Electrode assembly for lithium secondary battery, method for manufacturing the same, and lithium secondary battery containing the same

Abstract

The present invention relates to an electrode assembly for a lithium secondary battery, which can further improve the insulation between electrodes and the safety of the lithium secondary battery, and a manufacturing method thereof. The electrode assembly includes a positive electrode-insulating layer composite including a first insulating layer disposed on a positive electrode, and a negative electrode-insulating layer composite including a second insulating layer disposed on a negative electrode, the first or second insulating layer being a porous insulating layer including polymer particles or ceramic particles having an absolute value of a zeta potential of 25 mV or more, and the ratio of the sum of the thicknesses of the first and second insulating layers to the sum of the thicknesses of the positive electrode-insulating layer composite and the negative electrode-insulating layer composite can satisfy a certain range.

Description

[Technical Field]

[0001] Mutual citation of related applications (etc.) This application claims priority rights based on Korean Patent Application No. 10-2022-0072307 dated June 14, 2022, and Korean Patent Application No. 10-2023-0074427 dated June 9, 2023, and all content disclosed in the documents of said Korean patent applications is included herein as part of this specification.

[0002] The present invention relates to an electrode assembly for a lithium secondary battery that can further improve the insulation between electrodes and the safety of the lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. [Background technology]

[0003] Recently, as the application areas of lithium-ion batteries have rapidly expanded from power supply for electronic devices such as electrical, electronic, communications, and computers to power storage and supply for large-area equipment such as automobiles and energy storage devices, there is a growing demand for lithium-ion batteries that are high-capacity, high-output, long-lasting, and highly stable.

[0004] Generally, lithium secondary batteries include a positive electrode, a negative electrode, a separation membrane interposed between the positive and negative electrodes, an electrolyte, an organic solvent, etc. The positive electrode may generate oxygen due to its unstable structure when charged, and since the generation of oxygen poses a significant fire hazard, research and development efforts are being made to improve the safety of lithium secondary batteries.

[0005] Separation membranes are used to ensure electrical insulation between the positive and negative electrodes, and thin, porous membranes made of polyolefin are commonly used. However, polyolefin-based separation membranes tend to shrink in high-temperature environments, potentially failing to provide insulation between the positive and negative electrodes. If electrical insulation between the positive and negative electrodes becomes impossible, a short circuit can occur, potentially leading to ignition when it interacts with oxygen generated by the unstable positive electrode. In other words, if a short circuit occurs in a charged lithium-ion battery in a high-temperature environment, there is a risk of the lithium-ion battery catching fire.

[0006] To reduce the risk of ignition and improve safety, attempts were made to form a porous coating layer or the like as an alternative to the polyolefin-based porous separation membrane. However, when forming such a porous coating layer, problems arose such as insufficient electrical insulation between the positive and negative electrodes, or a decrease in the capacity characteristics or lifespan characteristics of the lithium secondary battery due to the formation of the porous coating layer. [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, the present invention provides an electrode assembly for a lithium secondary battery and a method for manufacturing the same, which can further improve the insulation between electrodes and the safety of the lithium secondary battery while maintaining the excellent electrochemical properties of the lithium secondary battery.

[0008] The present invention also provides a lithium secondary battery that includes the electrode assembly and exhibits excellent inter-electrode insulation, safety, and lifespan characteristics. [Means for solving the problem]

[0009] In one embodiment of the invention, the invention includes a positive electrode-insulating layer composite comprising a first insulating layer disposed on the positive electrode and a negative electrode-insulating layer composite comprising a second insulating layer disposed on the negative electrode, The first or second insulating layer is a porous insulating layer containing polymer particles or ceramic particles whose zeta potential is 25 mV or greater. An electrode assembly for a lithium secondary battery is provided, wherein the ratio of the sum of the thicknesses of the first and second insulating layers to the sum of the thicknesses of the positive electrode-insulating layer composite and the negative electrode-insulating layer composite is 19% to 30%.

[0010] Furthermore, relating to another embodiment of the invention, a method for manufacturing an electrode assembly is provided, comprising the steps of (S1) forming a first insulating layer on a positive electrode to form a positive electrode-insulating layer composite, (S2) forming a second insulating layer on a negative electrode to form a negative electrode-insulating layer composite, and (S3) laminating the positive electrode-insulating layer composite and the negative electrode-insulating layer composite, wherein the first or second insulating layer includes polymer particles or ceramic particles having an absolute value of zeta potential of 25 mV or more.

[0011] In yet another embodiment of the invention, a lithium secondary battery is provided, comprising a battery case, an electrolyte, and the electrode assembly. [Effects of the Invention]

[0012] An electrode assembly according to one embodiment of the invention includes a positive electrode-insulating layer composite and a negative electrode-insulating layer composite, each having a porous insulating layer of a predetermined thickness ratio formed on the positive electrode and the negative electrode, respectively. It has been confirmed that such an electrode assembly not only maintains excellent electrical insulation between electrodes while the porous insulating layer replaces the existing separation membrane, but also substantially prevents short circuits due to the shrinkage of the separation membrane, thereby significantly improving the safety of the lithium secondary battery.

[0013] Furthermore, it was confirmed that optimizing the thickness ratio of each insulator allows for superior electrochemical properties, such as the lifespan characteristics, of lithium secondary batteries containing such electrode assemblies.

