Nonaqueous electrolyte containing additive for nonaqueous electrolyte and lithium secondary battery containing the same

Abstract

The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, a compound represented by the following Chemical Formula 1 as a first additive, and a polymer including repeating units represented by the following Chemical Formulas 2-1, 2-2, and 2-3 as a second additive. JPEG2024531441000029.jpg52170 (In the above Chemical Formula 1, R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms, and R1 to R3 are each independently H, an alkyl group having 1 to 3 carbon atoms, or a nitrile group. In the above Chemical Formula 2-1, R4 is any one selected from the group consisting of H and the like. In the above Chemical Formula 2-2, R a is an alkyl group having 1 to 10 carbon atoms substituted with one or more nitrile groups, and R5 is any one selected from the group consisting of H, etc. In the above Chemical Formula 2-3, R b is a fluoroalkyl group having 1 to 10 carbon atoms, and R6 is any one selected from the group consisting of H, etc.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0005271, filed on January 13, 2022, and all the contents disclosed in the document of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to a non-aqueous electrolyte containing an additive for a non-aqueous electrolyte and a lithium secondary battery including the same.

Background Art

[0003] In recent years, the application fields of lithium secondary batteries have rapidly expanded not only to power supply for electronic devices such as electric, electronic, communication, and computer devices but also to power storage and supply for large-area devices such as automobiles and power storage devices. Along with this, the demand for secondary batteries with high capacity, high output, and high stability has been increasing.

[0004] Particularly, in lithium secondary batteries for automotive applications, high capacity, high output, and long-term life characteristics are important. For increasing the capacity of secondary batteries, a positive electrode active material with a high nickel content having high energy density but low stability may be used, or the secondary battery may be driven at a high voltage.

[0005] However, when driving a secondary battery under the above conditions, as charge and discharge progress, due to side reactions caused by deterioration of the electrolyte, the film formed on the surface of the positive / negative electrode or the structure of the electrode surface deteriorates, and transition metal ions may be eluted from the surface of the positive electrode. In this way, since the eluted transition metal ions are electrodeposited on the negative electrode and the passivation ability of the SEI is reduced, a problem occurs in that the negative electrode deteriorates.

[0006] Such a deterioration phenomenon of the secondary battery tends to accelerate when the potential of the positive electrode increases or the battery is exposed to a high temperature, and due to the deterioration phenomenon, a problem occurs in that the cycle characteristics of the secondary battery deteriorate.

[0007] In addition, when a lithium-ion battery is used continuously for a long time or left at a high temperature, a so-called swelling phenomenon occurs in which gas is generated and the thickness of the battery increases. The amount of gas generated at this time is known to depend on the state of such SEI.

[0008] Therefore, in order to solve such problems, research and development have been conducted on a method that can suppress the elution of metal ions in the positive electrode, form a stable SEI film on the negative electrode, reduce the swelling phenomenon of the secondary battery, and enhance the stability at high temperatures.

Summary of the Invention

Problems to be Solved by the Invention

[0009] As a result of conducting comprehensive research to solve the above problems, an object of the present invention is to provide an additive for non-aqueous electrolytes that can suppress the deterioration of the positive electrode, reduce the side reaction between the positive electrode and the electrolyte, and form a stable SEI film on the negative electrode.

[0010] Another object of the present invention is to provide a non-aqueous electrolyte having enhanced stability at high temperatures by including the additive for non-aqueous electrolytes.

[0011] Furthermore, an object of the present invention is to provide a lithium secondary battery in which the high-temperature cycle characteristics and high-temperature storage characteristics are improved and various performances are enhanced by including the non-aqueous electrolyte.

Means for Solving the Problems

[0012] To achieve the above object, the present invention provides a non-aqueous electrolyte including a lithium salt, an organic solvent, a compound represented by the following Chemical Formula 1 as a first additive, and a polymer including repeating units represented by the following Chemical Formula 2-1, Chemical Formula 2-2, and Chemical Formula 2-3 as a second additive.

[0013]

Chem.

[0014] In the chemical formula 1, R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms, and R 1 ~R 3 are each independently H, an alkyl group having 1 to 3 carbon atoms, or a nitrile group.

[0015]

Chemical formula

[0016] In the chemical formula 2-1, R 4 is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group.

[0017]

Chemical formula

[0018] In the chemical formula 2-2, R a is an alkyl group having 1 to 10 carbon atoms substituted with one or more nitrile groups, and R 5 is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group.

[0019]

Chemical formula

[0020] In the chemical formula 2-3, R b is a fluoroalkyl group having 1 to 10 carbon atoms, and R 6is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group.

[0021] The present invention also provides a lithium secondary battery containing the non-aqueous electrolyte.

