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

Abstract

The invention relates to a positive electrode and a rechargeable lithium battery including the same. A rechargeable lithium battery includes a positive electrode including a positive electrode current collector, a first active material layer on the positive electrode current collector, and a second active material layer on the first active material layer, where the first active material layer and the second active material layer each include first particles, and the second active material layer further includes second particles, the first particles including a compound represented by Chemical Formula 1, and the second particles including a compound represented by Chemical Formula 2. The first particles are olivine-based particles and the second particles are layered particles. The chemical formula 1 is Lia1Fex1B1y1PO4-b1, and the chemical formula 2 is Lia2Nix2Coy2Alz2B2w2O2-b2.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2024-0056957, 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 described herein relate to a positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including a positive electrode, and for example, to a positive electrode including a positive electrode active material layer having a bilayer structure and a rechargeable lithium battery including a positive electrode containing a positive electrode active material layer having a bilayer structure. Background Technology

[0004] Recently, the rapid proliferation of battery-powered electronic devices (such as mobile phones and / or laptops) and / or electric vehicles has significantly increased the demand for or expectation of rechargeable batteries with relatively high energy density and relatively high capacity. Accordingly, extensive research has been dedicated to enhancing (improving) the performance of rechargeable batteries (such as rechargeable lithium batteries).

[0005] Rechargeable lithium-ion batteries include a positive electrode and a negative electrode (each containing active materials that allow or facilitate the insertion and extraction of lithium ions) and an electrolyte. These batteries generate electrical energy through redox reactions (e.g., oxidation and reduction reactions) as lithium ions are inserted or extracted between the positive and negative electrodes. Summary of the Invention

[0006] One or more aspects of the embodiments involve a positive electrode having high energy density, high operating voltage, and high conductivity.

[0007] One or more aspects of the embodiments relate to rechargeable lithium batteries having high energy density, high operating voltage, and high low-temperature characteristics.

[0008] Other aspects will be set forth in part in the description which follows and in part will be obvious from the description or may be learned by practice of the embodiments presented in this disclosure.

[0009] In one or more embodiments of this disclosure, the positive electrode for a rechargeable lithium battery includes: a positive electrode current collector; a first active material layer (first positive electrode active material layer) on the positive electrode current collector; and a second active material layer (second positive electrode active material layer) on the first active material layer, wherein the first active material layer and the second active material layer each include first particles, the second active material layer further includes second particles, the first particles contain a compound of formula 1, and the second particles contain a compound of formula 2.

[0010] Chemical Formula 1

[0011] Li a1 Fe x1 B1 y1 PO 4-b1

[0012] In the above chemical formula 1, the following conditions must be met: 0.8≤a1≤1.2, 0.95≤x1≤0.999, 0.001≤y1≤0.05, 0≤b1≤0.05, and x1+y1=1. In the above chemical formula 1, B1 can be at least one element selected from the group consisting of Ti, Mg, V and Al.

[0013] Chemical formula 2

[0014] Li a2 Ni x2 Co y2 Al z2 B2 w2 O 2-b2

[0015] In the above chemical formula 2, the following conditions must be met: 0.8≤a2≤1.2, 0.8≤x2≤0.95, 0.02≤y2≤0.19, 0.001≤z2≤0.03, 0≤w2≤0.1, 0≤b2≤0.05, and x2+y2+z2+w2=1. In the above chemical formula 2, B2 can be at least one element selected from the group consisting of Ti, Mg, Zr and Al.

[0016] In one or more embodiments of this disclosure, the positive electrode for a rechargeable lithium battery includes a positive electrode current collector, a first active material layer on the positive electrode current collector, and a second active material layer on the first active material layer, wherein the first active material layer and the second active material layer each include a first particle in the form of a single particle, the second active material layer further includes a second particle, the first particle containing a compound of chemical formula 1, and the second particle containing a compound of chemical formula 2.

[0017] Chemical Formula 1

[0018] Li a1 Fex1 B1 y1 PO 4-b1

[0019] In the above chemical formula 1, the following conditions must be met: 0.8≤a1≤1.2, 0.95≤x1≤0.999, 0.001≤y1≤0.05, 0≤b1≤0.05, and x1+y1=1. In the above chemical formula 1, B1 can be at least one element selected from the group consisting of Ti, Mg, V and Al.

[0020] Chemical formula 2

[0021] Li a2 Ni x2 Co y2 Al z2 B2 w2 O 2-b2

[0022] In the above chemical formula 2, the following conditions must be met: 0.8≤a2≤1.2, 0.8≤x2≤0.95, 0.02≤y2≤0.19, 0.001≤z2≤0.03, 0≤w2≤0.1, 0≤b2≤0.05, and x2+y2+z2+w2=1. In the above chemical formula 2, B2 can be at least one element selected from the group consisting of Ti, Mg, Zr and Al.

[0023] In one or more embodiments of this disclosure, a rechargeable lithium battery includes: a positive electrode; a negative electrode including a negative electrode current collector and a layer of negative electrode active material on the negative electrode current collector; and a separator between the positive electrode and the negative electrode. Attached Figure Description

[0024] The accompanying drawings are included to provide a further understanding of this disclosure, and are incorporated in and form a part of this specification. The drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. In the drawings:

[0025] Figure 1 A conceptual diagram illustrating a rechargeable lithium battery according to one or more embodiments of the present disclosure;

[0026] Figures 2-5 Schematic diagrams of rechargeable lithium batteries according to one or more embodiments are shown for each. Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown, and Figure 4 and Figure 5 Showing pouch-type (types) of batteries;

[0027] Figure 6A cross-sectional view showing a positive electrode for a rechargeable lithium battery according to one or more embodiments of the present disclosure;

[0028] Figure 7 An enlarged view showing the first active material layer of the positive electrode for a rechargeable lithium battery according to one or more embodiments of the present disclosure;

[0029] Figure 8 An enlarged view showing the second active material layer of the positive electrode for a rechargeable lithium battery according to one or more embodiments of the present disclosure;

[0030] Figure 9 To show a scanning electron microscope (SEM) image of the first particle prepared in Preparation Example 1 of this disclosure;

[0031] Figure 10 To show a SEM image of the second particle in the form of a secondary particle prepared in Preparation Example 2 of this disclosure; and

[0032] Figure 11 To show a SEM image of the second particle, which is in the form of a single particle, prepared in Preparation Example 3 of this disclosure. Detailed Implementation

[0033] To fully understand the configuration and effects of this disclosure, one or more 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 exemplary embodiments described below and may be implemented in one or more suitable forms. Rather, the exemplary embodiments are provided only to disclose embodiments of this disclosure and to fully reveal the scope of this disclosure to those skilled in the art.

[0034] In this description, it will be understood that if (e.g., when) an element is referred to as being on another element, then the element may be directly on the other element, or an intervening element may exist between them. In the accompanying drawings, the dimensions (e.g., thickness) of some components are enlarged for the purpose of effectively explaining the technical content. The same reference numerals or symbols refer to the same elements throughout, and the specification may not provide a repeated description of them.

[0035] Unless otherwise specified in this description, singular expressions may include plural expressions. Additionally, unless otherwise specified, the phrase "A or B" may indicate "A but not B", "B but not A", and "A and B". The terms "comprises / includes" and / or "comprising / including" as used in this description do not exclude the presence or addition of one or more other components.

[0036] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated items. Expressions used herein such as “at least one of…”, “one of…”, and “selected from…” before / after a list of elements modify the entire list of elements, not individual elements of the list. For example, “at least one of a, b, and c”, “selected from at least one of a, b, and c”, etc., can indicate only a, only b, only c, (e.g., both a and b), (e.g., both a and c), (e.g., both b and c), all a, b, and c, or variations thereof.

[0037] As used herein, the term "combination thereof" may refer to a mixture, stack, complex, copolymer, alloy, blend, or reaction product of the components.

