Electrochemical cell distributor plate, method of manufacturing a distributor plate and electrochemical cell and method of operating an electrochemical cell

Abstract

The invention relates to a distributor plate (7) for an electrochemical cell (1), wherein the distributor plate (7) has a structure comprising ribs (12) having a surface (13) and main channels (11) having a floor (33), wherein secondary channels (15) on the surface (13) and, if necessary, on the floor (33) form a structuring (92), and wherein the distributor plate (7) has at least two regions (94) in which the structuring (92) of the surface (13) respectively differs from one another. The invention also relates to a method for producing a distributor plate (7), an electrochemical cell (1) and a method for operating an electrochemical cell (1).

Description

Technical Field

[0001] This invention relates to a distributor plate for an electrochemical cell, wherein the distributor plate has a structure including ribs and a main channel, the ribs having a surface and the main channel having a bottom surface. Furthermore, this invention relates to a method for manufacturing the distributor plate, an electrochemical cell including the distributor plate, and a method for operating the electrochemical cell. Background Technology

[0002] Electrochemical cells are electrochemical energy converters and are known in the form of fuel cells or electrolysis devices.

[0003] Fuel cells convert the chemical reaction energy of a continuously supplied fuel and oxidant into electrical energy. Among known fuel cells, hydrogen (H2) and oxygen (O2) are particularly converted into water (H2O), electricity, and heat.

[0004] Proton exchange membrane (PEM) fuel cells are also known. A PEM fuel cell has a membrane arranged in the center that is permeable to protons, i.e., hydrogen ions. The oxidant, particularly oxygen from the air, is thus spatially separated from the fuel, particularly hydrogen.

[0005] A fuel cell has an anode and a cathode. Fuel is supplied to the fuel cell at the anode and is catalytically oxidized into protons by releasing electrons, which then reach the cathode. The released electrons are extracted from the fuel cell and flow to the cathode via an external circuit.

[0006] An oxidant, particularly oxygen from the air, is supplied to the fuel cell at the cathode and reacts to form water by absorbing electrons and protons from the external circuit. The resulting water is then extracted from the fuel cell. The overall reaction is:

[0007] O2+4H + +4e - →2H2O

[0008] Here, a voltage is applied between the anode and cathode of the fuel cell. To increase this voltage, multiple fuel cells can be mechanically arranged in sequence to form a fuel cell stack and electrically connected in series. This fuel cell stack is also called a stack or fuel cell structure.

[0009] Electrochemical cell stacks typically have end plates, which press the individual cells together and provide stability to the stack. The end plates can also serve as the positive or negative electrodes of the stack for discharging current.

[0010] Electrodes—namely, anodes and cathodes—and membranes can be structurally combined to form a membrane electrode arrangement (MEA), also known as a membrane electrode assembly.

[0011] The electrochemical cell stack also includes bipolar plates, also known as gas distributor plates or distributor plates. The bipolar plates are used to uniformly distribute fuel onto the anode and oxidant onto the cathode. Furthermore, the bipolar plates typically have surface structures, particularly channel-like structures, for distributing fuel and oxidant onto the electrodes. Especially in fuel cells, these channel-like structures also serve to drain water produced during the reaction. Additionally, the bipolar plates can have a structure for conveying a cooling medium through the electrochemical cell to dissipate heat.

[0012] In addition to guiding the medium in terms of oxygen, hydrogen, and water, the bipolar plate ensures planar electrical contact with the membrane.

[0013] For example, fuel cell stacks typically comprise up to several hundred individual fuel cells, stacked layer by layer as so-called sandwiches. These individual fuel cells have an MEA and bipolar plate halves, respectively, on the anode side and the cathode side. Fuel cells particularly include anode and cathode monopolar plates, typically in the form of stamped sheet metal, which together form bipolar plates, thus creating channels for guiding gas and liquid, and through which a cooling medium flows.

[0014] In addition, electrochemical cells typically include a gas diffusion layer for gas distribution. This gas diffusion layer is positioned between the bipolar plates and the MEA, and is typically composed of carbon fiber nonwoven fabric, also known as a "gas diffusion backing" (GDB), on the channel side (i.e., in the direction of the adjacent bipolar plates), and of a microporous layer, also known as a "micro porous layer" (MPL), on the catalyst side (i.e., in the direction of the membrane).

[0015] Unlike fuel cells, electrolyzers are energy converters that preferentially split water into hydrogen and oxygen when a voltage is applied. Electrolyzers also include an electrolysis unit (MEA), bipolar plates, and a gas diffusion layer.

[0016] For the efficiency of electrochemical cells, especially those with polymer electrolyte membranes, it is particularly important to supply the electrode layers arranged on the membrane with the reaction gas uniformly.

[0017] Known distributor plates typically have channels and adjacent ribs forming a structure. The channels are also called main channels or flow channels, and the ribs are also called lands. The surfaces of the ribs, at least partially parallel to the extended plane of the distributor plate, include the contact surfaces of the distributor plate with the adjacent electrochemical cell gas diffusion layer. Gases such as hydrogen and oxygen flow from the channels of the distributor plate to the reaction zone on the membrane via the gas diffusion layer. The relatively poor supply of reactive gases to the gas diffusion layer, to the areas located on the ribs of the distributor plate, and thus to the corresponding areas of the MEA located below them, especially under flutenden conditions in the electrochemical cell, can lead to undesirable non-uniform current density distributions.

