KR20090093070A - Electrolyte comprising eutectic mixture and electrochemical device containing the same - Google Patents

Abstract

An electrolyte is provided to be usable as an electrolyte of an electrochemical device applying various negative electrode materials by comprising a eutectic mixture having high thermal and chemical stability and a lower value of electrochemical window. An electrolyte comprises a eutectic mixture. The eutectic mixture comprises (a) a fluorinated alkyl group-containing amide compound represented by chemical formula 1 or a fluorinated alkyl group-containing amide compound represented by chemical formula 2, and (b) ionizable lithium salts. The molar ratio of the fluorinated alkyl group-containing amide compound and lithium salts is 1 ~ 8 : 1.

Description

Electrolyte including an eutectic mixture and an electrochemical device having the same {ELECTROLYTE COMPRISING EUTECTIC MIXTURE AND ELECTROCHEMICAL DEVICE CONTAINING THE SAME}

The present invention relates to an electrolyte comprising an eutectic mixture and an electrochemical device having the same.

Electrochemical devices, such as lithium secondary batteries, electrolytic condensers, electric double layer capacitors, electrochromic display devices, and dye-sensitized solar cells, which are being researched for practical use in the future, are widely used in recent years. Various kinds of electrolytes are used in the back, and the importance thereof is increasing day by day.

Currently, the most widely used electrolytes include ionizable salts such as lithium salts such as ethylene carbonate, propylene carbonate, dimethoxy ethane, γ-butylo lactone (GBL), N, N It is a non-aqueous electrolyte solution dissolved in an organic solvent such as dimethyl formamide, tetrahydrofurane or acetonitrile.

By the way, the organic solvent used in such a non-aqueous electrolyte solution is not only easy to leak due to the low viscosity, but also highly volatile and may evaporate. It is also highly flammable. Accordingly, the electrochemical device having the same has problems in durability and stability.

In order to solve this problem, a method of using an imidazolium-based and ammonium-based ionic liquid as an electrolyte of a lithium secondary battery has been proposed. However, such an ionic liquid is reduced at a higher voltage than lithium ions at the negative electrode, or imidazolium and ammonium cations are inserted together at the negative electrode together with lithium ions, thereby degrading battery performance.

On the other hand, Korean Patent Registration Publication No. 10-751203, Korean Patent Publication No. 10-2007-85575 and the like have acetamide, urea, methylurea, caprolactam, valerictam, trifluoroacetamide, carbamate, formamide as electrolytes. And the like, and a eutectic mixture of an amide compound represented by a predetermined chemical formula and a lithium salt is disclosed. Since the eutectic mixture exhibits high thermal and chemical stability in addition to a relatively wide electrochemical window, problems such as evaporation and ignition of the electrolyte according to conventional organic solvents are solved.

Accordingly, the development of various eutectic mixtures useful as electrolytes has been accelerated, and in particular, the eutectic mixture electrolytes exhibiting a lower limit of the lower electrochemical window for application to electrochemical devices requiring various electrochemical properties. Need development

Accordingly, it is an object of the present invention to provide an electrolyte comprising a novel eutectic mixture exhibiting high thermal and chemical stability and an electrochemical device having the same.

In addition, another object of the present invention to provide an electrolyte and an electrochemical device comprising the eutectic mixture exhibiting a lower limit of the lower electrochemical window, in addition to the above object.

In order to achieve the above object, the electrolyte of the present invention is a eutectic mixture consisting of (a) a fluorinated alkyl group-containing amide compound represented by the following formula (1) or a fluorinated alkyl group-containing amide compound represented by the formula (2) and (b) an ionizable lithium salt (eutectic mixture).

In Chemical Formula 1,

R, R ₁ and R ₂ are each independently selected from hydrogen, halogen and alkyl group having 1 to 20 carbon atoms, alkylamine group, alkenyl group and aryl group, at least one of which is C _p F _q H A fluorinated alkyl group represented by _{2p + 2-q} , p is an integer from 1 to 8, q is an integer from 1 to 9,

X is any one selected from the group consisting of carbon, silicon, oxygen, nitrogen, phosphorus, sulfur and hydrogen, i) m is 0 if X is hydrogen, ii) m is 1 if X is oxygen or sulfur, i) M is 2 if X is nitrogen or phosphorus and i) m is 3 if X is carbon or silicon.

