Non-aqueous electrolytes and lithium secondary batteries containing them

Abstract

The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and a compound represented by the following Chemical Formula 1 as an additive. JPEG2025539657000072.jpg48170In the above Chemical Formula 1, n is an integer of 0 or 1; R1 is any one selected from the group consisting of R, an alkyl group having 1 to 10 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms which may be substituted with fluorine, an alkynyl group having 2 to 10 carbon atoms which may be substituted with fluorine, OR', OCOR', F, and CH2PO(R)2; and R' may be any one selected from the group consisting of an alkyl group having 1 to 10 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms which may be substituted with fluorine, an alkynyl group having 2 to 10 carbon atoms which may be substituted with fluorine, and PO(R)2. In the above Chemical Formula 1 and R1, R is a structure represented by the following Chemical Formula 2. JPEG2025539657000073.jpg58170In the above chemical formula 2, Rx and Ry are each independently either H or F.

Description

[Technical Field]

[0001] This application claims priority rights based on Korean Patent Application No. 10-2023-0117304, filed on September 4, 2023, and Korean Patent Application No. 10-2024-0119601, filed on September 3, 2024, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference.

[0002] This invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same. [Background technology]

[0003] In recent years, the application areas of lithium-ion batteries have rapidly expanded beyond power supply for electronic devices such as electrical, electronic, telecommunications, and computers to include power storage and supply for large-area devices such as automobiles and power storage devices. Consequently, there is an increasing demand for high-capacity, high-output, and highly stable secondary batteries.

[0004] In particular, high capacity, high output, and long lifespan characteristics are important for lithium-ion secondary batteries used in automobiles. To increase the capacity of secondary batteries, nickel-high content positive electrode active materials, which have high energy density but low stability, are sometimes used, or secondary batteries are driven at high voltages.

[0005] However, when a secondary battery is powered under the above conditions, as charging and discharging progress, side reactions caused by electrolyte degradation can degrade the coating or electrode surface structure formed on the positive / negative electrode surfaces, potentially leading to the elution of transition metal ions from the positive electrode surface. These eluted transition metal ions then electrodeposit onto the negative electrode, reducing the passivation capacity of the SEI, thus causing the negative electrode to degrade.

[0006] This degradation phenomenon in secondary batteries tends to accelerate when the potential of the positive electrode increases, or when the battery is exposed to heat generated during operation or to a high-temperature external environment.

[0007] Furthermore, when lithium secondary batteries are used continuously for long periods or left at high temperatures, gas is generated, causing the battery to swell, a phenomenon known as SEI. The amount of gas generated at this time is known to depend on the state of SEI.

[0008] Therefore, research and development efforts are underway to develop methods that can suppress the elution of metal ions at the positive electrode, form a stable SEI film at the negative electrode, reduce the swelling phenomenon of secondary batteries, and improve long-term lifespan and high-temperature durability in order to solve these problems. [Overview of the project] [Problems that the invention aims to solve]

[0009] As a result of conducting multifaceted research to solve the above problems, the present invention aims to provide an additive for non-aqueous electrolytes that can suppress the degradation of the positive electrode, reduce side reactions 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 non-aqueous electrolyte with enhanced stability at high temperatures by including the aforementioned additive for non-aqueous electrolytes.

[0011] Furthermore, the present invention aims to provide a lithium secondary battery in which high-temperature cycling characteristics and high-temperature storage characteristics are improved, and various other performance characteristics are enhanced, by including the non-aqueous electrolyte. [Means for solving the problem]

[0012] To achieve the above objective, the present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and a compound of the following chemical formula 1 as an additive.

[0013] [ka]

[0014] In the above chemical formula 1, n is an integer of 0 or 1, R1 is one selected from the group consisting of R, an alkyl group having 1 to 10 carbon atoms that may be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms that may be substituted with fluorine, an alkynyl group having 2 to 10 carbon atoms that may be substituted with fluorine, OR', OCOR', F, and CH2PO(R)2, and R' is one selected from the group consisting of an alkyl group having 1 to 10 carbon atoms that may be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms that may be substituted with fluorine, an alkynyl group having 2 to 10 carbon atoms that may be substituted with fluorine, and PO(R)2, and R has the structure represented by the following chemical formula 2.

[0015] [ka]

[0016] In the above chemical formula 2, Rx and Ry are each independently either H or F.

[0017] Furthermore, the present invention provides a lithium secondary battery containing the non-aqueous electrolyte. [Effects of the Invention]

[0018] The compound represented by chemical formula 1, provided as an additive for non-aqueous electrolytes in the present invention, is an additive that improves upon the problems of 1,3-propanesultone, which is widely used as an electrolyte additive for film formation. 1,3-propanesultone has the problem of increasing the resistance of lithium secondary batteries, making it difficult to add large amounts to the electrolyte, and it also generates toxic substances as a byproduct. Therefore, 1,3-propanesultone has the problem of degrading the output characteristics of lithium secondary batteries, and due to the limitation that it is difficult to add in large quantities, it is difficult to obtain sufficiently long-life characteristics.