Advantages of the Invention

[0022] The first additive according to the present invention is a compound containing both a propargyl group known to have metal ion adsorption performance and an imidazole group effective for the formation of an SEI film, and can form a stable ion-conductive film on the surface of the negative electrode. Thus, the generation of gas due to the side reaction between the positive electrode and the electrolyte can be suppressed, and the swelling of the cell can be significantly reduced.

[0023] The second additive according to the present invention can form a strong SEI (Solid Electrolyte Interphase) film having elasticity on the surface of the negative electrode. Thereby, a strong SEI layer is maintained even at high temperatures, preventing the deterioration of the negative electrode and suppressing the additional SEI formation reaction due to the decomposition of the solvent during the progress of the cycle.

[0024] Furthermore, when the first additive forms a polymeric SEI film, the second additive acts together to impart elasticity to the SEI film, thereby strengthening the strength of the SEI film. Thus, the film is not broken even against the drastic volume change of the negative electrode during charge and discharge, so that the negative electrode and the electrolyte do not form a new interface. Thereby, the additional decomposition reaction of the electrolyte during the charge and discharge process can be suppressed, and there is an effect of reducing the expansion of the cell due to the generation of gas.

[0025] That is, when the non-aqueous electrolyte of the present invention containing the polymer provided as an additive for the non-aqueous electrolyte of the present invention is used, an electrode-electrolyte interface that is stable even at high temperatures and has high durability can be formed. Therefore, a lithium secondary battery with improved high-temperature cycle characteristics and high-temperature storage characteristics and enhanced various performances can be realized.

Embodiments for Carrying Out the Invention

[0026] The terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings. The inventors should interpret them in accordance with the meaning and concept that conform to the technical idea of the present invention, in accordance with the principle that they can appropriately define the concept of the terms in order to explain their invention in the best way.

[0027] In this specification, terms such as "comprising", "including", or "having" are intended to specify the presence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the presence or addition possibility of one or more other features, numbers, steps, components, or combinations thereof.

[0028] Also, in this specification, in the description of "having a carbon number of a to b", "a" and "b" mean the number of carbon atoms contained in a specific functional group. That is, the functional group may contain "a" to "b" carbon atoms. For example, "an alkylene group having a carbon number of 1 to 5" means an alkylene group containing 1 to 5 carbon atoms, that is, -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, -CH 2 (CH 3 )CH-, -CH(CH 3 )CH 2 -, and -CH(CH 3 )CH 2 CH 2 - and the like.

[0029] Also, in this specification, the term "alkylene group" means a branched or unbranched divalent saturated hydrocarbon group.

[0030] Also, in this specification, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a cycloalkyl group, a cycloalkenyl group, and an aryl group may or may not be substituted. The "substitution" means that at least one or more hydrogens bonded to carbon are substituted with an element other than hydrogen, unless otherwise defined. For example, it means being substituted with an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkenyl group having 3 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, etc.

[0031] Hereinafter, the present invention will be described in detail.

[0032] 〔Non-aqueous electrolyte〕 The non-aqueous electrolyte according to the present invention may contain a second additive together with the first additive of the following Chemical Formula 1.

[0033]

Chemical formula

[0034] The first additive compound represented by the chemical formula 1 contains a propargyl group having a triple bond known to have metal ion adsorption performance and an oxygen atom. The propargyl group separated by the cleavage of the bond between the nitrogen (N) atom and the carbon (C) atom of the imidazole group adsorbs metal foreign substances such as Fe, Co, Mn, Ni eluted from the positive electrode during high-voltage charging, and these metal foreign substances are electrodeposited on the surface of the negative electrode. The resulting negative electrode deterioration phenomenon can be effectively suppressed. Further, in the compound represented by the chemical formula 1, the lone pair of the nitrogen (N) atom of the imidazole group reacts with alkyl carbonate, which is a decomposition product of ethylene carbonate (EC) used as an organic solvent, and is reduced on the surface of the negative electrode. Therefore, a stable ion conductive film can be formed on the surface of the negative electrode. Accordingly, not only can an additional electrolyte decomposition reaction during the charge and discharge process be suppressed, but also the intercalation and deintercalation of lithium ions from the negative electrode can be smoothed during overcharging or high-temperature storage, improving the cycle life characteristics and high-temperature storage performance of the secondary battery.

[0035] The second additive may include repeating units of the following chemical formula 2-1, chemical formula 2-2, and chemical formula 2-3.

[0036] [Chemical formula]

[0037] The repeating unit of the chemical formula 2-1 contained in the second additive contains a hydroxy group and imparts a hydrogen bond to the structure of the additive, and the hydrogen bond has an effect of assisting so as to withstand physical deterioration of the battery material.

[0038] In the chemical formula 2-1, R 4is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group. Preferably, R 4 is H or an alkyl group having 1 to 10 carbon atoms, and most preferably may be H.

