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EP-4740253-A1 - MEMBRANE ELECTRODE ASSEMBLY

EP4740253A1EP 4740253 A1EP4740253 A1EP 4740253A1EP-4740253-A1

Abstract

Disclosed is a membrane electrode assembly (6) for a fuel cell stack (2) comprising at least an electricity generating subassembly (14) comprising an ion-conducting membrane (16), and two electro catalyst layers (18, 20) being arranged at either side of the mem¬ brane serving as anode (18) and cathode (20), wherein the membrane electrode assembly further comprises at least one subgasket (26) surrounding the eiectricity generating sub¬ assembly (14), wherein at least one subgasket (26, 28) has a first side (26-1; 28-1) facing to the electricity generating subassembly (14) and a second side (16-2; 28-2) being oppo¬ site of the first side and facing away from the electricity generating subassembly (14), wherein at least one voltage monitoring interface element (10) is arranged at the mem¬ brane electrode assembly (6), which is adapted to contact a voltage providing component of the membrane electrode assembly (6) or of the fuel cell stack, wherein the voltage mon¬ itoring interface element (10) is entirely arranged at and supported by at least one side of the subgasket (26; 28), wherein the respective side (26-1, 28-1; 26-2, 28-2) of the subgas¬ ket (26; 28) which supports the voltage monitoring interface element (10) is at least par¬ tially exposed towards an external environment for providing a connection area (11).

Inventors

  • MUNTHE, Stefan

Assignees

  • PowerCell Sweden AB

Dates

Publication Date
20260513
Application Date
20240705

Claims (15)

