KR20050020067A - Electrolyte for lithium secondary battery and lithium secondary battery comprising same - Google Patents

Abstract

PURPOSE: An electrolyte for a lithium secondary battery and a lithium secondary battery containing the same are provided to inhibit swelling at high temperature, thus to improve storage properties at high temperature, while maintaining other properties such as capacity, efficiency, service life at low temperature. CONSTITUTION: The electrolyte for a lithium secondary battery comprises: a cyclic ester; an organic solvent comprising nitrile solvents represent by formula 1: R-C≡N, wherein R is an aliphatic hydrocarbon having C1-10, a halogenated aliphatic hydrocarbon, an aromatic hydrocarbon having C6-10 or a halogenated aromatic hydrocarbon: and a lithium salt. The lithium secondary battery comprises: the electrolyte; a positive electrode comprising a positive electrode active material which can (de)intercalate lithium; and a negative electrode comprising a negative electrode active material which can (de)intercalate lithium.

Description

ELECTROLYTE FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY COMPRISING SAME

[Industrial use]

The present invention relates to a lithium secondary battery electrolyte and a lithium secondary battery comprising the same, and more particularly, to a lithium secondary battery electrolyte having excellent storage characteristics and swelling characteristics at a high temperature, and a lithium secondary battery comprising the same.

[Prior art]

Recently, with the development of the high-tech electronic industry, it is possible to reduce the weight and weight of electronic equipment, thereby increasing the use of portable electronic devices. As a power source for such portable electronic devices, the necessity of a battery having a high energy density has been increased, and research on lithium secondary batteries has been actively conducted. Lithium-transition metal oxide is used as a positive electrode active material of a lithium secondary battery, and carbon (crystalline or amorphous) or a carbon composite material is used as a negative electrode active material. The active material is applied to a current collector with a suitable thickness and length, or the active material itself is coated in a film shape to be wound or laminated with a separator, which is an insulator, to form an electrode group, and then placed in a can or a similar container, and then injected with an electrolyte solution. To produce a rectangular secondary battery.

The electrolyte solution contains a lithium salt and an organic solvent. As the organic solvent, a two- to five-component solvent consisting of cyclic carbonates such as ethylene carbonate and propylene carbonate and linear carbonates such as dimethyl carbonate, ethylmethyl carbonate and diethyl carbonate was used. However, the solvents have a problem of exhibiting poor swelling characteristics in which an excessive swelling phenomenon occurs at a high temperature. The swelling phenomenon refers to a phenomenon in which a central portion of a specific surface is deformed, such as a battery swelling in a specific direction, by a gas generated by decomposition of an electrolyte solution inside a battery at a high temperature. Such a swelling phenomenon is not as severe as that of a lithium ion battery in a lithium polymer battery. However, as a cathode active material, a nickel-based active material (eg, LiNiMO ₂ , M = Co, Mn, Al, P, Fe, Mg, etc.) is used. Consisting of elements) is still a problem.

In order to suppress this swelling phenomenon, a lot of attempts have recently been made for a solvent using γ-butyrolactone having a high boiling point and high dielectric constant.

In this case, the mixture is mainly used in combination with ethylene carbonate, but in this case, there is a problem of high viscosity and wettability with respect to the separator, and it is often used in combination with other low boiling point and low dielectric constant solvents. However, there are still problems in high temperature swelling (Japanese Patent Laid-Open Nos. 2000-235868, 5,079,109, 5,272,022, 5,552,243, 5,521,017, 6,117,596 and 5,851,693 and "New thin lithium-ion batteries using a liquid electrolyte with thermal stability " Jornarl of Power sources, 97-98, 677 (2001), Notio Takami et al .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a lithium secondary battery electrolyte which can suppress high temperature swelling. Another object of the present invention is to provide a lithium secondary battery comprising the electrolyte solution. It is.

In order to achieve the above object, the present invention is an organic solvent comprising a cyclic ester and a nitrile-based solvent of formula (1); And it provides a lithium secondary battery electrolyte containing a lithium salt.

