Electrodes and electrode assemblies

Abstract

The electrode according to the present invention comprises an electrode active material layer and a coating layer formed on the electrode active material layer, the coating layer comprising predetermined polymer particles, a dispersant and a binder, the binder comprising one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene (PE), polypropylene, ethylene-propylene-diene polymer and sulfonated ethylene-propylene-diene polymer.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority rights under Korean Patent Application No. 10-2022-0069164 dated June 7, 2022, and Korean Patent Application No. 10-2023-0070307 dated May 31, 2023, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference.

[0002] The present invention relates to an electrode and an electrode assembly containing the same that can improve the high-temperature safety and lifespan characteristics of lithium secondary batteries. [Background technology]

[0003] With the increasing technological development and demand for electric vehicles and energy storage systems (ESS), the demand for batteries as an energy source is rapidly increasing, leading to research into batteries that can meet diverse requirements. In particular, research is actively progressing on lithium-ion secondary batteries that have high energy density and excellent lifespan and cycle characteristics, as power sources for such devices.

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

[0005] Separation membranes are used to ensure electrical insulation between the positive and negative electrodes, and thin membranes made of polyolefin are commonly used. However, polyolefin-based separation membranes tend to shrink in high-temperature environments, which can prevent them from insulating the positive and negative electrodes. When electrical insulation between the positive and negative electrodes becomes impossible, a short circuit occurs, and this can react with oxygen generated by the unstable positive electrode, potentially causing a fire. In other words, if a short circuit occurs in a charged lithium-ion secondary battery in a high-temperature environment, there is a risk of the lithium-ion secondary battery catching fire.

[0006] Therefore, there is a current need for technological development to improve the high-temperature safety of lithium-ion batteries. [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, the present invention provides an electrode and an electrode assembly containing the same that improve the high-temperature safety and life characteristics of lithium secondary batteries by forming a coating layer that replaces or assists the separation membrane. [Means for solving the problem]

[0008] One embodiment of the invention is an electrode comprising an electrode active material layer and a coating layer formed on the electrode active material layer, The coating layer comprises polymer particles having an absolute value of zeta potential of 25 mV or more; a dispersant; and a binder, wherein the binder comprises one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene (PE), polypropylene, ethylene-propylene-diene polymer, and sulfonated ethylene-propylene-diene polymer, and the binder is included in an amount of 12% to 32% by weight relative to the total weight of the coating layer, thereby providing an electrode.

[0009] Another embodiment of the invention is an electrode assembly comprising a first electrode, a second electrode, and a coating layer disposed between the first electrode and the second electrode, The coating layer comprises polymer particles having an absolute value of zeta potential of 25 mV or more; a dispersant; and a binder, wherein the binder comprises one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene (PE), polypropylene, ethylene-propylene-diene polymer, and sulfonated ethylene-propylene-diene polymer, and the binder is included in an amount of 12% to 32% by weight relative to the total weight of the coating layer, thereby providing an electrode assembly. [Effects of the Invention]

[0010] The electrode and electrode assembly according to the present invention ensure electrical insulation between the two electrodes by forming a coating layer of a predetermined composition on the electrode, which replaces or supplements an existing separation membrane.

[0011] Experiments conducted by the inventors confirmed that optimizing the composition of the coating layer significantly reduces damage such as cracks in the coating layer. Therefore, when charging a lithium secondary battery including the electrode assembly, minute short circuits between the positive and negative electrodes that may occur due to the localized concentration of lithium ions in cracks in the coating layer are prevented. As a result, the charging time of the battery can be shortened, and the safety of the battery can be improved.

[0012] Furthermore, in electrodes and electrode assemblies including the coating layer, the occurrence of short circuits due to shrinkage of the existing separation membrane is suppressed, and ignition due to high temperatures or external impacts can be reduced. In particular, the coating layer has superior adhesion to the active material layer compared to the polyolefin-based substrate of the existing separation membrane, and the polymer particles contained in the coating layer can have a higher melting point than the polyolefin-based substrate. Therefore, by replacing or supplementing the existing separation membrane with such a coating layer, the coating layer does not easily shrink even in high-temperature environments, preventing short circuits between electrodes, and thus improving the high-temperature safety of the battery.

[0013] In addition, when using a flame-retardant electrolyte to ensure high-temperature safety of lithium secondary batteries, the coating layer can exhibit higher impregnation of the flame-retardant electrolyte than the polyolefin-based substrate of existing separation membranes, thereby ensuring excellent safety and high lithium ion mobility.

[0014] Therefore, the electrodes and electrode assemblies of the present invention can greatly contribute to achieving excellent high-temperature safety and improved lifespan characteristics of lithium secondary batteries, as well as other electrochemical properties. [Brief explanation of the drawing]

[0015] [Figure 1] This is a photograph of the surface of the electrode coating layer manufactured in Example 1. [Figure 2] This is a photograph of the surface of the electrode coating layer manufactured in Example 2. [Figure 3] This is a photograph of the surface of the electrode coating layer manufactured in Comparative Example 1. [Figure 4] This is a photograph of the surface of the electrode coating layer manufactured in Comparative Example 2. [Figure 5] This graph shows the capacity retention rate of lithium secondary batteries containing electrodes manufactured in Example 1 and Example 2, respectively. [Modes for carrying out the invention]

[0016] Unless otherwise defined, all terms used herein (including technical and scientific terms) are used in a sense that can be commonly understood by a person of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries shall not be interpreted ideally or excessively unless explicitly defined otherwise.

