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 positive electrode including the same, and a lithium secondary battery including the same. More specifically, the positive electrode active material includes a first particle containing a compound expressed by Chemical Formula 1 below. The first particle includes at least one primary particle and the average size of the primary particle is 50 nm to 300 nm. [Chemical Formula 1] LiaMnxFe1-xMyPO4-b, in which 0.8≤a≤1.2, 0.2≤x≤0.8, 0≤y≤0.05, and 0≤b≤0.05 are satisfied, M is at least one element selected from the group consisting of Al, Mg, Zr, V, Zn, Nb, K, Y, B, and Cu, the first particle further contains Ti, and the content amount of Ti in the first particle is 1000 ppm to 9000 ppm.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] Recently, with the rapid replenishment of battery-powered electronic devices such as mobile phones, notebook computers, and electric vehicles, the demand for secondary batteries with high energy density and high capacity is rapidly increasing. Accordingly, research and development to improve the performance of lithium secondary batteries is actively progressing (Patent Document 1).

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

[0004] [Patent Document 1] Korean Patent No. 10-2553570 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a positive electrode active material having high energy density, high operating voltage, and high conductivity.

[0006] Another object of the present invention is to provide a lithium secondary battery having a high energy density, a high operating voltage, excellent low-temperature characteristics, and a long life. [Means for solving the problem]

[0007] A positive electrode active material according to an embodiment of the present invention includes first particles including a compound represented by the following Chemical Formula 1, wherein the first particles include at least one primary particle, and the average size of the primary particle may be 50 nm to 300 nm. [Chemical formula 1] Li a Mn x Fe 1-x M y PO 4-b In Chemical Formula 1, 0.8≦a≦1.2, 0.2≦x≦0.8, 0≦y≦0.05, and 0≦b≦0.05; M is at least one element selected from the group consisting of Al, Mg, Zr, V, Zn, Nb, K, Y, B, and Cu; the first particles further contain Ti, and the Ti content of the first particles may be 1000 ppm to 9000 ppm. [Effects of the Invention]

[0008] The positive electrode active material according to the present invention may have improved electrical conductivity, capacity, and energy density, and the lithium secondary battery according to the present invention may have improved low-temperature and life characteristics. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a conceptual diagram showing a lithium secondary battery according to an embodiment of the present invention; [Figure 2] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 3] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 4] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 5] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 6]2 is an enlarged view of a positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention. FIG. [Figure 7] 2 is an enlarged view of a positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention. FIG. [Figure 8] 1 is a flowchart illustrating a method for manufacturing a positive electrode active material according to an embodiment of the present invention. [Figure 9A] 1 is a SEM image of a positive electrode active material according to an embodiment of the present invention. [Figure 9B] 1 is a SEM image of a positive electrode active material according to a comparative example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] In this specification, when a component is referred to as being on another component, it means that the component may be directly formed on the other component, or that a third component may be interposed between them. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various forms and may undergo various modifications. The description of the present embodiments is provided solely to ensure complete disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0011] In this specification, when a component is referred to as being on another component, it means that it may be formed directly on the other component, or a third component may be interposed between them. Also, in the drawings, the thickness of the components is exaggerated for the sake of efficient explanation of the technical content. Parts designated with the same reference numerals throughout the specification refer to the same components.

[0012] Unless otherwise specified herein, the singular can also include the plural. Furthermore, unless otherwise specified, "A or B" can mean "including A, including B, or including A and B." As used herein, "comprises" and / or "comprising" does not exclude the presence or addition of one or more other elements to the referenced element.

[0013] As used herein, "combinations thereof" can mean mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0014] 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 or scanning electron microscope. Alternatively, the average particle size (D50) can be measured using a measuring device that uses dynamic light scattering, and data analysis can be performed to count the number of particles in each particle size range, after which the average particle size (D50) can be calculated. Alternatively, the average particle size (D50) can be measured using a laser diffraction method. More specifically, when measuring by the laser diffraction method, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT3000), and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W. The average particle size (D50) based on 50% of the particle size distribution in the measuring device can then be calculated.

[0015] 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.

