DE102015223040A1 - Fuel cell and fuel cell system with such - Google Patents

Abstract

The invention relates to a fuel cell (10), comprising - a membrane electrode assembly (14) and a bipolar plate (15), which are arranged on one another, - an elastic sealing element (17) between the bipolar plate (15) and the membrane -Electrode arrangement (14) is arranged, and - a single-cell voltage measuring device comprising an electrically conductive contact element (18), the bipolar plate (15) arranged in contact between the bipolar plate (15) and the sealing element (17) and at least is fixed by elastic deformation of the elastic sealing element (17).

Description

The invention relates to a fuel cell (or a fuel cell stack), a fuel cell system with such a fuel cell and a vehicle having such a fuel cell system.

Fuel cells use the chemical transformation of a fuel with oxygen to water to generate electrical energy. For this purpose, fuel cells contain as a core component the so-called membrane electrode assembly (MEA for membrane electrode assembly), which is a microstructure of an ion-conducting (usually proton-conducting) membrane and in each case on both sides of the membrane arranged catalytic electrode (anode and cathode). The latter mostly comprise supported noble metals, in particular platinum. In addition, gas diffusion layers (GDL) can be arranged on both sides of the membrane-electrode arrangement on the sides of the electrodes facing away from the membrane. As a rule, the fuel cell is formed by a multiplicity of stacked MEAs whose electrical powers add up. As a rule, bipolar plates (also called flow field plates or separator plates) are arranged between the individual membrane electrode assemblies, which ensure that the individual cells are supplied with the operating media, ie the reactants, and are usually also used for cooling. In addition, the bipolar plates provide an electrically conductive contact to the membrane-electrode assemblies.

During operation of the fuel cell, the fuel (anode operating medium), in particular hydrogen H ₂ or a hydrogen-containing gas mixture, is supplied to the anode via an anode-side open flow field of the bipolar plate, where an electrochemical oxidation of H ₂ to protons H ⁺ takes place with release of electrons (H ₂ → 2H ⁺ + 2e ^- ). Via the electrolyte or the membrane, which separates the reaction spaces gas-tight from each other and electrically isolated, takes place (water-bound or anhydrous) transport of the protons from the anode compartment into the cathode compartment. The electrons provided at the anode are supplied to the cathode via an electrical line. The cathode is supplied via a cathode-side open flow field of the bipolar plate oxygen or an oxygen-containing gas mixture (for example air) as a cathode operating medium, so that a reduction of O ₂ to O ^2- with absorption of the electrons takes place (½O ₂ + 2e ^- → O ^2-) , At the same time, the oxygen anions in the cathode compartment react with the protons transported via the membrane to form water (O ^2- + 2H ⁺ → H ₂ O).

Due to the electrical series connection of the individual cells of a fuel cell stack, the same current flows through each individual cell (I _stack = I _cell ) and ideally should be the same single cell voltage across each individual cell, the total voltage of the stack resulting from the sum of the single cell voltages of all cells (U _stack = N × U _cell ). Accordingly, the single-cell voltage can be determined in a first approach from the measured total voltage of the stack divided by the number N of cells. In practice, however, there are sometimes serious deviations of the individual cell voltages among one another. This results, for example, from reversible or irreversible degeneration phenomena of individual cells, uneven supply of the individual cells with the operating media, different temperatures of the individual cells, etc. However, for various reasons, the exact knowledge of the single cell voltages is desirable, for example, to avoid that these exceed a critical maximum.

For this reason, fuel cell stacks are known whose single cells or packets of single cells are equipped with a single cell voltage monitor (CVM for cell voltage monitor). For example, annular single-cell voltage measuring devices are known, which are stretched around the entire outer periphery of the bipolar plate in order to tap their voltage. This system has the advantage of being able to be used for a large number of different plate designs. The disadvantage, however, is that the assembly of the measuring device is expensive.

