KR101004399B1 - 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 a non-aqueous organic solvent; Lithium salts; And an additive, wherein the additive has a vinyl dimethylphenylsilane compound first additive of Formula 1 and a substituent selected from the group consisting of halogen, cyano group (CN), and nitro group (NO ₂ ). And second additives of carbonate derivatives.

[Formula 1]

Therefore, the present invention can provide a secondary battery having excellent life characteristics while reducing thickness expansion at high temperature.

Electrolyte, Expanded Thickness, Dimethylphenylsilane, Fluoroethylene Carbonate

Description

Electrolyte for lithium secondary battery and lithium secondary battery comprising same {Electrolyte for lithium secondary battery and lithium secondary battery comprising the same}

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 and a lithium secondary battery including the same, while reducing the thickness expansion rate at high temperature and excellent life characteristics.

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.

Lithium is the lightest metal on the planet, and therefore has the highest electric capacity per unit mass. Since lithium has a large thermodynamic oxidation potential, it can produce a high voltage battery. This is the most preferred cathode material in batteries, especially secondary batteries.

Lithium ion secondary batteries use a lithium metal mixed oxide capable of deintercalation and intercalation of lithium ions as a cathode active material, a carbon material or metal lithium as a cathode, and an appropriate amount of lithium electrolytic salt in a mixed organic solvent. It is composed by dissolving the electrolyte, and the energy density is high, about 200% of the NiCd battery per weight, about 160% of the Ni-MH battery, about 170% of the Ni-Cd battery per unit density, and about 105% of the Ni-MH battery, The self-discharge rate is less than about 5% per month at 20 ℃, about 1/3 lower than that of nickel-cadmium batteries or nickel-metal hydride batteries, and is environmentally friendly and normal because it does not use heavy metals that pollute the environment such as cadmium or mercury. It can have more than 500 charge / discharge cycles and has the advantage of long life.

In addition, lithium ion batteries generally have an average discharge voltage of 3.6-3.7 V, and the average discharge voltage of such lithium ion batteries is 3.6-3.7 V for other alkaline batteries or Ni-MH or Ni-Cd batteries. Compared to this, it is the biggest advantage to obtain high power.

However, in order to achieve such a high driving voltage, an electrolyte having an electrochemically stable composition is required at 2.75-4.2V, which is a charge / discharge voltage range of a lithium ion battery. Ethylene carbonate (EC) is used to meet these requirements. ), A combination of carbonates such as propylene carbonate (PC), dimethyl carbonate (Dimethyl Carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), It is a so-called non-aqueous mixture solvent.

However, the electrolyte solution having such a composition generally has disadvantages such as disadvantage in high rate charge and discharge because the ion conductivity is significantly lower than the so-called aqueous electrolyte solution used in Ni-MH or Ni-Cd batteries.

For example, in the case of ethylene carbonate, the freezing point is 36 ° C, which has a disadvantage in low temperature characteristics, but it is a solvent that is necessarily used for the electrical performance of the battery. It has a disadvantage that occurs a lot, dimethyl carbonate has a freezing point of 3 ℃ and a boiling point of about 90 ℃ low temperature properties, like EC, and high temperature neglect characteristics are particularly disadvantageous. Diethyl carbonate has excellent performance with freezing point -40 ℃ or lower and boiling point of 126 ℃, but has poor drawability with other solvents. Boiling point of freezing point below -30 ℃ is about 107 ℃ Even ethyl methyl carbonate has many unsatisfactory aspects such as temperature characteristics.

As these solvents have their own advantages and disadvantages, and there is a big difference in battery performance depending on how they are combined in actual use, the battery industry is constantly conducting tests to find more improved combinations. In general, EC / DMC / EMC, EC / EMC / DEC, EC / DMC / EMC / PC are frequently used.

On the other hand, the characteristics of the lithium secondary battery at a high temperature also depend a lot on the type of electrolytic salt. LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN (SO ₂ CF ₃ ) ₂ and LiN ( Materials such as SO ₂ CF ₂ CF ₃ ) ₂ act as a lithium ion source in a battery cell to enable the operation of a basic lithium secondary battery. In general, LiBF ₄ is a high temperature among electrolytic salts. It is said to be the best in terms of thermal stability at.

