Method of forming a gasket assembly for a PEM fuel cell assembly

Abstract

A thermoplastic carrier sheet is die-cut to have a size and shape matching that of a PEM bipolar plate. A plurality of holes are punched in the carrier sheet in the pattern of gasket beading to be formed subsequently. In a mold, liquid gasket resin fills the mold on both sides of the carrier sheet to form the gasket, flowing through the holes in the sheet and thereby causing the gasket to become mechanically attached to the sheet. A carrier element having a flange portion substantially identical with the outer profile of the bipolar plates is laminated to the sheet edge. During assembly of a fuel cell, the carrier element automatically positions the gasket correctly on the plate and prevents the gasket from twisting or shifting. In a currently preferred embodiment, a membrane electrode assembly is attached within an appropriate opening in the carrier sheet.

Description

TECHNICAL FIELD [0001] The present invention relates to proton-exchange membrane (PEM) fuel cells; more particularly, to gasketing for a PEM fuel cell; and most particularly, to an improved process for forming and using an elastomeric gasket to seal the edges of bipolar plates in a PEM fuel cell assembly. BACKGROUND OF THE INVENTION [0002] Proton-exchange membrane fuel cells are well known. In a PEM fuel cell, hydrogen atoms are ionized in an anode, migrate through a specialized membrane as hydrogen cations (protons), and combine with oxygen anions at a cathode to form water. Electrons from the hydrogen flow from the anode through an external circuit to the cathode, performing work in between. The membrane, typically with a catalyst coating sandwiched between layers of gas diffusion media (GDL), is know in the art as a membrane electrode assembly (MEA). A bipolar plate assembly is constructed by joining an individual anode and cathode plate. [0003] Fuel cell assemblies comprise a pl...

AI Technical Summary

Benefits of technology

[0010] Briefly described, in a method of forming a gasket assembly for a fuel cell assembly, a thermoplastic carrier sheet is die-cut to have a size and shape matching that of a bipolar plate, including various cutouts known in the art for passage of reactant gases, spent gases, coolant, and placement of a membrane electrode assembly. A plurality of holes are also punched in the carrier sheet in the pattern of gasket beading to be formed subsequently. In a gasket mold, liquid gasket material fills the mold on both sides of the carrier sheet to form gasket elements on both sides, flowing through the holes in the sheet and thereby causing the gasket elements to become mechanically attached to the sheet and to each other. Different liquid gasket materials can be used to suit the performance demands of the local environment. Preferably, a pre-molded plastic carrier element having a flange portion substantially identical with the outer profile of the bipolar plate is then overmolded onto the sheet. Alternately, locator features are provided in the outer regions of the sheet to aid in accurately locating the gasket elements.

[0011] During assembly of a fuel cell assembly, the plastic carrier element fits over a bipolar plate, automatically positioning the gasket correctly on the plate. The carrier sheet prevents the gasket from twisting or shifting. In a currently preferred embodiment, a membrane electrode assembly is attached as by ultrasonic welding within an appropriate opening in the carrier sheet.

Problems solved by technology

Bipolar plates typically are formed of a metals (such as titanium or stainless steel) or composites (such as a thermoset graphite-loaded vinyl ester polymer) and are easily damaged by twisting or other application of uneven stresses.

A problem exists in locating the gaskets properly with respect to the openings to be sealed.

Further, individual gaskets are thin, very pliable, and thus are easily twisted and deformed.

A misaligned or twisted gasket can cause leaks, broken bipolar plates, and stack failure.

Images