JP 2004288426 A discloses a fuel cell stack having a single cell voltage monitor that includes a sensing plug disposed in a recess between two carbon separators of the fuel cell stack. The measuring plug comprises two flat electrical cables, which are arranged on both sides of an insulating elastic body. The elastic body is compressed during insertion of the measuring plug to prevent falling out of the plug. The elastic body may have concave portions in which convex portions of the separators engage.

The invention is based on the object to propose a fuel cell that allows a single cell voltage monitoring at least selected cells, which is simple and easy to assemble.

This object is achieved by a fuel cell (or a fuel cell stack), a fuel cell system with such a fuel cell and a vehicle having such a fuel cell system with the features of the independent claims.

• – eine Membran-Elektroden-Anordnung und eine Bipolarplatte, die aufeinander angeordnet sind,
• – ein elastisches Dichtungselement, das zwischen der Bipolarplatte und der Membran-Elektroden-Anordnung angeordnet ist, und
• – eine Einzelzellspannungs-Messeinrichtung, die ein elektrisch leitfähiges Kontaktelement umfasst, welches die Bipolarplatte kontaktierend zwischen der Bipolarplatte und dem Dichtungselement angeordnet ist und zumindest durch elastische Verformung des elastischen Dichtungselements fixiert ist.

The fuel cell according to the invention, comprising:

• A membrane-electrode assembly and a bipolar plate arranged on top of each other,
• An elastic sealing element disposed between the bipolar plate and the membrane-electrode assembly, and
• - An individual cell voltage measuring device comprising an electrically conductive contact element, which is arranged in contact between the bipolar plate and the sealing element between the bipolar plate and is fixed at least by elastic deformation of the elastic sealing element.

The arrangement of the contact element between the bipolar plate and the sealing element ensures that a frictional fixing of the contact element is produced by elastic deformation of the sealing element. It is also advantageous that the fixing compressive force acts in the stacking direction and damage to the components of the fuel cell due to other forces are avoided. It should be noted that the tensioning of fuel cell stacks basically also takes place without a single cell voltage measuring device, so that the desired elastic deformation of the sealing element is usually present anyway. Therefore, in the simplest embodiment of the invention, this construction does not require any structural adaptations of the stack or its components, the bipolar plate or the membrane-electrode arrangement. Finally, the fuel cell according to the invention is characterized by a high level of robustness against shocks and by simple assembly.

In the context of this invention, the term "fuel cell" is understood to mean both an individual fuel cell and a stack of several individual cells, that is to say an alternating arrangement of bipolar plates and membrane-electrode arrangements. Furthermore, the term "bipolar plate" (also called a flow field or separator plate) is understood to mean an electrically conductive plate which is designed to supply at least one of the operating media to the catalytic electrodes. Bipolar plates in this sense also include monopolar plates, which are usually anageordnet at the two ends of a fuel cell stack.

The sealing element serves for the fluid-tight sealing of the fuel cell, in particular the electrode chambers, to the outside, so that the anode and cathode operating media can not escape to the outside.

In a preferred embodiment of the invention, it is provided that the elastic sealing element comprises a flat gasket which contacts at least one edge region of the membrane-electrode assembly in a circumferential manner or rests flatly on it. Flat gaskets have the advantage that the force acting on the contact element pressing force is distributed very evenly over the surface and thus on the one hand a good fixation of the contact element and on the other hand a secure electrical contact between the contact element and the bipolar plate is achieved. Alternatively, the sealing element may comprise a bead seal, which circumferentially contacts at least one edge region of the membrane-electrode assembly. There may also be a plurality of flat and / or bead seals, which are designed to circumferentially seal individual supply openings, which are provided in inactive areas of the membrane electrode assembly.

