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

Abstract

The invention discloses a positive electrode, a rechargeable lithium battery and a manufacturing method thereof. A rechargeable lithium battery includes a positive electrode including a current collector, an electrolyte, and a negative electrode. The positive electrode includes a first positive electrode active material layer on the current collector and a second positive electrode active material layer on the first positive electrode active material layer. The second positive electrode active material layer includes a positive electrode active material including a lithium composite transition metal oxide, a plurality of pores, and a residual layer between the positive electrode active material and the pores. The residual layer includes sulfur (S).

Description

[0001] This application claims priority to Korean Patent Application No. 10-2024-0150996, filed on October 30, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] Examples of this disclosure relate to a positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the 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 can be beneficial.

[0004] A rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte. The positive and negative electrodes contain active materials that can be inserted and extracted, and generate electrical energy from the oxidation and reduction reactions that occur during the insertion and extraction of lithium ions. Summary of the Invention

[0005] Example embodiments of this disclosure include rechargeable lithium batteries in which the impregnation properties of the electrolyte are improved to enhance battery capacity, lifespan characteristics, and fast-charging characteristics.

[0006] According to an example embodiment of this disclosure, a rechargeable lithium battery may include: a positive electrode, including a current collector; an electrolyte; and a negative electrode. The positive electrode may include a first positive electrode active material layer on the current collector; and a second positive electrode active material layer on the first positive electrode active material layer. The second positive electrode active material layer may include: a positive electrode active material, including a lithium complex transition metal oxide; a plurality of pores; and a residual layer between the positive electrode active material and the pores. The residual layer may include sulfur (S).

[0007] According to an example embodiment of this disclosure, a method for manufacturing a rechargeable lithium battery may include the following steps: coating a first positive electrode slurry onto a current collector to form a first positive electrode active material layer; coating a second positive electrode slurry onto the first positive electrode active material layer to form a second positive electrode active material layer; and providing an electrolyte onto the first and second positive electrode active material layers. The second positive electrode slurry may include additives. The step of providing the electrolyte may include releasing the additives from the second positive electrode active material layer; and causing the released additives to form a plurality of pores in the second positive electrode active material layer.

[0008] According to an example embodiment of this disclosure, the positive electrode for a rechargeable lithium battery may include a current collector; a first positive electrode active material layer on the current collector; and a second positive electrode active material layer on the first positive electrode active material layer. The second positive electrode active material layer may include: a positive electrode active material, including a lithium complex transition metal oxide; a plurality of pores; and a residual layer between the positive electrode active material and the pores. The residual layer may include sulfur (S). Attached Figure Description

[0009] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure is shown.

[0010] Figures 2 to 5 A simplified diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure is shown.

[0011] Figure 6 A cross-sectional view is shown illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure.

[0012] Figure 7 A cross-sectional view is shown illustrating the positive electrode of a rechargeable lithium battery according to an exemplary embodiment of the present disclosure.

[0013] Figure 8 An enlarged view of portion "M" illustrating an exemplary embodiment according to this disclosure is shown.

[0014] Figure 9 An enlarged view of portion “M” showing a comparative example according to this disclosure is displayed.

[0015] Figure 10 The diagram shows porosity as... Figure 7 The graph depicts a function in the X direction.

[0016] Figure 11 The graphs shown illustrate the temperature and voltage curves based on charging in each of the example and comparative examples.

[0017] Figure 12 This is a flowchart illustrating a method for manufacturing a rechargeable lithium battery according to an example embodiment. Detailed Implementation

[0018] To fully understand 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, exemplary embodiments are provided to illustrate the scope of this disclosure and to enable those skilled in the art to fully understand its scope.

[0019] In this specification, it is 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 be present between them. In the figures, the thickness of some components may be exaggerated for the purpose of effectively explaining the technical content. Throughout the specification, the same reference numerals denote the same elements.

[0020] Unless otherwise stated in this specification, singular expressions may include plural expressions. Furthermore, unless otherwise stated, 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 specification do not exclude the presence or addition of one or more other components.

[0021] In this specification, the term "themselves (or combinations thereof)" may refer to mixtures, stacks, complexes, copolymers, alloys, blends, or reaction products.

[0022] Unless otherwise defined in this specification, particle size may be the average particle size. Furthermore, particle size refers to the average particle size (D) of particles having a cumulative volume of approximately 50% of 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 (e.g., by a particle size analyzer, transmission electron microscopy (TEM) images, or scanning electron microscopy (SEM) images). Alternatively, data analysis can be performed using a dynamic light scattering measurement device to count the number of particles in each particle size range, from which the average particle size (D) can be calculated. 50 The average particle size (D) can be measured using laser scattering. 50 In the laser scattering method, target particles are dispersed in a dispersion solvent and introduced into a laser scattering particle measuring device (e.g., the MT3000, commercially available from Microtrac Ltd.). The particles are irradiated with 28 kHz ultrasound at a power of 60 W, and the average particle size (D) is then calculated using a 50% particle size distribution standard within the measuring device. 50 ).

