JP2007095983A - Manufacturing method of electrolyte for electrochemical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrolyte capable of markedly reducing the aging property degradation of an electrochemical element, in particular an electrochemical capacitor. <P>SOLUTION: The method of manufacturing the electrolyte for an electrochemical element includes a step of separating and refining alkyl imidazole (a), having an alkyl group at least in first and second places from a reaction product of glyoxal or its acetal, or its ketal (d1), ammonium (d2), aldehyde (d3), and primary amine (d4), preferably by distillation, thereby specifying the content of the alkyl imidazole (a0), having a hydrogen atom substituted for the second place to be 15 wt.% or lower for a total weight of (a) and (a0). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for producing an electrolytic solution for an electrochemical element. More specifically, the present invention relates to a method for producing a purified electrolyte solution for an electrochemical element, the main component of which is a quaternary salt of alkylimidazole having substituents at least at the 1-position and 2-position.

A quaternary salt of alkylimidazole having substituents at least at the 1-position and the 2-position is a compound useful as an electrolytic solution for electrochemical devices (for example, Patent Document 1).
As the method for producing the alkylimidazole, there is known a method for producing an alkylimidazole characterized by reacting glyoxal, aldehyde, primary amine and ammonia in an aqueous medium at a temperature of 20 to 150 ° C. in one step. (For example, Patent Documents 2 and 3).
JP2005-197666 Patent 1697394 JP2004-207451

In the conventional method for producing an alkylimidazole having a substituent at at least the 1-position and the 2-position, a by-product that is an alkylimidazole having no substituent at the 2-position may be obtained. In an electrolytic solution for an electrochemical device comprising a quaternary salt of an alkylimidazole containing such a by-product, sufficient performance may not be obtained. That is, the object of the present invention is an electrolysis for an electrochemical device comprising a quaternary salt of an alkyl imidazole having substituents at least at the 1-position and the 2-position, with few by-products, which is an alkyl imidazole having no substituent at the 2-position. It is to provide a method for producing a liquid.

［式中、Ｒ_１、及びＲ₂は炭素数１〜３のアルキル基であって、同じであっても異なっていてもよく、Ｒ₄及びＲ₅は水素原子又は炭素数１〜３のアルキル基であって、同じであっても異なっていてもよい。］

［式中、Ｒ_１、Ｒ₄及びＲ₅は一般式（１）と同じである。］
及び、第２の発明、グリオキサール類又はそのアセタール又はそのケタール（ｄ１）、アンモニア（ｄ２）、及びアルデヒド（ｄ３）の反応生成物から一般式（２）で示されるアルキルイミダゾール（ｂ）を分離、精製することにより、一般式（６）で示されるアルキルイミダゾール（ｂ０）の含有量を（ｂ）と（ｂ０）の合計重量に対して１５重量％以下にし、さらにアルキル化することで、一般式（３）で示されるアルキルイミダゾール（ａ０’）の含有量を一般式（１）で示されるアルキルイミダゾール（ａ’）と（ａ０’）の合計重量に対して、１５重量％以下にすることを特徴とする電気化学素子用電解液の製造方法。

［式中、Ｒ_１、及びＲ₂は炭素数１〜３のアルキル基であって、同じであっても異なっていてもよく、Ｒ₄及びＲ₅は水素原子又は炭素数１〜３のアルキル基であって、同じであっても異なっていてもよい。］

［式中、Ｒ₂、Ｒ₄及びＲ₅は一般式（１）と同じである。］

［式中、Ｒ_１、Ｒ₄及びＲ₅は一般式（１）と同じである。］

［式中、Ｒ₄及びＲ₅は一般式（１）と同じである。］ The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems.
That is, the present invention is represented by the general formula (1) from the reaction product of the first invention, glyoxal or its acetal or its ketal (d1), ammonia (d2), aldehyde (d3) and primary amine (d4). By separating and purifying the alkylimidazole (a), the content of the alkylimidazole (a0) represented by the general formula (3) is reduced to 15% by weight or less with respect to the total weight of (a) and (a0). A method for producing an electrolytic solution for an electrochemical element,

[Wherein R ₁ and R ₂ are alkyl groups having 1 to 3 carbon atoms, and may be the same or different, and R ₄ and R ₅ are a hydrogen atom or alkyl having 1 to 3 carbon atoms. Groups that may be the same or different. ]

[Wherein, R ₁ , R ₄ and R ₅ are the same as those in the general formula (1). ]
And the second invention, glyoxal or its acetal or its ketal (d1), ammonia (d2), and alkylimidazole (b) represented by the general formula (2) are separated from the reaction product of aldehyde (d3), By purifying, the content of the alkylimidazole (b0) represented by the general formula (6) is reduced to 15% by weight or less based on the total weight of (b) and (b0), and further alkylation is performed. The content of the alkylimidazole (a0 ′) represented by (3) should be 15% by weight or less based on the total weight of the alkylimidazole (a ′) and (a0 ′) represented by the general formula (1). A method for producing an electrolytic solution for an electrochemical element.

[Wherein R ₁ and R ₂ are alkyl groups having 1 to 3 carbon atoms, and may be the same or different, and R ₄ and R ₅ are a hydrogen atom or alkyl having 1 to 3 carbon atoms. Groups that may be the same or different. ]

[Wherein R ₂ , R ₄ and R ₅ are the same as those in the general formula (1). ]

[Wherein, R ₁ , R ₄ and R ₅ are the same as those in the general formula (1). ]

[Wherein, R ₄ and R ₅ are the same as those in the general formula (1). ]

Since the electrolytic solution for electrochemical devices produced by the method for producing an electrolytic solution for electrochemical devices of the present invention has an extremely high withstand voltage, it is possible to produce an electrochemical device with very little performance deterioration over time.

First, the first invention will be described.
The reaction product (e) of glyoxal or its acetal or its ketal (d1), ammonia (d2), aldehyde (d3) and primary amine (d4) is an alkylimidazole (a) represented by the above general formula (1) And an alkylimidazole (a0) represented by the general formula (3).

