Electrolyte additive, electrolyte for lithium secondary battery containing the same, and lithium secondary battery

Abstract

To provide an electrolyte additive, a lithium secondary battery electrolyte including the same, and a lithium secondary battery that improve the room temperature life characteristics of the lithium secondary battery while suppressing an increase in resistance during high-temperature storage.SOLUTION: An electrolyte additive according to an embodiment is represented by Chemical Formula 1. The detail regarding the Chemical Formula 1 is as described in the specification.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present description relates to an electrolyte additive, an electrolyte for a lithium secondary battery containing the same, and a lithium secondary battery. [Background technology]

[0002] Lithium secondary batteries are rechargeable and have an energy density per unit weight that is more than three times higher than conventional lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and nickel-zinc batteries, allowing for fast charging. As a result, they have been commercialized for use in laptops, mobile phones, power tools, and electric bicycles, and research and development is actively underway to further improve their energy density.

[0003] Such a lithium secondary battery is used by injecting an electrolyte into a battery cell including a positive electrode containing a positive electrode active material capable of intercalating and deintercalating lithium, and a negative electrode containing a negative electrode active material capable of intercalating and deintercalating lithium.

[0004] The electrolyte acts as a medium for transferring lithium ions between the negative electrode and the positive electrode, and is generally an organic solvent in which a lithium salt is dissolved. The electrolyte is important in determining the stability and performance of a lithium secondary battery.

[0005] The electrolyte solution is commonly prepared by adding a lithium salt such as LiPF6, LiBF4, or LiFSI to a mixed solvent of a highly dielectric cyclic carbonate such as propylene carbonate or ethylene carbonate and a linear carbonate such as diethyl carbonate, ethyl methyl carbonate, or dimethyl carbonate. As battery development in various fields becomes more active, the development of batteries that ensure stability over a wide temperature range is becoming more important. From the perspective of electrolytes, it is becoming more important to develop an optimal combination of an organic solvent and an additive that can improve life characteristics at room temperature while suppressing an increase in resistance during high-temperature storage. Summary of the Invention [Problem to be solved by the invention]

[0006] One embodiment provides an electrolyte additive that improves the room temperature life characteristics of a lithium secondary battery while suppressing an increase in resistance during high temperature storage.

[0007] Another embodiment provides an electrolyte for a lithium secondary battery comprising the additive.

[0008] Another embodiment provides a lithium secondary battery including the electrolyte solution. [Means for solving the problem]

[0009] One embodiment provides an electrolyte additive represented by the following Formula 1: [ka] In the above chemical formula 1, X is a halogen atom; L 1 ~L 3 are each a single bond, *-O-*, *-C(=O)O-*, a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenylene group having 2 to 10 carbon atoms, or a substituted or unsubstituted alkynylene group having 2 to 10 carbon atoms; A is a substituent represented by the following chemical formula 2: [ka] X 1 ~X 5 are nitrogen atoms or CR; X 1 ~X 5 at least two of which are nitrogen atoms; Each of the R's is a hydrogen atom, or two or more adjacent R's are bonded to each other to form a substituted or unsubstituted aromatic ring having 6 to 10 carbon atoms. X 1 ~X5 Three of the may be nitrogen atoms.

[0010] The A may be a substituent represented by the following chemical formula 2-1 or 2-2: [ka] . Said L 1 is a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, 2 and L 3 may all be single bonds.

[0011] The formula 1 can be represented by the following formula 1-1 or 1-2: [ka] In the above chemical formulas 1-1 and 1-2, X is a halogen atom; Said L 1 is a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms. The X may be a fluorine atom.

[0012] The formula 1 can be represented by the following formula 1-1-1 or 1-2-1: [ka] .

[0013] Another embodiment provides an electrolyte for a lithium secondary battery, comprising a non-aqueous organic solvent, a lithium salt, and the electrolyte additive according to the above embodiment.

[0014] The electrolyte additive may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the total electrolyte for lithium secondary batteries.

[0015] The non-aqueous organic solvent may include a carbonate, an ester, an ether, a ketone, an alcohol, or an aprotic solvent.

[0016] The non-aqueous organic solvent may be a carbonate solvent including ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).

[0017] The lithium salt may include one or more selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide: LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiN(C x F 2x+1 SO2)(C y F<00, where x and y are integers from 1 to 20), LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalato) borate: LiBOB), LiDFOB (lithium difluoro(oxalato) borate), and Li[PF2(C2O4)2] (lithium difluoro(bis oxalato)phosphate).

[0018] The concentration of the lithium salt may be 0.1 M to 2.0 M

[0019] Another embodiment provides a lithium secondary battery including a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material; and an electrolyte for a lithium secondary battery according to another embodiment described above.

[0020] The positive electrode active material may include a nickel-based positive electrode active material.

