Fuel Cell Stack

Abstract

A method for use in manufacturing a fuel cell stack includes assembling a membrane electrode assembly having a membrane between a first gas diffusion layer and a second gas diffusion layer. A bypass stopper is disposed in a space between the first gas diffusion layer of the membrane electrode assembly and the seal. The stopper is deformed on the seal but is prevented from deforming in the space such that the stopper inhibits bypass flow of reactants through the space between the gas diffusion layers and the seal in the direction of reactant flow during operation of the fuel cell. The membrane electrode assembly is disposed between a first fluid flow plate and a second fluid flow plate.

Description

[Technical field]

[0001] This application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Non-Provisional Patent Application No. 17 / 335,238, entitled Fuel Cell Stack, filed on June 1, 2021, which is incorporated by reference in its entirety.

[0002] The present invention relates generally to electrochemical cells, and more specifically to fuel cell systems and methods. [Background technology]

[0003] Fuel cells electrochemically convert fuel and oxidant into electricity and heat and can be classified according to the type of electrolyte (e.g., solid oxide, molten carbonate, alkaline, phosphoric acid, or solid polymer) used to effect ion transport during operation. Furthermore, fuel cell assemblies can be used in numerous environments (e.g., automotive, aerospace, industrial, residential) for numerous applications.

[0004] Proton exchange membrane (hereinafter "PEM") fuel cells convert the chemical energy of a fuel, such as hydrogen, and an oxidant, such as air, directly into electrical energy. The PEM is a sold polymer electrolyte that allows the passage of protons (i.e., H+ ions) from the "anode" side of the fuel cell to the "cathode" side of the fuel cell while inhibiting the passage of reactant fluids (e.g., hydrogen gas and air gas). A membrane electrode assembly (hereinafter "MEA") is positioned between two conductive plates, each of which has flow paths that direct fuel to the anode side and oxidant to the cathode side of the PEM.

[0005] The MEA may include a gas diffusion layer (GDL) and a seal surrounding the GDL. Bypass flow of reactants may flow in the flow direction around the active area of ​​the MEA between the GDL and the seal. Such bypass flow may result in a less efficient system because more reactants must flow to compensate for the flow around the active area, i.e., the bypass flow.

[0006] Two or more fuel cells can be connected together to increase the overall power output of the assembly. Typically, the cells are connected in series, where one side of a plate serves as the anode plate of one cell, and the other side of the plate is the cathode plate of the adjacent cell. These are commonly referred to as bipolar plates (hereinafter "BPP"). Alternatively, the anode plate of one cell is electrically connected to a separate cathode plate of the adjacent cell. Typically, these two plates are connected back-to-back and are often bonded together (e.g., by adhesive, welding, or polymer). The bonded pair is also commonly referred to as a bipolar plate, since the anode and cathode plates are electrically equivalent to positive and negative electrodes. A series of such connected multiple fuel cells is called a fuel cell stack or fuel cell system. The stack typically includes a means for directing fuel and oxidant into the flow field channels of the anode and cathode, respectively. The stack typically includes a means for directing a coolant fluid into the internal channels within the stack to absorb heat generated by the exothermic reaction of hydrogen and oxygen in the fuel cells. The stack typically includes means for exhausting excess fuel and oxidant gases as well as product water.

[0007] The stack also includes end plates, insulators, membrane electrode assemblies, gaskets, separator plates, electrical connectors, and collector plates, among other components, that are integrated together to form a working stack adapted to generate electricity. The various plates may abut and be interconnected to facilitate the performance of specific functions.

[0008] Thus, there is a need for improved fuel cell systems and improved fuel cell manufacturing methods that minimize inefficiencies. Summary of the Invention

[0009] In a first aspect, the present invention provides a method for use in the manufacture of a fuel cell stack, comprising assembling a membrane electrode assembly having a membrane between a first gas diffusion layer and a second gas diffusion layer. A bypass stopper is disposed in the space between the first gas diffusion layer of the membrane electrode assembly and the seal. The stopper is deformed on the seal but is prevented from deforming in the space such that the stopper inhibits bypass flow of reactants through the space between the seal and the gas diffusion layer. The membrane electrode assembly is disposed between a first fluid flow plate and a second fluid flow plate.

