Non-aqueous electrolytes and lithium secondary batteries containing them

Abstract

The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, a compound represented by Chemical Formula 1 as a first additive, and a compound represented by Chemical Formula 2 or Chemical Formula 3 as a second additive. In Chemical Formula 1, R 1 is any one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms which may be substituted with fluorine, an alkynyl group having 2 to 5 carbon atoms which may be substituted with fluorine, SO 2 R’, and COR’, where R’ is any one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms which may be substituted with fluorine, and an alkynyl group having 2 to 5 carbon atoms which may be substituted with fluorine, and R 2 and R 3 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. In Chemical Formula 2, R is an alkylene group having 1 to 3 carbon atoms which may be substituted with fluorine, and R 4 to R 6 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. In Chemical Formula 3, R 7 is an alkylene group having 1 to 8 carbon atoms which may be substituted with fluorine, and R 8 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. 10-2022-0171006, filed on 8 December 2022, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] This 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-ion batteries have rapidly expanded beyond power supply for electronic devices such as electrical, electronic, telecommunications, and computers to include power storage and supply for large-area devices such as automobiles and power storage devices. Consequently, there is an increasing demand for high-capacity, high-output, and highly stable secondary batteries.

[0004] In particular, high capacity, high output, and long lifespan characteristics are important for lithium-ion secondary batteries used in automobiles. To increase the capacity of secondary batteries, nickel-high content positive electrode active materials, which have high energy density but low stability, are sometimes used, or secondary batteries are driven at high voltages.

[0005] However, when a secondary battery is powered under the above conditions, as charging and discharging progress, side reactions caused by electrolyte degradation can degrade the coating or electrode surface structure formed on the positive / negative electrode surfaces, potentially leading to the elution of transition metal ions from the positive electrode surface. These eluted transition metal ions then electrodeposit onto the negative electrode, reducing the passivation capacity of the SEI, thus causing the negative electrode to degrade.

[0006] This degradation phenomenon in secondary batteries tends to accelerate further when the potential of the positive electrode increases or when the battery is exposed to high temperatures, and this degradation phenomenon leads to the problem of deterioration in the cycle characteristics of the secondary battery.

[0007] Furthermore, when lithium secondary batteries are used continuously for long periods or left at high temperatures, gas is generated, causing the battery to swell, a phenomenon known as SEI. The amount of gas generated at this time is known to depend on the state of SEI.

[0008] Therefore, in order to solve these problems, research and development are being attempted on methods that can suppress the elution of metal ions at the positive electrode, form a stable SEI film at the negative electrode, reduce the swelling phenomenon of secondary batteries, and improve stability at high temperatures. [Overview of the project] [Problems that the invention aims to solve]

[0009] As a result of conducting multifaceted research to solve the above problems, the present invention aims to provide a non-aqueous electrolyte with enhanced stability at high temperatures by including a non-aqueous electrolyte that suppresses the degeneration of the positive electrode, reduces side reactions between the positive electrode and the electrolyte, and can form a stable SEI film on the negative electrode.

[0010] In other words, the present invention aims to provide a lithium secondary battery in which high-temperature cycling characteristics, high-temperature storage characteristics, and thermal stability are improved, and various other performance characteristics are enhanced, by including the non-aqueous electrolyte. [Means for solving the problem]

[0011] To achieve the above objective, one embodiment of 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 3 as a second additive.

[0012] [ka]

[0013] In the above chemical formula 1, R1 is one selected from the group consisting of a C1-C5 alkyl group that may be substituted with fluorine, a C2-C5 alkenyl group that may be substituted with fluorine, a C2-C5 alkynyl group that may be substituted with fluorine, SO2R', and COR'; R' is one selected from the group consisting of a C1-C5 alkyl group that may be substituted with fluorine, a C2-C5 alkenyl group that may be substituted with fluorine, and a C2-C5 alkynyl group that may be substituted with fluorine; and R2 and R3 are each independently one selected from the group consisting of H, a C1-C5 alkyl group, and a C1-C5 alkoxy group.

[0014] [ka]

[0015] In the above chemical formula 2, R is a C1-C3 alkylene group that may be substituted with fluorine, and R4-R6 are each independently selected from the group consisting of H, a C1-C3 alkyl group, and a nitrile group.

[0016] [ka]

[0017] In the above chemical formula 3, R7 is an alkylene group having 1 to 8 carbon atoms that may be substituted with fluorine, and R8 is 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.

[0018] Furthermore, one embodiment of the present invention provides a lithium secondary battery containing the non-aqueous electrolyte. [Effects of the Invention]

[0019] The compound of chemical formula 1 provided as the first additive of the present invention is an oxazolidinone compound that readily forms a film on the surfaces of the positive and negative electrodes while its cyclic structure is cleaved. Specifically, because carbon has a lower electronegativity compared to nitrogen and oxygen in the oxazolidinone ring, it is easily reduced at the negative electrode, allowing for film formation. Conversely, at the positive electrode, the oxidation state of the transition metal of the positive electrode active material increases during charging, and the oxygen at C=O in the oxazolidinone ring strongly interacts with the positive electrode, allowing the cyclic structure to be cleaved and a film to be easily formed. Since the oxazolidinone ring structure is cleaved into a radical form, triggering additional crosslinking reactions, a strong and stable film can be formed. Furthermore, because the oxygen and nitrogen in the oxazolidinone ring structure have lone pairs of electrons, a film with high lithium mobility is formed when lithium ions are lithified and delithiated at the positive / negative electrodes. Therefore, the first additive of the present invention can suppress the decrease in the passivation capacity of SEI at high temperatures, prevent degradation of the negative electrode, and improve the performance of lithium secondary batteries.

