KR20220106667A - Electrolyte Solution And Secondary Battery Comprising The Same - Google Patents

Abstract

The present invention relates to an electrolyte and a secondary battery including the same. According to the present invention, provided is a secondary battery capable of improving charging efficiency and output due to low discharge resistance and having long lifespan and high-temperature capacity retention rates by suppressing generation of gas and an increase in thickness. The electrolyte of the present invention includes an organic solvent, lithium salt, a first additive and a second additive.

Description

Electrolyte solution and secondary battery including same {Electrolyte Solution And Secondary Battery Comprising The Same}

The present invention relates to an electrolyte and a secondary battery including the same, and more particularly, to an electrolyte for a battery comprising an electrolyte additive capable of improving the output characteristics and high-temperature storage characteristics of the battery, and significantly reducing the gas generation and thickness increase rate and secondary batteries.

Lithium secondary batteries enable smooth movement of lithium ions by putting an electrolyte between the positive and negative electrodes, and electricity is generated or consumed by redox reactions according to insertion and desorption from the positive and negative electrodes.

Lithium secondary batteries, which are mainly used as power sources for mobile IT devices such as mobile phones and power tools, are expanding their use for automobiles and energy storage as technology for large-capacity increases.

As such application fields expand and demand increases, better battery performance and stability than the characteristics required for conventional small batteries are required. In order to improve, various studies are being made on organic solvents and additives as components with electrolyte.

Conventionally, in the case of an electrolyte that does not contain an electrolyte additive or includes an electrolyte additive having poor properties, it is difficult to expect improvement in low-temperature output characteristics due to the formation of a non-uniform SEI film. Moreover, even when the electrolyte additive is included, if the input amount cannot be adjusted to the required amount, the anode surface is decomposed during a high-temperature reaction due to the electrolyte additive or the electrolyte causes an oxidation reaction, ultimately reducing the cycle characteristics and storage stability of the secondary battery there was a problem with

Korean Patent Registration No. 1295395

In order to solve the problems of the prior art as described above, the present invention is to provide an electrolyte for a battery including an electrolyte additive that can improve the output characteristics and high-temperature storage characteristics of the battery, and can significantly reduce the gas generation and thickness increase rate. The purpose.

Another object of the present invention is to provide an excellent secondary battery capable of reducing discharge resistance to improve battery output, improving recovery capacity at high temperatures, enabling long-term storage, and suppressing gas generation in the battery.

The above and other objects of the present invention can all be achieved by the present invention described below.

In order to achieve the above object, the present invention is an electrolyte comprising an organic solvent, a lithium salt, a first additive and a second additive,

The first additive has one double bond and contains 20% by weight or less of the compound represented by the following Chemical Formula 1, based on 100% by weight of the electrolyte,

The second additive is a compound composed of 3 to 5 atoms, having 2 to 4 atoms having an electronegativity of 3 or more, having at least one double bond and having an atomic group represented by the following Chemical Formula 2, the electrolyte solution 100 weight It provides an electrolyte, characterized in that it contains 0.01 to 10% by weight based on the %.

[Formula 1]

(In Formula 1, A is carbon (C), X ₁ , and X ₁ ' are independently carbon or oxygen, R ₁ , and R ₁ ' are independently a bond, substituted or unsubstituted carbon number. 1 to 10 alkylene, and contains at least one carbon.)

[Formula 2]

(In Formula 2, the solid line is a bond.)

The first additive may be a compound represented by Chemical Formula 3.

[Formula 3]

(In Formula 3, the solid line is a bond, and when a separate element is not described, the point where the bond and the bond meet is carbon, and the number of hydrogens satisfying the valence of the carbon is omitted.)

The second additive may be a compound represented by Formula 4 below.

[Formula 4]

이며, R₆ 및 R₇은 독립적으로 탄소수 1 내지 5의 알킬기 또는 탄소수 6 내지 10의 아릴기이다.) (In Formula 4, R ₄ is OR ₆ or R ₆ , R ₅ is R ₇ A, A is

and R ₆ and R ₇ are independently an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 10 carbon atoms.)

The second additive may be at least one selected from compounds represented by the following Chemical Formulas 5 to 6.

[Formula 5]

[Formula 6]

(In Formulas 5 to 6, A is phosphorus (P), sulfur (S) or nitrogen (N), and X ₁ , X ₂ , X ₃ , X ₁ ', X ₂ ' and X ₃ ' are independently bonded. (bond) or oxygen, n is an integer from 0 to 3, R ₁ , R ₂ , R ₃ , R ₁ ', R ₂ ' and R ₃ ' are independently a bond, substituted or unsubstituted carbon number. 1 to 10 alkylene, and contains at least one carbon.)

The second additive may be a compound represented by Chemical Formula 7.

[Formula 7]

(In Chemical Formula 7, the solid line is a bond, and when a separate element is not described, the point where the bond and the bond meet is carbon, and the number of hydrogens satisfying the valence of the carbon is omitted.)

The first additive and the second additive may be included in a weight ratio of 1:0.1 to 1.7 (first additive: second additive).

The lithium salt is LiPF ₆ , LiClO ₄ , LiTFSI, LiAsF ₆ , LiBF ₄ , LiBF ₆ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiBOB, LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiAlO ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiCH ₃ SO ₃ , LiBeTI, LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ) ₂ , LiN(CF ₃ SO ₂ ) _{2 ,} LiN(CaF _2a+1 SO ₂ )(C _b F _2b+1 SO ₂ ) (provided that a and b are natural numbers), LiCl, LiI, LiBr, and LiB (C ₂ O ₄ ) ₂ It may include one or more selected from the group consisting of.

The organic solvent is ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), Ethylmethyl carbonate (EMC), methylethyl carbonate (MEC), fluoroethylene carbonate (FEC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-butylene carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, butyl propionate, γ-butyrolactone, γ-valerolactone, γ -caprolactone, σ-valerolactone, and ε-caprolactone may include two or more selected from the group consisting of.

The electrolyte may include at least one third additive selected from the group consisting of a boron compound, a phosphorus compound, a sulfur compound, and a nitrogen-based compound in an amount of 10% by weight or less based on 100% by weight of the total electrolyte.

Also, the present invention

a compound having one double bond and represented by the following formula (1); and

It provides an electrolyte solution additive comprising a compound represented by the following formula (4).

[Formula 1]

(In Formula 1, A is carbon (C), X ₁ , and X ₁ ' are independently carbon or oxygen, R ₁ , and R ₁ ' are independently a bond, substituted or unsubstituted carbon number. 1 to 10 alkylene, and contains at least one carbon.)

[Formula 4]

이며, R₆ 및 R₇은 독립적으로 탄소수 1 내지 5의 알킬기 또는 탄소수 6 내지 10의 아릴기이다.) (In Formula 4, R ₄ is OR ₆ or R ₆ , R ₅ is R ₇ A, A is

and R ₆ and R ₇ are independently an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 10 carbon atoms.)