[0010] In a second aspect, the present invention provides a fuel cell system including a membrane electrode assembly having a membrane between a first gas diffusion layer and a second gas diffusion layer. A seal is disposed around the first gas diffusion layer, and a space is disposed between the first gas diffusion layer and the seal around the gas diffusion layer. A stopper is disposed in the space between the first gas diffusion layer and the seal such that the stopper inhibits bypass flow of reactants through the space from a first side of the first gas diffusion layer to a second side of the first gas diffusion layer in a direction of reactant flow during operation of the fuel cell. A first fluid flow plate and a second fluid flow plate are disposed on either side of the membrane electrode assembly. [Brief description of the drawings]

[0011] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the end of the specification. The foregoing and other features and advantages of this invention will be readily understood from the following detailed description of the preferred embodiment taken in conjunction with the accompanying drawings.

[0012] [Figure 1] 1 is a block diagram of a fuel cell system according to the present invention;

[0013] [Diagram 2] FIG. 2 is an exploded perspective view showing a portion of the fuel cell of the fuel cell system of FIG. 1.

[0014] [Diagram 3] 2 is a side view of a portion of a fuel cell of the fuel cell system of FIG. 1 during an assembly process.

[0015] [Figure 4] 2 is a side view of a portion of a fuel cell of the fuel cell system of FIG. 1 during an assembly process, showing the stopper occupying the space between the seal and the gas diffusion layer.

[0016] [Diagram 5] 2 is a side view of a portion of a fuel cell of the fuel cell system of FIG. 1 during an assembly process, showing the stopper occupying the space between the seal and the gas diffusion layer after the stopper has been compressed.

[0017] [Figure 6] 6 is an end view of a portion of a fuel cell of the fuel cell system of FIG. 5 during an assembly process, showing the stopper occupying the space between the seal and the gas diffusion layer.

[0018] [Figure 7] 2 is an end view of another example of a portion of a fuel cell of the fuel cell system of FIG. 1 during an assembly process, showing a number of stops occupying spaces between the seal and the gas diffusion layer. Detailed Description of the Invention

[0019] In accordance with the principles of the present invention, a fuel cell system and method are provided.

[0020] In the example shown in FIG. 1, the fuel cell system 10 is functionally capable of producing electricity with all its components and typically includes a fuel cell stack 20 and an energy storage device (30), referred to as an assembled or complete system. The fuel cells are supplied with fuel 13, e.g., hydrogen, through a fuel inlet 17. Excess fuel 18 is exhausted from the fuel cells through a purge valve 90 and may be diluted by a blower 40. In one example, the fuel cell stack 20 may have an open cathode configuration of a PEM fuel cell, where an oxidant and a coolant, e.g., air, may be combined and enter through an inlet air filter 10 coupled to an inlet 5 of the fuel cell 20. Excess coolant / oxidant and heat are exhausted from the fuel cell cathodes of the fuel cell stack 20 through an outlet 11 to a blower 40, which may exhaust the coolant / oxidant and / or excess fuel to waste exhaust 41, e.g., ambient atmosphere. Fuel and coolant / oxidant may be supplied by a fuel supply 7 and an oxidant supply 9 (e.g., air), respectively, and by other components of the rest of the plant, which may include compressors, pumps, valves, blowers, electrical connections and sensors.

[0021] Figure 2 shows an internal subassembly 100 of the fuel cell stack 20 of Figure 1, including a cathode end fluid flow plate 110 at its outer end 115 and an inboard flow plate seal 120. A membrane electrode assembly (MEA) 130 is located between seal 120 and a second flow plate seal 150. An anode flow plate 160 is located at a second end 165 of the subassembly 100.

