Lithium secondary batteries

Abstract

This disclosure provides a lithium secondary battery with improved high-temperature cycling performance. Specifically, the present invention relates to a lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode comprises lithium iron phosphate oxide as the positive electrode active material, and the positive electrode loading is 32 mg / cm³. 2 Up to 60 mg / cm 2 The electrolyte comprises a lithium salt, a first organic solvent, a second organic solvent, a first additive, and a second additive, wherein the first organic solvent is a cyclic lactone compound, the second organic solvent is a carbonate organic solvent, the first additive is lithium nitrate (LiNO3), and the second additive is a sulfonamide compound.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2023-0166121, filed on November 24, 2023, with the Korean Intellectual Property Office, and Korean Patent Application No. 10-2024-0164615, filed on November 18, 2024, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0003] This disclosure relates to a lithium secondary battery, and more specifically, to a lithium secondary battery with improved high-temperature cycling performance. Background Technology

[0004] In recent years, lithium-ion batteries have been used in many applications and portable electronic devices, such as mobile phones, personal digital assistants (PDAs), and laptops. In particular, due to growing concerns about environmental issues, there has been active research into lithium-ion batteries with high energy density and high discharge voltage as a power source for electric vehicles that can replace vehicles using fossil fuels (such as gasoline and diesel vehicles), which are major contributors to air pollution, and some of these lithium-ion batteries are already commercially available.

[0005] Meanwhile, in order to use lithium secondary batteries as the power source for electric vehicles, it is necessary to maintain a stable high output under high temperature and high voltage conditions. Therefore, in lithium secondary batteries, carbon materials and lithium metal, sulfur compounds, silicon compounds, tin compounds, etc. are considered as the main components of the negative electrode active material, and lithium-containing cobalt oxide (LiCoO2) or lithium nickel-based oxide are mainly used as the positive electrode active material.

[0006] However, in the case of lithium-containing cobalt oxides, energy density and output characteristics reach practical limits. In particular, if used in high-energy-density applications, the structural instability of lithium-containing cobalt oxides causes structural deformation under high-temperature charging conditions, oxygen release from the structure, and exothermic reactions with the electrolyte in the battery, potentially leading to secondary battery explosions. In the case of lithium nickel-based oxides, output decreases rapidly in the low SOC range (e.g., below 30%), thus significantly limiting the usable SOC range. Consequently, the application of nickel-based lithium transition metal oxides is restricted in areas where output characteristics are particularly important (e.g., electric vehicles). Specifically, lithium nickel-based oxides have low structural stability; therefore, if exposed to high temperatures or high voltages, the transition metal in the positive electrode active material dissolves or side reactions with the electrolyte occur, resulting in rapid degradation of battery performance.

[0007] Recently, in order to solve the above problems, a method has been studied to use lithium iron phosphate oxide with an olivine structure that has excellent high-temperature stability to replace lithium nickel-based oxide.

[0008] However, the aforementioned lithium iron phosphate oxides with olivine structure have a lower theoretical capacity than commonly used lithium nickel oxides. Therefore, when designing electrodes under the same conditions, they have the disadvantage of relatively lower energy density compared to lithium nickel oxides.

[0009] To address the aforementioned issues, high-load electrodes have been explored in recent years, where the amount of electrode active material coated per unit area (load) increases when lithium iron phosphate oxide is applied.

[0010] However, high-load electrodes are designed to increase the application of active materials and increase electrode density, resulting in very high electrode compression. Consequently, the internal porous structure of the electrode is insufficient, leading to a decrease in electrolyte impregnation performance. As mentioned above, if electrolyte impregnation performance deteriorates, there is a deterioration in charge transfer, which is the reaction between lithium ions and electrons, potentially causing an increase in battery resistance.

[0011] Therefore, there is a need to develop a new secondary battery structure that can improve electrolyte impregnation performance and charge transfer performance when manufacturing secondary batteries with high-load electrodes. Summary of the Invention

[0012] Technical issues

[0013] To address the aforementioned problems, this disclosure aims to provide a lithium secondary battery in which, when a high-load positive electrode is applied, an electrolyte with improved impregnation properties through a specific composition is used, thereby increasing charge transfer by forming a stable film on the electrode surface. As a result, the increase in resistance during high-temperature storage can be suppressed, and excellent cycle capacity retention can be ensured.

[0014] Technical solution

[0015] [1] This disclosure provides a lithium secondary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode comprises lithium iron phosphate oxide as the positive electrode active material, and the loading of the positive electrode is 32 mg / cm³. 2 Up to 60 mg / cm 2 The electrolyte comprises a lithium salt, a first organic solvent, a second organic solvent, a first additive, and a second additive, wherein the first organic solvent is a cyclic lactone compound, the second organic solvent is a carbonate organic solvent, the first additive is lithium nitrate (LiNO3), and the second additive is a sulfonamide compound.

[0016] [2] In the above [1], this disclosure provides a lithium secondary battery, wherein the lithium iron phosphate oxide is a compound represented by the following formula 1.

[0017] [Formula 1]

[0018] Li 1+a Fe x M y (PO 4-b )X' b

[0019] In the above [Equation 1], M is any element selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and X' is one or more elements selected from the group consisting of F, S, and N, where -0.5 ≤ a ≤ 0.5, 0 <x≤1,0≤y≤1,0≤b≤0.3。

[0020] [3] In [1] or [2] above, this disclosure provides a lithium secondary battery, wherein the lithium iron phosphate oxide is lithium iron phosphate (LiFePO4) or lithium manganese iron phosphate (LiFeMnPO4).

[0021] [4] In at least one of [1] to [3] above, this disclosure provides a lithium secondary battery, wherein the positive electrode loading is 40 mg / cm³. 2 Up to 60 mg / cm 2 .

[0022] [5] In at least one of [1] to [4] above, the present disclosure provides a lithium secondary battery, wherein the cyclic lactone compound includes γ-butyrolactone.

[0023] [6] In at least one of [1] to [5] above, the present disclosure provides a lithium secondary battery, wherein the carbonate organic solvent is a cyclic carbonate organic solvent.

[0024] [7] In at least one of [1] to [6] above, the present disclosure provides a lithium secondary battery, wherein the first organic solvent and the second organic solvent are present in a volume ratio of 50:50 to 99:1.

[0025] [8] In at least one of [1] to [7] above, the present disclosure provides a lithium secondary battery, wherein the content of the first additive is from 0.05% by weight to 3.0% by weight based on the total weight of the electrolyte.

[0026] [9] In at least one of [1] to [8] above, this disclosure provides a lithium secondary battery, wherein the sulfonamide compound includes a compound represented by formula 2 below.

[0027] [Equation 2]

[0028] In the above [Equation 2], R1 is selected from oxygen atom, nitrogen atom, sulfur atom, aryl group having 6 to 10 carbon atoms, heteroaryl group having 5 to 10 carbon atoms including one or more of N, O and S, and Any one of the groups, wherein R2 is a fluorine group, an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or... ,in, and One or more hydrogen atoms contained therein may be replaced by fluorine atoms, M1 is selected from the group consisting of lithium, sodium, potassium, tetraalkylammonium having 1 to 4 carbon atoms and tetraalkylphosphonium having 1 to 4 carbon atoms, l is an integer from 1 to 6, and m and n are each an integer from 2 to 20.