[0038] Unless otherwise specifically defined in this description, particle size may refer to the average particle size (average diameter). When the particles are spherical, "size" or "diameter" indicates the particle size or average particle size, and when the particles are non-spherical, "size" or "diameter" indicates the major axis length or average major axis length. Additionally, particle size indicates the average particle size (D) representing approximately 50% by volume of the cumulative volume in the particle size distribution. 50 Average particle size (D) 50 The average particle size (D) can be measured by methods suitable to those skilled in the art (e.g., by a particle size analyzer, transmission electron microscopy (TEM) images, or scanning electron microscopy (SEM) images). In one or more embodiments, a dynamic light scattering measurement device is used for data analysis, counting the number of particles for each particle size range, from which the average particle size (D) can be calculated. 50 The difference is that laser scattering can be used to measure the average particle size (D). 50 In the laser scattering method, target particles are dispersed in a dispersion solvent and introduced into a laser scattering particle diameter measuring device (e.g., the MT3000, commercially available from Microtrac, Inc.). The particles are irradiated with 28 kHz ultrasound at a power of 60 W, and then the average particle size (D) is calculated in the measuring device using a 50% standard particle size distribution. 50 ).

[0039] Figure 1 This is a cross-sectional view of a rechargeable lithium battery according to one or more embodiments of the present disclosure. See also... Figure 1 A rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0040] The positive electrode 10 and the negative electrode 20 may be spaced apart and / or separated from each other by a diaphragm 30 (e.g., spaced apart or separated). 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.

[0041] 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 membrane 30.

[0042] Positive electrode 10

[0043] 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 formed on the positive electrode current collector COL1. 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. (Refer to...) Figure 6 The positive electrode 10 according to one or more embodiments of the present disclosure is described in more detail. Al (aluminum) foil may be used in the positive electrode current collector COL1, but the present disclosure is not limited thereto.

[0044] negative electrode 20

[0045] 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).

[0046] 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.

[0047] The binder can be used to ensure good adhesion between the negative electrode active material particles and also to ensure good adhesion between the negative electrode active material and the negative electrode current collector COL2. The binder may include non-aqueous binders, aqueous binders, dry binders and / or combinations thereof (e.g., any suitable combination thereof).

[0048] 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 and / or combinations thereof (e.g., any suitable combination thereof).

[0049] The waterborne adhesive may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, 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 / or combinations thereof (e.g., any suitable combination thereof).

[0050] 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.

[0051] Dry adhesives can be polymeric materials capable of being fibrous. For example, dry adhesives can be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide and / or combinations thereof (e.g., any suitable combination thereof).

[0052] Conductive materials (e.g., electronic conductors) can be used to impart conductivity (e.g., electrical conductivity) to electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons can be used in the battery. Non-limiting examples may include: carbon-based materials (such as natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes); metallic materials including copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers (such as polyphenylene derivatives); and / or mixtures thereof (e.g., any suitable mixture thereof).

[0053] 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, and / or combinations thereof (e.g., any suitable combination thereof).

[0054] Negative electrode active material

[0055] The negative electrode active material 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.

[0056] Materials capable of reversibly embedding / desorbing lithium ions may include carbonaceous negative electrode active materials, such as, for example, crystalline carbon, amorphous carbon, and / or combinations thereof (e.g., any suitable combination thereof). The crystalline carbon may be graphite, such as natural graphite or artificial graphite that is amorphous, flaky, lamellar, spherical, or fibrous. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0057] Lithium metal alloys include alloys of lithium and metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0058] Materials capable of doping / dedoping lithium may be Si-based negative electrode active materials or Sn-based negative electrode active materials. The Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (0 < x ≤ 2), Si-Q alloys (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 / or combinations thereof (e.g., any suitable combination thereof)). The Sn-based negative electrode active materials may include Sn, SnO y (0 < y ≤ 2) (e.g., SnO2), Sn-based alloys, and / or combinations thereof (e.g., any suitable combination thereof).

[0059] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one or more embodiments, the silicon-carbon composite may include silicon particles (e.g., in the form of silicon particles) and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are aggregated (e.g., in the form of secondary particles) and an amorphous carbon coating (shell) on the surface of the secondary particles. The amorphous carbon may also be between the primary silicon particles, and, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in the amorphous carbon matrix.

[0060] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core.

[0061] The Si-based negative electrode active materials or the Sn-based negative electrode active materials may be used in combination with the carbonaceous negative electrode active materials.

[0062] Separator 30

[0063] Depending on the type of rechargeable lithium battery, the separator 30 may be present between the positive electrode 10 and the negative electrode 20. The separator 30 may include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer membrane of two or more layers thereof (such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polypropylene three-layer separator, a polypropylene / polypropylene / polypropylene three-layer separator, etc.).

[0064] The diaphragm 30 may include a porous substrate and a coating on the surface of the porous substrate (e.g., one or both surfaces (e.g., opposite surfaces)), the coating comprising organic materials, inorganic materials and / or combinations thereof (e.g., any suitable combination thereof).

[0065] The porous substrate may be a polymer membrane 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).

[0066] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers.

[0067] Inorganic materials may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BTiO3, Mg(OH)2, boehmite and / or combinations thereof (e.g., any suitable combination thereof), but this disclosure is not limited thereto.

[0068] Organic and inorganic materials can be mixed in a single coating, or coatings comprising organic materials and coatings comprising inorganic materials can be stacked. That is, a coating comprising organic materials can be placed on top of a coating comprising inorganic materials, or vice versa.

[0069] Electrolyte ELL

[0070] Electrolytes (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0071] Non-aqueous organic solvents can be used as media for transporting ions that participate in the electrochemical reactions of a battery.

[0072] Non-aqueous organic solvents may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents and / or combinations thereof (e.g., any suitable combination thereof).

[0073] 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.

[0074] Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, caprolactone, etc.

[0075] 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. Ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc. Aprotic solvents may include: nitriles, 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.

[0076] Non-aqueous organic solvents can be used alone or in combination of two or more.

[0077] Additionally, if (for example, when) a carbonate solvent is used, 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.

[0078] 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).

[0079] Rechargeable lithium batteries

[0080] Rechargeable lithium batteries can be classified according to their shape into cylindrical batteries, prismatic batteries, pouch batteries, coin-shaped batteries, etc. Figures 2-5 Schematic diagrams illustrating rechargeable lithium batteries according to one or more embodiments. Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown, and Figure 4 and Figure 5 Showing pouch-type (type) batteries. See also Figures 2-5 The rechargeable lithium battery 100 may include an electrode assembly 40 (including a separator 30 between a positive electrode 10 and a negative electrode 20) and a housing 50 (including the electrode assembly 40). The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. 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 inducing current generated in the electrode assembly 40 to the outside.

[0081] As a non-limiting example, rechargeable lithium batteries according to one or more embodiments can be used in automobiles, mobile phones and / or one or more suitable types (classes) of electronic devices.

[0082] Figure 6 This is a cross-sectional view showing a positive electrode for a rechargeable lithium battery according to one or more embodiments of the present disclosure.

[0083] See Figure 6 The positive electrode 10 for a rechargeable lithium battery may include the positive electrode current collector COL1 as described above (see Figure 1 ) and the positive electrode active material layer AML1 (see Figure 1 The positive electrode active material layer AML1 may include a first active material layer ATL1 and a second active material layer ATL2 stacked on the first active material layer ATL1.

[0084] Figure 7 An enlarged view showing the first active material layer of the positive electrode for a rechargeable lithium battery according to one or more embodiments of the present disclosure.

[0085] See Figure 7The first active material layer ATL1 may include first particles PTC1, first binder BND1, and first conductive material CDM1. The first active material layer ATL1 may further include components that can be used as a sacrificial positive electrode.

[0086] The first adhesive BND1 can bond the first particle PTC1 and the first conductive material CDM1. Additionally, the first adhesive BND1 can stably fix the first active material layer ATL1 to the positive electrode current collector COL1. For example, the first adhesive BND1 may include at least one selected from the group consisting of: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, and nylon, but this disclosure is not limited thereto.

