High temperature metal composite bipolar plates

Abstract

Bipolar plate may be formed of two layers made of different materials, a metal base layer 62 and a polymeric composite layer 64. The two layers may be electrically connected to one another, with chann

Description

15 05 25 FIELD OF THE DISCLOSURE

[0001] The present disclosure relates to fuel cells and methods for making the same. The disclosure has particular utility in the creation of high temperature metal composite bipolar plates (BPPs) for 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 such utility, although other utilities are contemplated including, by way of example, formation of batteries and other electronic devices. 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 (FC) 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 2H++2e’ at the anode of the cell, and Equation 1 O2+4H++4e‘ ->2H2O at the cathode of the cell. Equation 2 15 05 25

[0004] Proton Exchange Membrane (PEM) fuel cells are made from several layers of different materials. The heart of a PEM fuel cell is the membrane electrode assembly (MEA), which includes a PEM membrane, catalyst layers, and gas diffusion layers (GDLs).

[0005] Fig. la is a perspective view and Fig. lb is an exploded view which together illustrate a conventional PEM fuel cell 10. Fuel cell 10 includes a Proton Exchange Membrane (PEM) 12, typically formed in a specially treated polymer material that conducts only positive charged ions, and blocks electrodes.

[0006] Catalyst layers are provided on both sides of the PEM 12 - an anode catalyst layer 14 on one side, and a cathode catalyst layer 16 on the other. Gas Diffusion Layers (GDLs) 18, 20 sit to the outside of the catalyst layers 14, 16 and facilitate transport of reactants into the catalyst layers, as well as removal of the product water. The PEM 12, catalyst layers 14, 16 and the GDLs 18, 20 together make up the so-called Membrane Electrode Assembly (MEA) 22. The MEA 22 is the part of the fuel cell where power is produced.

[0007] Each individual MEA 22 produces less than one volt under typical operating condition, but most applications require higher voltages. Therefore, multiple MEAs 22 usually are connected in series by stacking them on top of one other to provide a usable output voltage. Each cell in the stack is sandwiched between two bipolar plates (BPPs) 24, 26 to separate it from neighboring cells. These plates 24, 26, which may be made of metal, carbon, or composites, provide electrical conduction between cells, as well as providing physical strength to the stack. The surfaces of the plates 24, 26 typically contain channels 28, 30 machined or stamped into the plates 24,26 to allow gases to flow over the MEA 22. Such flow channels are provided to distribute reactants over an active area of the fuel cell thereby maximizing performance and stability. Additional channels (not shown) inside each plate 24,26 may be used to circulate a liquid coolant. 15 05 25

[0008] Each MEA 22 in a fuel cell stack is sandwiched between two bipolar plates 24, 26, and gaskets 31, 33 are added around the edges of the MEA 22 to make a gas-tight seal. These gaskets usually are made of a rubbery polymer. Each fuel cell 10 includes current collectors 32, 34 and end plates 36, 38.

[0009] Large scale applications of lightweight, high temperature PEM (HT-PEM) fuel cells particularly for use in fuel cell powered vehicles including aircraft require bipolar plates (BPPs) that are i) highly thermally conductive, and ii) thin to improve heat rejection from the fuel cell stack without adding much weight. Metals such as aluminum, beryllium and magnesium and their alloys are excellent thermal conductors, but their application as a bipolar plate material is limited due to their relatively low modulus and relatively low elongation at break, which is important in the mechanical stamping and milling processes typically employed for forming, i.e., patterning the plates.

[00010] Previous attempts to form BPPs with deep narrow channels by mechanical stamping and milling processes of metals such as aluminum, beryllium and magnesium had limited success due to poor elongation and poor hardness of such metals. Traditional ways to achieve a desired metal plate shape modification required etching which is costly and environmentally undesirable, while mechanical processors such as stamping or rolling are limited in an ability to achieve deep channel formation. Moreover mechanical processes such as stamping and rolling create weak structural points, which could lead to cracks and deformations, and ultimately cell failure. Other metals that are well suited for deep, narrow channel patterning such as, e.g., stainless steel are heavy and do not provide enough thermal conductivity.

[00011] The present disclosure provides a metal and polymeric composite BPPs that combines high thermal conductivity (stamped / patterned metals) with expanded design capabilities 15 05 25 on the surface of the bipolar plates through the use of polymeric composites. More particularly, in accordance with the present disclosure we combine thin, and thus lightweight, sheets of highly conductive metal such as aluminum, beryllium or magnesium and their alloys with shaped, lightweight composite materials to create metal and polymer composite BPPs.

