JP2000003620A - Imidazolium fused salt type electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte showing high ionic property at room temperature and excellent in thermal stability by using an N-alkyl imidazolium salt obtained by reacting an N-alkyl imidazol compound having alkyl group in only one of 1-position and 3-position with an acid, or polymerizing a reaction product of the N-alkyl imidazol compound with an acid monomer. SOLUTION: An imidazol compound having a lower alkyl group in only one of 1-position and 3-position such as 1-methylimidazol, 1-ethylimidazol or the like is neutralized with an inorganic acid such as hydrobromic acid, hydrochloric acid, nitric acid, methane sulfonic acid or the like or an organic acid such acetic acid to provide an N-alkyl imidazolium salt. The salt is also used as a polymer by reacting it with an acid monomer such as acrylic acid followed by polymerization. Accordingly, an imidazol room temperature fused salt containing no impurity can be provided. Further, since a salt having various physical properties can be also provided by introducing various anion pairs in synthesis, this is useful as a solid electrolyte material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention shows high ionic conductivity at room temperature, and has excellent temperature stability and mechanical properties.
The present invention relates to an imidazolium-based room temperature molten salt electrolyte.

[0002]

2. Description of the Related Art As a method for synthesizing a molten salt at room temperature using an imidazolium compound, an anion exchange method in which a silver salt containing an acid anion is reacted with 1,3-dialkylimidazolium halide is known. According to this method,
Since the by-product silver halide is hardly soluble in the solvent, it has the advantage of easy purification, but it is difficult to prepare the desired room temperature molten salt due to limitations on the types of silver salts that can be used. In addition, since the process of synthesizing and purifying 1,3-dialkylimidazolium halide as a starting material is complicated, it has not been put to practical use.

JP-A-60-133669, JP-A-60-1
In 33670 and 60-136180,
1,3-dialkylimidazolium halide and 1,
Electrolytes using 2,3-trialkylimidazolium halides and aluminum halides are disclosed. However, electrolytes using these compounds are:
Although exhibiting high ionic conductivity at room temperature, aluminum halide is decomposed due to slight moisture contamination,
Further, there is a disadvantage that the phase state of the molten salt is unstable with respect to a temperature change. As a means for improving these, the present inventors have already prepared a molten salt polymer obtained by reacting an acid monomer or the like with an imidazole derivative such as 1,3-dialkylimidazolium halide or 1,2,3-trialkylimidazolium halide. Active ingredients and molten salt type polymer electrolytes are proposed. (JP-A-10-83821)

In recent years, room temperature molten salts, which are ionic liquids containing no solvent, have been expected as electrolytes for lithium secondary batteries. Some onium salts, such as imidazolium salts and pyridinium salts, form molten salts at room temperature.In particular, imidazolium salts having an organic acid anion as a counter ion have low viscosity at room temperature. is increasing. However, the synthesis of these imidazolium salts is quite complicated, and there are limitations on the organic salts to which the anion exchange method can be applied. Therefore, the effects of anionic species have not yet been sufficiently studied.

[0005]

SUMMARY OF THE INVENTION In an electrolyte using an imidazolium salt as an active ingredient, a compound in which various anions are introduced into the imidazolium salt is easily synthesized to provide a high ionic conductivity at room temperature with various physical properties. It is an object of the present invention to provide an electrolyte exhibiting the properties and having excellent temperature stability.

[0006]

As an electrolyte, an N-alkylimidazolium salt obtained by neutralizing an acid with an N-alkylimidazole compound having an alkyl group in only one of the first and third positions, or It has been found that the intended object can be achieved by using an N-alkyl imidazolium salt obtained by reacting the N-alkyl imidazole compound with an acid monomer and polymerizing the reaction product, thereby completing the present invention. Reached.

