Electrolyte solution for lithium secondary battery, and lithium secondary battery

Abstract

To provide an electrolyte solution for a lithium secondary battery, in which the high-temperature lifetime characteristic, storage characteristic, and stability are excellent.SOLUTION: An electrolyte solution for a lithium secondary battery, and a lithium secondary battery including the same are provided. The electrolyte solution for a lithium secondary battery includes a nonaqueous organic solvent, lithium salt, a first compound represented by the following chemical formula, and a second compound that is a phosphate compound.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery including the same. [Background technology]

[0002] In recent years, the demand for high-energy-density, high-capacity secondary batteries has rapidly increased due to the rapid spread of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles. Therefore, research and development to improve the performance of lithium secondary batteries has been actively pursued.

[0003] A lithium secondary battery is a battery that includes a cathode and an anode, which contain active materials that allow the intercalation and deintercalation of lithium ions, and an electrolyte. Electrical energy is produced through oxidation and reduction reactions that occur when lithium ions are inserted / deintercalated at the cathode and anode. Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an electrolyte for a lithium secondary battery that has excellent high-temperature life characteristics, storage characteristics, and stability.

[0005] Another object of the present invention is to provide a lithium secondary battery containing the electrolyte solution for lithium secondary batteries. [Means for solving the problem]

[0006] One embodiment of the present invention 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] [ka] ...chemical formula 1

[0008] [ka] ...Chemical formula 2

[0009] In the above Chemical Formula 1, X 1a is a fluoro group, a chloro group, a bromo group, or an iodo group, R 1a ~R 6a each independently represents hydrogen, halogen, a substituted or unsubstituted C1 to C20 alkyl 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 C3 to C20 cycloalkenyl group, a substituted or unsubstituted C3 to C20 cycloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C2 to C30 heterocyclic group; n is an integer of 0 or 1, In the above Chemical Formula 2, L 1b ~L 3b each independently represents a single bond or a substituted or unsubstituted C1 to C10 alkylene group; R 1b ~R 3b may each independently be hydrogen, halogen, a substituted or unsubstituted C1 to C20 alkyl 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 C3 to C20 cycloalkenyl group, a substituted or unsubstituted C3 to C20 cycloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C2 to C30 heterocyclic group.

[0010] Another embodiment of the present invention provides a lithium secondary battery including a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and the above-described electrolyte for a lithium secondary battery. [Effects of the Invention]

[0011] By using the electrolyte for a lithium secondary battery according to an embodiment, an increase in the resistance of the battery during high-temperature storage can be suppressed, and a lithium secondary battery with excellent life characteristics and stability can be realized. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a conceptual diagram illustrating a lithium secondary battery according to an embodiment of the present invention; [Figure 2] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment, the lithium secondary battery having a cylindrical battery shape. [Figure 3] 1 is a cross-sectional view showing a lithium secondary battery according to an embodiment. [Figure 4] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment, the battery having a prismatic shape. [Figure 5] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment, in the form of a pouch-shaped battery. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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 undergo various modifications. The description of the present embodiments is provided merely to complete the disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art to which the present invention pertains.

[0014] In this specification, when a component is referred to as being on another component, it means that it may be formed directly on the other component, or a third component may be interposed between them. Also, in the drawings, the thickness of the components is exaggerated for the sake of efficient explanation of the technical content. Parts designated with the same reference numerals throughout the specification refer to the same components.

[0015] Unless otherwise specified herein, the singular can also include the plural. Furthermore, unless otherwise specified, "A or B" can mean "including A, including B, or including A and B." As used herein, "comprises" and / or "comprising" does not exclude the presence or addition of one or more other elements to the referenced element.

[0016] As used herein, "combinations thereof" can mean mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0017] 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% in a particle size distribution. The average particle size (D50) can be measured by methods well known to those skilled in the art, such as using a particle size analyzer, a transmission electron microscope (TEM), or a scanning electron microscope (SEM). Alternatively, the average particle size (D50) can be measured using a measuring device that uses dynamic light scattering, and data analysis can be performed to count the number of particles in each particle size range, after which the average particle size (D50) can be calculated. Alternatively, the average particle size (D50) can be measured using a laser diffraction method. More specifically, when measuring by the laser diffraction method, 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., Microtrac MT 3000), and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W. The average particle size (D50) based on 50% of the particle size distribution in the measuring device can then be calculated.

