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 first additive and a second additive, and the first and second additives each comprise a compound represented by a specific chemical formula.

Description

[Technical Field]

[0001] This application claims priority rights under Korean Patent Application No. 10-2023-0046365 dated April 7, 2023, and Korean Patent Application No. 10-2023-0183781 dated December 15, 2023, and all content disclosed in the documents of the said Korean patent applications 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 one of the most suitable technologies for various applications among the electrical energy 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 a relatively high 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 also been considered due to their higher capacity compared to carbon-based active materials. [Overview of the project] [Problems that the invention aims to solve]

[0008] One objective of the present invention is to provide a non-aqueous electrolyte that enables the realization of a lithium secondary battery with improved lifespan and storage performance by forming an SEI (Solid Electrolyte Interphase) coating on the negative electrode that exhibits 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 first additive and a second additive, the first additive comprising a compound represented by the following chemical formula 1, and the second additive comprising a compound represented by the following chemical formula 2.

[0010] [ka]

[0011] [ka]

[0012] In the above chemical formula 1, R1 includes halogen, nitrile group, propargyl group, ester group, ether group, ketone group, carboxyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkoxy group, boron group, borate group, isocyanate group, isothiocyanate group, silyl group, siloxane group, sulfone group, sulfonate group, sulfate group, or two or more combinations thereof, and n is an integer from 0 to 6.

[0013] In the above chemical formula 2, R2 and R3 are independently selected from an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the following chemical formula 3, and at least one of R2 and R3 is selected from an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the following chemical formula 3, where m is an integer from 3 to 10.

[0014] [ka]

[0015] In the above chemical formula 3, L1 is a direct bond, an alkylene group having 1 to 10 carbon atoms, an ester group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more of these, R4 is an alkoxy group having 1 to 10 carbon atoms substituted with at least one fluorine atom, and * is a bonding site.

[0016] 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]

[0017] The non-aqueous electrolyte of the present invention is characterized by comprising, as additives, a first additive containing a compound of chemical formula 1 based on coumarin, and a second additive containing a compound of chemical formula 2 based on a cyclic siloxane. The first additive has strong reducing properties at the negative electrode, and a ring-opening reaction occurs rapidly during the formation of the initial SEI film, enabling the formation of a polymer-based SEI film, which contributes to the formation of an SEI film with excellent flexibility and resilience. The second additive can form a siloxane-based SEI film during negative electrode reduction, and contributes to the formation of an SEI film with a high shear modulus, excellent thermal safety, and excellent chemical and electrochemical safety. For example, radicals formed during the decomposition of the first additive promote the ring-opening reaction of the second additive, and through the organic action of the first and second additives, an SEI film with excellent flexibility, resilience, and durability can be formed on the negative electrode. As a result, lithium secondary batteries containing the non-aqueous electrolyte of the present invention can improve lifespan and storage performance, particularly at high temperatures. [Modes for carrying out the invention]

[0018] 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.

[0019] 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.

[0020] On the other hand, unless otherwise specified in the present invention, "*" means a connected portion (bonding site) between identical or different atoms or the terminal parts of a chemical formula.

[0021] 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.

[0022] 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.

[0023] As used herein, “approximately,” “abstractly,” and “substantially” are used to mean a range of numerical values ​​or degrees, or close to them, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly exploiting disclosures that refer to precise or absolute numerical values ​​provided for the understanding of the invention.

[0024] While silicon-based active materials have the advantage of high capacity when used as the negative electrode active material in lithium secondary batteries, they have the disadvantage of relatively large volume expansion / contraction during the charge / discharge process. Such large volume expansion / contraction reduces the conductivity of the negative electrode and causes a decrease in the lifespan of both the negative electrode and the lithium secondary battery. Furthermore, during the initial activation of a lithium secondary battery, a solid electrolyte interface layer (SEI film) is formed on the surface of the negative electrode. However, because silicon-based active materials expand significantly in volume, the SEI film cracks or new negative electrode surfaces are continuously generated. This leads to the continuous formation of the SEI film, accelerating electrolyte side reactions, increasing the thickness of the SEI film, and thus increasing resistance.

[0025] The non-aqueous electrolyte of the present invention provides a lithium secondary battery that overcomes these drawbacks by including, in addition to a lithium salt and an organic solvent, first and second additives represented by specific chemical formulas.

[0026] The present invention will be described in more detail below.

[0027] Non-aqueous electrolytes This invention relates to non-aqueous electrolytes.

[0028] For example, the non-aqueous electrolyte according to the present invention comprises a lithium salt, an organic solvent, and an additive, wherein the additive comprises a first additive and a second additive, the first additive comprises a compound represented by the following chemical formula 1, and the second additive comprises a compound represented by the following chemical formula 2.

[0029] [ka]

[0030] In the above chemical formula 1, R1 includes halogen, nitrile group, propargyl group, ester group, ether group, ketone group, carboxyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkoxy group, boron group, borate group, isocyanate group, isothiocyanate group, silyl group, siloxane group, sulfone group, sulfonate group, sulfate group, or two or more combinations thereof, and n is an integer from 0 to 6.