[0087] The first conductive material CDM1 can be used to improve the conductivity of the first active material layer ATL1. Any conductive material that does not cause a chemical change in the first active material layer ATL1 can be used as the first conductive material CDM1, but is not limited thereto. For example, the first conductive material CDM1 may include: carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes); metallic materials including copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers (such as polyphenylene derivatives); and / or mixtures thereof (e.g., any suitable mixture thereof).

[0088] Figure 8 An enlarged view showing the second active material layer of the positive electrode for a rechargeable lithium battery according to one or more embodiments of the present disclosure.

[0089] See Figure 8 The second active material layer ATL2 may include a first particle PTC1, a second particle PTC2, a second binder BND, and a second conductive material CDM2. The second active material layer ATL2 may further include components that can be used as a sacrificial positive electrode.

[0090] The second adhesive BND2 can bond the first particle PTC1, the second particle PTC2, and the second conductive material CDM2. Additionally, the second adhesive BND2 can stably fix the second active material layer ATL2 onto the first active material layer ATL1. In one or more embodiments, the second adhesive BND2 may include at least one selected from the group consisting of: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, and nylon, but this disclosure is not limited thereto.

[0091] The second conductive material CDM2 can be used to improve the conductivity of the second active material layer ATL2. Any conductive material that does not cause a chemical change in the second active material layer ATL2 can be used as the second conductive material CDM2, but is not limited thereto. In one or more embodiments, the second conductive material CDM2 may include: carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes); metallic materials including copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers (such as polyphenylene derivatives); and / or mixtures thereof (e.g., any suitable mixture thereof).

[0092] The following text will describe each of the first particle PTC1 and the second particle PTC2 in more detail.

[0093] First PTC1

[0094] See Figure 9 The first PTC1 particle may be in the form of a single particle. In this document, a single particle may refer to a particle of a single type (species) that has no grain boundaries within it. A single particle may refer to a single particle morphologically existing as an independent phase in which the particles do not aggregate (e.g., coalesce), a particle with a monolithic structure, a particle with an integral structure, or a non-aggregated (e.g., non-aggregated) particle. For example, a single particle may be a single crystal. In one or more embodiments, a single particle may be a particle containing several crystals. A single particle may be in the form of individually separated particles. In one or more embodiments, a single particle may be in the form of about 2 to about 100 single particles attached to each other.

[0095] In one or more embodiments, the first particle PTC1 may be a first primary particle in the form of a single, separately separated particle.

[0096] In one or more embodiments, the first particle PTC1 may be in the form of about 2 to about 100 first primary particles attached together. In this case, unlike the second single particle PTC2_2, which will be described in more detail later, the first particle PTC1 may not be spherical. The first particle PTC1 may be irregular in shape.

[0097] The first PTC1 particle 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, or about 1 μm. In one or more embodiments, the average particle size can be measured by a particle size analyzer. Average particle size (D) 50 It can indicate the diameter of particles that account for approximately 50% of the cumulative volume in the particle size distribution.

[0098] The minimum particle size of the first PTC1 (i.e., the particle size of the first primary particle) can be about 10 nm to about 900 nm, about 50 nm to about 500 nm, or about 200 nm to about 300 nm. In one or more embodiments, the minimum particle size of the first PTC1 (i.e., the particle size of the first primary particle) can indicate the diameter measured by randomly selecting about 30 first primary particles on an electron micrograph of the positive electrode active material. The size of the first primary particles can be substantially uniform.

[0099] In one or more embodiments, the first PTC1 particle may include a first coating on its surface. The first coating may completely cover the surface of the first PTC1 particle or may partially cover the surface of the first PTC1 particle. The first PTC1 particle includes a coating containing carbon (e.g., elemental carbon). For example, the first coating may include elemental carbon and / or carbon-containing compounds. The first 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 compounds (such as titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds) may be, for example, metal oxides, metal hydroxides, metal carbonates, complexes thereof, or mixtures thereof. The metal-containing compounds may further include other metallic or non-metallic elements. For example, the metal-containing compounds may further include lithium. The first PTC1 particle may have improved structural stability and electrical conductivity through the first coating. That is, the first coating may improve the structural stability and electrical conductivity of the first PTC1 particle.

[0100] The first particle PTC1 may include an olivine-type lithium compound represented by chemical formula 1.

[0101] Chemical Formula 1

[0102] Li a1 Fe x1 B1 y1 PO 4-b1

[0103] In the above chemical formula 1, the following conditions must be met: 0.8 ≤ a1 ≤ 1.2, 0.95 ≤ x1 ≤ 0.999, 0.001 ≤ y1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, and x1 + y1 = 1. B1 can be at least one element selected from the group consisting of Ti, Mg, V, and Al. B1 can be a dopant used to dope the first PTC1 particle. For example, B1 can be Ti.

[0104] The first PTC1 particle may further include carbon (carbon element) from (e.g., derived from) the aforementioned first active material layer. Based on a total of 100 wt% of the first PTC1 particle, the first PTC1 particle may have a carbon element content (e.g., amount) 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%.

[0105] In one or more embodiments, the first PTC1 particle may exist as a single particle, meaning it has no internal grain boundaries and does not aggregate with other particles. This single particle may be a single crystal or may contain several crystals, and may exist independently or in clusters of 2 to 100 particles. The average particle size ranges from 50 nm to 5 μm, with the primary particle size between 10 nm and 900 nm. The first PTC1 particle may include a surface coating that covers the entire or part of the surface to enhance structural stability and electrical conductivity. The coating may contain carbon or compounds of titanium, magnesium, and vanadium. The olivine-based lithium compound in the first PTC1 particle is represented by chemical formula 1.

[0106] Chemical Formula 1

[0107] Li a1 Fe x1 B1 y1 PO 4-b1 ,

[0108] Chemical Formula 1 includes elements in specific proportions, with Ti, Mg, V, and Al acting as dopants to improve battery performance. The first PTC1 particle may also have a carbon content of approximately 0.5 wt% to 5 wt%.

[0109] Second PTC2 particle

[0110] See Figure 8 The second particle PTC2 can have two types (categories) of particle form. For example, the second particle PTC2 can include secondary stage particles PTC2_1 and a second single particle PTC2_2. For example, the second particle PTC2 can have a bimodal particle size distribution. The secondary stage particles PTC2_1 and the second single particle PTC2_2 can be mixed in a weight ratio of about 1:9 to about 9:1 to prepare the bimodal second particle.

[0111] See Figure 8 and Figure 10 The second particle PTC2 is polycrystalline and may be a secondary particle PTC2_1 in which at least two second primary particles NNP are aggregated (e.g., coalesced). For example, a second particle PTC2 may include a plurality of second primary particles NNP aggregated (e.g., coalesced) together. The second particle PTC2 may be spherical or elliptical.

[0112] In one or more embodiments, the secondary stage PTC2_1 may include a second coating on its surface. The inclusion of the second coating on the secondary stage PTC2_1 effectively prevents or reduces structural collapse caused by repeated charging / discharging. Accordingly, the rechargeable lithium battery may have improved lifespan characteristics.

[0113] The second coating may comprise a boron-containing compound, an aluminum-containing compound, and / or a combination thereof (e.g., any suitable combination thereof) of a metal-containing compound. 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 comprise other metallic or non-metallic elements. For example, the second coating may further comprise lithium, manganese, and / or nickel.

[0114] Methods for measuring the metal content (e.g., amount) in the second coating of the secondary stage particles PTC2_1 may include scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS) of the secondary stage particles PTC2_1. Through the above analysis, the content (e.g., amount) of boron and / or aluminum in the second coating can be determined. In addition to SEM-EDS, methods for measuring the metal content (e.g., amount) in the second coating may include inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), etc.

[0115] The secondary particles PTC2_1 can have an average particle size (D) of about 10 μm to about 18 μm or about 12 μm to about 16 μm. 50 The average particle size of the second-stage particle PTC2_1 may be larger than the average particle size of the first particle PTC1. In one or more embodiments, the average particle size can be measured by a particle size analyzer. Average particle size (D) 50 It can indicate the diameter of particles with a cumulative volume of approximately 50 vol% in the particle size distribution.

