KR101373093B1 - Electrolyte for lithium secondary battery and lithium secondary battery comprising same - Google Patents

Abstract

The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery comprising the same, wherein the electrolyte is at least one lithium-borate salt having a non-aqueous organic solvent and a borate structure represented by the following Chemical Formula 1, the following Chemical Formula 2, or a combination thereof. And a lithium salt containing LiPF ₆ .

[Chemical Formula 1]

 (2)

(In Formula 1 to 2, R ₁ to R ₄ are the same or mutually C1 to C10 alkyl or alkyl ester, C1 to C10 halogenated alkyl group or halogenated alkyl ester, C6 to C12 aromatic group or C6 to C12 halogenated aromatic Ki)

Electrolyte solution of the present invention is excellent in high-temperature storage characteristics, compared to the electrolyte solution using a conventional LiPF ₆ lithium salt, it is possible to implement the battery performance of equal or more.

Electrolyte, Swelling, Lithium Secondary Battery, Borate

Description

ELECTROLYTE FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY COMPRISING SAME

[Industrial Applications]

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.

BACKGROUND ART [0002]

Recently, with the development of advanced electronic industry, it has become possible to reduce the size and weight of electronic equipment, and the use of portable electronic devices is increasing. The need for a battery having a high energy density as a power source for such portable electronic devices has been increased, and research on lithium secondary batteries has been actively conducted. Lithium-transition metal oxides are used as the cathode active material of the lithium secondary battery, and carbon (crystalline or amorphous) or carbon composite material is used as the anode 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. However, even in this case, an unstable surface electrolyte interface (SEI) film is formed on the negative electrode, which deteriorates the lifespan characteristics.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an electrolyte solution for a lithium secondary battery that can suppress high temperature swelling.

Another object of the present invention is to provide a lithium secondary battery comprising the electrolyte solution.

In order to achieve the above object, the present invention comprises a lithium salt comprising LiPF ₆ and at least one lithium-borate salt having a non-aqueous organic solvent and a borate structure represented by the following formula (1), (2) or a combination thereof Provided is an electrolyte solution for a lithium secondary battery.

[Chemical Formula 1]

 (2)

(In Formula 1 to 2, R ₁ to R ₄ are the same or mutually C1 to C10 alkyl or alkyl ester, C1 to C10 halogenated alkyl group or halogenated alkyl ester, C6 to C12 aromatic group or C6 to C12 halogenated aromatic Ki)

The present invention also provides a lithium secondary battery comprising a positive electrode including a positive electrode active material capable of intercalating and deintercalating the electrolyte lithium, and 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 electrolytic solution for a lithium secondary battery, which exhibits excellent high temperature leaving characteristics and battery characteristics equal to or higher than those of batteries using conventional LiPF ₆ lithium salts.

The electrolyte solution of the present invention includes LiPF ₆ and at least one lithium-borate salt having a borate structure represented by the following Chemical Formula 1 or 2 as a lithium salt or a combination thereof.

  These lithium salts are materials that act as a source of lithium ions in the battery and enable the operation of the basic lithium battery.

[Chemical Formula 1]

 (2)

In Formulas 1 to 2, R ₁ to R ₄ are the same or mutually C1 to C10 alkyl or alkyl ester, C1 to C10 halogenated alkyl group or halogenated alkyl ester, C6 to C12 aromatic group or C6 to C12 halogenated aromatic group to be.

Preferred lithium-borate salts include lithium bis (oxalatoborate: LiBOB), lithium bis (malonato borate) and lithium bis (perfluoropinacolato). ) One or more selected from the group consisting of (Lithium bis (perfluoropinacolato) borate).

In the electrolyte solution of the present invention, the concentration of the lithium salt is preferably 0.5 to 1.5M, more preferably 0.8 to 1.5M. If the concentration of the lithium salt is out of the above range, the battery performance is deteriorated, which is not preferable.

In addition, in the electrolyte solution of the present invention, the content of the lithium-borate salt is preferably 0.001 to 15.4 mol%, more preferably 0.001 to 10 mol% based on the total mol of the lithium salt. In addition, the content of the LiPF ₆ is preferably 99.999 to 84.6 mol% based on the total mol of the lithium salt. If the content of the lithium-borate salt is less than 0.001 mol%, there is no effect of suppressing swelling of the electrolyte, and if it exceeds 15.4 mol%, the high temperature standing (swelling) property is deteriorated, which is not preferable.

