Non-aqueous electrolyte solution for lithium secondary battery and lithium ion secondary battery containing the same

Abstract

The present invention provides a non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery including the same. Specifically, the non-aqueous electrolyte solution for a lithium secondary battery includes a lithium salt, an organic solvent, and a compound represented by Chemical Formula 1, thereby forming a robust solid electrolyte interface (SEI), thereby improving battery performance.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Korean Patent Application Nos. 10-2020-0149269, filed on November 10, 2020, and 10-2021-0152275, filed on November 8, 2021, the disclosures of which are incorporated herein by reference. Technical Field

[0004] The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery and a lithium ion secondary battery comprising the same. The non-aqueous electrolyte solution includes an additive capable of forming a robust solid electrolyte interface (SEI). Background Art

[0005] As the information society develops, personal IT devices and computer networks also develop, and with this, society's dependence on electrical energy increases, there is a need to develop technologies for efficiently storing and utilizing electrical energy.

[0006] Since secondary batteries can be miniaturized to fit personal IT devices and can be applied to electric vehicles and power storage devices, interest in secondary batteries as the most suitable technology for various applications has emerged. Among these secondary batteries, lithium-ion batteries (LIBs), as battery systems with high energy density, have attracted much attention and are currently used in various devices.

[0007] Lithium-ion batteries are generally composed of a positive electrode including a positive electrode active material formed of a transition metal oxide containing lithium, a negative electrode including a negative electrode active material capable of storing lithium ions, an electrolyte solution as a medium for transferring lithium ions, and a separator.

[0008] Lithium, graphite, and silicon-based anodes are representative active materials currently used in commercial lithium-ion batteries, where they are tested by 0.2 V and 0.5 V (vs. (Li / Li)) at 0. + )) exhibits charge and discharge capacity through electrochemical oxidation / reduction reactions below ). However, since the operating voltage range of lithium, graphite, and silicon-based anodes is lower than the electrochemical stability window of organic electrolytes, organic electrolytes become electrochemically unstable within these operating voltage ranges. Therefore, before the reductive decomposition of the electrolyte, a passivation layer, i.e., a solid electrolyte interface (SEI), which is a reductive decomposition product of the electrolyte, forms on the surface of the electrode.

[0009] SEI is a passivation layer with high lithium ion conductivity but low electron conductivity, where it not only inhibits additional reductive decomposition of the electrolyte but also has properties that enable lithium ion batteries to operate because it has properties that allow the transport of lithium ions but inhibit the transport of electrons.

[0010] However, when exposed to high temperatures for a long time, the SEI is damaged and loses its passivation ability. In this case, while the additional electrolyte decomposes, the lithium and electrons in the battery are consumed, thereby causing degradation of the electrochemical performance of the battery, or the internal temperature of the battery increases, causing thermal runaway.

[0011] Therefore, there is a need to develop novel electrolyte compositions that can form robust passivation layers on the surfaces of negative and positive electrodes. Summary of the Invention

[0012] Technical issues

[0013] One aspect of the present invention provides a non-aqueous electrolyte solution for a lithium secondary battery, which includes an additive capable of forming a robust passivation film on the surfaces of a positive electrode and a negative electrode.

[0014] Another aspect of the present invention provides a lithium secondary battery including the non-aqueous electrolyte solution for a lithium secondary battery.

[0015] Technical Solution

[0016] According to one aspect of the present invention, a non-aqueous electrolyte solution for a lithium secondary battery is provided, the non-aqueous electrolyte solution comprising: a lithium salt, an organic solvent, and a compound represented by Formula 1.

[0017] [Formula 1]

[0018]

[0019] In formula 1,

[0020] R is an alkylene group having 1 to 4 carbon atoms; and

[0021] R1 is an alkyl group having 1 to 5 carbon atoms substituted with at least one fluorine.

[0022] According to another aspect of the present invention, a lithium secondary battery is provided, comprising: a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; a separator disposed between the negative electrode and the positive electrode; and the non-aqueous electrolyte solution for a lithium secondary battery of the present invention.

[0023] Beneficial effects

[0024] Since the non-aqueous electrolyte solution for a lithium secondary battery of the present invention includes the compound represented by Formula 1 as an additive, and the compound represented by Formula 1 includes at least one nitrogen element and at least one fluorine element in its molecular structure, a stable passivation film can be formed on the surface of the positive electrode or the negative electrode. Therefore, a lithium secondary battery with improved high-temperature storage stability and high-temperature capacity characteristics can be achieved. DETAILED DESCRIPTION

[0025] First, before describing the present invention, it will be understood that the words or terms used in the specification and claims should not be interpreted as having the meanings defined in commonly used dictionaries. It will be further understood that based on the inventors' ability to appropriately define the meanings of words or terms to best explain the principles of the present invention, words or terms should be interpreted as having a meaning consistent with their meanings in the context of the relevant art and the technical concept of the present invention.

[0026] The terms used in this specification are only used to describe exemplary embodiments and are not intended to limit the present invention. Unless otherwise indicated, terms in the singular may include plural forms.

[0027] It will be further understood that the terms “include,” “comprises,” or “has” in this specification specify the presence of stated features, quantities, steps, elements, or a combination thereof, but do not preclude the presence or addition of one or more other features, quantities, steps, elements, or a combination thereof.

[0028] In this specification, unless otherwise specifically stated, the expression "%" means % by weight.

[0029] Before describing the present invention, the expressions "a" and "b" in the description of "a to b carbon atoms" in the specification each represent the number of carbon atoms included in a specific functional group. That is, the functional group can include "a" to "b" carbon atoms.

[0030] In addition, unless otherwise defined in the specification, the expression "substituted" means that at least one hydrogen bonded to carbon is substituted with an element other than hydrogen, such as an alkyl group having 1 to 5 carbon atoms or a fluorine element.

