Positive electrode active material for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

The invention relates to a positive electrode active material for a rechargeable lithium battery and a rechargeable lithium battery including the same. The positive electrode active material includes first particles including a first lithium composite oxide. The first particle includes a first primary particle extending in a radial direction from a center of the first particle toward a surface of the first particle and a second primary particle on the surface. The first primary particles have an aspect ratio of about 2 to about 15. The second primary particles have an aspect ratio of about 0.7 to about 3.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority and benefit of Korean Patent Application No. 10 - 2024 - 0006931, filed with the Korean Intellectual Property Office on January 16, 2024, the entire content of which is incorporated herein by reference. Technical field

[0003] Embodiments of the present disclosure relate to a positive electrode active material for a rechargeable lithium battery, a method for manufacturing the same, and a rechargeable lithium battery including the same. For example, the embodiments relate to a positive electrode active material including a layered lithium compound, a method for manufacturing the same, and a rechargeable lithium battery including the same. Background art

[0004] Recently, with the rapid popularization of electronic devices using batteries (such as mobile phones, laptop computers, and electric vehicles), the demand for rechargeable lithium batteries with high energy density and high capacity has increased rapidly. Therefore, in - depth research has been conducted to improve the performance of rechargeable lithium batteries.

[0005] A rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode and the negative electrode include active materials in which lithium ions can be intercalated and de - intercalated. When lithium ions are intercalated and de - intercalated, electrical energy generated by oxidation and reduction reactions is produced. Summary of the invention

[0006] Embodiments of the present disclosure provide a positive electrode active material having a high energy density and excellent high - temperature life.

[0007] Embodiments of the present disclosure provide a rechargeable lithium battery having a high energy density and excellent high - temperature life.

[0008] According to an embodiment of the present disclosure, the positive electrode active material may include first particles, and the first particles may include a first lithium composite oxide. The first lithium composite oxide may be represented by Chemical Formula 1.

[0009] Chemical Formula 1

[0010] Li a1 Ni x1 Ma 1-x1 O b1

[0011] In Chemical Formula 1, a1 can be from about 0.5 to about 1.5, x1 can be from about 0.6 to about 0.99, b1 can be from about 1.8 to about 2.2, 1 - x1 can be from about 0.01 to about 0.4, and Ma can represent at least one element selected from Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn. The first particle can include: a first primary particle extending in a radial direction from the center of the first particle toward the surface of the first particle; and a second primary particle on the surface of the first particle. The aspect ratio of the first primary particle can be from about 2 to about 15. The aspect ratio of the second primary particle can be from about 0.7 to about 3.

[0012] According to an embodiment of the present disclosure, the positive electrode active material can include a first particle, and the first particle includes a first lithium composite oxide. The first lithium composite oxide can be represented by Chemical Formula 1.

[0013] Chemical Formula 1

[0014] Li a1 Ni x1 Ma 1-x1 O b1

[0015] In Chemical Formula 1, a1 can be from about 0.5 to about 1.5, x1 can be from about 0.6 to about 0.99, b1 can be from about 1.8 to about 2.2, 1 - x1 can be from about 0.01 to about 0.4, and Ma can represent at least one element selected from Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn. The first particle can include: a first primary particle extending in a radial direction from the center of the first particle toward the surface of the first particle; and a second primary particle on the surface of the first particle. The angle between the radial direction and the a-axis of the first primary particle can be from about 0° to about 5°. The angle between the radial direction and the a-axis of the second primary particle can be from about 10° to about 80°.

[0016] According to an embodiment of the present disclosure, the rechargeable lithium battery can include the positive electrode active material discussed above. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, together with the specification, illustrate embodiments of the subject matter of the present disclosure and, together with the description, are used to explain the principles of the embodiments of the subject matter of the present disclosure.

[0018] Figure 1 A simplified conceptual diagram showing a rechargeable lithium battery according to some embodiments of the present disclosure is illustrated.

[0019] Figures 2 - 5 Illustrates a simplified diagram showing a rechargeable lithium battery according to an embodiment.

[0020] Figure 6 Illustrates an enlarged view of the positive electrode active material layer of a rechargeable lithium battery according to some embodiments of the present disclosure.

[0021] Figure 7 Illustrates an enlarged view of a cross-section of a first particle according to some embodiments of the present disclosure.

[0022] Figure 8 Illustrates Figure 7 A simplified enlarged cross-sectional view of cross-section M showing a first primary particle and a second primary particle depicted in

[0023] Figure 9A Illustrates a simplified cross-sectional view of a first primary particle and a second primary particle into which lithium ions have been embedded.

[0024] Figure 9B Illustrates a simplified cross-sectional view of a first primary particle and a second primary particle from which lithium ions have been de-embedded.

[0025] Figure 10 Illustrates an enlarged view of a cross-section of a first particle according to a comparative example of the present disclosure.

[0026] Figure 11A Illustrates a simplified cross-sectional view of a first primary particle according to a comparative example in which lithium ions have been embedded in the first particle.

[0027] Figure 11B Illustrates a simplified cross-sectional view of a first primary particle according to a comparative example from which lithium ions have been de-embedded from the first particle.

[0028] Figure 12 Illustrates a flowchart of a method for manufacturing a first particle according to some embodiments of the present disclosure.

[0029] Figure 13A , Figure 13B and Figure 13C Illustrates a scanning electron microscope (SEM) image of a cross-section of a first particle of Embodiment 1.

[0030] Figure 14A Illustrates a scanning electron microscope (SEM) image of a cross-section of a first particle of Embodiment 1.

[0031] Figure 14B Illustrates a scanning electron microscope (SEM) image of a cross-section of a first particle of Comparative Example 1.

[0032] Figure 15A An image showing the porosity of the first particles of Embodiment 1 is illustrated.

[0033] Figure 15B An image showing the porosity of the first particles of Comparative Example 1 is illustrated.

[0034] Figure 16A An image showing the cobalt element of the first particles of Embodiment 1 is illustrated.

[0035] Figure 16B An image showing the zirconium element of the first particles of Embodiment 1 is illustrated.

[0036] Figure 17A and Figure 17B and Figure 17C Graphs showing the results of measuring the amounts of transition metals Ni, Co, and Al in the shell and core of the first particles of Embodiment 1 are respectively illustrated.

[0037] Figure 18A and Figure 18B High-resolution transmission electron microscope (HR-TEM) measurement results of the thickness of the disordered layer on the surface of the first particles of Embodiment 1 and Comparative Example 1 are respectively illustrated.

[0038] Figure 19 The XRD spectrum of the first particles of Embodiment 1 is illustrated.

[0039] Figure 20 High-resolution transmission electron microscope (HR-TEM) measurement results of the core of the first particles of Embodiment 1 are illustrated.

[0040] Figure 21 High-resolution transmission electron microscope (HR-TEM) measurement results of the shell of the first particles of Embodiment 1 are illustrated. Detailed Description of the Invention

[0041] To fully understand the configuration and effects of the subject matter of the present disclosure, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be noted that the present disclosure is not limited to the following exemplary embodiments and can be implemented in various suitable forms. Instead, the exemplary embodiments are provided only to illustrate the subject matter of the present disclosure and to enable those of ordinary skill in the art to fully understand the scope of the present disclosure.

[0042] In this description, it will be understood that if an element is referred to as being "on" another element, the element can be directly on the other element or there can be intervening elements therebetween. In the drawings, the dimensions of some components (e.g., thickness) may be enlarged to effectively explain the technical content. Throughout the specification, the same reference numerals refer to the same elements.

[0043] Unless otherwise specifically stated in this description, singular expressions may include plural expressions. In an embodiment, unless otherwise specifically stated, the phrase "A or B" may indicate "A but not B", "B but not A", or "A and B". The terms "comprises / includes" and / or "comprising / including" used in this description do not exclude the presence or addition of one or more other components.

[0044] As used herein, the term "a combination thereof" may refer to a mixture, stack, composite, copolymer, alloy, blend, and / or reaction product of components.

[0045] Unless otherwise specifically defined in this description, the particle size may be an average particle size. In an embodiment, the particle size may indicate the average particle size (D 50 ) of the particles in which the cumulative volume in the particle size distribution is about 50% by volume. The average particle size (D 50 ) can be measured by any suitable method commonly used in the art, for example, by a particle size analyzer, transmission electron microscope (TEM) image, and / or scanning electron microscope (SEM) image. In an embodiment, a dynamic light scattering measurement device can be used for data analysis. The number of particles in each particle size range can be counted, and then the average particle size (D 50 ) value can be obtained by calculation. In an embodiment, the laser scattering method can be used to measure the average particle size (D 50 ). In the laser scattering method, the target particles are distributed in a distribution solvent, a laser scattering particle size measurement device (for example, MT3000 commercially available from Microtrac) is introduced, irradiated with ultrasonic waves at 28 kHz with a power of 60 W, and then the average particle size (D 50 ) is calculated in the measurement device based on the standard of 50% particle size distribution.

[0046] As a result of analyzing the elements on the surface of the positive electrode active material by using energy dispersive X-ray spectroscopy (EDS), SEM-EDS, and / or TEM-EDS, the term "atomic ratio" used in this description can be obtained. The elements that collide with the electron beam on the surface of the positive electrode active material can emit characteristic X-rays. The emitted characteristic X-rays can be analyzed by an EDS detector to determine the type and amount of the corresponding elements. The obtained amount can correspond to the atomic ratio.

[0047] Figure 1 A simplified conceptual diagram showing a rechargeable lithium battery according to some embodiments of the present disclosure is illustrated. Referring to Figure 1 , the rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0048] The positive electrode 10 and the negative electrode 20 can be spaced apart from each other by a separator 30. The separator 30 can be between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 can contact the electrolyte ELL. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated with the electrolyte ELL.

[0049] The electrolyte ELL can be a medium through which lithium ions are transported between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move through the separator 30 toward one selected from the positive electrode 10 and the negative electrode 20.

