JP2010111597A - Quaternary ammonium salt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quaternary ammonium salt that is an ordinary-temperature molten salt, which is liquid at ordinary temperature (25°C), and has a low viscosity and a high electroconductivity. <P>SOLUTION: The quaternary ammonium salt is represented by formula (1) (wherein R<SP>1</SP>is a 1-4C alkyl group; R<SP>2</SP>is a methoxymethyl group, a methoxyethyl group or an ethoxymethyl group; and n is a numerical value of 1-4). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a quaternary ammonium salt, an electrolyte, an electrolytic solution, and an electrochemical device.

  In recent years, demands for improving the output density and energy density of electrochemical devices such as batteries and capacitors are increasing, and from the viewpoint of voltage resistance, an organic solution is more frequently used than an aqueous solution. Examples of the organic electrolyte include an alkali metal salt or solid ammonium salt dissolved in an organic solvent such as propylene carbonate. The former is an electrolyte for a lithium ion battery, and the latter is an electrolyte for an electric double layer capacitor. in use. Organic electrolytes are inferior in electrical conductivity compared to aqueous systems, and many studies on organic solvents and electrolytes have been conducted to improve electrical conductivity. For example, an asymmetric ammonium salt is shown as an electrolyte of an electric double layer capacitor (Patent Document 1). In general, tetraethylammonium tetrafluoroborate or triethylmethylammonium tetrafluoroborate is used for the type and electrical conductivity of the tetraalkylammonium salt (Non-patent Document 1).

  In a nonaqueous electrolytic solution in which such a solid electrolyte is dissolved in a solvent, the electrical conductivity of the electrolytic solution varies with the concentration of the electrolyte. As the concentration increases, the ion concentration in the electrolyte increases, and the electrical conductivity increases, but eventually reaches a maximum point. The electrical conductivity reaches a maximum point and begins to decrease as the number of ions in the electrolyte increases, the increase in the interaction between solvent-ions and ions-ions makes it difficult for the electrolyte to dissociate, and at the same time the viscosity of the electrolyte Is considered to increase. If the electrolyte concentration further increases, it can no longer be dissociated and the electrolyte concentration is saturated. Therefore, there has been a problem that when the concentration of the electrolyte is increased, the electrolyte becomes difficult to dissolve. In addition, when an electrolytic solution in which a high concentration of electrolyte is dissolved is used in a low temperature environment, there is a problem that salt precipitation occurs and the electrical conductivity of the electrolytic solution is deteriorated.

  In recent years, a salt having a melting point near room temperature or a salt having a melting point equal to or lower than room temperature (room temperature molten salt) has been found. Such salts are known to dissolve in organic solvents at higher concentrations than ordinary electrolytes. The room temperature molten salt is mixed with the specific organic solvent in an arbitrary ratio. Therefore, it is possible to obtain a high concentration electrolytic solution that could not be achieved by dissolving a conventional solid electrolyte in an organic solvent, and it is difficult to cause a problem that a salt precipitates even in a low temperature environment even though the concentration is high. Furthermore, since the salt itself is a liquid at room temperature, the salt itself can be used as the electrolyte.

  N-methoxymethyl-N-methylpyrrolidinium tetrafluoroborate is known as such a quaternary ammonium salt having high electrical conductivity (Patent Document 2). The quaternary ammonium salt is a room temperature molten salt that is liquid at room temperature, and its electrical conductivity is 7.1 mS / cm at 25 ° C., and has high electrical conductivity.

In addition, N-methoxymethyl-N-methylpyrrolidinium.BF ₃ C ₂ F ₅ is known as a quaternary ammonium salt having a low viscosity and a low melting point and high conductivity and electrochemical stability (patent) Reference 3). The quaternary ammonium salt is a room temperature molten salt having a melting point of room temperature and a liquid, and its electric conductivity is 6.8 mS / cm at 25 ° C., and has a high electric conductivity.

On the other hand, a quaternary ammonium salt which is a liquid room temperature molten salt having a melting point of room temperature and high electrical conductivity is known (Patent Document 4, Non-Patent Documents 2 and 3). The quaternary ammonium salt has a fluorohydrogen ion as an anion, and an N-alkyl-N-alkylpyrrolidinium cation or the like has been studied as a cation.
However, there is a need for quaternary ammonium salts with lower viscosity and high electrical conductivity.
Japanese Patent Publication No. 3-58526 WO 2005/3108 WO 2005/63773 JP 2002-75797 A Ue et al., J. Electrochem. Soc. Vol. 141 2989-2996 (1994) Electrochemicaland Solid-State Letters, 7 (1) E41-E44 (2004) Functional Materials November 2004 Vol.24 No.11 P7-13

  An object of the present invention is to provide a quaternary ammonium salt which is a room temperature molten salt which is liquid at room temperature (25 ° C.) and has a low viscosity and high electrical conductivity.

