Positive electrode active material for lithium secondary battery, positive electrode including the same, and lithium secondary battery including the same

Abstract

To provide a positive electrode active material with high energy density, high average voltage, and an excellent lifetime characteristic despite its economical property.SOLUTION: The present invention relates to a positive electrode for a lithium secondary battery, and a lithium secondary battery including the same. More specifically, the positive electrode for a lithium secondary battery includes a current collector, a first positive electrode active material layer on the current collector, and a second positive electrode active material layer on the first positive electrode active material layer. The first positive electrode active material layer includes first particles containing a compound of Chemical Formula 1 and having an olivine structure, and second particles containing a compound of Chemical Formula 2 and having a spinel structure. The second active material layer includes third particles containing a compound of Chemical Formula 3 and having the olivine structure. The first particles have a secondary particle shape in which a plurality of primary particles are aggregated together.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery, a positive electrode including the same, and a lithium secondary battery including the same, and more particularly to a positive electrode active material including an olivine-based lithium compound, a positive electrode including the same, and a lithium secondary battery including the same. [Background technology]

[0002] Recently, with the rapid spread of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for high-energy-density and high-capacity secondary batteries has been increasing rapidly. Accordingly, research and development to improve the performance of lithium secondary batteries has been actively conducted.

[0003] A lithium secondary battery is a battery that includes a cathode and an anode, which contain active materials that allow the intercalation and deintercalation of lithium ions, and an electrolyte. Electrical energy is produced through oxidation and reduction reactions that occur when lithium ions are inserted / deintercalated at the cathode and anode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Korean Patent Application Publication No. 2021-0080249 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a positive electrode active material that is economical and has high energy density, high average voltage, and excellent life characteristics.

[0006] Another problem to be solved by the present invention is to provide a positive electrode that is economical and has a high energy density, a high average voltage, and excellent life characteristics.

Means for Solving the Problem

[0007] The lithium secondary battery positive electrode according to the concept of the present invention can include a current collector, a first positive electrode active material layer on the current collector, and a second positive electrode active material layer on the first positive electrode active material layer.

[0008] The first positive electrode active material layer can include a compound of Chemical Formula 1 below, first particles having an olivine structure, and a compound of Chemical Formula 2 below, second particles having a spinel structure. The second positive electrode active material layer can include a compound of Chemical Formula 3 below and third particles having an olivine structure. The first particles can have a secondary particle shape in which a plurality of primary particles are aggregated. [Chemical Formula 1] Li a1 Mn z1 Fe x1 B1 y1 PO 4-c1

[0009] In Chemical Formula 1, B1 is one or more elements selected from the group consisting of Al, Ti, V, and Mg, and 0.8 < a1 ≤ 1.2, 0.4 ≤ z1 ≤ 0.8, 0.2 ≤ x1 ≤ 0.6, 0 ≤ y1 ≤ 0.05, 0 < c1 ≤ 0.05 can be satisfied. [Chemical Formula 2] Li a2 Mn x2 B2 y2 O 4-c2

[0010] In Chemical Formula 2, B2 is one or more elements selected from the group consisting of Al and Mg, and 0.8 < a2 ≤ 1.2, 1.9 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, 0 < c2 ≤ 0.05 can be satisfied. [Chemical Formula 3]

[0011] Li a3 Mn z3 Fe x3 B3 y3 PO 4-c3 In Chemical Formula 3, B3 is one or more elements selected from the group consisting of Al, Ti, V, and Mg, and 0.8 < a3 ≤ 1.2, 0.4 ≤ z3 ≤ 0.8, 0 ≤ x3 ≤ 0.6, 0 ≤ y3 ≤ 0.05, 0 < c3 ≤ 0.05 may hold.

Advantages of the Invention

[0012] The positive electrode according to the present invention includes a first positive electrode active material layer containing olivine-based first particles with a size of several μm and spinel-based second particles with a size of several μm, and a second positive electrode active material layer containing olivine-based third particles with a size of several hundred nm to several μm laminated on the first active material layer, whereby the pallet density, capacity, and energy density can be improved. The positive electrode according to the present invention is easy to fabricate an electrode plate and can improve the resistance of the electrode plate. The lithium secondary battery according to the present invention can relatively improve the life characteristics.

Brief Description of the Drawings

[0013] [Figure 1] It is a conceptual diagram schematically showing a lithium secondary battery according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view showing a lithium secondary battery according to an embodiment. [Figure 3] It is a schematic view showing a lithium secondary battery according to an embodiment, which is in a cylindrical battery form. [Figure 4] It is a schematic view showing a lithium secondary battery according to an embodiment, which is in a rectangular battery form. [Figure 5] It is a schematic view showing a lithium secondary battery according to an embodiment, which is in a pouch battery form. [Figure 6] It is a cross-sectional view of a positive electrode for a lithium secondary battery according to an embodiment of the present invention. [Figure 7] It is an enlarged view of a first positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention. [Figure 8A] It is an enlarged view of a second positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention. [Figure 8B]3 is an enlarged view of a second positive electrode active material layer of a lithium secondary battery according to one embodiment of the present invention. FIG. [Figure 9] 1 is a SEM photograph of a first particle according to an embodiment of the present invention. [Figure 10] 1 is an SEM photograph of a second particle according to an embodiment of the present invention. [Figure 11A] 10 is an SEM photograph of a third particle according to one embodiment of the present invention. [Figure 11B] 10 is an SEM photograph of a third particle according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] In this specification, when a component is referred to as being on another component, it means that the component may be formed directly on the other component, or that a third component may be interposed between them. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various forms and may undergo various modifications. The description of the present embodiments is provided solely to ensure complete disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0015] In this specification, when a component is referred to as being on another component, it means that it may be formed directly on the other component, or that a third component may be interposed between them. Also, in the drawings, the thickness of the components is exaggerated for the sake of efficient explanation of the technical content. Parts designated with the same reference numerals throughout the specification refer to the same components.

[0016] Unless otherwise specified herein, the singular can also include the plural. Furthermore, unless otherwise specified, "A or B" can mean "including A, including B, or including A and B." As used herein, "comprises" and / or "comprising" does not exclude the presence or addition of one or more other elements to the referenced element.

[0017] As used herein, "combinations thereof" can mean mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0018] Unless otherwise defined herein, particle size refers to the average particle size. Furthermore, particle size refers to the average particle size (D50), which refers to the diameter of particles with a cumulative volume of 50% in a particle size distribution. The average particle size (D50) can be measured by methods well known to those skilled in the art, such as using a particle size analyzer or a transmission electron microscope (TEM) or scanning electron microscope (SEM) image. Alternatively, the average particle size (D50) can be measured using a measuring device that uses dynamic light scattering, and data analysis can be performed to count the number of particles in each particle size range, after which the average particle size (D50) can be calculated. Alternatively, the average particle size (D50) can be measured using a laser diffraction method. More specifically, when measuring by the laser diffraction method, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT3000), and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W. The average particle size (D50) based on 50% of the particle size distribution in the measuring device can then be calculated.

[0019] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment of the present invention. Referring to FIG. 1, the lithium secondary battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0020] The positive electrode 10 and the negative electrode 20 can be separated from each other by a separator 30. The separator 30 can be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 can be in contact with an electrolyte solution ELL. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated in the electrolyte solution ELL.

[0021] The electrolyte ELL can be a medium for transferring lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, the lithium ions can pass through the separator 30 and move toward the positive electrode 10 or the negative electrode 20.

[0022] positive electrode 10 The positive electrode 10 for a lithium secondary battery may include a current collector COL1 and a positive electrode active material layer AML1 formed on the current collector COL1. The positive electrode active material layer AML1 includes a positive electrode active material and may further include a binder and / or a conductive material. A detailed description of the positive electrode active material layer AML1 according to an embodiment of the present invention will be provided below with reference to FIGS. 7 to 8B. The current collector COL1 may be made of aluminum, but is not limited thereto.