[0031] Hereinafter, the present invention will be described in more detail.

[0032] Recently, with the expansion of the lithium-ion battery market, there is a need to develop a technology that can ensure the performance and stability of the battery at a temperature range higher than the typical high temperature environment (45°C to 60°C). For example, with respect to the solid electrolyte interface (SEI) as a passivation film, the passivation ability is maintained at 60°C, but it is disadvantageous because it loses its passivation ability because it thermally decomposes itself at high temperatures above 85°C or is damaged by materials formed by thermal decomposition of lithium salts. If the SEI deteriorates, a (recovery) film is formed, and additional reduction decomposition of the electrolyte occurs on the exposed surface of the electrode by receiving lithium and electrons from the electrode. This recovery process of the SEI continues until the lithium and electrons in the electrode are completely consumed. As described above, if the damage and recovery of the SEI at high temperature are repeated continuously, the electrochemical performance of the battery is reduced because the thickness of the film gradually increases to cause an increase in the polarization of the battery and severe deterioration of the charge and discharge capacity.

[0033] To improve this problem, the present invention aims to provide a non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery comprising the same, wherein the non-aqueous electrolyte solution includes an additive capable of forming a stable film containing nitrogen and / or fluorine on the surfaces of the positive electrode and the negative electrode.

[0034] Non-aqueous electrolyte solutions for lithium secondary batteries

[0035] The present invention provides a non-aqueous electrolyte solution for a lithium secondary battery, which includes a lithium salt, an organic solvent, and a compound represented by the following Formula 1.

[0036] [Formula 1]

[0037]

[0038] In formula 1,

[0039] R is an alkylene group having 1 to 4 carbon atoms; and

[0040] R1 is an alkyl group having 1 to 5 carbon atoms substituted with at least one fluorine.

[0041] (1) Lithium salt

[0042] As the lithium salt, any lithium salt generally used in an electrolyte solution for a lithium secondary battery can be used without limitation, and for example, the lithium salt may include Li + and may include as an anion at least one selected from the group consisting of: 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 - .

[0043] 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, LiAlO4, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), LiBETI (lithium bis(perfluoroethanesulfonyl)imide, LiN(SO2CF2CF3)2) and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, LiN(SO2CF3)2) or a mixture of two or more thereof. In addition to these, lithium salts commonly used in electrolyte solutions for lithium secondary batteries can be used without limitation.

[0044] The lithium salt may be appropriately changed within a generally available range, but may be included in the electrolyte solution at a concentration of 0.8 M to 4.0 M, for example, 1.0 M to 3.0 M, to obtain the best effect of forming a film for preventing corrosion of the electrode surface.

[0045] If the concentration of the lithium salt is less than 0.8 M, the effect of improving the cycle characteristics during low-temperature output and high-temperature storage is not significant due to the reduced mobility of lithium ions, and if the concentration of the lithium salt is greater than 4.0 M, the non-aqueous electrolyte solution impregnation ability may be reduced due to the excessive increase in the viscosity of the non-aqueous electrolyte solution, and the film-forming effect may be reduced.

[0046] (2) Organic solvents

[0047] Various organic solvents commonly used in lithium electrolytes can be used as the organic solvent without limitation. For example, the organic solvent can include a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, or a mixed organic solvent thereof.

[0048] The cyclic carbonate organic solvent is an organic solvent that dissociates the lithium salt in the electrolyte well due to its high dielectric constant as a highly viscous organic solvent, wherein a specific example of the cyclic carbonate organic solvent may be 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 wherein the cyclic carbonate organic solvent may include at least one selected from ethylene carbonate and propylene carbonate (PC).

[0049] Moreover, the linear carbonate organic solvent is an organic solvent with low viscosity and low dielectric constant, wherein a typical example of the linear carbonate organic solvent can be at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate, and the linear carbonate organic solvent can specifically include ethyl methyl carbonate (EMC).

[0050] The cyclic carbonate organic solvent and the linear carbonate organic solvent may be included in a volume ratio of 1:9 to 5:5, for example, 2:8 to 3:7.

[0051] In addition, in order to prepare an electrolyte solution with high ionic conductivity, in addition to cyclic carbonate organic solvents and / or linear carbonate organic solvents, the organic solvent may also include linear ester organic solvents and / or cyclic ester organic solvents having a low melting point and high stability at high temperatures.

[0052] As a representative example, the linear ester-based organic solvent may 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.

[0053] 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.

[0054] (3) First additive

[0055] Furthermore, the non-aqueous electrolyte solution for a lithium secondary battery of the present invention may include a compound represented by the following Formula 1 as a first additive.

[0056] [Formula 1]

[0057]

[0058] In formula 1,

[0059] R is an alkylene group having 1 to 4 carbon atoms; and

[0060] R1 is an alkyl group having 1 to 5 carbon atoms substituted with at least one fluorine.

[0061] Specifically, in Formula 1, R may be an alkylene group having 2 to 4 carbon atoms, and R1 may be an alkyl group having 1 to 4 carbon atoms substituted with at least one fluorine group.

[0062] In addition, in Formula 1, R1 may be an alkyl group having 1 to 3 carbon atoms substituted with at least one fluorine group.

[0063] Specifically, the compound represented by Formula 1 may be a compound represented by the following Formula 1a.

