Positive electrode and rechargeable lithium battery including same

Abstract

Examples of the present disclosure include a positive electrode and a rechargeable lithium battery including the positive electrode. 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. The first active material layer includes first particles, second particles, a first binder, and a first conductive material. The second active material layer includes third particles, a second binder, and a second conductive material. The first particles contain an olivine structured compound represented by Formula 1, the second particles contain a layered compound represented by Formula 2, the third particles contain an olivine structured compound represented by Formula 3, and the first active material layer and the second active material layer have a cobalt (Co) content of less than about 100 ppm, the first particle includes a plurality of first primary particles aggregated together. A formula 1 is Lia1Mnx1Fey1B1z1PO4-b1, a formula 2 is Lia2Nix2Mnz2Alc2Yd2O2-b2, and a formula 3 is Lia3Mnx3Fey3B3z3PO4-b3. The formula 1 is shown in the description.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0057127, filed on April 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Examples of this disclosure relate to a positive electrode and a rechargeable lithium battery including a positive electrode, and more specifically, to a positive electrode including an olivine-based lithium compound (an olivine-structured compound) and a rechargeable lithium battery including a positive electrode. Background Technology

[0004] The increasing prevalence of battery-powered electronics (such as mobile phones, laptops, and electric vehicles) has driven a growing demand for rechargeable lithium-ion batteries with high energy density and capacity. Accordingly, improving the performance of rechargeable lithium-ion batteries is beneficial.

[0005] Rechargeable lithium batteries typically include a positive electrode and a negative electrode (each of which includes an active material that allows lithium ions to insert and extract) and an electrolyte, and generate electrical energy through a redox reaction that occurs when lithium ions insert into or extract from the positive and negative electrodes. Summary of the Invention

[0006] Examples of this disclosure include a positive electrode for a rechargeable lithium-ion battery, which increases the adhesion of the positive electrode active material layer to the positive electrode current collector, reduces the resistance of the electrode plate, and facilitates the fabrication of the electrode plate. Examples of this disclosure also include rechargeable lithium-ion batteries having desired or improved capacity and lifetime characteristics, as well as high operating voltage and energy density.

[0007] Example embodiments of the present disclosure include a positive electrode for a rechargeable lithium battery, the positive electrode comprising: a positive electrode current collector; a first active material layer (first positive electrode active material layer) on the positive electrode current collector, the first active material layer comprising first particles, second particles, a first binder, and a first conductive material; and a second active material layer (second positive electrode active material layer) on the first active material layer, the second active material layer comprising third particles, a second binder, and a second conductive material. The first particles contain an olivine-structured compound represented by the following formula 1, the second particles contain a layered compound represented by the following formula 2, and the third particles contain an olivine-structured compound represented by the following formula 3. The first active material layer and the second active material layer have a cobalt (Co) content of less than about 100 ppm. The first particles include a plurality of first primary particles aggregated together, the first particles have an average particle size of about 3 μm to about 10 μm, the first primary particles have an average particle size of about 200 nm or less, the third particles are single particles, and the third particles have an average particle size of about 100 nm to about 2 μm.

[0008] Formula 1:

[0009] Li a1 Mn x1 Fe y1 B1 z1 PO 4-b1

[0010] In the above formula 1, 0.8 ≤ a1 ≤ 1.2, 0.4 ≤ x1 ≤ 0.8, 0 ≤ y1 ≤ 0.6, 0 ≤ z1 ≤ 0.05, 0 ≤ b1 ≤ 0.05 and x1 + y1 + z1 = 1 are satisfied, and B1 includes at least one of Al, Ti, V, and Mg.

[0011] Formula 2:

[0012] Li a2 Ni x2 Mn z2 Al c2 Y d2 O 2-b2

[0013] In the above formula 2, 0.8 < a2 ≤ 1.2, 0.7 ≤ x2 ≤ 0.8, 0.2 ≤ z2 ≤ 0.3, 0 ≤ c2 ≤ 0.02, 0 ≤ d2 ≤ 0.003, 0 ≤ b2 ≤ 0.05 and x2 + z2 + c2 + d2 = 1 are satisfied, and Y includes at least one of Ti, Mg, Zr, Mo, and Nb, and

[0014] Formula 3:

[0015] Li a3 Mn x3 Fe y3 B3z3 PO 4-b3

[0016] In Equation 3 above, 0.8≤a3≤1.2, 0.4≤x3≤0.8, 0≤y3≤0.6, 0≤z3≤0.05, 0≤b3≤0.05 and satisfying x3+y3+z3=1, and B3 includes at least one of Al, Ti, V and Mg.

[0017] In an exemplary embodiment 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, comprising first particles, second particles, a first binder, and a first conductive material; and a second active material layer on the first active material layer, the second active material layer comprising third particles, a second binder, and a second conductive material. The first particles contain a compound structured with olivine represented by Formula 1 below, the second particles contain a layered compound represented by Formula 2 below, and the third particles contain a compound structured with olivine represented by Formula 3 below. The first and second active material layers have a cobalt (Co) content of less than about 100 ppm. The first particles comprise a plurality of aggregated first primary particles having an average particle size of about 3 μm to about 10 μm, and the first primary particles having an average particle size of about 200 nm or less. The third particles comprise a plurality of aggregated fourth particles having an average particle size of about 3 μm to about 10 μm, each of the plurality of fourth particles being a primary particle, and the plurality of fourth particles having a particle size of about 200 nm or less.

[0018] Formula 1:

[0019] Li a1 Mn x1 Fe y1 B1 z1 PO 4-b1

[0020] In Equation 1 above, the following conditions must be met: 0.8 ≤ a1 ≤ 1.2, 0.4 ≤ x1 ≤ 0.8, 0 ≤ y1 ≤ 0.6, 0 ≤ z1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, and x1 + y1 + z1 = 1, and B1 includes at least one of Al, Ti, V, and Mg.

[0021] Formula 2:

[0022] Li a2 Ni x2 Mn z2 Al c2 Y d2 O 2-b2

[0023] In Formula 2 above, 0.8 < a2 ≤ 1.2, 0.7 ≤ x2 ≤ 0.8, 0.2 ≤ z2 ≤ 0.3, 0 ≤ c2 ≤ 0.02, 0 ≤ d2 ≤ 0.003, 0 ≤ b2 ≤ 0.05 and x2 + z2 + c2 + d2 = 1, and Y includes at least one of Ti, Mg, Zr, Mo, and Nb, and

[0024] Formula 3:

[0025] Li a3 Mn x3 Fe y3 B3 z3 PO 4-b3

[0026] In Formula 3 above, 0.8 ≤ a3 ≤ 1.2, 0.4 ≤ x3 ≤ 0.8, 0 ≤ y3 ≤ 0.6, 0 ≤ z3 ≤ 0.05, 0 ≤ b3 ≤ 0.05 and x3 + y3 + z3 = 1, and B3 includes at least one of Al, Ti, V, and Mg.

[0027] In an exemplary embodiment of the present disclosure, the rechargeable lithium battery includes the above positive electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, explain the principles of the present disclosure.

[0029] In the drawings:

[0030] Figure 1 is a simplified conceptual diagram showing a rechargeable lithium battery according to an exemplary embodiment of the present disclosure;

[0031] Figures 2-5 is a schematic diagram illustrating a rechargeable lithium battery according to an exemplary embodiment. Figure 2 shows a cylindrical battery, Figure 3 shows a prismatic battery, and Figure 4 and Figure 5 shows a pouch-type battery;

[0032] Figure 6 is a cross-sectional view showing a positive electrode for a rechargeable lithium battery according to an exemplary embodiment of the present disclosure; <​​​​​​​​

[0035] Figure 9 To show an enlarged view of the second active material layer according to another exemplary embodiment of this disclosure;

[0036] Figure 10 An enlarged view of the positive electrode active material layer according to a comparative example of the present disclosure is shown.

[0037] Figure 11 To illustrate a SEM image of a first particle according to an exemplary embodiment of this disclosure;

[0038] Figure 12 To illustrate a SEM image of a second particle according to an exemplary embodiment of this disclosure;

[0039] Figure 13 To illustrate a SEM image of a third particle in the form of a single particle according to an exemplary embodiment of this disclosure; and

[0040] Figure 14 To illustrate a SEM image of a third particle in the form of a secondary particle according to another exemplary embodiment of this disclosure. Detailed Implementation

[0041] To fully understand the configurations and effects of this disclosure, exemplary embodiments of the disclosure have been 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 can be implemented in various forms and modified differently. The exemplary embodiments provided herein are intended to make this disclosure thorough and complete, and to fully convey the scope of this disclosure to those skilled in the art.

[0042] In this document, it will be understood that when a component is referred to as being "on" another component, the component may be directly on the other component, or there may be an intermediate third component. Additionally, in the accompanying drawings, the dimensions (e.g., thickness) of the components are enlarged for the purpose of effectively describing the technical content. The same reference numerals refer to the same elements throughout the document.

[0043] The exemplary embodiments described herein will be explained with reference to cross-sectional and / or plan views, which serve as ideal example views of this disclosure. In the drawings, the thickness of the membranes and regions is enlarged for efficient description of the technical content. Therefore, the regions presented as examples in the drawings have general properties, and the shapes of the exemplary regions are used to illustrate specific shapes of the device regions. Therefore, this should not be construed as limiting the scope of this disclosure. Although terms (such as first, second, and third) are used to describe various components in the various exemplary embodiments herein, the components should not be limited to these terms. These terms are used only to distinguish one component from another. The exemplary embodiments described and illustrated herein include their exemplary implementations.

[0044] The terminology used herein is not intended to limit this disclosure, but rather to describe exemplary implementations. As used herein, the singular form also includes the plural form, unless the context clearly indicates otherwise. The meaning of “comprising” and / or “including” as used herein does not exclude the presence or addition of one or more other components in addition to those mentioned.

[0045] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, the relevant numerical values ​​are expected to include a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​increasing in increments such as 0.1%.