[0116] The secondary stage particle PTC2_1 may include a plurality of secondary primary particles NNPs. The minimum particle size of the secondary stage particle PTC2_1 (e.g., the particle size of the secondary primary particles NNPs) may be about 100 nm to about 800 nm, about 150 nm to about 600 nm, or about 200 nm to about 400 nm. In one or more embodiments, if (e.g., when) the secondary stage particle PTC2_1 is spherical, the minimum particle size of the secondary stage particle PTC2_1 (e.g., the particle size of the secondary primary particles NNPs) may indicate the diameter measured by randomly selecting about 30 secondary primary particles NNPs on an electron microscope image of the secondary stage particle PTC2_1. In one or more embodiments, if (e.g., when) the secondary stage particle PTC2_1 is non-spherical, the particle size of the secondary primary particles NNPs may indicate the diameter of a sphere having a volume measured by randomly selecting about 30 secondary primary particles NNPs on an electron microscope image of the secondary stage particle PTC2_1.

[0117] See Figure 8 and Figure 11 The second particle PTC2 may take the form of a second single particle PTC2_2. For example, the second single particle PTC2_2 may have a single particle form similar to the first particle PTC1 described above. The description of the single particle may be substantially the same as or similar to the previous description of the first particle PTC1. In one or more embodiments, the second single particle PTC2_2 may be in the form of being composed of a single particle. In one or more embodiments, the second single particle PTC2_2 may be in the form in which multiple single particles are attached together.

[0118] In one or more embodiments, the second single-particle PTC2_2 may include a second coating on its surface. The second single-particle PTC2_2 includes the second coating and can therefore effectively prevent or reduce structural collapse caused by repeated charging / discharging. Accordingly, the rechargeable lithium battery may have improved lifespan characteristics.

[0119] The second coating may comprise a boron-containing compound, an aluminum-containing compound, and / or a combination thereof (e.g., any suitable combination thereof) of a metal-containing compound. 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 comprise other metallic or non-metallic elements. For example, the second coating may further comprise lithium, manganese, and / or nickel.

[0120] Methods for measuring the metal content (e.g., amount) in the second coating of the second single particle PTC2_2 may include scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS) of the second single particle PTC2_2. Through the above analysis, the content (e.g., amount) of boron and / or aluminum in the second coating can be determined. In addition to SEM-EDS, methods for measuring the metal content (e.g., amount) in the second coating may include inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), etc.

[0121] The second single particle PTC2_2 may have an average particle size of about 2 μm to about 6 μm, about 3 μm to about 5 μm, or about 3.5 μm to about 4.5 μm. The average particle size of the second single particle PTC2_2 may be larger than the average particle size of the first particle PTC1 described above. In one or more embodiments, the average particle size can be measured by a particle size analyzer. Average particle size (D) 50 It can indicate the diameter of particles with a cumulative volume of approximately 50 vol% in the particle size distribution.

[0122] As described above, the second single particle PTC2_2 can be in a separate, isolated form. In one or more embodiments, the second single particle PTC2_2 can be in the form of multiple single particles attached together. Unlike the second primary particle PTC2_1, the multiple single particles attached together may not be spherical. For example, the multiple single particles attached together may be irregularly shaped.

[0123] The second particle PTC2, which may be in the form of a secondary stage particle PTC2_1 or a second single particle PTC2_2, may have an average particle size of about 6 μm to about 22 μm, about 8 μm to about 20 μm, or about 10 μm to about 18 μm. In one or more embodiments, the average particle size can be measured by a particle size analyzer. Average particle size (D) 50 It can indicate the diameter of particles at approximately 50% of the cumulative volume in the particle size distribution.

[0124] The second PTC2 particle is a nickel-based active material and may include lithium-nickel composite oxides. For example, the second PTC2 particle may include a high-nickel positive electrode active material containing a high content (e.g., amount) of nickel. High-nickel positive electrode active materials can achieve high capacity and high performance.

[0125] For example, the second particle PTC2 may include a layered lithium-nickel composite oxide represented by chemical formula 2.

[0126] Chemical formula 2

[0127] Li a2 Ni x2 Co y2Al z2 B2 w2 O 2-b2

[0128] In the above chemical formula 2, the following conditions can be met: 0.8≤a2≤1.2, 0.8≤x2≤0.95, 0.02≤y2≤0.19, 0.001≤z2≤0.03, 0≤w2≤0.1, 0≤b2≤0.05, and x2+y2+z2+w2=1.

[0129] B2 can be at least one element selected from the group consisting of Mg, Ti, Zr, and Al. B2 can be a dopant used to dope the second PTC2 particle. In Formula 3, the case where w2 is 0 indicates an undoped lithium-nickel composite oxide. For example, this case indicates that the lithium-nickel composite oxide has a layered structure represented by Formula 3.

[0130] Chemical formula 3

[0131] Li a3 Ni x3 Co y3 Al z3 O 2-b3

[0132] In the above chemical formula 3, the following conditions can be met: 0.8≤a3≤1.2, 0.8≤x3≤0.95, 0.02≤y3≤0.19, 0.001≤z3≤0.03, 0≤b3≤0.05, and x3+y3+z3=1.

[0133] The second active material layer ATL2 according to this disclosure includes a second PTC2 particle, and thus allows the rechargeable lithium battery to achieve high capacity and high energy density. In one or more embodiments, the second active material layer ATL2 (e.g., simultaneously) includes both a first PTC1 particle and a second PTC2 particle, and thus allows high energy density and excellent or suitable low-temperature characteristics.

[0134] In one or more embodiments, the second PTC2 particle can exist in two forms: as a secondary secondary particle (PTC2_1) or as a second single particle (PTC2_2), resulting in a bimodal particle size distribution. The secondary secondary particle PTC2_1 is a polycrystalline form in which the second primary particles (NNPs) aggregate, typically having a spherical or ellipsoidal shape with an average diameter between 10 μm and 18 μm. These secondary particles may include a coating containing compounds such as boron or aluminum to enhance structural stability and battery life. The second single particle PTC2_2 is similar to the first particle PTC1, and can exist independently or in clusters, with an average diameter ranging from 2 μm to 6 μm. This form also benefits from a coating to prevent structural collapse during charge and discharge cycles. Both forms of the second PTC2 particle incorporate specific elements to enhance battery performance, with the secondary particles typically being larger than the single particles. Additionally, the second PTC2 particle can be a nickel-based active material comprising a high-nickel-content lithium-nickel composite oxide represented by Formula 2.

[0135] Chemical formula 2

[0136] Li a2 Ni x2 Co y2 Al z2 B2 w2 O 2-b2 ,

[0137] This contributes to the high capacity and high performance of rechargeable lithium batteries.

[0138] See back Figure 6 The positive electrode active material layer AML1 according to one or more embodiments of the present disclosure will be described in more detail.

[0139] The positive electrode active material layer AML1 may include a first active material layer ATL1 and a second active material layer ATL2 stacked on the first active material layer ATL1.

[0140] The first active material layer ATL1 may include at least one of a first particle PTC1 and a second particle PTC2. The positive electrode of this disclosure includes the first particle PTC1, which is an olivine-like particle, in the first active material layer, and thus can improve the energy density.

[0141] The first active material layer ATL1 may further include a first adhesive BND1 and a first conductive material CDM1.

[0142] The second active material layer ATL2 may include second particles PTC2. The second particles PTC2 comprise a high-nickel positive electrode active material and can therefore achieve a higher capacity than the first particles PTC1. The second active material layer ATL2, including the second particles PTC2, can therefore improve powder compaction density, capacity, and energy density. For example, in the positive electrode of this disclosure, by placing the second active material layer containing the second particles PTC2 on the outermost surface of the positive electrode where the electrochemical reaction is most active, low-temperature characteristics can be significantly improved. The second active material layer ATL2 may further include the first particles PTC1.

