Wet electrolytic capacitors

• US 7,456,073 B2
• Filed: 08/28/2006
• Issued: 11/25/2008
• Est. Priority Date: 05/24/2005
• Status: Expired due to Fees

• Current Assignee: AVX Corporation (Kyocera Corporation)
• Original Assignee: AVX Corporation (Kyocera Corporation)
• Inventors: Ning, Gang, Jones, Brady, Fife, James A.
• Primary Examiner(s): Nguyen; Ha
• Assistant Examiner(s): NEWTON, VALERIE N
• Application Number:
  US11/510,966
• Publication Number:
  US 20060286761A1
• Time in Patent Office: 820 Days
• Field of Search: 438/381, 29/250.3, 361/516
• US Class Current: 438/381
• CPC Class Codes: H01G 9/035 Liquid electrolytes, e.g. impregnating materials H01G11/54 takes precedence
• CPC Class Codes: H01G 9/0425 specially adapted for cathode
• CPC Class Codes: H01G 9/145 Liquid electrolytic capacitors H01G11/00 takes precedence

Abstract

A wet electrolytic capacitor that includes an anode, cathode, and a liquid electrolyte disposed therebetween is provided. The cathode contains a metal oxide coating, such as NbO₂, in conjunction with other optional coatings to impart improved properties to the capacitor.

Claims

1. A method for forming a wet electrolytic capacitor, the method comprising:

anodizing a surface of an anode to form a dielectric film;

applying a particle suspension to a metal substrate of a cathode;

sintering the suspension to form an oxide coating, the oxide coating comprising a niobium oxide having an atomic ratio of niobium to oxygen of 1;

less than 2.5; and

disposing a liquid electrolyte between the anode and the cathode.

2. The method of claim 1, wherein the suspension comprises a niobium oxide having an atomic ratio of niobium to oxygen of 1:

less than 1.5.

3. The method of claim 1, wherein the suspension comprises Nb₂.

4. The method of claim 1, wherein the suspension comprises Nb₂O₅.

5. The method of claim 1, wherein the suspension has a solids content of from about 20% to about 80% by weight.

6. The method of claim 1, wherein the metal substrate is dipped into the suspension.

7. The method of claim 1, wherein the oxide coating is formed from multiple layers of the suspension.

8. The method of claim 7, wherein each of the layers has a thickness of less than about 150 μ

m.

9. The method of claim 1, wherein the suspension is sintered at a temperature of from about 800°

C. to about 1400°

C.

10. The method of claim 1, further comprising applying a conductive polymer coating, a protective coating, or both over the oxide coating.

11. The method of claim 1, wherein the liquid electrolyte is an aqueous solution of sulfuric acid.

12. The method of claim 1, wherein the suspension comprises NbO_0.7, NbO_1.0, NbO_1.1, NbO₂, or a combination thereof.

13. The method of claim 1, wherein the suspension comprises a niobium oxide having an atomic ratio of niobium to oxygen of 1:

0.5±

0.2.

14. The method of claim 1, wherein the metal substrate comprises a metal selected from the group consisting of tantalum, niobium, aluminum, hafnium, titanium, and combinations thereof.

15. The method of claim 1, wherein the anode comprises tantalum, niobium, electrically conductive oxides or nitrides thereof, or combinations of the foregoing.

16. The method of claim 1, wherein the oxide coating has a resisitivity of less than about 1×

10⁵ ohm-cm.

17. The method of claim 1, further comprising drying the suspension at a temperature of from about 500°

C. to about 150°

C.

18. The method of claim 1, wherein the suspension is sintered at a temperature of from about 600°

C. to about 2000°

C.

19. A method for forming a wet electrolytic capacitor containing an anode and a cathode, the method comprising:

applying a particle suspension to a metal substrate of the cathode;

sintering the suspension at a temperature of from about 800°

C. to about 1400°

C. to form an oxide coating, the oxide coating comprising a niobium oxide having an atomic ratio of niobium to oxygen of 1;

less than 1.5; and

disposing a liquid electrolyte between the anode and the cathode.

20. The method of claim 19, wherein the suspension comprises a niobium oxide having an atomic ratio of niobium to oxygen of 1:

0.5±

0.2.