[0039]

Chemical formula

[0040] The repeating unit of Chemical formula 2-2 contained in the second additive contains a nitrile group, so that it can be well electrodeposited on the negative electrode and easily form an SEI layer. Thereby, a strong SEI layer can be formed rapidly.

[0041] In Chemical formula 2-2, R a is an alkyl group having 1 to 10 carbon atoms substituted with one or more nitrile groups. Preferably, R a in Chemical formula 2-2 has 1 to 5 carbon atoms and may be a linear or branched alkyl group substituted with one or more nitrile groups. Most preferably, R a in Chemical formula 2-2 may be an alkyl group having 1 to 3 carbon atoms substituted with one or more nitrile groups. For example, R a is CH 2 CN or CH 2 CH 2 CN may also be possible.

[0042] In Chemical formula 2-2, R 5 is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group. Preferably, R5 may be H or an alkyl group having 1 to 10 carbon atoms, and most preferably may be H.

[0043]

Chemical formula

[0044] By including the repeating unit of Chemical Formula 2-3 in the second additive, an inorganic LiF can be easily generated, and a stable polymer-inorganic-based SEI layer can be formed. Therefore, it is possible to suppress a decrease in the passivation ability of SEI at high temperatures and prevent deterioration of the negative electrode.

[0045] In Chemical Formula 2-3, R b may be a fluoroalkyl group having 1 to 10 carbon atoms. From the viewpoint of forming a strong LiF-based inorganic SEI layer on the positive electrode and the negative electrode, R b is preferably a perfluoroalkyl group having 1 to 10 carbon atoms, and most preferably may be a perfluoroalkyl group having 1 to 5 carbon atoms.

[0046] In Chemical Formula 2-3, R 6 may be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group. Preferably, R 6 may be H or an alkyl group having 1 to 10 carbon atoms, and most preferably may be H.

[0047] The non-aqueous electrolyte according to the present invention may contain, as an additive, a polymer represented by the following Chemical Formula 2.

[0048]

Chemical formula

[0049] In Chemical Formula 2, R a is an alkyl group having 1 to 10 carbon atoms with one or more nitrile groups substituted thereon. Preferably, R in Chemical Formula 2 a has 1 to 5 carbon atoms and may be a linear or branched alkyl group with one or more nitrile groups substituted thereon. Most preferably, R in Chemical Formula 2 a may be an alkyl group having 1 to 3 carbon atoms with one or more nitrile groups substituted thereon. For example, R a is CH 2 CN or CH 2 CH 2 CN may also be possible.

[0050] In Chemical Formula 2, R b may be a fluoroalkyl group having 1 to 10 carbon atoms. From the viewpoint of forming a strong LiF-based inorganic SEI layer on the positive electrode and the negative electrode, R b is preferably a perfluoroalkyl group having 1 to 10 carbon atoms, and most preferably may be a perfluoroalkyl group having 1 to 5 carbon atoms.

[0051] In Chemical Formula 2, R 4 to R 6 may each independently be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group. Preferably, R 4 to R 6 may each independently be H or an alkyl group having 1 to 10 carbon atoms, and most preferably may be H.

[0052] In Chemical Formula 2, p, q, and r may each independently be an integer from 1 to 100. Preferably, p is an integer from 1 to 99, q is an integer from 1 to 99, and r may be an integer from 1 to 99. Most preferably, p is an integer from 1 to 80, q is an integer from 1 to 80, and r may be an integer from 1 to 80. When p, q, and r in Chemical Formula 2 satisfy the above ranges, there will be sufficient nitrile groups that can participate in the SEI layer formation reaction on the negative electrode during battery charging, and there is an effect that there are perfluoro groups that can sufficiently provide LiF that can participate in the SEI layer formation reaction on the negative electrode. Also, there is an advantage of imparting sufficient hydrogen bonds that can withstand physical deterioration of battery materials.

[0053] In the non-aqueous electrolyte according to the present invention, the first additive may be contained in an amount of 0.01 parts by weight to 2 parts by weight based on 100 parts by weight of the non-aqueous electrolyte. Preferably, it may be contained in an amount of 0.05 parts by weight to 2 parts by weight, more preferably 0.10 parts by weight to 1.5 parts by weight. When the content of the first additive satisfies the above range, the effect of forming a film on the negative electrode is sufficient, and there is an effect of excellent life characteristics and high-temperature storage characteristics at high temperatures.

[0054] In the non-aqueous electrolyte according to the present invention, the second additive may be contained in an amount of 0.01 parts by weight to 10 parts by weight based on 100 parts by weight of the non-aqueous electrolyte. Preferably, it may be contained in an amount of 0.05 parts by weight to 5 parts by weight, more preferably 0.10 parts by weight to 3 parts by weight. When the content of the second additive satisfies the above range, the effect of forming a film on the negative electrode is sufficient, and there is an effect of excellent life characteristics and high-temperature storage characteristics at high temperatures.

