Positive electrode and rechargeable lithium battery including same

Abstract

A positive electrode and a rechargeable lithium battery are disclosed. The positive electrode includes a current collector, a first active material layer on the current collector, and a second active material layer on the first active material layer. The first active material layer includes a first positive electrode active material and a first lithium-based additive. The second active material layer includes a second positive electrode active material and a second lithium-based additive. An amount of the second lithium-based additive in the second active material layer is greater than an amount of the first lithium-based additive in the first active material layer.

Description

[0001] This application claims priority to Korean Patent Application No. 10-2024-0133135, filed on September 30, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] Examples of this disclosure relate to a positive electrode and a rechargeable lithium battery including the positive electrode, and more specifically, to a positive electrode including a Ni-type additive and a rechargeable lithium battery including the positive electrode. Background Technology

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

[0004] A rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte. The positive and negative electrodes include active materials in which lithium ions can be inserted and extracted. When lithium ions are inserted and extracted, the rechargeable lithium battery generates electrical energy caused by oxidation and reduction reactions. Summary of the Invention

[0005] Example embodiments of this disclosure include a positive electrode with improved capacity and lifetime characteristics.

[0006] Example embodiments of this disclosure include a rechargeable lithium battery containing a positive electrode.

[0007] According to an exemplary embodiment of this disclosure, a positive electrode for a rechargeable lithium battery may include: a current collector; a first active material layer on the current collector; and a second active material layer on the first active material layer. The first active material layer may include a first positive electrode active material and a first lithium-based additive. The second active material layer may include a second positive electrode active material and a second lithium-based additive. Each or at least one of the first lithium-based additive and the second lithium-based additive may include at least one of a compound represented by chemical formula 1-1, a compound represented by chemical formula 1-2, and a compound represented by chemical formula 1-3. The amount of the second lithium-based additive in the second active material layer may be greater than the amount of the first lithium-based additive in the first active material layer.

[0008] Chemical formula 1-1: Li x1 NiO2.

[0009] Chemical formula 1-2: Li x2 FeO4.

[0010] Chemical Formulas 1-3: Li x3 Co (1-y-z-m) Zn y Al z M m O4.

[0011] In Chemical Formula 1-1, the subscript x1 can satisfy the relationship of 1.1 ≤ x1 ≤ 2.5.

[0012] In Chemical Formula 1-2, the subscript x2 can satisfy the relationship of 1.1 ≤ x2 ≤ 5.5.

[0013] In Chemical Formula 1-3, M can be at least one of Ti, Zr, Mn, and Ni or M can include at least one of Ti, Zr, Mn, and Ni, and the subscripts x3, y, z, and m can satisfy the relationships of 5 ≤ x3 ≤ 7, 0 < y ≤ 0.5, 0 < z ≤ 0.5, 0 < y + z + m < 1, and 0 ≤ m ≤ 0.5.

[0014] According to an exemplary embodiment of the present disclosure, a positive electrode for a rechargeable lithium battery may include: a current collector; and a positive electrode active material layer on the current collector. The positive electrode active material layer may include a positive electrode active material and a lithium-based additive. The lithium-based additive may include at least one of a compound represented by Chemical Formula 1-1, a compound represented by Chemical Formula 1-2, and a compound represented by Chemical Formula 1-3. The positive electrode active material layer may include a first portion adjacent to the current collector and a second portion adjacent to the surface of the positive electrode active material layer. The weight of the lithium-based additive may be in the range of about 1% to about 10% of the total weight of the positive electrode active material layer. The amount of the lithium-based additive in the second portion may be greater than the amount of the lithium-based additive in the first portion.

[0015] According to an exemplary embodiment of the present disclosure, a rechargeable lithium battery may include: the positive electrode discussed above; a negative electrode including a negative electrode active material; and a separator between the positive electrode and the negative electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a simplified conceptual diagram showing a rechargeable lithium battery according to an exemplary embodiment of the present disclosure.

[0017] Figures 2 to 5 is a simplified diagram showing a rechargeable lithium battery according to an exemplary embodiment of the present disclosure, where Figure 2 shows a cylindrical battery, Figure 3 shows a prismatic battery, Figure 4 and Figure 5 shows a pouch-type battery.

[0018] Figure 6This is a cross-sectional view showing the positive electrode of a rechargeable lithium battery according to an exemplary embodiment of the present disclosure.

[0019] Figure 7A and Figure 7B This is an enlarged view showing the positive electrode according to an exemplary embodiment of the present disclosure.

[0020] Figure 8 This is a cross-sectional view showing the positive electrode according to an exemplary embodiment of the present disclosure.

[0021] Figure 9 This is an enlarged view showing the positive electrode according to an exemplary embodiment of the present disclosure.

[0022] Figure 10 This is a diagram illustrating a method for manufacturing a positive electrode according to an exemplary embodiment of the present disclosure. Detailed Implementation

[0023] To fully understand the structure and effects of this disclosure, some exemplary embodiments of the disclosure have been described with reference to the accompanying drawings. However, it should be noted that this disclosure is not limited to the following exemplary embodiments, but can be implemented in various forms. Rather, the exemplary embodiments are provided merely to disclose the disclosure and to allow those skilled in the art to fully understand its scope.

[0024] In this specification, it is understood that when an element is referred to as being "on" another element, the element may be "directly on" said other element, or there may be intermediate elements present therein. In the accompanying drawings, the thickness of some components is exaggerated for the purpose of effectively illustrating the technical content. Throughout the specification, the same reference numerals denote the same elements.

[0025] Some exemplary embodiments detailed in this specification are discussed with reference to sectional views and / or plan views, which serve as ideal example views of this disclosure. In the drawings, the thickness of layers and regions may be exaggerated for the purpose of effectively explaining the technical content. Therefore, the regions shown as examples in the drawings have general characteristics, and the shapes of the regions shown as examples in the drawings are used to disclose specific shapes but do not limit the scope of this disclosure. It is understood that although the terms "first," "second," "third," etc., may be used herein to describe various elements, these elements may not be limited by these terms. These terms are used only to distinguish one element from another. The exemplary embodiments explained and illustrated herein include supplementary embodiments thereof.

[0026] Unless otherwise specified in this specification, singular expressions may include plural expressions. Furthermore, unless otherwise specified, the phrase "A or B" may mean "A but not B," "B but not A," and "A and B." The terms "including / comprises" and / or "have / contain" as used in this specification do not exclude the presence or addition of one or more other components.

[0027] In this specification, the term "combination of them" may refer to mixtures, stacks, complexes, copolymers, alloys, blends, or reaction products.

[0028] When the terms “about” or “basically” are used in conjunction with numerical values ​​in this specification, the numerical values ​​intended to be associated include a tolerance of ±10% around said value. When a range is specified, the range includes all values ​​within that range, such as increments of 0.1%.

[0029] Figure 1 This is a simplified conceptual diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure. (Refer to...) Figure 1 A rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0030] The positive electrode 10 and the negative electrode 20 can be spaced apart from each other by a diaphragm 30. The diaphragm 30 can be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the diaphragm 30 can be in contact with the electrolyte ELL. The positive electrode 10, the negative electrode 20, and the diaphragm 30 can be immersed in the electrolyte ELL.

