JPH0476488B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electrolytic solution for electrolytic capacitors containing a tetrafluoroborate salt of an organic amine compound as an electrolyte in an aprotic solvent. [Prior art] Conventionally, organic acids or their salts/glycol-based electrolytes have been mainly used as electrolytes for electrolytic capacitors for normal purposes, but in recent years, as the range of use of electronic devices has increased, capacitor performance has improved. With the increasing demand for improvements in electrolytes, the presence of water in electrolytes has become a major problem, and electrolytes that use aprotic solvents to replace organic acids or their salts and glycol-based electrolytes are attracting attention. . [Problem to be solved by the invention] However, the biggest problem with aprotic solvent-based electrolytes is how to obtain electrolytes with high conductivity. The search for highly dissociated organic carboxylic acids or their salts has been the main focus, but this goal has not yet been achieved, and it is unavoidable that solvents such as alcohols and glycols that generate water by reaction, and even those that do not contain water. Currently, it is necessary to ensure high conductivity by blending with an aprotic solvent. It is therefore an object of the present invention to provide a substantially non-aqueous high conductivity electrolyte using an aprotic solvent. [Means for Solving the Problems] The present inventors have achieved a substantially non-protic solvent by using an aprotic solvent and without using a solvent that reacts with acids such as alcohols and glycols to produce water. As a result of extensive research into an aqueous electrolyte that provides high conductivity, we found that organic amine salts of tetrafluoroboric acid (HBF ₄ ) have high solubility in aprotic solvents, high degree of dissociation, and high conductivity. The present invention was developed based on the discovery of the ability to impart a high degree of strength. That is, the electrolytic solution for an electrolytic capacitor according to the present invention is characterized in that it contains a tetrafluoroborate salt of a specific organic amine compound as an electrolyte in an aprotic solvent. One group of organic amine compounds targeted by the present invention includes a group of compounds containing one or two pyridine rings. Specifically, two pyridine compounds, dipyridyl compounds, alkylene groups, or alkenylene groups in which one or more of the hydrogen atoms bonded to the pyridine carbon are substituted with an alkyl group, alkenyl group, aryl group, or halogen. Compounds in which a pyridine ring is bonded, and quaternary amine compounds in which one alkyl group, alkenyl group, or aryl group is added to the nitrogen atom of pyridine are included as compounds in this group. (1) Compounds in which one or more of the hydrogen atoms bonded to the pyridine carbon are substituted with an alkyl group, alkenyl group, aryl group, or halogen; , an alkyl group such as an octyl group, a substituent being an alkenyl group having 2 to 15 carbon atoms such as a vinyl group, propenyl group, butenyl group, hexenyl group, geranyl group, a phenyl group, Aryl groups having 6 to 15 carbon atoms, such as mesityl and tolyl groups, and those in which the substituent atom is a halogen are particularly preferred since they provide an electrolyte with particularly high conductivity. Specific compound names of these are illustrated below. α-picoline, β-picoline, γ-picoline, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2-n-propylpyridine, 2-iso-propylpyridine, 2-n
-octylpyridine, 2-vinylpyridine, 2
-hexane-2-pyridine, 2-geranylpyridine, 2,3-dimethylpyridine, 2,6-dimethylpyridine, 3,4-dimethylpyridine,
3-ethyl-4-methylpyridine, 4-ethyl-2-methylpyridine, 6-ethyl-2-methylpyridine, 2,3,4-trimethylpyridine, 2,3,6-trimethylpyridine, 2,
4,5-trimethylpyridine, 2,4,6-trimethylpyridine, 2-ethyl-3,5-dimethylpyridine, 2-phenylpyridine, 4-tolylpyridine, 4-mesitylpyridine, 3-chloropyridine, 3 ,5-dibromopyridine. (2) Dipyridine compounds; 2,2'-diethyl-4,4'-dipyridyl,
4,4'-dimethyl-2,2'-dipyridyl. (3) 2 in alkylene group or alkenylene group
Compounds in which pyridine rings are bonded; Among these compounds, those in which the alkylene group is an alkylene group having 1 to 8 carbon atoms such as methylene group, ethylene group, propylene group, hexylene group, and those in which alkenylene group is Alkenylene groups having 2 to 8 carbon atoms, such as a vinylene group, propenylene group, and butenylene group, are particularly suitable because they provide an electrolyte with high conductivity. Specific compound names of these are illustrated below. 1,3-di-(4-pyridyl)-propane,
1,2-di-(4-pyridyl)-ethane, 1,2
-di-(4-pyridyl)-ethylene, 1,6-di-(4-pyridyl)-hexylene. (4) Quaternary ammonium compounds in which one alkyl group, alnickel group, or aryl group is added to the nitrogen atom of pyridine; Those with an alkyl group, substituents with 2 carbon atoms such as vinyl, propenyl, butenyl, hexenyl groups, etc.
to 15 alkenyl groups, and those whose substituent is an aryl group having 6 to 15 carbon atoms such as phenyl group, tolyl group, propylphenyl group, mesityl group, etc. are especially suitable for electrolytes with high conductivity. This is suitable because it gives Specific compound names of these are illustrated below. N-methyl-2-bromopyridine, N-vinyl-3,5-dimethylpyridine, N-phenyl-4-ethylpyridine, N-tolyl-4-butylpyridine. Furthermore, as another group of organic amine compounds that are the subject of the present invention, primary to tertiary amine compounds in which four groups selected from an alkyl group, an alkenyl group, an aryl group, or a hydrogen atom are added to a nitrogen atom, and quaternary Examples include ammonium (for quaternary ammonium, when the four groups added to the nitrogen atom are composed only of alkyl groups and aryl groups, all four groups are the same group). In these compounds, compounds having an alkyl group having 1 to 4 carbon atoms such as methyl group, ethyl group, propyl group, alkenyl group having 2 to 15 carbon atoms such as vinyl group, propenyl group, hexenyl group, geranyl group, etc. a compound having a group,
Compounds having an aryl group having 6 to 15 carbon atoms, such as a phenyl group, tolyl group, or mesityl group, are particularly suitable since they provide an electrolytic solution with particularly high conductivity. Specific compound names of these are illustrated below. () Primary amines; Methylamine, ethylamine, propylamine, isopropylamine, butylamine,
Amylamine, hexylamine, vinylamine, geranylamine, aniline, benzylamine. () Secondary amines; dimethylamine, diethylamine, dipropylamine, diisopropylamine, divinylamine, digeranylamine, diphenylamine, ditolylamine, N-methyl benzylamine. () Tertiary amines; trimethylamine, triethylamine, tripropylamine, tributylamine, trivinylamine, trigeranylamine, triphenylamine, N-dimethyl benzylamine. () Quaternary ammoniums; tetramethylammonium, vinyltrimethylammonium, tetraphenylammonium. The organic amine compound tetrafluoroborate used in the present invention is obtained by adding and stirring equimolar amounts of the organic amine compound to an aqueous solution of tetrafluoroboric acid to form a salt, and at this time, the reaction is controlled at pH. and adjust the pH to 6.5. After the reaction is completed, an anhydrous salt is obtained by heating and drying under reduced pressure. The obtained anhydrous salt is dissolved in a desired aprotic solvent to form an electrolytic solution. Aprotic solvents used in the present invention include (1) amide solvents; N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,
N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-
Ethylacetamide, N,N-diethylacetamide, hexamethylphosphorylamide. (2) Oxide type; dimethyl sulfoxide. (3) Nitrile type; acetonitrile. (4) Cyclic ketone type; γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate. are listed as representative examples, but are not limited to these. [Function] The electrolyte according to the present invention has high solubility in aprotic solvents and a high degree of dissociation, so that high conductivity can be achieved even in a non-aqueous electrolyte. [Example] As an example of the electrolytic solution for electrolytic capacitors according to the present invention, 10% by weight solutions of tetrafluoroboric acid (HBF ₄ ) salts of various organic amine compounds in various aprotic solvents were prepared, and these electrolytic solutions were prepared. Table 1 shows the results of investigating the conductivity of the liquid and the spark voltage. It should be noted that among the organic amine compounds of Examples in Table 1, those labeled as ionized have (BF ₄ ⁻ ) ions attached to the anion side to form salts. In addition, Me in the table is a methyl group, Et is an ethyl group, Bu
represents a butyl group.