[0017] The terms used herein are for illustrative purposes only and are not intended to limit the invention. In this specification, the singular form includes the plural form unless otherwise specified. The terms “comprises” and / or “comprising” as used in this specification do not exclude the presence or addition of one or more other components in addition to those mentioned.

[0018] In this specification, when a part is said to include a component, this means that, unless otherwise stated, it may further include other components rather than excluding them.

[0019] In this specification, "A and / or B" means "A" or "B" or "A and B".

[0020] In this specification, "%" means weight percent unless otherwise explicitly indicated.

[0021] In this specification, D 50 This refers to the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. 50 This can be measured, for example, using the laser diffraction method. The laser diffraction method can generally measure particle sizes from the submicron region to several millimeters in size, and can obtain results with high reproducibility and high resolution.

[0022] In this specification, "specific surface area" is measured by the BET method, specifically calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BELSORP-mini II from BEL Japan.

[0023] In this specification, "zeta potential" is an indicator of the degree of surface charge of a particle. In the present invention, the zeta potential of a particle can be measured by electrophoretic light scattering using a dynamic light scattering apparatus. Specifically, polymer particles can be dispersed in water or an alcohol-based solvent without a dispersant, and then the zeta potential of the particles can be measured by electrophoretic light scattering.

[0024] The electrodes and electrode assemblies according to embodiments of the invention will be described in detail below.

[0025] <Electrode> An electrode according to one embodiment of the invention comprises an electrode active material layer and a coating layer formed on the electrode active material layer, wherein the coating layer comprises polymer particles having an absolute value of zeta potential of 25 mV or more, a dispersant, and a binder, wherein the binder comprises one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene (PE), polypropylene, ethylene-propylene-diene polymer, and sulfonated ethylene-propylene-diene polymer, and the binder is included in an amount of 12% to 32% by weight relative to the total weight of the coating layer.

[0026] It is known that existing polyolefin-based separation membranes tend to shrink at high temperatures, which can lead to short circuits between the positive and negative electrodes, potentially reducing the high-temperature safety of lithium secondary batteries.

[0027] The electrode of the above embodiment has a coating layer formed on the electrode active material layer that replaces or assists such existing separation membranes, wherein the coating layer includes a binder of a certain type and content, and polymer particles that satisfy a certain range of zeta potential.

[0028] The absolute value of the zeta potential can define the surface polarity of the polymer particles, and having an absolute value above a certain level means that the surface polarity is high. In this way, by combining polymer particles with high surface polarity with a binder of a specific composition, it was confirmed that the coating layer not only exhibits porosity, good coating properties, and surface characteristics that replace the separation membrane, but also that cracks and other defects are substantially absent in the coating layer.

[0029] Furthermore, since the polymer particles may have a relatively high melting point, when a coating layer containing them is applied, short circuits due to shrinkage of the existing separation membrane are suppressed, making it possible to provide a lithium secondary battery that exhibits improved high-temperature safety. Taking it a step further, it has been confirmed that the capacity retention rate and life characteristics of the lithium secondary battery can be further improved by adjusting the range of binder content in the coating layer and the range of polymer particles and other elements excluding the binder.

[0030] In addition, the coating layer can improve the impregnation of the flame-retardant electrolyte, described later, compared to existing separation membranes. This is likely because the flame-retardant electrolyte has relatively higher polarity than existing electrolytes. Therefore, by combining the electrode of the above embodiment with a flame-retardant electrolyte, the safety of the lithium secondary battery can be further improved while ensuring high lithium ion mobility through the coating layer, thereby further improving the electrochemical properties of the battery.

[0031] In the electrode of the above embodiment, the coating layer is formed on an electrode active material layer, which will be described later. For example, the coating layer is formed on a positive electrode active material layer or a negative electrode active material layer.

[0032] In such a coating layer, the polymer particles may be particles that carry a surface charge, and such surface charge and surface polarity are defined by the absolute value range of their zeta potential. Specifically, the zeta potential is a physical property that defines the electrostatic repulsion or dispersibility between the polymer particles, and polymer particles with a large absolute value of the zeta potential can be uniformly dispersed on the electrode and exhibit good and uniform coating properties, and a plurality of fine and uniform pores that allow lithium ions to pass through are defined between these particles. Furthermore, with polymer particles that satisfy such a zeta potential, the coating layer can exhibit excellent impregnation properties for flame-retardant electrolytes containing flame-retardant solvents with relatively large polarity.

[0033] The zeta potential of the polymer particles can be measured, for example, by electrophoretic light scattering using a dynamic light scattering apparatus. In this case, the zeta potential can be measured when the polymer particles are dispersed in water or an alcohol-based solvent without any other dispersant. In a specific example, the zeta potential can be measured when the polymer particles are dispersed in water at a concentration of 0.1% by weight or less.

[0034] The absolute value of the zeta potential of the polymer particles may be 25mV or more, 35mV or more, or 45mV or more, or 100mV or less, 90mV or less, or 80mV or less. When the absolute value of the zeta potential satisfies the above numerical range, the flame-retardant electrolyte can be easily impregnated into the coating layer, a uniform reaction occurs throughout the electrode, and this can improve various performance characteristics of the lithium secondary battery, such as capacity, output, and lifespan.

[0035] Specific examples of the polymer particles include, but are not limited to, one or more selected from the group consisting of polyethylene oxide (PEO), polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA), polyalkyl (meth)acrylates, polystyrene, polyvinyl chloride, polycarbonate, polysulfone, polyethersulfone, polyetherimide, polyphenylsulfone, polyamideimide, polyimide, polybenzimidazole, polyetherketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate.

