Negative electrode and rechargeable lithium battery including same

Abstract

A negative electrode and a rechargeable lithium battery including the same are provided. In an example embodiment, the negative electrode includes: a current collector; and a negative electrode active material layer on the current collector and including a negative electrode active material and a high ion conductive binder. The high ionic conductive binder comprises: a first structural unit derived from a (meth) acrylic monomer; a second structural unit derived from a C1 to C10 alkylene glycol monomer; and a third structural unit derived from a zwitterionic vinyl monomer or a zwitterionic (meth) acryloyl monomer. A thickness of the negative electrode active material layer is greater than or equal to about 40 [mu] m. The negative electrode according to some example embodiments may increase the energy density of the rechargeable lithium battery while reducing the volume and weight of the rechargeable lithium battery and contributing to improving fast charging performance.

Description

Technical Field

[0001] A negative electrode and a rechargeable lithium battery including the negative electrode are disclosed. Background Technology

[0002] With the increasing prevalence of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, the demand for small, lightweight, and relatively high-capacity rechargeable lithium batteries is growing. Specifically, due to their light weight and high energy density, rechargeable lithium batteries can be used as a power source for portable devices.

[0003] Rechargeable lithium-ion batteries typically include a positive electrode, a negative electrode, and an electrolyte. The positive and negative electrodes contain active materials capable of inserting and deintercalating lithium ions, generating electrical energy through oxidation and reduction reactions as lithium ions are inserted and deintercalated from the positive and negative electrodes. Improving the negative electrode's energy density, reducing its size and weight, and enhancing its fast-charging performance may be advantageous. Summary of the Invention

[0004] Some example embodiments include a negative electrode that increases the energy density of the rechargeable lithium battery, reduces the size and weight of the rechargeable lithium battery, and improves fast charging performance.

[0005] In some example embodiments, the negative electrode includes: a current collector; and a negative electrode active material layer located on the current collector, comprising the negative electrode active material and a highly ionicly conductive binder. The highly ionicly conductive binder comprises: a first structural unit derived from a (meth)acrylic acid monomer; a second structural unit derived from a C1 to C10 alkylene glycol monomer; and a third structural unit derived from a zwitterionic vinyl monomer or a zwitterionic (meth)acryloyl monomer. The thickness of the negative electrode active material layer is greater than or equal to about 40 μm.

[0006] Some example embodiments include a rechargeable lithium battery that includes a negative electrode, a positive electrode, and an electrolyte.

[0007] According to some example embodiments, the negative electrode can increase the energy density of a rechargeable lithium battery while reducing its size and weight and helping to improve fast charging performance. Attached Figure Description

[0008] Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Detailed Implementation

[0009] Hereinafter, exemplary embodiments of the present disclosure are described in detail. However, these embodiments are exemplary, and the present disclosure is not limited thereto, and is defined by the scope of the claims.

[0010] As used herein, unless otherwise specifically defined, it is understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, the element may be directly on said other element, or there may be an intervening element.

[0011] As used herein, the singular may also include the plural unless otherwise specifically defined. Furthermore, unless otherwise stated, “A or B” may mean “including A, including B, or including both A and B”.

[0012] As used herein, “combination of” can mean a mixture, stack, complex, copolymer, alloy, blend or reaction product of the components.

[0013] As used herein, unless otherwise defined, particle size can be the average particle size. This average particle size represents the average particle size (D50), which is the diameter of particles representing 50% of the cumulative volume in a particle size distribution. The average particle size (D50) can be measured by methods known to those skilled in the art, for example, by using a particle size analyzer, transmission electron microscope, or scanning electron microscope. Alternatively, a dynamic light scattering measurement device can be used for data analysis, and the number of particles can be counted for each particle size range. Thus, the average particle size (D50) value can be readily obtained by calculation. Laser diffraction methods can also be used. When measured by laser diffraction, for example, the particles to be measured are dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size measurement device (e.g., the MT3000 available from Microtrac), using ultrasound at approximately 28 kHz, and after irradiation with an output of 60 W, the average particle size (D50) based on 50% of the particle size distribution in the measurement device can be calculated.

[0014] As used herein, unless otherwise specifically defined, “alkyl” means C1 to C20 alkyl, “alken” means C2 to C20 alken, “cycloalken” means C3 to C20 cycloalken, “heterocyclic alken” means C3 to C20 heterocyclic alken, “aryl” means C6 to C20 aryl, “arylalkyl” means C6 to C20 arylalkyl, “alkylene” means C1 to C20 alkylene, “arylene” means C6 to C20 arylene, “alkylarylene” means C6 to C20 alkylarylene, “heteroarylene” means C3 to C20 heteroarylene, and “alkoxide” means C1 to C20 alkoxide.

[0015] As used herein, unless otherwise specifically defined, “substituted” means that at least one hydrogen atom is replaced by at least one substituent such as or including: halogen atom (F, Cl, Br or I), hydroxyl, C1 to C20 alkoxy, nitro, cyano, amino (or amino), imino, azide, amido, hydrazyl, hydrazine, carbonyl, carbamoyl, thiol, ester, ether, carboxyl or a salt thereof, sulfonic acid or a salt thereof, phosphate 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.

[0016] As used herein, unless otherwise specifically defined, “heterogeneous” means that the chemical formula contains at least one heteroatom of at least one of N, O, S and P.

[0017] Furthermore, as used herein, unless otherwise specifically defined, “(meth)acrylate” means both “acrylate” and “methacrylate”, and “(meth)acrylic acid” means both “acrylic acid” and “methacrylic acid”.

[0018] As used herein, unless otherwise specifically defined, “combination” means blend or copolymerization.

[0019] In the chemical formulas of this specification, when no other specific definition is provided, hydrogen is bonded at the position where a chemical bond is not drawn as it should be.

[0020] In this specification, the weight-average molecular weight (Mw) can be a value measured using gel permeation chromatography (GPC).

[0021] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical value include 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%.

