Solid electrolytic capacitor element for use in dry conditions

1. A capacitor assembly that is hermetically sealed within a housing, wherein the housing defines an interior cavity within which the capacitor assembly is positioned, wherein the interior cavity has a dry, gaseous atmosphere having a relative humidity of about 10% or less, the capacitor assembly comprising a capacitor element that includes an anode that contains a dielectric formed on a sintered porous tantalum body and a solid electrolyte overlying the anode, wherein the sintered porous tantalum body is formed from a tantalum powder having a specific charge of from about 70,000 to about 800,000 μF*V/g and having a granular shape and an aspect ratio of about 4 or less, wherein the solid electrolyte includes an intrinsically conductive polymer containing repeating units having the following formula (I):

wherein,

R is (CH 2 ) a —O—(CH 2 ) b ;

a is from 0 to 10;

b is from 1 to 18;

Z is an anion;

X is a cation;

wherein the solid electrolyte contains one or more inner layers, the inner layer containing the intrinsically conductive polymer and being generally free of extrinsically conductive polymers; and

wherein the capacitor assembly exhibits a leakage current of about 100 microamps or less after being subjected to an applied voltage for 5 minutes.

2. The capacitor assembly of claim 1 , wherein the capacitor assembly exhibits a leakage current of about 25 microamps or less after being subjected to the applied voltage for 40 minutes.

3. The capacitor assembly of claim 1 , wherein a is 1 and b is 3 or 4.

4. The capacitor assembly of claim 1 , wherein Z is SO 3 .

5. The capacitor assembly of claim 1 , wherein X is an alkali metal.

6. The capacitor assembly of claim 1 , wherein the 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][1,4]dioxin-2-ylmethoxy)-1-propanesulphonic acid, salt), or a combination thereof.

7. The capacitor assembly of claim 1 , wherein the solid electrolyte contains from 5 to 15 inner layers.

8. The capacitor assembly of claim 1 , wherein the solid electrolyte contains one or more outer layers, wherein at least one of the outer layers is formed from a dispersion of particles that contain a polymeric counterion and an extrinsically conductive polymer having repeating units of the following formula (III):

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; or C 1 to C 4 hydroxyalkyl radical, or hydroxyl radical; and

q is an integer from 0 to 8.

9. The capacitor assembly of claim 8 , wherein at least one of the outer layers contains a hydroxyl-functional nonionic polymer.

10. The capacitor assembly of claim 1 , wherein the gaseous atmosphere contains an inert gas.

11. The capacitor assembly of claim 1 , wherein the valve metal powder has a specific charge of from about 100,000 to about 800,000 μF*V/g.

12. A capacitor assembly comprising:

a capacitor element that includes an anode that contains a dielectric formed on a sintered porous tantalum body and a solid electrolyte overlying the anode, wherein the sintered porous tantalum body is formed from a tantalum powder having a specific charge of from about 70,000 to about 800,000 μF*V/g and having a granular shape and an aspect ratio of about 4 or less, wherein the solid electrolyte includes an intrinsically conductive polymer containing repeating units having the following formula (I):

wherein,

R is (CH 2 ) a —O—(CH 2 ) b ;

a is from 0 to 10;

b is from 1 to 18;

Z is an anion; and

X is a cation;

a hermetically sealed housing that defines an interior cavity within which the capacitor element is positioned, wherein the interior cavity has a gaseous atmosphere that has a relative humidity of about 10% or less;

an anode termination that is in electrical connection with the anode body;

a cathode termination that is in electrical connection with the solid electrolyte;

wherein the solid electrolyte contains one or more inner layers, the inner layer containing the intrinsically conductive polymer and being generally free of extrinsically conductive polymers; and

wherein the capacitor assembly exhibits a leakage current of about 100 microamps or less after being subjected to an applied voltage for 5 minutes.

13. The capacitor assembly of claim 12 , wherein the gaseous atmosphere contains an inert gas.

14. The capacitor assembly of claim 12 , wherein a is 1 and b is 3 or 4.

15. The capacitor assembly of claim 12 , wherein Z is SO 3 .

16. The capacitor assembly of claim 12 , wherein X is an alkali metal.

17. The capacitor assembly of claim 12 , wherein the 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][1,4]dioxin-2-ylmethoxy)-1-propanesulphonic acid, salt), or a combination thereof.

18. The capacitor assembly of claim 12 , wherein the solid electrolyte contains from 5 to 15 inner layers.

19. The capacitor assembly of claim 12 , wherein the solid electrolyte contains one or more outer layers, wherein at least one of the outer layers are formed from a dispersion of particles that contain a polymeric counterion and an extrinsically conductive polymer having repeating units of the following formula (III):

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; or C 1 to C 4 hydroxyalkyl radical, or hydroxyl radical; and

q is an integer from 0 to 8.

20. The capacitor assembly of claim 19 , wherein at least one of the outer layers contains a hydroxyl-functional nonionic polymer.

21. The capacitor assembly of claim 12 , wherein the valve metal powder has a specific charge of from about 100,000 to about 800,000 μF*V/g.