Electrolyte for lithium secondary battery and lithium secondary battery comprising same

Abstract

The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery comprising same. The electrolyte comprises: a non-aqueous organic solvent; a lithium salt; and an additive, wherein the additive comprises a mixture of a first additive represented by chemical formula 1 and a second additive represented by chemical formula 2.

Description

Electrolyte for lithium secondary batteries and lithium secondary batteries including the same

[0001] The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery containing the same.

[0002] Recently, accompanied by the rapid proliferation of battery-powered electronic devices such as mobile phones, laptop computers, and electric vehicles, the demand for high-energy-density, high-capacity rechargeable batteries is rapidly increasing. Accordingly, research and development to improve the performance of lithium-ion batteries is actively underway.

[0003] A lithium secondary battery is a battery comprising a positive electrode and a negative electrode containing an active material capable of lithium ion intercalation and deintercalation, and an electrolyte, which produces electrical energy through oxidation and reduction reactions when lithium ions are intercalated or deintercalated from the positive and negative electrodes.

[0004] The electrolyte for these lithium secondary batteries consists of a lithium salt dissolved in a non-aqueous organic solvent. The characteristics of a lithium secondary battery are determined by complex reactions between the anode and the electrolyte, and between the cathode and the electrolyte. Therefore, the use of an appropriate electrolyte is one of the important variables for improving the performance of a lithium secondary battery.

[0005] One embodiment provides an electrolyte for a lithium secondary battery that provides a low gas generation rate, a low resistance increase rate, and a high capacity retention rate after storage at high temperature, and provides a high lifespan improvement effect at room temperature.

[0006] Another embodiment provides a lithium secondary battery comprising the above electrolyte.

[0007] One embodiment provides an electrolyte for a lithium secondary battery.

[0008] An electrolyte for a lithium secondary battery comprises a non-aqueous organic solvent; a lithium salt; and an additive, wherein the additive comprises a mixture of a first additive represented by the following chemical formula 1 and a second additive represented by the following chemical formula 2:

[0009] [Chemical Formula 1]

[0010]

[0011] (In the above chemical formula 1,

[0012] X, R 11 to R 16 , and n are the same as defined in the description of the invention below).

[0013] [Chemical Formula 2]

[0014]

[0015] (In the above chemical formula 2,

[0016] R 21 to R 24 is the same as defined in the description of the invention below).

[0017] Another embodiment provides a lithium secondary battery comprising a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte, wherein the electrolyte comprises the electrolyte.

[0018] An electrolyte according to one embodiment can improve the reliability of a battery at high temperatures by providing a low gas generation rate, a low resistance increase rate, and a high capacity retention rate after storage at high temperatures. An electrolyte according to one embodiment can provide a battery with a long lifespan by providing a high lifespan improvement effect at room temperature.

[0019] FIG. 1 is a conceptual diagram briefly illustrating a lithium secondary battery according to one embodiment of the present invention.

[0020] FIGS. 2 to 5 are cross-sectional views schematically illustrating a lithium secondary battery according to one embodiment.

[0021] Figure 6 shows the 1H-NMR results of Chemical Formula 2-3.

[0022] Figure 7 shows the 13C-NMR results of Chemical Formula 2-3.

[0023] Figure 8 shows the 1H-NMR results of chemical formula 2-10.

[0024] Figure 9 shows the 13C-NMR results of Chemical Formula 2-10.

[0025] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of these embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0026] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the components are exaggerated for the effective description of the technical content. Throughout the specification, parts indicated by the same reference numeral represent the same components.

[0027] Unless otherwise specified in this specification, the singular form may also include the plural. Additionally, unless otherwise specified, "A or B" may mean "comprising A, comprising B, or comprising A and B." As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components to the mentioned components.

[0028] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0029] In this specification, "substitution" means that, unless otherwise defined, at least one hydrogen of a substituent or compound is substituted with a deuterium, a halogen group, a hydroxyl group, an amino group, a C1 to C30 amine group, a nitro group, a C1 to C40 silyl group, a C1 to C30 alkyl group, a C1 to C10 alkylsilyl group, a C6 to C30 arylsilyl group, a C3 to C30 cycloalkyl group, a C3 to C30 heterocycloalkyl group, a C6 to C30 aryl group, a C2 to C30 heteroaryl group, a C1 to C20 alkoxy group, a C1 to C10 fluoroalkyl group, a cyano group, or a combination thereof.

[0030] Specifically, "substitution" may mean that at least one hydrogen in the substituent or compound is substituted with deuterium, a halogen group, a C1 to C30 alkyl group, a C1 to C10 alkylsilyl group, a C6 to C30 arylsilyl group, a C3 to C30 cycloalkyl group, a C3 to C30 heterocycloalkyl group, a C6 to C30 aryl group, a C2 to C30 heteroaryl group, a C1 to C10 fluoroalkyl group, or a cyano group. For example, "substitution" may mean that at least one hydrogen in the substituent or compound is substituted with deuterium, a halogen group, a C1 to C20 alkyl group, a C6 to C30 aryl group, a C1 to C10 fluoroalkyl group, or a cyano group. Alternatively, "substitution" may mean that at least one hydrogen in the substituent or compound is substituted with a deuterium, a halogen group, a C1 to C5 alkyl group, a C6 to C18 aryl group, a C1 to C5 fluoroalkyl group, or a cyano group. For example, "substitution" may mean that at least one hydrogen in the substituent or compound is substituted with a deuterium, a cyano group, a halogen group, a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, a biphenyl group, a terphenyl group, a trifluoromethyl group, or a naphthyl group.

[0031] Unless otherwise defined in this specification, "*" signifies a part connected to the same or different atoms or chemical formulas. Unless specifically stated otherwise in the chemical formulas described in this specification, hydrogen may be considered to be bonded in the structure of the chemical formula.

[0032] FIG. 1 is a conceptual diagram briefly illustrating a lithium secondary battery according to embodiments of the present invention. Referring to FIG. 1, the lithium secondary battery may include a positive electrode (10), a negative electrode (20), a separator (30), and an electrolyte (ELL).

[0033] The positive electrode (10) and the negative electrode (20) may be spaced apart from each other with a separator (30) in between. The separator (30) may be placed between the positive electrode (10) and the negative electrode (20). The positive electrode (10), the negative electrode (20), and the separator (30) may come into contact with an electrolyte (ELL). The positive electrode (10), the negative electrode (20), and the separator (30) may be impregnated within the electrolyte (ELL).

[0034] The electrolyte (ELL) may be a medium for transferring lithium ions between the positive electrode (10) and the negative electrode (20). Within the electrolyte (ELL), the lithium ions may pass through a separator (30) and move toward the positive electrode (10) or the negative electrode (20).

[0035] positive electrode (10)

[0036] A positive electrode (10) for a lithium secondary battery may include a current collector (COL1) and a positive electrode active material layer (AML1) formed on the current collector (COL1). The positive electrode active material layer (AML1) may include a positive electrode active material and may further include a binder and / or a conductive material.

[0037] For example, the anode (10) may further include an additive that can serve as a sacrificial anode.

[0038] The content of the positive active material in the positive active material layer (AML1) may be 90% to 99.5% by weight with respect to 100% by weight of the positive active material layer (AML1). The content of the binder and the conductive material may each be 0.5% to 5% by weight with respect to 100% by weight of the positive active material layer (AML1).

[0039] The above binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the current collector (COL1). Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0040] The above conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials in the form of metal powder or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0041] Al can be used as the current collector (COL1), but is not limited thereto.

