Non-aqueous electrolytes and lithium secondary batteries containing them

Abstract

The present invention provides a non-aqueous electrolyte containing a lithium salt, an organic solvent, and, as an additive, any one of the compounds of Chemical Formula 1 to Chemical Formula 5 below. [Chemical Formula 1] JPEG2026529027000043.jpg38170[Chemical Formula 2] JPEG2026529027000044.jpg52170[Chemical Formula 3] JPEG2026529027000045.jpg33170[Chemical Formula 4] JPEG2026529027000046.jpg53170[Chemical Formula 5] JPEG2026529027000047.jpg48170In Chemical Formula 1 to Chemical Formula 5 above, R is a structure represented by Chemical Formula 6 below. [Chemical Formula 6] JPEG2026529027000048.jpg54170In Chemical Formula 6 above, Rx and Ry are each independently either H or F. In Chemical Formula 3 above, n is an integer from 1 to 5, and m is an integer from 1 to 5. In Chemical Formula 4 and Chemical Formula 5 above, n is an integer from 1 to 5. In Chemical Formula 4 and Chemical Formula 5 above, R1 and R2 are each independently either H or F.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2023-0127480, filed on 22 September 2023, and all content disclosed in the said Korean Patent Application 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 expanded beyond power supply for electronic devices such as electrical, electronic, telecommunications, and computers to include power storage and supply for large-area equipment such as automobiles and power storage devices. to The market is expanding rapidly, and consequently, there is a growing 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 occurs when the potential of the positive electrode becomes high, or the battery of Drive inside The heat generated or exposure to a high-temperature external environment tends to further accelerate the process.

[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, in order to solve these problems, research and development is being conducted on methods that can suppress the elution of metal ions in the positive electrode, form a stable SEI film in the negative electrode, reduce the swelling phenomenon of secondary batteries, and improve long-term life characteristics and high-temperature durability. Forbidden Yes, they are. [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 relates to the positive electrode deterioration The objective is to provide an additive for non-aqueous electrolytes that suppresses side reactions between the positive electrode and the electrolyte, reduces side reactions between the positive electrode and the electrolyte, and can 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] [1] The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and one compound of any of the following chemical formulas 1 to 5 as an additive.

[0013] [Chemical formula 1] [ka]

[0014] [Chemical formula 2] [ka]

[0015] [Chemical formula 3] [ka]

[0016] [Chemical formula 4] [ka]

[0017] [Chemical formula 5] [ka]

[0018] In the aforementioned chemical formulas 1 to 5, R has the structure represented by the following chemical formula 6.

[0019] [Chemical formula 6] [ka]

[0020] In the aforementioned chemical formula 6, Rx and Ry are each independently either H or F.

[0021] In the above chemical formula 3, n is an integer from 1 to 5, and m is an integer from 1 to 5.

[0022] In chemical formulas 4 and 5, n is an integer between 1 and 5.

[0023] In chemical formulas 4 and 5, R1 and R2 are each independently either H or F.

[0024] [2] The present invention can provide the non-aqueous electrolyte described in [1] above, wherein R has a structure represented by the following chemical formula 6-1.

[0025] [Chemical formula 6-1] [ka]

[0026] [3] The present invention can provide the nonaqueous electrolyte described in [1] or [2] above, wherein the additive for nonaqueous electrolytes is contained in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the nonaqueous electrolyte.

[0027] [4] The present invention relates to the lithium salt being LiPF6, LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 A nonaqueous electrolyte according to any one of [1] to [3] above, which is one or more selected from LiAlCl4, LiAlO2, LiSO3CH3, LiSO3CF3, LiCO2CH3, LiCO2CF3, LiAsF6, LiSbF6, LiN(SO2F)2LiN(SO2CF2CF3)2, and LiN(SO2CF3)2. We can provide .

[0028] [5] The present invention can provide a non-aqueous electrolyte according to any one of [1] to [4] above, wherein the lithium salt is contained in a concentration of 0.5 M to 4.0 M.

[0029] [6] The present invention can provide a non-aqueous electrolyte according to any one of [1] to [5] above, 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.

