Membrane electrode assembly, manufacturing method thereof and fuel cell

1. A method for manufacturing a membrane electrode assembly (MEA) comprising:

coating a catalyst ink for forming a first electrode catalyst layer which comprises a catalyst loaded electron conducting material, a polymer electrolyte and a solvent on a substrate to form a first coated layer;

evaporating said solvent in said first coated layer to form at least one layer of at least two first electrode catalyst layers which have a difference in polymer electrolyte content ratio;

coating an ink for forming a filler layer which comprises a no-catalyst loaded electron conducting material or catalyst loaded electron conducting material, a polymer electrolyte and a solvent on said at least one layer of said at least two first electrode catalyst layers to form a coated filler layer;

evaporating said solvent in said coated filler layer to entirely form said at least two first electrode catalyst layers which have a difference in polymer electrolyte content ratio by forming said filler layer on said at least one layer of said at least two first electrode catalyst layers;

coating an electrolyte ink which comprises a polymer electrolyte and a solvent on said first electrode catalyst layer to form an electrolyte coated layer;

evaporating said solvent in said electrolyte coated layer to form a polymer electrolyte layer;

coating a catalyst ink for forming a second electrode catalyst layer which comprises said catalyst loaded electron conducting material, said polymer electrolyte and said solvent on said polymer electrolyte layer to form a second coated layer; and

evaporating said solvent in said second coated layer to form a second electrode catalyst layer.

2. The method according to claim 1 , wherein

a layer included in said at least two first electrode catalyst layers which is arranged adjacent to said polymer electrolyte layer is said filler layer and has a polymer electrolyte content ratio which is obtained from a formula 1 below and which is 1.2-5.0 times as large as that of another layer included in said at least two first electrode catalyst layers which is arranged adjacent to said substrate,

(polymer electrolyte content ratio)=(weight of polymer electrolyte)/(weight of no-catalyst loaded electron conducting material and catalyst loaded electron conducting material)  :<formula 1>.

3. The method according to claim 2 , further comprising:

preparing two types of ink in which said no-catalyst loaded electron conducting material or said catalyst loaded electron conducting material and said polymer electrolyte are dispersed in said solvent and which have a difference in a content ratio of said polymer electrolyte to a content of said no-catalyst loaded electron conducting material and said catalyst loaded electron conducting material, wherein

one of said two types of ink which has the lower content ratio of said polymer electrolyte to a content of said no-catalyst loaded electron conducting material and said catalyst loaded electron conducting material is used as said catalyst ink for forming a first electrode catalyst layer, and

the other of said two types of ink which has the higher content ratio of said polymer electrolyte to a content of said no-catalyst loaded electron conducting material and said catalyst loaded electron conducting material is used as said ink for forming a filler layer.

4. The method according to claim 3 , wherein

said polymer electrolyte included in said catalyst ink for forming said first electrode catalyst layer is the same as said polymer electrolyte included in said electrolyte ink.

5. The method according to claim 4 , wherein

a thickness of said at least two first electrode catalyst layers is 10 μm or less.