Flow field plate for fuel cell or redox flow battery having hydrophobic surface area and method of manufacturing the flow field plate

Abstract

A bipolar plate (1) for a fuel cell or flow battery is described that includes a substrate (3) and a channel (5) that extends from a channel inlet (7) in a surface of the substrate (3) to an interior (9) of the substrate (3). The surface of the substrate (3) is more hydrophobic in a first region (19) inside the channel (5) adjacent the channel inlet (7) than in a second region (21). This may, among other things, prevent moisture from entering and accumulating in the channel (5).

Description

[Technical Field]

[0001] The present invention relates to a bipolar plate for a fuel cell or flow battery and to a method for manufacturing such a bipolar plate. [Background technology]

[0002] Bipolar plates are intended to perform several different tasks for the fuel cells stacked to form the core of a fuel cell system. On the one hand, they are intended to interconnect adjacent fuel cells, i.e., physically and electrically connect the anode of one cell with the cathode of the adjacent cell. On the other hand, they should be able to distribute gases to the reaction space within the fuel cell via their surfaces, i.e., they should transport reactant gases to the reaction zone. For this purpose, bipolar plates typically have flow geometries (so-called flow fields) on both sides, which may be rolled, cast, or formed, allowing hydrogen to flow on one side and air to be supplied on the other. Bipolar plates also generally control the removal of water vapor or the release of heat and electrical energy. Furthermore, bipolar plates should provide gas isolation between adjacent cells, sealing from the outside, and cooling, if necessary.

[0003] Bipolar plates often have channels running through the interior of the bipolar plate's substrate. Such channels can perform specific tasks, for example, during the manufacture of the bipolar plate. For example, adhesives may be contained within such channels, with the help of which the two sub-substrates forming the bipolar plate are bonded together. Alternatively, channels may also be provided to implement other functions.

[0004] It has been observed that problems can occur when operating fuel cells or flow batteries under certain operating conditions, particularly at or after low temperatures, and these problems are suspected to be related to the bipolar plates used in the fuel cells or flow batteries. Summary of the Invention [Problem to be solved by the invention]

[0005] In particular, there may be a need for bipolar plates or fuel cells or flow batteries with bipolar plates that can operate reliably, including under low temperature or post-low temperature operating conditions. In particular, there may be a need for bipolar plates that are simple in design, inexpensive to manufacture, and / or that can operate particularly robustly. Furthermore, there may be a need for methods of manufacturing such bipolar plates. In particular, there may be a need for methods that can manufacture bipolar plates cheaply, with little effort, and / or reliably. Such a need may be met by the subject matter of the independent claims. Advantageous embodiments are defined in the dependent claims, set forth in the following description and shown in the drawings. [Means for solving the problem]

[0006] A first aspect of the present invention relates to a bipolar plate for a fuel cell or flow battery, the bipolar plate comprising a substrate and a channel extending from a channel inlet on a surface of the substrate into the substrate, the surface of the substrate being more hydrophobic in a first region inside the channel adjacent to the channel inlet than in a second region.

[0007] A second aspect of the present invention relates to a method of manufacturing a bipolar plate for a fuel cell or flow battery, the method comprising: providing a substrate having a structure for passing a channel through the interior of the substrate of the fabricated bipolar plate, the channel extending from a channel inlet on the surface of the substrate to the interior of the substrate; and treating the surface of the substrate in the first region inside the flow channel adjacent to the flow channel inlet so that the surface of the substrate in the first region is more hydrophobic than the surface of the substrate in the second region.

[0008] Without limiting the scope of the invention in any way, ideas and possible features regarding embodiments of the invention may be considered to be based, inter alia, on the ideas and findings described below. Briefly and broadly summarized, the underlying principle of the concept described herein can be understood as being based on the recognition that problems, such as those encountered in the operation of fuel cells or flow batteries, particularly at or after low temperatures, can be attributed to the fact that water penetrates into the channels of the bipolar plates, or water vapor condenses in these channels and then freezes, causing forces and / or damage to the bipolar plates due to the thermally induced expansion that occurs in this process. While the previous objective was to prevent water or water vapor from penetrating into or onto the channels by sealing means, it is proposed herein instead to make at least a portion of the surface of the substrate adjacent to the channel inlets, and preferably also the exposed areas of the surface inside the channels, particularly more hydrophobic than the rest of the surface of the substrate. This can prevent water from penetrating into the exposed areas of the channels and / or accumulating there by condensation.

