Fuel-cell power generation unit and fuel-cell stack

A fuel cell stack comprising a plurality of fuel cell electricity generation units arranged in a first direction;

• and first and second metal end plates which face each other in the first direction with the fuel cell electricity generation units intervening there between, wherein each fuel cell electricity generation unit comprises:
• a single cell including an electrolyte layer, and a cathode and an anode which face each other in the first direction with the electrolyte layer intervening there between;
• first and second metal interconnectors which face the single cell in the first direction;
• a metal separator having a through hole and a portion which surrounds the through hole and is bonded to a peripheral portion of the single cell, thereby separating a cathode chamber facing the cathode from an anode chamber facing the anode;
• a metal frame member disposed between the separator and the first interconnector facing one surface of the separator, the metal frame member having a through hole forming a first chamber, which is one of the anode chamber and the cathode chamber;
• and
• a gas sealing member disposed between the separator and the second interconnector facing the surface of the separator opposite the surface facing the frame member, the gas sealing member having a contact portion which is in contact with both the surface of the separator on the side toward the second interconnector and the surface of the second interconnector on the side toward the separator, thereby sealing a second chamber, which is the other of the anode chamber and the cathode chamber, wherein
• each fuel cell electricity generation unit has a contact overlap region overlapping with the contact portion in the first direction, the contact overlap region being a portion of the fuel cell stack;
• each of the gas sealing member, the separator, the frame member, the first interconnector, and the second interconnector of the fuel cell electricity generation unit and the first and second end plates is present in the contact overlap region;
• and
• at least one of a first weld portion sealing between the separator and the frame member and a second weld portion sealing between the frame member and the first interconnector is formed at a position whose distance from the periphery of the single cell in a second direction perpendicular to the first direction is greater than the distance between the periphery and the contact overlap region corresponding to the contact portion nearest to the single cell.