KR20220109338A - Non-aqueous electrolyte for secondary battery and secondary battery comprising the same - Google Patents

Abstract

The present invention provides a non-aqueous electrolyte for a lithium secondary battery capable of forming a robust SEI film and a lithium secondary battery having improved battery performance by including the same. Specifically, the non-aqueous electrolyte for the secondary battery may include: a lithium salt; a non-aqueous organic solvent; a first additive; and a second additive, wherein the first additive comprises an oligomer including a repeating unit derived from a monomer represented by chemical formula 1 and a repeating unit derived from a monomer represented by chemical formula 2, and the second additive comprises at least one selected from a group consisting of a nitrile-based compound, a lithium salt compound, and a cyclic carbonate compound.

Description

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

The present invention provides a non-aqueous electrolyte for a lithium secondary battery and a lithium secondary battery comprising the same.

Dependence on electric energy is increasing in modern society, and accordingly, the production of electric energy is further increasing. In order to solve the environmental problems that occurred during this process, new and renewable energy generation is in the spotlight as a next-generation power generation system.

In the case of such renewable energy, since it exhibits intermittent power generation characteristics, a large-capacity power storage device is essential in order to stably supply power. Among these power storage devices, lithium ion batteries are in the spotlight as devices with the highest energy density that have been commercialized.

A lithium ion battery consists of a positive electrode made of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte solution containing an organic solvent containing lithium salt, and a separator.

Since the double anode stores energy through the redox reaction of the transition metal, it is concluded that the transition metal oxide must be included. In addition, the negative electrode includes lithium, graphite and/or silicon-based active material capable of expressing charge/discharge capacity through an electrochemical oxidation/reduction reaction at 0.2 V or 0.5 V (vs. (Li/Li+)) or less, respectively.

Meanwhile, since the operating voltage range of the lithium, graphite, and silicon-based active materials is lower than the electrochemical stability window of the organic non-aqueous electrolyte, the organic non-aqueous electrolyte becomes electrochemically unstable in the operating voltage range of the negative active material. As a result, as the reductive decomposition of the non-aqueous electrolyte occurs prior to it, a passivation layer that is a reductive decomposition product of the non-aqueous electrolyte, that is, a solid electrolyte interphase (SEI) film, is formed on the electrode surface.

The SEI is a passivation layer with high lithium ion conductivity but low electron conductivity, and not only suppresses additional electrolyte reduction and decomposition, but also transmits lithium ions but inhibits electron permeation. have

However, the SEI is damaged when exposed to high temperatures for a long time and loses its passivation ability, and as a result, additional electrolyte decomposition occurs and additionally consumes lithium and electrons inside the cell, so the electrochemical performance of the cell deteriorates, or the inside of the cell A thermal runaway is caused by the increase in temperature.

In addition, as the positive electrode active material structurally collapses during repeated charging and discharging, the performance of the positive electrode is deteriorated. That is, when the structure of the anode is collapsed, metal ions eluted from the surface of the anode are electro-deposited on the cathode, thereby deteriorating the performance of the battery. This deterioration of battery performance tends to be accelerated when the potential of the positive electrode increases or the battery is exposed to high temperatures.

In order to improve these various problems, there is an urgent need to develop a non-aqueous electrolyte for a lithium secondary battery that can improve the performance and stability of a secondary battery by forming a strong film on the electrode surface even in a high-temperature environment.

US Patent Publication No. 2020-0203763

The present invention is to solve the above problems, and by including an oligomer containing an acrylate-based cyanide (-CN, cyanide) functional group as an additive and a compound capable of improving the film formation effect, high temperature stability is improved An object of the present invention is to provide a non-aqueous electrolyte for a lithium secondary battery.

In addition, the present invention is to provide a lithium secondary battery comprising the non-aqueous electrolyte for a lithium secondary battery.

According to one embodiment, the present invention

lithium salt; non-aqueous organic solvents; a first additive; and a second additive,

An oligomer comprising a repeating unit derived from a monomer represented by the following formula (1) and a repeating unit derived from a monomer represented by the following formula (2) as the first additive,

It provides a non-aqueous electrolyte for a lithium secondary battery comprising at least one selected from the group consisting of a nitrile compound, a lithium salt compound, and a cyclic carbonate compound as the second additive.

[Formula 1]

In Formula 1,

R' is hydrogen or an alkyl group having 1 to 3 carbon atoms,

R ₁ is an alkylene group having 1 to 20 carbon atoms or -(R ₂ ) _o O(R ₃ ) _p -, wherein R ₂ and R ₃ are each independently an alkylene group having 1 to 20 carbon atoms, and o is 1 to It is an integer of 3, and p is an integer of 0-3.

[Formula 2]

In Formula 2,

R" is hydrogen or an alkyl group having 1 to 3 carbon atoms,

R ₄ is an alkylene group having 1 to 10 carbon atoms,

R ₅ is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms.

According to another embodiment, the present invention

a positive electrode including a positive active material;

a negative electrode including an anode active material;

a separator interposed between the negative electrode and the positive electrode; and

A lithium secondary battery comprising the non-aqueous electrolyte for a secondary battery of the present invention is provided.

The non-aqueous electrolyte for a lithium secondary battery of the present invention includes an oligomer including a repeating unit having an acrylate-based cyanide functional group as a first additive, thereby forming a strong film on the surface of the positive electrode, Side reactions can be suppressed.

In addition, the non-aqueous electrolyte of the present invention includes a second additive capable of forming a stable film on the surface of the anode together with the first additive, thereby forming a solid passivation film with improved stability and durability on the surface of the anode to form a side reaction between the anode and the electrolyte can be prevented, and the effect of suppressing an increase in resistance can be realized.

When the non-aqueous electrolyte of the present invention is included, a lithium secondary battery with improved cycle characteristics and high temperature stability can be realized.

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

The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

Meanwhile, in the present invention, unless otherwise specified, "*" means a connected portion between the main chain of the oligomer or the terminal ends of the chemical formula.

In the present invention, the term 'substitution' means that a hydrogen atom bonded to a carbon atom of a compound is replaced with another substituent, and the position to be substituted is not limited as long as the position at which the hydrogen atom is substituted, that is, a position where the substituent is substitutable. In the above substitution, two or more substituents may be substituted, wherein the two or more substituents may be the same as or different from each other. The substituent is oxygen; at least one halogen group; nitrile group; nitro group; hydroxyl group; an alkyl group having 1 to 5 carbon atoms; cycloalkyl group; aryl group; and at least one selected from a heterocyclic group, or may include a structure in which two or more substituents among the exemplified substituents are connected to each other. Specifically, the substituent is at least one halogen group; It may be a hydroxyl group or an alkyl group having 1 to 5 carbon atoms.

In addition, in this specification, when "includes", "includes", "'consists of" or "have" is used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the case in which the plural is included is included unless specifically stated otherwise.

In this specification, "%" means % by weight unless otherwise explicitly indicated.

Non-aqueous electrolyte for secondary batteries

The non-aqueous electrolyte for a secondary battery according to the present invention is

lithium salt; non-aqueous organic solvents; a first additive; and a second additive;

An oligomer comprising a repeating unit derived from a monomer represented by the following formula (1) and a repeating unit derived from a monomer represented by the following formula (2) as the first additive,

The second additive may include at least one selected from the group consisting of a nitrile compound, a lithium salt compound, and a cyclic carbonate compound.

[Formula 1]

In Formula 1,

R' is hydrogen or an alkyl group having 1 to 3 carbon atoms,

R ₁ is an alkylene group having 1 to 20 carbon atoms or -(R ₂ ) _o O(R ₃ ) _p -, wherein R ₂ and R ₃ are each independently an alkylene group having 1 to 20 carbon atoms, and o is 1 to It is an integer of 3, and p is an integer of 0-3.

[Formula 2]

In Formula 2,

R" is hydrogen or an alkyl group having 1 to 3 carbon atoms,

R ₄ is an alkylene group having 1 to 10 carbon atoms,

R ₅ is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms.

(A) lithium salt

First, the lithium salt will be described.

As the lithium salt, those commonly used in electrolytes for lithium secondary batteries may be used without limitation, for example, including Li ⁺ as a cation and F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , B ₁₀ Cl ₁₀ ^- , AlCl ₄ ^- , AlO ₄ ^- , PF ₆ ^- , CF ₃ SO ₃ ^- , CH ₃ CO ₂ ^- , CF ₃ CO ₂ ^- , AsF ₆ ^- , SbF ₆ ^- , CH ₃ SO ₃ ^- , (CF ₃ CF ₂ SO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , 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 ^- , C ₄ F ₉ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- and SCN ^- may be at least one selected from the group consisting of.

Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF ₄ , LiClO ₄ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiAlO ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiCH ₃ SO ₃ , LiN(SO ₂ F) ₂ (Lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO ₂ CF ₂ CF ₃ ) ₂ (lithium bis(pentafluoroethanesulfonyl) imide, LiBETI) and LiN( SO ₂ CF ₃ ) ₂ (lithium bis(trifluoromethanesulfonyl) imide, LiTFSI) may include a single material or a mixture of two or more selected from the group consisting of, in particular, LiPF ₆ having high ionic conductivity, including at least one selected from LiFSI and LiTFSI can do.

The lithium salt may be appropriately changed within the range that can be used in general, but to be included in the electrolyte at a concentration of 0.8M to 4.0M, specifically, at a concentration of 1.0M to 3.0M, in order to obtain an optimal effect of forming a film for preventing corrosion of the electrode surface. can

When the concentration of the lithium salt is within the above range, the viscosity of the non-aqueous electrolyte can be controlled to realize optimal impregnation property, and the mobility of lithium ions can be improved to obtain the effect of improving the capacity characteristics and cycle characteristics of the lithium secondary battery. .

(B) non-aqueous organic solvent

In addition, the description of the non-aqueous organic solvent is as follows.

As the non-aqueous organic solvent, various organic solvents commonly used in non-aqueous electrolytes can be used without limitation, and decomposition due to oxidation reaction in the charging/discharging process of the secondary battery can be minimized, and desired properties can be exhibited together with additives. As long as it is possible, there is no limit to its type.

Specifically, the non-aqueous organic solvent may include (i) a cyclic carbonate-based organic solvent, (ii) a linear carbonate-based organic solvent, (iii) a linear ester-based organic solvent, or a mixed organic solvent thereof.

The (i) cyclic carbonate-based organic solvent is a high-viscosity organic solvent that well dissociates lithium salts in a non-aqueous electrolyte due to a high dielectric constant, and specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, At least one organic solvent selected from the group consisting of 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate and vinylene carbonate, among them, ethylene carbonate and propylene It may include at least one of carbonates.

The (ii) linear carbonate-based organic solvent is an organic solvent having a low viscosity and a low dielectric constant, and specific examples thereof include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC) , may include at least one selected from the group consisting of methylpropyl carbonate and ethylpropyl carbonate, and specifically may include one of dimethyl carbonate and ethylmethyl carbonate.