The electrolyte for a lithium ion battery composed of a solvent and an electrolytic salt reacts with the carbon constituting the negative electrode to form a thin film called SEI (Solid Electrolyte Interface) on the surface of the negative electrode, which affects ion and charge transfer. It is one of the main factors that causes the performance change.

However, in the formation reaction of the SEI film, the thickness of the battery expands during charging due to the generation of gases such as CO, CO ₂ , CH ₄ , and C ₂ H ₆ generated by decomposition of the carbonate-based organic solvent, and at a high temperature in a fully charged state. During storage (e.g., 4 days at 85 ° C after 4.2V 100% charge), the SEI membrane is gradually decayed by the increased electrochemical and thermal energy over time, and reacts with the new cathode surface where the surrounding electrolyte is exposed. Side reactions will continue to occur. At this time, the main gases generated are CO, CO ₂ , CH ₄ , C ₂ H _6, etc. according to the type of carbonate and the negative electrode active material used, and there is a problem that the pressure inside the battery increases due to the continuous gas generation. .

In connection with such problems of the SEI membrane, studies have been continuously made to further improve the physicochemical properties by changing the SEI formation reaction by adding an additive having high performance to the electrolyte, but none of these existing studies has been used for lithium ion. The problem caused by the formation of the SEI film at the high temperature of the battery may not be completely solved. Also, when certain additives are added to the electrolyte, the performance improvement of some items in the battery performance may be expected, but the performance of other items may be reduced. There are many cases.

Accordingly, the present invention is to solve the above-mentioned disadvantages and problems of the prior art, to provide a lithium secondary battery electrolyte and a lithium secondary battery comprising the same, while excellent in life characteristics while reducing the thickness expansion ratio at high temperature. There is a purpose.

The present invention is a non-aqueous organic solvent; Lithium salts; And an additive, wherein the additive includes a first additive of a vinyl dimethylphenylsilane compound of Formula 1 and a substituent selected from the group consisting of halogen, cyano group (CN), and nitro group (NO ₂ ). It provides a lithium secondary battery electrolyte and a lithium secondary battery comprising the same comprising a second additive of a carbonate derivative.

[Formula 1]

In addition, the present invention provides a lithium secondary battery electrolyte and a lithium secondary battery comprising the content of the first additive is 0.1 to 5% by weight based on 100% by weight of the total electrolyte.

In addition, the present invention provides a lithium secondary battery electrolyte and a lithium secondary battery comprising the content of the second additive is 0.1 to 10% by weight relative to the total 100% by weight of the electrolyte.

The present invention also provides a lithium secondary battery electrolyte and a lithium secondary battery comprising the second additive is fluoroethylene carbonate.

Accordingly, the lithium secondary battery electrolyte of the present invention and a lithium secondary battery comprising the same are 0.1 wt% to 5 wt% of a vinyl dimethylphenylsilane compound and 0.1 wt% to 10 wt% of fluoroethylene as an additive to the electrolyte solution. By adding carbonate, there is an effect of providing a secondary battery having excellent life characteristics while reducing thickness expansion at high temperatures.

Details of the above object and technical configuration of the present invention and the effects thereof will be more clearly understood by the following detailed description of the present invention.

The present invention provides a vinyl dimethylphenylsilane compound and a halogen of the following Chemical Formula 1 as an additive to an electrolyte containing a non-aqueous organic solvent and a lithium salt for the purpose of reducing the thickness expansion rate at high temperature and improving battery performance. It relates to a lithium secondary battery comprising a carbonate derivative having a substituent selected from the group consisting of a cyano group (CN) and a nitro group (NO ₂ ).

[Formula 1]

Hereinafter, a lithium secondary battery including an electrolyte according to the present invention will be described.

