Electrolyte for rechargeable lithium battery, rechargeable lithium battery including electrolyte, and compound

Abstract

The present application relates to an electrolyte for a rechargeable lithium battery, a rechargeable lithium battery including the electrolyte, and a compound, wherein the electrolyte includes a non-aqueous organic solvent, a lithium salt, and an additive.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from Korean Patent Application No. 10-2024-0051944, filed on April 18, 2024, which is hereby incorporated by reference in its entirety. Technical Field

[0003] Examples of the present disclosure relate to an electrolyte for a rechargeable lithium battery, a rechargeable lithium battery including the electrolyte, and a compound. Background Art

[0004] As the use of battery-powered electronic products, such as mobile phones, laptop computers, and electric vehicles, for example, increases, the demand for rechargeable lithium batteries that provide high energy density and high capacity also increases.

[0005] Rechargeable lithium batteries typically include a positive electrode and a negative electrode, each of which includes an active material and an electrolyte that allows for the intercalation and deintercalation of lithium ions. Rechargeable lithium batteries generate electrical energy through redox reactions that occur when lithium ions are intercalated into or deintercalated from the positive and negative electrodes.

[0006] In the case of a rechargeable lithium battery, in which a lithium salt is dissolved in a non-aqueous organic solvent and forms an electrolyte, the rechargeable lithium battery exhibits its characteristics through complex reactions between the positive electrode and the electrolyte, and between the negative electrode and the electrolyte. Therefore, using an appropriate electrolyte is a significant variable factor in improving the performance of rechargeable lithium batteries. Summary of the Invention

[0007] Examples of the present disclosure include an electrolyte for a rechargeable lithium battery having improved lifespan characteristics and stability at high temperatures.

[0008] Examples of the present disclosure also include rechargeable lithium batteries including an electrolyte.

[0009] Example embodiments of the present disclosure include an electrolyte for a rechargeable lithium battery, the electrolyte including at least a non-aqueous organic solvent, a lithium salt, and an additive represented by the following Formula 1.

[0010] [Formula 1]

[0011]

[0012] In the above formula 1,

[0013] R1 to R4 are each independently a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1 to C10 alkyl group, and

[0014] n is an integer of 1 to 5. For example, n is 1, 2, 3, 4 or 5.

[0015] In an exemplary embodiment of the present disclosure, a rechargeable lithium battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte. The electrolyte includes a non-aqueous organic solvent, a lithium salt, and an additive represented by Formula 1 above.

[0016] In an example embodiment of the present disclosure, a compound as an additive included in an electrolyte for a rechargeable lithium battery is represented by the following Formula 1-1:

[0017] [Formula 1-1]

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate example embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. In the drawings:

[0020] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure; and

[0021] Figures 2 to 5 is a schematic diagram illustrating a rechargeable lithium battery according to example embodiments. DETAILED DESCRIPTION

[0022] In order to fully understand the configuration and effects of the present disclosure, the exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be noted that the present disclosure is not limited to the exemplary embodiments described below and can be implemented in various forms and with various modifications. The exemplary embodiments are provided herein so that the present disclosure is thorough and complete and fully conveys the scope of the present disclosure to those skilled in the art.

[0023] In this document, it will be understood that when a component is referred to as being on another component, the component may be directly on the other component, or there may be a third component in between. In addition, in the drawings, the thickness of the components is exaggerated in order to effectively describe the technical content. The same reference numerals refer to the same elements throughout.

[0024] Unless otherwise specified herein, expressions in the singular may include expressions in the plural. In addition, unless otherwise specified, the phrase "A or B" may indicate "A but not B", "B but not A" or "A and B". The terms "comprises" and / or "comprising" used herein do not exclude the presence or addition of one or more other components.

[0025] The term "combination thereof as used herein can refer to a mixture, a stack, a composite, a copolymer, an alloy, a blend, or a reaction product of the components.

