Electrolyte for rechargeable lithium battery and rechargeable lithium battery

Abstract

To provide an electrolyte for a rechargeable lithium battery excellent in excellent impregnation, and a rechargeable lithium battery including the electrolyte for a rechargeable lithium battery.SOLUTION: An electrolyte for a rechargeable lithium battery comprises: a non-aqueous organic solvent; a lithium salt; a first compound represented by the upper chemical formula in the figure; and a second compound represented by the lower chemical formula. A rechargeable lithium battery comprises: a positive electrode that comprises a positive electrode active material; a negative electrode that comprises a negative electrode active material; and the electrolyte for a rechargeable lithium battery.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, the rapid spread of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles has led to a rapid increase in demand for high-energy-density, high-capacity secondary batteries, which has led to active research and development efforts to improve the performance of lithium secondary batteries.

[0003] A lithium secondary battery is a battery that includes a cathode and an anode, each containing an active material capable of intercalating and deintercalating lithium ions, and an electrolyte. Electrical energy is generated through oxidation and reduction reactions that occur when lithium ions are intercalated and deintercalated at the cathode and anode. Summary of the Invention [Problem to be solved by the invention]

[0004] One aspect is to provide an electrolyte solution for a lithium secondary battery that has excellent impregnation properties.

[0005] Another aspect is to provide a lithium secondary battery including the electrolyte. [Means for solving the problem]

[0006] One aspect provides an electrolyte solution for a lithium secondary battery, including a non-aqueous organic solvent, a lithium salt, a first compound represented by the following Chemical Formula 1, and a second compound represented by the following Chemical Formula 2:

[0007] [C1] [ka]

[0008] In Chemical Formula 1, R1A and R 1B are each independently a substituted or unsubstituted C2 to C10 alkyl group, and R 1A and R 1B At least one of the groups is a halogenated alkyl group represented by the following chemical formula A1.

[0009] [Chemical A1] C n H 2n+1-m X m

[0010] In Formula A1, X is F, Cl, Br, I, or a combination thereof, n is an integer from 2 to 10, and m is an integer from 2 to 2n+1.

[0011] [C2] [ka]

[0012] In Chemical Formula 2, L 2A and L 2B are each independently a single bond, a substituted or unsubstituted C1 to C5 alkylene group, a substituted or unsubstituted C2 to C5 alkenylene group, a substituted or unsubstituted C2 to C5 alkynylene group, or a substituted or unsubstituted C6 to C20 arylene group; A and B are each independently an unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C2 to C20 heteroaryl group.

[0013] At least one of A and B is a group represented by the following chemical formula A2.

[0014] [Chemical A2] [ka]

[0015] In chemical formula A2, R2A and R 2B are each independently hydrogen, halogen, a substituted or unsubstituted C1 to C10 alkyl group, or a substituted or unsubstituted C3 to C10 cycloalkyl group.

[0016] Another aspect provides a lithium secondary battery including a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and the above-described electrolyte solution for lithium secondary batteries. [Effects of the Invention]

[0017] The electrolyte for a lithium secondary battery according to one embodiment can improve impregnation characteristics, improve high-temperature life characteristics, and reduce electrode swelling. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a simplified conceptual diagram of a lithium secondary battery according to an embodiment of the present invention; [Figure 2] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to one embodiment. [Figure 3] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to one embodiment. [Figure 4] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to one embodiment. [Figure 5] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to one embodiment. [Figure 6] 1 shows photographs of test results of electrolyte impregnation according to Examples 1 to 5 and Comparative Examples 1 to 5. DETAILED DESCRIPTION OF THE INVENTION

[0019] In order to fully understand the configuration and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be embodied in various forms and can be modified in various ways. However, the description of the present embodiments is provided to ensure complete disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0020] In this specification, when a component is referred to as being on top of another component, it means that it may be formed directly on the other component, or that a third component may be interposed between them. Also, in the drawings, the thickness of the components may be exaggerated for the purpose of effectively explaining the technical content. Throughout the specification, parts designated with the same reference numerals refer to the same components.

[0021] Unless otherwise stated herein, the singular can also include the plural. Additionally, unless otherwise stated, "A or B" can mean "including A but not B," "including B but not A," and "including A and B." As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other elements to the referenced element.

