Positive electrode and lithium secondary battery containing the same

Abstract

This invention provides a positive electrode active material and binder that can achieve high density, high capacity, long lifespan, and high energy density, as well as a positive electrode and lithium secondary battery using these materials. [Solution] The positive electrode comprises a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, which contains a positive electrode active material, a copolymer binder, and an amine, wherein the copolymer binder contains a first structural unit containing a carboxyl group and a second nonionic structural unit, and the carboxyl group and the amine exist in the form of a salt. The positive electrode according to one embodiment maximizes capacity while minimizing production cost, ensures long life characteristics, and improves high-voltage characteristics and high-temperature storage characteristics. A lithium secondary battery to which this positive electrode is applied can exhibit high initial charge / discharge capacity and efficiency even under high-voltage driving conditions, and can achieve long life characteristics.

Description

Technical Field

[0001] It relates to a positive electrode and a lithium secondary battery including the same.

Background Art

[0002] Lithium secondary batteries having a high energy density while being easy to carry are mainly used as driving power sources for mobile information terminals such as mobile phones, notebook computers, and smartphones. Recently, research has been actively conducted to use lithium secondary batteries with a high energy density as driving power sources or power storage power sources for hybrid vehicles and electric vehicles.

[0003] In order to realize a lithium secondary battery suitable for such applications, various binders have been studied. Recently, in a situation where the demand for large-sized, high-capacity, or high-energy-density lithium secondary batteries has increased rapidly, there is a need to develop a binder that can increase the capacity while ensuring stability and enable driving at a high voltage.

Summary of the Invention

Problems to be Solved by the Invention

[0004] To provide a positive electrode active material and a binder capable of realizing high density, high capacity, long life characteristics, and a high energy density, a positive electrode and a lithium secondary battery to which the same are applied.

Means for Solving the Problems

[0005] In one embodiment, it includes a current collector and a positive electrode active material layer located on the current collector and including a positive electrode active material, a copolymer binder, and an amine. The copolymer binder includes a first structural unit containing a carboxyl group and a non-ionic second structural unit, and the carboxyl group and the amine provide a positive electrode present in the form of a salt.

[0006] In another embodiment, a method for producing a positive electrode is provided, comprising the steps of (a) producing a positive electrode composition comprising a positive electrode active material, a copolymer binder, a basic substance containing an amine group, and a volatile acidic substance, and (b) coating the positive electrode composition onto a current collector, wherein the copolymer binder comprises a first structural unit containing a carboxyl group and a second nonionic structural unit.

[0007] In other embodiments, a positive electrode composition is provided comprising a positive electrode active material, a copolymer binder, an amine, and a volatile acidic substance, wherein the copolymer binder comprises a first structural unit containing a carboxyl group and a second nonionic structural unit.

[0008] In another embodiment, a lithium secondary battery is provided that includes the positive electrode, the negative electrode, and the electrolyte. [Effects of the Invention]

[0009] One embodiment of the positive electrode maximizes capacity while minimizing production costs, ensures long lifespan, and improves high-voltage and high-temperature storage characteristics. A lithium secondary battery using this positive electrode can exhibit high initial charge / discharge capacity and efficiency even under high-voltage driving conditions, achieving long lifespan characteristics. [Brief explanation of the drawing]

[0010] [Figure 1] This figure schematically shows a lithium secondary battery according to one embodiment. [Figure 2] This figure schematically shows a lithium secondary battery according to one embodiment. [Figure 3] This figure schematically shows a lithium secondary battery according to one embodiment. [Figure 4] This figure schematically shows a lithium secondary battery according to one embodiment. [Modes for carrying out the invention]

[0011] The following describes specific embodiments in detail so that they can be easily implemented by a person with ordinary skill in the art. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0012] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0013] Here, "these combinations" refers to mixtures of components, laminates, composites, copolymers, alloys, blends, reaction products, etc.

[0014] Here, terms such as “include,” “equip,” or “possess” are intended to specify the presence of an implemented feature, figure, stage, component, or combination thereof, and should be understood not to preemptively exclude the possibility of the presence or addition of one or more other features, figures, stages, components, or combinations thereof.

[0015] In the drawings, thicknesses are shown enlarged to clearly represent various layers and regions, and similar parts are denoted by the same reference numerals throughout the specification. When a layer, film, region, plate, or other part is described as being "on top" of another part, this includes not only when it is "directly above" another part, but also when there is another part in between. Conversely, when a part is described as being "directly above" another part, it means that there is no other part in between.

[0016] Furthermore, in this context, "layer" includes not only the shapes formed on the entire surface when observed in a plan view, but also the shapes formed on some of the surfaces.

[0017] The average particle size can be measured by methods widely known to those skilled in the art, for example, by a particle size analyzer, or by transmission electron microscope images or scanning electron microscope images. Alternatively, it can be measured using dynamic light scattering, and the average particle size value can be calculated after performing data analysis to count the number of particles for each particle size range. Unless otherwise defined, the average particle size is the diameter (D) of the particle whose cumulative volume in the particle size distribution is 50% by volume. 50 ) can mean. Also, unless otherwise defined, the average particle size is the diameter (D) of the particle whose cumulative volume in the particle size distribution is 50% by volume, obtained by measuring the size (diameter or length of the major axis) of more than 20 random particles in a scanning electron microscope image. 50 This is taken as the average particle size.

