Electrode for rechargeable lithium batteries and method for manufacturing the same

Abstract

The present disclosure relates to an electrode for a rechargeable lithium battery and a method of preparing the same. The electrode includes an electrode current collector and an electrode active material layer on the electrode current collector. The electrode active material layer includes an active material and a first composite conductive material. The first composite conductive material includes first carbon nanostructures and a first polymer chemically bonded to surfaces of the first carbon nanostructures. The first polymer includes: first structural units derived from a (meth)acrylic monomer or a salt thereof; second structural units derived from a (meth)acrylonitrile monomer; and third structural units derived from a zwitterionic monomer.

Description

[0001] This application claims priority to Korean Patent Application No. 10-2024-0183431, filed on December 11, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] This disclosure relates to an electrode for a rechargeable lithium battery and a method for manufacturing the 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 large capacity has increased. Therefore, enhancing the performance of rechargeable lithium batteries can be advantageous.

[0004] Rechargeable lithium-ion batteries typically consist of a positive electrode, a negative electrode, and an electrolyte. Both the positive and negative electrodes contain active materials capable of inserting and deintercalating lithium ions. Electrical energy is generated through oxidation and reduction reactions as lithium ions move between the electrodes during charging and discharging. Summary of the Invention

[0005] Example embodiments of this disclosure include an electrode with improved capacity and lifetime characteristics, and a rechargeable lithium battery including the electrode.

[0006] Example embodiments of this disclosure include a method for manufacturing the electrode.

[0007] According to exemplary embodiments of this disclosure, an electrode for a rechargeable lithium battery may include an electrode current collector and an electrode active material layer on the electrode current collector. The electrode active material layer may include an active material and a first composite conductive material. The first composite conductive material may include a first carbon nanostructure and a first polymer chemically bonded to the surface of the first carbon nanostructure. The first polymer may include: a first structural unit derived from a (meth)acrylic acid monomer or a salt thereof and represented by chemical formula 1-1A or chemical formula 1-1B; a second structural unit derived from a (meth)acrylonitrile monomer and represented by chemical formula 1-2; and a third structural unit derived from a zwitterionic monomer and represented by chemical formula 1-3A or chemical formula 1-3B.

[0008] Chemical formula 1-1A: .

[0009] Chemical formula 1-1B: .

[0010] In chemical formulas 1-1A and 1-1B, R 1 They may be the same or different, and each independently contains or includes hydrogen atoms or C1 to C20 alkyl groups. M1 is or includes alkali metals.

[0011] Chemical formula 1-2: .

[0012] In chemical formulas 1-2, R 2 It may include hydrogen atoms or C1 to C20 alkyl groups.

[0013] Chemical formula 1-3A: .

[0014] Chemical formula 1-3B: .

[0015] In chemical formulas 1-3A and 1-3B, R 3 They may be the same or different, and each independently contains or includes hydrogen atoms or C1 to C20 alkyl groups. R 4 They may be the same or different, and each independently contains or includes hydrogen atoms or C1 to C20 alkyl groups. L 1 It is or includes *-(C=O)-NR 4 -CH2-* or *-(C=O)-O-*, and L 2 To L 4 Each is independently or includes a single bond or a C1 to C20 alkylene group.

[0016] The first polymer may also include a fourth structural unit, which is derived from an alkylene glycol monomer or a salt thereof and is represented by chemical formula 1-4A or chemical formula 1-4B.

[0017] Chemical formula 1-4A: .

[0018] Chemical formula 1-4B: .

[0019] In chemical formulas 1-4A and 1-4B, M2 is or includes alkali metals, and n is an integer in the range of 1 to 100.

[0020] According to exemplary embodiments of this disclosure, an electrode for a rechargeable lithium battery may include an electrode current collector and an electrode active material layer on the electrode current collector. The electrode active material layer may include an active material, a first composite conductive material, and a second composite conductive material. The first composite conductive material may include a first carbon nanostructure and a first polymer chemically bonded to the surface of the first carbon nanostructure. The second composite conductive material may include a second carbon nanostructure and a second polymer chemically bonded to the surface of the second carbon nanostructure. The first polymer and the second polymer may be different from each other, and the ionic conductivity of the first polymer may be greater than that of the second polymer.

[0021] The first polymer may include at least one of the following: a first structural unit derived from a (meth)acrylic acid monomer or a salt thereof and represented by chemical formula 1-1A or chemical formula 1-1B; a second structural unit derived from a (meth)acrylonitrile monomer and represented by chemical formula 1-2; a third structural unit derived from a zwitterionic monomer and represented by chemical formula 1-3A or chemical formula 1-3B; and a fourth structural unit derived from an alkylene glycol monomer or a salt thereof and represented by chemical formula 1-4A or chemical formula 1-4B.

[0022] The second polymer may include at least one of a fifth structural unit represented by chemical formula 2-1 and a sixth structural unit represented by chemical formula 2-2.

[0023] Chemical formula 2-1: .

[0024] Chemical formula 2-2: .

[0025] In chemical formulas 2-1 and 2-2, Both m and z are integers in the range of 1 to 100.

[0026] According to an example embodiment of this disclosure, a method for manufacturing an electrode for a rechargeable lithium battery may include the steps of: providing an electrode current collector; and forming an electrode active material layer on the electrode current collector. The electrode active material layer may include an active material and a first composite conductive material.

[0027] The preparation of the first composite conductive material may include introducing functional groups into the surface of a first carbon nanostructure and preparing a first mixture by mixing a first polymer and a first carbon nanostructure having functional groups.

[0028] The first polymer may include at least one of the following: a first structural unit derived from a (meth)acrylic acid monomer or a salt thereof and represented by chemical formula 1-1A or chemical formula 1-1B; a second structural unit derived from a (meth)acrylonitrile monomer and represented by chemical formula 1-2; a third structural unit derived from a zwitterionic monomer and represented by chemical formula 1-3A or chemical formula 1-3B; and a fourth structural unit derived from an alkylene glycol monomer or a salt thereof and represented by chemical formula 1-4A or chemical formula 1-4B.

[0029] A method for manufacturing an electrode for a rechargeable lithium battery may further include adding a second composite conductive material to the electrode active material layer. Preparing the second composite conductive material may include introducing functional groups onto the surface of a second carbon nanostructure and preparing a second mixture by mixing a second polymer with the second carbon nanostructure having functional groups.

[0030] The second polymer may include at least one of a fifth structural unit represented by chemical formula 2-1 and a sixth structural unit represented by chemical formula 2-2. Attached Figure Description

[0031] Figure 1 This is a simplified conceptual diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure.

[0032] Figures 2 to 5 This is a schematic diagram illustrating a rechargeable lithium battery according to an exemplary embodiment of the present disclosure. Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown. Figure 4 and Figure 5 A pouch-type battery is shown.

[0033] Figure 6 This is a cross-sectional view of an electrode for a rechargeable lithium battery according to an exemplary embodiment of the present disclosure.

[0034] Figure 7A This is an enlarged view used to illustrate the electrodes according to the disclosed example embodiments.

[0035] Figure 7B and Figure 7C This is an enlarged view showing electrodes according to other exemplary embodiments of the present disclosure.

[0036] Figure 8 This is an enlarged view showing the electrodes according to the comparative example.

[0037] Figure 9 This is a diagram illustrating a method for manufacturing an electrode according to an exemplary embodiment of the present disclosure.

[0038] Figure 10This is a schematic diagram of the preparation process of a composite conductive material according to an example embodiment of the present disclosure.

[0039] Figure 11 This is a SEM image of a composite conductive material according to an example embodiment of the present disclosure.

[0040] Figure 12 This is a flowchart illustrating a method for manufacturing an electrode for a rechargeable lithium battery according to an example embodiment. Detailed Implementation

[0041] To provide a full understanding of the structure and effects of this disclosure, some exemplary embodiments have been described with reference to the accompanying drawings. However, this disclosure is not limited to the following exemplary embodiments and can be implemented in various forms. The exemplary embodiments are provided merely to illustrate this disclosure and to enable those skilled in the art to fully understand its scope.

[0042] In this specification, when an element is described as being "on" another element, the element may be "directly on" said other element, or one or more intervening elements may be present between them. In the drawings, certain thicknesses may be exaggerated to better illustrate technical details. Throughout the specification, the same reference numerals denote the same elements.

[0043] The exemplary embodiments described herein can be illustrated using cross-sectional and / or plan views given as idealized examples of this disclosure. For clarity, the thickness of layers and regions in the figures may be exaggerated. The regions shown in the figures are for illustrative purposes and should not be construed as limiting the scope of this disclosure. While terms such as “first,” “second,” and “third” may be used to describe various elements, these terms are for distinction only and do not imply any particular order or hierarchy. The exemplary embodiments described and illustrated herein include complementary variations.

[0044] Unless otherwise expressly stated in this specification, the singular form may also include the plural form. Furthermore, unless otherwise expressly stated, the phrase "A or B" may mean "A but not B," "B but not A," and "A and B." The term "including / comprises" and its variations do not exclude the presence or addition of one or more other components.

[0045] In this specification, the phrase “combinations thereof” may refer to mixtures, stacks, complexes, copolymers, alloys, blends, or reaction products.

[0046] Unless otherwise specifically defined, the term "particle size" refers to the average particle size. Particle size can be expressed as the median particle size (D50) corresponding to the diameter of 50% by volume of particles in a cumulative particle size distribution. The average particle size (D50) can be measured using widely known methods, such as particle size analyzers, transmission electron microscopy (TEM) imaging, or scanning electron microscopy (SEM) imaging. Alternatively, dynamic light scattering can be used, in which particle counts within a size range are analyzed to calculate the average particle size (D50). Additionally, laser scattering can be employed, in which target particles are dispersed in a solvent, introduced into a laser scattering particle measurement device (e.g., the MT3000 from Microtrac Ltd.), irradiated with ultrasound at 28 kHz and 60 W, and subsequently analyzed to determine the D50 value based on a 50% by volume cumulative particle size distribution.

[0047] As used herein, unless otherwise specifically defined, the term "alkyl" refers to C1 to C20 alkyl, the term "alkenyl" may refer to C2 to C20 alkenyl, the term "cycloalkenyl" may refer to C3 to C20 cycloalkenyl, the term "heterocyclic alkenyl" may refer to C2 to C20 heterocyclic alkenyl, the term "aryl" may refer to C6 to C20 aryl, the term "arylalkyl" may refer to C6 to C20 arylalkyl, the term "alkylene" may refer to C1 to C20 alkylene, the term "arylene" may refer to C6 to C20 arylene, the term "alkylenearyl" may refer to C6 to C20 alkylenearyl, the term "heteroaryl" may refer to C3 to C20 heteroaryl, and the term "alkoxide" may refer to C1 to C20 alkoxide.