[00012] BPPs in accordance with the present disclosure consist of two plates made of two different materials: a metal base plate (preferably forming the anode plate) and a polymer composite plate (preferably forming the cathode plate). The two plates are electrically connected to each other. Anode and cathode channels are formed on outer surfaces of anode and cathode plates respectively.

[00013] A feature and advantage of the present disclosure is that the metal base plate layer provides high thermal conductivity, while the polymer composite material layer enables the formation of deep and narrow channels with well-defined comers on a surface of the BPP independent of the metal base plate. This is especially important for cathode and cooling channels.

[00014] The polymer composite layer is formed of a high Tg and chemically resistant polymeric composite material, which provides good electrical contact and anti-corrosion protection for metal parts of the plate under a wide range of operating temperatures. Preferred high Tg and chemically resistant polymeric material may be selected from the group consisting of polyvinylidene fluoride, a polysulfone 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 perfluoralkoxy, and mixtures thereof, and may include carbon nanotubes and / or carbon black, graphitized carbon particles, amorphous carbon particles and graphite sheets, and mixtures thereof. 15 05 25

[00015] In such embodiment the conductive carbon particles preferably 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.

[00016] In one embodiment the metal base plate is coated with multiple layers of metal or polymeric composite materials to improve the corrosion resistance and electrical contact conductivity of the bipolar plate material while maintaining its thermal and electronic properties. In such embodiment, it is important that at least one layer in the composite structure has high thermal conductivity to ensure sufficient heat redistribution along the BPP and, thus, reducing temperature gradients typical for air-cooled fuel cells. In such embodiment, a metal such as aluminum is used to provide the majority of the necessary thermal conductivity. In other embodiments, the metal also creates a highly thermally conductive base layer. While aluminum and its alloys are electrically conductive, the majority of the benefit of the use of aluminum is in its thermal conductivity. In yet other embodiments lightweight thermally conductive metals such as magnesium and beryllium, and their alloys are used to create the metal base layer. With the present disclosure, the problems associated with deep narrow channels in patterning the metal base layer are eliminated, since the patterning of deep narrow channels can largely and readily be produced in the polymeric composite layer.

[00017] In practice of the disclosure, a metal sheet, e.g.. formed of aluminum, is stamped or milled with relatively wide and shallow channels, and one or more shaped layers of composite polymeric material having relatively narrow and deep channels is formed on or bonded to the aluminum layer whereby to produce a rigid, lightweight, thermally and / or electrically conductive, and corrosion resistant BPP. By way of example, the channels formed in the metal layer may have 15 05 25 a width of 1.0 to 2.5 mm, optimally 1.5mm, and a height of 0.2 to 0.5 mm, optimally 0.5 mm. Channels formed in the polymer composite layer may have a width of 0.5 to 3 mm, optimally 1.0 to 2.0 mm, and a height of 0.3 to 2.0 mm, optimally 1.0 mm. The resulting composite BPP structures are arranged within a fuel cell stack.

[00018] In one embodiment, the composite polymeric material layer is preformed or patterned, and then bonded to the surface of the metal layer to create a BPP structure with deep and narrow channels, which improves reactant and / or heat flow throughout the stack.

[00019] In another embodiment the composite polymeric material is coated on the metal layer, and then patterned.

[00020] The polymeric composite materials can be preformed, or applied to and / or patterned on the metal layer surface by injection molding, overmolding, vacuum forming, slot-die coating, laser etching, chemical etching, spraying, extrusion, lamination, solvent casting, powder coating, sol-gel coating, formed additively such as by 3-D printing, or coating / slitting or the like. The polymeric composite material layer of the BPP may be modified and adapted to provide different electrical (Tg) thermal, e.g., coefficient of thermal expansion (CTE) / and conductivity, and chemical resistance properties. For example, in one embodiment a polyaniline material doped with carbon nanotubes can be applied to the metal layer to increase its electrical and thermal conductivity. In another embodiment the CTE of the polymeric composite layer can be modified to more closely match that of the metal layer.

[00021] In yet another embodiment, a functional layer may be embedded within the polymeric composite layer to improve the performance of the fuel cell. For example, a catalyst layer can be embedded in the polymeric composite layer. 15 05 25

[00022] In one embodiment the polymeric composite material contains a blend of a polymeric base material and electrically conductive particles such as carbon black, and carbon nanotubes. In other embodiments materials such as graphene sheets, metal wires, metal particles, double-walled carbon nanotubes, or ceramics, can be added to increase the electrical and / or thermal conductivity of the polymeric composite layer.

