WO2018093152A1 - Non-aqueous electrolyte for lithium secondary battery, and lithium secondary battery comprising same - Google Patents

Abstract

The present invention relates to an non-aqueous electrolyte and a lithium secondary battery comprising the same and, more specifically, to an non-aqueous electrolyte for a lithium secondary battery and a lithium secondary battery comprising the same, the non-aqueous electrolyte comprising: an ionizable lithium salt, an organic solvent, and an additive, wherein the additive is a mixed additive comprising lithium difluorophosphate: tertiary alkyl benzene: tetravinyl silane at a weight ratio of 1: 1 to 4: 0.05 to 0.5, and the additive is included in an amount of 2.5 to 4.5 wt% on the basis of the total weight of the non-aqueous electrolyte for the lithium secondary battery.

Description

Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery comprising same

Cross Citation with Related Application (s)

This application claims the benefit of priority based on Korean Patent Application No. 10-2016-0151998 of November 15, 2016 and Korean Patent Application No. 10-2017-0152232 of November 15, 2017. All content disclosed in the literature is included as part of this specification.

Technical Field

The present invention relates to a non-aqueous electrolyte for lithium secondary batteries and a lithium secondary battery comprising the same, and more particularly, to a non-aqueous electrolyte for lithium secondary batteries capable of improving high temperature durability and stability of a lithium secondary battery and a lithium secondary battery comprising the same.

As the demand for mobile devices increases, the demand for secondary batteries as energy sources is rapidly increasing, and lithium secondary batteries having high energy density and voltage are commercially used among these secondary batteries.

In the lithium secondary battery, charging and discharging are performed while repeating a process of intercalating and deintercalating lithium ions from a lithium metal oxide of a positive electrode to a carbon electrode of a negative electrode.

At this time, lithium ions are highly reactive and react with the carbon electrode to form Li ₂ CO ₃ , LiO, LiOH and the like to form a film on the surface of the negative electrode. Such a film is called a solid electrolyte interface (SEI) film. The SEI film formed at the beginning of charging prevents the reaction between lithium ions and the carbon negative electrode or other materials during charging and discharging, and serves as an ion tunnel passing only lithium ions between the electrolyte and the negative electrode. The ion tunnel serves to prevent the organic solvents of the non-aqueous electrolyte having a large molecular weight, which are solvated with lithium ions, move together to the carbon anode, thereby collapsing the structure of the carbon anode.

On the other hand, the organic solvent used in the non-aqueous electrolyte of the lithium secondary battery generally generates gas while being oxidized by the transition metal oxide emitted from the positive electrode when stored for a long time at high temperature, the battery swelling and electrode assembly deformation, etc. This happens. In addition, when stored at high temperature in a fully charged state (eg, stored at 60 ° C. after 100% charge at 4.2V), the negative electrode is exposed while the SEI film is gradually decayed, and thus the negative electrode continuously reacts with the electrolyte to continuously react the side reactions. While generating a gas such as CO, CO ₂ , CH ₄ , C ₂ H _{6 It} will eventually lead to deformation such as battery swelling due to the increase in battery pressure. When such a battery deformation causes an internal short circuit of the battery and battery degradation occurs, the battery may ignite or explode.

In order to solve this problem, a method of adding an SEI film forming material for preventing the collapse of the SEI film in the nonaqueous electrolyte has been proposed. However, while other side effects occur due to the electrolyte additive, another problem occurs that the overall performance of the secondary battery is reduced.

Thus, while minimizing side effects, the development of a non-aqueous electrolyte of a new configuration that can improve the high temperature and overcharge stability of the lithium secondary battery is continuously required.

Prior art literature

United States Patent Application Publication No. 8,986,880

In order to solve the above problems, the first technical problem of the present invention is to provide a non-aqueous electrolyte solution for a lithium secondary battery comprising an additive that can lower the interfacial resistance of the electrode surface and inhibit the side reaction of the electrolyte during high temperature storage. It is done.

Another object of the present invention is to provide a lithium secondary battery having improved high temperature storage characteristics and high temperature life characteristics by including the nonaqueous electrolyte solution for lithium secondary batteries.

In one embodiment for achieving the above object,

Including ionizable lithium salts, organic solvents, and additives,

The additive is lithium difluorophosphate (Lithium difluorophosphate: LiDFP): tertiary alkylbenzene represented by the following formula (1): tetra-vinyl silane (TVS) in a weight ratio of 1: 1 to 4: 0.05 to 0.5 It is a mixed additive to include,

The additive provides a non-aqueous electrolyte solution for a lithium secondary battery, which is included in an amount of 2.5% by weight to 4.5% by weight based on the total weight of the nonaqueous electrolyte solution for a lithium secondary battery.

[Formula 1]

In Chemical Formula 1,

R ₁ is tertiary alkyl having 4 to 5 carbon atoms.

In the nonaqueous electrolyte solution for lithium secondary batteries, the organic solvent includes a mixed solvent including at least two or more of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate, and ethyl methyl carbonate. can do.

In addition, in the non-aqueous electrolyte solution for the lithium secondary battery, the weight ratio of the lithium difluorophosphate as the additive: tertiaryalkylbenzene represented by the general formula (1): tetravinylsilane may be 1: 1.5 to 4: 0.1 to 0.2.

In this case, in the nonaqueous electrolyte solution for lithium secondary batteries, the concentration of lithium difluorophosphate in the nonaqueous electrolyte solution for lithium secondary batteries may be 1 × 10 ⁻² mol / kg to 0.5 mol / kg.

