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 operation voltage, and high conductivity.SOLUTION: The present invention relates to a positive electrode active material for a lithium secondary battery, a manufacturing method for the same, and a lithium secondary battery including the same. More specifically, the positive electrode active material includes first particles containing a compound of Chemical Formula 1 and second particles containing a compound of Chemical Formula 2. The positive electrode active material contains cobalt (Co) by 100 ppm or less.SELECTED DRAWING: Figure 6a

Description

[Technical Field]

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

[0002] Recently, with the rapid spread of electronic devices that use batteries, such as mobile phones, laptops, and electric vehicles, the demand for high-energy-density, high-capacity secondary batteries is rapidly increasing. As a result, research and development efforts to improve the performance of lithium secondary batteries are being actively conducted (Patent Document 1).

[0003] A lithium secondary battery is a battery that includes a cathode and an anode, each containing an active material capable of intercalating and deintercalating lithium ions, and an electrolyte. Electrical energy is produced through oxidation and reduction reactions that occur when lithium ions are intercalated and deintercalated at the cathode and anode.

[0004] In order to provide a positive electrode active material having a high energy density, a high operating voltage, and a high electrical conductivity, a technique using a mixture of different lithium transition metal oxides as a positive electrode material has been attempted. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Korean Patent No. 10-2227302 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a positive electrode active material having high energy density, high operating voltage, and high conductivity.

[0007] Another problem to be solved by the present invention is to provide a secondary battery including a positive electrode active material and having a high energy density, a high operating voltage, and a high conductivity.

Means for Solving the Problem

[0008] The positive electrode active material according to the concept of the present invention may include first particles containing a compound of Chemical Formula 1 below and second particles containing a compound of Chemical Formula 2 below. [Chemical Formula 1] Li a1 Mn z1 Fe x1 A y1 PO 4-c1 In Chemical Formula 1, 0.8 < a1 ≤ 1.2, 0.8 ≤ x1 ≤ 0.9, 0 ≤ y1 ≤ 0.05, 0.1 ≤ z1 ≤ 0.2, 0 < c1 ≤ 0.05, and x1 + y1 + z1 = 1, and A is at least one element selected from the group consisting of Ti, Mg, V, and Nb. [Chemical Formula 2] Li a2 Ni x2 Mn z2 X c2 O 2-b2 In Chemical Formula 2, 0.8 < a2 ≤ 1.2, 0.7 ≤ x2 ≤ 0.8, 0.2 ≤ z2 ≤ 0.3, 0 < b2 ≤ 0.05, 0 ≤ c2 ≤ 0.05, and x2 + z2 + c2 = 1, and X may be at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb. The content of cobalt (Co) in the positive electrode active material may be less than 100 ppm.

[0009] The positive electrode for a lithium secondary battery according to another concept of the present invention may include a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material, a conductive material, and a binder.

[0010] A lithium secondary battery according to another aspect of the present invention may include a positive electrode, a negative electrode including a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, and a separator between the positive electrode and the negative electrode. [Effects of the Invention]

[0011] The cathode active material according to the present invention may have improved mix density, capacity, high-voltage characteristics, and energy density by mixing olivine-based first particles of several micrometers in size with layered-type second particles of several micrometers in size. The cathode active material layer according to the present invention may be smoothly attached to the cathode current collector with a relatively small amount of binder. The lithium secondary battery according to the present invention may have a relatively high average voltage. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a conceptual diagram illustrating a lithium secondary battery according to an embodiment of the present invention; [Figure 2] 1 is a schematic diagram showing a lithium secondary battery according to an embodiment, which can be said to have a cylindrical battery shape. [Figure 3] 1 is a schematic diagram showing a lithium secondary battery according to an embodiment, which can be said to have a prismatic battery shape. [Figure 4] 1 is a schematic diagram showing a lithium secondary battery according to an embodiment, which can be said to have a pouch-type battery configuration. [Figure 5] 1 is a schematic diagram showing a lithium secondary battery according to an embodiment, which can be said to have a pouch-type battery configuration. [Figure 6a] 2 is an enlarged view of a positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention. FIG. [Figure 6b] FIG. 6B is an enlarged view of the positive electrode active material layer obtained by enlarging FIG. 6A. [Figure 6c] 2 is an enlarged view of a positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention. FIG. [Figure 7a] 1 is an SEM image of the positive electrode active material of Comparative Example 1-3 of the present invention. [Figure 7b] 1 is an SEM image of the positive electrode active material of Comparative Example 1-5 of the present invention. [Figure 8a]1 is an SEM image of the positive electrode active material of Comparative Example 1-7 of the present invention. [Figure 8b] 1 is an SEM image of the positive electrode active material of Comparative Example 1-6 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] In this specification, when a component is referred to as being on another component, it means that the component may be directly formed 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.

