Nonaqueous electrolyte and lithium secondary battery comprising same

Abstract

The present invention provides a non-aqueous electrolyte including a lithium salt, an organic solvent, and a compound represented by the following Formula 1 as an additive. [Formula 1] # imgabs0 # (In 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 optionally substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms optionally substituted with fluorine, an alkynyl group having 2 to 10 carbon atoms optionally substituted with fluorine, OR ', OCOR', F, and CH2PO (R) 2; 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 formula 1 and R1, R is shown in the following formula 2. [Formula 2] # imgabs 1 # In Formula 2, Rx and Ry are each independently H or F.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from 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, which are hereby incorporated by reference herein in their entirety. Technical Field

[0003] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same. Background Art

[0004] In recent years, the application areas of lithium secondary batteries have expanded rapidly. They are not only used as power sources for electronic equipment such as electrical, electronic, communication, and computers, but also for storing and supplying electricity to large-area devices such as vehicles and power storage devices. Therefore, the demand for secondary batteries with high capacity, high output, and high stability is increasing.

[0005] In particular, for lithium secondary batteries used in vehicles, high capacity, high output, and long life are becoming increasingly important. To achieve high capacity in secondary batteries, positive electrode active materials with high Ni content and high energy density but low stability can be used, or the secondary batteries can be driven at high voltage.

[0006] However, when a secondary battery is operated under these conditions, as charging and discharging proceed, the surface structure of the electrodes or the thin films formed on the positive and negative electrode surfaces may deteriorate due to side reactions caused by electrolyte degradation, leading to the dissolution of transition metal ions from the positive electrode surface. As mentioned above, the dissolved transition metal ions are electrodeposited on the negative electrode, reducing the passivation ability of the solid electrolyte interface (SEI), thus causing the problem of negative electrode degradation.

[0007] This secondary battery degradation phenomenon tends to further increase when the positive electrode potential increases, or when the battery is exposed to heat generated during battery operation or an external high-temperature environment.

[0008] Furthermore, when a lithium secondary battery is used continuously for a long period of time or left at high temperature, gas is generated, causing a so-called swelling phenomenon in which the thickness of the battery increases. It is known that the amount of gas generated at this time depends on the state of the SEI.

[0009] Therefore, in order to solve the above problems, research and development are underway to suppress the dissolution of metal ions from the positive electrode and form a stable SEI film on the negative electrode, thereby reducing the swelling phenomenon in the secondary battery and improving the durability at high temperatures. Summary of the Invention

[0010] Technical issues

[0011] Numerous studies have been conducted to solve the above problems. The present invention aims to provide an additive for a non-aqueous electrolyte that can inhibit the degradation of the positive electrode, reduce the side reactions between the positive electrode and the electrolyte, and form a stable SEI film on the negative electrode.

[0012] Furthermore, the present invention is also intended to provide a non-aqueous electrolyte having improved high-temperature stability by containing the above-mentioned additive for a non-aqueous electrolyte.

[0013] Furthermore, the present invention also provides a lithium secondary battery having improved high-temperature cycle characteristics and high-temperature storage characteristics by containing the above-mentioned non-aqueous electrolyte, thereby having improved overall performance.

[0014] Technical Solution

[0015] To achieve the above object, the present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and a compound represented by the following Formula 1 as an additive.

[0016] [Formula 1]

[0017]

[0018] In the above 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 that can be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms that can be substituted with fluorine, an alkynyl group having 2 to 10 carbon atoms that can be substituted with fluorine, OR', OCOR', F and CH2PO(R)2, R' is any one selected from the group consisting of an alkyl group having 1 to 10 carbon atoms that can be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms that can be substituted with fluorine, an alkynyl group having 2 to 10 carbon atoms that can be substituted with fluorine and PO(R)2, and R is shown in the following formula 2.

[0019] [Formula 2]

[0020]

[0021] In the above formula 2, Rx and Ry are each independently H or F.

[0022] Furthermore, the present invention provides a lithium secondary battery comprising the above nonaqueous electrolyte.

[0023] Beneficial effects

[0024] The compound represented by Formula 1 provided as a non-aqueous electrolyte additive of the present invention is an additive that solves the problems of 1,3-propane sultone, which is widely used as a film-forming electrolyte additive. 1,3-Propane sultone increases the resistance of lithium secondary batteries, making it difficult to add large amounts to the electrolyte and has the problem of producing toxic substances as byproducts. Therefore, 1,3-propane sultone has the problem of deteriorating the output characteristics of lithium secondary batteries, and it is difficult to obtain sufficient long-life characteristics due to the difficulty of adding large amounts.

[0025] The compound represented by Formula 1 provided as a non-aqueous electrolyte additive of the present invention contains two or more R structures derived from 1,3-propane sultone in the molecule, thereby forming a large amount of stable film on the positive electrode and the negative electrode without excessive application, thereby providing a lithium secondary battery with excellent high-voltage life characteristics, high-temperature life characteristics, and high-temperature durability.

[0026] In addition, the compound of Formula 1 can reduce the generation of toxic byproducts by connecting a P-containing linker to the 3-carbon of 1,3-propane sultone to cause a toxicity-inducing reaction. In addition, due to the unique properties of electron-rich phosphorus (P), when the P-containing linker forms a thin film on the positive and negative electrodes, the compound of Formula 1 exhibits improved lithium ion transport performance. Therefore, the compound of Formula 1 can form a stable CEI (cathode electrolyte interface) film and SEI (solid electrolyte interphase) film on the surface of the positive and negative electrodes. Therefore, it is possible to prevent the dissolution of transition metals caused by the degradation of the positive electrode active material under high voltage, and to prevent the degradation of the negative electrode by suppressing the degradation of the SEI passivation ability at high temperature.

