Positive electrode and method for manufacturing a positive electrode

Abstract

A positive electrode and a method for manufacturing a positive electrode are provided. The method for manufacturing a positive electrode includes the steps of forming a positive electrode active material and an aggregate including a carbon coating layer; forming a slurry including the positive electrode active material and the aggregate; and coating the slurry on a current collector and drying to form a positive electrode active material layer, wherein the carbon coating layer and the aggregate are formed of graphene particles, and wherein a form of the graphene particles includes at least one of a flake form or a cabbage form.

Description

[0001] This application claims priority and benefit to Korean Patent Application No. 10-2024-0183796, filed on December 11, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] One or more embodiments of this disclosure relate to a positive electrode and a method for manufacturing the positive electrode. Background Technology

[0003] Recently, with the rapid proliferation of battery-powered electronic devices (such as mobile phones and / or laptops) and / or electric vehicles, the demand for rechargeable batteries with high energy density and large capacity has been increasing significantly. In response, extensive research and development efforts have been undertaken to enhance the performance of such rechargeable batteries (specifically, rechargeable lithium batteries).

[0004] Rechargeable lithium-ion batteries typically consist of a positive electrode, a negative electrode, and an electrolyte. Each of the positive and negative electrodes contains active materials capable of inserting and deintercalating lithium ions. Electrical energy is generated through oxidation and reduction reactions as lithium ions move between the electrodes during charging and discharging. For example, electrical energy is generated when lithium ions are inserted into the positive electrode and / or deintercalated from the negative electrode during the discharge process. Summary of the Invention

[0005] One or more aspects of embodiments of this disclosure relate to a positive electrode having (possessing) low resistance and a method for manufacturing the positive electrode. Additional aspects will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practicing the embodiments given in the disclosure.

[0006] According to one or more embodiments of the present disclosure, a method for manufacturing a positive electrode may include the following steps: forming a positive electrode active material and aggregates comprising a carbon coating layer (e.g., in the form of particles); forming a slurry comprising the positive electrode active material and aggregates; and coating the slurry onto a current collector and drying it to form a layer of positive electrode active material, wherein both the carbon coating layer and the aggregates are formed of graphene particles, and wherein the form of the graphene particles may include at least one of sheet form or cabbage form.

[0007] According to one or more embodiments of the present disclosure, a method for manufacturing a positive electrode may include the following steps: forming a first slurry comprising a first positive electrode active material including a first carbon coating layer (e.g., in the form of particles) and a first aggregate; forming a second slurry comprising a second positive electrode active material including a second carbon coating layer (e.g., in the form of particles) and a second aggregate; coating the first slurry onto a current collector and drying it to form a first positive electrode active material layer; and coating the second slurry onto the first positive electrode active material layer and drying it to form a second positive electrode active material layer, wherein the first carbon coating layer and the first aggregate may both be formed of first graphene particles, and the second carbon coating layer and the second aggregate may both be formed of second graphene particles.

[0008] According to one or more embodiments of the present disclosure, the positive electrode may include a current collector and a positive electrode active material layer on the current collector, wherein the positive electrode active material layer may include: a positive electrode active material comprising a lithium nickel composite oxide and a carbon coating layer (e.g., in the form of particles); an aggregate; a conductive material comprising a carbon material having a one-dimensional nanostructure; and a binder, wherein the carbon coating layer and the aggregate may both be formed of graphene particles. Attached Figure Description

[0009] The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this disclosure. The drawings illustrate exemplary embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. The above and other aspects, features, and advantages of certain embodiments of the disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings.

[0010] Figure 1 This is a schematic concept diagram of a rechargeable lithium battery according to one or more embodiments of the present disclosure.

[0011] Figures 2 to 5 These are schematic diagrams of rechargeable lithium batteries according to one or more embodiments of this disclosure.

[0012] Figure 6 This is a cross-sectional view of the positive electrode according to one or more embodiments of the present disclosure.

[0013] Figure 7 According to one or more embodiments of this disclosure Figure 6 A magnified view of the positive electrode.

[0014] Figure 8 This is a schematic cross-sectional view of large particles of positive electrode active material according to one or more embodiments of the present disclosure.

[0015] Figure 9This is a schematic cross-sectional view of small particles of positive electrode active material according to one or more embodiments of the present disclosure.

[0016] Figure 10 This illustrates one or more embodiments according to the present disclosure. Figure 6 The diagram shows the distribution of carbon in the positive electrode active material layer in the third direction.

[0017] Figure 11 This is a cross-sectional view of the positive electrode according to one or more embodiments of the present disclosure.

[0018] Figures 12 to 15 According to one or more embodiments of this disclosure Figure 11 A magnified view of the positive electrode.

[0019] Figure 16 This illustrates one or more embodiments according to the present disclosure. Figure 11 The diagram shows the distribution of carbon in the positive electrode active material layer in the third direction.

[0020] Figure 17 This is a flowchart describing a method for manufacturing a positive electrode according to one or more embodiments of the present disclosure.

[0021] Figures 18 to 21 This is a schematic diagram illustrating the steps (e.g., actions or tasks) of a method for manufacturing a positive electrode according to one or more embodiments of the present disclosure.

[0022] Figure 22 This is a scanning electron microscope image of reduced graphene oxide (RGO) particles in sheet form according to Preparation Example 1 of this disclosure.

[0023] Figure 23 The image is a scanning electron microscope image of the first positive electrode active material and aggregate according to Example 1 of this disclosure.

[0024] Figure 24 This is a scanning electron microscope image of reduced graphene oxide (RGO) particles in the form of cabbage leaves, according to Preparation Example 2 of this disclosure.

[0025] Figure 25 The image shows a scanning electron microscope image of the second positive electrode active material and aggregate prepared according to Example 2 of this disclosure.

[0026] Figure 26 It is a scanning electron microscope image of a cross-section of the positive electrode according to Example 1 of this disclosure.

[0027] Figure 27 It is a scanning electron microscope image of a cross-section of the positive electrode according to Example 3 of this disclosure.

[0028] Figure 28 It is a scanning electron microscope image of the cross-section of the positive electrode according to Comparative Example 1 of this disclosure. Detailed Implementation

[0029] To fully understand the structure and effects of this disclosure, one or more exemplary embodiments will be described with reference to the accompanying drawings. However, this disclosure is not limited to the following exemplary embodiments and may be implemented in one or more suitable forms. The exemplary embodiments are provided merely to illustrate this disclosure and to enable those skilled in the art to fully understand its scope.

[0030] In this disclosure, if an element is described as "on" another element (e.g., when an element is described as "on" another element), it can be directly on said other element, or one or more intervening elements may exist between them. Conversely, if an element is described as "directly on" another element (e.g., when an element is described as "directly on" another element), there are no intervening elements between them. In the drawings, certain thicknesses may be exaggerated to better illustrate technical details. Throughout the disclosure, the same reference numerals denote the same elements, and for the sake of brevity, their repeated descriptions are not provided.

[0031] One or more embodiments described herein can be illustrated using sectional views and / or plan views given as idealized and illustrative examples of this disclosure. For clarity, the thickness of layers and regions in the figures may be exaggerated. The regions shown in the figures are for illustrative purposes and should not be construed as limiting the scope of this disclosure. While terms such as “first,” “second,” and “third” may be used to describe one or more suitable elements, these terms are used only for distinction and do not imply any particular order or hierarchy. For example, a first element discussed herein may be referred to as a second element without departing from the scope of the disclosure. The embodiments described and illustrated herein may include complementary variations.

[0032] The terminology used in this disclosure is for the purpose of explaining one or more suitable embodiments only and is not intended to limit the disclosure. Unless expressly stated otherwise, the singular forms may also include the plural forms. For example, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are also intended to include the plural forms. The terms “comprising / including” and / or variations thereof do not exclude the presence or addition of one or more other components. Additionally, the terms “comprising / including” or other similar terms include or support the terms “consisting of” and “substantially consisting of” indicating the presence of the stated features, quantities, steps, operations, elements, parts, and / or components without or substantially without other features, quantities, steps, operations, elements, parts, components, and / or groups thereof. Furthermore, when describing embodiments of this disclosure, the use of “may” refers to “one or more embodiments of this disclosure.”

[0033] In this disclosure, the phrase “combination of them” can refer to a mixture, stack, complex, copolymer, alloy, blend, or reaction product of the components.

[0034] Unless otherwise specifically defined, the terms "particle size" or "particle diameter" refer to the average particle size. The average particle size can be expressed as the median particle size (D50) corresponding to the diameter / size of particles at 50 vol% of a cumulative particle size distribution. In other words, D50 refers to the average diameter (or size) of the particles whose cumulative volume in a particle size distribution (e.g., a cumulative distribution) corresponds to 50 vol% of the particles, and is the value corresponding to the 50% particle size starting from the smallest particle when the total number of particles is 100% in a distribution curve accumulated in order from smallest to largest particle size. The average particle size (D50) can be measured using a wide range of suitable methods, such as a particle size analyzer (e.g., a HORIBA LA-950 laser particle size analyzer) or by imaging using transmission electron microscopy (TEM) or scanning electron microscopy (SEM). In one or more embodiments, dynamic light scattering can be used, where particle counts within an analytical size range are analyzed to calculate the average particle size (D50). In one or more embodiments, laser scattering can be employed, wherein the target particles are dispersed in a solvent, introduced into a laser scattering particle measurement device (e.g., an MT3000 from Microtrac), irradiated with ultrasound at 28 kHz and 60 W, and subsequently analyzed to determine the D50 value based on a 50 vol% cumulative particle size distribution. In this disclosure, "diameter / size" refers to the average particle diameter / size when the particles are spherical, and "diameter / size" refers to the average major axis length of the particles when the particles are non-spherical.

[0035] In this disclosure, the term "single particle" can refer to a single particle that exists alone without grain boundaries. Morphologically, a single particle can refer to a single particle existing as an independent phase in which particles do not aggregate with each other, a monolithic structure, a single integral structure, or a non-aggregated (e.g., non-clustered) particle. For example, a single particle can be a single crystal. In one or more embodiments, a single particle can be or include a particle comprising several crystals. A single particle can be independently separable. In one or more embodiments, a single particle can exist in a form in which fewer than 10 single particles are attached to each other.

[0036] In the publication, the phrases “A or B”, “A and / or B”, “A / B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, and “at least one of A, B or C” include any one or all possible combinations of the listed elements.

[0037] Figure 1 This is a schematic concept diagram of a rechargeable lithium battery according to one or more embodiments of the present disclosure. (Refer to...) Figure 1 A rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0038] The positive electrode 10 and the negative electrode 20 can be separated from each other by a diaphragm 30. The diaphragm 30 can be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20 and the diaphragm 30 can be in contact with the electrolyte ELL. For example, the positive electrode 10, the negative electrode 20 and the diaphragm 30 can be immersed in the electrolyte ELL.

[0039] The electrolyte ELL can be a medium used to transport lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move towards the positive electrode 10 or the negative electrode 20 through the membrane 30.

[0040] Positive electrode 10 The positive electrode 10 for a rechargeable lithium battery may include a current collector COL1 and a positive electrode active material layer AML1 on the current collector COL1. The positive electrode active material layer AML1 may include (e.g., in particulate form) a positive electrode active material, and may also include a binder and / or a conductive material (e.g., an electrically conductive material).

[0041] In one or more embodiments, the positive electrode 10 may further include an additive that can be used as a sacrificial positive electrode.

[0042] Based on 100 wt% of the total weight of the positive electrode active material layer AML1, the amount of positive electrode active material can be from about 90 wt% to about 99.5 wt%. Based on 100 wt% of the total weight of the positive electrode active material layer AML1, the amounts of binder and conductive material can both be from about 0.5 wt% to about 5 wt%.

[0043] The binder is used to ensure good adhesion between the positive electrode active material particles and also to ensure good adhesion of the positive electrode active material to the current collector COL1. As a non-limiting example, examples of binders may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, and / or nylon, etc.

[0044] Conductive materials (e.g., electrically conductive materials) can be used to impart conductivity (e.g., electrical conductivity) to electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons can be used in the battery. Non-limiting examples of conductive materials may include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, and / or silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0045] In one or more embodiments, aluminum (Al) can be used as the current collector COL1, but the embodiments disclosed herein are not limited thereto.

[0046] Positive electrode active material The positive electrode active material may include compounds capable of intercalating and deintercalating lithium (lithiation intercalation compounds). For example, in one or more embodiments, at least one of the composite oxides of lithium with metals selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0047] The composite oxide can be a lithium transition metal composite oxide. Non-limiting examples of composite oxides may include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, and / or combinations thereof.

[0048] In one or more embodiments, one or more compounds represented by any of the following chemical formulas may be used: Li a A 1-b X bO 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 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, and 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 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, and 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, and 0≤e≤0.1); Li a NiG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-b G b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn2G b O4 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-g G g PO4 (0.90 ≤ a ≤ 1.8 and 0 ≤ g ≤ 0.5); Li (3-f) Fe2(PO4)3 (0≤f≤2); and Li a FePO4 (0.90≤a≤1.8).

[0049] In the aforementioned chemical formula, A can be nickel (Ni), cobalt (Co), manganese (Mn), or a combination thereof; X can be Al, Ni, Co, Mn, chromium (Cr), iron (Fe), magnesium (Mg), strontium (Sr), vanadium (V), rare earth elements, or a combination thereof; D can be oxygen (O), fluorine (F), sulfur (S), phosphorus (P), or a combination thereof; G can be Al, Cr, Mn, Fe, Mg, lanthanum (La), cerium (Ce), Sr, V, or a combination thereof; and L 1 It can be Mn, Al, or a combination thereof.

