Negative electrode for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

A negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same are provided. The negative electrode includes: a negative electrode current collector; and a negative electrode active material layer on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a conductive material, a binder, and an additive.

Description

[0001] This patent application claims priority to Korean Patent Application No. 10-2024-0158040, filed on November 8, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode. Background Technology

[0003] The increasing prevalence of battery-powered electronic devices (such as mobile phones, laptops, and electric vehicles) has driven a growing demand for rechargeable lithium-ion batteries that exhibit high energy density and capacity. Therefore, improving the performance of rechargeable lithium-ion batteries can be beneficial.

[0004] A rechargeable lithium battery includes a positive electrode and a negative electrode, both of which include active materials for inserting and deintercalating lithium ions and an electrolyte. The rechargeable lithium battery generates electrical energy through redox reactions that occur as lithium ions are inserted into the positive electrode and deintercalated from the negative electrode or vice versa. Summary of the Invention

[0005] This disclosure describes a negative electrode for a rechargeable lithium battery that exhibits improved adhesion strength between the negative electrode active material layer and the negative electrode current collector.

[0006] This disclosure also describes rechargeable lithium batteries that exhibit improved heat resistance and safety.

[0007] Example embodiments of this disclosure include a negative electrode for a rechargeable lithium battery, the negative electrode comprising: a negative electrode current collector; and a negative electrode active material layer on the negative electrode current collector. The negative electrode active material layer comprises: a negative electrode active material; a binder; a conductive material; and an additive represented by Formula 1 or Formula 2 below.

[0008] [Formula 1]

[0009] In Formula 1 above, R1 to R6 are each independently a hydrogen atom or a substituted or unsubstituted C1 to C10 alkyl group.

[0010] [Equation 2]

[0011] In Equation 2 above, R7 to R 14 Each is independently a hydrogen atom or a substituted or unsubstituted C1 to C10 alkyl group.

[0012] In an exemplary embodiment of this disclosure, the rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte. The negative electrode is the negative electrode described above for a rechargeable lithium battery. Attached Figure Description

[0013] The accompanying drawings are included to provide a further understanding of this disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the disclosure. In the drawings: Figure 1 This is a simplified conceptual diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure; Figure 2 This is a cross-sectional view used to describe an exemplary embodiment of the negative electrode plate according to the present disclosure; and Figures 3 to 6 This is a schematic diagram illustrating a rechargeable lithium battery according to an exemplary embodiment of the present disclosure. Figure 3 A cylindrical battery is shown. Figure 4 A prism-shaped battery is shown, and Figure 5 and Figure 6 A pouch-type battery is shown. Detailed Implementation

[0014] To fully understand the structure and effects of this disclosure, exemplary embodiments of the disclosure have been described with reference to the accompanying drawings. However, it should be noted that this disclosure is not limited to the following embodiments and can be implemented in various forms and with various modifications. The exemplary embodiments provided herein are intended to make this disclosure thorough and complete, and to fully convey the scope of this disclosure to those skilled in the art.

[0015] It is understood here that when a component is referred to as being "on" another component, the component may be directly on the other component, or an intermediate third component may be present therein. Additionally, in the accompanying drawings, the thickness of components may be exaggerated for the purpose of effectively describing the technical content. The same reference numerals always denote the same elements.

[0016] The exemplary embodiments described herein are explained with reference to sectional views and / or plan views, which serve as ideal example views of this disclosure. In the drawings, the thickness of the membranes and regions may be exaggerated for the purpose of effectively describing the technical content. Therefore, the regions presented as examples in the drawings have general properties, and the shapes of the illustrated regions are used to illustrate the specific shapes of the device regions. Therefore, this should not be construed as limiting the scope of this disclosure. Although terms such as first, second, and third are used to describe various components in the various exemplary embodiments herein, the components should not be limited to these terms. These terms are used only to distinguish one component from another. The embodiments described and illustrated herein include complementary embodiments thereof.

[0017] The terminology used herein is not intended to limit this disclosure, but rather to describe exemplary embodiments. As used herein, the singular form includes the plural form as well, unless the context clearly indicates otherwise. The meaning of “comprising” and / or “including” as used herein does not exclude the presence or addition of one or more other components besides those mentioned.