[00023] In yet another embodiment electrically conductive polymers can be incorporated into the polymer composite layer, including polyanilines, poly thiophenes, poly(3,4-ethylenedioxythiophene), (PEDOT), poly(pyrroles), polyphenylsulfone (PPS), polyaniline (PANI), doped and undoped polybenzimidazole. In other embodiments, electrical and / or thermal conductive polymers and additives can be blended to further modify the polymer composite layer. For example, polysulfones can be blended with polythiophenes to improve the polymer composite layer’s chemical resistance while maintaining high thermal and / or electrical conductivity.

[00024] A particular feature and advantage of BPPs made in accordance with the present disclosure are high flexural and elastic moduli and high Tg of the patterned layer on the BPP which is a critical property for maintaining structural features at elevated operating temperatures. Without structural integrity any benefits to improved transport of working gas or coolant media from channel patterning are lost.

[00025] In one embodiment thermoplastic materials with high Tg and chemical resistance can be used to add mechanical stiffness to the polymer composite layer such as: poly vinylidene fluoride (PVDF), polybenzimidazole (PBI), polyether ether ketone (PEEK), Thermoplastic polyimide (TPI), polyethersulfone (PESU), polyphenylsulfone (PPSU), Fluorinated ethylenepropylene (FEP), perfluoroalkoxy (PFA), polyetherimide (PEI), or polyamide (PA). In another 15 05 25 embodiments, two or more polymer materials are applied in a multilayer structure, e.g. PA is applied first then coated with PEEK to maintain structural integrity at high operating temperatures.

[00026] In a further embodiment, thermoplastic materials can also be applied as polymeric composite blends. For example, PPSU can be blended with FIFE then applied to the BPP to improve the chemical resistance of the material.

[00027] Thermoset polymeric materials also can be applied as the polymer composite layer to provide structural integrity, e.g., thermally resistant epoxy coatings. The thermoset materials can be stamped on the surface of the metal layer in the desired structure and cured in place to preserve the desired geometric features. This process can be accomplished by laminating, casting, or overmolding. Thermoset materials provide additional dimensional stability at elevated temperatures as these materials soften at the Tg, but will not melt and flow. Thermoset materials can be blended with thermally and electrically conductive fillers to further modify the performance of the BPP. Thermoset polymeric precursors can also be applied directly to the metal layer in a molded pattern then converted by a UV, thermal, or microwave curing step. For example, a two component epoxy layer can be mixed and applied to the metal layer using a stamping mold then solidified directly on the surface following a thermal curing schedule.

[00028] A particular feature and advantage of the BPP structure according to the present disclosure is the ability to pattern the polymer composite layer in three dimensions using both layer by layer coating (z- direction) and material patterning (xy-direction) within the polymeric composite structure.

[00029] Direct patterning of desired features on the surface of the BPP allows control of the size and aspect ratio of features. For example, a rigid structural material can be applied in a desired geometry by overmolding in a precise location. Additionally, this process allows for precise 15 05 25 control of the size and aspect ratio of features enabling smaller geometries on the surface of the BPP.

[00030] The disclosure specifically targets lightweighting of fuel cells as the desired application. However, composite conductive structures like those discussed in this disclosure also can be applied to create lightweight, power dense battery structures, and other electronic devices.

[00031] According to aspect A of the present invention there is provided a bipolar plate (BPP) formed of two layers made of different materials which are connected together: a metal base layer and a polymeric composite layer formed of a high Tg chemically resistant polymeric composite material selected from the group consisting of poly vinylidene fluoride, a polysulfone 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 perfluoralkoxy, and mixtures thereof, wherein the metal base layer and the polymeric composite layer are electrically connected to one another, and wherein channels are formed in an outer surface of the metal base layer and in an outer surface of the polymeric composite layer wherein the channels formed in the outer surface of the metal base layer have a width of 1.0 to 2.5 mm and a height of 0.2 to 0.5 mm, and wherein the channels formed in the outer surface of the polymeric composite layer have a width of 0.5 to 3.0 mm and a height of 1.0 to 2.0 mm.

[00032] Preferably the channels formed in the polymeric composite layer are narrower than the channels formed in the metal layer.

[00033] Preferably the channels formed in the polymeric composite layer are deeper than the channels formed in the metal layer. 15 05 25

[00034] Preferably the chemically resistant polymeric material includes carbon nanotubes and / or carbon black, graphitized carbon particles, amorphous carbon particles and graphite layers, and mixtures thereof.