[0031] [ka]

[0032] In the above chemical formula 2, R2 and R3 are independently selected from an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the following chemical formula 3, and at least one of R2 and R3 is selected from an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the following chemical formula 3, where m is an integer from 3 to 10.

[0033] [ka]

[0034] In the above chemical formula 3, L1 is a direct bond, an alkylene group having 1 to 10 carbon atoms, an ester group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more of these, R4 is an alkoxy group having 1 to 10 carbon atoms substituted with at least one fluorine atom, and * is a bonding site.

[0035] (1) Lithium salt The lithium salt used in this invention is not limited to any particular lithium salt commonly used in non-aqueous electrolytes for lithium secondary batteries. For example, the lithium salt may contain Li as a cation. + It includes, 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 - 、および(CF3CF2SO2)2N - It may contain at least any one selected from the group consisting of.

[0036] For example, the lithium salt is 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).

[0037] The lithium salt may be included in the non-aqueous electrolyte at a concentration of about 0.5 M to 5 M, for example, about 0.8 M to 4 M, or about 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.

[0038] (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.

[0039] For example, 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.

[0040] Alternatively, the organic solvent may include a cyclic carbonate organic solvent, a linear carbonate organic solvent, or a mixture thereof.

[0041] The cyclic carbonate-based organic solvent is a highly viscous organic solvent with a high dielectric constant that readily dissociates lithium salts in the electrolyte. For example, 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, or it may contain at least one selected from the group consisting of ethylene carbonate (EC) and fluoroethylene carbonate (FEC). In one embodiment, fluoroethylene carbonate (FEC) may be included because it contributes to the formation of an inorganic (LiF)-containing SEI film.

[0042] Furthermore, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and may include, for example, at least one 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, or at least one selected from the group consisting of ethyl methyl carbonate (EMC) and diethyl carbonate (DEC). In one embodiment, diethyl carbonate (DEC) may be included because it can further improve the oxidative stability of the non-aqueous electrolyte.

[0043] The organic solvent may be a mixture of a cyclic carbonate organic solvent and a linear carbonate organic solvent. The cyclic carbonate organic solvent and the linear carbonate organic solvent may be mixed in a volume ratio of about 5:95 to 40:60, for example, about 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 properties can be satisfied, and excellent ionic conductivity properties can be achieved.

[0044] 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.

[0045] The linear ester organic solvent may include, for example, at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0046] Furthermore, the cyclic ester organic solvent may include, for example, at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0047] 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.

[0048] 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.

[0049] 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).

[0050] 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.

[0051] (3) Additives The non-aqueous electrolyte contains additives.

[0052] The aforementioned additive includes a first additive and a second additive.

[0053] The first additive contains a compound represented by the following chemical formula 1.

[0054] [ka]

[0055] In the above chemical formula 1, R1 includes halogen, nitrile group, propargyl group, ester group, ether group, ketone group, carboxyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkoxy group, boron group, borate group, isocyanate group, isothiocyanate group, silyl group, siloxane group, sulfone group, sulfonate group, sulfate group, or two or more combinations thereof, and n is an integer from 0 to 6.

[0056] The compound represented by chemical formula 1 contained in the first additive is, for example, a coumarin-based compound that exhibits strong reducing properties at the negative electrode and undergoes a rapid ring-opening reaction during the formation of the initial SEI film, thereby enabling the formation of a PEO-based polymer-type SEI film. Such a polymer-type SEI film exhibits excellent flexibility and resilience.

[0057] However, when the first additive is used alone, there is a risk that the thermal stability and chemical and electrochemical stability of the SEI coating will decrease, potentially leading to reduced durability. For example, when the first additive is used alone, it may be difficult to form a highly durable SEI coating on a negative electrode active material (e.g., a silicon-based active material) that undergoes volume expansion during charging and discharging. Furthermore, when the first additive is used alone, after the additive is reduced and radicals are formed, they may attack the carbonate-based solvent, potentially triggering an undesirable additional reduction reaction. For these reasons, the non-aqueous electrolyte according to the present invention uses a second additive based on a cyclic siloxane in combination with the first additive. By promoting the ring-opening reaction of the second additive through radical formation of the first additive, an SEI coating with excellent flexibility, resilience, and durability such as thermal stability can be formed on the negative electrode.

[0058] For example, the first additive has strong reducing properties at the negative electrode, and a rapid ring-opening reaction occurs during the formation of the initial SEI film, enabling the formation of a polymer-based SEI film, which contributes to the formation of an SEI film with excellent flexibility and resilience. The second additive can form a siloxane-based SEI film during negative electrode reduction, and contributes to the formation of an SEI film with a high shear modulus, excellent thermal safety, and excellent chemical and electrochemical safety. For example, the radicals formed during the decomposition of the first additive promote the ring-opening reaction of the second additive, and through the organic action of the first and second additives, an SEI film with excellent flexibility, resilience, and durability can be formed on the negative electrode. As a result, the lithium secondary battery containing the non-aqueous electrolyte according to the present invention can have improved lifespan and storage performance, particularly at high temperatures.

[0059] In the above chemical formula 1, R1 may be, for example, a halogen (the halogen may be selected from F, Cl, Br, and I, for example, F), a nitrile group, a propargyl group, an ester group, an ether group, or a combination of two or more of these. Such substituents can improve the reducing properties of the first additive, and can also improve lithium ion transfer performance along with the smooth formation of the SEI film of the first additive.