【table】

[Table] Next, electrolytic capacitors with a rated voltage of 25 V and a capacitance of 1 μF were manufactured using the electrolytes of Examples 1 to 12 and Reference Examples, and their initial values and high-temperature load tests (110°C, 1000 hours) were measured. Table 2 shows the results of examining the characteristics after implementation.

【table】

〔Effect of the invention〕

As described above, the electrolytic solution of the present invention is a non-aqueous electrolytic solution that has a high electrical conductivity comparable to or higher than that of conventional high-conductivity electrolytic solutions made of glycols, water, and organic acid salts. The deterioration of the dielectric film due to the addition of water and
It is possible to overcome drawbacks such as life characteristics and temperature characteristics, and to obtain an electrolytic capacitor that has wide temperature characteristics and stable characteristics over a long period of time.

Claims (1)

[Scope of Claims] 1. In an aprotic solvent, one or more of the hydrogen atoms shown in (a) and (b) shown below: pyridine is replaced with an alkyl group, an alkenyl group, or an aryl group. or halogen-substituted pyridine compounds, dipyridyl compounds, compounds in which two pyridine rings are bonded by an alkylene group or alkenylene group, and one alkyl group, alkenyl group, or aryl group on the nitrogen atom of pyridine. Quaternary ammonium compounds with added. (b): Primary to tertiary amine or quaternary ammonium with four selected from alkyl, alkenyl or aryl groups and hydrogen atoms added to the nitrogen atom (however, in the case of quaternary ammonium, an alkyl group is added to the nitrogen atom) and aryl groups, in which all four are the same). An electrolytic solution for an electrolytic capacitor containing a tetrafluoroborate salt of an organic amine compound selected from any of the above as an electrolyte.