The compound represented by Formula 1 and the compound represented by Formula 4 may be included in a weight ratio of 1:0.1 to 1.7 (first additive: second additive).

Also, the present invention

A secondary battery comprising a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte,

The electrolyte provides a lithium secondary battery, characterized in that the above-described electrolyte.

The secondary battery may have a discharge resistance value of 40 mΩ or less at 60°C.

The secondary battery may have a recovery capacity of 1000 mAh or more at 60°C.

The secondary battery may have a thickness increase rate of 10.81% or less at 60° C. calculated by Equation 1 below.

[Equation 1]

Thickness increase rate (%) = {(thickness after high temperature storage - initial thickness) / initial thickness} X 100

The secondary battery is calculated by Equation 2 below after 300 cycles The coulombic efficiency may be greater than or equal to 99.4%.

[Equation 2]

Coulombic efficiency (%) = (discharge capacity at 300 cycles / charge capacity at 300 cycles) X 100

The secondary battery may be an energy storage system (ESS) or a battery for a vehicle.

When the electrolyte for a battery according to the present invention is included in a secondary battery, the output can be improved by reducing the discharge resistance, and the recovery capacity at high temperature is improved to provide a secondary battery excellent in long-term lifespan and high-temperature capacity retention. .

In particular, the additive for a battery according to the present invention has the effect of providing a secondary battery with excellent performance and lifespan by suppressing gas generation and thickness increase in the battery.

Hereinafter, the electrolyte solution additive of the present invention, the electrolyte solution for a battery, and a secondary battery including the same will be described in detail.

The present inventors have been studying a secondary battery having improved output and excellent high temperature recovery capacity and lifespan characteristics in order to manufacture a battery that can be used as an automobile battery. It was confirmed that all of the purposes of the present invention can be achieved, and based on this, further research was made to complete the present invention.

The electrolyte solution additive of the present invention includes a first additive and a second additive, wherein the first additive has one double bond and is a compound represented by the following Chemical Formula 1, wherein the second additive is composed of 3 to 5 atoms, , It is characterized in that it is a compound having 2 to 4 atoms having an electronegativity of 3 or more, having at least one double bond and having an atomic group represented by the following Chemical Formula 2, in which case the discharge resistance is reduced to improve the output of the battery The recovery capacity at high temperature is improved, so that long-term storage is possible, and there is an excellent effect of maintaining the lifespan at high temperature.

[Formula 1]

(In Formula 1, A is carbon (C), X ₁ , and X ₁ ' are independently carbon or oxygen, R ₁ , and R ₁ ' are independently a bond, substituted or unsubstituted carbon number. 1 to 10 alkylene, and contains at least one carbon.)

[Formula 2]

(In Formula 2, the solid line is a bond.)

In addition, the electrolyte solution for a battery of the present invention is characterized in that it contains the electrolyte solution additive.

When the compound represented by Chemical Formula 1 is added to the electrolyte of a secondary battery, electrons are localized toward the O element due to the electronegativity difference between the A(=C) element and the O element directly connected thereto. Accordingly, element C becomes in an e-poor (δ+) state and an oxidation reaction is induced in an electrolyte containing lithium ions, forming a stable film on the electrode, specifically, the cathode. At this time, it is possible to prevent the decomposition of the electrolyte due to the stability of the film, and thereby cycle characteristics can be improved, and in particular, it does not decompose at a high temperature. There is an excellent effect of greatly improving the storability. In addition, since the increase in resistance is prevented, charging efficiency and output are improved, and gas generation due to a chemical reaction inside the battery is also suppressed, so that the safety of the battery can be improved. In addition, the capacity retention rate is improved by preventing the structural collapse of the electrode active material of the positive electrode and the negative electrode at a high temperature, thereby extending the lifespan.

As a specific example, the first additive may be a compound represented by the following Chemical Formula 3, and when a lithium secondary battery is constructed using an electrolyte containing the same, the terminal group of the compound has an effect of inhibiting the decomposition of the electrolyte, This has the effect of reducing the increase rate of internal resistance.

[Formula 3]

(In Formula 3, the solid line is a bond, and when a separate element is not described, the point where the bond and the bond meet is carbon, and the number of hydrogens satisfying the valence of the carbon is omitted.)

As a specific example, when it has the structure represented by Formula 3, it is a symmetrical structure and the electron flow in the molecule can be stabilized, so it is preferable in terms of molecular structure stabilization and chemical stability, ion mobility of the electrolyte, and prevention of side reactions of the electrode active material. In addition, the discharge resistance of the secondary battery including the same is lowered, the battery output is improved, the charge recovery capacity is increased at a high temperature, and the life efficiency is excellent, so it is preferable as an electrolyte additive for a battery.

The X ₁ , and X ₁ ' are each independently preferably carbon or oxygen, and the X ₁ , and X ₁ ' are all carbon, or when both are oxygen, they are chemically stable and inactive and the molecular structure is simplified. It is the most desirable from the viewpoint of stability. In particular, as a symmetrical structure, not only the electron flow in the molecule is stabilized, but also molecular rigidity is increased through this, which has a great advantage in improving the battery performance.

Each of R ₁ and R ₂ is independently a bond, substituted or unsubstituted C 1 to C 10 alkylene, and preferably includes at least one carbon, and R ₁ and R ₂ are both unsubstituted. In the case of alkylene having 1 to 10 carbon atoms, it is chemically stabilized to become inactive, and the molecular structure is simplified, so it is most preferable in terms of stability. In particular, in the case of alkylene having the same number of carbon atoms, as a symmetrical structure, electron flow in the molecule is stabilized, and molecular rigidity is increased through this, thereby greatly improving battery performance.

The electrolyte of the present invention may contain 20% by weight or less of the first additive based on 100% by weight of the total electrolyte, preferably 0.01 to 15% by weight. Within this range, the decomposition effect of the electrolyte is suppressed, and there is an advantage in that the life characteristics and cycle characteristics of the battery are improved.

The second additive may have, for example, an atomic group represented by the following Chemical Formula 2, and in this case, the stability of the electrolyte may be further improved by adsorbing to the metal surface of the electrode to suppress a side reaction between the electrode and the electrolyte, thereby The cycle characteristics, stability and lifespan of the battery can be improved.

[Formula 2]

(In Formula 2, the solid line is a bond.)

As used herein, the term "atomic group" refers to a polyatomic ion covalently bonded, unless otherwise specified.

The second additive may be a compound represented by Formula 4 below.

[Formula 4]

이며, R₆ 및 R₇은 독립적으로 탄소수 1 내지 5의 알킬기 또는 탄소수 6 내지 10의 아릴기이다.)(In Formula 4, R ₄ is OR ₆ or R ₆ , R ₅ is R ₇ A, A is

and R ₆ and R ₇ are independently an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 10 carbon atoms.)