In Chemical Formula 2,

R and R ₁ are each independently selected from hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkylamine group, an alkenyl group, an aryl group and an allyl group, at least one of which is C _p F _q H _{2p +} As a fluorinated alkyl group represented by _2-q , p is an integer of 1-8, q is an integer of 1-9,

X is any one selected from the group consisting of carbon, silicon, oxygen, nitrogen, phosphorus and sulfur, i) m is 0 if X is oxygen or sulfur, ii) m is 1 if X is nitrogen or phosphorus, iii) M is 2 if X is carbon or silicon,

n is an integer from 1 to 10.

In the electrolyte of the present invention, the fluorinated alkyl group-containing amide compound is N-fluoroethyl methyl carbamate, N-fluoroethyl ethyl carbamate, N-fluoroethyl-N-methyl methyl carbamate, N-fluoroethyl-N-methyl Ethyl carbamate, N-trifluoroethyl methyl carbamate, N-trifluoroethyl ethyl carbamate, N-fluoromethyl caprolactam, N-fluoromethyl oxazolidinone, N-fluorohexyl oxazolidinone, N, N-dimethyl Fluoroethyl carbamate, N, N-dimethyl fluoromethyl carbamate, fluoromethyl carbamate and the like.

Further, in the electrolyte of the present invention, as the lithium salt, the anion is ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, ^{_{(CF 3) 2 PF 4 -}} , (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF ^{_{3 CF 2 SO 3 -, (}} CF 3 SO 2) 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5 _{^{) 3 C -, (CF 3}} SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and the like can be given ^{_{-, (CF 3 CF 2 SO}} 2) 2 N.

In the electrolyte of the present invention, the molar ratio of the fluorinated alkyl group-containing amide compound and the lithium salt of the eutectic mixture is preferably 1 to 8: 1.

In addition, the electrolyte of the present invention may be a polymer electrolyte such as a solid phase or a gel phase of the polymer itself, and the polymer electrolyte may polymerize a precursor solution containing a monomer capable of forming a polymer by the eutectic mixture and a polymerization reaction. It may be a gel polymer electrolyte formed by, or a polymer electrolyte in a form in which the eutectic mixture is impregnated into a polymer.

The electrolyte of the present invention described above may be usefully applied to an electrochemical device such as a lithium secondary battery.

The electrolyte according to the present invention has the following effects.

First, since the novel eutectic mixture contained in the electrolyte of the present invention exhibits inherent characteristics of the eutectic mixture such as excellent thermal stability and chemical stability, problems such as evaporation, ignition and side reaction of the electrolyte according to the conventional organic solvent are greatly improved. do.

Second, since the eutectic mixture contained in the electrolyte of the present invention exhibits a lower limit of the lower electrochemical window, it can be usefully applied as an electrolyte of an electrochemical device requiring various electrochemical properties.

1 is a graph measuring reduction potentials of eutectic mixtures according to Examples 1 and 2 and Comparative Examples 1 and 2,

2 is a schematic cross-sectional view of a coin-type secondary battery,

Figure 3 is a graph measuring the charge and discharge efficiency of the secondary battery according to the preparation example and the control.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

The electrolyte of the present invention comprises a eutectic mixture composed of (a) a fluorinated alkyl group-containing amide compound represented by the following formula (1) or a fluorinated alkyl group-containing amide compound represented by the following formula (2) and (b) an ionizable lithium salt. .

<Formula 1>

In Chemical Formula 1,

R, R ₁ and R ₂ are each independently selected from hydrogen, halogen and alkyl group having 1 to 20 carbon atoms, alkylamine group, alkenyl group and aryl group, at least one of which is C _p F _q H A fluorinated alkyl group represented by _{2p + 2-q} , p is an integer of 1 to 8, q is an integer of 1 to 9,

X is any one selected from the group consisting of carbon, silicon, oxygen, nitrogen, phosphorus, sulfur and hydrogen, i) m is 0 if X is hydrogen, ii) m is 1 if X is oxygen or sulfur, i) M is 2 if X is nitrogen or phosphorus and i) m is 3 if X is carbon or silicon.