[0046] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an exemplary embodiment of the present disclosure. References Figure 1 A rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0047] The positive electrode 10 and the negative electrode 20 can be separated from each other by a diaphragm 30. The diaphragm 30 can be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20 and the diaphragm 30 can be in contact with the electrolyte ELL. The positive electrode 10, the negative electrode 20 and the diaphragm 30 can be immersed in the electrolyte ELL.

[0048] The electrolyte ELL may be or include a medium for transporting lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move through the separator 30 toward the positive electrode 10 or the negative electrode 20.

[0049] Positive electrode 10

[0050] 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 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 (e.g., an electrically conductive material).

[0051] For example, the positive electrode 10 may further include components constituting a sacrificial positive electrode.

[0052] Al foil may be included as the positive electrode current collector COL1, but the exemplary embodiments of this disclosure are not limited thereto.

[0053] Please refer to later Figure 6 The positive electrode 10 is described in detail.

[0054] negative electrode 20

[0055] 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).

[0056] 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.

[0057] The binder can be configured to attach the negative electrode active material particles to each other and to attach the negative electrode active material to the negative electrode current collector COL2. The binder may include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0058] Non-aqueous adhesives may include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, and combinations thereof.

[0059] The waterborne adhesive may be or include at least one of 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.

[0060] When the aqueous binder is or includes 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 an alkali metal salt thereof. The alkali metal may include at least one of Na, K, and Li.

[0061] Dry adhesives may be or include fibrous polymeric materials. For example, dry adhesives may be or include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0062] The conductive material can be configured to impart conductivity (e.g., electrical conductivity) to the electrode. Any material that does not cause a chemical change (e.g., does not cause an undesired chemical change in a rechargeable lithium battery) and conducts electrons can be included in the battery. Non-limiting examples thereof can include: carbonaceous materials, such as or including at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metallic materials, including at least one of copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0063] The negative electrode current collector COL2 can include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0064] Negative electrode active material

[0065] The negative electrode active material in the negative electrode active material layer AML2 can include at least one of a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and a transition metal oxide.

[0066] The material that reversibly intercalates / deintercalates lithium ions can include carbonaceous negative electrode active materials (such as, for example, crystalline carbon, amorphous carbon, or a combination thereof). Examples of crystalline carbon can be or include graphite (such as irregular, planar, flaky, spherical, or fibrous natural graphite or artificial graphite), and examples of amorphous carbon can be or include at least one of soft carbon (low-temperature fired carbon), hard carbon, mesophase pitch carbide, and calcined coke, etc.

[0067] The lithium metal alloy includes an alloy of lithium and a metal such as or including at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0068] The material capable of doping / dedoping lithium can be or include 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, a silicon-carbon composite, SiO x (0 < x ≤ 2) and at least one of a Si-Q alloy (where Q is or includes at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof). The Sn-based negative electrode active material can include Sn, SnO x (0 < x ≤ 2) (e.g., SnO2), Sn-based alloys, and combinations thereof.

[0069] Silicon-carbon composites can be or include composites of silicon and amorphous carbon. According to an example 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 may include secondary particles (cores) in which primary silicon particles are aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon may also be present between the primary silicon particles, and, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed within an amorphous carbon matrix.

[0070] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles, and an amorphous carbon coating on the surface of the core.

[0071] It may include Si-type negative electrode active materials or a combination of Sn-type negative electrode active materials and carbon-type negative electrode active materials.

[0072] Diaphragm 30

[0073] 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 at least one of polyethylene separator, polypropylene separator, polyvinylidene fluoride separator, or a multilayer film of two or more layers thereof (such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.).

[0074] The diaphragm 30 may include a porous substrate and a coating on one or both surfaces of the porous substrate, comprising organic materials, inorganic materials, or combinations thereof.

[0075] The porous substrate may be or comprise a polymer film formed of any one or more copolymers or mixtures of the following, or a polymer film comprising at least one or more copolymers or mixtures of the following: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., TEFLON).

[0076] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers.

[0077] Inorganic materials may include, but are not limited to, inorganic particles such as or including at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0078] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked.

[0079] Electrolyte ELL

[0080] Electrolytes (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0081] Non-aqueous organic solvents can serve as media for transporting ions that participate in the electrochemical reactions of a battery.

[0082] Non-aqueous organic solvents may be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0083] Carbonate solvents may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC).

[0084] Ester solvents may include at least one of the following: methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, caprolactone, etc.

[0085] Ether solvents may include at least one of 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 at least one of ethanol, isopropanol, etc., and aprotic solvents may include at least one of: nitrile solvents (such as R-CN (where R is a C2-C20 straight-chain hydrocarbon group, branched hydrocarbon group, 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.

[0086] Non-aqueous organic solvents may be included alone or in combination of two or more solvents.

[0087] 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.

[0088] In the embodiments, lithium salts dissolved in non-aqueous organic solvents supply lithium ions to the battery, ensuring basic operation of the rechargeable lithium battery and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include 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 At least one of SO2 (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0089] Rechargeable lithium batteries

[0090] Depending on the shape of the rechargeable lithium battery, rechargeable lithium batteries can be classified as cylindrical batteries, prismatic batteries, pouch batteries, or coin-shaped batteries, etc. Figures 2-5 A schematic diagram illustrating a rechargeable lithium battery according to an example embodiment. Figure 2 It explains the cylindrical battery. Figure 3 The prismatic battery was explained, and Figure 4 and Figure 5 This explains the pouch battery. (Reference) Figures 2-5 The rechargeable lithium battery 100 may include: an electrode assembly 40 comprising a separator 30 between a positive electrode 10 and a negative electrode 20, and a housing 50 comprising the electrode assembly 40. 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 The rechargeable lithium battery 100 shown may include Figure 5 The electrode terminal 70 described in the text, or, for example, Figure 4The positive electrode terminal 71 and negative electrode terminal 72, as illustrated in the diagram, form an electrical path for guiding the current generated in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0091] As a non-limiting example, the rechargeable lithium battery according to the example embodiment can be used in automobiles, mobile phones and / or various types of electrical devices.

[0092] Figure 6 A cross-sectional view illustrating the positive electrode of a rechargeable lithium battery according to an exemplary embodiment of the present disclosure. References Figure 6 As described above, the positive electrode 10 may include a positive electrode current collector COL1 and a positive electrode active material layer AML1. The positive electrode active material layer AML1 may be provided on the positive electrode current collector COL1.

[0093] The positive electrode active material layer AML1 may include positive electrode active material particles PTC1, PTC2, and PTC3 (first particle PTC1, second particle PTC2, and third particle PTC3), which will be described later. The positive electrode active material layer AML1 may contain approximately 90 wt% to approximately 99 wt% of the positive electrode active material particles PTC1, PTC2, and PTC3 relative to 100 wt% of the positive electrode active material layer AML1.

[0094] The positive electrode active material layer AML1 may include binders BND1 and BND2, which will be described later, and conductive materials CDM1 and CDM2. Relative to 100 wt% of the positive electrode active material layer AML1, the positive electrode active material layer AML1 may contain about 2.4 wt% to about 6 wt% of binders BND1 and BND2 and conductive materials CDM1 and CDM2, or at least one of them.

[0095] The positive electrode active material layer AML1 may include a first active material layer (first positive electrode active material layer) ATL1 and a second active material layer (second positive electrode active material layer) ATL2. Since the positive electrode active material layer AML1 includes the first active material layer ATL1 and the second active material layer ATL2, it can contain a large amount of nano-sized olivine-like compounds, increasing the binding force relative to the positive electrode current collector, thereby facilitating the fabrication of the electrode plate and reducing the resistance of the electrode plate. Furthermore, it can provide a rechargeable lithium battery with desired or improved performance.

[0096] The first active material layer ATL1 may have a thickness T1. In an example embodiment, the thickness T1 may increase with increasing weight of the first particle PTC1 and / or the second particle PTC2 included in the first active material layer ATL1. The second active material layer ATL2 may have a thickness T2. In an example embodiment, the thickness T2 may increase with increasing weight of the third particle PTC3 included in the second active material layer ATL2.

[0097] The thickness ratio T1:T2 of the first active material layer ATL1 and the second active material layer ATL2 can be approximately 3:7 to approximately 7:3. For example, the thickness ratio T1:T2 of the first active material layer ATL1 and the second active material layer ATL2 can be approximately 5:5. When the thickness ratio T1:T2 of the first active material layer ATL1 and the second active material layer ATL2 meets the above numerical range, the positive electrode active material layer AML1 has improved adhesion to the positive electrode current collector COL1, thus facilitating the fabrication of the electrode plate and reducing the resistance of the electrode plate. In addition, a rechargeable lithium battery with desired or improved performance can be provided.

[0098] Figure 7 An enlarged view of the first active material layer ATL1 according to an exemplary embodiment of the present disclosure is shown. Figure 8 An enlarged view is shown to illustrate the second active material layer ATL2 according to an exemplary embodiment of the present disclosure. Figure 9 An enlarged view of the second active material layer ATL2 according to another exemplary embodiment of this disclosure. Figure 10 An enlarged view of the positive electrode active material layer AML1 according to a comparative example of the present disclosure is shown.

[0099] refer to Figure 7 The first active material layer ATL1 may include a first particle PTC1, a second particle PTC2, and a first functional additive FAD1. The first functional additive FAD1 may include a first binder BND1 and a first conductive material CDM1.

[0100] The first active material layer ATL1 includes the second particle PTC2, thus reducing the content of the first functional additive FAD1. For example, the weight ratio of the first functional additive FAD1 in the first positive electrode active material layer ATL1 can be about 0.024 to about 0.06. The weight ratio of the first functional additive FAD1 in the first active material layer ATL1 can be defined as the weight of the first functional additive FAD1 relative to the total weight of the first active material layer ATL1.

