JP2002260729A - Electrolyte for non-aqueous electrolyte - Google Patents

Abstract

(57) [Summary] (Modified) [PROBLEMS] To provide an electrolyte which improves the safety of a lithium secondary battery, has flame retardancy, and can be used as a non-aqueous electrolyte having a low reduction potential. SOLUTION: The following general formula (I) such as 1-trimethylsilyl-3-methylimidazolium-bistrifluoromethylsulfonylamine salt is used. _{{Wherein, R 1, R 2, R} 3, R 4, and R ₅ independently _of one another, an alkyl group, a cycloalkyl group, an alkynyl group, or an alkenyl group, in the case of R _4, or trisubstituted silyl Group. When R ₅ is plural, they may be different from each other, and X ⁻ is a monovalent anion. An imidazolium salt having a trisubstituted silyl group represented by｝ is used as an electrolyte for a non-aqueous electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrolyte for a non-aqueous electrolyte used for a lithium battery or the like, a novel imidazole salt which can be used as an electrolyte for a non-aqueous electrolyte, and a method for producing the same.

[0002]

2. Description of the Related Art Many imidazolium salts are liquid at around normal temperature, and are excellent in nonflammability and non-volatility. Therefore, catalysts for organic reactions and their intermediates, and reactions such as chemical reaction or metal plating. Considered as a solvent. In addition, since they have relatively high electrochemical stability and good conductivity, they are also expected as electrolytes for primary batteries, secondary batteries, electric double layer capacitors, and wet solar cells. In particular, in recent years, imidazolium salts have been actively studied as flame-retardant electrolytes for lithium secondary batteries for the purpose of reducing the risk of ignition, which is a major problem of lithium secondary batteries.

For example, it is known that 1,2,3-trialkylimidazolium salts using ions such as halides, aluminum halides, boron halides and phosphorus halides as anion components can be used as electrolytes for secondary batteries. (JP-A-60-133669, JP-A-60-133670, and
-133580).

A salt using bistrifluoromethylsulfonylamine ion (hereinafter abbreviated as TFN ion) as an anion component and N, N'-dialkylimidazolium ion as a cation component is a viscous hydrophobic material at ambient temperature. It is known that it is an ionic liquid salt and can be used as a solvent for electrochemical systems such as electrochemical photovoltaic cells (Japanese Patent Application Laid-Open No. 08-259543). The above-mentioned salt is suitable as an electrolyte of a lithium secondary battery in which water prohibition is required, since conventional imidazolium salts are hydrophilic and hydrophobic and have improved water resistance. .

[0005] Incidentally, an electrolyte for a lithium secondary battery is required to be not oxidized or reduced at the positive electrode during charge and discharge, in addition to high conductivity and hydrophobicity. That is, when the charging is performed at an oxidation potential or higher of the electrolyte or at a reduction potential or lower, the electrolyte is deteriorated, and therefore, as an electrolyte for a lithium secondary battery having a general electrode configuration, its reduction potential (. electrolytic solution means a reduction limit potential which is the potential that starts to be reduced) is low, for example, as a guide I ^- / I ^3-
The absolute value of the difference between the oxidation potential (meaning the oxidation limit potential, which is the potential at which the electrolytic solution starts to be oxidized) and the reduction potential (potential window), which is approximately -2.5 V or less in potential with respect to the electrode system.
Is desired to be large (wide), for example, approximately 5 V or more as a guide.

[0006]

However, any of the conventionally known imidazolium salts has low reduction resistance as an electrolyte for a lithium secondary battery, and no imidazolium salt which does not cause decomposition to date has been known. . For example,
Japanese Patent Application Laid-Open No. H11-297355 discloses that bistrifluoromethylsulfonylamine-1-ethyl-3-methylimidazolium (hereinafter abbreviated as EMI-TFN salt) having high electric conductivity has a potential Δ-2 which is more noble than lithium at the time of charging. .2V
vs I ^- / I ^3- (However, vs ^I - / ^{I 3-} is, I ^- /
I means the potential for the ^3- electrode system. ) It is described that the decomposition reaction occurs in ①, and the stability as an electrolyte is not sufficient.

