Non-aqueous electrolyte containing an additive for non-aqueous electrolyte, and lithium secondary battery containing the same

Abstract

The present invention provides a non-aqueous electrolyte containing an additive for a non-aqueous electrolyte represented by the following chemical formula 1: JPEG2024521798000025.jpg57170 (In the above Chemical Formula 1, R1 to R5 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and an alkoxy group having 1 to 10 carbon atoms, and R may be an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms, or -OR' (R' is an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms).)

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0103602 filed on August 6, 2021, and Korean Patent Application No. 10-2022-0093930 filed on July 28, 2022, and all the contents disclosed in the documents of the Korean patent applications 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 is increasing.

[0004] In particular, 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 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 may be eluted from the surface of the positive electrode. In this way, since the eluted transition metal ions are electro-deposited on the negative electrode to reduce the passivation ability of the SEI, a problem occurs in that the negative electrode deteriorates.

[0006] Such a deterioration phenomenon of the secondary battery tends to be further accelerated when the potential of the positive electrode increases or the battery is exposed to a high temperature.

[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 where 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 methods 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 multi-faceted 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] According to one embodiment, in order to achieve the above object, the present invention provides a non-aqueous electrolyte containing an additive for non-aqueous electrolytes represented by the following Chemical Formula 1.

[0013]

Chemical Formula

[0014] In Chemical Formula 1, R1 to R5 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and an alkoxy group having 1 to 10 carbon atoms, and R may be an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms, or -OR' (R' is an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms).

[0015] According to another embodiment, the present invention provides a lithium secondary battery including the non-aqueous electrolyte.

Advantages of the Invention

[0016] The compound represented by Chemical Formula 1 provided as an additive for the non-aqueous electrolyte of the present invention is a compound based on a coumarin structure, and can form a stable SEI (Solid Electrolyte Interphase) film on the surface of the negative electrode while being rapidly reductively decomposed during charge and discharge. Therefore, it is possible to suppress a decrease in the passivation ability of SEI at high temperatures and prevent deterioration of the negative electrode. Further, the reactive oxygen compound generated in the positive electrode containing a high-content nickel positive electrode active material binds to the coumarin structure contained in the compound represented by Chemical Formula 1, and has an effect of suppressing decomposition of the electrolyte and generation of gas.

[0017] In addition, the compound represented by Chemical Formula 1 provided as an additive for the non-aqueous electrolyte of the present invention can form a dense film on the electrode by further containing an aliphatic unsaturated hydrocarbon group in the coumarin structure. Thereby, there is an effect of suppressing deterioration due to an interfacial reaction at high temperatures.

[0018] Therefore, when the non-aqueous electrolyte of the present invention containing the compound of Chemical Formula 1 is used, an electrode-electrolyte interface that is stable and has low resistance can be formed even at high temperatures, so that a lithium secondary battery with improved high-temperature cycle characteristics and high-temperature storage characteristics and improved various performances can be realized.

Embodiments for Carrying Out the Invention

[0019] 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.

[0020] 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.

[0021] Also, in this specification, in the description of "a to b carbon atoms", "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 1 to 5 carbon atoms" means an alkylene group containing 1 to 5 carbon atoms, that is, -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH)3CH2-, -CH(CH3)CH2-, and -CH(CH3)CH2CH2-. Further, in this specification, the term "alkylene group" means a branched or unbranched divalent unsaturated hydrocarbon group.

[0022] In addition, in this specification, both the alkyl group and the alkylene 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 heterocycloalkyl 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.

[0023] Hereinafter, the present invention will be described in more detail.

[0024] Non-aqueous electrolyte The non-aqueous electrolyte according to one embodiment of the present invention contains a compound represented by the following Chemical Formula 1 as an additive. A secondary battery containing the non-aqueous electrolyte of the present invention can suppress deterioration due to interfacial reaction at high temperatures and can be excellent in high-temperature cycle characteristics and high-temperature storage characteristics.

[0025]

Chemical formula

[0026] In Chemical Formula 1, each of R1 to R5 may independently be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and an alkoxy group having 1 to 10 carbon atoms. Preferably, each of R1 to R5 may be any one selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Most preferably, each of R1 to R5 may be H.