When the electrolyte solution additive including the compound represented by Formula 4 is added to the electrolyte solution of a secondary battery, electrons are localized toward the O element due to the electronegativity difference between the S element and the O element directly connected thereto. As a result, the element S becomes an electron-poor (δ+) state and an oxidation reaction is induced in an electrolyte containing lithium ions, forming a stable film on the electrode, a specific example, the cathode, and at the same time replacing the terminal The ionic conductivity is improved due to the added halogen substituent.

At this time, it is possible to prevent the decomposition of the electrolyte due to the stability of the film, and thereby cycle characteristics can be improved. There is an excellent effect of greatly improving. In addition, since the increase in resistance is prevented, charging efficiency and output are improved, and gas generation due to a chemical reaction inside the battery is also suppressed, so that the safety of the battery can be improved.

Specifically, the generation of gas inside the battery is mainly generated by the decomposition of electrolyte components, especially carbonate-based solvents, on the surface of the positive/negative electrode, and the positive/negative protective film is easily deteriorated or is further promoted due to oxygen radicals generated from the positive electrode. This material can inhibit the direct decomposition of the solvent by forming a protective film with excellent stability composed of N, S, O, and F components. Desorption of the oxygen element constituting the skeleton of the anode can be prevented.

In addition, the capacity retention rate is improved by preventing the structure collapse of the electrode active material of the positive electrode and the negative electrode at a high temperature, thereby extending the lifespan.

The second additive may be at least one selected from compounds represented by the following Chemical Formulas 5 to 6, and when a lithium secondary battery is constructed using an electrolyte containing the same, the terminal group of the compound has an effect of inhibiting the decomposition of the electrolyte. Thereby, there is an effect of reducing the increase rate of the internal resistance.

[Formula 5]

[Formula 6]

(In Formulas 5 to 6, A is phosphorus (P), sulfur (S) or nitrogen (N), and X ₁ , X ₂ , X ₃ , X ₁ ', X ₂ ' and X ₃ ' are independently bonded. (bond) or oxygen, n is an integer from 0 to 3, R ₁ , R ₂ , R ₃ , R ₁ ', R ₂ ' and R ₃ ' are independently a bond, substituted or unsubstituted carbon number. 1 to 10 alkylene, and contains at least one carbon.)

As a specific example, when the second additive has the structure represented by Chemical Formula 6, the electron flow in the molecule can be stabilized as a symmetrical structure, thereby greatly improving battery performance.

The compound represented by the formula (6) may preferably be a compound represented by the following formula (7), and in this case, the electron flow in the molecule is stabilized as a symmetrical structure, thereby greatly improving battery performance.

[Formula 7]

(In Chemical Formula 7, the solid line is a bond, and when a separate element is not described, the point where the bond and the bond meet is carbon, and the number of hydrogens satisfying the valence of the carbon is omitted.)

The electrolyte of the present invention may include 0.1 to 10% by weight of the second additive, preferably 0.1 to 5% by weight, based on 100% by weight of the total electrolyte. Within this range, the decomposition effect of the electrolyte is suppressed, and there is an advantage in that the life characteristics and cycle characteristics of the battery are improved.

The electrolyte of the present invention can maximize the effect of inhibiting side reactions of the electrolyte by using a combination of the first and second additives, and when a lithium secondary battery including the electrolyte is configured, the amount of gas generated when left at high temperature is reduced This has the effect of reducing the increase rate of internal resistance and ultimately improving the lifespan characteristics of the battery.

When the first additive and the second additive are included in a weight ratio of 1:0.1 to 1.7 (first additive: second additive), or 1:0.2 to 1.6, based on 100% by weight of the total electrolyte, the battery It may provide a stability improvement effect.

The non-aqueous solvent that may be included in the electrolyte of the present invention is not particularly limited as long as it can minimize decomposition due to oxidation reaction during the charging and discharging process of the battery, and can exhibit desired properties together with the additive. For example, a carbonate-based organic solvent, It may be an acetate-based organic solvent, a propionate-based organic solvent, or an ester-based organic solvent. These may be used alone, or two or more may be used in combination.

For example, in 10 to 100% by volume of the carbonate-based organic solvent, one or more selected from the group consisting of an acetate-based organic solvent, a propionate-based organic solvent, and an ester-based organic solvent may be mixed at a maximum of 90% by volume.

Among the non-aqueous solvents, the carbonate-based organic solvent is, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC) , dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl ethyl carbonate (MEC), fluoroethylene carbonate (FEC), methyl propyl carbonate (MPC) and one selected from the group consisting of ethyl propyl carbonate (EPC) may be more than

Among the carbonate-based organic solvents, more preferably, a carbonate-based organic solvent having high ionic conductivity capable of increasing the charging and discharging performance of a battery and a low-viscosity carbonate capable of appropriately adjusting the viscosity of the organic solvent having a high dielectric constant It may be preferable to use a mixture of organic solvents.

Specifically, an organic solvent of high dielectric constant selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof, and an organic solvent of low viscosity selected from the group consisting of ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, and mixtures thereof. It can be used by mixing.

Preferably, the high dielectric constant organic solvent and the low viscosity organic solvent are mixed in a volume ratio of 2:8 to 8:2, and more specifically, ethylene carbonate or propylene carbonate; ethyl methyl carbonate; And dimethyl carbonate or diethyl carbonate may be mixed in a volume ratio of 5:1:1 to 2:5:3, for example, 3:5:2 by volume.

As a specific example, the carbonate-based organic solvent may include ethylene carbonate (EC), diethyl carbonate (DEC) and ethylmethyl carbonate (EMC), and 10 to 40 wt% or 15 to 35 wt% of ethylene carbonate, 20 to 30% by weight or 22 to 28% by weight; 15 to 45% by weight, 20 to 40% by weight, 25 to 35% by weight or 27 to 33% by weight of diethyl carbonate; Ethylmethyl carbonate may be used in an amount of 30 to 60% by weight, 35 to 55% by weight, 40 to 50% by weight, or 42 to 48% by weight.

The acetate-based organic solvent may include, for example, methyl acetate, ethyl acetate, propyl acetate, and the like, but is not limited thereto.

The propionate-based organic solvent may include, for example, propionate, methylpropionate, and the like, but is not limited thereto.

The ester-based organic solvent may be γ-butyrolactone, γ-valerolactone, γ-gaprolactone, σ-valerolactone, ε-caprolactone, or the like.

The organic solvent may be used, for example, in an amount remaining after subtracting the content of components other than the organic solvent from the electrolyte, and in a specific example, may be used in an amount of 10 wt % or less of the total weight of the electrolyte.

When the organic solvent contains moisture, lithium ions in the electrolyte may be hydrolyzed, so that the moisture in the organic solvent is preferably controlled to be 150 ppm or less, preferably 100 ppm or less.