[0022] negative electrode According to some example embodiments, the negative electrode includes: a current collector; and a negative electrode active material layer, located on the current collector and comprising the negative electrode active material and a highly ionicly conductive binder. The highly ionicly conductive binder comprises: a first structural unit derived from a (meth)acrylic acid monomer; a second structural unit derived from a C1 to C10 alkylene glycol monomer; and a third structural unit derived from a zwitterionic vinyl monomer or a zwitterionic (meth)acryloyl monomer. The thickness of the negative electrode active material layer is greater than or equal to about 40 μm. The negative electrode active material layer may also comprise a conductive material.

[0023] The negative electrode is designed as a thick-film electrode with a negative electrode active material layer of approximately 40 μm or greater to increase capacity and energy density while reducing the amount of current collector and separator, thus significantly reducing the volume and weight of the rechargeable lithium battery, which can improve price competitiveness. However, the thick-film negative electrode may present the challenge of slowing down the movement of lithium ions, thereby degrading fast-charging performance. However, this can be addressed by using a highly ionicly conductive binder comprising a first structural unit, a second structural unit, and a third structural unit, which can increase the movement of lithium ions, improve resistance, and thus enhance fast-charging performance, while also providing the desired bond strength.

[0024] The negative electrode active material layer can have a thickness of about 40 μm or greater, for example, in the range of about 40 μm to about 1000 μm, about 50 μm to about 800 μm, about 60 μm to about 700 μm, about 70 μm to about 600 μm, about 80 μm to about 500 μm, about 90 μm to about 400 μm, or about 100 μm to about 300 μm. When the thickness of the negative electrode active material layer is within the above range, the energy density can be increased, but the amount of current collector and separator can be reduced. This significantly reduces the volume and weight of the rechargeable lithium battery and improves price competitiveness. In addition, a highly ionic conductive binder, as described below, can be applied to improve fast charging performance.

[0025] Negative electrode active material The negative electrode active material may include at least one of the following: materials capable of reversibly inserting / deintercalating lithium ions, lithium metal, lithium metal alloys, materials capable of doping / dedoping lithium, and transition metal oxides.

[0026] Materials capable of reversibly inserting / deintercalating lithium ions can include, for example, crystalline carbon, amorphous carbon, or combinations thereof as carbon-based negative electrode active materials. Crystalline carbon can be irregular or sheet-like, flake-like, substantially spherical, or fibrous natural or artificial graphite. Amorphous carbon can be or includes at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0027] The lithium metal alloy includes an alloy of lithium and a metal (such as or including at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn).

[0028] The material capable of doping / dedoping lithium can be or include a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material can include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is or includes at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof), and combinations of at least one of them. The Sn-based negative electrode active material can be or include at least one of Sn, SnO2, Sn-based alloys, and combinations thereof.

[0029] The silicon-carbon composite can be or include a composite of silicon and amorphous carbon. According to some example embodiments, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which silicon primary particles are assembled and an amorphous carbon coating layer (shell) on the surface of the secondary particles. Amorphous carbon can also be present between the silicon primary particles. For example, the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0030] The silicon-carbon composite can also include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer on the surface of the core.

[0031] The Si-based negative electrode active material or the Sn-based negative electrode active material can be mixed with a carbon-based negative electrode active material.

[0032] adhesive The binder is configured to adhere the negative electrode active material particles to each other and to adhere the negative electrode active material to the current collector. The high ionic conductivity binder according to some example embodiments includes a first structural unit derived from a (meth)acrylic monomer, a second structural unit derived from a C1 to C10 alkylene glycol monomer, and a third structural unit derived from an zwitterionic vinyl monomer or an zwitterionic (meth)acryloyl monomer. The negative electrode active material layer can further include at least one of a non-aqueous binder, an aqueous binder, a dry binder, and combinations thereof in addition to the high ionic conductivity binder.

[0033] Binders containing only the first and second structural units can increase the adhesion strength of the active material layer to the current collector, but are insufficient to improve the resistance of the negative electrode active material layer. Furthermore, binders containing only the first and second structural units are insoluble in water and cannot form an active material layer, and also have too low a viscosity to form a negative electrode active material layer. Therefore, highly ionicly conductive binders that also include a third structural unit in addition to the first and second structural units can increase lithium-ion transport and provide the desired adhesion strength.

[0034] Based on a 100wt% negative electrode active material layer, the content of a highly ionicly conductive binder can range from about 0.2wt% to about 5.0wt%, for example, from about 0.3wt% to about 2.0wt%, from about 0.3wt% to about 1.0wt%, from about 0.3wt% to about 0.8wt%, or from about 0.4wt% to about 0.8wt%. When a highly ionicly conductive binder is included within the above range, not only can the energy density be increased, but the amount of current collector and separator can also be reduced to significantly reduce the volume and weight of the rechargeable lithium battery, thereby improving price competitiveness, and additionally improving fast-charging performance.

[0035] The structural units are described in detail below.

[0036] The first structural unit derived from (meth)acrylic acid monomers can be represented by chemical formula 1-1 or chemical formula 1-2: Chemical formula 1-1:

[0037] Chemical formula 1-2: .

[0038] In chemical formulas 1-1 and 1-2, R 1 They may be the same or different, and each may be or include hydrogen atoms or C1 to C20 alkyl groups independently, and M1 may be or include alkali metals.

[0039] For example, the first structural unit can be derived from acrylic acid, R 1 It can consist entirely of or include hydrogen atoms, and M1 can be derived from metal ions in an electrolyte solution, such as lithium ions.

[0040] In some example embodiments, based on 100 wt% of the first, second, and third structural units, the content of the first structural unit can range from about 50 wt% to about 98 wt%, about 60 wt% to about 90 wt%, or about 70 wt% to about 80 wt%. Within these ranges, the highly ionicly conductive binder has a desired viscosity, which is beneficial for the fabrication of the active material layer and improves adhesive strength.

