Solid electrolytic capacitor for use at high temperatures

1. A capacitor comprising a capacitor element that includes:

an anode that contains a dielectric formed on a sintered porous body;

a solid electrolyte overlying the anode that contains manganese dioxide; and

a cathode coating that includes:

a barrier layer overlying the solid electrolyte, wherein the barrier layer contains a valve metal; and

a metallization layer overlying the barrier layer, wherein the metallization layer contains a metal that exhibits an electrical resistivity of about 150 nΩ·m or less (at a temperature of 20° C.) and an electric potential of about −0.5 V or more; and

wherein the cathode coating has a carbon content of about 2,000 ppm or less.

2. The capacitor of claim 1 , wherein the metallization layer includes gold, nickel, silver, tin, copper, platinum, iridium, palladium, or an alloy thereof.

3. The capacitor of claim 1 , wherein the metallization layer has a thickness of from about 0.1 to about 10 micrometers.

4. The capacitor of claim 1 , wherein the metallization layer is formed from a single layer.

5. The capacitor of claim 4 , wherein the single layer includes nickel or an alloy thereof.

6. The capacitor of claim 1 , wherein the metallization layer contains a first sublayer that overlies the barrier layer and a second sublayer that overlies the first sublayer.

7. The capacitor of claim 6 , wherein the second sublayer contains a noble metal.

8. The capacitor of claim 7 , wherein the noble metal is gold or an alloy thereof.

9. The capacitor of claim 6 , wherein the first sublayer contains nickel or an alloy thereof.

10. The capacitor of claim 1 , wherein the valve metal of the barrier layer includes tungsten, titanium, tantalum, vanadium, zinc, aluminum, molybdenum, hafnium, and zirconium, or an alloy thereof.

11. The capacitor of claim 10 , wherein the valve metal of the barrier layer includes an alloy of tungsten.

12. The capacitor of claim 1 , wherein the capacitor element has a carbon content of about 2,000 ppm or less.

13. The capacitor of claim 1 , further comprising:

an anode termination in electrical contact with the anode; and

a cathode termination in electrical contact with the cathode coating.

14. The capacitor of claim 13 , wherein a conductive adhesive electrically connects the cathode termination to the cathode coating.

15. The capacitor of claim 14 , wherein the conductive adhesive includes sinterable metal particles.

16. The capacitor of claim 15 , wherein the metal particles include silver.

17. The capacitor of claim 1 , wherein the anode body includes tantalum.

18. The capacitor of claim 1 , wherein the capacitor exhibits a capacitance of about 30 nanoFarads per square centimeter or more, an equivalence series resistance of about 500 mohms or less, and/or a dissipation factor of from about 1% to about 25%.

19. The capacitor of claim 18 , wherein the capacitor exhibits a capacitance of about 30 nanoFarads per square centimeter or more, an equivalence series resistance of about 500 mohms or less, and/or a dissipation factor of from about 1% to about 25%, after being exposed to a temperature of 250° C. for about 500 hours.

20. The capacitor of claim 1 , further comprising a housing within which the capacitor element is enclosed.

21. The capacitor of claim 20 , wherein the housing is formed from a resinous material that encapsulates the capacitor element.

22. The capacitor of claim 20 , wherein the housing defines an interior cavity within which the capacitor element is positioned, wherein the interior cavity has a gaseous atmosphere.

23. The capacitor of claim 22 , wherein the gaseous atmosphere contains an inert gas.