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

Abstract

The present invention relates to a positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same, and for example, the positive electrode 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 including a compound represented by Formula 1 and having an olivine structure and second particles including a compound represented by Formula 2 and having a spinel structure, and the second positive electrode active material layer includes third particles including a compound represented by Formula 1 and having a spinel structure. The third particle includes a compound represented by Formula 3 and having an olivine structure. The first particle is in the form of a secondary particle in which a plurality of primary particles are aggregated. A formula 1 is Lia1Mnz1Fex1B1y1PO4-c < 1 >, a formula 2 is Lia2Mnx2B2y2O4-c < 2 >, and a formula 3 is Lia3Mnz3Fex3B3y3PO4-c < 3 >.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2024-0056995, 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 positive electrode active materials, and rechargeable lithium batteries including positive electrodes, and for example, to positive electrode active materials including olivine-based lithium compounds (olivine-structured compounds), positive electrode active materials including spinel-based lithium compounds (spinel-structured compounds), positive electrodes including positive electrode active materials, and rechargeable lithium batteries including positive electrodes. Background Technology

[0004] The rapid proliferation of battery-powered electronics, such as mobile phones, laptops, and electric vehicles, has recently driven a surge 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 containing an active material that allows lithium ions to be inserted into and extracted from the positive and negative electrodes) and an electrolyte. The rechargeable lithium battery 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 an economical positive electrode active material that has 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 first particles and second particles, wherein the first particles comprise a compound represented by Formula 1 and having an olivine structure, and the second particles comprise a compound represented by Formula 2 and having a spinel structure.

[0010] The second positive electrode active material layer may include third particles, the third particles including a compound represented by Formula 3 and having an olivine structure, and

[0011] The first particles may be in the form of secondary particles in which a plurality of primary particles are aggregated (e.g., coalesced).

[0012] Formula 1

[0013] Li a1 Mn z1 Fe x1 B1 y1 PO 4-c1

[0014] 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, x1 + y1 + z1 = 1, and 0 ≤ c1 ≤ 0.05.

[0015] Formula 2

[0016] Li a2 Mn x2 B2 y2 O 4-c2

[0017] In Formula 2 above, B2 may be at least one element selected from the group consisting of Al and Mg, and may satisfy 0.8 < a2 ≤ 1.2, 1.9 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05.

[0018] Formula 3

[0019] Li a3 Mn z3 Fe x3 B3 y3 PO 4-c3

[0020] 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, x3 + y3 + z3 = 1, and 0 ≤ c3 ≤ 0.05. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are included to provide a further understanding of the embodiments of the present disclosure, and the accompanying drawings are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the present disclosure and, together with the description, are used to explain the principles of the present disclosure. In the drawings:

[0022] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present disclosure;

[0023] 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;

[0024] Figure 6 A cross-sectional view of a positive electrode for a rechargeable lithium battery according to an embodiment of the present disclosure.

[0025] 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;

[0026] Figure 8A and Figure 8B Each of these is an enlarged view showing the second positive electrode active material layer of a rechargeable lithium battery according to an embodiment of the present disclosure;

[0027] Figure 9 To illustrate a pair of SEM images of a first particle according to an embodiment of the present disclosure;

[0028] Figure 10 To illustrate a pair of SEM images of a second particle according to an embodiment of the present disclosure;

[0029] Figure 11A To illustrate a pair of SEM images of a third particle according to an embodiment of this disclosure; and

[0030] Figure 11B To illustrate a pair of SEM images of a third particle according to an embodiment of the present disclosure. Detailed Implementation

[0031] The embodiments of this disclosure will now be described clearly and in more detail to enable those skilled in the art to implement the subject matter of this disclosure. To sufficiently understand the configuration and effects of the subject matter of this disclosure, exemplary embodiments of this disclosure will be described with reference to the accompanying drawings. However, it should be noted that this disclosure is not limited to the embodiments described below and can be implemented in various suitable forms with various modifications. The embodiments described herein are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0032] In this document, it will be understood that if a component is referred to as being on another component, then that component may be directly on the other component, or an intervening third component may be present. In embodiments, the dimensions (e.g., thickness) of some 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.

[0033] Unless otherwise specified herein, singular expressions may include plural expressions. In implementation, unless otherwise specified, the phrase “A or B” may indicate “A but not B,” “B but not A,” or “A and B.” The terms “comprises” and / or “comprising” as used herein do not exclude the presence or addition of one or more other components.

[0034] As used herein, the term "combinations thereof" may refer to mixtures, stacks, complexes, copolymers, alloys, blends and / or reaction products.

[0035] Unless otherwise specified herein, particle size may be the average particle size (average size). In embodiments, particle size is defined as 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 (e.g., by a particle size analyzer, transmission electron microscopy, and / or scanning electron microscopy). In embodiments, the average particle size (D) is... 50 The average particle size (D) value can be obtained by measuring the object using a dynamic light scattering-based measuring device, performing data analysis, counting the number of particles in each particle size range, and then calculating the value from there. In this embodiment, the average particle size (D) is... 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. A commercially available laser diffraction particle size measurement device (e.g., the MT 3000 from Microtrac, Ltd.) is introduced, and ultrasonic waves at approximately 28 kHz are irradiated with approximately 60 W of power. The average particle size (D) based on a 50% particle size distribution can then be calculated within the measurement device. 50 ).

[0036] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present disclosure is shown. (Reference) Figure 1 A rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0037] 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.

[0038] 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.

[0039] Positive electrode 10

[0040] The positive electrode 10 for a rechargeable lithium battery may include a positive electrode current collector COL1 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). Reference will be made below. 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.

[0041] negative electrode 20

[0042] 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).

[0043] 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.

[0044] The binder can be used to ensure good adhesion between the negative electrode active material particles and to ensure good adhesion between the negative electrode active material and the negative electrode current collector COL2. The binder may include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] Negative electrode active material

[0052] 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.

[0053] Materials that can reversibly insert / deintercalate 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, plate-like, sheet-like, 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.

[0054] 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.

[0055] 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 is selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof). 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.

[0056] 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 amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which primary silicon particles are aggregated and an amorphous carbon coating (shells) 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 the amorphous carbon matrix and exist.

[0057] 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.

[0058] 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.

[0059] Separator 30

[0060] According to the type of the rechargeable lithium battery, the separator 3 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 of them (such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.).

[0061] 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.

[0062] The porous substrate may be a polymer film formed from any one of the following polymers or copolymers or mixtures thereof: 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).

[0063] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers.

[0064] 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.

[0065] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked.

[0066] Electrolyte ELL

[0067] Electrolytes (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0068] Non-aqueous organic solvents can be used as media for transporting ions that participate in the electrochemical reactions of a battery.