[0026] Herein, unless otherwise defined, "substituted" indicates that at least one hydrogen in a substituent or a compound is replaced by deuterium, halo, hydroxyl, amino, C1-C30 amine group, nitro, C1-C40 silyl group, C1-C30 alkyl group, C1-C10 alkylsilyl group, C6-C30 arylsilyl group, C3-C30 cycloalkyl group, C3-C30 heterocycloalkyl group, C6-C30 aryl group, C2-C30 heteroaryl group, C1-C20 alkoxy group, C1-C10 fluoroalkyl group, cyano, or a combination thereof.

[0027] Specifically, "substituted" can indicate that at least one hydrogen in a substituent or a compound is replaced by deuterium, halo, C1-C30 alkyl group, C1-C10 alkylsilyl group, C6-C30 arylsilyl group, C3-C30 cycloalkyl group, C3-C30 heterocycloalkyl group, C6-C30 aryl group, C2-C30 heteroaryl group, C1-C10 fluoroalkyl group, or cyano. For example, "substituted" can indicate that at least one hydrogen in a substituent or a compound is replaced by deuterium, halo, C1-C20 alkyl group, C6-C30 aryl group, C1-C10 fluoroalkyl group, or cyano. Further, "substituted" can indicate that at least one hydrogen in a substituent or a compound is replaced by deuterium, halo, C1-C5 alkyl group, C6-C18 aryl group, C1-C5 fluoroalkyl group, or cyano. For example, "substituted" can indicate that at least one hydrogen in a substituent or a compound is replaced by deuterium, cyano, halo, methyl, ethyl, propyl, butyl, phenyl, biphenyl, terphenyl, trifluoromethyl, or naphthyl. The alkyl group can include linear alkyl group and / or chain alkyl group. The cycloalkyl group can include cyclic alkyl group.

[0028] When the term "about" or "substantially" is used in the present specification in connection with a numerical value, it is intended to refer to a tolerance around the recited numerical value of ±10%. When a range is indicated, the range includes all values therebetween, such as in increments of 0.1%.

[0029] Figure 1 A simplified conceptual diagram of a rechargeable lithium battery according to an example embodiment of the present disclosure. Referring to Figure 1 The rechargeable lithium battery can include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

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

[0031] The electrolyte ELL can constitute a medium for transporting lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move toward the positive electrode 10 or the negative electrode 20 through the separator 30.

[0032] Positive electrode 10

[0033] The positive electrode 10 for the rechargeable lithium battery can 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 can include a positive electrode active material, and can further include a binder and / or a conductive material (e.g., an electrically conductive material).

[0034] For example, the positive electrode 10 can further include components that can constitute a sacrificial positive electrode.

[0035] The amount of the positive electrode active material can be about 90 wt% to about 99 wt% based on 100 wt% of the positive electrode active material layer AML1. The amounts of the binder and the conductive material can be about 0.5 wt% to about 5 wt% respectively based on 100 wt% of the positive electrode active material layer AML1.

[0036] The binder is configured to attach the positive electrode active material particles to each other sufficiently, and also attach the positive electrode active material to the positive electrode current collector COL1 sufficiently. Non-limiting examples of the binder can include at least one of polyvinyl alcohol, carboxymethyl cellulose, acrylonitrile rubber, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer including an oxirane, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon, etc.

[0037] The conductive material can impart electrical conductivity (e.g., electrically conductive) to the electrode. Any material that does not cause a chemical change in the battery (e.g., does not cause an undesirable chemical change in the rechargeable lithium battery) and conducts electrons can be used. Examples of the conductive material can include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials containing at least one of copper, nickel, aluminum, silver, etc. in the form of a metal powder or a metal fiber; conductive polymers such as polyphenylene derivatives; or a mixture thereof.

[0038] An Al foil can be used as the positive electrode current collector COL1, but is not limited thereto.

[0039] Positive electrode active material

[0040] The positive electrode active material may include a compound capable of intercalating and deintercalating lithium (lithiated intercalation compound). For example, at least one of a composite oxide of lithium and a metal including at least one of cobalt, manganese, and nickel may be used.

[0041] The composite oxide may be or include a lithium transition metal composite oxide. Examples of the lithium transition metal composite oxide may include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, nickel manganese oxides without cobalt, or combinations thereof.