[0018] As used herein, the term "combination thereof" may refer to mixtures, stacks, complexes, copolymers, alloys, blends, or reaction products.

[0019] Unless otherwise defined herein, particle size may refer to average particle size. Furthermore, particle size is defined as average particle size (D50), which refers to the diameter of particles representing approximately 50% by volume of the cumulative volume in a particle size distribution. Average particle size (D50) can be measured by methods widely known to those skilled in the art, for example, by a particle size analyzer, images from a transmission electron microscope (TEM), or images from a scanning electron microscope (SEM). Alternatively, average particle size (D50) can be measured, for example, using a measuring device employing dynamic light scattering, wherein data analysis is performed to count the number of particles for each particle size range, and the average particle size (D50) value can then be calculated. Alternatively, laser diffraction methods can be used to measure average particle size (D50). When using laser diffraction methods for measurement, for example, the target particles are dispersed in a dispersion medium and introduced into a commercially available laser diffraction particle size measuring device (e.g., the MT 3000 purchased from Macchico Ltd.), irradiated with ultrasound at approximately 28 kHz and a power of 60 W, and then the average particle size (D50) based on a 50% volume percentage particle size distribution in the measuring device can be calculated.

[0020] When the terms “about” or “basic” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical values ​​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%.

[0021] 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.

[0022] 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.

[0023] The electrolyte ELL can be or includes a medium for transferring 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.

[0024] Positive electrode 10 The positive electrode 10 for a rechargeable lithium battery may include a positive electrode current collector COL1 and a positive electrode active material layer AML1 on the positive electrode current collector COL1. The positive electrode active material layer AML1 may include a positive electrode active material and may also include a binder and / or a conductive material.

[0025] For example, the positive electrode 10 may also include additives that constitute the sacrificial positive electrode.

[0026] Relative to 100 wt% of the positive electrode active material layer AML1, the positive electrode active material layer AML1 may contain approximately 90 wt% to approximately 99.5 wt% of the positive electrode active material. Relative to 100 wt% of the positive electrode active material layer AML1, the binder and conductive material may each be in an amount ranging from approximately 0.5 wt% to approximately 5 wt%.

[0027] The binder can adhere the positive electrode active material particles to each other and to the positive electrode current collector COL1. Typical examples of binders may be or include 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 the exemplary embodiments of this disclosure are not limited thereto.

[0028] Conductive materials can impart conductivity to electrodes. Any material that does not cause undesirable chemical changes and is an electronically conductive material can be used in a battery. Examples of 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 at least one of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0029] Al can be used as the positive electrode current collector COL1, but the exemplary embodiments disclosed herein are not limited thereto.

[0030] Positive electrode active material Compounds capable of reversibly inserting and deintercalating lithium (lithiation intercalation compounds) can be used as positive electrode active materials in the positive electrode active material layer AML1. For example, at least one of lithium and a composite oxide of a metal such as or including at least one of cobalt, manganese, nickel, aluminum, and combinations thereof can be used.

[0031] The composite oxide can be or includes lithium transition metal composite oxides, and examples 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.

[0032] For example, the positive electrode active material can be or includes a high-nickel positive electrode active material, which has a nickel content in the range of about 80 mol% or more, about 85 mol% or more, about 90 mol% or more, about 91 mol% or more, or about 94 mol% or more, relative to 100 mol% of metals other than lithium from lithium transition metal complex oxides. High-nickel positive electrode active materials can exhibit high capacity and therefore can be used in high-capacity, high-density rechargeable lithium batteries.

[0033] Diaphragm 30 Depending on the type of rechargeable lithium battery, the separator 30 may be present between the positive electrode 10 and the negative electrode 20. The separator 30 may include at least one of the following: polyethylene, polypropylene, polyvinylidene fluoride, and multilayer films of two or more layers thereof, such as mixed multilayer films such as polyethylene / polypropylene bilayer separators, polyethylene / polypropylene / polyethylene trilayer separators, polypropylene / polyethylene / polypropylene trilayer separators, etc.

[0034] The diaphragm 30 may include a porous substrate and a coating on one or both surfaces of the porous substrate, comprising an organic material, an inorganic material, or a combination thereof.

