GB2614450A

GB2614450A - Coatings for aluminum-based bipolar plates

Info

Publication number: GB2614450A
Application number: GB2301023.4A
Authority: GB
Inventors: Nikitin Denis; Belousov Viktor; Shubenkov Sergei
Original assignee: Zeroavia Ltd
Current assignee: Zeroavia Ltd
Priority date: 2023-01-24
Filing date: 2023-01-24
Publication date: 2023-07-05
Also published as: GB202301023D0

Abstract

Electrically conductive, corrosion resistant element comprising conductive substrate coated with; a nickel containing layer including a metal selected from groups 7, 11 or 15 of the periodic table, and phosphorous; a layer containing a precious or noble metal formed on the nickel layer and; at least one polymer composite layer comprising a high Tg corrosion resistant polymer material containing conductive carbon particles on the noble/precious metal layer. The nickel layer may contain rhenium and/or tungsten. The carbon particles may be carbon black, graphitized carbon, amorphous carbon, nanotubes, graphene or mixtures thereof. The noble/precious metal may be gold, silver, platinum, palladium, iridium, osmium, rhodium or ruthenium. The polymer may be polyvinylidene fluoride, polyphenylsulfone or polyethersulfone or mixture thereof. Also included are claims to a fuel cell, and a fuel cell powered vehicle, preferably an aircraft, wherein the cell comprises a biopolar plate using the above material.

Description

COATINGS FOR ALUMINUM-BASED BIPOLAR PLATES

FIELD OF THE DISCLOSURE

[0001] The present disclosure relates to corrosion-resistant, electrically-conductive elements and methods for making the same. The disclosure has particular utility to the creation of corrosion-resistant, electrically-conductive elements for use as bipolar plates in Proton Exchange Membrane (PEM) fuel cells including in particular High Temperature Proton Exchange Membrane (HT-PEM) fuel cells for use in fuel cell powered vehicles, including aircraft and will be described in connection with said utility, although other utilities are contemplated.

BACKGROUND AND SUMMARY

[0002] This section provides background information related to the present disclosure which is not necessarily prior art. This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all its features.

[0003] A fuel cell is an electrochemical device that converts chemical energy produced by a reaction directly into electrical energy. A typical hydrogen fuel cell includes a proton exchange membrane (PEM), that permits only protons to pass between an anode and a cathode of the fuel cell. At the anode, diatomic hydrogen (a fuel) is reacted to produce hydrogen protons that pass through the PEM. The electrons produced by this reaction travel through circuitry that is external to the fuel cell to form an electrical current. At the cathode, oxygen is reduced and reacts with the hydrogen protons to form water. The anodic and cathodic reactions are described by the following equations: H2 4 2W-F2e-at the anode of the cell, and Equation I 02+41-r-F4e-2H20 at the cathode of the cell. Equation 2 [0004] There are two types of PEM fuel cells, so-called Low Temperature Proton Exchange Membrane fuel cells (LT-PEM) fuel cells which must be operated with hydrogen of high purity, typically more than about 99.9%, and High Temperature Proton Exchange Membrane fuel cells (HT-PEM) fuel cells which are far less sensitive to impurities and may be operated with reformate gas with hydrogen concentrations of 50-75%. In contrast to LT-PEM fuel cells which are sensitive to carbon monoxide concentrations of as little as several parts per million, HT-PEM fuel cells may be operated at hydrogen monoxide concentrations of up to 3 vol. %. Thus, HT-PEM fuel cells offer advantages over LT-PEM fuel cells in terms of fuel costs. However, HT-PEM fuel cells typically are operated at temperatures of 150 to 180 °C, which creates thermal management challenges, and typically employ highly corrosive phosphoric acid as an electrolyte, which traditionally has limited the materials that can be used for forming the bipolar plates elements for HT-PEM fuel cells to high temperature and acid resistant materials such as polybenzimidazole (PBI). PBI-based PEMs must be loaded or doped with high amounts of phosphoric acid to function efficiently. However, PBI-based PEMs can only be doped in phosphoric acid at relatively low loadings before mechanical properties start to significantly diminish. Furthermore the methods used to load PBI-based PEMs membranes with high amounts of phosphoric acid are relatively tedious, and include several steps which adds to costs. However, HT-PEM fuel cells offer significant advantages over LT-PEM fuel cells in that their waste heat is a higher temperature and thus may be rejected with less cooling drag per unit of energy. Thus, there is a long felt need to make practical HT-PEM fuel cells with long lifetimes despite the adverse temperatures and acidic electrolyte.

