CN116686123A

CN116686123A - Electrochemical cell and method for manufacturing an electrochemical cell

Info

Publication number: CN116686123A
Application number: CN202180088364.8A
Authority: CN
Inventors: A·艾费特
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2020-10-29
Filing date: 2021-10-06
Publication date: 2023-09-01
Also published as: WO2022089899A1; DE102020213585A1

Abstract

The invention relates to an electrochemical cell (1) comprising at least one membrane electrode assembly (4), a gas diffusion layer (5) and a distributor plate (7), wherein the distributor plate (7) has a structure comprising a spacer (12) having a surface (13) and a main channel (11) having a bottom surface (33), wherein at least one secondary channel (15) is present in the gas diffusion layer (5) and/or on the distributor plate (7), which leads to the bottom surface (33) of the main channel (11), wherein the at least one secondary channel (15) extends at least partially in the gas diffusion layer (5), and/or wherein at least two secondary channels (15) are present on one surface (13) of the spacer (12) and wherein the at least two secondary channels (15) communicate with each other via a reservoir (110). The invention further relates to a method for producing an electrochemical cell (1).

Description

Electrochemical cell and method for manufacturing an electrochemical cell

Technical Field

The present invention relates to an electrochemical cell comprising at least one membrane electrode assembly, a gas diffusion layer and a distributor plate, wherein the distributor plate has a structure comprising a parting bead having a surface and a main channel having a bottom surface. Furthermore, the invention relates to a method for producing an electrochemical cell.

Background

Electrochemical cells are electrochemical energy converters and are known in the form of fuel cells or electrolysers.

The fuel cell converts chemical reaction energy of the continuously supplied fuel and the oxidant into electric energy. In known fuel cells, in particular hydrogen (H ₂ ) And oxygen (O) ₂ ) Converted into water (H) ₂ O), electrical energy and heat.

In particular, proton exchange membrane (Proton Exchange Membrane =pem) fuel cells are known. Proton exchange membrane fuel cells have a centrally disposed membrane that is permeable to protons, i.e., hydrogen ions. The oxidizing agent, in particular oxygen in air, is thereby spatially separated from the fuel, in particular hydrogen.

The fuel cell has an anode and a cathode. Fuel is supplied to the fuel cell at the anode and is catalytically oxidized to protons with release of electrons, which reach the cathode. The released electrons are conducted away from the fuel cell and flow to the cathode via an external circuit.

An oxidant, in particular oxygen in air, is supplied to the fuel cell at the cathode and reacts to water by absorbing electrons and protons from the external circuit. The water thus produced is led out of the fuel cell. The total reaction is:

O ₂ +4H ⁺ +4e ^- →2H ₂ O

here, a voltage is present between the anode and the cathode of the fuel cell. To increase this voltage, a plurality of fuel cell units can be arranged mechanically in series as a fuel cell stack, also called a galvanic pile or a fuel cell structure, and electrically connected in series.

Stacks of electrochemical cells typically have end plates that compress the individual cells against each other and impart stability to the stack. The end plates can also be used as positive or negative electrodes of the stack for conducting out the current.

The electrodes, i.e., anode and cathode, and the membrane can be structurally combined into a Membrane Electrode Assembly (MEA), also known as Membrane ElectrodeAssembly.

The stack of electrochemical cells also has bipolar plates, also known as gas distributor plates or distributor plates. The bipolar plates serve to uniformly distribute the fuel to the anode and to uniformly distribute the oxidant to the cathode. Furthermore, bipolar plates generally have a surface structure, in particular a channel-like structure, for distributing fuel and oxidant to the electrodes. In particular in fuel cells, channel-like structures are also used for the removal of water produced during the reaction. Additionally, the bipolar plate can have a structure for transporting a cooling medium through the electrochemical cell to conduct heat away.

In addition to the medium guidance in oxygen, hydrogen and water, bipolar plates ensure planar electrical contact with the membrane.

