Use of the PVDF powder as a binder in the bipolar plates for fuel cell and electrolyzers

Abstract

A bipolar plate including one or more electrically conductive materials and a fluorinated polymer. The fluorinated polymer may have a melt viscosity of 1 to 25 kP, such as 1 to 20 kP. The bipolar plate may be formed from the fluorinated polymer in powder form, the powder having a volume average particle size of 0.5 to 100 μm, as measured by light scattering. A device including the bipolar plate, such as a hydrogen fuel cell or electrolyzer.

Description

USE OF THE PVDF POWDER AS A BINDER IN THE BIPOLAR PLATES FOR FUEL CELL AND ELECTROLYZERSTECHNICAL FIELD

[0001] Embodiments of the present disclosure related to a bipolar plate, a fuel cell or an electrolyzer including the bipolar plate, a fuel cell or an electrolyzer system including a stack of the fuel cells or electrolyzers, and methods for forming each. In a fuel cell or an electrolyzer, the separator between the anode side and the cathode side is the bipolar plate. Anode and cathode reactions occur on either side of the bipolar plate. A bipolar plate is generally thermally and electrically conductive and non-permeable to reactant gas molecules.BACKGROUND

[0002] A bipolar plate may be used in an electrolyzer and fuel cell devices, such as for hydrogen fuel cell. Fuel cells are electrochemical devices that convert chemical energy directly into electrical energy. Unlike conventional combustion-based power generation, fuel cells operate with high efficiency and minimal emissions. They achieve this by utilizing two electrodes, an anode, and a cathode, which is separated by the electrolyte. For fuels, the hydrogen is supplied to the anode and oxygen (from air) to the cathode. The resulting electrochemical reactions produces electricity, heat, and water as the only byproducts from the reaction. In the case of electrolyzers, a similar setup is used to product hydrogen from water and electricity. Devices are typically made of a stack of cells, where the bipolar plates are used to separate the anode side from the cathode side between the cells.

[0003] The bipolar plates maintain the interconnected structure between individual cells. Their primary function is to prevent reactant gases from the anode side and cathode side from crossing over (that is low to no gas permeability), and to allow electric conduction between the anode and cathode. In addition, they should be thermally conductive to take away heat generated to prevent overheating, and they ensure appropriate separation between adjacent cells and equal distribution of reactant gases and coolant via flow channels.

[0004] Bipolar plates (also known as separator plates) hold a critical position within the fuel cell and electrolyzer stack and are often made from materials such as graphite, graphite composites (composite bipolar plate) or metals like stainless steel (metal bipolar plate). The properties ofbipolar plates play a crucial role in ensuring the optimal performance and longevity of the fuel cell or the electrolyzer system. High electrical conductivity is a fundamental property of bipolar plates, which minimizes electrical losses within the stack, thereby enhancing the overall efficiency of the fuel cell. Fuel cells and electrolyzers operate in environments where corrosive gases and liquids are present. Bipolar plates have to exhibit excellent corrosion resistance to withstand the harsh conditions and ensure long-term durability. Corrosion is one of the limitations or challenges of the metal plates. Bipolar plates require mechanical properties (including flexural and tensile strength) to withstand the pressures exerted by the stack to prevent deformation, cracking, or failure, thereby ensuring consistent cell-to-cell contact. The gas impermeability of bipolar plates is crucial, leading to optimal electrochemical reactions and enhanced fuel cell or electrolyzer efficiency. Efficient thermal conductivity is essential to manage the heat and to maintain stable operating temperatures, and preventing overheating that could compromise system performance. The bipolar plate weight is important to improve overall efficiency as the composite bipolar plates could constitute up to 60% of the cell weight. Hence newer plates are designed to have lower thickness, typically less than 2 mm, preferably less than 1 mm. Cost minimization is another factor for bipolar plates, the bipolar plates can represent up to 30% of the cost of the fuel cell or electrolyzer stack especially for metal plate requiring corrosion protective coating. An important variable to the overall cost per KW of energy generated by the fuel cell or electrolyzer stack.

[0005] The main challenge with metal bipolar plate is the durability due to corrosion of the metal in acidic environment in the cell reducing the stack life. There are various coating technologies used to protect against corrosion, but the high cost of coatings limits their use.

[0006] The composite plates may be formed from electrically conductive materials and a polymer either thermoplastic or thermoset. The advantages of the composite bipolar plates are their good corrosion resistance, lower weight, and lower cost compared to metal plate solutions. However, they tend to have undesirable disadvantages such as lower electric conductivity and mechanical properties, as well as higher permeability to gases.

[0007] Thermoset or thermoplastic polymers are used for composite bipolar plates. Both types of binders can enable bipolar plates with good mechanical and dimensional stability. However, thermosets require relatively long processing time compared to thermoplastics.

[0008] In the case of thermosets, known bipolar plates are formed from thermosets in liquid form by adding them to the electrically conductive materials or in sheet, followed by a curing process to form a bipolar sheet.

[0009] In the case of thermoplastics, known bipolar plates are generally formed by use of a solvent, such as dispersing or dissolution of thermoplastic polymer material in solvent, adding the solution to the electrically conductive materials, and evaporate the solvent to form a plate. SUMMARY

[0010] Embodiments of the present disclosure use a fluorinated polymer in powder form as a binder in a dry process, to overcome challenges with use of a solvent, latex, or of a liquid resin. For example, the use of a fluorinated polymer in powder form decreases energy demand and the time involved in the process of producing a bipolar plate. Preferably the fluorinated polymer in powder form is thermoplastic.

[0011] Embodiments of the present disclosure do not require impregnation of the electrically conductive plate with a liquid resin. In embodiments, the fluorinated polymer in powder form is used in a dry state, for instance as a powder, and it is blended with the electrically conductive materials. In embodiments, such as during heating and / or compression steps, the fluorinated polymer may at least partially melt and may flow into pores and / or interstitial spaces of the electrically conductive materials in a plate. This can minimize or eliminate the presence of through-pores in a bipolar plate, reducing gas permeation.

[0012] Embodiments of the present disclosure can overcome challenges with the use of latex, solvent, or liquid resins, which have drawbacks such as high water consumption, high energy demand to dry the wet mix, as well as use and disposal of solvents.

[0013] For example, most known bipolar plates use a liquid resin (thermosets), which is impregnated into a plate of conductive particles to reduce or eliminate porosity. This is a timeconsuming process which is difficult to scale up. In contrast, embodiments of the present disclosure do not use a liquid resin and do not need to impregnate the electrically conductivematerials. The method described in the embodiments of the present disclosure will not need to impregnate the conductive particles with a binder in liquid form. In embodiments of the present application, the polymer in a dry state may be blended with the electrically conductive material, and during processing, such as heating and / or compression, the fluorinated polymer may deform, partially melt, and help fill pores and / or interstitial spaces, thereby reducing the gas permeation of the final plate.

