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

Abstract

To provide a positive electrode active material being economical and having high energy density, high average voltage, and an excellent lifetime characteristic, and moreover provide a positive electrode being economical and having high energy density, high average voltage, and an excellent lifetime characteristic.SOLUTION: 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. 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 and having a layered structure. Based on 100 parts by weight of the positive electrode active material, the content amount of the third particle is 10 parts by weight to 50 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 and a positive electrode containing the same, and more particularly to a positive electrode active material containing an olivine-based lithium compound and a positive electrode containing the same. [Background technology]

[0002] Recently, with the rapid spread of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for high-energy-density, 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.

[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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Korean Patent Publication No. 10-2013-0107597 Summary of the Invention [Problem to be solved by the invention]

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

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

[0007] The positive electrode active material according to the concept of the present invention may 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 and having a layered structure. Based on 100 parts by weight of the positive electrode active material, the content of the third particle may be 10 to 50 parts by weight.

[0008] [Chemical Formula 1] Li y2 ,

[0011] , , w1 , , y3 , , a3 , 4-c2 , , x2 , , ,

[0010] , 2-c3 , , z3 , x3 Mn x1 Fe y1 A z1 PO 4-c1 In Chemical Formula 1, 0.8 < a1 ≤ 1.2, 0.4 ≤ x1 ≤ 0.8, 0 ≤ y1 ≤ 0.6, 0 ≤ z1 ≤ 0.05, and 0 ≤ c1 ≤ 0.05, and A may be at least one element selected from the group consisting of Al, Ti, V, and Mg.

[0009] [Chemical Formula 2] Li a2 Mn x2 B y2 O 4-c2 In Chemical Formula 2, 0.8 < a2 ≤ 1.2, 1.9 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05, and B may be at least one element selected from the group consisting of Al and Mg.

[0010] [Chemical Formula 3] Li a3 Ni x3 Co y3 Mn z3 C w1 O 2-c3 In Chemical Formula 3, 0.8 < a3 ≤ 1.2, 0.5 ≤ x3 ≤ 0.8, 0 ≤ y3 ≤ 0.10, 0.1 ≤ z3 ≤ 0.35, 0 ≤ w1 ≤ 0.1, and 0 ≤ c3 ≤ 0.05, and C may be at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb.

[0011] A positive electrode for a lithium secondary battery according to another aspect 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 the above-described positive electrode active material, a conductive material, and a binder. [Effects of the Invention]

[0012] The cathode active material according to the present invention includes the first particles having an olivine structure, and thus may have improved economic efficiency, structural stability, and energy density.

[0013] The positive electrode active material according to the present invention may have improved average voltage and life characteristics by including the second particles having a spinel structure.

[0014] The positive electrode active material according to the present invention may have improved life characteristics and energy density by including the third particles having a layered structure.

[0015] The positive electrode active material according to the present invention may further include fourth particles, which may further improve the capacity and energy density.

[0016] The positive electrode active material according to the present invention may be economically efficient and have improved energy density, average voltage, and lifespan characteristics by mixing the first particles, second particles, and third particles in an appropriate ratio. When the positive electrode active material further includes the fourth particles, the capacity and energy density may be further improved. [Brief explanation of the drawings]

[0017] [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 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 8] 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 9] 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 10a] 1 is an SEM image of the positive electrode active material of Production Example 1-1 of the present invention. [Figure 10b] 1 is an SEM image of the positive electrode active material of Production Example 1-2 of the present invention. [Figure 11] 1 is an SEM image of the positive electrode active material of Production Example 1-3 of the present invention. [Figure 12] 1 is an SEM image of the positive electrode active material of Production Example 1-4 of the present invention. [Figure 13] 1 is an SEM image of the positive electrode active material of Production Example 1-5 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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 realized 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.

[0019] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component can be interposed between them. Also, in the drawings, the thickness of the components is exaggerated to effectively explain the technical content. Parts designated with the same reference numerals throughout this specification refer to the same components.

[0020] 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, elements referred to as "comprises" and / or "comprising" do not exclude the presence or addition of one or more other elements.

[0021] As used herein, "combinations thereof" can mean mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0022] 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 utilizes 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, in measurements using 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.

[0023] 1 is a conceptual 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.

[0024] 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 the electrolyte solution ELL. The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in the electrolyte solution ELL.

[0025] 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 migrate toward the positive electrode 10 or the negative electrode 20.

[0026] positive electrode 10 The positive electrode 10 for a lithium secondary battery may include a current collector COL1 and a positive electrode active material layer AML1 formed on the current collector COL1. The positive electrode active material layer AML1 includes a positive electrode active material and may further include a binder and / or a conductive material. A detailed description of the positive electrode active material layer AML1 according to an embodiment of the present invention will be provided below with reference to FIGS. 6 to 9. The current collector COL1 may be made of, but is not limited to, aluminum.

[0027] 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.

[0028] 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.

[0029] The binder serves to firmly adhere the negative active material particles to each other and to firmly adhere the negative 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.

[0030] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and combinations thereof.

[0031] The aqueous 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.

[0032] 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.

[0033] The dry binder is a polymeric material that can be fibrous, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, ethylene oxide, or a combination thereof.

[0034] The conductive material is used to impart conductivity to the electrode and may be any material that is electronically conductive and does not cause a chemical change 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.

[0035] As the current collector COL2, those 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 can be used.

[0036] 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.

[0037] The material capable of reversibly inserting / desorbing the 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 the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0038] As the alloy of the 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.

[0039] 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 (where 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.

[0040] 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 silicon-carbon 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. The 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.

[0041] 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 surface of the core.

[0042] The Si-based or Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0043] 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.

[0044] 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.

[0045] 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 polymers.

[0046] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0047] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0048] The organic material and the inorganic material may be mixed in one coating layer, or may be stacked in a coating layer containing an organic material and a coating layer containing an inorganic material.

[0049] Electrolyte ELL The electrolyte ELL for lithium secondary batteries contains a non-aqueous organic solvent and a lithium salt.

[0050] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0051] The non-aqueous organic solvent may be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, or a combination thereof.

[0052] Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0053] 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.

[0054] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that can be used include nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane and 1,4-dioxolane, and sulfolanes.

[0055] The non-aqueous organic solvents may be used alone or in combination of two or more.

[0056] 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.

[0057] The lithium salt is dissolved in an organic solvent and acts as a lithium ion source in the battery, enabling basic lithium secondary battery operation and promoting the movement of lithium ions between the positive electrode and the negative electrode. 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).

[0058] Lithium secondary battery Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 2 to 5 are schematic diagrams showing lithium secondary batteries according to embodiments, 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 housed. The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in 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 current generated in the positive electrode assembly 40 to the outside.

[0059] 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.