[0101] For example, the content of the first binder BND1 may be about 1.2 parts by weight to about 3 parts by weight relative to 100 parts by weight of the first active material layer ATL1. The content of the first conductive material CDM1 may be about 1.2 parts by weight to about 3 parts by weight relative to 100 parts by weight of the first active material layer ATL1.

[0102] refer to Figure 8 and Figure 9 The second active material layer ATL2 may include a third particle PTC3 and a second functional additive FAD2. The second functional additive FAD2 may include a second binder BND2 and a second conductive material CDM2.

[0103] In this document, the weight ratio of the second functional additive FAD2 in the second active material layer ATL2 may be equal to or greater than the weight ratio of the first functional additive FAD1 in the first active material layer ATL1. For example, the weight ratio of the second functional additive FAD2 in the second active material layer ATL2 may be greater than the weight ratio of the first functional additive FAD1 in the first active material layer ATL1.

[0104] For example, the weight ratio of the second functional additive FAD2 to the first functional additive FAD1 (weight ratio of the second functional additive FAD2 / weight ratio of the first functional additive FAD1) can be in the range of about 1 to about 4.5. Alternatively, the weight ratio of the second functional additive FAD2 to the first functional additive FAD1 (weight ratio of the second functional additive FAD2 / weight ratio of the first functional additive FAD1) can be in the range of about 1.6 to about 4.5 or about 1.6 to about 4. When the weight ratio of the second functional additive FAD2 to the first functional additive FAD1 meets the above numerical range, the positive electrode active material layer AML1 has improved adhesion to the positive electrode current collector COL1, thus facilitating the fabrication of the electrode plate and reducing the resistance of the electrode plate. Furthermore, a rechargeable lithium battery with desired or improved performance can be provided.

[0105] For example, the weight ratio of the second functional additive FAD2 in the second positive electrode active material layer ATL2 can be about 0.024 to about 0.1. Alternatively, the weight ratio of the second functional additive FAD2 in the second positive electrode active material layer ATL2 can be in the range of about 0.04 to about 0.1. The weight ratio of the second functional additive FAD2 in the second active material layer ATL2 can be defined as the weight of the second functional additive FAD2 relative to the total weight of the second active material layer ATL2.

[0106] The content of the second adhesive BND2 may be greater than the content of the first adhesive BND1. For example, relative to 100 parts by weight of the second active material layer ATL2, the content of the second adhesive BND2 may be about 1.2 parts by weight to about 5 parts by weight. For example, relative to 100 parts by weight of the second active material layer ATL2, the content of the second adhesive BND2 may be about 2 parts by weight to about 5 parts by weight.

[0107] The content of the second conductive material CDM2 can be greater than the content of the first conductive material CDM1. The content of the second conductive material CDM2 relative to 100 parts by weight of the second active material layer ATL2 can be approximately 1.2 parts by weight to approximately 5 parts by weight. For example, the content of the second conductive material CDM2 relative to 100 parts by weight of the second active material layer ATL2 can be approximately 2 parts by weight to approximately 5 parts by weight.

[0108] Binders BND1 and BND2 may be configured to attach positive electrode active material particles PTC1, PTC2, and PTC3 to each other, and also to attach positive electrode active material particles PTC1 and PTC2 to the positive electrode current collector COL1. Typical examples of binders BND1 and BND2 may be or include at least one 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 exemplary embodiments of this disclosure are not limited thereto.

[0109] Conductive materials CDM1 and CDM2 can be configured to impart conductivity (e.g., electrical conductivity) to the 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 included in the battery. Examples of conductive materials CDM1 and CDM2 may include: carbon-based materials (such as or including at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes); metallic materials, including at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0110] The interface between the first active material layer ATL1 and the second active material layer ATL2 cannot be clearly distinguished using SEM images or similar methods. However, the interface between the first active material layer ATL1 and the second active material layer ATL2 can be inferred by changing the differences in the composition and materials between the layers.

[0111] The first particle PTC1, the second particle PTC2, and the third particle PTC3 will be described in more detail below.

[0112] First PTC1

[0113] Return to reference Figure 7 The first particle PTC1 may be in a polycrystalline form and may include secondary particles (first primary particles) formed by the aggregation of at least two primary particles. That is, a first particle PTC1 may include multiple first primary particles NNP aggregated together. Each of the first primary particles NNP may be a primary particle.

[0114] The first PTC1 particle may have an average particle size (D) ranging from about 2 μm to about 15 μm, about 3 μm to about 10 μm, or about 3 μm to about 7 μm. 50 For example, the first particle PTC1 may have an average particle size of approximately 5 μm. In an example embodiment, the average particle size can be measured using a particle size analyzer. The average particle size can indicate the particle size when the cumulative volume in the particle size distribution is approximately 50 vol%.

[0115] The first PTC1 particle may have a maximum particle size (Dmax) of about 10 μm or larger or about 15 μm or larger.

[0116] The particle size of the first primary particle NNP may be smaller than the average particle size of the first particle PTC1. The first primary particle NNP may have a particle size of about 200 nm or smaller. For example, the first primary particle NNP may have a particle size in the range of about 10 nm to about 200 nm, about 20 nm to about 200 nm, about 50 nm to about 200 nm, or about 100 nm to about 200 nm. In an example embodiment, the particle size of the first primary particle NNP may indicate the diameter measured by randomly selecting about 30 first primary particle NNPs from an electron micrograph of the positive electrode active material. The first primary particle NNP may have a substantially uniform particle size.

[0117] When the particle sizes of the first PTC1 particle and the first primary NNP particle meet the above-mentioned range, and the size of the first primary NNP particle is substantially uniform, the rechargeable lithium battery containing the first PTC1 particle and the first primary NNP particle can have improved charge / discharge capacity and low-temperature capacity.

[0118] The first particle PTC1 may include an olivine-based lithium compound represented by Formula 1 below.

[0119] Formula 1:

[0120] Li a1 Mn x1 Fe y1 B1 z1 PO4-b1

[0121] In Equation 1 above, the following conditions must be met: 0.8 ≤ a1 ≤ 1.2, 0.4 ≤ x1 ≤ 0.8, 0 ≤ y1 ≤ 0.6 (for example, 0.2 ≤ y1 ≤ 0.6), 0 ≤ z1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, and x1 + y1 + z1 = 1. For example, z1 can be approximately 0.002.

[0122] B1 may include at least one of Al, Ti, V, and Mg. For example, B1 may include Ti. B1 may be or include a dopant that dops the first primary particle PTC1. B1 can control the size of the first primary particle NNP to be substantially uniform.

[0123] The doping amount of B1 can be in the range of about 500 ppm to about 3000 ppm. The doping amount of B1 can be defined as the weight of the dopant element B1 relative to the total weight of the metals other than lithium (i.e., Mn, Fe and B1) in the olivine-based lithium compound represented by Formula 1 above. When the doping amount of B1 meets the above range, the size of the first PTC1 particle can be controlled to be substantially uniform.

[0124] In an example embodiment, the first PTC1 particle may include a coating on its surface. The coating may cover the entire surface of the first PTC1 particle or a portion of its surface. The first PTC1 particle includes a coating containing carbon elements. For example, the coating may include elemental carbon and / or carbon-containing compounds. The first PTC1 particle may have improved structural stability or improved electrical conductivity through the coating.

[0125] The coating may further include at least one metal-containing compound selected from titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds. The metal-containing compound (such as or including at least one of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds) may be or include at least one of, for example, metal oxides, metal hydroxides, metal carbonates, complexes thereof, or mixtures thereof. The metal-containing compound may further include other metallic or non-metallic elements. For example, the metal-containing compound may further include lithium.

[0126] In an example embodiment, the first particle PTC1 may further include a grain boundary coating on the surface of each or at least one of the first primary particles NNP. 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 within the first particle PTC1. That is, the grain boundary coating may indicate a layer formed by material applied to the grain boundaries within the first particle PTC1. 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 titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds.

[0127] The interior of the first particle PTC1 can refer to the entire interior portion of the first particle PTC1 excluding its surface. For example, the interior of the first particle PTC1 can refer to the entire interior region from a depth of about 10 nm from the surface of the first particle PTC1 or from a depth of about 10 nm to about 2 μm.

[0128] The first PTC1 particle further includes a grain boundary coating, thus exhibiting greater structural stability and a substantially uniform coating formed on its surface. Additionally, the first PTC1 particle further includes a grain boundary coating, thus exhibiting further improved electrical conductivity.

[0129] The first PTC1 particle may further include carbon (carbon element) derived from the above-described coating and / or grain boundary coating. The first PTC1 particle may have a carbon element content in the range 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%.

[0130] The first PTC1 particle can be a substantially spherical shape in which the first primary NNP particles of nanoscale size are aggregated. The first PTC1 particle has tightly aggregated first primary NNP particles and therefore exhibits the following characteristics. The first PTC1 particle can be spherical or elliptical in shape. The average particle size (D) of the first PTC1 particle... 50 The porosity of the first PTC1 particle can range from approximately 2 μm to approximately 15 μm. The porosity can range from approximately 20% to approximately 40%. Porosity (n) can be defined as the pore volume (V). p Divide by the total volume of the particles (V) t ), or n = V p / V t The span value of the first PTC1 particle analyzed by the particle size analyzer is in the range of approximately 0.3 to approximately 0.75. In this specification, the span value can be expressed by equation (D). 90 -D 10 ) / D 50 Limited. D 10 D 50 and D 90 It can refer to the average particle size of particles with cumulative volumes of 10 vol%, 50 vol%, and 90 vol%, respectively, in the particle size distribution.

[0131] The first PTC1 particle can have a large Brunol-Emmett-Taylor (BET) specific surface area. For example, the first PTC1 particle can have a specific surface area of ​​approximately 10 m². 2 / g~approximately 30m 2 BET specific surface area in the range of / g. For example, the first PTC1 particle may have a BET specific surface area of ​​approximately 20m². 2 / g BET specific surface area.

[0132] Second PTC2 particle

[0133] Return reference Figure 7 , the second particle PTC2 may include a layered lithium compound represented by the following formula 2.

