KR102489610B1 - Rechargeable lithium battery - Google Patents

Abstract

[화학식 2]

[화학식 3]

[화학식 4]

a positive electrode including a positive electrode active material; and an electrolyte solution including a solvent and an additive, wherein the cathode active material includes a transition metal oxide containing lithium, the solvent includes hydrofluoroether, and the additive is a first additive represented by Formula 1 below. and a second additive represented by Formula 2 below, a third additive represented by Formula 3 below, and a fourth additive represented by Formula 4 below.
[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

Description

Lithium secondary battery {RECHARGEABLE LITHIUM BATTERY}

It relates to a lithium secondary battery.

As disclosed in Japanese Unexamined Patent Publication No. 2013-37905 (Patent Document 1), the lithium secondary battery includes a positive electrode active material layer and a negative electrode active material layer that electrochemically occlude and release lithium ions, and an electrolyte solution in which lithium ions are dissolved. do. The electrolyte solution impregnates the porous separator.

The technique disclosed in Patent Literature 1 aims to improve the cycle life of a lithium secondary battery, and in order to achieve this purpose, fluorinated ether is included in an electrolyte while having two types of pores with different characteristics.

However, cost competition is intensifying in batteries suitable for portable electronic devices (mobile devices) such as smart phones and tablet PCs. Under these circumstances, since the cost increases when using, for example, the solid solution oxide described in Patent Document 1 as a cathode material, high voltage is achieved by using a transition metal oxide containing lithium such as lithium cobalt oxide. are doing

In addition, recently, an electrolyte solution containing hydrofluoroether has been proposed in Japanese Patent Publication No. 2014-112526, Japanese Patent Publication No. 2013-211095, and Japanese Patent Publication No. 2011-129352. When such an electrolyte solution is used in a lithium secondary battery using a transition metal oxide containing lithium as a positive electrode material, there is a problem in that cycle life and storage characteristics when stored at high temperature are deteriorated.

One embodiment is to provide a lithium secondary battery that simultaneously improves cycle life characteristics and high-temperature storage characteristics.

One embodiment is a positive electrode including a positive electrode active material; and an electrolyte solution including a solvent and an additive, wherein the cathode active material includes a transition metal oxide containing lithium, the solvent includes hydrofluoroether, and the additive is a first additive represented by Formula 1 below. and a second additive represented by Chemical Formula 2 below, a third additive represented by Chemical Formula 3 below, and a fourth additive represented by Chemical Formula 4 below.

[Formula 1]

(In Formula 1 above,

R ¹ to R ³ are each independently substituted or unsubstituted with a 'vinyl group or C1 to C5 alkyl group' and substituted or unsubstituted with a C1 to C8 alkyl group not containing a double bond, or 'vinyl group or a C1 to C5 alkyl group' and a C1 to C8 alkyl group, a C2 to C8 alkenyl group, a C5 to C8 cycloalkyl group, a C6 to C8 aryl group, or a fluorine atom containing a double bond,

R ⁴ is a C1 to C8 alkylene group, a C2 to C8 alkynylene group, a C4 to C8 alkylene group having an ether group, a C1 to C8 alkylene group including a plurality of -CF ₂ - linking groups, or 'ether group and sulfide group' It is a C4 to C10 alkylene group having.)

[Formula 2]

(In Formula 2 above,

R ⁵ is a C2 to C6 alkylene group not containing a double bond, a C2 to C6 alkylene group, a C2 to C6 alkenylene group, or a C6 to C12 arylene group containing a double bond;

R ⁶ to R ¹¹ are each independently a C1 to C6 alkyl group or a C2 to C6 alkenyl group.)

[Formula 3]

(In Formula 3,

R ¹² and R ¹³ are each independently a hydrogen atom or a C1 to C8 alkyl group;

R ¹⁴ is a C1 to C8 alkyl group, a C2 to C8 alkenyl group, a C2 to C8 alkynyl group, or a C1 to C8 halogenated alkyl group unsubstituted or substituted with a vinyl group.)

[Formula 4]

(In Chemical Formula 4,

R ¹⁵ and R ¹⁶ are each independently a hydrogen atom or a C1 to C8 alkyl group;

R ¹⁷ is a C1 to C8 alkyl group, a C2 to C8 alkenyl group, a C2 to C8 alkynyl group, or a C1 to C8 halogenated alkyl group;

n is 1 or 2.)

The hydrofluoroether (HFE) is 2,2,2-trifluoroethylmethyl ether (CF ₃ CH ₂ OCH ₃ ), 2,2,2-trifluoroethyldifluoromethyl ether (CF ₃ CH ₂ OCHF ₂ ), 2,2,3,3,3-pentafluoropropylmethyl ether (CF ₃ CF ₂ CH ₂ OCH ₃ ), 2,2,3,3,3-pentafluoropropyldifluoromethyl ether (CF ₃ CF ₂ CH ₂ OCHF ₂ ), 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether (CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H), 1,1,2,2-tetrafluoroethylmethyl ether (HCF ₂ CF ₂ OCH ₃ ), 1,1,2,2-tetrafluoroethyl ethyl ether (HCF ₂ CF ₂ OCH ₂ CH ₃ ) , 1,1,2,2-tetrafluoroethylpropyl ether (HCF ₂ CF ₂ OC ₃ H ₇ ), 1,1,2,2-tetrafluoroethyl butyl ether (HCF ₂ CF ₂ OC ₄ H ₉ ) , 2,2,3,3-tetrafluoroethyldifluoromethyl ether (H(CF ₂ ) ₂ CH ₂ O(CF ₂ )H), 1,1,2,2-tetrafluoroethyl isobutyl ether (HCF ₂ CF ₂ OCH ₂ CH(CH ₃ ) ₂ ), 1,1,2,2-tetrafluoroethylisopentyl ether (HCF ₂ CF ₂ OCH ₂ C(CH ₃ ) ₃ ), 1,1,2 ,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HCF ₂ CF ₂ OCH ₂ CF ₃ ), 1,1,2,2-tetrafluoroethyl-2,2,3,3 -Tetrafluoropropyl ether (HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H), hexafluoroisopropylmethyl ether ((CF ₃ ) ₂ CHOCH ₃ ), 1,1,3,3,3-pentafluoro -2-trifluoromethylpropylmethyl ether ((CF ₃ ) ₂ CHCF ₂ OCH ₃ ), 1,1,2,3,3,3-hexafluoropropylmethyl ether (CF ₃ CHFCF ₂ OCH ₃ ), 1 ,1,2,3,3,3-hexafluoropropylethyl ether (CF ₃ CHFCF ₂ OCH ₂ CH ₃ ), 2,2,3,4,4,4-hexafluorobutyldifluoromethyl ether ( C F ₃ CHFCF ₂ CH ₂ OCHF ₂ ), or combinations thereof.

The content of the hydrofluoroether may be 10 to 60% by volume based on the total volume of the solvent.

The first additive may be included in an amount of 0.01 to 1.5% by weight based on the total weight of the electrolyte solution.

The additive includes the first additive and the second additive, and in this case, the second additive may be included in an amount of 0.05 to 1.00% by weight based on the total weight of the electrolyte solution.

The additive includes the first additive and the third additive, and in this case, the third additive may be included in an amount of 0.04 to 1.00% by weight based on the total weight of the electrolyte solution.

The additive includes the first additive and the fourth additive, and in this case, the fourth additive may be included in an amount of 0.01 to 1.00% by weight based on the total weight of the electrolyte solution.

The first additive may include at least one of disilane compounds represented by Chemical Formulas 1-1 to 1-9.

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 1-5]

[Formula 1-6]

[Formula 1-7]

[Formula 1-8]

[Formula 1-9]

The second additive may include a compound represented by Chemical Formula 2-1, a compound represented by Chemical Formula 2-2, or a combination thereof.

[Formula 2-1]

[Formula 2-2]

The third additive may include at least one of unsaturated phosphoric acid ester compounds represented by Chemical Formulas 3-1 to 3-8.

[Formula 3-1]

[Formula 3-2]

[Formula 3-3]

[Formula 3-4]

[Formula 3-5]

[Formula 3-6]

[Formula 3-7]

[Formula 3-8]

The fourth additive may include at least one of unsaturated phosphoric acid ester compounds represented by Chemical Formulas 4-1 to 4-4.

[Formula 4-1]

[Formula 4-2]

[Formula 4-3]

[Formula 4-4]

The lithium-containing transition metal oxide may be a lithium cobalt-based composite oxide.

The lithium secondary battery further includes a negative electrode including a negative electrode active material, and the negative electrode active material may be a carbon-based material, a silicon-based material, a tin-based material, a lithium metal oxide, and a mixture of two or more kinds of metal lithium. .

The solvent may further include fluoroethylene carbonate.

The content of the fluoroethylene carbonate may be 10 to 30% by volume based on the total volume of the solvent.

The oxidation-reduction potential of the lithium secondary battery may be 4.3V (vs. Li/Li ⁺ ) or more and 5.0V or less.

Details of other implementations are included in the detailed description below.

A lithium secondary battery with improved cycle life characteristics and high-temperature storage characteristics can be implemented.