[0036] The zeta potential of the polymer particles can be adjusted not only by the type of particle but also by the particle size or surface characteristics of these particles. Therefore, in order to achieve the zeta potential of the polymer particles, the dispersibility, or the appropriate porosity of the porous coating layer, the polymer particles have an average particle size D of 50 nm to 3 μm, or 50 nm to 2 μm, or 100 nm to 1.5 μm. 50 It can have.

[0037] The average particle size D of the polymer particles 50 If the average particle size D of the polymer particles is smaller than 50 nm, particle dispersibility decreases, causing interparticle aggregation, and the aggregated particles clog the pores, making it difficult to form a coating layer with a porous structure. 50 If the size is greater than 3 μm, the porous structure in the coating layer becomes simplified, leading to the problem of lithium dendrite formation during cell fabrication.

[0038] In addition, in order to control the surface properties of the polymer particles and thereby adjust the zeta potential, the polymer particles are included in the coating layer in a state in which they have been surface-treated with oxygen plasma or an ion beam.

[0039] The polymer particles described above are included in the coating layer at a content of 55% to 85% by weight, 55% to 80% by weight, or 65% to 75% by weight relative to the total weight of the coating layer. When the polymer particle content satisfies the above range, the dispersibility of the particles contained in the coating layer is improved, and pores are uniformly formed in the coating layer, which can significantly reduce cracks on the surface of the coating layer.

[0040] On the other hand, the dispersant suppresses the phenomenon of excessive aggregation of polymer particles in the coating layer, enabling the polymer particles to be effectively dispersed in the coating layer.

[0041] Such dispersants may include hydrogenated nitrile polymers, specifically hydrogenated nitrile copolymers, and more specifically, hydrogenated nitrile butadiene rubber (H-NBR).

[0042] The hydrogenated nitrile copolymer may be a copolymer containing α,β-unsaturated nitrile-derived structural units and hydrogenated conjugated diene-derived structural units, or a copolymer containing α,β-unsaturated nitrile-derived structural units, conjugated diene-derived structural units, and hydrogenated conjugated diene-derived structural units. Specifically, the hydrogenated nitrile copolymer may be a hydrogenated nitrile copolymer in which all of the conjugated diene-derived structural units are hydrogenated and no conjugated diene-derived structural units are included, or conversely, it may be a partially hydrogenated nitrile copolymer in which some of the conjugated diene-derived structural units are hydrogenated and hydrogenated conjugated diene-derived structural units are included together with the conjugated diene-derived structural units.

[0043] The hydrogenation method for the conjugated diene is carried out by a hydrogenation reaction known in the art, for example, a catalytic hydrogenation reaction using a catalyst system such as Rh, Ru, Pd, or Ir, and the hydrogenation rate can be adjusted by adjusting the amount of catalyst, reaction hydrogen pressure, reaction time, etc.

[0044] The hydrogenated nitrile copolymer can be produced by copolymerizing an α,β-unsaturated nitrile monomer with a conjugated diene monomer, and then hydrogenating the C=C double bond in the copolymer. The polymerization reaction and hydrogenation steps of the monomers are carried out by conventional methods.

[0045] As the α,β-unsaturated nitrile monomer, for example, acrylonitrile or methacrylonitrile can be used, and either one or a mixture of two or more of these can be used. As the conjugated diene monomer, for example, a conjugated diene monomer having 4 to 6 carbon atoms, such as 1,3-butadiene, isoprene, or 2,3-methylbutadiene can be used, and either one or a mixture of two or more of these can be used.

[0046] The α,β-unsaturated nitrile-derived structural units are present in the hydrogenated nitrile copolymer in an amount of 20% to 50% by weight, or 30% to 40% by weight. When this range is satisfied, the affinity between the hydrogenated nitrile copolymer and the organic solvent (e.g., N-methyl-2-pyrrolidone (NMP)) used as a medium for coating layer formation is at an appropriate level, making it easier to disperse polymer particles in the coating layer formation composition. As a result, pores are uniformly formed in the coating layer, and cracks on the surface of the coating layer can be significantly reduced.

[0047] The hydrogenated nitrile copolymer may have a weight-average molecular weight of 5,000 g / mol to 700,000 g / mol, or 5,000 g / mol to 600,000 g / mol, or 10,000 g / mol to 500,000 g / mol. When the weight-average molecular weight of the hydrogenated acrylonitrile-butadiene rubber (H-NBR) satisfies the above numerical range, polymer particles can be uniformly dispersed in the coating layer.

[0048] The dispersant described above is included in a content of 3% to 20% by weight, 5% to 20% by weight, or 5% to 15% by weight relative to the total weight of the coating layer. When the content of the dispersant satisfies the above range, the dispersibility of the particles contained in the coating layer is improved, and pores are uniformly formed in the coating layer, which can significantly reduce cracks on the surface of the coating layer.

[0049] On the other hand, the binder contained in the coating layer plays a role in improving the adhesion between the polymer particles and coating layer and the electrode active material layer.

[0050] The binder may contain one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene (PE), polypropylene, ethylene-propylene-diene polymer, and sulfonated ethylene-propylene-diene polymer, but may not contain one or more selected from the group consisting of polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and fluororubber. When the type of binder satisfies the above conditions, a coating layer with excellent adhesion is formed on the surface of the electrode, which can significantly reduce damage such as cracks on the surface of the coating layer.