[0022] As used herein, "combinations thereof" can mean mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0023] Unless otherwise defined herein, particle size may refer to the average particle size. Furthermore, particle size refers to the average particle size (D50), which refers to the diameter of particles with a cumulative volume of 50 vol% in a particle size distribution. The average particle size (D50) may be measured using a method well known to those skilled in the art, such as a particle size analyzer, or a transmission electron microscope or scanning electron microscope. Alternatively, the average particle size (D50) may be measured using a measuring device that uses dynamic light scattering, and data analysis may be performed to count the number of particles in each particle size range, followed by calculation. Alternatively, the average particle size (D50) may be measured using a laser diffraction method. When measuring by the laser diffraction method, more specifically, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size measuring device (e.g., MT 3000 manufactured by Microtrac), and ultrasonic waves of approximately 28 kHz are irradiated at an output of 60 W. After that, the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0024] As used herein, expressions such as "at least one of," "one of," "e.g., selected from among," when preceding a list of elements, modify the list of elements as a whole, not individual elements of the list. For example, "at least one of a, b, c," "at least one selected from a, b, c," and / or "at least one selected from a, b, c," etc., can refer to a only, b only, c only, both a and b (e.g., simultaneously), both a and c (e.g., simultaneously), both b and c (e.g., simultaneously), all of a, b, and c, or variations thereof.

[0025] The terms used herein are intended to describe particular embodiments only and are not intended to limit the disclosure. As used herein, the singular forms "a," "an," "the," and "the" are intended to include the plural, including "at least one," unless the content (e.g., quantity) clearly dictates otherwise. "At least one" should not be construed as being limited to the singular. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The terms "comprise" and / or "comprise," when used in the detailed description, specify the presence of stated features, regions, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.

[0026] Spatially relative terms such as "below," "below," "lower," "above," and the like may be used herein to easily describe the relationship between one element or feature and another. It will be understood that spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures were inverted (e.g., flipped over), elements described as "below" or "below" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an above and below orientation (e.g., simultaneously). The device may be in other orientations (rotated 90 degrees or at other orientations), and the spatially relative terms used herein can be interpreted accordingly.

[0027] The term "substantially" and similar terms are used as terms of approximation, not as terms of degree, and are intended to take into account inherent variations in measurements or calculations that would be recognized by one of ordinary skill in the art. Additionally, the term "about" and similar terms, when used herein in connection with a numerical value or numerical range, includes the stated value and values ​​within an acceptable range of deviation from the particular value that would be determined by one of ordinary skill in the art, taking into account the error associated with the measurement in question and the measurement of the particular quantity (e.g., limitations of the measurement system). For example, "about" can refer to within one or more standard deviations, or within ±30%, 20%, 10%, or 5% of the stated value.

[0028] Additionally, numerical ranges recited herein are intended to include all subranges of the same numerical precision subsumed within the recited range. For example, a range of "1.0 to 10.0" is intended to include all subranges between (and including) the recited minimum value of 1.0 and the recited maximum value of 10.0, i.e., having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as 2.4 to 7.6. Each maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein, and each minimum numerical limitation recited herein is intended to include all higher numerical limitations subsumed therein. Accordingly, applicants reserve the right to amend this specification (including the claims) to expressly recite any subranges subsumed within the ranges expressly recited herein.

[0029] Unless otherwise defined, the term "substituted" as used herein means that at least one hydrogen atom in a substituent or compound is replaced with 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, "substituted" may mean that at least one hydrogen atom in a substituent or compound is replaced 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, "substituted" may mean that at least one hydrogen atom in a substituent or compound is replaced 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, "substituted" may mean that at least one hydrogen atom in a substituent or compound is replaced with 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. As an example, "substituted" may mean that at least one hydrogen in a substituent or compound is replaced with 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] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment 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 solution ELL.

[0032] The positive electrode 10 and the negative electrode 20 may be separated from each other by a separator 30. The separator 30 may be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be in contact with an electrolyte solution ELL. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated in the electrolyte solution ELL.

[0033] The electrolyte solution ELL may be a medium for transferring lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte solution ELL, the lithium ions can pass through the separator 30 and move toward the positive electrode 10 or the negative electrode 20.

[0034] positive electrode 10 The lithium secondary battery positive electrode 10 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 includes a positive electrode active material and may further include a binder and / or a conductive material.

[0035] As an example, the cathode 10 may further include an additive that can act as a sacrificial cathode.

[0036] The content of the positive electrode active material in the positive electrode active material layer AML1 may be 90 wt% to 99.5 wt% relative to 100 wt% of the positive electrode active material layer AML1, and the contents of the binder and conductive material may be 0.5 wt% to 5 wt% each relative to 100 wt% of the positive electrode active material layer AML1.

[0037] The binder serves to firmly bind the positive electrode active material particles to each other and to firmly bind the positive electrode active material to the current collector COL1. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylic styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0038] The conductive material is used to impart conductivity to the electrodes, and any electron-conductive material that does not undergo chemical changes can be used as the conductive material for a battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0039] The current collector COL1 can be made of Al, but is not limited to this.

[0040] positive electrode active material The positive electrode active material in the positive electrode active material layer AML1 may be a compound capable of reversibly inserting and extracting lithium (lithiated intercalation compound). Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0041] The composite oxide may be a lithium transition metal composite oxide, but specific examples include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based oxide, cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0042] For example, a compound represented by any one of the following chemical formulas can be used: Li a A 1-b X b O 2-c D c (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05), Li a Mn 2-b X b O 4-c D c (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05), Li a Ni 1-b-c Co b X c 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 Mn2Gb 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).