In the nonaqueous electrolyte solution for lithium secondary batteries, the additive may be included in an amount of 2.5 wt% to 4.3 wt% based on the total weight of the nonaqueous electrolyte solution for the lithium secondary battery.

In the nonaqueous electrolyte solution for lithium secondary batteries, the nonaqueous electrolyte solution for lithium secondary batteries is selected from the group consisting of vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate, ethylene sulfate (Esa) and propane sultone (PS). It may further comprise at least one additive for forming the SEI film.

The additive for forming the SEI film may be included in at least 0.1% by weight to 2% by weight based on the total weight of the nonaqueous electrolyte.

In addition, in one embodiment of the present invention

In a lithium secondary battery comprising a negative electrode containing a negative electrode active material, a positive electrode containing a positive electrode active material and a nonaqueous electrolyte,

The positive electrode active material includes at least one or more of a compound represented by Formula 4 and a compound represented by Formula 5 below,

The nonaqueous electrolyte provides a lithium secondary battery including the nonaqueous electrolyte for a lithium secondary battery of the present invention.

[Formula 4]

Li (Ni _x Co _y Mn _z ) O ₂

In Chemical Formula 4,

0 <x <1, 0 <y <1, 0 <z <1, x + y + z = 1.

[Formula 5]

Li (Ni _x1 Co _y1 Mn _z1 ) O ₄

In Chemical Formula 5,

0 <x1 <2, 0 <y1 <2, 0 <z1 <2, and x1 + y1 + z1 = 2.

In the lithium secondary battery, the cathode active material is Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ , Li (Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ , Li (Ni _0.7 Mn _0.15 Co _0.15 ) O ₂ , and Li (Ni _0.8 Mn _0.1 Co _0.1 ) O ₂ may be selected from the group consisting of.

In addition, the cathode active material may further include a compound represented by Chemical Formula 6.

[Formula 6]

LiMnO ₂

In this case, the cathode active material may include 80 to 99 wt% of the compound represented by Formula 4 or 5 and 1 to 20 wt% of the compound represented by Formula 6.

According to one embodiment of the present invention, by including a mixed additive mixed in a specific ratio, it is possible to manufacture a non-aqueous electrolyte for lithium secondary battery capable of forming a stable SEI film on the surface of the negative electrode. In addition, by including this, not only can the interface resistance with the electrode be lowered by the stable SEI film formed on the surface of the cathode during initial charging, but also the secondary reaction of improved high temperature storage characteristics and lifespan by suppressing side reactions of the positive electrode active material at high voltage. The battery can be manufactured.

The following drawings, which are attached to this specification, illustrate exemplary embodiments of the present invention, and together with the contents of the present invention, serve to further understand the technical idea of the present invention. It should not be construed as limited.

1 is a graph showing the results of stability measurement during overcharging of the secondary battery of Example 1 according to Experimental Example 3 of the present invention.

2 is a graph showing the results of measuring stability during overcharging of the secondary battery of Comparative Example 10 according to Experimental Example 3 of the present invention.

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

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

Specifically, in one embodiment of the present invention

Ionizable lithium salts,

Organic solvents, and

Contains additives,

The additive is lithium difluorophosphate (Lithium difluorophosphate: LiDFP): tertiary alkylbenzene represented by the following formula (1): tetra-vinyl silane (TVS) in a weight ratio of 1: 1 to 4: 0.05 to 0.5 It is a mixed additive to include,

The additive provides a non-aqueous electrolyte solution for a lithium secondary battery, which is included in an amount of 2.5% by weight to 4.5% by weight based on the total weight of the nonaqueous electrolyte solution for a lithium secondary battery.

[Formula 1]

In Chemical Formula 1,

R ₁ is tertiary alkyl having 4 to 5 carbon atoms.

First, in the nonaqueous electrolyte solution for a lithium secondary battery according to an embodiment of the present invention, the ionizable lithium salts may be used without limitation, those conventionally used in a lithium secondary battery electrolyte, for example, Li ⁺ as a cation of the lithium salt. to include, and the anion is ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, AlO 4 -, AlCl 4 -, PF 6 -, _{^{SbF 6 -, AsF 6 -,}} BF 2 C 2 O 4 -, BC 4 O 8 -, PF 4 C 2 O 4 -, PF 2 C 4 O 8 -, (CF 3) 2 PF 4 -, (CF 3 ^{_{) 3 PF 3 -, (CF}} 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, C 4 F 9 SO 3 -, CF 3 CF 2 SO _{^{3 -, (CF 3 SO 2}} ) 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C - _{, (CF 3 SO 2) 3} C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - , and _{(CF 3 CF 2 SO 2)} 2 N - consisting of At least one selected from the group can be mentioned. Specifically, the lithium salt is LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , LiAlO ₄ , and LiCH ₃ SO ₃ It may include a single or a mixture of two or more selected from the group consisting of, in addition to these LiBTI (lithium bisperfluoroethanesulfonimide, LiN (SO ₂ C ₂ F) commonly used in the electrolyte of the lithium secondary battery _{5) 2), LiFSI (lithium} fluorosulfonyl imide, LiN (SO 2 F) 2) and LiTFSI (lithium (bis) trifluoromethanesulfonimide, LiN (SO 2 CF 3) 2) Li is already available, without limitation, an electrolyte salt, such as deuyeom represented by Can be. Specifically, the electrolyte salt is a single or two or more selected from the group consisting of LiPF ₆ , LiBF ₄ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiCH ₃ SO ₃ , LiFSI, LiTFSI and LiN (C ₂ F ₅ SO ₂ ) ₂ Mixtures may be included. However, the lithium salt does not include LiDFP which is a lithium salt contained in the mixed additive.

