Polymer based solid state capacitors and a method of manufacturing them
The present invention relates to a solid state capacitor having a conductive polymer cathode layer counter electrode that includes an acrylate binder and a method for its manufacture. In particular the present invention relates to a solid state capacitor comprising: providing a porous anode body of valve action material; forming a dielectric layer on said porous body; forming a cathode layer in contact with the dielectric layer, which cathode layer comprises a conductive polymer and an acrylic binder; and providing an anode terminal in electrical connection with the porous body anode and a cathode terminal in electrical connection with the cathode layer and a method for its manufacture.
1. A method of manufacturing a solid state capacitor comprising:
providing a porous anode body of valve action material;
forming a dielectric layer on said porous body;
applying a composition to a surface of the dielectric layer, the composition containing a thiophene monomer and an acrylic polymer binder, wherein the binder is hydroxyethylmethacrylate;
polymerizing the monomer to form a cathode layer that is in direct contact with said dielectric layer, which cathode layer comprises an intrinsically conductive thiophene polymer and the acrylic polymer binder; and
providing an anode terminal in electrical connection with the porous body anode and a cathode terminal in electrical connection with the cathode layer.
2. The method of claim 1 wherein said cathode layer comprises a dopant for the polymer.
3. The method of claim 2 wherein the dopant comprises a complex of a metal cation and an organic acid.
4. The method of claim 3 wherein the organic acid is a sulphonic acid.
5. The method of claim 4 wherein the dopant is Fe (III) tosylate.
6. The method of claim 1 wherein the binder is present in the polymer in a concentration of 0.1 to 20 wt %.
7. The method of claim 6 wherein the binder concentration is to 0.5 to 15 wt %.
8. The method of claim 1 wherein the monomer is polymerised electrochemically.
9. The method of claim 1 wherein the valve action material comprises tantalum metal or niobium metal or conductive niobium oxide.
10. The method according to claim 1 wherein the dielectric layer is formed by anodisation of the anode body and the formation voltage used in the anodisation is from 6 to 150 V.
11. The method of claim 1 , wherein the conductive thiophene polymer is poly(3,4-ethylenedioxythiophene).
12. A solid state capacitor comprising:
a porous anode body of valve action material;
a dielectric layer formed on said porous body;
a cathode layer in direct contact with said dielectric layer, which cathode layer comprises an in situ polymerized conductive thiophene polymer and an acrylic polymer binder, wherein the binder is hydroxyethylmethacrylate; and
an anode terminal in electrical connection with the porous body anode and a cathode terminal in electrical connection with the cathode layer.
13. The capacitor of claim 12 , wherein said cathode layer comprises a dopant for the polymer.
14. The capacitor of claim 13 , wherein the dopant comprises a complex of a metal cation and an organic acid.
15. The capacitor of claim 14 , wherein the organic acid is a sulphonic acid.
16. The capacitor of claim 14 , wherein the dopant includes Fe (III) tosylate.
17. The capacitor of claim 12 , wherein the binder is present in the polymer in a concentration of 0.1 to 20 wt %.
18. The capacitor of claim 12 , wherein the binder concentration is to 0.5 to 15 wt %.
19. The capacitor of claim 12 , wherein the valve action material comprises tantalum metal or niobium metal or conductive niobium oxide.
20. The capacitor of claim 12 , the capacitor having a DCL of less than 50 nA/CV.
21. The capacitor of claim 12 , wherein the conductive thiophene polymer is poly(3,4-ethylenedioxythiophene).