EP4728580A2 - Systems and methods for manufacturing a fuel cell interconnect - Google Patents

Abstract

The present disclosure generally relates to systems and methods comprising a bipolar plate interconnect. The bipolar plate interconnect includes a porous membrane metallurgically attached to a first side of a first stainless steel structure, and a nickel-phosphorous layer of non-uniform thickness positioned between the porous membrane and the stainless steel structure.

Description

SYSTEMS AND METHODS FOR MANUFACTURING A FUEL CELL INTERCONNECT

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This nonprovisional application claims the benefit and priority, under 35 U.S.C. § 119(e) and any other applicable laws or statutes, to U.S. Provisional Application Serial No. 63/508,172 filed on June 14, 2023, the entire disclosure of which is hereby expressly incorporated herein by reference.

TECHNICAL HELD

[0002] The present disclosure generally relates to systems and methods for fusing or connecting different layers of a fuel cell.

BACKGROUND

[0003] A fuel cell produces electrical energy from chemical energy with high efficiency and low emissions. A cathode reduces oxygen on one side and supplies ions to a hermetic electrolyte. The electrolyte conducts the oxygen ions at a high temperature to an anode, where the ions oxidize hydrogen to form water. A resistive load connecting the anode and the cathode conducts electrons to perform work.

[0004] Fuel cells (e.g., solid oxide fuel cells (SOFC)) utilizing ceramic sintering technology are limited by a maximum manufacturable cell size and sinter-based manufacturing facilities that require large capital investment. However, metal interconnect-supported fuel cells utilizing thermal spray deposition offer a variety of manufacturing benefits including a more rugged design.

[0005] The metal interconnect-supported fuel cells typically include a bipolar plate (BPP) integrating both the anode and the cathode surfaces. The anode metallic surface is required to be relatively smooth to prevent gross defects from forming when the anode and electrolyte coatings are deposited. Gross defects can result in low open circuit voltage (OCV) and poor power density and fuel utilization, resulting in lower operating efficiency. In addition, the metal interconnect needs to have a fuel flow field designed to allow sufficient reducing gas, typically H2 and CO, to reach the anode and electrolyte interface. This is typically achieved by bonding a porous membrane (e.g., a porous metallic membrane) to the flow field.

[0006] The porous membrane comprises uniform porosity, and is thin for cost and manufacturability considerations. The porous membrane needs to provide an adequate substrate for thermal spray deposition and efficient fuel cell performance during operation. Therefore, it is critical that the bonding technique implemented to bond the porous membrane to the metal interconnect does not disrupt the porous membrane properties.

[0007] Thus, the present disclosure is directed to the systems and methods for manufacturing fuel cell interconnects with a porous metallic membrane.

SUMMARY

[0008] Embodiments of the present disclosure are included to meet these and other needs.

[0009] In one aspect of the present disclosure described herein is a bipolar plate interconnect comprising a porous membrane metallurgically attached to a first side of a first stainless steel structure, and a nickel-phosphorous layer positioned between the porous membrane and the stainless steel structure.

[0010] In some embodiments, the nickel-phosphorous layer may be of non-uniform thickness. In some embodiments, the nickel-phosphorous layer may have a thickness of less than about 25 pm. In some embodiments, the nickel-phosphorous layer may consist of more than 0.2 wt% phosphorous. In some embodiments, the porous membrane may have a plurality of pores less than about 100 pm in diameter.

[0011] In some embodiments, the porous membrane may have a thickness of less than about 0.3 mm. In some embodiments, the first stainless steel structure may comprise 400 series stainless steel. In some embodiments, the porous membrane may comprise nickel, iron, chromium, or any combination thereof.

[0012] In some embodiments, the bipolar plate interconnect may comprise a second side of the first stainless steel structure that is metallurgically attached to a second stainless steel structure. In some embodiments, a braze material may be positioned between the second side of the first stainless steel structure and the second stainless steel structure. In some embodiments, a braze material may comprise nickel and chromium. In some embodiments, a braze material may not comprise phosphorus. In some embodiments, a braze material may have a thickness of more than about 10 pm. In some embodiments, the porous membrane, the nickel-phosphorous layer, the first stainless steel structure, the braze material, and the second stainless steel structure may be joined by heat treatment.

[0013] In another aspect of the present disclosure described herein is an intermediate bipolar plate assembly before heat treatment comprising a multi-layer nickel-phosphorous structure coated on a first side of a first stainless steel structure wherein a porous membrane is disposed onto a surface of the nickel-phosphorous structure, a nickel-based braze material in contact with a second side of the first stainless steel structure, and a second stainless steel structure in contact with the nickel-based braze material. The multi-layer nickel-phosphorous structure may be of non-uniform thickness.

[0014] In some embodiments, at least one layer of the multi-layer nickel-phosphorous structure may comprise about 8 wt% to about 12 wt% phosphorus. In some embodiments, the multi-layer nickel-phosphorous structure may also comprise at least one layer of nickel that does not contain phosphorus. In some embodiments, the multi-layer nickel-phosphorous structure may have an average thickness between about 1 pm and about 15 pm.

[0015] In some embodiments, the multi-layer nickel-phosphorous structure may comprise an active region and an in-active edge region, and wherein the active region is thicker than the in-active region by a factor that ranges from about 1.1 to about 2.5.

[0016] In another aspect of the present disclosure described herein is a method of coating a component of a bipolar interconnect comprising using a mask fixture positioned in contact with a stainless steel structure to mask areas of the stainless steel structure that is not configured to contact a porous membrane, and electroplating at least one nickel-phosphorus layer on the stainless steel structure. The masking fixture may not be not hermetically sealed with the stainless steel structure.

[0017] In some embodiments, the stainless steel structure may be perforated. In some embodiments, electroplating a nickel-phosphorus layer may comprise depositing the electroplating a nickel-phosphorus layer of non-uniform thickness. In some embodiments, at least one nickel layer may also be coated onto the stainless steel structure and is in contact with the nickel-phosphorus layer.

[0018] In another aspect of the present disclosure described herein is a solid oxide fuel cell or electrolysis cell bipolar plate interconnect comprising a porous membrane metallurgically attached to a first side of a first stainless steel structure, and a nickel-phosphorous layer positioned between the porous membrane and the first stainless steel structure, wherein the nickel-phosphorous layer is less than about 10 pm thick and comprises more than 0.2 wt% phosphorus, a second stainless steel structure attached to a second side of the first stainless steel structure, and a nickel-based layer positioned between the first and second stainless steel structure, wherein the nickel-based layer is more than 10 pm thick and does not include phosphorus. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout the drawings, wherein:

[0020] FIG. 1 A is a schematic view of an exemplary fuel cell system including an air delivery system, a hydrogen delivery system, and a fuel cell module including a stack of multiple fuel cells;

[0021] FIG. IB is a cutaway view of an exemplary fuel cell system including an air delivery system, hydrogen delivery systems, and a plurality of fuel cell modules each including multiple fuel cell stacks;