[0018] Water is produced during fuel cell operation on the side of the membrane where air, i.e., oxygen, is supplied. This water must be transported through a distributor plate to its channels and from there removed from the cell. Typical operating temperatures for membrane-based electrochemical cells are less than 120°C, so the water typically condenses and exists in a liquid state within a gas diffusion layer. In this gas diffusion layer, the direction of water transport is opposite to the direction of gas transport, and the accumulated water can strongly impede the tracking of reactant gases, especially oxygen.

[0019] The higher the power density of an electrochemical cell, the more water it produces, which may result in insufficient liquid water transported in the contact area between the gas diffuser layer and the air channel side of the distributor plate.

[0020] JP 2020-47441A describes an improved drainage system for bipolar plates, in which additional grooves are provided on the sides of the ribs in a direction parallel to the main channel.

[0021] JP 2020-47443A describes a bipolar plate with improved drainage, wherein the ribs of the bipolar plate have an additional channel system arranged transversely to the direction of the main channel. Each pair of channels in the additional channel system has a common outlet. Furthermore, a transverse structure in the main channel of the distributor plate is disclosed, which results in high pressure loss.

[0022] JP 2020-47440A also relates to a bipolar plate with an improved drainage system, wherein the ribs have recesses in the direction transverse to the main channel, and additional grooves are parallel to the direction of the main channel along the sides of the ribs. Summary of the Invention

[0023] A distributor plate for an electrochemical cell is proposed, wherein the distributor plate has a structure including ribs and a main channel, the ribs having a surface and the main channel having a bottom surface, wherein secondary channels on the surface and, if necessary, on the bottom surface form structured portions, and wherein the distributor plate has at least two regions in which the structured portions of the surface are different from each other.

[0024] Furthermore, a method for manufacturing a distributor plate is proposed, wherein a hydrophobic coating is first applied to a hydrophilic substrate (Grundplatte), and then layers of the hydrophobic coating with varying thicknesses are partially removed to create sub-channels, wherein the sub-channels have either hydrophobic or hydrophilic sub-channel surfaces depending on the thickness of the removed layers. In this context, hydrophobic and hydrophilic are particularly understood to mean that the coating has more hydrophobic surface properties than the substrate, and the hydrophobic sub-channel surface has more hydrophobic surface properties than the hydrophilic sub-channel surface.

[0025] Furthermore, an electrochemical cell including the distributor plate is proposed, wherein the distributor plate is particularly arranged in the cathode chamber of the electrochemical cell.

[0026] A further method for operating an electrochemical cell is proposed, wherein a mixture having a first component, particularly including oxygen, is guided into the distributor plate, and a mixture having a second component, particularly including water, is discharged from the distributor plate, wherein the structuring varies according to the local composition of the mixture. The composition of the mixture changes as it flows through the distributor plate due to reactions occurring on the membrane.

[0027] The electrochemical cell, preferably a fuel cell or electrolysis device, preferably includes at least a distributor plate, a gas diffusion layer, and a membrane or membrane electrode arrangement. In particular, a gas diffusion layer is arranged between the distributor plate and the membrane.

[0028] The gas diffusion layer preferably has a porous structure and is further preferably bonded to the distributor plate under a high pressure of about 10 to 15 bar. The membrane is preferably a polymer electrolyte membrane, which, for example, contains perfluorosulfonic acid (PFSA), especially Nafion, or is composed of perfluorosulfonic acid (PFSA), especially Nafion. Alkaline membranes can also be used.

[0029] Preferably, the gas diffusion layer comprises a nonwoven fabric, particularly a carbon fiber nonwoven fabric, and may include a microporous layer if necessary, wherein the nonwoven fabric is disposed on the side of the gas diffusion layer facing the distributor plate. More preferably, the gas diffusion layer is composed of a carbon fiber nonwoven fabric and, if necessary, a microporous layer. In the case of a nonwoven fabric, the gas permeability in the thickness direction, i.e., in the direction toward the membrane, can be similar to the gas permeability in the plane, i.e., in the direction parallel to the membrane.

[0030] Preferably, the distributor plate comprises carbon—such as graphite, metal—such as stainless steel or titanium, and / or an alloy containing such metal. More preferably, the distributor plate is made of carbon, metal, and / or alloy. In particular, the substrate of the distributor plate is made of carbon, metal, and / or alloy.

[0031] Subchannels, also known as drainage channels, capillary channels, grooves, or microscopically visible trench-like structures, are used to guide the generated, liquid reaction water from the ribs into one or more main channels. Subchannels are particularly positioned on the side of the distributor plate facing the adjacent gas diffusion layer in the electrochemical cell.

[0032] Additionally, the structured portion may include distributor channels, each having a larger diameter than the sub-channels. The distributor plate primarily supplies gas, particularly an oxygen-containing mixture, to the gas diffusion layer beneath the ribs of the bipolar plate and thus to the electrodes connected to this gas diffusion layer. The distributor channels guide the gas, particularly, to regions where the gas diffusion layer rests on the ribs. The distributor channels preferably connect two main channels, particularly two adjacent main channels.

[0033] The distributor channels are preferably arranged at an angle to the main channel. Preferably, the distributor channels are angled to the main channel at 20° to 70°, more preferably 30° to 60°, and especially 30° to 45°. The distributor channels have a cross-section, which is preferably rectangular, triangular, or U-shaped. The cross-section of the main channel is preferably at least fifty times larger than the cross-section of the distributor channels. The distributor channels can be arranged, for example, trapezoidal, wavy, parallel, cross-shaped, or honeycomb-shaped. The distributor channels are preferably arranged on the side of the distributor plate facing the adjacent gas diffusion layer in the electrochemical cell, particularly in the contact area.

[0034] The distributor plate, also known as a bipolar plate, preferably has a waveform structure, wherein the ribs and the main channel alternate and are more preferably arranged parallel to each other.