[0027] In the above Chemical Formula 1, R may be an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms or -OR' (where R' is an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms). Preferably, R may be an aliphatic unsaturated hydrocarbon group having 2 to 5 carbon atoms or -OR' (where R' is an aliphatic unsaturated hydrocarbon group having 2 to 5 carbon atoms). By further including an aliphatic unsaturated hydrocarbon group in the coumarin structure, a dense film can be formed on the electrode, thereby having the effect of suppressing deterioration due to the interfacial reaction at high temperatures.

[0028] In the above Chemical Formula 1, the aliphatic unsaturated hydrocarbon group may contain a triple bond. When R in Chemical Formula 1 contains a triple bond, a dense film can be formed on the electrode, thereby having the effect of suppressing deterioration due to the interfacial reaction at high temperatures.

[0029] Also, in the above Chemical Formula 1, R may be an alkenyl group or an alkynyl group having 2 to 5 carbon atoms.

[0030] Specifically, the compound represented by Chemical Formula 1 of the present invention may be a compound represented by the following Chemical Formula 1-1.

[0031]

Chemical Formula

[0032] In the above Chemical Formula 1-1, R may be an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms or -OR' (where R' is an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms). Preferably, R may be an aliphatic unsaturated hydrocarbon group having 2 to 5 carbon atoms or -OR' (where R' is an aliphatic unsaturated hydrocarbon group having 2 to 5 carbon atoms). By further including an aliphatic unsaturated hydrocarbon group in the coumarin structure, a dense film can be formed on the electrode, thereby having the effect of suppressing deterioration due to the interfacial reaction at high temperatures.

[0033] In the above Chemical Formula 1-1, the aliphatic unsaturated hydrocarbon group may contain a triple bond. When R in Chemical Formula 1-1 contains a triple bond, a dense film can be formed on the electrode, thereby having the effect of suppressing deterioration due to the interfacial reaction at high temperatures.

[0034] Also, in Chemical Formula 1-1, R may be an alkenyl group or an alkynyl group having 2 to 5 carbon atoms.

[0035] Specifically, the compound represented by Chemical Formula 1 of the present invention may be any one of the compounds represented by the following Chemical Formulas 2-1 to 2-8.

[0036]

Chem.

[0037]

Chem.

[0038]

Chem.

[0039]

Chem.

[0040]

Chem.

[0041]

Chem.

[0042]

Chem.

[0043] [Chemical formula]

[0044] In the present invention, the additive for the non-aqueous electrolyte may be contained in an amount of 0.01 part by weight to 5 parts by weight, preferably 0.1 part by weight to 1 part by weight, more preferably 0.1 part by weight to 0.5 part by weight, based on 100 parts by weight of the non-aqueous electrolyte. When the content of the compound represented by Chemical Formula 1 is less than the above range, the effect of suppressing electrode deterioration is not sufficiently achieved. When the content of the compound represented by Chemical Formula 1 exceeds the above range, there is a problem that the hydrocarbon group containing an unsaturated bond excessively increases the resistance of the secondary battery and the life characteristics deteriorate.

[0045] When the content of the compound represented by Chemical Formula 1 is less than 0.01 part by weight, the positive / negative electrode film formation effect becomes minute as the driving time increases, and the electrode interface protection effect may decrease. Further, when the content of the compound represented by Chemical Formula 1 exceeds 5 parts by weight, not only does the viscosity of the electrolyte increase due to the excessive additive, but also the decrease in ionic conductivity due to the increase in viscosity adversely affects the mobility of ions in the battery, and the rate characteristics and life characteristics may deteriorate during high-temperature storage. Furthermore, due to the decomposition of the excessive additive, the battery resistance increases, and side reactions and by-products may occur.

[0046] The non-aqueous electrolyte according to the present invention may further contain a lithium salt, an organic solvent, and optionally other electrolyte additives.

[0047] 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 - 、NO3 - 、N(CN)2 - 、BF4 - 、ClO4 - 、B 10Cl 10 - 、AlCl4 - 、AlO2 - 、PF6 - 、CF3SO3 - 、CH3CO2 - 、CF3CO2 - 、AsF6 - 、SbF6 - 、CH3SO3 - 、(CF3CF2SO2)2N - 、(CF3SO2)2N - 、(FSO2)2N - 、BF2C2O4 - 、BC4O8 - 、PF4C2O4 - 、PF2C4O8 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、C4F9SO3 - 、CF3CF2SO3 - 、CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、CF3(CF2)7SO3 - 、およびSCN - at least one selected from the group consisting of

[0048] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10It may contain a single substance or a mixture of two or more selected from the group consisting of LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide; LiFSI), LiN(SO2CF2CF3)2 (lithium bis(perfluoroethanesulfonyl)imide; LiBETI), and LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide; LiTFSI). In addition to these, lithium salts commonly used in the electrolyte of lithium secondary batteries can be used without limitation.