[0050] In one or more embodiments, the positive electrode active material may be, for example, a high-nickel positive electrode active material, having a nickel content (e.g., amount) of 100 mol% of the total metals other than lithium in the lithium transition metal complex oxide, greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. High-nickel positive electrode active materials can achieve high capacity and can be used in high-capacity, high-density rechargeable lithium batteries.

[0051] negative electrode 20 The negative electrode 20 for a rechargeable lithium battery may include a current collector COL2 and a negative electrode active material layer AML2 on the current collector COL2. The negative electrode active material layer AML2 may include (e.g., in particulate form) negative electrode active material, and may also include a binder and / or a conductive material (e.g., an electrically conductive material).

[0052] For example, in one or more embodiments, based on 100 wt% of the total weight of the negative electrode active material layer, the negative electrode active material layer AML2 may include about 90 wt% to about 99 wt% of the negative electrode active material, about 0.5 wt% to about 5 wt% of the binder, and about 0 wt% to about 5 wt% of the conductive material.

[0053] The binder can be used to ensure good adhesion between the negative electrode active material particles and also to ensure good adhesion between the negative electrode active material and the current collector COL2. The binder may include non-aqueous (e.g., water-insoluble) binders, aqueous (e.g., water-soluble) binders, dry binders, or combinations thereof.

[0054] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0055] Waterborne adhesives may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxygenated alcohol, 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.

[0056] When an aqueous binder is used as the negative electrode binder, it may also include a cellulose compound capable of imparting viscosity. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methylcellulose, methylcellulose, or an alkali metal salt thereof. The alkali metal may include Na, K, or Li.

[0057] Dry adhesives can be fibrous polymeric materials. For example, dry adhesives can be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0058] Conductive materials (e.g., electrically conductive materials or electronic conductors) can be used to impart conductivity (e.g., electrical conductivity) to electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons can be used in the battery. Non-limiting examples may include: carbon-based materials such as natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, and / or silver; conductive polymers such as polyphenylene derivatives; and / or mixtures thereof.

[0059] The current collector COL2 of the negative electrode may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0060] Negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 may include materials that can reversibly insert / deintercalate lithium ions, lithium metal, lithium metal alloys, materials capable of doping / dedoping lithium, and / or transition metal oxides.

[0061] Materials capable of reversibly inserting / deintercalating lithium ions can include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. Crystalline carbon can be graphite such as amorphous, flake, sheet, spherical, or fibrous natural or artificial graphite. Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonization products, and / or calcined coke, etc.

[0062] The lithium metal alloy may include an alloy of lithium and a metal selected from sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), silicon (Si), antimony (Sb), lead (Pb), indium (In), zinc (Zn), barium (Ba), radium (Ra), germanium (Ge), aluminum (Al), and tin (Sn).

[0063] The material capable of doping / dedoping lithium may be a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (except Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof). The Sn-based negative electrode active material may include Sn, SnO k (0 < k ≤ 2) (e.g., SnO2), a Sn-based alloy, or a combination thereof.

[0064] The silicon-carbon composite (e.g., in the form of particles) may be a composite of silicon and amorphous carbon. According to one or more embodiments, 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, in one or more embodiments, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are assembled and an amorphous carbon coating layer (shell) on the surface of the secondary particles. Amorphous carbon may also be between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in the amorphous carbon matrix.

[0065] In one or more embodiments, the silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer on the surface of the core.

[0066] In one or more embodiments, the Si-based negative electrode active material and / or the Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0067] Separator 30 Depending on the type (kind) of the rechargeable lithium battery, the separator 30 may be present between the positive electrode 10 and the negative electrode 20. The separator 30 may include polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, such as a hybrid multilayer film such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, and / or a polypropylene / polyethylene / polypropylene trilayer separator.

[0068] The diaphragm 30 may include a porous substrate and a coating layer on one or both (e.g., simultaneously) surfaces (e.g., two opposing surfaces) of the porous substrate, comprising organic materials, inorganic materials, or combinations thereof.

[0069] The porous substrate can be a polymer film formed from any one or a copolymer or mixture of two or more of the following: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., TEFLON).

[0070] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers.

[0071] Inorganic materials may include 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, but the embodiments disclosed herein are not limited thereto.

[0072] In one or more embodiments, organic and inorganic materials may be mixed in a coating layer, or a coating layer comprising organic materials and a coating layer comprising inorganic materials may be stacked.

[0073] Electrolyte ELL Electrolytes (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0074] Non-aqueous organic solvents can be used as a medium for transporting ions that participate in the electrochemical reactions of rechargeable lithium batteries.

[0075] Non-aqueous organic solvents can be carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0076] Carbonate solvents may 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 / or butyl carbonate (BC), etc.

[0077] Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, valonate lactone, and / or caprolactone, etc.

[0078] Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and / or tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol and / or isopropanol, etc., and aprotic solvents may include: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane and / or 1,4-dioxolane, etc.; and / or sulfolane, etc.

[0079] Non-aqueous organic solvents can be used alone or in combination of two or more of them.

[0080] Alternatively, if a carbonate solvent is used (e.g., when using a carbonate solvent), cyclic carbonates and chain carbonates can be mixed and used, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0081] Lithium salts dissolved in non-aqueous organic solvents supply lithium ions in rechargeable lithium batteries, enabling basic operation of the rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Non-limiting examples of lithium salts include those selected from 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+ The first of the following: (1SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0082] Rechargeable lithium batteries Rechargeable lithium batteries can be classified according to their shape as cylindrical, prismatic, pouch and / or coin type (type) batteries, etc. Figures 2 to 5 Each of these diagrams illustrates a rechargeable lithium battery according to one or more embodiments of the present disclosure. Figure 2A cylindrical battery is shown. Figure 3 A prismatic battery is shown. Figure 4 and Figure 5 A pouch-type (bag-type) battery is shown. (See reference...) Figures 2 to 5 The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20, and the electrode assembly 40 is housed within the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. In one or more embodiments, such as Figure 2 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of a sealed housing 50. In one or more embodiments, as Figure 3 As shown, the rechargeable lithium battery 100 may include a positive lead terminal 11, a positive terminal 12, a negative lead terminal 21, and a negative terminal 22. In one or more embodiments, as Figure 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include electrode terminals 70, which serve as electrical paths for guiding current formed in the electrode assembly 40 to the outside. The electrode terminals 70 may be, for example, a positive electrode terminal 71 and a negative electrode terminal 72.

[0083] As a non-limiting example, the rechargeable lithium battery according to one or more embodiments can be used in automobiles, mobile phones and / or one or more suitable types (classes) of electrical devices.

[0084] The positive electrode 10 of this disclosure will be described in more detail below.

[0085] Positive electrode 10 Figure 6 This is a cross-sectional view of the positive electrode 10 according to one or more embodiments of the present disclosure. Figure 7 According to one or more embodiments Figure 6 An enlarged view of region M in the image. Figure 8 and Figure 9 This is a schematic diagram illustrating the positive electrode active material AM in one or more embodiments. Figure 10 It is shown that according to one or more embodiments Figure 6 The amount of carbon in the positive electrode active material layer AML1 on the third-direction D3 (C cb The diagram is shown below. For ease of description, references to it will not be provided in the following text. Figures 1 to 5 The descriptions are of the same items, but the differences will be described in more detail.

[0086] Reference Figure 6 and Figure 7According to one or more embodiments of the present disclosure, the positive electrode 10 may include a current collector COL1 and a positive electrode active material layer AML1 formed on (e.g., on) the current collector COL1. In one or more embodiments, the positive electrode active material layer AML1 may be a single layer.

[0087] Thickness TK of the positive electrode active material layer AML1 AML1 It can be from approximately 20 micrometers (μm) to approximately 100 μm. For example, the thickness TK of the positive electrode active material layer AML1. AML1 It can be approximately 20 μm or larger, approximately 30 μm or larger, approximately 40 μm or larger, or approximately 50 μm or larger. For example, the thickness TK of the positive electrode active material layer AML1. AML1 It can be about 100 μm or smaller, about 90 μm or smaller, about 80 μm or smaller, about 70 μm or smaller, or about 60 μm or smaller.

[0088] The positive electrode active material layer AML1 may comprise the positive electrode active material AM and the aggregate GAG, and may also comprise the binder BND and / or the conductive material CDM. Each of the positive electrode active material AM and the aggregate GAG ​​may be in particulate form. The binder BND is described as described above.

[0089] Relative to (e.g., based on) 100 wt% of the total weight of the positive electrode active material layer AML1, the total amount of the positive electrode active material AM and aggregate GAG ​​in the positive electrode active material layer AML1 can be from about 90 wt% to about 99.5 wt%. For example, based on 100 wt% of the total weight of the positive electrode active material layer AML1, the total amount of the positive electrode active material AM and aggregate GAG ​​in the positive electrode active material layer AML1 can be about 90 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 97.5 wt% or more, or 98 wt% or more. For example, based on 100 wt% of the total weight of the positive electrode active material layer AML1, the total amount of the positive electrode active material AM and aggregate GAG ​​in the positive electrode active material layer AML1 can be equal to or greater than about 90 wt% and about 99.5 wt% or less, about 99 wt% or less, or about 98.5 wt% or less.

[0090] The amount of positive electrode active material AM in the positive electrode active material layer AML1 can be the remaining amount after deducting the amount of aggregate GAG ​​from the total amount of positive electrode active material AM and aggregate GAG ​​in the positive electrode active material layer AML1.

[0091] Reference Figure 7The positive electrode active material AM may include at least one of large-particle PC or small-particle SP. For example, in one or more embodiments, the positive electrode active material AM may include large-particle PC. For example, in one or more embodiments, the positive electrode active material AM may include small-particle SP. For example, in one or more embodiments, the positive electrode active material AM may include both large-particle PC and small-particle SP.

[0092] The average particle size (DPC) of large PC particles can be larger than the average particle size (DSP) of small SP particles. For example, in one or more embodiments, the average particle size (DPC) of large PC particles can be about 6.0 μm to about 20.0 μm, about 10.0 μm to about 20.00 μm, or about 10.0 μm to about 15.0 μm. For example, in one or more embodiments, the average particle size (DSP) of small SP particles can be about 1.0 μm to about 6.0 μm, about 2.0 μm to about 5.0 μm, or about 3.0 μm to about 5.0 μm. For example, the average particle size can be obtained by randomly selecting about 30 large PC particles and 30 small SP particles from an electron microscope image of the positive electrode active material AM, measuring their particle sizes, and using the diameter of the particles having a cumulative volume of 50 vol% in the particle size distribution as the average particle size. As another example, the average particle size can be measured using a particle size analyzer, and the diameter of the particles having a cumulative volume of 50 vol% in the particle size distribution can be used as the average particle size.

[0093] The positive electrode active material AM according to one or more embodiments of the present disclosure can exhibit a bimodal morphology comprising large PC particles and small SP particles with different average particle sizes. The small SP particles can fill the pores between the large PC particles, improving the packing density of the positive electrode active material layer AML1. For example, the positive electrode active material layer AML1 according to one or more embodiments of the present disclosure can have a relatively high energy density and a high capacity per unit volume.

[0094] For example, the weight ratio of large PC particles to small SP particles can be from about 95:5 to about 50:50. For example, in one or more embodiments, the weight ratio of large PC particles to small SP particles can be from about 90:10 to about 60:40, from about 90:10 to about 70:30, or from about 80:20 to about 70:30. In one or more embodiments, the weight ratio of large PC particles to small SP particles can be from about 5:95 to about 50:50. For example, in one or more embodiments, the amount of large PC particles in the positive electrode active material AM can be greater than the amount of small SP particles.

[0095] For example, in one or more embodiments, the positive electrode active material AM may consist only of large PC particles. For example, small SP particles may not be included.

[0096] Reference Figure 8 According to one or more embodiments of this disclosure, large-particle PC can be in a polycrystalline form and can have (e.g., be) secondary particles in which at least two (or more) primary particles PRP are aggregated (e.g., clustered). The large-particle PC can be spherical or elliptical in shape.

[0097] Large-particle PC may include a core COR and a carbon coating layer CTL. The core COR of large-particle PC may be in a polycrystalline form and may have (e.g., be) secondary particles in which at least two (or more) primary particles PRP are aggregated (e.g., agglomerated).

[0098] Reference Figure 9 According to one or more embodiments of this disclosure, the small particles SP can be in the form of a single particle, which refers to a single particle existing alone without grain boundaries. In terms of morphology, a single particle can refer to a single particle existing as an independent phase in which particles do not aggregate, a monolithic structure, a single integral structure, or a non-aggregated (e.g., non-clustered) particle. For example, the small particles SP can be a single crystal. The positive electrode active material AM can include small particles SP, enabling the achievement of high capacity, high energy density, and improved lifetime characteristics.

[0099] Small particles (SP) may include a core (COR') and a carbon coating layer (CTL').

[0100] Reference Figure 8 and Figure 9 In one or more embodiments, each of the core COR of large-particle PC and the core COR' of small-particle SP may include a lithium-nickel composite oxide. The lithium-nickel composite oxide may include lithium (Li) and a transition metal. The transition metal may include nickel (Ni). The amount of nickel (Ni) included in the lithium-nickel composite oxide is not limited.