[0029]

[10] In at least one of [1] to [9] above, this disclosure provides a lithium secondary battery, wherein, in [Formula 2] above, R1 is selected from phenylene, naphthyl, pyrrolyl, furanyl, thiophene, imidazolinyl, ... and R2 is any one of the groups, where R2 is fluoro, methyl, ethyl, propyl, trifluoromethyl, methoxy, ethoxy, or... or M1 is lithium, l is an integer of 1 or 2, and m and n are each integers from 2 to 10.

[0030]

[11] In at least one of [1] to

[10] above, the present disclosure provides a lithium secondary battery, wherein the first additive and the second additive are present in a weight ratio of 1:0.05 to 1:2.

[0031]

[12] In at least one of [1] to

[11] above, the present disclosure provides a lithium secondary battery, wherein the first additive and the second additive are present in a weight ratio of 1:0.1 to 1:2.

[0032]

[13] In at least one of [1] to

[12] above, the present disclosure provides a lithium secondary battery, wherein the negative electrode comprises a carbon-based active material, a silicon-based active material, or a mixture of a carbon-based active material and a silicon-based active material.

[0033] Beneficial effects

[0034] The lithium secondary battery disclosed herein can be used with an organic solvent containing a cyclic lactone compound as the main solvent, and with lithium nitrate (LiNO3) and sulfonamide (-S(=O)2-N) as the main solvent. -Ionic compounds with -S(=O)2-) units are used as electrolytes in two types of additives to improve electrolyte impregnation performance for high-load cathodes. Simultaneously, charge transfer performance on the surface of the high-load cathode can be improved by forming a low-resistance film on its surface. Therefore, the lithium secondary battery of this disclosure can have improved cycle performance and high-temperature storage performance. Detailed Implementation

[0035] It will be understood that the terms or words used in this specification and claims are for the purpose of describing exemplary embodiments only and should not be construed as having the meanings defined in common dictionaries, but should be interpreted as having meanings and concepts consistent with the technical concept of this disclosure, based on the principle that the inventors may appropriately define the concepts of the terms to best interpret the invention.

[0036] For example, in this specification, it should be understood that the terms “comprising,” “including,” or “having” are intended to specify the presence of the said feature, number, step, element, or combination thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, elements, or combinations thereof.

[0037] Furthermore, it should be understood in this specification that in the description of "a to b carbon atoms" herein, "a" and "b" each refer to the number of carbon atoms contained in a specific functional group. That is, a functional group can include "a" to "b" carbon atoms. For example, "alkylene with 1 to 5 carbon atoms" refers to an alkylene containing 1 to 5 carbon atoms, namely -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH2)CH-, -CH2CH2CH2CH2CH2-, -CH(CH2)CH2CH2-, etc.

[0038] Additionally, in this specification, the term "alkylene" refers to a branched or straight-chain aliphatic hydrocarbon group, or a functional group in the form of a group missing a hydrogen atom at each end of an aliphatic hydrocarbon group. In one embodiment, the alkylene group may be substituted or unsubstituted. Alkylenes include, but are not limited to, methylene, ethylene, propylene, isopropylene, butylene, isobutylene, tert-butylene, pentylene, 3-pentylene, etc., and in another embodiment, each may optionally be substituted.

[0039] Furthermore, in this specification, unless otherwise defined, “substitution” means that one or more hydrogen atoms bonded to carbon are replaced by another element such as fluorine.

[0040] Furthermore, in this specification, "loading capacity" refers to the amount of active material per unit area obtained by measuring the positive electrode active material layer containing lithium iron phosphate oxide with an olivine structure formed on the current collector, and is expressed in "mg / cm²". 2In this context, "load" refers to the sum of the individual loads on the two surfaces of the positive electrode.

[0041] This disclosure will be described in detail below.

[0042] The lithium secondary battery disclosed herein includes at least one of the disclosed configurations, and may include any combination of technically possible configurations among the disclosed configurations.

[0043] Lithium secondary batteries

[0044] This disclosure relates to a lithium secondary battery.

[0045] Specifically, this disclosure provides a lithium secondary battery, which includes a positive electrode, a negative electrode, a separator, and an electrolyte.

[0046] The positive electrode may include lithium iron phosphate oxide as the positive electrode active material.

[0047] The loading of the positive electrode can be 32 mg / cm³. 2 Up to 60 mg / cm 2 .

[0048] The electrolyte may include lithium salt, a first organic solvent, a second organic solvent, a first additive, and a second additive.

[0049] The first organic solvent may include cyclic lactone compounds.

[0050] The second organic solvent may include carbonate organic solvents.

[0051] The first additive may include lithium nitrate (LiNO3).

[0052] The second additive may include sulfonamide compounds.

[0053] (1) Positive electrode

[0054] The cathode of this disclosure may comprise lithium iron phosphate oxide as the cathode active material. Specifically, the lithium iron phosphate oxide may comprise a compound represented by Formula 1.

[0055] [Formula 1]

[0056] Li 1+a Fe x M y (PO 4-b )X' b

[0057] In the above [Equation 1], M is any element selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and X' is one or more elements selected from the group consisting of F, S, and N, where -0.5 ≤ a ≤ 0.5, 0 <x≤1,0≤y≤1,0≤b≤0.3。

[0058] The lithium iron phosphate oxide represented by Formula 1 above may include lithium iron phosphate (LiFePO4, LFP) or lithium manganese iron phosphate (LiFeMnPO4, LFMP) as representative examples.

[0059] The lithium iron phosphate oxide represented by Equation 1 above can be made using primary particles of nanoscale size to achieve high lithium-ion input and output, or it can be made using secondary particles formed by aggregating these primary particles into aggregates of primary particles. For example, if primary particles are used as lithium iron phosphate oxide with an olivine structure, the particle size can be from 50 nm to 2000 nm, more specifically from 200 nm to 1100 nm. Furthermore, if these primary particles are aggregated to form secondary particles as aggregates of primary particles, the average particle size (D) of the secondary particles is... 50 The diameter can range from 0.5 μm to 30 μm.

[0060] Because phosphorus and oxygen form strong covalent bonds within the tetrahedral structure of PO4, the lithium iron phosphate oxide represented by Equation 1 above ensures structural and thermal stability despite volume changes caused by charging and discharging. Furthermore, the surface of the lithium iron phosphate oxide represented by Equation 1 above can be coated with an amorphous layer of carbon or metal oxide. In this case, since the amorphous layer of carbon or metal oxide coated on the surface is not crystalline, lithium ions can be inserted and extracted through the amorphous layer of the shell via the lithium iron phosphate oxide in the core portion. The amorphous layer of carbon or metal oxide coated on the surface has excellent electronic conductivity and can transport lithium ions; therefore, it can also serve as a current path to the core of the lithium iron phosphate oxide as the active material, enabling high-rate charging and discharging. Additionally, if the surface of the lithium iron phosphate oxide is coated with an amorphous layer of carbon or metal oxide, unnecessary reactions between the core material and the electrolyte can be controlled, thereby further improving safety.

