Non-aqueous electrolyte and lithium secondary battery containing the same

Abstract

The present invention provides a non-aqueous electrolyte comprising a lithium salt and an organic solvent, the organic solvent containing a compound represented by the following Chemical Formula 1, the compound represented by Chemical Formula 1 being contained in an amount of 25 to 80% by weight based on the total weight of the non-aqueous electrolyte: JPEG2024534535000021.jpg54170 (In the above Chemical Formula 1, R1 and R2 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, and an aryl group having 6 to 20 carbon atoms, and X may be a perfluoroalkyl group having 1 to 5 carbon atoms.)

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0059547, filed on May 16, 2022, and all the contents disclosed in the document of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to a non-aqueous electrolyte 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 automobiles, 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, which has a 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 elute from the surface of the positive electrode. In this way, the eluted transition metal ions electro-deposit on the negative electrode and reduce the passivation ability of the SEI, resulting in a problem that the negative electrode deteriorates.

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

[0007] 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.

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

Summary of the Invention

Problems to be Solved by the Invention

[0009] As a result of conducting extensive research to solve the above problems, the present invention aims to provide a non-aqueous electrolyte containing an organic solvent 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] Furthermore, the present invention aims to provide a lithium secondary battery that has improved high-temperature cycle characteristics and high-temperature storage characteristics and enhanced performance by including the above non-aqueous electrolyte.

Means for Solving the Problems

[0011] According to one embodiment, in order to achieve the above object, the present invention provides a non-aqueous electrolyte containing a lithium salt and an organic solvent. The non-aqueous electrolyte of the present invention contains, as an organic solvent, a compound represented by the following Chemical Formula 1, and the compound represented by the Chemical Formula 1 is contained in an amount of 25 to 80% by weight based on the total amount of the non-aqueous electrolyte.

[0012]

Chem.

[0013] In Chemical Formula 1, R1 and R2 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, and an aryl group having 6 to 20 carbon atoms, and X may be a perfluoroalkyl group having 1 to 5 carbon atoms.

[0014] According to another embodiment, the present invention provides a lithium secondary battery including the non-aqueous electrolyte.

Advantages of the Invention

[0015] The non-aqueous electrolyte of the present invention contains, as an organic solvent, the compound represented by Chemical Formula 1. Since the compound represented by Chemical Formula 1 has a sulfonamide group, the formation of an organic film derived from carbonate, which is thermally unstable and has high electrolyte permeability, is minimized, and the generation of oxidation gas is suppressed. Therefore, the occurrence of side reactions between the positive electrode and the electrolyte at high voltage is reduced. As a result, the non-aqueous electrolyte of the present invention can suppress the deterioration of the positive electrode and reduce the side reactions between the positive electrode and the electrolyte, and thus has the effect of generating less gas. In particular, such an effect is further maximized when exposed to high temperatures.

[0016] In addition, in the compound represented by Chemical Formula 1, a perfluoroalkyl group is not directly connected to the sulfur atom of the sulfonamide group, but is connected via an oxygen atom. Due to such a feature, the terminal -CF3 is easily reduced to the form of LiF. That is, the compound represented by Chemical Formula 1 can form a polymer-inorganic film rich in inorganic substances such as LiF, so that the deterioration of the negative electrode due to the interfacial reaction is suppressed.

[0017] The compound represented by Chemical Formula 1 has excellent interaction with anions present in the electrolyte, and thus has high anion solvation ability. Therefore, the compound represented by Chemical Formula 1 has F at the negative electrode -Since the amount of the base inorganic film can be increased, a stable SEI (Solid Electrolyte Interphase) film can be formed on the surface of the negative electrode. Therefore, it is possible to suppress the decrease in the passivation ability of SEI at high temperatures and prevent the deterioration of the negative electrode, so that the life characteristics of the battery can be improved.

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

Mode 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 inventor 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 the inventor can appropriately define the concept of the terms in order to explain his invention in the best way.

[0020] In this specification, terms such as "comprising", "including", or "having" are intended to specify the presence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood to preclude in advance the presence or addition possibility of one or more other features, numbers, steps, components, or combinations thereof.