[0031] The electrolyte ELL can be a medium through which lithium ions transfer between the positive electrode 10 and the negative electrode 20, or a medium comprising the transfer of lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move through the separator 30 toward one of the positive electrode 10 and the negative electrode 20.

[0032] 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.

[0033] For example, the positive electrode 10 may also include additives that can be configured as a sacrificial positive electrode.

[0034] The amount of positive electrode active material in the positive electrode active material layer AML1, relative to 100 wt%, can range from about 90 wt% to about 99 wt%. The amount of binder and conductive material in the positive electrode active material layer AML1, relative to 100 wt%, can range from about 0.5 wt% to about 5 wt%.

[0035] The binder can be configured to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector COL1. The binder may include, for example, at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin and nylon, but this disclosure is not limited thereto.

[0036] Conductive materials may be included to provide conductivity to the electrodes, and any suitable conductive material that does not cause chemical changes in the battery may be included 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 one or more of copper, nickel, aluminum, and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0037] Aluminum (Al) may be included as the current collector COL1, but this disclosure is not limited thereto.

[0038] 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., lithium 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 at least one of cobalt, manganese, nickel and combinations thereof, or includes at least one of cobalt, manganese, nickel and combinations thereof.

[0039] 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.

[0040] 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 Dc (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 b O4 (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).

[0041] In the above chemical formula, A can be at least one of Ni, Co, Mn and combinations thereof, or include at least one of Ni, Co, Mn and combinations thereof; X can be at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof, or include at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; D can be at least one of O, F, S, P and combinations thereof, or include at least one of O, F, S, P and combinations thereof; G can be at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V and combinations thereof, or include at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V and combinations thereof; L 1 It can be at least one of Mn, Al and combinations thereof, or include at least one of Mn, Al and combinations thereof.

[0042] For example, the positive electrode active material can be a high-nickel positive electrode active material, or the positive electrode active material may include a high-nickel positive electrode active material. Relative to 100 mol% of metals other than lithium in the lithium transition metal complex oxide, 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%. High-nickel positive electrode active materials can achieve high capacity and therefore can be used in high-capacity and high-density rechargeable lithium batteries.

[0043] 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 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.

[0044] For example, the negative electrode active material layer AML2 may include a negative electrode active material in the range of about 90 wt% to about 99 wt%, a binder in the range of about 0.5 wt% to about 5 wt%, and a conductive material in the range of about 0 wt% to about 5 wt%.

[0045] The binder can be configured to improve the adhesion between the negative electrode active material particles and the adhesion between the negative electrode active material and the current collector COL2. The binder may include at least one of non-aqueous binders, aqueous binders, dry binders, and combinations thereof.

[0046] 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.

[0047] 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.

[0048] When an aqueous binder is included as the negative electrode binder, a cellulose compound capable of providing adhesion 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.

[0049] Dry adhesives may include at least one of the following: fibrous polymeric materials, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0050] Conductive materials may be included to provide conductivity to the electrodes, and any suitable conductive material that does not cause chemical changes in the battery may be included 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 one or more of copper, nickel, aluminum, and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0051] 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.

[0052] 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.

[0053] Materials capable of reversibly embedding and de-embedding lithium ions may include carbonaceous negative electrode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. For example, crystalline carbon may include graphite, such as natural graphite or artificial graphite that is non-shaped, flaky, lamellar, spherical, or fibrous, and amorphous carbon may include at least one of soft carbon, hard carbon, mesophase pitch carbon, and calcined coke.

[0054] Lithium metal alloys may include alloys of lithium and metals, where the metals include at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0055] 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 at least one of an alkali metal, alkaline earth metal, group 13 element, group 14 element (except Si), group 15 element, group 16 element, transition metal, rare earth element, and combinations thereof or Q includes at least one of an alkali metal, alkaline earth metal, group 13 element, group 14 element (except Si), group 15 element, group 16 element, transition metal, rare earth element, 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.

[0056] The silicon-carbon composite may be a composite of silicon and amorphous carbon or the silicon-carbon composite may 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) on the surface of the secondary particles. Amorphous carbon may also be present between the primary silicon particles, and for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0057] 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 on the surface of the core.

[0058] Si-based negative electrode active materials or Sn-based negative electrode active materials may be included in combination with carbonaceous negative electrode active materials.

[0059] Separator 30 Depending on the type of rechargeable lithium battery, the separator 30 may be present between the positive electrode 10 and the negative electrode 20. The separator 30 may include one or more of polyethylene, polypropylene, and polyvinylidene fluoride, and may have multiple layers, such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polypropylene trilayer separator, and a polypropylene / polypropylene / polypropylene trilayer separator.

[0060] The diaphragm 30 may include a porous substrate and a coating on one surface or two opposing surfaces of the porous substrate, the coating comprising an organic material, an inorganic material, or a combination thereof.

[0061] The porous substrate may be a polymer layer or may include a polymer layer, the polymer layer including polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon). TM The porous substrate may be a copolymer or mixture of two or more of the above-mentioned materials, or the porous substrate may include a copolymer or mixture of two or more of the above-mentioned materials.

[0062] Organic materials may include polyvinylidene fluoride copolymers or (meth)acrylic acid copolymers.

[0063] Inorganic materials may include inorganic particles such as 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, or inorganic materials may include inorganic particles 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.

[0064] 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.

[0065] Electrolyte ELL Electrolytes (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0066] Non-aqueous organic solvents can be constructed as media for transporting ions that participate in the electrochemical reactions of a battery.

[0067] 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.

[0068] Carbonate solvents may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC).

[0069] 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.

[0070] Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Ketone solvents may include cyclohexanone. Alcohol solvents may include at least one of ethanol and isopropanol, and aprotic solvents may include at least one of: nitriles, such as R-CN (wherein R is a hydrocarbon group having a C2 to C20 straight-chain, branched, or cyclic structure, and may include double bonds, aromatic rings, or ether groups); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane or 1,4-dioxolane; and sulfolane.

[0071] The non-aqueous organic solvent may be included alone or as a mixture of two or more of them.

[0072] Furthermore, when carbonate solvents are included, cyclic carbonates and chain carbonates can be mixed, and cyclic carbonates and chain carbonates can be mixed in a volume ratio ranging from about 1:1 to about 1:9.

[0073] Lithium salts can be materials that are dissolved in a non-aqueous organic solvent to serve as a source of lithium ions in a battery, and are configured to enable basic operation of a rechargeable lithium battery and facilitate the movement of lithium ions between the positive and negative electrodes. Lithium salts can include at least one of the following: 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+ 1SO2) (where x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFOP), and lithium bis(oxalate)borate (LiBOB).

[0074] Rechargeable lithium batteries Based on their shape, rechargeable lithium batteries can be classified into cylindrical, prismatic, pouch-shaped, and coin-shaped types. Figures 2 to 5 A simplified diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure is shown, wherein, Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown, 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, in which a separator 30 is disposed between a positive electrode 10 and a negative electrode 20. The rechargeable lithium battery 100 may also include a housing 50 in which the electrode assembly 40 is housed. 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, a negative electrode lead connector 21, and a negative electrode terminal 22. Figure 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include Figure 5 The electrode connector 70 shown, or Figure 4The 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.

