Electrode assembly and lithium secondary battery including the same

Abstract

The present invention includes a positive electrode, a negative electrode, and a coating layer positioned between the positive electrode and the negative electrode, The coating layer relates to an electrode assembly containing at least one selected from the group consisting of (a) oxide-based solid electrolyte particles, (b) polymer particles, and ceramic particles, and a lithium secondary battery including the same.

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10 - 2022 - 0181062 filed on December 21, 2022 and Korean Patent Application No. 10 - 2023 - 1087353 filed on December 20, 2023, and all the contents disclosed in the documents of the Korean patent applications are incorporated herein by reference in their entirety.

[0002] The present invention relates to an electrode assembly and a lithium secondary battery including the same.

Background Art

[0003] Recently, as the application fields of lithium secondary batteries have rapidly expanded not only to power supply for electronic devices such as electrical, electronic, communication, and computer devices but also to power storage supply for large - area devices such as automobiles and power storage devices, there is an increasing demand for lithium secondary batteries with high capacity, high output, long life, and high stability.

[0004] Generally, a lithium secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, an electrolyte, an organic solvent, and the like. The positive electrode may generate oxygen due to an unstable structure in a charged state, and when oxygen is generated, the risk of ignition is high, so research and development on methods to improve the safety of lithium secondary batteries have been attempted.

[0005] The separator is used to ensure electrical insulation between the positive electrode and the negative electrode, and a thin film made of polyolefin is generally used. However, in the case of a polyolefin - based separator, it may easily shrink in a high - temperature environment and may not be able to insulate between the positive electrode and the negative electrode. When electrical insulation between the positive electrode and the negative electrode cannot be achieved, a short - circuit may occur, and ignition may occur by acting with oxygen generated by the unstable positive electrode. That is, when a short - circuit occurs in a charged lithium secondary battery in a high - temperature environment, a problem that the lithium secondary battery catches fire may occur.

[0006] In addition, it is known that a solvent that is volatile and flammable is used as the electrolyte of a lithium secondary battery, but this has a problem that ignition is likely to occur.

[0007] To solve this problem, a flame-retardant electrolyte containing a flame-retardant solvent can be used, but such a flame-retardant electrolyte has a problem that it is not sufficiently impregnated into a conventional separator. If the electrolyte is not sufficiently impregnated in a lithium secondary battery, lithium ions cannot be sufficiently transmitted, so there are problems that the capacity, output, and life characteristics of the lithium secondary battery all decrease. In addition, if the electrolyte is not sufficiently impregnated in a lithium secondary battery, a non-uniform reaction occurs between the electrode and the electrolyte, and dendrites are generated, resulting in a short circuit.

[0008] Therefore, in order to solve such problems, research and development on a method that can enhance safety while maintaining various performances of a lithium secondary battery have been attempted.

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention is for solving such problems, and an electrode assembly having high high-temperature safety so as to prevent ignition and excellent battery performance due to high electrolyte impregnation property, and a lithium secondary battery including the same are provided.

Means for Solving the Problems

[0010] An electrode assembly according to an embodiment of the present invention includes a positive electrode, a negative electrode, and a coating layer positioned between the positive electrode and the negative electrode, wherein the coating layer includes at least one selected from the group consisting of (a) oxide-based solid electrolyte particles and (b) polymer particles and ceramic particles.

[0011] Here, the oxide-based solid electrolyte particles are LLTO-based compounds, Li 6 La 2 CaTa2 O 12 、 Li 6 La 2 ANb 2 O 12 (A is Ca or Sr), Li 2 Nd 3 TeSbO 12 、 Li 3 BO 2.5 N 0.5 、 Li 9 SiAlO 8 、 LAGP - type compounds, LATP - type compounds, Li 1+x Ti 2-x Al x Si y (PO 4 ) 3-y (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1), LiAl x Zr 2-x (PO 4 ) 3 (where 0 ≤ x ≤ 1), LiTi x Zr 2-x (PO 4 ) 3 (where 0 ≤ x ≤ 1), LISICON - type compounds, LIPON - type compounds, perovskite - type compounds, NASICON - type compounds, LLZO - type compounds, and LLZMO - type compounds, and may be selected from one of the group consisting of these or may contain two or more of these.

[0012] Also, the absolute value of the zeta potential of the polymer particles and the ceramic particles may each be 25 mV or more.

[0013] The polymer particles may contain one or more selected from the group consisting of, for example, polyethylene oxide (PEO), polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA), polystyrene, polyvinyl chloride, polycarbonate, polysulfone, polyethersulfone, polyetherimide, polyphenylsulfone, polyamideimide, polyimide, polybenzimidazole, polyether ketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate.

[0014] Also, the ceramic particles are boehmite, Al 2 O 3 、TiO 2 、Fe 2 O 3 、SiO 2 、ZrO 2 、Co 3 O 4 、SnO 2 、NiO, ZnO, V 2 O 5 、and may contain one or more selected from the group consisting of MnO.

[0015] At this time, the oxide-based solid electrolyte particles in the coating layer may be contained in an amount of 10% by weight to 90% by weight based on the total weight of the coating layer.

[0016] Specifically, the coating layer includes (a) oxide-based solid electrolyte particles and (b) polymer particles, and the polymer particles may include one or more selected from the group consisting of polyethylene oxide (PEO), polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA), polystyrene, polyvinyl chloride, polycarbonate, polysulfone, polyethersulfone, polyetherimide, polyphenylsulfone, polyamideimide, polyimide, polybenzimidazole, polyetherketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate.

[0017] That is, it may essentially include the oxide-based solid electrolyte particles and polymer particles. Further, the coating layer may further include one or more additives selected from the group consisting of a binder and a dispersant.

[0018] Furthermore, the thickness of the coating layer may be 3 micrometers to 30 micrometers.

[0019] On the other hand, in one example, the coating layer may be formed on the positive electrode or the negative electrode.

[0020] At this time, the electrode assembly may further include a separator, and the separator may be located between the positive electrode and the coating layer, or between the negative electrode and the coating layer.

[0021] Or, in another example, the coating layer may be composed of a first coating layer formed on the positive electrode and a second coating layer formed on the negative electrode.

[0022] At this time as well, the electrode assembly may further include a separator, and the separator may be located between the first coating layer and the second coating layer.

[0023] Alternatively, in another example, the electrode assembly may further include a separation membrane, and the coating layer may be formed on one or both surfaces of the separation membrane.

[0024] At this time, the separation membrane may be an SRS separation membrane having a structure in which an organic-inorganic hybrid layer containing inorganic particles and a binder is formed on one or both surfaces of a base substrate.

[0025] According to another embodiment of the present invention, the present invention also provides a lithium secondary battery including the electrode assembly, an electrolyte, and a battery case.

[0026] At this time, the electrolyte may be a flame-retardant electrolyte containing a flame-retardant solvent and a lithium salt.

[0027] The flame-retardant solvent may include one or more compounds selected from sulfone-based compounds, nitrile-based compounds, phosphate-based compounds, and fluorine-substituted carbonate-based compounds, and the lithium salt may include, for example, LiN(SO 2 CF 3 ) 2 and may include.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, the terms and words used in this specification and the claims should not be construed as being limited to ordinary or dictionary meanings. Based on the principle that the inventor can appropriately define the concept of the terms in order to explain his own invention in the best way, they must be construed in meanings and concepts consistent with the technical idea of the present invention.

[0030] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification should be used in a meaning commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Also, terms defined in commonly used dictionaries are not to be construed ideally or excessively unless specifically defined otherwise.

[0031] The terms used in this specification are for the purpose of describing embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless specifically stated otherwise in the text. The use of "comprises" and / or "comprising" in the specification does not exclude the presence or addition of one or more other components in addition to the recited components.

[0032] When it is said in this specification that a certain part includes a certain component, this means that, unless otherwise stated to the contrary, it does not exclude other components and may further include other components.

[0033] In this specification, the "zeta potential" is an index indicating the degree of surface charge of particles. The zeta potential of the polymer particles or ceramic particles contained in the coating layer in the present invention can be measured by the method of electrophoretic light scattering using dynamic light scattering equipment. As an example, after dispersing polymer particles or ceramic particles in a solvent such as water or alcohol without a dispersant, the value of the zeta potential can be measured.

