Non-aqueous electrolyte solution and lithium secondary battery comprising the same

Abstract

An object of the present application is to provide an electrolyte solution which is capable of suppressing deterioration of battery characteristics under high-temperature conditions, thereby having an excellent cycle life. Provided is a nonaqueous electrolyte solution including a compound which includes 5 to 20 mass% of nitrogen atoms and 25 to 70 mass% of sulfur atoms or oxygen atoms in a molecule, and which does not have a disulfide bond in the molecule, wherein the compound includes at least two sulfur atoms or oxygen atoms in the molecule.

Description

Technical Field

[0001] This invention relates to a non-aqueous electrolyte solution and a lithium secondary battery containing the solution.

[0002] This application claims the benefit of Japanese Patent Application No. 2019-235040, filed with the Japan Patent Office on December 25, 2019, the disclosure of which is incorporated herein by reference in its entirety. Background Technology

[0003] Lithium-ion batteries are widely used as storage batteries, not only in portable devices such as mobile phones or laptops, but also in vehicles, industrial applications, and even emerging applications such as drones. Compared with other types of rechargeable batteries, lithium-ion batteries have a relatively high energy density, but to manufacture lithium-ion batteries with even higher energy density, nickel-containing materials are considered as the positive electrode active material.

[0004] Lithium cobalt oxide (LCO) has long been used as the positive electrode active material for lithium-ion secondary batteries, but the use of nickel-cobalt-manganese (NCM) compounds containing nickel is increasing. Furthermore, the use of nickel-cobalt-aluminum (NCA) ternary materials is also being considered. This ternary material offers advantages in high energy density and is cost-competitive due to its reduced cobalt content.

[0005] Furthermore, silicon-containing materials are currently being developed as anode active materials. Due to their high theoretical capacity, silicon-containing materials hold particular promise for use in automotive applications requiring high capacity.

[0006] When positive and negative electrode active materials are used as described above, the optimal electrolyte solution should be considered. It is well known that trace amounts of water in the electrolyte solution can affect electrolyte degradation. For example, when LiPF6 is used as the electrolyte, the following reaction occurs: the electrolyte decomposes, producing acidic components.

[0007] LiPF6 + H2O → LiF + POF3 + 2HF

[0008] As is well known, the acidic components produced react with the surface of silicon-containing anode materials (such as SiO) or with the layer formed on that surface, which in turn increases impedance and degrades battery characteristics. Furthermore, when nickel-containing materials are used as cathode active materials, a large amount of alkali remains in the material, potentially accelerating the acid-generating reaction.

[0009] Patent Document 1 discloses the use of a non-aqueous electrolyte containing triborate to improve the high-temperature storage and cycle characteristics of lithium secondary batteries. However, Patent Document 1 discloses methods to reduce the impact on OH groups. - The effects on acids were disclosed, but the effects on acids were not disclosed.

[0010] Patent document 2 discloses the use of an electrolyte containing a specific silicon-containing compound to improve the lifespan and high-temperature stability of lithium secondary batteries. However, such silicon-containing compounds are generally difficult to prepare, and their effects are not well known.

[0011] Patent Document 3 discloses a non-aqueous electrolyte solution containing at least one additive selected from compounds containing nitrogen atoms with lone pairs of electrons to prevent the generation of hydrogen fluoride due to the use of a specific fluorinated acrylate as the electrolyte composition. However, Patent Document 3 demonstrates that while effective when graphite is used as the negative electrode, it does not resolve the effects on the negative electrode and the layer on the surface when silicon-containing materials are used.

[0012] [Related Literature]

[0013] [Patent Literature]

[0014] Patent Document 1: Japanese Patent Publication No. 2019-40701

[0015] Patent Document 2: Japanese Patent Publication No. 2019-71302

[0016] Patent Document 3: Japanese Patent Publication No. 2019-186078 Summary of the Invention

[0017] [Technical Issues]

[0018] Therefore, there is a need for an electrolyte solution that can deliver excellent battery characteristics and cycle life even when the positive electrode uses nickel-containing materials and the negative electrode uses silicon-containing materials, by stabilizing the properties of the electrolyte solution.

[0019] The present invention aims to solve the above-mentioned problems in the prior art. Therefore, the purpose of the present invention is to provide an electrolyte solution with a long cycle life by suppressing the degradation of battery characteristics under high temperature conditions.

[0020] [Technical Solution]

[0021] After carefully studying the above problems, the inventors unexpectedly discovered that when a compound containing a specific amount of nitrogen and sulfur or oxygen atoms and without disulfide bonds in the molecule is used as an electrolyte solution additive, a high capacity density can be maintained under high temperature conditions, and thus the present invention was derived.

[0022] The object of the present invention is achieved using a non-aqueous electrolyte solution comprising: a compound containing 5% to 20% by mass of nitrogen atoms and 25% to 70% by mass of sulfur atoms or oxygen atoms in the molecule and having no disulfide bonds in the molecule, wherein the compound contains at least two sulfur atoms or oxygen atoms in the molecule.

[0023] The compound may be a compound containing 5% to 20% by mass of nitrogen atoms and 25% to 70% by mass of sulfur atoms in the molecule and having no disulfide bonds in the molecule.

[0024] The compound may contain at least two sulfur atoms in its molecule.

[0025] The compound may contain at least three sulfur atoms in its molecule.

[0026] The compound may include at least one compound represented by the following chemical formulas 1 to 3:

[0027] [Chemical Formula 1]

[0028]

[0029] Wherein, R1 is an alkyl or phenyl group having 1 to 18 carbon atoms, R2 is an alkyl or phenyl group having 1 to 18 carbon atoms, R3 is an alkyl or phenyl group having 1 to 18 carbon atoms, R4 is an alkyl or phenyl group having 1 to 18 carbon atoms, and R5 is an alkylene group having 1 to 12 carbon atoms.

