Non-aqueous electrolyte and lithium secondary battery containing the same

Abstract

The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive contains a compound represented by a specific chemical formula. The non-aqueous electrolyte according to the present invention contains an additive excellent in electrode film protection, O2 scavenging effect, and HF scavenging effect, thereby improving the cycle characteristics and high-temperature storage characteristics of a lithium secondary battery containing the same.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0101640 filed on August 12, 2022, and all the contents disclosed in the literature of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to 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 is increasing.

[0004] In particular, in lithium secondary batteries for automotive applications, high capacity, high output, and long-term life characteristics are important. In order to increase the capacity of lithium secondary batteries, it is conceivable to use a positive electrode active material with a high nickel content that has a high energy density but low stability, or to drive the lithium secondary battery at a high voltage.

[0005] However, when driving a lithium secondary battery under the above conditions, as charge and discharge proceed, 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 can be eluted from the surface of the positive electrode. In this way, the eluted transition metal ions are electrodeposited on the negative electrode, reducing the passivation ability of the SEI (Solid electrolyte interface) film of the negative electrode, resulting in a problem that the negative electrode deteriorates. 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.

[0006] In addition, when a lithium secondary battery is continuously used 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.

[0007] 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 lithium secondary battery, and enhance the stability at high temperatures.

Summary of the Invention

Problems to be Solved by the Invention

[0008] One problem of the present invention is to provide a non-aqueous electrolyte that can reduce electrolyte side reactions by forming stable films on the positive / negative electrodes and has excellent O2 scavenging effect and HF scavenging effect.

[0009] Another problem of the present invention is to provide a lithium secondary battery that contains the aforementioned non-aqueous electrolyte, has improved high-temperature cycle characteristics and high-temperature storage performance, and has improved various performances.

Means for Solving the Problems

[0010] The present invention provides a non-aqueous electrolyte containing a lithium salt, an organic solvent, and an additive, wherein the additive contains a compound represented by the following Chemical Formula 1.

[0011]

Chem.

[0012] In the above Chemical Formula 1, R1 to R6 are each independently hydrogen, halogen, nitrile group, propargyl group, ester group, ether group, ketone group, carboxy 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 a combination of two or more thereof, and at least one of R1 to R6 contains an isocyanate group.

[0013] The present invention also provides a lithium secondary battery including 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.

Advantages of the Invention

[0014] The non-aqueous electrolyte of the present invention is characterized by containing a coumarin-based compound substituted with a substituent containing an isocyanate group as an additive. The additive can form a film with excellent durability on the positive / negative electrodes, thereby suppressing the elution of transition metals in the positive electrode and suppressing electrolyte side reactions at the electrodes. Further, the additive contains an isocyanate group as a substituent, which can remove the Lewis acid of the lithium salt that may occur when exposed to high temperatures (HF scavenging effect), and thus can prevent the decomposition of the organic solvent and the decomposition of the electrode film by such Lewis acid. Further, according to the non-aqueous electrolyte of the present invention, the reactive oxygen compound generated at the positive electrode binds to the coumarin structure contained in the compound represented by Chemical Formula 1, and has an effect of suppressing the decomposition and gas generation of the electrolyte (O2 scavenging effect).

[0015] Therefore, the lithium secondary battery including the aforementioned non-aqueous electrolyte can have improved high-temperature cycle characteristics and high-temperature storage characteristics.

Modes for Carrying Out the Invention

[0016] The terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings. In accordance with the principle that the inventors can appropriately define the concept of the terms in order to best explain their invention, they should be construed in a meaning and concept consistent with the technical idea of the present invention.

[0017] In this specification, terms such as "comprising", "including", or "having" are intended to specify the presence of implemented features, numbers, steps, components, or combinations thereof, and should be understood not to preclude in advance the presence or addition possibility of one or more other features, numbers, steps, components, or combinations thereof.

[0018] On the other hand, before explaining the present invention, unless otherwise specifically mentioned in the present invention, "*" means a connected part (bonding site) between the ends of the same or different atoms or chemical formulas.

[0019] Also, in this specification, in the description of "carbon number a to b", "a" and "b" mean the number of carbon atoms contained in the specific functional group. That is, the functional group may contain "a" to "b" carbon atoms. For example, "alkyl group having 1 to 5 carbon atoms" means an alkyl group containing 1 to 5 carbon atoms, that is, CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2CH2-, etc.

[0020] In addition, in this specification, the alkyl group, alkenyl group, or alkynyl group may or may not be substituted. The term "substituted" means that at least one or more hydrogens bonded to carbon are substituted with elements 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 cycloalkynyl 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, a 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, 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, an isocyanate group, an ether group, a sulfone group, a sulfonate group, a sulfate group, etc.

