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EP-3529816-B1 - SOLID ELECTROLYTIC CAPACITOR WITH IMPROVED PERFORMANCE AT HIGH TEMPERATURES AND VOLTAGES

EP3529816B1EP 3529816 B1EP3529816 B1EP 3529816B1EP-3529816-B1

Inventors

  • PETRZILEK, JAN
  • UHER, MILOSLAV
  • HOFIREK, TOMAS

Dates

Publication Date
20260506
Application Date
20171012

Claims (7)

  1. A capacitor assembly comprising a capacitor element, the capacitor element comprising: a porous anode body that contains a valve metal compound; a dielectric that overlies the anode body and includes an oxide of the valve metal compound; a solid electrolyte that overlies the dielectric, wherein the solid electrolyte includes at least one conductive polymer layer that contains a sulfonyl ion; and an organofunctional silane that is covalently bonded to the oxide of the dielectric and is capable of bonding to the sulfonyl ion, wherein the organofunctional silane compound is a diaminofunctional silane having the following general formula (III): wherein, R 1 , R 2 , and R 3 are independently alkyl, alkenyl, aryl, heteroaryl, cycloalkyl, heterocyclyl, halo, haloalkyl, or hydroxyalkyl; R4 and R5 are independently hydrogen, alkyl, independently alkyl, alkenyl, aryl, heteroaryl, cycloalkyl, heterocyclyl, halo, haloalkyl, hydroxyalkyl, or alternatively N, R4, and R5 together with one or more additional atoms form a ring structure; and Z 1 and Z 2 are independently an organic group.
  2. The capacitor assembly of claim 1, wherein the diaminofunctional silane is N-(2-aminoethyl)-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(6-aminohexyl)aminomethyltriethoxysilane, N-(6-aminohexyl)aminopropyltrimethoxysilane, N-(2-aminoethyl)-11-aminoundecyltrimethoxysilane), (aminoethylaminomethyl)-phenethyltrimethoxysilane, N-3-[(amino(polypropylenoxy)]-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylsilanetriol, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, (aminoethylamino)-3-isobutyldimethylmethoxysilane, or a combination thereof.
  3. The capacitor assembly of claim 1, wherein the anode body includes tantalum and the dielectric includes tantalum pentoxide.
  4. The capacitor assembly of claim 1, wherein the conductive polymer layer contains an extrinsically conductive polymer and a sulfonyl counterion, preferably wherein the extrinsically conductive polymer has repeating units of the following formula: wherein, R 7 is a linear or branched, C 1 to C 18 alkyl radical; C 5 to C 12 cycloalkyl radical; C 6 to C 14 aryl radical; C 7 to C 18 aralkyl radical; and q is an integer from 0 to 8.
  5. The capacitor assembly of claim 4, wherein the extrinsically conductive polymer is poly(3,4-ethylenedioxythiophene), and/or wherein the sulfonyl counterion is polystyrene sulfonic acid or a salt thereof.
  6. A method for forming a capacitor element according to claim 1, the method comprising: anodically oxidizing a sintered porous anode body to form a dielectric that includes an oxide of a valve metal compound; applying a solution to the anode that includes an organofunctional silane compound; applying a dispersion that contains conductive polymer particles and a sulfonyl counterion to form a conductive polymer layer; and bonding the organofunctional silane compound to the oxide of the dielectric, wherein the organofunctional silane that is covalently bonded to the oxide of the dielectric and is capable of bonding to the sulfonyl ion, wherein the organofunctional silane compound is a diaminofunctional silane having the following general formula (III): wherein, R 1 , R 2 , and R 3 are independently alkyl, alkenyl, aryl, heteroaryl, cycloalkyl, heterocyclyl, halo, haloalkyl, or hydroxyalkyl; R4 and R5 are independently hydrogen, alkyl, independently alkyl, alkenyl, aryl, heteroaryl, cycloalkyl, heterocyclyl, halo, haloalkyl, hydroxyalkyl, or alternatively N, R4, and R5 together with one or more additional atoms form a ring structure; and Z 1 and Z 2 are independently an organic group.
  7. The method of claim 6, wherein the solution includes an organic solvent.