Lithium salts that may be included in the electrolyte of the present invention are, for example, LiPF ₆ , LiClO ₄ , LiTFSI, LiAsF ₆ , LiBF ₄ , LiBF ₆ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiBOB, LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiAlO ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiCH ₃ SO ₃ , LiBeTI, LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) _{2 ,} LiN(CaF _2a+1 SO ₂ )(C _b F _2b+1 SO ₂ ) (provided that a and b are natural numbers) , LiCl, LiI, LiBr, and LiB(C ₂ O ₄ ) ₂ At least one selected from the group consisting of 2 may be used, preferably LiPF ₆ may be used. The a and b may be an integer of 1 to 4, for example.

When the lithium salt is dissolved in the electrolyte, the lithium salt functions as a source of lithium ions in the lithium secondary battery, and may promote movement of lithium ions between the positive electrode and the negative electrode. Accordingly, the lithium salt is preferably contained in a concentration of about 0.6 to 2M in the electrolyte. If the concentration of the lithium salt is less than 0.6M, the conductivity of the electrolyte may be lowered, and thus electrolyte performance may be deteriorated.

Considering the conductivity of the electrolyte and the mobility of lithium ions, the lithium salt may be included in the electrolyte at a concentration of 0.5 to 1.5M (mol/L), preferably in a concentration of 0.7 to 1.3M, and , More preferably, it may be included in a concentration of 0.8 to 1.1M. Within this range, the conductivity of the electrolyte is high, so that the performance of the electrolyte is excellent, and the viscosity of the electrolyte is low, so that the mobility of lithium ions is excellent.

The electrolyte may have, for example, a lithium ion conductivity of 0.3 S/m or more, or 0.3 to 10 S/m under a condition of 25° C., and cycle life characteristics of a lithium secondary battery may be further improved within the above range .

In addition to the electrolyte components, the electrolyte may further include an electrolyte additive that is generally used in the electrolyte for the purpose of improving battery life characteristics, suppressing reduction in battery capacity, and improving discharge capacity of a battery.

The electrolyte additive may be, for example, at least one selected from the group consisting of a boron compound, a phosphorus compound, a sulfur compound, and a nitrogen-based compound (hereinafter, also referred to as a 'third additive').

The third additive may be, for example, at least one selected from compounds represented by the following Chemical Formulas 8 to 20, and by including the third additive, it is possible to more effectively suppress the decomposition reaction of the electrolyte.

[Formula 8]

[Formula 9]

[Formula 10]

[Formula 11]

[Formula 12]

[Formula 13]

[Formula 14]

[Formula 15]

[Formula 16]

[Formula 17]

[Formula 18]

[Formula 19]

[Formula 20]

(In Chemical Formulas 8 to 20, the solid line is a bond, and when a separate element is not described, the point where the bond and the bond meet is carbon, and the number of hydrogens satisfying the valence of the carbon is omitted.)

The electrolyte of the present invention may include 10% by weight or less of the third additive based on 100% by weight of the total electrolyte, preferably 1 to 5% by weight. Within this range, the decomposition effect of the electrolyte is suppressed, and there is an advantage in that the life characteristics and cycle characteristics of the battery are improved.

In addition, the electrolyte additive may include, for example, metal fluoride, and when the metal fluoride is further included as the electrolyte additive, the influence of acid generated around the positive electrode active material is reduced, and the positive electrode By suppressing the reaction between the active material and the electrolyte, it is possible to improve a phenomenon in which the capacity of the battery is rapidly reduced.

Specifically, the metal fluoride is LiF, RbF, TiF, AgF, AgF2, BaF2, CaF2, CdF2, FeF2, HgF2, Hg2F2, MnF2, NiF2, PbF2, SnF2, SrF2, XeF2, ZnF2, AlF3, BF3, BiF3 CeF3, CrF3, DyF3, EuF3, GaF3, GdF3, FeF3, HoF3, InF3, LaF3, LuF3, MnF3, NdF3, PrF3, SbF3, ScF3, SmF3, TbF3, TiF3, TmF3, YF3, YbF3, TIF3, CeF3, TIF3, CeF3 HfF4, SiF4, SnF4, TiF4, VF4, ZrF44, NbF5, SbF5, TaF5, BiF5, MoF6, ReF6, SF6, WF6, CoF2, CoF3, CrF2, CsF, ErF3, PF3, PbF3, PbF4, ThF6 SeF4, TaF5 and SeF6 It may be at least one selected from the group consisting of.

The metal fluoride may be included, for example, in an amount of 0.1 to 10% by weight, or 0.2 to 5% by weight, based on the total weight of the electrolyte, and cycle life characteristics of the lithium secondary battery may be further improved within this range.

The electrolyte according to the present invention having the composition as described above suppresses the decomposition reaction of the electrolyte in a wide temperature range of -20 ° C to 60 ° C. can In addition, since the structure of the battery itself is the same as that of a general electrolyte secondary battery, there is an advantage in that it is easy to manufacture and is advantageous for mass production.

A lithium secondary battery according to the present invention includes a positive electrode; cathode; a separator provided between the anode and the cathode; and an electrolyte solution. The electrolyte may include the above-described electrolyte, and the positive electrode and the negative electrode may include a positive electrode active material and a negative electrode active material, respectively.

The positive electrode may be prepared by, for example, mixing a positive electrode active material, a binder, and optionally a conductive agent to prepare a composition for forming a positive electrode active material layer, and then applying it to a positive electrode current collector such as aluminum foil.

The positive active material may include, for example, conventional lithium composite metal oxides and lithium olivine-type phosphates used in lithium secondary batteries. Preferably, the positive active material includes at least one metal selected from the group consisting of cobalt, manganese, nickel and iron. and more preferably NCM (lithium nickel*?*?* oxide) may be used.

As a specific example, the cathode active material may be a lithium composite metal oxide having the formula Li[Ni _x Co _1-xy Mn _y ]O ₂ (where 0<x<0.5, 0<y<0.5), but is not limited thereto. Variables x and y of the formula Li[Ni _x Co _1-xy Mn _y ]O ₂ of the lithium composite metal oxide are, for example, 0.0001<x<0.5, 0.0001<y<0.5, or 0.001<x<0.3, 0.001<y <0.3.

As another example of the positive active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) may be used. Among the above compounds, LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _x Mn _(1-x) O ₂ (provided that 0<x<1), and LiMl _x M2 _y O ₂ (provided that 0≤x≤1, 0≤y≤1, 0≤x+y≤1, M1 and M2 are each independently any one selected from the group consisting of Al, Sr, Mg and La ), preferably at least one selected from the group consisting of.

In addition, among the positive active materials, lithium olivine-type phosphate may preferably include, for example, one or more selected from iron, cobalt, nickel and manganese, specifically LiFePO ₄ , LiCoPO ₄ and LiMnPO ₄ , etc. may include In addition, a compound in which some metals of the lithium olivine-type phosphate are substituted with other metals may also be possible.