[0030] [7] The present invention can provide the non-aqueous electrolyte according to any one of [1] to [6], further comprising 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.

[0031] [8] The present invention can provide a lithium secondary battery including a positive electrode, a negative electrode, and the non-aqueous electrolyte according to any one of [1] to [7].

[0032] [9] The present invention can provide the lithium secondary battery according to [8], wherein the positive electrode contains a lithium nickel-based oxide as a positive electrode active material.

[0033]

[10] The present invention provides the lithium secondary battery according to [8] or [9], wherein the negative electrode contains at least one selected from the group consisting of Si, Si-C, and SiO x (0 < x ≦ 2).

Advantages of the Invention

[0034] The compounds represented by Chemical Formula 1 to Chemical Formula 5 provided as additives for the non-aqueous electrolyte of the present invention are additives that improve the problems of 1,3-propanesultone, which is widely used as an electrolyte additive for film formation. 1,3-Propanesultone has problems such as increasing the resistance of lithium secondary batteries, making it difficult to add a large amount to the electrolyte, and generating toxic substances as by-products. Therefore, 1,3-propanesultone has a problem of Worsening affecting the output characteristics of lithium secondary batteries and being difficult to add in a large amount Ruta so that it has been difficult to obtain sufficient long-life characteristics.

[0035] The compounds represented by chemical formulas 1 to 5, provided as additives for non-aqueous electrolytes in the present invention, contain two or more R structures derived from 1,3-propanesultone in their molecules, thereby enabling the formation of a large amount of strong film on the positive / negative electrodes without the application of excess material. This makes it possible to provide lithium secondary batteries with excellent high-voltage life characteristics, high-temperature life characteristics, and high-temperature durability.

[0036] Therefore, by using the non-aqueous electrolyte of the present invention, which contains the compounds represented by chemical formulas 1 to 5, 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]

[0037] Terms and words used in this specification and in the claims are, General It should not be interpreted in a way that is limited to its literal or dictionary meaning, and the inventors is To explain my invention in the best possible way Use In accordance with the principle that the concept of a word can be appropriately defined, it should be interpreted in a way that is consistent with the technical idea of ​​this invention.

[0038] 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.

[0039] 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.

[0040] Furthermore, this specification of "Number of carbons a~b" andIn the description, "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, "C1-C5 alkyl group" refers to alkyl groups containing 1 to 5 carbon atoms, i.e., -CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CH(CH3)CH2CH3, -CH(CH2CH3)2, etc.

[0041] 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.

[0042] The present invention will be described in detail below.

[0043] 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.

[0044] Non-aqueous electrolytes The non-aqueous electrolyte of the present invention comprises a lithium salt, an organic solvent, and an additive for non-aqueous electrolytes, wherein the additive for non-aqueous electrolytes comprises one selected from the group consisting of compounds of chemical formula 1, chemical formula 2, chemical formula 3, chemical formula 4, and chemical formula 5.

[0045] [Chemical formula 1] [ka]

[0046] In the above chemical formula 1, R has the structure represented by the following chemical formula 6. The R group of the present invention has a structure in which it is linked to the linker via the carbon at the 3rd position of the propanesultone, which increases the overall length of the additive. Therefore, by applying the additive of the present invention, it is possible to form a coating in which the components are uniformly distributed over a wide area of ​​the positive / negative electrode.

[0047] [Chemical formula 6] [ka]

[0048] In the aforementioned chemical formula 6, Rx and Ry are each independently either H or F.

[0049] 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 film 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.

[0050] Furthermore, the compound of chemical formula 1 contains an oxygen element with a lone pair of electrons, and the coating formed by the decomposition of the compound of chemical formula 1 has the effect of having excellent lithium ion mobility.

[0051] [Chemical formula 2] [ka]

[0052] In the aforementioned chemical formula 2, R has the structure represented by the following chemical formula 6. The R group of the present invention has a structure in which it is linked to the linker via the carbon at the 3rd position of the propanesultone, which increases the overall length of the additive. Therefore, by applying the additive of the present invention, it is possible to form a coating in which the components are uniformly distributed over a wide area of ​​the positive / negative electrode.