[0016] The positive electrode 10 and the negative electrode 20 may be separated from each other by a separator 30. The separator 30 may be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be in contact with an electrolyte solution ELL. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated in the electrolyte solution ELL.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] For example, the negative electrode active material layer AML2 may contain 90 to 99% by weight of the negative electrode active material, 0.5 to 5% by weight of the binder, and 0 to 5% by weight of the conductive material.

[0021] The binder serves to firmly adhere the negative electrode active material particles to each other and to firmly adhere the negative electrode active material to the current collector COL 2. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0022] Examples of non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0023] 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.

[0024] When an aqueous binder is used as the negative electrode binder, it may further contain a cellulose-based compound that can impart viscosity. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be sodium, potassium, or lithium.

[0025] The dry binder can be a fiberizable polymeric material such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0026] The conductive material is used to impart conductivity to the electrode, and any material that is electronically conductive without causing a chemical change in the battery that is constructed can be used. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0027] The current collector COL2 can be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0028] 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, a lithium metal alloy, a material capable of being doped with and dedoped from lithium, or a transition metal oxide.

[0029] The material capable of reversibly intercalating / deintercalating lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite. Examples of amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0030] As the alloy of lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0031] As the substance that can be doped and undoped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (Q is selected from an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof), or a combination of these. The Sn-based negative electrode active material can be Sn, SnO2, a Sn-based alloy, or a combination of these.

[0032] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite can be in a form in which amorphous carbon is coated on the surface of silicon particles. For example, it can include secondary particles (cores) assembled from primary silicon particles and a first coating layer of amorphous carbon (shell) located on the surface of the secondary particles. Amorphous carbon can also be located between the primary silicon particles, and for example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed and present in an amorphous carbon matrix.

[0033] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and a first coating layer of amorphous carbon located on the surface of the core.

[0034] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by being mixed with a carbon-based negative electrode active material.

[0035] 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.

[0036] Separator 30 may 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.

[0037] 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, and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0038] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0039] 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.

[0040] The organic material and the inorganic material may be mixed in one first coating layer, or a first coating layer containing an organic material and a first coating layer containing an inorganic material may be laminated.

[0041] Electrolyte ELL The electrolyte ELL for lithium secondary batteries contains a non-aqueous organic solvent and a lithium salt.

[0042] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can migrate.

[0043] The non-aqueous organic solvent can be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, or a combination thereof.

[0044] Examples of carbonate solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0045] 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.

[0046] 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 sulfolane.

[0047] The non-aqueous organic solvents can be used alone or in combination of two or more.

[0048] When a carbonate-based solvent is used, a mixture of a cyclic carbonate and a chain carbonate can be used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0049] Lithium salts are dissolved in organic solvents and act as a source of lithium ions in the battery, enabling basic lithium secondary battery operation and facilitating the movement of lithium ions between the positive and negative electrodes. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1SO2) (x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethene sulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0050] 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 illustrating lithium secondary batteries according to embodiments, with FIG. 2 illustrating a cylindrical type, FIG. 3 illustrating a prismatic type, and FIGS. 4 and 5 illustrating pouch types. Referring to FIGS. 2 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 impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in FIG. 2. Also, in FIG. 3, the lithium secondary battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in FIGS. 4 and 5, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting current generated in the electrode assembly 40 to the outside.

[0051] 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.

[0052] 6 and 7 are enlarged views of a positive electrode active material layer of a lithium secondary battery according to an embodiment of the present invention. Referring to Figs. 6 and 7, as described above, the positive electrode active material layer AML1 (see Fig. 1) may include first particles PTC1, a conductive material CDM, and a binder BND. A plurality of first particles PTC1 may constitute a positive electrode active material according to an embodiment of the present invention.

[0053] The positive electrode active material layer AML1 may further include an additive that can serve as a sacrificial positive electrode.

[0054] The content of the positive electrode active material PTC1 in the positive electrode active material layer AML1 may be 90 wt % to 99.5 wt % relative to 100 wt % of the positive electrode active material layer AML1, and the contents of the binder and conductive material may be 0.5 wt % to 5 wt % respectively relative to 100 wt % of the positive electrode active material layer AML1.

[0055] The binder serves to firmly adhere the positive electrode active material particles to each other and to firmly adhere the positive electrode active material to the current collector COL1. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers 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.