[0018] Unless otherwise defined herein, the term "substituted" means that at least one hydrogen atom in a substituent or compound has been 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.

[0019] Specifically, "substituted" can mean that at least one hydrogen 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" can mean that at least one hydrogen 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" can mean that at least one hydrogen 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" can mean that at least one hydrogen in a substituent or compound is replaced with deuterium, cyano, halogen, methyl, ethyl, propyl, butyl, phenyl, biphenyl, terphenyl, trifluoromethyl, or naphthyl.

[0020] As used herein, unless otherwise defined, the term "alkyl group" refers to a straight-chain or branched-chain aliphatic hydrocarbon group. The alkyl group may be a "saturated alkyl group" that does not contain any double or triple bonds.

[0021] As used herein, unless otherwise defined, the term "alkenyl group" may refer to a straight-chain or branched-chain aliphatic hydrocarbon group, an aliphatic unsaturated alkenyl group containing one or more double bonds.

[0022] As used herein, unless otherwise defined, the term "alkynyl group" may refer to a straight-chain or branched-chain aliphatic hydrocarbon group, an aliphatic unsaturated alkynyl group containing one or more triple bonds.

[0023] 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.

[0024] 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.

[0025] The electrolyte ELL may be a medium for transferring lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, the lithium ions can pass through the separator 30 and move toward the positive electrode 10 or the negative electrode 20.

[0026] positive electrode 10 The lithium secondary battery positive electrode 10 can 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 can further include a binder and / or a conductive material.

[0027] As an example, the positive electrode 10 may further include an additive that can act as a sacrificial positive electrode.

[0028] 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.

[0029] The binder serves to firmly adhere the positive electrode active material particles to each other and to firmly adhere 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)acrylate styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0030] The conductive material is used to impart conductivity to the electrode, and any material that is electron-conductive without causing a chemical change in the battery that is constructed can be used. Examples of conductive materials 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.

[0031] The current collector COL1 can be made of Al, but is not limited to this.

[0032] positive electrode active material The positive electrode active material in the positive electrode active material layer AML1 may be a compound capable of reversibly intercalating and deintercalating lithium (lithiated intercalation compound). Specifically, one or more of composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0033] The composite oxide is a lithium transition metal composite oxide, and specific examples thereof include lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate compound, cobalt-nickel-manganese oxide, or a combination thereof.

[0034] As an example, a compound represented by any one of the following chemical formulas can be used.

[0035] 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 eO2(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)

[0036] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 is Mn, Al, or a combination thereof.

[0037] For example, the positive electrode active material may be a high-nickel-based 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 but not more than 99 mol% relative to 100 mol% of metals excluding lithium in a lithium transition metal composite oxide. The high-nickel-based positive electrode active material can realize high capacity and can therefore be applied to high-capacity, high-density lithium secondary batteries.

[0038] negative electrode 20 The negative electrode 20 for a lithium secondary battery includes 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 includes a negative electrode active material and may further include a binder and / or a conductive material.

[0039] For example, the negative electrode active material layer AML2 may contain 90 to 99% by weight of the negative electrode active material, 0.5 to 5% by weight of the binder, and 0 to 5% by weight of the conductive material.

[0040] The binder serves to firmly adhere the negative electrode active material particles to each other and to firmly adhere the negative electrode active material to the current collector COL 2. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0041] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and combinations thereof.

[0042] The aqueous binder may be selected from styrene-styrene rubber, (meth)acrylate styrene-styrene rubber, (meth)acrylonitrile-styrene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0043] When an aqueous binder is used as the negative electrode binder, a cellulose-based compound that can impart viscosity may be further included. 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.

[0044] The dry binder may be a polymeric substance that can be fiberized, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0045] The conductive material is used to impart conductivity to the electrode, and any material that is electron-conductive without causing a chemical change in the battery may be used. 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.

[0046] 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.

[0047] negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped with and dedoped from lithium, or a transition metal oxide.

[0048] As the substance capable of reversibly intercalating / deintercalating the lithium ions, a carbon-based negative electrode active material can be included, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-shaped, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, fired coke, and the like.

[0049] As the alloy of the 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.

[0050] As the substance capable of doping and undoping lithium, an Si-based negative electrode active material or an 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), an Si-Q alloy (where Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, an Sn-based alloy, or a combination thereof.