[0027] Therefore, when the non-aqueous electrolyte of the present invention containing the compound of Formula 1 as an additive is used, an electrode-electrolyte interface that is stable and has low resistance even at high temperatures can be formed, which simultaneously improves high-temperature cycle characteristics and high-temperature storage characteristics, thereby realizing a lithium secondary battery with improved overall performance. DETAILED DESCRIPTION

[0028] It should be understood that the terms or words used in the present invention and claims should not be interpreted as having the meanings defined in commonly used dictionaries, but should be interpreted as having meanings and concepts consistent with the technical ideas of the present invention based on the principle that the inventor appropriately defines the term concepts to best explain the present invention.

[0029] It should also be understood that the terms "include", "comprises" or "has" in the present invention specify the presence of the stated features, numbers, steps, elements or a combination thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, elements or a combination thereof.

[0030] Meanwhile, before describing aspects of the present invention, unless otherwise specified in the present invention, the expression “*” represents the same or different atoms or moieties connected to both ends of a formula.

[0031] In addition, in the expression "a to b carbon atoms" in the present invention, "a" and "b" respectively represent the number of carbon atoms contained in a specific functional group. That is, the functional group can include "a" to "b" carbon atoms. For example, "an alkyl group having 1 to 5 carbon atoms" refers to an alkyl group including 1 to 5 carbon atoms, i.e., -CH3, -CH2CH3, -CH2CH2CH3, -CH2C(CH3)H2, -CH(CH3)2, -CH(CH3)CH2CH3, -CH(CH2CH3)2, etc.

[0032] In addition, in the present specification, an alkyl group, an alkenyl group, or an alkynyl group may or may not have a substituent. Unless otherwise defined in the specification, the expression "substituted" means that at least one hydrogen bonded to carbon is replaced by an element other than hydrogen, for example, a halogen atom such as F and Cl.

[0033] Hereinafter, the present invention will be described in more detail.

[0034] The nonaqueous electrolyte and / or lithium secondary battery of the present invention may include at least one structure disclosed below, and may include any combination of technically possible structures among the following structures.

[0035] non-aqueous electrolytes

[0036] The non-aqueous electrolyte of the present invention includes a lithium salt, an organic solvent, and a non-aqueous electrolyte additive represented by the following formula 1:

[0037] [Formula 1]

[0038]

[0039] In the above formula 1, n is an integer of 0 or 1.

[0040] In the above formula 1, R1 is any one selected from the group consisting of R, an alkyl group having 1 to 10 carbon atoms which can be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms which can be substituted with fluorine, an alkynyl group having 2 to 10 carbon atoms which can be substituted with fluorine, OR', OCOR', F and CH2PO(R)2, and R' is any one selected from the group consisting of an alkyl group having 1 to 10 carbon atoms which can be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms which can be substituted with fluorine, an alkynyl group having 2 to 10 carbon atoms which can be substituted with fluorine and PO(R)2.

[0041] In the above formula 1 and R1, R is as shown in the following formula 2.

[0042] [Formula 2]

[0043]

[0044] In the above formula 2, Rx and Ry are each independently H or F.

[0045] The compound represented by Formula 1 provided as a non-aqueous electrolyte additive of the present invention contains two or more R structures derived from 1,3-propane sultone in the molecule, thereby forming a large amount of stable film on the positive electrode and the negative electrode without excessive application, thereby providing a lithium secondary battery with excellent high-voltage life characteristics, high-temperature life characteristics, and high-temperature durability.

[0046] In addition, the compound of Formula 1 can reduce the generation of toxic byproducts by connecting a P-containing linker to the 3-carbon of 1,3-propane sultone to cause a toxicity-inducing reaction. In addition, due to the unique properties of electron-rich phosphorus (P), when the P-containing linker forms a film on the positive and negative electrodes, the compound of Formula 1 improves the transport performance of lithium ions. Therefore, the compound of Formula 1 can form a stable CEI (cathode electrolyte interface) film and SEI (solid electrolyte interphase) film on the surface of the positive and negative electrodes. Therefore, the degradation of the negative electrode can be prevented by suppressing the collapse of the continuous structure caused by the release of oxygen at high temperature of the positive electrode and suppressing the decline in the passivation ability of the SEI.

[0047] Therefore, when the nonaqueous electrolyte containing the compound of Formula 1 of the present invention is used, an electrode-electrolyte interface that is stable and has low resistance even at high temperatures can be formed, which improves high-temperature cycle characteristics and high-temperature storage characteristics, thereby realizing a lithium secondary battery with improved overall performance.

[0048] For example, the compound of Formula 1 may be a compound represented by the following Formula 1-1.

[0049] [Formula 1-1]

[0050]

[0051] In the above formula 1-1, R1 is F, R or OR', and R' can be any one selected from the group consisting of an alkyl group having 1 to 10 carbon atoms which can be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms which can be substituted with fluorine, and an alkynyl group having 2 to 10 carbon atoms which can be substituted with fluorine.

[0052] In the above formula 1-1 and R1, R may be as shown in the following formula 2.

[0053] [Formula 2]

[0054]

[0055] In the above formula 2, Rx and Ry may each independently be H or F.

[0056] Specifically, the compound represented by the above Formula 1-1 may be any one of the compounds represented by the following Formulas 1-1a to 1-1f.

[0057] [Formula 1-1a]

[0058]

[0059] [Formula 1-1b]

[0060]

[0061] [Formula 1-1c]

[0062]

[0063] [Formula 1-1d]

[0064]

[0065] [Formula 1-1e]

[0066]

[0067] [Formula 1-1f]

[0068]

[0069] In the above Formulas 1-1a to 1-1f, R may be as shown in the following Formula 2-1.

[0070] [Formula 2-1]

[0071]

[0072] The compound of the above formula 1 may be a compound represented by the following formula 1-2.

[0073] [Formula 1-2]

[0074]

[0075] In the above formula 1-2, X may be -CH2- or -O-.