[0019] The compound represented by chemical formula 1, provided as an additive for non-aqueous electrolytes in the present invention, contains two or more R structures derived from 1,3-propanesultone in its molecule, which allows for the formation of a large amount of strong film on the positive / negative electrodes without the application of an excess amount, thereby providing a lithium secondary battery with excellent high-voltage life characteristics, high-temperature life characteristics, and high-temperature durability.

[0020] Furthermore, in the compound of chemical formula 1, the phosphorus-containing linker is linked to the carbon at position 3, which triggers the toxicity-inducing reaction of 1,3-propanesultone, thus reducing the generation of toxic byproducts. In addition, in the compound of chemical formula 1, due to the inherent properties of electron-rich phosphorus (P), lithium ion transport characteristics are improved when the P-containing linker forms a film on the positive / negative electrode. As a result, the compound of chemical formula 1 can form stable CEI (Cathode Electrolyte Interface) and SEI (Solid Electrolyte Interface) films on the positive / negative electrode surfaces. Therefore, it is possible to prevent the degradation of the positive electrode active material and the elution of transition metals at high voltages, suppress the decrease in the passivation capacity of the SEI at high temperatures, and prevent the degradation of the negative electrode.

[0021] Therefore, by using the non-aqueous electrolyte of the present invention, which contains the compound of chemical formula 1 as an additive, it is possible to form an electrode-electrolyte interface that is stable even at high temperatures and has low resistance. As a result, high-temperature cycle characteristics and high-temperature storage characteristics are improved, and a lithium secondary battery with improved performance can be realized. [Modes for carrying out the invention]

[0022] The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0023] In this specification, terms such as “includes,” “equip,” or “have” are intended to specify the presence of implemented features, figures, steps, components, or combinations thereof, and should be understood not to preemptively exclude the presence or possibility of adding one or more other features, figures, steps, components, or combinations thereof.

[0024] On the other hand, before describing the present invention, unless otherwise specifically mentioned in the present invention, "*" means a connected portion between identical or different atoms or the terminal parts of a chemical formula.

[0025] Furthermore, in this specification, when "a to b carbon atoms" is mentioned, "a" and "b" refer to the number of carbon atoms contained in a specific functional group. That is, the functional group may contain "a" to "b" carbon atoms. For example, "alkyl group with 1 to 5 carbon atoms" means alkyl groups containing 1 to 5 carbon atoms, i.e., -CH3, -CH2CH3, -CH2CH2CH3, -CH2C(CH3)H2, -CH(CH3)2, -CH(CH3)CH2CH3, -CH(CH2CH3)2, etc.

[0026] Furthermore, in this specification, alkyl groups, alkenyl groups, and alkynyl groups may or may not be substituted. Unless otherwise defined, "substitution" means that at least one hydrogen atom bonded to a carbon atom is replaced by an element other than hydrogen, such as a halogen atom like F or Cl.

[0027] The present invention will be described in detail below.

[0028] The non-aqueous electrolyte and / or lithium secondary battery according to the present invention comprises at least one of the configurations disclosed below, and may include any combination of technically possible configurations from the following configurations.

[0029] Non-aqueous electrolytes The non-aqueous electrolyte of the present invention comprises a lithium salt, an organic solvent, and a non-aqueous electrolyte additive represented by the following chemical formula 1.

[0030] [ka]

[0031] In the above chemical formula 1, n is an integer of 0 or 1.

[0032] In the above chemical formula 1, R1 is one selected from the group consisting of R, a C1-C10 alkyl group that may be substituted with fluorine, a C2-C10 alkenyl group that may be substituted with fluorine, a C2-C10 alkynyl group that may be substituted with fluorine, OR', OCOR', F, and CH2PO(R)2, and R' is one selected from the group consisting of a C1-C10 alkyl group that may be substituted with fluorine, a C2-C10 alkenyl group that may be substituted with fluorine, a C2-C10 alkynyl group that may be substituted with fluorine, and PO(R)2.

[0033] In the above chemical formulas 1 and R1, R has the structure represented by the following chemical formula 2.

[0034] [ka]

[0035] In the above chemical formula 2, Rx and Ry are each independently either H or F.

[0036] The compound of chemical formula 1 contains two or more R structures derived from 1,3-propanesultone in its molecule, which allows for the formation of a large, strong coating on the positive / negative electrodes without the application of excess material. This enables the provision of a lithium secondary battery with excellent high-voltage life characteristics, high-temperature life characteristics, and high-temperature durability.

[0037] Furthermore, in the compound of chemical formula 1, the phosphorus-containing linker is linked to the carbon at position 3, which triggers the toxicity-inducing reaction of 1,3-propanesultone, thereby reducing the generation of toxic byproducts. In addition, in the compound of chemical formula 1, due to the inherent properties of electron-rich phosphorus (P), lithium ion transport characteristics are improved when the P-containing linker forms a film on the positive / negative electrode. As a result, the compound of chemical formula 1 can form stable CEI (Cathode Electrolyte Interface) and SEI (Solid Electrolyte Interface) films on the positive / negative electrode surfaces. Therefore, it is possible to suppress the chain reaction of structural collapse due to oxygen desorption of the positive electrode at high temperatures, suppress the decrease in the passivation capacity of the SEI, and prevent the degradation of the negative electrode.