[0009] Possible details of embodiments of the bipolar plate and manufacturing method proposed herein are described below.

[0010] The substrate on which the bipolar plate is formed is typically plate-shaped. Thus, both the height and width of the substrate are significantly greater than the thickness of the substrate, i.e., greater than 10 times the thickness of the substrate. The substrate may have structures and / or textures on its outer surface, for example, for guiding reaction fluids along predetermined paths on the substrate surface and / or for extending the substrate surface. The substrate typically consists of a material that is very electrically conductive, or at least has such a material provided on its surface.

[0011] For example, according to one embodiment, the bipolar plate or its substrate may be formed from or consist of a graphite-containing material. As a carbon-containing material, graphite offers advantageous properties for many applications. For example, when used in bipolar plates, graphite provides very high electrical conductivity, high thermoelasticity, and sufficient mechanical strength. In particular, bipolar plates use graphite-containing materials in which graphite particles are embedded in a polymer matrix. The graphite particles impart desired electrical and / or thermal properties to the material. In particular, the polymer matrix serves to mechanically bind the graphite particles. The polymer matrix may include, for example, an epoxy resin. Thus, the graphite particles act as a filler, and the polymer matrix acts as a type of binder. In addition to the graphite particles and polymer, the material mixture may also contain other components, such as carbon black, other binders, or other components in similar forms. Advantageously, the graphite content of the graphite-containing material may be at least 60%, preferably at least 70%, or even at least 80%. Percentages may refer to volumetric values. Due to the high graphite content, the material can provide, among other things, very good electrical conductivity, which is particularly advantageous when used to form bipolar plates. Examples and possible properties of graphite-containing materials are described, inter alia, in the applicant's earlier patent application PCT / EP2020 / 078489. The graphite-containing materials described therein can be used in the bipolar plate embodiments described herein to provide localized hydrophobicity at their surfaces. The entire contents of the earlier patent application are incorporated herein by reference.

[0012] At least one internal channel, i.e., preferably an elongated void, is formed in the substrate. The channel extends from a channel inlet on the surface of the substrate into the substrate interior. In other words, at the channel inlet, the channel opens to the volume surrounding the substrate or to the atmosphere. The channel extends from the channel inlet to the substrate interior, and possibly to a channel outlet in another region of the substrate surface. The channel may have a cross-sectional dimension smaller than the thickness of the substrate. For example, the cross-sectional dimension may be less than half, preferably less than one-third, of the thickness of the substrate. The channel may have a circular or rectangular cross-section, or any other shape. The channel may be surrounded entirely by the material of the bipolar plate substrate. Alternatively, a portion of the channel may be covered by another material, such as a sealant, adhesive, or pressure-sensitive adhesive, introduced into the channel.

[0013] Previous attempts have been made to seal the channels in the substrate of bipolar plates against moisture penetration, for example by introducing a sealant into the channel, which fills and seals the channel at least at its inlet, preferably along the entire volume of the channel. However, it has been observed that reliably sealing the channels or their channel inlets can be difficult when manufacturing bipolar plates. For example, it can be difficult to apply the sealant so that the channels are completely filled or at least their channel inlets are adequately sealed. In most cases, the tolerances allowed are very small, which can make the manufacturing process unstable. Furthermore, it is often necessary to apply an excessive amount of sealant, for example, to allow the excess sealant to leak out of the channel inlet and thereby adequately seal the channel inlet. However, in this case, the excess sealant remains ineffective, resulting in excessive sealant consumption. Furthermore, it may be necessary to carry out repairs and / or inspections of the sealed channels and / or clean the tools used. Furthermore, the material requirements of the sealant may conflict with the technical requirements of the bipolar plate. Furthermore, there may be a risk of leakage between the channels and the sealant over time, for example, due to thermal stresses and related shape changes.