[0101] For example, in one or more embodiments, the lithium-nickel composite oxide can be a lithium-nickel composite oxide containing a large amount of nickel (Ni). For example, the lithium-nickel composite oxide can be a lithium-nickel composite oxide in which the amount of nickel (Ni) based on the total metals other than lithium is about 60 mol% or more, about 80 mol% or more, about 90 mol% or more, or about 91 mol% or more and 100 mol% or less, about 99.9 mol% or less, or about 99 mol% or less. For example, the lithium-nickel composite oxide can be a lithium-nickel composite oxide in which the molar number of nickel (Ni) relative to the total molar number of transition metals is about 60 mol% or more, about 80 mol% or more, about 90 mol% or more, or about 91 mol% or more and 100 mol% or less, about 99.9 mol% or less, or about 99 mol% or less. When the amount of nickel (Ni) meets the above ranges, the positive electrode active material AM can achieve high capacity and high performance.

[0102] For example, in one or more embodiments, lithium-nickel composite oxides may be represented by chemical formula 1.

[0103] Chemical Formula 1 Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In chemical formula 1, 0.9 ≤ a1 ≤ 1.8, 0.8 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, 0 ≤ z1 ≤ 0.2, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1. M 1 and M 2 Each element may be independently selected from one or more elements selected from the group consisting of aluminum (Al), boron (B), barium (Ba), calcium (Ca), cerium (Ce), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), molybdenum (Mo), niobium (Nb), silicon (Si), strontium (Sr), titanium (Ti), vanadium (V), tungsten (W), and zirconium (Zr), and X may be selected from one or more elements selected from the group consisting of F, P, and S.

[0104] For example, in one or more embodiments, in chemical formula 1, 0.85≤x1≤1, 0≤y1≤0.15, and 0≤z1≤0.15 may be satisfied; or 0.9≤x1≤1, 0≤y1≤0.1, and 0≤x1≤0.1 may be satisfied.

[0105] For example, x1+y1+z1=1.

[0106] For example, in one or more embodiments, the lithium nickel-based composite oxide may be represented by Chemical Formula 2. The compound represented by Chemical Formula 2 may be a lithium nickel cobalt-based composite oxide.

[0107] Chemical Formula 2 Li a2 Ni x2 Co y2 M 3 z2 O 2-b2 X b2 In Chemical Formula 2, 0.9 ≤ a2 ≤ 1.8, 0.8 ≤ x2 < 1, 0 < y2 ≤ 0.2, 0 ≤ z2 ≤ 0.2, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1. M 3 may be one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X may be one or more elements selected from the group consisting of F, P, and S.

[0108] For example, in one or more embodiments, in Chemical Formula 2, 0.85 ≤ x2 ≤ 0.99, 0.01 ≤ y2 ≤ 0.15, and 0.01 ≤ z2 ≤ 0.15 may be satisfied; or 0.9 ≤ x2 ≤ 0.99, 0.01 ≤ y2 ≤ 0.1, and 0.01 ≤ z2 ≤ 0.1 may be satisfied.

[0109] For example, x2 + y2 + z2 = 1.

[0110] For example, in one or more embodiments, the lithium nickel-based composite oxide may be represented by Chemical Formula 3. The compound represented by Chemical Formula 3 may be lithium nickel cobalt aluminum oxide or lithium nickel cobalt manganese oxide.

[0111] Chemical Formula 3 Li a3 Ni x3 Co y3 M 4 z3 M 5 w3 O 2-b3 X b3 In Chemical Formula 3, 0.9 ≤ a3 ≤ 1.8, 0.8 ≤ x3 ≤ 0.98, 0.01 ≤ y3 ≤ 0.19, 0.01 ≤ z3 ≤ 0.19, 0 ≤ w3 ≤ 0.19, 0.9 ≤ x3 + y3 + z3 + w3 ≤ 1.1, 0 ≤ b3 ≤ 0.1. M 4 may be one or more elements selected from the group consisting of Al and Mn, M5 It may be one or more elements selected from the group consisting of B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W and Zr, and X may be one or more elements selected from the group consisting of F, P and S.

[0112] For example, in one or more embodiments, in chemical formula 3, 0.85≤x3≤0.98, 0.01≤y3≤0.14, 0.01≤z3≤0.14, and 0≤w3≤0.14 can be satisfied; or 0.9≤x3≤0.98, 0.01≤y3≤0.09, 0.01≤z3≤0.09, and 0≤w3≤0.09 can be satisfied.

[0113] For example, x³ + y³ + z³ + w³ = 1.

[0114] The carbon coating layer CTL can be located on the core COR of large-particle PC. The carbon coating layer CTL' can be located on the core COR' of small-particle SP. For example, the carbon coating layers CTL and CTL' can be identified by analyzing the composition of the positive electrode active material AM. When the positive electrode active material AM includes carbon coating layers CTL and CTL', the lithium-nickel composite oxide constituting the core COR and COR' can be in direct contact with the carbon-based material constituting the carbon coating layers CTL and CTL', which can improve the conductivity of the positive electrode active material layer AML1. In addition, the amount of conductive material CDM in the electrode plate including the positive electrode active material AM can be reduced, thereby ensuring additional space within the electrode plate with the same mixture density. Therefore, the cracking of the positive electrode active material AM during electrode plate rolling can be prevented or reduced, and a rechargeable lithium battery with excellent or suitable lifespan can be provided.

[0115] The carbon coating layer CTL can be located on a portion of the surface of the core COR of a large PC particle. The carbon coating layer CTL' can be located on a portion of the surface of the core COR' of a small SP particle. For example, the carbon coating layers CTL and CTL' can exist as islands on the core COR of the large PC particle and the core COR' of the small SP particle, respectively. The carbon coating layers CTL and CTL' can expose portions of the surface of the core COR of the large PC particle and the core COR' of the small SP particle, respectively. Therefore, the positive electrode active material AM can serve as a pathway for lithium ion or electron movement.

[0116] The carbon coating layers CTL, CTL' may include carbon-based materials. In one or more embodiments, the carbon coating layers CTL, CTL' may include graphene. The carbon coating layers CTL, CTL' may be formed from graphene particles added later in the fabrication of the positive electrode active material AM and the aggregate GAG. Graphene is one of the allotropes of carbon and may have a structure in which carbon atoms aggregate (e.g., bond) to form a two-dimensional planar structure. Each of the carbon atoms may form a hexagonal lattice with the carbon atom located at the vertex of the hexagon. Graphene may be in sheet form.

[0117] For example, the lateral dimensions of graphene can be from about 0.1 μm to about 1000 μm. For example, the lateral dimensions of graphene can be from about 0.1 μm to about 500 μm, from about 0.1 μm to about 200 μm, from about 0.1 μm to about 100 μm, from about 0.1 μm to about 50 μm, from about 0.1 μm to about 10 μm, from about 0.1 μm to about 5 μm, or from about 0.1 μm to 3 μm. The lateral dimension of graphene can refer to the longest distance between any two ends joined together on the plane of a graphene sheet.

[0118] For example, the thickness of graphene can be less than or equal to about 1 nanometer (nm). For example, the thickness of graphene can be from about 0.1 nm to about 0.5 nm. The thickness of graphene can refer to the distance in the thickness direction of the graphene sheet.

[0119] For example, in one or more embodiments, graphene can be pure graphene. For example, pure graphene can be substantially oxygen-free. Pure graphene may not contain oxygen. Pure graphene can have good or suitable electrical conductivity, chemical stability, and mechanical strength.

[0120] In one or more embodiments, the graphene may be at least one of graphene oxide, reduced graphene oxide, or a combination thereof. Reduced graphene oxide may be a material containing reduced graphene oxide. By using reduced graphene oxide instead of pure graphene, costs can be reduced, and large-scale production can be made possible.

[0121] For example, unlike pure graphene, reduced graphene oxide can include some oxidized portions. Reduced graphene oxide can contain small amounts of oxygen. Defects can exist in reduced graphene oxide. As a result, reduced graphene oxide can improve or optimize interfacial reactions in rechargeable lithium-ion batteries, or increase lithium-ion storage capacity by adsorbing or diffusing lithium ions. Reduced graphene oxide can possess sufficient conductivity, chemical stability, and mechanical strength to improve or optimize the performance of rechargeable lithium-ion batteries.

[0122] For example, reduced graphene oxide can have carbon-oxygen covalent bonds. Carbon-oxygen covalent bonds can include CO, C=O, and / or OC=O, etc.

[0123] For example, in one or more embodiments, the composition of the carbon coating layers CTL, CTL' can be confirmed by X-ray photoelectron spectroscopy (XPS). As a result of XPS analysis, peaks corresponding to carbon-oxygen covalent bonds can be observed on the surface of the carbon coating layers CTL, CTL' formed using reduced graphene oxide. Conversely, on the surface of the carbon coating layers CTL, CTL' formed using pure graphene, the intensity of peaks corresponding to carbon-oxygen covalent bonds can be reduced or almost absent.

[0124] For example, in one or more embodiments, Raman spectroscopy can be used to confirm the composition of the carbon coatings CTL, CTL'. Defects in the reduced graphene oxide can be confirmed via the D band in Raman spectroscopy. In Raman spectroscopy, carbon coatings CTL, CTL' formed using reduced graphene oxide can have relatively large D band intensities and large D / G ratios. Conversely, carbon coatings CTL, CTL' formed using pure graphene can have reduced D band intensities and D / G ratios.

[0125] For example, in one or more embodiments, the composition of the carbon coating layers CTL, CTL' can be determined using Fourier transform infrared spectroscopy (FT-IR). In the FT-IR spectrum of the positive electrode active material AM comprising the carbon coating layers CTL, CTL' formed using reduced graphene oxide, peaks corresponding to carbon-oxygen covalent bonds can be observed. Conversely, in the FT-IR spectrum of the positive electrode active material AM comprising the carbon coating layers CTL, CTL' formed using pure graphene, peaks corresponding to carbon-oxygen covalent bonds can be reduced or almost absent.

[0126] For example, in one or more embodiments, the composition of the carbon coating layers CTL, CTL' can be determined using thermogravimetric analysis (TGA). A TGA plot for the positive electrode active material AM comprising the carbon coating layers CTL, CTL' formed using reduced graphene oxide can show the mass loss due to oxygen release upon heating. Conversely, a TGA plot for the positive electrode active material AM comprising the carbon coating layers CTL, CTL' formed using pure graphene can show less or no mass loss.

[0127] The conductivity of the graphene constituting the carbon coating layers CTL and CTL' can be greater than the conductivity of the carbon-based materials constituting the conductive material CDM. One or more embodiments of the positive electrode active material AM may include graphene, thereby further improving the conductivity of the positive electrode active material layer AML1.

[0128] The amount of carbon coating layers CTL and CTL' in the positive electrode active material AM can be from about 0.01 wt% to about 1 wt% relative to the total weight of the positive electrode active material AM. For example, the amount of carbon coating layers CTL and CTL' in the positive electrode active material AM can be about 0.01 wt% or more, about 0.05 wt% or more, or about 0.1 wt% or more relative to the total weight of the positive electrode active material AM. For example, the amount of carbon coating layers CTL and CTL' in the positive electrode active material AM can be about 1 wt% or less, about 0.5 wt% or less, about 0.3 wt% or less, or about 0.2 wt% or less relative to the total weight of the positive electrode active material AM. When the amount of carbon coating layers CTL and CTL' meets the above ranges, the positive electrode active material AM can have excellent or suitable conductivity. In addition, the amount of conductive material CDM in the electrode plate can be reduced, thereby ensuring additional space within the electrode plate with the same mixture density. Therefore, it is possible to prevent or reduce the cracking of the positive electrode active material AM during electrode plate rolling, and to provide rechargeable lithium batteries with excellent or suitable lifespan.

[0129] For example, in one or more embodiments, the carbon coating layers CTL, CTL' may use particles containing reduced graphene oxide (see...). Figure 18 The reduced graphene oxide (RGO) particles are formed in the form of flakes or cabbage-shaped particles. For example, if flake-shaped RGO particles are used (e.g., when using flake-shaped RGO particles), a larger amount of carbon coating layers CTLs, CTL' can be formed compared to cabbage-shaped RGO particles. For example, flake-shaped RGO particles can have a larger surface area capable of reacting with lithium nickel composite oxides than cabbage-shaped RGO particles. Flake-shaped RGO particles (which have a thin and flat morphology) can have a larger surface area capable of reacting with lithium nickel composite oxides compared to cabbage-shaped RGO particles (which are multilayered and have a circular morphology).

[0130] For example, the carbon concentration on the surface of the positive electrode active material AM is measured by X-ray photoelectron spectroscopy (XPS). XPS allows for comparison of the relative carbon concentration at the surface of the positive electrode active material AM formed using reduced graphene oxide particles in the form of sheets or cabbage leaves. For instance, XPS analysis results may show that the surface of the positive electrode active material AM formed using sheet-shaped reduced graphene oxide particles exhibits a stronger carbon signal compared to the surface of the positive electrode active material AM formed using cabbage-shaped reduced graphene oxide particles.

[0131] For example, the proportion of carbon present on the surface of the positive electrode active material AM (e.g., atomic percentage) can be measured by energy-dispersive X-ray spectroscopy (EDS). EDS analysis can detect that the proportion of carbon on the surface of the positive electrode active material AM formed using reduced graphene oxide particles in sheet form is greater than the proportion of carbon on the surface of the positive electrode active material AM formed using reduced graphene oxide particles in cabbage-like form.

[0132] For example, the presence or absence of the carbon coating layers CTL and CTL' on the surface of the positive electrode active material AM can be confirmed by Raman spectroscopy. In the case of positive electrode active material AM formed from reduced graphene oxide particles in the form of sheets, the peaks specific to the carbon coating layers CTL and CTL' appear stronger in the Raman spectrum compared to positive electrode active material AM formed from reduced graphene oxide particles in the form of cabbage leaves.