[0049] The lithium salt can be appropriately changed within the normally usable range. However, in order to obtain the effect of forming an optimal coating for preventing corrosion of the electrode surface, it may be contained in the electrolyte at a concentration of 0.5 M to 5.0 M, preferably 0.8 M to 2.5 M, more preferably 1.0 M to 2.0 M.

[0050] When the concentration of the lithium salt is less than 0.5 M, the condition of excessive lithium deficiency occurs, and the capacity and cycle characteristics of the lithium secondary battery deteriorate. When the concentration exceeds 5.0 M, the viscosity of the non-aqueous electrolyte increases excessively, resulting in a decrease in electrolyte impregnation and a decrease in ionic conductivity, which may cause performance deterioration due to an increase in battery resistance.

[0051] 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.

[0052] Specifically, the organic solvent may contain a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, or a mixed organic solvent thereof.

[0053] The cyclic carbonate-based organic solvent is a high-viscosity organic solvent and has a high dielectric constant, so it is an organic solvent that can well dissociate 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), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. Among them, it may contain ethylene carbonate.

[0054] 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, it may contain ethyl methyl carbonate (EMC).

[0055] 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.

[0056] 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.

[0057] In addition, 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.

[0058] On the other hand, the organic solvent may, if necessary, be added and used without being limited to the organic solvents commonly used in non-aqueous electrolytes. 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.

[0059] 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.

[0060] The glyme-based solvent has a higher dielectric constant and a lower surface tension than linear carbonate-based organic solvents and has less reactivity with metals, and may contain at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraethylene glycol dimethyl ether (TEGDME), but is not limited thereto.

[0061] 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, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0062] In addition, the non-aqueous electrolyte of the present invention may further contain a known electrolyte additive in the non-aqueous electrolyte as needed 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 low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, battery expansion suppression effect at high temperatures, and the like.

[0063] Such other electrolyte additives may include, as representative examples thereof, at least one or more additives for forming an SEI film selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0064] Examples of the cyclic carbonate compound include vinylene carbonate (VC) or vinyl ethylene carbonate.

[0065] Examples of the halogen-substituted carbonate compound include fluoroethylene carbonate (FEC).

[0066] Examples of the sultone compound include at least one or more compounds 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.

[0067] Examples of the sulfate compound include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0068] 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.

[0069] Examples of the borate compound include tetraphenylborate, lithium oxalyldifluoroborate (LiODFB), and lithium bisoxalate borate (LiB(C2O4)2, LiBOB).

[0070] Examples of the nitrile compound include at least one or more compounds 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.

[0071] 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.

[0072] 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), LiPO2F2, or LiBF4.

[0073] Among such other electrolyte additives, when further containing 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, suppressing the generation of gases that can be generated by the decomposition of the electrolyte at high temperatures, and improving the high - temperature stability of the secondary battery.

[0074] On the other hand, two or more of the other electrolyte additives may be mixed and used. Based on the total weight of the non - aqueous electrolyte, they may be contained in an amount of 0.01 to 20% by weight, specifically 0.01 to 10% by weight, and preferably 0.05 to 5% by weight. When the content of the other electrolyte additives is less than 0.01% by weight, the improvement effect on the high - temperature storage characteristics and high - temperature life characteristics of the battery is negligible. When the content of the other electrolyte additives exceeds 20% by weight, side reactions in the electrolyte may occur excessively during the charge and discharge of the battery. In particular, when the other electrolyte additives are added in excess, they are not sufficiently decomposed at high temperatures, so they may exist in an unreacted or precipitated state in the electrolyte at normal temperature. As a result, side reactions that reduce the life or resistance characteristics of the secondary battery may occur.

[0075] Lithium secondary battery The present invention also provides a lithium secondary battery including the non - aqueous electrolyte.

[0076] 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.

[0077] 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 interior of a battery case, and the non - aqueous electrolyte according to the present invention is injected to manufacture it.

[0078] (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.

[0079] 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.

[0080] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium. Specifically, it 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 (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2), etc.), a lithium-nickel-manganese-cobalt-based oxide (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 Coq1 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) oxide (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 the respective independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc.), and any one or two or more of these compounds may be included.

