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 is formed in two or more layers in the stacking direction of the positive electrode and the negative electrode, the coating layer includes a first coating layer in face-to-face contact with the negative electrode and a second coating layer not in face-to-face contact with the negative electrode, the first coating layer includes any one of the particles selected from the following i) to iii), and when i) or ii) is included in the first coating layer, the second coating layer includes iii), and when iii) is included in the first coating layer, the first coating layer includes i) or ii). The present invention relates to an electrode assembly and a lithium secondary battery. i) Oxide-based solid electrolyte particles and ceramic particles having an absolute value of zeta potential of 25 mV or more, ii) Oxide-based solid electrolyte particles, iii) Ceramic particles having an absolute value of zeta potential of 25 mV or more.

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, Korean Patent Application No. 10 - 2023 - 0057709 filed on May 3, 2023, and Korean Patent Application No. 10 - 2023 - 0187354 filed on December 20, 2023, and all contents disclosed in the documents of the Korean patent applications are included as part of this specification.

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

Background Art

[0003] In recent years, as the application fields of lithium secondary batteries have rapidly expanded not only to power supply for electronic devices such as electricity, electronics, communication, and computers but also to power storage supply for large - area devices such as automobiles and power storage devices, the demand for lithium secondary batteries with high capacity, high output, long life, and high stability has been increasing.

[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, etc. The positive electrode may generate oxygen due to an unstable structure in the charged state, and when oxygen is generated, there is a high risk of ignition, so research and development on methods to improve the stability 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, making it impossible to insulate between the positive electrode and the negative electrode. If electrical insulation between the positive electrode and the negative electrode becomes impossible, a short circuit may occur, and ignition may occur due to the action of oxygen generated by the unstable positive electrode. That is, when a short circuit occurs in a lithium secondary battery in a charged state in a high-temperature environment, there is a possibility that the lithium secondary battery may catch fire.

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

[0007] To solve this problem, all-solid-state batteries using a flame-retardant electrolyte containing a flame-retardant solvent are a solution. However, the flame-retardant electrolyte is not well impregnated into the conventional separator, and there is a problem that the cell performance deteriorates due to low ionic conductivity and high interfacial resistance between electrolyte particles. Also, if the electrolyte is not well impregnated in a lithium secondary battery, there is a problem that a non-uniform reaction occurs between the electrode and the electrolyte, dendrites are generated, and a short circuit occurs.

[0008] Therefore, in order to solve these problems, research and development on methods for improving the stability of lithium secondary batteries while maintaining and improving various performances have been attempted.

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention is for solving such problems, and aims to provide an electrode assembly with high high-temperature safety, prevention of ignition, high electrolyte impregnation property, and excellent battery performance, and a lithium secondary battery including the same.

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, and the coating layer is formed in two or more layers in the stacking direction of the positive electrode and the negative electrode. The coating layer includes a first coating layer in face-to-face contact with the negative electrode and a second coating layer not in face-to-face contact with the negative electrode. The first coating layer includes any particles selected from the following i) to iii). When i) or ii) is included in the first coating layer, the second coating layer includes iii). When iii) is included in the first coating layer, i) or ii) is included.

[0011] i) Oxide-based solid electrolyte particles and ceramic particles having an absolute value of zeta potential of 25 mV or more. ii) Oxide-based solid electrolyte particles. iii) Ceramic particles having an absolute value of zeta potential of 25 mV or more.

[0012] Here, the oxide-based solid electrolyte particles can include one or more lithium metal oxides or lithium metal phosphates selected from Nasicon-type solid electrolytes, Lisicon-type solid electrolytes, Garnet-type solid electrolytes, Perovskite-type solid electrolytes, and LiPON-type solid electrolytes. Specifically, it can include one or more selected from the group consisting of LAGP (lithium aluminum germanium phosphate)-based compounds, LLZO (lithium lanthanum zirconium oxide)-based compounds, LATP (lithium aluminum titanium phosphate)-based compounds, LLZTO (lithium lanthanum zirconium tantalum oxide)-based compounds, LLTO (lithium lanthanum titanium oxide)-based compounds, LSTP (lithium silicon titanium phosphate)-based compounds, and LGPO (lithium germanium phosphate)-based compounds.

[0013] In addition, the ceramic particles can include one or more selected from the group consisting of BN (boron nitride), 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 , LiF, and MnO. Specifically, the ceramic particles can be one or more selected from the group consisting of BN (boron nitride), boehmite, Al 2 O 3 , and LiF.

[0014] The second coating layer can be in face contact with the positive electrode.

[0015] At this time, the first coating layer includes iii), and the second coating layer can include i) or ii).

[0016] On the other hand, one or more of the first coating layer and the second coating layer can each further include polymer particles having an absolute value of the zeta potential of 25 mV or more. The polymer particles can 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] Further, the electrode assembly further includes a separation membrane, and the second coating layer may be in face contact with the positive electrode, the separation membrane, or both the positive electrode and the separation membrane. At this time, the first coating layer includes (iii), and the second coating layer may include (i) or (ii). Also, in this case, one or more of the first coating layer and the second coating layer may each further include polymer particles having an absolute zeta potential value of 25 mV or more, 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.

[0018] On the other hand, each of the coating layers may further include one or more additives selected from the group consisting of a binder and a dispersant.

[0019] The thickness of each of the coating layers can be 1 micrometer to 30 micrometers.

[0020] 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.

[0021] At this time, the electrolyte can be a nonflammable electrolyte containing a nonflammable solvent having a flash point of 100 °C or higher or no flash point and a lithium salt.

[0022] 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. The lithium salt may include, for example, LiN(SO 2 CF 3 ) 2 and the like.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0024] Hereinafter, the terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings. Based on the principle that the inventor can appropriately define the concept of the terms in order to explain his invention in the best way, they must be construed in a meaning and concept consistent with the technical idea of the present invention.

[0025] Unless otherwise defined, all terms (including technical and scientific terms) used herein shall be construed in a manner that is commonly understood by those of ordinary skill in the art to which this invention pertains. Also, terms defined in commonly used dictionaries shall not be interpreted ideally or overly unless specifically and clearly defined otherwise.

[0026] The terms used herein are for the purpose of describing embodiments and are not intended to limit the invention. In this specification, the singular form also includes the plural form unless otherwise specifically stated in the text. The terms "comprising" and / or "constituting" used herein do not exclude the presence or addition of one or more other components other than the recited components.

[0027] In this specification, when a certain part is described as including a certain component, it means that other components can be further included rather than excluding other components unless otherwise stated to the contrary.

[0028] In this specification, "zeta potential" is an index indicating the degree of surface charge of particles. In the present invention, the zeta potential of polymer particles or ceramic particles contained in the coating layer can be measured by the method of electrophoretic light scattering using a dynamic light scattering device. As an example, after dispersing polymer particles or ceramic particles in a solvent such as water or alcohol without a dispersant, the zeta potential value can be measured.

[0029] Hereinafter, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiment 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 should be understood that there may be various equivalents and modifications replacing them.

