Electrochemical cell with improved fluid flow design

Abstract

An electrochemical cell stack having a plurality of electrochemical cells stacked along a longitudinal axis. The electrochemical cell includes a membrane electrode assembly having an anode plate and a cathode plate, the membrane electrode assembly being interposed between the anode plate and the cathode plate. The electrochemical cell further includes an anode plate and a cathode plate, the membrane electrode assembly being interposed between the anode plate and the cathode plate, the anode plate defining a plurality of channels forming an anode flow field facing the anode catalyst layer. The electrochemical cell further includes a cathode flow field disposed between the cathode plate and the cathode catalyst layer, the cathode flow field including a porous structure. The electrochemical cell further includes an anode plate and a cathode plate, the membrane electrode assembly being interposed between the anode plate and the cathode plate, the anode plate defining a plurality of channels forming an anode flow field facing the anode catalyst layer. The electrochemical cell further includes a cathode flow field disposed between the cathode plate and the cathode catalyst layer, the cathode flow field including a porous structure.

Description

[Technical field]

[0001]

[0001] This application claims the benefit of U.S. Provisional Application No. 62 / 618,221, filed January 17, 2018, which is incorporated by reference in its entirety.

[0002] FIELD OF THE DISCLOSURE

[0002] This disclosure is directed to electrochemical cells, and more particularly, to electrochemical cells with improved fluid flow designs. [Background technology]

[0003]

[0003] Electrochemical cells, commonly classified as fuel cells or electrolysis cells, are devices used to generate electric current from a chemical reaction or to induce a chemical reaction using the flow of electric current. For example, fuel cells convert the chemical energy of a fuel (e.g., hydrogen, natural gas, methanol, gasoline, etc.) and an oxidant (air or oxygen) into electricity and the waste products of heat and water. A basic fuel cell includes a negatively charged anode, a positively charged cathode, and an ionically conductive material called an electrolyte.

[0004]

[0004] Different fuel cell technologies utilize different electrolyte materials. Proton exchange membrane (PEM) fuel cells, for example, utilize a polymeric ion conducting membrane as the electrolyte. In a hydrogen PEM fuel cell, hydrogen atoms are electrochemically split into electrons and protons (hydrogen ions) at the anode. The electrons then flow through a circuit to the cathode, generating electricity, while the protons diffuse through the electrolyte membrane to the cathode. At the cathode, the hydrogen protons combine with the electrons and oxygen (supplied to the cathode) to produce water and heat.

[0005]

[0005] An electrolytic cell represents a fuel cell operated in reverse. A basic electrolytic cell functions as a hydrogen generator by splitting water into hydrogen and oxygen gases when an external electrical potential is applied. The basic technology of a hydrogen fuel cell or electrolytic cell can be applied to electrochemical hydrogen operations such as electrochemical hydrogen compression, purification, or expansion. Electrochemical hydrogen operations have emerged as a viable alternative to the mechanical systems traditionally used for hydrogen management. The successful commercialization of hydrogen as an energy carrier and the long-term sustainability of a "hydrogen economy" will depend primarily on the efficiency and cost-effectiveness of fuel cells, electrolytic cells, and other hydrogen operation / management systems.

[0006] In operation, a single fuel cell can typically generate about 1 volt. To obtain a desired amount of power, individual fuel cells are combined to form a fuel cell stack, where the fuel cells are stacked together in sequence. Each fuel cell may include a cathode, an electrolyte membrane, and an anode. The cathode / membrane / anode assembly is typically a component of a "membrane electrode assembly" or "MEA" supported on both sides by bipolar plates. Reactant gases, i.e., fuel (e.g., hydrogen) and oxidant (e.g., air or oxygen), are supplied to the electrodes of the MEA through flow fields. In addition to providing mechanical support, the bipolar plates (also known as flow field plates or separator plates) physically separate the individual cells in the stack while electrically connecting them. Typically, a fuel cell stack includes manifolds and inlet ports for directing the fuel and oxidant to the anode and cathode flow fields, respectively. The fuel cell stack further includes an exhaust manifold and an outlet port for displacing excess fuel and oxidant. The fuel cell stack may further include a manifold for circulating a coolant fluid to help dissipate heat generated by the fuel cell stack.

[0007]

[0007] In order to maximize the active area of ​​the MEA utilized in a fuel cell, it is desirable to have a thorough and even distribution of fuel and oxidant throughout the flow field, which improves overall performance. However, prior art fuel cell designs have struggled to achieve a uniform and thorough distribution. In addition, it is desirable not to create excessive pressure drop along the fuel and oxidant flow paths, which could otherwise consume a portion of the electrical energy generated by the fuel cell stack and reduce the overall efficiency of the fuel cell stack. Thus, there is a continuing challenge to improve fuel cell flow designs.

[0008]

[0008] Another approach to improving the overall performance and power density of a fuel cell stack may be to reduce the pitch (i.e., spacing) between adjacent cells of the fuel cell stack and / or the cell thickness. The cell thickness may be reduced, for example, by reducing the thickness of the flow field of each individual fuel cell. However, this may be difficult to achieve without creating excessive pressure drops along the fuel and oxidant flow paths due to the reduction in flow paths caused by compression of the fuel cell stack, which may increase the load on the fuel cell stack. Summary of the Invention [Problem to be solved by the invention]

[0009]

[0009] In view of the above-mentioned circumstances, the present disclosure is directed to fuel cell and fuel cell stack designs having improved flow designs, as well as improved performance and power density. [Means for solving the problem]

[0010]

[0010] In one aspect, the disclosure is directed to an electrochemical cell stack having a plurality of electrochemical cells stacked along a longitudinal axis. The electrochemical cells may each include a membrane electrode assembly including a cathode catalyst layer, an anode catalyst layer, and a polymer membrane interposed between the cathode catalyst layer and the anode catalyst layer. The electrochemical cells may each further include an anode plate and a cathode plate, between which the membrane electrode assembly is interposed, the anode plate defining a plurality of channels forming an anode flow field facing the anode catalyst layer. The electrochemical cells may each further include a cathode flow field disposed between the cathode plate and the cathode catalyst layer, the cathode flow field including a porous structure. In some embodiments, each electrochemical cell may further comprise a first manifold section including an anode feed manifold, a cathode exhaust manifold, and a coolant exhaust manifold, and a second manifold section including an anode exhaust manifold, a cathode feed manifold, and a coolant feed manifold. The coolant exhaust manifold may be disposed between the anode feed manifold and the cathode exhaust manifold, and the coolant feed manifold may be disposed between the anode exhaust manifold and the cathode feed manifold. In some embodiments, the cathode exhaust manifold may be on one side of the coolant exhaust manifold and the anode feed manifold may be on the opposite side of the coolant exhaust manifold, while the cathode feed manifold is to the right of the coolant feed manifold and the anode exhaust manifold is to the left of the coolant feed manifold. In some embodiments, fluid flow between the anode feed manifold and the anode exhaust manifold through the anode flow field is cross-current and counter-current to fluid flow between the cathode exhaust manifold and the cathode feed manifold through the cathode flow field.In some embodiments, each electrochemical cell may further comprise a first manifold section including a first anode feed manifold, a second anode feed manifold, a first cathode exhaust manifold, a second cathode exhaust manifold, a first coolant exhaust manifold, and a second coolant exhaust manifold, and a second manifold section including a first anode exhaust manifold, a second anode feed manifold, a first cathode feed manifold, a second cathode feed manifold, a first coolant feed manifold, and a second coolant feed manifold. The first coolant exhaust manifold may be disposed between the first anode feed manifold and the first cathode exhaust manifold, and the second coolant exhaust manifold may be disposed between the second anode feed manifold and the second cathode exhaust manifold. The first coolant feed manifold may be disposed between the first anode exhaust manifold and the first cathode feed manifold, and the second coolant feed manifold may be disposed between the second anode exhaust manifold and the second cathode feed manifold. In some embodiments, the fluid flow between the first and second anode feed manifolds and the first and second anode exhaust manifolds through the anode flow field may be cross-current and countercurrent to the fluid flow between the first and second cathode exhaust manifolds and the first and second cathode feed manifolds through the cathode flow field. In some embodiments, the right and left halves of the anode and cathode plates may be laid out as a mirror image across a bisecting line. In some embodiments, the area of ​​the cathode exhaust manifold may be larger than the area of ​​the coolant exhaust manifold, and the area of ​​the coolant manifold may be larger than the area of ​​the anode feed manifold. In some embodiments, each electrochemical cell may further comprise a gas diffusion layer disposed adjacent each side of the membrane electrode assembly, hi some embodiments, the porous structure comprises at least nickel and chromium.The porous structure may include a nickel concentration of 60% to 80% by weight and a chromium concentration of 20% to 40% by weight, and at least one surface of the porous structure may include a chromium concentration of about 3% to about 50% by weight. The porous structure may include a chromium concentration of about 3% to about 6%, a tin concentration of about 10% to about 20%, and a nickel concentration of about 74% to about 87%.