[0005] Metals such as copper and nickel and their alloys as well as stainless steel have been proposed for use as materials for bipolar plates for HT-PEM fuel cells due to their mechanical properties, high electrical conductivity, low gas permeability high temperature resistance and relatively low cost of manufacture. However, such metals have problems in terms of the electrochemical processes that take place at their surface including (1) formation of nonconductive surface oxides (corrosion) in HT-PEM fuel cell environments resulting in a high contact resistance which eventually lowers the efficiency of the PEM fuel cell system; and (2) the dissolution of metal cations from the metals and metal alloys and their subsequent contamination of the membrane electrode assembly (e.g., anode, separator and cathode assembly) which eventually may lead to system failure.

[0006] To solve the corrosion problem, a prior practice has been to coat the surface of metal bipolar plates with a material that forms a barrier to corrosion and at the same time will not diminish the advantageous properties of the metallic bipolar plate. Corrosion barrier coatings that have been used on metal plate surfaces include nitrides such as chromium nitride (CrN) and titanium nitride (TiN). However, high vacuum conditions and high temperatures (ca. 900° C) required to ensure the formation of non-brittle phases of CrN needed for this approach limit its scale and therefore its cost-efficient manufacturability. In addition, the presence of metal ions from the barrier layer creates a potential for the diffusive contamination through the barrier layer into the membrane electrode assembly.

[0007] Light weight metals such as aluminum, magnesium and titanium and their alloys also have been proposed for use in forming bipolar plates for HT-PEM fuel cells particularly for use in hydrogen fuel cell powered aircraft, where weight is a significant factor. Aluminum, magnesium, and titanium and their alloys are strong, lightweight materials and exhibit high heat conductivity making them excellent materials for heat removal. Such lightweight and thermally-conductive materials enable effective heat removal from the fuel cell stack and increased power output per kg. However, aluminum, magnesium and titanium and their alloys readily dissolve in phosphoric acid.

[0008] Previous attempts to create aluminum, magnesium and titanium based bipolar plates have focused on metal coatings or plating to passivate or protect the metal surfaces. However, these metallic coatings (such as Au, Ti nitrides, Ni, Sn, Re and oxides thereof) require a thick layer to prevent corrosion, resulting in expensive and heavy weight bipolar plates. The present disclosure in one aspect provides aluminum, magnesium or titanium-based PEM plates with thin, lightweight highly protective, electrically conductive layers to improve the chemical compatibility of aluminum, magnesium and titanium bipolar plates within a IT-PEM operating environment.

[0009] More particularly the present disclosure creates a bipolar plate that is lightweight, conductive, and robust to the phosphoric acid corrosive environment in IT-PEM fuel cells, which increases the operational lifetime of the fuel cell system, and reduces system weight and volume resulting in a more dense power system. Indeed, HT-PEM fuel cells built using bipolar plates in accordance with the present disclosure as will be described below achieve power densities of up to 3-4 kW/kg. Improved contact between layers in the fuel cell stack also maintains efficient and consistent operation.

[00010] In one aspect of the disclosure there is provided an electrically conductive, corrosion-resistant element for use as a bipolar plate in a HT-PEM fuel cell comprising an electrically conductive metal substrate coated with a corrosion-resistant nickel-containing layer including a metal selected from Group 7, Group 11 or Group 15 of the Periodic Table, and phosphorous; a layer containing an electrically conductive corrosion-resistant noble metal or precious metal formed on the nickel-containing layer; and at least one polymer composite material layer comprising a high Tg and chemically resistant polymeric material containing conductive carbon particles on the noble metal or precious metal containing layer.