[0133] The thickness of the carbon coating layers CTL and CTL' can be about 10 nm or less. For example, in one or more embodiments, the thickness of the carbon coating layers CTL and CTL' can be about 1 nm to about 10 nm or about 1 nm to about 5 nm. When the thickness of the carbon coating layers CTL and CTL' meets the above range, the positive electrode active material AM can have excellent or suitable conductivity. In addition, the amount of conductive material CDM in the electrode plate can be reduced, thereby ensuring additional space within the electrode plate with the same mixture density. Therefore, cracking of the positive electrode active material AM during electrode plate rolling can be prevented or reduced, and a rechargeable lithium battery with excellent or suitable lifespan can be provided.

[0134] In one or more embodiments, the positive electrode active material AM may further include a transition metal coating layer located on the surface of each of the large-particle PC and the small-particle SP. The transition metal coating layer may be located on the entire surface or at least a portion of the surface of each of the large-particle PC or the small-particle SP. The transition metal coating layer may be located between the core COR, COR' and the carbon coating layers CTL, CTL'. For example, in one or more embodiments, the positive electrode active material AM may further include a transition metal coating layer located inside the large-particle PC on the surface of the primary particle PRP (i.e., coated along the interface of the primary particle PRP). For example, the transition metal coating layer may include, but is not limited to, nickel, cobalt, and / or aluminum. Each of the large-particle PC and the small-particle SP may include a transition metal coating layer, thereby effectively suppressing or reducing structural collapse due to repeated charging and discharging and improving lifetime characteristics.

[0135] Return to reference Figure 7 The conductive material CDM can include, for example, the carbon-based materials described above. For instance, the carbon-based materials can include at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes. The conductive material CDM can improve the adhesion between the positive electrode active materials AM.

[0136] In one or more embodiments, the carbon-based material constituting the conductive material CDM may have a one-dimensional nanostructure. A one-dimensional nanostructure can be defined, for example, as a structure in which the dimension of any one of the three dimensions is larger than the dimensions of the other two dimensions. For example, in one or more embodiments, a one-dimensional nanostructure can be defined as a nanostructure in which the length of the nanostructure is much larger than the diameter or width and thickness of the nanostructure.

[0137] The carbon-based materials constituting the conductive material CDM can have a length of about 1 μm to about 200 μm. For example, the carbon-based materials can have a length of about 5 μm to about 50 μm.

[0138] The aspect ratio of the carbon-based material constituting the conductive CDM can be from about 10 to about 3000. For example, in one or more embodiments, the aspect ratio of the carbon-based material can be from about 10 to about 2600, from about 20 to about 2500, or from about 30 to about 2400. The aspect ratio can be calculated as the ratio of the length of the carbon-based material to the diameter of the carbon-based material.

[0139] When the length and aspect ratio of the carbon-based material meet the above range, the positive electrode active material AM can be connected to each other, and sufficient contact area between the positive electrode active materials AM can be ensured.

[0140] For example, the structure and length of the carbon-based materials that make up the conductive material CDM can be confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and / or atomic force microscopy (AFM).

[0141] For example, the carbon-based materials that constitute conductive CDM can be identified using Raman spectroscopy. For instance, the radical breathing mode (RBM) peak can appear at approximately 70 cm⁻¹ in the Raman spectrum of conductive CDM. -1 Approximately 300cm -1 Within that range. For example, G - belt and G + The band can appear in the Raman spectrum of CDM for conductive materials.

[0142] For example, the carbon-based materials constituting conductive CDMs can be identified using X-ray photoelectron spectroscopy (XPS). In XPS spectra, peaks corresponding primarily to carbon-carbon covalent bonds can be observed on the surface of the conductive CDM. Additionally, XPS analysis reveals very few peaks corresponding to carbon-oxygen covalent bonds on the surface of the conductive CDM.

[0143] The amount of conductive material CDM may be from about 0.5 wt% to 2 wt% relative to (e.g., based on) 100 wt% of the total weight of the positive electrode active material layer AML1. For example, in one or more embodiments, the amount of conductive material CDM may be from about 0.5 wt% to about 1.5 wt% or from about 0.5 wt% to about 1 wt% relative to 100 wt% of the total weight of the positive electrode active material layer AML1.

[0144] In one or more embodiments, the weight ratio of the conductive material CDM to the positive electrode active material AM can be from about 0.7 / 99.5 to about 0.7 / 97. For example, the weight ratio of the conductive material CDM to the positive electrode active material AM can be about 0.7 / 99.5 or greater, about 0.7 / 99 or greater, about 0.7 / 98.5 or greater, or about 0.7 / 98 or greater. For example, the weight ratio of the conductive material CDM to the positive electrode active material AM can be about 0.7 / 97 or less, or about 0.7 / 97.5 or less.

[0145] Because the positive electrode 10 includes the positive electrode active material AM, the amount of conductive material CDM in the electrode plate can be reduced, thereby ensuring additional space within the electrode plate with the same mixture density. Therefore, the cracking of the positive electrode active material AM during electrode plate rolling can be prevented or reduced, and a rechargeable lithium battery with excellent or suitable lifespan can be provided.

[0146] Refer again Figure 7The aggregated GAG may include carbon-based materials. In one or more embodiments, the aggregated GAG may include graphene. The aggregated GAG may be formed from the positive electrode active material AM, which will be described later, and graphene particles added during the manufacture of the aggregated GAG.

[0147] The structure of aggregated GAGs is unrestricted. For example, aggregated GAGs can be spherical, elliptical, or amorphous (irregular or non-uniform). Aggregated GAGs can be formed when graphene particles break apart or aggregate together.

[0148] The particle size distribution (DGR) of aggregated GAGs can vary. Aggregated GAGs can have a particle size DGR of about 40 μm or smaller. For example, in one or more embodiments, the particle size DGR of aggregated GAGs can be about 1 μm to about 40 μm or about 1 μm to about 30 μm. For example, the particle size can be a value measured by selecting and measuring about 30 aggregated GAGs in an electron microscope image of the aggregated GAGs. When the particle size DGR of the aggregated GAGs meets the above range, a positive electrode with low resistance and a rechargeable lithium battery can be provided.

[0149] For example, compared to conductive materials like CDM, aggregated GAGs can have structures that expand in three dimensions. The structure of aggregated GAGs can be confirmed using methods such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and / or atomic force microscopy (AFM).

[0150] In one or more embodiments, the graphene constituting the aggregate GAG ​​can be pure graphene. For example, pure graphene can be substantially oxygen-free. Pure graphene may not contain oxygen. Pure graphene can have good or suitable electrical conductivity, chemical stability, and mechanical strength.

[0151] In one or more embodiments, the graphene constituting the aggregate GAG ​​can be at least one of graphene oxide, reduced graphene oxide, or a combination thereof. Reduced graphene oxide can be a material containing reduced graphene oxide. By using reduced graphene oxide instead of pure graphene, costs can be reduced, and large-scale production can be made possible.

[0152] In one or more embodiments, unlike pure graphene, reduced graphene oxide may include some oxidized portions. Reduced graphene oxide may include a small amount of oxygen. Defects may be present in reduced graphene oxide. As a result, reduced graphene oxide can improve or optimize interfacial reactions in rechargeable lithium-ion batteries, or increase lithium-ion storage capacity by adsorbing or diffusing lithium ions. Reduced graphene oxide can possess sufficient conductivity, chemical stability, and mechanical strength to improve or optimize the performance of rechargeable lithium-ion batteries.

[0153] For example, reduced graphene oxide can have carbon-oxygen covalent bonds. Carbon-oxygen covalent bonds can include CO, C=O, and / or OC=O, etc.

[0154] For example, the composition of aggregated GAGs can be confirmed by X-ray photoelectron spectroscopy (XPS). As a result of XPS analysis, peaks corresponding to carbon-oxygen covalent bonds can be observed on the surface of aggregated GAGs formed using reduced graphene oxide. Conversely, on the surface of aggregated GAGs formed using pure graphene, the intensity of peaks corresponding to carbon-oxygen covalent bonds can be reduced or almost absent.

[0155] For example, Raman spectroscopy can be used to confirm the composition of aggregated GAGs. Defects in reduced graphene oxide can be confirmed via the D-band in Raman spectroscopy. In Raman spectroscopy, aggregated GAGs formed using reduced graphene oxide can have relatively large D-band intensities and large D / G ratios. Conversely, aggregated GAGs formed using pure graphene can have reduced D-band intensities and D / G ratios.

[0156] For example, the composition of aggregated GAGs can be determined using Fourier transform infrared spectroscopy (FT-IR). In the FT-IR spectra of aggregated GAGs formed using reduced graphene oxide, peaks corresponding to carbon-oxygen covalent bonds can be observed. Conversely, in the FT-IR spectra of aggregated GAGs formed using pure graphene, peaks corresponding to carbon-oxygen covalent bonds are reduced or almost absent.

[0157] For example, the composition of aggregated GAGs can be determined using thermogravimetric analysis (TGA). A TGA plot for aggregated GAGs formed using reduced graphene oxide can show the mass loss due to the release of oxygen upon heating. Conversely, a TGA plot for aggregated GAGs formed using pure graphene can show less or no mass loss.

[0158] The graphene constituting the aggregate GAG ​​can be in sheet form. In one or more embodiments, the lateral dimensions of the graphene constituting the aggregate GAG ​​can be from about 0.1 μm to about 1000 μm. For example, the lateral dimensions of the graphene constituting the aggregate GAG ​​can be from about 0.1 μm to about 500 μm, from about 0.1 μm to about 200 μm, from about 0.1 μm to about 100 μm, from about 0.1 μm to about 50 μm, from about 0.1 μm to about 10 μm, from about 0.1 μm to about 5 μm, or from about 0.1 μm to about 3 μm.

[0159] For example, the thickness of graphene can be less than or equal to about 1 nm. For example, the thickness of graphene can be from about 0.1 nm to about 0.5 nm. The thickness of graphene can refer to the distance of the graphene sheet in the thickness direction.

[0160] Because the aggregated GAGs are formed from a portion of the added graphene particles, they can be included in the positive electrode active material layer AML1 in a relatively small amount. During the fabrication of the positive electrode active material layer AML1, the small amount of aggregated GAGs may not agglomerate to form blocks, or even if they do, they may form relatively small blocks. These blocks can be aggregated graphene particles. In one or more embodiments, the positive electrode active material layer AML1 may be substantially block-free. Therefore, a positive electrode with low resistance and a rechargeable lithium battery can be provided.

[0161] For example, reduced graphene oxide particles (RGO) in sheet form can form fewer aggregates (GAG) than reduced graphene oxide particles (RGO) in cabbage leaf form.

[0162] For example, the amount of aggregate GAG ​​can be measured by energy dispersive X-ray spectroscopy (EDS) on the positive electrode 10.

[0163] according to Figure 6 The positive electrode active material layer AML1 may have the following characteristics. Aggregates GAG in the positive electrode active material layer AML1 according to one or more embodiments of this disclosure may be primarily present within the positive electrode active material layer AML1. For example, some of the aggregates GAG may be distributed in the upper portion of the positive electrode active material layer AML1. The distribution of aggregates GAG in the positive electrode active material layer AML1 according to one or more embodiments of this disclosure may be relatively gradual in the third direction D3 (e.g., the thickness direction) of the positive electrode active material layer AML1. In one or more embodiments, reference may be made to... Figure 10 Describe the distribution of aggregate GAG ​​in the positive electrode active material layer AML1.

[0164] Reference Figure 10 The positive electrode active material layer AML1 can be divided into an upper portion UPL and a lower portion UWL along the third direction D3. The lower portion UWL can be located on the current collector COL1. The upper portion UPL can be located on the lower portion UWL. The thickness ratio of the upper portion UPL to the lower portion UWL can be 1:1.

[0165] Each of the upper UPL and lower LWL can include aggregates GAGs. For example, the amount of aggregates in the upper UPL can be slightly greater than the amount of aggregates in the lower LWL. However, the maximum amount of carbon (ΔC) in the upper UPL is limited. cb,UPL ) and the minimum carbon content (ΔC) in the lower LWL layer cb,LWL The difference (ΔC) between cb It can be relatively small.

[0166] For example, the amount of carbon in the positive electrode active material layer AML1 on the third-direction D3 can be examined (C cb This is used to confirm the distribution of aggregated GAGs. For example, the amount of carbon (C) cb The carbon content can be the average of the results of compositional analysis (EDS, etc.) performed at approximately 20 points at each depth of the positive electrode active material layer AML1, and the carbon content at each depth can be plotted sequentially on a graph.

[0167] The positive electrode active material layer AML1 according to one or more embodiments of the present disclosure may include small blocks. The blocks may be aggregated graphene particles. The blocks may be aggregated GAGs. The positive electrode active material layer AML1 according to one or more embodiments of the present disclosure may not include (e.g., may exclude) blocks, or may include relatively small blocks. The size of the blocks may be larger than the size of the GAGs. For example, the size of the blocks included in the positive electrode active material layer AML1 of the present disclosure may be greater than about 40 μm and less than about 50 μm.

[0168] Therefore, the positive electrode active material layer AML1 of this disclosure can provide a positive electrode 10 with low resistance.

[0169] In the following embodiments, for ease of description, references will not be provided. Figures 1 to 10 The descriptions are of the same items, but the differences will be described in more detail.

