KR102187691B1 - Electrolyte and lithium secondary battery comprising the same - Google Patents

Abstract

상기 식에서, X, Y 및 n은 명세서 중에서 정의한 바와 동일하다.The present invention relates to an electrolyte and a lithium secondary battery comprising the same, wherein the electrolyte comprises a compound of the following formula (1) as an electrolyte additive, thereby improving battery characteristics of a lithium secondary battery, particularly, a discharge maintenance rate at high voltage, and reducing gas generation. Inhibits and can improve overcharge protection properties:
[Formula 1]

In the above formula, X, Y, and n are the same as defined in the specification.

Description

Electrolyte and lithium secondary battery containing the same {ELECTROLYTE AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to an electrolyte solution capable of improving battery characteristics of a lithium secondary battery, particularly, a discharge retention rate at high voltage, suppressing gas generation, and improving overcharge prevention characteristics, and a lithium secondary battery including the same.

Lithium secondary batteries are not only portable power sources for mobile phones, notebook computers, digital cameras and camcorders, but also power tools, electric bicycles, hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (plug-in). HEV, PHEV) and other medium and large-sized power supplies are rapidly expanding their application.

With the expansion of such application fields and the increase in demand, the external shape and size of the battery are variously changed, and more excellent performance and stability than the characteristics required by the existing small battery are required. In order to meet these demands, the battery components must stably implement the performance of the battery under conditions where a large current flows.

Lithium secondary batteries are manufactured by using a material capable of intercalating and deintercalating lithium ions as a negative electrode and a positive electrode, installing a porous separator between the two electrodes, and injecting a liquid electrolyte. Electricity is generated or consumed by redox reactions following desorption.

In order to improve battery characteristics such as output characteristics, cycle characteristics, and storage characteristics of lithium-ion batteries, various studies have been made on non-aqueous solvents or additives as electrolyte-containing components. In addition, even when a specific compound is added to the electrolyte as an additive to improve battery performance, some of the battery performance can be expected to improve performance, but there is a problem in that the performance of other items is rather reduced.

Korean Patent Publication No. 2006-0075966 (published on July 4, 2006)

An object of the present invention is to provide an electrolyte solution capable of improving battery characteristics of a lithium secondary battery, particularly, a discharge retention rate at a high voltage, suppressing gas generation, and improving overcharge prevention characteristics.

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

In order to achieve the above object, the electrolyte solution according to an embodiment of the present invention contains a compound of Formula 1 as an electrolyte solution additive:

[Formula 1]

In Formula 1,

X and Y are each independently substituted or unsubstituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, a halogen group, a haloalkyl group having 1 to 6 carbon atoms, and an alkoxy group having 1 to 6 carbon atoms. 1 to 20 alkyl group, C 1 to C 20 alkoxy group, C 3 to C 30 cycloalkyl group, C 6 to C 30 aryl group, C 6 to C 30 aryloxy group, C 7 to C 30 arylalkyl group, ring nitrogen (N), oxygen (O), and sulfur (S) selected from the group consisting of a heterocycle group having 4 to 20 carbon atoms containing at least one hetero atom selected from the group consisting of, and a combination thereof, and

n is an integer of 1 to 3.

Preferably, in Formula 1, X and Y are each independently an alkyl group having 1 to 5 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an arylalkyl group having 7 to 12 carbon atoms, and combinations thereof. It is selected from the group consisting of, and n may be an integer of 1.

Even more preferably, the compound of Formula 1 may be bis (phenylsulfonyl) methane.

In addition, the compound of Formula 1 may be included in an amount of 0.1 to 10% by weight based on the total weight of the electrolyte.

In addition, the electrolyte may further contain an organic solvent and a lithium salt.

The organic solvent may be selected from the group consisting of an ester solvent, an ether solvent, a ketone solvent, an aromatic hydrocarbon solvent, an alkoxyalkane solvent, a carbonate solvent, and a mixture thereof.

The organic solvent may include a high dielectric constant organic solvent and a low viscosity organic solvent in a volume ratio of 2:8 to 8:2.