[0050] Positive electrode 10

[0051] The positive electrode 10 for a rechargeable lithium battery can include a positive electrode current collector COL1 and a positive electrode active material layer AML1 on the positive electrode current collector COL1. The positive electrode active material layer AML1 can include a positive electrode active material and can further include a binder and / or a conductive material (e.g., a conductive material). The positive electrode active material layer AML1 according to some embodiments of the present disclosure will be described in more detail below. An aluminum (Al) film can be used as the positive electrode current collector COL1, but the present disclosure is not limited thereto.

[0052] Negative electrode 20

[0053] The negative electrode 20 for a rechargeable lithium battery can include a negative electrode current collector COL2 and a negative electrode active material layer AML2 on the negative electrode current collector COL2. The negative electrode active material layer AML2 can include a negative electrode active material and can further include a binder and / or a conductive material (e.g., a conductive material).

[0054] For example, the negative electrode active material layer AML2 can include about 90 wt% to about 99 wt% of a negative electrode active material, about 0.5 wt% to about 5 wt% of a binder, and about 0 wt% to about 5 wt% of a conductive material (e.g., a conductive material).

[0055] The binder can be used to improve the attachment of the negative electrode active material particles to each other and can also be used to improve the attachment of the negative electrode active material particles to the negative electrode current collector COL2. The binder can include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0056] The non-aqueous binder can include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0057] The aqueous binder may include styrene-butadiene rubber, (meth)acrylic acid esterified styrene-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin rubber, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or a combination thereof.

[0058] If the aqueous binder is used as the binder in the negative electrode active material layer AML2, a cellulose compound capable of providing or increasing viscosity may be further included. The cellulose compound may include one or more selected from carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof. The alkali metal may include Na, K, and / or Li.

[0059] The dry binder may include fibrillatable polymer materials, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0060] The conductive material may be used to provide conductivity (for example, electrical conductivity) to the electrode, and any suitable conductive material that does not cause chemical changes in the battery (for example, undesired chemical changes in a rechargeable lithium battery) may be used as the conductive material constituting the battery. For example, the conductive material may include carbon materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and / or carbon nanotube); metal powders and / or metal fibers including one or more selected from copper, nickel, aluminum, and silver; conductive polymers (for example, electrically conductive polymers) (such as polyphenylene derivatives); or mixtures thereof.

[0061] The negative electrode current collector COL2 may include a copper foil, a nickel foil, a stainless steel foil, a titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal (for example, an electrically conductive metal), or a combination thereof.

[0062] Negative electrode active material

[0063] The negative electrode active material in the negative electrode active material layer AML2 may include a material capable of reversibly intercalating and deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and dedoping lithium, and / or a transition metal oxide.

[0064] The material capable of reversibly intercalating and deintercalating lithium ions may include carbon-based negative electrode active materials, for example, crystalline carbon, amorphous carbon, or a combination thereof. For example, crystalline carbon may include graphite (such as amorphous, flaky, sheet-like, spherical, and / or fibrous natural and / or artificial graphite), and amorphous carbon may include soft carbon, hard carbon, mesophase pitch carbon, and / or calcined coke.

[0065] The lithium metal alloy may include lithium and an alloy of a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0066] The material capable of doping and de-doping lithium may include a Si-based negative electrode active material and / 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 an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, or a combination thereof), or a combination thereof. The Sn-based negative electrode active material may include Sn, SnO x (0 < x ≤ 2) (e.g., SnO2), a Sn-based alloy, or a combination thereof.

[0067] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to an embodiment, the silicon-carbon composite may have a structure in which amorphous carbon is coated on the surface of silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are aggregated and an amorphous carbon coating (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 an amorphous carbon matrix.

[0068] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include: a core including crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core.

[0069] 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.

[0070] Separator 30

[0071] Based on the type (or kind) of the rechargeable lithium battery, the separator 30 may be between the positive electrode 10 and the negative electrode 20. The separator 30 may include one or more selected from a polyethylene separator, a polypropylene separator, and a polyvinylidene fluoride separator, and may have a multilayer separator thereof (such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, and a polypropylene / polyethylene / polypropylene trilayer separator).

[0072] The separator 30 may include a porous substrate and a coating on one surface or opposite surfaces (e.g., two opposite surfaces) of the porous substrate, the coating including an organic material, an inorganic material, or a combination thereof.

[0073] The porous substrate can be a polymer layer, and the polymer layer includes one selected from polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyaryl ether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (e.g., Teflon), or a copolymer or mixture including two or more of the above-mentioned materials.

[0074] The organic material can include polyvinylidene fluoride copolymers and / or (meth)acrylic copolymers.

[0075] The inorganic material can include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, or a combination thereof, but the present disclosure is not limited thereto.

[0076] The organic material and the inorganic material can be mixed together in one coating or can be a stack of a coating including the organic material and a coating including the inorganic material.

[0077] Electrolyte ELL

[0078] The electrolyte ELL for a rechargeable lithium battery can include a non-aqueous organic solvent and a lithium salt.

[0079] The non-aqueous organic solvent can be used as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0080] The non-aqueous organic solvent can include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or a combination thereof.

[0081] The carbonate solvents can include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and / or butylene carbonate (BC).

[0082] The ester solvents can include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and / or caprolactone.

[0083] Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and / or tetrahydrofuran. Ketone solvents may include cyclohexanone. Alcohol solvents may include ethanol and / or isopropyl alcohol. Aprotic solvents may include nitriles (such as, R-CN, where R is a hydrocarbon group having a straight-chain, branched-chain, or cyclic structure with C2 to C20 and may include double bonds, aromatic rings, and / or ether bonds); amides (such as, dimethylformamide); dioxolanes (such as, 1,3-dioxolane and / or 1,4-dioxolane); and / or sulfolane.

[0084] A single non-aqueous organic solvent may be used, or non-aqueous organic solvents may be used as a mixture of two or more substances.

[0085] In an embodiment, if a carbonate solvent is used, a cyclic carbonate and a linear carbonate may be mixed and used, and the cyclic carbonate and the linear carbonate may be mixed together at a volume ratio of about 1:1 to about 1:9.

[0086] The lithium salt may be a material dissolved in a non-aqueous organic solvent to serve as a source of lithium ions in a battery and to play a role in ensuring the basic operation of a rechargeable lithium battery and facilitating the movement of lithium ions between the positive electrode and the negative electrode. The lithium salt may include, for example, at least one selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N, lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+ 1SO2) (where x and y are integers between 1 and 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluoro bis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0087] Rechargeable lithium battery

[0088] Based on the shape of the rechargeable lithium battery, the rechargeable lithium battery may be classified into cylindrical, prismatic, pouch-type, and / or coin-type (or kind). In Figures 2 - 5 a simplified diagram showing a rechargeable lithium battery according to an embodiment is illustrated, Figure 2 showing a cylindrical battery, Figure 3 showing a prismatic battery, and Figure 4 and Figure 5 showing a pouch-type battery. Refer to Figures 2 - 4, the rechargeable lithium battery 100 may include an electrode assembly 40 in which a separator 30 is disposed between a positive electrode 10 and a negative electrode 20, and may also include a case 50 that houses the electrode assembly 40. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. As Figure 2 illustrated, the rechargeable lithium battery 100 may include a sealing member 60 that seals the case 50. In an embodiment, as Figure 3 illustrated, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As Figure 4 and Figure 5 shown, the rechargeable lithium battery 100 may include an electrode tab 70 ( Figure 5 ) or a positive electrode tab 71 and a negative electrode tab 72 ( Figure 4 ), and the electrode tab 70 serves as a circuit path for guiding the current generated in the electrode assembly 40 to the outside.

[0089] The rechargeable lithium battery according to an embodiment of the present disclosure may be applied to a motor vehicle, a mobile phone, and / or any other suitable electronic device, but the present disclosure is not limited thereto.

[0090] Figure 6 illustrates an enlarged view showing a positive electrode active material layer of a rechargeable lithium battery according to some embodiments of the present disclosure. Referring to Figure 6 , as discussed above, the positive electrode active material layer (see Figure 1 's AML1) may include first particles PTC1, second particles PTC2, a conductive material CDM (e.g., a conductive material CDM), and a binder BND. A plurality of first particles PTC1 and a plurality of second particles PTC2 may constitute the positive electrode active material according to some embodiments of the present disclosure. In an embodiment, the positive electrode active material layer AML1 may further include a plurality of agglomerates ZAG. In an embodiment, the positive electrode active material layer AML1 may further include a component that can serve as a sacrificial positive electrode.

[0091] With respect to 100 wt% of the positive electrode active material layer AML1, the total amount of the first particles PTC1 and the second particles PTC2 in the positive electrode active material layer AML1 may be in the range of about 90 wt% to about 99.5 wt%. With respect to 100 wt% of the positive electrode active material layer AML1, the amounts of the binder BND and the conductive material CDM may be about 0.5 wt% to about 5 wt%, respectively.

[0092] The binder BND can bind the first particles PTC1, the second particles PTC2, and the conductive material CDM to each other. For example, the binder BND can include at least one selected from polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon, but the present disclosure is not limited thereto.

[0093] The conductive material CDM can be used to improve the conductivity (e.g., electrical conductivity) of the positive electrode active material layer AML1. Any conductive material (e.g., any suitable electrical conductivity material) that does not cause a chemical change in the positive electrode active material layer AML1 (e.g., does not cause an undesired chemical change) can be used as the conductive material CDM without limitation. For example, the conductive material CDM can include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and / or carbon nanotube); metal powders and / or metal fibers including one or more of copper, nickel, aluminum, and silver; conductive polymers (e.g., electrically conductive polymers) (such as polyphenylene derivatives); or mixtures thereof.

[0094] Each of the first particles PTC1 and the second particles PTC2 will be described in detail below.

