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

Abstract

A positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same are provided, and for example, a positive electrode for a rechargeable lithium battery includes a positive electrode current collector, a first positive electrode active material layer on the positive electrode current collector, and a second positive electrode active material layer on the first positive electrode active material layer. The first positive electrode active material layer includes first particles having an olivine structure and second particles having a layered structure, and the second positive electrode active material layer includes third particles having an olivine structure. The first particle is a single particle, the third particle is in the form of a secondary particle in which a plurality of third primary particles are aggregated, and the average particle size of the second particle is greater than the average particle size of each of the first particle and the third particle.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2024-0057048, filed on April 29, 2024, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Embodiments of this disclosure relate to positive electrode active materials for rechargeable lithium batteries, positive electrodes including the same, and rechargeable lithium batteries including the positive electrodes, and for example, to positive electrode active materials including olivine-based lithium compounds, positive electrode active materials including layered lithium compounds, positive electrodes including the same, and rechargeable lithium batteries including the same. Background Technology

[0004] The recent rapid proliferation of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, has driven a dramatic increase in demand for rechargeable lithium-ion batteries with high energy density and capacity. Consequently, extensive research efforts have been undertaken to improve the performance of rechargeable lithium-ion batteries.

[0005] A rechargeable lithium battery includes a positive electrode and a negative electrode, each of which includes an active material and an electrolyte that allow lithium ions to be inserted into and extracted, and generates electrical energy through redox reactions that occur when lithium ions are inserted into or extracted from the positive and negative electrodes. Summary of the Invention

[0006] Embodiments of this disclosure provide economical positive electrode active materials that have high energy density, high average voltage and excellent lifetime.

[0007] Embodiments of this disclosure also provide an economical positive electrode that has high energy density, high average voltage and excellent lifetime.

[0008] Embodiments of this disclosure provide a positive electrode for a rechargeable lithium battery, comprising: a positive electrode current collector, a first positive electrode active material layer on the positive electrode current collector, and a second positive electrode active material layer on the first positive electrode active material layer.

[0009] The first positive electrode active material layer may include a first particle represented by Formula 1 and having an olivine structure, and a second particle represented by Formula 2 and having a layered structure, and the second positive electrode active material layer may include a third particle represented by Formula 3 and having an olivine structure. In this document, "the first particle represented by Formula 1 and having an olivine structure" means "the composition of the first particle is a compound represented by Formula 1, and the first particle has an olivine structure," and similar descriptions of the second particle, third particle, etc., should be understood in the same way.

[0010] The first particles may be in the form of single particles, the third particles may be in the form of secondary particles in which a plurality of third primary particles are aggregated, and the average particle diameter of the second particles may be greater than the average particle diameter of each of the first particles and the third particles.

[0011] Formula 1

[0012] Li a1 Mn z1 Fe x1 B1 y1 PO 4-c1

[0013] In Formula 1 above, B1 may be at least one element selected from the group consisting of Al, Ti, V, and Mg, and may satisfy 0.8 < a1 ≤ 1.2, 0.4 ≤ z1 ≤ 0.8, 0.2 ≤ x1 ≤ 0.6, 0 ≤ y1 ≤ 0.05, 0 ≤ c1 ≤ 0.05, and x1 + y1 + z1 = 1.

[0014] Formula 2

[0015] Li a2 Ni x2 Co y2 Mn z2 B2 b2 O 2-c2

[0016] In Formula 2 above, B2 may be at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb, and may satisfy 0.8 ≤ a2 ≤ 1.2, 0.5 ≤ x2 ≤ 0.8, 0.0 ≤ y2 ≤ 0.10, 0.1 ≤ z2 ≤ 0.35, 0 ≤ b2 ≤ 0.1, 0 ≤ c2 ≤ 0.05, and x2 + y2 + z2 + b2 = 1.

[0017] Formula 3

[0018] Li a3 Mn z3 Fe x3 B3 y3 PO 4-c3

[0019] In Formula 3 above, B3 may be at least one element selected from the group consisting of Al, Ti, V, and Mg, and may satisfy 0.8 < a3 ≤ 1.2, 0.4 ≤ z3 ≤ 0.8, 0 ≤ x3 ≤ 0.6, 0 ≤ y3 ≤ 0.05, 0 ≤ c3 ≤ 0.05, and x3 + y3 + z3 = 1. Description of the Drawings

[0020] The accompanying drawings are included to provide a further understanding of the subject matter of this disclosure, and are incorporated in and form a part of this specification. The drawings illustrate embodiments of this disclosure and, together with the description, serve to explain the principles of those embodiments. In the drawings:

[0021] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present disclosure;

[0022] Figures 2-5 To illustrate a schematic diagram of a rechargeable lithium battery according to an embodiment, and Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown, and Figures 4-5 A pouch-type battery is shown;

[0023] Figure 6 A cross-sectional view of a positive electrode for a rechargeable lithium battery according to an embodiment of the present disclosure.

[0024] Figure 7 An enlarged view showing the first positive electrode active material layer of a rechargeable lithium battery according to an embodiment of the present disclosure;

[0025] Figure 8 An enlarged view showing the second positive electrode active material layer of a rechargeable lithium battery according to an embodiment of the present disclosure;

[0026] Figure 9 To illustrate a pair of scanning electron microscope (SEM) images of a first particle according to an embodiment of the present disclosure;

[0027] Figure 10 To illustrate a pair of SEM images of a second particle according to an embodiment of the present disclosure; and

[0028] Figure 11 To illustrate a pair of SEM images of a third particle according to an embodiment of the present disclosure. Detailed Implementation

[0029] The embodiments of this disclosure will be described clearly and in more detail below to the extent that those skilled in the art can readily implement it. To fully understand the layout and effects of the subject matter of this disclosure, exemplary embodiments of the disclosure will be described with reference to the accompanying drawings. However, it should be noted that the subject matter of this disclosure is not limited to the embodiments described below and can be implemented in various suitable forms and with various modifications. The embodiments provided herein are intended to make this disclosure thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0030] In this document, it will be understood that when a component is referred to as being on another component, the component may be directly on the other component, or an intervening third component may be present. In embodiments, the dimensions (e.g., thickness) of components may be enlarged in the accompanying drawings to effectively describe the technical content of this disclosure. The same reference numerals refer to the same elements throughout.

[0031] Unless otherwise indicated herein, singular expressions may include plural expressions. In implementation, unless otherwise indicated, the phrase "A or B" may indicate "A but not B", "B but not A", or "A and B". The terms "comprises", "includes", "including", and / or "comprising" as used in this specification do not exclude the presence or addition of one or more other components.

[0032] As used herein, the term "combination thereof" may refer to mixtures, stacks, complexes, copolymers, alloys, blends and / or reaction products of the components.

[0033] As used herein, the terms "particle size," "particle diameter," etc., refer to the average particle size if (e.g., when) the particles are spherical, and the average major axis length if (e.g., when) the particles are non-spherical. Unless otherwise specified herein, particle size may refer to the average particle size. In embodiments, particle size is defined as the average particle size (D...). 50 The average particle size (D) indicates the diameter of particles that constitute 50% of the total volume in the particle size distribution. 50 The average particle size (D) can be measured by any suitable method commonly used in the art, for example, by a particle size analyzer, transmission electron microscopy, and / or scanning electron microscopy. In one embodiment, the average particle size (D) can be obtained by measuring the object using a dynamic light scattering-based measuring device, performing data analysis, counting the number of particles for each particle size range, and then calculating the value therefrom. 50 ) value. In the implementation, the average particle size (D) 50 The particle size distribution can be measured using laser diffraction methods. In measurements using laser diffraction methods, for example, the target particles are dispersed in a dispersion solvent, and a commercially available laser diffraction particle size measurement device (e.g., the MT 3000 available from Microtrac, Ltd.) is introduced, irradiated with ultrasound at a power of 60 W and a frequency of approximately 28 kHz. The average particle size (D) based on 50% of the particle size distribution in the measurement device can then be calculated. 50 ).

[0034] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present disclosure is shown. (Reference) Figure 1A rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0035] The positive electrode 10 and the negative electrode 20 may be separated from each other by a diaphragm 30. The diaphragm 30 may be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20 and the diaphragm 30 may be in contact with the electrolyte ELL. The positive electrode 10, the negative electrode 20 and the diaphragm 30 may be immersed in the electrolyte ELL.

[0036] The electrolyte ELL can be used as a medium for transporting lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move towards the positive electrode 10 or the negative electrode 20 through the separator 30.

[0037] Positive electrode 10

[0038] The positive electrode 10 for a rechargeable lithium battery may include a positive electrode current collector COL1 (hereinafter, the "positive electrode current collector") and a positive electrode active material layer AML1 on the positive electrode current collector. The positive electrode active material layer AML1 may include a positive electrode active material and may further include a binder and / or a conductive material (e.g., an electrically conductive material). (Refer to...) Figure 6 A detailed description of the positive electrode active material layer AML1 according to embodiments of the present disclosure is provided. Al foil can be used as the positive electrode current collector COL1, but embodiments of the present disclosure are not limited thereto.

[0039] negative electrode 20

[0040] The negative electrode 20 for a rechargeable lithium battery may 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 may include a negative electrode active material and may further include a binder and / or a conductive material (e.g., an electrically conductive material).

[0041] For example, the negative electrode active material layer AML2 may include about 90 wt% to about 99.5 wt% of negative electrode active material, about 0.5 wt% to about 5 wt% of binder and about 0 wt% to about 5 wt% of conductive material.

[0042] The binder can be used to ensure good adhesion between the negative electrode active material particles and to the negative electrode current collector COL2. The binder may include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0043] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0044] The waterborne adhesive can be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0045] When an aqueous binder is used as a binder in the negative electrode active material layer AML2, it may further include a cellulose compound capable of imparting viscosity. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts. The alkali metal may include Na, K, or Li.