The high dielectric constant organic solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof, and the low viscosity organic solvent is ethylmethylcarbonate, dimethyl carbonate ( It may be selected from the group consisting of dimethylcarbonate), diethylcarbonate, and mixtures thereof.

The organic solvent is one of ethylene carbonate and propylene carbonate; Ethyl methyl carbonate; And, one of dimethyl carbonate and diethyl carbonate may be included in a volume ratio of 5:1:1 to 2:5:3.

The lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , 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(C _a F _2a+1 SO ₂ )(C _b F _2b+1 SO ₂ ) (where a and b are natural numbers), LiCl, LiI, LiB(C ₂ O ₄ ) ₂ and mixtures thereof Can be selected from the group.

A lithium secondary battery according to another embodiment of the present invention includes a positive electrode including a positive electrode active material, a negative electrode disposed opposite to the positive electrode and including a negative electrode active material, and an electrolyte solution interposed between the positive electrode and the negative electrode, The electrolyte solution includes the compound of Formula 1 as an electrolyte solution additive.

Other specific details of the embodiments of the present invention are included in the detailed description below.

The electrolyte according to the present invention may improve battery characteristics of a lithium secondary battery, particularly, a discharge retention rate at a high voltage, suppress gas generation, and improve overcharge prevention characteristics.

1 is an exploded perspective view of a lithium secondary battery according to an embodiment of the present invention.
FIG. 2 is a graph showing the results of evaluating the effect of improving battery characteristics in Test Example 1 using a linear sweep voltammetry for the electrolyte solution of Example 1. FIG.
3 is a graph showing the results of observing the redox behavior of the electrolyte solution of Example 1 in Test Example 2 using cyclic voltammetry.
4 is a graph showing the results of evaluating the life characteristics of lithium secondary batteries including the electrolyte solutions of Examples 1 to 11 in Test Example 3.

The present invention is intended to illustrate specific embodiments and to be described in detail in the detailed description, since various transformations can be applied and various embodiments can be provided. However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all conversions, equivalents, and substitutes included in the spirit and scope of the present invention.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present invention, terms such as'comprise' or'have' are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance.

In the present specification, all compounds or functional groups may be substituted or unsubstituted unless otherwise specified. Here,'substituted' means that at least one hydrogen contained in the compound or functional group is a halogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group, a cycloalkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, a hydroxy group , A C 1 to C 10 alkoxy group, a carboxylic acid group, an aldehyde group, an epoxy group, a cyano group, a nitro group, an amino group, a sulfonic acid group, and a substituent selected from the group consisting of derivatives thereof.

In addition, unless otherwise specified, the term'combination thereof' in the present specification is a single bond, a double bond, a triple bond, an alkylene group having 1 to 10 carbon atoms (e.g., methylene (-CH ₂ -), ethylene (-CH ₂ CH ₂ -), etc.), a fluoroalkylene group having 1 to 10 carbon atoms (e.g., fluoromethylene (-CF ₂ -), perfluoroethylene (-CF ₂ CF ₂ -), etc.) , N, O, P, S, or a hetero atom such as Si or a functional group containing the same (specifically, an intramolecular carbonyl group (-C=O-), an ether group (-O-), an ester group (-COO- ), a heteroalkylene group including -S-, -NH- or -N=N-), or two or more functional groups are condensed or linked.

An electrolyte according to an embodiment of the present invention is characterized in that it contains a compound of Formula 1 as an electrolyte additive:

[Formula 1]

