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

Abstract

To provide a positive electrode active material having high energy density, high operation voltage, and high conductivity.SOLUTION: The present invention relates to a positive electrode active material for a lithium secondary battery, a manufacturing method for the same, and a lithium secondary battery including the same. More specifically, the positive electrode active material includes a first particle PTC1 containing a compound expressed by Chemical Formula 1 and having an olivine structure, a second particle PTC2 containing a compound expressed by Chemical Formula 2 and having a spinel structure, a third particle PTC3 containing a compound expressed by Chemical Formula 3 and having a layered structure, and a fourth particle PTC4 containing a compound expressed by Chemical Formula 4. The weight ratio of the fourth particle to the entire weight of the positive electrode active material is 0.5 wt% to 5 wt%. Lia1Mnb1Fex1-Ay1 PO4-c1 [Chemical Formula 1] Lia2Mnb2Bx2O4-c2 [Chemical Formula 2] Lia3 Nib3Cox3Mny3Cz1O2-c3 [Chemical Formula 3] Lia4Eb4Dx4O4-c4 [Chemical Formula 4]SELECTED DRAWING: Figure 6A

Description

[Technical Field]

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

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

[0003] A lithium secondary battery is a battery that includes a cathode and an anode, which contain active materials that allow the intercalation and deintercalation of lithium ions, and an electrolyte. Electrical energy is produced through oxidation and reduction reactions that occur when lithium ions are inserted / deintercalated at the cathode and anode. Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a positive electrode active material having high energy density, high operating voltage, and high conductivity.

[0005] Another problem to be solved by the present invention is to provide a lithium secondary battery having high energy density, high operating voltage, high charge / discharge efficiency, and excellent low-temperature characteristics. [Means for solving the problem]

[0006] The positive electrode active material according to the concept of the present invention includes 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, a third particle containing a compound of Chemical Formula 3 below and having a layered structure, and a fourth particle containing a compound of Chemical Formula 4 below. The weight ratio of the fourth particle to the total weight of the positive electrode active material is 0.5 wt% to 5 wt%.

[0007] [Chemical Formula 1] Li a1 Mn b1 Fe x1 A y1 PO 4-c1 In Chemical Formula 1, 0.8 ≦ a1 ≦ 1.2, 0.5 ≦ b1 ≦ 0.9, 0.1 ≦ x1 ≦ 0.5, 0.001 ≦ y1 ≦ 0.05, <c1 ≦ 0.05, and b1 + x1 + y1 = 1, and A is at least one element selected from the group consisting of Al, Ti, V, and Mg.

[0008] [Chemical Formula 2] Li a2 Mn b2 B x2 O 4-c2 In Chemical Formula 2, 0.8 ≦ a2 ≦ 1.2, 1.9 ≦ b2 ≦ 2.05, 0 ≦ x2 ≦ 0.05, and 0 ≦ c2 ≦ 0.05, and B is at least one element selected from the group consisting of Mg and Al.

[0009] [Chemical Formula 3] Li a3 Ni b3 Co x3 Mn y3 C z1 O 2-c3 In Chemical Formula 3, 0.8 ≦ a3 ≦ 1.2, 0.5 ≦ b3 ≦ 0.8, 0 ≦ x3 ≦ 0.10, 0.1 ≦ y3 ≦ 0.35, 0 ≦ z1 ≦ 0.1, 0 ≦ c3 ≦ 0.05, and b3 + x3 + y3 + z1 = 1, and C is at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb.

[0010] [Chemical formula 4] Li a4 E b4 D x4 O 4-c4 In the formula 4, 4.9≦a4≦6.1, 0.9≦b4≦1.1, 0≦x4≦0.015, and 0≦c4≦0.05, E is Fe or Co, and D includes Al.

[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 positive electrode active material, a conductive material, and a binder.

[0012] According to another aspect of the present invention, a positive electrode for a lithium secondary battery includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material according to claim 1, a conductive material, and a binder.

[0013] A lithium secondary battery according to another aspect of the present invention may include the positive electrode, a negative electrode current collector, a negative electrode including a negative electrode active material layer on the negative electrode current collector, and a separator between the positive electrode and the negative electrode. [Effects of the Invention]

[0014] The cathode active material according to the present invention may include olivine-based first particles having a size of several hundred nanometers. The cathode active material according to the present invention may include spinel-based second particles. The cathode active material according to the present invention may include layered third particles, which may include single-crystal fourth particles having a size of several micrometers and serving as a sacrificial cathode. This may improve the pellet density, capacity, and energy density of the cathode active material according to the present invention. The cathode active material layer according to the present invention may be smoothly attached to the cathode current collector even with a relatively small amount of binder. The lithium secondary battery according to the present invention may have a relatively high average voltage. [Brief explanation of the drawings]

[0015] [Figure 1]1 is a conceptual diagram illustrating a lithium secondary battery according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram showing a lithium secondary battery according to an embodiment, in which the battery has a cylindrical shape. [Figure 3] FIG. 3 is a schematic diagram showing a lithium secondary battery according to an embodiment, in which the battery has a prismatic shape. [Figure 4] FIG. 4 is a schematic diagram showing a lithium secondary battery according to an embodiment, in which the battery is in the form of a pouch. [Figure 5] FIG. 5 is a schematic diagram showing a lithium secondary battery according to an embodiment, in which the battery is in the form of a pouch. [Figure 6A] 2 is an enlarged view of a positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention. FIG. [Figure 6B] 2 is an enlarged view of a positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention. FIG. [Figure 7A] 1 is a SEM image of a first particle in the form of a single particle according to an embodiment of the present invention. [Figure 7B] 1 is a SEM image of primary particles in the form of secondary particles according to an embodiment of the present invention. [Figure 7C] 10 is an SEM image of a second particle according to an embodiment of the present invention. [Figure 7D] 10 is an SEM image of a third particle according to an embodiment of the present invention. [Figure 7E] 10 is an SEM image of a fourth particle according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] In this specification, when a component is referred to as being on another component, it means that the component can be formed directly on the other component, or that a third component can be interposed between them. However, the present invention is not limited to the embodiments disclosed below, and can be realized in various forms and can undergo various modifications. The description of the present embodiments is provided solely to ensure complete disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0017] 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 for the sake of efficient explanation of the technical content. Parts designated with the same reference numerals throughout the specification refer to the same components.

[0018] 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.

[0019] As used herein, "combinations thereof" can mean mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0020] 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, when measuring by the laser diffraction method, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT3000), and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W. The average particle size (D50) based on 50% of the particle size distribution in the measuring device can then be calculated.

[0021] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment of the present invention. Referring to FIG. 1, the lithium secondary battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte solution ELL.

[0022] 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.

[0023] The electrolyte ELL can be a medium for transferring lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, the lithium ions can pass through the separator 30 and move toward the positive electrode 10 or the negative electrode 20.

[0024] 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. 6A and 6B. The current collector COL1 may be made of, but is not limited to, aluminum.

[0025] negative electrode 20 The negative electrode 20 for a lithium secondary battery includes a current collector COL2 and a negative electrode active material layer AML2 located on the current collector COL2. The negative electrode active material layer AML2 includes a negative electrode active material and may further include a binder and / or a conductive material.

[0026] For example, the negative electrode active material layer AML2 may contain 90 to 99 wt % of the negative electrode active material, 0.5 to 5 wt % of the binder, and 0 to 5 wt % of the conductive material.

[0027] 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.

[0028] 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.

[0029] The water-based binder may be selected from styrene-styrene rubber, (meth)acrylate styrene-styrene rubber, (meth)acrylonitrile-styrene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0030] When an aqueous binder is used as the negative electrode binder, a cellulose-based compound that can impart viscosity may be further included. The cellulose-based compound may be 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.

[0031] The dry binder may be a polymeric material that can be fiberized, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0032] The conductive material is used to impart conductivity to the electrode, and any material that is electronically conductive without causing a chemical change in the battery may be used. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0033] As the current collector COL2, it is possible to use 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.

[0034] negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

[0035] Examples of the material capable of reversibly intercalating / deintercalating the lithium ions include carbon-based negative electrode active materials, which can include, for example, crystalline carbon, amorphous carbon, or combinations thereof. Examples of the crystalline carbon can include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon can include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0036] 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.

[0037] As the material capable of doping and undoping lithium, an 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), an 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 combinations thereof. The Sn-based negative electrode active material can be Sn, SnO2, a Sn-based alloy, or combinations thereof.

[0038] 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 assembling primary silicon particles and a first 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, coating the primary silicon particles with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0039] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core including crystalline carbon and silicon particles and a first coating layer of amorphous carbon located on the core surface.

