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 being economical and having high energy density and an excellent lifetime characteristic.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 a first particle containing a compound expressed by Chemical Formula 1 and having an olivine structure, a second particle containing a compound expressed by Chemical Formula 2 and having a spinel structure, and a third particle containing a compound expressed by Chemical Formula 3. The first particle and the second particle form a main active material. Based on 100 parts by weight of the positive electrode active material, the content amount of the main active material is 95 parts by weight to 99.5 parts by weight.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 increase in battery-powered electronic devices such as mobile phones, laptop computers, and electric vehicles, the demand for high-energy-density, high-capacity secondary batteries has been rapidly increasing. Accordingly, research and development efforts to improve the performance of lithium secondary batteries have been actively pursued.

[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 from the cathode and the anode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Korean Patent Application Publication No. 10-2021-0080249 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 and excellent life characteristics.

[0006] Another problem to be solved by the present invention is to provide an economical lithium secondary battery having high energy density and high efficiency. [Means for solving the problem]

[0007] According to the concept of the present invention, the positive electrode active material can include a first particle containing a compound of Chemical Formula 1 below and having an olivine structure, a second particle containing a compound of Chemical Formula 2 below and having a spinel structure, and a third particle containing a compound of Chemical Formula 3 below. The first particle and the second particle can constitute the main active material. Based on 100 parts by weight of the positive electrode active material, the content of the main active material is 95 to 99.5 parts by weight, and based on 100 parts by weight of the positive electrode active material, the content of the third particle can be 0.5 to 5 parts by weight. [Chemical Formula 1] Li a1 Fe x1 B y1 PO 4-b1 In Chemical Formula 1, 0.8 ≤ a1 ≤ 1.2, 0.95 ≤ x1 ≤ 1.0, 0 ≤ y1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, and x1 + y1 = 1, and B can be at least one element selected from the group consisting of Al, Ti, V, and Mg. [Chemical Formula 2] Li a2 Mn x2 Cy2O 4-b2 In Chemical Formula 2, 0.8 ≤ a2 ≤ 1.2, 1.9 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, and 0 ≤ b2 ≤ 0.05, and C can be at least one element selected from the group consisting of Al and Mg. [Chemical Formula 3] Li a3 Co x3 D y3 O 4-b3 In Chemical Formula 3, 5.9 < a3 ≤ 6.1, 0.9 ≤ x3 ≤ 1.05, 0 ≤ y3 ≤ 0.05, 0 ≤ b3 ≤ 0.05, and D can be at least one element selected from the group consisting of Al and Mg.

[0008] According to another aspect of the present invention, a positive electrode for a lithium secondary battery 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 the above-described positive electrode active material, a conductive material, and a binder.

[0009] According to yet another aspect of the present invention, a lithium secondary battery can include the above-described positive electrode active material. [Effects of the Invention]

[0010] The positive electrode active material according to the present invention includes olivine-based first particles, thereby improving economic efficiency, structural stability, and life characteristics.

[0011] The positive electrode active material according to the present invention can improve the average voltage by including the spinel-based second particles.

[0012] The positive electrode active material according to the present invention can improve the capacity and energy density by including a small amount of third particles that function as a sacrificial positive electrode.

[0013] The positive electrode active material according to the present invention can improve energy density and life characteristics while ensuring economic efficiency by mixing the first particles, the second particles, and the third particles in an appropriate ratio. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a conceptual diagram showing 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 configuration. [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 6] 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 7] 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 8A] 1 is an SEM image of the positive electrode active material of Production Example 1-1 of the present invention. [Figure 8B] 1 is an SEM image of the positive electrode active material of Production Example 1-2 of the present invention. [Figure 9] 1 is an SEM image of the positive electrode active material of Preparation Example 1-3 of the present invention. [Figure 10] 1 is an SEM image of the positive electrode active material of Preparation Example 1-4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] In order to fully understand the configuration and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various forms and may undergo various modifications. However, the description of the present embodiments is provided to ensure complete disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0016] 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.

[0017] 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.

[0018] As used herein, "combinations thereof" can mean mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0019] 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 using 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The dry binder is a fiberizable polymeric material, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, ethylene oxide, or combinations thereof.

[0031] The conductive material is used to impart conductivity to the electrode and may be any material that does not cause chemical changes in the constructed battery and is electronically conductive. 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.

[0032] 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.

[0033] 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, a lithium metal alloy, a material capable of doping or dedoping lithium, or a transition metal oxide.

[0034] 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 or artificial graphite. Examples of amorphous carbon include soft or hard carbon, mesophase pitch carbide, and calcined coke.

[0035] 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.

[0036] As a substance that can be doped or undoped 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.

[0037] 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) combined with primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon can also be located between the primary silicon particles. 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.

[0038] 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 an amorphous carbon coating layer located on the surface of the core.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 (registered trademark), and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0043] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0044] 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.

[0045] 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.

[0046] Electrolyte ELL The electrolyte ELL for lithium secondary batteries contains a non-aqueous organic solvent and a lithium salt.