According to a special embodiment, the elastic sealing element comprises a mesh structure which is designed to cover at least one edge region of the membrane-electrode arrangement. Alternatively, the mesh sealing element can cover the entire surface area of the membrane-electrode arrangement due to its material permeability. The net structure holds the individual flat and / or bead seals of the sealing element together. A sealing element comprising a network structure has the advantage that it can be easily placed on the membrane electrode arrangement or bipolar plate as a separate layer comprising all seals, so that the assembly of the fuel cell stack is simplified.

The sealing element may be materially connected to the membrane electrode assembly or be formed as a separate layer, which is arranged stacked between each of a membrane-electrode assembly and a bipolar plate.

Although a high contact pressure and a very good fixation of the contact element is already achieved by the elastic deformation of the sealing element, further measures can be provided to further improve it.

In an advantageous embodiment of the invention, the bipolar plate has a recess in which rests the contact element. Preferably, the contour of the recess substantially corresponds to the contour of the contact element. Through the depression, the contact element is even better fixed and prevents slipping within the plane of the plate. In addition, such a recess allows the use of comparatively thick contact elements. Preferably, the height of the recess is less than the thickness of the contact element, so as to continue to ensure a high contact pressure.

In one embodiment of the invention, the bipolar plate and / or the sealing element has fixing means for the positive fixing of the contact element. These supplement the frictional fixing by the elastic deformation of the sealing element. For this purpose, the contact element of the single-cell voltage measuring device can be equipped with corresponding fixing means, which are capable of forming a positive connection with the fixing means of the bipolar plate and / or of the sealing element. For example, the fixing means comprise at least one projection of the bipolar plate and / or of the sealing element, which engages in a form-fitting manner in at least one recess of the contact element corresponding thereto.

In one embodiment of the invention, the sealing element on pressure amplifying means for reinforcing acting on the contact element pressing force. For example, the pressure amplifying means are formed as at least one elevation facing in the direction of the contact element. By at least one survey, a local thickening of the sealing element is achieved and thus a selective reinforcement of the contact pressure. In this way, a more secure electrical contact between the contact element and bipolar plate is achieved.

Preferably, the fuel cell comprises a plurality of alternately stacked membrane-electrode assemblies and bipolar plates, that is, it is a fuel cell stack. In this case, all pairs of bipolar plate and membrane electrode assembly may have a single-cell voltage measuring device. In this embodiment, the voltage of each individual cell can be measured directly with high accuracy.

In an alternative embodiment, only individual pairs of bipolar plate and membrane electrode assembly on a single-cell voltage measuring device, in particular in a regular distribution. For example, each fifth, tenth or twentieth pair can each be equipped with a single-cell voltage measuring device so that the average cell voltage can be detected for packets of several individual cells. The equipment only selected individual cells with a single cell voltage measuring device is cheaper and less cabling.

Another aspect of the invention relates to a fuel cell system comprising a fuel cell or a fuel cell stack according to the invention. In particular, in addition to the fuel cell, the fuel cell system has an anode supply and a cathode supply with the corresponding peripheral components.

Another aspect of the invention relates to a vehicle having a fuel cell system with a fuel cell according to the invention. The vehicle is preferably an electric vehicle in which an electrical energy generated by the fuel cell system serves to supply an electric traction motor and / or a traction battery.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 a block diagram of a fuel cell system according to a preferred embodiment;

2 a plan view of a membrane-electrode assembly with sealing element;

3 a plan view of a bipolar plate,

4 a detail of an edge portion of a fuel cell according to the invention with contact element according to an embodiment, and

5 a detail of an edge portion of a sealing element with contact element according to an embodiment of the invention.

1 shows a total of 100 designated fuel cell system according to a preferred embodiment of the present invention. The fuel cell system 100 is part of a not further illustrated vehicle, in particular an electric vehicle having an electric traction motor, by the fuel cell system 100 is supplied with electrical energy.

