Coated graphite particle material

Abstract

The present invention provides a novel coated graphite particulate material comprising graphite particles coated with a layer of amorphous carbon, the coated graphite particulate material having a D of at least about 20 μm. 50 Particle size distribution (PSD) of approximately 3.0 m 2 / g and a crystallographic L of at least about 210 nm c The present invention relates to a coated graphite particle material characterized by a γ-value. The present invention also provides a method for producing the coated graphite particle material, and a polymer composite composition comprising the coated graphite particle material. The present invention further relates to a bipolar plate comprising the coated graphite particle material, and downstream products such as a fuel cell comprising the bipolar plate.

Description

[Technical Field]

[0001] The present invention relates to novel surface-coated graphite particle materials, including graphite particles coated with a layer of amorphous carbon, e.g., pyrolytic carbon, which can be prepared by a suitable coating technique, such as chemical vapor deposition (CVD). Also described herein are methods for producing such particle materials. Further disclosed herein are uses of the novel composite particle materials and downstream products thereof, such as compositions comprising the coated graphite particle materials as conductive materials in polymer composites, useful as bipolar plates in hydrogen (PEM) fuel cells or redox-flow batteries. [Background technology]

[0002] Hydrogen fuel cells are a research area that has attracted significant interest not only from the scientific community, but also from the general public and industry. The most common type of hydrogen fuel cell for many important applications (e.g., vehicular applications) is the polymer electrolyte membrane (PEM) fuel cell. In a PEM fuel cell (also known as a proton exchange membrane fuel cell, or PEMFC), an electrolyte membrane is sandwiched between a positive electrode (cathode) and a negative electrode (anode), which are physically separated but electrically connected into a fuel cell stack by bipolar plates.

[0003] Therefore, bipolar plates are essential components of PEM hydrogen fuel cells. To enable smooth operation of hydrogen fuel cells, bipolar plates must be airtight, exhibit good electrical and thermal conductivity, be easily processable, and be resistant to clamping forces and corrosion during operation. Because bipolar plates account for a large portion of a PEM fuel cell, using expensive materials can significantly increase the cost of the PEM fuel cell. Therefore, low-cost yet efficient materials are highly desirable for preparing bipolar plates. Furthermore, particularly for mobile applications, such as in vehicles, low-weight bipolar plates are desired to enable efficient and lightweight electric vehicles.

[0004] Metal bipolar plates are widely used due to their high electrical and thermal conductivity, high mechanical strength, and low cost (in the case of stainless steel). Additionally, metals can be easily formed into thin plates (<1 mm), making them attractive for automotive applications. However, metals are prone to corrosion, which compromises the lifetime of the fuel cell. To prevent this corrosion, metal plates require protective coatings (e.g., metal nitrides), which add additional processing steps and increase the cost of the metal plates while leaving a long-term risk of corrosion for applications requiring a 10,000-hour lifetime.

[0005] A promising alternative to these metal-based bipolar plates is a bipolar plate made of a polymer composite, in which carbon particulate material is embedded in a polymer matrix (which can be either a thermoplastic or thermosetting polymer). Ideally, a polymer-graphite composite-based bipolar plate would combine the advantages of good electrical conductivity, adequate thermal conductivity, low cost, low weight, and high durability to form a bipolar plate with highly advantageous properties. Typically, workable loading levels of carbon particulate material in bipolar plates can reach up to 80 or 85 wt. % graphite within the polymer matrix. However, while such loading allows for good electrical conductivity, such polymer composite compositions tend to form highly viscous polymer compositions prior to the formation of the bipolar plate, which are difficult to process in an efficient manner.

[0006] Carbonaceous particulate materials incorporated into such bipolar plates include synthetic graphite, (purified) natural graphite, expanded graphite, carbon fibers, carbon nanotubes, and / or amorphous graphite powders, such as carbon black. Natural and synthetic graphite particles are known in a variety of sizes and morphologies, e.g., more "spherical" (round) or more "flaky" (thin) shapes. Different carbon and graphite shapes are associated with different levels of anisotropy due to their three-dimensional orientation, with more spherical carbon structures having lower anisotropy. Isotropic carbon materials are generally considered advantageous for graphite-containing bipolar plates in PEM fuel cells, at least not because bipolar plates in fuel cells are typically characterized by lower through-thickness conductivity (conductivity across the fuel cell stack), particularly when flake-shaped particles (or other highly anisotropic materials) are used.

[0007] From a processing perspective, flowability problems are particularly prevalent with non-spherical particles, e.g., plate-like particles such as unmodified (i.e., "flaked") natural graphite. Due to their shape and adhesive forces, the particles tend to stick together, causing problems with processing, dosing, and dispersion of these particles in thermoplastic and thermoset matrices. Flake graphite also has a lower apparent density compared to spherical or other non-flake graphites, which also results in poor flowability.

[0008] Attempts have been made to improve the flowability of platelet-shaped graphite particles (such as synthetic or natural flake graphite), but measures such as grinding the particles or transforming them into spherical graphite typically result in a significant increase in the electrical and thermal resistivity in the matrix (which can be explained by changes in the shape / morphology of the particles). SI Heo et al., Adv. Comp. Mater., Vol. 15, No. 1, (2006) pp. 115-126 and T. Derieth et al., J. of New Mat. for Electr. Syst., 11 (2008) pp. 21-29 may be useful in providing readers skilled in the art with further insight into the relevance and influence of particle morphology on particle formulation and molding processes, as well as the electrical and mechanical properties of composites formed from the particles.

[0009] As mentioned above, carbon black is a particulate form of amorphous carbon. The structure of carbon black particles is typically composed of spherical amorphous primary particles, which are covalently bonded together to form larger aggregates. However, compared to graphite, amorphous carbon has significantly lower thermal conductivity. Conductive carbon black particles typically consist of primary particles 10–50 nm in size and agglomerates of larger composite particles, often exceeding 100 nm in diameter. Conductive carbon black aggregates form a conductive network in porous electrodes, thereby reducing electronic resistance (J.B. Donnet, R.P. Bansal, M.J. Wang, Carbon Black Science and Technology, 2nd ed., Marcel Dekker Inc., New York, 1993). The void volume within and between the large conductive carbon black aggregates created by the carbon black structure results in high oil absorption. Conductive carbon black typically has an oil absorption of greater than 150 mL / 100 g (measured according to ASTM D2414-01, see method described below).

[0010] Amorphous coatings of carbon on the surface of graphitic materials take advantage of the core properties of crystalline carbon, but are desirable for technical applications where a particle surface with a high degree of graphitization would degrade some of the application parameters associated with the surface properties of the graphitic material, such as high Braun-Emmett-Teller (BET) solid surface area (SSA), etc. Additionally, amorphous coatings are desirable for technical applications where the surface chemistry or morphology of the carbonaceous core would degrade some of the application parameters associated with the surface properties of the carbonaceous material.

[0011] Amorphous carbon coating can be achieved by several methods known in the art, such as pitch coating followed by carbonization at high temperatures, or by more modern techniques such as chemical vapor deposition (CVD). In any event, the amorphous carbon coated graphite particles of the present invention are believed to be unique compared to other surface coated graphite materials described in the literature.

[0012] For example, Guoping et al., Solid State Ionics, 176, 2005, pp. 905–909, reported that coating of crushed spherical natural graphite by CVD at temperatures between 900°C and 1200°C led to improved initial Coulombic efficiency and better cycling stability in lithium-ion batteries. Natarajan et al., Carbon, 39, 2001, pp. 1409–1413, reported CVD coating of synthetic graphite at temperatures between 700°C and 1000°C. The authors reported that CVD coating at temperatures around 800°C yielded the best results in terms of Coulombic efficiency (for lithium-ion batteries), while demonstrating reduced irregularity in the treated graphite particles (i.e., the intensity of the D-band, as determined by Raman spectroscopy, was reduced compared to untreated material). Interestingly, the authors reported an increase in the intensity of the D-band at 1000°C, suggesting increased irregularity on the graphite particle surface at higher temperatures. Finally, Ding et al., Surface & Coatings Technology, 200, 2006, pp. 3041-3048, also reported on CVD-coated graphite particles by contacting synthetic graphite with methane at 1000°C. They concluded that graphite particles coated by CVD at 1000°C for 30 minutes showed improved electrochemical properties compared to untreated graphite material.

[0013] WO 2013 / 149807 describes a surface modification process for synthetic graphite particles, obtainable by oxidation treatment or, alternatively, by chemical vapor deposition (CVD) coating, to provide graphite materials with improved surface properties. WO 2016 / 008951 discloses surface-modified carbonaceous materials, such as synthetic graphite, in which an unmodified carbon precursor is first subjected to an amorphous carbon coating (e.g., by CVD) and then the coated material is exposed to an oxygen-containing atmosphere. This procedure results in surface-modified carbonaceous particles that are more hydrophilic than the amorphous carbon-coated particles prior to surface oxidation ("activation").

[0014] In light of the above, there is a need for graphite particle materials that are particularly well-suited for use in bipolar plates. Ideally, such graphite materials, when used in typical polymer matrices for bipolar plates, should provide polymer composite compositions with excellent electrical and thermal properties while maintaining good processability (e.g., acceptable viscosity at the high loadings required for bipolar plates). Such graphite materials would enable the fabrication of bipolar plates that exhibit excellent thermal and electrical conductivity while remaining lightweight, durable, and corrosion-resistant. Summary of the Invention [Problem to be solved by the invention]

[0015] The inventors have surprisingly found that by carefully optimizing the physicochemical properties of graphite it is possible to provide graphite particles coated with amorphous carbon which have improved properties, in particular in terms of electrical and thermal conductivity, but also in terms of good processability during the manufacturing process of, for example, bipolar plates.

