Abstract: A method of producing a fuel cell stack is disclosed, the method including the steps of compressing the fuel cell stack at a first pressure and compressing the fuel cell stack at a second pressure higher than the first pressure, wherein a shorting resistance of fuel cells in the fuel cell stack is maximized and a durability of the fuel cell stack is maximized.

Abstract: A fuel cell system is provided including a fuel cell stack having a first end and second end. The fuel cell stack includes at least one fuel cell having a membrane-electrode assembly disposed between adjacent gas diffusion layers. The fuel cell system further includes a compression retention system having a plurality of compliant straps adapted to apply a compressive force to the fuel cell stack. The plurality of compliant straps are further adapted to accommodate an expansion of the fuel cell stack during an operation thereof and maintain the compressive force within a desired range.

Abstract: A fuel cell stack that includes a gas diffusion media for the end cells in the stack that has less of an intrusion into the flow field channels of the end cells that the other cells, so as to increase the flow rate through the flow channels in the end cells relative to the flow rate through the flow channels in the other cells. A different diffusion media can be used in the end cells than the nominal cells, where the end cell diffusion media has less of a channel intrusion as a result of diffusion media characteristics. Also, the same diffusion media could be used in the end cells as the nominal cells, but the end cell diffusion media layers could be thinner than the nominal cell diffusion media layers. Further, a higher amount of pre-compression can be used for the diffusion media in the end cells.

Abstract: The present invention provides for a construction for a bipolar plate for a fuel cell stack that enables the bipolar plate to be a more compliant member in the fuel cell stack. The bipolar plate can be configured to provide varying levels of compliance, as demanded by the design of the fuel cell stack. The bipolar plate can be more compliant than the diffusion media members and the active elements used to form the individual fuel cells. The compliant nature of the individual bipolar plates enables localized dimensional changes that occur within the fuel cell stack to be compensated by a localized deformation of the portions of the bipolar plate within that region. The bipolar plate has an internal coolant flow field where some opposing pairs of lands are spaced apart with a gap therebetween while other opposing pairs of lands are in contact with one another.

Abstract: A method of operating an electrochemical conversion assembly is provided. According to the method, an assembly warm-up operation is executed by increasing the temperature TSTACK of the membrane electrode assembly. Next, stoichiometry-based control of the relative humidity (RH) of one of the reactant flowfields is initiated when the temperature TSTACK exceeds a threshold temperature T0. The stoichiometry-based RH control comprises a reduction in the relative humidity from a value RHWET exceeding 100% relative humidity to a value RHDRY less than 100% relative humidity. The relative humidity value RHDRY is sufficiently low to permit reduction of an initial membrane hydration ?WET in the membrane electrode assembly.

Abstract: The present invention provides for a construction for a bipolar plate for a fuel cell stack that enables the bipolar plate to be a more compliant member in the fuel cell stack. The bipolar plate can be configured to provide varying levels of compliance, as demanded by the design of the fuel cell stack. The bipolar plate can be more compliant than the diffusion media members and the active elements used to form the individual fuel cells. The compliant nature of the individual bipolar plates enables localized dimensional changes that occur within the fuel cell stack to be compensated by a localized deformation of the portions of the bipolar plate within that region. The bipolar plate has an internal coolant flow field where some opposing pairs of lands are spaced apart with a gap therebetween while other opposing pairs of lands are in contact with one another.

Abstract: In accordance with one embodiment of the present invention, a method of operating an electrochemical conversion cell is provided wherein the method comprises the steps of (i) initiating a membrane dehydration sequence when the membrane is characterized by an initial membrane hydration ?WET and (ii) maintaining the membrane dehydration sequence until the membrane is characterized by a target membrane hydration ?DRY. According to the method, the membrane dehydration sequence is characterized by a drying rate that varies in a manner that substantially corresponds to a fatigue life contour map of the membrane. Additional methods and corresponding systems are contemplated.

Abstract: According to one embodiment of the present invention, a fuel cell life counter is configured to determine membrane degradation using fuel cell cycling data and S-N curve data for the membrane. According to another embodiment of the present invention, a method of managing remaining fuel cell life is provided where variables like membrane dehydration rate, water content, temperature, and heating/cooling rate are controlled as a function of the remaining life of the fuel cell. Additional embodiments are provided where fuel cell life counters and methods of managing remaining life are independent of S-N curve data and the use of fatigue life contour plots.

Abstract: An electrochemical conversion assembly (10) is provided comprising a plurality of electrochemical conversion cells arranged in a conductively coupled fuel cell stack (20), a condition sensor (30, 40) operatively coupled to the fuel cell stack (20), and a programmable controller operatively coupled to the condition sensor and the fuel cell stack. The condition sensor is configured to measure a rate of change of hydration in the proton exchange membrane and either the condition sensor or the programmable controller is configured to generate a signal indicative of the measured rate of change of hydration. The programmable controller is configured to facilitate control of at least one operating parameter of the electrochemical conversion assembly by monitoring the signal indicative of the measured rate of change of hydration. The condition sensor can be configured to detect a dimensional change or a change in compression of the conductively coupled fuel cell stack as the membrane hydration changes.

Abstract: Methods of producing an electrochemical conversion assembly comprising an electrochemical conversion cell are provided. The electrochemical conversion cells which comprises a membrane electrode assembly, first and second flowfield portions defined on opposite sides of the membrane electrode assembly, and, at least one vapor barrier layer disposed between the membrane electrode assembly and at least one of the flowfield portions. The method further includes selecting a desired mass transfer coefficient MTC for the at least one vapor barrier layer of at least about 0.05 cm and optimizing one or more of the porosity, the tortuosity, and the thickness of the vapor barrier layer to produce the desired MTC in the vapor barrier layer.