[00011] In one aspect one electrically conductive, corrosion-resistant nickel-containing layer includes rhenium. Rhenium and its oxides which have demonstrated corrosion resistance to phosphoric acid, and improved electrical conductivity. In other embodiments, plated nickel alloys can be doped with rhenium to improve corrosion resistance. Phosphorus is also a critical component for improving the material corrosion resistance of nickel alloys, and can be combined by electroless deposition with other metals including rhenium or tungsten to create a corrosion-resistant coating.

[00012] In still another aspect of the electrically conductive, corrosion-resistant element the electrically conductive corrosion-resistant metal noble metal or precious layer comprises a metal selected from the group consisting of gold, silver, platinum, palladium, iridium, osmium, rhodium, ruthenium, tungsten, titanium, zirconium, vanadium, niobium, tantalum and alloys and mixtures thereof.

[00013] In another aspect of the electrically conductive, corrosion-resistant element the conductive carbon particles in the high Tg and chemically resistant layer are selected from the group consisting of carbon black, graphitized carbon particles, amorphous carbon particles, carbon nanotubes, and graphene sheets, and mixtures thereof [oakum In still yet another aspect of the electrically conductive, corrosion-resistant element the polymeric composite material layer comprises one or more layers including a high Tg and chemically resistant polymeric material selected from the group consisting of pol y vinylidene tl uori de, a pol ysulfone polymer selected of the group consisting of polyphenylsulfone, polyethersulfone and mixtures thereof, a polyaniline, a polythiophene, a poly(pyrrole), a polybenzimidazole, a polyethersulfone, a fluorinated ethyl-polypropylene, a perfluorallwxy, and mixtures thereof.

[00015] In a further aspect of the electrically conductive, corrosion-resistant element the polymeric composite material layer(s) comprise multiple layers including a layer formed of polyvinylidene fluoride containing carbon nanotubes and/or carbon black or a mixture thereof, and a layer formed of polyphenylsulfone or polyethersulfone or a mixture thereof, and carbon nanotubes and/or carbon black and mixtures thereof.

[00016] In a further aspect of the electrically conductive, corrosion-resistant element the conductive carbon particles comprise carbon black particles comprising up to 25 mass % of the polymeric composite material layer(s), and/or carbon nanotubes comprising up to 20 mass % of the polymeric composite material layer, and mixtures thereof.

[00017] In a further aspect of the electrically conductive, corrosion-resistant element the metal substrate comprises a metal selected from the group consisting of aluminum, magnesium, titanium and an alloy thereof.

[00018] The present disclosure also provides a HT-PEM fuel cell, comprising: a bipolar plate, wherein the bipolar pplate comprises an electrically conductive, corrosion-resistant element as described above, and including an electrically conductive metal substrate coated with a corrosion-resistant nickel-containing layer including a metal selected from Group 7, Group 11 or Group 15 of the Periodic Table, and phosphorous; a layer containing an electrically conductive corrosion-resistant noble metal or precious metal formed on the nickel-containing layer; and at least one polymer composite material layer comprising a high Tg and corrosion-resistant polymeric material containing conductive carbon particles on the noble metal or precious metal containing layer.

rooms] In yet a further aspect, the fuel cell is a high temperature proton exchange membrane (HT-PEM) hydrogen fuel cell including a phosphoric acid electrolyte.

[00020] The present disclosure also provides a fuel cell powered vehicle comprising a fuel cell as above described.

[00021] In yet another aspect of the disclosure, the metal substrate comprises aluminum, magnesium or titanium and an alloy thereof, the vehicle comprises an aircraft, and the fuel cell comprises a HT-PEM hydrogen fuel cell including a phosphoric acid electrolyte.