1 is a cross-sectional view showing a lithium secondary battery according to an embodiment.
2 is a scanning electron microscope (SEM) photograph showing the state of the film on the surface of LiCoO ₂ particles after storing the lithium secondary batteries according to Example 1 and Comparative Example 1 at 60° C. for 24 hours.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims to be described later.

Unless otherwise specified herein, when a part such as a layer, film, region, plate, etc. is said to be “on” another part, this is not only the case where it is “directly on” the other part, but also the case where there is another part in the middle. include

Hereinafter, a lithium secondary battery according to an embodiment will be described with reference to FIG. 1 .

1 is a cross-sectional view showing a lithium secondary battery according to an embodiment.

Referring to FIG. 1 , a lithium secondary battery 10 may include a positive electrode 20 , a negative electrode 30 , and a separator layer 40 .

The ultimate charging voltage of the lithium secondary battery 10, that is, the redox potential, is, for example, 4.3V (vs. Li/Li ⁺ ) or more and 5.0V or less, specifically, 4.4V or more and 5.0V or less, more specifically , may be greater than or equal to 4.4V and less than or equal to 4.6V.

The shape of the lithium secondary battery 10 is not particularly limited, that is, it may be cylindrical, prismatic, laminated, or button-shaped.

The cathode 20 may include a current collector 21 and a cathode active material layer 22 formed on the current collector.

The current collector 21 may be any conductor, and may be made of, for example, aluminum, stainless steel, nickel coated steel, or the like.

The cathode active material layer 22 may include a cathode active material, and may further include a conductive material and a binder.

A cathode active material according to an embodiment may use a transition metal oxide containing lithium.

As the transition metal oxide containing lithium, LiCoO₂ Lithium cobalt-based composite oxide, LiNi, etc._xCo_yMn_zO₂ Lithium nickel cobalt manganese composite oxide, LiNiO, etc.₂ Lithium nickel-based composite oxide, such as LiMn₂O₄ and lithium manganese composite oxides such as the like. The positive electrode active material may be used alone or in combination of two or more. Among them, when a lithium cobalt-based composite oxide is used, deterioration in cycle life characteristics and high-temperature storage characteristics may be greater. According to one embodiment, cycle life characteristics and high-temperature storage characteristics may be greatly improved by using together with an electrolyte solution additive described later.

The content of the cathode active material is not particularly limited, and may be an amount applicable to a cathode active material layer of a lithium secondary battery.

Examples of the conductive material include carbon black such as Ketjen black and acetylene black, natural graphite and artificial graphite, but are not particularly limited as long as they are used to increase the conductivity of the anode.

The content of the conductive material is not particularly limited, and may be a content applicable to the cathode active material layer of a lithium secondary battery.

The binder is, for example, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, fluoro rubber (fluoroelastomer), polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, etc. may be mentioned, but the positive electrode active material and the conductive material are placed on the current collector 21 It is not particularly limited as long as it can be bound and at the same time has oxidation resistance and electrolyte stability that can withstand a high potential of the anode.

The content of the binder is not particularly limited, and may be an amount applicable to the cathode active material layer of a lithium secondary battery.

The density of the positive electrode active material layer 22 is not particularly limited. The density of the positive electrode active material layer 22 may be calculated by dividing the area density of the positive electrode active material layer 22 after rolling by the thickness of the positive electrode active material layer 22 after rolling.

The positive electrode active material layer 22 can be manufactured, for example, by the following method. First, a positive electrode mixture is prepared by dry mixing a positive electrode active material, a conductive material, and a binder. Subsequently, the positive electrode mixture is dispersed in an appropriate organic solvent such as N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry, and the positive electrode mixture slurry is applied on a current collector 21, dried and rolled Thus, a positive electrode active material layer can be prepared.

The negative electrode 30 may include a current collector 31 and an anode active material layer 32 formed on the current collector 31 .

The current collector 31 may be any conductive material, and may be, for example, copper (Cu), a copper alloy, aluminum, stainless steel, or nickel-plated steel.

The negative active material layer 32 may be any material as long as it is used as a negative active material layer of a lithium secondary battery. For example, the anode active material layer 32 may include an anode active material and may further include a binder.

The negative electrode active material may be used alone or in combination of two or more of a carbon-based material, a silicon-based material, a tin-based material, a lithium metal oxide, and metal lithium. The carbon-based material may be, for example, a graphite-based material such as artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, or natural graphite coated with artificial graphite. The silicon-based material may be, for example, silicon, silicon oxide, a silicon-containing alloy, a mixture of these and a graphite-based material, or the like. The silicon oxide may be represented by SiOx (0<x≤2). The tin-based material may be, for example, tin, tin oxide, a tin-containing alloy, a mixture of these and a graphite-based material, or the like. Examples of the lithium metal oxide include titanium oxide-based compounds such as Li ₄ Ti ₅ O ₁₂ .

For example, the negative electrode active material may be a mixture of a carbon-based material such as graphite-based material and a silicon-based material such as a silicon-containing alloy. In this case, the carbon-based material and the silicon-based material may be mixed in a weight ratio of 50:50 to 90:10, for example, 60:40 to 80:20. The content of silicon in the silicon-containing alloy may be 50% by weight or more based on the total amount of the silicon-containing alloy. According to one embodiment, when the negative electrode active material includes a silicon-based material, cycle life characteristics and high-temperature storage characteristics may be significantly improved at the same time as compared to a case where the silicon-based material is not included.

The binder may be the same type as the binder constituting the positive electrode active material layer 22 .

The content of the binder is not particularly limited, and may be any content as long as it is applied to the negative electrode active material layer of a lithium secondary battery.

The negative electrode active material layer 32 may further include a thickener such as carboxymethylcellulose (CMC). The content of the thickener may be used at 1/10 or more and 10/10 or less of the weight of the binder.

The density of the negative electrode active material layer 32 is not particularly limited. The density of the negative active material layer 32 may be calculated by dividing the areal density of the negative active material layer 32 after rolling by the thickness of the negative active material layer 32 after rolling.

The cathode 30 may be manufactured as follows. First, a slurry may be prepared by dispersing an anode active material and a binder in a solvent such as water or N-methyl-pyrrolidone, and the slurry may be coated on the current collector 31 and dried.

The separator layer 40 includes a separator and an electrolyte solution.

The separator is not particularly limited, and any separator may be used as long as it is used as a separator for a lithium secondary battery.

As the separator, a porous film or non-woven fabric exhibiting excellent high-rate discharge performance may be used alone or in combination.

Materials constituting the separator include, for example, polyolefin resin, polyester resin, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluoro Robinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone Copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, and vinylidene fluoride-ethylene-tetrafluoroethylene copolymers. Examples of the polyolefin-based resin include polyethylene and polypropylene, and examples of the polyester-based resin include polyethylene terephthalate and polybutylene terephthalate.

The thickness of the separator is not particularly limited.

The electrolyte solution may include a lithium salt, a solvent, and additives.

The lithium salt may be an electrolyte of an electrolyte solution. The lithium salt may be, for example, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , LiSO ₃ CF ₃ , LiN(SO ₂ CF ₃ ), LiN(SO ₂ CF ₂ CF ₃ ), LiC(SO ₂ CF ₂ CF ₃ ) ₃ , LiC(SO ₂ CF ₃ ) ₃ , LiI, LiCl, LiF, LiPF ₅ (SO ₂ CF ₃ ), LiPF ₄ (SO ₂ CF ₃ ) ₂ and the like. One or two or more of these lithium salts may be dissolved.

When the lithium salt is dissolved in an electrolyte solution, battery characteristics may be improved.

The concentration of the lithium salt is not particularly limited, and may be used at a concentration of, for example, 0.85 to 1.6 mol/L, for example, 0.9 to 1.40 mol/L. Battery characteristics may be improved when the concentration of the lithium salt is within the above range.

The solvent according to one embodiment may include hydrofluoroether (HFE).

The hydrofluoroether (HFE) is obtained by replacing some hydrogen atoms of ether with fluorine, and when used as a solvent, oxidation resistance can be improved.

