Inactive end cell assembly for fuel cells for improved electrolyte management and electrical contact

Abstract

An end cell for storing electrolyte in a carbonate fuel cell. The combination of a soft, compliant and resilient cathode current collector and an inactive anode part including a foam anode in each end cell mitigates electrical contact loss during operation of the fuel cell stack. In addition, an electrode reservoir in the positive end cell and an electrode sink in the negative end cell are provided, by which ribbed and flat cathode members inhibit electrolyte migration in the fuel cell stack.

What is claimed is:  
     
         1 . An apparatus for use in a fuel cell stack between an end plate of the fuel cell stack and the active cells of the fuel cell stack, the apparatus comprising: 
 an electrolyte storage assembly; and    a compliant, electrically conductive assembly adapted to promote electrical contact member between said electrolyte storage assembly and said end plate.    
     
     
         2 . An apparatus according to  claim 1 , wherein said electrolyte storage assembly has a first surface adapted to face said end plate and second and third side surfaces extending from said first surface, and said compliant, electrically conductive assembly includes a first part disposed between said first surface and said end plate and second and third parts disposed adjacent the second and third side surfaces, respectively, of said electrolyte storage assembly.  
     
     
         3 . An apparatus according to  claim 1 , wherein said electrolyte storage assembly has a first surface adapted to face said end plate and second and third side surfaces extending from said first surface, and said compliant, electrically conductive assembly includes one or more of a first part disposed between said first surface and said end plate and second and third parts disposed adjacent the second and third side surfaces, respectively, of said electrolyte storage assembly.  
     
     
         4 . An apparatus according to  claim 3 , wherein said first part includes a foam anode having opposing first and second surfaces and an anode current collector, said foam anode being adapted to abut said end cell at said first surface of said foam anode and abutting said anode current collector at said second surface of said foam anode.  
     
     
         5 . An apparatus according to  claim 4 , wherein said electrolyte storage assembly comprises: a ribbed cathode having one surface forming said first surface of said electrolyte storage assembly, a further surface opposing said one surface, ribs formed in one of said one surface and said other surface of said ribbed cathode, and first and second sides having said second and third surfaces of said storage assembly, respectively, and connecting said one surface and said other surface of said ribbed cathode; and a flat cathode abutting said ribs of said ribbed cathode and forming therewith channels.  
     
     
         6 . An apparatus according to  claim 6 , further comprising plate structure having a central part abutting the one of said one and other surfaces of said ribbed cathode opposing said ribs and first and second lip areas which extend outward of the lateral ends of said central area and then around and toward each other so as to define first and second cavities adjacent the first and second sides of said ribbed cathode, respectively, and wherein said second and third parts of said compliant, electrically conductive assembly serve as cathode current collectors and are disposed in said first and second cavities, respectively.  
     
     
         7 . An apparatus according to  claim 6 , wherein said anode current collector and said second and third parts of said compliant, electrically conductive assembly are each formed as a corrugated structure.  
     
     
         8 . An apparatus according to  claim 6 , wherein said ribbed cathode is made of material having approximately 65% porosity.  
     
     
         9 . An apparatus according to  claim 6 , wherein said flat cathode is made of material having approximately 70% porosity.  
     
     
         10 . An apparatus according to  claim 6  further comprising electrolyte stored in said channels and serving as an electrolyte reservoir.  
     
     
         11 . An apparatus according to  claim 6 , wherein said flat cathode is disposed between said anode current collector and said ribbed cathode and said ribbed cathode serves as an electrolyte sink capable of collecting and redistributing electrolyte, as well as storing electrolyte.  
     
     
         12 . An apparatus according to  claim 11 , further including a further anode current collector facing the one of said one and other surfaces of said ribbed cathode opposing said ribs and a standard anode disposed adjacent to said further anode current collector.  
     
     
         13 . An apparatus according to  claim 12 , further comprising a first bipolar plate defining a top pocket in which said further anode current collector and standard anode are disposed and a bottom pocket forming said plate structure and in which said ribbed cathode and said second and third parts of said compliant, electrically conductive assembly are disposed.  
     