[0014] 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 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.

[0015] 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.

[0016] As used herein, "combinations thereof" can mean mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0017] 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.

[0018] 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 solution ELL.

[0019] The positive electrode 10 and the negative electrode 20 may be separated from each other by a separator 30. The separator 30 may be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be in contact with an electrolyte solution ELL. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated in the electrolyte solution ELL.

[0020] 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.

[0021] 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 FIG. 6. The current collector COL1 may be made of, but is not limited to, aluminum.

[0022] negative electrode 20 The lithium secondary battery positive electrode 20 may include a current collector COL2 and a negative electrode active material layer AML2 formed 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.

[0023] For example, the negative electrode active material layer AML2 may contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0% to 5% by weight of the conductive material.

[0024] 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.

[0025] 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.

[0026] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyether resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0027] When an aqueous binder is used as the negative electrode binder, it may further contain a cellulose-based compound to 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.

[0028] The dry binder is a fiberizable polymeric material, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, ethylene oxide, or combinations thereof.

[0029] The conductive material is used to impart conductivity to the electrode and may be any material that is electronically conductive and does not cause chemical changes in the battery. 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.

[0030] As the current collector COL2, those selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metals, and combinations thereof can be used.

[0031] negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 includes a material capable of reversibly inserting / desorbing lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping or undoping lithium, or a transition metal oxide.

[0032] The material capable of reversibly inserting / desorbing lithium ions is a carbon-based negative electrode active material, which may include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, and examples of amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0033] 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.

[0034] As the material capable of doping or undoping 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.

[0035] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and the surfaces of the silicon particles coated with amorphous carbon. For example, the composite may include secondary particles (cores) formed by combining primary silicon particles, and an amorphous carbon coating layer (shell) located on the surfaces of the secondary particles. Amorphous carbon may also be located between the primary silicon particles; for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0036] The silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may comprise a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer disposed on the core.

[0037] The Si-based negative electrode active material or the Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0038] 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. Such separator 30 may be made of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, but 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.

[0039] Separator 30 may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0040] The porous substrate may be a polymer membrane made 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 copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon, and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0041] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0042] The inorganic materials may include, but are 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.

[0043] The organic material and the inorganic material may be mixed in one coating layer, or a coating layer containing an organic material and a coating layer containing an inorganic material may be stacked.

[0044] Electrolyte ELL The electrolyte ELL for lithium secondary batteries contains a non-aqueous organic solvent and a lithium salt.

[0045] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can migrate.

[0046] The non-aqueous organic solvent can be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, a non-quantum solvent, or a combination thereof.

[0047] Examples of carbonate solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl pyrrolyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0048] 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.

[0049] 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 non-quantum solvents that can be used include nitriles such as R-CN (R is a hydrocarbon group having 2 to 20 carbon atoms and having a linear, branched, or cyclic structure, and 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.

[0050] The non-aqueous organic solvents may be used alone or in combination of two or more.

[0051] 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 cyclic carbonate may be mixed in a volume ratio of 1:1 to 1:9.

[0052] 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+1 SO2) (x and y are positive numbers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0053] Lithium secondary battery Lithium secondary batteries may be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 2 to 5 are schematic diagrams illustrating a lithium secondary battery according to an embodiment, with FIG. 2 illustrating a cylindrical battery, FIG. 3 illustrating a prismatic battery, and FIGS. 4 and 5 illustrating pouch battery types. Referring to FIGS. 2 to 4, 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 housing 50 in which the electrode assembly 40 is embedded. 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 housing 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 the current generated in the positive electrode assembly 40 to the outside.

[0054] A 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.

[0055] FIG. 6a is an enlarged view of a positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention, and FIG. 6b is an enlarged view of FIG. 6a.

[0056] FIG. 6c is an enlarged view of a positive electrode active material layer of a lithium secondary battery according to another embodiment of the present invention.

[0057] 6a, 6b, and 6c, as described above, the positive electrode active material layer AML1 (see FIG. 1) may include first particles PTC1, second particles PTC2, a conductive material CDM, and a binder BND. The plurality of first particles PTC1 and the plurality of second particles PTC2 may constitute a positive electrode active material according to an embodiment of the present invention.

[0058] The content of the positive electrode active materials PTC1 and PTC2 in the positive electrode active material layer AML1 may be 90 to 99.5 wt % relative to 100 wt % of the positive electrode active material layer AML1, and the content of the binder BND and the conductive material CDM may be 0.5 to 5 wt % relative to 100 wt % of the positive electrode active material layer AML1.

