Positive electrode active material, method for manufacturing the same, and lithium secondary battery containing the same

Abstract

To provide a positive electrode active material and a battery containing the same, in which the fluidity is improved by including a carbon-based coating layer on the surface. [Solution] The present invention relates to a positive electrode active material, a method for producing the same, and a lithium secondary battery containing the same. A method for producing a positive electrode active material according to one embodiment of the present invention may include: crushing a carbon-based raw material to prepare carbon-based fine powder; mixing a lithium metal composite oxide with the carbon-based fine powder to prepare a mixed powder; and applying rotation to the mixed powder to form a carbon-based coating layer on the surface of the lithium metal composite oxide particles. The average particle size of the carbon-based fine powder may be 10 nm to 100 nm. Applying rotation may include applying rotation to the mixed powder at 1,000 rpm to 6,000 rpm for 2 minutes to 10 minutes.

Description

[Technical Field]

[0001] This invention relates to a positive electrode active material, a method for manufacturing the same, and a lithium secondary battery containing the same. [Background technology]

[0002] Recently, with the rapid proliferation of electronic devices that use batteries, such as mobile phones, laptops, and electric vehicles, the demand for high-energy-density, high-capacity rechargeable batteries is rapidly increasing. As a result, research and development to improve the performance of lithium-ion rechargeable batteries is being actively pursued.

[0003] A lithium secondary battery is a battery comprising a positive electrode and a negative electrode containing an active material capable of intercalation and deintercalation of lithium ions, and an electrolyte, which produces electrical energy through oxidation and reduction reactions when lithium ions are intercalated / deintercalated at the positive and negative electrodes. [Overview of the project] [Problems that the invention aims to solve]

[0004] The problem that this invention aims to solve is to provide a positive electrode active material and a battery containing the same, in which the fluidity is improved by including a carbon-based coating layer on the surface.

[0005] Another problem that the present invention aims to solve is to provide a method for producing a positive electrode active material in which the process of forming a carbon-based coating layer is simplified. [Means for solving the problem]

[0006] The method for manufacturing a positive electrode active material according to an embodiment of the present invention may include preparing carbon-based fine powder by pulverizing a carbon-based raw material, preparing a mixed powder by mixing a lithium metal composite oxide and the carbon-based fine powder, and applying rotation to the mixed powder to form a carbon-based coating layer on the surface of the lithium metal composite oxide particles. The average particle size of the carbon-based fine powder may be from 10 nm to 100 nm. Applying the rotation may include applying rotation of 1,000 rpm to 6,000 rpm to the mixed powder for 2 minutes to 10 minutes.

[0007] The positive electrode active material according to an embodiment of the present invention may include a lithium metal composite oxide and a carbon-based coating layer on the surface of the lithium metal composite oxide. The avalanche energy of the positive electrode active material may be from 6 mJ / kg to 13 mJ / kg. The avalanche angle of the positive electrode active material may be from 20° to 60°. The average particle size of the positive electrode active material may be from 0.5 μm to 15 μm.

Advantages of the Invention

[0008] The positive electrode active material according to an embodiment of the present invention may have improved fluidity.

[0009] The method for manufacturing a positive electrode active material according to an embodiment of the present invention can more easily and simply manufacture a positive electrode active material having optimal fluidity.

Brief Description of the Drawings

[0010] [Figure 1] It is a conceptual diagram briefly showing a lithium secondary battery according to an embodiment of the present invention. [Figure 2] It is a schematic diagram showing a lithium secondary battery according to an embodiment, showing a cylindrical battery form. [Figure 3] It is a schematic diagram showing a lithium secondary battery according to an embodiment, showing a rectangular battery form. [Figure 4] It is a schematic diagram showing a lithium secondary battery according to an embodiment, showing a pouch-type battery form. [Figure 5] This is a schematic diagram showing a lithium secondary battery according to one embodiment, which shows a pouch-type battery configuration. [Figure 6] This is a sequence diagram illustrating a method for manufacturing a positive electrode active material according to one embodiment of the present invention. [Figure 7] This is a schematic diagram showing one embodiment of a positive electrode active material produced by the manufacturing method of the present invention. [Figure 8] This is a schematic diagram showing one embodiment of a positive electrode active material produced by the manufacturing method of the present invention. [Figure 9a] This is a schematic diagram illustrating a method for measuring avalanche parameters. [Figure 9b] This is a schematic diagram illustrating a method for measuring avalanche parameters. [Figure 9c] This is a schematic diagram illustrating a method for measuring avalanche parameters. [Figure 10] These are the results of measuring the particle strength of the examples and comparative examples of the present invention. [Modes for carrying out the invention]

[0011] To fully understand the structure and effects of the present invention, preferred embodiments will be described with reference to the accompanying drawings. However, the present invention can be realized in various forms and modified in various ways, not limited to the embodiments disclosed below. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those with ordinary skill in the art of the present invention of the scope of the invention.