[0021] Hereinafter, the present invention will be described in more detail.

[0022] Non-aqueous electrolyte The present invention relates to a non-aqueous electrolyte. More specifically, the non-aqueous electrolyte may be a non-aqueous electrolyte for a lithium secondary battery.

[0023] The non-aqueous electrolyte according to the present invention includes a lithium salt, an organic solvent, and an additive, and the additive includes a compound represented by the following Chemical Formula 1.

[0024]

Chemical formula

[0025] In Chemical Formula 1, R1 to R6 are, independently of one another, hydrogen, halogen, nitrile group, propargyl group, ester group, ether group, ketone group, carboxy 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 a combination of two or more thereof, and at least one of R1 to R6 contains an isocyanate group.

[0026] The non-aqueous electrolyte of the present invention is characterized by containing, as an additive, a coumarin compound substituted with a substituent containing an isocyanate group. The additive can form a film excellent in durability on the positive / negative electrode, thereby suppressing the elution of transition metals in the positive electrode and suppressing the electrolyte side reaction of the electrode. Further, the additive contains an isocyanate group as a substituent, which can remove the Lewis acid of the lithium salt that may occur when exposed to high temperature (HF scavenging effect, HF Scavenging effect), and can prevent the decomposition of the organic solvent and the decomposition of the electrode film by such a Lewis acid. Further, according to the non-aqueous electrolyte according to the present invention, a reactive oxygen compound generated at the positive electrode binds to the coumarin structure contained in the compound represented by Chemical Formula 1, and has an effect of suppressing the decomposition and gas generation of the electrolyte (O2 scavenging effect, O2 Scavenging effect). Therefore, the lithium secondary battery containing the above non-aqueous electrolyte can improve the high-temperature cycle characteristics and high-temperature storage characteristics.

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

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

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

[0030] (2) Organic solvent The organic solvent is a non-aqueous solvent commonly used in lithium secondary batteries, and is not particularly limited as long as decomposition due to oxidation reaction or the like is minimized during the charge and discharge process of the secondary battery.

[0031] Specifically, the organic solvent may contain at least one 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.

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

[0033] The cyclic carbonate-based organic solvent is a high-viscosity organic solvent with a high dielectric constant, which easily dissociates lithium salts in electrolytes. Specifically, it may contain at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. More specifically, it may contain ethylene carbonate.

[0034] In addition, the linear carbonate-based organic solvent is an organic solvent with low viscosity and low dielectric constant. Specifically, it may contain 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. More specifically, it may contain ethyl methyl carbonate (EMC).

[0035] The organic solvent may be a mixture of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent. At this time, the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent may be mixed at a volume ratio of 10:90 to 40:60, specifically 10:90 to 30:70, and more specifically 15:85 to 30:70. When the mixing ratio of the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent satisfies the above range, both high dielectric constant and low viscosity characteristics can be satisfied, and excellent ionic conductivity characteristics can be realized.

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

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

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

[0039] On the other hand, the organic solvent may be additionally used as necessary without being limited to the organic solvents commonly used in non-aqueous electrolytes. For example, it may further include at least one or more of ether-based organic solvents, glyme-based solvents, and nitrile-based organic solvents.

[0040] 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 thereof can be used, but it is not limited thereto.

[0041] The glyme-based solvent has a high dielectric constant and a low surface tension compared to linear carbonate-based organic solvents, and is a solvent with low reactivity with metals. It may include at least one or more selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraethylene glycol dimethyl ether (TEGDME), but is not limited thereto.

[0042] 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.

[0043] (3) Additive The non-aqueous electrolyte according to the present invention contains a compound represented by the following Chemical Formula 1.

[0044] [Chemical Formula]

[0045] In Chemical Formula 1, R1 to R6 are each independently hydrogen, halogen, nitrile group, propargyl group, ester group, ether group, ketone group, carboxy 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 a combination of two or more thereof, and at least one of R1 to R6 contains an isocyanate group.

[0046] The compound represented by the above Chemical Formula 1 can form a film with excellent durability on the positive / negative electrode, thereby suppressing the elution of transition metals in the positive electrode and suppressing the electrolyte side reaction of the electrode. Further, the additive contains an isocyanate group as a substituent, which can remove the Lewis acid (e.g., HF, etc.) of the lithium salt that may occur when exposed to high temperature (HF scavenging effect, HF Scavenging effect), and thus can prevent the decomposition of the organic solvent and the decomposition of the electrode film by such Lewis acid. Further, according to the non-aqueous electrolyte according to the present invention, the reactive oxygen compound generated at the positive electrode binds to the coumarin structure contained in the compound represented by the above Chemical Formula 1, and has an effect of suppressing the decomposition of the electrolyte and gas generation (O2 scavenging effect, O2 Scavenging effect). Therefore, the compound represented by the above Chemical Formula 1 containing both coumarin and an isocyanate group can significantly improve the high-temperature life performance and high-temperature storage performance.