[0059] The binder BND may bind the first particles PTC1, the second particles PTC2, and the conductive material CDM to one another. As an example, the binder BND may include at least one selected from the group consisting of, but not limited to, 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)acrylic styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0060] The conductive material CDM can be used to improve the conductivity of the positive electrode active material layer AML1. Any conductive material that does not cause chemical changes in the positive electrode active material layer AML1 can be used as the conductive material CDM without limitation. For example, the conductive material CDM can include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, metal-based materials in the form of metal powders or metal fibers containing copper, nickel, aluminum, silver, etc., conductive polymers such as polyphenylene derivatives, or mixtures thereof.

[0061] 1st particle PTC1 The first particle PTC1 may contain an olivine-based lithium compound represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Mn z1 Fe x1 A y1 PO 4-c1 In Chemical Formula 1, 0.8 < a1 ≤ 1.2, 0.8 ≤ x1 ≤ 0.9, 0 ≤ y1 ≤ 0.05, 0.1 ≤ z1 ≤ 0.2, 0 < c1 ≤ 0.05, and x1 + y1 + z1 = 1 may hold.

[0062] A can be at least one element selected from the group consisting of Ti, Mg, V, and Nb. A can be a dopant doped into the first particle PTC1.

[0063] When doping Ti into the first particle PTC1, it is possible to achieve the effect of controlling the growth of the first primary particles NNP of the first particle PTC1, and as a result, the size of the first primary particles NNP of the first particle PTC1 can be made smaller. When doping Ti into the first particle PTC1, the size of the first primary particles NNP can be uniformly grown, and as a result, the low-temperature characteristics can be improved.

[0064] FIG. 6c is an enlarged view of a cathode active material according to an embodiment of the present invention. Referring to FIGS. 6c and 7a, the first particle 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 morphological phase in which particles exist as an independent phase without aggregation, a monolith structure, a single body structure, or a non-aggregated particle. 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 two to 100 first primary particles are attached to each other. In this specification, a first particle PTC1 that is a single particle may be defined as a first single particle SP1.

[0065] As an example, the average particle size may refer to the diameter of particles that make up 50% by volume of the cumulative volume in the particle size distribution (D50).

[0066] The average particle size (D50) of the first particles PTC1 may be a value measured by a chromatograph. Accordingly, the average particle size (D50) of the first single particles SP1 in FIG. 6c may be 0.1 μm to 2.5 μm. The average particle size (D50) of the first single particles SP1 according to this embodiment may be smaller than the average particle size (D50) of the second single particles SP2, which will be described later.

[0067] The first particle PTC1 according to this embodiment may include at least one first primary particle (or single particle). The size of the at least one first primary particle constituting one first particle PTC1 according to this embodiment may be 100 nm to 200 nm when measured using a scanning electron microscope (SEM). In one embodiment, the size of the first primary particle may refer to the diameter measured by randomly selecting about 30 first primary particles from an electron microscope image of the positive electrode active material. The size of the first primary particles may be uniform.

[0068] As an example, the first particles PTC1 may include a first 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.

[0069] The first 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.

[0070] 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.

[0071] 6a and 6b are enlarged views of a positive electrode active material layer according to an embodiment of the present invention. Figure 7b is an SEM image of a positive electrode active material according to an embodiment of the present invention. Referring to Figures 6a and 6b or 7b, the first particles PTC1 are polycrystalline and may include secondary particles formed by agglomeration of at least two or more first primary particles NNP. In other words, one first particle PTC1 may include a plurality of first primary particles NNP agglomerated together. The first particles PTC1, which are made up of a plurality of first primary particles NNP, may have a spherical or elliptical shape.

[0072] In this specification, the first particles PTC1, which are secondary particles, may be defined as first secondary particles PC1.

[0073] For example, the first particle PTC1 may include a coating layer on its surface. The coating layer may cover the entire surface of the first particle PTC1 or may cover only a portion of the surface of the first particle PTC1. The coating layer may be present inside the first particle PTC1. The coating layer may be formed by coating along the interfaces between the internal particles of the first particle PTC1. For example, the coating layer may include carbon and / or a carbon-containing compound. A uniform coating layer may be formed on the surface of the first particle PTC1, and the coating layer may improve structural stability. Further including a coating layer may improve electrical conductivity.

[0074] 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. Metal-containing compounds such as titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds may be, for example, metal oxides, metal hydroxides, metal carbonates, composites thereof, or mixtures thereof. The metal-containing compounds may further include other metals or non-metal elements. For example, the metal-containing compounds may further include lithium.

[0075] The metal-containing compound may further comprise at least one selected from the group consisting of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds. The metal-containing compounds, such as titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds, may be, for example, metal oxides, metal hydroxides, metal carbonates, composites thereof, or mixtures thereof. The metal-containing compounds may further comprise other metals or non-metal elements. For example, the metal-containing compounds may further comprise lithium.