[0022] The MEA 130 includes a membrane 140 between a cathode catalyst layer 125 and an anode catalyst layer 135. A cathode gas diffusion layer (GDL) 122 is disposed between the cathode catalyst layer 125 and a flow plate 110. An anode gas diffusion layer 148 is disposed between the anode catalyst layer 135 and a flow plate 160. Seals 120 and 150 may be received in the inner channels of flow plates 110 and 160, respectively.

[0023] 3 shows a cross-sectional side view of a portion of subassembly 100 having a peripheral space 210 between the outer surface of GDL 148 and the inner surface of seal 150, and a second peripheral space between GDL 122 and seal 120. Such spaces may be formed due to dimensional inaccuracies in the GDLs and seals during manufacture. The seal is shown separated from MEA 140 for ease of illustration, and its relative width perpendicular to its length would be smaller. The seal is shown in an uncompressed state.

[0024] 4 illustrates a cross-sectional side view of a portion of subassembly 100 with first reactant fluid bypass stop 200 and second reactant fluid stop 201 on either side of membrane 140 at periphery 131 of MEA 130, where first stop 200 and second stop 201 are in an undeformed or uncompressed state. The flow plate can have an inner surface that varies in a dimension perpendicular to its longitudinal dimension. For example, in an uncompressed state where the flow plate is not yet engaged, inner surface 109 of flow plate 110 can have a first distance 115 from membrane 140 and a second distance 117 that is closer from membrane 140. Similarly, inner surface 161 of flow plate 160 can have an inner surface that varies in distance from membrane 140.

[0025] 5 illustrates subassembly 100 as shown in FIG. 4 after a force has been applied to stopper 200 and stopper 201 by application of a force to flow plate 160 and / or flow plate 110. The force can be applied in a direction substantially perpendicular or nearly perpendicular to the longitudinal dimension of subassembly 100 and can compress the stopper (i.e., first stopper 200 and second stopper 201) except for the portion of the stopper that is located in (e.g., above and / or below) the space (e.g., space 210 and / or space 220) between the GDL (e.g., GDL 148 and / or GDL 122) and the seal (seal 150 and / or seal 120). For example, the seal can be a gasket having an inner surface that circumscribes the periphery of MEA 130 and bounds a cavity that receives MEA 130. In another example, such forces may be applied directly to the block 200, or to the block 200 and MEA 130, for example during the manufacturing process.

[0026] After a force is applied to the stopper directly or via a flow plate that receives such force, a portion of each stopper may be compressed and a portion of each stopper may remain uncompressed. For example, as shown in FIG. 5, the first longitudinal portion 205 of stopper 200 and the second longitudinal portion 207 of stopper 201 may remain uncompressed to inhibit the flow of reactants through spaces 210 and 220 during operation of the fuel cell. The third longitudinal portion 206 of stopper 200 and the fourth longitudinal portion 208 of stopper 201 may be compressed by the above-mentioned forces. For example, the compressed portions (e.g., third portion 206 and fourth portion 208) may remain compressed due to a force that holds them in a compressed state after the initial compression (e.g., in the case of elastically deformable stoppers), or the portions may remain compressed due to their plastic deformation.

[0027] The force may be applied directly to the stopper such that a portion of the stopper (e.g., first longitudinal portion 205 and second longitudinal portion 207) located in the space (e.g., space 210 and space 220) remains uncompressed, or the inner surface of the flow plate (e.g., inner surface 109 and inner surface 161) may be configured (e.g., shaped and sized) such that when a force is applied thereto, the inner surface does not exert a force longitudinally (i.e., with respect to the longitudinal dimension of the assembly) on the stopper located in the space (e.g., space 210 and space 220), thereby preventing first longitudinal portion 205 and second longitudinal portion 207 from being compressed.

[0028] The stoppers (e.g. stoppers 200 and 201) may remain outside the spaces (e.g. spaces 210 and 220) in the direction of reactant flow or may extend into the spaces while simultaneously inhibiting or preventing reactants from flowing into the spaces. The uncompressed regions of the stoppers (e.g. first longitudinal portion 205 and second longitudinal portion 207) may have the same thickness as the longitudinally adjacent GDL (approximately perpendicular to the longitudinal dimension of subassembly 100) and may inhibit reactant flow from the first side of the GDL to the opposite side around the active area of ​​the MEA.