[0056] The conductive material is used to impart conductivity to the electrode, and any material that is electron-conductive without causing a chemical change in the battery to be constructed can be used. Examples of the conductive material 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 containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0057] The first particles PTC1 will be described in more detail below.

[0058] 1st particle PTC1 The first particles PTC1 may include an olivine-based lithium compound represented by the following Chemical Formula 1. [Chemical formula 1] Li a Mn x Fe 1-x M y PO 4-b In Chemical Formula 1, 0.8≦a≦1.2, 0.2≦x≦0.8, 0≦y≦0.05, and 0≦b≦0.05 may be satisfied. For example, x may be 0.5 to 0.8 or 0.5 to 0.7. M may be at least one element selected from the group consisting of Al, Mg, Zr, V, Zn, Nb, K, Y, B, and Cu, and may be particularly Mg or V. M may be a dopant doped into the first particles PTC1.

[0059] The first particles may further include Ti, which may also be a dopant doped into the single particle PTC1. The first particles may have a powder resistivity of approximately 10 Ωcm to 90 Ωcm. When Ti is used as a dopant, it increases the crystallinity of Mn and Fe contained in the positive electrode active material, strengthening the structure of the active material and allowing the size of the single particles or primary particles to be controlled to be uniform. In addition, Ti doping can reduce the powder resistivity of the positive electrode active material, improving the electrical conductivity of lithium batteries and improving the charge / discharge efficiency, low-temperature characteristics, and life characteristics of lithium secondary batteries. Single particles and primary particles will be described in detail below.

[0060] The doping amount of Ti may be 500 ppm to 10,000 ppm, 1,000 ppm to 9,000 ppm, or 3,000 ppm to 6,000 ppm. The doping amount of Ti may be defined as the weight of Ti relative to the total weight of metals excluding lithium in the olivine-based lithium compound represented by Chemical Formula 1. In other words, the doping amount of Ti may be defined as the weight of Ti relative to the total weight of Fe, Mn, the doping element M, and Ti. When the doping amount of Ti satisfies the above range, the electrical conductivity and life characteristics of the positive electrode active material can be improved without a decrease in capacity.

[0061] The first particle PTC1 may include at least one primary particle. The average size of the primary particle may be 50 to 400 nm, 50 to 300 nm, or 100 to 200 nm. By using Ti as a dopant, the size of the primary particle can be uniformly controlled within the above range, thereby shortening the migration distance of lithium ions within the particle during charge and discharge, reducing resistance and increasing capacity. In addition, the uniform primary particle structure increases powder rolling density, reduces side reactions with the electrolyte, and improves battery life.

[0062] As an example, the first particles PTC1 may include a coating layer on their surfaces. The coating layer may cover the entire surface of the first particles PTC1 or may cover only a portion of the surface of the first particles PTC1. For example, the coating layer may include carbon and / or a carbon-containing compound. The coating layer may improve the structural stability and electrical conductivity of the first particles PTC1.

[0063] 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.

[0064] The first particles PTC1 may further contain carbon derived from the coating layer and / or particle size coating layer. The carbon element content in the first particles PTC1 may be 0.5% to 10% by weight, 1% to 5% by weight, or 1% to 2.5% by weight.

[0065] The first particles PTC1 may have a first average particle size, which may vary depending on the embodiment of FIG.

[0066] Referring again to FIG. 6, as an example, the first particle PTC1 may have a single particle shape. In this specification, a single particle may refer to a single particle having no internal grain boundary. A single particle may refer to a single particle, a monolith structure, a single structure, or a non-aggregated particle, in which particles are morphologically present in an independent phase and are not aggregated with each other. For example, a single particle may be a single crystal. Alternatively, a single particle may be a particle containing several crystals. A single particle may be in a singly isolated form. Alternatively, a single particle may be in a form in which 2 to 100 single particles are attached to each other. Alternatively, a single particle may be in a form in which multiple primary particles are aggregated.