[0051] The binder is included in an amount of 12% to 32% by weight, 12% to 28% by weight, 15% to 28% by weight, or 15% to 25% by weight relative to the total weight of the coating layer. If the binder content is less than 12% by weight relative to the total weight of the coating layer, the adhesion between the polymer particles and the electrode active material layer decreases, causing the coating layer to detach from the electrode active material layer and resulting in damage such as cracks in the coating layer. Furthermore, if the binder content exceeds 32% by weight relative to the total weight of the coating layer, the resistance of the coating layer increases with the increase in binder content, which increases the cell resistance and reduces the lifespan performance of the cell.

[0052] The aforementioned coating layer exhibits excellent impregnation properties for flame-retardant electrolytes, effectively replaces the role of a separation membrane, and reduces the resistance of the coating layer. Therefore, it can have a thickness of 5 μm to 50 μm, 10 μm to 45 μm, or 15 μm to 40 μm, and may contain multiple pores with a diameter of 10 nm or more, or 20 nm to 3 μm, or 50 nm to 1 μm. In this case, the thickness of the coating layer can refer to the total thickness of the coating layer formed on the positive and / or negative electrodes.

[0053] The aforementioned coating layer may have electrical insulating properties. In this case, the coating layer may, but is not limited to, a porous insulating layer.

[0054] Furthermore, the coating layer has the property of not easily shrinking even at high temperatures. Therefore, when one or more electrodes including the coating layer are stacked to form an electrode assembly without another separator membrane, short circuits between the positive and negative electrodes can be prevented even in high-temperature environments, thereby improving the high-temperature safety of the electrode assembly.

[0055] In the electrode of the above-described embodiment, the coating layer formed on the electrode active material layer can have excellent surface quality with significantly reduced damage such as cracks. Therefore, when one or more electrodes including the coating layer are stacked to form an electrode assembly without a separate separator film, and a lithium secondary battery is manufactured from the electrode assembly, minute short-circuit phenomena between the positive electrode and the negative electrode can be prevented.

[0056] According to one embodiment, the coating layer is formed by coating an electrode coating layer forming composition onto an electrode active material layer and drying it.

[0057] In this case, the solid content of the electrode coating layer forming composition may be 19% to 25% by weight, or 19% to 23% by weight, or 19% to 21% by weight. At this time, the solid content is defined as the total content of the components including the polymer particles, binder, and dispersant mentioned above, excluding the liquid medium such as an organic solvent used to dissolve or disperse these components. When the solid content of the electrode coating layer forming composition satisfies the above numerical range, the electrode coating layer forming composition can have a viscosity at a level that allows it to be coated onto the electrode active material layer.

[0058] Specifically, the viscosity of the electrode coating layer forming composition at 25°C may be 5000 cP to 7000 cP, or 5000 cP to 6800 cP, or 5500 cP to 6800 cP. When the viscosity of the electrode coating layer forming composition satisfies the above numerical range, the electrode coating layer forming composition can be coated onto the electrode active material layer to a uniform thickness.

[0059] On the other hand, in the electrode of the above embodiment, the electrode active material layer is formed on the electrode current collector. The above-described coating layer is formed on such an electrode active material layer, and the electrode active material layer and the coating layer are formed in contact with each other without the interposition of any other layer.

[0060] When the electrode in the above embodiment is a positive electrode, the positive electrode may include a positive electrode current collector, a positive electrode active material layer formed on the positive electrode current collector, and a coating layer formed on the positive electrode active material layer.

[0061] At this time, the positive electrode current collector only needs to have conductivity without inducing chemical changes in the battery, and is not particularly limited. For example, as the current collector, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment of the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used. The positive electrode current collector can have a thickness of 3 μm to 500 μm, and fine irregularities can also 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 films, sheets, foils, nets, porous bodies, foams, non-woven bodies, etc.

[0062] Also, the positive electrode active material layer can contain a positive electrode active material, and can further contain a conductive material, a binder, etc. as required.

[0063] The positive electrode active material is a compound capable of reversible insertion and extraction of lithium, and specifically, can include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 MnY2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxide (e.g., Li(Ni p Co q Mn r )O2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s2 are the atomic fractions of the respective independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, p2 + q2 + r2 + s2 = 1), etc.), lithium iron phosphate (e.g., Li 1+a Fe 1-x M x (PO 4-b )X b (where 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.), and one or two or more of these compounds are included.

[0064] Among these, in terms of enhancing the capacity characteristics and safety of the battery, the lithium metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2)O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2 etc.), lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2 etc.), or lithium nickel manganese cobalt aluminum oxide (e.g., Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 It may be oxyoxyl (O2), lithium iron phosphorus oxide (e.g., LiFePO4), or a mixture of one or more of these.

[0065] The positive electrode active material is present in an amount of 60% to 99% by weight, or 70% to 99% by weight, or 80% to 98% by weight, based on the total weight of the positive electrode active material layer.

[0066] On the other hand, the conductive material is a component for further improving the conductivity of the positive electrode active material, and such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. For example, carbon 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 crystalline structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0067] Typically, conductive material is included in an amount of 1% to 20% by weight, or 1% to 15% by weight, or 1% to 10% by weight, based on the total weight of the positive electrode active material layer.

[0068] Furthermore, the binder is a component that assists in bonding between the positive electrode active material and the conductive material, and to the positive electrode current collector.

[0069] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene (PE), polypropylene, ethylene-propylene-diene polymer, sulfonated ethylene-propylene-diene polymer, styrene-butadiene rubber, fluororubber, and various copolymers.

[0070] Typically, the binder is present in an amount of 1% to 20% by weight, or 1% to 15% by weight, or 1% to 10% by weight, based on the total weight of the positive electrode active material layer.