[0012] In this specification, where one component is referred to as being on top of another, it means that it can be formed directly on top of the other component, or that a third component may be interposed between them. Furthermore, in the drawings, the thickness of components is exaggerated for the sake of effective illustration of the technical content. Throughout the specification, parts indicated by the same reference numeral indicate the same component.

[0013] Unless otherwise specified herein, singular nouns may include plural nouns. Furthermore, unless otherwise specified herein, "A" or "B" may mean "including A, including B, or including A and B." As used herein, "comprises" and / or "comprising" do not imply that the mentioned component excludes the presence or addition of one or more other components.

[0014] In this specification, “these combinations” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the constituents.

[0015] In this specification, unless otherwise defined, particle size may refer to average particle size. Furthermore, particle size refers to the average particle size (D50), which means the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. Average particle size (D50) can be measured by known methods widely known to those skilled in the art, for example, by a particle size analyzer, or by photographs taken with a transmission electron microscope or scanning electron microscope. Alternatively, it can be measured using a dynamic light-scattering device, and the average particle size (D50) value can be calculated after data analysis to count the number of particles for each particle size range. Alternatively, it can be measured using the laser diffraction method. When measuring using laser diffraction, more specifically, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer (for example, the MT 3000 from Microtrac), and after irradiating with ultrasound at approximately 28 kHz at an output of 60 W, the average particle size (D50) based on the 50% standard of the particle size distribution in the analyzer can be calculated.

[0016] In this specification, unless otherwise defined, “substitution” means that at least one hydrogen atom in a substituent or compound is substituted with deuterium, a halogen group, a hydroxyl group, an amino group, a C1-C30 amine group, a nitro group, a C1-C40 silyl group, a C1-C30 alkyl group, a C1-C10 alkylsilyl group, a C6-C30 arylsilyl group, a C3-C30 cycloalkyl group, a C3-C30 heterocycloalkyl group, a C6-C30 aryl group, a C2-C30 heteroaryl group, a C1-C20 alkoxy group, a C1-C10 fluoroalkyl group, a cyano group, or a combination thereof.

[0017] More specifically, "substitution" may mean that at least one hydrogen atom in a substituent or compound is substituted with deuterium, a halogen group, a C1-C30 alkyl group, a C1-C10 alkylsilyl group, a C6-C30 arylsilyl group, a C3-C30 cycloalkyl group, a C3-C30 heterocycloalkyl group, a C6-C30 aryl group, a C2-C30 heteroaryl group, a C1-C10 fluoroalkyl group, or a cyano group. For example, "substitution" may mean that at least one hydrogen atom in a substituent or compound is substituted with deuterium, a halogen group, a C1-C20 alkyl group, a C6-C30 aryl group, a C1-C10 fluoroalkyl group, or a cyano group. Alternatively, "substitution" may mean that at least one hydrogen atom in a substituent or compound is substituted with deuterium, a halogen group, a C1-C5 alkyl group, a C6-C18 aryl group, a C1-C5 fluoroalkyl group, or a cyano group. For example, "substitution" may mean that at least one hydrogen atom in a substituent or compound is replaced by deuterium, a cyano group, a halogen group, a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, a biphenyl group, a terphenyl group, a trifluoromethyl group, or a naphthyl group.

[0018] Figure 1 is a simplified conceptual diagram showing a lithium secondary battery according to an embodiment of the present invention. Referring to Figure 1, the lithium secondary battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

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

[0020] The electrolyte ELL can be a medium for transferring lithium ions between the positive electrode 10 and the negative electrode 20. Within the electrolyte ELL, the lithium ions can move towards the positive electrode 10 or the negative electrode 20 by passing through the separator 30.

[0021] positive electrode 10 The positive electrode 10 for a lithium secondary battery may include a current collector COL1 and a positive electrode active material layer AML1 formed on the current collector COL1. The positive electrode active material layer AML1 includes a positive electrode active material and may further include a binder and / or a conductive material.

[0022] The content of the positive electrode active material in the positive electrode active material layer AML1 may be 90% to 99.5% by weight relative to 100% by weight of the positive electrode active material layer AML1. The content of the binder and conductive material may be 0.5% to 5% by weight, respectively, relative to 100% by weight of the positive electrode active material layer AML1.

[0023] The binder plays a role in ensuring that the positive electrode active material particles adhere well to each other and that the positive electrode active material adheres well to the current collector COL1. Typical examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, styrene-butadiene rubber (meth)acrylate, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0024] The conductive material is used to impart conductivity to the electrode, and in the battery being configured, any material can be used as long as it is an electron conductive material and does not cause a chemical change. Examples of the conductive material include carbon-based substances such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, metal-based substances in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc., conductive polymers such as polyphenylene derivatives, or mixtures thereof.

[0025] Al can be used as the current collector COL1, but is not limited thereto.