[0014] The drawings attached to the specification illustrate preferred embodiments of the present invention and, together with the content of the invention described above, serve to provide a better understanding of the technical concept of the present invention. Therefore, the present invention should not be interpreted as being limited solely to the matters described in such drawings. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a graph comparing the results of evaluating the electrical insulation characteristics of the electrode assemblies of Examples 1 to 3 and Comparative Examples 1 and 2, using a method that measures resistance under an applied voltage of 50V. [Figure 2] Figure 2 is a graph comparing the open-circuit voltage (OCV) profiles over time for lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 and 2. [Figure 3] Figure 3 is a graph showing the life characteristic evaluation results for lithium secondary batteries of Examples 1 to 3. [Modes for carrying out the invention]

[0016] Hereafter, terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or lexicographical meanings, but rather in a manner and concept consistent with the technical idea of ​​the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best describe their invention.

[0017] Unless otherwise defined, all terms used herein (including technical and scientific terms) should be used in a sense that is commonly understood by a person of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless explicitly defined otherwise.

[0018] The terms used herein are for illustrative purposes only and are not intended to limit the invention. In this specification, singular terms include plural terms unless otherwise specified in the text. The terms “comprises” and / or “comprising” as used in this specification do not preclude the presence or addition of one or more other components beyond those mentioned.

[0019] In this specification, when a part is said to include a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0020] In this specification, "A and / or B" means A or B or A and B.

[0021] In this specification, unless otherwise explicitly indicated, "%" means by weight.

[0022] In this specification, "zeta potential" is an indicator of the degree of surface charge of a particle. In this invention, the zeta potential of polymer particles or ceramic particles contained in an insulating layer can be measured by electrophoretic light scattering using dynamic light scattering equipment. As an example, the zeta potential can be measured after dispersing polymer particles or ceramic particles in a solvent such as water or alcohol without a dispersant.

[0023] The following provides a detailed explanation of electrode assemblies and other components related to the embodiment of the invention.

[0024] electrode assembly An electrode assembly according to one embodiment of the invention may be used in a lithium secondary battery. Such an electrode assembly includes a positive electrode-insulating layer composite including a first insulating layer disposed on the positive electrode, and a negative electrode-insulating layer composite including a second insulating layer disposed on the negative electrode, wherein the first or second insulating layer is a porous insulating layer containing polymer particles or ceramic particles having an absolute value of zeta potential of 25 mV or more, and the ratio of the sum of the thicknesses of the first and second insulating layers to the sum of the thicknesses of the positive electrode-insulating layer composite and the negative electrode-insulating layer composite may be 19% to 30%.

[0025] The positive electrode may include a positive electrode current collector and a positive electrode active material layer.

[0026] The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., but is not necessarily limited to these materials.

[0027] The positive electrode active material layer may contain a positive electrode active material, and may further contain a conductive material, a binder, etc., as needed.

[0028] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and may specifically include a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the lithium metal oxide may be a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), or a lithium-nickel-manganese oxide (e.g., LiNi 1-Y Mn Y O2(where 0 <Y<1)、LiMn 2-Z Ni ZO4 (where 0 < Z < 2, etc.), lithium-nickel-cobalt-based oxides (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1, etc.), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2, etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni p Co q Mn r )O2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2, etc.) or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni p2 Co q2 Mn r2 M s2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s2 are the atomic fractions of the respective independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, p2 + q2 + r2 + s2 = 1, etc.), etc., and any one or two or more of these compounds may be included.

[0029] Further, the positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, specifically, a lithium iron phosphate compound (e.g., LiFePO4), a lithium-manganese-iron phosphate compound (e.g., LiMn x Fe 1-x PO4, 0 < x < 1, etc.) may be included.

[0030] Among these, the lithium metal oxides that can improve the capacity characteristics and safety of the battery are LiCoO2, LiMnO2, LiNiO2, and lithium nickel manganese cobalt oxide (for example, Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2 etc.), lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2 etc.) or lithium nickel manganese cobalt aluminum oxide (e.g., Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 It may also be O2, or any one or more of these in a mixture.

[0031] The positive electrode active material may be included in an amount of 60 to 99% by weight, 70 to 99% by weight, or 80 to 98% by weight, based on the total weight of the positive electrode active material layer.

[0032] The conductive material may include, for example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystalline structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. However, it is not necessarily limited to these.

[0033] Furthermore, the binder may include, but is not limited to, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers.

[0034] The first or second insulating layer, or the first and second insulating layers, may each independently contain at least one of the polymer particles and the ceramic particles. In this case, the polymer particles and the ceramic particles may each independently have an absolute value of 25 mV or more for their zeta potential.

[0035] The absolute value of the zeta potential can define the surface polarity of the polymer particles or ceramic particles, and having an absolute value above a certain level can mean that the surface polarity is high. In this way, by combining particles with high surface polarity with a binder, etc., as described later, the first and / or second insulating layer can exhibit porosity, good coating properties, and surface characteristics that can replace existing separation films.

[0036] In particular, polymer particles or ceramic particles that satisfy these physical properties can have relatively high melting points, which can suppress short circuits caused by shrinkage of existing separation films when an insulating layer containing them is applied, making it possible to provide lithium secondary batteries that exhibit improved safety.

[0037] In addition, each of the insulating layers can improve the impregnation of the flame-retardant electrolyte, as described later, compared to existing separation membranes. This is thought to be because the flame-retardant electrolyte has relatively high polarity compared to existing electrolytes. Therefore, by combining the electrode assembly of the above embodiment with a flame-retardant electrolyte, it is possible to further improve the safety of the lithium secondary battery while ensuring high lithium ion mobility through the insulating layer and further improving the electrochemical properties of the battery.