[0046] Dry adhesives can be fibrous polymer materials. For example, dry adhesives can be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0047] Conductive materials can be used to impart conductivity (e.g., electrical conductivity) to electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in rechargeable lithium batteries) and conducts electrons can be used in the battery. Non-limiting examples may include carbon-based materials such as natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials including copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0048] The negative electrode current collector COL2 may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0049] Negative electrode active material

[0050] The negative electrode active material in the negative electrode active material layer AML2 may include materials that can reversibly insert / deintercalate lithium ions, lithium metal, lithium metal alloys, materials that can be doped / dedoped with lithium, or transition metal oxides.

[0051] Materials capable of reversibly inserting / deintercalating lithium ions may include carbon-based negative electrode active materials, such as, for example, crystalline carbon, amorphous carbon, or combinations thereof. Examples of crystalline carbon may be graphite, such as irregular, tabular, flake, spherical, or fibrous natural or artificial graphite, and examples of amorphous carbon may be soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbides, calcined coke, etc.

[0052] The lithium metal alloy includes an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0053] The material capable of doping / dedoping lithium can be a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material can include silicon, silicon-carbon composite, SiO x (0 < x ≤ 2), Si-Q alloy (where Q can be selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof). The Sn-based negative electrode active material can include Sn, SnO x (0 < x ≤ 2) (e.g., SnO2), Sn-based alloy, or a combination thereof.

[0054] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to an embodiment, the silicon-carbon composite can be in the form of silicon particles and an amorphous carbon coating on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) that aggregate primary silicon particles and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon can also be between the primary silicon particles, and, for example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0055] The silicon-carbon composite can further include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core.

[0056] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0057] Separator 30

[0058] According to the type of the rechargeable lithium battery, the separator 30 can be present between the positive electrode 10 and the negative electrode 20. The separator 30 can include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer film of two or more layers thereof, such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.

[0059] The separator 30 can include a porous substrate and a coating on one or both surfaces of the porous substrate, and the coating includes an organic material, an inorganic material, or a combination thereof.

[0060] The porous substrate may be a polymer film formed from any one of the following polymers or copolymers or mixtures thereof: polymers polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon).

[0061] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers.

[0062] Inorganic materials may include, but are not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and combinations thereof.

[0063] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked.

[0064] Electrolyte ELL

[0065] Electrolytes (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0066] Non-aqueous organic solvents can be used as media for transporting ions that participate in the electrochemical reactions of a battery.

[0067] Non-aqueous organic solvents may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0068] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), etc.

[0069] Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, caprolactone, etc.

[0070] Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include: nitrile solvents (such as R-CN, where R is a C2-C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether bonds, etc.); amides (such as dimethylformamide); dioxolane (such as 1,3-dioxolane, 1,4-dioxolane, etc.); sulfolane, etc.

[0071] Non-aqueous organic solvents can be used alone or in combination of two or more.

[0072] In addition, when using carbonate solvents, cyclic carbonates and chain carbonates can be mixed and used, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0073] Lithium salts dissolved in non-aqueous organic solvents supply lithium ions in batteries, ensuring basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2 (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0074] Rechargeable lithium batteries

[0075] Rechargeable lithium batteries can be classified according to their shape as cylindrical, prismatic, pouch, or coin-shaped batteries, etc. Figures 2-5 A schematic diagram illustrating a rechargeable lithium battery according to an embodiment. Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown, and Figure 4 and Figure 5 A pouch-type battery is shown. (Reference) Figures 2-5The rechargeable lithium battery 100 may include an electrode assembly 40 (including a separator 30 between a positive electrode 10 and a negative electrode 20) and a housing 50 (in which the electrode assembly 40 is housed). The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 2 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of a sealed housing 50. Figure 3 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include electrode terminals 70, which may be, for example, a positive electrode terminal 71 and a negative electrode terminal 72, serving as an electrical path for guiding the current generated in the electrode assembly 40 to the outside of the battery.

[0076] As a non-limiting example, the rechargeable lithium battery according to the embodiments can be used in automobiles, mobile phones and / or various types of electronic devices.

[0077] Figure 6 A cross-sectional view of the positive electrode for a rechargeable lithium battery according to an embodiment of the present disclosure is shown. (Reference) Figure 6 As described above, the positive electrode 10 for a rechargeable lithium battery may include a positive electrode current collector COL1 (see above). Figure 1 ) and the positive electrode active material layer AML1 (see Figure 1 The positive electrode active material layer AML1 may include a first positive electrode active material layer ATL1 and a second positive electrode active material layer ATL2 (hereinafter referred to as the "second positive electrode active material layer") stacked on the first positive electrode active material layer ATL1 (hereinafter referred to as the "first positive electrode active material layer").

[0078] The following sections will describe each of the first positive electrode active material layer ATL1 and the second positive electrode active material layer ATL2 in more detail.

[0079] First positive electrode active material layer ATL1

[0080] Figure 7 An enlarged view showing the first positive electrode active material layer ATL1 of the positive electrode for a rechargeable lithium battery according to an embodiment of the present disclosure.

[0081] The first positive electrode active material layer ATL1 may include a first particle PTC1 (hereinafter referred to as "first particle"), a second particle PTC2 (hereinafter referred to as "second particle" or "SP"), and a first functional additive ADD1. The first functional additive ADD1 may include a first binder BND1 and a first conductive material CDM1 (e.g., a first electrical conductivity material CDM1).

[0082] The first adhesive BND1 can bond (e.g., bond together) the first particle PTC1 and the first conductive material CDM1. In an embodiment, the first adhesive BND1 can stably fix the first positive electrode active material layer ATL1 to the positive electrode current collector COL1. For example, the first adhesive BND1 may include at least one selected from the group consisting of: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, and nylon, but is not limited thereto.

[0083] The first conductive material CDM1 can be used to improve the conductivity (e.g., electrical conductivity) of the first positive electrode active material layer ATL1. Any suitable conductive material that does not cause chemical changes (e.g., does not cause undesirable chemical changes) in the first positive electrode active material layer ATL1 can be used as the first conductive material CDM1 without limitation. For example, the first conductive material CDM1 may include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers and / or carbon nanotubes; metallic materials including copper, nickel, aluminum, silver, etc., in the form of metal powders and / or metal fibers; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0084] The following will describe in more detail each of the first particles PTC1 and the second particles PTC2 in the first positive electrode active material layer ATL1.

[0085] First PTC1

[0086] The first particle PTC1 may include an olivine-based lithium compound represented by Formula 1 below.

[0087] Formula 1

[0088] Li a1 Mn z1 Fe x1 B1 y1 PO 4-c1

[0089] In Equation 1 above, 0.8 < a1 ≤ 1.2, 0.4 ≤ z1 ≤ 0.8, 0.2 ≤ x1 ≤ 0.6, 0 ≤ y1 ≤ 0.05 (for example, 0.001 ≤ y1 ≤ 0.05), and 0 ≤ c1 ≤ 0.05 can be satisfied. B1 can be at least one element selected from the group consisting of Al, Ti, V, and Mg. B1 can be a dopant doped into the first particle PTC1. For example, B1 can be Ti.

[0090] The first particle PTC1 can further include a carbon element derived from the above positive electrode active material layer AML1. The first particle PTC1 can have a carbon element content of about 0.5 wt% to about 5 wt%, about 0.5 wt% to about 3 wt%, or about 0.5 wt% to about 2 wt%.

[0091] The first particle PTC1 can be in the form of a single particle. Herein, the term single particle can indicate a single type (or class) of particle without grain boundaries inside it. A single particle can indicate a single particle that exists as an independent phase morphologically (where the particles do not aggregate with each other), a particle with an integral structure, a particle with a one-piece structure, or a non-aggregated particle. For example, a single particle can be a single crystal. In an embodiment, a single particle can be a particle including several crystals. A single particle can be in a separated form. In an embodiment, a single particle can be in a form in which about 2 to about 100 first primary particles are attached to each other.

[0092] The first particle PTC1 can be a nano-morphology positive electrode active material. The first particle PTC1 can include at least one first primary particle. In an embodiment, the first particle PTC1 can be in the shape of a sphere or an ellipsoid in which the first primary particles are aggregated (for example, can be substantially spherical or substantially oval). For another example, even if the first primary particles are aggregated, the first particle PTC1 may not have a spherical shape but an irregular shape.

[0093] In an embodiment, the average particle size (D 50 ) can indicate the particle size at which the cumulative volume in the particle size distribution is about 50% by volume. In an embodiment, the average particle size (D 50 ) of the first particle PTC1 can be a value measured using a particle size analyzer.

[0094] In an embodiment, the first particle PTC1 can have an average particle size of about 500 nm to about 5 μm, about 100 nm to about 3 μm, about 500 nm to about 2.5 μm, or about 1 μm. The average particle size (D 50 ) of the first particle PTC1 can be smaller than the average particle size (D 50 ) of the second particle PTC2, which will be further described below.

[0095] The size of at least one first primary particle constituting the first particle PTC1 can be measured using a scanning electron microscope (SEM). In an embodiment, the size of the first primary particle can indicate the diameter measured by randomly selecting approximately 30 first primary particles from an electron micrograph of the positive electrode active material. The size of the first primary particle can be uniform (e.g., substantially uniform). At least one first primary particle constituting the first particle PTC1 can have a size of approximately 100 nm to approximately 200 nm, approximately 50 nm to approximately 150 nm, approximately 50 nm to approximately 100 nm, approximately 100 nm to approximately 150 nm, or approximately 200 nm to approximately 300 nm. The first primary particle can have a smaller average size than the second primary particle NNP_2, which will be further described below.

