Positive electrode additive for rechargeable battery, positive electrode paste including same, and rechargeable lithium battery including same

Abstract

The present invention relates to a positive electrode additive for a rechargeable lithium battery, a positive electrode slurry including the same, and a rechargeable lithium battery including the same, wherein the positive electrode additive may include a compound represented by Formula 1 below. Details about the above Formula 1 are as described in the specification.

Description

Technical Field

[0001] This invention relates to a positive electrode additive for rechargeable lithium batteries, a positive electrode slurry comprising the same, and a rechargeable lithium battery comprising the same. Background Technology

[0002] Recently, with the rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for rechargeable batteries with high energy density and high capacity has increased rapidly. Accordingly, research and development to improve the performance of rechargeable lithium batteries has been actively undertaken.

[0003] A rechargeable lithium battery is a battery that includes a positive electrode, a negative electrode, and an electrolyte. The positive and negative electrodes contain active materials that can insert and extract lithium ions. When lithium ions are inserted / extracted between the positive and negative electrodes, electrical energy is generated through oxidation and reduction reactions.

[0004] The solution of lithium salt dissolved in a non-aqueous organic solvent is used as the electrolyte in this rechargeable lithium battery. Rechargeable lithium batteries exhibit battery characteristics through complex reactions between the positive electrode and the electrolyte, and between the negative electrode and the electrolyte. Therefore, using a suitable electrolyte is one of the important variables for improving the performance of rechargeable lithium batteries. Summary of the Invention

[0005] Technical issues

[0006] This invention provides a positive electrode additive for rechargeable batteries that has a stabilizing effect on the positive electrode.

[0007] The present invention also provides a rechargeable lithium battery with excellent life characteristics and heat resistance.

[0008] Technical solutions

[0009] The positive electrode additive for a rechargeable battery according to embodiments of the present invention may include a compound represented by the following formula 1:

[0010] [Formula 1]

[0011]

[0012] In Equation 1 above,

[0013] Each of R1 to R6 above is independently hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, a substituted or unsubstituted C2 to C10 alkynyl group, an aldehyde group, a carboxyl group, or a heat-stabilizing group.

[0014] At least two of R1 to R6 above are thermally stable groups.

[0015] At least two thermally stable groups have the same or different formulas, and

[0016] At least two thermally stable groups are each independently represented by the following formula 2:

[0017] [Equation 2]

[0018]

[0019] In Equation 2 above,

[0020] R7 above is hydrogen or a substituted or unsubstituted C1~C10 alkyl group.

[0021] The positive electrode slurry for rechargeable batteries according to embodiments of the present invention may include the above-mentioned positive electrode additives, positive electrode active materials, binders, and conductive materials.

[0022] A rechargeable lithium battery according to an embodiment of the present invention may include: a positive electrode, including a positive electrode active material layer; a negative electrode, including a negative electrode active material layer; and an electrolyte. The positive electrode active material layer may include the aforementioned positive electrode additive, positive electrode active material, binder, and conductive material.

[0023] Beneficial effects

[0024] The positive electrode additive according to embodiments of the present invention can stabilize the positive electrode. Rechargeable lithium batteries including the positive electrode additive can exhibit excellent lifespan characteristics and heat resistance. Attached Figure Description

[0025] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present invention; and

[0026] Figures 2-5 To illustrate a schematic diagram of a rechargeable lithium battery according to an embodiment, and Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown, and Figure 4 and Figure 5 A pouch-type battery is shown. Detailed Implementation

[0027] To fully understand the configuration and effects of the invention, preferred embodiments of the invention are described with reference to the accompanying drawings. However, the invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, and various changes are possible. Rather, these embodiments are provided by way of description so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0028] In this specification, this means that when an element is referred to as being on another element, the element may be directly on the other element, or a third element may exist between the two. Additionally, in the accompanying drawings, the thickness of the components is enlarged for effective explanation of the technical content. Throughout this specification, the same reference numerals refer to the same elements.

[0029] In this specification, unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well. Additionally, unless otherwise specifically stated, the phrase “A or B” may indicate “including A but not B,” “including B but not A,” or “including A and B.” The terms “comprise” and / or “comprising” as used in this specification do not exclude the presence or addition of one or more other components.

[0030] In this specification, "combination thereof" may refer to mixtures, stacks, complexes, copolymers, alloys, blends, and reaction products of the components.