[0060] 6 to 9 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 FIGS. 6 and 7, as described above, the positive electrode active material layer AML1 (see FIG. 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 first active material according to an embodiment of the present invention. Referring to FIGS. 8 and 9, the positive electrode active material layer AML1 may further include fourth particles PTC4. The plurality of first particles PTC1, the plurality of second particles PTC2, the plurality of third particles PTC3, and the plurality of fourth particles PTC4 may constitute a second active material according to an embodiment of the present invention.

[0061] The content of the first 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, and 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, respectively.

[0062] When the positive electrode active material layer AML1 further includes fourth particles PTC4, the content of the second active materials PTC1, PTC2, PTC3, and PTC4 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 % respectively relative to 100 wt % of the positive electrode active material layer AML1.

[0063] The binder BND may bind the first particles PTC1, the second particles PTC2, the third particles PTC3, the fourth particles PTC4, and the conductive material CDM to one another. As an example, the binder BND may 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)acrylic styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0064] 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 a chemical change in the positive electrode active material layer AML1 can be used as the conductive material CDM. 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.

[0065] The first particles PTC1, the second particles PTC2, the third particles PTC3, and the fourth particles PTC4 will be described in more detail below.

[0066] 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 Mn x1 Fe y1 A z1 PO 4-c1

[0067] In Chemical Formula 1, 0.8 < a1 ≤ 1.2, 0.4 ≤ x1 ≤ 0.8, 0 ≤ y1 ≤ 0.6, 0 ≤ z1 ≤ 0.05, and 0 ≤ c1 ≤ 0.05, and A can be at least one element selected from the group consisting of Al, Ti, V, and Mg.

[0068] In one embodiment, in Chemical Formula 1, 0.8 < a1 ≤ 1.2, 0.4 ≤ x1 ≤ 0.8, 0.15 ≤ y1 ≤ 0.6, 0 ≤ z1 ≤ 0.05, 0 ≤ c1 ≤ 0.05, and x1 + y1 + z1 = 1. In other embodiments, in Chemical Formula 1, 0.8 < a1 ≤ 1.2, 0.4 ≤ x1 ≤ 0.8, 0.15 ≤ y1 ≤ 0.6, 0 ≤ z1 ≤ 0.05, 0 ≤ c1 ≤ 0.05, and 1 ≤ x1 + y1 + z1 ≤ 1.45.

[0069] The dopant can have the effect of controlling the uniform growth of the first primary particles of the first particle PTC1, thereby improving the charge-discharge efficiency, low-temperature characteristics, and life characteristics of the lithium secondary battery.

[0070] The first particle PTC1 has the advantages of high economy, excellent structural stability, and high energy density. Since it is mainly composed of Fe, it is relatively inexpensive, and due to its stable structure, the chemical changes can be relatively reduced even after repeated charge and discharge.

[0071] [[ID=I5]] The first particle PTC1 can be a lithium iron phosphate-based active material (hereinafter referred to as LFP) having an olivine crystal structure with a part of Fe substituted by Mn. By including Mn, the first particle PTC1 can have a higher average voltage and a higher energy density compared to LFP.

[0072] As an example, the first particle PTC1 can include a coating layer on its surface. The coating layer can cover the entire surface of the first particle PTC1 or a part of the surface of the first particle PTCI. For example, the coating layer can include carbon and / or a carbon-containing compound. The structural stability and electrical conductivity of the first particle PTC1 can be improved by the coating layer.

[0073] 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.

[0074] 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 5 wt %, 0.5 wt % to 3 wt %, or 0.5 wt % to 2 wt %.

[0075] 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 a form in which single particles and secondary particles are mixed. 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 will be described with reference to FIG. 7.

[0076] As an embodiment, 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 morphological phase in which particles exist as an independent phase that is not aggregated with each other, 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 2 to 100 single particles are attached to each other.

[0077] 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 ellipsoidal shape formed by aggregation of the first primary particles. In another embodiment, the first particles PTC1 may have a random shape rather than a spherical shape even if the first primary particles are aggregated.

[0078] When the first particles PTC1 are single particles, the first particles PTC1 may be provided in various sizes. For example, the average particle size of the first particles PTC1 may 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, may be 100 nm to 500 nm, or 100 nm to 200 nm.

[0079] In one embodiment, 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.

[0080] In one embodiment, 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.

[0081] When the first particles PTC1 are single particles, the porosity of the first particles PTC1 may be less than 20%. The span value of the first particles PTC1 analyzed with a particle size analyzer may fall outside the range of 0.3 to 0.75.

[0082] In another embodiment, referring again to FIG. 7, the first particles PTC1 may have a secondary particle shape. The secondary particles may be polycrystalline, meaning 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 ellipsoidal shape.

[0083] For example, when the first particles PTC1 are in the form of second primary particles, the first particles PTC1 may further include a grain boundary coating layer on the surface of each first primary particle. 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.

[0084] 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.

[0085] When the first particles PTC1 are secondary particles, 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. In addition, the first particles PTC1 may further include a grain boundary coating portion, which may further improve the electrical conductivity of the first particles PTC1.

[0086] 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.

[0087] 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 approximately 5 μm. In one embodiment, 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.

[0088] 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 50 nm to 150 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.

[0089] 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 primary particles PTC1 are in the form of secondary particles, the size of the first primary particles may be about 50 nm smaller than when the first particles PTC1 are in the form of single crystals.

[0090] 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-mentioned ranges and the size of the first primary particles is uniform, the charge / discharge capacity and low-temperature capacity of a lithium secondary battery including the first particles PTC1 can be improved.

[0091] When the first particles PTC1 are secondary particles, the porosity of the first particles PTC1 may be about 20% to 40%. The span value of the first particles PTC1 analyzed with a particle size analyzer may be 0.3 to 0.75.

[0092] When the first particle PTC1 is a secondary particle, the first particle PTC1 can be smoothly adhered to the current collector COL1 (see FIG. 1) in the positive electrode active material layer AML1 (see FIG. 1) with only a relatively small amount of binder BND. For example, the content of the binder BND can be from 0.5 wt% to 3 wt% based on 100 wt% of the positive electrode active material layer AML1. This may be 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. Since reducing the content of the binder contained in the positive electrode active material layer AML1 (see FIG. 1) can increase the content of the active material accordingly, it can have the effect of improving the capacity and energy density of the battery. Also, reducing the content of the binder that increases the resistance can have the effect of improving the electrical conductivity of the positive electrode.

[0093] 2nd particle PTC2 The second particle PTC2 may contain a lithium compound having a spinel structure represented by the following Chemical Formula 2. [Chemical Formula 2] Li a2 Mn x2 B y2 O 4-c2

[0094] In the Chemical Formula 2, 0.8 < a2 ≤ 1.2, 1.9 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05 may hold, and B may be at least one element selected from the group consisting of Al and Mg.

[0095] In one embodiment, in the Chemical Formula 2, 0.8 < a2 ≤ 1.2, 1.95 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, 0 ≤ c2 ≤ 0.05, and x2 + y2 = 2. In other embodiments, in the Chemical Formula 2, 0.8 < a2 ≤ 1.2, 1.95 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, 0 ≤ c2 ≤ 0.05, and 2 ≤ x2 + y2 ≤ 2.05.