[0038] Therefore, by using the non-aqueous electrolyte of the present invention containing the compound of chemical formula 1, it is possible to form an electrode-electrolyte interface that is stable even at high temperatures and has low resistance. As a result, high-temperature cycle characteristics and high-temperature storage characteristics are improved, and a lithium secondary battery with improved performance can be realized.

[0039] The compound of chemical formula 1 may be the compound represented by the following chemical formula 1-1.

[0040] [ka]

[0041] In the above chemical formula 1-1, R1 is F, R, or OR', and R' may be any one selected from the group consisting of a C1-C10 alkyl group that may be substituted with fluorine, a C2-C10 alkenyl group that may be substituted with fluorine, and a C2-C10 alkynyl group that may be substituted with fluorine.

[0042] In the above chemical formulas 1-1 and R1, R may be a structure represented by the following chemical formula 2.

[0043] [ka]

[0044] In the above chemical formula 2, Rx and Ry may each be independently either H or F.

[0045] Specifically, the compound represented by chemical formula 1-1 may be any one of the compounds represented by the following chemical formulas 1-1a to 1-1f.

[0046] [ka]

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] In the above chemical formulas 1-1a to 1-1f, R may be the structure represented by the following chemical formula 2-1.

[0053] [ka]

[0054] The compound of chemical formula 1 may be a compound represented by the following chemical formulas 1-2.

[0055] [ka]

[0056] In the above chemical formulas 1-2, X may be -CH2- or -O-.

[0057] In the above chemical formulas 1-2 and R1, R may be the structure represented by the following chemical formula 2.

[0058] [ka]

[0059] In the above chemical formula 2, Rx and Ry may each be independently either H or F.

[0060] Specifically, the compound represented by chemical formula 1-2 may be either one of the compounds represented by the following chemical formulas 1-2a and 1-2b.

[0061] [ka]

[0062] [ka]

[0063] In the aforementioned chemical formulas 1-2a to 1-2b, R may be the structure represented by the following chemical formula 2-1.

[0064] [ka]

[0065] The compound of chemical formula 1 may be a compound represented by the following chemical formulas 1-3.

[0066] [ka]

[0067] In the above chemical formulas 1-3, R1 is F, R, or OR', and R' may be any one selected from the group consisting of a C1-C10 alkyl group that may be substituted with fluorine, a C2-C10 alkenyl group that may be substituted with fluorine, and a C2-C10 alkynyl group that may be substituted with fluorine.

[0068] In the above chemical formulas 1-3 and R1, R may have the structure represented by the following chemical formula 2.

[0069] [ka]

[0070] In the above chemical formula 2, Rx and Ry may each be independently either H or F.

[0071] Specifically, the compound represented by chemical formula 1-3 may be any one of the compounds represented by the following chemical formulas 1-3a to 1-3f.

[0072] [ka]

[0073] [ka]

[0074] [ka]

[0075] [ka]

[0076] [Chemical formula]

[0077] [Chemical formula]

[0078] In the chemical formulas 1-3a to 1-3f, R may be a structure represented by the following chemical formula 2-1.

[0079] [Chemical formula]

[0080] The additive for non-aqueous electrolyte according to the present invention may be contained in a content of 0.1 parts by weight to 5 parts by weight, preferably 0.1 parts by weight to 3 parts by weight, more preferably 0.1 parts by weight to 1 part by weight, based on 100 parts by weight of the non-aqueous electrolyte. When the content of the compound represented by the chemical formula 1 satisfies the above range, the effect of forming a film on the positive electrode and the negative electrode is sufficient, the elution of transition metals from the positive electrode active material is suppressed, the deterioration of the negative electrode is also suppressed, and the lithium mobility of the electrolyte is appropriate and the resistance of the lithium secondary battery is small.

[0081] 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, as a cation, it contains Li + and as an anion, it contains 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 of the following groups can be selected.

[0082] Specifically, the lithium salts are LiCl, LiBr, LiI, LiBF4, LiClO4, and LiB 10 Cl 10 The electrolyte may include a single substance or a mixture of two or more substances 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 as electrolytes in lithium secondary batteries can be used without limitation.

[0083] The lithium salt may be appropriately changed within a range of normal use, but in order to obtain the optimal effect of forming a corrosion-preventive film on the electrode surface, it may be included in the electrolyte at a concentration of 0.5 M to 4.0 M, preferably 0.5 M to 3.0 M, and more preferably 0.8 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of the lithium secondary battery is sufficient, and the viscosity of the non-aqueous electrolyte is appropriate, and the electrolyte impregnation can be improved.

[0084] The organic solvent may include at least one organic solvent selected from the group consisting of cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

[0085] Specifically, the organic solvent may include a cyclic carbonate organic solvent, a linear carbonate organic solvent, or a mixture thereof.

[0086] The aforementioned cyclic carbonate-based organic solvent is a highly viscous organic solvent with a high dielectric constant that readily dissociates lithium salts in electrolytes. Specific examples include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and among these, ethylene carbonate may be included.

[0087] Furthermore, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant. Typical examples include at least one organic solvent 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 include ethyl methyl carbonate (EMC).

[0088] Furthermore, in order to produce an electrolyte having high ionic conductivity, the organic solvent may further contain at least one ester organic solvent selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents, in addition to at least one carbonate organic solvent selected from the group consisting of cyclic carbonate organic solvents and linear carbonate organic solvents.