[0047] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can migrate.

[0048] 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.

[0049] 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).

[0050] 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.

[0051] 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.

[0052] The non-aqueous organic solvents may be used alone or in combination of two or more.

[0053] 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.

[0054] 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).

[0055] 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 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 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.

[0056] 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.

[0057] 6 and 7 are enlarged views of a positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention. Referring to Figures 6 and 7, as described above, the positive electrode active material layer AML1 (see Figure 1) may include first particles PTC1, second particles PTC2, third particles PTC3, a conductive material CDM, and a binder BND. The plurality of first particles PTC1, the plurality of second particles PTC2, and the plurality of third particles PTC3 may constitute a positive electrode active material according to an embodiment of the present invention.

[0058] The positive electrode active material layer AML1 may further include an additive that can function as a sacrificial positive electrode.

[0059] The content of the positive electrode active materials PTC1, PTC2, and PTC3 in the positive electrode active material layer AML1 may be 90 wt % to 99.5 wt % relative to 100 wt % of the positive electrode active material layer AML1. The content of the binder BND and the conductive material CDM may be 0.5 wt % to 5 wt % relative to 100 wt % of the positive electrode active material layer AML1.

[0060] The binder BND can bind the first particles PTC1, the second particles PTC2, the third particles PTC3, and the conductive material CDM to one another. As an example, the binder BND 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 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.

[0061] A 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 a chemical change 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 fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, and the like; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0062] The first particles PTC1, the second particles PTC2, and the third particles PTC3 will be described in more detail below.

[0063] 1st particle PTC1 The first particles PTC1 may include a lithium compound having an olivine structure represented by the following Chemical Formula 1. [Chemical formula 1] Li a1 Fe x1 B y1 PO 4-b1

[0064] In Chemical Formula 1, 0.8≦a1≦1.2, 0.95≦x1≦1.0, 0≦y1≦0.05, 0≦b1≦0.05, and x1+y1=1, and B may be at least one element selected from the group consisting of Al, Ti, V, and Mg. B may be a dopant doped into the first particle PTC1.

[0065] The dopant can have the effect of controlling the uniform growth of the first primary particles of the first particles PTC1, thereby improving the charge / discharge efficiency, low temperature characteristics, and life characteristics of the lithium secondary battery.

[0066] The first particle PTC1 has the advantages of being highly economical, structurally stable, and having excellent lifespan characteristics. Because it is mainly composed of Fe, it is relatively inexpensive and structurally stable, so chemical changes can be relatively small even after repeated charging and discharging.

[0067] As an example, 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 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 improve the structural stability of the first particles PTC1 and thereby improve electrical conductivity.

[0068] The coating layer may further include at least one selected from the group consisting of an aluminum-containing compound, a titanium-containing compound, a magnesium-containing compound, and a vanadium-containing compound. Metal-containing compounds such as aluminum-containing compounds, 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.

[0069] The first particles PTC1 may further contain carbon derived from the 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 %.

[0070] The first particles PTC1 may be in the form of single particles and / or secondary particles. For example, the first particles PTC1 may exist only in the form of single particles, only in the form of secondary particles, or in the form of a mixture of single particles and secondary particles. Hereinafter, the first particles PTC1 in the form of single particles will be described with reference to FIG. 6, and the first particles PTC1 in the form of secondary particles PTC2 will be described with reference to FIG. 7.

[0071] As an example, referring to FIG. 6, the first particle PTC1 may have a single particle shape. In this specification, a single particle may refer to a single particle having no 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 and are not aggregated with each other. 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 isolated form. Alternatively, a single particle may be in a form in which 2 to 100 single particles are attached to each other.

[0072] When the first particles PTC1 are single particles, the first particles PTC1 may include at least one first primary particle. In one embodiment, the first particles PTC1 may have a spherical or elliptical shape formed by agglomeration 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 are agglomerated.

[0073] When the first particles PTC1 are single particles, the first particles PTC1 can be provided in various sizes. For example, the average particle size of the first particles PTC1 can be 0.5 μm to 2.5 μm, or about 1 μm. The minimum particle size of the first particles PTC1, i.e., the size of the first primary particles, can be 100 nm to 500 nm, or 200 nm to 300 nm.

[0074] As an example, the average particle size can be measured using a particle size analyzer. The average particle size can refer to the diameter of particles whose cumulative volume is 50% by volume (D50) in the particle size distribution.

[0075] As an example, the minimum particle size, i.e., the size of the first primary particles, may refer to the diameter measured by randomly selecting about 30 primary particles from an electron microscope photograph of the first particles PTC1.

[0076] When the first particles PTCl are single particles, the porosity of the first particles PTCl may be less than 30%. The Span value of the first particles PTCl analyzed by a particle size analyzer may be outside the range of 0.3 to 0.75.

[0077] As another example, referring again to FIG. 7, the first particles PTC1 may be in the form of secondary particles. The secondary particles may be in the form of polycrystals, which means that at least two or more first primary particles are aggregated together. In other words, one first particle PTC1 may include a plurality of first primary particles aggregated together. The first particles PTC1 may have a spherical or elliptical shape.

