Thin film solid oxide fuel cell and method for forming

DETAILED DESCRIPTION OF THE INVENTION It is preferred to fabricate a TFSOFC with a thin electrolyte layer to reduce the resistive loss in the electrolyte.
The electrolyte layer should be dense and pore-free to prevent gas leakage through it.
It is also preferred that porous electrodes be used to increase the gas transport rate.
These requirements increase the difficulty in the fabrication of TFSOFCs.
We disclose herein an epitaxial film growth method to make a TFSOFC with the combined structure of a dense thin film electrolyte with porous or gas-permeable electrodes.
As demonstrated in FIG.
1(a), the method first uses a thin dense metallic material 10, such as nickel foil, as a substrate for the cell fabrication and as the cell anode.
A dense but thin electrolyte layer 12 is then deposited on the substrate, as shown in FIG.
1(b), after which substrate 10 is made porous by lithographic patterning and etching, resulting in pores 14 (FIG.
1 (c)) developed in the substrate but not in the electrolyte.
Referring to FIG.
1(d), cathode 16 of the SOFC is deposited in thin film form on electrolyte 12, either before or after etching of anode 10.
Further processing can be used to improve the permeability and performance of the electrodes, as disclosed below.
The SOFCs fabricated by this method can then be packaged into stacks, as indicated in FIG.
1(e), where interconnects 18 couple the SOFCs.
A schematic example of a SOFC fabricated with the method provided here is shown in FIG.
2.
Metal substrate and anode 10 has been used in an epitaxial deposition process to form electrolyte layer 12.
Cathode 16 has been formed on electrolyte 12.
Pores 14 are fabricated in metal substrate 10 by etching or physical drilling.
A preferred embodiment of a process for making a thin film solid oxide fuel cell is described as follows.
It should be understood that the description of a preferred embodiment does not limit the scope of the methods and apparatus disclosed herein.
A nickel foil with a nominal thickness of 0