[0022] FIG. 1C is a perspective view of an exemplary repeating unit of a fuel cell stack of the fuel cell system of FIG. 1A;

[0023] FIG. ID is a cross-sectional view of an exemplary repeating unit of the fuel cell stack of FIG. 1C;

[0024] FIG. 2A is an exemplary repeating unit of a fuel cell stack of the fuel cell system of FIG. 1A illustrating nickel-based braze materials typically used for joining bipolar plates;

[0025] FIG. 2B is a cross-sectional view of FIG. 2A;

[0026] FIG. 3 illustrates a method for effective deposition of a nickel-phosphorous layer on a metal substrate;

[0027] FIG. 4 illustrates a metal substrate with an electroplated nickel-phosphorous layer;

10028 ] FIG. 5 illustrates a method for effective deposition of a nickel -phosphorous layer on a first metal substrate joined to a second metal substrate;

[0029] FIG. 6 illustrates a method to simultaneously braze a metallic porous membrane to the first metallic substrate and to braze the first metallic substrate to the second metallic substrate;

[0030] FIG. 7 is a graph showing a binary phase diagram for the nickel-phosphorous layer;

[0031] FIG. 8 illustrates one embodiment of a stainless steel structure bonded or joined to form a bipolar interconnect or bipolar plate;

[0032] FIG. 9A shows a masking fixture placed on a perforated steel structure during electroplating;

[0033] FIG. 9B shows a nickel-phosphorus layer applied to an area including a perforated region during electroplating; [0034] FIG. 9C shows an active region in the perforated steel structure after brazing;

[0035] FIG. 10A illustrates a ratio of thickness of an inactive edge region to an active region in one embodiment of a bipolar interconnect;

[0036] FIG. 10B illustrates a ratio of thickness of the inactive edge region to the active region in another embodiment of a bipolar interconnect;

[0037] FIG. 11 A is a graph showing wt% for phosphorous in the inactive edge region and active region;

[0038] FIG. 1 IB is a graph showing wt% for nickel in the inactive edge region and active region;

[0039] FIG. 11C is a graph showing wt% for chromium in the inactive edge region and active region; and

[0040] FIG. 1 ID is a scanning electron microscope (SEM) image of the surface of the stainless steel structure.

DETAILED DESCRIPTION

[0041] The present disclosure relates to systems and methods for manufacturing fuel cell interconnects with a porous metallic membrane. Specifically, the present disclosure relates to bipolar plate interconnects that include a porous membrane metallurgically attached to a metal structure, and a nickel-phosphorous layer positioned between the porous membrane and the metal structure.

[0042]

[0043] As shown in FIG. 1A, fuel cell systems 10 often include one or more fuel cell stacks 12 or fuel cell modules 14 connected to a balance of plant (BOP) 16, including various components, to support the electrochemical conversion, generation, and/or distribution of electrical power to help meet modem day industrial and commercial needs in an environmentally friendly way. As shown in FIGS. IB and 1C, fuel cell systems 10 may include fuel cell stacks 12 comprising a plurality of individual fuel cells 20. Each fuel cell stack 12 may house a plurality of fuel cells 20 assembled together in series and/or in parallel. The fuel cell system 10 may include one or more fuel cell modules 14 as shown in FIGS. 1A and IB.

[0044] Each fuel cell module 14 may include a plurality of fuel cell stacks 12 and/or a plurality of fuel cells 20. The fuel cell module 14 may also include a suitable combination of associated structural elements, mechanical systems, hardware, firmware, and/or software that is employed to support the function and operation of the fuel cell module 14. Such items include, without limitation, piping, sensors, regulators, current collectors, seals, and insulators.

[0045] The fuel cells 20 in the fuel cell stacks 12 may be stacked together to multiply and increase the voltage output of a single fuel cell stack 12. The number of fuel cell stacks 12 in a fuel cell system 10 can vary depending on the amount of power required to operate the fuel cell system 10 and meet the power need of any load. The number of fuel cells 20 in a fuel cell stack 12 can vary depending on the amount of power required to operate the fuel cell system 10 including the fuel cell stacks 12.

[0046] The number of fuel cells 20 in each fuel cell stack 12 or fuel cell system 10 can be any number. For example, the number of fuel cells 20 in each fuel cell stack 12 may range from about 100 fuel cells to about 1000 fuel cells, including any specific number or range of number of fuel cells 20 comprised therein (e.g., about 200 to about 800). In an embodiment, the fuel cell system 10 may include about 20 to about 1000 fuel cells stacks 12, including any specific number or range of number of fuel cell stacks 12 comprised therein (e.g., about 200 to about 800). The fuel cells 20 in the fuel cell stacks 12 within the fuel cell module 14 may be oriented in any direction to optimize the operational efficiency and functionality of the fuel cell system 10.

[0047] The fuel cells 20 in the fuel cell stacks 12 may be any type of fuel cell 20. The fuel cell 20 may be a polymer electrolyte membrane or proton exchange membrane (PEM) fuel cell, an anion exchange membrane fuel cell (AEMFC), an alkaline fuel cell (AFC), a molten carbonate fuel cell (MCFC), a direct methanol fuel cell (DMFC), a regenerative fuel cell (RFC), a phosphoric acid fuel cell (PAFC), or a solid oxide fuel cell (SOFC). In an exemplary embodiment, the fuel cells 20 may be a polymer electrolyte membrane or proton exchange membrane (PEM) fuel cell or a solid oxide fuel cell (SOFC).

[0048] In an embodiment shown in FIG. 1C, the fuel cell stack 12 includes a plurality of proton exchange membrane (PEM) fuel cells 20. Each fuel cell 20 includes a single membrane electrode assembly (MEA) 22 and a gas diffusion layers (GDL) 24, 26 on either or both sides of the membrane electrode assembly (MEA) 22 (see FIG. 1C). The fuel cell 20 further includes a bipolar plate (BPP) 28, 30 on the external side of each gas diffusion layers (GDL) 24, 26, as shown in FIG. 1C. The above-mentioned components, in particular the bipolar plate 30, the gas diffusion layer (GDL) 26, the membrane electrode assembly (MEA) 22, and the gas diffusion layer (GDL) 24 comprise a single repeating unit 50. [0049] The bipolar plates (BPP) 28, 30 are responsible for the transport of reactants, such as fuel 32 (e.g., hydrogen) or oxidant 34 (e.g., oxygen, air), and cooling fluid 36 (e.g., coolant and/or water) in a fuel cell 20. The bipolar plates (BPP) 28, 30 can uniformly distribute reactants 32, 34 to an active area 40 of each fuel cell 20 through oxidant flow fields 42 and/or fuel flow fields 44 formed on outer surfaces of the bipolar plates (BPP) 28, 30. The active area 40, where the electrochemical reactions occur to generate electrical power produced by the fuel cell 20, is centered, when viewing the stack 12 from a top-down perspective, within the membrane electrode assembly (MEA) 22, the gas diffusion layers (GDL) 24, 26, and the bipolar plate (BPP) 28, 30.