[0051] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in a form in which amorphous carbon is coated on the surface of silicon particles. The silicon-carbon composite can include, for example, secondary particles (cores) assembled from primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon can also be located between the primary silicon particles, for example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can exist dispersed in an amorphous carbon matrix.

[0052] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core including crystalline carbon and silicon particles and an amorphous carbon coating layer disposed on the core surface.

[0053] The Si-based or Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0054] 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. As such separator 30, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and it goes without saying that mixed multilayer films 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.

[0055] 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.

[0056] The porous substrate may be a polymer membrane formed 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, polyacetimide, 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.

[0057] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0058] 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.

[0059] 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.

[0060] Electrolyte ELL The electrolyte ELL for lithium secondary batteries includes a non-aqueous organic solvent, a lithium salt, and an electrolyte additive.

[0061] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0062] The non-aqueous organic solvent may be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, or a combination thereof.

[0063] Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0064] Examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate (PP), decanolide, mevalonolactone, valerolactone, and caprolactone.

[0065] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a hydrocarbon group having 2 to 20 carbon atoms and having a linear, branched, or cyclic structure, and 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.

[0066] The non-aqueous organic solvents can be used alone or in combination of two or more.

[0067] In addition, 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 carbonate may be mixed in a volume ratio of 1:1 to 1:9.

[0068] The lithium salt is dissolved in an organic solvent and acts as a lithium ion source in the battery, enabling basic lithium secondary battery operation and promoting the movement of lithium ions between the positive electrode and the negative electrode. 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+1 SO2) (x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethene sulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), and lithium bis(oxalato)borate (LiBOB).

[0069] The concentration of the lithium salt is preferably in the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within this range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to migrate effectively.

[0070] Hereinafter, an electrolyte for a lithium secondary battery according to an embodiment will be described.

[0071] According to one embodiment, the electrolyte for a lithium secondary battery 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:

[0072] The first compound may be represented by the following Chemical Formula 1:

[0073] [ka] ...chemical formula 1

[0074] In the above Chemical Formula 1, X 1a may be a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodo group (-I). For example, X 1a may be a fluoro group (-F).

[0075] R 1a ~R 6a may each independently be hydrogen, halogen, a substituted or unsubstituted C1 to C20 alkyl 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 C3 to C20 cycloalkenyl group, a substituted or unsubstituted C3 to C20 cycloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C2 to C30 heterocyclic group.

[0076] n may be an integer of 0 or 1.

[0077] The first compound represented by Formula 1 forms a solid electrolyte interface (SEI) film on the surface of the negative electrode, which has high high-temperature stability and excellent ionic conductivity, and can suppress side reactions of lithium salts due to the -POF functional group, thereby suppressing an increase in resistance due to the decomposition reaction of the electrolyte during high-temperature storage.

[0078] Specifically, the first compound can be coordinated with a thermal decomposition product of a lithium salt such as LiPF6 or an anion dissociated from the lithium salt to form a complex, and the formation of this complex stabilizes the anion, thereby suppressing undesirable side reactions between the anion and the electrolyte. As a result, the cycle life characteristics of the lithium secondary battery can be improved, and an increase in resistance within the lithium secondary battery can be prevented, significantly reducing the failure rate and significantly improving high-temperature storage characteristics.

[0079] In one embodiment, the formula 1 may be represented by the following formula 1-1 or 1-2.

[0080] [ka] ...Chemical formula 1-1

[0081] [ka] ...Chemical formula 1-2

[0082] In the above Chemical Formula 1-1 and Chemical Formula 1-2, X 1a may be a fluoro, chloro, bromo, or iodo group.

[0083] R 1a ~R 6a may each independently be hydrogen, halogen, a substituted or unsubstituted C1 to C20 alkyl 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 C3 to C20 cycloalkenyl group, a substituted or unsubstituted C3 to C20 cycloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C2 to C30 heterocyclic group.

[0084] In one embodiment, in Formula 1-1 and Formula 1-2, the R 1a , R 2a , R 3a , and R 4a are each hydrogen, and the R 5a and R 6a At least one of these may be a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkoxy group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group.

[0085] In one embodiment, the first compound represented by Chemical Formula 1 may be selected from the compounds listed in Group 1 below, and may be at least one selected from 2-fluoro-1,3,2-dioxaphospholane (s-fluoro-4-methyl-1,3,2-dioxaphospholane) and 2-fluoro-4-methyl-1,3,2-dioxaphospholane (2-fluoro-4-methyl-1,3,2-dioxaphospholane).