[0011]

[0011] In another aspect, the disclosure is directed to an electrochemical cell stack having a plurality of electrochemical cells stacked along a longitudinal axis. The electrochemical cells may each include a membrane electrode assembly including a cathode catalyst layer, an anode catalyst layer, and a polymer membrane interposed between the cathode catalyst layer and the anode catalyst layer. The electrochemical cells may each further include an anode plate and a cathode plate, between which the membrane electrode assembly is interposed, the anode plate defining a plurality of channels forming an anode flow field facing the anode catalyst layer. The electrochemical cells may each further include a cathode flow field disposed between the cathode plate and the cathode catalyst layer, the cathode flow field including a porous structure, the cathode plate including a pair of cathode flow field boundaries along the sides of the porous structure. In some embodiments, the pair of cathode flow field boundaries may extend from the cathode plate to the membrane electrode assembly and be configured to prevent oxidant from flowing around the cathode flow field. In some embodiments, the distance between the cathode flow field boundaries may be approximately equal to the width of the cathode flow field. In some embodiments, the cathode flow field boundaries may protrude from the cathode plate at a depth equal to the depth of the cathode flow field. In some embodiments, the cathode flow field boundaries may be generally rectangular in shape. In some embodiments, each electrochemical cell may further comprise a gas diffusion layer disposed adjacent each side of the membrane electrode assembly. In some embodiments, the porous structure comprises at least nickel and chromium. The porous structure comprises a nickel concentration of 60% to 80% by weight and a chromium concentration of 20% to 40% by weight, and at least one surface of the porous structure comprises a chromium concentration of about 3% to about 50% by weight. The porous structure includes a chromium concentration of about 3% to about 6%, a tin concentration of about 10% to about 20%, and a nickel concentration of about 74% to about 87%. In some embodiments, a first surface of the porous structure has a higher chromium concentration than an opposing second surface. The first surface can have a chromium concentration ranging from about 3% to about 50% by weight, and the second surface has a chromium concentration of less than about 3% by weight.A first surface of the porous structure can face the membrane electrode assembly. In some embodiments, the cathode plate of each cell can be formed from uncoated stainless steel.

[0012]

[0012] In another aspect, the present disclosure is directed to an electrochemical cell having a membrane electrode assembly including a cathode catalyst layer, an anode catalyst layer, and a polymer membrane interposed between the cathode catalyst layer and the anode catalyst layer. The electrochemical cell may further include an anode plate and a cathode plate, between which the membrane electrode assembly is interposed, the anode plate defining a plurality of channels forming an anode flow field facing the anode catalyst layer. The electrochemical cell may further include a cathode flow field disposed between the cathode plate and the cathode catalyst layer, the cathode flow field including a porous structure.

[0013]

[0013] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure, as claimed.

[0014]

[0014] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a side schematic view of multiple electrochemical cells (eg, fuel cells) stacked together, according to an exemplary embodiment. [Diagram 2]

[0016] 2 is a partially exploded side perspective view of a portion of the adjacent fuel cells of FIG. 1 according to an exemplary embodiment. [Diagram 3]

[0017] 3 is a side perspective view of FIG. 2 illustrating a fuel flow path through the fuel cell according to an exemplary embodiment. [Figure 4]

[0018] 3 is a side perspective view of FIG. 2 illustrating an oxidant flow path through a fuel cell according to an exemplary embodiment. [Diagram 5]

[0019] 3 is a side perspective view of FIG. 2 illustrating coolant fluid flow paths through adjacent fuel cells according to an exemplary embodiment. [Figure 6]

[0020] FIG. 3 is a front view of the anode plate of FIG. 2 according to an exemplary embodiment. [Figure 7A]

[0021] FIG. 7A is an enlarged view of a portion of FIG. [Figure 7B]

[0022] FIG. 7B is a cross-sectional schematic diagram of a portion of a fuel cell according to an exemplary embodiment. [Figure 8A]

[0023] FIG. 8A is an enlarged view of a portion of FIG. [Figure 8B]

[0024] FIG. 8B is a cross-sectional schematic view of a portion of FIG. 8A. [Figure 9]

[0025] 1 is a cross-sectional schematic diagram of a fuel cell according to an exemplary embodiment. [Figure 10]

[0026] 3 is a front view of the cathode plate of FIG. 2 according to an exemplary embodiment. [Figure 11A]

[0027] 3 is a front view of the cathode flow field of FIG. 2 according to an exemplary embodiment. [Figure 11B]

[0028] FIG. 13 is a front view of another embodiment of a cathode flow field in accordance with an exemplary embodiment; [Figure 11C]

[0029] FIG. 13 is a front view of another embodiment of a cathode flow field in accordance with an exemplary embodiment; [Figure 11D]

[0030] FIG. 11D is a cross-sectional view taken along section AA of FIG. 11C in accordance with an exemplary embodiment. [Figure 11E]

[0031] FIG. 11D is a cross-sectional view along section BB of FIG. 11C in accordance with an exemplary embodiment. [Figure 11F]

[0032] FIG. 13 is a front view of another embodiment of a cathode flow field in accordance with an exemplary embodiment; [Figure 12]

[0033] FIG. 2 is a side perspective view of a portion of adjacent fuel cells according to an exemplary embodiment. [Figure 13]

[0034] FIG. 13 is a front view of the anode plate of FIG. 12 according to an exemplary embodiment. [Figure 14]

[0035] FIG. 13 is a front view of the cathode plate of FIG. 12 according to an exemplary embodiment. [Figure 15]

[0036] FIG. 13 is a front view of the cathode flow field of FIG. 12 according to an exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016]

[0037] Reference will now be made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Although described in the context of electrochemical cells, and in particular fuel cells that use hydrogen, oxygen, and water, it will be understood that the devices and methods of the present disclosure may be used with various types of fuel cells and electrochemical cells, including, but not limited to, electrolysis cells, hydrogen purifiers, hydrogen expanders, and hydrogen compressors.

[0017]

[0038] Throughout this specification, the terms "generally parallel" and "generally perpendicular" may be used to describe an arrangement of one or more components with respect to an axis, plane, or other component. The degree of deviation from parallel and perpendicular that may be tolerated when describing an arrangement as "generally parallel" or "generally perpendicular" may vary. Permitted deviations may be less than about 20 degrees, such as, for example, less than about 10 degrees deviation, less than about 5 degrees deviation, and less than about 3 degrees deviation, less than about 2 degrees deviation, and less than about 1 degree deviation.

[0018]

[0039] FIG. 1 is a side schematic side view of a plurality of electrochemical cells, e.g., fuel cells 10, stacked together along a longitudinal axis 5 to form at least a portion of a fuel cell stack 11, according to an exemplary embodiment. The fuel cell 10 can include a cathode catalyst layer 12, which may be collectively referred to as a membrane electrode assembly (MEA) 18, and further referred to herein as a cathode, an anode catalyst layer 14, which may be further referred to herein as an anode, and a proton exchange membrane (PEM) 16 interposed between the cathode catalyst layer 12 and the anode catalyst layer 14. The PEM 16 can include a pure polymer membrane or a composite membrane with other materials, e.g., silica, heteropolyacid, layered metal phosphates, phosphates, and zirconium phosphates can be embedded within a polymer matrix. The PEM 16 can be permeable to protons while not conducting electrons. The cathode catalyst layer 12 and the anode catalyst layer 14 can include porous carbon electrodes containing catalysts. Catalytic materials such as platinum, platinum-cobalt alloys, non-PGMs can enhance the reaction of oxygen and fuel. In some embodiments, the cathode catalyst layer 12 and the anode catalyst layer 14 can have an average pore size of about 1 μm.

[0019]

[0040] The fuel cell 10 can include two bipolar plates, e.g., a cathode plate 20 and an anode plate 22. The cathode plate 20 can be disposed adjacent to the cathode catalyst layer 12, and the anode plate 22 can be disposed adjacent to the anode catalyst layer 14. The MEA 18 can be interposed between and enclosed by the cathode plate 20 and the anode plate 22. A cathode compartment 19 can be formed between the MEA 18 and the cathode plate 20, and an anode compartment 21 can be formed between the MEA 18 and the anode plate 22. The cathode plate 20 and the anode plate 22 can act as current collectors, provide access flow paths for fuel and oxidant to the respective electrode surfaces (e.g., the anode catalyst layer 14 and the cathode catalyst layer 12), and provide a flow path for the removal of water formed during operation of the fuel cell 10. The cathode plate 20 and the anode plate 22 may further define a flow passage for a coolant fluid (e.g., water, glycol, or a water-glycol mixture). For example, a coolant compartment 23 may be formed between the cathode plate 20 and the anode plate 22 of adjacent fuel cells 10, the coolant compartment 23 being configured to circulate the coolant fluid between the adjacent fuel cells 10. Heat generated by the fuel cells 10 may be transferred to the coolant fluid and transported elsewhere by the circulation of the coolant fluid. The cathode plate 20 and the anode plate 22 may be made of, for example, aluminum, steel, stainless steel, titanium, copper, Ni-Cr alloy, graphite, or any other suitable electrically conductive material.

[0020]

[0041] In some embodiments, for example, as illustrated in FIG. 1 , the fuel cell 10 may further include electrically conductive gas diffusion layers (e.g., cathode gas diffusion layer 24 and anode gas diffusion layer 26) within the fuel cell 10 on each side of the MEA 18. The gas diffusion layers 24, 26 act as diffusion media to allow gas and liquid transport within the cell, provide electrical conduction between the cathode plate 20, anode plate 22, and the MEA 18, aid in the removal of heat and process water from the fuel cell 10, and in some cases may provide mechanical support for the PEM 16. The gas diffusion layers 24, 26 may include woven or non-woven carbon cloth with the cathode catalyst layer 12 and anode catalyst layer 14 coated on the side facing the PEM 16. In some embodiments, the cathode catalyst layer 12 and anode catalyst layer 14 may be coated onto either the adjacent GDL 24, 26 or the PEM 16. In some embodiments, the gas diffusion layers 24, 26 may have an average pore size of about 10 μm.