[0053] [Chemical formula 6] [ka]

[0054] In the aforementioned chemical formula 6, Rx and Ry are each independently either H or F.

[0055] The compound of chemical formula 2 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 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.

[0056] Furthermore, the compound of chemical formula 2, due to its high-energy carbon-carbon chain and the presence of oxygen, which has a higher electron affinity than carbon, exhibits excellent durability of the film formed when the compound of chemical formula 2 decomposes, as well as superior lithium-ion mobility. That It is effective.

[0057] [Chemical formula 3] [ka]

[0058] In the above chemical formula 3, n is an integer from 1 to 5, and m is an integer from 1 to 5. Preferably, in the above chemical formula 3, n is 1 and m is 1.

[0059] In the aforementioned chemical formula 3, R has the structure represented by the following chemical formula 6. The R group of the present invention has a structure in which it is linked to the linker via the carbon at the 3rd position of the propanesultone, which increases the overall length of the additive. Therefore, by applying the additive of the present invention, it is possible to form a coating in which the components are uniformly distributed over a wide area of ​​the positive / negative electrode.

[0060] [Chemical formula 6] [ka]

[0061] In the aforementioned chemical formula 6, Rx and Ry are each independently either H or F.

[0062] The compound of chemical formula 3 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.

[0063] Furthermore, the compound of chemical formula 3 contains unsaturated bonds in a carbon-carbon-based chain with high bond energy, and a cross-linked polymer is formed in the coating that is formed when the compound of chemical formula 3 decomposes, thereby improving the durability of the coating. That It is effective.

[0064] [Chemical formula 4] [ka]

[0065] In the above chemical formula 4, n is an integer between 1 and 5.

[0066] In the above chemical formula 4, R1 and R2 are each independently either H or F.

[0067] In the aforementioned chemical formula 4, R has the structure represented by the following chemical formula 6. The R group of the present invention has a structure in which it is linked to the linker via the carbon at the 3rd position of the propanesultone, which increases the overall length of the additive. Therefore, by applying the additive of the present invention, it is possible to form a coating in which the components are uniformly distributed over a wide area of ​​the positive / negative electrode.

[0068] [Chemical formula 6] [ka]

[0069] In the aforementioned chemical formula 6, Rx and Ry are each independently either H or F.

[0070] The compound of chemical formula 4 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.

[0071] Furthermore, the compound of chemical formula 4 has the effect of improving the durability of the coating and lithium ion conductivity by forming a coating containing flexible chains based on carbon-carbon bonds with high bond energy. In addition, if the compound of chemical formula 4 contains F, the coating contains LiF, which has high physical strength, further enhancing the durability of the coating. So ru That It is effective.

[0072] [Chemical formula 5] [ka]

[0073] In the above chemical formula 5, n is an integer between 1 and 5.

[0074] In the above chemical formula 5, R1 and R2 are each independently either H or F.

[0075] In the aforementioned chemical formula 5, R has the structure represented by the following chemical formula 6. The R group of the present invention has a structure in which it is linked to the linker via the carbon at the 3rd position of the propanesultone, which increases the overall length of the additive. Therefore, by applying the additive of the present invention, it is possible to form a coating in which the components are uniformly distributed over a wide area of ​​the positive / negative electrode.

[0076] [Chemical formula 6] [ka]

[0077] In the aforementioned chemical formula 6, Rx and Ry are each independently either H or F.

[0078] The compound of chemical formula 5 contains two or more R structures derived from 1,3-propanesultone in its molecule, which allows for the formation of a large, strong film 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.

[0079] Furthermore, the compound of chemical formula 5, by containing oxygen with a lone pair of electrons in its chain, has the effect of exhibiting excellent lithium ion mobility in the coating formed by the decomposition of the compound of chemical formula 5. In addition, if the compound of chemical formula 5 contains F, the coating contains LiF, which has high physical strength, further enhancing the durability of the coating. So ru That It is effective.

[0080] In the aforementioned chemical formulas 1 to 5, R may be the structure represented by the following chemical formula 6-1.