[0064] [Formula 1a]

[0065]

[0066] The compound represented by Formula 1 is a compound containing at least one nitrogen element and fluorine element in a single molecular structure, wherein it can form a passivation film based on nitrogen (N) atoms and fluorine atoms on the surface of the positive and negative electrodes while electrochemically reducing and decomposing. The film based on nitrogen (N) atoms and fluorine atoms has the characteristics of not being easily decomposed and maintained when the battery is exposed to high temperature. Therefore, if a non-aqueous electrolyte solution of the present invention including a compound represented by Formula 1 as an additive is used, a more stable passivation film can be formed on the surface of the positive and negative electrodes. Therefore, since the degradation of the passivation film caused by SEI decomposition at high temperatures can be prevented, the negative electrode reduction reaction of the additional transition metal can be controlled, and the electrodeposition of the transition metal dissolved on the negative electrode during high temperature storage can be prevented, and therefore, a lithium secondary battery with improved high temperature storage and cycle performance can be achieved.

[0067] In particular, the compound represented by Formula 1 included as an electrolyte solution additive in the present invention can form a more stable Li-containing film on the surface of the electrode by including a "fluorine-substituted alkyl group", which, as a substituent of the benzene ring, is a more excellent leaving group. In contrast, in the case where a compound not containing a fluorine component in its structure (e.g., a compound represented by Formula 3 below) is used as an electrolyte solution additive, a stable Li-containing film may not be formed. In addition, in the case where a fluorine (F)-substituted compound (e.g., a compound represented by Formula 4 below) having a relatively low desorption effect is used instead of a "fluorine-substituted alkyl group" on the benzene ring as an electrolyte solution additive, because the effect of forming a Li-containing film is relatively reduced, the effect of improving the overall performance of the lithium secondary battery may be insignificant.

[0068] [Formula 3]

[0069]

[0070] [Formula 4]

[0071]

[0072] In addition, since the compound represented by Formula 1 included as the electrolyte solution additive in the present invention contains nitrogen in its structure, SEI containing nitrogen components can be formed on the surface of the electrode. Since SEI has a higher conductivity than that formed by the compound represented by the following Formula 2 which does not contain nitrogen in its structure, SEI containing C x H y O z (x, y and z are each independently an integer from 1 to 3) has better passivation performance and thus can form a more stable film.

[0073] [Formula 2]

[0074]

[0075] The compound represented by Formula 1 may be included in an amount of 0.01 to 5 wt %, specifically 0.5 to 5 wt %, and preferably 0.5 to 3 wt %, based on the total weight of the nonaqueous electrolyte solution for a lithium secondary battery.

[0076] In the case where the amount of the compound represented by Formula 1 satisfies the above range, the dissolution of transition metals of the positive electrode active material at high temperatures can be effectively suppressed by forming a stable film on the surface of the electrode (especially the positive electrode), while minimizing disadvantages such as side reactions caused by additives, reduction in capacity and increase in resistance, and excellent high-temperature durability can be achieved by effectively removing thermal decomposition products of the lithium salt.

[0077] If the amount of the compound represented by Formula 1 is less than 0.01% by weight, thermal decomposition products of the lithium salt can be initially removed during operation. However, as the operation time increases, the removal effect may be insignificant, and since the effect of forming a film on the surface of the positive electrode is insignificant, the effect of suppressing the dissolution of the transition metal may be reduced. In addition, if the amount of the compound represented by Formula 1 is greater than 5% by weight, by-products and side reactions caused by excessive additives may occur.

[0078] (4) Other additives

[0079] In addition, if necessary, the non-aqueous electrolyte solution for lithium secondary batteries of the present invention may further include other additives in addition to the compound represented by Formula 1, so as to prevent the occurrence of negative electrode collapse due to decomposition of the non-aqueous electrolyte solution in a high power environment, or to further improve low-temperature high-speed discharge characteristics, high-temperature stability, overcharge prevention, and the effect of suppressing battery swelling at high temperatures.

[0080] Examples of other additives may be at least one selected from the group consisting of halogen-unsubstituted or halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds or phosphite compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds and lithium salt compounds.

[0081] The halogen-unsubstituted or substituted carbonate compound may be, for example, vinylene carbonate (VC), vinylethylene carbonate or fluoroethylene carbonate (FEC).

[0082] The sultone compound may be, for example, at least one compound 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.

[0083] The sulfate compound may be, for example, ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyltrimethylene sulfate (MTMS).

[0084] The phosphate or phosphite compound can be, for example, at least one compound selected from the group consisting of difluorobis(difluorooxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphate, trimethylsilylphosphite, tris(2,2,2-trifluoroethyl)phosphate and tris(trifluoroethyl)phosphite.

[0085] The borate ester / salt compound may include tetraphenylborate, lithium oxalyldifluoroborate (LiODFB), or lithium bis(oxalatoborate) (LiB(C2O4)2; LiBOB).

[0086] The nitrile compound may be, for example, at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, octanonitrile, heptonitrile, cyclopentanenitrile, cyclohexanenitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, benzyl cyanide, 2-fluorophenyl cyanide and 4-fluorophenyl cyanide.

[0087] The benzene compound may be fluorobenzene, the amine compound may be triethanolamine or ethylenediamine, and the silane compound may be tetravinylsilane.

[0088] The lithium salt compound is a compound other than the lithium salt contained in the non-aqueous electrolyte solution, wherein the lithium salt compound may include LiPO 2 F 2 or LiBF 4 .

[0089] In the case where vinylene carbonate, vinyl ethylene carbonate, or succinonitrile is included among these other additives, a more robust SEI may be formed on the surface of the negative electrode during an initial activation process of the secondary battery.

[0090] In the case of including LiBF 4 , high-temperature stability of a secondary battery can be improved by suppressing generation of gas due to decomposition of an electrolyte solution during high-temperature storage.