[0069] Non-aqueous organic solvents may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0070] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), etc.

[0071] Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, caprolactone, etc.

[0072] 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.

[0073] Non-aqueous organic solvents can be used alone or in combination of two or more.

[0074] 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.

[0075] 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).

[0076] Rechargeable lithium batteries

[0077] 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 and a housing 50 including the electrode assembly 40, the electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20. 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.

[0078] 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.

[0079] 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 stacked on the first positive electrode active material layer ATL1.

[0080] 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.

[0081] First positive electrode active material layer ATL1

[0082] 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.

[0083] The first positive electrode active material layer ATL1 may include a first particle PTC1, a second particle PTC2, 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).

[0084] The first binder BND1 can bind (e.g., bond together) the first particles PTC1 and the first conductive material CDM1. In an embodiment, the first binder BND1 can stably fix the first positive electrode active material layer ATL1 to the positive electrode current collector COL1. For example, the first binder BND1 can 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, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon, but is not limited thereto.

[0085] 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 a chemical change (e.g., does not cause an undesired chemical change) 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 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 polyphenylene derivatives); or mixtures thereof.

[0086] Hereinafter, each of the first particles PTC1 and the second particles PTC2 in the first positive electrode active material layer ATL1 will be described in more detail.

[0087] First particles PTC1

[0088] The first particles PTC1 can include an olivine-type lithium compound represented by Formula 1 below.

[0089] Formula 1

[0090] Li a1 Mn z1 Fe x1 B1 y1 PO 4-c1

[0091] In Formula 1 above, 0.8 < a1 ≤ 1.2, 0.4 ≤ z1 ≤ 0.8, 0.2 ≤ x1 ≤ 0.6, 0 ≤ y1 ≤ 0.05, x1 + y1 + z1 = 1, and 0 ≤ c 1 ≤ 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 particles PTC1. For example, B1 can be Ti.

[0092] The first PTC1 particle may further include carbon (carbon element) derived from the above-mentioned positive electrode active material layer AML1. The first PTC1 particle may 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%.

[0093] The first PTC1 particle can be in the form of a single particle. Here, a single particle can refer to a single type (or species) of particles that have no grain boundaries within them. A single particle can refer to a single particle morphologically present in an independent phase (where particles do not aggregate), a particle with a monolithic structure, a particle with an integral structure, or a particle that is not aggregated. 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 of about 2 to about 100 first primary particles attached to each other.

[0094] The first PTC1 particle may be a nano-sized positive electrode active material. The first PTC1 particle may include at least one first primary particle. In one embodiment, the first PTC1 particle may be spherical or ellipsoidal in shape (e.g., it may be substantially spherical or substantially ellipsoidal). In another embodiment, even if the first primary particles are aggregated (e.g., coalesced), the first PTC1 particle may not have a spherical shape, but rather an irregular shape.

[0095] In an implementation, if the cumulative volume in the particle size distribution is approximately 50% by volume, the average particle size can indicate the particle size (D). 50 In the implementation, the average particle size (D) of the first particle PTC1 is... 50 This can be a value measured using a particle size analyzer.

[0096] In an embodiment, the first particle PTC1 may have an average particle size of about 500 nm to about 2.5 μm or about 500 nm to about 1 μm. 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 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). The first primary particle may have a size of about 100 nm to about 500 nm or about 100 nm to about 200 nm.

[0097] The first particle PTC1 is in a polycrystalline form and may include secondary particles in which at least two first primary particles NNP_1 are aggregated. For example, a first particle PTC1 may include multiple first primary particles NNP_1 aggregated together. The first particle PTC1 including multiple first primary particles NNP_1 may be spherical or ellipsoidal in shape (e.g., substantially spherical or substantially ellipsoidal).

[0098] In an implementation, if the cumulative volume in the particle size distribution is approximately 50% by volume, then the average particle size can indicate the particle size (D). 50 In the implementation, the average particle size (D) of the first particle PTC1 is... 50 This can be a value measured using a particle size analyzer.

[0099] The first primary particle PTC1, including at least one first primary particle NNP_1, may have an average particle size of about 500 nm to about 5 μm, about 500 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 first primary particle PTC1... 50 It can be smaller than the average particle size (D) of the second particle, PTC2. 50 This will be described further below.

[0100] The first particle PTC1 may include at least one primary particle (or a single particle). The size of at least one first primary particle NNP_1 constituting the first particle PTC1 can be measured using a scanning electron microscope (SEM). In an embodiment, the size of the first primary particle NNP_1 may indicate the diameter measured by randomly selecting approximately 30 first primary particles NNP_1 from an electron micrograph of the positive electrode active material. The size of the first primary particle NNP_1 may be uniform (e.g., substantially uniform).

[0101] At least one first primary particle NNP_1 constituting the first particle PTC1 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.

[0102] 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 metal-containing compound selected from the group consisting of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds. The metal-containing compound (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 compound may further include other metallic and / or non-metallic elements. For example, the metal-containing compound may further include lithium. Through the coating, the first PTC1 particle may have improved structural stability and electrical conductivity.

[0103] In an embodiment, the first particle PTC1 may further include a grain boundary coating on the surface of each first primary particle NNP_1. The grain boundary coating may be present within the first particle PTC1. The grain boundary coating may be formed as an application along the interface between the first primary particles NNP_1 within the first particle PTC1. For example, the grain boundary coating may refer to a layer formed by a material applied to the grain boundaries within the first particle PTC1.

[0104] The grain boundary coating may include elemental carbon and / or carbon-containing compounds. The grain boundary coating may further include at least one metal-containing compound selected from the group consisting of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds.

[0105] The interior of the first PTC1 can refer to the entire interior of the first PTC1 other than its surface. For example, the interior of the first PTC1 can refer to the entire interior region from a depth of about 10 nm from the surface of the first PTC1 or from a depth of about 10 nm to about 2 μm.

[0106] The first PTC1 particle further includes a grain boundary coating, thus providing 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 providing further improved electrical conductivity.

[0107] The first PTC1 particle may further include carbon 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 the first PTC1 particle is in the form of a secondary particle, the first PTC1 particle may have a higher carbon content than in the form of a single particle.

[0108] The first PTC particle PTC1 may be spherical (e.g., may have a substantially spherical) shape in which a plurality of first primary particles NNP_1 are aggregated. The first PTC particle PTC1 has the first primary particles NNP_1 tightly aggregated, and thus may exhibit the following characteristics. The first PTC particle PTC1 holds the above-mentioned coating and / or grain boundary coating well, and thus may have stronger conductivity and improved low-temperature characteristics. Since the adhesiveness of the electrode plate increases, the amount of the binder may be reduced. The first PTC particle PTC1 may be spherical or ellipsoidal (e.g., may have a substantially spherical or substantially ellipsoidal) shape.