[0026] positive electrode active material As the positive electrode active material in the positive electrode active material layer AML1, a compound capable of reversible insertion and extraction of lithium (lithiated intercalation compound) can be used. Specifically, one or more of composite oxides of metals selected from cobalt, manganese, nickel, and combinations thereof with lithium can be used.

[0027] The composite oxide can be a lithium transition metal composite oxide, and specific examples include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based oxides, cobalt-free nickel-manganese-based oxides, or combinations thereof.

[0028] As an example, a compound represented by any one of the following chemical formulas can be used. Li a A 1-b X b O 2-c D c (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li a Mn 2-b X b O 4-c D c (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li a Ni 1-b-c Co bX c O 2-α D α (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5, 0<α<2);Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5, 0<α<2);Li a Ni b Co c L 1 d G e O2(0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0≦e≦0.1);Li a NiG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a CoG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn 1-b G b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn2G b O4(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn 1-g G g PO4(0.90≦a≦1.8, 0≦g≦0.5);Li (3-f) Fe2(PO4)3(0≦f≦2);Li a FePO4 (0.90 ≤ a ≤ 1.8).

[0029] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L1 is Mn, Al, or a combination thereof.

[0030] As an example, the positive electrode active material may be a high-nickel positive electrode active material in which the nickel content relative to 100 mol% of the metal excluding lithium from the lithium transition metal composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, and 99 mol% or less. Since high-nickel positive electrode active materials can achieve high capacity, they can be applied to high-capacity, high-density lithium secondary batteries.

[0031] A detailed explanation of the positive electrode active material will be provided later.

[0032] negative electrode 20 The positive electrode 20 for the lithium secondary battery may include a current collector COL2 and a negative electrode active material layer AML2 formed on the current collector COL2. The negative electrode active material layer AML2 includes a negative electrode active material and may further include a binder and / or a conductive material.

[0033] 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.

[0034] The binder plays a role in ensuring that the negative electrode active material particles adhere well to each other and that the negative electrode active material adheres well to the current collector COL2. The binder can be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0035] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0036] The aqueous binder may be selected from styrene-butadiene rubber, styrene-butadiene (meth)acrylate rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyether resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0037] When an aqueous binder is used as the negative electrode binder, it may further contain a cellulosic compound that provides viscosity. This cellulosic compound may be a mixture of one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof. The alkali metal may be Na, K, or Li.

[0038] The dry binder is a polymeric substance that can be formed into fibers, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, ethylene oxide, or a combination thereof.

[0039] The conductive material is used to impart conductivity to the electrodes, and any electronically conductive material that does not cause chemical changes can be used in the battery that is constructed. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0040] As the current collector COL2, those selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metals, and combinations thereof can be used.

[0041] negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 includes a material that can reversibly insert / desorb lithium ions, lithium metal, an alloy of lithium metal, a material that can be doped or undoped with lithium, or a transition metal oxide.

[0042] The material that can reversibly insert / desorb the lithium ions is a carbon-based negative electrode active material, and may include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0043] 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.

[0044] As the material that can be doped or undoped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (where Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material can be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0045] 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 amorphous carbon coated on the surface of the silicon particles. For example, it may include secondary particles (core) which are aggregates of primary silicon particles, and an amorphous carbon coating layer (shell) located on the surface of these secondary particles. The amorphous carbon may also be located between the primary silicon particles, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0046] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and an amorphous carbon coating layer located on the surface of the core.

[0047] The Si-based or Sn-based anode active material may be used in combination with a carbon-based anode active material.

[0048] Separator 30 Depending on the type of lithium secondary battery, a separator 30 may be present between the positive electrode 10 and the negative electrode 20. Such a separator 30 may be made of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof. Of course, 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.

[0049] The separator 30 may include a porous substrate and a coating layer containing organic, inorganic, or a combination thereof located on one or both sides of the porous substrate.

[0050] The porous substrate may be a polymer film made of any one polymer selected from polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon®), or a copolymer or mixture of two or more of these polymers.

[0051] The aforementioned organic material may include polyvinylidene fluoride polymer or (meth)acrylic polymer.

[0052] The inorganic substances may include, but are not limited to, Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and inorganic particles selected from combinations thereof.

[0053] The organic and inorganic materials may exist mixed in a single coating layer, or they may exist in a form in which a coating layer containing organic materials and a coating layer containing inorganic materials are stacked on top of each other.

[0054] Electrolyte ELL The electrolyte ELL for lithium secondary batteries contains a non-aqueous organic solvent and a lithium salt.

[0055] The aforementioned non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0056] The non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0057] Examples of carbonate-based solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpyrrolyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0058] Suitable ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, and propionic acid (PP).

[0059] As ether-based solvents, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran may be used. As ketone-based solvents, cyclohexanone may be used. As alcohol-based solvents, ethyl alcohol and isopropyl alcohol may be used. As aprotic solvents, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include double bonds, aromatic rings, or ether groups), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane and 1,4-dioxolane, and sulfolanes may be used.