[Formula 1]

(In Formula 1, R is C ₁ to C ₁₀ aliphatic hydrocarbon or halogenated aliphatic hydrocarbon or C ₆ to C ₁₀ aromatic hydrocarbon or halogenated aromatic hydrocarbon)

The invention also the electrolyte; A positive electrode including a positive electrode active material capable of intercalating and deintercalating lithium; And it provides a lithium secondary battery comprising a negative electrode active material capable of intercalating and deintercalating lithium.

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

The present invention relates to an electrolyte solution containing a nitrile-based solvent for the purpose of improving swelling characteristics and battery performance at high temperature. The electrolyte solution of the present invention contains a solvent and a lithium salt containing a cyclic ester and a nitrile-based solvent.

The nitrile solvent is a compound represented by the following Chemical Formula 1.

[Formula 1]

In Formula 1, R is C ₁ to C ₁₀ aliphatic hydrocarbon or halogenated aliphatic hydrocarbon or C ₆ to C ₁₀ aromatic hydrocarbon or halogenated aromatic hydrocarbon. The aliphatic hydrocarbon or halogenated aliphatic hydrocarbon is more preferably R is a C ₃ to C _8.

Representative examples of the nitrile-based solvents include acetonitrile, propionitrile butyronitrile, t-butyl cyanide, valeronitrile, caprylonitrile or heptyl cyanide, and heptanenitrile ( heptanenitrile), cyclopentane carbonitrile, cyclohexane carbonnitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, 2-chlorobenozonitrile , 4-chlorobenzonitrile, dichlorobenzonitrile, trichlorobenzonitrile, 2-chloro-4-fluorobezonitrile, 4-chloro-2-fluorobenzonitrile, phenylacetonitrile, 2-fluorophenyl Preference is given to at least one solvent selected from the group consisting of acetonitrile and 4-fluorophenylacetonitrile.

In the electrolyte solution of the present invention, the content of the cyclic ester is preferably 10 to 95% by volume, the content of the nitrile solvent is preferably 5 to 90% by volume, and the content of the cyclic ester is 20 to 90% by volume. The nitrile solvent is more preferably 5 to 80% by volume. When the content of the nitrile-based solvent is less than 5% by volume, there is a problem of battery swelling, and when the content of the nitrile solvent is more than 90% by volume, battery performance is deteriorated. In addition, when the content of the cyclic ester is less than 10% by volume, there is a problem that the battery performance is deteriorated, and when the content of the cyclic ester exceeds 95% by volume, there is a problem of wettability and deterioration of battery performance.

The electrolyte of the present invention may also further comprise a linear ester. In this case, the content of the linear ester is preferably greater than 0 parts by volume and less than 70 parts by volume with respect to 100 parts by volume of the total volume of the cyclic ester and the nitrile solvent. If the content of the linear ester exceeds 70 parts by volume relative to the total volume, there is a problem of battery swelling.

The cyclic ester is at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone and ε-caprolactone It includes.

The linear ester is at least one solvent selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl acetate, ethyl acetate, methyl hexanoate, methyl formate and mixtures thereof It includes.

In addition, the present invention may further include a carbonate additive having a substituent selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ) and additives such as vinylene carbonate, divinyl sulfone, ethylene sulfite, and the like. have. Further addition of such additives is preferable because it can provide a battery having excellent electrochemical properties such as high temperature swelling characteristics, capacity, lifespan, and low temperature characteristics. As such carbonate additives, ethylene carbonate derivatives of the general formula (1) are preferred, and fluoroethylene carbonate is most preferred.

[Formula 1]

(Wherein X is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ).)

The carbonate additive is included in an amount of 0.01 to 10 parts by weight, preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the total electrolyte solution. When the amount of the carbonate additive is less than 0.01 parts by weight, it is difficult to expect the effect of suppressing gas generation inside the battery. When the amount of the carbonate additive is more than 10 parts by weight, the high temperature life is not good and the problem of swelling at high temperature occurs.

The lithium salt acts as a source of lithium ions in the battery to enable operation of the basic lithium battery, for example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2 + 1} SO ₂ ), where x and y Is a natural water) and LiSO ₃ CF _{3 It} includes one or more or a mixture thereof.

The concentration of the lithium salt can be used within the range of 0.6 to 2.0M, preferably 0.7 to 1.6M range. If the concentration of the lithium salt is less than 0.6M, the conductivity of the electrolyte is lowered and the performance of the electrolyte is lowered. If the lithium salt is more than 2.0M, the viscosity of the electrolyte is increased, thereby reducing the mobility of lithium ions.