[0109] The first PTC particle PTC1 may have a porosity of about 20% to about 40%. The span value of the first PTC particle PTC1 analyzed by a particle size analyzer may be about 0.3 to about 0.75. The porosity (n) may be defined as the pore volume (V p ) divided by the total volume (V t ) of the particle, or n = V p / V t . The span value is represented by (D 90 - D 10 ) / D 50 . As used herein, the term "D 10 " refers to the average particle diameter of the particles when the cumulative percentage reaches 10% by volume in the particle size distribution, and as used herein, the term "D 90 " refers to the average particle diameter of the particles when the cumulative percentage reaches 90% by volume in the particle size distribution.

[0110] The second PTC particle PTC2

[0111] The second PTC particle PTC2 may include a lithium compound having a spinel structure represented by the following formula 2.

[0112] Formula 2

[0113] Li a2 Mn x2 B2 y2 O 4-c2

[0114] In the above formula 2, 0.8 < a2 ≤ 1.2, 1.9 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05 may be satisfied. B2 may be at least one element selected from the group consisting of Al and Mg. B2 may be a dopant doped in the second PTC particle PTC2. The dopant may have the effect of controlling the uniform (e.g., substantially uniform) growth of the second primary particles NNP_2 constituting the second PTC particle PTC2, and improving the charge / discharge efficiency, low-temperature characteristics, and life characteristics of the rechargeable lithium battery. The second PTC particle PTC2 provides benefits including high output characteristics, high structural stability, high average voltage, and excellent life characteristics.

[0115] The second PTC2 particle may have a spinel structure, which can have both tetrahedral and octahedral lattice structures. The lattice structure provides various channels, allowing lithium ions to easily insert / deintercalate, resulting in superior output characteristics. The second PTC2 particle includes Mn, thus providing structural stability. This structural stability protects the electrochemical properties of the particle even at high voltages, allowing for high-voltage operation and providing excellent lifetime characteristics.

[0116] The second PTC2 particle is a lithium manganese oxide and may be a positive electrode material in which cobalt in the lithium cobalt oxide is replaced by manganese. In embodiments of this disclosure, the second PTC2 particle may have trace amounts of cobalt (Co), indicating that it contains virtually no Co (e.g., such that the second PTC2 particle is cobalt-free or substantially cobalt-free). For example, the second PTC2 particle may have a cobalt (Co) content of about 100 ppm or less. The positive electrode active material according to this disclosure is substantially cobalt (Co-free, thereby providing an economical rechargeable lithium battery with high capacity and operating voltage.

[0117] refer to Figure 7 The second particle PTC2 may be 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 including multiple second primary particles NNP_2 may be in the shape of an aggregated sphere (e.g., a generally spherical aggregate shape), and may have an irregular shape even if the second primary particles NNP_2 are aggregated.

[0118] In an implementation, if the cumulative volume in the particle size distribution is approximately 50% by volume, the average particle size can indicate the particle size (D). 50 In the implementation, the average particle size (D) of the second particle PTC2 is... 50 The value can be measured using a particle size analyzer. The second particle, PTC2, can have an average particle size (D) of approximately 3 μm to approximately 20 μm, approximately 3 μm to approximately 10 μm, approximately 4 μm to approximately 15 μm, or approximately 5 μm to approximately 10 μm. 50 For example, the second PTC2 particle can have an average particle size of approximately 8 μm (D). 50 ).

[0119] The second primary particle NNP_2 constituting the second particle PTC2 may have an average size of about 3 μm or smaller. For example, the second primary particle NNP_2 may have an average size of about 300 nm to about 3 μm, about 0.5 μm to about 3 μm, about 1 μm to about 3 μm, or about 2 μm to about 3 μm. In an embodiment, the size of the second primary particle 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 NNP_1. The difference in average size between the second primary particle NNP_2 and the first primary particle NNP_1 may be about 300 nm or larger.

[0120] In one embodiment, the second PTC2 particle may include a second coating on its surface. The second coating on the second PTC2 particle effectively prevents or reduces structural collapse caused by repeated charging / discharging.

[0121] The second coating may include a metal-containing compound, a magnesium-containing compound, or a combination thereof. The metal-containing compound in the second coating may be, for example, a metal oxide, a metal hydroxide, a metal carbonate, a complex thereof, or a mixture thereof. The metal-containing compound may further include other metals and / or non-metallic elements. For example, the second coating may further include lithium, manganese, and / or nickel.

[0122] Methods for measuring the metal content in the second coating of the second PTC2 particle may include scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS) of the second PTC2 particle. Through these analyses, the aluminum and / or magnesium content in the second coating can be determined. In addition to, or alternative to, SEM-EDS, methods for measuring the metal content in the second coating of the second PTC2 particle may include inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), etc.

[0123] 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 of the second particle PTC2 may be less than that of the first particle PTC1.

[0124] The first particle PTC1 and the second particle PTC2 constituting the first positive electrode active material layer ATL1 may include manganese (Mn).

[0125] The second PTC2 particle has a high manganese (Mn) content, thus improving the operating voltage of the rechargeable lithium battery compared to the first PTC1 particle. In this embodiment, the second PTC2 particle has a spinel structure, thus exhibiting a stable crystal structure and superior lifetime characteristics compared to the first PTC1 particle. The second PTC2 particle may also have low impedance (e.g., low resistance). In this embodiment, the second PTC2 particle, being manganese oxide, is almost unusable alone due to its low capacity and energy density.

[0126] The positive electrode active material layer according to this embodiment has a first PTC1 and a second PTC2 mixed together in a suitable or appropriate ratio (e.g., with adjusted manganese (Mn) content), thus exhibiting improved voltage and lifespan characteristics compared to batteries comprising common lithium iron phosphate compounds and / or lithium manganese iron phosphate compounds. By mixing the first PTC1 and the second PTC2 together within a suitable or appropriate range, a battery with a long lifespan can be obtained. The battery also has improved energy density, thus exhibiting superior performance for commercial applications.

[0127] The positive electrode active material layer according to this embodiment has first particles PTC1 and second particles PTC2 mixed together in a suitable or appropriate ratio, thus allowing for easy fabrication of the electrode plate. For example, compared to fabricating a positive electrode active material layer comprising a common lithium iron phosphate compound, the further inclusion of second particles PTC2 with a larger average particle size results in increased adhesion of the electrode plate. Consequently, less binder is required to fabricate the electrode plate. Firstly, a first positive electrode active material layer ATL1 comprising second particles PTC2 with low impedance (e.g., low resistance) is formed, and correspondingly, the electrode plate can have improved impedance (e.g., improved resistance).

[0128] Second positive electrode active material layer ATL2

[0129] Figure 8A and Figure 8B An enlarged view showing the second positive electrode active material layer ATL2 of the positive electrode for a rechargeable lithium battery according to an embodiment of the present disclosure.