[0021] The positive electrode active material may include a compound represented by Li x Ni y Mn (1-y) O2 (where 0.5 ≤ x ≤ 1.8, 0 < y < 1).​

[0022] The negative electrode active material can include graphite, silicon, or a combination thereof. [Effects of the Invention]

[0023] In one embodiment, the electrolyte additive is included in the electrolyte to improve the room temperature life characteristics of the lithium secondary battery while suppressing an increase in resistance during high temperature storage. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment of the present invention. [Figure 2] 1 is a graph showing the results of evaluation of CV characteristics of a negative electrode half cell according to an evaluation example of the present invention. [Figure 3] 1 is a graph showing the results of evaluation of CV characteristics of a negative electrode half cell according to an evaluation example of the present invention. [Figure 4] 1 is a graph showing the results of evaluation of CV characteristics of a positive electrode half cell as an evaluation example of the present invention. [Figure 5] 1 is a graph showing the results of evaluation of CV characteristics of a positive electrode half cell as an evaluation example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] DETAILED DESCRIPTION OF THE INVENTION The following detailed description of the present invention is provided by way of example only and is not intended to limit the scope of the present invention, which is defined solely by the claims that follow.

[0026] Unless otherwise defined, the term "substituted" as used herein means that at least one hydrogen atom in a substituent or compound is replaced with deuterium, a halogen group, a hydroxyl group, an amino group, a substituted or unsubstituted amine group having 1 to 30 carbon atoms, a nitro group, a substituted or unsubstituted silyl group having 1 to 40 carbon atoms, an alkyl group having 1 to 30 carbon atoms, an alkylsilyl group having 1 to 10 carbon atoms, an arylsilyl group having 6 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a heterocycloalkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 2 to 30 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, a cyano group, or a combination thereof.

[0027] In one embodiment of the present invention, "substituted" means that at least one hydrogen atom in a substituent or compound is substituted with deuterium, a halogen group, an alkyl group having 1 to 30 carbon atoms, an alkylsilyl group having 1 to 10 carbon atoms, an arylsilyl group having 6 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a heterocycloalkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 2 to 30 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, or a cyano group. In another specific embodiment of the present invention, "substituted" means that at least one hydrogen atom in a substituent or compound is substituted with deuterium, a halogen group, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, or a cyano group. In another specific embodiment of the present invention, "substituted" means that at least one hydrogen atom in a substituent or compound is substituted with deuterium, a halogen group, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 18 carbon atoms, a fluoroalkyl group having 1 to 5 carbon atoms, or a cyano group. In addition, in a specific example of the present invention, "substituted" means that at least one hydrogen atom in a substituent or compound is replaced with deuterium, a cyano group, a halogen group, a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, a bipenyl group, a terphenyl group, a trifluoromethyl group, or a naphthyl group.

[0028] Also, unless otherwise defined herein, "*" means a moiety connected to the same or different atoms or chemical formulae.

[0029] Lithium secondary batteries can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used, and into cylindrical, prismatic, coin, and pouch types depending on the shape, and into bulk and thin film types depending on the size. The structure and manufacturing methods of these batteries are widely known in the art, so detailed description will be omitted.

[0030] Here, a cylindrical lithium secondary battery will be described as an example of a lithium secondary battery. Figure 1 illustrates a schematic structure of a lithium secondary battery according to an embodiment. Referring to Figure 1, a lithium secondary battery 100 according to an embodiment includes a battery cell including a positive electrode 114, a negative electrode 112 facing the positive electrode 114, a separator 113 disposed between the positive electrode 114 and the negative electrode 112, and an electrolyte (not shown) impregnating the positive electrode 114, the negative electrode 112, and the separator 113; a battery container 120 containing the battery cell; and an encapsulation member 140 sealing the battery container 120.

[0031] (Electrolyte additive) An electrolyte additive according to one embodiment will be described below.

[0032] In lithium secondary batteries, the non-aqueous electrolyte decomposes during initial charging and discharging, forming a passivating film on the surfaces of the positive and negative electrodes, which can improve high-temperature storage characteristics. However, this film is formed by the thermal decomposition of HF, which is produced by the thermal decomposition of lithium salts (such as LiPF6) commonly used in lithium-ion batteries. - and PF5 -Acids such as nitroxide, thiamin, and thiamin may cause degradation. This acid attack causes the elution of transition metal elements from the positive electrode, resulting in changes in the surface structure, increasing the electrode's surface resistance. The loss of redox center metal elements reduces the theoretical capacity, resulting in a decrease in the actual capacity. Furthermore, these eluted transition metal ions are electrodeposited on the negative electrode, which reacts in a strong reduction potential range, consuming electrons. Furthermore, the electrodeposition of these eluted transition metal ions destroys the coating, exposing the negative electrode surface and causing additional electrolyte decomposition reactions. This results in increased negative electrode resistance and an increase in irreversible capacity, resulting in a continuous decrease in cell capacity.

[0033] On the other hand, an electrolyte additive according to an embodiment can solve the above problem. Specifically, the additive according to an embodiment of the present invention is represented by the following Chemical Formula 1:

[0034] [ka] In the above chemical formula 1, X is a halogen atom; L 1 ~L 3 are each independently a single bond, *-O-*, *-C(=O)O-*, a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenylene group having 2 to 10 carbon atoms, or a substituted or unsubstituted alkynylene group having 2 to 10 carbon atoms; A is a substituent represented by the following chemical formula 2: [ka] X 1 ~X 5 are nitrogen atoms or CR; X 1 ~X 5 at least two of which are nitrogen atoms; Each of the R's is a hydrogen atom, or two or more adjacent R's are bonded to each other to form a substituted or unsubstituted aromatic ring having 6 to 10 carbon atoms.