[0035] Preferably, the surfaces of the ribs each include at least one contact area, which may also be referred to as a contact surface, and adjacent gas diffusion layers abut against this contact area. Preferably, the contact areas of the ribs are arranged substantially parallel to the bottom surface of the main channel. "Substantially parallel" should be understood as follows: the plane in which the contact area is located forms an angle of less than 30°, more preferably less than 20°, more preferably less than 10°, and especially less than 5° with the bottom surface.

[0036] The secondary channels are preferably arranged at least partially on the sides. Preferably, the secondary channels are arranged in the contact area, and more preferably extend beyond the contact area at least to the sides.

[0037] Due to the porous structure of the gas diffusion layer, the natural outflow of water, which is typically in liquid form at high current densities, becomes difficult, potentially leading to water accumulation (wasserstau). This water accumulation can limit the power density of the electrochemical cell in the contact region.

[0038] Preferably, the rib has side sides, which are particularly included by the surface of the rib. More preferably, the surface of the rib includes two side sides for each rib, which respectively connect to the bottom surface of the adjacent main channel. The side sides may also be referred to as side edges and are preferably arranged at a side angle to the bottom surface, wherein the side angle is further preferably in the range of 90° to 135°, more preferably in the range of 90° to 125°, and particularly preferably in the range of 95° to 110°. Furthermore, the side sides are preferably arranged in an abgewinkelt arrangement relative to the contact area.

[0039] The main channels are preferably straight, and more preferably arranged parallel to each other on the distributor plate. The secondary channels each have a cross-section, which is preferably triangular—that is, V-shaped, circular, square, or polygonal. More preferably, the cross-section of the secondary channel is V-shaped. The cross-section of the secondary channel may be constant along its length, or it may vary in size and / or geometry.

[0040] Preferably, the width and / or depth of the sub-channel are 1 μm to 150 μm, more preferably 1 μm to 100 μm, particularly preferably 1 μm to 50 μm, more preferably 1 μm to 10 μm, and especially preferably 1 μm to 6 μm. Preferably, the distributor channel width and / or distributor channel depth are 10 μm to 400 μm, more preferably, the distributor channel width and / or distributor channel depth are greater than 50 μm and especially a maximum of 150 μm.

[0041] Preferably, the gas diffusion layer arranged adjacent to the distributor plate comprises fibers, and more preferably, the width of the sub-channel is smaller than the fiber diameter of the gas diffusion layer, which is, for example, about 8 μm. The width of the sub-channel may also be larger than the fiber diameter of the gas diffusion layer. The width of the sub-channel can be selected, in particular, depending on the structure of the adjacent gas diffusion layers, but the depth of the sub-channel can also be selected.

[0042] Furthermore, the depth and width, or diameter, of the secondary channels are chosen in such a way that they create a capillary effect, especially in water. The diameter is specifically understood as the maximum diameter of the cross-section.

[0043] Preferably, the distributor plate has at least a partial coating. This coating can be more hydrophilic or more hydrophobic than the material of the substrate of the distributor plate. In particular, the coating can be applied to the surface of the ribs to reduce the electrical contact resistance of the distributor plate. Furthermore, the coating can completely or partially cover the surface of the ribs and, if necessary, also the main channel.

[0044] The coating can be hydrophobic, and in particular, can exhibit a lotus effect. Hydrophobicity is preferably understood as having poorer wettability (Benetzbarkeit) than water wets steel with a smooth surface, and more preferably, a contact angle with respect to a water droplet greater than 70°, especially greater than 80°. The coating can be present, in particular, in the contact area to, for example, reduce contact resistance. Furthermore, the coating can be present on the bottom surface.

[0045] Preferably, the coating comprises carbon—such as carbon black or graphite, especially carbon particles—and a binder, especially an organic binder, such as a synthetic resin and / or polyvinylidene fluoride (PVDF). The binder can be thermoplastic or thermosetting. The coating preferably has a layer thickness in the range of 1 nm to 200 μm, more preferably 5 nm to 100 μm, and particularly preferably 5 nm to 50 μm. In the contact area of ​​the rib, a layer thickness greater than 5 μm is preferred. On the side and bottom surfaces, the layer thickness is preferably less than 1 μm.

[0046] Furthermore, the distributor plate may have at least a partial hydrophilic coating. Hydrophilicity is preferably understood as better wettability than water wets steel with a smooth surface; more preferably, the contact angle with respect to a water droplet is less than 40°, and especially less than 10°. Preferably, the secondary channel at least partially comprises a hydrophilic secondary channel surface and may have a hydrophilic coating, thereby drawing water into the secondary channel. Furthermore, the coating may have an internal structured portion, and the secondary channel may be formed through said internal structured portion. This internal structured portion is preferably hydrophilically constructed, so that water is drawn into the internal structured portion as if it were drawn into a wick.

[0047] In addition, the sides of the ribs and the bottom of the main channel can be hydrophilic or have a hydrophilic coating, which is used to drain water.

[0048] The contact area of ​​the rib can be hydrophobic or hydrophilic. If the contact area is hydrophilic, water will accumulate directly in that area, especially through wetting and / or condensation, and then be transported to the main channel through the secondary channel. If the contact area is hydrophobic, water will go directly to the secondary channel, for example, on the side of the rib, especially on the convex edge between the contact area and the side, and condense there before being transported to the main channel, especially the adjacent main channel.

[0049] The coating may include hydrophilic components, such as carbon oxide particles having hydroxide, carbonyl, and / or carboxyl groups, which have polymeric bonding, and these carbon oxide particles are particularly applicable to carbon distributor plates. Preferably, the coating has a surface roughness Ra in the range of 0.1 to 10 μm, and more preferably has a bulk peak-to-valley maximum distance in the range of 0.1 μm to 20 μm, more preferably 1 μm to 10 μm.