[0035] The porous substrate may be or include a polymer membrane, which is formed or includes any one of the following polymers or copolymers or mixtures of two or more of them, wherein any polymer is or includes at least one of polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon and polytetrafluoroethylene, or copolymers or mixtures of two or more of them.

[0036] Organic materials may include polyvinylidene fluoride polymers or (meth)acrylic acid polymers.

[0037] 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 are not limited thereto.

[0038] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked together.

[0039] Electrolyte ELL Electrolytes (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0040] Non-aqueous organic solvents can serve as media for transporting ions that participate in the electrochemical reactions of a battery.

[0041] 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.

[0042] 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).

[0043] Ester solvents may include at least one of the following: methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propylene propionate, decanoic acid lactone, mevalonate lactone, valproic acid lactone, caprolactone, etc.

[0044] Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc. 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); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0045] Non-aqueous organic solvents can be used alone or in combination of two or more solvents.

[0046] 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.

[0047] Lithium salts dissolved in organic solvents supply lithium ions in batteries, enabling the operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Typical examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of the following: (SO2) (where x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0048] The negative electrode according to an exemplary embodiment of the present disclosure is described in detail below. Figure 2 This is a cross-sectional view showing a negative electrode (negative electrode plate) according to an exemplary embodiment of the present disclosure.

[0049] negative electrode 20 Reference Figure 1 and Figure 2 The negative electrode 20 for a rechargeable lithium battery according to an example embodiment of the present disclosure may include a negative electrode current collector COL2 and a negative electrode active material layer AML2 located on the negative electrode current collector COL2. The negative electrode active material layer AML2 may include a negative electrode active material, a binder, a conductive material, and an additive represented by Formula 1 as described below.

[0050] The negative electrode 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.

[0051] The binder enables the negative electrode active material particles to adhere to each other and to adhere the negative electrode active material to the negative electrode current collector COL2. The binder may include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0052] 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, or combinations thereof.

[0053] The waterborne adhesive may be or 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.

[0054] When an aqueous binder is included as a negative electrode binder, it may also include a cellulose compound capable of imparting viscosity. The cellulose compound may include at least one 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.

[0055] Dry adhesives can be or include fibrous polymeric materials. For example, dry adhesives can be or include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0056] Conductive materials can impart conductivity to electrodes. Any material that does not cause undesirable chemical changes and is an electronically conductive material can be used in a battery. Examples of 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 powders or metal fibers, including at least one of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0057] For example, the negative electrode active material layer may include about 90 wt% to about 99 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.

[0058] The conductive material, binder, and negative electrode active material can be provided in a weight ratio of 1:a:b, wherein "a" can range from about 1 to about 3, and "b" can range from about 90 to about 99.

[0059] Negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 may include at least one of a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and a transition metal oxide.

[0060] The material capable of reversibly intercalating / deintercalating lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon may be graphite, such as natural graphite or artificial graphite in the form of irregular, planar, flaky, spherical, or fibrous, and examples of amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0061] The lithium metal alloy includes an alloy of lithium and a metal, the metal being 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.

[0062] The material capable of doping / dedoping lithium may 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 may be or include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is such as 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 a combination thereof). The Sn-based negative electrode active material may be or include at least one of Sn, SnO2, a Sn-based alloy, and a combination thereof.

[0063] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to an exemplary embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. The amorphous carbon may also be 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.

[0064] 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 an amorphous carbon coating on the surface of the core.

[0065] The Si-based negative electrode active material or the Sn-based negative electrode active material may be used in combination with the carbon-based negative electrode active material.

[0066] additive The additive according to the present disclosure may be represented by Formula 1 or Formula 2 below.

[0067] Formula 1: .

[0068] In Formula 1 above, R1 to R6 can each be independently or include hydrogen atoms or substituted or unsubstituted C1 to C10 alkyl groups.

[0069] For example, in Formula 1 above, R1 to R6 may all be or include C1 to C10 alkyl groups independently. For example, in Formula 1 above, R1 to R6 may all be or include hydrogen atoms independently. For example, in Formula 1 above, at least one of R1 to R6 may be or include C1 to C10 alkyl groups, and at least one of R1 to R6 may be or include hydrogen atoms.

[0070] In an example embodiment, the additive may include 1,3,5-trioxane (TRX) represented by the following formula 1-1: Equation 1-1: .

