Positive electrode for rechargeable lithium battery, method of manufacturing same, and rechargeable lithium battery including same

Abstract

Disclosed examples include a positive electrode, a method of manufacturing the same, and a rechargeable lithium battery. The positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector. The positive electrode active material layer includes a first positive electrode active material layer and a second positive electrode active material layer stacked on the positive electrode current collector. The first positive electrode active material layer includes a layered positive electrode active material. The second positive electrode active material layer includes an olivine-based positive electrode active material. The first positive electrode active material layer includes a first hole. The second positive electrode active material layer includes a second hole.

Description

[0001] This application claims priority to Korean Patent Application No. 10-2024-0106479, filed on August 9, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] Embodiments of this disclosure relate to a positive electrode for a rechargeable lithium battery, a method for manufacturing the positive electrode, and a rechargeable lithium battery including the positive electrode. More specifically, they relate to a multilayer positive electrode, a method for manufacturing the multilayer positive electrode, and a rechargeable lithium battery including the multilayer positive electrode. Background Technology

[0003] With the increasing prevalence of battery-powered electronic devices (such as mobile phones, laptops, and electric vehicles), the demand for rechargeable batteries with high energy density and high capacity is growing. Therefore, improving the performance of rechargeable lithium batteries would be beneficial.

[0004] A rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte. The positive and negative electrodes include active materials capable of inserting and deintercalating lithium ions. The rechargeable lithium battery generates electrical energy through oxidation and reduction reactions during lithium ion insertion and deintercalation. Summary of the Invention

[0005] Example embodiments of this disclosure include a positive electrode for a rechargeable lithium battery having desired or improved capacity and improved charge / discharge characteristics.

[0006] Example embodiments of this disclosure include rechargeable lithium batteries having desired or improved capacity and improved charge / discharge characteristics.

[0007] According to an example embodiment of this disclosure, the positive electrode for a rechargeable lithium battery may include a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector. The positive electrode active material layer may include a first positive electrode active material layer and a second positive electrode active material layer stacked (e.g., sequentially stacked) on the positive electrode current collector. The first positive electrode active material layer may include a layered positive electrode active material. The second positive electrode active material layer may include an olivine-based positive electrode active material. The first positive electrode active material layer may include a plurality of first pores. The second positive electrode active material layer may include a plurality of second pores.

[0008] According to an example embodiment of this disclosure, a method for manufacturing a positive electrode for a rechargeable lithium battery may include: providing a positive electrode current collector; forming a first positive electrode active material layer on the positive electrode current collector; performing a first pore-forming process on the first positive electrode active material layer to form a plurality of first pores; forming a second positive electrode active material layer on the first positive electrode active material layer on which the first pore-forming process has been performed; and performing a second pore-forming process on the second positive electrode active material layer to form a plurality of second pores. The first positive electrode active material layer may include a layered positive electrode active material. The second positive electrode active material layer may include an olivine-based positive electrode active material.

[0009] According to an example embodiment of this disclosure, a rechargeable lithium battery may include the positive electrode discussed above, a negative electrode including a negative electrode current collector and a negative electrode coating layer on the negative electrode current collector, and a separator between the positive electrode and the negative electrode. Attached Figure Description

[0010] Figure 1 A simplified conceptual diagram of a rechargeable lithium battery according to an example embodiment of the present disclosure is shown.

[0011] Figures 2 to 5 A diagram of a rechargeable lithium battery according to an example embodiment of the present disclosure is shown.

[0012] Figure 6 A cross-sectional view is shown illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure.

[0013] Figure 7 It shows Figure 6 An enlarged view of an example of part M depicted in the image.

[0014] Figure 8 An enlarged plan view is shown, partially illustrating a first positive electrode active material layer according to an exemplary embodiment of the present disclosure.

[0015] Figure 9 An enlarged plan view of the second positive electrode active material layer according to an exemplary embodiment of the present disclosure is shown.

[0016] Figure 10 and Figure 11 A cross-sectional view showing a positive electrode active material layer according to an example embodiment of the present disclosure is shown.

[0017] Figure 12 A cross-sectional view is shown illustrating a method for manufacturing a positive electrode according to an exemplary embodiment of the present disclosure.

[0018] Figure 13 This is a flowchart illustrating a method for manufacturing a positive electrode for a rechargeable lithium battery, based on various disclosed examples. Detailed Implementation

[0019] To provide a full understanding of the structure and effects of this disclosure, some 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 following exemplary embodiments and can be implemented in various forms. Rather, the exemplary embodiments are provided merely to disclose this disclosure and to enable those skilled in the art to fully understand its scope.

[0020] In this specification, it is understood that when an element is referred to as being "on" another element, the element may be "directly on" said other element, or an intervening element may be present between them. In the accompanying drawings, the thickness of some components is exaggerated for the purpose of effectively explaining the technical content. Throughout the specification, the same reference numerals denote the same elements.

[0021] Unless otherwise specifically indicated in this specification, singular expressions may include plural expressions. Furthermore, unless otherwise specifically indicated, the phrase "A or B" may mean "A but not B," "B but not A," and "A and B." The term "including / comprises" and / or variations thereof as used in this disclosure do not exclude the presence or addition of one or more other components.

[0022] As used herein, the term "combination thereof" may refer to mixtures, stacks, complexes, copolymers, alloys, blends, or reaction products.

[0023] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical value includes a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​within that range, such as increments of 0.1%.

[0024] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure is shown. (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.

[0025] 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.

[0026] The electrolyte ELL can be or includes a medium through which lithium ions are transported between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move toward one of the positive electrode 10 and the negative electrode 20 through the membrane 30.

[0027] Positive electrode 10 The positive electrode 10 for a rechargeable lithium battery may include a current collector COL1 and a positive electrode active material layer AML1 formed on the current collector COL1. The positive electrode active material layer AML1 may include a positive electrode active material, and may also include a binder and / or a conductive material.

[0028] For example, the positive electrode 10 may also include additives that can constitute a sacrificial positive electrode.

[0029] The amount of positive electrode active material relative to 100 wt% of the positive electrode active material layer AML1 can range from about 90 wt% to about 99 wt%. The amount of each of the binder and conductive material relative to 100 wt% of the positive electrode active material layer AML1 can range from about 0.5 wt% to about 5 wt%.

[0030] The binder can be configured to improve the adhesion between the positive electrode active material particles and also improve the adhesion of the positive electrode active material to the current collector COL1. The binder may include, for example, 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 this disclosure is not limited thereto.

[0031] Conductive materials can be configured to provide conductivity to electrodes and can include any suitable conductive material that does not cause chemical changes in the battery. Conductive materials can include, for example: 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; metal powders or metal fibers containing one or more of copper, nickel, aluminum, and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0032] Aluminum (Al) may be included as the current collector COL1, but this disclosure is not limited thereto.

[0033] Positive electrode active material The positive electrode active material in the positive electrode active material layer AML1 may include compounds that can reversibly insert and deintercalate lithium (e.g., lithiation intercalation compounds). For example, the positive electrode active material may include at least one composite oxide comprising lithium and a metal, wherein the metal is or includes at least one of cobalt, manganese, nickel, and combinations thereof.

[0034] The composite oxide may include lithium transition metal composite oxides, such as lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, and combinations thereof, at least one of these.

