Fuel cell stack

Abstract

In order to provide a fuel cell stack which can sufficiently use a current range that can originally be output by a fuel cell unit, and from which high output can be obtained even with a small size, a thickness of an oxygen flow field plate is made large for a fuel cell unit having a relatively high temperature during operation, and the thickness of the oxygen flow field plate is made small for a fuel cell unit having a relatively low temperature during operation.

1 . A fuel cell stack comprising a plurality of fuel cell units stacked, each having an oxygen supply layer on a side of one surface of an electrolyte membrane,
 wherein each of the oxygen supply layers has an opening opened to an atmosphere in at least a part of a side surface thereof, and diffuses oxygen in the atmosphere from the opening to the side of the one surface of the electrolyte membrane, and diffuses vapor from the side of the one surface of the electrolyte membrane to the opening, and   wherein ventilation performance of a gas from and to the atmosphere in each of the oxygen supply layers in all of the fuel cell units is adjusted such that an oxygen supply layer in a fuel cell unit having a higher water vapor partial pressure during operation has a higher ventilation performance of the gas than an oxygen supply layer in a fuel cell unit having a lower water vapor partial pressure during operation.