[0096] 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.

[0097] The second particles PTC2 have advantages such as high output characteristics, high structural stability, high average voltage, and excellent life characteristics. The second particles PTC2 may have a spinel structure composed of a tetrahedral and octahedral lattice structure. The lattice structure has various paths, allowing smooth insertion / extraction of lithium ions, resulting in excellent output characteristics. The second particles PTC2 may be structurally stable due to the inclusion of Mn. This structural stability maintains the electrochemical properties of the particles at high voltages, allowing them to operate at high voltages and providing excellent life characteristics.

[0098] The second particles PTC2 may be a lithium manganese oxide, a 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 practically eliminated. For example, the cobalt (Co) content of the second particles PTC2 may be 100 ppm or less. Because the cobalt (Co) content of the cathode active material according to the present invention is substantially eliminated, it may provide a secondary battery that is economical and has high capacity and operating voltage.

[0099] 6 and 7, the second particles PTC2 may be polycrystalline and 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 shape formed by agglomeration of the second primary particles, or may have a random shape even when the second primary particles are agglomerated.

[0100] The average particle size of the second particles PTC2 may be 3 μm to 20 μm, 3 μm to 10 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 6 μm. In one embodiment, 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.

[0101] 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 μm to 3 μm, 0.5 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.

[0102] For 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.

[0103] 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.

[0104] A method for measuring the content of metal in the second coating layer of the second particle PTC2 may include performing scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) on the second particle PTC2. The content of aluminum and / or magnesium in the second coating layer can be confirmed by the said analysis. As a method for measuring the content of metal 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.

[0105] Third particle PTC3 The third particle PTC3 may contain a lithium compound represented by the following Chemical Formula 3. [Chemical Formula 3] Li a3 Ni x3 Co y3 Mn z3 C w1 O 2-c3

[0106] In the Chemical Formula 3, 0.8 < a3 ≤ 1.2, 0.5 ≤ x3 ≤ 0.8, 0 ≤ y3 ≤ 0.10, 0.1 ≤ z3 ≤ 0.35, 0 ≤ w1 ≤ 0.1, and 0 ≤ c3 ≤ 0.05 can hold, and C can be at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb. The dopant can improve the surface stability and structural stability of the third particle PTC3.

[0107] In one embodiment, in Chemical Formula 3, 0.8 < a3 ≤ 1.2, 0.5 ≤ x3 ≤ 0.8, 0.05 ≤ y3 ≤ 0.10, 0.1 ≤ z3 ≤ 0.35, 0 ≤ w1 ≤ 0.1, 0 ≤ c3 ≤ 0.05, and x3 + y3 + z3 + w1 = 1. In other embodiments, 0.8 < a3 ≤ 1.2, 0.5 ≤ x3 ≤ 0.8, 0.05 ≤ y3 ≤ 0.10, 0.1 ≤ z3 ≤ 0.35, 0 ≤ w1 ≤ 0.1, 0 ≤ c3 ≤ 0.05, and in Chemical Formula 3, 1 ≤ x3 + y3 + z3 + w1 ≤ 1.25.

[0108] The content of Co in the third particle PTC3 can be 1 mol% or less. The content of Co means the content of Co with respect to the transition metal excluding Li in the third particle PTC3.

[0109] The third particle PTC3 has the advantages of high life characteristics and high energy density.

[0110] As one embodiment, referring to FIG. 6, the third particle PTC3 can have a single-particle shape. As used herein, a single particle can mean an independent particle without internal particle boundaries. A single particle is a morphological phase and can mean a single particle, a monolith structure, a single body structure, or a non-aggregated particle that exists as an independent phase where the particles are not aggregated with each other. As an example, a single particle can be a single crystal. Or, a single particle can be a particle containing several crystals. A single particle can be in a separately isolated form. Or, a single particle can be in a form where 2 to 100 single particles are attached to each other.

[0111] When the third particle PTC3 is a single particle, the third particle PTC3 can include at least one third primary particle. As one embodiment, the third particle PTC3 can have a spherical or elliptical shape in which the third primary particles are aggregated. As another embodiment, the third particle PTC3 can have a random shape without having a spherical shape even when the third primary particles are aggregated. Referring to FIGS. 10b, 11, and 12, when the third particle PTC3 has a shape in which the third primary particles are solidified, it can have a less structured shape than the first particle PTC1 in the form of the above-described second primary particles and the second particle PTC2 in the form of secondary particles. That is, it can have a more random shape.

[0112] For example, the third particles PTC3 may include a third coating layer on their surfaces. By including the third coating layer, the third particles PTC3 may be effectively prevented from collapsing due to repeated charging and discharging, thereby improving the lifespan of the secondary battery.

[0113] The third coating layer may include an aluminum-containing compound, a titanium-containing compound, a magnesium-containing compound, a zirconium-containing compound, a molybdenum-containing compound, a niobium-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.

[0114] The average particle size of the third particles PTC3 may be 2 μm to 15 μm, 2 μm to 10 μm, or 2 μm to 5 μm. For example, the average particle size of the third particles PTC3 may be 6 μm. The average particle size of the third particles PTC3 may be larger than the average particle size of the first particles PTC1. In one embodiment, 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.

[0115] When the third particles PTC3 have a shape in which a plurality of third primary particles are attached to each other, the average size of the third primary particles may be larger than the average particle size of the first particles PTC1.

[0116] The method for measuring the content of metal in the third coating layer of the third particle PTC3 may include performing scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) on the third particle PTC3. The content of aluminum, titanium, magnesium, zirconium, molybdenum, and / or niobium in the third coating layer can be confirmed by the said analysis. As the method for measuring the content of metal in the third coating layer, in addition to SEM-EDS, inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), etc. can also be used.

[0117] The third particle PTC3 is a nickel-based active material and may include a lithium nickel-based composite oxide. As an example, the third particle PTC3 may include a high-nickel-based cathode active material containing a high content of nickel. The high-nickel-based cathode active material can achieve high capacity and high performance.

[0118] 4th particle PTC4 The fourth particle PTC4 may include a lithium compound represented by Chemical Formula 4 below. [Chemical Formula 4] Li a4 Ni x4 Mn y4 D z4 O c4

[0119] In Chemical Formula 4, 1.1 < a4 ≤ 1.6, 0.2 ≤ x4 ≤ 0.5, 0.5 ≤ y4 ≤ 0.8, 0 ≤ z4 ≤ 0.05, and 2 ≤ c4 ≤ 2.3, and D is at least one element selected from the group consisting of transition metals with an oxidation number of 4. The dopant can improve the surface stability and structural stability of the fourth particle PTC4.

[0120] In one embodiment, in Chemical Formula 4, x4 + y4 + z4 = 1. In other embodiments, in Chemical Formula 4, 1 ≤ x4 + y4 + z4 ≤ 1.35.