[0095] The first particles PTC1 can have a first average particle diameter APD1, and the second particles PTC2 can have a second average particle diameter APD2. The second average particle diameter APD2 can be smaller than the first average particle diameter APD1. For example, the first average particle diameter APD1 can be in the range of about 6.0 μm to about 20.0 μm. The second average particle diameter APD2 can be in the range of about 1.0 μm to about 5.0 μm. In an embodiment of the present disclosure, the first particles PTC1 can be referred to as large particles, and the second particles PTC2 can be referred to as small particles. Each of the first particles PTC1 and the second particles PTC2 can have a granular shape and / or a spherical shape.

[0096] The positive electrode active material according to an embodiment of the present disclosure including large particles (e.g., PTC1) and small particles (e.g., PTC2) having different average particle diameters can have a bimodal shape. The small particles can fill the pores between the large particles, so the positive electrode active material layer AML1 can have an increased overall density. For example, the positive electrode active material layer AML1 according to some embodiments of the present disclosure can have a relatively high energy density per unit volume.

[0097] In an embodiment, the first particles PTC1 and the second particles PTC2 in the positive electrode active material may have a weight ratio of about 95:5 to about 50:50. In another embodiment, the first particles PTC1 and the second particles PTC2 in the positive electrode active material may have a weight ratio of about 5:95 to about 50:50. For example, in the positive electrode active material, the weight of the first particles PTC1 may be greater than the weight of the second particles PTC2, or the weight of the second particles PTC2 may be greater than the weight of the first particles PTC1.

[0098] In an embodiment, the positive electrode active material may include only the first particles PTC1. For example, the second particles PTC2 may be omitted.

[0099] The first particles PTC1 may include a first lithium composite oxide, and the second particles PTC2 may include a second lithium composite oxide. Each of the first lithium composite oxide and the second lithium composite oxide may include nickel (Ni) and zirconium (Zr). Each of the first lithium composite oxide and the second lithium composite oxide may further include at least one metal selected from cobalt (Co), manganese (Mn), and aluminum (Al).

[0100] For example, the first lithium composite oxide may be represented by Chemical Formula 1 below.

[0101] Chemical Formula 1

[0102] Li a1 Ni x1 Ma 1-x1 O b1

[0103] In Chemical Formula 1, the subscript "a1" may be in the range of about 0.5 to about 1.5, the subscript "x1" may be in the range of about 0.6 to about 0.99, the subscript "b1" may be in the range of about 1.8 to about 2.2, and the subscript "1 - x1" may be in the range of about 0.01 to about 0.4. The symbol Ma may represent at least one element selected from Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn. In an embodiment, the symbol Ma may represent Co, Al, and Mn. In the present disclosure, the term "transition metal" may include post-transition metals (such as, Al).

[0104] The first lithium composite oxide may further include boron (B) as a dopant. In an embodiment, the first lithium composite oxide may have a boron (B) concentration of about 1 ppm to about 2,000 ppm. Since the amount of boron (B) is extremely small (e.g., very small or negligible), boron may not be detectable in the first lithium composite oxide (e.g., the amount that cannot be detected includes boron).

[0105] The second lithium composite oxide can be represented by Chemical Formula 2 below.

[0106] Chemical Formula 2

[0107] Li a2 Ni x2 Mb 1-x2 Fl w2 O b2

[0108] In Chemical Formula 2, the subscript “a2” can be in the range of about 0.5 to about 1.5, the subscript “x2” can be in the range of about 0.6 to about 0.99, the subscript “b2” can be in the range of about 1.8 to about 2.2, and the subscript “1 - x2” can be in the range of about 0.01 to about 0.4. The subscript “w2” can be in the range of about 0.0005 to about 0.01. The symbol Mb can represent at least one element selected from Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn. In an embodiment, the symbol Mb can represent Co, Al, and Mn. The symbol Fl can represent at least one element selected from Zr, Sr, Y, La, Mo, Ce, Nb, and S. The element represented by the symbol Fl can be derived from the flux used when calcining the second particle PTC2.

[0109] The molar ratio of Ma in the first lithium composite oxide to the total transition metal elements included in the first lithium composite oxide (i.e., the composition ratio of Ma in the first lithium composite oxide) can be different from the molar ratio of Mb in the second lithium composite oxide to the total transition metal elements included in the second lithium composite oxide (i.e., the composition ratio of Mb in the second lithium composite oxide). For example, Ma in the first lithium composite oxide can represent Co and Al, and Mb in the second lithium composite oxide can represent Co and Mn. In another example, each of Ma and Mb can represent Co, Al, and Mn. The composition ratio of Al in the first lithium composite oxide can be greater than the composition ratio of Al in the second lithium composite oxide, and the composition ratio of Mn in the first lithium composite oxide can be less than the composition ratio of Mn in the second lithium composite oxide. The first lithium composite oxide can further include boron (B) as a dopant. The second lithium composite oxide may not include boron (B).

[0110] In an embodiment of the present disclosure, the subscript "x1" in Chemical Formula 1 or the molar ratio of Ni may be greater than about 0.8. If the first lithium composite oxide has a composition with a high Ni content (x1 > 0.8), the first lithium composite oxide can be calcined at a relatively low temperature. Therefore, in the method for manufacturing a positive electrode active material for a rechargeable lithium battery described below, the first particle PTC1 can be synthesized at a relatively low temperature. Ni in the first lithium composite oxide can affect the power and capacity of the rechargeable lithium battery. In the present disclosure, the first lithium composite oxide with a high nickel content can be used to provide a high-power rechargeable lithium battery. The subscript "x2" in Chemical Formula 2 or the molar ratio of Ni may also be greater than about 0.8. However, the subscript "x2" may be different from the subscript "x1".

[0111] An increase in the Ni content in the first lithium composite oxide and the second lithium composite oxide can lead to a decrease in the stability of the positive electrode or the rechargeable lithium battery. In an embodiment of the present disclosure, the first lithium composite oxide and the second lithium composite oxide may further include Co, so that the rechargeable lithium battery can improve the stability and capacity retention characteristics.

[0112] In an embodiment of the present disclosure, the first particle PTC1 may have a polycrystalline shape. The first particle PTC1 may include secondary particles in which at least two primary particles are aggregated.

[0113] In an embodiment, the first particle PTC1 may include a first coating CTL1 on its surface. The first coating CTL1 may cover the entire surface or at least a part of the surface of the first particle PTC1. Since the first particle PTC1 is coated with the first coating CTL1, the structural collapse due to repeated charging and discharging can be effectively suppressed or reduced, so as to improve the life characteristics at room temperature and high temperature.

[0114] The first coating CTL1 may include a metal-containing compound, for example, a cobalt compound and / or a zirconium compound. The metal-containing compound may include a metal oxide, a metal hydroxide, a metal carbonate, or any combination thereof.

[0115] The first coating CTL1 may further include a metal element and / or a non-metal element other than cobalt and zirconium. The first coating CTL1 may further include lithium, aluminum, manganese, and / or nickel. For example, the first coating CTL1 may include lithium cobalt zirconium oxide.

[0116] The amount of cobalt can range from about 20 at% to about 50 at% relative to the total amount of transition metals (e.g., Ni + Co + Al + Mn + Zr) in the first coating CTL1. The amount of zirconium can range from about 0.001 at% to about 1 at% relative to the total amount of transition metals in the first coating CTL1. In an embodiment, the amount of zirconium can be equal to or less than about 0.002 at% relative to the total amount of transition metals in the first coating CTL1. The amount of cobalt in the first coating CTL1 can be greater than the amount of zirconium in the first coating CTL1. The ratio of the amount of cobalt to the amount of zirconium (Co / Zr) in the first coating CTL1 can be equal to or greater than about 10,000.

[0117] In an embodiment of the present disclosure, the shape of the second particle PTC2 can be like that of a single particle. The single particle can be composed of one particle without grain boundaries therein. The single particle can be a single particle, a monolithic structure, a single unit structure (e.g., a single unit structure), or a non-aggregated particle (wherein the particles do not aggregate with each other but exist as independent phases from a morphological perspective). For example, the single particle can be single crystal (e.g., be single crystal). Since the positive electrode active material according to the embodiment includes the second particle PTC2 in the form of a single particle, high capacity, high energy density, and increased life characteristics can be achieved.

[0118] In an embodiment, the second particle PTC2 can include a second coating CTL2 on its surface. Since the second particle PTC2 is coated with the second coating CTL2, the structural collapse due to repeated charging and discharging can be effectively suppressed or reduced to improve the life characteristics at room temperature and high temperature.

[0119] The second coating CTL2 can include a metal-containing compound, e.g., a cobalt compound and / or a zirconium compound. The description of the second coating CTL2 can be the same as or similar to the description of the first coating CTL1.

[0120] The amount of cobalt can range from about 20 at% to about 50 at% relative to the total amount of transition metals in the second coating CTL2. The amount of zirconium can range from about 0.002 at% to about 0.2 at% relative to the total amount of transition metals in the second coating CTL2. In an embodiment, the amount of cobalt in the second coating CTL2 can be less than the amount of cobalt in the first coating CTL1. In an embodiment, the amount of zirconium in the second coating CTL2 can be greater than the amount of zirconium in the first coating CTL1.

[0121] According to some embodiments of the present disclosure, the amount of zirconium in the second coating CTL2 of the second particle PTC2 may be greater than the amount of zirconium in the first coating CTL1 of the first particle PTC1. Accordingly, the second particle PTC2 may increase the ionic conductivity on the surface. In the present disclosure, even if the second particle PTC2 is calcined at a relatively high temperature to have a single particle shape, the second coating CTL2 having a relatively large amount of zirconium may enable the rechargeable lithium battery to have improved durability and capacity retention characteristics.

[0122] The composition of each of the first coating CTL1 and the second coating CTL2 can be obtained by performing scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis and quantitative analysis on the particle surface. In addition to SEM-EDS, the composition can be measured by inductively coupled plasma mass spectrometry (ICP-MS) and / or inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0123] The first coating CTL1 and the second coating CTL2 according to some embodiments of the present disclosure may not be confirmed by electron microscope images. The first coating CTL1 and the second coating CTL2 can be confirmed by the presence of cobalt and zirconium on the particle surface using SEM-EDS.