[0014] To at least partially overcome the above-mentioned problems or drawbacks, an alternative approach to preventing moisture from entering or accumulating inside a channel is described herein. Here, a portion of the substrate surface inside the channel is specifically treated or specifically configured to establish a higher hydrophobicity than other regions of the substrate surface, particularly other regions of the substrate surface inside or adjacent to the channel. This more hydrophobic portion is referred to herein as a first region. The less hydrophobic region is referred to herein as a second region or a third region. The second region or the third region may be directly adjacent to the first region.

[0015] In the first region, the substrate surface may in particular be treated so that the contact angle that a water droplet forms with the surface is greater than 40°, preferably greater than 60°, or even greater than 80°. In particular, the substrate surface in the first region may be superhydrophobic, i.e. the contact angle may be greater than 90°. In particular, the contact angle in the first region may be greater than the contact angle in the second region, for example by more than 5°, preferably more than 10°, more than 20°, or even more than 30°.

[0016] By increasing the hydrophobicity of the substrate surface in the first region adjacent the channel inlet, the risk of liquid, particularly water, penetrating into the channel via the channel inlet may be significantly reduced.

[0017] According to one embodiment, it may be advantageous for the first region to surround the channel inlet in an annular shape. In other words, the entire surface surrounding the periphery of the channel inlet may preferably be particularly hydrophobic. In this way, the risk of liquid penetration can be further minimized. The hydrophobic channel inlet may act as a liquid barrier and prevent liquid from entering the channel, for example by capillary forces.

[0018] Furthermore, according to one embodiment, the first region may include a portion of the substrate surface inside the flow channel that is in gas communication with the flow channel inlet. In other words, in addition to a portion adjacent to the inlet, the first region may extend further into the flow channel, and in particular may include a portion of the substrate surface that can be reached by gas from the flow channel inlet. Gas communication between the flow channel inlet and the portion of the first region located further inside the flow channel may be achieved here by gas flow and / or gas diffusion.

[0019] The highly hydrophobic first region also includes a portion of the substrate surface inside the channel, which can reduce the risk of vapor, particularly water vapor, entering the channel interior through the channel inlet and forming droplets there by condensation.

[0020] According to one embodiment, the sub-substrate of the bipolar plate is composed of two plate-like substrates, which are bonded to each other at a bonding surface, with an overflow channel extending adjacent to the bonding surface, wherein the first region extends along at least a portion of the overflow channel, and the second region extends along at least a portion of the bonding surface. When manufacturing the bipolar plate, the two plate-like sub-substrates may initially be provided as separate components and then bonded to each other across the bonding surface.

[0021] In other words, the bipolar plate may be composed of two or more parts. The plate-like sub-substrates may be initially prefabricated as individual components. For example, structures in the form of recesses, grooves, etc. may be formed on one surface, and these structures form channels throughout the resulting substrate after the two sub-substrates are bonded together.

[0022] These structures may be configured to form joining surfaces at which two adjacent sub-substrates stacked on top of each other can be bonded to each other. The joining surfaces of the stacked sub-substrates may be configured so that they face each other and extend very close to each other, preferably parallel to each other. When bonding the two sub-substrates, an adhesive may be applied to one or both of the opposing joining surfaces.

[0023] The structure may further be configured such that at least one spillway is formed adjacent the bonding surface. In the area of ​​the spillway, the depression in the surface of the secondary substrate may be larger than in the area of ​​the bonding surface. Thus, the surface of the spillway of one secondary substrate may be spaced further away from the opposing surface of a second secondary substrate stacked on top than from the opposing bonding surface.

[0024] When bonding two sub-substrates, adhesive is initially applied preferably only to one or both bonding surfaces, but not to the spillway. However, when the two sub-substrates are pressed together, the adhesive can flow laterally into the spillway and at least partially fill the spillway. The spillway can thus absorb excess adhesive. Thus, the two sub-substrates can be efficiently bonded to each other without excess adhesive that would prevent the sub-substrates from being tightly pressed together. If desired, spillways may be located on opposite sides of the bonding surfaces.

[0025] Because the bonding surfaces are intended to serve to bond two sub-substrates together, and therefore the adhesive should adhere well to these bonding surfaces, it may be advantageous to form these bonding surfaces as relatively less hydrophobic, or even hydrophilic, second regions, so that the adhesive, which is typically processed in a liquid or flowable state, can adhere to the bonding surfaces over a large area and form an effectively adhesive material bond with the bonding surfaces.