[00022] According to aspect A of the present invention there is provided an electrically conductive, corrosion-resistant element comprising: an electrically conductive substrate coated with a corrosion-resistant nickel-containing layer including a metal selected from Group 7, Group 11 or Group 15 of the Periodic Table, and phosphorous; a layer containing a noble metal or precious metal formed on the nickel-containing layer; and at least one polymer composite material layer comprising a high Tg corrosion-resistant polymeric material containing conductive carbon particles on the noble metal or precious metal containing layer.

[00023] Preferably the nickel-containing layer includes rhenium.

[000241 Preferably the nickel-containing layer also includes tungsten.

[00025] Preferably the conductive carbon particles are selected from the group consisting of carbon black, graphitized carbon particles, amorphous carbon particles, carbon nanotubes, graphene and mixtures thereof.

[000261 Preferably the noble metal or precious metal containing layer comprises a metal selected from the group consisting of gold, silver, platinum, palladium, iridium, osmium, rhodium and ruthenium.

[000271 Preferably the at least one polymeric composite material layer comprises one or more layers including a polymeric material selected from the group consisting of polyvinylidene fluoride, and a polysulfone polymer selected of the group consisting of polyphenylsulfone, polyethersulfone, and a mixture thereof.

[00028] Preferably the polymeric composite material layer(s) comprise a first layer formed of polyvinylidene fluoride containing carbon nanotubes and carbon black, and a second polymeric composite material containing polyphenylsulfone or polyethersulfone or a mixture thereof, carbon nanotubes and carbon black.

[09029] Preferably the conductive carbon particles comprise carbon black, carbon nanotubes and mixtures thereof [09030] Preferably the polymer composite layer(s) contain up to 25% by mass carbon black and up to 20% by mass carbon nanotubes.

[000311 Preferably the electrically conductive substrate comprises a metal selected from the group consisting of aluminum, magnesium, titanium and an alloy thereof.

[00032] Preferably the nickel-containing layer also contains a metal selected from the group consisting of gold, tungsten, titanium, zirconium, vanadium, niobium and tantalum, and alloys thereof.

[000331 Preferably the polymeric composite material layer also includes one or a mixture of conductive polymers and/or high Tg and chemically resistant polymers.

1-000341 Preferably the conductive polymers are selected from the group consisting of a pol ythiophene, poly(3,4-eth ylenedi ox ythiophene) (PEDOT), a poly(pyrrole), a polyphenylsulfone (PPSU), and a polyaniline (PAN1).

1-000351 Preferably the high Tg, chemically resistant polymer is selected from the group consisting of polybenzimidazole (PBI), polyether ether ketone (PEEK), a thermoplastic polyimide (TPI), a polyethersulfone (PESU), a fluorinated ethylene-propylene (FEY). and a pert] noroall« y (PFA).

[00036] Preferably the electrically conductive substrate comprises a metal selected from the group consisting of copper, nickel and stainless steel.

[00037] According to aspect B of the present invention there is provided a fuel cell, comprising: a bipolar plate, wherein the bipolar plate comprises the electrically conductive, corrosion-resistant element as set out in aspect A of the present invention.

[00038] Preferably the fuel cell is a high temperature proton exchange membrane (HT-PEM) hydrogen fuel cell including a phosphoric acid electrolyte.

1-000391 According to aspect C of the present invention there is provided a fuel cell powered vehicle comprising a fuel cell as set out in aspect B of the present invention.

[00040] Preferably the vehicle comprises a fuel cell powered aircraft.

[000411 Preferably the fuel cell comprises a high temperature proton exchange membrane (HT-PEM) hydrogen fuel cell including a phosphoric acid electrolyte.

1-000421 Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for the purposes of illustration only and are not intended to limit the scope of the present disclosure.

Brief Description of the Drawings

[09043] Further features and advantages of the disclosure will be seen in the following detailed description, taken in conjunction with the accompanying drawings. The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations and are not intended to limit the scope of the present disclosure.