Accordingly, an object of the present invention is to provide an imidazolium salt which can be used as a non-aqueous electrolyte for a lithium secondary battery, is stable at the time of charging, and has both nonflammability.

[0008]

Means for Solving the Problems The present inventors have synthesized and evaluated various imidazolium salts in order to solve the above technical problems. As a result, they have found that the novel substituted imidazolium salts synthesized by the present inventors have a low reduction potential and a wide potential window. The result of performing further studies based on the look該知three-reduction potential (reduction limit potential) of certain substituted imidazolium salt having a substituted silyl group ^{-2.5 (V vs I - / I} 3-) below The potential window was 4.7 V or more, which was found to be suitable as a non-aqueous electrolyte for a lithium secondary battery, and the present invention was completed.

That is, the first invention relates to the following general formula (I)

[0010]

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Wherein R ₁ , R ₂ and R ₃ independently of one another are an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, Or an alkenyl group having 2 to 10 carbon atoms, wherein R ₄ is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, An alkenyl group or the following general formula (II)

[0012]

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(Wherein R ₁ ′, R ₂ ′ and R ₃ ′ independently represent an alkyl group having 1 to 10 carbon atoms,
A cycloalkyl group having 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms. Wherein R ₅ is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, 2 to 10 carbon atoms.
An alkynyl group or an alkenyl group having 2 to 10 carbon atoms, a is an integer of 0 to 3, and when a is 2 or 3,
A plurality of R ₅ may be different from each other, and X ⁻ is a monovalent anion. An electrolyte for a non-aqueous electrolyte, comprising a substituted imidazolium salt represented by｝.

In the electrolyte for a non-aqueous electrolyte of the present invention, X ⁻ in the general formula (I) is BF ₄ ⁻ , P
F ₆ ⁻ , RfSO ₃ ⁻ , or (SO ₂ Rf) N ⁻ (SO ₂ R
f ′) (where Rf and Rf ′ are each independently a perfluoroalkyl group having 1 to 9 carbon atoms), and a substituted imidazolium salt is used as an electrolyte for a lithium secondary battery. It has a feature that the stability at the time of charge and discharge when used is particularly high.

Some of the substituted imidazolium salts represented by the general formula (I) are known as silylating agents in organic synthesis reactions, but their reduction potentials and oxidation potentials have not been investigated. The fact that it has excellent features as an electrolyte for non-aqueous electrolytes has been clarified for the first time. In the electrolyte for a non-aqueous electrolyte of the present invention, the electron-donating trisubstituted silyl group is bonded to the nitrogen atom constituting the conjugate ring in the imidazolium cation,
It is considered that the energy level of the lowest unoccupied molecular orbital (LUMO) of the cation was increased, and as a result, the reduction potential was lowered and the stability was improved.

Further, among the substituted imidazolium salts represented by the general formula (I), those represented by the following general formula (III) have been synthesized for the first time by the present inventors.

That is, the second invention has the following general formula (II)
I)

[0018]

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In the formula, R ₁ , R ₂ and R ₃ each independently represent an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, Or an alkenyl group having 2 to 10 carbon atoms, wherein R ₄ is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, An alkenyl group or the following general formula (II)

[0020]

Embedded image

(Wherein R ₁ ′, R ₂ ′ and R ₃ ′ independently represent an alkyl group having 1 to 10 carbon atoms,
A cycloalkyl group having 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms. Wherein R ₅ is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, 2 to 10 carbon atoms.
An alkynyl group or an alkenyl group having 2 to 10 carbon atoms, a is an integer of 0 to 3, and when a is 2 or 3,
A plurality of R ₅ may be different from each other, and X ⁻ is (SO
^{_{2 Rf) N - (SO 2}} Rf ') ( where, Rf and Rf'
Are each independently a perfluoroalkyl group having 1 to 9 carbon atoms. ) Is a monovalent anion. ｝
Is a substituted imidazolium salt.

