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. Examples include a positive electrode for a rechargeable lithium battery including a positive electrode current collector, a first active material layer on the positive electrode current collector, and a second active material layer on the first active material layer. The first active material layer includes first particles containing an olivine structured compound represented by Formula 1, second particles containing a layered compound represented by Formula 2, a first conductive material, and a first binder. The second active material layer includes third particles containing an olivine structured compound represented by Formula 3, a second conductive material, and a second binder. The formula 1 is Lia1Fex1B1y1PO4-c1, the formula 2 is Lia2Nix2Coy2B2z2O2-c2, and the formula 3 is Lia3Fex3B3y3PO4-c3.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0057135, 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 in other examples, 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 use of battery-powered electronic devices (such as mobile phones, laptops, electric vehicles, etc.) has driven a rapid increase in demand for rechargeable lithium batteries with high energy density and high capacity. Accordingly, improving the performance of rechargeable lithium 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 be inserted into and extracted) and an electrolyte, and generate electrical energy through a redox reaction that occurs when lithium ions are inserted into or extracted from the positive and negative electrodes. Summary of the Invention

[0006] Examples of this disclosure include a positive electrode that allows for the easy fabrication of an electrode plate by increasing the adhesion between the positive electrode current collector and the positive electrode active material.

[0007] Examples of this disclosure also include positive electrodes with improved capacity and lifetime characteristics.

[0008] An exemplary embodiment of this disclosure includes 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, and a second active material layer (second positive electrode active material layer) on the first active material layer. The first active material layer comprises first particles containing a compound structured with olivine as represented by Formula 1, second particles containing a layered compound as represented by Formula 2, a first conductive material, and a first binder. The second active material layer comprises third particles containing a compound structured with olivine as represented by Formula 3, a second conductive material, and a second binder. The first and third particles are in the form of single particles, 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 second functional additive in the second active material layer to the weight ratio of the first functional additive in the first active material layer is in the range of about 1.0 to about 2.6.

[0009] Formula 1:

[0010] Li a1 Fe x1 B1 y1 PO 4-c1

[0011] In Formula 1 above, 0.8 < a1 ≤ 1.2, 0.95 ≤ x1 ≤ 0.999, 0.001 ≤ y1 ≤ 0.05, x1 + y1 = 1, and 0 ≤ c1 ≤ 0.05, and B1 is or includes at least one of Ti and a transition metal with an oxidation number of 4.

[0012] Formula 2:

[0013] Li a2 Ni x2 Co y2 B2 z2 O 2-c2

[0014] In Formula 2 above, 0.8 < a2 ≤ 1.2, 0.9 ≤ x2 ≤ 1.05, 0.03 ≤ y2 ≤ 0.10, 0.01 ≤ z2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05, and B2 is or includes at least one of Al and Mn, and

[0015] Formula 3:

[0016] Li a3 Fe x3 B3 y3 PO 4-c3

[0017] In Formula 3 above, 0.8 < a3 ≤ 1.2, 0.95 ≤ x3 ≤ 0.999, 0.001 ≤ y3 ≤ 0.05, x3 + y3 = 1, and 0 ≤ c3 ≤ 0.05, and B3 is or includes at least one of Ti and a transition metal with an oxidation number of 4.

[0018] In an exemplary embodiment of the present disclosure, a 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 containing an olivine-structured compound represented by Formula 1 restated below, second particles containing a layered compound represented by Formula 2 restated below, a first conductive material, and a first binder. The second active material layer includes third particles containing an olivine-structured compound represented by Formula 3 restated below, a second conductive material, and a second binder. The first particles and the third particles are in the form of single particles, and the content of the first binder in the first active material layer is less than the content of the second binder in the second active material layer.

[0019] Formula 1 (the same as Formula 1 discussed above):

[0020] Li a1 Fe x1 B1 y1 PO 4-c1

[0021] In the above Formula 1, 0.8 < a1 ≤ 1.2, 0.95 ≤ x1 ≤ 0.999, 0.001 ≤ y1 ≤ 0.05, x1 + y1 = 1, and 0 ≤ c1 ≤ 0.05, and B1 is or includes at least one of Ti and a transition metal with an oxidation number of 4,

[0022] Formula 2 (the same as Formula 2 discussed above):

[0023] Li a2 Ni x2 Co y2 B2 z2 O 2-c2

[0024] [[ID=|33]]In the above Formula 2, 0.8 < a2 ≤ 1.2, 0.9 ≤ x2 ≤ 1.05, 0.03 ≤ y2 ≤ 0.10, 0.01 ≤ z2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05, and B2 is or includes at least one of Al and Mn, and

[0025] Formula 3 (the same as Formula 3 discussed above):

[0026] Li a3 Fe x3 B3 y3 PO 4-c3

[0027] In the above Formula 3, 0.8 < a3 ≤ 1.2, 0.95 ≤ x3 ≤ 0.999, 0.001 ≤ y3 ≤ 0.05, x3 + y3 = 1, and 0 ≤ c3 ≤ 0.05, and B3 is or includes at least one of Ti and a transition metal with an oxidation number of 4.

[0028] In an exemplary embodiment of the present disclosure, the rechargeable lithium battery includes the above positive electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are included to provide a further understanding of the present disclosure, and the accompanying drawings are incorporated into and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with this description, are used to explain the principles of the present disclosure. In the drawings:

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

[0031] Figures 2-5 To illustrate a schematic diagram of a rechargeable lithium battery according to an exemplary embodiment, wherein... Figure 2 Explaining cylindrical batteries, Figure 3 Explaining the prismatic battery, and Figure 4 and Figure 5 Explaining pouch batteries;

[0032] Figure 6 A cross-sectional view illustrating the positive electrode of a rechargeable lithium battery according to an exemplary embodiment of the present disclosure;

[0033] Figure 7 An enlarged view illustrating the first active material layer according to an exemplary embodiment of the present disclosure;

[0034] Figure 8 An enlarged view illustrating the second active material layer according to an exemplary embodiment of the present disclosure;

[0035] Figure 9 To show a SEM image of the first particle of Preparation Example 1 according to the present disclosure;

[0036] Figure 10 To show a SEM image of the second particle (having a single particle form) of Preparation Example 2 according to the present disclosure;

[0037] Figure 11 To illustrate a SEM image of a second particle (having a secondary particle form) according to an exemplary embodiment of this disclosure; and

[0038] Figure 12 To show a SEM image of the third particle of Preparation Example 3 according to the present disclosure. Detailed Implementation

[0039] To fully understand the layout and effects of this disclosure, some exemplary embodiments of the disclosure will be described with reference to the accompanying drawings. However, it should be noted that this disclosure is not limited to the exemplary embodiments described below and can be implemented in various forms. Rather, exemplary embodiments are provided merely to disclose this disclosure and to enable those skilled in the art to fully understand its scope.

[0040] In this description, it should be understood that when an element is referred to as being "on" another element, the element may be directly on the other element, or an intervening element may exist between the two. In the accompanying drawings, the dimensions (e.g., thickness) of some components are enlarged for effective explanation of the technical content. Throughout the specification, the same reference numerals refer to the same elements.

