Negative electrode for rechargeable lithium battery, and jelly-roll type electrode assembly and rechargeable lithium battery including the same

Abstract

The present disclosure relates to a negative electrode for a rechargeable lithium battery, an electrode core type electrode assembly including the same, and a rechargeable lithium battery including the same, for example, the present disclosure relates to a negative electrode including a negative electrode current collector, a first negative electrode active material layer and a second negative electrode active material layer stacked on a first surface of the negative electrode current collector, and a third negative electrode active material layer and a fourth negative electrode active material layer stacked on a second surface of the negative electrode current collector. The content of a carbon-based negative electrode active material in the first negative electrode active material layer is greater than the content of a carbon-based negative electrode active material in the second negative electrode active material layer. The content of a carbon-based negative electrode active material in the third negative electrode active material layer is less than the content of a carbon-based negative electrode active material in the fourth negative electrode active material layer.

Description

[0001] This patent application claims priority to Korean Patent Application No. 10-2024-0174314, filed on November 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to a negative electrode for a rechargeable lithium battery, a core-type electrode assembly including the negative electrode, and a rechargeable lithium battery including the negative electrode. More specifically, it relates to a negative electrode for a rechargeable lithium battery in which a negative electrode active material layer is asymmetrically formed on both sides of a negative electrode current collector, a core-type electrode assembly including the negative electrode, and a rechargeable lithium battery including the negative 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 has increased. Therefore, improving the performance of rechargeable lithium batteries can be advantageous.

[0004] A rechargeable lithium battery includes a positive electrode and a negative electrode containing active materials capable of inserting and deintercalating lithium ions, as well as an electrolyte solution. Electrical energy is generated through oxidation and reduction reactions when lithium ions are inserted into or deintercalated from the positive and negative electrodes. Summary of the Invention

[0005] This disclosure describes a negative electrode for a rechargeable lithium battery having desired or improved rate performance, high capacity, and desired or improved lifetime performance.

[0006] This disclosure also describes a core-type electrode assembly having desired or improved rate performance, high capacity, and desired or improved lifetime performance.

[0007] Example embodiments of this disclosure include a negative electrode for a rechargeable lithium-ion battery, the negative electrode comprising a negative electrode current collector, a lower negative electrode active material layer formed on a first surface of the negative electrode current collector, and an upper negative electrode active material layer formed on a second surface of the negative electrode current collector. The lower negative electrode active material layer may include a first and a second negative electrode active material layer stacked (e.g., sequentially stacked) on the first surface of the negative electrode current collector. The upper negative electrode active material layer may include a third and a fourth negative electrode active material layer stacked (e.g., sequentially stacked) on the second surface of the negative electrode current collector. The first and fourth negative electrode active material layers may each comprise a carbon-based negative electrode active material. The second and third negative electrode active material layers may each comprise a carbon-based negative electrode active material and a silicon-based negative electrode active material. The content of carbon-based negative electrode active material in the first negative electrode active material layer is greater than the content of carbon-based negative electrode active material in the second negative electrode active material layer. The content of carbon-based negative electrode active material in the third negative electrode active material layer can be less than the content of carbon-based negative electrode active material in the fourth negative electrode active material layer.

[0008] In an exemplary embodiment of this disclosure, the core-type electrode assembly includes a positive electrode, a negative electrode, and a diaphragm between the positive and negative electrodes.

[0009] In an exemplary embodiment of this disclosure, the core-type electrode assembly includes a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes. The negative electrode may include a negative electrode current collector, a lower negative electrode active material layer on a first surface of the negative electrode current collector, and an upper negative electrode active material layer on a second surface of the negative electrode current collector. Each or at least one of the lower and upper negative electrode active material layers may include a carbon-based negative electrode active material and a silicon-based negative electrode active material. The content of the carbon-based negative electrode active material in the lower negative electrode active material layer may increase with proximity to the first surface, and the content of the carbon-based negative electrode active material in the upper negative electrode active material layer may decrease with proximity to the second surface.

[0010] In an example embodiment of this disclosure, the rechargeable lithium battery includes the aforementioned core-type electrode assembly. Attached Figure Description

[0011] The accompanying drawings are included to provide a further understanding of this disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, explain the principles of the disclosure. In the drawings: Figure 1 This is a simplified conceptual diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure; Figures 2 to 5 Each of these is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment, wherein... Figure 2 The rechargeable lithium battery in the design can be in cylindrical form. Figure 3 The rechargeable lithium battery in the design can be in the form of a prismatic battery. Figure 4 and Figure 5 The rechargeable lithium battery in the battery can be in the form of a pouch cell. Figure 6 and Figure 7 Each of these is a cross-sectional view showing a negative electrode according to an exemplary embodiment of the present disclosure; Figure 8 This is a cross-sectional view showing a core-type electrode assembly according to an exemplary embodiment of the present disclosure; and Figure 9 This is a cross-sectional view showing the negative electrode of a core-type electrode assembly according to an exemplary embodiment of the present disclosure. Detailed Implementation

[0012] To fully understand the structure and effects of this disclosure, exemplary embodiments of the disclosure are described in more detail below with reference to the accompanying drawings. However, this disclosure may be implemented in various forms and should not be construed as limited to the exemplary embodiments set forth herein, and various changes and modifications may be made. Rather, these exemplary embodiments are provided so that this disclosure is thorough and complete, and fully conveys the scope of this disclosure to those skilled in the art to which this disclosure pertains.

[0013] In this specification, it is understood that when an element is referred to as being "on" another element, the element may be formed directly on the other element, or a third element may be disposed between them. Additionally, in the accompanying drawings, the thickness of elements may be exaggerated for the purpose of effectively describing the technical content. The same reference numerals always denote the same elements.

[0014] Unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well. Furthermore, unless otherwise specified, the phrase "A or B" can mean "including A but not B," "including B but not A," or "including both A and B." The term "including" and / or variations thereof as used in this specification do not exclude the presence or addition of one or more other components.

[0015] As used herein, the term “combination of them” can refer to a mixture, stack, complex, copolymer, alloy, blend, or reaction product of the components.

[0016] As used herein, phrases such as “A or B”, “A and B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C” and “at least one of A, B or C” may each be included in any one of the items listed together in the corresponding phrases of these phrases, or all possible combinations thereof.

[0017] Unless otherwise defined herein, particle size can be the average particle size. Alternatively, particle size is defined as the average particle size (D50), which represents the diameter of particles that constitute approximately 50 vol% of the cumulative volume in a particle size distribution. The average particle size (D50) can be measured by methods known to those skilled in the art (e.g., using a particle size analyzer), or it can be measured using images from a transmission electron microscope (TEM) or a scanning electron microscope (SEM). Optionally, the average particle size (D50) can be measured using a dynamic light scattering measuring device, wherein data analysis is performed to count the number of particles in each particle size range, and then the average particle size (D50) value can be calculated. Furthermore, the average particle size can be measured using laser diffraction. In measurements using laser diffraction, target particles are dispersed in a dispersion medium and introduced into a commercially available laser diffraction particle size measurement device (e.g., the MT3000 available from Microtrac). The particles are then irradiated with ultrasound at approximately 28 kHz at a power of approximately 60 W. The average particle size (D50) based on approximately 50% of the particle size distribution in the measurement device can then be calculated.

[0018] 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%.

[0019] 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.

[0020] The positive electrode 10 and the negative electrode 20 can be separated from each other by a diaphragm 30. The diaphragm 30 can be located 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.

[0021] 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 towards one of the positive electrode 10 and the negative electrode 20 through the separator 30.

[0022] 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.

[0023] For example, the positive electrode 10 may also include additives that can constitute a sacrificial positive electrode.

[0024] 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 99.5 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%.

[0025] 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.

[0026] Conductive materials can provide electrodes that are conductive, and any suitable conductive material that does not cause chemical changes in the battery can be used as a 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; metal powders or metal fibers, including at least one of copper, nickel, aluminum, and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0027] Aluminum (Al) can be used as a current collector COL1, but this disclosure is not limited thereto.