For example, a fuel cell stack typically comprises up to several hundred individual fuel cells, which are stacked one on top of the other in layers, so-called sandwiches. These single fuel cell cells have an MEA and have bipolar plate halves on the anode side and on the cathode side, respectively. The fuel cell unit comprises, in particular, an anode unipolar plate and a cathode unipolar plate, typically in the form of stamped sheet materials, respectively, which together form a bipolar plate and thus form channels for guiding gases and liquids, and between which channels a cooling medium flows.

In addition, electrochemical cells typically include a gas diffusion layer for gas distribution. The gas diffusion layer is arranged between the bipolar plate and the MEA and is typically composed of a carbon fiber nonwoven fabric also known as "gas diffusion backing (gas diffusion backing)" (GDB) on the channel side, i.e. in the direction towards the adjoining bipolar plate, and a microporous layer also known as "micro porous layer" (MPL) on the catalyst side, i.e. in the direction towards the membrane.

In contrast to fuel cells, the electrolysis device is an energy converter, which preferably breaks down water into hydrogen and oxygen when a voltage is applied. The electrolysis device also has, inter alia, an MEA, bipolar plates and gas diffusion layers.

It is particularly important for the efficiency of an electrochemical cell, in particular an electrochemical cell having a polymer electrolyte membrane, that the electrode layers arranged on the membrane are uniformly supplied with the reaction gas.

The known distributor plates have, in particular, channels and corresponding adjoining or adjacent parting strips, which form a structure. The Channels are also called main Channels or passages (Channels), and the division bars are also called Lands (Lands). The surface of the spacer bar that is at least partially parallel to the plane of extension of the distributor plate comprises the contact surface of the distributor plate with the gas diffusion layer of the adjoining electrochemical cell. The gases, i.e. hydrogen and oxygen, pass from the channels of the distributor plate via the gas diffusion layer to the reaction zone on the membrane. The regions of the gas diffusion layer lying against the spacers of the distributor plate and thus the corresponding regions of the MEA lying therebelow are relatively poorly supplied with reactant gases, in particular under the conditions of flooding of the electrochemical cell, which may lead to an undesirable uneven current density distribution.

On the side of the membrane on which air, i.e. oxygen, is supplied, water is produced during operation of the fuel cell, which water must be transported through the gas diffusion layer to the channels of the distributor plate and removed therefrom from the cell. Typical operating temperatures for electrochemical cells with membranes are less than 120 ℃, such that water is typically condensed and present in liquid form in the gas diffusion layer. In the gas diffusion layer, the transport direction of water is opposite to that of gas, and accumulated water can seriously hinder replenishment of reaction gas, particularly oxygen.

The higher the power density of the electrochemical cell, the more water is produced, so that the transport of liquid water in the contact area between the gas diffusion layer and the air channel side of the distributor plate may be insufficient.

JP 2020-47441A describes an improved drainage system for bipolar plates in which additional grooves are provided in the flanks of the parting strips parallel to the direction of the main channel.

JP 2020-47443A describes a bipolar plate with improved drainage, wherein the parting strips of the bipolar plate have an additional channel system which is arranged transversely to the direction of the main channel. Each two channels of the additional channel system have a common outflow. Furthermore, a transverse structure in the main channel of the distributor plate is disclosed, which results in a high pressure loss.

JP 2020-47440A likewise relates to a bipolar plate with an improved drainage system, wherein the parting bead has indentations transversely to the direction of the main channel and additional grooves are present along the flanks of the parting bead parallel to the direction of the main channel.

Disclosure of Invention

An electrochemical cell is proposed, comprising at least one membrane electrode assembly, a gas diffusion layer and a distributor plate, wherein the distributor plate has a structure comprising a parting bead having a surface and a main channel having a bottom surface, wherein at least one secondary channel is present in the gas diffusion layer and/or on the distributor plate, which secondary channel leads to the bottom surface of the main channel, wherein the at least one secondary channel extends at least partially in the gas diffusion layer, and/or wherein at least two secondary channels are present on the surface of the parting bead and communicate with each other via a reservoir.

