate (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate) having a low viscosity can be preferably used as the nonaqueous organic solvent. In this case, mixing the cyclic carbonate and the linear carbonate in a volume ratio of 1:1 to 1:9 can be advantageous for achieving the above-mentioned performance.

[0140] Furthermore, as the non-aqueous organic solvent, a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:2 to 1:10; or a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 1-3:1 to 9:1 can be preferably used.

[0141] The lithium salt contained in the electrolyte is dissolved in the non-aqueous organic solvent and acts as a lithium ion source in the battery, enabling basic operation of the lithium secondary battery and promoting the movement of lithium ions between the positive electrode and the negative electrode.

[0142] Specifically, the lithium salt may be LiPF, LiClO, LiAsF, LiBF, LiSbF, LiAlO, LiAlCl, LiCFSO, LiC4F9SO, LiN(C2F5SO3), LiN(C2F5SO2), LiN(CF3SO2), LiFSI, LiTFSI, LiCl, LiI, LiB(C2O4), etc. Preferably, the lithium salt may be LiPF, LiFSI, LiTFSI, or a mixture thereof.

[0143] The lithium salt may be contained in the electrolyte at a concentration of 0.1 M to 2.0 M. The lithium salt contained in this concentration range provides the electrolyte with appropriate conductivity and viscosity, thereby enabling the electrolyte to exhibit excellent electrolyte performance.

[0144] Optionally, the electrolyte may contain additives for the purposes of improving the life characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery.

[0145] For example, the additive may be a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphate, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. The additive may be included in an amount of 0.1 to 5 wt % based on the total weight of the electrolyte. [Effects of the Invention]

[0146] According to the present invention, there is provided an electrode-integrated separator for a lithium secondary battery that can minimize the occurrence of defects and exhibit excellent insulating properties, and a method for manufacturing the same. [Brief explanation of the drawings]

[0147] [Figure 1] FIG. 1 is a scanning electron microscope (SEM) image of the surface of the porous layer of the electrode-integrated separator according to Example 2 of the present specification. [Figure 2] FIG. 2 is an SEM image of a cross section of a porous layer in an electrode-integrated separator according to Example 2 of the present specification. [Figure 3] FIG. 3 is an SEM image of the surface of the porous layer of the electrode-integrated separator according to Example 3 of the present specification. [Figure 4] FIG. 4 is an SEM image of a cross section of a porous layer in an electrode-integrated separator according to Example 3 of the present specification. [Figure 5] FIG. 5 is an SEM image of the surface of the porous layer of the electrode-integrated separator according to Example 4 of the present specification. [Figure 6]FIG. 6 is an SEM image of a cross section of a porous layer in an electrode-integrated separator according to Example 4 of the present specification. [Figure 7] FIG. 7 is an SEM image of the surface of the porous layer in the electrode-integrated separator according to Comparative Example 1 of the present specification. [Figure 8] FIG. 8 is an SEM image of a cross section of a porous layer in an electrode-integrated separator according to Comparative Example 1 of the present specification. DETAILED DESCRIPTION OF THE INVENTION

[0148] The functions and effects of the present invention will be described in more detail below through specific examples of the present invention. However, these examples are presented as examples to help understand the invention. The following examples are not intended to limit the scope of the invention in any way, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical concept of the present invention.

[0149] Example 1 An electrode material composition was prepared, consisting of 95.6 wt% of an active material composed of 90 wt% graphite active material (a 3:7 mixture of artificial graphite and natural graphite) and 10 wt% SiO; 1 wt% acetylene black as a conductive material; and 1.1 wt% carboxymethyl cellulose (CMC) and 2.3 wt% styrene butadiene rubber (SBR) as binders. The electrode material composition was applied to one side of an 8 μm thick copper current collector using a comma coater. This was then dried and rolled at 130°C to prepare a negative electrode plate with a layer of negative electrode active material. The negative electrode active material layer had a porosity of 24% and a thickness of 44 μm.

[0150] Angular boehmite (AlO(OH)) was used as inorganic fine particles; the green density was 1.35 g / cm 3 BET specific surface area by nitrogen adsorption / desorption: 63 m 2 / g; primary particle diameter 50 nm; secondary particle diameter 350 nm) and acicular boehmite (AlO(OH); green density 0.99 g / cm 3BET specific surface area by nitrogen adsorption / desorption: 101 m 2 / g; primary particle diameter 30 nm; secondary particle diameter 155 nm) was prepared.