[0038] On the other hand, the zeta potential of the polymer particles or ceramic particles can be measured, for example, by electrophoretic light scattering using dynamic light scattering equipment. In this case, the zeta potential of the polymer particles or ceramic particles can be measured while they are dispersed in water or an alcohol-based solvent without a separate dispersant. In a specific example, the zeta potential can be measured when the particles are dispersed in water at a concentration of 0.1% by weight or less.

[0039] The absolute value of the zeta potential of the polymer particles or ceramic particles may be 25mV or more, 35mV or more, or 45mV or more, and may be 100mV or less, 90mV or less, or 80mV or less. When the absolute value of the zeta potential satisfies the above numerical range, the flame-retardant electrolyte can be easily impregnated into each insulating layer, a uniform reaction can occur throughout the electrode, and thereby various performance characteristics such as capacity, output, and life characteristics of the lithium secondary battery can be improved.

[0040] Specific examples of the polymer particles include, but are not limited to, one or more selected from the group consisting of polyalkyl (meth)acrylates such as polyethylene oxide (PEO), polyphenylene sulfide (PPS), and polymethyl methacrylate (PMMA), polystyrene, polyvinyl chloride, polycarbonate, polysulfone, polyethersulfone, polyetherimide, polyphenylsulfone, polyamideimide, polyimide, polybendiimidazole, polyetherketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate.

[0041] Furthermore, specific examples of the ceramic particles may include, but are not limited to, one or more selected from the group consisting of aluminum oxide, titanium oxide, iron oxide, silicon oxide, zirconium oxide, cobalt oxide, tin oxide, nickel oxide, zinc oxide, vanadium oxide, and manganese oxide.

[0042] The zeta potential of the polymer particles or ceramic particles can be adjusted not only by the type of particle but also by the particle size or surface characteristics of these particles. To achieve the zeta potential, dispersibility, or appropriate porosity of each insulating layer, the polymer particles or ceramic particles have an average particle size D of 50 nm to 3 μm, 50 nm to 2 μm, or 100 nm to 1.5 μm. 50 It can have.

[0043] The average particle size D of the aforementioned particles 50 If the average particle size D of the particles is smaller than 50 nm, interparticle aggregation occurs due to a decrease in particle dispersibility, and the aggregated particles clog the pores, making it difficult to form an insulating layer with a porous structure. 50If the thickness is greater than 3 μm, the porous structure within the insulating layer is simplified, leading to the problem of lithium dendrite formation during cell fabrication.

[0044] In addition, for the purpose of controlling the surface properties of the polymer particles or ceramic particles and thereby adjusting the zeta potential, the polymer particles or ceramic particles may be included in each insulating layer in a state in which they have been surface-treated with oxygen plasma or an ion beam.

[0045] On the other hand, in one embodiment of the electrode assembly, the first insulating layer may be coated on the positive electrode, thereby forming a positive electrode-insulating layer composite. The first insulating layer can serve to electrically insulate the positive electrode and the negative electrode.

[0046] The first insulating layer may further contain, in addition to the polymer particles or ceramic particles described above, a dispersant, a binder, and the like.

[0047] The dispersant may include, for example, a hydrogenated nitrile polymer, and more specifically, a hydrogenated nitrile copolymer.

[0048] Specifically, the hydrogenated nitrile copolymer may be a copolymer containing structural units derived from α,β-unsaturated nitrile and structural units derived from hydrogenated conjugated diene, or a copolymer containing structural units derived from α,β-unsaturated nitrile, structural units derived from conjugated diene, and structural units derived from hydrogenated conjugated diene. As the α,β-unsaturated nitrile monomer, for example, acrylonitrile or methacrylonitrile may be used, and one or more of these may be used. As the conjugated diene monomer, for example, a conjugated diene monomer having 4 to 6 carbon atoms, such as 1,3-butadiene, isoprene, or 2,3-methylbutadiene, may be used, and one or more of these may be used.

[0049] More specifically, the hydrogenated nitrile copolymer may be hydrogenated nitrile butadiene rubber (H-NBR).

[0050] On the other hand, the binder plays a role in improving the adhesion between the insulating layer and the active material layer, where the absolute value of the zeta potential is 25 mV or higher. It also allows for the proper dispersion of the aforementioned polymer particles or ceramic particles on the binder, enabling the formation of a good porous insulating layer.

[0051] The binder may include, for example, one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, and fluororubber.

[0052] The first insulating layer may have a thickness of at least 5 μm, and may have a thickness of 10 to 30 μm, or 10 to 20 μm. When the thickness of the first insulating layer satisfies the above numerical range, it is possible to ensure that the electrode assembly of one embodiment has excellent electrical insulation properties.

[0053] Furthermore, the aforementioned first insulating layer may contain 55 to 85% by weight, or 60 to 80% by weight, of the polymer particles or ceramic particles, 10 to 35% by weight, or 11 to 33% by weight, of the binder, and 3 to 20% by weight, or 5 to 15% by weight, of the dispersant. Thus, the first insulating layer can be formed on the positive electrode active material layer in the form of a good porous insulating layer, exhibiting excellent electrical insulation properties.

[0054] On the other hand, the second insulating layer may be coated onto the negative electrode, thereby forming a negative electrode-insulating layer composite. The second insulating layer can serve to electrically insulate the positive electrode and the negative electrode.