[0067] Referring to FIG. 6, when the first particles PTC1 have a single particle morphology, the first particles PTC1 may exist as a single primary particle or as an aggregate of several primary particles. In this case, the minimum particle size of the first particles PTC1, i.e., the average size of the primary particles, may be 50 nm to 400 nm, 50 nm to 300 nm, or 100 nm to 200 nm. The average size of the primary particles may be determined by measuring the particle sizes of approximately 30 primary particles randomly selected from an electron microscope photograph and averaging the measured particle sizes. When each of the first particles PTC1 has a single particle morphology, the first particles PTC1 may be provided in various sizes. For example, the average particle size of the first particles PTC1 may range from about 500 nm to about 2.5 μm, or about 1 μm. In one or more embodiments, the average particle size may be measured using a particle size analyzer based on laser diffraction. In particular, the average particle size may be referred to as the particle size at 50% cumulative volume in the particle size distribution (D50).

[0068] 7, the first particles PTC1 may have a polycrystalline form and include secondary particles formed by agglomeration of at least two or more primary particles. In other words, one first particle PTC1 may include a plurality of second particles PTC2 agglomerated together. For example, each of the second particles PTC2 may be a primary particle. The first particles PTC1 may have a spherical or elliptical shape.

[0069] As an example, the first particle PTC1 may further include a grain boundary coating layer on the surface of each of the second particles PTC2. 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 second particles PTC2 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.

[0070] The interior of the first particle PTC1 described above may refer to the entire interior of the first particle PTC1 excluding the surface of the first particle PTC1. For example, the interior of the first particle PTC1 may refer to the region from a depth of about 10 nm from the surface of the first particle PTC1 to the entire inside, or from a depth of 10 nm to a depth of about 2 μm.

[0071] The first particle PTC1 further includes a grain boundary coating portion, which enhances structural stability and allows a uniform coating layer to be formed on the surface of the first particle PTC1. In addition, the first particle PTC1 further includes a grain boundary coating portion, which further improves the electrical conductivity of the first particle PTC1.

[0072] 7, when the first particles PTC1 are secondary particles, the average size of the primary particles (e.g., PTC2) within the first particles PTC1 may be 50 nm to 300 nm, or 50 nm to 200 nm. When the first particles PTC1 are secondary particles, the size of the primary particles may be smaller than when the first particles PTC1 are single particles. The average size of the primary particles may be the average value of particle sizes measured by randomly selecting about 30 primary particles from an electron microscope photograph.

[0073] When the first particles PTC1 are secondary particles, the average particle size of the first particles PTC1 may be 1 μm to 20 μm, 3 μm to 15 μm, or 5 μm to 10 μm. In one embodiment, the average particle size may be determined by measuring the particle sizes of approximately 30 first particles PTC1 randomly selected from an electron microscope photograph of the active material, and determining the diameter (D50) of the particles whose cumulative volume accounts for 50% by volume from the particle size distribution.

[0074] When the average particle size of the first particles satisfies the above range and the size of the primary particles is uniform, the charge / discharge capacity and low-temperature capacity of a lithium secondary battery including the same can be improved.

[0075] The first particles PTC1 may have a spherical shape formed by the aggregation of nano-sized primary particles. The first particles PTC1 may exhibit the following characteristics due to the primary particles being closely aggregated together: The first particles PTC1 may have a spherical or elliptical shape. The average particle size (D50) of the first particles PTC1 may be 1 μm to 20 μm. The porosity of the first particles PTC1 may be about 20% to about 60%. The Span value of the first particles PTC1 analyzed using a particle size analyzer may be 0.5 to 7.

[0076] A lithium secondary battery including the positive electrode active material of the present invention can have improved low-temperature characteristics. In one embodiment, the discharge capacity at −20° C. relative to the initial discharge capacity of the lithium secondary battery (discharge capacity at −20° C. / initial discharge capacity) can be 60% or more. For example, the discharge capacity at −20° C. relative to the initial discharge capacity of the lithium secondary battery of the present invention (discharge capacity at −20° C. / initial discharge capacity) can be 40% to 100%, 50% to 95%, or 60% to 90%.

[0077] A lithium secondary battery including the positive electrode active material of the present invention can have improved life characteristics. In one embodiment, the lithium secondary battery of the present invention can have a capacity retention rate of 94% or more after 50 charge / discharge cycles at a constant current of 1.0 C at the above-mentioned voltage. For example, the capacity retention rate can be 92% to 100%, or 94% to 100%.

