Flow field plate assembly for an electrochemical fuel cell

#The present invention relates to a flow field plate assembly for fuel cells. More particularly, the invention relates to a flow field plate assembly comprising two flow field plates that engage each other on their inner surfaces such that each inner channel on the inner surface of one plate overlaps an inner channel on the inner surface of the other plate essentially along its entire length. The present invention also relates to a flow field plate assembly comprising two flow field plates, one supporting the other against spreading under compressive load.

#Fuel cell systems are currently being developed for numerous applications, such as automobiles and stationary power plants, where they will be used to economically deliver power with significant environmental benefits.

#Preferred fuel cell types include solid polymer fuel cells that comprise a solid polymer electrolyte, otherwise referred to as an ion exchange membrane, and operate at relatively low temperatures. The membrane is disposed between two electrodes, namely a cathode and an anode, forming a membrane electrode assembly (“MEA”). Each electrode contains a catalyst layer, comprising an appropriate catalyst, located next to the solid polymer electrolyte. The catalyst induces the desired electrochemical reactions at the electrodes. During normal operation of a solid polymer electrolyte fuel cell, fuel is electrochemically oxidized at the anode catalyst, typically resulting in the generation of protons, electrons, and possibly other species depending on the fuel employed. The protons are conducted from the reaction sites at which they are generated, through the electrolyte, to electrochemically react with the oxidant at the cathode catalyst. The electrons pass through an external circuit, creating a flow of electricity.

#FIG. 1 is an exploded side view of a conventional fuel cell assembly, showing one membrane electrode assembly and the corresponding reactant and coolant fluid flow field plates.

#FIG. 2 is a perspective view of a flow field plate assembly showing two flow field plates aligned and assembled together in accordance with the present disclosure.

#FIG. 3 is a cross-sectional view of the first flow field plate of FIG. 2.

#FIG. 1 illustrates a conventional fuel cell assembly. For simplicity, a single cell, from a fuel cell stack is represented. It is to be understood that this represents a repeating unit of the fuel cell stack.

#This repeating unit 1 includes one membrane electrode assembly (MEA) 2 interposed between a flow field plate 3 and a flow field plate in an adjacent unit (not shown), similar to plate 4. The MEA comprises a solid polymer ion exchange membrane 5 sandwiched between an anode 6 and a cathode 7. The anode 6 and cathode 7 each contain a fluid diffusion layer 8 and 9 respectively and a catalyst layer 10 and 11 respectively, on the sides facing the membrane 5. Fluid distribution layers 8 and 9 serve as electrically conductive backings and mechanical supports for catalyst layers 10, 11, but fluid distribution layers 8 and 9 also serve to distribute the reactants from the flow field plates to the catalyst layer. The reactants, typically hydrogen and oxygen or oxygen-containing air, are supplied to the flow field plates 3 and 4 and then delivered through the fluid distribution channels 13 and 12 of the flow fields to the surfaces of the fluid distribution layers 8 and 9.

#As shown in FIG. 1 the flow field plate 4 contains channels 14 on the side facing the flat surface 15 of the flow field plate 3. The cooperating sides of the channel 14 and the flat surface 15 form a closed inner flow field channel for carrying a coolant fluid, typically water.