[0029] It is contemplated that the stopper (e.g. stopper 200 or stopper 201) may be non-porous and formed from an elastically deformable material, such as a foam (e.g. open-cell ethylene propylene diene monomer (EPDM) or open-cell silicone foam) or a plastically deformable material, such as an uncured elastomer, such as a clay material or an RTV elastomer. For example, stopper 200 may be formed from such an elastically deformable foam material and extend longitudinally over and over space 210 and past the space onto a portion of the seal (e.g. seal 150). As discussed above, a portion of the stopper (e.g. first longitudinal portion 205) at the space (e.g. space 210) may remain uncompressed and a portion in contact with the seal (e.g. third longitudinal portion 206) may be compressed in response to an applied force. The compressed portions (e.g., longitudinal portions 206) can be formed from materials that remain compressed while being held in compression by a force, are easily compressed (e.g., less than 1 pound per linear inch), and have minimal or negligible thickness (e.g., less than 0.003 inches) perpendicular to the longitudinal dimension of subassembly 100. In one example, the stoppers (e.g., stoppers 200 and 201) can be applied in beads that are uncured (e.g., RTV elastomer) or easily compressible (e.g., foam) and then the fuel cell stack (e.g., system 10) is constructed. When the stack components are compressed during the assembly process, the elastomer (e.g., RTV) and foam can be compressed and occupy any voids remaining in the areas where they were applied. In other words, the bypass stopper does not affect the original components (e.g., MEA 130) because it is relatively easy to compress (e.g., less than 1 pound per linear inch is required for such compression) and the voids that such a stopper fills are voids that would normally occur in the assembly, i.e., would occur in the absence of the stopper. The MEA 130 described above can be formed by a process that includes lamination of several sheet-like components (e.g., membrane 140, catalyst 125, catalyst 135) that are compressed or bonded using heat and / or adhesives.The block may be laminated and compressed during this process or as an additional step at the end of the MEA assembly process.

[0030] It is also contemplated that the stopper (e.g., stopper 200 or stopper 201) is formed from a plastically deformable material that deforms similarly to an elastically deformable type of material, but maintains its deformation when the applied force is removed. The seal 120 and the seal 150 can be formed from a different material than the stopper (e.g., stopper 200 and / or stopper 201). Alternatively, it is contemplated that the seal and stopper are formed separately but from the same material. For example, the stopper (e.g., stopper 200 or stopper 201) can be formed from a foam of an elastically deformable type of material (e.g., open-cell ethylene propylene diene monomer (EPDM) or open-cell silicone), from a room temperature curing material of a plastically deformable type of material, or the stopper can be formed from a clay. The stopper is easily compressible (e.g., less than 1 pound per linear inch) so that high pressure is not required during the compression process so that such forces do not deform or distort the fuel cell flow plate.

[0031] In one example, the seals (e.g., seal 150 and seal 120) may be formed of an elastomer that is applied by machine (e.g., a PVA brand device) with a robotic applicator. Once applied, such elastomers may be difficult or impossible to remove from the flow plate, making it difficult to reuse such flow plates at the end of their life or if the fuel cell is otherwise decommissioned. The seals may also be molded fluoropolymer elastomers or other types of room temperature vulcanizing (RTV) compounds. Machines may also be utilized to apply stops formed of fluoropolymer elastomers. As discussed above with respect to seals, such stops may be difficult or impossible to remove from the flow plate or MEA, such that the components to which such materials are applied must be discarded and not reused during a rebuild (e.g., when the fuel cell stack is disassembled, cleaned, old parts replaced, and rebuilt using reusable components such as fluid flow plates).