The electrolyte solution of the present invention also includes a non-aqueous organic solvent that serves as a medium through which ions involved in the electrochemical reaction of the cell can move.

As the non-aqueous organic solvent, at least one solvent selected from the group consisting of carbonate-based, ester-based, ether-based and ketone-based may be used. As the carbonate solvent, at least one solvent selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylmethyl carbonate, ethylene carbonate, propylene carbonate and butylene carbonate may be used. As the ester solvent, γ-butyrolactone, n-methyl acetate, n-ethyl acetate, n-propyl acetate, and the like may be used. In addition, dibutyl ether may be used as the ether solvent, and polymethylvinyl ketone may be used as the ketone solvent.

In the case of using a carbonate-based solvent in the non-aqueous organic solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, it is preferable to use the cyclic carbonate and the chain carbonate by mixing in a volume ratio of 1: 1 to 1: 9. The performance of the electrolytic solution is desirable when mixed in the above volume ratio.

The non-aqueous organic solvent may be used by mixing an aromatic hydrocarbon-based organic solvent with the carbonate solvent. In this case, the carbonate solvent and the aromatic hydrocarbon organic solvent are preferably used by mixing in a volume ratio of 1: 1 to 30: 1. The performance of the electrolyte solution may be desirable to be mixed in the volume ratio. As the aromatic hydrocarbon organic solvent, an aromatic compound represented by Chemical Formula 3 may be used.

(3)

In Formula 3, R 10 is halogen or an alkyl group having 1 to 10 carbon atoms, and q is an integer of 0 to 6.

As the aromatic hydrocarbon organic solvent, at least one solvent selected from the group consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, and xylene may be used.

The electrolyte solution of the present invention may further include carbonate additives 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. Can be. 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 represented by the following formula (4) are preferred, and fluoroethylene carbonate is most preferred.

[Chemical Formula 4]

X1 in Formula 4 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 an electrolyte solution (in the case of a polymer electrolyte, a polymer electrolyte composition). 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.

Such a lithium secondary battery electrolyte of the present invention may be used as a liquid electrolyte itself, or may further add a monomer and a polymerization initiator to the liquid electrolyte to form a polymer electrolyte. As a first method of forming a polymer electrolyte, the polymer electrolyte composition is injected into an electrode group consisting of a positive electrode, a separator, and a negative electrode into a battery case such as a metal can or a pouch, sealed, and heated at 40 to 100 ° C. for 30 minutes to 8 hours. do. At this time, the polymer electrolyte composition is cured to form a polymer electrolyte.

In the second method, the polymer electrolyte composition is cast on the surface of the positive electrode or the negative electrode and then irradiated with heat, ultraviolet rays or electron beams to prepare a positive electrode or negative electrode on which the positive or negative electrode surface is coated with a polymer electrolyte. The prepared positive electrode or negative electrode is injected into a battery case and sealed to manufacture a battery. In this case, a separate separator may be used, and the polymer electrolyte may also serve as a separator.

The monomer may be a monomer selected from the group consisting of a first monomer of Formula 5 or a mixture of a first monomer of Formula 5 and at least one second monomer selected from the group consisting of Formulas 6 to 11.

[Chemical Formula 5]

A-Polyester Polyol-B

(In the formula (5), the polyester polyol is a substance having a molecular weight of 100-10,000,000 produced by a condensation reaction of at least one alcohol derivative having two or more and six or less OH groups at one end with at least one dicarboxylic acid derivative,

A and B are the same as or independently from each other in the form of reacting the terminal OH group of the polyester polyol with CH ₂ = CR-C (= O)-, CH ₂ = CR-C-CH _2- , CH ₂ = CR-, CH ₂ = CR-OC (= O)-, CH ₂ = CH-CH ₂ -O-, CH ₂ = CH-S (= O) ₂ -or CH ₂ = CR-C (= O) -O-CH ₂ CH ₂ -NH-C (= 0)-and R is C ₁ to C ₁₀ hydrocarbon or C ₆ to C ₁₀ aromatic hydrocarbon).