[0042] positive electrode active material

[0043] As the positive active material in the positive active material layer (AML1), a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0044] The above composite oxide may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0045] As an example, a compound represented by any one of the following chemical formulas may be used. Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c 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); Lia Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0046] 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; L 1 is Mn, Al, or a combination thereof.

[0047] For example, the above-mentioned positive electrode active material may be a high-nickel positive electrode active material in which the nickel content relative to 100 mol% of the metal excluding lithium in the lithium transition metal composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less. The high-nickel positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density lithium secondary batteries.

[0048] Negative electrode (20)

[0049] A negative electrode (20) for a lithium secondary battery comprises a current collector (COL2) and a negative electrode active material layer (AML2) located on the current collector (COL2). The negative electrode active material layer (AML2) comprises a negative electrode active material and may further comprise a binder and / or a conductive material.

[0050] For example, the negative electrode active material layer (AML2) may contain 90% to 99% by weight of negative electrode active material, 0.5% to 5% by weight of binder, and 0% to 5% by weight of conductive material.

[0051] The above binder serves to effectively bond the negative electrode active material particles to each other and also to effectively bond the negative electrode active material to the current collector (COL2). As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof may be used.

[0052] Examples of the above-mentioned non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyimide, or combinations thereof.

[0053] The above-mentioned water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylenepropylenediene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0054] When a water-based binder is used as the above-mentioned cathode binder, a cellulose-based compound capable of imparting viscosity may be further included. As this cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. Na, K, or Li may be used as the alkali metal.

[0055] The above dry binder is a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0056] The above conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials in the form of metal powder or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0057] As the current collector (COL2), copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof may be used.

[0058] cathode active material

[0059] The negative electrode active material in the negative electrode active material layer (AML2) comprises a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0060] A material capable of reversibly intercalating / deintercalating the above lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0061] As the above lithium metal alloy, 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 may be used.

[0062] As a material capable of doping and undoping the above lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (wherein Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0063] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include a secondary particle (core) assembled from silicon primary particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particle. The amorphous carbon may also be located between the silicon primary particles, so that, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0064] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core.

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

[0066] Separator (30)

[0067] Depending on the type of lithium secondary battery, a separator (30) may be present between the positive electrode (10) and the negative electrode (20). As such a separator (30), polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and of course, a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0068] The separator (30) may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0069] The porous substrate may be a polymer membrane formed from any one of the following: polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyacetal; polyamide; polyimide; polycarbonate; polyetherketone; polyaryletherketone; polyetherimide; polyamideimide; polybenzimidazole; polyethersulfone; polyphenylene oxide; cyclic olefin copolymer; polyphenylene sulfide; polyethylene naphthalate; glass fiber; Teflon; and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0070] The above organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0071] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include, but is not limited to, inorganic particles selected from SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0072] The above organic and inorganic materials may exist mixed in a single coating layer, or may exist in a stacked form with a coating layer containing organic materials and a coating layer containing inorganic materials.

[0073] Electrolyte (ELL)

[0074] The electrolyte (ELL) for lithium secondary batteries contains a non-aqueous organic solvent and a lithium salt.

[0075] The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0076] The above-mentioned non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0077] The above carbonate-based solvents 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), butylene carbonate (BC), etc.

[0078] Ester-based solvents such as methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, and caprolactone may be used.

[0079] As ether-based solvents, dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. may be used. Additionally, as ketone-based solvents, cyclohexanone, etc. may be used. As alcohol-based solvents, ethyl alcohol, isopropyl alcohol, etc. may be used, and as aprotic solvents, nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane, 1,4-dioxolane; sulfolanes, etc. may be used.

[0080] The above-mentioned non-aqueous organic solvent can be used alone or in a mixture of two or more types.

[0081] In addition, when using a carbonate-based solvent, a mixture of cyclic carbonates and chain carbonates can be used, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0082] The above lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions within the battery, enabling the basic operation of a lithium secondary battery and facilitating the movement of lithium ions between the anode and cathode. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1It may include one or more selected from SO2)(x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFOP), and lithium bis(oxalate)borate (LiBOB).

[0083] lithium secondary battery

[0084] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, coin, etc., depending on their shape. FIGS. 2 to 5 are schematic diagrams illustrating lithium secondary batteries according to one embodiment, where FIG. 2 is a cylindrical battery, FIG. 3 is a prismatic battery, and FIGS. 4 and 5 are pouch-type batteries. Referring to FIGS. 2 to 4, the lithium secondary battery (100) may include an electrode assembly (40) having a separator (30) interposed 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 impregnated with an electrolyte (not shown). The lithium secondary battery (100) may include a sealing member (60) that seals the case (50) as in FIG. 2. In addition, in FIG. 3, the lithium secondary battery (100) may include a positive lead tab (11) and a positive terminal (12), a negative lead tab (21) and a negative terminal (22). As shown in FIG. 4 and FIG. 5, the lithium secondary battery (100) may include electrode tabs (70), namely a positive tab (71) and a negative tab (72), which serve as electrical passages for inducing current formed in the electrode assembly (40) to the outside.

[0085] Hereinafter, the electrolyte of a lithium secondary battery according to one embodiment of the present invention will be described in more detail.

[0086] An electrolyte for a lithium secondary battery according to one embodiment comprises the above-described non-aqueous organic solvent; a lithium salt; and an additive, wherein the additive comprises a mixture of a first additive represented by Chemical Formula 1 to be described later; and a second additive represented by Chemical Formula 2 to be described later.

[0087] The above electrolyte can be prepared by dissolving a lithium salt in a non-aqueous organic solvent, adding a first additive and a second additive, and then performing a mixing process. The process of mixing the electrolyte is widely known in the field of electrolyte manufacturing, and a person skilled in the art would be able to appropriately select and use it.

[0088] A non-aqueous organic solvent according to one embodiment of the present invention may include one or more of the non-aqueous organic solvents described above.

[0089] In one embodiment, the non-aqueous organic solvent may be a mixture containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) in a volume ratio of 10 to 30: 5 to 20: 60 to 80. Here, the volume ratio is a value based on 100 volume% of the total of ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC). Within the above range, it is easy to implement the effect of the mixture of additives described below, and the rate of reductive decomposition of the anode in the lithium secondary battery is slowed down, thereby further improving the battery life.

[0090] A lithium salt according to one embodiment of the present invention may include one or more selected from the group consisting of LiPF6, LiClO4, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiSO3CF3, LiBOB (Lithium bis(oxalate)borate), LiDFOB (Lithium difluoro(oxalato)borate), LiDFBP (Lithium difluoro(bisoxalato)phosphate), LiTFOP (Lithium Tetrafluoro Oxalato Phosphate), LiPO2F2, LiSbF6, LiAsF6, LiAlO2, LiAlCl4, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N, and LiC4F9SO3. According to one embodiment, LiPF6 may be used as the lithium salt.

[0091] The concentration of the lithium salt may be 0.1M to 3.0M. Specifically, the concentration of the lithium salt may be 0.5M or higher and 1.0M or higher. The concentration of the lithium salt may be 3.0M or lower, 2.5M or lower, and 2.0M or lower. In the present invention, when the concentration of the lithium salt is 0.1M to 2.0M, the conductivity and viscosity of the electrolyte can be appropriately maintained.

[0092] additives

[0093] An additive according to one embodiment of the present invention includes a first additive to be described below and a second additive to be described below.