[0089] Specific examples of such linear ester-based organic solvents include at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0090] Furthermore, the cyclic ester organic solvents include at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0091] On the other hand, the organic solvent may be further used with any organic solvent commonly used for non-aqueous electrolytes, without limitation, as needed. For example, it may further contain at least one or more organic solvents from among ether-based organic solvents, glyme-based solvents, and nitrile-based organic solvents.

[0092] The ether-based solvent may be any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these, but is not limited to these.

[0093] The aforementioned glyme-based solvent has a higher dielectric constant and lower surface tension compared to linear carbonate-based organic solvents, and is a solvent with low reactivity with metals. It may include, but is not limited to, at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME).

[0094] The nitrile solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited to these.

[0095] Furthermore, the non-aqueous electrolyte of the present invention may, if necessary, further contain known electrolyte additives in order to prevent the non-aqueous electrolyte from decomposing in a high-power environment, which can cause the collapse of the negative electrode, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and the effect of suppressing battery swelling at high temperatures.

[0096] Such other electrolyte additives may include, as representative examples, at least one SEI film-forming additive 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.

[0097] Examples of the aforementioned cyclic carbonate compounds include vinylene carbonate (VC) or vinylethylene carbonate.

[0098] Examples of halogen-substituted carbonate compounds include fluoroethylene carbonate (FEC).

[0099] Examples of the sultone compounds include at least one compound selected from the group consisting of 1,3-propanesultone (PS), 1,4-butanesultone, ethensultone, 1,3-propensultone (PRS), 1,4-butensultone, and 1-methyl-1,3-propensultone.

[0100] Examples of the sulfate compounds include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0101] Examples of the phosphate compound include one or more compounds selected from the group consisting of lithium difluoro(bisoxalato) phosphate, lithium difluorophosphate, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(2,2,2-trifluoroethyl) phosphite.

[0102] Examples of the borate compounds include tetraphenyl borate, lithium oxalyl difluoroborate (LiODFB), and lithium bisoxalate borate (LiB(C2O4)2, LiBOB).

[0103] Examples of the nitrile compounds include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0104] Examples of the benzene-based compound include fluorobenzene, examples of the amine-based compound include triethanolamine or ethylenediamine, and examples of the silane-based compound include tetravinylsilane.

[0105] The lithium salt compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and examples include lithium difluorophosphate (LiDFP), LiPO2F2, or LiBF4.

[0106] Among these other electrolyte additives, if a combination of vinylene carbonate (VC), 1,3-propanesultone (PS), and ethylene sulfate (Esa) is included, an even 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 may be produced by the decomposition of the electrolyte at high temperatures and improving the high-temperature stability of the secondary battery.

[0107] On the other hand, two or more of the other electrolyte additives may be used in mixture form, and may be present in an amount of 0.1% to 10% by weight, specifically 0.2% to 8% by weight, based on the total weight of the nonaqueous electrolyte, and preferably 0.5% to 8% by weight. When the content of the other electrolyte additives satisfies the above range, a better effect of improving ionic conductivity and cycle characteristics can be obtained.

[0108] Lithium-ion battery The present invention also provides a lithium secondary battery comprising the non-aqueous electrolyte.

[0109] 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.

[0110] In this case, the lithium secondary battery of the present invention can be manufactured by conventional methods known in the art. For example, it can be manufactured by forming an electrode assembly in which a positive electrode, a negative electrode, and a separator between the positive and negative electrodes are stacked in order, inserting the electrode assembly into the inside of a battery case, and injecting the non-aqueous electrolyte according to the present invention.

[0111] (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, and a solvent onto a positive electrode current collector.

[0112] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used.

[0113] 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 (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 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 a lithium-nickel-cobalt-transition metal (M) oxide (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 atomic fractions of independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, and p2 + q2 + r2 + s2 = 1), etc.) etc. may be mentioned, and any one or two or more of these compounds may be included.

[0114] Among them, from the point of view 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 (for example, 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.), lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), or lithium nickel manganese cobalt aluminum oxide (for example, Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 )O2), etc. may be used, and any one or two or more of these mixtures may be used.

[0115] Among them, from the point of view of being able to maximize the capacity characteristics of the battery, 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 3.

[0116] [Chemical Formula 3] Li x Nia Co b M 1 c M 2 d O2

[0117] In Chemical Formula 3, the M 1 is one or more selected from Mn and Al, and may preferably be Mn, or a combination of Mn and Al.

[0118] 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.

[0119] 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, more preferably 1.0 ≦ x ≦ 1.08 may be applicable.

[0120] 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, more preferably 0.80 ≦ a ≦ 0.90 may be applicable. When the nickel content satisfies the above range, high capacity characteristics can be realized.

[0121] The b represents the atomic fraction of cobalt among the metal elements excluding lithium in the lithium transition metal oxide, and 0 < b < 0.2, 0 < b ≦ 0.15, or 0.01 ≦ b ≦ 0.10 may be applicable.

[0122] The c represents the atomic fraction of M 1 among the metal elements excluding lithium in the lithium transition metal oxide, and 0 < c < 0.2, 0 < c ≦ 0.15, or 0.01 ≦ c ≦ 0.10 may be applicable.