The lithium salt may be appropriately changed within a conventionally usable range, and specifically, may be included as 0.1M to 2M in the nonaqueous electrolyte solution for a lithium secondary battery.

At this time, when the concentration of the lithium salt is 0.1M or less, the effect of improving the low temperature output and the high temperature cycle characteristics of the battery is insignificant, and when the lithium salt exceeds 2M, side reactions in the electrolyte are excessively generated during swelling. ) May occur, or may cause corrosion of the positive or negative current collector made of metal in the electrolyte.

In addition, in the non-aqueous electrolyte lithium secondary battery according to an embodiment of the present invention, the organic solvent can be minimized by the oxidation reaction in the charge and discharge process of the secondary battery, and can exhibit the desired characteristics with the additive An ester solvent may be used as the solvent.

Specific examples of the ester solvent may include at least one compound selected from the group consisting of a cyclic carbonate compound, a linear carbonate compound, a linear ester compound, and a cyclic ester compound.

The cyclic carbonate compound is ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2, Any one selected from the group consisting of 3-pentylene carbonate, vinylene carbonate and fluoroethylene carbonate (FEC), or a mixture of two or more thereof, and more specifically ethylene carbonate, propylene carbonate, vinylene carbonate and One or a mixture of two or more selected from the group consisting of fluoroethylene carbonate (FEC) can be mentioned.

In addition, specific examples of the linear carbonate compound include dimethyl carbonate (dimethyl carbonate, DMC), diethyl carbonate (diethyl carbonate, DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate Any one selected from, or a mixture of two or more thereof, and the like may be representatively used, and more specifically, any one selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, and ethylmethyl carbonate, or two of them. And mixtures of species or more.

The linear ester compound is any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate. The above mixture and the like can be used representatively, but is not limited thereto.

The cyclic ester compound is any one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, ε-caprolactone, or two or more thereof Mixtures may be used, but are not limited thereto.

In the ester solvent, the cyclic carbonate-based compound is a high viscosity organic solvent and has a high dielectric constant, and thus may be preferably used because it dissociates lithium salts in the electrolyte. The cyclic carbonate-based compound has low viscosity and low viscosity such as dimethyl carbonate and diethyl carbonate. When the dielectric constant linear carbonate compound and the linear ester compound are mixed in an appropriate ratio, an electrolyte having a high electrical conductivity can be made, and thus it can be more preferably used.

More specifically, the organic solvent may be used by mixing a cyclic carbonate compound and a linear carbonate compound, and representative examples thereof include ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate and ethyl methyl. It may include a mixed solvent including at least two or more of the carbonates.

In addition, the organic solvent may further use an ether solvent or an amide solvent.

As the ether solvent in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether and ethylpropyl ether, or a mixture of two or more thereof may be used. It is not limited to this.

In addition, in the nonaqueous electrolyte solution for a lithium secondary battery according to an embodiment of the present invention, lithium difluorophosphate represented by the following Chemical Formula 2, which is one of the additive components, is a component for implementing long-term life characteristics improvement effect of the secondary battery. In addition, the lithium ion component decomposed during the initial charge may form a stable SEI film on the surface of the negative electrode, and not only may improve Li mobility to the negative electrode in order to form the SEI film, but also lower the interface resistance. In addition, the difluorophosphate anion generated by decomposition during initial charging may be present on the surface of the anode, thereby improving anode stabilization and discharge characteristics.

[Formula 2]

In addition, in the nonaqueous electrolyte solution for lithium secondary batteries of the present invention, the tertiary alkylbenzene represented by Formula 1 included as one of the additives is a component capable of suppressing side reactions of the positive electrode active material at high voltage, and is a representative example of Butylbenzene (TBB), or tertiary pentylbenzene (TPB), and preferably tert-butyl benzene.

The tertiary alkylbenzene represented by Chemical Formula 1 forms a film while being oxidized at a potential of about 4.8 V to 5.0 V during overcharging, and the oxidized oxide is deposited on the cathode and the cathode facing separator, thereby transferring Li ions to the cathode. By suppressing the reactivity between the deposited Li and the electrolyte solution to suppress the voltage rise due to overcurrent, it is possible to improve the high temperature, high voltage and overcharge stability.

In addition, in the nonaqueous electrolyte solution for lithium secondary batteries of the present invention, the tetravinylsilane represented by the following Chemical Formula 3 included as one of the additives is a component capable of suppressing the reaction between lithium ions and the electrolyte, and the Si element contained therein is a positive electrode and By forming a solid ion conductive film through physical adsorption and electrochemical reaction on the surface of the negative electrode, it is possible to suppress side reactions of the positive electrode material at high voltage, thereby improving stability at high temperature.

[Formula 3]

In addition, in the non-aqueous electrolyte solution for a lithium secondary battery according to an embodiment of the present invention, the weight ratio of the lithium difluorophosphate: tertiaryalkylbenzene: tetravinylsilane represented by Chemical Formula 1 is 1: 1 to 4: 0.05 to 0.05. 0.5, specifically, 1: 1.5 to 4: 0.1 to 0.2.

