KR100814843B1 - Electrolyte for lithium secondary battery, and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a lithium secondary battery electrolyte, and a lithium secondary battery comprising the same, the electrolyte is polyether modified silicone oil; Carbonates; And lithium salts.

The electrolyte solution of the present invention is excellent in thermal stability and excellent in ion conductivity of lithium ions.

Lithium Secondary Battery, Electrolyte, Silicone Oil, Polyether Modified Silicone Oil, Carbonate Modified Silicone Oil

Description

ELECTROLYTE FOR LITHIUM SECONDARY BATTERY, AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME

1 is a schematic cross-sectional view of a lithium secondary battery according to an embodiment of the present invention.

FIG. 2 is a graph showing changes in differential capacity with respect to charging voltage during first charge of a lithium secondary battery including the electrolyte solutions of Example 1 and Comparative Examples 2 and 3. FIG.

3 is a graph showing the relationship between the cycle number and discharge capacity of a lithium secondary battery including the electrolyte solutions of Examples 1, 5 and Comparative Example 2. FIG.

[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 thermal stability and ion conductivity, and a lithium secondary battery comprising the same.

[Prior art]

Conventionally, the mixture which mixed cyclic ester, such as ethylene carbonate and a propylene carbonate, linear ester, such as dimethyl carbonate and a propionic acid ether, and cyclic ether, such as tetrahydrofuran, was used as electrolyte solution for lithium secondary batteries. However, since linear esters and cyclic ethers have a low flash point, the conventional electrolyte solution containing them at a ratio of several tens of volume% has a problem of low thermal stability. Japanese Patent Laid-Open No. 1996-78053, Japanese Patent Laid-Open No. 1999-214032, and Japanese Patent Laid-Open No. 2000-581123 utilize silicone oil as a solvent to improve thermal stability and environmental harmony. The electrolyte is disclosed.

However, the silicone oils described in Japanese Patent Application Laid-Open No. 1996-78053, Japanese Patent Application Laid-Open No. 1999-214032, and Japanese Patent Application Laid-Open No. 2000-581123 have excellent thermal stability, but the electrolyte solution of a lithium secondary battery When used as, there was a problem that the ion conductivity was not sufficient.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lithium secondary battery electrolyte having excellent thermal stability and ion conductivity of lithium ions, and a lithium secondary battery comprising the same.

In order to achieve the above object, the present invention is a polyether modified silicone oil; Carbonates; And it provides a lithium secondary battery electrolyte containing a lithium salt. It is preferable that the said electrolyte solution is a nonaqueous electrolyte solution.

The polyether-modified silicone oil preferably includes a compound selected from the group consisting of compounds represented by Formulas 1 to 5 below, and combinations thereof.

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

(In Formulas 1 to 5, k has a range of 1 to 9, l has a range of 0 to 3, m has a range of 0 to 1, n has a range of 1 to 2, R is CH ₃ or C ₆ H ₅ Any one of which Z is CH ₃ or C ₂ H ₅ Is either one)

Since the lithium secondary battery electrolyte includes a polyether-modified silicone oil selected from the group consisting of the compounds of Formulas 1 to 5, and combinations thereof, thermal stability of the electrolyte is improved, and ion conductivity of lithium ions is also increased.

The lithium secondary battery electrolyte may preferably further include a carbonate modified silicone oil.

It is preferable that flash point is 120 degreeC or more, and, as for the said silicone oil, it is more preferable that it is 160 degreeC or more. When the flash point of the said silicone oil is 120 degreeC or more, the possibility that the said silicone oil will ignite at high temperature will become low, and the thermal stability of electrolyte solution can be improved.

The carbonate is preferably selected from the group consisting of cyclic carbonates, chain carbonates, and combinations thereof, and more preferably, the cyclic carbonates are fluorinated cyclic carbonates. In addition, the cyclic carbonate is preferably included in 30 to 95% by volume relative to the total volume of the electrolyte.