[0060] In the chemical formula 1, n may be an integer selected from 0 to 6, for example, an integer selected from 1 to 6, or n may be 1. In the chemical formula 1, if n is 2 or greater, each R1 may be the same or different from one another.

[0061] In one embodiment, the compound represented by chemical formula 1 may include at least one selected from the group consisting of the compound represented by chemical formula 1-A and the compound represented by chemical formula 1-B.

[0062] [ka]

[0063] [ka]

[0064] In the aforementioned chemical formulas 1-A and 1-B, R1 is defined as in the aforementioned chemical formula 1.

[0065] The compounds represented by chemical formulas 1-A and 1-B have substituents at positions 3 and 7 of the ring structure (according to IUPAC nomenclature standards), respectively, and it is advantageous to synthesize them at these positions compared to other substitution positions.

[0066] For example, the compound represented by chemical formula 1 may include at least one selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-9. The compound represented by chemical formula 1 may include at least one selected from the group consisting of compounds represented by the following chemical formulas 1-1, 1-2, 1-3, and 1-4, since it is smoothly reduced by the negative electrode and is more advantageous in the formation of the SEI film, or in one embodiment it may include the compound represented by the following chemical formula 1-4.

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[0075] [ka]

[0076] The first additive may be present in the non-aqueous electrolyte in an amount of about 0.01% to 10% by weight, for example, about 0.05% to 7% by weight, about 0.1% to 2% by weight, or about 0.3% to 1% by weight. When the first additive is used within the above content range, a flexible and durable SEI coating can be formed on the negative electrode, and an increase in resistance in the event of excessive addition can be prevented.

[0077] The second additive may contain a compound represented by the following chemical formula 2.

[0078] [ka]

[0079] In the above chemical formula 2, R2 and R3 are independently selected from an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the following chemical formula 3, and at least one of R2 and R3 is selected from an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the following chemical formula 3, where m is an integer from 3 to 10.

[0080] [ka]

[0081] In the above chemical formula 3, L1 is a direct bond, an alkylene group having 1 to 10 carbon atoms, an ester group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more of these, R4 is an alkoxy group having 1 to 10 carbon atoms substituted with at least one fluorine atom, and * is a bonding site.

[0082] The second additive can form a siloxane-based SEI film during negative electrode reduction, and can contribute to the formation of an SEI film with a high shear modulus and excellent thermal, chemical, and electrochemical safety.

[0083] However, the second additive has a relatively low tendency to be reduced itself, so when used alone, it presents a problem in that a smooth ring-opening reaction is difficult. Therefore, when the second additive is used alone, it may be difficult to form the SEI film itself. However, the non-aqueous electrolyte according to the present invention is characterized by the use of the first additive in combination with the second additive. When the first additive is rapidly decomposed and forms radicals during initial activation, these radicals can promote the ring-opening reaction of the second additive. As a result, the organic action of the first and second additives makes it possible to form an SEI film on the negative electrode that is excellent in flexibility and resilience, as well as significantly improved durability. For example, the effect of using the first and second additives in combination can be further maximized when a silicon-based active material that undergoes a large volume change during charging and discharging is used as the negative electrode active material.

[0084] In the above chemical formula 2, R2 and R3 are independently selected from an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the above chemical formula 3. In this case, at least one of R2 and R3 is selected from an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the above chemical formula 3. In this case, for example, the reduction reaction of a cyclic siloxane compound can be further accelerated.

[0085] For example, R2 and R3 may be independently selected from C1-C5 alkyl groups, C2-C5 alkenyl groups, C2-C5 alkynyl groups, and substituents represented by the following chemical formula 3-1, and at least one of R2 and R3 may be selected from C2-C5 alkenyl groups, C2-C5 alkynyl groups, and substituents represented by the following chemical formula 3-1.

[0086] [ka]

[0087] In the above chemical formula 3-1, L1 is an alkylene group, a sulfone group, or a combination thereof having 1 to 5 carbon atoms, R4 is an alkoxy group having 1 to 5 carbon atoms substituted with at least one fluorine atom, and * is a bonding site.

[0088] For example, R2 and R3 may be independently selected from C1-C3 alkyl groups, C2-C3 alkenyl groups, C2-C3 alkynyl groups, and substituents represented by the following chemical formula 3-2, and at least one of R2 and R3 may be selected from C2-C3 alkenyl groups, C2-C3 alkynyl groups, and substituents represented by the following chemical formula 3-2. When the above range is used, an increase in resistance due to the inclusion of an excessive number of carbon atoms is prevented.

[0089] [ka]

[0090] In the above chemical formula 3-2, L1 is a methylene group, an ethylene group, a sulfone group, or a combination of two or more of these, R4 is one selected from the group consisting of -OCF3, -OCF2CF3, and -OCF2CF2CF3, and * is a binding site.

