Non-aqueous electrolytes and lithium secondary batteries containing them

Abstract

The present invention relates to a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive comprises a cyclic siloxane compound represented by a specific chemical formula.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2023-0052976 dated April 21, 2023, 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] With the development of the information society, personal IT devices and computer networks have advanced, and consequently, society as a whole has become more dependent on electrical energy. Therefore, there is a need to develop technologies for efficiently storing and utilizing electrical energy.

[0004] Rechargeable batteries are the most suitable technology for a wide range of applications among the technologies currently under development. Among these rechargeable batteries, there is growing interest in lithium-ion batteries, which not only can be miniaturized to a degree suitable for personal IT devices, but also have the highest energy density.

[0005] Typically, lithium-ion batteries are manufactured by injecting or impregnating an electrode assembly, consisting of a positive electrode, a negative electrode, and a porous separator, with a non-aqueous electrolyte.

[0006] As positive electrode active materials for such lithium secondary batteries, the use of lithium-containing cobalt oxide, layered crystalline LiMnO2, spinel crystalline LiMn2O4, lithium-containing nickel oxide (LiNiO2), and lithium nickel-cobalt-manganese transition metal oxides is being considered.

[0007] On the other hand, carbon-based active materials such as graphite have been used as negative electrode active materials, but in recent years, the use of silicon-based active materials has been considered because they have a higher capacity than carbon-based active materials. Although silicon-based active materials have the advantage of having a high capacity, they have the problem of very large volume expansion / contraction during the charge / discharge process. The degree of such large volume expansion / contraction significantly reduces the conductivity of the negative electrode and causes a decrease in lifespan performance. In addition, during initial activation, a solid electrolyte interface layer (SEI film) is formed on the surface of the negative electrode, but because silicon-based active materials have a large degree of volume expansion, cracking of the SEI film and the continuous generation of new negative electrode surfaces become problematic. This leads to problems such as the continuous occurrence of SEI film formation reactions, which accelerates electrolyte side reactions, resulting in a thicker SEI film and increased resistance. [Overview of the project] [Problems that the invention aims to solve]

[0008] One objective of the present invention is to solve the above-mentioned problems and to provide a non-aqueous electrolyte that can realize a lithium secondary battery with improved lifespan and storage performance by forming an SEI coating on the negative electrode that has excellent recovery properties and improved durability. [Means for solving the problem]

[0009] The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive comprises a compound represented by the following chemical formula 1.

[0010] [Chemical formula 1] [ka]

[0011] In the above chemical formula 1, R1 and R2 independently include F, Br, Cl, I, a nitrile group, an ester group, an ether group, a ketone group, a carboxyl group, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkenyl group, a substituted or unsubstituted C1-C10 alkynyl group, a substituted or unsubstituted C1-C10 alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, a substituent represented by the following chemical formula 2, or two or more combinations thereof, and at least one of R1 and R2 includes a substituent represented by the following chemical formula 2, with n being an integer from 3 to 8.

[0012] [Chemical formula 2] [ka] In the above chemical formula 2, L1 is an alkylene group, ester group, sulfone group, sulfonate group, sulfate group, or a combination of two or more of these having 1 to 10 carbon atoms, R3 is an alkoxy group having 1 to 10 carbon atoms substituted with at least one fluorine atom, and * is a bonding site.

[0013] Furthermore, the present invention provides a lithium secondary battery comprising a negative electrode, a positive electrode facing the negative electrode, a separator interposed between the negative electrode and the positive electrode, and the aforementioned non-aqueous electrolyte. [Effects of the Invention]

[0014] The non-aqueous electrolyte of the present invention is characterized by containing a cyclic siloxane compound of a specific structure, which includes an alkoxy group with one or more fluorine atoms substituted as an additive. The compound can form a polymer-type siloxane SEI film upon reduction at the negative electrode, and such a polymer-type siloxane SEI film has a high shear modulus and can contribute to the formation of an SEI film with excellent thermal stability and chemical and electrochemical stability. Furthermore, the alkoxy group with one or more fluorine atoms substituted in the cyclic siloxane compound enables the formation of an inorganic type SEI film such as LiF upon reduction at the negative electrode, improving the durability of the SEI film. In particular, since the alkoxy group is a good leaving group, it can strongly induce the SEI film formation reaction. As a result, lithium secondary batteries containing the non-aqueous electrolyte of the present invention can have improved lifespan and storage performance, especially at high temperatures. [Modes for carrying out the invention]

[0015] 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.

[0016] 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.

[0017] On the other hand, prior to describing the present invention, unless otherwise specifically mentioned in the present invention, "*" means a connected portion (bonding site) between identical or different atoms or the terminal parts of a chemical formula.

[0018] 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, "alkyl group with 1 to 5 carbon atoms" means alkyl groups containing 1 to 5 carbon atoms, i.e., CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2CH2-, etc.