[0096] The first particle PTC1 may include at least one primary particle (or a single particle). The size of the at least one first primary particle constituting the first particle PTC1 can be measured using a scanning electron microscope (SEM). In an embodiment, the size of the first primary particle may indicate the diameter measured by randomly selecting about 30 first primary particles from an electron micrograph of the positive electrode active material. The size of the first primary particle may be uniform (e.g., substantially uniform).

[0097] In an embodiment, the first PTC1 particle may include a coating on its surface. The coating may completely cover the surface of the first PTC1 particle or may partially cover the surface of the first PTC1 particle. For example, the coating may include elemental carbon and / or carbon-containing compounds. The coating may further include at least one selected from the group consisting of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds. The metal-containing compounds (such as titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds) may be, for example, metal oxides, metal hydroxides, metal carbonates, complexes thereof, or mixtures thereof. The metal-containing compounds may further include other metallic elements and / or non-metallic elements. For example, the metal-containing compounds may further include lithium. Due to the coating, the first PTC1 particle may have improved structural stability and electrical conductivity.

[0098] In one embodiment, the first particle PTC1 may include secondary particles in which at least two first primary particles are aggregated, and the first particle PTC1 may further include a grain boundary coating on the surface of each first primary particle. The grain boundary coating may be present inside the first particle PTC1. The grain boundary coating may be present along the interface between the first primary particles inside the first particle PTC1. For example, the grain boundary coating may refer to a layer of material formed by coating on the grain boundaries inside the first particle PTC1.

[0099] The grain boundary coating may include elemental carbon and / or carbon-containing compounds. The grain boundary coating may further include at least one selected from the group consisting of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds.

[0100] The interior of the first particle PTC1 can refer to the entire interior of the first particle PTC1 excluding its surface. For example, the interior of the first particle PTC1 can refer to the entire interior from a depth of about 10 nm relative to the surface of the first particle PTC1, or a region of the interior from about 10 nm to a depth of about 2 μm relative to the surface of the first particle PTC1.

[0101] The first PTC1 particle further includes a grain boundary coating, thus exhibiting greater structural stability and a uniform (e.g., substantially uniform) coating formed on its surface. In an embodiment, the first PTC1 particle further includes a grain boundary coating, thus exhibiting further improved electrical conductivity.

[0102] The first PTC1 particle may further include carbon elements derived from the aforementioned coating and / or grain boundary coating. The first PTC1 particle may have a carbon content of about 0.5 wt% to about 10 wt%, about 1 wt% to about 3 wt%, or about 1.5 wt% to about 2.5 wt%. For example, if in the form of secondary particles, the first PTC1 particle may have a higher carbon content than the first PTC1 particle in the form of a single particle.

[0103] The first PTC1 particle may be in the shape of a sphere in which multiple first primary particles are aggregated (e.g., it may be substantially spherical). The first PTC1 particle, having tightly aggregated first primary particles, can therefore exhibit the following characteristics. The first particle retains the aforementioned coating and / or grain boundary coating well, thus exhibiting higher electrical conductivity and improved low-temperature characteristics. Due to the increased adhesion of the electrode plate, the amount of binder can be reduced (e.g., the amount of binder used can be reduced). The first PTC1 particle may be in the shape of a sphere or an ellipsoid (e.g., it may be substantially spherical or substantially oval).

[0104] Second PTC2 particle

[0105] The second particle PTC2 may include a lithium compound with a layered structure represented by Formula 2 below.

[0106] Formula 2

[0107] Li a2 Ni x2 Co y2 Mn z2 B2 b2 O 2-c2

[0108] In Equation 2 above, the following conditions must be met: 0.8 ≤ a² ≤ 1.2, 0.5 ≤ x² ≤ 0.8, 0.0 ≤ y² ≤ 0.10, 0.1 ≤ z² ≤ 0.35, 0 ≤ b² ≤ 0.1 (e.g., 0.01 ≤ b² ≤ 0.1), 0 ≤ c² ≤ 0.05, and x² + y² + z² + b² = 1. B² can be at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb. B² can be a dopant used to dope the second PTC2 particle. The dopant allows the second PTC2 particle to have increased surface and structural stability.

[0109] The second particle, PTC2, is a combination of high-capacity nickel (e.g., high-concentration nickel), thermal stability, and stable electrochemical properties of low-priced manganese and cobalt, and may include layered compounds with superior electrochemical properties.

[0110] The second PTC2 particle is a nickel-based active material and may include lithium-nickel composite oxides. In one embodiment, the second PTC2 particle may include a high-nickel positive electrode active material comprising a high nickel content. High-nickel positive electrode active materials can achieve high capacity and high performance. In another embodiment, the second PTC2 particle may include a medium-nickel positive electrode active material comprising a medium nickel content. Medium-nickel positive electrode active materials can achieve high capacity and high performance. Including the second PTC2 particle according to embodiments of this disclosure allows rechargeable lithium batteries to achieve high capacity and high energy density.

[0111] refer to Figure 7 The second particle PTC2 can be in the form of a single particle. Herein, a single particle can refer to a single type (or class) of particle without grain boundaries. A single particle can refer to a single particle that exists morphologically as an independent phase (where the particles do not aggregate), a particle with a monolithic structure, a particle with an integral structure, or a non-aggregated particle. For example, a single particle can be a single crystal. In embodiments, a single particle can be a particle comprising several crystals. A single particle can be in a separated form. In embodiments, a single particle can be in the form in which about 2 to about 100 second primary particles NNP_2 are attached to each other. Herein, the second particle PTC2 in the form of a single particle can be defined as small particles SP2 and / or fine particles SP2.

[0112] If the second particle PTC2 is a single particle, it may include at least one second primary particle. In one embodiment, the second particle PTC2 may be in the shape of a sphere or ellipsoid in which the second primary particles NNP_2 are aggregated (e.g., it may be generally spherical or generally oval). In another embodiment, even if the second primary particles NNP_2 are aggregated, the second particle PTC2 may not have a spherical shape, but rather an irregular shape. If the second particle PTC2 is in the form in which the second primary particles NNP_2 are aggregated, it may be less structured than a second particle PTC2 in a polycrystalline form, as will be further described below. This means that the second particle PTC2 may be in a more irregular form.

[0113] In the implementation method, the average particle size (D) 50 This indicates the particle size at which the cumulative volume in the particle size distribution is approximately 50% by volume. In this embodiment, the average particle size (D) of the second particle PTC2 is... 50 The value can be measured using a particle size analyzer. Small particles SP2 can have an average particle size (D) of approximately 2 μm to approximately 5 μm, approximately 1 μm to approximately 4 μm, approximately 2 μm to approximately 3 μm, approximately 3 μm to approximately 7 μm, approximately 4 μm to approximately 6 μm, or approximately 5 μm. 50 ).

[0114] refer to Figure 7 The second particle PTC2 is in a polycrystalline form and may include secondary particles in which at least two second primary particles NNP_2 are aggregated. For example, a second particle PTC2 may include multiple second primary particles NNP_2 aggregated together. The second particle PTC2 comprising multiple second primary particles NNP_2 may be in a spherical shape (e.g., substantially spherical), or even if the second primary particles NNP_2 are aggregated, it may have an irregular shape. In this document, the second particle PTC2 as a single particle may be defined as a large particle PC2.

[0115] In the implementation method, the average particle size (D) 50 This indicates the particle size at which the cumulative volume in the particle size distribution is approximately 50% by volume. In embodiments, the large particles PC2 may have an average particle size (D) of approximately 10 μm to approximately 20 μm, approximately 12 μm to approximately 15 μm, approximately 12 μm to approximately 18 μm, approximately 14 μm to approximately 18 μm, approximately 15 μm to approximately 20 μm, or approximately 16 μm. 50 Larger PC2 particles can have a larger average particle size (D) than smaller SP2 particles. 50 The number of second primary particles NNP_2 constituting large PC2 particles can be greater than the number of second primary particles NNP_2 constituting small SP2 particles. For example, large PC2 particles can be more dense and structured than small SP2 particles.

[0116] The second PTC2 particle may include both large PC2 particles and small SP2 particles. The second PTC2 particle may have an average particle size (D) of approximately 3 μm to approximately 20 μm, approximately 4 μm to approximately 15 μm, approximately 4 μm to approximately 10 μm, approximately 10 μm to approximately 20 μm, approximately 12 μm to approximately 15 μm, or approximately 5 μm to approximately 12 μm. 50 For example, the second PTC2 particle can have an average particle size of approximately 11 μm (D). 50 The second PTC2 particle has a larger average particle size (D) than the first PTC1 and the third PTC3 particle. 50 ).

[0117] The second primary particle NNP_2 constituting the second particle PTC2 may have an average size of about 0.5 μm to about 5 μm, about 1 μm to about 3 μm, about 2 μm to about 3 μm, or about 2 μm. In an embodiment, the size of the second primary particle NNP_2 may indicate the diameter measured by randomly selecting about 30 primary particles from an electron micrograph of the positive electrode active material. The size of the second primary particle NNP_2 may be uniform (e.g., substantially uniform). The second primary particle NNP_2 may have a larger average size than the first primary particle.

[0118] In one embodiment, the second PTC2 particle may include a coating on its surface. The second particle, with its second coating, effectively prevents structural collapse (or reduces the likelihood or extent of structural collapse) caused by repeated charging / discharging. Accordingly, the rechargeable lithium battery may have improved lifespan characteristics.

[0119] The coating may include boron-containing compounds, aluminum-containing compounds, or combinations thereof. The metal-containing compounds in the coating (such as boron-containing compounds, aluminum-containing compounds, or combinations thereof) may be, for example, metal oxides, metal hydroxides, metal carbonates, their complexes, or mixtures thereof. The metal-containing compounds may further include other metallic and / or non-metallic elements. For example, the coating may further include lithium, manganese, and / or nickel.