[0050] The bipolar plates (BPP) 28, 30 may each be formed to have reactant flow fields 42, 44 formed on opposing outer surfaces of the bipolar plate (BPP) 28, 30, and formed to have coolant flow fields 52 located within the bipolar plate (BPP) 28, 30, as shown in FIG. ID. For example, the bipolar plate (BPP) 28, 30 can include fuel flow fields 44 for transfer of fuel 32 on one side of the plate 28, 30 for interaction with the gas diffusion layer (GDL) 26, and oxidant flow fields 42 for transfer of oxidant 34 on the second, opposite side of the plate 28, 30 for interaction with the gas diffusion layer (GDL) 24. As shown in FIG. ID, the bipolar plates (BPP) 28, 30 can further include coolant flow fields 52 formed within the plate (BPP) 28, 30, generally centrally between the opposing outer surfaces of the plate (BPP) 28, 30. The coolant flow fields 52 facilitate the flow of cooling fluid 36 through the bipolar plate (BPP) 28, 30 in order to regulate the temperature of the plate (BPP) 28, 30 materials and the reactants. The bipolar plates (BPP) 28, 30 are compressed against adjacent gas diffusion layers (GDL) 24, 26 to isolate and/or seal one or more reactants 32, 34 within their respective pathways 44, 42 to maintain electrical conductivity, which is required for robust operation of the fuel cell 20 (see FIGS. 1C and ID).

[0051] The fuel cell system 10 described herein, may be used in stationary and/or immovable power system, such as industrial applications and power generation plants. The fuel cell system 10 may also be implemented in conjunction with an air delivery system 18. Additionally, the fuel cell system 10 may also be implemented in conjunction with a hydrogen delivery system and/or a source of hydrogen 19 such as a pressurized tank, including a gaseous pressurized tank, cryogenic liquid storage tank, chemical storage, physical storage, stationary storage, an electrolysis system, or an electrolyzer. In one embodiment, the fuel cell system 10 is connected and/or attached in series or parallel to a hydrogen delivery system and/or a source of hydrogen 19, such as one or more hydrogen delivery systems and/or sources of hydrogen 19 in the BOP 16 (see FIG. 1A). In another embodiment, the fuel cell system 10 is not connected and/or attached in series or parallel to a hydrogen delivery system and/or a source of hydrogen 19.

[0052] The present fuel cell system 10 may also be comprised in mobile applications. In an exemplary embodiment, the fuel cell system 10 is in a vehicle and/or a powertrain 100. A vehicle 100 comprising the present fuel cell system 10 may be an automobile, a pass car, a bus, a truck, a train, a locomotive, an aircraft, a light duty vehicle, a medium duty vehicle, or a heavy-duty vehicle. Type of vehicles 100 can also include, but are not limited to commercial vehicles and engines, trains, trolleys, trams, planes, buses, ships, boats, and other known vehicles, as well as other machinery and/or manufacturing devices, equipment, installations, among others.

[0053] The vehicle and/or a powertrain 100 may be used on roadways, highways, railways, airways, and/or waterways. The vehicle 100 may be used in applications including but not limited to off highway transit, bobtails, and/or mining equipment. For example, an exemplary embodiment of mining equipment vehicle 100 is a mining truck or a mine haul truck.

[0054] In some embodiments, a metal support or substrate 152 such as stainless steel or other metal may be used as the bipolar plate (BPP) 28, 30 in the fuel cell 20. As shown in FIG. 2A, nickel-based braze materials 81 are typically used for joining such metal supports 152 at one or more joining interfaces of the flow fields 42, 44. Additionally, or alternatively, nickel- based braze materials 81 are typically used for joining such metal supports 152 at one or more joining interfaces of the flow fields 42, 44 to a porous membrane 154 as shown in FIG. 2B. In some embodiments, the porous membrane 154 is a metallic porous membrane 154.

[0055] The nickel-based braze materials 81 may predominately comprise a melt depressant such as phosphorous, boron or silicon. In some embodiments, the nickel-based braze materials 81 may predominately comprise nickel in addition to one or more of other elements including but not limited to chromium and iron. Such nickel-based braze materials 81 can be applied in a powder, paste, and/or foil form. Joining of the interfaces is more efficient when the nickel- based braze materials 81 have gap filling capacity and include a filler metal. The nickel-based braze materials 81 with gap filling capacity are designed to be able to bridge gaps and form a seal when used. For example, the nickel-based braze materials 81 consisting of about 11 wt% phosphorous nickel show excellent brazability and are commercially available under AWS specification BNi-6. The melting temperature for BNi-6 is about 891 °C, which is well below the melting temperature for nickel of about 1455 °C. [0056] However, using traditional application techniques to apply nickel-based brazing alloys or nickel-based braze materials 81 may damage the porous membrane 154. Traditional braze applications using nickel-based braze materials 81 can be achie ved using powder, tape, thick film, or foil materials. These application techniques apply too much nickel-based braze materials 81, which, when melted, can consume and destroy delicate microstructures such as those present in the porous membrane 154. Defects can form in the porous membrane 154 that can impact the electrochemically functional coatings. For instance, defects in the porous membrane 154 can propagate and cause undesirable pores or cracks in the electrode and electrolyte coatings. An alternative way to bond the porous membrane 154 to the flow field 42, 44, illustrated in FIG. 2A, may include the utilization of a thin film of braze material applied by electroless nickel (EN) plating. Electroless nickel (EN) plating is a braze application method than can substantially reduce the amount of nickel-based braze materials 81 used for joining metals compared to a traditional nickel-based braze methods.

[0057] Electroless nickel (EN) is a chemical method utilized for depositing an EN nickel coating or layer based on the reaction:

NiCl₂ + NaH₂PO₂ + H₂O -A Ni + 2HC1 + NaH₂PO₃ (1)

[0058] Such EN coatings or layers are amorphous and metastable, and contain dissolved phosphorous as a reaction byproduct. Such EN coatings can be deposited uniformly and conformably on parts with complex shapes, and do not require a conductive surface. Historically, EN coatings or layers have been used for corrosion resistance and wear resistance, due to higher density and hardness compared to electrolytic or electroplated nickel coatings or layers. ASTM B733 specifies phosphorous concentrations of about 2% to about 4 wt%, about 5% to about 9 wt%, and greater than about 10 wt% for low, medium, and high phosphorous coatings or layers. The EN coatings or layers may have a thickness of up to about 75 pm for hostile service conditions.

[0059] For some unique applications, EN coatings or layers can be used to apply a nickel- based braze material 81 when the brazing joint is narrow or thin, and the solution does not require gap filling properties. Nickel-Phosphorous (Ni-P) alloys have shown better results than Nickel-Boron (Ni-B) alloys because of the slower kinetics for phosphorous diffusion. However, EN deposition, including EN coatings or layers suffer from high cost, maintenance, and complexity, and therefore an alternative deposition method that is cost competitive is required. While electroplated nickel coatings or layers can be used to deposit nickel with uniform thickness, controlling the concentration of phosphorous (or other additives) in the coating or layer has historically been difficult.