[0028] Positive electrode active material The positive electrode active material in the positive electrode active material layer AML1 may include compounds capable of reversibly inserting and deintercalating 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.

[0029] Composite oxides 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.

[0030] 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 d G 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 bO4 (where 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a 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).

[0031] In the above chemical formulas, A can be or include at least one of Ni, Co, Mn, and combinations thereof; X can be or include at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D can be or include at least one of O, F, S, P, and combinations thereof; G can be or include at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; and L 1 It can be or include at least one of Mn, Al and combinations thereof.

[0032] 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 metals other than lithium 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.

[0033] 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.

[0034] For example, the negative electrode active material layer AML2 may include a negative electrode active material ranging from about 90 wt% to about 99 wt%, a binder ranging from about 0.5 wt% to about 5 wt%, and a conductive material ranging from about 0 wt% to about 5 wt%.

[0035] The binder can be configured to improve the adhesion between the negative electrode active material particles and also improve the adhesion between the negative electrode active material and the current collector COL2. The binder may include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0036] 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.

[0037] Waterborne adhesives may include at least one of 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.

[0038] 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.

[0039] Dry adhesives may include at least one of fibrillable polymeric materials, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0040] 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 used 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; metal powders or metal fibers, including one or more of copper, nickel, aluminum, and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0041] 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.

[0042] 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.

[0043] Materials capable of reversibly embedding and de-embedding lithium ions may include carbonaceous negative electrode active materials, for example, crystalline carbon, amorphous carbon, or a combination thereof. For example, crystalline carbon may include graphite, such as natural graphite or artificial graphite in the form of non-fixed shapes, sheets, flakes, spheres, or fibers, and amorphous carbon may include at least one of soft carbon, hard carbon, mesophase pitch carbon, and calcined coke.

[0044] Lithium metal alloys may include alloys of lithium and a metal that 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.

[0045] Materials capable of doping and de-doping lithium may include Si-based negative electrode active materials or Sn-based negative electrode active materials. 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 alkali metals, alkaline earth metals, group 13 elements, group 14 elements (except Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), and at least one of their combinations. Sn-based negative electrode active materials may include at least one of Sn, SnO2, Sn-based alloys, and their combinations.

[0046] 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 (shell) located on the surface of the secondary particles. Amorphous carbon may also be located between the primary silicon particles, and for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0047] 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.

[0048] Si-based negative electrode active materials or Sn-based negative electrode active materials may be used in combination with carbonaceous negative electrode active materials.

[0049] Diaphragm 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.

[0050] The diaphragm 30 may include a porous substrate and a coating located on one or opposite side of the porous substrate, the coating including organic materials, inorganic materials, or combinations thereof.

[0051] 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 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 the polymer layer may be a copolymer or mixture of two or more of the above materials.

[0052] Organic materials may include polyvinylidene fluoride copolymers or (meth)acrylic acid copolymers.

[0053] 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.

[0054] Organic and inorganic materials can be mixed in a coating, or they can exist as a stack of coatings containing organic materials and coatings containing inorganic materials.

[0055] Electrolyte ELL Electrolytes (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0056] Non-aqueous organic solvents can serve as media for transporting ions that participate in the electrochemical reactions of a battery.

[0057] 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.

[0058] 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), ethyl methyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC).

[0059] 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.

[0060] 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 ethanol or isopropanol. Aprotic solvents may include at least one of the following: nitriles, such as R-CN (wherein R is a hydrocarbon group having a C2 to C20 straight-chain structure, branched structure, 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.

[0061] Non-aqueous organic solvents can be used alone or in mixtures of two or more substances.

[0062] In addition, when using carbonate solvents, cyclic carbonates and chain carbonates can be mixed, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio ranging from about 1:1 to about 1:9.

[0063] Lithium salts can be or include materials that are dissolved in a non-aqueous organic solvent to form a lithium-ion supply source in the battery, enabling the basic operation of a rechargeable lithium battery 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).

[0064] 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, wherein, 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 4 The rechargeable lithium battery 100 may include an electrode assembly 40 and may also include a housing 50. In the electrode assembly 40, a separator 30 is located between a positive electrode 10 and a negative electrode 20. The electrode assembly 40 is housed within the housing 50. 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. Additionally, as... Figure 3 As shown, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12 connected to the positive electrode lead connector 11, a negative electrode lead connector 21, and a negative electrode terminal 22 connected to the negative electrode lead connector 21. Figure 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include Figure 5 The electrode connector 70 shown, or 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.

[0065] The following describes in detail some exemplary embodiments of a rechargeable lithium battery and electrodes included in a rechargeable lithium battery.

[0066] Figure 6 and Figure 7 Each of these is a cross-sectional view of the negative electrode 20 according to an exemplary embodiment of the present disclosure. Figure 8 This is a cross-sectional view of a core-type electrode assembly 40 according to an exemplary embodiment of the present disclosure. Figure 9 This is a cross-sectional view showing a portion of a negative electrode 20 included in a core-type electrode assembly according to an exemplary embodiment of the present disclosure. Hereinafter, reference is made to... Figures 6 to 9 The present disclosure describes in detail the negative electrode 20, the core-type electrode assembly 40 including the negative electrode 20, and the rechargeable lithium battery including the negative electrode 20, according to exemplary embodiments of the present disclosure.

[0067] Reference Figure 6According to an example embodiment of this disclosure, the negative electrode 20 for a rechargeable lithium battery may include a negative electrode current collector COL2, a lower negative electrode active material layer INAL on a first surface of the negative electrode current collector COL2, and an upper negative electrode active material layer ONAL on a second surface of the negative electrode current collector COL2. The lower negative electrode active material layer INAL may include a first negative electrode active material layer NAL1 and a second negative electrode active material layer NAL2. The upper negative electrode active material layer ONAL may include a third negative electrode active material layer NAL3 and a fourth negative electrode active material layer NAL4.

[0068] The thickness ratio of the lower negative electrode active material layer INAL to the upper negative electrode active material layer ONAL can be in the range of approximately 1:2 to approximately 2:1. The thickness ratio of the first negative electrode active material layer NAL1 to the second negative electrode active material layer NAL2 can be in the range of approximately 1:2 to approximately 2:1, and the thickness ratio of the third negative electrode active material layer NAL3 to the fourth negative electrode active material layer NAL4 can be in the range of approximately 1:2 to approximately 2:1. In the example embodiment, all of the thickness ratios of the lower negative electrode active material layer INAL to the upper negative electrode active material layer ONAL, the first negative electrode active material layer NAL1 to the second negative electrode active material layer NAL2, and the third negative electrode active material layer NAL3 to the fourth negative electrode active material layer NAL4 can be in the range of approximately 1:1.

[0069] According to an exemplary embodiment of this disclosure, the negative electrode 20 can improve its rate performance and lifetime characteristics by asymmetrically forming negative electrode active material layers on a first surface and a second surface that are opposite to each other. Each of the lower negative electrode active material layer INAL and the upper negative electrode active material layer ONAL is described in more detail below.

[0070] The lower negative electrode active material layer INAL According to an exemplary embodiment of this disclosure, the lower negative electrode active material layer INAL may include a first negative electrode active material layer NAL1 and a second negative electrode active material layer NAL2 stacked (e.g., sequentially stacked) on a first surface of the negative electrode current collector COL2. For example, the first negative electrode active material layer NAL1 may be in contact with the first surface of the negative electrode current collector COL2, and the second negative electrode active material layer NAL2 may be spaced apart from the negative electrode current collector COL2. The first negative electrode active material layer NAL1 may include a carbon-based negative electrode active material CM1. The second negative electrode active material layer NAL2 may include a carbon-based negative electrode active material CM2 and a silicon-based negative electrode active material SM2.

[0071] The carbon-based negative electrode active material CM may include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon may include graphite, such as natural graphite or artificial graphite having an irregular shape, plate-like, flaky, spherical, or fibrous shape, and examples of amorphous carbon may include at least one of soft carbon, hard carbon, mesophase pitch carbide, calcined coke, and the like. The carbon-based negative electrode active material CM1 included in the first negative electrode active material layer NAL1 may be the same as or different from the carbon-based negative electrode active material CM2 included in the second negative electrode active material layer NAL2.