[0035] The sulfonyl group substituted with the halogen atom (X) forms a lithium salt-based solid electrolyte interphase (SEI) on the surface of the negative or positive electrode, thereby reducing the interfacial resistance between the positive electrode and the electrolyte, accelerating lithium ion migration on the surface of the negative or positive electrode, and suppressing decomposition of the negative or positive electrode active material. In particular, as shown in the evaluation examples described below, the additive is preferentially oxidized over the solvent that forms a protective film on the surface of the positive electrode, forming a lithium salt-based SEI on the surface and passivating it.

[0036] In addition, two or more nitrogen atoms contained in the substituent represented by the chemical formula 2 provide lone electron pairs, and PF5 - By capturing and stabilizing the LiPF6 salt, the acid caused by the decomposition of the lithium salt can be removed.

[0037] On the other hand, the L 1 ~L 3 The sulfonyl group substituted with the halogen atom (X) and the substituent represented by Chemical Formula 2 are directly bonded or linked via a linking group.

[0038] Therefore, in the electrolyte additive represented by the formula 1, the sulfonyl group substituted with the halogen atom (X) and the substituent represented by the formula 2 are directly bonded or bonded to a linking group (L 1 , L 2 , L 3 , or a combination thereof), the above-mentioned problems can be solved, and the increase in resistance during high-temperature storage can be suppressed while improving the room-temperature life characteristics of the lithium secondary battery.

[0039] The electrolyte additive represented by Formula 1 will now be described in more detail.

[0040] In the sulfonyl group substituted with the halogen atom (X), the halogen atom (X) may be a fluorine atom (F), a chlorine atom (Cl), a bromine atom (Br), or an iodine atom (I). Specifically, the halogen atom (X) may be a fluorine atom (F) or a chlorine atom (Cl). For example, the halogen atom (X) may be a fluorine atom (F).

[0041] The A may be a pentagonal aromatic ring containing three nitrogen atoms or a derivative thereof. Specifically, the A may be a substituent represented by the formula 2, and the X 1 ~X 5 For example, A may be a substituent represented by the following chemical formula 2-1 or 2-2: [ka]

[0042] Said L 1 is a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, 2 and L 3 may all be single bonds. 1 may be a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms. More specifically, it may be a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms. For example, the above L 1 may be an unsubstituted alkylene group having 2 carbon atoms (*-CH2CH2-*).

[0043] The formula 1 can be represented by the following formula 1-1 or 1-2: [ka] In the above chemical formulas 1-1 and 1-2, X is a halogen atom; 1 is a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms.

[0044] Representative examples of Formula 1 are as follows: [ka] .

[0045] (electrolyte) An electrolyte for a lithium secondary battery according to another embodiment of the present invention includes a non-aqueous organic solvent, a lithium salt, and the electrolyte additive described above.

[0046] The additive may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the total electrolyte solution for lithium secondary batteries.

[0047] Specifically, the additive may be included in an amount of 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more, but may be included in an amount of 10 parts by weight or less, 5.0 parts by weight or less, 3.0 parts by weight or less, or 0.5 to 1.0 parts by weight, based on 100 parts by weight of the total electrolyte solution for lithium secondary batteries.

[0048] When the content of the additive is within the above range, an increase in resistance at high temperatures can be prevented, thereby realizing a lithium secondary battery with improved life and output characteristics.

[0049] The electrolyte for lithium secondary batteries may further include at least one other additive selected from the group consisting of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), adiponitrile (AN), succinonitrile (SN), 1,3,6-hexanetricyanide (HTCN), propene sultone (PST), propane sultone (PS), lithium tetrafluoroborate (LiBF), lithium difluorophosphate (LiPOF), and 2-fluorobipenyl (2-FBP).

[0050] By further including the other additives, the life span can be further improved, or gas generated from the positive and negative electrodes during high temperature storage can be effectively controlled.

[0051] The other additives may be included in an amount of 0.2 to 20 parts by weight, specifically 0.2 to 15 parts by weight, for example, 0.2 to 10 parts by weight, based on 100 parts by weight of the total electrolyte solution for lithium secondary batteries.

[0052] When the content of other additives is as described above, it can contribute to improving the battery performance by minimizing the increase in film resistance.

[0053] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0054] The non-aqueous organic solvent may be a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, or an aprotic solvent.

[0055] Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanolide, mevalonolactone, and caprolactone. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. The ketone solvent may be cyclohexanone, etc. The alcohol solvent may be ethyl alcohol, isopropyl alcohol, etc. The aprotic solvent may be R 1 -CN(R 1 (wherein R is a hydrocarbon group having 2 to 20 carbon atoms and having a linear, branched, or cyclic structure, and may contain a double bond, aromatic ring, or ether bond), nitriles such as dimethylformamide, amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, sulfolanes, etc. can be used.

[0056] The non-aqueous organic solvents may be used alone or in combination of two or more thereof. When two or more thereof are used in combination, the mixing ratio may be appropriately adjusted depending on the desired battery performance, as would be widely understood by those skilled in the art.

[0057] In addition, in the case of the carbonate-based solvent, it is preferable to use a mixture of cyclic carbonate and chain carbonate, and in this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of 1:9 to 9:1, the performance of the electrolyte can be excellent.

[0058] In particular, in one embodiment of the present invention, the non-aqueous organic solvent may contain the cyclic carbonate and the chain carbonate in a volume ratio of 2:8 to 5:5, and specifically, the cyclic carbonate and the chain carbonate may be contained in a volume ratio of 2:8 to 4:6.

