Screen printing method for making an electrochemical cell electrode

• US 4,185,131 A
• Filed: 06/28/1978
• Issued: 01/22/1980
• Est. Priority Date: 06/28/1978
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Rtx Corporation)
• Original Assignee: United Technologies Corporation (Rtx Corporation)
• Inventors: Petraglia, Vincent J., Goller, Glen J., Dews, George
• Primary Examiner(s): Esposito, Michael F.
• Application Number:
  US05/920,038
• Time in Patent Office: 573 Days
• Field of Search: 429/42, 427/115, 427/122, 427/113, 427/126, 427/125, 427/369, 427/376 R, 427/264, 427/265, 427/282
• US Class Current: 427/113
• CPC Class Codes: H01M 4/8807 Gas diffusion layers
• CPC Class Codes: H01M 8/0234 Carbonaceous material
• 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

Fuel cell electrodes of uniform quality are made on a continuous basis using screen printing. A wet floc is first made by floccing a co-suspension of carbon and hydrophobic polymer. The floc is dried, reduced to a fine powder, and re-suspended in an inking vehicle. The ink is then screen printed onto a porous substrate and the inking vehicle is removed such as by heating. The layer is compacted, sintered, and then catalyzed such as with platinum.

Claims

1. A method for making an electrochemical cell electrode comprising the steps of:

floccing a co-suspension of carbon particles and hydrophobic fluorocarbon polymer particles;

drying the floc so produced and reducing it to a powder;

resuspending the floc powder in an inking vehicle to form an ink;

screen printing the ink onto a porous substrate to form a layer;

drying the layer to remove the inking vehicle;

compacting the layer;

sintering the compacted layer; and

catalyzing the layer.

2. The method according to claim 1 wherein the substrate is carbon.

3. The method according to claim 1 wherein the hydrophobic polymer is PTFE.

4. The method according to claim 1 wherein the step of reducing the floc to a powder includes reducing the floc to a particle size of less than about ten microns in diameter.

5. The method according to claim 1 wherein the step of floccing comprises blending isopropanol, distilled water, and aqueous suspension of PTFE, and carbon powder to form a uniform co-suspension of carbon powder and PTFE, and causing the solids in said co-suspension to floc.

6. The method according to claim 3 wherein the weight percent of solids in the printed ink is 14-18%.

7. The method according to claim 6 wherein the inking vehicle is one of the following liquids or combinations thereof:

ethylene glycol, glycerin, dibasic alcohols, and tribasic alcohols.

8. The method for making an electrochemical cell electrode according to claim 1 wherein the hydrophobic polymer is PTFE;

the inking vehicle is one of the following liquids or combinations thereof;

ethylene glycol, glycerin, a dibasic alcohol and tribasic alcohols;

the substrate is porous carbon; and

the step of reducing the floc to a powder includes reducing the floc to a particle size of less than about ten microns.

9. A method for making an electrochemical call electrode using a powder made by floccing a co-suspension of carbon particles and hydrophobic fluorocarbon polymer particles, drying the floc so-produced and reducing it to a powder, comprising the steps of:

suspending the floc powder in an inking vehicle to form an ink;

screen printing the ink onto a porous substrate to form a layer;

drying the layer to remove the inking vehicle;

compacting the layer;

sintering the compacted layer; and

,

catalyzing the layer.

10. The method according to claim 9 wherein the polymer is PTFE and the dry floc powder has a particle size of less than about ten microns.