The (iii) linear ester-based organic solvent is a solvent with high stability during high-temperature and high-voltage driving compared to the cyclic carbonate-based organic solvent, and while improving the disadvantages of the cyclic carbonate-based organic solvent causing gas generation during high-temperature driving , high ionic conductivity can be realized.

The (iii) linear ester-based organic solvent is a representative example of at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate. and a solvent, and specifically may include at least one of ethyl propionate and propyl propionate.

In addition, the present invention may further include (iv) a cyclic ester-based organic solvent, if necessary, in order to prepare an electrolyte having a high ionic conductivity.

The (iv) cyclic ester-based organic solvent may include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone. .

Meanwhile, in the non-aqueous electrolyte of the present invention, the remainder except for the lithium salt and the first and second additives may be all non-aqueous organic solvents, unless otherwise stated.

(C) first additive

The non-aqueous electrolyte for a lithium secondary battery of the present invention may include an oligomer including an acrylate-based cyanide (-CN, cyanide) functional group as the first additive.

Specifically, the oligomer may include a repeating unit derived from a monomer represented by Formula 1 below and a repeating unit derived from a monomer represented by Formula 2 below.

[Formula 1]

In Formula 1,

R' is hydrogen or an alkyl group having 1 to 3 carbon atoms,

R ₁ is an alkylene group having 1 to 20 carbon atoms or -(R ₂ ) _o O(R ₃ ) _p -, wherein R ₂ and R ₃ are each independently an alkylene group having 1 to 20 carbon atoms, and o is 1 to It is an integer of 3, and p is an integer of 0-3.

[Formula 2]

In Formula 2,

R" is hydrogen or an alkyl group having 1 to 3 carbon atoms,

R ₄ is an alkylene group having 1 to 10 carbon atoms,

R ₅ is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms.

Specifically, since the oligomer of the present invention includes a repeating unit including a cyanide group (-CN, nitrile group) having a strong bonding force with a metal ion as an acrylate main chain and a terminal functional group, the electrode surface, especially the anode surface, and strong A bond can be formed to form a stable film. In addition, since the cyanide group has a high tendency to adsorb with metal ions eluted from the positive electrode by the secondary battery charging/discharging process or the chemical dissolution reaction of the electrolyte, the effect of inhibiting the elution of metal ions from the positive electrode, that is, inhibiting the generation of metal ions inside the battery The effect is excellent. Therefore, high temperature durability, high temperature storage characteristics, and high temperature stability of the secondary battery can be improved.

The oligomer included as the first additive in the present invention may include an oligomer represented by Formula 3 below.

[Formula 3]

In Formula 3,

R' and R" are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms,

R ₁ is an alkylene group having 1 to 10 carbon atoms or -(R ₂ ) _o O(R ₃ ) _p -, R ₂ and R ₃ are each independently an alkylene group having 1 to 10 carbon atoms, and o is 1 to 3 an integer, p is an integer from 0 to 3,

R ₄ is an alkylene group having 1 to 10 carbon atoms,

R ₅ is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms,

The mole ratio of n:m is 1:99 to 99:1.

On the other hand, in the oligomer of the present invention, "*" refers to a portion connected between the main chain of the oligomer or the terminal portions of the chemical formula, and both terminal groups of the oligomer may be the same or different from each other. Specifically, the ends of the oligomer are each independently an alkyl group, an alkoxy group, a hydroxyl group, an aldehyde group, an ester group, a halogen group, a halide group, a vinyl group, a (meth)acrylate group, a carboxyl group, a phenyl group, an amine group, an amide group, or It may be a sulfonyl group, and specifically, the terminal group may be an alkyl group having 1 to 5 carbon atoms.

Specifically, in Formula 3, R' and R" are each independently hydrogen or an alkyl group having 1 or 2 carbon atoms, and R ₁ is an alkylene group having 1 to 6 carbon atoms or -(R ₂ ) _o O(R ₃ ) _p -, R ₂ and R ₃ are each independently an alkylene group having 1 to 6 carbon atoms, o is an integer of 1 to 3, p is an integer of 0 to 3, R ₄ is an alkylene group having 1 to 6 carbon atoms, , R ₅ is an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, a heteroaryl group having 3 to 8 carbon atoms, or a cycloalkyl group having 3 to 8 carbon atoms, and the mole ratio of n:m is 20:80 to 90: It can be 10.

In addition, in Formula 3, R' and R" are each independently hydrogen or an alkyl group having 1 or 2 carbon atoms, and R ₁ is an alkylene group having 1 to 6 carbon atoms or -(R ₂ ) _o O(R ₃ ) _p - and R ₂ and R ₃ are each independently an alkylene group having 1 to 6 carbon atoms, o is an integer of 1 to 3, p is an integer of 0 to 3, R ₄ is an alkylene group having 1 to 6 carbon atoms, R ₅ is an aryl group having 6 to 8 carbon atoms, a heteroaryl group having 3 to 8 carbon atoms, or a cycloalkyl group having 3 to 8 carbon atoms, and the mole ratio of n:m may be 30:70 to 90:10.

More specifically, the oligomer represented by Chemical Formula 3 may include at least one selected from the group consisting of oligomers represented by the following Chemical Formulas 3A to 3F.

[Formula 3A]

In Formula 3A,

The mole ratio of n1:m1 is 1:99 to 99:1.

[Formula 3B]

In Formula 3B,

The mole ratio of n2:m2 is 1:99 to 99:1.

[Formula 3C]

In Formula 3C,

The mole ratio of n3:m3 is 1:99 to 99:1.

[Formula 3D]

In Formula 3D,

The mole ratio of n4:m4 is 1:99 to 99:1.

[Formula 3E]

In Formula 3E,

The mole ratio of n5:m5 is 1:99 to 99:1.

[Formula 3F]

In Formula 3F,

The mole ratio of n6:m6 is 1:99 to 99:1.

The weight average molecular weight (Mw) of the oligomer of the present invention can be controlled by the number of repeating units, and is about 1,000 g/mol to 1,500,000 g/mol, specifically 2,000 g/mol to 1,200,000 g/mol, more specifically 5,000 g/mol to 500,000 g/mol. When the weight average molecular weight of the oligomer is within the above range, affinity with the solvent of the non-aqueous electrolyte can be secured, and a uniform non-aqueous electrolyte with high ionic conductivity can be prepared.

The weight average molecular weight may be measured using a gel permeation chromatography (GPC) apparatus, and unless otherwise specified, the molecular weight may mean a weight average molecular weight. For example, in the present invention, measurement is performed using Agilent's 1200 series under GPC conditions, and the column used at this time may be Agilent's PL mixed B column, and the solvent may be THF.

In addition, the oligomer of the present invention may be included in an amount of 0.1 wt% to 5.0 wt% based on the total weight of the non-aqueous electrolyte for a lithium secondary battery.

When the oligomer content is included in the above range, it is possible to obtain the effect of improving stability and high temperature performance. Specifically, when the oligomer content is 0.1% by weight or more, stable film formation and flame retardant properties expression effects can be realized, and when the oligomer content is 5.0% by weight or less, it is possible to prevent a decrease in ionic conductivity of the non-aqueous electrolyte for lithium secondary batteries, and the surface It is possible to prevent the formation of a non-uniform film or increase of side reactions. In addition, since it is possible to prevent a decrease in moisture content by suppressing an increase in the viscosity of the non-aqueous electrolyte for a lithium secondary battery, the decrease in capacity characteristics can be improved.

Specifically, the oligomer of the present invention may be included in an amount of 0.1 wt% to 3.0 wt% based on the total weight of the non-aqueous electrolyte for a lithium secondary battery.

(D) second additive

The non-aqueous electrolyte for a lithium secondary battery of the present invention may further include a second additive to be mixed with the oligomer included as the first additive to bring about a synergistic effect of improving the film-forming effect on the electrode surface.

The second additive may include at least one selected from the group consisting of a nitrile compound, a lithium salt compound, and a cyclic carbonate compound.

(D-1) Nitrile compound

The non-aqueous electrolyte for a lithium secondary battery of the present invention may include a nitrile-based compound as a second additive.

The nitrile-based compound can improve the safety of the non-aqueous electrolyte due to low volatility of the solvent, such as being in a solid form at room temperature, and reduces the reaction between the electrode and the non-aqueous electrolyte by forming a uniform and strong film on the positive and negative electrodes when driving the battery By doing so, the durability and high rate charge/discharge characteristics of the battery can be improved.

The nitrile-based compound may include a compound including at least one cyanide group (-CN, nitrile group) as a terminal functional group, and specifically, succinonitrile (SN), adiponitrile (1,4-dicy Anobutane or 1,6-hexanedinitrile), dicyanobutene (DCB), ethylene glycol bis(propionitrile) ether, hexanetricarbonitrile (HTCN), acetonitrile, propionitrile, butyronitrile, valero Nitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2 -Fluorophenylacetonitrile and 4-fluorophenylacetonitrile, which may contain at least one selected from the group consisting of, more specifically, succinonitrile, which can serve as a complement to form a more stable SEI on the surface of the anode; It may include at least one selected from the group consisting of adiponitrile, dicyanobutene, ethylene glycol bis (propionitrile) ether, and hexane tricarbonitrile (HTCN).

The nitrile-based compound may be included in an amount of 0.01 to 100 parts by weight based on 1 part by weight of the oligomer as the first additive.

When the nitrile-based compound is included in the above content range, a stable and robust SEI film can be formed on the surface of the anode, and non-uniform film formation due to excessive use of additives, side reactions and resistance increase due to cathode reduction reaction, etc. are caused Since it can be suppressed, the effect of improving high temperature performance and stability can be exhibited.

Specifically, the weight ratio of the oligomer and the nitrile-based compound as the first additive may be 1:0.05 to 1:50 by weight, more specifically, 1:0.1 to 1:30 by weight.

(D-2) lithium salt compound

The non-aqueous electrolyte for a lithium secondary battery of the present invention may include a lithium salt compound as a second additive.

The lithium salt compound is a different compound from the lithium salt contained in the non-aqueous electrolyte, and forms a uniform and strong film on the positive and negative electrodes when the battery is driven, thereby reducing the side reaction between the electrode and the non-aqueous electrolyte, thereby preventing the decomposition of the solvent in the non-aqueous electrolyte. It may contain a compound having the form of a lithium salt capable of inhibiting it. By including such a lithium salt compound, the mobility of lithium ions can be improved, the durability of the battery can be improved, and the high-rate charge-discharge characteristics of the battery can be improved.

The lithium salt compound may be divided into (i) phosphate-based lithium and (ii) boron-based lithium.

The (i) phosphate-based lithium may include lithium difluorophosphate (LiDFP) or lithium difluorobis(oxalato)phosphate (LiDFOP).

Further, the (ii) boron-based lithium may be divided into (ii-1) boron halide-based lithium and (ii-2) boron oxalate-based lithium.

