Process for preparing a single pass gas diffusion electrode

• US 5,312,701 A
• Filed: 05/18/1993
• Issued: 05/17/1994
• Est. Priority Date: 06/23/1992
• Status: Expired due to Term

• Current Assignee: Electric Fuel Ltd.
• Original Assignee: Electric Fuel Ltd.
• Inventors: Khasin, Eric E., Goldstein, Jonathan R., Naimer, Neal, Sassen, Jonathan
• Primary Examiner(s): Skapars, Anthony
• Application Number:
  US08/062,835
• Time in Patent Office: 364 Days
• Field of Search: 429/42, 429/27, 429/212, 29/623.5, 29/623.1, 427/115, 264/6, 264/7, 264/49, 264/56, 264/105, 264/109, 264/127, 264/319, 204/290 R, 204/294, 204/284
• US Class Current: 429/405
• CPC Class Codes: H01M 4/86 Inert electrodes with catalytic activity, e.g. for fuel cells
• CPC Class Codes: H01M 4/96 Carbon-based electrodes
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y10T 29/49115 including coating or impregnating

Abstract

The invention provides a single pass wet fabrication process for preparing a gas diffusion electrode for metal-air batteries and fuel cells comprising:

a) preparing an active-layer forming dispersion containing catalyzed carbon black, hydrophilic fluorinated polymer and particulate hydrophobic fluorinated polymer in a liquid medium;

b) preparing a blocking-layer forming dispersion containing carbon black and particulate hydrophobic polymeric binders in a liquid medium;

c) filtering a first of the layer forming dispersions though filtering means to deposit a first layer of damp solids mass;

d) filtering a second of the layer forming dispersions through the first deposited damp solids mass before the drying or sintering of the first deposited damp solids mass in order to deposit a second layer of damp solids mass thereon in such a manner that lower components of the second layer of damp solids mass are intermixed with upper components of the first layer of deposited damp solids mass;

e) drying and compressing the composite first and second layers with a conductive metal mesh incorporated therein; and

f) heating the dried layers to a temperature above the sintering temperature of the hydrophobic polymer while applying pressure thereto thereby causing the polymeric materials of both layers to sinter and bond with each other and with other components of the layers.

Claims

1. A single pass wet fabrication process for preparing a gas diffusion electrode for metal-air batteries and fuel cells comprising:

a) preparing an active-layer forming dispersion containing catalyzed carbon black, hydrophilic fluorinated polymer and particulate hydrophobic fluorinated polymer in a liquid medium;

b) preparing a blocking-layer forming dispersion containing carbon black and particulate hydrophobic polymeric binders in a liquid medium;

c) filtering a first of said layer forming dispersions though filtering means to deposit a first layer of damp solids mass;

d) filtering a second of said layer forming dispersions through said first deposited damp solids mass before the drying or sintering of said first deposited damp solids mass in order to deposit a second layer of damp solids mass thereon in such a manner that lower components of said second layer of damp solids mass are intermixed with upper components of said first layer of deposited damp solids mass;

e) drying and compressing said composite first and second layers with a conductive metal mesh incorporated therein; and

f) heating said dried layers to a temperature above the sintering temperature of the hydrophobic polymer while applying pressure thereto thereby causing the polymeric materials of both layers to sinter and bond with each other and with other components of said layers.

2. A single pass wet fabrication process for preparing a gas diffusion electrode for metal-air batteries and fuel cells as claimed in claim 1 comprising:

a) filtering an active-layer forming dispersion containing catalyzed carbon black, hydrophilic fluorinated polymer and a particulate hydrophobic fluorinated polymer, in a liquid medium through a metal mesh to deposit a first layer of damp-solids mass thereon;

b) filtering a blocking-layer forming dispersion containing carbon black and particulate hydrophobic polymeric binders in a liquid medium through said active layer before the drying, pressing or sintering thereof to deposit a second layer of damp-solids mass thereon and intermixed with upper components thereof;

c) drying and compressing said composite first and second layers; and

d) heating said dried layers to a temperature above 270°

C. while applying pressure thereto, thereby causing the polymeric materials of both layers to sinter and bond with each other and with other components of said layers.

4. A single pass wet fabrication process for preparing a gas diffusion electrode, as claimed in claim 1, wherein at least one of said layer forming dispersions further contains structurally intact fibers precoated with sinterable polymeric material, which material when heat sintered results in said fibers being bonded to each other and to other components of said layer by said sintered polymeric material while maintaining their individual fibrous structure and strength.

5. A single pass wet fabrication process for preparing a gas diffusion electrode, as claimed in claim 4, wherein said precoated fibers are contained in said active layer forming dispersion.

6. A single pass wet fabrication process for preparing a gas diffusion electrode, as claimed in claim 4, wherein said precoated fibers are contained in said blocking layer forming dispersion.

7. A single pass wet fabrication process for preparing a gas diffusion electrode, as claimed in claim 4, wherein said fibers have a length of between about 100 and 5000 microns and a diameter of between about 5 and 500 microns.

8. A single pass wet fabrication process for preparing a gas diffusion electrode, as claimed in claim 4, wherein said intact fibers are carbon fibers coated with a fluoropolymer.

9. A single pass wet fabrication process for preparing a gas diffusion electrode, as claimed in claim 4, wherein said intact fibers are fluoropolymer fibers coated with a different fluoropolymeric material, said material having a lower sintering temperature than said fibers.

10. A single pass wet fabrication process for preparing a gas diffusion electrode, as claimed in claim, 1 wherein said drying and compression is carried out at a temperature of about 80°

-150°

C. and a pressure of about 150-350 kg/cm².

11. A single pass wet fabrication process for preparing a gas diffusion electrode, as claimed in claim 1, wherein said sintering is carried out at a pressure of about 5-25 kg/cm² and a temperature of about 270°

14 355°

C. for a period of 3-30 minutes.

12. A gas diffusion electrode for metal-air batteries and fuel cells whenever prepared by the process of claim 1.

3. A single pass wet fabrication process for preparing a gas diffusion electrode, as claimed in claim wherein a second mesh made of plastic or metal having a sintering temperature higher than the temperature used in step f) is incorporated into said composite layers before the sintering thereof.