First, the electrolyte according to the present invention includes a non-aqueous organic solvent, and the non-aqueous organic solvent may be carbonate, ester, ether or ketone. The carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC) ethylene carbonate (EC), Propylene carbonate (PC), butylene carbonate (BC) and the like can be used, and the ester is butyrolactone (BL), decanolide (decanolide), valerolactone, mevalonolactone (mevalonolactone) , Caprolactone, n-methyl acetate, n-ethyl acetate, n-propyl acetate, and the like may be used. The ether may be dibutyl ether, and the like, and the ketone may include polymethylvinyl ketone. The present invention is not limited to the type of nonaqueous organic solvent.

When the non-aqueous organic solvent is a carbonate-based organic solvent, it is preferable to use a mixture of cyclic carbonate and chain carbonate. In this case, the cyclic carbonate and the chain carbonate are preferably used in a volume ratio of 1: 1 to 1: 9, and more preferably in a volume ratio of 1: 1.5 to 1: 4. The performance of the electrolyte is preferable when mixed in the above volume ratio.

The electrolyte solution of the present invention may further include an aromatic hydrocarbon organic solvent in the carbonate solvent. An aromatic hydrocarbon compound may be used as the aromatic hydrocarbon organic solvent.

Specific examples of the aromatic hydrocarbon-based organic solvent include benzene, fluorobenzene, chlorobenzene, nitrobenzene, toluene, fluorotoluene, trifluorotoluene, xylene and the like. In the electrolyte containing an aromatic hydrocarbon-based organic solvent, the volume ratio of the carbonate solvent / aromatic hydrocarbon solvent is preferably 1: 1 to 30: 1. The performance of the electrolyte is preferable when mixed in the above volume ratio.

Next, the electrolyte according to the present invention comprises a lithium salt, the lithium salt acts as a source of lithium ions in the battery to enable the 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 ) ( CyF _{2x +1} SO ₂ ), where x and y are natural water and LiSO ₃ CF ₃ or one or more mixtures thereof.

At this time, 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, the performance of the electrolyte is lowered, and if it exceeds 2.0M, there is a problem that the mobility of lithium ions is reduced by increasing the viscosity of the electrolyte.

Next, the electrolyte according to the present invention includes a vinyl dimethylphenylsilane (vinyl dimethylphenylsilane) compound of [Formula 1] as an additive.

[Formula 1]

It is not common for additives to be included in battery manufacturing, and additives may be used for the purpose of improving the characteristics of each sector, for example, life characteristics, low temperature high rate discharge characteristics, high temperature safety, overcharge prevention, and high temperature swelling. In the present invention, it can be said that the additive is used in the present invention to improve the thickness expansion characteristics and the like at high temperature by suppressing the decomposition reaction of the solvent by the decomposition of the SEI film at high temperature storage.

Hereinafter, the SEI film generated on the surface of the anode by reacting carbon constituting the cathode with the electrolyte solution will be described in more detail. Lithium ions derived from lithium metal oxide used as a cathode during initial charging of a lithium ion battery may be used as a cathode. It moves to the carbon (crystalline or amorphous) electrode used and is intercalated into the carbon of the negative electrode. In this case, lithium is highly reactive, and thus reacts with the carbon negative electrode to form Li ₂ CO ₃ , Li ₂ O, LiOH, and the like. These form a film on the surface of the cathode, and this film corresponds to the SEI film.

Once formed, the SEI membrane prevents the reaction between lithium ions and carbon anodes or other materials during repeated charge and discharge cycles by using a battery, and passes only lithium ions between the electrolyte and the cathode. It will serve as).

Due to the ion tunnel effect, the SEI membrane blocks the migration of organic solvents, such as EC, DMC, DEC, etc., of a large molecular weight electrolyte into the carbon cathode, so that they are co-intercalated with lithium ions to the carbon cathode. It prevents the structure of the carbon anode from collapsing. Once this film is formed, the lithium ion no longer reacts side by side with the carbon anode or other materials, thereby reversibly maintaining the amount of lithium ion during charge and discharge of the battery. Will be.

In other words, the carbon material of the negative electrode reacts with the electrolyte during supercharging to form a passivation layer on the negative electrode surface to maintain stable charging and discharging without further decomposition of the electrolyte solution. The amount of charge consumed to form the layer is an irreversible capacity, which is characterized by not reversibly reacting when discharging. For this reason, a lithium ion battery can maintain a stable life cycle without exhibiting any irreversible reaction after the initial charge reaction. .