[0040] The Si-based or Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0041] Separator 30 Depending on the type of lithium secondary battery, a separator 30 may be present between the positive electrode 10 and the negative electrode 20. As such a separator 30, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof can be used, and it goes without saying that mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator can also be used.

[0042] Separator 30 can include a porous substrate and a first coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0043] The porous substrate may be a polymer membrane formed of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyacetimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon (registered trademark), and polytetrafluoroethylene, or a copolymer or mixture of two or more of these polymers.

[0044] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0045] 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.

[0046] The organic material and the inorganic material may be mixed in one first coating layer, or may be stacked in a form in which a first coating layer containing an organic material and a first coating layer containing an inorganic material are stacked.

[0047] Electrolyte ELL The electrolyte ELL for lithium secondary batteries contains a non-aqueous organic solvent and a lithium salt.

[0048] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can migrate.

[0049] The non-aqueous organic solvent can be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, or a combination thereof.

[0050] Examples of the carbonate solvent that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0051] 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.

[0052] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0053] The non-aqueous organic solvents can be used alone or in combination of two or more.

[0054] In addition, when a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed and used, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio of 1:1 to 1:9.

[0055] The lithium salt dissolves 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 integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0056] 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 type, FIG. 3 illustrating a prismatic type, and FIGS. 4 and 5 illustrating pouch 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 case 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 case 50, as shown in FIG. 2. Also, as shown in FIG. 3, the lithium secondary battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in FIGS. 4 and 5, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting current generated in the electrode assembly 40 to the outside.

[0057] 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.

[0058] 6A and 6B 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 FIG. 6A, as described above, the positive electrode active material layer AML1 (see FIG. 1) may include first particles PTC1, second particles PTC2, third particles PTC3, fourth particles PTC4, a conductive material CDM, and a binder BND. 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 positive electrode active material according to an embodiment of the present invention.

[0059] The content of the positive electrode active materials PTC1, PTC2, PTC3, and PTC4 in the positive electrode active material layer AML1 may be 90 wt% to 99.5 wt% relative to 100 wt% of the positive electrode active material layer AML1. The content of the binder BND and the conductive material CDM may be 0.5 wt% to 5 wt% each relative to 100 wt% of the positive electrode active material layer AML1.

[0060] The binder BND can bind the first particles PTC1, the second particles PTC2, the third particles PTC3, the fourth particles PTC4, and the conductive material CDM to one another. As an example, the binder BND can include, but is not limited to, at least one selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl fluoride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0061] 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 without limitation. For example, the conductive material CDM can include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0062] Hereinafter, the first particles PTC1, the second particles PTC2, the third particles PTC3, and the fourth particles PTC4 will be described in more detail.

[0063] 1st particle PTC1 Referring to FIG. 6A, the first particle PTC1 may have a single particle shape. As used herein, a single particle may refer to a single particle without an internal grain boundary. A single particle may refer to a single particle, a monolith structure, a single structure, or a non-aggregated particle, in which particles morphologically exist in an independent phase without cohesion with each other. For example, a single particle may be a single crystal. Alternatively, a single particle may be a particle containing several crystals. A single particle may be in a singly separated form. Alternatively, a single particle may be in a form in which 2 to 100 single particles are attached to each other.

[0064] The first particles PTC1 may be a nano-shaped cathode active material. The first particles PTC1 may include at least one first primary particle NNP. In one embodiment, the first primary particles NNP may be aggregated to have a particle shape similar to that of the second particles PTC2. Although the first particles PTC1 are aggregated first primary particles NNP, they may not be spherical like the second particles PTC2. That is, the first particles PTC1 may have a random shape.

[0065] The first particles PTC1 can be provided in various sizes. For example, the average particle size of the first particles PTC1 can be 500 nm to 2.5 μm, or about 1 μm. The minimum particle size of the first particles PTC1, i.e., the particle size of the primary particles, can be 100 nm to 500 nm, or 100 nm to 200 nm.

[0066] In one embodiment, the average particle size can be measured using a particle size analyzer. The average particle size can refer to the diameter of particles whose cumulative volume is 50% by volume (D50) in the particle size distribution.

[0067] In one embodiment, the minimum particle size, i.e., the particle size of the 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.

[0068] The porosity of the first particle PTC1 may be greater than 40%. The first particle PTC1 may be outside the range of 0.3 to 0.75 of the Span value analyzed by a particle size analyzer.

[0069] As one embodiment, the first particle PTC1 can include a first coating layer on its surface. The first coating layer can cover the entire surface of the first particle PTC1 or a part of the surface of the first particle PTC1. For example, the first coating layer can include carbon and / or a carbon-containing compound. The first coating layer can further include at least one selected from the group consisting of a titanium-containing compound, a magnesium-containing compound, an aluminum-containing compound, and a vanadium-containing compound. Metal-containing compounds such as titanium-containing compounds, magnesium-containing compounds, aluminum-containing compounds, and vanadium-containing compounds can be, for example, metal oxides, metal hydroxides, metal carbonates, their composites, or their mixtures. The metal-containing compounds can further include other metal or non-metal elements. For example, the metal-containing compounds may further include lithium. The first particle PTC1 can improve its structural stability and electrical conductivity by the first coating layer.

[0070] The first particle PTC1 can include an olivine-based lithium compound represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Mn b1 Fe x1 A y1 PO 4-c1

[0071] In Formula 1, 0.8 ≦ a1 ≦ 1.2, 0.5 ≦ b1 ≦ 0.9, 0.1 ≦ x1 ≦ 0.5, 0.001 ≦ y1 ≦ 0.05, 0 < c1 ≦ 0.05, and b1 + x1 + y1 = 1 can hold.

[0072] A may be at least one element selected from the group consisting of Mg, Ti, V, and Al. A may be a dopant doped into the first particles PTC1. For example, A may include Ti.

[0073] The first particles PTC1 may further contain carbon derived from the first 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%.

[0074] A method for measuring the elemental content in the first coating layer of the first particle PTC1 may include performing scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) on the first particle PTC1. The carbon and metal contents in the first coating layer may be confirmed through this analysis. In addition to SEM-EDS, methods for measuring the elemental content in the first coating layer may also include inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0075] 6B, the first particles PTC1 may have a secondary particle shape in which a plurality of particles are attached to each other. The secondary particles may have a form in which 2 to 100 first primary particles NNP are attached to each other. The first primary particles NNP are the smallest crystalline unit constituting the secondary particles and are distinguished from single particles. The first particles PTC1 may have a spherical or elliptical shape.

[0076] In one embodiment, the first particles PTC1 may include a coating layer on their surfaces. The coating layer may cover the entire surface of the first particles PTC1 or a portion of the surface of the first particles PTC1. For example, the coating layer may include carbon and / or a carbon-containing compound. The coating layer may improve the structural stability and electrical conductivity of the first particles PTC1.

[0077] The coating layer may further include at least one selected from the group consisting of a titanium-containing compound, a magnesium-containing compound, and a vanadium-containing compound. Metal-containing compounds such as titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds may be, for example, metal oxides, metal hydroxides, metal carbonates, composites thereof, or mixtures thereof. The metal-containing compounds may further include other metals or non-metal elements. For example, the metal-containing compounds may further include lithium.

[0078] In one embodiment, the first particle PTC1 may further include a grain boundary coating layer on the surface of each of the first primary particles NNP. The grain boundary coating layer may be present inside the first particle PTC1. The grain boundary coating layer may be formed by coating along the interface between the first primary particles NNP inside the first particle PTC1. In other words, the grain boundary coating layer may refer to a material coated on the grain boundaries inside the first particle PTC1. The grain boundary coating layer may include carbon and / or a carbon-containing compound. The grain boundary coating layer may further include at least one selected from the group consisting of a titanium-containing compound, a magnesium-containing compound, and a vanadium-containing compound.

[0079] The interior of the first particle PTC1 described above may refer to the entire interior of the first particle PTC1 excluding the surface of the first particle PTC1. For example, the interior of the first particle PTC1 may refer to the region from a depth of about 10 nm to the entire interior of the surface of the first particle PTC1, or from a depth of 10 nm to a depth of about 2 μm.

[0080] The first particles PTC1 further include a grain boundary coating portion, which enhances structural stability and allows a uniform coating layer to be formed on the surface of the first particles PTC1. In addition, the first particles PTC1 further include a grain boundary coating portion, which further improves the electrical conductivity of the first particles PTC1.

[0081] 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 first average particle size of the first particles PTC1 may be approximately 5 μm. The average particle size of the first particles PTC1 may be smaller than the average particle size of the second particles PTC2 described below. 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 whose cumulative volume is 50% by volume (D50) in the particle size distribution.