In the reaction product (e), the content of (a0) is about 16 to 35% by weight based on the total weight of (a) and (a0).

In the present invention, examples of the glyoxal or its acetal or its ketal (d1) include the following compounds.
(1) Dialdehydes such as glyoxal.
(2) Diketones such as biacetylene.
(3) Ketoaldehydes methyl glyoxal, ethyl glyoxal, propyl glyoxal, and the like.
(4) Acetals and ketals Glyoxal-bis-dimethylacetal, glyoxal-bis-methylethyl acetal and the like.

  Of these, glyoxal and methylglyoxal are preferable. Two or more of these may be used.

In the present invention, examples of the aldehyde (d3) include the following compounds.
Formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, isovaleraldehyde and the like.
Of these, preferred are formaldehyde, acetaldehyde, and propionaldehyde. Two or more of these may be used.

In the present invention, examples of the primary amines (d4) include the following compounds.
Methylamine, ethylamine, n-propylamine, isopropylamine, cyclopropylamine and the like.
Of these, methylamine, ethylamine, and propylamine are preferable. Two or more of these may be used.

In the present invention, examples of the alkylimidazole (a) include the following compounds.
1-ethyl-2-methylimidazole, 1,2-dimethylimidazole, 1-methyl-2-ethylimidazole, 1,2,4-trimethylimidazole, 1,4-dimethyl-2-ethylimidazole, 1-methyl-2 -Propylimidazole, 1-ethyl-2-propylimidazole and the like. Of these, 1-ethyl-2-methylimidazole, 1,2-dimethylimidazole, and 1,2,4-trimethylimidazole are preferable.

In the present invention, examples of the alkylimidazole (a0) include the following compounds.
2-methylimidazole, 2-ethylimidazole, 2,4-dimethylimidazole, 4-methyl-2-ethylimidazole, 2-propylimidazole, and the like. Of these, 2-methylimidazole and 2,4-dimethylimidazole are preferred.

The reaction of glyoxal or its acetal or its ketal (d1), ammonia (d2), aldehyde (d3) and primary amine (d4) is preferably carried out under the following conditions.
It is preferable to carry out under normal pressure or pressurization in an inert gas (for example, nitrogen etc.) atmosphere, and it is more preferable to carry out under normal pressure. The reaction is preferably performed by a batch method or a continuous method, but the batch method is more preferable in terms of operability. The reaction temperature is preferably 0 to 200 ° C, more preferably 0 to 150 ° C, and further preferably 20 to 100 ° C. The reaction rate is good at 0 ° C. or higher, and the reaction yield is good at 200 ° C. or lower. The reaction time is usually 1 minute to 100 hours, preferably 10 minutes to 50 hours, more preferably 30 minutes to 10 hours.
The details of the production method can be performed in accordance with, for example, the method described in JP-A-2004-207451.

The method of separating and purifying the alkylimidazole (a) represented by the general formula (1) from the reaction product (e) includes distillation, recrystallization, extraction with a solvent, silica gel, activated carbon, activated alumina, special molecular A method of adsorbing with an adsorbent such as a sieve is exemplified. Of these methods, distillation is preferred.
Distillation is preferably carried out using a distillation apparatus having 10 or more theoretical plates in a temperature range of 50 ° C. to 210 ° C., preferably 70 ° C. to 150 ° C., and a pressure of 30 kPa or less, preferably 15 kPa.

The reaction product (e) becomes a purified alkylimidazole (a) by the above separation and purification.
The purified alkylimidazole (a) contains alkylimidazole (a) and alkylimidazole (a0), but the content of alkylimidazole (a0) is preferably 15 with respect to the total weight of (a) and (a0). % By weight or less, more preferably 10% by weight or less, more preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

The content of (a), (a0), etc. can be measured, for example, by gas chromatography (hereinafter abbreviated as GC). GC conditions are: column: capillary column, carrier gas: helium, flow rate: 24.5 kPa (constant pressure), temperature: 60 ° C. to 250 ° C. at a rate of 10 ° C./min, detector: FID (for example, instrument: Model name (GC-17A), manufacturer (Shimadzu Corporation), column: DB-5 (length: 30 m, width: 0.53 mm, internal diameter: 1.5 μm) manufacturer (manufactured by J & W Scientific), calibration curve Then, the weight ratio of (a) and (a0) is calculated.

The electrolyte component of the electrolytic solution for electrochemical devices is composed of an imidazolium salt (A) represented by the general formula (4).

［式中、Ｒ_１、Ｒ₂、Ｒ₄及びＲ₅は一般式（１）と同じである。Ｒ₃は炭素数１〜３のアルキル基である。Ｘ⁻は対アニオンを示す。］

[Wherein R ₁ , R ₂ , R ₄ and R ₅ are the same as those in the general formula (1). R ₃ is an alkyl group having 1 to ₃ carbon atoms. X ⁻ represents a counter anion. ]

The imidazolium salt (A) is obtained by quaternizing the alkylimidazole (a) with an alkylating agent such as dialkyl carbonate or alkyl chloride, and acid-exchange the obtained carbonate ester salt or chloro salt with a counter anion. Is obtained.

The imidazolium salt (A) contains an imidazolium salt (A0) represented by the general formula (5).

［式中、Ｒ_１、Ｒ_３、Ｒ₄及び、Ｒ₅及びＸ⁻は一般式（４）と同じである。］

[Wherein R ₁ , R ₃ , R ₄ , R ₅ and X ⁻ are the same as those in the general formula (4). ]

The content of the imidazolium salt (A0) is preferably 15% by weight or less, more preferably 10% by weight or less, more preferably 5% by weight or less, particularly preferably based on the total weight of (A) and (A0). Is 2% by weight or less, very preferably 1% by weight or less.
The electrolyte for an electrochemical element is made of the imidazolium salt (A) itself, or is prepared by dissolving (A) in a non-aqueous solvent.
The electrolytic solution produced by the method for producing an electrolytic solution for electrochemical devices of the present invention has a small content of imidazolium salt (A0) as an impurity and a very high withstand voltage, so that the performance deterioration with time is extremely small. An electrochemical device can be manufactured.