[0094] The first additive described above can provide the effect of reducing HF generation by protecting the positive and negative electrode interfaces when applied to a battery and stabilizing LiPF6 when used as a lithium salt in the electrolyte. A mixture comprising the second additive in addition to the first additive can provide a low gas generation rate, a low resistance increase rate, and a high capacity retention rate by forming a robust and stable film at the positive and negative electrode interfaces even after high-temperature storage of the battery, without affecting the aforementioned effects resulting from the use of the first additive. Furthermore, the mixture can also provide a high lifespan improvement effect at room temperature.

[0095] When the mixture of the first additive and the second additive is applied as an additive to the electrolyte in a lithium secondary battery containing a lithium nickel-based composite oxide as a positive electrode active material, the battery life can be improved and the battery performance can be significantly improved even under high temperature conditions. In particular, the mixture can improve the battery life and significantly improve the battery performance even under high temperature conditions for a lithium secondary battery containing the lithium nickel-based composite oxide as a positive electrode active material under a voltage of 4.2V or higher.

[0096] First additive

[0097] A first additive according to one embodiment of the present invention is represented by the following chemical formula 1.

[0098] [Chemical Formula 1]

[0099]

[0100] (In the above chemical formula 1,

[0101] X is a fluoro group, chloro group, bromo group, or iodo group, and

[0102] R 11 to R 16Each is independently hydrogen, a cyano group, a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C1 to C20 alkoxy group, a substituted or unsubstituted C2 to C20 alkenyl group, a substituted or unsubstituted C2 to C20 alkynyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C2 to C20 heteroaryl group, and

[0103] n is an integer of 0 or 1).

[0104] An additive according to another embodiment of the present invention may be represented by the following chemical formula 1-1.

[0105] [Chemical Formula 1-1]

[0106]

[0107] (In the above chemical formula 1-1,

[0108] R 11 to R 16 , n are each the same as defined in Chemical Formula 1 above).

[0109] An additive according to another embodiment of the present invention may include one or more of the following chemical formulas 1-2 and 1-3.

[0110] [Chemical Formula 1-2]

[0111]

[0112] [Chemical Formula 1-3]

[0113]

[0114] (In the above chemical formulas 1-2 and 1-3,

[0115] R 11 to R 16 Each is identical to what is defined in Chemical Formula 1 above).

[0116] In one specific example, R 11 to R 16Each may be hydrogen or a substituted or unsubstituted C1 to C10 alkyl group, for example, hydrogen or a substituted or unsubstituted C1 to C5 alkyl group.

[0117] For example, the first additive may be one or more of the following chemical formulas 1-4 to 1-8: For example, the first additive may be one or more of the following chemical formulas 1-5, 1-6, and 1-8.

[0118] [Chemical Formula 1-4]

[0119]

[0120] [Chemical Formula 1-5]

[0121]

[0122] [Chemical Formula 1-6]

[0123]

[0124] [Chemical Formula 1-7]

[0125]

[0126] [Chemical Formula 1-8]

[0127]

[0128] The above-mentioned first additive can be manufactured by conventional methods known to those skilled in the art.

[0129] Second additive

[0130] When combined with the first additive, the second additive can provide a low gas generation rate, a low resistance increase rate, and a high capacity retention rate after high-temperature storage, and can also provide an effect of improving room-temperature life. In addition, the second additive can provide an effect of reducing electrolyte side reactions by protecting the anode and cathode interfaces.

[0131] A second additive according to one embodiment of the present invention is represented by the following chemical formula 2.

[0132] [Chemical Formula 2]

[0133]

[0134] (In the above chemical formula 2,

[0135] R 21 and R 22 Each is independently a single bond, a substituted or unsubstituted C1 to C20 alkylene group, a substituted or unsubstituted C1 to C20 alkoxylene group, a substituted or unsubstituted C2 to C20 alkenylene group, a substituted or unsubstituted C2 to C20 alkynylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C2 to C20 heteroarylene group, and

[0136] R 23 and R 24 Each is independently hydrogen, cyano, a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C1 to C20 alkoxy group, a substituted or unsubstituted C2 to C20 alkenyl group, a substituted or unsubstituted C2 to C20 alkynyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C2 to C20 heteroaryl group, and

[0137] R 23 and R 24 At least one of them is a substituted or unsubstituted C2 to C20 alkenyl group, hydrogen, a substituted or unsubstituted C1 to C20 alkyl group, or a cyano group).

[0138] First specific example

[0139] In one embodiment, R in Formula 2 above 23 and R 24 At least one of them may be a substituted or unsubstituted C2 to C20 alkenyl group.

[0140] A second additive according to another embodiment of the present invention may include one or more of the following chemical formulas 2-1 and 2-2:

[0141] [Chemical Formula 2-1]

[0142]

[0143] (In the above chemical formula 2-1,

[0144] R 21 and R 22 is the same as defined in the above Chemical Formula 2, and

[0145] R 23a and R 24a Each independently has a single bond or a substituted or unsubstituted C2 to C18 alkylene group,

[0146] R 25 and R 26 (each independently a hydrogen or methyl group).

[0147] [Chemical Formula 2-2]

[0148]

[0149] (In the above chemical formula 2-2,

[0150] R 21 and R 22 is the same as defined in the above Chemical Formula 2, and

[0151] R 23b and R 24b Each independently has a single bond or a substituted or unsubstituted C2 to C18 alkylene group,

[0152] R 23c and R 24c Each is independently a hydrogen or a substituted or unsubstituted C2 to C18 alkyl group,

[0153] However, R 23b and R 23c The total number of carbon atoms in the main chain is 18 or less, and

[0154] R 24b and R 24c The total number of carbon atoms in the main chain is 18 or less).

[0155] In one specific example, R 21 and R 22Each may independently be a single bond or a substituted or unsubstituted C1 to C20 alkylene group, for example, a single bond, a substituted or unsubstituted C1 to C5 alkylene group.

[0156] A second additive according to another embodiment of the present invention may include one or more of the following chemical formulas 2-3 to 2-5.

[0157] [Chemical Formula 2-3]

[0158]

[0159] [Chemical Formula 2-4]

[0160]

[0161] [Chemical Formula 2-5]

[0162]

[0163] Second specific example

[0164] In another embodiment, R in Formula 2 above 23 and R 24 At least one of them may be hydrogen or a substituted or unsubstituted C1 to C20 alkyl group.

[0165] In one specific example, R 21 and R 22 Each may independently be a single-bonded, substituted, or unsubstituted C1 to C20 alkylene group, a single-bonded, substituted, or unsubstituted C1 to C10 alkylene group, or a single-bonded, substituted, or unsubstituted C1 to C5 alkylene group.

[0166] In one specific example, R 23 and R 24 At least one of them may be hydrogen or a substituted or unsubstituted C1 to C20 alkyl group. R 23 and R 24 Both may be hydrogen or substituted or unsubstituted C2 to C20 alkyl groups. In one embodiment, R 23 and R 24Each may independently be a substituted or unsubstituted C2 to C10 alkyl group, or a substituted or unsubstituted C2 to C5 alkyl group. These are R 23 and R 24 The above-described effect may be significant compared to the compound of Formula 2, each having a C1 alkyl group that is independently substituted or unsubstituted.

[0167] In one specific example, R 21 and R 22 Each can be a single combination independently.

[0168] A second additive according to another embodiment of the present invention may include one or more of the following chemical formulas 2-6 and 2-7:

[0169] [Chemical Formula 2-6]

[0170]

[0171] [Chemical Formula 2-7]

[0172]

[0173] Third specific example

[0174] In another embodiment, R in Chemical Formula 2 above 23 and R 24 At least one of them may be cyanobacteria.