[0023] negative electrode 20 The negative electrode 20 for a lithium secondary battery includes a current collector COL2 and a negative electrode active material layer AML2 located on the current collector COL2. The negative electrode active material layer AML2 includes a negative electrode active material and may further include a binder and / or a conductive material.

[0024] For example, the negative electrode active material layer AML2 may contain 90 to 99 wt % of the negative electrode active material, 0.5 to 5 wt % of the binder, and 0 to 5 wt % of the conductive material.

[0025] The binder serves to firmly adhere the negative electrode active material particles to each other and to firmly adhere the negative electrode active material to the current collector COL 2. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0026] Examples of non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0027] The water-based binder may be selected from styrene-styrene rubber, (meth)acrylate styrene-styrene rubber, (meth)acrylonitrile-styrene 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.

[0028] When an aqueous binder is used as the negative electrode binder, it may further contain a cellulose-based compound that can impart viscosity. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be sodium, potassium, or lithium.

[0029] The dry binder can be a fiberizable polymeric material such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0030] The conductive material is used to impart conductivity to the electrode, and any material that is electronically conductive without causing a chemical change 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, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0031] The current collector COL2 may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0032] negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 includes a material capable of reversibly inserting / extracting lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped with and de-doped from lithium, or a transition metal oxide.

[0033] The material capable of reversibly inserting / extracting lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite. Examples of amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0034] As the alloy of lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0035] As a substance that can be doped and de-doped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (Q is 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), or a combination thereof. The Sn-based negative electrode active material can be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0036] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite can be in a form in which silicon particles are coated with amorphous carbon on the surface of the silicon particles. For example, it can include secondary particles (cores) assembled from primary silicon particles and a first coating layer (shell) of amorphous carbon located on the surface of the secondary particles. The amorphous carbon can also be located between the primary silicon particles, and for example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed and present in an amorphous carbon matrix.

[0037] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and a first coating layer of amorphous carbon located on the surface of the core.

[0038] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by mixing with a carbon-based negative electrode active material.

[0039] Separator 30 Depending on the type of lithium secondary battery, a separator 30 may be present between the positive electrode 10 and the negative electrode 20. As such separator 30, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and it goes without saying that mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0040] Separator 30 can include a porous substrate and a first coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0041] The porous substrate may be a polymer membrane formed of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyetherimide, polyamide imide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon (registered trademark), and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0042] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0043] 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.

[0044] The organic material and the inorganic material may be mixed in one first coating layer, or may be stacked in a form in which a first coating layer containing an organic material and a first coating layer containing an inorganic material are stacked.

[0045] Electrolyte ELL The electrolyte ELL for lithium secondary batteries contains a non-aqueous organic solvent and a lithium salt.

[0046] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can migrate.

[0047] The non-aqueous organic solvent can be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, or a combination thereof.

[0048] Examples of carbonate solvents that can be used 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).

[0049] Examples of ester solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone.

[0050] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0051] The non-aqueous organic solvents can be used alone or in combination of two or more.

[0052] When a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed together, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio of 1:1 to 1:9.

[0053] Lithium salts are dissolved in organic solvents and act as a source of lithium ions in the battery, enabling basic lithium secondary battery operation and facilitating the movement of lithium ions between the positive and negative electrodes. Representative 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, LiN(C x F 2x+1 SO2)(C y F 2y+1SO2) (x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethene sulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0054] Lithium secondary battery Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 2 through 5 are schematic diagrams illustrating lithium secondary batteries according to embodiments, with FIG. 2 illustrating a cylindrical type, FIG. 3 illustrating a prismatic type, and FIGS. 4 and 5 illustrating pouch types. Referring to FIGS. 2 through 5, a lithium secondary battery 100 may include an electrode assembly 40 having 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, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in FIG. 2. Also, in FIG. 3, the lithium secondary battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in FIGS. 4 and 5, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting current generated in the electrode assembly 40 to the outside.

[0055] The lithium secondary battery according to an embodiment of the present invention may be applied to automobiles, mobile phones, and / or various types of electrical devices, but the present invention is not limited thereto.

[0056] 6 is a cross-sectional view of a positive electrode for a lithium secondary battery according to an embodiment of the present invention. Referring to FIG. 6, the positive electrode 10 for a lithium secondary battery may include a current collector COL1 (see FIG. 1) and a positive electrode active material layer AML1 (see FIG. 1), as described above. The positive electrode active material layer AML1 may include a first positive electrode active material layer ATL1 and a second positive electrode active material layer ATL2 stacked on the first positive electrode active material layer ATL1.

[0057] Hereinafter, the first positive electrode active material layer ATL1 and the second positive electrode active material layer ATL2 will be described in more detail.

[0058] First positive electrode active material layer ATL1 FIG. 7 is an enlarged view of the first positive electrode active material layer ATL1 of the positive electrode for a lithium secondary battery according to an embodiment of the present invention.

[0059] The first positive electrode active material layer ATL1 may include first particles PTC1, second particles PTC2, and a first functional additive ADD1. The first functional additive ADD1 may include a first binder BND1 and a first conductive material CDM1.

[0060] The first binder BND1 can bind the first particles PTC1 and the first conductive material CDM1 to each other. The first binder BND1 can also stably fix the first positive electrode active material layer ATL1 to the current collector COL1. For example, the first binder BND1 can include, but is not limited to, at least one selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl fluoride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, an epoxy resin, a (meth)acrylic resin, a polyester resin, and nylon.

[0061] The first conductive material CDM1 can be used to improve the conductivity of the first positive electrode active material layer ATL1. Any conductive material that does not cause a chemical change in the first positive electrode active material layer ATL1 can be used as the first conductive material CDM1 without limitation. For example, the first conductive material CDM1 can include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0062] Hereinafter, each of the first particles PTC1 and the second particles PTC2 in the first positive electrode active material layer ATL1 will be described in more detail.

[0063] 1st particle PTC1 The first particles PTC1 can include an olivine-based lithium compound represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Mn z1 Fe x1 B1 y1 PO 4-c1

[0064] In Formula 1, 0.8 < a1 ≤ 1.2, 0.4 ≤ z1 ≤ 0.8, 0.2 ≤ x1 ≤ 0.6, 0 ≤ y1 ≤ 0.05, and 0 < c1 ≤ 0.05 can be satisfied. B1 can be one or more elements selected from the group consisting of Al, Ti, V, and Mg. B1 can be a dopant doped into the first particles PTC1. For example, B1 can include Ti.

[0065] The first particles PTC1 can further include carbon derived from the above-described positive electrode active material layer AML1. The carbon element content in the first particles PTC1 can be 0.5 wt% to 5 wt%, 0.5 wt% to 3 wt%, or 0.5 wt% to 2 wt%.

[0066] The first particles PTC1 may have a single particle shape. In this specification, a single particle may refer to a single particle without an internal grain boundary. A single particle may refer to a single particle, a monolith structure, a single structure, or a non-aggregated particle in which particles are morphologically present in an independent phase without aggregation. For example, a single particle may be a single crystal. Alternatively, a single particle may be a particle containing several crystals. A single particle may be in a singly separated form. Alternatively, a single particle may be in a form in which 2 to 100 first primary particles NNP_1 are attached to each other.

[0067] The first particles PTC1 may be a nano-shaped cathode active material. The first particles PTC1 may include at least one first primary particle NNP_1. In one embodiment, the first particles PTC1 may have a spherical or elliptical shape formed by aggregation of the first primary particles. In another embodiment, the first particles PTC1 may have a random shape, not a spherical shape, even if the first primary particles NNP_1 are aggregated.

[0068] In one embodiment, the average particle size may refer to the diameter of particles whose cumulative volume is 50% by volume (D50) in the particle size distribution. In one embodiment, the average particle size (D50) of the first particles PTC1 may be a value measured using a particle size analyzer.