[0018] Here, "or" is not interpreted in an exclusive sense; for example, "A or B" is interpreted as including A, B, A+B, etc.

[0019] The term "metal" is interpreted as a concept that includes general metals, transition metals, and metalloids.

[0020] "Nonionic" is interpreted as a compound not containing any ionic functional group, or any functional group that can be converted to an ionic functional group by protonation or deprotonation.

[0021] positive electrode In one embodiment, the positive electrode comprises a current collector and a positive electrode active material layer located on the current collector, comprising a positive electrode active material, a copolymer binder, and an amine, wherein the copolymer binder comprises a first structural unit containing a carboxyl group and a second nonionic structural unit, and the carboxyl group and the amine exist in the form of a salt. The positive electrode active material layer may optionally further contain a conductive material.

[0022] Generally, an organic solvent is included in the positive electrode active material layer, but this causes a problem that it is not easy to apply a binder having a property of dissolving in an aqueous solvent to the positive electrode active material layer. Therefore, by using a copolymer binder containing a nonionic structural unit in the positive electrode active material layer, the solubility of the copolymer binder in an organic solvent is improved, and at the same time, the carboxyl groups contained in the copolymer binder form a crosslinked structure with an amine, so that the adhesive force with the current collector can be improved and the interfacial resistance can be reduced even when a small amount of binder is used.

[0023] Cathode active material layer The positive electrode active material layer according to one embodiment is located on a current collector and contains a positive electrode active material, a copolymer binder, and an amine.

[0024] positive electrode active material As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used. Specifically, one or more of composite oxides of metals selected from cobalt, manganese, nickel, and combinations thereof and lithium can be used.

[0025] The composite oxide may be a lithium transition metal composite oxide, and specific examples include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free nickel-manganese-based oxides, or combinations thereof.

[0026] As an example, a compound represented by any one of the following chemical formulas can be used. Li a A 1-b X b O 2-c D c (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li a Mn 2-b X b O 4-c D c(0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05);Li a Ni 1-b-c Co b X c O 2-α D α (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5, 0<α<2);Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5, 0<α<2);Li a Ni b Co c L1 d G e O2(0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0≦e≦0.1);Li a NiG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a CoG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn 1-b G b O2(0.90≦a≦1.8, 0.001b≦0.1);Li a Mn2G b O4(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn 1-g G g PO4(0.90≦a≦1.8, 0≦g≦0.5);Li (3-f) Fe2(PO4)3(0≦f≦2);Li a FePO4 (0.90 ≤ a ≤ 1.8).

[0027] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L1 is Mn, Al, or a combination thereof.

[0028] The positive electrode active material may include, for example, a lithium nickel oxide represented by the following chemical formula 11, a lithium cobalt oxide represented by the following chemical formula 12, a lithium iron phosphate compound represented by the following chemical formula 13, a cobalt-free lithium nickel-manganese oxide represented by the following chemical formula 14, or a combination thereof. [Chemical formula 11] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In the aforementioned chemical formula 11, 0.9≦a1≦1.8, 0.3≦x1≦1, 0≦y1≦0.7, 0≦z1≦0.7, 0.9≦x1+y1+z1≦1.1, and 0≦b1≦0.1, M 1 and M 2 Each of the elements is independently selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0029] In the chemical formula 11, 0.6 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.4, and 0 ≤ z1 ≤ 0.4, or 0.8 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, and 0 ≤ z1 ≤ 0.2. [Chemical formula 12] Li a2 Co x2 M 3 y2 O 2-b2 X b2 In the aforementioned chemical formula 12, 0.9≦a2≦1.8, 0.7≦x2≦1, 0≦y2≦0.3, 0.9≦x2+y2≦1.1, and 0≦b2≦0.1, M 3X is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S. [Chemical formula 13] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3 In the aforementioned chemical formula 13, 0.9 ≤ a³ ≤ 1.8, 0.6 ≤ x³ ≤ 1, 0 ≤ y³ ≤ 0.4, and 0 ≤ b³ ≤ 0.1, M 4 X is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S. [Chemical formula 14] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4 In the above chemical formula 14, 0.9 ≤ a4 ≤ 1.8, 0.8 ≤ x4 < 1, 0 <y4≦0.2、0≦z4≦0.2、0.9≦x4+y4+z4≦1.1、および0≦b4≦0.1であり、M 5 X is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0030] As an example, the positive electrode active material may be a high-nickel positive electrode active material in which the nickel content relative to 100 mol% of the metal excluding lithium is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less. High-nickel positive electrode active materials can achieve high capacity and are applicable to high-capacity, high-density lithium secondary batteries.

[0031] In one embodiment, the positive electrode active material may include a lithium iron phosphate compound represented by chemical formula 13, such as lithium iron phosphate, lithium iron manganese phosphate, or a combination thereof.

[0032] The lithium iron phosphate compound is in particulate form, and the average particle size (D 50 The particle size may be 0.01 μm to 2 μm, for example, 0.1 μm to 1 μm, or 0.5 μm to 1 μm.