[0023] 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. 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 spaced apart 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 transfer between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move across the separator 30 toward one of the positive electrode 10 and the negative electrode 20.

[0027] In a rechargeable battery that includes a gel polymer electrolyte (or a semi-solid electrolyte) and a solid electrolyte, the rechargeable battery may include a solid electrolyte layer. In this case, the electrolyte layer may replace the separator 30 and the electrolyte ELL.

[0028] positive electrode 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 positive electrode active material and may also include a binder and / or conductive material. The amount of positive electrode active material in the positive electrode active material layer AML1 may range from about 90 wt% to about 99.5 wt% relative to 100 wt% of the positive electrode active material layer AML1. The amounts of binder and conductive material may each range from about 0.5 wt% to about 5 wt% relative to 100 wt% of the positive electrode active material layer AML1. The positive electrode active material layer AML1 may also include sacrificial positive electrode material and functional additives. The following description focuses on the positive electrode according to an exemplary embodiment of the present disclosure. Aluminum (Al) may be included as the current collector COL1, but the present disclosure is not limited thereto.

[0029] Positive electrode active material: As follows about Figure 7 The positive electrode active material layer AML1 discussed may include a first positive electrode active material layer LL and a second positive electrode active material layer HL on the first positive electrode active material layer LL. The first positive electrode active material layer LL may be disposed between the positive electrode current collector COL1 and the second positive electrode active material layer HL. The first positive electrode active material layer LL may be adjacent to the positive electrode current collector COL1, and the second positive electrode active material layer HL may be adjacent to the separator 30.

[0030] As follows about Figure 8The first positive electrode active material layer LL discussed may include a first positive electrode active material AM1 and a first pore PO1. The first positive electrode active material layer LL may include a plurality of first pore PO1s. The first positive electrode active material AM1 may include a compound capable of reversibly inserting and de-intercalating lithium (e.g., a lithiation intercalation compound). For example, the first positive electrode active material AM1 may include at least one type of composite oxide comprising lithium and a metal, wherein the metal is or includes at least one of cobalt, manganese, nickel, and combinations thereof.

[0031] The composite oxide can be or includes lithium transition metal composite oxides, such as at least one of lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium nickel cobalt oxide (NC), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium nickel manganese oxide (NM), lithium manganese oxide (LMO), lithium iron phosphate (LFP), and combinations thereof.

[0032] For example, the positive electrode active material may include a compound represented by one of the following chemical formulas: Li a A 1-b B b D2 (where 0.90≤a≤1 and 0≤b≤0.5), Li a E 1-b B b O 2-c D c (Where, 0.90≤a≤1, 0≤b≤0.5, and 0≤c≤0.05), LiE 2-b B b O 4-c D c (where 0 ≤ b ≤ 0.5 and 0 ≤ c ≤ 0.05), Li a Ni 1-b-c Co b B c D α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2), Li a Ni 1-b-c Co b B c O 2-α F α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2), Li a Ni 1-b-c Mn b B c D α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α≤2), Li a Ni1-b-c Mn b B c O 2-α F α (Where, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2), Li a Ni b E c G d O2 (where 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, and 0.001≤d≤0.1), Li a Ni b Co c Mn d G e O2 (where 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, and 0.001≤e≤0.1), Li a NiG b O2 (where 0.9≤a≤1 and 0.001≤b≤0.1), Li a CoG b O2 (where 0.90≤a≤1 and 0.001≤b≤0.1), Li a MnG b O2 (where 0.90≤a≤1 and 0.001≤b≤0.1), Li a Mn2G b O4 (where 0.90≤a≤1 and 0.001≤b≤0.1), QO2, QS2, LiQS2, V2O5, LiV2O5, LiIO2, LiNiVO4, Li 3-f J2(PO4)3 (where 0≤f≤2), Li 3-f Fe2(PO4)3 (where 0≤f≤2) and LiFePO4.

[0033] In the above chemical formulas, A may be or include at least one of Ni, Co, Mn and combinations thereof; B may be or include at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; D may be or include at least one of O, F, S, P and combinations thereof; E may be or include at least one of Co, Mn and combinations thereof; F may be or include at least one of F, S, P and combinations thereof; G may be or include at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V and combinations thereof; Q may be or include at least one of Ti, Mo, Mn and combinations thereof; I may be or include at least one of Cr, V, Fe, Sc, Y and combinations thereof; and J may be or include at least one of V, Cr, Mn, Co, Ni, Cu and combinations thereof.

[0034] For example, the first positive electrode active material AM1 may be or include 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%, 85 mol%, 90 mol%, 91 mol%, or 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. High-nickel positive electrode active materials can achieve high capacity and therefore can be used in high-capacity and high-density rechargeable lithium batteries. The first positive electrode active material AM1 may be present in an amount ranging from about 85 parts by weight to about 98 parts by weight relative to 100 parts by weight of the first positive electrode active material layer LL.

[0035] Positive electrode binder: The binder can be configured to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and 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.

[0036] Positive electrode conductive material: Conductive materials can be included to provide electrodes with conductivity, 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; metallic materials, in the form of metal powder or metal fibers, including one or more of copper, nickel, aluminum, and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0037] Negative electrode: 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.