[0034] Hereinafter, the examples described in this specification and the configurations shown in the drawings are only the most preferred example of the present invention and do not represent all of the technical ideas of the present invention. Therefore, at the time of this application, it must be understood that there can be various equivalents and modifications that can replace these.

[0035] According to an embodiment of the present invention, a positive electrode, a negative electrode, and a coating layer located between the positive electrode and the negative electrode are included. The coating layer provides an electrode assembly including one or more selected from the group consisting of (a) oxide-based solid electrolyte particles and (b) polymer particles and ceramic particles.

[0036] <Coating layer> The oxide-based solid electrolyte particles are LLTO-based compounds, Li 6 La 2 CaTa 2 O 12 、Li 6 La 2 ANb 2 O 12 (A is Ca or Sr), Li 2 Nd 3 TeSbO 12 、Li 3 BO 2.5 N 0.5 、Li 9 SiAlO 8 、LAGP-based compounds, LATP-based compounds, Li 1+x Ti 2-x Alx Si y (PO 4 ) 3-y (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1), LiAl x Zr 2-x (PO 4 ) 3 (where 0 ≤ x ≤ 1), LiTi x Zr 2-x (PO 4 ) 3 (where 0 ≤ x ≤ 1), a LISICON-based compound, a LIPON-based compound, a perovskite-based compound, a NASICON-based compound, an LLZO-based compound, an LLZMO-based compound, and may include any one selected from the group consisting of these or two or more thereof, and is not limited, but specifically, may be a LATP-based compound.

[0037] Here, the LLTO-based compound may be a compound containing Li, La, Ti, and O, and specifically, may be 3x La (2 / 3-x) TiO 2 1+x Al x Ge 2-x (PO 4 ) 3 (where 0 ≤ x ≤ 1), and the LATP-based compound is a compound containing Li, Al, Ti, P, and O, and specifically, may be 1+x Al x Ti 2-x (PO 4 ) 3 (where 0 ≤ x ≤ 1). Further, the LIPON-based compound may be a compound containing Li, P, O, and N, and the LLZO-based compound is a compound containing Li, La, Zr, and O, and specifically, may be 7 La 3 Zr 2 O 12 7-x La 3 Zr 2-x M​​x O 12( Here, 0 ≦ x ≦ 1).

[0038] When the oxide-based solid electrolyte particles are included in the coating layer, the resistance can be reduced according to the affinity of the oxide-based solid electrolyte particles themselves with the electrolyte, which is preferable.

[0039] The average diameter (D50) of the oxide-based solid electrolyte particles may be 50 nanometers to 10 micrometers, specifically, 50 nanometers to 5 micrometers, and more specifically, 50 nanometers to 1 micrometer.

[0040] If it is out of the above range and is excessively small, particle aggregation may occur due to a decrease in dispersibility. Conversely, if it is excessively large, the coating layer may have excessively large pores, and lithium dendrites may be easily formed through the pores, which is not preferable.

[0041] The oxide-based solid electrolyte particles may be contained in an amount of 10% by weight to 90% by weight based on the total weight of the coating layer, specifically, 10% by weight to 80% by weight, and more specifically, 10% to 60% by weight.

[0042] When the above range is satisfied, the lithium ion conductivity in the coating layer can be increased to reduce the resistance, and improved secondary battery performance can be exhibited.

[0043] On the other hand, the polymer particles may be particles having a surface charge. Or it may contain both particles having a surface charge and those not having a surface charge. The surface charge may be one that the particles themselves have, or even if not, it can also be formed through physical or chemical surface treatment.

[0044] Here, the absolute value of the zeta potential of the polymer particles may be 25 mV or more, specifically 35 mV or more, and more specifically 45 mV or more. When the absolute value of the zeta potential satisfies the numerical range, even when a flame-retardant electrolyte is applied to the lithium secondary battery including the electrode according to the present invention, the flame-retardant electrolyte can be easily impregnated into the coating layer, and a uniform reaction occurs throughout the electrode, and therefore, the performance such as the capacity, output, and life characteristics of the lithium secondary battery can be improved.

[0045] Specifically, the polymer particles may contain one or more selected from the group consisting of polyethylene oxide (PEO), polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA), polystyrene, polyvinyl chloride, polycarbonate, polysulfone, polyethersulfone, polyetherimide, polyphenylsulfone, polyamideimide, polyimide, polybenzimidazole, polyetherketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate, and are distinguished from the binder for binding the components, but are not limited thereto as long as they are substances used for polymer solid electrolyte particles. Specifically, the polymer particles may contain polymethyl methacrylate.

[0046] The average diameter (D50) of the polymer particles may be 50 nanometers to 3 micrometers, specifically 50 nanometers to 2 micrometers, and more specifically 50 nanometers to 1.5 micrometers.

[0047] When the average diameter (D50) of the polymer particles satisfies the numerical range, the dispersibility of the particles contained in the coating layer is improved, and pores of an appropriate size are uniformly formed in the coating layer, thereby improving the mobility of lithium ions. On the contrary, when the average diameter (D50) of the polymer particles is less than 50 nanometers, particle aggregation occurs due to a decrease in particle dispersibility, and the pores are clogged by the aggregated particles, which may reduce the mobility of lithium ions and increase the resistance. When the average diameter (D50) of the polymer particles is greater than 3 micrometers, as described above, there is a problem that a growth path for lithium dendrites may be formed.

[0048] The absolute value of the zeta potential of the ceramic particles may also be 25 mV or more, specifically, 35 mV or more, and more specifically, 45 mV or more. When the absolute value of the zeta potential satisfies the numerical range, even when a flame-retardant electrolyte is applied to a lithium secondary battery including the electrode according to the present invention, the flame-retardant electrolyte can be easily impregnated into the coating layer, and a uniform reaction occurs throughout the electrode, and therefore, the performance such as the capacity, output, and life characteristics of the lithium secondary battery can be improved.

[0049] Specifically, the ceramic particles may include one or more selected from the group consisting of boehmite, Al 2 O 3 、TiO 2 、Fe 2 O 3 、SiO 2 、ZrO 2 、Co 3 O 4 、SnO 2 、NiO, ZnO, V 2 O 5 、and MnO, but is not limited thereto. Specifically, it may include boehmite.

[0050] The average diameter (D50) of the ceramic particles may be from 30 nanometers to 5 micrometers, specifically, from 50 nanometers to 3 micrometers, and more specifically, from 50 nanometers to 1 micrometer.

[0051] When the average diameter (D50) of the ceramic particles is smaller, particle aggregation may occur due to a decrease in particle dispersibility. When it is larger, there is a problem that a growth path for lithium dendrites may be formed.

[0052] The average diameter (D50) described above means the particle diameter corresponding to 50% of the volume cumulative amount in the particle size distribution curve of the particles. The D50 can be measured, for example, using the laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron region to about several millimeters and can obtain highly reproducible and highly resolved results.

[0053] The polymer particles or the ceramic particles may be included alone or both may be included.

[0054] More specifically, the coating layer may contain polymer particles together with the oxide-based solid electrolyte particles. That is, the oxide-based solid electrolyte particles and the polymer particles may be essentially included. In this case, the lithium ion migration performance is excellent.

[0055] On the other hand, when both the polymer particles and the ceramic particles are included in the coating layer, the mixing ratio of the polymer particles and the ceramic particles may be from 3:7 to 7:3 based on weight, specifically, from 4:6 to 6:4.

[0056] When the above range is satisfied, it is possible to prevent a decrease in pore uniformity, heat resistance, and electrolyte impregnation property in the coating layer.

[0057] On the other hand, the coating layer may further contain one or more additives selected from the group consisting of a binder and a dispersant.

[0058] The dispersant suppresses the phenomenon that the polymer particles aggregate excessively within the coating layer, and the polymer particles are effectively dispersed and present in the coating layer.

[0059] The dispersant may contain a hydrogenated nitrile copolymer, specifically, it is a hydrogenated nitrile copolymer, and more specifically, it may be a hydrogenated nitrile butadiene rubber (H-NBR).