[0081] [Chemical formula 6-1] [ka]

[0082] The additive for non-aqueous electrolytes according to the present invention may be included in an amount of 0.1 to 5 parts by weight, preferably 0.1 to 3 parts by weight, and more preferably 0.1 to 1 part by weight, per 100 parts by weight of the non-aqueous electrolyte. ~Chemical formula 5 When the content of the compound represented by satisfies the above range, the film formation effect on the positive and negative electrodes is sufficient, the leaching of transition metals from the positive electrode active material is suppressed, the degradation of the negative electrode is also suppressed, the lithium mobility of the electrolyte is appropriate, and the resistance of the lithium secondary battery is low. That It is effective.

[0083] 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 medium for transferring ions. Typically, the lithium salt is, for example, Li as a cation. +including, as anions teeth 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 - [[ID=6)5]]C4F9SO3 - CF3CF2SO3 - CF3CF2(CF3)2CO - (CF3SO2)2CH - CF3(CF2)7SO3 - [[ID=)75]]and SCN - at least one selected from the group consisting of , used as anion is mentioned

[0084] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10The electrolyte may also 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 may also be included. of limit Without It is usable.

[0085] The lithium salt can be changed as appropriate within the range of normal use, but optimal Na To obtain the effect of forming a corrosion-preventive coating on the electrode surface, the lithium salt 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, the viscosity of the non-aqueous electrolyte is appropriate, and the electrolyte impregnation is improved. obtain .

[0086] 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.

[0087] Specifically, the organic solvent may include a cyclic carbonate organic solvent, a linear carbonate organic solvent, or a mixture thereof.

[0088] 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.

[0089] 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).

[0090] 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.

[0091] As a specific example of such linear ester-based organic solvents teeth Examples 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.

[0092] 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.

[0093] On the other hand, the organic solvent may be limited to organic solvents commonly used with non-aqueous electrolytes, as needed. Without Additional solvents may be used. For example, at least one or more organic solvents from among ether-based organic solvents, glyme-based solvents, and nitrile-based organic solvents may be further included.

[0094] 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.

[0095] The aforementioned glyme-based solvent has a higher dielectric constant and lower surface tension compared to linear carbonate-based organic solvents. metal The solvent is one that has low reactivity with the substance and may contain, but is not limited to, at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME).

[0096] The nitrile solvents mentioned above include acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, andIt may be one or more substances selected from the group consisting of 4-fluorophenylacetonitrile, but is not limited to these.

[0097] 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.

[0098] 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.

[0099] Examples of the aforementioned cyclic carbonate compounds include vinylene carbonate (VC) or vinylethylene carbonate.

[0100] Examples of halogen-substituted carbonate compounds include fluoroethylene carbonate (FEC).

[0101] 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.

[0102] Examples of the sulfate compounds include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0103] 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.

[0104] Examples of the borate compounds include tetraphenyl borate, lithium oxalyl difluoroborate (LiODFB), and lithium bisoxalate borate (LiB(C2O4)2, LiBOB).

[0105] 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.

[0106] 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.

[0107] 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.

[0108] Among these other electrolyte additives, vinylene carbonate (VC), 1,3-propanesultone (PS), and Further combinations of ethylene sulfate (Esa) include In this case, a stronger SEI film can be formed on the surface of the negative electrode during the initial activation process of the secondary battery, suppressing the generation of gases that may be produced by the decomposition of the electrolyte at high temperatures, and improving the high-temperature stability of the secondary battery.

[0109] On the other hand, the other electrolyte additives may be used in a mixture of two or more types, with a ratio of 0.1 based on the total weight of the non-aqueous electrolyte. weight% ~10% by weight, specifically 0.2 weight% It may be included in an amount of ~8% by weight, preferably 0.5%. weight% The content may be ~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.

[0110] Lithium-ion battery The present invention also provides a lithium secondary battery comprising the non-aqueous electrolyte.

[0111] 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.

[0112] In this case, the lithium secondary battery of the present invention can be manufactured by conventional methods known in the art. For example, the positive electrode, the negative electrode, and The electrode assembly can be formed by sequentially stacking separators between a positive electrode and a negative electrode, then inserting the electrode assembly into a battery case and injecting the non-aqueous electrolyte according to the present invention.