Considering the resistance to charging voltage and current density of the cathode material, the hydrofluoroether (HFE) is 2,2,2-trifluoroethylmethyl ether (CF ₃ CH ₂ OCH ₃ ), 2,2, 2-Trifluoroethyldifluoromethylether (CF ₃ CH ₂ OCHF ₂ ), 2,2,3,3,3-pentafluoropropylmethyl ether (CF ₃ CF ₂ CH ₂ OCH ₃ ), 2,2 ,3,3,3-pentafluoropropyldifluoromethyl ether (CF ₃ CF ₂ CH ₂ OCHF ₂ ), 2,2,3,3,3-pentafluoropropyl-1,1,2,2- Tetrafluoroethyl ether (CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H), 1,1,2,2-Tetrafluoroethylmethyl ether (HCF ₂ CF ₂ OCH ₃ ), 1,1,2,2- Tetrafluoroethylethyl ether (HCF ₂ CF ₂ OCH ₂ CH ₃ ), 1,1,2,2-Tetrafluoroethylpropyl ether (HCF ₂ CF ₂ OC ₃ H ₇ ), 1,1,2,2- Tetrafluoroethylbutyl ether (HCF ₂ CF ₂ OC ₄ H ₉ ), 2,2,3,3-tetrafluoroethyldifluoromethyl ether (H(CF ₂ ) ₂ CH ₂ O(CF ₂ )H) , 1,1,2,2-tetrafluoroethyl isobutyl ether (HCF ₂ CF ₂ OCH ₂ CH(CH ₃ ) ₂ ), 1,1,2,2-tetrafluoroethyl isopentyl ether (HCF ₂ CF ₂ OCH ₂ C(CH ₃ ) ₃ ), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HCF ₂ CF ₂ OCH ₂ CF ₃ ), 1,1, 2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H), hexafluoroisopropylmethyl ether ((CF ₃ ) ₂ CHOCH ₃ ), 1,1,3,3,3-pentafluoro-2-trifluoromethylpropylmethyl ether ((CF ₃ ) ₂ CHCF ₂ OCH ₃ ), 1,1,2,3,3,3- Hexafluoropropylmethyl ether (CF ₃ CHFCF ₂ OCH ₃ ), 1,1,2,3,3,3-hexafluoropropylethyl ether (CF ₃ CHFCF ₂ OCH ₂ CH ₃ ) and 2,2,3,4,4,4-hexafluorobutyldifluoromethyl ether (CF ₃ CHFCF ₂ CH ₂ OCHF ₂ ). Any one of these or a mixture of two or more may be used.

The content of the hydrofluoroether is not particularly limited, but may be 10 to 60 vol%, for example, 30 to 50 vol%, for example 35 to 50 vol%, based on the total volume of the solvent. . Battery characteristics may be improved when the content of hydrofluoroether is within the above range.

As the solvent, in addition to the hydrofluoroether, non-aqueous solvents used in conventional lithium secondary batteries may be additionally used without particular limitation.

Examples of the non-aqueous solvent include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone; chain esters such as methyl formate, methyl acetate, and methyl butyric acid; tetrahydrofuran or its derivatives; ethers such as 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane, and methyl diglyme; nitriles such as acetonitrile and benzonitrile; dioxolane or a derivative thereof; ethylene sulfide, sulfolane, sultone, ethylmethylsulfone, or derivatives thereof; etc. may be used alone or as a mixture of two or more, but is not limited thereto. When two or more non-aqueous solvents are mixed and used, the mixing ratio of each solvent can be applied as a mixing ratio usable in a conventional lithium secondary battery. Among these, the chain carbonates can be specifically used.

The content of the chain carbonates may be 5 to 60% by volume, for example, 20 to 50% by volume based on the total volume of the solvent. Battery characteristics may be improved when the content of the chain carbonate is within the above range.

As the solvent, fluoroethylene carbonate may be additionally used.

The content of the fluoroethylene carbonate may be 10 to 30% by volume, for example, 15 to 20% by volume based on the total volume of the solvent. When the content of fluoroethylene carbonate is within the above range, cycle life characteristics may be improved.

The additive may include a first additive represented by Chemical Formula 1, a group consisting of a second additive represented by Chemical Formula 2, a third additive represented by Chemical Formula 3, and a fourth additive represented by Chemical Formula 4 below. It may further include at least one selected from. For example, the additive includes a first additive represented by Formula 1 below, a second additive represented by Formula 2 below, a third additive represented by Formula 3 below, and a fourth additive represented by Formula 4 below. It may further include at least one selected from the group consisting of.

Hereinafter, each of the first to fourth additives will be described in detail.

1st additive

The first additive may be a disilane compound represented by Formula 1 below. One type of the first additive may be used, or two or more types may be mixed and used.

[Formula 1]

In Formula 1, R ¹ to R ³ are each independently a 'vinyl group or a C1 to C5 alkyl group', a C1 to C8 alkyl group unsubstituted or substituted with a double bond, or a 'vinyl group or a C1 to C5 alkyl group'. It may be a substituted or unsubstituted C1 to C8 alkyl group, a C2 to C8 alkenyl group, a C5 to C8 cycloalkyl group, a C6 to C8 aryl group, or a fluorine atom including a double bond. The C1 to C8 alkyl group is, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a secondary butyl group, a t-butyl group, a pentyl group, an isopentyl group, a secondary pentyl group, t-pentyl group, hexyl group, secondary hexyl group, heptyl group, secondary heptyl group, octyl group, secondary octyl group, 2-methylpentyl group, 2-ethylhexyl group and the like. The C2 to C8 alkenyl group is, for example, a 1,3-butadienyl group, a 1,2-propadienyl group, a 1,4-pentadienyl group, a vinylene group, a propenylene group, an isopropenylene group, and a butenyl group. and a rene group, a pentenylene group, a hexenylene group, a 1-propenylene-2,3-diyl group, an ethynylene group, a propynylene group, a butynylene group, a pentynylene group, and a hexynylene group. Examples of the C5 to C8 cycloalkyl group include a cyclopentyl group, a cyclohexyl group, and a cyclohexylmethyl group. Examples of the C6 to C8 aryl group include a phenyl group, a tolyl group, and a xylyl group. Some hydrogen atoms in the substituents may be substituted with halogen atoms, vinyl groups, C1 to C5 alkyl groups, and the like. For example, the C1 to C8 alkyl group may or may not include a double bond.

The C1 to C8 alkyl group including the double bond, for example, the propyl group including the double bond may be represented by Formula A below.

[Formula A]

In Formula 1, R ⁴ is a C1 to C8 alkylene group, a C2 to C8 alkynylene group, a C4 to C8 alkylene group having an ether group, a plurality of -CF ₂ -C1 to C8 alkylene groups including a linking group, or an 'ether group' and a C4 to C10 alkylene group having a 'sulfide group'. The C1 to C8 alkylene group may or may not include one or more -CF ₂ - linking groups. For example, a C5 to C8 alkylene group including 4 -CF ₂ -linking groups may be represented by Formulas B to E below.

[Formula B]

[Formula C]

[Formula D]

[Formula E]

Examples of the C1 to C8 alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, and a 2-methylbutylene group. The C2 to C8 alkynylene group is, for example, an ethynylene group, a propynylene group, a butynylene group, a pentynylene group, a hexynylene group, a heptynylene group, an octynylene group, a noninylene group, an ethyn-1,2-di weather, etc. The C4 to C8 alkylene group having an ether group may be, for example, a C4 to C8 alkylene group having an ether group including at least one of an oxygen atom and a sulfur atom including a thioether group. Specifically, 4-oxaheptylene group, 5-oxanonylene group, etc. are mentioned. The ether group may be represented by -O-, and the sulfide group may be represented by -S-. Some hydrogen atoms in the substituent may be replaced with halogen atoms.

Specific examples of the first additive include 1,2-bis (difluoromethoxysilyl) ethane, 1,3-bis (difluoromethylsilyl) propane, and 1,2-bis (difluoromethylsilyl) ethane. , 1,2-bis (difluoroethylsilyl) ethane, 1-difluoromethylsilyl-2-difluoroethylsilylethane, 1-difluoromethylsilyl-2-difluoropropylsilylethane, 1 ,3,3-tetraethyldisiloxane, 1,3-difluoro-1,1,3,3-tetrapropyldisiloxane, 1,3-difluoro-1,1,3,3-tetrabutyldi Siloxane, 1,3-difluoro-1,1,3,3-tetrapentyldisiloxane, 1,3-difluoro-1,1,3,3-tetrahexyldisiloxane, 1,2-bis( Fluorodimethylsilyl) ethane, 1,2-bis (fluorodiethylsilyl) ethane, 1,2-bis (fluorodipropylsilyl) ethane, 1,2-bis (fluorodibutylsilyl) ethane, 1-fluoro dimethylsilyl-2-fluoroethylsilylethane, 1,3-bis(fluorodimethylsilyl)propane, 1,3-bis(fluorodiethylsilyl)propane, 1,3-bis(fluorodipropylsilyl)propane, 1,3-bis(fluorodibutylsilyl)propane, 1,3-divinyl-1,1,3,3-tetraethyldisiloxane, 1,3-divinyl-1,1,3,3-tetrapropyl Disiloxane, 1,3-divinyl-1,1,3,3-tetrabutyldisiloxane, 1,3-divinyl-1,1,3,3-tetrapentyldisiloxane, 1,3-divinyl- 1,1,3,3-tetrahexyldisiloxane, 1,3-diethynyl-1,1,3,3-tetramethyldisiloxane, 1,3-diethynyl-1,1,3,3-tetraethyl Disiloxane, 1,3-diethynyl-1,1,3,3-tetrapropyldisiloxane, 1,3-diethynyl-1,1,3,3-tetrapentyldisiloxane, 2-((2-( 2-ethoxydifluorosilyl)ethyl)thio)propiodifluorosilane, 2,2'-(ethylenedithio)bis(difluoroethylsilane), and the like.

The first additive may specifically include at least one of the disilane compounds represented by the following Chemical Formulas 1-1 to 1-9, among which disilane compounds represented by the following Chemical Formulas 1-1 to 1-4 At least one may be more specifically included.