[0021]

[0042] The fuel cell 10 may further include flow fields disposed on each side of the MEA 18. For example, the fuel cell 10 may include a cathode flow field 28, which may include a porous structure disposed between the cathode plate 20 and the GDL 24, and an anode flow field 30, which may be formed by the anode plate 22, as described further herein. The flow fields may be configured to allow the fuel and oxidant on each side of the MEA 18 to flow through and reach the MEA 18. These flow fields desirably aid in the uniform distribution of fuel and oxidant to the cathode and anode catalyst layers 12, 14 to achieve high performance of the fuel cell 10. The GDL 24 may provide mechanical protection for the cathode catalyst layer 12 from the cathode flow field 28.

[0022]

[0043] Although only one fuel cell 10 in FIG. 1 includes reference numbers for cathode catalyst layer 12, anode catalyst layer 14, proton exchange membrane 16, membrane electrode assembly (MEA) 18, cathode compartment 19, cathode plate 20, anode compartment 21, anode plate 22, coolant compartment 23, gas diffusion layer 24, gas diffusion layer 26, cathode flow field 28, and anode flow field 30, it should be understood that other fuel cells 10 in the stack 11 may include the same elements.

[0023]

[0044] The fuel cell stack 11 may further include multiple fluid manifolds 31A, 31B extending along a longitudinal axis 5 defined by the series of stacked cathode plates 20 and anode plates 22 of the fuel cells 10. The fluid manifolds 31A, 31B may be configured to feed fuel (e.g., hydrogen) and oxidant (e.g., oxygen) to the MEA 18 of each fuel cell 10 and exhaust reactant products (e.g., unreacted fuel, unreacted oxidant, and water) from the MEA 18 of each fuel cell. The fluid manifolds 31A, 31B may further be configured to feed and exhaust coolant fluid through the coolant compartment 23. The direction of flow through the fluid manifolds 31A, 31B, the cathode compartment 19, the anode compartment 21, and the coolant compartment 23 may vary. For example, in some embodiments, the flow through the manifolds and compartments may be co-current, while in other embodiments, one or more of the flow paths may be counter-current. For example, in some embodiments, the flow of fuel through the anode compartment 21 may be countercurrent to the flow of oxidant through the cathode compartment 19. The fluid manifolds 31A, 31B may be fluidly connected to the MEA 18 via passages and ports. Although certain manifolds, passages, and ports may be identified herein by "feed" or "exhaust," and "inlet" or "outlet," it should be understood that these names may be determined based on the direction of flow, and that the direction of flow may be switched. Changing the direction of flow may change these names.

[0024]

[0045] FIG. 2 shows a partially exploded side perspective view of a portion of adjacent fuel cells 10. For example, FIG. 2 shows the MEA 18, GDL 24, and anode plate 22 of one fuel cell 10, as well as the cathode plate 20, cathode flow field 28, MEA 18, and GDL 24 of an adjacent fuel cell 10. The anode compartment 21 may be formed between adjacent MEA 18 and anode plate 22. The coolant compartment 23 may be formed between adjacent anode plate 22 and cathode plate 20. The cathode compartment 19 may be formed between adjacent cathode plate 20 and MEA 18 and may contain the cathode flow field 28. As shown in FIG. 2, the fuel cell 10 may include fluid manifolds 31A, 31B, which may further be referred to as upper and lower fluid manifolds. The fluid manifolds 31A, 31B may extend along a longitudinal axis.

[0025]

[0046] Figures 3-5 illustrate the flow paths of fuel, oxidant, and cooling fluid through a fuel cell 10 according to one illustrative embodiment. However, it should be understood that for other embodiments, the direction of one or more of the flow paths may be switched, for example, by reversing the direction of flow. Figure 3 illustrates the flow path for fuel circulated through the anode side of the MEA 18 of the fuel cell 10, Figure 4 illustrates the flow path for oxidant circulated through the cathode side of the MEA 18 of the fuel cell 10, and Figure 5 illustrates the flow path for coolant fluid circulated between adjacent fuel cells 10.

[0026]

[0047] 3, the first fluid manifold 31A may include at least one anode feed manifold 32 that may fluidly connect and direct fuel through at least one anode inlet passage 34, through at least one anode inlet port 36, and into the anode compartment 21. Fuel (e.g., unreacted fuel) from the anode compartment 21 may be directed from the anode compartment 21 through at least one anode outlet port 38, through at least one anode outlet passage 40, and into at least one anode exhaust manifold 42. The anode inlet passage 34 and anode outlet passage 40 may be located between the anode plate 22 and the cathode plate 20 of adjacent fuel cells 10. The anode inlet passage 34 and anode outlet passage 40, and the periphery of the anode feed manifold 32 and anode exhaust manifold 42 may be sealed by a surface gasket 43, as illustrated in FIG. The surface gasket 43 may be made of a polymeric or elastomeric material such as silicone, Viton, Buna, polyethylene, polypropylene, or any other suitable sealing material. The cross-sectional shape of the surface gasket 43 may be rectangular, triangular, semicircular, multi-tooth (triangular), or parabolic. The shape may be determined by acceptable leak rates, operating pressures, tolerance arrangements, or other significant sealing design parameters. The surface gasket 43 may be applied by any known method, such as injection molding, compression molding, pick-and-place, robotic dispensing, and may be directly bonded through a molding process or with the aid of a pressure- or temperature-sensitive adhesive. Curing of the surface gasket 43 may be accomplished by known processes, such as heat curing, ultraviolet light curing, or moisture curing.

[0027]

[0048] 4, the second fluid manifold 31B may include at least one cathode feed manifold 44 that may fluidly connect and direct oxidant through at least one cathode inlet passage 46, through at least one cathode inlet port 48, and into the cathode compartment 19. The oxidant from the cathode compartment 19 may be directed from the cathode compartment 19 through at least one cathode outlet port 50, through at least one cathode outlet passage 52, and into at least one cathode exhaust manifold 54. The cathode inlet passage 46 and the cathode outlet passage 52 may be located between the anode plate 22 and the cathode plate 20 of an adjacent fuel cell 10. The periphery of the cathode inlet passage 46 and the cathode outlet passage 52, as well as the cathode feed manifold 44 and the cathode exhaust manifold 54, may be sealed by a surface gasket 43, as illustrated in FIG.

[0028]

[0049] 5, the second fluid manifold 31B may include at least one coolant feed manifold 56 that may fluidly connect and direct coolant fluid through at least one coolant inlet passage 58 to a coolant flow field 86 in the coolant compartment 23. Within the coolant compartment 23, the coolant fluid may flow between the anode plate 22 and the cathode plate 20 through a coolant flow field 86 comprised of a plurality of coolant channels defined by the anode plate 22, as will be further described herein. Heat generated by adjacent fuel cells 10 may be transferred to the coolant fluid and removed from the fuel cells 10 by circulation of the coolant fluid. The coolant fluid from the coolant compartment 23 may be directed through at least one coolant outlet passage 60 and into at least one coolant exhaust manifold 62. The coolant inlet passages 58 and coolant outlet passages 60 may be located between the anode plates 22 and cathode plates 20 of adjacent fuel cells 10. The coolant inlet passages 58 and coolant outlet passages 60, and the periphery of the coolant feed manifold 56 and coolant exhaust manifold 62, may be sealed by a surface gasket 43, as illustrated in FIG.

[0029]

[0050] Figure 6 is a front view of an anode plate 22, according to an exemplary embodiment. The side visible in Figure 6 is the side that faces the anode side of the MEA 18 (i.e., anode catalyst layer 14 and gas diffusion layer 26) and is configured to define one side of the anode compartment 21 (see, e.g., Figures 1 and 2). The anode plate 22 can include various sections. These sections can include, for example, first and second manifold sections 31A and 31B, distribution channel sections, e.g., first and second anode distribution channels 68 and 70, and anode flow field 30. 6, the anode plate 22 may include, in a first manifold section 31A, an anode feed manifold 32, a cathode exhaust manifold 54, and a coolant exhaust manifold 62, while the second manifold section 31B may include an anode exhaust manifold 42, a cathode feed manifold 44, and a coolant feed manifold 56. It should be understood that the designations of the inlets and outlets for each manifold may be switched, for example, by switching the respective flow directions of the fuel, oxidant, or coolant fluid flow through the fuel cell 10.

[0030]

[0051] The cross-sectional area of ​​each manifold may vary. For example, as shown in FIG. 6, the cathode feed and exhaust manifolds 44, 54 may have a larger cross-sectional area than the coolant feed and exhaust manifolds 56, 62, while the coolant feed and exhaust manifolds 56, 62 may have a larger cross-sectional area than the anode feed and exhaust manifolds 32, 42. The cross-sectional area of ​​each passage may be determined based on a variety of variables, including, for example, the number of cells, the current density at peak power operating conditions, the design stoichiometry of the reactants, the difference between the inlet and outlet coolant temperatures, the flow resistance of the individual cells, the size of the active area, the fluid pressure, and the fluid flow rate. The cross-sectional area of ​​one or more passages may be sized to minimize fluid pressure variations along the length of the electrochemical cell stack, such as during high fluid flow rates.