[0055] Such a second insulating layer may have a different composition from the first insulating layer described above, but it may contain the same type of polymer particles or ceramic particles as the first insulating layer, or more appropriately, it may have the same composition as the first insulating layer, containing the same components in the same amounts, so that it can come into contact with the first insulating layer, exhibit excellent electrical insulation between electrodes, and serve as a replacement for existing separation films.

[0056] However, the thickness of the second insulating layer may differ from the thickness of the first insulating layer. Such a second insulating layer can have a thickness of at least 5 μm, and can have a thickness of 15 to 35 μm, 20 to 35 μm, or 20 to 30 μm. When the thickness of the second insulating layer satisfies the above numerical range, it is possible to ensure that the electrode assembly described later has excellent electrical insulation properties.

[0057] In the electrode assembly of the aforementioned embodiment, it is preferable that the first and second insulating layers satisfy a certain thickness ratio and thickness range so that the safety of the lithium secondary battery can be improved while the first and second insulating layers work together to exhibit excellent electrical insulation.

[0058] More specifically, the ratio of the sum of the thicknesses of the first and second insulating layers to the sum of the thicknesses of the positive electrode-insulating layer composite and the negative electrode-insulating layer composite may be 19.0% to 30.0%, or 19.5% to 29.0%, or 19.6% to 25.0%. In this case, the thickness ratio may be calculated as the ratio of the sum of the thicknesses of the first and second insulating layers to the sum of the thicknesses of the positive electrode and negative electrode, which include the current collector and active material layer, and the first and second insulating layers. The sum of the thicknesses of the first and second insulating layers may be 33 to 55 μm, or 33 to 50 μm, or 33 to 40 μm.

[0059] It has been confirmed that if the sum or ratio of the thicknesses of the first and second insulating layers becomes excessively small, sufficient electrical insulation between the electrodes may not be ensured. Conversely, if the sum or ratio of the thicknesses of the first and second insulating layers becomes excessively large, the resistance characteristics, capacitance characteristics, or life characteristics of the lithium secondary battery may deteriorate.

[0060] The positive electrode-insulating layer composite and the negative electrode-insulating layer composite described above may be stacked, and the first insulating layer and the second insulating layer may be arranged facing each other.

[0061] By arranging the first insulating layer and the second insulating layer opposite each other, the electrode assembly may be laminated in the order of, for example, positive electrode, first insulating layer, second insulating layer, and negative electrode. In other words, the first insulating layer and the second insulating layer may be in direct contact with each other without a separate separator or the like interposed between them. The first insulating layer and the second insulating layer can electrically insulate the positive electrode and the negative electrode from each other.

[0062] Furthermore, while the first insulating layer and the second insulating layer are formed simultaneously on one surface of the positive or negative electrode, in this case, the first insulating layer and the second insulating layer are formed on the positive and negative electrodes respectively and then joined together, thus achieving superior electrical insulation. This is because, when the insulating layer is formed simultaneously on one surface of the positive or negative electrode, microcracks are more likely to occur in the insulating layer, and current concentrates in these microcracks, inducing dendrite growth in the insulating layer. In contrast, when the first insulating layer and the second insulating layer are formed on the positive and negative electrodes respectively and then joined together, dendrite growth is suppressed, ensuring superior electrical insulation.

[0063] Therefore, the electrode assembly for the lithium secondary battery may not include a separate separation membrane.

[0064] On the other hand, in the electrode assembly of the aforementioned embodiment, the negative electrode included in the negative electrode-insulating layer composite may include a negative electrode current collector and a negative electrode active material layer.

[0065] The negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treatment with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used.

[0066] The negative electrode current collector can typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the negative electrode current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in a variety of forms such as film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0067] The negative electrode active material layer may contain a negative electrode active material and may further contain conductive materials, binders, etc., as needed.

[0068] The negative electrode active material may include at least one selected from the group consisting of lithium metal, carbon material capable of reversibly intercalating / deintercalating lithium ions, metal or alloys of these metals with lithium, metal composite oxides, lithium-doped and dedoped materials, and transition metal oxides.

[0069] As a carbon material capable of reversibly intercalating / deintercalating lithium ions, any carbon-based negative electrode active material commonly used in lithium-ion secondary batteries can be used without particular limitations. Typical examples include crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, while examples of amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, and calcined coke.

[0070] As the metal or an alloy of these metals and lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn or an alloy of these metals and lithium may be used.

[0071] As the metal composite oxide, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3(0 < x ≦ 1), Li x WO2(0 < x ≦ 1) and Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) selected from the group consisting of may also be used.

[0072] As the substance capable of doping and undoping lithium, Si, SiO x (0 < x ≦ 2), Si - Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements and combinations thereof, and is not Si), Sn, SnO2, Sn - Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements and combinations thereof, and is not Sn), etc. may be mentioned, and at least one of these and SiO2 may be mixed and used. As the element Y, it may be selected from the group consisting of 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, Ge, P, As, Sb, Bi, S, Se, Te, Po and combinations thereof.

[0073] Examples of the transition metal oxides include lithium-containing titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

[0074] The negative electrode active material may be included in an amount of 60 to 99% by weight, 70 to 99% by weight, or 80 to 98% by weight, based on the total weight of the negative electrode active material layer.