In Formula 1, X and Y are each independently an alkyl group having 1 to 20 carbon atoms (e.g., methyl group, ethyl group, isopropyl group, n-butyl group, tert-butyl group, sec-pentyl group, tert-pentyl group , Neopentyl group, 1-methylheptyl group, n-hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group, neohexyl group, etc.), alkoxy group having 1 to 20 carbon atoms (e.g., methoxy group , Ethoxy group, propoxy group, isopropoxy group, tert-butoxy group, etc.), a cycloalkyl group having 3 to 30 carbon atoms (e.g., a cyclopropyl group, a cyclobutyl group, a cycloheptyl group, a cyclohexyl group, a norbornyl group) , Adamantyl group, etc.), aryl group having 6 to 30 carbon atoms (eg, phenyl group, naphthyl group, etc.), aryloxy group having 6 to 30 carbon atoms (eg phenyloxy group, naphthyloxy group, etc.), carbon number 7 to 30 arylalkyl groups (e.g., benzyl group, phenethyl group, 3-phenylpropyl group, phenylbutyl group, 1-methyl-3-phenylpropyl group, naphthylmethyl group, etc.), nitrogen (N) in the ring, A heterocycle group having 4 to 20 carbon atoms containing at least one hetero atom selected from the group consisting of oxygen (O) and sulfur (S) (for example, thienyl group, furyl, benzothienyl, pyridyl, pyra Genyl, pyrimidinyl, pyridazinyl, quinolinyl, quinoxalinyl, imidazolyl, furanyl, benzofuranyl, thiazolyl, isoxazolyl, benzisoxazolyl, benzimidazolyl, triazolyl, pyrazolyl , Pyrrolyl, indolyl, pyridonyl, etc.), and may be selected from the group consisting of a combination thereof. Among them, it may be preferable to be selected from the group consisting of an alkyl group having 1 to 5 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms and an arylalkyl group having 7 to 12 carbon atoms, and combinations thereof, and It may be more preferable that it is an aryl group of 6-12, and it may be even more preferable that it is a phenyl group.

In addition, each of X and Y may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, a halogen group, a haloalkyl group having 1 to 6 carbon atoms, and an alkoxy group having 1 to 6 carbon atoms. Specific examples include fluoromethyl group, trifluoromethyl group, di(trifluoromethyl)methyl group, perfluoroethyl group, 2-chloroethyl group, 2-bromomethyl group, 4-methylphenyl group, 4-methyl-2-thienyl group And 3,4-ethyldioxythienyl group.

And in Formula 1, n is an integer of 1 to 3, preferably an integer of 1.

Among them, bis (phenylsulfonyl) methane of the following formula 2, wherein both X and Y in Formula 1 are phenyl groups, and n is an integer of 1 may be more preferable in terms of improving the battery characteristics. have:

[Formula 2]

The electrolyte additive of Formula 1 as described above can improve the battery characteristics of a lithium secondary battery, especially capacity retention at high voltage by forming a film on the positive electrode active material, and in particular, automobiles requiring high output, high voltage and high discharge efficiency characteristics. Compared to the conventional succinonitrile-based additives that have been applied to the battery, the discharge efficiency is significantly increased. In addition, the film formed on the anode surface acts as a protective film to block the active sites on the anode surface, preventing part of the transition metal from being eluted and deposited on the cathode during charging and discharging, and preventing side reactions and gas generated between the electrolyte and the anode. Suppression, it is possible to improve high temperature performance and overcharge characteristics.

The compound of Formula 1 may be included in an amount of 0.1 to 10% by weight based on the total weight of the electrolyte. If the content of the electrolyte additive is less than 0.1% by weight, the effect of the use of the electrolyte additive is insignificant, and if it exceeds 10% by weight, there is a concern that the initial capacity decreases. Preferably, it is contained in an amount of 1 to 3% by weight based on the total weight of the electrolyte solution to obtain a greater improvement effect.

The electrolyte may further include an organic solvent and a lithium salt in addition to the electrolyte additive.

The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of a battery can move. Specifically, as the organic solvent, an ester solvent, an ether solvent, a ketone solvent, an aromatic hydrocarbon solvent, an alkoxyalkane solvent, and a carbonate solvent may be used, and one of them may be used alone or in combination of two or more.

Specific examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, and ethyl pro. Ethyl propionate, γ-butyrolactone, decanolide, γ-valerolactone, mevalonolactone, γ-caprolactone -caprolactone), δ-valerolactone, or ε-caprolactone.

Specific examples of the ether-based solvent include dibutyl ether, tetraglyme, 2-methyltetrahydrofuran, or tetrahydrofuran.