However, Li-ion battery has the disadvantage that the SEI membrane is gradually decayed by the increased electrochemical and thermal energy over time when stored at high temperature in a fully charged state (for example, left at 85 ° C. for 4 days after 4.2V 100% charge). In this case, side reactions in which the carbonate-based solvent in the surrounding electrolyte react with the exposed negative electrode surface due to the membrane collapse occur continuously.

These side reactions continue to generate gas, and the main gases generated are CO, CO ₂ , CH ₄ , C ₂ H _6, etc., depending on the type of carbonate used as electrolyte and the type of negative electrode active material. Regardless of the type, such continuous gas generation causes the internal pressure of the lithium ion battery to increase at high temperatures, thereby causing the battery thickness to expand.

However, in the present invention, by adding the vinyl dimethylphenylsilane compound to the electrolyte, the formation of SEI during the initial charge faster than the conventional carbonate-based organic solvent to suppress decomposition of the carbonate-based organic solvent, When the battery is stored at high temperature after full charge, the expansion of the battery can be suppressed.

In other words, the vinyl dimethylphenylsilane compound is decomposed before the carbonate-based organic solvent, and the SEI reaction occurs at a voltage at this time. The SEI film formed at this time decomposes the carbonate-based organic solvent such as EC, DMC, In order to prevent the occurrence of gas due to decomposition of the carbonate-based organic solvent during initial charging, expansion of the battery can be suppressed.

In this case, the 2vinyl dimethylphenylsilane compound may be added in an amount of 0.1 to 5.0% by weight based on 100% by weight of the total electrolyte.

When the vinyl dimethylphenylsilane compound is added in less than 0.1% by weight, there is no effect of improving the thickness increase rate according to the present invention, 5.0% by weight of the vinyl dimethylphenylsilane compound (vinyl dimethylphenylsilane) compound If it exceeds, there is a problem that the life characteristics are not good.

Next, the electrolyte according to the present invention includes a carbonate derivative having a substituent selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ) as an additive. Adding an additive of the carbonate derivative is preferable because it can provide a battery having excellent electrochemical characteristics such as high temperature swelling characteristics, capacity, lifespan, and low temperature characteristics. As such an additive, an ethylene carbonate derivative represented by the following Chemical Formula 2 is preferable, and fluoroethylene carbonate is most preferred.

[Formula 2]

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

The additive is included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the total weight of the electrolyte. If the amount of the additive is less than 0.1 parts by weight, the life characteristics are not good, and if it exceeds 10 parts by weight, a problem of swelling at high temperature or the like occurs.

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

The positive electrode includes a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions. Representative examples of the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , or LiNi _{1- x - y} Co xMyO ₂ lithium such as (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1, M is a metal such as Al, Sr, Mg, La) - to use the transition metal oxide, and In the present invention, the type of the positive electrode is not limited.

The negative electrode includes a negative electrode active material capable of intercalating and deintercalating lithium ions. As the negative electrode active material, a carbon-based negative electrode active material such as crystalline carbon, amorphous carbon, or a carbon composite may be used. It does not limit the kind of said negative electrode.

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, the thickness increase rate was measured through the preferred examples and comparative examples of the present invention. However, the following examples are only preferred embodiments of the present invention and the present invention is not limited to the following examples.

Example 1

LiCoO2 as a positive electrode active material, polyvinylidene fluoride (PVDF) as a binder and carbon as a conductive agent were mixed in a weight ratio of 92: 4: 4, and then dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode slurry. . The slurry was coated on an aluminum foil having a thickness of 20 μm, dried, and rolled to prepare a positive electrode. Crystalline artificial graphite as a negative electrode active material and polyvinylidene fluoride (PVDF) as a binder were mixed at a weight ratio of 92: 8, and dispersed in N-methyl-2-pyrrolidone to prepare a negative electrode slurry. The slurry was coated on a copper foil having a thickness of 15 μm, dried, and rolled to prepare a negative electrode.