The present invention relates to the following inventions.
1. A quaternary ammonium salt represented by the formula (1).

（式中、Ｒ^１は、炭素数１〜４のアルキル基、Ｒ^２は、メトキシメチル基、メトキシエチル基、エトキシメチル基を示す。ｎは、１〜４の値を示す。）
２．上記第４級アンモニウム塩の少なくとも１種と、有機溶媒を含有する組成物。
３．有機溶媒が、環状炭酸エステル、鎖状炭酸エステル、ニトリル化合物およびスルホン化合物から選ばれる１種以上の有機溶媒である組成物。
４．第４級アンモニウム塩の少なくとも１種を含有する電気化学デバイス用電解液。
５．上記第４級アンモニウム塩の少なくとも１種と、有機溶媒を含有する電気化学デバイス用電解液。
６．第４級アンモニウム塩の少なくとも１種を含有する電気二重層キャパシタ用電解液。
７．上記第４級アンモニウム塩の少なくとも１種と、有機溶媒を含有する電気二重層キャパシタ用電解液。
８．上記電解液を使用する電気化学デバイス。
９．上記電解液を使用する電気二重層キャパシタ。

(In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms, R ² represents a methoxymethyl group, a methoxyethyl group, or an ethoxymethyl group. N represents a value of 1 to 4.)
2. A composition comprising at least one quaternary ammonium salt and an organic solvent.
3. A composition in which the organic solvent is one or more organic solvents selected from cyclic carbonates, chain carbonates, nitrile compounds, and sulfone compounds.
4). An electrolytic solution for an electrochemical device containing at least one quaternary ammonium salt.
5). An electrolytic solution for an electrochemical device containing at least one quaternary ammonium salt and an organic solvent.
6). An electrolytic solution for an electric double layer capacitor containing at least one quaternary ammonium salt.
7). An electrolytic solution for an electric double layer capacitor containing at least one quaternary ammonium salt and an organic solvent.
8). An electrochemical device using the above electrolytic solution.
9. An electric double layer capacitor using the above electrolyte.

  The quaternary ammonium salt of the present invention is a room temperature molten salt that is liquid at room temperature (25 ° C.), has a low viscosity, high electrical conductivity, and high electrochemical stability.

  The quaternary ammonium salt of the present invention is represented by the formula (1).

（式中、Ｒ^１は、炭素数１〜４のアルキル基、Ｒ^２は、メトキシメチル基、メトキシエチル基、エトキシメチル基を示す。ｎは、１〜４の値を示す。）

(In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms, R ² represents a methoxymethyl group, a methoxyethyl group, or an ethoxymethyl group. N represents a value of 1 to 4.)

The quaternary ammonium salt represented by the formula (1) of the present invention is composed of a quaternary ammonium cation and a fluorohydrogen anion. Examples of R ¹ of the quaternary ammonium cation include linear or branched alkyl groups having 1 to 4 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, and a tert-butyl group. The R ² of the quaternary ammonium cation can include a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group. The fluorohydrocarbon oxygenate anion, n is F (HF) n indicating the value of 1-4 ^- can be exemplified fluorohydrocarbon oxygenate anions represented by. n is not necessarily an integer, preferably a value of 1.5 to 3, more preferably a value of 2 to 2.5.