The boron halide-based lithium (ii-1) may include lithium tetrafluoroborate (LiBF ₄ ) or lithium tetrachloro borate (LiBCl ₄ ), and specifically lithium tetrafluoroborate (LiBF ₄ ). .

The (ii-2) boron oxalate-based lithium is lithium bis(oxalato) borate (LiBOB), lithium difluoro(oxalato) borate (lithium difluoto(oxalato) borate, LiODFB) , or lithium dichloro(oxalato)borate (LiODCB), especially in consideration of the optimization of high-temperature storage characteristics and lifespan characteristics, lithium bis(oxalato)borate (LiBOB) or lithium difluoro(oxalato) ) borate (LiODFB).

Specifically, the lithium salt compound is lithium difluorophosphate (LiDFP), lithium difluorobis (oxalato) phosphate (LiDFOP), LiBF ₄ , lithium bis (oxalato) borate (LiBOB), lithium difluoro It may include at least one selected from lo(oxalato)borate (LiODFB), and more specifically, lithium bis(oxalato)borate (LiBOB) and lithium difluoro(oxalato)borate (LiODFB). It may include at least one.

The non-aqueous electrolyte for a secondary battery of the present invention stabilizes the SEI film of the positive electrode and the negative electrode by mixing the lithium salt compound that can help form the negative electrode film together with the oligomer, so that the lithium secondary battery has high-rate charge-discharge characteristics and high-temperature storage characteristics , and overall performance such as life characteristics can be improved.

Meanwhile, when a lithium salt compound is included as the second additive, the lithium salt compound may be included in a weight ratio of 0.01 to 1:100 based on 1 part by weight of the oligomer as the first additive.

When the lithium salt compound is included in the content range, the ring (bond) is broken through an oxidation reaction, and radicals produced as by-products are further reacted with other cyclic carbonates, and in this process, a polymerization reaction proceeds and , it is possible to form a stable film on the surface of the anode while reacting to this mechanism.

Specifically, in order to prevent side reactions caused by the lithium salt compound remaining after film formation, the lithium salt compound is preferably included in an amount of 100 weight ratio or less, specifically 70 weight ratio or less. When the content of the lithium salt compound exceeds 100 weight ratio, since radicals generated in the reduction process cause side reactions such as the copolymer electrolyte, performance degradation may occur. In addition, the result of these side reactions may be accumulated on the electrode film to increase the resistance in the cell, or may cause deterioration such as high rate, high temperature durability and cycle characteristics due to decomposition of the electrolyte and additives.

In addition, the lithium salt compound is preferably included in a weight ratio of 0.01 or more in order to secure the amount of radicals. If the lithium salt compound is included in an amount of less than 0.01 weight ratio, the amount of radicals generated in the process of forming the film by the lithium salt compound is absolutely insufficient, and accordingly, the chain reaction for forming the film is lowered to cause defects on the surface of the film. As this occurs, performance degradation is affected.

Specifically, the first additive oligomer and lithium salt compound may be included in a weight ratio of 1:0.1 to 1:70.

(D-3) Cyclic carbonate-based compound

The non-aqueous electrolyte for a lithium secondary battery of the present invention may include a cyclic carbonate-based compound different from the non-aqueous organic solvent as the second additive.

The cyclic carbonate-based compound is an additive that can help in film formation together with the oligomer, and since it is possible to form a stable film by the double bond contained in the cyclic structure while being reduced on the surface of the anode, the electrolyte solution caused during the process of forming the cathode film It is effective in suppressing side reactions and gas generation. The film formed on the cyclic carbonate-based compound may affect lifespan and high temperature durability improvement.

The cyclic carbonate-based compound may include at least one selected from the group consisting of vinylene carbonate (VC), vinylethylene carbonate (VEC) and fluoroethylene carbonate (FEC), as a representative example thereof, and more specifically, vinylethylene carbonate ( VEC) and fluoroethylene carbonate (FEC).

Since the fluoroethylene carbonate can form a thin anode film compared to other fluorine-substituted or unsubstituted cyclic carbonate-based compounds, it is possible to lower the resistance in the cell, and thus is more effective in improving performance. In addition, since fluoroethylene carbonate can inhibit the reduction reaction of ethylene carbonate used as a non-aqueous organic solvent, it can help improve cycle characteristics. Therefore, the uniform and strong film formed thereby reduces the reaction between the electrode and the non-aqueous organic solvent, thereby further improving the durability and high-rate charge/discharge characteristics of the battery.

When the cyclic carbonate-based compound is included as the second additive, the cyclic carbonate-based compound may be included in an amount of 0.001 to 150 parts by weight based on 1 part by weight of the oligomer as the first additive.

When the cyclic carbonate-based compound is included in the above content ratio, it is possible to form a stable and robust SEI film on the surface of the anode, and non-uniform film formation due to excessive use of additives, side reactions and resistance increase due to cathode reduction reaction, etc. are caused Since it can be suppressed, the effect of improving high temperature performance and stability can be exhibited. That is, when the content of the cyclic carbonate-based compound is greater than or equal to 0.001 by weight, it is possible to form a stable film on the surface of the negative electrode, and the effect of improving high temperature life and safety may be exhibited. In addition, when the content of the cyclic carbonate-based compound is 150 weight ratio or less, it does not cause problems such as non-uniform film formation due to excessive use, prevention of side reactions due to cathodic reduction reaction and increase in resistance, and high temperature performance and safety can be improved.

Specifically, the weight ratio of the first additive oligomer and the cyclic carbonate-based compound may be 1:0.05 to 1:50 by weight, more specifically, 1:0.1 to 1:30 by weight.

The second additive may be used in an amount of less than 11 wt % based on the total weight of the non-aqueous electrolyte, and the relative weight ratio of the second additive to the first oligomer may be appropriately adjusted according to each type of the second additive.

As described above, the non-aqueous electrolyte for a lithium secondary battery of the present invention mixes with an acrylate-based oligomer including a cyanide terminal functional group and a second additive that can help to form a film, so that the surface of the positive electrode and the negative electrode Since more stable SEI can be formed, overall performance such as high-rate charge-discharge characteristics, high-temperature storage characteristics, and lifespan characteristics of the lithium secondary battery can be improved.

(E) third additive

In addition, the non-aqueous electrolyte for a lithium secondary battery of the present invention prevents the anode from decaying due to decomposition of the non-aqueous electrolyte in a high-output environment, or has low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and battery expansion inhibition effect at high temperature. For improvement, a third additive may be further included as needed.

Examples of the third additive include at least one selected from the group consisting of a sultone-based compound, a sulfate-based compound, a phosphate-based or phosphite-based compound, a benzene-based compound, an amine-based compound, and a silane-based compound.

The sultone-based compound is, for example, 1,3-propane sultone (PS), 1,4-butane sultone, ethenesultone, 1,3-propene sultone (PRS), 1,4-butene sultone and 1- It may be at least one compound selected from the group consisting of methyl-1,3-propene sultone.

The sulfate-based compound may be, for example, ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

The phosphate or phosphite compound is, for example, lithium difluoro (bisoxalato) phosphate, lithium difluorophosphate, tris (trimethylsilyl) phosphate, tris (trimethylsilyl) phosphite, tris (2) It may be at least one compound selected from the group consisting of ,2,2-trifluoroethyl) phosphate and tris (trifluoroethyl) phosphite.

The benzene-based compound may be fluorobenzene or the like, the amine-based compound may be triethanolamine or ethylenediamine, and the silane-based compound may be tetravinylsilane.

The third additive may be used by mixing two or more types of compounds, and may be included in an amount of 10% by weight or less based on the total weight of the non-aqueous electrolyte in order to prevent a side reaction with an excessive amount of the additive.

lithium secondary battery

Next, a lithium secondary battery according to the present invention will be described.

Lithium secondary battery according to the present invention

a positive electrode including a positive active material;

a negative electrode including an anode active material;

a separator interposed between the negative electrode and the positive electrode; and

Includes the non-aqueous electrolyte solution for a lithium secondary battery of the present invention described above.

The lithium secondary battery of the present invention can be manufactured by forming an electrode assembly in which a positive electrode, a negative electrode, and a separator are sequentially stacked between the positive and negative electrodes, stored in a battery case, and then adding the non-aqueous electrolyte of the present invention.

The method for manufacturing the lithium secondary battery of the present invention may be manufactured and applied according to a conventional method known in the art, and will be described in detail below.

(1) Anode

The positive electrode according to the present invention may include a positive electrode active material layer including a positive electrode active material, and if necessary, the positive electrode active material layer may further include a conductive material and/or a binder.

The positive active material is a compound capable of reversible intercalation and deintercalation of lithium, and is specifically made of nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe) and aluminum (Al). It may include at least one metal selected from the group and lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel or aluminum containing lithium, and in particular, having a high Ni content of 0.55 or more. Ni may include a lithium composite metal oxide.

Specifically, the positive active material is a representative example Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.20 Co _0.10 )O ₂ , Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ , Li(Ni _0.8 Co _0.15 Al _0.05 )O ₂ , Li(Ni _0.86 Mn _0.07 Co _0.05 Al _0.02 )O ₂ or Li(Ni _0.90 Mn _0.05 Co _0.05 )O ₂ etc. are mentioned.

On the other hand, in the case of the lithium composite metal oxide having a high Ni content, despite the advantage of realizing a high-capacity battery, Ni ²⁺ cations are eluted from the positive electrode into the non-aqueous electrolyte, and the Ni ²⁺ cations are the passivation film of the negative electrode ( SEI) reacts to decompose the SEI film, and as a result, a portion of the negative electrode active material is exposed to the non-aqueous electrolyte and a side reaction occurs, thereby reducing capacity and lifespan characteristics and increasing resistance. Accordingly, in the case of a lithium metal composite oxide having a high Ni content, despite the advantage of realizing a high-capacity battery, the lifespan characteristics of the battery may be deteriorated and resistance may be increased. In addition, in the case of the high-content Ni positive electrode active material, the transition metal elution may be accelerated by acceleration of structural collapse of the positive electrode due to exposure to high temperature, etc., and in particular, it may be accelerated when HF or the like is present in the non-aqueous electrolyte.

Therefore, in order to solve this problem, the lithium secondary battery of the present invention contains a lithium salt compound together with an oligomer containing an acrylate-based cyanide terminal functional group as a non-aqueous electrolyte component for a lithium secondary battery, and thus, on the electrode surface. By forming a strong film, side reactions of the electrolyte can be suppressed, and further deterioration of high-temperature durability, high-temperature capacity, and lifespan characteristics of the lithium secondary battery can be prevented.

