Fuel cell stack

A fuel cell stack including power generation units formed by stacking an even number of electrolyte electrode assemblies and metal separators alternately, the electrolyte electrode assemblies each including an anode, a cathode, and an electrolyte interposed between the anode and the cathode, a fuel gas flow field for supplying a fuel gas to the anode and an oxygen-containing gas flow field for supplying an oxygen-containing gas to the cathode being formed in each of power generation units, the fuel gas flow field and the oxygen-containing gas flow field each having an uneven buffer at least at one of a flow field inlet and a flow field outlet of the fuel gas flow field and the oxygen-containing gas flow field, the power generation units including a first power generation unit and a second power generation unit stacked alternately such that a coolant flow field is formed between the first power generation unit and the second power generation unit, wherein

• each of the first power generation unit and the second power generation unit includes at least first and second electrolyte electrode assemblies;
• the first electrolyte electrode assembly is stacked on a first metal separator, a second metal separator is stacked on the first electrolyte electrode assembly, the second electrolyte electrode assembly is stacked on the second metal separator, and a third metal separator is stacked on the second electrolyte electrode assembly,
• in the first power generation unit, bosses of the first metal separator are in a same phase as bosses of the third metal separator;
• in the second power generation unit, bosses of the first metal separator are in a same phase as bosses of the third metal separator;
• and
• bosses of the first metal separator of the first power generation unit are staggered from the bosses of the first metal separator of the second power generation unit in a direction perpendicular to the stacking direction.