[0020] The compound of chemical formula 2 or chemical formula 3, provided as a second additive of the present invention, contains a propagyl group in its molecule, which helps to improve high-temperature durability. The SEI film formed by the negative electrode reduction reaction of the compound of chemical formula 2 or chemical formula 3 contains a propagyl group, which acts as a cross-linking site within the SEI, enabling additional reactions. As additional cross-linking reactions proceed, a strong SEI film is formed, which is effective in suppressing the degradation of performance due to the electrodeposition of transition metals eluted from the positive electrode to the negative electrode. Furthermore, the cyclic carbonate functional group and imidazole functional group contained in the additive of chemical formula 2 or chemical formula 3 effectively suppress side reactions and degradation of the positive electrode surface by forming a stable CEI, improving performance and reducing the elution of transition metals that may occur during high-voltage charging. In other words, the compound of chemical formula 2 or chemical formula 3, provided as a second additive for non-aqueous electrolytes of the present invention, can form a stable ion-conducting film on the positive / negative electrode surface.

[0021] Therefore, when using the non-aqueous electrolyte of the present invention containing the first and second additives, the radicals generated as the ring structure of the first additive is cleaved promote the film formation reaction of the second additive. The film formed by the interaction of the first and second additives has oxazolidinone, imidazole, cyclic carbonate structures, or structures derived therefrom between the aliphatic alkyl groups, forming a film morphology with excellent lithium-ion transfer characteristics, thereby improving various performance characteristics such as charge-discharge characteristics and output characteristics of the lithium secondary battery. The film formed by the interaction of the first and second additives has excellent oxidation resistance, so it can suppress side reactions that occur in the positive / negative electrode films even in the acidic atmosphere of the electrolyte. In addition, the film formed by the interaction of the first and second additives has excellent durability against volume expansion of the negative electrode that occurs during charge-discharge. Therefore, the non-aqueous electrolyte of the present invention can form an electrode-electrolyte interface that is stable and highly durable even at high temperatures, and can suppress unwanted electrolyte decomposition side reactions, thereby realizing a lithium secondary battery with improved performance. [Modes for carrying out the invention]

[0022] The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0023] In this specification, terms such as “includes,” “equip,” or “have” are intended to specify the presence of implemented features, figures, steps, components, or combinations thereof, and should be understood not to preemptively exclude the presence or possibility of adding one or more other features, figures, steps, components, or combinations thereof.

[0024] Furthermore, in this specification, when "a to b carbon atoms" is mentioned, "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, "alkylene group with 1 to 5 carbon atoms" means an alkylene group containing 1 to 5 carbon atoms, i.e., -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH3)CH-, -CH(CH3)CH2-, and -CH(CH3)CH2CH2-, etc.

[0025] Furthermore, in this specification, the term "alkylene group" means a branched or unbranched divalent saturated hydrocarbon group.

[0026] Furthermore, in this specification, alkyl groups may or may not be substituted. Unless otherwise defined, "substitution" means that at least one hydrogen bonded to a carbon atom is replaced by an element other than hydrogen, for example, 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, etc.

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

[0028] Non-aqueous electrolytes The non-aqueous electrolyte according to the present invention may contain a lithium salt, an organic solvent, a compound of the following chemical formula 1 as a first additive, and a compound of the following chemical formula 2 or 3 as a second additive.

[0029] The non-aqueous electrolyte according to the present invention contains a compound represented by the following chemical formula 1 as a first additive. The compound of the following chemical formula 1 is an oxazolidinone compound, and it easily forms a film on the surfaces of the positive and negative electrodes while its cyclic structure is cleaved. Specifically, in the oxazolidinone ring, the electron density of carbon, which has lower electronegativity compared to nitrogen and oxygen, is low, so it is easily reduced at the negative electrode and a film can be formed. Conversely, at the positive electrode, the oxidation number of the transition metal of the positive electrode active material increases during charging, and the oxygen at C=O of the oxazolidinone ring strongly interacts with the positive electrode, so the cyclic structure is cleaved and a film can be easily formed. Since the oxazolidinone ring structure is cleaved into a radical form and causes an additional crosslinking reaction, a strong and stable film can be formed. In addition, because there is a lone pair of electrons between the oxygen and nitrogen in the oxazolidinone ring structure, a film with high lithium mobility is formed when lithium ions are lithified and delithiated at the positive / negative electrode. Therefore, the first additive of the present invention can suppress the decrease in the passivation capacity of SEI at high temperatures, prevent the deterioration of the negative electrode, and improve the performance of lithium secondary batteries.