[0061] Furthermore, in this disclosure, in order to design an electrode with high capacity, the loading of the positive electrode containing lithium iron phosphate oxide represented by Formula 1 above can be 32 mg / cm³. 2 Above (single-sided area load: 16 mg / cm²) 2 (Above), specifically 32 mg / cm 2 Up to 60 mg / cm 2 More preferably 40 mg / cm 2Up to 60 mg / cm 2 If the load on the positive electrode meets the above range, high capacity performance can be achieved.

[0062] The positive electrode may include a positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the positive electrode current collector. In this case, the positive electrode mixture layer may contain the aforementioned lithium iron phosphate oxide as the positive electrode active material.

[0063] Positive current collectors can typically have a thickness ranging from 3 μm to 500 μm.

[0064] Positive current collectors can have microscopic irregularities formed on their surface to improve the adhesion of the positive electrode active material. For example, positive current collectors can be used in various forms, such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0065] The positive electrode mixture layer can be disposed on at least one surface of the positive electrode current collector, specifically, it can be disposed on one or both surfaces of the positive electrode current collector.

[0066] Furthermore, to ensure sufficient capacity, the content of lithium iron phosphate oxide in the cathode mixture layer, as represented by Formula 1 above, can be from 80% to 99% by weight.

[0067] In addition to the aforementioned positive electrode active material, the positive electrode mixture layer may also contain a binder and / or a conductive material.

[0068] Adhesives are used to improve the bonding between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Examples of adhesives may include: fluoropolymer adhesives, including polyvinylidene fluoride (PVDF); rubber adhesives, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose adhesives, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyvinyl alcohol adhesives, including polyvinyl alcohol; polyolefin adhesives, including polyethylene and polypropylene; polyimide adhesives; polyester adhesives; and silane adhesives, and any one of them may be used alone or in mixtures of two or more of them.

[0069] The binder content in the positive electrode mixture layer can be from 0.1% to 15% by weight, preferably from 0.1% to 10% by weight.

[0070] Next, conductive materials are used to impart conductivity to the electrodes, and any conductive material can be used without particular limitation, as long as it has electronic conductivity and will not cause chemical changes in the battery to be constructed. Specifically, conductive materials can include: carbon powder, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermally cracked carbon black; graphite powder, such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers, such as carbon fibers or metal fibers; conductive powders, such as fluorocarbon powders, aluminum powders, or nickel powders; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; polyphenylene derivatives, etc.

[0071] The amount of conductive material added to the positive electrode mixture layer can be from 1% to 30% by weight.

[0072] The positive electrode can be manufactured by coating a positive electrode current collector with a positive electrode slurry, then drying and rolling the slurry. The positive electrode slurry includes a positive electrode active material and optional binders, conductive materials, and a solvent for forming the positive electrode slurry. Alternatively, the positive electrode can be manufactured by mixing a positive electrode active material with optional binders, conductive materials, etc., to prepare a membrane, and then laminating the membrane onto the positive electrode current collector.

[0073] In order to promote the dispersion of positive electrode active materials, binders and / or conductive materials, the solvent for forming the positive electrode slurry may include, for example, at least one selected from distilled water, N-methylpyrrolidone, ethanol, methanol or isopropanol, preferably N-methylpyrrolidone.

[0074] (2) Negative electrode

[0075] Next, the negative electrode will be explained.

[0076] The negative electrode may contain a negative electrode active material.

[0077] As a negative electrode active material, carbon-based active materials, silicon-based active materials, or a mixture of carbon-based and silicon-based active materials can be used.

[0078] As carbon-based active materials, various carbon-based active materials used in this field can be used, such as graphite materials, including natural graphite, artificial graphite, or condensate (Kish) graphite; pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microspheres, mesophase pitch, and high-temperature calcined carbon such as coke derived from petroleum or coal tar pitch, soft carbon, hard carbon, etc. There are no particular limitations on the shape of carbon-based active materials, and materials of various shapes can be used, such as irregular shapes, planar shapes, sheet shapes, spherical shapes, and fiber shapes.

[0079] Specifically, the carbon-based active material can be either natural graphite or artificial graphite, and natural graphite and artificial graphite can also be used together to increase the adhesion to the current collector, thereby suppressing the insertion and extraction of the active material.

[0080] In addition, the silicon-based active material can include, for example, one or more selected from metallic silicon (Si), silicon oxide (SiOx, where 0 < x < 2), silicon carbide (SiC), and Si-Y alloy (Y is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, or a combination thereof, and is not Si). The element Y can be selected from Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, (Db), Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

[0081] In terms of ensuring the structural stability during charge and discharge and reducing side reactions with the electrolyte solution, the average particle size (D 50 ) of the silicon-based active material can be 1 μm to 30 μm, preferably 2 μm to 15 μm.

[0082] The negative electrode of the present disclosure can include at least one negative electrode active material selected from carbon-based active materials and silicon-based active materials.

[0083] Specifically, the negative electrode of the present invention can include a mixture of a carbon-based active material and a silicon-based active material.

[0084] In this case, the weight ratio between the silicon-based active material and the carbon-based active material can be 1:99 to 30:70, specifically 3:97 to 15:85. If the mixing ratio between the silicon-based active material and the carbon-based active material satisfies the above range, the volume expansion of the silicon-based active material can be suppressed while improving the capacity characteristics, thereby ensuring excellent cycle performance.

[0085] The negative electrode can include a negative electrode current collector and a negative electrode mixture layer provided on at least one surface of the negative electrode current collector. In this case, the negative electrode active material can be included in the negative electrode mixture layer.

[0086] The negative electrode current collector is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. Specifically, as the negative electrode current collector, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel or aluminum cadmium alloy surface-treated with one of carbon, nickel, titanium, silver, etc. can be used.

[0087] Negative current collectors can typically have a thickness ranging from 3 μm to 500 μm.

[0088] Negative electrode current collectors can have microscopic irregularities formed on their surface to improve the adhesion of the negative electrode active material. For example, negative electrode current collectors can be used in various forms, such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0089] The negative electrode mixture layer is disposed on at least one surface of the negative electrode current collector. Specifically, the negative electrode mixture layer may be disposed on one or both surfaces of the negative electrode current collector.

[0090] To minimize the impact of volume expansion / contraction on the battery and to ensure that the secondary battery exhibits sufficient capacity, the content of the negative electrode active material in the negative electrode mixture layer can be from 60% to 99% by weight.

[0091] In addition to the negative electrode active material, the negative electrode mixture layer may further contain conductive materials and / or adhesives.