The negative electrode may be prepared by, for example, mixing a negative electrode active material, a binder, and optionally a conductive agent to prepare a composition for forming an anode active material layer, and then applying it to an anode current collector such as copper foil.

As the anode active material, for example, a compound capable of reversible intercalation and deintercalation of lithium may be used.

The negative active material may include, for example, at least one selected from the group consisting of tin, a tin compound, silicon, a silicon compound, lithium titanate, crystalline carbon, amorphous carbon, artificial graphite, and natural graphite.

In the present description, the tin compound or the silicon compound is a compound in which tin or silicon is bonded to one or more other chemical elements, respectively.

In addition to the carbonaceous material including the crystalline carbon, amorphous carbon, graphite, etc., a metal compound capable of alloying with lithium or a composite including a metal compound and a carbonaceous material may also be used as the negative electrode active material. For example, it may be graphite.

As the metal capable of alloying with lithium, for example, at least one of Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy may be used. In addition, a metal lithium thin film may be used as the negative electrode active material.

As the negative active material, any one or more selected from the group consisting of crystalline carbon, amorphous carbon, carbon composite material, lithium metal, and an alloy containing lithium in view of high stability may be used.

For example, a separator may be positioned between the above-described positive electrode and negative electrode, inserted into the cell, and then an electrolyte may be injected and sealed to complete the battery assembly. In this case, the lithium secondary battery including the above-described electrolyte, positive electrode, negative electrode and separator is, for example, a unit cell having a structure of positive electrode/separator/negative electrode, a bicell having a structure of positive electrode/separator/negative electrode/separator/positive electrode, or a unit cell It is a self-evident fact that the structure of can be formed as a structure of a repeated stacked cell.

In the secondary battery according to an embodiment of the present invention, by adding the first additive and the second additive to improve battery performance, the battery discharge resistance, output characteristics, and 60° C. measured by the Hybrid Pulse Power Characterization (HPPC) method At the above high temperature, there is an effect of improving battery characteristics such as capacity recovery characteristics and lifespan characteristics.

In the secondary battery according to another embodiment of the present invention, the battery discharge resistance, output characteristics, and 60 ℃ measured by the HPPC (Hybrid Pulse Power Characterization) method by adding a performance improving agent in addition to the first and second additives added to the electrolyte solution. At the above high temperature, there is an effect that the improvement effect of battery characteristics such as capacity recovery characteristics and lifespan characteristics is further improved.

Specifically, in the secondary battery of the present invention, the HPPC discharge resistance value measured at 60° C. may be 40 mΩ or less, and preferably 25 to 39 mΩ.

In this description, the HPPC discharge resistance value can be measured by a method specified in the document “Battery test manual for plug-in hybrid electric vehicles,” (2010, Idaho National Laboratory for the US Department of Energy.) It is an important indicator of battery characteristics such as battery output. In addition, the discharge resistance is a resistance value measured when the battery is discharged, and may provide improved output performance within the above range. The lower the discharge resistance, the less energy loss, the faster the charging speed, and the higher the output of the battery. The secondary battery of the present invention has excellent charging speed and output since the HPPC discharge resistance value is reduced by up to 23.6%, and is suitable for use as, for example, an automobile battery.

Specifically, the secondary battery of the present invention may have a recovery capacity of 1000 mAh or more, preferably 1000 to 1130 mAh, measured at 60°C.

In the present description, the recovery capacity indicates the capacity retention characteristics of a battery left for a long time, and the discharged electric capacity when the battery left for a long time is discharged to the end-of-discharge voltage, and the discharged battery after recharging the battery until the end-of-discharge voltage. The discharged electric capacity at the time of discharging was measured, respectively, and the two capacity values were compared. The higher the recovery capacity, the less the amount of natural discharge due to battery preservation (storage), which means that the battery can be stored for a long time. This is a very important characteristic in a battery. When the electrolyte solution additive of the present invention is added to the electrolyte solution for a battery, the recovery capacity is improved as described above, so that it can be stored for a longer period of time with a single charge.

In addition, the thickness of the secondary battery may be 4.1 mm or less, preferably 3.9 to 4.1 mm, measured at 60°C.

In addition, the secondary battery may have a thickness increase rate of 10.81% or less at 60°C calculated by Equation 1 below, preferably 2.63 to 10.81%.

[Equation 1]

Thickness increase rate (%) = {(thickness after high temperature storage - initial thickness) / initial thickness} X 100

In the present description, the thickness increase rate represents the swelling characteristic due to the generation of gas inside the battery, and the difference between the two values is compared by measuring the initial thickness of the pouch cell and the thickness after standing at high temperature, respectively. When a stable film is formed on the positive electrode and the negative electrode, the decomposition of the electrolyte component can be suppressed. Therefore, as the thickness increase rate is lower, stability according to repeated charging and discharging of the battery can be provided, thereby providing improved battery life.

In addition, the secondary battery may have a coulombic efficiency of 99.4% or more, preferably 99.4 to 99.8%, as measured by Equation 2 below.

[Equation 2]

Coulombic efficiency (%) = (discharge capacity at 300 cycles / charge capacity at 300 cycles) X 100

In the present description, the coulombic efficiency is calculated based on the charging capacity and the discharging capacity at 300 cycles, and has the effect of improving the charging and discharging efficiency .

Therefore, when the battery of the present invention is used as a vehicle battery, the improvement of output, which becomes important depending on the size of the vehicle, and climate change, at low and high temperatures, which are problems in the environment of automobiles exposed to sunlight while driving or parking, The performance and lifespan of the battery can be improved, thereby exhibiting excellent performance as an automobile battery.

The lithium secondary battery according to the present disclosure may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of separator and electrolyte used, and may be classified into a cylindrical shape, a square shape, a coin type, a pouch type, etc. according to the shape. It can be classified, and can be divided into a bulk type and a thin film type according to the size. The electrolyte solution according to the embodiment of the present disclosure is particularly excellent for application to a lithium ion battery, an aluminum laminate battery, and a lithium polymer battery.

The lithium secondary battery comprising the electrolyte according to the present disclosure can improve the lifespan characteristics and increase the internal resistivity, as well as reduce the thickness increase rate and the gas generation rate, especially at a high temperature of 45 ° C. or higher, for example 45 ° C. to 60 ° C., When the battery of the present invention is used as an automobile battery, performance at low and high temperatures, which is a problem due to the characteristics of automobiles exposed to sunlight while driving or parking, and climate change, which becomes important depending on the size of the automobile, Improvements can be made to exhibit excellent performance as an automobile battery.

That is, when the electrolyte additive according to the embodiments of the present invention and the electrolyte containing the same are applied to a secondary battery, the discharge resistance, output, recovery capacity and life efficiency are improved, so it is suitable for use as a secondary battery for automobiles, Portable devices such as mobile phones, laptop computers, digital cameras, and camcorders, electric vehicles such as hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), and medium and large-sized energy storage systems can be useful for

Hereinafter, preferred examples are presented to help the understanding of the present invention, but the following examples are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It goes without saying that such variations and modifications fall within the scope of the appended claims.