[0124] Figure 7 An enlarged view showing a cross-section of the first particle according to some embodiments of the present disclosure is illustrated. Figure 8 is illustrated Figure 7 The simplified enlarged cross-sectional view depicted in shows a cross-section M of the first primary particle and the second primary particle.

[0125] Referring to Figure 7 and Figure 8 The first particle PTC1 may include a plurality of crystal grains. The first particle PTC1 may include a plurality of primary particles PRP1, PRP2, and PRP3. The third primary particle PRP3 may be in the central portion of the first particle PTC1. The second primary particle PRP2 may be on the surface of the first particle PTC1. The first primary particle PRP1 may extend from the third primary particle PRP3 toward the second primary particle PRP2 in the radial direction RD.

[0126] The crystal grain may be the smallest unit having a single crystal orientation in the lithium composite oxide. For example, each of the primary particles PRP1 to PRP3 included in the first particle PTC1 may correspond to each crystal grain. The second particle PTC2 may be formed of a single crystal grain or formed of a plurality of aggregated crystal grains.

[0127] The first primary particle PRP1 may have a rod shape extending in the radial direction RD. The first primary particle PRP1 may have a major axis substantially parallel to the radial direction RD. Each of the second primary particle PRP2 and the third primary particle PRP3 may have an atypical shape with a small aspect ratio (e.g., an aspect ratio of 1:1). For example, the aspect ratio of the third primary particle PRP3 is about 0.7 to about 3.

[0128] In an embodiment of the present disclosure, the third primary particle PRP3 may be omitted. For example, the first primary particle PRP1 may extend from the center of the first particle PTC1 towards the second primary particle PRP2.

[0129] X-ray diffraction (XRD) analysis can be used to measure the grain size and / or the average size of the primary particles of the first particle PTC1. The first size may refer to the average size of the first primary particle PRP1. The second size may refer to the average size of the second primary particle PRP2. The third size may refer to the average size of the third primary particle PRP3. The first size may be in the range of about 200 nm to about 3,000 nm. The second size may be in the range of about 100 nm to about 1,500 nm. The third size may be in the range of about 100 nm to about 900 nm. For example, the first size may be greater than the second size. The first size may be about 1.5 times to about 30 times the second size. In an embodiment, the first size may be about 1.5 times to about 10 times the second size.

[0130] According to an embodiment of the present disclosure, the first primary particle PRP1 may have a first length LI1 in the radial direction RD. The first length LI1 may correspond to the first size. For example, the first length LI1 may be in the range of about 400 nm to about 3,000 nm.

[0131] The first primary particle PRP1 may have a first width WI1 in a direction ND intersecting the radial direction RD. For example, the first width WI1 may be in the range of about 200 nm to about 600 nm. The first width WI1 of the first primary particle PRP1 may gradually increase in the radial direction RD. For example, the first width WI1 of the first primary particle PRP1 adjacent to the second primary particle PRP2 may be greater than the first width WI1 of the first primary particle PRP1 adjacent to the third primary particle PRP3.

[0132] The first primary particle PRP1 may have a relatively large aspect ratio (LI1 / WI1). For example, the aspect ratio (LI1 / WI1) of the first primary particle PRP1 may be in the range of about 2 to about 15. For example, the aspect ratio (LI1 / WI1) of the first primary particle PRP1 may be in the range of about 5 to about 10.

[0133] The first length LI1 of the first primary particle PRP1 adjacent to the second primary particle PRP2 may be greater than the first length LI1 of the first primary particle PRP1 adjacent to the third primary particle PRP3. Among the plurality of first primary particles PRP1, the first primary particle PRP1 adjacent to the center of the first particle PTC1 may have a length smaller than the length of the first primary particle PRP1 adjacent to the surface of the first particle PTC1 among the plurality of first primary particles PRP1.

[0134] According to an embodiment of the present disclosure, the second primary particle PRP2 may have a second length LI2 in the radial direction RD. The second primary particle PRP2 may have a second width WI2 in a direction ND intersecting the radial direction RD. The second primary particle PRP2 may have a relatively small aspect ratio (LI2 / WI2). The aspect ratio (LI2 / WI2) of the second primary particle PRP2 may be in the range of about 0.7 to about 3. For example, the aspect ratio (LI2 / WI2) of the second primary particle PRP2 may be in the range of about 1 to about 3. Each of the second length LI2 and the second width WI2 may correspond to a second dimension. For example, each of the second length LI2 and the second width WI2 may be in the range of about 100 nm to about 1,500 nm.

[0135] According to some embodiments of the present disclosure, the first particle PTC1 may include boron (B) as a dopant. Thus, as Figure 8 shown, the first primary particle PRP1 may have an increased aspect ratio. As discussed below, the method of manufacturing the first particle PTC1 may include a first calcination process, a first coating process, a second coating process, and a second calcination process. Thus, the second primary particle PRP2 may be provided on the surface of the first particle PTC1. The first primary particle PRP1 may be provided with the second primary particle PRP2 having a small aspect ratio at its end (for example, the second primary particle PRP2 may be at the end of the first primary particle PRP1, and the second primary particle PRP2 has a small aspect ratio). Thus, lithium ions can be easily inserted into and de-inserted from the first particle PTC1, respectively.

[0136] The first primary particle PRP1 may have a first lateral surface SIS1. The first lateral surface SIS1 may be parallel to (or substantially parallel to) the radial direction RD. For example, the first lateral surface SIS1 may include the (003) plane.

[0137] Since the first particle PTC1 includes boron (B) as a dopant, the first lateral surface SIS1 of the first primary particle PRP1 may have an increased area (for example, an increased surface area). However, the first primary particle PRP1 may have (014) planes and (104) planes each having a relatively reduced area (for example, a relatively reduced surface area).

[0138] The crystal structure of the first primary particle PRP1 may have an a-axis arranged substantially parallel to the radial direction RD. Since the (003) plane or the first lateral surface SIS1 of the first primary particle PRP1 has an increased area (e.g., increased surface area), the first primary particle PRP1 may have an increased aspect ratio (LI1 / WI1) and improved orientation. For example, the angle between the radial direction RD and the a-axis of the first primary particle PRP1 may be in the range of about 0° to about 5°. The crystal structure of the first primary particle PRP1 may have a c-axis perpendicular to (or substantially perpendicular to) the radial direction RD. For example, the angle between the radial direction RD and the c-axis of the first primary particle PRP1 may be in the range of about 80° to about 100°.

[0139] As Figure 7 shown, grain boundaries GRB may be provided between adjacent first primary particles PRP1. The grain boundaries GRB may be substantially parallel to the radial direction RD. The electrolyte and metal ions (e.g., lithium ions) may move appropriately or satisfactorily through the grain boundaries GRB. In an embodiment, a rechargeable lithium battery including the first particle PTC1 may improve the efficiency of charging and discharging.

[0140] The second primary particle PRP2 may have a relatively small aspect ratio (LI2 / WI2) and low orientation (e.g., less oriented than the first primary particle PRP1). The crystal structure of the second primary particle PRP2 may have an a-axis that intersects the radial direction RD rather than being parallel to the radial direction RD. For example, the angle between the radial direction RD and the a-axis of the second primary particle PRP2 may be in the range of about 10° to about 80°. The a-axis of the second primary particle PRP2 may have a random direction.

[0141] During the charging and discharging process, the second primary particle PRP2 may contract and expand in the c-axis direction. The second primary particle PRP2 may contract and expand randomly. According to an embodiment of the present invention, the second primary particle PRP2 may be selectively provided on the surface of the first particle PTC1. Thus, even if the second primary particle PRP2 contracts and expands randomly, cracks do not occur (or substantially do not occur) in the first particle PTC1. The random contraction and expansion of the second primary particle PRP2 may ensure that the grain boundaries GRB are exposed at an appropriate or suitable level on the surface of the second primary particle PRP2. Thus, during the charging and discharging process, the movement of lithium ions and the electrolyte through the grain boundaries GRB can be appropriately or suitably controlled.

[0142] For example, referring to Figure 9A , grain boundaries GRB may be provided between adjacent first primary particles PRP1. The grain boundaries GRB in which lithium ions are embedded in the first particle PTC1 may have a first spacing ITV1.

[0143] Reference Figure 9B , if the rechargeable lithium battery is charged, lithium ions can be deintercalated from the first particle PTC1, causing the first primary particle PRP1 and the second primary particle PRP2 to contract. The primary particles can contract in the c-axis direction. Since the first primary particle PRP1 has substantially the same orientation, the first primary particle PRP1 can contract to have a reduced first width WI1. The contraction of the first primary particle PRP1 can cause the grain boundary GRB to have an increased second spacing ITV2.

[0144] Since the second primary particle PRP2 has a random orientation, even if the second primary particle PRP2 contracts, the second width WI2 of the second primary particle PRP2 will not change significantly compared to the first width WI1. For example, if the first particle PTC1 contracts, the change in the second width WI2 of the second primary particle PRP2 can be less than the change in the first width WI1 of the first primary particle PRP1.

[0145] Therefore, even if the grain boundary GRB has a relatively large second spacing ITV2, the second primary particle PRP2 can appropriately or suitably close or protect the grain boundary GRB spaced apart by the second spacing ITV2. Accordingly, excessive penetration of the electrolyte into the grain boundary GRB can be prevented or reduced, and side reactions and cracks in the first particle PTC1 can be prevented or reduced.

[0146] During the charging and discharging processes of the rechargeable lithium battery, the insertion and deintercalation of lithium ions can cause the primary particles to contract and expand in the c-axis direction. The contraction and expansion of the primary particles can generate cracks in the secondary particles. The cracks can allow the electrolyte to be introduced into the secondary particles. Side reactions of the electrolyte introduced through the cracks can generate impurity phases in the secondary particles.

