Electrolyte for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

Disclosed are an electrolyte solution for a rechargeable lithium battery and a rechargeable lithium battery including the electrolyte solution. The electrolyte comprises a non-aqueous organic solvent, a lithium salt and an additive. The additive includes a first compound represented by Chemical Formula 1 and a second compound represented by Chemical Formula 2. Detailed descriptions of Chemical Formula 1 and Chemical Formula 2 are given in this description. # imgabs0 #

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2024-0033271 filed in the Korean Intellectual Property Office on March 8, 2024, the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] Recently, with the rapid popularization of electronic devices using batteries (such as mobile phones, laptop computers and electric vehicles), interest in rechargeable lithium batteries with high energy density and high capacity has increased rapidly. Therefore, intensive research has been conducted to improve the performance of rechargeable lithium batteries.

[0005] A rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode and the negative electrode each include an active material in which intercalation and deintercalation (e.g., intercalation and deintercalation of lithium ions) are possible, and if lithium ions are intercalated and deintercalated, electric energy is generated due to oxidation and reduction reactions.

[0006] Non-aqueous organic solvents containing dissolved lithium salts serve as electrolytes for rechargeable lithium batteries. The characteristics of rechargeable lithium batteries are manifested through complex reactions between the positive electrode and the electrolyte, and between the negative electrode and the electrolyte. Accordingly, using a suitable or appropriate electrolyte is an important factor in improving rechargeable lithium batteries. Summary of the Invention

[0007] Embodiments of the present disclosure provide an electrolyte for a rechargeable lithium battery having improved high temperature lifespan and high temperature stability characteristics.

[0008] Embodiments of the present disclosure provide a rechargeable lithium battery including an electrolyte.

[0009] According to an embodiment of the present disclosure, an electrolyte for a rechargeable lithium battery may include: a non-aqueous organic solvent; a lithium salt; and an additive.

[0010] The additive may include a first compound represented by Chemical Formula 1 and a second compound represented by Chemical Formula 2.

[0011] Chemical formula 1

[0012]

[0013] In Chemical Formula 1,

[0014] X 1It may be a fluoro group, a chloro group, a bromo group or an iodo group.

[0015] R 1 ~R 6 They may each independently be hydrogen, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C2-C20 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C20 aryl or substituted or unsubstituted C2-C20 heteroaryl.

[0016] n can be an integer of 0 or 1.

[0017] Chemical formula 2

[0018]

[0019] In Chemical Formula 2,

[0020] R 7 ~R 9 They may each independently be hydrogen, halogen, substituted or unsubstituted C1-C10 alkyl, or substituted or unsubstituted C3-C10 cycloalkyl.

[0021] According to an embodiment of the present disclosure, a rechargeable lithium battery may include: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte for a rechargeable lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, together with the specification, illustrate embodiments of the presently disclosed subject matter and, together with the description, serve to explain principles of embodiments of the presently disclosed subject matter.

[0023] Figure 1 A simplified conceptual diagram showing a rechargeable lithium battery according to an embodiment of the present invention is illustrated.

[0024] Figures 2 to 5 A conceptual diagram showing a simplified diagram of a rechargeable lithium battery according to an embodiment, wherein Figure 2 shows a cylindrical battery, Figure 3 A prismatic cell is shown, and Figure 4 and Figure 5 A pouch-type battery is shown. DETAILED DESCRIPTION

[0025] In order to fully understand the configuration and effect examples of the subject matter of the present disclosure, some 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 following example embodiments and can be implemented in various suitable forms. On the contrary, the example embodiments are provided only to disclose the subject matter of the present disclosure and to enable those skilled in the art to fully understand the scope of the present disclosure.

[0026] In this description, it will be understood that if an element is referred to as being on another element, the element may be directly on the other element, or there may be intervening elements therebetween. In the drawings, the size (e.g., thickness) of some components may be exaggerated to effectively explain the technical content of the present disclosure. The same reference numerals throughout the specification refer to the same elements.

[0027] Unless otherwise specifically stated in this specification, expressions in the singular may include expressions in the plural. In an embodiment, unless otherwise specifically stated, the phrase "A or B" may indicate "A but not B", "B but not A", or "A and B". The terms "comprises / includes" and / or "comprising / including" used in this description do not exclude the existence or addition of one or more other components.

[0028] As used herein, the term "combination thereof" may refer to a mixture, stack, composite, copolymer, alloy, blend, and / or reaction product of the components.

[0029] Unless specifically defined otherwise in this description, the particle size may be an average particle size. In an embodiment, the particle size indicates the average particle size (D 50 The average particle size (D) can be measured by any appropriate method commonly used in the art, for example, by a particle size analyzer, a transmission electron microscope (TEM) image, and / or a scanning electron microscope (SEM) image. 50 In an embodiment, a dynamic light-scattering measurement device is used for data analysis to count the number of particles in each particle size range, and then the average particle size (D 50 ) value. In an embodiment, laser scattering method can be used to measure the average particle size (D 50 In the laser scattering method, target particles are dispersed in a dispersion solvent, introduced into a laser scattering particle measuring device (e.g., MT3000 commercially available from Microtrac, Inc.), irradiated with 28 kHz ultrasonic waves at a power of 60 W, and then the average particle size (D) is calculated in the measuring device based on the 50% particle size distribution standard. 50 ).

[0030] In this description, unless otherwise limited, the term "substituted" may refer to a substituent or a compound in which at least one hydrogen is replaced by deuterium, halo, hydroxy, amino, C1-C30 amine, 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.