[0078] As an example, when the first particles PTC1 are in the form of secondary particles, the first particles PTC1 may further include a grain boundary coating layer on the surface of each of the first primary particles. The grain boundary coating layer may be present inside the first particles PTC1. The grain boundary coating layer may be formed by coating along the interface between the first primary particles inside the first particles PTC1. In other words, the grain boundary coating layer may refer to a material coated on the grain boundaries inside the first particles PTC1. 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 an aluminum-containing compound, a titanium-containing compound, a magnesium-containing compound, and a vanadium-containing compound.

[0079] When the first particle PTC1 is a secondary particle, the interior of the first particle PTC1 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.

[0080] When the first particles PTC1 are secondary particles, 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.

[0081] When the first particles PTC1 are secondary particles, 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%. When the first particles PTC1 are secondary particles, the carbon content may be higher than when the first particles PTC1 are single particles.

[0082] When the first particles PTC1 are secondary particles, the average particle size of the first particles PTC1 may be 2 μm to 15 μm, 3 μm to 10 μm, or 3 μm to 7 μm. For example, the average particle size of the first particles PTC1 may be about 5 μm. In one example, the average particle size can be measured using a particle size analyzer. The average particle size may refer to the diameter of particles whose cumulative volume is 50% by volume (D50) in the particle size distribution.

[0083] When the first particles PTC1 are secondary particles, the average size of the first primary particles may be 200 nm or less. For example, the average size of the first primary particles may be 10 nm to 200 nm, 20 nm to 200 nm, 50 nm to 200 nm, or 100 nm to 200 nm. In one embodiment, the average size of the first primary particles may refer to the diameter measured by randomly selecting approximately 30 primary particles from an electron microscope image of the positive electrode active material. The size of the first primary particles may be uniform.

[0084] When the first particles PTC1 are secondary particles, the size of the first primary particles may be smaller than when the first particles PTC1 are single particles. For example, when the first particles PTC1 are in the form of secondary particles, the size of the first primary particles may be about 100 nm smaller than when the first particles PTC1 are in the form of single crystals.

[0085] When the first particles PTC1 are secondary particles, if the average particle size and the average size of the first primary particles of the first particles PTC1 satisfy the above-described ranges and the size of the first primary particles is uniform, the charge / discharge capacity and low-temperature capacity of a lithium secondary battery containing the same can be improved.

[0086] When the first particles PTC1 are secondary particles, 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.

[0087] When the first particle PTC1 is a secondary particle, the first particle PTC1 can be smoothly attached to the current collector COL1 (see FIG. 1) with only a relatively small amount of the binder BND. For example, the content of the binder BND can be 0.5% to 3% by weight based on 100% by weight of the positive electrode active material layer AML1. This is due to the increase in the interaction between the first particle PTC1 and the current collector COL1 (see FIG. 1) because the average particle size of the first particle PTC1 is large. Reducing the content of the binder contained in the positive electrode active material layer AML1 (see FIG. 1) can increase the active material content accordingly, thereby bringing about the effect of improving the capacity and energy density of the battery. Also, reducing the content of the binder that increases the resistance can bring about the effect of improving the electrical conductivity of the positive electrode. [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​The dopant can have the effect of controlling the uniform growth of the second primary particles, thereby improving the charge / discharge efficiency, low temperature characteristics, and life characteristics of the lithium secondary battery.

[0092] The second particles PTC2 have advantages of high output characteristics, high average voltage, and excellent structural stability. The second particles PTC2 may have a spinel structure composed of tetrahedral and octahedral lattice structures. The lattice structure has various passages, allowing smooth insertion / extraction of lithium ions, resulting in excellent output characteristics. The lattice structure may be made more stable by the Mn in the second particles PTC2. This structural stability allows the particles to maintain their electrochemical properties even at high voltages, allowing them to operate at high voltages.

[0093] The second particles PTC2 may be a lithium manganese oxide cathode material in which cobalt in lithium cobalt oxide is replaced with manganese. In one embodiment of the present invention, the cobalt (Co) content of the second particles PTC2 may be so small that it is essentially eliminated. For example, the cobalt (Co) content of the second particles PTC2 may be 100 ppm or less. The cathode active material according to the present invention substantially eliminates cobalt (Co), thereby providing an economical secondary battery with high capacity and operating voltage.

[0094] 6 and 7, the second particles PTC2 may have a polycrystalline form and may include secondary particles formed by agglomeration of at least two or more second primary particles. In other words, one second particle PTC2 may include a plurality of second primary particles agglomerated together. The second particles PTC2 may have a spherical form formed by agglomeration of the second primary particles, or may have a random form even when the second primary particles are agglomerated.

[0095] The average particle size 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 of the second particles PTC2 may be approximately 8 μm. In one example, the average particle size can be measured using a particle size analyzer. The average particle size may refer to the diameter of particles whose cumulative volume is 50% by volume (D50) in the particle size distribution.

