Polymer electrolyte fuel cell having improved current collector plates and method of forming the same

Abstract

A polymer electrolyte fuel cell may have a cell stack of a plurality of unit cells. Each of the unit cells includes a hydrogen-ion conductive polymer electrolyte membrane, an anode and a cathode sandwiching the polymer electrolyte membrane, an anode-side separator having a gas flow channel for supplying a fuel gas to the anode, and a cathode-side separator having a gas flow channel for supplying an oxidant gas to the cathode. A pair of current collector plates sandwiches the cell stack, and a pair of end plates clamps the cell stack and the current collector plates under pressure. The current collector plates have a conductive carbon material as a main component, and have a terminal section for connecting a power output cable in the vicinity of an inlet-side manifold for the fuel gas or the oxidant gas.

1 . A method of molding a current collector plate for a fuel cell stack, said method comprising: 
 evenly charging a molding compound into a mold, said molding compound comprising a conductive carbon material;    compressing said molding compound in said mold at a first temperature and a first pressure;    providing a metal plate with a conductive layer on a surface thereof;    opening the mold and inserting said metal plate into the mold;    charging a further amount of the molding compound into the mold to surround said metal plate with said molding compound; and    applying a second pressure and a second temperature to the mold to from a current collector plate having said metal plate embedded in said molding material, said second pressure being higher than said first pressure and said second temperature being higher than said first temperature.    
   
   
       2 . The method of  claim 1 , wherein said metal plate is made of brass and said conductive layer is platinum.  
   
   
       3 . The method of  claim 1 , wherein said metal plate is made of Ti and said conductive layer is TiN.  
   
   
       4 . The method of  claim 1 , wherein said metal plate is made of Al and said conductive layer is Ti—Al—N.  
   
   
       5 . The method of  claim 1 , wherein said metal plate is made of stainless steel SUS 316 and said conductive layer is Pb.  
   
   
       6 . The method of  claim 1 , wherein said metal plate is made of stainless steel SUS 316 and said conductive layer is In-doped tin oxide.  
   
   
       7 . The method of  claim 1 , wherein said step of providing said metal plate with a conductive layer on a surface thereof comprises: 
 decomposing a gas on a metal substrate, said gas being a mixture of silane, methane (CH 4 ) and diborane (PH 3 ) in a ratio wherein P/(Si+C)=10 atomic % with the mixture having a pressure of 10 Torr conductive layer is an n-type doped SiC layer and with the substrate at a predetermined temperature; and    depositing a gold electrode on the SiC layer.    
   
   
       8 . The method of  claim 7 , wherein said predetermined temperature is about 300° C.  
   
   
       9 . The method of  claim 8 , wherein said a time of said decomposing step is controlled to provide a thickness of said n-type doped SiC layer of 1000 Å.