[0060] The hydrogenated nitrile copolymer is a copolymer containing structural units derived from α,β-unsaturated nitrile and structural units derived from hydrogenated conjugated diene, or may be 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 can be used, and one kind alone or a mixture of two or more kinds thereof can be used. As the conjugated diene monomer, for example, conjugated diene monomers having 4 to 6 carbon atoms such as 1,3-butadiene, isoprene or 2,3-methylbutadiene can be used, and one kind alone or a mixture of two or more kinds thereof can be used.

[0061] Such a dispersant may be contained in an amount of 1% by weight to 20% by weight, specifically 1% by weight to 15% by weight, and more specifically 1% by weight to 10% by weight based on the total weight of the coating layer. When the content of the dispersant satisfies the above range, the dispersibility of the particles contained in the coating layer is improved, pores are uniformly formed in the coating layer, and cracks on the surface of the coating layer can be significantly reduced.

[0062] The binder plays a role in improving the adhesive force between the particles of the coating layer, the electrode, and the separator membrane.

[0063] The binder may include one or more selected from the group consisting of, for example, polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, and fluororubber. Specifically, the binder may include polyvinylidene fluoride.

[0064] The binder may be contained in an amount of 0.1% by weight to 20% by weight, specifically 0.5% by weight to 15% by weight, more specifically 1% by weight to 10% by weight, based on the total weight of the coating layer. If it is outside this range and too small, the effect of improving the adhesive force cannot be expected. If it is too large, the content of other particles will relatively decrease, which is not preferable.

[0065] The coating layer having such a configuration can have electrical insulation properties. In this case, the coating layer can correspond to a porous insulating layer, but is not limited thereto.

[0066] Since such a coating layer has the property of not easily shrinking even at high temperatures, when the coating layer is applied to an electrode assembly, a short circuit between the positive electrode and the negative electrode can be prevented even in a high-temperature environment, thus improving the high-temperature safety of the lithium secondary battery.

[0067] <Electrode assembly> Hereinafter, electrode assemblies with various structures will be described with reference to the drawings.

[0068] In one example, the coating layer may be formed on the positive electrode or the negative electrode.

[0069] Figures 1 to 3 disclose a configuration formed on either the positive electrode or the negative electrode of the coating layer.

[0070] Specifically, FIG. 1 schematically shows an electrode assembly having a structure in which the coating layer is formed on the negative electrode instead of the separator membrane. FIG. 2 schematically shows an electrode assembly having a structure in which the coating layer is formed on the negative electrode and a separator membrane is interposed between the coating layer and the positive electrode. FIG. 3 schematically shows an electrode assembly having a structure in which the coating layer is formed on the positive electrode and a separator membrane is interposed between the coating layer and the negative electrode.

[0071] First, referring to FIG. 1, an electrode assembly 100 according to an embodiment of the present invention includes a negative electrode 110, a positive electrode 120, and a coating layer 130.

[0072] The negative electrode 110 has a structure in which a negative electrode active material layer 112 is formed on a negative electrode current collector 111. Here, the negative electrode active material layer includes electrode materials such as a negative electrode active material, a conductive material, and a binder. Alternatively, although not shown in the drawing, the negative electrode may be a graphite electrode made of carbon (C), or may be a metal itself.

[0073] The negative electrode current collector 111 is not particularly limited as long as it has high conductivity without inducing a chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those surface-treated with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, an aluminum-cadmium alloy, etc. can be used.

[0074] The negative electrode current collector 111 can usually have a thickness of 3 μm to 500 μm. Similar to the positive electrode current collector, fine irregularities can be formed on the surface of the negative electrode current collector to strengthen the binding force of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a non-woven fabric body.

[0075] The negative electrode active material may contain at least one or more selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal, an alloy of these metals and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0076] As the carbon material capable of reversibly intercalating / deintercalating lithium ions, any carbon-based negative electrode active material generally used in a lithium ion secondary battery can be used without particular limitation. Representative examples thereof include crystalline carbon, amorphous carbon, or a combination of these. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0077] As the metal or the 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 can be used.

[0078] Examples of the metal composite oxide include PbO, PbO 2 , Pb 2 O 3 , Pb 3 O 4 , Sb 2 O 3 , Sb 2 O 4 , Sb 2 O 5 , GeO, GeO 2 , Bi 2 O 3 , Bi 2 O 4 , Bi 2 O 5 , LixFe2 O 3 (0 ≦ x ≦ 1), Li x WO 2 (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) can be used which is selected from the group consisting of.

[0079] As the substance capable of doping and undoping the lithium, Si, SiO x (0 < x ≦ 2), Si - Y alloy (wherein Y 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 transition metal, a rare earth element and combinations thereof, and is not Si), Sn, SnO 2 , Sn - Y (wherein Y 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 transition metal, a rare earth element and combinations thereof, and is not Sn), etc. can be mentioned, and also, at least one of these and SiO 2 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.

[0080] Examples of the transition metal oxide include lithium - containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, etc.

[0081] The negative electrode active material may be contained at 60 to 99% by weight, preferably 70 to 99% by weight, more preferably 80 to 98% by weight based on the total weight of the negative electrode active material layer.

[0082] The conductive material is a component for further improving the conductivity of the negative electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. 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 crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride powder; conductive powder such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. can be used.

[0083] The conductive material may be contained in an amount of 0.1 to 10% by weight, specifically 0.5 to 5% by weight, and more specifically 0.5 to 3% by weight based on the total weight of the negative electrode active material layer.

[0084] The binder is a component that aids 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, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0085] Generally, the binder may be contained in an amount of 0.5 to 10% by weight, specifically 0.5 to 5% by weight, and more specifically 0.5 to 3% by weight based on the total weight of the negative electrode active material layer.

[0086] When using the metal itself without forming a negative electrode active material layer on the negative electrode, it can be manufactured by physically bonding, rolling, or vapor-depositing the metal on the metal thin film itself or the negative electrode current collector. For the vapor deposition method, an electric vapor deposition method or a chemical vapor deposition method (chemical vapor deposition) can be used for the metal.

[0087] For example, the metal bonded / rolled / vapor-deposited on the metal thin film itself or the negative electrode current collector may include one metal selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In), or an alloy of two metals.

[0088] The positive electrode 120 has a structure in which a positive electrode active material layer 122 is formed on a positive electrode current collector 121. Here, the positive electrode active material layer contains electrode materials such as a positive electrode active material, a conductive material, and a binder.

[0089] The positive electrode current collector 121 is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. For example, as the current collector, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used.

[0090] The positive electrode current collector 121 can have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to enhance the adhesion to the positive electrode active material layer. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a non-woven fabric.

[0091] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may 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 is a lithium-manganese-based oxide (for example, LiMnO2 , LiMn 2 O 4 etc.), lithium-cobalt oxides (e.g., LiCoO 2 etc.), lithium-nickel oxides (e.g., LiNiO 2 etc.), lithium-nickel-manganese oxides (e.g., LiNi 1-Y Mn Y O 2 (where 0 < Y < 1), LiMn 2-Z Ni Z O 4 (where 0 < Z < 2 etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O 2 (where 0 < Y1 < 1 etc.), lithium-manganese-cobalt oxides (e.g., LiCo 1-Y2 Mn Y2 O 2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O 4 (where 0 < Z1 < 2 etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r )O 2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O 4 (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 )O 2 (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 independent elements respectively, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, p2 + q2 + r2 + s2 = 1) etc.), lithium iron phosphate (e.g., Li 1+a Fe 1-x Mx (PO 4-b )X b (Here, M is one or more selected from Al, Mg, and Ti, X is one or more selected from F, S, and N, -0.5 ≦ a ≦ 0.5, 0 ≦ x ≦ 0.5, 0 ≦ b ≦ 0.1), etc. may be mentioned, and one or two or more of these compounds may be included.

[0092] Among these, in terms of being able to enhance the capacity characteristics and safety of the battery, the lithium metal oxide is LiCoO 2 , LiMnO 2 , LiNiO 2 , lithium nickel manganese cobalt oxide (for example, Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O 2 , Li(Ni 0.6 Mn 0.2 Co 0.2 )O 2 , Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 , Li(Ni 0.7 Mn 0.15 Co 0.15 )O 2 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 etc.), lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O 2 etc.), or lithium nickel manganese cobalt aluminum oxide (for example, Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 )O 2 ), lithium iron phosphate (for example, LiFePO 4 ) etc. may be used, and one or two or more of these mixtures can be used.