[0086] [Group 1] [ka]

[0087] The first compound may be included in an amount of 0.01 to 5 wt % of the total weight of the electrolyte for lithium secondary batteries. For example, the first compound may be included in an amount of 0.1 to 5 wt %, 0.5 to 5 wt %, 0.5 to 3 wt %, or 0.5 to 2 wt %. In this case, a lithium secondary battery including the electrolyte may exhibit excellent high-temperature storage characteristics and life characteristics.

[0088] The second compound may be represented by the following Chemical Formula 2:

[0089] [ka] ...Chemical formula 2

[0090] In the above Chemical Formula 2, L 1b ~L 3b may each independently be a single bond or a substituted or unsubstituted C1 to C10 alkylene group.

[0091] R 1b ~R 3bmay each independently be hydrogen, halogen, a substituted or unsubstituted C1 to C20 alkyl 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 C3 to C20 cycloalkenyl group, a substituted or unsubstituted C3 to C20 cycloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C2 to C30 heterocyclic group.

[0092] The second compound represented by Formula 2 includes a phosphate-based compound and can prevent Ni cations derived from the positive electrode from being leached into the electrolyte. Accordingly, the second compound can prevent a decrease in life characteristics and an increase in resistance due to the decomposition reaction of the electrolyte when the lithium secondary battery is stored at high temperatures.

[0093] Specifically, phosphate-based compounds have a high affinity with Ni cations, thereby suppressing side reactions of Ni cations. In particular, they maintain a high affinity with Ni cations even when the battery is operating at high voltage, thereby suppressing the dissolution, oxidation, and disproportionation of Ni cations.

[0094] In one embodiment, Formula 2 may be represented by Formula 2-1 below.

[0095] [ka] Chemical formula 2-1

[0096] In the above chemical formula 2-1, R 1b ~R 3bmay each independently be hydrogen, halogen, a substituted or unsubstituted C1 to C20 alkyl 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 C3 to C20 cycloalkenyl group, a substituted or unsubstituted C3 to C20 cycloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C2 to C30 heterocyclic group.

[0097] In one embodiment, in Formula 2-1, R 1b ~R 3b may each independently be a substituted or unsubstituted C2 to C20 alkenyl group, or a substituted or unsubstituted C2 to C20 alkynyl group.

[0098] In one embodiment, Formula 2 may be represented by the following Formula 2-1-1:

[0099] [ka]

[0100] In one embodiment, Formula 2 may be represented by the following Formula 2-1-2:

[0101] [ka]

[0102] The second compound may be included in an amount of 0.01 to 20 wt % of the total weight of the electrolyte for the lithium secondary battery. For example, the second compound may be included in an amount of 0.5 to 20 wt %, 1 to 20 wt %, 1.5 to 20 wt %, 2 to 20 wt %, 3 to 20 wt %, 5 to 20 wt %, 10 to 20 wt %, or 10 to 15 wt %. In this case, a lithium secondary battery including the electrolyte may exhibit excellent high-temperature storage characteristics and life characteristics.

[0103] According to one embodiment, the electrolyte for a lithium secondary battery may contain the first compound and the second compound in a weight ratio of 1:0.2 to 1:20. Specifically, the first compound and the second compound may be contained in a weight ratio of 1:1 to 1:20, or may be contained in a weight ratio of 1:5 to 1:15. When these ranges are satisfied, a lithium secondary battery including the electrolyte may exhibit excellent high-temperature storage characteristics and life characteristics.

[0104] 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 embodiments, with FIG. 2 illustrating a cylindrical type, FIG. 3 illustrating a cross-sectional view, FIG. 4 illustrating a prismatic type, and FIG. 5 illustrating a pouch type. Referring to FIGS. 2 to 4, a 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 shown in FIG. 2. Also, as shown 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 current generated in the electrode assembly 40 to the outside.

[0105] 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.

[0106] Examples and comparative examples of the present invention will be described below. However, the examples described below are merely examples of the present invention, and the present invention is not limited to these examples. [Example]

[0107] Examples and Comparative Examples An electrolyte and a lithium secondary battery were manufactured as follows.

[0108] Example 1 (1) Electrolyte production An electrolyte solution was prepared by dissolving 1.5 M LiPF6 in a non-aqueous organic solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:10:70, and adding additives.