[0048] As used herein, unless otherwise specifically defined, the term "substitution" can mean the substitution of at least one hydrogen atom with a substituent selected from a halogen atom (F, Cl, Br, or I), hydroxyl, C1 to C20 alkoxy, nitro, cyano, amino, imino, azide, amido, hydrazine, hydrazone, carbonyl, carbamoyl, thiol, ester, ether, carboxyl or a salt thereof, sulfonic acid or a salt thereof, phosphoric acid or a salt thereof, C1 to C20 alkyl, C2 to C20 alkenyl, C2 to C20 alkynyl, C6 to C20 aryl, C3 to C20 cycloalkyl, C3 to C20 cycloalkenyl, C3 to C20 cycloalkynyl, C2 to C20 heterocyclic alkyl, C2 to C20 heterocyclic alkenyl, C2 to C20 heterocyclic alkynyl, C3 to C20 heterocyclic aryl, and combinations thereof.

[0049] As used herein, unless otherwise specifically defined, the term "heterogeneous" may refer to a chemical formula that includes at least one heteroatom from N, O, S, and P in addition to a carbon atom.

[0050] As used herein, unless otherwise specifically defined, the term "(meth)acrylate" may refer to both "acrylate" and "methacrylate", and the term "(meth)acrylic acid" may refer to both "acrylic acid" and "methacrylic acid".

[0051] As used herein, unless otherwise specifically defined, the term “combination” may refer to a blend or copolymer.

[0052] As used herein, unless otherwise specifically defined, the symbol “*” may refer to a junction having the same or different atoms or chemical formulas.

[0053] 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%.

[0054] 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.

[0055] The positive electrode 10 and the negative electrode 20 can be separated from each other by a diaphragm 30. The diaphragm 30 can be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20 and the diaphragm 30 can be in contact with the electrolyte ELL. The positive electrode 10, the negative electrode 20 and the diaphragm 30 can be immersed in the electrolyte ELL.

[0056] The electrolyte ELL can be or includes a medium for transporting lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move toward the positive electrode 10 or the negative electrode 20 through the separator 30.

[0057] 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 on the current collector. 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 (e.g., an electrically conductive material).

[0058] For example, the positive electrode 10 may also include additives that can constitute a sacrificial positive electrode.

[0059] The amount of positive electrode active material in the positive electrode active material layer AML1, relative to 100 wt% of the positive electrode active material layer AML1, can range from about 90 wt% to about 99.5 wt%. The amounts of binder and conductive material, relative to 100 wt% of the positive electrode active material layer AML1, can each range from about 0.5 wt% to about 5 wt%.

[0060] The binder can 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.

[0061] A conductive material can provide conductivity to the electrodes and any suitable conductive material that does not cause undesirable chemical changes in the battery can be used as a conductive material. Conductive materials may include, for example: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal powders or metal fibers, comprising one or more of copper, nickel, aluminum, and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0062] Aluminum (Al) can be used as a current collector COL1, but the present invention is not limited thereto.

[0063] 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 (which is or includes at least one of cobalt, manganese, nickel and combinations thereof).

[0064] 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.

[0065] 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); and Li a FePO4 (where 0.90≤a≤1.8).

[0066] 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; L 1 It can be or include at least one of Mn, Al and combinations thereof.

[0067] For example, the positive electrode active material can be or includes a high-nickel positive electrode active material, which has a nickel content equal to or greater than about 80 mol%, 85 mol%, 90 mol%, 91 mol%, or 94 mol% and equal to or less than about 99 mol% relative to 100 mol% of lithium-free metal in the lithium transition metal complex oxide. High-nickel positive electrode active materials can achieve high capacity and therefore can be used in rechargeable lithium batteries with high capacity and high density.

[0068] 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 positioned 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 (e.g., an electrically conductive material).

[0069] 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%.

[0070] The binder can improve the adhesion between the particles of the negative electrode active material and the adhesion of the negative electrode active material to the current collector COL2. The binder may include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0071] 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.

[0072] 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.

[0073] When using an aqueous binder as the negative electrode binder, it may also include a cellulose compound capable of providing viscosity. 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.

[0074] Dry adhesives may include fibrillable polymeric materials, such as at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0075] Conductive materials can provide conductivity to electrodes and any suitable conductive material that does not cause undesirable 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; metallic materials in the form of metal powder or metal fibers, including one or more of copper, nickel, aluminum, and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0076] 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.

[0077] 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.

[0078] Materials capable of reversibly inserting and deintercalating lithium ions can include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. For example, crystalline carbon can include graphite, such as amorphous, flake, sheet, spherical, or fibrous natural or artificial graphite, and amorphous carbon can include at least one of soft carbon, hard carbon, mesophase pitch carbon, and calcined coke.

[0079] A lithium metal alloy may include an alloy of lithium and a metal, where the metal is or includes at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0080] 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 an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (except Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof), and combinations of at least one of them. Sn-based negative electrode active materials may include at least one of Sn, SnO2, Sn-based alloys, and combinations thereof.

[0081] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to an exemplary embodiment, the silicon-carbon composite may have a structure in which amorphous carbon is coated on the surface of silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are assembled and an amorphous carbon coating layer (shells) positioned on the surface of the secondary particles. Amorphous carbon may also be present between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0082] The silicon-carbon composite may also include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and may also include an amorphous carbon coating layer on the surface of the core. The Si-based negative electrode active material or the Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0083] Diaphragm 30 Based on the type of rechargeable lithium battery, a separator 30 may be present between the positive electrode 10 and the negative electrode 20. The separator 30 may include one or more of polyethylene, polypropylene, and polyvinylidene fluoride and may have a multi-layer separator such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, and a polypropylene / polyethylene / polypropylene trilayer separator.

[0084] The separator 30 may include a porous substrate and a coating layer positioned on one surface or opposite surfaces of the porous substrate, and the coating layer includes an organic material, an inorganic material, or a combination thereof.

[0085] The porous substrate may be or include a polymer layer comprising 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. TM It may be or include at least one of polytetrafluoroethylene, or may be a copolymer or mixture comprising two or more of the above materials.

[0086] Organic materials may include polyvinylidene fluoride copolymers or (meth)acrylic acid copolymers.

[0087] Inorganic materials may include inorganic particles, such as or including at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but this disclosure is not limited thereto.

[0088] Organic and inorganic materials can be mixed in a single coating layer, or they can exist as a stack of coating layers including organic materials and coating layers including inorganic materials.

[0089] Electrolyte ELL Electrolytes (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0090] Non-aqueous organic solvents can serve as media for transporting ions that participate in the electrochemical reactions of a battery.

[0091] 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.

[0092] Carbonate solvents may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC).

[0093] 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.

[0094] 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, 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.

[0095] Non-aqueous organic solvents can be used alone or in mixtures of two or more solvents.

[0096] 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.

[0097] Lithium salts can be or include materials dissolved in non-aqueous organic solvents to form a supply source of lithium ions in the battery, and contribute to the basic operation of rechargeable lithium batteries and facilitate the movement of lithium ions between the positive and negative electrodes. Lithium salts can include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of the following: (SO2) (where x and y are integers in the range of 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluoro(oxalate)borate (LiODFB), lithium difluorobis(oxalate)phosphate (LiDFOP), and lithium bis(oxalate)borate (LiBOB).

[0098] Rechargeable lithium batteries Based on their shape, rechargeable lithium batteries can be classified into cylindrical, prismatic, pouch, and coin-shaped types. Figures 2 to 5 A simplified diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure is shown, wherein Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown. Figure 4 and Figure 5 A pouch-type battery is shown. (See reference) Figures 2 to 4The rechargeable lithium battery 100 may include an electrode assembly 40 in which a separator 30 is disposed between a positive electrode 10 and a negative electrode 20, and may also include a housing 50 therein housing the electrode assembly 40. The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in an electrolyte (not shown). Figure 2 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. 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 in the figure, or Figure 4 The positive electrode terminal 71 and negative electrode terminal 72 shown in the figure form an electrical path for externally guiding the current generated in the electrode assembly 40.

[0099] According to exemplary embodiments of this disclosure, a rechargeable lithium battery may include electrodes, a separator, and an electrolyte. For example, a rechargeable lithium battery according to an exemplary embodiment may include a positive electrode containing positive electrode active material, a negative electrode containing negative electrode active material, and a separator and an electrolyte between the positive and negative electrodes. At least one of the positive and negative electrodes may be discussed below; as an example, the positive electrode may be the following electrode.

[0100] Electrodes for rechargeable lithium batteries The following description focuses on electrodes according to exemplary embodiments of this disclosure.

[0101] Figure 6 This is a cross-sectional view of an electrode for a rechargeable lithium battery according to an exemplary embodiment of the present disclosure.

[0102] Reference Figure 6 Electrode 10 or 20 may include an electrode current collector COL and an electrode active material layer AML on the electrode current collector COL.

[0103] The electrode current collector COL may include the aforementioned current collector COL1 or current collector COL2.

[0104] For example, the electrode current collector COL may include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and combinations thereof.

[0105] In the example embodiment, aluminum (Al) can be used as the electrode current collector COL, but this disclosure is not limited thereto.

[0106] The electrode active material layer AML can be stacked on the electrode current collector COL. In other words, the electrode active material layer AML can be disposed on the electrode current collector COL.

[0107] The electrode active material layer AML may have a thickness TKL in a third direction D3 perpendicular to the first direction D1. The thickness TKL of the electrode active material layer AML may range from about 10 μm to about 170 μm. For example, the thickness TKL of the electrode active material layer AML may be about 10 μm or more, 11 μm or more, about 15 μm or more, about 20 μm or more, about 30 μm or more, or about 40 μm or more. For example, the thickness TKL of the electrode active material layer AML may be about 170 μm or less, about 160 μm or less, about 150 μm or less, about 140 μm or less, about 130 μm or less, about 120 μm or less, about 110 μm or less, about 100 μm or less, about 90 μm or less, about 80 μm or less, about 70 μm or less, about 60 μm or less, or about 50 μm or less. When the thickness TKL of the electrode active material layer AML meets the above range, the battery can exhibit increased lifespan and minimal or reduced volume change during charging and discharging.