[0041] The exemplary embodiments described herein are 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 conventional properties, and the shapes of the exemplary regions are used to illustrate the 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, these components should not be limited to these terms. These terms are merely used to distinguish one component from another. The exemplary embodiments described and illustrated herein include complementary exemplary embodiments.

[0042] Unless otherwise specified in this description, singular expressions may include plural expressions. Additionally, unless otherwise specified, the phrase "A or B" may indicate "A but not B", "B but not A", and "A and B". The terms "comprises / includes" and / or "comprising / including" as used in this description do not exclude the presence or addition of one or more other components.

[0043] As used herein, the term "combination thereof" may refer to mixtures, stacks, complexes, copolymers, alloys, blends, or reaction products.

[0044] Unless otherwise specifically defined in this description, particle size / size may refer to average particle size / average size. Additionally, particle size indicates the average particle size (D) representing approximately 50% by volume of the cumulative volume in the particle size distribution. 50 Average particle size (D) 50 The particle size can be measured using methods known to those skilled in the art, such as by a particle size analyzer, transmission electron microscopy (TEM) images, or scanning electron microscopy (SEM) images. Alternatively, a dynamic light scattering measurement device can be used for data analysis, counting the number of particles in each particle size range, and then calculating the average particle size (D). 50 The value is different; laser scattering methods can also be used to measure the average particle size (D). 50 In the laser scattering method, target particles are dispersed in a dispersion medium and introduced into a laser scattering particle size measurement device (e.g., the MT3000, commercially available from Microtrac, Inc.) and irradiated with ultrasonic waves at a power of 60 W and 28 kHz. The average particle size (D) is then calculated in the measurement device based on approximately 50% of the particle size distribution. 50 ).

[0045] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, they mean that the relevant numerical value includes a tolerance of ±10% around the stated value. The expression “up to” includes the quantity from zero to the stated upper limit and all values ​​in between. When a range is specified, the range includes all values ​​in between (e.g., an increment of 0.1%).

[0046] Figure 1 This is a cross-sectional view of an example embodiment of a rechargeable lithium battery according to the present disclosure. (Refer to...) 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 may be separated from each other by a diaphragm 30. The diaphragm 30 may be located between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20 and the diaphragm 30 may be in contact with the electrolyte ELL. The positive electrode 10, the negative electrode 20 and the diaphragm 30 may be immersed in the electrolyte ELL.

[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 toward the positive electrode 10 or the negative electrode 20 through the separator 30.

[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 formed on the positive electrode current collector COL1. The positive electrode active material layer AML1 may include a positive electrode active material and may further include a binder and / or a conductive material.

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

[0052] Al foil may be included in or constitute the positive electrode current collector COL1, but is not limited thereto.

[0053] The following is for reference. Figure 6 The positive electrode 10 according to an exemplary embodiment of the present disclosure 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 the negative electrode active material layer AML2 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 a negative electrode active material ranging from about 90 wt% to about 99.5 wt%, a binder ranging from about 0.5 wt% to about 5 wt%, and a conductive material ranging from about 0 wt% to about 5 wt%.

[0057] The binder can be configured to adhere the negative electrode active material particles to each other and also 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 used as a binder in the negative electrode active material layer AML2, it may further include a cellulose compound capable of imparting viscosity. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and 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] Conductive materials can be configured to impart conductivity (e.g., electrical conductivity) to the electrodes. In the battery, 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. Non-limiting examples may include: carbon-based materials (such as 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.

[0063] The negative electrode current collector COL2 may 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 may include at least one of a material that can reversibly intercalate / deintercalate lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and a transition metal oxide.

[0066] The material that can reversibly intercalate / deintercalate lithium ions may include a carbon-based negative electrode active material (such as, for example, crystalline carbon, amorphous carbon, or a combination thereof). The crystalline carbon may be graphite (such as amorphous, flaky, lamellar, spherical, or fibrous natural graphite or artificial graphite). The amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0067] The lithium metal alloy includes an alloy of lithium and a metal (such as Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn, or includes 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 may 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 may include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), 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 may include Sn, SnO x (0 < x ≤ 2) (such as, for example, SnO2), Sn-based alloys, and combinations thereof.

[0069] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to an exemplary embodiment, the silicon-carbon composite may 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 coalesced and an amorphous carbon coating (shell) on the surface of the secondary particles. The amorphous carbon may also be between the primary silicon particles, and, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in 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] Si-based or Sn-based negative electrode active materials can be combined with carbon-based negative electrode active materials.

[0072] Diaphragm 30

[0073] Depending on the type of rechargeable lithium battery, the separator 30 may be located 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, the coating comprising an organic material, an inorganic material, or a combination thereof.

[0075] The porous substrate may be or comprise a polymer film formed from any one or two 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 inorganic particles such as Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, or inorganic particles 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, but are not limited thereto.

[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 the following: nitrile solvents (such as R-CN (where R is a C2-C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether bonds, etc.)); amides (such as dimethylformamide); dioxolane (such as 1,3-dioxolane, 1,4-dioxolane, etc.); sulfolane, etc.

[0086] Non-aqueous organic solvents can be used 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 ranging from about 1:1 to about 1:9.

[0088] Lithium salts dissolved in non-aqueous organic solvents can supply lithium ions in batteries, ensuring basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2 (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0089] Rechargeable lithium batteries

[0090] Rechargeable lithium batteries can be classified according to their shape as cylindrical, prismatic, pouch, or coin-shaped batteries, etc. Figures 2-5 A schematic diagram illustrating a rechargeable lithium battery according to an example embodiment. Figure 2 Explaining cylindrical batteries, Figure 3 Explaining the prismatic battery, and Figure 4 and Figure 5 Explaining pouch batteries. (Reference) Figures 2-5 The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50 including the electrode assembly 40, the electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 2 As explained herein, the rechargeable lithium battery 100 may include a sealing member 60 of a sealed housing 50. Figure 3 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include Figure 5 The electrode terminals 70 described herein may include, for example, Figure 4 The 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 battery 100.

[0091] As a non-limiting example, a rechargeable lithium battery according to an exemplary embodiment may be applicable to, for example, an automobile, a mobile phone, and / or various types of electronic devices.

[0092] Hereinafter, the first particle PTC1, the second particle PTC2, the third particle PTC3, the first active material layer ATL1, the second active material layer ATL2, and the positive electrode having a bilayer structure are described in more detail with respect to Figures 6-8

[0093] First PTC1

[0094] The first particle PTC1 may include an olivine-structured lithium compound represented by Formula 1 below.

[0095] Formula 1:

[0096] Li a1 Fe x1 B1 y1 PO 4-c1

[0097] In Formula 1 above, 0.8 < a1 ≤ 1.2, 0.95 ≤ x1 ≤ 0.999, 0.001 ≤ y1 ≤ 0.05, x1 + y1 = 1, and 0 ≤ c1 ≤ 0.05 may be satisfied, and B1 may be or include at least one of Ti and a transition metal having an oxidation number of 4. B1 may be or include a dopant doped into the first particle PTC1. The transition metal having an oxidation number of 4 includes vanadium (V), chromium (Cr), zirconium (Zr), hafnium (Hf), molybdenum (Mo), niobium (Nb), and tantalum (Ta).

