Search

EP-3529815-B1 - SOLID ELECTROLYTIC CAPACITOR COMPRISING A SILANE AGENT BETWEEN THE ANODE AND THE CONDUCTIVE POLYMER

EP3529815B1EP 3529815 B1EP3529815 B1EP 3529815B1EP-3529815-B1

Inventors

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

Dates

Publication Date
20260506
Application Date
20171012

Claims (10)

  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 a conductive polymer and a hydroxy-functional polymer; and an organofunctional silane compound that is bonded to the oxide of the dielectric and is capable of bonding to the hydroxy-functional polymer, wherein the organofunctional silane compound has the following general formula (I): wherein, R 1 , R 2 , and R 3 are independently alkyl, alkenyl, aryl, heteroaryl, cycloalkyl, heterocyclyl, halo, haloalkyl, hydroxyalkyl, or a combination thereof; and X is a functional group that is capable of bonding to a hydroxyl group or is capable of being converted into a functional group that is capable of bonding to a hydroxyl group; and Z is alkyl, aryl, or a combination thereof that links the functional group X to the silicon atom.
  2. The capacitor assembly of claim 1, wherein at least one of R 1 , R 2 , and R 3 is a hydroxyalkyl, and/or X is an isocyanate.
  3. The capacitor assembly of claim 2, wherein the organosilane compound includes 3-isocyantopropyltriethoxysilane, 3-isocyantopropyltrimethoxysilane, 3-isocyanantopropylmethyldiethoxysilane, 3-isocyanantopropylmethyldiethoxysilane, or a combination thereof.
  4. The capacitor of claim 1, wherein X is a protecting group that is capable of being converted into a functional group that can react with the hydroxy-functional polymer, preferably wherein the protecting group includes a thiocyanate group, carbamate group, isocyanurate group, or a combination thereof, even more preferably wherein the organosilane compound includes (thiocyanatomethyl)phenethyl-trimethoxysilane, 3-thiocyanatopropyltriethoxysilane, N-(3-triethoxysilylpropyl)-o-t-butylcarbamate, triethoxysilylpropylethylcarbamate, N-trimethoxysilylpropylmethylcarbamate, tris(3-trimethoxysilylpropyl)isocyanurate, or a combination thereof.
  5. The capacitor assembly of claim 1, wherein the anode body includes tantalum and the dielectric includes tantalum pentoxide.
  6. The capacitor assembly of claim 1, wherein the solid electrolyte contains an extrinsically conductive polymer and a sulfonyl counterion, preferably wherein the extrinsically conductive polymer is poly(3,4-ethylenedioxythiophene), and/or wherein the sulfonyl counterion is polystyrene sulfonic acid or a salt thereof.
  7. The capacitor assembly of claim 1, wherein the conductive polymer is an intrinsically conductive polymer, preferably wherein the intrinsically conductive polymer is poly(4-(2,3-dihydrothieno-[3,4-b][1,4]dioxin-2-ylmethoxy)-1-butane-sulphonic acid, salt), poly(4-(2,3-dihydrothieno-[3,4-b][l,4]dioxin-2-ylmethoxy)-l-propanesulphonic acid, salt), or a combination thereof.
  8. The capacitor assembly of claim 1, wherein the solid electrolyte contains a layer formed from a dispersion of pre-polymerized conductive polymer particles, preferably wherein the hydroxy-functional polymer is contained within the layer.
  9. The capacitor assembly of claim 1, wherein the hydroxy-functional polymer has a molecular weight of from about 300 to about 1,200 grams per mole, preferably wherein the hydroxy-functional polymer is a polyalkylene ether,, even more preferably wherein the polyalkylene ether is a polyalkylene glycol.
  10. The capacitor assembly of claim 1, further comprising an external polymer coating that overlies the solid electrolyte and contains pre-polymerized conductive polymer particles and a cross-linking agent.

Description

Cross Reference to Related Application The present application claims filing benefit of United States Provisional Patent Application Serial No. 62/409,423 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. Documents JP2005085947A, EP1988128A1 and WO2009001772A1 disclose capacitor comprising conductive polymer electrolyte and a silane agent for the adhesion with the anode or cathode material. 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 a conductive polymer and a hydroxy-functional polymer. Further, the capacitor element comprises an organofunctional silane compound that is bonded to the oxide of the dielectric and is capable of bonding to the hydroxy-functional polymer. In accordance with present invention, an exemplary method for forming a capacitor element is disclosed that 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 hydroxy-functional polymer 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 discussion 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 and defined by the appended claims. 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 a conductive polymer and a hydroxy-functional polymer. Notably, an organofunctional silane compound is also employed that bonds with the oxide of the dielectric and is capable of bonding to the hydroxy-functional polymer contained in the solid electrolyte. Without intendi