The lithium salt may be LiPF ₆ , LiBF ₄ , Li [N (SO ₂ C ₂ F ₆ ) ₂ ], Li [B (OCOCF ₃ ) ₄ ], Li [B (OCOC ₂ F ₅ ) ₄ ], LiPF ₆ , Li [N (SO ₂ C ₂ F ₅ ) ₂ ], and combinations thereof, are preferably selected from the group consisting of 0.5 to 2.0 mol / L based on the total concentration of the electrolyte.

The present invention also provides a positive electrode; cathode; And it provides a lithium secondary battery comprising the electrolyte solution.

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

The lithium secondary battery of the present invention includes a positive electrode, a negative electrode and an electrolyte solution, the electrolyte solution, a polyether modified silicone oil containing a compound selected from the group consisting of the compounds of Formulas 1 to 5, and combinations thereof; Carbonates and lithium salts. In Formulas 1 to 5, k has a range of 1 to 9, l has a range of 0 to 3, m has a range of 0 to 1, n has a range of 1 to 2, and R Silver CH ₃ or C ₆ H ₅ Any one of which Z is CH ₃ or C ₂ H ₅ Which is either.

The electrolyte solution is obtained by dissolving a lithium salt in a mixed solvent of polyether modified silicone oil and carbonate. The carbonate is preferably selected from the group consisting of chain carbonates, cyclic carbonates, and combinations thereof, and fluorinated cyclic carbonates may be further added.

In addition, a gel electrolyte in which the electrolyte solution is impregnated with the polymer may be used. Polymers include polyethylene oxide (PEO), polypropylene oxide (PPO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethacrylate (PMA), polymethyl methacrylate (PMMA) Polymers or polymers thereof may be used.

Polyether-modified silicone oil, as shown in the above formulas 1 to 5, in the linear polysiloxane chain (SiR ₂ -O- (SiR ₂ O-) _k -SiR ₂ ) or cyclic polysiloxane, 1 to 2 poly Ether chain [(-(CH ₂ ) _l- (CH (CH ₃ ) CH ₂ ) _m -O- (C ₂ H ₄ 0) _n -Z) or (-(CH ₂ ) _l- (CH (CH ₃ ) CH ₂ ) _m -O- (C ₂ H ₄ 0) _n- (CH ₂ CH (CH ₃ )) _m- (CH ₂ ) _l )-]. The polyether-modified silicone oil has high thermal stability because it has a linear or cyclic polysiloxane chain, and the oxygen and lithium ions constituting the ether bond in the polyether chain are solvated to exhibit high ionic conductivity.

When the polyether-modified silicone oil is added to the electrolytic solution, the flash point of the electrolytic solution is increased, the thermal stability is improved, and the ion conductivity of lithium ions is improved. Moreover, by using the electrolyte solution containing polyether modified silicone oil as an electrolyte of a lithium secondary battery, the lithium secondary battery which is excellent in stability at high temperature and can be charged and discharged with high efficiency can be obtained.

It is preferable that the said electrolyte solution for lithium secondary batteries contains carbonate modified silicone oil further. When the electrolyte for the lithium secondary battery further includes a carbonate-modified silicone oil, the thermal stability of the electrolyte is further improved by interaction with the polyether-modified silicone oil, and the ion conductivity of lithium ions is further improved. As said carbonate modified silicone oil, X-22-1891-1 or X-22-1891-3 by Shinwol Chemical Co., Ltd. can be used preferably.

Moreover, it is preferable that a flash point is 120 degreeC or more, and, as for the said polyether modified silicone oil and carbonate modified silicone oil, it is more preferable that it is 160 degreeC or more. When a flash point is 120 degreeC or more, the flash point of electrolyte solution can be raised and the thermal stability of electrolyte solution can be improved.

In Chemical Formulas 1 to 5, k has a range of 1 to 9, l has a range of 0 to 3, m has a range of 0 to 1, n has a range of 1 to 2, R is CH ₃ or C ₆ H ₅ Any one of which Z is CH ₃ or C ₂ H ₅ Which is either.

When K exceeds 9, the thermal stability is improved, but the viscosity becomes high, so that lithium ions are not easily dissolved, and thus the ion conductivity is lowered. When K is less than 1, since silicone oil decomposes well, it is not preferable.

When l exceeds 3, since a viscosity becomes high and ionic conductivity falls, it is unpreferable.