[0123] The d represents the atomic fraction of M 2 among the metal elements excluding lithium in the lithium transition metal oxide, and 0 ≦ d ≦ 0.1, or 0 ≦ d ≦ 0.05 may be applicable.

[0124] The positive electrode active material may be present 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 in the positive electrode mixture slurry excluding the solvent.

[0125] The aforementioned binder is a component that assists in the bonding of the active material to the conductive material and to the current collector.

[0126] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers.

[0127] Typically, the binder may be present in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, based on the total weight of the solids in the positive electrode mixture slurry excluding the solvent.

[0128] 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 mixture slurry. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and may be used, 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 well-developed crystalline structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorinated carbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0129] Typically, the conductive material may be included in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, based on the total weight of the solid matter in the positive electrode mixture slurry excluding the solvent.

[0130] The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone) and may be used in an amount that results in a suitable viscosity when the positive electrode active material and selectively include a binder and conductive material are present. For example, the concentration of the solid content containing the positive electrode active material and selectively including the binder and conductive material may be 50% to 95% by weight, preferably 70% to 95% by weight, and more preferably 70% to 90% by weight.

[0131] (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, and a solvent onto a negative electrode current collector, or by using a graphite electrode made of carbon (C) or the metal itself as the negative electrode.

[0132] For example, when a negative electrode is manufactured by coating a negative electrode mixture slurry onto 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 chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. Also, similar to the positive electrode current collector, the bonding force of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0133] Furthermore, the negative electrode active material may include at least one selected from the group consisting of lithium metal, carbon material capable of reversibly intercalating / deintercalating lithium ions, metal or alloys of these metals with lithium, metal composite oxides, materials capable of doping and dedoping lithium, and transition metal oxides.

[0134] The carbon material that can reversibly intercalate / deintercalate lithium ions can be any carbon-based negative electrode active material commonly used in lithium-ion secondary batteries, and typical examples include crystalline carbon, amorphous carbon, or a combination of both. Examples of crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, while examples of amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, and calcined coke.

[0135] 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.

[0136] As the metal composite oxide, 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 consisting of can be used.

[0137] As the substance capable of doping and undoping lithium, Si, SiO x (0 < x ≦ 2), Si-Y alloy (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and a combination thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and a combination thereof, and is not Sn), etc. can be mentioned, and 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 a combination thereof.

[0138] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, and the like.

[0139] Among them, the negative electrode active material may be a mixture of graphite and SiO x (0 < x ≤ 2). From the viewpoint of increasing the capacity of the lithium secondary battery, the graphite and SiO x (0 < x ≤ 2) may be contained in a weight ratio of 99.5:0.5 to 70:30.

[0140] 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.

[0141] The binder is a component that aids in binding 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, and various copolymers thereof.

[0142] 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 matter excluding the solvent in the negative electrode binder slurry.

[0143] 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% to 20% by weight based on the total weight of the solid content in the negative electrode mixture slurry. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and may be used, 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 well-developed crystalline structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0144] The conductive material may be present in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, based on the total weight of the solid matter in the negative electrode mixture slurry excluding the solvent.

[0145] The solvent may contain water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that results in a suitable viscosity when the negative electrode active material and selectively the binder and conductive material are included. For example, the concentration of the solid content containing the negative electrode active material and selectively the binder and conductive material may be 50% to 95% by weight, preferably 70% to 90% by weight.

[0146] When a metal itself is used as the negative electrode, it can be manufactured by physically joining, rolling, or vapor-depositing the metal onto the metal thin film itself or onto the negative electrode current collector. As for the vapor deposition method, electro-deposit or chemical vapor deposition of the metal can be used.

[0147] For example, the metal bonded / rolled / deposited onto the metal thin film itself or the negative electrode current collector may include one metal or an alloy of two metals selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In).

[0148] (3) Separator Furthermore, the separator may be a conventional porous polymer film, such as a porous polymer film made from polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, used alone or in a laminated configuration. Alternatively, a conventional porous nonwoven fabric, such as a nonwoven fabric made from high-melting-point glass fibers or polyethylene terephthalate fibers, may be used, but is not limited to these. In addition, a coated separator containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and may be selectively used as a single-layer or multi-layer structure.

[0149] The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, rectangular, pouch-shaped, or coin-shaped, using a can.

[0150] The present invention will be described in more detail below 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 invention. It will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the described concept and technical idea, and it goes without saying that such variations and modifications fall within the scope of the appended claims.

[0151] Examples Example 1 (Manufacturing of non-aqueous electrolytes) A non-aqueous solvent was prepared by dissolving LiPF6 in an organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) = 20:70:10 volume ratio) to a concentration of 1.2 M. A non-aqueous electrolyte was prepared by adding 0.5 g of the compound of the following chemical formula 1-1a to 99.5 g of the non-aqueous solvent.

[0152] [ka]

[0153] The aforementioned R has the structure represented by the following chemical formula 2-1.

[0154] [ka]

[0155] (Manufacturing of lithium-ion batteries) Cathode active material (LiNi 0.60 Co 0.10 Mn 0.30 A positive electrode slurry (60% solids by weight) was prepared by adding O2, a conductive material (carbon black), and a binder (polyvinylidene fluoride) in a weight ratio of 97.6:0.8:1.6 to the solvent N-methyl-2-pyrrolidone (NMP). The positive electrode slurry was applied to one surface of a 13.5 μm thick positive electrode current collector (a thin aluminum film), and the positive electrode was manufactured by drying and roll pressing.