[0098] [[ID= thirty]]The first particle PTC1 provides benefits including high economic efficiency, high structural stability, and desired or improved life characteristics. The first particle PTC1 contains Fe as a component (e.g., a main component), and thus is relatively inexpensive, and due to its structural stability, its chemical change is relatively small even after repeated charge / discharge.

[0099] Figure 7 Reference Figure 9 and

[0100]

[0101] The first particle PTC1 may include at least one first primary particle. In an example embodiment, the first particle PTC1 may be substantially spherical or elliptical in shape, wherein the first primary particle is attached. In another example embodiment, even when the first primary particle is attached, the first particle PTC1 may not have a substantially spherical shape, but may have an irregular shape. Throughout the specification, the term "attached" is used to describe a single particle, while "aggregate" is used to describe secondary particles, to distinguish between the two. For reference, even a single particle may consist of primary particles attached in a manner that forms a cloud-like structure.

[0101] The first PTC1 particle can be provided in various sizes. For example, the first PTC1 particle can have an average particle size ranging from about 0.5 μm to about 2.5 μm or about 1 μm. The minimum particle size of the first PTC1 particle (i.e., the size of the first primary particle, for example, the particle size of the smaller first PTC1 particle, i.e., as used herein, "first primary particle" refers to the first PTC1 particle whose size corresponds to the minimum particle size) can be from about 100 nm to about 500 nm or from about 200 nm to about 300 nm.

[0102] In an example implementation, the average particle size can be measured using a particle size analyzer. Average particle size (D) 50 It can indicate the diameter of particles with a cumulative volume of approximately 50 vol% in the particle size distribution.

[0103] In an example implementation, the minimum particle size (i.e., the size of the first primary particle) can indicate the diameter measured by randomly selecting approximately 30 first primary particles from an electron microscope image of the first particle PTC1.

[0104] The dopant can control the uniform growth of the first primary particles of PTC1, thus allowing rechargeable lithium batteries to have improved charge / discharge efficiency, low-temperature characteristics and lifespan characteristics.

[0105] In an example embodiment, the first PTC1 particle may include a coating on its surface. The coating may completely cover the surface of the first PTC1 particle or may partially cover the surface of the first PTC1 particle. The first PTC1 particle may include a coating containing carbon elements. For example, the coating may include elemental carbon and / or carbon-containing compounds. With the coating, the first PTC1 particle may have improved structural stability and electrical conductivity.

[0106] The coating may further include at least one metal-containing compound selected from a titanium-containing compound and a compound of a transition metal having an oxidation number of 4. The metal-containing compound (such as a titanium-containing compound and a compound of a transition metal having an oxidation number of 4) may be or include, for example, at least one of metal oxides, metal hydroxides, metal carbonates, their complexes, and their mixtures. The metal-containing compound may further include other metal or non-metal elements. For example, the metal-containing compound may further include lithium.

[0107] The first PTC particle PTC1 further includes a coating, and thus may have greater structural stability and may have a uniform coating formed on its surface. Additionally, the first PTC particle PTC1 further includes a coating, and thus may have further improved conductivity.

[0108] The first PTC particle PTC1 may further include carbon (carbon element) derived from the above coating. The first PTC particle PTC1 may have a carbon element content ranging from about 0.5 wt% to about 5 wt%, from about 0.5 wt% to about 3 wt%, or from about 1.0 wt% to about 2.0 wt%. The first PTC particle PTC1 may have a lower carbon element content than that of the third PTC particle PTC3.

[0109] Second PTC2 particle

[0110] The second PTC particle PTC2 may include a layered lithium compound represented by Formula 2 below.

[0111] Formula 2:

[0112] Li a2 Ni x2 Co y2 B2 z2 O 2-c2

[0113] In Formula 2 above, 0.8 < a2 ≤ 1.2, 0.9 ≤ x2 ≤ 1.05, 0.03 ≤ y2 ≤ 0.10, 0.01 ≤ z2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05 may be satisfied, and B2 may be or include at least one of Al and Mn.

[0114] B2 may be or include Al.

[0115] In one or more embodiments, in Chemical Formula 2, 0.9 ≤ x2 ≤ 0.94, 0.05 ≤ y2 ≤ 0.09, 0.01 ≤ z2 ≤ 0.05, x2 + y2 + z2 = 1, and 0 ≤ c2 ≤ 0.05 may be satisfied. The second PTC particle PTC2 provides benefits such as, for example, high capacity and high energy density.

[0116] The second PTC2 particle is or includes a nickel-based active material, and may include lithium-nickel composite oxides. For example, the second PTC2 particle may include a high-nickel positive electrode active material containing a high nickel content. High-nickel positive electrode active materials can achieve high capacity and high performance.

[0117] In an example embodiment, the second PTC2 particle may include a second coating on its surface. The inclusion of the second coating on the second PTC2 particle effectively reduces or prevents structural collapse caused by repeated charging / discharging. Accordingly, the rechargeable battery may have improved lifespan characteristics.

[0118] The second coating may include at least one metal-containing compound selected from aluminum-containing compounds, titanium-containing compounds, magnesium-containing compounds, zirconium-containing compounds, molybdenum-containing compounds, niobium-containing compounds, and combinations thereof. The metal-containing compound in the second coating may be, for example, at least one selected from metal oxides, metal hydroxides, metal carbonates, their complexes, and mixtures thereof. The metal-containing compound may further include other metallic or non-metallic elements. For example, the second coating may further include at least one selected from lithium, manganese, and / or nickel.

[0119] Methods for measuring the metal content in the second coating of the second PTC2 particle may include scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS) of the second PTC2 particle. Through these analyses, the content of aluminum, titanium, magnesium, zirconium, molybdenum, and / or niobium in the second coating can be determined. Besides SEM-EDS, methods for measuring the metal content in the second coating may include inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), etc.

[0120] The Brunol-Emmett-Taylor (BET) specific surface area of ​​the second PTC2 particle can be smaller than that of the first PTC1 particle. The second PTC2 particle can have a BET specific surface area ranging from about 0.3 to about 0.6. The BET specific surface area indicates the surface area per unit mass. The smaller the BET, the smaller the contact surface between the positive electrode active material and the positive electrode current collector, resulting in a lower resistance relative to the electrode plate and greater adhesion. That is, even with the use of a small amount of binder, the positive electrode active material containing the second PTC2 particle with a small BET specific surface area can be advantageous for preparing the electrode plate.

[0121] The second PTC2 particles can be in the form of single particles and / or secondary particles. For example, the second PTC2 particles can be in the form of only single particles, only secondary particles, or a mixture of single and secondary particles. In an example embodiment, the second PTC2 particles can have a further improved density when having a bimodal form in which single and secondary particles are mixed. The mixing weight ratio of single and secondary particles in the bimodal form is 1:99 to 99:1. See below for reference. Figure 7 , Figure 10 and Figure 11 The second particle PTC2 is described as being in the form of a single particle and / or a secondary particle.

[0122] In the example implementation, refer to Figure 10 The second PTC2 particle can be in the form of a single particle. In this document, 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 the particles do not aggregate), 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. Alternatively, a single particle can be a particle containing several crystals. A single particle can be in an isolated form. Alternatively, a single particle can be in the form of approximately 2 to approximately 100 single particles attached to each other.

