Low contact resistance PEM fuel cell
View Patent ↗A PEM fuel cell having a current collector comprising a polymer composite and a diffusion media engaging said polymer composite. The polymer composite has a hyperconductive surface layer engaging the diffusion media to reduce the contact resistance therebetween. The hyperconductive surface layer is formed by depositing or smearing an electrically-conductive material on the surface of the polymer composite.
1. In a PEM fuel cell having at least one cell comprising (a) a pair of opposite polarity electrodes each having a first face exposed to a fuel cell reactant and a second face engaging a membrane-electrolyte interjacent said electrodes, (b) a porous, electrically-conductive media engaging said first face for distributing said reactant over, and conducting electrical current from, said first face, and (c) a current collector engaging said media for conducting electrical current from said media, said current collector comprising a composite having a first conductivity and comprising corrosion-proof, electrically conductive filler dispersed throughout an oxidation-resistant and acid-resistant, water-insoluble polymeric matrix, said current collector, including a face providing a flow field including a plurality of lands and grooves to flow reactant gas through a tortuous path from one side of the current collector to another side, the improvement comprising said current collector comprising a metal substrate supporting said composite and an oxidation-resistant and acid-resistant hyperconductive surface layer on said composite and engaging said media, said hyperconductive surface layer having a second conductivity greater than said first conductivity for shunting electrical current passing through said media into said surface layer to such of said filler as resides at the interface between said surface layer and said composite, and thereby reduce the contact resistance that would otherwise exist between said composite and said media absent said surface layer.
2. A fuel cell according to claim 1 wherein said filler is selected from the group consisting of gold, platinum, graphite, conductive carbon, palladium, rhodium, ruthenium, and the rare earth metals.
3. A fuel cell according to claim 1 wherein said filler comprises a plurality of particles.
4. A fuel cell according to claim 1 wherein said filler is fibrillose and oriented in the general direction that the electrical current flows through the composite.
5. A fuel cell according to claim 1 wherein said filler comprises continuous fibers that extend through the thickness of said composite.
6. A fuel cell according to claim 1 wherein at least one of said current collectors is a bipolar plate confronting the anode of one of said cells and the cathode of the next adjacent cell.
7. A fuel cell according to claim 1 wherein said metal substrate comprises a first acid-soluble metal underlying a second acid-insoluble, oxidizeable metal layer engaging said composite.
8. A fuel cell according to claim 1 wherein said metal is selected from the group consisting of titanium, stainless steel, and aluminum.
9. A fuel cell according to claim 1 wherein said polymer matrix is selected from the group consisting of epoxies, polyamide-imides, polyetherimides, polyphenols, fluro-elastomers, polyesters, phenoxy-phenolics, epoxide-phenolics, acrylics, and urethanes.
10. A PEM fuel cell according to claim 1 wherein said filler comprises graphite.
11. A PEM fuel cell according to claim 10 wherein said graphite is at least partially embedded in said surface.
12. A fuel cell according to claim 11 wherein said hyperconductive surface layer comprises a continuous, oxidation-resistant, and acid-resistant film on the surface of said composite confronting said media.
13. In a PEM fuel cell having at least one cell comprising (a) a pair of opposite polarity electrodes each having a first face exposed to a fuel cell reactant and a second face engaging a membrane-electrolyte interjacent said electrodes, (b) a porous, electrically- conductive media engaging said first face for distributing said reactant over, and conducting electrical current from, said first face, and (c) a current collector engaging said media for conducting electrical current from said media, said current collector comprising a composite having a first conductivity and comprising corrosion-proof, electrically conductive filler dispersed throughout an oxidation-resistant and acid-resistant, water-insoluble polymeric matrix, said current collector, including a face providing a flow field including a plurality of lands and grooves to flow reactant gas through a tortuous path from one side of the current collector to another side, said current collector comprising a first acid-soluble metal substrate, a second acid-insoluble and oxidizable metal over said first acid-soluble metal substrate, said composite over said second acid-insoluble and oxidizable metal, and an oxidation-resistant and acid-resistant hyperconductive surface layer on said composite and engaging said media, said hyperconductive surface layer having a second conductivity greater than said first conductivity for shunting electrical current passing through said media into said surface layer to such of said filler as resides at the interface between said surface layer and said composite, and thereby reduce the contact resistance that would otherwise exist between said composite and said media absent said surface layer.
14. A fuel cell according to claim 13 wherein said hyperconductive surface layer comprises a plurality of oxidation-resistant and acid-resistant, electrically conductive particles adhering to a surface of said composite confronting said media.
15. A fuel cell according to claim 13 wherein said hyperconductive surface layer comprises a continuous, oxidation-resistant, and acid-resistant film on a surface of said composite confronting said media.
16. In a PEM fuel cell having at least one cell comprising (a) a pair of opposite polarity electrodes each having a first face exposed to a fuel cell reactant and a second face engaging a membrane-electrolyte interjacent said electrodes, (b) a porous, electrically- conductive media engaging said first face for distributing said reactant over, and conducting electrical current from, said first face, and (c) a current collector engaging said media for conducting electrical current from said media and including a face providing a flow field including a plurality of lands and grooves to flow reactant gas through a tortuous path from one side of the current collector to another side, said current collector consisting essentially of a composite and a continuous, oxidation-resistant and acid-resistant hyperconductive surface layer on said composite and engaging said media, said composite having a first conductivity and comprising corrosion-proof, electrically conductive filler dispersed throughout an oxidation- resistant and acid-resistant, water-insoluble polymeric matrix, said hyperconductive surface layer having a second conductivity greater than said first conductivity for shunting electrical current passing through said media into said surface layer to such of said filler as resides at the interface between said surface layer and said composite, and thereby reduce the contact resistance that would otherwise exist between said composite and said media absent said surface layer.
17. A fuel cell according to claim 16 wherein said hyperconductive surface layer comprises a plurality of oxidation-resistant and acid-resistant, electrically conductive particles adhering to a surface of said composite confronting said media.
18. A fuel cell according to claim 17 wherein said particles comprise at least one of graphite, gold, platinum, conductive carbon, palladium, rhodium, ruthenium, or a rare earth metal.
19. A fuel cell according to claim 16 wherein said hyperconductive surface layer comprises a continuous, oxidation-resistant, and acid-resistant film on a surface of said composite confronting said media.
20. In a PEM fuel cell having at least one cell comprising (a) a pair of opposite polarity electrodes each having a first face exposed to a fuel cell reactant and a second face engaging a membrane-electrolyte interjacent said electrodes, (b) a porous, electrically-conductive media engaging said first face for distributing said reactant over, and conducting electrical current from, said first face, and (c) a current collector engaging said media for conducting electrical current from said media and including a face providing a flow field including a plurality of lands and grooves to flow reactant gas through a tortuous path from one side of the current collector to another side, said current collector comprising a composite and a continuous, oxidation-resistant and acid-resistant hyperconductive surface layer comprising a plurality of electrically conductive particles adhering to a surface of said composite and engaging said media, said composite having a first conductivity and comprising corrosion-proof, electrically conductive filler dispersed throughout an oxidation-resistant and acid-resistant, water-insoluble polymeric matrix, said hyperconductive surface layer having a second conductivity greater than said first conductivity for shunting electrical current passing through said media into said surface layer to such of said filler as resides at the interface between said surface layer and said composite, and thereby reduce the contact resistance that would otherwise exist between said composite and said media absent said surface layer.