[0014] As the industry has been primarily focused on use of a solvent or of a liquid resin, there is disclosure of solution viscosity, such as the solution viscosity of a polymer binder in liquid form. However, there is insufficient appreciation or understanding in the art of the melt viscosity of a fluorinated polymer, particularly in relation to how the melt viscosity of the fluorinated polymer affects the properties of a bipolar plate prepared therefrom.

[0015] Embodiments of the present application are based on the discovery that the use of a fluorinated polymer in powder form with a specific range of melt viscosity can significantly improve a bipolar plate prepared therefrom. In an embodiment, the fluorinated polymer in powder form may have a melt viscosity of 1 to 25 kP, such as 1 to 20 kP, such as 1 to 15kP, such as 2 to 12 kP.

[0016] When the fluorinated polymer in powder form had a melt viscosity below this range, the resulting bipolar plate has poor mechanical properties and low electrical conductivity through the plate. Because the powder polymer binder is not conductive, the polymer with the melt viscosity below the range may flow excessively, covering the surface of the electrically conductive material and reducing the electrical conductivity of the resulting bipolar plate. In addition, the polymer with the melt viscosity below the range has low mechanical strength, measured using the ASTM D638, due to low molecular weight and lower chain entanglement resulting in poor mechanical properties for the resulting bipolar plate.

[0017] When the fluorinated polymer in powder form had a melt viscosity above this range, the resulting bipolar plate also has undesirable performance characteristics such as poor mechanical properties and high gas permeation. The polymer with the melt viscosity above the range has high molecular weight and chain entanglement, which limits its ability to flow, whichcan be measured by ASTM D3835 at 232°C and 100 s’1. Poor ability to flow means poor ability to bond with multiple electrically conductive materials and poor bonding network to the electrically conductive materials hence, the bipolar plate made with polymer with the melt viscosity above the range has poor mechanical properties. In addition, it also limits the ability to flow into the interstitial space between electrically conductive materials, causing higher gas permeation for the bipolar plate made using the polymer having a melt viscosity above the range which is not desirable.

[0018] In an embodiment, the fluorinated polymer in powder form within this claimed viscosity range gives better property for the bipolar plate in terms of permeability to gas, mechanical properties, and electrical conductivity.

[0019] There is insufficient appreciation or understanding in the art of the particle size of the fluorinated polymer in powder form, particularly in relation to how the particle size of the fluorinated polymer in powder form affects the properties of a bipolar plate prepared therefrom.

[0020] Embodiments of the present application are based on the discovery that use of a fluorinated polymer in powder form within a specific range of particle size can significantly improve a bipolar plate prepared therefrom. In an embodiment, the fluorinated polymer in powder form may have a volume average particle size of 0.5-100 pm, such as 1- 50 pm, such as 1-25 pm. In another embodiment, particles of fluorinated polymer in powder form are composed of agglomerates of discrete particles, where the discrete particles have a volume average size of 20 to 500 nm, such as 50 to 300 nm.BRIEF DESCRIPTION OF THE FIGURES

[0021] FIG. 1 shows a chart showing the conductivity of plates formed from PVDF binder of various melt viscosities.

[0022] FIG. 2 shows a chart showing the permeability of plates formed from PVDF binder of various melt viscosities.DETAILED DESCRIPTION

[0023] The articles "a," "an," and "the" are used herein to refer to one or more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

[0024] As used herein, the term "about" means ±10% of the noted value. By way of example only, a composition comprising "about 30 wt. %" of a component could include from 27 wt. % of the component up to and including 33 wt. % of the component.

[0025] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0026] The word "comprising" is used in a manner consistent with its open-ended meaning, that is, to mean that a given product or process can optionally also have additional features or elements beyond those expressly described. It is understood that wherever embodiments are described herein with open-ended meaning, otherwise analogous embodiments described in terms of "consisting of" and / or "consisting essentially of" are also contemplated and within the scope of this disclosure.

[0027] For the purposes of defining the present technology, the transitional phrase "consisting of" may be introduced in the claims as a closed preamble term limiting the scope of the claims to the recited components or steps and any naturally occurring impurities. For the purposes of defining the present technology, the transitional phrase "consisting essentially of" may be introduced in the claims to limit the scope of one or more claims to the recited elements, components, materials, or method steps as well as any non-recited elements, components, materials, or method steps that do not materially affect the novel characteristics of the claimed subject matter.

[0028] The different aspects, alternatives and embodiments of the invention disclosed herein can be combined with one or more of the other aspects, alternatives and embodiments described herein. Two or more aspects can be combined.

[0029] Various examples and embodiments of the inventive subject matter disclosed here are possible and will be apparent to a person of ordinary skill in the art, given the benefit of this disclosure. In this disclosure reference to "embodiments" means that those embodiments arenon-limiting examples of the inventive subject matter, and there may be alternative embodiments which are not excluded.

[0030] Embodiments of the present disclosure relate to use of a composition including an electrically conductive material and fluorinated polymer in powder form for forming a bipolar plate. The fluorinated polymer may have a melt viscosity of 1 to 25 kP, such as 1 to 20 kP, such as 1 to 15 kP, such as 1 to 12 kP, such as 2 to 12 kP. The polymer particles may have a volume average particle size of 0.5 to 100 pm, such as 1 to 50 pm, such as 1 to 25 pm as measured by laser diffraction. Further, the polymer particles may be composed of agglomerates of discrete particles having a volume average size of 20 to 500 nm, such as 50 to 300 nm, as measured by SEM.

[0031] This melt viscosity range surprisingly provides for an improved bipolar plate, with a unique combination of high conductivity, low hydrogen permeability, and high mechanical properties. In the embodiments, the combination of melt viscosity range and small particle size of the polymer may provide improved bipolar plate performance, such as further improved combination of hydrogen permeability resistance, electrical conductivity, and mechanical properties while maintaining the other benefits of thermoplastic composite bipolar plates such as corrosion resistance, and lower weight.

[0032] TEST METHODS

[0033] The melt viscosity may be measured by ASTM D3835 at 232°C and 100 s’1.

[0034] The volume average particle size refers to a particle size of polymer in powder form. The volume average particle size may be measured by Malvern Masturizer 2000 particle size analyzer (laser diffraction). Volume average particle size is a d50 particle size.