[0042] As an example, the following compounds represented by any one or more of the following chemical formulae may be used. a A 1- b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5 and 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5 and 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5 and 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5 and 0<α<2); Li a Ni b Co c L 1 d G e O2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5 and 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8 and 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-b G bO2(0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8 and 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); or Li a FePO4(0.90≤a≤1.8).

[0043] In the above chemical formula, A is or includes Ni, Co, Mn, or a combination thereof; X is or includes Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is or includes O, F, S, P, or a combination thereof; G is or includes Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 is or includes Mn, Al, or a combination thereof.

[0044] The positive electrode active material can be or include, for example, a high-nickel-based positive electrode active material having a nickel content of greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol% based on 100 mol% of metals excluding lithium in a lithium transition metal composite oxide as a positive electrode active material. The high-nickel-based positive electrode active material can be capable of achieving a high capacity, and can be applied to a rechargeable lithium battery having a high capacity and a high density.

[0045] Negative electrode 20

[0046] The negative electrode 20 for the rechargeable lithium battery can include a negative electrode current collector COL2 and a negative electrode active material layer AML2 on the negative electrode current collector COL2. The negative electrode active material layer AML2 can include a negative electrode active material, and can further include a binder and / or an electrically conductive material (e.g., an electronically conductive material).

[0047] For example, the negative electrode active material layer AML2 can include about 90 wt% to about 99 wt% of a negative electrode active material, about 0.5 wt% to about 5 wt% of a binder, and about 0 wt% to about 5 wt% of an electrically conductive material.

[0048] The binder can be configured to sufficiently attach the negative electrode active material particles to each other, and also to sufficiently attach the negative electrode active material to the negative electrode current collector COL2. The binder can include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0049] The non-aqueous binder can include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide, polyimide, or a combination thereof.

[0050] The aqueous binder can include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoro rubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, or a combination thereof.

[0051] When the aqueous binder is used as a binder in the negative electrode active material layer AML2, a cellulose-based compound that can impart viscosity can be further included. The cellulose-based compound can include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof. The alkali metal can include at least one of Na, K, and Li.

[0052] The dry binder can be or include a polymer material capable of fibrillation. For example, the dry binder can be or include polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0053] The conductive material can be used to impart electrical conductivity (e.g., electronic conductivity) to the electrode. Any material that does not cause chemical changes in the battery (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons can be used. Non-limiting examples thereof can include: a carbon-based material such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; a metal-based material including at least one of copper, nickel, aluminum, silver, etc. in the form of a metal powder or a metal fiber; a conductive polymer such as a polyphenylene derivative; or a mixture thereof.

[0054] The negative electrode current collector COL2 can include a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0055] Negative electrode active material

[0056] The negative electrode active material can include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, or a transition metal oxide.

[0057] The material capable of reversibly intercalating / deintercalating lithium ions can include a carbon-based negative electrode active material, such as, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon can be graphite, such as, for example, amorphous, flaky, flake-like, spherical, or fibrous natural graphite or artificial graphite. The amorphous carbon can be soft carbon, hard carbon, meso-phase pitch carbonization product, calcined coke, or the like.

[0058] The lithium metal alloy includes lithium and an alloy of a metal 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.

[0059] The material capable of doping / de-doping lithium can be or include a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material can include silicon, a silicon-carbon composite, SiO x at least one of Sn (0 < x ≤ 2) and a Si-Q alloy (where Q includes an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, or a combination thereof). The Sn-based negative electrode active material can include Sn, SnO x at least one of Sn (0 < x ≤ 2) and a Si-Q alloy (where Q includes an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, or a combination thereof). The Sn-based negative electrode active material can include Sn, SnO

[0060] The silicon-carbon composite can be or include a composite of silicon and amorphous carbon. According to an example embodiment, the silicon-carbon composite can be or include silicon particles and amorphous carbon coated on surfaces of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which primary silicon particles are gathered and an amorphous carbon coating layer (shell) on surfaces of the secondary particles. The amorphous carbon can also be between the primary silicon particles, and, for example, the primary silicon particles can be coated with the amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0061] The silicon-carbon composite can further include crystalline carbon. For example, the silicon-carbon composite can include a core including crystalline carbon and silicon particles, and an amorphous carbon coating layer on a surface of the core.