[0026] In contrast, it may be advantageous to form the surface of the overflow channel with a stronger hydrophobicity. As is generally recognized, part of this surface may eventually be covered by adhesive that seeps laterally between the mating surfaces. However, the volume of the overflow channel is preferably selected so that it is not completely filled with adhesive, so that at least part of the overflow channel surface may remain exposed. To prevent moisture from accumulating on this part of the surface, this part may be configured as a first region with increased hydrophobicity.

[0027] Thus, according to one embodiment, in a completed bipolar plate according to one embodiment, the channels may be partially filled with a flow-processable adhesive, the first regions being those portions of the surface of the substrate inside the channels where the adhesive is not in contact with the substrate, and the second regions of the substrate forming those portions of the surface of the substrate inside the channels where the adhesive is in contact with the substrate.

[0028] In other words, a bipolar plate composed of two sub-substrates can have flow channels that are partially filled with adhesive, for example. The adhesive can be flowable during processing and then crosslink or solidify. The adhesive can then adhere to the joining surfaces of the two sub-substrates, bonding them together. The portions of the surfaces of the sub-substrates inside the flow channels where the adhesive is in contact with the joining surfaces are preferably configured as second regions with low hydrophobicity. In contrast, the portions of the surfaces of the sub-substrates that are not covered by adhesive after such a bonding process can be configured as first regions with high hydrophobicity.

[0029] Preferably, the first region inside the channel extends along the entire surface of the substrate where the adhesive is not in contact with the substrate.

[0030] In other words, the first region inside the flow channel is preferably sized and positioned such that after bonding the two sub-substrates together with the adhesive, all surface areas of the substrate inside the flow channel that are not covered by the adhesive are highly hydrophobic, among other things, this ensures that no weakly hydrophobic surfaces remain inside the flow channel on which, for example, penetrating water vapor can condense.

[0031] Various methods for treating the surface of a substrate to achieve hydrophobicity are generally known. For example, the surface may be coated with a material that is highly hydrophobic, such as by the absence of polar molecules and groups contained therein. Conversely, various suitable methods are known for treating the surface of a substrate to reduce hydrophobicity or to impart hydrophilicity. For example, the surface may be coated with a material that has at least some hydrophilicity due to polar molecules and groups contained therein. Alternatively, the surface may be specifically oxidized, for example, by treatment with fluorine or sulfur trioxide. Plasma or corona treatment may also produce less hydrophobic or more hydrophilic surface properties.

[0032] According to one embodiment, a first region of the substrate surface described herein may be treated to render it more hydrophobic by localized irradiation of the substrate surface with a laser.

[0033] The laser beam may be specifically directed at a first region of the substrate surface. A second region of the substrate surface may be left untreated or may be treated in another way to reduce hydrophobicity. The first and second regions of the substrate surface may be locally configured with different intensities of hydrophobicity using a laser. The laser beam may also be specifically directed at very small regions. In contrast, treating small regions using other techniques, such as coating with a hydrophobic material, can be a difficult process.

[0034] Thus, according to one embodiment, the first region of the completed bipolar plate can be locally treated with a laser to locally increase the hydrophobicity as desired.

[0035] The first region typically has characteristic microscopic properties due to the laser beam irradiation. For example, the laser-treated region may briefly melt and then harden, achieving the structural and / or compositional characteristics of the laser treatment. Alternatively or additionally, material may be locally removed or ablated from the surface using a high-energy laser beam. A plasma may be generated near the surface, which then vaporizes the material. Additionally or alternatively, the material may be chemically altered, i.e., "cracked," by the thermal effects caused by the laser irradiation and then remain, for example, as a carbon structure or transition to the gas phase. Overall, the laser treatment may produce a surface texture that is rougher than the non-laser-treated region. Alternatively or additionally, for example, the volume structure, particularly the crystalline structure, of the laser-treated material may change in a manner typical of laser treatment.

[0036] The laser may have properties that allow the material of the substrate to be melted or ablated on the laser-treated surface. The laser may be, for example, a pulsed laser, in particular a short-pulse laser capable of emitting laser pulses with durations in the sub-nanosecond range. The laser may be, for example, an infrared laser.