[0019] Furthermore, in this specification, alkyl groups or aryl groups may or may not be substituted. Unless otherwise defined, "substitution" means that at least one hydrogen bonded to a carbon 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, an alkyl group having 3 to 12 carbon atoms, an alkenyl group having 3 to 12 carbon atoms, an alkynyl group having 3 to 12 carbon atoms, an heterocycloalkyl group having 3 to 12 carbon atoms, an heterocycloalkenyl group having 3 to 12 carbon atoms, an heterocycloalkynyl group having 2 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, a nitro group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, or a haloaryl group having 6 to 20 carbon atoms.

[0020] The present invention will be described in more detail below.

[0021] Non-aqueous electrolytes This invention relates to non-aqueous electrolytes.

[0022] Specifically, the non-aqueous electrolyte according to the present invention comprises a lithium salt, an organic solvent, and an additive, wherein the additive comprises a compound represented by the following chemical formula 1.

[0023] [Chemical formula 1] [Chemical formula]

[0024] In the above Chemical formula 1, R1 and R2 are, independently of each other, F, Br, Cl, I, nitrile group, ester group, ether group, ketone group, carboxy group, substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, substituted or unsubstituted alkenyl group having 1 to 10 carbon atoms, substituted or unsubstituted alkynyl group having 1 to 10 carbon atoms, substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, boron group, borate group, isocyanate group, isothiocyanate group, silyl group, siloxane group, sulfone group, sulfonate group, sulfate group, a substituent represented by the following Chemical formula 2, or a combination of two or more thereof. At least one of R1 and R2 contains a substituent represented by the following Chemical formula 2, and n is an integer of 3 to 8.

[0025] [Chemical formula 2] [Chemical formula]

[0026] In the above Chemical formula 2, L1 is an alkylene group having 1 to 10 carbon atoms, ester group, sulfone group, sulfonate group, sulfate group, or a combination of two or more thereof, R3 is an alkoxy group having 1 to 10 carbon atoms with at least one fluorine substitution, and * is a bonding site.

[0027] (1) Lithium salt As the lithium salt used in the present invention, various lithium salts commonly used in non-aqueous electrolytes for lithium secondary batteries can be used without limitation. For example, the lithium salt contains Li as a cation + and, as an anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 -AlCl4 - PF6 - SbF6 - AsF6 - B 10 Cl 10 - BF2C2O4 - BC4O8 - PF4C2O4 - PF2C4O8 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - , C4F9SO3 - CF3CF2SO3 - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - CH3SO3 - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - , and (CF3CF2SO2)2N - It may include at least one selected from the group consisting of the following.

[0028] Specifically, the lithium salts are LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10The lithium salt may include at least one selected from the group consisting of LiBOB(LiB(C2O4)2), LiCF3SO3, LiFSI(LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI(LiN(SO2CF2CF3)2). Specifically, the lithium salt may include at least one selected from the group consisting of LiBF4, LiClO4, LiPF6, LiBOB(LiB(C2O4)2), LiCF3SO3, LiTFSI(LiN(SO2CF3)2), LiFSI((LiN(SO2F)2), and LiBETI(LiN(SO2CF2CF3)2).

[0029] The lithium salt may be included in the non-aqueous electrolyte at a concentration of 0.5 M to 5 M, specifically 0.8 M to 4 M, more specifically 0.8 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the lithium ion transport number (Li + The transference number and the degree of lithium ion dissociation are improved, which can enhance the battery's output characteristics.

[0030] (2) Organic solvents The aforementioned organic solvent is not particularly limited as long as it is a non-aqueous solvent commonly used in lithium secondary batteries, and its decomposition due to oxidation reactions during the charging and discharging process of the secondary battery is minimized.

[0031] Specifically, the organic solvent may include at least one selected from the group consisting of cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

[0032] Specifically, the organic solvent may include a cyclic carbonate organic solvent, a linear carbonate organic solvent, or a mixture thereof.

[0033] The cyclic carbonate-based organic solvent is a highly viscous organic solvent with a high dielectric constant that readily dissociates lithium salts in electrolytes. Specifically, it may contain at least one organic solvent selected from the group consisting of ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. More specifically, it may contain at least one selected from the group consisting of ethylene carbonate (EC) and fluoroethylene carbonate (FEC). Even more specifically, it may contain fluoroethylene carbonate (FEC) as it contributes to the formation of an inorganic (LiF)-containing SEI film.

[0034] Furthermore, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and may specifically include at least one selected from the group consisting of dimethyl carbonate (dimethyl carbonate, DMC), diethyl carbonate (diethyl carbonate, DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate. More specifically, it may include at least one selected from the group consisting of ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), and more specifically, it may include diethyl carbonate (DEC) because it can further improve the oxidative stability of non-aqueous electrolytes.