[0050] The coating can be applied, for example, by laser sintering, or by methods also used to apply metals, ceramics, polymers, or mixtures thereof onto a distributor plate according to a pattern. Another example of a coating method is spraying.

[0051] Alternatively, a coating material, such as powder, can be first applied to the distributor plate, then the coating material can be selectively removed from the contact area, followed by a selective (laser) sintering method. This allows, for example, the main channel to be coated only. The coating can be selectively applied, for example, by masking and / or screen printing.

[0052] The coating can also be applied surface-wise and then partially removed, for example by laser or mechanical means, thereby exposing the sub-channel and, in particular, forming the sidewalls of the sub-channel by the coating.

[0053] Sub-channels and, if necessary, distributor channels can also be introduced into the substrate of the distributor board—particularly a plate material—and / or can be introduced into the coating of the distributor board. In the latter case, the layer thickness is preferably greater than 5 μm. Sub-channels and, if necessary, distributor channels can also be coated or uncoated.

[0054] Preferably, the distributor plate has an inlet region and an outlet region, each having a port structure. The inlet and outlet regions are additionally present, particularly relative to the at least two regions. Through the port structures of the inlet or outlet regions, gas and / or liquid, especially mixtures, can be supplied to or discharged from the distributor plate. The at least two regions are, in particular, regions of the active surface of the distributor plate. The active surface is preferably rectangular.

[0055] Therefore, the function of the distributor board as a location is preferably structured differently, which in particular relates to the implementation of the secondary channels on the distributor board.

[0056] Different media supplies, i.e., different distributions and compositions of the mixture, typically exist in the at least two distinct regions, resulting in significant variations in gas supply, humidity, temperature distribution, and current distribution across the entire distributor plate—particularly the active surface of the distributor plate. For example, at 1.5 A / cm²... 2 At a current density of approximately 2 and an oxygen stoichiometry of approximately 2, there is approximately 11% oxygen by volume at the outlet in the main channel, while below the ribs near the electrodes, the mixture contains less than 3% oxygen by volume. At the inlet, for example, there is 21% oxygen by volume.

[0057] More preferably, the at least two regions are arranged sequentially between the inlet region and the outlet region. Accordingly, the supplied mixture preferably flows from the inlet region through the at least two regions to the outlet region, wherein, more preferably, it first flows through the first region and then through the second region. More preferably, the distributor plate has more than two regions in which the structured portions of the surface are different from each other.

[0058] The differences between different structural elements in different regions may involve the presence or absence of subchannels, the implementation of subchannels, and the presence or absence of one or more coatings.

[0059] Preferably, the structured portions of the at least two regions differ in the number of secondary channels per face, the geometry of these secondary channels, and / or the arrangement of these secondary channels. More preferably, the number of secondary channels per face increases in the direction from the inlet region to the outlet region. In each individual region, the number of secondary channels per face can be constant or variable. The secondary channels preferably have secondary channel surfaces, and in particular, with respect to each region, the ratio of secondary channel surface area per whole face increases in the direction from the inlet region to the outlet region. The secondary channels are particularly used for the discharge of liquid water. More liquid water is generated per face near the outlet region than near the inlet region, thus preferably, more secondary channels exist at locations where more liquid water is to be discharged.

[0060] Alternatively or additionally, the structured portions of the at least two regions may differ in the number of distributor channels on each side, the geometry of the distributor channels, and / or the arrangement of the distributor channels. Furthermore, the coating may vary, particularly in the material or composition and thickness of the coating, in the at least two regions.

[0061] Preferably, the structured parts are uniform in one of the at least two regions.

[0062] Furthermore, the distributor plate may have at least one planar area without secondary channels and / or distributor channels. In one embodiment, at least one of the two areas is a planar area without secondary channels. Correspondingly, no structured portion is present in the at least one planar area. Preferably, the planar area without secondary channels is arranged closer to the entrance area than the other area with structured portion among the at least two areas. More preferably, these planar areas follow, in particular, directly follow, the entrance area.

[0063] Preferably, at least a first area, a second area, and a third area are arranged sequentially from the entrance area to the exit area, especially in the given order.

[0064] In a preferred embodiment, the distributor plate has exactly three regions. During electrochemical cell operation, dry conditions typically dominate in the first region, which may also be called the entry region. Variable conditions typically dominate in the second region, which may also be called the intermediate region, where high temperatures and water production can be achieved. High humidity typically dominates in the third region, which may also be called the end region or output region, and a supersaturated mixture is present, which typically leads to water condensation.

[0065] Preferably, in this first region, at least one of the secondary channels merges into an end structure, wherein the at least one secondary channel branches into at least two sub-channels in the end structure, and in particular, the at least two sub-channels each have a smaller diameter than the secondary channel. Specifically, the at least two sub-channels have a corresponding cross-sectional size smaller than that of the secondary channel. This end structure can also be referred to as a finer structure or extension, thereby effectively increasing the surface area of ​​the liquid water, thus improving the discharge and / or evaporation of liquid water into the mixture guided in the main channel. More preferably, the end structure has at least three sub-channels, wherein at least one sub-channel can branch into at least two further sub-channels. Preferably, the at least one secondary channel and at least one of the sub-channels are partially sandwiched at an angle in the range of 20° to 70°, more preferably in the range of 30° to 60°, for example, 45°. Furthermore, the at least two sub-channels preferably terminate in an orientation substantially parallel to the secondary channel. Preferably, the sub-channels have a straight course between corresponding branches.