[0072] The Si-based negative electrode active material SM may be or include at least one of the following: silicon, silicon-carbon composite, SiO x (0 < x ≤ 2), Si-Q alloy (where Q is 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, or Q 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.

[0073] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to an exemplary embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include secondary particles (cores) in which silicon primary particles are assembled and a first amorphous carbon coating (shell) located on the surface of the secondary particles. Amorphous carbon may also be present between the silicon primary particles, so the silicon primary particles may be coated with amorphous carbon, for example. The secondary particles may be dispersed in an amorphous carbon matrix.

[0074] First negative electrode active material layer: The content of the carbon-based negative electrode active material CM1 in the first negative electrode active material layer NAL1 may be greater than the content of the carbon-based negative electrode active material CM2 in the second negative electrode active material layer NAL2. For example, based on 100 wt% of the first negative electrode active material layer NAL1, the carbon-based negative electrode active material CM1 in the first negative electrode active material layer NAL1 may be in the range of about 90 wt% to about 99 wt%, about 95 wt% to about 99 wt%, or about 96 wt% to about 98 wt%.

[0075] Although not shown, in addition to the carbon-based negative electrode active material CM1, the first negative electrode active material layer NAL1 may further contain a Si-based negative electrode active material. In this case, the Si-based negative electrode active material in the first negative electrode active material layer NAL1 may be the same as or similar to the Si-based negative electrode active material SM2 in the second negative electrode active material layer NAL2.

[0076] The content of silicon-based negative electrode active material in the first negative electrode active material layer NAL1 can be less than the content of silicon-based negative electrode active material SM2 in the second negative electrode active material layer NAL2. Based on 100 wt% of the first negative electrode active material layer NAL1, the content of silicon-based negative electrode active material in the first negative electrode active material layer NAL1 can be in the range of about 5 wt% or less. For example, the content of silicon-based negative electrode active material in the first negative electrode active material layer NAL1 can be in the range of about 0 wt% to about 5 wt% or about 0 wt% to about 2 wt%.

[0077] In other words, the first negative electrode active material layer NAL1 may include a small amount of silicon-based negative electrode active material, or may not include silicon-based negative electrode active material. Since the first negative electrode active material layer NAL1 includes silicon-based negative electrode active material in an amount ranging from about 5 wt% or less, the volume change due to charging and discharging can be small, and lifetime characteristics can be expected or improved.

[0078] The first negative electrode active material layer NAL1 may also include a conductive material. The conductive material provides conductivity to the electrode and may include any electronically conductive material that does not cause chemical changes in the battery. The conductive material may be, or includes, for example, carbon-based materials, metallic materials, conductive polymers, or combinations thereof.

[0079] In an example embodiment, the conductive material in the first negative electrode active material layer NAL1 may include a carbon-based material. The conductive material may include at least one of, for example, graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes. The content of conductive material in the first negative electrode active material layer NAL1, relative to 100 wt%, can be in the range of about 0.1 wt% to about 10 wt%, about 0.2 wt% to about 7 wt%, or about 0.5 wt% to about 5 wt%.

[0080] In addition to the negative electrode active material and the conductive material, the first negative electrode active material layer NAL1 may also include a binder. The binder enables the negative electrode active material particles to adhere to each other and also facilitates the adhesion of the negative electrode active material to the current collector COL2. Non-aqueous binders, aqueous binders, dry binders, or combinations thereof may be used as binders. Based on 100 wt% of the first negative electrode active material layer NAL1, the binder content in the first negative electrode active material layer NAL1 may range from about 0 wt% to about 10 wt%, from about 0.3 wt% to about 7 wt%, or from about 0.5 wt% to about 5 wt%.

[0081] Non-aqueous adhesives may include at least one of, for example, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinylidene fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, and combinations thereof.

[0082] Waterborne binders may include at least one of, for example, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, (meth)acrylic resin, and combinations thereof. When a waterborne binder is used as a negative electrode binder, it may also include cellulose compounds capable of imparting viscosity.

[0083] Dry adhesives can be or include fibrous polymeric materials, such as at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0084] Second negative electrode active material layer: The content of carbon-based negative electrode active material CM2 in the second negative electrode active material layer NAL2 can be less than the content of carbon-based negative electrode active material CM1 in the first negative electrode active material layer NAL1. The content of silicon-based negative electrode active material SM2 in the second negative electrode active material layer NAL2 can be greater than the content of silicon-based negative electrode active material in the first negative electrode active material layer NAL1.

[0085] The weight ratio of carbon-based negative electrode active material CM2 to silicon-based negative electrode active material SM2 in the second negative electrode active material layer NAL2 can be in the range of about 60:40 to about 99:1, about 70:30 to about 98:2, or about 80:20 to about 98:2.

[0086] When the content of silicon-based negative electrode active material SM2 in the second negative electrode active material layer NAL2 is too small, the capacity of the negative electrode may decrease, and an N / P reversal phenomenon may occur. When the content of silicon-based negative electrode active material SM2 in the second negative electrode active material layer NAL2 is too large, the volume of the negative electrode active material layer changes significantly during charging and discharging, thus potentially degrading the lifetime characteristics of the negative electrode 20. When the weight ratio of carbon-based negative electrode active material CM2 to silicon-based negative electrode active material SM2 in the second negative electrode active material layer NAL2 falls within the aforementioned range, the negative electrode 20 can have sufficient capacity and exhibit the desired or improved lifetime characteristics.

[0087] The second negative electrode active material layer NAL2 may also include a conductive material. The conductive material may be, or include, for example, carbon-based materials, metallic materials, conductive polymers, or combinations thereof. Based on the total weight of the second negative electrode active material layer NAL2, the content of the conductive material in the second negative electrode active material layer NAL2 may range from about 0.1 wt% to about 10 wt%, from about 0.3 wt% to about 7 wt%, or from about 0.5 wt% to about 5 wt%.

[0088] In an example embodiment, the second negative electrode active material layer NAL2 may comprise a needle-like carbon-based conductive material. The needle-like carbon-based conductive material has a needle-like particle shape and, for example, may have an aspect ratio (length / diameter) in the range of about 10 or greater. The aspect ratio of the needle-like carbon-based conductive material may, for example, range from about 20 to about 700, from about 50 to about 600, from about 60 to about 300, or from about 100 to about 300. For example, the needle-like carbon-based conductive material may comprise at least one of carbon nanotubes (CNTs), vapor-grown carbon fibers (VGCF), carbon nanofibers (CNF), and combinations thereof.

[0089] When the second negative electrode active material layer NAL2 comprises needle-shaped carbon-based conductive materials, the conductivity of the second negative electrode active material layer NAL2 can be improved, and the volume expansion can be reduced. The second negative electrode active material layer NAL2 comprises silicon-based negative electrode active material SM2, which has low conductivity and large volume change during charging and discharging. Due to its needle-shaped structure, the needle-shaped carbon-based conductive material can rapidly transport electrons, thus significantly improving the conductivity of the negative electrode active material layer with only a small amount of conductive material. In addition, the needle-shaped carbon-based conductive material can stabilize the structure of silicon particles and improve the lifetime of the negative electrode by physically compensating for the expansion of silicon particles.

[0090] In addition to the negative electrode active material and the conductive material, the second negative electrode active material layer NAL2 may also include a binder. The binder may be the same as or similar to the binder included in the first negative electrode active material layer NAL1. For example, the binder may include an aqueous binder, such as at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, and (meth)acrylic rubber, and may also include a cellulose compound that can impart viscosity.