[0030] [ka]

[0031] In the above chemical formula 1, R1 may be any one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms that may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms that may be substituted with fluorine, an alkynyl group having 2 to 5 carbon atoms that may be substituted with fluorine, SO2R', and COR'. Preferably, R1 is fluorine-substituted. In this case, an organic-inorganic composite film is formed, and a strong and durable film can be formed. Films containing organic components have excellent lithium transfer characteristics, but are prone to side reactions in an acidic electrolyte atmosphere, while inorganic films suppress side reactions in an acidic atmosphere, but have inferior lithium transfer characteristics. Therefore, when an organic-inorganic composite film is formed, the various characteristics of the lithium secondary battery are maximized.

[0032] The R' may be any one selected from the group consisting of a C1-C5 alkyl group that may be substituted with fluorine, a C2-C5 alkenyl group that may be substituted with fluorine, and a C2-C5 alkynyl group that may be substituted with fluorine.

[0033] In the above chemical formula 1, R2 and R3 may each be independently selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms, and preferably both R2 and R3 may be H.

[0034] Specifically, the compound of chemical formula 1 may be any one of the compounds represented by the following chemical formulas 1-1 to 1-6.

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] [ka]

[0041] The non-aqueous electrolyte according to the present invention contains a compound represented by the following chemical formula 2 or chemical formula 3 as a second additive. The compound of chemical formula 2 or chemical formula 3 contains a propagyl group, which makes it readily reducible on the surface of the negative electrode, allowing it to easily form a film on the surface of the negative electrode. Such a film has higher stability than SEI films formed by the reductive decomposition of general electrolytes, has low electronic conductivity which suppresses additional electrolyte decomposition reactions, and is less susceptible to damage from volume changes of the negative electrode. In other words, by using the compound of chemical formula 2 or chemical formula 3 as an additive to the electrolyte, the stability of the interface between the negative electrode and the electrolyte can be ensured.

[0042] The compound of chemical formula 2 contains a propagyl group with a triple bond and an oxygen atom, which are known to have metal ion adsorption properties. Therefore, the propagyl group, which is separated by bond splitting (cleavage) between the nitrogen (N) and carbon (C) atoms of the imidazole group, adsorbs to metallic foreign matter such as Fe, Co, Mn, and Ni dissolved from the positive electrode during high-voltage charging. This effectively suppresses the negative electrode degradation phenomenon that occurs when these metallic foreign matter electrodeposits onto the negative electrode surface. Furthermore, the lone pair of electrons of the nitrogen (N) atom of the imidazole group of the compound represented by chemical 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, thus forming a stable ion-conducting film on the negative electrode surface. Consequently, not only can additional electrolyte decomposition reactions during the charge-discharge process be suppressed, but the absorption and release of lithium ions from the negative electrode can also be facilitated during overcharging or high-temperature storage, improving the cycle life characteristics and high-temperature storage performance of the secondary battery.

[0043] [ka]

[0044] In the above chemical formula 2, R is a C1-C3 alkylene group that may be substituted with fluorine, and R4-R6 may each be independently selected from the group consisting of H, a C1-C3 alkyl group, and a nitrile group.

[0045] Specifically, the compound of chemical formula 2 of the present invention may be the compound of chemical formula 2-1 shown below.

[0046] [ka]

[0047] The compound of chemical formula 3 contains ester functional groups and unsaturated hydrocarbon groups in its molecular structure. During the initial charging process of a secondary battery, it decomposes before other components of the electrolyte, forming a film on the surface of the negative electrode that is mainly composed of carbon-oxygen single bond (CO) or carbon-oxygen double bond (C=O) based compounds. Furthermore, because the compound of chemical formula 3 contains a propagyl group, it is easily reduced on the surface of the negative electrode, allowing it to easily form a film on the negative electrode surface. Such a film has higher stability than SEI films formed by the reductive decomposition of general electrolytes, has low electronic conductivity which suppresses additional electrolyte decomposition reactions, and is less susceptible to damage from volume changes of the negative electrode.

[0048] [ka]

[0049] In the above chemical formula 3, R7 is an alkylene group having 1 to 8 carbon atoms that may be substituted with fluorine, and preferably an alkylene group having 1 to 5 carbon atoms.

[0050] In the above chemical formula 3, R8 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.

[0051] The compound of chemical formula 3 may be the compound of chemical formula 3-1 below.

[0052] [ka]

[0053] In the above chemical formula 3-1, n is a natural number from 1 to 8, preferably a natural number from 1 to 5, and most preferably a natural number from 1 to 3.

[0054] In the above chemical formula 3-1, R8 is H, an alkyl group having 1 to 10 carbon atoms, and preferably H or a methyl group.

[0055] Specifically, the compound of chemical formula 3 of the present invention may be the compound of chemical formula 3-2 shown below.