In addition, the positive active material may include, if necessary, a lithium-manganese-based oxide (eg, LiMnO ₂ , LiMn ₂ O ₄ , etc.), a lithium-cobalt-based oxide (eg, LiCoO ₂ , etc.) in addition to the lithium metal composite oxide as described above. ), lithium-nickel-based oxides (eg, LiNiO ₂ , etc.), lithium-nickel-manganese oxides (eg, LiNi _1-Y Mn _Y O ₂ (0<Y<1), LiMn _2-z Ni _z O ₄ (0<Z<2), lithium-nickel-cobalt oxide (eg, LiNi _1-Y1 Co _Y1 O ₂ (0<Y1<1), lithium-manganese-cobalt oxide (eg, LiNi 1-Y1 Co Y1 O 2 ) , LiCo _1-Y2 Mn _Y2 O ₂ (0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (0<Z1<2), lithium-nickel-manganese-cobalt oxides (eg, Li(Ni _p Co _q Mn _r1 )O ₂ (0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni _p1 Co _q1 Mn _r2 )O ₄ (0<p1<2,0<q1<2,0<r2<2, p1+q1+r2=2), or lithium-nickel-cobalt-transition metal (M) oxide (for example, Li(Ni _p2 Co _q2 Mn) _r3 M _S2 )O ₂ (M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, M wt% and Mo, and p2, q2, r3 and s2 are each independent atomic fractions of elements, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1) and the like may be further included.

The positive active material may be included in an amount of 80 to 98% by weight, more specifically 85 to 98% by weight, based on the total weight of the positive active material layer. When the positive active material is included in the above range, excellent capacity characteristics may be exhibited.

In addition, the conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black carbon powder such as; Graphite powder, such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, or nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of the solid content in the positive electrode active material layer.

In addition, the binder is a component serving to improve the adhesion between the positive active material particles and the adhesion between the positive active material and the current collector, and is typically added in an amount of 1 to 30 wt % based on the total weight of the solid content in the positive active material layer. . Examples of the binder include a fluororesin-based binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); Styrene-butadiene rubber (styrene butadiene rubber, SBR), acrylonitrile-butadiene rubber, styrene-rubber-based binder including isoprene rubber; Cellulose-based binders including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyalcohol-based binder comprising polyvinyl alcohol; Polyolefin-based binders including polyethylene and polypropylene; polyimide-based binders; polyester binder; and silane-based binders.

The positive electrode of the present invention as described above may be manufactured according to a method for manufacturing a positive electrode known in the art. For example, in the positive electrode, a positive electrode slurry prepared by dissolving or dispersing a positive electrode active material, a binder and/or a conductive material in a solvent is applied on a positive electrode current collector, followed by drying and rolling to form a positive electrode active material layer; Alternatively, the positive electrode active material layer may be cast on a separate support, and then a film obtained by peeling the support may be prepared by laminating on a positive electrode current collector.

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

The solvent may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount having a desirable viscosity when the positive active material and optionally a binder and a conductive material are included. For example, it may be included so that the solid content concentration in the active material slurry including the positive active material and, optionally, the binder and the conductive material is 10 wt% to 90 wt%, preferably 30 wt% to 80 wt%.

(2) cathode

Next, the cathode will be described.

The negative electrode according to the present invention includes an anode active material layer including an anode active material, and the anode active material layer may further include a conductive material and/or a binder, if necessary. In addition, the negative electrode according to the present invention may use a lithium metal electrode or a metal electrode such as Cu or Ni.

As the negative active material, various negative active materials used in the art, for example, a carbon-based negative active material capable of reversibly intercalating/deintercalating lithium ions, and a silicon-based negative electrode capable of doping and de-doping lithium It may include an active material or a mixture thereof.

Examples of the carbon-based negative active material include various carbon-based negative active materials used in the art, for example, graphite-based materials such as natural graphite, artificial graphite, and Kish graphite; pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, liquid crystal pitches (Mesophase pitches) and petroleum and coal tar pitch derived cokes (petroleum or coal tar pitch derived cokes) High-temperature calcined carbon, soft carbon, hard carbon, etc. may be used. The shape of the carbon-based anode active material is not particularly limited, and various shapes of materials such as amorphous, plate-like, scale-like, spherical or fibrous shape may be used.

Preferably, the carbon-based negative active material may include at least one of natural graphite and artificial graphite. More preferably, the carbon-based negative active material may include natural graphite and artificial graphite. When natural graphite and artificial graphite are used together, adhesion to the current collector is increased, thereby suppressing the detachment of the active material.

According to another embodiment, as the negative active material, a silicon-based negative active material may be mixed with the carbon-based negative active material.

The silicon-based negative active material is, for example, metal silicon (Si), silicon oxide (SiO _x , where 0<x<2) silicon carbide (SiC) and a Si-Y alloy (wherein Y is an alkali metal, alkaline earth metal, group 13) It is an element selected from the group consisting of elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, and may include at least one selected from the group consisting of (not Si). The element Y is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db (dubnium), 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.

Since the silicon-based negative active material exhibits higher capacity characteristics than the carbon-based negative active material, when the silicon-based negative active material is additionally included, better capacity characteristics may be obtained.

Meanwhile, the mixing ratio of the silicon-based negative active material: the carbon-based negative active material may be 3:97 to 99:1 by weight, preferably 5:95 to 15:85. When the mixing ratio of the silicon-based negative active material and the carbon-based negative active material satisfies the above range, the volume expansion of the silicon-based negative active material is suppressed while improving the capacity characteristics, thereby securing excellent cycle performance.

The negative active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative active material layer. When the content of the negative active material satisfies the above range, excellent capacity characteristics and electrochemical characteristics can be obtained.

Next, the conductive material is a component for further improving the conductivity of the anode active material, and may be added in an amount of 1 to 20 wt% based on the total weight of the solid content in the anode active material layer. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, or nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 1 to 30% by weight based on the total weight of the solid content in the negative active material layer. Examples of such a binder include a fluororesin binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); a rubber-based binder including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; Cellulose-based binders including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyalcohol-based binder comprising polyvinyl alcohol; Polyolefin-based binders including polyethylene and polypropylene; polyimide-based binders; polyester binder; and silane-based binders.

The negative electrode may be manufactured according to a method for manufacturing a negative electrode known in the art. For example, the negative electrode is a method of forming a negative electrode active material layer by applying a negative electrode active material slurry prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent on the negative electrode current collector, rolling and drying the negative electrode active material layer, or It can be prepared by casting the anode active material layer on a separate support and then laminating a film obtained by peeling the support on the anode current collector.

The negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. Carbon, nickel, titanium, silver, etc. surface-treated, aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, the bonding force of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a non-woven body.

The solvent may include water or an organic solvent such as NMP, alcohol, or the like, and may be used in an amount to achieve a desirable viscosity when the negative electrode active material and, optionally, a binder and a conductive material are included. For example, it may be included so that the solids concentration in the anode active material and, optionally, the active material slurry including the binder and the conductive material is 50 wt% to 75 wt%, preferably 40 wt% to 70 wt%.

(3) separator

The lithium secondary battery according to the present invention includes a separator between the positive electrode and the negative electrode.

The separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move, and can be used without any particular limitation as long as it is normally used as a separator in a lithium secondary battery. It is preferable that it is excellent in a moisture-wicking ability.

Specifically, the separator is a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer. Alternatively, a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, in order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may optionally be used in a single-layer or multi-layer structure.

The lithium secondary battery according to the present invention as described above can be usefully used in portable devices such as mobile phones, notebook computers, digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or battery pack is a power tool (Power Tool); electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Alternatively, it may be used as a power source for any one or more medium and large-sized devices in a system for power storage.

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

The lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source for a small device, but also can be preferably used as a unit cell in a medium or large battery module including a plurality of battery cells.

Hereinafter, examples will be given to describe the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

[Example]

I. Examples

Example 1-1.

(Manufacture of non-aqueous electrolyte for lithium secondary battery)

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20), and 0.05 wt% of LiODFB and 0.05 wt% of LiBOB as the second additive A non-aqueous electrolyte for a secondary battery was prepared by adding % by weight (see Table 1 below).

(Manufacture of lithium secondary battery)

A positive electrode active material (LiCoO ₂ ), carbon black as a conductive material, and polyvinylidene fluoride as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 98:1:1 to obtain a positive electrode slurry (solid content) 40% by weight) was prepared. The positive electrode slurry was applied to a positive electrode current collector (Al thin film) having a thickness of 20 μm, dried, and then roll press was performed to prepare a positive electrode.

A negative electrode active material (graphite), carbon black as a conductive material, SBR as a binder, and CMC as a thickener were added to NMP in a weight ratio of 95.6:1:2.3:1.1 to prepare a negative electrode slurry (solid content: 90% by weight). The negative electrode slurry was applied to a 10 μm-thick copper (Cu) thin film as a negative electrode current collector, dried, and then roll press was performed to prepare a negative electrode.

An electrode assembly was prepared by sequentially stacking the prepared positive electrode, a separator and a negative electrode made of a polyethylene porous film, and then storing the electrode assembly in a pouch-type battery case, and injecting 5 ml of the prepared non-aqueous electrolyte for secondary batteries into the pouch A lithium secondary battery was manufactured.

Example 1-2.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, n1:m1 mole ratio is 80:20) and 0.1 wt% of LiODFB and LiBOB 5.0 as the second additive A lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding a weight % (see Table 1 below).

Examples 1-3.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3A as a first additive (weight average molecular weight (Mw) = 12,000, n1:m1 mole ratio is 80:20), LiODFB 5.0 wt% and LiBOB 5.0 as a second additive A lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding weight % (see Table 1 below).

Examples 1-4.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1% by weight of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20), and 0.05% by weight of LiBOB as the second additive. A lithium secondary battery was prepared in the same manner as in Examples 1-1, except for preparing a non - aqueous electrolyte for a secondary battery (see Table 1 below).

Examples 1-5.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20), and 0.05 wt% of LiODFB as the second additive. A lithium secondary battery was prepared in the same manner as in Examples 1-1, except for preparing a non - aqueous electrolyte for a secondary battery (see Table 1 below).

Example 1-6.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 3.0 wt% of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20) and 0.5 wt% of LiODFB and 5.0 wt% of LiBOB as the second additive A lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding weight % (see Table 1 below).

Examples 1-7.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 5.0 wt% of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20) and 0.05 wt% of LiODFB and 5.0 wt% of LiBOB as the second additive A lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding weight % (see Table 1 below).

Examples 1-8.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 5.0 wt% of the oligomer represented by Formula 3A as a first additive (weight average molecular weight (Mw) = 12,000, n1:m1 mole ratio is 80:20) and 5.0 wt% of LiODFB 5.0 wt% and LiBOB 0.05 as a second additive A lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding weight % (see Table 1 below).

Examples 1-9.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 5.0 wt% of the oligomer represented by Formula 3A as a first additive (weight average molecular weight (Mw) = 12,000, n1:m1 mole ratio is 80:20) and 0.05 wt% of LiODFB and 0.05 wt% of LiBOB as a second additive A lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding weight % (see Table 1 below).