[0081] Among them, from the point of view of being able to improve the capacity characteristics and stability of the battery, the lithium metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, 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 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.). Also, considering the remarkable improvement effect by controlling the type and content ratio of the constituent elements forming the lithium composite metal oxide, the lithium composite metal 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(Ni0.7 Mn 0.15 Co 0.15 )O2, and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2 or the like may be used, and a mixture of any one or two or more of these may also be used.

[0082] Among them, from the viewpoint of being able to maximize the capacity characteristics of the battery, a positive electrode active material in which the nickel content is 80 atm% or more in the total transition metal content can be used. For example, the positive electrode active material may contain a lithium transition metal oxide represented by the following Chemical Formula 3.

[0083] [Chemical Formula 3] Li x Ni a Co b M 1 c M 2 d O2

[0084] In the Chemical Formula 3, the M 1 is one or more selected from Mn and Al, and preferably may be Mn, or a combination of Mn and Al.

[0085] M 2 may be one or more selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P, and S.

[0086] The x represents the atomic fraction of lithium in the lithium transition metal oxide, and 0.90 ≤ x ≤ 1.1, preferably 0.95 ≤ x ≤ 1.08, and more preferably 1.0 ≤ x ≤ 1.08 may be used.

[0087] The a represents the atomic fraction of nickel among the metal elements excluding lithium in the lithium transition metal oxide, and 0.80 ≤ a < 1.0, preferably 0.80 ≤ a ≤ 0.95, and more preferably 0.80 ≤ a ≤ 0.90 may be used. When the nickel content satisfies the above range, high capacity characteristics can be realized.

[0088] Said b represents the atomic fraction of cobalt among the metal elements excluding lithium in the lithium transition metal oxide, and may be 0 < b < 0.2, 0 < b ≤ 0.15, or 0.01 ≤ b ≤ 0.10.

[0089] Said c represents the atomic fraction of M among the metal elements excluding lithium in the lithium transition metal oxide, and may be 0 < c < 0.2, 0 < c ≤ 0.15, or 0.01 ≤ c ≤ 0.10. 1

[0090] Said d represents the atomic fraction of M among the metal elements excluding lithium in the lithium transition metal oxide, and may be 0 ≤ d ≤ 0.1 or 0 ≤ d ≤ 0.05. 2

[0091] Said cathode active material may be contained in an amount of 60 to 99% by weight, preferably 70 to 99% by weight, more preferably 80 to 98% by weight, based on the total weight of the solid content in the cathode binder slurry.

[0092] Said binder is a component that assists in binding the active material and the conductive material, etc., and binding to the current collector.

[0093] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene - propylene - diene, sulfonated ethylene - propylene - diene, styrene - butadiene rubber, fluororubber, various copolymers, and the like.

[0094] Usually, said binder may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight, based on the total weight of the solid content in the cathode binder slurry.

[0095] The conductive material is a component for further improving the conductivity of the positive electrode active material.

[0096] 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; conductive fibers such as carbon fibers, carbon nanotubes, and metal fibers; carbon fluoride powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0097] Generally, the conductive material may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight, based on the total weight of the solid content in the positive electrode binder slurry.

[0098] 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 and 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 a binder and a conductive material, is 50 to 95% by weight, preferably 70 to 95% by weight, more preferably 70 to 90% by weight.

[0099] (2) Negative electrode The negative electrode can be manufactured, for example, by coating a negative electrode binder slurry containing a negative electrode active material, a binder, a conductive material, and 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.

[0100] For example, when manufacturing a negative electrode by coating a negative electrode current collector with a negative electrode active material slurry, the negative electrode current collector generally has a thickness of 3 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, 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 films, sheets, foils, meshes, porous bodies, foams, non-woven fabric bodies, etc.

[0101] 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.

[0102] The carbon material capable of reversibly intercalating / deintercalating lithium ions is not particularly limited as long as it is a carbon-based negative electrode active material generally used in lithium-ion secondary batteries and can be used without particular limitation. Representative examples thereof include crystalline carbon, amorphous carbon, or both of these may be used. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature fired carbon) or hard carbon, mesophase pitch carbide, fired coke, etc.

[0103] 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.

[0104] Examples of the metal composite oxide include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3(0 ≦ x ≦ 1), Li x WO2(0 ≦ x ≦ 1), and Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, elements of Group 1, Group 2, Group 3 of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) selected from the group can be used.