[0016] Bipolar plates containing the novel coated graphite particulate material of the present invention exhibit, among other things, increased through-plane thermal conductivity and decreased electrical resistivity compared to bipolar plates containing otherwise identical uncoated particulate material. In addition, while the viscosity of polymer-graphite particle compositions generally increases with increasing graphite loading, it has been found that the viscosity of polymer compositions containing the graphite particles of the present invention remains lower than other graphite-polymer composite compositions. [Means for solving the problem]

[0017] Thus, in a first aspect, the present invention relates to a coated graphite particulate material comprising graphite particles coated with a layer of amorphous carbon, the coated graphite particulate material having a D of at least about 20 μm, optionally at least about 23 μm, or at least about 25 μm, or at least about 27 μm, or at least about 30 μm, or at least about 35 μm, or at least about 40 μm. 50 In this first embodiment, the coated graphite particulate material is characterized by a particle size distribution (PSD) having a particle size distribution (PSD) of about 3.0 m. 2 / g or less, optionally about 2.8m 2 / g or less than about 2.6m 2 In this first aspect, the coated graphite particulate material is characterized by a BET specific surface area (BET SSA) of at least about 210 nm, optionally at least about 250 nm, at least about 300 nm, at least about 400 nm, or at least about 500 nm. c Further, in this first aspect, the coated graphite particulate material is characterized by a Raman I value of at least about 0.25, at least about 0.3, at least about 0.35, at least about 0.4, at least about 0.45, or at least about 0.5. D / I G It is characterized by the ratio

[0018] In another aspect, the present invention provides a method for preparing the coated graphite particulate material described herein, the method comprising: (i) providing a graphite starting material having: a Raman I of less than about 0.4, optionally less than about 0.35, less than about 0.3, or less than about 0.25 D / I G ratio; a crystallographic L of at least about 210 nm, optionally at least about 250 nm, at least about 300 nm, at least about 400 nm, or at least about 500 nm c value; and A D of at least about 20 μm, optionally at least about 23 μm, at least about 25 μm, at least about 27 μm, at least about 30 μm, at least about 35 μm, or at least about 40 μm 50 particle size distribution (PSD) with and optionally, about 5 m 2 / g or less, approximately 4m 2 / g or less, or about 3m 2 / g; and a BET specific surface area of ​​at least about 0.6 g / cm 3 , at least about 0.7 g / cm 3 , at least about 0.8 g / cm 3 , or at least about 0.9 g / cm 3 tap density; and (ii) coating the graphite starting material with a layer of amorphous carbon, thereby forming a coated graphite particulate material.

[0019] In a further aspect, the present invention relates to coated graphite particulate material obtainable by the method according to the present disclosure.

[0020] Yet another aspect of the present invention relates to a composition comprising the coated graphite particulate material and at least one other carbon particulate material, wherein the at least one other carbon particulate material can be any one of natural graphite, synthetic graphite, expanded graphite, carbon fiber, carbon nanotubes, graphene, coke, carbon black, and mixtures thereof. The at least one other carbonaceous particulate material can typically be present in an amount of 1 wt.% to 80 wt.% based on the total weight of the composition. The composition comprising the coated graphite particulate material may alternatively or additionally further comprise at least one metal powder selected from the group consisting of titanium, aluminum, silver, nickel, copper, and mixtures thereof. In such embodiments, the at least one metal powder can optionally be present in an amount of 0.1 wt.% to 10 wt.% based on the total weight of the composition.

[0021] In a further aspect, the present invention also relates to a polymer composite comprising coated graphite particulate material or a composition comprising the coated graphite particulate material of the present invention embedded in a polymer matrix.

[0022] Furthermore, the present invention also relates to the use of the coated graphite particle material, or the composition comprising the coated graphite particle material, or the polymer composite material, for manufacturing a bipolar plate, optionally suitable for a fuel cell such as a proton exchange membrane (PEM) fuel cell, a redox-flow battery, or a water electrolysis device.

[0023] In yet another aspect, the present invention also relates to a bipolar plate comprising the coated graphite particulate material described herein, or a composition comprising the coated graphite particulate material, or the polymer composite material described herein, typically suitable for use in a fuel cell, such as a proton exchange membrane (PEM) fuel cell, a redox-flow battery, or a water electrolysis device, such as a proton exchange membrane (PEM) electrolyzer.

[0024] In a further aspect, the present invention provides a method for manufacturing a bipolar plate, the method comprising: (i) mixing the coated graphite particulate material or a composition comprising the coated graphite particulate material with a polymer to form a polymer composite; and (ii) forming a bipolar plate from the polymer composite material obtained in the first step; Suitable polymers may include thermoplastic or thermosetting polymers, or elastomers. In some embodiments, the mixing is carried out in an extruder. In some embodiments, the bipolar plate is manufactured by compression molding, injection molding, or extrusion of the polymer composite obtained in the first step, or by a roll-to-roll process.

[0025] In another aspect, the present invention also relates to the use of a bipolar plate as described above for manufacturing a fuel cell, such as a proton exchange membrane (PEM) fuel cell, or a redox-flow battery, or a water electrolysis device, such as a proton exchange membrane (PEM) electrolyzer.

[0026] Finally, the present invention relates to a fuel cell, such as a proton exchange membrane (PEM) fuel cell, a redox flow battery, or a water electrolysis device, such as a proton exchange membrane (PEM) electrolyzer, comprising the bipolar plate described herein. The present invention will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 shows SEM images of synthetic graphite available from Imerys Graphite & Carbon under the trade name TIMREX® KS 5-75TT (Comparative Example (“CE”) 1, top), natural graphite in a “potato shape” before CVD coating (Comparative Example 5, center), and CVD-coated spherical graphite (Comparative Example 8, bottom). [Figure 2] FIG. 2 shows the D50 in micrometers of the graphite particle materials used in the examples. [Figure 3] FIG. 3 shows the BET SSA values ​​(m / g) of the graphite particulate materials used in the examples, demonstrating that the coated graphite particulate materials according to the present invention exhibited lower BET SSA than comparable uncoated graphite particulate materials. [Figure 4] FIG. 4 shows the Lc values ​​in nm of the graphite particle materials used in the examples. [Figure 5] Figure 5 shows the ratio of ID to IG peaks in the Raman spectrum of the graphite particle material used in the examples. In general, the ID / IG ratio increases after coating. [Figure 6] Figure 6 shows the water contact angles in degrees for the graphite particle materials used in the examples. In general, the hydrophobicity increased after coating. [Figure 7]Figure 7 shows the surface energy (mJ / m2) of the graphite particle materials used in the examples. Generally, the surface energy decreased after coating. [Figure 8] 8 shows the angles of repose of the graphite particulate materials used in the examples (CE-4 was not measured). The graphite particulate materials according to the present invention exhibit a lower angle of repose (i.e., better flowability) compared to the comparative graphite particulate materials. [Figure 9] 9 plots the melt flow index (MFI) of the coated and uncoated graphite particle materials used in the examples at 80 wt % loading in polypropylene. The coated graphite particles according to the present invention exhibit both improved flowability as a powder and better processability as a polymer composite composition. [Figure 10] FIG. 10 is a plot of torque in Nm for various polymer compositions containing coated and uncoated synthetic and natural graphite particulate materials at 80 wt % loading with polypropylene. [Figure 11] Figure 11 shows the in-plate electrical resistivity (Ω*cm) for various plates containing coated and uncoated synthetic and natural graphite particulate materials at 80 wt% loading in polypropylene. Overall, plates made with coated particles exhibited lower electrical resistivity than plates containing the corresponding uncoated particles. [Figure 12] 12 shows the through-plate electrical resistivity (Ω*cm) for eight different plates containing the coated and uncoated synthetic and natural graphite particulate materials used in the examples at 80 wt. % loading in polypropylene. Overall, the plates made with the coated particles exhibited lower electrical resistivity than the plates containing the corresponding uncoated particles. [Figure 13] FIG. 13 shows the in-plate thermal conductivity (W / m*K) of various plates containing coated and uncoated synthetic and natural graphite particulate materials used in the examples at 80 wt % loading in polypropylene. [Figure 14] FIG. 14 shows the through-plate thermal conductivity (W / m*K) of various plates containing coated and uncoated synthetic and natural graphite particulate materials used in the examples at 80 wt % loading in polypropylene. [Figure 15] Figure 15 plots the area-specific electrical resistivity (mΩ*cm) for a compressed plate containing coated particles according to the present invention compared to a compressed plate containing uncoated graphite particulate material. The area-specific resistivity decreased significantly with increasing coating amount. [Figure 16] 16 shows the melt flow index (MFI) of coated and uncoated graphite particle material in polypropylene at both 50% and 60% weight loadings. The coated graphite particles according to the present invention demonstrate improved flowability as a powder and better processability as a polymer composite composition. [Figure 17] Figure 17 shows the in-plate electrical resistivity (Ω*cm) of various plates containing coated and uncoated synthetic and natural graphite particulate materials at 50 wt% and 60 wt% loadings in polypropylene. Overall, plates made with coated particles exhibited lower electrical resistivity than plates containing their uncoated counterparts, with the lowest IE3 values ​​and significantly improved electrical conductivity. [Figure 18] Figure 18 shows the through-plate electrical resistivity (Ω*cm) of various plates containing coated and uncoated synthetic and natural graphite particulate materials at 50 wt% and 60 wt% loadings in polypropylene. Overall, plates made with coated particles exhibited lower electrical resistivity than plates containing their uncoated counterparts, with the lowest IE3 values ​​and significantly improved electrical conductivity. [Figure 19] FIG. 19 shows the powder resistivity (mΩ*cm) of coated and uncoated synthetic and natural graphite particle materials at pressures of 10 kN / cm and 20 kN / cm, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0028] The inventors have surprisingly found that highly crystalline graphite particles, approximately 5 m 2 / g or less, or about 4m 2 / g or less, or about 3m 2 / g or less, or about 1.2m 2 / g ~ approx. 3.5m 2 It has been found that coating coated graphite particulate materials, particularly flaky or shaped / rounded particles, with a layer of non-graphitic (typically amorphous) carbon, having a BET SSA of 1 / g and an appropriate particle size distribution, results in coated graphite particulate materials with excellent properties and typically smaller BET SSAs, making them particularly useful as components in polymer-graphite composite compositions. In particular, it has been found that for bipolar plate applications, more isotropic natural graphite materials (i.e., materials that are shaped / rounded rather than flaky) provide superior results in terms of electrical and thermal conductivity and processability after coating. The polymer composite compositions containing the coated graphite particulate materials of the present invention are particularly useful as components of bipolar plates (e.g., bipolar plates used in polymer electrolyte membrane (PEM) fuel cells), enabling the production of bipolar plates with reduced weight and relatively low manufacturing costs, particularly for PEM fuel cells and the like. Bipolar plates containing coated graphite particle material according to the present invention exhibit improved electrical resistivity over plates containing comparable spherical particles, while still maintaining good processability during manufacturing.

