Interconnector for a fuel cell stack and method for production
An interconnector is made of ferritic chromium steel, on which a cupriferous layer is disposed. This layer prevents interdiffusion between the chromium steel and additional components with which the interconnector has direct contact. According to the state of the art, such diffusion occurs particularly if these additional components contain nickel. In addition, the interconnector may comprise a chromium-containing oxide layer as a barrier against interdiffusion. For this purpose, the interconnector steel can also be preoxidized before applying the cupriferous layer. The interconnector has a significantly longer service life than interconnectors according to the state of the art, and it has improved electrical conductivity because the electrical contact surface thereof is free of oxides and has high transverse conductivity.
1. An interconnector for a fuel cell made of ferritic chromium steel, comprising a cupriferous layer including at least 50 wt % copper or copper alloy, disposed in at least some regions of the surface thereof, and an additional chromium-containing oxide layer made of Cr 2 O 3 disposed at the interface between the cupriferous layer and the chromium steel, and wherein the cupriferous layer does not oxidize in an operating atmosphere of a fuel cell that includes the interconnector, the operating atmosphere including an oxidizing agent.
2. The interconnector according to claim 1 , comprising a further oxide layer is disposed within the cupriferous layer.
3. An interconnector according to any one of claim 1 or 2 , wherein the Cr 2 O 3 layer has a thickness of between 0.2 and 3 mm.
4. An interconnector according to any one of claims 1 or 2 , wherein the cupriferous layer, including the additional chromium-containing Cr 2 O 3 oxide layer, has a thickness of between 5 and 1000 mm.
5. The interconnector according to claim 4 , wherein the cupriferous layer, including the additional chromium-containing Cr 2 O 3 oxide layer, has a thickness of between 10 and 50 mm.
6. An interconnector according to any one of claim 1 or 2 , comprising at least one electrical contact means which is disposed on the cupriferous layer.
7. The interconnector according to claim 5 , comprising a nickeliferous contact means.
8. The interconnector according to claim 6 , comprising a wire mesh or netting made of nickel as a contact means.
9. The interconnector according to claim 7 , wherein the wire mesh or netting is attached to the cupriferous layer by means of spot welding or soldering.
10. A method for producing an interconnector for a fuel cell made of ferritic chromium steel, comprising a cupriferous layer made of copper or copper alloy, disposed in at least some regions of the surface thereof, and an additional chromium-containing oxide layer made of Cr 2 O 3 disposed at the interface between the cupriferous layer and the chromium steel, wherein the cupriferous layer made of copper, or copper alloy is applied to at least to some regions of the surface thereof, and the interconnector is subjected to a heat treating operation before application of the cupriferous layer.
11. The method according to claim 10 , wherein the heat treating operation is performed at a temperature above 800° C.
12. A method according to claim 10 , wherein during the heat treating operation, a mixture comprising 94 percent by volume argon, 4 percent by volume hydrogen, and 2 percent by volume water vapor is used as the oxidation gas.
13. A method according to claim 10 , wherein chromium diffuses from the interconnector into the copper-containing layer, thereby forming another oxide layer within the cupriferous layer.
14. The method according to claim 10 , wherein the heat treating operation is performed at a temperature above 1000° C.
15. The method according to claim 10 , wherein a further oxide layer is disposed within the cupriferous layer.