[0076] As an example, the first particle PTC1 may further include a grain boundary coating layer on the surface of each of the first primary particles NNP. 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 inside the first particle PTC1. In other words, 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 contain carbon and / or a carbon-containing compound. The grain boundary coating layer may further contain 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 the region from a depth of about 10 nm from the surface of the first particle PTC1 to the entire inside, or from a depth of 10 nm to a depth of about 2 μm.

[0079] The first particles PTC1 may further include a grain boundary coating portion, which may enhance structural stability and form a uniform coating layer on the surface of the first particles PTC1, and may further improve the electrical conductivity of the first particles PTC1.

[0080] The first particles PTC1 may further contain carbon derived from the coating layer and / or grain boundary coating layer. The carbon element content in the first particles PTC1 may be 0.5 to 10 wt %, 1 to 3 wt %, or 1.5 to 2.5 wt %. For example, the carbon content of the secondary particle-like first particles PTC1 shown in Figure 7b may be higher than the carbon content of the single particle-like first particles PTC1 shown in Figure 7a.

[0081] The first particles PTC1 may have a spherical shape formed by agglomeration of a plurality of first primary particles NNP. The first particles PTC1 may exhibit the following properties due to the first primary particles NNP 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 adhesive strength may reduce the capacity of the binder. The first particles PTC1 may have a spherical or elliptical shape.

[0082] As an example, the average particle size may be measured using a particle size analyzer. The average particle size may refer to the diameter of particles with a cumulative volume of 50% (D50) in the particle size distribution. The average particle size (D50) of the first secondary particles PC1 of the present invention measured using this method may be 3 μm to 10 μm.

[0083] The first particle PTC1 according to this embodiment may include at least one primary particle (or single particle). The size of at least one first primary particle NNP constituting one first particle PTC1 according to this embodiment may be 50 nm to 150 nm. Compared to the single particle first particle PTC1 shown in Figure 6c, the size of the first primary particle NNP constituting the first particle PTC1, which is a secondary particle according to this embodiment, may be smaller than the first primary particle NNP constituting the single particle first particle PTC1.

[0084] In one embodiment, the size of the first primary particles NNP may refer to the diameter measured by randomly selecting about 30 first primary particles NNP from an electron microscope photograph of the positive electrode active material. The size of the first primary particles NNP may be uniform.

[0085] The porosity of the first secondary particles PC1 may be about 20% to 40%. The Span value of the first secondary particles PC1 analyzed by a particle size analyzer may be 0.3 to 0.75.

[0086] When the first particles PTC1 are in the form of secondary particles, the first secondary particles PC1 have a large average particle size, so a relatively small amount of binder BND may be required to attach the first particles to the current collector COL1 (see FIG. 1). For example, the content of binder BND may be 0.5 wt % to 3 wt % relative to 100 wt % of the positive electrode active material layer AML1.

[0087] The lithium secondary battery containing the positive electrode active material of the present invention can have improved low-temperature characteristics. As an example, the capacity at -20°C compared to the initial capacity of the lithium secondary battery (capacity at -20°C / initial capacity) can be 40% or more. For example, the capacity at -20°C compared to the initial capacity of the lithium secondary battery of the present invention (capacity at -20°C / initial capacity) can be 40% to 100%, 50% to 100%, or 96% to 99%.

[0088] The lithium secondary battery containing the positive electrode active material of the present invention can have an improved operating voltage. As an example, the operating voltage range of the lithium secondary battery of the present invention can be 3V to 5V. For example, the operating voltage range can be 3V to 4.5V, or 3.5V to 4V.

[0089] The lithium secondary battery containing the positive electrode active material of the present invention can have improved life characteristics. As an example, the capacity retention rate of the lithium secondary battery of the present invention after charging and discharging 50 times at a constant current of 1.0C at the above-mentioned voltage can be 98% or more. For example, the capacity retention rate can be 98% to 100%, or 99.8% to 100%.

[0090] In the present invention, the first particle PTC1 can exist as a single particle or a secondary particle. In this specification, both the first single particle SP1 and the first secondary particle PC1 can be interpreted as meaning the first particle PC1. Also, the first particle PTC1 can be interpreted as encompassing the first single particle SP1 and the first secondary particle PC1.

[0091] 2nd particle PTC2 The second particle PTC2 can contain a layered lithium compound represented by the following chemical formula 2. [Chemical formula 2] Li a2 Ni x2 Mn z2 X c2 O 2-b2 In Chemical formula 2, 0.8 < a2 ≤ 1.2, 0.7 ≤ x2 ≤ 0.8, 0.2 ≤ z2 ≤ 0.3, 0 < b2 ≤ 0.05, 0 ≤ c2 ≤ 0.05, and x2 + z2 + c2 = 1 can hold.

[0092] X may be at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb. X may be a dopant doped into the second particles PTC2.