[0038] 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 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%.

[0039] Negative electrode binder: The binder can be configured to improve the adhesion between the negative electrode active material particles and to improve the adhesion between the negative electrode active material and the current collector COL2. The binder may include at least one of non-aqueous binders, aqueous binders, dry binders, and any combination thereof.

[0040] 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.

[0041] 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, 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.

[0042] When an aqueous binder is included as the negative electrode binder, a cellulose compound configured to provide 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.

[0043] 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.

[0044] Negative electrode conductive material: Conductive materials may be included to provide electrodes with conductivity, and any suitable conductive material that does not cause chemical changes in the battery may be included as the conductive material. For example, conductive materials 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, in the form of metal powder or metal fibers, including one or more of copper, nickel, aluminum, and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0045] Negative electrode current collector: Return to reference Figure 1 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.

[0046] Negative electrode active material: The negative electrode active material in the negative electrode active material layer AML2 may include at least one of the following: materials capable of reversibly inserting and de-intercalating lithium ions, lithium metal, lithium metal alloys, materials capable of doping and de-doping lithium, and transition metal oxides.

[0047] Materials capable of reversibly inserting and deintercalating lithium ions can include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. For example, crystalline carbon can include graphite, such as at least one of amorphous, flake, sheet, spherical, or fibrous natural graphite and artificial graphite, and amorphous carbon can include at least one of soft carbon, hard carbon, mesophase pitch carbon, and calcined coke.

[0048] Lithium metal alloys may include alloys of lithium and metals, wherein 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.

[0049] Materials capable of doping and undoping lithium may include Si-based negative electrode active materials or Sn-based negative electrode active materials. The Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (where 0 < x ≤ 2), Si-Q alloys (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), and combinations of at least one of them. The Sn-based negative electrode active materials may include Sn, SnO2, Sn-based alloys, and at least one of any combinations thereof.

[0050] 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 (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.

[0051] 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 located on the surface of the core.

[0052] The Si-based negative electrode active materials or the Sn-based negative electrode active materials may be included in combination with carbon-based negative electrode active materials.

[0053] Separator: Based 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 a multilayer separator such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, and a polypropylene / polyethylene / polypropylene trilayer separator.

[0054] The separator 30 may include a porous substrate and a coating located on one surface or opposite two surfaces of the porous substrate, and the coating includes an organic material, an inorganic material, or a combination thereof.

[0055] The porous substrate may be or include a polymer layer, which includes at least one of polyolefins (such as polyethylene and polypropylene), polyesters (such as at least one of 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™), or may be a copolymer or mixture of two or more of the above materials.

[0056] Organic materials may include polyvinylidene fluoride copolymers or (meth)acrylic acid copolymers.

[0057] Inorganic materials may include inorganic particles such as or including at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and combinations thereof, but this disclosure is not limited thereto.

[0058] Organic and inorganic materials can be mixed in a single coating, or they can be in the form of a stack of coatings that include organic materials and coatings that include inorganic materials.

[0059] electrolytes Electrolytes (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0060] Non-aqueous organic solvents can be configured as media for transporting ions that participate in the electrochemical reactions of a battery.

[0061] 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 in a mixture of two or more solvents.

[0066] Furthermore, when carbonate solvents are included, cyclic carbonates and chain carbonates can be mixed, and cyclic carbonates and chain carbonates can be mixed in a volume ratio ranging from about 1:1 to about 1:9.

[0067] Lithium salts can be or include materials dissolved in non-aqueous organic solvents to form a supply source of lithium ions in a battery, and play a role in enabling basic battery operation and facilitating 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 trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0068] Additives may include bicyclic sulfate compounds. Bicyclic sulfate compounds can form a solid electrolyte interphase (SEI) layer on the surface of the negative electrode or a protective layer on the surface of the positive electrode, and can have improved thermal stability, thereby improving the life characteristics of rechargeable lithium batteries at high temperatures.

[0069] Bicyclic sulfate compounds can be represented by the following chemical formula 1.

[0070] Chemical Formula 1:

[0071] In Formula 1, A1, A2, A3 and A4 may each be or include covalent, substituted or unsubstituted C1 to C5 alkylene, carbonyl or sulfinyl groups, wherein A1 and A2 are not covalently bonded at the same time, and A3 and A4 are not covalently bonded at the same time.

[0072] For example, at least one of A1, A2, A3, and A4 may be an unsubstituted C1 to C5 alkylene or a substituted C1 to C5 alkylene, wherein the substituent of the substituted C1 to C5 alkylene may be halogen, halogen-substituted or unsubstituted C1 to C20 alkyl, halogen-substituted or unsubstituted C2 to C20 alkenyl, halogen-substituted or unsubstituted C2 to C20 alkynyl, halogen-substituted or unsubstituted C3 to C20 cycloalkenyl, halogen-substituted or unsubstituted C3 to C20 heterocyclic, halogen-substituted or unsubstituted C6 to C40 aryl, halogen-substituted or unsubstituted C2 to C40 heteroaryl, or a polar functional group including one or more heteroatoms.