[0055] In the non-aqueous electrolyte solution of the present invention, the first additive and the second additive may be contained in a weight ratio of 1:0.01 to 1:40, preferably a weight ratio of 1:1.5 to 1:10, and most preferably a weight ratio of 1:1.5 to 1:5. The elasticity of the formed SEI film falls within an appropriate range, and the SEI film can be firmly maintained during charge and discharge or at high temperatures.

[0056] The non-aqueous electrolyte according to the present invention may contain a lithium salt. The lithium salt is used as an electrolyte salt in a lithium secondary battery and is used as a medium for transmitting ions. Usually, as the lithium salt, for example, it contains Li as a cation + and, as an anion, F - 、Cl - 、Br - 、I - 、NO 3 - 、N(CN) 2 - 、BF 4 - 、ClO 4 - 、B 10 Cl 10 - 、AlCl 4 - 、AlO 2 - 、PF 6 - 、CF 3 SO 3 - 、CH 3 CO 2 - 、CF 3 CO 2 - 、AsF 6 - 、SbF 6 - 、CH 3 SO 3 - 、(CF 3 CF 2 SO 2 ) 2 N - 、(CF 3 SO 2 ) 2 N - 、(FSO 2 ) 2 N - 、BF 2 C 2 O 4 - 、BC 4 O 8 - 、PF 4 C 2O 4 - 、 PF 2 C 4 O 8 - 、 (CF 3 ) 2 PF 4 - 、 (CF 3 ) 3 PF 3 - 、 (CF 3 ) 4 PF 2 - 、 (CF 3 ) 5 PF - 、 (CF 3 ) 6 P - 、 C 4 F 9 SO 3 - 、 CF 3 CF 2 SO 3 - 、 CF 3 CF 2 (CF 3 ) 2 CO - 、 (CF 3 SO 2 ) 2 CH - 、 CF 3 (CF 2 ) 7 SO 3 - 、 and at least any one selected from the group consisting of SCN - is mentioned.

[0057] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF 4 、 LiClO 4 、 LiB 10 Cl 10 、 LiAlCl 4 、 LiAlO 2 、 LiPF 6 、 LiCF 3 SO 3 、 LiCH 3 CO 2 、 LiCF3 CO 2 、LiAsF 6 、LiSbF 6 、LiCH 3 SO 3 、LiN(SO 2 F) 2 (Lithium bis(fluorosulfonyl)imide; LiFSI), LiN(SO 2 CF 2 CF 3 ) 2 (Lithium bis(perfluoroethanesulfonyl)imide; LiBETI), and LiN(SO 2 CF 3 ) 2 (Lithium bis(trifluoromethanesulfonyl)imide; LiTFSI), and may contain a single substance or a mixture of two or more selected from the group consisting of these. In addition to these, lithium salts usually used in the electrolyte of lithium secondary batteries can be used without limitation.

[0058] The lithium salt can be appropriately changed within the range that can be usually used. However, in order to obtain the optimum effect of forming a film for preventing corrosion of the electrode surface, it may be contained in the electrolyte at a concentration of 0.5 M to 4.0 M, preferably 1.0 M to 3.0 M, more preferably 1.5 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of the lithium secondary battery is sufficient, and the viscosity of the non-aqueous electrolyte is appropriate and the electrolyte impregnation property can be improved.

[0059] The non-aqueous electrolyte according to the present invention may contain an organic solvent. The non-aqueous organic solvent may contain at least one or more organic solvents selected from the group consisting of cyclic carbonate-based organic solvents, linear carbonate-based organic solvents, linear ester-based organic solvents, and cyclic ester-based organic solvents.

[0060] The additive according to the present invention is particularly effective when using a cyclic carbonate solvent. When using a conventional electrolyte additive together with a cyclic carbonate solvent, the SEI film formed by the decomposition of the cyclic carbonate solvent is difficult to maintain due to the volume change of the negative electrode that occurs as the cycle progresses, and there is a problem that the decomposition of the solvent continues to occur. As a result, there is a problem that the ionic conductivity of the electrolyte decreases and the cycle characteristics deteriorate. However, when using the polymer according to the present invention as an additive together with a cyclic carbonate solvent, a strong SEI film can be formed, and there is an effect that the cycle characteristics are maintained high.

[0061] The cyclic carbonate-based organic solvent is a high-viscosity organic solvent, and because of its high dielectric constant, it is an organic solvent that easily dissociates lithium salts in the electrolyte. Specific examples thereof include at least one or more organic solvents selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. Among them, fluoroethylene carbonate may be included.

[0062] In addition, the linear carbonate-based organic solvent is an organic solvent having a low viscosity and a low dielectric constant. Representative examples thereof include at least one or more organic solvents 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. Specifically, diethyl carbonate (DEC) may be included.