[0066] In this second region, the structuring section preferably additionally includes a distributor channel.

[0067] In this third region, at least one of the secondary channels preferably has a first portion at a first angle to the main channel and a second portion at a second angle to the main channel, the first angle being in the range of 30° to 150° and the second angle being in the range of less than 45°. Alternatively or additionally, at least one of the secondary channels may each have an end region, in which the depth of the at least one secondary channel decreases in the direction of the nearest main channel, particularly in the main flow direction, and / or the width of the at least one secondary channel increases in the direction of the nearest main channel. More preferably, in the end region, the depth continuously decreases and / or the width continuously increases. In particular, the diameter of the at least one secondary channel increases in the end region. The expression "in the direction of the nearest main channel" is understood to mean along the secondary channel from the rib, particularly the contact area, to the end region. The end region can also be referred to as a separation region. In the end region, water droplets are discharged from the secondary channel into the main channel, and separation of water droplets from the secondary channel occurs. The end region of the at least one secondary channel is preferably arranged on the side of the rib or on the bottom surface of the main channel. The end region is the transition between the bottom surface of the at least one secondary channel and the basic plane of the main channel. Furthermore, in this third region, the structuring section may additionally include a distributor channel.

[0068] Preferably, the first portion of the at least one secondary channel, particularly in the contact region, is arranged substantially orthogonally to the main channel, especially to the nearest main channel. "Substantially orthogonal" is understood to mean that the first angle is 60° to 120°, more preferably 80° to 100°, and particularly preferably 85° to 95°, for example, 90°. Preferably, the second portion of the corresponding secondary channel is arranged substantially parallel to the main channel, especially to at least one adjacent main channel. "Substantially parallel" is understood to mean that the second angle is less than 30°, more preferably less than 20°, more preferably less than 10°, and particularly preferably less than 5°. This arrangement at the second angle completes the orientation of the at least one secondary channel in the main channel, particularly near the end region, in the main flow direction.

[0069] Preferably, the secondary channels each have a curved orientation at least on the side of the rib. Alternatively or additionally, the secondary channels may have a straight orientation on the side, which has at least one, preferably more than one, directional change, which may also be referred to as a kink. The secondary channels extend substantially orthogonally to the main channel in the contact area, and preferably, especially before the end area, the orientation of the secondary channels is adapted to the orientation of the main channel. This adaptation preferably occurs on a curved track. Here, the orientation of the secondary channels changes from an orientation at a first angle relative to the main channel to an orientation at a second angle. Preferably, the first portion of each of the at least one secondary channel has a straight orientation.

[0070] In this first region, the secondary channel preferably has a hydrophobic secondary channel surface in the contact area. In this first region, hydrophilic surface properties are preferably present at least partially on the side and bottom surfaces.

[0071] In this second region, particularly in the contact region, the secondary channel preferably has a partially hydrophobic secondary channel surface and a partially hydrophilic secondary channel surface. More preferably, the secondary channels with hydrophobic secondary channel surfaces and the secondary channels with hydrophilic secondary channel surfaces are arranged alternately.

[0072] In this third region, especially in the contact region, there are preferably more secondary channels with hydrophilic secondary channel surfaces than with hydrophobic secondary channel surfaces.

[0073] To create a subchannel with a hydrophilic subchannel surface, a hydrophobic coating can be applied first, and then the coating can be removed along the subchannel, thereby exposing the hydrophilic surface of the substrate, such as a steel surface, to form the subchannel surface. Alternatively, the substrate may already have a subchannel with a hydrophilic subchannel surface pressed into the substrate. To create a subchannel with a hydrophobic subchannel surface, a hydrophobic coating can be applied first, and then the coating can be partially, but not completely, removed to create the subchannel without exposing the substrate again.

[0074] In this first region, the structuring is preferably designed with regard to the distribution of the mixture, particularly through the distribution of hydrophobic surfaces, and, if necessary, the evaporation of liquid water. In particular, the structuring in the first region facilitates the distribution of the mixture and, if necessary, the evaporation of liquid water.

[0075] In this second region, the structured portion is preferably designed with respect to water evaporation and, if necessary, the discharge of liquid water, particularly through the discharge of liquid water via a hydrophilic surface. Specifically, the structured portion in the second region is preferably designed to facilitate water evaporation and, if necessary, the discharge of liquid water.

[0076] In this third region, the structured portion is preferably designed for the discharge of liquid water. In particular, the structured portion in the third region facilitates the discharge of liquid water.

[0077] Especially in the cathode chamber, a dry mixture and less liquid water exist in the first region located near the inlet area. Correspondingly, there are few or no secondary channels. If secondary channels are present, the end regions, or end structures, can be optimized for the evaporation of liquid water, particularly the end structures enabling fan-shaped outflow portions of the secondary channels. Accordingly, secondary channels with hydrophobic surfaces are preferably present in the contact areas of the ribs to achieve better gas exchange. Secondary channels with hydrophilic surface properties and / or hydrophilic secondary channel surfaces are preferably present in the main channel to facilitate the outflow of any liquid water present.

[0078] Secondary channels preferably partially exist, particularly in a second region centrally located on the distributor plate or arranged between the first and third regions. Distributor channels are also preferably present, specifically for uniformly distributing the mixture on the active surface, especially in the contact area. The end regions or end structures of the secondary channels are preferably optimized for the evaporation of liquid water. Alternatively, the end regions or end structures may be optimized for the discharge of liquid water droplets. Preferably, hydrophilic secondary channel surfaces for carrying away liquid water and hydrophobic secondary channel surfaces for transporting the mixture, especially the gaseous mixture, are alternately present.