<Formula 2>

In Chemical Formula 2,

R and R ₁ are each independently selected from hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkylamine group, an alkenyl group, an aryl group and an allyl group, at least one of which is C _p F _q H _{2p +} As a fluorinated alkyl group represented by _2-q , p is an integer of 1-8, q is an integer of 1-9,

X is any one selected from the group consisting of carbon, silicon, oxygen, nitrogen, phosphorus and sulfur, i) m is 0 if X is oxygen or sulfur, ii) m is 1 if X is nitrogen or phosphorus, iii) M is 2 if X is carbon or silicon,

n is an integer from 1 to 10.

An electrochemical window is one of the indicators of electrochemical stability. In general, an electrochemical window region, referred to as a cell, is an oxidation measured in a half-cell using a reference electrode as lithium metal. It is the value which makes a reduction voltage into an upper limit and a lower limit. That is, in the electrochemical window region, the target material is electrochemically stable and difficult to be oxidized and reduced, whereas it can be easily oxidized and reduced outside the electrochemical window region. Therefore, in order to secure the reduction stability of the electrolyte itself, it is necessary to prevent the reduction decomposition reaction of the electrolyte due to the wide area of the electrochemical window. In particular, in order to use a negative electrode material having various potentials, it is necessary to develop a eutectic mixture having a low lower limit of an electrochemical window.

The present inventors have formed an eutectic mixture with a lithium salt using a fluorinated alkyl group-containing amide compound having the above-described structure, which is an amide compound such as acetamide, methyl carbamate, The lower limit of the electrochemical window is shown than the eutectic mixture of lithium salts. In addition, such eutectic mixtures exhibit high thermal and chemical stability unique to eutectic mixtures, unlike conventional nonaqueous electrolyte organic solvents.

In the electrolyte of the present invention, the fluorinated alkyl group-containing amide compound constituting the eutectic mixture includes N-fluoroethyl methyl carbamate, N-fluoroethyl ethyl carbamate, N-fluoroethyl-N-methyl methyl carbamate, and N-fluoro Ethyl-N-methyl ethyl carbamate, N-trifluoroethyl methyl carbamate, N-trifluoroethyl ethyl carbamate, N-fluoromethyl caprolactam, N-fluoromethyl oxazolidinone, N-fluorohexyl oxazolidinone, N, N-dimethyl fluoroethyl carbamate, N, N-dimethyl fluoromethyl carbamate, fluoromethyl carbamate, etc. are mentioned.

In the electrolyte of the present invention, the lithium salt constituting the eutectic mixture together with the aforementioned fluorinated alkyl group-containing amide compound can be represented by Li ⁺ X ^- as an ionizable lithium salt. In this lithium salt anion is not particularly ^{limited, F -, Cl -, Br} -, I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) _{^{2 PF 4 -, (CF 3}} ) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO _{^{3 -, (CF 3 SO 2}} ) 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C - _{, (CF 3 SO 2) 3} C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and the like can be given ^{_{-, (CF 3 CF 2 SO}} 2) 2 N.

The melting temperature of the eutectic mixture of the electrolyte according to the present invention may vary depending on R, R ₁ , X, and the like of Chemical Formula 1, but is preferably present in a liquid state at room temperature (25 ° C).

The eutectic mixture of the electrolyte according to the present invention may be prepared according to a conventional method known in the art, for example, the above-described fluorinated alkyl group-containing amide compound and lithium salt are mixed at room temperature, and then suitable temperature of 70 ° C. or lower. After the reaction in the purification can be prepared. At this time, the molar ratio of the fluorinated alkyl group-containing amide compound and the lithium salt of the prepared eutectic mixture is preferably 1 to 8: 1, more preferably 2 to 6: 1.

Since the electrolyte of the present invention includes a eutectic mixture containing lithium ions in itself, even when applied to a lithium secondary battery, a lithium salt may not be added separately, but a salt such as lithium salt may be, for example, 0 to 1 M / L. Of course, the concentration may further include. When further adding a lithium salt to the electrolyte, in order to improve solubility in the electrolyte, it is preferable to use a lithium salt having the same anion as that of the lithium salt constituting the eutectic mixture.