[0076] In the above formula 1-2 and R1, R may be as shown in the following formula 2.

[0077] [Formula 2]

[0078]

[0079] In the above formula 2, Rx and Ry may each independently be H or F.

[0080] Specifically, the compound represented by the above Formula 1-2 may be any one of the compounds represented by the following Formulas 1-2a to 1-2b.

[0081] [Formula 1-2a]

[0082]

[0083] [Formula 1-2b]

[0084]

[0085] In the above Formulas 1-2a and 1-2b, R may be as shown in the following Formula 2-1.

[0086] [Formula 2-1]

[0087]

[0088] The compound of the above formula 1 may be a compound represented by the following formula 1-3.

[0089] [Formula 1-3]

[0090]

[0091] In the above formula 1-3, R1 is F, R or OR', and R' can be any one selected from the group consisting of an alkyl group having 1 to 10 carbon atoms that can be substituted with fluorine, an alkenyl group having 2 to 10 carbon atoms that can be substituted with fluorine, and an alkynyl group having 2 to 10 carbon atoms that can be substituted with fluorine.

[0092] In the above formulas 1-3 and R1, R may be as shown in the following formula 2.

[0093] [Formula 2]

[0094]

[0095] In the above formula 2, Rx and Ry may each independently be H or F.

[0096] Specifically, the compound represented by the above Formula 1-3 may be any one of the compounds represented by the following Formulas 1-3a to 1-3f.

[0097] [Formula 1-3a]

[0098]

[0099] [Formula 1-3b]

[0100]

[0101] [Formula 1-3c]

[0102]

[0103] [Formula 1-3d]

[0104]

[0105] [Formula 1-3e]

[0106]

[0107] [Formula 1-3f]

[0108]

[0109] In the above Formulas 1-3a to 1-3f, R may be as shown in the following Formula 2-1.

[0110] [Formula 2-1]

[0111]

[0112] Based on 100 parts by weight of nonaqueous electrolyte, the content of the nonaqueous electrolyte additive of the present invention can be 0.1 to 5 parts by weight, preferably 0.1 to 3 parts by weight, more preferably 0.1 to 1 parts by weight. When the content of the compound represented by Formula 1 meets the above range, the effect of forming a film on the positive and negative electrodes is sufficient, thereby suppressing the dissolution of transition metals from the positive electrode active material and the degradation of the negative electrode. In addition, the lithium mobility of the electrolyte is suitable, so as to achieve the effect of reducing the resistance of the lithium secondary battery.

[0113] 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 serves as a medium for ion transport. Generally, the lithium salt may include Li + as a cation, and may contain at least one selected from the following as an anion: F - 、Cl - Br - , I - 、NO3 - 、N(CN)2 - 、BF4 - 、ClO4 - 、B 10 Cl 10 - 、AlCl4 - 、AlO2 - PF6 - CF3SO3 - 、CH3CO2 - CF3CO2 - 、AsF6 - 、SbF6- 、CH3SO3 - 、(CF3CF2SO2)2N - 、(CF3SO2)2N - 、(FSO2)2N - 、BF2C2O4 - BC4O8 - PF4C2O4 - PF2C4O8 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、C4F9SO3 - CF3CF2SO3 - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - CF3(CF2)7SO3 - and SCN - .

[0114] Specifically, the lithium salt may include a lithium salt selected from the group consisting of LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 , 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), or a mixture of two or more thereof. In addition to these, lithium salts commonly used in lithium secondary battery electrolytes can be used without restriction.

[0115] The lithium salt can be appropriately varied within the commonly used range, but in order to obtain the best effect of forming an anti-corrosion film on the electrode surface, the concentration of the lithium salt contained in the electrolyte can be 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, it has a sufficient effect of improving the cycle performance of the lithium secondary battery during high-temperature storage, and the viscosity of the non-aqueous electrolyte is appropriate, thereby improving the wettability of the electrolyte.

[0116] The organic solvent includes at least one selected from the group consisting of cyclic carbonate-based organic solvents, linear carbonate-based organic solvents, linear ester-based organic solvents, and cyclic ester-based organic solvents.

[0117] Specifically, the organic solvent may include a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, or a mixture thereof.

[0118] In addition, the cyclic carbonate organic solvent is an organic solvent with high viscosity and high dielectric constant, and is an organic solvent that can well dissociate lithium salts in the electrolyte. Specific examples thereof may 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, among which ethylene carbonate may be included.

[0119] In addition, linear carbonate organic solvents are organic solvents with low viscosity and low dielectric constant, wherein specific examples may include at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate, and specifically may include ethyl methyl carbonate (EMC).

[0120] In addition, in order to prepare an electrolyte with high ionic conductivity, in addition to including at least one carbonate organic solvent selected from cyclic carbonate organic solvents and linear carbonate organic solvents, the organic solvent may further include at least one ester organic solvent selected from linear ester organic solvents and cyclic ester organic solvents.

[0121] Specific examples of the linear ester organic solvent may include at least one selected from methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0122] In addition, the cyclic ester-based organic solvent may include at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0123] Meanwhile, if necessary, an organic solvent commonly used in non-aqueous electrolytes may be added without limitation. For example, at least one organic solvent selected from the group consisting of ether organic solvents, glyme organic solvents, and nitrile organic solvents may be further included.

[0124] As the ether solvent, any one selected from dimethyl ether, diethyl ether, dipropyl ether, ethyl methyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), and a mixture of two or more thereof may be used, but is not limited thereto.

[0125] Glyme solvents have a high dielectric constant and a low surface tension compared to linear carbonate organic solvents, and as solvents with low reactivity with metals, may include at least one selected from dimethoxyethane (glyme, DME), diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether (TEGDME), but are not limited thereto.