The lithium secondary battery including the electrolyte solution of the present invention includes a positive electrode and a negative electrode.

The cathode includes a cathode active material capable of reversibly intercalating and deintercalating lithium ions. Representative examples of the cathode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , or LiNi _1- Uses lithium-transition metal oxides such as _xy Co _x M _y O ₂ (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1, M is a metal such as Al, Sr, Mg, La, etc.) do.

The negative electrode includes a negative electrode active material capable of intercalating and deintercalating lithium ions, and the negative electrode active material uses crystalline or amorphous carbon or a carbon-based negative electrode active material of a carbon composite.

Applying the positive electrode and the negative electrode active material to the current collector of a thin plate with a suitable thickness and length, respectively, wound or laminated with a separator as an insulator to make an electrode group, and then put it in a can or a similar container, and then inject the electrolyte solution of the present invention A lithium secondary battery is manufactured. As the separator, a resin such as polyethylene or polypropylene may be used.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only one preferred embodiment of the present invention and the present invention is not limited to the following examples.

(Example 1)

An electrolyte solution was prepared by dissolving 1.5 M of LiBF ₄ in a mixed solvent in which ethylene carbonate, γ-butyrolactone, and valeronitrile were mixed at a volume ratio of 3: 6: 1.

A lithium secondary battery was manufactured using a positive electrode using a LiCoO ₂ positive electrode active material, a negative electrode using a graphite negative electrode active material, and the electrolyte solution. At this time, the amount of electrolyte used was 2.2 g.

(Example 2)

Was carried out in the same manner as in Example 1 except that the LiBF ₄ in a mixed solvent in a volume ratio of 1 using 1.5M dissolved electrolyte: the lactone and heptane acrylonitrile, ethylene carbonate, -butyrolactone γ- 3:06.

(Example 3)

Was carried out in the same manner as in Example 1 except that the LiBF ₄ in a solvent honhip mixed at a weight ratio of 1 using 1.5M dissolved electrolyte solution: ethylene carbonate, a lactone and a reel cap acrylonitrile γ- butynyl 3:06.

(Example 4)

Was conducted in the same manner as in Example 1, except that an electrolyte solution obtained by dissolving a 1.15M LiPF ₆ in a mixed solvent in a volume ratio of 1: ethylene carbonate, a lactone and a nitrile ballet as γ- butynyl 3:06.

(Example 5)

Was conducted in the same manner as in Example 1, except that an electrolyte solution obtained by dissolving a 1.15M LiPF ₆ in a mixed solvent in a volume ratio of 2: ethylene carbonate, a lactone and a nitrile ballet as γ- butynyl 3:05.

(Example 6)

Was conducted in the same manner as in Example 1, except that an electrolyte solution obtained by dissolving a 1.15M LiPF ₆ in a mixed solvent in a volume ratio of 2: ethylene carbonate, a lactone and a nitrile ballet as γ- butynyl 3:05.

(Example 7)

It was carried out in the same manner as in Example 1, but in a solvent mixture in a volume ratio of 2 was used to form an electrolytic solution obtained by dissolving a 1.15M LiPF _6: the acrylonitrile-ethylene carbonate, ethyl methyl carbonate and ballet 3:05.

(Example 8)

It was carried out in the same manner as in Example 1, but in a solvent mixture in a volume ratio of 1 was used to form an electrolytic solution obtained by dissolving a 1.15M LiPF _6: the acrylonitrile-ethylene carbonate, ethyl methyl carbonate and ballet 3:06.

(Example 9)

It was carried out in the same manner as in Example 1, but in a solvent mixture in a volume ratio of 2 was used to form an electrolytic solution obtained by dissolving a 1.15M LiPF _6: the acrylonitrile, ethylene carbonate, diethyl carbonate and ballet 3:05.

(Example 10)

The same procedure as in Example 1 was repeated except that an electrolyte solution containing 1.15 M of LiPF ₆ dissolved in a solvent containing ethylene carbonate, diethyl carbonate, and valeronitrile in a volume ratio of 3: 6: 1 was used.