[0033] In one example, the lithium iron phosphate compound may be in the form of first particles, second particles, or a mixture of first and second particles. The first particle may be an assembly of multiple nano-sized primary particles or a secondary particle. The first particle may be spherical or ellipsoidal in shape due to the close aggregation of primary particles. The average particle size of the first particle may be, for example, 2 μm to 15 μm, 3 μm to 12 μm, or 3 μm to 10 μm. The average particle size of the first particle may be larger than the average particle size of the second particle, which will be described later. The average particle size of the primary particles of the first particle may be, for example, 10 nm to 400 nm, 20 nm to 300 nm, or 50 nm to 200 nm. As an example, the average particle size of the first particle may be determined by arbitrarily selecting more than 30 first particles from electron microscope images of the lithium iron phosphate compound, measuring their particle size, and determining the diameter (D) of the particle with a cumulative volume of 50% in its particle size distribution. 50) may be taken as the average particle size. The average particle size of the primary particles of the first particle is determined by measuring the size of more than 30 primary particles from electron microscope images of the surface or cross-section of the first particle, and taking the diameter (D) of the particle whose cumulative volume is 50% in its particle size distribution. 50 ) may be used as the average particle size.

[0034] The porosity of the first particle may be approximately 20% to approximately 50%. For example, the porosity may be determined by measuring the area ratio of the portion occupied by voids within the particle using an image analysis program such as Image J in a scanning electron microscope image of the cross-section of the first particle.

[0035] The second particle may have a single particle form. The average particle size of the second particle may be, for example, 10 nm to 900 nm, 50 nm to 500 nm, or 100 nm to 300 nm. The average particle size of the second particle may be smaller than the average particle size of the first particle, or it may be the same as or larger than the average particle size of the primary particles of the first particle. As an example, the average particle size of the second particle may be determined by arbitrarily selecting more than 30 second particles from electron microscope images of lithium iron phosphate compounds, measuring their particle size, and determining the diameter (D) of the particle with a cumulative volume of 50% in its particle size distribution. 50 ) may be used as the average particle size.

[0036] The lithium iron phosphate compound may further include a carbon coating layer located on the surface of the particles. The carbon coating layer can improve the electrical conductivity of the lithium transition metal phosphorus oxide and reduce the resistance of the positive electrode. The carbon coating layer may be formed using at least one raw material selected from the group consisting of, for example, glucose, sucrose, lactose, starch, oligosaccharides, polyoligosaccharides, fructose, cellulose, polymers of furfuryl alcohol, block copolymers of ethylene and ethylene oxide, vinyl resins, cellulosic resins, phenolic resins, pitch resins, and tar resins. Specifically, the carbon coating layer may be formed by a firing process after placing the raw material on the surface of the lithium iron phosphate compound particles.

[0037] Copolymer binder A copolymer binder according to one embodiment comprises a first structural unit containing a carboxyl group and a second nonionic structural unit, wherein the carboxyl group exists in the form of a salt.

[0038] The copolymer binder incorporates structural units containing carboxyl groups in salt form, which form crosslinks with amine groups in salt form (described later). This allows even a small amount of binder to effectively adhere positive electrode active material particles to each other, effectively adhering the positive electrode active material to the current collector, thereby reducing the interfacial resistance of the positive electrode. Additionally, by incorporating nonionic structural units, the copolymer binder can be adapted to organic solvents, even if it is only soluble in aqueous solvents. Therefore, a copolymer binder and a positive electrode active material layer containing amines with such properties can improve adhesion even with a small amount of binder, reduce interfacial resistance, and improve battery performance and lifespan.

[0039] The following provides a detailed explanation of each structural unit.

[0040] The first structural unit can be derived from a monomer containing a carboxyl group, in which case the monomer containing a carboxyl group may include monocarboxylic acids and their derivatives, dicarboxylic acids and their derivatives, or combinations thereof. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β-diaminoacrylic acid. Examples of dicarboxylic acids include amidic acid, maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include maleic acids such as methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, and fluoromaleic acid; and maleate salts such as methylallyl, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate. Furthermore, acid anhydrides that generate carboxyl groups by hydrolysis can also be used. Examples of dicarboxylic acid acid anhydrides include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. In addition, monoesters and diesters of α,β-ethylenically unsaturated polycarboxylic acids such as monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, and dibutyl itaconate can also be used. The most preferred examples of monomers containing carboxyl groups include acrylic acid, amide acid, or combinations thereof.

[0041] The copolymer binder can contain 0.1 mol% to 20 mol% of the total copolymer binder, for example, 0.5 mol% to 15 mol%, or 1 mol% to 10 mol%. When the first structural units are contained within this range, the copolymer binder can prevent self-aggregation while maximizing crosslinking with the amine described later, thereby improving adhesion.

[0042] The nonionic second structural unit can be derived from a nonionic monomer, which may include acrylic monomers, imide monomers, or combinations thereof. In this case, the acrylic monomers may be alkyl acrylates such as acrylonitrile, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, etc.; methyl Alkyl methacrylate esters such as methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, etc.; or combinations thereof.Imide monomers include, for example, succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, N-(meth)acryloyl-8-oxyoctamethylenesuccinimide, and N-acryloylmorpholine; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, and N-cyclohexyl Examples include itaconimide monomers such as ruitaconimide and N-lauryluitaconimide, or combinations thereof. Polyimide monomers may include hexamethylenediamine, 4,4'-diphenyldiamine, dihydroxybenzydamine 1,2-bis(2-aminoethoxy)ethane, and polymers in which both ends are substituted with primary amines, as well as diisocyanate monomers such as hexamethylenediisocyanate, diphenylmethanediisocyanate, and diisocyanate-cyclohexane, but are not necessarily limited to these, and any nonionic monomer that can be used in the art is acceptable.

