Nonaqueous electrolyte and lithium secondary battery containing same

Abstract

The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, a compound represented by the following Chemical Formula 1 as a first additive, and a compound represented by the following Chemical Formula 2 or Chemical Formula 3 as a second additive: JPEG2025537357000030.jpg52170In the above Chemical Formula 1, R is any one selected from a perfluoroalkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, and an alkynyl group having 2 to 10 carbon atoms, JPEG2025537357000031.jpg65170In the above Chemical Formula 2, R1 is an alkylene group having 1 to 3 carbon atoms which may be substituted with fluorine, and R2 to R4 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 3 carbon atoms, and a nitrile group; JPEG2025537357000032.jpg58170In the above chemical formula 3, R5 is an alkylene group having 1 to 8 carbon atoms which may be substituted with fluorine, and R6 is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and a cycloalkyl group having 3 to 8 carbon atoms.

Description

[Technical Field]

[0001] This application claims priority based on Korean Patent Application No. 10-2023-0046159, filed with the Korean Intellectual Property Office on April 7, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same. [Background technology]

[0003] In recent years, the application areas of lithium secondary batteries have rapidly expanded from power supply for electronic devices such as electrical, electronic, communication, and computer equipment to power storage and supply for large-area devices such as automobiles and power storage devices. Accordingly, there has been an increasing demand for high-capacity, high-power, and highly stable secondary batteries.

[0004] In particular, high capacity, high power output, and long life characteristics are important for lithium secondary batteries for automotive applications. To achieve high capacity, secondary batteries may use positive electrode active materials with high nickel content, which have high energy density but low stability, or may be operated at high voltage. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a nonaqueous electrolyte that has improved stability at high voltages and high temperatures, capable of suppressing deterioration of a positive electrode, reducing side reactions between the positive electrode and an electrolyte, and forming a stable SEI (Solid Electrolyte Interphase) film on a negative electrode.

[0006] Another object of the present invention is to provide a lithium secondary battery containing the nonaqueous electrolyte, which has improved high-voltage cycle characteristics, high-temperature storage characteristics, and thermal stability, and thus has improved performance. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, a compound represented by the following Chemical Formula 1 as a first additive, and a compound represented by the following Chemical Formula 2 or Chemical Formula 3 as a second additive:

[0008] [ka]

[0009] In the above Chemical Formula 1, R is any one selected from a perfluoroalkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, and an alkynyl group having 2 to 10 carbon atoms.

[0010] [ka]

[0011] In the above chemical formula 2, R1 is an alkylene group having 1 to 3 carbon atoms which may be substituted with fluorine, and R2 to R4 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 3 carbon atoms, and a nitrile group.

[0012] [ka]

[0013] In the above Chemical Formula 3, R5 is an alkylene group having 1 to 8 carbon atoms which may be substituted with fluorine, and R6 is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and a cycloalkyl group having 3 to 8 carbon atoms.

[0014] The present invention also provides a lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and the non-aqueous electrolyte. [Effects of the Invention]

[0015] The compound of Formula 1 provided as the first additive of the present invention is a cyclic sulfate-based compound. The coating formed by the ring-opening reaction of the cyclic sulfate can help improve high-temperature durability and performance. In particular, the compound of Formula 1 can form a coating with high lithium mobility due to its structure containing a large amount of O due to the COO group. Furthermore, the compound contains functional groups such as fluorine, vinyl, and propargyl groups within its structure, which can contribute to improving battery stability by forming an organic / inorganic hybrid coating. Therefore, the first additive of the present invention can suppress the deterioration of SEI passivation ability at high temperatures, prevent anode degradation, and improve various performances of lithium secondary batteries, such as charge / discharge characteristics and output.

[0016] The compound of Formula 2 or Formula 3, which is provided as a second additive of the present invention, contains a propargyl group in its molecule, thereby improving high-temperature durability. The SEI film formed by the anode reduction reaction of the compound of Formula 2 or Formula 3 contains a propargyl group, which serves as a cross-link site within the SEI, enabling additional reactions. As the additional cross-linking reaction progresses, a strong SEI film is formed, effectively suppressing performance degradation due to electrodeposition of transition metals eluted from the cathode onto the anode. Furthermore, the cyclic carbonate functional group and imidazole functional group contained in the additive of Formula 2 or Formula 3 form a stable cathode electrolyte interphase (CEI), effectively suppressing side reactions on the cathode surface and cathode degradation, thereby improving performance and reducing the elution of transition metals that may occur during high-voltage charging. That is, the compound of Formula 2 or Formula 3, which is provided as a second additive for a non-aqueous electrolyte of the present invention, can form a stable ion-conductive film on the surfaces of the cathode and anode.