[0029] The term "about," as used herein in the context of a parameter or value referred to herein, encompasses a ±10% deviation of the given value, unless otherwise specified.

[0030] Coated graphite particle material of the present invention As mentioned above, the present invention relates in a first aspect to a coated graphite particulate material comprising graphite particles coated with a layer of amorphous carbon, the coated graphite particulate material being characterized by: (i) a D of at least about 20 μm 50 particle size distribution (PSD) with (ii) Approximately 3.0m 2 BET specific surface area (BET SSA) less than / g; (iii) a crystallographic L of at least about 210 nm c value (where this crystallographic L c "About" a value includes a deviation of ±5% of the given value; and (iv) a Raman I of at least about 0.25, at least about 0.3, at least about 0.35, at least about 0.4, at least about 0.45, or at least about 0.5 D / I G ratio.

[0031] In some embodiments, the coated graphite particulate material has a D of at least about 23 μm, or at least about 25 μm, or at least about 27 μm, or at least about 30 μm, or at least about 35 μm, or at least about 40 μm, or from about 20 μm to about 60 μm. 50 It is characterized by a particle size distribution (PSD) having

[0032] In some embodiments, the coated graphite particulate material is about 2.8 m 2 / g or less than about 2.6m 2 / g or less than about 2.4m 2 / g or less than about 2.2m 2 / g or less, or about 1.2m 2 / g~approx.3.0m 2 It is characterized by a BET specific surface area (BET SSA) in g / g.

[0033] In some embodiments, the coated graphite particulate material has a crystallographic L of at least about 250 nm, at least about 300 nm, at least about 400 nm, or at least about 500 nm, or from about 210 nm to about 800 nm. c It is characterized by its value.

[0034] In some embodiments, the coated graphite particulate material has a density of at least about 0.7 g / cm 3, at least about 0.8 g / cm 3 , or at least about 0.9 g / cm 3 In some embodiments, the tap density is about 0.7 g / cm 3 ~approx. 1.4g / cm 3 It may be.

[0035] In some embodiments, the coated graphite particulate material has a viscosity of at least about 2.22 g / cm 3 , or at least about 2.23 g / cm 3 In some embodiments, the xylene density is about 2.22 g / cm 3 ~Approx. 2.26g / cm 3 It may be.

[0036] In some embodiments, the Raman I D / I G The ratio may be from about 0.25 to about 0.75.

[0037] The laser used in Raman spectroscopy cannot penetrate graphite particles, making Raman a particularly useful spectroscopic technique for characterizing the surface properties of particulate materials (here, graphite particles). Therefore, in general, Raman R(I D / I G ) value depends on the one hand on the properties of the starting natural graphite material (and in particular its surface properties) before coating, and on the other hand on the properties and thickness of the coating with non-graphitic (e.g. amorphous) carbon, since surface amorphous carbon increases the intensity of the D band relative to the G band (compared to graphitic carbon).

[0038] Alternatively or additionally, the crystallographic c / 2 value of the coated graphite particulate material may be less than about 0.3360 nm, less than about 0.3358 nm, or less than about 0.3356 nm in some embodiments, and may be between about 0.3346 nm and about 0.3360 nm.

[0039] In some embodiments, the coated graphite particulate material has a D of at least about 10 μm, at least about 12 μm, at least about 15 μm, or at least about 20 μm. 10 Additionally, in the same or a different embodiment, the coated graphite particulate material can be further characterized by a particle size distribution (PSD) having a D of at least about 30 μm, at least about 40 μm, at least about 50 μm, at least about 55 μm, at least about 60 μm, at least about 70 μm, or at least about 80 μm. 90 In some embodiments, the coated graphite particulate material can be further characterized by a particle size distribution (PSD) having a D of about 10 μm to about 30 μm. 10 and / or D of about 30 μm to about 100 μm 90 can be characterized by

[0040] The coated graphite particulate material may optionally be further characterized by one or more of the following parameters:

[0041] In certain embodiments, the coated graphite particulate material can have a springback value of less than about 50%, less than about 45%, less than about 40%, less than about 35%, or less than about 30%. In some embodiments, the springback value can be between about 10% and about 35%.

[0042] In some embodiments, the angle of repose of the coated graphite particulate material may be less than about 40°, less than about 38°, or less than about 36°. In some embodiments, the angle of repose of the coated graphite particulate material may be from about 30° to about 40°.

[0043] The water contact angle of the coated graphite particulate material may, in certain embodiments, be at least about 70°, at least about 80°, or at least about 85°, and in some embodiments, the water contact angle may be from about 70° to about 110°.

[0044] In certain embodiments, the dispersive surface energy of the coated graphite particulate material is about 40 mJ / m2 Less than or about 35 mJ / m 2 Less than or about 30 mJ / m 2 In some embodiments, the dispersive surface energy is less than about 15 mJ / m 2 ~about 40mJ / m 2 It may be.

[0045] The coated graphite particulate material of some embodiments has a thermal conductivity of about 10 mJ / m 2 Less than or about 8 mJ / m 2 Less than or about 6 mJ / m 2 In some embodiments, the polar surface energy is less than about 2 mJ / m 2 ~about 10mJ / m 2 It may be.

[0046] Additionally or alternatively, in some embodiments, the coated graphite particulate material has a thermal conductivity of about 40 mJ / m 2 Less than, or about 34.6 mJ / m 2 Less than, or about 31 mJ / m 2 In some embodiments, the total surface free energy is less than about 26 mJ / m 2 ~34.6mJ / m 2 It may be.

[0047] In some embodiments, the coated graphite particulate material has a strength of 10 kN / cm 2 Approximately 8mΩ * Less than cm or approximately 7 mΩ * Additionally or alternatively, the coated graphite particulate material may be further characterized by a powder electrical resistivity of less than 20 kN / cm. 2 Approximately 6mΩ * Less than cm or about 5 mΩ * It can be further characterized by a powder electrical resistivity of less than 1 / 2 cm.

[0048] The initial graphite particles ("substrate graphite particles") to be coated according to the methods described herein can typically be any natural or synthetic graphite generally suitable for use as a conductive material in bipolar plates. The substrate particles can be characterized by any morphology, for example, plate-like (flake-like), "potato-shaped," rod-like, or (almost) spherical, provided that the particle size distribution (PSD) of the substrate particles is greater than or equal to about 20 μm D. 50 The preferred morphology of the substrate particles is "shaped" or spherical, with the substrate particles having a higher tap density, which is beneficial when subjected to a CVD process and also beneficial for powder flowability during application (e.g., easy feeding into an extruder).

[0049] Generally, the substrate graphite particles to be coated should have a suitable minimum size (e.g., D greater than about 20 μm), especially for applications such as conductive materials in polymer composite-based bipolar plates. 50 Apart from the size of the crystals, for example, the relatively high crystallographic L c The crystallinity of the crystalline carbon nanotubes should be relatively high, as indicated by a low c / 2 value (greater than 210 nm and less than 0.3360 nm, respectively). It will be understood by those skilled in the art that the coating does not significantly affect these values. Typically, the coating may slightly increase the particle size and slightly decrease the crystallinity and c / 2 value due to the contribution of the amorphous carbon surface.

[0050] In some embodiments, the substrate graphite particles are natural graphite (i.e., flaked or formed / rounded) with the appropriate PSD as outlined above. For bipolar plate applications in particular, it has been found that the more isotropic (i.e., formed / rounded) natural graphite material provides superior results in terms of electrical and thermal conductivity as well as processability.

[0051] The coating of the coated graphite particulate material according to the present invention is an amorphous carbon coating. Amorphous carbon coatings of carbonaceous particles are generally known in the art. In some embodiments, the amorphous carbon coating may be a pyrolytic carbon coating, where the amorphous carbon coating layer is obtained by, for example, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), or physical vapor deposition (PVD).

