ELECTRODE MORPHOLOGY VIA USE OF HIGH BOILING POINT CO-SOLVENTS IN ELECTRODE INKS

• US 20100099011A1
• Filed: 10/21/2008
• Published: 04/22/2010
• Est. Priority Date: 10/21/2008
• Status: Abandoned Application

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: HOUGHTALING, BRADLEY M., NAYAR, AMIT
• Application Number:
  US12/255,257
• Publication Number:
  US 20100099011A1
• Time in Patent Office: Days
• US Class Current: 429/481
• CPC Class Codes: H01M 4/8663 Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers
• CPC Class Codes: H01M 4/8807 Gas diffusion layers
• CPC Class Codes: H01M 4/8828 Coating with slurry or ink
• CPC Class Codes: H01M 4/8882 Heat treatment, e.g. drying, baking
• CPC Class Codes: H01M 8/1004 characterised by membrane-electrode assemblies [MEA] H01M8/12 takes precedence
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A method and device for operating a fuel cell system. The method includes applying a catalyst ink or related liquid that contains an electrocatalyst and electrolyte to a diffusion media so that the portion of the media that includes the electrocatalyst can function as a fuel cell electrode, specifically an anode or cathode. In addition to the electrocatalyst and electrolyte, the ink contains a solvent and a co-solvent, where the co-solvent has a boiling point that exceeds that of the solvent. Heating or related processing removes the solvent from the diffusion layer, but leaves at least some of the co-solvent in liquid form. This residual liquid reduces the likelihood of electrode cracking that may otherwise form during subsequent electrode processing.

Claims

1. A method of preparing an electrode assembly for a fuel cell, said method comprising:

applying a catalyst ink comprising an electrocatalyst material, an electrolyte, a solvent, and a co-solvent to a diffusion layer, where said co-solvent has a boiling point that exceeds at least that of said solvent; and

heating the catalyst ink to at least partially remove said solvent from said diffusion layer.

2. The method of claim 1, wherein said heating the catalyst ink to at least partially remove said solvent from said diffusion layer comprises heating the catalyst ink by an amount to remove a substantial entirety of the solvent.

3. The method of claim 1, wherein after said heating, at least a portion of said co-solvent remains in at least a portion of said electrode.

4. The method of claim 1, wherein at least a portion of said co-solvent remains in said electrode until substantially all of said solvent is removed from said electrode.

5. The method of claim 1, wherein at least a portion of said co-solvent remains in said electrode until completion of said heating.

6. The method of claim 1, wherein said electrolyte comprises a polymer electrolyte.

7. The method of claim 1, further comprising joining said electrode to a proton exchange membrane.

8. A method of preparing a diffusion media for a fuel cell, said method comprising:

applying a catalyst ink comprising an electrocatalyst material, an electrolyte, a solvent and a co-solvent to a diffusion layer, where said co-solvent has a boiling point that exceeds at least that of said solvent; and

heating the catalyst ink to at least partially remove said solvent from said diffusion layer.

9. The method of claim 8, wherein said co-solvent has a boiling point that is above at least about 100 degrees Celsius.

10. The method of claim 9, wherein said co-solvent has a boiling point that is above at least about 139 degrees Celsius.

11. The method of claim 9, wherein said co-solvent comprises alcohol.

12. The method of claim 9, wherein said co-solvent is selected from the group consisting of propylene glycol butyl ether, ethylene glycol, 1-pentanol, 2,3 butanediol and diacetone alcohol.

13. The method of claim 8, wherein said co-solvent comprises a mixture.

14. The method of claim 8, wherein said co-solvent comprises up to sixty five percent by weight of said catalytic ink solution.

15. The method of claim 14, wherein said co-solvent comprises up to ten percent by weight of said catalytic ink solution.

16. The method of claim 8, wherein said heating comprises leaving at least a portion of said co-solvent that is applied to said diffusion layer in an un-evaporated state even after said heating.

17. The method of claim 8, wherein said solvent comprises at least one of water and an alcohol.

18. A fuel cell comprising:

an anode configured to receive a first reactant through an anode diffusion media;

a cathode in ion exchange communication with said anode, said cathode configured to receive a second reactant through a cathode diffusion media where at least a portion of at least one of said anode diffusion media and said cathode diffusion media includes an electrocatalyst formed by application of an ink comprising said electrocatalyst, an electrolyte, a solvent and a co-solvent with a boiling point that exceeds that of said solvent such that upon curing said ink once applied to said at least one diffusion media, at least a portion of said co-solvent remains on said diffusion media even after said solvent has been substantially evaporated; and

a membrane disposed between said anode and said cathode to effect said ion exchange.

19. The fuel cell of claim 18, wherein said cathode and said cathode diffusion media are co-formed.

20. The fuel cell of claim 18, wherein said cathode and said cathode diffusion media comprise separate layers that are joined together to define a cathode assembly.

21. The fuel cell of claim 18, wherein said co-solvent is selected from the group consisting of propylene glycol butyl ether, ethylene glycol, 1-pentanol, 2,3 butanediol and diacetone alcohol.

22. The fuel cell of claim 18, further comprising a plurality of said fuel cells arranged as a fuel cell assembly.

23. The fuel cell assembly of claim 22, further comprising a system powered at least in part by said fuel cell assembly, said system comprising:

an anode flowpath configured to couple said plurality of fuel cells to a fuel source;

a cathode flowpath configured to couple said plurality of fuel cells to an oxygen source; and

an electrical circuit coupled to said assembly to accept said electric current therefrom; and

a load coupled to said electrical circuit.

24. The system of claim 23, wherein said load comprises a mobile platform.

25. The system of claim 24, wherein said mobile platform comprises a vehicle drivetrain.

26. The system of claim 24, wherein said mobile platform comprises an automobile with said assembly comprising a source of motive power.