(Example 11)

LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and LiCoO _{2 It} was carried out in the same manner as in Example 1 except for using a positive electrode active material mixed in an 8: 2 weight ratio and changing the amount of electrolyte used to 2.1g.

(Example 12)

LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and LiCoO _{2 It} was carried out in the same manner as in Example 2 except for using a positive electrode active material mixed in an 8: 2 weight ratio and changing the amount of electrolyte used to 2.1g.

(Example 13)

LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and LiCoO _{2 It} was carried out in the same manner as in Example 3 except for using a positive electrode active material mixed in an 8: 2 weight ratio and changing the amount of the electrolyte used to 2.1g.

(Example 14)

LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and LiCoO _{2 It} was carried out in the same manner as in Example 4 except for using a positive electrode active material mixed in an 8: 2 weight ratio and changing the amount of the electrolyte used to 2.1g.

(Example 15)

LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and LiCoO _{2 It} was carried out in the same manner as in Example 5 except for using a positive electrode active material mixed in an 8: 2 weight ratio and changing the amount of the electrolyte used to 2.1g.

(Example 16)

LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and LiCoO _{2 It} was carried out in the same manner as in Example 6 except for using a positive electrode active material mixed in an 8: 2 weight ratio and changing the amount of electrolyte used to 2.1g.

(Example 17)

The same procedure as in Example 11 was repeated except that an electrolyte solution in which 1.15 M of LiPF ₆ was dissolved in a solvent containing ethylene carbonate, diethyl carbonate, and valeronitrile in a volume ratio of 3: 5: 2 was used.

(Example 18)

It was carried out in the same manner as in Example 11, except in a solvent mixture of acetonitrile, ethylene carbonate, diethyl carbonate and ballet in a volume ratio of 30:55:15 was used an electrolyte solution obtained by dissolving an LiPF ₆ 1.15M.

(Example 19)

LiPF ₆ and LiBF ₄ was carried out in the same manner as in Example 1 except that the mixture was used in a 99.9: 0.1 weight ratio.

(Example 20)

LiPF ₆ and LiBF ₄ was carried out in the same manner as in Example 7, except that the mixture was used in a 99.9: 0.1 weight ratio.

(Comparative Example 1)

As in Example 1, except that an electrolyte solution in which LiPF ₆ 1.15M was dissolved in a mixed solvent of ethylene carbonate, ethylmethyl carbonate, propylene carbonate, and fluorobenzene in a volume ratio of 30: 55: 5: 10 was used. Was carried out.

(Comparative Example 2)

It carried out similarly to Example 1 except having used the electrolyte solution which melt | dissolved LiPF ₆ 1.15M in the mixed solvent which mixed ethylene carbonate, ethylmethyl carbonate, and fluorobenzene in the volume ratio of 3: 6: 1.

(Comparative Example 3)

Was conducted in the same manner as in Example 1, except that an electrolyte solution obtained by dissolving 1.5M LiBF ₄ in a mixed solvent in a volume ratio of 2: ethylene carbonate, a lactone and diethyl carbonate in butyronitrile γ- 4:04.

(Comparative Example 4)

Example 1, except that LiBF ₄ 1.5M was dissolved in a mixed solvent in which ethylene carbonate, γ-butyrolactone, fluorobenzene, and diethyl carbonate were mixed at a volume ratio of 3: 5: 1: 1. The same procedure was followed.

(Comparative Example 5)

As in Example 11, except that an electrolyte solution of LiPF ₆ 1.15M was dissolved in a mixed solvent in which ethylene carbonate, ethylmethyl carbonate, propylene carbonate, and fluorobenzene were mixed in a volume ratio of 30: 55: 5: 10. Was carried out.

(Comparative Example 6)

The same procedure as in Example 11 was repeated except that an electrolyte solution in which LiPF ₆ 1.15M was dissolved in a mixed solvent of ethylene carbonate, ethylmethyl carbonate, and fluorobenzene in a volume ratio of 3: 6: 1 was used.

(Comparative Example 7)

It was carried out in the same manner as in Example 11 except for using an electrolytic solution obtained by dissolving 1.5M LiBF ₄ in a mixed solvent in a volume ratio of 2: ethylene carbonate, a lactone and diethyl carbonate in butyronitrile γ- 4:04.