[00035] Preferably the metal base layer is formed of a metal selected from the group consisting of aluminum, beryllium, magnesium and alloys thereof.

[00036] According to aspect B of the present invention there is provided a fuel cell comprising a bipolar plate (BPP) formed of two layers made of different materials, a channeled metal base layer and a channeled polymeric composite layer according to aspect A of the present invention.

[00037] Preferably the channeled metal base layer forms the fuel cell anode plate, and the channeled polymeric composite layer forms the fuel cell cathode plate.

[00038] According to aspect C of the present invention there is provided a fuel cell stack comprising a plurality of fuel cells as according to aspect B of the present invention.

[00039] According to aspect D of the present invention there is provided a method for forming a bipolar plate (BPP) for a fuel cell, comprising providing a contoured metal base layer, and covering one surface of the contoured metal base layer with a polymeric composite layer formed of a polymeric composite material selected from the group consisting of polyvinylidene fluoride, a polysulfone 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 perfluoralkoxy, and mixtures thereof, and forming channels in a surface of the polymeric composite layer by direct patterning. 15 05 25

[00040] In one alternative the contoured metal base layer and polymeric composite layer are fixed to one another in a roll-to-roll process.

[00041] In another alternative the polymeric composite layer is formed on the contoured metal base layer.

[00042] In one alternative the contoured metal base layer and the polymeric composite layer are separately formed, and affixed to one another.

[00043] In one alternative the contoured base metal layer and polymeric composite layer are fixed to one another in a roll-to-roll process.

[00044] In another alternative the polymeric composite layer is formed on the contoured metal base layer.

[00045] In one alternative the contoured metal base layer and the polymeric composite layer are separately formed, and affixed to one another.

[00046] According to aspect F of the present invention there is provided a fuel cell powered vehicle comprising a fuel cell according to aspect B of the present invention.

[00047] Preferably the vehicle comprises a fuel cell powered aircraft.

[00048] Further areas of applicability will become apparent form the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. Brief Description of the Drawings

[00049] 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. 15 05 25 In the drawings: Fig. la is a perspective view and Fig. lb is an exploded view of a typical PEM FC in accordance with the prior art; Fig. 2 is a cross-sectional view of a BPP made in accordance with the present disclosure; Figs. 3-5 are flow diagrams illustrating processes for forming a BPP in accordance with the present disclosure; Fig. 6 is a cross-sectional view of a stack of fuel cells incorporating BPPs in accordance with the present disclosure; and Fig. 7 is a schematic depiction of a hydrogen fuel cell powered aircraft in accordance with the present disclosure. Detailed Description

[00050] 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.

[00051] 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 15 05 25 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.

[00052] 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.

[00053] 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 15 05 25 discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

[00054] 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.

[00055] As used herein the terms “component” and “subcomponent” are employed interchangeably to describe the several elements forming our HT-PEMs.

[00056] Referring to Fig. 2, a BPP 60 in accordance with the present disclosure comprises a shaped aluminum layer 62 and a polymer composite layer 64. Metal layer 62 is formed of aluminum having a thickness of 120-200 microns, and is patterned to include a plurality of hydrogen gas flow channels 66. Channels 66 typically are 0.5 mm tall and 1.5 mm wide, respectively. Composite layer 64 is formed on aluminum layer 62, and includes a plurality of air flow channels 68 extending in opposite direction to channel 66. Composite layer 64 is formed of polysulfone or polyethersulfone and is approximately 500 microns thick. Channels 68 typically are about 2mm wide and 1 mm high. Also shown in Fig 2 cooling channels 69. Channels 69 typically are 1 to 3 mm wide, optimally 2.0 mm wide and 0.5 to 2.0 mm tall, optimally 1.0 mm tall. 15 05 25

[00057] Referring to Fig. 3, in one embodiment a metal / polymeric composite BPP is formed as follows: starting with roll aluminum 70, the aluminum strip is patterned in accordance with the present disclosure in a rolling station 72 to form a contoured channeled shape as shown in Fig. 2. The resulting contoured channeled aluminum strip is then coated in step 74 with a polymeric composite material, and the polymeric composite material layer is then subjected to laser etching in a laser etching step 76 to form deep, narrow channels as shown in Fig. 2. The resulting structure is then cut to size in a cutting station 78 and assembled with an MEA to form a fuel cell in assembly station 80.