[0093] The cobalt (Co) content in the positive electrode active material may be less than 100 ppm. In other words, the positive electrode active material according to the present invention may be substantially free of cobalt (Co). The positive electrode active material according to the present invention may be a cobalt-free positive electrode active material. The Co content in the second particles may be less than the Al content in the second particles.

[0094] Positive electrode active materials for lithium secondary batteries can be expressed as layered cobalt-free (Co-free) positive electrode active materials, cobalt-free nickel-based positive electrode active materials, or cobalt-free nickel-manganese-based positive electrode active materials. Cobalt-free can mean that there is no cobalt, that no cobalt is used, or that only a very small amount of cobalt is contained.

[0095] For example, the second particles PTC2 may include a second coating layer on their surfaces. The coating layer may cover the entire surface of the second particles PTC2 or may cover only a portion of the surface of the second particles PTC2. The coating layer may include a boron-containing compound, a titanium-containing compound, an aluminum-containing compound, or a combination thereof. The metal-containing compound in the second coating layer may be, for example, a metal oxide, a metal hydroxide, a metal carbonate, a composite thereof, or a mixture thereof. The compounds constituting these coating layers may be crystalline or amorphous. The metal-containing compound may further include other metals or non-metal elements. For example, the second coating layer may further include lithium, manganese, and / or nickel. Surface modification using a coating layer may stabilize the structure and improve thermal stability.

[0096] Referring to Figures 6a, 6b, 6b, and 8b, the second particles PTC2 may have a single particle shape. In this specification, a single particle may refer to a single particle without an internal particle boundary. A single particle may refer to a morphological phase in which particles exist as an independent phase without agglomeration, a monolith structure, a single body structure, or a non-aggregated particle. For example, the single particle may be a single crystal. For example, the single particle may have a form in which multiple second primary particles MMP are attached to each other. Alternatively, the single particle may have a form in which 2 to 100 second primary particles MMP are attached to each other. In this specification, the second particles PTC2 that are single particles may be defined as second single particles SP2. In addition, in this specification, the second single particles SP2 may be defined as small particles.

[0097] As an example, the average particle size may refer to the diameter (D50) of particles with a cumulative volume of 50% in a particle size distribution. The average particle size (D50) of the second particles PTC2 may be a value measured using a chromatographic analyzer. Accordingly, the average particle size (D50) of the second single particles SP2 may be 3 μm to 7 μm. The average particle size (D50) of the second single particles SP2 may be larger than the average particle size (D50) of the first single particles SP1.

[0098] Referring to Figures 6a, 6b, 6c, and 8a, the second particles PTC2 may be polycrystalline and may include secondary particles formed by agglomeration of at least two or more second primary particles MMP. In other words, one second particle PTC2 may include a plurality of second primary particles MMP agglomerated together. The second particles PTC2 formed by a plurality of second primary particles MMP may have a spherical or elliptical shape. In this specification, the second particles PTC2, which are secondary particles, may be defined as first secondary particles PC2. In addition, in this specification, the second secondary particles PC2 may be defined as large particles.

[0099] As an example, the average particle size may refer to the diameter (D50) of particles with a cumulative volume of 50% in a particle size distribution. The average particle size (D50) of the second particles PTC2 may be a value measured using a spectrometer. Accordingly, the average particle size (D50) of the second secondary particles PC2 may be 12 μm to 18 μm. The average particle size (D50) of the second secondary particles PC2 may be larger than the average particle size (D50) of the first secondary particles PC1.

[0100] In the present invention, the second particles PTC2 may exist as single particles or secondary particles, and may be a positive electrode active material including second single particles SP2 and second secondary particles PC2.

[0101] In this specification, the second single particle SP2 and the second secondary particle PC2 may both be interpreted as meaning the second particle PTC2, and the second particle PTC2 may be interpreted as including the second single particle SP2 and the second secondary particle PC2 therein.

[0102] In the present invention, the positive electrode active material is said to be bimodal when the second particles PTC2 coexist in the form of single particles and secondary particles, or when the second particles PTC2 coexist in the form of large particles and small particles.

[0103] Hereinafter, a cathode active material according to an embodiment of the present invention will be described in more detail. The first particles PTC1 are a lithium iron phosphate compound with an olivine structure, which is very stable and has high chemical stability. While its stable structure generally provides superior lifespan characteristics compared to other cathode materials, its lifespan deteriorates when used at high voltages, limiting the operating voltage. The first particles PTC1 contain manganese (Mn), which can improve high-voltage characteristics and energy density compared to typical lithium iron phosphate compounds.

[0104] In the case of the first particles PTC1, manganese (Mn) may be eluted. The crystal grain size of the first particles PTC1 may become too small. As shown in FIG. 6c, if the size of the first particles PTC1 is too small, the adhesive strength between the current collector and the positive electrode active material may be weak, making electrode plate processing difficult and requiring a large amount of binder.