A film separator made of a polyethylene (PE) material having a thickness of 25 μm was put between the prepared electrodes and wound and compressed to insert a 30 mm × 48 mm × 6 mm square can.

An electrolyte solution was injected into the rectangular can to prepare a lithium secondary battery. In the electrolyte solution, 3.0 wt% of fluoroethylene carbonate (FEC) was added to a solvent having a composition of 1: 1: 1 of ethylene carbonate / ethylmethyl carbonate / diethyl carbonate, and an electrolyte solution was prepared so that LiPF ₆ was 1.0M. Vinyl dimethylphenylsilane (vinyl dimethylphenylsilane) was added to this electrolyte in the ratio of 1 weight%.

[Example 2]

The same procedure as in Example 1 was conducted except that 2 wt% of vinyl dimethylphenylsilane was added.

Example 3

The same procedure as in Example 1 was conducted except that 3 wt% of vinyl dimethylphenylsilane was added.

Example 4

The same procedure as in Example 1 was repeated except that vinyl dimethylphenylsilane was added at 4 wt%.

Example 5

The same procedure as in Example 1 was conducted except that 5 wt% of vinyl dimethylphenylsilane was added.

Comparative Example 1

The same procedure as in Example 1 was conducted except that 6 wt% of vinyl dimethylphenylsilane was added.

Comparative Example 2

The same procedure as in Example 1 was conducted except that 1 wt% of vinyl dimethylphenylsilane was added and 11 wt% of fluoroethylene carbonate (FEC) was added.

Comparative Example 3

The same procedure as in Example 1 was conducted except that no vinyl dimethylphenylsilane was added.

After charging the lithium batteries of Examples 1 to 5 and Comparative Examples 1 to 3 under CC-CV conditions at 4.2 V charging voltage at a current of 160 mA, the battery was discharged to 2.75 V at 160 mA current for 1 hour after being left for 1 hour. It was left. After this process three times, it was charged with 4.2V charging voltage for 2 hours and 30 minutes at 400mA current. After the initial assembly at this time was left in the 85 ℃ chamber for 5 hours compared to the thickness of the battery to measure the thickness increase rate at high temperature.

The measurement results are shown in Table 1 below.

TABLE 1

division Vinyldimethylphenylsilane
(weight%) FEC (% by weight) Initial thickness
(mm) Thickness increase rate (%) Example 1 One 3 4.59 8.8 Example 2 2 3 4.73 8.2 Example 3 3 3 4.78 8.0 Example 4 4 3 4.79 8.0 Example 5 5 3 4.80 8.3 Comparative Example 1 6 3 5.05 11.0 Comparative Example 2 One 11 5.12 20.5 Comparative Example 3 - 3 4.59 12.9

From the results shown in Table 1, it can be seen that Examples 1 to 5 according to the present invention have a very good rate of increase in thickness at high temperature compared to the initial thickness.

However, in the case of Comparative Example 3, which does not include vinyl dimethylphenylsilane, it can be seen that the thickness increase rate is not very good, about 13%, and 5% of vinyl dimethylphenylsilane. Also in the case of Comparative Example 1 exceeding it can be seen that the thickness increase rate is not good as 11%.

In addition, it can be seen that the thickness increase rate of Comparative Example 2 exceeding 10% of fluoroethylene carbonate (FEC) is not very good as about 20%.

Next, life characteristics were measured through the following preferred examples and comparative examples of the present invention.

Example 6

It carried out similarly to Example 1.

Example 7

It carried out similarly to Example 2.

Example 8

It carried out similarly to Example 5.

[Comparative Example 4]

It carried out similarly to the comparative example 1.

[Comparative Example 5]

It carried out similarly to the comparative example 2.

[Comparative Example 6]

It carried out similarly to the comparative example 3.

Comparative Example 7

The same procedure as in Example 1 was conducted except that 1 wt% of vinyl dimethylphenylsilane was added and fluoroethylene carbonate (FEC) was not added.