[0147] According to some embodiments of the present disclosure, the a-axis of the first primary particle PRP1 can be parallel to (or substantially parallel to) the radial direction RD, and the c-axis of the first primary particle PRP1 can be parallel to (or substantially parallel to) the direction ND intersecting the radial direction RD. Therefore, even if the first primary particle PRP1 contracts and expands in the direction ND, internal cracks in the first particle PTC1 can be prevented or reduced. In an embodiment, the randomly oriented second primary particle PRP2 can be selectively provided only on the surface of the first particle PTC1. Therefore, even if the second primary particle PRP2 contracts and expands, internal cracks in the first particle PTC1 can be prevented or reduced. In an embodiment, the positive electrode active material according to some embodiments of the present disclosure can improve the charge capacity / discharge capacity and life characteristics of the rechargeable lithium battery.

[0148] Grain boundary coating GCL( Figure 8) can be provided on the first lateral surface SIS1 of the first primary particle PRP1. For example, the grain boundary coating GCL can be provided on the grain boundary GRB. The first coating CTL1 ( Figure 8 ) can be provided on the second lateral surface SIS2 of the second primary particle PRP2. The first coating CTL1 can be substantially the same as discussed above.

[0149] The grain boundary coating GCL may not be present on the surface of the first particle PTC1, but may be present inside the first particle PTC1. The grain boundary coating GCL can be coated along the grain boundary GRB inside the first particle PTC1. In this description, the inside of the first particle PTC1 can indicate the entire inner part except the surface of the first particle PTC1. For example, the inside of the first particle PTC1 can mean the entire inside from the outer surface of the first particle PTC1 to a depth of about 10 nm, or the part from a depth of about 10 nm to a depth of about 2 μm.

[0150] In addition to the first coating CTL1, the first particle PTC1 according to this embodiment may further include a grain boundary coating GCL, so that the structural stability can be improved, and a symmetrical and uniform (e.g., substantially symmetrical and substantially uniform) coating can be produced on the surface. The amount of metal in the first coating CTL1 can be appropriately adjusted to increase the life characteristics and the initial charge efficiency / initial discharge efficiency without increasing the impedance (e.g., resistance).

[0151] The grain boundary coating GCL may include a metal-containing compound, for example, a cobalt compound and / or a zirconium compound. The metal-containing compound may include a metal oxide, a metal hydroxide, a metal carbonate, or any combination thereof.

[0152] The grain boundary coating GCL may further include a non-metal element and / or a metal element other than cobalt and zirconium. The grain boundary coating GCL may further include lithium, manganese, and / or nickel. For example, the grain boundary coating GCL may include lithium cobalt zirconium oxide.

[0153] Relative to the total amount of transition metals in the grain boundary coating GCL, the cobalt amount may be in the range of about 20 at% to about 50 at%. Relative to the total amount of transition metals in the grain boundary coating GCL, the zirconium amount may be equal to or less than about 0.1 at%. In an embodiment, since the grain boundary coating GCL has a very small (e.g., extremely small or negligible) amount of zirconium, zirconium may not be detectable (e.g., may include an undetectable amount of zirconium).

[0154] The amount of cobalt in the grain boundary coating GCL can be different from the amount of cobalt in the first coating CTL1. In an embodiment, the amount of cobalt in the grain boundary coating GCL can be greater than the amount of cobalt in the first coating CTL1. The amount of zirconium in the grain boundary coating GCL can be less than the amount of zirconium in the first coating CTL1. The ratio of the amount of cobalt to the amount of zirconium (Co / Zr) in the grain boundary coating GCL can be greater than the ratio of the amount of cobalt to the amount of zirconium (Co / Zr) in the first coating CTL1.

[0155] The core of the first particle PTC1 can have a porosity greater than the porosity of the shell of the first particle PTC1. The core of the first particle PTC1 is defined as the region indicating up to half of the radius from the center of the first particle PTC1 to the radius of the first particle PTC1. The shell of the first particle PTC1 can be defined as the remaining region surrounding the core.

[0156] The ratio of the porosity of the core of the first particle PTC1 to the average porosity of the first particle PTC1 can be in the range of about 1.5 to about 2.0. The core of the first particle PTC1 can be porous, and the shell of the first particle PTC1 can be dense (e.g., pore-free or relatively pore-free). The shell of the first particle PTC1 can include the first coating CTL1 and the grain boundary coating GCL, and can also include the second primary particle PRP2 referred to above Figure 9A and Figure 9B discussed. Therefore, the shell of the first particle PTC1 can have a dense structure without voids (or substantially without voids).

[0157] The shell of the first particle PTC1 can include nickel (Ni) and cobalt (Co). Relative to the total amount of nickel (Ni) and cobalt (Co) in the shell, the amount of nickel (Ni) in the shell can be in the range of about 70 at% to about 90 at%. The shell of the first particle PTC1 according to this embodiment can have the aforementioned amounts of nickel (Ni) and cobalt (Co), so as to have a low porosity and be dense (e.g., can have a relatively low porosity compared to the core and can be relatively dense compared to the core). The amount of Ni in the shell of the first particle PTC1 can be less than the amount of Ni in the core of the first particle PTC1. The amount of Co in the shell of the first particle PTC1 can be greater than the amount of Co in the core of the first particle PTC1.

[0158] Return reference Figure 6, the second particle PTC2 may include at least one crystal grain. XRD analysis can be used to measure the average size of the crystal grains of the first particle PTC1 (e.g., the first primary particle PRP1 to the third primary particle PRP3) and the average size of the crystal grains of the second particle PTC2. For example, the crystal grains of the second particle PTC2 may have an average size of about 100 nm to about 4,000 nm or about 500 nm to about 1,500 nm. The average size of the crystal grains of the first particle PTC1 may be smaller than the average size of the crystal grains of the second particle PTC2. The average size of the crystal grains of the second particle PTC2 may be about 1.1 times to about 3.5 times the average size of the crystal grains of the first particle PTC1.

[0159] According to an embodiment of the present disclosure, the second particle PTC2 can be formed by calcining using a flux. Therefore, the crystal grains of the second particle PTC2 can be formed to have a relatively large size. The second particle PTC2 may have relatively high durability and can prevent or reduce the formation of microcracks in the second particle PTC2.

[0160] The agglomerate ZAG can be provided in the space between the first particle PTC1 and the second particle PTC2. The agglomerate ZAG can be derived from a coating agent. The agglomerate ZAG may include a metal-containing compound, for example, a cobalt compound and / or a zirconium compound. For example, the agglomerate ZAG can be a cluster formed by the aggregation of a part of the coating agent that is not coated on the surfaces of the first particle PTC1 and the second particle PTC2.

[0161] The first particle PTC1 may have a secondary particle shape. If a rechargeable lithium battery is charged and discharged, microcracks are likely to form in the secondary particles of other active materials. However, in the embodiment of the present disclosure, in the first particle PTC1 according to some embodiments of the present disclosure, due to Figure 7 and Figure 8 the orientation and arrangement of the primary particles shown in, the formation of internal cracks can be prevented or reduced. According to some embodiments of the present disclosure, the shape of the second particle PTC2 can be like a single particle (or the second particle PTC2 can be a single particle). The second particle PTC2 can be denser and more durable than the first particle PTC1. Therefore, the occurrence of microcracks in the second particle PTC2 can be prevented or reduced. As a result, the stability and capacity retention rate characteristics of the rechargeable lithium battery according to the embodiment of the present disclosure can be improved.

[0162] Since the second particle PTC2 has an average particle size smaller than that of the first particle PTC1, the second particle PTC2 may have a specific surface area larger than that of the first particle PTC1. If the first particle PTC1 and the second particle PTC2 are applied to Figure 1For the positive electrode 10, compared with the first particulate PTC1, the second particulate PTC2 can contact the electrolyte ELL more (for example, the second particulate PTC2 can have a larger surface area in contact with the electrolyte ELL than the first particulate PTC1). Therefore, compared with the first particulate PTC1, the second particulate PTC2 can easily undergo side reactions with the electrolyte ELL. According to some embodiments of the present disclosure, the second particulate PTC2 can include a second coating CTL2, and the second coating CTL2 includes cobalt (Co) and / or zirconium (Zr). The second coating CTL2 can prevent or reduce side reactions between the second particulate PTC2 and the electrolyte ELL. For example, the second coating CTL2 of the present disclosure can prevent or reduce the deterioration of the second particulate PTC2 caused by the electrolyte ELL.

[0163] Figure 10 An enlarged view showing a cross-section of a first particulate according to a comparative example of the present disclosure is illustrated. Refer to Figure 10 , the first particulate PTC1 according to the comparative example may not include the second primary particulate PRP2 on its surface ( Figure 7 ). For example, the second primary particulate PRP2 on the surface (or shell) of the first particulate PTC1 can be omitted. The first primary particulate PRP1 extending in the radial direction may have an exposed end. The exposed end of the first primary particulate PRP1 can constitute the surface of the first particulate PTC1.

[0164] For example, the method of manufacturing the first particulate PTC1 according to the comparative example can omit the first coating process, the second coating process, and the second calcination process which will be further discussed below. The omission of the first coating process, the second coating process, and the second calcination process may not form the second primary particulate PRP2 on the surface of the first particulate PTC1.

[0165] Figure 11A A simplified cross-sectional view showing a first primary particulate according to a comparative example in which lithium ions have been embedded in the first particulate is illustrated. Figure 11B A simplified cross-sectional view showing a first primary particulate according to a comparative example in which lithium ions have been deintercalated from the first particulate is illustrated.

[0166] Refer to Figure 11A , the grain boundary GRB can be between adjacent first primary particulates PRP1. The grain boundary GRB in which lithium ions are embedded in the first particulate PTC1 ( Figure 10 ) can have a first spacing ITV1. For example, the grain boundary GRB can be exposed through the surface of the first particulate PTC1.

[0167] Refer to Figure 11B , if the rechargeable lithium battery is charged, lithium ions can be removed from the first particulate PTC1 ( Figure 10)Delithiation causes the first primary particle PRP1 to contract. The contraction of the first primary particle PRP1 can cause the grain boundary GRB to have an increased second spacing ITV2.