[0075] The following description focuses on the positive electrode according to an example embodiment of this disclosure.

[0076] Figure 6 This is a cross-sectional view showing the positive electrode of a rechargeable lithium battery according to an exemplary embodiment of the present disclosure.

[0077] Reference Figure 6 The positive electrode 10 may include a current collector COL1 and a positive electrode active material layer AML1 on the current collector COL1.

[0078] In an example embodiment, aluminum (Al) may be included as the current collector COL1, but this disclosure is not limited thereto.

[0079] The positive electrode active material layer AML1 may include a first active material layer ATL1 on the current collector COL1 and a second active material layer ATL2 on the first active material layer ATL1.

[0080] The first active material layer ATL1 may have a thickness TKL1, and the second active material layer ATL2 may have a thickness TKL2.

[0081] The thickness TKL of the positive electrode active material layer AML1 can be the sum of the thickness TKL1 of the first active material layer ATL1 and the thickness TKL2 of the second active material layer ATL2.

[0082] The thickness TKL of the positive electrode active material layer AML1 can range from about 10 μm to about 170 μm. For example, the thickness TKL of the positive electrode active material layer AML1 can be equal to or greater than about 10 μm, about 11 μm, about 15 μm, about 20 μm, about 30 μm, or about 40 μm. For example, the thickness TKL of the positive electrode active material layer AML1 can be equal to or less than about 170 μm, about 160 μm, about 150 μm, about 140 μm, about 130 μm, about 120 μm, about 110 μm, about 100 μm, about 90 μm, about 80 μm, about 70 μm, about 60 μm, or about 50 μm.

[0083] When the thickness TKL of the positive electrode active material layer AML1 falls within the above range, the battery can have increased lifespan and small or minimal volume change during charging and discharging.

[0084] The thickness TKL1 of the first active material layer ATL1 can be in the range of about 10 μm to about 150 μm. For example, the thickness TKL1 of the first active material layer ATL1 can be equal to or greater than about 15 μm, about 20 μm, about 30 μm, or about 40 μm. For example, the thickness TKL1 of the first active material layer ATL1 can be equal to or less than about 140 μm, about 130 μm, about 120 μm, about 110 μm, about 100 μm, about 90 μm, about 80 μm, about 70 μm, about 60 μm, about 50 μm, or about 40 μm.

[0085] The thickness TKL2 of the second active material layer ATL2 can be in the range of about 10 μm to about 150 μm. For example, the thickness TKL2 of the second active material layer ATL2 can be equal to or greater than about 15 μm, about 20 μm, about 30 μm, or about 40 μm. For example, the thickness TKL2 of the second active material layer ATL2 can be equal to or less than about 140 μm, about 130 μm, about 120 μm, about 110 μm, about 100 μm, about 90 μm, about 80 μm, about 70 μm, about 60 μm, about 50 μm, or about 40 μm.

[0086] When the thickness TKL1 of the first active material layer ATL1 falls within the above range, and when the thickness TKL2 of the second active material layer ATL2 falls within the above range, the battery can have increased lifespan and small or minimal volume change during charging and discharging.

[0087] In an example embodiment, increasing the weight of the positive electrode active material included in the first active material layer ATL1 can cause an increase in the thickness TKL1 of the first active material layer ATL1. In an example embodiment, increasing the weight of the positive electrode active material included in the second active material layer ATL2 can cause an increase in the thickness TKL2 of the second active material layer ATL2.

[0088] The first active material layer ATL1 and the second active material layer ATL2 can have a thickness ratio (TKL1:TKL2) in the range of about 1:9 to about 9:1. For example, the first active material layer ATL1 and the second active material layer ATL2 can have a thickness ratio (TKL1:TKL2) of about 5:5. When the thickness ratio (TKL1:TKL2) of the first active material layer ATL1 and the second active material layer ATL2 falls within the above range, the positive electrode active material layer AML1 can have improved adhesion to the current collector COL1, thus not only improving or maximizing the battery capacity and energy density, but also benefiting the electrode coating process.

[0089] Figure 7A and Figure 7B This is an enlarged view showing the positive electrode according to an exemplary embodiment of the present disclosure. Figure 7A and Figure 7B shows Figure 6 an enlarged view of the region “M” depicted in

[0090] Referring to Figure 7A and Figure 7B the first active material layer ATL1 may include a first cathode active material CAM1, a first lithium-based additive LAD1, a first binder BND1, and a first conductive material CDM1.

[0091] The first lithium-based additive LAD1 may improve the capacity of the cathode even in its relatively small amount and may compensate for the efficiency loss of the anode including a silicon-based active material simultaneously or contemporaneously.

[0092] The first lithium-based additive LAD1 may include at least one of a compound represented by Chemical Formula 1-1, a compound represented by Chemical Formula 1-2, and a compound represented by Chemical Formula 1-3.

[0093] Chemical Formula 1-1: Li x1 NiO2.

[0094] Chemical Formula 1-2: Li x2 FeO4.

[0095] Chemical Formula 1-3: Li x3 Co (1-y-z-m) Zn y Al z M m O4.

[0096] In Chemical Formula 1-1, the subscript x1 may satisfy the relationship of 1.1 ≤ x1 ≤ 2.5.

[0097] In Chemical Formula 1-2, the subscript x2 may satisfy the relationship of 1.1 ≤ x2 ≤ 5.5.

[0098] In Chemical Formula 1-3, M may be at least one of Ti, Zr, Mn, and Ni or M may include at least one of Ti, Zr, Mn, and Ni, and the subscripts x3, y, z, and m may satisfy the relationships of 5 ≤ x3 ≤ 7, 0 < y ≤ 0.5, 0 < z ≤ 0.5, 0 < y + z + m < 1, and 0 ≤ m ≤ 0.5.

[0099] In Chemical Formula 1-1, the subscript x1 may be in the range of about 1.1 to about 2.5, about 1.5 to about 2, about 2 to about 2.5, or about 1.8 to about 2.3. For example, x1 may be equal to about 2.

[0100] In chemical formulas 1-2, the subscript x2 can range from about 1.1 to about 5.5, about 2.5 to about 5.5, about 3 to about 5.5, or about 3.3 to about 5.3. For example, x2 can be equal to about 5.

[0101] When M is present in chemical formulas 1-3, M can be at least one of Ti, Zr, Mn, and Ni, or M can include at least one of Ti, Zr, Mn, and Ni. For example, M can be Zr or M can include Zr.

[0102] When m equals 0, chemical formula 1-3 can be represented as chemical formula 1-3A.

[0103] Chemical formula 1-3A: Li x3 Co (1-y-z) Zn y Al z O4.

[0104] According to an example embodiment, the first lithium additive LAD1 may include LNO (Li2NiO2), LFO (Li5FeO4), and LCZAO (Li6Co). 0.7 Zn 0.25 Al 0.05 At least one of O4).