Furthermore, a method for manufacturing an electrochemical cell is proposed, comprising at least the following steps:

a. a membrane electrode assembly, a gas diffusion layer and a face-type member are provided,

b. the at least one secondary channel is produced on the planar component and/or in the gas diffusion layer,

c. the main channel and the division bar are formed by the face-type member, so that the distributor plate is formed,

d. the membrane electrode assembly, gas diffusion layer and distributor plate are stacked so that an electrochemical cell is formed.

The electrochemical cell is preferably a fuel cell or an electrolyzer. In particular, the gas diffusion layers are each arranged between the gas distributor plate and the membrane or the membrane electrode assembly.

The gas diffusion layer preferably has a porous structure and further preferably rests on the distributor plate at a high pressure of about 10bar to 15 bar. The membrane is preferably a polymer electrolyte membrane, which contains or consists of, for example, perfluorosulfonic acid (PFSA), in particular Nafion. In addition, alkaline membranes can also be used.

Preferably, the gas diffusion layer comprises a nonwoven, in particular a carbon fiber nonwoven, and optionally a microporous layer, wherein the nonwoven is arranged on the side of the gas diffusion layer facing the distributor plate. It is further preferred that the gas diffusion layer comprises a carbon fiber nonwoven fabric and, if necessary, a microporous layer. In the case of nonwoven fabrics, the gas permeability in the thickness direction, i.e. in the direction towards the membrane, can be comparable to the gas permeability in the plane, i.e. in the direction parallel to the membrane.

Preferably, the distributor plate comprises carbon such as graphite, a metal such as stainless steel or titanium and/or an alloy containing the metal. Further preferably, the distributor plate is constructed of carbon, metal and/or alloy. In particular, the base plate of the distributor plate is composed of carbon, metal and/or alloy.

The at least one secondary channel can also be referred to as a drainage channel, capillary channel, groove or as a microscopically small, groove-like structure and serves to conduct the formed reaction water into the primary channel. The at least one secondary channel is arranged in particular on the side of the distributor plate that is directed towards the adjacently arranged gas diffusion layer in the electrochemical cell.

The distributor plate, which can also be referred to as bipolar plate, preferably has a wave-like structure, wherein the parting strips and the main channels are alternately and further preferably respectively arranged parallel to each other.

Preferably, the surfaces of the parting strips each comprise at least one contact region, which can also be referred to as a contact surface, against which the adjacently arranged gas diffusion layers rest. Preferably, the contact area of the division bar is arranged substantially parallel to the bottom surface of the main channel. "substantially parallel" is to be understood as follows: the plane in which the contact area is located encloses an angle of less than 30 °, more preferably less than 20 °, even more preferably less than 10 ° and in particular less than 5 °, with the bottom surface.

Due to the porous structure of the gas diffusion layer, the natural outflow of water, which is typically present in liquid form, becomes difficult at high current densities, so that water accumulation (wasperstau) can be present. This water accumulation can limit the power density of the electrochemical cell in the contact area.

Preferably, the division bar has a side face, which is in particular comprised by the surface of the division bar. It is further preferred that the surface of the spacer bar comprises two sides for each spacer bar, which sides respectively engage to the bottom surfaces of adjacent main channels. The flanks can also be referred to as flanks and are preferably arranged at a flank angle relative to the bottom surface, wherein the flank angle is further preferably in the range of 90 ° to 135 °, more preferably in the range of 90 ° to 125 °, in particular in the range of 95 ° to 110 °. The at least one secondary channel is preferably arranged at least partially on a side of the division bar. Furthermore, the lateral surface is preferably arranged in a bent manner (abgewinkelt) relative to the contact area. Preferably, the bottom surface is at least partially planar.

The main channels are preferably straight and are further preferably arranged parallel to each other on the distributor plate. The at least one secondary channel has a cross-section which is preferably triangular, i.e. V-shaped, round, square or polygonal. Preferably, the cross-section of the at least one secondary channel is V-shaped. The cross-section can be constant over the length of the at least one secondary channel or can vary in size and/or geometry. The cross-section of the primary channel is preferably larger than the cross-section of the at least one secondary channel by at least fifty times.