[0151] A mixture of 9.5 g of the angular boehmite and 0.5 g of the acicular boehmite was dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a dispersion. A polymer binder, poly(vinylidene fluoride-co-hexafluoropropylene), was added to the dispersion and mixed uniformly using a homogenizer to prepare a slurry with a solid content of 40%.

[0152] The slurry was applied onto the negative electrode active material layer using a dual slot die, and the solvent was evaporated at 100°C to form a porous layer with a thickness of 17 μm. The porous layer had a composition of 90 wt% of the inorganic fine particles and 10 wt% of the polymer binder.

[0153] The negative electrode plate on which the porous layer was formed was punched out to a size of 31 x 43 mm using a die punching machine to prepare a negative electrode part integrated separator.

[0154] A mixture of 94 wt% LiNiCoMnO2 (Ni:Co:Mn = 8:1:1) as the positive electrode active material, 3 wt% conductive carbon black (Super P; IMERYS Graphite & Carbon) as the conductive material, and 3 wt% polyvinylidene fluoride as the binder was uniformly dispersed in NMP to prepare a slurry. The slurry was applied to one side of an aluminum current collector, which was then dried and rolled to prepare a positive electrode plate with a layer of positive electrode active material. The positive electrode plate was then punched out using a die punching machine to prepare a 30 x 42 mm positive electrode part.

[0155] The positive electrode active material layer of the positive electrode part was disposed on the porous layer of the negative electrode part to abut against the porous layer of the negative electrode part to form an electrode facing body, and pressure lamination was performed at 90° C. to manufacture an electrode assembly.

[0156] The electrode assembly was housed in a pouch to form a small cell, and an electrolyte was injected into the pouch to fabricate five lithium secondary batteries.

[0157] The electrolyte used was a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, in which 0.5 M LiFSI, 0.7 M LiPF6, and 2 wt% vinylene carbonate (VC) were dissolved.

[0158] Example 2 A negative electrode integrated separator and a lithium secondary battery including the same were prepared in the same manner as in Example 1, except that a mixture of 9.0 g of the angular boehmite and 1.0 g of the acicular boehmite was used as the inorganic fine particles.

[0159] Example 3 A negative electrode integrated separator and a lithium secondary battery including the same were prepared in the same manner as in Example 1, except that a mixture of 8.0 g of the angular boehmite and 2.0 g of the acicular boehmite was used as the inorganic fine particles.

[0160] Example 4 A negative electrode integrated separator and a lithium secondary battery including the same were prepared in the same manner as in Example 1, except that a mixture of 7.0 g of the angular boehmite and 3.0 g of the acicular boehmite was used as the inorganic fine particles.

[0161] Example 5 As inorganic fine particles, instead of the mixture of angular boehmite and acicular boehmite, 9.5 g of angular boehmite (AlO(OH); green density 1.46 g / cm 3 BET specific surface area by nitrogen adsorption / desorption: 45m 2 / g; primary particle diameter 65 nm; secondary particle diameter 500 nm) and 0.5 g of acicular boehmite (AlO(OH); green density 0.81 g / cm 3 BET specific surface area by nitrogen adsorption / desorption: 118 m2 A separator and a lithium secondary battery including the same were manufactured in the same manner as in Example 1, except that a cellulose acylate polymer (aluminum cellulose, cellulose acetate, cellulose ester, cellulose ester, cellulose acetate ...

[0162] Comparative Example 1 As inorganic fine particles, instead of the mixture of the angular boehmite and the acicular boehmite, the angular boehmite (AlO(OH); green density 1.35 g / cm 3 BET specific surface area by nitrogen adsorption / desorption: 63 m 2 A negative electrode integrated separator and a lithium secondary battery including the same were manufactured in the same manner as in Example 1, except that 10.0 g of a cellulose acylate polymer (10.0 g / g; primary particle diameter 50 nm; secondary particle diameter 350 nm) was used alone.