[0091] On the other hand, in Chemical Formula 2, R2 may be an alkyl group having 1 to 10 carbon atoms, for example, an alkyl group having 1 to 5 carbon atoms, more specifically, an alkyl group having 1 to 3 carbon atoms. Also, in Chemical Formula 2, R3 may be selected from an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by Chemical Formula 3, or it may be selected from an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, and a substituent represented by Chemical Formula 3-1, or it may be selected from an alkenyl group having 2 to 3 carbon atoms, an alkynyl group having 2 to 3 carbon atoms, and a substituent represented by Chemical Formula 3-2. When R2 is an alkyl group and R3 is an unsaturated hydrocarbon group or a fluorine-substituted alkoxy group, an increase in resistance due to the presence of an excessive amount of unsaturated hydrocarbon groups is prevented.

[0092] The compound represented by chemical formula 2 may include, for example, at least one selected from the group consisting of compounds represented by the following chemical formulas 2-1 to 2-16, at least one selected from the group consisting of compounds represented by the following chemical formulas 2-1, 2-3, 2-4, 2-5, 2-7, 2-13, and 2-14, at least one selected from the group consisting of compounds represented by the following chemical formulas 2-1, 2-3, 2-5, and 2-7, or, in one embodiment, it may include the compound represented by the following chemical formula 2-3.

[0093] [ka]

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[0109] The second additive may be included in the non-aqueous electrolyte in an amount of about 0.01% to 10% by weight, for example, about 0.05% to 7% by weight, about 0.1% to 2% by weight, or about 0.3% to 1% by weight. When the content of the second additive satisfies the above range, it effectively forms an SEI coating with excellent durability, such as thermal stability, and prevents an increase in the resistance of the lithium secondary battery due to excessive addition, and the resulting decrease in lifespan performance.

[0110] The weight ratio of the first additive and the second additive may be approximately 1:99 to 99:1, for example, 15:85 to 85:15, or 40:60 to 60:40. When the weight ratio is as described above, the effects of using the first and second additives in combination are well-balanced, and as a result, improvements in the high-temperature life performance, high-temperature storage performance, and safety of the lithium secondary battery can be desirablely achieved.

[0111] The additive may further include an additional additive (third additive) along with the first and second additives. The additional additive may be included in the non-aqueous electrolyte to prevent decomposition of the non-aqueous electrolyte and subsequent anode collapse 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.

[0112] For example, the additional additive may be at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiBOB (Lithium bis-(oxalato)borate), TMSPa (3-trimethoxysilanyl-propyl-N-aniline), and TMSPi (Tris(trimethylsilyl)Phosphite), and may be vinylene carbonate, for example.

[0113] The aforementioned additional additive may be included in the non-aqueous electrolyte in an amount of about 0.1% to 15% by weight.

[0114] Lithium-ion rechargeable battery Furthermore, the present invention provides a lithium secondary battery containing the aforementioned non-aqueous electrolyte.

[0115] 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.

[0116] 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.

[0117] As explained above, the negative electrode, positive electrode, and separator will be described below.

[0118] (1) Negative electrode The aforementioned negative electrode contains a negative electrode active material.

[0119] The anode active material can be any substance used as an anode active material in the field, without limitation. The anode active material may include, for example, at least one selected from silicon-based active materials and carbon-based active materials, or it may include a silicon-based active material.

[0120] 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 non-aqueous electrolyte of the present invention 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.

[0121] The silicon-based active material may contain a compound represented by the following chemical formula A.

[0122] [Chemical formula A] SiO x (0≦x<2)

[0123] In the above chemical formula A, SiO2 does not react with lithium ions and therefore cannot store lithium; therefore, x may be within the above range.

[0124] The average particle size (D) of the silicon-based active material 50 The size of the ) can be approximately 1 μm to 20 μm.

[0125] 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 in one embodiment, it may include graphite. The graphite may include at least one selected from the group consisting of artificial graphite and natural graphite.

[0126] The average particle size (D) of the carbon-based active material 50 The thickness of the ) can be approximately 10 μm to 30 μm, for example, approximately 15 μm to 25 μm, in order to ensure structural stability during charging and discharging and to reduce side reactions with the electrolyte.

[0127] 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. The negative electrode active material is contained in the negative electrode active material layer.

[0128] 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. For example, 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 an aluminum-cadmium alloy.

[0129] The negative electrode current collector typically has a thickness of approximately 3 μm to 500 μm.

[0130] 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.

[0131] The negative electrode active material layer is disposed on at least one side of the negative electrode current collector. For example, the negative electrode active material layer may be disposed on one or both sides of the negative electrode current collector.

[0132] The negative electrode active material may be included in the negative electrode active material layer in an amount of approximately 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.

[0133] The negative electrode active material layer may further contain a conductive material and / or a binder together with the silicon-based active material.

[0134] 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.

[0135] For example, 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.

[0136] The binder may be present in the negative electrode active material layer in an amount of about 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.

[0137] 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. For example, 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.

[0138] The conductive material may be included in the negative electrode active material layer in an amount of about 1% to 20% by weight. When the amount is within this range, it can mitigate the increase in resistance due to the binder and form an excellent conductive network.

[0139] The thickness of the negative electrode active material layer may be approximately 5 μm to 500 μm, for example, 5 μm to 100 μm.

[0140] The negative electrode can be manufactured by coating 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 onto the negative electrode current collector, followed by drying and rolling.