Fig. 1 is a cross-sectional view of a corrosion-resistant electrically conductive element in accordance with one embodiment of the instant disclosure; Fig. 2 is a flow diagram illustrating a process for producing the corrosion-resistant electrically conductive element shown in Fig. I; Fig. 3 is cross sectional view similar to Fig. 1, of another embodiment of corrosion-resistant electrically conductive element in accordance with the present disclosure; Fig. 4 is a flow diagram similar to Fig. 2, illustrating a process for producing the corrosion-resistant electrically conductive element shown in Fig. 3; Fig. 5 is a cross-sectional view of a HT-PEM hydrogen fuel cell in accordance with the instant disclosure; and Fig. 6 is a schematic view of a HT-PEM hydrogen fuel cell powered aircraft in accordance with the instant disclosure.

Detailed Description

[00044] Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[00045] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an,-and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," -including," and "having," are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

[00046] When an element or layer is referred to as being on, 'engaged to," "connected to," or coupled to" another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., -between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

[00047] Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

[00048] Spatially relative terms, such as "inner, 'outer," "beneath," "below," "lower," -above," "upper,-and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below-or "beneath-other elements or features would then be oriented "above" the other elements or features. Thus, the example term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[000491 When an element or layer is referred to as being -corrosion-resistant' or "chemically resistant", it is with reference to the electrolyte used in the fuel cell. In the case of a HT-PEM fuel cell, the electrolyte may be phosphoric acid.

r000501 When a polymer is referred to as having a high glass transition temperature (Tg) it is in reference to the working temperature of a HT-PEM fuel cell, plus a margin of safety. For the purposes of the instant disclosure, a polymer having a Tg of 170-230 °C shall be considered as having a high glass transition temperature (Tg).

[00051] Referring to Figs. 1 and 2, an electrically conductive metal plate 10 is formed (e.g., stamped, rolled, or etched) to create a bare metal structure suitable for forming a bipolar plate in a High Temperature Proton Exchange Membrane (HT-PEM) hydrogen fuel cell. Metal plate 10 is formed of lightweight, conductive metal (e.g., aluminum, magnesium, or titanium) plate and is coated with a corrosion-resistant, nickel-containing metal layer 12 such as nickel/rhenium/phosphorus (NiReP) by electroless deposition or electroplating in a first plating step 30. A thin layer 14 of noble metal or a precious metal such as gold is then deposited over the NiReP layer 12 by electroless or electroplating in a second plating step 32. One or more layers of a corrosion-resistant high Tg polymer composite material 16A, 16B containing electrically conductive carbon particles, preferably carbon black 18 and/or carbon nanotubes 20 is then applied over the precious metal layer 14 in coating steps to create a composite aluminum bipolar plate 60.

[00052] Carbon black and carbon nanotubes are available commercially in a variety of sizes from a variety of sources. Commercially available carbon black may have a particle size of range of from about 20 nm to 350 nm or more. Preferred carbon black particle size range when used in accordance with the present disclosure is 40 to 60 nm. Commercially available carbon nanotubes typically have a diameter of about 1-3 nm, and a length that is much higher than its diameter, typically several pm. Preferred carbon nanotubes when used in accordance with the present disclosure have a length equal to or more than 5 microns and particle size distributions of D10 (1.2-1.45 nm), D50 (1.6-1.8nm), and D90 (1.9-2.2 nm) with an aspect ratio similar to an elongated tube.

[000531 Carbon black and carbon nanotubes may be incorporated into the PVDF and PSU layers at approximately the same or different ratio. However, the ratio of nanotubes to carbon black affects conductivity. Accordingly, the carbon black is loaded at a range of up to 25% by mass and nanotubes is loaded at a range of up to 20% by mass. Care should be taken to avoid adding more than about 25% by mass carbon black, since too much carbon black can serve as a bridge for phosphoric acid leading to degradation of the coating layer.