[0031] In more detail, the term "substituted" may indicate that at least one hydrogen of a substituent or compound is replaced by deuterium, a halide, a C1-C30 alkyl group, a C1-C10 alkylsilyl group, a C6-C30 arylsilyl group, a C3-C30 cycloalkyl group, a C3-C30 heterocycloalkyl group, a C6-C30 aryl group, a C2-C30 heteroaryl group, a C1-C10 fluoroalkyl group, or a cyano group. For example, the term "substituted" may indicate that at least one hydrogen of a substituent or compound is replaced by deuterium, a halide, a C1-C20 alkyl group, a C6-C30 aryl group, a C1-C10 fluoroalkyl group, or a cyano group. In an embodiment, the term "substituted" may indicate that at least one hydrogen of a substituent or compound is replaced by deuterium, a halide, a C1-C5 alkyl group, a C6-C18 aryl group, a C1-C5 fluoroalkyl group, or a cyano group. For example, the term "substituted" may indicate that at least one hydrogen of the substituent or compound is replaced by deuterium, cyano, halo, methyl, ethyl, propyl, butyl, phenyl, biphenyl, terphenyl, trifluoromethyl, or naphthyl.

[0032] The alkyl group may include a linear alkyl group and / or a branched alkyl group, and the cycloalkyl group may include a cyclic alkyl group.

[0033] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present disclosure is illustrated. Figure 1 , a rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0034] The positive electrode 10 and the negative electrode 20 may be separated from each other by a separator 30. The separator 30 may be between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may contact the electrolyte ELL. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with the electrolyte ELL.

[0035] The electrolyte ELL may be a medium through which lithium ions are transferred between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, the lithium ions may move toward one of the positive electrode 10 and the negative electrode 20 through the separator 30.

[0036] Positive electrode 10

[0037] The positive electrode 10 for a rechargeable lithium battery may include a positive electrode current collector COL1 and a positive electrode active material layer AML1 on the positive electrode current collector COL1. The positive electrode active material layer AML1 may include a positive electrode active material and further include a binder and / or a conductive material (e.g., an electrically conductive material).

[0038] For example, the positive electrode 10 may further include a component that may serve as a sacrificial positive electrode.

[0039] The amount of the positive electrode active material may be in the range of about 90 wt % to about 99 wt % based on 100 wt % of the positive electrode active material layer AML1. The amount of the binder and the conductive material may each be in the range of about 0.5 wt % to about 5 wt % based on 100 wt % of the positive electrode active material layer AML1.

[0040] The binder can be used to improve the attachment of the positive electrode active material particles to each other and can also be used to improve the attachment of the positive electrode active material to the positive electrode current collector COL 1. The binder may include, for example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethylene oxide-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and / or nylon, but the present disclosure is not limited thereto.

[0041] Conductive materials can be used to provide conductivity (e.g., electrical conductivity) to the electrodes, and any suitable conductive material that does not cause chemical changes in the rechargeable lithium battery (e.g., undesirable chemical changes in the rechargeable lithium battery) can be used as the conductive material constituting the rechargeable lithium battery. The conductive material may include, for example, carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes); metal powders and / or metal fibers containing one or more selected from copper, nickel, aluminum, and silver; conductive polymers (e.g., conductive polymers) such as polyphenylene derivatives; or mixtures thereof.

[0042] An aluminum (Al) foil may be used as the positive electrode current collector COL1 , but the present disclosure is not limited thereto.

[0043] Positive electrode active material

[0044] The positive electrode active material in the positive electrode active material layer AML1 may include a compound that can reversibly intercalate and deintercalate lithium (e.g., a lithiated intercalation compound). For example, the positive electrode active material may include at least one type of composite oxide including lithium and a metal selected from the group consisting of cobalt, manganese, nickel, and combinations thereof.

[0045] The composite oxide may include a lithium transition metal composite oxide, for example, a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a nickel manganese-based oxide not containing cobalt, or a combination thereof.

[0046] For example, the positive electrode active material may include a compound represented by one of the following chemical formulas: Li a A 1-b X b O 2- c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni 1-b- c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni b Co c L 1 d G e O2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1), Li 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 aMn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5), Li (3-f) Fe2(PO4)3(0≤f≤2) and Li a FePO4(0.90≤a≤1.8).

[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, a rare earth element 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 L 1 Mn, Al or a combination thereof.

[0048] For example, the positive electrode active material may be a high nickel-based positive electrode active material having a nickel content of about 80 mol% or more, about 85 mol% or more, about 90 mol% or more, about 91 mol% or more, or about 94 mol% or more and about 99 mol% or less, based on 100 mol% of the lithium-free metal in the lithium transition metal composite oxide (based on 100 mol% of the metal other than lithium). The high nickel-based positive electrode active material can achieve high capacity and can therefore be applied to high capacity and high energy density rechargeable lithium batteries.

[0049] Negative electrode 20

[0050] The negative electrode 20 for a rechargeable lithium battery may 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 may include a negative electrode active material and may further include a binder and / or a conductive material (e.g., an electrically conductive material).

[0051] For example, the negative electrode active material layer AML2 may 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 a conductive material (eg, an electrically conductive material).

[0052] The binder can be used to improve the attachment of the negative electrode active material particles to each other and also to improve the attachment of the negative electrode active material to the negative electrode current collector COL 2. The binder can include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0053] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0054] The aqueous binder may include styrene butadiene rubber, (meth)acrylated styrene butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol or a combination thereof.

[0055] If an aqueous binder is used as the binder in the negative electrode active material layer AML2, a cellulose compound capable of providing or increasing viscosity may be further included. The cellulose compound may include one or more selected from carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof. The alkali metal may include Na, K, and / or Li.