[0035] The organic solvent may be a mixture of a cyclic carbonate organic solvent and a linear carbonate organic solvent. In this case, the cyclic carbonate organic solvent and the linear carbonate organic solvent may be mixed in a volume ratio of 5:95 to 40:60, specifically, in a volume ratio of 7:93 to 25:75. When the mixing ratio of the cyclic carbonate organic solvent and the linear carbonate organic solvent satisfies the above range, both high dielectric constant and low viscosity characteristics can be achieved, resulting in excellent ionic conductivity.

[0036] Furthermore, in order to produce an electrolyte having high ionic conductivity, the organic solvent may further contain at least one ester-based organic solvent selected from the group consisting of linear ester-based organic solvents and cyclic ester-based organic solvents, in addition to at least one carbonate-based organic solvent selected from the group consisting of cyclic carbonate-based organic solvents and linear carbonate-based organic solvents.

[0037] The linear ester-based organic solvent may specifically include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0038] Furthermore, the cyclic ester organic solvent may specifically include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0039] 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.

[0040] 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.

[0041] 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, and 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).

[0042] 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.

[0043] (3) Additives The non-aqueous electrolyte contains additives.

[0044] The aforementioned additive contains a compound represented by the following chemical formula 1.

[0045] [Chemical formula 1] [ka]

[0046] In the above chemical formula 1, R1 and R2 independently include F, Br, Cl, I, a nitrile group, an ester group, an ether group, a ketone group, a carboxyl group, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkenyl group, a substituted or unsubstituted C1-C10 alkynyl group, a substituted or unsubstituted C1-C10 alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, a substituent represented by the following chemical formula 2, or two or more combinations thereof, and at least one of R1 and R2 includes a substituent represented by the following chemical formula 2, with n being an integer from 3 to 8.

[0047] [Chemical formula 2] [ka]

[0048] In the above chemical formula 2, L1 is an alkylene group, ester group, sulfone group, sulfonate group, sulfate group, or a combination of two or more of these having 1 to 10 carbon atoms, R3 is an alkoxy group having 1 to 10 carbon atoms substituted with at least one fluorine atom, and * is a bonding site.

[0049] The compound represented by chemical formula 1 is characterized in that R1 and / or R2 substituted with Si are cyclic siloxane compounds containing alkoxy groups having 1 to 10 carbon atoms substituted with at least one F, specifically substituents represented by chemical formula 2.

[0050] When the compound represented by chemical formula 1 is used as a non-aqueous electrolyte additive, the cyclic siloxane structure is opened during reduction at the negative electrode, forming a polymer-type siloxane SEI film. This polymer-type siloxane SEI film not only exhibits excellent flexibility and resilience, but also has a high shear modulus and excellent thermal stability, chemical stability, and electrochemical stability.

[0051] Furthermore, the compound represented by chemical formula 1 contains a substituent represented by chemical formula 2, and the substituent is reduced at the negative electrode to form an inorganic type SEI coating containing an inorganic substance such as LiF. Such an inorganic type SEI coating can significantly improve the durability of the SEI coating. In particular, the compound of chemical formula 1 according to the present invention forms the polymer-type / inorganic-type composite SEI coating described above, thereby improving the durability, flexibility, and stability of the SEI coating.

[0052] Furthermore, the substituents (R1 and / or R2) in the compound represented by chemical formula 1 are characterized by including a fluorine-substituted alkoxy group, specifically the substituent represented by chemical formula 2, and the fluorine-substituted alkoxy group is a somewhat weak electron-withdrawing group and functions as a good leaving group. This can induce and promote the formation of inorganic SEI films such as LiF.

[0053] Due to the effects described above, the non-aqueous electrolyte according to the present invention enables improvements in the lifespan and storage performance of lithium secondary batteries, particularly at high temperatures. In particular, the compound represented by chemical formula 1 can be more preferably applied to a negative electrode using a silicon-based active material. The Li of lithiated Si formed by the activation of the negative electrode containing the silicon-based active material and the F derived from the compound represented by chemical formula 1 can have a strong interation (glue effect), which is advantageous in forming a highly durable and resilient SEI coating for silicon-based active materials that undergo significant volume expansion during charging and discharging.

[0054] In the above chemical formula 1, R1 and R2 may independently include F, Br, Cl, I, a nitrile group, an ester group, an ether group, a ketone group, a carboxyl group, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkenyl group, a substituted or unsubstituted C1-C10 alkynyl group, a substituted or unsubstituted C1-C10 alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, a substituent represented by the following chemical formula 2, or two or more combinations thereof. In this case, at least one of R1 and R2 includes a substituent represented by the following chemical formula 2.

[0055] [Chemical formula 2] [ka]

[0056] In the above chemical formula 2, L1 is an alkylene group, ester group, sulfone group, sulfonate group, sulfate group, or a combination of two or more of these having 1 to 10 carbon atoms, R3 is an alkoxy group having 1 to 10 carbon atoms substituted with at least one fluorine atom, and * is a bonding site.