[0031]

[0052] The arrangement of the manifolds within the first manifold section 31A and the second manifold section 31B may also vary. As shown in FIG. 6, the arrangement of the manifolds may differ between the first manifold section 31A and the second manifold section 31B. In one illustrative example, as shown in FIG. 6, the coolant exhaust manifold 62 may be disposed between the anode feed manifold 32 and the cathode exhaust manifold 54, and the coolant feed manifold 56 may be disposed between the anode exhaust manifold 42 and the cathode feed manifold 44. In some embodiments, the cathode exhaust manifold 54 may be to the left of the coolant exhaust manifold 62 and the anode feed manifold 32 may be to the right of the coolant exhaust manifold 62, while the cathode feed manifold 44 may be to the right of the coolant feed manifold 56 and the anode exhaust manifold 42 may be to the left of the coolant feed manifold 56. Swapping the placement of the anode and cathode manifolds relative to the coolant manifold between the first manifold section 31A and the second manifold section 31B can be advantageous because it encourages diagonal cross counterflow flow, or "z-flow," rather than straight across flow. Diagonal cross counterflow flow can provide improved uniform distribution of fuel and oxidant within the anode compartment 21 and cathode compartment 19, which can improve fuel cell performance. Performance can be improved because diagonal cross counterflow flow can optimize the utilized active area. With a z-flow pattern, the stream path distance from inlet to outlet for one or more reactants can be substantially uniform, regardless of the flow path. This symmetry can result in fluids being distributed and flowing uniformly throughout the flow field. Uniform flow throughout the flow field 30 may result in more uniform and / or linear gradients in reactant composition and coolant temperature, which may result in a uniform and / or linear gradient in cell temperature.This may result in higher performance and / or lower discrepancy in performance between cells.

[0032]

[0053] The placement of the coolant manifolds 56, 62 in the center of the first and second fluid manifolds 31A, 31B may be advantageous because the central region of the coolant compartment is most likely to receive the greatest coolant fluid flow, which corresponds to the central region of the active area of ​​the fuel cell 10 where there may be a tendency for increased heat generation and / or higher operating temperatures. In other words, the region of the fuel cell 10 that will tend to operate at a higher temperature will correspond to the region that receives the greatest coolant fluid flow. In addition, the sides of the fuel cell 10 may be aided by ambient cooling, so it is advantageous to encourage coolant fluid flow through the central region of the coolant compartment 23 of each fuel cell.

[0033]

[0054] 6, disposed between the first and second manifold sections 31A, 31B and the anode flow field 30 are first and second anode distribution channels 68, 70. The first anode distribution channel 68 may be configured to distribute fuel provided from the anode feed manifold 32, via the anode inlet passage 34, through the anode inlet port 36, to the anode flow field 30. The second anode distribution channel 70 may be configured to collect fuel (e.g., unreacted fuel) from the anode flow field 30 and direct the fuel through the anode outlet port 38, to the anode exhaust manifold 42, via the anode outlet passage 40. The first anode distribution channel 68 and the second anode distribution channel 70 may be sandwiched between and defined by the MEA 18 and the anode plate 22. The periphery of the first anode distribution channel 68 and the second anode distribution channel 70 may be sealed by a surface gasket 43, as illustrated in Figure 6. In some embodiments, the width of the first anode distribution channel 68 and the width of the second anode distribution channel 70 may be generally equal to the width of the anode flow field 30.

[0034]

[0055] The first anode distribution channel 68 may be configured such that fuel supplied through the anode inlet port 36 may be distributed across the width of the first anode distribution channel 68 and directed to the anode flow field 30 through a plurality of openings 74. In some embodiments, each opening 74 may be configured as an orifice to create some back pressure on the fuel within the first anode distribution channel 68. The back pressure may aid in the distribution of the fuel within the first anode distribution channel 68, thus ensuring that the first anode distribution channel 68 is fully filled with fuel. In some embodiments, fully filling the first anode distribution channel 68 allows fuel to be delivered through all of the openings 74 to substantially all channels of the anode flow field 30. Overfilling the first anode distribution channel 68 may prevent or reduce the risk of shorting the fuel flow along the path of least resistance through the anode flow field 30, which may reduce the performance of the fuel cell 10 due to reduced active area utilization. In some embodiments, the orifice openings 74 may be sized to allow the minimum amount of back pressure required to ensure overfilling of the first anode distribution channel 68. As illustrated in FIG. 6, the second anode distribution channel 70 may be configured the same as the first anode distribution channel 68, with multiple orifice-shaped openings 74 fluidly connecting the channels of the anode flow field 30 and the second anode distribution channel 70. The openings 74 may have a smaller cross-sectional area than the corresponding channels in the anode flow field 30. The channels in the anode flow field 30 are shown as straight paths, but may also be wavy or zigzag paths. The channels in the anode flow field 30 have cross-sectional areas that are generally square, semicircular, parabolic, or any other suitable shape.

[0035]

[0056] Compression of the fuel cell 10 during bonding and the compressed state maintained during operation may compromise the flow path integrity in the distribution channels. For example, compression of the fuel cell 10 may cause the volume of the distribution channels to decrease, which may restrict the flow of fuel, oxidant, and coolant and increase the pressure drop through the fuel cell 10. To prevent or minimize contraction or collapse of the first anode distribution channel 68 and the second anode distribution channel 70 when the fuel cell 10 is compressed, the first anode distribution channel 68 and / or the second anode distribution channel 70 may include a plurality of support features 76 that extend throughout the distribution channels in some embodiments. The support features 76 may be formed as integral features of the anode plate 22. The support features 76 may be uniformly spaced throughout the first anode distribution channel 68 and the second anode distribution channel 70.

[0036]

[0057] In one illustrative embodiment, FIG. 7A shows an enlarged view of a portion of a plurality of dimple-shaped support features 76 that may be formed in the first anode distribution channel 68 and / or the second anode distribution channel 70. These dimple-shaped support features 76 may extend from the anode plate 22 in both directions along the longitudinal axis 5. For example, FIG. 7B shows a cross-sectional schematic of a dimple-shaped support feature 76 formed by the anode plate 22. The dimple-shaped support feature 76 may extend from the anode plate 22 in both directions to contact the cathode plate 20 on one side and the MEA 18 (e.g., a subgasket of the MEA 18) on the other side. As shown in FIG. 7B, between the anode plate 22 and the MEA 18 may be a space that forms the first anode distribution channel 68 or the second anode distribution channel 70 and allows for fuel flow. In other embodiments, other support features may be formed in other shapes besides dimples, including, for example, conical, hemispherical, cubical, and cylindrical shapes.

[0037]

[0058] As shown in FIG. 7B, on the opposite side of the anode plate 22, between the anode plate 22 and the cathode plate 20, there may be a space forming first and second coolant distribution channels 78, 80 that fluidly connect the coolant feed manifold 56, the coolant exhaust manifold 62 with the coolant flow field 86 contained by the coolant compartment 23. The first and second coolant distribution channels 78, 80 of the coolant compartment 23 may be configured similarly to the first and second anode distribution channels 68, 70. For example, the first and second coolant distribution channels 78, 80 may include a plurality of dimple-shaped support features 76 that are uniformly spaced throughout. The first and second coolant distribution channels 78, 80 may be configured to provide ample and uniform distribution to the coolant flow field 86 (see, e.g., FIG. 5). Additionally, in some embodiments, multiple orifice-shaped openings may fluidly connect the first and second coolant distribution channels 78, 80 with the coolant flow field 86 (see FIG. 5). These orifice-shaped openings may provide some back pressure to the coolant fluid within the first and / or second coolant distribution channels 78, 80 depending on the direction of flow, for example, to ensure uniform distribution and prevent or reduce the likelihood of short circuits along the path of least resistance.

[0038]

[0059] The number, distribution, and size of the support features 76 may be determined by taking into account various design considerations. For example, too many or too large support features 76 may result in excessive pressure drop in the distribution channels 68, 70, 78, 80, while too few or too small support features 76 may result in insufficient structural support and contraction of the distribution channels 68, 70, 78, 80 when under compression, which may further result in excessive pressure drop. According to an exemplary embodiment, the arrangement of the structural features is determined by the distance (D) between the support features 76. C ), and the thickness of the cathode plate 20 (t p ) can be expressed as a function of D C / t pThe ratio of D to D may be greater than about 3 but less than about 50. According to an exemplary embodiment, C may be about 1.5 mm, and t p can be about 0.1 mm, therefore, D C / t p The ratio may be about 15.

[0039]

[0060] Maintaining the integrity of the inlet and outlet port flow areas (e.g., preventing shrinkage) due to compression of the fuel cell during operation can be a challenge when gaskets are increasingly relied upon to create or maintain the flow areas. Shrinkage of the inlet and outlet ports can restrict the flow of reactants and reactant products and increase the pressure drop through the fuel cell. One or more anode inlet and outlet ports 36, 38 of the fuel cell 10 as described herein can be configured to prevent or avoid shrinkage due to compression.

[0040]

[0061] The anode inlet and outlet ports 36, 38 may be integrated into one or more support features 82. For example, as shown in FIGS. 8A and 8B , the anode inlet port 36 may be formed in a sidewall 84 of the support feature 82. The support feature 82 may extend from the anode plate 22 toward the MEA 18. As a result, the flow direction of the fuel may be redirected within the support feature 82 such that the flow direction through the anode inlet and outlet ports 36, 38 is generally parallel to the anode plate 22. In other words, this configuration may allow fuel through the anode inlet port 36 to be directed into the first anode distribution channel 68 in a direction generally parallel to, rather than perpendicular to, the anode plate 22. Similarly, this configuration may allow fuel through the anode outlet port 38 to be directed from the second anode distribution channel 70 in a direction generally parallel to, rather than perpendicular to, the anode plate 22.