[0091] upper negative electrode active material layer ONAL According to an exemplary embodiment of the present disclosure, the upper negative electrode active material layer ONAL may include a third negative electrode active material layer NAL3 and a fourth negative electrode active material layer NAL4, and the third negative electrode active material layer NAL3 and the fourth negative electrode active material layer NAL4 are stacked (e.g., stacked sequentially) on the second surface of the negative electrode current collector COL2. For example, the third negative electrode active material layer NAL3 may be in contact with the second surface of the negative electrode current collector COL2, and the fourth negative electrode active material layer NAL4 may be spaced apart from the negative electrode current collector COL2. The third negative electrode active material layer NAL3 may include a carbon-based negative electrode active material CM3 and a silicon-based negative electrode active material SM3. The fourth negative electrode active material layer NAL4 may include a carbon-based negative electrode active material CM4.

[0092] The carbon-based negative electrode active material CM included in the upper negative electrode active material layer ONAL may be the same as or similar to the carbon-based negative electrode active material CM included in the lower negative electrode active material layer INAL. For example, the carbon-based negative electrode active material CM may include crystalline carbon, amorphous carbon, or a combination thereof. The silicon-based negative electrode active material SM included in the upper negative electrode active material layer ONAL may be the same as or similar to the silicon-based negative electrode active material SM included in the lower negative electrode active material layer INAL. For example, the silicon-based negative electrode active material SM may include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2) and at least one of their combinations.

[0093] The third negative electrode active material layer: The third negative electrode active material layer NAL3 may have a composition that is the same as or similar to the composition of the second negative electrode active material layer NAL2. The weight ratio of the carbon-based negative electrode active material CM3 to the silicon-based negative electrode active material SM3 in the third negative electrode active material layer NAL3 may be in the range of about 60:40 to about 99:1, about 70:30 to about 98:2, or about 80:20 to about 98:2.

[0094] The third negative electrode active material layer NAL3 may further include a conductive material. The conductive material may be the same as or similar to the conductive material included in the second negative electrode active material layer NAL2. Based on the total weight of the third negative electrode active material layer NAL3, the content of the conductive material in the third negative electrode active material layer NAL3 may be in the range of about 0.1 wt% to about 10 wt%, about 0.3 wt% to about 7 wt%, or about 0.5 wt% to about 5 wt%.

[0095] In addition to the negative electrode active material and the conductive material, the third negative electrode active material layer NAL3 may also include a binder. The binder may be the same as or similar to the binder included in the second negative electrode active material layer NAL2. For example, the binder may include an aqueous binder, such as at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, and (meth)acrylic rubber, and may also include a cellulose compound that can impart viscosity.

[0096] Fourth negative electrode active material layer: The content of carbon-based negative electrode active material CM4 in the fourth negative electrode active material layer NAL4 can be greater than the content of carbon-based negative electrode active material CM3 in the third negative electrode active material layer NAL3. For example, based on 100 wt% of the fourth negative electrode active material layer NAL4, the content of carbon-based negative electrode active material CM4 in the fourth negative electrode active material layer NAL4 can be in the range of about 90 wt% to about 99 wt%, about 95 wt% to about 99 wt%, or about 96 wt% to about 98 wt%.

[0097] Although not shown, the fourth negative electrode active material layer NAL4 may also include a silicon-based negative electrode active material in addition to the carbon-based negative electrode active material CM4. Based on the total weight of the fourth negative electrode active material layer NAL4, the content of the silicon-based negative electrode active material in the fourth negative electrode active material layer NAL4 may be in the range of about 5 wt% or less. For example, the content of the silicon-based negative electrode active material in the fourth negative electrode active material layer NAL4 may be in the range of about 0 wt% to about 5 wt% or about 0 wt% to about 2 wt%.

[0098] The fourth negative electrode active material layer NAL4 may also include a conductive material. The conductive material may be the same as or similar to the conductive material included in the first negative electrode active material layer NAL1. For example, the conductive material may include carbon-based materials. The conductive material may include at least one of, for example, graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0099] In addition to the negative electrode active material and the conductive material, the fourth negative electrode active material layer NAL4 may also include a binder. The binder may be the same as or similar to the binder included in the first negative electrode active material layer NAL1. For example, the binder may include an aqueous binder, such as at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, and (meth)acrylic rubber, and may also include a cellulose compound that can impart viscosity.

[0100] Reference Figure 7According to another example embodiment of this disclosure, the negative electrode for a rechargeable lithium battery may include: a negative electrode current collector COL2; a lower negative electrode active material layer INAL on a first surface of the negative electrode current collector; and an upper negative electrode active material layer ONAL on a second surface of the negative electrode current collector. Each or at least one of the lower negative electrode active material layer INAL and the upper negative electrode active material layer ONAL may include a carbon-based negative electrode active material CM and a silicon-based negative electrode active material SM. The content of the carbon-based negative electrode active material CM in the lower negative electrode active material layer INAL may increase as it approaches the first surface, and the content of the carbon-based negative electrode active material CM in the upper negative electrode active material layer ONAL may decrease as it approaches the second surface.

[0101] The content of silicon-based negative electrode active material SM in the lower negative electrode active material layer INAL can decrease as it approaches the first surface of the negative electrode current collector COL2. The content of silicon-based negative electrode active material SM in the upper negative electrode active material layer ONAL can increase as it approaches the second surface. In other words, the upper negative electrode active material layer ONAL can exhibit a negative electrode active material content distribution that is opposite to that of the lower negative electrode active material layer INAL.

[0102] According to an exemplary embodiment of this disclosure, the lower negative electrode active material layer INAL includes a first region to a third region vertically disposed on a first surface of the negative electrode current collector COL2, wherein the first region is closer to the negative electrode current collector COL2 than the second and third regions, the second region is closer to the negative electrode current collector COL2 than the third region, and the content of carbon-based negative electrode active material increases from the third region toward the first region. The content of silicon-based negative electrode active material decreases from the third region toward the first region.

[0103] For example, the first region may be the region adjacent to the first surface of the negative electrode current collector COL2. The content of carbon-based negative electrode active material CM in the first region may be greater than the content of carbon-based negative electrode active material CM in the second and third regions. For example, the content of carbon-based negative electrode active material CM in the first region may be in the range of about 90 wt% to about 99 wt%, about 95 wt% to about 99 wt%, or about 96 wt% to about 98 wt%. The content of silicon-based negative electrode active material SM in the first region may be less than the content of silicon-based negative electrode active material SM in the second and third regions. For example, the content of silicon-based negative electrode active material SM in the first region may be in the range of about 0 wt% to about 5 wt% or about 0 wt% to about 2 wt%.

[0104] The second region can be located between the first and third regions. For example, the second region can be located in the center of the lower negative electrode active material layer INAL. The content of carbon-based negative electrode active material CM in the second region can be less than the content of carbon-based negative electrode active material CM in the first region, but can be greater than the content of carbon-based negative electrode active material CM in the third region. The content of silicon-based negative electrode active material SM in the second region can be greater than the content of silicon-based negative electrode active material SM in the first region, but can be less than the content of silicon-based negative electrode active material SM in the third region.

[0105] For example, the third region may be a region adjacent to the top surface of the lower negative electrode active material layer INAL (i.e., the interface between the lower negative electrode active material layer INAL and the separator 30). The content of carbon-based negative electrode active material CM in the third region may be less than the content of carbon-based negative electrode active material CM in the first and second regions. The content of silicon-based negative electrode active material SM in the third region may be greater than the content of silicon-based negative electrode active material SM in the first and second regions. The weight ratio of carbon-based negative electrode active material CM to silicon-based negative electrode active material SM in the third region may be in the range of about 60:40 to about 99:1, about 70:30 to about 98:2, or about 80:20 to about 98:2.

[0106] The third region may include a needle-shaped carbon-based conductive material, such as carbon nanotubes (CNTs), vapor-grown carbon fibers (VGCFs), and carbon nanofibers (CNFs), as the conductive material; or the third region may include a needle-shaped carbon-based conductive material comprising at least one of carbon nanotubes (CNTs), vapor-grown carbon fibers (VGCFs), and carbon nanofibers (CNFs) as the conductive material. The needle-shaped carbon-based conductive material can physically compensate for the volume change of the silicon-based negative electrode active material included in the third region, thereby improving the lifetime of the negative electrode.