[0052] Amorphous carbon coatings can also be obtained by (coal tar) pitch coating, wet coating or spray drying followed by carbonization, hydrothermal carbonization, or a sol-gel process.

[0053] In some preferred embodiments of the present invention, the pyrolytic surface coating of the graphite particle material can be achieved by chemical vapor deposition (CVD). In the case of carbon compounds such as graphite, the CVD process uniformly coats the surface of the graphite particles with largely disordered to irregular (e.g., amorphous) carbon-containing particles. As described in more detail below in describing the process for producing the coated graphite particle material of the present invention, generally, coated graphite particle materials characterized by given parameters can be obtained by chemical vapor deposition at temperatures ranging from about 500°C to about 1000°C by contacting the substrate graphite particles with a hydrocarbon-containing gas or alcohol vapor mixed with an inert carrier gas in a suitable furnace for a treatment time ranging from 3 to 120 minutes.

[0054] In certain embodiments, the layer of amorphous carbon may be present in the coated graphite particulate material in an amount greater than about 1 weight percent, or greater than about 2 weight percent, or in an amount of about 1 weight percent to about 15 weight percent, or in an amount of about 1 weight percent to about 10 weight percent, or in an amount of about 1 weight percent to about 6 weight percent, or in an amount of about 1 weight percent to about 5 weight percent, or in an amount of about 2 weight percent to about 10 weight percent, or in an amount of about 3 weight percent to about 8 weight percent, or in an amount of about 3 weight percent to about 7 weight percent, or in an amount of about 3 weight percent to about 6 weight percent, based on the total weight of the coated graphite particulate material.

[0055] Method for preparing coated graphite particle material of the present invention Another aspect of the present invention relates to a method for producing coated graphite particulate material according to the present invention. In its most general form, the method comprises: (i) providing a graphite starting material having: Raman I of less than about 0.4, or less than about 0.35, or less than about 0.3, or less than about 0.25, or from about 0.20 to about 0.40 D / I G ratio; A crystallographic L of at least about 210 nm, or at least about 250 nm, or at least about 300 nm, or at least about 400 nm, or at least about 500 nm, or from about 250 nm to about 800 nm c value; D of at least about 20 μm, or at least about 23 μm, or at least about 25 μm, or at least about 27 μm, or at least about 30 μm, or at least about 35 μm, or at least about 40 μm, or from about 25 μm to about 60 μm 50 particle size distribution (PSD) with At least about 0.6 g / cm 3 , or at least about 0.7 g / cm 3 , or at least about 0.8 g / cm 3 , or at least about 0.9 g / cm 3 tap density; and (ii) coating the graphite starting material with a layer of amorphous carbon, thereby forming a coated graphite particulate material according to the present invention.

[0056] In some embodiments, the graphite starting material is about 5 m 2 / g or less, or about 4m 2 / g or less, or about 3m 2 / g or less, or about 1.2m 2 / g ~ approx. 3.5m 2 / g。 As explained above, the BET SSA of the coated graphite particle material is typically (but not always) smaller than the BET SSA of the graphite starting material. Therefore, depending on the details of the coating process used, it is understood that suitable starting graphite particles should have a BET SSA that is close to the desired BET SSA of the coated product (although it may typically be slightly larger than the desired BET SSA of the coated product). Typically, the graphite starting material is uncoated and is coated by the process for preparing the coated graphite particle material of the present invention. However, in some embodiments, the graphite starting material may be a coated graphite material characterized by the parameters described in the preceding paragraph, which material is then further coated by the process described herein. In some embodiments, the graphite starting material is a coated graphite particle material according to the present invention, i.e., a coated graphite particle material characterized by parameters that satisfy the parameter ranges of both the starting material (described in the preceding paragraph) and the parameters described for the final product as defined herein. The multilayer coated graphite particulate material obtained by this embodiment of the method can have certain beneficial properties provided by the additional coating step, which more than compensate for the additional cost and effort associated with the additional coating.

[0057] In some embodiments, the layer of amorphous carbon deposited on the graphite starting material by the coating process can be obtained by a method selected from pyrolytic carbon chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), or physical vapor deposition (PVD).

[0058] In other embodiments, the layer of amorphous carbon can be obtained by (coal tar) pitch coating, wet coating followed by carbonization, spray drying followed by carbonization, hydrothermal carbonization, or a sol-gel process.

[0059] In some preferred embodiments of the present invention, the surface coating of the graphite particulate material in coating step (ii) of the process may preferably be achieved by chemical vapor deposition (CVD) of pyrolytic carbon onto the graphite starting material.

[0060] In some embodiments, the chemical vapor deposition (CVD) process is carried out by contacting the graphite particle material to be coated with a hydrocarbon gas or alcohol vapor mixed with an inert carrier gas. The hydrocarbon gas is preferably selected from aliphatic or aromatic hydrocarbons selected from the group consisting of methane, ethane, ethylene, propane, propene, acetylene, butane, isobutene, benzene, toluene, xylene, liquefied petroleum gas (LPG), natural gas, and combinations thereof. Particularly preferred hydrocarbon gases are acetylene, natural gas, methane, or propane. In some embodiments, the alcohol used in the CVD coating process (ii) is preferably selected from the group consisting of ethanol, propanol, isopropanol, and combinations thereof, with ethanol or propanol being particularly preferred. The hydrocarbon gas or alcohol vapor may also be mixed with an inert carrier gas such as nitrogen or argon, preferably nitrogen.

[0061] Appropriate gas flow rates for CVD coating generally depend on the specific circumstances (reactor type, load, residence time, and type of starting material) and can be determined by one of skill in the art using the information contained herein. In some embodiments, good results have been achieved using propane or acetylene gas at flow rates of about 1-5 L / min, about 1-3 L / min, or about 1-2 L / min, optionally in combination with an inert carrier gas at flow rates of about 1-10 L / min, about 1-8 L / min, about 2-5 L / min, or 2-3 L / min, although the exact flow rates will depend on the reactor type, the material being processed, and other process parameters. In other embodiments, a pre-prepared mixture of propane or acetylene gas with nitrogen or argon carrier gas can be used for the CVD coating process. For example, in a fluidized-bed reactor, coating can be achieved at higher flow rates, e.g., about 1-50 L / min, 10-25 L / min, or 20-25 L / min. In some embodiments, the ratio of propane or acetylene gas to inert carrier gas in the mixture is about 1:10 or 1:9. For liquid hydrocarbons (such as benzene, toluene, isopropanol, ethanol, etc.), hydrocarbon flows of 0.1 g / min to 10 g / min are used to provide coatings for about 0.1 kg to about 15 kg of feedstock, depending on the size of the equipment.

[0062] The CVD coating step according to certain embodiments of this aspect of the invention is typically carried out in a reactor with a residence time ranging from 10 to 180 minutes, 10 to 120 minutes, 10 to 60 minutes, or 20 to 40 minutes. In other words, the contact time between the graphite starting material and the hydrocarbon gas or alcohol vapor to achieve the CVD coating is usually 10 to 180 minutes, 10 to 120 minutes, 10 to 60 minutes, or 20 to 40 minutes.

[0063] It will be readily apparent to one skilled in the art that the treatment time must, of course, be adjusted to be long enough to deposit the desired amount of amorphous carbon onto the graphite particles.

[0064] The temperature of the CVD coating process is typically in the range of 500°C to 1200°C, but in many cases the temperature is typically in the range of 600°C to 1100°C, or 700°C to 1050°C.

[0065] The CVD coating process is generally carried out at a slight overpressure. Thus, in certain embodiments, the CVD coating process is carried out at a pressure of 0-80 mbar, 0-60 mbar, 0-50 mbar, 10-60 mbar, 10-50 mbar, or 0-40 mbar above atmospheric pressure. Thus, in certain embodiments, the CVD coating process involves a reactor temperature range of 500°C to 1200°C, optionally 600°C to 1100°C, or 700°C to 1050°C, with a constant flow of an inert carrier gas, such as nitrogen, fed to the reactor at a rate of about 1-10 L / min, and a hydrocarbon fed to the reactor at a rate of 1-5 L / min if the hydrocarbon is a gas, or 0.1 g / min to 10 g / min if the hydrocarbon is a liquid. In some embodiments, the hydrocarbon is acetylene, natural gas, methane, or propane, or a mixture thereof, or benzene or toluene, or a mixture thereof. In some embodiments, the CVD coating process can be carried out at a slight overpressure of 0 to 80 mbar, typically for a residence time in the reactor ranging from 10 to 180 minutes. In embodiments where the reactor is a fluidized-bed reactor, CVD coating can also be achieved at higher total flow rates (i.e., a combination of inert gas and hydrogen gas flows), e.g., at a total flow rate of about 1 to 50 L / min. In some embodiments of the CVD coating process described herein, a vertical (vertical) electrically heated fluidized-bed reactor can be used. Alternatively, in other embodiments of the CVD coating process described herein, the reactor is a rotary kiln reactor used in a continuous production facility. In certain embodiments of the continuous reactor facility, the rotary kiln reactor can be about 2 m long and configured with a 3 to 4° inclination and a rotation speed of 6 to 8 rpm.

[0066] In view of the inventive method described herein, another aspect of the present invention relates to a coated black particle material characterized by the above parameters obtainable by the method described herein.

[0067] Compositions containing the coated black particle material of the present invention In yet another aspect, the present invention relates to a composition comprising a coated graphite particulate material according to the present invention and further comprising at least one other carbon particulate material.