  Specific examples include N-methoxymethyl-N-methylpyrrolidinium fluorohydrogenate, N-methoxymethyl-N-ethylpyrrolidinium fluorohydrogenate, N-methoxymethyl-Nn-propylpyrrolidinium. Fluorohydrogenate, N-methoxymethyl-N-iso-propylpyrrolidinium fluorohydrogenate, N-methoxymethyl-Nn-butylpyrrolidinium fluorohydrogenate, N-methoxymethyl-N-iso- Butylpyrrolidinium fluorohydrogenate, N-methoxymethyl-N-tert-butylpyrrolidinium fluorohydrogenate, N-methoxyethyl-N-methylpyrrolidinium fluorohydrogenate, N-methoxyethyl-N- Ethyl pylori Nitrofluorohydrogenate, N-methoxyethyl-Nn-propylpyrrolidinium fluorohydrogenate, N-methoxyethyl-N-iso-propylpyrrolidinium fluorohydrogenate, N-methoxyethyl-Nn -Butylpyrrolidinium fluorohydrogenate, N-methoxyethyl-N-iso-butylpyrrolidinium fluorohydrogenate, N-methoxyethyl-N-tert-butylpyrrolidinium fluorohydrogenate, N-ethoxymethyl -N-methylpyrrolidinium fluorohydrogenate, N-ethoxymethyl-N-ethylpyrrolidinium fluorohydrogenate, N-ethoxymethyl-Nn-propylpyrrolidinium fluorohydrogenate, N-ethoxy Methyl-N-iso-propylpyrrolidinium fluorohydrogenate, N-ethoxymethyl-Nn-butylpyrrolidinium fluorohydrogenate, N-ethoxymethyl-N-iso-butylpyrrolidinium fluorohydrogenate N-ethoxymethyl-N-tert-butylpyrrolidinium fluorohydrogenate and the like.

  Although the manufacturing method of the quaternary ammonium fluorohydrogenate represented by Formula (1) of this invention is not limited, For example, it manufactures by making a quaternary ammonium chloride and anhydrous hydrogen fluoride react. Is done. Specifically, it can be obtained by reacting quaternary ammonium chloride with anhydrous hydrogen fluoride to remove by-product hydrogen chloride and excess anhydrous hydrogen fluoride.

  The amount of anhydrous hydrogen fluoride used is 1 molar equivalent or more, preferably 3.5 to 10 molar equivalents relative to the quaternary ammonium chloride. In order to suppress a rapid reaction, it is desirable to cool the quaternary ammonium chloride and the anhydrous hydrogen fluoride when mixing them. Considering the melting point of anhydrous hydrogen fluoride of -83.5 ° C. and the boiling point of 19.5 ° C., the reaction is preferably carried out at this temperature. After completion of the reaction, quaternary ammonium fluorohydrogenate can be obtained by removing by-product hydrogen chloride and excess anhydrous hydrogen fluoride by vacuum. Furthermore, if the operation of adding and removing anhydrous hydrogen fluoride is repeated several times, a highly pure quaternary ammonium fluorohydrogenate can be obtained.

Since the reaction uses hydrogen fluoride, it is desirable to use a resin-based reaction vessel in consideration of corrosion of metals and glass, and in particular, PFA (perfluororesin: tetrafluoroethylene (C ₂ F ₄ ) And a perfluoroalkoxyethylene copolymer) are preferred. Moreover, in order to suppress the mixing of moisture into the electrolytic solution, it is preferable to handle the quaternary ammonium salt in a glove box.
The quaternary ammonium salt obtained by the present invention has low viscosity (7 to 11 cP, 25 ° C.) and high electrical conductivity (73 to 80 mS / cm, 25 ° C.).

The quaternary ammonium salt represented by the formula (1) of the present invention can be used as an electrolyte for an electrochemical device. Examples of the electrochemical device include an electric double layer capacitor, a lithium secondary battery, a dye-sensitized solar cell, an electrochromic element, and a capacitor.
Moreover, the quaternary ammonium salt of the present invention is a room temperature molten salt that is liquid at room temperature (25 ° C.), and the salt itself can be used as an electrolyte.

  When using the quaternary ammonium salt represented by Formula (1) of this invention as an electrolyte, it can be mixed with an organic solvent as needed. Examples of the organic solvent include cyclic carbonate ester, chain carbonate ester, phosphate ester, cyclic ether, chain ether, lactone compound, chain ester, nitrile compound, amide compound, sulfone compound and the like.

  Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, 4-fluoro-1,3-dioxolan-2-one, 4- (trifluoromethyl) -1,3-dioxolan-2-one, and the like. Of these, ethylene carbonate and propylene carbonate are preferable.

  Examples of chain carbonates include dimethyl carbonate, ethyl methyl carbonate, methyl n-propyl carbonate, methyl isopropyl carbonate, n-butyl methyl carbonate, diethyl carbonate, ethyl n-propyl carbonate, ethyl isopropyl carbonate, n-butyl ethyl carbonate, di- Examples include n-propyl carbonate, diisopropyl carbonate, di n-butyl carbonate, fluoroethyl methyl carbonate, difluoroethyl methyl carbonate, trifluoroethyl methyl carbonate, and preferably dimethyl carbonate and ethyl methyl carbonate.