(Comparative Example 8)

Example 11, except that LiBF ₄ 1.5M was dissolved in a mixed solvent in which ethylene carbonate, γ-butyrolactone, fluorobenzene, and diethyl carbonate were mixed at a volume ratio of 3: 5: 1: 1. The same procedure was followed.

(Comparative Example 9)

As in Example 11, except that LiPF ₆ 1.3M was dissolved in a mixed solvent in which ethylene carbonate, ethylmethyl carbonate, propylene carbonate, and fluorobenzene were mixed in a volume ratio of 30: 55: 5: 15. Was carried out.

(Comparative Example 10)

It carried out similarly to Example 11 except having used the electrolyte solution which melt | dissolved LiPF ₆ 1.3M in the mixed solvent which mixed ethylene carbonate and ethylmethyl carbonate in the volume ratio of 3: 7.

After the lithium batteries of Examples 1 to 12 and Comparative Examples 1 to 8 were charged with constant current and constant voltage at 4.2 V and 20 mAh cut-off conditions at 0.5 C charge / discharge rate, they were left in an 85 hot air oven for 4 hours and then the thickness of the batteries. Was measured. The increase rate relative to the initial charge thickness is shown in Table 1 below.

Thickness increase rate (%) Example 1 1.1 Example 2 1.6 Example 3 1.1 Comparative Example 7 7.2 Comparative Example 8 6.2 Example 4 7 Example 5 6 Example 6 6 Example 7 7 Example 8 9 Example 9 1.5 Example 10 2.3 Comparative Example 5 95.1 Comparative Example 6 120 Example 11 4.9 Example 12 5.6 Example 13 5.5 Comparative Example 3 3.5 Comparative Example 4 3.8 Example 14 12.7 Example 15 10.4 Example 16 10.0 Example 19 1.1 Example 20 3.5 Example 17 20 Example 18 30 Comparative Example 9 120 Comparative Example 10 86 Comparative Example 1 30 Comparative Example 2 33

From the results shown in Table 1, it can be seen that the swelling characteristic is improved because the thickness increase rate of Examples 1 to 20 is smaller than Comparative Examples 1 to 10. In more detail, when Examples 4 to 5 and Comparative Examples 1 to 2 using ethylene carbonate and ethyl methyl carbonate were compared, the thickness increase rate of Examples 4 to 5 was significantly reduced compared to Comparative Examples 1 to 2. Able to know.

In addition, the battery of Examples 7 to 10 and the battery of Comparative Example 1 were subjected to constant current constant voltage charging at 1 C, cut-off to 4.2 V, 0.1 C (82 mAh), and constant current discharge at 1 C to cycle to 3 V cut-off conditions. The life characteristics were measured and the results are shown in FIG. 2. In FIG. 2, brown represents Comparative Example 1, purple represents Example 7, red represents Example 8, green represents Example 9, and brown represents Example 10. As shown in Figure 2, it can be seen that Examples 7 to 10 of the present invention exhibits cycle life characteristics equivalent to those of Comparative Example 1.

Electrolyte solution of the present invention can improve the storage characteristics and swelling characteristics at high temperatures compared to the conventional carbonate-based electrolyte, and can achieve the performance equivalent or more in the characteristics such as capacity, high rate, low temperature, life.

Claims (40)