[0035] In some cases, the polymer powder particles can be made of agglomerates of discrete particles with a volume average discrete particle size. This is the case for example when the polymer is produced by emulsion polymerization, where discrete polymer particles are first formed in a latex, and later agglomerate during a drying process into powder particles. The discrete polymer particles can be measured using the SEM imaging.

[0036] The flexural strength (flexibility) on plate is measured using ASTM D790 using a span of 1 inch and cross head speed of 0.07 in / min. The plate size rectangular and is 0.5 inches wide, 5 inches long and 0.3mm thick.

[0037] The tensile strength can be measured according to ASTM D638 using Type 1 bars and 4.5 in grip separation and 0.5 in / min cross head speed.

[0038] The mechanical strength of the polymer is measured according to ASTM D638 using Type 1 bars and 4.5 in grip separation and 2 in / min cross head speed.

[0039] The density may be measured according to ASTM 2854 using the weight and the physical dimensions of the part.

[0040] The electrical conductivity test is a through plan electrical conductivity test and is measured using Instron equipment that applies 280 N of force on the sample that is sandwich between two gold plated copper electrodes that are connected to ohmmeter to record resistance (@ 1mA). The electrodes are placed on the top and bottom of the sample (perpendicular to the plane of the plate). The current is applied for 3 minutes before taking the reading. The resistance is used to calculate the conductivity using the cross secton area and thickness of the sample. The sample size was 25.4mm (1 in ) diameter circle, and 0.3 mm thickness.

[0041] The permeability of the samples was measured on the 25.4mm (1 in ) diameter circle sample and 0.3 mm thickness that is assembled in the permeation cell with 20 psi of inlet pressure of dry helium at room temperature. The helium on the other side was detected accurately via ELD500 wet leak detector (gas leak detector). The helium leak rate (mbar.L / s) was then converted to permeability using the ideal gas law. The helium permeability is used to establish relative hydrogen permeability due to sight difference in size between the two molecules for the end application.

[0042] FLUORINATED POLYMER

[0043] The fluorinated polymer may comprise within its backbone at least one unit from a monomer selected from vinyl monomers containing at least one fluorine atom, vinyl monomers comprising at least one fluoroalkyl group and vinyl monomers comprising at least one fluoroalkoxy group. By vinyl we mean the monomer contains an unsaturated double bondbetween two carbon atoms. As an example, this monomer can be vinyl fluoride; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); a perfluoro(alkyl vinyl) ether such as perfluoro(methyl vinyl)ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) or perfluoro(propyl vinyl) ether (PPVE); perfluoro(l,3-dioxole); perfluoro(2,2-dimethyl-l,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2in which n is 1, 2, 3, 4 or 5; the product of formula RICH2OCF=CF2in which Ri is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R2OCF=CH2in which R2is F(CF2)Pand p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene or 2- trifluoromethyl-3,3,3-trifluoro-l-propene.

[0044] The fluorinated polymer can be a homopolymer or a copolymer. It may also comprise units from non-fluorinated monomers like ethylene.

[0045] Advantageously, the fluorinated polymer is a polyvinylidene fluoride polymer.

[0046] In other embodiments, the polyvinylidene fluoride polymer may be a copolymer comprising vinylidene fluoride units and units from one or more other monomers. Examples of other monomers are vinyl fluoride; trifluoroethylene; chlorotrifluoroethylene (CTFE); 1,2- difluoroethylene, tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl)ethers such as perfluoro(methyl vinyl)ether (PMVE), perfluoro(ethyl vinyl)ether (PEVE) or perfluoro(propyl vinyl)ether (PPVE); perfluoro(l,3-dioxole); perfluoro(2,2-dimethyl-l,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2in which n is 1, 2, 3, 4 or 5; the product of formula R'CH2OCF=CF2in which R' is hydrogen or F(CF2)zand z is 1, 2, 3 or 4; the product of formula R"OCF=CH2in which R" is F(CF2)zand z is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); 3,3,3-trifluoropropene or 2- trifluoromethyl-3,3,3-trifluoro-l-propene. Hexafluoropropylene is preferred. The polyvinylidene fluoride copolymer may also comprise units from ethylene monomer. Preferably, when the polyvinylidene fluoride polymer is a copolymer, it contains at least 60% by weight, morepreferably at least 70% by weight, even more preferably at least 80% by weight, of vinylidene fluoride units.

[0047] In some embodiments the fluorinated polymer is preferably a polyvinylidene fluoride homopolymer.

[0048] In some embodiments the fluorinated polymer is preferably a copolymer of VDF and HFP.

[0049] The fluorinated polymer may be a mixture of two or more of the abovementioned polymers.

[0050] In some embodiments, the total polymer used as binder for the bipolar plate is a combination of polymers comprising primarily the fluorinated polymer ("the first fluorinated polymer"), such as greater than 50 wt%. The combination of polymers may comprise 50-99 wt% based on total polymer in the bipolar plate, such as 60-95 wt%, such as 65-90 wt% of the fluorinated polymer, such as polyvinylidene fluoride polymer, and 1-50 wt%, such as 5-40 wt%, such as 10-35 wt% of a second polymer based on total polymer in the bipolar plate.

[0051] The second polymer may be at least one polymer selected from the group consisting of polyolefin (such as, polypropylene, polyethylene), polyamides, fluoropolymers, PEKK, and polyimides.

[0052] The second polymer preferably has a volume average particle size below 100 microns, or below 50 microns. In an embodiment, the second polymer has a melt viscosity of 0.05 to 29 kP, such as 0.1 to 25 kP, such as 1 to 25 kP.

[0053] BIPOLAR PLATE CONDUCTIVE COMPOSITION

[0054] A conductive composition is prepared that will be made into a bipolar plate. The conductive composition comprises fluorinated polymer in powder form and electrically conductive material. The fluorinated polymer in powder form and the electrically conductive material may be mixed, for example to achieve mixing as homogenously as possible. The mixing may be by dry blending the fluorinated polymer in powder form and the electrically conductive material. No solvent is used in the process to prepare the bipolar plate of this invention. The electrically conductive material, the fluorinated polymer and the optional second polymer are all in powder form and are combined as dry materials to form the conductive composition.

[0055] The electrically conductive material used in the invention may be one or more selected from carbon black, carbon nanotubes, graphene, graphite, expanded graphite, exfoliated graphite, graphite in the form of lamellas or platelets, carbon fibers, active coal, conductive carbon and a mixture thereof.

[0056] The electrically conductive material may have an aspect (L:D) ratio of 1 to 30, such as 1 to 20, such as 1 to 10.

[0057] In an embodiment, the composition may include the fluorinated polymer and electrically conductive material in a weight ratio of 0.5:95.5 to 35:65, such as 5:95 to 30:70 such as 10:90 to 30:70.