[0073] For example, at least one of A1, A2, A3, and A4 may be an unsubstituted C1 to C5 alkylene or a substituted C1 to C5 alkylene, wherein the substituents of the substituted C1 to C5 alkylene may include halogen, methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, trifluoromethyl, tetrafluoroethyl, phenyl, naphthyl, tetrafluorophenyl, pyrroleyl, or pyridyl, but this disclosure is not limited thereto, and any substituent that can be included as an alkylene may be available in the art.

[0074] For example, in bicyclic sulfate compounds represented by Formula 1, the alkylene substituents may be polar functional groups including heteroatoms, and the heteroatoms of the polar functional groups may include at least one of halogen, oxygen, nitrogen, phosphorus, sulfur, silicon, and boron.

[0075] In the example embodiment, the halogen substituent in the polar functional group including heteroatoms, such as alkyl, alkenyl, alkynyl, cycloalkyl, aryl, heteroaryl, alkylaryl, trialkylsilyl, or aralkyl, may be or include fluorine (F).

[0076] For example, bicyclic sulfate compounds may include one or more of the compounds represented by the following chemical formulas 1-1 to 1-7.

[0077] Chemical formula 1-1:

[0078] Chemical formulas 1-2:

[0079] Chemical formulas 1-3:

[0080] Chemical formulas 1-4:

[0081] Chemical formulas 1-5:

[0082] Chemical formulas 1-6:

[0083] Chemical formulas 1-7:

[0084] 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 of the present disclosure is shown, wherein Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown. Figure 4 and Figure 5 A pouch-type battery is shown. (See reference) Figures 2 to 4 The rechargeable lithium battery 100 may include an electrode assembly 40 in which a separator 30 is 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, the negative electrode 20, and the 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 connector 70 shown in the figure, or Figure 4 The positive electrode terminal 71 and negative electrode terminal 72 shown in the figure form an electrical path for guiding the current generated in the electrode assembly 40 to the outside.

[0085] The rechargeable lithium battery according to the exemplary embodiments of this disclosure can be used in, for example, motor vehicles, mobile phones and / or any other electronic devices, but this disclosure is not limited thereto.

[0086] The following description focuses on rechargeable lithium batteries and methods of manufacturing rechargeable lithium batteries according to exemplary embodiments of the present disclosure.

[0087] Figure 6A cross-sectional view is shown illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure. Figure 7 A cross-sectional view is shown illustrating the positive electrode of a rechargeable lithium battery according to an exemplary embodiment of the present disclosure. Figure 8 Examples of embodiments according to this disclosure are shown. Figure 7 A magnified view of part of the "M". (Refer to...) Figures 6 to 8 The second positive electrode active material layer HL according to an example of this disclosure is described in detail below.

[0088] Reference Figure 8 The second positive electrode active material layer HL may include a second positive electrode active material AM2, a second pore PO2, and a residual layer RF. The second positive electrode active material AM2 may include a lithium composite transition metal oxide. For example, the second positive electrode active material AM2 may include at least one of lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium nickel cobalt oxide (NC), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium nickel manganese oxide (NM), lithium manganese oxide (LMO), lithium iron phosphate (LFP), or combinations thereof. The second positive electrode active material AM2 may include the same material as the first positive electrode active material AM1.

[0089] The second positive electrode active material AM2 may include a plurality of second pores of PO2. The number of second pores of PO2 in the second positive electrode active material layer HL may be greater than the number of first pores of PO1 in the first positive electrode active material layer LL. The porosity of the second positive electrode active material layer HL may be greater than the porosity of the first positive electrode active material layer LL. The porosity of the first positive electrode active material layer LL can be defined as the ratio of the volume of its empty spaces to the volume of the first positive electrode active material layer LL. The porosity of the second positive electrode active material layer HL can be defined as the ratio of the volume of its empty spaces to the volume of the second positive electrode active material layer HL. The ratio of the porosity of the second positive electrode active material layer HL to the porosity of the first positive electrode active material layer LL may be in the range of about 1.5 to about 10.

[0090] The second pore PO2 can be formed during subsequent processes when the additive is dissolved by the electrolyte ELL and discharged from the second positive electrode active material layer HL. For example, the second pore PO2 can be formed simultaneously with the release of the additive in the second positive electrode active material layer HL into the electrolyte ELL.

[0091] Figure 10 The diagram shows porosity as... Figure 7 The graph depicts a function of the X-direction. The X-direction can be a vertical direction from the second positive electrode active material layer HL towards the first positive electrode active material layer LL. (Refer to...) Figure 10The porosity of the second positive electrode active material layer HL can decrease as the distance from the first positive electrode active material layer LL decreases. Optionally, the porosity of the second positive electrode active material layer HL can be constant, or it can increase as the distance from the first positive electrode active material layer LL decreases.

[0092] The porosity of the positive electrode 10 can vary discontinuously at the interfacial ITF between the first positive electrode active material layer LL and the second positive electrode active material layer HL. For example, the porosity of the positive electrode 10 can abruptly decrease at the boundary where it transitions from the second positive electrode active material layer HL to the first positive electrode active material layer LL. This may be due to the fact that the second positive electrode active material layer HL and the first positive electrode active material layer LL are manufactured with different positive electrode slurries and thus have different porosities.