[0071] On the other hand, if the electrode in the above embodiment is a negative electrode, the negative electrode may include a negative electrode current collector, a negative electrode active material layer formed on the negative electrode current collector, and a coating layer formed on the negative electrode active material layer. Alternatively, the negative electrode may include a graphite electrode made of carbon (C) and a coating layer formed on the graphite electrode. Alternatively, the negative electrode may include the metal itself and a coating layer formed on the metal.

[0072] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treatments with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. The negative electrode current collector can usually have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the negative electrode current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in a variety of forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric.

[0073] Furthermore, the negative electrode active material layer may contain a negative electrode active material and, if necessary, may further contain conductive materials, binders, etc.

[0074] The negative electrode active material may include at least one selected from the group consisting of lithium metal, carbon materials capable of reversibly inserting / de-inserting lithium ions, metals, or alloys of these metals with lithium, metal composite oxides, materials capable of lithium doping and de-doping, and transition metal oxides.

[0075] The carbon material from which lithium ions can be reversibly inserted / defused can be any carbon-based negative electrode active material commonly used in lithium-ion secondary batteries, and typical examples include crystalline carbon, amorphous carbon, or a combination of both. Examples of crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, while examples of amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, and calcined coke.

[0076] The aforementioned metals, or alloys of these metals with lithium, can be metals 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 alloys of these metals with lithium.

[0077] Examples of the aforementioned metal composite oxides include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, and Li x Fe2O3 (0 ≤ x ≤ 1), Li x WO2 (0 ≤ x ≤ 1) and Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8) selected from the group consisting of can be used.

[0078] As the substance capable of doping and de-doping lithium, Si, SiO x (0 < x ≤ 2), Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc. can be mentioned, and at least one of these and SiO2 may be mixed and used. As the element Y, 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 are selected from the group consisting of.

[0079] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, etc.

[0080] The negative electrode active material is contained in 60% to 99% by weight, or 70% to 99% by weight, or 80% to 98% by weight based on the total weight of the negative electrode active material layer.

[0081] Furthermore, the conductive material is a component for further improving the conductivity of the negative electrode active material, and such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. For example, carbon 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 crystalline structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0082] The conductive material is present in an amount of 1% to 20% by weight, or 1% to 15% by weight, or 1% to 10% by weight, based on the total weight of the negative electrode active material layer.

[0083] Furthermore, the binder is a component that assists in the bonding between the conductive material, the negative electrode active material, and the negative electrode current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene polymer, sulfonated ethylene-propylene-diene polymer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0084] Typically, the binder is present in an amount of 1% to 20% by weight, or 1% to 15% by weight, or 1% to 10% by weight, based on the total weight of the negative electrode active material layer.

[0085] When using the metal itself without forming a negative electrode active material layer on the negative electrode, it can be manufactured by physically joining, rolling, or vapor-depositing the metal onto the metal thin film itself or onto the negative electrode current collector. The vapor deposition method can be either electro-deposition or chemical vapor deposition.

[0086] For example, the metal bonded / rolled / deposited onto the metal thin film itself or the negative electrode current collector may include one metal or an alloy of two metals selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In).

[0087] <Electrode assembly> On the other hand, an electrode assembly according to another embodiment of the invention includes the electrode of the one embodiment described above. Such an electrode assembly of another embodiment includes a first electrode, a second electrode, and a coating layer disposed between the first electrode and the second electrode, wherein the coating layer includes polymer particles, a dispersant, and a binder, the binder includes one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene (PE), polypropylene, ethylene-propylene-diene polymer, and sulfonated ethylene-propylene-diene polymer, and the binder may be included in an amount of 12% to 32% by weight relative to the total weight of the coating layer.

[0088] The electrode assemblies of the other embodiments described above do not necessarily include existing polyolefin-based separation membranes. Specifically, instead of including existing separation membranes, the electrode assemblies may include a coating layer positioned between the first electrode and the second electrode, as described with respect to the electrode of one embodiment. For example, the first and second electrodes may be formed in contact with the coating layer, and no other layer may be interposed between the first and second electrodes and the coating layer.

[0089] The first and second electrodes may each be either a positive or negative electrode. For example, if the first electrode is a positive electrode, the second electrode may be a negative electrode, and if the first electrode is a negative electrode, the second electrode may be a positive electrode. In this case, the positive and negative electrodes are as described above.

[0090] The electrode assembly of the other embodiment may include a negative electrode and a positive electrode without a coating layer, along with a coating layer formed on the negative electrode, or it may include a positive electrode and a negative electrode without a coating layer, along with a coating layer formed on the positive electrode.

[0091] Alternatively, the electrode assembly may have a configuration in which a coating layer formed on the negative electrode and a coating layer formed on the positive electrode are in contact with each other. In this case, improved electrical insulation can result in the advantage of stable charging and discharging.

[0092] <Lithium-ion secondary battery> A lithium secondary battery including the electrode assembly described above will be explained.

[0093] Such a lithium secondary battery may include an electrode assembly and a flame-retardant electrolyte. In this case, the electrode assembly is as described above.

[0094] In this context, the flame-retardant electrolyte is defined as containing a flame-retardant solvent and lithium salt having a flash point of 100°C or higher, or having no flash point. The flame-retardant solvent can encompass substantially non-flammable organic solvents with no flash point, and organic solvents with high flash points of 100°C or higher, or 100°C to 250°C, or 110°C to 200°C, and low volatility. A lithium secondary battery containing such a flame-retardant electrolyte and lithium salt can exhibit excellent high-temperature safety. Furthermore, because the flame-retardant electrolyte can be uniformly impregnated into the coating layer containing the aforementioned polymer particles, excellent electrochemical properties of the lithium secondary battery can be achieved. The flash point defining the flame-retardant solvent can be measured by a closed or open method according to the standard methods of ASTM D93 or ASTM D1310.

