Plastic platelet fuel cells employing integrated fluid management

• US 5,863,671 A
• Filed: 05/17/1995
• Issued: 01/26/1999
• Est. Priority Date: 10/12/1994
• Status: Expired due to Fees

• Current Assignee: H Power Corporation (Plug Power Inc.)
• Original Assignee: H Power Corporation (Plug Power Inc.)
• Inventors: Janke, David E., Hayes, William A., Franklin, Jerrold E., Spear, Reginald G. Jr.
• Primary Examiner(s): Skapars, Anthony
• Application Number:
  US08/443,139
• Time in Patent Office: 1,350 Days
• Field of Search: 429/12, 429/26, 429/34, 429/35, 429/38, 429/39, 429/210, 429/129, 429/247
• US Class Current: 429/413
• CPC Class Codes: F28D 9/0075 the plates having openings therein for circulation of the heat-exchange medium from one conduit to another
• CPC Class Codes: F28F 2250/102 with change of flow direction
• CPC Class Codes: F28F 2260/02 having microchannels
• CPC Class Codes: F28F 3/04 the means being integral with the element
• CPC Class Codes: F28F 3/048 in the form of ribs integral with the element or local variations in thickness of the element, e.g. grooves, microchannels
• CPC Class Codes: H01M 2300/0082 Organic polymers
• CPC Class Codes: H01M 8/0202 Collectors; Separators, e.g. bipolar separators; Interconnectors
• CPC Class Codes: H01M 8/0206 Metals or alloys
• CPC Class Codes: H01M 8/0208 Alloys
• CPC Class Codes: H01M 8/021 Alloys based on iron
• CPC Class Codes: H01M 8/0228 in the form of layered or coated products
• CPC Class Codes: H01M 8/0234 Carbonaceous material
• CPC Class Codes: H01M 8/0245 in the form of layered or coated products
• 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 8/0263 having meandering or serpentine paths
• CPC Class Codes: H01M 8/0267 having heating or cooling means, e.g. heaters or coolant flow channels
• CPC Class Codes: H01M 8/04029 Heat exchange using liquids
• CPC Class Codes: H01M 8/04074 Heat exchange unit structures specially adapted for fuel cell
• CPC Class Codes: H01M 8/04119 : with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
• CPC Class Codes: H01M 8/2404 : Processes or apparatus for grouping fuel cells
• CPC Class Codes: H01M 8/242 : comprising framed electrodes or intermediary frame-like gaskets H01M8/2425, H01M8/244 take precedence
• CPC Class Codes: H01M 8/2483 : characterised by internal manifolds
• CPC Class Codes: Y02E 60/50 : Fuel cells
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product

Abstract

Improved fuel cell stacks constructed from a plurality of cells, each comprising a series of interrelated mono and bipolar collector plates (BSPs), which in turn are built up by lamination of a core of related non-conductiveplastic orceramic platelets sandwiched between conductive microscreen platelets of metal or conductive ceramic or plastic, with an electrode membrane (EMA) between adjacent BSPs. The platelets, both metal and plastic of the composite BSPs, are produced from sheet material with through and depth features formed by etching, pressing, stamping, casting, embossing and the like. Adjacent plates, each with correspondingly relieved features form serpentine channels within the resultant monolithic platelet/cell stack for integrated fluid and thermal management. The plastic platelets are particularly useful for PEM fuel cells employing H₂ and Air/O₂ as fuel. The platelets are easily made by printing (embossing) processes, and dies made by photolithographic etching for rapid redesign. Each BSP can be individually tailored to each type of membrane, fuel, and intra-cell location within the stack. As materials are cheap and easy to manufacture and assemble, lightweight fuel cells of very high power density are realizable. Industrial applicability includes both stationary and vehicular power supplies, in both micro and macro sizes.

Claims

1. A polar fidel cell separator assembly for a PEM fluid reactant fuel cell not having a graphite stencil layer comprising in operative combination:

a) at least one core platelet of thin sheet selected from a ceramic or plastic material having a first side and a second side,

b) at least one side of each platelet having integrated fluid distribution features permanently formed therein, said features being selected from at least one of fields, close-outs, splitters;

via bases, lands, tabs, metering orifices, channels, vias, mixers, filters, Coanda-effect circuits, diverters, and manifolds;

c) said features are interrelated and coordinate from platelet to platelet to provide in combination at least one permanent continuous microchannel fluid reactant flow field area; and

d) said core platelet is bonded to selected ones of a current collector platelet to form a unipolar terminal current collector, to another core platelet, or to at least one other core platelet and at least one current collector to form a monolithic bipolar separator, for association with an electrode membrane assembly to form a fel cell stack, said bonded platelets integrated in the same plane as an active field, and/or in a plane parallel thereto, with either a humidification and/or cooling field in the same separator assembly.

2. A polar fuel cell separator assembly as in claim 1 wherein said current collector platelet material is selected from conductive plastic, conductive ceramic, metallized plastic, metallized ceramic or composites thereof to facilitate electron conduction from anode to cathode.

3. A polar fuel cell separator assembly as in claim 2 Wwherein at least some of said features form at least one coolant field for thermal management.

4. A polar fuel cell separator assembly as in claim 1 wherein at least one of said features form at least one humidification field for humidifying a fuel or an oxidant reactant.

5. A polar fuel cell separator assembly as in claim 3 wherein at least one of said features form at least one humidification field for humidifying a fuel or an oxidant reactant.

6. A polar fuel cell separator as in claim 5 wherein said coolant field communicates with at least one of said humidification fields to provide heated humidification fluid to said humidification field.

7. A polar fuel cell separator as in claim 1 wherein said features are formed by a combination of depth forming and through forming.