[0141] The solvent for forming the negative electrode slurry includes, for example, at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, in order to facilitate the dispersion of the negative electrode active material, binder, and / or conductive material, and in one embodiment may include distilled water.

[0142] (2) Positive electrode The positive electrode includes a positive electrode active material.

[0143] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and includes, for example, a lithium transition metal composite oxide containing at least one transition metal selected from nickel, cobalt, manganese, and aluminum and lithium, or a lithium transition metal composite oxide containing a transition metal containing nickel, cobalt, and manganese and lithium.

[0144] For example, examples of the lithium transition metal composite oxide include 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 any one or more of these compounds may be included. Among them, from the viewpoint of enhancing the capacity characteristics and stability of the battery, the lithium transition metal composite oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel-manganese-cobalt oxide (e.g., 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.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), 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 may be Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc., and any one or more of these mixtures may be used.

[0145] In one embodiment, the positive electrode active material may be a lithium transition metal composite oxide containing about 60 mol% or more nickel based on the total number of moles of transition metal contained in the lithium transition metal composite oxide. For example, the positive electrode active material may be a lithium transition metal composite oxide in which the transition metal comprises nickel and at least one selected from manganese, cobalt, and aluminum, and the nickel may be contained in an amount of about 60 mol% or more, for example, about 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, the amount of by-products in the gas generated by structural collapse can be reduced.

[0146] Furthermore, the positive electrode active material may contain a lithium composite transition metal oxide represented by the following chemical formula B.

[0147] [Chemical formula B] Li 1+x (Ni a Co b Mn c M d )O2

[0148] 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。

[0149] In one embodiment, a, b, c, and d may be 0.70 ≤ a ≤ 0.95, 0.025 ≤ b ≤ 0.20, 0.025 ≤ c ≤ 0.20, and 0 ≤ d ≤ 0.05, respectively.

[0150] 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.

[0151] 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.

[0152] 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. The positive electrode active material layer may include the positive electrode active material described above.

[0153] The thickness of the positive electrode current collector is typically about 3 μm to 500 μm.

[0154] 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.

[0155] The positive electrode active material layer is disposed on at least one side of the positive electrode current collector. For example, the positive electrode active material layer may be disposed on one or both sides of the positive electrode current collector.

[0156] The positive electrode active material may be included in the positive electrode active material layer in an amount of approximately 80% to 99% by weight, taking into consideration the sufficient capacity exertion of the positive electrode active material.

[0157] The positive electrode active material layer may further include a binder and / or a conductive material along with the positive electrode active material.

[0158] The binder is a component that assists in the bonding of the active material to the conductive material and to the current collector, and may include, for example, 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.

[0159] The binder may be included in the positive electrode active material layer in an amount of approximately 1% to 20% by weight, or approximately 1.2% to 10% by weight, in order to ensure sufficient binding force between components such as the positive electrode active material.

[0160] 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. For example, the positive electrode 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; 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. In one embodiment, carbon nanotubes may be included to improve conductivity.

[0161] The conductive material may be included in the positive electrode active material layer in an amount of about 1% to 20% by weight, for example, about 1.2% to 10% by weight, in order to ensure sufficient electrical conductivity.

[0162] The thickness of the positive electrode active material layer may be approximately 5 μm to 500 μm, preferably 20 μm to 200 μm.

[0163] The positive electrode can be manufactured by coating a positive electrode slurry containing a positive electrode active material, and selectively a binder, a conductive material, and a solvent for forming the positive electrode slurry onto the positive electrode current collector, followed by drying and rolling.

[0164] (3) Separator The separator can be interposed between the positive electrode and the negative electrode.

[0165] The separator may be a conventional porous polymer film, such as a polyolefin polymer like ethylene monopolymer, propylene monopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, or ethylene / methacrylate copolymer, used alone or in a laminated configuration. 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.

[0166] 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.

[0167] The present invention will be described more specifically below with reference to 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.

[0168] 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) at a volume ratio of 10:90 was used.

[0169] To the organic solvent, LiPF6 as a lithium salt, the compound represented by the chemical formula 1-4 as a first additive, and the compound represented by the chemical formula 2-3 as a second additive were added to manufacture a non-aqueous electrolyte.

[0170] The LiPF6 was contained in the non-aqueous electrolyte at a molar concentration of 1.5M.

[0171] The compound represented by the chemical formula 1-4 was contained in the non-aqueous electrolyte at 0.5% by weight, and the compound represented by the chemical formula 2-3 was contained in the non-aqueous electrolyte at 0.5% by weight.

[0172] (Manufacture of Lithium Secondary Battery) A cathode 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 at a weight ratio of 97.74:0.70:1.56 to manufacture a cathode mixture slurry (solid content 75.5% by weight). The cathode mixture slurry was applied to one side of a cathode current collector (Al thin film) with a thickness of 12 μm, and drying and roll press were performed to manufacture a cathode.

[0173] An anode 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 at a weight ratio of 70.0:20.3:9.7 to manufacture an anode mixture slurry (solid content 26% by weight). The anode mixture slurry was applied to one side of an anode current collector (Cu thin film) with a thickness of 15 μm, and drying and roll press were performed to manufacture an anode.

[0174] 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.