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 1-5]

[Formula 1-6]

[Formula 1-7]

[Formula 1-8]

[Formula 1-9]

2nd additive

The second additive may be a disilane compound represented by Formula 2 below. One type of the second additive may be used, or a mixture of two or more types may be used.

[Formula 2]

In Formula 2, R ⁵ may be a C2 to C6 alkylene group without a double bond, a C2 to C6 alkylene group with a double bond, a C2 to C6 alkenylene group, or a C6 to C12 arylene group. Examples of the C2 to C6 alkylene group include an ethylene group, a propylene group, a butylene group, a pentamethylene group, and a hexamethylene group. The C2 to C6 alkylene group may include a double bond. For example, a C3 alkylene group including one double bond may be represented by Formula F below.

[Formula F]

Examples of the C6 to C12 arylene group include a 1,2-phenylene group, a 1,4-phenylene group, and a (1,1'-biphenyl)-4,4'-diyl group. Some hydrogen atoms in the substituent may be replaced with halogen atoms.

In Formula 2, R ⁶ to R ¹¹ may each independently be a C1 to C6 alkyl group or a C2 to C6 alkenyl group. The C1 to C6 alkyl group is, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a 2-propynyl group, a 3-fluoropropyl group, a 3-fluorobutyl group, a 4-fluoro A butyl group etc. are mentioned. The C2 to C6 alkenyl group is a 1,3-butadienyl group, a 1,2-propanedienyl group, a 1,4-pentadienyl group, a vinylene group, a propenylene group, an isopropenylene group, a butenylene group, and a pentenylene group. , hexenylene group, etc. are mentioned. Some hydrogen atoms in the substituent may be replaced with halogen atoms.

Specific examples of the second additive include bis(trimethylsilyl)acetylene dicarboxylate, bis(ethyldimethylsilyl)acetylene dicarboxylate, bis(dimethylpropylsilyl)acetylene dicarboxylate, and bis(dimethylbutylsilyl) Acetylene dicarboxylate, bis(dimethylvinylsilyl)acetylene dicarboxylate, fumarate bis(trimethylsilyl), maleate bis(trimethylsilyl), phthalate bis(trimethylsilyl), isophthalate bis(trimethylsilyl), terephthalate bis( trimethylsilyl), itaconic acid bis(trimethylsilyl), and the like.

More specifically, the second additive may include Formula 2-1, Formula 2-2, or a combination thereof.

[Formula 2-1]

[Formula 2-2]

Third Additive

The third additive may be an unsaturated phosphoric acid ester compound represented by Formula 3 below. The third additive may be used alone or in combination of two or more additives.

[Formula 3]

In Formula 3, R ¹² and R ¹³ may each independently be a hydrogen atom or a C1 to C8 alkyl group. The C1 to C8 alkyl group is a methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, secondary butyl group, t-butyl group, pentyl group, isopentyl group, secondary pentyl group, t-pentyl group , hexyl group, secondary hexyl group, heptyl group, secondary heptyl group, octyl group, secondary octyl group, 2-methylpentyl group, 2-ethylhexyl group and the like. Among these, in view of the low adverse effect on the movement of lithium ions and good charging characteristics, a hydrogen atom, a methyl group, an ethyl group, a propyl group, etc. can be used, specifically a hydrogen atom, a methyl group, etc. can be used, more specifically may use a hydrogen atom.

In Formula 3, R ¹⁴ may be a C1 to C8 alkyl group, a C2 to C8 alkenyl group, a C2 to C8 alkynyl group, or a C1 to C8 halogenated alkyl group unsubstituted or substituted with a vinyl group. Examples of each of the C1 to C8 alkyl group and the C2 to C8 alkenyl group are the same as those exemplified in the substituent description for R ¹ to R ³ in Formula 1 above. Examples of the C2 to C8 alkynyl group include an ethynyl group, a 2-propynyl group (also called 'propargyl'), a 3-butynyl group, a 1-methyl-2-propynyl group, and a 1,1-dimethyl-2-propynyl group. etc. can be mentioned. Examples of the C1 to C8 halogenated alkyl group include a chloromethyl group, a trifluoromethyl group, a 2-fluoroethyl group, a 2-chloroethyl group, a 2,2,2-trifluoroethyl group, a 2,2,2-trichloroethyl group, 1,1,2,2-tetrafluoroethyl group, pentafluoroethyl group, 3-fluoropropyl group, 2-chloropropyl group, 3-chloropropyl group, 2-chloro-2-propyl group, 3,3, 3-trifluoropropyl group, 2,2,3,3-tetrafluoropropyl group, heptafluoropropyl group, 2-chlorobutyl group, 3-chlorobutyl group, 4-chlorobutyl group, 3-chloro- 2-butyl group, 1-chloro-2-butyl group, 2-chloro-1,1-dimethylethyl group, 3-chloro-2-methylpropyl group, 5-chloropentyl group, 3-chloro-2-methylpropyl group , 3-chloro-2,2-dimethyl group, 6-chlorohexyl group, etc. are mentioned. Among these, the internal resistance of the lithium secondary battery is reduced, methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, 2-propynyl group, 3-chloropropyl group, 3-chlorobutyl group, 4- A chlorobutyl group or the like can be used, specifically, a methyl group, an ethyl group, a propyl group, a 2-propynyl group, or the like can be used, and more specifically, an ethyl group, a 2-propynyl group, or the like can be used.

Among specific examples of the third additive, examples of compounds in which R ¹² and R ¹³ are hydrogen atoms include methyl bis(2-propynyl)phosphate, ethyl bis(2-propynyl)phosphate, propyl bis(2-propynyl) Nyl)phosphate, butyl bis(2-propynyl)phosphate, pentyl bis(2-propynyl)phosphate, allyl bis(2-propynyl)phosphate, tris(2-propynyl)phosphate, 2-chloroethyl bis(2 -propynyl)phosphate, 2,2,2-trifluoroethyl bis(2-propynyl)phosphate, 2,2,2-trichloroethyl bis(2-propynyl)phosphate, etc. are mentioned.

Among specific examples of the third additive, examples of compounds in which R ¹² is the methyl group and R ¹³ is the hydrogen atom include methyl bis(1-methyl-2-propynyl)phosphate, ethyl bis(1-methyl-2- Propynyl)phosphate, propyl bis(1-methyl-2-propyl)phosphate, butyl bis(1-methyl-2-propynyl)phosphate, pentyl bis(1-methyl-2-propynyl)phosphate, allyl bis(1 -Methyl-2-propynyl)phosphate, 2-propynyl bis(1-methyl-2-propynyl)phosphate, tris(1-methyl-1-methyl-2-propynyl)phosphate, 2-chloroethyl bis( 1-methyl-2-propynyl)phosphate, 2,2,2-trifluoroethyl bis(1-methyl-2-propynyl)phosphate, 2,2,2-trichloroethyl bis(1-methyl-2 -propynyl) phosphate; etc. are mentioned.

Among specific examples of the third additive, examples of compounds in which R ¹² and R ¹³ are methyl groups include methyl bis(1,1-dimethyl-2-propynyl)phosphate, ethyl bis(1,1-dimethyl-2- Propynyl)phosphate, propyl bis(1,1-dimethyl-2-propynyl)phosphate, butyl bis(1,1-dimethyl-2-propynyl)phosphate, pentyl bis(1,1-dimethyl-2-propynyl) )phosphate, allyl bis(1,1-dimethyl-2-propynyl)phosphate, 2-propynyl bis(1,1-dimethyl-2-propynyl)phosphate, tris(1,1-dimethyl-2-propynyl) )phosphate, 2-chloroethyl bis(1,1-dimethyl-2-propynyl)phosphate, 2,2,2-trifluoroethyl bis(1,1-dimethyl-2-propynyl)phosphate, 2,2 , 2-trichloroethyl bis (1, 1-dimethyl-2-propynyl) phosphate; and the like.

Among specific examples of the third additive, methyl bis (2-propynyl) phosphate, ethyl bis (2-propynyl) phosphate, propyl bis (2-propynyl) phosphate, butyl bis (2-propynyl) phosphate, pentyl Bis (2-propynyl) phosphate, tris (2-propynyl) phosphate, 2-chloroethyl bis (2-propynyl) phosphate and the like can be used, specifically ethyl bis (2-propynyl) phosphate, propyl Bis (2-propynyl) phosphate, butyl bis (2-propynyl) phosphate, tris (2-propynyl) phosphate, etc. can be used, more specifically, ethyl bis (2-propynyl) phosphate, tris (2 -propynyl) phosphate and the like can be used.

More specifically, the third additive may include at least one of the unsaturated phosphoric acid ester compounds represented by the following Chemical Formulas 3-1 to 3-8, and specifically, the following Chemical Formulas 3-1, Chemical Formulas 3-2, or Unsaturated phosphoric acid ester compounds represented by combinations may be included.

[Formula 3-1]

[Formula 3-2]

[Formula 3-3]

[Formula 3-4]

[Formula 3-5]

[Formula 3-6]

[Formula 3-7]

[Formula 3-8]

4th additive

The fourth additive may be an unsaturated phosphoric acid ester compound represented by Formula 4 below. The fourth additive may be used alone or in combination of two or more additives.