The fuel cell system 100 comprises as a core component a fuel cell stack (fuel cell) 10 containing a plurality of stacked single cells 11 having alternately stacked membrane-electrode assemblies (MEAs) 14 and bipolar plates 15 be formed (see detail). Every single cell 11 thus includes one MEA each 14 , which has an ion-conducting polymer electrolyte membrane, not shown here in detail, and catalytic electrodes arranged thereon on both sides, namely an anode and a cathode, which carry out the respective partial reaction of the fuel cell conversion catalyze and in particular can be formed as coatings on the membrane. The anode and cathode electrodes comprise a catalytic material, such as platinum, supported on an electrically conductive high surface area support material, such as a carbon based material. Between a bipolar plate 15 and the anode thus becomes an anode compartment 12 formed and between the cathode and the next bipolar plate 15 the cathode compartment 13 , The bipolar plates 15 serve to supply the operating media in the anode and cathode rooms 12 . 13 and further provide the electrical connection between the individual fuel cells 11 ago. Optionally, gas diffusion layers may be interposed between the membrane-electrode assemblies 14 and the bipolar plates 15 be arranged.

To the fuel cell stack 10 to supply with the operating media, the fuel cell system 100 on the one hand, an anode supply 20 and on the other hand, a cathode supply 30 on.

The anode supply 20 includes an anode supply path 21 which feeds an anode operating medium (the fuel), for example hydrogen, into the anode spaces 12 of the fuel cell stack 10 serves. For this purpose, the anode supply path connects 21 a fuel storage 23 with an anode inlet of the fuel cell stack 10 , The anode supply 20 further includes an anode exhaust path 22 containing the anode exhaust gas from the anode chambers 12 via an anode outlet of the fuel cell stack 10 dissipates. The anode operating pressure on the anode sides 12 of the fuel cell stack 10 is about an actuating means 24 in the anode supply path 21 adjustable. In addition, the anode supply can 20 as shown, a fuel recirculation line 25 comprising the anode exhaust path 22 with the anode supply path 21 combines. The recirculation of fuel is common in order to return and utilize the fuel, which is mostly used in excess of stoichiometry, in the stack. In the fuel recirculation line 25 can be arranged another adjusting means with which the recirculation rate is adjustable.

The cathode supply 30 includes a cathode supply path 31 which is the cathode spaces 13 of the fuel cell stack 10 supplying an oxygen-containing cathode operating medium, in particular air which is drawn in from the environment. The cathode supply 30 further includes a cathode exhaust path 32 , which the cathode exhaust gas (in particular the exhaust air) from the cathode compartments 13 of the fuel cell stack 10 dissipates and optionally this feeds an exhaust system, not shown. For conveying and compressing the cathode operating medium is in the cathode supply path 31 a compressor 33 arranged. In the illustrated embodiment, the compressor 33 designed as a mainly electric motor driven compressor whose drive via a with a corresponding power electronics 35 equipped electric motor 34 he follows. The compressor 33 may also be through a in the cathode exhaust path 32 arranged turbine 36 (optionally with variable turbine geometry) are supported by a common shaft (not shown) driven.

The cathode supply 30 may also according to the illustrated embodiment, a wastegate line 37 having the cathode supply line 31 with the cathode exhaust gas line 32 connects, so a bypass of the fuel cell stack 10 represents. The wastegate pipe 37 allows excess air mass flow at the fuel cell stack 10 to pass without the compressor 33 shut down. One in the wastegate pipe 37 arranged adjusting means 38 serves to control the amount of the fuel cell stack 10 immediate cathode operating medium. All adjusting means 24 . 26 . 38 of the fuel cell system 100 can be designed as controllable or non-controllable valves or flaps. Corresponding further actuating means can be in the lines 21 . 22 . 31 and 32 be arranged to the fuel cell stack 10 isolate from the environment.