[0091] Two or more compounds can be mixed and used as other additives, and based on the gross weight of the non-aqueous electrolyte solution, the content of the other additives can be 0.01 wt % to 50 wt %, especially 0.05 wt % to 10 wt %, preferably 0.1 wt % to 5 wt %. If the amount of the other additives is less than 0.01 wt %, the effect of improving the low temperature output, high temperature storage characteristics and high temperature life characteristics of the battery is not significant, and if the amount of the other additives is greater than 50 wt %, side reactions may occur excessively during the charge and discharge of the battery due to excessive additives. In particular, when excessive other additives are added, the additives may not be fully decomposed at high temperatures, so that unreacted materials are formed in the electrolyte solution at room temperature, or they may exist in the form of precipitates. Therefore, side reactions that degrade the life or resistance characteristics of the secondary battery may occur.

[0092] lithium secondary batteries

[0093] Next, the lithium secondary battery of the present invention will be described.

[0094] The lithium secondary battery of the present invention includes a positive electrode, a negative electrode, a separator provided between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution. In this case, the non-aqueous electrolyte solution is the non-aqueous electrolyte solution of the present invention. Since the non-aqueous electrolyte solution has been described above, its description will be omitted, and the other components will be described below.

[0095] (1) Positive electrode

[0096] The positive electrode of the present invention may include a positive electrode active material layer including a positive electrode active material, and if necessary, the positive electrode active material layer may further include a conductive agent and / or a binder.

[0097] The positive electrode active material is a compound that can reversibly insert and deinsert lithium, wherein the positive electrode active material can specifically include a lithium composite metal oxide, wherein the lithium composite metal oxide includes lithium and at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe) and aluminum (Al), and can particularly include a high nickel (Ni) lithium composite metal oxide, wherein the Ni content is as high as 0.55 or more.

[0098] Regarding lithium composite metal oxides with high Ni content, although high-capacity batteries can be achieved, the following problems still exist: Ni 2+ Cations dissolve from the positive electrode into the electrolyte, Ni 2+The cations react with the passivation film (SEI) of the negative electrode to decompose the SEI, and thus, due to the side reaction caused by the exposure of part of the negative electrode active material to the electrolyte, the capacity and life characteristics deteriorate and the resistance increases. Therefore, with respect to lithium composite metal oxides with high Ni content, although the advantage is that a high-capacity battery can be achieved, the life characteristics of the battery may deteriorate and the resistance may increase. Moreover, for high-Ni positive electrode active materials, the acceleration of the structural collapse of the positive electrode due to high temperature exposure can enhance the dissolution of transition metals, and may be accelerated in particular when HF is present in the electrolyte.

[0099] Therefore, in order to solve this problem, the lithium secondary battery of the present invention adopts a non-aqueous electrolyte solution containing a compound represented by Formula 1 as an additive. Due to the compound additive, not only can the stability of the film on the surface of the positive electrode be improved, but also Lewis acid in the non-aqueous electrolyte solution can be removed to prevent degradation of the film. Therefore, the degradation of the high-temperature durability, high-temperature capacity and life characteristics of the lithium secondary battery can be prevented.

[0100] A typical example of lithium composite metal oxide can be Li(Ni 0.6 Mn 0.2 Co 0.2 )O2、Li(Ni 0.7 Mn 0.20 Co 0.10 )O2、Li(Ni 0.8 Mn 0.1 Co 0.1 )O2、Li[Ni 0.8 Co 0.15 Al 0.05 ]O2、Li[Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 ]O2 or Li(Ni 0.9 Mn 0.05 Co 0.05 )O2.

[0101] In addition, in addition to the above-mentioned lithium composite metal oxides, the positive electrode active material may also include lithium-manganese based oxides (such as LiMnO2, LiMn2O4, etc.), lithium-cobalt based oxides (such as LiCoO2, etc.), lithium-nickel based oxides (such as LiNiO2, etc.), lithium-nickel-manganese based oxides (such as LiNiO2, etc.), lithium-nickel-manganese based oxides (such as LiNiO2, etc.), lithium-cobalt based oxides (such as LiCo ...cobalt based oxides (such as LiCoO2, etc.), lithium-cobalt based oxides (such as LiCoO2, etc.), lithium-cobalt based oxides (such as LiCoO2, etc.), lithium-cobalt based 1-Y Mn Y O2 (where 0<Y<1), LiMn 2-Z Ni Z O4 (where 0<Z<2)), lithium-nickel-cobalt based oxides (such as LiNi 1-Y1 Co Y1O2 (where 0<Y1<1)), lithium-manganese-cobalt based oxides (such as LiCo 1-Y2 Mn Y2 O2 (where 0<Y2<1), LiMn 2-Z1 Co Z1 O4 (where 0<Z1<2)), lithium-nickel-manganese-cobalt based oxides (such as Li(Ni p Co q Mn r1 )O2 (wherein 0<p<1, 0<q<1, 0<r1<1 and p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (wherein 0<p1<2, 0<q1<2, 0<r2<2 and p1+q1+r2=2), or lithium-nickel-cobalt-transition metal (M) oxide (such as Li(Ni p2 Co q2 Mn r3 M S2 )O2 (wherein M is selected from the group consisting of aluminum (Al), iron (Fe), vanadium (V), chromium (Cr), titanium (Ti), tantalum (Ta), magnesium (Mg) and molybdenum (Mo), and p2, q2, r3 and s2 are the atomic fractions of each independent element, wherein 0<p2<1, 0<q2<1, 0<r3<1, 0<S2<1, and p2+q2+r3+S2=1).

[0102] The positive electrode active material may be present in an amount of 80 to 98 wt %, for example, 85 to 98 wt %, based on the total weight of the positive electrode active material layer. When the positive electrode active material content is within the above range, excellent capacity characteristics may be exhibited.

[0103] Next, a conductive agent is used to provide conductivity to the electrode, wherein any conductive agent may be used without particular limitation as long as it has suitable electronic conductivity without causing adverse chemical changes in the battery.