[0041] The second structural unit derived from C1 to C10 alkylene glycol monomers can be represented by chemical formula 2-1 or chemical formula 2-2: Chemical formula 2-1:

[0042] Chemical formula 2-2: .

[0043] In chemical formulas 2-1 and 2-2, M2 can be or includes an alkali metal, and n can be an integer in the range of about 1 to about 100.

[0044] For example, the second structural unit can be derived from ethylene glycol, in which case n can be in the range of 5 to 20 or 5 to 10, and M2 can be derived from metal ions in the electrolyte solution, such as lithium ions.

[0045] In some example embodiments, based on 100 wt% of the first, second, and third structural units, the content of the second structural unit can range from about 1 wt% to about 25 wt%, about 5 wt% to about 20 wt%, or about 10 wt% to about 15 wt%. Within the above ranges, a highly ionicly conductive binder can help to further reduce resistance by improving ionic conductivity.

[0046] The third structural unit derived from zwitterionic vinyl monomers or zwitterionic (meth)acryloyl monomers has both cationic and anionic functional groups in the molecule, and may have at least one of vinyl and (meth)acrylic groups for polymerization with other structural units.

[0047] The cationic functional group may be or includes a functional group that exhibits a monovalent or polyvalent positive charge in an aqueous solvent, and may be or include, for example, substituted or unsubstituted ammonium cations (NH4+). + It may contain, but is not limited to, at least one of the following: imidazolium cation, pyrazolium cation, pyridinium cation, piperidinium cation, piperazineium cation, sulfide cation, naphthium cation, and guanidineium cation. For example, the cationic functional group may be or include substituted or unsubstituted ammonium cations or imidazolium cations.

[0048] The anionic functional group may be or includes a functional group that exhibits a monovalent or polyvalent negative charge in an aqueous solvent, and may be or include a functional group having at least one of sulfur (S), nitrogen (N), carbon (C), phosphorus (P), and oxygen (O). For example, the anionic functional group may be or includes -SO3. - -CO2 - -O - -and-NR - At least one of them. Here, R can be or include substituted or unsubstituted alkyl groups having 1 to 10 carbon atoms or haloalkyl groups having 1 to 10 carbon atoms.

[0049] The third structural unit derived from zwitterionic vinyl monomers or zwitterionic (meth)acryloyl monomers can be represented by chemical formula 3-1 or chemical formula 3-2: Chemical formula 3-1:

[0050] Chemical formula 3-2: .

[0051] In chemical formulas 3-1 and 3-2, R 2 They may be the same or different, and each may independently be or include hydrogen atoms or C1 to C20 alkyl groups; R 3 They may be the same or different, and each may independently be or include hydrogen atoms or C1 to C20 alkyl groups; L 1 It may include or can include -(C=O)-NR 3 -CH2- or -(C=O)-O- ;and L 2 To L 4 Each can be independently or include a single bond or a C1 to C20 alkylene group.

[0052] The third structural unit derived from zwitterionic vinyl monomers or zwitterionic (meth)acryloyl monomers may be derived from at least one of sulfobetaine monomers, phosphate betaine monomers, carboxybetaine monomers, and imidazoline monomers, for example, from sulfobetaine monomers or vinylimidazoline sulfonate monomers.

[0053] When the third structural unit can be derived from sulfobetaine (SB) and can be represented by chemical formula 3-1, R 2 It may include or contain methyl groups; L 1 They can be the same or different, and each can be or include the other independently. -(C=O)-NR 3-CH2- or -(C=O)-O- ;and L 2 and L 3 It can be all or include ethylene.

[0054] When the third structural unit is derived from vinylimidazolium sulfonate (IMS) and represented by chemical formula 3-2, R 2 It may include or contain hydrogen atoms; and L 4 It can be or includes butylene.

[0055] In some example embodiments, based on 100 wt% of the first, second, and third structural units, the content of the third structural unit can range from about 1 wt% to about 25 wt%, about 5 wt% to about 20 wt%, or about 10 wt% to about 15 wt%. Within these ranges, the adhesive strength of the active material layer to the current collector can be increased, and the resistance can be reduced.

[0056] The weight ratio of the second structural unit to the third structural unit in the highly ionic conductive adhesive can be in the range of about 1:2 to about 3:1, for example, about 1:1 to about 3:1, about 1:1 to about 2:1, or about 1:1 to about 1.5:1. When the second and third structural units are included in the above weight ratio, the highly ionic conductive adhesive can increase the adhesive strength of the active material layer to the current collector and also reduce the resistance.

[0057] In some example embodiments, the highly ionic conductive binder for rechargeable lithium batteries may also include a fourth structural unit derived from (meth)acrylamide monomers.

[0058] (Methacrylamide) monomers may include amide or nitrile groups. For example, the fourth structural unit may be derived from acrylonitrile.

[0059] The fourth structural unit derived from (meth)acrylyl monomers can be represented by the following chemical formula 4.

[0060] Chemical formula 4: .

[0061] In chemical formula 4, R 4 It may include or contain hydrogen atoms or C1 to C20 alkyl groups.

[0062] The fourth structural unit can be derived from, for example, acrylonitrile. For example, R 4 It can be or includes hydrogen atoms.

[0063] In some example embodiments, based on 100 wt% of the first, second, third, and fourth structural units, the content of the first structural unit can range from about 30 wt% to about 70 wt%, the content of the second structural unit can range from about 1 wt% to about 15 wt%, the content of the third structural unit can range from about 1 wt% to about 15 wt%, and the content of the fourth structural unit can range from about 20 wt% to about 50 wt%. For example, based on 100 wt% of the first, second, third, and fourth structural units, the content of the first structural unit can range from about 40 wt% to about 60 wt%, the content of the second structural unit can range from about 2 wt% to about 10 wt%, the content of the third structural unit can range from about 2 wt% to about 10 wt%, and the content of the fourth structural unit can range from about 25 wt% to about 45 wt%. As another example, the content of the first structural unit can range from about 45 wt% to about 55 wt%, the content of the second structural unit can range from about 5 wt% to about 10 wt%, the content of the third structural unit can range from about 5 wt% to about 10 wt%, and the content of the fourth structural unit can range from about 30 wt% to about 40 wt%. Within the above ranges, the highly ionic conductive adhesive has a desired viscosity, which is beneficial for the fabrication of the active material layer and improves the adhesive strength.