Further, a third aspect of the present invention provides a compound represented by the following general formula (IV):

[0023]

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(Wherein, R ₁ , R ₂ and R ₃ independently represent an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, Or an alkenyl group having 2 to 10 carbon atoms, and Rf and Rf ′
Are each independently a perfluoroalkyl group having 1 to 9 carbon atoms. And a trisubstituted silyl perfluoroalkylsulfonylamide compound represented by the following general formula (V):

[0025]

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Wherein R ₄ is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms,
0 alkynyl group, alkenyl group having 2 to 10 carbon atoms, or the following general formula (II)

[0027]

Embedded image

(Wherein R ₁ ′, R ₂ ′ and R ₃ ′ independently represent an alkyl group having 1 to 10 carbon atoms,
A cycloalkyl group having 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms. Wherein R ₅ is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, 2 to 10 carbon atoms.
An alkynyl group or an alkenyl group having 2 to 10 carbon atoms, a is an integer of 0 to 3, and when a is 2 or 3,
A plurality of R ₅ may be different from each other. The method for producing a substituted imidazolium salt according to the present invention, characterized by mixing and reacting with an imidazole derivative represented by｝.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The electrolyte for a non-aqueous electrolyte according to the present invention comprises:
It is composed of a substituted imidazolium salt represented by the general formula (I).

In the general formula (I), R ₁ , R ₂ and R ₃ each independently represent an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, and 2 to 10 carbon atoms.
Or an alkenyl group having 2 to 10 carbon atoms. Here, as the alkyl group having 1 to 10 carbon atoms,
Examples include a methyl group, an ethyl group, a propyl group, and a hexyl group. Examples of the cycloalkyl group having 3 to 8 carbon atoms include a cyclopentyl group and a cyclohexyl group. Examples of the alkynyl group having 2 to 10 carbon atoms include an ethyl group,
Examples thereof include a propyl group and a hexyl group, and have 2 to 10 carbon atoms.
Examples of the alkenyl group include a vinyl group and an allyl group. From the viewpoint of electrical conductivity, it is preferable that each of these groups has 6 or less carbon atoms.

R ₄ in the general formula (I) is
C1-C10 alkyl group, C3-C8 cycloalkyl group, C2-C10 alkynyl group, C2-C2
10 alkenyl groups, or the following general formula (II)

[0032]

Embedded image

(Wherein R ₁ ′, R ₂ ′ and R ₃ ′ independently represent an alkyl group having 1 to 10 carbon atoms,
A cycloalkyl group having 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms. ).

As R ₄ , an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, and 2 to 1 carbon atoms
Examples of the alkynyl group of 0 and the alkenyl group of 2 to 10 carbon atoms include the same groups as those in R _{1 to} R ₃ . In addition, from the viewpoint of electric conduction, it is preferable that each of these groups has 6 or less carbon atoms, and a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group,
Or most preferably a t-butyl group.

Further, R ₁ ′, R ₂ ′,
And alkyl group having 1 to 10 carbon atoms in R ₃ ', cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or for even alkenyl group having 2 to 10 carbon atoms, R ₁ to R ₃ The same groups as those in are exemplified. However, when R ₄ is a trisubstituted silyl group represented by the general formula (II), R ₁ , R ₂ , R ₃ , R ₁ ′, R ₂ ′, and
In each group of R ₃ ′, the number of carbon atoms of each group is preferably 3 or less because the cation diameter is relatively small and the electric conductivity of the salt is high.

R ₅ in the general formula (I) is
Alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkenyl group an alkynyl group, or a C2-10 C2-10, R ₁ also these
Examples are the same groups as those described for R ₃ . Incidentally, a representative of the number of substituents for R ₅ is an integer of 0 to 3, when a is 2 or 3, the plurality of R ₅ may be different from each other.