[0047] In the above Chemical Formula 1, the substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, and substituted or unsubstituted alkoxy group may specifically be a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 1 to 10 carbon atoms, and a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, and more specifically, may be a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkenyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkynyl group having 1 to 5 carbon atoms, and a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms, respectively.

[0048] Specifically, in the compound represented by the above Chemical Formula 1, R2 to R6 may each be hydrogen, and R1 may contain an isocyanate group, and specifically, may include a compound represented by the following Chemical Formula 2.

[0049]

Chemical Formula

[0050] In Chemical Formula 2, the definition of R1 is the same as that in Chemical Formula 1, and R1 contains an isocyanate group.

[0051] When the compound represented by Chemical Formula 1 contains the compound represented by Chemical Formula 2, it is preferable in that the durability of the film can be further improved.

[0052] More specifically, the compound represented by Chemical Formula 1 may contain a compound represented by the following Chemical Formula 3.

[0053] [Chemical Formula]

[0054] In Chemical Formula 3, L1 is a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group, a substituted or unsubstituted alkynylene group, a sulfone group, a sulfonate group, or a combination of two or more thereof. At this time, the alkylene group may be an alkylene group having 1 to 5 carbon atoms, the alkenylene group may be an alkenylene group having 1 to 5 carbon atoms, and the alkynylene group may be an alkynylene group having 1 to 5 carbon atoms.

[0055] In the compound represented by Chemical Formula 3, the isocyanate group is substituted with coumarin via a linker (*-O-L1-*, * is a bonding site). The linker is preferable in that it can increase the oxygen content in the film formed on the positive / negative electrode and reduce the resistance of the positive / negative electrode.

[0056] More specifically, the compound represented by Chemical Formula 1 may contain at least one selected from the group consisting of a compound represented by the following Chemical Formula 4A and a compound represented by the following Chemical Formula 4B.

[0057] [Chemical Formula]

[0058]

Chem.

[0059] The compounds represented by the above Chemical Formula 4A and Chemical Formula 4B are preferable in that the isocyanate group is substituted with coumarin via a linker having a preferable length and functional groups, which can improve the durability of the film and reduce the resistance.

[0060] The compound represented by the above Chemical Formula 1 may be contained in the non-aqueous electrolyte in an amount of 0.01% by weight to 10% by weight, specifically 0.05% by weight to 5% by weight, more specifically 0.1% by weight to 3% by weight, and still more specifically 0.3% by weight to 2% by weight. When the content of the compound represented by the above Chemical Formula 1 satisfies the above range, the above-described electrode film formation effect, organic solvent decomposition prevention effect, electrolyte side reaction prevention effect, O2 scavenging effect, and HF scavenging effect can be sufficiently exhibited, and it is preferable in terms of preventing an increase in the resistance of the lithium secondary battery due to an excessive addition and a resulting decrease in the life performance.

[0061] The additive may further contain an additional additive together with the compound of the above Chemical Formula 1. The additional additive may be contained in the non-aqueous electrolyte to prevent the non-aqueous electrolyte from being decomposed in a high-power environment and causing the collapse of the negative electrode, or for low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, suppression of battery swelling at high temperatures, and the like.

[0062] Specifically, 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, LiBF4, LiPO2F2, LiODFB (lithium difluorooxalatoborate), LiBOB (lithium bis-(oxalato)borate), TMSPa (3-trimethoxysilanyl-propyl-N-aniline), and TMSPi (tris(trimethylsilyl)phosphite). Specifically, it may be at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, ethylene sulfate, LiPO2F2, LiBF4, and LiODFB.

[0063] The additional additive may be contained in the non-aqueous electrolyte at 0.1% to 15% by weight.

[0064] Lithium secondary battery The present invention also provides a lithium secondary battery including the aforementioned non-aqueous electrolyte.

[0065] Specifically, the lithium secondary battery may include 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.

[0066] 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.

[0067] (1) Positive electrode The positive electrode contains a positive electrode active material.

[0068] 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. At this time, the positive electrode active material may be included in the positive electrode active material layer.

[0069] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. Specifically, the positive electrode current collector may include at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, fired carbon, and an aluminum-cadmium alloy, preferably aluminum.

[0070] The thickness of the positive electrode current collector usually has a thickness of 3 μm to 500 μm.

[0071] The positive electrode current collector may strengthen the binding force of the positive electrode active material by forming fine irregularities on the surface. For example, the positive electrode current collector can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0072] The positive electrode active material layer is disposed on at least one side of the positive electrode current collector. Specifically, the positive electrode active material layer may be disposed on one side or both sides of the positive electrode current collector.