[0031] Unless otherwise specified in this specification, particle size may refer to average particle size. Furthermore, particle size means average particle size (D50), which refers to the diameter of particles that constitute approximately 50% of the total volume in the 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, or using transmission electron microscopy (TEM) images or scanning electron microscopy (SEM) images. In another method, average particle size can be measured using a measuring device employing dynamic light scattering, wherein the average particle size (D50) value is obtained by performing data analysis to count the number of particles in each particle size range. Alternatively, average particle size can be measured using laser diffraction methods. When measured by laser diffraction, more specifically, after dispersing the particles to be measured in a dispersion medium, the dispersion medium is introduced into a commercial laser diffraction particle size measuring instrument (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves at an output of about 28 kHz at about 60 W. The average particle size (D50) based on about 50% of the particle size distribution in the measuring instrument can then be calculated.

[0032] In this specification, unless otherwise specified, “substitution” means that at least one hydrogen atom of a substituent or compound is substituted by a deuterium, halogen, hydroxyl, amino, C1-C30 amino, nitro, C1-C40 silyl, C1-C30 alkyl, C1-C10 alkylsilyl, C6-C30 arylsilyl, C3-C30 cycloalkyl, C3-C30 heterocycloalkyl, C6-C30 aryl, C2-C30 heteroaryl, C1-C20 alkoxy, C1-C10 fluoroalkyl, cyano, or a combination thereof.

[0033] Specifically, "substitution" can mean that at least one hydrogen atom of a substituent or compound is substituted by a deuterium, halogroup, C1-C30 alkyl, C1-C10 alkylsilyl, C6-C30 arylsilyl, C3-C30 cycloalkyl, C3-C30 heterocycloalkyl, C6-C30 aryl, C2-C30 heteroaryl, C1-C10 fluoroalkyl, or cyano. For example, "substitution" can mean that at least one hydrogen atom of a substituent or compound is substituted by a deuterium, halogroup, C1-C20 alkyl, C6-C30 aryl, C1-C10 fluoroalkyl, or cyano. Alternatively, "substitution" can mean that at least one hydrogen atom of a substituent or compound is substituted by a deuterium, halogroup, C1-C5 alkyl, C6-C18 aryl, C1-C5 fluoroalkyl, or cyano. For example, "substitution" can mean that at least one hydrogen atom of a substituent or compound is replaced by deuterium, cyano, halogen, methyl, ethyl, propyl, butyl, phenyl, biphenyl, terphenyl, trifluoromethyl, or naphthyl.

[0034] Figure 1 A conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present invention. (Reference) Figure 1 A rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0035] The positive electrode 10 and the negative electrode 20 may be spaced apart from each other by the separator 30. The separator 30 may be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20 and the separator 30 may be in contact with the electrolyte ELL. The positive electrode 10, the negative electrode 20 and the separator 30 may be immersed in the electrolyte ELL.

[0036] The electrolyte ELL can be used as a medium for the transport of lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move towards the positive electrode 10 or the negative electrode 20 through the membrane 30.

[0037] Positive electrode 10

[0038] The positive electrode 10 for a rechargeable lithium battery may include a current collector COL1 and a positive electrode active material layer AML1 formed on the current collector COL1. The positive electrode active material layer AML1 may include a positive electrode active material and may further include a binder, a conductive material, and / or a positive electrode additive. The positive electrode additive will be described in detail later.

[0039] The amount of positive electrode active material in the positive electrode active material layer AML1 can be 90 wt% to 99.5 wt% relative to 100 wt% of the positive electrode active material layer AML1. The amount of each of the binder and conductive material can be 0.5 wt% to 5 wt% relative to 100 wt% of the positive electrode active material layer AML1.

[0040] The binder is used to bond the positive electrode active material particles well to each other and also to bond the positive electrode active material well to the current collector COL1. Examples of binders may include, but are not limited to, 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, nylon, etc.

[0041] Conductive materials are any materials used to impart electrical conductivity to electrodes without causing chemical changes and conducting electrons, and can be used in batteries constructed from such materials. Examples of conductive materials may include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes); metallic materials, including copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0042] Al can be used in current collectors COL1, but the material is not limited to this.

[0043] Positive electrode active material

[0044] 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. Specifically, a composite oxide of at least one lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0045] The composite oxide may be a lithium transition metal composite oxide, and specific examples may include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free nickel manganese oxides, or combinations thereof.

[0046] As an example, a compound represented by any of the following chemical formulas can be used. 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 O2-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 a NiG 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); Li a FePO4 (0.90≤a≤1.8).

[0047] In the above chemical formula, A is Ni, Co, Mn or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or a combination thereof; D is O, F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; and L1 is Mn, Al or a combination thereof.

[0048] For example, relative to 100 mol% of metals other than lithium in lithium transition metal composite oxides, the positive electrode active material can be a high-nickel positive electrode active material, wherein the nickel content is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, and 99 mol% or less. High-nickel positive electrode active materials can achieve high capacity and are therefore applicable to high-capacity, high-density rechargeable lithium batteries.