[0064] The highly ionic conductive binder according to some example embodiments may also include a lithium salt, in which case better lithium-ion conductivity can be achieved within the electrode, thereby improving the electrochemical performance of the battery. The highly ionic conductive binder may form chemical bonds such as ionic bonds with the cations and / or anions of the lithium salt, or the highly ionic conductive binder and the lithium salt may simply be mixed. The lithium salt may be or include any common lithium salt included in rechargeable lithium batteries without limitation, and may be or include at least one of, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, LiC4F9SO3, LiFSI, LiTFSI, LiOTf, LiDFOB, LiBOB, and combinations thereof.

[0065] In addition to the aforementioned highly ionic conductive binder, the negative electrode active material layer according to some example embodiments may also include at least one of a non-aqueous binder, an aqueous binder, a dry binder, and combinations thereof, and for example, may also include an aqueous binder.

[0066] 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.

[0067] 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, fluororubber, 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.

[0068] When an aqueous binder is included as the negative electrode binder, a cellulose compound capable of imparting viscosity may also be included. As a cellulose compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts may be mixed. The alkali metal may be or include at least one of Na, K, and Li.

[0069] Based on a 100wt% negative electrode active material layer, the content of the aqueous binder can range from about 0.1wt% to about 2.0wt%, for example, from about 0.2wt% to about 1.0wt%, from about 0.3wt% to about 1.0wt%, from about 0.3wt% to about 0.6wt%, or from about 0.4wt% to about 0.6wt%. Furthermore, based on the 100wt% negative electrode active material layer, the content of the cellulose compound can range from about 0.5wt% to about 2.0wt%, for example, from about 0.5wt% to about 1.5wt% or from about 1.0wt% to about 1.5wt%. When the aqueous binder and cellulose compound are included within the above ranges, not only can the energy density be increased, but the amount of current collector and separator can also be reduced, thereby significantly reducing the volume and weight of the rechargeable lithium battery, thus improving price competitiveness and fast-charging performance.

[0070] Methods for preparing highly ionic conductive adhesives The highly ionic conductive binder according to some example embodiments can be prepared by polymerizing a mixture of monomers using conventional methods known to those skilled in the art. The polymerization can be emulsion polymerization, suspension polymerization, solution polymerization, etc.

[0071] Emulsifiers may be or include at least one of the following: alkali metal salts of higher fatty acids, N-acryloyl amino acid salts, alkyl ether carbonates, acylated peptides, alkyl sulfonates, alkylbenzene sulfonates, alkyl amino acid salts, alkylnaphthalene sulfonates, sulfosuccinates, sulfonated oils, alkyl sulfates, alkyl ether sulfates, alkyl aryl ether sulfates, alkylamide sulfates, alkyl phosphates, alkyl ethoxy phosphates, and alkyl aryl ether phosphates, and combinations thereof. Examples of emulsifiers may be or include sodium dodecylbenzene sulfonate. Alkyl groups may be or include alkyl groups having about 1 to about 20 carbon atoms.

[0072] Based on the total content of 100 parts by weight of the monomer mixture, the emulsifier content can range from about 0.1 parts by weight to about 3 parts by weight or from about 0.1 parts by weight to about 2 parts by weight. When the emulsifier content is within the above range, the adhesive strength can be further improved, and a highly ionicly conductive adhesive with desired dimensions can be obtained for good dispersion.

[0073] The initiator may be or include an azo compound initiator, such as at least one of azobisisobutyronitrile, ammonium persulfate, potassium persulfate, hydrogen peroxide, tert-butyl hydroperoxide, and combinations thereof.

[0074] Based on the total content of 100 parts by weight of the monomer mixture, the content of the initiator can be in the range of about 0.1 parts by weight to about 3 parts by weight, or it can be about 0.1 parts by weight to about 2 parts by weight.

[0075] The weight-average molecular weight (Mw) of the highly ionic conductive binder can be in the range of about 20,000 g / mol to about 1,500,000 g / mol, for example, from about 50,000 g / mol to about 2,500,000 g / mol. Within the above range, the highly ionic conductive binder can be applied to the active material layer. Here, "weight-average molecular weight" can be a value calculated using gel permeation chromatography with polystyrene as the conversion base.

[0076] conductive materials The conductive material is included to provide electrode conductivity, and may include any electrically conductive material as the conductive material unless such electrically conductive material causes a chemical change. Examples of conductive materials include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metallic materials including at least one of metal powder or metal fiber of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0077] For example, the negative electrode active material layer may include about 90 wt% to about 99 wt% or about 90 wt% to about 99.5 wt% of negative electrode active material, about 0.5 wt% to about 5 wt% of binder, and about 0 wt% to about 5 wt% of conductive material.

[0078] The negative electrode current collector may include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof.

[0079] Rechargeable lithium batteries Based on their shape, rechargeable lithium batteries can be classified into cylindrical, prismatic, pouch-shaped, or coin-shaped batteries, etc. Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments, wherein, Figure 1 It is a cylindrical battery. Figure 2 It is a prismatic battery, and Figure 3 and Figure 4 It is a pouch battery. (See reference) Figures 1 to 4 The rechargeable lithium battery 100 includes an electrode assembly 40 and a housing 50 therein housing the electrode assembly 40. The electrode assembly 40 has a separator 30 disposed between a positive electrode 10 and a negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte solution (not shown). The rechargeable lithium battery 100 may include a sealing member 60 for sealing the housing 50, such as... Figure 1 As shown. Furthermore, in Figure 2 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 3 and Figure 4 As shown, the rechargeable lithium battery 100 includes Figure 4 The electrode connector 70 shown is or Figure 3 The positive electrode terminal 71 and negative electrode terminal 72 shown herein form an electrical path for guiding the current generated in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0080] A rechargeable lithium battery includes: a negative electrode; a positive electrode; and an electrolyte. Since the negative electrode has already been described above, its detailed explanation is omitted below.