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

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

[0065] Examples of the cyclic ester-based organic solvent include at least one or more organic solvents selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0066] On the other hand, the organic solvent may be additionally used by adding, without limitation, an organic solvent commonly used in non-aqueous electrolytes as necessary. 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.

[0067] As the ether-based solvent, 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 can be used, but it is not limited thereto.

[0068] The glyme-based solvent has a higher dielectric constant and a lower surface tension than linear carbonate-based organic solvents, and is a solvent with 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).

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

[0070] In addition, in order to prevent the non-aqueous electrolyte from being decomposed in a high-output environment and causing the collapse of the negative electrode, or to further improve the low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, battery expansion suppression effect at high temperature, etc., if necessary, the non-aqueous electrolyte may further contain a known electrolyte additive.

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

[0072] Examples of the cyclic carbonate-based compound include vinylene carbonate (VC) or vinyl ethylene carbonate.

[0073] Examples of the halogen-substituted carbonate compound include fluoroethylene carbonate (FEC).

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

[0075] Examples of the sulfate compound include ethylene sulfate (Ethylene Sulfate; Esa), trimethylene sulfate (Trimethylene sulfate; TMS), or methyl trimethylene sulfate (Methyl trimethylene sulfate; MTMS).

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

[0077] Examples of the borate compound include tetraphenylborate, lithium oxalyldifluoroborate (LiODFB), lithium bisoxalate borate (LiB(C 2 O 4 ) 2 , LiBOB).

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

[0079] Examples of the benzene compound include fluorobenzene, examples of the amine compound include triethanolamine or ethylenediamine, and an example of the silane compound is tetravinylsilane.

[0080] The lithium salt compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and examples thereof include lithium difluorophosphate (LiDFP), LiPO 2 F 2 or LiBF 4 and the like.

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

[0082] On the other hand, two or more of the other electrolyte additives may be used in combination, and based on the total weight of the non-aqueous electrolyte, they may be contained in an amount of 0.050% by weight to 20% by weight, specifically 0.10% by weight to 15% by weight, and preferably 0.30% by weight to 10% by weight. When the content of the other electrolyte additives satisfies the above range, more excellent ion conductivity and cycle characteristics improvement effects can be obtained.

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

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

[0085] At this time, the lithium secondary battery of the present invention can be manufactured by a conventional method known in the art. For example, after forming an electrode assembly in which a positive electrode, a negative electrode, and a separator are sequentially laminated between the positive electrode and the negative electrode, the electrode assembly is inserted into the inside of a battery case, and the non-aqueous electrolyte according to the present invention is injected to manufacture it.

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

[0087] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used.

[0088] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (for example, LiMnO 2 、LiMn 2 O 4 etc.), a lithium-cobalt-based oxide (for example, LiCoO 2 etc.), a lithium-nickel-based oxide (for example, LiNiO 2 etc.), a lithium-nickel-manganese-based oxide (for example, LiNi 1-Y Mn Y O 2 (where 0 < Y < 1), LiMn 2-Z Ni Z O 4 (where 0 < Z < 2) etc.), a lithium-nickel-cobalt-based oxide (for example, LiNi 1-Y1 Co Y1 O 2 (where 0 < Y1 < 1) etc.), a lithium-manganese-cobalt-based oxide (for example, LiCo 1-Y2 Mn Y2 O 2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O 4 (where 0 < Z1 < 2) etc.), a lithium-nickel-manganese-cobalt-based oxide (for example, Li(Ni p Co q Mn r )O 2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O 4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2) etc.), or a lithium-nickel-cobalt-transition metal (M) oxide (for example, Li(Ni p2 Co q2 Mn r2 M s2 )O 2(Here, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s2 are the atomic fractions of independent elements, respectively, where 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, and p2 + q2 + r2 + s2 = 1), etc.) etc. may be mentioned, and any one or two or more of these compounds may be included.

[0089] Among them, from the viewpoint of being able to improve the capacity characteristics and stability of the battery, the lithium metal oxide is LiCoO 2 , LiMnO 2 , LiNiO 2 , lithium nickel manganese cobalt oxide (for example, Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O 2 , Li(Ni 0.6 Mn 0.2 Co 0.2 )O 2 , Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 , Li(Ni 0.7 Mn 0.15 Co 0.15 )O 2 , and Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 etc.), or lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O 2 etc.) etc. may be used, and any one or two or more of these mixtures may be used.