[0130] refer to Figure 8A and Figure 8B 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 electrically conductive material CDM2). "SP3" refers to the third particle in the form of a single particle, and "PC3" refers to the first particle in the form of a secondary particle.

[0131] The second binder BND2 can bind the third particles PTC3 and the second conductive material CDM2. In an embodiment, the second binder BND2 can stably fix the second positive electrode active material layer ATL2 on the first positive electrode active material layer ATL1. In an embodiment, the second binder BND2 can 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, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon, but not limited thereto.

[0132] 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 conductive 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 polyphenylene derivatives); or a mixture thereof.

[0133] Third particles PTC3

[0134] The third particles PTC3 can include an olivine-type lithium compound represented by Formula 3 below.

[0135] Formula 3

[0136] Li a3 Mn z3 Fe x3 B3 y3 PO 4-c3

[0137] In Formula 3 above, 0.8 < a3 ≤ 1.2, 0.4 ≤ z3 ≤ 0.8, 0 ≤ x3 ≤ 0.6, 0 ≤ y3 ≤ 0.05, x3 + y3 + z3 = 1, and 0 ≤ c3 ≤ 0.05 can be satisfied. B3 can be at least one element selected from the group consisting of Al, Ti, V, and Mg. B3 can be a dopant doped into the third particles PTC3. For example, B3 can be Ti.

[0138] The third PTC3 particle may further include carbon derived from the aforementioned positive electrode active material layer AML1. The third PTC3 particle may have a carbon 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%.

[0139] The following description describes the characteristics (such as particle shape, size, and particle size) of the third particle PTC3 implementation.

[0140] The third PTC3 particle can be in the form of a single particle. Herein, a single particle can refer to a single type (or species) of particle that has no grain boundaries within it. The term single particle can refer to a single particle morphologically present in an independent phase (where particles do not aggregate), a particle with a monolithic structure, a particle with an integral structure, or a particle that is not aggregated. 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 of about 2 to about 100 third primary particles attached to each other.

[0141] The third PTC3 particle can be a nano-sized positive electrode active material. The third PTC3 particle can include at least one third primary particle. In one embodiment, the third PTC3 particle can be spherical or ellipsoidal in shape (e.g., substantially spherical or substantially ellipsoidal) in which the third primary particles are aggregated. In another embodiment, even if the third primary particles are aggregated, the third PTC3 particle may not have a spherical shape, but rather an irregular shape.

[0142] In an implementation, if the cumulative volume in the particle size distribution is approximately 50% by volume, the average particle size can indicate the particle size (D). 50 In the implementation, the average particle size (D) of the third particle PTC3 is... 50 This can be a value measured using a particle size analyzer.

[0143] In an embodiment, the third PTC3 particle may have an average particle size of about 500 nm to about 2.5 μm or about 500 nm to about 1 μm. The size of at least one third primary particle constituting the third PTC3 particle can be measured using a scanning electron microscope (SEM). In an embodiment, the size of the third primary particle may indicate the diameter measured by randomly selecting about 30 third primary particles from an electron micrograph of the positive electrode active material. The size of the third primary particle may be uniform (e.g., substantially uniform). The third primary particle may have a size of about 100 nm to about 500 nm or about 100 nm to about 200 nm.

[0144] The third particle PTC3 may be in a polycrystalline form and may include secondary particles in which at least two third primary particles NNP_3 are aggregated. For example, a third particle PTC3 may include multiple third primary particles NNP_3 aggregated together. The third particle PTC3 including multiple third primary particles NNP_3 may be spherical or ellipsoidal in shape (e.g., substantially spherical or substantially ellipsoidal).

[0145] In an implementation, if the cumulative volume in the particle size distribution is approximately 50% by volume, then the average particle size can indicate the particle size (D). 50 In the implementation, the average particle size (D) of the third particle PTC3 is... 50 This can be a value measured using a particle size analyzer.

[0146] 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 ).

[0147] 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).

[0148] 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.

[0149] In this paper, the "size" of a particle in the form of a single particle and the "average particle size" of the particle represent different concepts. This difference arises because the size of a single particle measured directly using SEM images differs from the average particle size measured using a particle size analyzer. As described in the specification, the size of a third particle in the form of a single particle can refer to the size of a single particle measured based on an SEM image. On the other hand, the average particle size (D... 50 ) is defined as the value measured using a particle size analyzer.

[0150] 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 metal-containing compound selected from the group consisting of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds. The metal-containing compound (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 compound may further include other metallic and / or non-metallic elements. For example, the metal-containing compound may further include lithium. Through the coating, the third PTC3 particle may have improved structural stability and electrical conductivity.

[0151] In an embodiment, the third PTC3 particle may further include a grain boundary coating on the surface of each of the third primary particles NNP_3. The grain boundary coating may be present within the third PTC3 particle. The grain boundary coating may be formed by coating 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 formed by material coated on the grain boundaries within the third PTC3 particle.

[0152] The grain boundary coating may include elemental carbon and / or carbon-containing compounds. The grain boundary coating may further include at least one metal-containing compound selected from the group consisting of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds.

[0153] The interior of the third PTC3 can refer to the entire interior of the third PTC3 excluding its surface. For example, relative to the surface of the third PTC3, the interior of the third PTC3 can refer to the entire interior region from a depth of about 10 nm from the surface of the third PTC3 or from a depth of about 10 nm to about 2 μm.

[0154] The third PTC3 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 third PTC3 particle further includes a grain boundary coating, thus exhibiting further improved electrical conductivity.

[0155] The third PTC3 particle may further include carbon 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 the third PTC3 particle is in the form of a secondary particle, it may have a higher carbon content than if it were in the form of a single particle.

[0156] The third PTC3 particle can be spherical (e.g., substantially 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 enhanced electrical conductivity and improved low-temperature properties. Due to increased adhesion of the electrode plate, the amount of binder can be reduced. The third PTC3 particle can be spherical or ellipsoidal (e.g., substantially spherical or substantially ellipsoidal).

[0157] 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.

[0158] The positive electrode active material layer AML1 according to embodiments of the present disclosure will be described in more detail below.