[0078] Method for producing positive electrode active material 8 is a flowchart illustrating a method for manufacturing a positive electrode active material according to an embodiment of the present invention. The method for manufacturing the first particles PTC1 according to an embodiment of the present invention will be described in more detail with reference to FIG.

[0079] The manganese iron phosphate precursor, the lithium source, the carbon source, and the dopant source may be mixed in a solvent (S100). For example, the solvent may be water, ethanol, or the like.

[0080] The manganese iron phosphate precursor can 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 can 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 0.8.

[0081] 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.

[0082] The carbon source may include at least one selected from the group consisting of glucose, sucrose, fructose, cellulose, starch, citric acid, polyacrylic acid, polyethylene glycol, and dopamine.

[0083] 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 an oxide of Ti or a chloride of Ti of Formula 1. The dopant source may further include an oxide or chloride of Mg, V, or B.

[0084] The mixture may be subjected to wet milling (S200). A typical temperature-controllable wet mill may be used for 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 wet milling. Through the wet milling process, particles in the mixture may be pulverized to a fine size.

[0085] In one embodiment of the present invention, the wet-milling step (S200) may be omitted. Specifically, in order to maximize the average particle size of the first particles PTC1 that are finally produced, the wet-milling step (S200) of the precursor particles may be omitted.

[0086] The solvent can be removed from the mixture to form a dried mixture (S300).

[0087] When producing the first particles PTC1 of FIG. 6 according to an embodiment of the present invention, forming the dried mixture may include subjecting the mixture to a direct evaporation method, such as static drying or spray drying.

[0088] 7, forming a dried mixture may include spray drying the mixture. Spray drying can be performed using commonly used spray drying equipment. For example, spray drying can be performed using at least one selected from an ultrasonic spray dryer, an air nozzle spray dryer, an ultrasonic nozzle spray dryer, a filter expansion droplet generator, and an electrostatic spray dryer.

[0089] The particles refined to the size of primary particles through the wet milling process can be agglomerated together through the spray drying process to form secondary particles. Therefore, the primary particles PTC1 can be formed in the form of secondary particles of a desired size by adjusting the flow rate and velocity of the carrier gas, temperature, residence time in the reactor, and internal pressure during the spray drying process.

[0090] As an example, 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), expressed as a percentage. As an example, the spray liquid may have a solid content of approximately 30 wt%.

[0091] If the solid content is less than 20%, the average particle size of the first particles PTC1 becomes small, which may result in problems such as low productivity.If the solid content is more than 40%, it may become difficult to control the average particle size of the first particles PTC1, and the size deviation of the first particles PTC1 may become large.

[0092] The spray liquid according to this embodiment may have a viscosity of 1500 mPa·s to 2500 mPa·s at a solids content. For example, the spray liquid may have a viscosity of about 2000 mPa·s.

[0093] In one embodiment, the input rate of the spray dryer may be 0.1 kg / min to 0.9 kg / min. The input rate of the spray dryer may be defined as the weight of the water and raw material mixture input per unit time. In one embodiment, the input rate of the spray dryer according to the present invention may be approximately 0.5 kg / min.

[0094] In one embodiment, spray drying can be carried out at a temperature between 100°C and 300°C. For example, spray drying can be carried out at a temperature between 200°C and 300°C, between 200°C and 300°C, or between 230°C and 270°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 between 200°C and 250°C. The second temperature can be between 80°C and 150°C.

[0095] The spray liquid may have an input pressure of 0.3 MPa to 0.7 MPa. For example, the spray liquid may have an input pressure of about 0.5 MPa.

[0096] When the input amount, input pressure, and temperature of the spray drying satisfy the described ranges, the first particles PTC1 can have a spherical morphology and a desired porosity.

[0097] The flow rate of the spray liquid for spray drying can 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 can occur. If the flow rate is greater than 80 ml / min, moisture condensation within the spray dryer can cause the mixture to be incompletely dried. The input pressure of the spray liquid can be 0.3 MPa to 0.7 MPa. For example, the input pressure of the spray liquid can be about 0.5 MPa.