[0156] A negative electrode slurry (60% solids by weight) was prepared by adding a negative electrode active material (graphite: SiO = 97.5:2.5 by weight ratio), a conductive material (carbon black), and a binder (SBR-CMC) in a weight ratio of 95.6:1.0:3.4 to the solvent N-methyl-2-pyrrolidone (NMP). The negative electrode slurry was applied to one surface of a 6 μm thick negative electrode current collector (Cu thin film), and the negative electrode was manufactured by drying and roll pressing.

[0157] In a dry room, a porous polymer separator was interposed between the positive electrode and negative electrode manufactured as described above, and then the non-aqueous electrolyte manufactured as described above was injected to produce a secondary battery.

[0158] Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of the compound of chemical formula 1-1b below was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0159] [ka]

[0160] The aforementioned R has the structure represented by the following chemical formula 2-1.

[0161] [ka]

[0162] Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of the compound of chemical formula 1-2a below was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0163] [ka]

[0164] The aforementioned R has the structure represented by the following chemical formula 2-1.

[0165] [ka] )

[0166] Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of the compound of chemical formula 1-1b below was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0167] [ka]

[0168] The aforementioned R has the structure represented by the following chemical formula 2-1.

[0169] [ka]

[0170] Example 5 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of the compound of chemical formula 1-3a below was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0171] [ka]

[0172] The aforementioned R has the structure represented by the following chemical formula 2-1.

[0173] [ka]

[0174] Example 6 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of the compound of chemical formula 1-3b below was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0175] [ka]

[0176] The aforementioned R has the structure represented by the following chemical formula 2-1.

[0177] [ka]

[0178] Example 7 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of the compound of chemical formula 1-3f below was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0179] [ka]

[0180] The aforementioned R has the structure represented by the following chemical formula 2-1.

[0181] [ka]

[0182] Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared using 100 g of the non-aqueous solvent prepared in Example 1.

[0183] Comparative Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of 1,3-propanesultone was added to 99.5 g of the nonaqueous solvent prepared in Example 1 to produce a nonaqueous electrolyte.

[0184] Comparative Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of the compound of chemical formula A below was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0185] [ka]

[0186] The aforementioned R' has the structure represented by the following chemical formula B.

[0187] [ka]

[0188] Experimental Example 1 - Evaluation of High-Temperature Cycle Characteristics (1) For each of the lithium secondary batteries produced in Examples 1-7 and Comparative Examples 1-3, a formation process was performed at 25°C at a rate of 0.1C for 3 hours. Then, at 25°C at a rate of 0.33C, the batteries were charged to 4.4V under CC-CV (constant current-constant voltage) conditions and discharged to 2.5V under CC conditions at a rate of 0.33C. This charge-discharge process constituted one cycle, and three initial charge-discharge cycles were performed.

[0189] Next, at a high temperature (45°C), each of the initially charged and discharged lithium secondary batteries was charged to 4.4V at a rate of 0.33C under CC-CV conditions, and then discharged to 2.5V at a rate of 0.33C under CC conditions. This charge-discharge process constituted one cycle, and 100 cycles were performed.

[0190] The capacity retention rate was calculated by substituting the capacity after the first cycle and the capacity after the 100th cycle into Equation 1 below. The results are shown in Table 1 below.

[0191] [Formula 1] Capacity retention rate (%) = (Discharge capacity after 100th cycle / Discharge capacity after 1st cycle) x 100

[0192] Experimental Example 2 - Evaluation of High-Temperature Cycle Characteristics (2) Each of the lithium secondary batteries manufactured in Examples 1 to 7 and the secondary batteries manufactured in Comparative Examples 1 to 3 was charged at 25°C under CC-CV (constant current-constant voltage) conditions up to 4.4V at a rate of 0.33C and discharged under CC conditions up to 2.5V at a rate of 0.33C. The above charge and discharge were regarded as one cycle, and the initial charge and discharge for 3 cycles were performed. Based on the discharge capacity of the third charge and discharge, the SOC (State Of Charge) was adjusted to 50%. When a discharge pulse was applied at 2.5C for 10 seconds at SOC (State Of Charge) 50%, the DC internal resistance was calculated from the voltage drop that appeared, and the resistance at this time was set as the initial resistance.

[0193] Thereafter, at a high temperature (45°C), each of the initially charged and discharged lithium secondary batteries was charged under CC-CV conditions up to 4.4V at a rate of 0.33C and discharged under CC conditions up to 2.5V at a rate of 0.33C. The above charge and discharge were regarded as one cycle, and after 100 cycles had progressed, each lithium secondary battery was transferred to a charger at room temperature (25°C), and when a discharge pulse was applied at 2.5C for 10 seconds at SOC (State Of Charge) 50%, the DC internal resistance was calculated from the voltage drop that appeared.

[0194] The initial resistance and the resistance after the 100th cycle were substituted into the following formula 2 to calculate the high-temperature cycle resistance increase rate. The results are shown in Table 2 below.