[0123] When the second PTC2 particle is a single particle, it may include at least one second primary particle. In an example embodiment, the second PTC2 particle may be substantially spherical or elliptical in shape with the second primary particle attached therein. In another example embodiment, even when the second primary particle is attached, the second PTC2 particle may not have a substantially spherical shape, but may have an irregular shape. The structuring of the second PTC2 particle can be less than when it is a single particle with the second primary particle attached therein, compared to when it is a secondary particle. This means that the second PTC2 particle can have a more irregular shape.

[0124] When the second particle is a single particle, the second particle PTC2 may have an average particle size ranging from about 3 μm to about 10 μm. The average particle size of the second particle PTC2 may be larger than the average particle size of the first particle PTC1. In an example embodiment, the average particle size can be measured using a particle size analyzer. Average particle size (D) 50 This indicates the diameter of particles whose cumulative volume is approximately 50 vol% in the particle size distribution. The average particle size (D) of the second particle... 50 The particle size (D) may be larger than the average particle size (D) of each or at least one of the first particle described above and the third particle described below. 50 ).

[0125] refer to Figure 9 and Figure 10 When the second particle PTC2 is a single particle, the average size of the second primary particle of the second particle PTC2 is greater than the average size of the first primary particle of the first particle PTC1.

[0126] In another example implementation, refer to Figure 11 The second PTC2 particle can be in the form of a secondary particle. The secondary particle can be polycrystalline, indicating that at least two secondary primary particles are aggregated therein. That is, a single second PTC2 particle can comprise multiple aggregated secondary primary particles NNP2 (…). Figure 7 The second PTC2 particle can be substantially spherical or elliptical in shape.

[0127] When the second particle is a secondary particle, the second PTC2 particle can have an average particle size ranging from about 10 μm to about 14 μm. (Reference) Figure 9 and Figure 11 The average particle size of the second particle, PTC2, may be equal to or greater than the average particle size of the first particle, PTC1. In an example embodiment, the average particle size can be measured using a particle size analyzer. Particle size indicates the diameter (D) of particles whose cumulative volume is approximately 50 vol% in the particle size distribution. 50 ).

[0128] In another example implementation, refer to Figure 7 The second particle can exhibit a bimodal form, in which a mixture of single-particle PTC2 (SP) and secondary-particle PTC2 (PC) is present. When it has a bimodal form, the second particle can have a further improved density. For a more detailed description... Figure 7 The second particle PTC2(PC) as a secondary particle indicates a form in which at least two second primary particles NNP2 are aggregated. The second particle PTC2(SP) as a single particle may indicate a form comprising at least one second primary particle. The second particle PTC2(SP) as a single particle has a larger size than the second primary particle PTC2(PC) as a secondary particle, and when the second primary particle is attached, the second particle PTC2(SP) may not have a substantially spherical shape, but may have an irregular shape.

[0129] Third PTC3

[0130] The third particle PTC3 may include an olivine-structured lithium compound represented by Formula 3 as restated below.

[0131] Formula 3:

[0132] Li a3 Fe x3 B3 y3 PO4-c3

[0133] In Equation 3 above, 0.8 < a3 ≤ 1.2, 0.95 ≤ x3 ≤ 0.999, 0.001 ≤ y3 ≤ 0.05, x3 + y3 = 1, and 0 ≤ c3 ≤ 0.05, and B3 is or includes at least one of Ti and a transition metal with an oxidation number of 4. B3 may be or include a dopant doped in the third particle PTC3.

[0134] Figure 8 The third particle PTC3 illustrated in provides benefits including high economic efficiency, high structural stability, and desired or improved life characteristics. The third particle PTC3 contains Fe as a main component, so it is relatively inexpensive, and due to its structural stability, its chemical change is relatively small even after repeated charge / discharge.

[0135] The dopant can have the effect of controlling the uniform growth of the third primary particles of the third particle PTC3, so that the rechargeable lithium battery can have improved charge / discharge efficiency, low-temperature characteristics, and life characteristics.

[0136] In an exemplary embodiment, the third particle PTC3 may include a coating on its surface. The coating may completely cover the surface of the third particle PTC3 or may partially cover the surface of the third particle PTC3. The third particle PTC3 may include a coating containing a carbon element. For example, the coating may include elemental carbon and / or a carbon-containing compound. Through the coating, the third particle PTC3 can have improved structural stability and conductivity.

[0137] The coating may further include at least one metal-containing compound selected from a titanium-containing compound and a compound containing a transition metal with an oxidation number of 4. The metal-containing compounds (such as titanium-containing compounds and compounds containing a transition metal with an oxidation number of 4) may be or include, for example, at least one of metal oxides, metal hydroxides, metal carbonates, their complexes, and their mixtures. The metal-containing compound may further include other metal or non-metal elements. For example, the metal-containing compound may further include lithium.

[0138] The third particle PTC3 further includes a coating, so it can have greater structural stability and can have a uniform coating formed on its surface. In addition, the third particle PTC3 further includes a coating, so it can have further improved conductivity.

[0139] The third particle PTC3 may further include a carbon element derived from the above coating. The third particle PTC3 may have a carbon element content ranging from about 0.5 wt% to about 5 wt%, from about 0.5 wt% to about 3 wt%, or from about 1.0 wt% to about 2 wt%.

[0140] Reference Figure 12The 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 without grain boundaries within it. A single particle can refer to a single particle morphologically present in an independent phase (where the particles do not aggregate), 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. Alternatively, a single particle can be a particle containing several crystals. A single particle can be in an isolated form. Alternatively, a single particle can be in the form of approximately 2 to approximately 100 single particles attached to each other.

[0141] The third PTC3 particle may include at least one third primary particle. In an example embodiment, the third PTC3 particle may be substantially spherical or elliptical in shape, in which a plurality of third primary particles are attached. In another example embodiment, even when the third primary particles are attached, the third PTC3 particle may not have a substantially spherical shape, but may have an irregular shape.

[0142] The third PTC3 particle can have various sizes. For example, the third PTC3 particle can have an average particle size ranging from about 0.5 μm to about 2.5 μm or about 1 μm. The minimum particle size of the third PTC3 particle (i.e., the size of the third primary particle, for example, the particle size of the 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) can be from about 100 nm to about 500 nm or from about 200 nm to about 300 nm.

[0143] In an example implementation, the average particle size can be measured using a particle size analyzer. Average particle size (D) 50 It can indicate the diameter of particles with a cumulative volume of approximately 50 vol% in the particle size distribution.

[0144] In an example implementation, the minimum particle size (i.e., the size of the third primary particle) can indicate the diameter measured by randomly selecting approximately 30 third primary particles from an electron microscope image of the third particle PTC3.

[0145] First active material layer ATL1

[0146] Figure 7 An enlarged view illustrating the first active material layer ATL1 of the positive electrode for a rechargeable lithium battery according to an exemplary embodiment of the present disclosure.

[0147] refer to Figure 7The 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. Although not shown in the figures, the second particle PTC2 may be in the form of a secondary particle, or it may be in a bimodal form as a mixture of a single particle and a secondary particle.

[0148] The first active material layer ATL1 comprises a mixture of first PTC1 particles and second PTC2 particles, thereby compensating for the low capacity and low energy density (limitations of lithium iron phosphate positive electrode active materials). That is, together they can achieve benefits such as the economic efficiency of the first PTC1 particles and the high capacity and high energy density of the second PTC2 particles.