[0098] The dried mixture may be calcined under an inert atmosphere (S400). The inert atmosphere may be a nitrogen atmosphere and / or an argon atmosphere. The calcination process may be performed in two stages, and the temperature of the first calcination may be 300°C to 600°C. The calcination time may be 1 hour to 10 hours, or 2 hours to 6 hours. The temperature of the second calcination process may be 600°C to 800°C immediately thereafter. The time of the second calcination process may be 4 hours to 24 hours, or 6 hours to 20 hours. By calcining the dried mixture, first particles PTC1 containing the compound of Formula 1 described above may be formed.

[0099] The fired first particles PTC1 may be subjected to a dry grinding process (S500). The fired mixture may be ground using an air jet mill or the like.

[0100] In producing the first particles PTC1 shown in FIG. 6, which is an embodiment of the present invention, the sintered mixture may be pulverized at a rotation speed of 7000 rpm or more. For example, the sintered mixture may be pulverized at a rotation speed of 7000 rpm to 10000 rpm, or 7500 rpm to 9000 rpm. This allows the first particles PTC1 to have a single particle morphology, as shown in FIG.

[0101] When preparing the first particles PTC1 of FIG. 7 according to another embodiment of the present invention, the sintered mixture can be pulverized at a rotation speed of 0 rpm to 7000 rpm. For example, the sintered mixture can be pulverized at a rotation speed of 4000 rpm to 7000 rpm, 4000 rpm to 6000 rpm, or 4500 rpm to 5000 rpm. Unlike the preparation of the positive electrode active material of FIG. 6, the pulverization step (S500) after sintering can be performed under relatively mild conditions. When preparing the positive electrode active material of FIG. 7, for example, the dry pulverization step (S500) may be omitted. When the rotation speed of the pulverization step (S500) satisfies the specified range, the first particles PTC1 can maintain the shape of secondary particles. As a result, the first particles PTC1 can have the shape of secondary particles, as shown in FIG. 7.

[0102] In the method for manufacturing the first particles PTC1 shown in FIG. 7 according to an embodiment of the present invention, a carbon source is introduced into a manganese iron phosphate precursor to uniformly form a carbon coating layer on the surfaces of the primary particles. The primary particles are then closely aggregated by spray drying to form dense secondary spherical particles. As a result, the first particles PTC1 may include stable carbon coating layers on both the exterior and interior of the first particles PTC1, thereby having a relatively high carbon content. The high carbon content of the first particles PTC1 shown in FIG. 7 may improve the conductivity of the positive electrode active material layer AML1.

[0103] 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 via 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.

[0104] The carbon and Ti contents of the present invention were measured by quantitative analysis of the particle surface using scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS). Other methods for measuring the Ti content include inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0105] The present invention will be described in more detail with reference to the following examples. However, these examples are for illustrative purposes only and the scope of the present invention is not limited to these examples.

[0106] Example 1: Preparation of single particle positive electrode active material particles Mn 0.6 Fe 0.4 Manganese iron phosphate precursor (PO4), lithium carbonate, and titanium dioxide were mixed. Titanium dioxide was added at 1000 ppm based on the total weight of the mixture. 10 wt% glucose was further added to the mixture. The mixture was subjected to a wet grinding process using a ball mill. The mixture was evaporated to dryness from a heating oven tray and then placed in a vacuum oven at 85°C for 4 hours. The dried mixture was calcined in a nitrogen atmosphere at 450°C for 4 hours, and then at 700°C for 12 hours. The calcined product was ground at a rotation speed of 8000 rpm to obtain primary particles in the form of single particles.

[0107] Example 2 Mn 0.6 Fe 0.4 A positive electrode active material was prepared in the same manner as in Example 1, except that PO4, a manganese iron phosphate precursor, lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.003, and titanium dioxide was added in an amount of 3000 ppm based on the total weight of the mixture.

[0108] Example 3 Mn 0.6 Fe 0.4 A positive electrode active material was prepared in the same manner as in Example 1, except that manganese iron phosphate precursor (PO), lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.006, and titanium dioxide was added in an amount of 6000 ppm based on the total weight of the mixture.

[0109] Example 4 Mn 0.6 Fe 0.4 A positive electrode active material was prepared in the same manner as in Example 1, except that PO4, a manganese iron phosphate precursor, lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.009, and titanium dioxide was added in an amount of 9000 ppm based on the total weight of the mixture.