[0134] Formula 2:

[0135] Li a2 Ni x2 Mn z2 Al c2 Y d2 O 2-b2

[0136] In the above formula 2, 0.8 < a2 ≤ 1.2, 0.7 ≤ x2 ≤ 0.8, 0.2 ≤ z2 ≤ 0.3, 0 ≤ c2 ≤ 0.02, 0 ≤ d2 ≤ 0.003, 0 ≤ b2 ≤ 0.05 and x2 + z2 + c2 + d2 = 1 can be satisfied. For example, c2 can be 0.004. For example, d2 can be 0.001.

[0137] Y may be or include a dopant that dopes the second particle PTC2. Y may include at least one of Ti, Mg, Zr, Mo, and Nb.

[0138] The cobalt (Co) content of the second particle PTC2 may be less than about 100 ppm. That is, the second particle PTC2 according to an exemplary embodiment of the present disclosure may substantially not contain cobalt (Co). The second particle PTC2 according to an exemplary embodiment of the present disclosure may be or include a cobalt-free positive electrode active material. The second particle PTC2 may have a Co content lower than the Al content.

[0139] The second particle PTC may be indicated as a layered cobalt-free positive electrode active material, a cobalt-free nickel-based positive electrode active material, or a cobalt-free nickel-manganese-based positive electrode active material. "Cobalt-free" may indicate no cobalt or substantially no cobalt, substantially no use of cobalt, or only contain a very small amount of cobalt.

[0140] In an exemplary embodiment, the second particle PTC2 may include a coating on its surface. The coating may substantially completely cover the surface of the second particle PTC2 or may partially cover the surface of the second particle PTC2. The coating may include at least one metal-containing compound such as a boron-containing compound, a titanium-containing compound, an aluminum-containing compound, and a combination thereof. The metal-containing compound in the coating may be or include at least one of, for example, metal oxides, metal hydroxides, metal carbonates, their complexes, and their mixtures. The compound forming the coating may be crystalline or amorphous. The metal-containing compound may further include other metal or non-metal elements. For example, the coating may further include at least one of lithium, manganese, and / or nickel. Surface modification using the coating may stabilize the structure and improve thermal stability.

[0141] The size of the second PTC2 particle can be measured in micrometers. When a first active material layer ATL1, comprising the first PTC1 particle and the second PTC2 particle, is introduced, the positive electrode active material layer AML1 can contain a large amount of nano-sized olivine compounds and exhibit greater binding force relative to the positive electrode current collector COL1. This, in turn, facilitates the fabrication of the electrode plate and reduces its resistance. Furthermore, it provides a rechargeable lithium battery with desired or improved performance.

[0142] For example, the second particle PTC2 can be in the form of a single particle. Herein, a single particle can refer to a single type of particle without grain boundaries within it. A single particle can refer to a single particle morphologically present in an independent phase (where particles do not aggregate together), a particle with an integral structure, a particle with a monolithic structure, or a non-aggregated particle. For example, a single particle can be a single crystal. In an example embodiment, a single particle can be in the form of multiple second primary particles MMPs attached or aggregated together. Alternatively, a single particle can be in the form of about 2 to about 100 second primary particles MMPs attached to each other. Herein, the second particle PTC2 in the form of a single particle can be defined as a second single particle SP2. Additionally, the second single particle SP2 can be defined as a small particle.

[0143] In the example implementation, the average particle size (D) 50 This indicates the particle size when the cumulative volume in the particle size distribution is approximately 50% by volume. The average particle size (D) of the second particle, PTC2, is... 50 The value can be measured using a particle size analyzer. Accordingly, the second single particle SP2 can have an average particle size (D) in the range of about 3 μm to about 7 μm or about 3 μm to about 4 μm. 50 The second single particle SP2 may have a larger average particle size (D) than the first primary particle NNP. 50 Larger average particle size (D) 50 ).

[0144] In another example, the second particle PTC2 is in a polycrystalline form and may include secondary particles in which at least two second primary particles MMP are aggregated. That is, a second particle PTC2 may include multiple second primary particles MMP aggregated together. The second particle PTC2 composed of multiple second primary particles MMP may be spherical or elliptical in shape. In this document, the second particle PTC2 in the form of secondary particles may be defined as a second secondary particle PC2. In addition, in this document, the second secondary particle PC2 may be defined as a large particle.

[0145] In the example implementation, the average particle size (D) 50This indicates the particle size when the cumulative volume in the particle size distribution is approximately 50% by volume. The average particle size (D) of the second particle, PTC2, is... 50 The value can be measured using a particle size analyzer. For example, the secondary stage particles PC2 can have an average particle size (D) of approximately 12 μm to approximately 18 μm. 50 The second-stage particle PC2 may have a larger average particle size (D) than the first particle PTC1. 50 Larger average particle size (D) 50 ).

[0146] In this paper, the second PTC2 particle may exist as a second single particle SP2 or a second secondary particle PC2. Alternatively, the second PTC2 particle may be or include a positive electrode active material comprising the second single particle SP2 and the second secondary particle PC2.

[0147] In this paper, both the second single particle SP2 and the second stage particle PC2 can be interpreted as referring to the second particle PTC2. Alternatively, the second particle PTC2 can be interpreted as referring to a particle containing both the second single particle SP2 and the second stage particle PC2.

[0148] In this paper, the case in which the second particle PTC2 exists in the positive electrode active material in the form of both single particles and secondary particles, or in the form of both large particles and small particles, can be referred to as bimodal.

[0149] The second PTC2 particle may have a small BET specific surface area. The second PTC2 particle may have a smaller BET specific surface area than the first PTC1 particle and / or the third PTC3 particle. For example, the second PTC2 particle may have a BET specific surface area of ​​approximately 0.8 μm. 2 / g~approximately 1.2m 2 The BET specific surface area is within the range of / g. For example, the second PTC2 particle may have a BET specific surface area of ​​approximately 1m². 2 / g BET specific surface area. Accordingly, it can be combined with nano-sized olivine compounds including a small amount of binder.

[0150] Third PTC3

[0151] Return to reference Figure 8The third PTC3 particle can be in the form of a single particle. In this document, a single particle can refer to a single type of particle that has no grain boundaries within it. A single particle can refer to a single particle morphologically present in an independent phase (where particles do not aggregate with each other), a particle with an integral structure, a particle with a monolithic structure, or a non-aggregated particle. For example, a single particle can be a single crystal. Optionally, a single particle can be or include particles containing several crystals. A single particle can be in an isolated form. Optionally, a single particle can be such that about 2 to about 100 single particles are attached to each other. That is, the third PTC3 particle can be provided in various sizes. For example, the third PTC3 particle can have an average particle size of about 1 μm. The third PTC3 particle can have a minimum particle size in the range of about 20 nm to about 500 nm or about 200 nm to about 300 nm (i.e., the size of the third primary particle, for example, the particle size of a smaller third PTC3 particle, i.e., as used herein, "third primary particle" refers to a third PTC3 particle whose size corresponds to the minimum particle size of a single particle). For example, the minimum particle size can indicate the diameter measured by randomly selecting about 30 primary particles (hereinafter, third primary particles) from an electron micrograph of the positive electrode active material.

[0152] The third PTC3 particle can have an average particle size (D) in the range of about 100 nm to about 2 μm or about 500 nm to about 2 μm. 50 For example, the third particle, PTC3, may have an average particle size of about 1 μm. In an example embodiment, the average particle size can be measured using a particle size analyzer. The average particle size can indicate the particle size when the cumulative volume in the particle size distribution is about 50 vol%.

[0153] The third particle PTC3 may include olivine-structured compounds of Formula 3 below.

[0154] Formula 3:

[0155] Li a3 Mn x3 Fe y3 B3 z3 PO 4-b3

[0156] In Equation 3 above, the following conditions must be met: 0.8 ≤ a3 ≤ 1.2, 0.4 ≤ x3 ≤ 0.8, 0 ≤ y3 ≤ 0.6 (for example, 0.2 ≤ y3 ≤ 0.6), 0 ≤ z3 ≤ 0.05, 0 ≤ b3 ≤ 0.05, and x3 + y3 + z3 = 1. For example, z3 can be approximately 0.002.

[0157] B3 may be or include a dopant of PTC3 doped with a third primary particle. B3 may include at least one of Al, Ti, V, and Mg. B3 controls the size of the third primary particle to be substantially uniform, thus enabling the rechargeable lithium battery to have improved charge / discharge efficiency, low-temperature properties, and lifespan characteristics.

[0158] In an example 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. The third PTC3 particle includes a coating containing carbon elements. For example, the coating may include elemental carbon and / or carbon-containing compounds. The third PTC3 particle may have improved structural stability and electrical conductivity through the coating.

[0159] The coating may further include at least one metal-containing compound selected from titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds. The metal-containing compound (such as or including at least one of titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds) may be or include at least one of, for example, metal oxides, metal hydroxides, metal carbonates, complexes thereof, or mixtures thereof. The metal-containing compound may further include other metallic or non-metallic elements. For example, the metal-containing compound may further include lithium.

[0160] The third PTC3 particle may further include carbon derived from the above-described coating. The carbon content in the third PTC3 particle may be in the range 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%.

[0161] The third PTC3 particle can have a large BET specific surface area. For example, the third PTC3 particle can have a specific surface area of ​​approximately 10 m². 2 / g~approximately 30m 2 BET specific surface area in the range of / g. For example, the third particle of PTC3 can have a BET specific surface area of ​​about 20m². 2 / g BET specific surface area.

[0162] When the third particle PTC3 is a single particle, the weight ratio of the second functional additive FAD2 in the second active material layer ATL2 can be equal to or greater than the weight ratio of the first functional additive FAD1 in the first active material layer ATL1. Optionally, the weight ratio of the second functional additive FAD2 in the second active material layer ATL2 can be greater than the weight ratio of the first functional additive FAD1 in the first active material layer ATL1. For example, the ratio of the weight ratio of the second functional additive to the weight ratio of the first functional additive can be in the range of about 1.6 to about 4.5.