[0069] In one embodiment, the first particles PTC1 may have an average particle size of 500 nm to 2.5 μm, or about 1 μm. The size of at least one first primary particle NNP_1 constituting the first particles PTC1 may be measured using a scanning electron microscope (SEM). In one embodiment, the size of the first primary particles NNP_1 may refer to the diameter measured by randomly selecting about 30 first primary particles NNP_1 from an electron microscope photograph of the positive electrode active material. The size of the first primary particles NNP_1 may be uniform. The size of the first primary particles NNP_1 may be 100 nm to 500 nm, or 100 nm to 200 nm.

[0070] The first particles PTC1 may have a polycrystalline form and may include secondary particles formed by agglomeration of at least two or more first primary particles NNP_1. In other words, one first particle PTC1 may include a plurality of first primary particles NNP_1 agglomerated together. The first particles PTC1 formed by a plurality of first primary particles NNP_1 may have a spherical or elliptical shape.

[0071] In one embodiment, the average particle size may refer to the diameter of particles whose cumulative volume is 50% by volume (D50) in the particle size distribution. In one embodiment, the average particle size (D50) of the first particles PTC1 may be a value measured using a particle size analyzer.

[0072] The first particles PTC1, which include at least one first primary particle NNP_1, may have an average particle size of 500 nm to 5 μm, 100 nm to 3 μm, 500 nm to 2.5 μm, 3 μm to 7 μm, 4 μm to 6 μm, or about 5 μm. The average particle size (D50) of the first particles PTC1 may be smaller than the average particle size (D50) of the second particles PTC2, which will be described later.

[0073] The first particle PTC1 may include at least one primary particle (or single particle). The size of the at least one first primary particle NNP_1 constituting the first particle PTC1 may be measured using a scanning electron microscope (SEM). In one embodiment, the size of the first primary particle NNP_1 may refer to the diameter measured by randomly selecting approximately 30 first primary particles NNP_1 from an electron microscope photograph of the positive electrode active material. The size of the first primary particles NNP_1 may be uniform.

[0074] The size of at least one first primary particle NNP_1 constituting the first particle PTC1 may be 100 nm to 200 nm, 50 nm to 150 nm, 50 nm to 100 nm, 100 nm to 150 nm, or 200 nm to 300 nm.

[0075] In one embodiment, the first particles PTC1 may include a coating layer on their surfaces. The coating layer may cover the entire surface of the first particles PTC1 or may cover only a portion of the surface of the first particles PTC1. For example, the coating layer may include carbon and / or a carbon-containing compound. The coating layer may further include at least one selected from the group consisting of a titanium-containing compound, a magnesium-containing compound, and a vanadium-containing compound. The metal-containing compound, such as a titanium-containing compound, a magnesium-containing compound, or a vanadium-containing compound, may be, for example, a metal oxide, a metal hydroxide, a metal carbonate, a composite thereof, or a mixture thereof. The metal-containing compound may further include other metals or non-metal elements. For example, the metal-containing compound may further include lithium. The coating layer may improve the structural stability and electrical conductivity of the first particles PTC1.

[0076] In one embodiment, the first particle PTC1 may further include a grain boundary coating layer on the surface of each of the first primary particles NNP_1. The grain boundary coating layer may be present inside the first particle PTC1. The grain boundary coating layer may be formed by coating along the interface between the first primary particles NNP_1 inside the first particle PTC1. Again, the grain boundary coating layer may refer to a material coated on the grain boundaries inside the first particle PTC1.

[0077] The grain boundary coating layer may include carbon and / or a carbon-containing compound. The grain boundary coating layer may further include at least one selected from the group consisting of a titanium-containing compound, a magnesium-containing compound, and a vanadium-containing compound.

[0078] The interior of the first particle PTC1 described above may refer to the entire interior of the first particle PTC1 excluding the surface of the first particle PTC1. For example, the interior of the first particle PTC1 may refer to a region from a depth of about 10 nm to the entire interior of the surface of the first particle PTC1, or from a depth of 10 nm to a depth of about 2 μm.

[0079] The first particles PTC1 further include a grain boundary coating portion, which enhances structural stability and allows a uniform coating layer to be formed on the surface of the first particles PTC1. In addition, the first particles PTC1 further include a grain boundary coating portion, which further improves the electrical conductivity of the first particles PTC1.

[0080] The first particles PTC1 may further contain carbon derived from the coating layer and / or the grain boundary coating layer. The carbon element content in the first particles PTC1 may be 0.5 wt% to 10 wt%, 1 wt% to 3 wt%, or 1.5 wt% to 2.5 wt%. For example, the carbon content in the first particles PTC1 in the form of secondary particles may be higher than the content in the form of single particles.

[0081] The first particles PTC1 may have a spherical shape formed by agglomeration of a plurality of first primary particles NNP_1. The first particles PTC1 may exhibit the following properties due to the first primary particles NNP_1 being closely agglomerated to one another: The above-described coating layer and / or grain boundary coating layer of the first particles are well maintained, thereby increasing electrical conductivity and improving low-temperature characteristics. The increased electrode plate binding strength reduces the binder capacity. The first particles PTC1 may have a spherical or elliptical shape.

[0082] The porosity of the first particles PTC1 may be about 20% to about 40%. The Span value of the first particles PTC1 analyzed with a particle size analyzer may be 0.3 to 0.75.

[0083] 2nd particle PTC2 The second particles PTC2 may include a lithium compound having a spinel structure represented by the following Chemical Formula 2. [Chemical formula 2] Li a2 Mn x2 B2 y2 O 4-c2

[0084] In Formula 2, 0.8 < a2 ≤ 1.2, 1.9 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, and 0 < c2 ≤ 0.05 may hold. B2 may be one or more elements selected from the group consisting of Al and Mg. B2 may be a dopant doped into the second particle PTC2. The dopant can exert an effect of controlling the uniform growth of the second primary particles NNP_2 constituting the second particle PTC2, and can improve the charge / discharge efficiency, low-temperature characteristics, and life characteristics of the lithium secondary battery. The second particle PTC2 has advantages of high output characteristics, high structural stability, high average voltage, and excellent life characteristics.

[0085] The second particle PTC2 can have a spinel structure composed of a tetrahedral and octahedral lattice structure. Since the lattice structure has various channels, lithium ions can be smoothly inserted / extracted, so that the output characteristics can be made excellent. Since the second particle PTC2 contains Mn, it can be structurally stable. Such structural stability has excellent life characteristics that can operate at a high voltage because it maintains the electrochemical characteristics of the particles even at a high voltage.

[0086] The second particle PTC2 can be lithium manganese oxide, a cathode material in which cobalt in lithium cobalt oxide is replaced with manganese. As one embodiment of the present invention, the cobalt (Co) content of the second particle PTC2 can be trace amounts substantially the same as being omitted. For example, the cobalt (Co) content of the second particle PTC2 can be 100 ppm or less. By substantially omitting cobalt (Co), the cathode active material according to the present invention can provide a secondary battery that is economical and has a high capacity and operating voltage.

[0087] 7, the second particles PTC2 may have a polycrystalline form and may include secondary particles formed by agglomerating at least two or more second primary particles NNP_2. In other words, one second particle PTC2 may include a plurality of second primary particles NNP_2 agglomerated together. The second particles PTC2 formed by a plurality of second primary particles NNP_2 may have an agglomerated spherical shape, or may have a random shape even when the second primary particles NNP_2 are aggregated.

[0088] In one embodiment, the average particle size may refer to the diameter of particles at 50% by volume (D50) of the cumulative volume in the particle size distribution. In one embodiment, the average particle size (D50) of the second particles PTC2 may be a value measured using a particle size analyzer. The average particle size (D50) of the second particles PTC2 may be 3 μm to 20 μm, 4 μm to 15 μm, or 5 μm to 10 μm. For example, the average particle size (D50) of the second particles PTC2 may be approximately 8 μm.

[0089] The average size of the second primary particles NNP_2 constituting the second particles PTC2 may be 3 μm or less. For example, the average size of the second primary particles NNP_2 may be 300 nm to 3 μm, 0.5 μm to 3 μm, 1 μm to 3 μm, or 2 μm to 3 μm. In one embodiment, the average size of the second primary particles may refer to the diameter measured by randomly selecting approximately 30 primary particles from an electron microscope photograph of the positive electrode active material. The size of the second primary particles NNP_2 may be uniform. The average size of the second primary particles NNP_2 may be larger than the average size of the first primary particles NNP_1. The difference between the average size of the second primary particles NNP_2 and the average size of the first primary particles NNP_1 may be 300 nm or more.