[0021] On the other hand, before explaining the present invention, unless otherwise specifically mentioned in the present invention, "*" means a connected part between the ends of the same or different atoms or chemical formulas.

[0022] In addition, in this specification, in the description of "carbon atoms a to b", "a" and "b" mean the number of carbon atoms contained in a specific functional group. That is, the functional group may contain "a" to "b" carbon atoms. For example, an "alkylene group having 1 to 5 carbon atoms" means an alkylene group containing 1 to 5 carbon atoms, that is, -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH3)CH-, -CH(CH3)CH2-, and -CH(CH3)CH2CH2-.

[0023] In addition, in this specification, the term "alkylene group" means a branched or unbranched divalent unsaturated hydrocarbon group.

[0024] In addition, in this specification, both the alkyl group and the alkylene group may or may not be substituted. The term "substituted", unless otherwise defined, means that at least one or more hydrogens bonded to carbon are substituted with elements other than hydrogen. For example, it means being substituted with an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkenyl group having 3 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, etc.

[0025] Hereinafter, the present invention will be described in more detail.

[0026] Non-aqueous electrolyte The non-aqueous electrolyte of the present invention contains a lithium salt and an organic solvent, and contains a compound represented by the following Chemical Formula 1 as the organic solvent.

[0027]

Chemical Formula

[0028] In Chemical Formula 1, R1 and R2 may each independently be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, and an aryl group having 6 to 20 carbon atoms. Preferably, R1 and R2 may each independently be an alkyl group having 1 to 5 carbon atoms. When there is a substituent with less steric hindrance in the sulfonamide group, it is more preferable because the ability to solvate lithium ions as an organic solvent is large.

[0029] In Chemical Formula 1, X may be a perfluoroalkyl group having 1 to 5 carbon atoms, and preferably, X may be CF3 or CF2CF3.

[0030] Specifically, the compound of Chemical Formula 1 may be any one selected from the group consisting of the compounds of Chemical Formulas 1a to 1f below, but is not limited thereto.

[0031]

Chemical Formula

[0032]

Chemical Formula

[0033]

Chemical Formula

[0034]

Chemical Formula

[0035]

Chemical Formula

[0036] [Chemical formula]

[0037] The compound represented by the above chemical formula 1 may be contained in an amount of 25 to 80% by weight, preferably 25 to 60% by weight, and most preferably 30 to 40% by weight, based on the total amount of the non-aqueous electrolyte. When the above range is satisfied, a sufficiently strong film can be formed on the negative electrode, and a lithium secondary battery with improved high-temperature life characteristics and high-temperature storage characteristics can be provided. In particular, when the compound represented by the chemical formula 1 is contained in an amount of less than 25% by weight based on the total amount of the non-aqueous electrolyte, a film containing sufficient LiF inorganic substance cannot be formed on the negative electrode, and there is a problem that the high-temperature cycle and high-temperature storage characteristics are not sufficient.

[0038] The compound represented by the above chemical formula 1 may be contained in an amount of 10 to 50% by volume, preferably 10 to 40% by volume, and most preferably 15 to 35% by volume, based on the total volume of the organic solvent. When all or part of the cyclic carbonate organic solvent conventionally used in the non-aqueous electrolyte is replaced with the compound represented by the chemical formula 1, the problem that the cyclic carbonate is exposed to a high voltage and generates a large amount of gas can be solved.

[0039] In addition to the compound represented by the chemical formula 1, the non-aqueous electrolyte of the present invention may contain at least one organic solvent 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 as the non-aqueous organic solvent. Preferably, the non-aqueous electrolyte of the present invention may further contain a compound represented by the chemical formula 1 and a linear carbonate-based organic solvent as the organic solvent.

[0040] The linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant. As representative examples thereof, 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 may be used. Specifically, it may contain diethyl carbonate (DEC).