[0059] More specifically, the cyclic carbonate and the chain carbonate may be contained in a volume ratio of 2:8 to 3:7.

[0060] For example, the non-aqueous organic solvent may be a carbonate-based solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 2:4:4.

[0061] The non-aqueous organic solvent may further include an aromatic hydrocarbon-based organic solvent in addition to the carbonate-based solvent, and the carbonate-based solvent and the aromatic hydrocarbon-based solvent may be mixed in a volume ratio of 1:1 to 30:1.

[0062] The aromatic hydrocarbon solvent may be an aromatic hydrocarbon compound represented by the following formula 4: [ka] In the above chemical formula 4, R 3 ~R 8 are the same or different and are selected from the group consisting of hydrogen, halogen, alkyl groups having 1 to 10 carbon atoms, haloalkyl groups having 1 to 10 carbon atoms, and combinations thereof.

[0063] Specific examples of the aromatic hydrocarbon solvent include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, toluene, fluorobenzene, fluoroisopropyl ether ... and combinations thereof.

[0064] The lithium salt is dissolved in a non-aqueous organic solvent and acts as a lithium ion source in the battery, enabling basic lithium secondary battery operation and promoting the movement of lithium ions between the positive electrode and the negative electrode. Representative examples of such lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI)), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiN(C x F 2x+1 SO2)(C y F 2y+1The lithium salt may be one or more selected from the group consisting of SO2) (where x and y are integers from 1 to 20), LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalato)borate (LiBOB)), LiDFOB (lithium difluoro(oxalato)borate), and Li[PF2(C2O4)2] (lithium difluoro(bisoxalato)phosphate). The lithium salt concentration is preferably in the range of 0.1M to 2.0M. Specifically, the lithium salt concentration may be 0.1M or more, 0.5M or more, 1.0M or more, or 1.15M or more; and may be 2.0M or less, 1.8M or less, 1.5M or less, or 1.3M or less. When the lithium salt concentration is within the above range, the electrolyte has appropriate conductivity and viscosity, thereby exhibiting excellent electrolyte performance and allowing lithium ions to migrate efficiently.

[0065] (lithium secondary battery) Yet another embodiment of the present invention provides a lithium secondary battery comprising: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and the aforementioned electrolyte.

[0066] The positive electrode includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0067] As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used.

[0068] Specifically, the positive electrode active material may be at least one of composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof, and may be at least one of lithium composite oxides represented by the following chemical formula 5: [Chemical formula 5] Lix M 1 y M 2 z M 3 1-y-z O 2±a X a In the above chemical formula 5, 0.5≦x≦1.8, 0≦a≦0.1, 0 <y≦1、0≦z≦1、0<y+z≦1、M 1 , M 2 and M 3 each independently comprise one or more elements selected from metals such as Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr, or La, and combinations thereof, and X comprises one or more elements selected from F, S, P, or Cl.

[0069] The positive electrode active material represented by Chemical Formula 5 includes LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi a Mn b Co c O2(a+b+c=1), LiNi a Mn b Co c Al d O2(a+b+c+d=1) and LiNi e Co f Al g It may be at least one selected from the group consisting of O2(e+f+g=1).

[0070] Of course, a composite oxide in which a portion of the metal is replaced with a metal other than the metal can also be used. The composite oxide may be a phosphate compound of the composite oxide, such as at least one selected from the group consisting of LiFePO4, LiCoPO4, and LiMnPO4. The composite oxide may also have a coating layer on its surface, or the composite oxide may be mixed with a composite oxide having a coating layer. This coating layer may contain at least one coating element compound selected from the group consisting of oxides of the coating element, hydroxides of the coating element, oxyhydroxides of the coating element, oxycarbonates of the coating element, and hydroxycarbonates of the coating element. The compounds forming these coating layers may be amorphous or crystalline. The coating element contained in the coating layer may be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The coating layer formation process may be performed using any coating method (e.g., spray coating, dipping, etc.) that does not adversely affect the physical properties of the positive electrode active material using such elements in the compound, and as this is well understood by those skilled in the art, a detailed description thereof will be omitted.

[0071] More specifically, the positive electrode active material may be a nickel-based positive electrode active material that necessarily contains nickel. In this case, in Formula 5, M 1 For example, the LiNi b Mn c Co d O2(b+c+d=1), LiNi b Mn c Co d Al e O2(b+c+d+e=1), and LiNi b Co d Al e The positive electrode active material selected from O2 (b+d+e=1) may be a high nickel (high Ni) positive electrode active material.b Mn c Co d O2 (b+c+d=1) and LiNi b Mn c Co d Al e In the case of O2 (b+c+d+e=1), the nickel content may be 60% or more (b≧0.6), or 80% or more (b≧0.8). b Co d Al e In the case of O2 (b+d+e=1), the nickel content may be 60% or more (b≧0.6), more specifically 80% or more (b≧0.8).

[0072] Meanwhile, the positive electrode active material may be a nickel-based cobalt-free (Co-free) positive electrode active material that contains nickel but does not contain cobalt. In this case, Chemical Formula 5 can be expressed as Chemical Formula 5-1 below: [Chemical formula 5-1] Li x Ni y Mn (1-y) O2 0.5≦x≦1.8, 0 <y<1であってもよい。

[0073] The content of the positive electrode active material may be 90 wt % to 98 wt % based on the total weight of the positive electrode composition.