[0030] According to an embodiment of the present invention, it includes a positive electrode, a negative electrode, and a coating layer located between the positive electrode and the negative electrode. The coating layer is formed in two or more layers in the stacking direction of the positive electrode and the negative electrode. The coating layer includes a first coating layer in face-to-face contact with the negative electrode and a second coating layer not in face-to-face contact with the negative electrode. The first coating layer includes any particles selected from the following i) to iii). When i) or ii) is included in the first coating layer, the second coating layer includes iii). When iii) is included in the first coating layer, an electrode assembly including i) or ii) is provided.

[0031] i) Oxide-based solid electrolyte particles and ceramic particles with an absolute value of zeta potential of 25 mV or more. ii) Oxide-based solid electrolyte particles. iii) Ceramic particles with an absolute value of zeta potential of 25 mV or more.

[0032] <Coating layer> The oxide-based solid electrolyte particles have a lithium ion supply source containing lithium in the structure, and any solid electrolyte in the form of a lithium metal oxide or a lithium metal phosphate can be used.

[0033] Specific examples thereof include one or more lithium metal oxides or lithium metal phosphates selected from Nasicon-type solid electrolytes, Lisicon-type solid electrolytes, Garnet-type solid electrolytes, Perovskite-type solid electrolytes, and LiPON-type solid electrolytes. More specific examples include one or more selected from the group consisting of LAGP (lithium aluminum germanium phosphate)-based compounds, LLZO (lithium lanthanum zirconium oxide)-based compounds, LATP (lithium aluminum titanium phosphate)-based compounds, LLZTO (lithium lanthanum zirconium tantalum oxide)-based compounds, LLTO (lithium lanthanum titanium oxide)-based compounds, LSTP (lithium silicon titanium phosphate)-based compounds, and LGPO (lithium germanium phosphate)-based compounds.

[0034] Among these, from the viewpoint of accelerating the desolvation of lithium ions at the interface between the active material layer and the coating layer and improving the ionic conductivity and output of the lithium secondary battery, Nasicon-type solid electrolytes or Garnet-type solid electrolytes can be preferably used. More specifically, Nasicon-type solid electrolytes such as the above-mentioned LAGP-based compounds or LATP-based compounds can be appropriately used.

[0035] When the coating layer contains the oxide-based solid electrolyte particles, it is preferable because the resistance can be reduced depending on the affinity of the oxide-based solid electrolyte particles themselves with the electrolyte.

[0036] The average diameter (D50) of the oxide-based solid electrolyte particles can be 50 nanometers to 10 micrometers, specifically 50 nanometers to 5 micrometers, and more specifically 50 nanometers to 1 micrometer.

[0037] If it is outside the above range and too small, aggregation between particles may occur due to reduced dispersibility. Conversely, if it is too large, the coating layer may have overly large pores, and lithium dendrites may be easily formed through the pores, which is not preferable.

[0038] When the above range is satisfied, the lithium ion conductivity in the coating layer can be enhanced, the resistance can be reduced, and improved secondary battery performance can be exhibited.

[0039] The absolute value of the zeta potential of the ceramic particles can 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 above 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. As a result, the performance such as the capacity, output, and life characteristics of the lithium secondary battery can be improved.

[0040] Specifically, the ceramic particles include, but are not limited to, one or more selected from the group consisting of BN (boron nitride), 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 LiF, and MnO. Specifically, it can include, but is not limited to, BN (boron nitride), boehmite, Al 2 O 3 and LiF. More specifically, it can include BN (boron nitride) and boehmite.

[0041] The average diameter (D50) of the ceramic particles is in the range smaller than the thickness of the coating layer, and may be 30 nanometers to 5 micrometers, specifically 50 nanometers to 3 micrometers, and more specifically 50 nanometers to 1 micrometer. Also, compared with the thickness of the coating layer, it may be 1 / 100 or more and 1 / 3 or less of the total thickness of the coating layer.

[0042] When the average diameter (D50) of the ceramic particles is smaller, there is a possibility of aggregation between particles due to a decrease in the dispersibility of the particles. When it is larger, there is a problem of forming a lithium dendrite growth path.

[0043] The average diameter (D50) described above means the particle size 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 sizes in the range from the submicron region to about several mm, and can obtain highly reproducible and highly resolved results.

[0044] According to the present invention, the coating layer needs to be in face contact with the negative electrode. When two or more coating layers are formed, in addition to the first coating layer in face contact with the negative electrode, the second coating layer can be in face contact with the positive electrode.

[0045] In this case, as described above, the first coating layer can contain particles selected from i) to iii). When i) or ii) is included in the first coating layer, the second coating layer contains iii). When iii) is included in the first coating layer, it can contain i) or ii). Since the first coating layer faces the negative electrode, if a side reaction occurs between the negative electrode and the first coating layer in the voltage range of the negative electrode, the efficiency may decrease and the capacity and energy density may decrease. Therefore, it is preferable to use a material with few side reactions with the negative electrode. Accordingly, it is preferable to contain ceramic particles with an absolute value of the zeta potential of iii) of 25 mV or more, which have relatively few side reactions. Specifically, BN (boron nitride), boehmite, Al 2 O 3 , and one or more ceramic particles selected from the group consisting of LiF can be included.

[0046] At this time, when a side reaction occurs between the second coating layer and the positive electrode in the voltage range of the positive electrode, the efficiency may decrease and the capacity and energy density may decrease. Therefore, it is preferable to use a material with few side reactions with the positive electrode. However, since the surface of the positive electrode is relatively more stabilized and the side reaction is not a major problem compared to the negative electrode, a material more advantageous for performance improvement can be used, and an oxide-based solid electrolyte can be included. Therefore, it can contain i) or ii).

[0047] Most specifically, the first coating layer contains one or more ceramic particles selected from the group consisting of BN (boron nitride), boehmite, Al 2 O 3 , and LiF, the absolute value of the zeta potential of which is 25 mV or more. The second coating layer contains BN (boron nitride), boehmite, Al 2 O 3It can include one or more selected from the group consisting of LiF and oxide-based solid electrolyte particles.

[0048] On the other hand, one or more of the first coating layer and the second coating layer can each further include polymer particles having an absolute value of zeta potential of 25 mV or more.

[0049] Here, the polymer particles can be particles with a surface charge. Or, it can include all particles with a surface charge and those without. The surface charge may be one that the particle itself has, or otherwise may be formed by physical or chemical surface treatment.

[0050] Here, the absolute value of the zeta potential of the polymer particles can 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, thereby improving the performance such as the capacity, output, and life characteristics of the lithium secondary battery.

[0051] Specifically, the polymer particles can 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, polyphenyl sulfone, polyamideimide, polyimide, polybenzimidazole, polyether ketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate, and is not limited thereto. Specifically, the polymer particles can include polymethyl methacrylate.

[0052] The average diameter (D50) of the polymer particles is in the range of 50 nanometers to 3 micrometers, specifically 50 nanometers to 2 micrometers, and more specifically 50 nanometers to 1.5 micrometers, which can be smaller than the thickness of the coating layer. Also, when compared with the thickness of the coating layer, it can be 1 / 100 or more and 1 / 3 or less of the thickness of the coating layer.