[0043] In the 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 is Mn, Al, or a combination thereof.

[0044] For example, the positive electrode active material may be a high-nickel positive electrode active material in which the nickel content is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less relative to 100 mol% of metals excluding lithium from the lithium transition metal composite oxide. High-nickel positive electrode active materials can achieve high capacity and are therefore applicable to high-capacity, high-density lithium secondary batteries.

[0045] negative electrode 20 The lithium secondary battery negative electrode 20 may include a current collector COL2 and a negative electrode active material layer AML2 formed on the current collector COL2. The negative electrode active material layer AML2 includes a negative electrode active material and may further include a binder and / or a conductive material.

[0046] For example, the negative electrode active material layer AML2 may contain 90 wt % to 99 wt % of the negative electrode active material, 0.5 wt % to 5 wt % of the binder, and 0 wt % to 5 wt % of the conductive material.

[0047] The binder serves to firmly bind the negative electrode active material particles to each other and to firmly bind the negative electrode active material to the current collector COL2. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0048] Non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0049] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyether resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0050] When an aqueous binder is used as the negative electrode binder, it may further contain a cellulose-based compound to impart viscosity. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be Na, K, or Li.

[0051] The dry binder may be a fiberizable polymeric material such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, ethylene oxide, or combinations thereof.

[0052] The conductive material is used to impart conductivity to the electrode, and any material that is electron-conductive and does not undergo chemical changes can be used as the conductive material for a battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0053] The current collector COL2 may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0054] negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 includes a material capable of reversibly inserting / extracting lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped with or dedoped from lithium, or a transition metal oxide.

[0055] The material capable of reversibly inserting / extracting lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite, such as amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite. Examples of amorphous carbon include soft or hard carbon, mesophase pitch carbide, and calcined coke.

[0056] As the alloy of lithium metal, 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 can be used.

[0057] As a substance that can be doped or undoped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or combinations thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or combinations thereof.

[0058] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one aspect, the silicon-carbon composite may be in a form in which amorphous carbon is coated on the surface of silicon particles. For example, it may include secondary particles (cores) combined with primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. Amorphous carbon may also be located between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed and present in an amorphous carbon matrix.

[0059] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core.

[0060] The Si-based negative electrode active material or the Sn-based negative electrode active material may be used in mixture with a carbon-based negative electrode active material.

[0061] Separator 30 Depending on the type of lithium secondary battery, a separator 30 may be present between the positive electrode 10 and the negative electrode 20. Such separator 30 may be made of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, but it goes without saying that 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 also be used.

[0062] Separator 30 can 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.

[0063] The porous substrate may be a polymer membrane made of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyetherimide, polyamide imide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon, and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0064] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0065] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0066] The organic material and the inorganic material may be mixed in one coating layer, or may be stacked in a form in which a coating layer containing an organic material and a coating layer containing an inorganic material are laminated.

[0067] Electrolyte ELL The electrolyte ELL for lithium secondary batteries contains a non-aqueous organic solvent, a lithium salt, and an electrolyte additive.

[0068] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0069] The non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, a non-quantum solvent, or a combination thereof.

[0070] As the carbonate solvent, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl pyrrolyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. may be used.

[0071] As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate (PP), decanolide, mevalonolactone, valerolactone, caprolactone, and the like may be used.

[0072] Examples of ether solvents that may be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that may be used include cyclohexanone. Examples of alcohol solvents that may be used include ethyl alcohol and isopropyl alcohol. Examples of non-quantum solvents that may be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane and 1,4-dioxolane, and sulfolanes.

[0073] The non-aqueous organic solvents may be used alone or in combination of two or more.

[0074] When a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed and used, and the cyclic carbonate and the chain cyclic carbonate may be mixed in a volume ratio of 1:1 to 1:9.

[0075] Lithium salts are substances dissolved in organic solvents and act as a source of lithium ions in the battery, enabling basic lithium secondary battery operation and facilitating the movement of lithium ions between the positive and negative electrodes. 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+1SO2) (x and y are positive numbers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), and lithium bis(oxalato)borate (LiBOB).

[0076] An electrolyte solution for a lithium secondary battery according to one embodiment will be described below.

[0077] An electrolyte solution for a lithium secondary battery according to one embodiment of the present invention may include a non-aqueous organic solvent, a lithium salt, a first compound represented by the following Chemical Formula 1, and a second compound represented by the following Chemical Formula 2:

[0078] [C1] [ka]

[0079] In Chemical Formula 1, R 1A and R 1B may each independently be a substituted or unsubstituted C2 to C10 alkyl group.

