KR20120007283A - Electrolyte comprising amide compound and electrochemical device containing the same - Google Patents

Abstract

PURPOSE: An amide compound-containing electrolyte is provided to have excellent thermal and chemical stability, and excellent room temperature and low temperature performance, to reduce the surface resistance of a cell, and to improve charging/discharging performance. CONSTITUTION: An electrolyte comprises: an ionizable lithium salt, an amide compound in the chemical formula 1, non-halogenated carbonate, and halogenated cyclic carbonate. In the chemical formula 1 R1, R2, R3, R4, and R5 is independently selected from hydrogen, halogen, C1-20 alkyl group, alkoxy group, alkoxyalkyl group, alkenyl group, and aryl group, and X is selected from oxygen, sulfur, nitrogen, phosphorus, carbon, and silicon.

Description

Electrolyte including an amide compound, and an electrochemical device having the same TECHNICAL FIELD

The present invention relates to an electrolyte comprising an amide compound and a halogenated cyclic carbonate compound, 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.

In particular, lithium secondary batteries have received the most attention as batteries having high energy density and long lifespan. Typically, a lithium secondary battery includes an anode made of a carbon material or a lithium metal alloy, a cathode made of a lithium metal oxide, and an electrolyte in which lithium salt is dissolved in an organic solvent.

The electrolyte is a medium for transferring ions between electrodes, must have sufficient ionic conductivity and low viscosity, and be a material that is electrochemically stable over the operating temperature and pressure range of the cell. Organic solvents widely used in electrolytes of lithium secondary batteries are ethylene carbonate, propylene carbonate, dimethoxy ethane, g-butyrolactone (GBL), and N, N-dimethyl. Dimethyl formamide, tetrahydrofurane or acetonitrile. However, since the organic solvents generally have high volatility and flammability, lithium secondary batteries employing the organic solvents have problems with overcharge, overdischarge, short circuit, and high temperature safety.

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.

Japanese Patent Laid-Open Publication No. 1997-259925 discloses a method of adding a non-combustible gas having a boiling point of 25 ° C. or lower when assembling an electrolyte. In Japanese Patent Laid-Open Publication No. 2006-179458 and Japanese Patent Laid-Open Publication No. 2005-190873, the addition of a phosphate ester to a carbonate electrolyte ensures nonflammability of the electrolyte, or US Patent Publication No. 6797437, a nonflammable solvent of perfluoroalkyl or perfluoroester. A method of adding at least 30% is illustrated.

However, the injection of non-combustible gases involves cell volume expansion and complex cell assembly processes, and phosphate ester additives cause cell performance degradation problems due to high reduction potentials. Furthermore, the exemplified addition of perfluoroalkyl phase separates upon mixing with the organic solvent electrolyte to precipitate lithium salts.

On the other hand, Korean Patent Registration Publication No. 10-751203, Korean Patent Publication No. 10-2007-85575, and the like, include acetamide, urea, methylurea, caprolactam, valerictam, trifluoroacetamide, carbamate, and form. A eutectic mixture of an amide compound represented by a predetermined formula such as an amide 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, research on electrolytes containing various amide compounds useful as electrolytes has been conducted in various aspects.

Accordingly, an object of the present invention is to provide an electrolyte and an electrochemical device having the same showing high thermal and chemical stability.

In addition, another object of the present invention is to provide an electrolyte and an electrochemical device having the same having excellent charge and discharge performance, in addition to the above object.

In order to achieve the above object, the electrolyte of the present invention comprises an ionizable lithium salt, an amide compound represented by the following formula (1), and (a) a non-halogenated carbonate and (b) a halogenated cyclic carbonate:

In Formula 1,

R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently substituted or unsubstituted with hydrogen, halogen, halogen, alkyl group having 1 to 20 carbon atoms, alkylamine group, alkoxy group, alkoxyalkyl group, alkenyl group and Any one selected from the group consisting of aryl groups,

X is any one selected from the group consisting of hydrogen, oxygen, sulfur, nitrogen, phosphorus, carbon and silicon, i) if X is hydrogen, R ₃ , R ₄ and R ₅ are absent, and ii) X is oxygen or sulfur Then R ₄ and R ₅ are absent and iii) R ₅ is absent when X is nitrogen or phosphorus.