[0049] negative electrode 20

[0050] The negative electrode 20 for a rechargeable lithium battery includes a current collector COL2 and a negative electrode active material layer AML2 on the current collector COL2. The negative electrode active material layer AML2 may include a negative electrode active material and may further include a binder and / or a conductive material.

[0051] For example, the negative electrode active material layer AML2 may include 90 wt% to 99 wt% of negative electrode active material, 0.5 wt% to 5 wt% of binder and 0 wt% to 5 wt% of conductive material.

[0052] The binder is used to bond the negative electrode active material particles well to each other, and also to bond the negative electrode active material well to the current collector COL2. The binder may include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0053] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0054] The waterborne adhesive can be selected from 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.

[0055] When an aqueous binder is used as a negative electrode binder, it may further include a cellulose-based compound capable of imparting viscosity. For the cellulose-based compound, at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts may be mixed and used. The alkali metal may include Na, K, or Li.

[0056] The dry binder may be a polymeric material capable of being fibrous, and for example, the dry binder may be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0057] Conductive materials can be used to impart conductivity to electrodes without causing chemical changes and to conduct electrons; any material that can be used in batteries made from such materials. Specific examples may include carbon-based materials (such as natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes); metallic materials, including copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0058] The current collector COL2 can be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof.

[0059] Negative electrode active material

[0060] The negative electrode active material in the negative electrode active material layer AML2 includes materials capable of reversibly inserting / deintercalating lithium ions, lithium metal, lithium metal alloys, materials capable of doping / dedoping lithium, or transition metal oxides.

[0061] Materials capable of reversibly inserting / deintercalating lithium ions can include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. Crystalline carbon can be, for example, graphite, such as amorphous, flake, sheet, spherical, or fibrous natural or artificial graphite. Amorphous carbon can be, for example, soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0062] Lithium metal alloys may include alloys of lithium and metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0063] Materials capable of being doped / dedoped with lithium can be Si-based or Sn-based negative electrode active materials. Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiOx (0 < x < 2), Si-Q alloys (where Q is selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof), or combinations thereof. Sn-based negative electrode active materials may include Sn, SnO2, Sn-based alloys, or combinations thereof.

[0064] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to 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 may include secondary particles (cores) in which primary silicon particles are assembled and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon may also be present between the primary silicon particles, and for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed within an amorphous carbon matrix.

[0065] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles, and an amorphous carbon coating on the surface of the core.

[0066] Si-based or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials.

[0067] Diaphragm 30

[0068] 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 polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof, as well as mixed multilayer films, such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, polypropylene / polypropylene / polypropylene three-layer separators, etc.

[0069] The diaphragm 30 may include a porous substrate and a coating on one or both surfaces of the porous substrate, the coating comprising an organic material, an inorganic material, or a combination thereof.

[0070] The porous substrate may be a polymer membrane formed from a copolymer or mixture of any one or two or more of the following: 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.

[0071] Organic materials may include polyvinylidene fluoride polymers or (meth)acrylic acid polymers.

[0072] Inorganic materials may include, but are not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and combinations thereof.

[0073] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked.

[0074] Electrolyte ELL

[0075] Electrolytes used in rechargeable lithium batteries (ELL) consist of non-aqueous organic solvents and lithium salts.

[0076] Non-aqueous organic solvents are used as media for transporting ions that participate in the electrochemical reactions of the battery.

[0077] Non-aqueous organic solvents may be carbonate solvents, ester solvents, ether solvents, ketone solvents or alcohol solvents, aprotic solvents or combinations thereof.

[0078] Carbonate solvents may include 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), butyl carbonate (BC), etc.

[0079] Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, valonate lactone, caprolactone, propyl propionate (PP), etc.

[0080] Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc. Aprotic solvents may include nitrile solvents (such as R-CN, where R can be a C2~C20 straight-chain, branched, or cyclic hydrocarbon group, and may contain double bonds, aromatic rings, or ether bonds), amides (such as dimethylformamide), dioxolane (such as 1,3-dioxolane, 1,4-dioxolane, etc.), sulfolane, etc.

[0081] Non-aqueous organic solvents can be used alone or in combination of two or more.

[0082] In addition, when using carbonate solvents, cyclic carbonates and chain carbonates can be mixed and used, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0083] Lithium salts are materials dissolved in organic solvents and supply lithium ions in the battery, thus ensuring the basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts may include those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of the following: (SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0084] Positive electrode additives

[0085] The positive electrode additive for rechargeable lithium batteries according to the present invention will be described in more detail below.