[0109] The additive was prepared by mixing a first compound represented by the following chemical formula 1-1 at 1 wt% based on 100 wt% of the total electrolyte solution, and a second compound represented by the following chemical formula 2-1-1 at 0.5 wt% based on 100 wt% of the total electrolyte solution.

[0110] [ka] ...Chemical formula 1-1

[0111] [ka] ...Chemical formula 2-1-1

[0112] 2) Manufacture of lithium secondary batteries LiNi as the positive electrode active material 0.88 Co 0.07 Al 0.05 O2, polyvinylidene fluoride as a binder, and Ketjen black as a conductive material were mixed in a weight ratio of 97:2:1 and dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0113] The positive electrode active material slurry was coated on an Al foil having a thickness of 14 μm, dried at 110° C., and pressed to prepare a positive electrode.

[0114] A mixture of artificial graphite and Si-C composite in a weight ratio of 93:7 was used as the negative active material. The negative active material and binder, styrene-styrene rubber binder, and carboxymethyl cellulose as a thickener were mixed in a weight ratio of 97:1:2 and dispersed in distilled water to prepare a negative active material slurry.

[0115] The Si-C composite has a core containing artificial graphite and silicon particles, and the surface of the core is coated with coal-based pitch.

[0116] The negative electrode active material slurry was coated on a Cu foil having a thickness of 10 μm, dried at 100° C., and then pressed to prepare a negative electrode.

[0117] The prepared positive and negative electrodes were assembled with a 25 μm thick polyethylene separator to prepare an electrode assembly, and an electrolyte was injected to prepare a lithium secondary battery.

[0118] Example 2 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the second compound was mixed as an additive in an amount of 1 wt % based on 100 wt % of the total electrolyte solution.

[0119] Example 3 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the second compound was mixed as an additive in an amount of 1.5 wt % based on 100 wt % of the total electrolyte solution.

[0120] Example 4 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the second compound was mixed as an additive in an amount of 2 wt % based on 100 wt % of the total electrolyte solution.

[0121] Example 5 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the second compound was mixed as an additive in an amount of 3 wt % based on 100 wt % of the total electrolyte solution.

[0122] Example 6 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the second compound was mixed as an additive in an amount of 5 wt % based on 100 wt % of the total electrolyte solution.

[0123] Example 7 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the second compound was mixed as an additive in an amount of 10 wt % based on 100 wt % of the total electrolyte solution.

[0124] Example 8 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the additives were prepared by mixing the first compound represented by the above Chemical Formula 1-1 in an amount of 1 wt % based on 100 wt % of the total electrolyte solution, and the second compound represented by the following Chemical Formula 2-1-2 in an amount of 0.5 wt % based on 100 wt % of the total electrolyte solution.

[0125] [ka] ...Chemical formula 2-1-2

[0126] Example 9 A lithium secondary battery was fabricated in the same manner as in Example 8, except that the second compound was mixed as an additive in an amount of 1 wt % based on 100 wt % of the total electrolyte solution.

[0127] Example 10 A lithium secondary battery was fabricated in the same manner as in Example 8, except that the second compound was mixed as an additive in an amount of 1.5 wt % based on 100 wt % of the total electrolyte solution.

[0128] Example 11 A lithium secondary battery was fabricated in the same manner as in Example 8, except that the second compound was mixed as an additive in an amount of 2 wt % based on 100 wt % of the total electrolyte solution.

[0129] Example 12 A lithium secondary battery was fabricated in the same manner as in Example 8, except that the second compound was mixed as an additive in an amount of 3 wt % based on 100 wt % of the total electrolyte solution.

[0130] Example 13 A lithium secondary battery was fabricated in the same manner as in Example 8, except that the second compound was mixed as an additive in an amount of 5 wt % based on 100 wt % of the total electrolyte solution.

[0131] Example 14 A lithium secondary battery was fabricated in the same manner as in Example 8, except that the second compound was mixed as an additive in an amount of 10 wt % based on 100 wt % of the total electrolyte solution.

[0132] Example 15 A lithium secondary battery was fabricated in the same manner as in Example 8, except that the second compound was mixed as an additive in an amount of 13 wt % based on 100 wt % of the total electrolyte solution.

[0133] Example 16 A lithium secondary battery was fabricated in the same manner as in Example 8, except that the second compound was mixed as an additive in an amount of 15 wt % based on 100 wt % of the total electrolyte solution.