[0108] In an example embodiment, the thickness TKL may be increased due to an increase in the weight of the active material included in the electrode active material layer AML.

[0109] Figure 7A This is an enlarged view showing the electrodes according to an exemplary embodiment of the present disclosure. Figure 7A It is shown Figure 6 An enlarged view of the region "M".

[0110] Reference Figure 7A The electrode active material layer AML can contact one surface of the electrode current collector COL. This one surface of the electrode current collector COL can be the surface where the electrode active material layer AML can contact the electrode current collector COL.

[0111] The electrode active material layer AML may include the active material CAM and the first composite conductive material CCM1.

[0112] When the electrode for a rechargeable lithium battery according to an exemplary embodiment of this disclosure is a positive electrode, any material that can be used as a positive electrode active material of a rechargeable lithium battery can be used as an active material CAM.

[0113] For example, active material CAMs may include compounds capable of reversibly inserting and deintercalating lithium (e.g., lithiation intercalation compounds). Active material CAMs may include lithium complex oxides represented by the following chemical formula 3.

[0114] Chemical Formula 3: Li x4 M 1 y M 2 z M 3 1-y-z O 2-a X a .

[0115] In Chemical Formula 3, 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 may each independently include at least one metal, such as or including 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.

[0116] X may include at least one element, such as or including at least one of F, S, P, and Cl.

[0117] In an exemplary embodiment, in Chemical Formula 3, M 1 may be Ni or include Ni, and may be 0.8 ≤ y ≤ 1 and 0 ≤ z ≤ 0.2.

[0118] For example, the active material CAM may include at least one of LMFP (LiMnFePO4, lithium manganese iron phosphate), LNM (lithium nickel manganese oxide, LiNiMnO2), LNCA (LiNiCoAlO2, lithium nickel cobalt aluminum), and LNCM (LiNiCoMnO2, lithium nickel cobalt manganese).

[0119] When the electrode for a rechargeable lithium battery according to an exemplary embodiment of the present disclosure is a negative electrode, any material that can be used as a negative electrode active material for a rechargeable lithium battery can be used as the active material CAM.

[0120] On the surface of the electrode active material layer AML, the first composite conductive material CCM1 may form a lithium ion path without binder migration. Additionally, the first composite conductive material CCM1 may include a first polymer containing functional groups effective for lithium ion transport, thereby exhibiting desired or improved ionic conductivity.

[0121] The first composite conductive material CCM1 may include a first carbon nanostructure and a first polymer chemically bonded to the surface of the first carbon nanostructure. The expression "chemically bonded" may mean "bonded via ionic or covalent bonds".

[0122] Since the first composite conductive material CCM1 is formed from or comprises chemically bonded first carbon nanostructures and a first polymer, the first carbon nanostructures can be effectively dispersed without agglomeration. Therefore, the first composite conductive material CCM1 can improve dispersibility and form conductive pathways to achieve high capacity even with small amounts. Furthermore, even when the active material CAM expands and contracts during battery operation due to charging and discharging, agglomeration caused by the migration of the first carbon nanostructures does not occur. Additionally, since the tensile strength of the first polymer is increased through the first carbon nanostructures, the first composite conductive material CCM1 can maintain conductive pathways, which can lead to an improved lifetime.

[0123] The first carbon nanostructure may include chain-like or elongated carbon materials that exhibit not only desired or improved mechanical strength, thermal conductivity and chemical stability, but also electronic conductivity.

[0124] The first carbon nanostructure can be manufactured by methods such as arc discharge, laser ablation, chemical vapor deposition, and high-pressure carbon monoxide separation (HIPCO).

[0125] The first carbon nanostructure can have a diameter in the nanometer range and a length in the micrometer range. For example, the first carbon nanostructure can have a diameter in the range of about 5 nm to about 100 nm, about 15 nm to about 90 nm, about 20 nm to about 80 nm, or about 30 nm to about 70 nm and a length in the range of about 10 μm to about 100 μm, about 15 μm to about 90 μm, about 20 μm to about 80 μm, or about 30 μm to about 70 μm.

[0126] For example, the first carbon nanostructure may include at least one of carbon nanotubes (CNTs), carbon nanofibers (CNFs), polyacetylene, graphene nanoribbons (GNRs), graphene sheets, fullerenes, nanodiamonds, mesoporous carbon, amorphous carbon, carbon quantum dots, nanoporous carbon, carbon black, nanohorns, and glassy carbon. For example, the first carbon nanostructure may include carbon nanotubes (CNTs). Carbon nanotubes (CNTs) may include single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs).

[0127] The first polymer may have properties that differ from those of the second polymer discussed below.

[0128] For example, the first polymer may have an ionic conductivity different from that of the second polymer described below. Ionic conductivity can be one of the physical properties that represents how efficiently a polymer transports ions, and can be measured by electrochemical methods such as impedance spectroscopy.

[0129] The ionic conductivity of the first polymer can be greater than that of the second polymer described below. According to an example embodiment, the ionic conductivity of the first polymer can be approximately 10. -2 S / cm to approximately 10 -3 Within the range of S / cm.

[0130] The first polymer may be or include a mixed polymer containing functional groups with desired or improved ionic conductivity, and may exhibit stable flexibility at high temperatures while maintaining high ionic conductivity.

[0131] For example, the first polymer may have a weight-average molecular weight (Mw) in the range of about 20,000 g / mol to about 2,500,000 g / mol or about 50,000 g / mol to about 1,500,000 g / mol.

[0132] In this specification, the term "weight-average molecular weight" may refer to a value calculated as a molecular weight by, for example, gel filtration chromatography.

[0133] The first polymer may include an ionic polymer. There is no limitation on the molecular weight of the ionic polymer, but it is advantageous that the ionic polymer has functional groups such as hydroxyl, carboxyl, or amino groups, and is compatible with the active material CAM and other additives included in the electrode composition to ensure that no problems occur during slurry preparation. It is also advantageous that the ionic polymer exhibits stable electrochemical properties during the charging and discharging of the rechargeable lithium battery.

[0134] According to an example embodiment, the first polymer may include at least one of a first structural unit represented by chemical formula 1-1A or chemical formula 1-1B, a second structural unit represented by chemical formula 1-2, a third structural unit represented by chemical formula 1-3A or chemical formula 1-3B, and a fourth structural unit represented by chemical formula 1-4A or chemical formula 1-4B.

[0135] The first structural unit represented by chemical formula 1-1A or chemical formula 1-1B can be derived from (meth)acrylic acid monomers or their salts.

[0136] Chemical formula 1-1A: .

[0137] Chemical formula 1-1B: .

[0138] In chemical formulas 1-1A and 1-1B, R 1 They may be the same or different, and may each be independently hydrogen atoms or C1 to C20 alkyl groups, and M1 may be or include alkali metals.

[0139] For example, the first structural unit can be derived from acrylic acid, R 1 All of them can be hydrogen atoms.

[0140] M1 can be derived from metal ions in the electrolyte, and for example, can be or include lithium atoms.

[0141] The second structural unit represented by chemical formula 1-2 can be derived from (meth)acrylonitrile monomers.

[0142] Chemical formula 1-2: .

[0143] In chemical formulas 1-2, R 2 It may include or contain hydrogen atoms or C1 to C20 alkyl groups.

[0144] The second structural unit can be derived from acrylonitrile. In this case, R 2 It can be or includes hydrogen atoms.

[0145] The third structural unit, represented by chemical formula 1-3A or chemical formula 1-3B, can be derived from zwitterionic monomers.

[0146] Chemical formula 1-3A: .

[0147] Chemical formula 1-3B: .

[0148] In chemical formulas 1-3A and 1-3B, R 3 They may be the same or different, and may each independently be or include hydrogen atoms or C1 to C20 alkyl groups, R 4 They may be the same or different, and may each independently be or include hydrogen atoms or C1 to C20 alkyl groups, L 1 It can be or include *-(C=O)-NR 4 -CH2-* or *-(C=O)-O-*, and L 2 To L 4 Each may be independently or include a single bond or a C1 to C20 alkylene group.

[0149] When the third structural unit is derived from sulfobetaine (SB) and represented by chemical formula 1-3A, R 3It may be or include methyl, L 1 They can be the same or different, and can all be or include *-(C=O)-NR independently. 4 -CH2-* or *-(C=O)-O-*, and L 2 and L 3 All of them can be or include ethylene.

[0150] When the third structural unit is derived from vinylimidazolium sulfonate (IMS) and represented by chemical formula 1-3B, R 3 It can be or includes hydrogen atoms, L 4 It can be or includes butylene.

[0151] The fourth structural unit, represented by chemical formula 1-4A or chemical formula 1-4B, can be derived from alkylene glycol monomers or their salts.

[0152] Chemical formula 1-4A: .

[0153] Chemical formula 1-4B: .

[0154] In chemical formulas 1-4A and 1-4B, M2 can be or includes an alkali metal, and n can be an integer in the range of 1 to 100.

[0155] For example, the fourth structural unit can be derived from ethylene glycol. In this case, n can be in the range of 5 to 20 or 5 to 10.

[0156] M2 can be derived from metal ions in the electrolyte, and for example, can be or include lithium atoms.

[0157] When the first polymer comprises the first to third structural units, the first structural unit may be included in an amount ranging from about 30 wt% to about 60 wt%, about 45 wt% to about 60 wt%, or about 45 wt% to about 60 wt% relative to the total weight of the first polymer; the second structural unit may be included in an amount ranging from about 32 wt% to about 55 wt%, about 35 wt% to about 55 wt%, or about 35 wt% to about 50 wt%; and the third structural unit may be included in an amount ranging from about 1 wt% to about 15 wt%, about 3 wt% to about 15 wt%, or about 5 wt% to about 15 wt%. Within the above ranges, the first to third structural units are coordinated to provide the advantages of high adhesion, desired or improved ionic conductivity, and low resistance.