Preferably, the width and/or depth of the at least one secondary channel is respectively 1 μm to 150 μm, further preferably 1 μm to 100 μm, particularly preferably 1 μm to 50 μm, more preferably 1 μm to 10 μm, particularly preferably 1 μm to 6 μm. Preferably, the gas diffusion layer, which is arranged in particular adjacent to the distributor plate, comprises fibers, and further preferably the width of the at least one secondary channel is smaller than the fiber diameter of the gas diffusion layer, which fiber diameter is for example about 8 μm. The width of the at least one secondary channel can also be greater than the fiber diameter of the gas diffusion layer. In particular, the width of the at least one secondary channel can be selected according to the structure of the adjacent gas diffusion layers, and the depth of the at least one secondary channel can also be selected accordingly. The at least one secondary channel is preferably straight. Furthermore, the width and/or the depth can be constant, increasing or decreasing.

Furthermore, in particular the depth and the width or the diameter of the at least one secondary channel are selected such that the at least one secondary channel forms a capillary effect, in particular a capillary effect in water. Diameter is understood in particular as the largest diameter of the cross section.

The at least one secondary channel can open into the end structure, wherein the secondary channel branches into at least two sub-channels in the end structure, and the at least two sub-channels each have a smaller diameter than the at least one secondary channel. In particular, the respective dimensions of the cross-sections of the at least two sub-channels are smaller than the dimensions of the cross-section of the at least one sub-channel. The end structure can also be referred to as a finer structure or expansion, effectively expanding the surface of the liquid water, so that the drainage of the liquid water and/or the volatilization of the liquid water into the gas phase guided in the main channel can be improved. It is further preferred that the end structure has at least three sub-channels, wherein at least one sub-channel can branch into further, at least two further sub-channels. The sub-channel and at least one of said sub-channels preferably partly enclose 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 at least one sub-channel. The sub-channels preferably have a straight course between the respective branches.

Preferably, the distributor plate is at least partially coated. The coating can be hydrophilic or more hydrophobic than the material of the substrate of the distributor plate. In particular, in order to reduce the electrical contact resistance of the distributor plate, a coating can be applied on the surface of the parting strip. Furthermore, the coating can completely cover the surface of the division bar and, if necessary, also the main channel, or can be present locally.

The coating can be hydrophobic and can have, in particular, a lotus effect. By "hydrophobic" is preferably understood that the wettability is inferior to that of steel with a smooth surface with water, more preferably the contact angle with respect to the water droplet is greater than 70 °, in particular greater than 80 °. The coating can be present in particular in the contact region, in order here, for example, to reduce the contact resistance. Furthermore, a coating can be present on the bottom surface.

Preferably, the coating comprises carbon, in particular carbon particles, such as carbon black or graphite, and comprises in particular an organic binder, for example synthetic resin and/or polyvinylidene fluoride (PVDF). The binder can be thermoplastic or thermosetting. The coating preferably has a layer thickness in the range from 1nm to 200 μm, more preferably in the range from 5nm to 100 μm, particularly preferably in the range from 5nm to 50 μm. In the contact area of the spacer, a layer thickness of more than 5 μm is preferably present. The layer thickness is preferably less than 1 μm on the sides and the bottom.

Furthermore, the distributor plate can have a hydrophilic coating at least in part. By "hydrophilic" is preferably understood that the wettability is better than that of steel with a smooth surface with water, more preferably the contact angle with respect to water droplets is less than 40 °, in particular less than 10 °. Preferably, the at least one secondary channel comprises a hydrophilic secondary channel surface and can have a hydrophilic coating such that water is drawn into the at least one secondary channel. Furthermore, the coating can have an internal structuring, and the at least one secondary channel can be formed by the internal structuring. The inner structured portion is preferably configured to be hydrophilic such that water is drawn into the inner structured portion, as is drawn into the wick.

Furthermore, both the sides of the division bar and the bottom of the main channel can be hydrophilic, which serves for the drainage of water.

The contact area of the spacer bar can be hydrophobic or hydrophilic. If the contact area is hydrophilic, water accumulates directly in the contact area, in particular by wetting and/or condensation, and is then transported away into the main channel via the at least one secondary channel. If the contact region is hydrophobic, the water passes in particular directly into at least one secondary channel on the side of the parting bead, in particular at the convex edge between the contact region and the side, and is condensed there and is then carried away into the main channel, in particular into the adjacent main channel.