[0060] The aforementioned non-aqueous organic solvents may be used alone or in combination of two or more.

[0061] Furthermore, when using carbonate-based solvents, cyclic carbonates and linear carbonates can be mixed, and the cyclic carbonates and linear cyclic carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0062] The aforementioned lithium salts dissolve in organic solvents and act as a source of lithium ions within the battery, enabling the basic operation of lithium secondary batteries and promoting the movement of lithium ions between the positive and negative electrodes. Typical 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, and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (where x and y are positive numbers from 1 to 20), may contain one or more selected from lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0063] Lithium-ion rechargeable battery Lithium secondary batteries can be classified into cylindrical, prismatic, pouch-type, coin-type, and other types depending on their form. Figures 2 to 5 are schematic diagrams showing a lithium secondary battery according to one embodiment, where Figure 2 is cylindrical, Figure 3 is prismatic, and Figures 4 and 5 are pouch-type batteries. Referring to Figures 2 to 4, the lithium secondary battery 100 may include an electrode assembly 40 with a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a housing 50 that houses the electrode assembly 40. The positive electrode 10, negative electrode 20, and separator 30 may be impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the housing 50, as shown in Figure 2. Also, in Figure 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 Figures 4 and 5, the lithium secondary battery 100 may include electrode tabs 70, namely a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical pathways for guiding the current formed in the positive electrode assembly 40 to the outside.

[0064] Method for manufacturing positive electrode active material Figure 6 is a sequence diagram illustrating a method for producing a positive electrode active material according to one embodiment of the present invention. The method for producing a positive electrode active material according to the present invention will be described in more detail with reference to Figure 6.

[0065] A method for producing a positive electrode active material according to one embodiment of the present invention may include: crushing a carbon-based raw material to prepare carbon-based fine powder (S100); mixing a lithium metal composite oxide with the carbon-based fine powder to prepare a mixed powder (S200); and applying rotation to the mixed powder to form a carbon-based coating layer on the surface of the lithium metal composite oxide particles (S300).

[0066] A carbon-based fine powder can be prepared by pulverizing a carbon-based raw material (S100). The carbon-based raw material may be at least one selected from the group consisting of graphite, carbon black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers.

[0067] The aforementioned grinding may include feeding the carbon-based raw material into a grinding device containing balls and operating the grinding device for 60 minutes. Preferably, operating the grinding device for 60 minutes means operating the grinding device for 10 minutes at a time, repeated six times, but with rest periods between each operation. Allowing rest periods can prevent the balls from overheating and cracking, and can grind the carbon-based raw material to a more uniform size.

[0068] In the container of the pulverizer, the mixed volume ratio of the carbon-based raw material to the balls may be 2:1 to 5:1, 2:1 to 4:1, or 2:1 to 3:1. The particle size of the balls may be 1 mm to 5 mm, 1 mm to 4 mm, or 1 mm to 3 mm. The rotational speed when the pulverizer is in operation may be 5000 rpm to 10000 rpm, 5000 rpm to 9000 rpm, 5000 rpm to 8000 rpm, 5000 rpm to 7000 rpm, or 5000 rpm to 6000 rpm. If the rotational speed deviates from the above range, the balls may break, or the carbon-based raw material may not be pulverized to the size intended for this invention.

[0069] The grinding apparatus may be one selected from the group consisting of a ball mill, a bead mill, a high-energy ball mill, a planetary mill, a stirred ball mill, and a vibration mill.

[0070] The aforementioned grinding process can be carried out by dry grinding, wet grinding, or mixed grinding. Dry grinding means grinding without adding any additional solvent. Wet grinding means grinding after adding any additional solvent. Mixed grinding means combining dry grinding and wet grinding.

[0071] By performing grinding that satisfies the grinding conditions described above, carbon-based fine powders with average particle sizes of 10 nm to 100 nm, 10 nm to 80 nm, 10 nm to 60 nm, or 10 nm to 50 nm can be prepared.

[0072] A mixed powder can be prepared by mixing a lithium metal composite oxide with the carbon-based fine powder (S200). The lithium metal composite oxide may have a small average particle size. In one embodiment, the average particle size of the lithium metal composite oxide may be 0.5 μm to 15 μm. In another embodiment, the average particle size of the lithium metal composite oxide may be 5 μm to 14 μm, or 5 μm or 13 μm.

[0073] The aforementioned lithium metal composite oxide may have a relatively non-spherical particle pattern. Non-spherical particles refer to particles that are not relatively spherical. For example, non-spherical particles may include elliptical particles, particles with flat patterns, or particles with many protrusions.

[0074] The lithium metal composite oxide may be in the form of single particles. A single particle may mean a single particle that does not have an internal grain boundary. A single particle may be a morphological phase, existing as an independent phase where particles are not aggregated with each other, a monolithic structure, a single-body structure, or a non-aggregated particle. For example, a single particle may be a single crystal. Alternatively, a single particle may be a particle containing several crystals. A single particle may be in a form that is isolated by itself. Alternatively, a single particle may be in a form where 2 to 100 single particles are attached to each other.