[0120] Methods for measuring the metal element content in the coating of the second PTC2 particle may include scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS) analysis of the second PTC2 particle. These analyses can determine the aluminum and / or magnesium content in the coating. In addition to, or as an alternative to, SEM-EDS, methods for measuring the metal element content in the coating may include inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), etc.

[0121] In some embodiments, the second PTC2 particles may be in the form of a mixture of large PC2 particles and small SP2 particles. In embodiments where the second PTC2 particles are in the form of a mixture of large PC2 particles and small SP2 particles in the positive electrode active material, the second PTC2 particles may be referred to as bimodal.

[0122] In this embodiment, the large PC2 particles may be present in a higher content than the small SP2 particles relative to the total content of the bimodal second PTC2 particles. In this embodiment, the content of the small SP2 particles may be from about 20 wt% to about 40 wt%, for example, from about 20 wt% to about 30 wt%, relative to the total content of the second PTC2 particles.

[0123] The second particle, PTC2, may have a smaller Brunol-Emmett-Taylor (BET) specific surface area than the first particle, PTC1. For example, the second particle may have a BET specific surface area of ​​about 0.3 to about 1.2.

[0124] The first positive electrode active material layer ATL1 will be described in more detail below. The first positive electrode active material layer ATL1 may include a first particle PTC1 and a second particle PTC2. In the first positive electrode active material layer ATL1, the weight (or mass) of the second particle PTC2 may be less than the weight (or mass) of the first particle PTC1.

[0125] Both the first PTC1 and the second PTC2 particles contain manganese (Mn) (i.e., manganese element), thus the rechargeable lithium battery can have an improved operating voltage. The second PTC2 particle contains nickel, thus the rechargeable lithium battery can have improved energy density and high capacity compared to a rechargeable lithium battery that includes the first PTC1 particle but not the second PTC2 particle.

[0126] The first PTC1 particle offers benefits such as high stability and long lifetime. Using the structurally stable first PTC1 particle as the positive electrode active material compensates for the relatively low stability and short lifetime of the second PTC2 particle.

[0127] The positive electrode active material layer according to embodiments of the present disclosure has a first particle PTC1 and a second particle PTC2 mixed together in a suitable or appropriate ratio, and therefore can have improved energy density, capacity and operating voltage compared to batteries comprising common lithium iron phosphate compounds or lithium manganese iron phosphate compounds.

[0128] Because the first PTC1 particle is very small, a large amount of binder BND can be used or is required to adhere the first PTC1 particle to the positive electrode current collector COL1 (see...). Figure 1 ).

[0129] The average particle size (D) of the second PTC2 particle50 The particle size can be several micrometers. In embodiments of this disclosure, a further component is provided that has a large average particle size (D). 50 The first positive electrode active material layer ATL1 consists of the second PTC2 particles, and correspondingly, the first positive electrode active material layer ATL1 can have improved adhesion to the positive electrode current collector COL1 while including a large number of nano-sized olivine compounds. For example, the electrode plate can be more easily prepared by the first positive electrode active material layer ATL1 in which the first PTC1 particles and the second PTC2 particles are mixed together.

[0130] In this embodiment, the electrode plate can be fabricated more easily by first adhering the first positive electrode active material layer ATL1 to the positive electrode current collector. By first forming the first positive electrode active material layer ATL1 with strong adhesion to the positive electrode current collector, the electrode plate can have improved impedance (e.g., resistance). In this embodiment, a rechargeable lithium battery with excellent performance can be provided.

[0131] Second positive electrode active material layer ATL2

[0132] Figure 8 An enlarged view showing the second positive electrode active material layer of the positive electrode for a rechargeable lithium battery according to an embodiment of the present disclosure.

[0133] refer to Figure 8 The second positive electrode active material layer ATL2 may include a third particle PTC3 and a second functional additive ADD2. The second functional additive ADD2 may include a second binder BND2 and a second conductive material CDM2 (e.g., a second electrical conductivity material CDM2).

[0134] The second adhesive BND2 can bond (e.g., bond together) the third particle PTC3 and the second conductive material CDM2. In an embodiment, the second adhesive BND2 can stably fix the second positive electrode active material layer ATL2 onto the first positive electrode active material layer ATL1. In an embodiment, the second adhesive BND2 may include at least one selected from the group consisting of: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, and nylon, but is not limited thereto.

[0135] The second conductive material CDM2 can be used to improve the conductivity (e.g., electrical conductivity) of the second positive electrode active material layer ATL2. Any suitable electrical conductivity material that does not cause a chemical change (e.g., does not cause an undesired chemical change) in the second positive electrode active material layer ATL2 can be used as the second conductive material CDM2 without limitation. In an embodiment, the second conductive material CDM2 can include: carbonaceous materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and / or carbon nanotube; metallic materials including copper, nickel, aluminum, silver, etc. in the form of metal powder and / or metal fiber; conductive polymers (e.g., electrically conductive polymers) such as poly(phenylene) derivatives; or mixtures thereof.

[0136] The third particle PTC3

[0137] The third particle PTC3 can include an olivine-based lithium compound represented by Formula 3 below.

[0138] Formula 3

[0139] Li a3 Mn z3 Fe x3 B3 y3 PO 4-c3

[0140] In Formula 3 above, 0.8 < a3 ≤ 1.2, 0.4 ≤ z3 ≤ 0.8, 0 ≤ x3 ≤ 0.6, 0 ≤ y3 ≤ 0.05 (e.g., 0.001 ≤ y3 ≤ 0.05), and 0 ≤ c3 ≤ 0.0可以得到满足。B3可以是选自由Al、Ti、V和Mg组成的组中的至少一种元素。B3可以是第三颗粒PTC3所掺杂的掺杂剂。例如,B3可以是Ti。

[0141] The third particle PTC3 can further include a carbon element derived from the above-mentioned positive electrode active material layer AML1. The third particle PTC3 can have a carbon element content of about 0.5 wt% to about 5 wt%, about 0.5 wt% to about 3 wt%, or about 0.5 wt% to about 2 wt%.

[0142] The third particle PTC3 is in a polycrystalline form and can include secondary particles in which at least two third primary particles NNP_3 are aggregated. For example, one third particle PTC3 can include a plurality of third primary particles NNP_3 aggregated together. The third particle PTC3 including a plurality of third primary particles NNP_3 can be in the shape of a sphere or an ellipsoid (e.g., can be substantially spherical or substantially oval).

[0143] In an embodiment, the average particle size (D 50 ) can indicate the particle size at which the cumulative volume in the particle size distribution is about 50% by volume. In an embodiment, the average particle size (D50 This can be a value measured using a particle size analyzer.

[0144] The third PTC3 particle, including at least one third primary particle NNP_3, may have an average particle size of about 50 nm to about 5 μm, about 100 nm to about 3 μm, about 500 nm to about 2.5 μm, about 3 μm to about 7 μm, about 4 μm to about 6 μm, or about 5 μm. The average particle size (D) of the third PTC3 particle is... 50 It can be smaller than the average particle size (D) of the second particle PTC2 mentioned above. 50 The average particle size of the first particle is smaller than that of the third particle.

[0145] The third particle PTC3 may include at least one primary particle (or a single particle). The size of at least one third primary particle NNP_3 constituting the third particle PTC3 can be measured using a scanning electron microscope (SEM). In an embodiment, the size of the third primary particle NNP_3 may indicate the diameter measured by randomly selecting approximately 30 third primary particles NNP_3 from an electron micrograph of the positive electrode active material. The size of the third primary particle NNP_3 may be uniform (e.g., substantially uniform).

[0146] At least one third primary particle NNP_3 constituting the third particle PTC3 may have a size of about 100 nm to about 200 nm, about 50 nm to about 150 nm, about 50 nm to about 100 nm, about 100 nm to about 150 nm, or about 200 nm to about 300 nm.

[0147] In an embodiment, the third PTC3 particle may include a coating on its surface. The coating may completely cover the surface of the third PTC3 particle or may partially cover the surface of the third PTC3 particle. For example, the coating may include elemental carbon and / or carbon-containing compounds. The coating may further include at least one selected from the group consisting of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds. The metal-containing compounds (such as titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds) may be, for example, metal oxides, metal hydroxides, metal carbonates, complexes thereof, or mixtures thereof. The metal-containing compounds may further include other metallic elements and / or non-metallic elements. For example, the metal-containing compounds may further include lithium. Due to the coating, the third PTC3 particle may have improved structural stability and electrical conductivity.

[0148] In an embodiment, the third PTC3 particle may further include a grain boundary coating on the surface of each third primary particle NNP_3. The grain boundary coating may be present within the third PTC3 particle. The grain boundary coating may be present along the interfaces between the third primary particles NNP_3 within the third PTC3 particle. For example, the grain boundary coating may refer to a layer of material formed on the grain boundaries within the third PTC3 particle.

[0149] The grain boundary coating may include elemental carbon and / or carbon-containing compounds. The grain boundary coating may further include at least one selected from the group consisting of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds.

[0150] The interior of the third PTC3 can refer to the entire interior of the third PTC3 excluding its surface. For example, the interior of the third PTC3 can refer to the entire interior from a depth of about 10 nm relative to the surface of the third PTC3, or a region of the interior from about 10 nm to about 2 μm relative to the surface of the third PTC3.

[0151] The third PTC3 particle further includes a grain boundary coating, thus exhibiting greater structural stability and a uniform (e.g., substantially uniform) coating on its surface. In an embodiment, the third PTC3 particle further includes a grain boundary coating, thus exhibiting further improved electrical conductivity.

[0152] The third PTC3 particle may further include carbon elements derived from the aforementioned coating and / or grain boundary coating. The third PTC3 particle may have a carbon content of about 0.5 wt% to about 10 wt%, about 1 wt% to about 3 wt%, or about 1.5 wt% to about 2.5 wt%. For example, if in the form of secondary particles, the third PTC3 particle has a higher carbon content than the third PTC3 particle in the form of single particles.