[0017] Therefore, when the nonaqueous electrolyte of the present invention containing both the first additive and the second additive is used, the radicals generated by the destruction of the ring structure of the first additive promote the film-forming reaction of the second additive. The film formed by the interaction between the first additive and the second additive has high durability at high temperatures and is effective in suppressing the elution of transition metals at the positive electrode. Furthermore, the film formed by the interaction between the first additive and the second additive has a film morphology with excellent lithium ion transport properties, improving various performances of lithium secondary batteries, such as the charge / discharge characteristics and output characteristics. The film formed by the interaction between the first additive and the second additive has excellent oxidation resistance, thereby suppressing side reactions occurring in the films on the positive and negative electrodes, even in an acidic electrolyte atmosphere. Furthermore, the film formed by the interaction between the first additive and the second additive has excellent durability against volume expansion of the negative electrode that occurs during charge and discharge. As a result, the nonaqueous electrolyte of the present invention can form an electrode-electrolyte interface that is stable and durable even at high temperatures and suppresses unnecessary electrolyte decomposition side reactions, thereby realizing lithium secondary batteries with improved performance. DETAILED DESCRIPTION OF THE INVENTION

[0018] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0019] As used herein, the terms "comprises," "comprises," or "having" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the presence or possible addition of one or more other features, numbers, steps, components, or combinations thereof.

[0020] In addition, in the description of "number of carbon atoms a to b" herein, "a" and "b" refer to the number of carbon atoms contained in a specific functional group. That is, the functional group may contain "a" to "b" carbon atoms. For example, an "alkylene group having 1 to 5 carbon atoms" refers to an alkylene group containing 1 to 5 carbon atoms, i.e., -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH3)CH-, -CH(CH3)CH2-, and -CH(CH3)CH2CH2-.

[0021] In addition, in this specification, the term "alkylene group" means a branched or unbranched divalent saturated hydrocarbon group.

[0022] Furthermore, in this specification, any alkyl group may be substituted or unsubstituted. Unless otherwise defined, the term "substituted" means that at least one hydrogen atom bonded to a carbon atom is substituted with an element other than hydrogen, such as an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkenyl group having 3 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a nitro group, a nitrile group, or the like.

[0023] In order to increase the capacity of lithium secondary batteries, a high-nickel positive electrode active material, which has high energy density but low stability, is used, or when the secondary battery is operated at high voltage, side reactions caused by electrolyte degradation as charging and discharging progress can cause the coating formed on the positive electrode surface or the electrode surface structure to deteriorate, resulting in the elution of transition metal ions from the positive electrode surface.The eluted transition metal ions are then electro-deposited on the negative electrode, reducing the passivation ability of the solid electrolyte interphase (SEI), resulting in the degradation of the negative electrode.

[0024] Such deterioration of secondary batteries tends to be accelerated when the potential of the positive electrode increases or when the battery is exposed to high temperatures, and this deterioration causes the problem of deterioration in the cycle characteristics of the secondary battery.

[0025] Furthermore, when a lithium secondary battery is used continuously for a long time or left at high temperatures, gas is generated and the thickness of the battery increases, a phenomenon known as swelling. It is known that the amount of gas generated at this time depends on the state of the SEI.

[0026] The present invention discloses a lithium secondary battery containing a nonaqueous electrolyte that can reduce the swelling phenomenon of the secondary battery and improve stability at high temperatures by suppressing the elution of metal ions at the positive electrode and forming a stable SEI film at the negative electrode.

[0027] The present invention will now be described in more detail.

[0028] non-aqueous electrolyte The non-aqueous electrolyte according to the present invention may include a lithium salt, an organic solvent, a compound represented by the following Chemical Formula 1 as a first additive, and a compound represented by the following Chemical Formula 2 or 3 as a second additive.

[0029] The nonaqueous electrolyte according to the present invention includes a compound represented by the following Chemical Formula 1 as a first additive. The compound represented by the following Chemical Formula 1 is a cyclic sulfate-based compound, and the coating formed by the ring-opening reaction of the cyclic sulfate can help improve high-temperature durability and performance. In particular, the compound represented by the Chemical Formula 1 can form a coating with high lithium mobility due to its structure containing a large amount of O due to the COO group. Furthermore, the compound contains functional groups such as fluorine, vinyl, and propargyl groups within its structure, which can contribute to improving battery stability by forming an organic / inorganic composite coating. Therefore, the first additive according to the present invention can suppress the deterioration of the SEI passivation ability at high temperatures, prevent anode degradation, and improve the performance of lithium secondary batteries.

[0030] [ka]

[0031] In Chemical Formula 1, R may be any one selected from a perfluoroalkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, and an alkynyl group having 2 to 10 carbon atoms. Preferably, R may be a perfluoroalkyl group having 1 to 3 carbon atoms or an alkenyl group having 2 to 5 carbon atoms, and most preferably, any one selected from the group consisting of CF3, CF2CF3, and ethenyl. When R is a perfluoroalkyl group, an organic-inorganic composite coating is formed, resulting in a strong and durable coating. Coatings containing organic components have excellent lithium transport properties but are prone to side reactions in the acidic electrolyte atmosphere. In addition, inorganic coatings suppress side reactions in acidic environments but have poor lithium transport properties. Therefore, when an organic-inorganic composite coating is formed, the various properties of lithium secondary batteries are maximized. When R is an alkenyl group or an alkynyl group, an additional crosslinking reaction can occur, resulting in the formation of a stronger coating.

[0032] Specifically, the compound of Chemical Formula 1 may be any one selected from the group consisting of the following Chemical Formulas 1-1 to 1-3.