[0159] 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 manganese (Mn) doping content M1 in the first particle PTC1, the manganese (Mn) doping content M2 in the second particle PTC2, and the manganese (Mn) doping content M3 in the third particle PTC3. Specifically, the manganese (Mn) doping content M1 in the first particle PTC1 can be defined as the product of the number of Mn atoms (z1) in the first particle PTC1 and the weight ratio of the first particle PTC1, divided by the molecular weight of the first particle PTC1. The manganese (Mn) doping content M2 in the second particle PTC2 can be defined as the product of the number of Mn atoms (z2) in the second particle PTC2 and the weight ratio of the second particle PTC2, divided by the molecular weight of the second particle PTC2. The manganese (Mn) doping content M3 in the third PTC3 particle can be defined as the product of the number of Mn atoms (z3) in the third PTC3 particle and the weight ratio of the third PTC3 particle, divided by the molecular weight of the third PTC3 particle. The specific equation is as follows. In the following equation, the weight ratio of the first PTC1 particle refers to the weight ratio of the first PTC1 particle relative to the total weight of the first PTC1 particle, the second PTC2 particle, and the third PTC3 particle. The number of Mn atoms (z1) in the first PTC1 particle is the number of Mn atoms per mole of the first particle. The number of Mn atoms (z2) in the second PTC2 particle is the number of Mn atoms per mole of the second particle. The number of Mn atoms (z3) in the third PTC3 particle is the number of Mn atoms per mole of the third particle.

[0160] Total Mn doping content = [Number of Mn atoms (z1) in the first PTC1 particle × Weight ratio of the first PTC1 particle / Molecular weight of the first PTC1 particle] + [Number of Mn atoms in the second PTC2 particle (z2) × Weight ratio of the second PTC2 particle / Molecular weight of the second PTC2 particle] + [Number of Mn atoms (z3) in the third PTC3 particle × weight ratio of the third PTC3 particle / molecular weight of the third PTC3 particle].

[0161] The total doping content of manganese (Mn) in the positive electrode or the positive electrode active material layer AML1 can be 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, or about 0.50 to about 0.60.

[0162] 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 PTC2 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 30 wt%.

[0163] 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.

[0164] Functional additives may include conductive material CDM (e.g., electrically conductive material CDM) and binder BND. The positive electrode active material layer includes functional additives, and accordingly, the positive electrode active material layer may have improved properties. For example, the materials in the positive electrode active material layer may bond well, the adhesion of the electrode plate may be improved, and the conductivity (e.g., electrical conductivity) of the positive electrode active material layer may be improved.

[0165] Compared to the first PTC1 in the form of a single particle, the first PTC1 in the form of secondary particles may contain a smaller amount of functional additive ADD required or used in the active material. In an embodiment, both the first PTC1 and the second PTC2 are included in the first positive electrode active material layer ATL1, and correspondingly, the weight ratio of the functional additive ADD required or used in the active material layer can be reduced.

[0166] For example, a relatively large amount of binder BND may be needed or used to adhere the first PTC1 particles with a small average particle size to the positive electrode current collector COL1, but a relatively small amount of binder BND may be needed or used to adhere the second PTC2 particles with a large average particle size to the positive electrode current collector COL1. This reduces the weight ratio of binder BND needed or used through the first positive electrode active material layer ATL1, which includes the first PTC1 particles and the second PTC2 particles.

[0167] The positive electrode active material layer AML1 disclosed herein includes a first positive electrode active material layer ATL1 having a relatively small amount of functional additives that are needed or used, thereby improving energy density.

[0168] A two-layer structure makes electrode plate fabrication easier. For example, a first positive electrode active material layer ATL1, in which first particles PTC1 and second particles PTC2 are mixed together, can be first stacked on the positive electrode current collector COL1, 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 electrode plate adhesion, is first stacked on the positive electrode current collector COL1, less first binder BND1 is needed or used, thereby improving energy density. For example, the first positive electrode active material layer ATL1 can be first stacked on the portion in contact with the positive electrode current collector COL1 to improve the impedance (e.g., resistance) of the electrode plate.

[0169] The weight percentage of the first binder BND1 in the first positive electrode active material layer ATL1 can be from about 1.2 wt% to about 2.0 wt%.

[0170] The weight percentage of the second binder BND2 in the second positive electrode active material layer ATL2 can be about 2.0 wt% to about 3.0 wt%.

[0171] The weight ratio of the first binder BND1 in the first positive electrode active material layer ATL1 may be lower than or equal to the weight ratio of the second binder BND2 in the second positive electrode active material layer ATL2. In an embodiment, the ratio of the weight ratio of the second binder BND2 in the second positive electrode active material layer ATL2 to the weight ratio of the first binder BND1 in the first positive electrode active material layer ATL1 may be about 0.8 to about 2.6.

[0172] The weight percentage of the first conductive material CDM1 in the first positive electrode active material layer ATL1 can be from about 1.2 wt% to about 2.0 wt%.

[0173] The weight percentage of the second conductive material CDM2 in the second positive electrode active material layer ATL2 can be approximately 2.0 wt% to approximately 3.0 wt%.

[0174] The weight ratio of the first conductive material CDM1 in the first positive electrode active material layer ATL1 may be lower than or equal to the weight ratio of the second conductive material CDM2 in the second positive electrode active material layer ATL2. In an embodiment, the ratio of the weight ratio of the second conductive material CDM2 in the second positive electrode active material layer ATL2 to the weight ratio of the first conductive material CDM1 in the first positive electrode active material layer ATL1 may be approximately 0.65 to approximately 4.5.

[0175] The weight percentage of the first functional additive ADD1 in the first positive electrode active material layer ATL1 can be from about 2.4 wt% to about 4.0 wt%.

[0176] The weight percentage of the second functional additive ADD2 in the second positive electrode active material layer ATL2 can be from about 4.0 wt% to about 6.0 wt%.

[0177] The weight ratio of the first functional additive ADD1 in the first positive electrode active material layer ATL1 may be lower than or equal to the weight ratio of the second functional additive ADD2 in the second positive electrode active material layer ATL2.

[0178] In an embodiment, the weight ratio of the second functional additive ADD2 in the second positive electrode active material layer ATL2 to the weight ratio of the first functional additive ADD1 in the first positive electrode active material layer ATL1 can be about 1.0 to about 2.0, about 1.5 to about 2.5, or about 1.5 to about 3.0.

[0179] The first positive electrode active material layer ATL1 may have a thickness T1. In an embodiment, T1 may increase with the 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 the 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 0.8 to about 1.5, about 0.8 to about 1.2, about 0.9 to about 1.2, or about 1. Within the above ranges, stability and lifetime characteristics can be improved, while excellent high-voltage performance and energy density are maintained.

[0180] In an embodiment, the positive electrode active material layer AML1 of this disclosure may have a powder compaction density of about 2.0 g / cc to about 2.5 g / cc.

[0181] 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 2The 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.

[0182] Rechargeable lithium batteries incorporating the positive electrode active material of this disclosure can have improved low-temperature characteristics. In embodiments, the initial discharge capacity of the rechargeable lithium battery at -20°C relative to its initial discharge capacity at 25°C (initial discharge capacity at -20°C / initial discharge capacity at 25°C) can be about 40% or greater. For example, the initial discharge capacity of the rechargeable lithium battery of this disclosure at -20°C relative to its initial capacity at 25°C (initial discharge capacity at -20°C / initial discharge capacity at 25°C) can be about 40% to about 100%, about 50% to about 100%, or about 96% to about 99%.