[0175] 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 in a content of 0.5% by weight, instead of the compound represented by chemical formula 1-4, as the first additive. For example, in Example 2, a different compound represented by chemical formula 1-1 from that of Example 1 was used as the first additive, and the compound represented by chemical formula 2-3 was used as the second additive, similar to that of Example 1, to manufacture a non-aqueous electrolyte and a lithium secondary battery.

[0176] 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 2-1 was added to the non-aqueous electrolyte in a content of 0.5% by weight, instead of the compound represented by chemical formula 2-3, as a second additive. For example, in Example 3, the compound represented by chemical formula 1-4 was used as the first additive, as in Example 1, and a different compound represented by chemical formula 2-1 was used as the second additive to manufacture a non-aqueous electrolyte and a lithium secondary battery.

[0177] Example 4 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first additive was added to the non-aqueous electrolyte at a content of 0.1% by weight instead of 0.5% by weight. For example, in Example 4, the compound represented by chemical formula 1-4 was used as the first additive and the compound represented by chemical formula 2-3 was used as the second additive, as in Example 1, but the first additive was used at a different content of 0.1% by weight than in Example 1, to manufacture the non-aqueous electrolyte and lithium secondary battery.

[0178] Example 5 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first additive was added to the non-aqueous electrolyte at a content of 2% by weight instead of 0.5% by weight. For example, in Example 5, the compound represented by chemical formula 1-4 was used as the first additive and the compound represented by chemical formula 2-3 was used as the second additive, as in Example 1, but the first additive was used at a different content of 2% by weight than in Example 1, to manufacture a non-aqueous electrolyte and a lithium secondary battery.

[0179] Example 6 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the second additive was added to the non-aqueous electrolyte at a content of 0.1% by weight instead of 0.5% by weight. For example, in Example 6, the compound represented by chemical formula 1-4 was used as the first additive and the compound represented by chemical formula 2-3 was used as the second additive, as in Example 1, but the content of the second additive was 0.1% by weight, a different content from Example 1, to manufacture the non-aqueous electrolyte and lithium secondary battery.

[0180] Example 7 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the second additive was added to the non-aqueous electrolyte at a content of 2% by weight instead of 0.5% by weight. For example, in Example 7, the compound represented by chemical formula 1-4 was used as the first additive and the compound represented by chemical formula 2-3 was used as the second additive, as in Example 1, but the content of the second additive was 2% by weight, a different content from Example 1, to manufacture the non-aqueous electrolyte and lithium secondary battery.

[0181] Example 8 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 1-2 was added to the non-aqueous electrolyte in a content of 0.5% by weight, instead of the compound represented by chemical formula 1-4, as the first additive. For example, in Example 8, a non-aqueous electrolyte and a lithium secondary battery were manufactured using a compound represented by chemical formula 1-2 different from that used in Example 1 as the first additive, and using a compound represented by chemical formula 2-3 as the second additive, similar to that used in Example 1.

[0182] Example 9 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 1-3 was added to the non-aqueous electrolyte in a content of 0.5% by weight, instead of the compound represented by chemical formula 1-4, as the first additive. For example, in Example 9, a non-aqueous electrolyte and a lithium secondary battery were manufactured using a compound represented by chemical formula 1-3 different from that used in Example 1 as the first additive, and using a compound represented by chemical formula 2-3 as the second additive, similar to that used in Example 1.

[0183] Example 10 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 1-8 was added to the non-aqueous electrolyte at a content of 0.5% by weight, instead of the compound represented by chemical formula 1-4, as the first additive. For example, in Example 10, a different compound represented by chemical formula 1-8 from that of Example 1 was used as the first additive, and a compound represented by chemical formula 2-3, similar to that of Example 1, was used as the second additive to manufacture a non-aqueous electrolyte and a lithium secondary battery.

[0184] Example 11 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that, as a second additive, the compound represented by chemical formula 2-4 was added to the non-aqueous electrolyte in a content of 0.5% by weight, instead of the compound represented by chemical formula 2-3.

[0185] Example 12 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that, as a second additive, the compound represented by chemical formula 2-5 was added to the non-aqueous electrolyte in a content of 0.5% by weight, instead of the compound represented by chemical formula 2-3.

[0186] Example 13 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that, as a second additive, the compound represented by chemical formula 2-13 was added to the non-aqueous electrolyte in a content of 0.5% by weight, instead of the compound represented by chemical formula 2-3.

[0187] 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 first and second additives were not added. For example, in Comparative Example 1, a non-aqueous electrolyte and a lithium secondary battery were manufactured without using the additives added in Example 1.

[0188] Comparative Example 2 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the second additive was not added.

[0189] Comparative Example 3 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first additive was not added. For example, in Comparative Example 3, the first additive used in Example 1 was not used, but the second additive was used to manufacture the non-aqueous electrolyte and lithium secondary battery.

[0190] Experimental example Experimental Example 1: Evaluation of High-Temperature Cycle Performance The lithium secondary batteries of Examples 1-13 and Comparative Examples 1-3, manufactured as described above, were charged to 4.2V and 0.05C at 45°C under CC / CV and 0.33C conditions using an electrochemical charger / discharger. One cycle consisted of charging to 3.0V under CC and 0.33C conditions, and 200 charge / discharge cycles were performed.