[0075] Furthermore, the conductive material is used as a component to further improve the conductivity of the negative electrode active material. Such a conductive material is not particularly limited as long as it does not induce a chemical change in the battery and is conductive. For example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystalline structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0076] The binder is a component that assists in the bonding between the conductive material, the negative electrode active material, and the negative electrode current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0077] Manufacturing method for electrode assemblies On the other hand, a method for manufacturing an electrode assembly according to another embodiment of the invention may include the following steps.

[0078] (S1) A step to form a positive electrode-insulating layer composite by forming a first insulating layer on the positive electrode. (S2) A step to form a negative electrode-insulating layer composite by forming a second insulating layer on the negative electrode. (S3) Step of laminating the positive electrode-insulating layer composite and the negative electrode-insulating layer composite.

[0079] Furthermore, as already explained with respect to one embodiment, the first or second insulating layer may contain polymer particles or ceramic particles having an absolute value of 25 mV or more in zeta potential. However, since the compositions of the positive electrode, negative electrode, first insulating layer, and second insulating layer have been explained in detail above, no further explanation regarding them will be provided.

[0080] In the manufacturing method of the other embodiment described above, first, a first insulating layer is formed on the positive electrode to form a positive electrode-insulating layer composite (S1). Specifically, after applying a slurry composition for forming a positive electrode active material layer onto a positive electrode current collector, the positive electrode is prepared by drying and rolling, a first insulating layer slurry is manufactured and applied to the prepared positive electrode, and then dried to form the first insulating layer, thereby forming a positive electrode-insulating layer composite.

[0081] The first insulating layer slurry may contain polymer particles or ceramic particles, a dispersant, a binder, a solvent, and the like.

[0082] Subsequently, a second insulating layer is formed on the negative electrode to form a negative electrode-insulating layer composite (S2).

[0083] Specifically, a second insulating layer slurry can be prepared and applied to the prepared negative electrode, and then dried to form a negative electrode-insulating layer composite.

[0084] The second insulating layer slurry may be prepared in the same manner as the first insulating layer slurry. However, the type and / or content of polymer particles or ceramic particles, dispersants, binders, and solvents may be appropriately adjusted to control the insulating properties.

[0085] Subsequently, the positive electrode-insulating layer composite and the negative electrode-insulating layer composite are laminated (S3).

[0086] The positive electrode-insulating layer composite and the negative electrode-insulating layer composite can be laminated such that the first insulating layer and the second insulating layer are in direct contact with each other.

[0087] As a result, the first insulating layer and the second insulating layer may be arranged facing each other. The first insulating layer and the second insulating layer may be arranged adjacent to each other, and the first insulating layer and the second insulating layer may serve to electrically insulate the positive electrode and the negative electrode.

[0088] Lithium-ion battery A lithium secondary battery according to yet another embodiment of the invention may include a battery case, an electrolyte, and the electrode assembly of the above-described embodiment. Since the electrode assembly includes a first insulating layer and a second insulating layer, sufficient electrical insulation characteristics can be ensured between the positive and negative electrodes without a separate separator membrane, and short circuits due to shrinkage of the existing separator membrane can be suppressed, thereby providing a lithium secondary battery with improved stability.

[0089] In particular, the resistance value when a voltage of 50V is applied between the positive and negative electrodes of the lithium secondary battery is 10 8 It can be greater than or equal to ohms, specifically 10 8 or 10 13 The value may be in ohms. Within the aforementioned numerical range, the positive electrode and the negative electrode may not short-circuit with each other, ensuring sufficient electrical insulation and improving battery stability.

[0090] The aforementioned battery case may be one of those commonly used in this field, and is not limited to its external shape depending on the battery's application. For example, it may be cylindrical, rectangular, pouch-type, or coin-type, but is not limited thereto.

[0091] The electrolyte may specifically include a flame-retardant electrolyte.

[0092] In this case, the flame-retardant electrolyte can be defined as one that has a flash point of 100°C or higher, or one that contains a flame-retardant solvent and lithium salt that have no flash point. In this case, the flame-retardant solvent can include organic solvents that are substantially non-flammable and have no flash point, and organic solvents that have a high flash point of 100°C or higher, or 100 to 250°C, or 110 to 200°C, and low volatility. By including such a flame-retardant electrolyte containing a flame-retardant solvent and lithium salt, the lithium secondary battery can exhibit superior high-temperature safety. Furthermore, since the flame-retardant electrolyte can be uniformly impregnated into the insulating layer containing the aforementioned polymer particles or ceramic particles, the electrochemical properties of the lithium secondary battery can be improved to be excellent. The flash point defining the flame-retardant solvent can be measured by a closed or open method according to the standard methods of ASTM D93 or ASTM D1310.

[0093] In a specific example, the flame-retardant solvent may be an organic solvent having low volatility and a functional group that can contribute to flame retardancy or non-flammability, such as a sulfone functional group, a fluorine-containing functional group such as a fluorine-substituted hydrocarbon group, a phosphorus-containing functional group such as a phosphate group or phosphonate group, and a nitrile functional group, and one or more such organic solvents may be used in mixture form. More specifically, the flame-retardant solvent may contain one or more organic solvents selected from the group consisting of sulfone compounds, nitrile compounds, phosphoric acid compounds, and fluorine-substituted carbonate compounds.

[0094] Among these, the sulfone compound may be a cyclic sulfone compound or a linear sulfone compound, and specifically, it may contain one or more selected from the group consisting of sulfolane, ethylmethylsulfone, dibutylsulfone, ethylvinylsulfone, methylpropylsulfone, ethyl-i-propylsulfone, ethyl-i-butylsulfone, i-propyl-i-butylsulfone, i-propyl-s-butylsulfone, and butyl-i-butylsulfone.