When the components of the additive are mixed in the ratio in the nonaqueous electrolyte of the present invention, the effect of suppressing side reactions with the electrolyte on the surface of the negative electrode and the positive electrode or reducing the gas generation during the charging of the lithium secondary battery, etc. Since it is possible to form a stable film that brings about, a secondary battery with improved overall performance can be manufactured.

In this case, when the content ratio of the tertiary alkylbenzene is less than 1, the overcharge stability effect of the battery is insignificant, and if it exceeds 4, an increase in resistance during discharge may occur due to a decrease in ion conductivity accompanied by an increase in viscosity in the electrolyte.

In addition, when the content ratio of the tetravinylsilane is less than 0.05, high temperature durability may be lowered, and when it exceeds 0.5, the resistance may increase.

In the nonaqueous electrolyte solution for lithium secondary batteries, the concentration of lithium difluorophosphate in the nonaqueous electrolyte solution for lithium secondary batteries may be 1 × 10 ⁻² mol / kg to 0.5 mol / kg.

In addition, the non-aqueous electrolyte additive may be included in an amount of 2.5 wt% to 4.5 wt%, specifically 2.5 wt% to 4.3 wt%, based on the total weight of the nonaqueous electrolyte.

In the present invention, by including the additive in the above amount in the non-aqueous electrolyte, it is possible to effectively implement the interface resistance reduction and side reaction suppression. If the content of the additive is less than 2.5% by weight, the effect of improving the physical properties of the secondary battery is insignificant, and if it exceeds 4.5% by weight, the change in battery thickness due to the suppression of gas generation may be suppressed because the additive is included in excess, Increasing resistance in the electrolyte may deteriorate capacity and life characteristics.

In addition, the nonaqueous electrolyte solution for lithium secondary batteries of the present invention is used to increase the gas reduction effect and the high temperature durability improvement effect, vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate, ethylene sulfate (Esa) and propane sultone (PS). It may further include at least one additive for forming the SEI film selected from the group consisting of).

The additive for forming the SEI film may be included in an amount of 0.1 wt% or more and at least 0.1 wt% to 2 wt% based on the total weight of the nonaqueous electrolyte. If the content of the second additive exceeds 2% by weight, the additive is used in the nonaqueous electrolyte as a whole, causing an increase in resistance and a decrease in capacity.

In addition, if necessary, the non-aqueous electrolyte of the present invention is an electrolyte additive commonly known for the purpose of improving charge and discharge characteristics, flame retardancy, etc., specifically pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme (glyme), hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy It may further comprise at least one additional additive selected from the group consisting of ethanol, and aluminum trichloride. In some cases, in order to impart nonflammability, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high temperature storage characteristics, and FEC (Fluoro-Ethylene) may be further included. Carbonate), PRS (1,3-propene sultone) may be further included.

In addition, in one embodiment of the present invention

In a lithium secondary battery comprising a negative electrode containing a negative electrode active material, a positive electrode containing a positive electrode active material and a nonaqueous electrolyte,

The positive electrode active material includes at least one or more of a compound represented by Formula 4 and a compound represented by Formula 5 below,

The nonaqueous electrolyte provides a lithium secondary battery including the nonaqueous electrolyte for a lithium secondary battery of the present invention.

[Formula 4]

Li (Ni _x Co _y Mn _z ) O ₂

In Chemical Formula 4,

0 <x <1, 0 <y <1, 0 <z <1, x + y + z = 1.

[Formula 5]

Li (Ni _x1 Co _y1 Mn _z1 ) O ₄

In Chemical Formula 5,

0 <x1 <2, 0 <y1 <2, 0 <z1 <2, and x1 + y1 + z1 = 2.

At this time, the positive electrode and the negative electrode constituting the lithium secondary battery of the present invention can be manufactured and used in a conventional manner.

First, the positive electrode may be manufactured by forming a positive electrode mixture layer on a positive electrode current collector. The cathode mixture layer may be formed by coating a cathode slurry including a cathode active material, a binder, a conductive material, a solvent, and the like on a cathode current collector, followed by drying and rolling.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, the positive electrode current collector may be formed of stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. Surface treated with nickel, titanium, silver, or the like may be used.

In addition, the cathode active material represented by Formula 4 or 5 is structurally much more stable than the cathode active material such as LiCoO ₂ because the three components have different valences and have a superlattice structure. Representative examples of the cathode active material include Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ , Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ , Li (Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ , Li (Ni _0.7 Mn _0.15 Co _0.15 ) O ₂ , Li (Ni _0.8 Mn _0.1 Co _0.1 ) O ₂ , and the like.

In addition, the cathode active material may be a lithium-manganese oxide (eg, LiMnO ₂ , LiMn ₂ O _{4 if necessary).} Etc.), lithium-cobalt-based oxides (e.g., LiCoO _2, etc.), lithium-nickel-based oxides (e.g., LiNiO _2, etc.), lithium-nickel-manganese-based oxides (e.g., LiNi _{1 - Y} Mn _Y O ₂ (where, 0 <Y <1), LiMn _2-z Ni _z O ₄ (where, 0 <z <2) and the like), lithium-nickel-cobalt-based oxide (for example, LiNi _{1- Y1} Co _Y1 O ₂ (here, 0 <Y1 <1), etc., lithium-manganese-cobalt based oxides (eg, LiCo _{1 -Y2} Mn _Y2 O ₂ (here, 0 <Y2 <1), LiMn _{2 - z1} Co _z1 O ₄ (where 0 <Z1 <2) and the like, or lithium-nickel-cobalt-transition metal (M) oxide (eg, Li (Ni _p2 Co _q2 Mn _r3 M _S2 ) O ₂ (wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are atomic fractions of the independent elements, respectively, 0 <p2 < 1, 0 <q2 <1, 0 <r3 <1, 0 <s2 <1, p2 + q2 + r3 + s2 = 1), and the like.