[Formula 4]

In Formula 4, R ¹⁵ and R ¹⁶ may each independently be a hydrogen atom or a C1 to C8 alkyl group. The C1 to C8 alkyl groups are the same as those exemplified in the substituent description of R ¹ to R ³ in Formula 1 above. Among these, in view of the low adverse effect on the movement of lithium ions and good charging characteristics, a hydrogen atom, a methyl group, an ethyl group, a propyl group, etc. can be used, specifically a hydrogen atom, a methyl group, etc. can be used, more specifically may use a hydrogen atom.

In Formula 4, R ¹⁷ may be a C1 to C8 alkyl group, a C2 to C8 alkenyl group, a C2 to C8 alkynyl group, or a C1 to C8 halogenated alkyl group. Examples of each of the C1 to C8 alkyl group and the C2 to C8 alkenyl group are the same as those exemplified in the substituent description for R ¹ to R ³ in Formula 1 above. The C2 to C8 alkynyl group and the C1 to C8 halogenated alkyl group are the same as those exemplified in the description of the substituent for R ¹⁴ in Formula 3 above. Among these, the internal resistance of the lithium secondary battery is reduced, methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, 2-propynyl group, 3-chloropropyl group, 3-chlorobutyl group, 4- A chlorobutyl group or the like can be used, specifically a methyl group, an ethyl group, a propyl group, a 2-propynyl group or the like can be used, and more specifically a methyl group, an ethyl group or the like can be used.

In Chemical Formula 4, n may be 1 or 2. Among these, n may be 2 from the viewpoint that phosphoric acid ester reaction from alkyne diol as a raw material is easy and a high yield is obtained. When n is 2, it can be represented as in Formula G below.

[Formula G]

Among specific examples of the fourth additive, examples of compounds in which n is 1 include 2-butyne-1,4-diol tetramethyl diphosphate, 2-butyne-1,4-diol tetraethyl diphosphate, 2-butyne- 1,4-diol tetrapropyl diphosphate, 2-butyne-1,4-diol tetraisopropyl diphosphate, 2-butyne-1,4-diol tetrabutyl diphosphate, 2-butyne-1,4-diol tetrapentyl Diphosphate, 2-butyne-1,4-diol tetrakis(2-propynyl)diphosphate, 2-butyne-1,4-diol tetrakis(3-chloropropyl) diphosphate, 2-butyne-1,4 -diol tetrakis(3-chlorobutyl) diphosphate, 2-butyne-1,4-diol tetrakis(4-chlorobutyl) diphosphate, etc., among which 2-butyne-1,4-diol tetra Methyl diphosphate, 2-butyne-1,4-diol tetraethyl diphosphate, 2-butyne-1,4-diol tetrapropyl diphosphate, 2-butyne-1,4-diol tetrakis(2-propynyl)di phosphate and the like can be used, and specifically, 2-butyn-1,4-diol tetramethyl diphosphate, 2-butyn-1,4-diol tetrakis(2-propynyl) diphosphate and the like can be used.

Among specific examples of the fourth additive, examples of compounds in which n is 2 include 2,4-hexadiin-1,6-diol tetramethyl diphosphate, 2,4-hexadiin-1,6-diol tetra Ethyl diphosphate, 2,4-hexadiin-1,6-diol tetrapropyl diphosphate, 2,4-hexadiin-1,6-diol tetraisopropyl diphosphate, 2,4-hexadiin-1 ,6-diol tetrabutyl diphosphate, 2,4-hexadiin-1,6-diol tetrapentyl diphosphate, 2,4-hexadiin-1,6-diol tetrakis(2-propynyl) diphosphate , 2,4-hexadiin-1,6-diol tetrakis (3-chloropropyl) diphosphate, 2,4-hexadiin-1,6-diol tetrakis (3-chlorobutyl) diphosphate, 2 ,4-hexadiin-1,6-diol tetrakis(4-chlorobutyl) diphosphate and the like, among which 2,4-hexadiin-1,6-diol tetramethyl diphosphate, 2, 4-hexadiin-1,6-diol tetraethyl diphosphate, 2,4-hexadiin-1,6-diol tetrapropyl diphosphate, 2,4-hexadiin-1,6-diol tetrakis ( 2-propynyl) diphosphate and the like can be used, specifically 2,4-hexadiin-1,6-diol tetramethyl diphosphate, 2,4-hexadiin-1,6-diol tetrakis ( 2-propynyl) diphosphate and the like can be used.

More specifically, the fourth additive may include at least one of the unsaturated phosphoric acid ester compounds represented by the following Chemical Formulas 4-1 to 4-4, and specifically, the following Chemical Formulas 4-1, Chemical Formulas 4-2, or Unsaturated phosphoric acid ester compounds represented by combinations may be included.

[Formula 4-1]

[Formula 4-2]

[Formula 4-3]

[Formula 4-4]

Cycle life characteristics and high-temperature storage characteristics may be improved by adding the first additive and at least one of the second to fourth additives to the electrolyte solution. For example, the electrolyte solution may include the first additive and the second additive, the first additive and the third additive, or the first additive and the fourth additive. For example, the electrolyte solution includes the first additive, the second additive, and the third additive, includes the first additive, the second additive, and the fourth additive, or includes the first additive and the third additive. 3 additives, and the fourth additive may be included. For example, the former solution may include all of the first additive, the second additive, the third additive, and the fourth additive.

Specifically, the first to fourth additives decompose preferentially over hydrofluoroether (HFE) contained in the electrolyte solution, for example, at a potential lower than that of the solvent, or the additives are adsorbed to the surface of the positive electrode active material. The first to fourth additives or their decomposition products cover the cathode active material, thereby inhibiting decomposition of hydrofluoroether. For example, the first to fourth additives themselves or decomposition products thereof cover the cathode active material, thereby suppressing contact between hydrofluoroether and the cathode active material. Accordingly, formation of a high-resistance film derived from a decomposition product of the solvent, particularly hydrofluoroether, on the positive electrode active material is suppressed, and deterioration in cycle characteristics and generation of decomposition gas of the electrolyte (HFE) during storage are suppressed.

The effect of adding the first to fourth additives is described in more detail as follows.

The terminal silyl group of the first additive tends to interact easily with part of the LiPF ₆ electrolyte or hydrofluoric acid slightly freed in the electrolyte solution, and decomposes earlier than the second to fourth additives on the anode, starting from the bond dissociation point. to form a film. An unsaturated group (such as an alkynyl group) between two silyl groups also contributes to film formation. Then, the second additive seems to have a decomposing action, and the carbonyl group in the structure is believed to impart ionic conduction to the coating. The third and fourth additives are more stable in chemical structure than the first and second additives, and have relatively high withstand voltage characteristics. As a result of adsorption and acceptance of the third and fourth additives to the cathode active material by the phosphonic acid site in the film derived from the first additive, it seems that a dense and low-resistance film that suppresses contact with hydrofluoroether was formed.

The first additive may be included in an amount of 0.01 to 1.5% by weight based on the total weight of the electrolyte, for example, 0.1 to 1.4% by weight, 0.2 to 1.4% by weight, or 0.4 to 1.3% by weight. When the content of the first additive is within the above range, cycle life characteristics and storage characteristics may be greatly improved.

The second additive may be included in an amount of 0.05 to 1.00% by weight, for example, 0.07 to 1.00% by weight, 0.07 to 0.6% by weight, or 0.1 to 0.6% by weight based on the total weight of the electrolyte solution. When the content of the second additive is within the above range, cycle life characteristics and storage characteristics may be greatly improved.

The third additive may be included in 0.04 to 1.00% by weight based on the total weight of the electrolyte solution, for example, 0.05 to 1.00% by weight, 0.07 to 1.00% by weight, 0.07 to 0.6% by weight, or 0.1 to 0.6% by weight. can be included When the content of the third additive is within the above range, cycle life characteristics and storage characteristics may be greatly improved.

The fourth additive may be included in 0.01 to 1.0% by weight based on the total weight of the electrolyte solution, for example, 0.05 to 1.0% by weight, 0.07 to 1.0% by weight, 0.1 to 0.7% by weight, 0.1 to 0.6% by weight, It may be included in 0.1 to 0.4% by weight. When the content of the fourth additive is within the above range, cycle life characteristics and storage characteristics may be greatly improved.

The electrolyte solution may further include various additives other than the first to fourth additives. These additives include negative electrode additives, positive electrode additives, ester-based additives, carbonate ester-based additives, sulfuric acid ester-based additives, phosphoric acid ester-based additives, boric acid ester-based additives, acid anhydride-based additives, and electrolyte-based additives. Additives etc. are mentioned. Any one of these may be added to the electrolyte solution, and a plurality of types of additives may be added to the electrolyte solution.

As described above, the electrolyte solution according to one embodiment includes the first additive and at least one of the second to fourth additives, thereby including a positive electrode including a transition metal oxide containing lithium as a positive electrode active material, and a hydrofluorocarbon Cycle life characteristics and storage characteristics of a lithium secondary battery using an electrolyte containing ether can be greatly improved.

Hereinafter, a method for manufacturing a lithium secondary battery will be described.