[0056] [ka]

[0057] When the non-aqueous electrolyte of the present invention, which includes the first and second additives, is used, the radicals generated as the ring structure of the first additive is cleaved promote the film formation reaction of the second additive. The film formed by the interaction of the first and second additives has oxazolidinone, imidazole, cyclic carbonate structures, or structures derived therefrom between the aliphatic alkyl-based film, forming a film morphology with excellent lithium-ion transfer characteristics, thereby improving various performance characteristics such as charge / discharge characteristics and output characteristics of the lithium secondary battery. The film formed by the interaction of the first and second additives has excellent oxidation resistance, so it can suppress side reactions that occur in the positive / negative electrode film even in an acidic electrolyte atmosphere. Furthermore, the film formed by the interaction of the first and second additives has excellent durability against volume expansion of the negative electrode that occurs during charge / discharge. Therefore, the non-aqueous electrolyte of the present invention can form an electrode-electrolyte interface that is stable and highly durable even at high temperatures, and can suppress unwanted electrolyte decomposition side reactions, thereby realizing a lithium secondary battery with improved performance.

[0058] In the non-aqueous electrolyte according to the present invention, the first additive may be contained at a content of 0.01 to 10 parts by weight, or 0.01 to 5 parts by weight, preferably 0.05 to 3.0 parts by weight, more preferably 0.10 to 2.0 parts by weight, based on 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 film on the negative electrode is sufficient, and there is an effect of being excellent in life characteristics at high temperature and high temperature storage characteristics.

[0059] In the non-aqueous electrolyte according to the present invention, the second additive may be contained at a content of 0.01 to 5 parts by weight, preferably 0.05 to 3.0 parts by weight, more preferably 0.10 to 2.5 parts by weight, based on 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 film on the negative electrode is sufficient, and there is an effect of being excellent in life characteristics at high temperature and high temperature storage characteristics.

[0060] In the non-aqueous electrolyte of the present invention, the first additive and the second additive may be contained at a weight ratio of 1:0.001 to 1:500, or 1:0.002 to 1:500, preferably 1:0.01 to 1:300, most preferably 1:0.02 to 1:250. When the above range is satisfied, the elasticity of the SEI film becomes an appropriate range, and the SEI film can be firmly maintained during charge and discharge or at high temperature.

[0061] 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 mediator for transmitting ions. Usually, as the lithium salt, for example, as a cation, it contains Li + 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 of the following groups can be selected.

[0062] Specifically, the lithium salts are LiCl, LiBr, LiI, LiBF4, LiClO4, and LiB 10 Cl 10The electrolyte may contain a single substance or a mixture of two or more substances selected from the group consisting of 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 as electrolytes in lithium secondary batteries can be used without limitation.

[0063] The lithium salt may be appropriately changed within a range of normal use, but in order to obtain the optimal effect of forming a corrosion-preventive film on the electrode surface, it may be included in the electrolyte at a concentration of 0.5 M to 5.0 M, preferably 1.0 M to 3.0 M, and more preferably 1.2 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of the lithium secondary battery is sufficient, and the viscosity of the non-aqueous electrolyte is appropriate, improving electrolyte impregnation.

[0064] The non-aqueous electrolyte according to the present invention may contain an organic solvent. The organic solvent may include at least one organic solvent selected from the group consisting of cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

[0065] The additive according to the present invention is particularly effective when using a cyclic carbonate solvent. When conventional electrolyte additives are used with a cyclic carbonate solvent, the SEI film formed by the decomposition of the cyclic carbonate solvent is difficult to maintain due to the volume change of the negative electrode that occurs as the cycle progresses, and the solvent continues to decompose. This leads to a decrease in the ionic conductivity of the electrolyte and a deterioration of the cycle characteristics. However, when using a combination of the additive according to the present invention with a cyclic carbonate solvent, a strong SEI film can be formed, and the cycle characteristics are maintained at a high level.

[0066] The aforementioned cyclic carbonate-based organic solvent is a highly viscous organic solvent with a high dielectric constant that readily dissociates lithium salts in electrolytes. Specific examples 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.

[0067] Furthermore, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and as a typical example, 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 may be used, and among these, diethyl carbonate (DEC) may be included.

[0068] Furthermore, in order to produce an electrolyte having high ionic conductivity, the organic solvent may further contain at least one ester organic solvent selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents, in addition to at least one carbonate organic solvent selected from the group consisting of cyclic carbonate organic solvents and linear carbonate organic solvents.

[0069] 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.

[0070] Furthermore, the cyclic ester organic solvents include at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0071] On the other hand, the organic solvent may be further used with any organic solvent commonly used for non-aqueous electrolytes, without limitation, as needed. For example, it may further contain at least one or more organic solvents such as ether-based organic solvents, glyme-based solvents, and nitrile-based organic solvents.

[0072] The ether-based solvent can 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 to these.

[0073] The aforementioned glyme-based solvent is a solvent that has a higher dielectric constant and lower surface tension than linear carbonate-based organic solvents, and has low reactivity with metals. It may include, but is not limited to, at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME).

[0074] The nitrile solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited to these.

[0075] Furthermore, the non-aqueous electrolyte of the present invention may, if necessary, further contain known electrolyte additives in order to prevent the non-aqueous electrolyte from decomposing in a high-power environment, which can cause the collapse of the negative electrode, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and the effect of suppressing battery swelling at high temperatures.