[0093] The positive electrode active material may be contained in an amount of 60 to 99% by weight, preferably 70 to 99% by weight, more preferably 80 to 98% by weight, based on the total weight of the positive electrode active material layer.

[0094] The descriptions of the conductive material and the binder are the same as those of the negative electrode active material layer.

[0095] On the other hand, the coating layer 130 is formed between the positive electrode 120 and the negative electrode 110.

[0096] At this time, the thickness t of the coating layer 130 may be 3 micrometers to 30 micrometers, specifically, 5 micrometers to 20 micrometers, more specifically, 5 micrometers to 15 micrometers. If it is outside the above range and is excessively thin, the effects intended by the present application cannot be obtained, and sufficient physical insulation between the positive electrode 120 and the negative electrode 110 cannot be ensured. If it is excessively thick, the resistance may increase, which is not preferable.

[0097] The thickness t of such a coating layer 130 can be easily measured through a thickness measuring instrument or a cross-sectional SEM photograph.

[0098] Also, the area of the coating layer 130 may be formed to an area that can entirely insulate the positive electrode 120 and the negative electrode 110. Specifically, when the negative electrode 110 is larger than the positive electrode 120, it is not limited as long as it has the same or a larger area as the positive electrode 120. However, for the ease of manufacturing processability, the coating layer 130 may be formed to an area corresponding to the entire area of the object to be coated.

[0099] FIG. 1 discloses, as an example, a structure in which a coating layer 130 is formed on a negative electrode 110. The coating layer 130 may be formed in an area corresponding to the negative electrode 110. Specifically, as an example, the coating layer 130 may be formed by coating and drying a composition for forming a coating layer on the negative electrode 110. Alternatively, the coating layer may be formed of a free-standing film and attached to the negative electrode 110, or may be formed by a method of coating and drying the composition for forming the coating layer on a substrate and then transferring it onto the negative electrode 110. The method is not limited. Also hereinafter, although a method of coating and drying a composition for forming a coating layer on an electrode or a separator will be described, the present invention is not limited thereto, and it goes without saying that it can be formed by various methods.

[0100] Although not shown in the drawings, it goes without saying that the coating layer can be formed in an area corresponding to the positive electrode by coating and drying a composition for forming a coating layer on the positive electrode.

[0101] In FIG. 1, the coating layer 130 serves as an electrical insulator instead of the separator.

[0102] On the other hand, referring to FIGS. 2 and 3, in another example, the electrode assembly has a structure further including a separator with the structure as shown in FIG. 1.

[0103] Specifically, referring to FIG. 2, the electrode assembly 200 includes a coating layer 230 between a positive electrode 220 and a negative electrode 210, and includes a separator 240 between the coating layer 230 and the positive electrode 220.

[0104] The coating layer 230 is formed, as an example, by coating and drying a composition for forming a coating layer on the negative electrode 210, and thus can be formed in an area corresponding to the negative electrode 210. The separator 240 is interposed between such a coating layer 230 and the positive electrode 220.

[0105] Here, the separation membrane can be used without any particular restrictions as long as it is commonly used for separation membranes in lithium secondary batteries. In particular, those with low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention ability are preferred.

[0106] For example, as the separation membrane, a porous polymer film containing polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof can be used. Also, a normal porous non-woven fabric, for example, a non-woven fabric made of high melting point glass fibers, polyethylene terephthalate fibers, etc. may be used as the separation membrane.

[0107] Alternatively, it may be an SRS (Safety Reinforced Separator) separation membrane having a structure in which an organic-inorganic mixed layer containing inorganic particles and a binder is formed on one or both sides of the base substrate.

[0108] Specifically, the base substrate of the SRS separation membrane may be a porous polymer film containing the polyolefin-based polymer.

[0109] The inorganic particles serve as a kind of spacer that enables the formation of empty spaces between the inorganic particles to form fine pores and can maintain the physical form. Also, since the inorganic particles generally have the property that their physical properties do not change even at a high temperature of 200 °C or higher, the formed organic-inorganic mixed layer has excellent heat resistance.

[0110] The inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles used in the present invention are not particularly limited as long as no oxidation and / or reduction reaction occurs within the operating voltage range of the applied battery. In particular, when using inorganic particles with ion transfer ability, the conductivity of ions in the electrochemical device can be increased to improve performance, so it is preferably as high as possible. Also, when the inorganic particles have a high density, it is not only difficult to disperse them during manufacturing, but there is also a problem of weight increase during the manufacture of secondary batteries, so it is preferably as low as possible. In addition, in the case of an inorganic substance with a high dielectric constant, it can contribute to an increase in the dissociation degree of electrolyte salts in the liquid electrolyte, for example, lithium salts, and improve the ionic conductivity of the electrolyte. Finally, in the case of inorganic particles with thermal conductivity, since they have excellent heat absorption ability, they can suppress the phenomenon where heat is locally concentrated to form a heat generation point leading to thermal runaway, so they are more preferable.

[0111] For the reasons described above, the inorganic particles are preferably one or more selected from the group consisting of (a) high dielectric constant inorganic particles having a dielectric constant of 1 or more, 5 or more, preferably 10 or more, (b) inorganic particles having piezoelectricity, (c) thermally conductive inorganic particles, and (d) inorganic particles having lithium ion transfer ability.

[0112] The piezoelectric inorganic particles refer to a substance that is an insulator under normal pressure but has the property of conducting electricity due to an internal structure change when a certain pressure is applied. It not only exhibits a high dielectric constant characteristic with a dielectric constant of 100 or more, but also has the function of generating a potential difference between both sides when a certain pressure is applied and it is stretched or compressed, causing charges to be generated and one side to be positively charged and the opposite side to be negatively charged respectively.

[0113] Examples of the inorganic particles having piezoelectricity include BaTiO 3 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr1-y Ti y O 3 (PLZT), Pb(Mg 3 Nb 2 / 3 )O 3 -PbTiO 3 (PMN-PT), hafnia (H f O 2 ) or mixtures thereof, etc., but not limited thereto.

[0114] The inorganic particles having the lithium ion transfer ability contain lithium element, but do not store lithium and are inorganic particles having a function of moving lithium ions. Since the inorganic particles having the lithium ion transfer ability may transfer and move lithium ions due to a kind of defect existing inside the particle structure, it is possible to prevent a decrease in lithium mobility and prevent a decrease in battery capacity.

[0115] Examples of the inorganic particles having the lithium ion transfer ability include lithium phosphate (Li 3 PO 4 ), lithium titanium phosphate (Li x Ti y (PO 4 ) 3 , 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO 4 ) 3 , 0 < x < 2, 0 < y < 1, 0 < z < 3), 14Li 2 O - 9Al 2 O 3 -38TiO 2 -39P 2 O 5 such as (LiAlTiP) x O y -based glass (glass) (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO 3 , 0 < x < 2, 0 < y < 3), Li 3.25Ge 0.25 P 0.75 S 4 such as lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), Li 3 such as lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), Li 3 PO 4 -Li 2 S-SiS 2 such as SiS 2 -based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), LiI-Li 2 S-P 2 S 5 such as P 2 S 5 -based glass (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), or mixtures thereof, etc., but not limited thereto.

[0116] In addition, examples of inorganic particles having a dielectric constant of 1 or more include SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2 O 3 , TiO 2 , SiC or mixtures thereof, etc., but not limited thereto.

[0117] The thermally conductive inorganic particles provide low thermal resistance but do not provide electrical conductivity, so they are substances having insulating properties. For example, aluminum nitride (AlN), boron nitride (BN), alumina (Al 2 O 3) It may be one or more selected from the group consisting of silicon carbide (SiC) and beryllium oxide (BeO), but is not limited thereto.

[0118] When the above-mentioned high dielectric constant inorganic particles, piezoelectric inorganic particles, heat conductive inorganic particles and inorganic particles having lithium ion transfer ability are mixed, these enhancing effects can be doubled.

