Fuel cell cathodes and their fuel cells
Fuel cell cathodes and instant startup fuel cells employing the cathodes. The cathodes operate through the valency change mechanism of redox couples which uniquely provide multiple degrees of freedom in selecting the operating voltages available for such fuel cells. Such cathodes provide the fuel cells in which they are used a “buffer” or “charge” of oxidizer available within the cathode at all times.
1. In a electrochemical cell, a cathode comprising:
a cathode active material including a valency change material for storing and supplying oxygen via a change in the valency state of said valency change material.
2. The cathode according to claim 1 , wherein said valency change material is a nickel hydroxide/nickel oxyhydroxide redox couple.
3. The cathode according to claim 1 , wherein said valency change material comprises a metal/metal oxide redox couple of an element selected from the group consisting of copper, silver, zinc and cadmium.
4. The cathode according to claim 1 , wherein said valency change material comprises a metal oxide/oxide redox couple of a metal selected from tin or manganese.
5. The cathode according to claim 1 , wherein said valency change material comprises a cobalt hydroxide/oxyhydroxide redox couple.
6. The cathode of claim 1 , further including a hydrophobic component.
7. The cathode of claim 6 , wherein said hydrophobic component comprises polytetrafluoroethylene.
8. The cathode of claim 7 , wherein said polytetrafluoroethylene is at least one of:
a) intimately mixed with said cathode active material;
b) graded within said cathode active material; or
c) a separate layer within said cathode.
9. The cathode of claim 1 , further including a current collector extending within said active material.
10. The cathode of claim 9 wherein said current collector comprises an electrically conductive mesh, grid, foam or expanded metal.
11. The cathode of claim 1 , further including a catalytic carbon component.
12. A cathode active material for a cathode comprising:
a valency change material for storing and supplying oxygen via a change in valency during use of said cathode.
13. The cathode active material according to claim 12 , wherein said valency change material is a nickel hydroxide/nickel oxyhydroxide redox couple.
14. The cathode active material according to claim 12 , wherein said valency change material comprises a metal/metal oxide redox couple of an element selected from the group consisting of copper, silver, zinc and cadmium.
15. The cathode active material according to claim 12 , wherein said valency change material comprises a metal oxide/oxide redox couple of a metal selected from tin or manganese.
16. The cathode active material according to claim 12 , wherein said valency change material comprises a cobalt hydroxide/oxyhydroxide redox couple.