Cyclic esters; And a nitrile-based solvent of Formula 1 below; And Lithium salt Electrolyte for lithium secondary battery comprising a. [Formula 1] (In Formula 1, R is C ₁ to C ₁₀ aliphatic hydrocarbon or halogenated aliphatic hydrocarbon or C ₆ to C ₁₀ aromatic hydrocarbon or halogenated aromatic hydrocarbon) The electrolyte of claim 1, wherein R is C ₃ to C ₈ aliphatic hydrocarbon or halogenated aliphatic hydrocarbon. The method of claim 1, wherein the nitrile-based solvent is acetonitrile, propionitrile, butyronitrile, t-butyl cyanide, valeronitrile, caprylonitrile or heptyl cyanide , Heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonnitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, 2- Chlorobenozonitrile, 4-chlorobenzonitrile, dichlorobenzonitrile, trichlorobenzonitrile, 2-chloro-4-fluorobezonitrile, 4-chloro-2-fluorobenzonitrile, phenylacetonitrile, 2 An electrolyte solution for at least one lithium secondary battery selected from the group consisting of -fluorophenylacetonitrile and 4-fluorophenylacetonitrile. The electrolyte of claim 1, wherein the electrolyte includes 10 to 95% by volume of the cyclic ester and 5 to 90% by volume of the nitrile solvent. The electrolyte of claim 1, wherein the organic solvent further comprises a linear ester of greater than 0 parts by volume and 70 parts by volume or less based on 100 parts by mass of the cyclic ester and the nitrile solvent. The group according to claim 1, wherein the cyclic ester is composed of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone and ε-caprolactone Electrolyte for lithium secondary battery which is at least one selected from or a mixture thereof. The group according to claim 5, wherein the linear ester is composed of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl acetate, ethyl acetate, methyl hexanoate, methyl formate, and mixtures thereof. Electrolyte for lithium secondary battery is selected from. The method of claim 1, wherein the lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , At least one selected from the group consisting of LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2 + 1} SO ₂ ) (where x and y are natural numbers) and LiSO ₃ CF ₃ Or a lithium secondary battery electrolyte mixture thereof. The method of claim 1, wherein the electrolyte further comprises a carbonate and vinylene carbonate, divinyl sulfone, ethylene sulfite additive having a substituent selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ) The electrolyte solution for lithium secondary batteries. The electrolyte of claim 9, wherein the carbonate additive is a carbonate represented by Chemical Formula 1 below. [Formula 1] Wherein X is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ). The electrolyte of claim 9, wherein the carbonate additive is fluoroethylene carbonate. The electrolyte of claim 9, wherein the carbonate additive is included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the total electrolyte. Cyclic esters; And a nitrile-based solvent of Formula 1 below; And an electrolyte containing a lithium salt; A positive electrode including a positive electrode active material capable of intercalating and deintercalating lithium; And A lithium secondary battery comprising a negative electrode active material capable of intercalating and deintercalating lithium. [Formula 1] (In Formula 1, R is C ₁ to C ₁₀ aliphatic hydrocarbon or halogenated aliphatic hydrocarbon or C ₆ to C ₁₀ aromatic hydrocarbon or halogenated aromatic hydrocarbon) The lithium secondary battery of claim 13, wherein R is C ₃ to C ₈ aliphatic hydrocarbon or halogenated aliphatic hydrocarbon. The method of claim 13, wherein the nitrile-based solvent is acetonitrile, propionitrile, butyronitrile, t-butyl cyanide, valeronitrile, caprylonitrile or heptyl cyanide , Heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonnitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, 2- Chlorobenozonitrile, 4-chlorobenzonitrile, dichlorobenzonitrile, trichlorobenzonitrile, 2-chloro-4-fluorobezonitrile, 4-chloro-2-fluorobenzonitrile, phenylacetonitrile, 2 A lithium secondary battery which is at least one solvent selected from the group consisting of -fluorophenylacetonitrile and 4-fluorophenylacetonitrile. The lithium secondary battery of claim 13, wherein the electrolyte includes 10 to 95% by volume of the cyclic ester and 5 to 90% by volume of the nitrile solvent. The lithium secondary battery of claim 13, wherein the organic solvent further comprises a linear ester of greater than 0 parts by volume and less than 70 parts by volume with respect to 100 parts by volume of the total volume of the cyclic ester and the nitrile solvent. The method of claim 13, wherein the lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , At least one selected from the group consisting of LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2 + 1} SO ₂ ) (where x and y are natural numbers) and LiSO ₃ CF ₃ Or a lithium secondary battery thereof. The method of claim 13, wherein the electrolyte further comprises a carbonate and vinylene carbonate, divinyl sulfone, ethylene sulfite additive having a substituent selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ) A lithium secondary battery. The electrolyte of claim 19, wherein the carbonate additive is a carbonate represented by Chemical Formula 1. [Formula 1] Wherein X is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ). 