[0060] The present disclosure is directed to systems and methods for effective deposition of nickel coatings or layers. FIG. 3 illustrates a method 60 comprising electroplated nickelphosphorous layers or coatings 58. The method 60 includes electroplating nickel-based braze materials 81 that contain a melt suppressant (e.g., phosphorous) on the substrate 152 during a plating process in step 62 to form the nickel-phosphorous layer 58, applying the porous membrane 154 onto the electroplated nickel-phosphorous layer 58 in step 64, and brazing the coated substrate 152 with the nickel-phosphorous layer 58 and the porous membrane 154 such that both are metallurgically bonded, attached, adhered, and/or joined in step 66. Brazing comprises heat treatment of the different layers (152, 154) in the presence of the braze materials 81. The method 60 may result in a uniform metallurgical bond between the porous membrane 154 and the flow fields 42, 44 in the substrate 152 (e.g., the bipolar plate (BPP) 28, 30) as shown in FIGS. 2A-2B. Such a uniform metallurgical bond may comprise strength and avoid defects in the porous membrane 154.

[0061] Referring back to FIG. 3, the electroplated nickel-phosphorous layers 58 may be formed by submerging the substrate 152 (e.g., bipolar plate (BPP) 28, 30 as shown in FIG. 2A) in a nickel plating bath 68 containing a dissolved phosphorous source in step 62. Conditions during the plating process may be optimized so that phosphorous is diffused into the electroplated nickel-phosphorous layers 58 during the plating operation. Conditions such as temperature, pH, phosphorous concentration in the plating bath 68, current density, and time may be controlled so that an appropriate phosphorous concentration is achieved in the electroplated nickel-phosphorous layer 58. The phosphorous concentration may range from about 11 w% to about 13 wt% including ay percentage or range comprised therein. In one embodiment, a commercially available nickel electrolyte solution, Umicore NIPHOS® 968, yields an electroplated nickel-phosphorous layers 58 containing between about 11 % and about 13 wt% phosphorous. In some embodiments, the amount of phosphorous is similar to that present in high-phosphorous EN coatings or layers.

[0062] FIG. 4 illustrates another method 70 of applying the electroplated nickelphosphorous layers 58 on the substrate 152. In some embodiments, such as those using stainless steel substrates 152 (e.g., bipolar plate (BPP) 28, 30), a nickel strike layer or coating 76 may be applied to enhance adhesion of the subsequent electroplated layers 58 in step 72. The nickel strike layer 76 may be positioned between the substrate 152 and the electroplated nickelphosphorous layers 58. This process may be repeated as shown in step 74.

[0063] In some embodiments, as shown in FIG. 5, a method 80 may include joining the porous membrane 154 and joining more than one metal substrates 152 simultaneously as shown in step 84. To bond more than one metal substrates 152, alternative and more conventional brazing methods and materials may be utilized. For instance, a nickel-based adhesion layer 83 comprising traditional braze material 81’ (e.g., BNi-9 (AWS A5.8M/A5.8)) that does not comprise phosphorous may be applied to join the metal substrate 152 as shown in step 82. The braze material 81’ may be applied to the metal substrate 152 by screen printing a paste containing the braze material 81’, applying the braze material 81’ using an adhesive, or applying the braze material 81’ by using a foil. In such cases, the phosphorous content of the electroplated nickel-phosphorous layer 58 used to join the metal substrate 152 to the porous membrane 154 may need to be optimized to align with the joining process of the more than more than one metal substrates 152.

[0064] The binary phase diagram 90 for the electroplated nickel-phosphorous layer 58 (shown in FIG. 6) is shown in FIG. 7. The temperature at which the nickel-phosphorous layer 58 melts (y-axis) and brazes the porous membrane 154 to the metal substrate 152 (shown in FIG. 6) is inversely proportional to the phosphorous content of the nickel-phosphorous layer 58 (x-axis). When the amount of phosphorous in the nickel-phosphorous layer 58 ranges from about 0 % to about 11%, the melting temperature of the nickel phosphorous alloy is above about 880 °C. When the amount of phosphorous in the nickel-phosphorous layer 58 further increases beyond 11 wt%, the melting temperature of the nickel-based braze material 81 used to form the nickel-phosphorous layer 58 increases with increasing phosphorous content.

[0065] FIG. 6 illustrates a method 100 to simultaneously braze the metallic porous membrane 154 to a first metallic substrate 152, 102 and to braze the first metallic substrate 152, 102 to a second metallic substrate 152, 104. First, at least one nickel strike layer 76 is deposited onto the first metallic substrate 102 as shown in step 110. This is followed by the deposition of at least one nickel-phosphorous layer 58 onto the nickel strike layer 76. This is followed by the deposition of another nickel strike layer 76. In some embodiments, the number of nickelphosphorous layers 58 deposited on the first metallic substrate 152, 102 may range from about one to twenty, including any number or range comprised therein.

[0066] Next, as shown in step 120, the porous membrane 154 is disposed onto the nickel strike layer 76. Finally, as shown in step 130, the first metallic substrate 102 and porous membrane 154 construct is placed adjacent to the second metallic substrate 104. The nickel- based adhesion layer 83 is applied between the two sheets of metallic substrate 102, 104. In some embodiments, the order of steps 110, 120, and 130 may be different.

[0067] In some embodiments, metal interconnect- supported fuel cells (e.g., fuel cell metal bipolar plates) typically include substrates 152 such as a 400-series stainless steel sheets stamped and joined together using a silicon-free nickel-based braze filler material, such as BNi- 9. BNi-9 solidus and liquidous temperature is 1055°C (AWS A5.8M/A5.8), with a recommended braze range of about 1065 °C to about 1205 °C. It is well known to those skilled in the art of braze bonding that there are certain process conditions necessary to produce a strong and hermetic bond between the substrate 152 sheets using BNi-9. However, it is not obvious how to braze the substrate 152 sheets together using BNi-9, and bond the porous membrane 154 to the substrate 152 using the nickel-phosphorous layers 58 so that the joint has adequate adhesion without any defects.

[0068] One defect that can occur is the formation of a void in the porous membrane 154. There are two mechanisms by which such void formation can occur. The first mechanism that may cause a defect involves the presence of an excessive amount of braze material 81’ between the metal substrate 152 and the porous membrane 154. Although BNi-9 may be the ideal braze material 81’ to use, traditional cost-competitive manufacturing techniques, such as screen printing paste, applying powder using an adhesive, or using a foil, utilize an excessive amount of braze material 81’ which, when melted, can consume the porous membrane 154. The consumption of the porous material 154 may generate larger than desired pores or a higher concentration of pores in some regions of the porous membrane 154, thereby destroying the functionality of the porous membrane 154. Utilizing the nickel-phosphorous layers 58 to braze the porous membrane 154 requires sufficient control of thickness to prevent consumption.