In addition, it will be apparent to those skilled in the art that the electrolyte of the present invention may further include various kinds of additives or organic solvents without departing from the object of the present invention.

Regardless of the type of electrolyte, all of the electrolytes of the present invention may be applied. For example, the electrolyte may be used as a liquid electrolyte or a polymer electrolyte such as a solid or gel phase of the polymer itself. When the electrolyte of the present invention is used as a liquid electrolyte, the above eutectic mixtures may be used alone, or may be used by further adding salts, organic solvents, additives and the like.

On the other hand, when the electrolyte of the present invention is a polymer electrolyte, the polymer electrolyte is a gel-like polymer by polymerization of a precursor solution containing a eutectic mixture and a monomer capable of forming a polymer by a polymerization reaction, or the eutectic mixture is a solid phase or It may be made of a polymer electrolyte in a form impregnated with a polymer such as gel.

(1) First, the gel polymer electrolyte produced by the polymerization reaction of the precursor solution will be described.

The gel polymer electrolyte according to one aspect of the present invention is formed by polymerizing a precursor solution containing (i) a eutectic mixture of Formula 1 and (ii) a monomer capable of forming a polymer by a polymerization reaction. Can be.

As the monomer (monomer) as the polymerization proceeds, all kinds of monomers capable of forming a gel polymer with the eutectic mixture is applicable, non-limiting examples thereof include vinyl monomers. Vinyl monomers have the advantage of very simple polymerization when mixed with eutectic mixtures to form gel polymers.

Non-limiting examples of vinyl monomers that can be used include acrylonitrile, methyl methacrylate, methyl acrylate, methacrylonitrile, methyl styrene, vinyl esters, vinyl chloride, vinylidene chloride, acrylamide, tetrafluoroethylene , Vinyl acetate, vinyl chloride, methyl vinyl ketone, ethylene, styrene, paramethoxy styrene, paracyano styrene, and the like, each of which may be used alone or in combination of two or more thereof.

The precursor solution may additionally include conventional polymerization initiators or photoinitiators, initiators are decomposed by heat or ultraviolet light to form radicals and react with monomers by free radical polymerization to form gel polymer electrolytes. do. Moreover, superposition | polymerization of a monomer can also be advanced, without using an initiator. In general, free radical polymerization is a reaction of initiation where active molecules or active points are formed, a growth reaction in which monomers are added at the end of an active chain to form an active point at the end of a chain, and a chain transfer reaction that moves an active point to other molecules. In addition, the reaction chain undergoes a stop reaction in which the active chain center is destroyed.

Non-limiting examples of thermal initiators that can be used include organic peroxides such as benzoyl peroxide, Acetyl peroxide, Dilauryl peroxide, Di-tert-butyl peroxide, Cumyl hydroperoxide, Hydrogen peroxide, and hydroperoxides, 2,2-Azobis (2). azo compounds such as -cyanobutane), 2,2-Azobis (Methylbutyronitrile), AIBN (Azobis (iso-butyronitrile), AMVN (Azobisdimethyl-Valeronitrile), and organic metals such as silver alkylated compounds. Non-limiting examples of photoinitiators formed by radicals include Chloroacetophenone, Diethoxy Acetophenone (DEAP), 1-phenyl-2-hydroxy-2-methyl propaneone (HMPP), 1-Hydroxy cyclrohexyl phenyl ketone, α-Amino Acetophenone, Benzoin Ether, Benzyl Dimethyl ketal, Benzophenone, Thioxanthone and 2-ethylAnthraquinone (2-ETAQ).

In addition to the components described above, the precursor solution of the gel polymer electrolyte according to the present invention may optionally contain other additives and the like known in the art.

Using the precursor solution described above to form a gel polymer electrolyte according to a conventional method known in the art, it is preferable to prepare a gel polymer electrolyte by the In - Situ polymerization reaction in the electrochemical device. In - Situ polymerization reaction is possible by heat or ultraviolet irradiation. The content ratio of the eutectic mixture and the monomer in the precursor solution is preferably adjusted to 0.5-0.95: 0.05-0.5. Since the degree of polymerization of the gel polymer can be controlled according to the polymerization time, polymerization temperature or light irradiation degree, which are reaction factors, The polymer is superpolymerized without leaking the electrolyte so that the volume does not shrink.