[0075] When the particles of the positive electrode active material are small, and / or non-spherical, and / or single-particulate, the particles may aggregate or become brittle during the manufacturing process of the positive electrode. This can lead to problems such as reduced fluidity. Therefore, the method for manufacturing the positive electrode active material according to the present invention may have an even more significant effect in improving fluidity when applied to lithium metal composite oxide particles that are small, and / or non-spherical, and / or single-particulate.

[0076] In one embodiment, the lithium metal composite oxide may include a lithium nickel-based oxide having a layered crystal structure, a lithium cobalt-based oxide having a layered crystal structure, a lithium iron phosphate-based compound having an olivine crystal structure, or a combination thereof.

[0077] The mixed powder may contain the lithium metal composite oxide and the carbon-based fine powder in a weight ratio of 99:1 to 99.7:0.3. The mixing may be dry mixing, wet mixing, chemical vapor deposition (CVD), or a combination thereof. Dry mixing means a mixing method without adding a separate solvent. Wet mixing means a mixing method with the addition of a separate solvent. Chemical vapor deposition (CVD) means a mixing method that utilizes plasma and heat.

[0078] Preferably, the mixing can be a dry mixing. Wet mixing may have poor process efficiency because it involves the additional steps of adding a mixed solvent and drying and removing the mixed solvent. Dry mixing has the advantage of being simple, easy, and easy to mix because it only requires adding the lithium metal composite oxide and the carbon-based fine powder.

[0079] The mixed powder can be rotated to form a carbon-based coating layer on the surface of the lithium metal composite oxide particles (S300). The rotation may be performed for 2 to 10 minutes, or for 5 to 10 minutes. The rotation speed may be 1,000 rpm to 6,000 rpm, or for 3,500 rpm to 4,500 rpm.

[0080] If the aforementioned rotation time conditions and rotation speed range are not satisfied, additional steps may be required for smooth coating. These additional steps may include applying heat, pre-treating the surface of the active material to modify it, or adding a coating-promoting substance such as a surfactant. In the case of lithium metal composite oxides that are sensitive to heat or undergo side reactions with coating-promoting substances, coating may not be performed smoothly. On the other hand, if the aforementioned rotation time conditions and rotation speed range are satisfied, a carbon-based coating layer can be easily formed on the surface of lithium metal composite oxide particles without any additional steps. The carbon-based coating layer according to the present invention may be formed by applying a strong rotational force and causing collision and adsorption between the lithium metal composite oxide and carbon-based fine powder.

[0081] The manufactured positive electrode active material may have an avalanche energy of 6 mJ / kg to 13 mJ / kg, or 7 mJ / kg to 10 mJ / kg. The manufactured positive electrode active material may have an avalanche angle of 20° to 60°, or 30° to 50°.

[0082] Larger values ​​for avalanche energy and avalanche angle indicate poorer particle fluidity. If the avalanche parameters exceed the range of the present invention, the particles may become excessively fluid, leading to separation during powder mixing and the formation of layers during drying. If the avalanche parameters are below the range of the present invention, aggregation may occur, resulting in poor electrode manufacturing. When the positive electrode active material satisfies the range of avalanche parameters of the present invention, the positive electrode can be manufactured most successfully. Process problems can be minimized, thereby improving processability and battery performance.

[0083] Figures 9a to 9c are schematic diagrams illustrating a method for measuring avalanche parameters. The fluidity of the cathode active material produced by the avalanche parameters can be evaluated.

[0084] Referring to Figure 9a, the manufactured positive electrode active material AML can be placed in a rotatable container CON capable of visual recording. The container CON may be, for example, a cylindrical drum with a camera attached. After placement, the container can be rotated at a relatively slow speed of 10 rpm, and the movement of the positive electrode active material can be recorded with a visual recording device. The shape of the positive electrode active material AML at the initial stage of rotation, as shown in Figure 9a, can be called the "building" state.

[0085] Referring to Figure 9b, as the container CON is continuously rotated, the positive electrode active material AML can rise along the walls of the container. As shown in Figure 9b, the state in which the positive electrode active material AML has risen to its maximum can be called the peak state.

[0086] Referring to Figure 9c, sustained rotation can cause the positive electrode active material AML, which was in the peak state, to collapse like an avalanche. This state can be called the rest state.