[0033] [ka]

[0034] [ka]

[0035] [ka]

[0036] The nonaqueous electrolyte according to the present invention includes a compound represented by Chemical Formula 2 or Chemical Formula 3 below as a second additive. The compound represented by Chemical Formula 2 or Chemical Formula 3 contains a propargyl group, which makes it easily reduced on the surface of the negative electrode, allowing it to easily form a coating on the surface of the negative electrode. This coating has the advantages of being more stable than SEI coatings formed by the reductive decomposition of typical electrolytes, suppressing additional electrolyte decomposition reactions due to its low electronic conductivity, and being less susceptible to damage caused by volumetric changes in the negative electrode. In other words, using the compound represented by Chemical Formula 2 or Chemical Formula 3 as an electrolyte additive ensures the stability of the interface between the negative electrode and the electrolyte.

[0037] The compound of Formula 2 contains a triple-bonded propargyl group and an oxygen atom, which are known to have metal ion adsorption properties. The propargyl group, which is released by bond cleavage between the nitrogen (N) and carbon (C) atoms of the imidazole group, adsorbs metal particles such as Fe, Co, Mn, and Ni leached from the positive electrode during high-voltage charging of a lithium secondary battery. This effectively prevents negative electrode degradation caused by electrodeposition of these metal particles on the negative electrode surface. Furthermore, the lone electron pair of the nitrogen (N) atom of the imidazole group in the compound of Formula 2 reacts with alkyl carbonate, a decomposition product of ethylene carbonate (EC), used as an organic solvent, and is reduced on the negative electrode surface, forming a stable ion-conductive coating on the negative electrode surface. This not only prevents additional electrolyte decomposition during charge and discharge, but also facilitates the intercalation and deintercalation of lithium ions from the negative electrode during overcharge or high-temperature storage, improving the cycle life and high-temperature storage performance of secondary batteries.

[0038] [ka]

[0039] In the above Chemical Formula 2, R1 is an alkylene group having 1 to 3 carbon atoms which may be substituted with fluorine, and R2 to R4 may each independently be any one selected from the group consisting of H, an alkyl group having 1 to 3 carbon atoms, and a nitrile group.

[0040] Specifically, the compound of Chemical Formula 2 of the present invention may be a compound of Chemical Formula 2-1 below.

[0041] [ka]

[0042] The compound of Formula 3 contains an ester functional group and an unsaturated hydrocarbon group in its molecular structure. During the initial charging process of a secondary battery, it decomposes before other components of the electrolyte, forming a coating on the surface of the anode primarily composed of compounds based on a carbon-oxygen single bond (CO) or a carbon-oxygen double bond (C=O). Furthermore, the compound of Formula 3 contains a propargyl group, making it easily reduced on the anode surface, allowing it to easily form a coating on the anode surface. This coating has the advantages of being more stable than the SEI coating formed by the reductive decomposition of a typical electrolyte, and its low electronic conductivity prevents further electrolyte decomposition reactions and makes it less susceptible to damage caused by volume changes in the anode.

[0043] [ka]

[0044] In the above chemical formula 3, R5 may be an alkylene group having 1 to 8 carbon atoms, which may be substituted with fluorine, and preferably an alkylene group having 1 to 5 carbon atoms.

[0045] In the above Chemical Formula 3, R6 may be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and a cycloalkyl group having 3 to 8 carbon atoms.

[0046] The compound of Formula 3 may be a compound of Formula 3-1 below.

[0047] [ka]

[0048] In the above chemical formula 3-1, the above n may be a natural number of 1 to 8, preferably a natural number of 1 to 5, and most preferably a natural number of 1 to 3.

[0049] In the above chemical formula 3-1, R6 may be H or an alkyl group having 1 to 10 carbon atoms, and preferably H or a methyl group.

[0050] Specifically, the compound of Chemical Formula 3 of the present invention may be a compound of Chemical Formula 3-2 below.

[0051] [ka]

[0052] When the nonaqueous electrolyte of the present invention, which contains a first additive and a second additive, is used, the radicals generated by the destruction of the ring structure of the first additive promote the film-forming reaction of the second additive. The film formed by the interaction between the first additive and the second additive has an oxadizolidine, imidazole, or cyclic carbonate structure, or a structure derived therefrom, present between the aliphatic alkyl group-based film, resulting in the formation of a film with excellent lithium ion transport properties, thereby improving various performance characteristics of lithium secondary batteries, such as the charge / discharge characteristics and output characteristics. The film formed by the interaction between the first additive and the second additive has excellent oxidation resistance, thereby suppressing side reactions occurring in the positive and negative electrode films, even in an acidic electrolyte environment. Furthermore, the film formed by the interaction between the first additive and the second additive has excellent durability against volume changes in the negative electrode that occur during charge and discharge. As a result, the nonaqueous electrolyte of the present invention can form an electrode-electrolyte interface that is stable and durable even at high temperatures, suppressing unnecessary electrolyte decomposition side reactions, thereby realizing lithium secondary batteries with improved performance.

[0053] In the non-aqueous electrolyte according to the present invention, the first additive may be contained in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5.0 parts by weight, and more preferably 0.10 to 3.0 parts by weight, per 100 parts by weight of the non-aqueous electrolyte. When the content of the first additive satisfies the above range, the effect of forming a coating on the negative electrode is sufficient, and excellent high-temperature life characteristics and high-temperature storage characteristics are achieved.