[0149] The first active material layer ATL1 comprises a mixture of first particles PTC1 and second particles PTC2 having a small BET specific surface area, and correspondingly, the weight ratio of the first functional additive FAD1 in the first active material layer ATL1 can be reduced. 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. When the particle size is too small, the adhesion between the positive electrode current collector and the positive electrode active material may be reduced, which can increase the resistance. As a result, the electrode plate may become difficult to process and may require a larger amount of binder. The first active material layer ATL1 according to an exemplary embodiment of the present disclosure includes second particles PTC2, which have a smaller BET specific surface area than lithium iron phosphate positive electrode active materials. This makes the first active material layer (ATL1) advantageous for electrode plate fabrication.

[0150] For example, the weight ratio of the first functional additive FAD1 in the first active material layer ATL1 can be in the range of about 2.4 to about 4.0.

[0151] The weight ratio of the first functional additive FAD1 in the first active material layer ATL1 may be less than or equal to the weight ratio of the second functional additive FAD2 in the second active material layer ATL2, as described below. The ratio of the weight ratio of the second functional additive FAD2 in the second active material layer ATL2 to the weight ratio of the first functional additive FAD1 in the first active material layer ATL1 may be in the range of about 1.0 to about 2.44 or about 1.0 to about 2.6.

[0152] The content of the first binder BND1 relative to 100 parts by weight of the first active material layer ATL1 can be in the range of about 1.2 parts by weight to about 2.0 parts by weight. The content of the first conductive material CDM1 relative to 100 parts by weight of the first active material layer ATL1 can be in the range of about 1.2 parts by weight to about 2.0 parts by weight. The content of the first binder BND1 in the first active material layer ATL1 can be lower than the content of the second binder BND2 in the second active material layer ATL2, as described below. When the first active material layer ATL1 meets the content ranges of the first binder and the first conductive material, the capacity and energy density of the battery can be maximized, and the electrode plates can be easily processed.

[0153] The first adhesive BND1 is configured to adhere positive electrode active material particles PTC1 and PTC2 (i.e., first particle PTC1 and second particle PTC2), and also to adhere positive electrode active material particles PTC1 and PTC2 to the positive electrode current collector COL1. Typical examples of the first adhesive BND1 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.

[0154] The first conductive material CDM1 can be configured to impart conductivity to the electrodes. In the battery, it can include any material that does not cause chemical changes in the battery and is electronically conductive. Examples of the first conductive material CDM1 may include: carbon-based materials (such as 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 fibers; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0155] The first active material layer ATL1 can be in contact with one surface of the positive electrode current collector COL1. Figure 6 ).

[0156] The first active material layer ATL1 may have a thickness T1. In an example embodiment, T1 may increase with the increase of the weight of the first particle PTC1 and / or the second particle PTC2 included in the first active material layer ATL1.

[0157] The first active material layer ATL1 contains less carbon than the second active material layer ATL2, which will be discussed further below. The carbon content included in the first active material layer can be defined as the amount of carbon included in the first active material layer relative to the weight of the first active material layer. That is, the carbon content included in the first active material layer can be defined as the weight of carbon included in the first active material layer / the weight of the first active material layer. The carbon content can be measured, for example, by carbon-sulfur analysis. However, the measurement method is not limited to this.

[0158] Second active material layer ATL2

[0159] Figure 8 An enlarged view showing the second active material layer ATL2 of the positive electrode for a rechargeable lithium battery according to an exemplary embodiment of the present disclosure.

[0160] refer to Figure 8 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.

[0161] The second binder BND2 is configured to effectively adhere the positive electrode active material particles PTC3. Typical examples of the second binder 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; however, exemplary embodiments of this disclosure are not limited thereto. The second binder BND2 may be the same as or different from the first binder BND1 described above.

[0162] The second conductive material CDM2 can be configured to impart conductivity to the electrodes. It can include any material in the battery that does not cause chemical changes and is electronically conductive. Examples of the second conductive material CDM2 include: carbon-based materials (such as 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 fibers; conductive polymers (such as polyphenylene derivatives); or mixtures thereof. The second conductive material CDM2 may be the same as or different from the first conductive material CDM1 described above.

[0163] 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 2.0 parts by weight to about 3.0 parts by weight. 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 2.0 parts by weight to about 3.0 parts by weight. The content of the second binder BND2 in the second active material layer ATL2 can be greater than the content of the first binder BND1 in the first active material layer ATL1. Optionally, the content of the second binder BND2 in the second active material layer ATL2 relative to the content of the first binder BND1 in the first active material layer ATL1 can be in the range of about 1.0 to about 2.5, about 1.0 to about 2.44, or about 1.3 to about 1.8.

[0164] When the contents of the second conductive material CDM2 and the second binder BND2 in the second active material layer ATL2 meet the above range, the battery capacity can be maximized, and the electrode plate can be easily processed.

[0165] 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. The weight ratio of the second functional additive FAD2 in the second active material layer ATL2 can be in the range of about 4.0 to about 6.0.

[0166] 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 1.0 to about 2.44 or about 1.0 to about 2.6. When the weight ratio of the second functional additive FAD2 to the first functional additive FAD1 satisfies any of the above-mentioned numerical ranges, the positive electrode active material layer AML1 has improved adhesion to the positive electrode current collector COL1, and accordingly, the battery capacity and energy density can be improved or maximized, and the electrode plate can be easily processed.

[0167] The second active material layer ATL2 can be coated to contact one surface of the first active material layer ATL1. One surface of the first active material layer ATL1 can be not in contact with the positive electrode current collector COL1. Figure 6 ) Surface in contact. For example, the positive electrode current collector COL1 ( Figure 6 The first active substance layer ATL1 and the second active substance layer ATL2 can be set sequentially.

[0168] The second active material layer ATL2 may have a thickness T2. In an example embodiment, T2 may increase with the weight of the third particle PTC3 included in the second active material layer ATL2.

[0169] The positive electrode includes a first active material layer and a second active material layer.

[0170] 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 located on the positive electrode current collector COL1.

[0171] The positive electrode active material layer AML1 may include positive electrode active material particles PTC1, PTC2, and PTC3 (i.e., first particle PTC1, second particle PTC2, and third particle PTC3). Relative to 100 wt% of the positive electrode active material layer AML1, 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.

[0172] The positive electrode active material layer AML1 may include binders BND1 and BND2 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, in the range of about 0.5 wt% to about 5 wt% of each or at least one of binders BND1 and BND2 and conductive materials CDM1 and CDM2.

[0173] The positive electrode active material layer AML1 may include a first active material layer ATL1 and a second active material layer ATL2. Because the first active material layer ATL1 is positioned below the second active material layer ATL2, the positive electrode active material layer AML1 can contain a large amount of nano-sized olivine-like compounds, while simultaneously increasing adhesion to the positive electrode current collector COL1. As a result, the electrode plate can be easily fabricated, and the resistance of the electrode plate can be reduced. For example, this configuration leads to a rechargeable lithium battery with desired or improved performance.

[0174] The first active material layer ATL1 may have a thickness T1. In an example embodiment, 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, T2 may increase with increasing weight of the third particle PTC3 included in the second active material layer ATL2.