Examples of the imidazolium salt (A) include salts composed of the following cations.
(1) 1,2,3-position substitution product 1,2,3-trimethylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-methyl-2-ethyl-3-methylimidazolium, 1,2 -Diethyl-3-methylimidazolium, 1,3-diethyl-2-methylimidazolium, 1,2,3-triethylimidazolium, 1-propyl-2,3-dimethylimidazolium and 1-isopropyl-2,3 -Dimethylimidazolium and the like.

(2) 1,2,3,4-position substituted 1,2,3,4-tetramethylimidazolium, 1-ethyl-2,3,4-trimethylimidazolium, 2-ethyl-1,3,4 Trimethylimidazolium, 1,2-diethyl-3,4-dimethylimidazolium, 1,3-diethyl-2,4-dimethylimidazolium, 1,2,3-triethyl-4-methylimidazolium, 1,2, 3-trimethyl-
4-ethylimidazolium, 1,4-diethyl-2,3-dimethylimidazolium, 2,
4-diethyl-1,3-dimethylimidazolium, 1,2,4-triethyl-3-methylimidazolium, 1,3,4-triethyl-2-methylimidazolium, 1,2,3,4
-Tetraethylimidazolium, 1-propyl-2,3,4-trimethylimidazolium, 1-isopropyl-2,3,4-trimethylimidazolium and the like.

(3) 1,2,3,5-position substitution product 1,2,3,5-tetramethylimidazolium, 1-ethyl-2,3,5-trimethylimidazolium, 1,2-diethyl-3,5- Dimethylimidazolium, 1,5-diethyl-2,3-dimethylimidazolium, 1,2,5-triethyl-3-methylimidazolium, 1-propyl-2,3,5-trimethylimidazolium and 1-isopropyl- 2,3,5-trimethylimidazolium and the like.

(4) 1,2,3,4,5-position substitution product 1,2,3,4,5-pentamethylimidazolium, 1-ethyl-2,3,4,5-tetramethylimidazolium, 2-ethyl -1,3,4,5-tetramethylimidazolium, 3-ethyl-1,2,4,5-tetramethylimidazolium, 4-ethyl-1,2,3,5-tetramethylimidazolium, 1, 2,3,4,5-pentaethylimidazolium, 1-propyl-2,3,4,5-tetramethylimidazolium, 1-isopropyl-2,3,4,5-tetramethylimidazolium and the like.

Among these cations, from the viewpoint of withstand voltage and solubility, etc., (1) 1,2,3-position substitution product, (2) 1,2,3,4-position substitution product and (3) 1,2,3, A cation which is a 5-position substitution product is preferred, and (1) and (2) are more preferred.
Particularly preferred among (1) and (2) are those having a methyl group at the 2-position, such as 1,2,3-trimethylimidazolium, 1,2,3,4-tetramethylimidazolium and 1- Ethyl-2,3-dimethylimidazolium is more preferred, then particularly preferred 1,2,3-trimethylimidazolium and 1-ethyl-2,3-dimethylimidazolium, most preferred 1-ethyl-2,3 -Dimethylimidazolium.

The counter anion X ⁻ is PF ₆ ⁻ , BF ₄ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , N (RfSO ₃ ) ₂ ⁻ , C (RfSO ₃ ) ₃ ⁻ , RfSO ₃ ⁻ , where Rf has 1 to 12 carbon atoms. Fluoroalkyl group), F ⁻ , ClO ₄ ⁻ , AlF ₄ ⁻ , AlCl ₄ ⁻ , TaF ₆ ⁻ , NbF ₆ ⁻ , SiF ₆ ⁻ , CN ⁻ or F (HF) _n ⁻ (n is a number from 1 to 4) An anion represented by PF ₆ ⁻ , BF ₄ ⁻ or N (RfSO ₃ ) ₂ ⁻ , particularly preferably PF ₆ ⁻ or An anion represented by BF ₄ ⁻ , most preferably an anion represented by BF ₄ ⁻ . In addition, Rf contained in the anion represented by N (RfSO ₃ ) ₂ ⁻ , C (RfSO ₃ ) ₃ ^— or RfSO ₃ ^— represents a fluoroalkyl group having 1 to 12 carbon atoms, and includes trifluoromethyl, pentafluoro Examples include ethyl, heptafluoropropyl and nonafluorobutyl. Of these, trifluoromethyl, pentafluoroethyl and heptafluoropropyl are preferable, trifluoromethyl and pentafluoroethyl are more preferable, and trifluoromethyl is particularly preferable.

Preferred examples of the imidazolium salt (A), 1,2,3-trimethyl imidazolium tetrafluoroborate (BF ₄ ^- salt), 1,2,3,4-tetramethyl imidazolium tetrafluoroborate, 1-ethyl 2,3-dimethyl-imidazolium tetrafluoroborate, 1,2,3-methylimidazolium hexafluorophosphate (PF ₆ ^- salt), 1,2,3,4-methylimidazolium hexafluorophosphate, 1-ethyl -2,3-dimethylimidazolium hexafluorophosphate and the like.

Examples of the imidazolium salt (A0) include those obtained by substituting the alkyl group at the 2-position of the corresponding imidazolium salt (A) with a hydrogen atom.
Specifically, the imidazolium salt (A0) includes salts composed of the following cations.
(1) 1,3-position substitution product 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,3-diethylimidazolium, 1-propyl-3-methylimidazolium and 1-isopropyl-3 -Methyl imidazolium and the like.

(2) 1,3,4-Substituted 1,3,4-trimethylimidazolium, 1-ethyl-3,4-dimethylimidazolium, 3-ethyl-1,4-dimethylimidazolium, 1,3-diethyl -4-methylimidazolium, 1,3-dimethyl-4-ethylimidazolium, 1,4-diethyl-3-methylimidazolium, 3,4-diethyl-1-methylimidazolium, 1,3,4-triethyl Imidazolium, 1-propyl-3,4-dimethylimidazolium, 1-isopropyl-3,4-dimethylimidazolium and the like.

