Fuel cell catalyst layer for improving power generation

Patent metadata

Field	Value
Publication number	US-10673075-B2
Application number	US-201715592631-A
Country	US
Kind code	B2
Filing date	May 11, 2017
Priority date	May 13, 2016
Publication date	Jun 2, 2020
Grant date	Jun 2, 2020

Abstract

A fuel cell includes: an electrolyte membrane; an anode catalyst layer; a cathode catalyst layer; and a cathode gas diffusion layer. The cathode catalyst layer includes an ionomer, the ionomer includes copolymers each of which has a hydrophilic block. The hydrophilic block is positioned at a terminal of a copolymer which includes a hydrophobic portion and a hydrophilic portion having a sulfonic acid group. The hydrophilic block has an aggregated structure of the hydrophilic portion. A gas diffusion resistance coefficient of the cathode gas diffusion layer is 3.2×10 −4 m or lower. The gas diffusion resistance coefficient is expressed by “Gas Diffusion Resistance Coefficient=Thickness of Cathode Gas Diffusion Layer/(Porosity of Cathode Gas Diffusion Layer) 4 ”.

First claim

What is claimed is:

1. A fuel cell comprising:
an electrolyte membrane;
an anode catalyst layer that is provided on a first surface of the electrolyte membrane;
a cathode catalyst layer that includes an ionomer and is provided on a second surface of the electrolyte membrane, the ionomer including copolymers each of which has a hydrophilic block, the hydrophilic block being positioned at a terminal of the copolymer including a hydrophobic portion and a hydrophilic portion which has a sulfonic acid group, the hydrophilic block having an aggregated structure of the hydrophilic portion; and
a cathode gas diffusion layer that is provided outside the cathode catalyst layer,
wherein a gas diffusion resistance coefficient of the cathode catalyst layer represented by the following expression is 3.2×10 −4 m or lower,
the gas diffusion resistance coefficient=a thickness of the cathode gas diffusion layer/(a porosity of the cathode gas diffusion layer) 4 ,

wherein the hydrophilic portion has a structure represented by the following Formula A1, and the hydrophobic portion has a structure represented by the following Formula B1,

where a represents an integer of 0 or more, and b represents an integer of 2 or more,

where Rf 1 and Rf 2 each independently represent fluorine or a perfluoroalkyl group having 1 to 10 carbon atoms.

2. The fuel cell according to claim 1 , wherein
the copolymer is a random copolymer having the hydrophilic portion at the terminal.

3. The fuel cell according to claim 1 , wherein
the number of repeats of the hydrophilic portion in the hydrophilic block is 11 to 16.

4. The fuel cell according to claim 1 , wherein
a lower melting point water content in the ionomer is 28 dry % to 38 dry %.

5. The fuel cell according to claim 1 , wherein
an oxygen permeability of the ionomer at a relative humidity of 30% or higher is 20×10 −12 mol/(cm 2 ×s×atm) or higher.

6. The fuel cell according to claim 1 , wherein
a portion of the copolymer other than the hydrophilic block includes a non-aggregated portion.

7. A fuel cell comprising:
an electrolyte membrane;
an anode catalyst layer that is provided on a first surface of the electrolyte membrane;
a cathode catalyst layer that includes an ionomer and is provided on a second surface of the electrolyte membrane, the ionomer including copolymers each of which has a hydrophilic block, the hydrophilic block being positioned at a terminal of the copolymer including a hydrophobic portion and a hydrophilic portion which has a sulfonic acid group, the hydrophilic block having an aggregated structure of the hydrophilic portion; and
a cathode gas diffusion layer that is provided outside the cathode catalyst layer,
wherein a gas diffusion resistance coefficient of the cathode catalyst layer represented by the following expression is 3.2×10 −4 m or lower,
the gas diffusion resistance coefficient=a thickness of the cathode gas diffusion layer/(a porosity of the cathode gas diffusion layer) 4 ,

wherein the hydrophilic portion has a structure represented by the following Formula A1, and the hydrophobic portion has a structure represented by the following Formula B1,

where a represents an integer of 0 or more, and b represents an integer of 2 or more,

where Rf 1 and Rf 2 each independently represent fluorine or a perfluoroalkyl group having 1 to 10 carbon atoms which has an ether bond in a middle of the perfluoroalkyl group.

8. The fuel cell according to claim 7 , wherein
the copolymer is a random copolymer having the hydrophilic portion at the terminal.

9. The fuel cell according to claim 7 , wherein
the number of repeats of the hydrophilic portion in the hydrophilic block is 11 to 16.

10. The fuel cell according to claim 7 , wherein
a lower melting point water content in the ionomer is 28 dry % to 38 dry %.

11. The fuel cell according to claim 7 , wherein
an oxygen permeability of the ionomer at a relative humidity of 30% or higher is 20×10 −12 mol/(cm 2 ×s×atm) or higher.

12. The fuel cell according to claim 7 , wherein
a portion of the copolymer other than the hydrophilic block includes a non-aggregated portion.

Assignees

• Toyota Motor Co Ltd

Inventors

• Kitao Noriyuki

Classifications

• H01M2250/20

  Fuel cells in motive systems, e.g. vehicle, ship, plane · CPC title

• H01M8/1067

  characterised by their physical properties, e.g. porosity, ionic conductivity or thickness · CPC title

• H01M4/8673 Primary

  Electrically conductive fillers · CPC title

• H01M8/1004 Primary

  characterised by membrane-electrode assemblies [MEA] (H01M8/12 takes precedence) · CPC title

• H01M4/8663

  Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers · CPC title