[0093] Return to reference Figures 6 to 8 The second positive electrode active material layer HL may include a residual layer RF between at least some of the second positive electrode active material AM2 and the second pore PO2. The residual layer RF may be disposed on the edge of the second pore PO2. The residual layer RF may be a thin film or a layer. The residual layer RF may be disposed only on the portion between the second positive electrode active material AM2 and the second pore PO2. Multiple residual layers RF may be disposed between one second pore PO2 and the second positive electrode active material AM2.

[0094] The residual layer RF may include sulfur (S). For example, the residual layer RF may include sulfur compounds. The residual layer RF may be derived from the additives of the electrolyte ELL discussed above. The residual layer RF may be or include compounds remaining after the additives are dissolved by the electrolyte ELL and discharged from the second positive electrode active material layer HL in subsequent processes. For example, the sulfur (S) in the residual layer RF may be derived from bicyclic sulfate compounds used as additives. The first positive electrode active material layer LL may not include the residual layer RF.

[0095] According to the examples of this disclosure, the porosity in the upper part of the positive electrode active material layer AML1 can be greater than the porosity in the lower part of the positive electrode active material layer AML1. Since a large number of substantially uniform pores are distributed in the upper part of the positive electrode active material layer AML1, the impregnation performance of the electrolyte ELL can be significantly improved. Furthermore, because only the upper part of the positive electrode active material layer AML1 has increased porosity, and the lower part of the positive electrode active material layer AML1 has relatively decreased porosity, not only can the impregnation performance of the electrolyte ELL relative to the positive electrode active material layer AML1 be improved, but the capacity reduction of the rechargeable lithium battery can also be reduced or prevented. Therefore, the rechargeable lithium battery can be prevented or substantially protected from overvoltage. As a result, the reliability and electrical characteristics of the rechargeable lithium battery can be improved.

[0096] Figure 9 The illustration shows a comparative example according to this disclosure. Figure 7 A magnified view of the "M" portion. In the following comparative embodiments, details consistent with the above references are omitted. Figure 8 The technical features discussed are repeated in detail, and their differences are discussed in detail.

[0097] Reference Figure 9 , Figure 9 The porosity of the first positive electrode active material layer LL can be greater than Figure 8 The porosity of the first positive electrode active material layer LL. The first positive electrode active material layer LL and the second positive electrode active material layer HL can have the same porosity. Figure 9 The number of PO1 pores in the first positive electrode active material layer LL can be greater than Figure 8 The number of first pores PO1 in the first positive electrode active material layer LL. The ratio of the porosity of the second positive electrode active material layer HL to the porosity of the first positive electrode active material layer LL can be in the range of about 0.7 to about 1.3. Including Figure 9 In the positive electrode 10 of the portion "M", each of the first positive electrode active material layer LL and the second positive electrode active material layer HL can have increased porosity. Therefore, the empty space of the positive electrode 10 can be significantly increased overall, and the capacity of the rechargeable lithium battery can be reduced. In summary, compared to the rechargeable lithium battery of the example according to this disclosure, the capacity and electrical characteristics of the rechargeable lithium battery according to the comparative example are reduced.

[0098] Manufacturing of rechargeable lithium batteries The following description focuses on a method of manufacturing a rechargeable lithium battery according to an example embodiment of the present disclosure.

[0099] A method for manufacturing a rechargeable lithium battery may include the following steps to manufacture the battery: manufacturing a positive electrode; manufacturing a negative electrode; and combining the positive and negative electrodes.

[0100] For example, the steps of manufacturing a positive electrode may include: coating a first positive electrode slurry onto a current collector COL1 to form a first positive electrode active material layer LL; coating a second positive electrode slurry onto the first positive electrode active material layer LL to form a second positive electrode active material layer HL; and providing an electrolyte ELL onto the first positive electrode active material layer LL and the second positive electrode active material layer HL.

[0101] The steps for forming the first positive electrode active material layer are as follows: The first positive electrode slurry can be prepared by mixing the first positive electrode active material AM1, the conductive material, and the binder with each other. In the mixing method, any suitable method (such as wet or dry) that can be used by those skilled in the art is feasible and is not limited to any particular method. The materials discussed above can be included as the first positive electrode active material AM1, the conductive material, and the binder.

[0102] The prepared first positive electrode slurry can be coated onto the current collector COL1, then dried and pressed to form the first positive electrode active material layer LL.

[0103] The steps for forming the second positive electrode active material layer are as follows: The second positive electrode slurry can be prepared by mixing the second positive electrode active material AM2, the conductive material, and the binder with each other. In the mixing method, any suitable method that can be used by those skilled in the art (such as wet or dry methods) is feasible and is not limited to any particular method. The materials discussed above can be included as the second positive electrode active material AM2, the conductive material, and the binder.

