US Patent 11101484 Electrochemical cell stack

An electrochemical cell stack includes an electrochemical cell disposed between a first separator and a second separator. The electrochemical cell includes an anode, a cathode, and a solid electrolyte layer disposed between the anode and the cathode. The solid electrolyte layer, containing a zirconia-based material as a main component, has an upstream part and a downstream part. The upstream part is positioned on the upstream side in the flow direction of a fuel gas in the fuel flow passage between the anode and the first separator. The downstream part is positioned on the downstream side in the flow direction. The upstream part includes a first region within 3 μm from the anode side surface, and a second region provided on the first region. An intensity ratio of tetragonal zirconia to cubic zirconia in a Raman spectrum of the first region is greater than that of the second region.