[0043] The nonionic second structural units may be present in an amount of 80 mol% or more relative to 100 mol% of the total copolymer binder, for example, in the range of 80 mol% to 99.9 mol%, 85 mol% to 99.5 mol%, or 90 mol% to 99 mol. When the nonionic second structural units are present in the above range, it is possible to improve adhesion by maximizing crosslinking with the amine described later, while preventing the copolymer binder itself from agglomerating.

[0044] The copolymer binder can be contained in an amount of 10% to 30% by weight relative to 100% by weight of the entire positive electrode active material layer, for example, 12% to 28% by weight, or 15% to 25% by weight. When the copolymer binder content falls within the above range, the flexibility of the electrode plates can be improved while increasing the adhesive strength of the electrode plates.

[0045] The weight-average molecular weight of the copolymer binder may be 100,000 g / mol or more, and may be, for example, 300,000 to 1,500,000 g / mol, 600,000 to 1,300,000 g / mol, or 900,000 to 1,100,000 g / mol. The weight-average molecular weight is a polystyrene equivalent value obtained by gel permeation chromatography. The adhesion strength of the electrode plates can be further improved within the weight-average molecular weight range of the second fluorine-based binder.

[0046] The positive electrode active material layer may further contain other types of binders in addition to the copolymer binder described above. Typical examples of additional binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylic styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0047] Amine The amine exists in salt form and forms crosslinks with the salt-form carboxyl groups contained in the copolymer binder. This allows even a small amount of binder to effectively adhere the positive electrode active material particles to each other, effectively adhering the positive electrode active material to the positive electrode current collector, thereby reducing the interfacial resistance of the positive electrode.

[0048] The aforementioned amines include primary amines such as methylamine, ethylamine, monoisopropylamine, n-butylamine, sec-butylamine, isobutylamine, t-butylamine, pentylamine, monoethanolamine, monopropanolamine, monoisopropanolamine, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1-propanol, 4-amino-1-butanol, 2-(2-aminoethoxy)ethanol, methyl(methoxymethyl)aminoethane, methyl(methoxymethyl)aminoethanol, methyl(butoxymethyl)aminoethanol; secondary amines such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, diisobutylamine, methylethylamine, methylpropylamine, methylisopropylamine, methylbutylamine, methylisobutylamine, diethanolamine, 2-(ethylamino)ethanol, 2-(methylamino)ethanol, dibutanolamine; trimethylamine, triethylamine, Tertiary amines such as tripropylamine, tributylamine, tripentylamine, dimethylethylamine, methyldiethylamine, methyldipropylamine, triethanolamine, N-methyldiethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, (butoxymethyl)diethylamine, (methoxymethyl)diethylamine, (methoxymethyl)diethanolamine and (hydroxyethyloxymethyl)diethylamine; alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, 2-aminoethanol, 2-(ethylamino)ethanol, 2-(methylamino)ethanol, N-methyldiethanolamine, N,N-dimethylethanolamine, N,N-diethylaminoethanol, 2-(2-aminoethylamino)-1-ethanol, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1-propanol, 4-amino-1-butanol, and dibutanolamine;Alkoxyamines such as (butoxymethyl)diethylamine, (methoxymethyl)diethylamine, (methoxymethyl)dimethylamine, (butoxymethyl)dimethylamine, (isobutoxymethyl)dimethylamine, (methoxymethyl)diethanolamine, (hydroxyethyloxymethyl)diethylamine, methyl(methoxymethyl)aminoethane, methyl(methoxymethyl)aminoethanol, methyl(butoxymethyl)aminoethanol, 2-(2-aminoethoxy)ethanol; 1-(2-hydroxyethyl)piperazine, 1-(2-aminoethyl)piperazine, 1-( It may include cyclic amines forming rings, such as 2-hydroxyethyl)methylpiperazine, N-(3-aminopropyl)morpholine, 2-methylpiperazine, 1-methylpiperazine, 1-amino-4-methylpiperazine, 1-benzylpiperazine, 1-phenylpiperazine, N-methylmorpholine, 4-ethylmorpholine, N-formylmorpholine, N-(2-hydroxyethyl)morpholine, N-(3-hydroxypropyl)morpholine, or combinations thereof, preferably alkanolamines, and most preferably 2-aminoethanol.

[0049] The amine can be contained in an amount of 0.1% to 1.0% by weight relative to 100% by weight of the entire positive electrode active material layer, for example, 0.1% to 0.5% by weight, or 0.1% to 0.2% by weight. When the amine content falls within this range, crosslinking with the copolymer binder described above can be maximized to improve adhesion.

[0050] conductive material The positive electrode active material layer may further contain a conductive material. The conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes in the battery that is constructed can be used. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, carbon nanotubes, and nanocarbons; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or combinations thereof.

[0051] The conductive material may be present in an amount of 1% to 4% by weight relative to 100% by weight of the entire positive electrode active material layer, for example, 1.5% to 3.5% by weight, or 1.5% to 3% by weight. When the content of the conductive material falls within the above range, the battery capacity is increased while reducing the resistance of the positive electrode, enabling operation at high voltages.