[0035] For example, the positive electrode active material may include a compound represented by one of the following chemical formulas: Li a A 1- b X b O 2-c D c (Where, 0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (Where, 0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (Where, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (Where, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni b Co c L 1 DG e O2 (where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, and 0≤e≤0.1); Li a NiG b O2 (where 0.90≤a≤1.8 and 0.001≤b≤0.1); Li a CoG b O2 (where 0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-b G b O2 (where 0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn2G b O4 (where 0.90≤a≤1.8 and 0.001≤b≤0.1); Lia Mn 1-g G g PO4 (where 0.90 ≤ a ≤ 1.8 and 0 ≤ g ≤ 0.5); Li (3-f) Fe2(PO4)3 (where 0≤f≤2); Li a FePO4 (where 0.90≤a≤1.8).

[0036] In the above chemical formula, A is or includes at least one of Ni, Co, Mn, and combinations thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is or includes at least one of O, F, S, P, and combinations thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; and L 1 It is or includes at least one of Mn, Al and combinations thereof.

[0037] For example, the positive electrode active material can be or includes a high-nickel positive electrode active material, wherein the nickel content of the high-nickel positive electrode active material is equal to or greater than about 80 mol%, equal to or greater than about 85 mol%, equal to or greater than about 90 mol%, equal to or greater than about 91 mol%, or equal to or greater than about 94 mol% and equal to or less than about 99 mol%, relative to 100 mol% of lithium-free metal in the lithium transition metal complex oxide, or equal to or greater than about 94 mol% and equal to or less than about 99 mol%. High-nickel positive electrode active materials can achieve high capacity and therefore can be used in high-capacity and high-density rechargeable lithium batteries.

[0038] Reference Figures 6 to 9 The positive electrode active material layer AML1 according to some example embodiments of the present disclosure is discussed in further detail.

[0039] negative electrode 20 The negative electrode 20 for a rechargeable lithium battery may include a current collector COL2 and a negative electrode active material layer AML2 located on the current collector COL2. The negative electrode active material layer AML2 may include a negative electrode active material, and may also include a binder and / or a conductive material.

[0040] For example, the negative electrode active material layer AML2 may include a negative electrode active material in the range of about 90 wt% to about 99.5 wt%, a binder in the range of about 0.5 wt% to about 5 wt%, and a conductive material in the range of about 0 wt% to about 5 wt%.

[0041] The binder can be configured to improve the adhesion between the negative electrode active material particles and also improve the adhesion of the negative electrode active material to the current collector COL2. The binder may include at least one of non-aqueous binders, aqueous binders, dry binders, and combinations thereof.

[0042] 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.

[0043] Waterborne adhesives may include at least one of the following: styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomers, polyethylene oxide, polyvinylpyrrolidone, polyepoxychlorohydrin, 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.

[0044] When an aqueous binder is included as the negative electrode binder, a cellulose compound capable of providing viscosity may also be included. The cellulose compound may include one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts. The alkali metal may include at least one of Na, K, and Li.

[0045] Dry adhesives may include fibrillable polymeric materials, such as at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0046] Conductive materials can be included to provide conductivity to the electrodes and can include any suitable conductive material that does not cause chemical changes in the battery. For example, conductive materials can 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; metal powders or metal fibers including one or more of copper, nickel, aluminum, and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0047] The 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.

[0048] Negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 may include at least one of a material capable of reversibly inserting and extracting lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and undoping lithium, and a transition metal oxide.

[0049] The material capable of reversibly inserting and extracting lithium ions may include a carbon-based negative electrode active material. For example, the crystalline carbon may include graphite, such as at least one of natural graphite or artificial graphite in an amorphous shape, a sheet shape, a flake shape, a spherical shape, and a fibrous shape, and the amorphous carbon may include at least one of soft carbon, hard carbon, mesophase pitch carbon, and calcined coke.

[0050] The lithium metal alloy may include an alloy of lithium and a metal, and the metal is 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.

[0051] The material capable of doping and undoping lithium may include at least one of a Si-based negative electrode active material and a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (where 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 a combination thereof), and a combination thereof. The Sn-based negative electrode active material may include at least one of Sn, SnO2, a Sn-based alloy, and a combination thereof.

[0052] 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 have a structure in which amorphous carbon is coated on the surface of silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are assembled and an amorphous carbon coating layer (shells) located on the surface of the secondary particles. Amorphous carbon may also be located between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0053] The silicon-carbon composite may also include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and may also include an amorphous carbon coating layer located on the surface of the core.

[0054] The Si-based negative electrode active material or the Sn-based negative electrode active material may be combined with the carbon-based negative electrode active material.

[0055] Separator 30 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 one or more of polyethylene, polypropylene, and polyvinylidene fluoride, and may have multiple layers of them, such as polyethylene / polypropylene bilayer separators, polyethylene / polypropylene / polypropylene trilayer separators, and polypropylene / polypropylene / polypropylene trilayer separators.

[0056] The diaphragm 30 may include a porous substrate and a coating layer located on one or opposite surfaces of the porous substrate, the coating layer including organic materials, inorganic materials or combinations thereof.

[0057] The porous substrate may be or include a polymer layer, which includes one of polyolefins (such as or including at least one of 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, Teflon and polytetrafluoroethylene, or may be or include copolymers or mixtures comprising two or more of the above materials.

[0058] Organic materials may include at least one of polyvinylidene fluoride copolymers and (meth)acrylic acid copolymers.

[0059] Inorganic materials may include inorganic particles such as or containing 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 this disclosure is not limited thereto.

[0060] Organic and inorganic materials can be mixed in a single coating layer, or they can exist as a stack of coating layers containing organic materials and coating layers containing inorganic materials.

[0061] Electrolyte ELL Electrolytes (ELLs) for rechargeable lithium-ion batteries may include non-aqueous organic solvents and lithium salts. The non-aqueous organic solvents may be configured as a medium for transporting ions that participate in the electrochemical reactions of the battery. Non-aqueous organic solvents may include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0062] 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).

[0063] Ester solvents may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, valproic acid lactone, and caprolactone.

[0064] Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Ketone solvents may include cyclohexanone. Alcohol solvents may include at least one of ethanol and isopropanol. Aprotic solvents may include at least one of: nitriles, such as R-CN (wherein R is a hydrocarbon group having a C2 to C20 straight-chain, branched, or cyclic structure, and may include double bonds, aromatic rings, or ether groups); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane or 1,4-dioxolane; and sulfolane.

[0065] Non-aqueous organic solvents may be included alone or as a mixture of two or more substances. Furthermore, when carbonate solvents are included, cyclic carbonates and chain carbonates may be mixed, and the cyclic carbonates and chain carbonates may be mixed in a volume ratio ranging from about 1:1 to about 1:9.

[0066] Lithium salts can be or include materials dissolved in non-aqueous organic solvents to form a supply source of lithium ions in the battery, and serve to enable the basic operation of the rechargeable lithium battery and facilitate the movement of lithium ions between the positive and negative electrodes. Lithium salts can include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of the following: (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).