[0087] Avalanche energy can represent the potential energy per unit volume (mJ / kg) of the positive electrode active material released when transitioning from the peak state to the resting state. This may be calculated by subtracting the "energy per unit volume in the resting state" from the "energy per unit volume in the peak state" of the positive electrode active material. The avalanche energy can be measured three times and its average value can be used. The "energy per unit volume of a state" can be measured by photographing the powder in that state, dividing the image into at least 10 pixels, and calculating the potential energy of each pixel based on the following equation (Equation 1). [Formula 1] Potential energy (mJ) = mass (kg) × height (m) × gravitational acceleration (9.8 m / s²) 2 ) × 1,000

[0088] The avalanche angle may represent the angle of the positive electrode active material in its peak state. This angle may represent the angle from the center point B of the edge of the positive electrode active material to the upper end A of the positive electrode active material, as shown in Figure 9b. The edge refers to the boundary of the positive electrode active material that is not in contact with the container. For example, in Figure 9b, the edge may be the boundary of the positive electrode active material connecting point A to point C. The upper end A refers to the highest point in the shape of the positive electrode active material shown in the visual data. The avalanche angle can be measured three times and the average value can be used.

[0089] As one embodiment, a method for determining the avalanche angle from a two-dimensional photographic image like the one in Figure 9b can be performed as follows: The highest point (A) of the positive electrode active material is identified along the vertical axis of the image. A wavy path connecting point A and point C is considered as an edge, and linear regression analysis is performed along edge AC. A regression line is obtained, and its midpoint is designated as the center point (B). Next, a line AB is drawn connecting point A and point B, and a horizontal reference line is extended from point B. The avalanche angle can be defined as the angle formed between line AB and the horizontal reference line from point B.

[0090] In one embodiment, the avalanche parameter may be measured by a method described in known patent documents (U.S. Registered Patent No. 08335343 or U.S. Registered Patent No. 08438914). In one embodiment, the avalanche energy and avalanche angle may be measured using a powder flowability analyzer (Revolution Powder Analyzer) from Mercury Scientific Inc. However, this only discloses one embodiment of the measurement of the avalanche parameter, and the measurement method is not limited thereto.

[0091] Figures 7 and 8 are schematic diagrams showing one embodiment of a positive electrode active material produced by the manufacturing method of the present invention. Referring to Figure 7, the positive electrode active material produced by the manufacturing method of the present invention may include a carbon-based coating layer (CTL) on the surface of lithium metal composite oxide particles (PTC). The carbon-based coating layer (CTL) may be formed on the entire surface of the lithium metal composite oxide particles (PTC) as shown in Figure 7, or on a portion of the surface of the lithium metal composite oxide particles (PTC) as shown in Figure 8.

[0092] The thickness of the carbon-based coating layer may be 5 nm to 10 nm, 5 mm to 9 mm, or 6 mm to 8 mm. The thickness of the carbon-based coating layer may be the average value of the coating layer thickness at 10 arbitrarily selected points. For example, the thickness of the carbon-based coating layer can be obtained by measuring the thickness of the coating layer at 10 arbitrary points within a single positive electrode active material and calculating the average. The particle strength of the positive electrode active material manufactured by the manufacturing method of the present invention may be 150 MPa to 250 MPa, or 160 MPa to 220 MPa, or 160 MPa to 190 MPa. The carbon-based coating layer can impart elasticity to the hard properties of the positive electrode active material. This can improve the fluidity of the positive electrode active material. In addition, the particle strength of the positive electrode active material can also be strengthened. This can significantly reduce the problem of particles cracking during processes such as rolling in the manufacturing process of the electrode.

[0093] The positive electrode active material according to the present invention may have excellent packing density. The packing density may be 3.7 g / cc to 4.0 g / cc, 3.8 g / cc to 4.0 g / cc, or 3.9 g / cc to 4.0 g / cc. The improvement in packing density may be a result of improved fluidity of the positive electrode active material. If the particles of the positive electrode active material are too small, there may be many empty spaces between the particles, resulting in a low packing density. If the particles are non-spherical, it may be difficult for the particles to adhere to each other, resulting in a low packing density. The method for producing the positive electrode active material according to the present invention is excellent in improving fluidity when applied to small particles and / or non-spherical particles, and therefore its packing density improvement effect may be particularly remarkable. "Packing density" can refer to the mass per unit volume (g / cc) of positive electrode active material powder compressed under a constant pressure. For example, it can be measured in accordance with ASTM B527.

[0094] Generally, fluidity problems and particle breakage problems can frequently occur in dry electrodes. Therefore, the positive electrode active material produced by the manufacturing method of the present invention may be particularly excellent when applied to dry electrodes. In dry electrodes, if the fluidity of the positive electrode active material is not good, aggregation may occur, which can lead to problems in the proper manufacture of the electrode. If the fluidity is too good, separation may occur during powder mixing, and layers may form during drying. Therefore, maintaining an optimal fluidity range may be particularly important. Furthermore, since the manufacturing method of the positive electrode active material according to the present invention can be carried out in a dry process from the step of preparing carbon-based fine powder to the step of manufacturing the positive electrode, it may have excellent processability when supplied to a dry process.