[0104] As specific examples of conductive agents, the following conductive materials can be used, for example: carbon powder, such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black or thermal black; graphite powder, such as natural graphite or artificial graphite with a well-developed crystal structure, or graphite; conductive fibers, such as carbon fibers and metal fibers; conductive powders, such as carbon fluoride powder, aluminum powder and nickel powder; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or polyphenylene derivatives.

[0105] The conductive agent may be included in an amount of 0.1 wt % to 10 wt %, for example 0.1 wt % to 5 wt %, based on the total weight of the positive electrode active material layer.

[0106] Next, the binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the current collector.

[0107] Specific examples of adhesives can be fluororesin adhesives, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber adhesives, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber or styrene-isoprene rubber; cellulose adhesives, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose or regenerated cellulose; polyol adhesives, including polyvinyl alcohol; polyolefin adhesives, including polyethylene or polypropylene; polyimide adhesives; polyester adhesives; and silane adhesives.

[0108] The binder may be included in an amount of 0.1 wt % to 15 wt %, for example 0.1 wt % to 10 wt %, based on the total weight of the positive active material layer.

[0109] The positive electrode of the present invention as described above can be prepared by a method for preparing a positive electrode known in the art. For example, the positive electrode can be prepared by a method in which a positive electrode current collector is coated with a positive electrode slurry prepared by dissolving or dispersing a positive electrode active material, a binder, and / or a conductive agent in a solvent, dried, and then rolled; or a method in which the positive electrode slurry is cast on a separate support and a film separated from the support is laminated on the positive electrode current collector.

[0110] The positive electrode current collector is not particularly limited as long as it has conductivity without causing 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 or silver, etc. can be used. In addition, the positive electrode current collector can generally have a thickness of 3 μm to 500 μm, and microscopic irregularities can be formed on the surface of the current collector to improve the adhesion of the positive electrode material. The positive electrode current collector can be used in various shapes, such as a film, a sheet, a foil, a mesh, a porous body, a foam body, a non-woven fabric body, etc.

[0111] The solvent may be a conventional solvent in the art, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone or water, and any one thereof or a mixture of two or more thereof may be used. If the positive electrode material mixture can be adjusted to have an appropriate viscosity in consideration of the coating thickness, manufacturing yield and processability of the positive electrode material mixture, the amount of the solvent used may be sufficient and is not particularly limited.

[0112] (2) Negative electrode

[0113] Next, the negative electrode will be described.

[0114] The negative electrode of the present invention includes a negative electrode active material layer containing a negative electrode active material, and if necessary, the negative electrode active material layer may further include a conductive agent and / or an adhesive.

[0115] Various negative electrode active materials used in the art can be used, for example, carbon-based negative electrode active materials, silicon-based negative electrode active materials, or mixtures thereof can be used as the negative electrode active material.

[0116] According to one embodiment, the negative electrode active material may include a carbon-based negative electrode active material, and as the carbon-based negative electrode active material, various carbon-based negative electrode active materials used in the art can be used, such as graphite-based materials, such as natural graphite, artificial graphite, and Kish graphite; pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase carbon microbeads, mesophase pitch, high-temperature calcined carbon, such as coke derived from petroleum or coal tar pitch, soft carbon, and hard carbon. The shape of the carbon-based negative electrode active material is not particularly limited, and materials of various shapes can be used, such as irregular shapes, planar shapes, sheet shapes, spherical shapes, or fiber shapes.

[0117] Preferably, the carbon-based negative electrode active material may include at least one of natural graphite and artificial graphite. More preferably, the carbon-based negative electrode active material may include natural graphite and artificial graphite. When natural graphite and artificial graphite are used together, the adhesion to the current collector can be increased to inhibit the exfoliation of the active material.

[0118] According to another embodiment, the negative electrode active material may include a carbon-based negative electrode active material and a silicon-based negative electrode active material.

[0119] Specific examples of the carbon-based negative electrode active material are the same as those described above.

[0120] The silicon-based negative electrode active material may, for example, include at least one selected from the group consisting of: metallic silicon (Si), silicon oxide (SiO x , where 0 < x < 2), silicon carbide (SiC), and Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si). The element Y may be selected from the group consisting of Mg, calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), Ti, zirconium (Zr), hafnium (Hf), (Rf), V, niobium (Nb), Ta, (Db), Cr, Mo, tungsten (W), (Sg), technetium (Tc), rhenium (Re), (Bh), Fe, lead (Pb), ruthenium (Ru), osmium (Os), (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), Al, gallium (Ga), tin (Sn), indium (In), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and combinations thereof.

[0121] Since silicon-based negative electrode active materials have higher capacity characteristics than carbon-based negative electrode active materials, better capacity characteristics can be obtained when silicon-based negative electrode active materials are further included. However, for a negative electrode including a silicon-based negative electrode active material, it contains more oxygen (O)-rich (O-rich) components in the SEI than a graphite negative electrode, and when a Lewis acid (such as HF or PF5) is present in the electrolyte solution, the SEI containing the O-rich component tends to decompose more easily. Therefore, for a negative electrode including a silicon-based negative electrode active material, it is necessary to suppress the formation of Lewis acids (such as HF and PF5) in the electrolyte solution or remove (or clear) the formed Lewis acids in order to stably maintain the SEI. Since the non-aqueous electrolyte solution of the present invention includes an electrolyte solution additive that can form a stable film on the positive electrode and the negative electrode, it can effectively suppress the decomposition of the SEI when a negative electrode including a silicon-based negative electrode active material is used.

[0122] The mixing ratio of the silicon-based negative electrode active material to the carbon-based negative electrode active material can be 3:97 to 99:1 by weight, for example, 5:95 to 15:85. When the mixing ratio of the silicon-based negative electrode active material to the carbon-based negative electrode active material satisfies the above range, since the volume expansion of the silicon-based negative electrode active material is suppressed and the capacity characteristics are improved, excellent cycle performance can be ensured.