[0170] Figure 11 This is a cross-sectional view of the positive electrode 10 according to one or more embodiments of the present disclosure. Figures 12 to 15 According to one or more embodiments Figure 11 A magnified view of region N. Figure 16 This illustrates one or more embodiments. Figure 11 The amount of carbon in the positive electrode active material layer AML1 on the third-direction D3 (C cb (The image is shown.)

[0171] Reference Figure 11 According to one or more embodiments of the present disclosure, the positive electrode 10 may include a current collector COL1 and a positive electrode active material layer AML1 formed on (e.g., on) the current collector COL1.

[0172] The positive electrode active material layer AML1 may include a first positive electrode active material layer AML12 and a second positive electrode active material layer AML14. The first positive electrode active material layer AML12 may be located on the current collector COL1. The second positive electrode active material layer AML14 may be located on the first positive electrode active material layer AML12.

[0173] The thickness of the positive electrode active material layer AML1 can be the same as described above.

[0174] The thickness of the first positive electrode active material layer (TK) AML12 ) and the thickness of the second positive electrode active material layer (TK) AML14 The thickness ratio of the first positive electrode active material layer (TK) can be from about 2:1 to about 1:2. For example, in one or more embodiments, the thickness (TK) of the first positive electrode active material layer is... AML12 ) and the thickness of the second positive electrode active material layer (TK) AML14 The thickness ratio of the first positive electrode active material layer (TK) can be approximately 1:1. AML12 ) and the thickness of the second positive electrode active material layer (TK) AML14 When the thickness ratio of GAG meets the above range, the aggregate GAG ​​can exist relatively inside the positive electrode active material layer AML1, so that a positive electrode with low resistance and a rechargeable lithium battery can be provided.

[0175] According to one or more embodiments, refer to Figure 12 The first positive electrode active material layer AML12 may include the first positive electrode active material AM1 and the first aggregate GAG1, and may also include the binder BND and / or the conductive material CDM. Similarly, the second positive electrode active material layer AML14 may include the first positive electrode active material AM1 and the first aggregate GAG1, and may also include the binder BND and / or the conductive material CDM.

[0176] The first positive electrode active material AM1 may include a carbon coating layer. The carbon coating layer may be formed using graphene particles. For example, the carbon coating layer of the first positive electrode active material AM1 may be formed using particles comprising reduced graphene oxide. For example, in one or more embodiments, the carbon coating layer of the first positive electrode active material AM1 may be formed using reduced graphene oxide particles in sheet form.

[0177] The first aggregate GAG1 can be formed using graphene particles. For example, in one or more embodiments, the first aggregate GAG1 can be formed using reduced graphene oxide particles. The first aggregate GAG1 can be formed using reduced graphene oxide particles in the form of sheets.

[0178] Relative to 100 wt% of the total weight of the first positive electrode active material layer AML12, the total amount of the first positive electrode active material AM1 and the first aggregate GAG1 in the first positive electrode active material layer AML12 can be from about 90 wt% to about 99.5 wt%. For example, the total amount of the first positive electrode active material AM1 and the first aggregate GAG1 in the first positive electrode active material layer AML12 can be about 90 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 97.5 wt% or more, or about 98 wt% or more. For example, relative to 100 wt% of the total weight of the first positive electrode active material layer AML12, the total amount of the first positive electrode active material AM1 and the first aggregate GAG1 in the first positive electrode active material layer AML12 can be equal to or greater than about 90 wt% and about 99.5 wt% or less, about 99 wt% or less, or about 98.5 wt% or less.

[0179] The amount of the first positive electrode active material AM1 in the first positive electrode active material layer AML12 may be the remaining amount after deducting the amount of the first aggregate GAG1 from the total amount of the first positive electrode active material AM1 and the first aggregate GAG1 in the first positive electrode active material layer AML12.

[0180] Relative to 100 wt% of the total weight of the second positive electrode active material layer AML14, the total amount of the first positive electrode active material AM1 and the first aggregate GAG1 in the second positive electrode active material layer AML14 can be from about 90 wt% to about 99.5 wt%. For example, the total amount of the first positive electrode active material AM1 and the first aggregate GAG1 in the second positive electrode active material layer AML14 can be about 90 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 97.5 wt% or more, or about 98 wt% or more. For example, relative to 100 wt% of the total weight of the second positive electrode active material layer AML14, the total amount of the first positive electrode active material AM1 and the first aggregate GAG1 in the second positive electrode active material layer AML14 can be equal to or greater than about 90 wt% and about 99.5 wt% or less, about 99 wt% or less, or about 98.5 wt% or less.

[0181] The amount of the first positive electrode active material AM1 in the second positive electrode active material layer AML14 may be the remaining amount after deducting the amount of aggregate GAG1 from the total amount of the first positive electrode active material AM1 and the first aggregate GAG1 in the second positive electrode active material layer AML14.

[0182] The first positive electrode active material AM1 may include at least one of large particles PC1 or small particles SP1. For example, in one or more embodiments, the first positive electrode active material AM1 may include large particles PC1. For example, in one or more embodiments, the first positive electrode active material AM1 may include small particles SP1. For example, in one or more embodiments, the first positive electrode active material AM1 may include both large particles PC1 and small particles SP1.

[0183] Large-particle PC1 may include a core and a carbon coating layer (see...) Figure 8 (COR, CTL). Small particles SP1 may include a core and a carbon coating layer (see COR, CTL). Figure 9 (COR', CTL' in the text).

[0184] According to one or more embodiments, refer to Figure 13 The first positive electrode active material layer AML12 may include a second positive electrode active material AM2 and a second aggregate GAG2, and may also include a binder BND and / or a conductive material CDM. Similarly, the second positive electrode active material layer AML14 may include the second positive electrode active material AM2 and the second aggregate GAG2, and may also include a binder BND and / or a conductive material CDM.

[0185] The second positive electrode active material AM2 may include a carbon coating layer. The carbon coating layer may be formed using graphene particles. For example, the carbon coating layer of the second positive electrode active material AM2 may be formed using particles comprising reduced graphene oxide. For example, in one or more embodiments, the carbon coating layer of the second positive electrode active material AM2 may be formed using reduced graphene oxide particles in a cabbage-like form.

[0186] The second aggregate GAG2 can be formed using graphene particles. For example, in one or more embodiments, the second aggregate GAG2 can be formed using reduced graphene oxide particles. The second aggregate GAG2 can be formed using reduced graphene oxide particles in a cabbage-like form.

[0187] Relative to 100 wt% of the total weight of the first positive electrode active material layer AML12, the total amount of the second positive electrode active material AM2 and the second aggregate GAG2 in the first positive electrode active material layer AML12 can be from about 90 wt% to about 99.5 wt%. For example, the total amount of the second positive electrode active material AM2 and the second aggregate GAG2 in the first positive electrode active material layer AML12 can be about 90 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 97.5 wt% or more, or about 98 wt% or more. For example, relative to 100 wt% of the total weight of the first positive electrode active material layer AML12, the total amount of the second positive electrode active material AM2 and the second aggregate GAG2 in the first positive electrode active material layer AML12 can be equal to or greater than about 90 wt% and about 99.5 wt% or less, about 99 wt% or less, or about 98.5 wt% or less.

[0188] The amount of the second positive electrode active material AM2 in the first positive electrode active material layer AML12 may be the remaining amount after deducting the amount of the second aggregate GAG2 from the total amount of the second positive electrode active material AM2 and the second aggregate GAG2 in the first positive electrode active material layer AML12.

[0189] Relative to 100 wt% of the total weight of the second positive electrode active material layer AML14, the total amount of the second positive electrode active material AM2 and the second aggregate GAG2 in the second positive electrode active material layer AML14 can be from about 90 wt% to about 99.5 wt%. For example, the total amount of the second positive electrode active material AM2 and the second aggregate GAG2 in the second positive electrode active material layer AML14 can be about 90 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 97.5 wt% or more, or about 98 wt% or more. For example, relative to 100 wt% of the total weight of the second positive electrode active material layer AML14, the total amount of the second positive electrode active material AM2 and the second aggregate GAG2 in the second positive electrode active material layer AML14 can be equal to or greater than about 90 wt% and about 99.5 wt% or less, about 99 wt% or less, or about 98.5 wt% or less.

[0190] The amount of the second positive electrode active material AM2 in the second positive electrode active material layer AML14 may be the remaining amount after deducting the amount of the second aggregate GAG2 from the total amount of the second positive electrode active material AM2 and the second aggregate GAG2 in the second positive electrode active material layer AML14.

[0191] The second positive electrode active material AM2 may include at least one of large PC2 particles or small SP2 particles. For example, in one or more embodiments, the second positive electrode active material AM2 may include large PC2 particles. For example, in one or more embodiments, the second positive electrode active material AM2 may include small SP2 particles. For example, in one or more embodiments, the second positive electrode active material AM2 may include both large PC2 particles and small SP2 particles.

[0192] Large-particle PC2 may include a core and a carbon coating layer (see...) Figure 8 (COR, CTL in the text). Small SP2 particles may include a core and a carbon coating layer (see...). Figure 9 (COR', CTL' in the text).

[0193] According to one or more embodiments, refer to Figure 14 The first positive electrode active material layer AML12 may include the first positive electrode active material AM1 and the first aggregate GAG1, and may also include the binder BND and / or the conductive material CDM. The second positive electrode active material layer AML14 may include the second positive electrode active material AM2 and the second aggregate GAG2, and may also include the binder BND and / or the conductive material CDM.

[0194] According to one or more embodiments, refer to Figure 15 The first positive electrode active material layer AML12 may include the second positive electrode active material AM2 and the second aggregate GAG2, and may also include the binder BND and / or the conductive material CDM. The second positive electrode active material layer AML14 may include the first positive electrode active material AM1 and the first aggregate GAG1, and may also include the binder BND and / or the conductive material CDM.

[0195] Reference Figure 16 ,according to Figure 11 Aggregates GAG1 and / or GAG2 in the positive electrode active material layer AML1 can both be primarily present within the positive electrode active material layer AML1. Aggregates GAG1 and / or GAG2 can both be uniformly (e.g., substantially uniformly) distributed within the positive electrode active material layer AML1. The distribution of aggregates GAG1 and / or GAG2 in the positive electrode active material layer AML1 can be more gradual along the third direction D3 of the positive electrode active material layer AML1.

[0196] For example, in one or more embodiments, the amount of carbon (C) in the first positive electrode active material layer AML12 AML12 The amount of carbon (C) in the second positive electrode active material layer AML14. AML14The amounts of carbon in the first positive electrode active material layer AML12 and the maximum amount of carbon in the second positive electrode active material layer AML14 can be substantially the same. For example, the difference (ΔC) between the minimum amount of carbon in the first positive electrode active material layer AML12 and the maximum amount of carbon in the second positive electrode active material layer AML14 cb It can be very small, and smaller than Figure 10 ΔC cb .

[0197] The positive electrode active material layer AML1 according to one or more embodiments of this disclosure may be substantially free of blocks.

[0198] Therefore, the positive electrode active material layer AML1 of this disclosure, which includes a first positive electrode active material layer AML12 and a second positive electrode active material layer AML14, can provide a positive electrode 10 with lower resistance.

[0199] Method for manufacturing a positive electrode Figure 17 This is a flowchart describing a method for manufacturing a positive electrode according to one or more embodiments of the present disclosure. Figures 18 to 21 It is a schematic diagram used to describe each step (e.g., action or task) of a manufacturing method according to one or more embodiments.

[0200] Reference Figure 17 A method for manufacturing a positive electrode according to one or more embodiments of the present disclosure may include the following steps: preparing a lithium nickel composite oxide (S100); forming a positive electrode active material and aggregate including a carbon coating layer by dry mixing of the lithium nickel composite oxide and reduced graphene oxide particles (S300); forming a slurry including the positive electrode active material, aggregate, conductive material, binder and solvent (S500); and coating the slurry onto a current collector, drying and rolling (S700).

[0201] The positive electrode active material AM may include lithium-nickel composite oxides and may include at least one of large or small particles (S100). For example, lithium-nickel composite oxides may be formed by a manufacturing method including the following steps: forming a nickel hydroxide (a1); mixing the nickel hydroxide and a lithium raw material (a2); and performing a heat treatment (a3). The manufacturing method according to one or more embodiments may be as follows.

[0202] Nickel hydroxides may include transition metals. Transition metals may include nickel (Ni), and may also include M of formula 1 as described above. 1 and M 2For example, in one or more embodiments, nickel hydroxides may include nickel (Ni) and cobalt (Co) as transition metals. For example, in one or more embodiments, nickel hydroxides may include aluminum (Al) and nickel (Ni) and cobalt (Co) as transition metals. In one or more embodiments, nickel hydroxides may include nickel (Ni), cobalt (Co), and manganese (Mn) as transition metals.

[0203] Nickel hydroxides can be obtained by coprecipitation (a1). For example, coprecipitation may involve dissolving a transition metal feedstock in a solvent such as distilled water and continuously introducing the transition metal salt solution along with a chelating agent and / or an alkaline aqueous solution into a reactor to induce precipitation. After collecting the precipitate as a slurry, the slurry solution can be filtered and dried to obtain nickel hydroxides.

[0204] The transition metal raw material may include salts of the aforementioned transition metals. The transition metal salts may be sulfates, nitrates, acetates, halides, and / or hydroxides, etc., and are not particularly limited, as long as they are soluble in a solvent. For example, in one or more embodiments, the transition metal raw material may include nickel salts, cobalt salts, and aluminum salts. In one or more embodiments, the transition metal raw material may include nickel salts, cobalt salts, and manganese salts. The transition metal raw materials can be mixed by adjusting the molar ratio to give the positive electrode active material high capacity characteristics.