The fuel cell system 100 may also be a humidifier module 39 exhibit. The humidifier module 39 on the one hand is in the cathode supply path 31 arranged so that it can be flowed through by the cathode operating gas. On the other hand, it is so in the cathode exhaust path 32 arranged so that it can be flowed through by the cathode exhaust gas. The humidifier 39 typically has a plurality of water vapor permeable membranes formed either flat or in the form of hollow fibers. In this case, one side of the membranes is overflowed by the comparatively dry cathode operating gas (air) and the other side by the comparatively moist cathode exhaust gas (exhaust gas). Driven by the higher partial pressure of water vapor in the cathode exhaust gas, there is a transfer of water vapor across the membrane in the cathode operating gas, which is moistened in this way.

Various other details of the anode and cathode supply 20 . 30 are in the simplified 1 not shown for reasons of clarity. Thus, in the anode and / or cathode exhaust path 22 . 32 a water separator may be installed to condense and drain the product water resulting from the fuel cell reaction. Finally, the Anode exhaust gas line 22 into the cathode exhaust gas line 32 lead, so that the anode exhaust gas and the cathode exhaust gas are discharged via a common exhaust system.

The 2 and 3 each show an exemplary membrane electrode assembly 14 and bipolar plate 15 according to the invention in a plan view.

Both components are subdivided into an active area AA and inactive areas IA. The active area AA is characterized by the fact that the fuel cell reactions take place in this area. For this purpose, the membrane electrode assembly 14 in the active region AA on both sides of the polymer electrolyte membrane, a catalytic electrode 143 on. The inactive areas IA can be subdivided into supply areas SA and distribution areas DA. Within the service areas SA are service openings 144 to 147 from the membrane electrode assembly 14 respectively 154 to 159 from the bipolar plate 15 arranged in the stacked state substantially aligned with each other and main supply channels within the fuel cell stack 10 form. The anode inlet openings 144 respectively 154 serve to supply the anode operating gas, so the fuel, for example hydrogen. The anode outlet openings 145 respectively 155 serve the discharge of the anode exhaust after overflow of the active area AA. The cathode inlet openings 146 respectively 156 serve to supply the cathode operating gas, which is in particular oxygen or an oxygen-containing mixture, preferably air. The cathode outlet openings 147 respectively 157 serve the discharge of the cathode exhaust gas after overflow of the active area AA. The coolant inlet openings 148 respectively 158 serve the supply and the coolant outlet 149 respectively 159 the discharge of the coolant.

The MEA 14 has an anode side 141 on that in 2 is visible. Thus, the illustrated catalytic electrode is 143 formed as an anode, for example as a coating on the polymer electrolyte membrane. In the 2 invisible cathode side 142 has a corresponding catalytic electrode, here the cathode. The polymer electrolyte membrane can spread over the entire spread of the membrane-electrode assembly 14 extend, but at least over the active area AA. In the inactive regions IA, a reinforcing carrier foil can be arranged, which encloses the membrane.

2 further shows a sealing element 17 , Preferably, on both sides of the membrane-electrode assembly 14 such a sealing element 17 arranged. The sealing element 17 has a flat gasket which is flat on the edge region of the membrane-electrode assembly 14 and it rests all around. In addition, the sealing element 17 have further flat gaskets (not shown), which the individual supply openings 144 to 147 revolve and seal. The sealing element 17 preferably further comprises a mesh structure which covers the entire membrane-electrode assembly 14 spans and holds the individual seals together. The sealing element 17 is formed of an elastically deformable material, in particular an elastomer. Synthetic and natural rubbers or rubbers are particularly suitable here. Particularly preferred are silicones, since these are particularly resistant to chemical and thermal influences. Preferably, both the at least one (flat) seal and the network structure of the same material and is integrally formed. The sealing element 17 is preferably cohesively with the membrane-electrode assembly 14 connected. This can be achieved by an adhesive layer or preferably by direct molding of the sealing element 17 to the support layer of the membrane-electrode assembly 14 for example, by an injection process.