[0175] In one embodiment, R in Formula 2 above 21 and R 22 Each may be an independently substituted or unsubstituted C1 to C20 alkylene group or a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C1 to C10 alkylene group or a substituted or unsubstituted C6 to C00 arylene group.

[0176] In one specific example, R 23 and R 24 One of them may be a cyano group, and the other may be a substituted or unsubstituted C1 to C20 alkyl group, or a substituted or unsubstituted C2 to C20 alkenyl group.

[0177] In one specific example, R 23 and R 24 Both can be cyano groups. In such cases, the effect of the above-described electrolyte can be significantly increased.

[0178] A second additive according to another embodiment of the present invention may be represented by the following chemical formula 2-8:

[0179] [Chemical Formula 2-8]

[0180]

[0181] (In the above chemical formula 2-8,

[0182] R 21 and R 22 is the same as defined in Chemical Formula 2 above).

[0183] A second additive according to another embodiment of the present invention may include one or more of the following chemical formulas 2-9 to 2-12.

[0184] [Chemical Formula 2-9]

[0185]

[0186] [Chemical Formula 2-10]

[0187]

[0188] [Chemical Formula 2-11]

[0189]

[0190] [Chemical Formula 2-12]

[0191]

[0192] The above second additive can be manufactured by conventional methods known to those skilled in the art.

[0193] In one embodiment, the mixture may be included in an amount of 95% by weight or more, for example, 95 to 100% by weight or 100% by weight, of the additive of the electrolyte. Within this range, the effect of the mixture described above is realized, and side reactions of the electrolyte can be suppressed.

[0194] The first additive may be included in an amount of 0.05 to 6 weight% or 0.05 to 5 weight% with respect to the total amount of the electrolyte. Within this range, the effect of the mixture described above can be realized. Specifically, the first additive may be included in an amount of 0.1 to 5 weight%, 1 to 3 weight%, or 0.5 to 2 weight% with respect to the total amount of the electrolyte. When the content of the first additive is within the above range, the effect of the mixture described above is significantly enhanced, and there may be an additional effect of not increasing the resistance of the battery.

[0195] The second additive may be included in an amount of 0.05 to 5 weight percent relative to the total weight of the electrolyte. Within this range, the effect of the mixture described above can be realized. Specifically, the second additive may be included in an amount of 0.05 to 3 weight percent, 0.1 to 2 weight percent, or 0.5 to 2 weight percent relative to the total amount of the electrolyte. When the content of the second additive is within the above range, the effect of the mixture described above is significantly enhanced, the rapid charging effect is improved, and there may be an additional effect of not increasing the resistance of the battery.

[0196] In the electrolyte, the ratio (weight ratio) of the content of the first additive to the content of the second additive may be 1:5 to 1:0.2. Within this range, it may be easy to achieve the effect of the mixture described above.

[0197] According to one embodiment, the ratio (weight ratio) of the content of the first additive to the content of the second additive may be 1:5 to 1:0.5. Within this range, there is an effect of suppressing resistance at high temperatures, and there may be no problem of the lifespan efficiency of the lithium secondary battery rapidly decreasing. For example, the weight ratio may be 1:2 to 1:0.5. Within this range, the effect of suppressing resistance at high temperatures and the effect of improving lifespan efficiency may be significant.

[0198] Thus, the electrolyte according to the present invention comprises a mixture of the first additive and the second additive in the combination of the above-described non-aqueous organic solvent and lithium salt, thereby simultaneously producing an effect of suppressing the increase in resistance during high-temperature storage in a lithium secondary battery containing a positive electrode active material, thereby enabling the realization of a lithium secondary battery with improved lifespan characteristics and stability.

[0199] In another embodiment of the present invention, a lithium secondary battery may be provided comprising: a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; and an electrolyte, wherein the electrolyte comprises a non-aqueous organic solvent; a lithium salt; and an additive, and the additive comprises a mixture of the first additive and the second additive described above.

[0200] The above-mentioned lithium secondary battery may be applied to automobiles, mobile phones, and / or various types of electric devices, etc., but the present invention is not limited thereto.

[0201] The above-mentioned positive electrode active material may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0202] As an example, a compound represented by any one of the following chemical formulas may be used. Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c 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 a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0203] 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; L 1 is Mn, Al, or a combination thereof.

[0204] The above positive active material may include, for example, a lithium nickel-based oxide represented by the following chemical formula 3, a lithium cobalt-based oxide represented by the following chemical formula 4, a lithium iron phosphate-based compound represented by the following chemical formula 5, a cobalt-free lithium nickel-manganese-based oxide represented by the chemical formula 6, or a combination thereof.

[0205] In one embodiment, the positive electrode active material may be a lithium nickel-based oxide represented by Chemical Formula 3 below. A battery comprising a positive electrode containing a lithium nickel-based oxide as a positive electrode active material and the electrolyte together may exhibit significant effects of providing a low gas generation rate, a low resistance increase rate, and a high capacity retention rate after high-temperature storage:

[0206] [Chemical Formula 3]

[0207] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0208] In the above chemical formula 3, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 Each is independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0209] In the above chemical formula 3, 0.6≤x1≤1, 0≤y1≤0.4, and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2.

[0210] [Chemical Formula 4]

[0211] Lia2 Co x2 M 3 y2 O 2-b2 X b2

[0212] In the above chemical formula 4, 0.9≤a2≤1.8, 0.7≤x2≤1, 0≤y2≤0.3, 0.9≤x2+y2≤1.1, and 0≤b2≤0.1, and M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0213] [Chemical Formula 5]

[0214] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0215] In the above chemical formula 5, 0.9≤a3≤1.8, 0.6≤x3≤1, 0≤y3≤0.4, and 0≤b3≤0.1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0216] [Chemical Formula 6]

[0217] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4

[0218] In the above chemical formula 6, 0.9≤a2≤1.8, 0.8≤x4<1, 0 <y4≤0.2, 0≤z4≤0.2, 0.9≤x4+y4+z4≤1.1, 및 0≤b4≤0.1이고 M 5 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0219] For example, the above-mentioned positive electrode active material may be a high-nickel positive electrode active material in which the nickel content relative to 100 mol% of the metal excluding lithium in the lithium transition metal composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less. The high-nickel positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density lithium secondary batteries.

[0220] In a specific embodiment, the negative electrode active material may include at least one of graphite and Si composites.

[0221] When the above-mentioned cathode active material includes a Si composite and graphite together, the Si composite and graphite may be included in the form of a mixture, in which case the Si composite:graphite may be included in a weight ratio of 1:99 to 50:50 based on a total of 100 parts by weight. More specifically, the Si composite:graphite may be included in a weight ratio of 3:97 to 20:80, 4:96 to 20:80, or 5:95 to 20:80.

[0222] The above Si composite comprises a core containing Si-based particles and an amorphous carbon coating layer, for example, the Si-based particles are a Si-C composite, SiO xIt may include one or more of (0 < x ≤ 2) and Si alloys. For example, the Si-C composite may include a core containing Si particles and crystalline carbon and an amorphous carbon coating layer located on the surface of the core. The crystalline carbon may include, for example, graphite, and more specifically, natural graphite, artificial graphite, or a mixture thereof.