[0095] In specific examples, the flame-retardant solvent may be an organic solvent having a functional group that can contribute to the low volatility and flame retardancy or non-flammability of the organic solvent, for example, a functional group selected from the group consisting of sulfone functional groups, fluorine-containing functional groups such as fluorine-substituted hydrocarbon groups, phosphorus-containing functional groups such as phosphate groups or phosphonate groups, and nitrile functional groups, and one or more such organic solvents may be used in mixture form. More specifically, the flame-retardant solvent may contain one or more organic solvents selected from the group consisting of sulfone compounds, nitrile compounds, phosphoric acid compounds, and fluorine-substituted carbonate compounds.

[0096] Of these, the sulfone compound may be a cyclic sulfone compound or a linear sulfone compound, and specifically, it may contain one or more selected from the group consisting of sulfolane, ethylmethylsulfone, dibutylsulfone, ethylvinylsulfone, methylpropylsulfone, ethyl-i-propylsulfone, ethyl-i-butylsulfone, i-propyl-i-butylsulfone, i-propyl-s-butylsulfone, and butyl-i-butylsulfone.

[0097] Furthermore, the nitrile compound may include one or more selected from the group consisting of malononitrile, succinonitrile, glutalonitrile, adiponitrile, suberonitrile, and sebaconitrile.

[0098] Furthermore, the phosphate compound may include one or more selected from the group consisting of dimethylmethyl phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, diethylethyl phosphate, dimethylmethyl phosphate, dimethyl(2-methoxyethoxy)methyl phosphonate, diethyl(2-methoxyethoxy)methyl phosphonate, and triphenyl phosphate.

[0099] In addition, the fluorine-substituted carbonate compounds include bis(2,2,3,3-tetrafluoropropyl) carbonate, methyl-2,2,2-trifluoroethyl carbonate, ethyl-2,2,2-trifluoroethyl carbonate, propyl-2,2,2-trifluoroethyl carbonate, methyl-2,2,2,2',2',2'-hexafluoro-i-propyl carbonate, and ethyl-2,2,2,2',2',2'-hexafluoro-i It may contain one or more selected from the group consisting of -propyl carbonate, di-2,2,2-trifluoroethyl carbonate, 2,2,2-trifluoroethyl-N,N-dimethyl carbonate, hexafluoro-i-propyl-N,N-dimethyl carbonate, 4-(2,2,3,3-tetrafluoropropoxymethyl)-[1,3]-dioxolan-2-one, and bis(2,2,3,3-pentafluoropropyl) carbonate.

[0100] On the other hand, the lithium salt contained in the flame-retardant electrolyte is used as a medium for transferring ions within a lithium secondary battery. The lithium salt is, for example, Li as a cation. + It contains, and as an anion, F - Cl - , Br - , I - NO3 - , N(CN)2- , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - F9SO3 , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and SCN - At least any one selected from the group consisting of is included.

[0101] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10It may contain a single substance or a mixture of two or more substances selected from the group consisting of LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (Lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), LiBETI (lithium bis(perfluoroethanesulfonyl)imide, LiN(SO2CF2CF3)2), and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, LiN(SO2CF3)2), but it is preferable to include LiN(SO2CF3)2 in terms of superior safety.

[0102] In addition to these, lithium salts commonly used as electrolytes in lithium secondary batteries can be used without restriction.

[0103] The concentration of the lithium salt can be appropriately changed within a range that is normally usable, but in order to obtain the optimal effect of forming a protective film to prevent corrosion on the electrode surface, it may be included in the flame retardant electrolyte at a concentration of 0.5 M to 6 M, or 1 M to 3 M, or 1 M to 2.5 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics of the lithium secondary battery during high-temperature storage is sufficient, the viscosity of the flame retardant electrolyte is appropriate, and the impregnation of the flame retardant electrolyte can be improved.

[0104] The lithium secondary battery described above can be manufactured by forming an electrode assembly by placing a coating layer between the positive electrode and the negative electrode, placing the electrode assembly in a cylindrical or rectangular battery case, and then injecting the flame-retardant electrolyte described above. Alternatively, the electrode assemblies can be stacked, impregnated with the flame-retardant electrolyte, and the resulting product placed in a battery case and sealed.

[0105] The aforementioned battery case can be one of those commonly used in this field, and there are no restrictions on its external shape depending on the battery's application. For example, it may be cylindrical, rectangular, pouch-type, or coin-type, but is not limited thereto.

[0106] The lithium secondary battery can be used not only as a battery cell for powering small devices, but also as a unit battery in medium- and large-sized battery modules containing a large number of battery cells. Preferred examples of the medium- and large-sized devices include electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems (ESS).

[0107] The present invention will be described in more detail below through specific examples. However, the following examples are merely illustrative for understanding the present invention and do not limit its scope. It will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the described concept and technical idea, and such variations and modifications naturally fall within the scope of the attached claims.

[0108] Examples and Comparative Examples First, in the following examples, the zeta potential of the polymer particles was measured by electrophoretic light scattering using a dynamic light scattering instrument (product name: ELS-Z) while the polymer particles were dispersed in an aqueous solvent at a temperature of 25°C in an amount of 0.1% by weight or less.

[0109] Furthermore, the flash point of the (flame-retardant) organic solvent contained in the (flame-retardant) electrolyte was measured using a sealed method according to the ASTM D93 standard method. Specifically, the organic solvent sample was filled into a sample container, the lid of the container was covered and sealed, and then the sample container was heated at a constant rate according to the standard method. The sample container was opened periodically during heating to check for flame generation, and the temperature at the point of flame generation was measured as the flash point.