[0095] Furthermore, the nitrile compound may include one or more selected from the group consisting of malnonitrile, succinonitrile, glutalonitrile, adiponitrile, suberonitrile, and sebaconitrile.

[0096] Furthermore, the phosphate compound may include one or more selected from the group consisting of dimethylmethyl phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, diethylethyl phosphate, dimethylmethyl phosphate, dimethyl(2-methoxyethoxy)methyl phosphonate, diethyl(2-methoxyethoxy)methyl phosphonate, and triphenyl phosphate.

[0097] In addition, the fluorine-substituted carbonate compounds include bis(2,2,3,3-tetrafluoropropyl) carbonate, methyl-2,2,2-trifluoroethyl carbonate, ethyl-2,2,2-trifluoroethyl carbonate, propyl-2,2,2-trifluoroethyl carbonate, methyl-2,2,2,2',2',2'-hexafluoro-i-propyl carbonate, and ethyl-2,2,2,2',2',2'-hexafluoropropyl It may contain one or more selected from the group consisting of oro-i-propyl carbonate, di-2,2,2-trifluoroethyl carbonate, 2,2,2-trifluoroethyl-N,N-dimethyl carbonate, hexafluoro-i-propyl-N,N-dimethyl carbonate, 4-(2,2,3,3-tetrafluoropropoxymethyl)-[1,3]-dioxolan-2-one, and bis(2,2,3,3-pentafluoropropyl) carbonate.

[0098] On the other hand, the lithium salt contained in the flame-retardant electrolyte is used as a medium for transferring ions in a lithium secondary battery. The lithium salt is, for example, Li as a cation. + It contains, and as an anion, F - Cl - , Br - , I - NO3 - , N(CN)2- , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and SCN - At least one selected from the group consisting of is included.

[0099] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10It may contain a single substance or a mixture of two or more substances selected from the group consisting of LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (Lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), LiBETI (Lithium bis(perfluoroethanesulfonyl)imide, LiN(SO2CF2CF3)2, and LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide, LiN(SO2CF3)2), but it is preferable to include Li(N(SO2CF3)2 in terms of superior stability.

[0100] In addition to these, lithium salts commonly used as electrolytes in lithium secondary batteries can be used without restriction.

[0101] The lithium salt can be appropriately changed within a range of normal use, but may be included in the electrolyte at a concentration of 1 M to 3 M, 1 M to 2.5 M, or 1 M to 2 M in order to obtain the optimal effect of forming a protective film on the electrode surface to prevent corrosion. When the concentration of the lithium salt satisfies the above range, the effect of improving cycle characteristics is sufficient, the viscosity of the flame-retardant electrolyte is appropriate, and the impregnation of the flame-retardant electrolyte can be improved during high-temperature storage of the lithium secondary battery.

[0102] The aforementioned lithium secondary batteries can be used not only as battery cells for powering small devices, but also preferably as unit batteries in medium- and large-sized battery modules containing a large number of battery cells. Preferred examples of such medium- and large-sized devices include electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems (ESS).

[0103] The present invention will be described in more detail below through specific examples. However, the following examples are merely illustrative to aid in understanding the present invention and do not limit its scope. It will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the described concept and technical idea, and it goes without saying that such variations and modifications fall within the scope of the attached claims.

[0104] Examples and Comparative Examples First, in the following examples, the zeta potential of polymer particles or ceramic particles was measured using electrophoretic light scattering with a dynamic light scattering system (product name: ELS-Z) while the particles were dispersed in an aqueous solvent at a temperature of 25°C in an amount of 0.1% by weight or less.

[0105] Example 1 Li(Ni) is used as the positive electrode active material. 0.8 Mn 0.1 Co 0.1 A positive electrode with a total thickness of 60 μm containing O2 (sum of the thickness of the positive electrode current collector and the positive electrode active material layer) and a negative electrode with a total thickness of 75 μm containing artificial graphite as the negative electrode active material (sum of the thickness of the negative electrode current collector and the negative electrode active material layer) were prepared.

[0106] It has a zeta potential of -50mV and an average particle size D 50 Polymethyl methacrylate (PMMA) polymer particles, each 1 μm in size, were dispersed in N-methyl-2-pyrrolidone (NMP) solvent in a mass ratio of PMMA:hydrogenated nitrile rubber (H-NBR) dispersant:polyvinylidene fluoride (PVDF) binder of 7:1:2 to produce an insulating layer slurry.

[0107] S1: The insulating layer slurry is applied to the positive electrode and dried to form a first insulating layer, thereby forming a positive electrode-insulating layer composite.

[0108] S2: The insulating layer slurry is applied to the negative electrode and dried to form a second insulating layer, thereby forming a negative electrode-insulating layer composite.

[0109] S3: The positive electrode-insulating layer composite and the negative electrode-insulating layer composite were laminated to manufacture an electrode assembly. At this time, the first insulating layer and the second insulating layer were arranged to face each other.

[0110] The thickness of the first insulating layer was 13 μm, and the thickness of the second insulating layer was 20 μm. The sum of the thicknesses of the first and second insulating layers was measured to be 33 μm. Based on this, the ratio of the sum of the thicknesses of the first and second insulating layers (33 μm) to the total thickness of the positive electrode, negative electrode, and first and second insulators (168 μm) was calculated to be approximately 19.64%.