[0081] positive electrode The positive electrode may include a current collector and a layer of positive electrode active material formed on the current collector. The layer of positive electrode active material includes a positive electrode active material and may also include a binder and / or a conductive material.

[0082] Based on a 100wt% positive electrode active material layer, the content of the positive electrode active material can be in the range of about 90wt% to about 99wt% or about 90wt% to about 99.5wt%, and based on the 100wt% positive electrode active material layer, the contents of the binder and the conductive material can be in the range of about 0.5wt% to about 5wt%, respectively.

[0083] The positive electrode active material can be or includes compounds capable of intercalating and deintercalating lithium (lithiation intercalation compounds). For example, it can include one or more types of composite oxides of lithium with metals (such as or including at least one of cobalt, manganese, nickel, and combinations thereof).

[0084] The composite oxide can be or includes lithium transition metal composite oxides, and examples of such composite oxides can include at least one of lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, and combinations thereof.

[0085] As an example, it may include compounds represented by any of the following chemical formulas. Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b- c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li aNiG b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4 (0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3 (0≤f≤2); and Li a FePO4 (0.90≤a≤1.8).

[0086] In the above chemical formula, A is or includes at least one of Ni, Co, Mn, and combinations thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is or includes at least one of O, F, S, P, and combinations thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; and L 1 It is or includes at least one of Mn, Al and combinations thereof.

[0087] The positive electrode active material may be or include at least one of the following: lithium nickel oxide represented by chemical formula 11, lithium cobalt oxide represented by chemical formula 12, lithium iron phosphate compound represented by chemical formula 13, cobalt-free lithium nickel manganese oxide represented by chemical formula 14, and combinations thereof.

[0088] Chemical Formula 11: Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 .

[0089] In chemical formula 11, 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.7, 0 ≤ z1 ≤ 0.7, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, M 1 and M 2Each is independently one or more of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more of F, P, and S.

[0090] In chemical formula 11, 0.6≤x1≤1, 0≤y1≤0.4, and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2.

[0091] Chemical formula 12: Li a2 Co x2 M 3 y2 O 2-b2 X b2 .

[0092] In chemical formula 12, 0.9 ≤ a² ≤ 1.8, 0.7 ≤ x² ≤ 1, 0 ≤ y² ≤ 0.3, 0.9 ≤ x² + y² ≤ 1.1, and 0 ≤ b² ≤ 0.1, M 3 X is or includes one or more of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0093] Chemical formula 13: Li a3 Fe x3 M 4 y3 PO 4-b3 X b3 .

[0094] In chemical formula 13, 0.9 ≤ a³ ≤ 1.8, 0.6 ≤ x³ ≤ 1, 0 ≤ y³ ≤ 0.4, and 0 ≤ b³ ≤ 0.1, M 4 X is or includes one or more of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0095] Chemical formula 14: Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4 .

[0096] In Chemical Formula 14, 0.9 ≤ a4 ≤ 1.8, 0.8 ≤ x4 < 1, 0 < y4 ≤ 0.2, 0 ≤ z4 ≤ 0.2, 0.9 ≤ x4 + y4 + z4 ≤ 1.1 and 0 ≤ b4 ≤ 0.1, M 5 is or includes one or more of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is or includes one or more of F, P, and S.

[0097] For example, the positive electrode active material may be or include a high-nickel type positive electrode active material. Based on 100 mol% of the metals other than lithium in the lithium transition metal composite oxide, the nickel content in the high-nickel type positive electrode active material is greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. The high-nickel type positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0098] The binder is configured to improve the bonding properties between the positive electrode active material particles and with the current collector. Examples of the binder may include at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate esterified styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon, but are not limited thereto.

[0099] A conductive material is included to provide electrode conductivity, and any electrically conductive material may be included as the conductive material, unless the electrically conductive material causes a chemical change in the battery. Examples of the conductive material may include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based materials including at least one of copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0100] The current collector may include Al, but is not limited thereto.

[0101] electrolyte The electrolyte for the rechargeable lithium battery may be or include, for example, an electrolyte solution, and the electrolyte solution may include a non-aqueous organic solvent and a lithium salt.

[0102] Non-aqueous organic solvents are configured as media for transporting ions that participate in the electrochemical reactions of a battery. Non-aqueous organic solvents may be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0103] 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). Esters may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, and caprolactone. 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. Additionally, ketone solvents may include cyclohexanone. Alcohol solvents may include at least one of ethanol and isopropanol. Aprotic solvents may include at least one of the following: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched or cyclic hydrocarbon group, and may include double bonds, aromatic rings or ether groups, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0104] Non-aqueous organic solvents may be included alone or in a mixture of two or more types of solvents, and when two or more types are included in the mixture, the mixing ratio can be adjusted as desired to achieve the desired battery performance, as is generally known to those skilled in the art.

[0105] 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.

[0106] Non-aqueous organic solvents may also include aromatic organic solvents. For example, carbonate solvents and aromatic organic solvents may be mixed and included in a volume ratio ranging from about 1:1 to about 30:1.

[0107] The electrolyte solution may also include at least one of vinyl ethyl carbonate, vinylene carbonate, and ethylene carbonate compounds to improve battery cycle life.

[0108] Examples of ethylene carbonate compounds may include at least one of fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0109] Lithium salts dissolved in organic solvents are configured to supply lithium ions in batteries to enable basic operation of rechargeable lithium batteries and improve lithium ion transport between the positive and negative electrodes. Examples of lithium salts may include 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 about 1 to about 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0110] The concentration of lithium salt can be in the range of about 0.1 M to about 2.0 M. When the concentration of lithium salt is within the above range, the electrolyte solution has the desired ionic conductivity and viscosity, thus achieving the desired or improved performance and allowing lithium ions to move efficiently.