[0158] When the first polymer comprises the first to fourth structural units, the first structural unit may be included in an amount ranging from about 30 wt% to about 60 wt%, about 45 wt% to about 60 wt%, or about 45 wt% to about 60 wt% relative to the total weight of the first polymer. The second structural unit may be included in an amount ranging from about 32 wt% to about 55 wt%, about 35 wt% to about 55 wt%, or about 35 wt% to about 50 wt%. The third structural unit may be included in an amount ranging from about 1 wt% to about 15 wt%, about 3 wt% to about 15 wt%, or about 5 wt% to about 15 wt%. The fourth structural unit may be included in an amount ranging from about 0.1 wt% to about 15 wt%, about 1 wt% to about 15 wt%, or about 3 wt% to about 10 wt%. In this case, the fourth structural unit can help to further reduce the resistance by increasing the ionic conductivity of the first polymer.

[0159] The first polymer may be included in an amount ranging from about 40 wt% to about 80 wt% relative to the total weight of the first composite conductive material CCM1. When the amount of the first polymer in the first composite conductive material CCM1 is greater than the above range, an increase in electrode internal resistance due to side reactions may occur. When the amount of the first polymer in the first composite conductive material CCM1 is less than the above range, the small amount of first polymer may be unevenly distributed.

[0160] According to an example embodiment, the amount of active material CAM can be in the range of about 90 wt% to about 99.5 wt% relative to the total weight of the electrode active material layer AML. When the electrode active material layer AML meets the above-mentioned range for the amount of active material CAM, it is possible to maximize or increase the battery capacity and energy density.

[0161] According to the example embodiment, the amount of the first composite conductive material CCM1 relative to the total weight of the electrode active material layer AML can range from about 0.1 wt% to about 5 wt%. When the amount of the first composite conductive material CCM1 in the electrode active material layer AML is greater than the above range, the electrode resistance may increase, and therefore the stability and performance of the battery may deteriorate. When the first composite conductive material CCM1 is not included in the electrode active material layer AML or the amount of the first composite conductive material CCM1 in the electrode active material layer AML is less than the above range, maximizing or improving the ionic conductivity may be challenging.

[0162] Figure 7B This is an enlarged view showing the electrodes according to another exemplary embodiment of the present disclosure. Figure 7B It is shown Figure 6 A magnified view of region "M". In this example embodiment, the referenced above is omitted. Figure 6 and Figure 7A The described technical features are repeated in detail, and the differences are also described in detail.

[0163] Reference Figure 7B According to another example embodiment of the present disclosure, electrodes 10, 20 may also include a binder BND in the electrode active material layer AML.

[0164] According to another example embodiment, the electrode active material layer AML may include an active material CAM, a first composite conductive material CCM1, and a binder BND.

[0165] The active substance CAM can be compared with the above. Figure 7A The active material CAM described is the same. The first composite conductive material CCM1 can be compared with the above. Figure 7A The first composite conductive material described is the same as CCM1.

[0166] The binder BND can improve the adhesion between the active material CAM particles and the adhesion between the active material CAM and the electrode current collector COL. For example, the binder BND may include at least one of rubber-based binders, acrylate-based binders, polyvinylidene fluoride-based binders, polyvinylpyrrolidone-based binders, nitrile-based binders, acetate-based binders, polyvinyl alcohol-based binders, cellulose-based binders, and combinations thereof, but this disclosure is not limited thereto.

[0167] Rubber adhesives may include at least one of, for example, styrene-butadiene rubber (SBR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), ethylene propylene diene monomer rubber (EPDM), and combinations thereof.

[0168] Acrylic adhesives may include at least one of, for example, polyacrylic acid (PAA), polymethyl methacrylate, polyisobutyl methacrylate, poly(2-ethylhexyl acrylate), and combinations thereof.

[0169] Polyvinylidene fluoride adhesives may include at least one of, for example, polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co-tetrafluoroethylene, polyvinylidene fluoride-co-trifluoroethylene, polyvinylidene fluoride-co-trifluorochloroethylene, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, and combinations thereof.

[0170] Polyvinylpyrrolidone adhesives may include, for example, polyvinylpyrrolidone.

[0171] Nitrile adhesives may include, for example, polyacrylonitrile, acrylonitrile-styrene-butadiene copolymer, or combinations thereof.

[0172] Acetate-based adhesives may include at least one of, for example, polyvinyl acetate, ethylene-co-vinyl acetate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and combinations thereof.

[0173] Polyvinyl alcohol adhesives may include, for example, polyvinyl alcohol.

[0174] Cellulose binders may include at least one of, for example, carboxymethyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl cellulose (HPC), methyl hydroxypropyl cellulose (MHPC), ethyl hydroxyethyl cellulose (EHEC), methyl ethyl hydroxyethyl cellulose (MEHEC), cellulose gum, and combinations thereof.

[0175] According to another example embodiment, the amount of active material CAM can be in the range of about 90 wt% to about 98 wt% relative to the total weight of the electrode active material layer AML. According to another example embodiment, the amount of first composite conductive material CCM1 can be in the range of about 0.1 wt% to about 5 wt% relative to the total weight of the electrode active material layer AML. According to another example embodiment, the amount of binder BND can be in the range of about 0.001 wt% to about 0.1 wt% relative to the total weight of the electrode active material layer AML. When the electrode active material layer AML meets the above-described ranges for the amounts of active material CAM, first composite conductive material CCM1, and binder BND, it is possible to maximize or increase the battery capacity and energy density.

[0176] Figure 7C This is an enlarged view showing the electrodes according to another exemplary embodiment of the present disclosure. Figure 7C It is shown Figure 6 A magnified view of region "M". In this example embodiment, the referenced above is omitted. Figure 6 , Figure 7A and Figure 7B The described technical features are repeated in detail, and the differences are also described in detail.

[0177] Reference Figure 7C According to another example embodiment of the present disclosure, electrodes 10, 20 may include an electrode current collector COL and an electrode active material layer AML on the electrode current collector COL.

[0178] Electrodes 10, 20 according to another example embodiment of the present disclosure may further include a second composite conductive material CCM2 in the electrode active material layer AML.

[0179] According to another example embodiment, the electrode active material layer AML may include active material CAM, a first composite conductive material CCM1, and a second composite conductive material CCM2.

[0180] The active substance CAM can be compared with the above. Figure 7A and Figure 7B The active material CAM described is the same. The first composite conductive material CCM1 can be compared with the above. Figure 7A and Figure 7B The first composite conductive material described is the same as CCM1.

[0181] According to another example embodiment, the electrode active material layer AML may include a second composite conductive material CCM2, in which a second carbon nanostructure is integrated with a second polymer containing functional groups having desired or improved adhesion, thereby ensuring both adhesion and lithium-ion pathways at the surface of the electrode active material layer AML. Therefore, compared to an electrode active material layer AML that only includes the binder BND, the electrode active material layer AML may exhibit desired or improved ionic conductivity.

[0182] The second composite conductive material CCM2 may include a second carbon nanostructure and a second polymer chemically bonded to the surface of the second carbon nanostructure. The expression "chemically bonded" can mean "bonded via ionic or covalent bonds".

[0183] Since the second composite conductive material CCM2 is formed by or includes chemically bonded second carbon nanostructures and a second polymer, the second carbon nanostructures can be effectively dispersed without agglomeration. Therefore, the second composite conductive material CCM2 can improve dispersibility, and even a small amount of CCM2 can form conductive pathways to achieve high capacity. Furthermore, even when the active material CAM expands and contracts during battery operation due to charging and discharging, agglomeration caused by the migration of the second carbon nanostructures does not occur. Additionally, since the tensile strength of the second polymer is increased through the second carbon nanostructures, the second composite conductive material CCM2 can maintain conductive pathways, which can lead to improved lifetime.

[0184] The second carbon nanostructure can be identical to the first carbon nanostructure described above in the electrode active material layer AML. For example, the second carbon nanostructure may include carbon nanotubes (CNTs). Carbon nanotubes (CNTs) may include single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs).

[0185] The second polymer may include an organic binder dissolved in an organic solvent. Organic binders can facilitate the achievement of various properties, such as adhesion, tensile strength, and elasticity. There are no limitations on the use of any polymer capable of serving as an organic binder as the second polymer.

[0186] The second polymer may include an adhesive polymer. There is no limitation on the molecular weight of the adhesive polymer, but it is advantageous that the adhesive polymer has functional groups (such as at least one of hydroxyl, carboxyl, and amine groups) and is compatible with the active material CAM and other additives included in the electrode composition to ensure that no problems occur during slurry preparation. It is also advantageous that the adhesive polymer exhibits stable electrochemical properties during the charging and discharging of the rechargeable lithium battery.

[0187] The second polymer may include functional groups with high adhesion and may have properties different from those of the first polymer.

[0188] For example, the second polymer may have an ionic conductivity different from that of the first polymer described above. The ionic conductivity of the second polymer may be less than that of the first polymer. According to an example embodiment, the ionic conductivity of the second polymer may be approximately 10. -4 S / cm to approximately 10 -3 Within the range of S / cm.

[0189] The second polymer can have the same glass transition temperature (T0) as the first polymer. g Different glass transition temperatures (T) g The glass transition temperature (T) of the second polymer g It can be lower than the glass transition temperature (T) of the first polymer. g ).

[0190] Glass transition temperature (T) g The glass transition temperature (T0) refers to the temperature at which a polymer transitions from a glassy state to a rubbery state, and can be one of the physical properties that affects the hardness and flexibility of a polymer. For example, the glass transition temperature (T0) of a polymer... g The glass transition temperature (T) of the second polymer, which can be higher than that described later, can be higher. g Glass transition temperature (T) g The weight can be measured by using differential scanning calorimetry (DSC) to measure heat flow changes or by using thermogravimetric analysis (TGA) to analyze weight changes with temperature. According to an example embodiment, the glass transition temperature (Tg) of the first polymer... g It can be in the range of approximately 40°C to approximately 100°C.

[0191] Due to its high adhesion, the second polymer retains its flexible properties even at low temperatures. Therefore, the second polymer can have a relatively lower glass transition temperature (T0) than the first polymer. g The glass transition temperature (T) g According to an example embodiment, the glass transition temperature (T) of the second polymer gIt can be in the range of approximately 10°C to approximately 40°C.

[0192] The second polymer may include at least one of polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyethylene (PE), polyethylene glycol (PEG), polyimide (PI), polyacrylamide (PAM), polystyrene (PS), polyurethane (PU), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), and combinations thereof. The second polymer may be used alone or as a mixture of two or more substances.

[0193] According to an example embodiment, the second polymer may include at least one of a fifth structural unit represented by chemical formula 2-1 and a sixth structural unit represented by chemical formula 2-2.

[0194] Chemical formula 2-1: .

[0195] Chemical formula 2-2: .