[0143] In one or more embodiments, the second PTC2 particles may be about 30 wt% to about 70 wt%, about 40 wt% to about 60 wt%, or about 45 wt% to about 55 wt%, relative to the total content (e.g., amount) of the first PTC1 and the second PTC2 particles in the second active material layer ATL2.

[0144] The second active material layer ATL2 may further include a second binder BND2 and a second conductive material CDM2.

[0145] Relative to 100 parts by weight of the first active material layer ATL1, the first active material layer ATL1 may include about 5 parts by weight to about 10 parts by weight of the first adhesive BND1.

[0146] Relative to 100 parts by weight of the second active material layer ATL2, the second active material layer ATL2 may include about 2 parts by weight to about 5 parts by weight of the second adhesive BND2.

[0147] The content (e.g., amount) of the first binder BND1 included in the first active material layer ATL1 may be greater than the content (e.g., amount) of the second binder BND2 included in the second active material layer ATL2.

[0148] The first PTC1, which is in the form of a single particle, has a very small average particle size, and accordingly, a large amount of the first binder BND1 is expected or required to adhere the first PTC1 particles to the positive electrode current collector COL1 (see...). Figure 1 Alternatively, the first PTC1 particle can be fixed to the first conductive material CDM1. In one or more embodiments, the second PTC2 particle has a larger average particle size than the first PTC1 particle, and accordingly, a relatively small amount of the second binder BND2 is expected or required to adhere the second PTC2 particle to the first active material layer ATL1 or to fix the second PTC2 particle to the second conductive material CDM2. Accordingly, the content (e.g., amount) of the second binder BND2 in the second active material layer ATL2 containing the second PTC2 particle can be reduced.

[0149] Relative to 100 parts by weight of the first active material layer ATL1, the first active material layer ATL1 may include about 10 parts by weight to about 15 parts by weight of the first conductive material CDM1.

[0150] Relative to 100 parts by weight of the second active material layer ATL2, the second active material layer ATL2 may include about 5 parts by weight to about 10 parts by weight of the second conductive material CDM2.

[0151] The weight of the first conductive material CDM1 included in the first active material layer ATL1 may be greater than the weight of the second conductive material CDM2 included in the second active material layer ATL2.

[0152] The amount of the second PTC2 particle relative to the total content (e.g., amount) of the first PTC1 and the second PTC2 particle in the positive electrode active material layer AML1 may be about 5 wt% to about 25 wt%, about 10 wt% to about 20 wt%, or about 15 wt% to about 20 wt%.

[0153] The amount of the second PTC2 particle relative to the total content (e.g., amount) of the first PTC1 and the second PTC2 particle in the second active material layer ATL2 may be about 30 wt% to about 70 wt%, about 40 wt% to about 60 wt%, or about 45 wt% to about 55 wt%.

[0154] The first active material layer ATL1 may have a thickness T1. In one or more embodiments, T1 may increase with an increase in the content (e.g., amount) of the first PTC1 particles included in the first active material layer ATL1. That is, an increase in the content of the first PTC1 particles may increase the thickness T1 of the first active material layer ATL1. The second active material layer ATL2 may have a thickness T2. In one or more embodiments, T2 may increase with an increase in the content (e.g., amount) of the second PTC2 particles included in the second active material layer ATL2. That is, an increase in the content of the second PTC2 particles may increase the thickness T2 of the second active material layer ATL2. In one or more embodiments, the magnitude of T2 relative to the sum of T1 and T2 (T2 / (T1+T2)) may be about 0.1 to about 0.5, about 0.2 to about 0.4, or about 0.25 to about 0.35. Within the above ranges, low-temperature characteristics can be improved while maintaining excellent or appropriate energy density.

[0155] In one or more embodiments, the first active material layer ATL1 may have a concentration of approximately 5 mg / cm³. 2 ~ Approximately 10 mg / cm 2 The loading level. The second active substance layer, ATL2, can have approximately 5 mg / cm³. 2 ~ Approximately 25 mg / cm 2 The load level.

[0156] In one or more embodiments, the positive electrode active material layer AML1 of this disclosure may have a powder compaction density of about 2.5 g / cc to about 3.0 g / cc.

[0157] A rechargeable lithium battery including a positive electrode according to one or more embodiments of this disclosure may have improved low-temperature characteristics.

[0158] The preparation examples, embodiments, and comparative examples of this disclosure will be described in more detail below. However, the following embodiments are presented only as one or more implementations of this disclosure, and this disclosure is not limited to the following embodiments.

[0159] Preparation Example 1: Preparation of the first particle of olivine-based active substance in single-particle form

[0160] Ferric phosphate precursor (FePO4), lithium carbonate, and titanium dioxide were mixed in a molar ratio of Fe:Li:Ti = 1:1.03:0.03. 10 wt% glucose was added to the mixture. The mixture was wet-milled by ball milling. The mixture was evaporated to dryness on a heated tray and then dried in a vacuum oven at 120°C for 4 hours. The dried mixture was calcined at 750°C for 10 hours under a nitrogen atmosphere. The calcined product was ground to obtain first particles in the form of single particles. Using scanning electron microscopy (SEM), the first primary particles constituting the first particles were found to have a particle size of approximately 200 nm to approximately 300 nm, and the first particles were found to have a density of approximately 1 μm. 50 Furthermore, scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS) revealed that the first particle contained 1.52 wt% carbon.

[0161] Preparation Example 2: Preparation of the second particles of a large-particle layered active substance in the form of secondary particles

[0162] High-nickel precursors were prepared using a co-precipitation method. For example, as raw materials for nickel-based metal hydroxides, nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and aluminum sulfate (Al2(SO4)3·18H2O) were stirred in distilled water as a solvent for 10–20 hours at a molar ratio of Ni:Co:Al = 88.5:10:1.5 to prepare a metal raw material mixture. The metal raw material mixture, ammonia, and sodium hydroxide were added to a reactor and reacted. The slurry solution in the reactor was filtered and washed with high-purity distilled water. The washed material was dried in a hot air oven at 210°C for 24 hours to obtain a large-particle precursor (NiSO4·6H2O) with an average particle size of approximately 14 μm. 0.885 Co 0.10 Al 0.015 (OH)2) powder.

[0163] The high-nickel precursor and anhydrous lithium hydroxide (LiOH) were dry-mixed using a Henschel mixer. Lithium and transition metals were mixed at a molar ratio of approximately 1:1. The transition metals were the sum of the transition metals contained in the high-nickel precursor (Ni+Co+Al). Flux was further added to the mixture, and the mixture was heat-treated (i.e., sintering) at approximately 750°C for 15 hours in an oxygen atmosphere to synthesize second particles as the active material for the high-nickel positive electrode. The second particles were then milled using a jet mill at a pressure of 3 bar.

[0164] The second particle was added to distilled water and rinsed. Boron oxide and aluminum oxide, corresponding to 3 mol% of the total amount of transition metal in the second particle, were added to perform boron and aluminum coating. The second particle was dried at about 150°C for about 12 hours and then heat-treated (i.e., surface-treated) at about 700°C for 15 hours in an oxygen atmosphere.

[0165] Preparation Example 3: Preparation of the second particle of a small, layered active substance in the form of a single particle

[0166] High-nickel precursors were prepared using a co-precipitation method. For example, as raw materials for nickel-based metal hydroxides, nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and aluminum sulfate (Al2(SO4)3·18H2O) were stirred in distilled water as a solvent for 30 hours at a molar ratio of Ni:Co:Al = 88.5:10:1.5 to prepare a metal raw material mixture. The metal raw material mixture, ammonia, and sodium hydroxide were added to a reactor and reacted. The slurry solution in the reactor was filtered and washed with high-purity distilled water. The washed material was dried in a hot air oven at 210°C for 24 hours to obtain a small-particle precursor (NiSO4·6H2O) with an average particle size of approximately 4 μm. 0.885 Co 0.10 Al 0.015 (OH)2) powder.