[0067] Rechargeable lithium batteries Based on their shape, rechargeable lithium batteries can be classified into cylindrical, prismatic, pouch, and coin-shaped types. Figures 2 to 5 A simplified diagram illustrating a rechargeable lithium battery according to an example embodiment is shown. Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown, and Figure 4 and Figure 5 A pouch-type battery is shown. (See reference) Figures 2 to 5 The rechargeable lithium battery 100 may include an electrode assembly 40 with a separator 30 disposed between a positive electrode 10 and a negative electrode 20, and may also include a housing 50 therein housing the electrode assembly 40. The positive electrode 10, negative electrode 20, and separator 30 may be immersed in an electrolyte (not shown). Figure 2 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. Furthermore, as... Figure 3 As shown, 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. Figure 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include Figure 5 The electrode terminals 70 shown are Figure 4 The positive electrode terminal 71 and negative electrode terminal 72 shown form an electrical path for guiding the current generated in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0068] The following description focuses on rechargeable lithium batteries according to some example embodiments of this disclosure.

[0069] Figure 6 This is a cross-sectional view illustrating a rechargeable lithium battery according to an exemplary embodiment of the present disclosure. (Refer to...) Figure 6 As shown above Figure 1 The rechargeable lithium battery discussed, according to an example embodiment of this disclosure, may include a positive electrode 10, a negative electrode 20, and a separator 30 between the positive electrode 10 and the negative electrode 20. Although in Figure 6 Although not explicitly shown, the rechargeable lithium battery according to an exemplary embodiment of this disclosure may also include an electrolyte ELL. The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in the electrolyte ELL.

[0070] The positive electrode 10 may include a positive electrode current collector COL1 and a positive electrode active material layer AML1 on the positive electrode current collector COL1. The negative electrode 20 may include a negative electrode current collector COL2 and a negative electrode active material layer AML2 on the negative electrode current collector COL2. The separator 30 may be disposed between the positive electrode active material layer AML1 and the negative electrode active material layer AML2.

[0071] According to an exemplary embodiment of this disclosure, the positive electrode active material layer AML1 may have a bilayer structure. For example, the positive electrode active material layer AML1 may include a first positive electrode active material layer CAL1 as the lower layer and a second positive electrode active material layer CAL2 as the upper layer. The first positive electrode active material layer CAL1 may be located on the positive electrode current collector COL1. The second positive electrode active material layer CAL2 may be located on the first positive electrode active material layer CAL1.

[0072] The first positive electrode active material layer CAL1 and the second positive electrode active material layer CAL2 may include different positive electrode active materials. The first positive electrode active material layer CAL1 and the second positive electrode active material layer CAL2 may have different compositions from each other. Each or at least one of the first positive electrode active material layer CAL1 and the second positive electrode active material layer CAL2 may include one of layered positive electrode active materials and olivine-based positive electrode active materials.

[0073] Layered positive electrode active material In an example embodiment, the first positive electrode active material layer CAL1 may include a layered positive electrode active material. The layered positive electrode active material may have a single-particle shape. In this specification, the term "single particle" may refer to a single particle in which there are no grain boundaries. A single particle may refer to a single particle, a monolithic structure, a single integral structure, or a non-aggregated particle that does not aggregate together but exists as an independent phase in terms of morphology. For example, a single particle may be a single crystal. Optionally, a single particle may be a particle comprising several crystals. Single particles may be independently separated. Optionally, a single particle may have a form in which about 2 to about 100 independent particles are attached to each other. In an example embodiment, the layered positive electrode active material may be shaped to resemble a single particle. In an example embodiment, the layered positive electrode active material may have a shape in which multiple single particles are attached to each other. Because the positive electrode active material according to this disclosure includes a layered positive electrode active material shaped to resemble a single particle, rechargeable batteries can achieve high capacity and high energy density.

[0074] In an example embodiment, the layered positive electrode active material may include a first coating layer on its surface. Because the layered positive electrode active material includes the first coating layer, it is possible to effectively reduce or suppress structural collapse that may occur due to repeated charging and discharging. Therefore, rechargeable batteries can improve cycle life characteristics.

[0075] The first coating layer may include at least one metal-containing compound, such as boron-containing compounds, aluminum-containing compounds, and combinations thereof. The metal-containing compound in the first coating layer may be or include at least one of, for example, metal oxides, metal hydroxides, metal carbonates, and their complexes or mixtures. The metal-containing compound may also include other metallic or non-metallic elements. For example, the first coating layer may also include one or more of lithium, manganese, and nickel.

[0076] Methods for measuring the amount of metal in the first coating layer of a layered positive electrode active material may include scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) of the layered positive electrode active material. The amount of boron and / or aluminum in the first coating layer can be determined by analysis. In addition to SEM-EDS, the amount of metal in the first coating layer can also be measured by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0077] Layered positive electrode active materials can include lithium-nickel composite oxides as nickel-based active materials. For example, layered positive electrode active materials can include high-nickel positive electrode active materials containing a large amount of nickel. High-nickel positive electrode active materials can achieve high capacity and high performance. For example, layered positive electrode active materials can include layered lithium-nickel composite oxides represented by the following chemical formula 1.

[0078] Chemical Formula 1: Li a1 Ni x1 Co y1 Mn z1 X c1 O 2-b1 In chemical formula 1, 0.8 ≤ a1 ≤ 1.2, 0.9 ≤ x1 ≤ 1.0, 0 ≤ y1 ≤ 0.1, 0 ≤ z1 ≤ 0.1, 0 ≤ c1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, and x1 + y1 + z1 + c1 = 1. X can be or include at least one of Al, Ti, Mg, Zr, Mo, and Nb. X can be or include dopants doped in the layered positive electrode active material.

[0079] Olivine-based positive electrode active materials In an example embodiment, the second positive electrode active material layer CAL2 may include an olivine-based positive electrode active material. The olivine-based positive electrode active material may have a single-particle shape. Each single particle may consist of approximately 2 to approximately 100 independent particles attached to each other.

[0080] In an example embodiment, the olivine-based positive electrode active material may include a second coating layer on its surface. The second coating layer may substantially completely or partially cover the surface of the olivine-based positive electrode active material. For example, the second coating layer may include carbon and / or carbon-containing compounds. The second coating layer may also include a metal-containing compound such as at least one of 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 a metal oxide, a metal hydroxide, a metal carbonate, or a complex or mixture thereof. The metal-containing compound may also include another metallic or non-metallic element. For example, the metal-containing compound may also include lithium. The second coating layer can improve the structural stability and conductivity of the olivine-based positive electrode active material. For example, the olivine-based positive electrode active material may include an olivine-based lithium compound represented by the following chemical formula 2.

[0081] Chemical formula 2: Li a2 Fe x2 B y2 PO 4-b2 In chemical formula 2, 0.8 ≤ a² ≤ 1.2, 0.1 ≤ x² ≤ 1.0, 0 ≤ y² ≤ 0.05, 0 ≤ b² ≤ 0.05, and x² + y² ≤ 1. For example, x² + y² = 1. B can be or includes at least one of Ti, Mg, V, and Nb. B can be or includes a dopant doped in olivine-based positive electrode active materials. For example, B can include Ti.

[0082] The olivine-based positive electrode active material may also include carbon derived from the second coating layer. The amount of carbon in the olivine-based positive electrode active material may be in the range of about 0.5 wt% to about 5 wt%, about 0.5 wt% to about 3 wt%, or about 0.5 wt% to about 2 wt%.