[0163] When the third particle PTC3 is a single particle, the content of the second functional additive FAD2 relative to 100 parts by weight of the second active material layer ATL2 can be in the range of about 4 parts by weight to about 10 parts by weight or about 6 parts by weight. For example, the content of the second binder BND2 relative to 100 parts by weight of the second active material layer ATL2 can be in the range of about 2 parts by weight to about 5 parts by weight or about 3 parts by weight. For example, the content of the second conductive material CDM2 relative to 100 parts by weight of the second active material layer ATL2 can be in the range of about 2 parts by weight to about 5 parts by weight or about 3 parts by weight. When the content of the second functional additive FAD2 meets any of the above ranges, the second active material layer ATL2 can achieve the desired bonding strength.

[0164] Return to reference Figure 9 The third PTC3 particle is in a polycrystalline form and may include secondary particles in which at least two primary particles (hereinafter, tertiary particles) are aggregated. That is, a third PTC3 particle may include multiple fourth PTC4 particles aggregated together. Each of the fourth PTC4 particles may be a primary particle. The third PTC3 particle may be spherical or elliptical in shape.

[0165] In an example embodiment, the third PTC3 particle may further include a grain boundary coating on the surface of each or at least one of the fourth PTC4 particles. The grain boundary coating may be present within the third PTC3 particle. The grain boundary coating may be formed as an application along the interfaces between the fourth PTC4 particles within the third PTC3 particle. That is, the grain boundary coating may indicate a layer formed by material coated on the grain boundaries within the third PTC3 particle. 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 titanium-containing compounds, magnesium-containing compounds, and vanadium-containing compounds.

[0166] The interior of the third PTC3 can refer to the entire interior portion of the third PTC3 excluding its surface. For example, the interior of the third PTC3 can refer to the entire interior region extending from the surface of the third PTC3 to a depth of about 10 nm or from about 10 nm to about 2 μm.

[0167] The third PTC3 particle further includes a grain boundary coating, thus exhibiting greater structural stability and a substantially uniform coating formed on its surface. Additionally, the third PTC3 particle further includes a grain boundary coating, thus exhibiting further improved electrical conductivity.

[0168] The third PTC3 particle may further include carbon derived from the above-mentioned coating and / or grain boundary coating. The carbon content in the third PTC3 particle may be in the range 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%.

[0169] When the third PTC3 particle is a secondary particle (tertiary particle), the third PTC3 particle may have an average particle size (D) in the range of about 2 μm to about 15 μm, about 3 μm to about 10 μm, or about 3 μm to about 7 μm. 50 For example, the third particle PTC3 may have an average particle size of about 5 μm. The third particle PTC3 may have an average particle size larger than that of the fourth particle PTC4, which will be described later. In the example embodiment, the average particle size can be measured by a particle size analyzer. The average particle size can indicate the particle size when the cumulative volume in the particle size distribution is about 50 vol%.

[0170] The fourth PTC4 particle may have a particle size of about 200 nm or smaller. For example, the fourth PTC4 particle may have a particle size in the range of about 10 nm to about 200 nm, about 20 nm to about 200 nm, about 50 nm to about 200 nm, or about 100 nm to about 200 nm. For example, the particle size may indicate the diameter measured by randomly selecting about 30 fourth PTC4 particles from an electron micrograph of the positive electrode active material. The fourth PTC4 particle may have a substantially uniform particle size. The fourth PTC4 particle may have a smaller particle size than the third primary particle. For example, the average particle size of the fourth PTC4 particle may be about 100 nm smaller than the average particle size of the third primary particle.

[0171] When the average particle size of the fourth particle meets the above-mentioned range and the average particle size of the fourth particle is substantially uniform, the rechargeable lithium battery containing the fourth particle can have improved charge / discharge capacity and low-temperature capacity.

[0172] The third PTC3 particle can be a spherical shape in which a fourth PTC4 particle of nanoscale size is aggregated. The third PTC3 particle, having a tightly aggregated fourth PTC4 particle, can therefore exhibit the following properties. The third PTC3 particle can be spherical or elliptical in shape. The third PTC3 particle can have an average particle size (D) in the range of about 2 μm to about 15 μm. 50 The third PTC3 particle can have a porosity of approximately 20% to approximately 40%. The span value of the third PTC3 particle, analyzed by a particle size analyzer, can be in the range of approximately 0.3 to approximately 0.75.

[0173] When the third particle PTC3 is a secondary particle (tertiary particle), the weight ratio of the second functional additive FAD2 in the second active material layer ATL2 can be equal to or greater than the weight ratio of the first functional additive FAD1 in the first active material layer ATL1. For example, the ratio of the weight ratio of the second functional additive to the weight ratio of the first functional additive can be in the range of about 1 to about 4.5. For example, the ratio of the weight ratio of the second functional additive to the weight ratio of the first functional additive can be about 1 part by weight to about 4.5 parts by weight, about 1.6 parts by weight to about 4.5 parts by weight, or about 1 part by weight to about 2.5 parts by weight.

[0174] When the third PTC3 particle is a secondary particle (tertiary particle), the content of the second functional additive FAD2 relative to 100 parts by weight of the second active material layer ATL2 can be in the range of about 2.4 parts by weight to 6.0 parts by weight or about 2.4 parts by weight. For example, the content of the second binder relative to 100 parts by weight of the second active material layer ATL2 can be in the range of about 1.2 parts by weight to about 3 parts by weight or about 1.2 parts by weight. For example, the content of the second conductive material relative to 100 parts by weight of the second active material layer ATL2 can be in the range of about 1.2 parts by weight to about 3 parts by weight or about 1.2 parts by weight. When the content of the second functional additive FAD2 meets any of the above ranges, the second active material layer ATL2 can achieve the desired bonding strength. When the third PTC3 particle is a secondary particle (tertiary particle), the particle shape of the third PTC3 particle as a secondary particle is different from the particle shape of the third PTC3 particle as a single particle, therefore the physical requirements of the surface for the binder can be lower.

[0175] When the third particle PTC3 is in the form of a secondary particle, it has a larger average particle size than when the third particle PTC3 is in the form of a single particle (the third secondary particle). Accordingly, even when the third particle PTC3 as a secondary particle contains a smaller amount of the second binder BND2 than when it is a single particle, the second active material layer ATL2 can still have the desired bonding strength.

[0176] according to Figure 10 In a comparative example of this disclosure, the positive electrode active material layer AML1 may comprise only nano-morphological positive electrode active material. The nano-morphological positive electrode active material includes olivine compounds and may include nano-sized particles NP. For example, the olivine compounds may be represented by formulas (such as Formula 1 and / or Formula 3 above). For example, in the nano-morphological positive electrode active material, the nano-sized particles NP may aggregate to form a structure with... Figure 7 The first particle PTC1 shown in the figure is in particle form or Figure 9 The third particle, PTC3, shown in the image has a similar particle form. Although the nano-sized particles aggregate (NP), it is similar to... Figure 7The first particle shown is PTC1 or Figure 9 Unlike the third particle PTC3 shown, the nano-shaped positive electrode active material may not be spherical. The nano-shaped positive electrode active material may have an irregular shape. The nano-shaped positive electrode active material can be provided in various sizes. For example, the nano-shaped positive electrode active material may have an average particle size in the range of about 500 nm to about 2.5 μm or about 1 μm. The nano-shaped positive electrode active material may have a minimum particle size in the range of about 100 nm to about 500 nm or about 200 nm to about 300 nm. In the example embodiment, the average particle size (D) can be measured by a particle size analyzer. 50 The average particle size indicates the particle size when the cumulative volume in the particle size distribution is about 50 vol%. For example, the minimum particle size can indicate the diameter measured by randomly selecting about 30 primary particles from an electron micrograph of the nanomorphic positive electrode active material. The minimum particle size can be about 100 nm larger than the average particle size of the first primary particle (NNP). The nanomorphic positive electrode active material can have a porosity greater than about 40%. The span values ​​of the nanomorphic positive electrode active material analyzed by a particle size analyzer can deviate from about 0.3 to about 0.75.

[0177] Return to reference Figure 7 According to an exemplary embodiment of this disclosure, the first active material layer ATL1 may include both a first particle PTC1 and a second particle PTC2.

[0178] The first PTC1 particle is or comprises a lithium iron phosphate compound with an olivine structure, exhibiting high stability and chemical stability. Compared to other positive electrode active materials, this lithium iron phosphate compound possesses desired or improved lifetime characteristics due to its stable structure; however, its lifetime characteristics can deteriorate at high voltages, thus limiting the usable operating voltage. The first PTC1 particle contains manganese (Mn) and, compared to typical lithium iron phosphate compounds, improves high-voltage characteristics and energy density.

[0179] like Figure 10 As shown, when the particle size is too small, the bonding force between the positive electrode current collector and the positive electrode active material is low. Consequently, the electrode plate may be difficult to process and may require a large amount of binder BND.

[0180] The second PTC2 particle may comprise a cobalt-free lithium nickel manganese oxide. The second PTC2 particle may be substantially cobalt-free, but may contain nickel, manganese, etc., as key components. Positive electrode active materials containing the second PTC2 particle are economical and can achieve high energy density.

[0181] When pressed, lithium nickel manganese oxides exhibit a higher powder compaction density than olivine-structured compounds, thus solving the problem of low electrode density observed in olivine-structured phosphate compounds.

[0182] like Figure 6 and Figure 7 As shown, when the first active material layer ATL1 is introduced between the positive electrode current collector COL1 and the second active material layer ATL2, and the second particle PTC2 is mixed with the first particle PTC1 in an appropriate ratio, the electrode plate can have improved adhesion and the requirement for binder BND can be reduced. Furthermore, mixing can improve capacity, density characteristics, high-temperature stability, and lifetime characteristics. Additionally, by mixing the second particle in a bimodal form of large and small particles, the density can be further improved.