[0105] As shown in Figures 6a and 6b, when the first particles PTC1 are made of secondary particles, the electrode plate adhesion strength is improved and the binder BND content can be reduced. When the first particles PTC1 are made of secondary particles, the carbon coating is well maintained, the conductivity is high, and low-temperature characteristics can be improved. As a result, the capacity can be increased and the life characteristics can be improved.

[0106] The second particles PTC2 may include a Co-free lithium nickel manganese oxide. The second particles PTC2 may be substantially free of cobalt (Co) and may include nickel, manganese, etc. as major components. A positive electrode active material including the second particles PTC2 may be economical and achieve high energy density.

[0107] Lithium nickel manganese oxides exhibit higher composite density when pressed than olivine structure compounds, and can therefore alleviate the problem of low electrode density that olivine structure phosphate compounds have.

[0108] In the present invention, by mixing the first particles PTC1 with the second particles PTC2 in an appropriate ratio, density characteristics, high temperature stability, and life characteristics can be improved. In addition, by mixing the second particles in a bimodal form of large particles and small particles, further improved density can be obtained.

[0109] In one embodiment, the content of the first particles PTC1 may be 60 wt% to 90 wt% of the total content of the first particles PTC1 and the second particles PTC2 in the positive electrode active material. In one embodiment, the content of the second particles PTC2, which are larger particles, may be 60 wt% to 80 wt% of the total content of the second particles PTC2 in the positive electrode active material. In one embodiment, the content of manganese (Mn) in the first particles PTC1 may be greater than the content of manganese (Mn) in the second particles PTC2 in the positive electrode active material. In one embodiment, the composite density of the positive electrode active material of the present invention may be 2.5 g / cc to 3.0 g / cc.

[0110] Comparative Example 1-1: Production of single particle-shaped first particles Iron phosphate precursor FePO4 and lithium carbonate were added at a molar ratio of 1:1.03. Glucose was also added at 7 wt% of the mixture mass. The mixture was subjected to a wet grinding process using a ball mill. The mixture was evaporated to dryness on a heating oven tray and then placed in a vacuum oven at 85°C for 4 hours. The dried mixture was calcined at 650°C for 10 hours under a nitrogen atmosphere. The calcined product was pulverized to obtain single-particle primary particles.

[0111] Comparative Example 1-2: Production of single particle-shaped first particles In the first particles of Comparative Example 1-1, the doping amount of Ti was increased to 2,000 ppm.

[0112] Comparative Example 1-3: Production of single particle-shaped first particles Iron phosphate precursor FePO4, manganese phosphate MnPO4, and lithium carbonate were added in a molar ratio of 0.85:0.15:1.03. Additionally, 7 wt% glucose and 2000 ppm TiO2 were added. The mixture was subjected to a wet grinding process using a ball mill. The mixture was evaporated to dryness on a heating furnace tray and then placed in a vacuum oven at 85°C for 4 hours. The dried mixture was then calcined at 650°C for 10 hours under a nitrogen atmosphere. The calcined product was then pulverized to obtain single-particle primary particles.

[0113] Comparative Example 1-4: Production of primary particles in the form of secondary particles Iron phosphate precursor FePO4 and potassium carbonate were added in a molar ratio of 1:1.03. 7 wt% glucose and 2000 ppm TiO2 were also added. The mixture was wet-pulverized using a ball mill. 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 700°C for 10 hours in a nitrogen atmosphere to obtain secondary particle-like positive electrode active material.

[0114] Comparative Example 1-5: Production of primary particles in the form of secondary particles Iron phosphate precursor FePO4, manganese phosphate MnPO4, and lithium carbonate were added in a molar ratio of 0.85:0.15:1.03. Additionally, 7 wt% glucose and 2000 ppm TiO2 were added based on the mixture mass. The mixture was subjected to a wet milling process using a ball mill. The Mn doping amount in the first particles of Comparative Example 1-4 was increased to 109,600 ppm.

[0115] 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 700°C for 10 hours in a nitrogen atmosphere to obtain secondary particle-like positive electrode active material.

[0116] Comparative Example 1-6: Production of single particle-shaped second particles Ni 0.75 Mn 0.23 Al 0.02 (OH)2 and LiOH were mixed in a molar ratio of 1:1.05 and subjected to a first heat treatment at 900°C for 8 hours in an oxygen atmosphere. 1.05 Ni 0.75 Mn 0.23 Al 0.02 O2 was used to prepare a second oxide having an average particle size (D50) of approximately 4 μm. Aluminum oxide was added to this oxide, and a second heat treatment was performed at 825°C for 8 hours in an oxygen atmosphere to prepare a positive electrode active material.

