Process for the producing of electrolytic capacitors
View Patent ↗Process for the production of electrolytic capacitors with low equivalent series resistance and low residual current, having a solid electrolyte formed from conducting polymers and an outer layer containing conducting polymers and a binder, electrolytic capacitors produced by the process and their use.
1. Process for the production of an electrolytic capacitor comprising at least the following process steps:
A) introducing a mixture containing precursors for the production of conducting polymers, one or more oxidizing agents and optionally counter-ions into a porous electrode body of an electrode material coated with a dielectric and optionally further layers, to impregnate said porous electrode body with said mixture,
B) exposing the electrode body impregnated with said mixture to an atmospheric relative humidity of greater than or equal to 70% and polymerizing said precursors to form a solid electrolyte, and
C) applying a solution or dispersion containing at least one conducting polymer and at least one binder to the porous electrode body and then drying.
2. Process according to claim 1 , wherein step B) is carried out at a temperature of less than 30° C.
3. Process according to claim 1 , wherein said precursors are selected from the group consisting of optionally substituted thiophenes, pyrroles and anilines.
4. Process according to claim 3 , wherein said optionally substituted thiophene is 3,4-ethylenedioxy-thiophene.
5. Process according to claim 1 , wherein said oxidizing agents are selected from the group consisting of alkali metal or ammonium peroxodisulfates, hydrogen peroxide, alkali metal perborates, iron(III) salts of organic acids, iron(III) salts of inorganic acids and iron(III) salts of inorganic acids that comprise organic radicals.
6. Process according to claim 1 , wherein said counter-ions are selected from the group consisting of anions of monomeric alkanesulfonic acids, anions of cycloalkanesulfonic acids and anions of aromatic sulfonic acids.
7. Process according to claim 1 , wherein said mixture employed in A) has an activation energy of 75 k/Jmole or above for the polymerization.
8. Process according to claim 1 , wherein the solution or dispersion applied in C) as conducting polymer contains optionally substituted polythiophenes, polypyrroles and/or polyanilines.
9. Process according to claim 8 , wherein said optionally substituted polythiophene is poly(3,4-ethylenedioxythiophene).
10. Process according to claim 1 , wherein the electrode material is a valve metal or a compound having comperable properties of metallic conductivity and which is oxidizable to form an oxide layer which does not permit current to flow equally in both directions.
11. Process according to claim 10 , wherein the valve metal or the compound is selected from the group consisting of tantalum, niobium, aluminum, titanium, zirconium, hafnium, vanadium, alloys or compounds of these metals with other elements, NbO and alloys or compounds of NbO with other elements.
12. Process according to claim 10 , wherein the dielectric is an oxide of the valve metal or an oxide of the compound having comparable properties.
13. Process according to claim 1 , wherein the mixture of step A) further comprises a solvent and that the solvent is evaporated from the mixture on the electrode body before the polymerization of the precursors.
14. Electrolytic capacitors produced by the process of claim 1 .
15. Electrolytic capacitor according to claim 14 , having a specific charge of greater than 5000 μC/g, based on the weight of the electrode body coated with a dielectric.
16. An electronic circuit comprising the electrolytic capacitor of claim 14 .