[0167] The high-nickel precursor and anhydrous lithium hydroxide (LiOH) were dry-mixed using a Henschel mixer. Lithium and transition metals were mixed at a molar ratio of approximately 1:1. The transition metals were the sum of the transition metals contained in the high-nickel precursor (Ni+Co+Al). Flux was further added to the mixture, and the mixture was heat-treated (i.e., sintering) at approximately 750°C for 15 hours in an oxygen atmosphere to synthesize second particles as the active material for the high-nickel positive electrode. The second particles were then milled using a jet mill at a pressure of 4 bar.

[0168] The second particle was added to distilled water and rinsed. Boron oxide and aluminum oxide, corresponding to 3 mol% of the total amount of transition metal in the second particle, were added to perform boron and aluminum coating. The second particle was dried at about 150°C for about 12 hours and then heat-treated (i.e., surface-treated) at about 700°C for 15 hours in an oxygen atmosphere.

[0169] In other words, Preparation Example 1 describes the fabrication of olivine-based active materials in single-particle form. Ferric phosphate precursor, lithium carbonate, and titanium dioxide were mixed with glucose and wet-milled. The mixture was dried. It was then calcined in a nitrogen atmosphere. The resulting product had a primary particle size between 200 nm and 300 nm and a density of approximately 1 μm. 50 It contains 1.52 wt% carbon.

[0170] Preparation Example 2 details the generation of large-particle layered active materials in the form of secondary particles. A high-nickel precursor was prepared using nickel sulfate, cobalt sulfate, and aluminum sulfate. These precursors were mixed, reacted, and dried to form a precursor with an average diameter of 14 μm. This precursor was then mixed with lithium hydroxide and heat-treated to produce a high-nickel positive electrode active material. The particles were then coated with boron oxide and aluminum oxide and subjected to further heat treatment.

[0171] Preparation Example 3 outlines the preparation of small-particle layered active materials in single-particle form. Similar to Example 2, a high-nickel precursor was prepared and mixed with lithium hydroxide. The mixture was heat-treated to form a high-nickel positive electrode active material, then coated with boron oxide and aluminum oxide and heat-treated. The resulting small-particle precursor had an average diameter of 4 μm.

[0172] Preparation Example 4: Mixing of the Second Particle

[0173] The second particle, which is in the form of a secondary particle prepared by Preparation Example 2, and the second particle, which is in the form of a single particle prepared by Preparation Example 3, are mixed at a weight ratio of 3:1 to prepare a bimodal second particle.

[0174] Example 1: A positive electrode comprising a first active material layer and a second active material layer, wherein the weight ratio of the first particle in the first active material layer to the first particle in the second active material layer to the second particle in the second active material layer is 90%:5%:5%.

[0175] The first active material slurry was prepared by dispersing the first particles, the first binder (polyvinylidene fluoride), and the first conductive material (carbon black) prepared by Preparation Example 1 in N-methylpyrrolidone at a weight ratio of 1:0.1:0.15.

[0176] The first particles prepared by Preparation Example 1, the bimodal second particles prepared by Preparation Example 4, the second binder (polyvinylidene fluoride), and the second conductive material (carbon black) were dispersed in N-methylpyrrolidone at a weight ratio of 1:1:0.05:0.1 to prepare a second active material slurry.

[0177] A first active material slurry is coated onto a 15 μm thick aluminum (Al) film serving as the positive electrode current collector and dried to form a first active material layer. A second active material slurry is coated onto the first active material layer and dried to form a second active material layer. In this case, the first and second active material layers are formed such that, relative to the total content (e.g., amount) of the first and second particles, the content (e.g., amount) of the first particles in the first active material layer is 90 wt%, the content (e.g., amount) of the first particles in the second active material layer is 5 wt%, and the content (e.g., amount) of the second particles in the second active material layer is 5 wt%. A positive electrode in which the aluminum current collector, the first active material layer, and the second active material layer are stacked in this order is prepared by roll forming.

[0178] Example 2: A positive electrode comprising a first active material layer and a second active material layer, wherein the weight ratio of the first particle in the first active material layer to the first particle in the second active material layer to the second particle in the second active material layer is 80%:10%:10%.

[0179] The positive electrode was prepared in essentially the same manner as in Example 1, except that a first active material layer and a second active material layer were formed such that, relative to the total content (e.g., amount) of the first particles in the first active material layer, the content (e.g., amount) of the first particles in the first active material layer was 80 wt%, the content (e.g., amount) of the first particles in the second active material layer was 10 wt%, and the content (e.g., amount) of the second particles in the second active material layer was 10 wt%.

[0180] Example 3: A positive electrode comprising a first active material layer and a second active material layer, wherein the weight ratio of the first particle in the first active material layer to the first particle in the second active material layer to the second particle in the second active material layer is 70%:15%:15%.

[0181] The positive electrode was prepared in essentially the same manner as in Example 1, except that a first active material layer and a second active material layer were formed such that, relative to the total content (e.g., amount) of the first particles in the first active material layer, the content (e.g., amount) of the first particles in the first active material layer was 70 wt%, the content (e.g., amount) of the first particles in the second active material layer was 15 wt%, and the content (e.g., amount) of the second particles in the second active material layer was 15 wt%.

[0182] Example 4: A positive electrode comprising a first active material layer and a second active material layer, wherein the weight ratio of the first particle in the first active material layer to the first particle in the second active material layer to the second particle in the second active material layer is 60%:20%:20%.

[0183] The positive electrode was prepared in essentially the same manner as in Example 1, except that a first active material layer and a second active material layer were formed such that, relative to the total content (e.g., amount) of the first particles in the first active material layer, the content (e.g., amount) of the first particles in the first active material layer was 60 wt%, the content (e.g., amount) of the first particles in the second active material layer was 20 wt%, and the content (e.g., amount) of the second particles in the second active material layer was 20 wt%.

[0184] Example 5: A positive electrode comprising a first active material layer and a second active material layer, wherein the weight ratio of the first particle in the first active material layer to the first particle in the second active material layer to the second particle in the second active material layer is 50%:25%:25%.

[0185] The positive electrode was prepared in essentially the same manner as in Example 1, except that a first active material layer and a second active material layer were formed such that, relative to the total content (e.g., amount) of the first particles in the first active material layer, the content (e.g., amount) of the first particles in the first active material layer was 50 wt%, the content (e.g., amount) of the first particles in the second active material layer was 25 wt%, and the content (e.g., amount) of the second particles in the second active material layer was 25 wt%.

[0186] Comparative Example 1: A positive electrode comprising a positive electrode active material layer having a first particle with a monolayer structure.

[0187] The first particles prepared by Preparation Example 1, the first binder (polyvinylidene fluoride), and the first conductive material (carbon black) were dispersed in N-methylpyrrolidone at a weight ratio of 1:0.1:0.15 to prepare a positive electrode active material slurry.

[0188] A slurry of positive electrode active material was coated onto a 15 μm thick aluminum (Al) film serving as the positive electrode current collector and then dried. A positive electrode in which the positive electrode active material layer is stacked on the aluminum current collector was prepared by roll forming.

[0189] Comparative Example 2: Positive electrode with a second particle active material layer having a monolayer structure

[0190] The second particles prepared by Preparation Example 4, the binder (polyvinylidene fluoride), and the conductive material (carbon black) were dispersed in N-methylpyrrolidone at a weight ratio of 1:0.05:0.1 to prepare a positive electrode active material slurry.

[0191] A slurry of positive electrode active material was coated onto a 15 μm thick aluminum (Al) film serving as the positive electrode current collector and then dried. A positive electrode in which the positive electrode active material layer is stacked on the aluminum current collector was prepared by roll forming.

[0192] Comparative Example 3: A positive electrode comprising a positive electrode active material layer with a monolayer structure, wherein the weight ratio of the first particle to the second particle is 80%:20%.

[0193] The first and second particles prepared in Preparation Examples 1 and 4 were mixed at a weight ratio of 4:1 to prepare a mixed positive electrode active material. The mixed positive electrode active material, binder (polyvinylidene fluoride), and conductive material (carbon black) were dispersed in N-methylpyrrolidone at a weight ratio of 1:0.1:0.15 to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a 15 μm thick aluminum (Al) film serving as the positive electrode current collector and dried. A positive electrode in which the positive electrode active material layers are stacked on the aluminum current collector was prepared by roll forming.