[0183] 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.

[0184] 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 greater. For example, the capacity retention rate can be approximately 98% to approximately 100% or approximately 99.8% to approximately 100%.

[0185] Method for preparing positive electrode active materials

[0186] The following describes 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.

[0187] Preparation Example 1: Preparation of PTC1 as a secondary particle

[0188] Manganese iron phosphate precursor (Mn) 0.6 Fe 0.4PO4), lithium carbonate, and titanium dioxide were mixed together in a molar ratio of (Mn+Fe):Li:Ti = 1:1.03:0.004. 10 wt% glucose was further added to the resulting mixture. The slurry mixture was spray-dried at a spray pressure of 0.5 MPa and a temperature of 230 °C, and then evaporated to dry. The dried mixture was calcined at 750 °C for 10 hours in a nitrogen atmosphere to obtain first particles in the form of secondary particles. The first primary particles in the first particles have an average size of about 50 nm to about 150 nm. Based on the initially added materials, the composition of the obtained first particles is Li 1.03 Mn 0.6 Fe 0.4 Ti 0.004 PO4 + C (derived from glucose). With the number of lithium atoms set to 1, the sum of the number of atoms of the other metal elements is approximately 1.

[0189] Preparation Example 2: Preparation of PTC2 in the form of secondary particles

[0190] 0.170 g of MnSO4·H2O and 0.228 g of (NH4)2S2O8 were dissolved in 100 ml of distilled water. Sulfuric acid was added to adjust the pH to 1, and the resulting mixture was reacted at 130 °C for 10 hours to obtain a solid precipitate. The precipitate was washed several times with distilled water and dried at 300 °C for 3 hours to obtain solid MnO2 with an average particle size of 5 μm.

[0191] Li2CO3 and synthesized MnO2 were mixed together to make the molar ratio of Li to Mn 1:2, and the resulting mixture was heated at 600℃ for 10 hours to synthesize LiMn2O4 particles with an average particle size of 7 μm and an average primary particle size of 0.5 μm to 2.5 μm.

[0192] Preparation Example 3-1: Preparation of a third PTC3 particle in the form of a single particle

[0193] 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 = 1:1.03:0.004. 10 wt% glucose was added to the resulting mixture. The mixture was subjected to a wet milling process by ball milling. The mixture was evaporated to dryness in a heated tray, and then placed in a vacuum oven at 120°C and dried 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 third particles in the form of single particles. The third particles had an average size of approximately 100 nm to approximately 200 nm. Based on the initially added materials, the composition of the obtained third particles was Li1.03 Mn 0.6 Fe 0.4 Ti 0.004 PO4 + C (derived from glucose). With the number of lithium atoms set to 1, the sum of the number of atoms of the other metal elements is approximately 1.

[0194] Preparation Example 3-2: Preparation of PTC3 in the form of secondary particles

[0195] The iron manganese 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 = 1:1.03:0.004. 10 wt% glucose was further added to the resulting slurry mixture. The 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 in a nitrogen atmosphere to obtain third particles in the form of secondary particles. The primary particles in the third particles had an average size of approximately 50 nm to approximately 150 nm. Based on the initially added materials, the composition of the obtained third particles was Li 1.03 Mn 0.6 Fe 0.4 Ti 0.004 PO4 + C (derived from glucose). With the number of lithium atoms set to 1, the sum of the number of atoms of the other metal elements is approximately 1.

[0196] Fabrication of single-layer electrode plates

[0197] Comparative Example 1-1

[0198] The first particles from Preparation Example 1 and the second particles from Preparation Example 2 were mixed together at a weight ratio of 30:70 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.

[0199] Comparative Examples 1-2

[0200] Except that the first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed together in a weight ratio of 42:58, the positive electrode active material slurry and the single-layer electrode plate were prepared in essentially the same manner as in Comparative Example 1-1.

[0201] Comparative Examples 1-3

[0202] Except that the first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed together in a weight ratio of 56:44, the positive electrode active material slurry and the single-layer electrode plate were prepared in essentially the same manner as in Comparative Example 1-1.

[0203] Comparative Examples 1-4

[0204] Except that the first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed together in a weight ratio of 70:30, the positive electrode active material slurry and the single-layer electrode plate were prepared in essentially the same manner as in Comparative Example 1-1.

[0205] Comparative Examples 1-5

[0206] Except that the first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed together in a weight ratio of 83:17, the positive electrode active material slurry and the single-layer electrode plate were prepared in essentially the same manner as in Comparative Example 1-1.

[0207] Comparative Examples 1-6

[0208] Except that the first particles of Preparation Example 1 and the second particles of Preparation Example 2 were mixed together in a weight ratio of 95:5, the positive electrode active material slurry and the single-layer electrode plate were prepared in essentially the same manner as in Comparative Example 1-1.

[0209] Comparative Examples 1-7

[0210] Except that the first particles of Preparation Example 1, the second particles of Preparation Example 2, and the third particles of Preparation Example 3-1 were mixed together in a weight ratio of 41.5:17:41.5, the positive electrode active material slurry and the single-layer electrode plate were prepared in essentially the same manner as in Comparative Example 1-1.

[0211] Fabrication of double-layer electrode plates

[0212] Example 1-1

[0213] The first particle from Preparation Example 1 and the second particle from Preparation Example 2 were dispersed in N-methylpyrrolidone with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particle from Preparation Example 3-1 was dispersed in N-methylpyrrolidone with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0214] A first positive electrode active material slurry is coated onto the 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.

[0215] In this case, a double-layer positive electrode active material layer is formed, such that the first, second, and third particles in the double-layer positive electrode active material layer exist in a weight ratio of 41.5:17:41.5. 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 using a roller press.

[0216] Examples 1-2

[0217] The first particle from Preparation Example 1 and the second particle from Preparation Example 2 were dispersed in N-methylpyrrolidone with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particle from Preparation Example 3-2 was dispersed in N-methylpyrrolidone with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0218] A first positive electrode active material slurry is coated onto the 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.

[0219] In this case, a double-layer positive electrode active material layer is formed, such that the first, second, and third particles in the double-layer positive electrode active material layer exist in a weight ratio of 41.5:17:41.5. 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 using a roller press.

[0220] Example 2-1

[0221] The first particle from Preparation Example 1 and the second particle from Preparation Example 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 3-1 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.

[0222] A first positive electrode active material slurry is coated onto the 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.

[0223] In this case, a double-layer positive electrode active material layer is formed, such that the first, second, and third particles in the double-layer positive electrode active material layer exist in a weight ratio of 35:30:35. 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 using a roller press.

