Electrochemical cell and bipolar assembly for an electrochemical cell

• US 20030232234A1
• Filed: 05/30/2003
• Published: 12/18/2003
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• Current Assignee: Lynntech Incorporated
• Original Assignee: Lynntech Incorporated
• Inventors: Yalamanchili, Rattaya, Boyer, Chris, Cisar, Alan J., Murphy, Oliver J., Andrews, Craig C., Salinas, Carlos E., Greenwald, Charles J.
• Granted Patent: US 7,125,625 B2
• Time in Patent Office: Days
• US Class Current: 429/437
• CPC Class Codes: H01M 8/0206 Metals or alloys
• CPC Class Codes: H01M 8/0213 Gas-impermeable carbon-containing materials
• CPC Class Codes: H01M 8/0221 Organic resins; Organic polymers
• CPC Class Codes: H01M 8/0223 Composites
• CPC Class Codes: H01M 8/023 Porous and characterised by the material
• CPC Class Codes: H01M 8/0232 Metals or alloys
• CPC Class Codes: H01M 8/0241 Composites
• CPC Class Codes: H01M 8/0247 characterised by the form characterised by a channel configuration H01M8/0258
• CPC Class Codes: H01M 8/0256 Vias, i.e. connectors passing through the separator material
• CPC Class Codes: H01M 8/026 characterised by grooves, e.g. their pitch or depth
• CPC Class Codes: H01M 8/0271 Sealing or supporting means around electrodes, matrices or membranes
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A bipolar assembly for use in electrochemical cell stacks, especially stacks operated at low pressure. The bipolar assembly is lightweight and provides a “post-type” flow field that operates with a low pressure drop. The bipolar assembly comprises a gas barrier having an array of electronically conducting posts disposed approximately perpendicular to the gas barrier. Each end of the posts is in electrical communication with the surface of an electrode. Because the bipolar assembly separates a cathode from an anode, the posts contact an anode electrode on one end and a cathode electrode on the other end. The posts provide current conduction through the stack as well as provide the flow fields for the electrochemical reactants. Optionally, the bipolar assembly may contain cooling fluid channels formed by adding additional gas barriers to the bipolar assembly. The space between the gas barriers form a channel through which cooling fluids may be circulated.

Claims

1. An assembly for use in an electrochemical cell stack comprising:

a gas barrier;

an array of electronically conductive protrusions disposed across the gas barrier, wherein the electronically conductive protrusions enable electrical communication between an anode opposite a first side of the gas barrier and a cathode opposite a second side of the gas barrier.

2. The assembly of claim 1, wherein at least one of the fluids is a gas.

3. The assembly of claim 1, wherein the protrusions are inserted into an array of regularly shaped holes or regularly shaped indentations in the gas barrier, and wherein the protrusions have a cross section approximately matching a cross section of the regularly shaped holes or regularly shaped indentations.

4. The assembly of claim 3, wherein the protrusions are inserted into holes, and wherein the gas barrier and the protrusions are metallic, the assembly further comprises seals around the protrusions formed by metallurgically bonding the protrusions to the gas barrier.

5. The assembly of claim 4, wherein the seal is formed with a metal having a melting point substantially lower than the metals of the protrusions or the gas barrier.

6. The assembly of claim 3, wherein the protrusions are inserted into holes, the assembly further comprising seals around the protrusions wherein the seals are made of polymeric material.

7. The assembly of claim 6, wherein the polymeric material is selected from epoxies, metal filled epoxies, carbon filled epoxies, self-vulcanizing silicones, metal filled self-vulcanizing silicones, or carbon filled self-vulcanizing silicones

8. The assembly of claim 6, wherein the gas barrier is a material selected from electronically conducting or electronically nonconducting materials.

9. The assembly of claim 3 wherein the protrusions are inserted into indentations and the gas barrier is electronically conductive.

10. The assembly of claim 1, wherein the protrusions a circular cross sectional shape.

11. The assembly of claim 1, wherein the protrusions have cross sectional shapes selected from circular, square, rectangular, triangular, diamond, oval, ovoid, pentagonal, hexagonal or heptagonal.

12. The assembly of claim 1, wherein the protrusions are arranged in a pattern selected from triangular or rectangular.

13. The assembly of claim 12, wherein the separation between protrusions is between about 1 mm and about 3 cm.

14. The assembly of claim 12, wherein the separation between protrusions is about 1 cm.

15. The assembly of claim 1, wherein the protrusions extend between adjacent cells through a distance between ¼

inch and {fraction (1/16)} inch.

16. The assembly of claim 1, wherein the anode and the cathode each have a fluid diffusion structure having an electronically conductive grid, wherein the metal grid acts as a current collector.

17. The assembly of claim 16, wherein the protrusions are in electrical communication with the grids.

18. The assembly of claim 16, wherein the grid is made of material selected from nickel, copper, aluminum, stainless steel, graphitized carbon, gold, palladium, ruthenium, platinum or combinations thereof.