[0095] Examples and comparative examples of the present invention are described below. However, the following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

[0096] Example 1 (Manufacturing of carbon-based fine powders) Ten grams of graphite were placed in a ball mill as a carbon-based raw material. The ball size was 2 mm. The mixing volume ratio of the carbon-based raw material to the balls was 2:1. The mill was rotated at 5000 rpm for 10 minutes, followed by a 5-minute rest period. This rotation was repeated a total of six times (60 minutes of rotation in total). A 10 nm carbon-based fine powder was produced.

[0097] (Manufacturing of positive electrode active material) LiNi 0.91 Co 0.06 Al 0.03 O2 was prepared. The lithium metal composite oxide and the carbon-based fine powder were mixed in a weight ratio of 99.7:0.3. The mixture was rotated at 4000 rpm for 5 minutes using a Nobilta mixer. A positive electrode active material containing a carbon-based coating layer on its surface was produced. The average particle size of the lithium metal composite oxide was 13 μm. The thickness of the carbon-based coating layer was 7 nm.

[0098] Example 2 The positive electrode active material was produced in the same manner as in Example 1, except that the mixing weight ratio of the lithium metal composite oxide and the carbon-based fine powder and the mixing time in the Nobilta mixer were changed. The changed conditions are listed in Table 1 below.

[0099] Comparative Example 1 The carbon-based fine powder and lithium metal composite oxide from Example 1 were mixed. The mixture was simply mixed in a Nobilta mixer without rotation.

[0100] Comparative Example 2 The positive electrode active material was prepared in the same manner as in Example 1, except that the rpm and mixing time of the Nobilta mixer were changed. The changed conditions are listed in Table 1 below.

[0101] Evaluation Example 1: Liquidity Assessment The powders of the examples and comparative examples were analyzed using a powder flowability analyzer from Mercury Scientific Inc.

[0102] Higher values ​​for avalanche energy, avalanche angle, and cohesion-T indicate poorer particle fluidity. Conversely, if these values ​​are too low, the particle fluidity may be excessively high, potentially leading to poor processability. Therefore, it is necessary to manufacture the product so that these values ​​are within an appropriate range.

[0103] The unit of cohesiveness T can be Pascals (Pa) or mJ / kg. Cohesiveness T (i.e., cohesive thickness) can represent the shear force at the interface between the powder moving upward with the sample drum and the powder flowing downward at the lower outer surface of the powder. This shear force can be calculated using a thickness parameter. Using this element, the volume, mass, and mean normal pressure of the sample powder within the thickness of the non-flowing surface can be calculated. The shear force of the non-flowing surface can be calculated by multiplying the normal pressure by the sine of the angle of the powder layer. For example, cohesiveness T can be measured by a powder analyzer.

[0104] Evaluation Example 2: Evaluation of Particle Strength The particle strength of the positive electrode active material was measured for the active materials of the examples and some comparative examples. Using a microcompression tester (Shimadzu MCT-W500-E), the particles of the positive electrode active material were placed on an optical microscope glass, and pressure was applied to the sample with a probe to measure the particle strength. In this case, the average value of five or more positive electrode active material particles was determined as the particle strength. The results are shown in Figure 10. Bare was evaluated only for the lithium metal composite oxide of Example 1.

[0105] Battery manufacturing The positive electrode active materials of the examples and comparative examples were mixed with a conductive material and a binder. To ensure sufficient fiber formation of the binder, the mixture was further mixed at 25°C at a speed of 4500 rpm for 22 minutes. No other solvent was used in the above process. The mixture was fed into an extruder and extruded to prepare a positive electrode sheet. The extrusion pressure was 45 MPa. The prepared positive electrode sheet was rolled to prepare a dry positive electrode film. The dry positive electrode film was placed on one side of a 12 μm thick aluminum thin film to produce a positive electrode.

[0106] Using the manufactured positive electrode, a coin cell was produced with lithium metal as the relative electrode, and a PTFE separator and a solution of 1.3M LiPF6 dissolved in EC (ethylene carbonate) + EMC (ethylmethyl carbonate) + DMC (dimethyl carbonate) (3:4:3 volume ratio) as the electrolyte.

[0107] Evaluation Example 3: Cycle Evaluation Cycle evaluation was performed on the manufactured batteries. In the first cycle, charging and discharging (cc mode) were performed with a current capacity of 0.1C in the voltage range of 4.35-2.8V (vs Li). Next, in the second cycle, charging was performed with a current capacity of 0.33C to 4.35V (vs Li) (cc mode), and then cut-off was performed with a current at a rate of 0.05C while maintaining 4.35V in constant voltage mode (cv mode), and discharge was performed with a current capacity of 0.2C to 2.8V (vs Li). To evaluate the cycle life, charge and discharge cycles were performed up to 50 times under the condition that the battery was charged with a constant current at a rate of 1C until the voltage reached 4.35V, and discharged with a constant current of 1C until the voltage reached 2.8V. The results are shown in Table 1 below.