[0163] Comparative Example 2 As inorganic fine particles, instead of the mixture of the angular boehmite and the acicular boehmite, the acicular boehmite (AlO(OH); green density 0.99 g / cm 3 BET specific surface area by nitrogen adsorption / desorption: 101 m 2 A negative electrode integrated separator and a lithium secondary battery including the same were manufactured in the same manner as in Example 1, except that 10.0 g of a cellulose acylate polymer (cellulose acetate / cellulose acetate stearate; primary particle diameter 30 nm; secondary particle diameter 155 nm) was used alone.

[0164] Comparative Example 3 As inorganic fine particles, instead of the mixture of angular boehmite and acicular boehmite, angular boehmite (AlO(OH); green density 1.46 g / cm 3 BET specific surface area by nitrogen adsorption / desorption: 37 m 2 A negative electrode integrated separator and a lithium secondary battery including the same were manufactured in the same manner as in Example 1, except that 10.0 g of a cellulose acylate polymer (cellulose acetate stearate, primary particle diameter 65 nm, secondary particle diameter 500 nm) was used alone.

[0165] Experimental Example 1 The green density of each of the inorganic fine particles used in the examples and comparative examples was obtained by the following method.

[0166] A cylindrical mold with a diameter of 16 mm is filled with 1 g of inorganic fine particles, and the density is 1 ton / cm 2 A pressure of 1000 kJ / cm was applied to produce a green pellet. The green pellet density (g / cm) was calculated from the measured volume of the green pellet and its weight (1 g). 3 ) was calculated.

[0167] Experimental Example 2 The nitrogen adsorption / desorption Brunauer-Emmett-Teller (BET) specific surface area of ​​the inorganic fine particles used in the examples and comparative examples was measured using a specific surface area analyzer (BEL Japan Inc., BELSORP-max). During the measurement, the temperature of the air oven attached to the analyzer was maintained at 40°C.

[0168] Experimental Example 3 The dielectric breakdown voltage (kV / mil) of the porous layer of each of the lithium secondary batteries (five samples per each) obtained in the Examples and Comparative Examples was measured as follows. Using a Hi-pot tester (Chroma 19055), the maximum voltage allowed before dielectric breakdown occurred was measured at a voltage increase rate of 100 V / sec. The measured maximum voltage was divided by the thickness of the porous layer to calculate the maximum voltage allowed per unit thickness, which is shown in Table 1 below.

[0169] Experimental Example 4 The resistance (ohm) and ionic conductivity (mS / cm) of the porous layer of the lithium secondary batteries (five samples per each) obtained in the Examples and Comparative Examples were measured as follows. The resistance of the porous layer was measured using electrochemical impedance spectroscopy (EIS) under an AC voltage with an amplitude of 10 Mv and a frequency of 104-105 Hz, followed by a Nyquist plot. The ionic conductivity was calculated by substituting the measured resistance, thickness, and area of ​​the porous layer, and is shown in Table 1 below.

[0170] Experimental Example 5 The lithium secondary batteries obtained in the examples and comparative examples were cycled at room temperature at 0.1 C-rate between 2.5 and 4.2 V. Furthermore, the charge capacity, discharge capacity, and discharge capacity retention rate during repeated cycling were measured through the capacity retention rate of the materials for 50 cycles.

[0171] [Table 1]

[0172] [Table 2]

[0173] Referring to Tables 1 and 2, it was confirmed that the porous layers according to the examples exhibited appropriate resistance and high ionic conductivity. In addition, it was confirmed that the porous layers according to the examples exhibited high tortuosity due to small pore size, resulting in high breakdown voltage and excellent life characteristics.

[0174] In contrast, the porous layer according to the comparative example exhibited a poorer breakdown voltage than the examples, and exhibited high resistance or low ionic conductivity.

[0175] Experimental Example 6 The surfaces and cross sections of the porous layers formed on the negative electrode plates according to Examples 2, 3, and 4 and Comparative Example 1 were observed using a scanning electron microscope, and the results are shown in FIGS.

[0176] FIG. 1 is an SEM image of the surface of the porous layer according to Example 2, and FIG. 2 is an SEM image of the cross section of the porous layer according to Example 2.

[0177] FIG. 3 is an SEM image of the surface of the porous layer according to Example 3, and FIG. 4 is an SEM image of the cross section of the porous layer according to Example 3.