[0052] The positive electrode active material layer may further contain an organic solvent, preferably N-methylpyrrolidone. Even if the positive electrode active material layer contains an organic solvent, the solubility in the organic solvent can be improved by using a copolymer binder containing nonionic structural units. At the same time, the carboxyl groups contained in the copolymer binder form a crosslinking structure with amine groups, thereby improving adhesion to the positive electrode current collector and reducing interfacial resistance even when using a small amount of binder.

[0053] Al can be used as the positive electrode current collector, but it is not limited to this.

[0054] Method for manufacturing a positive electrode In one embodiment, the present invention provides a method for producing a positive electrode, comprising the steps of (a) producing a positive electrode composition comprising a positive electrode active material, a copolymer binder, a basic substance containing an amine group, and a volatile acidic substance, and (b) applying the positive electrode composition onto a current collector, wherein the copolymer binder comprises a first structural unit containing a carboxyl group and a second nonionic structural unit.

[0055] The positive electrode composition will be described in detail below.

[0056] Cathode composition In one embodiment, a positive electrode composition is provided comprising a positive electrode active material, a copolymer binder, an amine, and a volatile acidic substance, wherein the copolymer binder comprises a first structural unit containing a carboxyl group and a second nonionic structural unit.

[0057] By using a copolymer binder containing nonionic structural units in the positive electrode composition, solubility in organic solvents can be improved. At the same time, the carboxyl groups contained in the copolymer binder form a cross-linking structure with amines, thereby improving adhesion to the positive electrode current collector and reducing interfacial resistance, even when using a small amount of binder.

[0058] The positive electrode active material, copolymer binder, and amine are the same as those described for the positive electrode, so a detailed explanation will be omitted.

[0059] The positive electrode composition may further contain a volatile acidic substance. By including a volatile acidic substance in the positive electrode composition, during the process of applying the positive electrode composition to the current collector and drying, the volatile acidic substance volatilizes, and the carboxyl groups are separated without dissolving, forming salts with amines and creating crosslinks. By forming crosslinks in this way, adhesion can be improved even with a small amount of binder, and interfacial resistance can be reduced.

[0060] The volatile acidic substances may include 2-acetyloxybenzoic acid, acetic acid, ascorbic acid, aspartic acid, benzoic acid, camphor sulfonic acid, cinnamic acid, citric acid, edetic acid, ethanesulfonic acid, fumaric acid, gluceptonic acid, gluconic acid, glutamic acid, glycolic acid, hydroxymaleic acid, hydroxynaphthalenecarboxylic acid, isethionic acid, lactic acid, lactobionic acid, lauric acid, maleic acid, malic acid, methanesulfonic acid, mucinic acid, oleic acid, oxalic acid, palmitic acid, pamoic acid, pantothenic acid, phenylacetic acid, phenylsulfonic acid, propionic acid, pyruvic acid, salicylic acid, stearic acid, tartaric acid, toluenesulfonic acid, trifluoroacetic acid, and valeric acid, or combinations thereof. Preferably, oxalic acid, maleic acid, acetic acid, or combinations thereof may be included.

[0061] The copolymer binder can be contained in an amount of 10% to 30% by weight relative to 100% by weight of the entire positive electrode composition, for example, 12% to 28% by weight, or 15% to 25% by weight. When the copolymer binder content falls within the above range, the flexibility of the electrode plates can be improved while increasing the adhesive strength of the electrode plates.

[0062] The amine can be contained in an amount of 0.1% to 1.0% by weight relative to 100% by weight of the entire positive electrode composition, for example, 0.1% to 0.5% by weight, or 0.1% to 0.2% by weight. When the amine content falls within this range, crosslinking with the copolymer binder described above can be maximized to improve adhesion.

[0063] The volatile acidic substance can be contained in an amount of 0.1% to 1.0% by weight per 100% by weight of the entire positive electrode composition, for example, 0.1% to 0.7% by weight, or 0.1% to 0.5% by weight. When the content of the volatile acidic substance falls within the above range, the acidity of the positive electrode composition can be adjusted so that the carboxyl groups form crosslinks with the amine, thereby improving adhesion.

[0064] The positive electrode composition may further contain an organic solvent, preferably N-methylpyrrolidone. Even if the positive electrode composition contains an organic solvent, the solubility in the organic solvent can be improved by using a copolymer binder containing nonionic structural units. At the same time, the carboxyl groups contained in the copolymer binder form a crosslinking structure with amine groups, thereby improving adhesion to the positive electrode current collector and reducing interfacial resistance even when using a small amount of binder.

[0065] Lithium-ion rechargeable battery In one embodiment, a lithium secondary battery is provided that includes the positive electrode, negative electrode, and electrolyte described above. As an example, the lithium secondary battery may include a positive electrode, a negative electrode, a separation membrane located between the positive electrode and the negative electrode, and an electrolyte.