[0041]

[0062] Such a configuration can prevent or avoid reduction in the flow path through the anode inlet and outlet ports 36, 38 because the support features 82 can be designed to withstand compression during operation, thus generally maintaining the cross-sectional area for flow. In comparison, prior art fuel cells often rely on gaskets to maintain clearance for flow, and under compression these gaskets compress, thereby reducing the available area available for fluid flow, which in turn restricts flow and thus causes increased pressure drop.

[0042]

[0063] The support features 82 may be of any suitable shape. For example, in one illustrative embodiment as shown in FIG. 8A, the support features 82 may be generally rectangular in shape with rounded edges. In other embodiments, the support features 82 may be circular, oval in shape, square in shape, etc. The support features 82 may each include one or more anode ports (e.g., anode inlet port 36 and anode outlet port 38). For example, in one illustrative embodiment as shown in FIG. 8A, the support features 82 may include five anode inlet ports 36 evenly spaced along the length of the support feature 82.

[0043]

[0064] The anode flow field 30 may be configured as a channel flow field facing and aligned with the active area of ​​the anode catalyst layer 14 on the anode side of the MEA 18. The anode flow field 30 may include multiple parallel channels extending between a first anode distribution channel 68 and a second anode distribution channel 70, as shown in FIG. 6. FIG. 9 is a cross-sectional schematic top view of a portion of the fuel cell 10. As shown in FIG. 9, the anode plate 22 may be shaped to form multiple channels 78A, 78C, which may be generally square, semi-cylindrical, or parabolic shaped ridged channels. The anode channel 78A, which may form the anode flow field 30, is open to the anode compartment 21 and may be configured to direct the flow of fuel across the GDL 26, so that the fuel can flow through the GDL 26 and reach the anode catalyst layer 14. The coolant channel 78C, which can form the coolant flow field 86, is open to the coolant compartment 23, is part of the coolant compartment 23, and can be configured to direct coolant fluid flow through the coolant compartment 23 so that heat generated by the fuel cell 10 can be transferred to the coolant fluid and transported away from the fuel cell 10 by circulation of the coolant fluid.

[0044]

[0065] The dimensions of the channels 78A, 78C may be determined based on numerous variables, including, for example, active area, power, compressive load on the fuel cell 10, desired or designed flow resistance, thickness and material properties (e.g., elasticity) of the anode and / or cathode plates, open flow field properties and / or thickness, gas diffusion layer properties and / or thickness, and designed flow resistance for the anode, cathode, and / or coolant fluids. In some embodiments, the width (A) of the coolant channel 78C may be equal to the width (B) of the anode side channel 78. In other embodiments, the width (B) of the anode channel 78A may be greater than or less than the width (A) of the coolant channel 78C. The combined width of the anode channel 78A and the coolant channel 78C may be referred to as (C). The anode channel and the coolant channel may have a depth (S). According to an exemplary embodiment, the ratio of C / S may be greater than about 1 and less than about 10. According to exemplary embodiments, the ratio of A / B may range from greater than about 1 to less than about 6, or greater than about 2, or less than about 4. These ratios are consistent with the preferred embodiment, but are not limited to the range of about 10 kg / cm. 2 from about 75kg / cm 2 The mechanical load due to compression can be determined based on the range of

[0045]

[0066] The square corrugated channel design as described herein provides improved fluid flow while also minimizing the fuel cell 10 thickness by consolidating the anode flow field 30 and the coolant flow field 86 into alternating channels on opposite sides of the anode plate 22. This consolidation allows the overall thickness (e.g., pitch) of the fuel cell 10 to be reduced. In addition, the square, ribbed geometry provides sufficient surface area contact between the anode plate 22 and the GDL 26 and cathode plate 20 to prevent deformation when under compression during operation. For example, if the channel is too narrow, the small surface area may act as a stress concentration point and may deform or damage adjacent components (e.g., GDL 26). Similarly, if the channel is triangular shaped ribs, the triangular points may create stress concentration points that may deform adjacent components.

[0046]

[0067] FIG. 10 is a front view of a cathode plate 20, according to an exemplary embodiment. The side visible in FIG. 10 is the side configured to face the adjacent anode plate 22 (see, e.g., FIG. 2). The cathode plate 20, like the anode plate 22, may include a first manifold section 31A and a second manifold section 31B. As shown in FIG. 10, the anode plate 22 may include an anode feed manifold 32, a cathode exhaust manifold 54, and a coolant exhaust manifold 62 in the first manifold section 31A, while the second manifold section 31B may include an anode exhaust manifold 42, a cathode feed manifold 44, and a coolant feed manifold 56. It should be understood that the designation of "inlet" or "outlet" for each manifold may be switched, for example, by switching the flow direction of fuel, oxidant, or coolant fluid through the fuel cell 10.

[0047]

[0068] The cathode plate 20 may include a plurality of cathode inlet ports 48 configured to fluidly connect the cathode compartments 19 and the cathode flow fields 28 with the cathode feed manifold 44 via the cathode inlet passages 46. The cathode plate 20 may further include a plurality of cathode outlet ports 50 configured to fluidly connect the cathode compartments 19 and the cathode flow fields 28 with the cathode exhaust manifold 54 via the cathode outlet passages 52. The cathode inlet and outlet passages 46, 52 may be located between the anode plate 22 and the cathode plate 20 of an adjacent fuel cell 10. The periphery of the cathode inlet and outlet passages 46, 52 and the cathode feed and exhaust manifolds 44, 54 may be sealed by a surface gasket 43, as illustrated in FIG.

[0048]

[0069] The cathode inlet and outlet ports 48, 50 may be of a generally rectangular shape, as illustrated in FIG. 10. The cathode plate 20 may be configured with at least two cathode inlet ports 48 arranged generally perpendicular to one another, as illustrated in FIG. 10. The cathode plate 20 may be configured with at least two cathode outlet ports 50 arranged generally perpendicular to one another, as illustrated in FIG. 10. The cathode plate 20 may be configured with at least one cathode inlet port 48 disposed at opposite ends of the cathode inlet passage 46. The cathode plate 20 may be configured with at least one cathode outlet port 50 disposed at opposite ends of the cathode outlet passage 52. The cathode plate may be configured with two cathode inlet ports 48 disposed at one end of the cathode inlet passage 46 and one cathode inlet port 48 disposed at the opposite end. The two cathode inlet ports 48 located at one end may be generally parallel to one another and generally perpendicular to the cathode inlet passage 46 located at the opposite end of the cathode inlet passage 46. The shape and arrangement of the cathode inlet ports 48 as described herein may facilitate improved distribution of the oxidant as it flows into the cathode compartment 19.

[0049]

[0070] A rectangular shaped cathode inlet port 48 may be advantageous compared to a round shaped port because the flow through the port turns 90 degrees immediately after passing through the port. The larger the perimeter of the hole relative to its area, the more "spill length" the fluid has and therefore the lower the velocity (and pressure drop) of the fluid as it makes the turn. The net result is that for two holes, one round and one rectangular, with the same cross-sectional area, the pressure drop in this application is lower for the rectangular port than for the round port. The rectangular orientation, with its long edges generally facing the incoming fluid flow, may also result in a larger "spill length" and lower pressure drop.

[0050]

[0071] The total inlet area of ​​the multiple cathode inlet ports 48 may be greater than the total outlet area of ​​the cathode outlet ports 50. The cathode outlet ports 50 having a total outlet area less than the total inlet area may create backpressure on the oxidant flow through the cathode compartment 19 and the cathode flow field 28. Such backpressure may facilitate improved distribution of the oxidant across the cathode compartments.

[0051]

[0072] 10, the cathode plate 20 may include surface features, such as a cathode flow field boundary 88 that protrudes outward from the cathode plate 20 toward the MEA 18 along a side of the cathode flow field 28 (see, e.g., FIG. 2). As shown in FIG. 10, the cathode flow field boundary 88 may span between the first fluid manifold 31A and the second fluid manifold 31B along opposite sides of the cathode plate 20. The cathode flow field boundary 88 may be configured to prevent or reduce the amount of oxidant flow that bypasses the cathode flow field 28 and the cathode catalyst layer 12 by flowing along the outside of the cathode flow field 28, rather than through the cathode flow field 28 to the cathode catalyst layer 12. For example, the cathode flow field boundaries 88 can act as boundary walls on each side of the cathode flow field 28, thus forcing oxidant flow through the cathode flow field 28. The cathode plate 20 can be configured such that the distance between the cathode flow field boundaries 88 is approximately equal to the width of the cathode flow field 28. The cathode flow field boundaries 88 can be configured to protrude from the cathode plate 20 at a depth equal to the depth of the cathode flow field 28. The cathode flow field boundaries 88 can be of a generally rectangular shape with rounded or chamfered outer corners, as shown in FIG. 10. The cathode flow field boundaries 88 can be positioned to provide a tight-fit along the edges of the cathode flow field 28 to prevent or limit any open flow area for fluid to "flow along" the peripheral length of the cathode flow field 28. In some embodiments, the cathode flow field boundary 88 may be formed by the cathode plate 20, or in some embodiments, the cathode flow field boundary 88 may be formed by applying a second material to the cathode plate 20 (e.g., a polymer, elastomer, surface gasket 43 material that is bonded to the plate in the shape of the cathode flow field boundary 88).

