Fuel cell with patterned electrolyte/electrode interface

• US 20020012825A1
• Filed: 05/08/2001
• Published: 01/31/2002
• Est. Priority Date: 05/08/2000
• Status: Active Grant

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company), Stanford University
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company), Stanford University
• Inventors: Lee, Sang-Joon J., Prinz, Friedrich B., Liu, Yaocheng, Saito, Yuji, Kuriyama, Nariaki, Sasahara, Jun, Kubota, Tadahiro, Cha, Suk Won, Chang-Chien, Amy, OʼHayre, Ryan
• Granted Patent: US 6,835,488 B2
• Time in Patent Office: Days
• US Class Current: 429/30
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 4/0485 Casting
• CPC Class Codes: H01M 4/86 Inert electrodes with catalytic activity, e.g. for fuel cells
• CPC Class Codes: H01M 8/0254 corrugated or undulated
• CPC Class Codes: H01M 8/0289 Means for holding the electrolyte solid polymer electrolytes H01M8/1018
• CPC Class Codes: H01M 8/1007 with both reactants being gaseous or vaporised H01M8/12 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A fuel cell contains an electrolyte sheet sandwiched between two electrodes. One or both electrode/electrolyte interfaces includes mesoscopic three-dimensional features in a prescribed pattern. The features increase the surface area-to-volume ratio of the device and can be used as integral channels for directing the flow of reactant gases to the reaction surface area, eliminating the need for channels in sealing plates surrounding the electrodes. The electrolyte can be made by micromachining techniques that allow very precise feature definition. Both selective removal and mold-filling techniques can be used. The fuel cell provides significantly enhanced volumetric power density when compared with conventional fuel cells.

Claims

1. A fuel cell comprising:

a) two electrodes; and

b) an electrolyte sheet sandwiched between said electrodes, thereby defining first and second interfaces between said electrolyte sheet and said electrodes, at least one of said interfaces having three-dimensional features in a prescribed pattern, wherein said prescribed pattern is selected to direct a flow of reactants from an inlet region of said fuel cell to an outlet region of said fuel cell such that said inlet region and said outlet region communicate with only a portion of said three-dimensional features.

2. The fuel cell of claim 1, wherein a ratio of a surface area of said at least one interface to a projected surface area of said at least one interface is greater than approximately 2.

3. The fuel cell of claim 1, wherein said first interface has three-dimensional structure in a first prescribed pattern and said second interface has three-dimensional structure in a second prescribed pattern.

4. The fuel cell of claim 3, wherein said first and second prescribed patterns are complementary such that a thickness of said electrolyte sheet is substantially constant between said first and second prescribed patterns.

5. The fuel cell of claim 1, wherein said prescribed pattern is selected in dependence on the type of reactant contacting said at least one interface.

6. The fuel cell of claim 1, wherein said electrolyte is a polymer.

7. The fuel cell of claim 6, wherein said polymer is a proton-exchange membrane.

8. The fuel cell of claim 6, wherein said polymer is shaped by a method selected from the group consisting of direct casting, injection molding, embossing, laser machining, laminated layer assembly, selective plasma etching, blow molding, and autoclaving.

9. The fuel cell of claim 1, wherein said electrolyte is a solid oxide.

10. The fuel cell of claim 9, wherein said solid oxide is an ion-exchange membrane.

11. The fuel cell of claim 9, wherein said solid oxide is shaped by a method selected from the group consisting of chemical vapor deposition, gel casting, powder sintering, and sol-gel processing.

12. The fuel cell of claim 1, wherein said three-dimensional features further comprise an additional pattern superimposed on said prescribed pattern, said additional pattern and said prescribed pattern having different length scales.

13. The fuel cell of claim 1, wherein said three-dimensional features have widths of between approximately 5 and 500 μ

m.

14. The fuel cell of claim 1, wherein said three-dimensional features have depth-to-width aspect ratios greater than approximately 1:

2.

15. The fuel cell of claim 1, wherein said electrodes comprise a conductive grid.

16. The fuel cell of claim 1, wherein said electrodes comprise a porous conductive material.

17. A fuel cell comprising:

a) two electrodes; and

b) an electrolyte sheet sandwiched between said electrodes, thereby defining first and second interfaces between said electrolyte sheet and said electrodes, at least one of said interfaces having three-dimensional features in a prescribed pattern, wherein said features are created by a selective removal method.

18. A method for making a fuel cell electrolyte, comprising:

a) providing a substrate; and

b) selectively removing predetermined regions of said substrate using a micromachining technique to create three-dimensional features in said substrate.

19. The method of claim 18 wherein said micromachining technique is selected from the group consisting of laser machining, selective plasma etching, focused ion beam milling, and mechanical abrasion.

20. The method of claim 18 wherein said three-dimensional features have widths of between approximately 5 and 500 μ

m.

21. A method for making a fuel cell electrolyte, comprising:

a) providing a mold having three-dimensional features; and

b) incrementally adding material to said mold.

22. The method of claim 21 wherein step (b) comprises a method selected from the group consisting of chemical vapor deposition, physical vapor deposition, and plasma spraying.

23. The method of claim 21, further comprising filling said mold with a sacrificial material.

24. The method of claim 21 wherein said three-dimensional features have widths of between approximately 5 and 500 μ

m.

25. A method for making a fuel cell electrolyte, comprising:

a) providing a mold having three-dimensional features; and

b) filling said mold with an electrolyte precursor in a non-solid state.

26. The method of claim 25 wherein step (b) comprises a method selected from the group consisting of direct casting, injection molding, screen printing, dip coating, and sol-gel processing.

27. The method of claim 25, further comprising treating said electrolyte precursor to obtain a solid electrolyte.

28. The method of claim 25, further comprising filling said mold with a sacrificial material.

29. The method of claim 25 wherein said three-dimensional features have widths of between approximately 5 and 500 μ

m.