[0126] The nitrile solvent may be at least one selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, octanonitrile, heptanenitrile, cyclopentanenitrile, cyclohexanenitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, benzyl cyanide, 2-fluorophenyl cyanide and 4-fluorophenyl cyanide, but is not limited thereto.

[0127] In addition, in order to prevent the non-aqueous electrolyte from decomposing under high output conditions, thereby causing collapse of the negative electrode, or to further improve the low-temperature high-rate discharge characteristics, high-temperature stability, overcharge protection and battery expansion inhibition effect at high temperatures, if necessary, the non-aqueous electrolyte of the lithium secondary battery of the present invention may further include known electrolyte additives in the above-mentioned non-aqueous electrolyte.

[0128] Examples of the additional electrolyte additive may be at least one selected from the group consisting of cyclic carbonate compounds, halogenated carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0129] The cyclic carbonate-based compound may include vinylene carbonate (VC) or vinyl ethylene carbonate.

[0130] The halogenated carbonate compound may include fluoroethylene carbonate (FEC).

[0131] The sultone compound may include at least one selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethane sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone.

[0132] The sulfate compound may include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyltrimethylene sulfate (MTMS).

[0133] The phosphate compound may be 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.

[0134] The borate ester / salt compound can be tetraphenylborate and lithium oxalyldifluoroborate (LiODFB) or lithium bis(oxalato)borate (LiB(C2O4)2, LiBOB).

[0135] The nitrile compound may include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, octanonitrile, heptanecarbonitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, benzyl cyanide, 2-fluorophenyl cyanide and 4-fluorophenyl cyanide.

[0136] The benzene compound may include fluorobenzene, the amine compound may include triethanolamine or ethylenediamine, and the silane compound may include tetravinylsilane.

[0137] The lithium salt compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and may be lithium difluorophosphate (LiDFP), LiPO2F2, or LiBF4.

[0138] Among the electrolyte additives, when a combination of vinylene carbonate (VC), 1,3-propane sultone (PS), and ethylene sulfate (Esa) is contained, a stronger SEI film can be formed on the negative electrode surface during the initial activation process of the secondary battery, and the generation of gas that may be generated due to the decomposition of the electrolyte at high temperature can be inhibited, thereby improving the high-temperature stability of the secondary battery.

[0139] Meanwhile, the additional electrolyte additive can be used as a mixture of two or more thereof, and its content can be 0.1 wt % to 10 wt %, specifically 0.2 wt % to 8 wt %, and preferably 0.5 wt % to 8 wt %, based on the total weight of the non-aqueous electrolyte. When the content of the additional electrolyte additive meets the above range, it has a more excellent effect of improving ionic conductivity and cycle performance.

[0140] lithium secondary batteries

[0141] The present invention also provides a lithium secondary battery comprising the non-aqueous electrolyte.

[0142] Specifically, the lithium secondary battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator provided between the positive electrode and the negative electrode, and the above-mentioned nonaqueous electrolyte.

[0143] At this time, the lithium secondary battery of the present invention can be manufactured by conventional methods known in the art. For example, the lithium secondary battery of the present invention can be manufactured by the following method: forming an electrode assembly (where a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode are stacked in sequence), then accommodating the electrode assembly in a battery case, and subsequently injecting the non-aqueous electrolyte of the present invention therein.

[0144] (1) Positive electrode

[0145] The positive electrode can be manufactured by coating a positive electrode mixture paste containing a positive electrode active material, a binder, a conductive material, a solvent, etc. on a positive electrode current collector.

[0146] The positive electrode current collector is not particularly limited as long as it has conductivity and does not cause adverse chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, fired carbon; or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. can be used.

[0147] The positive electrode active material is a compound capable of reversibly inserting and extracting lithium, and can specifically include lithium metal oxides containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium metal oxide can be lithium manganese-based oxides (for example, LiMnO2, LiMn2O4, etc.), lithium cobalt-based oxides (for example, LiCoO2, etc.), lithium nickel-based oxides (for example, LiNiO2, etc.), lithium nickel manganese-based oxides (for example, LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium nickel cobalt-based oxides (for example, LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium manganese cobalt-based oxides (for example, LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium nickel manganese cobalt-based oxides (for example, Li(Ni p Co q Mn r )O2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2), etc.), or lithium nickel cobalt transition metal (M) oxides (for example, Li(Ni p2 Coq2 Mn r2 M s2 )O2 (wherein, M is selected from Al, Fe, V, Cr, Ti, Ta, Mg and Mo, p2, q2, r2 and s2 are the atomic fractions of independent elements, respectively, wherein, 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc.), etc., and may contain any one or more compounds thereof.

[0148] Among them, the lithium metal oxide can 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 (e.g., Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 )O2) etc., and any one of them or a mixture of two or more thereof can be used.

[0149] Among them, a positive electrode active material with a Ni content of 80 atm% or more can be used to maximize the capacity characteristics of the battery. For example, the lithium transition metal oxide can include a compound represented by the following formula 3.

[0150] [Formula 3]

[0151] Li x Ni a Co b M 1 c M 2 d O2

[0152] In the above formula 3, M 1It may be one or more selected from Mn and Al, preferably Mn or a combination of Mn and Al.

[0153] M 2 It 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.

[0154] x represents the atomic fraction of lithium in the lithium transition metal oxide, which may be 0.90 ≤ x ≤ 1.1, preferably 0.95 ≤ x ≤ 1.08, and more preferably 1.0 ≤ x ≤ 1.08.

[0155] a represents the atomic fraction of nickel among all metal elements other than lithium in the lithium transition metal oxide, which may be 0.80 ≤ a < 1.0, preferably 0.80 ≤ a ≤ 0.95, and more preferably 0.80 ≤ a ≤ 0.90. When the content of nickel satisfies the above range, high-capacity characteristics can be achieved.