[0054] In the non-aqueous electrolyte according to the present invention, the second additive may be contained in an amount of 0.01 to 5 parts by weight, preferably 0.05 to 3.0 parts by weight, and more preferably 0.10 to 2.5 parts by weight, per 100 parts by weight of the non-aqueous electrolyte. When the content of the second additive satisfies the above range, the effect of forming a coating on the negative electrode is sufficient, and excellent high-temperature life characteristics and high-temperature storage characteristics are achieved.

[0055] In the nonaqueous electrolyte of the present invention, the first additive and the second additive may be included in a weight ratio of 1:0.001 to 1:500, preferably 1:0.01 to 1:300, and most preferably 1:0.02 to 1:250. When the weight ratio is within the above range, the elasticity of the SEI film is within an appropriate range, and the SEI film can be maintained strong during charge / discharge or at high temperatures.

[0056] The non-aqueous electrolyte according to the present invention may contain a lithium salt. The lithium salt is used as an electrolyte salt in a lithium secondary battery and is used as a medium for transferring ions. Typically, the lithium salt contains, for example, Li as a cation. + and as an anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 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 - , CF3(CF2)7SO3 - , and SCN - At least one selected from the group consisting of:

[0057] Specifically, the lithium salts include LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 , LiAlCl4, LiAlO2, LiPF6, LiSO3CF3, LiCO2CH3, LiCO2CF3, LiAsF6, LiSbF6, LiSO3CH3, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide; LiFSI), LiN(SO2CF2CF3)2 (lithium bis(perfluoroethanesulfonyl)imide; LiBETI), and LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide; LiTFSI). In addition to these, lithium salts commonly used in electrolytes for lithium secondary batteries can be used without any restrictions.

[0058] The lithium salt can be varied as appropriate within a range that is normally usable, but to obtain the optimum effect of forming a corrosion-preventing coating on the electrode surface, it may be contained in the electrolyte at a concentration of 0.1 M to 4.0 M, preferably 1.0 M to 3.0 M, and more preferably 1.2 M to 2.5 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics of the lithium secondary battery during high-temperature storage is sufficient, and the viscosity of the non-aqueous electrolyte is appropriate, allowing for improved electrolyte impregnation.

[0059] The nonaqueous electrolyte according to the present invention may include an organic solvent, which may include at least one organic solvent selected from the group consisting of a cyclic carbonate organic solvent, a linear carbonate organic solvent, a linear ester organic solvent, and a cyclic ester organic solvent.

[0060] The additive of the present invention is particularly effective when a cyclic carbonate solvent is used. When a conventional electrolyte additive is used together with a cyclic carbonate solvent, the SEI film formed by decomposition of the cyclic carbonate solvent is difficult to maintain due to volume changes in the negative electrode that occur as cycling progresses, resulting in the problem of continued solvent decomposition. This causes problems such as a decrease in the ionic conductivity of the electrolyte and a decrease in cycle performance. However, when a combination of the additive of the present invention and a cyclic carbonate solvent is used, a strong SEI film can be formed, and high cycle performance can be maintained.

[0061] The cyclic carbonate organic solvent is a highly viscous organic solvent that has a high dielectric constant and therefore easily dissociates the lithium salt in the electrolyte. Specific examples thereof include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and among these, fluoroethylene carbonate (FEC) may be included.

[0062] The linear carbonate organic solvent is an organic solvent having low viscosity and low dielectric constant, and typical examples thereof include at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, and may include diethyl carbonate (DEC).

[0063] In addition, in order to produce an electrolyte having high ionic conductivity, the organic solvent may further contain at least one or more ester organic solvents selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents in addition to at least one or more carbonate organic solvents selected from the group consisting of cyclic carbonate organic solvents and linear carbonate organic solvents.

[0064] Specific examples of such linear ester-based organic solvents include at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0065] The cyclic ester organic solvent may be at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0066] Meanwhile, the organic solvent may further include, as needed, any organic solvent commonly used in non-aqueous electrolytes, for example, at least one of an ether-based organic solvent, a glyme-based organic solvent, and a nitrile-based organic solvent.

[0067] The ether solvent may be any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these, but is not limited thereto.

[0068] The glyme-based solvent has a higher dielectric constant and lower surface tension than linear carbonate-based organic solvents and is less reactive with metals, and may include at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME), but is not limited thereto.

[0069] The nitrile solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0070] In addition, the non-aqueous electrolyte of the present invention may further contain a known electrolyte additive, as needed, to prevent the non-aqueous electrolyte from being decomposed and causing the collapse of the negative electrode in a high-power environment, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and the effect of suppressing battery expansion at high temperatures.

[0071] Representative examples of such other electrolyte additives may include at least one SEI film-forming additive selected from the group consisting of cyclic carbonate-based compounds, halogen-substituted carbonate-based compounds, sultone-based compounds, sulfate-based compounds, phosphate-based compounds, borate-based compounds, nitrile-based compounds, benzene-based compounds, amine-based compounds, silane-based compounds, and lithium salt-based compounds.

[0072] Examples of the cyclic carbonate compounds include vinylene carbonate (VC) and vinylethylene carbonate.