[0083] Still refer to Figure 6 According to an exemplary embodiment of this disclosure, a plurality of pores THO1, THO2 can be formed on each of the first positive electrode active material layer CAL1 and the second positive electrode active material layer CAL2 included in the positive electrode active material layer AML1, having a given size and depth. This can improve the uneven transport rate between the upper and lower portions of the layer on which the plurality of pores THO1, THO2 are formed, thereby enhancing the fast-charging characteristics of the battery.

[0084] The first positive electrode active material layer CAL1 may include multiple first pores THO1, and the second positive electrode active material layer CAL2 may include multiple second pores THO2.

[0085] Multiple first pores THO1 can be formed on the upper part of the first positive electrode active material layer CAL1, and can extend from the top surface of the first positive electrode active material layer CAL1 toward the bottom surface. The first pores THO1 can be adjacent to or in contact with a second positive electrode active material layer CAL2 disposed on the first positive electrode active material layer CAL1. Multiple second pores THO2 can be formed on the upper part of the second positive electrode active material layer CAL2, and can extend from the top surface of the second positive electrode active material layer CAL2 toward the bottom surface. Optionally, the second pores THO2 can be adjacent to or in contact with a second positive electrode active material layer CAL2 disposed on the first positive electrode active material layer CAL1. Figure 6 The third-party indicator extends in the opposite direction to D3. The second pore THO2 may be adjacent to or in contact with the membrane 30 disposed on the second positive electrode active material layer CAL2.

[0086] The density (or pitch) and depth of the first pore THO1 in the first positive electrode active material layer CAL1 can differ from the density (or pitch) and depth of the second pore THO2 in the second positive electrode active material layer CAL2. See below for reference. Figures 7 to 9 The density and depth of the first pore THO1 and the second pore THO2 will be discussed in further detail.

[0087] In an example embodiment, the volume occupied by the first pore THO1 can be in the range of about 1% to about 10% of the total volume of the first positive electrode active material layer CAL1. Furthermore, the volume occupied by the second pore THO2 can be in the range of about 1% to about 10% of the total volume of the second positive electrode active material layer CAL2.

[0088] Reference Figures 7 to 9 The following description focuses on the positive electrode for a rechargeable lithium battery according to exemplary embodiments of the present disclosure.

[0089] Figure 7 It is shown Figure 6 An enlarged view of an example of part M depicted in the image. Figure 8 This is a partially enlarged plan view showing the first positive electrode active material layer according to an exemplary embodiment of the present disclosure. Figure 9 This is a partially enlarged plan view showing the second positive electrode active material layer according to an exemplary embodiment of the present disclosure.

[0090] Reference Figure 7In an exemplary embodiment of this disclosure, a plurality of first pores THO1 can be formed with a relatively small depth and a relatively high density. The first pores THO1 can be spaced apart from each other at a given interval along one surface of the first positive electrode active material layer CAL1. Conversely, a plurality of second pores THO2 can be formed with a relatively low density and a relatively large depth. The second pores THO2 can be spaced apart from each other at a given interval along one surface of the second positive electrode active material layer CAL2.

[0091] Reference Figure 8 Multiple first holes THO1 may be arranged in a first direction D1 with a first pitch PI1. Each or at least one of the first holes THO1 may have a first diameter DI1. The hole forming process described later may allow the first holes THO1 to have different diameters from each other. The first diameter DI1 may refer to the average diameter. The first distance INT1 may be set as the interval between the first holes THO1 arranged adjacent to each other. The first pitch PI1 may be the sum of the first diameter DI1 and the first distance INT1.

[0092] In exemplary embodiments of this disclosure, the ratio of the first diameter DI1 to the first pitch PI1 can be in the range of about 0.1 to about 0.6, about 0.3 to about 0.6, about 0.2 to about 0.4, or about 0.1 to about 0.4. For example, the ratio (DI1 / PI1) can be in the range of about 0.2 to about 0.4.

[0093] When the ratio (DI1 / PI1) is less than about 0.2, the first depth (DEP1) of the first pore (THO1) may not be formed deep enough to allow the electrolyte to fully penetrate into the first positive electrode active material layer (CAL1). Conversely, when the ratio (DI1 / PI1) is greater than about 0.4, the size of the first pore (THO1) may become excessively large and may lead to a deterioration in the structural stability of the positive electrode active material layer (AML1). Furthermore, the first pore (THO1) may cause the first positive electrode active material layer (CAL1) to have a reduced volume, which may result in a reduction in the capacity of the positive electrode active material layer (AML1).

[0094] Reference Figure 9 Multiple second holes THO2 can be arranged in a first direction D1 with a second pitch PI2. Each or at least one of the second holes THO2 can have a second diameter DI2. The hole forming process described later may allow the second holes THO2 to have different diameters from each other. The second diameter DI2 may refer to the average diameter. The second distance INT2 can be set as the interval between second holes THO2 arranged adjacent to each other. The second pitch PI2 can be the sum of the second diameter DI2 and the second distance INT2.

[0095] In exemplary embodiments of this disclosure, the ratio of the second diameter DI2 to the second pitch PI2 can be in the range of about 0.1 to about 0.6, about 0.3 to about 0.6, about 0.2 to about 0.4, or about 0.1 to about 0.4. For example, the ratio (DI2 / PI2) can be in the range of about 0.2 to about 0.4.

[0096] When the ratio (DI2 / PI2) is less than about 0.2, the second depth (DEP2) of the second pore (THO2) may not be formed deep enough to allow the electrolyte to fully penetrate into the second positive electrode active material layer (CAL2). Conversely, when the ratio (DI2 / PI2) is greater than about 0.4, the size of the second pore (THO2) may become excessively large, leading to a deterioration in the structural stability of the positive electrode active material layer (AML1). Furthermore, the second pore (THO2) may cause the second positive electrode active material layer (CAL2) to have a reduced volume, which may result in a reduction in the capacity of the positive electrode active material layer (AML1).

[0097] As described above, Figure 8 and Figure 9 Enlarged planar views showing the first positive electrode active material layer CAL1 and the second positive electrode active material layer CAL2 are depicted respectively. Figure 8 The first positive electrode active material layer CAL1 shown can have the same properties as... Figure 9 The second positive electrode active material layer CAL2 shown has the same area. The number of first pores THO1 per unit area of ​​the first positive electrode active material layer CAL1 can be greater than the number of second pores THO2 per unit area of ​​the second positive electrode active material layer CAL2. According to an exemplary embodiment of this disclosure, the density of the plurality of first pores THO1 can be greater than the density of the plurality of second pores THO2.

[0098] In this specification, the term "density" may refer to the number of pores per unit area.

[0099] For example, Figure 8 The study depicted 46 first pores (THO1) formed in a unit area, and... Figure 9 Ten secondary pores of THO2 were depicted forming in a unit area. However, the number of pores is not limited to this. Figure 8 and Figure 9 The quantities shown can be varied depending on the hole pitch.

[0100] For example, the first pitch PI1 of the first hole THO1 can be smaller than the second pitch PI2 of the second hole THO2. In an example embodiment, the ratio of the second pitch PI2 to the first pitch PI1 can be in the range of about 2 to about 5.

[0101] According to an exemplary embodiment of this disclosure, the first diameter DI1 of the first hole THO1 may be smaller than the second diameter DI2 of the second hole THO2. In the exemplary embodiment, the ratio of the second diameter DI2 to the first diameter DI1 may be in the range of about 1.5 to about 3.