[0007] The imidazolium-based room temperature molten salt used as the electrolyte of the present invention is characterized by having a very low impurity content. That is, a conventionally known imidazolium-based room temperature molten salt causes deterioration in various physical properties, particularly ionic conductivity, due to mixing with an inorganic salt or the like, and thus has to be complicatedly purified. When a simple salt is mixed, the separation accuracy of the inorganic salt to be purified is not so much improved, and the efficiency is improved by producing a sparingly soluble silver salt, but the production of the silver salt is limited. Therefore, the desired purification could not be performed. According to the present invention, an N-alkylimidazolium salt obtained by neutralizing an acid with an N-alkylimidazole compound having an alkyl group at only one of the first and third positions as an electrolyte, or the N-alkyl These problems can be solved at once by using an N-alkyl imidazolium salt obtained by reacting an imidazole compound with an acid monomer and polymerizing the reaction product, thereby easily preparing a high-purity room temperature molten salt. And a molten salt having various characteristics into which various anions are introduced can be easily obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An N-alkyl imidazolium salt according to the present invention is an imidazole compound having an alkyl group at only one of the 1-position and the 3-position, such as 1
1 such as -methylimidazole, 1-ethylimidazole, etc.
An imidazole compound having a lower alkyl group at only one of the 3rd or 3rd position and an inorganic acid such as hydrobromic acid, hydrochloric acid, nitric acid, borofluoric acid, sulfurous acid, sulfuric acid, methanesulfonic acid, or an organic acid such as acetic acid. A compound obtained by neutralizing an acid. In order to react the N-alkylimidazole compound with the acid, the two are stirred and mixed in an aqueous solution at 0 to 20 ° C., excess water is distilled off from the reaction solution, and extraction is performed using an organic solvent such as diethyl ether. good. When an organic acid such as acetic acid is used as the acid, it should be distilled off during the purification process and dried under reduced pressure.

The room temperature molten salt of the present invention can be used as a polymer of an N-alkyl imidazolium salt by reacting an N-alkyl imidazolium salt with an acid monomer and polymerizing the acid monomer. Representative examples of the acid monomer to be reacted with the N-alkyl imidazolium salt include acrylic acid, methacrylic acid, and vinyl sulfonic acid.

[0010]

The present invention will be specifically described below with reference to examples. The progress of the neutralization reaction between the N-alkylimidazole compound and the acid in these tests was performed by H-NMR measurement and DSC measurement, and the chemical shift of the proton present at the 2-position of imidazole before and after the reaction was confirmed and confirmed. The temperature dependence (10 to 60 ° C.) of the ionic conductivity was measured by a two-terminal AC impedance method.

Example 1 N-ethylimidazole 10
To the resulting mixture, 12 ml of a 47% aqueous solution of hydrobromic acid was added, and the mixture was stirred for 12 hours while maintaining the temperature at 0 ° C., and then dried under reduced pressure to remove excess water. The crystals were dropped into diethyl ether, and the precipitated crystals were collected and dried at a temperature of 60 ° C. for 48 hours to obtain N-ethylimidazolium bromide (hereinafter referred to as “EtImBr”).
7.7 g (93% yield) were obtained. The result of H-NMR measurement and DSC measurement of this product is as shown in Table 1. The chemical shift of the proton present at the 2-position of imidazole before and after the reaction is shifted to a low magnetic field after the reaction. From this, the progress of the reaction was confirmed. This product has a melting point of 59.9
° C, and there were no impurities such as inorganic salts, and the temperature dependence (10 to 60 ° C) of the ionic conductivity was as shown in FIG.

Example 2 N-ethylimidazole 10
10 g of a 36% hydrochloric acid aqueous solution was added to
, And dried under reduced pressure to remove excess water, and the reaction product was stirred for 100 hours.
12. Drops were dropped into 0 ml of diethyl ether, and the precipitated crystals were collected, dried at a temperature of 60 ° C. for 48 hours, and N-ethylimidazolium chloride (hereinafter referred to as EtImCl).
5 g (95% yield) was obtained. The result of performing H-NMR measurement and DSC measurement of this product is as shown in Table 1,
The progress of the reaction was confirmed as in the above example. This product has a melting point of 57.5 ° C, contains no impurities such as inorganic salts, and has a temperature dependence of its ionic conductivity (10 to 60 ° C).
Was as shown in FIG.

Example 3 N-ethylimidazole 10
8 ml of a 61% nitric acid aqueous solution was added to the mixture, and the mixture was stirred for 12 hours while maintaining the temperature at 0 ° C., and then dried under reduced pressure to remove excess water.
The resulting crystals were collected and dried at a temperature of 60 ° C. for 48 hours to obtain 15.6 g of N-ethylimidazolium nitrate (hereinafter referred to as “EtImNO 3”).
(92% yield). H-NMR measurement and DS of this product
The results of the C measurement are as shown in Table 1. The progress of the reaction was confirmed in the same manner as in the above Examples. The content of impurities such as inorganic salts was completely absent, and the melting point was 31.3 ° C. ,
Temperature dependence of ionic conductivity of this product (10-60 ° C)
Was as shown in FIG.