[0119] There is no limitation on the size of the inorganic particles, but it is preferably in the range of 0.001 to 10 μm as much as possible for an appropriate porosity between the inorganic particles. If it is less than 0.001 μm, the dispersibility decreases and it is difficult to adjust the physical properties. If it exceeds 10 μm, the thickness increases and the mechanical properties decrease. Also, due to the overly large pore size, the sufficient role of the coating layer cannot be fulfilled, and the probability of internal short circuit during battery charge and discharge increases.

[0120] There is no particular limitation on the content of the inorganic particles, but the range of 1 to 99% by weight per 100% by weight of the mixture of the inorganic particles and the binder is preferable, and particularly 10 to 95% by weight is more preferable. If it is less than 1% by weight, the content of the binder becomes excessively large, and the pore size and porosity decrease due to the reduction of the empty space formed between the inorganic particles, and the mobility of lithium ions may decrease. Conversely, if it exceeds 99% by weight, the content of the binder is excessively small, so the mechanical properties of the coating layer decrease due to the weakening of the adhesive force between the inorganic substances.

[0121] On the other hand, the binder is not limited as long as it does not cause a side reaction with the electrolytic solution. In particular, a binder having as low a glass transition temperature (Tg) as possible can be used, and preferably, it is in the range of -200 to 200°C. This is because the mechanical properties of the final insulating film can be improved.

[0122] Also, the binder does not necessarily have to have ion conduction ability, but it is more preferable to use a polymer having ion conduction ability.

[0123] Therefore, it is preferable that the binder has as high a dielectric constant as possible. In fact, since the dissociation degree of salt in the electrolyte depends on the dielectric constant of the electrolyte solvent, the higher the dielectric constant of the polymer, the more the degree of salt dissociation in the electrolyte can be improved. The dielectric constant of the polymer is 1 or more, specifically, a range of 1.0 to 100 (measurement frequency = 1 kHz) can be used, and particularly preferably 10 or more.

[0124] In addition to the functions described above, the binder can have the characteristic of gelling upon impregnation with the liquid electrolyte and showing a high electrolyte impregnation rate (degree of swelling). In fact, when the binder is a polymer excellent in electrolyte impregnation rate, the electrolyte injected after battery assembly will penetrate into the polymer, and the polymer holding the absorbed electrolyte will have electrolyte ion conduction ability. Therefore, if possible, a polymer having a solubility parameter of 15 to 45 MPa 1 / 2 is preferable, and 15 to 25 MPa 1 / 2 and 30 to 45 MPa 1 / 2 is more preferable. When the solubility parameter is less than 15 MPa 1 / 2 and exceeds 45 MPa 1 / 2 it becomes difficult to be impregnated (swelled) by a normal liquid electrolyte for batteries.

[0125] Examples of such binder materials may be one or more selected from the group consisting of polyvinylidene fluoride - co - hexafluoropropylene, polyvinylidene fluoride - co - trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene - co - vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, and polyvinylalcohol.

[0126] The total thickness of the separation membrane may be 5 micrometers to 20 micrometers, specifically, 5 micrometers to 15 micrometers, and more specifically, 6 micrometers to 13 micrometers. When the thickness of the separation membrane satisfies the above range, it is possible to effectively prevent a short - circuit between the positive electrode and the negative electrode while minimizing the resistance value of the lithium secondary battery. As a result, it is possible to prevent a decrease in the energy density of the lithium secondary battery and improve the life characteristics.

[0127] Referring to FIG. 3, the electrode assembly 300 includes a coating layer 330 between the positive electrode 320 and the negative electrode 310, and a separation membrane 340 is included between the coating layer 330 and the negative electrode 310, and the structure is shown.

[0128] Since the coating layer 330 is formed by coating and drying the coating composition for forming the coating layer on the positive electrode 320, it can be formed in an area corresponding to the positive electrode 320, and the separation membrane 340 is interposed between such a coating layer 330 and the negative electrode 310.

[0129] The description of the separation membrane 340 is as described above.

[0130] In another example, the coating layer may be formed on both the positive electrode and the negative electrode. In other words, the coating layer may be composed of a first coating layer formed on the positive electrode and a second coating layer formed on the negative electrode.

[0131] FIGS. 4 to 5 disclose a configuration in which the coating layer is formed on both the positive electrode and the negative electrode.

[0132] Specifically, FIG. 4 schematically shows an electrode assembly in which the coating layer is formed on the positive electrode and the negative electrode instead of the separation membrane, and FIG. 5 schematically shows an electrode assembly in which a separation membrane is interposed between the coating layers.

[0133] Referring to FIG. 4, the electrode assembly 400 has a structure in which a coating layer 431 formed on the negative electrode 410 and a coating layer 432 formed on the positive electrode 420 are formed to abut against each other.

[0134] That is, instead of the separation membrane between the negative electrode 410 and the positive electrode 420, the coating layers 431 and 432 are located, and the coating layers 431 and 432 serve as electrical insulation.

[0135] Here, since the coating layer 431 is formed by coating and drying a composition for forming a coating layer on the negative electrode 410, it can have an area corresponding to the negative electrode 410, and the coating layer 432 is formed by coating and drying a composition for forming a coating layer on the positive electrode 410, so it can have an area corresponding to the positive electrode 420.

[0136] On the other hand, when formed on both electrodes in this way, the thicknesses (t 2 , t 1 ) of the coating layers 431 and 432 may each be 3 micrometers to 30 micrometers, specifically, 5 micrometers to 20 micrometers, and more specifically, 5 micrometers to 15 micrometers.

[0137] Also, the total thickness (t 1 +t 2 ) may be 10 micrometers to 50 micrometers, specifically, 10 micrometers to 30 micrometers.

[0138] On the other hand, referring to FIG. 5, in another example, the electrode assembly 500 has a structure further including a separator 540 with the same structure as that in FIG. 4.

[0139] Specifically, referring to FIG. 5, coating layers 531 and 532 are respectively formed on the negative electrode 510 and the positive electrode 520 of the electrode assembly 500, and the separator 540 is included between the coating layers 531 and 532.

[0140] As described above, since the coating layer 531 is manufactured by coating and drying a composition for forming a coating layer on the negative electrode 510, it may be formed in an area corresponding to the negative electrode 510, and the coating layer 532 is manufactured by coating and drying a composition for forming a coating layer on the positive electrode 520, so it may be formed in an area corresponding to the positive electrode 520.

[0141] The separation membrane 540 is as described above.

[0142] In another example, the electrode assembly may include a separation membrane and may have a structure in which the coating layer is formed on one or both surfaces of the separation membrane.

[0143] FIG. 6 discloses a configuration in which the coating layer is formed on the separation membrane.

[0144] Specifically, referring to FIG. 6, coating layers 631 and 632 are located between the negative electrode 610 and the positive electrode 620, and the coating layers 631 and 632 are formed on both surfaces of the separation membrane 640. Although not shown in the drawings, it is of course possible that the coating layer may be formed only on one surface of the separation membrane, for example, the surface facing the positive electrode 620 or the surface facing the negative electrode 610.

[0145] Since the coating layers 631 and 632 are formed by coating and drying a coating composition for forming a coating layer on both surfaces of the separation membrane 640, they may be formed in an area corresponding to the area of the separation membrane 640.

[0146] Thus, when the coating layers 631 and 632 are formed on both surfaces of the separation membrane 640, their thicknesses (t 4 , t 3 ) may each be 2 micrometers to 30 micrometers, specifically, 2 micrometers to 15 micrometers, and more specifically, 2 micrometers to 10 micrometers.

[0147] Also, their total thickness (t 3 + t 4 ) may be 4 micrometers to 50 micrometers, specifically, 4 micrometers to 20 micrometers.

[0148] <Lithium secondary battery> Next, the lithium secondary battery according to the present invention will be described.

[0149] The lithium secondary battery of the present invention may include the electrode assembly electrolyte and a battery case.

[0150] The electrolyte may be a non-aqueous lithium electrolyte containing a non-aqueous organic solvent and a lithium salt, or may be a flame-retardant electrolyte containing a flame-retardant solvent and a lithium salt.

