Fuel cell having metalized gas diffusion layer

#Field of the invention: The present invention relates to a fuel cell, and more specifically to a fuel cell incorporating a metalized gas diffusion layer which is disposed in ohmic electrical contact with an adjoining current collector, and wherein a substantially force independent contact resistance is established between the current collector and the gas diffusion layer during fuel cell operation.

#A fuel cell is a device which can readily convert chemical energy to electrical energy by the reaction of a fuel gas with a suitable oxidant supply. In a proton exchange membrane fuel cell, for example, the fuel gas is typically hydrogen, and the oxidant supply comprises oxygen (or more typically ambient air). In fuel cells of this type, a membrane electrode diffusion layer assembly is provided and which includes a solid polymer electrolyte with opposite anode and cathode sides. Appropriate electrodes are provided on the opposite anode and cathode sides. During operation, a fuel gas reacts with a catalyst present in the electrode on the anode side to produce hydrogen ions which migrate through the solid polymer electrolyte to the opposite cathode side. Meanwhile, an oxidant supply introduced to the cathode side is present to react with the hydrogen ions in the presence of catalyst which is incorporated into the electrode on that side, to produce water and a resulting electrical output.

#Many fuel cell designs have been provided through the years, and much research and development activity has been conducted to develop a fuel cell which meets the perceived performance and cost per watt requirements of various users. Despite decades of research, fuel cells have not been widely embraced except for narrow commercial applications. While many designs have emerged, and which have operated with various degrees of success, shortcomings in some peculiar aspect of their individual designs have resulted in difficulties which have detracted from their widespread commercial acceptance and perceived usefulness. For example, one of the perceived challenges for fuel cell designers is the reduction of contact resistance between the current collector and an adjacent gas diffusion layer and which is borne by the membrane electrode diffusion layer assembly. This contact resistance is generally speaking inversely related to the current output of the fuel cell. Consequently, lowering the contact resistance increases the overall current output of the fuel cell.

#Preferred embodiments of the invention are described below with reference to the following accompanying drawings.

#FIG. 1 is a greatly enlarged, fragmentary, vertical sectional view of a membrane electrode diffusion layer assembly, and accompanying current collector, and which illustrates the teachings of the present invention.

#FIG. 2 is a perspective view of a modular fuel cell power system which may utilize the present invention.

#This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).

#A fuel cell having a metalized gas diffusion layer in accordance with the teachings of the present invention is generally indicated by the numeral 10 in FIG. 1. As should be understood, FIG. 1 is a greatly enlarged, fragmentary, vertical sectional view taken through a portion of a membrane electrode diffusion layer assembly which is generally indicated by the numeral 11. The membrane electrode diffusion layer assembly (MEDLA) is received within or made integral with a fuel cell device such as what is seen in FIGS. 2 or 3 and which will be discussed in greater detail, hereinafter. For purposes of the present discussion, however, the membrane electrode diffusion layer assembly, as will be disclosed below, is useful in fuel cell devices which operate at temperatures of less than about 300 degrees C. Consequently, this invention is not useful in solid oxide fuel cell designs or other fuel cells which generally operate at temperatures greater than about 300 degrees C. As will be appreciated by a study of FIG. 1, aspects of the construction of the MEDLA can be expressed in terms of dimensions as measured along x, y and z axes. In this regard the x and y axis relate to length and width dimensions of an object, and the z axis relates to thickness of the same object.

#As seen in FIG. 1, a fuel cell employing the present invention will typically utilize an ion exchange membrane 12, such as may be purchased under the trade name “NAFION”. This ion exchange membrane is a thin, flexible and sheet-like material which is made from a fluor-polymer. This ion exchange membrane is available from the Dupont™ Company. The ion exchange membrane 12 has opposite anode and cathode sides 13 and 14 respectively.