[0057] Specifically, in order to prevent a decrease in reactivity due to steric hindrance, either R1 or R2 may contain the substituent represented by chemical formula 2. For example, in chemical formula 1, R1 may contain the substituent represented by chemical formula 2, while R2 may not contain the substituent represented by chemical formula 2. Specifically, in chemical formula 1, if R1 contains the substituent represented by chemical formula 2, R2 may be an alkyl group having 1 to 5 carbon atoms, more specifically an ethyl group or a methyl group, and even more specifically a methyl group.

[0058] In the above chemical formula 2, L1 is an alkylene group, ester group, sulfone group, sulfonate group, sulfate group, or a combination of two or more of these having 1 to 10 carbon atoms, R3 is an alkoxy group having 1 to 10 carbon atoms substituted with at least one fluorine atom, and * is a bonding site.

[0059] In the above chemical formula 2, L1 may specifically be an alkylene group having 1 to 10 carbon atoms, a sulfone group, or a combination thereof, more specifically an alkylene group having 1 to 5 carbon atoms, and even more specifically a methylene group or an ethylene group, since electron acceptance is easy during reduction at the negative electrode and the reducing power is further improved, and even more specifically an ethylene group.

[0060] In the above chemical formula 2, R3 is an alkoxy group having 1 to 10 carbon atoms with one or more fluorine atoms substituted, more specifically an alkoxy group having 1 to 5 carbon atoms with one or more fluorine atoms substituted, more specifically one selected from the group consisting of -OCF3, -OCF2CF3, and -OCF2CF2CF3, and even more specifically, -OCF3 in order to prevent a decrease in reactivity due to steric hindrance.

[0061] In the above chemical formula 1, n is an integer between 3 and 8, specifically 3 or 4, and more specifically 3. When n is between 3 and 8, R1 and / or R2 in each repeating unit may be the same or different from each other.

[0062] Specifically, the compound represented by chemical formula 1 may include at least one compound selected from the group consisting of chemical formulas 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8, 1-9, 1-10, 1-11, and 1-12. More specifically, it may include at least one compound selected from the group consisting of chemical formulas 1-1, 1-3, 1-9, and 1-10. Even more specifically, it may include at least one compound selected from the group consisting of chemical formulas 1-1 and 1-3. Even more specifically, it may include the compound represented by chemical formula 1-1.

[0063] [Chemical formula 1-1] [ka]

[0064] [Chemical formula 1-2] [ka]

[0065] [Chemical formula 1-3] [ka]

[0066] [Chemical formula 1-4] [ka]

[0067] [Chemical formula 1-5] [ka]

[0068] [Chemical formula 1-6] [ka]

[0069] [Chemical formula 1-7] [ka]

[0070] [Chemical formula 1-8] [ka]

[0071] [Chemical formula 1-9] [ka]

[0072] [Chemical formula 1-10] [ka]

[0073] [Chemical formula 1-11] [ka]

[0074] [Chemical formula 1-12] [ka]

[0075] The compound represented by chemical formula 1 may be present in an amount of 0.01% to 10% by weight, specifically 0.3% to 7% by weight, more specifically 0.5% to 5% by weight, and even more specifically 1% to 3% by weight, based on the weight of the non-aqueous electrolyte. When the compound represented by chemical formula 1 is used within the above content range, a flexible and highly durable SEI coating can be formed on the negative electrode, and an increase in resistance during excessive addition can be prevented.

[0076] The additive may further include additional additives along with the compound represented by chemical formula 1. These additional additives may be included in the non-aqueous electrolyte to prevent decomposition of the non-aqueous electrolyte and subsequent collapse of the negative electrode in high-power environments, or to provide low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and suppression of battery swelling at high temperatures.

[0077] Specifically, the aforementioned additional additives include lithium difluorophosphate (LiDFP), vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, and lithium bis-(oxalato)borate (LiBOB). It may contain at least one selected from the group consisting of bis-(oxalato)borate, 3-trimethoxysilanyl-propyl-N-aniline (TMSPa), and tris(trimethylsilyl)phosphite (TMSPi), and specifically, lithium difluorophosphate (LiDFP).

[0078] The aforementioned additional additive may be included in the non-aqueous electrolyte in an amount of 0.1% to 15% by weight, more specifically 0.3% to 3% by weight.

[0079] If the non-aqueous electrolyte further contains the additional additive, the weight ratio of the compound represented by chemical formula 1 to the additional additive may be 45:55 to 99:1, specifically 50:50 to 95:5, and more specifically 70:30 to 85:15. When the ratio is within the above range, the lifespan performance and high-temperature storage performance can be improved to a more favorable level.

[0080] Lithium-ion battery Furthermore, the present invention provides a lithium secondary battery containing the aforementioned non-aqueous electrolyte.