Specific examples of the cation component of the substituted imidazolium salt represented by the general formula (I), which is suitable as the electrolyte for a non-aqueous electrolyte of the present invention, include 1-methyl-3-trimethylsilylimidazolium cation, Ethyl-3
-Trimethylsilyl imidazolium cation, 1-n-
Propyl-3-trimethylsilylimidazolium cation, 1-isopropyl-3-trimethylsilylimidazolium cation, 1-n-butyl-3-trimethylsilylimidazolium cation, 1-tert-butyl-3
-Trimethylsilylimidazolium cation, 1-cyclopentyl-3-trimethylsilylimidazolium cation, 1- (1,1-dimethylpropyl) -3-trimethylsilylimidazolium cation, 1-methyl-3-
Ethyldimethylsilyl imidazolium cation, 1,3
-Ditrimethylsilyl imidazolium cation, 1-trimethylsilyl-3-ethyldimethylsilyl imidazolium cation, 1-trimethylsilyl-3-n-propyldimethylsilyl imidazolium cation, 1-trimethylsilyl-3-isopropyldimethylsilyl imidazolium cation, 1- Trimethylsilyl-3-n-butyldimethylsilyl imidazolium cation, and 1-
Trimethylsilyl-3-tert-butyldimethylsilyl imidazolium cation.

Further, X in the general formula (I)^-Is
It means a monovalent anion. X^-Is not particularly limited,
Cl^-, Br^-, I^-, AlCl_Four ^-, Al_TwoCl₇ ^-, Al_Three
Cl₈ ^-, NO_Two ^-, NO_Three ^-, BF_Four ^-, PF₆ ^-, RCO
_Two ^-(Where R is an alkyl group), RfCO_Two ^-, RfS
O_Three ^-, (RfSO_Two) (Rf'SO_Two) N^-, RSO_Four ^-,
(RfSO_Two) C_Three ^-Can take a known monovalent anion such as
You. Note that Rf and Rf ′ in the anion shown above are
Carbon such as trifluoromethyl group and nonafluorobutyl group
Number 1 to 9, preferably 1 to 3 perfluoroalkyl group
Means Oxidation for electrolyte of lithium secondary battery
Because the potential (oxidation limit potential) is high, X ^-Is
BF_Four ^-, PF₆ ^-Or (RfSO_Two) (Rf'SO_Two) N
^-It is preferred that

The substituted imidazolium salt represented by the above general formula (I) can take any combination of the above-mentioned cation component and anion component, but from the viewpoint of conductivity and stability, the cation component is 1-methyl- 3-trimethylsilyl imidazolium cation, 1-isopropyl-3
-Trimethylsilyl imidazolium cation, 1,3-
Bistrimethylsilyl imidazolium cation, and 1
-Trimethylsilyl-3-n-butyldimethylsilyl imidazolium cation, wherein the anion component is BF ₄ ⁻ , PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ (that is, T
Any one selected from the group consisting of (FN ion), (CF ₃ SO ₂ ) (C ₂ F ₇ SO ₂ ) N ⁻ , and (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) N ⁻ Is preferred.

The substituted imidazolium salt represented by the general formula (I) has an ionic conductivity of ¹ mScm ^-1 or more,
Not only does it have flame retardancy and has the property of being liquid to solid at room temperature, but its reduction potential is -2.5 (V vs.
I ⁻ / I ³⁻ ) or lower and the anion component is BF ₄ ⁻ ,
PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ (that is, TFN ion),
(CF ₃ SO ₂ ) (C ₂ F ₇ SO ₂ ) N ⁻ and (CF ₃ S
The oxidation potential of a salt such as O ₂ ) (C ₄ F ₉ SO ₂ ) N ⁻ is 2.4.
(V vs I ⁻ / I ³⁻ ) or higher, so that a liquid at room temperature is kept as it is, and a solid at room temperature is dissolved in a solvent such as propylene carbonate to form a lithium secondary battery or the like. It can be suitably used as a non-aqueous electrolyte.