[Example: Preparation of electrolyte solution for batteries]

Examples 1-1 to 1-2, Comparative Example 1-1, and Reference Example 1-1

As an organic solvent, LiPF ₆ as a lithium salt is dissolved in a carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC = 2:4:4 to a concentration of 1.15M, and as a first electrolyte additive, the following formula 1a (Formula 3) A compound represented by a compound represented by ), a compound represented by the following formula 1b (also represented by formula 14), a compound represented by the following formula 1c, and a compound represented by the following formula 2a (also represented by formula 7) as a second electrolyte additive was added according to the content shown in Table 1 to prepare an electrolyte solution for a battery.

[Formula 1a]

[Formula 1b]

[Formula 1c]

[Formula 2a]

division first additive type First additive content (wt%) Second additive type Second additive content (wt%) Example 1-1 Equation 1a 5 Equation 2a 3 Example 1-2 Equation 1a 5 Equation 2a 3 Equation 1b 5 Comparative Example 1-1 Equation 1a 5 - - Reference Example 1-1 Equation 1a 5 Equation 2a 3 formula 1c 10

Examples 2-1 to 2-3, and Comparative Example 2-1

As an organic solvent, LiPF ₆ as a lithium salt is dissolved in a carbonate-based mixed solvent having a volume ratio of EC:EMC:DMC = 2:4:4 to a concentration of 1.15M, and as a first electrolyte additive represented by the following formula 1d A compound (also represented by Formula 13) and a compound represented by Formula 1a below (also represented by Formula 16) and a compound represented by Formula 1b below (also represented by Formula 18), and a second electrolyte additive represented by Formula 2a The compound was added in the amount shown in Table 2 to prepare an electrolyte for a battery.

[Formula 1d]

division first additive type First additive content (wt%) Second additive type Second additive content (wt%) Example 2-1 expression 1d 10 Equation 2a 3 Example 2-2 expression 1d 5 Equation 2a 3 Equation 1b 5 Example 2-3 expression 1d 5 Equation 2a 3 Equation 1a 5 Equation 1b 5 Comparative Example 2-1 expression 1d 5 - -

Example 3-1, Comparative Example 3-1, and Reference Example 3-1

LiPF ₆ as a lithium salt is dissolved in a carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC = 2:4:4 to a concentration of 1.15M, and the compound represented by Formula 1b as a first electrolyte additive (Formula 18 ) and the compound represented by Formula 2a as a second electrolyte additive in the amount shown in Table 3 below to prepare an electrolyte for a battery.

division first additive type First additive content (wt%) Second additive type Second additive content (wt%) Example 3-1 Equation 1b 5 Equation 2a 3 Comparative Example 3-1 Equation 1b 5 - - Reference Example 3-1 Equation 1b 3 Equation 2a 3

Examples 4-1 to 4-2, and Comparative Examples 4-1 to 4-2

As an organic solvent, LiPF ₆ as a lithium salt is dissolved in a carbonate-based mixed solvent having a volume ratio of EC:EMC:DMC = 2:4:4 to a concentration of 1.15M, and as a first electrolyte additive, the following formula 1e (Formula 15) The compound represented by the compound represented by the formula 1f (also represented by the formula 16), the compound represented by the formula 1g below, and the compound represented by the formula 2a as the second electrolyte additive are shown in Table 4 below. An electrolyte solution for a battery was prepared by adding it according to the indicated content.

[Formula 1e]

[Formula 1f]

[Formula 1g]

division first additive type First additive content (wt%) Second additive type Second additive content (wt%) Example 4-1 Equation 1e 15 Equation 2a 3 Example 4-2 Equation 1e 10 Equation 2a 3 formula 1f 10 Comparative Example 4-1 Equation 1e 10 Equation 2a 3 1 g of formula 5 Comparative Example 4-2 Equation 1e 15 - -

Example 5-1, and Comparative Examples 5-1 to 5-3

As an organic solvent, LiPF ₆ as a lithium salt is dissolved in a carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC = 2:4:4 to a concentration of 1.15M, and the first electrolyte additive is represented by the following formula 1h A compound in which h is 1 and a cation is lithium (also represented by Formula 17), a compound represented by the following Formula 1h, h is 1 and a cation is sodium, a compound represented by Formula 1g, and a second electrolyte solution additive A battery electrolyte was prepared by adding the compound represented by Chemical Formula 2a as shown in Table 5 below.

[Formula 1h]

division first additive type First additive content (wt%) Second additive type Second additive content (wt%) Example 5-1 Formula 1h + lithium 0.5 Equation 2a 3 Comparative Example 5-1 Formula 1h + lithium 10 - - Comparative Example 5-2 Formula 1h + sodium 0.5 Equation 2a 3 Comparative Example 5-3 Formula 1h + lithium 10 Equation 2a 3 1 g of formula 5

manufacture of batteries

100 wt. % of a cathode mixture comprising 92 wt% of Li(Ni _0.8 Co _0.1 Mn _0.1 )O ₂ as a cathode active material, 4 wt% of carbon black as a conductive agent, and 4 wt% of polyvinylidene fluoride (PVdF) as a binder A positive electrode mixture slurry was prepared by adding 100 parts by weight of N-methyl-2-pyrrolidone (NMP) as a solvent. The positive electrode mixture slurry was applied to an aluminum (Al) thin film as a positive electrode current collector having a thickness of about 20 μm, dried to prepare a positive electrode, and then a positive electrode was prepared by roll press.

In addition, 100 parts by weight of a negative electrode mixture comprising carbon powder blended with artificial graphite and natural graphite as an anode active material, PVdF as a binder, and carbon black as a conductive material in 96 wt%, 3 wt% and 1 wt%, respectively, A negative electrode mixture slurry was prepared by adding 100 parts by weight of NMP as a solvent. The negative electrode mixture slurry was applied to a 10 μm-thick copper (Cu) thin film as a negative electrode current collector, dried to prepare a negative electrode, and then roll press was performed to prepare a negative electrode.

After preparing a pouch-type battery in a conventional manner with a separator consisting of three layers of polypropylene/polyethylene/polypropylene (PP/PE/PP) using the prepared positive and negative electrodes, Examples 1-1 to 5-1, comparison The electrolyte solution prepared in Examples 1-1 to 5-3, Reference Example 1-1, and Reference Example 3-1 was injected to complete the manufacture of a lithium secondary battery.

test example

In order to evaluate the performance of the secondary battery prepared above, each performance was measured by the following method, and the results are shown in Tables 6 to 7 below.

[HPPC discharge resistance evaluation]

It was measured according to the method prescribed in the document “Battery test manual for plug-in hybrid electric vehicles,” (2010, Idaho National Laboratory for the U.S. Department of Energy.).