[0030] [Chemical Formula 2]

[0031]

[0032] Wherein, R6 is hydrogen or an alkyl group having 1 to 18 carbon atoms, and R7 is hydrogen or an alkyl group having 1 to 18 carbon atoms.

[0033] [Chemical Formula 3]

[0034]

[0035] Among them, R 10 It is hydrogen or an alkyl group having 1 to 18 carbon atoms, R 11 It is hydrogen or an alkyl group having 1 to 18 carbon atoms, R 12 It is -SR 15 or -N(R) 16 (R) 17 ), R 15 It is hydrogen or an alkyl group having 1 to 18 carbon atoms, and in this case, R 16 and R 17 Each is an alkyl group having 1 to 18 carbon atoms, with or without substituents.

[0036] The compounds may include methylenebis(diethylthiocarbamate), ethylenebis(diethyldithiocarbamate), methylenebis(dipropylthiocarbamate), ethylenebis(dipropyldithiocarbamate), methylenebis(dibutyldithiocarbamate), ethylenebis(dibutyldithiocarbamate), methylenebis(dipentyldithiocarbamate), ethylenebis(dipentyldithiocarbamate), methylenebis(dihexyldithiocarbamate), ethylenebis(dihexyldithiocarbamate), 2,5-dimercapto-1,3,4-thiadiazole, and 2-hydrocarbon. At least one of the following: 2,5-bis(alkyldithio)-1,3,4-thiadiazole, 1,3,5-triazine-2,4,6-trithiol, 2-(dibutylamino)-1,3,5-triazine-4,6-dithiol, 6-(diisopropylamino)-1,3,5-triazine-2,4-dithiol, 6-(diisobutylamino)-1,3,5-triazine-2,4-dithiol, 6-diallylamino-1,3,5-triazine-2,4-dithiol, or 6-di(2-ethylhexyl)amino-1,3,5-triazine-2,4-dithiol.

[0037] The compound may include at least one of the compounds represented by chemical formula 1 or chemical formula 3.

[0038] The compounds may include methylene bis(diethylthiocarbamate), ethylene bis(diethyldithiocarbamate), methylene bis(dipropylthiocarbamate), ethylene bis(dipropyldithiocarbamate), methylene bis(dibutyldithiocarbamate), ethylene bis(dibutyldithiocarbamate), methylene bis(dipentyldithiocarbamate), ethylene bis(dipentyldithiocarbamate), methylene bis(dihexyldithiocarbamate), and methylene bis(dihexyldithiocarbamate). It contains at least one of the following: 1,3,5-triazine-2,4,6-trithiol, 2-(dibutylamino)-1,3,5-triazine-4,6-dithiol, 6-(diisopropylamino)-1,3,5-triazine-2,4-dithiol, 6-(diisobutylamino)-1,3,5-triazine-2,4-dithiol, 6-diallylamino-1,3,5-triazine-2,4-dithiol, or 6-di(2-ethylhexyl)amino-1,3,5-triazine-2,4-dithiol.

[0039] Based on the total mass of the non-aqueous electrolyte solution, the content of the compound can be from 0.1% by mass to 1% by mass.

[0040] The non-aqueous electrolyte solution of the present invention may further contain cyclic carbonates and chain carbonates.

[0041] The non-aqueous electrolyte solution of the present invention may further contain a lithium salt, and the lithium salt may be LiPF6.

[0042] In addition, the present invention relates to a lithium secondary battery comprising: a positive electrode, a negative electrode, and a non-aqueous electrolyte solution of the present invention disposed between the positive electrode and the negative electrode.

[0043] The positive electrode may contain nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) ternary materials.

[0044] The negative electrode may contain silicon-containing materials.

[0045] The initial capacity density of each positive electrode can be above 185 mAh / g.

[0046] [Beneficial Effects]

[0047] According to the present invention, an electrolyte solution with a long cycle life can be provided, wherein a compound containing 5% to 20% by mass of nitrogen atoms and 25% to 70% by mass of sulfur or oxygen atoms in the molecule and having no disulfide bonds in the molecule is used as an additive for the non-aqueous electrolyte solution, thereby preventing the generation of acid when water seeps into the lithium secondary battery, thereby suppressing the degradation of battery characteristics under high temperature conditions. Attached Figure Description

[0048] Figure 1 It is a graph showing the relationship between the number of cycles and the capacity obtained from the charge / discharge cycle test results of Examples 1 and 2 and Comparative Example 1.

[0049] Figure 2 It is a graph showing the relationship between the number of cycles and the capacity obtained from the charge / discharge cycle test results of Examples 3 and 4 and Comparative Example 1.

[0050] Figure 3 It is a graph showing the relationship between the number of cycles and the capacity obtained from the charge / discharge cycle test results of Examples 5 and 6 and Comparative Example 1.

[0051] Figure 4 It is a graph showing the relationship between the number of cycles and the capacity obtained from the charge / discharge cycle test results of Examples 7 and 8 and Comparative Example 1.

[0052] Figure 5 This is a graph showing the relationship between storage period and capacity obtained from the high-temperature storage test results of Examples 3 and 4 and Comparative Example 1.

[0053] Figure 6 This is a graph showing the relationship between storage period and capacity obtained from the high-temperature storage test results of Examples 5 and 6 and Comparative Example 1.

[0054] Figure 7 This is a graph showing the relationship between storage period and capacity obtained from the high-temperature storage test results of Examples 7 and 8 and Comparative Example 1. Detailed Implementation

[0055] The non-aqueous electrolyte solution of the present invention contains the following compound as an additive: containing 5% to 20% by mass of nitrogen atoms and 25% to 70% by mass of sulfur or oxygen atoms in the molecule, and having no disulfide bonds in the molecule.

