(a) Field of the Invention
The present invention generally relates to a membrane electrode assembly and more particularly relates to a manufacturing method of a membrane electrode assembly that is provided in a fuel cell system to transform chemical energy to electrical energy.
(b) Description of the Related Art
As is known to those skilled in the art, a fuel electric stack is a solid high-molecule electrolyte type of fuel cell (PEMC: proton exchange membrane fuel cell). Such a fuel cell is presently used for a vehicle.
In the solid high-molecule electrolyte type of fuel cell, hydrogen is supplied to an anode (fuel electrode) and oxygen is supplied to a cathode (air electrode).
The hydrogen ions (H+) supplied to the anode pass through an electrolyte membrane as a positive ion exchange membrane to be selectively transferred to the cathode through a catalyst of an electrode layer formed at both sides of the electrolyte membrane. Simultaneously electrons are transferred to the cathode through a conductive gas diffusion layer and a separating plate.
In the cathode, the hydrogen ions supplied through the electrolyte membrane and the electrons supplied through the separating plate react with oxygen from the air supplied to the cathode by an air supply device and generate water.
A current also is generated by the flow of electrons derived from hydrogen ions through a wire. Also, heat is collaterally generated from the water formation reaction.
In the fuel cell system, a stack generating electricity has a structure in which several or dozens of unit cells are laminated, each unit including a membrane electrode assembly and a separating plate.
Conventional manufacturing methods for a membrane electrode assembly (MEA) includes a direct coating method where an electrode is coated or applied onto an electrolyte membrane, and a decal method where an electrode is coated or applied onto a release paper and then printing the electrode onto an electrolyte membrane.
In such a decal method, an electrode slurry is coated on the release paper to reduce transformation of the electrolyte membrane by the slurry solvent. This method is advantageous in that a roller or plane plate press is usable to manufacture the MEA in the decal method.
In such a decal method or process a sub-gasket is joined to the MEA such as by means of a roller. However, in such a process where a roller is used to join the sub-gasket to the MEA, it is difficult to sustain tension of the membrane that is being used for the sub-gasket. It also is not uncommon to see a wrinkle be formed in the membrane during the joining process. In addition, the manufacturing process is complicated such that the cost thereof is increased as compared to other methods.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.