[0224] Example 2-2

[0225] The first particle from Preparation Example 1 and the second particle from Preparation Example 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 3-2 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.

[0226] A first positive electrode active material slurry is coated onto the 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.

[0227] In this case, a double-layer positive electrode active material layer is formed, such that the first, second, and third particles in the double-layer positive electrode active material layer exist in a weight ratio of 35:30:35. 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 using a roller press.

[0228] Comparative Example 2-1

[0229] The first particle from Preparation Example 1 and the second particle from Preparation Example 2 were dispersed in N-methylpyrrolidone with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particle from Preparation Example 3-1 was dispersed in N-methylpyrrolidone with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0230] 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. 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.

[0231] In this case, a double-layer positive electrode active material layer is formed, such that the first, second, and third particles in the double-layer positive electrode active material layer exist in a weight ratio of 41.5:17:41.5. 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 using a roller press.

[0232] Comparative Example 2-2

[0233] The first particle from Preparation Example 1 and the second particle from Preparation Example 2 were dispersed in N-methylpyrrolidone with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particle from Preparation Example 3-2 was dispersed in N-methylpyrrolidone with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0234] Unlike Examples 1-2, 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.

[0235] In this case, a double-layer positive electrode active material layer is formed, such that the first, second, and third particles in the double-layer positive electrode active material layer exist in a weight ratio of 41.5:17:41.5. 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 using a roller press.

[0236] Preparation of negative electrode

[0237] Graphite, binder (polyvinylidene fluoride), and 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.

[0238] Preparation of rechargeable lithium batteries

[0239] 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 used, which was prepared by mixing 1.3M LiPF6 with a mixed solvent (volume ratio: 2:6:2) containing ethylene carbonate (EC), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC).

[0240] Evaluation Example 1: Analysis of the surface of the active material in the positive electrode

[0241] The SEM image of the first particle prepared in Preparation Example 1 is shown in Figure 9 The SEM image of the second particle prepared in Preparation Example 2 is shown in the figure. Figure 10 The SEM image of the third particle prepared in Preparation Example 3-1 is shown in [the image]. Figure 11A The SEM image of the third particle prepared in Preparation Example 3-2 is shown in the figure. Figure 11B (Chinese) Reference Figure 9As can be seen, the first particle according to the embodiments of this disclosure takes the form of a spherical secondary particle in which fine first primary particles of nanoscale size are aggregated. (See reference...) Figure 10 As can be seen, the second particle according to the embodiments of this disclosure takes the form of a secondary particle in which a plurality of primary particles are aggregated. Compared with the first particle, the second particle takes on multiple forms and has larger primary particles.

[0242] Evaluation Example 2: Analysis of Positive Electrode Characteristics

[0243] The powder compaction density (PD) and energy density (ED) of the positive electrode active material layers prepared by Examples 1-1 to 2-2 and Comparative Examples 1-1 to 2-2 were measured, and the results are shown in Table 1.

[0244] Table 1

[0245]

[0246] For example, when calculating the total Mn doping content of Comparative Example 1-1 (e.g., the weight ratio of the first particle to the second particle = 30:70), the following results were obtained. Assuming that the molecular weights of the first particle and the second particle are approximately 157.21 and 180, respectively, and the number of Mn atoms per mole of the first particle and the number of Mn atoms per mole of the second particle are 0.6 and 2, respectively, the total Mn doping content can be calculated using the following equation: Total Mn doping content = [(30 × 0.6) / 157.21] + ([70 × 2) / 180] = 0.1145 + 0.7778 = 0.8923. Therefore, the Mn doping content of Comparative Example 1-1 is approximately 0.89, consistent with 0.9 in Table 1.

[0247] Referring to Table 1, it can be seen that the positive electrode active material layers according to Examples 1-1 to 2-2 have a higher energy density than those of Comparative Examples 1-1 to 1-4. Furthermore, even when compared to Comparative Examples 1-4, 1-5, or 1-7, each having a monolayer structure, the positive electrode active material layers according to Examples 1-1 to 2-2 are able to maintain similar levels of powder compaction density and energy density. It can be determined that the positive electrode active material layers according to Examples 1-1 to 2-2 above have a high energy density of 486 Wh / kg or greater, indicating that the positive electrode active material layers have an energy density suitable for commercial use.

[0248] Evaluation Example 3: Evaluation of Battery Properties

[0249] The properties of rechargeable lithium batteries prepared using the positive electrodes of Examples 1-1 to 2-2 and Comparative Examples 1-1 to 2-2 were evaluated.

[0250] For initial charging / discharging, the rechargeable lithium battery is initially charged at 25°C with a constant current of 0.2C and a constant voltage of 4.25V (approximately 0.05C cutoff). After resting for 10 minutes, it is discharged to 2.5V with a constant current of 0.2C to complete the initial charging and discharging, thereby obtaining the initial charging capacity (0.2C charging capacity) and the initial discharging capacity (0.2C discharging capacity). The efficiency (%) (0.2C efficiency) is expressed as initial discharging capacity / initial charging capacity. Subsequently, the initial discharge capacity after the 50th cycle was measured by repeatedly charging / discharging 50 times at 45°C and 1.0C (approximately 4.25V, approximately 0.05C cutoff) / 1.0C (approximately 3.0V, approximately 0.05C cutoff) and at 45°C and 2.0C (approximately 4.25V, approximately 0.05C cutoff) / 2.0C (approximately 3.0V, approximately 0.05C cutoff), and the lifetime (1C lifetime (%, 50 cycles) and 2C lifetime (%, 50 cycles)) are expressed as the discharge capacity after the 50th cycle / initial discharge capacity. In addition, a rechargeable lithium battery was prepared separately. The battery was then initially charged at approximately 25°C under constant current and constant voltage (approximately 4.25V, cutoff at approximately 0.05C) at a constant current of 0.2C. After resting for 10 minutes, it was discharged to 2.5V at a constant current of 0.2C. It was then further charged at -20°C under constant current (approximately 0.2C) and constant voltage (approximately 4.25V, cutoff at approximately 0.05C), and then discharged again at a constant current (approximately 0.2C) until the voltage reached 2.5V. The discharge capacity at 0.2C (discharge capacity at -20°C) was measured. 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. The results of evaluating the battery properties are shown in Table 2 below. A rechargeable lithium battery is charged to SOC50 at a constant current of 0.2C and discharged at 1.0C for 1 second to record the voltage and current. Then, it is discharged at a constant current of 0.2C for 1 second to record another voltage and current. The DC internal resistance (DCIR) is calculated from this. DCIR is measured as ΔV / ΔI (voltage change / current change).