[0092] Conductive materials are components used to further improve the conductivity of the negative electrode active material, and there are no particular limitations, as long as they are conductive and do not cause chemical changes in the battery. Examples of materials that can be used include: carbon powder, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermally cracked carbon black; graphite powder, such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers, such as carbon fibers or metal fibers; conductive powders, such as fluorocarbon powders, aluminum powders, or nickel powders; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0093] The content of conductive material in the negative electrode mixture layer can be less than 10% by weight, preferably 5% by weight.

[0094] Adhesives are components used to assist in bonding conductive materials, active materials, and current collectors, and are typically fluoropolymer adhesives, such as polyvinylidene fluoride (PVDF); rubber adhesives, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose adhesives, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyvinyl alcohol adhesives, including polyvinyl alcohol; polyolefin adhesives, including polyethylene and polypropylene; polyimide adhesives; polyester adhesives; silane adhesives, etc.

[0095] The content of binder in the negative electrode mixture layer can be from 0.1% to 15% by weight, preferably from 0.1% to 10% by weight.

[0096] The negative electrode can be manufactured by coating a negative electrode slurry, comprising a negative electrode active material and optional binders, conductive materials, and a negative electrode slurry forming solvent, onto a negative electrode current collector, followed by drying and rolling the negative electrode slurry. Alternatively, the negative electrode can be manufactured by preparing a membrane by mixing the negative electrode active material with optional binders, conductive materials, etc., and then laminating the membrane onto the negative electrode current collector.

[0097] In order to promote the dispersion of the negative electrode active material, binder and / or conductive material, the solvent for forming the negative electrode slurry may include, for example, at least one selected from distilled water, N-methylpyrrolidone, ethanol, methanol or isopropanol, preferably distilled water.

[0098] (3) Diaphragm

[0099] The separator is used to separate the negative electrode and the positive electrode and provide a transport path for lithium ions. Any separator can be used without particular limitation, as long as it is a separator commonly used in lithium secondary batteries. In particular, separators with low resistance to ion transport in non-aqueous electrolytes and thus excellent non-aqueous electrolyte moisture retention are preferred.

[0100] Specifically, as a separator, porous polymer membranes can be used, such as porous polymer membranes made from polyolefin polymers like ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, or ethylene / methacrylate copolymers, or membranes with two or more layers stacked together. Alternatively, typical porous nonwoven fabrics can be used, such as nonwoven fabrics made from high-melting-point glass fibers, polyethylene terephthalate fibers, etc. Furthermore, coated separators including ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and can optionally be used in single-layer or multi-layer structures.

[0101] (4) Electrolytes

[0102] Next, the electrolyte disclosed herein may include lithium salt, a first organic solvent, a second organic solvent, a first additive, and a second additive, and specific examples of each component are described below.

[0103] (4-1) Lithium salts

[0104] First, as the lithium salt, any lithium salt commonly used in electrolytes for lithium secondary batteries can be used without limitation; for example, the lithium salt can contain Li. + As a cation, and as an anion, it may contain components selected from F. - Cl - ,Br - I - N(CN)2 - BF4 - ClO4 - B 10Cl 10 - AlCl4 - AlO2 - PF6 - CF3SO3 - CH3CO2 - CF3CO2 - AsF6 - SbF6 - CH3SO3 - (CF3CF2SO2)2N - (CF3SO2)2N - (FSO2)2N - BF2C2O4 - BC4O8 - PF4C2O4 - PF2C4O8 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - C4F9SO3 - CF3CF2SO3 - CF3CF2(CF3)2CO - (CF3SO2)2CH - and CF3(CF2)7SO3 - Any one of them.

[0105] Specifically, lithium salts may include those selected from LiCl, LiBr, LiI, LiBF4, LiClO4, and LiB. 10 Cl 10The material may be a single material or a mixture of two or more of the following: LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF2CF3)2 (lithium bis(pentafluoroethanesulfonyl)imide, LiBETI), or LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide, LiTFSI). Specifically, it may include any one of LiBF4, LiPF6, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF2CF3)2 (lithium bis(pentafluoroethanesulfonyl)imide, LiBETI), or LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide, LiTFSI). In addition to the examples mentioned above, any lithium salt commonly used in the electrolyte of lithium secondary batteries can be used without limitation.

[0106] Although the typical range of lithium salts that can be used can be appropriately varied, in order to obtain the best effect of forming an anti-corrosion film on the electrode surface, lithium salts can be included in the electrolyte at a concentration of 0.8 M to 3.0 M, specifically 1.0 M to 2.0 M, preferably 1.0 M to 1.8 M.

[0107] If the concentration of lithium salt is within the above range, the viscosity of the electrolyte can be controlled to achieve optimal impregnation performance, and the transfer performance of lithium ions can be improved to improve the capacity performance and cycle performance of lithium secondary batteries.

[0108] (4-2) First organic solvent

[0109] Next, the first organic solvent will be described.

[0110] The first organic solvent may include cyclic lactone compounds.

[0111] Cyclic lactone compounds are compounds with high dielectric constant and high ionic conductivity, and can improve the charge transfer degradation caused by driving high-load electrodes.

[0112] Cyclic lactone compounds may include γ-butyrolactone.

[0113] Based on the total weight of the electrolyte, the content of the first organic solvent can be from 39% to 80% by weight, specifically from 48% to 80% by weight, more preferably from 52% to 70% by weight.

[0114] If the content of the first organic solvent meets the above range, the lithium-ion transfer performance can be improved, thereby achieving the effect of reducing battery resistance.

[0115] (4-3) Second organic solvent

[0116] Next, the second organic solvent will be explained.

[0117] The second organic solvent may include carbonate organic solvents to minimize decomposition caused by oxidation reactions, etc., during the charge and discharge process of the secondary battery, and to exhibit the desired performance together with the additives.

[0118] Specifically, the carbonate organic solvent may preferably include any one of cyclic carbonate organic solvents having high ionic conductivity and high dielectric constant and linear carbonate organic solvents having low viscosity and low dielectric constant, and may specifically include cyclic carbonate organic solvents.

[0119] Cyclic carbonate organic solvents may specifically include at least one selected from ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentene carbonate, 2,3-pentene carbonate, vinylene carbonate, or fluoroethylene carbonate (FEC), or preferably ethylene carbonate capable of maintaining stable SEI film passivation capability.

[0120] In addition, linear carbonate organic solvents may include at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, or ethyl propyl carbonate, or among these linear carbonate organic solvents, dimethyl carbonate (DMC) or ethyl methyl carbonate (EMC) may be selected from those having small molecular size and low viscosity.

[0121] If a cyclic carbonate organic solvent and a linear carbonate organic solvent are mixed and used as a second organic solvent, in order to ensure low viscosity performance, the cyclic carbonate organic solvent and the linear carbonate organic solvent can be mixed and used in a volume ratio of about 1:99 to 50:50, or in a volume ratio of 20:80 to 40:60.

[0122] Meanwhile, in this disclosure, the volume ratio of the first organic solvent to the second organic solvent can be 50:50 to 99:1, specifically 70:30 to 99:1, and more specifically 70:30 to 90:10.

