Solid electrolytic capacitor with improved performance at high voltages
A solid electrolytic capacitor that comprises a sintered porous anode, a dielectric layer that overlies the anode body, and a solid electrolyte overlying the dielectric layer is provided. The anode is formed from a finely divided powder (e.g., nodular or angular) having a relatively high specific charge. Despite the use of such high specific charge powders, high voltages can be achieved through a combination of features relating to the formation of the anode and solid electrolyte. For example, relatively high press densities and sintering temperatures may be employed to achieve “sinter necks” between adjacent agglomerated particles that are relatively large in size, which render the dielectric layer in the vicinity of the neck less susceptible to failure at high forming voltages.
1. A solid electrolytic capacitor comprising:
a sintered porous anode that is formed from a finely divided powder having a specific charge of greater than about 30,000 μF*V/g, wherein the powder contains particles having a three-dimensional shape;
a dielectric layer that overlies the anode body; and
a solid electrolyte overlying the dielectric layer, wherein the solid electrolyte comprises a plurality of pre-polymerized conductive polymer particles and a separate hydroxy-functional nonionic copolymer,
wherein the capacitor exhibits a breakdown voltage of about 60 V or more.
2. The solid electrolytic capacitor of claim 1 , wherein the particles are nodular.
3. The solid electrolytic capacitor of claim 1 , wherein the powder has a specific charge of from about 35,000 to about 45,000 μF*V/g.
4. The solid electrolytic capacitor of claim 1 , wherein the anode contains from about 2500 to about 6000 ppm oxygen.
5. The solid electrolytic capacitor of claim 1 , wherein the pre-polymerized particles are formed from a substituted polythiophene.
6. The solid electrolytic capacitor of claim 5 , wherein the pre-polymerized particles contain a monomeric or polymeric counteranion.
7. The solid electrolytic capacitor of claim 1 , wherein the pre-polymerized particles have an average size of from about 2 to about 50 nanometers.
8. The solid electrolytic capacitor of claim 1 , wherein the hydroxy-functional polymer is a polyalkylene ether.
9. The solid electrolytic capacitor of claim 8 , wherein the polyalkylene ether is a polyalkylene glycol.
10. The solid electrolytic capacitor of claim 1 , wherein the solid electrolyte contains a first layer that overlies the dielectric layer and a second layer that overlies the first layer, the first layer containing the plurality of the pre-polymerized particles and the second layer containing the hydroxy-functional nonionic polymer.
11. The solid electrolytic capacitor of claim 10 , wherein the second layer contains a plurality of pre-polymerized conductive polymer particles.
12. The solid electrolytic capacitor of claim 1 , further comprising an external polymer coating that overlies the solid electrolyte, wherein the external polymer coating contains a plurality of pre-polymerized conductive polymer particles.
13. The solid electrolytic capacitor of claim 12 , wherein the external polymer coating contains a first layer that overlies the solid electrolyte and a second layer that overlies the first layer, wherein the first layer contains a crosslinking agent and the second layer contains the pre-polymerized conductive polymer particles.
14. The solid electrolytic capacitor of claim 1 , further comprising an anode termination that is electrically connected to the anode and a cathode termination that is electrically connected to the solid electrolyte.
15. The solid electrolytic capacitor of claim 1 , wherein the capacitor exhibits a breakdown voltage of about 80 volts or more.
16. The solid electrolytic capacitor of claim 1 , wherein the capacitor exhibits p wet-to-dry capacitance of about 50% or more.
17. The solid electrolytic capacitor of claim 10 , wherein the concentration of hydroxy-functional nonionic polymers in the first layer is about 2 wt. % or less.
18. The solid electrolytic capacitor of claim 1 , wherein the particles contain poly(3,4-ethylenedioxythiophene).