[0068] In some embodiments, the at least one other carbon particulate material is selected from the group consisting of natural graphite, synthetic graphite, expanded graphite, carbon fiber, carbon nanotubes, graphene, coke, carbon black, and combinations thereof.

[0069] In some embodiments, the at least one other carbon particulate material is present in an amount of 1 to 80 wt%, 1 to 70 wt%, 1 to 60 wt%, 1 to 50 wt%, 1 to 40 wt%, 1 to 30 wt%, or 1 to 20 wt%, based on the total weight of the composition.

[0070] In some embodiments, compositions comprising coated graphite particulate material according to the present invention further comprise, instead of or in addition to the other carbon particulate materials described above, at least one metal powder selected from the group consisting of titanium, aluminum, silver, nickel, copper, and mixtures thereof. In some embodiments, the at least one metal powder is present in an amount of 0.1 wt. % to 10 wt. % based on the total weight of the composition.

[0071] Polymer composites containing the coated graphite particulate material of the present invention In an additional aspect, the present invention relates to a polymer composite comprising a coated graphite particulate material according to the present invention (or a composition comprising the coated graphite particulate material and at least one other carbon particulate material and / or at least one metal as described above) and a polymer. In these embodiments, the coated graphite particles are typically distributed, preferably homogeneously, within the polymer matrix.

[0072] In some embodiments of this aspect of the invention, the polymer is present in an amount of 5 wt% to 55 wt%, 6 wt% to 50 wt%, 7 wt% to 45 wt%, 8 wt% to 40 wt%, or 9 wt% to 35 wt%, preferably the polymer is present in an amount of 10 wt% to 30 wt%, based on the total weight of the polymer composite.

[0073] In certain embodiments, the polymer is selected from a thermoplastic polymer, a thermosetting polymer, an elastomer, or a mixture / blend of such polymers (or polymers modified with other polymers). Suitable polymers include, for example, polypropylene (PP), polyphenylene sulfide (PPS), fluorinated ethylene propylene (FEP), or polyvinylidene fluoride (PVDF). Suitable thermosetting polymers include epoxy resins, phenolic resins, or ethylene octene copolymers. Examples of suitable elastomers include synthetic or natural rubber.

[0074] In some embodiments of this aspect of the invention, the amount of coated graphite particulate material described herein or compositions comprising the coated graphite particulate material ranges from 45% to 95% by weight, or from 50% to 94% by weight, or from 55% to 93% by weight, or from 60% to 92% by weight, or from 65% to 91% by weight, based on the total weight of the polymer composite. In some preferred embodiments, the graphite particulate material or compositions comprising the coated graphite particulate material are present in an amount of from 70% to 90% by weight, based on the total weight of the polymer composite.

[0075] In some embodiments, the polymer composite may further comprise one or more of the following materials: expanded graphite, natural graphite, synthetic graphite, carbon fiber, carbon nanotubes, graphene, coke, carbon black, and metal powders such as titanium, aluminum, silver, nickel, copper, or mixtures thereof. In embodiments in which a metal powder is included in the polymer composite, the at least one metal powder is preferably present in an amount of 0.1 wt % to 10 wt %, based on the total weight of the polymer composite.

[0076] downstream products and uses and methods of producing these products Another aspect of the present invention relates to the use of a coated graphite particulate material, a graphite-containing composition, or a polymer composition according to the present invention for preparing a bipolar plate.

[0077] In some embodiments of this aspect of the invention, the bipolar plate is suitable for use in a fuel cell, in particular a proton exchange membrane (PEM) fuel cell, or a redox-flow battery, or a water electrolysis device such as a proton exchange membrane (PEM) electrolyzer.

[0078] While the coated graphite particulate material or compositions comprising same are particularly useful when used as the conductive material in bipolar plates, it will be appreciated that the coated graphite particulate material is also suitable for other applications where electrically and thermally conductive, lightweight, low cost, and chemically inert components are required, i.e., for example, conductive polymers for EMI shielding.

[0079] In related aspects, the invention further relates to a bipolar plate comprising the coated graphite particulate material, a composition comprising the coated graphite particulate material, or a polymer composite composition described herein. In some embodiments, the bipolar plate is suitable for use in a fuel cell, such as a proton exchange membrane (PEM) fuel cell, a redox-flow battery, or a water electrolysis device, such as a proton exchange membrane (PEM) electrolyzer.

[0080] Yet another aspect of the present invention relates to a method for producing a bipolar plate as described herein, comprising, in a first step, mixing a coated graphite particulate material as described herein or a composition comprising the coated graphite particulate material with a polymer to form a polymer composite as described herein, the second step of which comprises forming a bipolar plate from the polymer composite resulting from the mixing step.

[0081] In some embodiments of this aspect, the polymer to be mixed with the coated graphite particle material, or a composition containing the same, is selected from thermoplastic polymers, thermosetting polymers, elastomers, or mixtures / blends of such polymers (or polymers modified with other polymers). Suitable polymers include, for example, polypropylene (PP), polyphenylene sulfide (PPS), fluorinated ethylene propylene (FEP), or polyvinylidene fluoride (PVDF). Suitable thermosetting polymers include epoxy resins, phenolic resins, or ethylene octene copolymers. Examples of suitable elastomers include synthetic or natural rubber.

[0082] The mixing of the coated graphite particulate material or graphite comprising same with the polymer is, in some embodiments, carried out in an extruder. In some embodiments of the present invention, the second step of forming the bipolar plate can be achieved by techniques commonly known in the art, such as extrusion of the polymer composite material obtained in the mixing step, or by compression molding or injection molding, or by the so-called "roll-to-roll" process.

[0083] In a further, but related aspect, the present invention relates to the use of the bipolar plate described above for preparing a fuel cell, a redox-flow battery, or a water electrolysis device. In some embodiments, the fuel cell is preferably a proton exchange membrane (PEM) fuel cell, while in other embodiments, the water electrolysis device is preferably a proton exchange membrane (PEM) electrolyzer.

[0084] Finally, the invention relates to a fuel cell, preferably a proton exchange membrane (PEM) fuel cell, a redox-flow battery or a water electrolyser, preferably a proton exchange membrane (PEM) electrolyser, comprising a bipolar plate according to the invention.

[0085] It will be apparent to those skilled in the art that the above-described embodiments and the examples described below are merely examples of the multiple possibilities, particularly with regard to feature combinations. Therefore, the embodiments described herein should not be understood as limiting the present invention, the scope of which is defined by the scope of the appended claims.

[0086] Measurement method Suitable methods for determining the various properties and parameters used to define coated graphite particulate materials and compositions / downstream products containing them are described in more detail below.

[0087] Percentage (%) values ​​specified herein are by weight unless otherwise specified.

[0088] BET solid surface area, DFT micropore and mesopore volume and area Based on data recorded for liquid nitrogen absorption isotherms at 77 K in the pressure range of p / p = 0.04 to 0.26. Nitrogen gas adsorption was performed using a Quantachrome Autosorb-1. The monolayer volume can be determined according to the procedure proposed by Brunauer, Emmett, and Teller (Adsorption of Gases in Multi-molecular Layers, J. Am. Chem. Soc., 1938, 60, pp. 309-319). The specific surface area can then be calculated based on the cross-sectional area of ​​the nitrogen molecule, the monolayer volume, and the weight of the sample. Isotherms measured at 77 K in the pressure range of p / p = 0.01 to 1 were processed with DFT calculations to determine the pore size distribution, micropore and mesopore volume and area. References: Ravikovitch, P., Vishnyakov, A., Russo, R., Neinark, A., Langmuir, 16, 2000, pp. 2311-2320; Jagiello, J., Thommes, M., Carbon, 42, 2004, pp. 1227-1232

[0089] Particle Size Distribution (PSD) by Laser Diffraction The presence of particles in a coherent light beam causes diffraction. The dimensions of the diffraction pattern correlate with particle size. A collimated beam from a low-power laser illuminates a cell containing the sample. The beam exits the cell and is focused by an optical system. The distribution of light energy at the focal plane of this system is then analyzed. The electrical signal obtained from the optical detector is converted by a computer into a particle size distribution. This method gives the ratio of the total volume of particles to the discrete number of size classes that form the volumetric particle size distribution (PSD). Particle size distributions are typically calculated using the D 10 , D 50 and D 90 where 10% of the particle population (volume %) is defined by the value of D 10 50% (volume %) of the particle population has a size smaller than the value D 50 90% (volume %) of the particle population has a size smaller than the D 90 It has a size smaller than the value.

[0090] Particle size distributions (PSD) for products in the range up to 150 μm are measured by laser diffraction according to ISO 13320 using a Sympatec Helos dry system (without water). A laser beam illuminates a measurement chamber where the graphite sample is blown with compressed air, and the resulting diffraction pattern is collected by a Fourier optical system and interpreted using standard models of light scattering theory, such as the one developed by Mie (e.g., Wriedt, T. (2012), Mie Theory: A Review; Hergert, W., Wriedt, T. (Eds.), The Mie Theory; Springer Series in Optical Sciences, vol. 169, Springer, Berlin, Heidelberg; https: / / doi.org / 10.1007 / 978-3-642-28738-1 2). Three quantiles: 10% (D 10 ), 50%(D 50 ), 90%(D 90 ) calculate and report particle size distribution in μm.

[0091] X-ray diffraction XRD data were collected using a PANalytical X'Pert PRO diffractometer coupled to a PANalytical X'Celerator detector with the following characteristics shown in Table 1: [Table 1] Data were analyzed using PANalytical X'Pert HighScore Plus software.