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

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

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

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

[0094] The conductive material is a component for further improving the conductivity of the positive electrode active material, and may be added in an amount of 1 wt% to 20 wt% based on the total weight of the solid content in the positive electrode active material slurry. Such conductive materials are not particularly limited as long as they do not cause a chemical change in the battery and have conductivity. For example, carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powders such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

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

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

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

[0098] For example, when manufacturing a negative electrode by coating a negative electrode mixture slurry on the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 μm to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those with a surface treatment of carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, an aluminum-cadmium alloy, etc. may be used. Also, similar to the positive electrode current collector, the binding force of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and it may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

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

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

[0101] As the metal or an alloy of these metals and lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn, or an alloy of these metals and lithium can be used.

[0102] Examples of the metal composite oxide include PbO, PbO 2 , Pb 2 O 3 , Pb 3 O 4 , Sb 2 O 3 , Sb 2 O 4 , Sb 2 O 5 , GeO, GeO 2 , Bi 2 O 3 , Bi 2 O 4 , Bi 2 O 5 , Li x Fe 2 O 3 (0 ≦ x ≦ 1), Li x WO 2 (0 ≦ x ≦ 1), and Sn x Me 1-x Me’ y O z(Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, elements of Group 1, Group 2, Group 3 of the periodic table, halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8) selected from the group consisting of can be used.

[0103] As the substance capable of doping and undoping lithium, Si, SiO x (0 < x ≤ 2), Si-Y alloy (wherein Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO 2 , Sn-Y (wherein Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc. may be mentioned, and at least one of these and SiO 2 may be mixed and used. The element Y may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

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

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

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

[0107] Examples of the binder include polyvinylidene fluoride (PVDF), polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluorine rubber, various copolymers thereof, and the like. Specifically, styrene-butadiene rubber (SBR)-carboxymethyl cellulose (CMC) can be used from the viewpoint of high thickening property.

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

[0109] The conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 1% by weight to 20% by weight based on the total weight of the solid content in the negative electrode binder slurry. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, carbon powder such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

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

[0111] The solvent may contain water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a suitable viscosity when the negative electrode active material and optionally a binder and a conductive material are included. For example, it may be included such that the concentration of the solid content including the negative electrode active material and optionally the binder and the conductive material is 50% by weight to 95% by weight, preferably 70% by weight to 90% by weight.

[0112] When using the metal itself as the negative electrode, it can be manufactured by a method such as physically bonding, rolling, or vapor depositing the metal on the metal thin film itself or the negative electrode current collector. As the vapor deposition method, a method of electrically vapor depositing or chemically vapor depositing (chemical vapor deposition) the metal can be used.

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

[0114] (3) Separator Also, as the separator, a normal porous polymer film conventionally used as a separator, for example, a porous polymer film made of a polyolefin-based polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer may be used alone or in a laminated form, or a normal porous non-woven fabric, for example, a non-woven fabric made of high-melting glass fibers, polyethylene terephthalate fibers, etc. may be used, but it is not limited thereto. Further, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance may be used, and it may be selectively used in a single-layer or multi-layer structure.

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

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

[0117] The coating layer contains, as inorganic particles, Al2 O 3 , SiO 2 , TiO 2 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , SrTiO 3 , BaTiO 3 , Mg(OH) 2 , and one or more selected from MgF may be included. Here, the inorganic particles can improve the thermal stability of the separator. That is, the inorganic particles can prevent the separator from shrinking at high temperatures. And the binder polymer can fix the inorganic particles and also improve the mechanical stability of the separator.

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

[0119] Hereinafter, the present invention will be described more specifically with reference to specific examples. However, the following examples are merely illustrative for understanding the present invention and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications are possible within the scope of the description and the scope of the technical idea, and it goes without saying that such modifications and corrections belong to the scope of the appended claims.

[0120] 〔Synthesis Example〕 250 ml of a round-bottom flask was charged with PVA-CN (3 g, 0.01925 mol) and 87.5 ml of dimethylformamide and stirred. Perfluorobutanoic acid (3.3 g, 0.0288 mol) and dicyclohexylcarbodiimide (5.94 g, 0.0288 mol) were added to the mixed solution, and then the round-bottom flask was immersed in ice water. 4-Dimethylaminopyridine (0.15 g, 0.0012 mol) was dissolved in 12 ml of dimethylformamide and slowly added to the round-bottom flask. After 10 minutes, the ice water was removed, and the reaction was carried out at room temperature for 67 hours. The precipitate obtained after the reaction was filtered, and the remaining polymer solution was precipitated in distilled water. Then the precipitate was vacuum dried in a vacuum oven at 80 °C to obtain the polymer. The obtained polymer was a substance represented by Chemical Formula 2a.

[0121] [Chemical formula] (p = 1 to 20, q = 60 to 79, r = 1 to 20)

[0122] [Example] Example 1 (Manufacture of non-aqueous electrolyte) In an organic solvent (fluoroethylene carbonate (FEC): diethyl carbonate (DEC) = 10:90 by volume ratio), LiPF 6 was dissolved to a concentration of 1.5 M to produce a non-aqueous solvent. 0.1 g of the compound of Chemical Formula 1a below and 0.1 g of the polymer of Chemical Formula 2a below were added to 99.8 g of the non-aqueous solvent to produce a non-aqueous electrolyte.