[0096] The average size of the second primary particles constituting the second particles PTC2 may be 3 μm or less. For example, the average size of the second primary particles 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 image of the positive electrode active material. The size of the second primary particles may be uniform. The average size of the second primary particles may be larger than the average size of the first primary particles. The difference between the average size of the second primary particles and the average size of the first primary particles may be 300 nm or more.

[0097] As an example, 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.

[0098] The second coating layer may include an aluminum-containing compound, a magnesium-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 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.

[0099] The method for measuring the metal content in the second coating layer of the second particle PTC2 can include performing scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) on the second particle PTC2. Through the analysis, the content of aluminum and / or magnesium in the second coating layer can be confirmed. As methods for measuring the metal content in the second coating layer, in addition to SEM-EDS, inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), etc. can also be used.

[0100] Third particle PTC3 The third particle PTC3 can contain a lithium compound represented by Chemical Formula 3 below. [Chemical Formula 3] Li a3 Co x3 D y3 O 4-b3

[0101] In Chemical Formula 3, 5.9 < a3 ≤ 6.1, 0.9 ≤ x3 ≤ 1.05, 0 ≤ y3 ≤ 0.05, and 0 ≤ b3 ≤ 0.05 can hold. D can be at least one element selected from the group consisting of Al and Mg. The dopant can enhance the surface stability and structural safety of the third particle PTC3.

[0102] In one or more embodiments, in Chemical Formula 3, 5.9 < a3 ≤ 6.1, 0.95 ≤ x3 ≤ 1.0, 0 ≤ y3 ≤ 0.05, 0 ≤ b3 ≤ 0.05, and x3 + y3 = 1 may be satisfied.

[0103] The third particle PTC3 has the advantages of high capacity and high energy density.

[0104] As an example, as shown in FIG. 6, the third particles PTC3 may have a single particle morphology. In this specification, a single particle may refer to a single particle without an internal particle boundary. A single particle may refer to a single particle, a monolith structure, a single structure, or a non-aggregated particle, in which particles exist in an independent phase and are not aggregated with each other in morphology. 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 isolated form. Alternatively, a single particle may be in a form in which 2 to 100 single particles are attached to each other.

[0105] When the third particles PTC3 are single particles, the third particles PTC3 may include at least one third primary particle. In one embodiment, the third particles PTC3 may have a spherical or elliptical shape formed by agglomeration 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 are agglomerated.

[0106] Although Figures 6 and 7 show the third particles PTC3 having a shape including only one particle, the third particles PTC3 may also have a spherical or elliptical shape, or a random shape, in which two or more third primary particles are aggregated. For example, the third primary particles may have a random shape in which the third primary particles are aggregated, as shown in Figure 11. Referring to Figures 8b to 11, the shape in which the third primary particles are aggregated may be less regular than the shapes in which the first primary particles and the second primary particles are aggregated.

[0107] When the third particles PTC3 are single particles, the third particles PTC3 may be provided in various sizes. For example, the average particle size of the third particles PTC3 may be 2 μm to 8 μm. The minimum particle size of the third particles PTC3, i.e., the size of the third primary particles, may be 100 nm to 500 nm. The average particle size of the third particles PTC3 may be larger than the average particle size of the first particles PTC1. When the third particles PTC3 include multiple single particles, the average size of the third primary particles of the third particles PTC3 may be larger than the average size of the first primary particles.

[0108] In one embodiment, the third particles PTC3 may include a third coating layer on their surfaces. The coating layer may prevent the structure of the third particles PTC3 from being destroyed by repeated charge and discharge. This may improve the lifespan of the secondary battery.

[0109] The third coating layer may include an aluminum-containing compound, a magnesium-containing compound, or a combination thereof. The metal-containing compound in the third coating layer 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 third coating layer may further include lithium, manganese, and / or nickel.

[0110] Li derived from the third particles PTC3 may be used as irreversible Li, which migrates to the negative electrode during initial charge but does not return to the positive electrode during discharge. That is, the third particles PTC3 may serve as a sacrificial positive electrode. In one example, the third particles PTC3 may supply Li in the formation process, which is the initial charge / discharge step, and may not participate in subsequent charge / discharge processes.

[0111] The third particles PTC3 can participate in forming a solid electrolyte interface (SEI) film on the negative electrode surface during the chemical formation process. The Li derived from the third particles PTC3 can be converted into irreversible Li, which no longer participates in charge-discharge reactions.

[0112] Because the third particles PTC3 have high capacity and energy density, the amount of irreversible Li supplied during initial charge and discharge can be sufficient. The third particles PTC3 sacrifice Li derived from the main active material (described later) so that it is not classified as irreversible Li, thereby allowing the capacity of the main active material (described later) to be provided in the originally designed amount, ultimately resulting in increased battery capacity and energy density. The cathode active material according to the present invention can increase the capacity and energy density of a secondary battery by including an appropriate amount of the third particles PTC3.