[0151] As the non-aqueous organic solvent of the non-aqueous lithium electrolyte, examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate and other aprotic organic solvents can be used.

[0152] However, in the case of a non-aqueous lithium electrolyte containing such a non-aqueous organic solvent, it is a flammable solvent that is easy to volatilize and catch fire, and the safety of the battery may become a problem. Therefore, the electrolyte may be a flame-retardant electrolyte in detail.

[0153] The flame-retardant electrolyte may be an electrolyte that is difficult to volatilize and does not catch fire. As a result, when the flame-retardant electrolyte is applied to a lithium secondary battery, the high-temperature safety of the battery can be ensured.

[0154] On the one hand, the flame-retardant electrolyte has a problem of low wettability with respect to existing separation membranes for lithium secondary batteries (for example, polyolefin-based separation membranes). However, the coating layer according to the present invention enhances the wettability of the flame-retardant electrolyte, so that the use of the flame-retardant electrolyte is possible.

[0155] Here, the flame-retardant solvent can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. For example, the flame-retardant solvent may contain one or more compounds selected from sulfone-based compounds, nitrile-based compounds, phosphate-based compounds, and carbonate-based compounds substituted with fluorine.

[0156] The sulfone-based compound may be a cyclic sulfone-based compound or a linear sulfone-based compound. Specifically, it may contain one or more compounds selected from the group consisting of sulfolane, tetramethylene sulfone, dibutyl sulfone, ethyl vinyl sulfone, methyl propyl sulfone, ethyl-i-propyl sulfone, ethyl-i-butyl sulfone, i-propyl-i-butyl sulfone, i-propyl-s-butyl sulfone, and butyl-i-butyl sulfone.

[0157] The nitrile-based compound may contain one or more compounds selected from the group consisting of acetonitrile, succinonitrile, adiponitrile, malononitrile, glutaronitrile, suberonitrile, and sebaconitrile.

[0158] The phosphate-based compound may contain one or more compounds selected from the group consisting of dimethyl methyl phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, diethyl ethyl phosphate, dimethyl methyl phosphate, dimethyl(2-methoxyethoxy)methyl phosphonate, diethyl(2-methoxyethoxy)methyl phosphonate, and triphenyl phosphate.

[0159] The fluorine-substituted carbonate compound may contain one or more compounds selected from the group consisting of bis(2,2,3,3-tetrafluoro-propyl) 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, ethyl-2,2,2,2’,2’,2'-hexafluoro-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-pentafluoro-propyl) carbonate.

[0160] The lithium salt is used as a mediator for transmitting ions in the lithium secondary battery. The lithium salt contains, for example, Li as a cation + and, as an anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF 4 - , ClO 4 - , B 10 Cl 10 - , AlCl 4 - , AlO 2 - , PF 6 - , CF 3 , SO 3 - , CH 3 , CO 2 - , CF 3 , CO 2 - , AsF 6 - , SbF6 - 、CH 3 SO 3 - 、(CF 3 CF 2 SO 2 ) 2 N - 、(CF 3 SO 2 ) 2 N - 、(FSO 2 ) 2 N - 、BF 2 C 2 O 4 - 、BC 4 O 8 - 、PF 4 C 2 O 4 - 、PF 2 C 4 O 8 - 、(CF 3 ) 2 PF 4 - 、(CF 3 ) 3 PF 3 - 、(CF 3 ) 4 PF 2 - 、(CF 3 ) 5 PF - 、(CF 3 ) 6 P - 、C 4 F 9 SO 3 - 、CF 3 CF 2 SO 3 - 、CF 3 CF 2 (CF 3 ) 2 CO - 、(CF 3 SO 2 ) 2 CH - 、CF 3(CF 2 ) 7 SO 3 - and SCN - include at least any one selected from the group consisting of.

[0161] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF 4 , LiClO 4 , LiB 10 Cl 10 , LiAlCl 4 , LiAlO 2 , LiPF 6 , LiCF 3 SO 3 , LiCH 3 CO 2 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiCH 3 SO 3 , LiFSI (Lithium bis(fluorosulfonyl) imide, LiN(SO 2 F) 2 ), LiBETI (lithium bis(perfluoroethanesulfonyl) imide, LiN(SO 2 CF 2 CF 3 ), 2 and LiTFSI (lithium bis(trifluoromethanesulfonyl) imide, LiN(SO 2 CF 3 )) 2 ) may include a single substance or a mixture of two or more selected from the group consisting of, but in terms of excellent stability, it is preferable to include Li(N(SO 2 CF 3 )) 2 .

[0162] In addition to these, lithium salts commonly used in the electrolyte of lithium secondary batteries can be used without limitation.

[0163] The lithium salt can be appropriately changed within the range that can be normally used. However, in order to obtain the optimal effect of forming a film for preventing corrosion of the electrode surface, it may be contained in the electrolyte at a concentration of 1 M to 3 M, specifically, a concentration of 1 M to 2.5 M, and more specifically, a concentration of 1 M to 2 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of the lithium secondary battery is sufficient, the viscosity of the electrolyte is appropriate, and the electrolyte impregnation property can be improved.

[0164] In addition, for the purpose of improving charge-discharge characteristics, flame retardancy, etc., the electrolyte may be added with, for example, pyridine, triethyl phosphate, triethanolamine, cyclic ether, ethylenediamine, n-glyme, triamide hexaline, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. In some cases, for imparting non-flammability, it may further contain a halogen-containing solvent such as carbon tetrachloride and ethylene trifluoride, and for improving the high-temperature storage characteristics, it may further contain carbon dioxide gas, and may further contain FEC (Fluoro-Ethylene Carbonate), PRS (Propene sultone), etc.

[0165] The lithium secondary battery of the present invention can be manufactured by incorporating the electrode assembly into a battery case together with the electrolyte.

[0166] The battery case may be one commonly used in the art, and there is no limitation on the outer shape according to the use of the battery. For example, it may be a cylindrical shape, a rectangular shape, a pouch type, or a coin type, etc., but is not limited thereto.

[0167] The lithium secondary battery according to an embodiment of the present invention can be used not only for a battery cell used as a power source for a small device, but also preferably for a unit cell in a medium- and large-sized battery module including a large number of battery cells. Preferred examples of the medium- and large-sized devices include electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems (ESS).

[0168] Hereinafter, the present invention will be described in more detail through specific examples. However, the following examples are only illustrative for helping the understanding of the present invention and do not limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications are possible within the scope of the present base material and the technical idea, and such deformations and modifications naturally belong to the scope of the appended claims.

[0169] <Example 1> Manufacture of Composition for Forming Coating Layer Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (D50: 0.6 micrometer): boehmite (D50: 0.35 micrometer, zeta potential: 35 mV): polymethyl methacrylate (PMMA) polymer particles (D50: 1 micrometer, zeta potential: -50 mV): hydrogenated nitrile rubber (H-NBR): polyvinylidene fluoride (PVDF) were put into an N-methyl-2-pyrrolidone (NMP) solvent and dispersed so that the weight ratio was 60:10:10:5:15 to produce a composition for forming a coating layer.

[0170] The D50 was measured by using the laser diffraction method to measure the value of the volume accumulation rate of 50%, and the zeta potential value was measured by the electrophoretic light scattering method using dynamic light scattering equipment.

[0171] Manufacture of Negative Electrode Next, a copper (Cu) metal thin film with a thickness of 20 micrometers was prepared as the negative electrode current collector, and graphite as the negative electrode active material, carbon black as the conductive material, carboxymethyl cellulose (CMC) as the thickening agent, and PVDF as the binder were dispersed in water so that the weight ratio was 95:1:1.5:2.5. The resulting negative electrode slurry was coated at a thickness of 75 micrometers, dried, and rolled to produce a negative electrode.

[0172] Manufacture of the positive electrode A 15-micrometer-thick aluminum (Al) metal thin film was prepared as the positive electrode current collector, and Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 ; carbon nanotubes as the conductive material and PVDF as the binder were dispersed in NMP solvent so that the weight ratio was 96:1:3. The resulting positive electrode slurry was coated at a thickness of 60 micrometers, dried, and rolled to produce a positive electrode.