[0113] (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.

[0114] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or the surface of aluminum or stainless steel ni Ka -bon, nickel, titanium, silver, etc. that have been surface-treated may be used.

[0115] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium. Specifically, it may include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), a lithium-nickel-manganese-cobalt-based oxide (e.g., Li(Ni p Co q Mn 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 Coq2 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, respectively, where 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, and p2 + q2 + r2 + s2 = 1), etc.) etc. may be mentioned, and any one or two or more of these compounds may be included.

[0116] Among them, from the point that the capacity characteristics and stability of the battery can be enhanced, the lithium metal oxide may be 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., and any one or two or more of these mixtures may be used.

[0117] Among them, from the point that the capacity characteristics of the battery can be maximally enhanced, 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 7.

[0118] [Chemical Formula 7] Li x Ni a Co b M 1 c M 2 d O2

[0119] In the above Chemical Formula 7, the M 1 is one or more selected from Mn and Al, and may preferably be Mn, or a combination of Mn and Al.

[0120] 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.

[0121] 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.

[0122] 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 achieved.

[0123] 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.

[0124] 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.

[0125] The d represents the atomic fraction of M 2This represents the atomic fraction, and may be either 0≦d≦0.1 or 0≦d≦0.05.

[0126] The positive electrode active material is calculated based on the total weight of the solid matter in the positive electrode mixture slurry excluding the solvent, which is 60 weight% ~99% by weight, preferably 70% weight% ~99% by weight, more preferably 80 weight% It may be included in an amount of up to 98% by weight.

[0127] The aforementioned binder is a component that assists in the bonding of the active material to the conductive material and to the current collector.

[0128] 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.

[0129] Typically, the binder is calculated based on the total weight of the solids in the positive electrode mixture slurry, excluding the solvent, and is 1 weight% ~20% by weight, preferably 1 weight% ~15% by weight, comfort level 1 weight% It may be included in an amount of ~10% by weight.

[0130] The aforementioned conductive material is a component for further improving the conductivity of the positive electrode active material. positive electrode Based on the total weight of solids in the mixture slurry, 1 weight%It may be added in an amount of ~20% by weight. Such conductive materials are not particularly limited as long as they do not cause chemical changes in the battery and are 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; fluorinated carbon powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0131] Typically, the conductive material is calculated based on the total weight of the solid matter in the positive electrode mixture slurry excluding the solvent, 1 weight% ~20% by weight, preferably 1 weight% ~15% by weight, comfort level 1 weight% It may be included in an amount of ~10% by weight.

[0132] The solvent may contain 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 the binder and conductive material are included. For example, the concentration of the solid content containing the positive electrode active material and selectively the binder and conductive material is 50 weight% ~95% by weight, preferably 70% weight% ~95% by weight, comfort level 70 weight% It may be included in an amount of approximately 90% by weight.

[0133] (2) Negative electrode The negative electrode can be manufactured, for example, by coating a negative electrode 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.

[0134] 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 is generally 3 μmIt has a thickness of ~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, calcined carbon, copper or stainless steel surface ni Ka Materials with surface treatments such as carbon, nickel, titanium, and silver, or aluminum-cadmium alloys may be used. In addition, 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 films, sheets, foils, meshes, porous materials, foams, and nonwoven fabrics.

[0135] 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.

[0136] 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.

[0137] As the aforementioned metal or alloy of these metals with lithium, metals 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 alloys of these metals with lithium, can be used.

[0138] 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.

[0139] 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 alkali metals, alkaline earth kind 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 kind metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations 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 combinations thereof.

[0140] As the transition metal oxide, lithium - containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, etc. can be mentioned.

[0141] Among them, the negative electrode active material may be a mixture of graphite and a silicon-based active material. The silicon-based active material may be Si, SiO x (0 < x ≤ 2), or a Si-C composite. From the viewpoint of increasing the capacity of the lithium secondary battery, the graphite and the silicon-based active material may be contained in a weight ratio of 99.5:0.5 to 70:30.