When m exceeds 1, since a polyether chain becomes long and a viscosity becomes high and ionic conductivity falls, it is unpreferable.

If n is less than 1, the polyether chain connected to the polysiloxane chain is almost eliminated, and compatibility with the cyclic carbonate is lowered, which is not preferable. If n is greater than 2, the polyether chain is long and the viscosity becomes high, and the ion It is not preferable because conductivity is lowered.

When R is either CH ₃ or C ₆ H ₅ , and Z is either CH ₃ or C ₂ H ₅ , the synthesis of the polyether-modified silicone oil becomes easy.

The cyclic carbonate preferably includes a compound selected from the group consisting of ethylene carbonate, butylene carbonate, propylene carbonate, γ-butyrolactone, and combinations thereof. Since the cyclic carbonate dissolves lithium ions well, the ionic conductivity of the electrolyte solution itself can be increased.

The chain carbonate preferably contains a compound selected from the group consisting of dimethyl carbonate, methyl carbonate and diethyl carbonate, and a combination thereof. Since the chain carbonate has a low viscosity, it is possible to increase the ion conductivity by lowering the viscosity of the electrolyte solution itself. However, since the said chain carbonate has a low flash point, it is preferable not to add it excessively because it will lower the flash point of electrolyte solution.

As the fluorinated cyclic carbonate, fluorinated ethylene carbonate or monofluoroethylene carbonate is preferably used. By adding a fluorinated cyclic carbonate, the nonflammability of electrolyte solution can be improved and the safety of a lithium secondary battery can be improved. Moreover, the film | membrane by fluorinated cyclic carbonate is formed in the surface of a negative electrode, decomposition | disassembly of electrolyte solution is suppressed by this film | membrane, and the cycling characteristics of a lithium secondary battery can be improved. In addition, as decomposition of the electrolyte is suppressed, the amount of decomposition gas generated is also reduced.

Lithium salts include LiPF ₆ , LiBF ₄ , Li [N (SO ₂ C ₂ F ₆ ) ₂ ], Li [B (OCOCF ₃ ) ₄ ], Li [B (OCOC ₂ F ₅ ) ₄ ], LiPF ₆ , It is preferably selected from the group consisting of Li [N (SO ₂ C ₂ F ₅ ) ₂ ], and combinations thereof. In the present invention, since the Si-O bond of the polyether-modified silicone oil may be cleaved due to decomposition of LiPF ₆ , it is more preferable to use Li [N (SO ₂ C ₂ F ₅ ) ₂ ] as the lithium salt.

The concentration of the lithium salt is preferably 0.5 mol / L to 2.0 mol / L with respect to the total concentration in the nonaqueous electrolyte. By containing the said lithium salt in electrolyte solution, the ionic conductivity of electrolyte solution itself can be raised.

The content of the polyether-modified silicone oil is preferably in the range of 1% by volume to 70% by volume, and more preferably in the range of 5% by volume to 50% by volume with respect to the entire electrolyte solution. If the content of each silicone oil is less than 1% by volume, it is not preferable because the flash point of the electrolyte cannot be increased. If the content is more than 70% by volume, the viscosity of the electrolyte is high and ionic conductivity is not preferable.

In the electrolyte solution, the content of the cyclic carbonate is preferably in the range of 30% by volume to 95% by volume, and more preferably in the range of 50% by volume to 90% by volume. If the content of the cyclic carbonate is less than 30% by volume, it is not preferable because the ionic conductivity is lowered. If the content is more than 95% by volume, the viscosity of the electrolyte is increased and the ion conductivity is not preferable.

In the case where the chain carbonate is added to the electrolyte, the content of the chain carbonate is preferably in the range of 5% by volume to 70% by volume, and more preferably in the range of 10% by volume to 65% by volume. If the content of the chain carbonate is less than 5% by volume, the effect of adding the chain carbonate is not preferable. If the content of the chain carbonate is more than 70% by volume, the content of the cyclic carbonate and the respective silicone oils is relatively lowered, and the flash point of the electrolyte solution. It is not preferable because it is lowered.