Examples 1-10.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 5.0% by weight of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20) and 5.0% by weight of LiODFB as the second additive were added. A lithium secondary battery was prepared in the same manner as in Examples 1-1, except for preparing a non - aqueous electrolyte for a secondary battery (see Table 1 below).

Examples 1-11.

Preparation of a non-aqueous electrolyte for a secondary battery comprising an oligomer represented by Formula 3B (weight average molecular weight (Mw) = 12,500, mole ratio of n2:m2 is 80:20) instead of the oligomer represented by Formula 3A as the first additive A lithium secondary battery was prepared in the same manner as in Examples 1-1 , except that (see Table 1 below).

Examples 1-12.

Preparation of a non-aqueous electrolyte for a secondary battery comprising an oligomer represented by Formula 3B (weight average molecular weight (Mw) = 12,500, mole ratio of n2:m2 is 80:20) instead of the oligomer represented by Formula 3A as the first additive A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1 to 9 except that (see Table 1 below).

Examples 1-13.

As the first additive, instead of the oligomer represented by Formula 3A, the oligomer represented by Formula 3C (weight average molecular weight (Mw) = 15,500, the mole ratio of n3:m3 is 80:20) for preparing a non-aqueous electrolyte for a secondary battery. Except for that, a pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1 ( see Table 1 below).

Examples 1-14.

As the first additive, instead of the oligomer represented by Formula 3A, the oligomer represented by Formula 3C (weight average molecular weight (Mw) = 15,500, the mole ratio of n3:m3 is 80:20) to prepare a non-aqueous electrolyte for a secondary battery. A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-9, except that (see Table 1 below).

Examples 1-15.

The point of preparing a non-aqueous electrolyte for a secondary battery comprising the oligomer represented by Formula 3D (weight average molecular weight (Mw) = 13,300, n4:m4 mole ratio is 70:30) instead of the oligomer represented by Formula 3A as the first additive Except for that, a pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1 ( see Table 1 below).

Examples 1-16.

As the first additive, instead of the oligomer represented by Formula 3A, the oligomer represented by Formula 3D (weight average molecular weight (Mw) = 13,300, the mole ratio of n4:m4 is 70:30) to prepare a non-aqueous electrolyte solution for a secondary battery A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-9 except that (see Table 1 below).

Examples 1-17.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.04% by weight of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20) and 0.05% by weight of LiODFB and 0.05% by weight of LiBOB as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding weight % (see Table 1 below).

Examples 1-18.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.04 wt% of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20) and 0.05 wt% of LiODFB and 5.0 wt% of LiBOB as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding a weight % (see Table 1 below).

Examples 1-19.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.04 wt% of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20) and 5.0 wt% of LiODFB and 5.0 wt% of LiBOB as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding a weight % (see Table 1 below).

Examples 1-20.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 6.0 wt% of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20) and 0.05 wt% of LiODFB and 0.05 wt% of LiBOB as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding a weight % (see Table 1 below).

Example 1-21.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 6.0 wt% of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20) and 0.05 wt% of LiODFB and 5.0 wt% of LiBOB as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding a weight % (see Table 1 below).

Example 1-22.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 6.0 wt% of the oligomer represented by Formula 3A as the first additive (weight average molecular weight (Mw) = 12,000, the mole ratio of n1:m1 is 80:20) and 5.0 wt% of LiODFB and 5.0 wt% of LiBOB as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte for a secondary battery was prepared by adding a weight % (see Table 1 below).

Comparative Example 1-1.

Ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) was mixed in a volume ratio of 2:1:2.5:4.5, and then dissolved so that LiPF ₆ was 1.0M. A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1 except for preparing a non - aqueous electrolyte (see Table 1 below).

Comparative Example 1-2.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, a pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1 , except that 0.05 wt% of LiODFB and 0.05 wt% of LiBOB were added to prepare a non-aqueous electrolyte ( See Table 1 below).

Comparative Example 1-3.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, a pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1 , except that 5.0 wt% of LiODFB and 0.05 wt% of LiBOB were added to prepare a non-aqueous electrolyte ( See Table 1 below).

Comparative Example 1-4.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, only 0.1 wt% of the oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, n1:m1 mole ratio is 80:20) is added as the first additive to prepare a non-aqueous electrolyte except for the point prepared a pouch-type lithium secondary battery in the same manner as in Examples 1-1 ( see Table 1 below).

Comparative Example 1-5.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 5 wt% of an oligomer represented by the following formula (1A) (weight average molecular weight (Mw) = 7,500, o = 40) as a first additive and 5.0 wt% of LiODFB and 0.05 wt% of LiBOB as a second additive were added to the boiling water. A pouch - type lithium secondary battery was prepared in the same manner as in Examples 1-1 except for preparing an electrolyte solution (see Table 1 below).

[Formula 1A]

Comparative Example 1-6.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 5 wt% of an oligomer (weight average molecular weight (Mw) = 7,500, o = 40) composed of the repeating unit represented by Formula 1A as a first additive and 0.05 wt% of LiODFB and 0.05 wt% of LiBOB as a second additive A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1, except that a non - aqueous electrolyte was prepared by adding .

Comparative Example 1-7.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 5 wt% of an oligomer represented by the following formula 2A (weight average molecular weight (Mw) = 4,000, p = 40) and 0.05 wt% of LiODFB and 0.05 wt% of LiBOB are added as a first additive to prepare a non-aqueous electrolyte A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1 except for the point (see Table 1 below ) .

[Formula 2A]

Comparative Examples 1-8.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 5 wt% of an oligomer (weight average molecular weight (Mw) 4,000, p = 40) composed of the repeating unit represented by Formula 2A as a first additive and 5.0 wt% of LiODFB and 0.05 wt% of LiBOB as a second additive A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1, except that the non - aqueous electrolyte was prepared by adding it (see Table 1 below).

Comparative Examples 1-9.

Except for preparing a non-aqueous electrolyte for a secondary battery comprising an oligomer represented by the following formula (4) instead of the oligomer represented by the formula (3A) (weight average molecular weight (Mw) = 13,500, q:r mole ratio is 50:50) A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1 (see Table 1 below).

[Formula 4]

Comparative Examples 1-10.

Except for preparing a non-aqueous electrolyte for a secondary battery comprising the oligomer represented by the following formula 5 instead of the oligomer represented by the formula 3A (weight average molecular weight (Mw) = 14,200, the mole ratio of q1:r1 is 60:40) A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1 ( see Table 1 below).

[Formula 5]

First additive: oligomer Second additive: lithium salt compound
(content/wt%) chemical formula content
(wt%) LiODFB LiBOB Example 1-1 3A 0.1 0.05 0.05 Example 1-2 3A 0.1 5.0 Examples 1-3 3A 5.0 5.0 Examples 1-4 3A - 0.05 Examples 1-5 3A 0.05 - Examples 1-6 3A 3.0 0.5 5.0 Examples 1-7 3A 5.0 0.05 5.0 Examples 1-8 3A 5.0 0.05 Examples 1-9 3A 0.05 0.05 Examples 1-10 3A 5.0 - Examples 1-11 3B 0.1 0.05 0.05 Examples 1-12 3B 5.0 0.05 0.05 Examples 1-13 3C 0.1 0.05 0.05 Examples 1-14 3C 5.0 0.05 0.05 Examples 1-15 3D 0.1 0.05 0.05 Examples 1-16 3D 5.0 0.05 0.05 Examples 1-17 3A 0.04 0.05 0.05 Examples 1-18 3A 0.04 0.05 5.0 Examples 1-19 3A 0.04 5.0 5.0 Examples 1-20 3A 6.0 0.05 0.05 Example 1-21 3A 6.0 0.05 5.0 Example 1-22 3A 6.0 5.0 5.0 Comparative Example 1-1 - - - - Comparative Example 1-2 - - 0.05 0.05 Comparative Example 1-3 - - 5.0 0.05 Comparative Example 1-4 3A 0.1 - - Comparative Example 1-5 1A 5.0 5.0 0.05 Comparative Example 1-6 1A 0.05 0.05 Comparative Example 1-7 2A 0.05 0.05 Comparative Examples 1-8 2A 5.0 0.05 Comparative Example 1-9 4 0.1 0.05 0.05 Comparative Example 1-10 5 0.1 0.05 0.05

The abbreviations of the compounds in Table 1 are as follows.

LiBOB: Lithium bis(oxalato)borate

LiODFB: lithium difluoro(oxalato)borate

Example 2-1.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 0.0005 wt% of succinonitrile as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Examples 1-1, except that the non - aqueous electrolyte was prepared by adding it (see Table 2 below).

Example 2-2.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 0.0005 wt% of succinonitrile as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that 10.0 wt% of HTCN was added to prepare a non-aqueous electrolyte (see Table 2 below).

Example 2-3.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 0.0005 wt% of HTCN as a second additive were added. A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1 except for preparing the non-aqueous electrolyte (see Table 2 below).

Example 2-4.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 10.0 wt% of succinonitrile as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that 0.0005 wt% of HTCN was added to prepare a non-aqueous electrolyte (see Table 2 below).

Example 2-5.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 10.0 wt% of succinonitrile as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 2 below).

Example 2-6.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 10.0 wt% of HTCN as a second additive were added. A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1 except for preparing the non-aqueous electrolyte (see Table 2 below).

Example 2-7.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3F as the first additive (weight average molecular weight = 16,500 g/mol, n6:m6 mole ratio = 70:30) and 0.0005 wt% of succinonitrile as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 2 below).

Examples 2-8.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3F as a first additive (weight average molecular weight = 16,500 g/mol, n6:m6 mole ratio = 70:30) and 0.0005 wt% of succinonitrile as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that 10.0 wt% of HTCN was added to prepare a non-aqueous electrolyte (see Table 2 below).

Example 2-9.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3C as the first additive (weight average molecular weight = 15,500 g/mol, n3:m3 mole ratio = 80:20) and 0.0005 wt% of succinonitrile as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 2 below).

Examples 2-10.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3C as a first additive (weight average molecular weight = 15,500 g/mol, n3:m3 mole ratio = 80:20) and 0.0005 wt% of succinonitrile as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that 10.0 wt% of HTCN was added to prepare a non-aqueous electrolyte (see Table 2 below).

Example 2-11.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3D as the first additive (weight average molecular weight = 15,000 g/mol, n4:m4 mole ratio = 90:10) and 0.0005 wt% of succinonitrile as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 2 below).

Example 2-12.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3D as a first additive (weight average molecular weight = 15,000 g/mol, n4:m4 mole ratio = 90:10) and 0.0005 wt% of succinonitrile as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that 10.0 wt% of HTCN was added to prepare a non-aqueous electrolyte (see Table 2 below).

Examples 2-13.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 0.0001 wt% of succinonitrile as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 2 below).

Examples 2-14.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1% by weight of the oligomer represented by Formula 3E as the first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 0.0001% by weight of HTCN as the second additive were added. A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1 except for preparing the non-aqueous electrolyte (see Table 2 below).

Examples 2-15.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 15.0 wt% of succinonitrile as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 2 below).