[0058] The conductive composition may be formed by mixing, such as dry blending, one or more electrically conductive materials and particles of a fluorinated polymer. The mixing may be performed by any suitable means known in the art to blend dry materials such as planetary centrifugal mixer, Henschel high speed mixer, and acoustic mixer.

[0059] In an embodiment, a bipolar plate may be formed from any suitable conductive composition described herein.

[0060] The bipolar plate may be formed by any means of applying heat and / or pressure to the conductive composition, such as compression-molding or calendaring the conductive composition or using injection compression process.

[0061] The bipolar plate formation process may include pressing the conductive composition to a thickness of 0.1-5 mm, such as 0.1-3 mm, such as 0.2 to 1 mm, such as 0.2 to 0.9mm.

[0062] In an embodiment, the forming of the bipolar plate may include steps of providing the conductive composition and compressing the conductive composition into a compressed sheet using, for example, calendaring rolls or a compression mold. This compression step may be performed at a temperature, such as at 18-100 °C, such as at 20-50°C. The compression may be performed without any heating for the compression step.

[0063] The compression may be performed by any suitable means, such as by roll to roll compression or a compression molding.

[0064] The resultant compressed sheet may have a density of between 0.2 to 1 g / cm3, such as 0.3 to 0.8 g / cm3, such as 0.4 to 0.6 g / cm3.

[0065] In embodiments, the fluorinated polymer and the optional second polymer in the compressed sheet has not yet been melted and is sb’ll generally in powder form.

[0066] In an embodiment, the compressed sheet may be subsequently heated, after the compression, to a heating temperature generally above the melting point of the fluorinated polymer and the optional second polymer, if present, to melt the fluorinated polymers and the optional second polymer, if present, to form a heated sheet. When the optional second polymers are present in the conductive composition, the heating temperature may be above the melting point of whichever polymer of the fluorinated polymer or the second polymer has the highest melting point. The heating temperature may be 0-70°C above the highest melting point, such as l-50°C above the highest melting point, such as 25-50°C above the highest melting point. When no second polymer is present, the heating temperature may be 0-70°C above the fluorinated polymer melting point, such as l-50°C above the fluorinated polymer melting point, such as 25-50°C above the fluorinated polymer melting point.

[0067] In an embodiment, the heating is at a temperature of 120-260°C, such as 150-250°C, for a time period of 5-180 min, such as 15-150 min, such as 20-120 min, such as 20 to 60 min.

[0068] The heating may occur at any appropriate temperature and time period to allow the fluorinated polymer powders and in the case of second polymer being present, the fluorinated polymer and the second polymer to be able to flow.

[0069] The heating may be performed by any suitable means known in the art, such as radiation, inferred, microwave, convection, or conduction heating.

[0070] In an embodiment, the heated sheet (a compressed sheet which has been subsequently heated as described above) may be further calendared at a temperature below the melting point of the fluorinated polymer. If second polymers are present in the composition, the calendaring may be at a temperature below the melting point of whichever polymer of the fluorinated polymer or the second polymer has with the lowest melting point. In an embodiment, the calendaring may be between 50°C and a temperature of at least 10°C below the melting point of whichever polymer of the fluorinated polymer or the second polymer has with the lowest melting point. In the case where there is no second polymer, the calendaringmay be between 50°C and a temperature of at least 10°C below the melting point of the fluorinated polymer.

[0071] The calendaring may be between two rollers.

[0072] In an embodiment, the calendaring of the heated sheet (a compressed sheet which has been subsequently heated as described above) may occur with heated rollers. The heated rollers may be at a temperature of 50°C-155°C, such as 50°C-130°C, such as 50°C-100°C. In this compression the temperature is always below the melting point of the polymer with the lowest melting point. Calendaring may occur in multiple steps with multiple sets of rollers. A gap between rollers may be reduced as the sheet moves to each subsequent set of rollers.

[0073] In an embodiment, the calendaring of the heated sheet (a compressed sheet which has been subsequently heated as described above) achieves a density above the density of the compressed sheet. The final density after calendaring is generally between 0.6 to 2.0 g / cm3, such as 0.9 to 2.0 g / cm3, such as 0.6 to 1.2 g / cm3, such as 0.6-0.9 g / cm3.

[0074] In an embodiment, the calendared sheet may be a bipolar plate. In an embodiment, the calendared sheet may be embossed to form a bipolar plate.

[0075] Embossing could be used to create flow field channels in the plate.

[0076] The embossing creates Flow field channels. The embossing can be achieved by compression stamping or calendaring (embossing rollers).

[0077] In an embodiment, the embossing of the calendared sheet creates additional surface area.

[0078] In an embodiment, the embossing of the calendared sheet increases the density above 1.5 gm / cc, such as above 1.7 gm / cc, such as above 1.8 gm / cc, such as above 1.9 gm / cc, such as above 2 gm / cc.

[0079] In an embodiment, a bipolar plate may be formed by any suitable method, such as any embodiment described herein.

[0080] In an embodiment, a bipolar plate includes one or more electrically conductive materials and a fluorinated polymer.

[0081] In an embodiment, the fluorinated polymer may have a melt viscosity of 1 to 25 kP, such as 1 to 20 kP, such as 1 to 15 kP, such as 1 to 12 kP, such as 2 to 12 kP.

[0082] In an embodiment, the bipolar plate may be formed from the fluorinated polymer that was in powder form, the powder particles having a volume average particle size of 0.5 to 100 pm, such as 0.1 to 50 pm, such as 1-25 pm.

[0083] In an embodiment, the bipolar plate may be formed from the fluorinated polymer that was in powder form, the powder particles having a volume average discrete particle size of 20 to 500 nm, such as 50 to 300 nm, as measured by SEM.

[0084] In an embodiment, the bipolar plate has a helium permeability of less than 1012cc / (cm2.s.Pa), such as less than 1013cc / (cm2.s.Pa), such as less than 1014cc / (cm2.s.Pa). Using procedure discussed above using helium leak detector at 20 psi inlet pressure on the sample of 25.4mm (1 in) diameter circle with 0.3 mm thickness.

[0085] In an embodiment, the bipolar plate has a plate thickness of 0.1 to 5 mm, 0.1 to 3 mm, such as 0.2 to 1 mm, such as 0.2 to 0.9 mm.

[0086] In an embodiment, the bipolar plate has an electrical conductivity of greater than 40 S / cm, such as greater than 70 S / cm, such as greater than 100 S / cm.

[0087] In an embodiment, the bipolar plate has a flexibility of 5 MPa or higher, such as 10 or higher, such as 20 or higher. The flexibility may be measured according to ASTM D-790.