[0082] The particle size of the first primary particles NNP of the first particles PTC1 may be 10 nm to 400 nm, 20 nm to 300 nm, 50 nm to 200 nm, or 100 nm to 200 nm. In one embodiment, the particle size of the first primary particles NNP may refer to the diameter measured by randomly selecting about 30 first primary particles NNP from an electron microscope photograph of the positive electrode active material. The particle size of the first primary particles NNP may be uniform.

[0083] The first particles PTC1 may have a spherical shape formed by the aggregation of nano-sized first primary particles NNP. The first particles PTC1 may exhibit the following characteristics due to the first primary particles NNP closely agglomerating to each other: The first particles PTC1 may have a spherical or elliptical shape. The average particle size (D50) of the first particles PTC1 may be 2 μm to 15 μm. The porosity of the first particles PTC1 may be about 20% to about 40%. The Span value of the first particles PTC1 analyzed with a particle size analyzer may be 0.3 to 0.75.

[0084] 2nd particle PTC2 The second particles PTC2 may have a single particle shape, similar to the first particles PTC1 described above. The description of the single particle may be the same as or similar to that of the first particles PTC1 described above. In one embodiment, the second particles PTC2 may have a shape composed of one single particle. In another embodiment, the second particles PTC2 may have a shape in which a plurality of single particles are attached to each other. The cathode active material according to the present invention includes the second particles PTC2 in a single particle shape, thereby achieving high capacity and high energy density of the secondary battery.

[0085] In another embodiment of the present invention, the second particles PTC2 may have a secondary particle shape. Referring to Figures 6A and 6B, the second particles PTC2 may have a polycrystalline form, including 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 aggregated.

[0086] In one embodiment, the second particles PTC2 may include a second coating layer on their surfaces. By including the second coating layer, the second particles PTC2 can effectively prevent structural collapse due to repeated charge and discharge, thereby improving the lifespan of the secondary battery.

[0087] The second coating layer may include a boron-containing compound, an aluminum-containing compound, or a combination thereof. The metal-containing compound in the second coating layer may be, for example, a metal oxide, a metal hydroxide, a metal carbonate, a composite thereof, or a mixture thereof. The 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, etc.

[0088] The average particle size of the second particles PTC2 may be 3 μm to 20 μm, 4 μm to 15 μm, or 5 μm to 10 μm. For example, the average particle size of the second particles PTC2 may be 6 μm. The average particle size of the second particles PTC2 may be larger than the average particle size of the first particles PTC1 described above. When the second particles PTC2 include multiple single particles, the average size of the single particles of the second particles PTC2 may be larger than the average particle size of the first particles PTC1.

[0089] In one embodiment, approximately 30 second primary particles are randomly selected from an electron microscope photograph of the positive electrode active material, and their particle sizes are measured. The diameter (D50) of the particles at 50% of the cumulative volume in the particle size distribution is defined as the average particle size. The second primary particles may be uniform in size. The second primary particles may have a smaller average size than the first primary particles. The difference in average size between the second primary particles and the first primary particles may be 300 nm or more.

[0090] The second particles PTC2 may include a lithium compound having a spinel structure represented by the following Chemical Formula 2. [Chemical formula 2] Li a2 Mn b2 B x2 O 4-c2

[0091] In Formula 2, 0.8≦a2≦1.2, 1.9≦b2≦2.05, 0≦x2≦0.05, and 0≦c2≦0.05, and B may be at least one element selected from the group consisting of Mg and Al. B may be a dopant doped into the second particles PTC2. For example, B may include Ti.

[0092] Third particle PTC3 The third particles PTC3 may have a single particle shape, similar to the first particles PTC1 described above. The description of the single particle may be the same as or similar to that of the first particles PTC1 described above. In one embodiment, the third particles PTC3 may have a shape composed of one single particle. In another embodiment, the third particles PTC3 may have a shape in which a plurality of single particles are attached to each other. The cathode active material according to the present invention includes the third particles PTC3 in a single particle shape, thereby achieving high capacity and high energy density of the secondary battery.

[0093] The third particles PTC3 according to one embodiment of the present invention may have a secondary particle shape in which a plurality of particles are attached to each other, similar to the above-described particles PTC1. The secondary particles may have a form in which 2 to 100 second primary particles are attached to each other. The second primary particles may be larger than or the same as the first primary particles. The second primary particles are the smallest crystalline units constituting the secondary particles and are distinguished from single particles. The third particles PTC3 may have a spherical or elliptical shape.

[0094] In one embodiment, the third particles PTC3 may include a third coating layer on their surfaces. By including the third coating layer, the third particles PTC3 can effectively prevent structural collapse due to repeated charge and discharge, thereby improving the lifespan of the secondary battery.

[0095] The third coating layer may include a boron-containing compound, an aluminum-containing compound, or a combination thereof. The metal-containing compound in the second coating layer may be, for example, a metal oxide, a metal hydroxide, a metal carbonate, a composite thereof, or a mixture thereof. The 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, etc.

[0096] 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. When the third particles PTC3 include multiple single particles, the average size of the single particles of the third particles PTC3 may be larger than the average particle size of the first particles PTC1.

[0097] In one embodiment, approximately 30 third particles PTC3 are randomly selected from an electron microscope photograph of the positive electrode active material, and their particle sizes are measured. The diameter (D50) of the particles whose cumulative volume is 50% by volume in the particle size distribution can be determined as the average particle size.

[0098] A method for measuring the metal content in the third coating layer of the third particles PTC3 may include performing scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) on the third particles PTC3. The boron and / or aluminum content in the third coating layer may be determined through this analysis. In addition to SEM-EDS, methods for measuring the metal content in the third coating layer may also include inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0099] The third particles PTC3 may include a lithium-nickel composite oxide as a nickel-based active material. For example, the third particles PTC3 may include a high-nickel-based positive electrode active material containing a high content of nickel. The high-nickel-based positive electrode active material may achieve high capacity and high performance.

[0100] Specifically, the third particles PTC3 may include a lithium nickel-based composite oxide having a layered structure represented by the following Chemical Formula 3. [Chemical formula 3] Lia3 Ni b3 Co x3 Mn y3 C z1 O 2-c3

[0101] In Formula 3, 0.8≦a3≦1.2, 0.5≦b3≦0.8, 0≦x3≦0.10, 0.1≦y3≦0.35, 0≦z1≦0.1, 0≦c3≦0.05, and b3+x3+y3+z1=1, and C may be at least one element selected from the group consisting of Al, Ti, MgZr, Mo, and Nb. C may be a dopant doped into the third particles PTC3.

[0102] 4th particle PTC4 The fourth particles PTC4 may have a single particle shape, similar to the first particles PTC1 described above. The description of the single particle may be the same as or similar to that of the first particles PTC1 described above. In one embodiment, the fourth particles PTC4 may have a shape composed of one single particle. In another embodiment, the fourth particles PTC4 may have a shape in which a plurality of single particles are attached to each other. The cathode active material according to the present invention includes the fourth particles PTC4 in a single particle shape, thereby achieving high capacity and high energy density of the secondary battery.

[0103] In one embodiment, the fourth particles PTC4 may include a fourth coating layer on the surface thereof. By including the fourth coating layer, the fourth particles PTC4 can effectively prevent structural collapse due to repeated charge and discharge, thereby improving the lifespan characteristics of the secondary battery.

[0104] 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, etc.

[0105] The average particle size of the fourth particles PTC4 may be 2 μm to 15 μm, 2 μm to 10 μm, or 4 μm to 10 μm. 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 multiple single particles, the average size of the single particles of the fourth particles PTC4 may be larger than the average particle size of the fourth particles PTC4.

[0106] In one embodiment, approximately 30 fourth particles PTC4 are randomly selected from an electron microscope photograph of the positive electrode active material, and the particle sizes are measured. The diameter (D50) of the particles whose cumulative volume is 50% by volume in the particle size distribution can be determined as the average particle size.

[0107] The fourth particles PTC4 may include a lithium compound represented by the following Chemical Formula 4.

[0108] [Chemical formula 4] Li a4 E b4 D x4 O 4-c4 In Formula 4, 4.9≦a4≦6.1, 0.9≦b4≦1.1, 0≦x4≦0.015, and 0≦c4≦0.05, E is Fe or Co, and D includes Al. In particular, when E is Fe, a4 can be 5, and when E is Co, a4 can be 6.

[0109] The fourth particles PTC4 may further include carbon derived from the coating layer. The carbon element content in the fourth particles PTC4 may be 0.5 wt% to 5 wt%, 0.5 wt% to 3 wt%, or 0.5 wt% to 2 wt%. The carbon content of the fourth particles PTC4 may be lower than the carbon content of the first particles PTC1. This is because the fourth particles PTC4, as single particles, are less likely to form a coating layer smoothly than the first particles PTC1, which are secondary particles.