(3) 1,3,5-position substitution product 1,3,5-trimethylimidazolium, 1-ethyl-3,5-dimethylimidazolium, 1,3-diethyl-3-methylimidazolium, 1,5-diethyl -3-methylimidazolium, 1,3,5-triethylimidazolium, 1-propyl-3,5-dimethylimidazolium, 1-isopropyl-3,5-dimethylimidazolium and the like.

(4) 1,3,4,5-position substitution product 1,3,4,5-tetramethylimidazolium, 1-ethyl-3,4,5-trimethylimidazolium, 3-ethyl-1,4,5- Trimethylimidazolium, 4-ethyl-1,3,5-trimethylimidazolium, 1,3,4,5-tetraethylimidazolium, 1-propyl-3,4,5-trimethylimidazolium and 1-isopropyl-3, 4,5-trimethylimidazolium and the like.

Examples of combinations of imidazolium salt (A) and imidazolium salt (A0) include 1,2,3-trimethylimidazolium tetrafluoroborate and 1,3-dimethylimidazolium tetrafluoroborate, 1,2,3, 4-tetramethylimidazolium tetrafluoroborate and 1,3,4-trimethylimidazolium tetrafluoroborate, 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium tetrafluoroborate Etc.

The contents of the imidazolium salt (A) and the imidazolium salt (A0) can be quantified by high performance liquid chromatography (HPLC). The HPLC conditions are: column: polymer-coated filler, mobile phase: phosphate buffer (pH 2-3), flow rate: 0.5 ml / min, detector: UV, temperature: 40 ° C. (for example, instrument: Model name (LC-10A), manufacturer (Shimadzu Corporation), column: Develosil C30-UG (4.6 mmφ × 25 cm) manufacturer (Nomura Chemical), mobile phase: phosphoric acid concentration 10 mmol / l, sodium perchlorate concentration 100 mmol / l aqueous solution, flow rate: 0.8 ml / min, detector: UV (210 nm), injection volume: 20 μl, column temperature: 40 ° C.). Using the calibration curve, the weight ratio of (A) and (A0) is calculated.

As the non-aqueous solvent, known ones can be used, which can be appropriately selected in consideration of the solubility and electrochemical stability of the imidazolium salt (A). Examples include the following. Two or more of these can be used in combination.

Ether: C4-12 chain ether (diethyl ether, methyl isopropyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, etc.) And a cyclic ether having 4 to 12 carbon atoms {tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 4-butyldioxolane and crown ether (1,4,7,10,13,16-hexaoxacyclooctadecane, etc.) And so on.

Amides: chain amides having 3 to 6 carbon atoms (N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylpropionamide, hexamethylphosphorylamide, etc.) and cyclic having 4 to 6 carbon atoms Amides (such as pyrrolidinone, N-methylpyrrolidinone and N-vinylpyrrolidinone).
Carboxylic acid esters: chain esters having 3 to 8 carbon atoms (such as methyl acetate, methyl propionate and dimethyl adipate) and cyclic esters having 4 to 5 carbon atoms (γ-butyrolactone, α-acetyl-γ-butyrolactone, β-butyrolactone, γ-valerolactone, δ-valerolactone, etc.).
Nitrile: Nitriles having 2 to 5 carbon atoms (acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, 3-ethoxypropionitrile, acrylonitrile, etc.).
Carbonate: C3-C4 chain carbonate (dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, etc.) and C3-C4 cyclic carbonate (ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, etc.).
Sulphoxide: chain sulphoxide having 2 to 6 carbon atoms (such as dimethyl sulphoxide and dipropyl sulphoxide).
Sulfone: cyclic sulfone having 4 to 6 carbon atoms (sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, etc.).
Nitro compounds: nitromethane, nitroethane, etc.
Other cyclic compounds: N-methyl-2-oxazolidinone, 3,5-dimethyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and the like.

Of these, carbonate, sulfone, carboxylic acid ester and nitrile are preferable, carbonate, sulfone and nitrile are more preferable, ethylene carbonate, propylene carbonate and sulfolane are particularly preferable, and propylene carbonate and sulfolane are most preferable. These non-aqueous solvents may be a mixture of two or more, but in the case of a mixture, propylene carbonate, ethylene carbonate, butylene carbonate, sulfolane, methyl sulfolane, acetonitrile, γ-butyrolactone, dimethyl carbonate, ethyl methyl carbonate and Preferably, the main component is at least one selected from the group consisting of diethyl carbonate, more preferably at least one selected from the group consisting of propylene carbonate, ethylene carbonate, sulfolane, acetonitrile, and γ-butyrolactone. Particularly preferably, the main component is at least one selected from the group consisting of propylene carbonate, sulfolane, and acetonitrile. Here, “main component” means that 50 to 99% by weight, preferably 70 to 90% by weight, of the non-aqueous solvent is contained.
As mentioned above, when the main component is at least one selected from the group consisting of propylene carbonate, ethylene carbonate, sulfolane, acetonitrile and γ-butyrolactone, it is selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate. It is preferable to use at least one kind as a co-solvent. As the co-solvent, dimethyl carbonate and ethyl methyl carbonate are more preferable, and dimethyl carbonate is particularly preferable. Here, “use as a secondary solvent” means containing 1 to 50% by weight, preferably 10 to 30% by weight, of the non-aqueous solvent.

The content (% by weight) of the nonaqueous solvent in the electrolytic solution is preferably 30 to 95, more preferably 40 to 90, particularly preferably 50 to 85, and most preferably 60 to 60, based on the weight of the electrolytic solution. 80. Within this range, salt precipitation at low temperatures is unlikely to occur, and the performance deterioration of the electrochemical capacitor over time can be further improved.

