Silicone seal for bipolar plates in a PEM fuel cell

Abstract

Seal means for sealing a bipolar plate to a membrane in a PEM fuel cell stack. The seal includes a thin layer of a cross-linkable silicone composition disposed between the bipolar plate and the membrane. The layer is applied as a liquid to either the plate or the membrane and preferably is polymerized prior to assembly of the stack. A preferred means for applying the composition to the bipolar plate is screen printing. Preferably, the layer has a thickness between 0.001 and 0.005 inch. The resulting fuel cell stack exhibits superior leak resistance. In a currently preferred embodiment, a layer of the silicone composition is provided at interfaces between a membrane and both an anode side and a cathode side of a bipolar plate.

What is claimed is:  
     
         1 . A membrane seal for bipolar plates in a proton exchange membrane fuel cell module, comprising a first seal element disposed against a first edge portion of a membrane between said membrane and a first bipolar plate surface, wherein said seal element is formed as an elastomeric layer.  
     
     
         2 . A membrane seal in accordance with  claim 1  wherein said first seal element is formed as a layer of low viscosity fluid composition coated on one of said first edge portion and said first bipolar plate surface.  
     
     
         3 . A membrane seal in accordance with  claim 2  wherein said composition includes an organopolysiloxane.  
     
     
         4 . A membrane seal in accordance with  claim 2  wherein said composition is applied to said one of said first edge portion and said first bipolar plate surface by screen printing.  
     
     
         5 . A membrane seal in accordance with  claim 1  wherein said first seal element is formed as a cross-linked polymer.  
     
     
         6 . A membrane seal in accordance with  claim 1  wherein a thickness of said first seal element is between about 0.001 inch and about 0.005 inch.  
     
     
         7 . A fuel cell module including a proton exchange membrane and a first bipolar plate, the module comprising an elastomeric first seal element disposed against a first edge portion of said membrane between said membrane and said first bipolar plate.  
     
     
         8 . A fuel cell module in accordance with  claim 7  wherein said first seal element includes an organopolysiloxane.  
     
     
         9 . A fuel cell module in accordance with  claim 7  wherein a thickness of said first seal element is between about 0.001 inch and about 0.005 inch.  
     
     
         10 . A fuel cell module in accordance with  claim 7  including a second bipolar plate, the module comprising an elastomeric second seal element disposed against a second edge portion of said membrane between said membrane and said second bipolar plate.  
     
     
         11 . A fuel cell assembly comprising a plurality of fuel cell modules, wherein at least one of said modules includes a proton exchange membrane and a bipolar plate and an elastomeric seal element disposed against an edge portion of said membrane between said membrane and said bipolar plate.  
     
     
         12 . A fuel cell assembly in accordance with  claim 11  wherein said elastomeric seal element is formed from a composition containing an organopolysiloxane.  
     
     
         13 . A fuel cell assembly in accordance with  claim 11  wherein a thickness of said seal element is between about 0.001 inch and about 0.005 inch.