[0069] The thickness of the nickel-phosphorous layers 58 may range from about 1 pm to about 25 m including any thickness or range comprised therein. In the preferred embodiment, the average thickness nickel-phosphorous layers 58 ranges from about 2 pm to about 10 pm including any thickness or range comprised therein. Electroplating offers a technique that is capable of applying thin films of nickel-phosphorous layer 58 and/or nickel strike layers 76 that do not destroy the inherent properties of the porous membrane 154 during the brazing process. [0070] A second mechanism that may cause a defect is the utilization of a material that bonds the porous membrane 154 at a temperature that is significantly lower than the temperature at which the metal substrate 152 join together. When BNi-9 is used as the braze material 81’ to bond consecutive metal substrates 152 and the nickel-phosphorous layers 58 is used to bond the porous membrane 154 to the metal substrate 152, the nickel-phosphorous layers 58 must melt sufficiently close to the melting temperature of the braze material 81’ (e.g., BNi-9).

[0071] It has been experimentally shown that the nickel-phosphorous layers 58 melting temperature is more than about 100 °C less than the melting temperature of BNi-9 (1055 °C). Thus, there exists a probability for the generation of voids in the porous membrane 154. The braze temperature of BNi-9 ranges from about 1065 °C to about 1205 °C including any temperature or range comprised therein. If the nickel-phosphorous layers 58 melting temperature is higher than the braze temperature of BNi-9. , then the porous membrane 154 will not join to the substrate 152. According to AWS A5.8M/A5.8, the maximum recommended braze temperature for BNi-9 is about 1205 °C. Therefore, the temperature for a successful simultaneous braze using nickel-phosphorous layers 58 and BNi-9 ramy range from about 955 °C to about 1205 °C. According to the binary phase diagram 90 for the electroplated nickelphosphorous layer 58 is shown in FIG. 7, this temperature range corresponds to a phosphorous concentration of 9.3 wt% P and 4.6 wt% P, respectively. Thus, in one preferred embodiment, phosphorous content in the nickel-phosphorous layers 58 is about 8.4 wt% or less.

[0072] In one embodiment, electrolytic deposition or electroplating of nickel -phosphorous layers 58 may contain about 12 wt% phosphorous. In other embodiments, electrolytic deposition of nickel-phosphorous layers 58 may contain about 10 wt% phosphorous. Values below 10 wt% phosphorous are more difficult to control with reproducibility. Therefore, achieving the preferred embodiment for phosphorous content (8.4 wt%) to bond the porous membrane to stainless steel requires a third nickel-phosphorous layers 58 to be deposited. A layered structure provides the required phosphorous concentration by considering all the layers (e.g., three layers) together. Thus, the phosphorous of the total electroplated structure can be optimized for the desired melting temperature, such that:

CT = C2 * (m2 / mi) (2)

[0073] Where, CT is the total amount of phosphorous in the electroplated layers by wt%, C2 is the wt% of phosphorous in each electroplated nickel-phosphorous layers 58, m2 is the mass of each electroplated nickel-phosphorous layers 58, and mi is the total mass of all electroplated layers. The mass of the coatings or layers are a function of density (p) and volume, or area (A) and thickness (t): m = At / p (3) and, m = Ati / p i + At2 / p 2 + Ats / p 3 (4) Therefore,

CT = C2 * (A t2 / p 2) / (A ti / pi + A t2 / P2 + A t3 / p3) (5) or,

CT = C2 * (12 / P2) / (ti / pi + I2 / P2 + I3 / pa) (6)

10074] The amount of phosphorous within the entire electroplated structure, CT, may be optimized to be below about 9.3 wt%. In some embodiments, the amount of phosphorous within the entire electroplated structure, CT, may range between about 4.6 wt% and about 8.4 wt% including any percentage or range comprised therein. Additionally, the lower limit of CT can be adjusted according to the braze process conditions desired. This is especially important when considering two or more braze materials that are being used to join components within the same operation.

[0075] The features illustrated or described in connection with one exemplary embodiment may be combined with any other feature or element of any other embodiment described herein. Such modifications and variations are intended to be included within the scope of the present disclosure. Further, a person skilled in the art will recognize that terms commonly known to those skilled in the art may be used interchangeably herein.

[0076] The above embodiments are described in sufficient detail to enable those skilled in the art to practice what is claimed and it is to be understood that logical, mechanical, and electrical changes may be made without departing from the spirit and scope of the claims. The detailed description is, therefore, not to be taken in a limiting sense.

Example 1

[0077] In one embodiment, as shown in FIG. 8, one or more stainless steel (e.g., 441 stainless steel) structures 152 are bonded or joined to form a bipolar interconnect or bipolar plate 160. A porous membrane 154 is bonded to one of the metal structures 152, 156.

[0078] The stainless steel structures 152 and are formed by stamping, punching, chemical etching, and/or using other sheet metal forming techniques. One of the stainless steel structures 152 is a perforated steel structure 156 that includes a perforated region 157. The stainless steel structures 152, 162 that is assembled adjacent to the perforated stainless steel structure 156 includes the fuel flow fields 44. Adjacent to the fuel flow field 44 is a stainless steel structures 152, 158 that separates the fuel flow field 44 from the stainless steel structures 152, 164 that includes the oxidant flow fields 42. Those skilled in the art would understand that functional layers including anode, electrolyte, and cathode would be further deposited onto the bipolar plate and would be essential for fuel cell 20 operation.

[0079] In some embodiments, the perforated stainless steel structure 156 may require a cleaning step to remove any residual processing oils, especially when using stamping was utilized to form the perforated stainless steel structure 156. Additionally, the surface of the perforated stainless steel structure 156 may be treated mechanically to increase surface roughness to a Rz of 4 microns. Additionally, chemical techniques may be utilized to roughen the perforated stainless steel structure 156 surface.

[0080] A nickel-based adhesion layer 170 is applied between each pair of the stainless steel structures 152. The thickness of the nickel-based adhesion layer 170 may range from 10 pm to 150 pm, including any thickness or range of thickness comprised therein. In some embodiments, the nickel-based adhesion layer 170 has a thickness of about 10 pm to about 100 pm, including any value and range comprised therein. In some embodiments, the nickel-based adhesion layer 170 is at least about 10 pm in thickness. In some embodiments, the nickel-based adhesion layer 170 does not contain phosphorous. In some embodiments, the stainless steel structures 152 comprises 400 series stainless steel. In some embodiments, the stainless steel structures 152 includes flow fields 42, 44 that are parallel to the sheet surface

[0081] One or more nickel -based strike layers 172, 176 may be applied by electroplating. The first nickel-based strike layers 172 may be deposited at a current density of 2.0 A/cm² using a nickel sulfamate electrolyte bath and nickel anode. After rinsing in deionized water, one or more layers of nickel-phosphorus layer or coating 174 is electroplated using a nickel sulfate based electrolyte with a dissolved phosphorous source. In some embodiments, the nickel electrolyte is a commercially available Umicore NIPHOS® 968 electrolyte system and sulfur- activated nickel anode. In some embodiments, the bipolar plate 160 may comprise one to ten layers of a nickel-phosphorus layer 174 including any number comprised therein may be applied.