[0056] The dry binder may include a fiberizable polymer material, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0057] Conductive materials can be used to provide electrical conductivity (e.g., electrical conductivity) to the electrodes, and any suitable conductive material that does not cause chemical changes in the rechargeable lithium battery (e.g., undesirable chemical changes in the rechargeable lithium battery) can be used as the conductive material constituting the rechargeable lithium battery. For example, the conductive material may include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes); metal powders and / or metal fibers including one or more selected from copper, nickel, aluminum, and silver; conductive polymers (e.g., conductive polymers) (e.g., polyphenylene derivatives); or mixtures thereof.

[0058] The negative electrode current collector COL2 may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal (eg, an electrically conductive metal), or a combination thereof.

[0059] Negative electrode active material

[0060] The negative electrode active material in the negative electrode active material layer AML2 may include a material that can reversibly intercalate and deintercalate lithium ions, lithium metal, a lithium metal alloy, a material that can dope and dedope lithium, and / or a transition metal oxide.

[0061] The material that can reversibly intercalate and deintercalate lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. For example, the crystalline carbon may include graphite (such as amorphous, flaky, sheet-like, spherical, and / or fibrous natural graphite and / or artificial graphite), and the amorphous carbon may include soft carbon, hard carbon, mesophase pitch carbon, and / or calcined coke.

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

[0063] The material that can be doped and undoped with lithium may include a Si-based negative electrode active material and / or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is 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), or a combination thereof. The Sn-based negative electrode active material may include Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0064] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to an embodiment, the silicon-carbon composite may have a structure in which amorphous carbon is coated on the surface of silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are aggregated, and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon may also be between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

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

[0066] The Si-based negative electrode active material and / or the Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0067] In an embodiment, the negative electrode active material may include a carbon-based negative electrode active material and / or a silicon-based negative electrode active material (i.e., a Si-based negative electrode active material). The negative electrode active material may include carbon (C) and silicon (Si). For example, the carbon-based negative electrode active material may include graphite, and the silicon-based negative electrode active material may include silicon nanoparticles.

[0068] The weight ratio of the silicon nanoparticles to the graphite may be in the range of about 0.001 to about 20 or about 1 to about 10. If the weight ratio of the silicon nanoparticles to the graphite is within the above range, it may increase the buffering effect on the volume expansion of the silicon nanoparticles to achieve excellent conductivity and improve the life characteristics.

[0069] The silicon nanoparticles may be nanosized silicon particles. The silicon nanoparticles may have an average particle size in the range of about 50 nm to 300 nm, for example, about 80 nm to 200 nm. Nanosized silicon particles can facilitate the intercalation and deintercalation of lithium ions and achieve low ionic resistance, thereby suppressing or reducing volume expansion and improving lifespan characteristics.

[0070] Diaphragm 30

[0071] Depending on the type (or kind) of the rechargeable lithium battery, the separator 30 may be between the positive electrode 10 and the negative electrode 20. The separator 30 may include one or more selected from a polyethylene separator, a polypropylene separator, and a polyvinylidene fluoride separator, and may be a multilayer separator thereof (such as a polyethylene / polypropylene double-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, and / or a polypropylene / polyethylene / polypropylene three-layer separator).

[0072] The separator 30 may include a porous substrate and a coating layer on one surface or opposite surfaces (eg, two opposite surfaces) of the porous substrate, the coating layer including an organic material, an inorganic material, or a combination thereof.

[0073] The porous substrate may be a polymer layer comprising one selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetals, polyamides, polyimides, polycarbonates, polyetherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (e.g., Teflon), and / or may be a copolymer and / or mixture comprising two or more of the above-mentioned materials.

[0074] The organic material may include a polyvinylidene fluoride-based copolymer and / or a (meth)acrylic acid-based copolymer.

[0075] The inorganic material may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, or combinations thereof, but the present disclosure is not limited thereto.

[0076] The organic material and the inorganic material may be mixed together in one coating layer, or may be a stack of a coating layer including an organic material and a coating layer including an inorganic material.

[0077] Electrolyte ELL

[0078] The electrolyte ELL for a rechargeable lithium battery may include a non-aqueous organic solvent and a lithium salt.

[0079] The non-aqueous organic solvent may serve as a medium for transporting ions participating in the electrochemical reaction of the rechargeable lithium battery.

[0080] The non-aqueous organic solvent may include a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent, or a combination thereof.

[0081] The carbonate-based solvent may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC) and / or butylene carbonate (BC).

[0082] The ester solvent may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonolactone, valerolactone, caprolactone and / or propyl propionate (PP).

[0083] Ether solvents may include dibutyl ether, tetraglyme, diglyme, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran and / or tetrahydrofuran. Ketone solvents may include cyclohexanone. Alcohol solvents may include ethanol and / or isopropanol. Aprotic solvents may include nitriles (such as R-CN, where R is a hydrocarbon group having a C2 to C20 linear, branched or cyclic structure and may include a double bond, an aromatic ring and / or an ether group); amides (such as dimethylformamide); dioxolanes (such as 1,3-dioxolane and / or 1,4-dioxolane); and / or sulfolane.

[0084] The nonaqueous organic solvent may be used alone or as a mixture of two or more species.

[0085] In an embodiment, if a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed together and used, and the cyclic carbonate and the chain carbonate may be mixed together in a volume ratio of about 1:1 to about 1:9.

[0086] The lithium salt may be a material dissolved in a non-aqueous organic solvent to serve as a supply source of lithium ions in a rechargeable lithium battery, and plays a role in ensuring the basic operation of the rechargeable lithium battery and promoting the movement of lithium ions between the positive electrode and the negative electrode. The lithium salt may include, for example, a material 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)(Cy F 2y+1 SO2) (wherein x and y are integers between 1 and 20), at least one of lithium trifluoromethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP) and lithium bis(oxalato)borate (LiBOB).

[0087] The electrolyte of the rechargeable lithium battery according to some embodiments of the present disclosure will be described in more detail below.