[Chemical Formula 6]

CH ₂ = CR1-C (= O) -OX

[Formula 7]

CH ₂ = CR1-OX

[Formula 8]

CH ₂ = CR1-OC (= O) -X

[Chemical Formula 9]

CH ₂ = CH-CH ₂ -OX

[Formula 10]

CH ₂ = CH-S (= O) ₂ -X

(11)

CH ₂ = CR1-C (= O) -O-CH ₂ CH ₂ -NH-C (= O) -OX

(In Chemical Formulas 6 to 11, R1 is H, C ₁ to C ₁₀ hydrocarbon or aromatic hydrocarbon, and X is C ₁ to C ₂₀ hydrocarbon, halogenated hydrocarbon, aromatic hydrocarbon or halogenated aromatic hydrocarbon. )

In Formula 5, examples of the alcohol derivative forming the polyester polyol include polyethylene glycol, polypropylene glycol, alkane diol, ethoxylated alkanediol, and propoxylated alkane. diol), trimethylolpropane, ethoxylated trimethylolpropane, propoxylated trimethylolpropane, ditrimethylolpropane, ethoxylated ditrimethylolpropane, propoxylated ditrimethylolpropane, pentaerythritol, ethoxylated Toxylated pentaerythritol, propoxylated pentaerythritol, dipentaerythritol, ethoxylated dipentaerythritol, propoxylated dipentaerythritol, bisphenol A, ethoxylated bisphenol A and propoxylated bisphenol A It is selected from the group consisting of.

Representative examples of such polyester polyols include the following general formula (12).

[Chemical Formula 12]

In Formula 12, X, Y and Z are the same or independently from each other a divalent or higher alkylene oxide or a repeating unit thereof, an alkylene imine or a repeating unit and a repeating unit selected from the group consisting of alkylene groups,

x, y and z are each an integer from 1 to 20,

1, m and n each have a value of 0 or 1 or more, and can be appropriately adjusted according to the molecular weight of the desired polymer.

In Formula 5, A and B are the same or independently from each other (meth) acryl, vinyl (Vinyl), allyl (Allyl), vinylsulfonyl (Vinylsulfonyl) and urethane (meth) acrylic (Urethane ( meth) acryl) is preferably selected from the group consisting of (meth) acryl, vinyl, vinylsulfonyl and urethane (meth) acryl.

As for the content of the said monomer, 0.01-20 weight% is preferable with respect to the whole polymer electrolyte composition, and 0.1-10 weight% is more preferable. When the content of the monomer is less than 0.01% by weight, it shows excessive swelling characteristics, and when it exceeds 10% by weight, battery performance is lowered, which is not preferable.

The polymerization initiator may initiate polymerization of the monomer, and any material may be used as long as it does not deteriorate battery performance. As a representative example, one or two or more organic peroxides or azo compounds may be mixed.

The organic peroxides include di (4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethylhexyl peroxy dicarbonate, di-isopropyl peroxy dicarbonate, di-3-methoxy butyl peroxy dicarbonate , t-butyl peroxy isopropylcarbonate, t-butyl peroxy 2-ethylhexyl carbonate, 1,6-bis (t-butyl peroxycarbonyloxy) hexane, diethylene glycol-bis (t-butyl peroxy carbonate Diacyl peroxides such as dioxy percarbonate, dibenzoyl peroxide, dilauroyl peroxide, bis-3,5,5-trimethyl hexanoyl peroxide, and the like. Pivalate, t-amyl peroxypivalate, t-butyl peroxy-2-ethyl-hexanoate, t-hexylperoxy pivalate, t-butyl peroxy neodecanoate, t -Butyl peroxy neoheptanoate, t-hexylperoxy pivalate, 1,1,3, 3-tetramethylbutyl peroxy neodecarbonate, 1,1,3,3-tetramethyl butyl 2-ethylhexanoate, t-amyl peroxy 2-ethyl hexanoate, t-butyl peroxy isobutyrate, t Amylperoxy 3,5,5-trimethyl hexanoyl, t-butyl peroxy 3,5,5-trimethyl hexanoate, t-butyl peroxy acetate, t-butyl peroxy benzoate, di-butylperoxy Peroxy esters, such as a trimethyl adipate, can be used, As said azo type compound, 2,2'- azo-bis (2, 4- dimethylvaleronitrile) or 1,1'- azo-bis (cyano) Cyclo-hexane) can be used.