The coating can comprise hydrophilic components, such as oxidized carbon particles having hydroxide groups, carbonyl groups and/or carboxyl groups, with polymer binders, which can be used in particular for carbon distributor plates. Preferably, the coating has a surface roughness Ra in the range of 0.1 μm to 10 μm, and further preferably has a maximum peak-to-valley distance (bulkpeak-to-valley maximum distance) in the range of 0.1 μm to 20 μm, more preferably in the range of 1 μm to 10 μm.

The coating can be applied, for example, by laser sintering, or can be applied by the following method: the method is also used to apply metal, ceramic, polymer or mixtures thereof in a pattern to a distributor plate. Another example of a coating method is spray coating.

Alternatively, it is also possible to first apply a coating material, such as a powder, to the distributor plate, which is removed locally in a targeted manner, for example again, from the contact region, and then to carry out a selective (laser) sintering process. Thus, for example, only the main channel can be provided with a coating. The coating can be performed selectively, for example by masking and/or screen printing.

The coating can also be applied in a planar manner and subsequently removed partially, for example by laser means or mechanical means, so that the at least one secondary channel is exposed and in particular the side walls of the at least one secondary channel are formed from the coating.

The at least one secondary channel can be introduced into the base plate of the distributor plate, in particular a sheet metal, and/or into the coating of the distributor plate. In the latter case mentioned, the layer thickness is preferably greater than 5 μm. The at least one secondary channel can be coated or uncoated.

The at least one secondary channel can extend on or in the surface of the spacer bar and/or at least partially in the gas diffusion layer. Preferably, the at least one secondary channel extends partly in the gas diffusion layer and partly on the surface of the spacer.

On this surface, the at least one secondary channel preferably has a semi-open contour, so that the at least one secondary channel has a cross-section, which is for example V-shaped or has a semi-circular shape. In the case of the at least one secondary channel extending in the gas diffusion layer, the at least one secondary channel is preferably completely surrounded by the gas diffusion layer and can also comprise a part of the gas diffusion layer.

The at least one secondary channel can extend to the bottom surface of the primary channel, or the at least one secondary channel can for example end on a side or on a gas diffusion layer and water guided in the at least one secondary channel can flow out of the at least one secondary channel into the primary channel and onto the bottom surface of the primary channel. These cases are all covered by the following expressions: the at least one main channel opens to the bottom surface.

When the at least one secondary channel extends at least partially in the gas diffusion layer, the at least one secondary channel preferably extends substantially perpendicular to the bottom surface in the gas diffusion layer. The term "substantially perpendicular" is to be understood as follows: the at least one secondary channel is arranged in the gas diffusion layer at an angle in the range of 60 ° to 120 °, preferably in the range of 80 ° to 100 °, for example 90 °, with respect to the bottom surface. It is further preferred that the at least one secondary channel meets the surface of the spacer bar substantially perpendicularly from the gas diffusion layer. From the surface, water then flows from the at least one secondary channel in the gas diffusion layer, in particular via the side surfaces, onto the bottom surface.

Preferably, the at least one secondary channel is configured in the gas diffusion layer by perforation and/or chemical modification of the gas diffusion layer. Chemical modification is in particular produced by using a plasma. The preferred chemical modification is the presence of a hydrophilic secondary channel surface in the gas diffusion layer, but the remainder of the gas diffusion layer is hydrophobic.

Preferably, the at least one secondary channel has a hydrophilic secondary channel surface. It is further preferred that the hydrophilic secondary channel surface is formed by the hydrophilic base plate of the distributor plate, the hydrophilic coating of the distributor plate and/or by the fibres of the gas diffusion layer having a hydrophilic fibre surface.