[0223] When the positive electrode contains a lithium nickel-based oxide and the negative electrode contains graphite, the effect of improving the high-temperature stability of the lithium secondary battery can be maximized. The operating voltage of the lithium secondary battery of the above combination is 4.2 V or higher, so it may operate even at high voltage.

[0224] Examples and comparative examples of the present invention are described below. However, the following examples are merely one example of the present invention, and the present invention is not limited to the following examples.

[0225] Synthetic example

[0226] 12.0 g of diallylurea is placed in a round-bottom flask, and 70 g of dichloromethane is added to it and stirred at room temperature (25°C). Once the diallylurea is completely dissolved, a solution of 10.8 g of oxalyl chloride dissolved in 30 g of dichloromethane is slowly added dropwise, then the temperature is raised to 40°C and stirred for 2 hours. When the reaction is complete, the product is washed with water and filtered to obtain the compound represented by the chemical formula 2-3 below.

[0227] The compound of Chemical Formula 2-3 below was prepared using the above method, and the structure of Chemical Formula 2-3 below was confirmed through the NMR of Figures 6 and 7.

[0228] [Chemical Formula 2-3]

[0229]

[0230] Examples and Comparative Examples

[0231] (1) Preparation of electrolyte

[0232] An electrolyte was prepared by dissolving 1.5 M LiPF6 in a carbonate-based solvent mixed with ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate in a volume ratio of 20:10:70 (based on a total volume of 100 volumes), adding the first additive and the second additive, and mixing. Specifically, the amounts of the first additive and the second additive used are shown in Table 1 below.

[0233] As the first additive, a compound represented by the following chemical formula 1-5 was used: As the second additive, a compound of the following chemical formula 2-3 prepared in the above synthesis example was used.

[0234] [Chemical Formula 1-5]

[0235]

[0236] [Chemical Formula 2-3]

[0237]

[0238] (2) Manufacturing of lithium secondary batteries

[0239] LiNi as a positive electrode active material 0.75 Mn 0.23 Al 0.02 An anode slurry was prepared by mixing O297 wt%, artificial graphite powder as a conductive material, 0.5 wt%, carbon black (Ketjenblack), 0.2 wt%, acrylonitrile rubber, and 1.5 wt%, adding the mixture to N-methyl-2-pyrrolidone (NMP), and stirring for 30 minutes using a mechanical stirrer. The slurry was applied to a thickness of about 60 μm on a 20 μm thick aluminum current collector using a doctor blade, dried in a hot air dryer at 100 ℃ for 0.5 hours, dried once more under vacuum conditions at 120 ℃ for 4 hours, and then rolled to produce an anode.

[0240] A cathode slurry was prepared by mixing 98 wt% of a cathode active material, in which a graphite and Si composite was mixed in a weight ratio of 95.8:4.2, 1 wt% of styrene-butadiene rubber (SBR), and 1 wt% of carboxymethylcellulose (CMC), adding the mixture to distilled water, and stirring for 60 minutes using a mechanical stirrer. The slurry was applied to a thickness of about 60 μm onto a 10 μm thick copper current collector using a doctor blade, dried in a hot air dryer at 100 ℃ for 0.5 hours, dried once more under vacuum conditions at 120 ℃ for 4 hours, and then rolled to produce a cathode.

[0241] An electrode assembly was manufactured by assembling the above positive electrode and the above negative electrode with a separator made of polyethylene material with a thickness of 16 μm, and a circular lithium secondary battery was manufactured by injecting the above electrolyte.

[0242] Evaluation example

[0243] The lithium secondary battery was evaluated in the following manner.

[0244] Evaluation 1: Capacity retention (Ret) and capacity recovery (Rec) after high-temperature storage

[0245] The lithium secondary batteries of the examples and comparative examples were subjected to 0.5C CC / CV charging (4.2V, 0.05C CUT-OFF) and 0.5C CC discharging (2.5V CUT-OFF) at 25°C twice, and the second discharge capacity C1 was measured. After storing the charged lithium secondary batteries at 60°C for 30 days, they were left at room temperature for an additional 30 minutes, and the discharge capacity C2 was measured by 0.5C CC discharging (2.5V CUT-OFF). The capacity retention rate (unit: %) was calculated as follows and listed in Table 1 below.

[0246] Capacity retention rate (%) = C2 / C1 × 100.

[0247] After measuring the capacity retention rate of the lithium secondary batteries of the examples and comparative examples in the same manner as above, the discharge capacity was measured by charging at a 0.5C-rate CC / CV (4.2V, 0.05C cut-off) and discharging at a 0.5C-rate CC (2.5V cut-off).

[0248] The capacity recovery rate (unit: %) was calculated as a percentage by dividing the discharge capacity after measuring the capacity retention rate by the initial capacity measured above.

[0249] Capacity recovery rate (%) = (Discharge capacity after capacity retention rate measurement / Initial capacity) × 100.

[0250] Evaluation 2: High-temperature storage characteristics evaluation DCIR growth rate

[0251] For the lithium secondary batteries according to the examples and comparative examples, the initial DC resistance (DCIR, unit: mΩ) was measured using the △V / △I (change in voltage / change in current) value, the maximum energy state inside the battery was made to a fully charged state (SOC 100%), and after storing it at 60°C for 30 days in this state, the DC resistance was measured, and the DCIR increase rate (unit: %) was calculated according to the following formula.

[0252] [ceremony]

[0253] DCIR growth rate (%) = (DCIR after 30 days at 60℃ / Initial DCIR) × 100.

[0254] Evaluation 3: Evaluation of High Temperature (60℃) Gas Generation Characteristics

[0255] High-temperature gas generation characteristics were evaluated for lithium secondary batteries according to the examples and comparative examples. To this end, the maximum energy state inside the battery was set to a fully charged state (SOC 100%), and after storing at a high temperature (60°C) for 30 days, the amount of gas generated (unit: mL) was evaluated. The gas generation reduction rate (unit: %) was evaluated as (amount of gas generated in Comparative Example 1 - amount of gas generated in the examples and comparative examples) × 100 relative to the amount of gas generated in Comparative Example 1. The higher the gas generation reduction rate, the better the gas generation reduction effect at high temperatures.

[0256] Evaluation 4: Capacity retention rate after 200 cycles of room temperature life

[0257] Room temperature charge-discharge characteristics were evaluated for lithium secondary batteries according to the examples and comparative examples. To this end, 200 charge-discharge cycles of the lithium secondary batteries were performed under conditions of 25°C, 0.33C charge (CC / CV, 4.2V, 0.025C Cut-off) / 1.0C discharge (CC, 2.5V Cut-off). The capacity retention rate (unit: %) was calculated according to the following formula.

[0258] Capacity retention rate (%) = (Discharge capacity after 200 cycles / Discharge capacity after 1 cycle) × 100.

[0259]

[0260] The results of the above evaluations 1 to 4 are shown in Table 1 below.

[0261] Chemical Formula 1-5 Chemical Formula 2-3 Volume Retention Rate Volume Recovery Rate DCIR Increase Rate Gas Generation Amount Gas Generation Decrease Rate Room Temperature Life Content (Wt%) Content (Wt%) Example 1 10.59 1.59 3.810 1.20.90 31.89 3.2 Example 2 119 1.59 3.710 2.20.88 33.39 3.3 Example 3 129 1.49 3.510 30.86 34.89 3.1 Comparative Example 1008 7.58 9.712 51.3208 8.1 Comparative Example 2018 8.29 2.510 30.98 25.79 2.2 Comparative Example 3 108 7.79 0.1112 51.1115.99 0.1

[0262]

[0263] The molar concentration (M) of the lithium salt in the electrolyte refers to the amount (number of moles) of the lithium salt dissolved per 1 L of the electrolyte, the volume ratio of the non-aqueous organic solvent refers to the volume ratio of EC:EMC:DMC, and the weight % of the first additive and the second additive refers to the relative weight of the additives to 100 weight % of the total electrolyte (lithium salt + non-aqueous organic solvent + additive).