8. A polar fuel cell separator as in claim 2 wherein said core platelet is disposed between a pair of spaced apart microscreen collector platelets, or between a microscreen collector platelet and an endplate, and said pair of microscreen platelets and said microscreen and endplate combination are in electrical communication with each other by means selected from one or more current bridges, current tabs, spring clips, edge jumpers, pleated conductive current bridges, edge bus bars, internal bus bars, or combinations thereof.

9. A polar fuel cell separator assembly as in claim 8 wherein said core platelets are plastic and said features therein are formed by compression techniques selected from stamping, embossing, punching, compression molding of sheet stock and injection molding.

10. A polar fuel cell separator assembly as in claim 9 wherein at least some of said features are formed on each side of said core platelet.

11. A polar fuel cell separator assembly as in claim 10 wherein said core comprises at least a pair of platelets bonded to each other, a first of which is an anode flow fluid platelet and a second of which comprises a cathode flow field platelet.

12. A polar fuel cell separator assembly as in claim 11 which includes bonded to said platelet core a pair of microscreen platelets, including a first anode microscreen platelet and a second cathode-microscreen platelet.

13. A polar fuel cell separator assembly as in claim 12 wherein said microscreen platelet includes areas having apertures therein, said apertures being selected from round holes, hexagons, slots, Tees, chevrons, squares, diamonds, triangles, elllipsoids and NACA ports.

30. A polar fnel cell separator assembly as in claim 4 wherein said humidification field is coplanar wit said reactant flow field.

31. A polar fuel cell separator assembly as in claim 30 wherein, in assembly with an electrode membrane, said humidification field of an anode or cathode side of a first separator assembly is in cross-membrane humidification communication with a reactant gas humidifing field of a cathode or anode side of an adjacent separator.

32. A polar fuel cell separator assembly as in claim 31 fwherein said humidification field is in communication with a coolant field to provide heated humidification fluid to said humidification field.

33. A polar fuel cell separator assembly as in claim 32 wherein said reactant gas humidifying field is disposed upstream of the electrode membrane active field for said reactant, and said coolant field is upstream of said humidification field to provide for countercurrent cross-membrane humidifying of said reactant gas with heated coolant fluid vapors passing through said membrane.

14. A platelet for a polar fuel cell separator assembly for a PEM fluid reactant fuel cell not having a graphite stencil layer comprsing:

a) a thin sheet material platelet selected oTom ceramic, plastic, conductive plastic, conductive ceramic, metallized plastic, metallized ceramic or composites thereof, each said sheet having a first side and a second side;

b) at least one side of said platelet having microchannel fluid distribution features formed therein, said features being selected from at least one of fields, metering orifices, channels, vias, via bases, lands, tabs, mixers, filters, diverters, splitters, Coanda-effect circuits, and manifolds, said platelet integrates in the same plane as an active field, and/or in a plane parallel thereto, with either a humidification an/or cooling field in the same separator assembly; and

c) said features, in cooperation with corresponding ones of said features in other platelets in said fuel cell separator provide at least one microchannel fluid reactant flow field area.

15. A platelet as in claim 14 wherein said features in said flow field area include through features forming a microscreen current collector platelet.

16. A platelet as in claim 15 wherein said sheet is selected from electrically non-conductive plastic or electrically non-conductiveceramic, and includefeatures therein forming a core platelet selected from an anode flow field platelet and a cathode flow field platelet.

17. A platelet as in claim 16 wherein said features include features forming at least one microchannel coolant field.

18. A platelet as in claim 17 wherein said features include features forming at least one microchannel humidification field.

19. A platelet as in claim 18 it wherein said coolant field and said humidification field microchannels are in communication to provide counterflow humidification of reactant gases.

20. A platelet as in claim 19 wherein said reactant flow field area is formed in an external surface of a plurality of platelets forming a core, and said coolant field is interior thereof and disposed with an area coordinate with said reactant flow field area.

21. A platelet as in claim 20 wherein a platelet includes on said first surface at least one reactant flow field area and on said second surface said coolant field.

22. A platelet as in claim 21 wherein said first surface includes at least one humidification microchannel area.

23. A platelet as in claim 14 wherein said microchannels are tailored in length, cross-sectional dimensions and serpentine configuration to the reactant fluid composition and viscosity.

24. A fuel cell stack comprising in operative combination:

a) a plurality of cells comprising;

i) bipolar separators and membrane electrode assemblies in a stacked array;

ii) an anode separator end plate at one end of said stack in contact with one of said membrane electrode assemblies;

iii) a cathode separator end plate at a second end of said stack in contact with a membrane electrode assembly;

b) said bipolar separator, and said anode and cathode separators include core platelets as in claim 18; and

c) said cells are assembled in sequence under compression to form an operating cell.

25. A fuel cell stack as in claim 24 wherein said features include at least one microchannel coolant field area.

26. A fuel cell stack as in claim 25 wherein said features include at least one microchannel humidification field for a fuel or an oxidant in communication with said coolant field to provide heated fluid to said humidification field.

27. A fuel cell stack as in claim 26 wherein said fields are tailored in length, microchannel cross-section dimension and serpentine configuration for H₂ as fuel and air/O₂ as an oxidant.

28. A fuel cell stack as in claim 27 wherein said separators include electrically non-conductive core platelets of plastic or ceramic laminated between current collector microscreen platelets formed of diffusion bonded metal selected from Ti, Al, Cu, W, Niobium, stainless steel, alloys, laminates, platings and composites thereof.

29. A fuel cell stack as in claim 28 wherein:

a) said membrane electrode assembly is selected from a carbon paper coated PEM and a carbon paperless PEM, and

b) said separators include awindow frame platelet in contact with said carbon paper coated PEM or a window screen platelet in contact with said carbon paperless PEM.