[0183] The amount of first PTC1 particles is approximately 30 wt% to approximately 40 wt% relative to the total content of first PTC1 particles, second PTC2 particles, and third PTC3 particles included in the first active material layer ATL1 and the second active material layer ATL2. For example, the amount of first PTC1 particles is approximately 35 wt% relative to the total content of first PTC1 particles, second PTC2 particles, and third PTC3 particles included in the first active material layer ATL1 and the second active material layer ATL2.

[0184] The amount of the second particle PTC2 is in the range of about 15 wt% to about 30 wt% relative to the total content of the first active material layer ATL1, the second active material layer ATL2, and the third active material layer ATL2. For example, the amount of the second particle PTC2 is about 20 wt% to about 30 wt% or about 30 wt% relative to the total content of the first active material layer ATL1 and the second active material layer ATL2.

[0185] The amount of the second PTC2 particle is about 40 wt% to about 60 wt% relative to the total content of the first PTC1 and the second PTC2 particles included in the first active material layer ATL1. For example, the amount of the second PTC2 particle is about 45 wt% to about 50 wt% relative to the total content of the first PTC1 and the second PTC2 particles included in the first active material layer ATL1.

[0186] Return to reference Figure 8 and Figure 9According to an exemplary embodiment of this disclosure, the second active material layer ATL2 may include a third particle PTC3. The content of the third particle PTC3 can be obtained by excluding the content of the first particle PTC1 and the second particle PTC2 from the total amount of the first particle PTC1, the second particle PTC2, and the third particle PTC3 included in the first active material layer ATL1 and the second active material layer ATL2. For example, the amount of the third particle PTC3 is about 30 wt% to about 40 wt% relative to the total content of the first particle PTC1, the second particle PTC2, and the third particle PTC3 included in the first active material layer ATL1 and the second active material layer ATL2. For example, the amount of the third particle PTC3 is about 35 wt% relative to the total content of the first particle PTC1, the second particle PTC2, and the third particle PTC3 included in the first active material layer ATL1 and the second active material layer ATL2.

[0187] When the contents of the first PTC1, second PTC2, and third PTC3 particles meet the above-mentioned range, the positive electrode active material layer AML1 can have improved adhesion to the positive electrode current collector COL1. Accordingly, a rechargeable lithium battery with reduced resistance can be provided. Furthermore, when the contents of the first PTC1, second PTC2, and third PTC3 particles meet the above-mentioned range, a rechargeable lithium battery with desired or improved performance can be provided.

[0188] The total Mn doping amount can be in the range of about 0.46 to about 0.52. For example, the total Mn doping amount can be about 0.49 to about 0.50. The total Mn(A+B) doping amount can be defined as the sum of the Mn doping amount (A) contained in the first active material layer ATL1 and the Mn doping amount (B) contained in the second active material layer ATL2. The Mn doping amount (A) contained in the first active material layer ATL1 can be defined as the sum of the product of the Mn doping amount (x1 in Formula 1) in the first particle PTC1 and the weight ratio of the first particle PTC1 and the Mn doping amount (z2 in Formula 2) in the second particle PTC2 and the weight ratio of the second particle PTC2. The Mn doping amount (B) included in the second active material layer ATL2 can be defined as the product of the Mn doping amount (x3 in Formula 3) in the third particle PTC3 and the weight ratio of the third particle PTC3. The weight ratio of the first PTC1 particle refers to the weight ratio of the first PTC1 particle to the first PTC1 particle, the second PTC2 particle, and the third PTC3 particle included in the first active material layer ATL1 and the second active material layer ATL2. The weight ratio of the second PTC2 particle refers to the weight ratio of the second PTC2 particle to the first PTC1 particle, the second PTC2 particle, and the third PTC3 particle included in the first active material layer ATL1 and the second active material layer ATL2. The weight ratio of the third PTC3 particle refers to the weight ratio of the third PTC3 particle to the first PTC1 particle, the second PTC2 particle, and the third PTC3 particle included in the first active material layer ATL1 and the second active material layer ATL2.

[0189] When the total Mn doping amount meets any of the above ranges, the positive electrode active material layer AML1 can have improved adhesion to the positive electrode current collector COL1. Accordingly, a rechargeable lithium battery with reduced resistance can be provided. Additionally, a rechargeable lithium battery with desired or improved performance can be provided.

[0190] The positive electrode for a rechargeable lithium battery according to an exemplary embodiment of this disclosure has the following effects.

[0191] A relatively large amount of binder BND is required to bind small nano-sized particles (NP) with a small average particle size (see [link to binder]). Figure 10 ) bonded to the positive electrode current collector COL1 (see Figure 1A relatively small amount of the first binder BND1 is required to fix the first particles PTC1, having a large average particle size, and / or the second particles PTC2, having a small BET specific surface area and a large average particle size, onto the first active material layer ATL1. The positive electrode active material layer AML1 according to an exemplary embodiment of this disclosure includes the first particles PTC1, the second particles PTC2, and the third particles PTC3, and the introduction of the first active material layer ATL1 and the second active material layer ATL2 allows for the inclusion of a large amount of nano-sized olivine compounds, increasing adhesion to the positive electrode current collector, thereby facilitating electrode plate fabrication and reducing electrode plate resistance. Furthermore, a rechargeable lithium battery with desired or improved capacity and lifetime characteristics, as well as high operating voltage and energy density, can be provided.

[0192] The present disclosure will now be described in more detail through embodiments. However, the embodiments are merely illustrative of the present disclosure, and the scope of the present disclosure is not limited to the embodiments described below.

[0193] Preparation Example 1: Preparation of Nickel Manganese Oxide (NMX) Particles

[0194] Ni 0.75 Mn 0.23 Al 0.02 (OH)₂ and LiOH were mixed in a molar ratio of 1:1.05, and the mixture was subjected to an initial heat treatment at 900°C in an oxygen atmosphere for 8 hours to obtain Li 1.05 Ni 0.75 Mn 0.23 Al 0.02 The composition of O2 and its average particle size (D) 50 The oxide is approximately 4 μm in size. Alumina was added to the oxide, and the mixture was then subjected to a secondary heat treatment at 825 °C in an oxygen atmosphere for 8 hours to prepare NMX particles. The NMX particles are derived from LiNi... 0.75 Mn 0.23 Al 0.02 O2 represents.

[0195] Preparation Example 2: Preparation of Lithium Manganese Iron Phosphate (LMFP) Particles in Secondary Particle Form

[0196] Manganese iron phosphate precursor (Mn) 0.6 Fe 0.4PO4), lithium carbonate, magnesium oxide, and titanium dioxide were added to water in a molar ratio of (Mn+Fe):Li:Mg:Ti = 1:1.03:0.01:0.004. 10 wt% glucose was further added to the mixture. The slurry mixture was spray-dried and evaporated at a spray pressure of 0.5 MPa and a temperature of 230 °C to achieve dryness. The dried mixture was calcined in a nitrogen atmosphere at 750 °C for 10 hours to obtain LMFP particles in the form of secondary particles. The LMFP particles in the form of secondary particles were approximately composed of LiMn... 0.6 Fe 0.4 The formula for PO4.

[0197] Preparation Example 3: Preparation of LMFP particles in single-particle form

[0198] Manganese iron phosphate precursor (Mn) 0.6 Fe 0.4 PO4), lithium carbonate, magnesium oxide, and titanium dioxide were added to water in a molar ratio of (Mn+Fe):Li:Mg:Ti = 1:1.03:0.01:0.004. 10 wt% glucose was further added to the mixture. The mixture was subjected to a wet milling process using a ball mill. The mixture was evaporated on a heated tray to dry, and then placed in a vacuum oven at 85°C for 4 hours. The dried mixture was calcined in a nitrogen atmosphere at 650°C for 10 hours. The calcined product was milled at a rotational speed of 8000 rpm to obtain LMFP particles in single-particle form. The LMFP particles in single-particle form consisted of approximately LiMn... 0.6 Fe 0.4 The formula for PO4.

[0199] Example 1: Preparation of a positive electrode comprising a first active material layer and a second active material layer

[0200] NMX particles, LMFP particles in the form of secondary particles, a first binder (polyvinylidene fluoride), and a first conductive material (carbon black) are dispersed in N-methylpyrrolidone in a weight ratio of 0.460:0.516:0.012:0.012 to prepare a first active material slurry (first positive electrode active material slurry).

[0201] A second active material slurry (second positive electrode active material slurry) is prepared by dispersing LMFP particles in single-particle form, a second binder (polyvinylidene fluoride), and a second conductive material (carbon black) in N-methylpyrrolidone at a weight ratio of 0.94:0.03:0.03.

[0202] A first active material slurry was 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 was coated onto the first active material layer and dried to form a second active material layer. The first and second active material layers were configured such that the weight ratio of NMX particles in the first active material layer, LMFP particles in the form of secondary particles, and LMFP particles in the second active material layer in the form of single particles was 30:35:35. A positive electrode in which the aluminum current collector, the first active material layer, and the second active material layer were stacked in this order was prepared by roll forming. The thickness ratio of the first and second active material layers was 5:5.

[0203] Example 2: Preparation of a positive electrode comprising a first active material layer and a second active material layer

[0204] The positive electrode was prepared in essentially the same manner as in Example 1, except that LMFP particles in the form of secondary particles, a second binder (polyvinylidene fluoride), and a second conductive material (carbon black) were dispersed in N-methylpyrrolidone at a weight ratio of 0.976:0.012:0.012 to prepare a second active material slurry. The thickness ratio of the first active material layer to the second active material layer was 5:5.

[0205] Comparative Example 1: Preparation of a positive electrode including an active material layer

[0206] NMX particles, a first binder (polyvinylidene fluoride), and a first conductive material (carbon black) were dispersed in N-methylpyrrolidone at a weight ratio of 0.976:0.012:0.012 to prepare a first active material slurry. The first active material slurry was 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 positive electrode in which the aluminum current collector and the first active material layer were stacked in this order was prepared by roll forming.