     
         14 . An apparatus according to  claim 13 , further comprising a second bipolar plate situated between said flat cathode and said end plate and defining a pocket facing said end plate in which said anode current collector and foam anode are disposed.  
     
     
         15 . An apparatus according to  claim 14 , wherein said apparatus is adapted to be disposed at a negative end of said fuel cell stack and wherein said standard anode is disposed between said further anode current collector in the top pocket of said first bipolar plate and a last fuel cell in the fuel cell stack at said negative end.  
     
     
         16 . An apparatus according to  claim 6 , further comprising a bipolar plate defining a top pocket in which said anode current collector is disposed, and a bottom pocket defining said plate structure and in which said ribbed cathode and said second and third parts of said compliant, electrically conductive assembly are disposed.  
     
     
         17 . An apparatus according to  claim 16 , wherein said bipolar plate is made of electrically conductive material.  
     
     
         18 . An apparatus according to  claim 16 , wherein said second and third parts of said compliant, electrically conductive assembly accommodate mechanical deformation of the ribbed cathode during operation of said fuel cell stack.  
     
     
         19 . An apparatus according to  claim 18 , further comprising a shim disposed beneath each said second and third parts of said compliant, electrically conductive assembly in the bottom pocket of said bipolar plate.  
     
     
         20 . An apparatus according to  claim 18 , wherein an oxidizing gas flows through the channels formed between said flat cathode and said ribbed cathode.  
     
     
         21 . An apparatus according to  claim 20 , wherein a reducing gas flows perpendicular to said flow of oxidizing gas through further channels.  
     
     
         22 . An apparatus according to  claim 21 , wherein said oxidizing gas is oxygen and said reducing gas is hydrogen.  
     
     
         23 . An apparatus according to  claim 21 , wherein said flow of oxidizing gas through said channels uniformly oxidizes the surface of said ribbed cathode.  
     
     
         24 . An apparatus according to  claim 21 , further comprising matrix strips disposed along two opposite sides of said foam anode parallel to the direction of reducing gas flow.  
     
     
         25 . An apparatus according to  claim 24 , further comprising matrix strips disposed along opposite sides of said flat cathode parallel to the direction of oxidizing gas flow.  
     
     
         26 . An apparatus according to  claim 25 , wherein said matrix strips provide a gas seal between said oxidizing gas flow and said reducing gas flow.  
     
     
         27 . An apparatus according to  claim 18 , further comprising a further foam anode following said flat cathode and a further anode current collector facing said further foam anode.  
     
     
         28 . An apparatus according to  claim 27 , further comprising a cathode current collector following said further anode current collector and a standard cathode facing said cathode current collector.  
     
     
         29 . An apparatus according to  claim 28 , further comprising a second bipolar plate defining a top pocket in which said further anode current collector is disposed and a bottom pocket in which said cathode current collector is disposed.  
     
     
         30 . An apparatus according to  claim 29 , further comprising a metallic sheet separating said flat cathode from said further foam anode.  
     
     
         31 . An apparatus according to  claim 30 , wherein said apparatus is adapted to be disposed at a positive end of said fuel cell stack and wherein said standard cathode is adapted to be disposed between said cathode current collector and a first fuel cell in the fuel cell stack at said positive end of the stack.  
     
     
         32 . An end cell for storing electrolyte in a carbonate fuel cell stack, comprising: 
 an inactive anode part adjacent to an end plate of the stack; and    a ribbed cathode part separated from said end plate by said inactive anode part;    wherein said inactive anode part comprises a foam anode and an anode current collector, and wherein said ribbed cathode part comprises a flat cathode, a ribbed cathode, and a compliant cathode current collector; and    wherein said inactive anode part and said ribbed cathode part maintain electrical contact and provide electrolyte storage in said end cell.    
     
     
         33 . An end cell according to  claim 32 , further comprising an active electrode part separating said end cell from active fuel cells in said fuel cell stack, said active electrode part comprising an active electrode and a current collector.  
     
     
         34 . An end cell according to  claim 32 , wherein said active electrode part comprises a standard cathode and a cathode current collector.  
     