[0113] According to one embodiment of the present invention, the third particle PTC3 may include LiCoO. LiCoO can provide many Li atoms during the formation process and thus provide more irreversible Li. This can enhance the effect of the sacrificial positive electrode. Specifically, LiCoO can be decomposed between 3.0 V and 4.0 V to provide six Li atoms. LiCoO is merely an example, and the present invention is not limited to the above example.

[0114] When the content of the third particle PTC3 included in the positive electrode active material is within a specific content range, it can simultaneously compensate for irreversible Li without affecting the battery characteristics targeted when designing the main active material, which will be described later. The content range of the third particle PTC3 will be described later.

[0115] Main active material The main active material according to the embodiment of the present invention will be described in more detail with reference to FIGS.

[0116] The first particles PTC1 and the second particles PTC2 may constitute a main active material, and the content of the main active material may be 95 to 99.5 parts by weight based on 100 parts by weight of the positive electrode active material.

[0117] A lithium iron phosphate-based positive electrode active material (first particle, PTC1) having an olivine crystal structure has the advantages of being inexpensive, structurally stable, and having excellent lifespan characteristics compared to other positive electrode materials. A lithium manganese oxide-based positive electrode active material (second particle, PTC2) having a spinel structure has the advantage of having a high average voltage. The positive electrode active material according to the present invention contains a mixture of the first particle PTC1 and the second particle PTC2 as the main active material, thereby achieving both the advantages of the first particle PTC1 and the second particle PTC2. That is, it is inexpensive, has excellent lifespan characteristics, and can operate at a high average voltage.

[0118] The mixing ratio of the first particles PTC1 to the second particles PTC2 may be 40:60 to 90:10, 55:45 to 37:63, or 46:54 to 37:63 by weight. In the main active material composed of the first particles PTC1 and the second particles PTC2, the Mn content relative to the metal elements excluding lithium in the main active material may be 40 mol% to 75 mol%, or 50 mol% to 70 mol%. This may be an amount similar to the manganese content in a typical lithium manganese iron phosphate-based positive electrode active material (hereinafter referred to as LMFP).

[0119] The cathode active material according to the present invention may exhibit electrochemical properties similar to those of LMFP and may be easily manufactured and processed by appropriately mixing first particles PTC1 and second particles PTC2 to satisfy the Mn content range. LMFPs operate at a high average voltage and may be an alternative to alleviate the low average voltage issue of lithium iron phosphate-based cathode active materials (hereinafter referred to as LFPs). However, LMFPs may have limitations that make them difficult to manufacture and process when applied to actual processes. The cathode active material according to the present invention may exhibit properties similar to those of LMFP and may be easily manufactured and processed by adjusting the Mn content of the main active material using second particles PTC2.

[0120] positive electrode active material The positive electrode active material according to the embodiment of the present invention will be described in more detail with reference to FIGS.

[0121] The positive electrode active material according to the present invention may include the above-described first particles PTC1, second particles PTC2, and third particles PTC3.

[0122] The first particles PTC1 and second particles PTC2 have the disadvantage of having a relatively low energy density compared to other positive electrode materials. The positive electrode active material according to the present invention can have high capacity and energy density by further including third particles PTC3 that function as a sacrificial positive electrode in addition to the first particles PTC1 and second particles PTC2.

[0123] The content of the third particles PTC3 may be 0.5 to 5 parts by weight, or 0.5 to 1 part by weight, based on 100 parts by weight of the positive electrode active material. When the content of the third particles PTC3 satisfies this range, it can compensate for irreversible Li without affecting the battery characteristics targeted in the design of the main active material. In other words, when the content of the third particles PTC3 satisfies this range, it can improve capacity and energy density characteristics while minimizing reductions in lifespan and stability of the positive electrode active material.

[0124] The content of the third particles PTC3 in the positive electrode active material can be determined within a range that does not cause the charge / discharge efficiency of the positive electrode to fall below that of the negative electrode. This is because if the charge / discharge efficiency of the positive electrode is higher than that of the negative electrode, the excess may be wasted. Charge / discharge efficiency refers to the initial discharge amount relative to the initial charge amount. For example, the charge / discharge efficiency of a graphite negative electrode may be 90% or 91.5%, and the charge / discharge efficiency of the positive electrode may be 95%. In this case, the positive electrode active material may further include the third particles PTC3 within a range that does not cause the charge / discharge efficiency of the positive electrode to fall below 90% or 91.5%. By considering this range, energy density characteristics can be improved without suffering any loss in life characteristics.

[0125] The positive electrode active material according to the present invention may have a high pellet density (PD). In one embodiment, the compressed density of the positive electrode active material according to the present invention may be 2 g / cc to 5 g / cc, or 2.5 g / cc to 4 g / cc, or 2.5 g / cc to 3.0 g / cc. This may be higher than the pellet density of common LFPs. The high pellet density can contribute to improved life characteristics and increased energy density of lithium secondary batteries. The uniform and dense distribution of the active material helps maintain consistent electrochemical reactions during charge and discharge, thereby contributing to improved life characteristics. The ability to fit more active material into a limited space allows for the storage of more energy per unit volume, contributing to increased energy density.