In the 3 illustrated bipolar plate 15 also has a visible cathode side in the illustration 152 on and an invisible anode side 151 , In typical embodiments, the bipolar plate is 15 composed of two joined plate halves, the anode plate and the cathode plate. On the illustrated cathode side 152 are resource channels 153 formed as open channel-like channel structures, which the cathode inlet opening 156 with the cathode outlet opening 157 connect. Only five exemplary resource channels are shown 153 , where usually a much larger number is available. Likewise, the not visible here anode side 151 corresponding resource channels, which the anode inlet opening 154 with the anode outlet opening 155 connect. These operating medium channels for the anode operating medium are also designed as open, channel-like channel structures. Inside the bipolar plate 15 , in particular between the two plate halves, extend enclosed coolant channels, which the coolant inlet opening 158 with the coolant outlet opening 151 connect. With the broken lines are in 3 optional additional seals indicated, due to the sealing element 17 but can also fall away,

In 3 is also a recess 150 indicated in the edge region of the bipolar plate 15 is trained. The depression 150 serves the Recording a contact element of a single cell voltage measuring device, as shown in the following figures.

Usually, in a fuel cell stack 10 a variety of membrane-electrode assemblies 14 and bipolar plates 15 so alternately arranged one another and pressed in the stacking direction, for example via clamping elements. In each case one anode side 151 a bipolar plate 15 an anode side 141 a membrane electrode assembly 14 facing and a cathode side 152 a bipolar plate 15 a cathode side 141 a membrane electrode assembly 14 ,

4 shows a section of a fuel cell 10 , the one border area of a bipolar plate 15 and one with a sealing element 17 equipped membrane-electrode assembly 14 shows. For better visibility, the membrane-electrode assembly 14 as an exploded view spaced from the bipolar plate 15 shown.

In the depression 150 the bipolar plate 15 is a contact element 18 arranged a single cell voltage measuring device, not shown, which serves as a measuring sensor for detecting the voltage. The contact element 18 has a strip-shaped blank of an electrically conductive material. The contact element 18 is connected via not shown electrical lines to the measuring device. In operation of the fuel cell 10 detects the contact element 18 the voltage (half-cell voltage) of the single cell.

This in 4 shown sealing element 17 is according to an embodiment of the invention at the position of the contact element 18 with pressure boosters 171 equipped, in the present example, as five in the direction of the contact element 18 pointing surveys are formed. Through the pressure booster / elevations 171 that is achieved on the contact element 18 acting contact pressure is increased. As a result, a particularly secure electrical contacting of the bipolar plate 15 achieved. The surveys 171 can have any contour and be present in any number.

Another embodiment of the contact element 18 and a sealing member corresponding thereto 14 shows 5 , in turn, only a section of a peripheral region of a with a sealing element 17 equipped membrane-electrode assembly 14 shows. In this embodiment, the sealing element 17 as well as the contact element 18 with fixatives 172 . 181 fitted. In detail, the contact element 18 for example, two recesses 181 on while the sealing element 17 hereby corresponding projections 172 has, in particular the form-fitting manner in the recesses 181 of the contact element 18 intervention. By the fixative 172 . 181 is in addition to the acting in the stacking direction (z-direction) frictional fixing a positive fixation of the contact element 18 inside the fuel cell stack 10 achieved. This ensures that a lateral displacement of the contact element 18 is prevented and also facilitates the assembly of the stack.

LIST OF REFERENCE NUMBERS

100

The fuel cell system

10

fuel cell stack

11

single cell

12

anode chamber

13

cathode space

14

Membrane electrode assembly (MEA)

141

anode side

142

cathode side

143

catalytic electrode / anode

144

Supply opening / anode inlet opening

145

Supply opening / anode outlet opening

146

Supply opening / cathode inlet opening

147

Supply opening / cathode outlet opening

148

Supply opening / coolant inlet opening

149

Supply opening / coolant outlet opening

15

Bipolar plate (separator plate, flow field plate)

150

deepening

151

anode side

152

cathode side

153

Resource channel (reactant channel)