The water content (ppm) in the electrolytic solution for electrochemical elements is preferably 300 or less, more preferably 100 or less, particularly preferably 50 or less, based on the capacity of the electrolytic solution, from the viewpoint of electrochemical stability. . Within this range, it is possible to suppress deterioration of the electrochemical device over time.
The water content in the electrolytic solution can be measured by the Karl Fischer method (JIS K0113-1997, coulometric titration method).
Examples of the method of setting the water content in the electrolytic solution in the above range include a method of using a sufficiently dried electrolyte salt (A) and a non-aqueous solvent sufficiently dehydrated in advance.
Examples of the drying method include a method of heating and drying under reduced pressure (for example, heating at 150 ° C. under a reduced pressure of 20 Torr) and evaporating and removing a trace amount of water contained therein.
As the dehydration method, heat dehydration under reduced pressure (for example, heating at 100 Torr) to evaporate and remove a trace amount of water, molecular sieve (manufactured by Nacalai Tesque, 3A 1/16, etc.), activated alumina powder And a method using a dehydrating agent.
In addition to these, the electrolytic solution is heated and dehydrated under reduced pressure (for example, heated at 100 ° C. under reduced pressure of 100 Torr) to evaporate and remove a trace amount of water, molecular sieve, activated alumina powder, etc. And a method of using a dehydrating agent. These methods may be performed alone or in combination. Of these, the method of drying (A) by heating under reduced pressure and the method of adding molecular sieve to the electrolyte are preferred.

In the present invention, the electrochemical element includes an electrochemical capacitor, an electrochemical cell, an electrochemical sensor, and the like.

Next, the second invention will be described.
The reaction product (e ′) of glyoxal or its acetal or its ketal (d1), ammonia (d2), and aldehyde (d3) is an alkylimidazole (b) represented by the above general formula (2) and a general formula ( It is a mixture containing the alkylimidazole (b0) etc. shown by 6).

［式中、Ｒ₄及びＲ₅は一般式（２）と同じである。］

[Wherein, R ₄ and R ₅ are the same as those in the general formula (2). ]

In the reaction product (e ′), the content of (b0) is about 16 to 35% by weight based on the total weight of (b) and (b0).

In the present invention, examples of the alkylimidazole (b) include the following compounds.
2-methylimidazole, 2-ethylimidazole, 2,4-dimethylimidazole, 4-methyl-2-ethylimidazole, 2-propylimidazole, and the like. Of these, 2-methylimidazole and 2,4-dimethylimidazole are preferred.
In the present invention, examples of the alkylimidazole (b0) include the following compounds.
Imidazole, 4-methylimidazole, 4,5-dimethylimidazole, etc.

The reaction of glyoxal or its acetal or its ketal (d1), ammonia (d2), and aldehyde (d3) is preferably carried out under the following conditions.
It is preferable to carry out under normal pressure or pressurization in an inert gas (for example, nitrogen etc.) atmosphere, and it is more preferable to carry out under normal pressure. The reaction is preferably performed by a batch method or a continuous method, but the batch method is more preferable in terms of operability. The reaction temperature is preferably 0 to 200 ° C, more preferably 0 to 150 ° C, and further preferably 20 to 100 ° C. The reaction rate is good at 0 ° C. or higher, and the reaction yield is good at 200 ° C. or lower. The reaction time is usually 1 minute to 100 hours, preferably 10 minutes to 50 hours, more preferably 30 minutes to 10 hours.

The method for separating and purifying the alkylimidazole (b) represented by the general formula (1) from the reaction product (e ′) includes distillation, recrystallization, extraction with a solvent, silica gel, activated carbon, activated alumina, special A method of adsorbing with an adsorbent such as a molecular sieve is exemplified. Of these methods, distillation or recrystallization is preferred.
Distillation is preferably carried out using a distillation apparatus having 10 or more theoretical plates in a temperature range of 50 ° C. to 210 ° C., preferably 70 ° C. to 150 ° C., and a pressure of 30 kPa or less, preferably 15 kPa.
Recrystallization is performed by dissolving in a polar solvent such as methanol or ethanol and mixing with an ether solvent.

The reaction product (e ′) becomes a purified alkylimidazole (b) by the above separation and purification.
The purified alkylimidazole (b) contains at least alkylimidazole (b) and imidazole (b0), but the content of imidazole (b0) is preferably 15 with respect to the total weight of (b) and (b0). % By weight or less, more preferably 10% by weight or less, more preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

Next, the purified alkylimidazole (b) is alkylated to obtain the alkylimidazole (a ′) represented by the general formula (1).
Examples of the alkylating agent (c) include the following compounds (1) to (7).
(1) Carbonic acid diester Dimethyl carbonic acid, methyl ethyl carbonic acid, diethyl carbonic acid, methyl-i-propyl carbonic acid, di-n-propyl carbonic acid and the like.
(2) Alkyl halides Methyl chloride, methyl bromide, methyl iodide, ethyl chloride, ethyl bromide, ethyl iodide, n-propyl chloride, isopropyl chloride, n-propyl bromide, isopropyl bromide, n-iodide Propyl, isopropyl iodide and the like.
(3) Sulfuric acid diester Dimethyl sulfate, diethyl sulfate, di-n-propyl sulfate, diisopropyl sulfate and the like.
(4) Carboxylic acid ester Methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl acrylate, methyl methacrylate, methyl lactate, methyl oxalate, methyl benzoate and the like.
(5) Nitric acid ester Dimethyl nitrate, di-n-propyl nitrate and the like.
(6) Sulfonic acid ester Methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, methyl benzenesulfonate, ethyl benzenesulfonate, methyl p-toluenesulfonate, ethyl p-toluenesulfonate, etc. .

  Of these, carbonic acid diesters and alkyl halides are preferred.

Alkylation can also be carried out under an inert gas (for example, nitrogen) atmosphere at normal pressure or under pressure. The reaction rate is improved by pressurization. The pressure is usually 1 × 10 ⁵ to 1 × 10 ⁷ Pa, the reaction temperature is usually 0 to 300 ° C., preferably 20 to 250 ° C., more preferably 50 to 200 ° C. The reaction time is usually 1 minute to 200 hours, preferably 30 minutes to 100 hours.