[0073] The positive electrode active material layer may contain a positive electrode active material.

[0074] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, specifically, a lithium transition metal composite oxide containing at least one transition metal of nickel, cobalt, manganese, and aluminum and lithium, preferably, a lithium transition metal composite oxide containing a transition metal containing nickel, cobalt, and manganese and lithium may be included.

[0075] For example, as the lithium transition metal composite oxide, lithium-manganese-based oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (e.g., LiCoO2, etc.), lithium-nickel-based oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese-based oxides (e.g., 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 (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni p Co q Mn 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 (e.g., 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.) etc. may be mentioned, and any one or two or more of these compounds may be included. Among them, from the viewpoint of being able to enhance the capacity characteristics and stability of the battery, the lithium transition metal composite oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel-manganese-cobalt oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )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 (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), etc. may be, and considering the significance of the improvement effect by controlling the types and content ratios of the constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide is Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc. may be, and any one or two or more of these mixtures can be used.

[0076] More specifically, the positive electrode active material may be a lithium transition metal composite oxide, and may contain 60 mol% or more of nickel based on the total number of moles of transition metals contained in the lithium transition metal composite oxide. Specifically, the positive electrode active material may be a lithium transition metal composite oxide, the transition metal may include nickel; and at least one selected from manganese, cobalt, and aluminum, and the nickel may be contained in an amount of 60 mol% or more, specifically 60 mol% to 90 mol%, based on the total number of moles of the transition metals. When using a lithium transition metal composite oxide using such nickel in a high content together with the aforementioned non-aqueous electrolyte, it is preferable in that by-products in the gas generated by structural collapse can be reduced.

[0077] Further, the positive electrode active material may include a lithium composite transition metal oxide represented by the following Chemical Formula 5.

[0078] [Chemical Formula 5] Li 1+x (Ni a Co b Mn c M d )O2

[0079] In Chemical Formula 5, M is one or more 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 atomic fractions of independent elements, respectively, where 0 ≦ x ≦ 0.2, 0.50 ≦ a < 1, 0 < b ≦ 0.25, 0 < c ≦ 0.25, 0 ≦ d ≦ 0.1, and a + b + c + d = 1.

[0080] Preferably, 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.

[0081] Further, 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.

[0082] Further, a, b, c, and d may each be 0.85 ≦ a ≦ 0.90, 0.05 ≦ b ≦ 0.10, 0.05 ≦ c ≦ 0.10, and 0 ≦ d ≦ 0.03.

[0083] On the other hand, the positive electrode active material may contain a hyper-lithiated manganese-rich oxide in which Mn is contained in an amount of 50 mol% or more in all metals excluding lithium, and the molar ratio of lithium to transition metals exceeds 1.

[0084] When the hyper-lithiated manganese-rich oxide is used as the positive electrode active material, during the initial activation process, active oxygen is generated in the process of decomposition of the rock salt phase hyper-lithiated manganese-rich oxide. The active oxygen attacks and decomposes an organic solvent such as ethylene carbonate, generating gas and resistive by-products and deteriorating the physical properties of the battery. However, in the present invention, since the non-aqueous electrolyte contains the compound represented by Chemical Formula 1 having a greater reactivity with active oxygen than the organic solvent, the active oxygen generated in the initial activation process binds to the compound represented by Chemical Formula 1 prior to the organic solvent, and side effects due to the decomposition of the organic solvent can be minimized.

[0085] The hyper-lithiated manganese-rich oxide may be a compound represented by the following Chemical Formula 6.

[0086] [Chemical Formula 6] Li 1+s [Ni t Co u Mn V M 1 w O 2+z

[0087] In Chemical Formula 6, M 1is one or more 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 0.05 ≦ s ≦ 1, 0 ≦ t ≦ 0.5, 0 ≦ u ≦ 0.3, 0.5 ≦ v < 1.0, 0 ≦ w ≦ 0.2, 0 ≦ z ≦ 1 may hold, preferably 0.05 ≦ s ≦ 1.0, 0.1 ≦ t ≦ 0.5, 0 ≦ u ≦ 0.1, 0.5 ≦ v < 1.0, 0 ≦ w ≦ 0.2, 0 ≦ z ≦ 1, and more preferably 0.10 ≦ s ≦ 0.50, 0.1 ≦ t ≦ 0.5, 0 ≦ u ≦ 0.1, 0.6 ≦ v < 1.0, 0 ≦ w ≦ 0.1, 0 ≦ z ≦ 0.50 may hold.

[0088] More specifically, the over-lithiated manganese-rich oxide may be a compound represented by the following Chemical Formula 6-1.