[0056] The compound included as an additive in the non-aqueous electrolyte solution of the present invention may be a compound containing 5% to 20% by mass nitrogen atoms and 25% to 70% by mass sulfur atoms in its molecule and having no disulfide bonds, or a compound containing 5% to 20% by mass nitrogen atoms and 25% to 70% by mass oxygen atoms in its molecule and having no disulfide bonds. Ideally, it should be a compound containing 5% to 20% by mass nitrogen atoms and 25% to 70% by mass sulfur atoms in its molecule and having no disulfide bonds.

[0057] There is no specific limitation on the mass ratio of nitrogen atoms to sulfur atoms or oxygen atoms in the compound molecule, but it is preferably 5:1 to 1:10, more preferably 2:1 to 1:8, and most preferably 1:1 to 1:6.

[0058] Furthermore, the compound contains at least two or three sulfur atoms or oxygen atoms in its molecule, and may contain at least two or three sulfur atoms or at least two or three oxygen atoms in its molecule. Preferably, the compound contains at least two or three sulfur atoms in its molecule.

[0059] In one embodiment, the compound included as an additive in the non-aqueous electrolyte solution of the present invention may include one or a combination of two or more compounds represented by the following chemical formulas 1 to 3.

[0060] [Chemical Formula 1]

[0061]

[0062] Wherein, R1 is an alkyl or phenyl group having 1 to 18 carbon atoms, R2 is an alkyl or phenyl group having 1 to 18 carbon atoms, R3 is an alkyl or phenyl group having 1 to 18 carbon atoms, R4 is an alkyl or phenyl group having 1 to 18 carbon atoms, and R5 is an alkylene group having 1 to 12 carbon atoms.

[0063] [Chemical Formula 2]

[0064]

[0065] Wherein, R6 is hydrogen or an alkyl group having 1 to 18 carbon atoms, and R7 is hydrogen or an alkyl group having 1 to 18 carbon atoms.

[0066] [Chemical Formula 3]

[0067]

[0068] Among them, R 10 It is hydrogen or an alkyl group having 1 to 18 carbon atoms, R 11 It is hydrogen or an alkyl group having 1 to 18 carbon atoms, R 12 It is -SR 15 or -N(R) 16 (R) 17 ), R 15 It is hydrogen or an alkyl group having 1 to 18 carbon atoms, and in this case, R 16 and R 17 Each is an alkyl group having 1 to 18 carbon atoms, with or without substituents.

[0069] In the above chemical formula 1, R1 is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 2 to 12 carbon atoms. R2 is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 2 to 12 carbon atoms. R3 is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 2 to 12 carbon atoms. R4 is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 2 to 12 carbon atoms. Furthermore, R1 to R4 are preferably the same.

[0070] In the above chemical formula 1, R5 is preferably an alkylene group having 1 to 6 carbon atoms, and more preferably an alkylene group having 1 to 3 carbon atoms.

[0071] In the above chemical formula 2, R6 is preferably hydrogen or an alkyl group having 1 to 18 carbon atoms, more preferably hydrogen or an alkyl group having 2 to 12 carbon atoms. R7 is preferably hydrogen or an alkyl group having 1 to 18 carbon atoms, more preferably hydrogen or an alkyl group having 2 to 12 carbon atoms.

[0072] In the above chemical formula 3, R 10 Preferably, it is hydrogen or an alkyl group having 1 to 18 carbon atoms, more preferably hydrogen or an alkyl group having 2 to 12 carbon atoms. R 11 Preferably, it is hydrogen or an alkyl group having 1 to 18 carbon atoms, more preferably hydrogen or an alkyl group having 2 to 12 carbon atoms. R 12 It is -SR 15 or -N(R) 16 (R) 17 ), and in this case, R 15It is hydrogen or an alkyl group having 1 to 18 carbon atoms, preferably, R 16 and R 17 Each is independently an alkyl group having 1 to 18 carbon atoms, with or without substituents, and preferably a thio group, an alkylthio group having 2 to 12 carbon atoms, a dialkylamino group having 2 to 12 carbon atoms, or a diallylalkylamino group having 2 to 12 carbon atoms.

[0073] The compounds represented by the above chemical formula 1 may include methylene bis(diethylthiocarbamate), ethylene bis(diethyldithiocarbamate), methylene bis(dipropylthiocarbamate), ethylene bis(dipropyldithiocarbamate), methylene bis(dibutyldithiocarbamate), ethylene bis(dibutyldithiocarbamate), methylene bis(dipentyldithiocarbamate), ethylene bis(dipentyldithiocarbamate), methylene bis(dihexyldithiocarbamate), and ethylene bis(dihexyldithiocarbamate).

[0074] In one embodiment, the compound included as an additive in the non-aqueous electrolyte solution of the present invention is preferably a thiadiazole compound represented by the above-described chemical formula 2. The thiadiazole compound represented by the above-described chemical formula 2 preferably includes 2,5-dimercapto-1,3,4-thiadiazole or its derivatives, as well as, for example, 2-alkyldithio-5-mercapto-1,3,4-thiadiazole and 2,5-bis(alkyldithio)-1,3,4-thiadiazole.

[0075] Preferably, the compound included as an additive in the non-aqueous electrolyte solution of the present invention is methylene bis(dibutyl dithiocarbamate) or 2,5-dimercapto-1,3,4-thiadiazole.

[0076] In addition, the triazine compounds represented by the above chemical formula 3 may include 1,3,5-triazine-2,4,6-trithiol, 2-(dibutylamino)-1,3,5-triazine-4,6-dithiol, 6-(diisopropylamino)-1,3,5-triazine-2,4-dithiol, 6-(diisobutylamino)-1,3,5-triazine-2,4-dithiol, 6-diallylamino-1,3,5-triazine-2,4-dithiol, and 6-di(2-ethylhexyl)amino-1,3,5-triazine-2,4-dithiol.

[0077] The compound included as an additive in the non-aqueous electrolyte solution of the embodiments of the present invention may include at least one of the compounds represented by chemical formula 1 or chemical formula 3.

[0078] The compound represented by chemical formula 1 has higher electrolyte solution stability (lower acid content) than the compound represented by chemical formula 2, and the compound represented by chemical formula 3 is easier to synthesize and introduce substituents, thus having more advantages than the compound represented by chemical formula 2.