[0251] Table 2

[0252]

[0253] Referring to Table 2, it can be seen that compared with the monolayer positive electrodes of Comparative Examples 1-4, 1-5 and 1-7, the positive electrodes according to Examples 1-1 to 2-2 have improved capacity retention after at least 50 cycles at 1C and 2C rates.

[0254] Compared to a single-layer structure containing the same positive electrode active material, a bilayer structure provides improved adhesion and stability of the positive electrode active material, thereby improving battery performance. Fewer functional additives are required in the fabrication of the positive electrode, thus improving energy density.

[0255] Furthermore, the second particle with low resistance is included in the first positive electrode active material layer in contact with the positive electrode current collector, thereby reducing the resistance of the positive electrode. It is evident that the positive electrodes of Examples 1-1 to 2-2 according to this disclosure have significantly reduced resistance compared to the positive electrodes of Comparative Examples 1-4, 1-5, and 1-7, and even compared to Comparative Examples 2-1 and 2-2, which each have a double-layer structure, the positive electrodes of Examples 1-1 to 2-2 according to this disclosure have significantly reduced resistance.

[0256] Examples 1-1 to 2-2 are positive electrodes in which the first particle, the second particle, and the third particle are suitably or appropriately mixed together, and can be used as long-life positive electrodes with excellent characteristics in terms of average voltage, energy density, and overall lifetime characteristics.

[0257] Evaluation Example 4: Content of functional additives in the positive electrode active material layer

[0258] The weight ratio of functional additives required to prepare the positive electrode in the monolayer structure of Comparative Examples 1-1 to 1-7 was measured.

[0259] The weight ratio of functional additives in the first positive electrode active material layer and the weight ratio of functional additives in the second positive electrode active material layer required for preparing the positive electrodes in the bilayer structures of Comparative Examples 2-1 and 2-2 were measured.

[0260] The weight ratio of functional additives in the first positive electrode active material layer and the weight ratio of functional additives in the second positive electrode active material layer of the positive electrodes in Examples 1-1 to 2-2 were measured. The weight ratios of functional additives in the positive electrode active material layer are shown in Table 3 below.

[0261] Table 3

[0262]

[0263] Referring to examples of this disclosure, the weight ratio of the first positive electrode active material layer may be lower than that of the second positive electrode active material layer. According to another embodiment of this disclosure, the weight ratio of the first positive electrode active material layer may be the same as that of the second positive electrode active material layer. Stacking the first positive electrode active material layer on the positive electrode current collector requires less functional additives, and conversely, by first forming the first positive electrode active material layer comprising the first positive electrode active material slurry, it is advantageous to prepare the electrode plate, which facilitates the preparation of the positive electrode.

[0264] Unlike the examples of this disclosure, in Comparative Example 2-1, the positive electrode active material forming the first positive electrode active material layer and the positive electrode active material forming the second positive electrode active material layer are formed in opposite directions. In this case, it can be seen that a large amount of functional additives may be required to form the first positive electrode active material layer on the positive electrode current collector.

[0265] The positive electrode according to this disclosure includes a first positive electrode active material layer and a second positive electrode active material layer. The first positive electrode active material layer includes first olivine particles with a size of several micrometers and second spinel particles with a size of several micrometers. The second positive electrode active material layer includes third olivine particles with a size of hundreds of nanometers to several micrometers and is stacked on the first positive electrode active material layer, thus achieving improved powder compaction density, capacity, and energy density. In the positive electrode according to embodiments of this disclosure, the electrode plate can be easily fabricated and has improved resistance. The rechargeable lithium battery according to this disclosure can have a relatively improved lifespan.

[0266] The above description presents 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 simply altered in design. Furthermore, this disclosure will also include techniques that can be easily modified and implemented using the embodiments. 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 includes first particles and second particles, the first particles include a compound represented by Formula 1 and having an olivine structure, and the second particles include a compound represented by Formula 2 and having a spinel structure, The second positive electrode active material layer includes third particles, the third particles include a compound represented by Formula 3 and having an olivine structure, and The first particles are in the form of secondary particles in which a plurality of primary particles are aggregated, 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, x1 + y1 + z1 = 1, and 0 ≤ c1 ≤ 0.05, Formula 2 Li a2 Mn x2 B2 y2 O 4-c2 Where in Formula 2 above, B2 is at least one element selected from the group consisting of Al and Mg, and satisfies 0.8 < a2 ≤ 1.2, 1.9 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05, 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, x3 + y3 + z3 = 1, and 0 ≤ c3 ≤ 0.

05.

2. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the third particles are in the form of secondary particles in which a plurality of primary particles are aggregated, The primary particles of the third particles have an average 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 third particles are in the form of single particles, and The third particle has an average particle size D of 0.5 μm to 2.5 μm. 50 .

4. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the weight ratio of the second particles is 15 wt% to 30 wt% relative to the total weight of the first particles, the second particles, and the third particles in the positive electrode.

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

60.

6. 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.

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

8. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the first particles have a porosity of 20% to 40%.

9. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the span value of the first particles analyzed by a particle size analyzer is 0.3 to 0.

75.

10. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the second particles are in the form of secondary particles in which a plurality of primary particles are aggregated, and The secondary particles have an average particle size D of 3μm to 10μm. 50 .

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 includes first particles, second particles and a first functional additive, the first particles include a compound represented by Formula 1 and having an olivine structure, the second particles include a compound represented by Formula 2 and having a spinel structure, the second positive electrode active material layer includes third particles and a second functional additive, the third particles include a compound represented by Formula 3 and having an olivine structure, the first functional additive and the second functional additive each include 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, x1 + y1 + z1 = 1, and 0 ≤ c1 ≤ 0.05, Formula 2 Li a2 Mn x2 B2 y2 O 4-c2 wherein in Formula 2 above, B2 is at least one element selected from the group consisting of Al and Mg, and satisfies 0.8 < a2 ≤ 1.2, 1.9 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05, 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, and 0 ≤ c3 ≤ 0.

05.

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 in the second positive electrode active material layer to the weight ratio of the first functional additive in the first positive electrode active material layer is 1.5 to 3.

0.

13. The positive electrode for a rechargeable lithium battery according to claim 11, wherein the weight ratio of the first functional additive in the first positive electrode active material layer 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 in the second positive electrode active material layer is 4.0 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 ratio of the second particle to the total weight of the first particle, the second particle, and the third particle in the positive electrode is 15 wt% to 30 wt%.

17. 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.

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

60.

19. The positive electrode for a rechargeable lithium battery as claimed in claim 11, wherein the second particle is in the form of a secondary particle in which a plurality of primary particles are aggregated, and The secondary particles have an average particle size D of 3μm to 10μm. 50 .

20. A rechargeable lithium battery comprising a positive electrode according to any one of claims 1 to 19.

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