[0134] Example 17 A lithium secondary battery was fabricated in the same manner as in Example 9, except that the first compound was used as an additive in an amount of 0.5 wt % based on 100 wt % of the total electrolyte solution.

[0135] Example 18 A lithium secondary battery was fabricated in the same manner as in Example 9, except that the first compound was used as an additive in an amount of 2 wt % based on 100 wt % of the total electrolyte solution.

[0136] Example 19 A lithium secondary battery was fabricated in the same manner as in Example 9, except that the first compound was used as an additive in an amount of 3 wt % based on 100 wt % of the total electrolyte solution.

[0137] Comparative Example 1 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the electrolyte solution was prepared without adding any additives.

[0138] Comparative Example 2 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the second compound was not added as an additive.

[0139] Comparative Example 3 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the first compound was not mixed as an additive.

[0140] Evaluation example 1: High temperature charge / discharge characteristics (DCIR, @60℃, 500 cycles) The lithium secondary batteries prepared in Examples 1 to 19 and Comparative Examples 1 to 3 were subjected to 500 charge / discharge cycles at 60°C, 2.5 V to 4.5 V, and 0.5 CC-rate. DC resistance (DCIR, mΩ) was measured as a △V (△change in voltage / △change in current). The results are shown in Tables 1 and 2 below.

[0141] Evaluation example 2: High temperature storage characteristics (DCIR, @90℃, 30 days) The initial DC resistance (DCIR) was measured in terms of ΔV (change in voltage / change in current) for the lithium secondary batteries fabricated in Examples 1 to 19 and Comparative Examples 1 to 3. The maximum energy state inside the battery was fully charged (SOC 100%), and the batteries were stored at room temperature (60°C) for 30 days, after which the DC resistance was measured. The DCIR increase rate (%) was calculated using Equation 1 below, and the results are shown in Tables 1 and 2 below.

[0142] [Formula 1] DCIR increase rate = {DCIR after 30 days / initial DCIR-1}X100(%)

[0143] Evaluation example 3: High temperature stability evaluation (CID open time, @90℃) The lithium secondary batteries fabricated in Examples 1 to 19 and Comparative Examples 1 to 3 were charged and discharged twice at 0.2C / 0.5C, and then subjected to one charge / discharge experiment each at a standard charge / discharge current density of 0.5C / 0.2C, a charge cut-off voltage of 4.25V, and a discharge cut-off voltage of 2.5V. After leaving the batteries in a 90°C chamber for 140 hours, the time point at which the CID (Current Interrupt Device) was activated was measured, and the results are shown in Tables 1 and 2 below.

[0144] The results of evaluating the high temperature charge / discharge characteristics, high temperature storage characteristics, and stability of the lithium secondary batteries fabricated in Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Table 1 below.

[0145] [Table 1]

[0146] The results of evaluating the high temperature charge / discharge characteristics, high temperature storage characteristics, and stability of the lithium secondary batteries fabricated in Examples 8 to 19 and Comparative Examples 1 to 3 are shown in Table 2 below.

[0147] [Table 2]

[0148] Referring to Tables 1 and 2, it can be seen that Examples 1 to 19 have improved charge / discharge characteristics and storage characteristics at high temperatures compared to Comparative Examples 1 to 3.

[0149] Referring to Tables 1 and 2, it can be seen that Examples 1 to 19 containing the second compound have a longer CID open time than Comparative Examples 1 to 3. That is, it can be seen that the lithium secondary battery according to the present embodiment has a more excellent effect of suppressing gas generation when left at high temperatures.

[0150] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to this and can be implemented in various modified forms within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is natural that this also falls within the scope of the present invention. [Explanation of symbols]

[0151] 100 Lithium secondary battery 10 positive electrode 11 Positive electrode lead tab 12 Positive terminal 20 negative electrode 21 Negative electrode lead tab 22 Negative terminal 30 Separator 40 Electrode assembly 50 cases 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: 【Chemistry 1】 ...Chemical formula 1 【Chemistry 2】 ...Chemical formula 2 In the above Chemical Formula 1, X １ａ is a fluoro, chloro, bromo, or iodo group; R １ａ ~R ６ａ each independently represents hydrogen, halogen, a substituted or unsubstituted C1 to C20 alkyl 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 C3 to C20 cycloalkenyl group, a substituted or unsubstituted C3 to C20 cycloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C2 to C30 heterocyclic group; n is an integer of 0 or 1; In the above Chemical Formula 2, L １ｂ ~L ３ｂ are each independently a single bond or a substituted or unsubstituted C1 to C10 alkylene group; R １ｂ ~R ３ｂ are each independently hydrogen, halogen, a substituted or unsubstituted C1 to C20 alkyl 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 C3 to C20 cycloalkenyl group, a substituted or unsubstituted C3 to C20 cycloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C2 to C30 heterocyclic group.