In the electrolyte solution of the present invention, the polymerization initiator is sufficient to be present in an amount capable of causing a polymerization reaction of the monomer, and in general, it is suitably present in an amount of 0.01 to 5% by weight based on the total weight of the monomer.

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 embodiments and comparative examples of the present invention will be described. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

(Example 1)

0.02 mol of polyester polyol (DR1515, "DAERYUNG Enterprise Co. Ltd.", Mn = 1500) prepared by condensation reaction of ethylene glycol, diethylene glycol, trimethylolpropane and adipic acid, 30 g methylene chloride as reaction solvent, catalyst 0.04 mol of triethylamine was added thereto, and a mixed solution of 0.04 mol of acryloyl chloride and 15 g methylene chloride was added dropwise to the mixed solution stirred in a cooling bath. After completion of the dropwise addition, the mixture was warmed to 40 ° C. and stirred for 6 hours, and then, the precipitated salt was filtered off, and then the reaction solvent, methylene chloride, was removed by evaporation. A monomer SP1 of about 25000 was prepared.

[Chemical Formula 13]

In Formula 13, l, m, and n are 0 or 1 or more, and the weight average molecular weight is adjusted to about 25000.

The above prepared monomer 7% by weight and an ethylene carbonate / ethyl methyl carbonate / propylene carbonate /-fluoro-benzene (30/55/5/10% by volume 1.3M LiPF ₆ in a mixed solvent of LiBOB and 0.001M dissolved lithium salt of the formula 93% by weight of the prepared liquid electrolyte was mixed, and 2% by weight of perhexyl pivalate was added to the mixed solution as an initiator, dissolved and mixed to prepare a polymer electrolyte composition. It was.

The battery assembly was a positive electrode prepared using a LiCoO ₂ positive electrode active material, a conductive material, and a polyvinylidene fluoride binder at 96: 2: 2% by weight, and an artificial graphite and polyvinylidene fluoride binder 94: 6% by weight. It was prepared by winding the negative electrode and polyethylene separator prepared by (winding).

Subsequently, the battery assembly in which the polymer electrolyte composition was injected was sealed and heated in an oven at 70 ° C. for 2 hours and 30 minutes to prepare a lithium secondary battery.

(Example 2)

Except for using 1.1M LiPF ₆ and 0.2M LiBOB as a lithium salt it was carried out in the same manner as in Example 1.

(Example 3)

The same process as in Example 1 was performed except that 3 parts by weight of fluoroethyl carbonate was further added to 100 parts by weight of the polymer electrolyte composition.

(Comparative Example 1)

A lithium salt was carried out in the same manner as in Example 1, except that 1.3M LiPF ₆ was used.

* Evaluation of high temperature leaving characteristics

After the batteries charged with the lithium secondary batteries of Examples 1 to 3 and Comparative Example 1 under 0.5C / 4.2V and 20 mA cut-off conditions were left in an oven at 90 ° C. for 4 hours, the thickness was measured, and the thickness increase was performed. Table 1 shows.

Example 1 Example 2 Example 3 Comparative Example 1 Thickness increase 5% 4% 6% 20%

As shown in Table 1, it can be seen that the battery of Examples 1 to 3 is very small increase in thickness when left at a high temperature compared to Comparative Example 1. Therefore, it can be seen that the high temperature leaving characteristic is very excellent.

In addition, the capacity remaining ratio was 94% in all 300 charge / discharge cycle life measurements of the batteries prepared according to Example 1 and Comparative Example 1.

According to these results, it can be seen that the batteries of Examples 1 to 3 have very excellent high temperature leaving characteristics while maintaining the charge / discharge cycle life characteristics.

Electrolyte solution of the present invention is excellent in high-temperature storage characteristics, compared to the electrolyte solution using a conventional LiPF ₆ lithium salt, it is possible to implement the battery performance of equal or more.