[0194] Comparative Example 4: Positive electrode including a second active material layer without the first particles

[0195] The first active material slurry was prepared by dispersing the first particles, the first binder (polyvinylidene fluoride), and the first conductive material (carbon black) prepared by Preparation Example 1 in N-methylpyrrolidone at a weight ratio of 1:0.1:0.15.

[0196] The second active material slurry was prepared by dispersing the second particles, the second binder (polyvinylidene fluoride), and the second conductive material (carbon black) prepared by Preparation Example 4 in N-methylpyrrolidone at a weight ratio of 1:0.05:0.1.

[0197] A first active material slurry is coated onto a 15 μm thick aluminum (Al) film serving as the positive electrode current collector and dried to form a first active material layer. A second active material slurry is coated onto the first active material layer and dried to form a second active material layer. In this case, the first and second active material layers are formed such that, relative to the total content (e.g., amount) of the first and second particles, the content (e.g., amount) of the first particles in the first active material layer is 80 wt%, and the content (e.g., amount) of the second particles in the second active material layer is 20 wt%. A positive electrode in which the aluminum current collector, the first active material layer, and the second active material layer are stacked in this order is prepared by roll forming.

[0198] Comparative Example 5: A positive electrode having a first active material layer stacked on a second active material layer

[0199] The positive electrode was prepared in essentially the same manner as in Example 4, except that the aluminum current collector, the second active material layer, and the first active material layer were stacked in this order. For example, the second active material layer was placed on the aluminum current collector, and the first active material layer was placed on the second active material layer.

[0200] Preparation of negative electrode

[0201] Graphite, a binder (PVDF), and a conductive material (carbon black) were mixed 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.

[0202] Preparation of rechargeable lithium batteries

[0203] The prepared positive and negative electrodes were used to prepare coin cell full cells. A polypropylene membrane (Celgard 3510) was used as the separator. As the electrolyte, an electrolyte obtained by mixing 1.3M LiPF6 with ethylene carbonate (EC), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC) (volume ratio 2:6:2) was used.

[0204] Evaluation Example 1: Surface Analysis of Positive Electrode Active Material

[0205] SEM images of the first and second particles prepared in Preparation Examples 1 to 3 are shown in... Figures 9-11 (See also) Figure 9 The first particle according to one or more embodiments of this disclosure is determined to be in the form of a fine single particle having a size of several hundred nanometers. See also Figure 10 The second particle, in the form of a secondary particle according to one or more embodiments of this disclosure, is determined to have a secondary particle size of several micrometers. The second particle, in the form of a secondary particle, is determined to be a secondary particle in which a plurality of second primary particles are aggregated (e.g., coalesced). See also Figure 11 It is determined that the second particle, which is in the form of a single particle according to one or more embodiments of the present disclosure, is in the form of a single particle having a size of several micrometers.

[0206] Evaluation Example 2: Analysis of Positive Electrode Characteristics

[0207] The content (e.g., amount) of each particle according to Examples 1 to 5 and Comparative Examples 1 to 5 is shown in Table 1.

[0208] Table 1

[0209]

[0210] The thickness and powder compaction density (PD) of each of the positive electrode active material layers in the prepared positive electrode were measured, and the results are shown in Table 2.

[0211] Table 2

[0212]

[0213] Evaluation Example 3: Properties of Battery Characteristics

[0214] The properties of rechargeable lithium batteries prepared using the positive electrodes of Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated.

[0215] For the initial charge / discharge, at 25°C, the rechargeable lithium battery was initially charged with a constant current of 0.1C and a constant voltage of 4.2V (approximately 0.05C cutoff). After resting for 10 minutes, it was discharged to 3.0V with a constant current of 0.1C to obtain the initial charge capacity (charge at 4.2V) and the initial discharge capacity (discharge at 4.2V). The efficiency (efficiency at 4.2V (%)) is expressed as initial charge capacity / initial discharge capacity. Subsequently, the battery was repeatedly charged / discharged 50 times at 45°C and at 1.0C (approximately 4.2V, approximately 0.05C cutoff) / 1.0C (approximately 3.0V, approximately 0.05C cutoff). The lifetime (lifetime at 4.2V (%, 50 cycles)) is expressed as discharge capacity after the 50th cycle / initial discharge capacity. 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. Additionally, a coin cell was prepared, and its 0.1C discharge capacity was measured at -20°C according to the following method. Specifically, the battery was initially charged at approximately 25°C under constant current (approximately 0.1C) and constant voltage (approximately 4.2V, approximately 0.05C cutoff). After resting for approximately 10 minutes, it was discharged under constant current (approximately 0.1C) until the voltage reached 3.0V. Then, the battery was further charged at approximately -20°C under constant current (approximately 0.1C) and constant voltage (approximately 4.2V, approximately 0.05C cutoff), and discharged under constant current (approximately 0.1C) until the voltage reached 3.0V to measure the initial discharge capacity at approximately -20°C. The results of evaluating the battery characteristics are shown in Table 3. Then, the battery was charged and discharged at 0.2C / 0.2C rates within a voltage range of 3.0V to 4.45V at 25°C to calculate the energy density. The energy density was obtained using the following calculation equation: {average drive voltage (V) × capacity (Ah) / cell weight (kg)}, where the capacity was calculated by multiplying the positive electrode weight (g) by the discharge capacity (mAhg).

[0216] Table 3

[0217]

[0218] Referring to Table 3, it is determined that the rechargeable lithium batteries according to Examples 1 to 5 of this disclosure are significantly superior to the rechargeable lithium battery according to Comparative Example 1 in terms of energy density. Furthermore, it is determined that the rechargeable lithium batteries according to Examples 1 to 5 are superior to the rechargeable lithium battery according to Comparative Example 2 in terms of cell efficiency and lifespan characteristics.

[0219] Furthermore, it was determined that the rechargeable lithium battery according to Example 4 outperformed the rechargeable lithium batteries according to Comparative Examples 3 and 4 in terms of energy density and capacity at -20°C (low temperature characteristics). For example, it was determined (e.g., simultaneously) that in terms of energy density and low temperature characteristics, the positive electrode of Example 4, which has a double-layer structure and includes both the first particle and the second particle in the upper layer (e.g., simultaneously), was superior to the positive electrode of Comparative Example 3, which has a single-layer structure and simply mixes the first particle and the second particle, and the positive electrode of Comparative Example 4, which has a double-layer structure and includes only the second particle in the upper layer.

[0220] Furthermore, it was determined that the rechargeable lithium battery according to Example 4 significantly outperformed the rechargeable lithium battery according to Comparative Example 5 in terms of capacity at -20°C (low-temperature characteristics). For example, it was determined that the positive electrode of Comparative Example 5, which has a bilayer structure but includes a first particle and a second particle in the lower layer, has slightly worse low-temperature characteristics than that of Example 4.

[0221] The positive electrode according to this disclosure has a bilayer structure (in which a second active material layer containing a mixture of olivine particles and layered particles is stacked on a first active material layer based on olivine particles), and can therefore have improved energy density and low-temperature characteristics.

[0222] Rechargeable lithium batteries including the positive electrode according to this disclosure have excellent or adequate energy density and low-temperature characteristics.

[0223] Those skilled in the art will recognize, based on the entirety of this disclosure, that each suitable feature of the various embodiments of this disclosure may be combined or combined with one another in part or in whole, and may be technically interlocked and operated in various suitable ways, and that each embodiment may be implemented independently of one another or in combination with one another in any suitable way, unless otherwise stated or implied.

[0224] In the context of this application, and unless otherwise defined, the terms “use,” “using,” and “used” may be considered synonymous with the terms “utilize,” “utilizing,” and “utilized,” respectively.