[0105] The first lithium additive, LAD1, can have an average particle size (D) in the range of about 1 μm to about 50 μm. 50 For example, the first lithium additive LAD1 can have an average particle size (D) equal to or less than about 45 μm, about 40 μm, or about 35 μm. 50 For example, the first lithium additive LAD1 can have an average particle size (D) in the range of about 1 μm to about 45 μm, about 2 μm to about 40 μm, or about 5 μm to about 30 μm. 50 Average particle size (D) 50 ( ) can be the median diameter measured using a laser particle size distribution analyzer.

[0106] like Figure 7A As shown, the amount of the first lithium additive LAD1 in the first active material layer ATL1 can be less than the amount of the second lithium additive LAD2 in the second active material layer ATL2, which will be discussed below.

[0107] Optionally, such as Figure 7B As shown, the first lithium additive LAD1 may not be included in the first active material layer ATL1. In this case, the first active material layer ATL1 may not have the first lithium additive LAD1.

[0108] For example, the first lithium-based additive LAD1 may be present in the first active material layer ATL1 in an amount within the range of about 0 wt% to about 5 wt%.

[0109] According to the exemplary embodiment, in the first active material layer ATL1, the first positive electrode active material CAM1 and the first lithium-based additive LAD1 may be included in a weight ratio within the range of about 95:5 to about 100:0.

[0110] Relative to 100 parts by weight of the first positive electrode active material CAM1, the first lithium-based additive LAD1 may be included in an amount equal to or less than about 5 parts by weight. For example, relative to 100 parts by weight of the first positive electrode active material CAM1, the first lithium-based additive LAD1 may be included in an amount equal to or less than about 4 parts by weight, about 2 parts by weight, about 1 part by weight, or about 0.8 part by weight.

[0111] When the amount of the first lithium-based additive LAD1 in the first active material layer ATL1 is greater than the above range, the internal resistance of the positive electrode may increase due to side reactions.

[0112] The first positive electrode active material CAM1 may include a compound (e.g., a lithium intercalation compound) that can reversibly intercalate and deintercalate lithium. The first positive electrode active material CAM1 may include a lithium composite oxide represented by Chemical Formula 2.

[0113] Chemical Formula 2: Li x4 M 1 y M 2 z M 3 1-y-z O 2-a X a .

[0114] In Chemical Formula 2, the subscripts x4, a, y, and z may satisfy the relationships of 0.5 ≤ x4 ≤ 1.8, 0 ≤ a ≤ 0.05, 0 < y ≤ 1, 0 ≤ z ≤ 1, and 0 ≤ y + z ≤ 1, and M 1 、M 2 and M 3 may each independently include at least one of Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr, La, and combinations thereof, and X may include at least one of F, S, P, and Cl.

[0115] In the exemplary embodiment, in Chemical Formula 2, M 1It may be or include Ni, and the subscripts y and z may satisfy the relationship of 0.8 ≤ y ≤ 1 and 0 ≤ z ≤ 0.2. For example, the first positive electrode active material CAM1 may include LMFP (lithium manganese iron phosphate, LiMn x Fe 1-x PO (0 < x < 1)), LNMX (lithium nickel manganese oxide, LiNiMnO2), LNCA (lithium nickel cobalt aluminum oxide, LiNiCoAlO2), or LNCM (lithium nickel cobalt manganese oxide, LiNiCoMnO2).

[0116] The first binder BND1 may be configured to not only bond the particles of the first positive electrode active material CAM1 to each other, but also improve the adhesion of the positive electrode active material to the current collector. For example, it may include at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon, but the present disclosure is not limited thereto.

[0117] A first conductive material CDM1 may be included to provide conductivity to the positive electrode 10, and any suitable conductive material that does not cause a chemical change in the battery may be included as the conductive material. For example, carbon-based materials such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; metal materials such as metal powders or metal fibers including one or more of copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0118] According to an exemplary embodiment, the first positive electrode active material CAM1 may be present in an amount within the range of about 90 wt% to about 98 wt% based on the total weight of the first active material layer ATL1. According to an exemplary embodiment, the first binder BND1 may be present in an amount within the range of about 1 wt% to about 5 wt% based on the total weight of the first active material layer ATL1. According to an exemplary embodiment, the first conductive material CDM1 may be present in an amount within the range of about 1 wt% to about 5 wt% based on the total weight of the first active material layer ATL1.

[0119] When the first active material layer ATL1 satisfies the amount ranges of the first positive electrode active material CAM1, the first binder BND1, and the first conductive material CDM1, it may be possible to improve or maximize the battery capacity and energy density.

[0120] A second active material layer ATL2 can be formed to contact one surface of the first active material layer ATL1. One surface of the first active material layer ATL1 can be a surface where the first active material layer ATL1 is not in contact with the current collector (see...). Figure 6 The surface in contact with COL1. For example, the current collector COL1, the first active material layer ATL1, and the second active material layer ATL2 can be stacked, for example, sequentially stacked.

[0121] The second active material layer ATL2 may include a second positive electrode active material CAM2, a second lithium additive LAD2, a second binder BND2, and a second conductive material CDM2.

[0122] The second positive electrode active material CAM2 can be the same as or substantially the same as the first positive electrode active material CAM1 in the first active material layer ATL1 discussed above. The second binder BND2 can be the same as or substantially the same as the first binder BND1 in the first active material layer ATL1 discussed above. The second conductive material CDM2 can be the same as or substantially the same as the first conductive material CDM1 in the first active material layer ATL1 discussed above.

[0123] According to an example embodiment, the second positive electrode active material CAM2 may be present in an amount ranging from about 90 wt% to about 98 wt% relative to the total weight of the second active material layer ATL2. According to an example embodiment, the second binder BND2 may be present in an amount ranging from about 1 wt% to about 5 wt% relative to the total weight of the second active material layer ATL2. According to an example embodiment, the second conductive material CDM2 may be present in an amount ranging from about 1 wt% to about 5 wt% relative to the total weight of the second active material layer ATL2.

[0124] When the second active material layer ATL2 meets the quantity range of the second positive electrode active material CAM2, the quantity range of the second binder BND2, and the quantity range of the second conductive material CDM2, it can improve or maximize the battery capacity and energy density.

[0125] The second lithium additive LAD2 may be the same as or different from the first lithium additive LAD1 in the first active material layer ATL1 discussed above.

[0126] like Figure 7A and Figure 7B As shown, the amount of the second lithium additive LAD2 in the second active material layer ATL2 can be greater than the amount of the first lithium additive LAD1 in the first active material layer ATL1. According to an example embodiment, the amount of the second lithium additive LAD2 in the second active material layer ATL2 can be equal to or greater than twice the amount of the first lithium additive LAD1 in the first active material layer ATL1.

[0127] For example, the second lithium additive LAD2 may be present in the second active material layer ATL2 in an amount ranging from about 1 wt% to about 10 wt%. According to an example embodiment, the second active material layer ATL2 may include the second positive electrode active material CAM2 and the second lithium additive LAD2 in a weight ratio ranging from about 90:10 to about 99:1.