[0062] The Si-based negative electrode active material or the Sn-based negative electrode active material can be combined with the carbon-based negative electrode active material.

[0063] Separator 30

[0064] According to a type of the rechargeable lithium battery, a separator 30 can be between the positive electrode 10 and the negative electrode 20. The separator 30 can include polyethylene, polypropylene, polyvinylidene fluoride, or a multi-layer thin film of two or more layers thereof, such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, or the like.

[0065] The separator 30 can include a porous substrate and a coating layer on one surface or both surfaces of the porous substrate, the coating layer including an organic material, an inorganic material, or a combination thereof.

[0066] The porous substrate can be or include a polymeric film formed of or containing a copolymer or a mixture of any one of the following polymers or two or more thereof: a polyolefin (including at least one of polyethylene and polypropylene), a polyester (such as polyethylene terephthalate and polybutylene terephthalate), a polyacetal, a polyamide, a polyimide, a polycarbonate, a polyether ketone, a polyaryletherketone, a polyetherimide, a polyamideimide, a polybenzimidazole, a polyethersulfone, a polyphenylene ether, a cyclic olefin copolymer, a polyphenylene sulfide, a polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon).

[0067] The organic material can include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0068] The inorganic material can include inorganic particles including Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, or a combination thereof, but is not limited thereto.

[0069] The organic material and the inorganic material can be mixed in one coating layer, or can exist in the form of a coating layer including the organic material and a coating layer including the inorganic material stacked.

[0070] Electrolyte ELL

[0071] The electrolyte ELL for the rechargeable lithium battery can include a non-aqueous organic solvent and a lithium salt.

[0072] The non-aqueous organic solvent can constitute a medium for transporting ions participating in an electrochemical reaction of the battery.

[0073] The non-aqueous organic solvent can be or include a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0074] The carbonate-based solvent can include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), etc.

[0075] The ester-based solvent can include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, methyl hydroxymethylgutarate lactone, valerolactone, and hexanolactone, etc.

[0076] The ether-based solvent can include at least one of dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran, etc. In addition, the ketone-based solvent can include cyclohexanone, etc. The alcohol-based solvent can include at least one of ethanol and isopropanol, etc. The aprotic solvent can include: nitriles such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and can include a double bond, an aromatic ring, or an ether bond), etc.; amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolanes, etc.

[0077] The non-aqueous organic solvent can be used alone or in combination of two or more.

[0078] In addition, when the carbonate-based solvent is used, a cyclic carbonate and a chain carbonate can be used in combination, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of about 1:1 to about 1:9.

[0079] The lithium salt dissolved in the non-aqueous organic solvent supplies lithium ions in the battery, ensures the basic operation of the rechargeable lithium battery, and improves the transport of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt include at least one of 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 SO2)(wherein x and y are integers of 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0080] Rechargeable lithium battery

[0081] The rechargeable lithium battery can be classified into a cylindrical battery, a prismatic battery, a pouch-type battery, or a coin-type battery, etc. according to its shape. Figures 2 to 5A schematic diagram illustrating a rechargeable lithium battery according to example embodiments. Figure 2 A cylindrical battery is shown, Figure 3 A prismatic cell is shown, and Figure 4 and Figure 5 Pouch type battery shown. Figures 2 to 5 , 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 case 50 in which the electrode assembly 40 is housed. The positive electrode 10, the negative electrode 20, and the separator 30 may be provided with an electrolyte (in Figures 2 to 5 (not shown) impregnation. Figure 2 As shown in , the rechargeable lithium battery 100 may include a sealing member 60 that seals the case 50. Figure 3 In the embodiment, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. Figure 4 and Figure 5 As shown in FIG, the rechargeable lithium battery 100 may include Figure 5 The electrode tab 70 illustrated in FIG. 1 may be, for example, Figure 4 The positive electrode tab 71 and the negative electrode tab 72 illustrated in FIG. 4 and constitute an electrical path for guiding current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100 .