[0173] Manufacture of the electrode assembly The composition for forming the coating layer was coated on the negative electrode active material layer of the negative electrode at a thickness of 30 micrometers and dried to form a coating layer.

[0174] Subsequently, an electrode assembly was manufactured by arranging the coating layer and the positive electrode active material layer of the positive electrode in contact with each other as shown in FIG. 1.

[0175] Manufacture of the lithium secondary battery The electrode assembly was impregnated with an electrolyte in which LiN(SO 2 CF 3 ) 2 (LiFSI) was dissolved to a concentration of 1.5 M in the nonflammable solvent sulfolane, and then incorporated into a battery case to manufacture a lithium secondary battery.

[0176] <Example 2> In Example 1, a composition for forming a coating layer, a positive electrode, and a negative electrode were manufactured.

[0177] Manufacture of Electrode Assembly The composition for forming a coating layer was coated on the negative electrode active material layer of the negative electrode with a thickness of 20 micrometers and dried to form a coating layer.

[0178] The composition for forming a coating layer was coated on the positive electrode active material layer of the positive electrode with a thickness of 20 micrometers and dried to form a coating layer.

[0179] Thereafter, an electrode assembly was manufactured by arranging as shown in FIG. 4 so that the coating layer of the negative electrode and the coating layer of the positive electrode were in contact with each other.

[0180] Manufacture of Lithium Secondary Battery The electrode assembly was impregnated with an electrolyte in which LiN(SO 2 CF 3 )(LiFSI) was dissolved to a concentration of 1.5 M in a nonflammable solvent sulfolane, and was built into a battery case to manufacture a lithium secondary battery. 2 (LiFSI) was dissolved to a concentration of 1.5 M in a nonflammable solvent sulfolane, and was built into a battery case to manufacture a lithium secondary battery.

[0181] <Example 3> As in Example 1, a composition for forming a coating layer, a positive electrode, and a negative electrode were manufactured.

[0182] Manufacture of Electrode Assembly The composition for forming a coating layer was coated on the positive electrode active material layer of the positive electrode with a thickness of 20 micrometers and dried to form a coating layer.

[0183] Thereafter, an electrode assembly was manufactured by arranging as shown in FIG. 3 so that the coating layer of the positive electrode and the negative electrode active material layer of the negative electrode faced each other and a separator made of a polyolefin material (thickness: 15 micrometers) was sandwiched therebetween.

[0184] Manufacture of Lithium Secondary Battery The electrode assembly was impregnated with an electrolyte prepared by dissolving LiN(SO 2 CF 3 ) 2 (LiFSI) to a concentration of 1.5 M in the nonflammable solvent sulfolane, and then placed in a battery case to fabricate a lithium secondary battery.

[0185] <Example 4> In Example 3, when fabricating the lithium secondary battery, an electrolyte prepared by dissolving LiPF 6 to a concentration of 1 M in an organic solvent (ethylene carbonate: ethyl methyl carbonate = 30:70 by volume ratio) was used. The electrode assembly and the lithium secondary battery were fabricated in the same manner as in Example 3.

[0186] <Example 5> A composition for forming a coating layer, a positive electrode, and a negative electrode were fabricated as in Example 1.

[0187] Fabrication of Electrode Assembly The composition for forming a coating layer was coated on both sides of a polyolefin-based separator (thickness: 10 micrometers) to a thickness of 10 micrometers each, and then dried to form a coating layer.

[0188] Thereafter, an electrode assembly was fabricated by arranging the coating layer, the positive electrode active material layer of the positive electrode, and the negative electrode active material layer of the negative electrode in contact with each other as shown in Figure 6.

[0189] Fabrication of Lithium Secondary Battery The electrode assembly was impregnated with an electrolyte prepared by dissolving LiN(SO 2 CF 3 ) 2 (LiFSI) to a concentration of 1.5 M in the nonflammable solvent sulfolane, and then placed in a battery case to fabricate a lithium secondary battery.

[0190] <Example 6> Fabrication of Composition for Forming Coating Layer Li 1.3 Al 0.3 Ti 1.7 (PO4 ) 3 (D50: 0.6 micrometer): The weight ratio of boehmite (D50: 0.35 micrometer, zeta potential: 35 mV): polyvinylidene fluoride (PVDF) is 60:25:15. It was put into an N-methyl-2-pyrrolidone (NMP) solvent and dispersed to produce a composition for forming a coating layer.

[0191] An electrode assembly and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the composition for forming a coating layer was used.

[0192] <Example 7> Manufacture of Composition for Forming Coating Layer Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (D50: 0.6 micrometer): The weight ratio of polymethyl methacrylate (PMMA) polymer particles (D50: 1 micrometer, zeta potential: -50 mV): hydrogenated nitrile rubber (H-NBR): polyvinylidene fluoride (PVDF) is 60:20:5:15. It was put into an N-methyl-2-pyrrolidone (NMP) solvent and dispersed to produce a composition for forming a coating layer.

[0193] An electrode assembly and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the composition for forming a coating layer was used.

[0194] <Example 8> Manufacture of Composition for Forming Coating Layer Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3(D50: 0.6 micrometers): Boehmite (D50: 0.35 micrometers, zeta potential: 35 mV): Polymethyl methacrylate (PMMA) polymer particles (D50: 1 micrometer, zeta potential: -50 mV): Hydrogenated nitrile rubber (H-NBR): Polyvinylidene fluoride (PVDF) were put into an N-methyl-2-pyrrolidone (NMP) solvent and dispersed to produce a composition for forming a coating layer so that the weight ratio became 10:60:10:5:15.

[0195] An electrode assembly and a lithium secondary battery were produced in the same manner as in Example 1, except that the composition for forming the coating layer was used.

[0196] <Comparative Example 1> As in Example 1, a positive electrode and a negative electrode were produced.

[0197] Manufacture of Electrode Assembly The positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode were opposed to each other, and a separator made of a polyolefin material (thickness: 15 micrometers) was sandwiched therebetween, and the electrode assembly was manufactured in the same manner as the electrode assembly of a general lithium secondary battery.

[0198] Manufacture of Lithium Secondary Battery The electrode assembly was impregnated with an electrolyte in which LiPF 6 was dissolved to be 1 M in an organic solvent (ethylene carbonate: ethyl methyl carbonate = 30:70 volume ratio), and was built into a battery case to manufacture a lithium secondary battery.

[0199] <Comparative Example 2> In Comparative Example 1, when manufacturing the lithium secondary battery, except that an electrolyte in which LiN(SO 2 CF 3 ) 2 (LiFSI) was dissolved to be 1.5 M was used, an electrode assembly and a lithium secondary battery were manufactured in the same manner as in Comparative Example 1.

[0200] <Comparative Example 3> As in Example 1, a positive electrode and a negative electrode were manufactured.

[0201] Manufacture of the composition for forming the coating layer Al 2 O 3 (D50: 1 micrometer, zeta potential: -20 mV): The composition for forming the coating layer was manufactured by dispersing it in an NMP solvent so that the weight ratio of polyvinylidene fluoride (PVDF) was 85:15.

[0202] Manufacture of the electrode assembly The composition for forming the coating layer was coated on the negative electrode active material layer of the negative electrode with a thickness of 20 micrometers and dried to form a coating layer.

[0203] The composition for forming the coating layer was coated on the positive electrode active material layer of the positive electrode with a thickness of 20 micrometers and dried to form a coating layer.

[0204] Then, the electrode assembly was manufactured by arranging them so that the coating layer of the negative electrode and the coating layer of the positive electrode were in contact with each other.

[0205] Manufacture of the lithium secondary battery The electrode assembly was impregnated with an electrolyte in which LiN(SO 2 CF 3 ) 2 (LiFSI) was dissolved to 1.5 M, and the lithium secondary battery was manufactured by incorporating it into a battery case.

[0206] <Comparative Example 4> Boehmite (D50: 0.35 micrometer, zeta potential: 35 mV): Al 2 O 3 (D50: 1 micrometer, zeta potential: -20 mV): The composition for forming the coating layer was manufactured by dispersing it in an N-methyl-2-pyrrolidone (NMP) solvent so that the weight ratio of polyvinylidene fluoride (PVDF) was 10:75:15.

[0207] An electrode assembly and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the composition for forming the coating layer was used.