[0086] In an embodiment, the positive electrode additive may include a compound represented by the following formula 1:

[0087] [Formula 1]

[0088]

[0089] In Equation 1 above,

[0090] R1 to R6 above can each independently be hydrogen, substituted or unsubstituted C1 to C10 alkyl, substituted or unsubstituted C2 to C10 alkenyl or substituted or unsubstituted C2 to C10 alkynyl, aldehyde, carboxyl or heat-stabilizing group.

[0091] At least two of R1 to R6 above can be thermally stable groups.

[0092] At least two thermally stable groups may have the same or different formulas, and

[0093] At least two thermally stable groups can each be independently represented by the following formula 2:

[0094] [Equation 2]

[0095]

[0096] In Equation 2 above,

[0097] R7 above can be hydrogen or a substituted or unsubstituted C1~C10 alkyl group.

[0098] Thermally stabilizing groups are key functional groups that enable positive electrode additives to exert their positive electrode stabilizing effect. The positive electrode stabilizing function is more pronounced at high voltages and / or high temperatures.

[0099] Specifically, examples of aldehyde groups may include, but are not limited to, formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, etc. More preferably, the aldehyde group may be formaldehyde, i.e., -C(=O)H.

[0100] Specifically, examples of the carboxyl group may include, but are not limited to, formic acid, acetic acid, propionic acid, butyric acid, etc. More preferably, the carboxyl group may be formic acid, i.e., -C(=O)OH.

[0101] In an embodiment, R1 may be a thermally stable group, and at least one of R2, R3, R5 and R6 may be a thermally stable group.

[0102] In embodiments, R1 may be a thermally stable group, and at least one of R2 and R6 may be a thermally stable group. For example, a compound represented by Formula 1 above may have two thermally stable groups, and the two thermally stable groups may be located in the ortho position.

[0103] In embodiments, R1 may be a thermally stable group, and at least one of R3 and R5 may be a thermally stable group. For example, a compound represented by Formula 1 above may have two thermally stable groups, and the two thermally stable groups may be located in the meta position.

[0104] In the embodiments, R1 and R6 above can each independently be hydrogen, substituted or unsubstituted C1~C5 alkyl, substituted or unsubstituted C2~C5 alkenyl or substituted or unsubstituted C2~C5 alkynyl, -C(=O)H, -C(=O)OH and thermally stable groups.

[0105] In the embodiments, R1 and R6 above can each independently be hydrogen, substituted or unsubstituted C1~C3 alkyl, substituted or unsubstituted C2~C3 alkenyl or substituted or unsubstituted C2~C3 alkynyl, -C(=O)H, -C(=O)OH and thermally stable groups.

[0106] Additives may include at least one compound selected from the group consisting of formulas 1A to 1F below:

[0107] [Formula 1A]

[0108]

[0109] [Formula 1B]

[0110]

[0111] [Formula 1C]

[0112]

[0113] [Formula 1D]

[0114]

[0115] [Formula 1E]

[0116]

[0117] [Formula 1F]

[0118] .

[0119] When a compound has the structure of Formula 1 described above, the additive containing that compound can best perform its positive electrode stabilizing function. For example, even when it includes a compound containing at least two thermally stabilizing groups, the positive electrode stabilizing effect of the additive may not be significant if the compound does not satisfy the structure of Formula 1 described above.

[0120] The additive according to the invention exhibits enhanced positive electrode stabilization at high voltages and / or high temperatures. That is, it can effectively prevent battery fires when the battery is exposed to heat. Specifically, the high voltage can be about 3.5 V or higher, about 4.0 V or higher, about 4.25 V or higher, or about 4.5 V or higher. The high temperature can be about 60°C or higher, about 100°C or higher, or about 140°C or higher. At high voltages and / or high temperatures, the additive stabilizes the positive electrode by removing unstable oxygen (e.g., reactive oxygen). Unstable oxygen can be generated in lithium-ion batteries during repeated charging and discharging. Unstable oxygen can attack the surface of the positive electrode, consequently leading to its degradation. The additive according to the invention can significantly improve the degradation of the positive electrode by effectively removing unstable oxygen.

[0121] Positive electrode paste

[0122] The positive electrode slurry according to the present invention may include a positive electrode additive, a positive electrode active material, a binder, and a conductive material. The positive electrode slurry according to the present invention can be obtained by dispersing the positive electrode additive in a dispersion medium and then mixing the dispersion with the positive electrode active material, binder, and conductive material.