[0156] b represents the atomic fraction of cobalt among all metal elements other than lithium in the lithium transition metal oxide, which may be 0 < b < 0.2, 0 < b ≤ 0.15, or 0.01 ≤ b ≤ 0.10.

[0157] c represents the atomic fraction of element M among all metal elements other than lithium in the lithium transition metal oxide 1 and may be 0 < c < 0.2, 0 < c ≤ 0.15, or 0.01 ≤ c ≤ 0.10.

[0158] d represents the atomic fraction of element M among all metal elements other than lithium in the lithium transition metal oxide 2 and may be 0 ≤ d ≤ 0.1 or 0 ≤ d ≤ 0.05.

[0159] Based on the total weight of the solids other than the solvent in the positive electrode mixture slurry, the content of the positive electrode active material may be 60% to 99% by weight, preferably 70% to 99% by weight, and more preferably 80% to 98% by weight.

[0160] The binder is a component that helps the binding between the active material and the conductive material and the binding with the current collector.

[0161] Examples of the binder may be polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene - propylene - diene monomer (EPDM), sulfonated EPDM, styrene - butadiene rubber, fluororubber, and various copolymers thereof.

[0162] Generally, the binder may be present in an amount of 1 to 20 wt %, preferably 1 to 15 wt %, and more preferably 1 to 10 wt %, based on the total weight of solids excluding the solvent in the positive electrode mixture slurry.

[0163] The conductive material is a component used to further improve the conductivity of the positive electrode active material, and its addition amount can be 1% to 20% by weight of the total weight of the solid content in the positive electrode mixture slurry. There is no particular limitation on the conductive material, as long as it has conductivity and does not cause chemical changes in the battery. For example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a developed crystal structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorocarbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. can be used.

[0164] Generally, the content of the conductive material may be 1 to 20 wt %, preferably 1 to 15 wt %, and more preferably 1 to 10 wt %, based on the total weight of the solid matter excluding the solvent in the positive electrode mixture slurry.

[0165] The solvent may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and its amount may be such that a preferred viscosity is achieved when the positive electrode active material and optional binder and conductive agent are included. For example, the solvent content may be such that the concentration of the solid matter including the positive electrode active material and optional binder and conductive agent is 50 wt % to 95 wt %, preferably 70 wt % to 95 wt %, and more preferably 70 wt % to 90 wt %.

[0166] (2) Negative electrode

[0167] For example, the negative electrode can be manufactured by coating a negative electrode mixture slurry containing a negative electrode active material, a binder, a conductive material, and a solvent on a negative electrode current collector. A graphite electrode formed of carbon (C) or metal itself can also be used as the negative electrode.

[0168] For example, in the case of manufacturing the negative electrode by coating the negative electrode mixture slurry on the negative electrode current collector, the thickness of the negative electrode current collector is generally 3μm to 500μm. The negative electrode current collector is not particularly limited as long as it has high conductivity and does not cause adverse chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy can be used. In addition, as with the positive electrode current collector, microscopic irregularities can be formed on the surface of the negative electrode current collector to improve the adhesion of the negative electrode active material. The negative electrode current collector can be used in various shapes, such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0169] In addition, the negative electrode active material may include at least one selected from lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of lithium and the metal, a metal composite oxide, a material that can be doped and dedoped with lithium, or a transition metal oxide.

[0170] As a carbon material capable of reversibly intercalating / deintercalating lithium ions, a carbon-based negative electrode active material commonly used in lithium ion secondary batteries can be used without particular limitation, and as a typical example, crystalline carbon and / or amorphous carbon can be used. Examples of crystalline carbon include graphite such as irregular, planar, flaky, spherical or fibrous natural graphite or artificial graphite, and examples of amorphous carbon include soft carbon (low temperature sintered carbon) or hard carbon, mesophase pitch carbide and fired coke, etc.

[0171] As the metal or the alloy of lithium with the metal, 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 lithium with the metal can be used.

[0172] As the metal composite oxide, one selected from the following can be used: 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 Groups I, II and III of the periodic table, or halogen; 0 <x≤1;1≤y≤3;1≤z≤8)。

[0173] Materials that can be doped and undoped with lithium can include Si, SiO x (0 < x ≤ 2), Si-Y alloys (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, or combinations thereof, but not Si), Sn, SnO2, and Sn-Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, or combinations thereof, but not Sn), and mixtures of SiO2 and at least one of them can be used. Element Y can 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.

[0174] Transition metal oxides can include lithium-containing titanium composite oxides (LTO), vanadium oxides, and lithium vanadium oxides.

[0175] Among them, the negative electrode active material can be a mixture of graphite and SiO x (0 < x ≤ 2). In terms of improving the capacity of the lithium secondary battery, the weight ratio of graphite and SiO x (0 < x ≤ 2) can be 99.5:0.5 to 70:30.

[0176] Based on the total weight of the solids other than the solvent in the negative electrode mixture slurry, the content of the negative electrode active material can be 60% by weight to 99% by weight, preferably 70% by weight to 99% by weight, and more preferably 80% by weight to 98% by weight.

[0177] The binder is a component that helps the binding between the conductive agent, the active material, and the current collector. Examples of the binder can be polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0178] Generally, based on the total weight of the solids other than the solvent in the negative electrode mixture slurry, the content of the binder can be 1% by weight to 20% by weight, preferably 1% by weight to 15% by weight, and more preferably 1% by weight to 10% by weight.

[0179] The conductive material is a component used to further improve the conductivity of the negative electrode active material, and its addition amount can be 1% to 20% by weight of the total weight of the solid content in the negative electrode mixture slurry. There is no particular limitation on the conductive material, as long as it has conductivity and does not cause chemical changes in the battery. For example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a developed crystal structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorocarbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. can be used.