[0126] A lithium secondary battery including the positive electrode active material according to the present invention may have a high average voltage. In one embodiment, the average voltage of the lithium secondary battery according to the present invention may be 3 V to 4 V. In one embodiment, the average voltage range of the present invention may be 3.5 V to 3.7 V, which may be higher than the average voltage of common LFPs. Since energy density is proportional to the average voltage, the above-mentioned high average voltage can contribute to an increase in energy density.

[0127] A lithium secondary battery including the positive electrode active material according to the present invention may have a high energy density. In one embodiment, the energy density of the lithium secondary battery according to the present invention may be 300 Wh / kg to 600 Wh / kg, 400 Wh / kg to 500 Wh / kg, or 430 Wh / kg to 480 Wh / kg.

[0128] Lithium secondary batteries including the cathode active material according to the present invention may have long lifespan characteristics. In one embodiment, the lithium secondary battery according to the present invention may have a capacity retention rate of 95% or more after 50 charge / discharge cycles under specific current and voltage conditions. For example, after initial charging at a constant current (0.2 C) and constant voltage (4.25 V) and initial discharging to 2.5 V under a constant current (0.2 C) condition, and then 50 charge / discharge cycles at 0.2 C / 0.2 C, the capacity retention rate may be 95% to 100%, or 98% to 100%. This may be higher than the lifespan characteristics of conventional LFPs.

[0129] Examples of the present invention and comparative examples are described below. However, the following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0130] Preparation Example 1-1: Preparation of first particles in single particle form Iron phosphate precursor Fe1PO4, lithium carbonate, and titanium dioxide were mixed in a molar ratio of Fe:Li:Ti = 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 primary particles in the form of single particles. The average size of the primary particles within the primary particles was approximately 200nm to 300nm.

[0131] Preparation Example 1-2: Preparation of primary particles in the form of secondary particles Iron phosphate precursor Fe1PO4, lithium carbonate, and titanium dioxide were mixed in a molar ratio of Fe:Li:Ti = 1:1.03:0.004. 10 wt% glucose was further 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 100 nm to approximately 200 nm.

[0132] Production Example 1-3: Production of second particles 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 mixture was then reacted at 130°C for 10 hours to obtain a solid precipitate. The resulting 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.

[0133] Li2CO3 and the 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.

[0134] Production Example 1-4: Production of third particles LiO and CoO were mixed in a molar ratio of 6:1. The mixed powder was sintered at 600°C for 24 hours under a nitrogen atmosphere and then naturally cooled. The cooled powder was milled at 6000 rpm using an air jet mill to obtain third particles. The chemical formula of the third particles was Li6CoO4.

[0135] Manufacturing Example 2-1: Manufacturing of main active material The first particles (single particle form) of Preparation Example 1-1 and the second particles of Preparation Example 1-3 were mixed in a weight ratio of 46:54 to prepare a main active material, in which the Mn content of the metal elements excluding lithium in the main active material was 60 mol%.

[0136] Manufacturing Example 2-2 The first particles (single particle form) of Preparation Example 1-1 and the second particles of Preparation Example 1-3 were mixed in a weight ratio of 55:45 to prepare a main active material, in which the Mn content of the metal elements excluding lithium in the main active material was 50 mol%.

[0137] Manufacturing Example 2-3 The primary particles (secondary particle form) of Preparation Example 1-2 and the secondary particles of Preparation Example 1-3 were mixed in a weight ratio of 46:54 to prepare a main active material, in which the Mn content of the metal elements excluding lithium in the main active material was 60 mol%.

[0138] Manufacturing Example 2-4 The primary particles (secondary particle form) of Preparation Example 1-2 and the secondary particles of Preparation Example 1-3 were mixed in a weight ratio of 55:45 to prepare a main active material, in which the Mn content of the metal elements excluding lithium in the main active material was 50 mol%.

[0139] Comparative Example 1 The first particles in the form of secondary particles of Preparation Example 1-2 and the second particles of Preparation Example 1-3 were mixed in a weight ratio of 59:41 to prepare an active material, in which the Mn content of the metal elements excluding lithium in the active material was 45 mol%.

[0140] Comparative Example 2 The first particles in the form of secondary particles of Preparation Example 1-2 and the second particles of Preparation Example 1-3 were mixed in a weight ratio of 32:68 to prepare an active material, in which the Mn content of the metal elements excluding lithium in the active material was 75 mol%.

[0141] Example 1: Preparation of final positive electrode active material The main active material of Preparation Example 2-2 and the third particles of Preparation Example 1-4 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material. The weight ratio of the first particles (single particles):second particles:third particles was 54.7:44.8:0.5.

[0142] Example 2 The main active material of Preparation Example 2-2 and the third particles of Preparation Example 1-4 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material. The weight ratio of the first particles (single particles):second particles:third particles was 54.5:44.6:1.0.

[0143] Example 3 The main active material of Preparation Example 2-4 and the third particles of Preparation Example 1-4 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material. The weight ratio of the first particles (secondary particles):second particles:third particles was 54.7:44.8:0.5.