[0071] In example embodiments, the additive may include at least one of the following compounds represented by Formulas 1-2, Formulas 1-3, Formulas 1-4, or any combination thereof: Equation 1-2: .

[0072] Equation 1-3: .

[0073] Equation 1-4: .

[0074] Formula 2: .

[0075] In Equation 2 above, R7 to R 14 Each can be independently composed of or include hydrogen atoms or substituted or unsubstituted C1 to C10 alkyl groups.

[0076] For example, in Equation 2 above, R7 to R 14 It can be entirely or independently composed of C1 to C10 alkyl groups. For example, in Formula 2 above, R7 to R... 14 It can be or include hydrogen atoms independently. For example, in Equation 2 above, R7 to R 14 At least one of them may be or include a C1 to C10 alkyl group, and R7 to R 14 At least one of them can be or includes a hydrogen atom.

[0077] In an example embodiment, the additive may include 1,4-dioxane represented by the following formula 2-1: Equation 2-1: .

[0078] In example embodiments, the additive may include compounds represented by Formula 2-2 below, compounds represented by Formula 2-3 below, compounds represented by Formula 2-4 below, or any combination thereof: Equation 2-2: .

[0079] Equation 2-3: .

[0080] Equation 2-4: .

[0081] The content of the additive relative to the total weight of the negative electrode active material can range from about 0.1 wt% to about 5 wt%, about 0.1 wt% to about 4 wt%, about 0.1 wt% to about 3 wt%, or about 0.2 wt% to about 2 wt%. For example, the content of the additive relative to the total weight of the negative electrode active material can range from 0.2 wt% to about 1 wt%.

[0082] When the amount of additive is less than the above range, a film may not be fully formed on the negative electrode. When the amount of additive is greater than the above range, the battery may have reduced capacity and reduced lifespan due to increased resistance of the negative electrode film caused by excessive decomposition reaction.

[0083] In example embodiments, the additive may include dioxane or trioxane. A film made of dioxane or trioxane can be formed on a solid electrolyte interphase (SEI) layer containing LiF to form an organic-inorganic composite film. The organic-inorganic composite film enables the negative electrode to exhibit improved interfacial stability and lifetime characteristics at high temperatures in rechargeable lithium batteries. Therefore, the additive forms an electrochemically stable film on the surface of the negative electrode through a ring-opening reaction, thereby reducing or suppressing dendrite formation. Here, "ring-opening reaction" refers to a reaction in which the rings in a cyclic compound break to form a chain compound.

[0084] When the negative electrode active material layer AML2 includes additives, the negative electrode active material layer AML2 can exhibit improved adhesion strength between the negative electrode active material layer AML2 and the negative electrode current collector COL2, and can enable the rechargeable lithium battery to exhibit improved stability and battery life characteristics. For example, the adhesion strength between the negative electrode current collector COL2 and the negative electrode active material layer AML2 can be in the range of about 0.2 gf / mm to about 0.4 gf / mm.

[0085] Rechargeable lithium batteries Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch-shaped, or coin-shaped batteries. Figures 3 to 6 This is a schematic diagram illustrating a rechargeable lithium battery according to an exemplary embodiment of the present disclosure. Figure 3 A cylindrical battery is shown. Figure 4 A prism-shaped battery is shown, and Figure 5 and Figure 6 A pouch-type battery is shown.

[0086] Reference Figures 3 to 5 The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20, and is housed within the housing 50. The positive electrode 10, negative electrode 20, and separator 30 may be impregnated with an electrolyte (not shown). Figure 3 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. Additionally, in Figure 4 In this context, 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. For example... Figure 5 and Figure 6 As shown, the rechargeable lithium battery 100 may include Figure 6 The electrode terminal 70 shown, or for example Figure 5 The positive electrode terminal 71 and negative electrode terminal 72 shown in the figure form an electrical path for guiding the current formed in the electrode assembly 40 to the outside of the battery 100.

[0087] As a non-limiting example, the rechargeable lithium battery according to exemplary embodiments of this disclosure can be applied to, for example, automobiles, mobile phones and / or various types of electrical devices.

[0088] A rechargeable lithium battery according to an example embodiment of this disclosure may include a positive electrode, the negative electrode described above, and an electrolyte.