Description

Cross Reference to Related Application The present application claims filing benefit of United States Provisional Patent Application Serial No. 62/409,425 having a filing date of October 18, 2016. Background of the Invention Solid electrolytic capacitors (e.g., tantalum capacitors) are typically made by pressing a metal powder (e.g., tantalum) around a metal lead wire, sintering the pressed part, anodizing the sintered anode, and thereafter applying a solid electrolyte. Intrinsically conductive polymers are often employed as the solid electrolyte due to their advantageous low equivalent series resistance ("ESR") and "non-burning/non-ignition" failure mode. For example, such electrolytes can be formed through in situ chemical polymerization of a 3,4-dioxythiophene monomer ("EDOT") in the presence of a catalyst and dopant. However, conventional capacitors that employ in situ polymerized polymers tend to have a relatively high leakage current ("DCL") and fail at high voltages, such as experienced during a fast switch on or operational current spike. In an attempt to overcome these issues, dispersions have also been employed that are formed from a complex of poly(3,4-ethylenedioxythiophene) and poly(styrene sulfonate ("PEDOT:PSS"). While the PEDOT:PSS dispersions can result in some improved properties, the capacitance of such materials tends to significantly degrade at high temperatures, particularly when subjected to relatively high voltages. Document US2013078366A1 discloses a method of manufacturing a solid electrolytic capacitor, the method comprising forming a bonding layer containing a silane compound on a dielectric film. As such, a need currently exists for a solid electrolytic capacitor having an improved performance. Summary of the Invention In accordance with claim 1 of the present invention, a capacitor assembly is disclosed that comprises a capacitor element. The capacitor element comprises a porous anode body that contains a valve metal compound, a dielectric that overlies the anode body and includes an oxide of the valve metal compound, and a solid electrolyte that overlies the dielectric. The solid electrolyte includes at least one conductive polymer layer that contains a sulfonyl ion. Further, the capacitor element comprises an organofunctional silane that is bonded to the oxide of the dielectric and is capable of bonding to the sulfonyl ion. In accordance with another embodiment of the present invention, a method for forming a capacitor element is disclosed. The method comprises anodically oxidizing a sintered porous anode body to form a dielectric that includes an oxide of a valve metal compound; applying a solution to the anode that includes an organofunctional silane compound; applying a dispersion that contains conductive polymer particles and a sulfonyl counterion to form a conductive polymer layer; and bonding the organofunctional silane compound to the oxide of the dielectric. Other features and aspects of the present invention are set forth in greater detail below. Brief Description of the Drawings A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the appended figures in which: Fig. 1 is a cross-sectional view of one embodiment of a capacitor assembly of the assembly of the present invention;Fig. 2 is a cross-sectional view of another embodiment of a capacitor assembly of the assembly of the present invention;Fig. 3 is a cross-sectional view of yet another embodiment of a capacitor assembly of the assembly of the present invention; andFig. 4 is a top view of still another embodiment of a capacitor assembly of the assembly of the present invention. Detailed Description of Representative Embodiments It is to be understood by one of ordinary skill in the art that the present description is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary construction. Generally speaking, the present invention is directed to a capacitor assembly of claim 1 that is capable of exhibiting good electrical properties even under a wide variety of different conditions. More particularly, the capacitor contains a capacitor element that includes a porous anode body that contains a valve metal compound (e.g., tantalum), a dielectric that overlies the anode body and includes an oxide of the valve metal compound (e.g., tantalum pentoxide), and a solid electrolyte that overlies the dielectric. The solid electrolyte includes at least one conductive polymer layer that contains sulfonyl ions. The layer may, for instance, be "extrinsically" conductive in that it contains a complex of a conductive polymer doped with a sulfonyl ion (e.g., polystyrene sulfonate). In other embodiments, the layer may be "intrinsically" conduct