[0142] The negative electrode active material is 60 weight% to 99% by weight, preferably 70 weight% to 99% by weight, more preferably 80 weight% to 98% by weight, based on the total weight of the solid content in the negative electrode binder slurry.

[0143] The binder is a component that aids in binding 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, and the like.

[0144] Generally, the binder is 1 weight% to 20% by weight, preferably 1 weight% to 15% by weight, more preferably 1 weight% to 10% by weight, based on the total weight of the solid matter excluding the solvent in the negative electrode binder slurry.

[0145] The conductive material is a component for further improving the conductivity of the negative electrode active material, and is 1 weight%It may be added in an amount of ~20% by weight. Such conductive materials are not particularly limited as long as they do not cause chemical changes in the battery and are 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.

[0146] The conductive material is calculated based on the total weight of the solid matter in the negative electrode mixture slurry excluding the solvent, which is 1 weight% ~20% by weight, preferably 1 weight% ~15% by weight, comfort level 1 weight% It may be included in an amount of ~10% by weight.

[0147] 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.

[0148] When using metal itself as the negative electrode, the metal is physically bonded to the metal thin film itself or onto the negative electrode current collector. do ,rolling do , or vapor deposition do etc. of It can be manufactured by the following method. As the deposition method, a method of electrodeposition or chemical vapor deposition of metal can be used.

[0149] 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).

[0150] (3) Separator Furthermore, as a separator, conventional from As separators, ordinary porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, may be used alone or in laminated form. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used, but are not limited to these. Furthermore, coated separators containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and may be used selectively as single-layer or multi-layer structures.

[0151] 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.

[0152] 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.

[0153] Examples Example 1 (Manufacturing of non-aqueous electrolytes) LiPF6 in an organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) = 20:70:10 volume ratio) of Dissolve to a concentration of 1.2M Let A non-aqueous solvent was prepared, and 0.5 g of the compound of the following chemical formula 1 was added to 99.5 g of the non-aqueous solvent to prepare a non-aqueous electrolyte.

[0154] [Chemical formula 1] [ka]

[0155] before R has the structure represented by the following chemical formula 6-1. 。

[0156] [Chemical formula 6-1] [ka]

[0157] (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.

[0158] 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.

[0159] In a dry room, a porous polymer separator is interposed between the positive electrode and the negative electrode manufactured as described above. Let Afterward, the non-aqueous electrolyte produced as described above was injected to manufacture a secondary battery.

[0160] 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 2 was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0161] [Chemical formula 2] [ka]

[0162] before R has the structure represented by the following chemical formula 6-1. 。

[0163] [Chemical formula 6-1] [ka]

[0164] 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 3 was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0165] [Chemical formula 3] [ka]

[0166] before R has the structure represented by the following chemical formula 6-1. 。

[0167] [Chemical formula 6-1] [ka]

[0168] 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 4 was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0169] [Chemical formula 4] [ka]

[0170] before R has the structure represented by the following chemical formula 6-1. 。

[0171] [Chemical formula 6-1] [ka]

[0172] 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 5 was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0173] [Chemical formula 5] [ka]

[0174] beforeGroup R is a structure represented by the following chemical formula 6-1 。

[0175] [Chemical formula 6-1] [Chemical formula]

[0176] Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was manufactured using 100 g of the non-aqueous solvent manufactured in Example 1.

[0177] Comparative Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of 1,3-propane sultone was added to 99.5 g of the non-aqueous solvent manufactured in Example 1 to manufacture a non-aqueous electrolyte.

[0178] 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 the following chemical formula A was added to 99.5 g of the non-aqueous solvent manufactured in Example 1 to manufacture a non-aqueous electrolyte.

[0179] [Chemical formula A] [Chemical formula]

[0180] before Group R' is a structure represented by the following chemical formula B 。

[0181] [Chemical formula B] [Chemical formula]

[0182] Comparative Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of the compound of the following chemical formula C was added to 99.5 g of the non-aqueous solvent manufactured in Example 1 to manufacture a non-aqueous electrolyte.