In the electrolyte of the present invention, the amide compound is N-methoxy methyl carbamate, N-methoxy ethyl carbamate, N-methoxy-N-methyl methyl carbamate, N-methoxy-N-methyl ethyl carba Mate, N-methoxy-N-methyl propylcarbamate, N-methoxy-N-methyl butylcarbamate, N-methoxy N-methyl trifluoroethyl carbamate, N-methoxy N-methyl 2-fluoro Roethyl carbamate, N-methoxy N-methyl pentafluoropropyl carbamate, N-methoxy-N-methyl 2- (perfluorohexyl) ethyl carbamate, N-methoxy-N-methyl 6- ( Perfluorobutyl) hexyl carbamate, N-methoxyethyl methyl carbamate, N-methoxyethyl-N-methyl methyl carbamate, N-methoxymethyl-N-methyl methyl carbamate, N-methyl-N- Methoxyethyl methoxyethyl carbamate, N-methyl-N-methoxyethyl methoxymethyl carbamate, N-methoxyethyl trifluoroethyl carbamate, N-methoxyethyl-N-methyl Refluoroethyl carbamate, N-methoxymethyl-N-methyl trifluoroethyl carbamate, N-methoxymethyl trifluoroethyl carbamate, N-methoxymethyl-N-ethyl trifluoroethyl carbamate , N-methoxyethyl-N-ethyl trifluoroethyl carbamate, N-methoxyethyl fluoroethyl carbamate, N-methoxyethyl-N-methyl fluoroethyl carbamate, N-methoxymethyl-N -Methyl fluoroethyl carbamate, N-methoxymethyl fluoroethyl carbamate, N-methoxymethyl-N-ethyl fluoroethyl carbamate, N-methoxyethyl-N-ethyl fluoroethyl carbamate, N -Methoxyethyl pentafluoropropyl carbamate, N-methoxyethyl-N-methyl pentafluoropropyl carbamate, N-methoxymethyl-N-methyl pentafluoropropyl carbamate, N-methoxymethyl pentafluoro Ropropyl carbamate, N-methoxymethyl-N-ethyl pentafluoropropyl carbame , N-methoxyethyl-N-ethyl pentafluoropropyl carbamate, N-methoxyethyl hexafluoro-2-propyl carbamate, N-methoxyethyl-N-methyl hexafluoro-2-propyl carbamate Mate, N-methoxymethyl-N-methyl hexafluoro-2-propyl carbamate, N-methoxymethyl hexafluoro-2-propyl carbamate, N-methoxymethyl-N-ethyl hexafluoro-2 -Propyl carbamate, N-methoxyethyl-N-ethyl hexafluoro-2-propyl carbamate, etc. can be used individually or in mixture of 2 or more types, respectively.

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 halogenated cyclic carbonate is preferably reduced at a higher potential (Li / Li +) than the amide compound to form an SEI film. Such halogenated cyclic carbonate may be, for example, a halogenated cyclic carbonate. Ethylene carbonate can be used.

In Chemical Formula 2,

X and Y are each independently hydrogen, chlorine, or fluorine, and X and Y are not simultaneously hydrogen.

In the electrolyte of the present invention, the non-halogenated carbonate can be used without limitation as long as it is a non-halogenated carbonate used as an organic solvent of the electrolyte. For example, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC) , Dimethyl carbonate (DMC), dipropyl carbonate (DPC), butylene carbonate, methyl propyl carbonate, ethyl propyl carbonate and ethyl methyl carbonate (EMC) and the like can be used, but is not limited thereto.

Optionally, the electrolyte of the present invention may further comprise vinylene carbonate as an additive.