[0052]

[0073] In some embodiments, rather than applying a surface gasket 43 to both the cathode plate 20 and the anode plate 22, all of the surface gaskets 43 described herein may be applied to both sides of the cathode plate 20, which may be generally flat. By consolidating all of the surface gaskets 43 only on the cathode plate 20, which may be generally flat, this may reduce both tooling and processing costs. For example, because the anode plate 22 has channels 78A, 78C, which makes the anode plate 22 not generally flat, applying a surface gasket to the anode plate 22 may be more complicated, thus increasing tooling and processing costs.

[0053]

[0074] To further reduce tooling and processing costs, in some embodiments, alignment features 112 (see, e.g., FIGS. 6 and 10) may be incorporated into the surface gasket to aid in joining each fuel cell 10 and aligning multiple fuel cells 10 to the fuel cell stack 11. For example, the alignment feature 112 (see FIG. 6) of the anode plate 22 may be a hole that aligns with a surface gasket protrusion, which may be the alignment feature 112 (see FIG. 10) of the cathode plate 20. The protrusion may elastically deform upon insertion through the hole in the anode plate 22 and recover on the other side, thus forming an interference fit. Utilizing an interference fit to join the cell 10 and stack 11 may avoid the need for some welding operations in the joining process.

[0054]

[0075] FIG. 11A is a front view of a cathode flow field 28 according to an exemplary embodiment. The side visible in FIG. 11A is the side configured to face the adjacent cathode plate 20 (see, for example, FIG. 2). The cathode flow field 28 may include a porous structure, in particular a porous metal foam structure having a porous three-dimensional network structure. The porous structure may be in the form of a sheet with two opposing surfaces. In some embodiments, the porous metal foam structure may have an average pore size of about 50 to 500 μm. The cathode flow field 28 may include a first cathode distribution channel 90 and a second cathode distribution channel 92 recessed in the surface of the porous metal foam structure facing the cathode plate 20. The cathode flow field 28 may have a thickness of, for example, about 0.2 mm to about 1.5 mm. The first cathode distribution channel 90 and / or the second cathode distribution channel 92 may be recessed within the cathode flow field to a depth between about 10% and about 75% of the thickness.

[0055]

[0076] The first cathode distribution channel 90 may extend generally from one side to the other of the cathode flow field 28 along a bottom edge of the cathode flow field 28. The second cathode distribution channel 92 may extend generally from one side to the other of the cathode flow field 28 along a top edge of the cathode flow field 28. When the cathode flow field 28 is disposed adjacent to the cathode plate 20, the cathode inlet port 48 may be aligned with the first cathode distribution channel 90 and the cathode outlet port 50 may be aligned with the second cathode distribution channel 92.

[0056]

[0077] The cathode flow field 28 may include a plurality of support features 94 formed throughout the first cathode distribution channel 90 and / or the second cathode distribution channel 92. The support features 94 may be generally cylindrical, dimpled, or other suitable shape. The height of the one or more support features 94 may be approximately equal to the recess depth of the first cathode distribution channel 90 and / or the second cathode distribution channel 92. The first cathode distribution channel 90, the second cathode distribution channel 92, and the support features 94 may be formed by stamping, rolling, or otherwise plastically deforming the porous metallic foam structure that forms the cathode flow field 28.

[0057]

[0078] The first and second cathode distribution channels 90, 92 may be configured to promote uniform flow distribution of oxidant along the width of the cathode flow field 28 by providing an open flow path for the oxidant to flow along before flowing into the pores of the porous metallic foam structure. The support features 94 may be configured to provide adequate support during mechanical compression, and also during operation, to prevent or reduce deformation or deflection of the cathode plate 20 into the first and second cathode distribution channels 90, 92, thereby maintaining the open flow path provided by the first and second cathode distribution channels 90, 92 when the fuel cell 10 is compressed.

[0058]

[0079] 11B, 11C, and 11F are front views of additional embodiments of cathode flow fields 28', 28'', 28'". In some embodiments, cathode flow fields 28', 28'', 28'" may be utilized in fuel cell 10 in place of cathode flow field 28. Cathode flow fields 28', 28'', 28'" may include all of the features of cathode flow field 28 as described herein, as well as additional features as will be described below. The side visible in FIGS. 11B, 11C, and 11F may be the side configured to face an adjacent cathode plate 20 or the side configured to face an adjacent MEA 18.

[0059]

[0080] The cathode flow field 28', 28'' may include a plurality of feed (or first) channels 101 and a plurality of exhaust (or second) channels 102. The feed channels 101 and exhaust channels 102 may be stamped, cut, molded, or otherwise formed within the cathode flow field 28' on the surface facing the cathode plate 20. As shown in FIGS. 11B and 11C, the feed channel 101 may begin at the first cathode distribution channel 90, be in fluid communication with the first cathode distribution channel 90, and extend toward the second cathode distribution channel 92. The exhaust channel 102 may terminate at the second cathode distribution channel 92, be in fluid communication with the second cathode distribution channel 92, and extend toward the first cathode distribution channel 90. The feed channel 101 and the exhaust channel 102 may be interdigitated, as shown in FIG. 11B, such that the exhaust channel 102 may be disposed between adjacent feed channels 101. In some embodiments, the feed channel 101 and the exhaust channel 102 may be substantially free of obstructions to fluid flow to allow for improved oxidant distribution. In some embodiments, the feed channel 101 and the exhaust channel 102 may include dimples (not shown) similar to the dimples 94 found in the first and second cathode distribution channels 90, 92.

[0060]

[0081] It is contemplated that in certain embodiments, the multiple feed channels 101 and exhaust channels 102 may have different configurations, shapes, and / or cross-sectional areas. For example, in FIG. 11B, the width of the feed and exhaust channels 101, 102 may vary along the length of the cathode flow field 28'. In FIG. 11B, the feed channel 101 starts wide at or near the first cathode distribution channel 90 and narrows to a point as it extends toward the second cathode distribution channel 92, while the exhaust channel starts at a point and widens as it extends toward the second cathode distribution channel 92. In some embodiments, the distal end of the feed channel 101 may be flat rather than a point as shown in FIG. 11B. Similarly, in some embodiments, the proximal end of the exhaust channel 102 may be flat rather than a point as shown in FIG. 11B. With this arrangement, there is no direct fluid communication between the feed channel 101 and the exhaust channel 102. Rather, the oxidant distributed to the feed channel 101 by the first cathode distribution channel 90 may flow through the multiple feed channels 101 and may be forced to diffuse through the porous structure of the cathode flow field 28' to the adjacent exhaust channel 102.

[0061]

[0082] FIG. 11C illustrates another arrangement of the feed channel 101 and the drain channel 102 relative to the cathode flow field 28″, where the width of the feed and drain channels 101, 102 remain approximately the same along the length of the cathode flow field 28″. While the width of the feed and drain channels 101, 102 remain approximately the same, the depth of the feed and drain channels 101, 102 may vary along the length of the cathode flow field 28″. For example, FIG. 11D illustrates a cross-section of the cathode flow field 28″ along cross-section AA through the feed channel 101. As shown in FIG. 11D, the feed channel 101 may begin deepest (i.e., maximum depth fd1) at or near the first cathode distribution channel 90 and the depth may decrease as it extends toward the second cathode distribution channel 92. As shown in Figure 11D, the depth may decrease at a constant rate (e.g., linearly) or in some embodiments, the depth may decrease at a variable rate (e.g., non-linearly, exponentially). As shown in Figure 11D, the feed channel 101 may dead-end flat at the distal end with a minimum depth (fd2). In other embodiments, the feed channel 101 may dead-end at the distal end with a zero minimum depth fd2.

[0062]

[0083] FIG. 11E shows a cross-section of the cathode flow field 28″ along cross-section BB through the exhaust channel 102. As shown in FIG. 11E, the exhaust channel 102 may start shallowest (i.e., minimum depth dd1) at or near the first cathode distribution channel 90 and the depth may increase as it extends toward the second cathode distribution channel 92. The exhaust channel 102 may be deepest (i.e., maximum depth dd2) at or near the second cathode distribution channel 92. As shown in FIG. 11E, the depth may increase at a constant rate (e.g., linearly) or, in some embodiments, the depth may increase at a variable rate (e.g., nonlinearly, exponentially). As shown in FIG. 11E, the exhaust channel 102 may start flat at the proximal end with a minimum depth (dd1). In other embodiments, the exhaust channel 101 may begin at the proximal end with a zero minimum depth dd1.

[0063]

[0084] By varying the width (see, e.g., FIG. 11B ) or depth (see, e.g., FIGS. 11C-E ) of the feed and exhaust channels 101, 102, the cross-sectional area available for oxidant flow along the cathode flow field 28′, 28″ can be varied (e.g., increased in the exhaust channel 102 or decreased in the feed channel 101). The increase or decrease in the available flow area in the feed and exhaust channels 101, 102 along the length of the cathode flow field 28′, 28″ can be configured to correspond with the volume of oxidant that has diffused from the feed channel 101 into the porous structure and from the porous structure into the exhaust channel 102, such that the flow rate of oxidant along the feed channel 101 and exhaust channel 102 remains approximately constant. In other words, the cross-sectional area of ​​the feed channel 101 can be decreased at a rate equal to the rate at which oxidant flows out of the feed channel 101 and diffuses into the porous structure, such that the velocity of the oxidant remains approximately constant. Similarly, the cross-sectional area of ​​the exhaust channel 102 may increase at a rate equal to the rate at which the oxidant flows into the exhaust channel 102 and out of the porous structure such that the velocity of the oxidant remains approximately constant. In some embodiments, the width and depth of the feed and exhaust channels 101, 102 may both vary. For example, in some embodiments, Figures 11D and E may represent the cross-section of Figure 11B in addition to Figure 11C.