Specific examples of the ketone-based solvent include cyclohexanone. Specific examples of the aromatic hydrocarbon-based organic solvent include benzene, fluorobenzene, chlorobenzene, iodobenzene, toluene, fluorotoluene, or xylene. (xylene), etc. are mentioned. Examples of the alkoxyalkane solvent include dimethoxy ethane or diethoxy ethane.

Specific examples of the carbonate solvent include dimethylcarbonate (DMC), diethylcarbonate (DEC), dipropylcarbonate (DPC), methylpropylcarbonate (MPC), and ethylpropylcarbonate (EPC). , Methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylenes carbonate (BC), or fluoro Ethylene carbonate (fluoroethylene carbonate, FEC), etc. are mentioned.

Among them, it is preferable to use a carbonate-based solvent as the organic solvent, and more preferably among the carbonate-based solvents, a carbonate-based organic solvent having a high dielectric constant having a high ionic conductivity that can increase the charge/discharge performance of the battery, and the intrinsic It may be desirable to mix and use a low-viscosity carbonate-based organic solvent capable of appropriately controlling the viscosity of the total organic solvent. Specifically, an organic solvent having a high dielectric constant selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof, and an organic solvent having a low viscosity selected from the group consisting of ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, and mixtures thereof It can be mixed and used. Even more preferably, the high-k 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; In addition, dimethyl carbonate or diethyl carbonate may be mixed and used in a volume ratio of 5:1:1 to 2:5:3, preferably in a volume ratio of 3:5:2.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt includes LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , 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(C _a F _2a+1 SO ₂ )(C _b F _2b+1 SO ₂ ) (however, a and b are natural numbers, preferably 1≦a≦20, and 1≦b≦20), LiCl, LiI, LiB(C ₂ O ₄ ) ₂ and a mixture thereof may be selected from the group consisting of, and preferably lithium hexafluorophosphate (LiPF ₆ ) is used.

When the lithium salt is dissolved in an electrolytic solution, the lithium salt functions as a source of lithium ions in a lithium secondary battery, and can promote the movement of lithium ions between the positive electrode and the negative electrode. Accordingly, the lithium salt is preferably included in the electrolyte at a concentration of about 0.6 mol% to 2 mol%. When the concentration of the lithium salt is less than 0.6 mol%, the conductivity of the electrolyte may be lowered, resulting in a decrease in electrolyte performance, and when the concentration of the lithium salt exceeds 2 mol%, the viscosity of the electrolyte may increase, resulting in lower mobility of lithium ions. Considering the conductivity of the electrolyte and mobility of lithium ions, the lithium salt may be more preferably adjusted to about 0.7 mol% to 1.6 mol% in the electrolyte.

In addition to the components of the electrolyte, the electrolyte further includes additives (hereinafter referred to as'other additives') that can be generally used in the electrolyte for the purpose of improving battery life characteristics, suppressing reduction in battery capacity, and improving battery discharge capacity. can do.

Specific examples of the other additives include vinylene carbonate (VC), metal fluoride (eg, LiF, RbF, TiF, AgF, AgF2, BaF ₂ , CaF ₂ , CdF ₂ , FeF ₂ , HgF) ₂ , Hg ₂ F ₂ , MnF ₂ , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF ₃ , DyF ₃ , EuF ₃ , GaF _{3, GdF 3, FeF 3,} HoF 3, InF 3, LaF 3, LuF 3, MnF 3, NdF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, TmF 3, YF 3, _{YbF 3, TIF 3, CeF 4} , GeF 4, HfF 4, SiF 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, SF 6 , WF ₆ , CoF ₂ , CoF ₃ , CrF ₂ , CsF, ErF ₃ , PF ₃ , PbF ₃ , PbF ₄ , ThF ₄ , TaF ₅ , SeF _6, etc.), glutaronitrile (GN), suk Sinonitrile (SN), adiponitrile (AN), 3,3'-thiodipropionitrile (TPN), vinylethylene carbonate (VEC), Fluoroethylene carbonate (FEC), difluoroethylenecarbonate, fluorodimethylcarbonate, fluoroethylmethylcarbonate, lithium bis (oxalato) borate (Lit) hium bis (oxalato) borate, LiBOB), lithium difluoro (oxalate) borate (LiDFOB), lithium (malonato oxalato) borate (Lithium (malonato oxalato) borate, LiMOB), etc. These may be mentioned, and these may be included alone or in combination of two or more.