When fluorinated cyclic carbonate is added to the electrolyte, the content of fluorinated cyclic carbonate is preferably in the range of 0.1% by volume to 25% by volume, more preferably in the range of 0.5% by volume to 10% by volume. If the content of the fluorinated cyclic carbonate is less than 0.1% by volume, it is not preferable because the formation of the film formed on the surface of the negative electrode is insufficient and the decomposition of the electrolyte cannot be suppressed, and when the content is more than 25% by volume, the viscosity of the electrolyte is It is unpreferable since it becomes high and ion conductivity falls.

The polyether-modified silicone oil is obtained by reacting a polyether compound containing a double bond such as a polysiloxane substituting a part of the R group with hydrogen (CH ₂ = CH-).

In addition, the polyether-modified silicone oil prepared as described above contains Pt (platinum) as a catalyst component and butylated hydroxyl toluene (BHT) as a polymerization inhibitor in several to several tens of ppm. Since Pt and BHT are substances which adversely affect the cycle characteristics, it is preferable to remove them as much as possible. In this invention, it is preferable that Pt contained in a polyether modified silicone oil is at least 5 ppm, and BHT is less than 60 ppm, and it is more preferable that Pt and BHT are respectively below a detection limit.

The present invention also provides a positive electrode; cathode; And it provides a lithium secondary battery comprising the electrolyte solution.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

1 is a schematic cross-sectional view of a rechargeable lithium battery according to one embodiment of the present invention.

Referring to FIG. 1, a lithium secondary battery according to an exemplary embodiment of the present invention is described. The lithium secondary battery 1 includes a positive electrode 11, a negative electrode 12, and a space between the positive electrode 11 and the negative electrode 12. The electrode assembly 14 including the existing separator 13 is placed in the case 15, and then the electrolyte is injected into the upper portion of the case 15 and sealed with the cap plate 16 and the gasket 17. .

The positive electrode can be formed into a sheet or disc shape by mixing a positive electrode active material powder, a binder such as polyvinylidene fluoride, and a conductive agent such as carbon black. The positive electrode active material powder or the like may be formed in a sheet form or a disc shape and laminated on a metal current collector.

The positive electrode active material is preferably a composite oxide of lithium and an element selected from the group consisting of cobalt, manganese, nickel, and combinations thereof, and specifically, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , V ₂ O ₅ , and combinations thereof. In addition, a compound capable of intercalation and deintercalation of lithium, such as TiS, MoS, an organic disulfide compound, or an organic polysulfide compound, may be used.

As the separator, a known separator such as a porous polypropylene film, a porous polyethylene film, or the like can be used.

The negative electrode can be formed into a sheet or disc shape by mixing a negative electrode active material powder capable of intercalation and deintercalation of lithium and a binder such as polyvinylidene fluoride. A conductive agent such as carbon black may be further mixed with the mixture of the negative electrode active material powder and the polyvinylidene fluoride. The negative electrode active material powder or the like may be formed in a sheet or disc shape and laminated on a metal current collector. As the negative electrode active material, carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, graphitized mesocarbon microbeads, and amorphous carbon may be used. In addition to the carbonaceous material, a metallic compound capable of alloying with lithium, or a composite containing a metallic compound and a carbonaceous material may also be used as the negative electrode active material. As a metal which can be alloyed with lithium, Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, Al alloy, etc. can be illustrated. Moreover, a metal lithium thin film can also be used as a negative electrode active material.

The electrolyte solution of the lithium secondary battery contains the polyether-modified silicone oil, thereby improving thermal stability of the electrolyte solution and improving high temperature characteristics and heat resistance of the lithium secondary battery. Moreover, when each said silicone oil is contained in electrolyte solution, ionic conductivity does not fall and the high rate discharge characteristic of a lithium secondary battery is improved.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention and the present invention is not limited by the following examples.

(Example 1)

Diethyl carbonate (DEC) and ethylene carbonate (EC) were mixed at a volume ratio DEC: EC = 70: 30, and LiPF ₆ was added at a concentration of 1.3 mol / L to prepare a solution. 10 mass% of polyether modified silicone oil represented by following formula (6) was added to the said solution, and the electrolyte solution of Example 1 was prepared.