[00054] Preferably multiple layers I 6A, I 6B... of the corrosion-resistant high Tg polymer composite material are applied to the corrosion-resistant metal coating 14. By way of example, one layer I 6A may be poly vinylidene fluoride (PVDF) polymer material containing carbon black and graphene nanoparticles. Another layer 16B... may be a PSU polymer material (e.g., polyphenylsulfone (PPSU) or polyethersulfone (PESU)) containing carbon black and carbon nanotubes. Each polymer composite material layer I 6A, I 613... may he applied in a layer-onlayer technique using spray coating. Spray coating gives more consistent coverage of polymeric layers. A number of high Tg polymeric composite material layers may be applied. The high Tg polymeric layers I GA, 16B... also may be applied using dipping, brush painting, blade coating, thermal spraying, plasma deposition, flow coating, spin coating, sol-gel, dip coating, powder coating, or surface grafting techniques.

r000551 A representative electrically conductive corrosion-resistant element in accordance with the present disclosure comprises a 200 pm thick aluminum plate substrate 12, having a 5 pm thick electrodeposited nickel/rhenium/phosphorous metallic (NiReP) coating layer 14, on which is electroless coated a 5 nm thick layer of gold. A first 3 pm thick polymer composite layer, formed of polyvinylidene fluoride (PVDF) containing a mixture of carbon black particles and carbon nanotubes, is spray coated over the gold layer. A second 5 pm thick polymer composite layer formed of polyphenylsulfone (PPSU) or polyethersultbne (PESU) containing a mixture of carbon nanotubes and carbon black, is spray coated over the PVDF-layer.

[00056] Polymers from the PSU family improve corrosion resistance and lower contact resistance at elevated operating temperatures. Preferred are polyphenylsulfone (PPSU) and polyethersulfone (PESU). In other embodiments, only one PSU polymer material may be used. In another embodiment two or more layers may be combined, e.g., to provide a blended PPSUPVDF composite.

[00057] Referring to Figs. 3 and 4, in accordance with another embodiment a conductive, a lightweight metal sheet 40 formed of aluminum, magnesium or titanium is stamped or etched in a forming step 50 to create a contoured bipolar metal structure 42 having one or more channels 60.

[00058] The contoured metal plate structure 42 is then coated with a NiReP layer 44 in a first plating step 52. As before the nickel containing layer may be applied by electroplating.

[00059] A thin layer (5nm) of gold 46 is applied to the surface of the nickel containing alloy layer using electroless plating or electroplating in a second plating step 54. The electroplated layer coating the alloyed corrosion-resistant structure is selected for improved conductivity, corrosion resistance as well as inert properties. One or preferably multiple layers 48A, 48B... of polymeric composite containing carbon black particles 56 and graphite nanotubes 58 are applied in a coating step or steps 56A, 56B... as before, to create a contoured composite aluminum bipolar plate 80.

[000601 As before, the nickel layer and the corrosion-resistant metal layer are applied using electroless plating or electrolytic plating. in other embodiments metal coatings may be applied using chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition, low pressure CVD, sputtering, chemical bath deposition, laser beam evaporation, sol-gel deposition, molecular beam epitaxy, vacuum thermal evaporation, or spray pyrolysis.

[00061] Referring to Fig. 5, composite aluminum bipolar plates 80 of Fig. 3 are incorporated as a bipolar plate in a high temperature PEM fuel cell 90 equipped to run on hydrogen gas.

[00062] Fig. 6 illustrates an aircraft 70 including two electric motors 72A, 72B which are weighted by two parallel HT-PEM hydrogen fuel cells 60A, 60B in accordance with the present disclosure.

[00063] Various changes may be made in the above disclosure. For example, in other embodiments multiple layers of high Tg polymer composite material layers may be arranged in a different order, or combined and stacked to access unique es example, one layer of PPSU and one layer of PESU may be coated on a layer of PVDF to create a three layered polymer composite structure. Alternatively, two or more layers of PPSU composite may be applied to the PVDF layer.