[0110] Example 5 Mn0.5 Fe 0.5 A positive electrode active material was prepared in the same manner as in Example 1, except that PO4, a manganese iron phosphate precursor, lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.003, and titanium dioxide was added in an amount of 3000 ppm based on the total weight of the mixture.

[0111] Example 6 Mn 0.5 Fe 0.5 A positive electrode active material was prepared in the same manner as in Example 1, except that manganese iron phosphate precursor (PO), lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.006, and titanium dioxide was added in an amount of 6000 ppm based on the total weight of the mixture.

[0112] Comparative Example 1 Mn without titanium dioxide 0.6 Fe 0.4 A positive electrode active material was prepared in the same manner as in Example 1, except that the manganese iron phosphate precursor (PO4) and lithium carbonate were mixed in a molar ratio of 1:1.03.

[0113] Comparative Example 2 Mn without titanium dioxide 0.5 Fe 0.5 A positive electrode active material was prepared in the same manner as in Example 1, except that the manganese iron phosphate precursor (PO4) and lithium carbonate were mixed in a molar ratio of 1:1.03.

[0114] Comparative Example 3 Mn 0.6 Fe 0.4 A positive electrode active material was prepared in the same manner as in Example 1, except that PO4, a manganese iron phosphate precursor, lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.0005, and titanium dioxide was added in an amount of 500 ppm based on the total weight of the mixture.

[0115] Comparative Example 4 Mn 0.6 Fe 0.4A positive electrode active material was prepared in the same manner as in Example 1, except that PO4, a manganese iron phosphate precursor, lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.01, and titanium dioxide was added in an amount of 10,000 ppm based on the total weight of the mixture.

[0116] Comparative Example 5 Mn 0.5 Fe 0.5 A positive electrode active material was prepared in the same manner as in Example 1, except that PO4, a manganese iron phosphate precursor, lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.0005, and titanium dioxide was added in an amount of 500 ppm based on the total weight of the mixture.

[0117] Comparative Example 6 Mn 0.5 Fe 0.5 A positive electrode active material was prepared in the same manner as in Example 1, except that PO4, a manganese iron phosphate precursor, lithium carbonate, and titanium dioxide were mixed in a molar ratio of 1:1.03:0.01, and titanium dioxide was added in an amount of 10,000 ppm based on the total weight of the mixture.

[0118] [Table 1]

[0119] Referring to Table 1, it can be seen that in Examples 1 to 6, i.e., when the Ti content is 1000 ppm to 9000 ppm, the primary particle size is controlled to 50 nm to 300 nm. It can also be seen that when the primary particle size is within the above range, the powder resistivity is less than 75 Ωcm. The Ti content (ppm) shown in Examples 1 to 6 and Comparative Examples 3 to 6 refers to the Ti content relative to the total weight of metals other than lithium in the compound.

[0120] Evaluation example 1: Analysis of the surface of the positive electrode active material Figure 9a shows an SEM image of the primary particles prepared in Example 1. Figure 9b shows an SEM image of the primary particles prepared in Comparative Example 3. Referring to Figures 9a and 9b, it can be seen that the primary particles in Example 1 were smaller in size and more uniformly formed.

[0121] (Lithium secondary battery manufacturing) A 2032-type coin half-cell was fabricated using the prepared cathode and a lithium metal counter electrode. 95 wt% of the final cathode active material, 3 wt% of polyvinylidene fluoride binder, and 2 wt% of carbon black conductive material were mixed in N-methylpyrrolidone solvent to prepare a cathode active material slurry. The cathode active material slurry was applied to an aluminum current collector, dried, and then rolled to prepare a cathode.

[0122] A porous polyethylene (PE) film separator (approximately 16 μm thick) was placed between the positive electrode and the lithium metal counter electrode, and an electrolyte solution was injected to fabricate a lithium secondary battery. The electrolyte solution used was a mixture of 1.3 M LiPF6 and a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethylene carbonate (DMC) in a volume ratio of 3:4:3.

[0123] Evaluation example 2: Battery characteristic evaluation The characteristics of the lithium secondary batteries manufactured using the positive electrode active materials of Examples 1 to 6 and Comparative Examples 1 to 6 were evaluated.