After standing at 60 ℃ for 5 hours, the measured voltage value, the charge/discharge current value corresponding to the C-rate, the current change amount (∆I), the discharge voltage change amount (∆V), the charge voltage change amount (∆V), the discharge resistance, the charge The resistance was measured, and the result of calculating the resistance value with the slope value obtained by the amount of change in current and voltage by briefly flowing the charge/discharge current for each C-rate for a certain time is shown in the initial discharge resistance items in Tables 6 to 7 below.

[High temperature recovery capacity evaluation]

The charging conditions were a constant current of 1.0C and a voltage of 4.2V until the charging current became 1/10C. As the discharge conditions, after charging and discharging by discharging to 3.0V at a constant current of 1.0C, (initial) recovery capacity was measured.

After charging under the same charging and discharging conditions, it was stored in a thermostat at 60°C for 4 weeks, and then discharged to a discharge voltage of 3V at room temperature at 25°C, and the remaining capacity was measured. After performing 100 times under the same charge and discharge conditions, the recovery capacity was measured and the average value thereof was calculated.

[Evaluation of cathodic expansion]

The thickness of the secondary battery was measured in a state in which a pouch cell was placed between the compression plates using a compression-type thickness measuring device manufactured by Mitutoyo, and compressed with a weight of 300 g. In order to exclude the cooling effect, the thickness increase rate by substituting the result of measuring the thickness immediately after taking it out of the oven at 60 ℃ (expansion thickness) and the thickness value measured in the same way after storage in a constant temperature bath at 60 ℃ for 4 weeks into Equation 1 below (%) was calculated.

[Equation 1]

Thickness increase rate (%) = {(thickness after high temperature storage - initial thickness) / initial thickness} X 100

[Coulomb Efficiency Evaluation]

The secondary battery was charged with a constant current at 45° C. at a current of 1C rate until the voltage reached 4.20V (vs. Li), and then cut-off at a current of 0.05C rate while maintaining 4.20V in the constant voltage mode. did. Then, it was discharged at a constant current of 1C rate until the voltage reached 3.0V (vs. Li) during discharging.

After 300 cycles, the coulombic efficiency was calculated by substituting the charge capacity and the discharge capacity into Equation 2 below.

[Equation 2]

Coulombic efficiency (%) = (discharge capacity at 300 cycles / charge capacity at 300 cycles) X 100

division First additive (wt%) 2nd additive
(wt%) initial discharge resistance
(mΩ) After high temperature storage
recovery capacity
(mAh) initial thickness
(mm) expansion
thickness
(mm) thickness increase rate
(%) Coulomb Efficiency
(%) Example 1-1 1a
(5) Equation 2a
(3) 32.68 1096 3.7 4.0 8.11 99.6 Example 1-2 1a (5) +1b (5) Equation 2a
(3) 38.57 1000 3.7 4.1 10.81 99.4 Example 2-1 Expression 1d(10) Equation 2a
(3) 29.08 11.08 3.7 3.9 5.41 99.7 Example 2-2 Equation 1d(5) + Equation 1b(5) Equation 2a
(3) 34.34 1056 3.8 4.0 5.26 99.6 Example 2-3 Equation 1d(5)+Equation 1a(5)+
Equation 1b(5) Equation 2a
(3) 36.40 1024 3.7 4.1 10.81 99.5 Example 3-1 Equation 1b(5) Equation 2a
(3) 36.32 1032 3.8 4.0 5.26 99.5 Example 4-1 Equation 1e
(15) Equation 2a
(3) 25.17 1123 3.8 3.9 2.63 99.8 Example 4-2 Equation 1e(10) + Equation 1f(10) Equation 2a
(3) 29.64 1101 3.7 3.9 5.41 99.7 Example 5-1 Formula 1h + lithium (0.5) Equation 2a
(3) 28.31 1128 3.7 3.9 5.41 99.7

division First additive (wt%) 2nd additive
(wt%) initial discharge resistance
(mΩ) After high temperature storage
recovery capacity
(mAh) initial thickness
(mm) expansion
thickness
(mm) thickness increase rate
(%) Coulomb Efficiency
(%) Comparative Example 1-1 Equation 1a
(5) - 41.66 991 3.8 4.3 13.16 99.4 Reference Example 1-1 Equation 1a(5) + Equation 1c (10) Equation 2a(3) 32.68 1096 3.7 4.0 8.11 99.6 Comparative Example 2-1 Expression 1d(5) - 38.31 1007 3.7 4.2 13.51 99.5 Comparative Example 3-1 Equation 1b(5) - 48.40 989 3.7 4.8 29.73 99.2 Reference Example 3-1 Equation 1b (3) Equation 2a
(3) 36.32 1032 3.8 4.0 5.26 99.5 Comparative Example 4-1 Equation 1e(10)+
1 g of formula (5) Equation 2a
(3) 25.17 1123 3.7 3.9 5.41 99.8 Comparative Example 4-2 Equation 1e(15) - 34.57 1076 3.7 4.0 8.11 99.5 Comparative Example 5-1 Formula 1h+lithium (10) - 34.80 1066 3.7 4.1 10.81 99.5 Comparative Example 5-2 Formula 1h + sodium
(0.5) Equation 2a
(3) 30.87 1080 3.8 4.0 5.26 99.5 Comparative Example 5-3 Formula 1h + Lithium (10) + Formula 1g (5) Equation 2a
(3) 28.31 1128 3.7 3.9 5.41 99.7

As shown in Tables 6 and 7, in the case of the secondary batteries of Examples 1-1 to 5-1 using the electrolyte additive of the present invention, the discharge resistance value was 25.17 to 38.57 mΩ, but the first additive and the second battery In Comparative Examples 1-1 to 5-3 using only one of the two additives, it was found to be as high as 25.17 to 48.40 mΩ, and it was confirmed that the discharge resistance value was lowered by up to 48% by using the electrolyte additive of the present invention. This indicates that the output of the battery is improved by the electrolyte additive of the present invention.

In addition, as shown in Table 1, the secondary batteries of Examples 1-1 to 5-1 using the electrolyte additive of the present invention had a high temperature recovery capacity of 1000 to 1128 mAh, whereas the first additive and the second additive were In the case of Comparative Examples 1-1 to 5-3 using only one of them, it was similarly shown as 989 to 1128 mAh.

In addition, as a result of confirming the expansion of the negative electrode, in the case of the secondary batteries of Examples 1-1 to 5-1 using the electrolyte additive of the present invention, the thickness increase rate was 2.63 to 10.81%, whereas only one of the first additive and the second additive was used. In the case of Comparative Examples 1-1 to 5-3 used, it can be seen that it is 5.26 to 29.73%, which is at most 27.1%p (% points) lower than that of the Example of the present invention. This means that by using the electrolyte additive of the present invention, the capacity retention rate of the battery is improved while repeating 300 cycles at a high temperature of 60° C. compared to using the conventional electrolyte additive, and thus, using the electrolyte additive of the present invention, high temperature storage and lifespan It showed an improvement in performance.