Example 4 N-ethylimidazole 10
To the resulting mixture, 18 ml of a 42% aqueous solution of fluoboric acid was added, and the mixture was stirred for 12 hours while maintaining the temperature at 0 ° C., and then dried under reduced pressure to remove excess water. The solution was added dropwise to diethyl ether, and the precipitated crystals were collected and dried at a temperature of 60 ° C. for 48 hours.
Ethylimidazolium fluoroborate (EtImBF4
18.4 g (95% yield). H- of this product
The results of the NMR measurement and the DSC measurement are as shown in Table 1. The progress of the reaction was confirmed in the same manner as in the above Examples, the content of impurities such as inorganic salts was completely absent, and the glass transition temperature was The temperature dependence of the ion conductivity of this product at -86.4 ° C. (10 to 60 ° C.) was as shown in FIG.

Example 5 N-ethylimidazole 10
After stirring for 12 hours while maintaining the temperature at 0 ° C., the reaction product was dropped into 1,000 ml of stirring diethyl ether, and the precipitated crystals were collected and collected at 60 ° C. And dried at a temperature of 48 hours for 19.5 g of N-ethyl imidazolium methanesulfonate (referred to as EtImCH3SO3) (yield: 96).
%). The results of H-NMR measurement and DSC measurement of this product are as shown in Table 1, and the progress of the reaction was confirmed in the same manner as in the above Examples, and the content of impurities such as inorganic salts was completely absent. Its melting point was 55.3 ° C., and the temperature dependence (10-60 ° C.) of the ion conductivity of this product was as shown in FIG.

Example 6 N-ethylimidazole 10
After adding 198 ml of 5% aqueous sulfurous acid to the resulting mixture and stirring the mixture for 12 hours while maintaining the temperature at 0 ° C., the reaction product was added dropwise to 1000 ml of stirring diethyl ether, and the precipitated crystals were collected and collected. At 48 ° C. for 48 hours, and dried with N-ethylimidazolium sulfite (EtImH
18.6 g (referred to as SO3) was obtained (yield 91%). The results of H-NMR measurement and DSC measurement of this product are as shown in Table 1, and the progress of the reaction was confirmed in the same manner as in the above Examples, and the content of impurities such as inorganic salts was completely absent.
The glass transition temperature was −51.7 ° C., and the temperature dependence of ionic conductivity (10 to 60 ° C.) of the product was as shown in FIG.

Example 7 N-ethylimidazole 10
6 ml of 99.7% acetic acid was added to the resulting mixture, and the mixture was stirred for 12 hours while maintaining the temperature at 0 ° C., and then the reaction product was added dropwise to 1000 ml of stirring diethyl ether. After removal, the precipitate was collected by vacuum drying, and 15.9 g of N-ethylimidazolium acetate (EtImCH3COO) was collected.
(98% yield). H-NMR measurement and DS of this product
The results of the C measurement are as shown in Table 1. The progress of the reaction was confirmed in the same manner as in the above Examples. The content of impurities such as inorganic salts was completely absent, and the glass transition temperature was -5.
1.7 ° C, temperature dependence of ionic conductivity of this product (10
６０60 ° C.) as shown in FIG.

[0018]

[Table 1]

Example 8 N-methylimidazole 10
g of 14% of 47% hydrobromic acid was added to the mixture at a temperature of 0 ° C.
After stirring for 12 hours while maintaining the reaction mixture at room temperature, the reaction product was added dropwise to 1000 ml of stirring diethyl ether, and the diethyl ether was distilled off at room temperature. 17.1 g (yield 97%) of N-methylimidazolium bromide (denoted as MeImBr) was obtained. The results of H-NMR measurement and DSC measurement of this product are as shown in Table 2, and the progress of the reaction was confirmed as in the above Examples, and the content of impurities such as inorganic salts was completely absent. The melting point is 71.7 ° C, and the temperature dependence of the ionic conductivity of this product (10 to 60 ° C)
Was as shown in FIG.