[0041] The cyclic carbonate-based organic solvent is an organic solvent having high viscosity and high dielectric constant, and is an organic solvent that easily dissociates lithium salts in the electrolyte. Specific examples thereof include at least one or more organic solvents selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0042] In addition, the organic solvent may further contain at least one or more ester-based organic solvents selected from the group consisting of linear ester-based organic solvents and cyclic ester-based organic solvents in order to produce an electrolyte having high ionic conductivity.

[0043] 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.

[0044] 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.

[0045] On the other hand, the organic solvent may be used by adding, without limitation, the organic solvents usually used in non-aqueous electrolytes as necessary. For example, it may further contain at least one or more organic solvents such as ether-based organic solvents, glyme-based solvents, and nitrile-based organic solvents.

[0046] 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.

[0047] The glyme-based solvent has a higher dielectric constant and a lower surface tension than linear carbonate-based organic solvents, and is a solvent with less reactivity with metals, and may contain at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME), but is not limited thereto.

[0048] 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.

[0049] The lithium salt contained in the non-aqueous electrolyte of the present invention is used as an electrolyte salt in a lithium secondary battery and is used as a mediator for transmitting ions. Usually, as the lithium salt, for example, Li as a cation+ including, as an anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 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 - , and SCN - at least one selected from the group consisting of

[0050] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10, it 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, LiFSI (lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), LiBETI (lithium bis(perfluoroethanesulfonyl)imide, LiN(SO2CF2CF3)2), and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, LiN(SO2CF3)2). In addition to these, lithium salts commonly used in the electrolyte of lithium secondary batteries can be used without limitation.

[0051] The lithium salt can be appropriately changed within the range that can be normally used. 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 0.1 M to 5.0 M, preferably 0.5 M to 3.0 M, more preferably 1.0 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of the lithium secondary battery is sufficient, the viscosity of the non-aqueous electrolyte is appropriate, and the electrolyte impregnation property is improved.

[0052] Further, the non-aqueous electrolyte of the present invention prevents the non-aqueous electrolyte from being decomposed in a high-power environment and causing the collapse of the negative electrode, or further improves the low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, battery expansion suppression effect at high temperature, etc. Therefore, if necessary, the non-aqueous electrolyte may further contain a known electrolyte additive.

[0053] Such other electrolyte additives may contain, as a representative example, at least one or more SEI film-forming additives 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.

[0054] Examples of the cyclic carbonate compound include vinylene carbonate (VC) or vinyl ethylene carbonate.

[0055] Examples of the halogen-substituted carbonate compound include fluoroethylene carbonate (FEC).

[0056] Examples of the sultone compound include at least one compound selected from the group consisting of 1,3-propanesultone (PS), 1,4-butanesultone, ethenesultone, 1,3-propenesultone (PRS), 1,4-butenesultone, and 1-methyl-1,3-propenesultone.

[0057] Examples of the sulfate compound include ethylene sulfate (Ethylene Sulfate; Esa), trimethylene sulfate (Trimethylene sulfate; TMS), or methyl trimethylene sulfate (Methyl trimethylene sulfate; MTMS).

[0058] 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.

[0059] Examples of the borate compound include tetraphenylborate, lithium oxalyldifluoroborate (LiODFB), and lithium bisoxalate borate (LiB(C2O4)2, LiBOB).

[0060] Examples of the nitrile compound include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0061] Examples of the benzene compound include fluorobenzene. Examples of the amine compound include triethanolamine or ethylenediamine. An example of the silane compound is tetravinylsilane.

[0062] 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.

[0063] Among such other electrolyte additives, when further containing a combination of vinylene carbonate (VC), 1,3-propane sultone (PS), and ethylene sulfate (Esa), a stronger SEI film can be formed on the surface of the negative electrode during the initial activation process of the secondary battery, the generation of gas that may be generated by the decomposition of the electrolyte at high temperature can be suppressed, and the high-temperature stability of the secondary battery can be improved.

[0064] 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 0.1 to 10% by weight, specifically 0.2 to 8% by weight, and preferably 0.5 to 8% by weight. When the content of the other electrolyte additives satisfies the above range, a more excellent improvement effect on ion conductivity and cycle characteristics can be obtained.