(2) As another method for producing a polymer electrolyte containing a eutectic mixture according to the present invention, the eutectic mixture may be injected into a solid polymer or a gel polymer already formed, so that the eutectic mixture is impregnated in the polymer.

Non-limiting examples of the polymers that can be used include polymethyl methacrylate, polyvinylidene difluoride, polyvinyl chloride, polyethylene oxide, polyhydroxyethyl methacrylate, etc., alone or in combination of two or more thereof. have. This method can simplify the manufacturing process compared to the In - Situ method described above.

(3) According to the present invention, as another method for preparing a polymer electrolyte containing a eutectic mixture, a method of forming a polymer electrolyte by dissolving the polymer and the eutectic mixture in a solvent and then removing the solvent may be used. At this time, the eutectic mixture is in the form contained in the polymer matrix.

The solvent that can be used is not particularly limited, and non-limiting examples thereof include toluene, acetone, acetonitrile, THF, and the like. In addition, the solvent removal method is not particularly limited, and conventional methods such as applying heat may be used.

The electrolyte comprising the eutectic mixture according to the present invention is applicable to conventional electrochemical devices known in the art, where various electrochemical properties are required depending on the purpose of use.

Non-limiting examples of the electrochemical device include all kinds of primary, secondary, fuel cells, solar cells, electrochromic devices, electrolytic capacitors (capacitors) or the like, specific examples thereof are lithium Secondary batteries, electric double layer capacitors, dye-sensitized solar cells, electrochromic devices and the like.

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

Example 1

6.4 g of N-fluoroethyl methyl carbamate and 2 g of LiPF _{6 were} placed in a round bottom flask, and stirred slowly for 2 hours under a nitrogen atmosphere to obtain 8.4 g of a eutectic mixture.

Example 2

7.1 g of N-fluoroethyl ethyl carbamate and 2 g of LiPF _{6 were} placed in a round bottom flask, and stirred slowly for 2 hours under a nitrogen atmosphere to obtain 9.1 g of a eutectic mixture.

Example 3

8.3 g of N-trifluoroethyl methylcarbamate and 2 g of LiPF _{6 were} placed in a round bottom flask, and stirred slowly for 2 hours under a nitrogen atmosphere to obtain 10.3 g of a eutectic mixture.

Comparative Example 1

2.1 g of methyl carbamate and 2 g of LiTFSI were placed in a round bottom flask, and stirred slowly for 2 hours under a nitrogen atmosphere to obtain 4.1 g of a eutectic mixture.

Comparative Example 2

1.6 g of acetamide and 2 g of LiTFSI were placed in a round bottom flask, and stirred slowly for 2 hours under a nitrogen atmosphere to obtain 3.6 g of a eutectic mixture.

In order to evaluate the electrochemical window of the eutectic mixture prepared according to the above-described examples and comparative examples, it was carried out as follows.

As the sample, the eutectic mixtures prepared in Examples 1 and 2 and the eutectic mixtures of Comparative Examples 1 and 2 were used, and the ratios of the eutectic mixtures used were all 4: 1 in amide compound and salt ratio. The reduction potential of the eutectic mixture was measured using cyclic voltammetry, wherein the working electrode was made of glassy carbon, the reference electrode was lithium metal, the counter electrode was lithium metal, and the scanning speed was 50 mV / s. The results are shown in Table 1 and FIG. 1. The reduction potentials of the eutectic mixtures in which the fluorinated alkyl groups of Examples 1 and 2 were substituted were 0.45 V, respectively, which showed a lower reduction potential than that of the eutectic mixtures of Comparative Examples 1 and 2.