[0079] The compounds may include methylbis(diethylthiocarbamate), ethylenebis(diethyldithiocarbamate), ethylenebis(dipropylthiocarbamate), ethylenebis(dipropyldithiocarbamate), ethylenebis(dibutyldithiocarbamate), ethylenebis(dibutyldithiocarbamate), ethylenebis(dipentyldithiocarbamate), ethylenebis(dipentyldithiocarbamate), ethylenebis(dihexyldithiocarbamate), ethylenebis(dihexyl... At least one of the following: dithiocarbamate, 1,3,5-triazine-2,4,6-trithiol, 2-(dibutylamino)-1,3,5-triazine-4,6-dithiol, 6-(diisopropylamino)-1,3,5-triazine-2,4-dithiol, 6-(diisobutylamino)-1,3,5-triazine-2,4-dithiol, 6-diallylamino-1,3,5-triazine-2,4-dithiol, or 6-di(2-ethylhexyl)amino-1,3,5-triazine-2,4-dithiol.

[0080] Based on the total mass of the non-aqueous electrolyte solution, the content of the compound included as an additive in the non-aqueous electrolyte solution of the present invention is preferably 0.1 to 1% by mass, more preferably 0.2 to 0.9% by mass, and most preferably 0.3 to 0.8% by mass. When the content of the compound as an additive is within the above range, acid production reaction in the battery can be effectively suppressed.

[0081] The compounds included as additives in the non-aqueous electrolyte solutions of the present invention can be used alone or in combination. When used in combination, the sum of the amounts is preferably within the range described above.

[0082] Preferably, the non-aqueous electrolyte solution of the present invention further comprises an organic solvent, such as cyclic carbonates, linear carbonates, ether compounds, ester compounds, and amide compounds. These organic solvents can be used alone or in combination. Preferably, the non-aqueous electrolyte solution of the present invention comprises cyclic carbonates and linear carbonates as organic solvents.

[0083] Cyclic carbonates may include at least one of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), methyl vinylene carbonate, ethyl vinylene carbonate, 1,2-diethyl vinylene carbonate, vinyl ethylene carbonate (VEC), 1-methyl-2-vinyl ethylene carbonate, 1-ethyl-2-vinyl ethylene carbonate, 1-methyl-2-vinyl ethylene carbonate, 1,1-divinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, 1,1-dimethyl-2-methylene ethylene carbonate, 1,1-diethyl-2-methylene ethylene carbonate, ethynyl ethylene carbonate, 1,2-diethynyl ethylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, or chloroethylene carbonate. In addition, the chain carbonate may include at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), isopropyl methyl carbonate, methyl butyl carbonate, diethyl carbonate (DEC), ethyl propyl carbonate, ethyl butyl carbonate, dipropyl carbonate, or propyl butyl carbonate.

[0084] Cyclic carbonates may include fluorine-containing cyclic carbonates. Fluorine-containing cyclic carbonates may include fluoroethylene carbonate, trifluoromethylethylene carbonate, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, 4-fluoro-1,3-dioxolane-2-one, trans- or cis-4,5-difluoro-1,3-dioxolane-2-one, or 4-ethynyl-1,3-dioxolane-2-one.

[0085] In particular, among carbonates, cyclic carbonates (such as ethylene carbonate and propylene carbonate) are high-viscosity organic solvents, and because cyclic carbonates have high dielectric constants, they readily dissociate from lithium salts in electrolytes, making their use ideal. Moreover, it is preferred that cyclic carbonates be mixed in optimal proportions with chain carbonates (such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) that have low viscosity and low dielectric constants to prepare electrolyte solutions with high electronic conductivity.

[0086] The non-aqueous electrolyte solution of the present invention may further comprise ether compounds, such as cyclic ethers or chain ethers. Examples of cyclic ethers may include tetrahydrofuran and 2-methyltetrahydrofuran. Furthermore, the non-aqueous electrolyte solution of the present invention may further comprise chain ethers. Examples of chain ethers may include dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl propyl ether.

[0087] The non-aqueous electrolyte solution of the present invention may further comprise ester compounds, such as carboxylic acid esters. Examples of carboxylic acid esters may include methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl valerate, ethyl valerate, propyl valerate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, ε-caprolactone, or compounds of these carboxylic acid esters in which hydrogen is partially replaced by fluorine.

[0088] In addition to the above, the non-aqueous electrolyte solution of the present invention may contain any other type of solvent, such as polyether, sulfur-containing solvent and phosphorus-containing solvent, without departing from the purpose of the present invention.

[0089] The non-aqueous electrolyte solution of the present invention may contain a mixture of cyclic carbonates and chain carbonates, wherein the volume ratio of cyclic carbonates to chain carbonates is preferably 1:9 to 9:1, more preferably 2:8 to 8:2.

[0090] The non-aqueous electrolyte solution of the present invention may contain an electrolyte commonly used in secondary batteries. The electrolyte acts as a transport medium for ions participating in the electrochemical reactions in the secondary battery. In particular, the present invention can be used as an electrolyte solution for lithium secondary batteries, and in this case, it contains a lithium salt as the electrolyte.

[0091] The lithium salts included in the non-aqueous electrolyte solution of the present invention may include, for example, LiPF6, LiBF4, and LiB. 12 F 12, LiAsF6, LiFSO3, Li2SiF6, LiCF3CO2, LiCH3CO2, LiCF3SO3, LiC4F9SO3, LiCF3CF2SO3, LiCF3(CF2)7SO3, LiCF3CF2(CF3)2CO, Li( CF3SO2)2CH, LiNO3, LiN(CN)2, LiN(FSO2)2, LiN(F2SO2)2, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiC(CF3SO2)3, LiP(CF3)6, LiPF(CF3) 5. LiPF2(CF3)4, LiPF3(CF3)3, LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF2C2O4, LiBC4O8, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2, LiSbF6, LiAlO4, LiAlF4, LiSCN, LiClO4, LiCl, LiF, LiBr, LiI, LiAlCl4. In particular, inorganic salts are preferred, such as LiPF6, LiBF4, LiAsF6, and LiClO4. Lithium salts can be used alone or in combination.