[0053] 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 appropriate size are uniformly formed in the coating layer, thereby improving the mobility of lithium ions. On the other hand, when the average diameter (D50) of the polymer particles is smaller than 50 nanometers, aggregation between particles occurs due to a decrease in particle dispersibility, and the pores are clogged by the aggregated particles, which can reduce the mobility of lithium ions and increase the resistance. When the average diameter (D50) of the polymer particles is larger than 3 micrometers, as described above, there is a problem of forming a lithium dendrite growth path.

[0054] When the oxide-based solid electrolyte particles and / or the ceramic particles are included together with the polymer particles, the polymer particles can be included in an amount of 10% to 40% by weight, specifically 20% to 40% by weight, and more specifically 20% to 30% by weight, based on the total weight of each coating layer.

[0055] On the other hand, in the coating layer in which the oxide-based solid electrolyte particles are mixed with the ceramic particles, the oxide-based solid electrolyte particles and the ceramic particles can be mixed at a weight ratio of 9:1 to 1:9, specifically 7:3 to 3:7.

[0056] When the above range is satisfied, the pore uniformity, heat resistance, and electrolyte impregnation property in the coating layer are the most excellent.

[0057] As another specific example, the electrode assembly may further include a separation membrane. At this time, the second coating layer may be in face-to-face contact with the positive electrode, the separation membrane, or both the positive electrode and the separation membrane.

[0058] Also in this case, as described above, the first coating layer can contain particles selected from i) to iii). When i) or ii) is included in the first coating layer, the second coating layer contains iii). When iii) is included in the first coating layer, i) or ii) can be included. Also, for the same reason as described above, the first coating layer facing the negative electrode contains iii), and the second coating layer can contain i) or ii). Most specifically, the first coating layer contains one or more ceramic particles selected from the group consisting of the BN (boron nitride), boehmite, Al 2 O 3 and LiF, and the second coating layer preferably contains one or more selected from the group consisting of BN (boron nitride), boehmite, Al 2 O 3 , LiF, and oxide-based solid electrolyte particles. On the other hand, at this time, one or more of the first coating layer and the second coating layer can further contain polymer particles each having an absolute value of the zeta potential of 25 mV or more.

[0059] Here, the polymer particles can be particles having a surface charge. Or it can contain all particles with a surface charge and those without. The surface charge may be one that the particle itself has, or otherwise it can also be formed by physical or chemical surface treatment.

[0060] Here, the absolute value of the zeta potential of the polymer particles can 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, thereby improving the performance such as the capacity, output, and life characteristics of the lithium secondary battery.

[0061] Specifically, the polymer particles can include, but are not limited to, 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, polyether ketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate. Specifically, the polymer particles can include polymethyl methacrylate.

[0062] The average diameter (D50) of the polymer particles can be in the range of 50 nanometers to 3 micrometers, specifically 50 nanometers to 2 micrometers, and more specifically 50 nanometers to 1.5 micrometers, which is smaller than the thickness of the coating layer. Also, when compared with the thickness of the coating layer, it can be 1 / 100 or more and 1 / 3 or less of the thickness of the coating layer.

[0063] 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 other hand, when the average diameter (D50) of the polymer particles is less than 50 nanometers, aggregation occurs between the particles due to a decrease in the dispersibility of the particles, and the pores are clogged by the aggregated particles, reducing the mobility of lithium ions and increasing the resistance. When the average diameter (D50) of the polymer particles is greater than 3 micrometers, as described above, there is a problem of forming a lithium dendrite growth path.

[0064] When the oxide-based solid electrolyte particles and / or the ceramic particles are included together with the polymer particles, the polymer particles can be included in an amount of 10% to 40% by weight based on the total weight of each coating layer. Specifically, they can be included in an amount of 20% to 40% by weight, and more specifically, 20% to 30% by weight.

[0065] Also, in the coating layer in which the oxide-based solid electrolyte particles are mixed with the ceramic particles, the oxide-based solid electrolyte particles and the ceramic particles can be mixed at a weight ratio of 9:1 to 1:9, specifically, 7:3 to 3:7.

[0066] When the above range is satisfied, the pore uniformity, heat resistance, and electrolyte impregnation property in the coating layer are the most excellent.

[0067] On the other hand, each of the coating layers can further contain one or more additives selected from the group consisting of a binder and a dispersant.

[0068] The dispersant suppresses the phenomenon that the polymer particles aggregate excessively in the coating layer, enabling the polymer particles to be effectively dispersed and present in the coating layer.

[0069] The dispersant can include a hydrogenated nitrile copolymer, specifically, it can include a hydrogenated nitrile copolymer, more specifically, hydrogenated nitrile butadiene rubber (H-NBR).

[0070] 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, and can 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-dimethylbutadiene can be used, and one kind alone or a mixture of two or more kinds thereof can be used.

[0071] Such a dispersant can be contained in an amount of 1% to 15% by weight, specifically 1% to 10% by weight, more specifically 1% to 5% by weight, based on the total weight of each 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 thus cracks on the surface of the coating layer can be significantly reduced.

[0072] The binder plays a role in improving the adhesive force between the particles of the coating layer, the electrode, and the separator membrane.

[0073] The binder can 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, polyvinyl pyrrolidone (PVP), polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, and fluororubber. Specifically, the binder can include polyvinylidene fluoride.

[0074] The binder can be contained in an amount of 0.1 wt% to 15 wt%, specifically 0.5 wt% to 10 wt%, more specifically 1 wt% to 5 wt% based on the total weight of each coating layer. If it is outside this range, when it is too small, the effect of improving adhesion cannot be expected, and when it is too large, the content of other particles relatively decreases, which is not preferable.

[0075] 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.

[0076] 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 is prevented even in a high-temperature environment, so that the high-temperature safety of the lithium secondary battery can be improved.

[0077] <Electrode Assembly> Hereinafter, electrode assemblies with various structures will be described with reference to the drawings.

[0078] As an example, the coating layer can be entirely coated on the positive electrode, entirely coated on the negative electrode, or one or more coating layers can be coated on each of the positive electrode and the negative electrode.

[0079] Figures 1 to 2 show a structure formed on either the positive electrode or the negative electrode of the coating layer, and Figure 3 shows a structure in which the coating layer is formed on each of the positive electrode and the negative electrode.

[0080] Specifically, Figure 1 schematically shows an electrode assembly 100 having a structure in which all of the two or more coating layers are formed on the positive electrode instead of the separator, Figure 2 schematically shows an electrode assembly 200 having a structure in which all of the two or more coating layers are formed on the negative electrode instead of the separator, and Figure 3 schematically shows an electrode assembly 300 having a structure in which one layer of the two or more coating layers is formed on the positive electrode and one layer is formed on the negative electrode.

[0081] First, referring to Figure 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.

[0082] 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 contains electrode materials such as a negative electrode active material, a conductive material, and a binder. Alternatively, although not shown in the drawings, the negative electrode may be a graphite electrode made of carbon (C), or may be a metal itself.