[0111] diaphragm Depending on the type of rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, multilayer films of two or more layers thereof, and hybrid multilayer films (such as polyethylene / polypropylene double-layer separators, polyethylene / polypropylene / polyethylene triple-layer separators, polypropylene / polypropylene / polypropylene triple-layer separators, etc.).

[0112] The membrane may include a porous substrate and a coating layer on one or both surfaces of the porous substrate, comprising organic materials, inorganic materials or combinations thereof.

[0113] The porous substrate may be or include a polymer membrane, which is formed of any one of at least one of the following polymers or copolymers or mixtures of two or more of them, or includes or contains any one of the following polymers or copolymers or mixtures of two or more of them: polyolefins (such as polyethylene and polypropylene), polyesters (such as at least one of polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetheretherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and TEFLON (polytetrafluoroethylene).

[0114] The porous substrate can have a thickness in the range of about 1 μm to about 40 μm, for example, in the range of about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 10 μm to about 15 μm.

[0115] In one example, the organic material of the coating may include the aforementioned binder according to some example embodiments. That is, in some example embodiments, the separator for a rechargeable lithium battery includes a porous substrate and a coating on one or both surfaces of the porous substrate, wherein the coating includes the aforementioned binder. In the coating, the binder content, together with the inorganic material, can range from about 1 wt% to about 100 wt%, for example, the binder content can range from about 1 wt% to about 10 wt%, about 1 wt% to about 5 wt%, or about 80 wt% to about 100 wt%, about 90 wt% to about 100 wt%, or about 91 wt% to about 99 wt%, etc. The separator including the aforementioned binder in the coating can exhibit desired or improved heat resistance and mechanical strength.

[0116] Organic materials may include (meth)acrylic acid copolymers, which include a first structural unit and a second structural unit, wherein the first structural unit is derived from (meth)acrylamide, and the second structural unit includes at least one structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0117] Inorganic materials may include, but are not limited to, inorganic particles containing at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. 50It can be in the range of about 1 nm to about 2000 nm, for example, about 100 nm to about 1000 nm or about 100 nm to about 700 nm.

[0118] Organic and inorganic materials can be mixed in a coating layer, or a coating layer containing organic materials and a coating layer containing inorganic materials can be stacked together.

[0119] The thickness of the coating can be in the range of about 0.5 μm to about 20 μm, for example, about 1 μm to about 10 μm or about 1 μm to about 5 μm.

[0120] 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.

[0121] Preparation Example 1 Based on 100 parts by weight of water, approximately 2 parts by weight of a surfactant were mixed. Subsequently, 20 parts by weight of a monomer mixture comprising 50 wt% acrylic acid (AA), 35 wt% acrylonitrile (AN), 8 wt% sulfobetaine (SB), and 7 wt% ethylene glycol (EG) were mixed. The monomer mixture was then emulsion polymerized by mixing approximately 0.5 parts by weight of an azo compound initiator to prepare a highly ionicly conductive binder comprising a copolymer. Emulsion polymerization was carried out at approximately 75°C for 4 hours under conditions of pH 3 to 5.

[0122] Preparation Example 2 The highly ionic conductive adhesive was prepared in essentially the same manner as in Preparation Example 1, except that a monomer mixture comprising 55 wt% acrylic acid (AA) and 45 wt% acrylonitrile (AN) was used.

[0123] Preparation Example 3 The highly ionic conductive adhesive was prepared in essentially the same manner as in Preparation Example 1, except that a monomer mixture comprising 50 wt% acrylic acid (AA) and 50 wt% sulfobetaine (SB) was used.

[0124] Preparation Example 4 The highly ionic conductive adhesive was prepared in essentially the same manner as in Preparation Example 1, except that a monomer mixture comprising 45 wt% acrylic acid (AA), 40 wt% acrylonitrile (AN), and 15 wt% sulfobetaine (SB) was used.

[0125] Preparation Example 5 The highly ionic conductive adhesive was prepared in essentially the same manner as in Preparation Example 1, except that a monomer mixture comprising 45 wt% acrylic acid (AA), 40 wt% acrylonitrile (AN), and 15 wt% ethylene glycol (EG) was used.

[0126] Example 1 (1) Manufacturing of the negative electrode A negative electrode active material slurry was prepared by mixing 93.9 wt% graphite negative electrode active material, 4 wt% silicon-carbon composite negative electrode active material, 0.5 wt% of the high ionic conductive binder from Preparation Example 1, 0.5 wt% carboxymethyl cellulose (CMC), 1.0 wt% styrene-butadiene rubber (SBR), and 0.1 wt% conductive material in an aqueous solvent. The negative electrode active material slurry was coated onto a copper foil current collector, then dried and pressed to fabricate a negative electrode with a negative electrode active material layer of 150 μm thickness. The thickness of the negative electrode active material layer was measured by taking a scanning electron microscope image of the cross-section of the final negative electrode obtained by pressing.

[0127] (2) Manufacturing of the positive electrode 97.0wt% LiNi 0.88 Co 0.105 Al 0.015 O2 positive electrode active material, 1.5 wt% polyvinylidene fluoride binder and 1.5 wt% carbon nanotube conductive material are mixed to prepare a positive electrode active material layer slurry, which is then coated onto an aluminum foil current collector, dried and pressed to manufacture the positive electrode.

[0128] (3) Preparation of electrolyte solution The electrolyte solution was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 2:4:4 to prepare an organic solvent, and then dissolving the lithium salt of LiPF6 in the organic solvent at a concentration of 1.15 M.

[0129] (4) Manufacturing of rechargeable lithium battery cells A positive electrode and a negative electrode are assembled with a polyethylene separator coated with an acrylamide functional layer to obtain an electrode assembly, and an electrolyte solution is injected therein after the electrode assembly is housed in a prismatic housing to manufacture a rechargeable lithium battery cell.