[0065] Lithium secondary battery The present invention also provides a lithium secondary battery including the non-aqueous electrolyte.

[0066] 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.

[0067] 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.

[0068] (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.

[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 conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel may be used.

[0070] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (for example, LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (for example, LiCoO2, etc.), a lithium-nickel-based oxide (for example, LiNiO2, etc.), a lithium-nickel-manganese-based oxide (for example, LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z NiZ 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 r )O2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2, etc.), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni p2 Co q2 Mn r2 M s2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s2 are the atomic fractions of the respective independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, p2 + q2 + r2 + s2 = 1, etc.), etc. may be mentioned, and any one or two or more of these compounds may be included.

[0071] Among them, from the viewpoint of being able to enhance 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 Mn0.15 Co 0.15 )O2, and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), or lithium nickel manganese cobalt aluminum oxide (e.g., Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 )O2), etc. may be used, and a mixture of any one or two or more of these may also be used.

[0072] Among them, from the point that the capacity characteristics of the battery can be enhanced most, a positive electrode active material with a nickel content of 80 atm% or more may be used. For example, the lithium transition metal oxide may include those represented by the following Chemical Formula 2.

[0073] [Chemical Formula 2] Li x Ni a Co b M 1 c M 2 d O2

[0074] In the Chemical Formula 2, the M 1 is one or more selected from Mn and Al, and preferably may be Mn, or a combination of Mn and Al.

[0075] M 2 may be one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb.

[0076] 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.

[0077] Said a represents the atomic fraction of nickel among the metal elements excluding lithium in the lithium transition metal oxide, where 0.80 ≦ a < 1.0, preferably 0.80 ≦ a ≦ 0.95, and more preferably 0.80 ≦ a ≦ 0.90. When the nickel content satisfies the above range, high-capacity characteristics can be realized.

[0078] Said b represents the atomic fraction of cobalt among the metal elements excluding lithium in the lithium transition metal oxide, where 0 < b < 0.2, 0 < b ≦ 0.15, or 0.01 ≦ b ≦ 0.10 may be applicable.

[0079] Said c represents the atomic fraction of M among the metal elements excluding lithium in the lithium transition metal oxide 1 and 0 < c < 0.2, 0 < c ≦ 0.15, or 0.01 ≦ c ≦ 0.10 may be applicable.

[0080] Said d represents the atomic fraction of M among the metal elements excluding lithium in the lithium transition metal oxide 2 and 0 ≦ d ≦ 0.1 or 0 ≦ d ≦ 0.05 may be applicable.

[0081] Said positive electrode active material may be contained in an amount of 60 to 99% by weight, preferably 70 to 99% by weight, and more preferably 80 to 98% by weight, based on the total weight of the solid matter excluding the solvent in the positive electrode mixture slurry.

[0082] Said binder is a component that aids in binding the active material and the conductive material, etc., and binding to the current collector.

[0083] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, various copolymers, and the like.

[0084] 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 excluding the solvent in the positive electrode active material slurry.

[0085] The conductive material is a component for further improving the conductivity of the positive electrode active material, and may be added in an amount of 1 to 20% by weight based on the total weight of the solid content in the positive electrode active material slurry. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, carbon powder such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride powder; conductive powder 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 can be used.

[0086] 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 matter excluding the solvent in the positive electrode active material slurry.

[0087] 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.

[0088] (2) Negative electrode The negative electrode can be manufactured, for example, by coating a negative electrode mixture slurry containing a negative electrode active material, a binder, a conductive material, a solvent, etc. on a negative electrode current collector, or a graphite electrode made of carbon (C) or the metal itself can be used as the negative electrode.

