DE1914420A1 - Electrolytic capacitor - Google Patents

Description

Dipl.-Phys. Leo Thul 'Iy I 4 4 2 U

Patent attorney

Stuttgart-Feuerbach

Short street 8

Case: Z.D.Koväcs-G.W.Keller-M.M.Mahdi 4-6-2 International Standard Electric Corp., New York, U.S.A.

Electrolytic capacitor

The invention relates to an electrolytic capacitor with two electrodes, in particular made of aluminum, tantalum or niobium or their alloys, at least one of which is provided with a dielectric layer, in particular an oxide layer and an electrolyte in contact with the electrodes, which is an ionic substance in a solvent contains.

It is a special characteristic of aluminum electrolytic capacitors, daid it during operation, even more if it is stored without tension, at elevated temperature to. tend to increase in capacity and residual current. This phenomenon is attributed to the corrosion of the aluminum. With the current state of knowledge, the causes are not yet known in detail and are of a complex nature. Various ions present, especially the chloride, sulfate, nitrate, iron and copper ions, shorten diu service life of the capacitors and are - albeit in traces - always present in the finished capacitors. Furthermore, the amount of water present in the electrolyte and the pH value of the electrolyte solution play a very important role. Furthermore, the electrical properties, in particular the temperature characteristics, of the electrolytic capacitors largely determined by the electrolyte used.

Kb / b - H.3 1969 - 2 -

8Ü9844 / 1188

Z.D. Koväcs et al 4-6-2-2

19H42Q

Such electrolytic capacitors are made up of a pair of electrodes, at least one of which is made up of a Metal consists of a dielectric oxide film Trägb on its surface. This oxide film can be formed by anodic Air oxidation, applied chemically or physically and is in contact with a conductive electrolyte on its surface.

The increase in capacity and residual current depends on a progressive increase Change in the oxide film during operation. For example, in the case of aluminum electrodes the oxide film originally had a uniform, weak interference color When the capacitor is in use, dull spots appear in places. Similar Phenomena also occur with electrodes made of other metals that form an oxide film, such as tantalum and mob.

The invention is based on the finding that electrolytes that are completely anhydrous or contain only small amounts of water (less than 1 ^c / o) can be produced. This is in an electrolytic capacitor of the type mentioned according to FIG. Invention accomplished by dari the electrolyte as a solvent contains one or more high-boiling aliphatic cyano alcohols alone or in a mixture with one or more other polar solvents. It is important that these solvents have high polarity, high boiling points and low freezing points.

The salts of boric acid, oxycarboxylic acids, Picric acid - ii-.j3.jK «. With ammonia, alkyl or Arylamines are used, which in substantial amounts in the solvents mentioned are soluble, the jslectrisehen. Conduct electricity well, on so-called. Oxidizing valve metals act and in contrast to the aqueous boric acid and

- 5 9098U / 1188

Glycölhaltigen. Electrolytes also "strong" with prolonged use cause reduced changes to the oxide film.

As already mentioned, certain ions, water and pH values of the solution that deviate from an optimum have a corrosive effect Metals, especially on aluminum. In contrast, the electrolytes used in electrolytic capacitors according to the invention are used largely anhydrous; depending on the concentration of the constituents, they show a neutral or weakly acidic reaction. the The above-mentioned disadvantages are therefore largely avoided by using these electrolytes. Of particular advantage is also that the Elektrclyte of electrolytic capacitors according to the invention for an extended working temperature range of the capacitors can be used and that their electrical properties hardly change in this temperature range change. In contrast to aqueous boric acid and glycol containing Capacitors have significantly better loss factors at elevated temperatures than puncture time.

The following are examples of the electrolytes of the electrolytic capacitors specified according to the invention.

Example 1:

5 parts of orthoboric acid. are dissolved in 95 parts of 3-hydroxypropionitrile and 1.5 parts of triethanolamine are added with stirring. The result is a thin, clear solution that has a specific resistance of 1200 JX. * Cm at 5 ° C. The maximum voltage of this electrolyte is 51 ^ volts.

Example 2: -

7 parts of orthoboric acid are dissolved in 93 parts of 3-hydroxypropionitrile and 5, D parts of iriethanolamine are added with stirring. The electrolyte solution obtained has a specific resistance vi
at 370 volts,

Resistance of 837YV.'cm at pO ° C. The maximum voltage is

909844/1188

Z.D. Kovacs et al 4-6-2- - 4 -

example 3:

10 parts of orthoboric acid are dissolved in 90 parts of 3-hydroxypropionitrile and 2.5 parts of diethylamine are added with stirring. The specific resistance of the electrolyte at 50 ^° C., the maximum voltage is 160 volts.