[0066] Lithium-ion batteries can be classified into cylindrical, prismatic, pouch-type, coin-type, and other types depending on their form. Figures 1 to 4 are schematic diagrams showing a lithium-ion battery according to one embodiment, with Figure 1 being cylindrical, Figure 2 being prismatic, and Figures 3 and 4 being pouch-type batteries. Referring to Figures 1 to 4, the lithium-ion battery 100 can include an electrode assembly 40 with a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, negative electrode 20, and separator 30 may be immersed in an electrolyte (not shown). The lithium-ion battery 100 can include a sealing member 60 that seals the case 50, as shown in Figure 1. Also, in Figure 2, the lithium-ion battery 100 can include a positive electrode lead tab 11 and a positive electrode terminal 12, and a negative electrode lead tab 21 and a negative electrode terminal 22. As shown in Figures 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, namely a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical pathways for inducing the current formed in the electrode assembly 40 to the outside.

[0067] negative electrode The negative electrode may include a current collector and a negative electrode active material layer located on the current collector, the negative electrode active material layer comprising a negative electrode active material and further comprising a binder, a conductive material, or a combination thereof.

[0068] negative electrode active material The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0069] The materials capable of reversibly intercalating / deintercalating lithium ions may include, for example, crystalline carbon, amorphous carbon, or a combination thereof, as carbon-based anode active materials. 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 or hard carbon, mesophase pitch carbide, and calcined coke.

[0070] The lithium metal alloy can be an alloy of lithium with a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0071] As the substance capable of doping and undoping lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. As the Si-based negative electrode active material, silicon, a silicon-carbon composite, SiOx (0 < x ≦ 2), a Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof), or a combination thereof may be used. As the Sn-based negative electrode active material, Sn, SnO2, a Sn alloy, or a combination thereof may be used.

[0072] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle diameter (D 50 ) of the silicon-carbon composite particles may be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in a form in which silicon particles are coated with amorphous carbon on the surface of the silicon particles. For example, it may include secondary particles (cores) formed by granulating primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon may also be located between the primary silicon particles, and for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed and present in an amorphous carbon matrix.

[0073] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and an amorphous carbon coating layer located on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. Examples of the amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0074] When the silicon-carbon composite contains silicon and amorphous carbon, the content of silicon may be 10% to 50% by weight based on 100% by weight of the silicon-carbon composite, and the content of amorphous carbon may be 50% to 90% by weight. When the composite contains silicon, amorphous carbon, and crystalline carbon, based on 100% by weight of the silicon-carbon composite, the content of silicon may be 10% to 50% by weight, the content of crystalline carbon may be 10% to 70% by weight, and the content of amorphous carbon may be 20% to 40% by weight.

[0075] Also, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. The average particle diameter (D 50 ) of the silicon particles (primary particles) may be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist alone as silicon, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon may be represented by SiO x (0 < x ≦ 2). At this time, the atomic content ratio of Si:O indicating the degree of oxidation may be 99:1 to 33:67. In this specification, unless otherwise defined, the average particle diameter (D 50 ) means the diameter of the particles with a cumulative volume of 50% in the particle size distribution.

[0076] The Si-based or Sn-based anode active material can be used in combination with a carbon-based anode active material. When using a mixture of the Si-based or Sn-based anode active material and the carbon-based anode active material, the mixing ratio may be 1:99 to 90:10 by weight.

[0077] binder The binder plays a role in ensuring that the negative electrode active material particles adhere well to each other and that the negative electrode active material adheres well to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0078] Examples of non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0079] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylicated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0080] When using an aqueous binder as the negative electrode binder, it may further contain a cellulosic compound capable of imparting viscosity. This cellulosic compound can be a mixture of one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof. The alkali metal can be Na, K, or Li.

[0081] The dry binder is a fiberizable polymeric substance, which may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0082] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not cause chemical changes in the battery that is constructed can be used. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0083] The content of the negative electrode active material may be 95% to 99.5% by weight relative to 100% by weight of the negative electrode active material layer, and the content of the binder may be 0.5% to 5% by weight relative to 100% by weight of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0.5% to 5% by weight of the conductive material.

[0084] Current collector The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof, and may be in the form of foil, sheet, or foam. The thickness of the negative electrode current collector may be, for example, 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0085] electrolyte The electrolyte for lithium secondary batteries may, for example, be an electrolyte solution, which may contain a non-aqueous organic solvent and a lithium salt.

[0086] Non-aqueous organic solvents serve as a medium through which ions involved in the electrochemical reactions of the battery can move. Non-aqueous organic solvents may be carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvents, aprotic solvents, or combinations thereof.

[0087] Suitable carbonate solvents include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Suitable ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone. Suitable ether solvents include dibutyl ether, tetraglyceride, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Suitable ketone solvents include cyclohexanone. Suitable alcohol solvents include ethyl alcohol and isopropyl alcohol. Suitable aprotic solvents include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group with 2 to 20 carbon atoms, and may include double bonds, aromatic rings, or ether groups); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0088] Non-aqueous organic solvents can be used individually or in combination of two or more. When using a mixture of two or more, the mixing ratio can be appropriately adjusted according to the desired performance of the battery, and this is generally understood by those working in this field.

[0089] When using carbonate-based solvents, cyclic carbonates and linear carbonates can be mixed and used together, and the cyclic carbonates and linear carbonates may be mixed in a volume ratio of 1:1 to 1:9.

[0090] The non-aqueous organic solvent may further contain aromatic hydrocarbon organic solvents. For example, carbonate solvents and aromatic hydrocarbon organic solvents can be mixed and used in a volume ratio of 1:1 to 30:1.

[0091] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate, or ethylene carbonate compounds to improve battery life.