[0264]

[0265] synthesis

[0266] Referring to Table 1 above, it can be confirmed that the electrolyte of the example provides a low gas generation rate, a low resistance increase rate, and a high capacity retention rate after high-temperature storage in a lithium secondary battery based on the results of evaluations 1 to 4, and provides a high lifespan at room temperature, thereby providing reliability and a long lifespan of the battery at high temperatures.

[0267] However, referring to Table 1 above, Comparative Example 3, which does not include the second additive of the present invention, had lower effects compared to the example. In addition, Comparative Example 2, which includes only the second additive of the present invention, and Comparative Example 1, which does not include both the first additive and the second additive of the present invention, also had lower effects compared to the example.

[0268]

[0269] Examples and Comparative Examples

[0270] (1) Preparation of electrolyte

[0271] An electrolyte was prepared by dissolving 1.5 M LiPF6 in a carbonate-based non-aqueous organic solvent mixed with ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate in a volume ratio of 20:10:70 (based on a total volume of 100), adding a first additive and a second additive, and mixing. Specifically, the contents of the first additive and the second additive are shown in Table 2 below.

[0272] As the first additive, a compound represented by the following chemical formula 1-5 was used: As the second additive, a compound of the following chemical formula 2-1 was used. Chemical formulas 1-5 and 2-6 were each purchased as products.

[0273] [Chemical Formula 1-5]

[0274]

[0275] [Chemical Formula 2-6]

[0276]

[0277] (2) Manufacturing of lithium secondary batteries

[0278] LiNi as a positive electrode active material 0.75 Mn 0.23 Al 0.02 An anode slurry was prepared by mixing O297 wt%, artificial graphite powder as a conductive material (0.5 wt%), carbon black (Ketjenblack) (0.8 wt%), acrylonitrile rubber (0.2 wt%), and polyvinylidene fluoride (PVdF) (1.5 wt%), adding the mixture to N-methyl-2-pyrrolidone (NMP), and stirring for 30 minutes using a mechanical stirrer. The slurry was applied to a thickness of about 60 μm on a 20 μm thick aluminum current collector using a doctor blade, dried in a hot air dryer at 100 ℃ for 0.5 hours, dried once more under vacuum conditions at 120 ℃ for 4 hours, and rolled to produce an anode.

[0279] A cathode slurry was prepared by mixing 98 wt% of a cathode active material, in which a graphite and Si composite was mixed in a weight ratio of 95.8:4.2, 1 wt% of styrene-butadiene rubber (SBR), and 1 wt% of carboxymethylcellulose (CMC), adding the mixture to distilled water, and stirring for 60 minutes using a mechanical stirrer. The slurry was applied to a thickness of about 60 μm on a 10 μm thick copper current collector using a doctor blade, dried in a hot air dryer at 100 ℃ for 0.5 hours, dried once more under vacuum conditions at 120 ℃ for 4 hours, and then rolled to produce a cathode.

[0280] An electrode assembly was manufactured by assembling the above positive electrode and the above negative electrode with a separator made of polyethylene material with a thickness of 16 μm, and a circular lithium secondary battery was manufactured by injecting the above electrolyte.

[0281] Evaluation example

[0282] The lithium secondary battery was evaluated in the following manner.

[0283] Evaluation 5: Capacity Retention (Ret) and Capacity Recovery (Rec) after High-Temperature Storage

[0284] The lithium secondary batteries of the examples and comparative examples were subjected to 0.5C CC / CV charging (4.2V, 0.05C CUT-OFF) and 0.5C CC discharging (2.5V CUT-OFF) at 25°C twice, and the second discharge capacity C1 was measured. After storing the charged lithium secondary batteries at 60°C for 30 days, they were left at room temperature for an additional 30 minutes, and the discharge capacity C2 was measured by 0.5C CC discharging (2.5V CUT-OFF). The capacity retention rate (unit: %) was calculated as follows.

[0285] Capacity retention rate (%) = C2 / C1 × 100.

[0286] After measuring the capacity retention rate of the lithium secondary batteries of the examples and comparative examples in the same manner as above, the discharge capacity was measured by charging at a 0.5C-rate CC / CV (4.2V, 0.05C cut-off) and discharging at a 0.5C-rate CC (2.5V cut-off).

[0287] The capacity recovery rate (unit: %) was calculated as a percentage by dividing the discharge capacity after measuring the capacity retention rate by the initial capacity measured above.

[0288] Capacity recovery rate (%) = (Discharge capacity after capacity retention rate measurement / Initial capacity) × 100.

[0289] Evaluation 6: High-temperature storage characteristics evaluation DCIR growth rate

[0290] For the lithium secondary batteries according to the examples and comparative examples, the initial DC resistance (DCIR, unit: mΩ) was measured using the △V / △I (change in voltage / change in current) value, the maximum energy state inside the battery was made to a fully charged state (SOC 100%), and after storing it at 60°C for 30 days in this state, the DC resistance was measured, and the DCIR increase rate (unit: %) was calculated according to the following formula.

[0291] [ceremony]

[0292] DCIR growth rate (%) = (DCIR after 30 days at 60℃ / Initial DCIR) × 100.

[0293] Evaluation 7: Evaluation of High-Temperature Storage Gas Generation Characteristics

[0294] High-temperature gas generation characteristics were evaluated for lithium secondary batteries according to the examples and comparative examples. To this end, the maximum energy state inside the battery was set to a fully charged state (SOC 100%), and after storing at 60°C for 30 days, the amount of gas generated (unit: mL) was evaluated. The gas generation reduction rate (unit: %) was evaluated as (amount of gas generated in Comparative Example 4 - amount of gas generated in the examples and comparative examples) x 100 relative to the amount of gas generated in Comparative Example 4. The higher the gas generation reduction rate, the better the gas generation reduction effect after high-temperature storage.

[0295]

[0296] The results of the above evaluations 5 to 7 are shown in Table 2 below.

[0297] Chemical Formula 1-5 Chemical Formula 2-6 Weight Specific Volume Retention Rate Volume Recovery Rate DCIR Increase Rate Gas Generation Amount Gas Generation Decrease Rate Content (Weight%) Content (Weight%) Example 4 10.52 : 190.492.4110.50.9329.5 Example 5 111 : 191.592.8107.70.9230.3 Example 6 120.5 : 191.492.7108.10.9131.1 Example 7 313 : 190.592.51100.9329.5 Example 8 80.210.2 : 190.592.4110.30.9329.5 Example 9 515 : 190.492.4110.70.9329.5 Comparative Example 400087.589.71251.320 Comparative Example 501-87.9911091.0520.5 Comparative Example 610-87.790.1112.51.1115.9

[0298]

[0299] *Additive (the weight% of chemical formula 1-5 and chemical formula 2-6 refers to the relative weight of the additive to the total electrolyte (lithium salt + non-aqueous organic solvent + 100 weight% of the additive).