[0110] Example 1 (1) Manufacturing of compositions for forming electrode coating layers It has a zeta potential of -50mV and an average particle size D 50 A composition for forming an electrode coating layer was prepared by dispersing 1 μm polymethyl methacrylate (PMMA) polymer particles, hydrogenated nitrile rubber (H-NBR) dispersant, and polyvinylidene fluoride (PVDF) binder in N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 7:1:2. At this time, the solid content of the electrode coating layer forming composition was 21% by weight, and the viscosity at 25°C was 6000 cP.

[0111] (2) Manufacturing of the negative electrode Next, a 20 μm thick copper (Cu) metal thin film was prepared as a negative electrode current collector, and a 55 μm thick negative electrode active material layer containing artificial graphite was formed on one surface of the copper metal thin film as the negative electrode active material. Subsequently, the electrode coating layer forming composition was coated onto the negative electrode active material layer and dried to form a 30 μm thick coating layer on the negative electrode active material layer, thereby manufacturing the negative electrode.

[0112] (3) Manufacturing of lithium secondary batteries Li(Ni) is used as the positive electrode active material. 0.8 Mn 0.1 Co 0.1 A 60 μm positive electrode containing O2 was prepared.

[0113] An electrode assembly was manufactured by placing the coating layer of the negative electrode, manufactured by the method described above, in contact with the positive electrode.

[0114] A flame-retardant electrolyte was prepared by dissolving LiN(SO2CF3)2(LiTFSI) in a flame-retardant solvent sulfolane (flash point: approximately 165°C) to a concentration of 1.5M. After placing the electrode assembly in a battery case, the flame-retardant electrolyte was injected to produce a lithium secondary battery.

[0115] Example 2 It has a zeta potential of -50mV and an average particle size D50 An electrode coating layer forming composition was prepared in the same manner as in Example 1, except that the weight ratio of 1 μm polymethyl methacrylate (PMMA) polymer particles, hydrogenated nitrile rubber (H-NBR) dispersant, and polyvinylidene fluoride (PVDF) binder was 6:1:3 when dispersed in an N-methyl-2-pyrrolidone (NMP) solvent. At this time, the solid content of the electrode coating layer forming composition was 21% by weight, and the viscosity at 25°C was 6200 cP.

[0116] The negative electrode and lithium secondary battery were manufactured in the same manner as in Example 1, except that the electrode coating layer forming composition was used.

[0117] Comparative Example 1 An electrode coating layer forming composition was prepared in the same manner as in Example 1, except that a hydrogenated nitrile rubber (H-NBR) dispersant was not used, and the polymethyl methacrylate (PMMA) polymer particles and polyvinylidene fluoride (PVDF) dispersant were mixed in a weight ratio of 9:1. At this time, the solid content of the electrode coating layer forming composition was 21% by weight, and the viscosity at 25°C was 6500 cP.

[0118] The negative electrode and lithium secondary battery were manufactured in the same manner as in Example 1, except that the electrode coating layer forming composition was used.

[0119] Comparative Example 2 An electrode coating layer forming composition was prepared in the same manner as in Example 1, except that polytetrafluoroethylene (PTFE) was used as the binder. At this time, the solid content of the electrode coating layer forming composition was 21% by weight, and the viscosity at 25°C was 6600 cP.

[0120] The negative electrode and lithium secondary battery were manufactured in the same manner as in Example 1, except that the electrode coating layer forming composition was used.

[0121] Comparative Example 3 (1) Manufacturing of the negative electrode Unlike Example 1, the negative electrode was manufactured in the same manner as in Example 1, except that a coating layer was not formed on the negative electrode active material layer.

[0122] (2) Manufacturing of lithium secondary batteries Li(Ni) is used as the positive electrode active material. 0.8 Mn 0.1 Co 0.1 A 60 μm positive electrode containing O2 was prepared.

[0123] A lithium secondary battery was manufactured in the same manner as in Example 1, except that a separation membrane made of polyolefin material was interposed between the manufactured negative electrode and positive electrode to manufacture the electrode assembly.

[0124] Experimental Example 1 - Evaluation of Coatability of Coating Layers The surfaces of the electrode coating layers produced in Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Figures 1 to 4.

[0125] Specifically, Figure 1 is a photograph of the surface of the electrode coating layer manufactured in Example 1, Figure 2 is a photograph of the surface of the electrode coating layer manufactured in Example 2, Figure 3 is a photograph of the surface of the electrode coating layer manufactured in Comparative Example 1, and Figure 4 is a photograph of the surface of the electrode coating layer manufactured in Comparative Example 2.

[0126] Furthermore, the presence or absence of cracks was observed on the surface of the coating layer with the naked eye, as shown in Table 1 below.

[0127] O: Cracks exist on the surface of the coating layer. X: No cracks are present on the surface of the coating layer.

[0128] [Table 1]

[0129] As shown in Table 1 and Figures 1 to 4 above, the coating layer in the electrode of Comparative Example 1, which does not use a dispersant (H-NBR), differs from the coating layers in the electrodes of Example 1 and Example 2 in that cracks have formed on the surface.

[0130] Furthermore, it can be confirmed that the coating layer in the electrode of Comparative Example 2, which uses polytetrafluoroethylene (PTFE) instead of polyvinylidene fluoride (PVDF) as a binder, differs from the coating layers in the electrodes of Example 1 and Example 2 in that cracks have formed on the surface.