[0191] The capacity retention rate was calculated using the following formula, and the results are shown in Table 1 below.

[0192] Capacity retention rate (%) = {(Discharge capacity after 200 cycles / Discharge capacity after 1 cycle)} × 100

[0193] Experimental Example 2: Evaluation of High-Temperature Storage Performance The lithium secondary batteries of Examples 1-13 and Comparative Examples 1-3, 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 3.0V 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.

[0194] 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.

[0195] The capacity retention rate was evaluated using the following formula, and the results are shown in Table 1 below.

[0196] Capacity retention rate (%) = (Discharge capacity after 8 weeks of storage / Initial discharge capacity) × 100

[0197] [Table 1]

[0198] Referring to Table 1 above, the lithium secondary batteries of Examples 1 to 13 manufactured using the non-aqueous electrolyte according to the present invention have a capacity retention rate of 80% or more after 200 cycles and after 8 weeks of storage, respectively. In contrast, Comparative Examples 1 to 3 to which the present invention is not applied show a capacity retention rate of 80% or less under the same conditions. It was confirmed that the lithium secondary batteries of Examples 1 to 13 to which the present invention was applied exhibited a significantly superior level of capacity retention rate during high-temperature cycle charge and discharge and high-temperature storage compared to Comparative Examples 1 to 3. That is, it can be seen that the lithium secondary battery containing the non-aqueous electrolyte according to the present invention containing the above-described first additive and second additive has improved life performance and storage performance, and particularly improved life performance and storage performance at high temperatures.

[0199] As described above, the embodiments of the present invention have been described with reference thereto. However, those skilled in the relevant technical field or those having ordinary knowledge in the relevant technical field can understand that the present invention can be variously modified and changed without departing from the spirit and technical scope of the present invention described in the appended claims. Therefore, the technical scope of the present invention is not limited to the content described in the detailed description of the specification, but is determined only by the claims.

Claims

1. It contains lithium salts, organic solvents, and additives. The aforementioned additive includes a first additive and a second additive, The first additive comprises a compound represented by the following chemical formula 1, The second additive is a non-aqueous electrolyte containing a compound represented by the following chemical formula 2. 【Chemistry 1】 【Chemistry 2】 In the above chemical formula 1, R １ n includes halogens, nitrile groups, propargyl groups, ester groups, ether groups, ketone groups, carboxyl groups, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkoxy groups, boron groups, borate groups, isocyanate groups, isothiocyanate groups, silyl groups, siloxane groups, sulfone groups, sulfonate groups, sulfate groups, or two or more combinations thereof, where n is an integer from 0 to 6. In the above chemical formula 2, R ２ and R ３ R is independently selected from alkyl groups having 1 to 10 carbon atoms, alkenyl groups having 2 to 10 carbon atoms, alkynyl groups having 2 to 10 carbon atoms, and substituents represented by the following chemical formula 3. ２ and R ３ At least one of is selected from an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the following chemical formula 3, where m is an integer from 3 to 10. 【Transformation 3】 In the above chemical formula 3, L １ R is a direct bond, an alkylene group having 1 to 10 carbon atoms, an ester group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more of these. ４ This is an alkoxy group having 1 to 10 carbon atoms with at least one fluorine atom substituted, and * indicates a bonding site.

2. The non-aqueous electrolyte according to claim 1, wherein the compound represented by chemical formula 1 includes at least one selected from the group consisting of the compound represented by the following chemical formula 1-A and the compound represented by the following chemical formula 1-B. 【Chemistry 4】 【Transformation 5】 In the aforementioned chemical formulas 1-A and 1-B, R １ This is as defined in Chemical Formula 1 above.

3. The non-aqueous electrolyte according to claim 1, wherein the compound represented by chemical formula 1 includes at least one selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-9. 【Transformation 6】 【Transformation 7】 【Transformation 8】 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】 【Chemistry 13】 【Chemistry 14】

4. The nonaqueous electrolyte according to claim 1, wherein the first additive is contained in an amount of 0.01% to 10% by weight based on the weight of the nonaqueous electrolyte.

5. In the above chemical formula (2), R ２ is an alkyl group having 1 to 10 carbon atoms, and R ３ is selected from an alkenyl group having 2 to 10 carbon atoms and an alkynyl group having 2 to 10 carbon atoms. The non-aqueous electrolyte according to claim 1.

6. The non-aqueous electrolyte according to claim 1, wherein the compound represented by chemical formula 2 includes at least one selected from the group consisting of compounds represented by the following chemical formulas 2-1 to 2-16. 【Chemistry 15】 【Chemistry 16】 【Chemistry 17】 [Chemistry 18] 【Chemistry 19】 【Chemistry 20】 【Chemistry 21】 【Chemistry 22】 【Chemistry 23】 【Chemistry 24】 【Chemistry 25】 【Chemistry 26】 【Chemistry 27】 【Chemistry 28】 【Chemistry 29】 【Transformation 30】

7. The nonaqueous electrolyte according to claim 1, wherein the second additive is included in an amount of 0.01% to 10% by weight based on the weight of the nonaqueous electrolyte.

8. The non-aqueous electrolyte according to claim 1, wherein the weight ratio of the first additive and the second additive is about 1:99 to 99:

1.