Claims (39)

Non-aqueous organic solvent; And To include a lithium-borate salt having a borate structure represented by the formula (1) and a lithium salt comprising LiPF ₆ , An amount of the lithium borate salt is 0.001 to 15.4 mol% based on the total mol of the lithium salt. [Chemical Formula 1]

The method of claim 1, The lithium salt has a concentration of 0.5 to 1.5M lithium secondary battery electrolyte. The method of claim 2, The lithium salt concentration is 0.8 to 1.5M lithium secondary battery electrolyte. delete The method of claim 1, An amount of the lithium borate salt is 0.001 to 10 mol% based on the total amount of lithium salts. The method of claim 1, The LiPF ₆ content is 99.999 to 84.6 mol% based on the total mol of lithium salt. The method according to claim 6, The LiPF ₆ content is 99.999 to 90 mol% based on the total amount of lithium salts. delete The method of claim 1, The non-aqueous organic solvent is at least one solvent selected from the group consisting of carbonate-based, ester-based, ether-based and ketone-based electrolyte for lithium secondary batteries. 10. The method of claim 9, The carbonate-based lithium secondary battery is at least one solvent selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, methylethyl carbonate, ethylene carbonate, propylene carbonate and butylene carbonate Electrolyte solution. The method of claim 1, The non-aqueous organic solvent is a mixed electrolyte of a carbonate solvent and an aromatic hydrocarbon organic solvent. The method of claim 11, The aromatic hydrocarbon-based organic solvent is an electrolyte for a lithium secondary battery is an aromatic compound of the formula (3). (3)

(In Formula 3, R10 is a halogen or an alkyl group having 1 to 10 carbon atoms and q is an integer of 0 to 6) The method of claim 11, The aromatic hydrocarbon-based organic solvent is at least one solvent selected from the group consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, and xylene. The method of claim 1, The electrolyte further comprises an additive selected from the group consisting of carbonate, vinylene carbonate, divinyl sulfone and ethylene sulfite 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. 15. The method of claim 14, The electrolyte solution further comprises a carbonate additive having a substituent selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ). 16. The method of claim 15, The carbonate additive is a lithium secondary battery electrolyte is a carbonate of the formula (4). [Chemical Formula 4]

X1 in Formula 4 is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ). 17. The method of claim 16, The carbonate additive is fluoroethylene carbonate electrolyte for a lithium secondary battery. The method of claim 1, The electrolyte solution is a polymer electrolyte lithium secondary battery electrolyte further comprising a monomer and a polymerization initiator. 19. The method of claim 18, The monomer is selected from the group consisting of a first monomer of the formula (5) or a mixture of the first monomer of the formula (5) and at least one second monomer selected from the group consisting of the following formulas (6) to (11). [Chemical Formula 5] A-Polyester Polyol-B (In the formula (5), the polyester polyol is a substance having a molecular weight of 100-10,000,000 produced by the condensation reaction of one or more alcohol derivatives having two or more and six or less OH groups at one end with one or more dicarboxylic acid derivatives, A and B are the same as or independently from each other in the form of reacting the terminal OH group of the polyester polyol with CH ₂ = CR-C (= O)-, CH ₂ = CR-C-CH _2- , CH ₂ = CR-, CH ₂ = CR-OC (= O)-, CH ₂ = CH-CH ₂ -O-, CH ₂ = CH-S (= O) ₂ -or CH ₂ = CR-C (= O) -O-CH ₂ CH ₂ -NH-C (= 0)-and R is C ₁ to C ₁₀ hydrocarbon or C ₆ to C ₁₀ aromatic hydrocarbon). [Chemical Formula 6] CH ₂ = CR1-C (= O) -OX [Formula 7] CH ₂ = CR1-OX [Formula 8] CH ₂ = CR1-OC (= O) -X [Chemical Formula 9] CH ₂ = CH-CH ₂ -OX [Formula 10] CH ₂ = CH-S (= O) ₂ -X (11) CH ₂ = CR1-C (= O) -O-CH ₂ CH ₂ -NH-C (= O) -OX (In Chemical Formulas 6 to 11, R1 is H, C ₁ to C ₁₀ hydrocarbon or aromatic hydrocarbon, and X is C ₁ to C ₂₀ hydrocarbon, halogenated hydrocarbon, aromatic hydrocarbon or halogenated aromatic hydrocarbon. ) 19. The method of claim 18, The polymerization initiator is an electrolyte solution for a lithium secondary battery, which is an organic peroxide or azo compound. Lithium-borate salt having a non-aqueous organic solvent and a borate structure represented by the following formula (1) and a lithium salt comprising LiPF ₆ , the content of the lithium borate salt is 0.001 to 15 mol% based on the total mole of the lithium salt Phosphorus electrolyte; A positive electrode comprising a positive electrode active material capable of intercalating and deintercalating lithium; And A negative electrode including a negative electrode active material capable of intercalating and deintercalating lithium ≪ / RTI > [Chemical Formula 1]