[0123] If the mixing ratio of the first organic solvent and the second organic solvent meets the above-mentioned range, high ion transfer performance can be achieved, and battery performance with low resistance can be ensured. That is, if the volume ratio of the first organic solvent is 50 or higher, ion transfer performance can be ensured, and if the volume ratio is 99 or lower, battery life performance can be improved by forming a stable film.

[0124] Additionally, if necessary, the electrolyte disclosed herein may also contain a third organic solvent.

[0125] The third type of organic solvent may include linear ester organic solvents.

[0126] As a representative example, linear ester organic solvents may include at least one organic solvent selected from methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate or butyl propionate, specifically, at least one of ethyl propionate and propyl propionate.

[0127] (4-4) First Additive

[0128] Next, the first additive will be explained.

[0129] The first additive may include lithium nitrate (LiNO3).

[0130] During the activation step, the lithium nitrate (LiNO3) contained in the first additive can form an inorganic film containing lithium-nitrogen bonds and lithium-oxygen bonds on the surface of the negative electrode. Since the inorganic film increases the surface energy and acts as an ion carrier capable of uniformly transporting lithium ions, it can improve the electrode impregnation performance of the electrolyte and induce more efficient charge transfer reactions.

[0131] In addition, the lithium nitrate (LiNO3) contained in the first additive can form coordination bonds with transition metals dissolved from the positive electrode at high temperatures, or with Lewis acids produced by the decomposition products of lithium salts, thereby preventing transition metal ions from electrodepositing on the surface of the negative electrode and thus preventing the loss of reversible lithium, thereby reducing the degradation of cycle performance.

[0132] Meanwhile, the first additive may be included in the electrolyte in a specific amount. Specifically, based on the total weight of the electrolyte, the content of the first additive may be from 0.05% by weight to 3.0% by weight, more specifically from 0.05% by weight to 2.0% by weight, more specifically from 0.1% by weight to 2.0% by weight, and preferably from 0.1% by weight to 1.5% by weight.

[0133] If the content of the first additive disclosed herein meets the above-mentioned range, an inorganic film containing lithium-nitrogen bonds and lithium-oxygen bonds is uniformly formed on the surface of the negative electrode, thus acting as an effective ion carrier rather than a resistor. In other words, if the content of the first additive is 0.05% by weight or more, battery performance degradation can be prevented by suppressing the increase in battery resistance, and if the content of the first additive is 3.0% by weight or less, side reactions between the electrolyte and the electrode can be suppressed by forming a robust film, thereby preventing the generation of unnecessary activation gases, etc., and thus preventing degradation of high-temperature cycling and high-temperature storage performance.

[0134] Meanwhile, the content of the first additive in the preferred electrolyte and the loading of the positive electrode satisfy the following relationship 1.

[0135] [Relation 1]

[0136] 0.0001 ≤ ≤0.050

[0137] In Equation 1 above, A is the total amount of electrolyte injected into the lithium secondary battery (g), B is the content of lithium nitrate (LiNO3) in the injected electrolyte (wt%), and C is the loading of the positive electrode (g / cm³). 2 D represents the total surface area (cm²) of the positive electrode current collector. 2 ).

[0138] If the content of the first additive in the electrolyte of this disclosure satisfies the above-mentioned relationship, the impregnation performance of the electrolyte on the negative electrode can be improved, and an effective inorganic film that can improve ion transfer performance can be formed, thereby ensuring excellent battery performance.

[0139] (4-5) Second additive

[0140] Next, the second additive will be explained.

[0141] In this disclosure, a sulfonamide compound may be included as a second additive.

[0142] Sulfonamide compounds may include compounds represented by formula 2 below.

[0143] [Equation 2]

[0144] In the above [Equation 2], R1 is selected from oxygen atom, nitrogen atom, sulfur atom, aryl group having 6 to 10 carbon atoms, heteroaryl group having 5 to 10 carbon atoms including one or more of N, O and S, and Any one of the groups, wherein R2 is a fluorine group, an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or... ,in, and One or more hydrogen atoms contained therein may be replaced by fluorine atoms, M1 is selected from the group consisting of lithium, sodium, potassium, tetraalkylammonium having 1 to 4 carbon atoms, tetraalkylphosphonium having 1 to 4 carbon atoms, l is an integer from 1 to 6, and m and n are each an integer from 2 to 20.

[0145] Specifically, the sulfonylimide compound represented by Formula 2 above, included as a second additive, can be a sulfonylimide (disulfonylimide, -S(=O)2-N) compound in which the vinyl group is extended by the conjugated functional group (R1) of the sulfonylimide group. - Ionic compounds bonded to one side of the -S(=O)2-) unit. Ionic compounds contain a negative charge in their molecular structure, and therefore readily migrate to the positive electrode and are oxidized and decomposed upon activation, thereby enabling the uniform formation of organic films and / or robust inorganic films containing lithium-nitrogen / oxygen / sulfur bonds on the positive electrode surface.

[0146] As mentioned above, with lithium ions (Li + In contrast, the compound represented by Formula 2 has the property of being electrochemically oxidized at a potential near 4.0V. Therefore, if it is used as an electrolyte additive in a secondary battery using lithium iron phosphate oxide electrodes, the compound can be reduced earlier than organic solvents, thereby forming a robust film on the positive electrode surface at the start of activation. As a result, additional electrolyte oxidative decomposition on the positive electrode surface can be prevented during repeated cycle driving, thereby suppressing the increase in resistance and reducing the overall performance degradation of the lithium secondary battery.

[0147] Meanwhile, in the above [Equation 2], R1 is selected from phenylene, naphthyl, pyrrolyl, furanyl, thiophene, imidazolinyl, ... and R2 is any one of the groups, where R2 is fluoro, methyl, ethyl, propyl, trifluoromethyl, methoxy, ethoxy, or... or M1 is lithium, l is an integer of 1 or 2, and m and n are each integers from 2 to 10.

[0148] More specifically, the compound represented by Formula 2 above can be any one of the groups consisting of compounds represented by Formulas 2-1 to 2-35 below, and preferably, is any one of the groups consisting of compounds represented by Formulas 2-1 to 2-3, 2-8 to 2-10, 2-15 to 2-17, 2-22 to 2-24 and 2-29 whose structures simultaneously contain vinyl and phenyl (therefore easier oxidative decomposition at low voltage).

[0149] [Equation 2-1]

[0150] [Equation 2-2]

[0151] [Equation 2-3]

[0152] [Equation 2-4]

[0153] [Equation 2-5]

[0154] [Equation 2-6]

[0155] [Equation 2-7]

[0156] In equation 2-7 above, n1 is an integer from 2 to 5.

[0157] [Equation 2-8]

[0158] [Equation 2-9]

[0159] [Equation 2-10]

[0160] [Equation 2-11]

[0161] [Equation 2-12]

[0162] [Equation 2-13]

[0163] [Equation 2-14]

[0164] In Equation 2-14 above, n2 is an integer from 2 to 5.

[0165] [Equation 2-15]

[0166] In Equation 2-15 above, m1 is an integer from 2 to 5.

[0167] [Equation 2-16]

[0168] In Equation 2-16 above, m2 is an integer from 2 to 5.

