Fuel cell stack with cooling fins and use of expanded graphite in fuel cells

Abstract

For an improved cooling a fuel cell stack ( ) with cooling fins extending around the periphery of the stack, the section of the stack has a somewhat longitudinal shape. In detail, the stack comprises: a plurality of fuel cells electrically connected in series and having equivalent active section areas and circumferences, each fuel cell comprising a laminate of layers, these comprising an electrolyte membrane and catalyst, electrode and gas diffusion layers the functions of which may be combined in any combination in multifunction layers; end and separator plates delimiting each cell; and cooling layers ( ) the cooling function of which also may be combined with other layers in respective multifunction layers, the cooling layers each projecting beyond the circumferential outer periphery ( ) of the laminate of the outer layers thereby comprising an inner active section area ( ) and a peripheral cooling fin area ( ). For extending the circumference of the active area ( ) and thereby the section of the cooling layer and the area of the fins, the ratio ( ) of circumference ( ) and active area ( ) of the stack ( ), defined by the geometrical shape of the active area ( ), extends the corresponding ratio of a square active area. Also describe is the use of expanded graphite for one or several of the following components of a fuel cell: bipolar plate, electrode, and gas diffusion layer.