[0128] The second lithium additive LAD2 may be included in an amount ranging from about 1 part by weight to about 10 parts by weight relative to 100 parts by weight of the second positive electrode active material CAM2. For example, the second lithium additive LAD2 may be included in an amount equal to or less than about 8 parts by weight, about 7 parts by weight, about 6 parts by weight, or about 5 parts by weight relative to 100 parts by weight of the second positive electrode active material CAM2.

[0129] When the amount of the second lithium additive LAD2 in the second active material layer ATL2 exceeds the above range, the internal resistance of the positive electrode may increase, which may reduce the stability and performance of the battery.

[0130] When the amount of the second lithium additive LAD2 in the second active material layer ATL2 is equal to zero or less than the above range, it may be challenging to improve or maximize the effect of improving the energy density of the battery.

[0131] Lithium-based additives LAD1 and LAD2 may have the following drawbacks: an increase in the amount of silicon in the negative electrode (e.g., about 5 wt% or higher) may lead to increased side reactions and gas generation, which could result in reduced efficiency. The positive electrode 10 according to an example embodiment of this disclosure can overcome this drawback.

[0132] In the positive electrode 10 according to an exemplary embodiment of the present disclosure, since the first active material layer ATL1 is introduced between the current collector COL1 and the second active material layer ATL2, and since the first lithium additive LAD1 and the second lithium additive LAD2 are mixed in the first active material layer ATL1 and the second active material layer ATL2 at corresponding desired ratios, the battery can be improved in terms of capacity, density characteristics, high-temperature stability, and lifespan characteristics. For example, in the positive electrode 10 according to an exemplary embodiment of the present disclosure, the second active material layer ATL2 may include a second lithium additive LAD2 in an amount greater than that of the first lithium additive LAD1 in the first active material layer ATL1, thus improving or maximizing utilization efficiency while reducing or minimizing the amount of lithium additives LAD1 and LAD2 added. Simultaneously or concurrently, the positive electrode active materials CAM1 and CAM2 can be supplemented with lithium to achieve high capacity and high energy density.

[0133] According to the example embodiment, the sum of the weight of the first lithium additive LAD1 and the weight of the second lithium additive LAD2 can be in the range of about 1% to about 10% of the total weight of the positive electrode active material layer AML1.

[0134] Figure 8 This is an enlarged view showing the positive electrode according to an exemplary embodiment of the present disclosure. Figure 9 It is shown Figure 8 A magnified view of region "N". In the example embodiments below, the references above are omitted. Figure 6 and Figure 7A The discussion includes a detailed description of redundant technical features and a thorough discussion of their differences.

[0135] Reference Figure 8 and Figure 9 According to an example embodiment of the present disclosure, the positive electrode 10' may include a single layer of positive electrode active material AML1'.

[0136] The positive electrode 10' may include a current collector COL1' and a positive electrode active material layer AML1' formed on the current collector COL1'.

[0137] In an example embodiment, aluminum (Al) may be included as the current collector COL1', but this disclosure is not limited thereto.

[0138] The positive electrode active material layer AML1' can be formed to contact a surface of the current collector COL1'. This surface of the positive electrode active material layer AML1' can be the surface of the positive electrode active material layer AML1' that contacts the current collector COL1'. For example, the positive electrode 10' can be configured such that the current collector COL1' and the positive electrode active material layer AML1' are stacked, for example, sequentially stacked.

[0139] The positive electrode active material layer AML1' can be disposed on the current collector COL1' and can have a thickness TKL'. For example, the thickness TKL' of the positive electrode active material layer AML1' can be in the range of about 10 μm to about 170 μm.

[0140] The positive electrode active material layer AML1' may include the positive electrode active material CAM', the lithium additive LAD', the binder BND', and the conductive material CDM'.

[0141] The positive electrode active material CAM' is essentially the same as the first positive electrode active material CAM1 discussed above. The binder BND' is essentially the same as the first binder BND1 discussed above. The conductive material CDM' is essentially the same as the first conductive material CDM1 discussed above. The lithium additive LAD' is essentially the same as the first lithium additive LAD1 discussed above.

[0142] According to an example embodiment, the positive electrode active material CAM' may be present in an amount ranging from about 90 wt% to about 98 wt% relative to the total weight of the positive electrode active material layer AML1'. According to an example embodiment, the binder BND' may be present in an amount ranging from about 1 wt% to about 5 wt% relative to the total weight of the positive electrode active material layer AML1'. According to an example embodiment, the conductive material CDM' may be present in an amount ranging from about 1 wt% to about 5 wt% relative to the total weight of the positive electrode active material layer AML1'.

[0143] When the positive electrode active material layer AML1' meets the quantity range of positive electrode active material CAM', the quantity range of binder BND', and the quantity range of conductive material CDM', it is possible to improve or maximize battery capacity and energy density.

[0144] According to an example embodiment, the lithium additive LAD' may be present in an amount ranging from about 1 wt% to about 10 wt% of the total weight of the positive electrode active material layer AML1'.

[0145] The positive electrode active material layer AML1' may include a first portion RG1 adjacent to the current collector COL1' and a second portion RG2 adjacent to the surface of the positive electrode active material layer AML1'. For example, the first portion RG1 may be the area of ​​the positive electrode active material layer AML1' in contact with the current collector COL1'. The second portion RG2 may be the area of ​​the positive electrode active material layer AML1' that is not in contact with the current collector COL1'.

[0146] In the positive electrode active material layer AML1', the amount of lithium additive LAD' in the second portion RG2 can be greater than the amount of lithium additive LAD' in the first portion RG1. According to an example embodiment, in the positive electrode active material layer AML1', the amount of lithium additive LAD' in the second portion RG2 can be twice the amount of lithium additive LAD' in the first portion RG1.

[0147] In the first portion RG1, the lithium additive LAD' may be present in an amount ranging from about 0 wt% to about 5 wt%. For example, the first portion RG1 may include the lithium additive LAD' or the first portion RG1 may not include the lithium additive LAD'. According to an example embodiment, the first portion RG1 may include the positive electrode active material CAM' and the lithium additive LAD' in a weight ratio ranging from about 95:5 to about 100:0.

[0148] The lithium additive LAD' may be included in an amount equal to or less than about 5 parts by weight relative to 100 parts by weight of the positive electrode active material CAM'. For example, the lithium additive LAD' may be included in an amount equal to or less than about 4 parts by weight, 2 parts by weight, 1 part by weight, or 0.8 parts by weight relative to 100 parts by weight of the positive electrode active material CAM'.

[0149] When the amount of lithium additive LAD' in the first part RG1 exceeds the above range, the internal resistance of the positive electrode may increase due to side reactions.

[0150] In the second part RG2, the lithium additive LAD' may be present in an amount ranging from about 1 wt% to about 10 wt%. According to an example embodiment, the second part RG2 may include the positive electrode active material CAM' and the lithium additive LAD' in a weight ratio ranging from about 90:10 to about 99:1.

[0151] The lithium additive LAD' may be included in an amount ranging from about 1 part by weight to about 10 parts by weight relative to 100 parts by weight of the positive electrode active material CAM'. For example, the lithium additive LAD' may be included in an amount equal to or less than about 8 parts by weight, about 7 parts by weight, about 6 parts by weight, or about 5 parts by weight relative to 100 parts by weight of the positive electrode active material CAM'.