[0121] The fourth particle PTC4 has the advantages of high capacity and high energy density.

[0122] The fourth particles PTC4 may be in the form of single particles and / or secondary particles. Hereinafter, the fourth particles PTC4 in the form of single particles will be described with reference to Fig. 8, and the fourth particles PTC4 in the form of secondary particles will be described with reference to Fig. 13.

[0123] In one embodiment, referring to FIG. 8, the fourth particle PTC4 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, 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 single, separate form. Alternatively, a single particle may be in a form in which 2 to 100 single particles are attached to each other.

[0124] When the fourth particles PTC4 are single particles, the fourth particles PTC4 may include at least one fourth primary particle. In one embodiment, the fourth particles PTC4 may have a spherical or ellipsoidal shape formed by agglomeration of the fourth primary particles. In another embodiment, the fourth particles PTC4 may have a random shape rather than a spherical shape, even if the fourth primary particles are agglomerated.

[0125] Although Figures 8 and 9 show fourth particles PTC4 having a shape containing only one particle, the single-particle fourth particles PTC4 may be spherical or elliptical, or may have a random shape, being formed by agglomeration of two or more fourth primary particles.

[0126] When the fourth particles PTC4 are single particles, the fourth particles PTC4 may be provided in various sizes. For example, the average particle size of the fourth particles PTC4 may be 3 μm to 7 μm. The minimum particle size of the fourth particles PTC4, i.e., the size of the fourth primary particles, may be 100 nm to 300 nm. The average particle size of the fourth particles PTC4 may be larger than the average particle size of the first particles PTC1. When the fourth particles PTC4 include a plurality of single particles, the average size of the fourth primary particles of the fourth particles PTC4 may be larger than the average size of the first primary particles of the first particles PTC1.

[0127] For example, the fourth particles PTC4 may include a fourth coating layer on their surfaces. The coating layer may prevent the structure of the fourth particles PTC4 from collapsing due to repeated charging and discharging. As a result, the coating layer may improve the lifespan of the secondary battery.

[0128] The fourth coating layer may include a boron-containing compound, an aluminum-containing compound, or a combination thereof. The metal-containing compound in the fourth 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 fourth coating layer may further include lithium, manganese, and / or nickel.

[0129] In another embodiment, referring to FIG. 13 , the fourth particles PTC4 may have a secondary particle shape. The secondary particles may be polycrystalline, meaning an agglomeration of at least two or more fourth primary particles. In other words, one fourth particle PTC4 may include a plurality of fourth primary particles agglomerated together. More specifically, the secondary particle-shaped fourth particles PTC4 may be in the form of an aggregate that can be divided into a group of unit structures. The aggregate that can be divided into a group of unit structures may have lower aggregate sphericity than the secondary particle-shaped first particles PTC1. The aggregate that can be divided into a group of unit structures may have less distinct boundaries between the aggregates than the secondary particle-shaped first particles PTC1. For example, the fourth primary particles may have a random aggregated shape as shown in Fig. 13. Referring to Fig. 10b and Fig. 13, the aggregated shape of the fourth primary particles may be relatively less regular than the aggregated shape of the first primary particles described above.

[0130] When the fourth particles PTC4 are secondary particles, the fourth particles PTC4 may have an average particle size of 5 μm to 10 μm. For example, the fourth particles PTC4 may have an average particle size of approximately 7 μm. The fourth particles PTC4 may have an average particle size smaller than the average particle size of the first particles PTC1. In one embodiment, 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.

[0131] When the fourth particles PTC4 are secondary particles, the fourth primary particles may have an average size of 500 nm or less. For example, the fourth primary particles may have an average size of 100 nm to 500 nm. In one embodiment, the average size of the fourth 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 fourth primary particles may be uniform.

[0132] For example, when the fourth particles PTC4 are in the form of second primary particles, the fourth particles PTC4 may further include a grain boundary coating layer on the surface of each fourth primary particle. The grain boundary coating layer may be present inside the fourth particles PTC4. The grain boundary coating layer may be formed by coating along the interface between the fourth primary particles inside the fourth particles PTC4. In other words, the grain boundary coating layer may refer to a material coated on the grain boundaries inside the fourth particles PTC4. The grain boundary coating layer may include at least one element selected from the group consisting of transition metals with an oxidation state of 4. For example, the grain boundary coating layer may include a boron-containing compound, an aluminum-containing compound, or a combination thereof.

[0133] When the fourth particle PTC4 is a secondary particle, the interior of the fourth particle PTC4 may mean the entire interior of the fourth particle PTC4 excluding the surface of the fourth particle PTC4. For example, the interior of the fourth particle PTC4 may mean the region from a depth of about 10 nm from the surface of the fourth particle PTC4 to the entire inside, or from a depth of 10 nm to a depth of about 2 μm.

[0134] When the fourth particles PTC4 are secondary particles, the fourth particles PTC4 may further include a grain boundary coating portion, thereby enhancing structural stability and forming a uniform coating layer on the surface of the fourth particles PTC4. In addition, the fourth particles PTC4 may further include a grain boundary coating portion, thereby further improving the life characteristics of the secondary battery.

[0135] According to one embodiment of the present invention, the fourth particles PTC4 may be substantially free of cobalt (Co). For example, the cobalt (Co) content of the fourth particles PTC4 may be 100 ppm or less. In addition, the second particles PTC2 may also be substantially free of cobalt (Co). Since the positive electrode active material according to the present invention is substantially free of cobalt (Co), it is possible to provide a secondary battery that is economical and has high capacity and operating voltage. The fourth particles PTC4 according to one embodiment of the present invention are Li 1.5 Ni 0.25 Mn 0.75 O2. This is just one embodiment, and the present invention is not limited to the above embodiment.

[0136] The fourth particle, PTC4, is a lithium-rich manganese oxide (LMR) that has a structure in which a layered phase (LiMnO2) and a rock salt phase (Li2MnO3) are mixed. During the charge and discharge process, the rock salt phase is activated, and additional capacity is generated through the oxygen redox reaction, enabling high capacity to be achieved.

[0137] First active material The first active material according to an embodiment of the present invention will be described in more detail with reference to Figures 6 and 7. The first active material according to the present invention may include first particles PTC1, second particles PTC2, and third particles PTC3.

[0138] In the first active material, 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 50 to 85 parts by weight based on 100 parts by weight of the first active material.

[0139] In the main active material, the mixing ratio of the first particles PTC1 to the second particles PTC2 may be 40:60 to 70:30, or 40:60 to 65:35 by weight.

[0140] The Mn content of the main active material may be 50 mol % to 90 mol %, or 60 mol % to 80 mol %, and refers to the content of Mn relative to the metal elements excluding lithium in the main active material.