[0144] Example 4 The main active material of Preparation Example 2-4 and the third particles of Preparation Example 1-4 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material. The weight ratio of the first particles (secondary particles):second particles:third particles was 54.5:44.6:1.0.

[0145] Comparative Example 3 The main active material of Preparation Example 2-2 and the third particles of Preparation Example 1-4 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material. The weight ratio of the first particles (single particles):second particles:third particles was 54.2:44.3:1.5.

[0146] Comparative Example 4 The main active material of Preparation Example 2-4 and the third particles of Preparation Example 1-4 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material. The weight ratio of the first particles (secondary particles):second particles:third particles was 54.2:44.3:1.5.

[0147] Cathode manufacturing A positive electrode active material slurry was prepared by mixing 95 wt% of the final positive electrode active material, 3 wt% of polyvinylidene fluoride binder, and 2 wt% of carbon black conductive material in N-methylpyrrolidone solvent. The positive electrode active material slurry was applied to an aluminum current collector, dried, and then rolled to prepare a positive electrode.

[0148] Anode manufacturing The Si-graphite composite, binder, and 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.

[0149] Lithium secondary battery manufacturing A 2032-type coin half-cell was fabricated using the prepared positive electrode and a lithium metal 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 solution 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.

[0150] Evaluation example 1: Analysis of the surface of the positive electrode active material An SEM image of the primary particles (single particle form) prepared in Preparation Example 1-1 is shown in Figure 8A. An SEM image of the primary particles (secondary particle form) prepared in Preparation Example 1-2 is shown in Figure 8B. An SEM image of the secondary particles prepared in Preparation Example 1-3 is shown in Figure 9. An SEM image of the tertiary particles prepared in Preparation Example 1-4 is shown in Figure 10.

[0151] 8A, the first particles according to Preparation Example 1-1 of the present invention are nano-sized, single particles. FIG. 8B shows that the second particles according to Preparation Example 1-2 of the present invention are spherical secondary particles formed by agglomeration of multiple primary particles. Furthermore, the primary particles according to Preparation Example 1-2 are smaller and more uniform in size than the primary particles according to Preparation Example 1-1.

[0152] Referring to FIG. 9, it can be seen that the secondary particles according to Preparation Example 1-3 of the present invention are in the form of secondary particles formed by aggregation of primary particles.

[0153] Referring to FIG. 10, it can be seen that the third particles according to Preparation Example 1-4 of the present invention are in the form of single particles.

[0154] Evaluation Example 2: Evaluation of main active material and battery The average pressed density (PD) of the main active materials of Preparation Examples 2-3 and 2-4 and the characteristics of lithium secondary batteries fabricated using the main active materials were evaluated. The average pressed density (PD) of the positive electrode active materials of Comparative Examples 1 and 2 and the characteristics of lithium secondary batteries fabricated using the positive electrode active materials were evaluated. This evaluation was performed without the third particle PTC3 to observe the change in characteristics depending on the Mn content in the main active material.

[0155] The lithium secondary battery was initially charged at a constant current (0.2 C) and a constant voltage (4.25 V), and after a 10-minute rest, discharged to 2.5 V at a constant current (0.2 C). It was then charged and discharged 50 times at 0.2 C / 0.2 C. The battery characteristics were evaluated and are shown in Table 1. The Mn content refers to the amount of Mn in the main active material relative to the total metal elements excluding lithium.

[0156] [Table 1]

[0157] Referring to Table 1, it can be seen that the batteries according to Preparation Examples 2-3 and 2-4 of the present invention have substantially the same efficiency as the batteries according to Comparative Examples 1 and 2. It can be seen that the batteries according to Preparation Examples 2-3 and 2-4 of the present invention have higher average voltages and higher energy densities than the battery according to Comparative Example 1. It can be seen that the batteries according to Preparation Examples 2-3 and 2-4 of the present invention have superior life spans and higher composite densities than the battery according to Comparative Example 2. That is, it can be seen that when the Mn content relative to the metal elements excluding lithium in the main active material is 50 mol% to 70 mol%, it is possible to achieve excellent life spans and excellent energy density characteristics while minimizing efficiency reduction and average voltage reduction.

[0158] Evaluation Example 3: Evaluation of active materials The average pressed density (PD) of the positive electrode active materials of Examples 1 to 4 and Comparative Examples 1 to 4 was measured, and the results are shown in Table 2. The average pressed density was measured by placing 3 g of the positive electrode active material in a pellet mold and applying a force of US 4.0 tons for 30 seconds.

[0159] [Table 2]

[0160] Referring to Table 2, it can be seen that the batteries according to Examples 1 and 2 of the present invention have a higher average pressed density than the battery according to Comparative Example 3. It can also be seen that the batteries according to Examples 3 and 4 of the present invention have a higher average pressed density than the battery according to Comparative Example 4. That is, it can be seen that when the content of the third particles PTC3 is 0.5 to 1 part by weight based on 100 parts by weight of the positive electrode active material, the average pressed density is excellent.