[0123] [Chemical formula]

[0124] [Chemical formula] (p = 1 to 20, q = 60 to 79, r = 1 to 20)

[0125] (Manufacture of lithium secondary battery) Cathode active material (LiNi 0.85 Co0.05 Mn 0.08 Al 0.02 O 2 ) and a conductive material (carbon nanotube) and a binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP) which is a solvent at a weight ratio of 97.74:0.7:1.56 to produce a positive electrode slurry (solid content 75.5 wt%). The positive electrode slurry was applied to one surface of a positive electrode current collector (Al thin film) with a thickness of 15 μm, and dried and roll pressed to produce a positive electrode.

[0126] A negative electrode active material (silicon; Si), a conductive material (carbon black), and a binder (styrene-butadiene rubber (SBR)-carboxymethyl cellulose (CMC)) were added to N-methyl-2-pyrrolidone (NMP) which is a solvent at a weight ratio of 70:20.3:9.7 to produce a negative electrode slurry (solid content 26 wt%). The negative electrode slurry was applied to one surface of a negative electrode current collector (Cu thin film) with a thickness of 15 μm, and dried and roll pressed to produce a negative electrode.

[0127] In a dry room, after interposing a polyolefin-based porous separator coated with inorganic particles Al 2 O 3 between the positive electrode and the negative electrode manufactured above, the non-aqueous electrolyte manufactured above was injected to manufacture a secondary battery.

[0128] Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 0.1 g of the compound of Chemical Formula 1a and 3 g of the polymer of Chemical Formula 2a were added to 96.9 g of the non-aqueous solvent manufactured in Example 1 to manufacture a non-aqueous electrolyte.

[0129] Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that 1.5 g of the compound of Chemical Formula 1a and 0.1 g of the polymer of Chemical Formula 2a were added to 98.4 g of the non-aqueous solvent manufactured in Example 1 to manufacture a non-aqueous electrolyte.

[0130] Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of the compound of Chemical Formula 1a and 2 g of the polymer of Chemical Formula 2a were added to 97.5 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0131] Example 5 A secondary battery was manufactured in the same manner as in Example 1, except that 1.5 g of the compound of Chemical Formula 1a and 3 g of the polymer of Chemical Formula 2a were added to 95.5 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0132] Example 6 LiPF was dissolved in an organic solvent (fluoroethylene carbonate (FEC): diethyl carbonate (DEC) = 10:90 volume ratio) 6 to a concentration of 1.5 M to produce a non-aqueous solvent. 0.1 g of the compound of the following Chemical Formula 1a and 0.1 g of the polymer of the following Chemical Formula 2b were added to 99.8 g of the non-aqueous solvent to produce a non-aqueous electrolyte.

[0133] [Chemical formula]

[0134] [Chemical formula] (p = 1 to 20, q = 60 to 79, r = 1 to 20)

[0135] A secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte was used.

[0136] Example 7 LiPF was dissolved in an organic solvent (fluoroethylene carbonate (FEC): diethyl carbonate (DEC) = 10:90 volume ratio) 6 to a concentration of 1.5 M to produce a non-aqueous solvent. 0.1 g of the compound of the following Chemical Formula 1a and 0.1 g of the polymer of the following Chemical Formula 2c were added to 99.8 g of the non-aqueous solvent to produce a non-aqueous electrolyte.

[0137] [Chemical formula]

[0138] [Chemical formula] (p = 1 to 20, q = 60 to 79, r = 1 to 20)

[0139] A secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte was used.

[0140] Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was manufactured using 100 g of the non-aqueous solvent manufactured in Example 1.

[0141] Comparative Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 1.5 g of the compound of Chemical Formula 1a was added to 98.5 g of the non-aqueous solvent manufactured in Example 1 to manufacture a non-aqueous electrolyte.

[0142] Comparative Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that 3 g of the polymer of Chemical Formula 2a was added to 97 g of the non-aqueous solvent manufactured in Example 1 to manufacture a non-aqueous electrolyte.

[0143] [Experimental Example 1 - Evaluation of High-Temperature Cycle Characteristics] The cycle characteristics of each of the secondary batteries manufactured in Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated.

[0144] Specifically, each of the batteries manufactured in Examples 1 to 7 and Comparative Examples 1 to 3 was charged at a constant current of 1C to 4.2V at 45°C and discharged at a constant current of 0.5C to 3.0V. One cycle was defined as such, and after 250 cycles of charge and discharge, the capacity retention rate with respect to the initial capacity after one cycle was measured. The results are shown in Table 1 below.