[0083] The negative electrode current collector 111 is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, a surface-treated product of copper or stainless steel with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. can be used.

[0084] 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.

[0085] The negative electrode active material can include 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.

[0086] As the carbon material capable of reversibly intercalating / deintercalating lithium ions, any carbon-based negative electrode active material generally used in lithium-ion secondary batteries can be used without particular limitation. Representative examples thereof include crystalline carbon, amorphous carbon, or a combination thereof. 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.

[0087] 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 can be used.

[0088] 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 , LixFe 2 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 selected from the group consisting of.

[0089] As substances 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, SnO 2 , 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. can be mentioned, and at least one of these and SiO 2 can also be mixed and used. As the element Y, it can 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.

[0090] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, etc.

[0091] The negative electrode active material can 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 negative electrode active material layer.

[0092] 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 does not cause a chemical change in the battery and has conductivity. For example, carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powders 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 powders; 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; conductive materials such as polyphenylene derivatives, etc. can be used.

[0093] The conductive material can be contained in an amount of 0.1 to 10% by weight, specifically 0.5 to 5% by weight, more specifically 0.5 to 3% by weight, based on the total weight of the negative electrode active material layer.

[0094] 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, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene - propylene - diene monomer, sulfonated ethylene - propylene - diene monomer, styrene - butadiene rubber, fluororubber, and various copolymers thereof.

[0095] Normally, the binder can be contained in an amount of 0.5 to 10% by weight, specifically 0.5 to 5% by weight, more specifically 0.5 to 3% by weight, based on the total weight of the negative electrode active material layer.

[0096] When using the metal itself without forming a negative electrode active material layer on the negative electrode, it can be manufactured by methods such as 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 electrical vapor deposition method or a chemical vapor deposition method can be used.

[0097] For example, the metal bonded / rolled / vapor-deposited on the metal thin film itself or the negative electrode current collector can 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.

[0098] 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.

[0099] The positive electrode current collector 121 is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. 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.

[0100] The positive electrode current collector 121 can have a thickness of 3 μm to 500 μm, and fine irregularities can 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.

[0101] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, can 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 respective independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, and p2 + q2 + r2 + s2 = 1), etc.), lithium iron phosphate (e.g., Li 1+a Fe1-x M x (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. can be mentioned, and one or two or more of these compounds can be included.

[0102] 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.

[0103] The positive electrode active material can 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.

[0104] The description of the conductive material and the binder is the same as that of the negative electrode active material layer.

[0105] On the other hand, the coating layer 130 is formed between the positive electrode 120 and the negative electrode 110.

[0106] Here, the coating layer 130 includes a first coating layer 132 facing the negative electrode 110. It also includes a second coating layer 131 facing the positive electrode 120.

[0107] At this time, the second coating layer 131 can be first coated on the positive electrode 120, and then the first coating layer 132 can be coated on the second coating layer 131 to form.

[0108] At this time, the respective thicknesses (t1, t2) of the first coating layer 132 and the second coating layer 131 can be 1 micrometer to 30 micrometers, specifically 3 micrometers to 20 micrometers, more specifically 5 micrometers to 15 micrometers. Also, the total thickness (T) can be 3 micrometers to 50 micrometers. If it exceeds the above range and is too 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 too thick, the resistance may increase, which is not preferable.

[0109] Also, the ratio of these thicknesses (t1, t2) can be 1:9 to 9:1, specifically 3:7 to 7:3, more specifically 6:4 to 4:6, and most specifically 5:5.

[0110] Such a ratio of the thicknesses (t1, t2) can be appropriately selected in consideration of the characteristics of the battery to be manufactured.

[0111] The total thickness (T) of such a coating layer 130 and the thicknesses (t1, t2) of the respective coating layers 131, 132 can be easily measured through a thickness measuring instrument or a cross-sectional SEM photograph.

[0112] Also, the area of the coating layers 131, 132 can be formed to be 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, there is no limitation as long as it has the same area as or a larger area than the positive electrode 120. However, for the ease of manufacturing processability, the coating layers 131, 132 can be formed to have an area corresponding to the entire area of the object to be coated.

[0113] FIG. 1 discloses, as an example, a structure in which a second coating layer 131 is formed on a positive electrode 120 and a first coating layer 132 is formed on the second coating layer 131. The second coating layer 131 can be formed in an area corresponding to the positive electrode 120, and the first coating layer 132 can be formed in an area corresponding to the second coating layer 131. Therefore, the areas of the second coating layer 131 and the first coating layer 132 can be the same. Of course, as long as the positive electrode 120 and the negative electrode 110 can be insulated from each other as a whole, there is no limitation. The second coating layer 131 can be formed wider, and the first coating layer 132 can be formed smaller than the second coating layer 131. Specifically, each of the coating layers 131 and 132 can be formed, as an example, by coating and drying a composition for forming the second coating layer on the positive electrode 120, and coating and drying a composition for forming the first coating layer on the second coating layer 131. At this time, the composition for forming the second coating layer and the composition for forming the first coating layer can be applied and dried separately or together, and can be formed simultaneously or sequentially in terms of time. Alternatively, the coating layers 131 and 132 can be formed of a free-standing film and attached to the positive electrode 120, or can be formed by a method of coating and drying the composition for forming the second coating layer and the composition for forming the first coating layer on a substrate and then transferring them onto the positive electrode 120, and the method is not limited. Also hereinafter, the method of forming the composition for forming the first coating layer and the composition for forming the second coating layer by coating and drying them on an electrode or a separator will be described, but it is not limited thereto, and of course, they can be formed by various methods.

[0114] In FIG. 1, the coating layer 130 serves together as an electrical insulator in place of the separator.

[0115] On the one hand, referring to FIG. 2, an electrode assembly 200 having a structure in which a coating layer 230 is formed between a positive electrode 220 and a negative electrode 210 is shown. The positive electrode 220 has a structure in which a positive electrode active material layer 222 is formed on a positive electrode current collector 221, and the negative electrode 210 has a structure in which a negative electrode active material layer 212 is formed on a negative electrode current collector 211.

[0116] At this time, the coating layer 230 also includes a second coating layer 231 facing the positive electrode 220 and a first coating layer 232 facing the negative electrode 210, similar to the electrode assembly 100 of FIG. 1.

[0117] However, different from FIG. 1, the first coating layer 232 can be first coated on the negative electrode 210, and then the second coating layer 231 can be coated on the first coating layer 232 to form.

[0118] Therefore, the areas of the coating layers 231 and 232 are areas that can entirely insulate the positive electrode 220 and the negative electrode 210, and can be formed in areas corresponding to the entire area of the object to be coated for ease of manufacturing processability.