[000641 Also, the high Tg polymer composite material layers may be applied for different functional purposes. For example, the PVDF layer may be incorporated for its barrier and adhesion promotion properties. In yet another embodiment, alternative methods for improved adhesion may be used to improve contact of the PSU layer with the nickel-containing corrosion-resistant layer such as plasma treatment, application of adhesion promoter compounds, or use of an alternative polymer material. In yet another embodiment the PSU layer is incorporated for its high glass transition temperature and improved chemical resistance to corrosion. The molecular weight of PSU influences the glass transition temperature (Tg) of the PSU layer. Thus, the PSU materials may be selected to meet the appropriate operating conditions of the HT-PEM fuel cell.

[09065] In yet other embodiments, the polymer materials may be blended to take advantage of properties exhibited by each material. For example, a polymer with good metal adhesion properties such as PVDF or epoxy-based coatings may be blended with highly chemically resistant materials such as polyether ether ketone (PEEK) or PPSU.

1-000661 In other embodiments, conductive structures such as aluminum or carbon structures, graphene sheets, multiwalled carbon nanotubes, graphitized carbon particles, amorphous carbon particles, metal oxides, metallic particles, coated metal structures, wires or mats also may be melt embedded or blended in the high Tg polymer composite layer (e.g. polysulfone) and then adhered to the PVDF layer to improve electrical connectivity through the composite high-temperature polymer coating layers.

[09067] Additionally, the high Tg polymer composite layer may be applied to a composite plate structure composed of the PVDF or PS U matrix filled with conductive metal or carbon particles, creating an entirely polymer-based and corrosion-resistant bipolar plate structure.

[09068] In yet other embodiments, distinct PVDF and PSU layers may be applied at different thicknesses, composite filler ratios, or omitted to achieve different properties. Also, thickness, chemical composition, glass transition temperature (Tg), conductivity, etc. may be adjusted by changing the molecular weight of components in the composite blend. The molecular weight of PSU in the blend may be adjusted to achieve a Tg range of 170-230°C while maintaining low contact resistance.

[00069] The polymeric layer improves the corrosion resistance and adds barrier properties to the bipolar plate. In other embodiments, conductive polymers also may be blended into the composite material to affect the electronic properties of the bipolar plate. Other high Tg conductive polymers that can serve this purpose include polyanilines, polythiophenes, poly(3,4-ethylenedioxythiophene) (PEDOT). poly(pyrr 1 polyphenylsulfone (PPSU), and polyaniline (PAN!). In other embodiments high Tg and chemically resistant polymers such as polybenzimidazole (PBI), polyether ether ketone (PEEK), Thermoplastic polyimide (TPI), polyethersulfone (PESU), Fluorinated ethylene-propylene (PEP), perfluoroallcoxy (PFA), also may be used to create composite structural layers.

[00070] While presented here for use in HT-PETVI fuel cell systems, this metal and polymer composite material has other potential applications, including battery manufacturing, electrolyzers, and electronics circuit board and device manufacturing. Also, where weight is not as much a consideration such as in the case of terrestrial and water vehicles, or in the case of stationary HT-PEM fuel cell powered installations, the electrically conductive substrate may be formed of other, higher density metals such as copper, nickel or stainless steel.

[00071] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. Various changes and advantages may be made in the above disclosure without departing from the spirit and scope thereof.