[0196] In chemical formulas 2-1 and 2-2, m and z can both be integers in the range of 1 to 100.

[0197] For example, the fifth structural unit can be derived from polyvinyl alcohol (PVA). For example, the sixth structural unit can be derived from polyacrylonitrile (PAN).

[0198] For example, the second polymer may include at least one of polyvinyl alcohol-polyacrylonitrile (PVA-PAN) copolymer, polyvinyl alcohol-polyethylene glycol (PVA-PEG) copolymer, polyacrylic acid-polyacrylonitrile (PAA-PAN) copolymer, and combinations thereof.

[0199] The second polymer may be included in an amount ranging from about 40 wt% to about 80 wt% relative to the total weight of the second composite conductive material CCM2. When the amount of the second polymer in the second composite conductive material CCM2 exceeds the above range, an increase in electrode internal resistance due to side reactions may occur. When the amount of the second polymer in the second composite conductive material CCM2 is below the above range, the small amount of second polymer may be unevenly distributed.

[0200] According to another example embodiment, the amount of active material CAM can be in the range of about 90 wt% to about 99.5 wt% relative to the total weight of the electrode active material layer AML.

[0201] According to another example embodiment, the amount of the first composite conductive material CCM1 relative to the total weight of the electrode active material layer AML can range from about 0.1 wt% to about 5 wt%. When the amount of the first composite conductive material CCM1 in the electrode active material layer AML exceeds the above range, the electrode resistance may increase, and therefore the stability and performance of the battery may deteriorate. When the first composite conductive material CCM1 is not included in the electrode active material layer AML, or when the amount of the first composite conductive material CCM1 in the electrode active material layer AML is less than the above range, it may be difficult to maximize or improve the ionic conductivity.

[0202] According to another example embodiment, the amount of the second composite conductive material CCM2 relative to the total weight of the electrode active material layer AML can range from about 0.1 wt% to about 5 wt%. When the amount of the second composite conductive material CCM2 in the electrode active material layer AML exceeds the above range, the electrode resistance may increase, and therefore the stability and performance of the battery may deteriorate. When the second composite conductive material CCM2 is not included in the electrode active material layer AML, or when the amount of the second composite conductive material CCM2 in the electrode active material layer AML is less than the above range, it may be difficult to maximize or increase the improvement effect of adhesion.

[0203] According to another example embodiment, the first composite conductive material CCM1 and the second composite conductive material CCM2 in the electrode active material layer AML can be mixed in a ratio ranging from 7:3 to 3:7. When the ratio of the composite conductive materials CCM1 and CCM2 in the electrode active material layer AML exceeds the above range, it may be difficult to maximize or improve the ionic conductivity and adhesion.

[0204] According to another example embodiment, the electrode active material layer AML may include a small amount of binder BND or conductive material CDM separate from the composite conductive materials CCM1 and CCM2. For example, the amount of binder BND in the electrode active material layer AML may be in the range of about 0.1 wt% or less, and the amount of conductive material CDM may be in the range of about 0.1 wt% or less. Since the electrode active material layer AML includes a fairly small amount of binder BND or conductive material CDM, it can be considered that the binder BND or conductive material CDM is substantially omitted.

[0205] Figure 8 This is an enlarged view showing the electrodes according to the comparative example. Figure 8 This is shown in the case of electrodes according to the comparative example. Figure 6 An enlarged view of the region "M".

[0206] Reference Figure 8According to the comparative example, electrodes 10 and 20 may include an electrode current collector COL and an electrode active material layer AML on the electrode current collector COL.

[0207] Typically, electrodes 10 and 20 in the comparative examples may include an active material CAM, a conductive material CDM, and a binder BND in the electrode active material layer AML.

[0208] The active ingredient CAM and the binder BND can be the same as the active ingredient and binder mentioned above.

[0209] The conductive material CDM can provide conductivity for electrodes 10 and 20, and can utilize any suitable conductive material that does not cause undesirable chemical changes in the battery, such as: carbon-based materials, including at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber and carbon nanotube; metallic materials, such as metal powder or metal fiber including at least one of copper, nickel, aluminum and silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0210] like Figure 6 and Figures 7A to 7C As shown, the electrode active material layer AML according to this disclosure may include a first composite conductive material CCM1 and a second composite conductive material CCM2 corresponding to the conductive material CDM and the binder BND in the electrode active material layer AML according to the comparative example.

[0211] According to the example embodiment, the binder BND or conductive material CDM may not be present in the electrode active material layer AML, or may be present in small amounts. That is, the amount of binder BND or conductive material CDM in the electrode active material layer AML can be substantially equal to 0 wt%.

[0212] According to the comparative example, the total amount of binder BND and conductive material CDM in the electrode active material layer AML can be greater than the amount of composite conductive materials CCM1 and CCM2 in the electrode active material layer AML according to the example embodiment. Since the composite conductive materials CCM1 and CCM2 include a structure in which carbon nanostructures and polymers are densely bonded, even a small amount of composite conductive materials CCM1 and CCM2 can maximize or increase conductivity and adhesion.

[0213] For example, the total amount of binder BND and conductive material CDM in the electrode active material layer AML according to the comparative example can be in the range of about 1 to about 3 times the amount of composite conductive materials CCM1 and CCM2 in the electrode active material layer AML according to the example embodiment.

[0214] The electrode active material layer AML according to the example embodiment may include composite conductive materials CCM1 and CCM2 that integrate polymer and carbon nanostructure, instead of including binder BND and conductive material CDM, thereby having a relatively large porosity than the electrode active material layer AML according to the comparative example.

[0215] For example, the porosity of the electrode active material layer AML according to the comparative example can be in the range of about 10% to about 15%, and the porosity of the electrode active material layer AML according to the example embodiment can be in the range of about 20% to about 30%.

[0216] Therefore, since a pathway for lithium ion reduction is provided in the electrode active material layer AML according to the example embodiment, lithium ions can easily migrate within the electrode active material layer AML. In other words, the ionic conductivity of the electrode active material layer AML according to the example embodiment can be improved.

[0217] In electrodes 10 and 20 according to the example embodiments, by mixing the first composite conductive material CCM1 and the second composite conductive material CCM2 and adding them to the electrode active material layer AML, the adhesion between the electrode current collector COL and the electrode active material layer AML can be improved, the ionic conductivity in the electrode active material layer AML can be enhanced, and the lithium ion pathway on the surface of the electrode active material layer AML can be ensured.

[0218] Methods for manufacturing electrodes Figure 9 This is a diagram illustrating a method for manufacturing an electrode according to an exemplary embodiment of the present disclosure.

[0219] Reference Figure 9 A method for manufacturing an electrode according to an example embodiment of the present disclosure may include providing an electrode current collector COL and forming an electrode active material layer AML on the electrode current collector COL.

[0220] The electrode current collector COL and the electrode active material layer AML are constructed in the same way as the electrodes 10 and 20 according to the above example embodiments, so their detailed description is omitted below.

[0221] In an example embodiment, the electrode active material layer AML may include the above-mentioned reference. Figure 7A The active material CAM and the first composite conductive material CCM1 are described.

[0222] According to an example embodiment, forming the electrode active material layer AML may be performed in a wet process or a dry process. In the example embodiment, the electrode active material layer AML may be formed by a wet process, but is not limited thereto.

[0223] In a wet process, the active material CAM and the first composite conductive material CCM1 can be mixed in a solvent to prepare an electrode mixture, and the mixture can be coated, dried, and rolled onto the electrode current collector COL. The solvent in the slurry can be or includes solvents commonly used in the art, and can include at least one of, for example, dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone, water, and combinations thereof.

[0224] In the dry process, the active material CAM and the first composite conductive material CCM1 in a dry state can be dry-mixed to prepare an electrode mixture without solvent, and the mixture can be set and rolled onto the electrode current collector COL.

[0225] In another example embodiment, the electrode active material layer AML may include the above reference. Figure 7B The active material CAM, the first composite conductive material CCM1, and the binder BND are described.

[0226] According to another example embodiment, forming the electrode active material layer AML may be performed in a wet process or a dry process.

[0227] For example, in a wet process, the active material CAM, the first composite conductive material CCM1, and the binder BND can be mixed in a solvent to prepare an electrode mixture. Alternatively, in a dry process, the active material CAM, the first composite conductive material CCM1, and the binder BND can be dry-mixed in a solvent-free state to prepare an electrode mixture.

[0228] In another example embodiment, the electrode active material layer AML may include the above reference. Figure 7C The active material CAM, the first composite conductive material CCM1, and the second composite conductive material CCM2 are described.

[0229] According to another example embodiment, forming the electrode active material layer AML may be performed in a wet process or a dry process.

[0230] For example, in a wet process, the active material CAM, the first composite conductive material CCM1, and the second composite conductive material CCM2 can be mixed in a solvent to prepare an electrode mixture. Alternatively, in a dry process, the active material CAM, the first composite conductive material CCM1, and the second composite conductive material CCM2 can be dry-mixed in the absence of a solvent to prepare an electrode mixture.

[0231] Figure 10 This is a schematic diagram illustrating a process for preparing a composite conductive material chemically bonded to a polymer according to the present disclosure. (Refer to...) Figure 10The following describes in detail the methods for preparing composite conductive materials CCM1 and CCM2.

[0232] The first composite conductive material CCM1 may include a first carbon nanostructure and a first polymer chemically bonded to the surface of the first carbon nanostructure. The second composite conductive material CCM2 may include a second carbon nanostructure and a second polymer chemically bonded to the surface of the second carbon nanostructure.

[0233] Each or at least one of the first carbon nanostructure and the second carbon nanostructure may include at least one of carbon nanotubes (CNTs), carbon nanofibers (CNFs), polyacetylene, graphene nanoribbons (GNRs), graphene sheets, fullerenes, nanodiamonds, mesoporous carbon, amorphous carbon, carbon quantum dots, nanoporous carbon, carbon black, nanohorns, glassy carbon, and combinations thereof.

[0234] The first polymer may be different from the second polymer, and the ionic conductivity of the first polymer may be greater than that of the second polymer.

[0235] The first polymer may include at least one of the following: a first structural unit derived from a (meth)acrylic acid monomer or a salt thereof and represented by the above chemical formula 1-1A or 1-1B; a second structural unit derived from a (meth)acrylonitrile monomer and represented by the above chemical formula 1-2; a third structural unit derived from a zwitterionic monomer and represented by the above chemical formula 1-3A or 1-3B; and a fourth structural unit derived from an alkylene glycol monomer or a salt thereof and represented by the above chemical formula 1-4A or 1-4B.