[0180] Generally, the binder may be present in an amount of 1 to 20 wt %, preferably 1 to 15 wt %, and more preferably 1 to 10 wt %, based on the total weight of solids excluding the solvent in the negative electrode mixture slurry.

[0181] The solvent may include an organic solvent such as water or N-methyl-2-pyrrolidone (NMP), and its amount may be such that a preferred viscosity is achieved when the negative electrode active material and optionally a binder and a conductive agent are included. For example, the solvent may be included so that the solid concentration of the negative electrode active material and optionally a binder and a conductive agent is 50% to 95% by weight, more preferably 70% to 90% by weight.

[0182] When a metal itself is used as the negative electrode, the negative electrode can be manufactured by physically bonding, rolling, or depositing the metal on the metal film itself or the negative electrode current collector. The deposition method can be electroplating or chemical vapor deposition.

[0183] For example, the metal bonded / rolled / deposited on the metal film itself or the negative electrode current collector may include one metal selected from lithium (Li), nickel (Ni), tin (Sn), copper (Cu) and indium (In) or an alloy of two thereof.

[0184] (3) Diaphragm

[0185] In addition, as a separator, a conventional porous polymer film commonly used as a separator can be used alone or in its laminated form, for example, a porous polymer film prepared from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer. Alternatively, a conventional porous non-woven fabric can be used, for example, a non-woven fabric formed of glass fiber or polyethylene terephthalate fiber with a high melting point, but the present invention is not limited thereto. In addition, a coated separator containing a ceramic component or a polymer material can be used to ensure heat resistance or mechanical strength, and can be selectively used in a single-layer structure or a multilayer structure.

[0186] The shape of the lithium secondary battery of the present invention is not particularly limited, but a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape may be used.

[0187] Hereinafter, the present invention will be described in detail with reference to the examples. However, the present invention can be implemented in many different forms and should not be construed as being limited to the embodiments described herein. It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope and spirit of the present disclosure, and such modifications and variations are naturally encompassed within the present invention as defined by the appended claims.

[0188] Experimental example

[0189] Example 1

[0190] (Preparation of non-aqueous electrolyte)

[0191] A non-aqueous solvent was prepared by dissolving LiPF6 to 1.2 M using an organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) = 20:70:10 volume ratio), and 0.5 g of the compound of the following formula 1-1a was introduced into 99.5 g of the non-aqueous solvent to prepare a non-aqueous electrolyte.

[0192] [Formula 1-1a]

[0193]

[0194] R is shown in formula 2-1 below.

[0195] [Formula 2-1]

[0196]

[0197] (Preparation of lithium secondary battery)

[0198] The positive electrode active material particles (LiNi 0.60 Co 0.10 Mn 0.30 O2), a conductive material (carbon black), and a binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 97.6:0.8:1.6 to prepare a positive electrode slurry (solid content: 60 wt%). The positive electrode slurry was coated on one surface of a positive electrode current collector (Al film) with a thickness of 13.5 μm, and then dried and roll-pressed to prepare a positive electrode.

[0199] The negative electrode active material (graphite:SiO = 97.5:2.5 weight ratio): conductive material (carbon black) and binder (SBR-CMC) were added to N-methyl-2-pyrrolidone (NMP) as a solvent at a weight ratio of 95.6:1.0:3.4 to prepare a negative electrode slurry (solid content: 60 weight%). The negative electrode slurry was coated on one surface of a negative electrode current collector (Cu film) with a thickness of 6 μm, and then dried and roll-pressed to prepare a negative electrode.

[0200] In a drying room, a porous polymer separator is placed between the positive electrode and the negative electrode prepared above, and the prepared non-aqueous electrolyte is injected therein to prepare a secondary battery.

[0201] Example 2

[0202] A secondary battery was prepared in the same manner as in Example 1, except that 0.5 g of the compound of the above Formula 1-1b was introduced into 99.5 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0203] [Formula 1-1b]

[0204]

[0205] R is shown in formula 2-1 below.

[0206] [Formula 2-1]

[0207]

[0208] Example 3

[0209] A secondary battery was prepared in the same manner as in Example 1, except that 0.5 g of the compound of the above Formula 1-2a was introduced into 99.5 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0210] [Formula 1-2a]

[0211]

[0212] R is shown in formula 2-1 below.

[0213] [Formula 2-1]

[0214]

[0215] Example 4

[0216] A secondary battery was prepared in the same manner as in Example 1, except that 0.5 g of the compound of the above Formula 1-1b was introduced into 99.5 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0217] [Formula 1-1b]

[0218]

[0219] R is shown in formula 2-1 below.

[0220] [Formula 2-1]

[0221]

[0222] Example 5

[0223] A secondary battery was prepared in the same manner as in Example 1, except that 0.5 g of the compound of the above Formula 1-3a was introduced into 99.5 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0224] [Formula 1-3a]

[0225]

[0226] R is shown in formula 2-1 below.

[0227] [Formula 2-1]

[0228]

[0229] Example 6

[0230] A secondary battery was prepared in the same manner as in Example 1, except that 0.5 g of the compound of the above Formula 1-3b was introduced into 99.5 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0231] [Formula 1-3b]

[0232]

[0233] R is shown in formula 2-1 below.

[0234] [Formula 2-1]

[0235]

[0236] Example 7

[0237] A secondary battery was prepared in the same manner as in Example 1, except that 0.5 g of the compound of the above Formula 1-3f was introduced into 99.5 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0238] [Formula 1-3f]

[0239]

[0240] R is shown in formula 2-1 below.

[0241] [Formula 2-1]

[0242]

[0243] Comparative Example 1

[0244] A secondary battery was prepared in the same manner as in Example 1, except that 100 g of the nonaqueous solvent prepared in Example 1 was used to prepare the nonaqueous electrolyte.