[0092] There are no specific limitations on the electrolyte, but based on the total mass of the non-aqueous electrolytic solution, its content can be from 0.1 mol / L to less than 5 mol / L, preferably from 0.5 mol / L to less than 3 mol / L, and more preferably from 0.5 mol / L to 2 mol / L. When the amount of electrolyte is within the above range, sufficient battery characteristics can be obtained.

[0093] The non-aqueous electrolyte solution of the present invention may contain at least one other type of additive. Other additives may include flame retardants, wetting agents, stabilizers, corrosion inhibitors, gelling agents, overcharge inhibitors, and negative electrode film-forming agents.

[0094] Furthermore, the present invention relates to a lithium secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte solution of the present invention disposed between the positive and negative electrodes.

[0095] Lithium batteries incorporating the non-aqueous electrolyte solution of the present invention may include any positive and negative electrodes commonly used in lithium secondary batteries, and may be configured to house them together with the non-aqueous electrolyte solution of the present invention in a container. Furthermore, a separator may be provided between the positive and negative electrodes.

[0096] The positive electrode used in the lithium secondary battery of the present invention can be manufactured, for example, by coating a positive electrode slurry containing a positive electrode active material, a binder, a conductive material and a solvent onto a positive electrode current collector and then drying and rolling it.

[0097] The positive electrode current collector includes any type of positive electrode current collector that has conductivity and does not cause chemical changes in the lithium secondary battery of the present invention, and may include, for example, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel treated with carbon, nickel, titanium, and silver on the surface.

[0098] The positive electrode active material is a compound capable of reversibly intercalating and deintercalating lithium. Specifically, it may include a lithium composite metal oxide composed of at least one metal selected from cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium composite metal oxide may include lithium-manganese-based oxides (such as LiMnO2, LiMnO 24 ), lithium-cobalt-based oxides (such as LiCoO2), lithium-nickel-based oxides (such as LiNiO2), lithium-nickel-manganese-based oxides (such as LiNi 1-y1 Mn y1 O2(0 < y1 < 1), LiMn 2-z1 Ni z1 O(0 < Z1 < 2)), lithium-nickel-cobalt-based oxides (such as LiNi 1-y2 Co y2 O(0 < y2 < 1)), lithium-manganese-cobalt-based oxides (such as LiCo 1- y3 Mn y3 O(0 < y3 < 1), LiMn 2-z2 Co z2 O(0 < Z2 < 2)), lithium-nickel-manganese-cobalt-based oxides (such as Li(Ni p1 Co q1 Mn r1 ))O(0 < p1 < 1, 0 < q1 < 1, 0 < r1 < 1, p1 + q1 + r1 = 1), or Li(Ni p2 Co q2 Mn r2 ))O(0 < p2 < 2, 0 < q2 < 2, 0 < r2 < 2, p2 + q2 + r2 = 2)), or lithium-nickel-cobalt-transition metal (M) oxides (such as Li(Ni p3 Co q3 Mn r3 M S3 ))O(M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p3, q3, r3, and s3 are the atomic ratios of the respective elements, 0 < p3 < 1, 0 < q3 < 1, 0 < r3 < 1, 0 < s3 < 1, p3 + q3 + r3 + s3 = 1)) at least one of them.

[0099] Lithium-based composite metal oxides are preferably lithium-containing composite metal oxides that include nickel metal and lithium to improve the capacity characteristics and stability of the battery. Specifically, in terms of cost, lithium-nickel-based oxides (e.g., LiNiO2) and lithium-nickel-manganese-cobalt oxides (e.g., Li(NiO2)) are preferred. 0.6 Mn 0.2 Co 0.2 O2, Li(Ni) 0.5 Mn 0.3 Co 0.2 O2 or Li(Ni) 0.8 Mn 0.1 Co 0.1 O2), or lithium-nickel-cobalt-aluminum oxides (e.g., Li(Ni) ...)2). 0.8 Co 0.15 Al 0.05 (O2), especially nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) ternary materials, such as lithium-nickel-manganese-cobalt oxide or lithium-nickel-cobalt-aluminum oxide.

[0100] Based on the total solid mass in the cathode slurry, the content of the cathode active material is preferably 80% to 99% by mass. When the amount of cathode active material is within the above range, high energy density and capacity can be obtained.

[0101] The adhesive is used to assist in the bonding between the positive electrode active material and the conductive material, as well as between the positive electrode active material and the current collector, and its content is preferably from 1% to 30% by mass based on the total solid mass in the positive electrode slurry. Examples of adhesives may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber.

[0102] The conductive material imparts conductivity without causing chemical changes in the lithium secondary battery of the present invention, and its content is preferably 0.5% to 50% by mass, more preferably 1% to 20% by mass, based on the total solid mass in the positive electrode slurry. When the content of the conductive material is within the above range, electronic conductivity can be improved and high energy density and capacity can be obtained.

[0103] Conductive materials may include, for example: carbon powders such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked carbon black; graphite powders such as natural graphite, artificial graphite, and graphite with a crystalline structure; conductive fibers such as carbon fibers and metal fibers; metal powders such as aluminum powder and nickel powder; conductive whiskers of zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0104] The solvent may include any type of solvent capable of making the slurry containing the positive electrode active material, binder, and conductive material a positive electrode material, for example, it may include: organic solvents such as NMP (N-methyl-2-pyrrolidone), dimethylformamide (DMF), acetone, dimethylacetamide, and water. Furthermore, the amount of solvent used can give the positive electrode slurry a suitable viscosity; for example, the amount of solvent used can give the solids concentration in the slurry 10% to 60% by mass, preferably 20% to 50% by mass.