[0090] In one embodiment, the second particles PTC2 may include a second coating layer on the surface thereof, which can effectively prevent the second particles PTC2 from collapsing due to repeated charging and discharging.

[0091] The second coating layer can include an aluminum-containing compound, a magnesium-containing compound, or a combination thereof. The metal-containing compound in the second coating layer can be, for example, a metal oxide, a metal hydroxide, a metal carbonate, a composite thereof, or a mixture thereof. The metal-containing compound can further include other metals or non-metal elements. For example, the second coating layer can further include lithium, manganese, and / or nickel, etc.

[0092] A method for measuring the metal content in the second coating layer of the second particles PTC2 may include performing scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) on the second particles PTC2. The aluminum and / or magnesium content in the second coating layer may be determined through the analysis. In addition to SEM-EDS, methods for measuring the metal content in the second coating layer may also include inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0093] The first positive electrode active material layer ATL1 may include first particles and second particles, and the weight of the second particles PTC2 may be smaller than that of the first particles PTC1 in the first positive electrode active material layer ATL1.

[0094] The first particles PTC1 and second particles PTC2 constituting the first positive electrode active material layer ATL1 may contain manganese (Mn).

[0095] The second particles PTC2 have a high manganese (Mn) content, which can improve the operating voltage of the secondary battery compared to the first particles PTC1. In addition, the second particles PTC2 have a spinel structure, which makes the crystal structure stable and allows for better life characteristics compared to the first particles PTC1. The second particles PTC2 can reduce resistance. However, the second particles PTC2, which are manganese oxide, have a problem in that they are difficult to use alone due to their low capacity and energy density.

[0096] The positive electrode active material layer according to this embodiment can have improved voltage and life characteristics compared to batteries containing general lithium-cobalt-based compounds or lithium manganese iron phosphate compounds by mixing the first particles PTC1 and the second particles PTC2 in an appropriate ratio, i.e., by adjusting the manganese (Mn) content. A battery with a long life can be provided by mixing the first particles PTC1 and the second particles PTC2 in an appropriate range. The energy density can also be improved, resulting in excellent performance suitable for commercial use.

[0097] The cathode active material layer according to this embodiment mixes the first particles PTC1 and the second particles PTC2 in an appropriate ratio, which facilitates the manufacture of an electrode plate. More specifically, compared to a cathode active material layer containing a typical lithium iron phosphate compound, the second particles PTC2, which have a larger average particle size, are additionally included, thereby increasing the binding strength of the electrode plate. As a result, the amount of binder required for electrode plate manufacture can be reduced. The resistance of the electrode plate can be improved by first forming the first cathode active material layer ATL1, which contains the second particles PTC2, which have low resistance.

[0098] Second positive electrode active material layer ATL2 8A and 8B are enlarged views of a second positive electrode active material layer of a positive electrode for a lithium secondary battery according to an embodiment of the present invention.

[0099] 8A and 8B, the second positive electrode active material layer ATL2 may include third particles PTC3 and a second functional additive ADD2. The second functional additive ADD2 may include a second binder BND2 and a second conductive material CDM2.

[0100] 8B, the third particles PTC3 may be in the form of a single particle. The third particles SP3 may refer to third particles in the form of a single particle.

[0101] 8A, the third particles PTC3 may be polycrystalline and may include secondary particles formed by aggregation of at least two third primary particles NNP_3. The third particles PC3 may represent third particles having a polycrystalline form.

[0102] The second binder BND2 can bind the third particles PTC3 and the second conductive material CDM2 to each other. The second binder BND1 can also stably fix the second positive electrode active material layer ATL2 on the first positive electrode active material layer ATL1. In one embodiment, the second binder BND2 can include, but is not limited to, at least one selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl fluoride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, an epoxy resin, a (meth)acrylic resin, a polyester resin, and nylon.

[0103] The second conductive material CDM2 can be used to improve the conductivity of the second positive electrode active material layer ATL2. Any conductive material that does not cause chemical changes in the second positive electrode active material layer ATL2 can be used as the second conductive material CDM2 without limitation. As one embodiment, the second conductive material CDM2 can include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0104] Third particle PTC3 The third particle PTC3 can include an olivine-based lithium compound represented by Chemical Formula 3 below. [Chemical Formula 3] Li a3 Mn z3 Fe x3 B3 y3 PO 4-c3

[0105] In Formula 3, 0.8 < a3 ≤ 1.2, 0.4 ≤ z3 ≤ 0.8, 0 ≤ x3 ≤ 0.6, 0 ≤ y3 ≤ 0.05, 0 < c3 ≤ 0.05 can hold. B3 can be one or more elements selected from the group consisting of Al, Ti, V, and Mg. B3 can be a dopant doped into the third particle PTC3. For example, B3 can include Ti.

[0106] The third particle PTC3 can further include carbon derived from the above-described positive electrode active material layer AML1. The carbon element content in the third particle PTC3 can be 0.5 wt% to 5 wt%, 0.5 wt% to 3 wt%, or 0.5 wt% to 2 wt%.

[0107] Describe the characteristics of the third particle PTC3 with respect to particle morphology, size, particle diameter, etc.

[0108] The third particles PTC3 may have a single particle shape. In this specification, a single particle may refer to a single particle without an internal grain boundary. A single particle may refer to a single particle, a monolith structure, a single structure, or a non-aggregated particle in which particles are morphologically present in an independent phase without aggregation. For example, a single particle may be a single crystal. Alternatively, a single particle may be a particle containing several crystals. A single particle may be in a singly separated form. Alternatively, a single particle may be in a form in which 2 to 100 third primary particles NNP_3 are attached to each other.

[0109] The third particles PTC3 may be a nano-shaped positive electrode active material. The third particles PTC3 may include at least one third primary particle NNP_3. In one embodiment, the third particles PTC3 may have a spherical or elliptical shape formed by aggregation of the third primary particles. In another embodiment, the third particles PTC3 may have a random shape, not a spherical shape, even if the third primary particles NNP_3 are aggregated.

[0110] In one embodiment, the average particle size may refer to the diameter of particles whose cumulative volume is 50% by volume (D50) in the particle size distribution. In one embodiment, the average particle size (D50) of the third particles PTC3 may be a value measured using a particle size analyzer.

[0111] In one embodiment, the average particle size of the third particles PTC3 may be 500 nm to 2.5 μm, or about 1 μm. The size of at least one third primary particle NNP_3 constituting the third particles PTC3 may be measured using a scanning electron microscope (SEM). In one embodiment, the size of the third primary particles NNP_3 may refer to the diameter measured by randomly selecting about 30 third primary particles NNP_3 from an electron microscope photograph of the positive electrode active material. The size of the third primary particles NNP_3 may be uniform. The size of the third primary particles NNP_3 may be 100 nm to 500 nm, or 100 nm to 200 μm.

[0112] The third particles PTC3 may have a polycrystalline form and may include secondary particles formed by agglomeration of at least two or more third primary particles NNP_3. In other words, one third particle PTC3 may include a plurality of third primary particles NNP_3 agglomerated together. The third particles PTC3 formed by a plurality of third primary particles NNP_3 may have a spherical or elliptical shape.

[0113] In one embodiment, the average particle size may refer to the diameter of particles whose cumulative volume is 50% by volume (D50) in the particle size distribution. In one embodiment, the average particle size (D50) of the third particles PTC3 may be a value measured using a particle size analyzer.

[0114] The third particles PTC3, which include at least one third primary particle NNP_3, may have an average particle size of 50 nm to 5 μm, 100 nm to 3 μm, 500 nm to 2.5 μm, 3 μm to 7 μm, 4 μm to 6 μm, or about 5 μm. The average particle size (D50) of the third particles PTC3 may be smaller than the average particle size (D50) of the second particles PTC2.