[0205] Nickel hydroxides can be mixed with lithium feedstock in a certain proportion (a2). For example, in one or more embodiments, nickel hydroxides and lithium feedstock can be mixed in a molar ratio of about 1:1. There are no particular limitations on the lithium feedstock, as long as it is a material commonly used in the manufacture of positive electrode active materials. For example, lithium feedstock may include lithium salts such as lithium carbonate, lithium nitrate, lithium hydroxide, or lithium sulfate.

[0206] The mixture of nickel hydroxide and lithium feedstock can be heat-treated by placing it into a furnace (a3). The heat treatment temperature can be from about 700°C to about 1,000°C. The heat treatment can be performed in an oxidizing atmosphere such as air and / or oxygen. The heat treatment time can be from about 10 hours to about 30 hours. For example, in one or more embodiments, a preliminary calcination can be further performed at about 150°C to about 800°C prior to the heat treatment.

[0207] In one or more embodiments, a grinding process may be performed further after heat treatment. The grinding process allows for the production of lithium-nickel composite oxides with a desired or suitable average particle size.

[0208] Reference Figure 18The positive electrode active material AM and aggregate GAG ​​(S300) can be formed by mixing lithium nickel composite oxide (LNC) and graphene in a mixer MXR using a dry process. In one or more embodiments, reduced graphene oxide particles (RGO) can be used as the graphene. Through this step (e.g., an action or task), graphene can be coated onto the surface of the lithium nickel composite oxide (LNC). This allows a carbon coating layer to be formed on the surface of the lithium nickel composite oxide (LNC).

[0209] In one or more embodiments, lithium nickel composite oxide (LNC) can be formed by the manufacturing method described in S100 above.

[0210] As an example, graphene can be provided by reducing graphene oxide. When graphene oxide is reduced, reduced graphene oxide particles (RGOs) can be obtained. RGOs can comprise a single layer of graphene sheet or multiple graphene sheets. RGOs can also be aggregates of graphene.

[0211] The form of reduced graphene oxide (RGO) particles can vary depending on the reduction conditions. For example, RGO particles can be in at least one of the following forms: sheet form or cabbage leaf form.

[0212] Reduced graphene oxide (RGO) particles in sheet form can have relatively flat surfaces. For example, RGO particles in sheet form can be relatively flat in shape. For example, RGO particles in sheet form can be in the shape of an olive. For example, RGO particles in sheet form can have a structure in which one of its three dimensions is smaller than the other two dimensions. For example, RGO particles in sheet form can have a structure composed of multiple graphene sheets of a single layer or several layers.

[0213] For example, in one or more embodiments, the long axis of the reduced graphene oxide particles (RGO) in sheet form can be from about 1 μm to about 40 μm. For example, the long axis of the reduced graphene oxide particles (RGO) in sheet form can be about 1 μm or larger, about 2 μm or larger, about 3 μm or larger, about 4 μm or larger, or about 5 μm or larger. For example, the long axis of the reduced graphene oxide particles (RGO) in sheet form can be about 40 μm or smaller, about 35 μm or smaller, or about 30 μm or smaller.

[0214] For example, the long axis can be calculated by averaging the values ​​measured by randomly selecting about 30 reduced graphene oxide particles (RGOs) in an electron micrograph of the particles.

[0215] For example, the ratio of the minor axis to the major axis of reduced graphene oxide (RGO) particles in sheet form can be from about 0.1 to about 0.6. For example, the ratio of the minor axis to the major axis of reduced graphene oxide (RGO) particles in sheet form can be from about 0.2 to about 0.5 or from about 0.3 to about 0.4.

[0216] For example, in one or more embodiments, reduced graphene oxide particles (RGO) in sheet form can be formed by reducing graphene oxide under relatively mild conditions. For example, reduced graphene oxide particles (RGO) in sheet form can be formed by reducing graphene oxide under substantially uniform pH conditions in a pH range of about 7 to about 10 with the addition of an appropriate or suitable amount of reducing agent. For example, in one or more embodiments, reduced graphene oxide particles (RGO) in sheet form can be formed by reducing graphene oxide under substantially uniform high temperature conditions in a range of about 600°C to about 1000°C. For example, in one or more embodiments, reduced graphene oxide particles (RGO) in sheet form can be formed by reducing graphene oxide and then slowly drying it at a low temperature.

[0217] Reduced graphene oxide particles in the form of a cabbage leaf can be, for example, spherical or elliptical. The cabbage leaf form can be, for example, wrinkled or folded. Reduced graphene oxide particles in the form of a cabbage leaf can be, for example, in which multiple graphene sheets are stacked in layers or irregularly. The cabbage leaf form can be multilayered.

[0218] For example, in one or more embodiments, the long axis of the cabbage-shaped reduced graphene oxide particles (RGO) can be from about 1 μm to about 40 μm. For example, the long axis of the cabbage-shaped reduced graphene oxide particles (RGO) can be about 1 μm or larger, about 2 μm or larger, about 3 μm or larger, about 4 μm or larger, or about 5 μm or larger. For example, the long axis of the cabbage-shaped reduced graphene oxide particles (RGO) can be about 40 μm or smaller, about 35 μm or smaller, or about 30 μm or smaller.

[0219] For example, the long axis can be calculated by averaging the values ​​measured by randomly selecting about 30 reduced graphene oxide particles (RGOs) in an electron micrograph of the particles.

[0220] For example, the ratio of the minor axis to the major axis of reduced graphene oxide (RGO) particles in the form of cabbage leaves can be from about 0.7 to about 1.0. For example, the ratio of the minor axis to the major axis of reduced graphene oxide (RGO) particles in the form of cabbage leaves can be from about 0.8 to about 0.9.

[0221] For example, in one or more embodiments, reduced graphene oxide particles (RGOs) in a cabbage-like form can be formed by reducing graphene oxide under relatively harsh conditions. For example, the concentration of the reducing agent or the induction of incomplete reduction can be achieved by adjusting the concentration of the reducing agent or by using methods such as adding a small amount of reducing agent or slightly including an oxidizing agent. For example, in one or more embodiments, reduced graphene oxide particles (RGOs) in a cabbage-like form can be formed by rapid heat treatment at a high temperature in the range of about 600°C to about 1000°C or by controlling the heating rate.

[0222] For example, reduced graphene oxide particles (RGOs) in a cabbage-like form can be formed by atomizing a dispersion of graphene oxide using an ultrasonic atomizer to form aerosol droplets, which can then be passed through a tube furnace preheated to approximately 800°C by a carrier gas. Rapid evaporation can cause the aerosol droplets to contract, and the graphene oxide can be first concentrated and then compressed, allowing the formation of reduced graphene oxide particles (RGOs) in a cabbage-like form.

[0223] Lithium nickel composite oxide (LNC) and reduced graphene oxide (RGO) particles can be mixed in a weight ratio of about 99:1 to about 99.99:0.01. For example, in one or more embodiments, the lithium nickel composite oxide (LNC) and reduced graphene oxide (RGO) particles can be mixed in a weight ratio of about 99:1 to about 99.9:0.1, about 99.5:0.5 to about 99.9:0.1, or about 99.6:0.4 to about 99.8:0.2. When the weight ratio of lithium nickel composite oxide (LNC) to reduced graphene oxide (RGO) particles meets the above ranges, the positive electrode active material AM can have excellent or suitable conductivity.

[0224] Dry coating can be a coating in which solvent is omitted (e.g., not provided) during the coating process. Dry coating simplifies the coating process and makes coating easier to perform. Additionally, if dry coating is used (e.g., when using dry coating), the thickness of the carbon coating layers CTL, CTL' can be easily adjusted.

[0225] For example, in one or more embodiments, dry coating can be performed at a rotational speed of about 1,000 rpm to about 5,000 rpm. For example, dry coating can be performed at a rotational speed of about 2,000 rpm to about 4,000 rpm.

[0226] For example, in one or more embodiments, dry coating may be performed for about 2 to about 30 minutes. For example, dry coating may be performed for about 5 to about 20 minutes.

[0227] When the rotation speed and coating time in dry coating meet the above-mentioned ranges, a positive electrode active material AM comprising the aforementioned carbon coating layer and aggregate GAG ​​can be formed. A carbon coating layer can be formed on at least a portion of the surface of a lithium nickel composite oxide (LNC). Aggregates GAG can be formed when reduced graphene oxide (RGO) particles break down or aggregate together.

[0228] The carbon coating can be formed from reduced graphene oxide (RGO) particles. For example, when using RGO particles in sheet form, a larger amount of carbon coating layers (CTLs, CTL') can be formed compared to when using RGO particles in cabbage-like form. For example, RGO particles in sheet form can have a larger surface area capable of reacting with lithium nickel composite oxides (LNCs) than RGO particles in cabbage-like form. RGO particles in sheet form with a thin and flat morphology can have a larger surface area capable of reacting with lithium nickel composite oxides (LNCs) than RGO particles in cabbage-like form with a multilayered and circular morphology.

[0229] For example, when equal amounts of reduced graphene oxide particles (RGO) are added and mixed, RGO particles in flake form can form more carbon coatings than aggregates (GAG). Similarly, when equal amounts of reduced graphene oxide particles (RGO) are added and mixed, RGO particles in cabbage-shaped form can form more aggregates (GAG) than carbon coatings (CTL, CTL').

[0230] Because a portion of the reduced graphene oxide (RGO) particles forms aggregates called GAGs, it can contain a small amount of aggregates called GAGs.

[0231] For example, in one or more embodiments, reduced graphene oxide particles (RGO) in sheet form can form fewer aggregates (GAG) compared to reduced graphene oxide particles (RGO) in cabbage-like form.

[0232] Because reduced graphene oxide (RGO) particles break down or aggregate to form aggregates called gas aggregates (GAGs), the particle size of these aggregates can vary. For example, the particle size of aggregated GAGs can be about 40 μm or smaller. Alternatively, the particle size can be about 1 μm to about 40 μm or about 1 μm to about 30 μm. For example, the particle size can be a value measured by selecting and measuring about 30 aggregated GAGs in an electron microscope image of the aggregates.

[0233] For example, in one or more embodiments, as described above, the aggregated GAG can be formed from reduced graphene oxide particles (RGO) and therefore may include some oxidized portions. The reduced graphene oxide constituting the aggregated GAG may include a small amount of oxygen. Defects may be present in the reduced graphene oxide constituting the aggregated GAG.

[0234] The graphene constituting the aggregate GAG ​​can be in sheet form. For example, in one or more embodiments, the lateral dimensions of the graphene constituting the aggregate GAG ​​can be from about 0.1 μm to about 1000 μm. For example, the lateral dimensions of the graphene constituting the aggregate GAG ​​can be from about 0.1 μm to about 500 μm, from about 0.1 μm to about 200 μm, from about 0.1 μm to about 100 μm, from about 0.1 μm to about 50 μm, from about 0.1 μm to about 10 μm, from about 0.1 μm to about 5 μm, or from about 0.1 μm to about 3 μm.

[0235] For example, the thickness of graphene can be less than or equal to about 1 nm. For example, the thickness of graphene can be from about 0.1 nm to about 0.5 nm. The thickness of graphene can refer to the distance of the graphene sheet in the thickness direction.

[0236] Reference Figure 19 The positive electrode active material AM, aggregate GAG, conductive material CDM, and binder BND can be dissolved or dispersed in solvent SVT to form a slurry (S500). The conductive material CDM and binder BND can be used in conjunction with the above-mentioned... Figures 1 to 7 The conductive material CDM and the adhesive BND are described as the same.

[0237] The solvent can be a solvent commonly used in the art, and may include at least one of, for example, dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone, water, and / or combinations thereof.

[0238] The weight ratio of the conductive material CDM to the positive electrode active material AM can be from about 0.7 / 99.5 to about 0.7 / 97. For example, in one or more embodiments, the weight ratio of the conductive material CDM to the positive electrode active material AM can be about 0.7 / 99.5 or greater, about 0.7 / 99 or greater, about 0.7 / 98.5 or greater, or about 0.7 / 98 or greater. For example, the weight ratio of the conductive material CDM to the positive electrode active material AM can be about 0.7 / 97 or less, or about 0.7 / 97.5 or less.

[0239] Because the positive electrode 10 includes the positive electrode active material AM, the amount of conductive material CDM in the electrode plate can be reduced, thereby ensuring additional space within the electrode plate with the same mixture density. Therefore, as described later, the cracking of the positive electrode active material AM during electrode plate rolling can be prevented or reduced, and a rechargeable lithium battery with excellent or suitable lifespan can be provided.

[0240] The positive electrode can be formed by coating the above slurry onto the current collector, then drying and rolling it (S700).

[0241] For example, refer to Figure 20 The slurry can be applied to the current collector to have a mixture density of about 3 g / cc to about 4 g / cc and about 20 g / cm³. 2 Approximately 30g / cm 2 The load level (S700a). Therefore, it is possible to form according to Figure 6 The positive electrode 10.

[0242] For example, due to the evaporation of the solvent SVT during the dry process, some of the aggregates GAG can move, and a portion of the moved aggregates GAG can be distributed in the upper portion of the positive electrode active material layer AML1. For example, due to the evaporation of the solvent SVT during the dry process, a portion of the conductive material and / or binder can move and is mainly distributed in the upper portion of the positive electrode active material layer AML1.