[0074] The content of the conductive material and the binder may be 1 wt % to 5 wt % each based on the total weight of the positive electrode composition.

[0075] The conductive material is used to impart conductivity to the positive electrode, and any material can be used as long as it does not cause a chemical change in the constructed battery and is electronically conductive. Examples of such a conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber of copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and conductive materials containing mixtures of these.

[0076] The binder serves to firmly adhere the positive electrode active material particles to each other and to firmly adhere the positive electrode active material to the current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon.

[0077] The positive electrode current collector may be made of Al, but is not limited thereto.

[0078] The negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector and containing a negative electrode active material.

[0079] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped with and dedoped from lithium, or a transition metal oxide.

[0080] The material capable of reversibly intercalating / deintercalating lithium ions may be any carbon-based negative electrode active material commonly used in lithium secondary batteries, and representative examples thereof include crystalline carbon, amorphous carbon, or a combination of these. Examples of crystalline carbon include amorphous, plate-like, flake-like, spherical, or fibrous graphite, such as natural graphite or artificial graphite. Examples of amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0081] As the alloy of the lithium metal, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0082] As the substance capable of doping and undoping lithium, Si, Si-C composite, SiO x (0 < x < 2), Si-Q alloy (where Q is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element excluding Si, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and a combination thereof), Sn, SnO2, Sn-R 11 (where R 11 is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element excluding Si, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and a combination thereof), etc. can be mentioned, and at least one of these can also be used by mixing with SiO2.

[0083] The elements Q and R 11 As such, those 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, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and a combination thereof can be used.

[0084] Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, or lithium titanium oxide.

[0085] In a specific embodiment, the negative electrode active material can include graphite, silicon, or a combination thereof. More specifically, it can include at least one of graphite and Si composite.

[0086] The Si composite includes a core containing Si-based particles and an amorphous carbon coating layer. For example, the Si-based particles can include one or more of Si particles, Si-C composites, SiO x (0 < x ≦ 2) and Si alloy.

[0087] As an example, the Si composite includes a void in the central part of the core containing the Si-based particles. The radius of the central part corresponds to 30% to 50% of the radius of the negative electrode active material, and the average particle size of the Si-based particles may be 10 nm to 200 nm.

[0088] In this specification, the average particle size may be the particle size (D50) at 50% as the volume ratio in the cumulative size-distribution curve.

[0089] When the average particle size of the Si-based particles is within the above range, the volume expansion generated during charge and discharge can be suppressed, and the disconnection of the conductive path due to particle crushing during charge and discharge can be prevented.

[0090] The core containing the Si-based particles additionally contains amorphous carbon. At this time, the central part does not contain amorphous carbon, and the amorphous carbon exists only on the surface part of the negative electrode active material.

[0091] At this time, the surface part means the region from the outermost surface of the central part to the outermost surface of the negative electrode active material.

[0092] Also, the Si-based particles are substantially uniformly included in the negative electrode active material as a whole, that is, they exist at a substantially uniform concentration in the central part and the surface part.

[0093] The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or a combination thereof.

[0094] For example, the Si-C composite can include Si particles and crystalline carbon.

[0095] The Si particles may be contained in an amount of 1 to 60 wt % based on the total weight of the Si-C composite, for example, 3 to 60 wt %.

[0096] The crystalline carbon may be, for example, graphite, and specifically may be natural graphite, artificial graphite, or a combination thereof.

[0097] The crystalline carbon may have an average particle size of 5 μm to 30 μm.

[0098] When the negative electrode active material includes both graphite and a Si composite, the graphite and the Si composite may be included in the form of a mixture, and in this case, the graphite and the Si composite may be included in a weight ratio of 99:1 to 50:50.

[0099] More specifically, the graphite and the Si composite may be contained in a weight ratio of 97:3 to 80:20, or 95:5 to 80:20.

[0100] The amorphous carbon precursor may be coal-based pitch, mesophase pitch, petroleum-based pitch, coal-based oil, petroleum-based heavy oil, or a polymer resin such as a phenol resin, a furan resin, or a polyimide resin.

[0101] The content of the negative electrode active material in the negative electrode active material layer may be 95 wt % to 99 wt % based on the total weight of the negative electrode active material layer.

[0102] In one embodiment of the present invention, the negative electrode active material layer includes a binder and may optionally further include a conductive material. The content of the binder in the negative electrode active material layer may be 1 wt% to 5 wt% based on the total weight of the negative electrode active material layer. When the negative electrode active material layer further includes a conductive material, the negative electrode active material may be 90 wt% to 98 wt%, the binder 1 wt% to 5 wt%, and the conductive material 1 wt% to 5 wt% may be used.

[0103] The binder serves to firmly adhere the negative active material particles to each other and to the current collector, and may be a water-insoluble binder, a water-soluble binder, or a combination thereof.

[0104] The non-water-soluble binder may be polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0105] The water-soluble binder may be a rubber-based binder or a polymer resin binder. The rubber-based binder may be selected from styrene butadiene rubber, acrylated styrene butadiene rubber (SBR), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polytetrafluoroethylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0106] When a water-soluble binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included as a thickener. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be sodium, potassium, or lithium. The amount of the thickener used may be 0.1 to 3 parts by weight per 100 parts by weight of the negative electrode active material.