Examples 2-16.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 15.0 wt% of HTCN as a second additive were added. A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1 except for preparing the non-aqueous electrolyte (see Table 2 below).

Example 2-17.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 0.0001 wt% of succinonitrile as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that 10.0 wt% of HTCN was added to prepare a non-aqueous electrolyte (see Table 2 below).

Example 2-18.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 10.0 wt% of succinonitrile as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that 0.0001 wt% of HTCN was added to prepare a non-aqueous electrolyte (see Table 2 below).

Example 2-19.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 6.0 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 6.0 wt% of succinonitrile as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that 6.0 wt% of HTCN was added to prepare a non-aqueous electrolyte (see Table 2 below).

Examples 2-20.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 6.0 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 6.0 wt% of succinonitrile as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 2 below).

Example 2-21.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 6.0 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 6.0 wt% of HTCN as a second additive were added. A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1 except for preparing the non-aqueous electrolyte (see Table 2 below).

Example 2-22.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.05 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 6.0 wt% of succinonitrile as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 2 below).

Example 2-23.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.05 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 6.0 wt% of succinonitrile as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that 6.0 wt% of HTCN was added to prepare a non-aqueous electrolyte (see Table 2 below).

Example 2-24.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.05 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) and 6.0 wt% of HTCN as a second additive were added. A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1 except for preparing the non-aqueous electrolyte (see Table 2 below).

Comparative Example 2-1.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E (weight average molecular weight = 13,000 g/mol, n5:m5 mole ratio = 80:20) was added to prepare a non-aqueous electrolyte solution. A pouch-type lithium secondary battery was prepared in the same manner as in 2-1 (see Table 2 below).

First additive:
oligomer Second additive: nitrile-based compound
(content/wt%) chemical formula content (wt%) SN HTCN Example 2-1 3E 0.1 0.0005 - Example 2-2 3E 0.0005 10 Example 2-3 3E - 0.0005 Example 2-4 3E 10 0.0005 Example 2-5 3E 10 - Example 2-6 3E - 10 Example 2-7 3F 0.0005 - Examples 2-8 3F 0.0005 10 Examples 2-9 3C 0.0005 - Example 2-10 3C 0.0005 10 Example 2-11 3D 0.0005 - Example 2-12 3D 0.0005 10 Examples 2-13 3E 0.0001 - Examples 2-14 3E - 0.0001 Examples 2-15 3E 15 - Examples 2-16 3E - 15 Example 2-17 3E 0.0001 10 Example 2-18 3E 10 0.0001 Example 2-19 3E 6 6 6 Examples 2-20 3E 6 - Example 2-21 3E - 6 Example 2-22 3E 0.05 6 - Example 2-23 3E 6 6 Example 2-24 3E - 6 Comparative Example 2-1 3E 0.1 - -

Abbreviations of compounds in Table 2 are as follows.

SN: succinonitrile

HTCN: Hexanetricarbonitrile

Example 3-1.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight (Mw) = 15,000, n5:m5 mole ratio is 60:40), 0.0001 wt% of vinylethylene carbonate as a second additive, and A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that 0.0001 wt% of fluoroethylene carbonate was added to prepare a non-aqueous electrolyte (see Table 3 below).

Example 3-2.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight (Mw) = 15,000, n5:m5 mole ratio is 60:40), 0.0001 wt% of vinylethylene carbonate as a second additive, and A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that 10 wt% of fluoroethylene carbonate was added to prepare a non-aqueous electrolyte (see Table 3 below).

Example 3-3.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight (Mw) = 15,000, n5:m5 mole ratio is 60:40), 5.0 wt% of vinylethylene carbonate as a second additive, and A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that 0.0001 wt% of fluoroethylene carbonate was added to prepare a non-aqueous electrolyte (see Table 3 below).

Example 3-4.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight (Mw) = 15,000, n5:m5 mole ratio is 60:40), 5.0 wt% of vinylethylene carbonate as a second additive, and A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that 10 wt% of fluoroethylene carbonate was added to prepare a non-aqueous electrolyte (see Table 3 below).

Example 3-5.

A non-aqueous electrolyte is prepared by adding the oligomer represented by Formula 3F (weight average molecular weight = 15,000 g/mol, mole ratio of n6:m6 = 50:50) instead of the oligomer represented by Formula 3E as the first additive prepared a pouch-type lithium secondary battery in the same manner as in Example 3-1 (see Table 3 below).

Example 3-6.

Except for preparing a non-aqueous electrolyte by adding the oligomer represented by Formula 3F (weight average molecular weight = 15,000 g/mol, mole ratio of n6:m6 = 50:50) instead of the oligomer represented by Formula 3E as the first additive prepared a pouch-type lithium secondary battery in the same manner as in Example 3-2 (see Table 3 below).

Example 3-7.

Except for preparing a non-aqueous electrolyte by adding the oligomer represented by Formula 3C (weight average molecular weight = 14,300 g/mol, mole ratio of n3:m3 = 60:40) instead of the oligomer represented by Formula 3E as the first additive prepared a pouch-type lithium secondary battery in the same manner as in Example 3-1 (see Table 3 below).

Example 3-8.

Except for preparing a non-aqueous electrolyte by adding the oligomer represented by Formula 3C (weight average molecular weight = 14,300 g/mol, mole ratio of n3:m3 = 60:40) instead of the oligomer represented by Formula 3E as the first additive prepared a pouch-type lithium secondary battery in the same manner as in Example 3-2 (see Table 3 below).

Example 3-9.

Except for preparing a non-aqueous electrolyte by adding the oligomer represented by Formula 3D (weight average molecular weight = 12,000 g/mol, mole ratio of n4:m4 = 60:40) instead of the oligomer represented by Formula 3E as the first additive prepared a pouch-type lithium secondary battery in the same manner as in Example 3-1 (see Table 3 below).

Example 3-10.

Except for preparing a non-aqueous electrolyte by adding the oligomer represented by Formula 3D (weight average molecular weight = 12,000 g/mol, mole ratio of n4:m4 = 60:40) instead of the oligomer represented by Formula 3E as the first additive prepared a pouch-type lithium secondary battery in the same manner as in Example 3-2 (see Table 3 below).

Example 3-11.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.05 wt% of the oligomer represented by Formula 3E as a first additive (weight average molecular weight (Mw) = 15,000, n5:m5 mole ratio is 60:40), 0.00005 wt% of vinylethylene carbonate as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that 0.00005 wt% of fluoroethylene carbonate was added to prepare a non-aqueous electrolyte (see Table 3 below).

Example 3-12.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 6 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight (Mw) = 15,000, the mole ratio of n5:m5 is 60:40), 0.006 wt% of vinylethylene carbonate as a second additive and A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that 0.006 wt% of fluoroethylene carbonate was added to prepare a non-aqueous electrolyte (see Table 3 below).

Examples 3-13.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight (Mw) = 15,000, n5:m5 mole ratio is 60:40) and 0.0001 wt% of vinylethylene carbonate as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 3 below).

Example 3-14.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight (Mw) = 15,000, the mole ratio of n5:m5 is 60:40) and 0.0001 wt% of fluoroethylene carbonate as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that a non-aqueous electrolyte was prepared by adding .

Examples 3-15.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight (Mw) = 15,000, the mole ratio of n5:m5 is 60:40), and 5.0 wt% of vinylethylene carbonate as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 3 below).

Examples 3-16.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight (Mw) = 15,000, the mole ratio of n5:m5 is 60:40), and 10 wt% of fluoroethylene carbonate as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that a non-aqueous electrolyte was prepared by adding .

Example 3-17.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1% by weight of the oligomer represented by Formula 3E as the first additive (weight average molecular weight (Mw) = 15,000, the mole ratio of n5:m5 is 60:40), and 10% by weight of vinylethylene carbonate as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that the non-aqueous electrolyte was prepared by adding it (see Table 3 below).

Example 3-18.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E as the first additive (weight average molecular weight (Mw) = 15,000, the mole ratio of n5:m5 is 60:40) and 15 wt% of fluoroethylene carbonate as the second additive A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that a non-aqueous electrolyte was prepared by adding .

Comparative Example 3-1.

In a non-aqueous organic solvent mixed with ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 2: 1: 2.5: 4.5, 1.0 M of LiPF ₆ was added After dissolving as much as possible, 0.1 wt% of the oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000, n5:m5 mole ratio of 60:40) was added to prepare a non-aqueous electrolyte solution. A pouch-type lithium secondary battery was prepared in the same manner as in 3-1 (see Table 3 below).

First additive: oligomer Second additive: cyclic carbonate-based compound
(content/wt%) chemical formula content (wt%) VEC FEC Example 3-1 3E 0.1
0.0001 0.0001 Example 3-2 3E 0.0001 10 Example 3-3 3E 5.0 0.0001 Example 3-4 3E 5.0 10 Example 3-5 3F 0.0001 0.0001 Example 3-6 3F 0.0001 10 Example 3-7 3C 0.0001 0.0001 Example 3-8 3C 0.0001 10 Example 3-9 3D 0.0001 0.0001 Example 3-10 3D 0.0001 10 Example 3-11 3E 0.05 0.00005 0.00005 Example 3-12 3E 6 0.006 0.006 Example 3-13 3E 0.1 0.0001 - Example 3-14 3E - 0.0001 Example 3-15 3E 5.0 - Examples 3-16 3E - 10 Example 3-17 3E 10 - Example 3-18 3E - 15 Comparative Example 3-1 3E - -

The abbreviations of the compounds in Table 3 are as follows.

VEC: Vinylethylene carbonate

FEC: fluoroethylene carbonate

II. Experimental example

Experimental Example 1-1: Evaluation of capacity retention at high temperature (45° C.)

Lithium secondary batteries prepared in Examples 1-1 to 1-4, 1-6 to 1-9 and 1-11 to 1-22 and Comparative Examples 1-1 and 1-4 to 1-10 After the formation of the lithium secondary battery at 200 mA current (0.1C rate) was performed, the discharge capacity at this time was set as the initial capacity, and the measured resistance was set as the initial resistance.

Then, 100 cycles of 4.2V, 660 mA (0.33C, 0.05C cut-off) CC/CV charge and 2.5 V, 660 mA (0.33C) CC discharge were performed as 1 cycle at high temperature (45℃). Then, the discharge capacity and resistance were measured.

After 100 cycles, the discharge capacity and the initial capacity were compared to calculate the capacity retention rate, and the results are shown in Table 4 below.

Experimental Example 1-2: Evaluation of high temperature (45°C) storage characteristics

Lithium secondary batteries prepared in Examples 1-1 to 1-4, 1-6 to 1-9 and 1-11 to 1-22 and Comparative Examples 1-1 and 1-4 to 1-10 Charge the lithium secondary battery up to 4.2V at a rate of 0.33C, respectively, under constant current/constant voltage conditions, and perform 0.05C cut-off charging, and set the discharge capacity after discharging at 0.33C and 2.5V to the initial capacity, and the resistance at this time was set as the initial resistance.