[0107] Based on the total weight of the lower negative electrode active material layer INAL, the content of conductive material in the lower negative electrode active material layer INAL can be in the range of about 0.1wt% to about 10wt%, about 0.3wt% to about 7wt%, or about 0.5wt% to about 5wt%.

[0108] According to an exemplary embodiment of this disclosure, the upper negative electrode active material layer ONAL includes a fourth to a sixth region vertically disposed on the second surface of the negative electrode current collector COL2, wherein the fourth region is closer to the negative electrode current collector COL2 than the fifth and sixth regions, the fifth region is closer to the negative electrode current collector COL2 than the sixth region, and the content of the carbon-based negative electrode active material CM decreases from the sixth region toward the fourth region. The content of the silicon-based negative electrode active material SM increases from the sixth region toward the fourth region.

[0109] For example, the fourth region may be the region adjacent to the second surface of the negative electrode current collector COL2. The content of carbon-based negative electrode active material CM in the fourth region may be less than the content of carbon-based negative electrode active material CM in the fifth and sixth regions. The content of silicon-based negative electrode active material SM in the fourth region may be greater than the content of silicon-based negative electrode active material SM in the fifth and sixth regions. The weight ratio of carbon-based negative electrode active material CM to silicon-based negative electrode active material SM in the fourth region may be in the range of approximately 60:40 to approximately 99:1, approximately 70:30 to approximately 98:2, or approximately 80:20 to approximately 98:2.

[0110] The fourth region may include at least one needle-shaped carbon-based conductive material, such as carbon nanotubes (CNTs), vapor-grown carbon fibers (VGCFs), and carbon nanofibers (CNFs). The needle-shaped carbon-based conductive material physically compensates for the volume change of the silicon-based negative electrode active material included in the fourth region, thus improving the lifetime of the negative electrode.

[0111] The fifth region can be located between the fourth and sixth regions. For example, the fifth region can be located in the center of the upper negative electrode active material layer ONAL. The content of carbon-based negative electrode active material CM in the fifth region can be greater than that in the fourth region, but less than that in the sixth region. The content of silicon-based negative electrode active material SM in the fifth region can be less than that in the fourth region, but greater than that in the sixth region.

[0112] For example, the sixth region may be a region adjacent to the top surface of the upper negative electrode active material layer ONAL (i.e., the interface between the upper negative electrode active material layer ONAL and the separator 30). The content of carbon-based negative electrode active material CM in the sixth region may be greater than the content of carbon-based negative electrode active material CM in the fourth and fifth regions. For example, the content of carbon-based negative electrode active material CM in the sixth region may be in the range of about 90 wt% to about 99 wt%, about 95 wt% to about 99 wt%, or about 96 wt% to about 98 wt%.

[0113] The content of silicon-based negative electrode active material SM in the sixth region can be less than the content of silicon-based negative electrode active material SM in the fourth and fifth regions. For example, the content of silicon-based negative electrode active material SM in the sixth region can be in the range of about 0 wt% to about 5 wt% or about 0 wt% to about 2 wt%.

[0114] Based on the total weight of the upper negative electrode active material layer ONAL, the content of conductive material in the upper negative electrode active material layer ONAL can be in the range of about 0.1wt% to about 10wt%, about 0.3wt% to about 7wt%, or about 0.5wt% to about 5wt%.

[0115] Electrode assembly Reference Figure 8 According to an example embodiment of this disclosure, the electrode assembly may be a core-type electrode assembly 40. The core-type electrode assembly 40 may be an electrode assembly in which a sheet-type negative electrode 20, a sheet-type positive electrode 10, and a sheet-type diaphragm 30 are wound in a spiral shape. For example, the core-type electrode assembly may include: a sheet-type negative electrode 20, in which a negative electrode active material layer is loaded on both sides of a negative electrode current collector; a sheet-type positive electrode 10, in which a positive electrode active material layer is loaded on both sides of a positive electrode current collector; and sheet-type diaphragms 32 and 34 disposed between the positive and negative electrodes.

[0116] The plate-type negative electrode 20 can be referenced above. Figure 6 and Figure 7 The negative electrode described. That is, the sheet-type negative electrode 20 may include a negative electrode current collector COL2, a lower negative electrode active material layer INAL on a first surface of the negative electrode current collector COL2, and an upper negative electrode active material layer ONAL on a second surface of the negative electrode current collector COL2.

[0117] The sheet-type positive electrode 10 may include: a positive electrode current collector COL1; a lower positive electrode active material layer ICAL on a first surface of the positive electrode current collector COL1; and an upper positive electrode active material layer OCAL on a second surface of the positive electrode current collector COL1.

[0118] The core-type electrode assembly 40 may have a structure in which the second separator 34 is on the outer surface of the upper negative electrode active material layer ONAL, and in which a unit structure of stacked (e.g., sequentially stacked) lower positive electrode active material layer ICAL / positive electrode current collector COL1 / upper positive electrode active material layer OCAL / first separator 32 / lower negative electrode active material layer INAL / negative electrode current collector COL2 / upper negative electrode active material layer ONAL / second separator 34 is wound such that the lower positive electrode active material layer ICAL and the lower negative electrode active material layer INAL point toward the winding center 80.

[0119] In the core-type electrode assembly 40, the upper positive electrode active material layer OCAL can be positioned further away from the winding center 80 of the electrode assembly than the lower positive electrode active material layer ICAL. In an example embodiment, the thickness of the upper positive electrode active material layer OCAL can be the same as or greater than the thickness of the lower positive electrode active material layer ICAL. For example, the thickness ratio of the upper positive electrode active material layer OCAL to the lower positive electrode active material layer ICAL can be in the range of about 1 to about 4, about 1 to about 3, or about 1.1 to about 2.5.

[0120] In the core-type electrode assembly (or "wound electrode assembly") 40, the upper negative electrode active material layer ONAL can be positioned further away from the winding center 80 of the electrode assembly than the lower negative electrode active material layer INAL. In an example embodiment, the thickness of the upper negative electrode active material layer ONAL can be the same as or similar to the thickness of the lower negative electrode active material layer INAL. For example, the thickness ratio of the upper negative electrode active material layer ONAL to the lower negative electrode active material layer INAL can be in the range of about 1:2 to about 2:1. For example, the thickness ratio of the upper negative electrode active material layer ONAL to the lower negative electrode active material layer INAL can be about 1:1.

[0121] Reference Figure 9 In the negative electrode 20 according to the example embodiment, the first negative electrode active material layer NAL1 can be positioned further away from the winding center 80 than the second negative electrode active material layer NAL2, and the fourth negative electrode active material layer NAL4 can be positioned further away from the winding center 80 than the third negative electrode active material layer NAL3. That is, in order of proximity to the winding center 80, the negative electrode 20 includes: the second negative electrode active material layer NAL2, the first negative electrode active material layer NAL1, the negative electrode current collector COL2, the third negative electrode active material layer NAL3, and the fourth negative electrode active material layer NAL4.

[0122] The second negative electrode active material layer NAL2, closest to the winding center 80, may include carbon-based and silicon-based negative electrode active materials as negative electrode active materials. The weight ratio of carbon-based to silicon-based negative electrode active materials in the second negative electrode active material layer NAL2 may be in the range of about 60:40 to about 99:1, about 70:30 to about 98:2, or about 80:20 to about 98:2.

[0123] The second negative electrode active material layer NAL2 and the upper positive electrode active material layer OCAL can be disposed facing each other, and the first separator 32 is located between the second negative electrode active material layer NAL2 and the upper positive electrode active material layer OCAL, thereby facilitating the reaction during battery charging and discharging. When the second negative electrode active material layer NAL2 includes a given amount of silicon-based negative electrode active material with desired or improved capacity and good reactivity with lithium ions, the capacity of the negative electrode can be increased, and the high-rate characteristics of the negative electrode can be improved.

[0124] The limitation of silicon-based negative electrode active materials is that volume changes during charging and discharging accelerate the degradation of the negative electrode. Because the second negative electrode active material layer NAL2 is subjected to enhanced compressive stress PR1, compared to the first, third, and fourth negative electrode active material layers NAL1, NAL3, and NAL4, even with a given amount of silicon-based negative electrode active material, volume changes during charging and discharging can be reduced or suppressed, thereby reducing or preventing lifetime degradation.