[0081] Specifically, the lithium secondary battery according to the present invention includes a negative electrode, a positive electrode facing the negative electrode, a separator interposed between the negative electrode and the positive electrode, and the aforementioned non-aqueous electrolyte.

[0082] The lithium secondary battery can be manufactured by housing an electrode assembly, which includes the negative electrode, a positive electrode facing the negative electrode, and a separator interposed between the negative electrode and the positive electrode, in a battery case, and then injecting the aforementioned non-aqueous electrolyte.

[0083] As explained above, the negative electrode, positive electrode, and separator will be described below.

[0084] (1) Negative electrode The aforementioned negative electrode contains a negative electrode active material.

[0085] The anode active material can be any substance used as an anode active material in the field without limitation. Specifically, the anode active material may include at least one selected from silicon-based active materials and carbon-based active materials, and more specifically, it may include a silicon-based active material.

[0086] While the silicon-based active material exhibits higher capacity compared to the carbon-based active material, it suffers from the problem of significant volume expansion / contraction during charging and discharging. However, when the silicon-based active material and the aforementioned non-aqueous electrolyte are used together, a flexible, highly resilient, and durable SEI coating can be formed on the negative electrode. This prevents electrolyte side reactions, enabling the realization of a lithium secondary battery with high lifespan and storage performance.

[0087] The silicon-based active material may contain a compound represented by the following chemical formula A.

[0088] [Chemical formula A] SiO x (0≦x<2)

[0089] In the above chemical formula A, since SiO2 does not react with lithium ions and therefore cannot store lithium, it is preferable that x is within the above range. More specifically, the silicon-based active material may be Si.

[0090] The average particle size (D) of the silicon-based active material 50 The particle size may be between 1 μm and 20 μm.

[0091] The carbon-based active material may include at least one selected from the group consisting of graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably includes graphite. The graphite may include at least one selected from the group consisting of artificial graphite and natural graphite.

[0092] The average particle size (D) of the carbon-based active material 50 The thickness of the ) may be 10 μm to 30 μm, preferably 15 μm to 25 μm, in order to ensure structural stability during charging and discharging and to reduce side reactions with the electrolyte.

[0093] The negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. In this case, the negative electrode active material is included in the negative electrode active material layer.

[0094] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. Specifically, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy.

[0095] The negative electrode current collector typically has a thickness of 3 μm to 500 μm.

[0096] The negative electrode current collector may have fine irregularities formed on its surface to strengthen the bonding force of the negative electrode active material. For example, the negative electrode current collector can be used in various forms such as film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0097] The negative electrode active material layer is disposed on at least one side of the negative electrode current collector. Specifically, the negative electrode active material layer may be disposed on one or both sides of the negative electrode current collector.

[0098] The negative electrode active material may be included in the negative electrode active material layer in an amount of 60% to 99% by weight, in order to minimize the effect of volume expansion / contraction on the battery and to achieve sufficient capacity in a secondary battery.

[0099] The negative electrode active material layer may further contain a conductive material and / or a binder together with the silicon-based active material.

[0100] The binder can be used to improve the adhesion between the negative electrode active material layer and the negative electrode current collector described later, or to improve the bonding force between silicon-based active materials.

[0101] Specifically, the binder may contain at least one selected from the group consisting of styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluoro rubber, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyethylene glycol (PEG), polyacrylonitrile (PAN), and polyacrylamide (PAM), in order to further improve electrode adhesion and provide sufficient resistance to volume expansion / contraction of the silicon-based active material.

[0102] The binder may be present in the negative electrode active material layer in an amount of 1% to 30% by weight. When the amount is within this range, the negative electrode active material can be bound more effectively, the problem of volume expansion of the active material can be minimized, and the dispersion of the binder during the production of the slurry for forming the negative electrode active material layer can be facilitated, improving the coating properties and phase stability of the slurry.

[0103] The conductive material is used to assist and improve the conductivity of a secondary battery and is not particularly limited as long as it does not cause chemical changes and is conductive. Specifically, the conductive material may include at least one selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives.

[0104] The conductive material may be included in the negative electrode active material layer in an amount of 1% to 20% by weight. When it is within this range, it is preferable because it can mitigate the increase in resistance due to the binder and form an excellent conductive network.

[0105] The thickness of the negative electrode active material layer may be 5 μm to 500 μm, preferably 5 μm to 100 μm.

[0106] The negative electrode can be manufactured by coating a negative electrode current collector with a negative electrode slurry containing a negative electrode active material and selectively a binder, a conductive material, and a solvent for forming the negative electrode slurry, followed by drying and rolling.

[0107] The solvent for forming the negative electrode slurry may include, for example, at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate the dispersion of the negative electrode active material, binder, and / or conductive material.

[0108] (2) Positive electrode The positive electrode includes a positive electrode active material.