[0080] In Chemical Formula 1, R 1A and R 1B At least one of R may be a halogenated alkyl group represented by the following chemical formula A1. 1A and R 1B Any one of R may be a halogenated alkyl group represented by the following chemical formula A1: 1A and R 1B The other of R may be a substituted or unsubstituted C2 to C10 alkyl group. 1A and R 1B may be a halogenated alkyl group represented by the following chemical formula A1.

[0081] [Chemical A1] C n H 2n+1-m Xm In Formula A1, X can be F, Cl, Br, I, or a combination thereof.

[0082] In Formula A1, n may be an integer from 2 to 10.

[0083] In Formula A1, m can be an integer from 2 to 2n+1.

[0084] As an example, X may be F.

[0085] [C2] [ka]

[0086] In Chemical Formula 2, L 2A and L 2B Each of L may independently be a single bond, a substituted or unsubstituted C1 to C5 alkylene group, a substituted or unsubstituted C2 to C5 alkenylene group, a substituted or unsubstituted C2 to C5 alkynylene group, or a substituted or unsubstituted C6 to C20 arylene group. 2A is a single bond, A may be directly linked to S by a single bond. 2B is a single bond, then B may be directly linked to S by a single bond.

[0087] In Chemical Formula 2, A and B may each independently be an unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C2 to C20 heteroaryl group.

[0088] In Chemical Formula 2, at least one of A and B may be a group represented by Chemical Formula A2 below. For example, at least one of A and B may be a group represented by Chemical Formula A2 below, and the other of A and B may be a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C2 to C20 heteroaryl group. In another embodiment, both A and B may be groups represented by Chemical Formula A2 below.

[0089] [Chemical A2] [ka]

[0090] In chemical formula A2, R 2A and R 2B may each independently be hydrogen, halogen, a substituted or unsubstituted C1 to C10 alkyl group, or a substituted or unsubstituted C3 to C10 cycloalkyl group.

[0091] As an example, the first compound may include 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, or a mixture thereof.

[0092] As an example, Chemical Formula 1 may be represented by the following Chemical Formula 1-1.

[0093] [C1-1] [ka] 1,1,2,2-Tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (CAS No.: 16627-68-2)

[0094] A high electrode mixing density can improve energy density, but may result in a relative decrease in the electrolyte impregnation characteristics. Fluorine-based compounds can improve the wettability of the electrolyte and the adhesive strength of the electrodes, and can reduce the surface tension of the electrolyte.

[0095] The first compound can be added to an electrolyte solution for a lithium secondary battery to improve the impregnation characteristics of the electrolyte solution. The first compound can improve the impregnation characteristics of the electrolyte solution in a lithium secondary battery using an electrode with a high mixing density.

[0096] The first compound may be contained in an amount of 0.1 to 20 wt % of the total amount of the electrolyte solution for lithium secondary batteries.

[0097] As a specific example, the first compound may be contained in an amount of 0.1 to 15 wt %, 0.1 to 10 wt %, 1 to 10 wt %, or 5 to 10 wt % of the total amount of the electrolyte solution for lithium secondary batteries.

[0098] In lithium secondary batteries, the non-aqueous electrolyte is decomposed during initial charging and discharging, and a passivating film is formed on the surface of the positive and negative electrodes, improving high-temperature storage characteristics. However, the film is formed by the thermal decomposition of HF, which is produced by the thermal decomposition of lithium salts (such as LiPF6) widely used in lithium-ion batteries. - and PF5 - The positive electrode may be deteriorated by acids such as PF5. Such acid attack causes the elution of transition metal elements at the positive electrode, resulting in a change in the surface structure, which increases the surface resistance of the electrode. Furthermore, the theoretical capacity decreases due to the loss of the metal elements that play a central role in redox reactions, which can lead to a decrease in the actual capacity. Furthermore, the eluted transition metal ions are not only electrodeposited on the negative electrode, which reacts in a strong reduction potential range, consuming the battery, but also destroying the coating during electrodeposition, exposing the negative electrode surface, which can trigger further decomposition reactions of the electrolyte. As a result, the resistance of the negative electrode increases, the irreversible capacity increases, and the cell capacity decreases continuously. In the present invention, the triazole group and sulfone group of the compound represented by the above-mentioned Chemical Formula 2 provide unshared electron pairs, resulting in the formation of PF5. -By capturing and stabilizing the LiPF6 salt, the acid caused by the decomposition of the lithium salt can be removed.

[0099] The sulfonic acid group contained in Chemical Formula 2 forms a coating on the surface of the positive electrode to inhibit decomposition of the positive electrode active material, thereby inhibiting gas generation and elution of transition metals due to decomposition of the positive electrode active material.

[0100] In addition, the compound represented by Chemical Formula 2 can strengthen the solid electrolyte interfase (SEI) film on the surface of the negative electrode while preventing deterioration of the SEI film and elution of transition metals from the positive electrode during high-temperature storage.