The method for obtaining an electrolytic solution for an electrochemical device by further quaternizing alkylimidazole (a ′) and then performing an acid exchange reaction is the same as in the first invention.
Alkyl imidazole (a ′) is the same compound as alkyl imidazole (a). A by-product which is an alkylimidazole having no substituent at the 2-position in the alkylimidazole (a ′), and a secondary product having no substituent at the 2-position obtained by further quaternization and then an acid exchange reaction. The content of the organism is the same as in the first invention.

Hereinafter, although an example and a comparative example explain the present invention, the present invention is not limited to this. Hereinafter, “parts” means “parts by weight” unless otherwise specified.

Example 1
A reaction flask equipped with a stirrer, thermometer, dropping funnel, reflux condenser, and nitrogen gas inlet tube was charged with a mixture of 31 parts of ethylamine (70% aqueous solution) and 32 parts of ammonia (28% aqueous solution) while stirring. A homogeneous solution was obtained. While maintaining the temperature at 45 ° C. or lower, a mixed solution of 69 parts of glyoxal (40% aqueous solution) and 71 parts of acetaldehyde (30% aqueous solution) was dropped from the dropping funnel. The mixture of glyoxal and acetaldehyde was added dropwise over 5 hours. After completion of the addition, the mixture was reacted at 40 ° C. for 1 hour to give 1-ethyl-2-methylimidazole (a-1) and 1-ethylimidazole (b-1). ) Mixture (M-1) was obtained. As a result of HPLC analysis, the weight ratio of (a-1) to (b-1) was (80:20). Next, dehydration was performed by gradually reducing the pressure from 80 ° C. and normal pressure to 5.0 kPa, followed by purification under distillation at a temperature of 105 ° C. and a pressure of 1.0 kPa to obtain a mixture (M-2). . As a result of HPLC analysis, the weight ratio of (a-1) to (b-1) was 85:15.
Next, 100 parts of the mixture (M-2) obtained in a stainless steel autoclave with a reflux condenser, 135 parts of dimethyl carbonate, and 192 parts of methanol were charged and uniformly dissolved. Next, the temperature was raised to 130 ° C. The reaction was performed at a pressure of 0.8 MPa for 80 hours. NMR analysis of the reaction product showed that 1-ethyl-2,3-dimethylimidazolium monomethyl carbonate and 1-ethyl-3-dimethylimidazolium monomethyl carbonate were produced. 427 parts of the resulting reaction mixture was placed in a flask, and 207 parts of a borohydrofluoric acid aqueous solution (purity 42% by weight) was gradually added dropwise over about 30 minutes at room temperature with stirring. Carbon dioxide gas was generated along with the dripping. After generation | occurrence | production of foam | bubble was stopped, the reaction liquid was moved to the rotary evaporator and the whole quantity of solvent was removed. In the flask, 83 parts of a yellowish brown transparent liquid remained. When this solution was subjected to NMR analysis, the main components were 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate (hereinafter abbreviated as EDMI) and 1-ethyl-3-methylimidazolium tetrafluoroborate (hereinafter abbreviated as EMI). From the HPLC analysis, the weight ratio was 85:15. 210 g of the obtained mixture of EDMI and EMI was uniformly dissolved in propylene carbonate to make the whole 1 liter, and the electrolytic solution of the present invention was prepared.

Example 2
The mixture (M-2) of 1-ethyl-2-methylimidazole (a-1) and 1-ethylimidazole (b-1) obtained in Example 1 was further subjected to conditions of a temperature of 105 ° C. and a pressure of 1.0 kPa. To obtain a mixture (M-3) of (a-1) and (b-1). As a result of HPLC analysis, the weight ratio of (a-1) to (b-1) was 90:10.
When the resulting mixture was treated in the same manner as in Example 1, a yellowish brown transparent liquid was obtained. When this liquid was analyzed by NMR, the main components were EDMI and EMI, and the weight ratio was 90:10 by HPLC analysis. 211 g of the obtained mixture of EDMI and EMI was uniformly dissolved in propylene carbonate to make the whole 1 liter, and the electrolytic solution of the present invention was prepared.

Example 3
The mixture (M-2) of 1-ethyl-2-methylimidazole (a-1) and 1-ethylimidazole (b-1) obtained in Example 2 was further subjected to conditions of a temperature of 105 ° C. and a pressure of 1.0 kPa. To obtain a mixture (M-3) of (a-1) and (b-1). As a result of HPLC analysis, the weight ratio of (a-1) to (b-1) was 95: 5.
When the resulting mixture was treated in the same manner as in Example 1, a yellowish brown transparent liquid was obtained. As a result of NMR analysis of this solution, the main components were EDMI and EMI, and the weight ratio was 95: 5 by HPLC analysis. 211 g of the obtained mixture of EDMI and EMI was uniformly dissolved in propylene carbonate to make the whole 1 liter, and the electrolytic solution of the present invention was prepared.

Example 4
The mixture (M-3) of 1-ethyl-2-methylimidazole (a-1) and 1-ethylimidazole (b-1) obtained in Example 3 was further subjected to conditions of a temperature of 105 ° C. and a pressure of 1.0 kPa. The mixture (M-4) of (a-1) and (b-1) was obtained by refine | purifying by distillation. As a result of HPLC analysis, the weight ratio of (a-1) to (b-1) was 98: 2.
When the obtained mixture was treated in the same manner as in Example 1, a yellowish brown transparent liquid remained. As a result of NMR analysis of this liquid, the main components were EDMI and EMI, and the weight ratio was 98: 2 by HPLC analysis. 212 g of the obtained mixture of EDMI and EMI was uniformly dissolved in propylene carbonate to make the whole 1 liter, and the electrolytic solution of the present invention was prepared.