     
         35 . An end cell according to  claim 34 , further comprising a second inactive anode part disposed between and maintaining electrical contact with the ribbed cathode part and the active electrode part.  
     
     
         36 . An end cell according to  claim 35 , wherein said second inactive anode part comprises a foam anode and anode current collector.  
     
     
         37 . An end cell according to  claim 32 , wherein said active electrode part comprises a standard anode and an anode current collector.  
     
     
         38 . A fuel cell assembly comprising: 
 a fuel cell stack having a plurality of fuel cells stacked in an electrical series;    a positive end plate at a first end of said stack;    a negative end plate at a second end of said stack; and    an end cell disposed at each of said first and second ends of said stack between said positive and negative end plates and said plurality of fuel cells;    wherein said end cells each include a ribbed cathode part that provides electrolyte storage for said fuel cell assembly.    
     
     
         39 . A fuel cell assembly according to  claim 38 , each of said end cells comprising an inactive anode part adjacent said end plate, a ribbed cathode part separated from said end plate by said inactive anode part, and an active electrode part separating said end cell from said fuel cells in said stack, wherein the ribbed cathode part and the inactive anode part inhibit electrical contact loss in said end cell during operation of said stack.  
     
     
         40 . A fuel cell assembly according to  claim 39 , wherein the active electrode part on the first end of said stack comprises a standard cathode and a cathode current collector, and wherein the active electrode part on the second end of said stack comprises a standard anode and an anode current collector.  
     
     
         41 . A fuel cell assembly according to  claim 40 , wherein the end cell disposed at the first end of said stack between said positive end plate and said fuel cells further comprises a second inactive anode part disposed between the ribbed cathode part and the active cathode, said second inactive anode part adapted to further inhibit electrical contact loss between the ribbed cathode part and the active cathode at the first end of the stack.  
     
     
         42 . A fuel cell assembly according to  claim 41 , wherein said inactive anode part in each of said end cells, and said second inactive anode part in the end cell disposed at the first end of the stack, each comprises a foam anode and an anode current collector.  
     
     
         43 . A fuel cell assembly comprising: 
 a fuel cell stack having a plurality of fuel cells stacked in an electrical series;    a positive end plate at a first end of said stack;    a negative end plate at a second end of said stack; and    an end cell disposed at each of said first and second ends of said stack between said positive and negative end plates and said fuel cells;    wherein each of said end cells includes an inactive anode part that inhibits electrical contact loss in each of said end cells.    
     
     
         44 . A fuel cell assembly comprising: 
 a fuel cell stack having a plurality of active fuel cells stacked in an electrical series;    end plate at a first end of said stack; and    an apparatus disposed between said end plate and the active cells of the fuel cell stack, the apparatus comprising:    an electrolyte storage assembly; and    a compliant, electrically conductive assembly adapted to promote electrical contact between said electrolyte storage assembly and said end plate.    
     
     
         45 . A fuel cell assembly according to  claim 44 , wherein said electrolyte storage assembly has a first surface adapted to face said end plate and second and third side surfaces extending from said first surface, and said compliant, electrically conductive assembly includes a first part disposed between said first surface and said end plate and second and third parts disposed adjacent the second and third side surfaces, respectively, of said electrolyte storage assembly.  
     
     
         46 . A fuel cell assembly according to  claim 45 , wherein said electrolyte storage assembly has a first surface adapted to face said end plate and second and third side surfaces extending from said first surface, and said compliant, electrically conductive assembly includes one or more of a first part disposed between said first surface and said end plate and second and third parts disposed adjacent the second and third side surfaces, respectively, of said electrolyte storage assembly.  
     
     
         47 . A fuel cell assembly according to  claim 46 , wherein said first part includes a foam anode having opposing first and second surfaces and an anode current collector, said foam anode being adapted to abut said end cell at said first surface of said foam anode and abutting said anode current collector at said second surface of said foam anode.  
     