[0236] For example, the first polymer may be or include copolymers prepared by combining a first structural unit to a fourth structural unit.

[0237] According to one example embodiment, the first structural unit may be derived from acrylic acid. The second structural unit may be derived from acrylonitrile. The third structural unit may be derived from sulfobetaine (SB) or vinylimidazolium sulfonate (IMS). The fourth structural unit may be derived from ethylene glycol.

[0238] The second polymer may include at least one of the fifth structural unit represented by the above chemical formula 2-1 and the sixth structural unit represented by the above chemical formula 2-2.

[0239] The second polymer may include a fifth structural unit, a sixth structural unit, and copolymers thereof. For example, the fifth structural unit may be derived from polyvinyl alcohol (PVA). For example, the sixth structural unit may be derived from polyacrylonitrile (PAN).

[0240] According to an example embodiment, the second polymer may include at least one of polyvinyl alcohol-polyacrylonitrile (PVA-PAN) copolymer, polyvinyl alcohol-polyethylene glycol (PVA-PEG) copolymer, and polyacrylic acid-polyacrylonitrile (PAA-PAN) copolymer.

[0241] Reference Figure 10 The preparation of the first composite conductive material CCM1 may include introducing functional groups into the surface of a first carbon nanostructure and preparing a first mixture by mixing a first polymer and a first carbon nanostructure having functional groups.

[0242] The preparation of the second composite conductive material CCM2 may include introducing functional groups into the surface of the second carbon nanostructure and preparing a second mixture by mixing a second polymer and the second carbon nanostructure having functional groups.

[0243] For chemical modification, a pretreatment process can be performed to introduce functional groups (such as carboxyl groups (-COOH), hydroxyl groups (-OH)) into the surface of each of the first and second carbon nanostructures.

[0244] Introducing functional groups may include a pretreatment process that utilizes at least one of wet treatment using strong acid, plasma treatment, and dry treatment using vacuum ultraviolet irradiation.

[0245] The preparation of the first mixture may include mixing a first polymer and a first carbon nanostructure having functional groups. For example, the prepared first mixture can be obtained by adding the first carbon nanostructure to a solvent containing the first polymer. The prepared first mixture may induce a chemical reaction to induce chemical bonds.

[0246] The preparation of the second mixture may include mixing a second polymer and a second carbon nanostructure having functional groups. For example, the prepared second mixture can be obtained by adding the second carbon nanostructure to a solvent containing the second polymer. The prepared second mixture may induce a chemical reaction to induce chemical bonds.

[0247] Each of the first and second mixtures can be stirred and heat-treated to carry out a chemical reaction. In one example, stirring and heat treatment can be performed at a temperature ranging from about 60°C to about 90°C.

[0248] For example, each or at least one of the first mixture and the second mixture may also include a crosslinking agent and a catalyst for activating the chemical reaction.

[0249] The first mixture that has undergone the reaction can be dried to finally prepare a first composite conductive material CCM1 in which the first carbon nanostructure and the first polymer are chemically bonded. The second mixture that has undergone the reaction can be dried to finally prepare a second composite conductive material CCM2 in which the second carbon nanostructure and the second polymer are chemically bonded.

[0250] According to another example embodiment, a first composite conductive material CCM1 can be prepared by mixing a first polymer and a first carbon nanostructure having functional groups to form a first mixture, and then evaporating or gelling the first mixture to induce self-assembly of the natural arrangement of the first carbon nanostructure and the first polymer. In the first composite conductive material CCM1, self-assemblies can be used for its preparation, and the self-assemblies can have a specific structure in which the first carbon nanostructures are arranged between the first polymer chains. Furthermore, according to another example embodiment, a second composite conductive material CCM2 can be prepared by mixing a second polymer and a second carbon nanostructure having functional groups to form a second mixture, and then evaporating or gelling the second mixture to induce self-assembly of the natural arrangement of the second carbon nanostructure and the second polymer. In the second composite conductive material CCM2, self-assemblies can be used for its preparation, and can have a specific structure in which the second carbon nanostructures are arranged between the second polymer chains.

[0251] On the other hand, when polymers and functionalized carbon nanostructures are simply mixed to be used as composite conductive materials, it may be difficult to induce chemical bonds between them during electrode fabrication. Even if physical bonds are formed, their binding force may be weaker than that of chemical bonds, potentially reducing the effectiveness of reducing or inhibiting the aggregation of carbon nanostructures. The expression "physical bonding" can represent the simple mixing of components without altering the chemical properties of each component.

[0252] According to the example embodiments, the composite conductive materials CCM1 and CCM2 can form chemical bonds between the carbon nanostructure and the polymer to improve the dispersion of the carbon nanostructure, thereby forming conductive pathways even in small quantities. As a result, the amount of active material in the electrode active material layer can be increased to achieve high capacity. Furthermore, even when the active material expands and contracts due to charging and discharging during lithium battery operation, conductive pathways can be maintained without agglomeration of carbon nanostructures, thus improving the lifespan characteristics of the lithium battery.

[0253] Then, rolling, cutting, and grooving processes can be performed (e.g., sequentially) on the electrodes 10 and 20 manufactured by the above process. The positive electrode 10, separator 30, and negative electrode 20 are stacked to provide electrolyte ELL, thereby manufacturing a rechargeable lithium battery according to this disclosure.

[0254] Figure 12This is a flowchart illustrating a method for manufacturing electrodes for a rechargeable lithium battery according to an example embodiment. Figure 12 In this method 1200, the steps include an operation 1210 of providing an electrode current collector and an operation 1220 of forming an electrode active material layer on the electrode current collector. For example, the electrode active material layer includes an active material and a first composite conductive material. In another example, preparing the first composite conductive material includes introducing functional groups onto the surface of a first carbon nanostructure and preparing a first mixture by mixing a first polymer and the first carbon nanostructure having functional groups.

[0255] In yet another example, the first polymer includes at least one of a first structural unit derived from a (meth)acrylic acid monomer or a salt thereof and represented by formula 1-1A or formula 1-1B, a second structural unit derived from a (meth)acrylonitrile monomer and represented by formula 1-2, a third structural unit derived from a zwitterionic monomer and represented by formula 1-3A or formula 1-3B, and a fourth structural unit derived from an alkylene glycol monomer or a salt thereof and represented by formula 1-4A or formula 1-4B.

[0256] Chemical formula 1-1A: .

[0257] Chemical formula 1-1B: .

[0258] In chemical formulas 1-1A and 1-1B, R 1 They may be the same or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group, and M1 includes an alkali metal.

[0259] Chemical formula 1-2: .

[0260] In chemical formulas 1-2, R 2 It is a hydrogen atom or a C1 to C20 alkyl group.

[0261] Chemical formula 1-3A: .

[0262] Chemical formula 1-3B: .

[0263] In chemical formulas 1-3A and 1-3B, R 3 Whether identical or different, and both independently comprising hydrogen atoms or C1 to C20 alkyl groups, R 4 Identical or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group, L 1Including *-(C=O)-NR 4 -CH2-* or *-(C=O)-O-*, and L 2 To L 4 Each independently includes a single bond or a C1 to C20 alkylene group.

[0264] Chemical formula 1-4A: .

[0265] Chemical formula 1-4B: .

[0266] In chemical formulas 1-4A and 1-4B, M2 includes alkali metals, and n is an integer in the range of 1 to 100.

[0267] In another example, the first composite conductive material comprises a first carbon nanostructure and a first polymer chemically bonded to the surface of the first carbon nanostructure. In yet another example, the method further includes adding a second composite conductive material to the electrode active material layer, wherein preparing the second composite conductive material includes introducing functional groups into the surface of the second carbon nanostructure and preparing a second mixture by mixing a second polymer and the second carbon nanostructure having functional groups.

[0268] In yet another example, the second composite conductive material includes a second carbon nanostructure and a second polymer chemically bonded to the surface of the second carbon nanostructure, the second polymer including at least one of a fifth structural unit represented by chemical formula 2-1 and a sixth structural unit represented by chemical formula 2-2.

[0269] Chemical formula 2-1: .

[0270] Chemical formula 2-2: .

[0271] In chemical formulas 2-1 and 2-2, m and z are both integers in the range of 1 to 100.

[0272] Examples and comparative examples of this disclosure are described below. However, the following examples are merely examples of this disclosure, and this disclosure is not limited to these examples.

[0273] Preparation Example 1: Preparation of the First Polymer The azo compound initiator was mixed with water relative to 100 parts by weight of a monomer mixture comprising 51 wt% acrylic acid (AA), 39 wt% acrylonitrile (AN), 5 wt% sulfobetaine (SB), and 5 wt% ethylene glycol (ethylene glycol repetition number (n) = 8). The initiator was used at 0.2 parts by weight relative to 100 parts by weight of the monomer mixture.

[0274] The obtained mixture was emulsion polymerized to prepare a solution comprising a first polymer, the first polymer being a copolymer having a first structural unit derived from acrylic acid, a second structural unit derived from acrylonitrile, a third structural unit derived from sulfobetaine, and a fourth structural unit derived from ethylene glycol (ethylene glycol repeating number (n) = 8). The first polymer prepared was an AA-AN-SB-EG copolymer having a weight-average molecular weight of 720,500 g / mol.

[0275] Preparation Example 2: Preparation of the First Composite Conductive Material Two g of multi-walled carbon nanotubes (MWCNTs) with a diameter of approximately 1 nm and a length of approximately 25 μm were pretreated for 24 hours at 40 °C using 300 mL of 20 wt% nitric acid solution. One g of the pretreated CNTs was then immersed in 200 mL of a solution prepared by mixing concentrated sulfuric acid and concentrated nitric acid in a 3:1 (v / v%) ratio. The mixture was then sonicated at room temperature for 3 hours, followed by stirring at 70 °C for 6 hours. Subsequently, the acid solution adhering to the CNTs was thoroughly removed by filtration and washing several times with pure water, and the CNTs were dried in a vacuum oven at 80 °C for 24 hours to prepare CNTs with introduced carboxyl groups (-COOH).

[0276] 3g of the prepared first polymer and 27g of anhydrous dimethylacetamide (DMAc) were mixed in a reaction vessel, and the mixture was stirred and heated at 100°C for 6 hours under a nitrogen atmosphere to completely dissolve the first polymer in DMAc.