Example 9 N-methylimidazole 10
After adding 12 ml of 36% hydrochloric acid to the resulting mixture and stirring the mixture for 12 hours while maintaining the temperature at 0 ° C., the reaction product was added dropwise to 1,000 ml of stirring diethyl ether.
After distilling off diethyl ether at room temperature, vacuum drying was performed to collect the precipitated crystals, and 13.7 g of N-methylimidazolium chloride (hereinafter referred to as MeImCl) was obtained (yield: 9).
5%). The results of H-NMR measurement and DSC measurement of this product are as shown in Table 2, and the progress of the reaction was confirmed in the same manner as in the above Examples, and the content of impurities such as inorganic salts was completely absent. The melting point was 40.5 ° C., and the temperature dependence of the ion conductivity of this product (10 to 60 ° C.) was as shown in FIG.

Example 10 N-methylimidazole 1
10 ml of a 61% nitric acid aqueous solution was added to
After stirring for 12 hours while maintaining the temperature at ° C., the reaction product was added dropwise to 1000 ml of stirring diethyl ether, and the diethyl ether was distilled off at room temperature, followed by vacuum drying to collect precipitated crystals. 16.6 g of N-methylimidazolium nitrate (referred to as MeImNO3)
(94% yield). H-NMR measurement and DS of this product
The results of the C measurement are as shown in Table 2. The progress of the reaction was confirmed in the same manner as in the above Examples. The content of impurities such as inorganic salts was completely absent, and the melting point was 69.7 ° C. Temperature dependence of ionic conductivity of this product (10-60 ° C)
Was as shown in FIG.

Example 11 N-methylimidazole 1
20 g of a 42% aqueous solution of fluoboric acid was added to 0 g, and the mixture was stirred for 12 hours while maintaining the temperature at 0 ° C. Then, the reaction product was added dropwise to 1000 ml of stirring diethyl ether, and diethyl ether was added at room temperature. After vacuum distillation, the precipitated crystals were recovered by vacuum drying to obtain 20.0 g (yield 97%) of N-methylimidazolium fluoroboronate (MeImBF4). H-NM of this product
The results of the R measurement and the DSC measurement are as shown in Table 2, and the progress of the reaction was confirmed in the same manner as in the above Examples.
There is no content of impurities such as inorganic salts, the melting point is 36.9 ° C, and the temperature dependence of the ion conductivity of this product (1
0-60 ° C.) was as shown in FIG.

Example 12 N-methylimidazole 1
8 g of methanesulfonic acid was added to 0 g, and this was added at a temperature of 0 ° C.
After maintaining for 12 hours, the reaction product was added dropwise to 1000 ml of stirring diethyl ether, diethyl ether was distilled off at room temperature, and vacuum drying was performed to collect the precipitated crystals. 20.1 g (yield: 93%) of N-methylimidazolium methanesulfonate (hereinafter referred to as MeImCH3SO3) was obtained. H-NM of this product
The results of the R measurement and the DSC measurement are as shown in Table 2, and the progress of the reaction was confirmed in the same manner as in the above Examples.
The content of impurities such as inorganic salts was completely absent, the melting point was 129.5 ° C., and the temperature dependence of ionic conductivity (10 to 60 ° C.) of the product was as shown in FIG.

Example 13 N-methylimidazole 1
After adding 197 ml of a 5% aqueous solution of sulfurous acid to 0 g, stirring the mixture for 12 hours while maintaining the temperature at 0 ° C., the reaction product was added dropwise to 1000 ml of stirring diethyl ether, and the diethyl ether was distilled off at room temperature. After that, the resulting crystals were collected by vacuum drying and collected, and N-methylimidazolium sulfite (hereinafter referred to as MeImHSO3) 1
8.2 g (91% yield) was obtained. The results of H-NMR measurement and DSC measurement of this product are as shown in Table 2, and the progress of the reaction was confirmed in the same manner as in the above Examples, and the content of impurities such as inorganic salts was completely absent. Melting point 40.1
° C and the temperature dependence of the ionic conductivity of this product (10-60
° C) was as shown in FIG.

Example 14 N-methylimidazole 1
6 g of 99.7% acetic acid was added to 0 g, and the mixture was stirred for 12 hours while maintaining the temperature at 0 ° C. Then, the reaction product was added dropwise to 1000 ml of stirring diethyl ether, and the diethyl ether was distilled off at room temperature. After that, the precipitate was collected by vacuum drying, and 16.9 g of N-methylimidazolium acetate (referred to as EtImCH3COO) was recovered.
(98% yield). H-NMR measurement and DS of this product
The results of the C measurement are as shown in Table 2. The progress of the reaction was confirmed in the same manner as in the above Examples, the content of impurities such as inorganic salts was completely absent, the melting point was 45.3 ° C, and The temperature dependence (10 to 60 ° C.) of the ionic conductivity of this product was as shown in FIG.