The method for producing the substituted imidazolium salt represented by the general formula (I) is not particularly limited, and it may be produced by any synthetic method. In general, the synthesis method differs depending on the anion component contained in the salt, and when the anion component is Cl ⁻ , Br ⁻ , I ⁻ , or RfSO ₃ ⁻ or the like, direct quaternization of the corresponding imidazole derivative It can be synthesized by a reaction. Further, when the anion component is B
In the case of F ₄ ⁻ , PF ₆ ⁻ , Al ₃ Cl ₈ ⁻ , Al ₂ Cl ₇ ⁻ or the like, it can be synthesized by reacting an imidazolium halide with a metal salt.

However, the substituted imidazolium salt represented by the general formula (III), which is a novel salt,
N, N'-dialkylimidazolium cation and TFN
JP-A-08-25954 discloses a method for producing a salt with ions.
In the case where the method of ion-exchanging an imidazolium halide and a lithium bisperfluoroalkylsulfonylamine in an aqueous medium as described in the public information of No. 3 is adopted, mixing of decomposed products in ion exchange and moisture Since it is difficult to obtain the target compound due to contamination of the compound, the compound is preferably produced by the following method.

That is, the compound is preferably produced by mixing and reacting the trisubstituted silyl perfluoroalkylsulfonylamide compound represented by the general formula (IV) with the imidazole derivative represented by the general formula (V). It is. By adopting such a method, it is possible to synthesize the target substance while avoiding contamination of impurities and increase in water content.

The substituted silyl perfluoroalkylsulfonylamide compound used in the above production method is, as shown in the following formula, an allylsilane compound and (RfSO ₂ )
It can be obtained by reacting with (Rf′SO ₂ ) NH.

[0045]

Embedded image

Where R₁, R_Two, R_Three, Rf, and R
f ′ is the same as that in the general formula (III).
Righteous.反 応 In the reaction shown in the above formula,
(RfSO _Two) (Rf'SO_Two) NH to molar ratio
Allyl silane compound of 1-1.
After dripping without using, about 70-80 ° C for about 1 hour
The heating can be performed by heating.

The method of reacting the trisubstituted silyl perfluoroalkylsulfonylamide compound obtained by the above reaction with the imidazole derivative represented by the above general formula (V) is preferably carried out by mixing and contacting the two. Can be performed. By mixing both, the following formula

[0048]

Embedded image

Where R ₁ , R ₂ , R ₃ , Rf and R
f ′ has the same meaning as that in the general formula (III). The reaction indicated by｝ proceeds spontaneously, and the desired product can be obtained.

More specifically, the reaction is preferably carried out in an experimental apparatus in which mixing of water is avoided. Also,
In the reaction, one of the trisubstituted silyl perfluoroalkylsulfonylamide compound or the imidazole derivative represented by the general formula (V) is cooled to 0 ° C. or lower, and then the other is gradually heated to a molar ratio of 1: 1. It progresses by dripping and stirring. After completion of the dropwise addition, the mixture is allowed to stand at room temperature with stirring to obtain the desired substituted imidazolium salt.

The thus obtained substituted imidazolium salt can be used without particular purification.

[0052]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
The properties of the compounds shown in Examples and Comparative Examples are values measured by the following methods.

(1) NMR Measurement 10 to 20 mg of a sample was dissolved in 0.4 ml of deuterated chloroform or methanol containing 0.3% of tetramethylsilane, and dissolved in JEOL's nuclear magnetic resonance apparatus JN.
¹³ C and ²⁹ Si nuclei were measured by M-LA500. The peak position was determined with reference to the chemical shift positions of ¹³ C and ²⁹ Si nuclei of tetramethylsilane (0 ppm each) contained in the deuterated solvent.