[0102] Figure 8 and Figure 9 The holes THO1 and THO2 are depicted by way of example and have generally circular planar shapes. The planar shapes and arrangements of holes THO1 and THO2 are not limited to those shown in the figures. For example, holes THO1 and THO2 may have generally elliptical or generally polygonal planar shapes, but this disclosure is not particularly limited thereto.

[0103] Return to reference Figure 7 The average depth of the first hole THO1 can be a first depth DEP1, and the average depth of the second hole THO2 can be a second depth DEP2. The first depth DEP1 can be different from the second depth DEP2. The first hole THO1 can be formed to be relatively shallower than the second hole THO2. In an example embodiment, the ratio of the second depth DEP2 to the first depth DEP1 can be in the range of about 1.2 to about 3.

[0104] The first positive electrode active material layer CAL1 may have a first thickness TK1, and the second positive electrode active material layer CAL2 may have a second thickness TK2.

[0105] In exemplary embodiments of this disclosure, the ratio of the first depth DEP1 to the first thickness TK1 of the first positive electrode active material layer CAL1 can be in the range of about 0.1 to about 0.5, about 0.3 to about 0.5, about 0.2 to about 0.4, or about 0.1 to about 0.4. For example, the ratio (DEP1 / TK1) can be in the range of about 0.2 to about 0.4. The first thickness TK1 of the first positive electrode active material layer CAL1 can be in the range of about 10 μm to about 200 μm, about 30 μm to about 200 μm, or about 50 μm to about 150 μm. The second thickness TK2 of the second positive electrode active material layer CAL2 can be in the range of about 100 μm to about 400 μm, about 100 μm to about 300 μm, or about 150 μm to about 300 μm.

[0106] When the ratio of the first depth DEP1 to the first thickness TK1 of the first positive electrode active material layer CAL1 is less than about 0.2, the transport rate of lithium ions in the first positive electrode active material layer CAL1 may decrease, resulting in a decrease in the battery charge / discharge rate. The ratio of the second thickness TK2 to the first thickness TK1 may be in the range of about 1 to 4, about 1.3 to about 3.8, or about 1.5 to about 3.3.

[0107] In an exemplary embodiment of this disclosure, the ratio of the second depth DEP2 to the second thickness TK2 of the second positive electrode active material layer CAL2 can be in the range of about 0.3 to about 0.7, about 0.3 to about 0.6, about 0.4 to about 0.7, or about 0.5 to about 0.7. For example, the ratio (DEP2 / TK2) can be in the range of about 0.5 to about 0.7.

[0108] When the ratio of the second depth DEP2 to the second thickness TK2 of the second positive electrode active material layer CAL2 is greater than approximately 0.7, the depth of the second pore THO2 may become excessively large, leading to a deterioration in the structural stability of the second positive electrode active material layer CAL2. The second pore THO2 may cause the second positive electrode active material layer CAL2 to have a reduced volume, which may result in a reduction in the capacity of the positive electrode active material layer AML1.

[0109] According to an example of this disclosure, a plurality of first pores THO1 can be configured to allow the first positive electrode active material layer CAL1 to contact the electrolyte ELL. According to an example of this disclosure, a plurality of second pores THO2 can be configured to allow the second positive electrode active material layer CAL2 to contact the electrolyte ELL. Therefore, by forming a plurality of first pores THO1 and second pores THO2 on the first positive electrode active material layer CAL1 and the second positive electrode active material layer CAL2 respectively, the lithium-ion transport rate can be increased. As a result, the rechargeable lithium battery according to an example of this disclosure can have improved charge and discharge characteristics.

[0110] According to the examples of this disclosure, the reduction in volume of the positive electrode active material layer AML1 caused by the plurality of pores THO1, THO2 may not be significant. Therefore, the plurality of pores THO1, THO2 according to the exemplary embodiments of this disclosure can cause a significant increase in the charge / discharge rate of the rechargeable lithium battery without causing a significant reduction in battery capacity.

[0111] Figure 10 This is a cross-sectional view showing the positive electrode active material layer according to an exemplary embodiment of the present disclosure. (Refer to...) Figure 10 The pore formation process can be performed only on the first positive electrode active material layer CAL1, which is one of the first positive electrode active material layers CAL1 and CAL2. Compared to forming multiple pores THO1 and THO2 on both the first positive electrode active material layer CAL1 and CAL2, forming multiple first pores THO1 on only the first positive electrode active material layer CAL1 can reduce the decrease in battery capacity. Compared to forming multiple pores THO1 and THO2 on both the first positive electrode active material layer CAL1 and CAL2, forming multiple first pores THO1 on only the first positive electrode active material layer CAL1 may reduce conductivity.

[0112] Figure 11 This is a cross-sectional view showing the positive electrode active material layer according to an exemplary embodiment of the present disclosure. (Refer to...) Figure 11 The pore formation process can be performed only on the second positive electrode active material layer CAL2, which is one of the first positive electrode active material layers CAL1 and CAL2. Compared to forming multiple pores THO1 and THO2 on both the first and second positive electrode active material layers CAL1 and CAL2, forming multiple second pores THO2 on only the second positive electrode active material layer CAL2 can reduce the decrease in battery capacity. Compared to forming multiple pores THO1 and THO2 on both the first and second positive electrode active material layers CAL1 and CAL2, forming multiple second pores THO2 on only the second positive electrode active material layer CAL2 may reduce conductivity.

[0113] Manufacturing of positive electrode Figure 12 A cross-sectional view is shown illustrating a method for manufacturing a positive electrode according to an exemplary embodiment of the present disclosure.

[0114] Reference Figure 12 A method for manufacturing a positive electrode according to an example embodiment of the present disclosure may include: providing a positive electrode current collector COL1; forming a first positive electrode active material layer CAL1 on the positive electrode current collector COL1; performing a first pore forming process on the first positive electrode active material layer CAL1 to form a plurality of first pores THO1; forming a second positive electrode active material layer CAL2 on the first positive electrode active material layer CAL1 that has undergone the first pore forming process; and performing a second pore forming process on the second positive electrode active material layer CAL2 to form a plurality of second pores THO2. The first positive electrode active material layer CAL1 may include the above-described... Figure 7 The layered positive electrode active material discussed earlier. The second positive electrode active material layer CAL2 may include the layer on top of... Figure 7 The olivine-based positive electrode active materials discussed in the article.

[0115] Preparation of the first positive electrode active material layer The following describes in detail a method for preparing a first positive electrode active material layer according to some example embodiments of the present disclosure. A high-nickel precursor can be prepared. The high-nickel precursor may include the above-described chemical formula 1. The amount of Ni in the high-nickel precursor relative to the total metal content may be greater than about 80 at%. In example embodiments, the high-nickel precursor may further include Co and Mn.

[0116] In an example embodiment, high-nickel precursors can be obtained via a co-precipitation method. For instance, a co-precipitation method may include dissolving a transition metal feedstock in a solvent such as distilled water, and inducing precipitation by continuously supplying a transition metal salt solution, along with a chelate and an alkaline aqueous solution, to a reactor. The precipitate can be collected as a slurry, and the slurry solution can then be filtered and dried to obtain a metal composite oxide or a high-nickel precursor.