[0117] Comparative Example 1-7: Production of secondary particles Ni 0.75 Mn 0.23 Al 0.02 (OH)2 and LiOH were mixed in a molar ratio of 1:1.05 and subjected to a first heat treatment at 850°C for 8 hours in an oxygen atmosphere. 1.05 Ni 0.75 Mn 0.23 Al 0.02 O2 was used to prepare a second oxide having an average particle size (D50) of approximately 14 μm. Aluminum oxide was added to this oxide, and a second heat treatment was performed at 825°C for 8 hours in an oxygen atmosphere to prepare a positive electrode active material.

[0118] It is in the form of secondary particles formed by agglomeration of multiple primary particles, and LiNi 0.75 Mn0.22 Al 0.03 A second particle of O2 composition was produced.

[0119] Comparative Example 1-8: Preparation of bimodal second particles Second particles were prepared by mixing the second particles of Comparative Example 1-6 and the second particles of Comparative Example 1-7 in a ratio of 30:70.

[0120] Example 1-1: Preparation of a mixture of first particles and second particles The first particles of Comparative Example 1-5 and the second particles of Comparative Example 1-6 were mixed in a ratio of 70:30 to produce a positive electrode active material.

[0121] Example 1-2: Preparation of a mixture of first particles and second particles The first particles of Comparative Example 1-5 and the second particles of Comparative Example 1-8 were mixed in a ratio of 80:20 to produce a positive electrode active material.

[0122] Examples 1-3: Preparation of a mixture of first particles and second particles The first particles of Comparative Example 1-5 and the second particles of Comparative Example 1-8 were mixed in a ratio of 70:30 to produce a positive electrode active material.

[0123] Examples 1-4: Preparation of a mixture of first particles and second particles The first particles of Comparative Example 1-5 and the second particles of Comparative Example 1-8 were mixed in a ratio of 60:40 to produce a positive electrode active material.

[0124] The positive electrode active materials produced are summarized in Table 1 below.

[0125] [Table 1]

[0126] Cathode manufacturing 95% by weight of the final positive electrode active material, 3% by weight of polyvinylidene fluoride binder, and 2% by weight of carbon black conductive material were mixed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry. The positive electrode active material slurry was applied to an aluminum current collector, dried, and then rolled to prepare a positive electrode.

[0127] Anode manufacturing Graphite, a binder, and a conductive material were mixed in N-methylpyrrolidone solvent to prepare a negative electrode active material slurry, which was then coated on a copper current collector, dried, and rolled to prepare a negative electrode.

[0128] Lithium secondary battery manufacturing A 2032-type coin half-cell was fabricated using the prepared positive electrode and a lithium metal counter electrode as the counter electrode. A separator (approximately 16 μm thick) made of porous polyethylene (PE) film was placed between the positive electrode and the lithium metal counter electrode, and an electrolyte was injected to fabricate a lithium secondary battery. The electrolyte used was a mixture of 1.3 M LiPF6 with a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethylene carbonate (DMC) in a volume ratio of 3:4:3.

[0129] Evaluation example 1: Analysis of the surface of the positive electrode active material Figure 7b shows an SEM image of the first particles prepared in Comparative Examples 1-5. Figure 8b shows an SEM image of the second particles prepared in Comparative Examples 1-6. Figure 8a shows an SEM image of the second particles prepared in Comparative Examples 1-7. Referring to Figure 7b, it can be seen that the first particles are spherical secondary particles of several microns in size. Referring to Figures 8a and 8b, it can be seen that the second particles have a larger average particle size than the first particles.

[0130] Evaluation example 2: Evaluation of battery characteristics The characteristics of secondary batteries fabricated using the positive electrode active materials of the Examples and Comparative Examples were evaluated.

[0131] The lithium secondary battery was initially charged at a constant current (0.2C), rested for 10 minutes, and then discharged at a constant current (0.2C) to 3.0V to evaluate the average voltage. It was then charged and discharged 50 times at 1.0C / 1.0C at 45°C. An additional coin cell was fabricated and initially charged at a constant current (0.2C), rested for 10 minutes, and then discharged at a constant current (0.2C) to 3.0V to evaluate the average voltage. The capacity was then measured at -20°C. The battery characteristics evaluation results are shown in Table 2 below.

[0132] [Table 2]

[0133] Referring to Table 2, Example 1-1 of the present invention is a mixture of first particle PTC1 and second particle PTC2, which is a single particle, and it can be seen that the voltage is improved and the charge / discharge capacity is also increased compared to Comparative Examples 1-4 to 1-7.

[0134] The cathode active materials according to Examples 1-2 to 1-4 of the present invention are characterized in that the second particles PTC2 are bimodal, unlike Example 1-1. As a result, it can be seen that the evaluation voltage and average voltage are improved compared to the secondary batteries according to Comparative Examples 1-4 and 1-5, and the performance is also improved compared to Example 1-1.