Then, charging and 0.05C cut-off charging were performed under constant current/constant voltage conditions up to 4.2V at a rate of 0.33C, and the residual capacity and resistance after storage at 60°C for 10 weeks (weeks) were measured. The capacity retention rate was calculated by comparing the measured discharge capacity and the initial capacity after storage at a high temperature for 10 weeks, and the results are shown in Table 4 below.

electrolyte Capacity retention (%) after 100 cycles at high temperature (45°C) Capacity retention rate (%) after 10 weeks of storage at high temperature (45℃) Example 1-1 95 95 Example 1-2 97 96 Examples 1-3 97 96 Examples 1-4 96 98 Examples 1-6 96 97 Examples 1-7 98 96 Examples 1-8 97 95 Examples 1-9 97 96 Examples 1-11 97 98 Examples 1-12 95 98 Examples 1-13 98 98 Examples 1-14 96 97 Examples 1-15 97 97 Examples 1-16 97 96 Examples 1-17 89 88 Examples 1-18 87 84 Examples 1-19 86 87 Examples 1-20 86 88 Example 1-21 87 85 Example 1-22 85 85 Comparative Example 1-1 74 72 Comparative Example 1-4 82 88 Comparative Example 1-5 83 82 Comparative Example 1-6 81 84 Comparative Example 1-7 85 81 Comparative Examples 1-8 80 80 Comparative Example 1-9 80 79 Comparative Example 1-10 78 79

Looking at the results of Table 4, in the case of the secondary batteries of Comparative Examples 1-1 and 1-4 to 1-10, which do not include both the first additive and the second additive of the present invention, it is difficult to form a uniform film. Therefore, compared to the secondary batteries having the non-aqueous electrolytes of Examples 1-1 to 1-4, 1-6 to 1-9, and 1-11 to 1-22 of the present invention, the capacity retention rate after high temperature cycle and the capacity after high temperature storage It can be seen that the retention rates are all deteriorated.

On the other hand, in the case of the lithium secondary batteries of Examples 1-17 to 1-22 containing a little or a little more of the oligomer of the present invention, the film-forming effect is lowered or a side reaction is caused, and in Examples 1-1 to 1- It can be seen that the capacity retention rate is relatively reduced compared to the secondary batteries of 4, 1-6 to 1-9 and 1-11 to 1-16.

Experimental Example 2-1: Evaluation of capacity retention at high temperature (45° C.)

After the formation of the lithium secondary batteries prepared in Examples 2-1 to 2-24 and the lithium secondary batteries prepared in Comparative Examples 1-9 and 1-10 at 200 mA current (0.1C rate) was performed, , The discharge capacity at this time was set as the initial capacity, and the measured resistance was set as the initial resistance.

Then, 100 cycles of 4.2V, 660 mA (0.33C, 0.05C cut-off) CC/CV charge and 2.5 V, 660 mA (0.33C) CC discharge were performed as one cycle at high temperature (45℃). Then, the discharge capacity was measured.

After 100 cycles, the discharge capacity and the initial capacity were compared to calculate the capacity retention rate, and the results are shown in Table 5 below.

Experimental Example 2-2: Evaluation of high temperature (45°C) storage characteristics

The lithium secondary batteries prepared in Examples 2-1 to 2-24 and the lithium secondary batteries prepared in Comparative Examples 1-9 and 1-10 were charged under constant current/constant voltage conditions up to 4.2V at a rate of 0.33C, respectively, and cut by 0.05C After performing off-charging and discharging to 0.33C and 2.5V, the discharge capacity was set as the initial capacity, and the resistance at this time was set as the initial resistance.

Then, charging and 0.05C cut-off charging were performed under constant current/constant voltage conditions up to 4.2V at a rate of 0.33C, and the residual capacity and resistance after storage at 60°C for 10 weeks (weeks) were measured. The capacity retention rate was calculated by comparing the measured discharge capacity and the initial capacity after storage at a high temperature for 10 weeks, and the results are shown in Table 5 below.

at high temperature (45℃)
Capacity retention after 100 cycles (%) Capacity retention rate (%) after 10 weeks of storage at high temperature (45℃) Example 2-1 98 97 Example 2-2 97 96 Example 2-3 99 97 Example 2-4 98 98 Example 2-5 98 96 Example 2-6 99 97 Example 2-7 98 98 Examples 2-8 98 98 Examples 2-9 98 96 Example 2-10 97 97 Example 2-11 98 97 Example 2-12 98 97 Examples 2-13 85 80 Examples 2-14 88 82 Examples 2-15 89 85 Examples 2-16 86 84 Example 2-17 84 88 Example 2-18 82 89 Example 2-19 82 84 Examples 2-20 84 81 Example 2-21 83 82 Example 2-22 79 80 Example 2-23 81 82 Example 2-24 80 83 Comparative Example 1-9 80 79 Comparative Example 1-10 78 79

Referring to Table 5, in the case of the secondary batteries of Comparative Examples 1-9 and 1-10 that do not include both the first additive and the second additive of the present invention, it is difficult to form a uniform film. It can be seen that both the capacity retention rate after a high temperature cycle and the capacity retention rate after high temperature storage are deteriorated compared to the secondary batteries having the nonaqueous electrolyte of Examples 2-1 to 2-24.

On the other hand, in the case of the lithium secondary batteries of Examples 2-1 to 2-18, after a high temperature cycle compared to the secondary batteries of Examples 2-19 to 2-24 having a non-aqueous electrolyte containing a little or a little oligomer. It can be seen that both the capacity retention rate and the capacity retention rate after high-temperature storage are improved. This effect is achieved by suppressing electrode degradation that may occur during high-temperature performance evaluation by improving the film-forming effect when the oligomer and nitrile-based compound in a specific content ratio are included, and at the same time suppressing side reactions of the electrolyte that may occur on the surface of the electrode. This seems to be because it is possible to prevent an increase in resistance due to the generation of by-products that may occur.

Experimental Example 3-1: Capacity retention rate evaluation at high temperature (45°C)

The lithium secondary batteries prepared in Examples 3-1 to 3-10 and 3-13 to 3-18, the lithium secondary batteries prepared in Comparative Example 1-1, and Comparative Examples 1-9 and 1-10 After the formation was performed at 200 mA current (0.1C rate) for the lithium secondary battery and the lithium secondary battery prepared in Comparative Example 3-1, the discharge capacity at this time was set as the initial capacity, and the measured resistance was set as the initial resistance.

Then, 100 cycles of 4.2V, 660 mA (0.33C, 0.05C cut-off) CC/CV charge and 2.5 V, 660 mA (0.33C) CC discharge were performed as one cycle at high temperature (45℃). Then, the discharge capacity was measured.

After 100 cycles, the discharge capacity and the initial capacity were compared to calculate the capacity retention rate, and the results are shown in Table 6 below.

Experimental Example 3-2: Evaluation of high temperature (45°C) storage characteristics

The lithium secondary batteries prepared in Examples 3-1 to 3-14 and 3-16 to 3-18, the lithium secondary batteries prepared in Comparative Example 1-1, and Comparative Examples 1-9 and 1-10 prepared in Comparative Examples 1-10 After charging the lithium secondary battery and the lithium secondary battery prepared in Comparative Example 3-1 under constant current/constant voltage conditions up to 4.2V at 0.33C rate and 0.05 C cut-off charging, respectively, after discharging to 0.33C and 2.5V The discharge capacity was set as the initial capacity, and the resistance at this time was set as the initial resistance.

Then, charging and 0.05C cut-off charging were performed under constant current/constant voltage conditions up to 4.2V at a rate of 0.33C, and the residual capacity and resistance after storage at 60°C for 10 weeks (weeks) were measured. The capacity retention rate was calculated by comparing the measured discharge capacity and the initial capacity after storage at a high temperature for 10 weeks, and the results are shown in Table 6 below.

at high temperature (45℃)
Capacity retention after 100 cycles (%) Capacity retention rate (%) after 10 weeks of storage at high temperature (45℃) Example 3-1 98 99 Example 3-2 97 98 Example 3-3 96 97 Example 3-4 95 98 Example 3-5 99 98 Example 3-6 97 98 Example 3-7 98 98 Example 3-8 97 99 Example 3-9 98 97 Example 3-10 97 99 Example 3-11 - 87 Example 3-12 - 88 Example 3-13 90 81 Example 3-14 91 80 Example 3-15 89 - Examples 3-16 86 87 Example 3-17 84 88 Example 3-18 89 85 Comparative Example 3-1 81 87 Comparative Example 1-1 85 84 Comparative Example 1-9 80 79 Comparative Example 1-10 78 79

Referring to Table 6, the lithium secondary battery according to the embodiment of the present invention is Comparative Examples 1-1, 3-1, and 1-9 having a non-aqueous electrolyte containing neither the first nor the second additive of the present invention. And it can be seen that both the capacity retention rate after high-temperature cycle and the capacity retention rate after high-temperature storage are improved compared to the secondary batteries of 1-10.

Specifically, by including the cyclic carbonate and the oligomer together as an additive, a stable film is formed to suppress electrode degradation that may occur during high-temperature performance evaluation, and at the same time suppress the side reaction of the electrolyte that may occur on the electrode surface. This seems to be because it is possible to prevent an increase in resistance due to the generation of by-products.

In particular, in the case of the lithium secondary batteries of Examples 3-1 to 3-10 provided with the non-aqueous electrolyte containing two types of cyclic carbonate compounds as the second additive, an implementation with a non-aqueous electrolyte containing only one cyclic carbonate compound It can be seen that, compared to the secondary batteries of Examples 3-13 to 3-18, the capacity retention rate after a high temperature cycle and the capacity retention rate after high temperature storage are more improved.

In addition, in the case of the secondary battery of Example 3-11 containing a little less oligomer, the absolute amount of the polymer for forming the film was insufficient to form an unstable film, so compared to the secondary batteries of Examples 3-1 to 3-10 It can be seen that the capacity retention rate is relatively low after high-temperature storage. In addition, in the case of the secondary battery of Example 3-12 containing a rather large amount of oligomer, the charge transfer effect of lithium ions decreased due to an increase in ionic conductivity due to an increase in the viscosity of the electrolyte, and the secondary batteries of Examples 3-1 to 3-10 Compared to that, it can be seen that the capacity retention rate is relatively low after high-temperature storage.

Experimental Example 1-3: Safety evaluation

The lithium secondary batteries prepared in Examples 1-1 to 1-19 and the lithium secondary batteries prepared in Comparative Examples 1-1 to 1-10 were charged under constant current/constant voltage conditions up to 4.2V at a rate of 0.33C, respectively, and cut by 0.05C After performing off-charging and discharging to 0.33C and 2.5V, the discharge capacity was set as the initial capacity, and the resistance at this time was set as the initial resistance.