[0117] In this disclosure, the transition metal feedstock may include a metal salt of Ni. The transition metal feedstock may also include a metal salt of at least one of Co and Mn. The metal salt may include at least one of sulfates, nitrates, acetates, halides, and hydroxides, and is not particularly limited, as long as the material is soluble in a solvent. According to an example embodiment, the transition metal feedstock may include at least one of nickel salts, cobalt salts, and manganese salts. The transition metal feedstocks can be mixed by adjusting the molar ratio so that the high-nickel precursor has a nickel content equal to or greater than about 80 at%

[0118] High-nickel precursors and lithium sources can be mixed in a certain ratio to form a mixture. For example, high-nickel precursors and lithium sources can be mixed in a molar ratio of about 1:1. The lithium source may include at least one of lithium oxide, lithium hydroxide, lithium chloride, lithium nitrate, lithium nitrite, lithium formate, lithium acetate, lithium oxalate, lithium carbonate, lithium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, and lithium citrate.

[0119] The solvent can be removed from the mixture to form a dry mixture. The dry mixture can be calcined. The temperature of the calcination process can be in the range of about 700°C to about 1,000°C or about 900°C to about 1,000°C. The calcination process can be performed in an oxidizing atmosphere (such as air or oxygen, for example). The heat treatment time of the calcination process can be in the range of about 10 hours to about 30 hours. In the exemplary embodiments of this disclosure, a preliminary calcination process can be performed additionally at a temperature in the range of about 150°C to about 800°C prior to the calcination process.

[0120] In exemplary embodiments of this disclosure, the calcination process can be performed after a flux is additionally introduced into the mixture. The flux may be or include a compound comprising at least one of Zr, La, S, and Nb. The use of a flux can advantageously morph the layered positive electrode active material included in the first positive electrode active material layer into a single-particle shape. Furthermore, the layered positive electrode active material can have an increased average particle size.

[0121] The calcination process can form layered positive electrode active materials from a mixture including high-nickel precursors and lithium sources. A pulverization process can then be performed on the synthesized positive electrode active materials.

[0122] A coating process can be performed on the pulverized layered positive electrode active material. For example, the layered positive electrode active material and coating material can be added to a solvent and mixed in the solvent. The coating material may include, for example, boron and / or aluminum. The layered positive electrode active material can be filtered and dried, and then a surface treatment can be performed on the layered positive electrode active material. The surface treatment may include a heat treatment process performed in an oxidizing atmosphere (such as air or oxygen, for example). The surface treatment can be performed at a temperature in the range of about 500°C to about 800°C.

[0123] In exemplary embodiments of this disclosure, the coating process may include a dry coating process. For example, layered positive electrode active material and coating raw materials may be introduced into a dry coating apparatus without any solvent and may be stirred to mix with each other. Surface treatment may be performed on the resulting dry mixture.

[0124] Preparation of the second positive electrode active material layer The following describes in detail a method for preparing a second positive electrode active material layer according to some exemplary embodiments of the present disclosure. An iron phosphate precursor, a lithium source, a carbon source, and a dopant source can be added to and mixed in a solvent. For example, the solvent can be water or ethanol. The iron phosphate precursor can be or include at least one of a compound containing all of iron (F) and phosphorus (P), and a mixture of a compound containing iron (F) and a compound containing phosphorus (P). For example, the iron phosphate precursor can include FePO4·H2O or a mixture of FeSO4 and H3PO4.

[0125] The lithium source may include at least one of lithium oxide, lithium hydroxide, lithium chloride, lithium nitrate, lithium nitrite, lithium formate, lithium acetate, lithium oxalate, lithium carbonate, lithium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, and lithium citrate.

[0126] Carbon sources may include at least one of glucose, sucrose, fructose, cellulose, starch, citric acid, polyacrylic acid, polyethylene glycol, and dopamine.

[0127] The dopant source may include oxides and / or chlorides of a dopant metal. For example, the dopant source may include at least one of titanium oxide, magnesium oxide, vanadium oxide, and niobium oxide.

[0128] Wet milling can be performed on mixtures. Wet milling can use common wet mills that can control the temperature. For example, wet milling can use at least one of bead mills, ball mills, attire mills, apex mills, super mills, and basket mills. In the wet milling process, particles in the mixture can be pulverized into fine sizes.

[0129] Solvents can be removed from the mixture to form a dry mixture. In exemplary embodiments of this disclosure, the formation of a dry mixture may include performing direct evaporation on the mixture. For example, direct evaporation may include static drying or spray drying.

[0130] The dry mixture can be calcined under an inert atmosphere. The inert atmosphere can be a nitrogen atmosphere and / or an argon atmosphere. The calcination temperature can be in the range of about 500°C to about 1,000°C or about 600°C to about 800°C. The calcination process can be carried out for about 4 hours to about 20 hours or about 6 hours to about 12 hours. Calcination of the dry mixture can form an olivine-based positive electrode active material comprising compounds represented by the above chemical formula 2. The calcined olivine-based positive electrode active material can be subjected to a dry pulverization process.

[0131] At least one of the formation of the first positive electrode active material layer CAL1 and the second positive electrode active material layer CAL2 can be performed by a wet process or a dry process. In an example embodiment, the first positive electrode active material layer CAL1 can be formed by a wet process, and the second positive electrode active material layer CAL2 can be formed by a dry process. In an example embodiment, the first positive electrode active material layer CAL1 can be formed by a dry process, and the second positive electrode active material layer CAL2 can also be formed by a dry process. However, this disclosure is not limited thereto.

[0132] The wet process can be performed by mixing the positive electrode active material, conductive material, and binder in a solvent to prepare a positive electrode mixture, and then coating the mixture onto a current collector, drying, and pressing it. The solvent in the slurry can be or includes solvents commonly used in the art, for example, it may include at least one of dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone, water, and combinations thereof.

[0133] The dry process can be performed as follows: the positive electrode active material, dry conductive material and dry binder are dry mixed in the absence of solvent to prepare a positive electrode mixture, and the mixture is placed on a current collector and pressed.

[0134] Each of the first and second hole forming processes can be performed using one of laser, stamp, and roller, but this disclosure is not limited thereto. In example embodiments, such as Figure 12 As shown, holes THO1 and THO2 can be physically formed by molds STP1 and STP2 having small protrusions PRJ1 and PRJ2 on them.

[0135] For example, a plurality of first holes THO1 can be formed using a first mold STP1 that includes a first protrusion PRJ1. A plurality of second holes THO2 can be formed using a second mold STP2 that includes a second protrusion PRJ2.

[0136] The protrusion length of the first protrusion PRJ1 may differ from the protrusion length of the second protrusion PRJ2. For example, the protrusion length of the first protrusion PRJ1 may be less than the protrusion length of the second protrusion PRJ2. The diameter of the first protrusion PRJ1 may also differ from the diameter of the second protrusion PRJ2. For example, the diameter of the first protrusion PRJ1 may be less than the diameter of the second protrusion PRJ2.

[0137] The first protrusion PRJ1 and the second protrusion PRJ2 may independently have at least one of a conical shape, a pyramidal shape, a cylindrical shape, and a prism shape, but this disclosure is not limited thereto.