[0073] The halogen-substituted carbonate compounds include fluoroethylene carbonate (FEC).

[0074] The sultone compound includes at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone.

[0075] Examples of the sulfate-based compounds include ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate (MTMS).

[0076] The phosphate-based compound may be one or more compounds selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, tris(2,2,2-trifluoroethyl)phosphate, and tris(2,2,2-trifluoroethyl)phosphite.

[0077] Examples of the borate-based compounds include tetraphenylborate, lithium difluoro(oxalato)borate (LiODFB), and lithium bisoxalatoborate (LiB(C2O4)2, LiBOB).

[0078] Examples of the nitrile compound include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0079] The benzene-based compound may be fluorobenzene, the amine-based compound may be triethanolamine or ethylenediamine, and the silane-based compound may be tetravinylsilane.

[0080] The lithium salt-based compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and examples thereof include lithium difluorophosphate (LiDFP), LiPO2F2, and LiBF4.

[0081] Among these other electrolyte additives, when a combination of vinylene carbonate (VC), 1,3-propane sultone (PS), ethylene sulfate (Esa), and lithium difluorophosphate (LiDFP) is further included, a stronger SEI film can be formed on the surface of the negative electrode during the initial activation process of the secondary battery, and the generation of gas that may be generated by decomposition of the electrolyte at high temperatures can be suppressed, thereby improving the high-temperature stability of the secondary battery.

[0082] Meanwhile, the other electrolyte additives may be used in combination of two or more kinds, and may be included in an amount of 0.050 wt % to 20 wt %, specifically 0.10 wt % to 15 wt %, and preferably 0.30 wt % to 10 wt %, based on the total weight of the non-aqueous electrolyte. When the content of the other electrolyte additives satisfies the above range, better improvements in ionic conductivity and cycle characteristics can be obtained.

[0083] Lithium secondary battery The present invention also provides a lithium secondary battery containing the non-aqueous electrolyte.

[0084] Specifically, the lithium secondary battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte.

[0085] The lithium secondary battery of the present invention can be manufactured by a conventional method known in the art. For example, the secondary battery of the present invention can be manufactured by forming an electrode assembly in which a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode are sequentially stacked, inserting the electrode assembly into a battery case, and injecting the nonaqueous electrolyte according to the present invention into the battery case.

[0086] (1) Positive electrode The positive electrode may be prepared by coating a positive electrode mixture slurry containing a positive electrode active material, a binder, a conductive material, and a solvent on a positive electrode current collector.

[0087] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like may be used.

[0088] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), a lithium-nickel-manganese-cobalt-based oxide (e.g., Li(Ni p Co q Mn r )O2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2), etc.), or a lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2)O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s2 are the atomic fractions of independent elements, respectively, where 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, and p2 + q2 + r2 + s2 = 1), etc.), and one or more of these compounds may be included.

[0089] Among them, from the viewpoint of enhancing the capacity characteristics and stability of the battery, the lithium metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), and one or more mixtures of these may be used.

[0090] The positive electrode active material may be contained at 60% to 99% by weight, preferably 70% to 99% by weight, more preferably 80% to 98% by weight, based on the total weight of the solid matter excluding the solvent in the positive electrode binder slurry.

[0091] The binder is a component that aids in binding the active material and conductive material, etc., and binding to the current collector.

[0092] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers.

[0093] Typically, the binder may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 1 to 10% by weight, based on the total weight of the solid content excluding the solvent in the positive electrode mixture slurry.

[0094] The conductive material is a component for further improving the conductivity of the positive electrode active material and may be added in an amount of 1 wt % to 20 wt % based on the total weight of the solid content in the positive electrode mixture slurry. Such a conductive material is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity, and examples thereof include carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, and graphite with highly developed crystalline structures; conductive fibers such as carbon fibers and metal fibers; carbon fluoride powders; conductive 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.

[0095] Typically, the conductive material may be contained in an amount of 1 wt % to 20 wt %, preferably 1 wt % to 15 wt %, and more preferably 1 wt % to 10 wt %, based on the total weight of solids in the positive electrode mixture slurry excluding the solvent.

[0096] The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone) and may be used in an amount that provides a suitable viscosity when the positive electrode active material, and optionally a binder and a conductive material, are contained. For example, the solvent may be contained so that the concentration of the solids including the positive electrode active material, and optionally a binder and a conductive material, is 50% by weight to 95% by weight, preferably 70% by weight to 95% by weight, and more preferably 70% by weight to 90% by weight.

[0097] (2) Negative electrode The negative electrode may be prepared by coating a negative electrode mixture slurry containing a negative electrode active material, a binder, a conductive material, and a solvent on a negative electrode current collector, or a graphite electrode made of carbon (C) or a metal itself may be used as the negative electrode.

[0098] For example, when the negative electrode is manufactured by coating the negative electrode mixture slurry onto the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, etc. may be used. Furthermore, like the positive electrode current collector, the negative electrode current collector may have fine irregularities on its surface to strengthen the binding force of the negative electrode active material, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, or nonwoven fabric.