The anode 20 can be manufactured as follows. First, a slurry is prepared by dispersing a mixture of a cathode active material, a conductive material, and a binder in a solvent, for example, N-methyl-2-pyrrolidone. Then, the slurry is applied on the current collector 21 and dried to form the positive electrode active material layer 22 . At this time, the method of application is not particularly limited, and examples thereof include a knife coater method and a gravure coater method. The application process below can be performed in the same way. Subsequently, the cathode 20 may be formed by compressing the cathode active material layer 22 to a density within the above range by using a compressor.

The negative electrode 3 may be manufactured in the same way as the positive electrode 20 . For example, first, a mixture of the negative electrode active material and the binder is dispersed in a solvent such as N-methyl-2-pyrrolidone or water to prepare a slurry, and then the slurry is applied on the current collector 31 and dried. An anode active material layer 32 is formed. Subsequently, the negative electrode 30 may be formed by compressing the negative electrode active material layer 32 to have a density within the above range by using a compressor.

The separator 40a may be manufactured as follows. First, a coating solution is prepared by mixing a resin constituting the porous layer 42 and a water-soluble organic solvent in a weight ratio of 5 to 10:90 to 95. Examples of the water-soluble organic solvent include N-methyl-2-pyrrolidone, dimethyl acetamido (DMAc), and tripropylene glycol (TPG). Then, the coating liquid is applied to both sides or one side of the substrate 41 to a thickness of 1 to 5 μm. Subsequently, the substrate 41 coated with the coating liquid is treated with a coagulating liquid to solidify the resin in the coating liquid. Here, as a method of treating the substrate 41 coated with the coating liquid with the coagulating liquid, for example, a method in which the substrate 41 coated with the coating liquid is impregnated with the coagulating liquid, and the substrate 41 coated with the coating liquid ), and the like. Accordingly, the separator 40a can be formed. Here, the coagulating liquid is obtained by mixing water with the above water-soluble organic solvent, for example. The mixing amount of water may be 40 to 80% by volume based on the total volume of the coagulating solution. Next, the separator 40a is washed with water and dried to remove water and a water-soluble organic solvent from the separator 40a.

Then, by inserting the separator 40a between the positive electrode 20 and the negative electrode 30, an electrode structure is manufactured. When the porous layer 42 is formed on only one surface of the substrate 41, the cathode 30 is opposed to the porous layer 42. Then, the manufactured electrode structure is processed into a desired shape, for example, a cylindrical shape, an angular shape, a laminated shape, a button shape, etc., and inserted into a container of the above shape. Further, by injecting a desired electrolyte solution into the container, each pore in the separator 40a is impregnated with the electrolyte solution. Thus, a lithium secondary battery is manufactured.

Hereinafter, specific embodiments of the present invention are presented. However, the embodiments described below are only intended to specifically illustrate or explain the present invention, and the present invention should not be limited thereto. In addition, since the content not described herein can be sufficiently technically inferred by those skilled in the art, the description thereof will be omitted.

Example One

98% by weight of LiCoO ₂ , 1% by weight of polyvinylidene fluoride, and 1% by weight of Ketjen Black were dispersed in N-methyl-2-pyrrolidone to prepare a slurry, and then the slurry was coated on an aluminum current collector foil. By coating and drying, a positive electrode active material layer was formed. Subsequently, the positive electrode active material layer was pressed with a press to make the positive electrode active material layer have a density of 4.0 g/cm ³ , thereby manufacturing a positive electrode.

A slurry was prepared by dispersing 90% by weight of an anode active material, 7% by weight of polyacrylic acid, and 2% by weight of conductive carbon in water, a mixture of silicon alloy (containing 70 atomic% of silicon) and artificial graphite in a weight ratio of 30:70. , The slurry was coated on an aluminum current collector foil as a current collector and dried to form a negative electrode active material layer. Subsequently, the negative electrode active material layer was pressed with a press to make the negative electrode active material layer have a density of 1.45 g/cm ³ , thereby manufacturing a negative electrode.

Then, a separator (Mitsubishi Resin's Seperent, thickness 20 μm) was disposed between the positive electrode and the negative electrode to prepare an electrode structure.

Then, the electrode structure was inserted into a test container.

Fluoroethylene carbonate (FEC), ethylmethylsulfone (EMS), dimethyl carbonate (DMC), hydrofluoroether (HFE) as H(CF ₂ ) ₂ CH ₂ O(CF ₂ )H as 12:3:45: A basic electrolyte solution was prepared by dissolving LiPF ₆ in a solvent mixed at a volume ratio of 40 to a concentration of 1.3 mol/L. Subsequently, an experimental electrolyte solution was prepared by adding a first additive represented by Chemical Formula 1-1 and a third additive represented by Chemical Formula 3-1 to the basic electrolyte solution. The first additive was added in an amount of 0.2% by weight based on the total weight of the experimental electrolyte solution, and the third additive was added in an amount of 0.2% by weight based on the total weight of the experimental electrolyte solution.

Subsequently, the lithium secondary battery of Example 1 was manufactured by injecting the test electrolyte solution into the test container and sealing the opening.

Example 2 to 18 and comparative example 1 to 10

A lithium secondary battery was manufactured in the same manner as in Example 1, except that the type and amount of additives in Example 1 were changed as shown in Tables 1 and 2 below.

(evaluation)

Rating 1: SEM Picture

2 is a scanning electron microscope (SEM) photograph showing the state of the film on the surface of LiCoO ₂ particles after storing the lithium secondary batteries according to Example 1 and Comparative Example 1 at 60° C. for 24 hours.

Referring to FIG. 2 , in the case of Comparative Example 1, beam traces when taking an SEM image were observed on the surface of LiCoO ₂ particles, that is, a portion surrounded by a square of the SEM image of Comparative Example 1 in FIG. 2 . This shows that a film derived from hydrofluoroether (HFE), for example, a decomposition product of HFE, is formed on the surface of the LiCoO ₂ particles.

Evaluation 2: Cycle life test

A cycle test was performed on the lithium secondary batteries according to Examples 1 to 18 and Comparative Examples 1 to 10.

Specifically, at the first temperature of 25°C, constant current constant voltage charging was performed at 0.2 mA/cm ² until the battery voltage reached 4.4V, and discharging was performed until the battery voltage reached 3.0V. This charging and discharging was performed twice.

Then, at a temperature of 45°C, a charge/discharge cycle in which constant current constant voltage charging is performed at 2 mA/cm ² until the battery voltage reaches 4.4 V, and constant current discharge is performed at 2 mA/cm ² until the battery voltage reaches 3.0 V. was performed 300 times.

Then, the discharge capacity (mAh) in each cycle was measured. Measurement of discharge capacity was performed by TOSCAT3000 (Toyo system co., ltd.).

In Tables 3 and 4 below, the capacity retention rate after 300 cycles when the initial discharge capacity at 45°C is 100 is shown as the result of the cycle test.

Evaluation 3: storage test

A storage test was performed on the lithium secondary batteries according to Examples 1 to 18 and Comparative Examples 1 to 10.

Specifically, constant current constant voltage charging was performed at 0.2 mA/cm ² at a temperature of 25° C. until the battery voltage reached 4.4 V, and discharging was performed until the battery voltage reached 3.0 V. Such charging and discharging was performed twice, and the discharge capacity of the second time was set to an initial value of 100.

Subsequently, constant current constant voltage charging was performed at 0.2 mA/cm ² at a temperature of 25°C until the battery voltage reached 4.4 V, and then the battery was transferred to a thermostat with an internal temperature of 60°C and allowed to stand for 30 days.

Further, after being transferred to a thermostat with a temperature inside the tank of 25°C and left to stand for 12 hours, discharging was performed at a current density of 0.2 mA/cm ² until the battery voltage reached 3.0 V. The discharge capacity at this time is taken as the residual capacity, and the residual capacity is the capacity before storage in the thermostatic chamber at 60 ° C., that is, the capacity ratio of the second discharge capacity at 25 ° C. to the initial value of 100. Tables 3 and 4 shown in

In addition, the amount of increase in battery volume before measuring the remaining capacity relative to the battery volume before storage in a thermostat at 60 ° C. is shown in Tables 3 and 4 below as a volume increase rate when the battery volume before storage is 100.