Example 5
The mixture (M-4) of 1-ethyl-2-methylimidazole (a-1) and 1-ethylimidazole (b-1) obtained in Example 4 was further subjected to conditions of a temperature of 105 ° C. and a pressure of 1.0 kPa. To obtain a mixture (M-5) of (a-1) and (b-1). As a result of HPLC analysis, the weight ratio of (a-1) to (b-1) was 99: 1.
When the obtained mixture was treated in the same manner as in Example 1, a yellowish brown transparent liquid remained. When this liquid was analyzed by NMR, the main components were EDMI and EMI, and the weight ratio was 99: 1 by HPLC analysis. 212 g of the obtained mixture of EDMI and EMI was uniformly dissolved in propylene carbonate to make the whole 1 liter, and the electrolytic solution of the present invention was prepared.

Example 6
The electrolyte solution of the present invention was prepared by uniformly dissolving 210 g of the mixture of EDMI and EMI obtained in Example 1 in sulfolane to a total of 1 liter.

Example 7
The electrolyte solution of the present invention was prepared by uniformly dissolving 211 g of a mixture of EDMI and EMI obtained in Example 2 in sulfolane to make the whole 1 liter.

Example 8
The electrolyte solution of the present invention was prepared by uniformly dissolving 210 g of the mixture of EDMI and EMI obtained in Example 1 in a mixed solvent of propylene carbonate and dimethyl carbonate (weight ratio 6: 4) to make 1 liter as a whole.

Example 9
The electrolyte solution of the present invention was prepared by uniformly dissolving 211 g of the mixture of EDMI and EMI obtained in Example 2 in a mixed solvent of propylene carbonate and dimethyl carbonate (weight ratio 6: 4) to make 1 liter as a whole. .

Example 10
210 g of the mixture of EDMI and EMI obtained in Example 1 was uniformly dissolved in a mixed solvent of propylene carbonate and ethyl methyl carbonate (weight ratio 7: 3) to make the whole 1 liter, and the electrolytic solution of the present invention was prepared. It was.

Example 11
The electrolyte solution of the present invention was prepared by uniformly dissolving 211 g of the mixture of EDMI and EMI obtained in Example 2 in a mixed solvent of propylene carbonate and ethyl methyl carbonate (weight ratio 7: 3) to make 1 liter as a whole. It was.

Example 12
A reaction flask equipped with a stirrer, a thermometer, a dropping funnel, a reflux condenser, and a nitrogen gas inlet tube was charged with 64 parts of ammonia (28% aqueous solution) to obtain a homogeneous solution while stirring. While maintaining the temperature at 45 ° C. or lower, 69 parts of glyoxal (40% aqueous solution) and 71 parts of acetaldehyde (30% aqueous solution) were dropped from the dropping funnel. The mixture of glyoxal and acetaldehyde was added dropwise over 5 hours. After completion of the addition, the mixture was reacted at 40 ° C. for 1 hour, and a mixture of 2-methylimidazole (b-1) and imidazole (b0-1) (M-1) Got. As a result of HPLC analysis, the weight ratio of (b-1) to (b0-1) was (80:20). Next, the pressure was gradually reduced from 120 ° C. and normal pressure to 2.0 kPa to remove volatile components, followed by extraction with water. Then, it refine | purified by recrystallization and obtained the mixture (M-2). When this was analyzed by HPLC, the weight ratio of (a-1) to (b-1) was 85:15. Furthermore, 100 parts of the mixture (M-2) obtained in a stainless steel autoclave with a reflux condenser, 215 parts of diethyl carbonate, and 193 parts of tetrahydrofuran were charged and uniformly dissolved. Next, the temperature was raised to 170 ° C. Reaction was performed at a pressure of 0.9 MPa for 30 hours to obtain a mixture (M-3). Next, 100 parts of the mixture (M-3) obtained in a stainless steel autoclave with a reflux condenser, 135 parts of dimethyl carbonate, and methanol were obtained. 192 parts were charged and dissolved uniformly. Next, the temperature was raised to 130 ° C. The reaction was performed at a pressure of 0.8 MPa for 80 hours. NMR analysis of the reaction product showed that 1-ethyl-2,3-dimethylimidazolium monomethyl carbonate and 1-ethyl-3-dimethylimidazolium monomethyl carbonate were produced. 427 parts of the resulting reaction mixture was placed in a flask, and 207 parts of a borohydrofluoric acid aqueous solution (purity 42% by weight) was gradually added dropwise over about 30 minutes at room temperature with stirring. Carbon dioxide gas was generated along with the dripping. After generation | occurrence | production of foam | bubble was stopped, the reaction liquid was moved to the rotary evaporator and the whole quantity of solvent was removed. In the flask, 83 parts of a yellowish brown transparent liquid remained. When this solution was subjected to NMR analysis, the main components were 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate (hereinafter abbreviated as EDMI) and 1-ethyl-3-methylimidazolium tetrafluoroborate (hereinafter abbreviated as EMI). From the HPLC analysis, the weight ratio was 85:15. 210 g of the obtained mixture of EDMI and EMI was uniformly dissolved in propylene carbonate to make the whole 1 liter, and the electrolytic solution of the present invention was prepared.

Comparative Example 1
A mixture (M-1) of 1-ethyl-2-methylimidazole (a-1) and 1-ethylimidazole (b-1) obtained in Example 1 was methylated after simple distillation, and a mixture of EDMI and EMI Got. This mixture had a weight ratio of 80:20 by HPLC analysis. 208 g of the obtained mixture of EDMI and EMI was uniformly dissolved in propylene carbonate to make the whole 1 liter, and the electrolytic solution of the present invention was prepared.

Comparative Example 2
The mixture (M-1) of 2-methylimidazole (b-1) and imidazole (b0-1) obtained in Example 12 was extracted with water. Thereafter, ethylation was carried out in the same manner as in Example 12, followed by methylation to obtain a mixture of EDMI and EMI. This mixture had a weight ratio of 80:20 by HPLC analysis. 208 g of the obtained mixture of EDMI and EMI was uniformly dissolved in propylene carbonate to make the whole 1 liter, and the electrolytic solution of the present invention was prepared.