[0183] [Chemical formula C] [ka]

[0184] Comparative 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 D below was added to 99.5 g of the non-aqueous solvent prepared in Example 1 to produce a non-aqueous electrolyte.

[0185] [Chemical formula D] [ka]

[0186] Experimental Example 1 - Evaluation of High-Temperature Cycle Characteristics (1) For each of the lithium secondary batteries produced in Examples 1-5 and the secondary batteries produced in Comparative Examples 1-5, the temperature was set at 25°C to 0.1C. rate After a 3-hour formation process, at 25°C, 0.33°C rate It was charged to 4.4V under CC-CV (constant current-constant voltage) conditions, and then 0.33C rate The battery was then discharged to 2.5V under CC conditions. This charge-discharge cycle was considered one cycle, and three initial charge-discharge cycles were performed.

[0187] Next, the initially charged and discharged lithium secondary batteries are subjected to a high temperature (45°C) at 0.33C. rate Charged to 4.4V under CC-CV conditions, and at 0.33C rate The battery was then discharged to 2.5V under CC conditions. This charge-discharge cycle was considered one cycle, and 100 cycles were performed.

[0188] 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 the table below. 1 As shown.

[0189] [Formula 1] Capacity retention rate (%) = (Discharge capacity after 100th cycle / Discharge capacity after 1st cycle) X 100

[0190] Experimental Example 2 - Evaluation of High-Temperature Cycle Characteristics (2) Each of the lithium secondary batteries manufactured in Examples 1 to 5 and the secondary batteries manufactured in Comparative Examples 1 to ⑤ was charged under CC-CV (constant current-constant voltage) conditions up to 4.4V at 25°C at 0.33C, and discharged under CC conditions up to 2.5V at 0.33C. rate up to 4.4V under CC-CV (constant current-constant voltage) conditions at 0.33C, and discharged under CC conditions up to 2.5V at 0.33C. rate The above charge and discharge was defined as 1 cycle, and the initial charge and discharge for 3 cycles was 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.

[0191] Thereafter, at 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 0.33C, and discharged under CC conditions up to 2.5V at 0.33C. The above charge and discharge was defined as 1 cycle, and after 100 cycles had progressed, each lithium secondary battery was transferred to a charger at normal 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. rate up to 4.4V under CC-CV conditions at 0.33C, and discharged under CC conditions up to 2.5V at 0.33C. rate The above charge and discharge was defined as 1 cycle, and after 100 cycles had progressed, each lithium secondary battery was transferred to a charger at normal 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.

[0192] The initial resistance and the resistance after the 100th cycle were substituted into Equation 2 below to calculate the high-temperature cycle resistance increase rate. The results are shown in Table 1 below.

[0193] [Equation 2] Resistance increase rate (%) = {(Resistance after 100th cycle - Initial resistance) / first time Initial resistance} X 100

[0194] [Table 1]

[0195] As shown in Table 1, Honpatsu Examples 1-5, which used the additive for non-aqueous electrolytes of the present invention, showed improved capacity retention and resistance increase compared to Comparative Examples 1-5, which did not use the additive. The additive of the present invention, in which a linker is linked to the carbon at the 3rd position of propanesultone, has a longer overall additive length compared to the additive of chemical formula A, in which a linker is linked to the carbon at the 4th position of propanesultone. As a result, the lithium secondary batteries of Examples 1-5, which contain the additive of the present invention, have an increased surface area covered by the coating on the positive / negative electrodes, and are considered to have superior high-temperature life characteristics compared to the lithium secondary battery of Comparative Example 3.

[0196] Furthermore, the additive of the present invention has a longer overall additive length compared to the additives of chemical formulas C and D, which have shorter linker lengths between propane-sultone substituents. As a result, the lithium secondary batteries of Examples 1 to 5 containing the additive of the present invention have an increased surface area covered by the coating on the positive / negative electrodes, and are therefore considered to have superior high-temperature life characteristics compared to the lithium secondary batteries of Comparative Examples 4 and 5.