electrolyte composition Basic Electrolyte (Solvent) additive LiPF ₆
(mol/L) FEC
(volume%) EMS
(volume%) DMC
(volume%) HFE
(volume%) 1st additive
(weight%) 2nd additive
(weight%) Third Additive
(weight%) 4th additive
(weight%) Other Additives
(weight%) Example 1 1.3 15 0 45 40 0.20 (Formula 1-1) - 0.20 (Formula 3-1) - - Example 2 1.3 12 3 45 40 0.20 (Formula 1-1) 0.20 (Formula 2-1) - - - Example 3 1.3 12 3 45 40 0.20 (Formula 1-1) - 0.40 (Formula 3-1) - - Example 4 1.3 12 3 45 40 0.20 (Formula 1-1) - - 0.20 (Formula 4-1) - Example 5 1.3 12 3 45 40 0.20 (Formula 1-1) 0.20 (Formula 2-1) 0.20 (Formula 3-1) - - Example 6 1.3 12 3 45 40 0.20 (Formula 1-1) - - 0.20 (Formula 4-1) - Example 7 1.3 12 3 45 40 0.20 (Formula 1-1) - 0.20 (Formula 3-1) 0.20 (Formula 4-1) - Example 8 1.3 12 3 45 40 0.40 (Formula 1-1) - 0.20 (Formula 3-1) - - Example 9 1.3 12 3 45 40 0.80 (Formula 1-1) - 0.20 (Formula 3-1) - - Example 10 1.3 12 3 45 40 1.00 (Formula 1-1) - 0.20 (Formula 3-1) - - Example 11 1.3 12 3 45 40 0.20 (Formula 1-1) - 0.20 (Formula 3-1) - 1 (SN) Example 12 1.3 12 3 45 40 0.20 (Formula 1-1) - 0.20 (Formula 3-1) - 1 (SN),
1 (VC) Example 13 1.3 12 3 45 40 0.20 (Formula 1-1) - 0.20 (Formula 3-1) - 1 (SN),
0.3 (LiFOB) Example 14 1.3 12 3 45 40 0.20 (Formula 1-1) - 0.20 (Formula 3-1) - 1 (SN),
0.5 (LiBOB) Example 15 1.3 12 3 45 40 0.05 (Formula 1-1) - 0.20 (Formula 3-1) - - Example 16 1.3 12 3 45 40 0.10 (Formula 1-1) - 0.20 (Formula 3-1) - - Example 17 1.3 12 3 45 40 0.14 (Formula 1-1) - 0.20 (Formula 3-1) - - Example 18 1.3 12 3 45 40 1.30 (Formula 1-1) - 0.20 (Formula 3-1) - -

electrolyte composition Basic Electrolyte (Solvent) additive LiPF ₆
(mol/L) FEC
(volume%) EMS
(volume%) DMC
(volume%) HFE
(volume%) 1st additive
(weight%) 2nd additive
(weight%) Third Additive
(weight%) 4th additive
(weight%) Other Additives
(weight%) Comparative Example 1 1.3 12 3 45 40 - - - - - Comparative Example 2 1.3 12 3 45 40 - - - - 3 (SN) Comparative Example 3 1.3 12 3 45 40 - - - - 3 (PS) Comparative Example 4 1.3 12 3 45 40 0.20 (Formula 1-1) - - - - Comparative Example 5 1.3 12 3 45 40 - 0.20 (Formula 2-1) - - - Comparative Example 6 1.3 12 3 45 40 - - 0.20 (Formula 3-1) - - Comparative Example 7 1.3 12 3 45 40 - - - 0.20 (Formula 4-1) - Comparative Example 8 1.3 12 3 45 40 - 0.20 (Formula 2-1) 0.20 (Formula 3-1) - - Comparative Example 9 1.3 12 3 45 40 - 0.20 (Formula 2-1) - 0.20 (Formula 4-1) - Comparative Example 10 1.3 12 3 45 40 - - 0.20 (Formula 3-1) 0.20 (Formula 4-1) -

45℃ cycle test 60℃ * 30 days storage test Capacity retention rate
(%@300 ^th ) Volume increase rate
∇V (%) remaining capacity
(%) Example 1 73 10 70 Example 2 78 5 73 Example 3 81 2 81 Example 4 71 5 74 Example 5 77 6 76 Example 6 70 3 76 Example 7 74 3 74 Example 8 83 One 73 Example 9 83 One 80 Example 10 73 5 74 Example 11 78 One 84 Example 12 85 One 80 Example 13 88 One 90 Example 14 89 One 88 Example 15 46 44 43 Example 16 69 16 61 Example 17 70 13 66 Example 18 48 2 69

45℃ cycle test 60℃ * 30 days storage test Capacity retention rate
(%@300th) Volume increase rate
∇V (%) remaining capacity
(%) Comparative Example 1 35 94 10 Comparative Example 2 42 64 15 Comparative Example 3 30 36 33 Comparative Example 4 53 25 51 Comparative Example 5 42 31 40 Comparative Example 6 38 60 41 Comparative Example 7 42 35 45 Comparative Example 8 39 45 48 Comparative Example 9 44 30 42 Comparative Example 10 40 35 39

In Tables 1 and 2, SN is succinonitrile, VC is vinylene carbonate, PS is 1,3-propane sultone, LiFOB is lithium difluoro (oxalate) borate, LiBOB is lithium bis (oxalate) borate indicates In addition, the addition amount of the additive represents the weight% with respect to the total weight of the experimental electrolyte solution (basic electrolyte solution (solvent) + additives). Also, "-" indicates that no additive is added.

Referring to Tables 3 and 4, in the case of Examples 1 to 18 in which the first additive and at least one of the second to fourth additives were added, the capacity retention rate after 300 cycles increased, and the volume increase rate of the battery also increased. It can be seen that it is small and the remaining capacity after storage also increases. From this, it can be seen that cycle life characteristics and storage characteristics are greatly improved by adding the first additive and at least one of the second to fourth additives to the basic electrolyte solution.

In addition, as the range of the addition amount of the first additive is narrowed to 0.1 to 1% by weight, 0.2 to 0.8% by weight, and 0.4 to 0.8% by weight, it can be seen that the effect of improving cycle life characteristics and storage characteristics is higher. .

Example 19

A lithium secondary battery was manufactured in the same manner as in Example 1, except that the composition of the basic electrolyte and the type and amount of additives added to the basic electrolyte in Example 1 were changed as shown in Table 5 below.

Example 20 to 44 and comparative example 11

A lithium secondary battery was manufactured in the same manner as in Example 19, except that the type and amount of additives in Example 19 were changed as shown in Table 5 below.

(evaluation)

Evaluation 4: Cycle life test

A cycle test was performed on the lithium secondary batteries according to Examples 19 to 44 and Comparative Example 11.

Specifically, at the first temperature of 25°C, constant current constant voltage charging was performed at 0.2 mA/cm ² until the battery voltage reached 4.4V, and discharging was performed until the battery voltage reached 3.0V. This charging and discharging was performed twice.

Then, at a temperature of 45°C, a charge/discharge cycle in which constant current constant voltage charging is performed at 2 mA/cm ² until the battery voltage reaches 4.4 V, and constant current discharge is performed at 2 mA/cm ² until the battery voltage reaches 3.0 V. was performed 200 times.

Then, the discharge capacity (mAh) in each cycle was measured. Measurement of discharge capacity was performed by TOSCAT3000 (Toyo system co., ltd.).

In Table 6 below, the capacity retention rate after 200 cycles when the initial discharge capacity at 45°C is 100 is shown as a result of the cycle test.

Rating 5: storage test

A storage test was performed on the lithium secondary batteries according to Examples 19 to 44 and Comparative Example 11.

Specifically, constant current constant voltage charging was performed at 0.2 mA/cm ² at a temperature of 25° C. until the battery voltage reached 4.4 V, and discharging was performed until the battery voltage reached 3.0 V. Such charging and discharging was performed twice, and the discharge capacity of the second time was set to an initial value of 100.

Subsequently, constant current constant voltage charging was performed at 0.2 mA/cm ² at a temperature of 25°C until the battery voltage reached 4.4 V, and then the battery was transferred to a thermostat with an internal temperature of 60°C and allowed to stand for 15 days.

Further, after being transferred to a thermostat with a temperature inside the tank of 25°C and left to stand for 12 hours, discharging was performed at a current density of 0.2 mA/cm ² until the battery voltage reached 3.0 V. The discharge capacity at this time was taken as the remaining capacity, and this remaining capacity was shown in Table 6 below as a capacity ratio with respect to the initial value of 100 for the capacity before storage in a thermostat at 60 ° C, that is, the second discharge capacity at 25 ° C. .

In addition, the amount of increase in battery volume before measuring the remaining capacity relative to the battery volume before storage in a thermostat at 60 ° C is shown in Table 6 below as a volume increase rate when the battery volume before storage is 100.