[0111] Example 2 The procedure was the same as in Example 1, except that the thickness of the insulating layer was different.

[0112] The thickness of the first insulating layer was 20 μm, and the thickness of the second insulating layer was 30 μm. The sum of the thicknesses of the first and second insulating layers was measured to be 50 μm. Based on this, the ratio of the sum of the thicknesses of the first and second insulating layers (50 μm) to the total thickness of the positive electrode, negative electrode, and first and second insulators (185 μm) was calculated to be approximately 27.03%.

[0113] Example 3 The procedure was the same as in Example 1, except that the thickness of the insulating layer was different.

[0114] The thickness of the first insulating layer was 20 μm, and the thickness of the second insulating layer was 35 μm. The sum of the thicknesses of the first and second insulating layers was measured to be 55 μm. Based on this, the ratio of the sum of the thicknesses of the first and second insulating layers (55 μm) to the total thickness of the positive electrode, negative electrode, and first and second insulators (190 μm) was calculated to be approximately 28.95%.

[0115] Comparative Example 1 Li(Ni) is used as the positive electrode active material.0.8 Mn 0.1 Co 0.1 A positive electrode with a total thickness of 60 μm containing O2 (sum of the thickness of the positive electrode current collector and the positive electrode active material layer) and a negative electrode with a total thickness of 75 μm containing artificial graphite as the negative electrode active material (sum of the thickness of the negative electrode current collector and the negative electrode active material layer) were prepared.

[0116] It has a zeta potential of -50mV and an average particle size D 50 Polymethyl methacrylate (PMMA) polymer particles, each 1 μm in size, were dispersed in N-methyl-2-pyrrolidone (NMP) solvent to produce an insulating layer slurry, with the mass ratio of PMMA:hydrogenated nitrile rubber (H-NBR) dispersant:polyvinylidene fluoride (PVDF) binder being 7:1:2.

[0117] The insulating layer slurry was applied to the negative electrode and dried to form a negative electrode-insulating layer composite. Subsequently, the positive electrode was laminated on the negative electrode-insulating layer composite to manufacture an electrode assembly. The total thickness of the insulating layer was measured to be 36 μm. Based on this, the ratio of the thickness of the insulating layer on the negative electrode (36 μm) to the total thickness of the positive electrode, negative electrode, and the insulating layer on the negative electrode (171 μm) was calculated to be approximately 21.05%.

[0118] Comparative Example 2 The procedure was the same as in Example 1, except that the thickness of the insulating layer was different.

[0119] The thickness of the first insulating layer was 10 μm, and the thickness of the second insulating layer was 20 μm. The sum of the thicknesses of the first and second insulating layers was measured to be 30 μm. Based on this, the ratio of the sum of the thicknesses of the first and second insulating layers (30 μm) to the total thickness of the positive electrode, negative electrode, and first and second insulators (165 μm) was calculated to be approximately 18.18%.

[0120] Experimental Example 1: Comparison of Electrical Insulation Characteristics (1) Hi-pot tests were performed on the electrode assemblies of Examples 1 to 3 and Comparative Examples 1 and 2. The Hi-pot test was performed by roll laminating the positive and negative electrodes at 80°C to create a monocell, and then applying a voltage to the monocell. The resistance value relative to the total thickness of the insulating layer was measured under a voltage of 50V. The experimental results are shown in Figure 1.

[0121] Referring to Figure 1, in Example 1, the first insulating layer and the second insulating layer are formed on the positive and negative electrodes respectively, and then stacked, with a total insulating layer thickness of 33 μm, a thickness ratio of approximately 19.64%, and approximately 10 10 It was shown to have a high resistance value and excellent insulating properties.

[0122] Examples 2 and 3 also have a structure in which the first insulating layer and the second insulating layer are formed on the positive and negative electrodes, respectively, and the total thickness of the insulating layers is 50 μm and 55 μm, respectively, and the thickness ratio of these is approximately 27.03% and approximately 28.95%, and approximately 10 10 It was confirmed to have a high resistance value and excellent insulating properties.

[0123] However, in the case of Comparative Example 1, it has a structure in which one insulating layer is formed on the negative electrode and then the positive electrode is stacked on top of it, and the thickness of the insulating layer is 36 μm, and although the thickness ratio is relatively thick at 21.05%, approximately 10 3 It was shown to have low resistance values ​​and poor insulation properties.

[0124] In the case of Comparative Example 2, the first insulating layer and the second insulating layer are formed on the positive and negative electrodes respectively, and then stacked, with a total insulating layer thickness of 30 μm, and a thickness ratio of approximately 19.18%, and approximately 10 3 It was shown to have low resistance values ​​and poor insulation properties.

[0125] Experimental Example 2: Comparison of Electrical Insulation Characteristics (2) Open-circuit voltage (OCV) profiles were measured for Examples 1 to 3 and Comparative Examples 1 and 2. After injecting the electrode assemblies of the Examples and Comparative Examples with a carbonate-based electrolyte, a room-temperature wetting process was performed, and the voltage was measured at 1-minute intervals or every 20 mV of voltage change. The results are shown in Figure 2.

[0126] Referring to Figure 2, in Examples 1 to 3, as time progressed, the OCV voltage became approximately 0.30 to 0.35 V and was maintained at a relatively constant level.