[0076] Such other electrolyte additives may include, as representative examples, at least one SEI film-forming additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0077] Examples of the aforementioned cyclic carbonate compounds include vinylene carbonate (VC) or vinylethylene carbonate.

[0078] Examples of halogen-substituted carbonate compounds include fluoroethylene carbonate (FEC).

[0079] Examples of the sultone compounds include at least one compound selected from the group consisting of 1,3-propanesultone (PS), 1,4-butanesultone, ethensultone, 1,3-propensultone (PRS), 1,4-butensultone, and 1-methyl-1,3-propensultone.

[0080] Examples of the sulfate compounds include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0081] Examples of the phosphate compound include 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.

[0082] Examples of the borate compounds include tetraphenyl borate, lithium difluoro(oxalate) borate (LiODFB), and lithium bisoxalate borate (LiB(C2O4)2, LiBOB).

[0083] Examples of the nitrile compounds include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0084] Examples of the benzene-based compound include fluorobenzene, examples of the amine-based compound include triethanolamine or ethylenediamine, and examples of the silane-based compound include tetravinylsilane.

[0085] The lithium salt compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and examples include lithium difluorophosphate (LiDFP), LiPO2F2, or LiBF4.

[0086] If the other electrolyte additives further include a combination of vinylene carbonate (VC), 1,3-propanesultone (PS), ethylene sulfate (Esa), and lithium difluorophosphate (LiDFP), an even stronger SEI film can be formed on the surface of the negative electrode during the initial activation process of the secondary battery, thereby suppressing the generation of gases that may be produced by the decomposition of the electrolyte at high temperatures and improving the high-temperature stability of the secondary battery.

[0087] On the other hand, two or more of the other electrolyte additives may be used in mixture form, and may be included in an amount of 0.050% to 20% by weight, specifically 0.10% to 15% by weight, based on the total weight of the nonaqueous electrolyte, preferably 0.30% to 10% by weight. When the content of the other electrolyte additives satisfies the above range, a better improvement in ionic conductivity and cycle characteristics can be obtained.

[0088] Lithium-ion rechargeable battery The present invention also provides a lithium secondary battery comprising the non-aqueous electrolyte.

[0089] Specifically, the lithium secondary battery includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and the aforementioned non-aqueous electrolyte.

[0090] In this case, the lithium secondary battery of the present invention can be manufactured by conventional methods known in the art. For example, it can be manufactured by forming an electrode assembly in which a positive electrode, a negative electrode, and a separator between the positive and negative electrodes are sequentially stacked, inserting the electrode assembly into a battery case, and injecting the non-aqueous electrolyte according to the present invention.

[0091] (1) Positive electrode The positive electrode can be manufactured by coating a positive electrode mixture slurry containing a positive electrode active material, a binder, a conductive material, and a solvent onto a positive electrode current collector.

[0092] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used.

[0093] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and may specifically include a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the lithium metal oxide may be a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), or a lithium-nickel-manganese oxide (e.g., LiNi 1-Y Mn YO2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (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 lithium-nickel-cobalt-transition metal (M) oxides (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 the respective independent elements, 0 < p2 < 1, 0 < q2 < 1,​​​​​​​​​​​​​​​​​​​​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 (For example, O2) and other similar substances may be used, and one or more of these may be used as a mixture.

[0095] In particular, a positive electrode active material with a nickel content of 80 atm% or more can be used because it can best enhance the battery's capacity characteristics. For example, the lithium transition metal oxide may include one represented by the following chemical formula 4.

[0096] [Chemical formula 4] Li x Ni a Co b M 1 c M 2 d O2

[0097] In the aforementioned chemical formula 4, the M 1 This is one or more selected from Mn and Al, preferably Mn, or a combination of Mn and Al.

[0098] M 2 This may be one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb.

[0099] The above x represents the atomic fraction of lithium in the lithium transition metal oxide, and may be 0.90 ≤ x ≤ 1.1, preferably 0.95 ≤ x ≤ 1.08, and more preferably 1.0 ≤ x ≤ 1.08.

[0100] The a represents the atomic fraction of nickel among the metal elements excluding lithium in the lithium transition metal oxide, and 0.80 ≦ a < 1.0, preferably 0.80 ≦ a ≦ 0.95, more preferably 0.85 ≦ a ≦ 0.90. When the nickel content satisfies the above range, high-capacity characteristics can be realized.

[0101] The b represents the atomic fraction of cobalt among the metal elements excluding lithium in the lithium transition metal oxide, and 0 < b < 0.2, 0 < b ≦ 0.15, or 0.01 ≦ b ≦ 0.10.

[0102] The c represents the atomic fraction of M among the metal elements excluding lithium in the lithium transition metal oxide, and 0 < c < 0.2, 0 < c ≦ 0.15, or 0.01 ≦ c ≦ 0.10. 1

[0103] The d represents the atomic fraction of M among the metal elements excluding lithium in the lithium transition metal oxide, and 0 ≦ d ≦ 0.1, or 0 ≦ d ≦ 0.05. 2

[0104] The positive 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 matter excluding the solvent in the positive electrode mixture slurry.