[0110] The fourth particles PTC4 can participate in the formation of a solid electrolyte interface (SEI) film on the negative electrode surface during charge and discharge. The fourth particles PTC4 are converted into irreversible Li, which no longer participates in charge and discharge reactions. This can lead to a problem of a decrease in the capacity of the positive electrode active material layer AML1.

[0111] According to an embodiment of the present invention, the fourth particles PTC4 may include an oxide containing Fe. The fourth particles PTC4 may serve as a sacrificial positive electrode that can replenish irreversible Li. The fourth particles PTC4 may be decomposed during the formation process to provide Li, and may not subsequently participate in the charge / discharge process.

[0112] For example, LiFeO4 can be decomposed between 3.7 V and 3.9 V to provide four Li atoms per one Li. When the fourth particle PTC4 containing the compound is used in the content range described below, it can adequately compensate for irreversible Li.

[0113] According to an embodiment of the present invention, the fourth particles PTC4 may include LiFeO, LiFeO, LiFeO, or a combination thereof. For example, the fourth particles PTC4 may include LiFeO. LiFeO can provide many Li atoms during the formation process, thereby more effectively replenishing irreversible Li. This can enhance the effect of the sacrificial positive electrode.

[0114] The fourth particle PTC4 according to an embodiment of the present invention may include an oxide containing Co. For example, LiCoO4 may be used as a compound constituting the fourth particle PTC4. The compound may decompose between 3.7 V and 3.9 V to provide four Li atoms per one Li. When the fourth particle PTC4 including the compound is used in the content range described below, the compound may adequately compensate for irreversible Li.

[0115] According to an embodiment of the present invention, the fourth particles PTC4 may include LiCoO, LiCoO, LiCoO, or a combination thereof. For example, the fourth particles PTC4 may include LiCoO. LiCoO can provide many Li atoms during the formation process, thereby more effectively replenishing irreversible Li. This allows for a greater sacrificial positive electrode effect.

[0116] 6A and 6B, a cathode active material according to an embodiment of the present invention will be described in more detail. The cathode active material may include first particles PTC1, second particles PTC2, third particles PTC3, and fourth particles PTC4. The mixing ratio of the first particles PTC1 to the third particles PTC3 to the fourth particles PTC4 in the cathode active material may be 90:10 to 50:50. Alternatively, the mixing ratio may be 95:5 to 99.5:0.5. The content of the first particles PTC1 to the third particles PTC3 in the cathode active material may be greater than the content of the fourth particles PTC4.

[0117] 6A and 6B, the cathode active material according to the embodiment of the present invention will be described in more detail. 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 80 to 90 parts by weight based on 100 parts by weight of the cathode active material.

[0118] Lithium cobalt-based positive electrode active material (first particle, PTC1) with an olivine crystal structure is cheaper than other positive electrode materials and has excellent stability and lifespan characteristics, but its low energy density makes it difficult to use at high voltages. Lithium manganese oxide-based positive electrode active material (second particle, PTC2) with a spinel structure has high operating voltage, excellent stability, and is inexpensive, but like the first particle, PTC1, it has low energy density.

[0119] The cathode active material according to the present invention uses a mixture of first particles PTC1 and second particles PTC2 as the main active material, which is inexpensive and stable, while exhibiting high operating voltage and excellent life characteristics. The relatively low energy density can be improved by adding third particles PTC3, which have excellent capacity and output characteristics. Furthermore, the addition of fourth particles PTC4, which function as a sacrificial cathode, can achieve even higher capacity and density.

[0120] The mixing ratio of the first particles PTC1 to the second particles PTC2 may be 4:6 to 6:4, or 4.5:5.5 to 5.5:4.5 by weight. The Mn content in the main active material composed of the first particles PTC1 and the second particles PTC2 may be 50 mol % to 80 mol %, 60 mol % to 80 mol %, or 50 mol % to 90 mol %, relative to 100 mol % of the total transition metals excluding lithium in the main active material.

[0121] The content of the third particles PTC3 may be 10 to 30 parts by weight based on 100 parts by weight of the positive electrode active material. When the content of the third particles PTC3 satisfies the above range, the capacity characteristics can be improved while minimizing deterioration in the life and stability of the positive electrode active material.

[0122] The positive electrode active material according to the present embodiment can improve the capacity and operating voltage compared to a general LMFP battery by mixing the first to third particles PTC1 to PTC3 and the fourth particle PTC4 in an appropriate ratio.

[0123] The compound of Chemical Formula 4 may have lower electrical conductivity than the compound of Chemical Formula 1. The present invention can improve electrical conductivity and energy density by using the fourth particle PTC4 as a single particle.

[0124] The first particles PTC1 have the advantages of high stability and long lifespan. By using the structurally stable first particles PTC1 as the main material of the positive electrode active material, the relatively low stability and short lifespan of the fourth particles PTC4 can be compensated for.

[0125] The positive electrode active material of the present invention can improve pellet density, capacity, and energy density by mixing fourth particles PTC4 having a size of several microns with first particles PTC1 having a size of several hundred nanometers. In one embodiment, the positive electrode active material of the present invention can have a compressed density of 2.0 g / cc to 2.9 g / cc. A lithium secondary battery including the positive electrode active material of the present invention can have improved low-temperature characteristics.

[0126] Because the first particles PTC1, which are single particles, have a very small average particle size, a large amount of binder BND may be required to adhere the first particles PTC1 to the current collector COL1 (see FIG. 1). The cathode active material of the present invention includes not only the first to third particles PTC1, PTC2, and PTC3, but also the fourth particles PTC4, which have a large average particle size, thereby enabling the cathode active material layer AML1 to adhere smoothly to the current collector COL1. That is, the fourth particles PTC4 can reduce the amount of binder BND in the cathode active material layer AML1.

[0127] A lithium secondary battery (see FIG. 1) including the positive electrode active material according to the above-described embodiment of the present invention may have an average voltage of 3.5 V to 3.8 V when discharged at 0.1 C between 2.5 V and 4.25 V. In addition, the energy density of the lithium secondary battery according to the present invention may be 450 Wh / Kg to 600 Wh / kg, 500 Wh / Kg to 600 Wh / kg, or 500 Wh / Kg to 550 Wh / kg.

[0128] *Production method of positive electrode active material A method for manufacturing the first particles PTC1 according to an embodiment of the present invention will now be described in detail. An iron phosphate precursor, a lithium source, a carbon source, and a dopant source can be mixed in a solvent. For example, the solvent can be water, ethanol, or the like. The iron phosphate precursor can be a compound containing both iron (Fe) and phosphorus (P), or a mixture of an iron (Fe)-containing compound and a phosphorus (P)-containing compound. For example, the iron phosphate precursor can include FePO4·H2O or a mixture of FeSO4 and H3PO4.

[0129] The lithium source may include at least one selected from the group consisting of lithium oxide, lithium hydroxide, lithium chloride, lithium nitrate, lithium nitrite, lithium formate, lithium acetate, lithium oxalate, lithium carbonate, lithium phosphate, lithium dihydrogen phosphate, lithium dihydrogen phosphate, and lithium citrate.

[0130] The carbon source can include at least one selected from the group consisting of glucose, sucrose, fructose, cellulose, starch, citric acid, polyacrylic acid, polyethylene glycol, and dopamine.

[0131] The dopant source may include an oxide containing a dopant metal and / or a chloride containing a dopant metal, for example, the dopant source may include at least one selected from the group consisting of titanium oxide, magnesium oxide, vanadium oxide, and niobium oxide.

[0132] The mixture may be subjected to wet milling. A typical temperature-controllable wet mill may be used for the wet milling. Specifically, at least one selected from a bead mill, a ball mill, an attrition mill, an apex mill, a super mill, and a basket mill may be used for the wet milling. Through the wet milling process, particles in the mixture may be pulverized to a fine size.

[0133] The solvent can be removed from the mixture to form a dried mixture. In one embodiment, forming the dried mixture can include subjecting the mixture to direct evaporation. For example, direct evaporation can include static drying or spray drying.

[0134] The dried mixture may be calcined under an inert atmosphere. The inert atmosphere may be a nitrogen atmosphere and / or an argon atmosphere. The temperature of the calcination process may be 500°C to 1000°C or 600°C to 800°C. The calcination process may be performed for 4 hours to 20 hours, or 6 hours to 12 hours. By calcining the dried mixture, first particles PTC1 containing the compound of Formula 1 described above may be formed.

[0135] The fired first particles PTC1 may be subjected to a dry grinding process, so that the first particles PTC1 may have a single particle shape as shown in FIG. 6A.

[0136] A method for producing the first particles PTC1 according to an embodiment of the present invention will now be described in more detail. A manganese iron phosphate precursor, a lithium source, a carbon source, and a dopant source may be mixed in a solvent. For example, the solvent may be water, ethanol, or the like.