[0152] When the amount of lithium additive LAD' in the second part RG2 exceeds the above range, the stability, capacity and performance of the battery may be reduced.

[0153] When the amount of lithium additive LAD' in the second part RG2 is equal to zero or less than the above range, it may be difficult to improve or maximize the effect of improving the energy density of the battery.

[0154] When the positive electrode active material layer AML1' exists in the positive electrode 10' in a monolayer form, the lithium additive LAD' is distributed in the second part RG2 in a larger amount than in the first part RG1, thus enabling the improvement of possible side reactions in the monolayer positive electrode active material layer AML1'.

[0155] In an exemplary embodiment of this disclosure, a rechargeable lithium battery may be provided, which includes the positive electrode discussed above, a negative electrode including a negative electrode active material, a separator disposed between the positive electrode and the negative electrode, and an electrolyte.

[0156] The negative electrode may include a negative electrode current collector and a negative electrode active material layer containing negative electrode active material formed on the negative electrode current collector.

[0157] The negative electrode active material may include a material capable of reversibly inserting and extracting lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and undoping lithium, or a transition metal oxide.

[0158] The negative electrode active material may include a silicon-based oxide having an increased capacity, capable of increasing the energy density of the battery, and capable of achieving high power performance.

[0159] When including a silicon-based oxide as the negative electrode active material, the negative electrode active material may include at least one of a carbon-based active material and a silicon-based active material.

[0160] The carbon-based active material and the silicon-based active material may be included in a weight ratio within the range of about 95:5 to about 10:90. According to an exemplary embodiment, the silicon-based active material may be present in an amount within the range of about 5 wt% to about 10 wt% relative to the total weight of the negative electrode active material.

[0161] The silicon-based active material may include at least one of a Si-C composite, SiO2 (where 0 < x ≤ 2), and a silicon alloy. For example, the Si-C composite may include a core containing crystalline carbon and silicon particles, and may further include an amorphous carbon coating on the surface of the core. The crystalline carbon may include graphite, for example, natural graphite, artificial graphite, or a mixture thereof.

[0162] The electrolyte may be prepared by a mixing process of dissolving a lithium salt in a non-aqueous organic solvent, and an additive may be added thereto. The electrolyte mixing process is known in the field of electrolyte manufacturing, and those skilled in the art can appropriately select and use it.

[0163] In an exemplary embodiment, the non-aqueous organic solvent may include at least one of ethyl methyl carbonate (EMC), ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), propyl propionate (PP), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC), and butylene carbonate (BC).

[0164] In an exemplary embodiment, the lithium salt may include at least one of LiPF6, LiClO4, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiSO3CF3, LiBOB, LiFOB, LiDFBP, LiTFOP, LiPO2F2, LiSbF6, LiAsF6, LiAlO2, LiAlCl4, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N, and LiC4F9SO3.

[0165] In exemplary embodiments, the lithium salt may have a concentration ranging from about 0.1 M to about 2.0 M. For example, the lithium salt may have a concentration equal to or greater than about 0.5 M or about 1.0 M. The lithium salt may have a concentration equal to or less than about 2.0 M, about 1.7 M, or about 1.5 M. In this disclosure, when the lithium salt has a concentration ranging from about 0.1 M to about 2.0 M, the electrolyte may maintain its conductivity and viscosity.

[0166] Manufacturing of positive electrode Figure 10 This is a diagram illustrating a method for manufacturing a positive electrode according to an exemplary embodiment of the present disclosure.

[0167] Reference Figure 10 A method for manufacturing a positive electrode according to an example embodiment of the present disclosure may include: providing a current collector COL1; forming a first active material layer ATL1 on the current collector COL1; and forming a second active material layer ATL2 on the first active material layer ATL1.

[0168] In the example embodiment, as described above regarding Figure 7A The first active material layer ATL1 discussed may include a first positive electrode active material CAM1, a first lithium-based additive LAD1, a first binder BND1, and a first conductive material CDM1. Furthermore, as mentioned above... Figure 7A The second active material layer ATL2 discussed may include a second positive electrode active material CAM2, a second lithium additive LAD2, a second binder BND2, and a second conductive material CDM2.

[0169] The current collector COL1, the first active material layer ATL1, and the second active material layer ATL2 are the same as or substantially the same as the current collector COL1, the first active material layer ATL1, and the second active material layer ATL2 of the positive electrode 10 according to the example embodiment, and therefore their detailed description is omitted below.

[0170] In an example embodiment, the formation of at least one of the first active material layer ATL1 and the second active material layer ATL2 may include performing a wet process or a dry process. In an example embodiment, the first active material layer ATL1 may be formed by a wet process, and the second active material layer ATL2 may be formed by a dry process. Optionally, the first active material layer ATL1 may be formed by a dry process, and the second active material layer ATL2 may be formed by a wet process. However, this disclosure is not limited thereto.

[0171] The wet process can be carried out in such a way that the positive electrode active material, conductive material, binder, and lithium additives are mixed in a solvent to prepare a positive electrode mixture, which is then coated onto a current collector, followed by drying and pressing. The solvent in the slurry can be a solvent commonly included in the art, or the solvent in the slurry can include solvents commonly included in the art, and for example, the solvent in the slurry can include at least one of dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone, water, and combinations thereof.

[0172] The dry process can be carried out in such a way that a dry positive electrode active material, a dry conductive material, a dry binder and a dry lithium additive are dry-mixed to prepare a positive electrode mixture in the absence of solvent, and the mixture is then set and pressed onto a current collector.

[0173] The positive electrode manufactured through the above process can then undergo (e.g., sequentially) a rolling process, a cutting process, and a grooving process. The positive electrode 10, the separator 30, and the negative electrode 20 can be stacked, and then an electrolyte ELL can be provided to manufacture a rechargeable lithium battery according to an example of this disclosure.

[0174] Some embodiments and comparative examples of this disclosure are described below. However, the following embodiments are merely examples, and this disclosure is not limited to the exemplary embodiments discussed below.

[0175] Example 1: Fabrication of a positive electrode including a double-layer active material layer The first active material slurry is prepared by dispersing the positive electrode active material, conductive material, binder and lithium additive in N-methylpyrrolidone at a weight ratio of 100:1:1:2.

[0176] A second active material slurry was prepared by dispersing the positive electrode active material, conductive material, binder and lithium additive in N-methylpyrrolidone at a weight ratio of 100:1:1:5.

[0177] A mixture of LMFP (LiMnFePO4) and LNMX (LiNiMnO2) was used as the positive electrode active material, carbon black as the conductive material, and polyvinylidene fluoride (PVdF) as the binder. Li2NiO2 was used as a lithium additive.

[0178] A first active material slurry is coated onto a positive electrode current collector or aluminum (Al) foil with a thickness of 15 μm and dried to form a first active material layer with a thickness of approximately 30 μm. A second active material slurry is coated onto the first active material layer and dried to form a second active material layer with a thickness of approximately 30 μm. Roll forming is then performed to manufacture a positive electrode in which the aluminum current collector, the first active material layer, and the second active material layer are sequentially stacked.