[0138] The positive electrode can then undergo rolling, cutting, and slit processes sequentially. The positive electrode 10, separator 30, and negative electrode 20 can be stacked, and an electrolyte ELL can be provided to manufacture a rechargeable lithium battery according to this disclosure.

[0139] Figure 13 This is a flowchart illustrating a method for manufacturing a positive electrode for a rechargeable lithium battery according to various disclosed examples. Figure 13 In this method 1300, operation 1310 includes providing a positive electrode current collector. Operation 1320 includes forming a first positive electrode active material layer on the positive electrode current collector. Operation 1330 includes performing a first hole-forming process on the first positive electrode active material layer to form a plurality of first holes. For example, forming the plurality of first holes is performed using a first mold including a first protrusion. Operation 1340 includes forming a second positive electrode active material layer on the first positive electrode active material layer to which the first hole-forming process has been performed. Operation 1350 includes performing a second hole-forming process on the second positive electrode active material layer to form a plurality of second holes. In an example, forming the plurality of second holes is performed using a second mold including a second protrusion. For example, the protrusion length of the first protrusion is less than the protrusion length of the second protrusion. In another example, the diameter of the first protrusion is less than the diameter of the second protrusion. In yet another example, the first protrusion and the second protrusion independently have one of a conical shape, a pyramidal shape, a cylindrical shape, and a prismatic shape. The first positive electrode active material layer may include a layered positive electrode active material, and the second positive electrode active material layer includes an olivine-based positive electrode active material. In the example, at least one of forming the first positive electrode active material layer and forming the second positive electrode active material layer is performed by a wet process or a dry process. In other examples, each or at least one of the first and second hole forming processes is performed using a laser, a mold, and a roller.

[0140] Example 1 To prepare the first positive electrode active material layer, a co-precipitation process was used to prepare a high-nickel precursor. For example, nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and manganese sulfate (MnSO4·H2O) in a molar ratio of 92:5:2 as nickel-based metal hydroxides were dissolved in distilled water as a solvent to prepare a metal raw material mixture solution. The metal raw material mixture solution, ammonium hydroxide, and sodium hydroxide were added to a reactor and reacted in the reactor. The slurry solution in the reactor was filtered and washed with high-purity distilled water. The washed material was dried in a hot blast furnace at 210°C for 24 hours to obtain a small particle precursor (NiSO4·6H2O) with a particle size of approximately 4 μm. 0.92 OCo 0.05 Mn 0.02 Powder of (OH)2.

[0141] Using a Henschel mixer, the high-nickel precursor and anhydrous lithium hydroxide (LiOH) are dry-mixed. Lithium and transition metals are mixed at a molar ratio of approximately 1:1. The transition metals are the sum of the transition metals contained in the high-nickel precursor (Ni + Co + Mn). A flux is additionally added to the mixture, and the mixture is heat-treated (or calcined) at approximately 750°C for 15 hours to synthesize the high-nickel positive electrode active material. The high-nickel positive electrode active material is then pulverized using a jet mill at a pressure of 3 bar.

[0142] The high-nickel positive electrode active material or the first positive electrode active material is added to distilled water and washed with distilled water. Boron and aluminum coating is performed by introducing boron oxide and aluminum oxide, which are present in an amount of 3 mol% relative to the total amount of transition metals in the high-nickel positive electrode active material. The first positive electrode active material is dried at 150°C for 12 hours and then heat-treated (or surface-treated) at approximately 700°C for 15 hours in an oxygen atmosphere.

[0143] To prepare the second positive electrode active material layer, FePO4·H2O (as a precursor of iron phosphate), lithium carbonate, 2500 ppm titanium dioxide, and 8 wt% glucose were mixed in water at a molar ratio of 1:1.03. The mixture was wet-milled using a ball mill. The mixture was then evaporated and dried on a heated furnace tray, and subsequently placed in a vacuum oven at 85°C and dried for 4 hours. The dried mixture was calcined at 650°C for approximately 10 hours. The calcined mixture was then pulverized to obtain the second positive electrode mixture in single-particle form.

[0144] A first positive electrode active material is coated onto an aluminum current collector. The coated first positive electrode active material is first dried at 80°C, and then pressed to form a first positive electrode active material layer. A hole-forming process using a mold is performed on the first positive electrode active material layer to form a first hole. A second positive electrode mixture is placed on the first positive electrode active material layer in which the first hole is formed, and then pressed to form a second positive electrode active material layer.

[0145] In the hole forming process for forming the first hole THO1, the hole is processed such that the ratio of the first depth to the first thickness (DEP1 / TK1) is equal to 0.25 and the ratio of the first diameter to the first pitch (DI1 / PI1) is equal to 0.3, thereby manufacturing the positive electrode of Example 1.

[0146] Example 2 The first positive electrode active material of Example 1 was coated onto an aluminum current collector. The coated first positive electrode active material was first dried at 80°C, and then pressed to form a first positive electrode active material layer. No pore-forming process was performed on the first positive electrode active material layer, and the second positive electrode mixture of Example 1 was placed on the first positive electrode active material layer and pressed to form a second positive electrode active material layer. A pore-forming process using a mold was performed on the second positive electrode active material layer to form a second pore.

[0147] In the hole forming process used to form the second hole THO2, the hole is machined such that the ratio of the second depth to the second thickness (DEP2 / TK2) is equal to 0.4 and the ratio of the second diameter to the second pitch (DI2 / PI2) is equal to 0.3.

[0148] Example 3 The first positive electrode active material of Example 1 was coated onto an aluminum current collector. First, the coated first positive electrode active material was dried at 80°C, and then pressed to form a first positive electrode active material layer. A hole-forming process using a mold was performed on the first positive electrode active material layer to form a first hole. The second positive electrode mixture of Example 1 was placed on the first positive electrode active material layer in which the first hole was formed, and then pressed to form a second positive electrode active layer. A hole-forming process using a mold was performed on the second positive electrode active layer to form a second hole.

[0149] In the hole-forming process for forming the first hole THO1, the hole is machined such that the ratio of the first depth to the first thickness (DEP1 / TK1) is equal to 0.25 and the ratio of the first diameter to the first pitch (DI1 / PI1) is equal to 0.3. In the hole-forming process for forming the second hole THO2, the hole is machined such that the ratio of the second depth to the second thickness (DEP2 / TK2) is equal to 0.4 and the ratio of the second diameter to the second pitch (DI2 / PI2) is equal to 0.3. In this case, the hole is machined such that the ratio of the second depth to the first depth (DEP2 / DEP1) is equal to 2 and the ratio of the second pitch to the first pitch (PI2 / PI1) is equal to 3.5, thereby manufacturing the positive electrode of Example 3 (see Figure 7 ).

[0150] Comparative Example 1 A monolayer of positive electrode active material is prepared, comprising only the second positive electrode active material of Example 1, without performing a separate pore formation process.

[0151] Comparative Example 2 A monolayer of positive electrode active material, comprising only the first positive electrode active material of Example 1, is prepared, and the pore formation process is not performed separately.

[0152] Comparative Example 3 The first positive electrode active material layer and the second positive electrode active material layer of Example 1 were prepared without performing the pore formation process separately.

[0153] The positive electrodes of Examples 1 to 3 and Comparative Example 3 are summarized and shown in Table 1 below.

[0154] Table 1:

[0155] Evaluation Example 1: Energy Density The pore depth and energy density of the positive electrode layers according to Examples 1 to 3 and Comparative Examples 1 to 3 were measured and are shown in Table 2 below.