[0124] The lithium secondary battery was initially charged at a constant current (0.2 C) and a constant voltage (4.45 V), and after a 10-minute rest, discharged to 2.5 V at a constant current (0.2 C) to perform initial charge-discharge. Thereafter, charge-discharge was performed at 0.2 C / 0.2 C at -20°C. Thereafter, charge-discharge was repeated 50 times at 1.0 C / 1.0 C at 45°C. The average voltage and capacity at 45°C were measured during the charge-discharge cycle. The battery characteristic evaluation results are shown in Table 2 below.

[0125] [Table 2]

[0126] Referring to Table 2, it was confirmed that the secondary batteries according to Examples 1 to 6 of the present invention have excellent low-temperature capacity and lifespan characteristics. Specifically, it was confirmed that the secondary batteries according to Examples 1 to 6 of the present invention have similar or higher -20°C capacity compared to Comparative Examples 1 to 6. In addition, it was confirmed that the secondary batteries according to Examples 2 to 6 exhibit high-temperature lifespan characteristics of 98% or more, which is greater than that of the secondary batteries according to Comparative Examples 1 to 6.

[0127] 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]

[0128] 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 granule 50: Case 60: Sealing material 70: Electrode tab 71: Positive electrode tab 72: Negative electrode tab

Claims

1. A positive electrode active material including first particles containing a compound represented by the following Chemical Formula 1: The first particles include at least one primary particle; The primary particle size is 50 nm to 300 nm. [Chemical formula 1] Li a Mn x Fe 1-x M y PO 4-b In the formula 1, 0.8≦a≦1.2, 0.2≦x≦0.8, 0≦y≦0.05, and 0≦b≦0.05, and M is at least one element selected from the group consisting of Al, Mg, Zr, V, Zn, Nb, K, Y, B, and Cu; the first particles further contain Ti, The Ti content of the first particles is 1000 ppm to 9000 ppm.

2. 2. The positive electrode active material according to claim 1, wherein x is 0.5 to 0.

8.

3. 2. The positive electrode active material according to claim 1, wherein M is Mg or V.

4. the first particles include a coating layer containing carbon; The positive electrode active material of claim 1 , wherein the carbon content in the first particles is 1.0 to 2.5 wt %.

5. the first particles have a single particle form; The positive electrode active material of claim 1 , wherein the first particles have a first average particle size of 0.2 μm to 2.5 μm.

6. The first particles include a plurality of primary particles aggregated together, The positive electrode active material of claim 1 , wherein the second average particle size of the first particles is 1 μm to 20 μm.

7. The cathode active material of claim 6 , wherein the average size of the primary particles is 20 nm to 200 nm.

8. the first particles further include particle size coating layers on interfaces between the plurality of primary particles; The positive electrode active material according to claim 6 , wherein the particle size coating layer contains carbon.

9. The positive electrode active material of claim 6 , wherein the porosity of the first particles is 20% to 60%.

10. The positive active material of claim 6 , wherein the first particles have a Span value of 0.5 to 7 as analyzed by a particle size analyzer.

11. The positive electrode active material of claim 1 , wherein the first particles have a powder resistivity of 10 Ωcm to 90 Ωcm.

12. 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 of claim 1 , a conductive material, and a binder.

13. 13. The positive electrode for a lithium secondary battery according to claim 12, 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.

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

15. 13. The positive electrode for a lithium secondary battery according to claim 12, wherein the content of the conductive material is 0.5 to 5 parts by weight based on 100 parts by weight of the positive electrode active material layer.

16. The positive electrode for a lithium secondary battery according to claim 12, wherein the conductive material comprises a carbon-based material, a metal-based material in the form of a metal powder or metal fiber, a conductive polymer, or a mixture thereof.

17. A lithium secondary battery including a positive electrode, a negative electrode, a separator, and an electrolyte solution, A lithium secondary battery, wherein the positive electrode comprises the positive electrode active material according to claim 1 .

18. 18. The lithium secondary battery according to claim 17, wherein the capacity at −20° C. relative to the initial capacity (capacity at −20° C. / initial capacity) is 60% or more.

19. 18. The lithium secondary battery according to claim 17, wherein the capacity retention rate after 50 charge / discharge cycles at a constant current of 1 C at a voltage of 2.5 V to 4.45 V is 94% or more.

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