[0082] The prepared electrolyte includes about 14 g/L dissolved phosphorus. A current density of 3.7 A/cm² is used to deposit the nickel-phosphorus layers 174. The nickel- phosphorus layers 174 may be about an average of about 2.5 pm in thickness with a phosphorus concentration of about 9.8% is deposited. Further, an edge 186 of the nickel-phosphorous layer 174, outside of an active region 182, is thicker and is about 3.1 pm (shown in FIG. 9). After rinsing in deionized water, a second nickel-based strike layer 176 of about 1.0 pm average thickness is similarly deposited over the nickel-phosphorus layer 174. The bipolar interconnect 160 may be rinsed in deionized water and dried between the different deposition steps. Based on equation (6), the amount of effective phosphorus in the nickel coatings or layers is about 6.9 wt%.

[0083] As shown in FIGS. 9A-9C, the perforated steel structure 156 may include the perforated region 157 and a non-perforated 181. FIG. 9A shows a masking fixture 184 placed on the non-perforated steel structure 156 during electroplating. The nickel-phosphorus layer 174 is applied to a coated area 188 including the perforated region 157 and a surrounding edge region 183 as shown in FIG. 9B.

[0084] An active region 182 is defined as a region above the perforated region 157 in the perforated steel structure 156 that is joined to the porous membrane 154 after brazing as shown in FIG. 9C. Further, a cathode 190 is eventually applied to the active region 182₁ thereby defining the region of the fuel cell 20 that is electrochemically active. The active region 182 is exposed to fuel and is electrochemically active. In some embodiments, the active region 182 is about as 2 mm from the edge 186 of the perforated steel structure 156.

[0085] The majority of the porous membrane 154 is comprised within the active region 182, however, a small portion the porous membrane 154 positioned around the perimeter of the coated area 188 is defined as an inactive edge region 177. In some embodiments, the nickelphosphorus layer 174 may have non-uniform thickness across the coated area 188. For example, the inactive edge region 177 of the nickel-phosphorus layer 174 may be thicker than the active region 182 of the nickel-phosphorus layer 174. It may be advantageous to have a thicker nickel- phosphorus layer 174 at the inactive edge region 177 for adhesion of the porous membrane 154. Alternatively, in other embodiments, the inactive edge region 177 of the nickel-phosphorus layer 174 may be thinner or of the same thickness as the active region 182 of the nickel- phosphorus layer 174.

[0086] In some embodiments, as shown in FIGS. 10A and 10B, after heat treatment, a ratio of the thickness of the inactive edge region 177 of the nickel-phosphorus layer 174 to the active region 182 (illustrated in FIG. 9) may range from about 1.1 to about 2.5, including any value of range comprised therein . Area of the bipolar interconnect 160 in FIG. 10B is about 1.9 times larger than the area of the bipolar interconnect 160 in FIG. 10A. These measurements reflect the coating or layer thickness before brazing. All measurements of thickness were made using a top-down XRF instrument calibrated for nickel coatings or layers on stainless steel.

[0087] FIGS. 11A-11D illustrate the wt% of phosphorous, nickel, and chromium in the active region 182, the inactive edge region 177 the active region 182, and the uncoated region of the perforated steel structure 156 (illustrated in FIG. 9). FIGS. 11A is a graph showing wt% for phosphorous in the inactive edge region 177 and active region 182. FIG. 11B is a graph showing wt% for nickel in the inactive edge region 177 and active region 182. FIG. 11C is a graph showing wt% for chromium in inactive edge region 177 and active region 182. FIG. 11D is a scanning electron microscope (SEM) image of the surface of the stainless steel structure 156.

[0088] As described, each of the stainless steel structures 152, 158, 162, 164 have the braze material 81’ (e.g., BNi-9) applied to their surface to form the nickel-based adhesion layer 170. Each bipolar interconnect 160 was assembled with the perforated stainless steel structures 152, 156 on the top. The nickel-phosphorus layer 174 was positioned on the perforated stainless steel structures 152, 156. Each of the layers 152, 154, 172, 158, 162, 164, was flush with the adjacent layers 152, 154, 172, 158, 162, 164, and the entire bipolar interconnect 160 is heat-treated in vacuum according to AWS A5.8M/A5.8 brazing guidelines for BNi-9, to simultaneously join each component.

[0089] The brazed bipolar interconnect 160 was inspected to gauge quality. The brazed bipolar interconnect 160 was pneumatically tested using methods described in US Patent No. 11404710B2. The testing showed that brazed joints 178 were hermetically sealed using BNi-9. Further, the electroplated nickel-phosphorus layer 172 were bonded to the porous membrane 154 without any defects that would be caused by too much nickel-phosphorous material, or too high of phosphorus content that can permeate the porous membrane 154 and destroy the inherent pores and porosity of the porous membrane 154. Additionally, there were no defects due to an excess of nickel-phosphorous material that would permeate and densify the structure of the porous membrane 154, impacting the permeation through the porous membrane 154. Additionally, there were no defects due to scarcity of nickel-phosphorous that can result in regions in the porous membrane 154 that are not metallurgical adhered to the perforated stainless steel structure 156.

Example 2

[0090] In one embodiment, the nickel-phosphorus layers 174 were applied while the masking fixture 184 masked areas of the perforated stainless steel structures 156 that are not in contact with the porous membrane 154. The masking fixture 184 is positioned in close proximity to the stainless steel structures 156 and is configured to substantially reduce the current density underneath the masking fixture 184. In some embodiments, the masking fixture 184 may be a polypropylene masking fixture 184. Such masking eliminates deposition of electrolytic nickel in the nickel-phosphorous layers 174. The ability to mask the perforated stainless steel structures 156 without forming a hermetic seal is an advantage of electrolytic deposition as compared to electroless deposition of nickel and simplifies and reduces the cost of high- volume manufacturing.

[0091] In one embodiment, nickel-phosphorus layers 174 is about 12 mm more dimensionally than the porous membrane 154 that is subsequently disposed onto the perforated stainless steel structures 156. In some embodiments, the amount of the nickel-phosphorus layers 174 on the surface of the perforated stainless steel structures 156 that is not in contact with the porous membrane 154 may need to be optimized, since nickel-phosphorous alters the surface properties of the stainless steel structures 156. For example, the nickel-phosphorus layers 174 may increase the hardness of the stainless steel structures 156 surface. A hardened stainless steel structures 156 surface increases the likelihood of coating or layer adhesion issues in subsequent deposition processes on the fuel cell 20.

[0092] In some embodiments, a method of electroplating the stainless steel structures 152 with nickel containing phosphorus includes using the masking fixture 184 positioned to be in contact with but not hermetically sealed to the stainless steel structures 156. The method may further include using tools to reduce the thickness of the nickel-phosphorous layer 174 at the edges 177.

[0093] In some embodiments, the porous membrane 154 is more than 12 mm smaller than the first masking fixture 184 in any dimension parallel to the surface of the stainless steel structures 156. The porous membrane 154 is joined to the stainless steel structures 156 using the electroplated stainless steel structures 156, The resulting bonded porous membrane 154 is no more than 12 mm smaller than the nickel-phosphorous 174 in any dimension parallel to the surface of the stainless steel structures 156.