In addition, the electrolyte of the present invention may be a liquid electrolyte, may be a polymer electrolyte such as a solid phase or a gel phase of the polymer itself, and the polymer electrolyte contains a monomer capable of forming a polymer by the electrolyte and a polymerization reaction. The polymer electrolyte may be a gel-like polymer electrolyte formed by polymerization of a precursor solution, or the electrolyte may be a polymer electrolyte in a form impregnated with 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 electrolyte of the present invention exhibits excellent thermal stability and chemical stability, problems such as evaporation, ignition, side reaction of the electrolyte according to the conventional organic solvents are greatly improved, and have excellent room temperature performance and low temperature performance. .

Second, the electrolyte of the present invention can reduce the interface resistance of the battery by including a halogenated cyclic carbonate, it is possible to improve the charge and discharge performance.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
1 is a graph measuring the impedance of a secondary battery manufactured according to Example 1, Example 2 and Comparative Example 1.
Figure 2 is a graph measuring the discharge capacity of the cycle of the battery prepared according to Example 1 and Comparative Example 1.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, 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 an ionizable lithium salt, an amide compound represented by the following formula (1), and (a) a non-halogenated carbonate and (b) a halogenated cyclic carbonate:

[Formula 1]

In Formula 1,

R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently substituted or unsubstituted with hydrogen, halogen, halogen, alkyl group having 1 to 20 carbon atoms, alkylamine group, alkoxy group, alkoxyalkyl group, alkenyl group and Any one selected from the group consisting of aryl groups,

X is any one selected from the group consisting of hydrogen, oxygen, sulfur, nitrogen, phosphorus, carbon and silicon, i) if X is hydrogen, R ₃ , R ₄ and R ₅ are absent, and ii) X is oxygen or sulfur Then R ₄ and R ₅ are absent and iii) R ₅ is absent when X is nitrogen or phosphorus.

The electrolyte of the present invention may include a amide compound represented by Formula 1, and may exhibit high thermal and chemical stability. Specifically, since the vapor pressure is higher than that of the conventional organic solvent, problems such as evaporation and ignition of the electrolyte according to use can be solved, thereby improving charge / discharge performance of the battery. In addition, the electrolyte of the present invention has characteristics such as a wide electrochemical window, a wide temperature range liquid phase, a high solvation ability, a non-coordinated binding property, etc., and thus exhibits performance and safety of the cell, particularly good high temperature stability. In particular, when the amide compound and the lithium salt form a eutectic mixture, these properties may be further improved.

Moreover, the carbonyl group (C = O) and amine group (-NR ₂ ) in the amide compound according to the present invention can weaken the bond between the cation and anion of the ionizable lithium salt, or weaken the bond in another amide compound. . Therefore, the electrolyte of the present invention can maintain high ionic conductivity even at room temperature, preferably -20 ° C or lower, more preferably -40 ° C or lower, thereby improving the room temperature performance and the low temperature performance of the battery.