[0089] [Chemical Formula 6-1] XLi2MnO3·(1-X)Li[Ni 1-y-z-w Mn y Co z M 1 w O2 In the Chemical Formula 6-1, M 1 is one or more 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 0.1 ≦ X ≦ 0.5, 0.5 ≦ y < 1, 0 ≦ z ≦ 0.3, 0 ≦ w ≦ 0.2 may hold, preferably 0.2 ≦ X ≦ 0.5, 0.5 ≦ y < 1, 0 ≦ z ≦ 0.1, 0 ≦ w ≦ 0.2, and more preferably 0.3 ≦ X ≦ 0.5, 0.6 ≦ y < 1, 0 ≦ z ≦ 0.1, 0 ≦ w ≦ 0.2 may hold.

[0090] Considering sufficient capacity exhibition of the positive electrode active material and the like, the positive electrode active material may be contained in the positive electrode active material layer at 80% by weight to 99% by weight, preferably 92% by weight to 98.5% by weight.

[0091] The positive electrode active material layer may further contain a binder and / or a conductive material together with the aforementioned positive electrode active material.

[0092] The binder is a component that binds active materials, conductive materials, etc., and assists in binding to the current collector. Specifically, it may include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, preferably polyvinylidene fluoride.

[0093] From the perspective of sufficiently ensuring the binding force between components such as the positive electrode active material, the binder may be contained in the positive electrode active material layer at 1% by weight to 20% by weight, preferably 1.2% by weight to 10% by weight.

[0094] The conductive material is used to assist and improve the conductivity of the secondary battery, and is not particularly limited as long as it does not cause a chemical change and has conductivity. Specifically, the positive electrode conductive material may include at least one selected from the group consisting of graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives, and preferably may include carbon black from the perspective of improving conductivity.

[0095] From the perspective of sufficiently ensuring electrical conductivity, the conductive material may be contained in the positive electrode active material layer at 1% by weight to 20% by weight, preferably 1.2% by weight to 10% by weight.

[0096] The thickness of the positive electrode active material layer may be 30 μm to 400 μm, preferably 40 μm to 110 μm.

[0097] The positive electrode can be manufactured by coating a positive electrode active material and a positive electrode slurry selectively containing a binder, a conductive material, and a solvent for forming the positive electrode slurry on the positive electrode current collector, followed by drying and rolling.

[0098] The solvent for forming the positive electrode slurry may contain an organic solvent such as NMP (N-methyl-2-pyrrolidone). The content of the solid component of the positive electrode slurry may be 40% by weight to 90% by weight, specifically 50% by weight to 80% by weight.

[0099] (2) Negative electrode The negative electrode faces the positive electrode.

[0100] The negative electrode contains a negative electrode active material.

[0101] 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. At this time, the negative electrode active material may be included in the negative electrode active material layer.

[0102] The 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. Specifically, examples of the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, fired carbon, those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, and aluminum-cadmium alloys.

[0103] The negative electrode current collector usually has a thickness of 3 μm to 500 μm.

[0104] The negative electrode current collector may enhance the binding force of the negative electrode active material by forming fine irregularities on its surface. For example, the negative electrode current collector can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0105] The negative electrode active material layer is disposed on at least one side of the negative electrode current collector. Specifically, the negative electrode active material layer may be disposed on one side or both sides of the negative electrode current collector.

[0106] The negative electrode active material layer may contain a negative electrode active material.

[0107] The negative electrode active material is a material capable of reversibly intercalating / deintercalating lithium ions, and may include at least one selected from the group consisting of carbon-based active materials, (semi)metal-based active materials, and lithium metal. Specifically, it may include at least one selected from the group consisting of carbon-based active materials and (semi)metal-based active materials.

[0108] The carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably may include at least one selected from the group consisting of artificial graphite and natural graphite.

[0109] The average particle diameter (D 50 ) may be 10 μm to 30 μm, preferably 15 μm to 25 μm, from the viewpoint of achieving structural stability during charge and discharge and reducing side reactions with the electrolyte.

[0110] Specifically, the (semi) metallic active material may include at least one (semi) 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, V, Ti, and Sn; an alloy of at least one (semi) 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, V, Ti, and Sn and lithium; an oxide of at least one (semi) 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, V, Ti, and Sn; lithium titanate (LTO); lithium vanadium oxide; and the like.

[0111] More specifically, the (semi) metallic active material may include a silicon-based active material.

[0112] The silicon-based active material may include a compound represented by SiO x (0 ≦ x < 2). Since SiO2 does not react with lithium ions, it cannot store lithium. Therefore, x is preferably within the above range, and more preferably, the silicon-based active material may be SiO.