[0079] In the third region, it is generally expected that a large amount of liquid water will form on the membrane, thus requiring the removal of this large amount of liquid water from the contact area. Accordingly, in the third region, it is preferable that there are more secondary channels per face, especially per unit area, than in the first and second regions, wherein these secondary channels are further preferably combined with distributor channels for distributing the mixture, especially the gaseous mixture. The end structure or end region of the secondary channels is further preferably optimized for removing liquid water droplets, wherein the secondary channels are preferably curved such that the flow of the mixture in the main channel can squeeze the liquid water out of the secondary channels. The secondary channels are preferably shaped at their ends corresponding to the end regions and have a corresponding cross-sectional configuration, especially expansion, thereby creating wider and flatter separation regions in which the flow of the mixture is provided with sufficient water surface to form droplets. Furthermore, the presence of a hydrophilic and / or hydrophobic coating can play a supporting role here, guiding water from the secondary channels to the separation regions or end regions, where droplet formation is promoted. The coating can be implemented similarly to that in the second region, wherein, in the third region, there is preferably more hydrophilic secondary channel surface for water removal and less hydrophobic secondary channel surface for gas transport.

[0080] Advantages of the invention

[0081] By varying the structure of the distributor plate in different regions, the flow behavior can be matched to local reaction conditions, thereby purposefully promoting oxygen supply followed by water discharge, for example, in a fuel cell. Accordingly, the different local conditions and requirements within the active surface of the electrochemical cell are taken into account. Through differently structured, and potentially differently coated, regions, water discharge and gas supply are optimized according to the local conditions present in each region.

[0082] Due to the curved orientation of the secondary channel, in the contact area, the secondary channel has an orientation approximately perpendicular to the main flow direction of the main channel, thus providing a short transport path for liquid water. Conversely, in the droplet separation region of the main channel, the secondary channel, due to its curvature, has an orientation approximately parallel to the main flow direction, thereby supporting the separation of water droplets from the secondary channel.

[0083] The expansion of the secondary channel at its ends, achieved through the end region, allows the mixture flow in the main channel to more easily blow liquid water out of the secondary channel and export it as droplets. The separation of the coatings, particularly the hydrophilic and hydrophobic coatings described herein, further improves droplet separation. Attached Figure Description

[0084] Embodiments of the invention are described in more detail below with reference to the accompanying drawings.

[0085] The attached diagram shows:

[0086] Figure 1 Based on the schematic diagram of an existing electrochemical cell,

[0087] Figure 2 Fuel cell structure with distributor plate

[0088] Figure 3 The contact area between the gas diffusion layer and the distributor plate.

[0089] Figure 4 The section of the distributor board that has a secondary channel within the distributor channel.

[0090] Figure 5 : Cross-sectional view along the first plane,

[0091] Figure 6 : Cross-sectional view along the second plane,

[0092] Figure 7 The section of the distributor plate with sub-channels and end structures.

[0093] Figure 8 Another implementation of the end structure,

[0094] Figure 9 Another implementation of the end structure

[0095] Figure 10 The distributor board has sections with secondary channels and additional secondary channels.

[0096] Figure 11 The section of the distributor plate with a secondary channel having a curved orientation.

[0097] Figure 12 The end area of ​​the secondary channel,

[0098] Figure 13 A top view of a distributor panel with at least two zones, and

[0099] Figure 14 : One implementation of the second region of the distributor plate. Detailed Implementation

[0100] In the following description of embodiments of the invention, the same or similar elements are denoted by the same reference numerals, and in some cases, repeated descriptions of these elements are omitted. The drawings are for illustrative purposes only, showing the subject matter of the invention.

[0101] Figure 1An electrochemical cell 1 according to the prior art is schematically shown, which is in the form of a fuel cell. The electrochemical cell 1 has a membrane 2 as an electrolyte. The membrane 2 separates the cathode chamber 39 from the anode chamber 41.

[0102] In the cathode chamber 39 and the anode chamber 41, an electrode layer 3, a gas diffusion layer 5, and a distributor plate 7 are respectively arranged on the membrane 2. The composite of the membrane 2 and the electrode layer 3 can also be referred to as the membrane electrode arrangement 4.

[0103] The distributor plate 7 has a main channel 11 for supplying gases to the gas diffusion layer 5, such as oxygen 43 in the cathode chamber 39 and hydrogen 45 in the anode chamber 41. On the distributor plate 7, the main channel 11 alternates with ribs 12.

[0104] On the surface 13 of the rib 12, contact areas 47 are respectively arranged between the distributor plate 7 and the adjacent gas diffusion layer 5. In addition, the rib 12 has a side surface 31, and the main channel 11 has a bottom surface 33.

[0105] Figure 2 A fuel cell structure is shown, comprising multiple distributor plates 7 and a membrane electrode arrangement 4, the membrane electrode arrangement including a membrane 2. Oxygen 43, or air containing oxygen 43, and hydrogen 45 are directed to the membrane electrode arrangement 4 through the distributor plates 7. Water 51 is discharged in a main channel 11 of the distributor plate 7, and oxygen 43, or air containing oxygen 43, is supplied in the main channel. Furthermore, the distributor plates 7 are used to guide coolant 49.

[0106] Figure 3 The contact area 47 between the gas diffusion layer 5 and the distributor plate 7 is shown. The rib 12 of the distributor plate 7 is in contact with the gas diffusion layer 5 here. Furthermore, a coating 37 is disposed on the rib 12 of the distributor plate 7. Hydrogen gas 45 passes from the main channel 11 through the gas diffusion layer 5 to the electrode layer 3 disposed on the membrane 2.