[0123] The negative electrode active material may be present in an amount of 80 to 99 wt % based on the total weight of the negative electrode active material layer. When the amount of the negative electrode active material satisfies the above range, excellent capacity characteristics and electrochemical properties may be obtained.

[0124] Next, the conductive agent is a component for further improving the conductivity of the negative electrode active material, wherein any conductive agent can be used without particular limitation, as long as it has conductivity without causing adverse chemical changes in the battery, and the conductive agent can be the same as or different from the conductive agent used during the preparation of the positive electrode. Specifically, as the conductive agent, the following conductive materials can be used, for example: carbon powder, such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black or thermal black; graphite powder, such as natural graphite or artificial graphite with a well-developed crystal structure, or graphite; conductive fibers, such as carbon fibers and metal fibers; conductive powders, such as carbon fluoride powder, aluminum powder and nickel powder; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or polyphenylene derivatives.

[0125] The conductive agent may be added in an amount of 10 wt % or less, for example, 5 wt % or less, based on the total weight of the negative electrode active material layer.

[0126] The binder is a component that helps to bond the conductive agent, active material, and current collector. The binder can be the same as or different from the binder used during the preparation of the positive electrode. Specifically, the binder can include fluororesin binders, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose binders, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyol binders, including polyvinyl alcohol; polyolefin binders, including polyethylene or polypropylene; polyimide binders; polyester binders; and silane binders.

[0127] The binder may be added in an amount of 0.1 wt % to 10 wt % based on the total weight of the negative electrode active material layer.

[0128] The negative electrode can be prepared by a method for preparing a negative electrode known in the art. For example, the negative electrode can be prepared by a method in which a positive electrode current collector is coated with a negative electrode slurry prepared by dissolving or dispersing a negative electrode active material and an optional binder and a conductive agent in a solvent, roll-pressed, and dried; or the negative electrode slurry can be cast on a separate support and then a film separated from the support is laminated on the negative electrode current collector.

[0129] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing adverse chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium or silver, or aluminum-cadmium alloy can be used. In addition, the negative electrode current collector can generally have a thickness of 3 μm to 500 μm, and similar to the positive electrode current collector, microscopic irregularities can be formed on the surface of the current collector to improve the adhesion of the negative electrode material. The negative electrode current collector can be used in various shapes, such as a film, sheet, foil, mesh, porous body, foam body, non-woven fabric body, etc.

[0130] The solvent may be a commonly used solvent in the art and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone or water, and any one thereof or a mixture of two or more thereof may be used. If the negative electrode material mixture can be adjusted to have an appropriate viscosity in consideration of the coating thickness, manufacturing yield and processability of the negative electrode material mixture, the amount of the solvent used may be sufficient and is not particularly limited.

[0131] (3) Diaphragm

[0132] The lithium secondary battery of the present invention includes a separator between a positive electrode and a negative electrode.

[0133] The separator separates the negative electrode and the positive electrode and provides a movement path for lithium ions, wherein any separator can be used without particular limitation as long as it is commonly used as a separator in lithium secondary batteries, and in particular, a separator having high moisture retention capacity for electrolyte solution and low resistance to the transfer of electrolyte ions can be used.

[0134] Specifically, porous polymer film can be used, for example, a porous polymer film prepared by polyolefin polymer (for example, ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer), or a laminated structure with two or more layers thereof. In addition, typical porous nonwoven fabrics can be used, for example, a nonwoven fabric formed by high-melting-point glass fiber or polyethylene terephthalate fiber. In addition, a coated diaphragm including ceramic component or polymeric material can be used to ensure heat resistance or mechanical strength, and a diaphragm with a single layer or multilayer structure can be alternatively used.

[0135] The lithium secondary battery of the present invention as described above can be suitably used in portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0136] Therefore, according to another embodiment of the present invention, a battery module including the above-mentioned lithium secondary battery as a unit cell and a battery pack including the battery module are provided.

[0137] The battery module or battery pack can be used as a power source for at least one of the following medium and large devices; power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0138] The shape of the lithium secondary battery of the present invention is not particularly limited, but a cylindrical type using a can, a prismatic type, a pouch type, or a coin type may be used.

[0139] The lithium secondary battery of the present invention can be used not only in a battery cell used as a power source for small devices but also as a unit cell in medium- and large-sized battery modules including a plurality of battery cells.

[0140] Hereinafter, the present invention will be described in detail based on specific embodiments.

[0141] Example

[0142] Example 1

[0143] (Preparation of non-aqueous electrolyte solution)

[0144] After dissolving LiPF6 in a non-aqueous organic solvent in which 99.9 g of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 30:70 so that the concentration of LiPF6 was 1.0 M, the non-aqueous electrolyte solution for the lithium secondary battery of the present invention was prepared by adding 0.1 g of the compound represented by Formula 1a.

[0145] (Preparation of positive electrode)

[0146] Lithium nickel-manganese-aluminum oxide (Li(Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 )O2, carbon black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder (weight ratio of 90:5:5) were added to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a positive electrode active material slurry (solid content 48 wt%). The positive electrode active material slurry was coated on a 100 μm thick positive electrode current collector (Al film), dried, and then roll-pressed to prepare a positive electrode.

[0147] (Preparation of negative electrode)

[0148] The negative electrode active material (artificial graphite: SiO = 94.5:5.5, weight ratio), PVDF as a binder, and carbon black as a conductive agent were added to NMP as a solvent at a weight ratio of 95:2:3 to prepare a negative electrode active material slurry (solid content: 70 wt%). A 90 μm thick negative electrode current collector (Cu thin film) was coated with the negative electrode active material slurry, dried, and then roll-pressed to prepare a negative electrode.