Examples of the phosphate ester include trimethyl phosphate, triethyl phosphate, ethyldimethyl phosphate, diethylmethyl phosphate, and the like.
Examples of the cyclic ether include tetrahydrofuran and 2-methyltetrahydrofuran.
Examples of the chain ether include dimethoxyethane.
Examples of the lactone compound include γ-butyrolactone and γ-valerolactone.
Examples of chain esters include methyl formate, methyl acetate, ethyl acetate, and methyl propionate.
Examples of the nitrile compound include acetonitrile.
Examples of the amide compound include dimethylformamide.
Examples of the sulfone compound include, but are not limited to, sulfolane and methyl sulfolane.
A cyclic carbonate, a chain carbonate, a lactone compound, and a sulfone compound are preferable. These solvents may be used alone or in combination of two or more.

  A method for preparing an electrolytic solution for an electric double layer capacitor using the quaternary ammonium salt represented by the formula (1) of the present invention will be described. The working environment is not particularly limited as long as the atmosphere adversely affects the performance of the electric double layer capacitor, so long as the atmosphere does not mix, but the preparation work is performed in a glove box with an inert atmosphere such as argon or nitrogen. It is preferable to do.

  An electric double layer capacitor can be suitably produced using the electrolytic solution obtained above. As this electric double layer capacitor, a laminated (laminated) type in which electrodes are stacked and accommodated in a can body, a wound type in which the electrodes are wound and accommodated, or an insulating gasket electrically insulated It can be used for any of the so-called coin molds made of metal cans. Moreover, it is not limited to these shapes. Hereinafter, as an example, the structure of a laminated electric double layer capacitor will be described.

  1 and 2 are views showing a laminated electric double layer capacitor. The electrode 3 and the aluminum tab 1 are bonded to each other, are disposed to face each other via the separator 4, and are stored in the laminate container body 2. The electrode is composed of a polarizable electrode portion made of a carbon material such as activated carbon and a current collector portion. The laminate container body 2 is sealed by thermocompression bonding so that moisture and air from the outside of the container do not enter.

  The polarizable electrode material is preferably a material having a large specific surface area and high electrical conductivity, and needs to be electrochemically stable with respect to the electrolyte within the range of applied voltage to be used. Examples of such a material include a carbon material, a metal oxide material, and a conductive polymer material. In view of cost, the polarizable electrode material is preferably a carbon material.

  As the carbon material, an activated carbon material is preferable, and specific examples include sawdust activated carbon, coconut shell activated carbon, pitch coke activated carbon, phenol resin activated carbon, polyacrylonitrile activated carbon, and cellulose activated carbon.

  Examples of the metal oxide material include ruthenium oxide, manganese oxide, and cobalt oxide. Examples of the conductive polymer material include a polyaniline film, a polypyrrole film, a polythiophene film, and a poly (3,4-ethylenedioxythiophene) film.

  For the electrode, the polarizable electrode material is kneaded with a binder such as PTFE, and the pressure-molded one is bound to a current collector such as an aluminum foil with a conductive adhesive, or the polarizable electrode material is It can be obtained by mixing a binder together with a thickener such as CMC or an organic solvent such as pyrrolidone together with a binder, and applying the paste to a current collector such as an aluminum foil, followed by drying.

  The separator preferably has high electronic insulation, excellent wettability of the electrolyte, and high ion permeability, and needs to be electrochemically stable within the applied voltage range. The material of the separator is not particularly limited, but papermaking made of rayon, Manila hemp or the like; polyolefin-based porous film; polyethylene nonwoven fabric; polypropylene nonwoven fabric or the like is preferably used.

  When the quaternary ammonium salt represented by the formula (1) of the present invention is used, an electrolyte solution having low viscosity, high electrical conductivity, and high electrochemical stability can be obtained. it can. In addition, when the electrolytic solution is used, an electric double layer capacitor having a high energy density can be surprisingly obtained.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, it is not limited to these at all.

