Patent ID: 7235325

Claim:
A single cell for a low operating temperature solid oxide fuel cell, the single cell comprising: a first solid electrolyte having an oxide ion conductivity at 800° C. of at least 0.015 S/cm and a bending strength of at least 600 MPa; a fuel electrode bonded to one side of the first solid electrolyte, the fuel electrode comprising a cermet of a catalyst and a second solid electrolyte having an oxide ion conductivity at 800° C. of at least 0.08 S/cm; an air electrode bonded to the other side of the first solid electrolyte, the air electrode comprising a compound of a first perovskite type oxide with a third solid electrolyte; and an intermediate layer comprising a fourth solid electrolyte interposed between the air electrode and the first solid electrolyte; wherein a surface roughness of the fuel electrode is in a range of 5 to 25 μm in maximum roughness depth and in a range of 3 to 20 μm in average roughness height Rz; and wherein a surface roughness of the air electrode is in a range of 3 to 20 μm in maximum roughness depth Rmax and in a range of 2 to 18 μm in average roughness height Rz, when measured by a laser optical non-contact 3D shape measurement device.