[0089] For example, when manufacturing a negative electrode by coating a negative electrode mixture slurry on the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 μm to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those with a surface treatment of carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. may be used. Also, similar to the positive electrode current collector, the binding force of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and it may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

[0090] The negative electrode active material layer manufactured by coating on the negative electrode current collector may contain SiOx (0 ≦ x < 2), that is, Si or SiO x (0 < x < 2) with respect to the whole negative electrode active material layer. Also, the negative electrode active material layer may contain 10 wt% or more of SiOx (0 ≦ x < 2), preferably 10 wt% to 20 wt% of SiOx (0 ≦ x < 2), more preferably 10 wt% to 15 wt% of SiOx (0 ≦ x < 2) with respect to its total weight. When the content of SiOx (0 ≦ x < 2) satisfies the above range, a large-capacity lithium secondary battery can be manufactured.

[0091] As an additional negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used for the negative electrode active material.

[0092] 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, an alloy of these metals and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0093] As the carbon material capable of reversibly intercalating / deintercalating lithium ions, any carbon-based negative electrode active material generally used in lithium ion secondary batteries can be used without particular limitation. Representative examples thereof include crystalline carbon, amorphous carbon, or a combination of these. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0094] 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.

[0095] 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) can be used.

[0096] Examples of the substance capable of doping and undoping lithium include Si-Y alloys (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 may be mixed with SiO2 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.

[0097] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, etc.

[0098] 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.

[0099] The binder is a component that assists 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, fluorine rubber, various copolymers thereof, etc.

[0100] Generally, the binder may be contained in an amount of 1% by weight to 20% by weight, preferably 1% by weight to 15% by weight, more preferably 1% by weight to 10% by weight, based on the total weight of the solids excluding the solvent in the negative electrode binder slurry.

[0101] The conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 1% by weight to 20% by weight based on the total weight of the solid content in the negative electrode binder slurry. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powders such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride powders; 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.

[0102] The conductive material may be contained in an amount of 1% by weight to 20% by weight, preferably 1% by weight to 15% by weight, more preferably 1% by weight to 10% by weight, based on the total weight of the solids excluding the solvent in the negative electrode binder slurry.

[0103] The solvent may contain water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a suitable viscosity when the negative electrode active material and optionally a binder and a conductive material are included. For example, it may be included such that the concentration of the solid content including the negative electrode active material and optionally a binder and a conductive material is 50% by weight to 95% by weight, preferably 70% by weight to 90% by weight.

[0104] 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.

[0105] 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.

[0106] (3) Separator Also, as the separator, a normal porous polymer film conventionally used as a separator, for example, a porous polymer film made of a polyolefin-based polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, may be used alone or by laminating them. Alternatively, a normal porous non-woven fabric, for example, a non-woven fabric made of high-melting glass fibers, polyethylene terephthalate fibers, etc. may be used, but it is not limited thereto. Further, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and it may be selectively used as a single-layer or multi-layer structure.

[0107] The outer shape of the lithium secondary battery of the present invention is not particularly limited, and it may be, for example, a cylindrical shape, a rectangular shape, a pouch shape, or a coin shape using a can.

[0108] 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 technical idea, and it goes without saying that such variations and modifications belong to the scope of the appended claims.

[0109] Example Example 1 (Manufacture of non-aqueous electrolyte) A non-aqueous solvent was produced by mixing the compound of Chemical Formula 1a and ethyl methyl carbonate (EMC) at a volume ratio of 30:70. To this, LiPF6 was dissolved to be 1 M, vinylene carbonate (VC) was 0.5 wt%, 1,3-propanesultone (PS) was 0.5 wt%, and ethylene sulfate (ESa) was 1 wt% to produce a non-aqueous electrolyte. The compound of Chemical Formula 1a was contained at 33 wt% based on the total non-aqueous electrolyte.

[0110]

Chemical formula

[0111] (Manufacture of lithium secondary battery) The positive electrode active material (LiNi 0.86 Co 0.05 Mn 0.07 Al 0.02 O2), a conductive material (carbon black), and a binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP) as a solvent at a weight ratio of 97.5:1.0:1.5 to produce a positive electrode slurry (solid content 50 wt%). The positive electrode slurry was applied to one side of a positive electrode current collector (Al thin film) with a thickness of 12 μm, and drying and roll press were performed to produce a positive electrode.