Potential window (V vs. Li / Li ⁺ ) Example 1 0.45-4.6 Example 2 0.45-4.6 Comparative Example 1 0.6 to 4.4 Comparative Example 2 0.7 to 4.4

Production Example

(Anode manufacturing)

LiCoO ₂ as a positive electrode active material, artificial graphite as a conductive material, polyvinylidene fluoride as a binder was mixed in a weight ratio of 94: 3: 3, and N-methylpyrrolidone was added to the resulting mixture to prepare a slurry. The prepared slurry was applied to aluminum foil, and dried at 130 ° C. for 2 hours to prepare a positive electrode.

(Cathode production)

Negative electrode active material _{Li 4/3 Ti 5/3} O 4, an artificial graphite and a binder 94: 3 mixed in a weight ratio of 3, and N- methylpyrrolidone was added to prepare a slurry. The prepared slurry was applied to a copper foil and dried at 130 ° C. for 2 hours to prepare a negative electrode.

(Secondary Battery Assembly)

A positive electrode and a negative electrode prepared as described above were prepared in 1 cm ² , and a separator was interposed therebetween. Injecting the eutectic mixture prepared in Example 1 here to complete the secondary battery as shown in FIG. In Fig. 2, reference numeral 1 denotes an anode, 2 a cathode, 3 a separator and an electrolyte, 4 a spacer, 5 a coin can container, 6 a coin can lid, and 7 a seal rubber.

Control

A secondary battery was manufactured in the same manner as in Preparation Example, except that a 1M LiPF ₆ solution having a volume ratio of ethylene carbonate: ethyl methyl carbonate 1: 2 was used instead of the eutectic mixture of Example 1.

Evaluation of Room Temperature Performance of Secondary Battery

The secondary battery of the above-mentioned Production Examples and control 0.5mAcm ^- respectively charged and discharged at a ² to measure the discharge capacity and charge-discharge efficiency of the cycle.

As a result, the battery of the control group using the electrolyte containing the conventional carbonate solvent and the battery of the preparation example using the eutectic mixture of the present invention as the electrolyte, the discharge capacity of more than 90% after the thirtieth cycle as shown in FIG. And a charge-discharge efficiency of 99%. In FIG. 3, the solid line represents a preparation example, and the dotted line represents a control group. From this, it was found that the eutectic mixture electrolyte of the present invention can exhibit a performance comparable to that of a conventionally commercialized liquid electrolyte at room temperature.

Electrolyte SET  Experiment

The self-extinguishing time (SET) of the eutectic mixtures prepared in Examples 1 to 3 was measured. This experiment was conducted by soaking 125 mg of eutectic mixture electrolyte in a 0.5 cm bundle of glass wool, heating it for 5 seconds with a gas lighter fire, and then measuring the time for the fire to be extinguished.

As a control, ethylene carbonate (EC), which is a battery electrolyte solvent, was found to be on fire for approximately 55 seconds (SET ₀ = 55 seconds). = 0 second), and its relative comparison value (1-SET / SET ₀ ) was 1.0. Thus, the eutectic mixture of the present invention was very excellent in flame retardancy. For reference, according to the relative comparison value (1-SET / SET ₀ ), it is classified into flammability, combustion delay, and flame retardancy, and the criterion is 0 <flammability <0.67 <combustion delay <0.9 <flame retardancy <1 ( J. Power Sources , 135 (2004), 291).

Therefore, it was found that when the eutectic mixture according to the present invention is used as an electrolyte, it has better flame retardancy than when using a conventional electrolyte and further improves the safety of the battery.

Claims (17)