[0115] The third particles PTC3 may include at least one primary particle (or single particle). The size of the at least one third primary particle NNP_3 constituting the third particles PTC3 may be measured using a scanning electron microscope (SEM). In one embodiment, the size of the third primary particles NNP_3 may refer to the diameter measured by randomly selecting approximately 30 third primary particles NNP_3 from an electron microscope photograph of the positive electrode active material. The size of the third primary particles NNP_3 may be uniform.

[0116] The size of at least one third primary particle NNP_3 constituting the third particle PTC3 may be 100 nm to 200 nm, 50 nm to 150 nm, 50 nm to 100 nm, 100 nm to 150 nm, or 200 nm to 300 nm.

[0117] In one embodiment, the third PTC3 particles may include a coating layer on their surfaces. The coating layer may cover the entire surface of the third PTC3 particles or a portion of the surface of the third PTC3 particles. For example, the coating layer may include carbon and / or a carbon-containing compound. The coating layer may further include at least one selected from the group consisting of a titanium-containing compound, a magnesium-containing compound, and a vanadium-containing compound. The metal-containing compound, such as a titanium-containing compound, a magnesium-containing compound, or a vanadium-containing compound, may be, for example, a metal oxide, a metal hydroxide, a metal carbonate, a composite thereof, or a mixture thereof. The metal-containing compound may further include other metals or non-metal elements. For example, the metal-containing compound may further include lithium. The coating layer may improve the structural stability and electrical conductivity of the third PTC3 particles.

[0118] In one embodiment, the third particle PTC3 may further include a grain boundary coating layer on the surface of each of the third primary particles NNP_3. The grain boundary coating layer may be present inside the third particle PTC3. The grain boundary coating layer may be formed by coating along the interface between the third primary particles NNP_3 inside the third particle PTC3. Again, the grain boundary coating layer may refer to a material coated on the grain boundaries inside the third particle PTC3.

[0119] The grain boundary coating layer may include carbon and / or a carbon-containing compound. The grain boundary coating layer may further include at least one selected from the group consisting of a titanium-containing compound, a magnesium-containing compound, and a vanadium-containing compound.

[0120] The interior of the third particle PTC3 described above may refer to the entire interior of the third particle PTC3 excluding the surface of the third particle PTC3. For example, the interior of the third particle PTC3 may refer to a region from a depth of about 10 nm to the entire inside of the surface of the third particle PTC3, or from a depth of 10 nm to a depth of about 2 μm.

[0121] The third particles PTC3 further include a grain boundary coating portion, which enhances structural stability and allows a uniform coating layer to be formed on the surface of the third particles PTC3. In addition, the third particles PTC3 further include a grain boundary coating portion, which further improves the electrical conductivity of the third particles PTC3.

[0122] The third particles PTC3 may further contain carbon derived from the coating layer and / or the grain boundary coating layer. The carbon element content in the third particles PTC3 may be 0.5 wt% to 10 wt%, 1 wt% to 3 wt%, or 1.5 wt% to 2.5 wt%. For example, the carbon content in the third particles PTC3 in the form of secondary particles may be higher than that in the form of single particles.

[0123] The third particles PTC3 may have a spherical shape formed by agglomeration of a plurality of third primary particles NNP_3. The third particles PTC3 may exhibit the following properties due to the third primary particles NNP_3 being closely agglomerated to one another: The above-described coating layer and / or grain boundary coating layer of the third particles are well maintained, thereby increasing electrical conductivity and improving low-temperature characteristics. The increased electrode plate binding strength reduces the binder capacity. The third particles PTC3 may have a spherical or elliptical shape.

[0124] The porosity of the third particles PTC3 may be about 20% to about 40%. The Span value of the third particles PTC3 analyzed with a particle size analyzer may be 0.3 to 0.75.

[0125] The positive electrode active material layer AML1 according to an embodiment of the present invention will be described in more detail below.

[0126] The positive electrode or the positive electrode active material layer AML1 may contain manganese (Mn). The total doping amount of manganese (Mn) can be calculated by the following formula: Total Mn doping amount = [Number of Mn atoms in the first particle (z1) × Weight ratio of the first particle / Molecular weight of the first particle] + [Number of Mn atoms in the second particle (x2) × Weight ratio of the second particle / Molecular weight of the second particle] + [Number of Mn atoms in the third particle (z3) × Weight ratio of the third particle / Molecular weight of the third particle] In the above formula, the weight ratio of the first particles may refer to the weight ratio of the first particles to the total weight of the first particles, the second particles, and the third particles.

[0127] The total doping amount of manganese (Mn) in the positive electrode active material layer AML1 may be 0.50 to 0.90, 0.50 to 0.70, 0.60 to 0.80, 0.60 to 0.70, or 0.50 to 0.60.

[0128] The weight of the second particles PTC2 relative to the total weight of the first particles PTC1, the second particles PTC2, and the third particles PTC3 in the positive electrode active material layer AML1 may be 5 wt% to 20 wt%, 10 wt% to 20 wt%, 15 wt% to 30 wt%, 20 wt% to 30 wt%, or 25 wt% to 25 wt%.

[0129] According to an embodiment of the present invention, the positive electrode active material layer AML1 may have a double layer structure in which a second positive electrode active material layer ATL2 is stacked on a first positive electrode active material layer ATL1. The positive electrode active material layer AML1 may include a functional additive ADD. The first positive electrode active material layer ATL1 may include a first functional additive ADD1, and the second positive electrode active material layer ATL2 may include a second functional additive ADD2. The functional additive ADD may refer to at least one of the first functional additive ADD1 and the second functional additive ADD2.

[0130] The functional additives may include a conductive material CDM and a binder BND. The inclusion of the functional additives can improve the performance of the positive electrode active material layer. For example, the functional additives can better bind materials in the positive electrode active material layer to each other, improving the electrode plate adhesion and the conductivity of the positive electrode active material layer.

[0131] When the first particles PTC1 have a secondary particle shape, the amount of functional additive ADD required in the active material can be reduced compared to when the first particles PTC1 have a single particle shape. Also, by including both the first particles PTC1 and the second particles PTC2 in the first positive electrode active material layer ATL1, the weight ratio of the functional additive ADD required in the active material layer can be reduced.

[0132] For example, a relatively large amount of binder BND1 is required to adhere first particles PTC1, which have a small average particle size, to current collector COL1, but a relatively small amount of binder BND is required to adhere second particles PTC2, which have a large average particle size, to current collector COL1. The weight ratio of the binder BND required can be reduced by using the first positive electrode active material layer ATL1 including the first particles PTC1 and the second particles PTC2.

[0133] The positive electrode active material layer AML1 of the present invention includes the first positive electrode active material layer ATL1 which requires a relatively small amount of functional additive, thereby enabling improvement in energy density.

[0134] The dual-layer structure facilitates the fabrication of electrode plates. More specifically, a first cathode active material layer ATL1, which contains a mixture of first particles PTC1 and second particles PTC2, can be first laminated on a current collector, and then a second cathode active material layer ATL2 can be laminated on the first cathode active material layer ATL1. This reduces the amount of binder BND required compared to when the first cathode active material layer ATL1, which has excellent electrode plate binding strength, is first laminated on the current collector, resulting in improved energy density. In particular, by first laminating the first cathode active material layer ATL1 on the portion that contacts the current collector, the resistance of the electrode plate can be improved.

[0135] The weight ratio of the first binder BND1 in the first positive electrode active material layer ATL1 may be 1.2 wt % to 2.0 wt %.

[0136] The weight ratio of the second binder BND2 in the second positive electrode active material layer ATL2 may be 2.0 wt % to 3.0 wt %.

[0137] The weight ratio of the first binder BND1 in the first positive electrode active material layer ATL1 may be smaller than the weight ratio of the second binder BND2 in the second positive electrode active material layer ATL2. In one embodiment, the ratio of the weight ratio of the second binder BND2 to the weight ratio of the first binder BND1 may be 0.8 to 2.6.