[0112] The negative electrode active material (artificial graphite: SiO = 95:5 by weight), the conductive material (carbon black), and the binder (SBR-CMC) were added to N-methyl-2-pyrrolidone (NMP), which is a solvent, at a weight ratio of 95:1.5:3.5 to produce a negative electrode slurry (solid content 60% by weight). The negative electrode slurry was applied to one side of a negative electrode current collector (Cu thin film) with a thickness of 6 μm, and drying and roll press were performed to produce a negative electrode.

[0113] In a dry room, after interposing a polyolefin-based porous separator coated with inorganic particles Al2O3 between the positive electrode and the negative electrode manufactured above, the non-aqueous electrolyte manufactured above was injected to produce a secondary battery.

[0114] Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous solvent manufactured by mixing the compound of Chemical Formula 1a and ethyl methyl carbonate (EMC) at a volume ratio of 40:60 was used. The compound of Chemical Formula 1a was contained at 42% by weight based on the total non-aqueous electrolyte.

[0115] Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous solvent manufactured by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 30:70 was used.

[0116] Comparative Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous solvent manufactured by mixing the compound of the following Chemical Formula A and ethyl methyl carbonate (EMC) at a volume ratio of 30:70 was used.

[0117]

Chemical formula

[0118] Comparative Example 3 A secondary battery was produced in the same manner as in Example 1, except that a non-aqueous solvent prepared by mixing the compound of Chemical Formula 1a and ethyl methyl carbonate (EMC) at a volume ratio of 15:85 was used. The compound of Chemical Formula 1a was contained at 20% by weight based on the total non-aqueous electrolyte.

[0119] Experimental Example 1 - Evaluation of high-temperature cycle characteristics The cycle characteristics were evaluated for each of the secondary batteries produced in Example 1, Example 2, and Comparative Examples 1 to 3.

[0120] Specifically, each of the batteries produced in Example 1, Example 2, and Comparative Examples 1 to 3 was charged at a constant current of 0.33C to 4.2V at 45°C and then discharged at a constant current of 0.33C to 3.0V. One cycle was defined as such, and after 250 charge-discharge cycles, the capacity retention rate after 250 cycles with respect to the initial capacity was measured. The results are shown in Table 1 below.

[0121]

Table 1

[0122] As shown in Table 1, Examples 1 and 2 using the additive for non-aqueous electrolytes of the present invention had a higher capacity retention rate and better life characteristics compared to Comparative Examples 1 and 2 that did not use it. In particular, Compound A used in the secondary battery of Comparative Example 2 differed from the compound of Chemical Formula 1 of the present application in that the terminal CF3 was directly linked to the sulfur atom of the sulfonamide group, while in the present invention, the terminal CF3 was linked to the sulfur atom of the sulfonamide group via oxygen. -CF3 is a strong EWG (electron withdrawing group), and when directly linked to a sulfur atom, it is considered difficult to be reduced to the form of LiF. In contrast, when the terminal exists in the form of -OCF3 as in the compound of Chemical Formula 1, it becomes a weak EWG, the formation reaction of LiF is easy, and it is easy to form a polymer-inorganic composite film on the negative electrode, so it is considered to have excellent capacity retention at high temperatures. In Comparative Example 3, the content of the compound represented by Chemical Formula 1 was less than 25% by weight based on the total non-aqueous electrolyte, and since the coating did not contain sufficient LiF, it is considered inferior in the effect of improving coating durability.

[0123] 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 and 2 and Comparative Examples 1 to 3.

[0124] Specifically, each of the secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 3 was fully charged to 4.2 V and then stored at 60 °C for 8 weeks.

[0125] Before storage, the volume of the fully charged secondary battery was measured and set as the volume of the initial secondary battery.

[0126] After 8 weeks, the volume of the stored secondary battery was measured, and the volume increase during the 8-week storage period was calculated. The percentage of the increased volume with respect to the volume of the initial secondary battery was calculated to derive the volume increase rate after 8 weeks. The results are shown in Table 2 below.