[0130] Example 2 The negative electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that 93.9 wt% of graphite negative electrode active material, 4 wt% of silicon-carbon composite negative electrode active material, 0.7 wt% of the high ion conductive binder of Example 1, 0.3 wt% of carboxymethyl cellulose (CMC), 1.0 wt% of styrene-butadiene rubber (SBR) and 0.1 wt% of conductive material were mixed in an aqueous solvent to prepare the negative electrode active material layer slurry.

[0131] Example 3 The negative electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that 93.4 wt% of graphite negative electrode active material, 4 wt% of silicon-carbon composite negative electrode active material, 0.5 wt% of the high ion conductive binder of Example 1, 0.5 wt% of carboxymethyl cellulose (CMC), 1.5 wt% of styrene-butadiene rubber (SBR) and 0.1 wt% of conductive material were mixed in an aqueous solvent to prepare the negative electrode active material layer slurry.

[0132] Example 4 The negative electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that 93.9 wt% of graphite negative electrode active material, 4 wt% of silicon-carbon composite negative electrode active material, 0.3 wt% of the high ion conductive binder of Example 1, 0.7 wt% of carboxymethyl cellulose (CMC), 1.0 wt% of styrene-butadiene rubber (SBR) and 0.1 wt% of conductive material were mixed in an aqueous solvent to prepare the negative electrode active material layer slurry.

[0133] Example 5 The negative electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that 93.7 wt% of graphite negative electrode active material, 4 wt% of silicon-carbon composite negative electrode active material, 1.0 wt% of the high ionic conductive binder of Example 1, 0.2 wt% of carboxymethyl cellulose (CMC), 1.0 wt% of styrene-butadiene rubber (SBR) and 0.1 wt% of conductive material were mixed in an aqueous solvent to prepare the negative electrode active material layer slurry.

[0134] Comparison Example 1 The negative electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that the contents of the high ionic conductive binder, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in the negative electrode were varied as shown in Table 1.

[0135] Comparison Examples 2 to 5 The negative electrode and the rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that the binder used in Preparation Example 2 was used in Comparative Example 2, the binder used in Preparation Example 3 was used in Comparative Example 3, the binder used in Preparation Example 4 was used in Comparative Example 4, and the binder used in Preparation Example 5 was used instead of the highly ion-conductive binder used in Preparation Example 1 in Comparative Example 5.

[0136] Refer to Example 1 The negative electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that 93.4 wt% of graphite negative electrode active material, 4 wt% of silicon-carbon composite negative electrode active material, 0.1 wt% of the high ionic conductive binder of Example 1, 0.9 wt% of carboxymethyl cellulose (CMC), 1.5 wt% of styrene-butadiene rubber (SBR), and 0.1 wt% of conductive material were mixed in an aqueous solvent to prepare the negative electrode active material layer slurry.

[0137] Table 1 shows the adhesive design details for the example and comparative examples.

[0138] Evaluation Example 1: Electrode Plate Adhesion Strength The adhesive strength between the current collector and the active material layer of the negative electrode was measured using a Universal Testing Machine (UTM) tensile strength tester, according to the example and comparative examples. Samples were prepared by attaching a glass slide (length × width = 7 cm × 2.5 cm) to one side of double-sided adhesive tape (length × width = 4 cm × 2.5 cm) and each of the negative electrodes (length × width = 7 cm × 2.5 cm) to the other side of the double-sided adhesive tape. The samples were mounted on the UTM tensile strength tester, and the adhesive strength was measured by peeling the negative electrode from the glass slide at a peel angle of 180°, a peel temperature of 25°C, and a peel speed of 100 mm / min. The results are shown in Table 2.

[0139] Evaluation Example 2: Evaluation of Battery Cell Characteristics 1. Charging rate The battery cells were evaluated by charging each binder of the example and comparative examples to a cutoff voltage of 4.25V at a constant current of 1.0C at 25°C. In the corresponding charging method, the percentage (%) of "maximum charging capacity / total battery capacity" was calculated using the maximum charging capacity of the battery cell when it reached 4.25V, which is shown as the charging rate in Table 1.

[0140] 2. DC internal resistance (DC-IR; DC internal resistance) Battery cells with a single cell capacity of 75 mAh, manufactured using the binders of the example and comparative examples, were charged at a constant current / constant voltage under conditions of 0.2C, 4.25V, and 0.05C cutoff, paused for 10 minutes, discharged at a constant current of 0.33C under conditions of 2.80V cutoff, and paused for 10 minutes at 25°C for the first charge and discharge cycle. Then, at SOC50 (based on the state where 100% of the total charge capacity is charged to 50% of the charge capacity, which also represents the state where it is discharged to 50% during discharge), the voltage drop (V) that occurs when a 1C current passes through for 10 seconds was measured. This voltage drop was then used to measure the DC internal resistance (DC-IR), and the results are shown in Table 1.

[0141] 3.200-cycle life retention rate The battery cells of the example and comparative examples were charged to 4.2V at a constant current rate of 0.5C, and then cut off at a constant voltage mode at 0.025C at 25°C. Subsequently, the battery cells were discharged to 2.5V at a rate of 0.5C, and this charge and discharge cycle was repeated 200 times to evaluate the capacity retention, i.e., cycle life characteristics, based on the number of cycles. The results are shown in Table 1 below.

[0142] Table 1:

[0143] Referring to Table 1, compared to Comparative Example 1 (which does not include a highly ionic conductive binder) and Comparative Examples 2 to 5 (which do not include at least one of the structural units), all examples including a highly ionic conductive binder comprising all of the first to third structural units in the negative electrode active material layer with a thickness of 40 μm or greater exhibit improved electrode plate adhesion strength and battery characteristics. Furthermore, compared to Comparative Example 1 (which does not include a highly ionic conductive binder), Reference Example 1, which includes all of the first to third structural units in the negative electrode active material layer with a thickness of 40 μm or greater, exhibits improved electrode plate adhesion strength and battery characteristics; the electrode plate adhesion strength and battery characteristics of Reference Example 1 are inferior to those of the examples.