In the electrolyte of the present invention, specific examples of the aforementioned amide compound include N-methoxy methyl carbamate, N-methoxy ethyl carbamate, N-methoxy-N-methyl methyl carbamate, and N-methoxy-N -Methyl ethyl carbamate, N-methoxy-N-methyl propyl carbamate, N-methoxy-N-methyl butyl carbamate, N-methoxy N-methyl trifluoroethyl carbamate, N-methoxy N- Methyl 2-fluoroethyl carbamate, N-methoxy N-methyl pentafluoropropyl carbamate, N-methoxy-N-methyl 2- (perfluorohexyl) ethyl carbamate, N-methoxy-N- Methyl 6- (perfluorobutyl) hexyl carbamate, N-methoxyethyl methyl carbamate, N-methoxyethyl-N-methyl methyl carbamate, N-methoxymethyl-N-methyl methyl carbamate, N- Methyl-N-methoxyethyl methoxyethyl carbamate, N-methyl-N-methoxyethyl methoxymethyl carbamate, N-methoxyethyl trifluoroethyl carbamate, N- Methoxyethyl-N-methyl trifluoroethyl carbamate, N-methoxymethyl-N-methyl trifluoroethyl carbamate, N-methoxymethyl trifluoroethyl carbamate, N-methoxymethyl-N-ethyl Trifluoroethyl carbamate, N-methoxyethyl-N-ethyl trifluoroethyl carbamate, N-methoxyethyl fluoroethyl carbamate, N-methoxyethyl-N-methyl fluoroethyl carbamate, N -Methoxymethyl-N-methyl fluoroethyl carbamate, N-methoxymethyl fluoroethyl carbamate, N-methoxymethyl-N-ethyl fluoroethyl carbamate, N-methoxyethyl-N-ethyl fluoro Roethyl carbamate, N-methoxyethyl pentafluoropropyl carbamate, N-methoxyethyl-N-methyl pentafluoropropyl carbamate, N-methoxymethyl-N-methyl pentafluoropropyl carbamate, N -Methoxymethyl pentafluoropropyl carbamate, N-methoxymethyl-N-ethyl pentaple Oropropyl carbamate, N-methoxyethyl-N-ethyl pentafluoropropyl carbamate, N-methoxyethyl hexafluoro-2-propyl carbamate, N-methoxyethyl-N-methyl hexafluoro-2 -Propyl carbamate, N-methoxymethyl-N-methyl hexafluoro-2-propyl carbamate, N-methoxymethyl hexafluoro-2-propyl carbamate, N-methoxymethyl-N-ethyl hexafluoro Ro-2-propyl carbamate, N-methoxyethyl-N-ethyl hexafluoro-2-propyl carbamate, and mixtures of two or more thereof, and the like.

In the electrolyte of the present invention, the lithium salt described above 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 (CF ₃ CF ₂ SO ₂ ) ₂ N ^- and the like can be exemplified.

On the other hand, the electrolyte of the present invention contains a non-halogenated carbonate.

Specifically, since the ionic conductivity is generally determined by the mobility of ions moving in the electrolyte solution, the factors affecting the ionic conductivity are the viscosity of the electrolyte solution and the ion concentration in the solution. The lower the viscosity of the solution, the more free movement of ions in the solution and the higher the ionic conductivity. The higher the concentration of ions in the solution, the higher the amount of ions, the charge transporter, and the higher the ionic conductivity. The amide compound has a relatively high viscosity, but the electrolyte of the present invention uses a non-halogenated carbonate in combination to lower the viscosity and increase the ion conductivity to improve charge and discharge performance.

The non-halogenated carbonate included in the electrolyte of the present invention may be used as long as it is a non-halogenated carbonate compound that is commonly used in nonaqueous electrolytes of lithium secondary batteries. Non-limiting examples of such carbonate compounds include propylene carbonate (PC) and ethylene carbonate ( EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), butylene carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethyl methyl carbonate (EMC), etc., alone or two or more, respectively. It can be mixed and used.

Carbonate-based organic solvent according to the invention is preferably included in 5 to 200 parts by weight relative to 100 parts by weight of the amide compound. If the content is less than 5 parts by weight, the viscosity of the electrolyte is not high to maintain excellent ion conductivity, if more than 200 parts by weight may degrade the battery safety due to decomposition reactions.

In addition, the electrolyte of the present invention includes a halogenated cyclic carbonate as an additive.

The carbonate-based organic solvent used in the present invention may decompose at the surface of the electrode during the charge and discharge process, causing a negative electrode structure collapse due to internal reaction of the battery and co-interlation with lithium ions. This problem can be solved by forming a solid electrolyte interface (SEI) film on the surface of the anode by electrical reduction of the organic solvent. However, the SEI film is one of the main factors that affect the performance of the battery by affecting the ion and charge transfer, the properties of the SEI film is known to vary greatly depending on the type of the solvent used as the electrolyte, the characteristics of the additives and the like.