[0088] An electrolyte for a rechargeable lithium battery according to an embodiment may include a non-aqueous organic solvent, a lithium salt, and additives.

[0089] The additive may include a first compound represented by Chemical Formula 1 below and a second compound represented by Chemical Formula 2 below.

[0090] Chemical formula 1

[0091]

[0092] In Chemical Formula 1,

[0093] X 1 It may be a fluoro group, a chloro group, a bromo group or an iodo group.

[0094] R 1 ~R 6 They may each independently be hydrogen, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C2-C20 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C20 aryl or substituted or unsubstituted C2-C20 heteroaryl.

[0095] In an embodiment, n may be an integer of 0 or 1.

[0096] Chemical formula 2

[0097]

[0098] In Chemical Formula 2,

[0099] R 7 ~R 9 They may each independently be hydrogen, halogen, substituted or unsubstituted C1-C10 alkyl, or substituted or unsubstituted C3-C10 cycloalkyl.

[0100] The electrolyte can be prepared by a mixing process in which a lithium salt is dissolved in a non-aqueous organic solvent and the first compound and the second compound are added to the resulting mixture. The electrolyte mixing process can be any suitable process commonly used in the field of electrolyte manufacturing, and those skilled in the art should be able to appropriately select and use the electrolyte mixing process after reading this disclosure.

[0101] The non-aqueous organic solvent may include at least one selected from ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC) and butylene carbonate (BC).

[0102] In an embodiment, the non-aqueous organic solvent may be a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).

[0103] For example, the amount of ethylene carbonate (EC) that can be included is about 10% to about 30% by volume relative to the total volume of the non-aqueous organic solvent. The amount of ethyl methyl carbonate (EMC) solvent that can be included is about 5% to about 20% by volume relative to the total volume of the non-aqueous organic solvent. The amount of dimethyl carbonate (DMC) solvent that can be included is about 50% to about 80% by volume relative to the total volume of the non-aqueous organic solvent.

[0104] In an embodiment, the lithium salt may include LiPF6.

[0105] The lithium salt may have a concentration of about 0.1 M to about 2.0 M. For example, the lithium salt may have a concentration equal to or greater than about 0.5 M or equal to or greater than 1.0 M. The lithium salt may have a concentration equal to or less than about 2.0 M, equal to or less than about 1.7 M, or equal to or less than about 1.5 M. In the present disclosure, if the lithium salt has a concentration of about 0.1 M to about 2.0 M, the electrolyte may appropriately or suitably maintain its conductivity (e.g., ionic or electrical conductivity) and viscosity.

[0106] First compound

[0107] The first compound according to an embodiment of the present disclosure may be represented by Chemical Formula 1 below.

[0108] Chemical formula 1

[0109]

[0110] In Chemical Formula 1,

[0111] X 1 It may be a fluoro group, a chloro group, a bromo group or an iodo group.

[0112] R1 ~R 6 They may each independently be hydrogen, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C2-C20 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C20 aryl or substituted or unsubstituted C2-C20 heteroaryl.

[0113] In an embodiment, n may be an integer of 0 or 1.

[0114] The first compound may form a solid electrolyte interface (SEI) layer having high temperature stability and excellent ionic conductivity on the surface of the negative electrode. In an embodiment, the first compound may reduce gas generation due to decomposition reactions occurring in the electrolyte during high temperature storage. For example, the -PO2F functional group of the first compound may stabilize the thermal decomposition products of a lithium salt (such as LiPF6) and / or ions dissociated from the lithium salt to reduce the generation of gases (such as HF). The formation of an excellent SEI layer and the reduction in gas generation may contribute to improving the life characteristics of the battery and reducing the internal resistance.

[0115] If the first compound is used together with a high-nickel positive electrode active material and a negative electrode active material including graphite and silicon nanoparticles, the improvement in the lifespan characteristics and the reduction in internal resistance of the rechargeable lithium battery at high temperatures caused by the first compound can be more significant. For example, silicon nanoparticles can be used to increase battery capacity, but due to side reactions between the silicon nanoparticles and the electrolyte, there may be a problem of increased internal resistance of the battery (e.g., battery internal resistance). If the first compound is introduced as an additive, the side reactions between the silicon nanoparticles and the electrolyte can be suppressed or reduced, which can not only minimize or reduce the increase in battery internal resistance (e.g., battery internal resistance), but also maximize or increase battery capacity.

[0116] The first compound may include a cyclic phospholane derivative. Compared to linear phosphite derivatives, cyclic phospholane derivatives can provide rechargeable lithium batteries with significantly improved lifespan characteristics. This may be because linear phosphite derivatives induce side reactions of LiPF6 due to dissociated -PO2F functional groups and cause gas generation due to decomposition reactions of the electrolyte during high-temperature storage.

[0117] In an embodiment, Chemical Formula 1 may be represented by the following Chemical Formula 1A or the following Chemical Formula 1B.

[0118] Chemical Formula 1A

[0119]

[0120] Chemical formula 1B

[0121]

[0122] In Chemical Formula 1A and Chemical Formula 1B,

[0123] X 1 It may be a fluoro group, a chloro group, a bromo group or an iodo group.

[0124] R 1 ~R 6 They may each independently be hydrogen, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkoxy group, a substituted or unsubstituted C2-C10 alkenyl group, or a substituted or unsubstituted C2-C10 alkynyl group.

[0125] In an embodiment, R of Chemical Formula 1A 3 and R 4 Each may be hydrogen.

[0126] Selected from R 5 and R 6 At least one of them may be a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkoxy group, a substituted or unsubstituted C2-C10 alkenyl group, or a substituted or unsubstituted C2-C10 alkynyl group.