[0131] Experimental Example 2 - Evaluation of Life Characteristics of Lithium Secondary Batteries The lithium secondary batteries manufactured in Example 1 and Example 2 were charged and discharged at 0.1C in CC / CV charging mode with an upper voltage limit of 4.2V and CC discharge mode with a lower voltage limit of 3V. After that, 500 cycles of 4.2V to 3V charging and discharging were performed at 0.2C / 0.2C, and the capacity retention rate was measured at 100-cycle intervals. The measurement results are shown in Table 2 and Figure 5 below, respectively. Figure 5 is a graph of the capacity retention rate of lithium secondary batteries containing the electrodes manufactured in Example 1 and Example 2, respectively.

[0132] [Table 2]

[0133] As shown in Table 2 and Figure 5, both the lithium secondary batteries of Example 1 and Example 2 were confirmed to exhibit excellent capacity retention and life characteristics for 200 cycles or less.

[0134] Taking it a step further, in Example 1, where the binder content is 20% by weight relative to the total weight of the coating layer, it can be confirmed that the battery capacity retention rate after 200 cycles is even better compared to Example 2, where the binder content is 30% by weight relative to the total weight of the coating layer.

[0135] Experimental Example 3 - High-Temperature Safety Evaluation of Lithium-ion Secondary Batteries The results of the hot box test performed on the lithium secondary batteries manufactured in Example 1 and Comparative Example 3 are shown in Table 3 below. Specifically, the hot box test was conducted by increasing the temperature from 25°C at a rate of 5°C / min, holding the temperature at 100°C, 120°C, 140°C, 150°C, 160°C, 170°C, and 180°C for 30 minutes each, and then increasing the temperature to 200°C at a rate of 2°C / min. In this case, the ignition start temperature is shown in Table 3 below.

[0136] On the other hand, in the case of lithium secondary batteries manufactured from the negative electrodes of Comparative Example 1 and Comparative Example 2, respectively, charge and discharge performance did not emerge from the initial stages of the cell, and high-temperature safety evaluation was omitted.

[0137] [Table 3]

[0138] As shown in Table 3 above, in the case of a lithium secondary battery using the negative electrode of Example 1 instead of using an existing polyolefin material separation membrane, it can be confirmed that high-temperature safety is improved compared to the lithium secondary battery using the negative electrode and polyolefin material separation membrane of Comparative Example 3.

Claims

1. An electrode comprising an electrode active material layer and a coating layer formed on the electrode active material layer, The coating layer comprises polymer particles with an absolute value of 25 mV or more of zeta potential; a dispersant; and a binder. The binder comprises one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene (PE), polypropylene, ethylene-propylene-diene polymer, and sulfonated ethylene-propylene-diene polymer. The binder is included in an amount of 12% to 32% by weight relative to the total weight of the coating layer. The dispersant comprises a hydrogenated nitrile polymer, and the electrode is provided with the dispersant.

2. The electrode according to claim 1, wherein the polymer particles are contained in an amount of 55% to 85% by weight relative to the total weight of the coating layer.

3. The electrode according to claim 1 or 2, wherein the dispersant is included in an amount of 3% to 20% by weight relative to the total weight of the coating layer.

4. The average particle size D of the polymer particles ５０ The electrode according to claim 1, wherein the thickness is 50 nm to 3 μm.

5. The electrode according to claim 1, wherein the polymer particles include one or more selected from the group consisting of polyethylene oxide (PEO), polyphenylene sulfide (PPS), polymethyl (meth)acrylate, polystyrene, polyvinyl chloride, polycarbonate, polysulfone, polyethersulfone, polyetherimide, polyphenylsulfone, polyamideimide, polyimide, polybenzimidazole, polyetherketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate.

6. The electrode according to claim 1, wherein the coating layer has a thickness of 5 μm to 50 μm and includes a plurality of pores having a diameter of 10 nm or more.

7. First electrode and, The second electrode and An electrode assembly comprising a coating layer disposed between the first electrode and the second electrode, The coating layer comprises polymer particles with an absolute value of 25 mV or more of zeta potential; a dispersant; and a binder. The binder comprises one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene (PE), polypropylene, ethylene-propylene-diene polymer, and sulfonated ethylene-propylene-diene polymer. The binder is included in an amount of 12% to 32% by weight relative to the total weight of the coating layer. The dispersant comprises an electrode assembly containing a hydrogenated nitrile polymer.

8. The electrode assembly according to claim 7, wherein the polymer particles are included in an amount of 55% to 85% by weight relative to the total weight of the coating layer.

9. The electrode assembly according to claim 7, wherein the dispersant is included in an amount of 3% to 20% by weight relative to the total weight of the coating layer.

10. The average particle size D of the polymer particles ５０ The electrode assembly according to claim 7, wherein the thickness is 50 nm to 3 μm.

11. The electrode assembly according to claim 7, wherein the polymer particles include one or more selected from the group consisting of polyethylene oxide (PEO), polyphenylene sulfide (PPS), polymethyl (meth)acrylate, polystyrene, polyvinyl chloride, polycarbonate, polysulfone, polyethersulfone, polyetherimide, polyphenylsulfone, polyamideimide, polyimide, polybenzimidazole, polyetherketone, polyphthalamide, polybutylene terephthalate, and polyethylene terephthalate.

12. The electrode assembly according to any one of claims 7 to 11, wherein the coating layer has a thickness of 5 μm to 50 μm and contains a plurality of pores having a diameter of 10 nm or more, and the electrode assembly does not contain a separation membrane.

13. The electrode assembly according to claim 7, wherein the first electrode and the second electrode are in contact with the coating layer.

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