[0082] Hereinafter, an electrolyte of a rechargeable lithium battery according to example embodiments of the present disclosure will be described in more detail.

[0083] An electrolyte for a rechargeable lithium battery according to example embodiments includes a non-aqueous organic solvent, a lithium salt, and additives.

[0084] The additive according to an example embodiment of the present disclosure may be represented by the following Formula 1:

[0085] [Formula 1]

[0086]

[0087] In the above formula 1,

[0088] R1 to R4 may each independently be a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1 to C10 alkyl group, and n may be an integer from 1 to 5. For example, when n is 1, the cyclic sulfur derivative portion may be a pentagonal ring.

[0089] R1 to R4 in the above formula 1 may be hydrogen. For example, the above formula 1 may be represented by the following formula 1-1 or formula 1-2.

[0090] [Formula 1-1]

[0091]

[0092] [Formula 1-2]

[0093]

[0094] In an example embodiment, the additive included in the electrolyte for a rechargeable lithium battery according to the present disclosure can be or include a compound represented by the following Formula 1-1:

[0095] [Formula 1-1]

[0096]

[0097] The additive according to an example embodiment of the present disclosure can be or include an aromatic ring compound having two ring structures, in which a ring containing a sulfonic acid group (-SO3-) and a benzene ring are fused.

[0098] The additive according to an example embodiment of the present disclosure has a sulfonic acid (-SO3-) functional group, and can thus form a stable film on the surface of the positive electrode, thereby reducing or inhibiting decomposition of the positive electrode active material. Accordingly, gas generation caused by decomposition of the positive electrode active material can be reduced or inhibited.

[0099] The benzene ring included in the additive according to an example embodiment of the present disclosure can reduce or inhibit decomposition of the positive electrode active material by forming a cathode electrolyte interface (CEI) film on the surface of the positive electrode through oxidation. Accordingly, gas generation caused by decomposition of the positive electrode active material can be reduced or inhibited.

[0100] The additive according to an example embodiment of the present disclosure can have a more stable and stronger binding force through the fusion of the carbon atom next to the oxygen atom of the aromatic benzene ring and the sulfone ring. These structural properties reduce or inhibit the elution of transition metals, and can effectively reduce or inhibit positive electrode degradation.

[0101] Accordingly, through the two ring structures, the additive according to an example embodiment of the present disclosure can more effectively contribute to the stability and cycle life characteristics of a rechargeable lithium battery at high voltage.

[0102] The content of the additive can be about 0.01 wt% to about 10 wt% with respect to the total amount of the electrolyte. For example, the content of the additive can be in the range of about 0.05 wt% to about 3 wt% with respect to the total amount of the electrolyte. When the content of the additive is less than the above range, a film can not be sufficiently formed on the lithium-based positive electrode and negative electrode, and when the content of the additive is greater than the above range, the capacity and life of the battery can decrease due to an increase in the resistance of the positive electrode and negative electrode.

[0103] The electrolyte according to the example embodiment can be prepared by a method of using a mixing process in which a lithium salt is dissolved in a non-aqueous organic solvent, and an additive is added. The process of mixing the electrolyte can be known in the field of electrolyte preparation, and will be appropriately selected and used by those skilled in the art.

[0104] The non-aqueous organic solvent can include at least one of ethylmethyl carbonate (EMC), ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), propyl propionate (PP), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and butylene carbonate (BC).

[0105] For example, the non-aqueous organic solvent can be or include a mixed solvent of ethylmethyl carbonate (EMC), ethylene carbonate (EC), and dimethyl carbonate (DMC).

[0106] For example, the content of ethylmethyl carbonate (EMC) can be about 30 vol% to about 50 vol% with respect to the total amount of the non-aqueous organic solvent. The content of ethylene carbonate (EC) can be about 10 vol% to about 30 vol% with respect to the total amount of the non-aqueous organic solvent. The content of dimethyl carbonate (DMC) can be about 30 vol% to about 50 vol% with respect to the total amount of the non-aqueous organic solvent.