[0138] The weight ratio of the first conductive material CDM1 in the first positive electrode active material layer ATL1 may be 1.2 wt % to 2.0 wt %.

[0139] The weight ratio of the second conductive material CDM2 in the second positive electrode active material layer ATL2 may be 2.0 wt % to 3.0 wt %.

[0140] The weight ratio of the first conductive material CDM1 in the first positive electrode active material layer ATL1 may be smaller than the weight ratio of the second conductive material CDM2 in the second positive electrode active material layer ATL2. In one embodiment, the ratio of the weight ratio of the second conductive material CDM2 to the weight ratio of the first conductive material CDM1 may be 0.65 to 4.5.

[0141] The weight ratio of the first functional additive ADD1 in the first positive electrode active material layer ATL1 may be 2.4 wt % to 4.0 wt %.

[0142] The weight ratio of the second functional additive ADD2 in the second positive electrode active material layer ATL2 may be 4.0 wt % to 6.0 wt %.

[0143] The weight ratio of the first functional additive ADD1 in the first positive electrode active material layer ATL1 may be smaller than the weight ratio of the second functional additive ADD2 in the second positive electrode active material layer ATL2.

[0144] In one embodiment, the weight ratio of the second functional additive to the weight ratio of the first functional additive may be 1.0 to 2.0, 1.5 to 2.5, or 1.5 to 3.0.

[0145] The first positive electrode active material layer ATL1 may have a thickness T1. In one embodiment, T1 may increase as the weight of the first particles PTC1 and the second particles PTC2 included in the first positive electrode active material layer ATL1 increases. The second positive electrode active material layer ATL2 may have a thickness T2. In one embodiment, T2 may increase as the weight of the third particles PTC3 included in the second active material layer ATL2 increases. In one embodiment, the ratio of T2 to T1 (T2 / T1) may be 0.4 to 2.0, 0.8 to 1.5, 0.9 to 1.2, or about 1. Within this range, excellent high voltage performance and energy density may be maintained while improving stability and life characteristics.

[0146] In one embodiment, the compressed density of the positive electrode active material layer AML1 of the present invention may be 2.0 g / cc to 2.5 g / cc.

[0147] In one embodiment, the loading level of the first positive electrode active material layer ATL1 is 5 mg / cm 2 ~10mg / cm 2 The loading level of the second positive electrode active material layer ATL2 may be 5 mg / cm. 2 ~25mg / cm 2 It could be.

[0148] A lithium secondary battery including the positive electrode active material of the present invention can have improved low-temperature characteristics. In one embodiment, the capacity at −20° C. relative to the initial capacity of the lithium secondary battery (capacity at −20° C. / initial capacity) may be 40% or more. For example, the capacity at −20° C. relative to the initial capacity of the lithium secondary battery of the present invention (capacity at −20° C. / initial capacity) may be 40% to 100%, 50% to 100%, or 96% to 99%.

[0149] A lithium secondary battery including the positive electrode active material of the present invention can have an improved operating voltage. In one embodiment, the operating voltage range of the lithium secondary battery of the present invention may be 3 V to 5 V. For example, the operating voltage range may be 3 V to 4.5 V, or 3.5 V to 4 V.

[0150] A lithium secondary battery including the positive electrode active material of the present invention can have improved life characteristics. In one embodiment, the lithium secondary battery of the present invention can have a capacity retention rate of 98% or more after 50 charge / discharge cycles at a constant current of 0.1 C at the above-mentioned voltage. For example, the capacity retention rate can be 98% to 100%, or 99.8% to 100%.

[0151] Method for producing positive electrode active material Hereinafter, the present invention will be described with reference to Preparation Examples, Examples, and Comparative Examples. However, the following Examples are merely examples of the present invention, and the present invention is not limited to the following Examples.

[0152] Preparation Example 1: Preparation of secondary particle-type first particles PTC1 Mn 0.6 Fe 0.4 Manganese iron phosphate precursor (PO4), lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.004. 10 wt% glucose was added to the mixture. The slurry mixture was spray-dried at a spray pressure of 0.5 MPa and a temperature of 230°C, followed by evaporation. The dried mixture was calcined at 750°C for 10 hours in a nitrogen atmosphere to obtain primary particles in the form of secondary particles. The average size of the primary particles within the primary particles was approximately 50 nm to approximately 150 nm.

[0153] Preparation Example 2: Preparation of secondary particles PTC2 0.170g of MnSO4H2O and 0.228g of (NH4)2S2O8 were dissolved in 100ml of distilled water, and sulfuric acid was added to adjust the pH to 1. The reaction was carried out at 130°C for 10 hours to obtain a solid precipitate. The obtained precipitate was washed several times with distilled water and dried at 300°C for 3 hours to obtain solid MnO2 with an average particle size of 5μm.

[0154] Li2CO3 and synthesized MnO2 were mixed so that the molar ratio of Li to Mn was 1:2, and heated at 600°C for 10 hours to synthesize LiMn2O4 particles with an average particle size of 7 μm and an average primary particle size of 0.5 μm to 2.5 μm.

[0155] Preparation Example 3-1: Preparation of single particle type third particle PTC3 Mn 0.6 Fe 0.4 Manganese iron phosphate precursor (PO4), lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.004. 10 wt% glucose was added to the mixture. The mixture was wet-pulverized using a ball mill. The mixture was evaporated to dryness in a heating oven tray and then placed in a vacuum oven at 120°C for 4 hours. The dried mixture was calcined at 750°C for 10 hours under a nitrogen atmosphere. The calcined product was pulverized to obtain third particles in the form of single particles. The average size of the third particles was approximately 100 nm to approximately 200 nm.

[0156] Preparation Example 3-2: Preparation of secondary particle-type third particles PTC3 Mn 0.6 Fe 0.4 Manganese iron phosphate precursor (PO4), lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.004. 10 wt% glucose was added to the mixture. The slurry mixture was spray-dried at a spray pressure of 0.5 MPa and a temperature of 230°C, followed by evaporation. The dried mixture was calcined at 750°C for 10 hours in a nitrogen atmosphere to obtain third particles in the form of secondary particles. The average size of the primary particles within the third particles was approximately 50 nm to approximately 150 nm.

[0157] Single-layer electrode plate manufacturing Comparative Example 1-1 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed in a weight ratio of 30:70 and dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a positive electrode active material slurry. The positive electrode active material slurry was applied to a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0158] Comparative Example 1-2 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed in a weight ratio of 42:58 to prepare a positive electrode active material slurry in the same manner as in Comparative Example 1-1, and a single-layer electrode plate was manufactured.

[0159] Comparative Examples 1-3 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed in a weight ratio of 56:44 to prepare a positive electrode active material slurry in the same manner as in Comparative Example 1-1, and a single-layer electrode plate was manufactured.

[0160] Comparative Examples 1-4 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed in a weight ratio of 70:30 to prepare a positive electrode active material slurry in the same manner as in Comparative Example 1-1, and a single-layer electrode plate was manufactured.

[0161] Comparative Examples 1-5 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed in a weight ratio of 83:17 to prepare a positive electrode active material slurry in the same manner as in Comparative Example 1-1, and a single-layer electrode plate was manufactured.

[0162] Comparative Examples 1-6 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed in a weight ratio of 95:5 to prepare a positive electrode active material slurry in the same manner as in Comparative Example 1-1, and a single-layer electrode plate was manufactured.

[0163] Comparative Examples 1-7 The first particles of Preparation Example 1, the second particles of Preparation Example 2, and the third particles of Preparation Example 3-1 were mixed in a weight ratio of 41.5:17:41.5 to prepare a positive electrode active material slurry in the same manner as in Comparative Example 1-1, and a single-layer electrode plate was manufactured.

[0164] Double-layered electrode plate manufacturing Example 1-1 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particles of Preparation Example 3-1 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0165] The first positive electrode active material slurry was applied to a positive electrode current collector and dried to form a first positive electrode active material layer, and the second positive electrode active material slurry was applied to the first positive electrode active material layer and dried to form a second positive electrode active material layer.