22. The method of claim 21, Concentration of the lithium salt is 0.5 to 1.5M lithium secondary battery. 23. The method of claim 22, The lithium salt has a concentration of 0.8 to 1.5M lithium secondary battery. delete 22. The method of claim 21, Lithium-borate salt content is a lithium secondary battery is 0.001 to 10 mol% based on the total mol of lithium salt. 22. The method of claim 21, The LiPF ₆ content is 99.999 to 84.6 mol% based on the total mol of lithium salts. 27. The method of claim 26, The LiPF ₆ content is 99.999 to 90 mol% based on the total mol of lithium salt. delete 22. The method of claim 21, The non-aqueous organic solvent is at least one solvent selected from the group consisting of carbonate-based, ester-based, ether-based and ketone-based lithium secondary batteries. 30. The method of claim 29, The carbonate-based lithium secondary battery is at least one solvent selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylmethyl carbonate, ethylene carbonate, propylene carbonate and butylene carbonate . 22. The method of claim 21, The non-aqueous organic solvent is a lithium secondary battery that is a mixed solvent of a carbonate solvent and an aromatic hydrocarbon organic solvent. 32. The method of claim 31, The aromatic hydrocarbon-based organic solvent is a lithium secondary battery is an aromatic compound of the formula (3). (3)

(In Formula 3, R10 is a halogen or an alkyl group having 1 to 10 carbon atoms and q is an integer of 0 to 6) 32. The method of claim 31, The aromatic hydrocarbon-based organic solvent is at least one solvent selected from the group consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, and xylene. 22. The method of claim 21, The electrolyte further comprises an additive selected from the group consisting of carbonate, vinylene carbonate, divinyl sulfone and ethylene sulfite having a substituent selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ). A lithium secondary battery. 35. The method of claim 34, The electrolyte solution further comprises a carbonate additive having a substituent selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ). 35. The method of claim 34, The carbonate additive is a lithium secondary battery is a carbonate of the formula (4). [Chemical Formula 4]

X1 in Formula 4 is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ). 35. The method of claim 34, The electrolyte is a lithium secondary battery which is a polymer electrolyte formed by further comprising a monomer and a polymerization initiator. 39. The method of claim 37, The monomer is selected from the group consisting of a first monomer of the formula (5) or a mixture of the first monomer of the formula (5) and at least one second monomer selected from the group consisting of the following formulas (6) to (11). [Chemical Formula 5] A-Polyester Polyol-B (In the formula (5), the polyester polyol is a substance having a molecular weight of 100-10,000,000 produced by the condensation reaction of one or more alcohol derivatives having two or more and six or less OH groups at one end with one or more dicarboxylic acid derivatives, A and B are the same as or independently from each other in the form of reacting the terminal OH group of the polyester polyol with CH ₂ = CR-C (= O)-, CH ₂ = CR-C-CH _2- , CH ₂ = CR-, CH ₂ = CR-OC (= O)-, CH ₂ = CH-CH ₂ -O-, CH ₂ = CH-S (= O) ₂ -or CH ₂ = CR-C (= O) -O-CH ₂ CH ₂ -NH-C (= 0)-and R is C ₁ to C ₁₀ hydrocarbon or C ₆ to C ₁₀ aromatic hydrocarbon). [Chemical Formula 6] CH ₂ = CR1-C (= O) -OX [Formula 7] CH ₂ = CR1-OX [Formula 8] CH ₂ = CR1-OC (= O) -X [Chemical Formula 9] CH ₂ = CH-CH ₂ -OX [Formula 10] CH ₂ = CH-S (= O) ₂ -X (11) CH ₂ = CR1-C (= O) -O-CH ₂ CH ₂ -NH-C (= O) -OX (In Chemical Formulas 6 to 11, R1 is H, C ₁ to C ₁₀ hydrocarbon or aromatic hydrocarbon, and X is C ₁ to C ₂₀ hydrocarbon, halogenated hydrocarbon, aromatic hydrocarbon or halogenated aromatic hydrocarbon. ) 39. The method of claim 37, The polymerization initiator is an electrolyte solution for a lithium secondary battery, which is an organic peroxide or azo compound.