     
         48 . A fuel cell assembly according to  claim 47 , wherein said electrolyte storage assembly comprises: a ribbed cathode having one surface forming said first surface of said electrolyte storage assembly, a further surface opposing said one surface, ribs formed in one of said one surface and said other surface of said ribbed cathode, and first and second sides having said second and third surfaces of said storage assembly, respectively, and connecting said one surface and said other surface of said ribbed cathode; and a flat cathode abutting said ribs of said ribbed cathode and forming therewith channels.  
     
     
         49 . A fuel cell assembly according to  claim 48 , wherein said apparatus further comprises plate structure having a central part abutting the one of said one and other surface of said ribbed cathode opposing said ribs and first and second lip areas which extend outward of the lateral ends of said central area and then around and toward each other so as to define first and second cavities adjacent the first and second sides of said ribbed cathode, respectively, and wherein said second and third parts of said compliant, electrically conductive assembly serve as cathode current collectors and are disposed in said first and second cavities, respectively.  
     
     
         50 . A fuel cell assembly according to  claim 49 , wherein said anode current collector and said second and third parts of said compliant, electrically conductive assembly are each formed as a corrugated structure.  
     
     
         51 . A fuel cell assembly according to  claim 49 , wherein said ribbed cathode is made of material having approximately 65% porosity.  
     
     
         52 . A fuel cell assembly according to  claim 49 , wherein said flat cathode is made of material having approximately 70% porosity.  
     
     
         53 . A fuel cell assembly according to  claim 49 , wherein said apparatus further comprises electrolyte stored in said channels and serving as an electrolyte reservoir.  
     
     
         54 . A fuel cell assembly according to  claim 49 , wherein said flat cathode is disposed between said anode current collector and said ribbed cathode and said ribbed cathode serves as an electrolyte sink capable of collecting and redistributing electrolyte, as well as storing electrolyte, and wherein said apparatus further comprises: 
 an anode current collector facing one of said one and other surface of said ribbed cathode opposing said ribs and a standard anode disposed adjacent to said further anode current collector;    a first bipolar plate defining a top pocket in which said further anode current collector and standard anode are disposed and a bottom pocket forming said plate structure and in which said ribbed cathode and said second and third parts of said compliant, electrically conductive assembly are disposed; and    a second bipolar plate situated between said flat anode and said end plate and defining a pocket facing said end plate in which said anode current collector and foam anode are disposed.    
     
     
         55 . A fuel cell assembly according to  claim 54 , wherein said end cell is disposed at the negative end of said fuel cell stack and wherein said standard anode is disposed between said further anode current collector in the top pocket of said first bipolar plate and a last fuel cell in the fuel cell stack at said negative end.  
     
     
         56 . A fuel cell assembly according to  claim 49 , wherein said apparatus further comprises: 
 a bipolar plate defining a top pocket in which said anode current collector is disposed, and a bottom pocket defining said plate structure and in which said ribbed cathode and said second and third parts of said compliant, electrically conductive assembly are disposed;    a further foam anode following said flat cathode and a further anode current collector facing said further foam anode;    a cathode current collector following said further anode current collector and a standard cathode facing said cathode current collector; and    a second bipolar plate defining a top pocket in which said further anode current collector is disposed and a bottom pocket in which said cathode current collector is disposed.    
     
     
         57 . A fuel cell assembly according to  claim 56 , wherein said end plate is at the positive end of said fuel cell stack and wherein said standard cathode is adapted to be disposed between said cathode current collector and a first fuel cell in the fuel cell stack at said positive end of the stack.  
     
     
         58 . A fuel cell assembly according to  claim 57 , wherein an oxidizing gas flows through the channels formed between said flat cathode and said ribbed cathode and wherein a reducing gas flows perpendicular to said flow of oxidizing gas through further channels and said apparatus further comprises: 
 matrix strips disposed along two opposite sides of each of said foam anode and further foam anode parallel to the direction of reducing gas flow;    matrix strips disposed along opposite sides of said flat cathode parallel to the direction of oxidizing gas flow; and    a metallic sheet separating said flat cathode from said further foam anode.    
     
     
         59 . A fuel cell assembly according to  claim 58 , wherein said apparatus further comprises a shim disposed beneath each said second and third parts of said compliant, electrically conductive assembly in the bottom pocket of said bipolar plate.