[0125] In addition to the negative electrode active material, the second negative electrode active material layer NAL2 may also include a conductive material. In an example embodiment, the conductive material may include needle-shaped carbon-based conductive materials. For example, needle-shaped carbon-based conductive materials may include at least one of carbon nanotubes (CNTs), vapor-grown carbon fibers (VGCFs), carbon nanofibers (CNFs), and combinations thereof. Needle-shaped carbon-based conductive materials can physically compensate for the expansion of silicon particles, thus stabilizing the structure of the silicon particles and improving the conductivity of the negative electrode.

[0126] The first negative electrode active material layer NAL1 may include a carbon-based negative electrode active material as the negative electrode active material. The content of the carbon-based negative electrode active material in the first negative electrode active material layer NAL1 may be greater than the content of the carbon-based negative electrode active material in the second negative electrode active material layer NAL2. Based on the total weight of the first negative electrode active material layer NAL1, the content of the carbon-based negative electrode active material in the first negative electrode active material layer NAL1 may be approximately 90 wt%. The first negative electrode active material layer NAL1 may also include a silicon-based negative electrode active material, wherein the content of the silicon-based negative electrode active material in the first negative electrode active material layer NAL1 may be approximately 2 wt% or less.

[0127] The first negative electrode active material layer NAL1 does not include silicon-based negative electrode active materials, or only includes a small amount of silicon-based negative electrode active materials, and includes a large amount of structurally stable and highly reversible carbon-based negative electrode active materials, which can help improve the lifespan of the negative electrode 20.

[0128] The thickness ratio of the first negative electrode active material layer NAL1 and the second negative electrode active material layer NAL2 can be in the range of about 1:2 to about 2:1. When the thickness ratio of the first negative electrode active material layer NAL1 and the second negative electrode active material layer NAL2 falls within the above range, the negative electrode can have desired or improved rate performance and desired or improved lifetime performance.

[0129] The third negative electrode active material layer NAL3 can have a composition similar to that of the second negative electrode active material layer NAL2. The weight ratio of carbon-based negative electrode active material to silicon-based negative electrode active material in the third negative electrode active material layer NAL3 can be in the range of approximately 60:40 to approximately 99:1, approximately 70:30 to approximately 98:2, or approximately 80:20 to approximately 98:2. In other words, the third negative electrode active material layer NAL3 includes a given amount of silicon-based negative electrode active material, thus increasing the capacity of the negative electrode and improving rate performance.

[0130] Although the compressive stress PR1 applied to the third negative electrode active material layer NAL3 is smaller than that applied to the second negative electrode active material layer NAL2, since the third negative electrode active material layer NAL3 is sandwiched between the structurally stabilized negative electrode current collector COL2 and the fourth negative electrode active material layer NAL4, even when the third negative electrode active material layer NAL3 includes a given amount of silicon, the volume change caused by charging and discharging can be reduced or suppressed.

[0131] The fourth negative electrode active material layer NAL4 may include carbon-based negative electrode active materials as the negative electrode active material. The fourth negative electrode active material layer NAL4 may include a larger amount of carbon-based negative electrode active material than the third negative electrode active material layer NAL3. For example, the content of carbon-based negative electrode active material in the fourth negative electrode active material layer NAL4 may be in the range of about 90 wt% to about 99 wt% or about 95 wt% to about 98 wt%. The fourth negative electrode active material layer NAL4 may also include silicon-based negative electrode active materials, but the content of silicon-based negative electrode active material in the fourth negative electrode active material layer NAL4 may be about 2 wt% or less.

[0132] The fourth negative electrode active material layer, NAL4, located furthest from the winding center, experiences the smallest compressive stress PR1 while simultaneously experiencing the largest tensile stress PR2. Therefore, compared to the first, second, and third negative electrode active material layers NAL1 and NAL2, the fourth negative electrode active material layer NAL4 has a higher risk of cracking and delamination. The fourth negative electrode active material layer NAL4 comprises only carbon-based negative electrode active materials with small volume changes and stable structures, or includes carbon-based negative electrode active materials and a small amount of silicon-based negative electrode active materials. This reduces the risk of cracking and delamination and improves the lifespan of the fourth negative electrode active material layer NAL4.

[0133] The thickness ratio of the third negative electrode active material layer NAL3 to the fourth negative electrode active material layer NAL4 can be in the range of about 1:2 to about 2:1. When the thickness ratio of the third negative electrode active material layer NAL3 to the fourth negative electrode active material layer NAL4 falls within the above range, the negative electrode can have the desired or improved capacity and the desired or improved lifetime characteristics.

[0134] In the negative electrode 20 for a rechargeable lithium battery according to the example embodiment, since the silicon-based negative electrode active material is concentrated in the second negative electrode active material layer NAL2 and the third negative electrode active material layer NAL3, which are closer to the winding center, high-rate characteristics can be improved while reducing or suppressing the expansion of the silicon-based negative electrode active material. Furthermore, since the carbon-based negative electrode active material is concentrated in the first negative electrode active material layer NAL1 and the fourth negative electrode active material layer NAL4, which are further away from the winding center 80, the negative electrode can have improved lifetime characteristics. In other words, the negative electrode 20 for a rechargeable lithium battery according to this disclosure asymmetrically forms negative electrode active material layers on both sides of the negative electrode current collector COL2, thus simultaneously improving both rate characteristics and lifetime characteristics.

[0135] According to another exemplary embodiment of this disclosure, in Figure 8 In the wound electrode assembly 40 shown, each of the lower negative electrode active material layer INAL and the upper negative electrode active material layer ONAL includes a carbon-based negative electrode active material CM and a silicon-based negative electrode active material SM. The content of the carbon-based negative electrode active material CM in the lower negative electrode active material layer INAL can increase as it approaches the first surface of the negative electrode current collector COL2, and the content of the carbon-based negative electrode active material CM in the upper negative electrode active material layer ONAL can decrease as it approaches the second surface of the negative electrode current collector COL2.

[0136] The content of silicon-based negative electrode active material SM in the lower negative electrode active material layer INAL can decrease as it approaches the first surface of the negative electrode current collector COL2. The content of silicon-based negative electrode active material SM in the upper negative electrode active material layer ONAL can increase as it approaches the second surface of the negative electrode current collector COL2. In other words, the upper negative electrode active material layer ONAL can exhibit a negative electrode active material content distribution that is opposite to that of the lower negative electrode active material layer INAL.

[0137] exist Figure 9 In the negative electrode 20 for a rechargeable lithium battery according to this disclosure, each of the lower negative electrode active material layer INAL and the upper negative electrode active material layer ONAL is configured such that the content of silicon-based negative electrode active material SM increases as it approaches the winding center 80, thereby improving rate performance while reducing or suppressing the volume expansion of the silicon-based negative electrode active material. Furthermore, each of the lower negative electrode active material layer INAL and the upper negative electrode active material layer ONAL is configured such that the content of carbon-based negative electrode active material increases as it moves away from the winding center 80, thereby improving the lifetime characteristics of the negative electrode.

[0138] The present disclosure is described in more detail below by way of examples. However, the following examples are for illustrative purposes only, and the scope of the present disclosure is not limited to the exemplary embodiments.

[0139] Example Preparation of the first negative electrode paste: Graphite powder was prepared as the negative electrode active material. A mixture of styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) in a weight ratio of approximately 1:1 was prepared as a binder, and carbon nanotubes (CNTs) were prepared as the conductive material. The negative electrode active material, binder, and conductive material were mixed in a weight ratio of 97.5:2:0.5 to prepare a first negative electrode slurry.