Claims

What is Claimed: An electrically conductive, corrosion-resistant element comprising: an electrically conductive substrate coated with a corrosion-resistant nickel-containing layer including a metal selected from Group 7, Group 11 or Group 15 of the Periodic Table, and phosphorous; a layer containing a noble metal or precious metal formed on the nickel-containing layer; and at least one polymer composite material layer comprising a high Tg corrosion-resistant polymeric material containing conductive carbon particles on the noble metal or precious metal containing layer.
2. The electrically conductive, corrosion-resistant element of claim 1, wherein the nickel-containing layer includes rhenium.
3. The electrically conductive, corrosion-resistant element of claim 1 or claim 2, wherein the nickel-containing layer also includes tungsten.
4. The electrically conductive, corrosion-resistant element of any preceding claim, wherein the conductive carbon particles are selected from the group consisting of carbon black, graphitized carbon particles, amorphous carbon particles, carbon nanotubes, graphene and mixtures thereof.
5. The electrically conductive, corrosion-resistant element of any preceding claim, wherein the noble metal or precious metal containing layer comprises a metal selected from the group consisting of gold, silver, platinum, palladium, iridium, osmium, rhodium and ruthenium.
6. The electrically conductive, corrosion-resistant element of any preceding claim, wherein the at least one polymeric composite material layer comprises one or more layers including a polymeric material selected from the group consisting of polyvinylidene fluoride, and a polysulfone polymer selected of the group consisting of polyphenylsultene, polyethersultbne, and a mixture thereof
7. The electrically conductive, corrosion-resistant element of any preceding claim, wherein the polymeric composite material layer(s) comprise a first layer formed of polyvinylidene fluoride containing carbon nanotubes and carbon black, and a second polymeric composite material containing polyphenylsulfone or polyethersulfone or a mixture thereof, carbon nanotubes and carbon black.
8. The electrically conductive, corrosion-resistant element of any preceding claim, wherein the conductive carbon particles comprise carbon black, carbon nanotubes and mixtures thereof.
9. The electrically conductive, corrosion-resistant element of claim 8, wherein the polymer composite layer(s) contain up to 25% by mass carbon black and up to 20% by mass carbon nanotubes.
10. The electrically conductive, corrosion-resistant element of any preceding claim, wherein the electrically conductive substrate comprises a metal selected from the group consisting of aluminum, magnesium, titanium and an alloy thereof.Ii.
The electrically conductive, corrosion-resistant element of any preceding claim, wherein the nickel-containing layer also contains a metal selected from the group consisting of gold, tungsten, titanium, zirconium, vanadium, niobium and tantalum, and alloys thereof.
12. The electrically conductive, corrosion-resistant element of any preceding claim, wherein the polymeric composite material layer also includes one or a mixture of conductive polymers and/or high Tg and chemically resistant polymers.
13. The electrically conductive, corrosion-resistant element of claim 12, wherein the conductive polymers are selected from the group consisting of a polythiophene, poly(3,4-ethylenedioxythiophene) (PEDOT), a poly(pyrrole), a polyphenylsulfone (PPSU), and a polyaniline (PANT).
14. The electrically conductive corrosion-resistant element of claim 12 or claim 13, wherein the high Tg, chemically resistant polymer is selected from the group consisting of polybenzimidazole (PBD, polyether ether ketone (PEEK), a thermoplastic polyimide (TPI), a polyethersulfone (PESU), a fluorinated ethylene-propylene (PEP), and a perfluorealkoxy (PFA),
15. The electrically conductive corrosion-resistant element of any preceding claim, wherein the electrically conductive substrate comprises a metal selected from the group consisting of copper, nickel and stainless steel.
16. A fuel cell, comprising: a bipolar plate, wherein the bipolar plate comprises the electrically conductive, corrosion-resistant element as claimed in any of claims 1 to 15.
17. The fuel cell of claim 16, wherein the fuel cell is a high temperature proton exchange membrane (HT-PEM) hydrogen fuel cell including a phosphoric acid electrolyte.
18. A fuel cell powered vehicle comprising a fuel cell as claimed in claim 16 or claim 17.
19. The fuel cell powered vehicle as claimed in claim 18, wherein the vehicle comprises a fuel cell powered aircraft.
20. The fuel cell powered aircraft as claimed in claim 19, wherein the fuel cell comprises a high temperature proton exchange membrane (HT-PEM) hydrogen fuel cell including a phosphoric acid electrolyte.