[0123] The content of positive electrode additives in the positive electrode slurry can be approximately 0.1 parts by weight to approximately 10 parts by weight relative to 100 parts by weight of the positive electrode active material. Specifically, the content of positive electrode additives can be approximately 0.1 parts by weight to approximately 5 parts by weight, approximately 0.1 parts by weight to approximately 3 parts by weight, or approximately 0.1 parts by weight to approximately 1 part by weight relative to 100 parts by weight of the positive electrode active material. The content of positive electrode additives can be indicated as the total weight of positive electrode additives in the positive electrode slurry relative to the total weight of the positive electrode active material in the positive electrode slurry. When the content of positive electrode additives meets the above range, the positive electrode stabilization effect can be maximized. This effect is even better at high temperatures.

[0124] When the content of the positive electrode additive is less than the above range, the additive may not be able to effectively remove unstable oxygen, and therefore may not have a positive electrode stabilizing effect. When the content of the positive electrode additive is greater than the above range, the additive itself may act as a resistive material, and therefore may not have a positive electrode stabilizing effect.

[0125] The positive electrode active material may include Ni. The positive electrode active material may be a high-nickel positive electrode active material. In the positive electrode active material, the Ni content may be approximately 80 mol% or more relative to 100 mol% of metals other than lithium.

[0126] The active material for the positive electrode may include Ni, Co, and Al.

[0127] The positive electrode slurry can have a viscosity of approximately 1,000 cP to approximately 10,000 cP. Specifically, the positive electrode slurry can have a viscosity of approximately 1,000 cP to approximately 5,000 cP or approximately 2,000 cP to approximately 4,000 cP. By adjusting the amount of dispersion medium added during the preparation of the positive electrode slurry, a slurry meeting the viscosity range can be prepared. When the positive electrode slurry meets the above viscosity range, the positive electrode stabilization effect of the positive electrode additive can be maximized.

[0128] When the viscosity of the positive electrode slurry is less than the above range, the slurry may be lost when it is applied to the positive electrode current collector. When the viscosity of the positive electrode slurry is greater than the above range, excessive slurry application may occur, leading to an increase in the thickness of the positive electrode active material layer.

[0129] The viscosity of the positive electrode slurry can be measured at room temperature (25°C) using a Type B viscometer. However, the viscometer measuring device is not limited to those described, and any device capable of properly measuring the viscosity of liquids is applicable without limitation.

[0130] The positive electrode slurry may have a solids concentration of approximately 0.01 parts by weight to approximately 15 parts by weight. Specifically, the slurry may have a solids concentration of approximately 0.01 parts by weight to approximately 10 parts by weight or approximately 0.01 parts by weight to approximately 5 parts by weight. The solids concentration of the slurry indicates the positive electrode active material, binder, conductive material, and positive electrode additives included in the slurry. The solids concentration in the slurry may be the total weight of the solids in the slurry relative to the total weight of the slurry. That is, the solids concentration may be indicated as "(weight of solids) / (weight of slurry)". When the solids concentration meets the above range, the positive electrode stabilization effect of the positive electrode additives can be maximized.

[0131] The positive electrode paste may contain positive electrode active material, conductive material and binder in a weight ratio of a:b:c. Here, a may be about 90 to about 99, b may be about 0.5 to about 5 and c may be about 0.5 to about 5.

[0132] Rechargeable lithium batteries

[0133] Rechargeable lithium batteries can be classified according to their shape as cylindrical, prismatic, pouch, or coin-shaped batteries, etc. Figures 2-5 To illustrate a schematic diagram of a rechargeable lithium battery according to an embodiment, and Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown, and Figure 4 and Figure 5 A pouch-type battery is shown. (Reference) Figures 2-4 The rechargeable lithium battery 100 may include: an electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20; and a housing 50 housing the electrode assembly 40. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). The rechargeable lithium battery 100 may include a sealing member 60 for sealing the housing 50, such as... Figure 2 As shown. In Figure 3 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 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include electrode terminals 70 (which may be, for example, positive electrode terminal 71 and negative electrode terminal 72) as electrical paths for guiding current formed in the electrode assembly 40 to the outside.

[0134] The rechargeable lithium battery according to the embodiments can be used in automobiles, mobile phones and / or various types of electronic devices as a non-limiting example.

[0135] The rechargeable lithium battery according to the present invention may include: a positive electrode including a positive electrode active material layer; a negative electrode including a negative electrode active material layer; and an electrolyte. The positive electrode active material layer may include a positive electrode additive, a positive electrode active material, a binder, and a conductive material according to claim 1.