[0104] The additives in the second positive electrode slurry may include the same materials as the additives in the electrolyte ELL. For example, the additives in the second positive electrode slurry may include bicyclic sulfate compounds. Optionally, the first positive electrode slurry may not contain any additives, or may contain very little or substantially little additives. The ratio of the additive concentration of the second positive electrode slurry to the additive concentration of the first positive electrode slurry may be in the range of about 100 to about 1,000.

[0105] The prepared second positive electrode slurry can be coated onto the first positive electrode active material layer LL, then dried and pressed to form the second positive electrode active material layer HL.

[0106] The steps for manufacturing a negative electrode: A negative electrode active material, binder, and conductive material can be mixed to prepare a negative electrode active material slurry. The prepared negative electrode active material slurry can be coated onto a negative electrode current collector, then dried and pressed to manufacture the negative electrode.

[0107] The steps in manufacturing a battery: The positive and negative electrodes manufactured as described above can be combined to produce a finished rechargeable lithium battery. A separator can be placed between the positive and negative electrodes, and an electrolyte can be introduced to manufacture the battery. Alternatively, an electrolyte layer can be disposed between the positive and negative electrodes to manufacture a stacked battery.

[0108] This disclosure can be applied to any battery equipped with a positive electrode active material, such as a conventional lithium-ion battery, an all-solid-state battery, or a semi-solid-state battery. Furthermore, the shape of the finished battery is not limited, and the battery can be manufactured in common configurations, such as prismatic, pouch, or cylindrical shapes.

[0109] In manufacturing a rechargeable lithium battery according to an example of this disclosure, an additive may be mixed into a second positive electrode slurry to form a second positive electrode active material layer HL. The subsequent step of providing an electrolyte may include releasing the additive from the second positive electrode active material layer HL and causing the released additive to form a plurality of pores in the second positive electrode active material layer HL.

[0110] For example, when the electrolyte ELL is introduced into the electrode assembly, the additives included in the second positive electrode active material layer HL can be released into the electrolyte ELL. Since the space in the positive electrode is occupied by the additives in solid form, the second positive electrode active material layer HL can include pores, each with a large volume, formed substantially uniformly in the space where the additives are discharged, when the additives can be separated into the electrolyte ELL.

[0111] The second positive electrode active material layer HL may include unreleased portions of the additive within the second positive electrode active material layer HL, and the electrolyte ELL may include portions of the additive released into the electrolyte ELL. The unreleased additive may remain in the second positive electrode active material layer HL as a residual layer RF. Therefore, the residual layer RF may include sulfur (S).

[0112] The additives included in the second positive electrode active material layer HL and the additives included in the electrolyte ELL can be the same as each other, but can have different amounts of each other. Furthermore, since the additives are compounds included as common additives for rechargeable lithium batteries, the electrolyte ELL can include these additives to improve battery performance and stability.

[0113] Since a large number of pores are basically uniformly distributed in the second positive electrode active material layer HL compared to the first positive electrode active material layer LL, the impregnation performance of the second positive electrode active material layer HL can be significantly or substantially improved, and lithium-ion pathways can be obtained to improve the battery's capacity, life characteristics and fast charging performance.

[0114] Figure 12 This is a flowchart illustrating a method for manufacturing a rechargeable lithium battery according to an example embodiment. Figure 12In method 1200, operation 1210 includes coating a first positive electrode slurry onto a current collector to form a first positive electrode active material layer. Operation 1220 includes coating a second positive electrode slurry onto the first positive electrode active material layer to form a second positive electrode active material layer. For example, the second positive electrode slurry includes additives. In another example, the ratio of the additive concentration of the second positive electrode slurry to the additive concentration of the first positive electrode slurry is in the range of about 100 to about 1,000. In yet another example, the second positive electrode active material layer further includes positive electrode active material and a residual layer between the positive electrode active material and a plurality of pores, wherein the residual layer includes sulfur (S). In another example, the porosity of the second positive electrode active material layer is greater than the porosity of the first positive electrode active material layer. In another example, the porosity of the rechargeable lithium battery decreases at the interface between the first and second positive electrode active material layers.

[0115] Operation 1230 includes providing an electrolyte on a first positive electrode active material layer and a second positive electrode active material layer. In an example, the step of providing the electrolyte includes releasing an additive from the second positive electrode active material layer and causing the released additive to form a plurality of pores in the second positive electrode active material layer. In the example, the additive is represented by chemical formula 1: .

[0116] In Formula 1, A1, A2, A3 and A4 each independently include a covalent bond, a substituted or unsubstituted C1 to C5 alkylene group, a carbonyl group or a sulfinyl group, A1 and A2 are not covalent bonds at the same time, and A3 and A4 are not covalent bonds at the same time.

[0117] The following describes detailed exemplary embodiments for implementing this disclosure. This disclosure may include not only the foregoing exemplary embodiments, but also embodiments that can be easily redesigned or modified. Furthermore, this disclosure may cover techniques that can be readily implemented through modifications of the exemplary embodiments. Therefore, the scope of this disclosure should not be limited to the foregoing exemplary embodiments, but should be defined by the following claims and their equivalents.