[0101] As an example, L 1 and L 2 At least one of may be a substituted or unsubstituted C1 to C5 alkylene group.

[0102] As an example, L 1 and L 2 may each independently be a substituted or unsubstituted C1 to C5 alkylene group.

[0103] As an example, L 1 and L 2 At least one of may be a substituted or unsubstituted C2 to C5 alkylene group.

[0104] As an example, L 1 and L 2 may each independently be a substituted or unsubstituted C2 to C5 alkylene group.

[0105] As an example, Chemical Formula 2 may be represented by Chemical Formula 2-1 below.

[0106] [Case 2-1] [ka]

[0107] In Chemical Formula 2-1, L 1 and L 2 may each independently be a substituted or unsubstituted C2 to C5 alkylene group.

[0108] In Chemical Formula 2-1, R 21A , R 21B , R 21C , and R 21D may each independently be hydrogen, halogen, a substituted or unsubstituted C1 to C10 alkyl group, or a substituted or unsubstituted C3 to C10 cycloalkyl group.

[0109] In one embodiment, the second compound can be selected from the compounds listed in Group 1 below.

[0110] [Group 1] [ka] [ka]

[0111] The second compound may be contained in an amount of 0.1 to 10 wt % of the total amount of the electrolyte solution for lithium secondary batteries.

[0112] As a specific example, the second compound may be contained in an amount of 0.5 to 10 wt %, 1 to 10 wt %, or 1 to 5 wt % of the total amount of the electrolyte solution for a lithium secondary battery.

[0113] As an example, the electrolyte for a lithium secondary battery may contain the first compound and the second compound in a weight ratio of 1:1 to 20:1.

[0114] As a specific example, the electrolyte for a lithium secondary battery may contain the first compound and the second compound in a weight ratio of 1:1 to 15:1, 1:1 to 10:1, or 5:1 to 10:1.

[0115] When the mixing ratio of the first compound and the second compound is as described above, the degree of improvement in the impregnation characteristics of the electrolyte can be maximized.

[0116] The first compound and the second compound may be contained in an amount of 0.001 to 30 wt % of the total amount of the electrolyte solution for a lithium secondary battery.

[0117] For example, the first compound and the second compound may be included in an amount of 0.01 to 25 wt%, 0.01 to 15 wt%, 0.01 to 10 wt%, 0.1 to 10 wt%, or 1 to 10 wt% of the total amount of the electrolyte for a lithium secondary battery. Within these ranges, an increase in resistance at high temperatures can be prevented, and a lithium secondary battery with improved life and output characteristics can be realized.

[0118] The electrolyte for lithium secondary batteries may further contain at least one compound selected from vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), adiponitrile (AN), succinic acid nitrile (SN), 1,3,6-hexanetricyanide (HTCN), propene sultone (PST), propane sultone (PS), lithium tetrafluoroborate (LiBF), lithium difluorophosphate (LiPOF), and 2-fluorobiphenyl (2-FBP).

[0119] By further including the other additives mentioned above, the life span can be further improved or gas generated at the positive and negative electrodes during high temperature storage can be effectively controlled.

[0120] The other additives may be contained in an amount of 0.1 to 20 wt %, more specifically 0.2 to 15 wt %, for example 0.2 to 10 wt %, of the total amount of the electrolyte for a lithium secondary battery.

[0121] If the content of other additives is as described above, it can minimize the increase in film resistance and contribute to improving electrical performance.

[0122] Lithium secondary battery Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 2 to 5 are schematic diagrams showing lithium secondary batteries according to one embodiment, with FIG. 2 illustrating a cylindrical battery, FIG. 3 illustrating a prismatic battery, and FIGS. 4 and 5 illustrating pouch battery types. Referring to FIGS. 2 and 4, a lithium secondary battery 100 may include an electrode assembly 40 including a positive electrode 10, a negative electrode 20, and a separator 30 interposed between them, and a housing 50 in which the electrode assembly 40 is embedded. 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 housing 50, as shown in FIG. 2. Also, in FIG. 3, the lithium secondary battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in FIGS. 4 and 5, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting the current generated in the positive electrode assembly 40 to the outside.

[0123] The lithium secondary battery according to an embodiment of the present invention may be applied to automobiles, mobile phones, and / or various types of electrical devices, but the present invention is not limited thereto.

[0124] Examples and comparative examples of the present invention will be described below, but the following examples are merely examples of the present invention and the present invention is not limited to the following examples. [Example]

[0125] Examples and Comparative Examples An electrolyte and a lithium secondary battery were manufactured as follows.