Example 4?

7 parts of ammonium picrate are dissolved in 50 parts of ethylene glycol and 50 parts of 3-hydroxypropionitrile. The specific resistance of the solution is 210 Λ cm at 50 ⁰ C. The solution remains liquid ^{down to -6O 0 C.}

example 5 '

10 parts of picric acid and 6.3 parts of triethanolamine are dissolved in 100 parts of 3-hydroxypropionitrile. The specific resistance is 21μ-Acm at 50 ⁰ C, the maximum voltage is 180 volts.

Example 6;

10 parts of picric acid, 4.6 parts of diethanolamine are in 100 parts of 3-hydroxypropionitrile dissolved with 20 parts of butyloxyethanol. The electrolyte solution obtained has a specific one

Resistance of 230_n_cm at 5O ⁰ C.

example 1\

9.6 parts of D (-) lactic acid and 3.4 parts of diethylamine are dissolved in 50 parts of £ -hydroxisobutyronitrile and 50 parts of 3-hydroxypropionitrile. The specific resistance of the solution is 270 JX cm at 50 °.

In the following there are some more typical data about the Ver keep the capacitors impregnated with the above mentioned electrolytes listed.

9 0 9 8ΑΛ / 1188

Z.D. Kovacs et al 4-6-2

For comparison, aluminum wound capacitors from
100 AiF and 15 V with an electrolyte listed above
impregnated, then formed and then given to a temperature endurance test. The same type of capacitor was made with aqueous, glycolic and boric acid electrolytes and treated as above. The ambient temperature in the life test was +85 ⁰ C. Table 1 shows the electrical properties of the known electrolytic capacitor in dependence on the duration of the test, while Table 2 shows the electrical
Also contains values of the capacitor produced according to the invention as a function of the test duration.

G Tabel S. <r 1 t 1 I. I. Impedance b . 20 kHz Test duration (/ ui ¹ ) daily ) I. ^{} ( 1} B 1 A) A) (A) (Hours.) 117 (* , 0 , 4 : / u 1 0 , 90 0.35 O 145 6th , 0 , 2 2, 1 92 , 63 0.68 200 10 Tabel ,8th 2, 0 , 45 C. daily , -3 2 , 20 Impedance b . 20 kHz Test duration (/ ^ F) C * ,8th _τ , 80 (χι ) (Hours.) . 109 6th 0.26 0 107 5 0.27 200 106 5 0.31 500 108 5 0.22 1000 106 5 0.25 1500 System: 7 claims

909844/1188

Claims (6)

Z.D. Koväcs et al 4-6-2 191AA? Q Claims Electrolytic capacitor with two electrodes, in particular made of aluminum, tantalum or Mob or their alloys, of which at least one with a dielectric * layer, in particular Oxide layer, and an electrolyte in contact with the electrodes, which is in a solvent contains an ionogenic substance, characterized in that the electrolyte is used as a solvent or several high-boiling aliphatic cyano alcohols alone or in a mixture with one or more other polar ones Contains solvents. 2.) Electrolytic capacitor according to claim 1, characterized in that dai3 at least 20% of the electrolyte solvent aliphatic cyano alcohols. 3.) Electrolytic capacitor according to claim 1 or 2, characterized in that that the electrolyte solvent contains 3-hydroxypropionitrile. 4.) Electrolytic capacitor according to one of claims I to 3, characterized characterized in that the electrolyte solvent is 2-methyllactonitrile contains. 5 ·) electrolytic capacitor according to one of claims 1 to 4, characterized characterized in that the electrolyte solvent as another polar solvent is an alcohol, ether alcohol or a nitrile of aliphatic carboxylic acids or carboxamides contains. Kb / b - 3/14/1969 - 2 - 909844/1188 ZDKoväcs et al 4-6-2 - Jt '- I dl 4420 6.) Electrolytic capacitor according to one of claims 1 to 5, characterized in that characterized in that boric acid, aliphatic dicarboxylic acid, Picric acid, aliphatic hydroxycarboxylic acid, orthophosphoric acid or mixtures thereof are included. 7 ·) Electrolytic capacitor according to one of claims 1 to 6, characterized characterized in that in the electrolyte solvent as the cation-forming substance ammonia, aliphatic and / or aromatic amine, aliphatic hydroxyl-containing amine or mixtures thereof are included. 118 «