[0089] The positive electrode may include a positive electrode active material, and the positive electrode active material may include a lithium composite oxide represented by the following Formula 3.

[0090] Formula 3: Li x M 1 y M 2 z M 3 1-y-z O 2-a X a .

[0091] x, a, y, and z may satisfy 0.5 ≤ x ≤ 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 of nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), boron (B), barium (Ba), calcium (Ca), cerium (Ce), chromium (Cr), iron (Fe), molybdenum (Mo), niobium (Nb), silicon (Si), strontium (Sr), magnesium (Mg), titanium (Ti), vanadium (V), tungsten (W), zirconium (Zr), and lanthanum (La) and combinations thereof.

[0092] X may include at least one of fluorine (F), sulfur (S), phosphorus (P), and chlorine (Cl).

[0093] For example, the positive electrode active material may include lithium cobalt oxide (LiCoO2).

[0094] Hereinafter, examples of the present disclosure will be described in more detail by way of example. However, the examples are merely illustrative of the present disclosure, and the scope of the present disclosure is not limited to the following examples.

[0095] Example 1 (1) Fabrication of the negative electrode An additive is added to an aqueous solvent in which artificial graphite as the negative electrode active material, styrene-butadiene rubber (SBR) as the binder, and carboxymethyl cellulose (CMC) as the thickener are mixed at a weight ratio of 97.6:1.5:0.9 to prepare a negative electrode slurry. The additive is added in an amount of 0.2 wt% relative to the total weight of the negative electrode active material (artificial graphite).

[0096] A compound represented by the following Formula 1-1 is used as the additive.

[0097] Formula 1-1: .

[0098] The prepared negative electrode slurry was applied to both sides of a 10 μm thick copper foil using a reverse roller coater to achieve 8.4 mg / cm². 2 Up to 8.7 mg / cm 2 The loading level (L / L) is then dried at 120°C. The negative electrode active material layer is rolled using a roller press to achieve a pellet density of 1.4 g / cc to 1.7 g / cc, thereby manufacturing the negative electrode (negative electrode plate).

[0099] The pellet density can be measured within the range of 3.0000g ± 0.0004g of the negative electrode active material. For example, the negative electrode active material is held under a pressure of 3 tons for 30 seconds using a 13mm KBr pellet mold, the reduction in height is measured, and then the weight per unit volume is measured, which can be converted into density.

[0100] (2) Manufacturing of the positive electrode A slurry of positive electrode active material was prepared by mixing and dispersing lithium cobalt oxide (LCO, LiCoO2) as the positive electrode active material, polyvinylidene fluoride as the binder, and carbon nanotubes (CNTs) as the conductive material in an N-methylpyrrolidone at a weight ratio of 98.7:0.9:0.4.

[0101] The prepared positive electrode active material slurry was applied to one side of an aluminum current collector with a thickness of 10 μm using a reverse roller coating machine to achieve 19.8 mg / cm². 2 The loading level (L / L) was then dried at 110°C. The positive electrode active material layer was rolled using a roller press to achieve a pellet density of 3.70 g / cc, thereby manufacturing the positive electrode.

[0102] Example 2 The negative and positive electrodes were manufactured in the same manner as in Example 1, except that 0.5 wt% of an additive was added to prepare the negative electrode slurry, which was then applied to achieve 8.6 mg / cm³. 2 Up to 8.9 mg / cm 2 The load level.

[0103] Example 3 The negative and positive electrodes were manufactured in the same manner as in Example 1, except that 1 wt% of an additive was added to prepare the negative electrode slurry, which was then applied to achieve 8.6 mg / cm³. 2 Up to 8.9 mg / cm 2 The load level.

[0104] Example 4 The negative and positive electrodes were manufactured in the same manner as in Example 1, except that 5 wt% of an additive was added to prepare the negative electrode slurry, which was then applied to achieve 8.6 mg / cm³. 2 Up to 8.9 mg / cm 2 The load level.

[0105] Example 5 The negative and positive electrodes are manufactured in the same manner as in Example 1, except that an additive represented by the following formula 2-1 is used.

[0106] Equation 2-1: .

[0107] Example 6 The negative and positive electrodes were manufactured in the same manner as in Example 5, except that 0.5 wt% of an additive was added to prepare the negative electrode slurry, which was then applied to achieve 8.6 mg / cm³. 2 Up to 8.9 mg / cm 2 The load level.