20. The electrolyte of claim 19, wherein the carbonate additive is fluoroethylene carbonate. The electrolyte of claim 19, wherein the carbonate additive is included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the total electrolyte. Cyclic esters; And a nitrile-based solvent of Formula 1 below; And Lithium salt containing LiBF ₄ Electrolyte for lithium secondary battery comprising a. [Formula 1] (In Formula 1, R is C ₁ to C ₁₀ aliphatic hydrocarbon or halogenated aliphatic hydrocarbon or C ₆ to C ₁₀ aromatic hydrocarbon or halogenated aromatic hydrocarbon) The electrolyte of claim 23, wherein R is C ₃ to C ₈ aliphatic hydrocarbon or halogenated aliphatic hydrocarbon. The method of claim 23, wherein the nitrile-based solvent is acetonitrile, propionitrile, butyronitrile, t-butyl cyanide, valeronitrile, caprylonitrile or heptyl cyanide , Heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonnitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, 2- Chlorobenozonitrile, 4-chlorobenzonitrile, dichlorobenzonitrile, trichlorobenzonitrile, 2-chloro-4-fluorobezonitrile, 4-chloro-2-fluorobenzonitrile, phenylacetonitrile, 2 An electrolyte solution for a lithium secondary battery, which is at least one solvent selected from the group consisting of -fluorophenylacetonitrile and 4-fluorophenylacetonitrile. The electrolyte of claim 23, wherein the electrolyte includes 10 to 95% by volume of the cyclic ester, and 5 to 90% by volume of the nitrile solvent. The electrolyte of claim 23, wherein the organic solvent further comprises a linear ester of greater than 0 parts by volume and 70 parts by volume or less with respect to 100 parts by volume of the total volume of the cyclic ester and the nitrile solvent. The method of claim 23, wherein the electrolyte further comprises a carbonate and vinylene carbonate, divinyl sulfone, ethylene sulfite additive having a substituent selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ) The electrolyte solution for lithium secondary batteries. The electrolyte of claim 28, wherein the carbonate additive is a carbonate represented by Chemical Formula 1. [Formula 1] Wherein X is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ). The electrolyte of claim 28, wherein the carbonate additive is fluoroethylene carbonate. The electrolyte of claim 28, wherein the carbonate additive is included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the total electrolyte. Cyclic esters; And a nitrile-based solvent of Formula 1 below; And a lithium salt including LiBF ₄ ; A positive electrode including a positive electrode active material capable of intercalating and deintercalating lithium; And A lithium secondary battery comprising a negative electrode active material capable of intercalating and deintercalating lithium. [Formula 1] (In Formula 1, R is C ₁ to C ₁₀ aliphatic hydrocarbon or halogenated aliphatic hydrocarbon or C ₆ to C ₁₀ aromatic hydrocarbon or halogenated aromatic hydrocarbon) 33. The rechargeable lithium battery of claim 32, wherein R is C ₃ to C ₈ aliphatic hydrocarbon or halogenated aliphatic hydrocarbon. 33. The method of claim 32, wherein the nitrile-based solvent is acetonitrile, propionitrile, butyronitrile, t-butyl cyanide, valeronitrile, caprylonitrile or heptyl cyanide , Heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonnitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, 2- Chlorobenozonitrile, 4-chlorobenzonitrile, dichlorobenzonitrile, trichlorobenzonitrile, 2-chloro-4-fluorobezonitrile, 4-chloro-2-fluorobenzonitrile, phenylacetonitrile, 2 A lithium secondary battery which is at least one solvent selected from the group consisting of -fluorophenylacetonitrile and 4-fluorophenylacetonitrile. The lithium secondary battery of claim 32, wherein the electrolyte includes 10 to 95% by volume of the cyclic ester, and 5 to 90% by volume of the nitrile solvent. 33. The lithium secondary battery of claim 32, wherein the organic solvent further comprises a linear ester of greater than 0 parts by volume and less than 70 parts by volume with respect to 100 parts by volume of the total amount of the cyclic ester and the nitrile solvent. 33. The method of claim 32, wherein the electrolyte further comprises carbonate and vinylene carbonate, divinyl sulfone, and ethylene sulfite additives having a substituent selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ). A lithium secondary battery. The lithium secondary battery of claim 32, wherein the carbonate additive is a carbonate represented by Chemical Formula 1. [Formula 1] Wherein X is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ). 33. The rechargeable lithium battery of claim 32, wherein the carbonate additive is fluoroethylene carbonate. The lithium secondary battery of claim 32, wherein the carbonate additive is included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the total electrolyte.