[0099] In addition, the negative electrode active material may include at least one selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of such a metal and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0100] As the carbon material capable of reversibly intercalating / deintercalating the lithium ions, any carbon-based negative electrode active material generally used in lithium ion secondary batteries can be used without particular limitation, and representative examples thereof include crystalline carbon, amorphous carbon, or both of these may be used. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0101] As the metal or an alloy of these metals and lithium, a metal selected from the group consisting of 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 and lithium can be used.

[0102] Examples of the metal composite oxide include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3 (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 Group 1, Group 2, Group 3 of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) can be selected and used from the group consisting of.

[0103] As the substance capable of doping and undoping lithium, Si, SiO x(0 < x ≤ 2), Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO₂, Sn-Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc. may be mentioned, and also, at least one of these may be mixed with SiO₂ and used. The element Y may be selected from the group consisting of 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, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0104] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, etc.

[0105] The additive according to the present invention is particularly effective when Si or SiO x (0 < x ≤ 2) is used as the negative electrode active material. Specifically, when using a Si-based negative electrode active material, if a strong SEI layer is not formed on the surface of the negative electrode during initial activation, the life characteristics will be promoted to decline due to severe volume expansion and contraction during the progress of the cycle. However, since the additive according to the present invention can form a strong SEI layer on the surface of the negative electrode while having elasticity, a secondary battery using a Si-based negative electrode active material can have excellent life characteristics and storage characteristics.

[0106] The negative electrode active material may be contained in an amount of 60% to 99% by weight, preferably 70% to 99% by weight, more preferably 80% to 98% by weight, based on the total weight of the solid content in the negative electrode mixture slurry.

[0107] Examples of the binder include polyvinylidene fluoride (PVDF), polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof. Specifically, styrene-butadiene rubber (SBR)-carboxymethyl cellulose (CMC) can be used because of its high viscosity increasing property.

[0108] Typically, the binder may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 1 to 10% by weight, based on the total weight of solids in the negative electrode mixture slurry excluding the solvent.

[0109] The conductive material is a component for further improving the conductivity of the negative electrode active material and may be added in an amount of 1 wt % to 20 wt % based on the total weight of the solid content in the negative electrode mixture slurry. The conductive material is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity, and examples thereof include carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, and graphite with highly developed crystalline structures; conductive fibers such as carbon fibers and metal fibers; carbon fluoride powders; conductive 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.

[0110] The conductive material may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 1 to 10% by weight, based on the total weight of solids in the negative electrode mixture slurry excluding the solvent.

[0111] The solvent may include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a suitable viscosity when containing the negative electrode active material, and optionally a binder and a conductive material, etc. For example, the solvent may be contained so that the concentration of solids including the negative electrode active material, and optionally a binder and a conductive material, is 50 wt % to 95 wt %, preferably 70 wt % to 90 wt %.

[0112] When a metal is used as the anode, the anode can be fabricated by physically bonding, rolling, or depositing a metal on a metal thin film or the anode current collector. The metal deposition method can be electrochemical deposition or chemical vapor deposition.

[0113] For example, the metal thin film itself or the metal bonded / rolled / deposited on the negative electrode current collector may include one metal or an alloy of two metals selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In).

[0114] (3) Separator The separator may be a conventional porous polymer film, such as a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, either alone or in a laminate, or a conventional porous nonwoven fabric, such as a nonwoven fabric made of a high-melting point glass fiber or polyethylene terephthalate fiber, but is not limited to these. Furthermore, to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may be selectively used as a single-layer or multi-layer structure.

[0115] Specifically, the separator included in the electrode assembly of the present invention may be a safety reinforced separator (SRS) having a coating layer containing a ceramic component or a polymer material formed thereon to ensure heat resistance or mechanical strength.

[0116] Specifically, the separator included in the electrode assembly of the present invention may include a porous separator substrate and a porous coating layer that is coated on one or both sides of the separator substrate. The coating layer may include a mixture of inorganic particles selected from metal oxides, metalloid oxides, metal fluorides, metal hydroxides, and combinations thereof, and a binder polymer that binds and fixes the inorganic particles to each other.

[0117] The coating layer may contain inorganic particles selected from one or more of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, YO3, SrTiO3, BaTiO3, Mg(OH)2, and MgF. The inorganic particles can improve the thermal stability of the separator. That is, the inorganic particles can prevent the separator from shrinking at high temperatures. The binder polymer can fix the inorganic particles and improve the mechanical stability of the separator.

[0118] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0119] The present invention will be described in more detail below with reference to specific examples. However, the following examples are merely illustrative for understanding the present invention and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the present description and technical concept, and it goes without saying that such changes and modifications fall within the scope of the appended claims.

[0120] Example Example 1 (Production of non-aqueous electrolyte) A non-aqueous solvent was prepared by dissolving LiPF in an organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) = 20:70:10 volume ratio) to a concentration of 1.2 M, and 0.01 g of a compound represented by the following Formula 1-1 and 0.01 g of a compound represented by the following Formula 2-1 were added to 99.98 g of the non-aqueous solvent to prepare a non-aqueous electrolyte.

[0121] [ka]

[0122] [ka]

[0123] (Lithium secondary battery manufacturing) Cathode active material (LiNi 0.6 Co 0.1 Mn 0.3 A cathode slurry (solid content 75.5 wt%) was prepared by adding O2, a conductive material (carbon nanotubes), and a binder (polyvinylidene fluoride) to a solvent, N-methyl-2-pyrrolidone (NMP), in a weight ratio of 97.74:0.7:1.56. The cathode slurry was applied to one side of a 15 μm-thick cathode current collector (Al thin film), dried, and roll-pressed to prepare a cathode.

