Integrally molded gasket for a fuel cell assembly

Abstract

A fuel cell membrane electrode assembly (MEA) comprising first and second gas diffusion layers and an ion exchange membrane disposed between the diffusion layers. Each diffusion layer includes an inner surface facing the membrane, an outer surface opposite the inner surface, and a side surface defining a perimeter of the diffusion layers. An outboard region extends about the diffusion layers at the perimeter. The outboard region surrounds an inboard region. The outboard region has a low density region proximate to the side surface and a high density region between the low density region and the inboard portion. A seal is mounted at the low density region. The high density region prevents portions of the seal from entering the inboard region thereby damaging the MEA. The seal includes a first rim having a smaller radius than a second rim. The smaller radius allows the seal to fit between adjacent support plates and increases the durability of the seal.

1 . A fuel cell membrane electrode assembly comprising: 
 a first gas diffusion layer;    a second gas diffusion layer opposite said first gas diffusion layer;    an ion exchange membrane disposed between said first gas diffusion layer and said second gas diffusion layer;    each one of said first gas diffusion layer and said second gas diffusion layer include: 
 an inner surface facing said ion exchange membrane;  
 an outer surface opposite said inner surface;  
 a side surface between said outer surface and said inner surface defining a perimeter of said first and said second diffusion layers respectively;  
 an outboard region extending about a periphery of each of said first layer and said second layer at said perimeter; and  
 an inboard region at least substantially surrounded by said outboard region, said inboard region including an inboard low density region;  
 said outboard region including: 
 an outboard low density region at least proximate to said side surface and said perimeter; and  
 an outboard high density region between said outboard low density region and said inboard low density region, said first and said second diffusion layers having a greater density at said high density region than at said low density regions; and  
 
   a seal mounted to said outboard low density region so as to cover said outer surface and said side surface of each of said first and second diffusion layers at said outboard low density region.    
     
     
         2 . The membrane electrode assembly of  claim 1 , wherein said first and said second gas diffusion layers include porous electrodes.  
     
     
         3 . The membrane electrode assembly of  claim 1 , wherein said outer surface is closer to said inner surface at said outboard high density region than at said outboard and said inboard low density regions, such that said first and said second diffusion layers are thinner at said outboard high density region than at said outboard and said inboard low density regions.  
     
     
         4 . The membrane electrode assembly of  claim 1 , wherein said ion exchange membrane extends laterally beyond said first and said second gas diffusion layers.  
     
     
         5 . The membrane electrode assembly of  claim 1 , wherein said seal includes an elastomeric material.  
     
     
         6 . The membrane electrode assembly of  claim 1 , wherein said seal comprises at least one of silicone, fluorosilicone elastomer, fluorocarbon elastomer, and ethylene propylene diene monomer elastomer.  
     
     
         7 . The membrane electrode assembly of  claim 4 , wherein said seal covers said membrane.  
     
     
         8 . The membrane electrode assembly of  claim 1 , wherein said seal further comprises a first seal bead and a second seal bead; 
 wherein said first bead impregnates said first and said second gas diffusion layers and said second bead is laterally offset from said first and said second gas diffusion layers.    
     
     
         9 . The membrane electrode assembly of  claim 8 , wherein said first bead and said second bead are each at least substantially cylindrical; and 
 wherein said first bead has a smaller radius than said second bead.    
     
     
         10 . The membrane electrode assembly of  claim 1 , wherein said seal impregnates said first gas diffusion layer and said second gas diffusion layer to provide a barrier that is at least substantially impermeable to gas.  
     
     
         11 . A fuel cell membrane electrode assembly comprising: 
 a first gas diffusion layer;    a second gas diffusion layer;    an ion exchange membrane disposed between said first and said second gas diffusion layers;    each one of said first diffusion layer and said second diffusion layer include: 
 an inner surface facing said ion exchange membrane;  
 an outer surface opposite said inner surface;  
 a side surface between said outer surface and said inner surface defining a perimeter of said first and said second layers respectively; and  
   a seal having a first rim integral with a second rim, said first rim is mounted to said outer surface and said side surface of each of said first layer and said second layer, said second rim is laterally offset from said first and said second layers;    wherein said seal impregnates said first gas diffusion layer and said second gas diffusion layer to provide a barrier between said first and said second gas diffusion layers that is at least substantially impermeable to gas; and    wherein said first rim has a smaller volume than said second rim.    
     
     
         12 . The membrane electrode assembly of  claim 11 , wherein said first and said second gas diffusion layers comprise porous electrodes.  
     
     
         13 . The membrane electrode assembly of  claim 11 , wherein said first and said second rims are at least substantially cylindrical, said first rim having a smaller radius than said second rim.  
     
     
         14 . The membrane electrode assembly of  claim 11 , each one of said first layer and said second layer further comprising an outboard region extending about a periphery of said first layer and said second layer respectively at said side surface, each of said outboard regions having a low density region proximate to said side surface and a high density region distal to said side surface; 
 wherein said high density region is up to about 50% more dense than said low density region.    
     