[0126] Example 1 (1) Electrolyte production An electrolyte solution was prepared by dissolving 1.3 M LiPF in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propyl carbonate (EPC), and propyl propionate (PP) were mixed in a volume ratio of 10:15:30:45, and adding a first compound represented by the following Chemical Formula 1-1 and a second compound represented by the following Chemical Formula 2-1-1.

[0127] The electrolyte was prepared by mixing 5 wt% of the first compound with 100 wt% of the total electrolyte solution, and 1 wt% of the second compound with 100 wt% of the total electrolyte solution.

[0128] [Case 1-1] [ka] 1,1,2,2-Tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (CAS No.: 16627-68-2)

[0129] [Case 2-1-1] [ka]

[0130] (2) Manufacture of lithium secondary batteries LiCoO2 as a positive electrode active material, polyvinylidene fluoride as a binder, and acetylene black as a conductive material were mixed in a weight ratio of 96:3:1, and dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0131] The positive electrode active material slurry was coated on an Al foil having a thickness of 15 μm, dried at 100° C., and then pressed to prepare a positive electrode.

[0132] Artificial graphite was used as the negative electrode active material, and the negative electrode active material was mixed with styrene-butadiene rubber binder and carboxymethyl cellulose in a weight ratio of 98:1:1, respectively, and dispersed in distilled water to prepare a negative electrode active material slurry.

[0133] The negative electrode active material slurry was coated on a Cu foil with a thickness of 10 μm, dried at 100° C., and then rolled to prepare a negative electrode, with the mixed density of the negative electrode being 1.7 g / cc.

[0134] The positive and negative electrodes were assembled with a 10 μm thick polyethylene separator to prepare an electrode assembly, and an electrolyte was injected to prepare a lithium secondary battery.

[0135] Example 2 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 1, except that 10 wt % of the first compound and 1 wt % of the second compound were added when preparing the electrolyte solution.

[0136] Example 3 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 1, except that 10 wt % of the first compound and 2 wt % of the second compound were added when preparing the electrolyte solution.

[0137] Example 4 An electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 3, except that the mixing density of the negative electrode was adjusted to 1.75 g / cc when manufacturing the negative electrode.

[0138] Example 5 An electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 3, except that the mixed density of the negative electrode was adjusted to 1.8 g / cc when manufacturing the negative electrode.

[0139] Comparative Example 1 An electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first compound and the second compound were not added when preparing the electrolyte, and the mixed density was adjusted to 1.65 g / cc when preparing the negative electrode.

[0140] Comparative Example 2 An electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first compound and the second compound were not added when preparing the electrolyte, and the mixed density was adjusted to 1.67 g / cc when preparing the negative electrode.

[0141] Comparative Example 3 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first compound and the second compound were not added when preparing the electrolyte solution.

[0142] Comparative Example 4 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 1, except that 5 wt % of the first compound was added and no second compound was added when preparing the electrolyte solution.

[0143] Comparative Example 5 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 1, except that 1 wt % of the second compound was added when preparing the electrolyte solution, and no first compound was added.

[0144] Evaluation example The negative electrode and the lithium secondary battery were evaluated by the following methods.

[0145] Evaluation 1: Impregnation of the electrolyte into the negative electrode The negative electrode according to Example 1 was prepared into a test piece measuring 3 cm x 4 cm. 1 g of the electrolyte according to Example 1 was dropped onto the test piece and left for 1 minute. A photograph of the area of ​​the electrolyte on the surface of the negative electrode was taken and shown in Figure 6. The amount of electrolyte immersed in the test piece out of 100 wt% of the electrolyte dropped onto the test piece was evaluated on a scale of 0 to 5 according to the following criteria, and the evaluation results are shown in Table 1 below.

[0146] 0: When the amount of electrolyte immersed in the specimen is 0 wt% or more but less than 10 wt% 1: When the amount of electrolyte immersed in the specimen is 10 wt% or more but less than 20 wt% 2: When the amount of electrolyte immersed in the specimen is 20 wt% or more but less than 40 wt% 3: When the amount of electrolyte immersed in the specimen is 40 wt% or more but less than 60 wt% 4: When the amount of electrolyte immersed in the specimen is 60 wt% or more but less than 80 wt% 5: When the amount of electrolyte immersed in the specimen is 80 wt% or more but less than 100 wt%

[0147] Examples 2 to 5 and Comparative Examples 1 to 5 were also evaluated in the same manner, and the evaluation results are shown in Table 1 below.

[0148] Incidentally, FIG. 6(1) is a photograph taken after the electrolyte solution of Example 1 was used and the battery was left standing for 1 minute according to Evaluation 1.

[0149] FIG. 6(2) is a photograph taken after the electrolyte solution of Example 2 was used and the battery was left standing for 1 minute according to Evaluation 1.

[0150] FIG. 6(3) is a photograph taken after the electrolyte solution of Example 3 was used and the battery was left standing for 1 minute according to Evaluation 1.