[0026]

[Table 2]

Example 15 N-ethylimidazole 1
0 g and 52 g of vinyl sulfonic acid (25% aqueous solution) were mixed and stirred for 3 hours while maintaining the temperature at 0 ° C., then the solvent was concentrated and ether was added dropwise to add N-ethyl imidazolium vinyl sulfonic acid (EtImVySO 3 and 2)
1.5 g (97% yield) was synthesized. The melting point of this product is -1
At 0 ° C., H-NMR measurement and DSC measurement showed that the chemical shift of EtImVySO3 was 8.986 p.
pm (N-ethylimidazole is 7.565
ppm), the progress of the reaction was confirmed, and there were no impurities such as inorganic salts.

Example 16 1.0 g of N-ethylimidazolium vinylsulfonic acid obtained in Example 15
Is dissolved in methanol, azobisisobutyronitrile is added as a polymerization initiator at a ratio of 1% to the vinyl group, and radical polymerization is performed at 65 ° C. for 3 hours to obtain a molten salt represented by the following formula. A polymer was obtained.

[0029]

Embedded image

The molten salt polymer of N-ethylimidazolium vinylsulfonic acid is a colorless glassy solid, and the progress of the reaction is confirmed by disappearance of peaks based on vinyl groups such as 910 and 990 cm ^-1 in the IR spectrum. did. The glass transition temperature of the product is -40 ° C, and the ionic conductivity at 30 ° C is 2.5 × 10
⁻⁵ , which is considered to be an excellent ion conductor.

Example 17 N-methylimidazole 1
0 g and 57 g of vinyl sulfonic acid (25% aqueous solution) were mixed, stirred for 3 hours while maintaining the temperature at 0 ° C., concentrated, and then ether was added dropwise to add N-methyl imidazolium vinyl sulfonic acid (hereinafter referred to as MeImVySO 3). 22.3
g (yield 92%) was synthesized. When this product was subjected to H-NMR measurement and DSC measurement, the chemical shift of MeImVySO3 was 5.860 ppm (7.518 ppm for N-methylimidazole), and the progress of the reaction was confirmed.

Example 18 1.0 g of N-methylimidazolium vinylsulfonic acid obtained in Example 17
Is dissolved in methanol, azobisisobutyronitrile is added as a polymerization initiator at a ratio of 1% to the vinyl group, and radical polymerization is performed at 65 ° C. for 3 hours to obtain N-
A molten salt polymer of methyl imidazolium vinyl sulfonic acid was obtained. The 1-methyl imidazolium vinyl sulfonic acid molten salt polymer is a colorless glassy solid,
The progress of the reaction depends on the viscosity change and the IR spectrum.
The disappearance of the peak at 40 cm ^-1 was confirmed by NMR. The glass transition temperature of this product was 7 ° C, and the ionic conductivity at 30 ° C was 3.0 × 10 ^−5, which was confirmed to be a good ionic conductor.

[0033]

According to the present invention, an imidazole-based room temperature molten salt containing no impurities can be provided, and various counter anions can be introduced simultaneously with the synthesis of the imidazolium salt, which is suitable for mass production. And an imidazolium salt having various physical properties. The molten salt of the present invention exhibits high ionic conductivity at room temperature, and is excellent in temperature stability and mechanical properties, and thus is useful as a solid electrolyte material.

[Brief description of the drawings]

FIG. 1 is a correlation diagram showing the temperature dependence of the ionic conductivity of an N-ethylimidazolium salt.

FIG. 2 is a correlation diagram showing the temperature dependence of the ionic conductivity of an N-methylimidazolium salt.

Claims (2)

[Claims] 1. An imidazolium-based molten salt comprising as an active ingredient an N-alkylimidazolium salt obtained by reacting an N-alkylimidazole compound having an alkyl group at only one of the first and third positions with an acid. Type electrolyte. 2. An N-alkyl imidazolium salt obtained by reacting an N-alkyl imidazole compound having an alkyl group only at one of the first and third positions with an acid monomer and polymerizing the reaction product is effective. An imidazolium-based molten salt electrolyte as a component.