[0108] Comparison Example 1 The negative and positive electrodes were manufactured in the same manner as in Example 1, except that no additives were added to prepare the negative electrode slurry, which was then applied to achieve 8.5 mg / cm³. 2 Up to 8.7 mg / cm 2 The load level.

[0109] Comparison Example 2 The negative and positive electrodes were manufactured in the same manner as in Example 1, except that 10 wt% of an additive was added to prepare the negative electrode slurry, which was then applied to achieve 8.5 mg / cm³. 2 Up to 8.7 mg / cm 2 The load level.

[0110] Evaluation 1: Evaluation of the properties of the negative electrode plate The negative electrode slurry viscosity, negative electrode adhesion strength, and peel strength of the upper / lower negative electrode portion were evaluated based on the example and comparative examples.

[0111] The viscosity of the negative electrode slurry prepared in the example and comparative examples was measured and is shown in Table 1 below. The viscosity was measured using a rheometer (Anton Parr) at 25°C for 10 seconds. -1 The shear rate is used to measure the viscosity of the negative electrode slurry.

[0112] The negative electrode adhesion strength was measured using the following method. The negative electrode plate, according to the example and comparative example, was cut into pieces 25mm wide and 100mm long. Adhesive tape (Celotape from Nichiban Co., Ltd.) was used. ® Samples for evaluating the adhesion strength of the negative electrode were prepared by attaching one side of the negative electrode active material layer to a glass substrate using No. 405 as the adhesive surface. The samples were mounted on a peel tester (Instron 3400 series), and the stress was measured when the current collector was peeled off at a rate of 300 mm / min at a 180° angle. The measurement was performed five times, and the average value was calculated as the peel strength. The adhesion strength (i.e., peel strength) was calculated according to Equation 1 below, and the results are shown in Table 1 below.

[0113] Equation 1: Adhesive strength (gf / mm) = Measured force (gf) / Length of adhesive area (mm).

[0114] The peel strength of the upper and lower negative electrode portions was measured using a Surface and Interface Cutting Analysis System (SAICAS) as a diagonal cutting device. A blade with a 1 mm wide diamond-shaped edge was inserted obliquely from the electrode surface at a constant speed (horizontal: 6 μm / s, vertical: 0.6 μm / s). After reaching the interface between the current collector and the electrode layer, the horizontal stress applied to the blade during horizontal movement at a constant speed (6 μm / s) was used as the peel strength for comparison. The peel strength was calculated according to Equation 2 below, and the results are shown in Table 1 below.

[0115] Equation 2: Peel strength (kN / m) = Measured force (N) / Length of peeled area (m).

[0116] A higher adhesive strength (i.e., peel strength) indicates enhanced interfacial adhesion between the negative electrode current collector and the negative electrode active material layer or between the negative electrode active material layer itself, which means increased resistance to peeling from the negative electrode current collector or between the negative electrode active material layers.

[0117] Table 1:

[0118] Evaluation 2: Evaluation of charge / discharge characteristics The negative electrode fabricated in the example and comparative examples was used to fabricate a coin-type half-cell negative electrode for a rechargeable lithium battery. A 10 μm thick Li foil was used as the counter electrode (positive electrode), and a 20 μm thick polyethylene separator was assembled to fabricate the electrode assembly while using the negative electrode. An electrolyte was then injected into the assembly to fabricate the CR2032 type coin-type half-cell negative electrode for a rechargeable lithium battery using a typical method. As the electrolyte, 1.3 M LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC), propylene carbonate (PC), and propylene propionate (PP) mixed in a volume ratio of 10:20:70.

[0119] The manufactured negative electrode-rechargeable lithium battery is charged at 25°C with a constant current of 0.1C and a voltage of 0.01V, and then charged to a constant current of 0.1C while maintaining a voltage of 0.01V. Subsequently, the negative electrode-rechargeable lithium battery is discharged to a voltage of 1.5V with a constant current of 0.1C (formation process).