[0245] Comparative Example 2

[0246] A secondary battery was prepared in the same manner as in Example 1, except that 0.5 g of 1,3-propane sultone was introduced into 99.5 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0247] Comparative Example 3

[0248] A secondary battery was prepared in the same manner as in Example 1, except that 0.5 g of the compound of the following formula A was introduced into 99.5 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0249] [Formula A]

[0250]

[0251] R' is shown in Formula B below.

[0252] [Formula B]

[0253]

[0254] Experimental Example 1-High Temperature Cycle Characteristics Evaluation (1)

[0255] After the lithium secondary batteries prepared in Examples 1 to 7 and the secondary batteries prepared in Comparative Examples 1 to 3 were subjected to a formation process at a rate of 0.1C for 3 hours at 25°C, they 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. The charge and discharge was set to 1 cycle, and then three cycles of initial charge and discharge were performed.

[0256] Then, each of the initially charged and discharged lithium secondary batteries was charged to 4.4 V at a rate of 0.33 C under CC-CV conditions at a high temperature (45° C.), and discharged to 2.5 V at a rate of 0.33 C under CC conditions. Charging and discharging was set as 1 cycle, and 100 cycles were performed.

[0257] The capacity after the first cycle and the capacity after the 100th cycle were substituted into the following equation 1 to calculate the capacity retention rate. The results are shown in Table 2 below.

[0258] [Equation 1]

[0259] Capacity retention (%) = (discharge capacity after 100 cycles) / (discharge capacity after 1 cycle) × 100

[0260] Experimental Example 2-High Temperature Cycle Characteristics Evaluation (2)

[0261] The lithium secondary batteries prepared in Examples 1 to 7 and the secondary batteries prepared in Comparative Examples 1 to 3 were respectively charged to 4.4V at a rate of 0.33C under CC-CV conditions at 25°C, and discharged to 2.5V at a rate of 0.33C under CC conditions. The charge and discharge were set to 1 cycle, and then three cycles of initial charge and discharge were performed. Based on the discharge capacity of the third charge and discharge, the SOC (state of charge) was set to 50%. At 50% SOC (state of charge), the DC internal resistance was calculated by applying a 2.5C discharge pulse for 10 seconds to obtain a voltage drop, and the resistance value at this time was set to the initial resistance.

[0262] Then, each of the lithium secondary batteries that had undergone initial charge and discharge was charged to 4.4 V at a rate of 0.33 C under CC-CV conditions at a high temperature (45° C.), and discharged to 2.5 V at a rate of 0.33 C under CC conditions. Charging and discharging was set as one cycle, and after 100 cycles, each lithium secondary battery was transferred to a charger / discharger at room temperature (25° C.), and the DC internal resistance was calculated by the voltage drop that occurred when a 2.5 C discharge pulse was applied for 10 seconds at 50% SOC (state of charge).

[0263] The initial resistance and the resistance after the 100th cycle were substituted into the following equation 2 to calculate the high-temperature cycle resistance increase rate. The results are shown in Table 2 below.

[0264] [Equation 2]

[0265] Resistance increase rate (%) = [(resistance after 100 cycles - initial resistance) / initial resistance] × 100

[0266] [Table 1]

[0267]

[0268] As shown in Table 1, it can be understood that Examples 1 to 7 using the non-aqueous electrolyte additive of the present invention have improved capacity retention and resistance increase rates compared to Comparative Examples 1 to 3 in which the non-aqueous electrolyte additive of the present invention is not used. In the lithium secondary batteries of Examples 1 to 7 using the additive of the present invention (wherein the linking group is connected to the 3-carbon atom of propane sultone), the total length of the additive becomes longer than that of the lithium secondary battery using the additive of Comparative Example 3 (wherein the linking group is connected to the 4-carbon atom of propane sultone). Therefore, it is believed that the additive of the present invention can increase the area covered by the film, thereby obtaining excellent high temperature life performance.

[0269] Experimental Example 3-High Temperature Storage Characteristics Evaluation (1)

[0270] The lithium secondary batteries prepared in Examples 1 to 7 and the secondary batteries prepared in Comparative Examples 1 to 3 were charged to 4.4 V at a rate of 0.33 C under CC-CV conditions at 25°C, and discharged to 2.5 V at a rate of 0.33 C under CC conditions. The charge and discharge cycle was set as one cycle, and then three cycles of initial charge and discharge were performed. The discharge capacity of the third charge and discharge cycle was set as the initial discharge capacity. The batteries were then charged to 4.4 V at a rate of 0.33 C under CC-CV conditions and then stored at 60°C for 5 weeks.

[0271] Each lithium secondary battery was transferred to a room temperature (25°C) charger / discharger and then charged to 4.4 V at a rate of 0.33C under CC-CV conditions and discharged to 2.5 V at a rate of 0.33C under CC conditions. The discharge capacity after the third charge / discharge cycle and the initial capacity were substituted into the following equation 3 to calculate the high-temperature storage capacity retention rate. The results are shown in Table 2.

[0272] [Equation 3]

[0273] Capacity retention (%) = (high-temperature discharge capacity after 5 weeks of storage / initial discharge capacity) × 100

[0274] Experimental Example 4-High Temperature Storage Characteristics Evaluation (2)

[0275] The lithium secondary batteries prepared in Examples 1 to 7 and the secondary batteries prepared in Comparative Examples 1 to 3 were respectively charged to 4.4V at a rate of 0.33C under CC-CV conditions at 25°C, and discharged to 2.5V at a rate of 0.33C under CC conditions. The charge and discharge were set to 1 cycle, and then three cycles of initial charge and discharge were performed. Based on the discharge capacity of the third charge and discharge, the SOC (state of charge) was set to 50%. At 50% SOC (state of charge), the DC internal resistance was calculated by applying a 2.5C discharge pulse for 10 seconds. The resistance value at this time was set to the initial resistance. Subsequently, the batteries were charged to 4.4V at a rate of 0.33C under CC-CV conditions and then stored at 60°C for 5 weeks.