[0300]

[0301] synthesis

[0302] Referring to Table 2 above, the electrolyte of the example can increase the reliability of the battery at high temperatures by providing a low gas generation rate, a low resistance increase rate, and a high capacity retention rate after storage at high temperatures. However, referring to Table 2 above, the comparative example that does not include one or more of the first additive and the second additive of the present invention can be expected to be significantly lacking in improving high-temperature performance, as the reduction rate of gas generation is relatively low and the resistance increase rate is high.

[0303]

[0304] Synthetic example

[0305] A compound of chemical formula 2-10 was prepared, and the structure of chemical formula 2-10 was confirmed through the NMR of Figures 8 and 9.

[0306] [Intermediate Manufacturing]

[0307]

[0308] 1,1'-carbonyldiimidazole (24.0 g, 149.8 mmol) is placed in a round-bottom flask, and 100 g of tetrahydrofuran solvent is added dropwise and stirred. Then, 3-aminopropionitrile (21.0 g, 299.6 mmol) is added, the temperature is raised to 60°C and stirred for 18 hours. When the reaction is complete, the temperature is lowered to room temperature, filtered, washed with tetrahydrofuran, and dried to synthesize the above intermediate.

[0309] The above intermediate (10.0 g, 60.02 mmol) was placed in a round-bottom flask, 50 g of tetrahydrofuran solvent was added dropwise, and the mixture was stirred at room temperature. Oxalyl chloride (11.5 g, 90.3 mmol) was dissolved in 30 g of tetrahydrofuran solvent and slowly added dropwise, then the temperature was raised to 60 degrees and stirred for 4 hours. When the reaction was complete, the temperature was lowered to room temperature, filtered, washed with tetrahydrofuran solvent, and dried to synthesize the compound of Formula 2-10. It was confirmed through Figures 8 and 9 that the prepared compound was the compound of Formula 2-10.

[0310] [Chemical Formula 2-10]

[0311]

[0312] Examples and Comparative Examples

[0313] (1) Preparation of electrolyte

[0314] An electrolyte was prepared by dissolving 1.5 M LiPF6 in a carbonate-based solvent mixed with ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate in a volume ratio of 20:10:70 (based on a total volume of 100), adding a first additive and a second additive, and mixing. Specifically, the amounts of the first additive and the second additive used are shown in Table 1 below.

[0315] As the first additive, a compound represented by the following chemical formula 1-5 was used: As the second additive, a compound of the following chemical formula 2-10 prepared in the above synthesis example was used.

[0316] [Chemical Formula 1-5]

[0317]

[0318] [Chemical Formula 2-10]

[0319]

[0320] (2) Manufacturing of lithium secondary batteries

[0321] LiNi as a positive electrode active material 0.75 Mn 0.23 Al 0.02A cathode active material slurry was prepared by mixing O297 wt%, artificial graphite powder as a conductive material (0.5 wt%), carbon black (Ketjenblack) (0.8 wt%), acrylonitrile rubber (0.2 wt%), and polyvinylidene fluoride (PVdF) (1.5 wt%), adding the mixture to N-methyl-2-pyrrolidone (NMP), and stirring for 30 minutes using a mechanical stirrer. The slurry was applied to a thickness of about 60 μm on a 20 μm thick aluminum current collector using a doctor blade, dried in a hot air dryer at 100 ℃ for 0.5 hours, dried again under vacuum conditions at 120 ℃ for 4 hours, and then rolled to produce a cathode.

[0322] A cathode active material slurry was prepared by mixing 98 wt% of a cathode active material, in which graphite and Si composites were mixed in a weight ratio of 95.8:4.2, 1 wt% of styrene-butadiene rubber (SBR), and 1 wt% of carboxymethylcellulose (CMC), adding the mixture to distilled water, and stirring for 60 minutes using a mechanical stirrer. The slurry was applied to a thickness of about 60 μm on a 10 μm thick copper current collector using a doctor blade, dried in a hot air dryer at 100 ℃ for 0.5 hours, dried once more under vacuum conditions at 120 ℃ for 4 hours, and then rolled to produce a cathode.

[0323] An electrode assembly was manufactured by assembling the above positive electrode and the above negative electrode with a separator made of polyethylene material with a thickness of 16 μm, and a circular lithium secondary battery was manufactured by injecting the above electrolyte.

[0324]

[0325] Evaluation example

[0326] The lithium secondary battery was evaluated in the following manner.

[0327] Evaluation 8: Capacity retention rate and capacity recovery rate after high-temperature storage

[0328] The lithium secondary batteries of the examples and comparative examples were subjected to 0.5C CC / CV charging (4.2V, 0.05C CUT-OFF) and 0.5C CC discharging (2.5V CUT-OFF) at 25°C twice, and the second discharge capacity C1 was measured. After storing the charged lithium secondary batteries at 60°C for 30 days, they were left at room temperature for an additional 30 minutes, and the discharge capacity C2 was measured by 0.5C CC discharging (2.5V CUT-OFF). The capacity retention rate (unit: %) was calculated as follows.

[0329] Dose Retention Rate (%) = C2 / C1 × 100(%)

[0330] After measuring the capacity retention rate of the lithium secondary batteries of the examples and comparative examples in the same manner as above, the discharge capacity was measured by charging at a 0.5C-rate CC / CV (4.2V, 0.05C cut-off) and discharging at a 0.5C-rate CC (2.5V cut-off).

[0331] The capacity recovery rate (unit: %) was calculated as a percentage by dividing the discharge capacity after measuring the capacity retention rate by the initial capacity measured above.

[0332] Capacity Recovery Rate (%) = (Discharge Capacity after Capacity Retention Rate Measurement / Initial Capacity) × 100

[0333] Evaluation 9: High-temperature storage characteristics evaluation DCIR growth rate

[0334] For the lithium secondary batteries according to the examples and comparative examples, the initial DC resistance (DCIR, unit: mΩ) was measured using the △V / △I (change in voltage / change in current) value, the maximum energy state inside the battery was made to a fully charged state (SOC 100%), and after storing it at 60°C for 30 days in this state, the DC resistance was measured, and the DCIR increase rate (unit: %) was calculated according to the following formula.

[0335] [ceremony]

[0336] DCIR growth rate (%) = (DCIR after 30 days at 60℃ / Initial DCIR) x 100.

[0337] Evaluation 10: Evaluation of High Temperature (60℃) Gas Generation Characteristics

[0338] High-temperature gas generation characteristics were evaluated for lithium secondary batteries according to the examples and comparative examples. To this end, the maximum energy state inside the battery was set to a fully charged state (SOC 100%), and after storing at a high temperature (60°C) for 30 days, the amount of gas generated (unit: mL) was evaluated. The gas generation reduction rate (unit: %) was evaluated as (amount of gas generated in Comparative Example 7 - amount of gas generated in the examples and comparative examples) x 100 relative to the amount of gas generated in Comparative Example 1. The higher the gas generation reduction rate, the better the gas generation reduction effect at high temperatures.

[0339] Evaluation 11: Capacity retention rate after 200 cycles of room temperature life

[0340] Room temperature charge-discharge characteristics were evaluated for lithium secondary batteries according to the examples and comparative examples. To this end, 200 charge-discharge cycles of the lithium secondary batteries were performed under conditions of 25°C, 0.33C charge (CC / CV, 4.2V, 0.025C Cut-off) / 1.0C discharge (CC, 2.5V Cut-off). The capacity retention rate (unit: %) was calculated according to the following formula.

[0341] Capacity retention rate (%) = (Discharge capacity after 200 cycles / Discharge capacity after 1 cycle) x 100.