9. 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 ).

10. 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.

11. 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.

12. The aforementioned organic solvents include cyclic carbonate organic solvents and linear carbonate organic solvents. The aforementioned cyclic carbonate-based organic solvent includes fluoroethylene carbonate. The non-aqueous electrolyte according to claim 1, wherein the linear carbonate-based organic solvent comprises diethyl carbonate.

13. 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 a non-aqueous electrolyte, The aforementioned non-aqueous electrolyte is It contains lithium salts, organic solvents, and additives. The aforementioned additive includes a first additive and a second additive, The first additive comprises a compound represented by the following chemical formula 1, A lithium secondary battery comprising the second additive, which is represented by the following chemical formula 2. 【Chemistry 31】 【Chemistry 32】 In the above chemical formula 1, R １ n includes halogens, nitrile groups, propargyl groups, ester groups, ether groups, ketone groups, carboxyl groups, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkoxy groups, boron groups, borate groups, isocyanate groups, isothiocyanate groups, silyl groups, siloxane groups, sulfone groups, sulfonate groups, sulfate groups, or two or more combinations thereof, where n is an integer from 0 to 6. In the above chemical formula 2, R ２ and R ３ R is independently selected from alkyl groups having 1 to 10 carbon atoms, alkenyl groups having 2 to 10 carbon atoms, alkynyl groups having 2 to 10 carbon atoms, and substituents represented by the following chemical formula 3. ２ and R ３ At least one of is selected from an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the following chemical formula 3, where m is an integer from 3 to 10. 【Transformation 33】 In the above chemical formula 3, L １ R is a direct bond, an alkylene group having 1 to 10 carbon atoms, an ester group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more of these. ４ This is an alkoxy group having 1 to 10 carbon atoms with at least one fluorine atom substituted, and * indicates a bonding site.

14. The aforementioned negative electrode includes a negative electrode active material. The lithium secondary battery according to claim 13, wherein the negative electrode active material includes a silicon-based active material.

15. The step includes adding lithium salts and additives to an organic solvent, The aforementioned additive includes a first additive and a second additive, The first additive comprises a compound represented by the following chemical formula 1, A method for producing a non-aqueous electrolyte, wherein the second additive contains a compound represented by the following chemical formula 2. 【Transformation 34】 【Chemistry 35】 In the above chemical formula 1, R １ n includes halogens, nitrile groups, propargyl groups, ester groups, ether groups, ketone groups, carboxyl groups, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkoxy groups, boron groups, borate groups, isocyanate groups, isothiocyanate groups, silyl groups, siloxane groups, sulfone groups, sulfonate groups, sulfate groups, or two or more combinations thereof, where n is an integer from 0 to 6. In the above chemical formula 2, R ２ and R ３ R is independently selected from alkyl groups having 1 to 10 carbon atoms, alkenyl groups having 2 to 10 carbon atoms, alkynyl groups having 2 to 10 carbon atoms, and substituents represented by the following chemical formula 3. ２ and R ３ At least one of is selected from an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a substituent represented by the following chemical formula 3, where m is an integer from 3 to 10. 【Transformation 36】 In the above chemical formula 3, L １ R is a direct bond, an alkylene group having 1 to 10 carbon atoms, an ester group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more of these. ４ This is an alkoxy group having 1 to 10 carbon atoms with at least one fluorine atom substituted, and * indicates a bonding site.

16. The method for producing a non-aqueous electrolyte according to claim 15, wherein the compound represented by chemical formula 1 includes at least one selected from the group consisting of the compound represented by the following chemical formula 1-A and the compound represented by the following chemical formula 1-B. 【Chemistry 37】 【Transformation 38】 In the aforementioned chemical formulas 1-A and 1-B, R １ This is as defined in Chemical Formula 1 above.

17. The method for producing a non-aqueous electrolyte according to claim 15, wherein the compound represented by chemical formula 1 includes at least one selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-9. 【Chemistry 39】 【Chemistry 40】 【Chemistry 41】 【Chemistry 42】 【Chemistry 43】 【Chemistry 44】 【Chemistry 45】 【Chemistry 46】 【Chemistry 47】

18. The method for producing a non-aqueous electrolyte according to claim 15, wherein the first additive is included in an amount of 0.01% to 10% by weight based on the weight of the non-aqueous electrolyte.

19. In the above chemical formula 2, R ２ R is an alkyl group having 1 to 10 carbon atoms. ３ The method for producing a non-aqueous electrolyte according to claim 15, wherein is selected from an alkenyl group having 2 to 10 carbon atoms and an alkynyl group having 2 to 10 carbon atoms.

20. The method for producing a non-aqueous electrolyte according to claim 15, wherein the compound represented by chemical formula 2 includes at least one selected from the group consisting of compounds represented by the following chemical formulas 2-1 to 2-16. 【Chemistry 48】 【Chemistry 49】 [Transformation 50] 【Chemistry 51】 【Chemistry 52】 【Chemistry 53】 【Chemistry 54】 【Transformation 55】 【Transformation 56】 【Chemistry 57】 【Chemistry 58】 【Chemistry 59】 【Transformation 60】 【Chemistry 61】 【Transformation 62】 【Transformation 63】

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