[0136] The positive electrode active material layer 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:

[0137] [Formula 3]

[0138] Li x M 1 y M 2 z M 3 1-y-z O 2-a X a

[0139] It may satisfy 0.5 ≤ x ≤ 1.8, 0 ≤ a ≤ 0.05, 0 < y ≤ 1, 0 ≤ z ≤ 1, and 0 ≤ y + z ≤ 1,

[0140] M 1 、M 2 and M 3 may each independently include at least one element selected from the group consisting of metals and combinations thereof such as 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

[0141] X may include at least one element selected from fluorine (F), sulfur (S), phosphorus (P), or chlorine (Cl).

[0142] In one embodiment, in the above formula 3, M 1 may be Ni. Alternatively, in the above formula 3, M 1 may be Ni, M 2 may be Co, and M 3 may be Al.

[0143] The negative electrode active material may be a carbon-based negative electrode active material, a Si-based negative electrode active material, a Sn-based negative electrode active material, or a combination thereof.

[0144] In an embodiment, the negative electrode active material may be a carbon-based negative electrode active material and a Si-based negative electrode active material.

[0145] During repeated charging and discharging, rechargeable lithium batteries may generate reactive oxygen species (ROS) due to irreversible structural changes in the positive and negative electrodes. ROS can act as a primary agent for attacking internal battery materials and accelerate battery degradation. Degradation caused by ROS is particularly pronounced at high voltages and / or high temperatures.

[0146] Due to the stabilizing effect of the positive electrode additive, the rechargeable lithium battery according to the present invention effectively prevents the degradation of the positive electrode. The rechargeable lithium battery according to the present invention exhibits excellent electrochemical performance. This effect is further enhanced at high voltages and / or high temperatures.

[0147] Hereinafter, embodiments and comparative examples of the present invention will be described. However, the following embodiments are merely presented as examples of implementation of the present invention, and the present invention is not limited to the following embodiments.

[0148] Example 1-1

[0149] (1) Preparation of positive electrode paste

[0150] A positive electrode additive comprising a compound represented by Formula 1A below is dispersed in N-methylpyrrolidone. This dispersion is then mixed with a positive electrode active material, a conductive material, and a binder. The amount of N-methylpyrrolidone added is adjusted to achieve a viscosity of 3,000 cP in the mixed solution to prepare a positive electrode slurry.

[0151] The active material of the positive electrode is LiNi 0.91 Co 0.08 Al 0.01 O2, Ketjen black as the conductive material, and polyvinylidene fluoride as the binder. The positive electrode active material, conductive material, and binder exist in a weight ratio of 97.7:1.2:1.1.

[0152] The content of positive electrode additive is 0.5 parts by weight relative to 100 parts by weight of positive electrode active material.

[0153] [Formula 1A]

[0154] .

[0155] (2) Preparation of rechargeable lithium batteries

[0156] The positive electrode active material slurry prepared according to the above description was coated on a 14 μm thick aluminum current collector, dried at 110 °C, and then pressed to prepare the positive electrode.

[0157] A mixture of artificial graphite and silicon nanoparticles in a weight ratio of 93:7, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a tackifier were mixed in a weight ratio of 97:1:2 and dispersed in distilled water to prepare a slurry of negative electrode active material.

[0158] The negative electrode active material slurry was coated onto a 10 μm thick copper current collector, dried at 100°C, and then pressed to prepare the negative electrode.

[0159] Electrode components were fabricated by assembling a positive electrode, a negative electrode, and a 25 μm thick polyethylene separator, and an electrolyte was injected to prepare a rechargeable lithium battery.

[0160] Examples 1-2

[0161] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Examples 1-1, except that the amount of additives was 0.1 parts by weight.

[0162] Examples 1-3

[0163] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Examples 1-1, except that the amount of additives was 1.0 parts by weight.

[0164] Example 2-1

[0165] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Examples 1-1, except that the material represented by Formula 1B below was used as the positive electrode additive.

[0166] [Formula 1B]

[0167] .

[0168] Example 2-2

[0169] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Example 2-1, except that the amount of additives was 0.1 parts by weight.

[0170] Example 2-3

[0171] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Example 2-1, except that the amount of additives was 1.0 parts by weight.

[0172] Example 3-1

[0173] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Examples 1-1, except that the material represented by the following Formula 1C was used as the positive electrode additive.

[0174] [Formula 1C]

[0175] .

[0176] Example 3-2

[0177] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Example 3-1, except that the amount of additives was 0.1 parts by weight.

[0178] Example 3-3

[0179] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Example 3-1, except that the amount of additives was 1.0 parts by weight.

[0180] Example 4-1

[0181] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Examples 1-1, except that the material represented by the following Formula 1D was used as the positive electrode additive.

[0182] [Formula 1D]

[0183] .

[0184] Example 4-2

[0185] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Example 4-1, except that the amount of additives was 0.1 parts by weight.