In particular, since the amide compound used in the present invention has a relatively high viscosity and a high bonding strength with lithium ions, the movement of lithium at the electrode interface may be further limited according to the properties of the SEI film, thereby providing an interface resistance and initial capacity. In order to improve the selection of the additive for forming the SEI film is very important.

The inventors of the present invention solve the above problem by using a cyclic carbonate substituted with halogen in combination with the amide compound according to the present invention. Halogen-substituted cyclic carbonate used in combination with the amide compound according to the present invention is a relatively thin and dense SEI film formed by reduction decomposition at the negative electrode can improve the performance of the battery, in particular improve the room temperature charge and discharge performance. The reason for this effect is that the halogenated cyclic carbonate is reduced during the initial charging of the battery, and it is judged to form a more robust and dense SEI film by forming a single layer or overlapping SEI film through repetitive / cross polymerization. no.

The halogenated cyclic carbonate applicable to the present invention is not particularly limited as long as the halogenated cyclic carbonate can be used as an electrolyte. For example, halogenated ethylene carbonate, halogenated propylene carbonate, etc. may be mentioned, but it is not limited to this. Preferably, halogenated ethylene carbonate represented by the following formula (2) may be used.

[Formula 2]

In Chemical Formula 2,

X and Y are each independently hydrogen, chlorine, or fluorine, and X and Y are not simultaneously hydrogen.

Halogenated cyclic carbonate according to the present invention is preferably included 2 to 10 parts by weight relative to 100 parts by weight of the total electrolyte. If the content is less than 2 parts by weight, the effect of improving the charging and discharging performance is insignificant. If the content is more than 10 parts by weight, no further increase in effect in proportion to the addition amount can be expected.

In the electrolyte of the present invention, the weight ratio of the non-halogenated carbonate and the halogenated cyclic carbonate is preferably 1: 0.04 to 0.2. If the weight ratio of the halogenated cyclic carbonate to less than 0.04 part by weight of the non-halogenated carbonate is less than 0.04, the SEI film by the halogenated cyclic carbonate corresponding to the decomposition reaction of the non-halogenated carbonate is not dense, and the charge and discharge performance is not sufficiently improved. No further increase in proportion can be expected.

Optionally, the electrolyte of the present invention may further comprise vinylene carbonate as an additive.

Vinylene carbonate can suppress the side reaction between the electrode and the electrolyte by forming an SEI film on the surface of the cathode during charging. However, when vinylene carbonate is used alone, an organic film of a polymer or oligomer form formed while they are reduced on the negative electrode may act as a resistance component that inhibits movement and dissociation of lithium and electrolyte conjugates. Therefore, it is preferable to use together with the halogenated cyclic carbonate additive of this invention.

The vinylene carbonate according to the present invention is preferably included in an amount of 1 to 5 parts by weight based on 100 parts by weight of the total electrolyte in terms of suppressing gas generation in the battery.

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 a polymer electrolyte, it is a gel polymer electrolyte formed by polymerization of a precursor solution containing a monomer capable of forming a polymer by the above-described electrolyte and a polymerization reaction, or the electrolyte is in a solid phase. Or a polymer electrolyte in a form impregnated with a polymer such as gel.

First, the gel-like 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 comprises (i) an electrolyte comprising the amide compound, the lithium salt, the non-halogenated carbonate and the halogenated cyclic carbonate as described above, and (ii) a monomer capable of forming a polymer by a polymerization reaction ( It can be formed by polymerizing a precursor solution containing a monomer).

Monomers are applicable to all kinds of monomers capable of forming a gel polymer with the electrolyte as the polymerization proceeds, and non-limiting examples thereof include vinyl monomers. Vinyl monomers have the advantage that the polymerization is very simple when mixed with the electrolyte to form a gel polymer.