[0153] The third PTC3 particle may be in the shape of a sphere (e.g., approximately spherical) in which multiple third primary particles NNP_3 are aggregated. The third PTC3 particle, with its tightly aggregated third primary particles NNP_3, exhibits the following characteristics. The third particle effectively retains the aforementioned coating and / or grain boundary coating, thus exhibiting higher electrical conductivity and improved low-temperature properties. Due to increased adhesion to the electrode plate, the amount of binder (e.g., the amount of binder used) can be reduced. The third PTC3 particle may be in the shape of a sphere or ellipsoid (e.g., approximately spherical or approximately oval).

[0154] The third PTC3 particle can have a porosity of approximately 20% to approximately 40%. The span value of the third PTC3 particle, as analyzed by a particle size analyzer, can be approximately 0.3 to approximately 0.75.

[0155] The positive electrode active material layer AML1 according to embodiments of the present disclosure will be described in more detail below.

[0156] Relative to the total weight of the first particle PTC1, the second particle PTC2, and the third particle PTC3 in the positive electrode active material layer AML1, the amount of the second particle may be about 5 wt% to about 20 wt%, about 10 wt% to about 20 wt%, about 15 wt% to about 30 wt%, about 20 wt% to about 30 wt%, or about 25 wt% to about 35 wt%.

[0157] The positive electrode or positive electrode active material layer AML1 may include manganese (Mn). The total doping content of manganese (Mn) can be defined as the sum of the doping content M1 of manganese (Mn) included in the first positive electrode active material layer ATL1 and the doping content M2 of manganese (Mn) included in the second positive electrode active material layer ATL2. The doping content M1 of manganese (Mn) included in the first positive electrode active material layer ATL1 can be defined as the sum of the product of the doping content of manganese (Mn) in the first particle PTC1 (z1 in Equation 1 above) and the weight ratio (or amount) of the first particle PTC1, and the product of the doping content of manganese (Mn) in the second particle PTC2 (z2 in Equation 2 above) and the weight ratio (or amount) of the second particle PTC2. The doping content M2 of manganese (Mn) included in the second positive electrode active material layer ATL2 can be defined as the product of the doping content of manganese (Mn) in the third particle PTC3 (z3 in Equation 3 above) and the weight ratio (or amount) of the third particle PTC3.

[0158] The total doping content of manganese (Mn) in the positive electrode (i.e., the positive electrode active material layer AML1) can be about 0.40 to about 0.90, about 0.40 to about 0.60, about 0.50 to about 0.90, about 0.50 to about 0.70, about 0.60 to about 0.80, about 0.60 to about 0.70, about 0.50 to about 0.60, or about 0.50.

[0159] According to embodiments of the present disclosure, the positive electrode active material layer AML1 may have a bilayer structure in which a second positive electrode active material layer ATL2 is stacked on the first positive electrode active material layer ATL1. The positive electrode active material layer AML1 may include a functional additive ADD. The first positive electrode active material layer ATL1 may include a first functional additive ADD1, and the second positive electrode active material layer ATL2 may include a second functional additive ADD2. The functional additive ADD may indicate at least one of the first functional additive ADD1 and the second functional additive ADD2.

[0160] Functional additives may include conductive material CDM (e.g., electrically conductive material CDM) and binder BND. Including functional additives, and accordingly, the positive electrode active material layer may have improved performance. For example, the materials in the positive electrode active material layer can be well bonded, the adhesion of the electrode plate can be improved, and the conductivity (e.g., electrical conductivity) of the positive electrode active material layer can be improved.

[0161] The first PTC1 particle has a very small particle size, and therefore exhibits poor adhesion relative to the positive electrode current collector COL1, hindering the easy fabrication of the electrode plate (or reducing the ease of fabricating the electrode plate). In embodiments, if only the first PTC1 particle is used to prepare the active material layer, a large amount of functional additives may be used or required. For example, a relatively large amount of binder BND may be used or required to adhere the first PTC1 particle with a small average particle size to the positive electrode current collector, but a relatively small amount of binder BND may be used or required to adhere the second PTC2 particle with a large average particle size to the positive electrode current collector. The amount of binder BND used or required can be reduced by including the first positive electrode active material layer ATL1 comprising the first PTC1 particle and the second PTC2 particle.

[0162] In the positive electrode active material layer AML1 of this disclosure, a bilayer structure can be applied, wherein a first positive electrode active material layer ATL1 is first bonded to the positive electrode current collector using or requiring a relatively small amount of functional additives, and a second positive electrode active material layer ATL2 is bonded to the first positive electrode active material layer ATL1.

[0163] In the positive electrode active material layer AML1 of this disclosure, a bilayer structure can be applied, which includes a first positive electrode active material layer ATL1 that uses or requires a relatively small amount of functional additives and a second positive electrode active material layer ATL2 provided on the first positive electrode active material layer ATL1.

[0164] The electrode plate can be fabricated more easily by using a bilayer structure. For example, a first positive electrode active material layer ATL1, in which first particles PTC1 and second particles PTC2 are mixed together, can be stacked on a positive electrode current collector, and a second positive electrode active material layer ATL2 can be stacked on the first positive electrode active material layer ATL1. If the first positive electrode active material layer ATL1, which has excellent adhesion to the electrode plate, is first stacked on the positive electrode current collector, fewer functional additives can be used or required, resulting in improved energy density. In an embodiment, the first positive electrode active material layer ATL1, which has greater adhesion to the positive electrode current collector, can be prepared first, so the electrode plate can have improved impedance (e.g., resistance).

[0165] The weight percentage (or amount) of the first binder BND1 in the first positive electrode active material layer ATL1 can be about 1.2 wt% to about 2 wt% (e.g., based on 100 wt% of the first positive electrode active material layer ATL1).

[0166] The weight percentage (or amount) of the second binder BND2 in the second positive electrode active material layer ATL2 can be from about 1.5 wt% to about 3.0 wt% (e.g., based on 100 wt% of the second positive electrode active material layer ATL2).

[0167] The weight ratio (or amount) of the first binder BND1 in the first positive electrode active material layer ATL1 may be equal to or less than the weight ratio (or amount) of the second binder BND2 in the second positive electrode active material layer ATL2. In an embodiment, the ratio of the weight ratio (or amount) of the second binder BND2 to the weight ratio (or amount) of the first binder BND1 may be about 1 to about 2.5 or about 1 to about 1.35.

[0168] The weight percentage (or amount) of the first conductive material CDM1 in the first positive electrode active material layer ATL1 can be about 1.2 wt% to about 2.0 wt% (based on 100 wt% of the first positive electrode active material layer ATL1).

[0169] The weight percentage (or amount) of the second conductive material CDM2 in the second positive electrode active material layer ATL2 can be about 1.5 wt% to about 3.0 wt% (based on 100 wt% of the second positive electrode active material layer ATL2).

[0170] The weight ratio (or amount) of the first conductive material CDM1 in the first positive electrode active material layer ATL1 may be equal to or less than the weight ratio (or amount) of the second conductive material CDM2 in the second positive electrode active material layer ATL2. In an embodiment, the ratio of the weight ratio (or amount) of the second conductive material CDM2 to the weight ratio (or amount) of the first conductive material CDM1 may be about 1 to about 2.5 or about 1 to about 1.35.

[0171] The weight percentage (or amount) of the first functional additive ADD1 in the first positive electrode active material layer ATL1 can be about 2.4 wt% to about 4.0 wt% (based on 100 wt% of the first positive electrode active material layer ATL1).

[0172] The weight percentage (or amount) of the second functional additive ADD2 in the second positive electrode active material layer ATL2 can be about 3.0 wt% to about 6.0 wt% (based on 100 wt% of the second positive electrode active material layer ATL2).

[0173] The weight ratio (or amount) of the first functional additive ADD1 in the first positive electrode active material layer ATL1 may be equal to or lower than the weight ratio (or amount) of the second functional additive ADD2 in the second positive electrode active material layer ATL2.

[0174] In an embodiment, the weight ratio (or amount) of the second functional additive to the weight ratio (or amount) of the first functional additive may be about 1 to about 2.5 or about 1 to about 1.35.

[0175] The first positive electrode active material layer ATL1 may have a thickness T1. In an embodiment, T1 may increase with increasing weight of the first particle PTC1 and the second particle PTC2 included in the first positive electrode active material layer ATL1. The second positive electrode active material layer ATL2 may have a thickness T2. In an embodiment, T2 may increase with increasing weight of the third particle PTC3 included in the second positive electrode active material layer ATL2. In an embodiment, the ratio of T2 to T1 (T2 / T1) may be about 0.4 to about 2.0, about 0.9 to about 1.5, about 0.8 to about 1.2, or about 1. Within the above ranges, stability and lifetime characteristics can be improved while maintaining excellent high voltage performance and energy density.

[0176] In an embodiment, the positive electrode active material layer AML1 of this disclosure may have a pressing density of about 2.3 g / cc to about 2.8 g / cc.

[0177] In this embodiment, the first positive electrode active material layer ATL1 may have a concentration of approximately 5 mg / cm³. 2 ~ Approximately 10 mg / cm 2 The loading level. The second positive electrode active material layer ATL2 can have approximately 5 mg / cm². 2 ~ Approximately 25 mg / cm 2 The load level.

[0178] Rechargeable lithium batteries incorporating the positive electrode active material of this disclosure can have improved low-temperature characteristics. In embodiments, the ratio of the capacity of the rechargeable lithium battery at -20°C (i.e., the initial discharge capacity at -20°C) to the initial capacity of the rechargeable lithium battery (i.e., the initial discharge capacity at 25°C) (capacity at -20°C / initial capacity) can be about 40% or greater. For example, the ratio of the capacity at -20°C to the initial capacity of the rechargeable lithium battery of this disclosure (capacity at -20°C / initial capacity) can be about 40% to about 100%, about 50% to about 100%, or about 96% to about 99%.