[0032] In another example, the stopper may be formed of a metal portion of a flow plate, such as that described above, that extends from the edge of a standard flow plate and is deformable in response to a force perpendicular to the longitudinal dimension of the flow plate, for example extending over the above-mentioned spaces (e.g., spaces 210 and 220) to inhibit the inflow of reactants. Such deformation of the stopper extending from the flow plate may be plastic deformation. As described above, the stopper (e.g., stopper 200 and stopper 201) may be positioned, compressed, and stacked or otherwise held in place in a particular desired location during assembly of the MEA and fuel cell stack. Such plastically deformed stoppers may need to be replaced during fuel cell rebuilds. If it is desired to rebuild a fuel cell having a stopper formed of foam, such foam stoppers may be recovered and reused in the regenerated fuel cell, or new foam stoppers may be utilized.

[0033] The above-mentioned stoppers (e.g. stopper 200 and stopper 201) are omitted from FIG. 2 for clarity, but in a complete subassembly, they may be present continuously around the GDL (e.g. GDL 148 or GDL 122) as shown in FIG. 6, or may be present in discrete, specific portions as shown in FIG. 7. FIG. 6 is an end view of subassembly 100 with GDL 148 surrounded by stopper 200 surrounded by seal 150. In another example shown in FIG. 7, multiple stoppers (e.g. multiple instances of stopper 200) may be placed at various discrete locations around GDL 148, but do not continuously surround the GDL. Such an arrangement can be used when there are spaces between the GDL and the seal, similar to spaces 210 and 220 described above, but located at various locations around the GDL and do not continuously surround the GDL.

[0034] As discussed above, subassembly 100 may include GDLs (e.g., GDLs 122 and 148) adjacent to a seal (e.g., seal 120 or seal 150). Spaces (e.g., space 210, space 220) may exist in the surrounding areas during assembly of these components due to inaccuracies in manufacturing these components. The use of stops (e.g., stop 200 and stop 201) allows for less strict dimensional tolerances when forming the GDLs and seals because the stops can be used to prevent bypass flow of reactants that would reduce the efficiency of the fuel cell by restricting the flow of reactants through such spaces.

[0035] The load may be any type of stationary or mobile load device, such as an industrial electric vehicle or a forklift truck. The fuel cell (e.g., fuel cell system 20) may be any type of fuel cell, such as a proton exchange membrane fuel cell, a solid oxide fuel cell, or any other fuel cell that would be known to one skilled in the art. The energy storage device may be any type of battery or other energy storage method, such as a lithium ion battery, a lead acid battery, a compressed air energy storage device, a water storage device, a capacitor, an ultracapacitor, or any other device for energy storage.

[0036] The terminology used herein is merely for the purpose of describing particular embodiments and is not intended to limit the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It is further understood that the terms "comprise" (and any form of such terms, e.g., "comprises" and "comprising"), "have" (and any form of such terms, e.g., "has" and "having"), "include" (and any form of such terms, e.g., "includes" and "including"), and "contain" (and any form of such terms, e.g., "contains" and "containing") are open-ended linking verbs. As a result, a method or device that "includes," "has," "comprises," or "contains" one or more steps or elements possesses, but is not limited to possessing only, those one or more steps or elements. Similarly, a method step or device element that "includes," "has," "comprises," or "contains" one or more features possesses, but is not limited to possessing only, those one or more features. Furthermore, a device or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways not recited.

[0037] To promote an understanding of the principles of the invention, reference will be made herein to embodiments of the invention and specific language will be used to describe the embodiments of the invention, but it will be understood that no limitation of the scope of the invention is intended thereby, and that any changes and further modifications in the described embodiments, and any further applications of the principles of the invention as illustrated in the embodiments, as would normally occur to one skilled in the art to which the invention pertains, are contemplated and protected.

[0038] Although preferred embodiments have been described in detail herein, it will be apparent to those skilled in the art that various modifications, additions, substitutions, and the like, can be made therein without departing from the spirit of the invention, and therefore are deemed to be within the scope of the invention as defined in the appended claims.