As the cathode active material, the lithium composite metal oxide may be LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , or lithium nickel cobalt aluminum oxide (eg, Li (Ni _0.8 Co _0.15 Al _0.05 ) O _2, etc.).

The cathode active material may be included in an amount of 90 wt% to 99 wt%, specifically 90 wt% to 95 wt%, based on the total weight of solids in the cathode slurry.

When the content of the positive electrode active material is 90% by weight or less, the energy density may be lowered and the capacity may be lowered.

The binder is a component that assists the bonding between the positive electrode active material and the conductive material and the current collector, and is generally added in an amount of 1 to 30 wt% based on the total weight of solids in the positive electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoro Low ethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers, and the like.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive material include carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. Carbon powder; Graphite powders such as natural graphite, artificial graphite, or graphite with very advanced crystal structure; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of solids in the positive electrode slurry.

The conductive material is Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, etc., Ketjenblack, EC series (Armak Company) Armak Company), Vulcan XC-72 (Cabot Company), and Super P (manufactured by Timcal) can also be used.

The solvent may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount that becomes a desirable viscosity when including the positive electrode active material and optionally a binder and a conductive material. For example, the concentration of the solids in the positive electrode active material and, optionally, the slurry including the binder and the conductive material may be 10 wt% to 70 wt%, preferably 20 wt% to 60 wt%.

In addition, the negative electrode may be prepared by forming a negative electrode mixture layer on the negative electrode current collector. The negative electrode mixture layer may be formed by coating a slurry including a negative electrode active material, a binder, a conductive material, a solvent, and the like on a negative electrode current collector, followed by drying and rolling.

The negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like on the surface, aluminum-cadmium alloy and the like can be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

In addition, the anode active material may be a lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of these metals and lithium, a metal composite oxide, and may dope and undo lithium. At least one selected from the group consisting of materials, and transition metal oxide transition metal oxides.

As the carbon material capable of reversibly intercalating / deintercalating the lithium ions, any carbon-based negative electrode active material generally used in a lithium ion secondary battery may be used without particular limitation. Examples thereof include crystalline carbon, Amorphous carbons or these may be used together. Examples of the crystalline carbon include graphite such as amorphous, plate, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, calcined coke, or the like.

The metals or alloys of these metals with lithium include Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al And a metal selected from the group consisting of Sn or an alloy of these metals with lithium may be used.

The metal complex oxide may include PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , Bi ₂ O ₅ , Li _x Fe ₂ O ₃ (0 ≦≦ _x ≦≦ 1), Li _x WO ₂ (0 ≦≦ _x ≦≦ 1), and Sn _x Me _1-x Me ' _y O _z (Me : Mn, Fe, Pb, Ge; Me ': Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 <x≤≤1;1≤≤y≤≤3; 1 ≦≦ z ≦≦ 8) may be used.

Examples of the material capable of doping and undoping lithium include Si, SiO _x (0 <x <2), Si-Y alloys (wherein Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, Is an element selected from the group consisting of rare earth elements and combinations thereof, not Si), Sn, SnO ₂ , Sn-Y (Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth) element and an element selected from the group consisting of, Sn and the like are not), and may also use a mixture of at least one of these with SiO _2. As the element Y, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, and the like.

The negative active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of solids in the negative electrode slurry.

The binder is a component that assists the bonding between the conductive material, the active material and the current collector, and is typically added in an amount of 1 to 30 wt% based on the total weight of solids in the negative electrode slurry. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, Polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers thereof, and the like.

The conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 1 to 20 wt% based on the total weight of solids in the negative electrode slurry. Such a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The solvent may include an organic solvent such as water or NMP, alcohol, etc., and may be used in an amount that becomes a desirable viscosity when including the negative electrode active material and optionally a binder and a conductive material. For example, the concentration of the solids in the slurry including the negative electrode active material and, optionally, the binder and the conductive material may be 50 wt% to 75 wt%, preferably 50 wt% to 65 wt%.

In addition, the lithium secondary battery of the present invention may further include a separator.

The separator is a conventional porous polymer film used in general lithium secondary batteries, for example, polyolefin-based such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer The porous polymer film made of a polymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. no.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, square, pouch type, or coin type using a can.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

Example 1.

(Non-aqueous electrolyte preparation)

Additive (Lithium difluorophosphate: tertiary butylbenzene) to 97.3 g of a non-aqueous organic solvent consisting of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (30:70 (vol%)) dissolved in 1.0 M LiPF ₆ : Tetravinylsilane = 1: 1.5: 0.2 weight ratio) 2.7g was mixed to prepare a non-aqueous electrolyte (see Table 1 below).

(Secondary Battery Manufacturing)

N-methyl-2-pyrroli as a solvent in a weight ratio of Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ as a positive electrode active material, carbon black as a conductive material and polyvinylidene fluoride as a binder in a 96: 2: 2 weight ratio The positive electrode active material slurry (solid content concentration 50% by weight) was prepared by adding it to pig (NMP). The positive electrode active material slurry was applied to an aluminum (Al) thin film, which is a positive electrode current collector having a thickness of about 20 μm, dried to prepare a positive electrode, and then roll rolled to prepare a positive electrode.