154

Supply opening / anode inlet opening

155

Supply opening / anode outlet opening

156

Supply opening / cathode inlet opening

157

Supply opening / cathode outlet opening

158

Supply opening / coolant inlet opening

159

Supply opening / coolant outlet opening

17

sealing element

171

Pressure intensifier / survey

172

Fixative / projection

18

contact element

181

Fixer / recess

20

anode supply

21

Anode supply path

22

Anode exhaust gas path

23

fuel tank

24

actuating means

25

Brennstoffrezirkulationsleitung

30

cathode supply

31

Cathode supply path

32

Cathode exhaust path

33

compressor

34

electric motor

35

power electronics

36

turbine

37

Waste gate line

38

actuating means

39

humidifier

AA

Active area (reaction area, active area)

IA

Inactive area

SA

Supply area

THERE

Distribution area

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2004288426 A [0006]

Claims (10)

Fuel cell ( 10 ), comprising - a membrane electrode assembly ( 14 ) and a bipolar plate ( 15 ), which are arranged on top of each other, - an elastic sealing element ( 17 ) sandwiched between the bipolar plate ( 15 ) and the membrane-electrode assembly ( 14 ), and - a single cell voltage measuring device, which is an electrically conductive contact element ( 18 ) comprising the bipolar plate ( 15 ) contacting between the bipolar plate ( 15 ) and the sealing element ( 17 ) is arranged and at least by elastic deformation of the elastic sealing element ( 17 ) is fixed. Fuel cell ( 10 ) according to claim 1, characterized in that the elastic sealing element ( 17 ) comprises a flat gasket or a bead seal, which at least one edge region of the membrane-electrode assembly ( 14 ) contacted all around. Fuel cell ( 10 ) according to one of the preceding claims, characterized in that the elastic sealing element ( 17 ) comprises a network structure, which is formed, at least one edge region of the membrane electrode assembly ( 14 ) or the membrane electrode assembly ( 14 ) over the entire area. Fuel cell ( 10 ) According to one of the preceding claims, characterized in that the bipolar plate ( 15 ) a recess ( 150 ), in which the contact element ( 18 ) is present. Fuel cell ( 10 ) According to one of the preceding claims, characterized in that the bipolar plate ( 15 ) and / or the sealing element ( 17 ) Fixative ( 172 . 181 ) for fixing the contact element ( 18 ), in particular for the positive fixing. Fuel cell ( 10 ) according to claim 5, characterized in that the fixing agent ( 172 . 181 ) at least one projection ( 172 ) of the bipolar plate ( 15 ) and / or the sealing element ( 17 ), which in at least one corresponding recess ( 181 ) of the contact element ( 18 ) engages positively. Fuel cell ( 10 ) according to one of the preceding claims, characterized in that the sealing element ( 17 ) Pressure intensifier ( 171 ) for reinforcing one on the contact element ( 18 ) acting pressing force, wherein the pressure intensifying means ( 171 ) in particular as at least one in the direction of the contact element ( 18 ) pointing survey is formed. Fuel cell ( 10 ) according to one of claims 1 to 7, characterized in that the fuel cell ( 10 ) a plurality of alternately stacked membrane electrode assemblies ( 14 ) and bipolar plates ( 15 ), wherein all pairs of bipolar plate ( 15 ) and membrane electrode assembly ( 14 ) comprise a single cell voltage measuring device (10). Fuel cell ( 10 ) according to one of claims 1 to 7, characterized in that the fuel cell ( 10 ) a plurality of alternately stacked membrane electrode assemblies ( 14 ) and bipolar plates ( 15 ), wherein only individual pairs of bipolar plate ( 15 ) and membrane electrode assembly ( 14 ) comprise a single-cell voltage measuring device (10), in particular in regular distribution. Fuel cell system ( 100 ) comprising a fuel cell ( 10 ) according to any one of the preceding claims.

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