[0105] The negative electrode used in the lithium secondary battery of the present invention can be manufactured, for example, by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material and a solvent onto a negative electrode current collector, and then drying and rolling it.

[0106] The thickness of the negative electrode current collector is typically 3 to 500 μm. The negative electrode current collector includes any type of negative electrode current collector that has high conductivity and does not cause chemical changes in the lithium secondary battery of this invention. Examples include: copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel with a surface treated with carbon, nickel, titanium, and silver, and aluminum-cadmium alloys. Furthermore, similar to the positive electrode current collector, the surface of the negative electrode current collector can have a fine texture to increase the adhesion of the negative electrode active material. The negative electrode current collector can take various shapes, such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0107] The negative electrode active material may include at least one material selected from the following: lithium metal, carbon material capable of reversibly inserting and de-inserting lithium ions, metals and metal-lithium alloys, metal composite oxides, materials capable of doping and de-doping lithium, and transition metal oxides.

[0108] Carbon materials capable of reversibly inserting and deintercalating lithium ions can include any type of carbon-based anode active material commonly used in lithium secondary batteries, such as at least one of crystalline carbon and amorphous carbon. Examples of crystalline carbon can include amorphous, plate-like, flake-like, spherical, or fibrous graphite, such as natural graphite and artificial graphite. Examples of amorphous carbon can include soft carbon (low-temperature sintered carbon) or hard carbon, mesophase pitch carbides, and sintered coke.

[0109] The metal or the alloy of the metal with lithium may contain a metal selected from Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn, or an alloy of these metals with lithium.

[0110] The metal composite oxide can be selected from PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, and Li. xFe2O3 (0 ≤ x ≤ 1), Li x WO2 (0 ≤ x ≤ 1) and Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of Groups 1, 2 and 3 of the Periodic Table, halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8).

[0111] Materials capable of doping and undoping lithium may include Si, SiO x (0 < x < 2), Si - Y alloy (Y is at least one selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals and rare earth elements, excluding Si), Sn, SnO2, Sn - Y (Y is at least one selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals and rare earth elements, excluding Sn), and mixtures of at least one of them with SiO2. Y may be at least one 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, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po.

[0112] Transition metal oxides may include lithium - containing titanium composite oxides (LTO), vanadium oxides, lithium vanadium oxides.

[0113] The negative electrode active material of the lithium secondary battery of the present invention preferably includes a silicon - containing material, for example, Si, SiO x (0 < x < 2), Si - Y alloy (Y is at least one selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals and rare earth elements, excluding Si), and mixtures of at least one of them with SiO2. In particular, it is more desirable to use SiO.

[0114] Based on the total mass of solids in the negative electrode slurry, the content of the negative electrode active material is preferably 80% to 99% by mass.

[0115] The adhesive is used to assist in the bonding between the conductive material, the negative electrode active material, and the current collector, and its content is preferably 1 to 30% by mass based on the total solid mass in the negative electrode slurry. Examples of adhesives may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber.

[0116] The conductive material further improves the conductivity of the negative electrode active material, and its content is preferably from 1% to 20% by mass based on the total solid mass in the negative electrode slurry. The conductive material includes any type of conductive material that is conductive without causing chemical changes in the lithium secondary battery, such as: graphite, such as natural graphite and artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal cracking carbon black; conductive fibers, such as carbon fibers and metal fibers; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0117] The solvent includes any type of solvent capable of making the slurry containing the negative electrode active material, binder, and conductive material a negative electrode material, and may include, for example, organic solvents such as water, NMP, and ethanol. Furthermore, the amount of solvent used allows the negative electrode slurry to have a suitable viscosity; for example, it allows the solids concentration in the slurry to be 50% to 75% by mass, preferably 50% to 65% by mass.

[0118] The separator of the lithium secondary battery of the present invention serves to prevent internal short circuits between the two electrodes and electrolyte wetting. The separator can be manufactured as follows: a separator composition is prepared by mixing polymer resin, filler and solvent, and the separator composition is directly coated on the electrode and dried to form a separator, or it can be manufactured as follows: the separator composition is cast on a support and dried, and then the separator separated from the support is stacked on the electrode.

[0119] The diaphragm may include porous polymer membranes commonly used in diaphragms, such as porous polymer membranes made of polyolefin polymers (e.g., ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers), used alone or in a laminate, or commonly used porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers and polyethylene terephthalate fibers, but not limited thereto.

[0120] The pore size of porous membranes is typically 0.01 to 50 μm, and the porosity is 5% to 95%. In addition, the thickness of porous membranes can typically be 5 to 300 μm.

[0121] The charging voltage of the lithium secondary battery of the present invention is preferably 4.0V or higher, more preferably 4.1V or higher. Furthermore, when the lithium secondary battery of the present invention is fully charged, the positive electrode potential is preferably 4.0V or higher.

[0122] Furthermore, the initial capacity density of each positive electrode of the lithium secondary battery of the present invention is preferably 185 mAh / g or higher.

[0123] The lithium secondary battery of the present invention is not limited to a specific shape, and can be cylindrical, prismatic, pouch-shaped or coin-shaped.

[0124] Example

[0125] The present invention will now be described in more detail with reference to embodiments and comparative examples, but the scope of the invention is not limited to these examples.

[0126] (Example 1)

[0127] Manufacturing the Positive Electrode

[0128] 96.5 parts by weight of nickel-cobalt-manganese (NCM) ternary material (Li(Ni)) was used as the positive electrode active material. 0.8 Mn 0.1 Co 0.1 A positive electrode slurry was prepared by dispersing 1.5 parts by weight of acetylene black (as a conductive material) and 2 parts by weight of polyvinylidene fluoride (as a binder) in N-methyl-2-pyrrolidone (as a solvent). The prepared positive electrode slurry was uniformly coated on aluminum foil, heated and vacuum dried, and then pressed to manufacture the positive electrode.