In the gas diffusion layer, the at least one secondary channel is preferably at least partially present in the microporous layer (MPL). Further preferably, the at least one secondary channel is at least partially perforated into the gas diffusion layer such that water can be transported along the at least one secondary channel within the gas diffusion layer and the gas diffusion layer is penetrable for water in the at least one secondary channel. Instead of perforations, there can be chemical modification of the gas diffusion layer, which is characterized in particular by hydrophilic properties. The chemical modification is preferably generated by plasma. Thus, hydrophilic, porous sub-channels can be specifically formed in the porous, hydrophobic gas diffusion layer. The position of the at least one secondary channel preferably matches the position of the at least one secondary channel on the surface of the spacer bar such that the water is guided in a targeted manner first in the gas diffusion layer and then on the surface of the spacer bar.

The reservoir can also be referred to as a reservoir, recess or collection point. In particular, the reservoir is a recessed sub-region of the surface of the spacer bar. The reservoir preferably has a reservoir depth which is at least as great as the depth of the at least one secondary channel. The reservoir serves in particular as a water reservoir if more water is produced than is discharged directly through the at least one secondary channel.

Preferably, the at least two secondary channels open into the reservoir opposite each other, which can also be described as the secondary channels being interrupted by the reservoir.

The reservoir preferably has a round, square or triangular shape, in particular in plan view. The diameter of the reservoir is preferably smaller than the main channel width, and the diameter of the reservoir is further preferably 50% to 70% of the main channel width, in terms of the main channel width.

Preferably, the reservoir is arranged on the side. Thus, for example, a first part of the at least one secondary channel can be present in the gas diffusion layer and essentially perpendicular to the bottom surface, wherein then a second part of the at least one secondary channel can open along the side surface into a reservoir arranged on the side surface, and then a further secondary channel can open from the reservoir to the bottom surface.

The reservoir can also be arranged on the bottom surface of the main channel.

At least two reservoirs can be present on the distributor plate, wherein preferably the at least two reservoirs communicate with one another via a bridge channel. The bridge channel can be configured identically to the at least one secondary channel, wherein the bridge channel is characterized in that the bridge channel starts from the first reservoir and ends at the second reservoir.

The at least one secondary channel is preferably manufactured by means of plasma and/or embossing. It is further preferred that the at least one secondary channel is first produced, in particular on a planar component, i.e. on the distributor plate, and that the primary channel and the spacer are subsequently formed, in particular by embossing. Accordingly, step b.) is preferably performed before step c.. Alternatively, it is also possible to carry out step c before step b.

Advantages of the invention

The at least one secondary channel serves to provide improved drainage of liquid water which forms on the membranes of the electrochemical cell and must be transported out of the electrochemical cell. In this case, the water is first of all guided out of the gas diffusion layer in a targeted manner, so that the gas that reacts on the membrane can better reach the membrane. Accordingly, the performance of the electrochemical cell is improved.

By means of the at least one secondary channel extending at least partially in the gas diffusion layer, which is hydrophobic in the remaining position, can be opened up, so that the produced liquid water can better flow out into the primary channel. The transport of water is improved and at the same time the transport of gas to the catalytic part on the membrane is assisted, since the liquid water in the gas diffusion layer no longer forms an obstacle for the inflow of gas.

Water can accumulate in the reservoir and then be transported away further through the secondary channel. The storage thus serves as an intermediate memory.

Through the bridge channel, the two reservoirs can be in fluid communication, so that an equilibrium of the water quantity between the two reservoirs can be performed.

Drawings

Embodiments of the present invention are explained in more detail with reference to the drawings and the following description.

The drawings show:

figure 1 is a schematic view of an electrochemical cell according to the prior art,

figure 2 is a fuel cell construction with a distributor plate,

figure 3 is a contact area between the gas diffusion layer and the distributor plate,

figure 4 is a perspective view of one embodiment of a distributor plate,

figure 5 is a perspective view of another embodiment of a distributor plate,

FIG. 6 is a cross-sectional view of a contact area between a gas diffusion layer and a distributor plate having secondary channels, an

Fig. 7 is a different embodiment of the reservoir.

Detailed Description

In the following description of embodiments of the invention, identical or similar elements are denoted by the same reference numerals, wherein repeated descriptions of these elements are omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

Fig. 1 schematically shows an electrochemical cell 1 according to the prior art 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.