[0119] FIG. 2 discloses, as an example, a structure in which a first coating layer 232 is formed on the negative electrode 210 and a second coating layer 231 is formed on the first coating layer 232. However, the first coating layer 232 can be formed in an area corresponding to the negative electrode 210, and the second coating layer 231 can be formed in an area corresponding to the first coating layer 232. Therefore, the areas of the first coating layer 232 and the second coating layer 231 can be the same. Of course, as long as the area can entirely insulate the positive electrode 220 and the negative electrode 210, there is no limitation. The first coating layer 232 can be formed wider, and the second coating layer 231 can be formed smaller than the first coating layer 232. Specifically, each of the coating layers 231 and 232 can be formed, as an example, by coating and drying a composition for forming the first coating layer on the negative electrode 210, and the composition for forming the second coating layer can be coated and dried on the first coating layer 232.

[0120] The thickness, manufacturing method, etc. of the other coating layer 230 are as described in FIG. 1 above.

[0121] Also, referring to FIG. 3, as another example, an electrode assembly 300 having a structure in which a coating layer 330 is formed between the positive electrode 320 and the negative electrode 310 is shown. The positive electrode 320 has a structure in which a positive electrode active material layer 322 is formed on a positive electrode current collector 321, and the negative electrode 310 has a structure in which a negative electrode active material layer 312 is formed on a negative electrode current collector 311.

[0122] At this time, the coating layer 330 also includes a second coating layer 331 facing the positive electrode 320 and a first coating layer 332 facing the negative electrode 310, similar to the electrode assembly 100 of FIG. 1.

[0123] However, different from FIG. 1, the second coating layer 331 can be formed by coating on the positive electrode 320, and the first coating layer 332 can be formed by coating on the negative electrode 310.

[0124] Therefore, the areas of the coating layers 331 and 332 are such that they can entirely insulate the positive electrode 320 and the negative electrode 310, and for ease of manufacturing processability, they can be formed to correspond to the overall area of the object to be coated.

[0125] FIG. 3 discloses, as an example, a structure in which a first coating layer 332 is formed on the negative electrode 310 and a second coating layer 331 is formed on the positive electrode 320. However, the first coating layer 332 can be formed to have an area corresponding to the negative electrode 310, and the second coating layer 331 can be formed to have an area corresponding to the positive electrode 320. Therefore, the first coating layer 332 can be formed wider than the second coating layer 331. Of course, the first coating layer 332 and the second coating layer 331 can be formed to have the same area. Specifically, each of the coating layers 331 and 332 can be formed, as an example, by coating and drying a composition for forming the first coating layer on the negative electrode 310, and by coating and drying a composition for forming the second coating layer on the positive electrode 320.

[0126] The thickness, manufacturing method, etc. of the other coating layer 330 are as described with reference to FIG. 1 above.

[0127] On the other hand, the electrode assembly can further include a separator.

[0128] Therefore, FIGS. 4 to 7 show electrode assemblies 400, 500, 600, and 700 having the structure as shown in FIG. 1 and further including a separator.

[0129] At this time, the coating layer may be entirely coated on the negative electrode, or one or more coating layers may be respectively coated on the positive electrode and the negative electrode, or may be entirely coated on one surface of the separator facing the negative electrode, or one or more coating layers may be respectively coated on both surfaces of the separator. FIGS. 4 to 5 show configurations in which the coating layer is formed on the positive electrode and the negative electrode respectively, or only on the negative electrode, and FIGS. 6 to 7 show configurations in which the coating layer is formed on one surface or both surfaces of the separator.

[0130] Specifically, FIG. 4 schematically shows an electrode assembly 400 having a structure in which a separator is interposed between two or more coating layers in the electrode assembly 300 of FIG. 3, and FIG. 5 schematically shows an electrode assembly 500 having a structure in which a separator is interposed between the positive electrode and two or more coating layers in the electrode assembly 200 of FIG. 2. Although not shown in the drawings, in the electrode assemblies of FIGS. 1 to 3, the separator can be in any form as long as it is interposed between the positive electrode and the coating layer or between the coating layers. Hereinafter, a representative description will be given with reference to FIGS. 4 to 5.

[0131] Of course, although FIGS. 4 to 5 will be described with reference to FIGS. 1 to 3 in terms of structure, the coating layer facing the electrode and the coating layer facing the separator can be compositionally different as required as described above.

[0132] First, referring to FIG. 4, an electrode assembly 400 having a structure in which a coating layer 430 and a separator 440 are formed between a positive electrode 420 and a negative electrode 410 is shown. The positive electrode 420 has a structure in which a positive electrode active material layer 422 is formed on a positive electrode current collector 421, and the negative electrode 410 has a structure in which a negative electrode active material layer 412 is formed on a negative electrode current collector 411.

[0133] At this time, as shown in FIG. 3, the coating layer 430 includes a second coating layer 431 facing the positive electrode 420 and a first coating layer 432 facing the negative electrode 410. The second coating layer 431 can be formed by coating on the positive electrode 420, and the first coating layer 432 can be formed by coating on the negative electrode 410.

[0134] Therefore, the description of the width, manufacturing method, thickness, etc. of the coating layers 431 and 432 is as described in FIG. 3 above.

[0135] However, a separator 440 can be further included between the first coating layer 432 and the second coating layer 431 of the electrode assembly 400 in FIG. 4.

[0136] Here, the separator can be used without particular limitation as long as it is usually used as a separator in a lithium secondary battery. In particular, a separator having a low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention ability is preferred.

[0137] For example, as the separator, 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 laminated structure of two or more layers thereof can be used. Also, a normal porous non-woven fabric, for example, a non-woven fabric such as high melting point glass fiber and polyethylene terephthalate fiber can be used as the separator.

[0138] The thickness of the separator can 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 separator 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.

[0139] On the one hand, referring to FIG. 5, an electrode assembly 500 is shown having a structure in which a coating layer 530 and a separator 540 are formed between a positive electrode 520 and a negative electrode 510. The positive electrode 520 has a structure in which a positive electrode active material layer 522 is formed on a positive electrode current collector 521, and the negative electrode 510 has a structure in which a negative electrode active material layer 512 is formed on a negative electrode current collector 511.

[0140] At this time, the coating layer 530 includes a first coating layer 532 facing the negative electrode 510 and a second coating layer 531 facing the separator. At this time, the second coating layer 531 corresponds to the second coating layer in FIG. 2 in terms of manufacturing method and structure. Therefore, as shown in FIG. 2, the first coating layer 532 can be coated on the negative electrode 510, and the second coating layer 531 can be coated on the first coating layer 532 to form.

[0141] Therefore, the description of the width, manufacturing method, thickness, etc. of the coating layers 531 and 532 is as described in FIG. 2 above.

[0142] However, the electrode assembly 500 in FIG. 5 can further include a separator 540 between the positive electrode 520 and the second coating layer 531.

[0143] On the other hand, as another example of the structure in which the electrode assembly includes the separator, FIGS. 6 and 7 show a structure in which the coating layer is formed on one or both surfaces of the separator. Specifically, in FIG. 6, a structure in which one or more coating layers are respectively coated on both surfaces of the separator is shown, and in FIG. 7, a structure in which all the coating layers are coated on one surface of the separator facing the negative electrode is shown.