[0127]

Table 2

[0128] As shown in Table 2 above, it was confirmed that the secondary batteries of Examples 1 and 2 had a lower volume increase rate after 8 weeks and stable performance at high temperatures compared to the secondary batteries of Comparative Examples 1 and 2. In particular, Compound A used in the secondary battery of Comparative Example 2 is different from the compound of Chemical Formula 1 of the present application in that the terminal CF3 is directly connected to the sulfur atom of the sulfonamide group, while the terminal CF3 is connected to the sulfur atom of the sulfonamide group via oxygen. -CF3 is a strong EWG (Electron withdrawing group), and when directly connected to the sulfur atom, it is considered difficult to be reduced to the form of LiF. On the other hand, when the terminal exists in the form of -OCF3 as in the compound of Chemical Formula 1, it becomes a weak EWG, and the formation reaction of LiF is easy, and it is easy to form a polymer-inorganic composite film on the negative electrode. Therefore, the side reaction between the negative electrode and the electrolyte is suppressed, and it is considered excellent in the volume change rate when stored at high temperature for a long time. In Comparative Example 3, the content of the compound represented by Chemical Formula 1 is less than 25% by weight based on the whole non-aqueous electrolyte, and since the coating does not contain sufficient LiF, it is considered inferior in the effect of improving the coating durability.

Claims

1. A non-aqueous electrolyte containing a lithium salt and an organic solvent, wherein the organic solvent contains a compound represented by the following Chemical Formula 1, and the non-aqueous electrolyte contains the compound represented by Chemical Formula 1 in an amount of 25 to 80% by weight based on the total amount of the non-aqueous electrolyte. 【Chemical 1】 (In the above Chemical Formula 1, R １ and R ２ are each independently any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, and an aryl group having 6 to 20 carbon atoms, X is a perfluoroalkyl group having 1 to 5 carbon atoms.)

2. R １ and R ２ The non-aqueous electrolyte according to claim 1, wherein each of them is independently an alkyl group having 1 to 5 carbon atoms.

3. wherein X is CF ３ or CF ２ CF ３ The non-aqueous electrolyte according to claim 1

4. The non-aqueous electrolyte according to Claim 1, wherein the compound of Chemical Formula 1 is any one selected from the group consisting of compounds of the following Chemical Formulas 1a to 1f. 【Chemical 2】 [Chemical Formula 3] 【Chemical Formula 4】 【Chemical Formula 5】 [Chemical Formula 6] 【Chemical Formula 7】

5. The non-aqueous electrolyte according to Claim 1, wherein the compound represented by Chemical Formula 1 is contained in an amount of 10 to 50% by volume based on the total volume of the organic solvent.

6. The non-aqueous electrolyte according to Claim 1, wherein the organic solvent further contains a linear carbonate compound.

7. The non-aqueous electrolyte according to Claim 1, wherein the lithium salt is contained at a concentration of 0.5 M to 5.0 M.

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

9. The non-aqueous electrolyte according to Claim 1, further containing at least one compound selected from the group consisting of a cyclic carbonate compound, a halogen-substituted carbonate compound, a sultone compound, a sulfate compound, a phosphate compound, a borate compound, a nitrile compound, a benzene compound, an amine compound, a silane compound, and a lithium salt compound as an additive.

10. A positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, and the non-aqueous electrolyte according to any one of Claims 1 to 9, a lithium secondary battery.

11. The lithium secondary battery according to Claim 10, wherein the positive electrode active material layer contains a lithium nickel-based oxide represented by the following Chemical Formula 2 as a positive electrode active material. [Chemical Formula 2] Li ｘ Ni ａ Co ｂ M １ ｃ M ２ ｄ O ２ (In the chemical formula 2, M １ is Mn, Al, or a combination thereof, and M ２ is one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and 0.90 ≦ x ≦ 1.1, 0.80 ≦ a < 1.0, 0 < b < 0.2, 0 < c < 0.2, 0 ≦ d ≦ 0.1.)

12. The lithium secondary battery according to Claim 10, wherein the negative electrode active material layer contains SiO x (0 ≤ x < 2) as a negative electrode active material.

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