[0208] <Experimental Example 1> A hot box test was performed on the lithium secondary batteries of Examples 1 to 5 and Comparative Examples 1 and 2.

[0209] The hot box test was conducted by increasing the temperature from 25°C at a rate of 5°C / min, maintaining it at 100°C, 120°C, 140°C, 150°C, 160°C, 170°C, and 180°C for 30 minutes each, and then increasing the temperature to 200°C at a rate of 2°C / min.

[0210] Then, the temperature at which ignition started was shown in Table 1.

[0211]

Table 1

[0212] Referring to Table 1 above, it can be confirmed that the lithium secondary battery according to the present invention is superior in thermal stability, and it can be confirmed that more improved thermal stability can be obtained when a flame-retardant electrolyte is used.

[0213] On the other hand, in the case of the hot box test for comparing thermal stability, the closer the state of charge of the lithium secondary battery is to full charge, the lower the thermal stability. Therefore, comparison must be made under the same fully charged state. However, in the case of the lithium secondary battery of Comparative Example 3, since it cannot be impregnated with an electrolyte using a flame-retardant solvent from the beginning, it cannot be fully charged, and it is difficult to compare thermal stability under equivalent conditions. Therefore, it was omitted from the evaluation results.

[0214] <Experimental Example 2> The initial capacity and capacity retention rate were measured for the lithium secondary batteries of Examples 1 to 8 and Comparative Examples 1 to 4, and the results are shown in Table 2 below.

[0215] The capacity retention rate was calculated as the ratio of the capacity after 200 cycles to the initial capacity after subjecting each of the manufactured lithium secondary batteries to 200 cycles of charging to 4.2 V at a constant current of 0.33C at 25°C and discharging to 3.0 V at a constant current of 0.33C in one cycle.

[0216] [Table 2]

[0217] Referring to Table 2, it can be confirmed that the performance of the lithium secondary battery according to the present invention is superior to that of Comparative Examples 2 to 4. This is because when using a flame retardant solvent, the oxide solid electrolyte particles act as an electrolyte to enhance the mobility of lithium ions, and the polymer particles improve the impregnation property of the electrolyte.

[0218] Those having ordinary knowledge in the field to which the present invention pertains can make various applications and modifications within the scope of the present invention based on the above content.

[0219] [Industrial Applicability] In the electrode assembly according to the present invention, a coating layer is located between the positive electrode and the negative electrode, and the coating layer includes one or more selected from the group consisting of polymer particles and ceramic particles together with oxide-based solid electrolyte particles, so that the insulation between the positive electrode and the negative electrode is effectively maintained by the coating layer that does not easily shrink even in a high-temperature environment, and thus there is an effect of improving high-temperature safety.

[0220] In addition, since the coating layer according to the present invention has electrical insulation properties by itself, it can not only play the role of a separator even without a separator, but also, when used together with a separator, can prevent the shrinkage of the separator and further enhance the electrical insulation while having heat resistance, so it is more effective in terms of high-temperature safety.

[0221] Furthermore, since the coating layer according to the present invention uses oxide-based solid electrolyte particles, even when the electrolyte impregnation property is somewhat low, it can serve as an electrolyte between the positive electrode and the negative electrode, thus improving the phenomenon of increased resistance in the lithium secondary battery.

[0222] In addition, when the coating layer according to the present invention contains both oxide-based solid electrolyte particles and polymer particles used in polymer-based solid electrolyte particles, it can exhibit an even more improved effect.

[0223] Furthermore, when a flame-retardant electrolyte is used as the electrolyte, not only can the safety be further improved by suppressing ignition, but also the problem of a decrease in electrolyte impregnation property that may occur due to the flame-retardant electrolyte can be solved by the coating layer according to the present invention as described above. Therefore, even when using a flame-retardant electrolyte, there is an effect of improving the performance of the lithium secondary battery.

Claims

1. An electrode assembly including a positive electrode, a negative electrode, and a coating layer positioned between the positive electrode and the negative electrode, wherein the coating layer includes at least one selected from the group consisting of (a) oxide-based solid electrolyte particles and (b) polymer particles and ceramic particles.

2. The oxide-based solid electrolyte particles are LLTO-based compounds, Li ６ La ２ CaTa ２ O １２ , Li ６ La ２ ANb ２ O １２ (where A is Ca or Sr), Li ２ Nd ３ TeSbO １２ , Li ３ BO ２．５ N ０．５ , Li ９ SiAlO ８ , LAGP-based compounds, LATP-based compounds, Li １＋ｘ Ti ２－ｘ Al ｘ Si ｙ (PO ４ ) ３－ｙ (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1), LiAl ｘ Zr ２－ｘ (PO ４ ) ３ (where 0 ≤ x ≤ 1), LiTi ｘ Zr ２－ｘ (PO ４ ) ３ (where 0 ≤ x ≤ 1), LISICON-based compounds, LIPON-based compounds, perovskite-based compounds, NASICON-based compounds, LLZO-based compounds, and LLZMO-based compounds, and is one selected from the group consisting of these or includes two or more of these, the electrode assembly according to claim 1.

3. The electrode assembly according to claim 1, wherein the absolute value of the zeta potential of each of the polymer particles and the ceramic particles is 25 mV or more.

4. The electrode assembly according to claim 1, wherein the polymer particles include at least one selected from the group consisting of polyethylene oxide (PEO), polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA), polystyrene, polyvinyl chloride, polycarbonate, polysulfone, polyethersulfone, polyetherimide, polyphenyl sulfone, polyamideimide, polyimide, polybenzimidazole, polyether ketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate.

5. The ceramic particles are boehmite, Al ２ O ３ TiO ２ Fe ２ O ３ SiO ２ ZrO ２ Co ３ O ４ SnO ２ NiO, ZnO, V ２ O ５ and at least one selected from the group consisting of MnO, the electrode assembly according to claim 1.

6. The electrode assembly according to claim 1, wherein the oxide-based solid electrolyte particles are contained in an amount of 10% by weight to 90% by weight based on the total weight of the coating layer.

7. The coating layer includes (a) oxide-based solid electrolyte particles and (b) polymer particles, and the polymer particles include at least one selected from the group consisting of polyethylene oxide (PEO), polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA), polystyrene, polyvinyl chloride, polycarbonate, polysulfone, polyethersulfone, polyetherimide, polyphenyl sulfone, polyamideimide, polyimide, polybenzimidazole, polyether ketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate. The electrode assembly according to claim 1.

8. The electrode assembly according to claim 1, wherein the coating layer further includes at least one additive selected from the group consisting of a binder and a dispersant.

9. The electrode assembly according to claim 1, wherein the thickness of the coating layer is 3 micrometers to 30 micrometers.

10. The electrode assembly according to claim 1, wherein the coating layer is formed on the positive electrode or the negative electrode.

11. The electrode assembly according to claim 10, further comprising a separator, wherein the separator is located between the positive electrode and the coating layer or between the negative electrode and the coating layer.

12. The electrode assembly according to claim 1, wherein the coating layer comprises a first coating layer formed on the positive electrode and a second coating layer formed on the negative electrode.

13. The electrode assembly according to claim 12, further comprising a separator, wherein the separator is located between the first coating layer and the second coating layer.

14. The electrode assembly according to claim 1, further comprising a separator, wherein the coating layer is formed on one or both surfaces of the separator.

15. The electrode assembly according to any one of claims 11, 13, and 14, wherein the separator is an SRS separator having a structure in which an organic-inorganic hybrid layer containing inorganic particles and a binder is formed on one or both surfaces of a base substrate.

16. A lithium secondary battery comprising the electrode assembly according to claim 1, an electrolyte, and a battery case.

17. The lithium secondary battery according to claim 16, wherein the electrolyte is a flame-retardant electrolyte containing a flame-retardant solvent and a lithium salt.

18. The lithium secondary battery according to claim 17, wherein the flame-retardant solvent contains one or more compounds selected from sulfone-based compounds, nitrile-based compounds, phosphate-based compounds, and carbonate-based compounds substituted with fluorine.

19. The lithium salt contains LiN(SO ２ CF ３ ). ２ The lithium secondary battery according to claim 17.

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