2. 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 or 1-2. 【Transformation 3】 ...Chemical formula 1-1 【Chemistry 4】 ...Chemical formula 1-2 In the above Chemical Formula 1-1 and Chemical Formula 1-2, X １ａ is a fluoro, chloro, bromo, or iodo group; R １ａ ~R ６ａ are each independently hydrogen, halogen, a substituted or unsubstituted C1 to C20 alkyl 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 C3 to C20 cycloalkenyl group, a substituted or unsubstituted C3 to C20 cycloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C2 to C30 heterocyclic group.

3. In the formula 1-1 and the formula 1-2, the R １ａ , R ２ａ , R ３ａ , and R ４ａ are each hydrogen, and ５ａ and R ６ａ 3. The electrolyte solution for a lithium secondary battery according to claim 2, wherein at least one of the groups is a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkoxy group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group.

4. The electrolyte for a lithium secondary battery according to claim 1 , wherein the first compound is at least one selected from the compounds listed in Group 1 below: [Group 1] 【Transformation 5】

5. 2. The electrolyte solution for a lithium secondary battery according to claim 1, wherein the first compound is contained in an amount of 0.01 to 5 wt % of the total weight of the electrolyte solution for a lithium secondary battery.

6. 2. 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: 【Transformation 6】 ...Chemical formula 2-1 In the above chemical formula 2-1, R １ｂ ~R ３ｂ are each independently hydrogen, halogen, a substituted or unsubstituted C1 to C20 alkyl 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 C3 to C20 cycloalkenyl group, a substituted or unsubstituted C3 to C20 cycloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C2 to C30 heterocyclic group.

7. In the above formula 2-1, R １ｂ ~R ３ｂ and each independently represent a substituted or unsubstituted C2 to C20 alkenyl group or a substituted or unsubstituted C2 to C20 alkenyl group.

8. The electrolyte for a lithium secondary battery according to claim 1, wherein the chemical formula 2 is represented by the following chemical formula 2-1-1. 【Transformation 7】 ...Chemical formula 2-1-1

9. The electrolyte for a lithium secondary battery according to claim 1, wherein the chemical formula 2 is represented by the following chemical formula 2-1-2: 【Transformation 8】 ...Chemical formula 2-1-2

10. 2. The electrolyte for a lithium secondary battery according to claim 1, wherein the second compound is contained in an amount of 0.01 to 20 wt % of the total weight of the electrolyte for a lithium secondary battery.

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 1:0.2 to 1:

20.

12. 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 1:5 to 1:

15.

13. 2. The electrolyte solution for a lithium secondary battery according to claim 1, wherein the non-aqueous organic solvent comprises a carbonate-based solvent.

14. 14. The electrolyte solution for a lithium secondary battery according to claim 13, wherein the carbonate-based solvent includes ethylene carbonate (EC), methyl ethyl carbonate (MEC), and dimethyl carbonate (DMC).

15. The lithium salt is LiPF ６ The electrolyte solution for a lithium secondary battery according to claim 1, comprising:

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 any one of claims 1 to 14.

17. The lithium secondary battery according to claim 16, wherein the positive electrode active material is represented by the following chemical formula 3: [Chemical formula 3] Li ａ Ni １－ｂ－ｃ Co ｂ X ｃ O ２－α Dα In the above Chemical Formula 3, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5, 0<α<2, X includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof, and D includes at least one of O, F, S, P, or a combination thereof.

18. 18. The lithium secondary battery according to claim 17, wherein X is Mn, Al, or a combination thereof.

19. The lithium secondary battery according to claim 16 , wherein the negative electrode active material comprises a carbon-based negative electrode active material or a Si-based negative electrode active material.

20. 17. The lithium secondary battery according to claim 16, which operates at a high voltage of 4.2 V or more.

Images