[0109] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium. Specifically, it may include a lithium transition metal composite oxide containing at least one transition metal selected from nickel, cobalt, manganese, and aluminum and lithium, preferably a lithium transition metal composite oxide containing a transition metal containing nickel, cobalt, and manganese and lithium.

[0110] For example, as the lithium transition metal composite oxide, lithium-manganese-based oxides (such as LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (such as LiCoO2, etc.), lithium-nickel-based oxides (such as LiNiO2, etc.), lithium-nickel-manganese-based oxides (such as LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (such as LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (such as 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 (such as Li(Ni p Co q Mn r1 )O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (such as Li(Ni p2 Co q2 Mn r3 M S2)O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are the atomic fractions of independent elements, respectively, where 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc.) and the like may be mentioned, and any one or two or more of these compounds may be included. Among them, from the viewpoint of being able to enhance the capacity characteristics and stability of the battery, the lithium transition metal composite oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel-manganese-cobalt oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O^2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), etc. may be, and considering the significance of the improvement effect by controlling the types and content ratios of the constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide is 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, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc. may be, and any one or two or more of these mixtures can be used.

[0111] It should be noted that there may be some inaccuracies in the chemical formula representation in the original text, and the translation is based on the content as presented. Also, the "<00000xx>" tags are left unchanged as required.More specifically, the positive electrode active material may be a lithium transition metal composite oxide containing 60 mol% or more nickel based on the total number of moles of transition metal contained in the lithium transition metal composite oxide. Specifically, the positive electrode active material may be a lithium transition metal composite oxide in which the transition metal includes nickel and at least one selected from manganese, cobalt, and aluminum, and the nickel may be contained in an amount of 60 mol% or more, specifically 60 mol% to 90 mol%, based on the total number of moles of transition metal. When such a lithium transition metal composite oxide with a high nickel content is used together with the aforementioned non-aqueous electrolyte, it is preferable because it can reduce by-products in the gas generated by structural collapse.

[0112] Furthermore, the positive electrode active material may contain a lithium composite transition metal oxide represented by the following chemical formula B.

[0113] [Chemical formula B] Li 1+x (Ni a Co b Mn c M d )O2

[0114] In the chemical formula B, M is one or more elements selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 1+x, a, b, c, and d are the atomic fractions of independent elements, where 0≦x≦0.2 and 0.50≦a<1, 0 <b≦0.25、0<c≦0.25、0≦d≦0.1、a+b+c+d=1である。

[0115] Preferably, a, b, c, and d are 0.70 ≤ a ≤ 0.95, 0.025 ≤ b ≤ 0.20, 0.025 ≤ c ≤ 0.20, and 0 ≤ d ≤ 0.05, respectively.

[0116] Furthermore, a, b, c, and d may be 0.80 ≤ a ≤ 0.95, 0.025 ≤ b ≤ 0.15, 0.025 ≤ c ≤ 0.15, and 0 ≤ d ≤ 0.05, respectively.

[0117] Furthermore, a, b, c, and d may be 0.85≦a≦0.90, 0.05≦b≦0.10, 0.05≦c≦0.10, and 0≦d≦0.03, respectively.

[0118] The positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector. In this case, the positive electrode active material layer may include the aforementioned positive electrode active material.

[0119] The thickness of the positive electrode current collector is typically between 3 μm and 500 μm.

[0120] The positive electrode current collector may have fine irregularities formed on its surface to strengthen the bonding force with the negative electrode active material. For example, the positive electrode current collector can be used in various forms such as film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0121] The positive electrode active material layer is disposed on at least one side of the positive electrode current collector. Specifically, the positive electrode active material layer may be disposed on one or both sides of the positive electrode current collector.

[0122] The positive electrode active material may be included in the positive electrode active material layer in an amount of 80% to 99% by weight, taking into consideration the sufficient capacity exertion of the positive electrode active material.

[0123] The positive electrode active material layer may further include a binder and / or a conductive material along with the positive electrode active material.

[0124] The binder is a component that assists in the binding of the active material to the conductive material and to the current collector, and specifically may contain at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-dientelpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, preferably polyvinylidene fluoride.

[0125] The binder may be included in the positive electrode active material layer in an amount of 1% to 20% by weight, preferably 1.2% to 10% by weight, from the viewpoint of ensuring sufficient binding force between components such as the positive electrode active material.

[0126] The conductive material is used to assist and improve the conductivity of a secondary battery and is not particularly limited as long as it does not cause chemical changes and is conductive. Specifically, the positive electrode conductive material may contain at least one selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives, and preferably contains carbon nanotubes in order to improve conductivity.

[0127] The conductive material may be included in the positive electrode active material layer in an amount of 1% to 20% by weight, preferably 1.2% to 10% by weight, in order to ensure sufficient electrical conductivity.

[0128] The thickness of the positive electrode active material layer may be 5 μm to 500 μm, preferably 20 μm to 200 μm.