The other additives may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

According to another embodiment of the present invention, there is provided a lithium secondary battery including the electrolyte. The lithium secondary battery according to the embodiment of the present invention may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery according to the type of separator and electrolyte used, and according to the shape, the lithium secondary battery It can be classified into, etc., and can be divided into bulk type and thin film type according to the size. The electrolyte solution according to an embodiment of the present invention may be particularly excellent for application to lithium ion batteries, aluminum laminate batteries, and lithium polymer batteries.

Specifically, the lithium secondary battery includes a positive electrode including a positive electrode active material disposed opposite each other, a negative electrode including a negative electrode active material, and the electrolyte solution interposed between the positive electrode and the negative electrode.

1 is an exploded perspective view of a lithium secondary battery 1 according to an embodiment of the present invention. Referring to FIG. 1, a lithium secondary battery 1 according to another embodiment of the present invention includes a negative electrode 3, a positive electrode 5, a separator 7 between the negative electrode 3 and the positive electrode 5 By placing the electrode assembly 9 and placing it in the case 15 and injecting a nonaqueous electrolyte so that the cathode 3, the anode 5 and the separator 7 are impregnated with the electrolyte. have.

Conductive lead members 10 and 13 for collecting electric current generated during battery operation may be attached to the negative electrode 3 and the positive electrode 5, respectively, and the lead members 10 and 13 are respectively a positive electrode 5 And it is possible to induce the current generated in the negative electrode 3 to the positive and negative terminals.

The positive electrode 5 is prepared by mixing a positive electrode active material, a conductive agent, and a binder to prepare a composition for forming a positive electrode active material layer, and then coating the positive electrode active material layer-forming composition on a positive electrode current collector such as aluminum foil, and rolling it. can do.

As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (reitiated intercalation compound) may be used. Specifically, an olivine-type lithium metal compound represented by the following formula (3) may be used.

[Formula 3]

_{Li x M y M 'z XO} 4-w Y w

(In Formula 3, the M and M'are each independently Fe, Ni, Co, Mn, Cr, Zr, Nb, Cu, V, Mo, Ti, Zn, Al, Ga, Mg, B, and combinations thereof An element selected from the group consisting of, X is an element selected from the group consisting of P, As, Bi, Sb, Mo, and combinations thereof, and Y is selected from the group consisting of F, S, and combinations thereof. Element, 0<x≤1, 0<y≤1, 0<z≤1, 0<x+y+z≤2, and 0≤w≤0.5.)

Among the above compounds, LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _x Mn _(1-x) O ₂ (however, 0<x<1), LiM _lx M _2y O ₂ (However, 0≤x≤1, 0≤y≤1, 0≤x+y≤1, M ₁ and M ₂ are each independently selected from the group consisting of Al, Sr, Mg, and La It may be desirable to use one selected from the group consisting of) and mixtures thereof.

The negative electrode 3, like the positive electrode 5, is prepared by mixing a negative electrode active material, a binder, and optionally a conductive agent to prepare a composition for forming a negative electrode active material layer, and then coating it on a negative electrode current collector such as copper foil. I can.

As the anode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. As a specific example of the negative active material, a carbonaceous material such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon may be used. In addition, in addition to the carbonaceous material, a metal compound capable of alloying with lithium or a composite including a metal compound and a carbonaceous material may be used as the negative electrode active material.

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

As the negative active material, any one selected from the group consisting of crystalline carbon, amorphous carbon, carbon composites, lithium metal, lithium-containing alloys, and mixtures thereof may be used in view of high stability.

On the other hand, since the electrolytic solution is the same as previously described in the electrolytic solution, the description thereof will be omitted. The lithium secondary battery may be manufactured by a conventional method, and a detailed description thereof will be omitted herein. In this embodiment, a pouch-type lithium secondary battery has been described as an example, but the technology of the present invention is not limited to a pouch-type lithium secondary battery, and any shape may be possible as long as it can be operated as a battery.