[0141] When the main active material satisfies the above mixing ratio range and Mn content range, it can minimize the decrease in energy density of the main active material while improving the poor life characteristics and difficult processing characteristics of the first particles PTC1. That is, when the mixing ratio range and Mn content range are met, the main active material can maintain the advantages of the first particles PTC1, such as economic efficiency and structural stability, while improving life characteristics and making it easier to process in actual processes. More specifically, the purpose of preparing the main active material by mixing the first particles PTC1 and the second particles PTC2 may be to improve the poor life characteristics and difficult processing characteristics of the first particles PTC1. Although this process is unintended, it may result in a partial decrease in the energy density of the main active material. When the main active material satisfies the above mixing ratio range and Mn content range, it can minimize the decrease in energy density. The decrease in energy density can be compensated for by adding the third particles PTC3, which will be described later.

[0142] The first active material may include first particles PTC1, second particles PTC2, and third particles PTC3. The first particles PTC1 and second particles PTC2 may constitute a main active material, and the first active material may further include third particles PTC3 in addition to the main active material. In the first active material, the mixing ratio of the main active material to the third particles PTC3 may be 50:50 to 85:15 by weight. In the first active material, the Mn content of the first active material may be 50 mol % to 70 mol %. The Mn content refers to the content of Mn relative to the metal elements excluding lithium in the first active material.

[0143] Based on 100 parts by weight of the positive electrode active material, the content of the third particles PTC3 may be 10 parts by weight to 50 parts by weight, or 15 parts by weight to 50 parts by weight, or 30 parts by weight to 50 parts by weight.

[0144] The first active material includes first particles PTC1, second particles PTC2, and third particles PTC3 so as to satisfy the above-mentioned mixing ratio range and Mn content range, thereby providing the advantages of all of the first particles PTC1, second particles PTC2, and third particles PTC3. More specifically, the first active material can provide the advantages of the first particles PTC1, such as economy, structural stability, and high energy density, the advantages of the second particles PTC2, such as high average voltage and excellent life characteristics, and the advantages of the third particles PTC3, such as excellent life characteristics and high energy density. In other words, the energy density, average voltage, and life characteristics can be improved while maintaining economy.

[0145] The positive electrode active material according to the present invention may have a high pellet density (PD). For example, the pellet density (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. A high pellet density may contribute to improved life characteristics and increased energy density of lithium secondary batteries. The uniform and dense distribution of the active material helps to maintain consistent electrochemical reactions during charge and discharge processes, thereby contributing to improved life characteristics. Because more active material can be packed into a limited space, more energy can be stored per unit volume, contributing to increased energy density.

[0146] A lithium secondary battery including the first 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 3.6 V to 3.8 V. Since energy density is proportional to the average voltage, the above-mentioned high average voltage may contribute to an increase in energy density.

[0147] A lithium secondary battery including the first 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 400 Wh / Kg to 600 Wh / Kg, 450 Wh / Kg to 600 Wh / Kg, or 500 Wh / Kg to 600 Wh / Kg.

[0148] A lithium secondary battery including the first active material according to the present invention may have long life characteristics. In one embodiment, the lithium secondary battery according to the present invention may have a capacity retention rate of 97% or more after 50 charge / discharge cycles under specific current and voltage conditions. In one embodiment, the battery is initially charged at a constant current (0.2 C) and a constant voltage (4.25 V), initially discharged to 2.5 V at a constant current (0.2 C), and then charged / discharged 50 times at 0.2 C / 0.2 C, and the capacity retention rate may be 95% to 100%, or 97% to 99%.

[0149] Second active material The second active material according to the embodiment of the present invention will be described in more detail with reference to FIGS.

[0150] The second active material of the present invention may include the above-described first particles PTC1, second particles PTC2, third particles PTC3, and fourth particles PTC4. The second active material of the present invention may further include the above-described fourth particles PTC4 in addition to the above-described first active material.

[0151] The second active material according to the present invention can further increase the capacity and energy density by further including fourth particles PTC4 in addition to the above-described first particles PTC1, second particles PTC2, and third particles PTC3.

[0152] The content of the fourth particles PTC4 may be 5 to 35 parts by weight, or 15 to 25 parts by weight, based on 100 parts by weight of the second active material. When the content of the fourth particles PTC4 satisfies this range, the capacity and energy density can be further increased while minimizing the decrease in lifespan and stability of the second active material.

[0153] The second active material of the present invention may include first particles PTC1, second particles PTC2, third particles PTC3, and fourth particles PTC4. The first particles PTC1, second particles PTC2, and third particles PTC3 may constitute a first active material. In the second active material, the mixing ratio of the first active material to the fourth particles PTC4 may be 75:25 to 85:15 by weight. Alternatively, the mixing ratio may be 65:35 to 95:5. In the second active material, the Mn content of the second active material may be 50 mol% to 60 mol%. The Mn content of the second active material refers to the content of Mn relative to the metal elements excluding lithium in the second active material. In this case, the Mn content of the first active material may be 50 mol% to 80 mol%.

[0154] When the second active material satisfies the above-mentioned mixing ratio range, Mn content of the second active material, and Mn content range of the first active material, it can maximize energy density while minimizing reductions in average voltage and lifespan. That is, within the above-mentioned mixing ratio range, Mn content of the second active material, and Mn content range of the first active material, the second active material can further improve energy density while maintaining the advantages of the first active material, such as economy, structural stability, high lifespan characteristics, and ease of processing. More specifically, the purpose of preparing the second active material by mixing the first active material with the fourth particles PTC4 may be to prepare a cathode active material with a higher energy density than the first active material. Although this process is unintended, it may result in a partial reduction in the average voltage and lifespan of the second active material. When the second active material satisfies the above-mentioned mixing ratio range, Mn content of the second active material, and Mn content range of the first active material, it can minimize reductions in average voltage and lifespan.

[0155] A lithium secondary battery including the second 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 400 Wh / Kg to 650 Wh / Kg, 500 Wh / Kg to 600 Wh / Kg, or 550 Wh / Kg to 600 Wh / Kg.

[0156] The second active material according to the present invention may have a high pellet density (PD). For example, the pellet density (compressed density) of the second 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. A high pellet density may 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 processes, thereby contributing to improved life characteristics. Because more active material can be packed into a limited space, more energy can be stored per unit volume, contributing to increased energy density.

[0157] A lithium secondary battery including the second 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 3.6 V to 3.8 V. Since energy density is proportional to the average voltage, the above-mentioned high average voltage may contribute to an increase in energy density.

[0158] A lithium secondary battery including the second active material according to the present invention may have long life characteristics. In one embodiment, the lithium secondary battery according to the present invention may have a capacity retention rate of 97% or more after 50 charge / discharge cycles under specific current and voltage conditions. In one embodiment, the battery is initially charged at a constant current (0.2 C) and a constant voltage (4.25 V), initially discharged to 2.5 V at a constant current (0.2 C), and then charged / discharged 50 times at 0.2 C / 0.2 C, and the capacity retention rate may be 95% to 100%, or 97% to 99%.