[0169] [Equation 2-17]

[0170] In Equation 2-17 above, m3 is an integer from 2 to 5.

[0171] [Equation 2-18]

[0172] In Equation 2-18 above, m4 is an integer from 2 to 5.

[0173] [Equation 2-19]

[0174] In Equation 2-19 above, m5 is an integer from 2 to 5.

[0175] [Equation 2-20]

[0176] In Equation 2-20 above, m6 is an integer from 2 to 5.

[0177] [Equation 2-21]

[0178] In Equation 2-21 above, n3 and m7 are each an independent integer from 2 to 5.

[0179] [Equation 2-22]

[0180] In Equation 2-22 above, m8 is an integer from 2 to 5.

[0181] [Equation 2-23]

[0182] In Equation 2-23 above, m9 is an integer from 2 to 5.

[0183] [Equation 2-24]

[0184] In Equation 2-24 above, m10 is an integer from 2 to 5.

[0185] [Equation 2-25]

[0186] In Equation 2-25 above, m11 is an integer from 2 to 5.

[0187] [Equation 2-26]

[0188] In Equation 2-26 above, m12 is an integer from 2 to 5.

[0189] [Equation 2-27]

[0190] In Equation 2-27 above, m13 is an integer from 2 to 5.

[0191] [Equation 2-28]

[0192] In Equation 2-28 above, n4 and m14 are each an independent integer from 2 to 5.

[0193] [Equation 2-29]

[0194] [Equation 2-30]

[0195] [Equation 2-31]

[0196] [Equation 2-32]

[0197] [Equation 2-33]

[0198] [Equation 2-34]

[0199] [Equation 2-35]

[0200] In equation 2-35 above, n5 is an integer from 2 to 5.

[0201] In the electrolyte disclosed herein, the weight ratio of the first additive to the second additive may be 1:0.05 to 1:2, 1:0.1 to 1:2, or more preferably 1:0.1 to 1:1.

[0202] If the composition ratio of the first and second additives meets the above-mentioned range, a stable film can be formed on the surfaces of the positive and negative electrodes, thereby improving overall high-temperature performance (cycle performance, OCV stability, etc.). In other words, if the weight ratio of the second additive is less than 2, a uniform film can be formed on the negative electrode surface, preventing the film from acting as a resistor and preventing corrosion of the positive and negative current collectors. However, if the content of the second additive is slightly higher, the increased content of the second additive that is reduced and decomposed on the negative electrode surface leads to an increased film thickness, potentially causing the film to act as a resistor. Furthermore, the undecomposed second additive remaining after activation may cause corrosion of the positive current collector.

[0203] (4-6) Other additives

[0204] Meanwhile, to prevent the electrolyte from decomposing in a high-output environment and causing negative electrode collapse, or to further improve low-temperature high-rate discharge performance, high-temperature stability, overcharge protection, and the effect of suppressing battery expansion at high temperatures, the lithium secondary battery of the present invention may, if necessary, contain other additives in the electrolyte. If other additives are included, these other additives may be referred to as third additives.

[0205] Representative examples of the other additives mentioned above may include any additive selected from cyclic carbonates, sulfonyl lactones, phosphates / esters, borates / esters, nitriles, benzenes, amines, silanes, or lithium salts.

[0206] Cyclic carbonate compounds can be vinylene carbonate (VC).

[0207] Sulfolide compounds can be selected from any one of 1,3-propanesulfonyl lactone (PS), 1,4-butanesulfonyl lactone, ethylenesulfonyl lactone, 1,3-propenesulfonyl lactone (PRS), 1,4-butenesulfonyl lactone or 1-methyl-1,3-propenesulfonyl lactone.

[0208] The phosphate / ester compound may be one or more compounds selected from lithium difluorobis(oxalato) phosphate, lithium difluorophosphate, tri(trimethylsilyl) phosphate, tri(2,2,2-trifluoroethyl) phosphate, or tri(trifluoroethyl) phosphate.

[0209] The borates / esters can be tetraphenylborates or lithium oxaloyl difluoroborate.

[0210] Nitrile compounds can be selected from any one of butadionitrile, adiponitrile, acetonitrile, propionitrile, butadionitrile, valerate, octanoic acid, heptanonitrile, cyclopentanoic acid, cyclohexanoic acid, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, or 4-fluorophenylacetonitrile.

[0211] Benzene compounds can be fluorobenzene, amine compounds can be triethanolamine, ethylenediamine, etc., and silane compounds can be tetravinylsilane.

[0212] Lithium salt compounds are compounds that are different from lithium salts contained in electrolytes, and can be one or more compounds selected from LiPO2F2, LiODFB, lithium bis(oxalatoborate) (LiBOB, (LiB(C2O4)2)), LiBF4 or LiDFOP.

[0213] The other additives mentioned above can be used in mixtures of two or more, and their content can be less than 10% by weight, specifically from 0.01% to 8.0% by weight, preferably from 0.05% to 5.0% by weight, based on the total weight of the electrolyte. If the content of the other additives meets the above range, side reactions caused by unreacted additives can be suppressed, and the effects of improving the low-temperature output of the battery, as well as improving the high-temperature storage performance and high-temperature life performance of the battery can be further enhanced.

[0214] The lithium secondary battery disclosed herein, as described above, can be effectively used in portable devices such as mobile phones, laptops, and digital cameras, as well as in electric vehicles such as hybrid electric vehicles (HEVs).

[0215] The external shape of the lithium secondary battery disclosed herein is not particularly limited, but it can be cylindrical, square, bag-shaped, coin-shaped, etc., using a can.

[0216] The lithium secondary battery disclosed herein can be used in battery cells for use as power sources in small devices, and can also preferably be used as a unit cell in medium to large battery modules comprising multiple battery cells.

[0217] The present disclosure will be described in detail below with reference to embodiments. However, embodiments of the present disclosure may be modified in various other forms, and the scope of the present disclosure should not be construed as limited to the embodiments described below. Embodiments of the present disclosure are provided to describe the present disclosure more fully to those skilled in the art.

[0218] [Example]

[0219] Example 1

[0220] (Preparation of electrolytes)

[0221] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 0.05 wt% of lithium nitrate (LiNO3) as a first additive and 0.1 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive and the second additive = 1:2) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0222] (The manufacture of the positive electrode)

[0223] A positive electrode active material (LiFePO4), a conductive material (carbon black), and a binder (polyvinylidene fluoride, PVDF) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 96:1:3 to prepare a positive electrode active material slurry (67% by weight solids). The positive electrode active material slurry was coated onto a 15 μm thick positive electrode current collector (Al film), dried, and rolled to fabricate the positive electrode (double-sided loading: 48 mg / cm²). 2 Single-sided area loading: 24 mg / cm² 2 ).

[0224] (Manufacturing of the negative electrode)

[0225] A negative electrode active material (artificial graphite), CMC-SBR as a binder, and carbon black as a conductive material were added to distilled water as a solvent in a weight ratio of 96:3.5:0.5 to prepare a negative electrode active material slurry (solid content: 53 wt%). The negative electrode active material slurry was coated onto a negative electrode current collector (Cu film) with a thickness of 8 μm, dried, and rolled to manufacture the negative electrode.