[0037] According to one embodiment, a first region inside the channel can be treated to create a surface texture that creates a lotus effect.

[0038] As a result of the formation of complex microscopic and nanoscale surface structures, droplets can only form a very small area of ​​contact with the surface and therefore can bead up on the textured surface. This effect is also called the lotus effect and can describe the strong hydrophobicity or superhydrophobicity of the surface. The surface texture may be formed by a large number of small, closely spaced depressions and / or trenches.

[0039] For example, surface texture can be created by scanning a laser beam along a regular or irregular path over the surface to be textured, briefly melting, agitating and / or ablating material on the surface.

[0040] According to one embodiment, the same laser used to treat the substrate surface in the first region may be used to treat the substrate surface in a second and / or third region of the surface to increase hydrophobicity.

[0041] It has been recognized that, with appropriately adapted process control, laser processing can strengthen and weaken the hydrophobicity of a surface. Therefore, it can be particularly advantageous to create first and second regions with different hydrophobicities on the substrate of a bipolar plate by localized treatment with the same laser. If necessary, a third region of the substrate surface can also be treated with the same laser. For example, the substrate surface in the third region can have a surface layer removed by laser processing. In particular, in the case of graphite-containing materials with a polymer matrix, for example, a polymer layer formed on the surface can be opened or removed by laser processing. This can simplify process control and / or reduce the amount of equipment required.

[0042] In particular, according to more specific embodiments, the laser parameters under which the laser is operated when processing the second and / or third regions of the substrate surface may be selected to be different from those selected when processing the first region of the substrate surface.

[0043] For example, it has been recognized that when laser parameters that result in the formation of a surface texture that creates a lotus effect are used, the first region can be advantageously configured to have strong hydrophobic properties. On the other hand, when other laser parameters are used, it has been observed that the surface properties become less hydrophobic or even hydrophilic. For example, it has been observed that when irradiated with very powerful, short laser pulses, graphite-containing materials can acquire hydrophilic properties. In this regard, another patent application entitled "Method for forming a hydrophilic surface on a graphite-containing material and a method for producing a bipolar plate and a fuel cell or flow battery therewith" has been filed by the present applicant. This further patent application describes the laser processing also used in the bipolar plate embodiments described herein, and details of their manufacture using the same or similar methods, the entire contents of which are incorporated herein by reference.

[0044] Embodiments of the bipolar plates disclosed herein may inhibit liquid or moisture penetration into the flow channels of the substrates, which may prevent damage from, for example, water expansion and freezing. For example, shorter application times and reduced material usage may be possible for applying adhesive between bonded sub-substrates. Overall, a more robust process, wider tolerance range, stable process capability, lower process costs, and / or less waste may be achieved.

[0045] It should be noted that possible features and advantages of embodiments of the present invention are described herein partly with reference to bipolar plates and partly with reference to methods for manufacturing bipolar plates. Those skilled in the art will recognize that features described for individual embodiments can be transferred, adapted and / or substituted in a suitable manner similar to other embodiments, in order to arrive at further embodiments of the present invention and possibly synergistic effects.

[0046] Advantageous embodiments of the present invention are further described below with reference to the accompanying drawings, in which neither the drawings nor the description should be construed as limiting the invention in any way. [Brief explanation of the drawings]

[0047] [Figure 1] FIG. 2 is a plan view of a bipolar plate according to an embodiment of the present invention. [Figure 2] FIG. 1 is a cross-sectional view of a bipolar plate according to one embodiment of the present invention. [Figure 3] FIG. 2 is an enlarged view of a portion marked A in FIG. [Figure 4] FIG. 3 is an enlarged view of a portion marked B in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0048] The drawings are only schematic and are not to scale. The same reference symbols in different drawings indicate the same or identically acting features.

[0049] Figure 1 shows a highly schematic plan view of a bipolar plate 1 of the kind that can be used in a fuel cell or flow battery. Figure 2 shows a schematic cross-section of the bipolar plate 1.