[0137] The manganese iron phosphate precursor may be a compound containing all of manganese (Mn), iron (Fe), and phosphorus (P); a mixture of a manganese (Mn)-containing compound and a compound containing iron (Fe) and phosphorus (P); or a mixture of a manganese (Mn)-containing compound, an iron (Fe)-containing compound, and a phosphorus (P)-containing compound. For example, the manganese iron phosphate precursor may be a compound containing Mn x Fe 1-x PO4·H2O; a mixture of MnCO3 and FePO4·H2O; or a mixture of MnCO3, FeSO4, and H3PO4; where x can be from 0.5 to 0.9.

[0138] The mixture can be subjected to wet milling.

[0139] The solvent can be removed from the mixture to form a dried mixture. Forming the dried mixture can include subjecting the mixture to a direct evaporation method. For example, a direct evaporation method can include static drying or spray drying. To form the first particles PTC1 as single particles, it may be desirable to use static drying.

[0140] The dried mixture may be calcined under an inert atmosphere. By calcining the dried mixture, first particles PTC1 including the compound of Chemical Formula 1 may be formed. The calcined first particles PTC1 may be subjected to a dry-milling process. As a result, the first particles PTC1 may have a single particle shape.

[0141] A method for producing the secondary particle form of the first particles PTC1 according to an embodiment of the present invention will now be described in more detail. In one embodiment of the present invention, the wet pulverization may be omitted. Specifically, in order to maximize the average particle size of the resulting first particles PTC1, the wet pulverization of the precursor particles may be omitted.

[0142] A dried mixture can be formed by removing the solvent from the mixture. In one embodiment of the present invention, forming the dried mixture can include spray drying the mixture. Spray drying can be performed using a commonly used spray drying device. For example, spray drying can be performed using at least one selected from an ultrasonic spray drying device, an air nozzle spray drying device, an ultrasonic nozzle spray drying device, a filter expansion droplet generating device, and an electrostatic spray drying device.

[0143] The particles refined to the size of primary particles NNP in the wet milling process can aggregate with each other to form secondary particles in the spray drying process. Therefore, the primary particles PTC1 can be formed into secondary particles of a desired size by adjusting the flow rate and velocity of the carrier gas, temperature, residence time in the reactor, internal pressure, etc. in the spray drying process.

[0144] In one embodiment, the mixture to be spray-dried may have a total solid content of 20% to 40%. The solid content may refer to the weight of the solid material (i.e., the dried mixture) remaining after the solvent has evaporated relative to the total weight of the mixture (i.e., the spray liquid), converted into a percentage. For example, the spray liquid may have a solid content of approximately 30 wt%.

[0145] If the solid content is less than 20%, the average particle size of the first particles PTC1 will be small, which may result in low productivity.If the solid content is more than 40%, it will be difficult to control the average particle size of the first particles PTC1, which may result in large size deviations of the first particles PTC1.

[0146] The spray liquid according to this embodiment may have a viscosity of 1500 mPa·s to 2500 mPa·s at the above solids content. For example, the spray liquid may have a viscosity of about 2000 mPa·s.

[0147] In one embodiment, spray drying can be performed at a temperature of 100°C to 300°C. The propellant gas (e.g., air) used in spray drying can be introduced at a first temperature and discharged at a second temperature. For example, the first temperature can be 200°C to 250°C. The second temperature can be 80°C to 150°C.

[0148] The flow rate of the spray liquid for spray drying may be 30 ml / min to 80 ml / min. If the flow rate is less than 30 ml / min, problems such as nozzle clogging and reduced productivity may occur. If the flow rate is greater than 80 ml / min, moisture condensation within the spray dryer may cause the mixture to be incompletely dried. The input pressure of the spray liquid may be 0.3 MPa to 0.7 MPa. For example, the input pressure of the spray liquid may be about 0.5 MPa.

[0149] The dried mixture may be calcined under an inert atmosphere. The inert atmosphere may be a nitrogen atmosphere and / or an argon atmosphere. The temperature of the calcination process may be 500°C to 1000°C or 600°C to 800°C. The calcination process may be performed for 4 hours to 20 hours, or 6 hours to 12 hours. By calcining the dried mixture, first particles PTC1 containing the compound of Chemical Formula 1 described above may be formed.

[0150] A method for producing the secondary particle form of the first particle PTC1 according to the present invention will be described in detail. A carbon source is introduced into the iron phosphate precursor to uniformly form a carbon coating layer on the surface of the primary NNP particles. The primary NNP particles then closely aggregate through spray drying to form dense secondary spherical particles. The second particle PTC2 according to one embodiment of the present invention can be obtained by the following procedure. 0.170 g of MnSO4H2O and 0.228 g of (NH4)2S2O8 were dissolved in 100 ml of distilled water, and sulfuric acid was added to adjust the pH to 1. The mixture was then reacted at 130°C for 10 hours to obtain a solid precipitate. The resulting precipitate was washed several times with distilled water and dried at 300°C for 3 hours to obtain solid MnO2 with an average particle size of 5 μm.

[0151] Li2CO3 and the synthesized MnO2 are mixed so that the molar ratio of Li to Mn is 1:2, and heated at 600°C for 10 hours to synthesize LiMn2O4 particles with an average particle size of 7 μm.

[0152] A method for manufacturing the third particle PTC3 according to one embodiment of the present invention will now be described in detail. A nickel-based precursor may be prepared. The nickel-based precursor may include Ni of Formula 3 above. The content of Ni relative to the total content of metals in the nickel-based precursor may be greater than 50 at%. In one embodiment, the nickel-based precursor may further include Co and Mn.

[0153] In one embodiment, the nickel-based precursor is obtained by a co-precipitation method. For example, the co-precipitation method may include dissolving a transition metal source material in a solvent such as distilled water, and sequentially introducing the transition metal salt solution, a chelating agent, and a basic aqueous solution into a reactor to cause precipitation. The precipitate is collected in the form of a slurry, and the slurry solution is filtered and dried to obtain the nickel-based precursor, which is a metal composite oxide.

[0154] In the present invention, the transition metal source material may include a metal salt of Ni. The transition metal source material may further include a metal salt of at least one of Co and Mn. The metal salt may be a sulfate, nitrate, acetate, halide, hydroxide, etc., and is not particularly limited as long as it is soluble in the solvent. The transition metal source material according to this embodiment may include a nickel salt, a cobalt salt, and a manganese salt. The transition metal source materials may be mixed by adjusting the molar ratio so that the nickel-based precursor has a Ni content of 50 at% or more.

[0155] The nickel-based precursor and the lithium source may be mixed in a certain ratio to form a mixture. For example, the nickel-based precursor and the lithium source may be mixed in a molar ratio of about 1:1. The lithium source may include at least one selected from the group consisting of lithium oxide, lithium hydroxide, lithium chloride, lithium nitrate, lithium nitrite, lithium formate, lithium acetate, lithium oxalate, lithium carbonate, lithium phosphate, lithium dihydrogen phosphate, lithium dihydrogen phosphate, and lithium citrate.

[0156] The solvent may be removed from the mixture to form a dried mixture. The dried mixture may then be calcined. The temperature for the calcination process may be 700°C to 1,000°C or 900°C to 1,000°C. The calcination process may be performed in an oxidizing atmosphere such as air or oxygen. The heat treatment time for the calcination process may be 10 hours to 30 hours. In another embodiment of the present invention, pre-calcination may be performed at 150°C to 800°C before the calcination process.

[0157] In one embodiment of the present invention, the firing process can be performed after adding a flux to the mixture. The flux can be a compound containing at least one metal selected from the group consisting of Zr, La, S, and Nb. By using the flux, the third particles PTC3 can be smoothly formed into a single particle form. In addition, the average particle size of the third particles PTC3 can be increased.

[0158] The third particles PTC3 may be formed from the mixture containing the nickel-based precursor and the lithium source through the calcination process, and the synthesized third particles PTC3 may be subjected to a pulverization process.

[0159] A coating process can be performed on the pulverized third particles PTC3. Specifically, the third particles PTC3 and a coating raw material can be mixed in a solvent. For example, the coating raw material can include boron and / or aluminum. After filtering and drying the third particles PTC3, a surface treatment can be performed on the third particles PTC3. The surface treatment can include a heat treatment process in an oxidizing atmosphere such as air or oxygen. The surface treatment can be performed at a temperature of 500°C to 800°C.

[0160] In another embodiment of the present invention, the coating process may include a dry coating process. For example, the third particles PTC3 and the coating raw material may be mixed in a dry coating machine without a solvent and then stirred. The resulting dry mixture may be subjected to the surface treatment.