[0243] Rolling can be performed using a rolling mill. Rolling can be performed to achieve a desired or suitable thickness of the positive electrode active material layer AML1. For example, in one or more embodiments, rolling can be performed to achieve a thickness of about 20 μm to about 100 μm for the positive electrode active material layer AML1. For example, rolling can be performed to achieve a thickness of about 20 μm or greater, about 30 μm or greater, about 40 μm or greater, or about 50 μm or greater for the positive electrode active material layer AML1. For example, rolling can be performed to achieve a thickness of about 100 μm or less, about 90 μm or less, about 80 μm or less, or about 70 μm or less for the positive electrode active material layer AML1.

[0244] Because the positive electrode active material layer AML1 includes a small amount of aggregates GAG, the positive electrode active material layer AML1 may not include the aforementioned blocks, or even if it does, it may include relatively small blocks.

[0245] According to one or more embodiments, refer to Figure 21 The first slurry can be coated and dried on the current collector to have a density of approximately 10 g / cm³. 2 Approximately 15 g / cm 2The loading level can then be adjusted, and a second slurry can be coated and dried to achieve a loading level of approximately 10 g / cm³. 2 Approximately 15 g / cm 2 The loading level (S700b). The mixture density can be loaded from about 3 g / cc to about 4 g / cc. Thus, it is possible to form according to... Figure 11 The positive electrode 10 includes a first positive electrode active material layer AML12 and a second positive electrode active material layer AML14.

[0246] The first slurry may include a first positive electrode active material and a first aggregate, the first positive electrode active material including a first carbon coating layer. The first carbon coating layer and the first aggregate may be formed from first reduced graphene oxide particles. The first reduced graphene oxide particles may be in the form of flakes or cabbage leaves.

[0247] The second slurry may include a second positive electrode active material and a second aggregate, the second positive electrode active material including a second carbon coating layer. The second carbon coating layer and the second aggregate may be formed from second reduced graphene oxide particles. The second reduced graphene oxide particles may be in the form of flakes or cabbage leaves.

[0248] By forming with Figure 20 The positive electrode active material layer AML1 consists of two layers of the same thickness, even if the solvent SVT evaporates during the dry process, the distribution is based on... Figure 21 The amount of aggregates GAG1 or GAG2 in the upper portion of the positive electrode active material layer AML1 (i.e., the second positive electrode active material layer AML14) can also be less than that distributed according to... Figure 20 The amount of GAG aggregates in the upper portion of the positive electrode active material layer AML1. The aggregates GAG1 and GAG2 can be relatively uniformly (e.g., substantially uniformly) distributed within the positive electrode active material layer AML1. The positive electrode active material layer AML1 can be substantially free of clumps.

[0249] The present disclosure will be described in more detail below with reference to examples. However, these examples are intended to illustrate the present disclosure, and the scope of the present disclosure is not limited to these examples.

[0250] Preparation Example 1: Preparation of AM1, the active material of the first positive electrode, and GAG1 aggregate Preparation of lithium-nickel composite oxides (LiNi) comprising large particles with an average particle size of 12 μm and small particles with an average particle size of 4 μm. 0.91 Co 0.075 Al 0.015 O2).

[0251] Graphene oxide was reduced to prepare reduced graphene oxide particles (RGO) primarily in sheet form (transverse graphene size = 0.1 μm to 1000 μm). Scanning electron microscopy (SEM) images of the reduced graphene oxide particles (RGO) in sheet form are shown in... Figure 22 In the middle. For example Figure 22 As shown, reduced graphene oxide particles (RGOs) in sheet form are blocks of graphene primarily possessing a thin and flat morphology. In scanning electron microscopy (SEM) images of RGOs in sheet form, 30 RGOs were randomly selected, and their long and short axes were measured. The results showed that the average long axis ranged from 5 μm to 30 μm, and the average ratio of the short axis to the long axis was 0.33.

[0252] Lithium-nickel composite oxide and reduced graphene oxide particles (RGO) in sheet form were added to a mixer (NOBILTA, Hosokawa Micron Co., Ltd.) at a weight ratio of 99.7:0.3 and mixed at 3000 rpm for 10 minutes to form a first positive electrode active material AM1 with carbon coating layers CTL and CTL' formed thereon, and aggregates GAG1. Mixing was performed under these conditions to form carbon coating layers CTL and CTL' on at least a portion of the surface of the lithium-nickel composite oxide. Furthermore, the reduced graphene oxide particles (RGO) broke apart or aggregated (e.g., agglomerated) to form aggregates GAG1.

[0253] Figure 23 The image shows scanning electron microscope (SEM) images of the first positive electrode active material AM1 and the aggregate GAG1. White circles indicate relatively large aggregates of GAG1. As a result of randomly selecting approximately 30 aggregates of GAG1 in the SEM image and measuring their particle size, the particle size of the aggregates of GAG1 ranges from 1 μm to 30 μm. The first positive electrode active material AM1 comprises carbon coating layers CTL, CTL', and has a thickness of 5 nm.

[0254] Preparation Example 2: Preparation of the second positive electrode active material AM2 and aggregate GAG2 Preparation of lithium-nickel composite oxides (LiNi) comprising large particles with an average particle size of 12 μm and small particles with an average particle size of 4 μm. 0.91 Co 0.075 Al 0.015 O2).

[0255] Graphene oxide was reduced to prepare reduced graphene oxide particles (RGOs) predominantly in a cabbage-like form (i.e., in cabbage-like shape), with lateral dimensions of graphene ranging from 0.1 μm to 1000 μm. Scanning electron microscopy (SEM) images of the predominantly cabbage-like reduced graphene oxide particles (RGOs) are shown in... Figure 24 The reduced graphene oxide particles (RGOs) in cabbage-like form are multilayered blocks of graphene with a predominantly circular morphology. Scanning electron microscopy (SEM) images of the cabbage-like RGO particles show approximately 30 randomly selected particles, with their major and minor axes measured. The results indicate that, on average, the major axis ranges from 5 μm to 30 μm, and the ratio of the minor axis to the major axis is 0.83.

[0256] Lithium-nickel composite oxide and reduced graphene oxide particles (RGO) in cabbage-like form were added to a mixer (NOBILTA, Hosokawa Micron Co., Ltd.) at a weight ratio of 99.7:0.3 and mixed at 3000 rpm for 10 minutes to form a second positive electrode active material AM2 with carbon coating layers CTL and CTL' formed thereon, and aggregates GAG2. Mixing was performed under these conditions to form carbon coating layers CTL and CTL' on at least a portion of the surface of the lithium-nickel composite oxide. Furthermore, the reduced graphene oxide particles (RGO) broke apart or aggregated (e.g., agglomerated) to form aggregates GAG2.

[0257] Scanning electron microscopy (SEM) images of the second positive electrode active material AM2 and aggregate GAG2 are shown. Figure 25 In the image, white circles represent relatively large aggregates of GAG2. As a result of randomly selecting approximately 30 aggregates of GAG2 in a scanning electron microscope (SEM) image and measuring their particle size, the aggregates of GAG2 ranged in size from 1 μm to 30 μm. The second positive electrode active material AM2 comprises carbon coating layers CTL and CTL' with a thickness of 5 nm.

[0258] Example 1 The first slurry was prepared by mixing 98.4 wt% of the first positive electrode active material AM1 and aggregate GAG1, 0.7 wt% of the conductive material (carbon nanotubes) and 0.9 wt% of the binder (polyvinylidene fluoride) in N-methylpyrrolidone solvent.

[0259] The first slurry was coated onto an aluminum current collector, dried, and rolled to fabricate the positive electrode. The first slurry was coated onto the current collector with a mixture density of 3.9 g / cc and a density of 20 g / cm³. 2 The load level was determined. Rolling was performed using a roller press, resulting in a total thickness of 63.3 μm for the current collector and the positive electrode active material layer AML1.

[0260] Example 2 The second slurry was prepared by mixing 98.4 wt% of the second positive electrode active material AM2 and aggregate GAG2, 0.7 wt% of the conductive material (carbon nanotubes) and 0.9 wt% of the binder (polyvinylidene fluoride) in N-methylpyrrolidone solvent.

[0261] The positive electrode is prepared in essentially the same manner as in Example 1, except that a second slurry is coated onto the aluminum current collector.

[0262] Example 3 The first slurry was prepared by mixing 98.4 wt% of the first positive electrode active material AM1 and aggregate GAG1, 0.7 wt% of the conductive material (carbon nanotubes) and 0.9 wt% of the binder (polyvinylidene fluoride) in N-methylpyrrolidone solvent.

[0263] The first slurry was coated onto the aluminum current collector to achieve a concentration of 10 g / cm³. 2 The load level is adjusted and the first drying is performed, then the first slurry is coated again to achieve a load of 10 g / cm³. 2 The load level was adjusted and the mixture was dried a second time, followed by rolling to fabricate the positive electrode. Rolling was performed using a rolling mill, resulting in a total thickness of 63.3 μm for both the current collector and the positive electrode active material layer AML1. The mixture density was 3.9 g / cc.

[0264] Example 4 The first slurry was prepared by mixing 98.4 wt% of the first positive electrode active material AM1 and aggregate GAG1, 0.7 wt% of the conductive material (carbon nanotubes) and 0.9 wt% of the binder (polyvinylidene fluoride) in N-methylpyrrolidone solvent.

[0265] The second slurry was prepared by mixing 98.4 wt% of the second positive electrode active material AM2 and aggregate GAG2, 0.7 wt% of the conductive material (carbon nanotubes) and 0.9 wt% of the binder (polyvinylidene fluoride) in N-methylpyrrolidone solvent.

[0266] In addition to coating the first slurry onto the aluminum current collector to achieve a concentration of 10 g / cm³, 2 The load level is determined and the first drying is performed, then a second slurry is coated on top to achieve a load of 10 g / cm³. 2 The positive electrode is prepared in essentially the same manner as in Example 3, except for the load level and the second drying.

[0267] Example 5 The first slurry was prepared by mixing 98.4 wt% of the first positive electrode active material AM1 and aggregate GAG1, 0.7 wt% of the conductive material (carbon nanotubes) and 0.9 wt% of the binder (polyvinylidene fluoride) in N-methylpyrrolidone solvent.

[0268] The second slurry was prepared by mixing 98.4 wt% of the second positive electrode active material AM2 and aggregate GAG2, 0.7 wt% of the conductive material (carbon nanotubes) and 0.9 wt% of the binder (polyvinylidene fluoride) in N-methylpyrrolidone solvent.

[0269] In addition to coating the aluminum current collector with a second slurry to achieve a density of 10 g / cm³, 2 The load level and the first drying and then the first slurry is coated on it to have a load level of 10 g / cm 2 The positive electrode was prepared in essentially the same manner as in Example 3, except for the loading level and the second drying. Example 6 The second slurry was prepared by mixing 98.4 wt% of the second positive electrode active material AM2 and aggregate GAG2, 0.7 wt% of the conductive material (carbon nanotubes) and 0.9 wt% of the binder (polyvinylidene fluoride) in N-methylpyrrolidone solvent.

[0270] In addition to coating the aluminum current collector with a second slurry to achieve a density of 10 g / cm³, 2 The load level is adjusted and the first drying is performed, followed by a second coating of slurry with a density of 10 g / cm³. 2 The positive electrode is prepared in essentially the same manner as in Example 3, except for the load level and the second drying.

[0271] Comparison Example 1 A slurry was prepared by mixing 98.4 wt% of the positive electrode active material and reduced graphene oxide particles (RGO) in sheet form (weight ratio of positive electrode active material to reduced graphene oxide particles in sheet form = 99.7:0.3), 0.7 wt% of conductive material (carbon nanotubes), and 0.9 wt% of binder (polyvinylidene fluoride) in an N-methylpyrrolidone solvent. As the positive electrode active material, a lithium-nickel composite oxide (LiNi) containing large particles with an average particle size of 12 μm and small particles with an average particle size of 4 μm was prepared. 0.91 Co 0.075 Al 0.015 O2).

[0272] The positive electrode is prepared in essentially the same manner as in Example 1, except that the above slurry is coated onto the aluminum current collector.

[0273] Comparison Example 2 A slurry was prepared by mixing 98.4 wt% of the positive electrode active material and cabbage-shaped reduced graphene oxide particles (RGO) in a cabbage-shaped form (weight ratio of positive electrode active material to cabbage-shaped reduced graphene oxide particles = 99.7:0.3), 0.7 wt% of conductive material (carbon nanotubes), and 0.9 wt% of binder (polyvinylidene fluoride) in an N-methylpyrrolidone solvent. As the positive electrode active material, a lithium-nickel composite oxide (LiNi) containing large particles with an average particle size of 12 μm and small particles with an average particle size of 4 μm was prepared. 0.91 Co 0.075 Al 0.015 O2).

[0274] The positive electrode is prepared in essentially the same manner as in Example 1, except that the above slurry is coated onto the aluminum current collector.

[0275] Preparation of rechargeable lithium batteries One of the above positive electrodes and lithium metal as the counter electrode are used, with a polyethylene-polypropylene multilayer separator placed between them. As the electrolyte, a solution obtained by adding 1.0 M of lithium LiPF6 salt to a solvent obtained by mixing ethylene carbonate and diethyl carbonate in a 50:50 volume ratio is used. The electrolyte is injected to prepare a coin half-cell.

[0276] Table 1

[0277] Evaluation Example 1: Cross-sectional Analysis of the Positive Electrode Figures 26 to 28 These are scanning electron microscope images of cross-sections of the positive electrode according to Example 1, Example 3, and Comparative Example 1, respectively. Figure 28 The white circles in the image show the blocks formed by the agglomeration of reduced graphene oxide particles.