In addition, carbon powder (graphite) as a negative electrode active material, polyvinylidene fluoride as a binder and carbon black as a conductive material were added to NMP as a solvent in a 96: 3: 1 weight ratio to prepare a negative electrode active material slurry (solid content concentration of 60% by weight). It was. The negative electrode active material slurry was applied to a copper (Cu) thin film, which is a negative electrode current collector having a thickness of 10 μm, and dried to prepare a negative electrode, followed by roll press, to prepare a negative electrode.

Then, the positive electrode and the negative electrode thus prepared were laminated together with a polyethylene porous film to prepare an electrode assembly by a conventional method, and then put it in a battery case and inject the non-aqueous electrolyte, and then sealed to manufacture a lithium secondary battery. .

Example 2.

Except for including 97.4 g of the non-aqueous organic solvent in the step of preparing the non-aqueous electrolyte solution of Example 1 containing 2.6 g of an additive (weight ratio of lithium difluorophosphate: tertiary butylbenzene: tetravinylsilane = 1: 1.5: 0.1) In the same manner as in Example 1, a non-aqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Example 3.

Except for including 9 g of the non-aqueous organic solvent in the preparation step of Example 1, 4.5 g of an additive (lithium difluorophosphate: tertiary butylbenzene: tetravinylsilane = 1: 4: 0.5 weight ratio) In the same manner as in Example 1, a nonaqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Example 4.

Except that in the non-aqueous electrolyte preparation step of Example 1 97.5g of the non-aqueous organic solvent, 2.5g of additives (lithium difluorophosphate: tertiarybutylbenzene: tetravinylsilane = 1: 1: 0.05), In the same manner as in Example 1, a nonaqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Example 5.

In the non-aqueous electrolyte preparation step of Example 1, 96.8 g of the non-aqueous organic solvent includes 2.7 g of an additive (lithium difluorophosphate: tertiary butylbenzene: tetravinylsilane = 1: 1.5: 0.1), and propane sultone (PS A non-aqueous electrolyte and a secondary battery including the same were prepared in the same manner as in Example 1, except that 0.5 g was further included (see Table 1 below).

Example 6.

In the nonaqueous electrolyte preparation step of Example 5, except that 95.8 g of the non-aqueous organic solvent includes an additive 2.7 g, 0.5 g propane sultone (PS) as an additive for forming an SEI film, and 1 g of ethylene sulfate (Esa). In the same manner as in Example 5, a nonaqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Example 7.

2.7 g of an additive (lithium difluorophosphate: tertiary butylbenzene: tetravinylsilane = 1: 1.5: 0.1 weight ratio) to 95.3 g of the non-aqueous organic solvent in the non-aqueous electrolyte preparation step of Example 1, which is an additive for SEI film formation A non-aqueous electrolyte and a secondary battery including the same were prepared in the same manner as in Example 1, except that 0.5 g of vinylene carbonate, 0.5 g of propane sultone (PS), and 1 g of ethylene sulfate (Esa) were included. 1).

Comparative Example 1.

Example 1 and except that in the non-aqueous electrolyte preparation step of Example 1 92.5g of the non-aqueous organic solvent includes 2.5g of additives (lithium difluorophosphate: tertiary butylbenzene = 1: 1.5 weight ratio) In the same manner, a non-aqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Comparative Example 2.

The same method as in Example 1, except that 97.5 g of the non-aqueous organic solvent in the step of preparing the non-aqueous electrolyte solution includes 2.5 g of an additive (tertiarybutylbenzene: tetravinylsilane = 1.5: 0.1 weight ratio) To prepare a non-aqueous electrolyte and a secondary battery comprising the same (see Table 1 below).

Comparative Example 3.

Except for including 2.05 g of additive (lithium difluorophosphate: tertiary butylbenzene: tetravinylsilane = 1: 1: 0.05 weight ratio) to 97.95 g of the non-aqueous organic solvent in the non-aqueous electrolyte preparation step of Example 1 In the same manner as in Example 1, a nonaqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Comparative Example 4.

Except for including 5.5g of an additive (lithium difluorophosphate: tertiary butylbenzene: tetravinylsilane = 1: 4: 0.5 weight ratio) to 94.5g of the non-aqueous organic solvent in the nonaqueous electrolyte preparation step of Example 1 In the same manner as in Example 1, a nonaqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Comparative example  5.

9 g of the non-aqueous organic solvent in the non-aqueous electrolyte preparation step of Example 1, containing 0.5 g of an additive (weight ratio of lithium difluorophosphate: tertiary butylbenzene: tetravinylsilane tetravinylsilane = 1: 1.5: 0.1) Except that, a non-aqueous electrolyte and a secondary battery including the same were prepared in the same manner as in Example 1 (see Table 1 below).

Comparative Example 6.

Except for including 5.0 g of an additive (lithium difluorophosphate: tertiary butylbenzene: tetravinylsilane = 1: 1.5: 0.1 weight ratio) to 95 g of the non-aqueous organic solvent in the non-aqueous electrolyte preparation step of Example 1, In the same manner as in Example 1, a nonaqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Comparative Example 7.

Except for including 2.7 g of an additive (lithium difluorophosphate: tertiary butylbenzene: tetravinylsilane = 1: 0.8: 0.6 weight ratio) to 97.3 g of the non-aqueous organic solvent in the non-aqueous electrolyte preparation step of Example 1 In the same manner as in Example 1, a nonaqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Comparative Example 8.