[0161] According to one embodiment of the present invention, the fourth particle PTC4 can be LFO, which can mitigate Li-ion stock loss. LFO can refer to a compound having the composition LiFeO. LFO is effective for graphite anodes and can also be used as a pre-lithiation source for Si anodes. LFO is a Li-rich cathode material and can have high anion redox reactivity. LFO can also be introduced as an additive in the cathode, which can result in low energy density due to the presence of by-products in the cathode matrix. Additionally, the particle size of the starting material, FeO, is one of the factors that determine the reactivity of LFO.

[0162] In addition, the fourth particles PTC4 according to an embodiment of the present invention may be LCO, which can mitigate Li-ion inventory loss. LCO may refer to a compound having a composition of LiCoO.

[0163] The first to third particles PTC1 to PTC3 and the fourth particle PTC4 prepared by the above-described methods may be mixed together to prepare a positive electrode active material according to the present invention. The weight ratio of the fourth particles PTC4 to the total weight of the positive electrode active material may be 90:10 to 50:50, or 95:5 to 99.5:0.5.

[0164] The main active material composed of the first particles PTC1 and the second particles PTC2 may be present in an amount of 70 to 90 parts by weight based on 100 parts by weight of the positive electrode active material. The Mn content in the main active material composed of the first particles PTC1 and the second particles PTC2 may be 50 to 80 mol%, 50 to 60 mol%, or 55 to 80 mol%, based on 100 mol% of the total transition metals excluding lithium in the main active material.

[0165] Carbon elemental analysis according to an embodiment of the present invention can be performed using an Elementar Micro Cube elemental analyzer. Specific operating methods and conditions are as follows: 1-2 mg of sample is weighed into a tin cup, placed on an automatic sampling tray, and introduced into a combustion tube through a ball valve. The sample is then burned at a combustion temperature of 1000°C. The burned gas is then reduced using reduced copper to form carbon dioxide. Carbon dioxide is detected using a TCD detector.

[0166] According to an embodiment of the present invention, the carbon content is measured by quantitative analysis of the particle surface using scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS). Other methods for measuring the composition include inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0167] Examples and comparative examples of the present invention will be described below. However, the following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0168] Preparation Example 1: Preparation of first particles in single particle form Mn 0.6 Fe 0.4 Iron phosphate precursor (PO4), lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.004. 12 wt% glucose was added to the mixture. The mixture was subjected to a wet grinding process using a ball mill. The mixture was evaporated to dryness in a heating oven tray and then placed in a vacuum oven at 120°C for 4 hours. The dried mixture was calcined at 750°C for 10 hours under a nitrogen atmosphere. The calcined product was pulverized to obtain secondary particles in the form of single particles. The average size of the secondary particles was approximately 100 nm to approximately 300 nm.

[0169] Preparation Example 2: Preparation of second particles in single particle form 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 12, 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.

[0170] Li2CO3 and the synthesized MnO2 were mixed so that the molar ratio of Li to Mn was 1:2, and heated at 600°C for 10 hours to synthesize LiMn2O4 particles with an average particle size of 7 μm.

[0171] Preparation Example 3: Preparation of third particles in the form of single particles and secondary particles A nickel-based precursor was manufactured 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 small-particle precursors (NiSO4·6H2O) with an average particle size of approximately 4 μm. 0.6 Co 0.1 Mn 0.3 (OH)2) powder was obtained.

[0172] 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 heat treatment (i.e., a calcination process) was performed in an oxygen atmosphere at approximately 850°C for 15 hours 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.

[0173] The third particles were washed by adding them to distilled water. Boron oxide and aluminum oxide were added in an amount of 3 mol% based on the total transition metals in the third particles to perform boron and aluminum coating. The third particles were dried at 150°C for 12 hours and then heat-treated (i.e., surface-treated) in an oxygen atmosphere at about 700°C for 15 hours.

[0174] Preparation Example 4-1: Preparation of single particle form fourth particle (LFO) To prepare Li5FeO4, LiOH·H2O and olivine Fe2O3 were mixed in a Li:Fe ratio of 5:1. The mixed powder was then ground in a Spex mill for 30 minutes, followed by pelletization at a pressure of 6.1 to 6.3 tons. The pellets were synthesized at 850 °C for 20 hours. An air jet mill was used for powder grinding at 6000 rpm.

[0175] Preparation Example 4-2: Preparation of fourth particles (LCO) in single particle form To prepare Li6CoO4, LiO and CoO were mixed in a Li:Co ratio of 6:1. The mixed powder was then sintered at 600 °C for 24 hours in a nitrogen atmosphere and allowed to cool naturally. The powder was then ground using an air jet mill at 6000 rpm.

[0176] Preparation Example 5-1: Preparation of Mixture 1 by Mixing Main Mixture 1 and Third Particles Mixture 1 was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 2 in a weight ratio of 65:35 to prepare main mixture 1 (the Mn content in the mixture was 60 mol%) with the third particles of Preparation Example 3 in a weight ratio of 90:10. At this time, the Mn content in mixture 1 was 60 mol%.

[0177] Preparation Example 5-2: Preparation of Mixture 2 by Mixing Main Mixture 1 and Third Particles Mixture 2 was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 2 in a weight ratio of 65:35 to prepare main mixture 1 (the Mn content in the mixture was 60 mol%) with the third particles of Preparation Example 3 in a weight ratio of 80:20. At this time, the Mn content in mixture 2 was 60 mol%.

[0178] Preparation Example 5-3: Preparation of Mixture 3 by Mixing Main Mixture 1 and Third Particles Mixture 3 was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 2 in a weight ratio of 65:35 to prepare main mixture 1 (the Mn content in the mixture was 60 mol%) with the third particles of Preparation Example 3 in a weight ratio of 70:30. In this case, the Mn content in mixture 3 was 60 mol%.

[0179] Preparation Example 5-4: Preparation of Mixture 4 by Mixing Main Mixture 2 and Third Particles Mixture 4 was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 2 in a weight ratio of 50:50 to prepare main mixture 2 (the Mn content in the mixture was 70 mol%) with the third particles of Preparation Example 3 in a weight ratio of 90:10. In this case, the Mn content in mixture 4 was 55 mol%.

[0180] Preparation Example 5-5: Preparation of Mixture 5 by Mixing Main Mixture 2 and Third Particles Mixture 5 was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 2 in a weight ratio of 50:50 to prepare main mixture 2 (the Mn content in the mixture was 70 mol%) with the third particles of Preparation Example 3 in a weight ratio of 80:20. In this case, the Mn content in mixture 5 was 55 mol%.

[0181] Preparation Example 5-6: Preparation of Mixture 6 by Mixing Main Mixture 2 and Third Particles Mixture 6 was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 2 in a weight ratio of 50:50 to prepare main mixture 2 (the Mn content in the mixture was 70 mol%) with the third particles of Preparation Example 3 in a weight ratio of 70:30. In this case, the Mn content in mixture 6 was 55 mol%.

[0182] Preparation Example 5-7: Preparation of Mixture 7 by Mixing Main Mixture 3 and Third Particles Mixture 7 was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 2 in a weight ratio of 40:60 to prepare main mixture 3 (the Mn content in the mixture was 80 mol%) with the third particles of Preparation Example 3 in a weight ratio of 90:10. In this case, the Mn content in mixture 7 was 60 mol%.

[0183] Preparation Example 5-8: Preparation of Mixture 8 by Mixing Main Mixture 3 and Third Particles Mixture 8 was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 2 in a weight ratio of 40:60 to prepare main mixture 3 (the Mn content in the mixture was 80 mol%) with the third particles of Preparation Example 3 in a weight ratio of 80:20. In this case, the Mn content in mixture 8 was 55 mol%.