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 disposed on the membrane 2, respectively. The composite of the membrane 2 and the electrode layer 3 can also be referred to as a membrane electrode assembly 4.

The distributor plate 7 has a main channel 11 for gas supply to the gas diffusion layer 5, for example oxygen 43 in the cathode chamber 39 and hydrogen 45 in the anode chamber 41 to the gas diffusion layer 5. On the distributor plate 7, the main channels 11 alternate with the parting strips 12.

On the surface 13 of the parting bead 12, contact areas 47 are formed between the distributor plate 7 and the adjacently arranged gas diffusion layers 5, respectively. Furthermore, the division bar 12 has side faces 31 and the main channel 11 has a bottom face 33.

Fig. 2 shows a fuel cell structure comprising a plurality of distributor plates 7 and a membrane electrode assembly 4 comprising a membrane 2. Oxygen 43 or air with oxygen 43 contained therein and hydrogen 45 are directed to the membrane electrode assembly 4 by the distributor plate 7. The water 51 is discharged in the main channel 11 of the distributor plate 7, in which the oxygen 43 or the air containing the oxygen 43 is supplied. Furthermore, the distributor plate 7 serves for guiding the coolant 49.

Fig. 3 shows the contact area 47 between the gas diffusion layer 5 and the distributor plate 7. The parting strips 12 of the distributor plate 7 are in contact with the gas diffusion layer 5 in the contact region 47, the gas diffusion layer 5 bearing the membrane electrode assembly 4. Oxygen 43 passes from the main channel 11 of the distributor plate 7 through the gas diffusion layer 5 to the membrane electrode assembly 4. The water 51 formed on the membrane electrode assembly 4 during the reaction accumulates on the division bars 12. If the water 51 does not sufficiently flow out through the main channels 11 of the distributor plate 7, the flow of oxygen 43 through the gas diffusion layer 5 is hindered.

Fig. 4 shows a perspective view of an embodiment of a distributor plate 7, which has been produced from a planar component 8. First, the secondary channel 15 with the reservoir 110 on the surface 13 of the subsequent division bar 12 is applied to the planar component 8. The planar component 8 is then modified by embossing, so that the parting bead 12 and the main channel 11 are formed.

In the illustration shown, two distributor plates 7 can be seen, between which a coolant 49 can be led.

The distributor plate 7 made of the planar component 8 has a contact area 47 on the surface 13 and a side 31. The main channels 11 each have a base 33 along which a main flow direction 53 of a mixture 42, in particular of a gas comprising oxygen 43, is defined, which mixture is guided through the main channels 11.

The side faces 31 each have a plurality of secondary channels 15 which open onto the bottom face 33 of an adjacent primary channel 11. On one of the side surfaces 31, the plurality of sub-passages 15 communicate with each other via the reservoir 110. The secondary channel 15 has a width 29 and a depth 27 and can have a V-shaped or rounded cross-section 35, respectively.

The water 51 flows out of the contact region 47 via the secondary channel 15 onto the bottom 33 of the main channel 11, wherein the water 51 can accumulate in the reservoir 110 on the side 31.

Fig. 5 shows a perspective view of a further embodiment of a distributor plate 7, which has been produced from a planar component 8. The surface 13 has first been provided with parallel arranged secondary channels 15, after which the division bar 12 and the main channel 11 are shaped from the planar member 8 such that the secondary channels 15 are present on the contact areas 47 and the side faces 31 of the division bar 12 of the distributor plate 7 and on the bottom face 33 of the main channel 11. Side 31 meets bottom 33 at edge 59.

In the embodiment shown, the contact region 47 has a hydrophobic coating 37, while the secondary channel 15 has a hydrophilic secondary channel surface 112.

Fig. 6 shows a cross-sectional view of the contact region 47 between the gas diffusion layer 5 and the distributor plate 7, wherein the gas diffusion layer 5 has a microporous layer (MPL) 116.