Except for including 92.7 g of the non-aqueous organic solvent in the non-aqueous electrolyte preparation step of Example 1, 2.7 g of an additive (lithium difluorophosphate: tert-butylbenzene: tetravinylsilane = 1: 4.3: 0.04 weight ratio) In the same manner as in Example 1, a nonaqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Comparative Example 9.

In the non-aqueous electrolyte preparation step of Example 1, 2.6.g of an additive (lithium difluorophosphate: tertiary butylbenzene: tetravinylsilane = 1: 1.5: 0.1 weight ratio) was added to 97.4 g of the non-aqueous organic solvent, and a secondary battery was prepared. A nonaqueous electrolyte and a secondary battery including the same were prepared in the same manner as in Example 1, except that LiCoO ₂ was used as the cathode active material in the step (see Table 1 below).

Comparative Example 10.

In the step of preparing the non-aqueous electrolyte of Example 1, except that 97.5 g of the non-aqueous organic solvent includes 2.5 g of an additive (lithium difluorophosphate: tetravinylsilane = 1: 0.1 weight ratio), the same as in Example 1 By the method, a non-aqueous electrolyte and a secondary battery including the same were prepared (see Table 1 below).

Experimental Example

Experimental Example  1: Comparison of high temperature storage characteristics

Initial capacities of the secondary batteries prepared in Examples 1 to 7 and Comparative Examples 1 to 9 were measured. Subsequently, after storage at 60 ° C. for 12 weeks, the battery was charged at 1 C up to 4.25 V / 38 mA at CC / CV conditions at room temperature, and then discharged at 1 C up to 3.0 V under CC conditions, and the capacity after 12 weeks was measured. Capacity retention rate was calculated using Equation 1 below, and the results are shown in Table 1 below.

In addition, the initial resistance of the secondary batteries prepared in Examples 1 to 7 and Comparative Examples 1 to 9 were measured. Subsequently, after storing for 12 weeks at 60 ℃, discharge for 10 seconds from 50% SOC to 5C at room temperature, the resistance after 12 weeks was measured by the voltage difference generated. Using the following equation 2 to calculate the resistance increase rate, the results are shown in Table 1 below.

In addition, the initial thickness of the secondary batteries prepared in Examples 1 to 7 and Comparative Examples 1 to 9 was measured, and after changing the battery thickness after storage at 60 ° C. for 12 weeks, the thickness of the battery was obtained by using Equation 3 below. The rate of change was measured.

[Equation 1]

Capacity retention rate = (capacity after 12 weeks / initial capacity) × 100

[Equation 2]

Resistance growth rate = ((resistance after 12 weeks / initial resistance) × 100) -100

[Equation 3]

Battery thickness change rate = ((battery thickness after 12 weeks / battery thickness of 0 weeks) x 100) -100

Experimental Example  2: high temperature life characteristics comparison

The secondary batteries prepared in Examples 1 to 7 and Comparative Examples 1 to 9 were charged at 1C to 4.25V / 38mA at CC / CV conditions at 45 ° C., and then discharged at 1C to 3.0V under CC conditions. After 800 cycles of charging and discharging, the capacity of the secondary battery was measured. Subsequently, high temperature lifetime characteristics were calculated using Equation 4 below, and the results are shown in Table 1 below.

In addition, the resistance was measured using a voltage difference generated by discharging the secondary batteries prepared in Examples 1 to 7 and Comparative Examples 1 to 9 after discharge at 5 ° C. for 10 seconds at 50 ° C. at 50 ° C. after 800 cycles. . Next, the resistance change rate was calculated using Equation 5 below, and the results are shown in Table 1 below.

[Equation 4]

Capacity Retention Rate = (800 Cycles / 1 Cycle) × 100

[Equation 5]

Resistance Growth Rate = ((800 Cycle Resistance / Initial Cycle Resistance) × 100) -100

As shown in Table 1, the secondary batteries of Examples 1 to 7 have a capacity of 86% or more after high temperature storage, an increase in resistance was suppressed to less than 21.5%, and the increase in battery thickness was excellent at about 28.5% or less. Can be. In addition, it can be seen that the capacity after 800 cycles at a high temperature is maintained at 82% or more, and the increase in resistance is suppressed to less than 44%.

However, in the case of the secondary battery of Example 7, by containing a small amount of VC having a relatively low oxidation potential in the non-aqueous electrolyte, the CO ₂ is issued at the positive electrode during high temperature storage, the battery thickness is lower than the secondary batteries of Examples 1 to 6 It can be seen that the increase.

On the other hand, the secondary battery of Comparative Example 1, which does not include lithium difluorophosphate, and the secondary battery of Comparative Example 2, which does not contain tetravinylsilane, and the additives of the additive components, Comparative Examples 3 and 5 In the case of the secondary batteries of Comparative Examples 4 and 6, wherein the secondary batteries and the additive content of more than 4.5% by weight, compared with the lithium secondary batteries of Examples 1 to 7 with the nonaqueous electrolyte of the present invention, resistance after high temperature storage In addition to the increase rate and the cell thickness increase rate, it can be seen that most of them are degraded in most cases such as capacity retention rate and resistance increase rate after 800 cycles at high temperature.

In particular, the secondary battery of Comparative Example 7 in which a small amount of tertiaryalkylbenzene is included in the additive component, and the tetravinylsilane is included in a large amount, and the secondary battery of Comparative Example 8 in which a large amount of tertiary alkylbenzene is included and a small amount of tetravinylsilane is included. In the case of, compared with the lithium secondary batteries of Examples 1 to 7 with the nonaqueous electrolyte of the present invention, not only the resistance increase rate and battery thickness increase rate after high temperature storage, but also the capacity retention rate and resistance increase rate after 800 cycles at a high temperature are remarkably increased. It can be seen that the degradation.