In addition, as a result of the evaluation of the coulombic efficiency, the secondary battery using the electrolyte additive of the present invention was 99.4 to 99.8%, whereas in Comparative Examples 1 and 2, it was 99.2 and 99.8%, up to 0.6%p ( % points) is low. This means that by using the electrolyte additive of the present invention, the capacity retention rate of the battery is improved while repeating 300 cycles at a high temperature of 60° C. compared to using the conventional electrolyte additive. It can be seen that the cycle characteristics and life efficiency of the

Therefore, when the electrolyte additive of the present invention and the electrolyte containing the same are applied to a secondary battery, the discharge resistance, output, recovery capacity, and lifespan efficiency are improved, so that it is suitable for use as a secondary battery for an energy storage system (ESS), automobile, etc. It can be seen that suitable

Claims (17)

An electrolyte comprising an organic solvent, a lithium salt, a first additive and a second additive, comprising:
The first additive has one double bond and contains 20% by weight or less of the compound represented by the following Chemical Formula 1, based on 100% by weight of the electrolyte,
The second additive is a compound composed of 3 to 5 atoms, having 2 to 4 atoms having an electronegativity of 3 or more, having at least one double bond and having an atomic group represented by the following Chemical Formula 2, the electrolyte solution 100 weight Electrolyte, characterized in that it contains 0.01 to 10% by weight based on %.
[Formula 1]

(In Formula 1, A is carbon (C), X ₁ , and X ₁ ' are independently carbon or oxygen, R ₁ , and R ₁ ' are independently a bond, substituted or unsubstituted carbon number. 1 to 10 alkylene, and contains at least one carbon.)
[Formula 2]

(In Formula 2, the solid line is a bond.) According to claim 1,
The electrolyte solution, characterized in that the first additive is a compound represented by the following formula (3).
[Formula 3]

(In Formula 3, the solid line is a bond, and when a separate element is not described, the point where the bond and the bond meet is carbon, and the number of hydrogens satisfying the valence of the carbon is omitted.) The method of claim 1,
The second additive is an electrolyte, characterized in that it has an atomic group represented by the following formula (4).
[Formula 4]

(In Formula 4, R ₄ is OR ₆ or R ₆ , R ₅ is R ₇ A, and A is

and R ₆ and R ₇ are independently an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 10 carbon atoms.) According to claim 1,
The second additive is an electrolyte, characterized in that at least one selected from compounds represented by the following formulas 5 to 6.
[Formula 5]

[Formula 6]

(In Formulas 5 to 6, A is phosphorus (P), sulfur (S) or nitrogen (N), and X ₁ , X ₂ , X ₃ , X ₁ ', X ₂ ' and X ₃ ' are independently bonded. (bond) or oxygen, n is an integer from 0 to 3, R ₁ , R ₂ , R ₃ , R ₁ ', R ₂ ' and R ₃ ' are independently a bond, substituted or unsubstituted carbon number. 1 to 10 alkylene, and contains at least one carbon.) 5. The method of claim 4,
The electrolyte solution, characterized in that the second additive is a compound represented by the formula (7).
[Formula 7]

(In Chemical Formula 7, the solid line is a bond, and when a separate element is not described, the point where the bond and the bond meet is carbon, and the number of hydrogens satisfying the valence of the carbon is omitted.) According to claim 1,
An electrolyte solution comprising the first additive and the second additive in a weight ratio of 1:0.1 to 1.7 (first additive: second additive). According to claim 1,
The lithium salt is LiPF ₆ , LiClO ₄ , LiTFSI, LiAsF ₆ , LiBF ₄ , LiBF ₆ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiBOB, LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiAlO ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiCH ₃ SO ₃ , LiBeTI, LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ) ₂ , LiN(CF ₃ SO ₂ ) _{2 ,} LiN(CaF _2a+1 SO ₂ )(C _b F _2b+1 SO ₂ ) (provided that a and b are natural numbers), LiCl, LiI, LiBr, and LiB (C ₂ O ₄ ) ₂ Electrolytic solution comprising at least one selected from the group consisting of. According to claim 1,
The organic solvent is ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), Ethylmethyl carbonate (EMC), methylethyl carbonate (MEC), fluoroethylene carbonate (FEC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-butylene carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, butyl propionate, γ-butyrolactone, γ-valerolactone, γ -Caprolactone, σ- valerolactone, and ε-caprolactone, characterized in that it comprises two or more selected from the group consisting of. According to claim 1,
The electrolyte solution, characterized in that it comprises 10% by weight or less of at least one third additive selected from the group consisting of a boron compound, a phosphorus compound, a sulfur compound, and a nitrogen-based compound, based on 100% by weight of the total electrolyte. a compound having one double bond and represented by the following formula (1); and
An electrolyte additive comprising a compound represented by the following formula (4).
[Formula 1]

(In Formula 1, A is carbon (C), X ₁ , and X ₁ ' are independently carbon or oxygen, R ₁ , and R ₁ ' are independently a bond, substituted or unsubstituted carbon number. 1 to 10 alkylene, and contains at least one carbon.)
[Formula 4]

(In Formula 4, R ₄ is OR ₆ or R ₆ , R ₅ is R ₇ A, and A is

and R ₆ and R ₇ are independently an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 10 carbon atoms.) 11. The method of claim 10,
An electrolyte solution additive comprising the compound represented by Formula 1 and the compound represented by Formula 4 in a weight ratio of 1:0.1 to 1.7 (first additive: second additive). A secondary battery comprising a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte,
The electrolyte is a lithium secondary battery, characterized in that the electrolyte of any one of claims 1 to 9. 13. The method of claim 12,
The secondary battery, a lithium secondary battery, characterized in that the discharge resistance value of 40 mΩ or less at 60 ℃. 13. The method of claim 12,
The secondary battery is a lithium secondary battery, characterized in that the recovery capacity is 1000 mAh or more at 60 ℃. 13. The method of claim 12,
The secondary battery is a lithium secondary battery, characterized in that the thickness increase rate at 60 ℃ calculated by the following Equation 1 is 10.81% or less.
[Equation 1]
Thickness increase rate (%) = {(thickness after high temperature storage - initial thickness) / initial thickness} X 100 13. The method of claim 12,
The secondary battery is calculated by Equation 2 below after 300 cycles A lithium secondary battery, characterized in that the coulombic efficiency is 99.4% or more.
[Equation 2]
Coulombic efficiency (%) = (discharge capacity at 300 cycles / charge capacity at 300 cycles) X 100 13. The method of claim 12,
The secondary battery is a lithium secondary battery, characterized in that the energy storage system (ESS) or a battery for automobiles.