[0105] The binder is a component that aids in binding the active material and the conductive material, etc., and binding to the current collector.

[0106] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluorine rubber, various copolymers, and the like.

[0107] ​​Typically, the binder may be present 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 solids in the positive electrode mixture slurry excluding the solvent.

[0108] 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% to 20% by weight based on the total weight of the solid content in the negative electrode slurry. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and may be used, for example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a well-developed crystalline structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; 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.

[0109] Typically, the conductive material may be included 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 matter in the positive electrode mixture slurry excluding the solvent.

[0110] The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone) and may be used in an amount that results in a suitable viscosity when the positive electrode active material and selectively include a binder and conductive material are present. For example, the concentration of the solid content containing the positive electrode active material and selectively including the binder and conductive material may be 50% to 95% by weight, preferably 70% to 95% by weight, and more preferably 70% to 90% by weight.

[0111] (2) Negative electrode The negative electrode 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, or by using a graphite electrode made of carbon (C) or the metal itself as the negative electrode.

[0112] For example, when a negative electrode is manufactured by coating a negative electrode mixture slurry onto the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 μm 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 with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. Also, similar to the positive electrode current collector, the bonding force of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and it may be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0113] Furthermore, the negative electrode active material may include at least one selected from the group consisting of lithium metal, carbon material capable of reversibly intercalating / deintercalating lithium ions, metal or alloys of these metals with lithium, metal composite oxides, materials capable of doping and dedoping lithium, and transition metal oxides.

[0114] The carbon material that can reversibly intercalate / deintercalate lithium ions can be any carbon-based negative electrode active material commonly used in lithium-ion secondary batteries, and typical examples include crystalline carbon, amorphous carbon, or a combination of both. Examples of crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, while examples of amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, and calcined coke.

[0115] 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.

[0116] 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) selected from the group consisting of can be used.

[0117] Examples of the substance capable of doping and undoping lithium include 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. Also, at least one of these and SiO2 may be mixed 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.

[0118] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, and the like.

[0119] 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 a Si-based negative electrode active material is used, 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 intense volume expansion - contraction during the progress of the cycle. However, the additive according to the present invention can form a strong SEI layer while having elasticity, so that a secondary battery using a Si-based negative electrode active material can have excellent life characteristics and storage characteristics.

[0120] 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 binder slurry.

[0121] Examples of the binder include polyvinylidene fluoride (PVDF), polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene monomer, sulfonated ethylene - propylene - diene monomer, styrene - butadiene rubber, fluorine rubber, various copolymers thereof, and the like. Specifically, styrene - butadiene rubber (SBR) - carboxymethyl cellulose (CMC) can be used because of its high thickening property.

[0122] Generally, the binder may be contained in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, more preferably 1% to 10% by weight, based on the total weight of the solid matter excluding the solvent in the negative electrode binder slurry.

[0123] 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% to 20% by weight based on the total weight of the solid content in the negative electrode mixture slurry. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and may be used, for example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a well-developed crystalline structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; 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.

[0124] The conductive material may be present 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 matter in the negative electrode mixture slurry excluding the solvent.

[0125] The solvent may contain water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that results in a suitable viscosity when the negative electrode active material and selectively the binder and conductive material are included. For example, the concentration of the solid content containing the negative electrode active material and selectively the binder and conductive material may be 50% to 95% by weight, preferably 70% to 90% by weight.

[0126] When a metal itself is used as the negative electrode, it can be manufactured by physically joining, rolling, or vapor-depositing the metal onto the metal thin film itself or onto the negative electrode current collector. As for the vapor deposition method, electro-deposit or chemical vapor deposition of the metal can be used.

[0127] For example, the metal bonded / rolled / deposited onto the metal thin film itself or 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).

[0128] (3) Separator Furthermore, the separator may be a conventional porous polymer film, such as a porous polymer film made from polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, used alone or in a laminated configuration. Alternatively, a conventional porous nonwoven fabric, such as a nonwoven fabric made from high-melting-point glass fibers or polyethylene terephthalate fibers, may be used, but is not limited to these. In addition, a coated separator containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and may be selectively used as a single-layer or multi-layer structure.

[0129] Specifically, as the separator included in the electrode assembly of the present invention, an SRS (safety reinforced separator) separator may be used, which has a coating layer containing ceramic components or polymer substances formed on it in order to ensure heat resistance or mechanical strength.

[0130] Specifically, the separator included in the electrode assembly of the present invention comprises a porous separator substrate and a porous coating layer that is applied to one or both sides of the separator substrate, wherein the coating layer may contain a mixture of inorganic particles selected from metal oxides, metalloid oxides, metal fluorides, metal hydroxides, and combinations thereof, and a binder polymer that connects and fixes the inorganic particles to each other.

[0131] The coating layer may contain one or more inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, and MgF2. Here, 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. Furthermore, the binder polymer can fix the inorganic particles and improve the mechanical stability of the separator.

[0132] The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, rectangular, pouch-shaped, or coin-shaped, using a can.

[0133] 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 invention. It will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the described concept and technical idea, and it goes without saying that such variations and modifications fall within the scope of the appended claims.