[0144] While examples of this disclosure have been described in conjunction with what are now considered to be practical exemplary embodiments, it will be understood that the disclosure is not limited to the disclosed exemplary embodiments. Rather, the disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0145] Symbol Explanation 100: Rechargeable lithium battery; 10: Positive electrode 11: Positive electrode lead connector; 12: Positive electrode terminal 20: Negative electrode; 21: Negative electrode lead connector 22: Negative electrode terminal; 30: Diaphragm 40: Electrode assembly; 50: Housing 60: Sealing component; 70: Electrode terminal piece 71: Positive electrode connector; 72: Negative electrode connector.

Claims

1. A negative electrode, the negative electrode comprising: current collector; as well as A negative electrode active material layer is located on the current collector and includes a negative electrode active material and a highly ionic conductive binder; The highly ionic conductive adhesive comprises: a first structural unit derived from (meth)acrylic acid monomers; a second structural unit derived from C1 to C10 alkylene glycol monomers; and a third structural unit derived from zwitterionic vinyl monomers or zwitterionic (meth)acryloyl monomers. The thickness of the active material layer of the negative electrode is greater than or equal to 40 μm.

2. The negative electrode according to claim 1, wherein, The thickness of the negative electrode active material layer is in the range of 40 μm to 1000 μm.

3. The negative electrode according to claim 1, wherein, The thickness of the negative electrode active material layer is in the range of 100 μm to 300 μm.

4. The negative electrode according to claim 1, wherein, The negative electrode active material includes at least one of carbon-based negative electrode active materials and silicon-based negative electrode active materials.

5. The negative electrode according to claim 1, wherein, Based on the 100wt% negative electrode active material layer, the content of the highly ionic conductive binder is in the range of 0.2wt% to 5.0wt%.

6. The negative electrode according to claim 1, wherein, Based on the 100wt% negative electrode active material layer, the content of the highly ionic conductive binder is in the range of 0.4wt% to 0.8wt%.

7. The negative electrode according to claim 1, wherein, The first structural unit is represented by chemical formula 1-1 or chemical formula 1-2, and The second structural unit is represented by chemical formula 2-1 or chemical formula 2-2: Chemical formula 1-1: Chemical formula 1-2: In chemical formulas 1-1 and 1-2: R 1 They may be the same or different, and each independently comprises a hydrogen atom and one of C1 to C20 alkyl groups; and M1 includes alkali metals. Chemical formula 2-1: Chemical formula 2-2: Specifically, in chemical formulas 2-1 and 2-2: M2 includes alkali metals, and n is an integer between 1 and 100.

8. The negative electrode according to claim 1, wherein, The zwitterionic vinyl monomer or the zwitterionic (meth)acryloyl monomer includes at least one cationic functional group, wherein the at least one cationic functional group includes at least one of substituted or unsubstituted ammonium cations, imidazolium cations, pyrazolium cations, pyridinium cations, piperidinium cations, piperazineium cations, sulfide cations, naphthium cations, and guanidinium cations.

9. The negative electrode according to claim 1, wherein, The zwitterionic vinyl monomer or the zwitterionic (meth)acryloyl monomer includes at least one anionic functional group, and the at least one anionic functional group includes -SO3. - -CO2 - -O - -and-NR - At least one of them, Wherein, R includes substituted or unsubstituted C1 to C10 alkyl or C1 to C10 haloalkyl.

10. The negative electrode according to claim 1, wherein, The zwitterionic vinyl monomers or the zwitterionic (meth)acryloyl monomers include at least one of sulfobetaine monomers, phosphate betaine monomers, carboxybetaine monomers, and imidazoline monomers.

11. The negative electrode according to claim 1, wherein, The third structural unit is represented by one of chemical formulas 3-1 and 3-2: Chemical formula 3-1: Chemical formula 3-2: Specifically, in chemical formulas 3-1 and 3-2: R 2 They may be the same or different, and each independently comprises a hydrogen atom and one of C1 to C20 alkyl groups. R 3 They may be the same or different, and each independently comprises a hydrogen atom and one of C1 to C20 alkyl groups. L 1 include -(C=O)-NR 3 -CH2- and -(C=O)-O- One of them, and L 2 To L 4 Each independently comprises a single bond and one of C1 to C20 alkylene groups.

12. The negative electrode according to claim 1, wherein, Based on 100wt% of the first structural unit, the second structural unit, and the third structural unit: The content of the first structural unit is in the range of 50wt% to 98wt%. The content of the second structural unit is in the range of 1 wt% to 25 wt%, and The content of the third structural unit is in the range of 1 wt% to 25 wt%.

13. The negative electrode according to claim 1, wherein, The highly ionic conductive binder also includes a fourth structural unit derived from (meth)acrylyl monomers.

14. The negative electrode according to claim 13, wherein, The (meth)acrylamide monomers include one of an amide group and a nitrile group.

15. The negative electrode according to claim 13, wherein, The fourth structural unit is represented by chemical formula 4: Chemical formula 4: In chemical formula 4, R 4 It includes hydrogen atoms and one of C1 to C20 alkyl groups.

16. The negative electrode according to claim 13, wherein, Based on 100wt% of the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit: The content of the first structural unit is in the range of 30wt% to 70wt%. The content of the second structural unit is in the range of 1 wt% to 15 wt%. The content of the third structural unit is in the range of 1 wt% to 15 wt%, and The content of the fourth structural unit is in the range of 20wt% to 50wt%.

17. The negative electrode according to claim 1, wherein, The highly ionic conductive binder also includes lithium salts.

18. The negative electrode according to claim 1, wherein, In addition to the highly ionic conductive binder, the negative electrode active material layer also includes an aqueous binder.

19. The negative electrode according to claim 18, wherein, The negative electrode active material layer also includes cellulose compounds.

20. A rechargeable lithium battery, said rechargeable lithium battery comprising: The negative electrode according to any one of claims 1 to 19; Positive electrode; as well as Electrolyte.

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