[0092] Representative examples of the aforementioned ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0093] Lithium salts are substances that dissolve in organic solvents and act as a source of lithium ions in batteries, enabling the operation of basic lithium secondary batteries and facilitating the movement of lithium ions between the positive and negative electrodes. Typical examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (where x and y are integers from 1 to 20) may contain one or more selected from lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0094] The lithium salt concentration should ideally be within the range of 0.1 M to 2.0 M. When the lithium salt concentration falls within this range, the electrolyte has appropriate ionic conductivity and viscosity, resulting in excellent performance and effective lithium ion movement.

[0095] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Suitable separators include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof. Mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators can also be used.

[0096] The separator may include a porous substrate and a coating layer containing organic, inorganic, or a combination thereof located on one or both sides of the porous substrate.

[0097] The porous substrate may be a polymer film formed from one polymer selected from polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon®, and polytetrafluoroethylene, or from copolymers or mixtures of two or more of these polymers.

[0098] The porous substrate can have a thickness of approximately 1 μm to 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0099] The organic material may include a (meth)acrylic copolymer comprising a first structural unit derived from (meth)acrylamide, and a second structural unit comprising at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0100] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. The average particle size (D) of the inorganic particles is 50 The wavelength range may be 1 nm to 2000 nm, for example, 100 nm to 1000 nm or 100 nm to 700 nm.

[0101] The organic and inorganic materials may be present mixed in a single coating layer, or in a form in which a coating layer containing organic materials and a coating layer containing inorganic materials are laminated together.

[0102] The thickness of the coating layer may be 0.5 μm to 20 μm, or for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0103] Examples and comparative examples of the present invention are described below. The following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0104] Example 1 1. Manufacturing of the positive electrode A positive electrode composition was prepared by mixing 90% by weight of LiFePO4 as the positive electrode active material, 5% by weight of a polyacrylate solution containing 10 mol% of carboxyl groups as a binder, 0.18% by weight of 2-aminoethanol, 0.18% by weight of oxalic acid, and 4.64% by weight of Super P as a conductive material in 30 ml of N-methylpyrrolidone solvent. The prepared positive electrode composition was coated onto an aluminum foil current collector, dried, and rolled to produce a positive electrode.

[0105] 2. Manufacturing of the negative electrode A negative electrode composition was prepared by mixing 97.5% by weight of graphite negative electrode active material, 1.5% by weight of carboxymethylcellulose, and 1% by weight of styrene-butadiene rubber in an aqueous solvent. The negative electrode composition was coated onto a copper foil current collector, which was then dried and rolled to produce the negative electrode.

[0106] 3. Manufacturing of lithium-ion batteries A lithium secondary battery was manufactured using a conventional method with a polytetrafluoroethylene separator and an electrolyte solution prepared by dissolving 1M LiPF6 in a solvent containing a 3:7 volume ratio mixture of ethylene carbonate and dimethyl carbonate.

[0107] Example 2 The cathode and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that in the production of the cathode, 90% by weight of LiFePO4, 5% by weight of a polyimide solution containing 10 mol% of carboxyl groups, 0.17% by weight of 2-aminoethanol, 0.33% by weight of oxalic acid, and 4.5% by weight of Super P were mixed.

[0108] Comparative Example 1 The positive electrode and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that PVdF was mixed instead of polyacrylate in the manufacturing of the positive electrode, and oxalic acid was not mixed.

[0109] Comparative Example 2 The positive electrode and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that oxalic acid was not mixed in the manufacturing of the positive electrode.

[0110] Comparative Example 3 The cathode and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that PVdF was mixed instead of polyacrylate in the production of the cathode, and 2-aminoethanol was not mixed.

[0111] Comparative Example 4 The positive electrode and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that 2-aminoethanol was not mixed in the manufacturing of the positive electrode.

[0112] Evaluation Example 1: Adhesion Strength Evaluation The positive electrodes manufactured according to the examples and comparative examples were prepared by cutting them to a size of 25 mm in width and 100 mm in length. Double-sided tape with an area of ​​20 mm in width and 40 mm in length was attached to an acrylic plate with an area of ​​40 mm in width and 100 mm in length. After attaching the prepared positive electrodes to the double-sided tape, they were lightly pressed five times with a hand roller. This was then mounted on a UTM (20 kgf Load cell), and approximately 25 mm of one side of the positive electrode was peeled off. The positive electrode was then fixed to the upper clip of a tensile strength machine, and the tape attached to one side of the positive electrode was fixed to the lower clip. The 180° peel strength was measured while peeling at a speed of 100 mm / min. At this time, the 180° peel strength was expressed as adhesive strength, and the results are shown in Table 1 below.

[0113] Evaluation Example 2: Interfacial Resistance Evaluation The resistance of the positive electrode plates for lithium secondary batteries manufactured according to the examples and comparative examples was evaluated using the 46-pin resistance measurement method. The mixture resistance and interfacial resistance were measured, and the results are shown in Table 1 below.

[0114] [Table 1]

[0115] Referring to Table 1, it can be confirmed that, in the case of lithium secondary batteries manufactured according to the examples, the adhesion strength with the positive electrode current collector is equivalent to or improved compared to the comparative example, while the interfacial resistance is reduced.