(2) Elemental Analysis Carbon, hydrogen, nitrogen, and oxygen were accurately measured by weighing 1 to 2 mg of a sample and measured with an element analyzer MT-5 manufactured by Yanagimoto Seisakusho. Sulfur, fluorine and chlorine are samples 5-10
mg was accurately weighed and the gas generated by burning in a flask in an oxygen atmosphere was absorbed in water, and each was quantified as sulfate ion, fluoride ion and chloride ion by ion chromatography DX-120 manufactured by DIONEX.

(3) Withstand voltage measurement For each of the salts of Examples 1 to 10, C manufactured by Hokuto Electronics Co., Ltd.
Sweep speed 10mVs using V measurement device HSV-100
A cyclic voltammogram was prepared at ec ⁻¹ , and the reduction potential and oxidation potential of each salt were determined based on this. The electric potential is determined by an iodine couple (I ⁻ / I ₃ ⁻ ) reference electrode (EMI-
(A solution obtained by dissolving 15 mM I ₂ and 60 mM tetrapropylammonium iodide in TFN salt and immersing a platinum wire in the solution). In the cyclic voltammogram, the lower side of the potential flowing at a current density of 1 mAcm ^-2 or more was determined as the reduction potential, and the higher side was determined as the oxidation potential.

(4) Ionic Conductivity Among the salts of Examples 1 to 10, a compound which is liquid at room temperature is an electrical conductivity cell CG-511 manufactured by Toa Denpa Kogyo Co., Ltd.
LCR Hitester manufactured by Hioki Electric Co., Ltd.
Was used to measure the electrical conductivity.

Example 1 14.1 g of (CF ₃ SO ₂ ) ₂ NH under a nitrogen atmosphere
Then, 5.9 g of allyltrimethylsilane was gradually added dropwise to the mixture, and the mixture was allowed to stand for 1 hour and distilled at 80 ° C. for 1 hour to obtain 17.2 g of trimethylsilylbistrifluoromethylsulfonylamine. The obtained compound (15.0 g) was placed at 0 ° C. in a nitrogen atmosphere.
1-trimethylsilyl-3-methylimidazolium-TFN salt (electric conductivity: 2.4 mScm ^-1 ) which is a transparent viscous liquid by gradually dropping 3.5 g of 1-methylimidazole while cooling the mixture. 6 g were obtained. Table 1 shows the peak positions of ¹³ C, ²⁹ Si-NMR spectra of the salts synthesized as described above, and Table 2 shows their elemental analysis values. The withstand voltage (in the form of reduction potential to oxidation potential) of the synthesized electrolyte is shown in Table 1. Described)
Are shown in Table 3.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

Example 2 A transparent viscous liquid 1-trimethylsilyl-3 was prepared in the same manner as in Example 1 except that 4.7 g of 1-isopropylimidazole was used instead of 1-methylimidazole.
18.3 g of -isopropyl imidazolium-TFN salt (electric conductivity: 7.9 mScm ^-1 ) was obtained. Table 1 shows the peak positions of the ¹³ C, ²⁹ Si-NMR spectrum of the salt synthesized as described above, Table 2 shows the elemental analysis values thereof, and Table 3 shows the withstand voltage of the synthesized electrolyte.

Example 3 In place of 1-methylimidazole of Example 1, 1-te
The same procedure was carried out except that the amount of rt-butylimidazole was changed to 5.3 g, and a white gel-like solid, 1-trimethylsilyl-
17. 3-tert-butylimidazolium-TFN salt
5 g were obtained. ¹³ C, ²⁹ Si of the salt synthesized as described above
Table 1 shows the peak positions of the -NMR spectrum, Table 2 shows the elemental analysis values thereof, and Table 3 shows the withstand voltage of the synthesized electrolyte.

Example 4 A white gel-like solid, 1,3-bistrimethylsilylimidazolium-TFN salt, was obtained in the same manner as in Example 1 except that 6.0 g of 1-trimethylsilylimidazole was used instead of 1-methylimidazole. 19.3 g were obtained. Table 1 shows the peak positions of the ¹³ C, ²⁹ Si-NMR spectrum of the salt synthesized as described above, and Table 2 shows its elemental analysis values.
Table 3 shows the withstand voltage of the synthesized electrolyte.