[0151] FIG. 6(4) is a photograph taken after the electrolyte solution of Example 4 was used and the battery was left standing for 1 minute according to Evaluation 1.

[0152] FIG. 6(5) is a photograph taken after the electrolyte solution of Example 5 was used and the battery was left standing for 1 minute according to Evaluation 1.

[0153] FIG. 6(6) is a photograph taken after the electrolyte solution of Comparative Example 1 was used and the battery was left standing for 1 minute according to Evaluation 1.

[0154] FIG. 6(7) is a photograph taken after the electrolyte solution of Comparative Example 2 was used and the battery was left standing for 1 minute according to Evaluation 1.

[0155] FIG. 6(8) is a photograph of the battery after it was left for 1 minute according to Evaluation 1 using the electrolyte solution of Comparative Example 3.

[0156] FIG. 6(9) is a photograph of the battery after it was left for 1 minute according to Evaluation 1 using the electrolyte solution of Comparative Example 4.

[0157] FIG. 6 (10) is a photograph of the battery after it was left for 1 minute according to Evaluation 1 using the electrolyte solution of Comparative Example 5.

[0158] [Table 1] [Table 1]

[0159] Evaluation 2: Evaluation of high-temperature charge-discharge cycle characteristics The lithium secondary battery was subjected to 200 charge / discharge cycles under the conditions of 45°C, 0.33C charge (CC / CV, 4.3V, 0.025C cut-off) / 1.0C discharge (CC, 2.5V cut-off).

[0160] The thickness increase rate was calculated according to the following formula 1, and the capacity retention rate was calculated according to the following formula 2. The results are shown in Table 2 below.

[0161] [Formula 1] Thickness increase rate = {(fully charged thickness after 200 cycles) - (fully charged thickness after 1 cycle)} * 100 In Equation 1, "fully charged thickness" means the thickness of a lithium secondary battery measured after charging to 100% SOC (a state in which the battery is charged to 100% charge capacity when the total charge capacity of the battery is 100%) after each cycle.

[0162] [Formula 2] Capacity retention rate = (discharge capacity after 200 cycles / discharge capacity after 1 cycle) * 100

[0163] [Table 2] [Table 2]

[0164] General Referring to Tables 1 and 2 and FIGS. 6 to 15, when an electrolyte solution containing no first or second compound was used (Comparative Examples 1 to 3), the impregnation of the electrolyte into the negative electrode decreased as the mixed density of the negative electrode increased from 1.65 g / cc to 1.7 g / cc, resulting in an increase in the thickness of the battery and a decrease in its lifespan.

[0165] When the mixed density of the negative electrode is the same at 1.7 g / cc, when an electrolyte containing a mixed compound of the first compound and the second compound is used (Examples 1 to 3), the impregnation of the electrolyte into the negative electrode is improved, the thickness of the battery is reduced, and the lifespan is extended, compared to when an electrolyte containing no first compound or second compound or only one of the first compound or second compound is used (Comparative Examples 3 to 5).

[0166] When an electrolyte solution containing a compound obtained by mixing the first compound and the second compound is used, even if the mixed density of the negative electrode is increased from 1.7 g / cc to 1.8 g / cc (Examples 4 and 5), the increase in the thickness of the battery and the decrease in its lifespan are suppressed.

[0167] The electrolyte for a lithium secondary battery according to one or more embodiments can improve impregnation, high-temperature life, and electrode expansion.

[0168] The battery management system (BMS) device according to the embodiments of the present disclosure described herein, and / or any other related devices or components, can be implemented using any suitable hardware, firmware (e.g., application-specific integrated circuits), software, or a combination of software, firmware, and hardware. For example, one or more suitable components of the device may be formed on a single integrated circuit (IC) chip or on separate IC chips. Furthermore, one or more suitable components of the device may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or on a single substrate. The computer program instructions are stored in memory implemented in the computing device, for example, using standard memory devices such as random access memory (RAM). The computer program instructions may also be stored on other non-transitory computer-readable media, such as, for example, a CD-ROM, a flash drive, and / or the like. Those skilled in the art should also recognize that the functionality of one or more suitable computing devices may be combined or integrated into a single computing device, or the functionality of a particular computing device may be distributed across one or more other computing devices, without departing from the scope of the present disclosure.