[0118] Example 1 Formation of the first positive electrode active material layer: It will be used as the positive electrode active material (Gen.6, Ni) 91 LiNi (V2) 0.91 Co 0.66 Al 0.13 V 0.02 O2 (hereinafter referred to as NCA), polyvinylidene fluoride as a binder, and carbon nanotubes as a conductive material are mixed in a weight ratio of 97:2:1, and the mixture is dispersed in N-methylpyrrolidone to prepare a first positive electrode slurry.

[0119] The first positive electrode slurry was coated onto an Al foil current collector with a thickness of 14 μm, and dried and pressed at 200 °C to form the first positive electrode active material layer.

[0120] Formation of the second positive electrode active material layer: It will be used as the positive electrode active material (Gen.6, Ni) 91 LiNi (V2) 0.91 Co 0.66 Al 0.13 V 0.02 O2 (hereinafter referred to as NCA), polyvinylidene fluoride as a binder, and carbon nanotubes as a conductive material are mixed in a weight ratio of 97:2:1, and the mixture is dispersed in N-methylpyrrolidone to prepare a basic positive electrode slurry. A compound represented by chemical formula 1-1 is added as an additive to the basic positive electrode slurry to prepare a second positive electrode slurry. For reference, the expression "wt%" in the following positive electrode slurry compositions is based on the total amount of the positive electrode slurry (positive electrode active material + binder + conductive material + additive).

[0121] Chemical formula 1-1:

[0122] The second positive electrode slurry is coated onto the first positive electrode active material layer, and then dried and pressed at 200°C to form the second positive electrode active material layer.

[0123] Manufacturing of negative electrode and electrolyte: Artificial graphite as the negative electrode active material, styrene-butadiene rubber as a binder, and carboxymethyl cellulose as a thickener were mixed in a weight ratio of 97:1:2, and the mixture was dispersed in distilled water to prepare a negative electrode active material slurry. The negative electrode active material slurry was coated onto a copper foil current collector with a thickness of 10 μm, and then dried and pressed at 100 °C to manufacture the negative electrode.

[0124] Electrolytes were prepared by dissolving 1.5 M LiPF6 lithium salt in a non-aqueous organic solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in the aforementioned order at a volume ratio of 20:10:70.

[0125] Manufacturing of rechargeable lithium batteries: After placing a 25 μm thick multilayer polyethylene-polypropylene separator between the positive and negative electrodes to obtain an electrode assembly, the electrode assembly is inserted into a circular battery casing, and then an electrolyte is introduced to manufacture the rechargeable lithium battery of Example 1.

[0126] Example 2 The rechargeable lithium battery was manufactured using the same method as in Example 1, except that 0.1 wt% of the compounds represented by chemical formulas 1-2 were mixed as additives to prepare the second positive electrode slurry.

[0127] Chemical formulas 1-2:

[0128] Comparative Example 1 A rechargeable lithium battery was manufactured using the same method as in Example 1, except that a second positive electrode active material layer was formed without adding additives to the second positive electrode slurry.

[0129] Comparative Example 2 A rechargeable lithium battery was manufactured using the same method as in Example 1, except that 0.1 wt% of a compound represented by chemical formula 1-1 was also mixed as an additive into the first positive electrode slurry to prepare the first positive electrode active material layer.

[0130] Table 1 below lists the examples and comparative examples manufactured as described above.

[0131] Table 1:

[0132] Evaluation 1: Overvoltage The overvoltage of each of the rechargeable lithium batteries according to Example 1, Example 2, and Comparative Example 1 was evaluated. For example, charging time and lithium deposition were evaluated based on the state of charge (SOC) at 4.25V and 4.3V cutoff at 30°C. The results are listed in Table 2 below. Figure 11 The graphs shown illustrate the temperature and voltage of Example 1 and Comparative Example 1 with a cutoff voltage of 4.25V.

[0133] Table 2:

[0134] Refer to Table 2 and Figure 11 The rechargeable lithium batteries according to Examples 1 and 2 did not exhibit overvoltage, but the rechargeable lithium battery according to Comparative Example 1 did. For example, in the case of Comparative Example 1, an overvoltage of 4.250V was generated at a charging rate of 3.1C with a cutoff of 4.25V. In addition, high voltages of 4.250V, 4.261V, and 4.253V were generated at charging rates of 2.6C, 3.1C, and 3.5C with a cutoff of 4.3V, respectively.

[0135] Furthermore, compared to the rechargeable lithium battery according to Comparative Example 1, the rechargeable lithium battery according to Example 1 exhibits high temperatures during charging. Since high temperatures may be advantageous for fast charging, the rechargeable lithium battery according to Example 1 is more suitable for fast charging compared to the rechargeable lithium battery according to Comparative Example 1.

[0136] Furthermore, in Comparative Example 1, the state of charge (SOC) reached 78.4% but did not reach 80.0%. The lithium deposition amounts in Examples 1 and 2 were relatively lower than those in Comparative Example 1. Therefore, it can be determined that when the additive is provided to the upper part of the positive electrode active material layer to increase porosity, overvoltage phenomena are prevented and lithium deposition amounts are reduced. As a result, the reliability and electrical characteristics of the rechargeable lithium battery according to this disclosure can be improved compared to ordinary rechargeable lithium batteries.