[0105] Examples of the substance that can dope and undope lithium include Si, SiO x (0 < x ≦ 2), Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc. Also, at least one of these and SiO2 may be mixed and used. The element Y may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0106] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadate, and the like.

[0107] The negative electrode active material may be contained in an amount of 60 to 99% by weight, preferably 70 to 99% by weight, more preferably 80 to 98% by weight, based on the total weight of the solid content in the negative electrode binder slurry.

[0108] The binder is a component that aids in the bonding between the conductive material, the active material, and the current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0109] Generally, the binder may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight, based on the total weight of the solid content in the negative electrode binder slurry.

[0110] The conductive material is a component for further improving the conductivity of the negative electrode active material, and is not particularly limited as long as it has conductivity without causing a chemical change in the battery. 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; conductive fibers such as carbon fibers, carbon nanotubes, or metal fibers; carbon fluoride powder; conductive powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0111] The conductive material may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight, based on the total weight of the solid content in the negative electrode active material slurry.

[0112] 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, a conductive material, etc. 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% to 95% by weight, preferably 70% to 90% by weight.

[0113] When using the metal itself as the negative electrode, it can be manufactured by methods 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.

[0114] For example, the metal bonded / 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.

[0115] (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 polymer such as a homopolymer of ethylene, a homopolymer of propylene, 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 nonwoven fabric, for example, a nonwoven fabric made of high melting point 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 as a single layer or a multilayer structure.

[0116] 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.

[0117] 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 changes belong to the scope of the appended claims.

[0118] Examples Example 1 (Production of non-aqueous electrolyte) LiPF6 was dissolved in an organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 3:7 by volume ratio) to be 1.0 M, vinylene carbonate (VC) was 0.5 wt%, 1,3-propane sultone (PS) was 0.5 wt%, ethylene sulfate (Esa) was 1.0 wt%, and lithium difluorophosphate (LiDFP) was 0.8 wt% to produce a non-aqueous solvent. 0.1 g of 7-ethynylcoumarin (the compound of Chemical Formula 2-1) was added to 99.9 g of the non-aqueous solvent to produce a non-aqueous electrolyte.

[0119] (Manufacture of Lithium Secondary Battery) Positive electrode active material (LiNi 0.85 Co 0.05 Mn 0.07 Al 0.03 O2), conductive material (carbon nanotube), and binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP), which is a solvent, at a weight ratio of 98.0:0.7:1.3 to produce a positive electrode mixture slurry (solid content: 76.5% by weight). The positive electrode mixture slurry was applied to one surface of a positive electrode current collector (Al thin film) with a thickness of 12 μm, followed by drying and roll pressing to produce a positive electrode.

[0120] Negative electrode active material (artificial graphite), conductive material (carbon black), and binder (styrene-butadiene rubber) were added to distilled water, which is a solvent, at a weight ratio of 96.5:1.5:2.0 to produce a negative electrode mixture slurry (solid content: 50% by weight). The negative electrode mixture slurry was applied to one surface of a negative electrode current collector (Cu thin film) with a thickness of 8 μm, followed by drying and roll pressing to produce a negative electrode.

[0121] In a dry room, a polyethylene porous film separator was interposed between the positive electrode and the negative electrode manufactured above, and then the non-aqueous electrolyte manufactured above was injected to produce a secondary battery.

[0122] Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 0.3 g of 7-ethynylcoumarin (the compound of Chemical Formula 2-1) was added to 99.7 g of the non-aqueous solvent manufactured in Example 1 to produce a non-aqueous electrolyte.

[0123] Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of 7-ethynylcoumarin (the compound of Chemical Formula 2-1) was added to 99.5 g of the non-aqueous solvent manufactured in Example 1 to produce a non-aqueous electrolyte.

[0124] Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that 1.0 g of 7-ethynylcoumarin (the compound of Chemical Formula 2-1) was added to 99.0 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0125] Example 5 A secondary battery was manufactured in the same manner as in Example 2, except that 0.3 g of 7-(propargyloxy)-coumarin (the compound of Chemical Formula 2-6) was added instead of 0.3 g of 7-ethynylcoumarin (the compound of Chemical Formula 2-1) to 99.7 g of the non-aqueous solvent produced in Example 2 to produce a non-aqueous electrolyte.

[0126] Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was produced using 100 g of the non-aqueous solvent produced in Example 1.

[0127] Experimental Example 1 - Evaluation of High-Temperature Cycle Characteristics The cycle characteristics of each of the secondary batteries manufactured in Examples 1 to 5 and Comparative Example 1 were evaluated.