[0127] In an embodiment, the first compound may be one selected from the compounds listed in the following Group 1. That is, the first compound may be at least one selected from 2-fluoro-1,3,2-dioxaphospholane and 2-fluoro-4-methyl-1,3,2-dioxaphospholane.

[0128] Group 1

[0129]

[0130] Based on 100 parts by weight of the electrolyte for a rechargeable lithium battery, the first compound may have an amount of about 0.2 parts by weight to about 5.0 parts by weight. For example, based on 100 parts by weight of the electrolyte for a rechargeable lithium battery, the first compound may have an amount of about 0.5 parts by weight to about 1.5 parts by weight. The amount of the first compound may refer to the weight of the first compound included in the electrolyte based on the total weight of the electrolyte. If the amount of the first compound satisfies the above range, it is possible to maximize or increase the effect of reducing gas generation at high temperatures and the effect of forming an excellent SEI layer.

[0131] Second compound

[0132] The second compound according to an embodiment of the present disclosure may be represented by Chemical Formula 2 below.

[0133] Chemical formula 2

[0134]

[0135] In Chemical Formula 2,

[0136] R 7 ~R 9 They may each independently be hydrogen, halogen, substituted or unsubstituted C1-C10 alkyl, or substituted or unsubstituted C3-C10 cycloalkyl.

[0137] The second compound may have the effect of reducing gas generation and inhibiting or reducing the dissolution of the transition metal included in the positive electrode. Therefore, the rechargeable lithium battery can improve life characteristics and reduce internal resistance. For example, the triazole group of the second compound can form a film on the surface of the positive electrode by coordinating with the transition metal contained in the positive electrode active material, thereby reducing the gas generated by the side reaction at the interface between the positive electrode and the electrolyte, and inhibiting or reducing the degradation of the positive electrode surface. These effects can be more pronounced at high temperatures.

[0138] The second compound may include a 1,2,4-triazolyl group. Compared to a 1,2,3-triazolyl group, a 1,2,4-triazolyl group can significantly improve the high-temperature characteristics of a rechargeable lithium battery. For example, if a 1,2,4-triazolyl group is used with a high-nickel positive electrode active material, the 1,2,4-triazolyl group may be more effective. Compared to a 1,2,4-triazolyl group, if a 1,2,3-triazolyl group forms a film on the positive electrode surface by coordinating with the transition metal contained in the high-nickel positive electrode active material, the spatial arrangement of the 1,2,3-triazolyl group with the nickel may be less effective.

[0139] In an embodiment, the second compound may be represented by Chemical Formula 2A.

[0140] Chemical formula 2A

[0141]

[0142] Based on 100 parts by weight of the electrolyte for a rechargeable lithium battery, the amount of the second compound that can be included is from about 1 part by weight to about 5 parts by weight. The amount of the second compound may refer to the weight of the second compound included in the electrolyte based on the total weight of the electrolyte. If the amount of the second compound satisfies the above range, the suppression or reduction of degradation of the positive electrode surface and the reduction of gas generation at high temperatures can be maximized or increased to maximize or increase the improvement of the life characteristics of the rechargeable lithium battery and the reduction of internal resistance (e.g., internal resistance).

[0143] additive

[0144] The electrolyte for a rechargeable lithium battery according to the present disclosure may include a non-aqueous organic solvent, a lithium salt, and an additive. The additive may include a first compound and a second compound.

[0145] If the second compound is used in combination with the first compound, a synergistic effect may be produced. The combination of the first compound and the second compound can suppress or reduce the generation of gas, improve the capacity retention rate, and enhance the life characteristics of the rechargeable lithium battery. For example, the effect of the first compound in forming an excellent SEI layer and reducing gas generation and the effect of the second compound in suppressing or reducing the dissolution of the transition metal of the positive electrode and reducing gas generation can be produced simultaneously to maximize or increase the improvement in the characteristics of the rechargeable lithium battery. At high temperatures, this synergistic effect may be more pronounced.

[0146] Based on 100 parts by weight of the electrolyte for a rechargeable lithium battery, the amount of the additive that may be included is about 1.2 parts by weight to 10 parts by weight. The amount of the additive may refer to the weight of the additive included in the electrolyte based on the total weight of the electrolyte. If the amount of the additive satisfies the above range, the rechargeable lithium battery can be maximized or improved in terms of suppressing or reducing gas generation, increasing capacity retention, and enhancing life characteristics. At high temperatures, this improvement in battery characteristics may be more pronounced.

[0147] The weight ratio of the second compound to the first compound in the electrolyte may be in the range of about 0.1 to about 25. For example, the weight ratio of the second compound to the first compound in the electrolyte may be in the range of about 1 to about 5. Within the weight ratio range mentioned above, the improvement of the high temperature characteristics of the rechargeable lithium battery can be maximized or increased. If the weight ratio of the second compound to the first compound is less than the above range, the Coulomb effect may be abruptly reduced, and if the weight ratio of the second compound to the first compound is greater than the above range, a film may not be properly or sufficiently formed on the surface of the positive electrode.

[0148] Rechargeable lithium battery

[0149] Based on the shape of the rechargeable lithium battery, the rechargeable lithium battery can be classified into cylindrical, prismatic, pouch and / or coin types (or categories). Figures 2 to 5 , which illustrates a simplified conceptual diagram showing a rechargeable lithium battery according to an embodiment, Figure 2 shows a cylindrical battery, Figure 3 A prismatic cell is shown, and Figure 4 and Figure 5 Pouch type battery is shown. Figures 2 to 4 , the rechargeable lithium battery 100 may include an electrode assembly 40 in which a separator 30 is between a positive electrode 10 and a negative electrode 20, and may also include 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 impregnated with an electrolyte. Figure 2 As explained in FIG. 1 , the rechargeable lithium battery 100 may include a sealing member 60 that seals the housing 50. In an embodiment, as Figure 3 As explained in Figure 4 and Figure 5 As shown in Figure 5 , the rechargeable lithium battery 100 may include an electrode tab 70 ([[]] Figure 4 ) serving as a circuit path for guiding the current generated in the external lead electrode assembly 40, or a positive electrode tab 71 and a negative electrode tab 72 ([[]]

[0150] The rechargeable lithium battery according to an embodiment of the present disclosure may be applied to a motor vehicle, a mobile phone, and / or any other suitable electronic device, but the present disclosure is not limited thereto.