[0107] The lithium salt can be or include at least one of LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), and LiC4F9SO3. According to the example embodiment, LiPF6may be used as the lithium salt.

[0108] The lithium salt can have a concentration of about 0.1 M to about 2.0 M. For example, the lithium salt can have a concentration of about 0.5 M or more or about 1.0 M or more. The lithium salt can have a concentration of about 2.0 M or less, about 1.7 M or less, or about 1.5 M or less. In the present disclosure, when the lithium salt has a concentration of about 0.1 M to about 2.0 M, the conductivity and viscosity of the electrolyte can be appropriately maintained.

[0109] In another example embodiment of the present disclosure, a rechargeable lithium battery can be provided, which includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte including a non-aqueous organic solvent, a lithium salt, and the above-described additive represented by Formula 1.

[0110] The positive electrode active material of the rechargeable lithium battery can include at least one of a cobalt-free nickel-manganese-based oxide, a lithium-nickel-based oxide, a lithium-cobalt-based oxide, a lithium-manganese-based oxide, and a lithium-iron-phosphate-based compound. Specifically, the positive electrode active material of the rechargeable lithium battery can be, for example, a cobalt-free nickel-manganese-based oxide.

[0111] In the rechargeable lithium battery using an electrolyte according to the disclosure, 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.

[0112] The Si-based negative electrode active material can include a core including Si-based particles and a coating layer including amorphous carbon. The Si-based particles can include silicon particles, silicon-carbon composites, SiO x at least one of Si and Si alloy.

[0113] The rechargeable lithium battery can operate at a high voltage of about 4.4 V or more.

[0114] As a non-limiting example, the rechargeable lithium battery can be used for, for example, automobiles, mobile phones, and / or various types of electronic devices.

[0115] Hereinafter, embodiments and comparative examples of the disclosure will be described. However, the following examples are presented only as exemplary embodiments of the disclosure, and the disclosure is not limited to the following examples.

[0116] Examples and comparative examples

[0117] Synthesis Example 1

[0118] 0.1 mmol of 2-hydroxybenzyl alcohol and 0.125 mmol of sodium bisulfite were added dropwise to a Schlenk flask containing 100 ml of H2O, and then stirred under reflux for 24 hours. Thereafter, excess phosphorus oxychloride was added to the compound obtained by precipitating the filtrate, and the mixture was reacted without a solvent (neat) at 125°C for 1 hour. Subsequently, a compound represented by Formula 1-1 below was obtained as an additive by purification using a Soxhlet extractor:

[0119] [Formula 1-1]

[0120]

[0121] * 1H NMR (400 MHz, CDC13): d 4.50 (s, 2H), 7.10 (d, J = 8.2 Hz, 1H) 7.20 (dd, J = 8.2, 7.6 Hz, 1H), 7.33 (d, J = 7.4 Hz, 1H), 7.40 (dd, J = 7.6, 7.4 Hz, 1H).

[0122] Example 1

[0123] (1) Preparation of electrolyte

[0124] 1.15 M LiPF6was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), methyl ethyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:40:40, and 0.5 wt% of the additive prepared in Synthesis Example 1 represented by Formula 1-1 was added with respect to the total amount of the electrolyte to prepare the electrolyte.

[0125] Here, the additive represented by Formula 1-1 prepared in Synthesis Example 1 was used.

[0126] (2) Preparation of rechargeable lithium battery

[0127] 97 wt% of NMX (LiNiMnO) as a positive electrode active material, 0.5 wt% of artificial graphite powder, 0.8 wt% of carbon black, 0.2 wt% of acrylonitrile rubber, and 1.5 wt% of polyvinylidene fluoride (PVdF) as a conductive material were mixed and added to N-methylpyrrolidone, and then the mixture was stirred for 30 minutes using a mechanical stirrer to prepare a positive electrode active material slurry. The positive electrode active material slurry was applied to an aluminum current collector 20 μm thick using a doctor blade so as to be 60 μm thick, dried in a hot air dryer at 100°C for 0.5 hours, dried again under vacuum at 120°C for 4 hours, and then roll-pressed to prepare a positive electrode.