[00058] Referring to Fig. 4, in an alternative embodiment, a metal / polymeric composite BPP in accordance with the present disclosure is formed by a roll-to-roll process, as follows: rolls of aluminum 81 and polymeric composite material 82 are patterned in rolling stations 83, 84, respectively to form contoured channeled shapes as shown in Fig. 2. The resulting patterned aluminum strip and patterned polymeric composite strip are then adhered together in an assembly station 86, and the resulting contoured aluminum / contoured polymeric composite assembly are then cut to size in a cutting station 88 and assembled with an MEA to form a fuel cell in assembly station 90.

[00059] Referring to Fig. 5, in another alternative embodiment, a metal polymeric composite BPP in accordance with the present disclosure is formed as follows: aluminum plates 91 are patterned in a stamping station 92 to form contoured channeled shapes as shown in Fig. 2. The contoured shaped aluminum plates are then coated on one side with a polymeric composite material at a coating station 94, and the polymeric composite material is then molded in a press in molding station 96 to form deep narrow channels as shown in Fig. 2. The resulting contoured 15 05 25 aluminum / contoured polymeric composite assembly is then assembled with an MEA to form a fuel cell in assembly station 98.

[00060] Referring to Fig. 6, a plurality of fuel cells are stacked together with BPPs made in accordance with the present disclosure to form a fuel cell stack.

[00061] Fig. 7 illustrates an aircraft 140 including two electric motors 142, 144 which are powered by two parallel HT-PEM hydrogen fuel cells 146, 148 incorporating BPPs made in accordance with the present disclosure.

[00062] Also, while the foregoing disclosure is focused primarily on HT-PEM fuel cell applications, the devices and manufacturing process disclosed can be adapted for use in electronic devices, and battery manufacturing which are given as exemplary sockets, pins and the like, particularly those designed for high temperature environments.

[00063] 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

15 05 251. A bipolar plate (BPP) formed of two layers made of different materials which are connected together: a metal base layer and a polymeric composite layer formed of a high Tg chemically resistant polymeric composite material selected from the group consisting of poly vinylidene fluoride, a poly sulfone 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 perfluoralkoxy, and mixtures thereof, wherein the metal base layer and the polymeric composite layer are electrically connected to one another, and wherein channels are formed in an outer surface of the metal base layer and in an outer surface of the polymeric composite layer wherein the channels formed in the outer surface of the metal base layer have a width of 1.0 to 2.5 mm and a height of 0.2 to 0.5 mm, and wherein the channels formed in the outer surface of the polymeric composite sheet have a width of 0.5 to 3.0 mm and a height of 1.0 to 2.0 mm.

2. The BPP according to claim 1, wherein the channels formed in the polymeric composite layer are narrower than the channels formed in the metal layer.

3. The BPP according to claim I or claim 2, wherein the channels formed in the polymeric composite layer are deeper than the channels formed in the metal layer.

4. The BPP of claim 1, wherein the chemically resistant polymeric material includes carbon nanotubes and / or carbon black, graphitized carbon particles, amorphous carbon particles and graphite sheets, and mixtures thereof.

5. The BPP of any of claims 1-4, wherein the metal base layer is formed of a metal selected from the group consisting of aluminum, beryllium, magnesium and alloys thereof.15 05 256. A fuel cell comprising a bipolar plate (BPP) formed of two layers made of different materials, a channeled metal base layer and a channeled polymeric composite layer as claimed in any of claims 1-5.

7. The fuel cell according to claim 6, wherein the channeled metal base layer forms the fuel cell anode plate, and the channeled polymeric composite layer forms the fuel cell cathode plate.

8. A fuel cell stack comprising a plurality of fuel cells as claimed in claim 6 or claim 7.

9. A method for forming a bipolar plate (BPP) for a fuel cell as claimed in any one of claims1-5, comprising providing a contoured metal base layer, and covering one surface of the contoured metal layer sheet with a polymeric composite layer formed of a polymeric composite material selected from the group consisting of polyvinylidene fluoride, a polysulfone 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 ethylpolypropylene, a perfluoralkoxy, and mixtures thereof, and forming channels in a surface of the polymeric composite layer by direct patterning.

10. The method according to claim 9, wherein the contoured metal base layer and contoured polymeric composite layer are fixed to one another in a roll-to-roll process.

11. The method according to claim 9, wherein the polymeric composite layer is formed on the contoured metal base layer.

12. The method according to claim 9, wherein the contoured metal base layer and the polymeric composite layer are separately formed, and affixed to one another.

13. A fuel cell powered vehicle comprising a fuel cell as claimed in claim 6.

14. The fuel cell powered vehicle a claimed in claim 13, wherein the vehicle comprises a fuelcell powered aircraft.

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