[0129] The positive electrode can be manufactured by coating a positive electrode current collector with a positive electrode slurry containing a positive electrode active material and selectively a binder, conductive material, and solvent for forming the positive electrode slurry, followed by drying and rolling.

[0130] (3) Separator The separator can be interposed between the positive electrode and the negative electrode.

[0131] The separator may be a conventional porous polymer film used as a separator, such as a porous polymer film made from polyolefin polymers such as ethylene monopolymer, propylene monopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, used alone or in a laminated form. Alternatively, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used, but is not limited to these. Furthermore, 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.

[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 do not limit its scope. It will be obvious to those skilled in the art that various modifications and alterations are possible within the scope and technical concept described herein, and it goes without saying that such modifications and alterations fall within the scope of the appended claims.

[0134] Examples and Comparative Examples Example 1 (Manufacture of Non-aqueous Electrolyte) As the organic solvent, a mixture of fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) in a volume ratio of 10:90 was used.

[0135] To the organic solvent, LiPF6 as a lithium salt, the compound represented by the chemical formula 1-1 as an additive, and lithium difluorophosphate (LiDFP) were added to manufacture a non-aqueous electrolyte.

[0136] The LiPF6 was contained in the non-aqueous electrolyte at a molar concentration of 1.5 M.

[0137] The compound represented by the following chemical formula 1-1 was contained in the non-aqueous electrolyte at 2% by weight, and lithium difluorophosphate was contained in the non-aqueous electrolyte at 0.5% by weight.

[0138] (Manufacture of Lithium Secondary Battery) The positive electrode active material (Li[Ni 0.85 Co 0.05 Mn 0.07 Al 0.03 O2), a conductive material (carbon nanotube), and a binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 97.74:0.70:1.56 to manufacture a positive electrode mixture slurry (solid content 75.5% by weight). The positive electrode mixture slurry was applied to one side of a positive electrode current collector (Al thin film) with a thickness of 12 μm, and drying and roll press were performed to manufacture a positive electrode.

[0139] The negative electrode active material (silicon-based active material, Si), a conductive material (carbon black), and a binder (styrene-butadiene rubber) were added to distilled water as a solvent in a weight ratio of 70.0:20.3:9.7 to manufacture a negative electrode mixture slurry (solid content 26% by weight). The negative electrode mixture slurry was applied to one side of a negative electrode current collector (Cu thin film) with a thickness of 15 μm, and drying and roll press were performed to manufacture a negative electrode.

[0140] In a dry room, a polyethylene porous film separator was interposed between the positive electrode and negative electrode manufactured as described above, and then the non-aqueous electrolyte manufactured as described above was injected to produce a secondary battery.

[0141] Example 2 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by chemical formula 1-1 was added to the non-aqueous electrolyte at a content of 0.5% by weight instead of 2% by weight.

[0142] Example 3 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by chemical formula 1-1 was added to the non-aqueous electrolyte at a content of 5% by weight instead of 2% by weight.

[0143] Example 4 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by chemical formula 1-9 was added to the non-aqueous electrolyte in a content of 2% by weight instead of the compound represented by chemical formula 1-1.

[0144] Comparative Example 1 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by chemical formula 1-1 was not added.

[0145] Comparative Example 2 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a compound represented by chemical formula X was added to the non-aqueous electrolyte at a content of 2% by weight instead of the compound represented by chemical formula 1-1.

[0146] [Chemical formula X] [ka]

[0147] Comparative Example 3 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a compound represented by chemical formula Y was added to the non-aqueous electrolyte at a content of 2% by weight instead of the compound represented by chemical formula 1-1.

[0148] [Chemical formula Y] [ka]

[0149] Comparative Example 4 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a compound represented by chemical formula Z was added to the non-aqueous electrolyte at a content of 2% by weight instead of the compound represented by chemical formula 1-1.

[0150] [Chemical formula Z] [ka]

[0151] Experimental example Experimental Example 1: Evaluation of High-Temperature Cycle Performance The lithium secondary batteries of Examples 1-4 and Comparative Examples 1-4, manufactured as described above, were charged to 4.2V and 0.05C at 45°C under CC / CV and 1C conditions using an electrochemical charger / discharger, and then discharged to 3.0V under CC and 0.5C conditions. This process was defined as one cycle, and 200 charge / discharge cycles were performed.

[0152] The capacity retention rate was calculated using the following formula, and the results are shown in Table 1 below.

[0153] Capacity retention rate (%) = {(Discharge capacity after 200 cycles / Discharge capacity after 1 cycle)} × 100

[0154] Experimental Example 2: Evaluation of High-Temperature Storage Performance The lithium secondary batteries of Examples 1-4 and Comparative Examples 1-4, manufactured as described above, were charged to 4.2V and 0.05C at 25°C under CC / CV and 0.33C conditions, and then discharged to 2.5V at 0.33C to perform initial charge and discharge. Subsequently, they were charged to 4.2V and 0.05C at 25°C under CC / CV and 0.33C conditions, and then stored at 60°C for 8 weeks.