[0179] Manufacturing of rechargeable lithium batteries A negative electrode active material consisting of 98 wt% graphite and silicon composite in a 92:8 weight ratio, 1 wt% styrene-butadiene rubber (SBR), and 1 wt% carboxymethyl cellulose (CMC) was mixed and added to distilled water. The mixture was stirred for 60 minutes using a mechanical stirrer to prepare a negative electrode active material slurry. The slurry was coated onto a 10 μm thick copper current collector with a thickness of 60 μm using a doctor blade. It was dried in a hot air dryer at 100 °C for 0.5 hours, then dried again under vacuum at 120 °C for 4 hours, and finally rolled to fabricate the negative electrode.

[0180] An electrolyte was prepared by dissolving 1.15 M LiPF6 in a non-aqueous organic solvent comprising ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) mixed in a volume ratio of 20:40:40.

[0181] The positive electrode, negative electrode, and 16 μm thick polyethylene separator are assembled to manufacture the electrode assembly, and an electrolyte is introduced to manufacture the rechargeable lithium battery.

[0182] Example 2 The positive electrode and rechargeable lithium battery were manufactured using the same method as in Example 1, except that lithium additives were not used when preparing the first active material slurry, and the positive electrode active material, conductive material and binder were mixed in the first active material slurry in a weight ratio of 100:1:1.

[0183] Example 3 The positive electrode and the rechargeable lithium battery were manufactured in the same manner as in Example 1, except that when manufacturing the positive electrode, the positive electrode active material, conductive material, binder and lithium additives were mixed in the second active material slurry in a weight ratio of 100:1:1:10.

[0184] Example 4 The positive electrode and the rechargeable lithium battery were manufactured using the same method as in Example 1, except that Li5FeO4 was used instead of Li2NiO2 as a lithium additive when manufacturing the positive electrode.

[0185] Example 5 The positive electrode and rechargeable lithium battery were manufactured using the same method as in Example 1, except that Li6Co was used when manufacturing the positive electrode. 0.7 Zn 0.25 Al 0.05 O4 replaces Li2NiO2 as a lithium additive.

[0186] Comparative Example 1: Fabrication of a positive electrode including a monolayer of active material The first active material slurry is prepared by dispersing the positive electrode active material, conductive material, binder and lithium additive in N-methylpyrrolidone at a weight ratio of 100:1:1:2.

[0187] A mixture of LMFP (LiMnFePO4) and NMX (NiMnO2) was used as the positive electrode active material, carbon black as the conductive material, and polyvinylidene fluoride (PVdF) as the binder. Li2NiO2 was used as a lithium additive.

[0188] A first active material slurry is coated onto a positive electrode current collector or aluminum (Al) foil with a thickness of 15 μm and dried to form a first active material layer with a thickness of approximately 30 μm. Roll forming is then performed to fabricate a positive electrode in which the aluminum current collector and the first active material layer are sequentially stacked.

[0189] The same method as in Example 1 was used to manufacture a rechargeable lithium battery using the positive electrode manufactured in Comparative Example 1.

[0190] Comparative Example 2 The positive electrode and rechargeable lithium battery were manufactured using the same method as in Example 1, except that when manufacturing the positive electrode, the positive electrode active material, conductive material, binder, and lithium additives were mixed in the first active material slurry at a weight ratio of 100:1:1:5, and during the preparation of the second active material slurry, the positive electrode active material, conductive material, and binder were mixed in the second active material slurry at a weight ratio of 100:1:1 without adding lithium additives.

[0191] Comparative Example 3 The positive electrode and the rechargeable lithium battery were manufactured using the same method as in Example 1, except that when manufacturing the positive electrode, the positive electrode active material, conductive material, binder and lithium additives were mixed in the first active material slurry in a weight ratio of 100:1:1:5, and when manufacturing the positive electrode, the positive electrode active material, conductive material, binder and lithium additives were mixed in the second active material slurry in a weight ratio of 100:1:1:2.

[0192] Comparative Example 4 The positive electrode and the rechargeable lithium battery were manufactured using the same method as in Example 1, except that when manufacturing the positive electrode, the positive electrode active material, conductive material, binder and lithium additives were mixed in a first active material slurry at a weight ratio of 100:1:1:3, and when manufacturing the positive electrode, the positive electrode active material, conductive material, binder and lithium additives were mixed in a second active material slurry at a weight ratio of 100:1:1:3.

[0193] Comparative Example 5 The positive electrode and the rechargeable lithium battery were manufactured using the same method as in Example 1, except that when manufacturing the positive electrode, the positive electrode active material, conductive material, binder and lithium additives were mixed in the first active material slurry at a weight ratio of 100:1:1:2, and when manufacturing the positive electrode, the positive electrode active material, conductive material, binder and lithium additives were mixed in the second active material slurry at a weight ratio of 100:1:1:20.

[0194] Table 1 below lists the composition of the positive electrode according to the embodiments and comparative examples.

[0195] Table 1:

[0196] Evaluation Example The following methods were used to evaluate rechargeable lithium batteries.

[0197] Evaluation Example 1: Charge-Discharge Cycle Characteristics For each rechargeable lithium battery manufactured in the examples and comparative examples, after 300 charge-discharge cycles at 25°C, under the conditions of 0.5C charging (constant current (CC) / constant voltage (CV), 4.25V, 0.05C cutoff) / 0.5C discharging (CC, 2.8V cutoff), the discharge capacity was measured to calculate the capacity retention rate, and the results are shown in Table 2 below. The capacity retention rate was calculated according to Equation 1 below.

[0198] Equation 1: Capacity retention (%) = (Discharge capacity after 300 cycles / Initial discharge capacity) × 100 Table 2:

[0199] Evaluation Example 2: Gas Generation The gas generation characteristics of the rechargeable lithium batteries according to the examples and comparative examples were evaluated. The rechargeable lithium batteries according to the examples and comparative examples were charged to 4.2V at 60°C and then stored for 30 days.

[0200] To determine the effect of gas generation, the initial gas generation and the gas generation after 30 days of storage were measured for each rechargeable lithium battery manufactured in the examples and comparative examples, and the gas generation rate was calculated according to Equation 2 below, and the results are listed in Table 3 below.

[0201] Equation 2: Gas production rate (%) = (Gas production after 30 days / Initial gas production) × 100 Table 3:

[0202] Overall evaluation Referring to Table 2 above, it was determined that, compared with the cases in which the positive electrode according to the comparative example was used, the capacity retention rate based on charge-discharge cycles at room temperature was improved in the cases in which the positive electrode according to the present disclosure was used (Examples 1 to 5).

[0203] Referring to Table 3 above, it was determined that the rechargeable lithium battery manufactured according to the comparative example had a relatively high gas generation rate at high temperature (60°C) compared to the rechargeable lithium battery manufactured according to the embodiments. Therefore, the rechargeable lithium battery using the positive electrode according to this disclosure can effectively reduce or suppress gas generation at high temperature (60°C).