In addition, in the case of the secondary battery of Comparative Example 9 using LCO instead of the ternary positive electrode active material as the positive electrode active material, compared with the secondary batteries of Examples 1 to 7, the resistance increase rate and battery thickness increase rate after high temperature storage, after 800 cycles at high temperature It can be seen that both the capacity retention rate and the resistance increase rate are deteriorated.

Experimental Example 3.

The secondary batteries prepared in Example 1 and Comparative Example 10 were each overcharged at a constant current / constant voltage (CC / CV) condition to 8.5 V at 1 C (775 mAh) / 12 V from a charged state at 25 ° C., and the temperature of the battery at that time and Voltage changes were measured and shown in FIGS. 1 and 2.

Referring to FIG. 1, the secondary battery of Example 1 delays a voltage increase caused by overcurrent while consuming electrons near 4.85V during overcharge, thereby suppressing the cell from overcharging (in FIG. 1).

Line). Therefore, it is possible to prevent the temperature of the secondary battery from rapidly increasing during overcharging (in FIG. 1).

Line). That is, it can be seen that the secondary battery of Example 1 gradually decreases after the temperature is increased to 130 ° C.

On the other hand, the secondary battery of Comparative Example 10 has a sudden temperature change from 4.8V portion (about 35 minutes) to 200 ℃ (Fig. 2

Line), the battery overheats, causing ignition and explosion. Therefore, it can be seen that the secondary battery of Comparative Example 10 cannot measure the voltage after the 4.8V portion (about 35 minutes) (see FIG. 2).

Line).

From these results, it can be seen that the stability of the secondary battery is lowered when tertiary benzene which is one of the additive components is not included in the nonaqueous electrolyte of the present invention.

Claims (11)

1. Ionizable lithium salts,

   Organic solvents, and

   Contains additives,

   The additive is a mixed additive containing lithium difluorophosphate, tertiary alkylbenzene represented by the following Chemical Formula 1, and tetravinylsilane in a weight ratio of 1: 1 to 4: 0.05 to 0.5,

   The additive is a non-aqueous electrolyte lithium secondary battery that will be included in 2.5 to 4.5% by weight based on the total weight of the non-aqueous electrolyte for lithium secondary battery.

   [Formula 1]

   

   In Chemical Formula 1,

   R ₁ is tertiary alkyl having 4 to 5 carbon atoms.
2. The method according to claim 1,

   The organic solvent is a non-aqueous electrolyte lithium secondary battery that is a mixed solvent containing at least two or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate and ethyl methyl carbonate.
3. The method according to claim 1,

   The lithium difluorophosphate: tertiary alkylbenzene represented by the formula (1): the weight ratio of tetravinylsilane is 1: 1.5 to 4: 0.1 to 0.2 non-aqueous electrolyte for lithium secondary battery.
4. The method according to claim 1,

   The concentration of the lithium difluoro phosphate in the non-aqueous electrolyte for lithium secondary batteries is 1 × 10 ^-2 mol / kg to 0.5 mol / kg nonaqueous electrolyte for lithium secondary batteries.
5. The method according to claim 1,

   The additive is a non-aqueous electrolyte lithium secondary battery that is contained in a 2.5 to 4.3% by weight based on the total weight of the non-aqueous electrolyte for lithium secondary battery.
6. The method according to claim 1,

   The non-aqueous electrolyte for lithium secondary batteries may further include at least one additive for forming an SEI film selected from the group consisting of vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate, ethylene sulfate (Esa) and propane sultone (PS). Non-aqueous electrolyte solution for lithium secondary batteries containing.
7. The method according to claim 6,

   The additive for forming the SEI film is a non-aqueous electrolyte solution for a lithium secondary battery that is contained in at least 0.1% by weight to 2% by weight based on the total weight of the nonaqueous electrolyte.
8. In a lithium secondary battery comprising a negative electrode containing a negative electrode active material, a positive electrode containing a positive electrode active material and a nonaqueous electrolyte,

   The positive electrode active material includes at least one or more of a compound represented by Formula 4 and a compound represented by Formula 5 below,

   The non-aqueous electrolyte is a lithium secondary battery comprising a non-aqueous electrolyte for lithium secondary battery of claim 1.

   [Formula 4]

   Li (Ni _x Co _y Mn _z ) O ₂

   In Chemical Formula 4,

   0 <x <1, 0 <y <1, 0 <z <1, x + y + z = 1.

   [Formula 5]

   Li (Ni _x1 Co _y1 Mn _z1 ) O ₄

   In Chemical Formula 5,

   0 <x1 <2, 0 <y1 <2, 0 <z1 <2, and x1 + y1 + z1 = 2.
9. The method according to claim 8,

   The cathode active material is Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ , A lithium secondary battery comprising one selected from the group consisting of Li (Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ , Li (Ni _0.7 Mn _0.15 Co _0.15 ) O ₂ , and Li (Ni _0.8 Mn _0.1 Co _0.1 ) O ₂ .
10. The method according to claim 8,

    The cathode active material further comprises a compound represented by the following formula (6).

    [Formula 6]

    LiMnO ₂
11. The method according to claim 10,

    The positive active material is a lithium secondary battery comprising 80% to 99% by weight of the compound represented by Formula 4 or 5 and 1% to 20% by weight of the compound represented by Formula 6.

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