[0064]

[0085] 11B and 11C, there may be a separation section formed between the feed channel 101 and the exhaust channel 102, which may be referred to as a land section 104. The thickness of the land section 104 between the feed channel 101 and the exhaust channel 102 may be fixed, or in some embodiments, the thickness may vary. For example, the thickness may be greatest closest to the first cathode distribution channel 90 (e.g., between the proximal end of the feed channel 101 and the distal end of the exhaust channel), and the thickness may decrease toward the second cathode distribution channel 92. In other embodiments, the thickness may be least close to the first cathode distribution channel 90, and the thickness may increase toward the second cathode distribution channel 92. In other embodiments, the thickness of the land section 104 may be thickest or thinnest approximately halfway between the first cathode distribution channel 90 and the second cathode distribution channel 92. In some embodiments, a plurality of microchannels 106 may be formed in the land section 104 within the cathode flow field 28', 28''. The microchannels 106 may be formed along the entire length of the land section 104 or only a portion. The microchannels 106 may be configured to fluidly connect the feed channel 101 with the exhaust channel 102 to create a preferred flow path for the oxidant compared to the porous network provided by the cathode flow field 28', 28''. For these embodiments, the oxidant may flow from the feed channel 101 to the exhaust channel 102 through the microchannels in conjunction with, or rather than diffusing. The microchannels 106 may be sized and spaced in such a manner as to provide oxidant availability to a majority of the catalytic sites that would otherwise be shadowed by the land section of the cathode flow field 28', 28''.

[0065]

[0086] The number of feed and exhaust channels 101, 102 may be adjusted based on one or more different parameters including, for example, the width of the cathode flow fields 28', 28'', the width of the feed channels 101, the width of the exhaust channels 102, the application of the fuel cell 10, the intended or designed operating pressure for the oxidant, the intended or designed operating flow rate for the oxidant, the intended or designed power output for the fuel cell 10, or any combination of these parameters.

[0066]

[0087] The cathode flow field 28', 28'' may offer several benefits. For example, the feed channel 101 and the exhaust channel 102 provide a larger cross-sectional area through which the oxidant can flow, which may reduce the pressure drop across the porous flow field compared to other porous flow field structures. In addition to the feed channel 101 and the exhaust channel 102, microchannels may also provide an increased cross-sectional area through which the oxidant gas can flow between the feed channel 101 and the exhaust channel 102, which may further reduce the pressure drop across the porous flow field. By reducing the pressure drop, the amount of energy (e.g., blower power) required to pressurize the oxidant may be reduced, which in turn may improve the overall performance and efficiency of the fuel cell 10 (e.g., improve power density and reduce parasitic loads). Additionally, the features of the cathode flow field 28', 28'' may more uniformly distribute fresh oxidant within the porous flow field to increase the oxygen concentration near the outlet of the cathode flow field. (e.g., feed channel 101, exhaust channel 102, and microchannels). This can allow the incoming flow of oxidant to remain oxygen-rich, for example, until the flow is distributed through the porous body, which can result in better cell voltage and, potentially, higher current density.

[0067]

[0088] The cathode flow field may include a plurality of channels 110 formed (e.g., pressed, embossed, or cut) into the surface of the cathode flow field 28''', as shown in FIG. 11F. The plurality of channels 110 may include a first set of channels 110A that begin at the first cathode distribution channel 90 and extend approximately halfway toward the second cathode distribution channel 92. The first set of channels 110A may be configured to allow fresh oxidant (e.g., not yet consumed) to proceed directly to the second half of the cathode flow field 28''', where the oxidant may often have a lower oxygen concentration. The first set of channels 110A may be sized such that they are on top of the lands. The other channels 110 may be configured to reduce the overall pressure drop and aid in mixing and / or uniform distribution. For some embodiments, common materials used for the cathode flow field 28''' may have non-uniformities that result in non-uniform pressure drop and flow characteristics. The channels 110 are designed to help address this issue by allowing for more uniform pressure drop and flow characteristics. The first set of channels 110A further helps reduce the flow rate and thus the flow velocity at the leading edge of the active area, which in turn reduces moisture removal in that region providing better operation and performance in dry conditions. This further helps balance the humidity and oxygen concentration distribution along the flow path of the cathode flow field 28''', which balances the current and temperature distribution across the active area as a result of the electrochemical reactions. This improves the durability and reliability of the fuel cell and stack. In some embodiments, the first set of channels 110A may be positioned opposite any flow channels on the anode or coolant side of the fuel cell to avoid the potential for high velocity effects to constructively interfere and increase the risk of the cell potentially drying out.

[0068]

[0089] The porous structure making up the cathode flow field 28 may include one or more metals and / or alloys. For example, the porous structure may include at least nickel (Ni) and chromium (Cr) (e.g., NiCr) or a combination of nickel, tin (Sn) and chromium (e.g., NiSnCr). For NiCr embodiments of the porous structure, the concentration by mass of chromium may range from about 20% to about 40%, while nickel may make up the balance - about 60% to about 80%. For NiSnCr embodiments of the porous structure, the concentration of chromium may range from about 3% to about 6%, and the concentration of tin may range from about 10% to about 20%, while nickel may make up the balance - about 74% to about 87%.

[0069]

[0090] In some embodiments, at least one surface of the porous structure may include a chromium concentration ranging from about 3% to about 50% by weight. For example, the chromium concentration of one or both surfaces of the porous structure forming the cathode flow field 28 may range from about 3% to about 50% by weight, about 5% to about 40% by weight, or about 7% to about 40% by weight. Increasing the chromium concentration of the surface of the porous metal body may be advantageous because it increases the corrosion resistance of the porous structure in an acidic environment. For example, when at least one of the surfaces of the porous structure forming the cathode flow field has a chromium concentration ranging from about 3% to about 50% by weight, a bipolar plate including the porous structure may advantageously be highly corrosion resistant in a substantially acidic environment at the cathode. The improved corrosion resistance provided by the porous structure as described herein may advantageously allow the cathode plate to be formed from uncoated stainless steel rather than the coated stainless steel that has traditionally been used for its corrosion resistant attributes.

[0070]

[0091] In some embodiments, one surface of the porous structure may have a higher chromium concentration than the other surface of the porous structure. In such instances, the surface with the higher chromium concentration may be advantageously more corrosion resistant. The surface with the higher chromium concentration may be configured to face the MEA 18. In some embodiments, the more corrosion resistant surface of the porous structure may have a chromium concentration ranging from about 3% to about 50% by weight, while the less corrosion resistant surface of the metallic porous structure may have a chromium concentration less than about 3% chromium by weight.

[0071]

[0092] Various embodiments of the porous structure described herein may be formed by one or more electroplating processes. For example, in some embodiments, a resin molded body may initially be used as a substrate for the three-dimensional network structure. The resin molded body may include one or more of polyurethane, melamine, polypropylene, polyethylene, or the like. The resin molded body may include pores within its three-dimensional network structure. In some embodiments, the resin molded body may have a porosity ranging from about 80% to about 98% and may have a pore size of about 50 μm to about 500 μm. In some embodiments, the resin molded body may have a thickness of about 150 μm to about 5,000 μm, about 200 μm to 2,000 μm, or about 300 μm to about 1,200 μm.

[0072]

[0093] To form a porous structure, a metal layer can be plated onto the resin compact. For the NiCr embodiment of the porous structure, for example, a nickel layer and a chromium layer can be plated onto the resin compact. For the NiSnCr embodiment of the porous structure, for example, a nickel layer, a tin layer, and a chromium layer can be plated onto the resin compact. The resin compact can be subjected to an electrical conductive treatment, such as electroless plating (autocatalytic plating), vapor deposition, sputtering, and / or application of a conductive metal, such as nickel particles, tin particles, and / or carbon particles. A nickel layer and / or a tin layer can then be electroplated onto the surface of the three-dimensional structure or skeleton of the treated resin compact. For example, when the resin compact is coated with a conductive layer, a nickel layer can be subsequently formed on the skeleton of the resin compact by an electroplating process. After the nickel layer is formed, a tin layer can be subsequently formed on the skeleton of the resin compact by another electroplating process. Alternatively, when the resin compact is coated with a conductive layer, a tin layer may be electroplated first, followed by electroplating of a nickel layer. In some embodiments, chemical vapor deposition may be used to add chromium to a substantially nickel structure.

[0073]

[0094] In some embodiments, one or more metal layers, such as a nickel layer and / or a tin layer, are plated onto the skeleton of the resin molding, and then a chromium layer is added by an electroplating process. In some embodiments, the chromium plating layer can be formed such that the chromium concentration of at least one surface of the porous structure ranges from about 3% to about 50% by weight. After the chromium plating layer is plated or the nickel and / or tin plating layer is plated, the porous structure can be formed by removing the initial resin molding by a heat treatment. For example, the porous structure can be heated in an inert or reducing atmosphere at a temperature in the range of about 900° C. to about 1300° C.