[0127] However, in Comparative Examples 1 and 2, it was confirmed that the OCV voltage decreased to below 0.1V after electrolyte injection. This is because the inferior insulating properties of the insulating layer in Comparative Examples 1 and 2 caused internal micro-short circuits between the electrodes. This confirmed that the electrical insulation properties of Examples 1 to 3 were superior to those of Comparative Examples 1 and 2.

[0128] Experimental Example 3 - Evaluation of Life Characteristics of Lithium-ion Secondary Batteries After manufacturing lithium secondary batteries by injecting carbonate-based electrolytes into the electrode assemblies of Examples 1 to 3, their life characteristics (capacity retention rate) were evaluated by the following method.

[0129] Each lithium secondary battery was charged and discharged at 0.1C in CC / CV charging mode with an upper voltage limit of 4.2V and CC discharge mode with a lower voltage limit of 3V. After that, 500 cycles of 4.2V to 3V charging and discharging were performed at 0.2C / 0.2C, and the capacity retention rate was measured at 100-cycle intervals. The capacity retention rate measurement results for Examples 1 to 3 are shown in Figure 3.

[0130] Referring to Figure 3, it was confirmed that Examples 1 to 3 exhibited excellent capacity retention rates of 95% or more for 200 cycles or less. Furthermore, Example 1 (total thickness of insulating layer: 33 μm; thickness ratio: approximately 19.64%) was confirmed to exhibit superior lifetime characteristics compared to Example 2 (total thickness of insulating layer: 50 μm; thickness ratio: approximately 27.03%) and Example 3 (total thickness of insulating layer: 55 μm; thickness ratio: approximately 28.95%).

Claims

1. A positive electrode-insulating layer composite including a first insulating layer placed on the positive electrode, A negative electrode-insulating layer composite including a second insulating layer disposed on the negative electrode, The first or second insulating layer has an absolute value of 25 mV to 90 mV for its zeta potential, and an average particle size D ５０ A porous insulating layer containing polymer particles or ceramic particles having a size of 50 nm to 2 μm, Each of the first and second insulating layers contains 60% to 80% by weight of the polymer particles or the ceramic particles. The zeta potential is measured by electrophoretic light scattering with the polymer particles or ceramic particles dispersed in water at a concentration of 0.1% by weight or less. An electrode assembly for a lithium secondary battery, wherein the ratio of the sum of the thicknesses of the first and second insulating layers to the sum of the thicknesses of the positive electrode-insulating layer composite and the negative electrode-insulating layer composite is 19% to 30%.

2. The first and second insulating layers each have a thickness of 5 μm or more. The electrode assembly for a lithium secondary battery according to claim 1, wherein the sum of the thicknesses of the first and second insulating layers is 33 to 55 μm.

3. The electrode assembly for a lithium secondary battery according to claim 1, wherein the first and second insulating layers are in direct contact.

4. The electrode assembly for a lithium secondary battery according to claim 1, wherein the electrode assembly for the lithium secondary battery does not include a separate separation membrane.

5. The positive electrode-insulating layer composite and the negative electrode-insulating layer composite are stacked, The electrode assembly for a lithium secondary battery according to claim 1, wherein the first and second insulating layers are arranged facing each other.

6. The electrode assembly for a lithium secondary battery according to claim 1, wherein the thickness of the first insulating layer is 10 to 20 μm, and the thickness of the second insulating layer is 20 to 35 μm.

7. The electrode assembly for a lithium secondary battery according to claim 1, wherein the first and second insulating layers each independently comprise polymer particles or ceramic particles and a binder.

8. The electrode assembly for a lithium secondary battery according to claim 1, wherein the first and second insulating layers have the same composition as each other.

9. The electrode assembly for a lithium secondary battery according to claim 1, wherein the polymer particles include one or more selected from the group consisting of polyethylene oxide, polyphenylene sulfide, polymethyl (meth)acrylate, polystyrene, polyvinyl chloride, polycarbonate, polysulfone, polyethersulfone, polyetherimide, polyphenylsulfone, polyamideimide, polyimide, polybendiimidazole, polyetherketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate.

10. The electrode assembly for a lithium secondary battery according to any one of claims 1 to 9, wherein the ceramic particles include one or more selected from the group consisting of boehmite, aluminum oxide, titanium oxide, iron oxide, silicon oxide, zirconium oxide, cobalt oxide, tin oxide, nickel oxide, zinc oxide, vanadium oxide, and manganese oxide.

11. (S1) A step of forming a positive electrode-insulating layer composite by forming a first insulating layer on the positive electrode, (S2) The step of forming a second insulating layer on the negative electrode to form a negative electrode-insulating layer composite, (S3) The step of laminating the positive electrode-insulating layer composite and the negative electrode-insulating layer composite, The first or second insulating layer has an absolute value of 25 mV to 90 mV for its zeta potential, and an average particle size D ５０ It contains polymer particles or ceramic particles that are 50 nm to 2 μm in size. Each of the first and second insulating layers contains 60% to 80% by weight of the polymer particles or the ceramic particles. The method for manufacturing an electrode assembly for a lithium secondary battery according to claim 1, wherein the zeta potential is measured by electrophoretic light scattering while the polymer particles or ceramic particles are dispersed in water at a concentration of 0.1% by weight or less.

12. Battery case and Electrolytes, A lithium secondary battery comprising the electrode assembly described in claim 1.

13. The resistance value when a voltage of 50V is applied between the positive and negative electrodes of the lithium secondary battery is 10 ８ The lithium secondary battery according to claim 12, wherein the resistance is greater than or equal to ohms.

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