[0107] The conductive material is used to impart conductivity to the electrodes, and any electron-conductive material that does not cause a chemical change in the constructed battery can be used. Examples of such conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber of copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and conductive materials containing mixtures of these.

[0108] The negative electrode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0109] Depending on the type of lithium secondary battery, a separator may be present between the positive electrode and the negative electrode. The separator may be a porous substrate or a composite porous substrate.

[0110] The porous substrate is a substrate containing voids through which lithium ions can move. The porous substrate may be made of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof. Of course, a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0111] The composite porous substrate may include a porous substrate and a functional layer disposed on the porous substrate. The functional layer may be, for example, at least one of a heat-resistant layer and an adhesive layer, from the viewpoint of enabling additional functions to be added. For example, the heat-resistant layer may include a heat-resistant resin and, optionally, a filler.

[0112] The adhesive layer may also include an adhesive resin and, optionally, a filler.

[0113] The filler may be an organic filler or an inorganic filler.

[0114] Examples and comparative examples of the present invention will be described below. However, the following examples are merely one embodiment of the present invention, and the present invention is not limited to the following examples. [Example]

[0115] (Synthesis example: synthesis of additives) The additives were prepared according to the following published procedure: J. Org. Chem., Vol. 44, No. 22, 1979. The appropriate triazole was reacted with ethenesulfonyl fluoride (ESF) in dimethylformamide (DMF).

[0116] Synthesis Example 1: Synthesis of the compound represented by chemical formula 1-1-1 A solution of ESF (5.5 g, 0.05 mol) in 10 mL of DMF was added to a solution of benzotriazole (5.96 g, 0.05 mol) in DMF (20 mL). The reaction mixture was stirred at 45 °C for 4 hours. The DMF was removed using a rotary evaporator at 60 °C, and toluene was added to the residue. The precipitated product was filtered, washed with toluene, and dried in vacuo to obtain the compound represented by the following chemical formula 1-1-1 (2-(1H-1,2,3-benzotriazol-1-yl)ethanesulfonyl fluoride). [ka] 1H NMR (400MHz, CDCl3) 4.17 (m, 2H), 5.17 (t, 2H), 7.44 (1m, 1H), 7.60 (m, 1H), 8.10 (d, 1H); 19F NMR (376MHz, CDCl3) 57.44.

[0117] Synthesis Example 2: Synthesis of the compound represented by chemical formula 1-2-1 To a solution of triazole (4.49 g, 0.065 mol) in DMF (25 mL) was added a solution of ESF (7.72 g, 0.07 mol) in 10 mL of DMF. The reaction mixture was stirred at room temperature for 4 hours. The DMF was removed using a rotary evaporator at 60 °C, and toluene was added to the residue. The precipitated product was filtered, washed with toluene, and dried in vacuo to obtain the compound represented by the following chemical formula 1-2-1 (2-(1H-1,2,4-triazol-1-yl)ethanesulfonyl fluoride). [ka] . 1H NMR (400MHz, CDCl3) 4.01 (m, 2H), 4.73 (t, 2H), 8.01 (s, 1H), 8.19 (s, 1H); 19F NMR (376MHz, CDCl3) 57.83.

[0118] Comparative Synthesis Example 1: Synthesis of Compound Represented by Chemical Formula A The compound represented by formula 1-1-1 (4.5 g, 0.02 mol) was reacted with glacial acetic acid (30 ml) at 100°C for 48 hours. The reaction mixture was then dried in a vacuum, and acetone was added to the residue. The precipitated product was filtered, washed with anhydrous acetone, and dried in a vacuum to obtain a compound represented by formula A below. [ka]

[0119] Comparative Synthesis Example 2: Synthesis of Compound Represented by Chemical Formula B A solution of benzotriazole (5.96 g, 0.05 mol) in methyl ethyl ketone (MEK) (50 ml) was reacted with methyl vinyl sulfone (5.3 g, 0.05 mol) and potassium bicarbonate. The reaction mixture was refluxed for 24 hours, then filtered using a rotary evaporator to remove the solvent and dried in vacuo to obtain the compound represented by the following chemical formula B. [ka]

[0120] (Example: Production of Electrolyte Solution) Example 1 The electrolyte solution of Example 1 was prepared by mixing the following lithium salt, non-aqueous organic solvent, and additives. Lithium salt: LiPF6 1.15M Non-aqueous organic solvent: ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate (EC:EMC:DMC = 20:40:40 volume ratio) Additive: 0.5 parts by weight of the compound represented by chemical formula 1-1-1 (However, in the electrolyte composition, "parts by weight" refers to the relative weight of the additive to 100 parts by weight of the entire electrolyte (lithium salt + non-aqueous organic solvent) excluding the additive.) Then, as Example 1, a lithium secondary battery cell was suitably produced using the above-mentioned electrolytic solution.

[0121] Example 2 An electrolyte solution of Example 2 was prepared in the same manner as in Example 1, except that the compound represented by Formula 1-2-1 was used as the electrolyte additive instead of the compound represented by Formula 1-1-1.

[0122] In addition, a lithium secondary battery of Example 2 was fabricated in the same manner as in Example 1, except that the electrolyte solution of Example 2 was used.