[0074]

[0095] In some embodiments, fuel cells 10 as described herein may be modified to increase the active area of ​​each fuel cell 10. For example, fuel cells 10 may be modified such that the active area is doubled by doubling the width of the active area. FIG. 12 shows a side perspective view of a portion of an adjacent fuel cell 10', where the active area may be twice (2x) the size of the active area of ​​fuel cell 10 (see, e.g., FIG. 2). Fuel cell 10' may be laid out such that the left half of fuel cell 10' may be laid out the same as fuel cell 10, while the right half of fuel cell 10' may be laid out as a mirror reflection of the left half along the bisecting line between the two halves. In some embodiments, the left and right halves may be laid out the same, rather than as a mirror reflection. Fuel cell 10' may include the same elements as fuel cell 10 as described herein, except that it is wider and the left and right halves are laid out as a mirror reflection.

[0075]

[0096] As shown in FIG. 12, similar to the fuel cell 10, the fuel cell 10' can include a cathode catalyst layer 12', an anode catalyst layer 14', and a proton exchange membrane (PEM) 16' disposed between the cathode catalyst layer 12' and the anode catalyst layer 14', which can be collectively referred to as a membrane electrode assembly (MEA) 18'. The fuel cell 10' can include two bipolar plates, a cathode plate 20' and an anode plate 22'. The cathode plate 20' can be disposed adjacent to the cathode catalyst layer 12', and the anode plate 22' can be disposed adjacent to the anode catalyst layer 14'. The MEA 18' can be interposed between and enclosed between the cathode plate 20' and the anode plate 22'. The fuel cell 10' may further include electrically conductive gas diffusion layers (e.g., a cathode gas diffusion layer 24' and an anode gas diffusion layer 26') within the fuel cell 10 on each side of the MEA 18. The fuel cell 10' may further include flow fields disposed on each side of the MEA 18'. For example, the fuel cell 10' may include a cathode flow field 28', which may include a porous structure disposed between the cathode plate 20' and the GDL 24', and an anode flow field 30', which may be formed by the anode plate 22'. The fuel cell may further include a plurality of fluid manifolds 31A', 31B' extending along a longitudinal axis 5 defined by the series of stacked cathode plates 20' and anode plates 22'. It should be understood that the components, features, operation, and advantages described herein with respect to fuel cell 10 are equally applicable to fuel cell 10' based at least on the similarities as illustrated by Figures 2 and 12. Figures 13, 14, and 15 show front views of anode plate 22', cathode plate 20', and cathode flow field 28' according to an exemplary embodiment of fuel cell 10'. In some embodiments, fuel cell 10 may be modified to increase the active area three-fold rather than two-fold as is done for fuel cell 10', by repeating the layout of the features of fuel cell 10 (e.g., manifolds, passages, and ports, etc.).

[0076]

[0097] The foregoing description has been presented for purposes of illustration. It is not exhaustive or limited to the precise form or embodiment disclosed. Modifications, adaptations, and other applications of the embodiments will be apparent from consideration of the specification and practice of the disclosed embodiments. For example, the described embodiments of the fuel cell 10 may be adapted for use with various electrochemical cells. For example, although the present disclosure focuses primarily on fuel cells with anode channel flow fields and cathode porous flow fields, it is contemplated that some of these features may be utilized in fuel cells utilizing anode and cathode flow fields or fuel cells utilizing anode and cathode porous flow fields.

[0077]

[0098] Furthermore, although illustrative embodiments have been described herein, the scope includes any embodiment having equivalent elements, modifications, omissions, combinations (e.g., aspects across various embodiments), adaptations, and / or alterations based on the present disclosure. The elements in the claims should be broadly interpreted based on the language used in the claims and should not be limited to the examples described in the specification or during the prosecution of this application, which examples should be construed as non-exclusive. Furthermore, the steps of the disclosed methods can be modified in any manner, including rearranging steps and / or inserting or deleting steps.

[0078]

[0099] The features and advantages of the present disclosure are apparent from the detailed specification, and thus, the appended claims are intended to encompass all cells and cell stacks that fall within the true spirit and scope of the present disclosure. As used herein, the indefinite articles "a" and "an" mean "one or more." Similarly, the use of a plural term does not necessarily denote a plurality, unless the term is unambiguous in a given context. Words such as "and" or "or" mean "and / or" unless specifically indicated otherwise. Furthermore, since numerous modifications and changes will readily occur from a consideration of the present disclosure, it is not desired to limit the present disclosure to the exact construction and operation illustrated and described, and thus, all suitable modifications and equivalents that fall within the scope of the present disclosure may be resorted to.

[0079]

[0100] Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present disclosure being indicated by the following claims.

Claims

1. 1. An electrochemical cell stack comprising a plurality of electrochemical cells stacked along a longitudinal axis, each electrochemical cell comprising: a membrane electrode assembly including a cathode catalyst layer, an anode catalyst layer, and a polymer membrane interposed between the cathode catalyst layer and the anode catalyst layer; an anode plate and a cathode plate, the membrane electrode assembly being interposed between the anode plate and the cathode plate, the anode plate defining a plurality of channels forming an anode flow field facing the anode catalyst layer; a cathode flow field disposed between the cathode plate and the cathode catalyst layer, the cathode flow field comprising a porous structure and a first cathode distribution channel recessed in a surface of the porous structure facing the cathode plate; a first manifold section including a first anode feed manifold, a first cathode exhaust manifold, and a first coolant exhaust manifold; and a second manifold section including a first anode exhaust manifold, a first cathode feed manifold, and a first coolant feed manifold. Equipped with the first coolant exhaust manifold is disposed between the first anode feed manifold and the first cathode exhaust manifold, and the first coolant feed manifold is disposed between the first anode exhaust manifold and the first cathode feed manifold; the first cathode distribution channel is configured to provide a flow path between the first cathode feed manifold and the porous structure that promotes uniform flow distribution of oxidant along a width of the cathode flow field, the direction along the width of the cathode flow field being perpendicular to a general direction of oxidant flow in the cathode flow field; Electrochemical cell stack.

2. 2. The electrochemical cell stack of claim 1 , wherein the cathode exhaust manifold is on one side of the coolant exhaust manifold and the anode feed manifold is on an opposite side of the coolant exhaust manifold, while the cathode feed manifold is to the right of the coolant feed manifold and the anode exhaust manifold is to the left of the coolant feed manifold.

3. 3. The electrochemical cell stack of claim 2, wherein fluid flow through the anode flow field between the anode feed manifold and the anode exhaust manifold is cross-current and counter-current to fluid flow through the cathode flow field between the cathode exhaust manifold and the cathode feed manifold.

4. 4. An electrochemical cell stack according to claim 1 , wherein an area of ​​the cathode exhaust manifold is greater than an area of ​​the coolant exhaust manifold, and an area of ​​the coolant exhaust manifold is greater than an area of ​​the anode feed manifold.

5. 5. The electrochemical cell stack of claim 1 , wherein each electrochemical cell further comprises a gas diffusion layer disposed adjacent each side of the membrane electrode assembly.

6. 6. The electrochemical cell stack of claim 1 , wherein the porous structure comprises at least nickel and chromium.

7. 7. The electrochemical cell stack of claim 6, wherein the porous structure comprises a nickel concentration of 60% to 80% by weight and a chromium concentration of 20% to 40% by weight, and at least one surface of the porous structure comprises a chromium concentration of 3% to 50% by weight.

8. 7. The electrochemical cell stack of claim 6, wherein the porous structure comprises a chromium concentration of 3% to 6%, a tin concentration of 10% to 20%, and a nickel concentration of 74% to 87%.

9. An electrochemical cell comprising: a membrane electrode assembly including a cathode catalyst layer, an anode catalyst layer, and a polymer membrane interposed between the cathode catalyst layer and the anode catalyst layer; an anode plate and a cathode plate, the membrane electrode assembly being interposed between the anode plate and the cathode plate, the anode plate defining a plurality of channels forming an anode flow field facing the anode catalyst layer; a cathode flow field disposed between the cathode plate and the cathode catalyst layer, the cathode flow field comprising a porous structure and a first cathode distribution channel recessed in a surface of the porous structure facing the cathode plate; a first manifold section including a first anode feed manifold, a second anode feed manifold, a first cathode exhaust manifold, a second cathode exhaust manifold, a first coolant exhaust manifold, and a second coolant exhaust manifold; and a second manifold section including a first anode exhaust manifold, a second anode exhaust manifold, a first cathode feed manifold, a second cathode feed manifold, a first coolant feed manifold, and a second coolant feed manifold. Equipped with the first cathode distribution channel is configured to provide a flow path between the first cathode feed manifold and the porous structure that promotes uniform flow distribution of oxidant along a width of the cathode flow field, the direction along the width of the cathode flow field being perpendicular to a general direction of oxidant flow in the cathode flow field; Electrochemical cell.

10. 10. The electrochemical cell of claim 9, wherein fluid flow through the anode flow field between the first and second anode feed manifolds and the first and second anode exhaust manifolds is cross-current and counter-current to fluid flow through the cathode flow field between the first and second cathode exhaust manifolds and the first and second cathode feed manifolds.

11. 10. The electrochemical cell of claim 9, wherein half and the other half of the anode and cathode plates are laid out as mirror images across a bisecting line.

Images