As described above, the lithium secondary battery including the electrolyte according to the embodiment of the present invention can exhibit low DC-IR characteristics, high high temperature storage characteristics, and improved output characteristics, and thus, mobile phones and notebook computers requiring a fast charging speed. It can be useful in portable devices such as computers, digital cameras, camcorders, electric vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and mid- to large-sized energy storage systems. have.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

Example 1. Preparation of electrolyte

1.0M LiPF ₆ as a lithium salt, a mixed solvent in which ethylene carbonate (EC), ethylmethylcarbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 3:5:2 as an organic solvent, and as an electrolyte solution additive An electrolytic solution was prepared using 1% by weight of bis(phenylsulfonyl)methane based on the total weight of the electrolytic solution.

Examples 2 to 11. Preparation of electrolyte

An electrolyte solution was prepared in the same manner as in Example 1, except that the compound shown in Table 1 below was used as an electrolyte solution additive in the amount described with respect to the total weight of the electrolyte solution:

[Formula 1]

The electrolyte solution additive of Formula 1 Other additives X Y n content Kinds content Example 1 Phenyl group Phenyl group One 1% by weight - - Example 2 Phenyl group Phenyl group One 3% by weight - - Example 3 Phenyl group Phenyl group One 10% by weight - - Example 4 Ethyl group Ethyl group One 1% by weight - - Example 5 Cyclohexyl group Cyclohexyl group One 1% by weight - - Example 6 Benzyl group Benzyl group One 1% by weight - - Example 7 Thienyl Thienyl One 1% by weight - - Example 8 Benzimidazolyl Benzimidazolyl One 1% by weight - - Example 9 4-methylphenyl group 4-methylphenyl group One 1% by weight - - Example 10 4-trifluorophenyl group 4-trifluorophenyl group One 1% by weight - - Example 11 Phenyl group Phenyl group One 1% by weight SN 1% by weight

In the above table, SN means succinonitrile.

Comparative Example 1. Preparation of electrolyte

An electrolyte was prepared in the same manner as in Example 1, except that an electrolyte solution additive was not used.

Comparative Example 2. Preparation of electrolyte

An electrolyte was prepared in the same manner as in Example 1, except that 1% by weight of succinonitrile (SN) was used instead of bis(phenylsulfonyl)methane as an electrolyte solution additive.

Comparative Example 3. Preparation of electrolyte

An electrolyte was prepared in the same manner as in Example 1, except that 1% by weight of methylenebis (benzene sulfonate) was used instead of bis (phenylsulfonyl) methane as an electrolyte solution additive. I did.

Preparation Examples 1 to 11. Preparation of lithium secondary battery

A composition for forming a positive electrode active material layer comprising 85% by weight of lithium cobalt oxide (LiCoO ₂ ) as a positive electrode active material, 7.5% by weight of polyvinylidene fluoride as a binder, and 7.5% by weight of super-P carbon as a conductive material is an aluminum foil as a current collector It was coated on and dried to prepare a cathode. In addition, a composition for forming a negative electrode active material layer containing 88% by weight of artificial graphite as an anode active material, 4% by weight of Super-P carbon as a conductive material, and 8% by weight of polyvinylidene fluoride as a binder was coated on a copper foil as a current collector. Dry to prepare a negative electrode. After placing a separator on the positive electrode prepared above and placing a carbon negative electrode thereon, the electrolyte solutions prepared in Examples 1 to 11 were respectively injected, and vacuum-packed with an aluminum pouch to prepare a lithium secondary battery.

Test Example 1: Evaluation of battery characteristics

In order to evaluate the effect of improving the battery characteristics of the battery containing the electrolyte according to the present invention, the electrolyte of Example 1 was injected into a beaker cell, and the battery characteristics were evaluated using a linear sweep voltammetry (LSV) Evaluated. At this time, a platinum electrode was used as an electrode. The results are shown in FIG. 2.

As shown in FIG. 2, when the electric potential was changed from the initial electric potential of 3.0V to 7.0V, the current density remained almost constant up to the electric potential of 6.5V, and the current density increased rapidly from 6.5V.