[0156] Table 2:

[0157] Evaluation 2: Cycle life characteristics The cycle life characteristics of the monomers manufactured using the positive electrode active material layers according to Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated and are shown in Table 3 below. Table 3 lists the number of cycles until the battery performance reaches 80% and the average efficiency after 100 cycles.

[0158] Table 3:

[0159] Referring to Table 2, compared to Comparative Examples 1 to 3, Examples 1 to 3 showed almost no decrease in specific capacity. Since the loss of the positive electrode active material only occurred at a level that did not affect battery performance, the specific capacity of the battery did not decrease significantly.

[0160] Referring to Table 3, Examples 1 to 3 exhibit improved cycle life characteristics compared to Comparative Examples 1 to 3. Therefore, the rechargeable lithium-ion batteries according to some exemplary embodiments of this disclosure include both layered positive electrode active materials and olivine-based positive electrode active materials, and a pore-forming process is performed on each positive electrode active material layer, which improves the battery's long cycle life characteristics.

[0161] In summary, since the rechargeable lithium battery according to some example embodiments of the present disclosure includes pores of appropriate size and depth, high specific capacity of the positive electrode and improved lithium-ion transport rate are achieved, thereby realizing desired or improved charge / discharge characteristics.

[0162] In this disclosure, multiple pores can be formed in each of the upper and lower portions constituting the positive electrode active material layer, thus providing a physical transport path for lithium ions. Furthermore, the lithium ion diffusion channels can be widened and shortened by configuring the pores to allow each positive electrode active material layer to contact the electrolyte, which can increase the lithium ion transport rate. Therefore, the rechargeable lithium battery according to this disclosure can exhibit desired or improved capacity and excellent charge / discharge characteristics.

[0163] While some exemplary embodiments of this disclosure have been discussed with reference to the accompanying drawings, it is understood that various changes in form and detail may be made therein without departing from the spirit and scope of this disclosure. It will be apparent to those skilled in the art that various substitutions, modifications, and alterations may be made therein without departing from the scope and spirit of this disclosure.

Claims

1. A positive electrode for a rechargeable lithium battery, the positive electrode comprising: Positive electrode current collector; as well as The positive electrode active material layer is located on the positive electrode current collector. The positive electrode active material layer includes a first positive electrode active material layer and a second positive electrode active material layer stacked on the positive electrode current collector. The first positive electrode active material layer comprises a layered positive electrode active material. The second positive electrode active material layer includes olivine-based positive electrode active materials. The first positive electrode active material layer includes a plurality of first pores, and The second positive electrode active material layer includes a plurality of second pores.

2. The positive electrode according to claim 1, wherein: The first positive electrode active material layer comprises a compound of formula 1. The second positive electrode active material layer includes a compound of chemical formula 2. Chemical Formula 1: Li a1 Ni x1 Co y1 Mr z1 X c1 O 2-b1 In chemical formula 1, 0.8 ≤ a1 ≤ 1.2, 0.9 ≤ x1 ≤ 1.0, 0 ≤ y1 ≤ 0.1, 0 ≤ z1 ≤ 0.1, 0 ≤ c1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, and x1 + y1 + z1 + c1 = 1. X includes at least one of Al, Ti, Mg, Zr, Mo, and Nb. Chemical formula 2: Li a2 Fe x2 B y2 PO 4-b2 In chemical formula 2, 0.8 ≤ a² ≤ 1.2, 0.1 ≤ x² ≤ 1.0, 0 ≤ y² ≤ 0.05, 0 ≤ b² ≤ 0.05, and x² + y² ≤ 1. B includes at least one of Ti, Mg, V and Nb.

3. The positive electrode according to claim 1, wherein: The volume occupied by the plurality of first pores is in the range of 1% to 10% of the total volume of the first positive electrode active material layer, and The volume occupied by the plurality of second pores is in the range of 1% to 10% of the total volume of the second positive electrode active material layer.

4. The positive electrode according to claim 1, wherein: The plurality of first holes have a first pitch. The plurality of second holes have a second pitch, and The first pitch is smaller than the second pitch.

5. The positive electrode according to claim 4, wherein: The average diameter of the plurality of first holes is the first diameter. The average diameter of the plurality of second holes is the second diameter. The ratio of the first diameter to the first pitch is in the range of 0.2 to 0.4, and The ratio of the second diameter to the second pitch is in the range of 0.2 to 0.

4.

6. The positive electrode according to claim 4, wherein, The ratio of the second pitch to the first pitch is in the range of 2 to 5.

7. The positive electrode according to claim 1, wherein, The density of the plurality of first pores is greater than the density of the plurality of second pores.

8. The positive electrode according to claim 1, wherein: The average depth of the plurality of first holes is the first depth. The average depth of the plurality of second holes is the second depth, and The first depth is less than the second depth.

9. The positive electrode according to claim 8, wherein, The ratio of the second depth to the first depth is in the range of 1.2 to 3.

10. The positive electrode according to claim 1, wherein: The thickness of the first positive electrode active material layer is in the range of 50 μm to 150 μm, and The thickness of the second positive electrode active material layer is in the range of 150 μm to 300 μm.

11. The positive electrode according to claim 1, wherein, The ratio of the thickness of the second positive electrode active material layer to the thickness of the first positive electrode active material layer is in the range of 1.5 to 3.

3.

12. The positive electrode according to claim 1, wherein: The plurality of first holes are configured to allow the first positive electrode active material layer to contact the electrolyte, and The plurality of second holes are configured to allow the second positive electrode active material layer to contact the electrolyte.

13. A method for manufacturing a positive electrode for a rechargeable lithium battery, the method comprising the steps of: Provide a positive electrode current collector; A first positive electrode active material layer is formed on the positive electrode current collector; A first pore formation process is performed on the first positive electrode active material layer to form a plurality of first pores; A second positive electrode active material layer is formed on the first positive electrode active material layer after the first hole formation process has been performed; as well as A second pore formation process is performed on the second positive electrode active material layer to form multiple second pores. Wherein, the first positive electrode active material layer comprises a layered positive electrode active material, and The second positive electrode active material layer includes olivine-based positive electrode active materials.

14. The method according to claim 13, wherein, At least one of the steps of forming the first positive electrode active material layer and forming the second positive electrode active material layer is performed via a wet process and a dry process.

15. The method according to claim 13, wherein, At least one of the first hole forming process and the second hole forming process is performed using a laser, a printing mold, and a roller.

16. The method of claim 13, wherein: The step of forming the plurality of first holes is performed using a first mold including a first protrusion, and The step of forming the plurality of second holes is performed using a second mold including a second protrusion.

17. The method according to claim 16, wherein, The protrusion length of the first protrusion is less than the protrusion length of the second protrusion.

18. The method according to claim 16, wherein, The diameter of the first protrusion is smaller than the diameter of the second protrusion.

19. The method of claim 16, wherein, The first protrusion and the second protrusion each have one of the following shapes: conical, pyramidal, cylindrical, and prismatic.

20. A rechargeable lithium battery, said rechargeable lithium battery comprising: The positive electrode according to any one of claims 1 to 12; The negative electrode includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector; as well as A diaphragm is located between the positive electrode and the negative electrode.

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