[0184] Example 1-1: Preparation of a mixture of single particle form mixture 1 and particle 4 Mixture 1 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0185] Example 1-2: Preparation of a mixture of single particle form mixture 1 and particle 4 Mixture 1 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0186] Examples 1-3: Preparation of a mixture of single particle form mixture 1 and particle 4 Mixture 1 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0187] Examples 1-4: Preparation of a mixture of single particle form mixture 2 and particle 4 Mixture 2 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0188] Examples 1-5: Preparation of a mixture of single particle form mixture 2 and particle 4 Mixture 2 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0189] Examples 1-6: Preparation of a mixture of single particle form mixture 2 and particle 4 Mixture 2 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0190] Examples 1-7: Preparation of a mixture of single particle form mixture 3 and particle 4 Mixture 3 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0191] Examples 1-8: Preparation of a mixture of single particle form mixture 3 and particle 4 Mixture 3 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0192] Examples 1-9: Preparation of a mixture of single particle form mixture 3 and particle 4 Mixture 3 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0193] Examples 1-10: Preparation of a mixture of single particle form mixture 4 and particle 4 Mixture 4 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0194] Examples 1-11: Preparation of a mixture of single particle form mixture 4 and particle 4 Mixture 4 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0195] Examples 1-12: Preparation of a mixture of single particle form mixture 4 and particle 4 Mixture 4 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0196] Examples 1-13: Preparation of a mixture of single particle form mixture 5 and particle 4 Mixture 5 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0197] Examples 1-14: Preparation of a mixture of single particle form mixture 5 and particle 4 Mixture 5 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0198] Examples 1-15: Preparation of a mixture of single particle form mixture 5 and particle 4 Mixture 5 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0199] Examples 1-16: Preparation of a mixture of single particle form mixture 6 and particle 4 Mixture 6 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0200] Examples 1-17: Preparation of a mixture of single particle form mixture 6 and particle 4 Mixture 6 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0201] Examples 1-18: Preparation of a mixture of single particle form mixture 6 and particle 4 Mixture 6 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0202] Examples 1-19: Preparation of a mixture of single particle form mixture 7 and particle 4 Mixture 7 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0203] Examples 1-20: Preparation of a mixture of single particle form mixture 7 and particle 4 Mixture 7 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0204] Examples 1-21: Preparation of a mixture of single particle form mixture 7 and particle 4 Mixture 7 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0205] Example 1-22: Preparation of a mixture of single particle form mixture 8 and 4th particle Mixture 8 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0206] Example 1-23: Preparation of a mixture of single particle form mixture 8 and 4th particle Mixture 8 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0207] Examples 1-24: Preparation of a mixture of single particle form mixture 8 and particle 4 Mixture 8 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0208] Example 2-1: Preparation of a mixture of secondary particle type mixture 1 and fourth particle Mixture 1 containing the first particles in the form of secondary particles and the fourth particles of Preparation Example 4-1 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0209] Example 2-2: Preparation of a mixture of secondary particle type mixture 1 and fourth particle A positive electrode active material was prepared by mixing the mixture 1 containing the first particles in the form of secondary particles and the fourth particles of Preparation Example 4-1 in a weight ratio of 99:1.

[0210] Example 3-1: Preparation of a mixture of single particle form mixture 1 and particle 4 Mixture 1 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0211] Example 3-2: Preparation of a mixture of single particle form mixture 1 and particle 4 Mixture 1 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0212] Example 3-3: Preparation of a mixture of single particle form mixture 1 and particle 4 Mixture 1 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0213] Examples 3-4: Preparation of a mixture of single particle form mixture 2 and particle 4 Mixture 2 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0214] Examples 3-5: Preparation of a mixture of single particle form mixture 2 and particle 4 Mixture 2 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0215] Examples 3-6: Preparation of a mixture of single particle form mixture 2 and particle 4 Mixture 2 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0216] Examples 3-7: Preparation of a mixture of single particle form mixture 3 and particle 4 Mixture 3 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0217] Examples 3-8: Preparation of a mixture of single particle form mixture 3 and particle 4 Mixture 3 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0218] Examples 3-9: Preparation of a mixture of single particle form mixture 3 and particle 4 Mixture 3 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0219] Examples 3-10: Preparation of a mixture of single particle form mixture 4 and particle 4 Mixture 4 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0220] Examples 3-11: Preparation of a mixture of single particle form mixture 4 and particle 4 Mixture 4 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0221] Examples 3-12: Preparation of a mixture of single particle form mixture 4 and particle 4 Mixture 4 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0222] Examples 3-13: Preparation of a mixture of single particle form mixture 5 and particle 4 Mixture 5 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0223] Examples 3-14: Preparation of a mixture of single particle form mixture 5 and particle 4 Mixture 5 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0224] Examples 3-15: Preparation of a mixture of single particle form mixture 5 and particle 4 Mixture 5 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0225] Example 3-16: Preparation of a mixture of single particle form mixture 6 and particle 4 Mixture 6 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0226] Example 3-17: Preparation of a mixture of single particle form mixture 6 and particle 4 Mixture 6 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0227] Example 3-18: Preparation of a mixture of single particle form mixture 6 and particle 4 Mixture 6 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0228] Example 3-19: Preparation of a mixture of single particle form mixture 7 and particle 4 Mixture 7 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0229] Examples 3-20: Preparation of a mixture of single particle form mixture 7 and particle 4 Mixture 7 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0230] Example 3-21: Preparation of a mixture of single particle form mixture 7 and particle 4 Mixture 7 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0231] Example 3-22: Preparation of a mixture of single particle form mixture 8 and particle 4 Mixture 8 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0232] Example 3-23: Preparation of a mixture of single particle form mixture 8 and particle 4 Mixture 8 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0233] Examples 3-24: Preparation of a mixture of single particle form mixture 8 and particle 4 Mixture 8 containing the first particles in the form of single particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 98.5:1.5 to prepare a positive electrode active material.

[0234] Example 4-1: Preparation of a mixture of secondary particle type mixture 1 and fourth particle Mixture 1 containing the first particles in the form of secondary particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99.5:0.5 to prepare a positive electrode active material.

[0235] Example 4-2: Preparation of a mixture of secondary particle type mixture 1 and fourth particle Mixture 1 containing the first particles in the form of secondary particles and the fourth particles of Preparation Example 4-2 were mixed in a weight ratio of 99:1 to prepare a positive electrode active material.

[0236] Comparative Example 1-1: Production of a positive electrode active material consisting only of third particles A positive electrode active material consisting only of the third particles in the form of single particles of Production Example 3 was produced.

[0237] Comparative Example 1-2: Production of a positive electrode active material consisting only of second particles A positive electrode active material consisting only of the second particles in the form of single particles of Production Example 2 was produced.

[0238] Comparative Example 1-3: Production of a positive electrode active material consisting only of first particles A positive electrode active material consisting only of the first particles of Production Example 1 was produced.

[0239] Comparative Example 1-4: Production of positive electrode active material consisting only of fourth particles A positive electrode active material consisting only of the fourth particles in the form of single particles of Production Example 4 was produced.

[0240] Comparative Example 1-5: Preparation of Positive Electrode Active Material Using Main Mixture 1 A positive electrode active material was prepared by mixing Comparative Example 1-3 and Comparative Example 1-2 in a weight ratio of 65:35, where the Mn content in the mixture was 60 mol %.

[0241] Comparative Example 1-6: Preparation of Positive Electrode Active Material Using Main Mixture 2 A positive electrode active material was prepared by mixing Comparative Example 1-3 and Comparative Example 1-2 in a weight ratio of 50:50, where the Mn content in the mixture was 70 mol %.

[0242] Comparative Example 1-7: Preparation of Positive Electrode Active Material Using Main Mixture 3 A positive electrode active material was prepared by mixing Comparative Example 1-3 and Comparative Example 1-2 in a weight ratio of 40:60, where the Mn content in the mixture was 80 mol %.

[0243] Comparative Example 1-8: Preparation of positive electrode active material from mixture 1 A positive electrode active material was prepared by mixing Comparative Example 1-5 and Comparative Example 1-1 in a weight ratio of 90:10, where the Mn content in the mixture was 60 mol %.

[0244] Comparative Example 1-9: Preparation of positive electrode active material using mixture 2 A positive electrode active material was prepared by mixing Comparative Example 1-5 and Comparative Example 1-1 in a weight ratio of 80:20, where the Mn content in the mixture was 60 mol %.

[0245] Comparative Example 1-10: Preparation of positive electrode active material using mixture 3 A positive electrode active material was prepared by mixing Comparative Example 1-5 and Comparative Example 1-1 in a weight ratio of 70:30, where the Mn content in the mixture was 60 mol %.

[0246] Comparative Example 1-11: Preparation of positive electrode active material using mixture 4 A positive electrode active material was prepared by mixing Comparative Example 1-6 and Comparative Example 1-1 in a weight ratio of 90:10, where the Mn content in the mixture was 55 mol%.

[0247] Comparative Example 1-12: Preparation of positive electrode active material using mixture 5 A positive electrode active material was prepared by mixing Comparative Example 1-6 and Comparative Example 1-1 in a weight ratio of 80:20, where the Mn content in the mixture was 55 mol%.

[0248] Comparative Example 1-13: Preparation of positive electrode active material using mixture 6 A positive electrode active material was prepared by mixing Comparative Example 1-6 and Comparative Example 1-1 in a weight ratio of 70:30, where the Mn content in the mixture was 55 mol%.

[0249] Comparative Example 1-14: Preparation of positive electrode active material using mixture 7 A positive electrode active material was prepared by mixing Comparative Example 1-7 and Comparative Example 1-1 in a weight ratio of 90:10, where the Mn content in the mixture was 60 mol %.

[0250] Comparative Example 1-15: Preparation of positive electrode active material using mixture 8 A positive electrode active material was prepared by mixing Comparative Example 1-7 and Comparative Example 1-1 in a weight ratio of 80:20, where the Mn content in the mixture was 55 mol%.