[0197] Experimental Example 3 - Evaluation of High-Temperature Storage Characteristics (1) The lithium secondary batteries produced in Examples 1-5 and the secondary batteries produced in Comparative Examples 1-5 were subjected to a 0.33C test at 25°C. rate It was charged to 4.4V under CC-CV (constant current-constant voltage) conditions, and then 0.33C rate The battery was discharged to 2.5V 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. After that, 0.33C rate The batteries were charged to 4.4V under CC-CV (constant current-constant voltage) conditions and stored at 60°C for 5 weeks.

[0198] After that, each of the lithium secondary batteries was transferred to a charger / discharger at room temperature (25°C), and then 0.33C rate Charged to 4.4V under CC-CV conditions, and at 0.33C rate It was then discharged to 2.5V under CC conditions. Discharge capacity obtained after 5 weeks of high-temperature storage and initial discharge capacity The high-temperature storage capacity retention rate was calculated by substituting the values ​​into Equation 3 below. The results are shown in Table 2 below.

[0199] [Formula 3] Capacity retention rate (%) = (Discharge capacity after 5 weeks of high-temperature storage / Initial discharge capacity) x 100

[0200] Experimental Example 4 - Evaluation of High-Temperature Storage Characteristics (2) The lithium secondary batteries produced in Examples 1-5 and the secondary batteries produced in Comparative Examples 1-5 were each subjected to a temperature of 0.33C at 25°C. rate It was charged to 4.4V under CC-CV (constant current-constant voltage) conditions, and then 0.33C rate The battery was discharged to 2.5V 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 (pulse) of 2.5C was applied for 10 seconds, and this resistance was set as the initial resistance. Subsequently, 0.33C rate The batteries were charged to 4.4V under CC-CV (constant current-constant voltage) conditions and stored at 60°C for 5 weeks.

[0201] 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.

[0202] 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.

[0203] [Formula 4] Resistance increase rate (%) = {(Resistance after 5 weeks of high-temperature storage - Initial resistance) / Initial resistance} x 100

[0204] Experimental Example 5 - Evaluation of High-Temperature Storage Characteristics (3) The lithium secondary batteries produced in Examples 1-5 and the secondary batteries produced in Comparative Examples 1-5 were each subjected to a temperature of 0.33C at 25°C. rate The battery was charged to 4.4V under CC-CV (constant current-constant voltage) conditions, and its volume was measured at room temperature using the buoyancy method. This was defined as the initial volume (0%). After storing the volume-measured battery at 60°C for 5 weeks, it was transferred to a charger / discharger at room temperature (25°C), and the capacity retention rate in Experimental Example 3 was measured. Then, at 25°C, the volume was reduced to 0.33C. rate The battery was fully charged to 4.4V under CC-CV (constant current-constant voltage) conditions, and its 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 rate of increase in the high-temperature storage volume. The results are shown in Table 2 below.

[0205] [Formula 5] Volume increase rate (%) = {(Volume after 5 weeks of high-temperature storage - Initial volume) / Initial volume} x 100

[0206] [Table 2]

[0207] As shown in Table 2 above, secondary batteries of Examples 1 to 5 teeth Compared to the secondary batteries of Comparative Examples 1-5 、It was found that the capacity retention rate, resistance increase rate, and volume increase rate were all improved after 5 weeks. The additive of the present invention, in which a linker is linked to the carbon at the 3rd position of the propanesultone, has a longer overall additive length compared to the additive of chemical formula A, in which a linker is linked to the carbon at the 4th position of the propanesultone. As a result, the lithium secondary batteries of Examples 1 to 5 containing the additive of the present invention have an increased area covered by the coating on the positive / negative electrodes, and are considered to have superior high-temperature storage characteristics compared to the lithium secondary battery of Comparative Example 3. Furthermore, the additive of the present invention has a longer overall additive length compared to the additives of chemical formulas C and D, in which the linker length between the propanesultone substituents is shorter. As a result, the lithium secondary batteries of Examples 1 to 5 containing the additive of the present invention have an increased area covered by the coating on the positive / negative electrodes, and are considered to have superior high-temperature storage characteristics compared to the lithium secondary batteries of Comparative Examples 4 and 5.

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