[0226] (Manufacturing of secondary batteries)

[0227] The positive and negative electrodes manufactured by the above method are stacked sequentially with a polyethylene porous membrane to manufacture an electrode assembly according to conventional methods. The electrode assembly is then housed in a pouch-type secondary battery casing, and the electrolyte prepared above is injected into the casing to manufacture a lithium secondary battery.

[0228] Example 2

[0229] (Preparation of electrolytes)

[0230] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 0.1 wt% of lithium nitrate (LiNO3) as a first additive and 0.1 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (the weight ratio of the first additive and the second additive is 1:1) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0231] (Manufacturing of secondary batteries)

[0232] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0233] Example 3

[0234] (Preparation of electrolytes)

[0235] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.5 wt% of lithium nitrate (LiNO3) as a first additive and 0.15 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive to the second additive = 1:0.1) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0236] (Manufacturing of secondary batteries)

[0237] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0238] Example 4

[0239] (Preparation of electrolytes)

[0240] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 3.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.15 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive to the second additive = 1:0.05) were added. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0241] (Manufacturing of secondary batteries)

[0242] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0243] Example 5

[0244] (Preparation of electrolytes)

[0245] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.1 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive to the second additive = 1:0.1) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0246] (Manufacturing of secondary batteries)

[0247] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0248] Example 6

[0249] (Preparation of electrolytes)

[0250] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0251] (Manufacturing of secondary batteries)

[0252] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0253] Example 7

[0254] (Preparation of electrolytes)

[0255] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 2.0 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive and the second additive = 1:2) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0256] (Manufacturing of secondary batteries)

[0257] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0258] Example 8

[0259] (Preparation of electrolytes)

[0260] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by Formula 2-1 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0261] (Manufacturing of secondary batteries)

[0262] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0263] Example 9

[0264] (Preparation of electrolytes)

[0265] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by Formula 2-2 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0266] (Manufacturing of secondary batteries)

[0267] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0268] Example 10

[0269] (Preparation of electrolytes)

[0270] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by formula 2-9 as a second additive (weight ratio of the first additive and the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0271] (Manufacturing of secondary batteries)

[0272] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0273] Example 11

[0274] (Preparation of electrolytes)

[0275] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by formula 2-10 as a second additive (weight ratio of the first additive and the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0276] (Manufacturing of secondary batteries)

[0277] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0278] Example 12

[0279] (Preparation of electrolytes)

[0280] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by Formula 2-15 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0281] (Manufacturing of secondary batteries)

[0282] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0283] Example 13

[0284] (Preparation of electrolytes)

[0285] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by Formula 2-16 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0286] (Manufacturing of secondary batteries)

[0287] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0288] Example 14

[0289] (Preparation of electrolytes)

[0290] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by Formula 2-17 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0291] (Manufacturing of secondary batteries)

[0292] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0293] Example 15

[0294] (Preparation of electrolytes)

[0295] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by formula 2-22 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0296] (Manufacturing of secondary batteries)

[0297] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0298] Example 16

[0299] (Preparation of electrolytes)

[0300] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by formula 2-24 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0301] (Manufacturing of secondary batteries)

[0302] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0303] Example 17

[0304] (Preparation of electrolytes)

[0305] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by formula 2-29 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0306] (Manufacturing of secondary batteries)

[0307] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0308] Example 18

[0309] (Preparation of electrolytes)

[0310] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 99:1. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0311] (Manufacturing of secondary batteries)

[0312] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0313] Example 19

[0314] (Preparation of electrolytes)

[0315] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 50:50. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0316] (Manufacturing of secondary batteries)

[0317] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0318] Example 20

[0319] (Preparation of electrolytes)

[0320] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 4.0 wt% of lithium nitrate (LiNO3) as a first additive and 4.0 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (the weight ratio of the first additive and the second additive is 1:1) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0321] (Manufacturing of secondary batteries)

[0322] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0323] Example 21

[0324] (Preparation of electrolytes)

[0325] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 3.0 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive and the second additive = 1:3) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0326] (Manufacturing of secondary batteries)

[0327] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0328] Example 22

[0329] (Preparation of electrolytes)

[0330] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 40:60. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive and the second additive = 1:0.5) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare the electrolyte for lithium secondary batteries of this disclosure.

[0331] (Manufacturing of secondary batteries)

[0332] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0333] Example 23

[0334] (The manufacture of the positive electrode)

[0335] A positive electrode active material (LiFePO4), a conductive material (carbon black), and a binder (polyvinylidene fluoride, PVDF) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 96:1:3 to prepare a positive electrode active material slurry (67% by weight solids). The positive electrode active material slurry was coated onto a 15 μm thick positive electrode current collector (Al film), dried, and rolled to fabricate the positive electrode (double-sided loading: 32 mg / cm²). 2 Single-sided area loading: 16 mg / cm² 2 ).

[0336] (Manufacturing of secondary batteries)

[0337] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the positive electrode manufactured above was used.

[0338] Example 24

[0339] (The manufacture of the positive electrode)

[0340] A positive electrode active material (LiFePO4), a conductive material (carbon black), and a binder (polyvinylidene fluoride, PVDF) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 96:1:3 to prepare a positive electrode active material slurry (67% by weight solids). The positive electrode active material slurry was coated onto a 15 μm thick positive electrode current collector (Al film), dried, and rolled to fabricate the positive electrode (double-sided loading: 60 mg / cm²). 2 Single-sided area loading: 30 mg / cm² 2 ).

[0341] (Manufacturing of secondary batteries)

[0342] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the positive electrode manufactured above was used.

[0343] Comparative Example 1

[0344] (Preparation of electrolytes)

[0345] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 14.0 wt% of lithium nitrate (LiNO3) was added as a first additive, followed by 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) as other additives to prepare an electrolyte.

[0346] (Manufacturing of secondary batteries)

[0347] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0348] Comparative Example 2

[0349] (Preparation of electrolytes)

[0350] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of a sulfonylimide compound represented by formula 2-8 was added as a second additive, followed by the addition of 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) as other additives to prepare an electrolyte.

[0351] (Manufacturing of secondary batteries)

[0352] A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that the electrolyte prepared above was injected.

[0353] Comparative Example 3

[0354] (Preparation of electrolytes)

[0355] LiPF6 was dissolved to 1.0 M in an organic solvent in which ethylene carbonate and ethyl methyl carbonate were mixed in a volume ratio of 30:70. Then, 1.0 wt% of lithium nitrate (LiNO3) as a first additive and 0.5 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive to the second additive = 1:0.5) were added. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare an electrolyte.

[0356] (Manufacturing of secondary batteries)

[0357] A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that the electrolyte prepared above was injected.

[0358] Comparative Example 4

[0359] (Preparation of electrolytes)

[0360] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 1.0 wt% of LiBF4 as a first additive and 1.0 wt% of a sulfonylimide compound represented by formula 2-8 as a second additive (weight ratio of the first additive and the second additive = 1:1) were added thereto. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare an electrolyte.