[0128] 98 wt% of a negative electrode active material in which artificial graphite and silicon-carbon composite were mixed in a weight ratio of 93:7, 1 wt% of styrene-butadiene rubber (SBR), and 1 wt% of carboxymethyl cellulose (CMC) were mixed, and then added to distilled water and stirred for 60 minutes using a mechanical stirrer to prepare a negative electrode active material slurry. The negative electrode active material slurry was applied to a copper current collector 10 μm thick using a doctor blade so as to be 60 μm thick, dried in a hot air dryer at 100°C for 0.5 hours, dried again under vacuum at 120°C for 4 hours, and then roll-pressed to prepare a negative electrode.

[0129] An electrode assembly was prepared by assembling the positive electrode, the negative electrode, and a polyethylene separator 10 μm thick, and an electrolyte was injected to prepare a rechargeable lithium battery.

[0130] Example 2

[0131] An electrolyte and a rechargeable lithium battery were prepared in substantially the same manner as in Example 1, except that 0.1 wt% of an additive represented by Formula 1-1 was used.

[0132] Example 3

[0133] An electrolyte and a rechargeable lithium battery were prepared in substantially the same manner as in Example 1, except that 1.0 wt% of an additive represented by Formula 1-1 was used.

[0134] Example 4

[0135] An electrolyte and a rechargeable lithium battery were prepared in substantially the same manner as in Example 1, except that 3.0 wt% of an additive represented by Formula 1-1 was used.

[0136] Example 5

[0137] An electrolyte and a rechargeable lithium battery were prepared in substantially the same manner as in Example 1, except that an additive represented by the following Formula 1-2 was used.

[0138] [Formula 1-2]

[0139]

[0140] Comparative Example 1

[0141] An electrolyte and a rechargeable lithium battery were prepared in substantially the same manner as in Example 1, except that an additive represented by Formula 1-1 was not used during the preparation of the electrolyte.

[0142] Comparative Example 2

[0143] An electrolyte and a rechargeable lithium battery were prepared in substantially the same manner as in Example 1, except that an additive represented by the following Formula 1-3 was used.

[0144] [Formula 1-3]

[0145]

[0146] Evaluation examples

[0147] The rechargeable lithium battery was evaluated in the following manner.

[0148] Evaluation 1: Evaluation of high-temperature storage characteristics (DC-IR increase rate)

[0149] The value of ΔV / ΔI (voltage change amount / current change amount) as an initial direct current internal resistance (initial DC-IR) of the rechargeable lithium battery prepared according to the examples and comparative examples was measured, and then the maximum energy state inside the battery was set to a fully charged state (SOC 100%) and stored under the condition at a high temperature (60°C) for 30 days, the DC-IR was measured, and the DC-IR increase rate (%) was calculated according to Equation 1 below, and the results are shown in Table 1 below.

[0150] Equation 1

[0151] DC-IR increase rate (%) = (DC-IR after 30 days / initial DC-IR) * 100

[0152] [Table 1]

[0153]

[0154] Evaluation 2: Evaluation of high-temperature gas generation characteristics

[0155] The high-temperature gas generation characteristics of the rechargeable lithium batteries according to the examples and comparative examples were evaluated. For this purpose, the rechargeable lithium batteries according to the examples and comparative examples were charged to about 4.25 V at about 45°C, and then left to stand at about 60°C for about 7 days.

[0156] In order to determine the gas reduction effect, the initial gas generation amount of the battery and the gas generation amount of the battery on the 7th day of standing were each measured, and the results are shown in Table 2 below.

[0157] [Table 2]

[0158]

[0159] Evaluation 3: Evaluation of room temperature and high-temperature charge / discharge cycle characteristics

[0160] The rechargeable lithium batteries prepared in the examples and comparative examples were subjected to 0.33C charge (CC / CV, 4.45 V cut-off) / 1.0C discharge (CC, 3.0 V cut-off) 200 times cycles at room temperature (25°C) and at high temperature (45°C), and then the discharge capacity was measured and the capacity retention rate was calculated, and the results are shown in Table 3 below. The capacity retention rate was calculated according to Equation 2 below.