     
         15 . The membrane electrode assembly of  claim 14 , wherein said first rim impregnates said low density region.  
     
     
         16 . The membrane electrode assembly of  claim 15 , wherein said second rim extends laterally beyond said first and said second diffusion layers.  
     
     
         17 . The membrane electrode assembly of  claim 11 , wherein said ion exchange membrane extends laterally beyond said first and said second gas diffusion layers.  
     
     
         18 . The membrane electrode assembly of  claim 11 , wherein said seal includes an elastomeric material.  
     
     
         19 . The membrane electrode assembly of  claim 11 , wherein said seal comprises at least one of silicone, fluorosilicone elastomer, fluorocarbon elastomer, and ethylene propylene diene monomer elastomer.  
     
     
         20 . A fuel cell comprising: 
 a first support plate;    a second support plate;    a membrane electrode assembly positioned between said first support plate and said second support plate, said membrane electrode assembly comprising: 
 a first electrode adjacent said first support plate;  
 a second electrode opposite said first electrode and adjacent said second support plate; and  
 an ion exchange membrane disposed between said first electrode and said second electrode;  
 each one of said first electrode and said second electrode include: 
 an inner surface facing said ion exchange membrane;  
 an outer surface opposite said inner surface, said outer surface of said first electrode facing said first support plate and said outer surface of said second electrode facing said second support plate;  
 a side surface between said outer surface and said inner surface defining a perimeter of said first and said second electrodes respectively;  
 an outboard region extending about a periphery of each of said first electrode and said second electrode at said perimeter;  
 an inboard region at least substantially surrounded by said outboard region;  
 said outboard region including a low density region proximate to said side surface and a high density region that is inboard of, and adjacent to, said low density region;  
 a seal mounted to said outboard low density region so as to cover said outer surface and said side surface of each of said first and said second diffusion layers;  
 
   wherein said seal impregnates said low density region of said outboard region to provide a barrier between said first and said second gas diffusion layers that is at least substantially impermeable to gas.    
     
     
         21 . The fuel cell of  claim 20 , further comprising a fuel cell stack including a plurality of said fuel cells.  
     
     
         22 . The fuel cell of  claim 20 , wherein said first and said second electrodes are porous.  
     
     
         23 . The fuel cell of  claim 20 , wherein said outer surface is closer to said inner surface at said high density region than at said low density region.  
     
     
         24 . The fuel cell of  claim 20 , wherein said inboard region and said low density region have the same density.  
     
     
         25 . The fuel cell of  claim 20 , wherein said seal comprises an elastomeric material.  
     
     
         26 . The fuel cell of  claim 20 , wherein said seal comprises at least one of silicone, fluorosilicone elastomer, fluorocarbon elastomer, and ethylene propylene diene monomer elastomer.  
     
     
         27 . The fuel cell of  claim 20 , wherein said seal further comprises a first annular projection and a second annular projection; 
 wherein said first projection impregnates said first and said second electrodes and said second projection is laterally offset from said first and said second electrodes.    
     
     
         28 . The fuel cell of  claim 27 , wherein said first and said second projections are at least substantially cylindrical, said first projection having a smaller radius than said second projection.  
     
     
         29 . A method for manufacturing a fuel cell membrane electrode assembly having an ion exchange membrane affixed between a first gas diffusion layer and a second gas diffusion layer, the method comprising the steps of: 
 positioning the first and the second gas diffusion layers with the membrane in-between between two halves of a thermo-mold assembly, each mold half having a protruding region that mirrors the location of a high density region to be formed in the first and second gas diffusion layers at an outboard region that extends about a periphery of the first and second diffusion layers;    closing the mold halves under heat such that the protruding regions of the mold halves compress the first and the second diffusion layers at the high density regions to increase the density of the first and second diffusion layers at the high density regions;    injecting an elastomeric material that is heated to a liquid within a cavity of the closed mold, the cavity located about the periphery of the membrane electrode assembly at a low density region that is outboard of the high density region, the liquid elastomer flows within and impregnates the first and second diffusion layers at the low density region; and    curing the liquid elastomeric material to form an elastomeric seal that is impregnated within the first and second diffusion layers at the low density region and extends around side surfaces of the first and second diffusion layers at a perimeter of the first and second diffusion layers.    
     
     
         30 . The method of  claim 29 , wherein said injecting step further comprises injecting the liquid elastomeric material within the cavity having an inner chamber connected to an outer chamber surrounding the inner chamber such that the seal formed after said curing step includes an inner rim and an outer rim, the inner rim impregnates the first and second gas diffusion layers and the outer rim extends laterally from the first and second gas diffusion layers.  
     
     
         31 . The method of  claim 30 , wherein the inner chamber has a smaller volume than the outer chamber such that the inner rim of the seal has a smaller diameter than the outer rim.