[0094] In some embodiments, the nickel-phosphorous layers 174 may be about 0.1 pm to about 20 pm in thickness, including any value or range comprised therein. For example, the nickel-phosphorous layers 174 may be about 0.1 pm to about 1 pm, about 1 pm to about 5 pm, about 5 pm to about 10 pm, or about 10 pm to about 20 pm in thickness.

[0095] In some embodiments, the porous membrane 154 includes pores of about 0.1 pm to about 50 pm in diameter, including any value or range comprised therein. For example, the porous membrane 154 includes pores of about 0.1 pm to about 1 pm, about 1 pm to about 10 pm, about 10 pm to about 30 pm, about 30 pm to about 60 pm, about 60 pm to about 80 pm, or about 80 pm to about 100 pm in diameter. In some embodiments, the porous membrane 154 includes pores of about 100 m or less in diameter. In some embodiments, the porous membrane 154 has a thickness of about 0.1 mm to about 0.3 mm, including any value or range comprised therein. In one embodiment, the porous membrane 154 comprises a thickness of about 0.25 mm. In one embodiment, the porous membrane 154 comprises a thickness of about 130 pm and a filter rating of about 15 pm to about 50 pm. In some embodiments, the porous membrane 154 includes nickel, iron, chromium, or any combination thereof.

[0096] In some embodiments, as shown in FIG. 2B, the stainless steel structures 156 may include one more vias 159 that is configured to allow fluid transport from the fuel flow fields 44. In some embodiments, one via 159 may be greater than about 0.25 mm. The porous membrane 154 may completely cover the one or more vias 159. In some embodiments, the via 159 may comprise an area is at least 25% of the porous membrane 154 area.

[0097] In some embodiments, the bipolar interconnect or bipolar plate 160 shown in FIG. 8 may comprise in order of adjacency, the stainless steel structures 152, 164, the nickel-based adhesion 170, the stainless steel structures 152, at least one nickel-phosphorous layers 174 containing phosphorous, and a porous membrane 154, in contact with one another. The bipolar interconnect or bipolar plate 160 may be subjected to heat to bond the different layers together. [0098] In some embodiments, the nickel-phosphorous layers 174 may include about 10 wt% to about 15 wt% phosphorus, including any percentage or range comprised therein. In some embodiments, the nickel-phosphorous layers 174 may include about 8 wt% to about 12 wt% phosphorus, including any percentage or range comprised therein.

[0099] In some embodiments, the bipolar interconnect or bipolar plate 160 may include coatings or layers without phosphorous. In some embodiments, the bipolar interconnect or bipolar plate 160 may include at least two nickel-phosphorous layers 174. In some embodiments, the bipolar interconnect or bipolar plate 160 may include at least one coating or layer containing phosphorus.

[0100] In some embodiments, the nickel-phosphorous layers 174 may include a combined amount of phosphorous that ranges from about 4 wt% to about 10 wt%, including any percentage or range comprised therein. In some embodiments, the nickel-phosphorous layers 174 may combine to a thickness between about 2 pm and 5 pm, including any thickness or range comprised therein.

[0101] The current disclosure is directed to a method of joining and/or bonding the porous membrane 154 to the stainless steel structures 156 by electroplating one or more nickelphosphorous layers 174 that contains phosphorous to actively lower the temperature required for metallic joining 955 °C to 1205 °C In some embodiments, during this high temperature joining and/or bonding process, the nickel-phosphorous layers 174 is redistributed due to thermal treatment.

[0102] The following described aspects of the present invention are contemplated and non-limiting:

[0103] A first aspect of the present invention relates to a bipolar plate interconnect. The bipolar plate interconnect comprises a porous membrane metallurgically attached to a first side of a first stainless steel structure, and a nickel-phosphorouslayer positioned between the porous membrane and the stainless steel structure.

[0104] A second aspect of the present invention relates to an intermediate bipolar plate assembly before heat treatment. The intermediate bipolar plate assembly comprises a multilayer nickel-phosphorous structure coated on a first side of a first stainless steel structure, and a porous membrane disposed onto a surface of the nickel-phosphorous structure. The intermediate bipolar plate assembly comprises a nickel-based braze material in contact with a second side of the first stainless steel structure, and a second stainless steel structure in contact with the nickel-based braze material. The multi-layer nickel-phosphorous structure is of non- uniform thickness.

[0105] A third aspect of the present invention relates to a method of coating a component of a bipolar interconnect. The method comprises using a mask fixture positioned in contact with a stainless steel structure to mask areas of the stainless stell structure that is not configured to contact a porous membrane, and electroplating at least one nickel-phosphorus layer on the stainless steel structure. The masking fixture is not hermetically sealed with the stainless steel structure.

[0106] A third aspect of the present invention relates to a solid oxide fuel cell or electrolysis cell bipolar plate interconnect. The a solid oxide fuel cell or electrolysis cell bipolar plate interconnect comprise a porous membrane metallurgically attached to a first side of a first stainless steel structure, and a nickel-phosphorous layer positioned between the porous membrane and the first stainless steel structure. The nickel-phosphorous layer is less than about 10 |im thick and comprises more than 0.2 wt% phosphorus. A second stainless steel structure is attached to a second side of the first stainless steel structure, and a nickel-based layer is positioned between the first and second stainless steel structure. The nickel-based layer is more than 10 m thick and does not include phosphorus. [0107] In the first aspect of the present invention, the bipolar plate interconnect may comprise the nickel-phosphorous layer is of non-uniform thickness. In the first aspect of the present invention, the thickness of the the nickel-phosphorous layer may be less than about 25 pm.

[0108] In the first aspect of the present invention, the nickel-phosphorous layer may consist of more than 0.2 wt% phosphorous. In the first aspect of the present invention, the porous membrane may have a plurality of pores less than about 100 pm in diameter.

[0109] In the first aspect of the present invention, the first stainless steel structure may comprise 400 series stainless steel. In the first aspect of the present invention, the porous membrane may comprise nickel, iron, chromium, or any combination thereof.

[0110] In the first aspect of the present invention, a second side of the first stainless steel structure may be metallurgically attached to a second stainless steel structure. In the first aspect of the present invention, a braze material may be positioned between the second side of the first stainless steel structure and the second stainless steel structure. In the first aspect of the present invention, the braze material may comprise nickel and chromium. In the first aspect of the present invention, braze material may not comprise phosphorus. In the first aspect of the present invention, the braze material may have a thickness of more than about 10 pm. In the first aspect of the present invention, the porous membrane, the nickel-phosphorous layer, the first stainless steel structure, the braze material, and the second stainless steel structure may be joined by heat treatment.

[0111] In the second aspect of the present invention, at least one layer of the multi-layer nickel-phosphorous structure may comprise about 8 wt% to about 12 wt% phosphorus. In the second aspect of the present invention, the multi-layer nickel-phosphorous structure may comprise at least one layer of nickel that does not contain phosphorus. In the second aspect of the present invention, the multi-layer nickel-phosphorous structure may have an average thickness between about 1 pm and about 15 pm.