[0195] [Formula 2] Resistance increase rate (%) = {(Resistance after the 100th cycle - Initial resistance) / Initial resistance} X 100

[0196]

Table 1

[0197] As shown in Table 1, Examples 1-7, which used the non-aqueous electrolyte additive of the present invention, showed improvements in both capacity retention and resistance increase compared to Comparative Examples 1-3, which did not use the additive. The lithium secondary batteries of Examples 1-7, which used the additive of the present invention in which a linker was linked to the third carbon of the propane-sultone, had a longer overall additive length compared to the lithium secondary battery of Comparative Example 3, which used the additive in which a linker was linked to the fourth carbon of the propane-sultone. Therefore, it is thought that the additive of the present invention increases the area covered by the coating and exhibits excellent high-temperature life characteristics.

[0198] Experimental Example 3 - Evaluation of High-Temperature Storage Characteristics (1) The lithium secondary batteries manufactured in Examples 1-7 and the secondary batteries manufactured in Comparative Examples 1-3 were charged to 4.4V at a rate of 0.33C under CC-CV (constant current-constant voltage) conditions at 25°C, and discharged to 2.5V at a rate of 0.33C under CC conditions. This charge-discharge cycle was considered one cycle, and three initial charge-discharge cycles were performed. In this case, the discharge capacity of the third charge-discharge cycle was set as the initial discharge capacity. Subsequently, the batteries were charged to 4.4V at a rate of 0.33C under CC-CV (constant current-constant voltage) conditions and stored at 60°C for 5 weeks.

[0199] Subsequently, each of the lithium secondary batteries was transferred to a charger / discharger at room temperature (25°C), charged to 4.4V under CC-CV conditions at a rate of 0.33C, and discharged to 2.5V under CC conditions at a rate of 0.33C. The high-temperature storage capacity retention rate was calculated by substituting the discharge capacity of the third charge / discharge and the initial capacity into Equation 3 below. The results are shown in Table 2 below.

[0200] [Formula 3] Capacity retention rate (%) = (Discharge capacity after 5 weeks of high-temperature storage / Initial discharge capacity) x 100

[0201] Experimental Example 4 - Evaluation of High-Temperature Storage Characteristics (2) The lithium secondary batteries manufactured in Examples 1-7 and the secondary batteries manufactured in Comparative Examples 1-3 were each charged to 4.4V at a rate of 0.33C under CC-CV (constant current-constant voltage) conditions at 25°C, and discharged to 2.5V at a rate of 0.33C under CC conditions. This charge-discharge cycle was considered one cycle, and three initial charge-discharge cycles were performed. Based on the discharge capacity of the third charge-discharge cycle, the State of Charge (SOC) was adjusted to 50%. At a State of Charge of 50%, the DC internal resistance was calculated from the voltage drop that appeared when a discharge pulse was applied at 2.5C for 10 seconds, and this resistance was set as the initial resistance. Subsequently, the batteries were charged to 4.4V at a rate of 0.33C under CC-CV (constant current-constant voltage) conditions and stored at 60°C for 5 weeks.

[0202] Subsequently, each of the lithium secondary batteries was transferred to a charger / discharger at room temperature (25°C), and the DC internal resistance was calculated from the voltage drop that appeared when a discharge pulse (SOC) of 50% was applied at 2.5C for 10 seconds.

[0203] The initial resistance and the high-temperature storage resistance were substituted into Equation 4 below to calculate the rate of increase in high-temperature storage resistance. The results are shown in Table 2 below.

[0204] [Formula 4] Resistance increase rate (%) = {(Resistance after 5 weeks of high-temperature storage - Initial resistance) / Initial resistance} x 100

[0205] Experimental Example 5 - Evaluation of High-Temperature Storage Characteristics (3) The lithium secondary batteries manufactured in Examples 1-7 and the secondary batteries manufactured in Comparative Examples 1-3 were each charged to 4.4V at 25°C at a rate of 0.33C under CC-CV (constant current-constant voltage) conditions, and their volume was measured at room temperature using the buoyancy method. This was defined as the initial volume (0%). After storing the volume-measured batteries at 60°C for 5 weeks, they were transferred to a charger / discharger at room temperature (25°C), and the capacity retention rate in Experimental Example 3 was measured. Then, the batteries were fully charged to 4.4V at 25°C at a rate of 0.33C under CC-CV (constant current-constant voltage) conditions, and their volume was measured using the buoyancy method. The initial volume and the high-temperature storage volume were substituted into Equation 5 below to calculate the high-temperature storage volume increase rate. The results are shown in Table 2 below.

[0206] [Formula 5] Volume increase rate (%) = {(Volume after 5 weeks of high-temperature storage - Initial volume) / Initial volume} x 100

[0207] [Table 2]

[0208] As shown in Table 2 above, the secondary batteries of Examples 1 to 7 show improved capacity retention rate, resistance increase rate, and volume increase rate after 5 weeks compared to the secondary batteries of Comparative Examples 1 to 3. The lithium secondary batteries of Examples 1 to 7, which use the additive of the present invention in which a linker is linked to the third carbon of propane sultone, have a longer overall additive length compared to the lithium secondary battery of Comparative Example 3, which uses the additive in which a linker is linked to the fourth carbon of propane sultone. From this, it is considered that the additive of the present invention increases the area covered by the coating and exhibits excellent high-temperature storage characteristics.