[0134] Examples Example 1 (Manufacturing of non-aqueous electrolytes) A non-aqueous solvent was prepared by dissolving LiPF6 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. 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 2-1 to 99.98 g of the non-aqueous solvent.

[0135] [ka]

[0136] [ka]

[0137] (Manufacturing of lithium-ion batteries) Cathode active material (LiNi 0.85 Co 0.05 Mn 0.08 Al 0.02 A positive electrode slurry (solid content 75.5% by weight) was prepared by adding O2, a conductive material (carbon nanotube), and a binder (polyvinylidene fluoride) in a weight ratio of 97.74:0.7:1.56 to the solvent N-methyl-2-pyrrolidone (NMP). The positive electrode slurry was applied to one surface of a 15 μm thick positive electrode current collector (a thin Al film), and the positive electrode was manufactured by drying and roll pressing.

[0138] A negative electrode slurry (26% solids by weight) was prepared by adding a negative electrode active material (silicon; Si), a conductive material (carbon black), and a binder (styrene-butadiene rubber (SBR)-carboxymethylcellulose (CMC)) in a weight ratio of 70:20.3:9.7 to the solvent N-methyl-2-pyrrolidone (NMP). The negative electrode slurry was applied to one surface of a 15 μm thick negative electrode current collector (Cu thin film), and the negative electrode was manufactured by drying and roll pressing.

[0139] In a dry room, a polyolefin-based porous separator coated with inorganic Al2O3 particles was interposed between the positive and negative electrodes manufactured as described above, and then the non-aqueous electrolyte manufactured as described above was injected to produce a secondary battery.

[0140] 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 to 99.98 g of the non-aqueous solvent prepared in Example 1.

[0141] [ka]

[0142] 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.

[0143] Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that a nonaqueous 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 nonaqueous solvent prepared in Example 1.

[0144] Example 5 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of chemical formula 1-1 and 0.01 g of the compound of chemical formula 2-1 were added to 89.99 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0145] Example 6 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of chemical formula 1-1 and 0.01 g of the compound of chemical formula 3-2 were added to 89.99 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0146] Example 7 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of chemical formula 1-1 and 5 g of the compound of chemical formula 2-1 were added to 85 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0147] Example 8 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of chemical formula 1-1 and 5 g of the compound of chemical formula 3-2 were added to 85 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0148] 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 0.01 g of the compound of chemical formula 1-2 and 0.01 g of the compound of chemical formula 2-1 to 99.98 g of the non-aqueous solvent prepared in Example 1.

[0149] [ka]

[0150] Example 10 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of chemical formula 1-3 and 0.01 g of the compound of chemical formula 2-1 were added to 99.98 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0151] [ka]

[0152] 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 0.01 g of the compound of chemical formula 1-4 and 0.01 g of the compound of chemical formula 2-1 to 99.98 g of the non-aqueous solvent prepared in Example 1.

[0153] [ka]

[0154] 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 1-5 and 0.01 g of the compound of chemical formula 2-1 to 99.98 g of the non-aqueous solvent prepared in Example 1.

[0155] [ka]

[0156] 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 0.01 g of the compound of chemical formula 1-6 and 0.01 g of the compound of chemical formula 2-1 to 99.98 g of the non-aqueous solvent prepared in Example 1.

[0157] [ka]

[0158] 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 chemical formula 1-1 was added to 99.99 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0159] Comparative Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of chemical formula 1-1 was added to 90 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0160] 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 chemical formula 2-1 was added to 99.99 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0161] Comparative Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that 5 g of the compound of chemical formula 2-1 was added to 95 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0162] 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 chemical formula 3-2 was added to 99.99 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0163] Comparative Example 6 A secondary battery was manufactured in the same manner as in Example 1, except that 5 g of the compound of chemical formula 3-2 was added to 95 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0164] Experimental Example 1 - Evaluation of High-Temperature Cycle Characteristics The cycle characteristics of each secondary battery manufactured in Examples 1-13 and Comparative Examples 1-6 were evaluated.

[0165] Specifically, each battery manufactured in Examples 1 to 13 and Comparative Examples 1 to 6 was charged at 45°C at a rate of 0.33C to 4.2V under constant current / constant voltage conditions (0.05C cutoff), and discharged to 3.0V at a constant current of 0.33C. This constituted one cycle, and after 200 charge-discharge cycles, the capacity retention rate after 200 cycles relative to the initial capacity after one cycle was measured. In addition, the resistance increase rate after 200 cycles relative to the initial resistance after one cycle was measured. The results are shown in Table 1 below.

[0166] [Table 1]

[0167] Experimental Example 2 - Evaluation of High-Temperature Storage Characteristics The high-temperature storage characteristics were evaluated for each secondary battery manufactured in Examples 1-13 and Comparative Examples 1-6.

[0168] Specifically, the secondary batteries of Examples 1 to 13 and Comparative Examples 1 to 6 were fully charged to 4.2V and then stored at 60°C for 8 weeks.

[0169] Before saving, the capacity of the fully charged rechargeable battery was measured and set as the initial capacity of the rechargeable battery.