[0107] Figure 4 A perspective top view of a section of distributor plate 7 with sub-channels 15 partially arranged within distributor channels 60 is shown. The distributor plate alternately has main channels 11 and ribs 12. A main flow direction 53 exists along the main channels 11. An arrangement angle 72 is marked relative to the orientation of the main channels 11. Furthermore, each main channel 11 has an axis of symmetry 55.

[0108] Each rib 12 has a surface 13, and the portion of these surfaces that is bent relative to the bottom surface 33 of the main channel 11 is called a side surface 31. A distributor channel 60 is arranged in the contact area 47 of the surface 13 of the rib 12. The bottom surface 33 of the main channel 11 is connected to the side surface 31 of the rib 12.

[0109] Each of the four distributor channels 60 has a secondary channel 15, which leads to an adjacent main channel 11 or to an adjacent side channel 31, thereby connecting the corresponding distributor channel 60 to the main channel 11 or to the side channel 31.

[0110] The secondary channels 15 extend partially within the distributor channels 60, with the secondary channels 15 disposed in the bottom 88 of the distributor channels 60. Correspondingly, the secondary channels 15 are partially disposed in the contact region 47 with the gas diffusion layer 5.

[0111] The first portion 17 of each sub-channel 15 is arranged at a first angle 19 to the adjacent main channel 11, and the second portion 21 of each sub-channel 15 is arranged at a second angle 23 to the adjacent main channel 11. The sub-channels 15 shown here have a curved orientation, so that their arrangement relative to the adjacent main channel 11 varies with this orientation. The sub-channels 15 are arranged substantially perpendicular to the main channel 11 on the distributor channel 60, and substantially parallel to the main channel 11 in or near the main channel 11.

[0112] The first secondary channel 82 terminates on the planar portion 62 of the bottom surface 33 of the adjacent main channel 11. The second secondary channel 84 terminates on the edge 59 between the bottom surface 33 of the main channel 11 and the side surface 31 of the rib 12. The third secondary channel 86 terminates on the side surface 31 of the rib 12, so that water 51 can flow from the side surface 31 to the bottom surface 33 of the adjacent main channel 11. A first cross-section 78 and a second cross-section 80 are also marked.

[0113] Figure 5 Show along in Figure 4 The diagram shows a cross-sectional view of the first cross-section 78. A distributor channel 60 is arranged in the surface 13 of the rib 12, and a sub-channel 15 is located in the bottom 88 of the distributor channel 60, the sub-channel having a depth 27 and a width 29.

[0114] Figure 6 Show along in Figure 4 The diagram shows a cross-sectional view of the second plane 80. A second secondary channel 84 is arranged on the edge 59 between the side surface 31 and the bottom surface 33. A third secondary channel 86 is located in the side surface 31 of the rib 12.

[0115] Figure 7 A perspective top view of a section of distributor plate 7 with distributor channel 60 is shown, which merges into an end structure 64 having more than two sub-channels 66. Multiple sub-channels 66 exist, each having the same length 90, but arranged staggered from one another. The end structure 64 is arranged on the bottom surface 33 of the main channel 11.

[0116] Figure 8 Another embodiment of the end structure 64 is shown, wherein the sub-channels 66 have different lengths 90, and the lengths 90 within the end structure 64 decrease from the inside to the outside.

[0117] Figure 9 Another embodiment of the end structure 64 with sub-channels 66 is shown, wherein the sub-channels 66 are arranged in groups that are staggered from each other.

[0118] Figure 10 A perspective top view of a section of distributor plate 7 showing a distributor channel 60, a sub-channel 15, and an additional sub-channel 70. Sub-channel 15 is partially arranged within distributor channel 60 and merges entirely into the additional sub-channel 70, which is arranged along the axis of symmetry 55 of main channel 11. In the illustrated embodiment, the arrangement angle 72 of the additional sub-channel 70 is 0°, and correspondingly, the additional sub-channel 70 extends parallel to main channel 11. Furthermore, the width 29 and depth 27 of the sub-channel 15 increase in the outflow direction within distributor channel 60.

[0119] Figure 11 A top view of a section of distributor plate 7 with a sub-channel 15 is shown, the sub-channel 15 having a curved direction at the transition from the first section 17 to the second section 21.

[0120] The first part 17 of the secondary channel 15 is arranged at a first angle 19 relative to the main channel 11 with the main flow direction 53. The second part 21 of the secondary channel 15 is arranged at a second angle 23 relative to the main channel 11 and the main flow direction 53.

[0121] The secondary channel 15 also has an end region 25 that flows into the main channel 11, so that water droplets of water 51 are separated from the secondary channel 15 into the main channel 11.

[0122] Figure 12 The end region 25 of the secondary channel 15 is shown. In the illustrated embodiment, the secondary channel 15 has a V-shaped cross-section 35. The secondary channel 15 has a reduced depth 27 and an increased width 29 in the end region 25. Due to the changed geometry of the secondary channel 15 in the end region 25, water 51 accumulated in the secondary channel 15 separates from the secondary channel 15 in the form of droplets and is entrained in the main flow direction 53 of the main channel 11. The end region 25 may have a coating 37.

[0123] Figure 13 A top view of the distributor plate 7 with three regions 94 is shown, in which the structured portions 92 of the surfaces 13 of the ribs 12 are different from each other.

[0124] The distributor plate 7 shown has, in sequence, an inlet region 96 with port structures 100, a first region 104, a second region 106, a third region 108, and an outlet region 98, also with port structures 100, along the main flow direction 53 of the mixture 42. These three regions 94 collectively represent the active surface 102 of the distributor plate 7. The structured portions 92 in the regions 94 are matched to local reaction conditions, because the oxygen content 43 in the mixture 42 decreases along the main flow direction 53, while the water content 51 in the mixture 42, and therefore the liquid content, increases.