[0186] Example 4-3

[0187] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Example 4-1, except that the amount of additives was 1.0 parts by weight.

[0188] Example 5-1

[0189] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Examples 1-1, except that the material represented by the following Formula 1E was used as the positive electrode additive.

[0190] [Formula 1E]

[0191] .

[0192] Example 5-2

[0193] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Example 5-1, except that the amount of additives was 0.1 parts by weight.

[0194] Example 5-3

[0195] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Example 5-1, except that the amount of additives was 1.0 parts by weight.

[0196] Example 6-1

[0197] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Examples 1-1, except that the material represented by the following Formula 1F was used as the positive electrode additive.

[0198] [Formula 1F]

[0199] .

[0200] Example 6-2

[0201] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Example 6-1, except that the amount of additives was 0.1 parts by weight.

[0202] Example 6-3

[0203] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Example 6-1, except that the amount of additives was 1.0 parts by weight.

[0204] Comparative Example 1

[0205] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Examples 1-1, except that the positive electrode slurry did not include the positive electrode additive according to the present invention.

[0206] Comparative Example 2

[0207] The positive electrode slurry and rechargeable lithium battery were prepared in the same manner as in Examples 1-1, except that the material represented by Formula 4 below was used as the positive electrode additive in an amount of 0.5 parts by weight.

[0208] [Formula 4]

[0209] .

[0210] Evaluation Example 1: Lifetime Assessment at High Temperatures

[0211] For the rechargeable lithium batteries of the examples and comparative examples, 200 charge / discharge cycles were performed to calculate the capacity retention and the rate of change of resistance (DC-IR). The charging conditions were "45°C, 1.0 C, 4.25 V, and 0.05 C cutoff". The discharging conditions were "45°C, 1.0 C, and 2.8 V cutoff". The capacity retention was calculated according to Equation 1 below, and the rate of change of DC-IR was calculated according to Equation 2 below. The results are described in Table 1 below.

[0212] [Equation 1]

[0213] Capacity retention (%) = (Discharge capacity after 200 cycles / Discharge capacity after 1 cycle) * 100

[0214] [Equation 2]

[0215] DC-IR change rate (%) = {(DC-IR after 200 cycles / DC-IR after 1 cycle) - 1} * 100

[0216] Evaluation Example 2: Evaluation of Battery Characteristics After High-Temperature Storage

[0217] The rechargeable lithium batteries of the examples and comparative examples were charged under the conditions of "25°C, 1.0 C, 4.25 V, and 0.05 C cutoff", and the initial battery characteristics were measured. The rechargeable lithium batteries were placed at 60°C for 4 weeks, and then the battery characteristics were measured. The open circuit voltage (OCV) change rate, AC resistance (AC-IR) change rate, capacity retention rate, and capacity recovery rate were calculated according to Equations 3 to 6 below, and the results are shown in Table 2 below.

[0218] [Equation 3] OCV change rate (%) = {(OCV of the battery after 4 weeks of storage / OCV of the initial battery) - 1} x 100

[0219] [Equation 4] AC-IR change rate (%) = {(AC-IR of the battery after 4 weeks of storage / AC-IR of the initial battery) - 1} x 100

[0220] [Equation 5] Capacity retention rate (%) = {Discharge capacity of the battery after 4 weeks of storage / Initial discharge capacity of the battery} x 100

[0221] [Equation 6] Capacity recovery rate (%) = {Second discharge capacity of the battery after charging after 4 weeks of storage / Initial discharge capacity of the battery} x 100

[0222] [Table 1]

[0223]

[0224] [Table 2]

[0225]

[0226] Assessment Example 3: Assessment of Heat Exposure

[0227] The rechargeable lithium batteries prepared in the examples and comparative examples were exposed to the target temperature (high temperature) for 1 hour, and then the presence of fire was assessed, as shown in Table 3 below. The heating rate was maintained at 5 °C / min when the temperature was increased from room temperature to the target temperature.

[0228] [Table 3]

[0229]

[0230] * N = Number of battery cells being evaluated

[0231] * F = Fire exists (failure)

[0232] * OK = No fire occurred

[0233] Referring to Tables 1-3, it was determined that the embodiments according to the present invention are superior to the comparative examples in terms of battery life at high temperatures, battery characteristics after high-temperature storage, and evaluation results of thermal exposure. That is, it was determined that the rechargeable lithium battery including the positive electrode additive according to the present invention has excellent battery characteristics and heat resistance, especially at high temperatures.

[0234] While preferred embodiments of the invention have been described above, the scope of the invention is not limited to these embodiments. Various modifications may be made to the embodiments without departing from the spirit and scope of the invention as defined by the claims, and such modifications are included within the scope of the invention.