Claims

1. A non-aqueous electrolyte comprising a lithium salt, an organic solvent, and a compound of the following chemical formula 1 as an additive: 【Chemistry 1】 In the above chemical formula 1, n is an integer of 0 or 1. R １ R, a C1-C10 alkyl group that may be substituted with fluorine, a C2-C10 alkenyl group that may be substituted with fluorine, a C2-C10 alkynyl group that may be substituted with fluorine, OR', OCOR', F, and CH ２ PO(R) ２ It is one of the groups consisting of, R' is an alkyl group having 1 to 10 carbon atoms that may be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms that may be substituted with fluorine, an alkynyl group having 2 to 10 carbon atoms that may be substituted with fluorine, and PO(R) ２ It is one of the groups consisting of, R has the structure represented by the following chemical formula 2, 【Chemistry 2】 In the above chemical formula 2, Rx and Ry are each independently either H or F.

2. The non-aqueous electrolyte according to claim 1, wherein the compound of chemical formula 1 is the compound of chemical formula 1-1 below: 【Transformation 3】 In the above chemical formula 1-1, R １ is F, R, or OR', where R' is one selected from the group consisting of C1-C10 alkyl groups that may be substituted with fluorine, C2-C10 alkenyl groups that may be substituted with fluorine, and C2-C10 alkynyl groups that may be substituted with fluorine. R has the structure represented by the following chemical formula 2, 【Chemistry 4】 In the above chemical formula 2, Rx and Ry are each independently either H or F.

3. The non-aqueous electrolyte according to claim 1, wherein the compound of chemical formula 1 is the compound of chemical formula 1-2 below: 【Transformation 5】 In the above chemical formulas 1-2, X is -CH ２ - or -O-, R has the structure represented by the following chemical formula 2, 【Transformation 6】 In the above chemical formula 2, Rx and Ry are each independently either H or F.

4. The non-aqueous electrolyte according to claim 1, wherein the compound of chemical formula 1 is a compound of the following chemical formulas 1-3: 【Transformation 7】 In the above chemical formulas 1 and 3, R １ is F, R, or OR', where R' is one selected from the group consisting of C1-C10 alkyl groups that may be substituted with fluorine, C2-C10 alkenyl groups that may be substituted with fluorine, and C2-C10 alkynyl groups that may be substituted with fluorine. R has the structure represented by the following chemical formula 2, 【Transformation 8】 In the above chemical formula 2, Rx and Ry are each independently either H or F.

5. The non-aqueous electrolyte according to claim 1, wherein the compound of chemical formula 1 is one of the compounds of chemical formulas 1-1a to 1-1f below: 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】 【Chemistry 13】 【Chemistry 14】 In the above chemical formulas 1-1a to 1-1f, R has the structure represented by the following chemical formula 2-1. 【Chemistry 15】

6. The non-aqueous electrolyte according to claim 1, wherein the compound of chemical formula 1 is one of the compounds of chemical formulas 1-2a and 1-2b below: 【Chemistry 16】 【Chemistry 17】 In the aforementioned chemical formulas 1-2a to 1-2b, R has the structure represented by the following chemical formula 2-1. [Chemistry 18]

7. The non-aqueous electrolyte according to claim 1, wherein the compound of chemical formula 1 is one of the compounds of chemical formulas 1-3a to 1-3f below: 【Chemistry 19】 【Chemistry 20】 【Chemistry 21】 【Chemistry 22】 【Chemistry 23】 【Chemistry 24】 In the above chemical formulas 1-3a to 1-3f, R has the structure represented by the following chemical formula 2-1. 【Chemistry 25】

8. The non-aqueous electrolyte according to Claim 1, wherein the compound of chemical formula 1 is one of the compounds of chemical formulas 1-1f and 1-3f below: 【Chemistry 26】 【Chemistry 27】 In the aforementioned chemical formulas 1-1f and 1-3f, R has the structure represented by the following chemical formula 2-1. 【Chemistry 28】

9. The nonaqueous electrolyte according to any one of claims 1 to 8, wherein the compound of chemical formula 1 is contained in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the nonaqueous electrolyte.

10. where the lithium salt is LiPF ６ , LiCl, LiBr, LiI, LiBF ４ , LiClO ４ , LiB １０ Cl １０ , LiAlCl ４ , LiAlO ２ , LiSO ３ CH ３ , LiSO ３ CF ３ , LiCO ２ CH ３ , LiCO ２ CF ３ , LiAsF ６ , LiSbF ６ , 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 any one of claims 1 to 8, which is one or more selected from the above.

11. The non-aqueous electrolyte according to any one of claims 1 to 8, wherein the lithium salt is contained in a concentration of 0.5 M to 4.0 M.

12. The non-aqueous electrolyte according to any one of claims 1 to 8, wherein the organic solvent comprises at least one organic solvent selected from the group consisting of cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

13. A non-aqueous electrolyte according to any one of claims 1 to 8, further comprising, as an additive, one or more compounds 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.

14. Positive electrode and, The negative electrode and, A lithium secondary battery comprising a non-aqueous electrolyte according to any one of claims 1 to 8.

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