Example 1 (N-methoxymethyl-N-methylpyrrolidinium fluorohydrogenate)
N-methoxymethyl-N-methylpyrrolidinium chloride (15.226 g, 0.09208 mol) dried at 60 ° C. was placed in a PFA resin reaction vessel (diameter 2.54 cm, length 30 cm) in a glove box, This was sealed with a stainless steel valve joint and connected to a stainless steel vacuum reaction line connected to a gas trap or an alkali trap. After evacuation, anhydrous hydrogen fluoride (about 10 ml) was added to N-methoxymethyl-N-methylpyrrolidinium chloride under cooling (−50 ° C. or lower), and the reaction was slowly returned to room temperature. Byproduct HCl and excess anhydrous hydrogen fluoride were removed under vacuum. Further, introduction of hydrogen fluoride and vacuum removal were repeated twice, and after sufficiently removing chloride ions, the pressure was reduced to 1 Pa under vacuum at room temperature to remove volatile substances and the target N-methoxymethyl-N -Methylpyrrolidinium fluorohydrogenate was obtained. It was a room temperature molten salt that was liquid at room temperature.

Elemental analysis: H: 9.17, C: 42.88, N: 7.20, O: 9.69, F: 31.06 (in mass%)
From the ratio of C and F, n = 2.2.
IR analysis: Absorption bands attributed to fluorohydrogen ions were observed at the following positions. F (HF) n ⁻ (cm ⁻¹ ): 1827 (strong), 2005 (medium), 2612 (medium, broad), 2774 (weak)

The viscosity and electrical conductivity of the obtained N-methoxymethyl-N-methylpyrrolidinium fluorohydrogenate were measured. The measurement results are shown in Table 1.
The capacitor was evaluated using an acrylic resin coin cell shown in FIG. The obtained N-methoxymethyl-N-methylpyrrolidinium fluorohydrogenate was used as the electrolytic solution. The electrode used was a sheet electrode (active carbon (2000 m ² / g) 85 wt%, PTFE 10 wt%, carbon black 5 wt%) that had been dried under vacuum at 200 ° C. to a diameter of 10 mm. A hydrophilic PTFE filter (thickness 25 μm) dried under vacuum at 200 ° C. was used as the separator, and a platinum plate was used as the current collector. The capacity (C) is calculated by charging the battery with a constant potential, and then the amount of electricity (Q) when discharging with a constant current (6.37 mA / cm ² , where the surface area is the apparent surface area) is the charge voltage (V). It was calculated from the relational expression of C = Q / V by dividing. The charging voltage was increased from 1.0 V every 0.1 V, and the measurement was performed up to a voltage slightly larger than the potential at which the capacity showed the maximum value. The energy density (W) was calculated from the relational expression W = (CV ² ) / 2. The measurement results are shown in Table 2.

Comparative Example 1 (N-ethyl-N-methylpyrrolidinium fluorohydrogenate)
N-ethyl-N-methylpyrrolidinium fluorohydrogenate was obtained in the same manner as in Example 1 except that N-ethyl-N-methylpyrrolidinium chloride was used as a raw material.
Table 1 shows the viscosity and electrical conductivity of the obtained N-ethyl-N-methylpyrrolidinium fluorohydrogenate.
Capacitor characteristics were measured in the same manner as in Example 1 except that N-ethyl-N-methylpyrrolidinium fluorohydrogenate was used as the electrolytic solution. The measurement results are shown in Table 2.

It is a front view of the laminate type electric double layer capacitor of the present invention. It is an internal block diagram of the laminate type electric double layer capacitor of this invention. It is an internal block diagram of the acrylic resin coin cell type electric double layer capacitor of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aluminum tab 2 Laminate container 3 Electrode 4 Separator 5 Acrylic resin 6 Current collector 7 Separator 8 Gasket 9 Electrode

Claims (10)

A quaternary ammonium salt represented by the formula (1).

(In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms, R ² represents a methoxymethyl group, a methoxyethyl group, or an ethoxymethyl group. N represents a value of 1 to 4.) The quaternary ammonium salt according to claim 1, wherein R ² is a methoxymethyl group. A composition comprising at least one quaternary ammonium salt according to claim 1 and an organic solvent. The composition according to claim 3, wherein the organic solvent is one or more organic solvents selected from cyclic carbonates, chain carbonates, nitrile compounds, and sulfone compounds. The electrolyte solution for electrochemical devices containing at least 1 sort (s) of the quaternary ammonium salt of Claim 1. The electrolyte solution for electrochemical devices containing the composition of Claim 3. An electrolytic solution for an electric double layer capacitor comprising at least one quaternary ammonium salt according to claim 1. An electrolytic solution for an electric double layer capacitor containing the composition according to claim 3. The electrochemical device using the electrolyte solution in any one of Claims 5-6. The electric double layer capacitor which uses the electrolyte solution in any one of Claims 7-8.

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