[0144] First, referring to FIG. 6, an electrode assembly 600 having a structure in which a coating layer 630 and a separator 640 are formed between a positive electrode 620 and a negative electrode 610 is shown. Here, the positive electrode 620 has a structure in which a positive electrode active material layer 622 is formed on a positive electrode current collector 621, and the negative electrode 610 has a structure in which a negative electrode active material layer 612 is formed on a negative electrode current collector 611.

[0145] At this time, the coating layer 630 includes a second coating layer 631 facing the positive electrode 620 and a first coating layer 632 facing the negative electrode 610.

[0146] However, the first coating layer 632 and the second coating layer 631 can be formed by coating both sides of the separator 640. That is, the coating layers 631 and 632 can be formed by coating and drying a first coating layer forming composition and a second coating layer forming composition on both sides of the separator 640.

[0147] Therefore, the areas of the coating layers 631 and 632 are large enough to insulate the positive electrode 620 and the negative electrode 610 entirely, and can be formed to correspond to the entire area of the object to be coated for ease of manufacturing processability, so they can be formed to correspond to the area of the separator 640. Of course, as long as the positive electrode 620 and the negative electrode 610 can be insulated entirely, it is also possible to form them smaller than the area of the separator 640.

[0148] Explanations of other aspects such as the thickness of the coating layers 631 and 632 are as described with reference to FIG. 1 above.

[0149] On the other hand, referring to FIG. 7, an electrode assembly 700 having a structure in which a coating layer 730 and a separator 740 are formed between a positive electrode 720 and a negative electrode 710 is shown. Here, the positive electrode 720 has a structure in which a positive electrode active material layer 722 is formed on a positive electrode current collector 721, and the negative electrode 710 has a structure in which a negative electrode active material layer 712 is formed on a negative electrode current collector 711.

[0150] At this time, the coating layer 730 includes a second coating layer 731 facing the separator 740 and a first coating layer 732 facing the negative electrode 710.

[0151] However, the second coating layer 731 and the first coating layer 732 can be formed by coating the entire surface of one side of the separator 740. That is, the composition for forming the second coating layer is first coated and dried on one side of the separator 740 to form the second coating layer 731, and then the composition for forming the first coating layer is coated and dried on the second coating layer 731 to form the first coating layer 732.

[0152] Thereafter, it can be laminated in a direction facing the first coating layer 732 and the negative electrode 710.

[0153] Therefore, the areas of the coating layers 731 and 732 are such that the positive electrode 720 and the negative electrode 710 can be insulated from each other entirely. For the ease of the manufacturing process, the areas can be formed to correspond to the entire area of the object to be coated, so they can be formed to correspond to the area of the separator 740. Of course, as long as the positive electrode 720 and the negative electrode 710 can be insulated from each other entirely, the areas of the coating layers 731 and 732 can be different from each other and can also be formed smaller than the area of the separator 740.

[0154] Also, although not shown in the drawings, in FIG. 7, it is needless to say that the second coating layer 731 is further included between the positive electrode 720 and the separator 740.

[0155] Furthermore, although the drawings show two layers, as long as at least one coating layer faces the negative electrode, it is not limited, and of course, a configuration in which three or more layers are formed is also included.

[0156] <Lithium secondary battery> Next, the lithium secondary battery according to the present invention will be described.

[0157] The lithium secondary battery of the present invention can include the electrode assembly electrolyte and the battery case.

[0158] The electrolyte can be a non-aqueous lithium electrolyte containing a non-aqueous organic solvent and a lithium salt, or can be a flame-retardant electrolyte containing a flame-retardant solvent whose flash point is not measurable (substantially non-flammable) or has a flash point of 100°C or higher and a lithium salt.

[0159] Examples of the non-aqueous organic solvent of the non-aqueous lithium electrolyte include aprotic organic solvents such as 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 pyruvate, ethyl propionate, etc.

[0160] However, in the case of a non-aqueous lithium electrolyte containing such a non-aqueous organic solvent, it is a flammable solvent that is volatile and easily catches fire, and there is a possibility that the safety of the battery becomes a problem. Therefore, the electrolyte can preferably be a flame-retardant electrolyte.

[0161] The flame-retardant electrolyte can be an electrolyte that does not easily 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.

[0162] 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, due to the coating layer according to the present invention, the wettability of the flame-retardant electrolyte is enhanced, so that the use of the flame-retardant electrolyte is possible.

[0163] Here, the flame-retardant solvent having a flash point of 100 °C or higher or having no flash point can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. For example, the flame-retardant solvent can contain one or more compounds selected from sulfone-based compounds, nitrile-based compounds, phosphate-based compounds, and carbonate-based compounds substituted with fluorine.

[0164] The sulfone-based compound is a cyclic sulfone-based compound or a linear sulfone-based compound. Specifically, it can 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.

[0165] The nitrile-based compound can contain one or more compounds selected from the group consisting of acetonitrile, succinonitrile, adiponitrile, malononitrile, glutaronitrile, suberonitrile, and sebaconitrile.

[0166] The phosphate-based compound can 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.

[0167] The fluorine-substituted carbonate compound can include 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.

[0168] The lithium salt is used as a mediator for transmitting ions in a lithium secondary battery. The lithium salt contains, for example, Li as a cation + and contains F as an anion - , Cl - , Br - , I - , NO 3 - , 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- , SbF 6 - , 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 - At least one selected from the group consisting of can be mentioned.

[0169] 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 ) can include a single substance or a mixture of two or more selected from the group consisting of, and from the aspect of excellent stability, it is preferable to include Li(N(SO 2 CF 3 ) 2 .

[0170] In addition to these, lithium salts commonly used in the electrolyte of lithium secondary batteries can be used without limitation.

[0171] The lithium salt can be appropriately changed within the range of normal use. However, in order to obtain the optimal effect of forming a film for preventing corrosion of the electrode surface, it can be contained in the electrolyte at a concentration of 1M to 3M, specifically, a concentration of 1M to 2.5M, and more specifically, a concentration of 1M to 2M. 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.

[0172] In addition, for the purpose of improving charge and discharge characteristics, flame retardancy, etc., 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. can also be added to the electrolyte. In some cases, for imparting non-flammability, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene can be further included, carbon dioxide gas can be further included to improve high-temperature storage characteristics, and FEC (Fluoro-Ethylene Carbonate), PRS (Propene sultone), etc. can also be further included.

[0173] The lithium secondary battery of the present invention can be manufactured by incorporating the electrode assembly together with the electrolyte into a battery case.

[0174] The battery case can adopt those commonly used in the art, and there is no limitation on the outer shape according to the use of the battery. For example, it can be cylindrical, rectangular, pouch type or coin type, etc., but not limited thereto.

[0175] 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 used as a unit cell for a medium and large battery module including a large number of battery cells. Preferred examples of the medium and large devices include electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, energy storage systems (ESS), and the like.

[0176] Hereinafter, the present invention will be described more specifically through specific examples. However, the following examples are 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 description and the technical idea, and such variations and modifications naturally belong to the scope of the appended claims.