[0175] The thickness ratio T1:T2 of the first active material layer ATL1 and the second active material layer ATL2 can be in the range of about 3:7 to about 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 about 5:5. When the thickness ratio T1:T2 of the first active material layer ATL1 and the second active material layer ATL2 meets any numerical range, the positive electrode active material layer AML1 has improved adhesion to the positive electrode current collector COL1, and accordingly, the capacity and energy density of the battery can be improved or maximized, and the electrode plate can be easily processed.

[0176] In the exemplary embodiments of this disclosure, such as Figure 6 and Figure 7 As shown, a first active material layer ATL1 is introduced between the positive electrode current collector COL1 and the second active material layer ATL2. The first active material layer ATL1 contains a suitable proportion of second particles PTC2 and first particles PTC1. This configuration improves the adhesion of the electrode plate and reduces the need for binder BND1. Furthermore, it leads to improvements in capacity, density characteristics, high-temperature stability, and lifetime characteristics. Moreover, the inclusion of second particles PTC2 in a bimodal form (including a mixture of single particles and secondary particles) further enhances the density.

[0177] The first particle PTC1 is in the range of 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 first particle PTC1 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.

[0178] The second particle PTC2 is in the range of about 10 wt% to about 30 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 second particle PTC2 is in the range of about 20 wt% to about 30 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.

[0179] The third particle PTC3 comprises approximately 30 wt% to approximately 40 wt% of 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 third particle PTC3 comprises approximately 35 wt% of 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.

[0180] The second particle PTC2 is in the range of about 30 wt% to about 60 wt% relative to the total content of the first particle PTC1 and the second particle PTC2 included in the first active material layer ATL1. For example, the second particle PTC2 is in the range of about 45 wt% to about 50 wt% relative to the total content of the first particle PTC1 and the second particle PTC2 included in the first active material layer ATL1.

[0181] When the contents of the first PTC1, second PTC2, and third PTC3 particles meet any of the above-mentioned ranges, the positive electrode active material layer AML1 can have improved adhesion relative 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 any of the above-mentioned ranges, a rechargeable lithium battery with desired or improved performance can be provided.

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

[0183] Preparation Example 1: Preparation of the first particle (single particle form)

[0184] Ferric phosphate precursor (FePO4), lithium carbonate, and titanium dioxide were mixed in a molar ratio of Fe:Li:Ti = 1:1.03:0.004. 10 wt% glucose was further added to the mixture. The mixture was then wet-milled by ball milling. The mixture was evaporated to dryness on a heated tray, and then placed in a vacuum oven at 85°C and dried for 4 hours. The dried mixture was calcined at 750°C for 10 hours under a nitrogen atmosphere. The calcined product was milled at 8000 rpm to obtain first particles in the form of single particles. The first particles had an average particle size of 0.5 μm to 2.5 μm. The first primary particles of the first particles had a size of 200 nm to 300 nm.

[0185] Preparation Example 2: Preparation of the second particle (single particle form)

[0186] Ni 0.92 Co0.07 Al 0.01 (OH)₂ and LiOH were mixed in a molar ratio of (Ni+Co+Al):Li = 1:1.05, and the mixture was subjected to a first heat treatment at 810°C for 8 hours in an oxygen atmosphere to obtain Li 1.05 Ni 0.92 Co 0.07 Al 0.01 O2 composition and average particle size (D) 50 The oxide is approximately 4 μm in size. Alumina was added to the oxide, and the mixture was subsequently subjected to a second heat treatment at 740 °C for 8 hours in an oxygen atmosphere to prepare second particles in single-particle form. The second particles are composed of the formula LiNi. 0.92 Co 0.07 Al 0.01 O2 represents.

[0187] Preparation Example 3: Preparation of the third particle (single particle form)

[0188] Ferric phosphate precursor (FePO4), lithium carbonate, and titanium dioxide were mixed in a molar ratio of Fe:Li:Ti = 1:1.03:0.004. 10 wt% glucose was further added to the mixture. The mixture was then wet-milled by ball milling. The mixture was evaporated to dryness on a heated tray and then placed in a vacuum oven at 85°C for 4 hours. The dried mixture was calcined at 750°C for 10 hours under a nitrogen atmosphere. The calcined product was milled at 8000 rpm to obtain third particles in the form of single particles. The third particles had an average particle size of 0.5 μm to 2.5 μm. The third primary particles of the third particles had a size of 200 nm to 300 nm.

[0189] Example 1: Preparation of a positive electrode comprising a first active material layer and a second active material layer

[0190] The first particle from Preparation Example 1 and the second particle from Preparation Example 2 were dispersed in N-methylpyrrolidone with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a first positive electrode active material slurry. The third particle from Preparation Example 3 was dispersed in N-methylpyrrolidone with a conductive material (carbon black) and a binder (polyvinylidene fluoride) to prepare a second positive electrode active material slurry.

[0191] A first positive electrode active material slurry is coated onto the positive electrode current collector and dried to form a first active material layer. A second positive electrode active material slurry is coated onto the first active material layer and dried to form a second active material layer.

[0192] In this case, a double-layer positive electrode active material layer is formed, such that the first, second, and third particles in the double-layer positive electrode active material layer exist in a weight ratio of 35:30:35. A positive electrode in which the positive electrode current collector, the first active material layer, and the second active material layer are stacked in this order is prepared using a roller press.

[0193] Example 2

[0194] The positive electrode was prepared in essentially the same manner as in Example 1, except that a second particle in a bimodal form was used instead of the second particle (single particle form) from Preparation Example 2.

[0195] The method for preparing the second particle in a bimodal form is as follows:

[0196] Ni 0.92 Co 0.07 Al 0.01 (OH)₂ and LiOH were mixed in a molar ratio of (Ni+Co+Al):Li = 1:1.05, and a flux was added to the mixture. The mixture was then subjected to a first heat treatment at 750°C for 15 hours in an oxygen atmosphere to obtain particles after the first heat treatment.

[0197] The particles after the first heat treatment were ground using a jet mill at a pressure of 3 bar, and then washed with distilled water. After washing, alumina was added to the particles after the first heat treatment, and the mixture was dried at 150°C for 12 hours. The dried mixture was then subjected to a second heat treatment at 700°C for 15 hours in an oxygen atmosphere to prepare second particles in the form of secondary particles.

[0198] The second particles in the form of secondary particles and the second particles in the form of single particles from Preparation Example 2 were mixed at a weight ratio of 2:8 to prepare the second particles in the form of bimodal particles.

[0199] Comparative Example 1: Preparation of a positive electrode including an active material layer

[0200] The first particle from Preparation Example 1 and the second particle from Preparation Example 2 were mixed at a weight ratio of 30:70 and dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a monolayer positive electrode.

[0201] Comparative Example 2

[0202] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that the first particle of Preparation Example 1 and the second particle of Preparation Example 2 were mixed in a weight ratio of 40:60.

[0203] Comparative Example 3

[0204] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that the first particle of Preparation Example 1 and the second particle of Preparation Example 2 were mixed in a weight ratio of 50:50.

[0205] Comparative Example 4

[0206] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that the first particle of Preparation Example 1 and the second particle of Preparation Example 2 were mixed in a weight ratio of 60:40.

