Gas diffusion layer and method for manufacturing same, composite powder for gas diffusion layer, membrane electrode assembly, and fuel cell

A composite powder for a gas diffusion layer, comprising:

• conductive particles;
• conductive fibers;
• and
• a polymer resin,
• wherein an average particle diameter D50 of the composite powder is 30 μm or more and 300 μm or less, and
• in the composite powder, pores having a peak in a range of a pore radius of 0.1 μm or more and 0.3 μm or less are present in a Log differential pore volume graph measured by a mercury intrusion method,
• wherein the composite powder for a gas diffusion layer has, inside the composite powder for a gas diffusion layer, pores with a pore radius of 0.055 μm or more and 0.4 μm or less having a pore volume of 0.90 mL/g or less in a Log differential pore volume graph measured by a mercury intrusion method.

A method for manufacturing a gas diffusion layer, the method comprising:

• stirring and kneading conductive particles, conductive fibers, and a polymer resin with a dispersion solvent to obtain a kneaded product of the conductive particles, the conductive fibers, and the polymer resin;
• firing the kneaded product at a temperature equal to or higher than a decomposition temperature of the dispersion solvent to remove the dispersion solvent to obtain a solid;
• pulverizing the solid to obtain a composite powder containing the conductive particles, the conductive fibers, and the polymer resin;
• and
• rolling the composite powder with a roll to form a sheet to obtain a gas diffusion layer containing a sheet.