[0178] FIG. 5 is an SEM image of the surface of the porous layer according to Example 4, and FIG. 6 is an SEM image of the cross section of the porous layer according to Example 4.

[0179] FIG. 7 is an SEM image of the surface of the porous layer according to Comparative Example 1, and FIG. 8 is an SEM image of the cross section of the porous layer according to Comparative Example 1.

[0180] The volume ratios of the first and second inorganic particles in the porous layer were quantitatively calculated using the contrast ratio difference of each particle through rule-based computational vision analysis of a cross-sectional SEM image of the porous layer. The volume ratios (volume of the first inorganic particles relative to 100% volume of the second inorganic particles) in the following regions A1 and A2 of the porous layer were calculated and are shown in Table 3.

[0181] [Table 3]

[0182] *Area A1: Within 20% of the total thickness of the porous layer from one side of the porous layer facing the electrode substrate *Area A2: A region from one surface of the porous layer facing the electrode substrate to the 20% to 70% point of the total thickness of the porous layer

[0183] Referring to Figures 1 to 4, it can be seen that in the porous layers according to Examples 2 and 3, the acicular boehmite particles (second inorganic fine particles) were distributed on the surface of the porous layers, occupying a larger volume than the angular boehmite particles (first inorganic fine particles).

[0184] Referring to Figures 5 and 6, it can be seen that the acicular boehmite particles in the porous layer of Example 4 are locally aggregated compared to Examples 2 and 3, but that the pores are densely formed overall.

[0185] In contrast, referring to FIGS. 7 and 8, it can be seen that the porous layer according to Comparative Example 1 has larger pores and is less dense than the porous layer according to the Examples.

[0186] Although the present invention has been described above with reference to limited examples and drawings, it goes without saying that the present invention is not limited thereto, and that various modifications and variations can be made by those skilled in the art within the scope of the technical concept of the present invention and the scope of the claims set forth below.

Claims

1. a porous layer laminated on an electrode substrate, the porous layer comprises a polymeric binder and inorganic fine particles dispersed on the polymeric binder; The inorganic fine particles include two or more types of inorganic fine particles having different green densities measured under the same pressure condition. Electrode-integrated separator for lithium secondary batteries.

2. The inorganic fine particles are 1 ton / cm ２ 1.2 g / cm measured under a pressure of ３ to 1.5 g / cm ３ First inorganic fine particles having a green density of 1 ton / cm ２ 0.7 g / cm measured under a pressure of ３ to 1.1 g / cm ３ and second inorganic fine particles having a green density of The electrode-integrated separator for a lithium secondary battery according to claim 1 .

3. 3. The electrode-integrated separator for a lithium secondary battery according to claim 2, wherein the second inorganic fine particles occupy a larger volume than the first inorganic fine particles within a region of 20% of the total thickness of the porous layer from one surface of the porous layer facing the electrode substrate.

4. 4. The electrode-integrated separator for a lithium secondary battery according to claim 3, wherein the first inorganic fine particles occupy a volume of 50% or less of the second inorganic fine particles within a region of 20% of the total thickness of the porous layer from one surface of the porous layer facing the electrode substrate.

5. 3. The electrode-integrated separator for a lithium secondary battery according to claim 2, wherein the second inorganic fine particles occupy a smaller volume than the first inorganic fine particles in a region from a surface of the porous layer facing the electrode substrate to a point between 20% and 70% of the total thickness of the porous layer.

6. 6. The electrode-integrated separator for a lithium secondary battery according to claim 5, wherein the first inorganic fine particles occupy a volume of 120% or more of the second inorganic fine particles in a region from a surface of the porous layer facing the electrode substrate to a point between 20% and 70% of the total thickness of the porous layer.

7. The inorganic fine particles are Nitrogen adsorption / desorption for 40 m ２ / g to 80m ２ / g Brunauer-Emmett-Teller (BET) specific surface area of ​​first inorganic fine particles; 90m by nitrogen adsorption / desorption ２ / g to 120m ２ and second inorganic fine particles having a Brunauer-Emmett-Teller (BET) specific surface area of ​​1 / g; The electrode-integrated separator for a lithium secondary battery according to claim 1 .

