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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic external appearance view showing an example of a fuel cell stack according to the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of the fuel cell stack of the present invention;

FIG. 3 is a graph showing a temperature distribution for each fuel cell unit in the fuel cell stack.

FIG. 4 is a graph showing an output current for each fuel cell unit in the fuel cell stack.

FIG. 5 is a graph showing current-voltage characteristics for various thicknesses of an oxygen flow field plate in a fuel cell unit of an air breathing fuel cell.

FIG. 6 is a graph showing a relationship between the thickness of the oxygen flow field plate in the fuel cell unit of the air breathing fuel cell and the maximum current value thereof.

FIG. 7 is a cross-sectional view showing the structure of a fuel cell stack of Comparative Example of the prior art.

FIG. 8 is a graph showing current-voltage characteristics when the fuel cell units including oxygen flow field plates having the same thickness are separately allowed to generate electric power at different temperatures.

FIG. 9 is a graph showing a relationship between the oxygen partial pressure in an oxygen flow field plate and the maximum current value.

Claims

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 the 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 water vapor from the side of the one surface of the electrolyte membrane to the opening, andwherein an area of an opening of one fuel cell unit having a temperature higher than a temperature of another fuel cell unit during generation of electric power is larger than an area of an opening of the another fuel cell unit.

2. A fuel cell stack comprising at least three 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 the 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 water vapor from the side of the one surface of the electrolyte membrane to the opening, andwherein the oxygen supply layer of the fuel cell unit provided in a middle of the stack is thicker than each of the oxygen supply layers of the fuel cell units provided at both ends of the stack.

3. 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 the 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, andwherein ventilation performance of a gas from and to the atmosphere in an oxygen supply layer of one fuel cell unit having a water vapor partial pressure higher than a water vapor partial pressure of another fuel cell unit during operation is higher than ventilation performance of a gas from and to the atmosphere in an oxygen supply layer of the another fuel cell unit.