Then, charging is performed under constant current/constant voltage conditions to 4.2V at 0.33C rate and 0.05C cut-off charging is performed, and for each fully charged cell, the temperature is raised to 140°C at 5°C/min condition, and then for 1 hour. While maintaining 140°C, a stability evaluation experiment was performed by observing whether ignition or explosion occurred.

The results are shown in Table 7 below. In this case, the case where the battery did not ignite or explode (pass) was denoted by O, and the case where the battery ignited or exploded (fail) was denoted by ×.

electrolyte Stability evaluation results in high temperature storage Example 1-1 O Example 1-2 O Examples 1-3 O Examples 1-4 O Examples 1-5 O Examples 1-6 O Examples 1-7 O Examples 1-8 O Examples 1-9 O Examples 1-10 O Examples 1-11 O Examples 1-12 O Examples 1-13 O Examples 1-14 O Examples 1-15 O Examples 1-16 O Examples 1-17 × Examples 1-18 × Examples 1-19 × Comparative Example 1-1 × Comparative Example 1-2 × Comparative Example 1-3 × Comparative Example 1-4 × Comparative Example 1-5 × Comparative Example 1-6 × Comparative Example 1-7 × Comparative Examples 1-8 × Comparative Example 1-9 × Comparative Example 1-10 ×

Referring to Table 7, in the case of secondary batteries having the non-aqueous electrolytes of Examples 1-1 to 1-16 including the lithium salt compound of the present invention and the oligomer together, the first additive and the second additive of the present invention It can be seen that the secondary batteries of Comparative Examples 1-1 to 1-10, which are not included, have excellent high-temperature storage stability.

On the other hand, in the case of the lithium secondary batteries of Examples 1-17 to 1-19 containing a little less of the oligomer of the present invention, as the film formation effect is lowered, the high temperature stability compared to the secondary batteries of Examples 1-1 to 1-16 It can be seen that this is relatively low.

Experimental Example 2-3: Safety evaluation

The lithium secondary batteries prepared in Examples 2-1 to 2-12 and the lithium secondary batteries prepared in Comparative Examples 1-1 and 2-1 were charged under constant current/constant voltage conditions up to 4.2V at a rate of 0.33C, respectively, and 0.05 C cut-off charging was performed, and the discharge capacity after discharging to 0.33C and 2.5V was set as the initial capacity, and the resistance at this time was set as the initial resistance.

Then, charging is performed under constant current/constant voltage conditions to 4.2V at 0.33C rate and 0.05C cut-off charging is performed, and for each fully charged cell, the temperature is raised to 140°C at 5°C/min condition, and then for 1 hour. While maintaining 140°C, a stability evaluation experiment was performed by observing whether ignition or explosion occurred.

The results are shown in Table 8 below. In this case, the case where the battery did not ignite or explode (pass) was denoted by O, and the case where the battery ignited or exploded (fail) was denoted by ×.

electrolyte Stability evaluation results in high temperature storage Example 2-1 O Example 2-2 O Example 2-3 O Example 2-4 O Example 2-5 O Example 2-6 O Example 2-7 O Examples 2-8 O Examples 2-9 O Example 2-10 O Example 2-12 O Comparative Example 1-1 × Comparative Example 2-1 ×

Referring to Table 8, in the case of the secondary batteries of Examples 2-1 to 2-12 provided with the nonaqueous electrolyte containing both the first additive and the second additive of the present invention, Comparative Examples 1-1 and 2 It can be seen that the high-temperature storage stability is superior to that of the secondary battery of -1.

Experimental Example 3-3: Safety evaluation

The lithium secondary battery prepared in Examples 3-1 to 3-10 and 3-12 and the lithium secondary battery prepared in Comparative Example 3-1 were respectively charged at a rate of 0.33C to 4.2V under constant current/constant voltage conditions and cut by 0.05C After performing off-charging and discharging to 0.33C and 2.5V, the discharge capacity was set as the initial capacity, and the resistance at this time was set as the initial resistance.

Then, charging is performed under constant current/constant voltage conditions to 4.2V at 0.33C rate and 0.05C cut-off charging is performed, and for each fully charged cell, the temperature is raised to 140°C at 5°C/min condition, and then for 1 hour. While maintaining 140°C, a stability evaluation experiment was performed by observing whether ignition or explosion occurred.

The results are shown in Table 9 below. In this case, the case where the battery did not ignite or explode (pass) was denoted by O, and the case where the battery ignited or exploded (fail) was denoted by ×.

electrolyte Stability evaluation results in high temperature storage Example 3-1 O Example 3-2 O Example 3-3 O Example 3-4 O Example 3-5 O Example 3-6 O Example 3-7 O Example 3-8 O Example 3-9 O Example 3-10 O Example 3-12 O Comparative Example 3-1 ×

Looking at the results of Table 9, in the case of the secondary batteries of Examples 3-1 to 3-10 and 3-12 having the non-aqueous electrolyte containing the oligomer of the present invention and two types of cyclic carbonate-based compounds together, Comparative Examples It can be seen that the high-temperature storage stability is superior to that of the secondary battery of 3-1.

Claims (14)

lithium salt; non-aqueous organic solvents; a first additive; and a second additive;
An oligomer comprising a repeating unit derived from a monomer represented by the following formula (1) and a repeating unit derived from a monomer represented by the following formula (2) as the first additive,
A non-aqueous electrolyte for a lithium secondary battery comprising; at least one selected from the group consisting of a nitrile compound, a lithium salt compound, and a cyclic carbonate compound as the second additive:
[Formula 1]

In Formula 1,
R' is hydrogen or an alkyl group having 1 to 3 carbon atoms,
R ₁ is an alkylene group having 1 to 20 carbon atoms or -(R ₂ ) _o O(R ₃ ) _p -, wherein R ₂ and R ₃ are each independently an alkylene group having 1 to 20 carbon atoms, and o is 1 to is an integer of 3, and p is an integer from 0 to 3,

[Formula 2]

In Formula 2,
R" is hydrogen or an alkyl group having 1 to 3 carbon atoms,
R ₄ is an alkylene group having 1 to 10 carbon atoms,
R ₅ is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms.
The method according to claim 1,
The lithium salt is at least one selected from LiPF ₆ , LiFSI and LiTFSI.
The method according to claim 1,
The oligomer is a non-aqueous electrolyte for a lithium secondary battery comprising an oligomer represented by the following Chemical Formula 3:
[Formula 3]

In Formula 3,
R' and R" are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms,
R ₁ is an alkylene group having 1 to 10 carbon atoms or -(R ₂ ) _o O(R ₃ ) _p -, R ₂ and R ₃ are each independently an alkylene group having 1 to 10 carbon atoms, and o is 1 to 3 an integer, p is an integer from 0 to 3,
R ₄ is an alkylene group having 1 to 10 carbon atoms,
R ₅ is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms,
The mole ratio of n:m is 1:99 to 99:1.
4. The method of claim 3,
In Formula 3,
R' and R" are each independently hydrogen or an alkyl group having 1 or 2 carbon atoms,
R ₁ is an alkylene group having 1 to 6 carbon atoms or -(R ₂ ) _o O(R ₃ ) _p -, R ₂ and R ₃ are each independently an alkylene group having 1 to 6 carbon atoms, and o is 1 to 3 an integer, p is an integer from 0 to 3,
R ₄ is an alkylene group having 1 to 6 carbon atoms,
R ₅ is an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, a heteroaryl group having 3 to 8 carbon atoms, or a cycloalkyl group having 3 to 8 carbon atoms,
The mole ratio of n:m is 1:99 to 99:1 for a lithium secondary battery non-aqueous electrolyte.
4. The method of claim 3,
In Formula 3,
R' and R" are each independently hydrogen or an alkyl group having 1 or 2 carbon atoms,
R ₁ is an alkylene group having 1 to 6 carbon atoms or -(R ₂ ) _o O(R ₃ ) _p -, R ₂ and R ₃ are each independently an alkylene group having 1 to 6 carbon atoms, and o is 1 to 3 an integer, p is an integer from 0 to 3,
R ₄ is an alkylene group having 1 to 6 carbon atoms,
R ₅ is an aryl group having 6 to 8 carbon atoms, a heteroaryl group having 3 to 8 carbon atoms, or a cycloalkyl group having 3 to 8 carbon atoms,
The mole ratio of n:m is 1:99 to 99:1 for a lithium secondary battery non-aqueous electrolyte.
4. The method of claim 3,
The oligomer represented by Chemical Formula 3 is at least one selected from the group consisting of oligomers represented by the following Chemical Formulas 3A to 3F. Non-aqueous electrolyte for a lithium secondary battery:
[Formula 3A]

In Formula 3A,
The mole ratio of n1:m1 is 1:99 to 99:1.

[Formula 3B]

In Formula 3B,
The mole ratio of n2:m2 is 1:99 to 99:1.

[Formula 3C]

In Formula 3C,
The mole ratio of n3:m3 is 1:99 to 99:1.

[Formula 3D]

In Formula 3D,
The mole ratio of n4:m4 is 1:99 to 99:1.

[Formula 3E]

In Formula 3E,
The mole ratio of n5:m5 is 1:99 to 99:1.

[Formula 3F]

In Formula 3F,
The mole ratio of n6:m6 is 1:99 to 99:1.
The method according to claim 1,
The oligomer is a non-aqueous electrolyte for a lithium secondary battery that is included in an amount of 0.1 wt % to 5 wt % based on the total weight of the non-aqueous electrolyte.
The method according to claim 1,
The nitrile-based compound is succinonitrile, adiponitrile, dicyanobutene, ethylene glycol bis(propionitrile) ether, hexanetricarbonitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile , heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylaceto A non-aqueous electrolyte for a lithium secondary battery comprising at least one selected from the group consisting of nitrile and 4-fluorophenylacetonitrile.
The method according to claim 1,
The weight ratio of the oligomer and the nitrile compound is 1:0.01 to 1:100 for a lithium secondary battery non-aqueous electrolyte.
The method according to claim 1,
The lithium salt compound is selected from the group consisting of LiBF ₄ , lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluorophosphate and lithium difluorobis(oxalato)phosphate. At least one non-aqueous electrolyte for a lithium secondary battery.
The method according to claim 1,
The weight ratio of the oligomer and the lithium salt compound is 1:0.01 to 1:100 for a lithium secondary battery non-aqueous electrolyte.
The method according to claim 1,
The cyclic carbonate-based compound is at least two or more selected from the group consisting of vinylene carbonate (VC), vinylethylene carbonate (VEC) and fluoroethylene carbonate (FEC).
The method according to claim 1,
The weight ratio of the oligomer and the cyclic carbonate-based compound is 1:0.001 to 1:150 for a lithium secondary battery non-aqueous electrolyte.
a positive electrode including a positive active material;
a negative electrode including an anode active material;
a separator interposed between the negative electrode and the positive electrode; and
A lithium secondary battery comprising the non-aqueous electrolyte for a lithium secondary battery of claim 1.