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, where the initiator is decomposed by heat or ultraviolet light to form radicals and reacts with the monomers by free radical polymerization to form a gel polymer electrolyte. do. Moreover, superposition | polymerization of a monomer can also be advanced, without using an initiator. In general, free radical polymerization is an initiation reaction in which reactive molecules or active points are formed, a growth reaction in which a monomer is 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 alkylated silvers. 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 inside the electrochemical device. In-Situ polymerization reaction is possible by heat or ultraviolet irradiation. The weight ratio of the electrolyte and the monomer in the precursor solution is preferably 0.5 to 0.95: 0.05 to 0.5 in terms of having a viscosity suitable for use as a gel polymer electrolyte. Since the degree of polymerization of the gel polymer can be adjusted according to the polymerization time, polymerization temperature or light irradiation degree, which are reaction factors, the polymer is controlled so that the polymer is not polymerized and the volume is not shrunk without leaking the electrolyte.

As another method for producing a polymer electrolyte according to the present invention, the electrolyte may be injected into a solid polymer or gel polymer already formed, so that the electrolyte may be prepared in a form in which the electrolyte is impregnated with 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.

As another method of preparing a polymer electrolyte according to the present invention, a method of forming a polymer electrolyte by dissolving the electrolyte and the polymer in a solvent and then removing the solvent may be used. At this time, the electrolyte 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 according to the present invention is applicable to conventional electrochemical devices known in the art, which require various electrochemical properties depending on the purpose of use.

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

Taking the lithium secondary battery as an example, the electrolyte of the present invention described above may be manufactured as a lithium secondary battery by injecting an electrode structure composed of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. As the positive electrode, the negative electrode, and the separator constituting the electrode structure, all those conventionally used for manufacturing a lithium secondary battery may be used.

As a specific example, a lithium-containing transition metal oxide may be preferably used as the cathode active material. For example, Li _x CoO ₂ (0.5 <x <1.3), Li _x NiO ₂ (0.5 <x <1.3), and Li _x MnO ₂ (0.5 <x <1.3), Li _x Mn ₂ O ₄ (0.5 <x <1.3), Li _x (Ni _a Co _b Mn _c ) O ₂ (0.5 <x <1.3, 0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), Li _x Ni _1-y Co _y O ₂ (0.5 <x <1.3, 0 <y <1), Li _x Co _1-y Mn _y O ₂ (0.5 <x <1.3, 0≤y <1), Li _x Ni _1-y Mn _y O ₂ (0.5 <x <1.3, O≤y <1), Li _x (Ni _a Co _b Mn _c ) O ₄ (0.5 <x <1.3, 0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li _x Mn _2-z Ni _z O ₄ (0.5 <x <1.3, 0 <z <2), Li _x Mn _2-z Co _z O ₄ (0.5 <x <1.3, 0 <z <2), Li _x CoPO ₄ (0.5 <x <1.3) and Li _x FePO ₄ Any one selected from the group consisting of (0.5 <x <1.3) or a mixture of two or more thereof may be used. In addition to these oxides, sulfides, selenides, and halides may also be used.

As the negative electrode active material, a carbon material, lithium metal, silicon, tin, or the like, into which lithium ions may be occluded and released, may be used. Preferably, a carbon material may be used, and as the carbon material, both low crystalline carbon and high crystalline carbon may be used. Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is natural graphite, Kish graphite, pyrolytic carbon, liquid crystal pitch carbon fiber. High temperature calcined carbon such as (mesophase pitch based carbon fiber), meso-carbon microbeads, Mesophase pitches and petroleum or coal tar pitch derived cokes. In this case, the negative electrode may include a binder, and the binder may include vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, Various kinds of binder polymers, such as polymethylmethacrylate, may be used.

In addition, as the separator, conventional porous polymer films conventionally used as separators, for example, polyolefins such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer, etc. The porous polymer film made of the polymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. It is not.

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

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. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

1. Preparation of Electrolyte

Example 1

N-methoxy-N-methyl 2,2,2-trifluoroethyl carbamate (MMTFEC): ethylene carbonate (EC): ethylmethyl carbonate (EMC) = 1.2M LiPF ₆ electrolyte having a composition of 55:30:15 was prepared. After that, 3% by weight of fluoroethylene carbonate (FEC) and 2% by weight of vinylene carbonate (VC) were added to the electrolyte to prepare an electrolyte.