Test Example 2: Evaluation of battery characteristics

With respect to the electrolyte prepared in Example 1, an electrode containing graphite and lithium metal was used as a negative electrode active material, respectively, and the redox behavior was observed and evaluated using cyclic voltammetry. The results are shown in FIG. 3.

As shown in FIG. 3, it was possible to know the decomposition potential of the electrolyte while changing the potential from the initial potential of 0V to 3.0V, and through this, it was determined whether or not a film was formed at the cathode.

Test Example 3: Evaluation of life characteristics

In order to evaluate the life characteristics of the lithium secondary battery containing the electrolyte according to the present invention due to charging and discharging, the electrolytes prepared in Examples 1 to 11 were respectively injected into Battronix ^® batteries (manufactured by Battronix), and then at 25°C. Charged at 4.35V (0.5C rate) under CC (constant current)/CV (constant vlotage) conditions, and after rest for 10 minutes, discharged to 3.0V under CC (0.5C rate) conditions. At this time, the normal capacity was 1000mAh. The charging and discharging were performed as 1 cycle and 100 cycles were repeated to measure the capacity and capacity retention rate according to charging and discharging. The results are shown in FIG. 4.

As a result of the experiment, the batteries including the electrolyte solutions of Examples 1 to 11 corresponding to the present invention exhibited excellent capacity retention due to the effect of forming a film on the positive electrode active material of the additive added in the electrolyte solution.

As described above, one embodiment of the present invention has been described, but those of ordinary skill in the relevant technical field add, change, delete or add components within the scope not departing from the spirit of the present invention described in the claims. Various modifications and changes can be made to the present invention by means of the like, and this will also be said to be included within the scope of the present invention.

1: lithium secondary battery
3: cathode 5: anode
7: separator 9: electrode assembly
10, 13 lead member 15 case

Claims (11)

An electrolyte solution containing the compound of Formula 1 as an electrolyte solution additive:
[Formula 1]

In Formula 1,
X and Y are each independently selected from the group consisting of a cyclohexyl group, a thienyl group, and a benzimidazolyl group, and n is an integer of 1 to 3. delete delete The method of claim 1,
An electrolyte solution containing 0.1 to 10% by weight of the compound of Formula 1 based on the total weight of the electrolyte. The method of claim 1,
The electrolyte solution further comprises an organic solvent and a lithium salt. The method of claim 5,
The electrolyte solution wherein the organic solvent is selected from the group consisting of an ester solvent, an ether solvent, a ketone solvent, an aromatic hydrocarbon solvent, an alkoxyalkane solvent, a carbonate solvent, and a mixture thereof. The method of claim 5,
The electrolyte solution wherein the organic solvent comprises an organic solvent having a high dielectric constant and an organic solvent having a low viscosity in a volume ratio of 2:8 to 8:2. The method of claim 7,
The high dielectric constant organic solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof,
The low-viscosity organic solvent is selected from the group consisting of ethylmethylcarbonate, dimethylcarbonate, diethylcarbonate, and mixtures thereof. The method of claim 5,
The organic solvent is one of ethylene carbonate and propylene carbonate; Ethyl methyl carbonate; And one of dimethyl carbonate and diethyl carbonate in a volume ratio of 5:1:1 to 2:5:3. The method of claim 5,
The lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , 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(C _a F _2a+1 SO ₂ )(C _b F _2b+1 SO ₂ ) (where a and b are natural numbers), LiCl, LiI, LiB(C ₂ O ₄ ) ₂ and mixtures thereof The electrolyte is selected from the group. A positive electrode including a positive electrode active material,
A negative electrode disposed opposite to the positive electrode and including a negative electrode active material, and
It includes an electrolyte solution interposed between the positive electrode and the negative electrode,
The electrolyte is a lithium secondary battery comprising the compound of Formula 1 as an electrolyte additive:
[Formula 1]

In Formula 1,
X and Y are each independently selected from the group consisting of a cyclohexyl group, a thienyl group, and a benzimidazolyl group, and n is an integer of 1 to 3.

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