8. The inorganic fine particles are First inorganic fine particles having a secondary particle diameter of 250 nm to 550 nm; and second inorganic fine particles having a secondary particle diameter of 50 nm to 230 nm. The electrode-integrated separator for a lithium secondary battery according to claim 1 .

9. The electrode-integrated separator for a lithium secondary battery according to claim 2 , wherein the first inorganic fine particles and the second inorganic fine particles have different particle shapes.

10. The electrode-integrated separator for a lithium secondary battery according to claim 9 , wherein the first inorganic fine particles and the second inorganic fine particles are made of the same type of component.

11. The first inorganic fine particles are angular particles, The second inorganic fine particles are acicular particles. The electrode-integrated separator for a lithium secondary battery according to claim 9.

12. 3. The electrode-integrated separator for a lithium secondary battery according to claim 2, wherein the inorganic fine particles include the first inorganic fine particles and the second inorganic fine particles in a weight ratio of 1:1 to 100:

1.

13. The inorganic fine particles are SrTiO ３ , SnO ２ , CeO ２ , MgO, NiO, CaO, ZnO, ZrO ２ , Y ２ O ３ , Al ２ O ３ , boehmite (AlO(OH)), Al(OH) ３ , TiO ２ , SiC, BaTiO ３ , Pb(Zr,Ti)O ３ , Pb １－ｘ La ｘ Zr １－ｙ Ti ｙ O ３ , Pb(Mg １／３ Nb ２／３ )O ３ -PbTiO ３ , HfO ２ , Li ３ PO ４ , Li ｘ Ti ｙ (PO ４ ) ３ (0 < x < 2, 0 < y < 3), Li ｘ Al ｙ Ti ｚ (PO ４ ) ３ (0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) ｘ O ｙ (0 < x < 4, 0 < y < 13), Li ｘ La ｙ TiO ３ (0 < x < 2, 0 < y < 3), Li ｘ Ge ｙ P ｚ S ｗ (0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), Li ｘ N ｙ (0 < x < 4, 0 < y < 2), Li ｘ Si ｙ S ｚ (0 < x < 3, 0 < y < 2, 0 < z < 4), and Li ｘ P ｙ S ｚ 2. The electrode-integrated separator for a lithium secondary battery according to claim 1, wherein x is at least one selected from the group consisting of (0<x<3, 0<y<3, 0<z<7).

14. 2. The electrode-integrated separator for a lithium secondary battery according to claim 1, wherein the polymer binder is at least one compound selected from the group consisting of polyvinylidene fluoride, poly(vinylidene fluoride-co-trichloroethylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-tetrafluoroethylene), poly(vinylidene fluoride-co-hexafluoropropylene), spandex, butyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, and polyvinyl acetate.

15. 2. The electrode-integrated separator for a lithium secondary battery according to claim 1, wherein the porous layer comprises 1 to 90 wt % of the polymer binder and 10 to 99 wt % of the inorganic fine particles.

16. the electrode substrate includes an electrode active material layer laminated on an electrode current collector layer, The porous layer is laminated on the electrode active material layer. The electrode-integrated separator for a lithium secondary battery according to claim 1 .

17. applying a slurry containing a polymeric binder, inorganic fine particles, and a solvent onto an electrode substrate to form a porous layer; The inorganic fine particles include two or more types of inorganic fine particles having different green densities measured under the same pressure condition. The method for producing the electrode-integrated separator for a lithium secondary battery according to claim 1.

18. 18. The method of claim 17, wherein the slurry has a solid content of 30 to 80 wt %.

19. 18. The method for producing an electrode-integrated separator for a lithium secondary battery according to claim 17, wherein the solvent is at least one selected from the group consisting of methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone, dibutyl ether, tetrahydrofuran, cyclohexanone, benzene, fluorobenzene, N-methyl-2-pyrrolidone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, dimethylformamide, 1,3-dioxolane, and sulfolane.

20. 18. The method of claim 17, wherein the forming of the porous layer is performed by evaporating the solvent from the slurry coated on the electrode substrate at a temperature of 80°C to 130°C.

21. A lithium secondary battery comprising the electrode-integrated separator for lithium secondary batteries according to claim 1.

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