Claims

1. A positive electrode additive for rechargeable batteries, comprising: Compounds represented by the following formula 1: [Formula 1] In Equation 1 above, Each of R1 to R6 above is independently hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, a substituted or unsubstituted C2 to C10 alkynyl group, an aldehyde group, a carboxyl group, or a heat-stabilizing group. At least two of R1 to R6 above are the heat-stabilizing groups. At least two of the said thermally stable groups have the same or different formulas, and At least two of the said thermally stabilizing groups are each independently represented by the following formula 2: [Equation 2] In Equation 2 above, R7 above is hydrogen or a substituted or unsubstituted C1~C10 alkyl group.

2. The positive electrode additive for rechargeable batteries as claimed in claim 1, wherein the aldehyde group is -C(=O)H.

3. The positive electrode additive for rechargeable batteries as claimed in claim 1, wherein the carboxyl group is -C(=O)OH.

4. The positive electrode additive for a rechargeable battery as described in claim 1, wherein R1 is the heat-stabilizing group, and At least one of R2, R3, R5 and R6 is the heat-stabilizing group.

5. The positive electrode additive for a rechargeable battery as claimed in claim 4, wherein at least one of R2 and R6 is the thermally stabilizing group.

6. The positive electrode additive for a rechargeable battery as claimed in claim 4, wherein at least one of R3 and R5 is the thermally stabilizing group.

7. The positive electrode additive for a rechargeable battery as claimed in claim 1, wherein R1 and R6 above are each independently hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl or substituted or unsubstituted C2-C5 alkynyl, -C(=O)H, -C(=O)OH and a heat-stabilizing group.

8. The positive electrode additive for a rechargeable battery as claimed in claim 1, wherein R1 and R6 above are each independently hydrogen, substituted or unsubstituted C1-C3 alkyl, substituted or unsubstituted C2-C3 alkenyl or substituted or unsubstituted C2-C3 alkynyl, -C(=O)H, -C(=O)OH and a heat-stabilizing group.

9. The positive electrode additive for a rechargeable battery as claimed in claim 1, wherein the additive comprises at least one compound selected from the group consisting of formulas 1A to 1F: [Formula 1A] [Formula 1B] [Formula 1C] [Formula 1D] [Formula 1E] [Formula 1F] 。 10. A positive electrode slurry for a rechargeable battery, comprising: The positive electrode additive according to claims 1 to 9; Positive electrode active material; Adhesive; and Conductive materials.

11. The positive electrode slurry for a rechargeable battery as claimed in claim 10, wherein the additive content is 0.1 to 3 parts by weight relative to 100 parts by weight of the positive electrode active material.

12. The positive electrode paste for a rechargeable battery according to claim 10, wherein the content of the additive is 0.1 to 1 part by weight based on 100 parts by weight of the positive electrode active material.

13. The positive electrode paste for a rechargeable battery according to claim 10, wherein the positive electrode active material includes Ni, and the content of the Ni is 80 mol% or more.

14. The positive electrode paste for a rechargeable battery according to claim 10, wherein the positive electrode active material includes Ni, Co, and Al.

15. The positive electrode paste for a rechargeable battery according to claim 10, wherein the positive electrode active material, the conductive material, and the binder are present in a weight ratio of a:b:c, where a is 90 to 99, where b is 0.5 to 5, and where c is 0.5 to 5.

16. A rechargeable lithium battery, comprising: a positive electrode including a positive electrode active material layer; a negative electrode including a negative electrode active material layer; and an electrolyte, wherein the positive electrode active material layer includes: the positive electrode additive according to claims 1 to 9; a positive electrode active material; a binder; and a conductive material.

17. The rechargeable lithium battery according to claim 16, wherein the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium composite oxide represented by the following formula 3: Li x M 1 y M 2 z M 3 1-y-z O 2-a X a [Formula 3] M 1 M 2 and M 3 Each independently includes at least one element selected from the metals and combinations thereof, namely Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr, or La, and satisfying 0.5 ≤ x ≤ 1.8, 0 ≤ a ≤ 0.05, 0 < y ≤ 1, 0 ≤ z ≤ 1, and 0 ≤ y + z ≤ 1, 18. The rechargeable lithium battery of claim 17, wherein the M above... 1 For Ni. X includes at least one element selected from F, S, P, or Cl.

19. The rechargeable lithium battery according to claim 16, wherein the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based negative electrode active material, a Si-based negative electrode active material, a Sn-based negative electrode active material, or a combination thereof.

20. The rechargeable lithium battery according to claim 19, wherein the negative electrode active material includes a carbon-based negative electrode active material and a Si-based negative electrode active material.

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