[0179] Rechargeable lithium batteries incorporating the positive electrode active material of this disclosure can have improved operating voltage. In embodiments, the rechargeable lithium battery of this disclosure can have an operating voltage range of about 3V to about 5V. For example, the operating voltage range can be about 3V to about 4.5V or about 3.5V to about 4V.

[0180] Rechargeable lithium batteries incorporating the positive electrode active material of this disclosure can have improved lifespan characteristics. In an embodiment, after 50 charge / discharge cycles at a constant current of 1.0C at the aforementioned voltage, the rechargeable lithium battery of this disclosure can have a capacity retention rate of approximately 98% or higher. For example, the capacity retention rate can be approximately 98% to approximately 100% or approximately 99.8% to approximately 100%.

[0181] Method for preparing positive electrode active materials

[0182] The following will describe preparation examples, embodiments, and comparative examples of this disclosure. However, the following embodiments are presented only as implementations of this disclosure, and this disclosure is not limited to the following embodiments.

[0183] Preparation Example 1: Preparation of the first PTC1 particle

[0184] Manganese iron phosphate precursor (Mn) 0.6 Fe 0.4 PO4, lithium carbonate, and titanium dioxide were mixed together in a molar ratio of (Mn+Fe):Li:Ti of 1:1.03:0.004. 10 wt% glucose was added to the resulting mixture. The mixture was then wet-milled by ball milling. The mixture was evaporated to dryness on a heated plate and then placed in a vacuum oven at 120°C for 4 hours. The dried mixture was calcined at 750°C for 10 hours under a nitrogen atmosphere. The calcined product was ground to obtain first particles in the form of single particles. The first particles had an average size of approximately 100 nm to approximately 200 nm.

[0185] Preparation Example 2-1: Preparation of PTC2 in the form of small particles

[0186] Small-particle precursors were prepared using a co-precipitation method. Specifically, nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and manganese sulfate (MnSO4·H2O) were dissolved in distilled water as a solvent in a molar ratio of 60:10:30 to prepare a metal raw material mixture. The metal raw material mixture, ammonia, and sodium hydroxide were added to a reactor and reacted. The resulting slurry solution in the reactor was filtered and washed with high-purity distilled water. The washed material was dried in a hot air oven at 210°C for 24 hours to obtain a small-particle precursor (NiSO4·6H2O) with an average particle size of approximately 4 μm. 0.6 Co0.1 Mn 0.3 (OH)2) powder.

[0187] Small-particle precursors and anhydrous lithium hydroxide (LiOH) were dry-mixed together using a Henschel mixer. Lithium and transition metals were mixed together at a molar ratio of approximately 1:1. The transition metals were the sum of transition metals included in the intermediate nickel precursor (Ni + Co + Mn). Flux was further added to the resulting mixture, and the mixture was heat-treated (e.g., sintering process) at approximately 910°C in an oxygen atmosphere for 8 hours to synthesize small lithium composite oxide particles. The particles were milled using a jet mill at a pressure of 3 bar. The particles were formed from the formula LiNi 0.6 Co 0.1 Mn 0.3 O2 represents the addition of aluminum oxide to oxides (from the formula LiNi). 0.6 Co 0.1 Mn 0.3 The mixture is then subjected to a second heat treatment at 800°C for 8 hours in an oxygen atmosphere (represented by O2) to prepare the positive electrode active material. The second particle is made of LiNi... 0.6 Co 0.1 Mn 0.3 O2 represents.

[0188] Preparation Example 2-2: Preparation of PTC2 in the form of large particles

[0189] Large-particle precursors were prepared using a co-precipitation method. Specifically, nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and manganese sulfate (MnSO4·H2O) were dissolved in distilled water as a solvent in a molar ratio of 60:10:30 to prepare a metal raw material mixture. A diluted solution of ammonia (NH4OH) and sodium hydroxide (NaOH) as a precipitant was prepared to form a complex. Subsequently, the metal raw material mixture, ammonia, and sodium hydroxide were added to a reactor. Sodium hydroxide was added to maintain the pH of the resulting mixture in the reactor. The mixture was allowed to react for approximately 20 hours while being stirred in the reactor. The slurry solution in the reactor was filtered and washed with high-purity distilled water. The resulting washed material was dried in a hot air oven at 750°C for 24 hours to obtain a large-particle precursor (NiSO4·6H2O) with a particle size of approximately 18 μm. 0.6 Co 0.1 Mn 0.3 (OH)2) powder.

[0190] Large-particle precursors and anhydrous lithium hydroxide (LiOH) were dry-blended together using a Henschel mixer. Lithium and transition metals were mixed together at a molar ratio of approximately 1:1. The transition metals were the sum of the transition metals included in the large-particle precursors (Ni + Co + Mn). The resulting mixture was heat-treated (e.g., sintering process) at approximately 750°C in an oxygen atmosphere for 15 hours to synthesize large lithium composite oxide particles. The particles were then milled using a jet mill at a pressure of 3 bar. The particles were formed from the formula LiNi 0.6 Co 0.1 Mn 0.3 O2 represents the addition of aluminum oxide to oxides (from the formula LiNi). 0.6 Co 0.1 Mn 0.3 O2 (representing O2), and then the resulting mixture was subjected to a second heat treatment at 800°C for 8 hours in an oxygen atmosphere to prepare the positive electrode active material. The second particle is made of LiNi 0.6 Co 0.1 Mn 0.3 O2 represents.

[0191] Preparation Example 2-3: Preparation of the second Particle of Bimodal PTC2

[0192] The small particles from Preparation Example 2-1 and the large particles from Preparation Example 2-2 were mixed together at a weight ratio of 30:70 to prepare the second bimodal particle.

[0193] Preparation Example 3: Preparation of the third PTC3 particle

[0194] Manganese iron phosphate precursor (Mn) 0.6 Fe 0.4 PO4, lithium carbonate, and titanium dioxide were mixed together in a molar ratio of 1:1.03:0.004. 10 wt% glucose was further added to the resulting mixture. The resulting slurry mixture was spray-dried and evaporated to dryness at a spray pressure of 0.5 MPa and a temperature of 230 °C. The dried mixture was calcined at 750 °C for 10 hours under a nitrogen atmosphere to obtain tertiary particles in the form of secondary particles. The primary particles in the form of tertiary particles had an average size of approximately 50 nm to approximately 150 nm.

[0195] Fabrication of single-layer electrode plates

[0196] Comparative Example 1-1

[0197] The first particles from Preparation Example 1 and the second particles from Preparation Example 2-1 were mixed together at a weight ratio of 30:70, and dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0198] Comparative Examples 1-2

[0199] The first particles from Preparation Example 1 and the second particles from Preparation Example 2-1 were mixed together at a weight ratio of 40:60 and dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0200] Comparative Examples 1-3

[0201] The first particles from Preparation Example 1 and the second particles from Preparation Example 2-1 were mixed together at a weight ratio of 50:50 and dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0202] Comparative Examples 1-4

[0203] The first particles from Preparation Example 1 and the second particles from Preparation Example 2-1 were mixed together at a weight ratio of 60:40 and dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0204] Comparative Examples 1-5

[0205] The first particles from Preparation Example 1 and the second particles from Preparation Example 2-1 were mixed together at a weight ratio of 70:30 and dispersed in N-methylpyrrolidone along with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0206] Comparative Examples 1-6

[0207] The first particles from Preparation Example 1 and the second particles from Preparation Example 2-1 were mixed together at a weight ratio of 80:20 and dispersed in N-methylpyrrolidone along with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0208] Comparative Examples 1-7

[0209] The first particles from Preparation Example 1 and the second particles from Preparation Example 2-1 were mixed together at a weight ratio of 90:10 and dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0210] Comparative Examples 1-8

[0211] The first particle from Preparation Example 1, the second particle from Preparation Example 2-1, and the third particle from Preparation Example 3 were mixed together in a weight ratio of 35:30:35 and dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0212] Comparative Example 2-1

[0213] The first particles from Preparation Example 1 and the second particles from Preparation Example 2-2 were mixed together at a weight ratio of 70:30 and dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0214] Comparative Example 2-2

[0215] The first particles from Preparation Example 1 and the second particles from Preparation Examples 2-3 were mixed together at a weight ratio of 70:30 and dispersed in N-methylpyrrolidone along with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a single-layer electrode plate.

[0216] Fabrication of double-layer electrode plates

[0217] Example 1-1

[0218] The first particle from Preparation Example 1 and the second particle from Preparation Example 2-1 were dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a first positive electrode active material slurry. The third particle from Preparation Example 3 was dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a second positive electrode active material slurry.

[0219] A first positive electrode active material slurry is coated onto a positive electrode current collector and dried to form a first positive electrode active material layer. A second positive electrode active material slurry is coated onto the first positive electrode active material layer and dried to form a second positive electrode active material layer.

[0220] In this case, the active material layer is formed such that the first, second, and third particles in the bilayer positive electrode exist in a weight ratio of 30:40:30. A positive electrode in which the positive electrode current collector, the first positive electrode active material layer, and the second positive electrode active material layer are stacked in this order is prepared by roll forming.

[0221] Examples 1-2

[0222] The first particle from Preparation Example 1 and the second particle from Preparation Example 2-2 were dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a first positive electrode active material slurry. The third particle from Preparation Example 3 was dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a second positive electrode active material slurry.

[0223] A first positive electrode active material slurry is coated onto a positive electrode current collector and dried to form a first positive electrode active material layer. A second positive electrode active material slurry is coated onto the first positive electrode active material layer and dried to form a second positive electrode active material layer.