[0113] The average particle size (D 50 ) of the silicon-based active material may be 1 μm to 30 μm, preferably 2 μm to 15 μm, in order to achieve structural stability during charge and discharge and reduce side reactions with the electrolyte.

[0114] The negative electrode active material may be contained in the negative electrode active material layer at 60% to 99% by weight, preferably 75% to 95% by weight.

[0115] The negative electrode active material layer may further include a binder and / or a conductive material together with the negative electrode active material.

[0116] The binder is used to improve the adhesion between the negative electrode active material layer and the negative electrode current collector and thus improve the performance of the battery. For example, it may include at least any one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and substances in which hydrogen thereof is substituted with Li, Na, Ca, etc., or may include various copolymers thereof.

[0117] The binder may be contained in the negative electrode active material layer at 0.5% to 10% by weight, preferably 1% to 5% by weight.

[0118] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, 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; conductive materials such as polyphenylene derivatives may be used.

[0119] The conductive material may be contained in the negative electrode active material layer at 0.5% to 10% by weight, preferably 1% to 5% by weight.

[0120] The thickness of the negative electrode active material layer may be 10 μm to 100 μm, preferably 50 μm to 80 μm.

[0121] The negative electrode can be manufactured by coating at least one surface of a negative electrode current collector with a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and / or a solvent for forming the negative electrode slurry, followed by drying and rolling.

[0122] The solvent for forming the negative electrode slurry may include, for example, at least one selected from the group consisting of distilled water, NMP (N-methyl-2-pyrrolidone), ethanol, methanol, and isopropyl alcohol, preferably including distilled water, from the viewpoint of facilitating the dispersion of the negative electrode active material, the binder, and / or the conductive material. The solid content of the negative electrode slurry may be 30% by weight to 80% by weight, specifically 40% by weight to 70% by weight.

[0123] (3) Separator 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 point glass fibers, polyethylene terephthalate fibers, etc. may be used, but is not limited thereto. Further, a coated separator containing a ceramic component or a polymer substance may be used to ensure heat resistance or mechanical strength, and may be selectively used in a single-layer or multi-layer structure.

[0124] The outer shape of the lithium secondary battery of the present invention is not particularly limited, and may be, for example, a cylindrical shape, a rectangular shape, a pouch shape, or a coin shape using a can.

[0125] Hereinafter, the present invention will be described in more detail with 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 variations and modifications belong to the scope of the appended claims.

[0126] Examples and Comparative Examples Example 1 (Manufacture of Non-aqueous Electrolyte) As the organic solvent, a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 was used.

[0127] To the organic solvent, LiPF6 as a lithium salt; a compound represented by the following Chemical Formula 4A; and as additional additives, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, ethylene sulfate, LiPO2F2, LiBF4, and LiODFB; were added to produce a non-aqueous electrolyte.

[0128] The LiPF6 was contained in the non-aqueous electrolyte at a concentration of 1.2 M.

[0129] The compound represented by the following Chemical Formula 4A was contained in the non-aqueous electrolyte at 0.5 wt%.

[0130] Also, the non-aqueous electrolyte contained vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, ethylene sulfate, LiPO2F2, LiBF4, and LiODFB at a content of 0.5 wt% each.

[0131]

Chemical Formula

[0132] (Manufacture of Lithium Secondary Battery) Positive electrode active material (Li1.35 [Ni 0.360 Co 0.005 Mn 0.635 [O2, over-lithiated manganese-rich oxide), 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 96.0:1.5:2.5 to produce a positive electrode mixture slurry (solid content 65 wt%). The positive electrode mixture slurry was coated on one side of a positive electrode current collector (Al thin film) with a thickness of 12 μm, and dried and roll pressed to produce a positive electrode.

[0133] A negative electrode active material (a mixture of artificial graphite and natural graphite in a weight ratio of 50.3:49.7), a conductive material (carbon black), and a binder (styrene-butadiene rubber) were added to distilled water, which is a solvent, at a weight ratio of 96.7:1.0:2.3 to produce a negative electrode mixture slurry (solid content 50 wt%). The negative electrode mixture slurry was coated on one side of a negative electrode current collector (Cu thin film) with a thickness of 8 μm, and dried and roll pressed to produce a negative electrode.

[0134] In a dry room, after interposing a polyethylene porous film separator between the positive electrode and the negative electrode manufactured above, the non-aqueous electrolyte manufactured above was injected to manufacture a secondary battery.

[0135] Example 2 In Example 1, except that 0.1 wt% of the compound represented by Chemical Formula 4A was added to the non-aqueous electrolyte, a non-aqueous electrolyte and a secondary battery were manufactured in the same manner as in Example 1.