[0116] Evaluation Example 3: Battery Performance Evaluation The lithium secondary batteries manufactured in the examples and comparative examples were charged to 3.65V at 25°C with a constant current of 0.2C, then the voltage was maintained until the current value was 0.05C, and then discharged to 2.5V with a constant current of 0.2C to complete the first charge-discharge cycle. Next, the batteries were charged to 3.65V at 25°C with a constant current of 0.2C, then the voltage was maintained until the current value was 0.05C, and then discharged to 2.5V with a constant current of 0.2C to complete the second charge-discharge cycle. The discharge capacity of the second cycle is shown in Table 2 below as "3.65V capacity".

[0117] Next, the battery underwent more than 50 cycles of charging at 1.0C and discharging at 1.0C within a voltage range of 3.0V to 3.65V at 45°C. The ratio of the discharge capacity after 50 cycles to the discharge capacity after 2 cycles was calculated and expressed as "3.65V Lifetime" in Table 2 below.

[0118] [Table 2]

[0119] Referring to Table 2, it can be confirmed that the lithium secondary batteries manufactured according to the examples had equivalent or improved capacity and lifespan characteristics compared to the comparative examples.

[0120] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art that utilize the basic concepts defined in the following claims also fall within the scope of the present invention. [Explanation of Symbols]

[0121] 100: Lithium secondary battery, 10: Positive electrode 11: Positive lead tab, 12: Positive terminal 20: Negative electrode, 21: Negative electrode lead tab 22: Negative terminal, 30: Separator 40: Electrode assembly, 50: Case 60: Sealing member, 70: Electrode tab 71: Positive tab, 72: Negative tab

Claims

1. Current collector and, A positive electrode active material layer located on the current collector, comprising a positive electrode active material, a copolymer binder, and an amine, Includes, The copolymer binder comprises a first structural unit containing a carboxyl group and a second nonionic structural unit. The carboxyl group and the amine exist in the form of a salt at the positive electrode.

2. The positive electrode active material is the positive electrode according to claim 1, represented by the following chemical formula 13: [Chemical formula 13] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3 In the above chemical formula 13, 0.9 ≤ a³ ≤ 1.8, 0.6 ≤ x³ ≤ 1, 0 ≤ y³ ≤ 0.4, and 0 ≤ b³ ≤ 0.1, M 4 X is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

3. The first structural unit is derived from a monomer containing a carboxyl group, The positive electrode according to claim 1, wherein the monomer containing the carboxyl group comprises a monocarboxylic acid and its derivatives, a dicarboxylic acid and its derivatives, or a combination thereof.

4. The positive electrode according to claim 1, comprising 0.1 mol% to 20 mol% of the first structural unit with respect to 100 mol% of the entire copolymer binder.

5. The aforementioned second structural unit is derived from a nonionic monomer, The positive electrode according to claim 1, wherein the nonionic monomer includes an acrylic monomer, an imide monomer, or a combination thereof.

6. The positive electrode according to claim 1, wherein the amine includes a primary amine, a secondary amine, a tertiary amine, an alkanolamine, an alkoxyamine, a cyclic amine, or a combination thereof.

7. The positive electrode according to claim 1, comprising 10 to 30% by weight of the copolymer binder and 0.1 to 1.0% by weight of the amine, based on 100% by weight of the entire positive electrode active material layer.

8. The positive electrode according to claim 1, further comprising N-methylpyrrolidone in the positive electrode active material layer.

9. (a) A step of producing a positive electrode composition comprising a positive electrode active material, a copolymer binder, a basic substance containing an amine group, and a volatile acidic substance, (b) The step of applying the positive electrode composition onto the current collector, Includes, A method for producing a positive electrode, wherein the copolymer binder comprises a first structural unit containing a carboxyl group and a second nonionic structural unit.

10. It comprises a positive electrode active material, a copolymer binder, an amine, and a volatile acidic substance. The copolymer binder is a cathode composition comprising a first structural unit containing a carboxyl group and a second nonionic structural unit.

11. The first structural unit is derived from a monomer containing a carboxyl group, The cathode composition according to claim 10, wherein the monomer containing the carboxyl group comprises a monocarboxylic acid and its derivatives, a dicarboxylic acid and its derivatives, or a combination thereof.

12. The positive electrode composition according to claim 10, comprising 0.1 mol% to 20 mol% of the first structural unit with respect to 100 mol% of the entire copolymer binder.

13. The aforementioned second structural unit is derived from a nonionic monomer, The positive electrode composition according to claim 10, wherein the nonionic monomer includes an acrylic monomer, an imide monomer, or a combination thereof.

14. The positive electrode composition according to claim 10, wherein the amine comprises a primary amine, a secondary amine, a tertiary amine, an alkanolamine, an alkoxyamine, a cyclic amine, or a combination thereof.

15. The positive electrode composition according to claim 10, wherein the volatile acidic substance includes oxalic acid, malic acid, acetic acid, or a combination thereof.

16. The positive electrode composition according to claim 10, comprising 10% to 30% by weight of the copolymer binder, 0.1% to 1.0% by weight of the amine, and 0.1% to 1.0% by weight of the volatile acidic substance, based on 100% by weight of the entire positive electrode composition.

17. The positive electrode composition according to claim 10, further comprising N-methylpyrrolidone in the positive electrode composition.

18. A positive electrode according to any one of claims 1 to 8, The negative electrode and, Electrolytes, Lithium-ion secondary batteries, including lithium-ion batteries.

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