[0224] In this case, the active material layer is formed such that the first, second, and third particles in the bilayer positive electrode exist in a weight ratio of 30:40:30. A positive electrode in which the positive electrode current collector, the first positive electrode active material layer, and the second positive electrode active material layer are stacked in this order is prepared by roll forming.

[0225] Examples 1-3

[0226] The first particles from Preparation Example 1 and the second particles from Preparation Examples 2-3 were dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a first positive electrode active material slurry. The third particles from Preparation Example 3 were dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a second positive electrode active material slurry.

[0227] A first positive electrode active material slurry is coated onto a positive electrode current collector and dried to form a first positive electrode active material layer. A second positive electrode active material slurry is coated onto the first positive electrode active material layer and dried to form a second positive electrode active material layer.

[0228] In this case, the active material layer is formed such that the first, second, and third particles in the bilayer positive electrode exist in a weight ratio of 30:40:30. A positive electrode in which the positive electrode current collector, the first positive electrode active material layer, and the second positive electrode active material layer are stacked in this order is prepared by roll forming.

[0229] Example 2-1

[0230] The active material layer is formed in essentially the same manner as in Examples 1-1, except that the first, second, and third particles in the bilayer positive electrode are present in a weight ratio of 35:30:35.

[0231] Example 2-2

[0232] The active material layer is formed in essentially the same manner as in Examples 1-2, except that the first, second, and third particles in the bilayer positive electrode are present in a weight ratio of 35:30:35.

[0233] Example 2-3

[0234] The active material layer is formed in essentially the same manner as in Examples 1-3, except that the first, second, and third particles in the bilayer positive electrode are present in a weight ratio of 35:30:35.

[0235] Example 3-1

[0236] The active material layer is formed in essentially the same manner as in Examples 1-1, except that the first, second, and third particles in the bilayer positive electrode are present in a weight ratio of 40:20:40.

[0237] Example 3-2

[0238] The active material layer is formed in essentially the same manner as in Examples 1-2, except that the first, second, and third particles in the bilayer positive electrode are present in a weight ratio of 40:20:40.

[0239] Example 3-3

[0240] The active material layer is formed in essentially the same manner as in Examples 1-3, except that the first, second, and third particles in the bilayer positive electrode are present in a weight ratio of 40:20:40.

[0241] Comparative Example 3-1

[0242] The first particle from Preparation Example 1 and the second particle from Preparation Example 2-1 were dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a first positive electrode active material slurry. The third particle from Preparation Example 3 was dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a second positive electrode active material slurry.

[0243] Unlike Example 1-1, the second positive electrode active material slurry is first coated onto the positive electrode current collector and dried to form the first positive electrode active material layer. Subsequently, the first positive electrode active material slurry is coated onto the first positive electrode active material layer and dried to form the second positive electrode active material layer.

[0244] Comparative Example 3-2

[0245] The first particle from Preparation Example 1 and the second particle from Preparation Example 2-1 were dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a first positive electrode active material slurry. The third particle from Preparation Example 3 was dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a second positive electrode active material slurry.

[0246] Unlike Example 2-1, the second positive electrode active material slurry is first coated onto the positive electrode current collector and dried to form the first positive electrode active material layer. Then, the first positive electrode active material slurry is coated onto the first positive electrode active material layer and dried to form the second positive electrode active material layer.

[0247] Comparative Example 3-3

[0248] The first particle from Preparation Example 1 and the second particle from Preparation Example 2-1 were dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a first positive electrode active material slurry. The third particle from Preparation Example 3 was dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a second positive electrode active material slurry.

[0249] Unlike Example 3-1, the second positive electrode active material slurry is first coated onto the positive electrode current collector and dried to form the first positive electrode active material layer. Then, the first positive electrode active material slurry is coated onto the first positive electrode active material layer and dried to form the second positive electrode active material layer.

[0250] The composition and structure of the electrode plates of Comparative Examples 1-1 to 1-8, Comparative Examples 2-1, 2-2 and 3-1 to 3-3, and Examples 1-1 to 1-3, 2-1 to 2-3 and 3-1 to 3-3 are shown in Table 1.

[0251] Preparation of negative electrode

[0252] Graphite, a binder (PVDF), and a conductive material (carbon black) were mixed together in an N-methylpyrrolidone solvent at a weight ratio of 95:3:2 to prepare a negative electrode active material slurry. The negative electrode active material slurry was coated onto a copper current collector, dried, and rolled to prepare the negative electrode.

[0253] Preparation of rechargeable lithium batteries

[0254] The prepared positive and negative electrodes were used to prepare coin half-cell cells. A polypropylene membrane (Celgard 3510) was used as the separator. As the electrolyte, an electrolyte solution was prepared by mixing 1.3 M LiPF6 with a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC) (volume ratio: 2:6:2).

[0255] Table 1

[0256]

[0257] Evaluation Example 1: Analysis of the surface of the active material in the positive electrode

[0258] A pair of SEM images of the first particle prepared in Preparation Example 1 are shown in Figure 9 In the middle. A pair of SEM images of the second particles prepared in Preparation Examples 2-3 are shown. Figure 10 In the middle. A pair of SEM images of the third particle prepared in Preparation Example 3 are shown. Figure 11 (Chinese) Reference Figure 9 As can be seen, the first particle according to the embodiments of this disclosure is in the form of a small, single particle of nanoscale size. (See reference...) Figure 10 Therefore, it can be seen that the second particle according to the embodiments of this disclosure is in the form of a single particle or in the form of a plurality of single particles aggregated therein. Compared with the first particle, the second particle takes various suitable forms and has a larger particle size. (See reference...) Figure 11 It can be seen that the third particle takes the form of a sphere in which multiple third primary particles are aggregated.

[0259] Evaluation Example 2: Evaluation of Active Substances

[0260] The powder compaction density (PD) of the positive electrode active material layers prepared by Examples 1-1 to 3-3 and Comparative Examples 1-1 to 3-3 was measured, and the results are shown in Table 2. It can be seen that the positive electrode active material layers according to one or more embodiments have a powder compaction density of 2.50 (g / cc) to 2.70 (g / cc).

[0261] Table 2

[0262]

[0263] Referring to Table 2, it can be seen that when compared with the positive electrode active material layers of Comparative Examples 1-4 to 1-6, which each have a single-layer structure, the positive electrode active material layers of Examples 1-1 to 1-3 are able to maintain the powder compaction density at a similar level.

[0264] Evaluation Example 3: Evaluation of Battery Characteristics

[0265] The characteristics of rechargeable lithium batteries prepared using the positive electrodes of Examples 1-1 to 3-3 and Comparative Examples 1-1 to 3-3 were evaluated.

[0266] For the initial charge / discharge, the rechargeable lithium battery was initially charged at 25°C with a constant current of 0.2C and a constant voltage of 4.25V (0.05C cutoff). After resting for 10 minutes, it was discharged to 2.5V with a constant current of 0.2C, thus obtaining the initial charge capacity (0.2C charge capacity (mAh / g)) and the initial discharge capacity (0.2C discharge capacity (mAh / g)). The efficiency (%) at 0.2C is expressed as initial discharge capacity / initial charge capacity. Subsequently, the charge / discharge cycle was repeated 50 times at 45°C and 1.0C (4.25V, 0.05C cutoff) / 1.0C (to 2.5V). The average voltage was obtained by integrating the area under the discharge voltage curve (voltage-capacity plot) after the initial charge and discharge of the battery cell, and then dividing the integral by the discharge capacity. In addition, a rechargeable lithium battery was prepared and charged at 25°C with a constant current of 0.2C and a constant voltage of 4.25V (cutoff at 0.05C). After standing for 10 minutes, it was discharged to 2.5V with a constant current of 0.2C. Then, it was charged at -20°C with a constant current of 0.2C and a constant voltage of 4.25V (cutoff at 0.05C), and discharged to 2.5V with a constant current of 0.2C at -20°C. The capacity at -20°C (mAh / g) was measured. The results of evaluating the battery characteristics are shown in Table 3 below.

[0267] Table 3

[0268]

[0269]

[0270] Referring to Table 3, it can be seen that the rechargeable lithium batteries according to Examples 1-1 to 3-3 have improved 1C life compared to the rechargeable lithium batteries according to Comparative Examples 1-1 to 1-7. Considering the charge / discharge efficiency and average voltage of the rechargeable lithium batteries according to Examples 1-1 to 3-3, the rechargeable lithium batteries can be used as batteries with excellent overall characteristics.

[0271] Evaluation Example 4: Content of functional additives in the active substance layer

[0272] The weight ratio (or amount) of functional additives used or required in preparing the monolayer positive electrodes of Comparative Examples 1-1 to 2-2 was measured.

[0273] The weight ratio (or amount) of functional additives in the first positive electrode active material layer and the weight ratio (or amount) of functional additives in the second positive electrode active material layer were measured in preparation of the bilayer positive electrodes of Comparative Examples 3-1 to 3-3.

[0274] The weight ratio (or amount) of functional additives in the first positive electrode active material layer and the weight ratio (or amount) of functional additives in the second positive electrode active material layer of the positive electrodes in Examples 1-1 to 3-3 were measured. The weight ratio (or amount) of functional additives in the active material layers is shown in Table 4.

[0275] Table 4

[0276]

[0277] For example, when comparing Comparative Examples 1-8, which have a monolayer structure and the same proportion of positive electrode active material as in Examples 2-1 of this disclosure, it is evident that in Examples 2-1, which have a bilayer structure, the total amount of functional additives used or required to form the positive electrode active material layer is smaller. Compared to a monolayer structure with the same content, the reduced content of functional additives results in an improved energy density for the active material layer.