[0361] (Manufacturing of secondary batteries)

[0362] A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that the electrolyte prepared above was injected.

[0363] Comparative Example 5

[0364] (Preparation of electrolytes)

[0365] LiPF6 was dissolved to 1.0 M in an organic solvent in which γ-butyrolactone and ethylene carbonate were mixed in a volume ratio of 70:30. Then, 0.1 wt% of lithium nitrate (LiNO3) as a first additive and 0.1 wt% of lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2, LiTFSI) as a second additive (weight ratio of first additive to second additive = 1:1) were added. Subsequently, 3.0 wt% of vinylene carbonate (VC) and 1.0 wt% of ethylene sulfate (Esa) were added as other additives to prepare an electrolyte.

[0366] (Manufacturing of secondary batteries)

[0367] A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that the electrolyte prepared above was injected.

[0368] Comparative Example 6

[0369] (The manufacture of the positive electrode)

[0370] A positive electrode active material (LiFePO4), a conductive material (carbon black), and a binder (polyvinylidene fluoride, PVDF) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 96:1:3 to prepare a positive electrode active material slurry (67% by weight solids). The positive electrode active material slurry was coated onto a 15 μm thick positive electrode current collector (Al film), dried, and rolled to fabricate the positive electrode (double-sided loading: 62 mg / cm²). 2 Single-sided area loading: 31 mg / cm² 2 ).

[0371] (Manufacturing of secondary batteries)

[0372] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the positive electrode manufactured above was used.

[0373] [Experimental Example]

[0374] Experimental Example 1. Evaluation of High-Temperature (45℃) Cycling Characteristics

[0375] Each lithium secondary battery prepared in the examples and comparative examples was charged to 64% SOC at a rate of 0.1C at a high temperature (55°C), and then subjected to aging (48 hours) and degassing processes for activation.

[0376] After the activation process is completed, each lithium secondary battery is charged to 3.8 V at a constant current / constant voltage rate of 0.1 C at room temperature (25°C), and then discharged to 2.5 V at a constant current rate of 0.33 C at room temperature to confirm the initial capacity.

[0377] Subsequently, each lithium-ion battery was charged to 3.8 V at a constant current / constant voltage rate of 0.33 C under high temperature (45°C), and then discharged to 2.5 V at a constant current rate of 0.33 C. This entire process was set as one cycle, and 100 cycles were performed, after which the discharge capacity was measured. The lithium-ion batteries were driven using a PNA-0506 charge / discharger (manufacturer: PNE solution).

[0378] The high-temperature cycling capacity retention rate (%) was calculated using the 100th discharge rate relative to the initial capacity obtained, and the results are shown in Table 1 below.

[0379] [Table 1]

[0380] Referring to Table 1 above, it can be confirmed that, compared with the lithium secondary batteries of Comparative Examples 1 to 6, the capacity retention rate (%) of the lithium secondary batteries manufactured in Examples 1 to 24 of this disclosure after high-voltage high-temperature cycling is improved.

[0381] Although this disclosure has been described with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes in form and detail may be made without departing from the spirit and scope of this disclosure as set forth in the appended claims. Therefore, the scope of this disclosure is not intended to be limited to what is set forth in the detailed description of the specification, but is intended to be defined by the appended claims.

Claims

1. A lithium secondary battery, comprising: A positive electrode, a negative electrode, a separator, and an electrolyte, wherein, the positive electrode includes lithium iron phosphate oxide as a positive electrode active material, and The loading of the positive electrode is 32 mg / cm³. 2 Up to 60 mg / cm 2 , the electrolyte includes a lithium salt, a first organic solvent, a second organic solvent, a first additive, and a second additive, wherein, the first organic solvent is a cyclic lactone compound, the second organic solvent is a carbonate organic solvent, the first additive is lithium nitrate (LiNO3), and the second additive is a sulfonylimide compound.

2. The lithium secondary battery according to claim 1, wherein, The lithium iron phosphate oxide is a compound represented by the following formula 1: [Formula 1] Li 1+a Fe x M y (PO 4-b )X' b In the above [Formula 1], M is any one selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, X' is one or more elements selected from the group consisting of F, S, and N, and -0.5 ≤ a ≤ 0.5, 0 < x ≤ 1, 0 ≤ y ≤ 1, and 0 ≤ b ≤ 0.

3.

3. The lithium secondary battery according to claim 2, wherein, The lithium iron phosphate oxide is lithium iron phosphate (LiFePO4) or lithium iron manganese phosphate (LiFeMnPO4).

4. The lithium secondary battery according to claim 1, wherein, The loading of the positive electrode is 40 mg / cm³. 2 Up to 60 mg / cm 2 .

5. The lithium secondary battery according to claim 1, wherein, The cyclic lactone compound includes γ-butyrolactone.

6. The lithium secondary battery according to claim 1, wherein, The carbonate organic solvent is a cyclic carbonate organic solvent.

7. The lithium secondary battery according to claim 1, wherein, The first organic solvent and the second organic solvent are present in a volume ratio of 50:50 to 99:

1.

8. The lithium secondary battery according to claim 1, wherein, Based on the total weight of the electrolyte, the content of the first additive is 0.05 wt% to 3.0 wt%.

9. The lithium secondary battery according to claim 1, wherein, The sulfonylimide compound includes a compound represented by the following formula 2: [Formula 2] In the above [Formula 2], R1 is selected from oxygen, nitrogen, sulfur, aryl groups having 6 to 10 carbon atoms, heteroaryl groups having 5 to 10 carbon atoms including one or more of N, O, and S, and... Any one of the groups formed, R2 is a fluorine group, an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or a fluorine-substituted group. , in, and One or more hydrogen atoms contained therein are replaced by fluorine atoms. M1 is any one selected from the group consisting of lithium, sodium, potassium, tetraalkylammonium having 1 to 4 carbon atoms, and tetraalkylphosphonium having 1 to 4 carbon atoms, l is an integer from 1 to 6, and m and n are each integers from 2 to 20.

10. The lithium secondary battery according to claim 9, wherein, In the above [Formula 2], R1 is selected from phenylene, naphthyl, pyrrolylene, furanyl, thiophene, and imidazolinyl. and Any one of the groups formed, R2 is a fluorinated group, methyl group, ethyl group, propyl group, trifluoromethyl group, methoxy group, ethoxy group, etc. or , M1 is lithium, l is an integer of 1 or 2, and m and n are each integers from 2 to 10.

11. The lithium secondary battery according to claim 1, wherein, The first additive and the second additive are present in a weight ratio of 1:0.05 to 1:

2.

12. The lithium secondary battery according to claim 1, wherein, The first additive and the second additive are present in a weight ratio of 1:0.1 to 1:

2.

13. The lithium secondary battery according to claim 1, wherein, The negative electrode contains a carbonaceous active material, a silicon-based active material, or a mixture of a carbonaceous active material and a silicon-based active material.

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