[0277] After cooling the reaction vessel to room temperature, 30 g of carboxylated CNTs were added, and the mixture was sonicated for 10 minutes, followed by stirring for 1 hour. Subsequently, the reaction vessel was heated, and the mixture was stirred at 90°C and reacted for 24 hours. After the reaction was complete, the solution in the reaction vessel was poured into 200 mL of ethanol solution to precipitate the reaction product, which was then filtered, washed, and dried to prepare a first composite conductive material with the first polymer bonded to the surface of the CNTs.

[0278] Preparation Example 3: Preparation of the Second Composite Conductive Material Two g of multi-walled carbon nanotubes (MWCNTs) with a diameter of approximately 1 nm and a length of approximately 25 μm were pretreated for 24 hours at 40 °C using 300 mL of 20 wt% nitric acid solution. One g of the pretreated CNTs was then immersed in 200 mL of a solution prepared by mixing concentrated sulfuric acid and concentrated nitric acid in a 3:1 (v / v%) ratio. The mixture was then sonicated at room temperature for 3 hours, followed by stirring at 70 °C for 6 hours. Subsequently, the acid solution adhering to the CNTs was thoroughly removed by filtration and washing several times with pure water, and the CNTs were dried in a vacuum oven at 80 °C for 24 hours to prepare CNTs with introduced carboxyl groups (-COOH).

[0279] Polyvinyl alcohol-polyacrylonitrile (PVA-PAN) copolymer was prepared as the second polymer.

[0280] 3g of the second polymer and 27g of anhydrous dimethylacetamide (DMAc) were mixed in a reaction vessel, and the mixture was stirred and heated at 100°C for 6 hours under a nitrogen atmosphere to completely dissolve the second polymer in DMAc.

[0281] After cooling the reaction vessel to room temperature, 30 g of carboxylated CNTs were added, and the mixture was sonicated for 10 minutes, followed by stirring for 1 hour. Subsequently, the reaction vessel was heated, and the mixture was stirred at 90°C and reacted for 24 hours. After the reaction was complete, the solution in the reaction vessel was poured into 200 mL of ethanol solution to precipitate the reaction product, which was then filtered, washed, and dried to prepare a second composite conductive material with the second polymer bonded to the surface of the CNTs.

[0282] Example 1: Manufacturing of the positive electrode The positive electrode active material and the prepared first composite conductive material are dispersed in N-methylpyrrolidone at a weight ratio of 100:1 to prepare the first active material slurry.

[0283] The prepared first active material slurry was coated onto an aluminum (Al) film with a thickness of about 15 μm, which serves as the positive electrode current collector, and dried to form an electrode active material layer with a thickness of about 60 μm.

[0284] Perform rolling to create a positive electrode on which an electrode active material layer is stacked on an aluminum current collector.

[0285] In Example 1, LiNiCoAlO2 is used as the positive electrode active material.

[0286] Example 2 The positive electrode is manufactured in the same manner as in Example 1, except that a second active material slurry is used instead of the first active material slurry.

[0287] Specifically, a second active material slurry is prepared by dispersing the positive electrode active material, the prepared first composite conductive material, and the binder in N-methylpyrrolidone at a weight ratio of 100:1:0.1.

[0288] In Example 2, LiNiCoAlO2 is used as the positive electrode active material and polyvinylidene fluoride (PVdF) is used as the binder.

[0289] Example 3 The positive electrode is manufactured in the same manner as in Example 1, except that a third active material slurry is used instead of the first active material slurry.

[0290] Specifically, a third active material slurry is prepared by dispersing the positive electrode active material, the prepared first composite conductive material, and the second composite conductive material in N-methylpyrrolidone at a weight ratio of 100:1:1.

[0291] Example 4 The positive electrode is manufactured in the same manner as in Example 3, except that when manufacturing the positive electrode, the positive electrode active material, the first composite conductive material, and the second composite conductive material are mixed in a weight ratio of 100:1.2:0.8 as the composition of the third active material slurry.

[0292] Example 5 The positive electrode is manufactured in the same manner as in Example 1, except that in the manufacture of the first composite conductive material, AA-AN-SB copolymer is used instead of AA-AN-SB-EG copolymer as the first polymer.

[0293] Specifically, the AA-AN-SB copolymer was prepared by the following method.

[0294] An azo compound initiator was mixed with water relative to 100 parts by weight of a third monomer mixture comprising 50 wt% acrylic acid (AA), 40 wt% acrylonitrile (AN), and 10 wt% sulfobetaine (SB). The initiator was used at 0.2 parts by weight relative to 100 parts by weight of the third monomer mixture. The resulting mixture was emulsion polymerized to prepare an AA-AN-SB copolymer having a first structural unit derived from acrylic acid, a second structural unit derived from acrylonitrile, and a third structural unit derived from sulfobetaine.

[0295] Comparison Example 1 The positive electrode is manufactured in the same manner as in Example 1, except that a fourth active material slurry is used instead of the first active material slurry.

[0296] Specifically, a fourth active material slurry is prepared by dispersing the positive electrode active material, conductive material, and binder in N-methylpyrrolidone at a weight ratio of 100:0.9:0.1.

[0297] In Comparative Example 1, LiNiCoAlO2 was used as the positive electrode active material, carbon nanotubes (CNTs) were used as the conductive material, and polyvinylidene fluoride (PVdF) was used as the binder.

[0298] Comparison Example 2 The positive electrode is manufactured in the same manner as in Example 1, except that a fifth active material slurry is used instead of the first active material slurry.

[0299] Specifically, a fifth active material slurry is prepared by dispersing the positive electrode active material and the prepared second composite conductive material in N-methylpyrrolidone at a weight ratio of 100:1.

[0300] Comparison Example 3 The positive electrode is manufactured in the same manner as in Example 3, except that when manufacturing the positive electrode, the positive electrode active material, the first composite conductive material, and the second composite conductive material are mixed in a weight ratio of 100:0.9:0.1 as the composition of the third active material slurry.

[0301] Compare Example 4 The positive electrode is manufactured in the same manner as in Example 3, except that when manufacturing the positive electrode, the positive electrode active material, the first composite conductive material, and the second composite conductive material are mixed in a weight ratio of 100:0.1:0.9 as a component of the third active material slurry.

[0302] The composition of the positive electrode according to the example and comparative examples is shown in Table 1 below.

[0303] Table 1:

[0304] Evaluation Example 1: Confirmation of the Structure of Composite Conductive Materials The first composite conductive material prepared in the example was imaged using a scanning electron microscope (SEM).

[0305] Figure 11 This is a SEM image of the first composite conductive material prepared in the example.

[0306] Reference Figure 11 When the first composite conductive material prepared in the example is observed by scanning electron microscopy (SEM), it can be seen that the first polymer is located within 500 nm of the surface of the carbon nanostructure.

[0307] Similarly, when the second composite conductive material prepared in the example was observed by scanning electron microscopy (SEM), the second polymer was located within 500 nm of the surface of the carbon nanostructure.

[0308] Evaluation Example 2: Evaluation of Adhesion and Ionic Conductivity The peel strength of the positive electrodes prepared in the example and comparative examples was measured according to the method of ASTM D3330. The instrument used for measurement was a UTM, Instron 3345.

[0309] Specifically, positive electrode plates with active material layers on both surfaces of the current collectors prepared in the example and comparative examples were cut into 25mm × 150mm sizes to prepare 20 samples for each. At room temperature, after applying an adhesive to a glass substrate, the positive electrode plates were attached to the adhesive, rolled, one end of the positive electrode plate was folded 180 degrees, and then pulled at a speed of 100mm / min in the opposite direction to one end while the applied force was measured. The evaluation results are shown in Table 2 below.

[0310] The surface resistance of the positive electrodes fabricated in the example and comparative examples was measured.

[0311] The surface resistivity was measured five times at room temperature (approximately 25°C) using a Laresta-GP (MCP-T600, MITSUBISHI CHEMICAL). The results are shown in Table 2 below.

[0312] Table 2:

[0313] As shown in Table 2, the peel strength of the example positive electrode is increased compared to the positive electrode of the comparative example. Therefore, the example positive electrode exhibits significantly improved adhesion between the positive electrode active material layer and the current collector compared to the positive electrode of the comparative example. In addition, the example electrode exhibits improved ionic conductivity at room temperature compared to the electrode of the comparative example.

[0314] Evaluation Example 3: Evaluation of Charge-Discharge Cycle Characteristics Manufacturing of rechargeable lithium batteries: A negative electrode active material was prepared by mixing 98 wt% of a graphite and Si composite at a weight ratio of 92:8, 1 wt% of styrene-butadiene rubber (SBR), and 1 wt% of carboxymethyl cellulose (CMC), then adding it to distilled water and stirring the mixture for 60 minutes using a mechanical stirrer. The slurry was then coated onto a copper current collector with a thickness of approximately 60 μm (10 μm) using a doctor blade, dried at 100°C for 0.5 hours in a hot air dryer, and then dried again at 120°C under vacuum for 4 hours. Finally, the mixture was rolled to fabricate the negative electrode.

[0315] Electrolytes were prepared by dissolving 1.15 M LiPF6 in a non-aqueous organic solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:40:40.

[0316] A positive electrode, a negative electrode, and a 16 μm thick polyethylene separator are assembled to manufacture an electrode assembly, and an electrolyte is injected into the electrode assembly to manufacture a rechargeable lithium battery.

[0317] For each of the rechargeable lithium-ion batteries manufactured in the example and comparative examples, the discharge capacity was measured to calculate the capacity retention rate after 300 charge-discharge cycles were performed at 25°C, under the conditions of 0.5C charging (CC / CV, 4.25V, 0.05C cutoff) / 0.5C discharging (CC, 2.8V cutoff). The results are shown in Table 3 below. The capacity retention rate was calculated according to Equation 1 below.

[0318] Formula 1: Capacity retention rate (%) = (Discharge capacity after 300 cycles / Initial discharge capacity) × 100.

[0319] Table 3:

[0320] Referring to Table 3, compared with the case corresponding to the electrode according to the comparative example, the capacity retention rate during charge-discharge cycles at room temperature is improved in the case corresponding to the electrode according to the example of this disclosure (Examples 1 to 5).

[0321] The electrode according to this disclosure can be applied to an electrode active material layer comprising a composite conductive material having desired or improved ionic conductivity, and can have the effect of improving the lifespan characteristics of a rechargeable lithium battery.