[0124] Anode active material (natural graphite), conductive material (carbon black), and binder (styrene-butadiene rubber (SBR)-carboxymethyl cellulose (CMC)) were mixed in a weight ratio of 70:20.3:9.7 with N-methyl-2-pyrrolidone (NMP) as a solvent to prepare anode slurry (solid content 26 wt%). The anode slurry was applied to one side of a 15 μm-thick anode current collector (Cu thin film), dried, and roll-pressed to prepare anode.

[0125] In a dry room, a polyolefin-based porous separator coated with inorganic particles Al2O3 was interposed between the positive electrode and negative electrode prepared above, and the non-aqueous electrolyte prepared above was then injected to prepare a secondary battery.

[0126] Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.01 g of the compound of Chemical Formula 1-1 and 0.01 g of the compound of Chemical Formula 3-2 below to 99.98 g of the non-aqueous solvent prepared in Example 1.

[0127] [ka]

[0128] Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.01 g of the compound of Chemical Formula 1-1 and 5 g of the compound of Chemical Formula 2-1 to 94.99 g of the non-aqueous solvent prepared in Example 1.

[0129] Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.01 g of the compound of Chemical Formula 1-1 and 5 g of the compound of Chemical Formula 3-2 to 94.99 g of the non-aqueous solvent prepared in Example 1.

[0130] Example 5 A secondary battery was manufactured in the same manner as in Example 1, except that 5 g of the compound of Chemical Formula 1-1 and 1 g of the compound of Chemical Formula 2-1 were added to 94 g of the nonaqueous solvent manufactured in Example 1 to prepare a nonaqueous electrolyte.

[0131] Example 6 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 10 g of the compound of Chemical Formula 1-1 and 0.01 g of the compound of Chemical Formula 2-1 to 89.99 g of the non-aqueous solvent prepared in Example 1.

[0132] Example 7 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 10 g of the compound of Chemical Formula 1-1 and 5 g of the compound of Chemical Formula 2-1 to 85 g of the non-aqueous solvent prepared in Example 1.

[0133] Example 8 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 10 g of the compound of Chemical Formula 1-1 and 0.01 g of the compound of Chemical Formula 3-2 to 89.99 g of the non-aqueous solvent prepared in Example 1.

[0134] Example 9 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 10 g of the compound of Chemical Formula 1-1 and 5 g of the compound of Chemical Formula 3-2 to 85 g of the non-aqueous solvent prepared in Example 1.

[0135] Example 10 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.01 g of a compound represented by the following Chemical Formula 1-2 and 0.01 g of a compound represented by the following Chemical Formula 2-1 to 99.98 g of the non-aqueous solvent prepared in Example 1.

[0136] [ka]

[0137] Example 11 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 10 g of the compound of Chemical Formula 1-2 and 0.01 g of the compound of Chemical Formula 2-1 to 89.99 g of the non-aqueous solvent prepared in Example 1.

[0138] Example 12 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.01 g of the compound of Chemical Formula 1-2 and 5 g of the compound of Chemical Formula 2-1 to 94.99 g of the non-aqueous solvent prepared in Example 1.

[0139] Example 13 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 10 g of the compound of Chemical Formula 1-2 and 5 g of the compound of Chemical Formula 2-1 to 85 g of the non-aqueous solvent prepared in Example 1.

[0140] Example 14 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.01 g of a compound represented by the following Formula 1-3 and 0.01 g of a compound represented by the following Formula 2-1 to 99.98 g of the non-aqueous solvent prepared in Example 1.

[0141] [ka]

[0142] Example 15 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 10 g of the compound of Chemical Formula 1-3 and 0.01 g of the compound of Chemical Formula 2-1 to 89.99 g of the non-aqueous solvent prepared in Example 1.

[0143] Example 16 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.01 g of the compound of Chemical Formula 1-3 and 5 g of the compound of Chemical Formula 2-1 to 94.99 g of the non-aqueous solvent prepared in Example 1.

[0144] Example 17 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 10 g of the compound of Chemical Formula 1-3 and 5 g of the compound of Chemical Formula 2-1 to 85 g of the non-aqueous solvent prepared in Example 1.

[0145] Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Formula 1-1 was added to 99.99 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0146] Comparative Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of Formula 1-1 was added to 90 g of the non-aqueous solvent prepared in Example 1 to prepare a non-aqueous electrolyte.

[0147] Comparative Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Formula 2-1 was added to 99.99 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0148] Comparative Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that 5 g of the compound of Formula 2-1 was added to 95 g of the non-aqueous solvent manufactured in Example 1 to prepare a non-aqueous electrolyte.

[0149] Comparative Example 5 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Formula 3-2 was added to 99.99 g of the nonaqueous solvent manufactured in Example 1 to prepare a nonaqueous electrolyte.

[0150] Comparative Example 6 A secondary battery was manufactured in the same manner as in Example 1, except that 5 g of the compound of Formula 3-2 was added to 95 g of the non-aqueous solvent manufactured in Example 1 to prepare a non-aqueous electrolyte.