[0207] Comparative Example 5

[0208] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that the first particle of Preparation Example 1 and the second particle of Preparation Example 2 were mixed in a weight ratio of 70:30.

[0209] Comparative Example 6

[0210] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that the first particle of Preparation Example 1 and the second particle of Preparation Example 2 were mixed in a weight ratio of 80:20.

[0211] Comparative Example 7

[0212] The positive electrode was prepared in essentially the same manner as in Comparative Example 1, except that the first particle of Preparation Example 1 and the second particle of Preparation Example 2 were mixed in a weight ratio of 90:10.

[0213] Comparative Example 8

[0214] The first particle from Preparation Example 1, the second particle from Preparation Example 2, and the third particle from Preparation Example 3 were mixed in a weight ratio of 35:30:35 and dispersed together with a conductive material (carbon black) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a positive electrode current collector and dried to prepare a monolayer positive electrode.

[0215] Comparative Example 9

[0216] The positive electrode was prepared in the same manner as in Example 1, except that the weights of the first binder, the first conductive material, the second binder, and the second conductive material were changed. The weight changes were adjusted so that the weight ratio of the second functional additive to the first functional additive was 0.75.

[0217] Comparative Example 10

[0218] The positive electrode was prepared in the same manner as in Example 1, except that the weights of the first binder, the first conductive material, the second binder, and the second conductive material were changed. The weight changes were adjusted so that the weight ratio of the second functional additive to the first functional additive was 3.33.

[0219] Preparation of rechargeable lithium batteries

[0220] 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) formed of 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 mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 3:4:3.

[0221] Evaluation Example 1: Analysis of the surface of the active material in the positive electrode

[0222] SEM images of each of the first, second, and third particles prepared in Preparation Examples 1 to 3 are shown in the figure. Figure 9 , Figure 10 and Figure 12 middle.

[0223] refer to Figure 9 According to Preparation Example 1 of this disclosure, the first particle is in the form of a single particle.

[0224] refer to Figure 10 According to Example 2 of this disclosure, the second particle is in the form of a single micron-sized particle. (See reference...) Figure 9 and Figure 10 When the second particle is in the form of a single particle, the average particle size (D) of the second particle is... 50 ) is greater than the average particle size of the first particle (D) 50 ).

[0225] refer to Figure 11 According to an exemplary embodiment of this disclosure, the second particle is in the form of a substantially spherical secondary particle in which fine second primary particles of nanoscale size are aggregated.

[0226] refer to Figure 12 The third particle in Preparation Example 3 according to this disclosure is in the form of a single particle.

[0227] Evaluation Example 2: Evaluation of Active Substances

[0228] 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 1 below. The powder compaction density was measured by placing 3 grams of the positive electrode active material into a powder compaction mold and applying a force of approximately 4.0 US tons for approximately 30 seconds. The powder compaction density (PD) of the positive electrode active materials according to the embodiments was 2.64 g / cc to 2.75 g / cc. The weight ratios of the first, second, and third particles in Table 1 refer to the percentage of the weight of the first, second, and third particles relative to the total weight of the first, second, and third particles, respectively.

[0229] Table 1:

[0230]

[0231] *1) Use the second particle, which has a bimodal shape.

[0232] Evaluation Example 3: Evaluation of Battery Properties

[0233] The characteristics of rechargeable lithium batteries prepared using positive electrode active materials from the respective examples and comparative examples were evaluated.

[0234] For the initial charge / discharge, the rechargeable lithium battery was initially charged at 25°C at a constant current and constant voltage (approximately 4.2V, approximately 0.05C cutoff) at 0.2C. After a 10-minute rest period, it was discharged to 3.0V at a constant current of 0.2C, yielding the initial charge capacity at 0.2C and the initial discharge capacity at 0.2C. The efficiency (efficiency at 0.2C (%)) was expressed as the initial charge capacity at 0.2C / the initial discharge capacity at 0.2C. The average voltage was then evaluated. Subsequently, the charge / discharge cycle was repeated 50 times at 45°C and 1.0C (approximately 4.2V, approximately 0.05C cutoff) / 1.0C (approximately 3.0V, approximately 0.05C cutoff) to measure the discharge capacity after the 50th cycle. The lifetime (lifetime at 1C (%, 50 cycles)) was expressed as the discharge capacity after the 50th cycle / the initial discharge capacity. A rechargeable lithium battery was prepared and subsequently initially charged at approximately 25°C under constant current and constant voltage (approximately 4.2V, cutoff at approximately 0.05C) at 0.2C. After resting for 10 minutes, it was discharged to 3.0V at a constant current of 0.2C. It was then recharged at -20°C under constant current (approximately 0.2C) and constant voltage (approximately 4.2V, cutoff at approximately 0.05C), followed by discharge at a constant current (approximately 0.2C) until the voltage reached 3.0V to measure the discharge capacity at -20°C. 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 then calculated by charging and discharging the battery at a rate of 0.2C / 0.2C within a voltage range of 3.0V to 4.45V at 25°C. The energy density was obtained using the following equation: {average driving voltage (V) × capacity (Ah) / cell weight (kg)}, where the capacity was calculated by multiplying the positive electrode weight (g) by the discharge capacity (mAhg). The rechargeable lithium battery was charged to SOC50 at a constant current of 0.2C and discharged at 1.0C for 1 second to record voltage and current, then discharged at a constant current of 0.2C for 1 second to record another voltage and current, thereby calculating the DC internal resistance (DCIR). DCIR was measured as ΔV / ΔI (voltage change / current change). The results of the battery performance evaluation are shown in Table 2 below.

[0235] The weight of the second particle in Table 2 indicates the weight of the second particle relative to the total weight of the first, second, and third particles.

[0236] Table 2:

[0237]

[0238] *2) Use the second particle, which has a bimodal shape.

[0239] Referring to Table 2, the rechargeable lithium batteries including the positive electrodes according to Examples 1 and 2 have efficiency, capacity, lifetime, resistance, and energy density that are substantially the same as or higher than those of the rechargeable lithium batteries including the positive electrode according to Comparative Example 8. That is, even when the mixing ratio of the first, second, and third particles is the same, the performance of the battery including a double-layer positive electrode active material is improved compared to the performance of a battery including only a single layer of positive electrode active material.

[0240] Evaluation Example 4: Evaluation of Resistance and Adhesion

[0241] The DC internal resistance (DCIR) and adhesion of rechargeable lithium batteries prepared using positive electrode active materials from the Examples and Comparative Examples were evaluated, and the results are shown in Table 3 below.

[0242] For initial charge / discharge, the rechargeable lithium battery was initially charged at 25°C under constant current and constant voltage (approximately 4.2V, approximately 0.05C cutoff) at 0.2C. After resting for 10 minutes, it was discharged to 3.0V at a constant current of 0.2C, and the average voltage was then evaluated. The rechargeable lithium battery was charged to SOC50 at a constant current of 0.2C and discharged at 1.0C for 1 second to record the voltage and current, followed by another discharge at a constant current of 0.2C for 1 second to record the voltage and current again, thereby calculating the DC internal resistance (DCIR). DCIR was measured as ΔV / ΔI (voltage change / current change).

[0243] The contents of the first functional additive and the second functional additive, as well as the weight ratio of the second functional additive to the weight ratio of the first functional additive (weight ratio of FAD2 / weight ratio of FAD1) were calculated.