[0149] (Preparation of Secondary Battery)

[0150] After preparing an electrode assembly by a conventional method of sequentially stacking a polyethylene porous film with the positive electrode and negative electrode prepared by the above method, the electrode assembly is placed in a pouch-type secondary battery case, and the non-aqueous electrolyte solution for lithium secondary batteries prepared above is injected therein to prepare a lithium secondary battery.

[0151] Example 2.

[0152] A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving LiPF6 in 99.5 g of a non-aqueous organic solvent so that the concentration of LiPF6 was 1.0 M, a non-aqueous electrolyte solution for a lithium secondary battery of the present invention was prepared by adding 0.5 g of the compound represented by Formula 1a.

[0153] Example 3.

[0154] A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving LiPF6 in 99 g of a non-aqueous organic solvent so that the concentration of LiPF6 was 1.0 M, a non-aqueous electrolyte solution (B-3) for a lithium secondary battery of the present invention was prepared by adding 1.0 g of a compound represented by Formula 1a.

[0155] Example 4.

[0156] A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving LiPF6 in 98.5 g of a non-aqueous organic solvent so that the concentration of LiPF6 was 1.0 M, a non-aqueous electrolyte solution for a lithium secondary battery of the present invention was prepared by adding 1.5 g of the compound represented by Formula 1a.

[0157] Example 5.

[0158] A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving LiPF6 in 98 g of a non-aqueous organic solvent so that the concentration of LiPF6 was 1.0 M, a non-aqueous electrolyte solution for a lithium secondary battery of the present invention was prepared by adding 2.0 g of the compound represented by Formula 1a.

[0159] Example 6.

[0160] A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving LiPF6 in 97 g of a non-aqueous organic solvent so that the concentration of LiPF6 was 1.0 M, a non-aqueous electrolyte solution for a lithium secondary battery of the present invention was prepared by adding 3.0 g of the compound represented by Formula 1a.

[0161] Example 7.

[0162] A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving LiPF6 in 93 g of a non-aqueous organic solvent so that the concentration of LiPF6 was 1.0 M, a non-aqueous electrolyte solution for a lithium secondary battery of the present invention was prepared by adding 7.0 g of the compound represented by Formula 1a.

[0163] Comparative Example 1.

[0164] A lithium secondary battery was prepared in the same manner as in Example 1, except that no additive was included in the non-aqueous organic solvent.

[0165] Comparative Example 2.

[0166] A lithium secondary battery was prepared in the same manner as in Example 1, except that a non-aqueous electrolyte solution was prepared by adding a compound of the following Formula 2 as an additive instead of the compound represented by Formula 1a.

[0167] [Formula 2]

[0168]

[0169] Comparative Example 3.

[0170] A lithium secondary battery was prepared in the same manner as in Example 1, except that a non-aqueous electrolyte solution was prepared by adding a compound of the following Formula 3 as an additive instead of the compound represented by Formula 1a.

[0171] [Formula 3]

[0172]

[0173] Comparative Example 4.

[0174] A lithium secondary battery was prepared in the same manner as in Example 1, except that a non-aqueous electrolyte solution was prepared by adding a compound of the following Formula 4 as an additive instead of the compound represented by Formula 1a.

[0175] [Formula 4]

[0176]

[0177] Experimental example

[0178] Experimental Example 1: Evaluation of Capacity Retention and Resistance Increase at High Temperature (45°C)

[0179] The lithium secondary batteries prepared in Examples 1 to 7 and the lithium secondary batteries prepared in Comparative Examples 1 to 4 were formed at a current of 200 mA (0.1C rate), and the discharge capacity in this case was set as the initial capacity, and the measured resistance was set as the initial resistance.

[0180] Then, after constant current / constant voltage (CC / CV) charging at 660 mA (0.33 C, 0.05 C cutoff) to 4.2 V and CC discharge at 660 mA (0.33 C) to 2.5 V were set as one cycle to perform 200 cycles at a high temperature (45° C.), the discharge capacity and resistance were measured.

[0181] After calculating the capacity retention rate by comparing the discharge capacity after 200 cycles with the initial capacity and calculating the resistance increase rate by comparing the resistance after 200 cycles with the initial resistance, the results are presented in Table 1 below.

[0182] [Table 1]

[0183]

[0184] Referring to Table 1, for the lithium secondary batteries of Examples 1 to 7 of the present invention, it is understood that the capacity retention rate and the resistance increase rate of the secondary batteries of Comparative Example 1 including a non-aqueous organic solvent containing no additive, the capacity retention rate and the resistance increase rate of the secondary batteries of Comparative Example 2 including a non-aqueous electrolyte solution containing a compound of Formula 2 as an additive, and the capacity retention rate and the resistance increase rate of the secondary batteries of Comparative Examples 3 and 4 including a non-aqueous electrolyte solution containing a compound of Formula 3 or 4 as an additive are improved even after 200 cycles at high temperatures. In this case, for the secondary battery of Comparative Example 1 including a non-aqueous organic solvent containing no additive, it is understood that the solvent (such as ethylene carbonate (EC)) is reductively decomposed, so that when the lithium ion transfer capacity is reduced, the resistance value increases compared to the resistance value of the lithium secondary batteries of Examples 1 to 7.

[0185] Experimental Example 2: Evaluation of high temperature (45°C) storage characteristics

[0186] The lithium secondary batteries prepared in Examples 1 to 7 and the lithium secondary batteries prepared in Comparative Examples 1 to 4 were each charged to 4.2 V at a rate of 0.33 C, charged at a rate of 0.05 C, and discharged to 2.5 V at a rate of 0.33 C under constant current / constant voltage conditions. The discharge capacity was set as the initial capacity, and the resistance in this case was set as the initial resistance.