[0135] Also, it can be seen that the secondary batteries according to Examples 1-1 to 1-4 of the present invention have increased charge / discharge efficiency and significantly improved capacity at -20°C compared to the secondary batteries according to Comparative Examples 1-6 to 1-8.

[0136] Evaluation example 3: Evaluation of active material density characteristics The average pellet density (PD) and capacity per volume of the positive electrode active materials in the above Examples and Comparative Examples were measured, and the results are shown in Table 3.

[0137] [Table 3]

[0138] Referring to Table 3, it can be seen that the positive electrode active material according to Example 1-1 of the present invention has higher average mixture density and capacity per unit volume than the positive electrode active materials according to Comparative Examples 1-4 to 1-7. The cathode active materials according to Examples 1-2 to 1-4 of the present invention are bimodally mixed with the second particles PTC2, and it can be seen that the average mixture density and capacity per unit volume are further increased compared to the cathode active material according to Example 1-1. The above is a specific embodiment for carrying out the present invention. The present invention includes not only the above-described embodiment but also embodiments that can be easily modified or changed. The present invention also includes 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 embodiment, but should be determined not only by the claims below but also by equivalents to the claims of the present invention.

Claims

1. First particles including a compound represented by the following Chemical Formula 1: and second particles including a compound represented by the following Chemical Formula 2: [Chemical formula 1] Li a1 Mn z1 Fe x1 A y1 2O 4-c1 In Chemical Formula 1, 0.8<a1≦1.2, 0.8≦x1≦0.9, 0≦y1≦0.05, 0.1≦z1≦0.2, 0<c1≦0.05, and x1+y1+z1=1; A is at least one element selected from the group consisting of Ti, Mg, V, and Nb; [Chemical formula 2] Li a2 Ni x2 Mn z2 X c2 O 2-b2 In Chemical Formula 2, 0.8<a2≦1.2, 0.7≦x2≦0.8, 0.2≦z2≦0.3, 0<b2≦0.05, 0≦c2≦0.05, and x2+z2+c2=1, and X is at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb; The content of cobalt (Co) in the positive electrode active material is less than 100 ppm.

2. The positive electrode active material of claim 1 , wherein the second particles include small particles and large particles.

3. The positive electrode active material of claim 1 , wherein the average particle size of the small particles of the second particles is 3 μm to 7 μm.

4. The positive electrode active material of claim 1 , wherein the average particle size of the large second particles is 12 μm to 18 μm.

5. 2. The positive electrode active material of claim 1, wherein the content of the large particles of the second particles is 60% by weight to 80% by weight with respect to the total content of the second particles.

6. The positive electrode active material of claim 1 , wherein the content of the first particles is 60 wt % to 90 wt % of the total content of the first particles and the second particles.

7. The positive electrode active material according to claim 1 , wherein z1 is greater than z2.

8. The positive electrode active material of claim 1 , wherein the first particles have a secondary particle shape formed by agglomeration of a plurality of primary particles.

9. The positive electrode active material of claim 8 , wherein the first particles have an average particle size (D50) of 3 μm to 10 μm.

10. The positive electrode active material of claim 8 , wherein the first particles have a first primary particle size of 50 nm to 150 nm.

11. The positive active material of claim 8 , wherein the first particles have a Span value of 0.3 to 0.75 as analyzed by a particle size analyzer.

12. The positive electrode active material of claim 8 , wherein the first particles have a porosity of 20% to 40%.

13. 2. The positive electrode active material according to claim 1, wherein the positive electrode active material has a compressed density of 2.5 g / cc to 3.0 g / cc.

14. a positive electrode current collector; a positive electrode active material layer on the positive electrode current collector, A positive electrode for a lithium secondary battery, wherein the positive electrode active material layer comprises the positive electrode active material according to claim 1 , a conductive material, and a binder.

15. 15. The positive electrode for a lithium secondary battery according to claim 14, wherein the content of the binder is 0.5 to 5 parts by weight with respect to 100 parts by weight of the positive electrode active material layer.

16. 15. The positive electrode for a lithium secondary battery according to claim 14, 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, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

17. 15. The positive electrode for a lithium secondary battery according to claim 14, wherein the content of the conductive material is 0.5 to 5 parts by weight with respect to 100 parts by weight of the positive electrode active material layer.

18. 15. The positive electrode for a lithium secondary battery according to claim 14, wherein the conductive material comprises a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, or carbon nanotube; a metal-based material in the form of a metal powder or metal fiber containing copper, nickel, aluminum, silver, or the like; a conductive polymer such as a polyphenylene derivative; or a mixture thereof.

19. The positive electrode according to claim 14; a negative electrode including a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector; a separator between the positive electrode and the negative electrode.

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