[0120] For the discharge rate (2.0C / 0.2C), each rechargeable lithium battery was charged at 25°C with a constant current of 0.2C and a voltage of 0.01V, and then charged to a constant current of 0.01C while maintaining a voltage of 0.01V. Each rechargeable lithium battery was discharged to a voltage of 1.5V at constant currents of 0.2C, 0.5C, and 2.0C. The formation efficiency and discharge rate (2.0C / 0.2C) were calculated according to Equations 3 and 4 below, and the results are shown in Table 2 below.

[0121] Equation 3: Formation efficiency (%) = (discharge capacity / charge capacity) × 100.

[0122] Equation 4: Discharge rate (2.0C / 0.2C) (%) = (Discharge capacity at 2.0C / Discharge capacity at 0.2C) × 100.

[0123] Table 2:

[0124] Evaluation 3: Evaluation of lifespan at room temperature A coin-type full cell was fabricated using the negative and positive electrodes, polyethylene separator, and electrolyte prepared in the example and comparative examples. As the electrolyte, 1.3 M LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC), propylene carbonate (PC), and propylene propionate (PP) mixed in a volume ratio of 10:20:70.

[0125] The manufactured rechargeable lithium-ion batteries were subjected to 200 charge-discharge cycles under the conditions of "charge at 25°C and 1.0C (CC / CV, 4.5V 0.02C cutoff) / discharge at 1.0C (CC, 3.0V cutoff)" to determine battery characteristics. The DC internal resistance (DC-IR) was determined at SOC 20 by applying a 1C current for 10 seconds and using "dR=dV / dI". Lifetime retention was calculated according to Equation 5 below. The results are shown in Table 3 below.

[0126] Equation 5: Lifetime retention rate (%) = (Discharge capacity after 200 cycles / Initial discharge capacity) × 100.

[0127] Table 3:

[0128] Evaluation 4: Evaluation of heat exposure A pouch battery was manufactured using the negative and positive electrodes, a polyethylene separator, and an electrolyte prepared in the example and comparative examples. The manufactured positive electrode was stamped to a size of 3 cm × 4 cm, and the manufactured negative electrode was stamped to a size of 3.2 cm × 4.2 cm. Subsequently, a PE separator was sandwiched between the manufactured positive and negative electrodes, and a pouch battery sealed in an aluminum pouch was prepared using an electrolyte containing 1.3 M LiPF6 in a non-aqueous organic solvent containing ethylene carbonate (EC), propylene carbonate (PC), and propylene propionate (PP) mixed in a volume ratio of 10:20:70. The designed capacity of the manufactured battery was 36 mAh.

[0129] The manufactured rechargeable lithium batteries were exposed to a target temperature (high temperature) for 1 hour, and then evaluated for ignition. The results are shown in Table 4 below. The heating rate was maintained at 5 °C / min as the temperature increased from room temperature to the target temperature.

[0130] Table 4:

[0131] *N (i.e., the number after " / " in Table 4) = the number of batteries evaluated.

[0132] *F = Ignition (failure).

[0133] *OK = Not ignited.

[0134] Overall evaluation Referring to Table 1 above, it can be seen that the negative electrodes (Examples 1 to 6) using additives according to the concept of this disclosure are superior to the negative electrodes of the comparative examples in terms of peel strength (i.e., adhesive strength).

[0135] Referring to Tables 2 and 3 above, it can be seen that the rechargeable lithium batteries (Examples 1 to 6) using additives according to the concept of this disclosure exhibit higher discharge rate and lifespan characteristics at room temperature than the rechargeable lithium batteries of the comparative examples. For example, the rechargeable lithium batteries using additives according to the concept of this disclosure have a lifespan retention of about 85% or greater at room temperature and a discharge rate in the range of about 120% to about 151%.

[0136] Referring to Table 4 above, it is determined that the rechargeable lithium batteries (Examples 1 to 6) using the additives according to the concept of this disclosure exhibit better thermal exposure evaluation results than the rechargeable lithium batteries of the comparative examples. For example, the rechargeable lithium batteries using the additives according to the concept of this disclosure have an ignition point in the range of about 148°C or greater. That is, it is determined that the rechargeable lithium batteries using the additives according to this disclosure exhibit higher heat resistance.

[0137] The negative electrode for a rechargeable lithium battery according to the example embodiment can exhibit improved adhesion strength between the negative electrode active material layer and the negative electrode current collector.