[0177] In the following, the D50 of the particles was measured by using the laser diffraction method to measure the value of 50% volume cumulative rate, and the zeta potential value was measured by the electrophoretic light scattering method using a dynamic light scattering equipment.

[0178] <Example 1> Manufacture of Composition for Forming First Coating Layer BN (D50: 1 micrometer, zeta potential: -38 mV): polyvinylidene fluoride (PVDF) was put into an N-methyl-2-pyrrolidone (NMP) solvent so that the weight ratio was 90:10 and dispersed to manufacture a composition for forming a first coating layer.

[0179] Manufacture of Composition for Forming Second Coating Layer Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3(D50: 0.6 micrometers): Polyvinylidene fluoride (PVDF) was put into an N-methyl-2-pyrrolidone (NMP) solvent and dispersed so that the weight ratio became 85:15, and a composition for forming a second coating layer was produced.

[0180] Manufacture of the negative electrode Next, a 20-micrometer-thick copper (Cu) metal thin film 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 put into water and dispersed so that the weight ratio was 95:1:1.5:2.5, and the resulting negative electrode slurry was coated to a thickness of 75 micrometers, dried, and rolled to manufacture a negative electrode.

[0181] 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 put into an NMP solvent and dispersed so that the weight ratio was 96:1:3, and the resulting positive electrode slurry was coated to a thickness of 60 micrometers, dried, and rolled to manufacture a positive electrode.

[0182] Manufacture of the electrode assembly The composition for forming the first coating layer was coated to a thickness of 10 micrometers on the negative electrode active material layer of the negative electrode and dried to form a first coating layer. The composition for forming the second coating layer was coated to a thickness of 10 micrometers on the first coating layer and dried to form a second coating layer.

[0183] Then, a separator made of a polyolefin material (thickness: 15 micrometers) was placed between the second coating layer and the positive electrode active material layer of the positive electrode, and an electrode assembly was manufactured by arranging them as shown in Figure 5 so that the separator was in contact with the positive electrode active material layer.

[0184] Manufacture of 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 then the electrode assembly was built into a battery case to manufacture a lithium secondary battery.

[0185] <Example 2> In Example 1, a first coating layer was formed by coating one side of a polyolefin-based separator (thickness: 15 micrometers) with the composition for forming the first coating layer, and a second coating layer was formed by coating the other side of the separator with the composition for forming the second coating layer to manufacture a separator assembly. A lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrode assembly was manufactured by arranging the separator assembly between the positive electrode and the negative electrode such that the first coating layer faced the negative electrode as shown in FIG. 6.

[0186] <Example 3> A positive electrode and a negative electrode were manufactured as in Example 1.

[0187] Manufacture of Electrode Assembly The composition for forming the second coating layer was coated on the negative electrode active material layer of the negative electrode to a thickness of 10 micrometers and dried to form a second coating layer. A separator assembly was manufactured by coating both sides of the polyolefin-based separator (thickness: 15 micrometers) with the composition for forming the first coating layer to a thickness of 5 micrometers each and drying to form a first coating layer.

[0188] Thereafter, the negative electrode, the separator assembly, and the positive electrode were laminated to manufacture an electrode assembly.

[0189] Manufacture of 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 1.5M in a nonflammable solvent sulfolane (flash point: about 160 - 170 degrees), and a lithium secondary battery was manufactured by incorporating it into a battery case.

[0190] <Example 4> A positive electrode and a negative electrode were manufactured as in Example 1 above.

[0191] Manufacture of Electrode Assembly The composition for forming the first coating layer was coated on one surface of the negative electrode active material layer of the negative electrode to a thickness of 10 micrometers and dried to form the first coating layer. The composition for forming the second coating layer was coated on one surface of the positive electrode active material layer of the positive electrode to a thickness of 10 micrometers and dried to form the first coating layer. Then, these first coating layer and the second coating layer were laminated so as to face each other to manufacture an electrode assembly.

[0192] Manufacture of 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 1.5M in a nonflammable solvent sulfolane (flash point: about 160 - 170 degrees), and a lithium secondary battery was manufactured by incorporating it into a battery case.

[0193] <Comparative Example 1> A positive electrode and a negative electrode were manufactured as in Example 1 above.

[0194] 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 arranged to face each other, and a separator made of a polyolefin material (thickness: 15 micrometers) was placed between them, and an electrode assembly was manufactured in the same manner as the electrode assembly of a general lithium secondary battery.

[0195] Manufacture of 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 flame - retardant solvent sulfolane, and a lithium secondary battery was manufactured by incorporating it into a battery case.

[0196] <Comparative Example 2> A positive electrode and a negative electrode were manufactured in the same manner as in Example 1.

[0197] Manufacture of Electrode Assembly The composition for forming the second coating layer of Example 1 was coated on the negative electrode active material layer of the negative electrode to a thickness of 20 micrometers and dried to form a coating layer.

[0198] Thereafter, a separator made of a polyolefin material (thickness: 15 micrometers) was placed between the coating layer and the positive electrode active material layer of the positive electrode, and an electrode assembly was manufactured by arranging them so that the separator and the positive electrode active material layer were in contact.

[0199] Manufacture of 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 flame - retardant solvent sulfolane, and a lithium secondary battery was manufactured by incorporating it into a battery case.

[0200] <Comparative Example 3> A positive electrode and a negative electrode were manufactured in the same manner as in Example 1.

[0201] Manufacture of Electrode Assembly In Example 1, in the composition for forming the second coating layer, Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3A second coating layer-forming composition was produced in the same manner as in Example 1, except that polymethyl methacrylate (PMMA) polymer particles (D50: 1 micrometer, zeta potential: -50 mV) were used instead of (D50: 0.6 micrometer). The second coating layer-forming composition was coated on the negative electrode active material layer of the negative electrode to a thickness of 20 micrometers and dried to form a coating layer.

[0202] Subsequently, a separator made of a polyolefin material (thickness: 15 micrometers) was inserted between the coating and the positive electrode active material layer of the positive electrode, and an electrode assembly was manufactured by arranging them so that the separator and the positive electrode active material layer were in contact with each other.

[0203] Manufacture of 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, and the resulting solution was incorporated into a battery case to manufacture a lithium secondary battery.

[0204] <Comparative Example 4> A positive electrode and a negative electrode were manufactured in the same manner as in Example 1.

[0205] Manufacture of Electrode Assembly In Example 1, the second coating layer-forming composition was coated on the negative electrode active material layer of the negative electrode to a thickness of 10 micrometers and dried to form a second coating layer. The second coating layer-forming composition was also coated on the positive electrode active material layer of the positive electrode to a thickness of 10 micrometers and dried to form a second coating layer.

[0206] Subsequently, a separator made of a polyolefin material (thickness: 15 micrometers) was inserted between the second coating layers as shown in Figure 4, and an electrode assembly was manufactured.

[0207] Manufacture of 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 a lithium secondary battery was fabricated by incorporating the impregnated assembly into a battery case.

[0208] <Comparative Example 5> The positive and negative electrodes were fabricated in the same manner as in Example 1.