Example 5 Instead of 1-methylimidazole of Example 1, 1-n-
Propyl dimethyl silylimidazole 7.2 g
The same procedure was followed except that 1-trimethyl, a transparent viscous liquid
Lucilyl-3-n-propyldimethylsilylimidazoli
TFN salt (electrical conductivity 1.0mScm^-1) 20.3
g was obtained. Of the salt synthesized as above ¹³C,²⁹Si-
Table 1 shows the peak positions of the NMR spectrum and their elemental analysis.
The values are shown in Table 2 and the withstand voltage of the synthesized electrolyte is shown in Table 3.
Was.

Example 6 Instead of 1-methylimidazole of Example 1, 1-te
The same operation was performed except that rt-butyldimethylsilylimidazole was used in an amount of 7.8 g, to obtain 20.7 g of a 1-trimethylsilyl-3-tertbutyldimethylsilylimidazolium-TFN salt as a gel-like solid. Table 1 shows the ¹³ C, ²⁹ Si-NMR spectrum peak positions of the salts synthesized as described above, Table 2 shows their elemental analysis values, and Table 3 shows the withstand voltage of the synthesized electrolyte.

Example 7 7.5 g of 1-trimethylsilylimidazole was added to 7.5 g of ethyl trifluoromethanesulfonate in a nitrogen atmosphere.
g was gradually added dropwise, and the mixture was stirred for 4 hours.
Trimethylsilyl-3-ethyl imidazolium -CF ₃
14.0 g of the SO ₃ salt were obtained. Table 1 shows the peak positions of the ¹³ C, ²⁹ Si-NMR spectrum of the salt synthesized as described above.
Table 2 shows the elemental analysis values, and Table 3 shows the withstand voltage of the synthesized electrolyte.

Example 8 In a nitrogen atmosphere, 2.8 g of methyl chloride was gradually added dropwise to 7.5 g of 1-trimethylsilylimidazole, and the mixture was refluxed at 90 ° C. for 12 hours. After removing the excess methyl chloride, 14.1 g of aluminum trichloride was gradually added dropwise to give 2: 1.
23.7 g of (mol / mol) transparent liquid 1-trimethylsilyl-3-methylimidazolium-aluminum chloride (electrical conductivity: 3.7 mScm ^-1 ) was obtained. Table 1 shows the peak positions of the ¹³ C, ²⁹ Si-NMR spectrum of the salt synthesized as described above, and Table 2 shows its elemental analysis values.
Table 3 shows the withstand voltage of the synthesized electrolyte.

Example 9 In a nitrogen atmosphere, 7.5 g of 1-trimethylsilylimidazole was added to 100 ml of carbon tetrachloride, and 2.8 g of methyl chloride was gradually added dropwise and refluxed at 90 ° C. for 8 hours. After removing excess methyl chloride, 10.5 g of silver boron tetrafluoride was added to separate the carbon tetrachloride solution. The carbon tetrachloride was dried under vacuum to obtain 11.7 g of ¹ -trimethylsilyl-3-methylimidazolium boron tetrafluoride (electric conductivity 4.2 mScm ^-1 ) as a transparent liquid. Table 1 shows the ¹³ C, ²⁹ Si-NMR spectrum peak positions of the salts synthesized as described above, Table 2 shows their elemental analysis values, and Table 3 shows the withstand voltage of the synthesized electrolyte.

Example 10 A transparent liquid, 1-trimethylsilyl-3-methylimidazolium-6, was prepared in the same manner as in Example 9, except that silver hexafluoride was replaced with 13.6 g of silver hexafluoride. Phosphorus fluoride salt (electrical conductivity 3.1 mScm ^-1 ) 12.8
g was obtained. The salt of ¹³ C, ²⁹ Si-
Table 1 shows the peak position of the NMR spectrum, Table 2 shows its elemental analysis value, and Table 3 shows the withstand voltage of the synthesized electrolyte.