[0137] The positive electrode of the rechargeable lithium battery according to the example embodiment may include an upper portion with relatively high porosity, thereby improving the impregnation performance of the electrolyte.

[0138] The method for manufacturing a rechargeable lithium battery according to the example embodiment can solve or address the stability and performance issues of rechargeable lithium batteries.

Claims

1. A rechargeable lithium battery, said rechargeable lithium battery comprising: Positive electrode, including current collector; Electrolytes; as well as negative electrode, The positive electrode includes: A first positive electrode active material layer is placed on the current collector; and The second positive electrode active material layer is located on top of the first positive electrode active material layer. The second positive electrode active material layer includes: Positive electrode active materials include lithium complex transition metal oxides; Multiple holes; and A residual layer exists between the positive electrode active material and the pore. The residual layer includes sulfur.

2. The rechargeable lithium battery according to claim 1, wherein, The porosity of the second positive electrode active material layer is greater than that of the first positive electrode active material layer.

3. The rechargeable lithium battery according to claim 1, wherein, The electrolyte includes additives. The additives include bicyclic sulfate compounds.

4. The rechargeable lithium battery according to claim 3, wherein, The bicyclic sulfate ester compound is represented by chemical formula 1. Chemical Formula 1: In chemical formula 1, A1, A2, A3, and A4 each independently include a covalent bond, a substituted or unsubstituted C1 to C5 alkylene group, a carbonyl group, or a sulfinyl group. A1 and A2 are not both covalent bonds, and A3 and A4 are not covalent bonds at the same time.

5. The rechargeable lithium battery according to claim 4, wherein, The compound represented by chemical formula 1 includes at least one of the compounds represented by chemical formulas 1-1 to 1-7. Chemical formula 1-1: Chemical formula 1-2: Chemical formulas 1-3: Chemical formulas 1-4: Chemical formulas 1-5: Chemical formulas 1-6: Chemical formulas 1-7: 。 6. The rechargeable lithium battery according to claim 3, wherein, The residual layer is derived from the additive.

7. The rechargeable lithium battery according to claim 3, wherein, The pores in the second positive electrode active material layer are formed due to the release of additives from the second positive electrode active material layer into the electrolyte.

8. The rechargeable lithium battery according to claim 3, wherein, The first positive electrode active material layer does not include the residual layer.

9. The rechargeable lithium battery according to claim 1, wherein, The positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium manganese oxide, and lithium iron phosphate.

10. The rechargeable lithium battery according to claim 1, wherein, The positive electrode also includes at least one of a binder and a conductive material.

11. The rechargeable lithium battery according to claim 1, wherein, The electrolyte includes an organic solvent and a lithium salt.

12. The rechargeable lithium battery according to claim 1, wherein, The porosity of the positive electrode decreases at the interface between the first positive electrode active material layer and the second positive electrode active material layer.

13. A method for manufacturing a rechargeable lithium battery, the method comprising the following steps: The first positive electrode slurry is coated onto the current collector to form the first positive electrode active material layer; The second positive electrode slurry is coated onto the first positive electrode active material layer to form the second positive electrode active material layer; as well as Electrolytes are provided on the first positive electrode active material layer and the second positive electrode active material layer. The second positive electrode paste includes additives, and The step of providing the electrolyte includes: Release the additive from the second positive electrode active material layer; and The released additive forms multiple pores in the second positive electrode active material layer.

14. The method according to claim 13, wherein, The ratio of the additive concentration of the second positive electrode slurry to the additive concentration of the first positive electrode slurry is in the range of 100 to 1,000.

15. The method according to claim 13, wherein, The second positive electrode active material layer further includes: Positive electrode active material; and A residual layer exists between the positive electrode active material and the plurality of pores. The residual layer includes sulfur.

16. The method according to claim 13, wherein, The porosity of the second positive electrode active material layer is greater than that of the first positive electrode active material layer.

17. The method according to claim 13, wherein, The porosity of the rechargeable lithium battery decreases at the interface between the first positive electrode active material layer and the second positive electrode active material layer.

18. The method according to claim 13, wherein, The additive is represented by chemical formula 1. Chemical Formula 1: In chemical formula 1, A1, A2, A3, and A4 each independently include a covalent bond, a substituted or unsubstituted C1 to C5 alkylene group, a carbonyl group, or a sulfinyl group. A1 and A2 are not both covalent bonds, and A3 and A4 are not covalent bonds at the same time.

19. A positive electrode for a rechargeable lithium battery, the positive electrode comprising: current collector; A first positive electrode active material layer is disposed on the current collector; as well as The second positive electrode active material layer is located on top of the first positive electrode active material layer. The second positive electrode active material layer includes: Positive electrode active materials include lithium complex transition metal oxides; Multiple holes; and A residual layer exists between the positive electrode active material and the pore. The residual layer includes sulfur.

20. The positive electrode according to claim 19, wherein, The porosity of the second positive electrode active material layer is greater than that of the first positive electrode active material layer.

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