[0159] Examples of the present invention and comparative examples are described below, but the following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

[0160] Production Example 1-1: Production of single particle-shaped first particles Mn 0.6 Fe 0.4Manganese iron phosphate precursor PO4, lithium carbonate, and titanium dioxide were mixed in a molar ratio of (Mn+Fe):Li:Ti = 1:1.03:0.004. 10 wt% glucose was added to the mixture. The mixture was subjected to a wet grinding process using ball milling. 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 single-particle primary particles. The average size of the primary particles of the primary particles PTC1 was approximately 100 nm to approximately 200 nm.

[0161] Production Example 1-2: Production of primary particles in the form of secondary particles Mn 0.6 Fe 0.4 Manganese iron phosphate precursor PO4, lithium carbonate, and titanium dioxide were mixed in a molar ratio of (Mn+Fe):Li:Ti = 1:1.03:0.004. 10 wt% glucose was added to the mixture. The slurry mixture was spray-dried at a spray pressure of 0.5 MPa and a temperature of 230°C, followed by evaporation. The dried mixture was calcined at 750°C for 10 hours in a nitrogen atmosphere to obtain primary particles in the form of secondary particles. The average size of the primary particles within the primary particles was approximately 50 nm to 150 nm.

[0162] Production Example 1-3: Production of second particles After dissolving 0.170g of MnSO4H2O and 0.228g of (NH4)2S2O8 in 100ml of distilled water, sulfuric acid was added to adjust the pH to 1, and the mixture was 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.

[0163] Li2O3 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 form LiMn2O4 particles with an average particle size of 7 μm.

[0164] Production Example 1-4: Production of third particles A nickel-based precursor was produced using the coprecipitation method. Specifically, nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and manganese sulfate (MnSO4·H2O) were dissolved in distilled water as a solvent in a molar ratio of 6:1:2 to prepare a metal raw material mixture. The metal raw material mixture, ammonia water, and sodium hydroxide were added to a reactor and reacted. The slurry solution in the reactor was filtered and washed with high-purity distilled water. The washed material was dried in a hot air oven at 210°C for 24 hours to obtain a precursor (NiSO4·6H2O) with an average particle size of approximately 4 μm. 0.6 Co 0.1 Mn 0.3 (OH)2) powder was obtained.

[0165] A nickel-based precursor and anhydrous lithium hydroxide (LiOH) were dry mixed using a Henschel mixer. Lithium and transition metals were mixed in a molar ratio of approximately 1:1. The transition metals were the sum of the transition metals (Ni, Co, and Mn) contained in the nickel-based precursor. A melting agent was added to the mixture, and the mixture was heat-treated (i.e., calcined) at approximately 850°C for 15 hours in an oxygen atmosphere to synthesize third particles, which are nickel-based positive electrode active materials. The third particles were then pulverized in a jet mill at a pressure of 3 bar.

[0166] The third particles were washed by adding them to distilled water. Boron oxide and aluminum oxide, which were 3 mol% of the total transition metals in the third particles, were added to perform boron and aluminum coating. The third particles were dried at 150°C for 12 hours and then heat-treated (i.e., surface treatment) at approximately 700°C in an oxygen atmosphere for 15 hours. The chemical formula of the produced third particles was LiNi 0.6 Co 0.1 Mn 0.3 It was O2.

[0167] Production Example 1-5: Production of fourth particles (Ni 0.35 Mn 0.65A transition metal precursor, )(OH)2, and a lithium source, Li2CO3, were mixed in a weight ratio of (Ni+Mn):Li = 1:1.3. The mixture was fired at 600°C for 10 hours in an oxygen atmosphere to obtain secondary particles. The average size of the secondary particles was 5 to 10 μm, and the average size of the primary particles was approximately 100 nm to approximately 500 nm.

[0168] Manufacturing Example 2-1: Manufacturing of main active material The first particles of Preparation Example 1-1 and the second particles of Preparation Example 1-3 were mixed in a mass ratio of 65:35 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%.

[0169] Manufacturing Example 2-2 The first particles of Preparation Example 1-1 and the second particles of Preparation Example 1-3 were mixed in a mass ratio of 50:50 to prepare a main active material, in which the Mn content of the metal elements excluding lithium in the main active material was 70 mol%.

[0170] Manufacturing Example 2-3 The first particles of Preparation Example 1-1 and the second particles of Preparation Example 1-3 were mixed in a mass ratio of 40:60 to prepare a main active material, in which the Mn content of the metal elements excluding lithium in the main active material was 80 mol%.

[0171] Example 1-1: Preparation of first active material The main active material of Preparation Example 2-1 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 70:30 to prepare a first active material. The Mn content of the first active material was 50 mol %.

[0172] Example 1-2 The main active material of Preparation Example 2-2 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 85:15 to prepare a first active material. The Mn content of the first active material was 65 mol %.

[0173] Examples 1-3 The main active material of Preparation Example 2-2 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 70:30 to prepare a first active material. The Mn content of the first active material was 60 mol %.

[0174] Examples 1-4 The main active material of Preparation Example 2-2 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 60:40 to prepare a first active material. The Mn content of the first active material was 55 mol %.

[0175] Examples 1-5 The main active material of Preparation Example 2-3 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 80:20 to prepare a first active material. The Mn content of the first active material was 70 mol %.

[0176] Examples 1-6 The main active material of Preparation Example 2-3 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 70:30 to prepare a first active material. The Mn content of the first active material was 65 mol %.

[0177] Examples 1-7 The main active material of Preparation Example 2-3 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 60:40 to prepare a first active material. The Mn content of the first active material was 60 mol %.

[0178] Examples 1-8 The main active material of Preparation Example 2-3 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 50:50 to prepare a first active material. The Mn content of the first active material was 55 mol %.

[0179] Examples 1-9 The main active material of Preparation Example 2-1 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 90:10 to prepare a first active material. The Mn content of the first active material was 60 mol %.

[0180] Examples 1-10 The main active material of Preparation Example 2-1 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 80:20 to prepare a first active material. The Mn content of the first active material was 60 mol %.

[0181] Examples 1-11 The main active material of Preparation Example 2-1 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 70:30 to prepare a first active material. The Mn content of the first active material was 60 mol %.

[0182] Examples 1-12 The main active material of Preparation Example 2-2 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 90:10 to prepare a first active material. The Mn content of the first active material was 55 mol%.

[0183] Examples 1-13 The main active material of Preparation Example 2-2 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 80:20 to prepare a first active material. The Mn content of the first active material was 55 mol%.

[0184] Examples 1-14 The main active material of Preparation Example 2-2 and the third particles of Preparation Example 1-4 were mixed in a mass ratio of 70:30 to prepare a first active material. The Mn content of the first active material was 55 mol %.

[0185] Example 2-1: Preparation of second active material The first active material of Example 1-9 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 85:15 to prepare a second active material.