The impurity contents of the electrolytic solutions used in Examples 1 to 12 and Comparative Examples 1 and 2 were all at the following levels. Water content is 10ppm or less. Tertiary amine salt 1 mmol / kg or less, BF ₄ ^- the hydrolyzate 100ppm or less, sulfuric acid and sulfate salts 1ppm or less, glycol 10ppm or less, sodium, magnesium, potassium, chromium, manganese, iron, cobalt, nickel, copper , Zinc and lead ion content are all 1ppm or less.

Using the electrolytic solutions of Examples 1 to 12 and Comparative Examples 1 and 2, a wound type electric double layer capacitor (size: φ18 mm × L40 mm, standard: 2.3 V) was prepared, and this wound type electric double layer capacitor Was used to evaluate the withstand voltage of the electrolyte by measuring self-discharge characteristics (residual voltage after self-discharge). Table 1 shows the residual voltage after self-discharge.
Next, a method for measuring self-discharge characteristics will be described. The wound type electric double layer capacitor prepared above charged at 2.5 V for 24 hours at room temperature was allowed to stand at room temperature for 50 hours, and then the voltage across the terminals of this wound type electric double layer capacitor was measured. The voltage between the terminals after 24 hours obtained by this measurement was defined as the residual voltage. The withstand voltage is higher as the residual voltage is higher, and the withstand voltage is lower as the residual voltage is lower.

Using the wound type electric double layer capacitor, a high temperature load test of 65 ° C. and 2.5 V was performed, and the capacity retention after 1000 hours is shown in Table 1.
Capacity maintenance rate (%) = [(capacity after 1000 hours) / (initial capacity)] × 100
Next, a capacity measuring method will be described. A wound electric double layer capacitor charged at 2.5 V for 1 hour at room temperature is discharged at a constant current of 500 mA using a constant current load device, and the voltage across the wound electric double layer capacitor is 1.5 V. The capacity was calculated from the time during the change from 1.0 to 1.0V. The capacity calculation method is C = i × Δt / ΔV from the relationship of Q = i × t = C × V. In this measurement, i = 0.5 (A), ΔV = 1.5−1.0 = 0.5 (V). Here, Q is the discharge charge amount (C), i is the discharge current (A), t is the discharge time (sec), C is the capacity (F), and V is the voltage (V).

From Table 1, the electric double layer capacitor using the electrolyte solution of Examples 1 to 12 of the present invention has a residual voltage after self-discharge and the electric double layer capacitor using the electrolyte solution of Comparative Examples 1 and 2. High capacity retention. Therefore, the electrolytic solution of the present invention can increase the withstand voltage of the electrochemical capacitor, improve performance deterioration with time, and constitute a highly reliable electrochemical capacitor.

Since the electrolytic solution obtained from the method for producing an electrolytic solution for an electrochemical device of the present invention is excellent in withstand voltage, an electrochemical device produced using this electrolytic solution, particularly an electrochemical capacitor, is different from a conventional electrochemical device. Compared to secondary batteries such as power storage elements used in combination with memory backups for various electronic devices, backup power sources for various power sources, and solar cells, because performance degradation over time is negligible. As a device, it can be applied to a power source for driving a motor that requires a large current, a power source for a power tool such as an electric tool, and a power source for a power source for an electric vehicle.

Claims (7)

The alkylimidazole (a) represented by the general formula (1) is separated and purified from the reaction product of glyoxal or its acetal or its ketal (d1), ammonia (d2), aldehyde (d3) and primary amine (d4). Thus, the content of the alkylimidazole (a0) represented by the general formula (3) is 15% by weight or less based on the total weight of (a) and (a0). Manufacturing method of electrolyte solution.

[Wherein R ₁ and R ₂ are alkyl groups having 1 to 3 carbon atoms, and may be the same or different, and R ₄ and R ₅ are a hydrogen atom or alkyl having 1 to 3 carbon atoms. Groups that may be the same or different. ]

[Wherein, R ₁ , R ₄ and R ₅ are the same as those in the general formula (1). ] The method for producing an electrolytic solution according to claim 1, wherein the alkylimidazole (a) is separated and purified by distillation. The method for producing an electrolytic solution according to claim 1 or 2, wherein the quaternized product of the alkylimidazole (a) is subjected to an acid exchange reaction. By separating and purifying the alkylimidazole (b) represented by the general formula (2) from the reaction product of glyoxal or its acetal or its ketal (d1), ammonia (d2), and aldehyde (d3), the general formula The alkylimidazole (b0) content represented by (6) is set to 15% by weight or less based on the total weight of (b) and (b0), and further alkylated to obtain an alkyl represented by the general formula (3). The content of imidazole (a0 ′) is 15% by weight or less based on the total weight of alkylimidazole (a ′) and (a0 ′) represented by the general formula (1). Manufacturing method of electrolyte solution.

[Wherein R ₁ and R ₂ are alkyl groups having 1 to 3 carbon atoms, and may be the same or different, and R ₄ and R ₅ are a hydrogen atom or alkyl having 1 to 3 carbon atoms. Groups that may be the same or different. ]

[Wherein R ₂ , R ₄ and R ₅ are the same as those in the general formula (1). ]

[Wherein, R ₁ , R ₄ and R ₅ are the same as those in the general formula (1). ]

[Wherein, R ₄ and R ₅ are the same as those in the general formula (1). ] The method for producing an electrolytic solution according to claim 4, wherein the alkylimidazole (b) is separated and purified by distillation or recrystallization. The method for producing an electrolytic solution according to claim 4 or 5, wherein an acid exchange reaction is performed on a quaternized product of alkylimidazole (a '). The alkyl imidazole (a) or the alkyl imidazole (a ') contains at least one selected from the group consisting of 1-ethyl-2-methylimidazole, 1,2-dimethylimidazole and 1,2,4-trimethylimidazole. The manufacturing method of the electrolyte solution of any one of -6.