Abstract: One aspect of the invention includes the discovery that pinholes in the membrane of the membrane electrode assembly may be caused by hygroexpansive ratcheting. In one embodiment of the invention, a fuel cell stack including a plurality of cells each having a membrane electrode assembly each including a membrane manufactured by an extrusion method and operated so that the rate of drying during humidity cycling is sufficiently low to reduce or eliminate build up stresses in the membrane electrode assembly.

Abstract: A method for reducing the compression set of GDL during the fuel cell operation and a method for reducing the intrusion of the GDL into flow-field channels, both achieved by pre-compression preconditioning the GDL before placing it into the fuel cell. This preconditioning is performed in order to reduce the loss of compression during the life of the stack and the mal-distribution of reactant gases, and ultimately achieve the benefits of higher power output and more stable performance.

Abstract: The present invention is directed to addressing performance issues attributable to membrane electrode assemblies, and the components thereof, in electrochemical conversion cells. In accordance with one embodiment of the present invention, a device comprising at least one electrochemical conversion cell is provided. The cell is configured to convert first and second reactants to electrical energy and comprises a membrane electrode assembly and at least one membrane reinforcement layer. The combination of elastic modulus and thickness of the reinforcement layer and the bond between the reinforcement layer and the membrane electrode assembly are sufficient to enhance the structural integrity of the membrane electrode assembly beyond the operational degradation threshold of the assembly.

Abstract: The invention relates to an imaging member comprising an imaging layer and a base wherein said base comprises a closed cell foam core sheet and adhered thereto an upper and lower flange sheet, wherein said foam core sheet has a modulus of between 100 and 2758 MPa and a tensile toughness between 0.344 and 35 MPa, and wherein said upper and lower flange sheet has a modulus of between and 1380 and 20000 MPa and a toughness between 1.4 and 210 MPa.

Abstract: A multi-layer diffusion medium substrate having improved mechanical properties is disclosed. The diffusion medium substrate includes at least one stiff layer and at least one compressible layer. The at least one stiff layer has a greater stiffness in the x-y direction as compared to the at least one compressible layer. The at least one compressible layer has a greater compressibility in the z direction. A method of fabricating a multi-layer diffusion medium substrate is also disclosed.

Abstract: The invention relates to an imaging member comprising an imaging layer and a base wherein said base comprises a closed cell foam core sheet and adhered thereto an upper and lower flange sheet, wherein said foam core sheet has a modulus of between 100 and 2758 MPa and a tensile toughness between 0.344 and 35 MPa, and wherein said upper and lower flange sheet has a modulus of between and 1380 and 20000 MPa and a toughness between 1.4 and 210 MPa.

Abstract: A method and apparatus are taught for cutting a sheet material comprising the steps of engaging a first side of the laminated web structure with a crack initiator having a high rake angle, the crack initiator extending from a first cutter base having a low rake angle; simultaneously engaging a second side of the laminated web structure with a second cutter; generating a first crack in the first side of the laminated web structure with the crack initiator, generating a second crack in the second side of the laminated web structure with the second cutter, and propagating the first crack and the second crack to intersect. The crack initiator extends from a cutter base to a height of at least 5 ?m. The high rake angle of the crack initiator is in the range of from about 30° to about 70°. The cutter base has a low rake angle that is at least about 15° less than the high rake angle of the crack initiator.

Abstract: A method and apparatus are taught for cutting a sheet material comprising the steps of engaging a first side of the laminated web structure with a crack initiator having a high rake angle, the crack initiator extending from a first cutter base having a low rake angle; simultaneously engaging a second side of the laminated web structure with a second cutter; generating a first crack in the first side of the laminated web structure with the crack initiator; generating a second crack in the second side of the laminated web structure with the second cutter; and propagating the first crack and the second crack to intersect. The crack initiator extends from a cutter base to a height of at least 5 ?m. The high rake angle of the crack initiator is in the range of from about 30° to about 70°. The cutter base has a low rake angle that is at least about 15° less than the high rake angle of the crack initiator.

Abstract: An electrically conductive element and a related assembly are provided for use in an electrochemical cell. The electrically conductive separator plate has an upper boundary and a lower boundary. The upper boundary has at least one land formed therein, where the land has a surface defining a first plane and the lower boundary defines a second plane. The first plane extends towards said second plane, so as to intersect with said second plane at an angle greater than zero. An assembly further comprises a compliant layer which substantially conforms to the angled land surfaces, thereby enhancing contact pressure between and across a plurality of components in the compliant layer. A method of assembling such a separator assembly in a fuel cell is also provided.

Abstract: The present invention provides for a construction for a bipolar plate for a fuel cell stack that enables the bipolar plate to be a more compliant member in the fuel cell stack. The bipolar plate can be configured to provide varying levels of compliance, as demanded by the design of the fuel cell stack. The bipolar plate can be more compliant than the diffusion media members and the active elements used to form the individual fuel cells. The compliant nature of the individual bipolar plates enables localized dimensional changes that occur within the fuel cell stack to be compensated by a localized deformation of the portions of the bipolar plate within that region. The bipolar plate has an internal coolant flow field where some opposing pairs of lands are spaced apart with a gap therebetween while other opposing pairs of lands are in contact with one another.