[0186] Example 2-2 The first active material of Example 1-9 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 80:20 to prepare a second active material.

[0187] Example 2-3 The first active material of Example 1-9 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 75:25 to prepare a second active material.

[0188] Examples 2-4 The first active material of Example 1-10 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 85:15 to prepare a second active material.

[0189] Examples 2-5 The first active material of Example 1-10 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 80:20 to prepare a second active material.

[0190] Examples 2-6 The first active material of Example 1-10 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 75:25 to prepare a second active material.

[0191] Examples 2-7 The first active material of Example 1-11 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 85:15 to prepare a second active material.

[0192] Examples 2-8 The first active material of Example 1-11 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 80:20 to prepare a second active material.

[0193] Examples 2-9 The first active material of Example 1-11 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 75:25 to prepare a second active material.

[0194] Example 2-10 The first active material of Example 1-12 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 85:15 to prepare a second active material.

[0195] Example 2-11 The first active material of Example 1-12 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 80:20 to prepare a second active material.

[0196] Example 2-12 The first active material of Example 1-12 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 75:25 to prepare a second active material.

[0197] Example 2-13 The first active material of Example 1-13 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 85:15 to prepare a second active material.

[0198] Example 2-14 The first active material of Example 1-13 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 80:20 to prepare a second active material.

[0199] Example 2-15 The first active material of Example 1-13 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 75:25 to prepare a second active material.

[0200] Example 2-16 The first active material of Example 1-14 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 85:15 to prepare a second active material.

[0201] Example 2-17 The first active material of Example 1-14 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 80:20 to prepare a second active material.

[0202] Example 2-18 The first active material of Example 1-14 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 75:15 to prepare a second active material.

[0203] Comparative Example 1 The first active material of Example 1-9 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 95:5 to prepare a second active material.

[0204] Comparative Example 2 The first active material of Example 1-9 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 90:10 to prepare a second active material.

[0205] Comparative Example 3 The first active material of Example 1-9 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 70:30 to prepare a second active material.

[0206] Comparative Example 4 The first active material of Example 1-9 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 65:35 to prepare a second active material.

[0207] Comparative Example 5 The first active material of Example 1-10 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 95:5 to prepare a second active material.

[0208] Comparative Example 6 The first active material of Example 1-10 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 90:10 to prepare a second active material.

[0209] Comparative Example 7 The first active material of Example 1-10 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 70:30 to prepare a second active material.

[0210] Comparative Example 8 The first active material of Example 1-10 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 65:35 to prepare a second active material.

[0211] Comparative Example 9 The first active material of Example 1-11 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 95:5 to prepare a second active material.

[0212] Comparative Example 10 The first active material of Example 1-11 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 90:10 to prepare a second active material.

[0213] Comparative Example 11 The first active material of Example 1-11 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 70:30 to prepare a second active material.

[0214] Comparative Example 12 The first active material of Example 1-11 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 65:35 to prepare a second active material.

[0215] Comparative Example 13 The first active material of Example 1-12 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 95:5 to prepare a second active material.

[0216] Comparative Example 14 The first active material of Example 1-12 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 90:10 to prepare a second active material.

[0217] Comparative Example 15 The first active material of Example 1-12 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 70:30 to prepare a second active material.

[0218] Comparative Example 16 The first active material of Example 1-12 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 65:35 to prepare a second active material.

[0219] Comparative Example 17 The first active material of Example 1-13 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 95:5 to prepare a second active material.

[0220] Comparative Example 18 The first active material of Example 1-13 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 90:10 to prepare a second active material.

[0221] Comparative Example 19 The first active material of Example 1-13 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 70:30 to prepare a second active material.

[0222] Comparative Example 20 The first active material of Example 1-13 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 65:35 to prepare a second active material.

[0223] Comparative Example 21 The first active material of Example 1-14 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 95:5 to prepare a second active material.

[0224] Comparative Example 22 The first active material of Example 1-14 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 90:10 to prepare a second active material.

[0225] Comparative Example 23 The first active material of Example 1-14 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 70:30 to prepare a second active material.

[0226] Comparative Example 24 The first active material of Example 1-14 and the fourth particles of Preparation Example 1-5 were mixed in a mass ratio of 65:35 to prepare a second active material.

[0227] Cathode manufacturing 95 wt% of the final positive electrode active material, 3 wt% of polyvinylidene fluoride binder, and 2 wt% 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.

[0228] Anode manufacturing The Si-graphite composite, binder, and 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.

[0229] 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 solution 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.

[0230] Evaluation example 1: Analysis of the surface of the positive electrode active material An SEM image of the first particles (single particles) prepared in Preparation Example 1-1 is shown in Figure 10a. An SEM image of the first particles (secondary particles) prepared in Comparative Example 1-2 is shown in Figure 10b. An SEM image of the second particles prepared in Preparation Example 1-3 is shown in Figure 11. An SEM image of the third particles prepared in Preparation Example 1-4 is shown in Figure 12. An SEM image of the fourth particles prepared in Preparation Example 1-5 is shown in Figure 13.

[0231] 10a, the first particles according to Preparation Example 1-1 of the present invention are nano-sized single particles. 10b, the second particles according to Preparation Example 1-2 of the present invention are spherical secondary particles formed by the aggregation 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.

[0232] Referring to FIG. 11, it can be seen that the secondary particles according to Preparation Example 1-3 of the present invention are secondary particles formed by aggregation of primary particles.

[0233] Referring to FIG. 12, 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.

[0234] Referring to FIG. 13, it can be seen that the fourth particles according to Preparation Example 1-5 of the present invention are secondary particles formed by aggregation of primary particles.

[0235] Evaluation example 2: Evaluation of active materials The pellet densities (compressed densities) (PD) of the positive electrode active materials of Preparation Example 1-2, Examples 1-1 to 2-18, and Comparative Examples 1 to 24 were measured, and the results are shown in Tables 1 and 2. The average pellet densities (compressed densities) were 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.

[0236] Evaluation example 3: Battery evaluation The characteristics of the lithium secondary batteries manufactured using the positive electrode active materials of Preparation Example 1-2, Examples 1-1 to 2-18, and Comparative Examples 1 to 24 were evaluated, and the results are shown in Tables 1 and 2 below.

[0237] The lithium secondary battery was initially charged at a constant current (0.2 C) and a constant voltage (4.25 V), and then allowed to rest for 10 minutes before being discharged at a constant current (0.1 C) to 2.5 V. The initial charge-discharge cycle was then repeated 50 times at 0.2 C / 0.2 C. The evaluation results of the battery characteristics are shown in Tables 1 and 2 below.