[0207] Comparative Example 2: Preparation of a positive electrode including an active material layer

[0208] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that LMFP particles in the form of secondary particles, a first binder (polyvinylidene fluoride), and a first conductive material (carbon black) were dispersed in N-methylpyrrolidone in a weight ratio of 0.976:0.012:0.012 to prepare a first active material slurry.

[0209] Comparative Example 3: Preparation of a positive electrode including an active material layer

[0210] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that LMFP particles in single-particle form, the first binder (polyvinylidene fluoride), and the first conductive material (carbon black) were dispersed in N-methylpyrrolidone in a weight ratio of 0.94:0.03:0.03 to prepare the first active material slurry.

[0211] Comparative Example 4: Preparation of a positive electrode including an active material layer

[0212] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that NMX particles and LMFP particles in the form of secondary particles were mixed at a weight ratio of 70:30, and the mixture was dispersed together with a first binder (polyvinylidene fluoride) and a first conductive material (carbon black) in N-methylpyrrolidone to prepare a first active material slurry.

[0213] Comparative Example 5: Preparation of a positive electrode including an active material layer

[0214] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that NMX particles and LMFP particles in the form of secondary particles were mixed at a weight ratio of 60:40, and the mixture was dispersed together with a first binder (polyvinylidene fluoride) and a first conductive material (carbon black) in N-methylpyrrolidone to prepare a first active material slurry.

[0215] Comparative Example 6: Preparation of a positive electrode including an active material layer

[0216] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that NMX particles and LMFP particles in the form of secondary particles were mixed in a weight ratio of 50:50, and the mixture was dispersed together with a first binder (polyvinylidene fluoride) and a first conductive material (carbon black) in N-methylpyrrolidone to prepare a first active material slurry.

[0217] Comparative Example 7: Preparation of a positive electrode including an active material layer

[0218] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that NMX particles and LMFP particles in the form of secondary particles were mixed in a weight ratio of 40:60, and the mixture was dispersed together with a first binder (polyvinylidene fluoride) and a first conductive material (carbon black) in N-methylpyrrolidone to prepare a first active material slurry.

[0219] Comparative Example 8: Preparation of a positive electrode including an active material layer

[0220] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that NMX particles and LMFP particles in the form of secondary particles were mixed at a weight ratio of 30:70, and the mixture was dispersed together with a first binder (polyvinylidene fluoride) and a first conductive material (carbon black) in N-methylpyrrolidone to prepare a first active material slurry.

[0221] Comparative Example 9: Preparation of a positive electrode including an active material layer

[0222] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that NMX particles and LMFP particles in the form of secondary particles were mixed at a weight ratio of 20:80, and the mixture was dispersed together with a first binder (polyvinylidene fluoride) and a first conductive material (carbon black) in N-methylpyrrolidone to prepare a first active material slurry.

[0223] Comparative Example 10: Preparation of a positive electrode including an active material layer

[0224] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that NMX particles and LMFP particles in the form of secondary particles were mixed at a weight ratio of 10:90, and the mixture was dispersed together with a first binder (polyvinylidene fluoride) and a first conductive material (carbon black) in N-methylpyrrolidone to prepare a first active material slurry.

[0225] Comparative Example 11: Preparation of a positive electrode including an active material layer

[0226] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that NMX particles, LMFP particles in the form of secondary particles, and LMFP particles in the form of single particles were mixed in a weight ratio of 30:35:35, and the mixture was dispersed together with a first binder (polyvinylidene fluoride) and a first conductive material (carbon black) in N-methylpyrrolidone to prepare a first active material slurry. The amounts of the first binder and the first conductive material are shown in Table 2.

[0227] Comparative Example 12: Preparation of a positive electrode including an active material layer

[0228] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that NMX particles and LMFP particles in single-particle form were mixed at a weight ratio of 30:70, and the mixture was dispersed together with a first binder (polyvinylidene fluoride) and a first conductive material (carbon black) in N-methylpyrrolidone to prepare a first active material slurry. The amounts of the first binder and the first conductive material are shown in Table 2.

[0229] Comparative Example 13: Fabrication of a positive electrode comprising a first active material layer and a second active material layer

[0230] A positive electrode with a weight ratio of FAD2 to FAD1 of 1 was prepared.

[0231] The positive electrode was prepared in essentially the same manner as in Example 1, except that NMX particles, LMFP particles in the form of secondary particles, a first binder (polyvinylidene fluoride), and a first conductive material (carbon black) were dispersed in N-methylpyrrolidone in a weight ratio of 0.460:0.516:0.012:0.012 to prepare a first active material slurry, and LMFP particles in the form of single particles, a second binder (polyvinylidene fluoride), and a second conductive material (carbon black) were dispersed in N-methylpyrrolidone in a weight ratio of 0.976:0.012:0.012 to prepare a second active material slurry.

[0232] Comparative Example 14: Fabrication of a positive electrode comprising a first active material layer and a second active material layer

[0233] A positive electrode with a weight ratio of FAD2 to FAD1 of 4.2 was prepared.

[0234] The positive electrode was prepared in essentially the same manner as in Example 1, except that NMX particles, LMFP particles in the form of secondary particles, a first binder (polyvinylidene fluoride), and a first conductive material (carbon black) were dispersed in N-methylpyrrolidone in a weight ratio of 0.460:0.516:0.012:0.012 to prepare a first active material slurry, and LMFP particles in the form of single particles, a second binder (polyvinylidene fluoride), and a second conductive material (carbon black) were dispersed in N-methylpyrrolidone in a weight ratio of 0.90:0.05:0.05 to prepare a second active material slurry.

[0235] Preparation of rechargeable lithium batteries

[0236] A 2032-type coin-type half-cell was prepared using a prepared positive electrode and a lithium metal counter electrode. A separator (thickness: approximately 16 μm) forming a porous polyethylene (PE) membrane was placed between the positive electrode and the lithium metal counter electrode, and an electrolyte was injected to prepare a rechargeable lithium battery. The electrolyte was prepared by mixing 1.3 M LiPF6 with a solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 3:4:3.

[0237] The examples and comparative examples are summarized in Tables 1 and 2 below. Referring to Tables 1 and 2, Examples 1 and 2 include LMX particles and LMFP particles and have a bilayer structure. On the other hand, Comparative Examples 1 to 12 include LMX particles and LMFP particles, but have a monolayer structure. Comparative Examples 13 and 14 differ from Example 1 only in the weight ratio of FAD2 to FAD1.

[0238] Table 1:

[0239]

[0240] Table 2:

[0241]

[0242] Evaluation Example 1: Analysis of the surface of the active material in the positive electrode

[0243] SEM images of each of the first, second, and third particles prepared in Preparation Examples 1 to 3 are shown in [the image]. Figures 11-14 As shown in the image. (Reference) Figure 11 According to Example 2, the first particle is in the form of a spherical secondary particle composed of multiple primary particles aggregated therein. (Reference) Figure 12 The second particle prepared according to Example 1 is in the form of a micron-sized fine single particle. (Reference) Figure 13 The third particle in Preparation Example 3 is in the form of a fine, single particle with a nanometer size. (Reference) Figure 14 According to Preparation Example 2, the third particle is in the form of a spherical secondary particle in which multiple primary particles are aggregated.

[0244] Evaluation Example 2: Evaluation of Positive Electrode Active Material

[0245] The powder compaction density (PD) of the positive electrode active materials of the examples and comparative examples was measured, and the results are shown in Table 3 below.

[0246] Table 3:

[0247] project Powder compaction density (g / cc) Example 1 2.58 Example 2 2.59 Comparative Example 1 3.10 Comparative Example 2 2.41 Comparative Example 3 2.35 Comparative Example 4 2.89 Comparative Example 5 2.82 Comparative Example 6 2.76 Comparative Example 7 2.69 Comparative Example 8 2.62 Comparative Example 9 2.55 Comparative Example 10 2.48 Comparative Example 11 2.60 Comparative Example 12 2.58 Comparative Example 13 2.52 Comparative Example 14 2.50

[0248] Referring to Table 3, the powder compaction density of the positive electrode active material layer according to Examples 1 and 2 ranges from 2.58 g / cc to 2.59 g / cc.

[0249] Evaluation Example 3: Evaluation of Resistance and Adhesion

[0250] The characteristics of rechargeable lithium batteries prepared using each positive electrode active material from the Examples and Comparative Examples were evaluated.

[0251] For the initial charge / discharge, the rechargeable lithium battery was initially charged at 25°C with a constant current and constant voltage (4.45V) at 0.2C (0.05C cutoff). After resting for 10 minutes, it was discharged to 3.0V with a constant current of 0.2C, thus obtaining the initial charge capacity and initial discharge capacity at 0.2C. The efficiency (%) at 0.2C is expressed as the initial discharge capacity at 0.2C / the initial charge capacity at 0.2C. The rechargeable lithium battery was charged to SOC50 with a constant current of 0.2C and then rested at SOC50 for 1 hour. After that, the rechargeable lithium battery was discharged at 1.0C for 10 seconds and then rested for 10 seconds. At this time, the difference between the voltage after discharge and the voltage after 10 seconds of rest was divided by the current to calculate the battery resistance (DCIR). The results are shown in Table 4 below.

[0252] Table 4:

[0253]

[0254] Referring to Table 4, compared to rechargeable lithium batteries including positive electrodes according to Comparative Examples 2, 3, and 12, rechargeable lithium batteries including positive electrodes according to Examples 1 and 2 exhibit higher discharge capacity and lower resistance. Correspondingly, the addition of NMX particles to the positive electrode active material layer increases the bonding strength of the positive electrode containing olivine compounds.

[0255] Furthermore, compared to rechargeable lithium batteries including the positive electrodes according to Comparative Examples 13 and 14, rechargeable lithium batteries including the positive electrodes according to Examples 1 and 2 have lower resistance. Accordingly, when the weight ratio of the second functional additive to the weight ratio of the first functional additive meets a desired range, the bonding force of the positive electrode can be increased.