[0140] Preparation of the second negative electrode paste: Graphite powder was prepared as the active material for a carbon-based negative electrode, and a silicon-carbon composite (silicon to carbon weight ratio of 6:4) was prepared as the active material for a silicon-based negative electrode. The graphite powder and silicon-carbon composite were mixed at a weight ratio of approximately 86:14 to prepare the negative electrode active material. A mixture of styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) in a weight ratio of 1:1 was prepared as a binder, and carbon nanotubes (CNTs) were prepared as a conductive material. The negative electrode active material, binder, and conductive material were mixed at a weight ratio of 97.5:2:0.5 to prepare a second negative electrode slurry.

[0141] Manufacturing of the negative electrode: A first negative electrode slurry is coated onto the bottom surface of a copper foil current collector with a thickness of approximately 10 μm to form a first negative electrode active material layer. The coated electrode plate is dried at approximately 100°C for approximately 1 hour. A second negative electrode slurry is coated onto each of the first negative electrode active material layer (the first negative electrode active material layer formed on the bottom surface) and the top surface of the copper foil current collector to form a second negative electrode active material layer and a third negative electrode active material layer. The coated electrode plate is dried at approximately 100°C for approximately 1 hour or longer. The first negative electrode slurry is coated onto the third negative electrode active material layer (the third negative electrode active material layer formed on the top surface) to form a fourth negative electrode active material layer. The coated electrode plate is dried and rolled to manufacture the final negative electrode.

[0142] Manufacturing of the positive electrode: Add and mix positive electrode active material (LiNi) 0.6 Co 0.2 Mn 0.2 An active material slurry is prepared using a binder solution of O2, carbon conductive material (Super P), and polyvinylidene fluoride (PVDF). The weight ratio of active material: conductive material: binder in the active material slurry is approximately 98:1:1. The active material slurry is coated onto both sides (top and bottom surfaces) of an aluminum current collector with a thickness of approximately 12 μm. The resulting material is dried at approximately 120°C for approximately 1 hour or longer, and then rolled to produce a positive electrode comprising a lower positive electrode active material layer (formed on the bottom surface) and an upper positive electrode active material layer (formed on the top surface). The coating is performed such that the thickness ratio of the lower to upper positive electrode active material layers is approximately 1:1.5.

[0143] Manufacturing of core-type electrode assemblies: A polyethylene (PE) membrane (manufactured by Celgard) with a thickness of approximately 20 μm was prepared as a first separator, and a polyethylene (PE) membrane (manufactured by Celgard) with a thickness of approximately 12 μm was prepared as a second separator. The first separator was disposed between the upper positive electrode active material layer and the second negative electrode active material layer, and the second separator was disposed on the outer surface of the fourth negative electrode active material layer. Then, a structure in which the obtained positive electrode, the first separator, the obtained negative electrode, and the second separator were sequentially disposed (lower positive electrode active material layer / Al / upper positive electrode active material layer / first separator / second negative electrode active material layer / first negative electrode active material layer / Cu / third negative electrode active material layer / fourth negative electrode active material layer / second separator) was wound to manufacture a core-type electrode assembly.

[0144] Manufacturing of rechargeable lithium batteries: The manufactured electrode assembly is sealed in a cylindrical housing and injected with an electrolyte solution to manufacture a cylindrical rechargeable lithium battery. In the electrolyte solution, a lithium salt of 1.3M LiPF6 is added to a solvent mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1.

[0145] Comparison Example 1 Preparation of negative electrode paste: Graphite powder was prepared as the active material for a carbon-based negative electrode, and a silicon-carbon composite (silicon to carbon weight ratio of 6:4) was prepared as the active material for a silicon-based negative electrode. The graphite powder and silicon-carbon composite were mixed at a weight ratio of approximately 86:14 to prepare the negative electrode active material. A mixture of styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) in a weight ratio of approximately 1:1 was prepared as a binder, and carbon nanotubes (CNTs) were prepared as a conductive material. The negative electrode active material, binder, and conductive material were mixed at a weight ratio of approximately 97.5:2:0.5 to manufacture a negative electrode slurry.

[0146] Manufacturing of the negative electrode: The manufactured negative electrode slurry is simultaneously coated onto both sides (top and bottom surfaces) of a copper foil current collector with a thickness of approximately 10 μm to form a first negative electrode active material layer and a second negative electrode active material layer. The coated electrode plate is dried at approximately 100°C for approximately 1 hour or longer and then rolled to manufacture the final negative electrode.

[0147] Manufacturing of rechargeable lithium batteries: The positive electrode, the core-type electrode assembly, and the rechargeable lithium battery are manufactured in the same manner as in the example.

[0148] Comparison Example 2 Manufacturing of negative electrode paste: The first negative electrode slurry and the second negative electrode slurry are manufactured in the same manner as in the example.

[0149] Manufacturing of the negative electrode: A first negative electrode paste is applied to both sides of a 10 μm thick copper foil current collector to form a first negative electrode active material layer and a third negative electrode active material layer. The coated electrode plate is dried at approximately 100°C for approximately 1 hour or longer. A second negative electrode paste is applied to the first negative electrode active material layer (formed on the bottom surface) and the third negative electrode active material layer (formed on the top surface) to form a second negative electrode active material layer (formed on top of the first negative electrode active material layer) and a fourth negative electrode active material layer (formed on top of the third negative electrode active material layer). The coated electrode plate is dried at approximately 100°C for approximately 1 hour or longer and rolled to produce the final negative electrode.

[0150] Manufacturing of rechargeable lithium batteries: The positive electrode, the core-type electrode assembly, and the rechargeable lithium battery are manufactured in the same manner as in Example 1.

[0151] Comparison Example 3 Manufacturing of negative electrode paste: The first negative electrode slurry and the second negative electrode slurry are manufactured in the same manner as in the example.

[0152] Manufacturing of the negative electrode: A second negative electrode paste is coated to the same thickness on both sides of a 10 μm thick copper foil current collector to form a first negative electrode active material layer and a third negative electrode active material layer. The coated electrode plate is dried at approximately 100°C for approximately 1 hour or longer. The first negative electrode paste is then coated to the same thickness onto the first negative electrode active material layer (the first negative electrode active material layer formed on the bottom surface) and the third negative electrode active material layer (the third negative electrode active material layer formed on the top surface) to form a second negative electrode active material layer (the second negative electrode active material layer formed on the first negative electrode active material layer) and a fourth negative electrode active material layer (the fourth negative electrode active material layer formed on the third negative electrode active material layer). The coated electrode plate is dried at approximately 100°C for approximately 1 hour or longer and then rolled to manufacture the final negative electrode.

[0153] Manufacturing of rechargeable lithium batteries: The positive electrode, the core-type electrode assembly, and the rechargeable lithium battery are manufactured in the same manner as in Example 1.

[0154] Evaluation Example 1 For lithium batteries manufactured according to the example and comparative examples, lifespan characteristics are evaluated using the following methods.

[0155] The lithium-ion battery was charged at approximately 25°C with a constant current at a current rate of 0.33C until the voltage reached approximately 4.2V (relative to Li). Then, in constant voltage mode, the battery was stopped at a current rate of approximately 0.05C while maintaining the voltage at approximately 4.2V. Subsequently, during discharge, the battery was discharged at a constant current rate of approximately 1C until the voltage reached approximately 2.5V (relative to Li) (formation cycle). The lithium-ion battery that had undergone formation cycling was then charged at approximately 25°C with a constant current at a rate of approximately 0.5C until the voltage reached approximately 4.2V (relative to Li). Subsequently, during discharge, the battery was discharged at a constant current rate of approximately 1.4C until the voltage reached approximately 2.5V (relative to Li), and these cycles were repeated under the same conditions for 500 cycles (500 repetitions). A 10-minute rest period was applied after each charge / discharge cycle. The experimental results of the charge and discharge experiments at room temperature are presented in Table 1 below. The capacity retention rate for the 500th cycle is defined by Equation 1 below.

[0156] Equation 1: Capacity retention rate [%] = [Discharge capacity at 500th cycle / Discharge capacity at 1st cycle] Table 1:

[0157]

[0158] Evaluation Example 2 The characteristics of lithium batteries manufactured according to the example and comparative examples are evaluated using the following methods.