[0238] [Table 1]

[0239] [Table 2]

[0240] Referring to Table 1, it can be seen that batteries including the first active materials according to Examples 1-1 to 1-14 of the present invention have higher average voltages, higher life spans, higher pellet densities (compressed densities), and substantially the same or better energy densities than batteries including only the first particles PTC1 of Preparation Example 1-1. In other words, it can be seen that the first active materials exhibit improved average voltages, life spans, and energy densities while maintaining economic efficiency within the blending weight ratios and Mn content ranges of the examples in Table 1. Referring to Table 2, it can be seen that batteries including the second active materials according to Examples 2-1 to 2-3 of the present invention have higher life spans, the same or better pellet densities (compressed densities), and better energy densities than batteries including the cathode active materials according to Comparative Examples 1 to 4. It can be seen that Comparative Examples 3 and 4 are sections where the efficiency characteristics fall below that of a typical anode, thereby defeating the purpose of blending.

[0241] Referring to Table 2, it can be seen that the batteries including the second active materials according to Examples 2-4 to 2-6 of the present invention have the same or better pellet density (compressed density) and similar or better energy density than the batteries including the positive electrode active materials according to Comparative Examples 5 to 8. It can be seen that Comparative Examples 7 and 8 are sections where the efficiency characteristics are lower than that of a typical negative electrode, defeating the purpose of the blending.

[0242] Referring to Table 2, it can be seen that the batteries including the second active materials according to Examples 2-7 to 2-9 of the present invention have higher average voltages, the same or better pellet densities (compressed densities), and similar or better energy densities than the batteries including the positive electrode active materials according to Comparative Examples 9 to 12. It can be seen that Comparative Examples 11 and 12 are sections where the efficiency characteristics are lower than that of a typical negative electrode, defeating the purpose of the blending.

[0243] Referring to Table 2, it can be seen that the batteries including the second active materials according to Examples 2-10 to 2-12 of the present invention have higher average voltages, the same or better pellet densities (compressed densities), and similar or better energy densities than the batteries including the positive electrode active materials according to Comparative Examples 13 to 16. It can be seen that Comparative Examples 15 to 16 are sections where the efficiency characteristics are lower than that of a typical negative electrode, defeating the purpose of blending.

[0244] Referring to Table 2, it can be seen that the batteries including the second active materials according to Examples 2-13 to 2-15 of the present invention have higher average voltages, the same or better pellet densities (compressed densities), and similar or better energy densities than the batteries including the cathode active materials according to Comparative Examples 17 to 20. It can be seen that Comparative Examples 19 to 20 are sections where the efficiency characteristics are lower than that of a typical anode, thus defeating the purpose of blending.

[0245] Referring to Table 2, it can be seen that the batteries including the second active materials according to Examples 2-16 to 2-18 of the present invention have higher average voltages, the same or better pellet densities (compressed densities), and similar or better energy densities than the batteries including the positive electrode active materials according to Comparative Examples 21 to 24. It can be seen that Comparative Examples 23 to 24 are sections where the efficiency characteristics are lower than that of a typical negative electrode, defeating the purpose of blending.

[0246] To summarize the results of Table 2, the second active materials according to Examples 2-1 to 2-18 of the present invention can improve capacity and energy density characteristics while minimizing the decrease in efficiency of the second active material within the range of the mixing weight ratio and Mn content of the examples in Table 2. [Explanation of symbols]

[0247] 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: Cabinet 60: Sealing material 70: Electrode tab 71: Positive electrode tab 72: Negative electrode tab

Claims

1. A positive electrode active material, 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: Third particles having a layered structure and including a compound represented by the following Chemical Formula 3: Including, The positive electrode active material, wherein the content of the third particles is 10 to 50 parts by weight based on 100 parts by weight of the positive electrode active material. [Chemical formula 1] Li a1 Mn x1 Fe y1 A z1 2O 4-c1 (In the above Chemical Formula 1, 0.8<a1≦1.2, 0.4≦x1≦0.8, 0≦y1≦0.6, 0≦z1≦0.05, and 0≦c1≦0.05, and A is at least one element selected from the group consisting of Al, Ti, V, and Mg.) [Chemical formula 2] Li a2 Mn x2 B y2 O 4-c2 (In the above Chemical Formula 2, 0.8<a2≦1.2, 1.9≦x2≦2.05, 0≦y2≦0.05, and 0≦c2≦0.05, and B is at least one element selected from the group consisting of Al and Mg.) [Chemical formula 3] Li a3 Ni x3 Co y3 Mn z3 C w1 O 2-c3 (In the above Chemical Formula 3, 0.8<a3≦1.2, 0.5≦x3≦0.8, 0≦y3≦0.10, 0.1≦z3≦0.35, 0≦w1≦0.1, and 0≦c3≦0.05, and C is at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb.)

2. The positive electrode active material of claim 1 , further comprising fourth particles comprising a compound represented by the following Chemical Formula 4: [Chemical formula 4] Li a4 Ni x4 Mn y4 D z4 O c4 (In the above Chemical Formula 4, 1.1<a4≦1.6, 0.2≦x4≦0.5, 0.5≦y4≦0.8, 0≦z4≦0.05, and 2≦c4≦2.3, and D is at least one element selected from the group consisting of transition metals having an oxidation number of 4.)

3. The positive electrode active material of claim 2 , wherein the content of the fourth particles is 15 to 25 parts by weight based on 100 parts by weight of the positive electrode active material.

4. the first to third particles constitute a first active material; the first to fourth particles constitute a second active material; The Mn content of the first active material is 50 mol% to 80 mol%, The positive electrode active material of claim 2 , wherein the second active material has a manganese content of 50 mol % to 60 mol %.

5. The positive electrode active material of claim 2 , wherein the fourth particles have a fourth average particle size of 5 μm to 10 μm.

6. The positive electrode active material of claim 4 , wherein the content of the third particles is 30 to 50 parts by weight based on 100 parts by weight of the first active material.

7. the first and second particles constitute a main active material; the first to third particles constitute a first active material; 2. The positive electrode active material of claim 1, wherein the content of the main active material is 50 to 85 parts by weight based on 100 parts by weight of the first active material.

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

9. the first and second particles constitute a main active material; 2 . The positive electrode active material of claim 1 , wherein the mixing ratio of the first particles to the second particles in the main active material is 40:60 to 65:35 by weight.

10. the first particles have a single particle shape; The positive electrode active material of claim 1 , wherein the first particles have a first average particle size of 0.5 μm to 2.5 μm.

11. the first particles have a secondary particle shape formed by agglomeration of a plurality of first primary particles, The first particles have a first average particle size of 3 μm to 10 μm; The positive electrode active material of claim 1 , wherein the first primary particles have an average size of 50 nm to 150 nm.

12. The positive electrode active material of claim 1 , wherein the second particles have a second average particle size of 3 μm to 10 μm.

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, 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.

16. 16. The positive electrode for a lithium secondary battery according to 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. The binder includes 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)acrylic styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon. The positive electrode for a lithium secondary battery according to claim 15.

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. The positive electrode according to claim 15 . a negative electrode including a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector; A separator disposed between the positive electrode and the negative electrode Includes a rechargeable lithium battery.

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