[0092] Interlayer spacing c / 2 The interlayer spacing c / 2 was determined by X-ray diffraction. The angular positions of the peak maxima in the reflection profile were determined, and the Bragg equation was applied to calculate the interlayer spacing (Klug and Alexander, X-Ray Diffraction Procedures, John Wiley & Sons Inc., New York, London (1967)). To avoid problems due to the low absorption coefficient of carbon, instrument adjustments, and sample non-planarity, an internal standard of silicon powder was added to the sample, and the graphite peak positions were recalculated based on the positions of the silicon peaks. The graphite sample was mixed with the silicon standard powder by adding a mixture of polyglycol and ethanol. The resulting slurry was then spread onto a glass plate using a blade with a 150 μm gap and allowed to dry.

[0093] Crystallite size L c The crystallite size was determined by analyzing the

[0002] diffraction profile and determining the half-width of the peak profile. Peak broadening should be affected by the crystallite size, as proposed by Scherrer (P. Scherrer, Göttinger Nachrichten, 2, 98, 1918). However, this broadening is also influenced by other factors, such as X-ray absorption, Lorentz polarization, and atomic scattering factors. Several methods have been proposed to take these effects into account by using an internal silicon standard and applying correction functions to the Scherrer equation. In this study, we used the method suggested by Iwashita (N. Iwashita, C. Rae Park, H. Fujimoto, M. Shiraishi, and M. Inagaki, Carbon, 42, 2004, pp. 701-714). Sample preparation was the same as for the c / 2 measurement described above.

[0094] xylene density The analysis is based on the liquid exclusion principle as defined in DIN 51 901. Approximately 2.5 g (accuracy 0.1 mg) of powder was weighed in a 25 mL pycnometer. Xylene was added under vacuum (15 Torr). After a residence time of several hours at atmospheric pressure, the pycnometer was adjusted and weighed. Density indicates the ratio of mass to volume. The mass is given by the weight of the sample, and the volume is calculated from the difference in weight between the pycnometer filled with xylene with sample powder and the pycnometer filled with xylene without sample powder. Reference: DIN 51 901

[0095] Tap Density 100 g of dry graphite powder was carefully poured into a graduated cylinder. The cylinder was then fixed onto an eccentric shaft-based tapping device and actuated with 400 strokes. A volume reading was taken and the resulting density was calculated. Reference: DIN-ISO 787-11

[0096] Raman spectroscopy Raman analysis was performed using a HORIBA Scientific LabRAM-ARAMIS Micro-Raman spectrometer with a 632.8 nm HeNe laser.

[0097] I D / I G The ratio ("R value") is based on the ratio of the intensities of the so-called bands D and G. These peaks are located at 1350 cm -1 and 1580cm -1 It is measured at a temperature of 1000 K and is characteristic for carbon materials. a The value is I G / I D Calculate by multiplying the ratio by 5.8.

[0098] Springback value Springback is a source of information about the elasticity of compressed graphite powder. A specified amount of powder was poured into a die with a diameter of 20 mm. After inserting a punch to seal the die, the air was evacuated from the die. A compressive force of 1.5 metric tons was applied, resulting in a springback of 0.477 tonnes / cm². 2 A pressure of 1000 kJ / cm was obtained and the height of the powder was recorded. This height was recorded again after the pressure was released. Springback is the difference in height in % compared to the height under pressure.

[0099] angle of repose The angle of repose was measured using a Hosokawa Powder Tester PT-S according to ATMD 6393 (D6393 / D6393M-21). The angle of repose according to Carr is determined by dropping a powder sample through a vibrating sieve and funnel onto a horizontal circular platform and measuring the angle of the powder cone relative to the edge of the circular platform. Carr's angle of repose = tan -1 [H / R] where H=height of the powder pile in mm and R=radius of the circular platform in mm.

[0100] Water contact angle and surface energy Water contact angles were measured using a Kruess Force Tensiometer K100 according to the Washburn method (Edward W. Washburn: The Dynamics of Capillary Flow, Phys. Rev., 17, 374, (1921)). Generally, the Washburn method monitors the penetration of a liquid into a porous solid by capillary action over time, as defined by the Washburn equation:

[0101] Graphite particles were used as the solid powder material for this measurement, and the liquid probe materials included n-heptane (purity >99%) for determining the capillary constant, and water (Milli-Q grade) and diiodomethane (purity >99%) for determining the contact angle.

[0102] 1.0 gram of graphite powder was used for the measurements. The graphite powder was subjected to a pre-compression step under a load of 500 g for 60 seconds. All measurements were carried out at room temperature: 22-25°C. The following parameters were measured: Capillary constant: n-heptane uptake; Contact angle 1: water uptake; Contact angle 2: Diiodomethane uptake

[0103] The calculation of the surface free energy SFE was carried out using the OWRK model and Advance software (Kruess), which is expressed as the total surface free energy and is divided into polar and dispersive parts.

[0104] powder resistivity 1.5 g of graphite particles were compressed inside an insulating die (a glass fiber reinforced polymer ring with an inner diameter of 11.3 mm, inserted into a larger steel ring for additional mechanical support) between two charged brass pistons (1.13 cm diameter). The relative position of the pistons within the die (i.e., the height of the powder sample) was measured using a length gauge, while the applied force was controlled during the experiment. The voltage drop across the sample at a known constant current of 105 mA was measured at a voltage of 20 kN / cm. 2The measurements were carried out in situ using a piston as an electrode (two-point resistance measurement) at different pressures up to 1000 kJ / cm.

[0105] Ohm's law was used to calculate the sample resistance, assuming that the contact resistance between the piston and the sample could be neglected (the calculated resistance was attributed entirely to the sample). Sample resistivity was calculated using the nominal inner diameter of the mold (1.13 cm) and the measured sample height, in mΩ. * The values ​​are expressed in kN / cm. During the experiment, the polymer ring deformed elastically as a result of the lateral expansion of the sample (lateral strain), which can be ignored for comparison purposes. The tabulated values ​​are in 10 kN / cm. 2 and 20kN / cm 2 The electrical resistivity is shown for pressures of 1000 kJ / cm. References: Probst, Carbon 40(2002), pp.201-205 Grivei, KGK Kautschuk Gummi Kunststoffe 56, Jahrgang, Nr.9 / 2003 Spahr, Journal of Power Sources 196(2011), pp.3404-3413

[0106] pH value 1 g of graphite powder is dispersed in 50 mL of distilled water with 2 drops of imbentin® and measured by a pH meter with a calibrated pH electrode.

[0107] Determination of polymer composition Viscosity (Melt Flow Index) The melt flow index (MFI) of the graphite-polymer compounds was measured according to ISO 1133. In Example 2, 21.6 kg was used for the measurement at 230° C. In Example 5, 5 kg was used for the measurement at 230° C.

[0108] Viscosity (torque) The viscosity of the compound in the molten state was estimated by the torque value automatically generated by an internal mixer with a fixed chamber and rotor design (Haake Polylab OS equipped with Rheomix 610) by adding a fixed volume of plastic material evaluated at the chamber temperature at which the polymer melts.

[0109] Thermal Conductivity (TC) Test Thermal conductivity tests were performed at room temperature using a Laserflash (NETZSCH LFA 447) according to ASTM E1461. Through-plane measurements were performed on a 60 x 60 x 2 mm 3 10 x 10 x 2 mm cut from a bipolar plate 3 The test was carried out on a sample of 60 x 60 x 2 mm 3 From 10 x 3 x 2 mm 3 In-plane measurements were performed by cutting four samples of this material, rotating them 90° (on their sides), and then inserting them into a sample holder for laminated samples.

[0110] Electrical volume resistivity (VR) The electrical volume resistivity was measured using the four-point contact method according to ISO 3915.

[0111] In-plane VR Silver paint (usually ethyl acetate based) is applied evenly to both ends of the test specimen. When the paint has dried, alligator clamps are attached to the silver-painted area and a current is applied using a Schuetz MR1012S. Two wedge-shaped electrodes (distance between the tips of the wedges: 20 mm) are placed in the middle and the voltage drop is measured using a Schuetz MR1012S. The electrical resistivity is calculated according to the following formula: ρ=R * (H * W) / L In the formula, ρ is the resistivity (unit: Ω * cm), R is the resistance (unit: Ω), L is the distance between the electrodes, H is the thickness of the specimen, and W is the width of the specimen.

[0112] Through-plane VR The setup used for this measurement was a planar stack consisting of two metal plates as current electrodes, two graphite sheets (contact interlayer), the sample sandwiched between the graphite sheets, and two thin gold wires (diameter = 0.125 mm) as measurement electrodes placed between the sample and the graphite foil. 2 A pressure of 0.05 mm is applied to the stack to reduce contact resistance through the press. The electrical resistance is measured using a Schuetz MR1012S, and the electrical resistivity is calculated according to the following formula: ρ=R * (L * W) / t In the formula, ρ is the resistivity (unit: Ω * cm), R is the resistance (unit: Ω), t is the thickness of the sample, L is the length of the specimen, and W is the width of the specimen.