[0123] Example 3 An electrolyte solution of Example 3 was prepared in the same manner as in Example 1, except that 0.2 parts by weight of the compound represented by Formula 1-1-1 was used as an electrolyte additive.

[0124] In addition, a lithium secondary battery of Example 3 was fabricated in the same manner as in Example 1, except that the electrolyte solution of Example 3 was used.

[0125] Example 4 An electrolyte solution of Example 4 was prepared in the same manner as in Example 1, except that 1.0 part by weight of the compound represented by Formula 1-1-1 was used as an electrolyte additive.

[0126] In addition, a lithium secondary battery of Example 4 was fabricated in the same manner as in Example 1, except that the electrolyte solution of Example 4 was used.

[0127] Example 5 An electrolyte solution of Example 5 was prepared in the same manner as in Example 2, except that 1.0 part by weight of the compound represented by Formula 1-2-1 was used as an electrolyte additive.

[0128] In addition, a lithium secondary battery of Example 5 was fabricated in the same manner as in Example 1, except that the electrolyte solution of Example 5 was used.

[0129] Comparative example 1 (Ref.) A lithium secondary battery was fabricated in the same manner as in Example 1, except that no additive was used.

[0130] Comparative Example 2 An electrolyte solution of Comparative Example 2 was prepared in the same manner as in Example 1, except that the compound represented by Formula A was used as the electrolyte additive instead of the compound represented by Formula 1-1-1.

[0131] In addition, a lithium secondary battery of Comparative Example 2 was fabricated in the same manner as in Example 1, except that the electrolyte solution of Comparative Example 2 was used.

[0132] Comparative Example 3 An electrolyte solution of Comparative Example 3 was prepared in the same manner as in Example 1, except that the compound represented by Formula B was used as the electrolyte additive instead of the compound represented by Formula 1-1-1.

[0133] In addition, a lithium secondary battery of Comparative Example 3 was fabricated in the same manner as in Example 1, except that the electrolyte solution of Comparative Example 3 was used.

[0134] The compositions of the electrolyte additives according to Examples 1 to 8 and Comparative Examples 1 to 3 are shown in Table 1 below.

[0135] [Table 1]

[0136] For reference, in Table 1 above, the molar concentration (M) of the lithium salt means the amount (number of moles) of the lithium salt dissolved in 1 L of the electrolyte, the volume ratio of the non-aqueous organic solvent means the volume ratio of EC:EMC:DMC, and the weight part of the additive means the relative weight of the additive to 100 parts by weight of the entire electrolyte (lithium salt + non-aqueous organic solvent) excluding the additive.

[0137] (Evaluation example: evaluation of lithium secondary batteries) Evaluation 1: Lifetime characteristics at room temperature and resistance characteristics before and after high-temperature storage (1) Room temperature life characteristics The lithium secondary batteries according to Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated for room temperature life characteristics, and the results are shown in Table 2.

[0138] Specifically, the lithium secondary battery was charged and discharged for 150 cycles under the conditions of 25°C, 0.33C charge (CC / CV, 4.3V, 0.025C cut-off) / 1.0C discharge (CC, 2.5V cut-off), and then the lifespan (capacity retention rate) was calculated using the following Equation 1. [Formula 1] Capacity maintenance rate = (capacity after 150 cycles / capacity after 1 cycle)*100

[0139] (2) Resistance characteristics before and after high-temperature storage The direct current internal resistance (DC-IR) characteristics of the lithium secondary batteries according to Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated before and after high-temperature storage. The results are shown in Table 2.

[0140] Specifically, the initial DC resistance (DC-IR) of the lithium secondary battery was measured using a ΔV / ΔI (change in voltage / change in current) value, and then the maximum energy state inside the battery was set to a fully charged state (SOC 100%). After storing the battery in this state at a high temperature (60°C) for 30 days, the DC resistance was measured and the DCIR increase rate (%) was calculated using the following Equation 2. [Formula 2] DC-IR increase rate = (DC-IR after 30 days storage at 60°C - initial DC-IR) / initial DC-IR * 100

[0141] [Table 2]

[0142] Referring to Table 2, an electrolyte additive according to one embodiment is included in the electrolyte to improve the room temperature life characteristics of the lithium secondary battery while suppressing an increase in resistance during high temperature storage.

[0143] Evaluation example 2: Circulating current characteristics For the lithium secondary batteries according to Examples 1 and 2 and Comparative Example 1, the cyclic voltammetry characteristics were evaluated for the cases where the working electrode was the negative electrode and the positive electrode, respectively, and the results are shown in FIGS. 2 and 3.

[0144] (1) Negative electrode half cell Artificial graphite having a D50 of 5 μm as a negative electrode active material, polyvinylidene fluoride as a binder, and acetylene black as a conductive material were mixed in a weight ratio of 96:2:2 and dispersed in N-methylpyrrolidone to prepare a negative electrode active material slurry.

[0145] The negative electrode active material slurry was coated on an Al foil having a thickness of 14 μm, dried at 110° C., and pressed to prepare a positive electrode.

[0146] A 10 μm thick Li foil was used as the counter electrode (cathode), and a 25 μm thick polyethylene separator was assembled using the negative electrode to prepare an electrode assembly. The electrolyte was then injected into the electrode assembly to prepare a CR2032 coin-half cell type lithium secondary battery in a conventional manner.