[0168] If lithium ions are delithiated, the size of the outwardly exposed grain boundary GRB can become larger. The increased grain boundary GRB can allow the electrolyte to easily penetrate into the first particle PTC1( Figure 10 ). As a result, problems of cracks and side reactions can occur in the first particle PTC1.

[0169] However, in the embodiments of the present disclosure, in the first particle PTC1 according to some embodiments of the present disclosure, as referred to above Figure 9A and Figure 9B discussed, even if lithium ions are delithiated through the second primary particle PRP2 on the surface of the first particle PTC1( Figure 7 ), excessive exposure of the grain boundary GRB can be prevented or reduced. The embodiments of the present disclosure can prevent or reduce the occurrence of cracks and impurity phases in the first particle PTC1.

[0170] Figure 12 Illustrates a flowchart showing a method of manufacturing a first particle according to some embodiments of the present disclosure. Referring to Figure 12 , a precursor of the first particle can be prepared. The precursor can include Ni and Ma in Chemical Formula 1 discussed above. Ma can represent at least one element selected from Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn. For example, Ma can represent Co and Al.

[0171] In an embodiment, the precursor can be obtained by a coprecipitation method. For example, the coprecipitation method can include dissolving a transition metal raw material in a solvent (such as distilled water) and continuously (or substantially continuously) supplying a transition metal salt solution, a chelating agent, and an aqueous alkali solution to a reactor. The precipitate can be collected in the form of a slurry solution, and then the slurry solution can be filtered and dried to obtain a metal composite hydroxide, oxide, and / or precursor.

[0172] In the present disclosure, the transition metal raw material may include a metal salt of at least one element selected from Ni, Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn. The metal salt may include a sulfate, a nitrate, an acetate, a halide, and / or a hydroxide, and there is no specific limitation as long as the metal salt is soluble in a solvent. The transition metal raw material according to some embodiments may include a nickel salt, a cobalt salt, and an aluminum salt. The transition metal raw materials may be mixed by adjusting the molar ratio so that the positive electrode active material has a high-capacity characteristic. For example, the molar ratio may determine the subscript "x1" of Chemical Formula 1.

[0173] The precursor, the lithium source, and the dopant source may be mixed together in certain proportions to form a mixture (S100). For example, the precursor and the lithium source may be mixed together at a molar ratio of about 1:1. The lithium source may be used without specific limitation as long as it is a suitable lithium source commonly used for manufacturing the positive electrode active material. For example, the lithium source may include a lithium salt (such as lithium carbonate, lithium nitrate, lithium hydroxide, and / or lithium sulfate).

[0174] The dopant source may include boron (B) of Chemical Formula 1 discussed above. The dopant source and the precursor may be mixed together at a molar ratio of about 0.0003 to about 0.2. For example, the dopant source may include boron oxide and / or boric acid.

[0175] The mixture may be added to a furnace, and a first calcination process may be performed at a first temperature (S200). The first temperature may be in the range of about 500°C to about 1,000°C. For example, the first temperature may be in the range of about 700°C to about 900°C. The first calcination process may be performed in an oxidizing atmosphere (such as air and / or oxygen). The heat treatment time of the first calcination process may be in the range of about 5 hours to about 30 hours. In another embodiment of the present disclosure, before the first calcination process, a preliminary calcination process may be additionally performed at a temperature of about 150°C to about 800°C.

[0176] The first calcination process may form first particles PTC1 ( Figure 7 ) from a mixture including the precursor, the lithium source, and the dopant source. The dopant source and the first calcination process may be controlled so that the first particles PTC1 have a secondary particle shape as shown in Figure 7 . In an embodiment, the synthesized first particles PTC1 may be subjected to a grinding process. The ground first particles PTC1 may have a first average particle diameter APD1 discussed in Figure 6 .

[0177] The first particles PTC1 ( Figure 7)Perform the first coating process (S300). In an embodiment, the first coating process may be a wet coating process. The first coating process may include coating the first particulate PTC1 with cobalt (Co).

[0178] For example, the first particulate PTC1( Figure 7 ) may be mixed with a first coating raw material. The first particulate PTC1 and the first coating raw material may be added to a solvent (e.g., distilled water) and mixed together. The first coating raw material may be a cobalt compound. For example, the cobalt compound may include cobalt oxide, but the present disclosure is not limited thereto. The first particulate PTC1 and the first coating raw material may be mixed together using a stirrer. The first particulate PTC1 and the first coating raw material may be filtered and dried.

[0179] The first coating process may form a first coating CTL1 on the surface of the first particulate PTC1( Figure 7 ), and may also form a grain boundary coating GCL( Figure 8 ) inside the first particulate PTC1. For example, a wet coating process may be used to form the grain boundary coating GCL appropriately or satisfactorily.

[0180] The dried first particulate PTC1( Figure 7 ) may be subjected to a second coating process (S400). In an embodiment, the second coating process may be a dry coating process. The second coating process may include coating the first particulate PTC1 with zirconium (Zr).

[0181] For example, the first particulate PTC1( Figure 7 ) and a second coating raw material may be mixed together without a solvent. The first particulate PTC1 and the second coating raw material may be added to a dry coater, and then stirred and mixed together. The second coating raw material may be a zirconium compound. The zirconium compound may include zirconium oxide, but the present disclosure is not specifically limited thereto.

[0182] The first particulate PTC1( Figure 7 ) that has undergone the second coating process may be added to a furnace, and a second calcination process (S500) may be performed at a second temperature. The second temperature may be in the range of about 150 °C to about 800 °C. The second temperature may be less than the first temperature of the first calcination process. The second calcination process may be performed in an oxidizing atmosphere (such as air and / or oxygen).

[0183] The second calcination process may form a first coating CTL1( Figure 7 ) from the cobalt compound and the zirconium compound provided on the first particulate PTC1( Figure 8 ). The grain boundary coating GCL( Figure 7 ) may be formed from the cobalt compound provided to the grain boundary GRB( Figure 8)。The first coating process initially forms the first coating CTL1 and the grain boundary coating GCL, and their complete crystallization occurs after the second calcination process.

[0184] The amount of cobalt in the first coating CTL1 ( Figure 8 ) can be less than the amount of cobalt in the grain boundary coating GCL ( Figure 8 ). The amount of zirconium in the first coating CTL1 can be greater than the amount of zirconium in the grain boundary coating GCL. This may be because the second coating process is carried out as a drying process, so it is difficult to supply the zirconium compound to the grain boundaries GRB ( Figure 7 ) inside the first particles PTC1 ( Figure 7 ).

[0185] The second particles PTC2 ( Figure 7 ) can be formed by a method similar to the method used to form the first particles PTC1 ( Figure 7 ). Precursors of the first particles PTC1 and the second particles PTC2 are produced using different methods. However, the processes after the production of the precursors are very similar. The precursor of the second particles PTC2 can be formed to have an average particle size smaller than the average particle size of the precursor of the first particles PTC1. In an embodiment, the first calcination process for forming the second particles PTC2 may not include a dopant source, and a flux may be used instead of the dopant source.

[0186] The first particles PTC1 ( Figure 7 ) and the second particles PTC2 ( Figure 6 ) can be mixed together to manufacture a positive electrode active material according to some embodiments of the present disclosure. In an embodiment, the first particles PTC1 and the second particles PTC2 can be mixed together in a weight ratio of about 95:5 to about 50:50. The first particles PTC1 and the second particles PTC2 can be mixed together in a weight ratio of about 5:95 to about 50:50. Since the first particles PTC1 are mixed with the second particles PTC2 having an average particle size different from the average particle size of the first particles PTC1, a positive electrode active material having a bimodal shape can be prepared. In an embodiment, the second particles PTC2 can be omitted.

[0187] In addition to using the positive electrode active material according to some embodiments of the present disclosure, the positive electrode active material layer AML1 ( Figure 1 ) can be manufactured by a common manufacturing method. For example, the first particles PTC1 ( Figure 7 ) of the present disclosure, the second particles PTC2 ( Figure 7 ), the binder BND ( Figure 6 ) and the conductive material CDM ( Figure 6 ) (for example, the conductive material CDM ( Figure 6)) can be dissolved and / or dispersed in a solvent to produce a mixture. The binder BND and the conductive material CDM can be the same as those in the positive electrode active material layer AML1 discussed above. The mixture can be coated on the positive electrode current collector COL1 ( Figure 6 ) and then can be dried and pressed to produce the positive electrode 10 ( Figure 1 ). Figure 1 )

[0188] The solvent can be any suitable solvent commonly used in the art. For example, it can include at least one selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, and any combination thereof.

[0189] In an embodiment, the mixture can be cast on a certain support to produce a film or the positive electrode active material layer AML1. The positive electrode 10 can be produced by laminating the positive electrode active material layer AML1 on the positive electrode current collector COL1.

[0190] In this document, the subject matter of the present disclosure will be described in more detail with reference to some embodiments. The following embodiments are provided for illustrative purposes only and should not be construed as limiting the scope of the present disclosure.

[0191] Embodiment 1: Manufacture of Positive Electrode Active Material

[0192] Preparation 1: Manufacture of Large Particle Precursor

[0193] The co-precipitation method is used to manufacture the large particle precursor. The nickel-based metal hydroxide (Ni 0.90 Co 0.07 Al 0.03 (OH)2) is used as the large particle precursor.

[0194] Nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and aluminum sulfate (Al2(SO4)3·H2O) with a molar ratio of 90:7:3 are used as raw materials for the nickel-based metal hydroxide and dissolved in distilled water as the solvent to prepare a metal raw material mixture solution. Dilute ammonia water (NH4OH) solution and sodium hydroxide (NaOH) as the precipitating agent are prepared to form a composite compound. Then, the metal raw material mixture solution, ammonia water, and sodium hydroxide are added to the reactor. Sodium hydroxide is added to the reactor to maintain the pH of the mixture in the reactor. The reaction is carried out for about 20 hours while stirring the mixture in the reactor.