[0113] Area specific electrical resistivity The area-specific electrical resistance measurements were carried out using the 4-pole measurement method on a test device at Zentrum fuer Brennstoffzellen Technik GmbH (https: / / web.archive.org / web / 20221215171732 / https: / / www.zbt.de / nc / en / news / news-anzeige-eng / detail / News / measurement-specification-and-measuring-device-for-electrical-conductance-developed-beppel-project / ). Dimensions: 60 × 60 × 2 mm 3 The measurement of the plate is carried out between two gas diffusion layers based on polished and galvanized copper measuring electrodes. For the measurement, the sample is placed between the two electrodes, which are then pressed against the surface of the sample and a preset current is applied. During this process, two voltages are observed: the voltage at the measuring electrodes (Uges) and the voltage at the measuring tip (Utip). The voltages are saved by the software and are required for the calculation of the bulk and contact resistance. The measurement is carried out at a pressure of 20 bar. [Example]

[0114] Example 1 A variety of different coated graphite particulate materials were prepared according to the methods described herein and compared to a variety of known / commercially available coated and uncoated synthetic and natural graphite particulate materials.

[0115] In this Example 1, 800 grams of natural formed graphite was loaded into a vertical, electrically heated, fluidized-bed reactor at ambient temperature. The reactor was heated to 875-950°C under a constant flow of nitrogen gas to fluidize the feedstock. Nitrogen or other inert gas was used to prevent oxidation of the graphite at temperatures above 500°C. Once this temperature was reached, hydrocarbon vapor (benzene, toluene) was introduced into the reactor using nitrogen. The amount of hydrocarbon was controlled to achieve the appropriate coating weight. For a 2% coating (such as IE 2), approximately 25 g of liquid hydrocarbon was required. For a 4% coating (such as IE 1 and IE 3), twice the amount of hydrocarbon (approximately 50 g) was required. Once all the hydrocarbon was delivered, the reactor was purged and cooled under nitrogen. Similarly, rotary kilns can be used for the continuous production of coated natural compacted graphite. In such cases, a 2 m long rotary kiln, rotating at 6-8 rpm with a 3-4° inclination, is heated to 950-1050 °C and natural graphite (approximately 1 g / cm) is added. 3 The feed rate of the hydrocarbon (having a tap density of 1000 MPa) is about 2 kg / h, and the flow rate of the linear hydrocarbon (e.g., methane, acetylene, or propane) is 2-3 L / min together with 1 L / min of nitrogen.

[0116] Coated graphite particulate materials according to the present invention (IE 1-IE 3) were compared with uncoated particulate material and CVD-coated particulate material commonly known in the art. Inventive Examples IE 2 and IE 3 were prepared from the same base graphite material (Comparative Example 5, "CE 5") and had different amounts of coating (2 wt % and 4 wt %).

[0117] Comparative Example 1 (CE 1) is an uncoated synthetic graphite already used in bipolar plates (e.g., Imerys' commercial product TIMREX® KS5-75TT). It has a particle size distribution optimized for this application (low amount of fine particles (high D 10 The graphite has a particle size distribution with a PSD of >15 μm. Comparative Example 2 (CE 2) is a related uncoated potato-shaped synthetic graphite, but with a smaller PSD. Comparative Example 3 (CE 3) is a natural graphite with an uncoated (spherical) shape (see center of Figure 1).

[0118] Comparative Example 4 (CE 4) is another uncoated synthetic graphite with a more hydrophilic surface. Comparative Example 5 (CE 5) is the uncoated extruded natural graphite used to prepare Inventive Examples IE 2 and IE 3, as described above.

[0119] Comparative Example 6 (CE 6) is a CVD-coated (4 wt%) version of Comparative Example 1 (CE 1), while Comparative Example 7 (CE 7) is the corresponding CVD-coated (4 wt%) version of Comparative Example 2 (CE 2). Finally, Comparative Example 8 (CE 8) is the corresponding CVD-coated (4 wt%) version of Comparative Example 3 (CE 3) (e.g., commercial product GHDR15-4 by Imerys).

[0120] [Table 2-1]

[0121] [Table 2-2]

[0122] Exemplary coated graphite particulate materials according to the present invention were further compared to comparative coated particulate materials.

[0123] [Table 3]

[0124] Figures 2-8 and 19 are graphs of some important parameters from Tables 2 and 3.

[0125] Example 2 Graphite-filled polymer composites were prepared using all uncoated and coated graphite particulate materials from Example 1. Each graphite powder (80 wt%) was mixed with polypropylene (Moplen HP501L from Lyondell Basell, 20 wt%) in an internal mixer (HAAKE Rheomix 600 OS) at 190°C and 100 rpm for 5 minutes.

[0126] Table 4 compares some processability parameters (melt flow index (MFI) and torque values) for the corresponding polymer composite compositions containing either CE 1-CE 8 or IE 1-IE 3.

[0127] [Table 4]

[0128] Figures 9 and 10 further illustrate the different torque and melt flow indices obtained for selected examples.

[0129] Example 3 All eleven polymer compositions from Example 2 were used to compression mold 60 x 60 x 2 mm sized molded articles using a LabTech Scientific LP-S-20 press (at 210°C and 70 bar). 3 Plates were prepared from which 50 x 12 x 2 mm 3 (for measuring electrical resistivity) and 10 x 10 x 2 mm 3 The samples (for thermal conductivity measurement) were cut by water jet.

[0130] Table 5 summarizes the thermal conductivity and electrical volume resistivity data for bipolar plates containing these 11 graphite materials (both in-plane and through-plane). The average thermal conductivity (TC) was calculated as the square root of the in-plane TC multiplied by the through-plane TC. The anisotropy of thermal conductivity was calculated as the in-plane TC divided by the through-plane TC. In contrast, the anisotropy of electrical volume resistivity (VR) was calculated as the through-plane VR divided by the through-plane VR.

[0131] [Table 5]

[0132] 11-14 further show the in-plane and through-thickness electrical resistivity and thermal conductivity of selected exemplary bipolar plates at 80 wt % graphite loading.

[0133] Example 4 The area-specific contact resistivity and area-specific bulk resistivity were measured for bipolar plates containing graphite materials of CE 5 (material as uncoated substrate for IE 2 and IE 3), IE 2 (corresponding to CE 5 with 2 wt. % CVD coating), and IE 3 (corresponding to CE 5 with 4 wt. % CVD coating).

[0134] The results are shown in Figure 15, which shows that a 2% CVD coating strongly reduces bulk resistivity, and a 4% CVD coating further reduces contact resistivity. Lower contact resistivity is beneficial because conventional bipolar plates often require post-treatment (e.g., polishing, plasma, or laser treatment) to reduce the contact resistivity of the bipolar plate.

[0135] Example 5 Polymer compounds containing either 50% or 60% by weight of the graphite materials CE 1, CE 3, CE 5, CE 8, and IE 3 were prepared in a Leistritz ZSE 27 mm twin-screw extruder. The polymer used was PP412MN40 from Sabic, a highly flowable copolymer polypropylene / polyene with an MFI of 45 g / 10 min (230°C, 2.16 kg).

[0136] The graphite material was added to the polymer melt via a side feeder. The compound was extruded at 300 rpm, 230°C, and a total output of 15 kg / h.

[0137] The viscosity (Melt Flow Index) MFI was measured on the compounded samples, measurements were carried out at 230°C and 5 kg. Table 6 summarizes the results: [Table 6]

[0138] 16 shows that increasing the graphite particle loading results in higher viscosity and a concomitant decrease in the measured melt flow index (MFI), which indicates a decrease in processability. It is also clear that this decrease is influenced by the nature of the graphite particle material used.

[0139] IE 3 has a high MFI value (low viscosity) at both 50% and 60% by weight that is much higher than CE 1, CE 3, and CE 5 and comparable to CE 8.

[0140] The compounds were injection molded using a Billon Proxima 50T. Before molding, the materials were dried at 80 °C for 2-3 hours, and molding was carried out in a mold at 230 °C. The geometry of the injection molded samples was 60 × 60 × 2 mm according to ISO D2. 3 From this, a 50×12×2mm diameter plate is used for electrical resistivity measurement. 3 The samples were cut by water jet.

[0141] The electrical volume resistivity (VR) was measured in two directions: in-plane and through-plane. The results are summarized in Table 7: [Table 7]

[0142] 17 and 18 show the in-plane and through-plane electrical resistivity of selected exemplary bipolar plates having 50% and 60% by weight loadings of coated graphite particulate material in the polymer composition.

[0143] IE 3 has the smallest electrical volume resistivity at both 50% and 60% by weight, and has a much smaller electrical volume resistivity than CE 1, CE 3, CE 5, and CE 8 in both the plane and thickness directions.

Claims

1. 1. A coated graphite particulate material comprising graphite particles coated with a layer of amorphous carbon, said coated graphite particulate material being characterized by: (i) a D of at least about 20 μm, at least about 23 μm, at least about 25 μm, at least about 27 μm, at least about 30 μm, at least about 35 μm, or at least about 40 μm ５０ Particle size distribution (PSD) having: (ii) Approximately 3.0m ２ / g, approximately 2.8 m ２ / g, approximately 2.6 m ２ / g, approximately 2.4 m ２ / g or less than about 2.2 m ２ / g BET specific surface area (BET SSA) of less than 1.5g; (iii) a crystallographic L of at least about 210 nm, at least about 250 nm, at least about 300 nm, at least about 400 nm, or at least about 500 nm ｃ value; and (iv) a Raman I of at least about 0.25, at least about 0.3, at least about 0.35, at least about 0.4, at least about 0.45, or at least about 0.5 Ｄ / I Ｇ ratio.