[Formula 6]

(Example 2)

An electrolyte solution of Example 2 was prepared in the same manner as in Example 1, except that 10 mass% of the polyether-modified silicone oil represented by the following Formula (7) was added instead of the polyether-modified silicone oil of Example 1.

[Formula 7]

(Example 3)

An electrolyte solution of Example 3 was prepared in the same manner as in Example 1 except that 10 mass% of the polyether-modified silicone oil represented by the following formula (8) was added instead of the polyether-modified silicone oil of Example 1.

[Formula 8]

(Example 4)

An electrolyte solution of Example 4 was prepared in the same manner as in Example 1 except that 10 mass% of the polyether-modified silicone oil represented by the following formula (9) was added instead of the polyether-modified silicone oil of Example 1.

[Formula 9]

(Comparative Example 1)

An electrolyte solution of Comparative Example 1 was prepared in the same manner as in Example 1, except that 10 mass% of the polyether-modified silicone oil represented by the following Chemical Formula 10 was added instead of the polyether-modified silicone oil of Example 1.

[Formula 10]

(Comparative Example 2)

An electrolytic solution of Comparative Example 2 was prepared in the same manner as in Example 1 except that 10 mass% of the polyether-modified silicone oil represented by the following formula (11) was added instead of the polyether-modified silicone oil of Example 1.

[Formula 11]

(Comparative Example 3)

DEC and EC volume ratio DEC: EC = 70: is mixed at a ratio of 30, the LiPF ₆ is added in a concentration of 1.3 mol / L to prepare a solution formed, which was the solution to the electrolytic solution of Comparative Example 3.

Hereinafter, the pouch type lithium secondary battery manufacturing method using the electrolyte solution of said Examples 1-4 and Comparative Examples 1-3 is demonstrated.

LiCoO ₂ as the positive electrode active material, polyvinylidene fluoride binder, carbon black as the conductive agent, positive electrode and graphite as the current collector Al foil, negative electrode active material, polyvinylidene fluoride binder, Cu thin film as the current collector The polypropylene separator is placed between the cathodes and wound in a spiral manner. The positive electrode, the negative electrode, and the separator were inserted into the battery container, and after the injection of the electrolyte solutions of Examples 1 to 4 and Comparative Examples 1 to 3, the inlet of the battery container was sealed to manufacture a battery having a design charge / discharge capacity of 820 mAh.

Next, for each battery, constant current charging was performed at 0.2 C until the battery voltage reached 4.2 V, and then constant voltage charging was performed for 9 hours. The initial discharge capacity of each battery was measured by discharging the battery at 0.2C until the battery voltage became 2.75V. The results are shown in Table 1.

Moreover, after performing the overcharge test which continuously charges each battery at 0.2C for 24 hours, the presence or absence of the bursting of the battery was evaluated. The results are shown in Table 1.

Composition ratio of silicone oil (mass%) Initial capacity (mAh) Overcharge test result Example 1 10 866 No burst Example 2 10 830 No burst Example 3 10 864 No burst Example 4 10 833 No burst Comparative Example 1 10 780 No burst Comparative Example 2 10 782 No burst Comparative Example 3 _ 879 rupture

As shown in Table 1, it can be seen that the lithium secondary battery provided with the electrolyte solutions of Examples 1 to 4 has a high initial capacity and high safety against overcharging. On the other hand, it can be seen that in Comparative Examples 1 and 2, the discharge capacity is lowered as compared with Examples 1 to 4. Moreover, although the discharge capacity is favorable in Comparative Example 3, it can be seen that the battery is ruptured when overcharging is performed, and there is a problem in safety.

FIG. 2 is a graph showing a change in differential capacity with respect to a charging voltage during first charging of a battery using the electrolyte solutions of Example 1 and Comparative Examples 2 and 3. FIG. This differential capacity is different from the charging voltage. As shown in FIG. 2, it can be seen that in Example 1, the differential volume is lower than that in Comparative Example 2, and decomposition of the electrolyte solution is suppressed. This is presumably because the decomposition of the silicone oil was suppressed because the polysiloxane chain of Example 1 was longer than the polysiloxane chain of Comparative Example 2.