[0088] In an embodiment, the bipolar plate has a density of 0.8-2.1 g / cm3, such as 0.8-1.95 g / cm3, such as 1.6-1.9 g / cm3. The density may be measured according to ASTM 2854.

[0089] In an embodiment, the bipolar plate may be used in a device. The device may include a hydrogen fuel cell. The device may include an electroylzer.

[0090] In an embodiment, the hydrogen fuel cell device can be a proton exchange membrane fuel cell, phosphoric acid fuel cell, or an alkaline fuel cell.

[0091] In an embodiment, the bipolar plate may be used as an electrode in a redox flow battery. The bipolar plate may be an electrode in a redox flow battery.

[0092] In an embodiment, the bipolar plate may be used as an electrode in a Vanadium flow battery. The bipolar plate may be an electrode in a Vanadium flow battery.

[0093] In an embodiment, the bipolar plate may be used as an electrode in an electrodialysis system. The plate may be a component of an electrode in a redox flow battery or an electrodialysis system.EXAMPLES

[0094] PVDF materials: PVDF 1 has a melt viscosity of 50 kP (High); PVDF 2 has a melt viscosity of 23 kP (medium-high); PVDF 3 has a melt viscosity of 10 kP (medium); PVDF 4 has a melt viscosity of 5kP (medium-low); PVDF 5 is 0.3kP (low). The volume average particle size of all the PVDF samples was 5-micron (d50). The PVDF samples are homopolymers.

[0095] The resins used for testing were PVDF polymer powders with different melt viscosities. The bipolar plates were made into flat sheet using a compression molding process with conductive graphite material (as the electrically conductive material) and PVDF polymer in powder form. The conductive graphite material was mixed with the PVDF powder (in dry form) to create a well dispersed blend. The mix was then used to make a plate using a 2.25 inch diameter round mold. The compression was done using 20 metric ton pressure for about 1 minute followed by heating of the plate to above the melting point of the polymer (MP was 175°C), to a temperature of 227C (440F) for about 30 minutes. Once cool, additional compression was performed using 20 metric ton of pressure in absence of heat. The plates produced this way were used for testing for electrical conductivity and permeability. The samples size for both tests were 1 inch disc with 0.3 mm thickness. The electrical conductivity test (through plan) was done using the method mentioned above at 280N force and 1 mA current. The permeability was calculated from leak rate using the method discussed above. The samples were 25.4mm (1 in) diameter circle with a 0.3 mm thickness and 20 psi inlet pressure using dry helium at room temperature.

[0096] Example 1: In Example 1, a flat bipolar plate was formed from each of the three PVDF samples (PVDF 1, PVDF 3, and PVDF 4), using the method described above. The conductivity of each bipolar plate was measured and is shown in FIG. 1. The results show the trend that the high melt viscosity PVDF provides a bipolar plate with the highest conductivity, and that the medium-low melt viscosity PVDF provides a bipolar plate with low conductivity. The horizontal line represents 40 S / cm a minimum conductivity that could be commercially reasonable for a bipolar plate. The medium-low melt viscosity PVDF 4 was still well above the minimum.

[0097] The permeability though the plates of each bipolar plate was measured and is shown in FIG. 1. The medium low melt viscosity PVDF 4 gives least permeability through the plate, as seen in FIG. 2. This is believed to be because a PVDF 4 with lower melt viscosity can flow well in the interstitial space between the electrically conductive materials, creating blockage for reactant gases.

[0098] PVDF 1 with high viscosity results in a plate with poor mechanical properties and gas permeation resistance. High viscosity PVDF of 50 kP has higher molecular weight and better strength. However, due to poor flowability of the polymer it does not have a sufficiently strong bonding between conductive materials making the overall plate mechanically weak. In addition, lack of flowability of the polymer (the melt viscosity is outside the limit of the invention) also effects permeability for reactant gases, because the high viscosity PVDF polymer did not fill the interstitial space between electrically conductive materials the permeability is too high to be effective as a bipolar plate.

[0099] Example 2: In Example 2, a flat bipolar plate is formed from each of PVDF 2 and PVDF 5 using the method described above. The expected conductivity and permeability of each bipolar plate is shown in FIG. 1.

[0100] PVDF 5 with low viscosity of 0.3 kP results in a plate with poor mechanical properties and electrical conductivity. As the low viscosity of 0.3kP resin, on melt, will flow excessively to cover the surface of the electrically conductive material and reduce the electrical conductivity. The lower viscosity will also mean a lower molecular weight / chain entanglement, causing poor strength for the PVDF resin which translates into poor strength for plate.