[0278] Evaluation Example 5: Evaluation of Resistance and Adhesion

[0279] The characteristics of rechargeable lithium batteries prepared using positive electrodes from the respective examples and comparative examples were evaluated.

[0280] For initial charge / discharge, the rechargeable lithium battery was initially charged at 0.2C with a constant current of 4.25V (0.05C cutoff) at 25°C, and after resting for 10 minutes, discharged to 3.0V with a constant current of 0.2C. The average voltage and current density were then evaluated. The average voltage (average drive voltage) was obtained by integrating the area under the discharge voltage curve (voltage-capacity plot) after the initial charge and discharge of the battery cell, and then dividing the integral by the discharge capacity. The energy density was obtained using the formula {average drive voltage (V) × capacity (Ah) / battery cell weight (kg)}, where capacity was calculated by multiplying the positive electrode weight (g) by the discharge capacity (mAh / g). The rechargeable lithium battery was charged to SOC50 with a constant current of 0.2C, then rested at SOC50 for 1 hour, and discharged at 1.0C for 10 seconds, followed by a 10-second rest. In this case, the cell resistance (DC-IR) is calculated by dividing the difference between the voltage at the end of discharge and the voltage after 10 seconds of rest by the current. The results are shown in Table 5 below.

[0281] Table 5

[0282]

[0283] When Examples 1-1, 2-1, and 3-1 are compared with Comparative Examples 1-4, 1-5, and 1-6, respectively, it is evident that Examples 1-1, 2-1, and 3-1 exhibit significantly reduced resistance values. This demonstrates that when a double-layer structure is applied, the electrode plate exhibits improved adhesion and reduced resistance compared to an electrode plate with a single-layer structure.

[0284] Accordingly, a dual-layer structure is provided in embodiments according to the present disclosure, so that the electrode plate can have reduced impedance (e.g., resistance) and improved energy density.

[0285] The positive electrode according to this disclosure comprises: a first positive electrode active material layer comprising first olivine particles with a size of hundreds of nanometers to several micrometers and layered second particles with a size of several micrometers; and a second positive electrode active material layer comprising third olivine particles with a size of several micrometers and stacked on the first positive electrode active material layer, thereby achieving improved powder compaction density, capacity, and energy density. In the positive electrode according to this disclosure, the electrode plate can be readily fabricated and has improved impedance (e.g., resistance). The rechargeable lithium battery according to this disclosure can have a relatively improved lifespan.

[0286] The foregoing description provides exemplary embodiments for carrying out the subject matter of this disclosure. This disclosure will include the above-described embodiments and embodiments that can be easily modified or whose design can be simply changed. Furthermore, this disclosure will also include techniques that can be easily modified and implemented using the embodiments of this disclosure. Therefore, the scope of this disclosure should not be limited to the above-described embodiments, but should be defined by the claims and their equivalents.

Claims

1. A positive electrode for a rechargeable lithium battery, comprising: A positive electrode current collector; A first positive electrode active material layer on the positive electrode current collector; And A second positive electrode active material layer on the first positive electrode active material layer, Wherein the first positive electrode active material layer comprises first particles represented by Formula 1 and having an olivine structure, and second particles represented by Formula 2 and having a layered structure, The second positive electrode active material layer comprises third particles represented by Formula 3 and having an olivine structure, The first particles are in the form of single particles, the third particles are in the form of secondary particles in which a plurality of third primary particles are aggregated, and the average particle size of the second particles is greater than the average particle size of each of the first particles and the third particles, Formula 1 Li a1 Mn z1 Fe x1 B1 y1 PER 4-c1 Where in Formula 1 above, B1 is at least one element selected from the group consisting of Al, Ti, V, and Mg, and satisfies 0.8 < a1 ≤ 1.2, 0.4 ≤ z1 ≤ 0.8, 0.2 ≤ x1 ≤ 0.6, 0 ≤ y1 ≤ 0.05, 0 ≤ c1 ≤ 0.05, and x1 + y1 + z1 = 1, Formula 2 Li a2 Ni x2 Co y2 Mr z2 B2 b2 O 2-c2 Where in Formula 2 above, B2 is at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb, and satisfies 0.8 ≤ a2 ≤ 1.2, 0.5 ≤ x2 ≤ 0.8, 0.0 ≤ y2 ≤ 0.10, 0.1 ≤ z2 ≤ 0.35, 0 ≤ b2 ≤ 0.1, 0 ≤ c2 ≤ 0.05, and x2 + y2 + z2 + b2 = 1, and Formula 3 Li a3 Mn z3 Fe x3 B3 y3 PO 4-c3 Where in Formula 3 above, B3 is at least one element selected from the group consisting of Al, Ti, V, and Mg, and satisfies 0.8 < a3 ≤ 1.2, 0.4 ≤ z3 ≤ 0.8, 0 ≤ x3 ≤ 0.6, 0 ≤ y3 ≤ 0.05, 0 ≤ c3 ≤ 0.05, and x3 + y3 + z3 = 1.

2. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the third primary particles have a size of 50 nm to 150 nm, and The third particle has an average particle size D of 3μm to 7μm. 50 .

3. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the weight ratio of the second particles is 20 wt% to 30 wt% relative to the total amount of the first particles, the second particles, and the third particles in the positive electrode.

4. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the total doping content of manganese Mn in the positive electrode is 0.50 to 0.

60.

5. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the thickness ratio of the second positive electrode active material layer to the first positive electrode active material layer is 0.8 to 1.

2.

6. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the second particles including large particles and small particles have a bimodal particle size distribution.

7. The positive electrode for a rechargeable lithium battery as described in claim 6, wherein the small particles have an average particle size D of 2 μm to 5 μm. 50 .

8. The positive electrode for a rechargeable lithium battery as described in claim 6, wherein the large particles have an average particle size D of 10 μm to 20 μm. 50 .

9. The positive electrode for a rechargeable lithium battery according to claim 6, wherein the content of the small particles is lower than the content of the large particles relative to the total content of the second particles.

10. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the amount of the small particles of the second particles is 20 wt% to 30 wt% relative to the total content of the second particles.

11. A positive electrode for a rechargeable lithium battery, comprising: a positive electrode current collector; a first positive electrode active material layer on the positive electrode current collector; and a second positive electrode active material layer on the first positive electrode active material layer, wherein the first positive electrode active material layer comprises first particles represented by Formula 1 and having an olivine structure, second particles represented by Formula 2 and having a layered structure, and a first functional additive, the second positive electrode active material layer comprises third particles represented by Formula 3 and having an olivine structure, and a second functional additive, the average particle size of the first particles is smaller than the average particle size of the third particles, each of the first functional additive and the second functional additive comprises a conductive material and a binder, and the weight ratio of the first functional additive in the first positive electrode active material layer is lower than or equal to the weight ratio of the second functional additive in the second positive electrode active material layer, Formula 1 Li a1 Mn z1 Fe x1 B1 y1 PER 4-c1 wherein in Formula 1 above, B1 is at least one element selected from the group consisting of Al, Ti, V, and Mg, and satisfies 0.8 < a1 ≤ 1.2, 0.4 ≤ z1 ≤ 0.8, 0.2 ≤ x1 ≤ 0.6, 0 ≤ y1 ≤ 0.05, 0 ≤ c1 ≤ 0.05, and x1 + y1 + z1 = 1, Formula 2 Li a2 Ni x2 Co y2 Mr z2 B2 b2 O 2-c2 wherein in Formula 2 above, B2 is at least one element selected from the group consisting of Al, Ti, Mg, Zr, Mo, and Nb, and satisfies 0.8 ≤ a2 ≤ 1.2, 0.5 ≤ x2 ≤ 0.8, 0.0 ≤ y2 ≤ 0.10, 0.1 ≤ z2 ≤ 0.35, 0 ≤ b2 ≤ 0.1, 0 ≤ c2 ≤ 0.05, and x2 + y2 + z2 + b2 = 1, and Formula 3 Li a3 Mn z3 Fe x3 B3 y3 PO 4-c3 wherein in Formula 3 above, B3 is at least one element selected from the group consisting of Al, Ti, V, and Mg, and satisfies 0.8 < a3 ≤ 1.2, 0.4 ≤ z3 ≤ 0.8, 0 ≤ x3 ≤ 0.6, 0 ≤ y3 ≤ 0.05, 0 ≤ c3 ≤ 0.05, and x3 + y3 + z3 = 1.

12. The positive electrode for a rechargeable lithium battery according to claim 11, wherein the ratio of the weight ratio of the second functional additive to the weight ratio of the first functional additive is about 1 to about 2.

5.

13. The positive electrode for a rechargeable lithium battery according to claim 11, wherein the weight ratio of the first functional additive is 2.4 wt% to 4.0 wt%.

14. The positive electrode for a rechargeable lithium battery according to claim 11, wherein the weight ratio of the second functional additive is 3.0 wt% to 6.0 wt%.

15. The positive electrode for a rechargeable lithium battery as claimed in claim 11, wherein the binder comprises at least one selected from the group consisting of: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, and nylon.

16. The positive electrode for a rechargeable lithium battery as claimed in claim 11, wherein the weight percentage of the second particle is 20 wt% to 30 wt% relative to the total weight of the first particle, the second particle, and the third particle in the positive electrode.

17. The positive electrode for a rechargeable lithium battery as claimed in claim 11, wherein the total doping content of manganese (Mn) in the positive electrode is 0.50 to 0.

60.

18. The positive electrode for a rechargeable lithium battery as claimed in claim 11, wherein the thickness ratio of the second positive electrode active material layer to the first positive electrode active material layer is 0.8 to 1.

2.

19. The positive electrode for a rechargeable lithium battery as claimed in claim 11, wherein the second particle has a BET specific surface area of ​​0.3 to 1.

2.

20. A rechargeable lithium battery, comprising a positive electrode as described in any one of claims 1 to 19.

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