[0147] The lithium secondary battery was cycled 1 to 3 times at a scan rate of 0.1 mV / s while varying the applied voltage from 3 V to 0 V. The cyclic voltammetry characteristics were evaluated, and the results are shown in Figures 2 and 3.

[0148] (2) Positive electrode half cell LiNi with a D50 of 5 μm as the positive electrode active material 0.8 Mn 0.2 O2, polyvinylidene fluoride as a binder, and acetylene black as a conductive material were mixed in a weight ratio of 96:2:2, and dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0149] The positive electrode active material slurry was coated on an Al foil having a thickness of 14 μm, dried at 110° C., and then pressed to prepare a positive electrode.

[0150] A 10 μm thick Li foil was used as the counter electrode (negative electrode), and a 25 μm thick polyethylene separator was assembled using the positive electrode to prepare an electrode assembly. The electrolyte was then injected into the electrode assembly to prepare a CR2032 coin-half cell type lithium secondary battery in a conventional manner.

[0151] The lithium secondary battery was cycled 1 to 3 times at a scan rate of 0.1 mV / s while varying the applied voltage from 3 V to 4.5 V. The cyclic voltammetry characteristics were evaluated, and the results are shown in Figures 4 and 5.

[0152] 2 to 5 show that an additive according to an embodiment can form an SEI on the surface of a negative electrode or a positive electrode to passivate it.

[0153] In particular, when using a nickel-based cobalt-free (Co-free) positive electrode active material, which must contain nickel but does not contain cobalt, the additive oxidizes preferentially over the solvent that forms a protective film on the positive electrode surface, forming a lithium salt-based SEI on the surface and passivating it.

[0154] In summary, the electrolyte additive of one embodiment represented by Examples 1 to 5 is a compound in which the sulfonyl group substituted with the halogen atom (X) and the substituent represented by Formula 2 are directly bonded or bonded to a linking group (L 1 , L 2 , L 3 , or a combination thereof), which solves the above-mentioned problems and has the effect of improving the room temperature life characteristics of the lithium secondary battery while suppressing an increase in resistance during high temperature storage.

[0155] Although the preferred embodiment of the present invention has been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and it is to be understood that these modifications also fall within the scope of the present invention. [Explanation of symbols]

[0156] 100: Lithium secondary battery 112: Negative electrode 113: Separator 114: Positive electrode 120:Battery container 140: Enclosure material

Claims

1. The electrolyte additive is added in an amount of 0.1 parts by weight or more and 3 parts by weight or less based on 100 parts by weight of the total electrolyte solution for lithium secondary batteries, and is represented by the following chemical formula 1-1 or 1-2: 【Chemistry 4】 (In the above chemical formulas 1-1 and 1-2, X is a halogen atom; L １ is a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms).

2. The electrolyte additive according to claim 1 , wherein X is a fluorine atom.

3. The electrolyte additive according to claim 1, wherein the chemical formula 1 is represented by the following chemical formula 1-1-1 or 1-2-1: 【Transformation 5】 。

4. An electrolyte solution for a lithium secondary battery, comprising a non-aqueous organic solvent, a lithium salt, and the electrolyte additive according to claim 1, The electrolyte for a lithium secondary battery contains the electrolyte additive in an amount of 0.1 to 3 parts by weight based on 100 parts by weight of the total electrolyte for a lithium secondary battery.

5. 5. The electrolyte solution for a lithium secondary battery according to claim 4, wherein the non-aqueous organic solvent comprises a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, or an aprotic solvent.

6. 6. The electrolyte solution for a lithium secondary battery according to claim 5, wherein the non-aqueous organic solvent is a carbonate-based solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).

7. The lithium salt is LiPF ６ , LiBF ４ , LiSbF ６ , LiAsF ６ , Li(FSO ２ ) ２ N (lithium bis(fluorosulfonyl)imide: LiFSI), LiC ４ F ９ SO ３ , LiClO ４ , LiAlO ２ , LiAlCl ４ , LiPO ２ F ２ , LiN(C ｘ F ２ｘ＋１ SO ２ ) (C ｙ F ２ｙ＋１ SO ２ ) (wherein x and y are integers from 1 to 20), LiCl, LiI, LiB(C ２ O ４ ) ２ (lithium bis(oxalato)borate: LiBOB), LiDFOB (lithium difluoro(oxalato)borate), and Li[PF ２ (C ２ O ４ ) ２ 5. The electrolyte solution for a lithium secondary battery according to claim 4, comprising one or more selected from the group consisting of lithium difluoro(bis oxalato)phosphate.

8. 8. The electrolyte for a lithium secondary battery according to claim 7, wherein the concentration of the lithium salt is 0.1M to 2.0M.

9. a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and The electrolyte solution for a lithium secondary battery according to any one of claims 4 to 8. A lithium secondary battery comprising:

10. The lithium secondary battery according to claim 9 , wherein the positive electrode active material comprises a nickel-based positive electrode active material.

11. The positive electrode active material is Li ｘ Ni ｙ Mn （１－ｙ） O ２ 11. The lithium secondary battery according to claim 10, comprising a compound represented by the formula: (where 0.5≦x≦1.8, 0<y<1).

12. 11. The lithium secondary battery of claim 10, wherein the negative electrode active material comprises graphite, silicon, or a combination thereof.

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