Oxygen 43 rises from the main channel 11 and water 51 flows out into the main channel 11. In order to remove the water 51 in a targeted manner, the secondary channels 15 extend from the side faces 31 of the parting strips 12 into the gas diffusion layer 5, wherein the secondary channels 15 extend in the gas diffusion layer 5 essentially perpendicularly to the bottom face 33 of the main channel 11, so that the water 51 can flow out directly and in the shortest possible way as a function of gravity. The first portion 118 of each secondary channel 15 is located in the gas diffusion layer 5, while the second portion 120 of that secondary channel 15 is arranged on the side 31 of the parting bead 12. The water 51 can accumulate in the main channel 11 and then flow out.

Fig. 7 shows a different embodiment of the reservoir 110. At least two sub-passages 15 communicate with each other via the reservoir 110, respectively. In the illustrated representation, two of the reservoirs 110 communicate with each other via a bridge channel 114. The reservoir 110 is shown on a planar component 8 which can then be stamped so that the reservoir 110 is arranged on the surface 13 of the future division bar 12.

The present invention is not limited to the embodiments described herein and the aspects emphasized therein. Rather, various modifications which are within the scope of the actions of the person skilled in the art are possible within the scope given by the claims.

Claims

1. An electrochemical cell (1) comprising at least one membrane electrode assembly (4), a gas diffusion layer (5) and a distributor plate (7),

wherein the distributor plate (7) has a structure comprising a division bar (12) having a surface (13) and a main channel (11) having a bottom surface (33),

wherein at least one secondary channel (15) is present in the gas diffusion layer (5) and/or on the distributor plate (7), said at least one secondary channel leading to a bottom surface (33) of the main channel (11),

wherein the at least one secondary channel (15) extends at least partially in the gas diffusion layer (5) and/or at least two secondary channels (15) are present on the surface (13) of the parting bead (12), and the at least two secondary channels (15) communicate with each other via a reservoir (110).

2. Electrochemical cell (1) according to claim 1, characterized in that the at least one secondary channel (15) in the gas diffusion layer (5) extends substantially perpendicular to the bottom surface (33).

3. Electrochemical cell (1) according to any one of the foregoing claims, characterized in that the at least one secondary channel (15) is formed in the gas diffusion layer (5) by perforation and/or chemical modification of the gas diffusion layer (5).

4. Electrochemical cell (1) according to any of the preceding claims, characterized in that the reservoir (110) has a round, square or triangular shape.

5. Electrochemical cell (1) according to any of the preceding claims, characterized in that the surface (13) comprises a side (31) and the reservoir (110) is arranged on the side (31).

6. Electrochemical cell (1) according to any one of the foregoing claims, characterized in that at least two reservoirs (110) are present on the surface (13), and that the at least two reservoirs (110) communicate with each other through a bridge channel (114).

7. Electrochemical cell (1) according to one of the preceding claims, characterized in that the distributor plate (7) has at least partially a coating (37) and, if necessary, the at least one secondary channel (15) is introduced into the coating (37).

8. Electrochemical cell (1) according to any of the preceding claims, characterized in that the at least one secondary channel (15) has a hydrophilic secondary channel surface (112).

9. A method for manufacturing an electrochemical cell (1) according to any one of claims 1 to 8, the method comprising at least the steps of:

a. a membrane electrode assembly (4), a gas diffusion layer (5) and a planar member (8) are provided,

b. the at least one sub-channel (15) is produced on the planar component (8) and/or in the gas diffusion layer (5),

c. the main channel (11) and the parting bead (12) are formed by the planar element (8) such that the distributor plate (7) is formed,

d. -stacking the membrane electrode assembly (4), the gas diffusion layer (5) and the distributor plate (7) such that the electrochemical cell (1) is formed.

10. Method according to claim 9, characterized in that the at least one secondary channel (15) is manufactured by means of plasma and/or embossing.

11. Method according to claim 9 or 10, characterized in that a coating (37) is applied in a planar manner and subsequently removed again in sections, such that the at least one secondary channel (15) is exposed and in particular the side walls of the at least one secondary channel (15) are formed by the coating (37), the removal being effected in particular by laser methods or mechanical methods.

12. The method according to any one of claims 9 to 11, wherein step b.) is performed before step c.