[0151] The rechargeable lithium battery according to an embodiment of the present disclosure may include: a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte for the rechargeable lithium battery described above.

[0152] The positive electrode active material may include a lithium composite oxide represented by Chemical Formula 3 below.

[0153] Chemical Formula 3

[0154] Li x M 1 <000008Q>M [[ID=J0]] 2 z M 3 1-y-z O 2-a X a

[0155] In Chemical Formula 3, x, y, z, and a may be 0.5 ≤ x ≤ 1.8, 0 ≤ a ≤ 0.05, 0 < y ≤ 1, 0 ≤ z ≤ 1, and 0 ≤ y + z ≤ 1.

[0156] M 1 , M 2 and M 3 may each independently include at least one element selected from Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr, and La.

[0157] X may include at least one element selected from F, S, P, and Cl.

[0158] In an embodiment, in Chemical Formula 3, M 1 may be Ni, y may be 0.8 ≤ y ≤ 1, and z may be 0 ≤ z ≤ 0.2. In an embodiment, in Chemical Formula 3, M 1 may be Ni, M2 Can be Co, and M 3 It may be Al. In an embodiment, in Chemical Formula 3, M 1 Can be Ni, M 2 Can be Co, and M 3 It may be Mn.

[0159] The negative electrode active material may include 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.

[0160] In an embodiment, the negative electrode active material may include a carbon-based negative electrode active material and / or a Si-based negative electrode active material. For example, the carbon-based negative electrode active material may include graphite, and the Si-based negative electrode active material may include silicon nanoparticles. The weight ratio of the silicon nanoparticles to the graphite may be in the range of about 0.001 to about 20. If the graphite and the silicon nanoparticles meet the above combination and weight ratio, the high-temperature performance of the rechargeable lithium battery may have the greatest or increased improvement.

[0161] In a rechargeable lithium battery according to an embodiment of the present disclosure, the electrolyte may decompose during the initial charge-discharge period, forming a film with passivation ability on the surface of the positive electrode and the negative electrode to improve high-temperature storage characteristics. Due to the acid (such as HF and PF5) generated by the thermal decomposition of lithium salts (LiPF6, etc.) widely used in rechargeable lithium batteries, the film may deteriorate. This acid corrosion can cause transition metals to dissolve from the positive electrode and increase the internal resistance of the battery due to structural changes on the surface. Therefore, due to the loss of metal elements as redox (reduction and oxidation) centers, the theoretical capacity can be reduced, which can lead to a decrease in capacity. The dissolved transition metal ions can be electrodeposited on the negative electrode, which reacts in a strong reduction potential range. Therefore, during electrodeposition, electrons can be consumed and the film can be destroyed, which in turn can expose the surface of the negative electrode and cause additional electrolyte decomposition reactions. Therefore, the surface resistance and irreversible capacity of the negative electrode can be increased, resulting in a problem of continuous reduction in battery cell capacity.

[0162] In the present disclosure, the triazole group of the second compound represented by the above Chemical Formula 2 may provide an unshared electron pair to capture PF5 and stabilize the LiPF6 salt, with the result that it is possible to remove the acid caused by the decomposition of the lithium salt.

[0163] The positive electrode active material of the rechargeable lithium battery may include one or more selected from lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium iron phosphate compounds, and nickel manganese oxides that do not contain cobalt. In an embodiment, the positive electrode active material of the rechargeable lithium battery may include nickel, cobalt, and aluminum. In an embodiment, the positive electrode active material of the rechargeable lithium battery may include nickel, cobalt, and manganese.

[0164] The negative electrode active material of the rechargeable lithium battery may include a carbon-based negative electrode active material, a silicon-based negative electrode active material, or any combination thereof. In an embodiment, the negative electrode active material of the rechargeable lithium battery may include a carbon-based negative electrode active material and a silicon-based negative electrode active material. For example, the carbon-based negative electrode active material may include graphite, and the silicon-based negative electrode active material may include silicon nanoparticles. The weight ratio of the silicon nanoparticles to the graphite may be in the range of about 0.001 to about 20.

[0165] Examples and comparative examples of the present disclosure will be described below. The following examples are merely exemplary embodiments of the present disclosure, and the present disclosure is not limited to the following examples.

[0166] Example 1

[0167] (1) Preparation of electrolyte

[0168] 1.5 M LiPF 6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed together at a volume ratio of about 20:10:70, and additives were added to prepare an electrolyte.

[0169] The additive includes 1 part by weight of the first compound based on 100 parts by weight of the electrolyte and 1 part by weight of the second compound based on 100 parts by weight of the electrolyte.

[0170] A material represented by the following Chemical Formula 1C and a material represented by the following Chemical Formula 2A are used as the first compound and the second compound, respectively.

[0171] Chemical formula 1C

[0172]

[0173] Chemical formula 2A

[0174]

[0175] (2) Manufacturing of rechargeable lithium batteries

[0176] LiNi as the positive electrode active material 0.91 Co 0.07 Al 0.02 O2, polyvinylidene fluoride as a binder, and Ketjen black as a conductive material were mixed together at a weight ratio of 97:2:1, and the mixture was dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0177] The positive electrode active material slurry was coated on an aluminum current collector with a thickness of 14 μm, dried at 110° C., and then pressed to fabricate a positive electrode.