The lithium batteries of Examples 6 to 8 and Comparative Examples 4 to 7 were charged for 2 hours and 30 minutes under CC-CV conditions at 4.2V charging voltage at a current of 800mA, and then 3.2V cut-off discharge at a current of 800mA. This process was carried out 100 times and 300 times, respectively, and the remaining capacity relative to the initial capacity was measured to express 100 times and 300 times as a percentage (%).

The measurement results are shown in Table 2 below.

TABLE 2

division Vinyldimethylphenylsilane
(weight%) FEC (% by weight) 100 times
Volume(%) 300 times
Volume(%) Example 6 One 3 97 89 Example 7 2 3 97 89 Example 8 5 3 98 87 Comparative Example 4 6 3 95 82 Comparative Example 5 One 11 98 90 Comparative Example 6 - 3 95 87 Comparative Example 7 One - 88 52

From the results shown in Table 2, it can be seen that Examples 6 to 7, Comparative Example 5, Comparative Example 6 according to the present invention is very good capacity 300 times.

However, in the case of Comparative Example 4 in which vinyl dimethylphenylsilane exceeds 5%, the capacity of 300 times is 82%.

In addition, in the case of Comparative Example 7, which does not contain fluoroethylene carbonate (FEC) and includes only vinyl dimethylphenylsilane, the capacity of 100 times is not good, and in particular, the capacity of 300 times is not very good. have.

Therefore, in the present invention, based on the measurement values of Table 1 and Table 2, vinyl dimethylphenylsilane (vinyl dimethylphenylsilane) is included in the range of 0.1% to 5% by weight relative to 100% by weight of the total electrolyte, fluoroethylene carbonate It is preferable to include (FEC) in the range of 0.1% to 10% by weight relative to 100% by weight of the total electrolyte, thereby providing a secondary battery having excellent life characteristics while reducing thickness expansion at high temperatures.

Although the present invention has been shown and described with reference to the preferred embodiments as described above, it is not limited to the above embodiments and those skilled in the art without departing from the spirit of the present invention. Various changes and modifications will be possible.

Claims (10)

Non-aqueous organic solvents; Lithium salts; And Contains additives, The additive may include a first additive of a vinyl dimethylphenylsilane compound of Formula 1 and a second carbonate derivative having a substituent selected from the group consisting of halogen, cyano group (CN), and nitro group (NO ₂ ). Electrolyte for lithium secondary battery containing an additive. [Formula 1]

The method of claim 1, The content of the first additive is a lithium secondary battery electrolyte, characterized in that 0.1 to 5% by weight relative to the total 100% by weight of the electrolyte. The method of claim 1, The content of the second additive is a lithium secondary battery electrolyte, characterized in that 0.1 to 10% by weight relative to the total 100% by weight of the electrolyte. The method of claim 1, The second additive is an ethylene carbonate derivative represented by the following formula (2) for a lithium secondary battery electrolyte. [Formula 2]

(Wherein X is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ).) The method of claim 1, The second additive is fluoroethylene carbonate, characterized in that the lithium secondary battery electrolyte. An electrolyte comprising a non-aqueous organic solvent, a lithium salt, and an additive; A positive electrode including a positive electrode active material capable of intercalating and deintercalating the lithium; And A negative electrode including a negative electrode active material capable of intercalating and deintercalating the lithium; The additive may include a first additive of a vinyl dimethylphenylsilane compound of Formula 1 and a second carbonate derivative having a substituent selected from the group consisting of halogen, cyano group (CN), and nitro group (NO ₂ ). Lithium secondary battery containing an additive. [Formula 1]

The method of claim 6, The content of the first additive is a lithium secondary battery, characterized in that 0.1 to 5% by weight based on 100% by weight of the total electrolyte. The method of claim 6, The content of the second additive is a lithium secondary battery, characterized in that 0.1 to 10% by weight relative to the total 100% by weight of the electrolyte. The method of claim 6, The second additive is a lithium secondary battery, characterized in that the ethylene carbonate derivative of the formula (2). [Formula 2]

(Wherein X is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ).) The method of claim 6, The second additive is a lithium secondary battery, characterized in that fluoroethylene carbonate.