[0187] Then, the residual capacity and resistance of each lithium secondary battery were measured after being charged to 4.2 V at a rate of 0.33C and a cutoff charge of 0.05C under constant current / constant voltage conditions and stored at 60°C for 10 weeks. The capacity retention rate was calculated by comparing the discharge capacity measured after storage at high temperature for 10 weeks with the initial capacity, and the resistance increase rate was calculated by comparing the resistance measured after storage at high temperature for 10 weeks with the initial resistance. The results are presented in Table 2 below.

[0188] [Table 2]

[0189]

[0190] Referring to Table 2, for the lithium secondary batteries of Examples 1 to 7 of the present invention, it is understood that the capacity retention rate and the resistance increase rate of the secondary batteries of Comparative Example 1 comprising a non-aqueous organic solvent containing no additives, the capacity retention rate and the resistance increase rate of the secondary batteries of Comparative Example 2 comprising a non-aqueous electrolyte solution containing a compound of Formula 2 as an additive, and the capacity retention rate and the resistance increase rate of the secondary batteries of Comparative Examples 3 and 4 comprising a non-aqueous electrolyte solution containing a compound of Formula 3 or 4 as an additive are improved after high temperature storage. That is, for the secondary battery of Comparative Example 1 comprising a non-aqueous organic solvent containing no additives, it is understood that the solvent (such as ethylene carbonate (EC)) is reductively decomposed, and therefore, when the lithium ion transfer capacity is reduced, the resistance value increases compared to the resistance value of the lithium secondary batteries of Examples 1 to 7.

[0191] Experimental Example 3: Evaluation of Voltage Drop Rate (%) after High-Temperature Storage

[0192] After the lithium secondary batteries prepared in Examples 1 to 7 and the lithium secondary batteries prepared in Comparative Examples 1 to 4 were each charged to 4.2 V at a rate of 0.33 C under constant current / constant voltage conditions at room temperature (25° C.) and fully charged (state of charge (SOC) 100%) to a cutoff current of 50 mA, the initial voltage (4.2 V) before high temperature storage was measured using a PNE-0506 charge / discharge device (manufacturer: PNEsolution).

[0193] Subsequently, after each lithium secondary battery was stored at a high temperature of 72° C. for 60 days, the voltage drop rate (%) was evaluated. The voltage drop rate (%) was calculated according to the following [Equation 1]. The measurement results are listed in Table 3 below.

[0194] [Equation 1]

[0195] Voltage drop rate (%) = {(voltage after 60 days - initial voltage) / initial voltage} × 100

[0196] [Table 3]

[0197]

[0198] The expression "voltage drop" refers to a phenomenon in which, when the transition metal dissolved from the positive electrode consumes electrons while being reduced on the negative electrode side, or when the film (SEI) is not properly formed on the negative electrode, the electrolyte solution increases the voltage of the negative electrode while being easily reduced and decomposed, thereby lowering the voltage of the entire battery.

[0199] Referring to Table 3, the lithium secondary batteries of Examples 1 to 6 of the present invention have a voltage drop rate (%) of about 3.57% or less after storage at 72°C for 60 days, wherein it can be understood that the voltage drop rate (%) of the secondary battery of Comparative Example 1 comprising a non-aqueous organic solvent containing no additive, the secondary battery of Comparative Example 2 comprising a non-aqueous electrolyte solution containing a compound of Formula 2 as an additive, and the secondary batteries of Comparative Examples 3 and 4 comprising a non-aqueous electrolyte solution containing a compound of Formula 3 or 4 as an additive is improved. It can be understood that due to the increase in resistance caused by the use of excessive additives, the voltage drop rate (%) of the lithium secondary battery of Example 7 after storage at 72°C for 60 days is higher than the voltage drop rate (%) of the lithium secondary batteries of Examples 1 to 6.

Claims

1. A non-aqueous electrolyte solution for a lithium secondary battery, comprising: lithium salts, organic solvents, and The compound represented by Formula 1, [Formula 1] In formula 1, R is an alkylene group having 1 to 4 carbon atoms; and R1 is an alkyl group having 1 to 5 carbon atoms substituted with at least one fluorine, The content of the compound represented by Formula 1 is 0.01 wt % to 5 wt % based on the total weight of the non-aqueous electrolyte solution for a lithium secondary battery.

2. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1, wherein In Formula 1, R is an alkylene group having 2 to 4 carbon atoms, and R1 is an alkyl group having 1 to 4 carbon atoms substituted with at least one fluorine.

3. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 2, wherein In Formula 1, R1 is an alkyl group having 1 to 3 carbon atoms substituted with at least one fluorine group.

4. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1, wherein The compound represented by Formula 1 is a compound represented by Formula 1a, [Formula 1a] 。 5. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1, wherein The compound represented by Formula 1 is present in an amount of 0.1 wt % to 5 wt % based on the total weight of the non-aqueous electrolyte solution for a lithium secondary battery.

6. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 5, wherein The compound represented by Formula 1 is present in an amount of 0.5 wt % to 5 wt % based on the total weight of the non-aqueous electrolyte solution for a lithium secondary battery.

7. The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, further comprising at least one other additive selected from the group consisting of halogen-unsubstituted or halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds or phosphite compounds, borate compounds, nitrile compounds, amine compounds, silane compounds and lithium salt compounds.

8. A lithium secondary battery comprising: a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; a separator disposed between the negative electrode and the positive electrode; and The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1.

9. The lithium secondary battery according to claim 8, wherein The positive electrode active material includes lithium and at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), and aluminum (Al).

10. The lithium secondary battery according to claim 8, wherein The negative electrode active material includes at least one selected from a carbon-based negative electrode active material and a silicon-based negative electrode active material.

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