[0161] Evaluation Example 4: Battery Evaluation II The characteristics of the lithium secondary batteries prepared using the positive electrode active materials of Examples 1 to 4 and Comparative Examples 3 and 4 were evaluated, and the results are shown in Table 3. The evaluation conditions were the same as those in Evaluation Example 2.

[0162] [Table 3]

[0163] Referring to Table 3, it can be seen that the batteries according to Examples 1 and 2 have the same or better efficiency and lifespan, and substantially the same or better energy density, compared to the battery according to Comparative Example 3. It can also be seen that the batteries according to Examples 3 and 4 have the same or better efficiency and lifespan, and substantially the same energy density, compared to the battery according to Comparative Example 4. It can also be seen that the batteries according to Examples 3 and 4 have higher charge / discharge capacity, efficiency, lifespan, and energy density, compared to the batteries according to Examples 1 and 2. That is, it can be seen that the first particles PTC1 included in the positive electrode active material are more superior when they are in the form of secondary particles than when they are in the form of single particles. [Explanation of symbols]

[0164] 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: Case 60: Sealing material 70: Electrode tab 71: Positive electrode tab 72: Negative electrode tab

Claims

1. First particles having an olivine structure and including a compound represented by the following Chemical Formula 1: Second particles having a spinel structure and including a compound represented by the following Chemical Formula 2: and third particles including a compound of Chemical Formula 3: the first particles and the second particles constitute a main active material, The content of the main active material is 95 to 99.5 parts by weight based on 100 parts by weight of the positive electrode active material, The content of the third particles is 0.5 to 5 parts by weight based on 100 parts by weight of the positive electrode active material, [Chemical formula 1] Li a1 Fe x1 B y1 PO 4-b1 In the formula 1, 0.8≦a1≦1.2, 0.95≦x1≦1.0, 0≦y1≦0.05, 0≦b1≦0.05, and x1+y1=1; B is at least one element selected from the group consisting of Al, Ti, V, and Mg; [Chemical formula 2] Li a2 Mn x2 Cy 2 O 4-b2 In the formula 2, 0.8≦a2≦1.2, 1.9≦x2≦2.05, 0≦y2≦0.05, and 0≦b2≦0.05; C is at least one element selected from the group consisting of Al and Mg; [Chemical formula 3] Li a3 Co x3 D y3 O 4-b3 In Chemical Formula 3, 5.9<a3≦6.1, 0.9≦x3≦1.05, 0≦y3≦0.05, and 0≦b3≦0.05, and D is at least one element selected from the group consisting of Al and Mg.

2. The positive electrode active material of claim 1 , wherein the Mn content of the main active material is 50 mol % to 70 mol %.

3. The positive electrode active material of claim 1 , wherein the mixing ratio of the first particles to the second particles is 55:45 to 37:63 by weight.

4. The positive electrode active material of claim 1 , wherein the content of the third particles is 0.5 to 1 part by weight based on 100 parts by weight of the positive electrode active material.

5. 10. The cathode active material of claim 1, wherein the third particles are configured to be electrochemically inactive after initial cycles.

6. the first particles have a single particle form; the first particles include at least one first primary particle; The first particles have a first average particle size of 0.5 μm to 2.5 μm; The positive electrode active material of claim 1 , wherein the first primary particles have an average size of 200 nm to 300 nm.

7. The first particles include a plurality of first primary particles that are aggregated together, The positive electrode active material of claim 1 , wherein the second particles include at least one second primary particle.

8. a first average particle size of the first particles is 3 μm to 10 μm; The positive electrode active material of claim 7 , wherein the first primary particles have an average size of 100 nm to 200 nm.

9. The positive electrode active material of claim 7 , wherein an average size of the first primary particles is smaller than an average size of the second primary particles.

10. The positive electrode active material of claim 7 , wherein the second primary particles have an average size of 0.5 μm to 3 μm.

11. the first particles include a first coating layer containing carbon; The positive electrode active material of claim 1 , wherein the carbon content in the first particles is 1.5 to 2.5 wt %.

12. The positive electrode active material of claim 1 , wherein the third particles have a single particle form.

13. The positive electrode active material of claim 1 , wherein the first particles have a porosity of 20% to 40%.

14. The positive electrode active material of claim 1 , wherein the first particles have a Span value of 0.3 to 0.75 as analyzed by a particle size analyzer.

15. a positive electrode current collector; a positive electrode active material layer on the positive electrode current collector, The 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.

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

17. 16. The positive electrode for a lithium secondary battery according to claim 15, 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.

18. 16. The positive electrode for a lithium secondary battery according to claim 15, wherein the conductive material is present in an amount of 0.5 to 5 parts by weight based on 100 parts by weight of the positive electrode active material layer.

19. The conductive material comprises a carbon-based material, a metal-based material in the form of a metal powder or metal fiber, a conductive polymer, or a mixture thereof; The positive electrode for a lithium secondary battery according to claim 15.

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

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