[0151] Experimental Example 1: Evaluation of high-temperature cycle characteristics The cycle characteristics of each of the secondary batteries produced in Examples 1 to 17 and Comparative Examples 1 to 6 were evaluated.

[0152] Specifically, each battery manufactured in Examples 1 to 17 and Comparative Examples 1 to 6 was charged at 45°C under constant current / constant voltage conditions (0.05C cutoff) at a 0.33C rate to 4.2V and then discharged at a constant current of 0.33C to 3.0V, counting as one cycle. After 200 charge / discharge cycles, the capacity retention rate after 200 cycles relative to the initial capacity after one cycle was measured. The resistance increase rate after 200 cycles relative to the initial resistance after one cycle was also measured. The results are shown in Table 1 below.

[0153] [Table 1]

[0154] Experimental Example 2 - Evaluation of high-temperature storage characteristics The secondary batteries produced in Examples 1 to 17 and Comparative Examples 1 to 6 were evaluated for high-temperature storage characteristics.

[0155] Specifically, each of the secondary batteries of Examples 1 to 17 and Comparative Examples 1 to 6 was fully charged to 4.2 V and then stored at 60° C. for 8 weeks.

[0156] Before storage, the capacity of the fully charged secondary battery was measured and set as the initial capacity of the secondary battery.

[0157] After 8 weeks, the capacity of the stored secondary battery was measured, and the capacity loss during the 8-week storage period was calculated. The percentage of the lost capacity relative to the initial capacity of the secondary battery was calculated to determine the capacity retention rate after 8 weeks. In addition, the percentage of the increased resistance relative to the initial resistance of the secondary battery was calculated to determine the resistance increase rate after 8 weeks. The results are shown in Table 2 below.

[0158] [Table 2]

Claims

1. A lithium salt, an organic solvent; a compound of the following formula 1 as a first additive; A non-aqueous electrolyte comprising: a compound represented by the following Chemical Formula 2 or Chemical Formula 3 as a second additive: 【Chemistry 1】 In the above Chemical Formula 1, R is any one selected from a perfluoroalkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, and an alkynyl group having 2 to 10 carbon atoms; 【Chemistry 2】 In the above Chemical Formula 2, R １ represents an alkylene group having 1 to 3 carbon atoms which may be substituted by fluorine, R ２ ~R ４ are each independently any one selected from the group consisting of H, an alkyl group having 1 to 3 carbon atoms, and a nitrile group; 【Transformation 3】 In the above Chemical Formula 3, R ５ represents an alkylene group having 1 to 8 carbon atoms which may be substituted by fluorine, R ６ is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and a cycloalkyl group having 3 to 8 carbon atoms.

2. 2. The non-aqueous electrolyte according to claim 1, wherein the compound of Chemical Formula 1 is any one selected from the group consisting of the following Chemical Formulas 1-1 to 1-3: 【Chemistry 4】 【Transformation 5】 【Transformation 6】

3. 3. The nonaqueous electrolyte according to claim 1, wherein the compound of Chemical Formula 2 is a compound of Chemical Formula 2-1: 【Transformation 7】

4. The nonaqueous electrolyte according to claim 1 or 2, wherein the compound of Chemical Formula 3 is a compound of Chemical Formula 3-1: 【Transformation 8】 In the above chemical formula 3-1, wherein n is a natural number from 1 to 8; R ６ is H or a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms.

5. The nonaqueous electrolyte according to claim 1 or 2, wherein the compound of Chemical Formula 3 is a compound of Chemical Formula 3-2 below: 【Chemistry 9】

6. The non-aqueous electrolyte of claim 1 , wherein the first additive is contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.

7. 3. The non-aqueous electrolyte of claim 1, wherein the second additive is contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.

8. 3. The non-aqueous electrolyte according to claim 1, wherein the first additive and the second additive are contained in a weight ratio of 1:0.001 to 1:

500.

9. The lithium salts include LiCl, LiBr, LiI, and LiBF. ４ , LiClO ４ , LiB １０ Cl １０ , LiAlCl ４ , LiAlO ２ , LiPF ６ , LiSO ３ CF ３ , LiCO ２ CH ３ , LiCO ２ CF ３ , LiAsF ６ , LiSbF ６ , LiSO ３ CH ３ , LiN(SO ２ F) ２ , LiN(SO ２ CF ２ CF ３ ) ２ , and LiN(SO ２ CF ３ ) ２ The non-aqueous electrolyte according to claim 1 or 2, wherein the non-aqueous electrolyte is one or more selected from the group consisting of:

10. 3. The non-aqueous electrolyte according to claim 1, wherein the lithium salt is contained at a concentration of 0.1 M to 4.0 M.

11. 3. The nonaqueous electrolyte according to claim 1, wherein the organic solvent comprises at least one organic solvent selected from the group consisting of a cyclic carbonate organic solvent, a linear carbonate organic solvent, a linear ester organic solvent, and a cyclic ester organic solvent.

12. A positive electrode and a negative electrode; A separator; A lithium secondary battery comprising the nonaqueous electrolyte according to claim 1 or 2.

13. An electronic device comprising the lithium secondary battery according to claim 12.

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