[0322] While this disclosure has been described with reference to exemplary embodiments, it should be understood that these exemplary embodiments are provided for illustrative purposes only and do not limit the scope of this disclosure. Various modifications and equivalent arrangements may be made without departing from the spirit and scope of the appended claims. Therefore, the described embodiments should be considered as examples and not as limitations on this disclosure.

Claims

1. An electrode for a rechargeable lithium battery, the electrode comprising: An electrode current collector; And An electrode active material layer on the electrode current collector, Wherein the electrode active material layer comprises an active material and a first composite conductive material, Wherein the first composite conductive material comprises a first carbon nanostructure and a first polymer chemically bonded to the surface of the first carbon nanostructure, Wherein the first polymer comprises: a first structural unit, derived from a (meth)acrylic monomer or its salt and represented by Chemical Formula 1-1A or Chemical Formula 1-1B; a second structural unit, derived from a (meth)acrylonitrile monomer and represented by Chemical Formula 1-2; and a third structural unit, derived from an amphoteric ion monomer and represented by Chemical Formula 1-3A or Chemical Formula 1-3B, Chemical Formula 1-1A: ； Chemical Formula 1-1B: ； Wherein, in Chemical Formula 1-1A and Chemical Formula 1-1B, R 1 They may be the same or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group. M1 comprises an alkali metal, Chemical Formula 1-2: ； Wherein, in Chemical Formula 1-2, R 2 Includes hydrogen atoms or C1 to C20 alkyl groups, Chemical Formula 1-3A: ； Chemical Formula 1-3B: ； Wherein, in Chemical Formula 1-3A and Chemical Formula 1-3B, R 3 They may be the same or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group. R 4 They may be the same or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group. L 1 Including *-(C=O)-NR 4 -CH2-* or *-(C=O)-O-*, and L 2 To L 4 Each independently includes a single bond or a C1 to C20 alkylene group.

2. The electrode according to claim 1, wherein, The first polymer further comprises a fourth structural unit, the fourth structural unit being derived from an alkylene glycol monomer or its salt and represented by Chemical Formula 1-4A or Chemical Formula 1-4B, Chemical Formula 1-4A: ； Chemical Formula 1-4B: ； Wherein, in Chemical Formula 1-4A and Chemical Formula 1-4B, M2 comprises an alkali metal, and n is an integer in the range of 1 to 100.

3. The electrode according to claim 1, wherein, The first carbon nanostructure comprises at least one of carbon nanotubes, carbon nanofibers, polyacetylene, graphene nanoribbons, graphene sheets, fullerenes, nanodiamonds, mesoporous carbon, amorphous carbon, carbon quantum dots, nanoporous carbon, carbon black, nanohorns, and glassy carbon.

4. The electrode according to claim 1, wherein, Relative to the total weight of the first composite conductive material, the amount of the first polymer is in the range of 40 wt% to 80 wt%, and Wherein the amount of the first composite conductive material in the electrode active material layer is in the range of 0.1 wt% to 5 wt%.

5. The electrode according to claim 1, wherein, The active material is represented by Chemical Formula 3, Chemical Formula 3: Li x4 M 1 y M 2 z M 3 1-y-z O 2-a X a Wherein, in Chemical Formula 3, 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 includes 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 comprises one or more of F, S, P, and Cl.

6. The electrode according to claim 1, wherein, The electrode active material layer further comprises a binder, and Wherein the binder comprises at least one of rubber-based binders, acrylate-based binders, polyvinylidene fluoride-based binders, polyvinylpyrrolidone-based binders, nitrile-based binders, acetate-based binders, polyvinyl alcohol-based binders, cellulose-based binders, and combinations thereof.

7. An electrode for a rechargeable lithium battery, the electrode comprising: An electrode current collector; And An electrode active material layer on the electrode current collector, Wherein the electrode active material layer comprises an active material, a first composite conductive material, and a second composite conductive material, Wherein the first composite conductive material comprises a first carbon nanostructure and a first polymer chemically bonded to the surface of the first carbon nanostructure, The second composite conductive material comprises a second carbon nanostructure and a second polymer chemically bonded to the surface of the second carbon nanostructure. Wherein, the first polymer and the second polymer are different from each other, and The ionic conductivity of the first polymer is greater than that of the second polymer.

8. The electrode according to claim 7, wherein, The glass transition temperature of the second polymer is lower than that of the first polymer.

9. The electrode according to claim 7, wherein, At least one of the first carbon nanostructure and the second carbon nanostructure includes at least one of carbon nanotubes, carbon nanofibers, polyacetylene, graphene nanoribbons, graphene sheets, fullerenes, nanodiamonds, mesoporous carbon, amorphous carbon, carbon quantum dots, nanoporous carbon, carbon black, nanohorns, and glassy carbon.

10. The electrode according to claim 7, wherein, The first polymer comprises: The first structural unit is derived from (meth)acrylic acid monomers or their salts and is represented by chemical formula 1-1A or chemical formula 1-1B; The second structural unit, derived from (meth)acrylonitrile monomers and represented by chemical formulas 1-2; and The third structural unit, derived from zwitterionic monomers, is represented by chemical formula 1-3A or chemical formula 1-3B. Chemical formula 1-1A: ； Chemical formula 1-1B: ； Among them, in chemical formulas 1-1A and 1-1B, R 1 They may be the same or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group. M1 includes alkali metals. Chemical formula 1-2: ； Among them, in chemical formulas 1-2, R 2 Includes hydrogen atoms or C1 to C20 alkyl groups, Chemical formula 1-3A: ； Chemical formula 1-3B: ； Among them, in chemical formulas 1-3A and 1-3B, R 3 They may be the same or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group. R 4 They may be the same or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group. L 1 Including *-(C=O)-NR 4 -CH2-* or *-(C=O)-O-*, and L 2 To L 4 Each independently includes a single bond or a C1 to C20 alkylene group.

11. The electrode according to claim 10, wherein, The first polymer further includes a fourth structural unit, which is derived from an alkylene glycol monomer or a salt thereof and is represented by chemical formula 1-4A or chemical formula 1-4B. Chemical formula 1-4A: ； Chemical formula 1-4B: ； Among them, in chemical formulas 1-4A and 1-4B, M2 includes alkali metals, and n is an integer in the range of 1 to 100.

12. The electrode according to claim 7, wherein, The second polymer includes at least one of polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, polyethylene, polyethylene glycol, polyimide, polyacrylamide, polystyrene, polyurethane, polyvinyl butyral, polyvinylpyrrolidone, and combinations thereof.

13. The electrode according to claim 7, wherein, The second polymer includes at least one of a fifth structural unit represented by chemical formula 2-1 and a sixth structural unit represented by chemical formula 2-2. Chemical formula 2-1: ； Chemical formula 2-2: ； In both chemical formulas 2-1 and 2-2, m and z are integers in the range of 1 to 100.

14. The electrode according to claim 7, wherein, The amount of the first polymer relative to the total weight of the first composite conductive material is in the range of 40 wt% to 80 wt%. The amount of the second polymer relative to the total weight of the second composite conductive material is in the range of 40 wt% to 80 wt%. Wherein, the amount of the first composite conductive material in the electrode active material layer is in the range of 0.1 wt% to 5 wt%, and The amount of the second composite conductive material in the electrode active material layer is in the range of 0.1 wt% to 5 wt%.

15. The electrode according to claim 7, wherein, The ratio of the first composite conductive material to the second composite conductive material in the electrode active material layer is in the range of 7:3 to 3:

7.

16. The electrode according to claim 7, wherein, The electrode active material layer is essentially free of binders.

17. A method for manufacturing an electrode for a rechargeable lithium battery, the method comprising the steps of: Provide electrode current collectors; as well as An electrode active material layer is formed on the electrode current collector. The electrode active material layer comprises an active material and a first composite conductive material, and The preparation of the first composite conductive material includes: introducing functional groups onto the surface of a first carbon nanostructure; and preparing a first mixture by mixing a first polymer and the first carbon nanostructure having the functional groups. The first polymer comprises at least one of the following: a first structural unit derived from a (meth)acrylic acid monomer or a salt thereof and represented by chemical formula 1-1A or chemical formula 1-1B; a second structural unit derived from a (meth)acrylonitrile monomer and represented by chemical formula 1-2; a third structural unit derived from a zwitterionic monomer and represented by chemical formula 1-3A or chemical formula 1-3B; and a fourth structural unit derived from an alkylene glycol monomer or a salt thereof and represented by chemical formula 1-4A or chemical formula 1-4B. Chemical formula 1-1A: ； Chemical formula 1-1B: ； Among them, in chemical formulas 1-1A and 1-1B, R 1 They may be the same or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group, and M1 includes alkali metals. Chemical formula 1-2: ； Among them, in chemical formulas 1-2, R 2 Includes hydrogen atoms or C1 to C20 alkyl groups, Chemical formula 1-3A: ； Chemical formula 1-3B: ； Among them, in chemical formulas 1-3A and 1-3B, R 3 They may be the same or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group. R 4 They may be the same or different, and each independently includes a hydrogen atom or a C1 to C20 alkyl group. L 1 Including *-(C=O)-NR 4 -CH2-* or *-(C=O)-O-*, and L 2 To L 4 Each independently includes a single bond or a C1 to C20 alkylene group. Chemical formula 1-4A: ； Chemical formula 1-4B: ； Among them, in chemical formulas 1-4A and 1-4B, M2 includes alkali metals, and n is an integer in the range of 1 to 100.

18. The method according to claim 17, wherein, The first composite conductive material comprises the first carbon nanostructure and the first polymer chemically bonded to the surface of the first carbon nanostructure.

19. The method of claim 17, further comprising adding a second composite conductive material to the electrode active material layer, and in, The preparation of the second composite conductive material includes: introducing functional groups into the surface of a second carbon nanostructure; and preparing a second mixture by mixing a second polymer and the second carbon nanostructure having the functional groups.

20. The method according to claim 19, wherein, The second composite conductive material comprises the second carbon nanostructure and the second polymer chemically bonded to the surface of the second carbon nanostructure, and The second polymer includes at least one of a fifth structural unit represented by chemical formula 2-1 and a sixth structural unit represented by chemical formula 2-2. Chemical formula 2-1: ； Chemical formula 2-2: ； In both chemical formulas 2-1 and 2-2, m and z are integers in the range of 1 to 100.

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