[0101] ASPECTS

[0102] Aspects of the present disclosure include the following:1. A bipolar plate comprising one or more electrically conductive materials and a fluorinated polymer, wherein the fluorinated polymer has a melt viscosity of 1 to 25 kP, such as1 to 20 kP, such as 1 to 15 kP, such as 1 to 12 kP, such as 2 to 12 kP.2. The bipolar plate of aspect 1, wherein the bipolar plate is formed from the fluorinated polymer in powder form, the powder having a volume average particle size of 0.5 to 100 pm, such as 1 to 50 pm, such as 1 to 25 pm.3. The bipolar plate of any of aspects 1 to 2, wherein the bipolar plate is formed from the fluorinated polymer in powder form, fluorinated polymer composed of agglomerates of discrete particles wherein the discrete particles having a volume average particle size of 20 to 500 nm, such as 50 to 300 nm, as measured by SEM (scanning electron microscope).4. The bipolar plate of any of aspects 1 to 3, wherein the fluorinated polymer comprises a polyvinylidene fluoride polymer.5. The bipolar plate of any of aspects 1 to 4, wherein the fluorinated polymer comprises a homopolymer or copolymer of PVDF.6. The bipolar plate of any of aspects 1 to 5, wherein the plate comprises a second polymer, wherein the fluorinated polymer comprises 50-99 wt%, such as 60-95 wt%, such as 65- 90 wt%, of the total polymer in the plate and the second polymer comprises 1-50 wt%, such as 5-40 wt%, such as 10-35 wt%, of the total polymer in the bipolar plate.7. The bipolar plate of aspect 6, wherein the second polymer comprises at least one polymer selected from the group consisting of polyolefin (such as, polypropylene, polyethylene), polyamides, fluoropolymers, PEAK, and polyimides.8. The bipolar plate of any of aspects 6 to 7, wherein the second polymer has a volume average particle size below 100 microns, and wherein the second polymer has a melt viscosity of 0.05 to 29 kP, such as 0.1 to 25 kP, such as 1 to 25 kP.9. The bipolar plate of any of aspects 1 to 8, wherein the electrically conductive material is selected from the group consisting of carbon black, carbon nanotubes, graphene, graphite, expanded graphite, exfoliated graphite, carbon fibers, active coal, conductive carbon and a mixture thereof.10. The bipolar plate of any of aspects 1 to 9, wherein the electrically conductive material has an aspect ratio of 1 to 30, such as 1 to 20, such as 1 to 10. 111. The bipolar plate of any of aspects 1 to 10, wherein the fluorinated polymer and electrically conductive material are in a ratio of 0.5:95.5 to 35:65, such as 5:95 to 30:70 such as10:90 to 30:70.12. The bipolar plate of any of aspects 1 to 11, wherein the bipolar plate has a helium permeability of less than 1012cc / (cm2.s.Pa), such as less than 1013cc / (cm2.s.Pa), such as less than 1014cc / (cm2.s.Pa) for 1 inch disc of 0.3 mm thickness.13. The bipolar plate of any of aspects 1 to 12, wherein the bipolar plate has a plate thickness of 0.1 to 5 mm, such as 0.1 to 3 mm, such as 0.2 to 1 mm, such as 0.2 to 0.9 mm.14. The bipolar plate of any of aspects 1 to 13, wherein the bipolar plate has an electrical conductivity of greater than 40 S / cm, such as greater than 70 S / cm, such as greater than 100 S / cm.15. The bipolar plate of any of aspects 1 to 14, wherein the bipolar plate has a flexibility of 5 MPa or higher, such as 10 or higher, such as 20 or higher, measured by ASTM D-790.16. The bipolar plate of any of aspects 1 to 15, wherein the bipolar plate has a density of 0.8-2.1 g / cm3, such as 0.8-1.95g / cm3, such as 1.6-1.9 g / cm3, measured by ASTM 2854.17. The bipolar plate of any of aspects 1 to 16, wherein the one or more electrically conductive materials and a fluorinated polymer were dry mixed.18. A device comprising the bipolar plate of any of aspects 1 to 17, wherein the device is a hydrogen fuel cell or an electrolyzer.19. The device of aspect 18, wherein the hydrogen fuel cell is selected from the group consisting of a proton exchange membrane fuel cell, a phosphoric acid fuel cell, and an alkaline fuel cell.20. A device comprising the bipolar plate of any of aspects 1 to 17, wherein the device is an electrolyzer.21. A device comprising the bipolar plate of any of aspects 1 to 17, wherein the plate is used as an electrode in a redox flow battery or for electrodialysis.22. A method for producing a bipolar plate, comprising:- mixing, such as dry blending, one or more electrically conductive materials and a fluorinated polymer in powder form to form a conductive composition, wherein the fluorinatedpolymer has a melt viscosity of 1 to 25 kP, such 1 to 20 kP, such as 1 to 15 kP, such as 1 to 12 kP, such as 2 to 12 kP.- forming the bipolar plate by compression-molding or calendaring the conductive composition.23. The method of aspect 22, wherein the fluorinated polymer in powder form has a volume average particle size of 0.5 to 100 pm, such as 1 to 50 pm, such as 1-25.24. The method of any of aspects 22 to 23, wherein the fluorinated polymer in powder form can be composed of agglomerates of discrete particles having a volume average particle size of 20 to 500 nm, such as 50 to 300 nm, as measured by SEM.25. The method of any of aspects 22-24, wherein the fluorinated polymer comprises a polyvinylidene fluoride polymer.26. The method of any of aspects 22-25, wherein the fluorinated polymer comprises a homopolymer or copolymer of PVDF.27. The method of any of aspects 22-26, wherein the bipolar plate comprises a second polymer, wherein the fluorinated polymer comprises 50-99 wt%, such as 60-95 wt%, such as 65- 90 wt%, of the total polymer in the bipolar plate and the second polymer comprises 1-50 wt%, such as 5-40 wt%, such as 10-35 wt%, of of the total polymer in the bipolar plate.28. The method of aspect 1 , wherein the second polymer comprises at least one polymer selected from the group consisting of polyolefin (such as, polypropylene, polyethylene), polyamides, fluoropolymers, PEAK, and polyimides.29. The method of any of aspects 27 to 28, wherein the second polymer has a volume average particle size below 100 microns, and wherein the second polymer has a melt viscosity of 0.05 to 29 kP, such as 0.1 to 25 kP, such as 1 to 25 kP.30. The method of any of aspects 22 to 29, wherein the electrically conductive material is selected from the group consisting of carbon black, carbon nanotubes, graphene, graphite, expanded graphite, exfoliated graphite, carbon fibers, active coal, conductive carbon and a mixture thereof.31. The method of any of aspects 22 to 30, wherein the electrically conductive material has an aspect ratio (L:D) of 1 to 30, such as 1 to 20, such as 1 to 10.32. The method of any of aspects 22 to 31, wherein the fluorinated polymer and electrically conductive material are in a ratio of 0.5:95.5 to 35:65, such as 5:95 to 30:70 such as 10:90 to 30:70.33. The method of any of aspects 22 to 32, wherein forming the bipolar plate comprises pressing the dry blended composition to a thickness of 0.1-5 mm, such as 0.1-3 mm, such as 0.2 to 1 mm, such as 0.2 to 0.9mm.34. The method of any of aspects 22 to 33, wherein forming the bipolar plate by compression-molding or calendaring comprises:- compressing the conductive composition, such as at a temperature of 18 to 100°C, such as 18- 75°C, into a compressed sheet with a density of between 0.2 to 1 g / cm3, such as 0.3 to 0.8 g / cm3, such as 0.4 to 0.6 g / cm3;- heating the compressed sheet to a temperature above the melting point of the fluorinated polymer to melt the fluorinated polymer; and- calendaring the heated sheet at a temperature between 50°C and a temperature of at least 10°C below the melting point of the fluorinated polymer to achieve a density above the density of the compressed sheet.35. The method of aspect 34, wherein the heating is at a temperature of 120-260°C, such as 150-250°C, for a time period of 15-180 min, such as 15-150 min, such as 20-120 min, such as 20- 60.36. The method of any of aspects 34-35, wherein compressing comprises roll to roll compression / calendaring or compression molding.37. The method of any of aspects 34-36, further comprising stamping the calendared sheet to higher density above 1.5 gm / cc, such as above 1.7 gm / cc, such as above 1.8 gm / cc, such as above 1.9 gm / cc, such as above 2 gm / cc.38. The method of any of aspects 34-37, further comprising embossing to create flow field pattern.39. The method of any of aspects 34-38, further comprising embossing to create additional surface area.40. The method of any of aspects 38-39, further comprising using calendaring rolls and compression molding.41. A bipolar plate formed from the method of any of aspects 22-40.42. The bipolar plate of aspect 41, wherein the bipolar plate has a hydrogen permeability of less than 1012cc / (cm2.s.Pa), such as less than 1013cc / (cm2.s.Pa), such as less than 1014cc / (cm2.s.Pa).43. The bipolar plate of any of aspects 41 to 42, wherein the bipolar plate has a plate thickness of 0.1 to 5 mm, such as 0.1 to 3 mm, such as 0.2 to 1 mm, such as 0.2 to 0.7 mm.44. The bipolar plate of any of aspects 41 to 43, wherein the bipolar plate has an electrical conductivity of greater than 40 S / cm, such as greater than 70 S / cm, such as greater than 100 S / cm.45. The bipolar plate of any of aspects 41 to 44, wherein the bipolar plate has a flexibility of 5 MPa or higher, such as 10 or higher, such as 20 or higher, measured by ASTM D-790.46. The bipolar plate of any of aspects 41 to 45, wherein the bipolar plate has a density of 0.8-2.1 g / cm3, such as 0.8-1.95 g / cm3, such as 1.6-1.9 g / cm3, measured by ASTM 2854.47. A device comprising the bipolar plate of any of aspects 41 to 46, wherein the device is a hydrogen fuel cell.48. The device of aspect 47, wherein the hydrogen fuel cell is selected from the group consisting of a proton exchange membrane fuel cell, a phosphoric acid fuel cell, and an alkaline fuel cell.49. A device comprising the bipolar plate of any of aspects 41 to 46, wherein the device is an electrolyzer.50. A device comprising the bipolar plate of any of aspects 41 to 46, wherein the plate is a component of an electrode in a redox flow battery or an electrodialysis system.51. A device comprising the bipolar plate of any of aspects 41 to 46, wherein the plate is an electrode in a vanadium flow battery.52. A composition comprising an electrically conductive material and a fluorinated polymer in powder form, wherein the fluorinated polymer has a melt viscosity of 1 to 25 kP, such as 1 to 20 kP, such as 1 to 15 kP, such as 1 to 12 kP, such as 2 to 12 kP.53. The composition of aspect 52, wherein the bipolar plate is formed from the fluorinated polymer in powder form, the powder having a volume average particle size of 0.5 to 100 pm, such as 1 to 50 pm, such as 1-25 pm.54. The composition of any of aspects 52-53, wherein the bipolar plate is formed from the fluorinated polymer in powder form, powder can be composed of agglomerates of discrete particles wherein the discrete particles having a volume average particle size of 20 to 500 nm, such as 50 to 300 nm, as measured by SEM.55. The composition of any of aspects 52-54, wherein the fluorinated polymer comprises a polyvinylidene fluoride polymer.56. The composition of any of aspects 52-55, wherein the fluorinated polymer comprises a homopolymer or copolymer of PVDF,57. The composition of any of aspects 52-56, wherein the bipolar plate comprises a second polymer, wherein the fluorinated polymer comprises 50-99 wt%, such as 60-95 wt%, such as 65- 90 wt%, of the total polymer in the bipolar plate and the second polymer comprises 1-50 wt%, such as 5-40 wt%, such as 10-35 wt%, of the total polymer in the bipolar plate.58. The composition of aspect 57, wherein the second polymer comprises at least one polymer selected from the group consisting of polyolefin (such as, polypropylene, polyethylene), polyamides, fluoropolymers, PEAK, and polyimides.59. The composition of any of aspects 57-58, wherein the second polymer has a volume average particle size below 50 microns, and wherein the second polymer has a melt viscosity of 0.05 to 29 kP, such as 0.1 to 25 kP, such as 1 to 25 kP.60. The composition of any of aspects 52-59, wherein the electrically conductive material is selected from the group consisting of carbon black, carbon nanotubes, graphene, graphite, expanded graphite, exfoliated graphite, carbon fibers, active coal, conductive carbon and a mixture thereof.61. The composition of any of aspects 52-60, wherein the electrically conductive material has an aspect ratio of 1 to 30, such as 1 to 20, such as 1 to 10.62. The composition of any of aspects 52-61, wherein the fluorinated polymer and electrically conductive material will be used in a ratio of 0.5:95.5 to 35:65, such as 5:95 to 30:70 such as 10:90 to 30:70.63. The bipolar plate of any of any of the precious claim wherein no solvent is present.64. The method of any of the precious claims wherein no solvent is added in the method.65. The composition of any of the precious claims wherein no solvent is present.66 A bipolar plate comprising one or more electrically conductive materials and at least one fluorinated polymer, wherein the fluorinated polymer has a melt viscosity of 1 to 15 kP, wherein the bipolar plate is formed using the fluorinated polymer in powder form, the powder having a volume average particle size of 1 to 50 pm, wherein the fluorinated polymer comprises a homopolymer or copolymer of polyvinylidene fluoride polymer.67. A method for producing a bipolar plate, comprising: a) mixing, by dry blending, one or more electrically conductive materials and a fluorinated polymer in powder form, to form a conductive composition, wherein the fluorinated polymer comprises a homopolymer or copolymer of polyvinylidene fluoride polymer, has a melt viscosity of 1 to 15 kP, and a powder volume average particle size of 1 to 50 pm, b) compressing the conductive composition, such as at a temperature of 18- 75°C, into a compressed sheet with a density of between 0.3 to 0.8 g / cm3, c) heating the compressed sheet to a temperature above the melting point of the fluorinated polymer to melt the fluorinated polymer; and d) calendaring the heated sheet at a temperature between 50°C and a temperature of at least 10°C below the melting point of the fluorinated polymer, wherein the electrically conductive material is selected from the group consisting of carbon black, carbon nanotubes, graphene, graphite, expanded graphite, exfoliated graphite, carbon fibers, active coal, conductive carbon and a mixture thereof, wherein the fluorinated polymer and electrically conductive material are in a ratio of 5:95 to 30:70.