[0159] The lithium-ion battery was charged at a constant current at a rate of approximately 0.33C until the voltage reached approximately 4.2V (relative to Li). Then, in constant voltage mode, the battery was cut off at a current rate of approximately 0.05C while maintaining the voltage at approximately 4.2V. Subsequently, during discharge, the battery was discharged at a constant current at a rate of approximately 1C (formation cycle). The lithium-ion battery that underwent formation cycling was charged at a constant current rate of approximately 0.33C at approximately 25°C until the voltage reached approximately 4.2V (relative to Li). Then, in constant voltage mode, the battery was cut off at a current rate of approximately 0.05C while maintaining the voltage at approximately 4.2V. Afterward, a discharge was performed at each of the following C rates: approximately 0.2C, approximately 0.33C, approximately 0.5C, approximately 1C, approximately 1.5C, approximately 2C, and approximately 3C (charging voltage approximately 4.2V, discharging voltage approximately 2.5V), and the discharge capacity at each C rate was measured. The magnification characteristics are evaluated according to Equation 2 below, and the evaluation results are presented in Table 2 below.

[0160] Equation 2: C-rate characteristic [%] = [Discharge capacity at each C-rate / Discharge capacity at approximately 0.2C rate] × 100 Table 2:

[0161] Referring to Tables 1 and 2, compared to the rechargeable lithium battery according to Comparative Example 1, the rechargeable lithium battery according to the example has desired or improved rate performance and lifespan characteristics. Compared to the rechargeable lithium battery according to Comparative Example 2, the rechargeable lithium battery according to the example has desired or improved lifespan characteristics and a similar level of rate performance. And compared to the rechargeable lithium battery according to Comparative Example 3, the rechargeable lithium battery according to the example has a similar level of lifespan characteristics and desired or improved rate performance.

[0162] The negative electrode for a rechargeable lithium battery according to this disclosure includes a negative electrode active material layer with an asymmetric structure on both sides of the negative electrode current collector, thereby improving rate performance and lifetime characteristics. The rechargeable lithium battery according to this disclosure can have desired or improved rate performance and desired or improved lifetime characteristics.

[0163] Although exemplary embodiments of the present disclosure have been described with reference to the accompanying drawings, the present disclosure may be implemented in other specific forms without altering the technical concept or essential features of the disclosure. Therefore, the above exemplary embodiments are for illustrative purposes only and not for limitation.

Claims

1. A negative electrode for a rechargeable lithium battery, the negative electrode comprising: Negative electrode current collector; The lower negative electrode active material layer is on the first surface of the negative electrode current collector; as well as The upper negative electrode active material layer is located on the second surface of the negative electrode current collector. The lower negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer, which are stacked on the first surface of the negative electrode current collector. The upper negative electrode active material layer includes a third negative electrode active material layer and a fourth negative electrode active material layer, which are stacked on the second surface of the negative electrode current collector. At least one of the first negative electrode active material layer and the fourth negative electrode active material layer includes a carbon-based negative electrode active material. At least one of the second and third negative electrode active material layers includes a carbon-based negative electrode active material and a silicon-based negative electrode active material. The content of carbon-based negative electrode active material in the first negative electrode active material layer is greater than the content of carbon-based negative electrode active material in the second negative electrode active material layer, and The content of carbon-based negative electrode active material in the third negative electrode active material layer is less than the content of carbon-based negative electrode active material in the fourth negative electrode active material layer.

2. The negative electrode according to claim 1, in, The content of carbon-based negative electrode active material in the first negative electrode active material layer is in the range of 90wt% to 99wt%, and The content of carbon-based negative electrode active material in the fourth negative electrode active material layer is in the range of 90wt% to 99wt%.

3. The negative electrode according to claim 1, wherein: The weight ratio of carbon-based negative electrode active material to silicon-based negative electrode active material in the second negative electrode active material layer is in the range of 80:20 to 98:2; and The weight ratio of carbon-based negative electrode active material to silicon-based negative electrode active material in the third negative electrode active material layer is in the range of 80:20 to 98:

2.

4. The negative electrode according to claim 1, wherein: At least one of the second negative electrode active material layer and the third negative electrode active material layer further includes a conductive material; and The conductive material includes needle-shaped carbon-based conductive materials.

5. The negative electrode according to claim 4, wherein: The content of conductive material in the second negative electrode active material layer is in the range of 0.1 wt% to 10 wt%; and The content of conductive material in the active material layer of the third negative electrode is in the range of 0.1 wt% to 10 wt%.

6. The negative electrode according to claim 1, wherein: The first negative electrode active material layer further includes a silicon-based negative electrode active material; and The content of silicon-based negative electrode active material in the first negative electrode active material layer is in the range of 2 wt% or less.

7. The negative electrode according to claim 1, wherein: The fourth negative electrode active material layer further includes a silicon-based negative electrode active material; and The content of silicon-based negative electrode active material in the fourth negative electrode active material layer is in the range of 2 wt% or less.

8. The negative electrode according to claim 1, wherein, At least one of the first negative electrode active material layer and the fourth negative electrode active material layer further includes a conductive material.

9. The negative electrode according to claim 1, wherein: The first negative electrode active material layer is in contact with the first surface of the negative electrode current collector; and The third negative electrode active material layer is in contact with the second surface of the negative electrode current collector.

10. The negative electrode according to claim 1, wherein, The thickness ratio of the lower negative electrode active material layer to the upper negative electrode active material layer is in the range of 1:2 to 2:

1.

11. The negative electrode according to claim 1, wherein: The thickness ratio of the first negative electrode active material layer to the second negative electrode active material layer is in the range of 1:2 to 2:1; and The thickness ratio of the third negative electrode active material layer to the fourth negative electrode active material layer is in the range of 1:2 to 2:

1.

12. A core-type electrode assembly, the core-type electrode assembly comprising: Positive electrode, negative electrode, and a membrane between the positive electrode and the negative electrode. The negative electrode includes: Negative electrode current collector; The lower negative electrode active material layer is on the first surface of the negative electrode current collector; and The upper negative electrode active material layer is located on the second surface of the negative electrode current collector. Wherein, at least one of the lower negative electrode active material layer and the upper negative electrode active material layer includes a carbon-based negative electrode active material and a silicon-based negative electrode active material. The content of carbon-based negative electrode active material in the lower negative electrode active material layer increases as it approaches the first surface, and The content of carbon-based negative electrode active material in the upper negative electrode active material layer decreases as it approaches the second surface.

13. The electrode assembly according to claim 12, wherein: The content of silicon-based negative electrode active material in the lower negative electrode active material layer decreases as it approaches the first surface; and The content of silicon-based negative electrode active material in the upper negative electrode active material layer increases as it approaches the second surface.

14. The core-type electrode assembly according to claim 12, wherein, At least one of the lower negative electrode active material layer and the upper negative electrode active material layer further includes a conductive material.

15. The core-type electrode assembly according to claim 14, wherein: The content of conductive material in the upper negative electrode active material layer is in the range of 0.1 wt% to 10 wt%; and The content of conductive material in the lower negative electrode active material layer is in the range of 0.1wt% to 10wt%.

16. The electrode assembly according to claim 12, wherein, The thickness ratio of the lower negative electrode active material layer to the upper negative electrode active material layer is in the range of 1:2 to 2:

1.

17. The electrode assembly according to claim 12, wherein, Compared to the lower negative electrode active material layer, the upper negative electrode active material layer is further away from the winding center of the electrode assembly.

18. The core-type electrode assembly according to claim 12, wherein: The positive electrode includes a positive electrode current collector, a lower positive electrode active material layer on the bottom surface of the positive electrode current collector, and an upper positive electrode active material layer on the top surface of the positive electrode current collector; and Compared to the lower positive electrode active material layer, the upper positive electrode active material layer is further away from the winding center of the electrode assembly.

19. The core-type electrode assembly according to claim 18, wherein, The thickness ratio of the upper positive electrode active material layer to the lower positive electrode active material layer is in the range of 1 to 4.

20. A rechargeable lithium battery, the rechargeable lithium battery comprising a core-type electrode assembly according to any one of claims 12 to 19.

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