[0244] Table 3:

[0245]

[0246] Referring to Table 3, compared with rechargeable lithium batteries including positive electrodes according to Comparative Examples 9 and 10, rechargeable lithium batteries including positive electrodes according to Examples 1 and 2 have lower DC internal resistance (DCIR). That is, when the weight ratio of the second functional additive to the weight ratio of the first functional additive (weight ratio of FAD2 / weight ratio of FAD1) meets the target range of this disclosure, the adhesion to the positive electrode current collector can be increased.

[0247] The positive electrode according to this disclosure comprises a first particle and a third particle, each having an olivine structure, thus providing improved economic efficiency and average voltage.

[0248] The positive electrode according to this disclosure includes a second particle having a layered structure, thus having improved capacity and energy density.

[0249] The positive electrode according to this disclosure has a second particle and a first particle mixed and disposed in a first active material layer, thus making the electrode plate easier to prepare.

[0250] The positive electrode according to this disclosure has first, second, and third particles mixed and placed in a desired or optimal ratio to form a bilayer structure, thereby improving battery characteristics and facilitating the fabrication of electrode plates.

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; And A second active material layer on the first active material layer, Wherein the first active material layer comprises first particles containing an olivine-structured compound represented by Formula 1, second particles containing a layered compound represented by Formula 2, a first conductive material, and a first binder, The second active material layer comprises third particles containing an olivine-structured compound represented by Formula 3, a second conductive material, and a second binder, The first particles and the third particles are in the form of single particles, 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 ratio of the weight ratio of the second functional additive in the second active material layer to the weight ratio of the first functional additive in the first active material layer is in the range of 1.0 to 2.6, Formula 1: Li a1 Fe x1 B1 y1 PER 4-c1 Where in Formula 1, 0.8 < a1 ≤ 1.2, 0.95 ≤ x1 ≤ 0.999, 0.001 ≤ y1 ≤ 0.05, x1 + y1 = 1, and 0 ≤ c1 ≤ 0.05, and B1 includes at least one of Ti and a transition metal with an oxidation number of 4, Formula 2: Li a2 Ni x2 Co y2 B2 z2 O 2-c2 Where in Formula 2, 0.8 < a2 ≤ 1.2, 0.9 ≤ x2 ≤ 1.05, 0.03 ≤ y2 ≤ 0.10, 0.01 ≤ z2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05, and B2 includes at least one of Al and Mn, and Formula 3: Li a3 Fe x3 B3 y3 PO 4-c3 Where in Formula 3, 0.8 < a3 ≤ 1.2, ​ ​ The second particle has an average particle size D ranging from 3 μm to 10 μm. 50 . ​ ​ The second particle has an average particle size D ranging from 10 μm to 14 μm. 50 . ​ ​ The first particle has an average particle size D ranging from 0.5 μm to 2.5 μm. 50 . ​ ​ The third particle has an average particle size D ranging from 0.5 μm to 2.5 μm. 50 . ​ 7. The positive electrode for a rechargeable lithium battery as claimed in claim 1, wherein the BET specific surface area of ​​the second particle is smaller than that of the first particle.

8. The positive electrode for a rechargeable lithium battery as claimed in claim 1, wherein the first particle comprises a coating containing carbon elements, and The first particle contains carbon elements in the range of 1.0 wt% to 2.0 wt%.

9. The positive electrode for a rechargeable lithium battery as claimed in claim 1, 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.

10. The positive electrode for a rechargeable lithium battery as claimed in claim 1, wherein, relative to the total weight of the first particle, the second particle, and the third particle included in the first active material layer and the second active material layer, The amount of the second particle is in the range of 10wt% to 30wt%.

11. The positive electrode for a rechargeable lithium battery as claimed in claim 1, wherein, relative to the total weight of the first particle, the second particle, and the third particle included in the first active material layer and the second active material layer, The amount of the second particle is in the range of 20wt% to 30wt%.

12. The positive electrode for a rechargeable lithium battery as described in claim 1, wherein: The content of the first adhesive is in the range of 1.2 parts by weight to 2.0 parts by weight relative to 100 parts by weight of the first active material layer, and The content of the second adhesive is in the range of 2.0 parts by weight to 3.0 parts by weight relative to 100 parts by weight of the second active material layer.

13. The positive electrode for a rechargeable lithium battery as claimed in claim 1, wherein the ratio of the content of the second binder in the second active material layer to the content of the first binder in the first active material layer is in the range of 1.0 to 2.

44.

14. The positive electrode for a rechargeable lithium battery as claimed in claim 1, wherein the first particle and the third particle comprise a coating containing carbon elements, and The first active material layer contains fewer carbon elements than the second active material layer.

15. A positive electrode for a rechargeable lithium battery, the positive electrode comprising: Positive electrode current collector; A first active material layer on the positive electrode current collector; and A second active material layer on top of the first active material layer The first active material layer comprises first particles containing a compound structured with olivine as represented by Formula 1, second particles containing a layered compound as represented by Formula 2, a first conductive material, and a first binder. The second active material layer includes third particles containing a compound structured with olivine as represented by Formula 3, a second conductive material, and a second binder. The first particle and the third particle are in the form of a single particle, and The content of the first binder in the first active material layer is less than the content of the second binder in the second active material layer. Formula 1: Li a1 Fe x1 B1 y1 PER 4-c1 Among them, in Formula 1, 0.8 < a1 ≤ 1.2, 0.95 ≤ x1 ≤ 0.999, 0.001 ≤ y1 ≤ 0.05, x1 + y1 = 1, and 0 ≤ c1 ≤ 0.05, and B1 includes at least one of Ti and transition metals with an oxidation number of 4. Formula 2: Li a2 Ni x2 Co y2 B2 z2 O 2-c2 Among them, in Formula 2, 0.8 < a2 ≤ 1.2, 0.9 ≤ x2 ≤ 1.05, 0.03 ≤ y2 ≤ 0.10, 0.01 ≤ z2 ≤ 0.05, and 0 ≤ c2 ≤ 0.05, and B2 includes at least one of Al and Mn, and Formula 3: Li a3 Fe x3 B3 y3 PO 4-c3 Among them, in Formula 3, 0.8 < a3 ≤ 1.2, 0.95 ≤ x3 ≤ 0.999, 0.001 ≤ y3 ≤ 0.05, x3 + y3 = 1, and 0 ≤ c3 ≤ 0.05, and B3 includes at least one of Ti and transition metals with an oxidation number of 4.

16. The positive electrode for a rechargeable lithium battery according to claim 15, 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.

17. The positive electrode for a rechargeable lithium battery according to claim 15, wherein relative to the total weight of the first particles, the second particles and the third particles included in the first active material layer and the second active material layer, the amount of the second particles is in the range of 10 wt% to 30 wt%.

18. The positive electrode for a rechargeable lithium battery according to claim 15, wherein: relative to 100 parts by weight of the first active material layer, the content of the first binder is in the range of 1.2 parts by weight to 2.0 parts by weight, and relative to 100 parts by weight of the second active material layer, the content of the second binder is in the range of 2.0 parts by weight to 3.0 parts by weight.

19. A rechargeable lithium battery comprising the positive electrode according to any one of claims 1 to 18.

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