2. 10. The coated graphite particle material of claim 1, further characterized by at least one of the following: (i) at least about 0.7 g / cm ３ , at least about 0.8 g / cm ３ , or at least about 0.9 g / cm ３ tap density of; (ii) at least about 2.22 g / cm ３ , or at least about 2.23 g / cm ３ xylene density; (iii) a crystallographic c / 2 value of less than about 0.3360 nm, less than about 0.3358 nm, or less than about 0.3356 nm; (iv) a D of at least about 10 μm, at least about 12 μm, at least about 15 μm, or at least about 20 μm １０ and / or a particle size distribution (PSD) having (v) a D of at least about 30 μm, at least about 40 μm, at least about 50 μm, at least about 55 μm, at least about 60 μm, at least about 70 μm, or at least about 80 μm ９０ Particle size distribution (PSD) having

3. 3. The coated graphite particle material of claim 1 or 2, further characterized by at least one of the following: (i) a springback value of less than about 50%, less than about 45%, less than about 40%, less than about 35%, or less than about 30%; (ii) an angle of repose of less than about 40°, less than about 38°, or less than about 36°; (iii) a water contact angle of at least about 70°, at least about 80°, or at least about 85°; (iv) Approximately 40mJ / m ２ Less than about 35 mJ / m ２ Less than or about 30 mJ / m ２ Dispersion surface energy less than (v) Approximately 10mJ / m ２ Less than about 8 mJ / m ２ Less than, or about 6 mJ / m ２ polar surface energy less than (vi) Approximately 40mJ / m ２ Less than about 34.6 mJ / m ２ Less than, or about 31 mJ / m ２ or (vi) a total surface free energy of less than 10 kN / cm ２ So, about 8mΩ ＊ less than cm, or about 7 mΩ ＊ powder electrical resistivity of less than 1 / 3 cm; and / or (vii) 20kN / cm ２ So, about 6mΩ ＊ less than cm, or about 5 mΩ ＊ Powder electrical resistivity less than cm.

4. 4. The coated graphite particle material according to claim 1, wherein the layer of amorphous carbon is present in the coated graphite particle material in an amount greater than about 1% by weight, or greater than about 2% by weight, or in an amount of about 1% to about 15% by weight, or in an amount of about 1% to about 10% by weight, or in an amount of about 1% to about 6% by weight, or in an amount of about 1% to about 5% by weight, or in an amount of about 2% to about 10% by weight, or in an amount of about 3% to about 8% by weight, or in an amount of about 3% to about 7% by weight, or in an amount of about 3% to about 6% by weight, based on the total amount of the coated graphite particle material.

5. 5. The coated graphite particle material according to any one of claims 1 to 4, wherein the amorphous carbon is a pyrolytic carbon coating, preferably the layer of amorphous carbon is a chemical vapor deposition (CVD) coating.

6. A method for preparing the coated graphite particle material of any one of claims 1 to 5, comprising: (i) providing a graphite starting material having: Raman I less than about 0.4, less than about 0.35, less than about 0.3, or less than about 0.25 Ｄ / I Ｇ ratio; Crystallographic L of at least about 210 nm, at least about 250 nm, at least about 300 nm, at least about 400 nm, or at least about 500 nm ｃ value; and D of at least about 20 μm, at least about 23 μm, at least about 25 μm, at least about 27 μm, at least about 30 μm, at least about 35 μm, or at least about 40 μm ５０ Particle size distribution (PSD) having: and preferably about 5 m ２ / g or less, about 4m ２ / g or less than about 3m ２ / g BET specific surface area (BET SSA) of less than 1.5g; and preferably at least about 0.6 g / cm ３ , at least about 0.7 g / cm ３ , at least about 0.8 g / cm ３ , or at least about 0.9 g / cm ３ a tap density of (ii) coating the graphite starting material with a layer of amorphous carbon, thereby forming the coated graphite particulate material according to any one of claims 1 to 5.

7. 7. The method of claim 6, wherein the coated graphite particulate material has a BET specific surface area that is less than the BET specific surface area of ​​the graphite starting material.

8. 8. The method of claim 6 or 7, wherein the layer of amorphous carbon is deposited by a method selected from pitch coating, atomic layer deposition (ALD), physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), wet coating followed by carbonization, spray drying followed by carbonization, hydrothermal carbonization, or sol-gel, preferably wherein the layer is formed by chemical vapor deposition (CVD) or plasma-enhanced chemical vapor deposition (PECVD).

9. The coated graphite particle material according to any one of claims 1 to 5, obtained by the method according to any one of claims 6 to 8.

10. A composition comprising the coated graphite particulate material of any one of claims 1 to 5 and 9, further comprising: (i) at least one other carbon particulate material; wherein optionally, the at least one other carbon particulate material is selected from the group consisting of natural graphite, synthetic graphite, expanded graphite, carbon fiber, carbon nanotubes, graphene, coke, and carbon black; and / or wherein the at least one other carbon particulate material is present in an amount of from 1 wt. % to 80 wt. %, from 1 wt. % to 70 wt. %, from 1 wt. % to 60 wt. %, from 1 wt. % to 50 wt. %, from 1 wt. % to 40 wt. %, from 1 wt. % to 30 wt. %, or from 1 wt. % to 20 wt. %, based on the total weight of the composition; and / or (ii) at least one metal powder selected from the group consisting of titanium, aluminum, silver, nickel, copper, and mixtures thereof; wherein, optionally, said at least one metal powder is present in an amount of 0.1% to 10% by weight.

11. A polymer composite material comprising the coated graphite particle material according to any one of claims 1 to 5 and 9 or the composition according to claim 10, and a polymer, where, optionally, (i) the polymer is present in an amount of 5 wt % to 55 wt %, 6 wt % to 50 wt %, 7 wt % to 45 wt %, 8 wt % to 40 wt %, or 9 wt % to 35 wt %, based on the total weight of the polymer composite; Preferably, the polymer is present in an amount of 10% to 30% by weight based on the total weight of the polymer composite; (ii) the polymer is selected from a thermoplastic polymer, preferably selected from the group comprising polypropylene (PP), polyphenylene sulfide (PPS), fluorinated ethylene propylene (FEP) and polyvinylidene fluoride (PVDF); a thermosetting polymer, preferably selected from the group comprising epoxy resins and phenolic resins; an elastomer, preferably selected from the group comprising synthetic or natural rubber, and ethylene-octene copolymers; or a blend of these polymers or these polymers modified with other polymers; and / or (iii) ) the amount of the coated graphite particle material according to any one of claims 1 to 5 and 9 or the composition according to claim 10 is 45 wt % to 95 wt %, 50 wt % to 94 wt %, 55 wt % to 93 wt %, 60 wt % to 92 wt %, or 65 wt % to 91 wt %, based on the total weight of the polymer composite; Preferably, the coated graphite particle material or composition is present in an amount of 70% to 90% by weight based on the total weight of the polymer composite. Polymer composites.

12. 12. The polymer composite material of claim 11, further comprising one or more of the following materials: Expanded graphite, natural graphite, synthetic graphite, carbon fibers, carbon nanotubes, graphene, coke, carbon black, and metal powders such as titanium, aluminum, silver, nickel, copper, or mixtures thereof; wherein optionally, the at least one metal powder is present in an amount of 0.1 wt. % to 10 wt. %, based on the total weight of the polymer composite. Polymer composites.

13. Use of the coated graphite particle material according to any one of claims 1 to 5 and 9, or the composition according to claim 10, or the polymer composite material according to claim 11 or 12 for producing a bipolar plate, comprising: wherein, optionally, said bipolar plate is suitable for use: (i) a fuel cell, preferably a proton exchange membrane (PEM) fuel cell; (ii) a redox-flow battery; or (iii) A water electrolysis device, preferably a proton exchange membrane (PEM) electrolysis device.

14. A bipolar plate comprising the coated graphite particle material according to any one of claims 1 to 5 and 9, or the composition according to claim 10, or the polymer composite according to claim 11 or 12, Wherein optionally bipolar plates are suitable for: (i) a fuel cell, preferably a proton exchange membrane (PEM) fuel cell; (ii) a redox-flow battery; or (iii) A water electrolysis device, preferably a proton exchange membrane (PEM) electrolysis device.

15. 15. A method for manufacturing a bipolar plate according to claim 14, comprising: (i) mixing the coated graphite particle material according to any one of claims 1 to 5 and 9 or the composition according to claim 10 with a polymer to form the polymer composite material according to claim 11 or 12; wherein, optionally, the polymer is selected from a thermoplastic polymer, preferably selected from the group comprising polypropylene (PP), polyphenylene sulfide (PPS), fluorinated ethylene propylene (FEP) and polyvinylidene fluoride (PVDF); a thermosetting polymer, preferably selected from the group comprising epoxy resins and phenolic resins; an elastomer, preferably selected from the group comprising synthetic or natural rubber, and ethylene-octene copolymers; or a blend of these polymers or these polymers modified with other polymers; Further, optionally, the mixing is carried out in an extruder; and (ii) forming a bipolar plate from the polymer composite material obtained in step (i); wherein, optionally, said bipolar plate is manufactured by compression molding, injection molding, or extrusion, or roll-to-roll process of said polymer composite material obtained in step (i).

16. Use of a bipolar plate according to claim 14 for producing: (i) a fuel cell, preferably a proton exchange membrane (PEM) fuel cell; (ii) a redox-flow battery; or (iii) A water electrolysis device, preferably a proton exchange membrane (PEM) electrolysis device.

17. A fuel cell, preferably a proton exchange membrane (PEM) fuel cell; a redox-flow battery; or a water electrolysis device, preferably a proton exchange membrane (PEM) electrolysis device, comprising a bipolar plate according to claim 14.

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