In addition, when Example 1 is compared with Comparative Example 3, the profile of Example 1 is almost the same as that of Comparative Example 3 in which no silicone oil is added, and the electrolyte solution decomposition of Example 1 is the same as that of Comparative Example 3. It can be seen that it is suppressed.

(Example 5)

Diethyl carbonate (DEC) and ethylene carbonate (EC) are mixed in a ratio of volume ratio DEC: EC = 70: 30, and LiPF ₆ is added to a solution represented by the formula (6) to a solution represented by the concentration of 1.3 mol / L. 10 mass% of ether-modified silicone oil and 5 mass% of monofluoroethylene carbonate (FEC) were added, and the electrolyte solution of Example 5 was produced.

Except using the electrolyte solution of Example 5, it carried out similarly to Example 1, and manufactured the pouch type lithium secondary battery whose design charge / discharge capacity is 820mAh.

The battery using the electrolytic solution prepared in Example 5 was subjected to constant current charging until the battery voltage reached 4.2V at 0.2C, followed by constant voltage charging for 9 hours. Then, charging and discharging tests were carried out by repeating the cycle 20 times as a step of discharging the battery until the battery voltage became 2.75V at 0.2C. Discharge capacities at the 20th cycle are shown in Table 2 and FIG. 3.

Moreover, the charge / discharge test was done also about the lithium secondary battery of Example 1 and the comparative example 2 similarly to the above. Discharge capacities at 20 cycles are shown in Table 2 and FIG. 3.

Composition ratio of silicone oil (mass%) Composition ratio of FEC (mass%) Discharge Capacity (20 Cycles) (mAh) Example 1 10 _ 679 Example 5 10 5 741 Comparative Example 2 10 _ 617

As shown in FIG. 3 and Table 2, it turns out that the discharge capacity after 20 cycles of the lithium secondary battery provided with the electrolyte solution of Example 1 and 5 becomes high compared with the comparative example 2. As shown in FIG.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Since the electrolyte solution for a lithium secondary battery of the present invention includes a polyether modified silicone oil selected from the group consisting of the compounds of Formulas 1 to 5 and combinations thereof, thermal stability and ionic conductivity of the electrolyte solution are improved. Thereby, the lithium secondary battery which is excellent in stability at high temperature and which can carry out high efficiency charge and discharge can be obtained. In addition, the safety of the battery can be improved.

Claims (32)

Polyether-modified silicone oil containing a compound selected from the group consisting of a compound of the formula 1 to 5, and combinations thereof; Carbonates; And Lithium salt Electrolyte for lithium secondary battery comprising a. [Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

(In formulas 1 to 5, k has a range of 1 to 9, l has a range of 0 to 3, n has a range of 1 to 2, and R is CH ₃ or C ₆ H ₅ . Either one, Z is either CH ₃ or C ₂ H ₅ , In Formulas 1 and 2, m is 1, and in Formulas 3 to 5, m is in a range of 0 to 1.) The method of claim 1, The electrolyte solution is a lithium secondary battery electrolyte further comprising a carbonate modified silicone oil. The method of claim 1, The silicon oil is a lithium secondary battery electrolyte is contained in 1% by volume to 70% by volume with respect to the whole electrolyte. The method of claim 3, The silicon oil is a lithium secondary battery electrolyte is contained in 5% by volume to 50% by volume with respect to the whole electrolyte solution. The method of claim 1, The silicone oil is a lithium secondary battery electrolyte that has a flash point of 120 ℃ or more. The method of claim 1, Wherein the carbonate is selected from the group consisting of cyclic carbonate, chain carbonate, and combinations thereof. The method of claim 6, The cyclic carbonate is a lithium secondary battery electrolyte is contained in 30 to 95% by volume relative to the total volume of the electrolyte. The method of claim 7, wherein The cyclic carbonate is a lithium secondary battery electrolyte that is contained in 50 to 90% by volume relative to the total volume of the electrolyte. The method of claim 6, The chain carbonate is a lithium secondary battery electrolyte that is contained in 5 to 70% by volume relative to the total volume of the electrolyte. The method of claim 9, The chain carbonate is a lithium secondary battery electrolyte that is contained in 10 to 65% by volume relative to the total volume of the electrolyte. The method of claim 6, The cyclic carbonate is a fluorinated cyclic carbonate electrolyte for a lithium secondary battery. The method of claim 11, The fluorinated cyclic carbonate is a lithium secondary battery electrolyte that is contained in 0.1 to 25% by volume relative to the total volume of the electrolyte. The method of claim 12, The fluorinated cyclic carbonate is a lithium secondary battery electrolyte that is contained in 0.5 to 10% by volume relative to the total volume of the electrolyte. The method of claim 1, The electrolyte solution is a lithium secondary battery electrolyte further comprises fluoroethylene carbonate (FEC). The method of claim 1, The lithium salt may be LiPF ₆ , LiBF ₄ , Li [N (SO ₂ C ₂ F ₆ ) ₂ ], Li [B (OCOCF ₃ ) ₄ ], Li [B (OCOC ₂ F ₅ ) ₄ ], LiPF ₆ , Li [N (SO ₂ C ₂ F ₅ ) ₂ ], and a lithium secondary battery electrolyte solution selected from the group consisting of these. The method of claim 1, The lithium salt is a lithium secondary battery electrolyte is contained in 0.5 to 2.0 mol / L relative to the total concentration of the electrolyte. anode; cathode; And an electrolyte solution, The electrolyte solution is a lithium secondary battery comprising a polyether-modified silicone oil, carbonate, and a lithium salt containing a compound selected from the group consisting of compounds of Formulas 1 to 5 and combinations thereof. [Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