[0278] Reference Figures 26 to 28 It can be confirmed that, unlike the positive electrode active material in the positive electrode according to Comparative Example 1, the positive electrode active material in the positive electrodes according to Examples 1 and 3 includes a carbon coating layer. Furthermore, it is confirmed that, unlike the positive electrode active material in the positive electrode according to Comparative Example 1, the positive electrode active material in the positive electrodes according to Examples 1 and 3 did not crack even after the electrode plate was rolled.

[0279] Furthermore, a block was observed in the positive electrode according to Comparative Example 1, and the size of the block was relatively large. Conversely, the size of the block observed in the positive electrode according to Example 1 was much smaller than that in the positive electrode of Comparative Example 1. No block was observed in the positive electrode according to Example 3.

[0280] Furthermore, compared to the positive electrode according to Example 1, the positive electrode according to Example 3 was found to have fewer aggregates distributed in the upper portion of the positive electrode active material layer AML1. It was confirmed that, compared to the positive electrode according to Example 1, the positive electrode according to Example 3 showed a relatively uniform distribution of aggregates within the positive electrode active material layer AML1.

[0281] Evaluation Example 2: Performance Evaluation of the Positive Electrode The mixture resistance was evaluated based on the positive electrodes of Examples 1 to 6 and Comparative Examples 1 and 2.

[0282] The mixture resistance of each of the positive electrodes according to the example and comparative examples was measured at 25°C using an electrode resistance measurement system (RM2610 manufactured by Hiokki). In the electrode resistance measurement system, a probe was placed on the positive electrode with the active material layer of the positive electrode facing the probe. A constant current was passed through the surface of the active material of the positive electrode, and the volume resistivity of the active material layer and the interfacial resistance between the active material layer and the current collector were measured by the surface potential distribution. The volume resistivity of the active material layer was considered as the mixture resistance of the active material layer.

[0283] The results are shown in Table 2.

[0284] Table 2

[0285] Referring to Table 2, the positive electrodes according to Examples 1 to 6 all have low mixture resistance compared to the positive electrodes according to Comparative Examples 1 and 2.

[0286] For example, the positive electrodes according to Example 1 and Example 2 both have a lower mixture resistance than the positive electrodes according to Comparative Example 1 and Comparative Example 2. It is confirmed that the positive electrodes according to Example 1 and Example 2, which include a positive electrode active material containing a carbon coating layer and aggregates and reduce bulk, lower the resistance of the positive electrode and improve its conductivity.

[0287] Furthermore, compared to the positive electrodes according to Examples 1 and 2, the positive electrodes according to Examples 3 to 6 all exhibit lower mixture resistance. It is confirmed that the positive electrodes according to Examples 3 to 6, comprising a positive electrode active material with a carbon coating layer and aggregates, do not consist of blocks and allow the aggregates to be uniformly (e.g., substantially uniformly) distributed within the positive electrode active material layer, which further reduces the resistance of the positive electrode and increases its conductivity. In the context of this disclosure, "uniformly distributed" means that the aggregates (formed from reduced graphene oxide particles) are uniformly and consistently dispersed throughout the positive electrode active material layer. This means that the aggregates diffuse in a manner that avoids aggregation or concentration in specific areas, ensuring that the electrical properties are consistent throughout the electrode. This uniform distribution helps maintain low resistance and high conductivity throughout the electrode, resulting in better performance and efficiency of the rechargeable lithium battery.

[0288] The examples demonstrate how several methods and processes achieve beneficial properties such as low resistance and improved conductivity in the positive electrode. First, the positive electrode active material in Examples 1 through 6 includes a carbon coating layer, which enhances conductivity by providing conductive pathways for electrons, thereby reducing the overall resistance. Additionally, the incorporation of aggregates formed from reduced graphene oxide particles helps improve the structural integrity and conductivity of the electrode material. The uniform distribution of these aggregates, particularly in the bilayer structure, ensures consistent electrical properties throughout the electrode.

[0289] Furthermore, compared to the comparative examples, Examples 1 and 2 show a reduction in block formation, which can lead to lower resistance and increased conductivity. By reducing or minimizing block formation, the electrode maintains lower resistance and better performance. The enhanced mixing and coating processes in Examples 3 through 6 ensure uniform distribution of aggregates, prevent high resistance in localized areas, and promote efficient electron flow through the electrode.

[0290] Cross-sectional analysis using scanning electron microscopy images confirmed the presence of the carbon coating and the uniform distribution of the aggregates. The electrodes in Examples 1 and 3 showed no cracking after rolling, unlike the comparative example, indicating better mechanical stability and lower resistance. Performance evaluation using the electrode resistance measurement system showed that the mixture resistance of the positive electrodes in Examples 1 through 6 was lower than that in the comparative example, validating the improved conductivity and lower resistance achieved by the method used in the examples.

[0291] The positive electrode according to one or more embodiments of this disclosure can have low resistance. Because lower resistance translates to better conductivity and improved energy transfer during battery operation, this characteristic is used to enhance the overall performance and efficiency of rechargeable lithium batteries.

[0292] The method for manufacturing a positive electrode according to one or more embodiments of this disclosure can produce a positive electrode having the aforementioned beneficial characteristics. By enhancing the distribution of aggregates and ensuring the presence of a carbon coating layer, this method contributes to the development of high-performance rechargeable lithium batteries with excellent electrical properties.

[0293] In this disclosure, when expressions such as “at least one of…”, “one of…”, and “selected from…” precede / follow a column of elements, they modify the entire column of elements but not the individual elements of that column. For example, “at least one of a, b, or c”, “at least one of a, b, and c”, “at least one of a to c”, etc., can mean only a, only b, only c, both a and b (e.g., simultaneously), both a and c (e.g., simultaneously), both b and c (e.g., simultaneously), all of a, b, and c, or variations thereof. The “ / ” used herein may be interpreted as “and” or “or” depending on the context.

[0294] In the context of this disclosure, unless otherwise defined, the term “use” and its variations may be considered synonymous with the term “utilize” and its variations, respectively.

[0295] In this disclosure, the term "group" as used herein refers to a group in the periodic table of elements according to the group 1 to group 18 system of the International Union of Pure and Applied Chemistry ("IUPAC").

[0296] As used herein, the terms “basically,” “about,” and similar terms are used as approximations rather than terms of degree and are intended to explain the inherent biases in measured or calculated values ​​that would be recognized by one of ordinary skill in the art. As used herein, “about” or “approx.” also includes the stated value and means within an acceptable range of deviation for a particular value, as determined by one of ordinary skill in the art, taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” may mean within one or more standard deviations, or within ±30%, ±20%, ±10%, or ±5% of the stated value.

[0297] Any numerical range listed herein is intended to include all subranges containing the same numerical precision within the listed range. For example, the range “1.0 to 10.0” is intended to include all subranges between the listed minimum value 1.0 and the listed maximum value 10.0 (and including both the listed minimum value 1.0 and the listed maximum value 10.0), i.e., having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as 2.4 to 7.6. Any maximum numerical limit listed herein is intended to include all lower numerical limits contained therein, and any minimum numerical limit listed in this specification is intended to include all higher numerical limits contained therein. Therefore, the applicant reserves the right to amend this specification (including the claims) to expressly list any subranges contained within the ranges expressly listed herein.

[0298] Battery management devices, battery management systems (BMS) devices, and / or any other related devices or components according to embodiments of the invention described herein can be implemented using any suitable hardware, firmware (e.g., application-specific integrated circuits), software, or a combination of software, firmware, and hardware. For example, various components of the device can be formed on an integrated circuit (IC) chip or a discrete IC chip. Furthermore, various components of the device can be implemented on a flexible printed circuit film, a tape-on-a-carrier package (TCP), a printed circuit board (PCB), or formed on a substrate. Additionally, various components of the device can be processes or threads running on one or more processors in one or more computing devices, executing computer program instructions, and interacting with other system components to perform the various functions described herein. The computer program instructions are stored in memory, which can be implemented in a computing device using standard memory devices, such as random access memory (RAM). The computer program instructions can also be stored in other non-transitory computer-readable media, such as CD-ROMs, flash drives, etc. Furthermore, those skilled in the art will recognize that, without departing from the scope of this disclosure, the functions of various computing devices can be combined or integrated into a single computing device, or the functions of a particular computing device can be distributed across one or more other computing devices.

[0299] Those skilled in the art will understand that, in view of the overall content of this disclosure, each suitable feature of the various embodiments of this disclosure may be combined in part or in whole, or combined with one another, and may be technically interlocked and operated in a variety of suitable ways, and unless otherwise stated or implied, each embodiment may be implemented independently of one another or in any suitable combination with one another.

[0300] While this disclosure has been described with reference to exemplary embodiments, it should be understood that these embodiments are provided for illustrative purposes only and do not limit the scope of this disclosure. Various modifications and equivalent arrangements may be made without departing from the spirit and scope of the appended claims and their equivalents. Therefore, the described embodiments should be considered as examples and not as limitations on this disclosure.

Claims

1. A method comprising the following steps: Forming aggregates and positive electrode active materials including a carbon coating layer; A slurry comprising the positive electrode active material and the aggregate is formed; as well as The slurry is coated onto the current collector and dried to form a positive electrode active material layer. The carbon coating and the aggregate are formed from graphene particles. The graphene particles are in at least one of the following forms: sheet form and cabbage-like form. The method described herein is a method for manufacturing a positive electrode.

2. The method according to claim 1, wherein, The graphene particles include at least one of graphene oxide, reduced graphene oxide, and combinations thereof.

3. The method according to claim 1, wherein, The steps of forming the aggregate and the positive electrode active material including the carbon coating layer include: The lithium-nickel composite oxide and the graphene particles are mixed using a dry process. The mixing is performed using a mixer at a speed of 1000 rpm to 5000 rpm for 2 to 30 minutes.

4. The method according to claim 3, wherein, The weight ratio of the lithium-nickel composite oxide to the graphene particles is 99:1 to 99.99:0.

01.

5. The method according to claim 3, wherein, The carbon coating layer is formed on at least a portion of the surface of the lithium-nickel composite oxide.

6. The method according to claim 1, wherein, The graphene particles in the form of the sheet have a short axis to long axis ratio of 0.1 to 0.

6.

7. The method according to claim 1, wherein, The graphene particles in the form of the cabbage have a short axis to long axis ratio of 0.7 to 1.

0.

8. The method according to claim 1, wherein, The aggregates have a particle size of 1 μm to 40 μm.

9. The method according to claim 1, wherein, The steps for forming the positive electrode active material layer include: The slurry is coated onto the current collector to have a mixture density of 3 g / cc to 4 g / cc and 20 g / cm³. 2 Up to 30g / cm 2 The load level.

10. A method comprising the following steps: A first slurry is formed comprising a first positive electrode active material and a first aggregate, wherein the first positive electrode active material includes a first carbon coating layer; A second slurry is formed comprising a second positive electrode active material and a second aggregate, wherein the second positive electrode active material includes a second carbon coating layer; The first slurry is coated onto the current collector and dried to form a first positive electrode active material layer; as well as The second slurry is coated onto the first positive electrode active material layer and dried to form the second positive electrode active material layer. The first carbon coating layer and the first aggregate are formed from first graphene particles. Wherein, the second carbon coating layer and the second aggregate are formed from second graphene particles, and The method described herein is a method for manufacturing a positive electrode.

11. The method according to claim 10, wherein, Each of the first graphene particle and the second graphene particle includes at least one of graphene oxide, reduced graphene oxide, and combinations thereof.

12. The method according to claim 10, wherein, The first graphene particle is in the form of a thin sheet, and The second graphene particle is in the form of a sheet.

13. The method according to claim 10, wherein, The first graphene particle is in the form of a thin sheet, and The second graphene particle is in the form of a cabbage.

14. The method of claim 10, wherein, The first graphene particle is in the shape of a cabbage leaf, and The second graphene particle is in the form of a sheet or a cabbage.

15. The method according to claim 10, wherein, The step of forming the first positive electrode active material layer includes: coating the first slurry onto the current collector to have a density of 10 g / cm³. 2 Up to 15g / cm 2 The load level, and The step of forming the second positive electrode active material layer includes: coating the second slurry onto the first positive electrode active material layer to achieve a concentration of 10 g / cm³. 2 Up to 15g / cm 2 The load level.

16. A positive electrode, the positive electrode comprising: current collector; as well as The positive electrode active material layer is on the current collector. The positive electrode active material layer comprises: a positive electrode active material, including a lithium-nickel composite oxide and a carbon coating layer; an aggregate; a conductive material, including a carbon material with a one-dimensional nanostructure; and a binder. Both the carbon coating and the aggregate are formed from graphene particles.

17. The positive electrode according to claim 16, wherein, The graphene particles include at least one of graphene oxide, reduced graphene oxide, and combinations thereof.

18. The positive electrode according to claim 16, wherein, The graphene particles are in at least one of the following forms: sheet form and cabbage form.

19. The positive electrode according to claim 16, wherein, The positive electrode active material layer includes: The first positive electrode active material layer and the second positive electrode active material layer are stacked sequentially. The first positive electrode active material layer includes: a first carbon coating layer on the surface of the lithium-nickel composite oxide; and a first aggregate. The first carbon coating and the first aggregate are formed from first graphene particles, and The second positive electrode active material layer comprises: a second carbon coating layer on the surface of the lithium-nickel composite oxide; and a second aggregate. The second carbon coating and the second aggregate are formed from second graphene particles, and The first graphene particle and the second graphene particle are each independently in at least one of the following forms: sheet form and cabbage form.

20. The positive electrode according to claim 16, wherein, The aggregates are uniformly distributed within the positive electrode active material layer.

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