[0155] After 8 weeks of storage, the lithium secondary battery was charged to 4.2V and 0.05C at 25°C and 0.33C, and then discharged to 3.0V at 0.33C, and its discharge capacity was measured.

[0156] The capacity retention rate was evaluated using the following formula, and the results are shown in Table 1 below.

[0157] Capacity retention rate (%) = (Discharge capacity after 8 weeks of storage / Initial discharge capacity) × 100

[0158] [Table 1]

[0159] Referring to Table 1 above, it can be confirmed that the lithium secondary batteries of Examples 1 to 4 using the non-aqueous electrolyte according to the present invention exhibit a significantly superior level of capacity retention during high-temperature cycle charging and discharging and high-temperature storage compared to Comparative Examples 1 to 4 which do not use the non-aqueous electrolyte.

Claims

1. It contains lithium salts, organic solvents, and additives. The aforementioned additive is a non-aqueous electrolyte containing a compound represented by the following chemical formula 1. [Chemical formula 1] 【Chemistry 1】 (In the above chemical formula 1, R １ and R ２ These independently comprise F, Br, Cl, I, a nitrile group, an ester group, an ether group, a ketone group, a carboxyl group, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkenyl group, a substituted or unsubstituted C1-C10 alkynyl group, a substituted or unsubstituted C1-C10 alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, a substituent represented by the following chemical formula 2, or two or more combinations thereof. The aforementioned R １ and R ２ At least one of these includes a substituent represented by the following chemical formula 2: n is an integer between 3 and 8. [Chemical formula 2] 【Chemistry 2】 In the above chemical formula 2, L １ This is an alkylene group, ester group, sulfone group, sulfonate group, sulfate group having 1 to 10 carbon atoms, or a combination of two or more of these. R ３ This is an alkoxy group having 1 to 10 carbon atoms with at least one fluorine atom substituted on it. * indicates a binding site.

2. The non-aqueous electrolyte according to claim 1, wherein n in the chemical formula 1 is 3 or 4.

3. The aforementioned R ３ is one selected from the group consisting of -OCF ３ , -OCF ２ CF ３ , and -OCF ２ CF ２ CF ３ The non-aqueous electrolyte according to claim 1, comprising one kind selected from the group consisting of

4. The aforementioned R １ The R includes the substituent represented by the chemical formula 2, ２ The non-aqueous electrolyte according to claim 1, wherein the substituent represented by the chemical formula 2 is not included.

5. The aforementioned R ２ The non-aqueous electrolyte according to claim 4, wherein is an alkyl group having 1 to 5 carbon atoms.

6. The non-aqueous electrolyte according to claim 1, wherein the compound represented by chemical formula 1 comprises at least one compound selected from the group consisting of the following chemical formulas: 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8, 1-9, 1-10, 1-11, and 1-12. [Chemical formula 1-1] 【Transformation 3】 [Chemical formula 1-2] 【Chemistry 4】 [Chemical formula 1-3] 【Transformation 5】 [Chemical formula 1-4] 【Transformation 6】 [Chemical formula 1-5] 【Transformation 7】 [Chemical formula 1-6] 【Transformation 8】 [Chemical formula 1-7] 【Chemistry 9】 [Chemical formula 1-8] 【Chemistry 10】 [Chemical formula 1-9] 【Chemistry 11】 [Chemical formula 1-10] 【Chemistry 12】 [Chemical formula 1-11] 【Chemistry 13】 [Chemical formula 1-12] 【Chemistry 14】

7. The nonaqueous electrolyte according to any one of claims 1 to 6, wherein the compound represented by chemical formula 1 is included in an amount of 0.01% to 10% by weight based on the weight of the nonaqueous electrolyte.

8. The lithium salts mentioned above are LiCl, LiBr, LiI, and LiBF. ４ LiClO ４ LiAlO ４ LiAlCl ４ LiPF ６ LiSbF ６ LiAsF ６ LiB １０ Cl １０ , LiBOB(LiB(C ２ O ４ ) ２ ), LiCF ３ SO ３ , LiFSI (LiN(SO ２ F) ２ ), LiCH ３ SO ３ LiCF ３ CO ２ LiCH ３ CO ２ , and LiBETI(LiN(SO ２ CF ２ CF ３ ) ２ The non-aqueous electrolyte according to claim 1, comprising at least one selected from the group consisting of ).

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

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

11. The negative electrode and, A positive electrode opposite the negative electrode, A separator interposed between the negative electrode and the positive electrode, A lithium secondary battery comprising the non-aqueous electrolyte described in claim 1.

12. The aforementioned negative electrode includes a negative electrode active material. The lithium secondary battery according to claim 11, wherein the negative electrode active material includes a silicon-based active material.

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