[0166] The active material layers were formed so that the weight ratio of the first particles, second particles, and third particles in the double-layered positive electrode was 41.5:17:41.5. Roll pressing was performed to fabricate a positive electrode in which the current collector, the first positive electrode active material layer, and the second positive electrode active material layer were sequentially stacked.

[0167] Examples 1-2 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particles of Preparation Example 3-2 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0168] The first positive electrode active material slurry was applied to a positive electrode current collector and dried to form a first positive electrode active material layer, and the second positive electrode active material slurry was applied to the first positive electrode active material layer and dried to form a second positive electrode active material layer.

[0169] The active material layers were formed so that the weight ratio of the first particles, second particles, and third particles in the double-layered positive electrode was 41.5:17:41.5. Roll pressing was performed to fabricate a positive electrode in which the current collector, the first positive electrode active material layer, and the second positive electrode active material layer were sequentially stacked.

[0170] Example 2-1 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particles of Preparation Example 3-1 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0171] The first positive electrode active material slurry was applied to a positive electrode current collector and dried to form a first positive electrode active material layer, and the second positive electrode active material slurry was applied to the first positive electrode active material layer and dried to form a second positive electrode active material layer.

[0172] At this time, the active material layer was formed so that the weight ratio of the first particles, second particles, and third particles in the double-layered positive electrode was 35:30:35. A roll press was performed to manufacture a positive electrode in which the current collector, the first positive electrode active material layer, and the second positive electrode active material layer were sequentially stacked.

[0173] Example 2-2 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particles of Preparation Example 3-2 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0174] The first positive electrode active material slurry was applied to a positive electrode current collector and dried to form a first positive electrode active material layer, and the second positive electrode active material slurry was applied to the first positive electrode active material layer and dried to form a second positive electrode active material layer.

[0175] At this time, the active material layer was formed so that the weight ratio of the first particles, second particles, and third particles in the double-layered positive electrode was 35:30:35. A roll press was performed to manufacture a positive electrode in which the current collector, the first positive electrode active material layer, and the second positive electrode active material layer were sequentially stacked.

[0176] Comparative Example 2-1 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particles of Preparation Example 3-1 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0177] Unlike Example 1-1, the second positive electrode active material slurry was first coated on the positive electrode current collector and dried to form a first positive electrode active material layer, and then the first positive electrode active material slurry was coated on the first positive electrode active material layer and dried to form a second positive electrode active material layer.

[0178] The active material layers were formed so that the weight ratio of the first particles, second particles, and third particles in the double-layered positive electrode was 41.5:17:41.5. Roll pressing was performed to fabricate a positive electrode in which the current collector, the first positive electrode active material layer, and the second positive electrode active material layer were sequentially stacked.

[0179] Comparative Example 2-2 The first particles of Preparation Example 1 and the second particles of Preparation Example 2 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particles of Preparation Example 3-2 were dispersed in N-methylpyrrolidone together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0180] Unlike Examples 1 and 2, the second positive electrode active material slurry was first coated on the positive electrode current collector and dried to form a first positive electrode active material layer, and then the first positive electrode active material slurry was coated on the first positive electrode active material layer and dried to form a second positive electrode active material layer.

[0181] The active material layers were formed so that the weight ratio of the first particles, second particles, and third particles in the double-layered positive electrode was 41.5:17:41.5. Roll pressing was performed to fabricate a positive electrode in which the current collector, the first positive electrode active material layer, and the second positive electrode active material layer were sequentially stacked.

[0182] Anode manufacturing Graphite, a binder, and a conductive material were mixed in N-methylpyrrolidone solvent to prepare a negative electrode active material slurry. The negative electrode active material slurry was applied to a copper current collector, dried, and then rolled to prepare a negative electrode.

[0183] Lithium secondary battery manufacturing A coin half cell was fabricated using the prepared positive and negative electrodes. A polypropylene membrane (Celgard 3510) was used as the separator. The electrolyte was a solution prepared by mixing 1.3M LiPF6 with a mixed solvent of EC (ethylene carbonate): DEC (diethyl carbonate): FEC (fluoroethylene carbonate) (2:6:2 volume ratio).

[0184] Evaluation example 1: Analysis of the surface of the positive electrode active material FIG. 9 shows an SEM image of the first particles prepared in Preparation Example 1. FIG. 10 shows an SEM image of the second particles prepared in Preparation Example 2. Referring to FIG. 9, it can be seen that the first particles according to an embodiment of the present invention are spherical secondary particles formed by the aggregation of fine nano-sized primary particles. Referring to FIG. 10, it can be seen that the second particles according to an embodiment of the present invention are secondary particles formed by the aggregation of multiple primary particles. Compared to the first particles, it can be seen that the second particles have various shapes and the primary particle size is larger.

[0185] Evaluation example 2: Positive electrode characteristic analysis The pellet density (PD) and energy density (ED) of the positive electrode active material layers prepared in Examples 1-1 to 2-2 and Comparative Examples 1-1 to 2-2 were measured, and the results are shown in Table 1.

[0186] [Table 1]

[0187] Referring to Table 1, it can be seen that the positive electrode active material layers according to Examples 1-1 to 2-2 have higher energy densities than those of Comparative Examples 1-1 to 1-4. Furthermore, compared to the single-layer structures of Comparative Examples 1-4, 1-5, and 1-7, the pellet density and energy density can be maintained at similar levels. It can be seen that the positive electrode active material layers according to the embodiments have high energy densities of 485 Wh / kg or more, which can mean that they have energy densities suitable for commercial use.

[0188] Evaluation example 3: Battery characteristic evaluation The characteristics of the lithium secondary batteries fabricated using the positive electrodes of Examples 1-1 to 2-2 and Comparative Examples 1-1 to 2-2 were evaluated.

[0189] The lithium secondary battery was initially charged under constant current (0.2C) and constant voltage (4.25V) conditions, and after a 10-minute rest, discharged at a constant current (0.2C) until the voltage reached 2.5V. The initial charge-discharge cycle was then performed by repeating 50 charge-discharge cycles at 1.0C / 1.0C at 45°C. An additional coin cell was also fabricated and the 0.2C capacity was measured at -20°C. The battery characteristic evaluation results are shown in Table 2 below.

[0190] [Table 2]

[0191] Referring to Table 2, the positive electrodes of Examples 1-1 to 2-2 had improved capacity retention rates when tested for 50 cycles or more at 1C rate and 2C rate, compared to the positive electrodes of Comparative Examples 1-4, 1-5, and 1-7 having a single layer structure.

[0192] The double layer structure improves the binding strength and stability of the active material compared to a single layer structure containing the same active material, thereby improving battery performance. A smaller amount of functional additives is required for cathode production, resulting in improved energy density.

[0193] Furthermore, the inclusion of low-resistance second particles in the first positive electrode active material layer in contact with the current collector reduces the resistance of the positive electrode, which is significantly lower than the positive electrodes of Comparative Examples 1-4, 1-5, and 1-7, and is also significantly lower than the double-layer structures of Comparative Examples 2-1 and 2-2.

[0194] In the case of Examples 1-1 to 2-2, the first particles, the second particles, and the third particles are appropriately mixed, and when the average voltage, the energy density, and the life characteristics are taken into consideration as a whole, the positive electrode can be used as a long-life positive electrode with excellent characteristics.

[0195] Evaluation Example 4: Content of functional additives in active material layer The weight ratio of functional additives required for manufacturing the positive electrodes of the single-layer structures of Comparative Examples 1-1 to 1-7 was measured.

[0196] The weight ratio of the functional additive in the first positive electrode active material layer and the weight ratio of the functional additive in the second positive electrode active material layer required for manufacturing the positive electrodes in the double layer structures of Comparative Examples 2-1 and 2-2 were measured.

[0197] The weight ratios of the functional additives in the first and second positive electrode active material layers of the positive electrodes of Examples 1-1 to 2-2 were measured. The weight ratios of the functional additives in the active material layers are shown in Table 3 below.