[0256] Evaluation Example 4: Evaluation of Battery Properties

[0257] The characteristics of rechargeable lithium batteries prepared using each positive electrode active material from the Examples and Comparative Examples were evaluated.

[0258] For the initial charge / discharge, the rechargeable lithium battery was initially charged at 25°C with a constant current and constant voltage (4.45V, 0.05C cutoff) at 0.2C. After resting for 10 minutes, it was discharged to 3.0V with a constant current of 0.2C, and then the average voltage and energy density were evaluated. 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 energy density was obtained by using the following calculation equation: {average drive voltage (V) × capacity (Ah) / battery cell weight (kg)}, where the capacity was calculated by multiplying the positive electrode weight (g) by the discharge capacity (mAhg). Subsequently, the charge / discharge cycle was repeated 50 times at 45°C and 1.0C (4.45V, 0.05C cutoff) / 1.0C (3.0V). Lifetime (lifetime at 1C (%, @ 50 cycles)) is expressed as the discharge capacity after the 50th cycle / the initial discharge capacity. In addition, coin cell batteries were prepared, and then initially charged at 25°C with a constant current and constant voltage (4.45V, 0.05C cutoff) at 0.2C. After resting for 10 minutes, the batteries were discharged to 3.0V with a constant current of 0.2C, and then recharged at -20°C with a constant current and constant voltage (4.45V, 0.05C cutoff), and then discharged to 3.0V with a constant current of 0.2C to measure the initial discharge capacity at -20°C. The evaluation results of the battery properties are shown in Table 5 below.

[0259] Table 5:

[0260]

[0261] Referring to Tables 4 and 5, the rechargeable lithium batteries including the positive electrodes according to Examples 1 and 2 have desired or improved capacity and lifespan characteristics, as well as high operating voltage and energy density.

[0262] The positive electrode for a rechargeable lithium battery according to an exemplary embodiment of this disclosure contains a large amount of nano-sized olivine compounds and increases the bonding force with respect to the positive electrode current collector, thus facilitating the fabrication of the electrode plate and reducing the resistance of the electrode plate.

[0263] The rechargeable lithium battery according to the exemplary embodiments of this disclosure may have desired or improved capacity and life characteristics, as well as high operating voltage and energy density.

[0264] The above embodiments and comparative examples are provided to highlight the characteristics of one or more exemplary implementations; however, it will be understood that the embodiments and comparative examples should not be construed as limiting the scope of the exemplary implementations, nor should the comparative examples be construed as being outside the scope of the exemplary implementations.

[0265] Furthermore, it will be understood that the exemplary implementations are not limited to the specific details described in the embodiments and comparative examples.

Claims

1. A positive electrode for a rechargeable lithium battery, the positive electrode comprising: A positive electrode current collector; A first active material layer on the positive electrode current collector, the first active material layer comprising first particles, second particles, a first binder, and a first conductive material; And A second active material layer on the first active material layer, the second active material layer comprising third particles, a second binder, and a second conductive material, Wherein the first particles comprise an olivine-structured compound represented by the following Formula 1, The second particles comprise a layered compound represented by the following Formula 2, The third particles comprise an olivine-structured compound represented by the following Formula 3, The first active material layer and the second active material layer have a cobalt content of less than 100 ppm, The first particles comprise a plurality of first primary particles aggregated together, The first particles have an average particle size in the range of 2 μm to 15 μm, The first primary particles have an average particle size in the range of 200 nm or less, The third particles are single particles, and The third particles have an average particle size in the range of 100 nm to 2 μm, Formula 1: Li a1 Mn x1 Fe y1 B1 z1 PER 4-b1 Where in Formula 1, 0.8 ≤ a1 ≤ 1.2, 0.4 ≤ x1 ≤ 0.8, 0 ≤ y1 ≤ 0.6, 0 ≤ z1 ≤ 0.05, 0 ≤ b1 ≤ 0.05 and x1 + y1 + z1 = 1 are satisfied, and B1 comprises at least one of Al, Ti, V, and Mg, Formula 2: Li a2 Ni x2 Mr z2 Al c2 Y d2 O 2-b2 Where in Formula 2, 0.8 < a2 ≤ 1.2, 0.7 ≤ x2 ≤ 0.8, 0.2 ≤ z2 ≤ 0.3, 0 ≤ c2 ≤ 0.02, 0 ≤ d2 ≤ 0.003, 0 ≤ b2 ≤ 0.05 and x2 + z2 + c2 + d2 = 1 are satisfied, and Y comprises at least one of Ti, Mg, Zr, Mo, and Nb, and Formula 3: Li a3 Mn x3 Fe y3 B3 z3 PO 4-b3 Where in Formula 3, 0.8 ≤ a3 ≤ 1.2, 0.4 ≤ x3 ≤ 0.8, 0 ≤ y3 ≤ 0.6, 0 ≤ z3 ≤ 0.05, 0 ≤ b3 ≤ 0.05 and x3 + y3 + z3 = 1 are satisfied, and B3 comprises at least one of Al, Ti, V, and Mg.

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

3. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the total doping amount of Mn in Formula 1, Formula 2, and Formula 3 is in the range of 0.46 to 0.

52.

4. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the thickness ratio of the first active material layer and the second active material layer is in the range of 3:7 to 7:

3.

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

6. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the second particles are single crystals.

7. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the second particles have an average particle size in the range of 3 μm to 7 μm.

8. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the second particle has a particle size of 0.8 μm. 2 / g~1.2m 2 BET specific surface area in the range of / g.

9. The positive electrode for a rechargeable lithium battery according to claim 1, wherein: the first binder and the first conductive material constitute a first functional additive, the second binder and the second conductive material constitute a second functional additive, and the weight ratio of the first functional additive in the first active material layer is lower than the weight ratio of the second functional additive in the second active material layer.

10. The positive electrode for a rechargeable lithium battery according to claim 9, wherein the ratio of the weight ratio of the second functional additive to the weight ratio of the first functional additive is in the range of 1.6 to 4.

5.

11. A positive electrode for a rechargeable lithium battery, the positive electrode comprising: a positive electrode current collector; a first active material layer on the positive electrode current collector, the first active material layer including first particles, second particles, a first binder and a first conductive material; and a second active material layer on the first active material layer, the second active material layer including third particles, a second binder and a second conductive material, wherein the first particles include an olivine-structured compound represented by the following formula 1, the second particles include a layered compound represented by the following formula 2, the third particles include an olivine-structured compound represented by the following formula 3, the first active material layer and the second active material layer have a cobalt content of less than 100 ppm, the first particles include a plurality of first primary particles aggregated together, the first particles have an average particle size in the range of 2 μm to 15 μm, the first primary particles have an average particle size in the range of 200 nm or less, the third particles include a plurality of fourth particles aggregated together, the third particles have an average particle size in the range of 2 μm to 15 μm, and each of the plurality of fourth particles is a primary particle, and the plurality of fourth particles have a particle size in the range of 200 nm or less, Formula 1: Li a1 Mn x1 Fe y1 B1 z1 PER 4-b1 wherein in Formula 1, 0.8 ≤ a1 ≤ 1.2, 0.4 ≤ x1 ≤ 0.8, 0 ≤ y1 ≤ 0.6, 0 ≤ z1 ≤ 0.05, 0 ≤ b1 ≤ 0.05 and x1 + y1 + z1 = 1, and B1 includes at least one of Al, Ti, V and Mg, Formula 2: Li a2 Ni x2 Mr z2 Al c2 Y d2 O 2-b2 wherein in Formula 2, 0.8 < a2 ≤ 1.2, 0.7 ≤ x2 ≤ 0.8, 0.2 ≤ z2 ≤ 0.3, 0 ≤ c2 ≤ 0.02, 0 ≤ d2 ≤ 0.003, 0 ≤ b2 ≤ 0.05 and x2 + z2 + c2 + d2 = 1, and Y includes at least one of Ti, Mg, Zr, Mo and Nb, and Formula 3: Li a3 Mn x3 Fe y3 B3 z3 PO 4-b3 wherein in Formula 3, 0.8 ≤ a3 ≤ 1.2, 0.4 ≤ x3 ≤ 0.8, 0 ≤ y3 ≤ 0.6, 0 ≤ z3 ≤ 0.05, 0 ≤ b3 ≤ 0.05 and x3 + y3 + z3 = 1, and B3 includes at least one of Al, Ti, V and Mg.

12. The positive electrode for a rechargeable lithium battery according to claim 11, wherein the content of the second particle is in the range of 15 wt% to 30 wt% relative to the total content of the first particle, the second particle and the third particle.

13. The positive electrode for a rechargeable lithium battery according to claim 11, wherein the total doping amount of Mn in formulas 1, 2 and 3 is in the range of 0.46 to 0.

52.

14. The positive electrode for a rechargeable lithium battery according to claim 11, wherein the thickness ratio of the first active material layer to the second active material layer is in the range of 3:7 to 7:

3.

15. The positive electrode for a rechargeable lithium battery according to claim 11, wherein the second particle is a single crystal.

16. The positive electrode for a rechargeable lithium battery according to claim 11, wherein the second particle has an average particle size in the range of 3 μm to 7 μm.

17. The positive electrode for a rechargeable lithium battery according to claim 11, wherein the second particle has a particle size of 0.8 μm. 2 / g~1.2m 2 BET specific surface area in the range of / g.

18. The positive electrode for a rechargeable lithium battery according to claim 11, wherein: The first adhesive and the first conductive material constitute the first functional additive. The second adhesive and the second conductive material constitute the second functional additive, and The weight ratio of the first functional additive in the first active material layer is equal to or lower than the weight ratio of the second functional additive in the second active material layer.

19. The positive electrode for a rechargeable lithium battery according to claim 18, wherein the weight ratio of the second functional additive to the weight ratio of the first functional additive is in the range of 1 to 4.

5.

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

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