[0145]

Table 1

[0146] As shown in Table 1, Examples 1 to 7 using the combination of the first additive and the second additive had a higher capacity retention rate and better life characteristics than Comparative Example 1 using no additive, Comparative Example 2 using only the first additive, and Comparative Example 3 using only the second additive.

[0147] 〔Experimental Example 2 - Evaluation of High - Temperature Storage Characteristics〕 The high - temperature storage characteristics were evaluated for each of the secondary batteries manufactured in Examples 1 to 7 and Comparative Examples 1 to 3.

[0148] Specifically, each of the secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 3 was fully charged to 4.2 V and then stored at 60 °C for 8 weeks.

[0149] Before storage, the capacity of the fully charged secondary battery was measured and set as the capacity of the initial secondary battery.

[0150] After 8 weeks, the capacity of the stored secondary battery was measured, and the capacity decreased during the 8 - week storage period was calculated. The percentage ratio of the decreased capacity to the capacity of the initial secondary battery was calculated to derive the capacity retention rate after 8 weeks. The results are shown in Table 2 below.

[0151]

Table 2

[0152] As shown in Table 2 above, Examples 1 to 7 using the combination of the first additive and the second additive had a higher capacity retention rate after 8 weeks and confirmed stable performance at high temperatures compared to the secondary batteries of Comparative Example 1 using no additive, Comparative Example 2 using only the first additive, and Comparative Example 3 using only the second additive.

Claims

1. A lithium salt; An organic solvent; A compound represented by the following chemical formula 1 as a first additive, A non-aqueous electrolyte comprising, as a second additive, a polymer including repeating units represented by the following chemical formulas 2-1, 2-2, and 2-3: 【Chemistry 1】 (In the above Chemical Formula 1, R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms; R １ ~R ３ are each independently H, an alkyl group having 1 to 3 carbon atoms, or a nitrile group; 【Chemistry 2】 In the above Chemical Formula 2-1, R ４ is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group; 【Chemistry 3】 In the above Chemical Formula 2-2, R ａ is an alkyl group having 1 to 10 carbon atoms substituted with one or more nitrile groups, R ５ is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group; 【Chemistry 4】 In the above Chemical Formula 2-3, R ｂ is a fluoroalkyl group having 1 to 10 carbon atoms, R ６ is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group.

2. 2. The nonaqueous electrolyte according to claim 1, wherein the second additive comprises a polymer represented by the following formula 2: 【Chemistry 5】 (In the above Chemical Formula 2, R ４ ~R ６ each independently represents one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen atom, and a nitrile group; R ａ is an alkyl group having 1 to 10 carbon atoms substituted with one or more nitrile groups, R ｂ is a fluoroalkyl group having 1 to 10 carbon atoms, p, q, and r are each independently an integer from 1 to 100.

3. In the above Chemical Formula 2-2, R ａ is CH ２ CN or CH ２ CH ２ CN. The non-aqueous electrolyte of claim 1 .

4. In the above Chemical Formula 2-3, R ｂ The non-aqueous electrolyte according to claim 1 , wherein is a perfluoroalkyl group having 1 to 5 carbon atoms.

5. 2. The non-aqueous electrolyte of claim 1, wherein the first additive is a compound represented by the following formula 1a, and the second additive is a compound represented by the following formula 2a: 【Chemistry 6】 【Chemistry 7】 (wherein p is an integer from 1 to 20, q is an integer from 60 to 79, and r is an integer from 1 to 20.) 6. The nonaqueous electrolyte of claim 1, wherein the first additive is a compound represented by the following chemical formula 1a, and the second additive is a compound represented by the following chemical formula 2b: 【Chemistry 8】 【Chemistry 9】 (p=1-20, q=60-79, r=1-20) 7. The nonaqueous electrolyte of claim 1, wherein the first additive is a compound represented by the following chemical formula 1a, and the second additive is a compound represented by the following chemical formula 2c: 【Chemistry 10】 【Chemistry 11】 (p=1-20, q=60-79, r=1-20)

8. The non-aqueous electrolyte of claim 1 , wherein the first additive is present in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.

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

10. The non-aqueous electrolyte of claim 1 , wherein the first additive and the second additive are contained in a weight ratio of 1:0.01 to 1:

40.

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

12. The non-aqueous electrolyte according to claim 1 , wherein the lithium salt is contained at a concentration of 0.5M to 4.0M.

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

14. The non-aqueous electrolyte according to claim 1 , wherein the organic solvent includes a cyclic carbonate-based organic solvent.

15. The non-aqueous electrolyte according to claim 14 , wherein the cyclic carbonate organic solvent is fluoroethylene carbonate (FEC).

16. A positive electrode and A negative electrode; A lithium secondary battery comprising the nonaqueous electrolyte according to claim 1 .

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