19. The assembly of claim 16, wherein the grid is made of titanium.

20. The assembly of claim 16, wherein the grid is a form selected from perforated flat plate, perforated foil, woven wire cloth, non-woven conductive cloth, wherein the perforations or openings have a size less than the area of contact with the protrusions.

21. The assembly of claim 1, wherein the protrusions are made of material selected from graphitic carbon, aluminum, titanium or magnesium.

22. The assembly of claim 1, wherein the protrusions are made of any electronically conductive material.

23. The assembly of claim 1, wherein the gas barrier is electronically conductive, the gas barrier is made of material selected from aluminum, titanium, magnesium, or graphitic carbon sheet.

24. The assembly of claim 23, wherein the gas barrier is porous with pores permitting fluid communication through the plate and said pores filled with a hydrophilic material that prevents the passage of fluid through the membrane but permits the passage of water.

25. The assembly of claim 24 where the hydrophilic material is a polymer.

26. The assembly of claim 25 where the polymer is selected from polyperfluorosulfonic acid, sulfonated polystyrene, sulfonated trifluorostyrene, polyacrylamides, sulfonated styrene copolymers, and blends and copolymers of these materials.

27. The assembly of claim 24 where the hydrophilic material is an inorganic material.

28. The assembly of claim 27 where the inorganic material is selected from phosphates, polyphosphates, hydrous silicates, and the like.

29. The assembly of claim 1 wherein the gas barrier is electronically conductive, the gas barrier is made of a material selected from conductive polymer composites formed from a non-conductive polymer filled with a conductive material such as metal or carbon.

30. The assembly of claim 1 wherein the gas barrier is made of an intrinsically electronically conductive polymer.

31. The assembly of claim 1, wherein the gas barrier is non-electronically conductive, the gas barrier is made of polymer selected from polycarbonate, polytetrafluoroethylene, polyamide, or polyethersulfone.

32. The assembly of claim 31, wherein the gas barrier is porous with pores permitting fluid communication through the plate and said pores filled with a hydrophilic material that prevents the passage of fluid through the membrane but permits the passage of water.

33. The assembly of claim 32 where the hydrophilic material is a polymer.

34. The assembly of claim 33 where the polymer is selected from polyperflourosulfonic acid, sulfonated polystyrene, sulfonated trifluorostyrene, polyacrylamides, sulfonated styrene copolymers, and blends an copolymers of these materials.

35. The assembly of claim 32 where the hydrophilic material is an inorganic material.

36. The assembly of claim 35 where the inorganic material is selected from phosphates, polyphosphates, hydrous silicates, and the like.

37. The assembly of claim 1, wherein the protrusions form flow fields having a void volume of between about 50% and about 99%.

38. The assembly of claim 1, wherein the protrusions form flow fields having a void volume of between about 80% and about 95%.

39. A fluid-cooled assembly for use in an electrochemical cell stack comprising:

at least two gas barriers, wherein a first gas barrier opposes an anode electrode and a last gas barrier opposes a cathode electrode and wherein the gas barriers are approximately parallel; and

an array of electronically conductive protrusions disposed across the gas barriers, wherein the electronically conductive protrusions enable electrical communication between the anode electrode and the cathode electrode.

40. The assembly of claim 39, wherein the protrusions are inserted into an array of regularly shaped holes, regularly shaped indentations, or combinations thereof in the gas barriers, and wherein the protrusions have a cross section approximately matching a cross section of the regularly shaped holes or regularly shaped indentations.

41. The assembly of claim 40, wherein the protrusions are inserted into holes, and wherein the gas barriers and the protrusions are metallic, the assembly further comprises seals around the protrusions formed by metallurgically bonding the protrusions to the gas barriers.

42. The assembly of claim 41, wherein the seal is formed with a metal having a melt point substantially lower than the metals of the protrusions or the gas barriers.

43. The assembly of claim 40, wherein the protrusions are inserted into holes, the assembly further comprising seals around the protrusions wherein the seals are made of polymeric material.

44. The assembly of claim 43, wherein the polymeric material is selected from epoxies, metal filled epoxies, carbon filled epoxies, self-vulcanizing silicones, metal filled self-vulcanizing silicones, or carbon filled self-vulcanizing silicone.

45. The assembly of claim 40, wherein the gas barriers are made of materials selected from electronically conducting materials, electronically nonconducting material, or combinations thereof.

46. The assembly of claim 39, wherein the protrusions are inserted into indentations, the gas barrier is electronically conductive.

47. The assembly of claim 39, wherein the protrusions are of any cross sectional shape.

48. The assembly of claim 39, wherein the protrusions have cross sectional shapes selected from circular, square, rectangular, triangular, diamond, oval, ovoid, pentagonal, hexagonal or heptagonal.