[0138] The rechargeable lithium battery according to the example embodiment can exhibit improved stability and desired or improved lifespan characteristics.

[0139] Although exemplary embodiments of the present disclosure have been described above with reference to the accompanying drawings, the present disclosure may be applied in other specific forms without altering its technical concept or essential characteristics. Therefore, the above exemplary embodiments are to be considered illustrative rather than restrictive in all respects.

Claims

1. A negative electrode for a rechargeable lithium battery, the negative electrode comprising: A negative electrode current collector; And A negative electrode active material layer on the negative electrode current collector, Wherein, the negative electrode active material layer comprises: a negative electrode active material; a binder; a conductive material; and an additive represented by Formula 1 or Formula 2; Formula 1: ； Wherein, R1 to R6 each independently comprise a hydrogen atom or a substituted or unsubstituted C1 to C10 alkyl group, and Formula 2: ； Among them, R7 to R 14 Each of them independently includes a hydrogen atom or a substituted or unsubstituted C1 to C10 alkyl group.

2. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The additive comprises 1,3,5-trioxane represented by the following Formula 1-1: Formula 1-1: 。 3. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The additive comprises at least one of a compound represented by the following Formula 1-2, a compound represented by the following Formula 1-3, a compound represented by the following Formula 1-4, and combinations thereof: Formula 1-2: ； Formula 1-3: ； And Formula 1-4: 。 4. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The conductive material, the binder, and the negative electrode active material are provided in a weight ratio of 1:a:b, The range of "a" is from 1 to 3, and The range of "b" is from 90 to 99.

5. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The additive is provided in an amount within the range of 0.1 wt% to 5 wt% relative to the total weight of the negative electrode active material.

6. The negative electrode for a rechargeable lithium battery according to claim 5, wherein, The additive is provided in an amount within the range of 0.2 wt% to 1 wt% relative to the total weight of the negative electrode active material.

7. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The negative electrode active material comprises at least one of a carbon-based negative electrode active material, a Si-based negative electrode active material, a Sn-based negative electrode active material, and combinations thereof.

8. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The negative electrode active material comprises graphite.

9. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The binder comprises at least one of a non-aqueous binder, an aqueous binder, a dry binder, and combinations thereof.

10. The negative electrode for a rechargeable lithium battery according to claim 9, wherein, The aqueous binder comprises at least one of styrene-butadiene rubber, (meth)acrylate-modified styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, poly(ethylene oxide), polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene terpolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

11. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The negative electrode active material layer has a pellet density within the range of 1.4 g / cc to 1.7 g / cc.

12. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The adhesion strength between the negative electrode current collector and the negative electrode active material layer is within the range of 0.2 gf / mm to 0.4 gf / mm.

13. A rechargeable lithium battery, the rechargeable lithium battery comprising: A positive electrode; A negative electrode; And An electrolyte, Wherein, the negative electrode comprises the negative electrode according to Claim 1.

14. The rechargeable lithium battery according to claim 13, wherein, The positive electrode comprises a positive electrode active material, and The positive electrode active material comprises a lithium composite oxide represented by Formula 3: Formula 3: Li x M 1 y M 2 z M 3 1-y-z O 2-a X a x, a, y, and z satisfy 0.5 ≤ x ≤ 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 nickel, cobalt, manganese, aluminum, boron, barium, calcium, cerium, chromium, iron, molybdenum, niobium, silicon, strontium, magnesium, titanium, vanadium, tungsten, zirconium, and lanthanum, and combinations thereof, and X comprises at least one of fluorine, sulfur, phosphorus, and chlorine.

15. The rechargeable lithium battery according to claim 14, wherein, The positive electrode active material comprises lithium cobalt oxide.

16. The rechargeable lithium battery of claim 13, wherein the rechargeable lithium battery has a lifetime retention rate of 85% or greater at room temperature.

17. The rechargeable lithium battery according to claim 13, wherein the rechargeable lithium battery has an ignition point in the range of 148°C or greater.

18. The rechargeable lithium battery according to claim 13, wherein the rechargeable lithium battery has a discharge rate in the range of 120% to 151%.

19. The rechargeable lithium battery according to claim 13, wherein, The rechargeable lithium battery includes one of the following: cylindrical battery, prismatic battery, pouch battery, and coin-shaped battery.

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