[0276] Each lithium secondary battery was transferred to a charger / discharger at room temperature (25° C.), and the DC internal resistance was calculated from the voltage drop that occurred after applying a 2.5 C discharge pulse for 10 seconds.

[0277] The initial resistance and high temperature storage resistance were substituted into the following equation 4 to calculate the high temperature storage resistance increase rate. The results are shown in Table 2 below.

[0278] [Equation 4]

[0279] Resistance increase rate (%) = {(resistance after 5 weeks of high-temperature storage - initial resistance) / initial resistance} × 100

[0280] Experimental Example 5-High Temperature Storage Characteristics Evaluation (3)

[0281] The lithium secondary batteries prepared in Examples 1 to 7 and the secondary batteries prepared in Comparative Examples 1 to 3 were charged to 4.4V at a rate of 0.33C under CC-CV conditions at 25°C, and the volume was measured using the buoyancy method at room temperature. It is set to the initial volume (0%). The battery after measuring the volume was stored at 60°C for 5 weeks, and then transferred to a charger / discharger at room temperature (25°C), charged to 4.4V at a rate of 0.33C under CC-CV conditions at 25°C, and the volume was measured using the buoyancy method. The initial volume and the high temperature storage volume were substituted into the following equation 5 to calculate the high temperature storage volume increase rate. The results are shown in Table 2 below.

[0282] [Equation 5]

[0283] Volume increase rate (%) = {(volume after 5 weeks of high temperature storage - initial volume) / initial volume} × 100

[0284] [Table 2]

[0285]

[0286] As shown in Table 2, it can be understood that the secondary batteries of Examples 1 to 7 have improved capacity retention, resistance increase rate, and volume increase rate compared to the secondary batteries of Comparative Examples 1 to 3. In the lithium secondary batteries of Examples 1 to 7 using the additive of the present invention (wherein the linking group is connected to the 3-carbon atom of propane sultone), the total length of the additive is longer than that of the lithium secondary battery of Comparative Example 3 using the additive (wherein the linking group is connected to the 4-carbon atom of propane sultone). Therefore, it is believed that the additive of the present invention can increase the area covered by the film, thereby obtaining excellent high temperature storage performance.

Claims

1. A non-aqueous electrolyte comprising a lithium salt, an organic solvent, and a compound of formula 1 as an additive: [Formula 1] in, In 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, R' is 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, R is shown in formula 2, [Formula 2] In Formula 2, Rx and Ry are each independently H or F.

2. The nonaqueous electrolyte according to claim 1, in, The compound of formula 1 is a compound of formula 1-1, [Formula 1-1] In Formula 1-1, R1 is F, R or OR', and R' is 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, and an alkynyl group having 2 to 10 carbon atoms which may be substituted with fluorine, R is shown in formula 2, [Formula 2] In Formula 2, Rx and Ry are each independently H or F.

3. The nonaqueous electrolyte according to claim 1, in, The compound of formula 1 is a compound of formula 1-2, [Formula 1-2] Wherein, in formula 1-2, X is -CH2- or -O-, R is shown in formula 2, [Formula 2] In Formula 2, Rx and Ry are each independently H or F.

4. The nonaqueous electrolyte according to claim 1, in, The compound of formula 1 is a compound of formula 1-3, [Formula 1-3] In Formula 1-3, R1 is F, R or OR', and R' is 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, and an alkynyl group having 2 to 10 carbon atoms which may be substituted with fluorine. R is shown in formula 2, [Formula 2] In Formula 2, Rx and Ry are each independently H or F.

5. The nonaqueous electrolyte according to claim 1, in, The compound of formula 1 is any one of the compounds of formulas 1-1a to 1-1f, [Formula 1-1a] [Formula 1-1b] [Formula 1-1c] [Formula 1-1d] [Formula 1-1e] [Formula 1-1f] Wherein, in Formulas 1-1a to 1-1f, R is as shown in Formula 2-1, [Formula 2-1] 6. The nonaqueous electrolyte according to claim 1, in, The compound of formula 1 is any one of the compounds of formula 1-2a to 1-2b, [Formula 1-2a] [Formula 1-2b] Wherein, in formulas 1-2a to 1-2b, R is as shown in formula 2-1, [Formula 2-1] 7. The nonaqueous electrolyte according to claim 1, in, The compound of formula 1 is any one of the compounds of formulas 1-3a to 1-3f, [Formula 1-3a] [Formula 1-3b] [Formula 1-3c] [Formula 1-3d] [Formula 1-3e] [Formula 1-3f] In Formulas 1-3a to 1-3f, R is as shown in Formula 2-1, [Formula 2-1] 8. The nonaqueous electrolyte according to claim 1, in, The compound of Formula 1 may be present in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.

9. The nonaqueous electrolyte according to claim 1, in, The lithium salt is selected from LiPF6, LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 , one or more of LiAlCl4, LiAlO2, LiSO3CH3, LiSO3CF3, LiCO2CH3, LiCO2CF3, LiAsF6, LiSbF6, LiN(SO2F)2, LiN(SO2CF2CF3)2 and LiN(SO2CF3)2.

10. The nonaqueous electrolyte according to claim 1, in, The lithium salt is included in a molar concentration of 0.5M to 4.0M.

11. The nonaqueous electrolyte according to claim 1, in, The organic solvent includes at least one selected from the group consisting of a cyclic carbonate organic solvent, a linear carbonate organic solvent, a linear ester organic solvent, and a cyclic ester organic solvent.

12. The nonaqueous electrolyte according to claim 1, It also includes at least one selected from cyclic carbonate compounds, halogenated carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds and lithium salt compounds as an additive.

13. A lithium secondary battery comprising: positive electrode; a negative electrode; and The non-aqueous electrolyte according to any one of claims 1 to 12.

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