[0136] Example 3 In Example 1, except that 3.0 wt% of the compound represented by Chemical Formula 4A was added to the non-aqueous electrolyte, a non-aqueous electrolyte and a secondary battery were manufactured in the same manner as in Example 1.

[0137] Example 4 In Example 1, an electrolyte and a secondary battery were produced in the same manner as in Example 1, except that a compound represented by the following Chemical Formula 4B was added to the non-aqueous electrolyte at 0.5% by weight instead of the compound represented by Chemical Formula 4A.

[0138]

Chem.

[0139] Example 5 In Example 4, an electrolyte and a secondary battery were produced in the same manner as in Example 4, except that a compound represented by Chemical Formula 4B was added to the non-aqueous electrolyte at 0.1% by weight.

[0140] Example 6 In Example 4, an electrolyte and a secondary battery were produced in the same manner as in Example 4, except that a compound represented by Chemical Formula 4B was added to the non-aqueous electrolyte at 3.0% by weight.

[0141] Comparative Example 1 An electrolyte and a lithium secondary battery were produced in the same manner as in Example 1, except that the compound represented by Chemical Formula 4A was not added.

[0142] Comparative Example 2 An electrolyte and a lithium secondary battery were produced in the same manner as in Example 1, except that a compound represented by the following Chemical Formula A was added instead of the compound represented by Chemical Formula 4.

[0143]

Chem.

[0144] Experimental Example Experimental Example 1: Evaluation of High-Temperature Cycle Capacity Retention Rate The lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 2 manufactured above were charged to 4.35 V at 45 °C under the conditions of CC / CV and 0.33C up to 1 / 40C using an electrochemical charger / discharger, and then discharged to 2.0 V under the conditions of CC and 0.33C. One cycle was defined as such, and charge and discharge were performed for 300 cycles to measure the capacity retention rate.

[0145] The capacity retention rate was calculated by the following formula, and the results are shown in Table 1 below.

[0146] Capacity retention rate (%) = {(discharge capacity after 300 cycles / discharge capacity after 1 cycle)} × 100

[0147] Experimental Example 2: Evaluation of high-temperature cycle resistance increase rate The lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 2 manufactured above were charged to 4.35 V at 45 °C under the conditions of CC / CV and 0.33C, and then discharged to 2.5 V under the conditions of CC and 0.33C. One cycle was defined as such, and charge and discharge were performed for 300 cycles.

[0148] After one cycle of charge and discharge, the discharge capacity after 1 cycle was measured using an electrochemical charger / discharger. After adjusting the SOC to 50% of SOC, a 2.5C pulse was applied for 10 seconds, and the initial resistance was calculated from the difference between the voltage before the pulse application and the voltage after the application.

[0149] After 300 cycles of charge and discharge, the resistance after 300 cycles was calculated by the same method as above, and the resistance increase rate was calculated using the following formula, and the results are shown in Table 1 below.

[0150] Resistance increase rate (%) = (resistance after 300 cycles - initial resistance) / initial resistance × 100

[0151] Experimental Example 3: Evaluation of volume increase rate after high-temperature cycle charge and discharge With respect to the lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 2 manufactured above, charge and discharge were performed 300 cycles in the same manner as in Experimental Example 1. At this time, the volume (initial volume) of the lithium secondary battery before charge and discharge was measured, and the volume of the lithium secondary battery after 300 cycles was measured. The volume increase rate was calculated by the following formula, and the results are shown in Table 3 below.

[0152] Volume increase rate (%) = {(Volume of lithium secondary battery after 300 cycles - Initial volume) / (Initial volume)} × 100

[0153]

Table 1

[0154] Referring to Table 1, the lithium secondary batteries of Examples 1 to 6 using the non-aqueous electrolyte containing the compound represented by Chemical Formula 1 are excellent in high-temperature cycle life performance compared to the lithium secondary batteries of Comparative Examples 1 to 2, and it can be confirmed that the resistance increase rate due to cycling is low and the volume increase due to cycling is small.

[0155] Experimental Example 4: Evaluation of capacity retention rate after high-temperature storage The lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 2 manufactured above were charged to 4.35 V at 1 / 40 C under CC / CV conditions at 0.33 C and discharged to 2.5 V at 0.33 C at 25 °C to perform initial charge and discharge. Then, after charging to 4.35 V at 1 / 40 C under CC / CV conditions at 0.33 C at 25 °C, they were stored at 60 °C for 12 weeks. After storage, the secondary batteries were charged to 4.35 V at 1 / 40 C under CC / CV conditions at 0.33 C at 25 °C and discharged to 2.0 V at 0.33 C, and the discharge capacity was measured.

[0156] The capacity retention rate was evaluated by the following formula, and the results are shown in Table 2 below.