[0112] In the second aspect of the present invention, the multi-layer nickel-phosphorous structure may comprise an active region and an in-active edge region. In the second aspect of the present invention, the active region may be thicker than the in-active region by a factor that ranges from about about 1.1 to about 2.5.

[0113] In the third aspect of the present invention, the stainless steel structure may be perforated. In the third aspect of the present invention, electroplating a nickel phosphorus coating may comprise depositing the electroplating a nickel phosphorus coating of non-uniform thickness. In the third aspect of the present invention, at least one nickel coating may also be coated onto the stainless steel structure and may be in contact with the nickel phosphorus coating.

[0114] As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the presently described subject matter are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features, numerical ranges of units, measurements, and/or values comprise, consist essentially or, or consist of all the numerical values, units, measurements, and/or ranges including or within those ranges and/or endpoints, whether those numerical values, units, measurements, and/or ranges are explicitly specified in the present disclosure or not.

[0115] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms “first,” “second,” “third” and the like, as used herein do not denote any order or importance, but rather are used to distinguish one element from another. The term “or” is meant to be inclusive and mean either or all of the listed items. In addition, the terms “connected” and “coupled” are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect.

[0116] Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The term “comprising” or “comprises” refers to a composition, compound, formulation, or method that is inclusive and does not exclude additional elements, components, and/or method steps. The term “comprising” also refers to a composition, compound, formulation, or method embodiment of the present disclosure that is inclusive and does not exclude additional elements, components, or method steps.

[0117] The phrase “consisting of’ or “consists of’ refers to a compound, composition, formulation, or method that excludes the presence of any additional elements, components, or method steps. The term “consisting of” also refers to a compound, composition, formulation, or method of the present disclosure that excludes the presence of any additional elements, components, or method steps. [0118] The phrase “consisting essentially of” or “consists essentially of” refers to a composition, compound, formulation, or method that is inclusive of additional elements, components, or method steps that do not materially affect the characteristic(s) of the composition, compound, formulation, or method. The phrase “consisting essentially of’ also refers to a composition, compound, formulation, or method of the present disclosure that is inclusive of additional elements, components, or method steps that do not materially affect the characteristic(s) of the composition, compound, formulation, or method steps.

[0119] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” and “substantially” is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged. Such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.

[0120] As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances, the modified term may sometimes not be appropriate, capable, or suitable.

[0121] It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used individually, together, or in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the subject matter set forth herein without departing from its scope. While the dimensions and types of materials described herein are intended to define the parameters of the disclosed subject matter, they are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the subject matter described herein should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. [0122] This written description uses examples to disclose several embodiments of the subject matter set forth herein, including the best mode, and also to enable a person of ordinary skill in the art to practice the embodiments of disclosed subject matter, including making and using the devices or systems and performing the methods. The patentable scope of the subject matter described herein is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

[0123] While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

WHAT IS CLAIMED IS:

1. A bipolar plate interconnect comprising: a porous membrane metallurgic ally attached to a first side of a first stainless steel structure, and a nickel-phosphorouslayer positioned between the porous membrane and the stainless steel structure.

2. The bipolar plate of claim 1, wherein the nickel-phosphorous layer is of non-uniform thickness.

3. The bipolar plate interconnect of claim 1, wherein the nickel-phosphorous layer is less than about 25 pm.

4. The bipolar plate interconnect of claim 1 , wherein the nickel-phosphorous layer consists of more than 0.2 wt% phosphorous.

5. The bipolar plate interconnect of claim 1, wherein the porous membrane has a plurality of pores less than about 100 pm in diameter.

6. The bipolar plate interconnect of claim 1 , wherein the porous membrane has a thickness of less than about 0.3 mm.

7. The bipolar plate interconnect of claim 1, wherein the first stainless steel structure comprises 400 series stainless steel.

8. The bipolar plate interconnect of claim 1, wherein the porous membrane comprises nickel, iron, chromium, or any combination thereof.

9. The bipolar plate interconnect of claim 1, wherein a second side of the first stainless steel structure is metallurgically attached to a second stainless steel structure.

10. The bipolar plate interconnect of claim 9, wherein a braze material is positioned between the second side of the first stainless steel structure and the second stainless steel structure.

11. The bipolar plate interconnect of claim 10, wherein a braze material comprises nickel and chromium.

12. The bipolar plate interconnect of claim 10, wherein a braze material does not comprise phosphorus.

13. The bipolar plate interconnect of claim 10, wherein a braze material has a thickness of more than about 10 |im.

14. The bipolar plate interconnect of claim 10, wherein the porous membrane, the nickel-phosphorous layer , the first stainless steel structure, the braze material, and the second stainless steel structure are joined by heat treatment.

15. An intermediate bipolar plate assembly before heat treatment comprising: a multi-layer nickel-phosphorous structure coated on a first side of a first stainless steel structure, wherein a porous membrane is disposed onto a surface of the nickelphosphorous structure, a nickel-based braze material in contact with a second side of the first stainless steel structure, and a second stainless steel structure in contact with the nickel-based braze material, wherein the multi-layer nickel-phosphorous structure is of non-uniform thickness.

16. The assembly of claim 15, wherein at least one layer of the multi-layer nickelphosphorous structure comprises about 8 wt% to about 12 wt% phosphorus.

17. The assembly of claim 16, wherein the multi-layer nickel-phosphorous structure also comprises at least one layer of nickel that does not contain phosphorus.

18. The assembly of claim 15, wherein the multi-layer nickel-phosphorous structure has an average thickness between about 1 pm and about 15 pm.

19. The assembly of claim 18, wherein the multi-layer nickel-phosphorous structure comprises an active region and an in-active edge region, and wherein the active region is thicker than the in-active region by a factor that ranges from about about 1.1 to about 2.5.

20. A method of coating a component of a bipolar interconnect comprising: using a mask fixture positioned in contact with a stainless steel structure to mask areas of the stainless stell structure that is not configured to contact a porous membrane, and electroplating at least one nickel-phosphorus layer on the stainless steel structure, wherein the masking fixture is not hermetically sealed with the stainless steel structure.

21. The method of claim 20, wherein the stainless steel structure is perforated.

22. The method of claim 19, wherein electroplating a nickel phosphorus coating comprises depositing the electroplating a nickel phosphorus coating of non-uniform thickness.

23. The method of claim 19, wherein at least one nickel coating is also coated onto the stainless steel structure and is in contact with the nickel phosphorus coating.

24. A solid oxide fuel cell or electrolysis cell bipolar plate interconnect comprising: a porous membrane metallurgic ally attached to a first side of a first stainless steel structure, and a nickel-phosphorous layer positioned between the porous membrane and the first stainless steel structure, wherein the nickel-phosphorous layer is less than about 10 pm thick and comprises more than 0.2 wt% phosphorus, a second stainless steel structure attached to a second side of the first stainless steel structure, and a nickel-based layer positioned between the first and second stainless steel structure, wherein the nickel-based layer is more than 10 pm thick and does not include phosphorus.