[0125] Figure 14 The second, intermediate region 124 of the distributor plate 7 is shown. The rib 12 has a coating 37 in the contact area 47, wherein the coating 37 has hydrophobic surface properties 134. Conversely, the side surface 31 of the rib 12 and the bottom surface 33 of the adjacent main channel 11 have hydrophilic surface properties 136. A plurality of secondary channels 15 are arranged in the contact area 47 of the rib 12, wherein secondary channels 15 having hydrophobic secondary channel surfaces 130 are alternately arranged with secondary channels 15 having hydrophilic secondary channel surfaces 132. The secondary channels 15 having hydrophilic secondary channel surfaces 132 extend from the contact area 47 onto the side surface 31.

[0126] The hydrophobic secondary channel surface 130 is formed by applying a hydrophobic coating 37 to a hydrophilic substrate 8 and then partially removing the hydrophobic coating 37 to form the secondary channel 15. The thickness 138 of the hydrophobic coating 37 is then removed.

[0127] The hydrophilic secondary channel surface 132 is formed by applying a hydrophobic coating 37 to a hydrophilic substrate 8, and then partially and completely removing the hydrophobic coating 37, thereby exposing some portions of the hydrophilic substrate 8 and forming the hydrophilic secondary channel surface 132. To form the hydrophilic secondary channel surface 132, the hydrophobic coating 37 may be removed only, or the substrate 8 may be further imprinted to create deeper secondary channels 15.

[0128] The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, various modifications that are within the scope of the claims and are of skill to those skilled in the art are possible.

Claims

1. A distributor plate (7) for an electrochemical cell (1), wherein, The distributor plate (7) has a structure including ribs (12) and a main channel (11), the ribs having a surface (13) and the main channel having a bottom surface (33). Among them, the sub-channels (15) on the surface (13) form a structured part (92), and The distributor plate (7) has at least two regions (94) in which the structured portions (92) of the surface (13) are different from each other. The distributor plate (7) has an inlet area (96) and an outlet area (98), each having a port structure (100), and the at least two areas (94) are arranged sequentially between the inlet area (96) and the outlet area (98). The feature is that at least a first region (104), a second region (106), and a third region (108) are arranged sequentially in the direction from the entrance region (96) to the exit region (98), wherein, - In the first region (104), at least one of the sub-channels (15) merges into the end structure (64), wherein the at least one sub-channel (15) branches into at least two sub-channels (66) in the end structure (64). - In the second region (106), the structuring section (92) additionally includes a distributor channel (60), wherein the distributor channel (60) has a larger diameter than the sub-channel (15), and / or - In the third region (108), at least one of the secondary channels is arranged to have a first portion (17) at a first angle (19) to the main channel (11) and a second portion (21) at a second angle (23) to the main channel (11), the first angle being in the range of 30° to 150°, the second angle being in the range of less than 45°, and / or At least one of the sub-channels (15) has an end region (25) in which the depth (27) of the at least one sub-channel decreases in the direction of the nearest main channel (11) and / or the width (29) of the at least one sub-channel (15) increases in the direction of the nearest main channel (11).

2. The distributor plate (7) according to claim 1, characterized in that, The number of secondary channels (15) on each side increases in the direction from the entrance area (96) to the exit area (98).

3. The distributor plate (7) according to claim 1 or 2, characterized in that, At least the first region (104), the second region (106), and the third region (108) are arranged sequentially in the direction from the entrance region (96) to the exit region (98). The surface (13) of the rib (12) includes a contact area (47) and a side surface (31), and wherein, - In the first region (104), the subchannel (15) has a hydrophobic subchannel surface (130) in the contact region (47), while at least partially hydrophilic surface properties (136) are present on the side surface (31) and the bottom surface (33). - In the second region (106), the subchannel (15) has a partially hydrophobic subchannel surface (130) and a partially hydrophilic subchannel surface (132), and / or - In the third region (108), there are more subchannels (15) with a hydrophilic subchannel surface (132) than with a hydrophobic subchannel surface (130).

4. The distributor plate (7) according to claim 1 or 2, characterized in that, The subchannel (15) has a width (29) and / or depth (27) ranging from 1µm to 150µm.

5. The distributor plate (7) according to claim 1 or 2, characterized in that, The secondary channels (15) on the surface (13) and on the bottom surface (33) form a structured section (92).

6. The distributor plate (7) according to claim 1 or 2, characterized in that, The at least two sub-channels (66) each have a smaller diameter than the at least one secondary channel (15).

7. The distributor plate (7) according to claim 1 or 2, characterized in that, The structured section (92) additionally includes the distributor channel (60).

8. The distributor plate (7) according to claim 3, characterized in that, Sub-channels (15) with hydrophobic sub-channel surfaces (130) and sub-channels (15) with hydrophilic sub-channel surfaces (132) are arranged alternately.

9. A method for manufacturing a distributor plate (7) according to any one of claims 1 to 8, wherein, First, a hydrophobic coating (37) is applied to a hydrophilic substrate (8), and then layers of the hydrophobic coating (37) with different thicknesses (138) are partially removed to create the sub-channel (15), and the sub-channel has a hydrophobic sub-channel surface (130) or a hydrophilic sub-channel surface (132) depending on the thickness (138) of the removed layer.

10. An electrochemical cell (1), said electrochemical cell comprising a distributor plate (7) according to any one of claims 1 to 8, wherein, The distributor plate (7) is arranged in the cathode chamber (39) of the electrochemical cell (1).

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