[0342] Chemical Formula 1-5 Chemical Formula 2-10 Capacity Retention Rate Capacity Recovery Rate DCIR Increase Rate Gas Generation Amount Gas Generation Decrease Rate Room Temperature Life Capacity Retention Rate Content (WH%) Content (WH%) Example 10 10.58 4.28 5.8 105.4 0.97 23.09 1.2 Example 11 18 4.48 6.3 102.8 0.95 24.69 2.0 Example 12 128 4.38 6.1 103.5 0.96 23.89 1.9 Comparative Example 7 008 3.78 5.8 119.6 1.26 87.5 Comparative Example 8 018 3.58 5.8 106.6 1.04 17.58 8.1 Comparative Example 9 108 2.68 4.8 107.7 1.1 12.78 8.0

[0343]

[0344] The weight % of the additive refers to the relative weight of the additive to 100 weight % of the total electrolyte (lithium salt + non-aqueous organic solvent + additive).

[0345]

[0346] synthesis

[0347] Referring to Table 3 above, it can be sufficiently anticipated that the electrolyte of the example can improve high-temperature performance in a lithium secondary battery based on the results of evaluations 8 to 11.

[0348] However, referring to Table 3 above, Comparative Examples 8 and 9, which do not include one or more of the first and second additives of the present invention, have a relatively high ratio of gas generation, so it can be expected that they are significantly lacking in improving high-temperature performance.

[0349]

[0350] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

Claims

1. A non-aqueous organic solvent; a lithium salt; and an additive, comprising, The above additive comprises a mixture of a first additive represented by the following chemical formula 1 and a second additive represented by the following chemical formula 2, for an electrolyte for a lithium secondary battery: [Chemical Formula 1] (In the above chemical formula 1, X is a fluoro group, chloro group, bromo group, or iodo group, and R 11 to R 16 Each is independently hydrogen, a cyano group, a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C1 to C20 alkoxy group, a substituted or unsubstituted C2 to C20 alkenyl group, a substituted or unsubstituted C2 to C20 alkynyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C2 to C20 heteroaryl group, and n is an integer of 0 or 1). [Chemical Formula 2] (In the above chemical formula 2, R 21 and R 22 Each is independently a single bond, a substituted or unsubstituted C1 to C20 alkylene group, a substituted or unsubstituted C1 to C20 alkoxylene group, a substituted or unsubstituted C2 to C20 alkenylene group, a substituted or unsubstituted C2 to C20 alkynylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C2 to C20 heteroarylene group, and R 23 and R 24 Each is independently hydrogen, cyano, a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C1 to C20 alkoxy group, a substituted or unsubstituted C2 to C20 alkenyl group, a substituted or unsubstituted C2 to C20 alkynyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C2 to C20 heteroaryl group, and R 23 and R 24 At least one of them is a substituted or unsubstituted C2 to C20 alkenyl group, hydrogen, a substituted or unsubstituted C1 to C20 alkyl group, or a cyano group).

2. In Paragraph 1, The above-mentioned first additive is an electrolyte for a lithium secondary battery comprising one or more of the following chemical formulas 1-2 and 1-3: [Chemical Formula 1-2] [Chemical Formula 1-3] (In the above chemical formulas 1-2 and 1-3, R 11 to R 16 Each is identical to what is defined in Chemical Formula 1 above).

3. In Paragraph 1 or 2, The above-mentioned first additive is an electrolyte for a lithium secondary battery comprising one or more of the following chemical formulas 1-4 to 1-8: [Chemical Formula 1-4] [Chemical Formula 1-5] [Chemical Formula 1-6] [Chemical Formula 1-7] [Chemical Formula 1-8] .

4. In any one of paragraphs 1 through 3, The above second additive is an electrolyte for a lithium secondary battery comprising one or more of the following chemical formulas 2-1, 2-2, and 2-8: [Chemical Formula 2-1] (In the above chemical formula 2-1, R 21 and R 22 is the same as defined in the above Chemical Formula 2, and R 23a and R 24a Each is independently a single bond or a substituted or unsubstituted C2 to C18 alkylene group), [Chemical Formula 2-2] (In the above chemical formula 2-2, R 21 and R 22 is the same as defined in the above Chemical Formula 2, and R 23b and R 24b Each independently has a single bond or a substituted or unsubstituted C2 to C18 alkylene group, R 23c and R 24c Each is independently a hydrogen or a substituted or unsubstituted C2 to C18 alkyl group, However, R 23b and R 23c The total number of carbon atoms in the main chain is 18 or less, and R 24b and R 24c The total number of carbon atoms in the main chain is 18 or less), [Chemical Formula 2-8] (In the above chemical formula 2-8, R 21 and R 22 is the same as defined in Chemical Formula 2 above).

5. In any one of paragraphs 1 through 4, The above second additive comprises one or more of the following chemical formulas 2-3 to 2-7 and 2-9 to 2-12, in an electrolyte for a lithium secondary battery: [Chemical Formula 2-3] [Chemical Formula 2-4] [Chemical Formula 2-5] [Chemical Formula 2-6] [Chemical Formula 2-7] [Chemical Formula 2-9] [Chemical Formula 2-10] [Chemical Formula 2-11] [Chemical Formula 2-12] .

6. In any one of paragraphs 1 through 5, The first additive is included in an amount of 0.05 to 5 weight percent with respect to the total amount of the electrolyte, and The above second additive is included in an amount of 0.05 to 5 weight percent relative to the total amount of the electrolyte, for a lithium secondary battery electrolyte.

7. In any one of paragraphs 1 through 6, An electrolyte for a lithium secondary battery, wherein the weight ratio of the content of the first additive to the content of the second additive in the electrolyte is 5:1 to 0.2:

1.

8. In any one of paragraphs 1 through 7, The above mixture is an electrolyte for a lithium secondary battery containing 95% by weight or more of the additives of the above electrolyte.

9. In any one of paragraphs 1 through 8, The above non-aqueous organic solvent is An electrolyte for a lithium secondary battery, comprising a mixture of ethylene carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 10 to 30: 5 to 20: 60 to 80.

10. In any one of paragraphs 1 through 9, The above lithium salt is one or more selected from the group consisting of LiPF6, LiClO4, LiBF4, (lithium bis(fluorosulfonyl)imide (LiFSI), LiTFSI, LiSO3CF3, LiBOB, LiFOB, LiDFBP, LiTFOP, LiPO2F2, LiSbF6, LiAsF6, LiAlO2, LiAlCl4, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N, and LiC4F9SO3, for use as an electrolyte for a lithium secondary battery.

11. In any one of paragraphs 1 through 10, An electrolyte for a lithium secondary battery having a lithium salt concentration of 0.1M to 2.0M.

12. Anode comprising a positive active material; A cathode comprising a cathode active material; and A lithium secondary battery comprising an electrolyte according to any one of claims 1 to 11.

13. In Paragraph 12, The above positive active material comprises a lithium nickel-based oxide, in a lithium secondary battery.

14. In Paragraph 13, The above lithium nickel-based oxide is a lithium secondary battery represented by the following chemical formula 3: [Chemical Formula 3] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In the above chemical formula 3, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 Each is independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

15. In any one of paragraphs 12 through 14, A lithium secondary battery in which the above-mentioned negative electrode active material comprises at least one of graphite and Si composite.

16. In any one of paragraphs 12 through 15, A lithium secondary battery having an operating voltage of 4.2 V or higher.

17. In any one of paragraphs 12 through 16, The above lithium secondary battery is a lithium secondary battery that is a cylindrical, prismatic, pouch-type, or coin-type battery.

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