[0157] Capacity retention rate (%) = (Discharge capacity after 12-week storage / Initial discharge capacity) × 100

[0158] Experimental Example 5: Evaluation of Resistance Increase Rate after High-Temperature Storage The lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 2 manufactured above were initially charged and discharged by the same method as in Experimental Example 4. After confirming the capacity at room temperature, they were charged at SOC50 based on the discharge capacity and discharged at a current of 3C for 10 seconds. The resistance was measured from the voltage drop difference at this time as the initial resistance. After storage at 60°C for 12 weeks, the resistance was measured by the same method as the final resistance, and the resistance increase rate was calculated by the following formula. The results are shown in Table 2 below.

[0159] Resistance increase rate (%) = (Final resistance - Initial resistance) / (Initial resistance) × 100

[0160] Experimental Example 6: Evaluation of Volume Increase Rate after High-Temperature Storage The lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 2 manufactured above were initially charged and discharged by the same method as in Experimental Example 4. Each battery was set to SOC50 based on the discharge capacity and the volume was measured, which was defined as the initial volume. After high-temperature storage at 60°C for 12 weeks at SOC100%, the measured volume was defined as the final volume, and the volume increase rate of the battery was calculated by the following formula. The results are shown in Table 2 below.

[0161] Volume increase rate (%) = (Final volume - Initial volume) / (Initial volume) × 100

[0162] [Table 2]

[0163] Referring to Table 2, it can be confirmed that the lithium secondary batteries of Examples 1 to 6 using the non-aqueous electrolyte containing the compound represented by Chemical Formula 1 are excellent in high-temperature storage life performance, have a low resistance increase rate, and little volume increase, compared with the lithium secondary batteries of Comparative Examples 1 to 2.

Claims

1. A non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive includes a compound represented by the following Chemical Formula 1: 【Chemical 1】 (In the above chemical formula 1, R １ ~R ６ are, independently of each other, hydrogen, halogen, nitrile group, propargyl group, ester group, ether group, ketone group, carboxy 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 a combination of two or more thereof, and R １ to R ６ At least one of them contains an isocyanate group.)

2. The non-aqueous electrolyte according to Claim 1, wherein the compound represented by Chemical Formula 1 includes a compound represented by the following Chemical Formula 2: 【Chemical Formula 2】 (In the above chemical formula 2, R １ is defined as in the above chemical formula 1, R １ contains an isocyanate group.)

3. The non-aqueous electrolyte according to Claim 1, wherein the compound represented by Chemical Formula 1 includes a compound represented by the following Chemical Formula 3: 【Chemical Formula 3】 (In the chemical formula 3, L １ is a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group, a substituted or unsubstituted alkynylene group, a sulfone group, a sulfonate group, or a combination of two or more thereof.)

4. 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 a compound represented by the following Chemical Formula 4A and a compound represented by the following Chemical Formula 4B. 【Chemical 4】

5. The non-aqueous electrolyte according to Claim 1, wherein the compound represented by Chemical Formula 1 is contained in the non-aqueous electrolyte in an amount of 0.01% by weight to 10% by weight.

6. The lithium salt is LiCl, LiBr, LiI, 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 ), and the non-aqueous electrolyte according to claim 1, comprising at least one selected from the group consisting of.

7. 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.

8. The non-aqueous electrolyte according to Claim 1, wherein the organic solvent includes at least one selected from the group consisting of a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent, and a cyclic ester-based organic solvent.

9. The additive is at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiPO ２ F ２ , LiODFB (lithium difluorooxalate borate), LiBOB (lithium bis(oxalato)borate), TMSSa (3-trimethoxysilyl-propyl-N-aniline), and TMSSi (tris(trimethylsilyl)phosphine), and further includes at least one additional additive selected from the group consisting of the non-aqueous electrolyte according to claim 1.

10. 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 non-aqueous electrolyte according to Claim 1, a lithium secondary battery.

11. The lithium secondary battery according to Claim 10, wherein the positive electrode active material includes a hyper-lithiated manganese-rich oxide containing 50 mol% or more of Mn in all metals excluding lithium and having a molar ratio of lithium to transition metal exceeding 1.

12. The lithium secondary battery according to Claim 11, wherein the hyper-lithiated manganese-rich oxide is a compound represented by the following Chemical Formula 6: [Chemical Formula 6] Li １＋ｓ [Ni ｔ Co ｕ Mn Ｖ M １ ｗ O ２＋ｚ (In Chemical Formula 6, M1 is one or more 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, 0.05 ≦ s ≦ 1, 0 ≦ t ≦ 0.5, 0 ≦ u ≦ 0.3, 0.5 ≦ v < 1.0, 0 ≦ w ≦ 0.2, 0 ≦ z ≦ 1.)

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