[0128] Specifically, each of the batteries manufactured in Examples 1 to 5 and Comparative Example 1 was charged at a constant current of 0.33C to 4.2V at 45°C and discharged at a constant current of 0.33C to 3.0V. One cycle was defined as such, and after 100 cycles of charge and discharge, the capacity retention rate with respect to the initial capacity after 100 cycles was measured. The results are shown in Table 1 below.

[0129]

Table 1

[0130] As shown in Table 1, it was confirmed that Examples 1 to 5 using the additive for non-aqueous electrolytes of the present invention had a higher capacity retention rate and excellent life characteristics compared to Comparative Example 1 which did not use it.

[0131] 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 5 and Comparative Example 1.

[0132] Specifically, each of the secondary batteries of Examples 1 to 5 and Comparative Example 1 was fully charged to 4.2 V and then stored at 60 °C for 8 weeks.

[0133] Before storage, the thickness of the cell body portion of the fully charged secondary battery was measured with a flat plate measuring instrument and set as the thickness of the initial secondary battery.

[0134] After 8 weeks, the thickness of the cell body portion of the stored secondary battery was further measured with a flat plate measuring instrument, and the increased thickness during the 8-week storage period was calculated. The percentage ratio of the increased thickness to the thickness of the initial secondary battery was calculated to derive the thickness increase rate after 8 weeks. The results are shown in Table 2 below.

[0135]

Table 2

[0136] As shown in Table 2 above, it was confirmed that the secondary batteries of Examples 1 to 5 had a lower thickness increase rate after 8 weeks and less gas generation at high temperature compared to the secondary battery of Comparative Example 1.

Claims

1. A non-aqueous electrolyte containing an additive for non-aqueous electrolytes represented by the following Chemical Formula 1. 【Chemical 1】 (In the above chemical formula 1, R １ ~R ５ is each independently any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and an alkoxy group having 1 to 10 carbon atoms, R is an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms, or -OR' (where R' is an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms).

2. The non-aqueous electrolyte according to Claim 1, wherein R contains a triple bond.

3. The non-aqueous electrolyte according to Claim 1, wherein R is an alkenyl group having 2 to 5 carbon atoms or an alkynyl group having 2 to 5 carbon atoms.

4. The non-aqueous electrolyte according to Claim 1, wherein the additive for non-aqueous electrolytes represented by Chemical Formula 1 is at least one selected from the group consisting of compounds represented by the following Chemical Formula 1-1. 【Chemical 2】 (In Chemical Formula 1-1, R is an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms, or -OR' (where R' is an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms).)

5. The non-aqueous electrolyte according to Claim 1, wherein the additive for non-aqueous electrolytes represented by Chemical Formula 1 is at least one selected from the group consisting of compounds represented by the following Chemical Formulas 2-1 to 2-8. 【Chemical Formula 3】 [Chemical Formula 4] 【Chemical Formula 5】 ​ 【Chemical Formula 7】 [Chemical 8] 【Chemical Formula 9】 【Chemical Formula 10】

6. The non-aqueous electrolyte according to Claim 1, wherein the additive for non-aqueous electrolytes is contained in an amount of 0.01 parts by weight to 5 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.

7. The non-aqueous electrolyte according to Claim 1, further comprising a lithium salt and an organic solvent.

8. The lithium salt is LiCl, LiBr, LiI, LiBF ４ , LiClO ４ , Li₂B₁₀Cl₁₀, 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 7, which is one or more selected from the group consisting of

9. The non-aqueous electrolyte according to Claim 7, wherein the lithium salt is contained at a concentration of 0.5 M to 5.0 M.

10. The non-aqueous electrolyte according to Claim 7, wherein the organic solvent contains at least one organic solvent 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.

11. 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, A lithium secondary battery comprising the non-aqueous electrolyte according to any one of Claims 1 to 10.

12. The lithium secondary battery according to Claim 11, wherein the positive electrode active material contains a lithium transition metal oxide represented by the following Chemical Formula 3. [Chemical Formula 3] Li ｘ Ni ａ Co ｂ M １ ｃ M ２ ｄ O ２ (In Chemical Formula 3, M １ is one or more selected from Mn and Al, M ２ is one or more selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P, and S, 0.90 ≤ x ≤ 1.1, 0.80 < a < 1.0, 0 < b < 0.2, 0 < c < 0.2, 0 ≤ d ≤ 0.1.)

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