[0198] [Table 3]

[0199] According to one embodiment of the present invention, the weight ratio of the first positive electrode active material layer may be smaller than the weight ratio of the second positive electrode active material layer. According to another embodiment of the present invention, the weight ratio of the first positive electrode active material layer may be the same as the weight ratio of the second positive electrode active material layer. By first forming the first positive electrode active material layer through the combination of the first positive electrode active material slurry, the amount of functional additive required to laminate the first positive electrode active material layer on the current collector can be reduced, resulting in easier cathode manufacturing, and electrode plate manufacturing can be facilitated.

[0200] Unlike the embodiment of the present invention, Comparative Example 2-1 is a case where the active material constituting the first positive electrode active material layer and the active material constituting the second positive electrode active material layer are reversed, and in this case, it is found that the amount of functional additive required to form the first positive electrode active material layer on the current collector is increased.

[0201] The above-described content is a specific example for carrying out the present invention. The present invention may include not only the above-described examples, but also examples that can be simply modified or easily changed. The present invention may also include techniques that can be easily implemented by modifying the embodiments. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be defined by the following claims as well as equivalents to the claims of the present invention. [Explanation of symbols]

[0202] 100 Lithium secondary battery 10 positive electrode 11 Positive electrode lead tab 12 Positive terminal 20 negative electrode 21 Negative electrode lead tab 22 Negative terminal 30 Separator 40 Electrode assembly 50 cases 60 Sealing member 70 Electrode tab 71 Positive electrode tab 72 Negative electrode tab

Claims

1. A current collector; a first positive electrode active material layer on the current collector; a second positive electrode active material layer on the first positive electrode active material layer, The first positive electrode active material layer includes first particles having an olivine structure, which includes a compound represented by Chemical Formula 1 below, and second particles having a spinel structure, which includes a compound represented by Chemical Formula 2 below: The second positive electrode active material layer includes third particles having an olivine structure, the third particles including a compound represented by the following Chemical Formula 3: The first particles have a secondary particle shape formed by agglomeration of a plurality of primary particles. [Chemical formula 1] Li a1 Mn z1 Fe x1 B1 y1 PO 4-c1 In Formula 1, B1 is one or more elements selected from the group consisting of Al, Ti, V, and Mg, and 0.8<a1≦1.2, 0.4≦z1≦0.8, 0.2≦x1≦0.6, 0≦y1≦0.05, and 0<c1≦0.05; [Chemical formula 2] Li a2 Mn x2 B2 y2 O 4-c2 In Formula 2, B2 is one or more elements selected from the group consisting of Al and Mg, and 0.8<a2≦1.2, 1.9≦x2≦2.05, 0≦y2≦0.05, and 0<c2≦0.05; [Chemical formula 3] Li a3 Mn z3 Fe x3 B3 y3 PO 4-c3 In Formula 3, B3 is one or more elements selected from the group consisting of Al, Ti, V, and Mg, and 0.8<a3≦1.2, 0.4≦z3≦0.8, 0≦x3≦0.6, 0≦y3≦0.05, and 0<c3≦0.

05.

2. the third particles have a secondary particle shape formed by agglomeration of a plurality of primary particles, the average size of the plurality of primary particles of the third particles is 50 nm to 150 nm; The positive electrode for a lithium secondary battery according to claim 1 , wherein the third particles have an average particle size (D50) of 3 μm to 7 μm.

3. the third particles have a single particle shape, 2. The positive electrode for a lithium secondary battery according to claim 1, wherein the third particles have an average particle size (D50) of 0.5 μm to 2.5 μm.

4. 2. The positive electrode for a lithium secondary battery according to claim 1, wherein a weight ratio of the second particles to a total weight of the first particles, the second particles, and the third particles in the positive electrode is 15 wt % to 30 wt %.

5. 2. The positive electrode for a lithium secondary battery according to claim 1, wherein the total doping amount of manganese (Mn) in the positive electrode is 0.50 to 0.

90.

6. 2. The positive electrode for a lithium secondary battery according to claim 1, wherein a thickness ratio of the second positive electrode active material layer to the first positive electrode active material layer is 0.8 to 1.

2.

7. an average size of the plurality of primary particles of the first particle is 50 nm to 150 nm; The positive electrode for a lithium secondary battery according to claim 1 , wherein the first particles have an average particle size (D50) of 3 μm to 7 μm.

8. The positive electrode for a lithium secondary battery according to claim 1 , wherein the porosity of the first particles is 20% to 40%.

9. 2. The positive electrode for a lithium secondary battery according to claim 1, wherein the first particles have a Span value of 0.3 to 0.75 as analyzed by a particle size analyzer.

10. the second particles have a secondary particle shape formed by agglomeration of a plurality of primary particles, 2. The positive electrode for a lithium secondary battery according to claim 1, wherein the average particle size (D50) of the secondary particles is 3 μm to 10 μm.

11. A current collector; a first positive electrode active material layer on the current collector; a second positive electrode active material layer on the first positive electrode active material layer, The first positive electrode active material layer includes first particles having an olivine structure, which include a compound represented by Chemical Formula 1 below; second particles having a spinel structure, which include a compound represented by Chemical Formula 2 below; and a first functional additive: The second positive electrode active material layer includes a compound represented by the following Chemical Formula 3, and includes third particles having an olivine structure and a second functional additive: each of the first and second functional additives includes a conductive material and a binder; A positive electrode for a lithium secondary battery, wherein a weight ratio of the first functional additive in the first positive electrode active material layer is smaller than a weight ratio of the second functional additive in the second positive electrode active material layer. [Chemical formula 1] Li a1 Mn z1 Fe x1 B1 y1 PO 4-c1 In Formula 1, B1 is one or more elements selected from the group consisting of Al, Ti, V, and Mg, and 0.8<a1≦1.2, 0.4≦z1≦0.8, 0.2≦x1≦0.6, 0≦y1≦0.05, and 0<c1≦0.05; [Chemical formula 2] Li a2 Mn x2 B2 y2 O 4-c2 In Formula 2, B2 is one or more elements selected from the group consisting of Al and Mg, and 0.8<a2≦1.2, 1.9≦x2≦2.05, 0≦y2≦0.05, and 0<c2≦0.05; [Chemical formula 3] Li a3 Mn z3 Fe x3 B3 y3 PO 4-c3 In Formula 3, B3 is one or more elements selected from the group consisting of Al, Ti, V, and Mg, and 0.8<a3≦1.2, 0.4≦z3≦0.8, 0≦x3≦0.6, 0≦y3≦0.05, and 0<c3≦0.

05.

12. 12. The positive electrode for a lithium secondary battery according to claim 11, wherein the weight ratio of the second functional additive to the first functional additive is 1.5 to 3.

0.

13. 12. The positive electrode for a lithium secondary battery according to claim 11, wherein the weight ratio of the first functional additive is 2.4 wt% to 4.0 wt%.

14. 12. The positive electrode for a lithium secondary battery according to claim 11, wherein the weight ratio of the second functional additive is 4.0 wt% to 6.0 wt%.

15. 12. The positive electrode for a lithium secondary battery of claim 11, wherein the binder comprises at least one selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, an epoxy resin, a (meth)acrylic resin, a polyester resin, and nylon.

16. 12. The positive electrode for a lithium secondary battery according to claim 11, wherein a total weight of the second particles is 15 wt% to 30 wt% of a total weight of the first particles, the second particles, and the third particles in the positive electrode.

17. 12. The positive electrode for a lithium secondary battery according to claim 11, wherein a thickness ratio of the second positive electrode active material layer to the first positive electrode active material layer is 0.8 to 1.

2.

18. 12. The positive electrode for a lithium secondary battery according to claim 11, wherein a total doping amount of manganese (Mn) in the positive electrode is 0.50 to 0.

90.

19. 12. The positive electrode for a lithium secondary battery according to claim 11, wherein a total doping amount of manganese (Mn) in the positive electrode is 0.50 to 0.

60.

20. A lithium secondary battery comprising the positive electrode according to claim 1.

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