Thereafter, LiCoO ₂ was used as the cathode active material, artificial graphite was used as the anode active material, and a lithium secondary battery was manufactured by a conventional method using an aluminum laminate packaging material.

Example 2

An electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that 5 wt% of FEC was added without adding VC to the electrolyte.

Comparative Example 1

An electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that 5 wt% of VC was added without adding FEC to the electrolyte.

Experimental Example 1: Impedance Measurement of Secondary Battery

Impedance was measured using Potentiostat for the batteries of Examples 1 and 2 and Comparative Example 1, and the results are shown in FIG. 1. Impedance measurements were made by charging the cell to 4.2V and then applying a small voltage (10mV) at a frequency of 3kHz to 100mHz and measuring the resulting current response.

As shown in Figure 1, the battery of Examples 1 to 2 it can be seen that the impedance is significantly reduced than the battery of Comparative Example 1. From this, it can be seen that among the VC and FEC capable of forming the SEI film, FEC reduces the impedance when used in the electrolyte of the present invention.

Experimental Example 2: Evaluation of Charge / Discharge Performance of Secondary Battery

<Initial capacity measurement>

The secondary batteries of Examples 1 and 2 and Comparative Example 1 prepared according to the above method were charged at a constant current of 0.5 C (400 mA) at 25 ° C., and after the voltage of the battery became 4.2 V, the charging current was at a constant voltage of 4.2 V. Initial charging was carried out until the value became 50 mA. The battery initially charged was discharged at a constant current of 0.2 C until the battery voltage reached 3 V, and the discharge capacity at this time was regarded as the initial capacity, and the values thereof are shown in Table 1 below.

Initial capacity (mAh) Example 1 1049.8 Example 2 1049.2 Comparative Example 1 1022.1

<Initial capacity measurement>

The batteries of Example 1 and Comparative Example 1 were charged at a constant current of 1C = 980 mA at 23 ° C., and after the voltage of the battery became 4.2 V, the first charge was performed at a constant voltage of 4.2 V until the charging current value became 50 mA. Was performed. The discharged battery was discharged until the battery voltage reached 3V at a constant current of 1C for the battery that was charged once. Subsequently, the results obtained by repeatedly performing the above charge and discharge cycles for 100 cycles are illustrated in FIG. 2.

As shown in Table 1 and Figure 2, the battery of the present invention using the FEC can be confirmed that the initial capacity is improved. This initial capacity difference leads to charge / discharge cycle characteristics, and as shown in FIG. 2, the discharge capacity of the battery of the present invention using FEC on a 100 cycle basis is about 10% increased.

From this, it can be seen that the electrolyte containing the halogenated cyclic carbonate of the present invention reduces the battery impedance and improves charge and discharge performance through improved SEI film properties.

Claims (12)

Ionizable lithium salts;
An amide compound represented by Formula 1 below; And
(a) non-halogenated carbonates and (b) halogenated cyclic carbonates;
Electrolyte Containing:
[Formula 1]