[0195] The slurry solution in the reactor is filtered and rinsed with high-purity distilled water. The rinsed material is dried in a hot air oven at 190 °C for 24 hours to obtain a large particle precursor (Ni 0.90 Co0.07 Al 0.03 (OH)2) powder.

[0196] Preparation 2: Manufacture of large-particle lithium composite oxide

[0197] The large-particle precursor of Preparation 1, anhydrous lithium hydroxide (LiOH), and boric acid (H3BO3) are dry-mixed together using a Henschel mixer. Lithium, transition metals, and boron are mixed together in a molar ratio of approximately 1:1:0.01. The transition metals refer to the total sum of the transition metals included in the large-particle precursor (Ni + Co + Al). The mixture is heat-treated in an oxygen atmosphere at approximately 800 °C for 10 hours (first calcination process) to synthesize the first particles or the first lithium composite oxide. The first particles are ground using a jet mill under a pressure of 3 bar.

[0198] Cobalt oxide corresponding to 3 mol% of the total sum of the transition metals in the first particles is added to perform a wet coating process (first coating process). The first particles coated with cobalt are dried at 150 °C for 12 hours. After the first particles are dried, zirconium oxide corresponding to 0.1 mol% of the total sum of the transition metals in the first particles is added to perform a dry coating process (second coating process). The first particles coated with zirconium are heat-treated in an oxygen atmosphere at approximately 700 °C for 15 hours (second calcination process). Thus, the positive electrode active material is obtained.

[0199] Embodiment 2: Manufacture of rechargeable lithium battery

[0200] 96 g of the positive electrode active material of Embodiment 1, 2 g of polyvinylidene fluoride, 47 g of N-methylpyrrolidone as a solvent, and 2 g of carbon black as a conductive material (e.g., electrically conductive material) are mixed together to manufacture an active material slurry.

[0201] The active material slurry is coated on an aluminum film using a doctor blade to form a thin electrode plate. The thin electrode plate is dried at 135 °C for 3 hours or longer, and then compressed and vacuum-dried to form a positive electrode.

[0202] The positive electrode and a lithium metal counter electrode are used to manufacture a 2032-type coin cell single body. A separator formed of a porous polyethylene (PE) film (having a thickness of approximately 16 μm) is inserted between the positive electrode and the lithium metal counter electrode. An electrolyte is introduced to manufacture a 2032-type coin cell single body. The electrolyte is a solution in which 1.1 M of LiPF6 is dissolved in a solvent (where ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed together in a volume ratio of 3:5).

[0203] Comparative Example 1: Manufacture of positive electrode active material

[0204] The positive electrode active material is manufactured in substantially the same method as that of Embodiment 1, except that the first coating process, the second coating process, and the second calcination process are omitted in Preparation 2.

[0205] Evaluation Example 1: Internal Shape Analysis (SEM) of Positive Electrode Active Material

[0206] After sampling the internal cross section of the positive electrode active material produced in Embodiment 1, the internal cross section of the positive electrode active material was captured with a scanning electron microscope (SEM) to perform internal shape analysis. Thus, the arrangement of primary particles within the first particle was analyzed.

[0207] S-4800 from Hitachi and Magellan 400L from FEI were used as scanning electron microscopes. Sample cross sections were pre-treated using IM4000PLUS from Hitachi at 6 kV and 320 μA for 1 hour. Scanning electron microscope analysis was performed at 3 keV to 30 keV.

[0208] Figure 13A , Figure 13B and Figure 13C The SEM image of the cross section of the first particle of Embodiment 1 is shown. Figures 13A - 13C , can be found on the surface of the first particle as Figure 8 Radially structured first primary particles PRP1 and second primary particles PRP2 are shown in FIG. It can be determined that the first primary particles PRP1 have a high orientation in the radial direction RD, and the second primary particles PRP2 have a low orientation in the radial direction RD.

[0209] Figure 14A and Figure 14B SEM images showing cross sections of the first particles of Embodiment 1 and the first particles of Comparative Example 1 are shown respectively. Figure 14A , can be found on the surface of the first particle as Figure 8 The radially structured first primary particles PRP1 and second primary particles PRP2 are shown in FIG. Figure 14B , only the following can be found Figure 10 For example, it can be determined that the second primary particle PRP2 ( Figure 8 ).

[0210] exist Figure 14A The first primary particle PRP1 ( Figure 8 ) was measured to have an average aspect ratio of about 8. The average aspect ratio of the second primary particles PRP2 shown in the SEM image was measured to have an average aspect ratio of about 2.

[0211] Evaluation Example 2: Analysis of Internal Composition and Porosity of Positive Electrode Active Material

[0212] The nickel amount and the cobalt amount in the shell of the first particle were measured by SEM analysis performed in Evaluation Example 1 and energy dispersive X-ray spectroscopy (EDS) performed together with the SEM analysis, and the Ni amount in the shell relative to the total amount of Ni and Co was calculated. SEM-EDS analysis was performed at a targeted depth of 500 nm of the exposed surface of the cross section taken along the central portion of the particle. In addition, the porosity of the first particle was measured by SEM image analysis of the particle cross section. The results are listed in Table 1 below, and the porosity / total average porosity of the core is calculated. Figure 15A and Figure 15B These are an image showing the porosity of the first particles of Embodiment 1 and an image showing the porosity of the first particles of Comparative Example 1, respectively.

[0213] Table 1

[0214]

[0215] Refer to Table 1 and Figure 15A and Figure 15B , it can be found that the first particle of Comparative Example 1 has a relatively large amount of Ni in the shell. The low Ni / (Ni+Co) ratio of Embodiment 1 in Table 1 (i.e., the amount of Ni in the shell relative to the total amount of Ni and Co) indirectly indicates that the amount of Co is relatively high. In contrast, it can be found that the first particle of Embodiment 1 has a relatively small amount of Ni in the shell. For example, the first particle of Embodiment 1 has a relatively large amount of Co in the shell. It can be determined that the first particle of Embodiment 1 has a relatively large core porosity and a relatively small shell porosity. In this sense, it can be determined that the first particle of Embodiment 1 includes a porous core and a dense shell. It can be determined that the first particle of Comparative Example 1 has a relatively large core porosity and also has a relatively large shell porosity. In this sense, it can be determined that the first particle of Comparative Example 1 has a porous core and a porous shell. Because the aforementioned atypically shaped second primary particle PRP2 ( Figure 7 ) constitutes the first particle PTC1 of Embodiment 1 ( Figure 7 ) shell, so the shell of the first particle PTC1 of embodiment 1 may have a reduced porosity. This can be seen from the reference Figure 9A and Figure 9B Found in the description.

[0216] Evaluation Example 3: Analysis of Shell / Surface Composition and Porosity of Positive Electrode Active Material

[0217] Figure 16A This is an image showing the cobalt element in the first particles of Embodiment 1 by SEM-EDS analysis performed in Evaluation Example 2. In addition, Figure 16BAn image showing the zirconium element in the first particles of Embodiment 1 is presented by energy dispersive X-ray spectroscopy (EDS) analysis using a transmission electron microscope (TEM). TEM-EDS analysis was performed using a Titan Cubed G2 60-300 from FEI Company and a Spectra 300 from Thermo Fisher Scientific.

[0218] Reference Figure 16A , it was determined that cobalt exists in the form of a coating on the surface of the first particles. It was also determined that cobalt exists in the form of a grain boundary coating on the grain boundaries inside the first particles. Reference Figure 16B , it was determined that zirconium exists in the form of a coating on the outer periphery of the surface of the first particles except for the inside.

[0219] Evaluation Example 4: Analysis of the Coating of the Positive Electrode Active Material

[0220] The SEM-EDS analysis performed in Evaluation Example 2 was used to measure and compare the amounts of transition metals (Ni, Co, and Al) in the shell and core of the first particles of Embodiment 1. The results are plotted in Figures 17A - 17C .

[0221] Reference Figures 17A - 17C , the core and shell of the first particles have almost the same amount of aluminum (Al) of approximately 1.5 at%. It was observed that the amount of Ni in the core of the first particles is greater than the amount of Ni in the shell of the first particles. It was observed that the amount of Co in the core of the first particles is less than the amount of Co in the shell of the first particles. This may be due to the fact that the first particles of Embodiment 1 are coated with a cobalt layer, which is appropriately or satisfactorily formed on the particle surface and on the grain boundaries adjacent to the particle surface, so the amount of Co in the shell relatively increases. It was also observed that the Co coating is difficult to penetrate to the core of the first particles.

[0222] The SEM-EDS and TEM-EDS analyses performed in Evaluation Example 3 were used to measure the amounts of cobalt and zirconium relative to the total amount of lithium and transition metals in the surface (or shell) of the first particles of Embodiment 1, and the results are listed in Table 2 below.

[0223] Table 2

[0224]

[0225] Referring to Table 2, it can be seen that in the positive electrode active material of Embodiment 1, the surface coating has a relatively large amount of cobalt and a relatively small amount of zirconium. It can also be seen that the ratio of the amount of cobalt to the amount of zirconium is relatively large.

[0226] Evaluation Example 5: HR-TEM Analysis of the Surface of the Positive Electrode Active Material

[0227] A high-resolution transmission electron microscope (HR-TEM) was used to measure the thickness of the disordered layer on the surface of the first particles of Embodiment 1 and the first particles of Comparative Example 1. The results are illustrated in Figure 18A and Figure 18B .

[0228] Referring to Figure 18B , it can be determined that, in the case of the first particles of Comparative Example 1, the surface disordered layer has a relatively large thickness of 1.91 nm to 5.28 nm. Referring to Figure 18A , it can be determined that, in the case of the first particles of Embodiment 1, the surface disordered layer has a relatively small thickness of 0.89 nm to 3.71 nm. In this sense, the first particles of Embodiment 1 may have relatively small surface defects, and the positive electrode active material may increase performance and lifespan.