[0178] Artificial graphite and silicon nanoparticles as a negative electrode active material mixed together in a weight ratio of 93:7, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener were mixed together in a weight ratio of 97:1:2, and the mixture was dispersed in distilled water to prepare a negative electrode active material slurry.

[0179] The negative electrode active material slurry was coated on a copper current collector with a thickness of 10 μm, dried at 100° C., and then pressed to fabricate a negative electrode.

[0180] The positive electrode, the negative electrode, and a polyethylene separator having a thickness of 25 μm were assembled together to manufacture an electrode assembly, and an electrolyte was introduced to manufacture a rechargeable lithium battery.

[0181] Example 2

[0182] An electrolyte and a rechargeable lithium battery were manufactured by substantially the same method as Example 1, except that the additive included 1 part by weight of the first compound and 2 parts by weight of the second compound based on 100 parts by weight of the electrolyte.

[0183] Example 3

[0184] An electrolyte and a rechargeable lithium battery were manufactured by substantially the same method as Example 1, except that the additive included 1 part by weight of the first compound and 3 parts by weight of the second compound based on 100 parts by weight of the electrolyte.

[0185] Example 4

[0186] An electrolyte and a rechargeable lithium battery were manufactured by substantially the same method as Example 1, except that the additive included 1 part by weight of the first compound and 4 parts by weight of the second compound based on 100 parts by weight of the electrolyte.

[0187] Example 5

[0188] An electrolyte and a rechargeable lithium battery were manufactured by substantially the same method as Example 1, except that the additive included 1 part by weight of the first compound and 5 parts by weight of the second compound based on 100 parts by weight of the electrolyte.

[0189] Comparative Example 1

[0190] An electrolyte and a rechargeable lithium battery were manufactured by substantially the same method as that of Example 1, except that no additive was added.

[0191] Comparative Example 2

[0192] An electrolyte and a rechargeable lithium battery were manufactured by substantially the same method as Example 1, except that the additive included 1 part by weight of the first compound based on 100 parts by weight of the electrolyte, and did not include the second compound.

[0193] Comparative Example 3

[0194] An electrolyte and a rechargeable lithium battery were manufactured by substantially the same method as Example 1, except that the additive did not include the first compound and included 1 part by weight of the second compound based on 100 parts by weight of the electrolyte.

[0195] Comparative Example 4

[0196] An electrolyte and a rechargeable lithium battery were manufactured by a method substantially the same as that of Example 1, except that the additive included 1 part by weight of the first compound based on 100 parts by weight of the electrolyte and 1 part by weight of 1,2,3-triazole based on 100 parts by weight of the electrolyte instead of the second compound.

[0197] Evaluation Example 1: Capacity retention under high-temperature storage

[0198] The high-temperature capacity retention rate was measured to evaluate the high-temperature characteristics. The rechargeable lithium batteries manufactured according to the embodiments and comparative examples were charged to SOC 100% at room temperature (25°C) under constant current-constant voltage (CC / CV), 0.33C, 4.25V and 0.025C cutoff conditions, and the discharge capacity was measured at room temperature (25°C) under constant current (CC), 0.5C and 2.5V cutoff conditions, and then the rechargeable lithium batteries were stored at 55°C for 90 days. Afterwards, the discharge capacity was measured as the discharge capacity after storage at 55°C for 90 days to calculate the high-temperature capacity retention rate. The results are listed in Table 1 below. The high-temperature capacity retention rate was calculated according to Equation 1 below.

[0199] Equation 1

[0200] Capacity retention (%) = (discharge capacity after storage at 55°C for 90 days / initial discharge capacity) × 100

[0201] Evaluation Example 2: Resistance increase rate under high-temperature storage

[0202] The rechargeable lithium batteries manufactured according to the embodiments and comparative examples were charged to SOC 100% at room temperature (25°C) under constant current-constant voltage (CC / CV), 0.33C, 4.25V and 0.025C cutoff conditions, and then the initial battery resistance (DC-IR) and the battery resistance (DC-IR) after storage at 55°C for 90 days were measured. The resistance increase rate was measured and the results are listed in Table 1 below. In the initial fully charged state, after discharging at 1C for 30 seconds, the battery resistance (DC-IR) (for example, the battery resistance (DC-IR) after 90 days and the initial battery resistance (DC-IR)) were obtained by using Ohm's law ΔR=ΔV / ΔI, which is calculated based on the difference between the current and voltage when different currents are applied. The resistance increase rate was calculated according to the following equation 2.

[0203] Equation 2

[0204] Resistance increase rate (%) = [[Battery resistance after 90 days (DC-IR) / Initial battery resistance (DC-IR)] - 1] × 100 Evaluation Example 3: Gas generation under high temperature storage

[0205] The rechargeable lithium batteries manufactured according to Examples and Comparative Examples were charged at 4.25 V at 55° C., stored at 55° C. for 90 days, and then the gas generation amount (ml) was measured using refinery gas analysis (RGA). The results are listed in Table 1 below.

[0206] Table 1

[0207]

[0208] Referring to Table 1, it can be determined that the capacity retention rate at high temperature (55° C.) in the case where the electrolyte includes the first compound and the second compound according to an embodiment of the present disclosure (Examples 1 to 5) is similar or excellent compared to the case where the electrolyte does not include the first compound and the second compound (Comparative Example 1), the case where the electrolyte includes only the first compound (Comparative Example 2), the case where the electrolyte includes only the second compound (Comparative Example 3), and the case where the electrolyte includes the first compound and 1,2,3-triazole (Comparative Example 4).