49. The assembly of claim 39, wherein the protrusions are arranged in a pattern selected from triangular or rectangular.

50. The assembly of claim 49, wherein the separation between protrusions is from 1 mm to 3 cm.

51. The assembly of claim 49, wherein the separation between protrusions is from 1 cm to 2 cm.

52. The assembly of claim 39, wherein the protrusions extend between adjacent cells through a distance between ½

inch and {fraction (1/16)} inch.

53. The assembly of claim 39, wherein the anode and the cathode each have a fluid diffusion structure having an electronically conductive grid, wherein the metal grid acts as a current collector.

54. The assembly of claim 53, wherein the protrusions are in electrical communication with the grids.

55. The assembly of claim 53, wherein the grid is made of material selected from nickel, copper, aluminum, stainless steel, graphitized carbon, gold, palladium, ruthenium, platinum or combinations thereof.

56. The assembly of claim 53, wherein the grid is made of titanium.

57. The assembly of claim 53, wherein the grid is a form selected from perforated flat plate, perforated foil, woven wire cloth, non-woven conductive cloth, wherein the perforations or openings have a size less than the area of contact with any one of the protrusions.

58. The assembly of claim 39, wherein the protrusions are made of material selected from graphitic carbon, aluminum, titanium or magnesium.

59. The assembly of claim 39, wherein the protrusions are made of any electronically conductive material.

60. The assembly of claim 39, wherein the gas barrier is electronically conductive, the gas barrier is made of material selected from aluminum, titanium, magnesium, or graphitic carbon sheet.

61. The assembly of claim 39, wherein the gas barrier is porous with pores permitting fluid communication through the plate and said pores filled with a hydrophilic material that prevents the passage of fluid through the membrane but permits the passage of water.

62. The assembly of claim 61 where the hydrophilic material is a polymer.

63. The assembly of claim 62 where the polymer is selected from polyperfluorosulfonic acid, sulfonated polystyrene, sulfonated trifluorostyrene, polyacrylamides, sulfonated styrene copolymers, and blends and copolymers of these materials.

64. The assembly of claim 61 where the hydrophilic material is an inorganic material.

65. The assembly of claim 64 where the inorganic material is selected from phosphates, polyphosphates, hydrous silicates, and the like.

66. The assembly of claim 39 wherein the gas barrier is electronically conductive, the gas barrier is made of a material selected from conductive polymer composites formed from a non-conductive polymer filled with a conductive material such as metal or carbon.

67. The assembly of claim 39 wherein the gas barrier is made of an intrinsically electronically conductive polymer.

68. The assembly of claim 39, wherein the gas barrier is electronically nonconductive, and wherein the gas barrier is made of polymer selected from polycarbonate, polytetrafluoroethylene, polyamide, or polyethersulfone.

69. The assembly of claim 68, wherein the gas barrier is porous with pores permitting fluid communication through the plate and said pores filled with a hydrophilic material that prevents the passage of fluid through the membrane but permits the passage of water.

70. The assembly of claim 69 where the hydrophilic material is a polymer.

71. The assembly of claim 70 where the polymer is selected from polyperfluorosulfonic acid, sulfonated polystyrene, sulfonated trifluorostyrene, polyacrylamides, sulfonated styrene copolymers, and blends and copolymers of these materials.

72. The assembly of claim 69 where the hydrophilic material is an inorganic material.

73. The assembly of claim 72 where the inorganic material is selected from phosphates, polyphosphates, hydrous silicates, and the like.

74. The assembly of claim 39, wherein all the gas barriers are made of the same material.

75. The assembly of claim 39, wherein all the gas barriers are not made of the same materials.

76. The assembly of claim 39, wherein the protrusions form flow fields leave a void volume of between about 50% and about 99%.

77. The. assembly of claim 39, wherein the protrusions form flow fields having a void volume of between about 80% and about 95%.

78. The assembly of claim 39, wherein at least one of the fluids is a gas.

79. An electrochemical cell stack comprising:

a plurality of membrane and electrode assemblies;

bipolar assemblies disposed between each of the plurality of membrane and electrode assemblies, wherein the bipolar assemblies comprise a gas barrier, and an array of electronically conductive protrusions disposed across the gas barrier, wherein the electronically conductive protrusions enable electrical communication between an anode opposite a first side of the gas barrier and a cathode opposite a second side of the gas barrier.

80. The stack of claim 79, wherein the protrusions are made of metal.

81. The stack of claim 79, wherein the protrusions have two ends that form opposing contact surfaces for making electrical communication with the electrodes.

82. The stack of claim 79, wherein the electrical communication from one face of the bipolar assemblies to the opposing face of the bipolar assemblies is provided by the protrusions

83. The stack of claim 79, further comprising:

current collectors disposed in electrical communication between the protrusions and the membrane and electrode assemblies.

84. The stack of claim 79, wherein the current collectors extend across the entire face of the bipolar assemblies.

85. The stack of claim 79, wherein the current collectors are discrete elements associated with individual protrusions.