[0204] The positive electrode according to this disclosure may include a bilayer active material layer with different amounts of lithium additives, thereby improving its lifetime characteristics.

[0205] While this disclosure has been described in conjunction with what is now considered to be exemplary embodiments, it will be understood that this disclosure is not limited to the disclosed exemplary embodiments, but is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and therefore the foregoing embodiments can be understood as examples not limiting this disclosure in any way.

Claims

1. A positive electrode for a rechargeable lithium battery, the positive electrode comprising: a current collector; a first active material layer on the current collector; and a second active material layer on the first active material layer, wherein the first active material layer comprises a first positive electrode active material and a first lithium-based additive, wherein the second active material layer comprises a second positive electrode active material and a second lithium-based additive, wherein at least one of the first lithium-based additive and the second lithium-based additive comprises at least one of a compound represented by Chemical Formula 1-1, a compound represented by Chemical Formula 1-2, and a compound represented by Chemical Formula 1-3, wherein an amount of the second lithium-based additive in the second active material layer is greater than an amount of the first lithium-based additive in the first active material layer, Chemical Formula 1-1: Chemical Formula 1-2: Li x1 NiO2 Chemical Formula 1-3: Li x2 FeO4 wherein, in Chemical Formula 1-1, 1.1 ≤ x1 ≤ 2.5, Li x3 Co (1-y-z-m) Zn y Al z M m O4 wherein, in Chemical Formula 1-2, 1.1 ≤ x2 ≤ 5.5, and wherein, in Chemical Formula 1-3, M comprises at least one of Ti, Zr, Mn, and Ni, 5 ≤ x3 ≤ 7, 0 < y ≤ 0.5, 0 < z ≤ 0.5, 0 < y + z + m < 1, and 0 ≤ m ≤ 0.

5. At least one of the first active material layer and the second active material layer further comprises a binder and a conductive material.

2. The positive electrode according to claim 1, wherein At least one of the first positive electrode active material and the second positive electrode active material is represented by Chemical Formula 2, 3. The positive electrode of claim 1, wherein, Chemical Formula 2: wherein, in Chemical Formula 2, Li x4 M 1 y M 2 z M 3 1-y-z O 2-a X a 0.5 ≤ x4 ≤ 1.8, 0 ≤ a ≤ 0.05, 0 < y ≤ 1, 0 ≤ z ≤ 1, and 0 ≤ y + z ≤ 1, X comprises at least one of F, S, P, and Cl. M 1 , M 2 and M 3 each independently comprises at least one of Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr, La, and combinations thereof, and A thickness ratio of the first active material layer to the second active material layer is in a range of 1:9 to 9:

1.

4. The positive electrode of claim 3, wherein, In Chemical Formula 2, 0.8≤y≤1, 0≤z≤0.2, and M 1 includes Ni.

5. The positive electrode of claim 1, wherein, 6.The positive electrode of claim 1, wherein: an amount of the first lithium-based additive in the first active material layer is in a range of 0 wt% to 5 wt%. The average particle diameter D of the first lithium-based additive 50 in the range of 1 μm to 50 μm, and The average particle diameter D of the second lithium-based additive 50 In the range of 1 μm to 50 μm.

7. The positive electrode of claim 1, wherein, an amount of the second lithium-based additive in the second active material layer is in a range of 1 wt% to 10 wt%.

8. The positive electrode of claim 1, wherein, a weight ratio of the first positive electrode active material to the first lithium-based additive in the first active material layer is in a range of 95:5 to 100:

0.

9. The positive electrode of claim 1, wherein, a weight ratio of the second positive electrode active material to the second lithium-based additive in the second active material layer is in a range of 90:10 to 99:

1.

10. The positive electrode of claim 1, wherein, 11.A positive electrode for a rechargeable lithium battery, the positive electrode comprising: a current collector; a positive electrode active material layer on the current collector, wherein the positive electrode active material layer comprises a positive electrode active material and a lithium-based additive, wherein the lithium-based additive comprises at least one of a compound represented by Chemical Formula 1-1, a compound represented by Chemical Formula 1-2, and a compound represented by Chemical Formula 1-3, wherein the positive electrode active material layer comprises a first portion adjacent to the current collector and a second portion adjacent to a surface of the positive electrode active material layer. ​ ​ wherein the lithium-based additive has a weight in a range of 1% to 10% of a total weight of the positive electrode active material layer, wherein the amount of the lithium-based additive in the second portion is greater than the amount of the lithium-based additive in the first portion, Chemical Formula 1-1: Li x1 NiO2 Chemical Formula 1-2: Li x2 FeO4 Chemical Formula 1-3: Li x3 Co (1-y-z-m) Zn y Al z M m O4 wherein, in Chemical Formula 1-1, 1.1 ≤ x1 ≤ 2.5, wherein, in Chemical Formula 1-2, 1.1 ≤ x2 ≤ 5.5, and wherein, in Chemical Formula 1-3, M includes at least one of Ti, Zr, Mn, and Ni, 5 ≤ x3 ≤ 7, 0 < y ≤ 0.5, 0 < z ≤ 0.5, 0 < y + z + m < 1, and 0 ≤ m ≤ 0.

5.

12. The positive electrode of claim 11, wherein, the positive electrode active material is represented by Chemical Formula 2, Chemical Formula 2: Li x4 M 1 y M 2 z M 3 1-y-z O 2-a X a wherein, in Chemical Formula 2, 0.5 ≤ x4 ≤ 1.8, 0 ≤ a ≤ 0.05, 0 < y ≤ 1, 0 ≤ z ≤ 1, and 0 ≤ y + z ≤ 1, M 1 , M 2 and M 3 each independently comprises at least one of Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr, La, and combinations thereof, and X includes at least one of F, S, P, and Cl.

13. The positive electrode of claim 11, wherein, The average particle diameter D of the lithium-based additive 50 in the range of 1 μm to 50 μm.

14. The positive electrode of claim 11, wherein, The amount of the lithium-based additive in the first portion is in a range of 0wt% to 5wt%.

15. The positive electrode of claim 11, wherein, The amount of the lithium-based additive in the second portion is in a range of 1wt% to 10wt%.

16. The positive electrode of claim 11, wherein, The weight ratio of the positive electrode active material to the lithium-based additive in the first portion is in a range of 95:5 to 100:

0.

17. The positive electrode of claim 11, wherein, The weight ratio of the positive electrode active material to the lithium-based additive in the second portion is in a range of 90:10 to 99:

1. 18.A rechargeable lithium battery, the rechargeable lithium battery comprising: the positive electrode according to any one of claims 1 to 17; a negative electrode including a negative electrode active material; and a separator between the positive electrode and the negative electrode.

19. The rechargeable lithium battery of claim 18, wherein, the negative electrode active material includes a carbon-based active material and a silicon-based active material, wherein the weight ratio of the carbon-based active material to the silicon-based active material is in a range of 95:5 to 10:

90.

20. The rechargeable lithium battery of claim 18, wherein, The rechargeable lithium battery is one of a cylindrical battery, a prismatic battery, a pouch-type battery, and a coin-type battery.

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