[0169] Although the preferred embodiment of the present invention has been described above, the present invention is not limited thereto and can be embodied in various modifications within the scope of the claims, the embodiments for implementing the invention, and the accompanying drawings, and it is of course understood that these also fall within the scope of the present invention. [Explanation of symbols]

[0170] 100: Lithium secondary battery 10: Positive electrode 11: Positive electrode lead tab 12: Positive electrode terminal 20: Negative electrode 21: Negative electrode lead tab 22: Negative terminal 30: Separator 40: Electrode assembly 50: Housing 60: Sealing member 70: Electrode tab 71: Positive electrode tab 72: Negative electrode tab

Claims

1. a non-aqueous organic solvent; A lithium salt, A first compound represented by the following chemical formula 1: and a second compound represented by the following chemical formula 2: [Chemical formula 1] 【Chemical 1】 In the above Chemical Formula 1, R １Ａ and R １Ｂ are each independently a substituted or unsubstituted C2 to C10 alkyl; R １Ａ and R １Ｂ At least one of the groups is a halogenated alkyl group represented by the following chemical formula A1: [Chemical A1] C ｎ H ２ｎ＋１－ｍ X ｍ In the formula A1, X is F, Cl, Br, I, or a combination thereof; n is an integer from 2 to 10; and m is an integer from 2 to 2n+1; [Chemical 2] 【Chemistry 2】 In the above Chemical Formula 2, L ２Ａ and L ２Ｂ each independently represents a single bond, a substituted or unsubstituted C1 to C5 alkylene group, a substituted or unsubstituted C2 to C5 alkenylene group, a substituted or unsubstituted C2 to C5 alkynylene group, or a substituted or unsubstituted C6 to C20 arylene group; A and B are each independently a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C2 to C20 heteroaryl group; At least one of A and B is a group represented by the following chemical formula A2: [Chemical A2] 【Chemistry 3】 In the above chemical formula A2, R ２Ａ and R ２Ｂ are each independently hydrogen, halogen, a substituted or unsubstituted C1 to C10 alkyl group, or a substituted or unsubstituted C3 to C10 cycloalkyl group.

2. The R １Ａ and R １Ｂ and each independently represent a halogenated alkyl group represented by the chemical formula A1.

3. 2. The electrolyte solution for a lithium secondary battery according to claim 1, wherein X is F.

4. 2. The electrolyte for a lithium secondary battery according to claim 1, wherein the first compound comprises 1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, or a mixture thereof.

5. 2. The electrolyte for a lithium secondary battery according to claim 1, wherein the Chemical Formula 1 is represented by the following Chemical Formula 1-1: [Chemical formula 1-1] 【Chemistry 4】

6. Said L １ and L ２ 2. The electrolyte solution for a lithium secondary battery according to claim 1, wherein at least one of the groups is a substituted or unsubstituted C1 to C5 alkylene group.

7. Said L １ and L ２ 2. The electrolyte for a lithium secondary battery according to claim 1, wherein at least one of the groups is a substituted or unsubstituted C2 to C5 alkylene group.

8. Said L １ and L ２ and each independently represent a substituted or unsubstituted C2 to C5 alkylene group.

9. The electrolyte for a lithium secondary battery according to claim 1, wherein the chemical formula 2 is represented by the following chemical formula 2-1: [Chemical formula 2-1] 【Chemistry 5】 In the above chemical formula 2-1, L １ and L ２ are each independently a substituted or unsubstituted C2 to C5 alkylene group; R ２１Ａ , R ２１Ｂ , R ２１Ｃ , and R ２１Ｄ are each independently hydrogen, halogen, a substituted or unsubstituted C1 to C10 alkyl group, or a substituted or unsubstituted C3 to C10 cycloalkyl group.

10. The electrolyte for a lithium secondary battery according to claim 1 , wherein the second compound includes at least one of compounds listed in the following first group: [Group 1] 【Chemistry 6】 【Chemistry 7】

11. 2. The electrolyte solution for a lithium secondary battery according to claim 1, wherein the first compound and the second compound are contained in a weight ratio of 1:1 to 20:

1.

12. 2. The electrolyte solution for a lithium secondary battery according to claim 1, wherein the first compound and the second compound are contained in a weight ratio of 5:1 to 10:

1.

13. The electrolyte solution for a lithium secondary battery according to claim 1 , wherein the first compound is contained in an amount of 0.1 to 20 wt % of the total amount of the electrolyte solution for a lithium secondary battery.

14. The electrolyte solution for a lithium secondary battery according to claim 1 , wherein the second compound is contained in an amount of 0.1 to 10 wt % of the total amount of the electrolyte solution for a lithium secondary battery.

15. Vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), adiponitrile (AN), succinonitrile (SN), 1,3,6-hexanetricyanide (HTCN), propene sultone (PST), propane sultone (PS), lithium tetrafluoroborate (LiBF ４ ), lithium difluorophosphate (LiPO ２ F ２ 2. The electrolyte solution for a lithium secondary battery according to claim 1, further comprising at least one compound selected from the group consisting of 2-fluorobiphenyl (2-FBP), ... and 2-fluorobiphenyl (2-FBP).

16. a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; A lithium secondary battery comprising the electrolyte solution for lithium secondary batteries according to claim 1 .

17. 17. The lithium secondary battery according to claim 16, wherein the negative electrode has a mixed density of 1.7 g / cc or greater.

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