Cathode coating for a wet electrolytic capacitor

• US 20080232031A1
• Filed: 03/20/2007
• Published: 09/25/2008
• Est. Priority Date: 03/20/2007
• Status: Active Grant

• Current Assignee: AVX Corporation (Kyocera Corporation)
• Original Assignee: AVX Corporation (Kyocera Corporation)
• Inventors: Ning, Gang
• Granted Patent: US 7,554,792 B2
• Time in Patent Office: Days
• US Class Current: 361/509
• 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 comprises an anode, cathode, and working electrolyte is provided. The cathode contains a coating disposed over a surface of a current collector, wherein the coating comprises a plurality of electrochemically-active particles and a binder. The binder is formed from an amorphous polymer having a glass transition temperature of about 100° C. or more.

Claims

1. A wet electrolytic capacitor comprising:

an anode, wherein the anode includes tantalum, niobium, or an electrically conductive oxide thereof;

a dielectric film formed over and within the anode through anodization of the anode;

a cathode containing a coating disposed over a surface of a current collector, wherein the coating comprises a plurality of electrochemically-active particles and a binder, the binder being formed from an amorphous polymer having a glass transition temperature of about 100°

C. or more, wherein the binder is in the form of particles having a D₉₀ particle size distribution of about 150 micrometers or less; and

a working electrolyte disposed between the cathode and the anode, wherein the working electrolyte contains an aqueous solution that includes an acid.

2. The wet electrolytic capacitor of claim 1, wherein the amorphous polymer has a glass transition temperature of about 150°

C. or more.

3. The wet electrolytic capacitor of claim 1, wherein the amorphous polymer has a glass transition temperature of about 250°

C. or more.

4. The wet electrolytic capacitor of claim 1, wherein the amorphous polymer is a thermoplastic polyimide.

5. The wet electrolytic capacitor of claim 4, wherein the polyimide is a poly(amide-imide), poly(ether-imide), or a combination thereof.

6. The wet electrolytic capacitor of claim 5, wherein the polyimide is a poly(amide-imide) formed from trimellitic acid or a derivative thereof, and an aromatic diamine.

7. The wet electrolytic capacitor of claim 1, wherein the binder is in the form of particles having a D₉₀ particle size distribution of about 75 micrometers or less.

8. The wet electrolytic capacitor of claim 1, wherein the binder constitutes from about 1 wt. % to about 40 wt. % of the coating.

9. The wet electrolytic capacitor of claim 1, wherein the binder constitutes from about 5 wt. % to about 20 wt. % of the coating.

10. The wet electrolytic capacitor of claim 1, wherein the electrochemically-active particles include a metal, metal oxide, carbonaceous particles, or a combination thereof.

11. The wet electrolytic capacitor of claim 1, wherein the electrochemically-active particles include activated carbon.

12. The wet electrolytic capacitor of claim 1, wherein the electrochemically-active particles constitute from about 50 wt. % to about 99 wt. % of the coating.

13. The wet electrolytic capacitor of claim 1, wherein the electrochemically-active particles constitute from about 70 wt. % to about 95 wt. % of the coating.

14. The wet electrolytic capacitor of claim 1, wherein the coating further comprises a conductive filler.

15. The wet electrolytic capacitor of claim 1, wherein the current collector comprises a metal.

31. The wet electrolytic capacitor of claim 1, wherein the anode includes tantalum.

32. The wet electrolytic capacitor of claim 1, wherein the anode includes an electrically conductive oxide of niobium.

33. The wet electrolytic capacitor of claim 32, wherein the dielectric film includes niobium pentoxide.

34. The wet electrolytic capacitor of claim 33, wherein the electrically conductive oxide has an atomic ratio of niobium to oxygen of 1 :

less than 1.5.

35. The wet electrolytic capacitor of claim 33, wherein the electrically conductive oxide has an atomic ratio of niobium to oxygen of 1:

1.0±

0.2.

16-19. -19. (canceled)

20. A wet electrolytic capacitor comprising:

an anode, wherein the anode includes tantalum, niobium, or an electrically conductive oxide thereof;

a dielectric film formed over and within the anode through anodization of the anode;

a cathode containing a coating disposed over a surface of a current collector, wherein the coating comprises a plurality of activated carbon particles and a binder, the binder being formed from an amorphous poly(amide-imide) polymer having a glass transition temperature of about 100°

C. or more, wherein the binder is in the form of particles having a D₉₀ particle size distribution of about 150 micrometers or less; and

a working electrolyte disposed between the cathode and the anode, wherein the working electrolyte contains an aqueous solution that includes an acid.

21. The wet electrolytic capacitor of claim 20, wherein the amorphous poly(amide-imide) polymer has a glass transition temperature of about 150°

C. or more.

22. The wet electrolytic capacitor of claim 20, wherein the amorphous poly(amide-imide) polymer has a glass transition temperature of about 250°

C. or more.

23. The wet electrolytic capacitor of claim 20, wherein the amorphous poly(amide-imide) polymer is formed from trimellitic acid or a derivative thereof, and an aromatic diamine.

24. The wet electrolytic capacitor of claim 20, wherein the binder is in the form of particles having a D₉₀ particle size distribution of about 75 micrometers or less.

25. The wet electrolytic capacitor of claim 20, wherein the binder constitutes from about 1 wt. % to about 40 wt. % of the coating.

26. The wet electrolytic capacitor of claim 20, wherein the binder constitutes from about 5 wt. % to about 20 wt. % of the coating.

27. The wet electrolytic capacitor of claim 20, wherein the electrochemically-active particles constitute from about 50 wt. % to about 99 wt. % of the coating.

28. The wet electrolytic capacitor of claim 20, wherein the electrochemically-active particles constitute from about 70 wt. % to about 95 wt. % of the coating.

29. The wet electrolytic capacitor of claim 20, wherein the coating further comprises a conductive filler.

30. (canceled)