[0209] Fabrication of Electrode Assembly In Example 1, in the composition for forming the second coating layer, instead of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (D50: 0.6 micrometer), polymethyl methacrylate (PMMA) polymer particles (D50: 1 micrometer, zeta potential: -50 mV) were used.

[0210] Then, in Example 1, the composition for forming the second coating layer was coated on the negative electrode active material layer of the negative electrode to a thickness of 10 micrometers and dried to form a second coating layer, and the composition for forming the first coating layer was coated on the positive electrode active material layer of the positive electrode to a thickness of 10 micrometers and dried to form a first coating layer.

[0211] Thereafter, as shown in Fig. 4, a separator made of a polyolefin material (thickness: 15 micrometers) was placed between the first coating layer and the second coating layer to fabricate an electrode assembly.

[0212] Fabrication of 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 a lithium secondary battery was fabricated by incorporating the impregnated assembly into a battery case.

[0213] <Experimental Example 1> The initial capacity and discharge capacity of the lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 5 were measured, and the results are shown in Table 1 below.

[0214] The initial efficiency was calculated as the ratio of the discharge capacity to the charge capacity.

[0215]

Table 1

[0216] Referring to Table 1, 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 5, and exhibits performance similar to that of Comparative Example 1 of the lithium secondary battery without an electrolyte layer. From this, when using a flame-retardant solvent, low ionic conductivity, high interfacial resistance between electrolyte particles, and side reactions of the material used in the electrolyte layer in contact with the positive and negative electrodes may become problems. When an electrolyte layer containing a substance with low reactivity and a substance with good electrolyte impregnation property are formed in separate layers as in the present invention, it can be seen that better effects are exerted.

[0217] On the other hand, referring to Examples 1 to 4 and Comparative Example 4, it can be seen that it is most preferably effective when oxide-based solid electrolyte particles are not contained on the negative electrode side and are contained on the positive electrode side.

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

Industrial Applicability

[0219] In the electrode assembly according to the present invention, between the positive electrode and the negative electrode, a coating layer formed in two or more layers in the stacking direction is located. The coating layer contains a specific composition by components that are in face-to-face contact with each other, thereby imparting impregnation property to the electrolyte, and effectively maintaining insulation between the positive electrode and the negative electrode by a coating layer that does not easily shrink even in a high-temperature environment, and has the 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 separation membrane even without a separation membrane, but also, when used together with a separation membrane, has the role of preventing the shrinkage of the separation membrane and can have heat resistance while further enhancing electrical insulation, so it is more effective for high-temperature safety.

[0221] Furthermore, with respect to the problem of cell performance degradation due to low ionic conductivity and high interfacial resistance between electrolyte particles that may appear when using a non-flammable electrolyte together, the electrode assembly according to the present invention can also minimize side reactions with the electrode active material by including two or more coating layers such that coating layers with more appropriate compositions face each other depending on the type of the facing electrode, and has the effect of improving the performance of the lithium secondary battery.

[0222] Furthermore, when a non-flammable electrolyte is used together as an electrolyte, not only can the safety be further improved by suppressing ignition, but also the problem of reduced electrolyte impregnation property that may appear due to the non-flammable electrolyte can be solved by including particles with surface charges in the coating layer.

Claims

1. An electrode assembly comprising a positive electrode, a negative electrode, and a coating layer positioned between the positive electrode and the negative electrode, wherein the coating layer is formed of two or more layers in the stacking direction of the positive electrode and the negative electrode, the coating layer includes a first coating layer in face-to-face contact with the negative electrode and a second coating layer not in face-to-face contact with the negative electrode, the first coating layer includes any one of the particles selected from the following i) to iii), and when i) or ii) is included in the first coating layer, the second coating layer includes iii), and when iii) is included in the first coating layer, i) or ii) is included: i) Oxide-based solid electrolyte particles and ceramic particles having an absolute value of zeta potential of 25 mV or more, ii) Oxide-based solid electrolyte particles, iii) Ceramic particles having an absolute value of zeta potential of 25 mV or more.

2. The electrode assembly according to claim 1, wherein the oxide-based solid electrolyte particles include one or more lithium metal oxides or lithium metal phosphates selected from NASICON-type solid electrolytes, LISICON-type solid electrolytes, GARNET-type solid electrolytes, PEROVSKITE-type solid electrolytes, and LiPON-type solid electrolytes.

3. The electrode assembly according to claim 1, wherein the oxide-based solid electrolyte particles include one or more selected from the group consisting of LAGP (lithium aluminum germanium phosphate)-based compounds, LLZO (lithium lanthanum zirconium oxide)-based compounds, LATP (lithium aluminum titanium phosphate)-based compounds, LLZTO (lithium lanthanum zirconium tantalum oxide)-based compounds, LLTO (lithium lanthanum titanium oxide)-based compounds, LSTP (lithium silicon titanium phosphate)-based compounds, and LGPO (lithium germanium phosphate)-based compounds.

4. The ceramic particles include one or more selected from the group consisting of BN (boron nitride), 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 , LiF, and MnO, and the electrode assembly according to claim 1.

5. The ceramic particles are one or more selected from the group consisting of BN (boron nitride), boehmite, Al ２ O ３ , and LiF. The electrode assembly according to claim 4.

6. The electrode assembly according to claim 1, wherein the second coating layer is in face-to-face contact with the positive electrode.

7. The electrode assembly according to claim 1, wherein the first coating layer includes iii), and the second coating layer includes i) or ii).

8. The electrode assembly according to claim 1, wherein one or more of the first coating layer and the second coating layer further comprise polymer particles each having an absolute value of zeta potential of 25 mV or more.

9. The electrode assembly according to claim 8, wherein the polymer particles 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, polyether ketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate.

10. The electrode assembly according to claim 1, further comprising a separator membrane, wherein the second coating layer is in face-to-face contact with the positive electrode, the separator membrane, or both the positive electrode and the separator membrane.

11. The electrode assembly according to claim 10, wherein the first coating layer includes (iii), and the second coating layer includes (i) or (ii).

12. The electrode assembly according to claim 10, wherein one or more of the first coating layer and the second coating layer further comprise polymer particles each having an absolute value of zeta potential of 25 mV or more.

13. The electrode assembly according to claim 12, wherein the polymer particles 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, polyether ketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate.

14. The electrode assembly according to claim 1, wherein the coating layer further comprises one or more additives selected from the group consisting of a binder and a dispersant, respectively.

15. The electrode assembly according to claim 1, wherein the thickness of the coating layer is 1 micrometer to 30 micrometers, respectively.

16. A lithium secondary battery comprising the electrode assembly according to any one of claims 1 to 15, an electrolyte, and a battery case.

17. The lithium secondary battery according to claim 16, wherein the electrolyte is a nonflammable electrolyte containing a nonflammable solvent having a flash point of 100 °C or higher or having no flash point and a lithium salt.

18. The lithium secondary battery according to claim 17, wherein the nonflammable 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 is LiN(SO ２ CF ３ ). ２ The lithium secondary battery according to claim 17, comprising the same.

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