electrolyte composition Basic Electrolyte (Solvent) additive LiPF ₆
(mol/L) FEC
(volume%) EMS
(volume%) DMC
(volume%) HFE
(volume%) 1st additive
(weight%) 2nd additive
(weight%) Third Additive
(weight%) 4th additive
(weight%) Other Additives
(weight%) Comparative Example 11 1.3 12 3 45 40 0.80 (Formula 1-1) - - - - Example 19 1.3 12 3 45 40 0.80 (Formula 1-1) - 0.20 (Formula 3-1) - - Example 20 1.3 12 3 45 40 0.80 (Formula 1-2) - 0.20 (Formula 3-1) - - Example 21 1.3 12 3 45 40 0.80 (Formula 1-3) - 0.20 (Formula 3-1) - - Example 22 1.3 12 3 45 40 0.80 (Formula 1-4) - 0.20 (Formula 3-1) - - Example 23 1.3 12 3 45 40 0.80 (Formula 1-4) 0.20 (Formula 2-1) - - - Example 24 1.3 12 3 45 40 0.80 (Formula 1-4) - 0.20 (Formula 3-1) - - Example 25 1.3 12 3 45 40 0.80 (Formula 1-4) - - 0.20 (Formula 4-2) - Example 26 1.3 12 3 45 40 0.80 (Formula 1-4) 0.05 (Formula 2-1) - - - Example 27 1.3 12 3 45 40 0.80 (Formula 1-4) 0.07 (Formula 2-1) - - - Example 28 1.3 12 3 45 40 0.80 (Formula 1-4) 0.10 (Formula 2-1) - - - Example 29 1.3 12 3 45 40 0.80 (Formula 1-4) 0.38 (Formula 2-1) - - - Example 30 1.3 12 3 45 40 0.80 (Formula 1-4) 0.60 (Formula 2-1) - - - Example 31 1.3 12 3 45 40 0.80 (Formula 1-4) 1.00 (Formula 2-1) - - - Example 32 1.3 12 3 45 40 0.80 (Formula 1-4) - 0.04 (Formula 3-1) - - Example 33 1.3 12 3 45 40 0.80 (Formula 1-4) - 0.07 (Formula 3-1) - - Example 34 1.3 12 3 45 40 0.80 (Formula 1-4) - 0.10 (Formula 3-1) - - Example 35 1.3 12 3 45 40 0.80 (Formula 1-4) - 0.40 (Formula 3-1) - - Example 36 1.3 12 3 45 40 0.80 (Formula 1-4) - 0.60 (Formula 3-1) - - Example 37 1.3 12 3 45 40 0.80 (Formula 1-4) - 1.00 (Formula 3-1) - - Example 38 1.3 12 3 45 40 0.80 (Formula 1-4) - - 0.05 (Formula 4-2) - Example 39 1.3 12 3 45 40 0.80 (Formula 1-4) - - 0.07 (Formula 4-2) - Example 40 1.3 12 3 45 40 0.80 (Formula 1-4) - - 0.10 (Formula 4-2) - Example 41 1.3 12 3 45 40 0.80 (Formula 1-4) - - 0.40 (Formula 4-2) - Example 42 1.3 12 3 45 40 0.80 (Formula 1-4) - - 0.60 (Formula 4-2) - Example 43 1.3 12 3 45 40 0.80 (Formula 1-4) - - 0.66 (Formula 4-2) - Example 44 1.3 12 3 45 40 0.80 (Formula 1-4) - - 1.00 (Formula 4-2) -

45℃ cycle test 60℃ * 15 days storage test Capacity retention rate
(%@200 ^th ) Volume increase rate
∇V (%) remaining capacity
(%) Comparative Example 11 65 15 60 Example 19 84 3 84 Example 20 82 4 79 Example 21 85 2 72 Example 22 86 2 88 Example 23 77 2 78 Example 24 85 2 81 Example 25 81 2 79 Example 26 62 12 62 Example 27 70 7 68 Example 28 74 3 77 Example 29 83 2 85 Example 30 73 One 84 Example 31 66 0 75 Example 32 62 9 62 Example 33 68 8 68 Example 34 73 5 68 Example 35 80 2 85 Example 36 73 0 84 Example 37 68 0 72 Example 38 58 16 53 Example 39 63 11 63 Example 40 76 6 74 Example 41 71 2 73 Example 42 69 One 66 Example 43 57 One 41 Example 44 47 One 41

The content in Table 5 represents the weight% with respect to the total weight of the experimental electrolyte solution (basic electrolyte solution + additives). Also, "-" indicates that no additive is added.

Referring to Table 6, for the type of the first additive, the additives represented by Chemical Formula 1-4 > Chemical Formula 1-3 > Chemical Formula 1-1 > Chemical Formula 1-2 showed high improvement in cycle life characteristics and storage characteristics. can know

In addition, as the range of the addition amount of the second additive is narrowed to 0.07 to 1% by weight, 0.07 to 0.4% by weight, and 0.1 to 0.4% by weight, it can be seen that the improvement effect of cycle life characteristics and storage characteristics is higher. .

In addition, as the range of the addition amount of the third additive narrows to 0.07 to 1% by weight, 0.07 to 0.6% by weight, and 0.1 to 0.6% by weight, it can be seen that the effect of improving cycle life characteristics and storage characteristics is higher. .

In addition, it can be seen that as the range of the addition amount of the fourth additive narrows to 0.1 to 0.6% by weight and 0.1 to 0.4% by weight, the effect of improving cycle life characteristics and storage characteristics becomes higher.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It falls within the scope of the right of invention.

10 Lithium secondary battery
20 anode
21 whole house
22 cathode active material layer
30 cathode
31 whole house
32 negative electrode active material layer
40 separator layer

Claims (16)

a positive electrode including a positive electrode active material; and
Including an electrolyte solution containing a solvent and additives,
The cathode active material includes a transition metal oxide containing lithium,
The solvent includes hydrofluoroether,
The additive is
Including a first additive represented by the following formula 1-1 to formula 1-4,
At least one selected from the group consisting of a second additive represented by the following Chemical Formula 2-1, a third additive represented by the following Chemical Formula 3-1, and a fourth additive represented by the following Chemical Formulas 4-1 to 4-2 is to include,
The first additive is a lithium secondary battery that is included in 0.4 to 0.8% by weight based on the total weight of the electrolyte solution.
[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 2-1]

[Formula 3-1]

[Formula 4-1]

[Formula 4-2]

In paragraph 1,
The hydrofluoroether (HFE) is 2,2,2-trifluoroethylmethyl ether (CF ₃ CH ₂ OCH ₃ ), 2,2,2-trifluoroethyldifluoromethyl ether (CF ₃ CH ₂ OCHF ₂ ), 2,2,3,3,3-pentafluoropropylmethyl ether (CF ₃ CF ₂ CH ₂ OCH ₃ ), 2,2,3,3,3-pentafluoropropyldifluoromethyl ether (CF ₃ CF ₂ CH ₂ OCHF ₂ ), 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether (CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H), 1,1,2,2-tetrafluoroethylmethyl ether (HCF ₂ CF ₂ OCH ₃ ), 1,1,2,2-tetrafluoroethyl ethyl ether (HCF ₂ CF ₂ OCH ₂ CH ₃ ) , 1,1,2,2-tetrafluoroethylpropyl ether (HCF ₂ CF ₂ OC ₃ H ₇ ), 1,1,2,2-tetrafluoroethyl butyl ether (HCF ₂ CF ₂ OC ₄ H ₉ ) , 2,2,3,3-tetrafluoroethyldifluoromethyl ether (H(CF ₂ ) ₂ CH ₂ O(CF ₂ )H), 1,1,2,2-tetrafluoroethyl isobutyl ether (HCF ₂ CF ₂ OCH ₂ CH(CH ₃ ) ₂ ), 1,1,2,2-tetrafluoroethylisopentyl ether (HCF ₂ CF ₂ OCH ₂ C(CH ₃ ) ₃ ), 1,1,2 ,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HCF ₂ CF ₂ OCH ₂ CF ₃ ), 1,1,2,2-tetrafluoroethyl-2,2,3,3 -Tetrafluoropropyl ether (HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H), hexafluoroisopropylmethyl ether ((CF ₃ ) ₂ CHOCH ₃ ), 1,1,3,3,3-pentafluoro -2-trifluoromethylpropylmethyl ether ((CF ₃ ) ₂ CHCF ₂ OCH ₃ ), 1,1,2,3,3,3-hexafluoropropylmethyl ether (CF ₃ CHFCF ₂ OCH ₃ ), 1 ,1,2,3,3,3-hexafluoropropylethyl ether (CF ₃ CHFCF ₂ OCH ₂ CH ₃ ), 2,2,3,4,4,4-hexafluorobutyldifluoromethyl ether ( C F ₃ CHFCF ₂ CH ₂ OCHF ₂ ), or a lithium secondary battery including a combination thereof.
In paragraph 1,
The content of the hydrofluoroether is 10 to 60% by volume based on the total volume of the lithium secondary battery.
delete In paragraph 1,
The additive includes the first additive and the second additive,
The second additive is included in an amount of 0.05 to 1.00% by weight based on the total weight of the electrolyte solution.
In paragraph 1,
The additive includes the first additive and the third additive,
The third additive is included in an amount of 0.04 to 1.00% by weight based on the total weight of the electrolyte solution.
In paragraph 1,
The additive includes the first additive and the fourth additive,
The fourth additive is included in an amount of 0.01 to 1.00% by weight based on the total weight of the electrolyte solution.
delete delete delete delete In paragraph 1,
The lithium secondary battery wherein the lithium-containing transition metal oxide is a lithium cobalt-based composite oxide.
In paragraph 1,
The lithium secondary battery further includes a negative electrode including a negative electrode active material,
The negative electrode active material is a lithium secondary battery that is a carbon-based material, a silicon-based material, a tin-based material, a lithium metal oxide, or a mixture of two or more kinds of metal lithium.
In paragraph 1,
The lithium secondary battery of claim 1, wherein the solvent further comprises fluoroethylene carbonate.
In paragraph 14,
The content of the fluoroethylene carbonate is 10 to 30% by volume based on the total volume of the solvent lithium secondary battery.
In paragraph 1,
The oxidation-reduction potential of the lithium secondary battery is 4.3V (vs. Li / Li ⁺ ) or more and 5.0V or less.

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