(In formulas 1 to 5, k has a range of 1 to 9, l has a range of 0 to 3, n has a range of 1 to 2, and R is CH ₃ or C ₆ H ₅ . Either one, Z is either CH ₃ or C ₂ H ₅ , In Formulas 1 and 2, m is 1, and in Formulas 3 to 5, m is in a range of 0 to 1.) The method of claim 17, The electrolyte is a lithium secondary battery further comprising a carbonate modified silicone oil. The method of claim 17, The silicon oil is a lithium secondary battery that is contained in 1% by volume to 70% by volume with respect to the whole electrolyte solution. The method of claim 19, The silicon oil is a lithium secondary battery that is contained in 5% by volume to 50% by volume relative to the entire electrolyte. The method of claim 17, The silicone oil is a lithium secondary battery having a flash point of 120 ℃ or more. The method of claim 17, The carbonate is a lithium secondary battery is selected from the group consisting of cyclic carbonate, chain carbonate, and combinations thereof. The method of claim 22, The cyclic carbonate is a lithium secondary battery that is contained in 30 to 95% by volume relative to the total volume of the electrolyte. The method of claim 23, wherein The cyclic carbonate is a lithium secondary battery that is contained in 50 to 90% by volume relative to the total volume of the electrolyte. The method of claim 22, The chain carbonate is a lithium secondary battery containing 5 to 70% by volume relative to the total volume of the electrolyte. The method of claim 25, The chain carbonate is a lithium secondary battery containing 10 to 65% by volume relative to the total volume of the electrolyte. The method of claim 22, Wherein the cyclic carbonate is a fluorinated cyclic carbonate lithium secondary battery. The method of claim 27, The fluorinated cyclic carbonate is a lithium secondary battery containing 0.1 to 25% by volume based on the total volume of the electrolyte. The method of claim 28, The fluorinated cyclic carbonate is a lithium secondary battery containing 0.5 to 10% by volume based on the total volume of the electrolyte. The method of claim 17, The electrolyte is a lithium secondary battery further comprises fluoroethylene carbonate (FEC). The method of claim 17, The lithium salt may be LiPF ₆ , LiBF ₄ , Li [N (SO ₂ C ₂ F ₆ ) ₂ ], Li [B (OCOCF ₃ ) ₄ ], Li [B (OCOC ₂ F ₅ ) ₄ ], LiPF ₆ , Li A lithium secondary battery selected from the group consisting of [N (SO ₂ C ₂ F ₅ ) ₂ ], and combinations thereof. The method of claim 17, The lithium salt is a lithium secondary battery that is contained in 0.5 to 2.0 mol / L with respect to the total concentration of the electrolyte.

Images