[0161] Equation 2

[0162] Capacity retention rate (%) = (discharge capacity after 200 cycles / initial discharge capacity) * 100

[0163] [Table 3]

[0164]

[0165] Overall evaluation

[0166] Referring to Table 1, when the electrolytes containing the additive according to example embodiments of the present disclosure (Examples 1 to 5) were used, they exhibited improved storage performance at high temperature (60° C.) compared to the electrolyte containing no additive represented by Formula 1-1 (Comparative Example 1).

[0167] Referring to Table 2, it was found that the rechargeable lithium batteries prepared according to Comparative Examples 1 and 2 generated a large amount of gas when stored at a high temperature (60° C.) compared to the rechargeable lithium batteries prepared according to Examples 1 to 5. Accordingly, the rechargeable lithium battery according to the present disclosure using the additive specifically represented by Formula 1 can effectively reduce or suppress the generation of gas at a high temperature (60° C.).

[0168] It was found that Comparative Example 2, in which a cyclic compound containing only a sulfonic acid group (-SO3-) was used as an additive, generated a large amount of gas when stored at a relatively high temperature (60°C) compared to the Examples.

[0169] Referring to Table 3, the electrolyte containing the additive according to the exemplary embodiment of the present disclosure has improved cycle characteristics and life characteristics of the battery at room temperature and under high temperature storage conditions, compared to the comparative example.

[0170] The electrolyte for a rechargeable lithium battery according to example embodiments stabilizes an electrode while reducing or suppressing an increase in resistance, and may thus produce effects of improving lifespan characteristics and stability at high temperatures.

[0171] Although the exemplary embodiments of the present disclosure have been described above, the scope of the present disclosure is not limited to the exemplary embodiments. Various modifications may be made to the exemplary embodiments without departing from the spirit and scope of the present disclosure as defined by the claims, and these modifications are included within the scope of the present disclosure.

Claims

1. An electrolyte for a rechargeable lithium battery, the electrolyte comprising: a non-aqueous organic solvent; a lithium salt; and an additive represented by the following Formula 1: Formula 1 wherein in the above Formula 1, R1 to R4 are each independently a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1 to C10 alkyl group, and n is an integer of 1 to 5. 2.The electrolyte for a rechargeable lithium battery according to claim 1, wherein the additive is represented by one of the following Formulae 1-1 and 1-2: 3.The electrolyte for a rechargeable lithium battery according to claim 1, wherein the amount of the additive is 0.01 wt% to 10 wt% with respect to the total weight of the electrolyte. 4.The electrolyte for a rechargeable lithium battery according to claim 1, wherein the non-aqueous organic solvent comprises at least one of methyl ethyl carbonate, ethylene carbonate, dimethyl carbonate, propylene carbonate, propyl propionate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.

5. The electrolyte for rechargeable lithium batteries according to claim 1, wherein the lithium salt comprises at least one of LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, Li(FSO2)2N, LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium bis(oxalato)borate, wherein x and y are integers of 1 to 20. 6.The electrolyte for a rechargeable lithium battery according to claim 1, wherein the lithium salt has a concentration of 0.1 M to 2.0 M. 7.A rechargeable lithium battery comprising: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and the electrolyte according to any one of claims 1 to 6. 8.The rechargeable lithium battery according to claim 7, wherein the positive electrode active material comprises at least one of a cobalt-free nickel-manganese-based oxide, a lithium-nickel-based oxide, a lithium-cobalt-based oxide, a lithium-manganese-based oxide, and a lithium-iron-phosphate-based compound. 9.The rechargeable lithium battery according to claim 7, 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, and a Sn-based negative electrode active material. 10.The rechargeable lithium battery according to claim 9, wherein the Si-based negative electrode active material comprises a silicon-carbon composite. 11.The rechargeable lithium battery according to claim 7, wherein the rechargeable lithium battery is configured to operate at a high voltage of 4.4 V or more. 12.A compound represented by the following Formula 1-1: Formula 1-1 ​

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