In Chemical Formula 1,
R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently substituted or unsubstituted with hydrogen, halogen, halogen, alkyl group having 1 to 20 carbon atoms, alkylamine group, alkoxy group, alkoxyalkyl group, alkenyl group and Any one selected from the group consisting of aryl groups,
X is any one selected from the group consisting of hydrogen, oxygen, sulfur, nitrogen, phosphorus, carbon and silicon, i) if X is hydrogen, R ₃ , R ₄ and R ₅ are absent, and ii) X is oxygen or sulfur R ₄ and R ₅ are absent if iii) R ₅ is absent if X is nitrogen or phosphorus. The method of claim 1,
The amide compound is N-methoxy methyl carbamate, N-methoxy ethyl carbamate, N-methoxy-N-methyl methyl carbamate, N-methoxy-N-methyl ethyl carbamate, N-methoxy-N -Methyl propyl carbamate, N-methoxy-N-methyl butyl carbamate, N-methoxy N-methyl trifluoroethyl carbamate, N-methoxy N-methyl 2-fluoroethyl carbamate, N-meth Methoxy N-methyl pentafluoropropyl carbamate, N-methoxy-N-methyl 2- (perfluorohexyl) ethyl carbamate, N-methoxy-N-methyl 6- (perfluorobutyl) hexyl carbamate , N-methoxyethyl methyl carbamate, N-methoxyethyl-N-methyl methyl carbamate, N-methoxymethyl-N-methyl methyl carbamate, N-methyl-N-methoxyethyl methoxyethyl carbamate , N-methyl-N-methoxyethyl methoxymethyl carbamate, N-methoxyethyl trifluoroethyl carbamate, N-methoxyethyl-N-methyl trifluoroethyl carbamate, N- Methoxymethyl-N-methyl trifluoroethyl carbamate, N-methoxymethyl trifluoroethyl carbamate, N-methoxymethyl-N-ethyl trifluoroethyl carbamate, N-methoxyethyl-N- Ethyl trifluoroethyl carbamate, N-methoxyethyl fluoroethyl carbamate, N-methoxyethyl-N-methyl fluoroethyl carbamate, N-methoxymethyl-N-methyl fluoroethyl carbamate, N -Methoxymethyl fluoroethyl carbamate, N-methoxymethyl-N-ethyl fluoroethyl carbamate, N-methoxyethyl-N-ethyl fluoroethyl carbamate, N-methoxyethyl pentafluoropropyl carba Mate, N-methoxyethyl-N-methyl pentafluoropropyl carbamate, N-methoxymethyl-N-methyl pentafluoropropyl carbamate, N-methoxymethyl pentafluoropropyl carbamate, N-methoxy Methyl-N-ethyl pentafluoropropyl carbamate, N-methoxyethyl-N-ethyl penta Fluoropropyl carbamate, N-methoxyethyl hexafluoro-2-propyl carbamate, N-methoxyethyl-N-methyl hexafluoro-2-propyl carbamate, N-methoxymethyl-N-methyl hexa Fluoro-2-propyl carbamate, N-methoxymethyl hexafluoro-2-propyl carbamate, N-methoxymethyl-N-ethyl hexafluoro-2-propyl carbamate and N-methoxyethyl-N -An electrolyte characterized in that any one selected from the group consisting of ethyl hexafluoro-2-propyl carbamate or a mixture of two or more thereof. The method of claim 1,
The lithium salt of 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 _{(CF 3 CF 2 SO 2)} 2 N - electrolyte, characterized in that at least one selected from the group consisting of. The method of claim 1,
The halogenated cyclic carbonate is reduced at a higher potential (Li / Li +) than the amide compound to form an SEI film. The method of claim 1,
The halogenated cyclic carbonate is an electrolyte characterized in that the halogenated ethylene carbonate represented by the formula (2):
(2)

In Chemical Formula 2,
X and Y are each independently hydrogen, chlorine, or fluorine, and X and Y are not simultaneously hydrogen. The method of claim 1,
The halogenated cyclic carbonate is an electrolyte comprising 2 to 10 parts by weight relative to 100 parts by weight of the total electrolyte. The method of claim 1,
The non-halogenated carbonates are propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), butylene carbonate, methylpropyl carbonate, ethylpropyl carbonate and ethyl Electrolyte, characterized in that any one or a mixture of two or more selected from the group consisting of methyl carbonate (EMC). The method of claim 1,
The mixed weight ratio of (a) non-halogenated carbonate and (b) halogenated cyclic carbonate is a: b = 1: 0.04-0.2. The method of claim 1,
The electrolyte is characterized in that it further comprises vinylene carbonate. The method of claim 1,
The electrolyte is a polymer electrolyte. 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 10. The method of claim 11,
The electrochemical device is an electrochemical device, characterized in that the lithium secondary battery.

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