[0129] <The Manufacturing of the Negative Electrode>

[0130] A negative electrode slurry was prepared by dispersing 96 parts by weight of a 9:1 mixture of graphite and SiO as the negative electrode active material, 1.0 part by weight of acetylene black as the conductive material, and 3.0 parts by weight of styrene-butadiene rubber and carboxymethyl cellulose as binders in water. The prepared negative electrode slurry was uniformly coated on copper foil, heated and vacuum dried, and then pressed to manufacture the negative electrode.

[0131] <Preparation of Non-Aqueous Electrolyte Solutions>

[0132] A solution was prepared by dissolving 1 M LiPF6 in a solvent containing 30 parts (by volume) of ethylene carbonate (EC) and 70 parts (by volume) of ethyl methyl carbonate (EMC). 0.5 parts by weight of methylene bis(dibutyldithiocarbamate) (Sanyo Chemical Industries) (Al) and 0.5 parts by weight of ethylene carbonate were added to 100 parts by weight of the resulting solution to obtain the non-aqueous electrolyte solution of the present invention.

[0133] Manufacturing of Lithium-ion Secondary Batteries

[0134] The positive electrode, negative electrode, non-aqueous electrolyte solution, and polyolefin membrane used in the above method are manufactured with an area of ​​12 cm² on opposite sides. 2 pouch-type batteries.

[0135] (Example 2)

[0136] The non-aqueous electrolyte solution and the lithium secondary battery containing the solution were manufactured in the same manner as in Example 1, except that 2,5-dimercapto-1,3,4-thiadiazole (Sanyo Chemical Industries) (A2) was added to the non-aqueous electrolyte solution instead of methylene bis(dibutyldithiocarbamate).

[0137] (Example 3)

[0138] The non-aqueous electrolyte solution and the lithium secondary battery containing the solution were manufactured in the same manner as in Example 1, except that 1,3,5-triazine-2,4,6-trithiol (Sanyo Chemical Industries) (A3) was added to the non-aqueous electrolyte solution instead of methylene bis(dibutyldithiocarbamate).

[0139] (Example 4)

[0140] The non-aqueous electrolyte solution and the lithium secondary battery containing the solution were manufactured in the same manner as in Example 1, except that 2-(dibutylamino)-1,3,5-triazine-4,6-dithiol (Sanyo Chemical Industries) (A4) was added to the non-aqueous electrolyte solution instead of methylene bis(dibutyldithiocarbamate).

[0141] (Example 5)

[0142] The non-aqueous electrolyte solution and the lithium secondary battery containing the solution were manufactured in the same manner as in Example 1, except that 6-(diisopropylamino)-1,3,5-triazine-2,4-dithiol (Sanyo Chemical Industries) (A5) was added to the non-aqueous electrolyte solution instead of methylene bis(dibutyldithiocarbamate).

[0143] (Example 6)

[0144] The non-aqueous electrolyte solution and the lithium secondary battery containing the solution were manufactured in the same manner as in Example 1, except that 6-(diisobutylamino)-1,3,5-triazine-2,4-dithiol (Sanyo Chemical Industries) (A6) was added to the non-aqueous electrolyte solution instead of methylene bis(dibutyldithiocarbamate).

[0145] (Example 7)

[0146] The non-aqueous electrolyte solution and the lithium secondary battery containing the solution were manufactured in the same manner as in Example 1, except that 6-diallylamino-1,3,5-triazine-2,4-dithiol (Sanyo Chemical Industries) (A7) was added to the non-aqueous electrolyte solution instead of methylene bis(dibutyldithiocarbamate).

[0147] (Example 8)

[0148] The non-aqueous electrolyte solution and lithium secondary battery were prepared in the same manner as in Example 1, except that 6-di(2-ethylhexyl)amino-1,3,5-triazine-2,4-dithiol (Sanyo Chemical Industries) (A8) was added to the non-aqueous electrolyte solution instead of methylene bis(dibutyldithiocarbamate).

[0149] (Comparative Example 1)

[0150] The non-aqueous electrolyte solution and the lithium secondary battery containing the solution were manufactured in the same manner as in Example 1, except that methylene bis(dibutyldithiocarbamate) was not added to the non-aqueous electrolyte solution.

[0151] Evaluation of non-aqueous electrolyte solutions and lithium secondary batteries

[0152] (1) Measurement of acid content

[0153] The acid content measurements of the electrolyte solutions from Examples 1 and 2 before and after storage at 60°C for one week are shown in Table 1 below. The acid content was measured by placing 10g of the electrolyte solution sample into 100g of pure water, neutralizing with 0.1mol / L NaOH reagent, and titrating. The concentration was calculated assuming the generated acid was all hydrogen fluoride (HF).

[0154] Table 1

[0155]

[0156] As can be seen from the results in Table 1, in Examples 1 and 2, where an electrolyte solution containing methylene bis(dibutyldithiocarbamate) or 2,5-dimercapto-1,3,4-thiadiazole was used as the non-aqueous electrolyte solution, the amount of acid produced was reduced. Furthermore, particularly in Example 1 using methylene bis(dibutyldithiocarbamate), the acid content after storage was significantly reduced, thus demonstrating an effect of reducing acid content.

[0157] (2) Charge / discharge cycle test

[0158] Charge-discharge cycle tests were conducted using lithium secondary batteries manufactured in Examples 1 to 8 and Comparative Example 1 at a constant current of 0.5C and a maximum charging voltage of 4.20V, with a minimum discharging voltage of 2.50V. To accurately monitor the capacity at the 50th, 100th, and 200th cycles, a constant current of 0.1C was used.