[0050] The bipolar plate 1 comprises a substrate 3, which may be made of, for example, a graphite-containing material. A channel 5 passes through the substrate 3. The channel 5 extends from a channel inlet 7 to an interior 9 of the substrate 3. In the example shown, the channel 5 is annular and passes near the periphery of the bipolar plate 3. A plurality of channel inlets 7 are provided. The channel inlets 7 may serve as openings to vent the annular region of the channel 5 and extend towards the outer edge of the substrate 3. In the example shown, a further opening is provided away from the outer edge towards the centre of the substrate 3, which may also be referred to as a channel inlet 7 or alternatively as a channel outlet 11.

[0051] A first region 19 of the surface of the substrate 3 inside the channel 5 is treated or configured to be more hydrophobic than the second region 21. The first region 19 extends, on the one hand, up to the channel inlet 7 and preferably surrounds it in an annular manner. On the other hand, the first region 19 inside the channel 5 also extends partly into the interior 9 of the substrate 3, in particular where the inner surface of the substrate is exposed inside the channel 5, so that gas or vapor coming from the channel inlet 7 can reach this part of the first region 19. Furthermore, the first region 19 may extend up to the channel outlet 11 and preferably surround it in an annular manner.

[0052] The bipolar plate 1 may be manufactured using two sub-substrates 13. The sub-substrates 13 may be configured with localized depressions near the outer periphery of the sub-substrate 13, forming a bonding surface 15 on the one hand and overflow channels 17 on both sides adjacent to the bonding surface 15 on the other hand. The bonding surface 15 and the overflow channels 17 form an annular ring around the central region of the bipolar plate 1. The bonding surface 15 is configured as a second region 21 with less hydrophobicity or even hydrophilicity, while the surface in contact with the overflow channels 17 is configured as a first region 19 with more hydrophobicity. The sub-substrates 13 of the bipolar plate 1 have a surface structure 31 in the central region of their outward-facing surface, which serves, for example, to guide the reaction gases in a targeted manner (for clarity, this is only shown in FIG. 2 and not in FIG. 1). The sub-substrates 13 have other surface structures on their inward-facing surface, for example, to form cooling channels 33 inside the bipolar plate 1.

[0053] The surface of the substrate 3 in the first region 19 may be irradiated, for example, with a laser 27. The laser parameters of this laser 27 may be set such that a microscopic and / or nanoscale structure of a surface texture 25 is formed on the surface of the first region 19, which produces a lotus effect and / or a chemical and / or physical effect and thus a strong hydrophobicity. In Figure 3, such a surface texture 25 is represented diagrammatically in a locally enlarged cross section.

[0054] The second region 21 may not be irradiated with the laser 27, or other laser parameters may be set to reduce the hydrophobicity or to impart hydrophilicity to the second region 21. Similarly, the third region 29 may also be treated with the laser 27, for example, with suitable laser parameters to specifically impart strong hydrophilicity.

[0055] To bond the two sub-substrates 13 together, an adhesive 23, e.g., in the form of a flowable adhesive, is applied between the bonding surfaces 15. The low hydrophobicity or hydrophilicity of the second regions 21 defined therein allows the adhesive 23 to adhere strongly to the bonding surfaces 15. When the two sub-substrates 13 are pressed together, excess adhesive 23 can flow laterally into the overflow channels 17. However, it is not necessary to apply excessive adhesive 23, as is often the case in conventional methods, where the entire overflow channels 17 up to the channel inlets 7 are filled with adhesive 23 to seal the entire channels 5. Instead, portions of the overflow channels 17 can remain exposed, and thus their inner surfaces can remain uncovered. The strong hydrophobicity of the first regions 19 defined therein means that moisture cannot adhere to these exposed surfaces inside the channels 5, even though they are in gas communication with the channel inlets 7. This avoids frost damage due to freezing of moisture inside the channels 5.