[0108] [Table 1]

[0109] Referring to Table 1 and Figure 10, it can be confirmed that the positive electrode active materials of Examples 1 and 2 have superior fluidity compared to the comparative example. As a result, it can be confirmed that the capacity retention rate of the lithium secondary batteries produced by Examples 1 and 2 is also superior to that of the comparative example.

Claims

1. The process involves crushing carbon-based raw materials to prepare carbon-based fine powder, A mixed powder is prepared by mixing lithium metal composite oxide and the carbon-based fine powder, The mixed powder is rotated to form a carbon-based coating layer on the surface of the lithium metal composite oxide particles, Includes, The average particle size of the carbon-based fine powder is 10 nm to 100 nm. The aforementioned rotation includes applying rotation to the mixed powder at 1,000 rpm to 6,000 rpm for 2 minutes to 10 minutes. A method for manufacturing a positive electrode active material.

2. The carbon-based raw material includes at least one selected from the group consisting of graphite, carbon black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers. A method for producing a positive electrode active material according to claim 1.

3. The analysis of the carbon-based raw materials includes dry grinding. A method for producing a positive electrode active material according to claim 1.

4. Preparing carbon-based fine powder is The carbon-based raw material is fed into a pulverizing device that includes balls, The pulverizing device is operated for 60 minutes, Includes, In the container of the pulverizer, the volume ratio of the carbon-based raw material to the balls is 2:1 to 5:

1. The particle size of the aforementioned balls is 1 mm to 5 mm. The rotational speed when operating the aforementioned crushing device is 5,000 rpm to 10,000 rpm. A method for producing a positive electrode active material according to claim 1.

5. The aforementioned grinding device is a ball mill. Operating the pulverizing device for 60 minutes includes operating the pulverizing device for 10 minutes at a time, repeating this six times. A break time is placed between each of the aforementioned operations. A method for producing a positive electrode active material according to claim 4.

6. The lithium metal composite oxide includes a lithium nickel-based oxide having a layered crystal structure, a lithium cobalt-based oxide having a layered crystal structure, a lithium iron phosphate-based compound having an olivine crystal structure, or a combination thereof. The average particle size of the lithium metal composite oxide is 0.5 μm to 15 μm. The lithium nickel oxide particles are in the form of single particles. A method for producing a positive electrode active material according to claim 1.

7. The aforementioned mixed powder is The lithium metal composite oxide and the carbon-based fine powder are contained in a weight ratio of 99:1 to 99.7:0.

3. A method for producing a positive electrode active material according to claim 1.

8. The aforementioned mixing includes dry mixing. A method for producing a positive electrode active material according to claim 1.

9. The rotational speed at which the aforementioned rotation is applied is 3,500 rpm to 4,500 rpm. A method for producing a positive electrode active material according to claim 1.

10. The manufactured positive electrode active material has an avalanche energy of 6 mJ / kg to 13 mJ / kg. A method for producing a positive electrode active material according to claim 1.

11. The manufactured positive electrode active material has an avalanche angle of 20° to 60°. A method for producing a positive electrode active material according to claim 1.

12. The manufactured positive electrode active material has an avalanche energy and an avalanche angle. The avalanche energy and avalanche angle were measured using a Revolution Powder Analyzer from Mercury Scientific Inc. A method for producing a positive electrode active material according to claim 1.

13. The thickness of the carbon-based coating layer is 5 nm to 10 nm. A method for producing a positive electrode active material according to claim 1.

14. The particle strength of the positive electrode active material is 150 MPa to 250 MPa. A method for producing a positive electrode active material according to claim 1.

15. It is a positive electrode active material, The material comprises a lithium metal composite oxide and a carbon-based coating layer on the surface of the lithium metal composite oxide. The avalanche energy of the positive electrode active material is 6 mJ / kg to 13 mJ / kg. The avalanche angle of the positive electrode active material is 20° to 60°. The average particle size of the positive electrode active material is 0.5 μm to 15 μm. Cathode active material.

16. The positive electrode active material according to claim 15, wherein the carbon-based coating comprises carbon-based fine powder having an average particle size of about 10 nm to about 100 nm.

17. The lithium metal composite oxide includes a lithium nickel-based oxide having a layered crystal structure, a lithium cobalt-based oxide having a layered crystal structure, a lithium iron phosphate-based compound having an olivine crystal structure, or a combination thereof. The lithium nickel oxide particles are in the form of single particles. The positive electrode active material according to claim 15.

18. The packing density of the positive electrode active material is 3.7 g / cc to 4.0 g / cc. The positive electrode active material according to claim 15.

19. The thickness of the carbon-based coating layer is 5 nm to 10 nm. The positive electrode active material according to claim 15.

20. A positive electrode comprising the positive electrode active material described in claim 15, A negative electrode containing a negative electrode active material, A separator interposed between the negative electrode and the positive electrode, including, Lithium-ion rechargeable battery.

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