[0159] Figures 1 to 4 This is a graph showing the relationship between the number of cycles and the capacity obtained as test results. Figure 1 In the relatively early stages, Examples 1 and 2 showed significant differences in capacity retention compared to Comparative Example 1, and in Comparative Example 1, the capacity was significantly reduced in the non-aqueous electrolyte solution without the addition of additives. Meanwhile, it can be seen that in Examples 1 and 2, where the non-aqueous electrolyte solution contained methylene bis(dibutyldithiocarbamate) (A1) or 2,5-dimercapto-1,3,4-thiadiazole (A2), the capacity was maintained for a longer period. Figures 2 to 4 As can be seen, in Comparative Example 1, where no additives were added to the non-aqueous electrolyte solution, the capacity decreased significantly. However, in Examples 3 to 8, where the non-aqueous electrolyte solution contained 1,3,5-triazine-2,4,6-trithiol, 2-(dibutylamino)-1,3,5-triazine-4,6-dithiol, 6-(diisopropylamino)-1,3,5-triazine-2,4-dithiol, 6-(diisobutylamino)-1,3,5-triazine-2,4-dithiol, 6-diallylamino-1,3,5-triazine-2,4-dithiol, and 6-(di(2-ethylhexyl)amino-1,3,5-triazine-2,4-dithiol), the capacity was maintained for a long time.

[0160] (3) Storage test at 60℃

[0161] Using the lithium secondary batteries manufactured in Examples 3 to 8 and Comparative Example 1, the degree of degradation was evaluated as follows: the discharge capacity was measured at 25°C and a constant current of 0.5C (upper limit of charging voltage 4.2V, lower limit of discharge voltage 2.50V), and the remaining capacity (upper limit of charging voltage 4.35V) was measured after storing the fully charged lithium secondary batteries at a constant current of 0.5C in an oven at 60°C for 2 weeks and 4 weeks in a constant current of 0.5C. Figures 5 to 7 It is a graph showing the relationship between the number of cycles and the capacity obtained as test results.

[0162] exist Figures 5 to 7 In this context, the capacity that immediately decreases after 2 and 4 weeks is the "remaining capacity." The remaining capacity after 2 weeks increases again due to recharging to 4.2V. In other words, the remaining capacity within 4 weeks is the capacity measured after 2 weeks, recharged to 4.2V, and stored at 60°C for another 2 weeks.

[0163] Industrial applicability

[0164] The non-aqueous electrolyte solution of the present invention inhibits the generation of acid, thereby maintaining capacity after repeated charging / discharging under high temperature conditions.

Claims

1. A lithium secondary battery, comprising: The cathode contains nickel-containing materials. Anodes containing silicon materials, and Non-aqueous electrolyte solutions in, The non-aqueous electrolyte solution comprises: Compounds represented by chemical formula 1: [Chemical Formula 1] Wherein, R1 is an alkyl or phenyl having 1 to 18 carbon atoms, R2 is an alkyl or phenyl having 1 to 18 carbon atoms, R3 is an alkyl or phenyl having 1 to 18 carbon atoms, R4 is an alkyl or phenyl having 1 to 18 carbon atoms, and R5 is an alkylene having 1 to 12 carbon atoms.

2. The lithium secondary battery of claim 1, further comprising at least one compound represented by chemical formula 2 and chemical formula 3: [Chemical Formula 2] in, R6 is hydrogen or an alkyl group having 1 to 18 carbon atoms, and R7 is hydrogen or an alkyl group having 1 to 18 carbon atoms. [Chemical Formula 3] Among them, R 10 It is hydrogen or an alkyl group having 1 to 18 carbon atoms, R 11 It is hydrogen or an alkyl group having 1 to 18 carbon atoms, R 12 It is -SR 15 or -N(R) 16 (R) 17 ), R 15 It is hydrogen or an alkyl group having 1 to 18 carbon atoms, and in this case, R 16 and R 17 Each is an alkyl group having 1 to 18 carbon atoms, with or without substituents.

3. The lithium secondary battery as described in claim 1, wherein, The compound represented by Formula 1 includes at least one of methylene bis(diethylthiocarbamate), ethylene bis(diethyldithiocarbamate), methylene bis(dipropylthiocarbamate), ethylene bis(dipropyldithiocarbamate), methylene bis(dibutyldithiocarbamate), ethylene bis(dibutyldithiocarbamate), methylene bis(dipentyldithiocarbamate), ethylene bis(dipentyldithiocarbamate), methylene bis(dihexyldithiocarbamate), and ethylene bis(dihexyldithiocarbamate).

4. The lithium secondary battery as described in claim 2, wherein, The compounds represented by chemical formula 2 include at least one of 2,5-dimercapto-1,3,4-thiadiazole, 2-alkyldithio-5-mercapto-1,3,4-thiadiazole, and 2,5-bis(alkyldithio)-1,3,4-thiadiazole.

5. The lithium secondary battery as described in claim 2, wherein, The compounds represented by chemical formula 3 include at least one of 1,3,5-triazine-2,4,6-trithiol, 2-(dibutylamino)-1,3,5-triazine-4,6-dithiol, 6-(diisopropylamino)-1,3,5-triazine-2,4-dithiol, 6-(diisobutylamino)-1,3,5-triazine-2,4-dithiol, 6-diallylamino-1,3,5-triazine-2,4-dithiol, and 6-di(2-ethylhexyl)amino-1,3,5-triazine-2,4-dithiol.

6. The lithium secondary battery as described in claim 1, wherein, Based on the total mass of the non-aqueous electrolyte solution, the content of the compound is from 0.1% by mass to 1% by mass.

7. The lithium secondary battery as described in claim 1, wherein, The non-aqueous electrolyte solution further comprises cyclic carbonates and chain carbonates.

8. The lithium secondary battery as described in claim 1, wherein, The non-aqueous electrolyte solution further contains lithium salt.

9. The lithium secondary battery as described in claim 8, wherein, The lithium salt is LiPF6.

10. The lithium secondary battery as described in claim 1, wherein, The positive electrode contains a nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) ternary material.

11. The lithium secondary battery as described in claim 1, wherein, The initial capacity density of each positive electrode is above 185 mAh / g.

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