[0225] Furthermore, when describing embodiments of the inventive concept, the use of "may" refers to "one or more embodiments of the inventive concept." Also, the term "exemplary" is intended to indicate or illustrate.

[0226] Unless the context clearly indicates otherwise, the singular forms “a”, “an” and “the” as used herein are intended to also include the plural forms.

[0227] The battery manufacturing apparatus, battery management system (BMS) apparatus, and / or any other related apparatus or components described herein according to embodiments of the present invention can be implemented using any suitable hardware, firmware (e.g., application-specific integrated circuits), software, or a combination of software, firmware, and hardware. For example, various components of the apparatus may be formed on an integrated circuit (IC) chip or on a separate IC chip. Furthermore, various components of the apparatus may be implemented on a flexible printed circuit film, a tape-on-a-chip (TCP), or a printed circuit board (PCB), or formed on a substrate. Furthermore, various components of the apparatus may be processes or threads running on one or more processors in one or more computing devices, executing computer program instructions and interacting with other system components to perform the various functions described herein. The computer program instructions are stored in memory, which may be implemented using standard memory devices (such as random access memory (RAM) in the computing device). The computer program instructions may also be stored in other non-transient computer-readable media such as CD-ROMs, flash drives, etc. And, those skilled in the art will recognize that, without departing from the scope of this disclosure, the functions of various computing devices may be combined or integrated into a single computing device, or the functions of a particular computing device may be distributed across one or more other computing devices.

[0228] Although one or more embodiments of this disclosure have been described with reference to the accompanying drawings, it should be understood that this disclosure is not intended to be limited to these embodiments. Rather, those skilled in the art can make one or more suitable changes and modifications within the spirit and scope of the claims. Therefore, the foregoing one or more embodiments should be understood in all respects as illustrative rather than restrictive.

Claims

1. A positive electrode, comprising: Positive electrode current collector; A first active material layer on the positive electrode current collector; and A second active material layer on top of the first active material layer The first active material layer and the second active material layer each include first particles. The second active material layer further includes second particles, and The first particle comprises a compound represented by chemical formula 1, and the second particle comprises a compound represented by chemical formula 2: Chemical Formula 1 Li a1 Fe x1 B1 y1 PER 4-b1 , In chemical formula 1, the following conditions are met: 0.8 ≤ a1 ≤ 1.2, 0.95 ≤ x1 ≤ 0.999, 0.001 ≤ y1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, and x1 + y1 = 1. In chemical formula 1, B1 is at least one element selected from the group consisting of Ti, Mg, V, and Al. Chemical formula 2 Li a2 Ni x2 Co y2 Al z2 B2 w2 O 2-b2 , In chemical formula 2, the following conditions are met: 0.8 ≤ a² ≤ 1.2, 0.8 ≤ x² ≤ 0.95, 0.02 ≤ y² ≤ 0.19, 0.001 ≤ z² ≤ 0.03, 0 ≤ w² ≤ 0.1, 0 ≤ b² ≤ 0.05, and x² + y² + z² + w² = 1. In chemical formula 2, B2 is at least one element selected from the group consisting of Ti, Mg, Zr, and Al, and The positive electrode is used in a rechargeable lithium battery.

2. The positive electrode for a rechargeable lithium battery as described in claim 1, wherein the content of the second particles is in the range of 5 wt% to 25 wt% relative to the total content of the first particles and the second particles in the first active material layer and the second active material layer.

3. The positive electrode for a rechargeable lithium battery as described in claim 1, wherein the content of the second particles is in the range of 40 wt% to 60 wt% relative to the total content of the first particles and the second particles in the second active material layer.

4. The positive electrode for a rechargeable lithium battery as claimed in claim 1, wherein the second active material layer has a thickness of 0.1 to 0.5 relative to the total thickness of the first active material layer and the second active material layer.

5. The positive electrode for a rechargeable lithium battery as claimed in claim 1, wherein the second particle has an average particle size D of 8 μm to 20 μm. 50 .

6. The positive electrode for a rechargeable lithium battery as claimed in claim 1, wherein the second particle comprises a second secondary particle in the form of a secondary particle and a second single particle in the form of a single particle.

7. The positive electrode for a rechargeable lithium battery as described in claim 6, wherein the secondary particles have an average particle size D of 12 μm to 16 μm. 50 .

8. The positive electrode for a rechargeable lithium battery as claimed in claim 6, wherein the second single particle has an average particle size D of 3 μm to 5 μm. 50 .

9. The positive electrode for a rechargeable lithium battery as described in claim 1, wherein, The second particle includes a second coating, and The second coating comprises a boron-containing compound, an aluminum-containing compound, or a combination thereof.

10. The positive electrode for a rechargeable lithium battery as described in claim 1, wherein, The first active material layer further includes a first binder and a first conductive material. The second active material layer further includes a second binder and a second conductive material, and The content of the first adhesive is greater than the content of the second adhesive.

11. The positive electrode for a rechargeable lithium battery as described in claim 1, wherein, The first active substance layer has 5 mg / cm 2 ~10mg / cm 2 The load level, and The second active substance layer has 5 mg / cm 2 ~25mg / cm 2 The load level.

12. A positive electrode, comprising: Positive electrode current collector; A first active material layer on the positive electrode current collector; and A second active material layer on top of the first active material layer The first active material layer and the second active material layer each include a first particle in the form of a single particle. The second active material layer further includes second particles, and The first particle comprises a compound represented by chemical formula 1, and the second particle comprises a compound represented by chemical formula 2: Chemical Formula 1 Li a1 Fe x1 B1 y1 PER 4-b1 , In chemical formula 1, the following conditions are met: 0.8 ≤ a1 ≤ 1.2, 0.95 ≤ x1 ≤ 0.999, 0.001 ≤ y1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, and x1 + y1 = 1. In chemical formula 1, B1 is at least one element selected from the group consisting of Ti, Mg, V, and Al. Chemical formula 2 Li a2 Ni x2 Co y2 Al z2 B2 w2 O 2-b2 , In chemical formula 2, the following conditions are met: 0.8 ≤ a² ≤ 1.2, 0.8 ≤ x² ≤ 0.95, 0.02 ≤ y² ≤ 0.19, 0.001 ≤ z² ≤ 0.03, 0 ≤ w² ≤ 0.1, 0 ≤ b² ≤ 0.05, and x² + y² + z² + w² = 1. In chemical formula 2, B2 is at least one element selected from the group consisting of Ti, Mg, Zr, and Al, and The positive electrode is used in a rechargeable lithium battery.

13. The positive electrode for a rechargeable lithium battery as described in claim 12, wherein, The first particle includes at least one first primary particle. The first primary particle has a particle size of 200 nm to 300 nm, and The first particle has an average particle size D of 0.5 μm to 2.5 μm. 50 .

14. The positive electrode for a rechargeable lithium battery as claimed in claim 12, wherein the amount of the second particles is in the range of 5 wt% to 25 wt% relative to the total content of the first particles and the second particles in the first active material layer and the second active material layer.

15. The positive electrode for a rechargeable lithium battery as claimed in claim 12, wherein the amount of the second particles is in the range of 40 wt% to 60 wt% relative to the total content of the first and second particles in the second active material layer.

16. The positive electrode for a rechargeable lithium battery as claimed in claim 12, wherein the second active material layer has a thickness of 0.1 to 0.5 relative to the total thickness of the first active material layer and the second active material layer.

17. The positive electrode for a rechargeable lithium battery as claimed in claim 12, wherein the second particle comprises a second secondary particle in the form of a secondary particle and a second single particle in the form of a single particle.

18. The positive electrode for a rechargeable lithium battery as described in claim 17, wherein, The secondary particles have an average particle size D of 12μm to 16μm. 50 ,and The second single particle has an average particle size D of 3 μm to 5 μm. 50 .

19. The positive electrode for a rechargeable lithium battery as described in claim 12, wherein, The first active substance layer has 5 mg / cm 2 ~10mg / cm 2 The load level, and The second active substance layer has 5 mg / cm 2 ~25mg / cm 2 The load level.

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

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