[0209] Referring to Table 1, it can be determined that the electrolyte includes the first and second compounds according to the embodiment of the present disclosure (Examples 1 to 5) and the resistance increase rate at high temperature (55° C.) is low compared to the case where the electrolyte does not include the first and second compounds (Comparative Example 1), the case where the electrolyte includes only the first compound (Comparative Example 2), the case where the electrolyte includes only the second compound (Comparative Example 3), and the case where the electrolyte includes the first compound and 1,2,3-triazole (Comparative Example 4). For example, it can be determined that Examples 1 to 5 have an excellent effect of reducing the resistance increase rate.

[0210] Referring to Table 1, it can be confirmed that the electrolyte does not include the first and second compounds (Comparative Example 1), the electrolyte includes only the first compound (Comparative Example 2), the electrolyte includes only the second compound (Comparative Example 3), and the electrolyte includes the first compound and 1,2,3-triazole (Comparative Example 4). In the case where the electrolyte includes the first and second compounds according to the embodiment of the present disclosure (Examples 1 to 5), the amount of gas generated at high temperature (55° C.) is low. For example, it can be confirmed that Examples 1 to 5 have an excellent effect of reducing gas generation.

[0211] The electrolyte for a rechargeable lithium battery according to an embodiment may have the effects of suppressing or reducing gas generation, improving capacity retention, and enhancing life characteristics of the rechargeable lithium battery. These effects may be more significant at high temperatures.

[0212] Although the subject matter of the present disclosure has been described in conjunction with what are presently considered example embodiments, it should be understood that the disclosure is not limited to the disclosed embodiments and is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents. Therefore, the foregoing embodiments should be construed as examples and not limiting the disclosure in any way.

Claims

1. An electrolyte for a rechargeable lithium battery, the electrolyte comprising: A non-aqueous organic solvent; A lithium salt; And An additive, Wherein the additive comprises a first compound represented by Chemical Formula 1 and a second compound represented by Chemical Formula 2, Chemical Formula 1 Wherein, in Chemical Formula 1, X 1 is a fluoro group, a chloro group, a bromo group or an iodo group, R 1 ~R 6 are each independently hydrogen, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C2-C20 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C20 aryl, or substituted or unsubstituted C2-C20 heteroaryl, and n is an integer of 0 or 1, Chemical Formula 2 Wherein, in Chemical Formula 2, R 7 ~R 9 Each is independently hydrogen, halogen, substituted or unsubstituted C1-C10 alkyl, or substituted or unsubstituted C3-C10 cycloalkyl, wherein "substituted" means that at least one hydrogen of the substituent is replaced by deuterium, halogen, hydroxy, amino, C1-C30 amine, 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, or cyano.

2. The electrolyte according to claim 1, wherein based on 100 parts by weight of the electrolyte for the rechargeable lithium battery, the amount of the first compound is 0.2 parts by weight to 5.0 parts by weight.

3. The electrolyte according to claim 1, wherein based on 100 parts by weight of the electrolyte for the rechargeable lithium battery, the amount of the second compound is 1 part by weight to 5 parts by weight.

4. The electrolyte according to claim 1, wherein based on 100 parts by weight of the electrolyte for the rechargeable lithium battery, the amount of the additive is 1.2 parts by weight to 10 parts by weight.

5. The electrolyte according to claim 1, wherein the weight ratio of the second compound to the first compound in the additive is in the range of 0.1 to 25.

6. The electrolyte according to claim 1, wherein the weight ratio of the second compound to the first compound in the additive is in the range of 1 to 5.

7. The electrolyte according to claim 1, wherein Chemical Formula 1 is represented by Chemical Formula 1A or Chemical Formula 1B, Chemical Formula 1A Chemical Formula 1B in, In Chemical Formula 1A and Chemical Formula 1B, X 1 is a fluoro, chloro, bromo or iodo group, and R 1 ~R 6 Each is independently hydrogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C1-C10 alkoxy, substituted or unsubstituted C2-C10 alkenyl, or substituted or unsubstituted C2-C10 alkynyl.

8. The electrolyte according to claim 7, wherein: R in Chemical Formula 1A 3 and R 4 are each hydrogen, and Selected from R 5 and R 6 At least one of them is a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkoxy group, a substituted or unsubstituted C2-C10 alkenyl group, or a substituted or unsubstituted C2-C10 alkynyl group.

9. The electrolyte according to claim 1, wherein the first compound is one selected from the compounds listed in Group 1, Group 1 10. The electrolyte according to claim 1, wherein the second compound is represented by Chemical Formula 2A, Chemical Formula 2A 11. 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 10.

12. The rechargeable lithium battery according to claim 11, wherein the positive electrode active material comprises a lithium composite oxide represented by Chemical Formula 3, Chemical Formula 3 Li x M 1 y M 2 z M 3 1-y-z O 2-a X a , Where 0.5 ≤ x ≤ 1.8, 0 ≤ a ≤ 0.05, 0 < y ≤ 1, 0 ≤ z ≤ 1 and 0 ≤ y + z ≤ 1, Among them, M 1 、M 2 and M 3 Each independently comprises at least one element selected from Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr and La, and Where X includes at least one element selected from F, S, P and Cl.

13. The rechargeable lithium battery according to claim 12, wherein In Chemical Formula 3, M 1 For Ni, 0.8≤y≤1 and 0≤z≤0.

2.

14. The rechargeable lithium battery according to claim 11, wherein the negative electrode active material comprises 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.

15. The rechargeable lithium battery according to claim 11, wherein the negative electrode active material comprises a carbon-based negative electrode active material and a Si-based negative electrode active material, Where the carbon-based negative electrode active material comprises graphite, and Where the Si-based negative electrode active material comprises silicon nanoparticles.

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