[0170] After 8 weeks, the capacity of the stored secondary batteries was measured, and the decrease in capacity during the 8-week storage period was calculated. The capacity retention rate after 8 weeks was derived by calculating the percentage of the decreased capacity relative to the initial capacity of the secondary batteries. In addition, the resistance increase rate after 8 weeks was derived by calculating the percentage of the increased resistance relative to the initial resistance of the secondary batteries. The results are shown in Table 2 below.

[0171] [Table 2]

[0172] Experimental Example 3 - Evaluation of Thermal Stability The thermal stability of each secondary battery manufactured in Examples 1-13 and Comparative Examples 1-6 was evaluated.

[0173] Specifically, the lithium secondary batteries manufactured in the above examples and comparative examples underwent an activation process, and were then charged at 25°C at a rate of 0.33C to 4.2V under constant current / constant voltage conditions (0.05C cutoff) until they reached a state of charge of 100%. After the fully charged batteries were heated to 140°C at a heating rate of 5°C / min, they were left for 1 hour, and a hot box evaluation experiment was conducted to check for ignition. If no ignition occurred, it was evaluated as Pass, and if ignition occurred, it was evaluated as Fail. The results are shown in Table 3 below.

[0174] [Table 3]

Claims

1. Lithium salts and Organic solvents containing ethylene carbonate, The first additive is the compound of chemical formula 1 below, A non-aqueous electrolyte comprising, as a second additive, a compound of the following chemical formula 2 or chemical formula 3. 【Chemistry 1】 In the aforementioned chemical formula 1, R １ This includes C1-C5 alkyl groups that may be substituted with fluorine, C2-C5 alkenyl groups that may be substituted with fluorine, C2-C5 alkynyl groups that may be substituted with fluorine, and SO ２ One selected from the group consisting of R' and COR', R' is one selected from the group consisting of a C1-C5 alkyl group that may be substituted with fluorine, a C2-C5 alkenyl group that may be substituted with fluorine, and a C2-C5 alkynyl group that may be substituted with fluorine. R ２ and R ３ Each of these is independently selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. 【Chemistry 2】 In the aforementioned chemical formula 2, R is an alkylene group having 1 to 3 carbon atoms that may be substituted with fluorine. R ４ ~R ６ Each of these is independently selected from the group consisting of H, an alkyl group having 1 to 3 carbon atoms, and a nitrile group. 【Transformation 3】 In the aforementioned chemical formula 3, R ７ This is an alkylene group having 1 to 8 carbon atoms that may be substituted with fluorine. R ８ is one selected from the group consisting of H, alkyl groups having 1 to 10 carbon atoms, and cycloalkyl groups having 3 to 8 carbon atoms.

2. The non-aqueous electrolyte according to claim 1, wherein the compound of chemical formula 1 is one selected from the following chemical formulas 1-1 to 1-6. 【Chemistry 4】 【Transformation 5】 【Transformation 6】 【Transformation 7】 【Transformation 8】 【Chemistry 9】

3. The non-aqueous electrolyte according to claim 1, wherein the compound of chemical formula 2 is the compound of chemical formula 2-1 shown below. 【Chemistry 10】

4. The non-aqueous electrolyte according to claim 1, wherein the compound of chemical formula 3 is the compound of chemical formula 3-1 shown below. 【Chemistry 11】 In the aforementioned chemical formula 3-1, The aforementioned n is a natural number from 1 to 8. R ８ is H, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms.

5. The non-aqueous electrolyte according to claim 1, wherein the compound of chemical formula 3 is the compound of chemical formula 3-2 shown below. 【Chemistry 12】

6. The nonaqueous electrolyte according to claim 1, wherein the first additive is contained in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the nonaqueous electrolyte.

7. The nonaqueous electrolyte according to claim 1, wherein the second additive is contained in an amount of 0.01 to 5 parts by weight per 100 parts by weight of the nonaqueous electrolyte.

8. 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 mentioned above are 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, which is one or more selected from the group consisting of the following.

10. The non-aqueous electrolyte according to claim 1, wherein the lithium salt is contained at a concentration of 0.5 M to 5.0 M.

11. The non-aqueous electrolyte according to claim 1, wherein the organic solvent further comprises at least one organic solvent selected from the group consisting of linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

12. A positive electrode containing a positive electrode active material layer, A negative electrode containing a negative electrode active material layer, A lithium secondary battery comprising a non-aqueous electrolyte according to any one of claims 1 to 11.

13. The lithium secondary battery according to claim 12, wherein the positive electrode active material layer contains a lithium nickel-based oxide represented by the following chemical formula 4 as the positive electrode active material. [Chemical formula 4] Li ｘ Ni ａ Co ｂ M １ ｃ M ２ ｄ O ２ In the above chemical formula 4, M １ M is Mn, Al, or a combination thereof. ２ x is one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and satisfies 0.90 ≤ x ≤ 1.1, 0.80 ≤ a < 1.0, 0 < b < 0.2, 0 < c < 0.2, and 0 ≤ d ≤ 0.

1.

14. The negative electrode active material layer is composed of SiO as the negative electrode active material. ｘ A lithium secondary battery according to claim 12, including (0 ≤ x < 2).