(a) a fluorinated alkyl group-containing amide compound represented by formula (1) or a fluorinated alkyl group-containing amide compound represented by formula (2), and (b) ionizable lithium salts An electrolyte comprising an eutectic mixture consisting of. <Formula 1> In Chemical Formula 1, R, R ₁ and R ₂ are each independently selected from hydrogen, halogen and alkyl group having 1 to 20 carbon atoms, alkylamine group, alkenyl group and aryl group, at least one of which is C _p F _q H A fluorinated alkyl group represented by _{2p + 2-q} , p is an integer of 1 to 8, q is an integer of 1 to 9, X is any one selected from the group consisting of carbon, silicon, oxygen, nitrogen, phosphorus, sulfur and hydrogen, i) m is 0 if X is hydrogen, ii) m is 1 if X is oxygen or sulfur, i) M is 2 if X is nitrogen or phosphorus and i) m is 3 if X is carbon or silicon. <Formula 2> In Chemical Formula 2, R and R ₁ are each independently selected from hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkylamine group, an alkenyl group, an aryl group and an allyl group, at least one of which is C _p F _q H _{2p +} As a fluorinated alkyl group represented by _2-q , p is an integer of 1-8, q is 1-9 recognized water, X is any one selected from the group consisting of carbon, silicon, oxygen, nitrogen, phosphorus and sulfur, i) m is 0 if X is oxygen or sulfur, ii) m is 1 if X is nitrogen or phosphorus, iii) M is 2 if X is carbon or silicon, n is an integer from 1 to 10. The fluorinated alkyl group-containing amide compound according to claim 1, wherein the fluorinated alkyl group-containing amide compound is N-fluoroethyl methyl carbamate, N-fluoroethyl ethyl carbamate, N-fluoroethyl-N-methyl methyl carbamate, N-fluoroethyl-N-methyl ethyl Carbamate, N-trifluoroethyl methyl carbamate, N-trifluoroethyl ethyl carbamate, N-fluoromethyl caprolactam, N-fluoromethyl oxazolidinone, N-fluorohexyl oxazolidinone, N, N-dimethyl fluoro Electrolyte, characterized in that any one selected from the group consisting of ethyl carbamate, N, N-dimethyl fluoromethyl carbamate and fluoromethyl carbamate. The method of claim 1, wherein the lithium salt anion is ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) ^{_{2 PF 4 -, (CF 3}} ) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO ^{_{3 -, (CF 3 SO 2}} ) 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C - _{, (CF 3 SO 2) 3} C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and _{(CF 3 CF 2 SO 2)} 2 N - electrolyte, characterized in that at least one selected from the group consisting of. The electrolyte according to claim 1, wherein the eutectic mixture has a molar ratio of the fluorinated alkyl group-containing amide compound and a lithium salt of 1 to 8: 1. The electrolyte of claim 1, wherein the electrolyte further comprises a lithium salt. The electrolyte of claim 5, wherein the anion of the lithium salt is the same as the anion of the lithium salt constituting the eutectic mixture. The electrolyte of claim 5, wherein the lithium salt has a concentration of 0 to 1 M / L. The electrolyte of claim 1, wherein the electrolyte is a polymer electrolyte. 9. The polymer electrolyte according to claim 8, wherein the polymer electrolyte is a gel polymer electrolyte formed by polymerization of a precursor solution containing (i) the eutectic mixture and (ii) a monomer capable of forming a polymer by a polymerization reaction. Characterized by an electrolyte. 10. The electrolyte of claim 9, wherein said monomer is a vinyl monomer. The method of claim 10, wherein the vinyl monomer is acrylonitrile, methyl methacrylate, methyl acrylate, methacrylonitrile, methyl styrene, vinyl esters, vinyl chloride, vinylidene chloride, acrylamide, tetrafluoroethylene And vinyl acetate, vinyl chromide, methyl vinyl ketone, ethylene, styrene, paramethoxy styrene, and paracyano styrene. Any one or a mixture of two or more thereof. The electrolyte of claim 9, wherein the content ratio of the eutectic mixture and the monomer in the precursor solution is 0.5 to 0.95: 0.05 to 0.5. 10. The electrolyte of claim 9, wherein the gel polymer electrolyte is prepared by in-situ polymerization in an electrochemical device. 9. The electrolyte of claim 8 wherein the polymer electrolyte is impregnated with the eutectic mixture in a polymer. The method of claim 14, wherein the polymer is any one selected from the group consisting of polymethyl methacrylate, polyvinylidene difluoride, polyvinyl chloride, polyethylene oxide and polyhydroxyethyl methacrylate or a mixture of two or more thereof. It is an electrolyte characterized by the above-mentioned. In the electrochemical device comprising a positive electrode, a negative electrode and an electrolyte, The electrolyte is an electrochemical device, characterized in that the electrolyte of any one of claims 1 to 15. The electrochemical device of claim 16, wherein the electrochemical device is a lithium secondary battery.