[0251] Cathode manufacturing A positive electrode active material slurry was prepared by mixing 95 wt% of the final positive electrode active material, 3 wt% of polyvinylidene fluoride binder, and 2 wt% of carbon black conductive material in N-methylpyrrolidone solvent. The positive electrode active material slurry was applied to an aluminum current collector, dried, and then rolled to prepare a positive electrode.

[0252] Anode manufacturing Graphite, a binder, and a conductive material were mixed in N-methylpyrrolidone solvent to prepare a negative electrode active material slurry, which was then coated on a copper current collector, dried, and rolled to prepare a negative electrode.

[0253] Lithium secondary battery manufacturing A coin full cell was fabricated using the prepared positive and negative electrodes. A polypropylene membrane (Celgard 3510) was used as the separator. The electrolyte was a solution prepared by mixing 1.3M LiPF6 with a mixed solvent of EC (ethylene carbonate), DEC (diethyl carbonate), and FEC (fluoroethylene carbonate) (volume ratio: 2:6:2).

[0254] Evaluation example 1: Analysis of the surface of the positive electrode active material An SEM image of the first particles prepared in Example 1 is shown in Figure 7A. An SEM image of the second particles having a single crystal structure is shown in Figure 7B. Referring to Figure 7A, it can be seen that the first particles according to an embodiment of the present invention are in the form of fine single particles of nano size. Referring to Figure 7B, it can be seen that the second particles according to an embodiment of the present invention are in the form of single crystals of μm size. It can be seen that the second particles have a single crystal structure and are larger in size than the first particles when compared to Figure 7A.

[0255] Evaluation example 2: Active material evaluation The average pellet density (PD) of the positive electrodes of representative examples and comparative examples among Examples 1-1 to 1-24, Examples 3-1 to 3-24, and Comparative Examples 1-1 to 1-15 is shown in Table 1. The average pellet density was measured by placing 3 g of the positive electrode active material in a pellet mold and applying a force of US 3.3 tons for 30 seconds.

[0256] Evaluation example 3: Battery characteristic evaluation The characteristics of lithium secondary batteries manufactured using the positive electrode active materials of Examples 1-1 to 1-24 and 3-1 to 3-24 were evaluated.

[0257] Lithium secondary batteries were prepared in the form of coin cells and powder, and initially charged at a constant current (0.2 C) and constant voltage (5 V). After a 10-minute rest, they were discharged at a constant current (0.2 C) until the voltage reached 3.0 V. The initial charge-discharge tests were performed. The positive electrode energy density was measured using additional powder samples. The battery performance evaluation results are shown in Tables 1 to 4 below.

[0258] [Table 1]

[0259] [Table 2]

[0260] [Table 3]

[0261] [Table 4]

[0262] Referring to Tables 1 and 2, it was confirmed that the secondary batteries according to Examples 1-1 to 1-24 and 3-1 to 3-24 of the present invention had excellent capacity and efficiency characteristics. Specifically, when Table 1 is compared with Table 3, it was confirmed that the secondary batteries according to Examples 1-1, 1-2, 1-4, 1-5, 1-10, 1-11, 1-13, 1-14, 1-19, 1-20, 1-22, and 1-23 of the present invention had higher efficiencies. Furthermore, when Table 2 is compared with Table 4, it was confirmed that the secondary batteries according to Examples 3-1, 3-2, 3-4, 3-5, 3-10, 3-11, 3-13, 3-14, 3-19, 3-20, 3-22, and 3-23 had higher efficiencies. Furthermore, referring to Tables 1 to 4, it can be seen that the positive electrode active materials according to the embodiments have similar average compressed densities to the positive electrode active materials according to the comparative examples.

[0263] Furthermore, referring to Tables 1 and 2, the embodiment according to the present invention is characterized in that by mixing single crystal NCM, it is possible to achieve a higher energy density than 511 Wh / kg of Comparative Examples 1-3 which contain only LMFP, and the density and life characteristics are also improved.

[0264] In addition, in the embodiment of the present invention, it was confirmed that the energy density was maximized by mixing the fourth particles, which are sacrificial positive electrodes, into the mixture of the first to third particles in an amount of 1.5 wt % or less based on the total weight of the positive electrode active material.

[0265] This confirms that the optimal weight ratio of the fourth particles to the total weight of the positive electrode active material is 99.5:0.5 and 99:1.

[0266] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and it is natural that these also fall within the scope of the present invention. [Explanation of symbols]

[0267] 100 Lithium secondary battery 10 positive electrode 11 Positive electrode lead tab 12 Positive terminal 20 negative electrode 21 Negative electrode lead tab 22 Negative terminal 30 Separator 40 Electrode assembly 50 cases 60 Sealing member 70 Electrode tab 71 Positive electrode tab 72 Negative electrode tab

Claims

1. A 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: a third particle having a layered structure and including a compound represented by the following Chemical Formula 3; and fourth particles comprising a compound of Chemical Formula 4: The weight ratio of the fourth particles to the total weight of the positive electrode active material is 0.5 wt % to 5 wt %. [Chemical formula 1] Li a1 Mn b1 Fe x1- A y1 2O 4-c1 (In the above chemical formula 1, 0.8≦a1≦1.2, 0.5≦b1≦0.9, 0.1≦x1≦0.5, 0.001≦y1≦0.05, 0<c1≦0.05, and b1+x1+y1=1, and A is at least one element selected from the group consisting of Al, Ti, V, and Mg.) [Chemical formula 2] Li a2 Mn b2 B x2 O 4-c2 (In the above chemical formula 2, 0.8≦a2≦1.2, 1.9≦b2≦2.05, 0≦x2≦0.05, and 0≦c2≦0.05, and B is at least one element selected from the group consisting of Mg and Al.) [Chemical formula 3] Li a3 Ni b3 Co x3 Mn y3 C z1 O 2-c3 (In the chemical formula 3, 0.8≦a3≦1.2, 0.5≦b3≦0.8, 0≦x3≦0.10, 0.1≦y3≦0.35, 0≦z1≦0.1, 0≦c3≦0.05, and b3+x3+y3+z1=1; and C is at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb.) [Chemical formula 4] Li a4 E b4 D x4 O 4-c4 (In the above chemical formula 4, 4.9≦a4≦6.1, 0.9≦b4≦1.1, 0≦x4≦0.015, and 0≦c4≦0.05, E is Fe or Co, and D is Al.)

2. 10. The cathode active material of claim 1, wherein the fourth particles are configured to be electrochemically inactivated after a first cycle.

3. The positive electrode active material of claim 1 , wherein a weight ratio of the fourth particles to the total weight of the positive electrode active material is 0.5 wt % to 1.5 wt %.

4. the first particles and the second particles constitute a main active material, 2. The positive electrode active material of claim 1, wherein the content of the main active material is 70 to 90 parts by weight based on 100 parts by weight of the positive electrode active material.

5. the first particles and the second particles constitute a main active material, 2. The cathode active material of claim 1, wherein the Mn content of the main active material is 50 mol % to 80 mol % relative to 100 mol % of the total of transition metals excluding lithium in the main active material.

6. The positive electrode active material of claim 1 , wherein the mixing ratio of the first particles to the second particles is 4:6 to 6:4 by weight.

7. the first particles include at least one first primary particle; The positive electrode active material of claim 1 , wherein the second particles have a secondary particle shape formed by agglomeration of a plurality of second primary particles.

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

9. the first particles have a single particle shape, the first particles have a first average particle size of 0.5 μm to 2.5 μm; The positive electrode active material of claim 7 , wherein the first primary particles have an average size of 100 nm to 200 nm.

10. the first particles include a plurality of primary particles aggregated together, The first particles have a first average particle size of 3 μm to 10 μm; The positive electrode active material of claim 7 , wherein the first primary particles have an average size of 50 nm to 150 nm.

11. The average size of the second primary particles is 0.5 μm to 2.5 μm. The positive electrode active material according to claim 7 .

12. the first particles include a first coating layer including carbon; The positive electrode active material of claim 7 , wherein the carbon content in the first particles is 1.5 wt % to 2.5 wt %.

13. the third particle has a shape in which a plurality of single particles are adhered to each other, The positive electrode active material according to claim 1 , wherein a first average particle size of the first particles is smaller than an average size of the plurality of single particles.

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

15. The positive electrode active material according to claim 1 , wherein at least one of the third particles and the fourth particles has a single particle shape.

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

17. 2. The positive electrode active material according to claim 1, wherein the positive electrode active material has a compressed density of 2.0 g / cc to 2.9 g / cc.

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

19. 19. The positive electrode for a lithium secondary battery of claim 18, 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.

20. The positive electrode according to claim 18 ; a negative electrode including a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector; a separator between the positive electrode and the negative electrode.

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