[0056] Finally, it should be noted that terms such as "having" and "comprising" do not exclude other elements or steps, and terms such as "one" or "a" do not exclude a plurality. It should further be noted that features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps of other of the above embodiments. Reference signs in the claims should not be considered as limiting. [Explanation of symbols]

[0057] 1 bipolar plate 3. Circuit Board 5 Flow path 7 Flow path inlet 9 Inside the board 11 Flow path outlet 13 Sub-board 15 Joint surface 17 Overflow channel 19 First area 21 Second area 23 Adhesive 25 Surface Textures 27 Laser 29 Third area 31 Surface structure 33 Cooling Channel

Claims

1. A bipolar plate (1) for a fuel cell or flow battery, comprising: A substrate (3), a flow channel (5) extending from a flow channel inlet (7) on the surface of the substrate (3) to an interior (9) of the substrate (3); The surface of the substrate (3) is more hydrophobic in a first region (19) adjacent to the channel inlet (7) inside the channel (5) than in a second region (21); The first region (19) annularly surrounds the flow channel inlet (7), The flow channel (5) is partially filled with a flowable processable adhesive (23), the first region (19) forms a portion of the surface of the substrate (3) inside the flow channel (5) where the adhesive (23) is not in contact with the substrate (3); A bipolar plate (1), wherein the second region (21) of the substrate (3) forms a portion of the surface of the substrate (3) inside the flow channel (5) where the adhesive (23) is in contact with the substrate (3).

2. 2. The bipolar plate of claim 1, wherein the first region (19) comprises a portion of the surface of the substrate (3) inside the channel (5) that is in gas communication with the channel inlet (7).

3. The substrate (3) of the bipolar plate (1) is composed of two plate-shaped sub-substrates (13), The two plate-shaped sub-substrates (13) are joined together with a joining surface (15) in between, an overflow channel (17) extending adjacent said joining surface (15); The first region (19) extends along at least a portion of the spillway (17), The second region (21) extends along at least a portion of the joining surface (15).

3. A bipolar plate according to claim 1 or 2.

4. the first region (19) extends along the entire surface of the substrate (3) inside the channel (3) that is not in contact with the adhesive (23); 2. The bipolar plate of claim 1.

5. said first region (19) being locally treated by a laser (27) to provide a local increase in hydrophobicity; A bipolar plate according to any one of claims 1 to 4.

6. the first region (19) has a surface texture (25) that creates a lotus effect; A bipolar plate according to any one of claims 1 to 5.

7. The bipolar plate (1) is made of a graphite-containing material; A bipolar plate according to any one of claims 1 to 6.

8. A method for manufacturing a bipolar plate (1) for a fuel cell or flow battery, comprising the steps of: providing a substrate (3) of the manufactured bipolar plate (1) having a structure in which a channel (5) passes through the substrate (3), the channel (5) extending from a channel inlet (7) on the surface of the substrate (3) to the interior (9) of the substrate (3); treating the surface of the substrate (3) in the first region (19) inside the channel (5) adjacent the channel inlet (7) so that the surface of the substrate (3) in the first region (19) is more hydrophobic than the surface of the substrate (3) in the second region (21); Including, The first region (19) annularly surrounds the flow channel inlet (7), The flow channel (5) is partially filled with a flowable processable adhesive (23), the first region (19) forms a portion of the surface of the substrate (3) inside the flow channel (5) where the adhesive (23) is not in contact with the substrate (3); The method, wherein the second region (21) of the substrate (3) forms a portion of the surface of the substrate (3) inside the channel (5) where the adhesive (23) is in contact with the substrate (3).

9. The substrate (3) comprises two plate-shaped sub-substrates (13), A joining surface (15) is formed on the two plate-shaped sub-substrates (13), and an overflow channel (17) is formed adjacent to the joining surface (15), The method, wherein the first region (19) extends along at least a portion of the spillway (17) and the second region (21) extends along at least a portion of the joining surface (15), The method further includes a step of joining the two plate-shaped sub-substrates (13) to each other with the joining surface (15) interposed therebetween. The method of claim 8.

10. the first area (19) is treated by locally irradiating the surface of the substrate (3) with a laser, 10. The method according to claim 8 or 9.

11. further comprising treating the substrate (3) with the laser (27) in the second area (21) of the surface of the substrate (3) and / or in a third area (29) of the surface of the substrate (3), The method of claim 10.

12. the laser (27) is operated with different laser parameters when processing the second and / or third regions (21, 29) of the surface of the substrate (3) than when processing the first region (19) of the surface of the substrate (3); The method of claim 11.

13. the first area (19) of the surface of the substrate (3) is formed by treatment with a surface texture (25) that produces a lotus effect; 13. The method according to any one of claims 8 to 12.

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