[0229] Evaluation Example 6: XRD Analysis of Positive Electrode Active Material

[0230] The positive electrode active material manufactured in Embodiment 1 was subjected to XRD analysis, and the results are plotted in Figure 19 . Figure 19 The XRD analysis results of the positive electrode active material manufactured in Comparative Example 1 are also shown in

[0231] Referring to Figure 19 , the peak intensity ratio (I(003) / I(104)) of the main peak of the (003) plane to the secondary peak of the (104) plane was obtained from the XRD spectrum, and the full width at half maximum (FWHM) with respect to the (003) plane was obtained from the XRD spectrum. The FWHW was used to calculate the grain size. It can be determined that the first particles of Embodiment 1 have a grain size of 85.0 nm. It can be determined that I(003) / I(104) of Embodiment 1 is relatively large, and the orientation of the (003) plane is increased.

[0232] As a result, the positive electrode active material of Embodiment 1 may have high structural stability, and thus can stably intercalate and deintercalate lithium ions to increase lifespan characteristics.

[0233] Evaluation Example 7: Measurement of the Angle between the Radial Direction and the a-Axis of the Primary Particles Included in the Positive Electrode Active Material

[0234] A high-resolution transmission electron microscope (HR-TEM) was used to measure the core and shell of the first particles of Embodiment 1, and the results are shown in Figure 20 and Figure 21 . Referring to Figure 20 , the first primary particles constituting the core of the first particles of Embodiment 1 can be determined. The angle between the radial direction and the a-axis of the first primary particles was measured to be approximately 0°. For example, it can be determined that the radial direction and the a-axis of the first primary particles are substantially parallel to each other.

[0235] Reference Figure 21 The angle between the radial direction and the a-axis of the second primary particles that form the shell of the first particles of Embodiment 1 changes differently. For example, the angle between the radial direction and the a-axis of one second primary particle is measured to be about 21°, but the angle between the radial direction and the a-axis of another second primary particle is measured to be about 42°. In this sense, the a-axis direction of the second primary particles is random.

[0236] Evaluation Example 8: Life Characteristics of Rechargeable Lithium Batteries

[0237] The capacity retention rate of the 2032 coin cell of Embodiment 2 was evaluated by using a charge-discharge machine (Model: TOYO-3100 manufactured by TOYO Corporation).

[0238] The 2032 coin cell assembled for evaluating the initial capacity (initial charge capacity, initial discharge capacity) and the ratio of the initial discharge capacity to the initial charge capacity as the initial efficiency characteristic was charged at a constant current of 0.2C at 25°C until the voltage reached 4.3V, then charged at a constant voltage until the current reached 0.05C, and the fully charged cell was left for about 10 minutes, and then discharged at a constant current of 0.2C until the voltage reached 3V. To evaluate the capacity retention rate of repeated charge and discharge, the 2032 coin cell was charged at a constant current of 1C at 45°C until the voltage reached 4.4V, then charged at a constant voltage until the current reached 0.05C, and the fully charged cell was left for about 10 minutes, and then discharged at a constant current of 1C until the voltage reached 3V, and this charge and discharge cycle was repeated 60 times.

[0239] A 2032 coin cell was manufactured in the same manner as Embodiment 2 by using the positive electrode active material of Comparative Example 1. The 2032 coin cell of Comparative Example 1 was evaluated by the same method as discussed above. The results are listed in Table 3.

[0240] Table 3

[0241]

[0242]

[0243] Referring to Table 3, it can be seen that the capacity retention rate (or life characteristics) of Comparative Example 1 is much smaller than that of Embodiment 1. In the case of Comparative Example 1, it can be considered that Figure 10 the non-uniformity of the coating and the morphology of the first particles as shown in Figure 7The particle morphology and uniform coating shown in [the figure] result in a reduced resistance and an increased particle stability, thereby improving the high-temperature long-life characteristics.

[0244] The positive electrode active material according to an embodiment of the present disclosure may include radially structured first primary particles and second primary particles having an atypical shape provided at one end of the first primary particles. The morphology of the positive electrode active material may enable the positive electrode active material to have a uniform (or substantially uniform) coating, which may improve the structural stability. The positive electrode active material according to the present disclosure may prevent or reduce the occurrence of internal cracks due to shrinkage and expansion, so that the rechargeable lithium battery may improve the charge capacity / discharge capacity and the life characteristics.

[0245] Although the subject matter of the present disclosure has been described in connection with the presently contemplated exemplary embodiments, it should be understood that the present disclosure is not limited to the disclosed embodiments, and is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the claims and their equivalents. Therefore, the foregoing embodiments should be understood as illustrative and not in any way limiting the present disclosure.

Claims

1. A positive electrode active material, comprising: The first particle, wherein the first particle comprises a first lithium composite oxide, wherein the first lithium composite oxide is represented by Chemical Formula 1, Chemical Formula 1 Li a1 Ni x1 Ma 1-x1 O b1 , wherein, in Chemical Formula 1, a1 is 0.5 to 1.5, x1 is 0.6 to 0.99, b1 is 1.8 to 2.2, 1 - x1 is 0.01 to 0.4, and Ma represents at least one element selected from Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn, wherein the first particle comprises: first primary particles extending from the center of the first particle towards the surface of the first particle in the radial direction; and second primary particles on the surface of the first particle, wherein the aspect ratio of the first primary particles is 2 to 15, and wherein the aspect ratio of the second primary particles is 0.7 to 3.

2. The positive electrode active material according to claim 1, wherein the angle between the radial direction and the a-axis of the first primary particle is 0° to 5°.

3. The positive electrode active material according to claim 1, wherein the first primary particle comprises a (003) plane extending in the radial direction.

4. The positive electrode active material according to claim 1, wherein the first primary particle has a width in a direction intersecting the radial direction, and wherein the width of the first primary particle gradually increases in the radial direction.

5. The positive electrode active material according to claim 1, wherein the angle between the radial direction and the a-axis of the second primary particle is 10° to 80°.

6. The positive electrode active material according to claim 1, wherein the second primary particle is at one end of the first primary particle.

7. The positive electrode active material according to claim 1, wherein the first particle further comprises a third primary particle at the center of the first particle, wherein the first primary particles extend from the third primary particle towards the second primary particles, and wherein the aspect ratio of the third primary particles is 0.7 to 3.

8. The positive electrode active material according to claim 1, wherein the first particle comprises a core and a shell, wherein the amount of Ni in the core is greater than the amount of Ni in the shell, wherein the amount of Co in the shell is greater than the amount of Co in the core, and wherein the amount of Ni in the shell is 70 at% to 90 at% relative to the total amount of Ni and Co in the shell.

9. The positive electrode active material according to claim 1, wherein the first particle further comprises a first coating on the surface, wherein the first coating comprises cobalt and zirconium, wherein the amount of cobalt is 20 at% to 50 at% relative to the total amount of transition metals in the first coating, and wherein the amount of zirconium is 0.001 at% to 1 at% relative to the total amount of transition metals in the first coating.

10. The positive electrode active material according to claim 1, wherein the first particle comprises a core and a shell, and The ratio of the porosity of the core to the average porosity of the first particles is 1.5 to 2.

0.

11. The positive electrode active material according to claim 1, wherein the first particles have a first average particle size, and wherein the first average particle size is 6.0 μm to 20.0 μm.

12. The positive electrode active material according to claim 1, further comprising second particles, the second particles comprising a second lithium composite oxide, wherein the first average particle size of the first particles is greater than the second average particle size of the second particles, wherein the second lithium composite oxide is represented by Chemical Formula 2, Chemical Formula 2 Li a2 Ni x2 Mb 1-x2 Fl w2 O b2 , Among them, In Chemical Formula 2, a2 is 0.5 to 1.5, x2 is 0.6 to 0.99, b2 is 1.8 to 2.2, 1 - x2 is 0.01 to 0.4, w2 is 0.0005 to 0.01, Mb represents at least one element selected from Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn, and Fl represents at least one element selected from Zr, Sr, Y, La, Mo, Ce, Nb, and S.

13. The positive electrode active material according to claim 12, wherein the average size of the crystal grains of the second particles is greater than the average size of the first primary particles and the second primary particles.

14. A positive electrode active material, comprising: The first particles, the first particles comprising a first lithium composite oxide, wherein the first lithium composite oxide is represented by Chemical Formula 1, Chemical Formula 1 Li a1 Ni x1 Ma 1-x1 O b1 , wherein, in Chemical Formula 1, a1 is 0.5 to 1.5, x1 is 0.6 to 0.99, b1 is 1.8 to 2.2, 1 - x1 is 0.01 to 0.4, and Ma represents at least one element selected from Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn, wherein the first particles comprise: first primary particles extending from the center of the first particles toward the surface of the first particles in the radial direction; and second primary particles on the surface of the first particles, wherein the angle between the radial direction and the a-axis of the first primary particles is 0° to 5°, and wherein the angle between the radial direction and the a-axis of the second primary particles is 10° to 80°.

15. The positive electrode active material according to claim 14, wherein the first particles comprise: a first coating on the surface; and a grain boundary coating on the lateral surfaces of the first primary particles, wherein each of the first coating and the grain boundary coating comprises cobalt and zirconium, and wherein the ratio of the amount of cobalt to the amount of zirconium in the grain boundary coating is greater than the ratio of the amount of cobalt to the amount of zirconium in the first coating.

16. The positive electrode active material according to claim 14, wherein the length of the first primary particles in the radial direction is 400 nm to 3,000 nm.

17. The positive electrode active material according to claim 14, wherein the first particles have a first average particle diameter, and wherein the first average particle diameter is 6.0 μm to 20.0 μm.

18. The positive electrode active material according to claim 14, wherein the first particles include a core and a shell, wherein the amount of Ni in the core is greater than the amount of Ni in the shell, and wherein the amount of Co in the shell is greater than the amount of Co in the core.

19. The positive electrode active material according to claim 14, wherein the first particles include a core and a shell, wherein the ratio of the porosity of the core to the average porosity of the first particles is 1.5 to 2.

0.

20. A rechargeable lithium battery, comprising the positive electrode active material according to any one of claims 1 to 19.

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