[0103] While the embodiments of the present disclosure have been described with particular reference to certain embodiments thereof, it will be understood that changes and modifications may be made by those of ordinary skill within the scope and spirit of the following claims.

Claims

CLAIMS:1 A bipolar plate comprising one or more electrically conductive materials and at least one fluorinated polymer, wherein the fluorinated polymer has a melt viscosity of 1 to 25 kP, such as1 to 20 kP, such as 1 to 15 kP, such as 1 to 12 kP, such as 2 to 12 kP.

2. The bipolar plate of claim 1, wherein the bipolar plate is formed using the fluorinated polymer in powder form, the powder having a volume average particle size of 0.5 to 100 pm, such as 1 to 50 pm, such as 1-25 pm.

3. The bipolar plate of any of claims 1 to 2, wherein the bipolar plate is formed from the fluorinated polymer in powder form, the fluorinated polymer composed of agglomerates of discrete particles wherein the discrete particles have a volume average particle size of 20 to 500 nm, such as 50 to 300 nm, as measured by SEM.

4. The bipolar plate of any of claims 1 to 3, wherein the fluorinated polymer comprises a polyvinylidene fluoride polymer.

5. The bipolar plate of any of claims 1 to 4, wherein the fluorinated polymer comprises a homopolymer or copolymer of PVDF.

6. The bipolar plate of any of claims 1 to 5, wherein the bipolar plate comprises a second polymer, wherein the fluorinated polymer comprises 50-99 wt%, such as 60-95 wt%, such as 65- 90 wt%, of the total polymer in the bipolar plate and the second polymer comprises 1-50 wt%, such as 5-40 wt%, such as 10-35 wt%, of the total polymer in the bipolar plate.

7. The bipolar plate of claim 6, wherein the second polymer comprises at least one polymer selected from the group consisting of polyolefin (such as, polypropylene, polyethylene), polyamides, fluoropolymers, PEAK, and polyimides.

8. The bipolar plate of any of claims 1 to 7, wherein the electrically conductive material is selected from the group consisting of carbon black, carbon nanotubes, graphene, graphite, expanded graphite, exfoliated graphite, carbon fibers, active coal, conductive carbon and a mixture thereof.

9. The bipolar plate of any of claims 1 to 8, wherein the fluorinated polymer and electrically conductive material are in a weight ratio of 0.5:95.5 to 35:65, such as 5:95 to 30:70, such as 10:90 to 30:70.

10. The bipolar plate of any of claims 1 to 9, wherein the bipolar plate has a helium permeability of less than 1012cc / (cm2.s.Pa), such as less than 1013cc / (cm2.s.Pa), such as less than 1014cc / (cm2.s.Pa).

11. The bipolar plate of any of claims 1 to 10, wherein the bipolar plate has a plate thickness of 0.1 to 5 mm, such as 0.1 to 3 mm, such as 0.2 to 1 mm, such as 0.2 to 0.9 mm.

12. The bipolar plate of any of claims 1 to 11, wherein the bipolar plate has an electrical conductivity of greater than 40 S / cm, such as greater than 70 S / cm, such as greater than 100 S / cm.

13. The bipolar plate of any of claims 1 to 12, wherein the bipolar plate has a flexibility of 5 MPa or higher, such as 10 MPa or higher, such as 20 MPa or higher measured by ASTM D790.

14. The bipolar plate of any of claims 1 to 13, wherein the bipolar plate has a density of 0.8- 2.1 g / cm3, such as 1 -1.95 g / cm3, such as 1.4 to 1.9 g / cm3, such as 1.6-1.9 g / cm3, measured by ASTM 2854.

15. A device comprising the bipolar plate of any of claims 1 to 14, wherein the device is a hydrogen fuel cell.

16. A device comprising the bipolar plate of any of claims 1 to 14, wherein the device is an electrolyzer.

17. A device comprising the bipolar plate of any of claims 1 to 14, wherein the device is a redox flow battery.

18. A method for producing a bipolar plate, comprising: a) mixing, such as dry blending, one or more electrically conductive materials and a fluorinated polymer in powder form to form a conductive composition, wherein the fluorinated polymer has a melt viscosity of 1 to 25 kP, such as 1 to 20 kP, such as 1 to 15 kP, such as 1 to 12 kP, such as 2 to 12 kP. b) forming the bipolar plate by compression-molding or calendaring the conductive composition.

19. The method of claim 18, wherein the particles of the fluorinated polymer have a volume average particle size of 0.5 to 100 pm, such as 1 to 50 pm, such as 1-25 pm.

20. The method of any of claims 18 to 19, wherein the fluorinated polymer in powder form is composed of agglomerates of discrete particles having a volume average particle size of 20 to 500 nm, such as 50 to 300 nm, as measured by SEM.

21. The method of any of claims 18-20, wherein the fluorinated polymer comprises a polyvinylidene fluoride polymer.

22. The method of any of claims 18-21, wherein the fluorinated polymer comprises a homopolymer or copolymer of PVDF.

23. The method of any of claims 18-22, wherein the bipolar plate comprises a second polymer, wherein the fluorinated polymer comprises 50-99 wt%, such as 60-95 wt%, such as 65- 90 wt%, of the total polymer in the bipolar plate and the second polymer comprises 1-50 wt%, such as 5-40 wt%, such as 10-35 wt%, of the total polymer in the bipolar plate.

24. The method of claim 23, wherein the second polymer comprises at least one polymer selected from the group consisting of polyolefin (such as, polypropylene, polyethylene), polyamides, fluoropolymers, PEAK, and polyimides.

25. The method of any of claims 18 to 24, wherein the electrically conductive material is selected from the group consisting of carbon black, carbon nanotubes, graphene, graphite, expanded graphite, exfoliated graphite, carbon fibers, active coal, conductive carbon and a mixture thereof.

26. The method of any of claims 18 to 25, wherein the electrically conductive material has an aspect ratio (L:D) of 1 to 30, such as 1 to 20, such as 1 to 10.

27. The method of any of claims 18 to 26, wherein the fluorinated polymer and electrically conductive material are in a ratio of 0.5:95.5 to 35:65, such as 5:95 to 30:70 such as 10:90 to 30:70.

28. The method of any of claims 18 to 27, wherein forming the bipolar plate comprises pressing the dry blended composition to a thickness of 0.1-5 mm, such as 0.1-3 mm, such as 0.2 to 1 mm, such as 0.2 to 0.9mm.

29. The method of any of claims 18 to 28, wherein forming the bipolar plate comprises: 1a) compressing the conductive composition, such as at a temperature of 18 to 100°C, such as 18- 75°C, into a compressed sheet with a density of between 0.2 to 1 g / cm3, such as 0.3 to 0.8 g / cm3, such as 0.4 to 0.6 g / cm3; b) heating the compressed sheet to a temperature above the melting point of the fluorinated polymer to melt the fluorinated polymer; and c) calendaring the heated sheet at a temperature between 50°C and a temperature of at least 10°C below the melting point of the fluorinated polymer to achieve a density above the density of the compressed sheet.

30. The method of claim 29, wherein the heating is at a temperature of 120-260°C, such as 150-250°C, for a time period of 15-180 min, such as 15-150 min, such as 20-120 min, such as 20- 60 min.

31. The method of any of claims 29-30, wherein compressing comprises roll to roll compression or compression molding.

32. A bipolar plate formed from the method of any of claims 18-31.

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