Comparative Examples 1 to 3 EMI-TFN salt (Comparative Example 1), 1-ethyl-3-methylimidazolium-boron tetrafluoride (Comparative Example 2), and 1-butyl-3-methylimidazolium salt The withstand voltage of the hexafluorophosphate (Comparative Example 3) was measured. Table 3 shows the results.

As shown in Table 3, the compound represented by the general formula (I)
It can be seen that the electrolyte composed of the substituted imidazolium salt represented by has higher reduction resistance (lower reduction potential) than the imidazolium salt (Comparative Examples 1 to 3) which is conventionally known for use as an electrolyte.

[0072]

The electrolyte for a non-aqueous electrolyte of the present invention has not only flame retardancy but also high resistance to reduction. For this reason, for example, when used with an electrolyte for a lithium secondary battery, not only is there a low risk of ignition or the like, but also the electrolyte is not reduced even after repeated charging and discharging, and excellent cycle characteristics are obtained. Can be expected.

Claims (4)

[Claims] 1. A compound represented by the following general formula (I) In the formula, R ₁ , R ₂ , and R ₃ each independently represent an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or a carbon number 2-1
0 is an alkenyl group, and R ₄ is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, and 2 carbon atoms.
Or an alkynyl group having 10 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or the following general formula (II): Wherein R ₁ ′, R ₂ ′, and R ₃ ′ are, independently of one another,
An alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms. ), Wherein R ₅ is an alkyl group having 1 to 10 carbon atoms,
8 is a cycloalkyl group, an alkynyl group having 2 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, and a is 0
When a is 2 or 3, a plurality of R ₅ may be different from each other, and X ⁻ is a monovalent anion. An electrolyte for a non-aqueous electrolyte, comprising a substituted imidazolium salt represented by｝. 2. X in the general formula (I)^-But BF_Four
^-, PF₆ ^-, RfSO_Three ^-Or (SO_TwoRf) N^-(SO_Two
Rf ') (provided that Rf and Rf' are each independently
It is a perfluoroalkyl group having 1 to 9 carbon atoms. )
Characterized by comprising a substituted imidazolium salt
Item 2. The electrolyte for a non-aqueous electrolytic solution according to Item 1. 3. The following general formula (III): In the formula, R ₁ , R ₂ , and R ₃ each independently represent an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or a carbon number 2-1
0 is an alkenyl group, and R ₄ is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, and 2 carbon atoms.
Or an alkynyl group having 10 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or the following general formula (II): Wherein R ₁ ′, R ₂ ′, and R ₃ ′ are, independently of one another,
It is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms. ), Wherein R ₅ is an alkyl group having 1 to 10 carbon atoms,
8 is a cycloalkyl group, an alkynyl group having 2 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, and a is 0
When a is 2 or 3, a plurality of R ₅ may be different from each other, and X ⁻ is (SO ₂ Rf) N ⁻
(SO ₂ Rf ′) (where Rf and Rf ′ are each independently a perfluoroalkyl group having 1 to 9 carbon atoms). A substituted imidazolium salt represented by｝. 4. The following general formula (IV): (Wherein, R ₁ , R ₂ and R ₃ independently represent an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or 2-1
0 is an alkenyl group, and Rf and Rf ′ are each independently a perfluoroalkyl group having 1 to 9 carbon atoms. And a trisubstituted silyl perfluoroalkylsulfonylamide compound represented by the following general formula (V): In the formula, R ₄ is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a compound represented by the following general formula ( II) Wherein R ₁ ′, R ₂ ′, and R ₃ ′ are, independently of one another,
An alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms. ), Wherein R ₅ is an alkyl group having 1 to 10 carbon atoms,
8 is a cycloalkyl group, an alkynyl group having 2 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, and a is 0
When a is 2 or 3, a plurality of R ₅ may be different from each other. 4. The method for producing a substituted imidazolium salt according to claim 3, wherein the reaction is carried out by mixing with an imidazole derivative represented by｝.