Claims

1. A method of use in manufacturing a fuel cell stack: assembling a membrane electrode assembly so as to have a membrane between a first gas diffusion layer and a second gas diffusion layer; installing a bypass stopper in a space between the first gas diffusion layer of the membrane electrode assembly and the seal; deforming the stopper on the seal and ensuring that the stopper in the space does not deform, such that during operation of the fuel cell, the stopper suppresses a bypass flow of reactants passing through the space from a first side surface of the first gas diffusion layer to a second side surface of the first gas diffusion layer in the direction in which the reactants flow; and installing the membrane electrode assembly between a first fluid flow plate and a second fluid flow plate.

2. The method according to claim 1, wherein the space and the stopper are located outside the periphery of the gas diffusion layer and inside the periphery of the seal.

3. The method according to claim 1, wherein deforming the stopper includes compressing the stopper by applying a force to the stopper in a direction substantially perpendicular to the longitudinal dimension of the membrane electrode assembly.

4. The method according to claim 1, wherein deforming the stopper includes applying a force to the stopper by applying a force to a first flow plate in contact with the stopper in a direction substantially perpendicular to the longitudinal dimension of the membrane electrode assembly, thereby compressing the stopper.

5. The method according to claim 1, wherein the stopper has a width dimension in a direction perpendicular to the longitudinal dimension of the membrane electrode assembly, which is substantially equal to the width dimension of the gas diffusion layer in a direction perpendicular to the longitudinal dimension of the membrane electrode assembly.

6. The method according to claim 1, wherein the stopper includes a first stopper, and further includes a second stopper installed in a second space outside the periphery of the second gas diffusion layer on the opposite side of the membrane with respect to the seal and the gas diffusion layer and inside the periphery of the second seal.

7. The method according to claim 1, wherein deforming the stopper includes elastically deforming the stopper by compressing the stopper by applying a force to the stopper in a direction substantially perpendicular to the longitudinal dimension of the membrane electrode assembly.

8. The method according to claim 1, wherein deforming the stopper includes plastically deforming the stopper by compressing the stopper by applying a force to the stopper in a direction substantially perpendicular to the longitudinal dimension of the membrane electrode assembly.

9. The method according to claim 1, wherein the stopper is non-porous and elastically deformable.

10. The method according to claim 1, further comprising laminating a membrane electrode assembly, a stopper, and a seal to maintain the stopper on the seal.

11. Installing the membrane electrode assembly between a first fluid flow plate and a second fluid flow plate includes that the inner surface of the fluid flow plate is configured such that the stopper in the space is not deformed and the stopper on the seal is maintained in a deformed state, the method according to claim 1.

12. A membrane electrode assembly having a membrane between a first gas diffusion layer and a second gas diffusion layer; A seal around the first gas diffusion layer; A space between the first gas diffusion layer and the seal around the gas diffusion layer; A stopper installed in the space between the first gas diffusion layer and the seal, the stopper being configured to suppress a bypass flow of reactants through the space from a first side surface of the first gas diffusion layer to a second side surface of the first gas diffusion layer in a direction in which reactants flow during operation of the fuel cell; and A first fluid flow plate and a second fluid flow plate installed sandwiching the membrane electrode assembly A fuel cell system comprising.

13. The fuel cell system according to claim 12, wherein the stopper includes a non-deformed portion at the location of the space and a deformed portion at the location of the seal.

14. The inner surface of the fluid flow plate is configured such that the stopper in the space is not deformed and the stopper on the seal is maintained in a deformed state, the fuel cell system according to claim 12.

15. The membrane electrode assembly, the stopper, and the seal maintain the stopper on the seal in a deformed state, the fuel cell system according to claim 12.

16. The stopper is non-porous and elastically deformable, the fuel cell system according to claim 12.

17. The stopper has a width dimension in a direction perpendicular to the longitudinal dimension of the membrane electrode assembly, which is substantially equal to the width dimension of the gas diffusion layer in a direction perpendicular to the longitudinal dimension of the membrane electrode assembly, the system according to claim 12.

18. The stopper includes a first stopper and further includes a second stopper installed in a second space outside the periphery of the second gas diffusion layer and inside the periphery of the second seal on the opposite side of the membrane with respect to the seal and the gas diffusion layer, the system according to claim 12.

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