  1. 1 . Membrane electrode assembly (6) for a fuel cell stack (2) comprising at least an electricity generating subassembly (14) comprising an ion-conducting membrane (16), and two electro catalyst layers (18, 20) being arranged at either side of the membrane serving as anode (18) and cathode (20), wherein the membrane electrode assembly further comprises at least one subgasket (26) surrounding the electricity generating subassembly (14), wherein at least one subgasket (26, 28) has a first side (26-1 ; 28-1) facing to the electricity generating subassembly (14) and a second side (16-2; 28-2) being opposite of the first side and facing away from the electricity generating subassembly (14), characterized in that at least one voltage monitoring interface element (10) is arranged at the membrane electrode assembly (6), which is adapted to contact a voltage providing component of the membrane electrode assembly (6) or of the fuel cell stack, wherein the voltage monitoring interface element (10) is entirely arranged at and supported by at least one side of the subgasket (26; 28), wherein the respective side (26-1 , 28-1 ; 26-2, 28- 2) of the subgasket (26; 28) which supports the voltage monitoring interface element (10) is at least partially exposed towards an external environment for providing a connection area (11).
  2. 2. Membrane electrode assembly (6) according to claim 1 , wherein at least one of the at least one voltage monitoring interface element (10) is arranged at the second side (26-2; 28-2) of the subgasket (26; 28) and adapted to get in direct or indirect contact with a bipolar plate sandwiching the membrane electrode assembly (6) in the assembled state of a fuel cell stack.
  3. 3. Membrane electrode assembly (6) according to claim 1 or 2, wherein the membrane electrode assembly (6) further comprises an anode sided gas diffusion layer (26), preferably made of electrically conductive fibers, and a cathode sided gas diffusion layer (28), preferably made of electrically conductive fibers, wherein the gas diffusion layers (22, 24) sandwich at least the electricity generating subassembly (14), and wherein at least one of the at least one voltage monitoring interface element (10) is arranged at the second side of the subgasket and is in contact with the anode sided (26) and/or cathode sided (28) gas diffusion layer.
  4. 4. Membrane electrode assembly (6) according to any one of the preceding claims, wherein at least one of the at least one voltage monitoring interface element (10) is arranged at the first side (26-1 ; 28-1) of the at least one subgasket (26; 28) and is in contact with at least one of the electro catalyst layers (18, 20) of the electricity generating subassembly (14), particularly in contact with the anode (18) and/or cathode (20).
  5. 5. Membrane electrode assembly (6) according to claim 4, wherein the membrane electrode assembly (6) further comprises an anode sided subgasket (26) surrounding a periphery of the anode (18), and a cathode sided subgasket (28) surrounding a periphery of the cathode (20), and wherein the at least one voltage monitoring interface element (10) is arranged between the anode sided subgasket (26) and the cathode sided subgasket (28), and wherein one of the subgaskets (26, 28) is recessed in relation to the other subgasket (26, 28) in at least one location for forming the connection area (11), in which the voltage monitoring interface element (10) is exposed to the environment.
  6. 6. Membrane electrode assembly (6) according to any one of the preceding claims, wherein the at least one subgasket (26, 28) has at least one tunnel-like opening (30) extending from the first (26-1 ; 28-1) to the second side (26-2; 28-2) of the subgasket (26; 28), and at least one of the at least one voltage monitoring interface element (10) has a first part (19a) which is arranged at the first side (16-1 ; 28-1) of the subgasket (26; 28) and is in contact with the electro catalyst layer (18, 20), a second part (10b) which extends through the tunnel-like opening (30) in the subgasket (26, 28), and a third part (10c) which is arranged at the second side (16-2; 28-2) of the subgasket and is exposed to the environment for providing the connection area (11).
  7. 7. Membrane electrode assembly (6) according to any one of the preceding claims, wherein at least one of the subgaskets (26, 28) further comprises at least one strip (31) which protrudes from the periphery of the membrane electrode assembly (6), and wherein the voltage monitoring interface element (10) has at least one protruding connecting element which projects over the periphery of the membrane electrode assembly (6), wherein preferably a size and/or form of the at least one strip (31) of the subgasket is designed for supporting the at least one protruding connecting element.
  8. 8. Membrane electrode assembly (6) according to any one of the preceding claims, wherein the voltage monitoring interface element (10) is designed as elongated element having a length, which is along its length in contact with at least one of the anode (18), the cathode (20), the membrane (6), the subgaskets (26, 28), and/or the gas diffusion layers (22, 24).
  9. 9. Membrane electrode assembly (6) according to any one of claim 1 to 8, wherein the voltage monitoring interface element (10) has an elongated main body (86), which is attached to the at least one subgaskets (26, 28) and further comprises at least one discrete inner electric connecting element (13) which extends from the elongated main body (86) in direction of the anode (18), the cathode (20), the membrane (6), and/or the gas diffusion layers and is in contact with at least one of the anode (18), the cathode (20), the membrane (6), and/or the gas diffusion layers (22, 24).
  10. 10. Membrane electrode assembly (6) according to any one of the preceding claims, wherein at least a first voltage monitoring interface element (10) and a second voltage monitoring interface element (10) are provided wherein the at least one first voltage monitoring interface element (10) is arranged at a reactant or coolant inlet side (61) of the membrane electrode assembly (6) and the at least one second voltage monitoring interface element (10) is arranged at a reactant or coolant outlet side (63) of the membrane electrode assembly (6).
  11. 11 . Membrane electrode assembly (6) according to any one of the preceding claims, wherein the voltage monitoring interface element (10) is designed as electrically conducting coating, particularly a silver or gold coating, of the at least one subgasket.
  12. 12. Membrane electrode assembly (6) according to any one of the preceding claims, wherein the voltage monitoring interface element (10) is a foil made from an electrically conducting material, particularly a silver foil or gold foil, which is attached to at least one of the anode (18), the cathode (20), the membrane (6), the subgaskets (26, 28), and/or the gas diffusion layers (22, 24).
  13. 13. Fuel cell stack (2) comprising a plurality of bipolar plates consisting of an anode plate (18) and a cathode plate (20), which are attached to each other, wherein the bipolar plates are alternatingly stacked with a plurality of membrane electrode assemblies so that the bipolar plates sandwich the membrane electrode assemblies (6), characterized in that the membrane electrode assembly (6) is a membrane electrode assembly according to any one of claim 1 to 12.
  14. 14. Fuel cell stack (2) according to claim 13, further comprising a voltage monitoring unit (8) comprising a plug-like element (82) having a plurality of contact pin elements (84) which are designed to connect to the voltage monitoring interface element (10) in the connection area, where the voltage monitoring interface element is exposed to the environment.
  15. 15. Fuel cell stack (2) according to claim 13, further comprising a voltage monitoring unit (8) comprising a plug-like element (82) having a plurality of contact clamp elements (84) which are designed to connect to the voltage monitoring interface element (10) by clamping the voltage monitoring interface element (10) in the connection area, where the voltage monitoring interface element is exposed to the environment.

Description

Membrane electrode assembly Description: The present invention relates to a membrane electrode assembly according to the preamble of claim 1. The invention also relates to a fuel cell stack comprising such a membrane electrode assembly. Usually, an electric cell stack comprises a plurality of stacked electric plates which are separated from each other by insulating layers. In the special case of a fuel cell stack, the electric plates are bipolar plates, and the insulating layers are multi-layer membrane electrode assemblies. The bipolar plates themselves are a combination of an anode plate and a cathode plate which are fixed to each other, wherein adjacent bipolar plates are then separated, or with other words sandwiched, by the membrane electrode assemblies. The cathode and anodes plate which form the bipolar plates are usually electrically transmitting metal or graphite plates, so called flow field plates, having a flow field for the reactants at one side and a flow field for a cooling fluid on the other side. In the assembled state of the bipolar plates, the flow field plates are placed on top of each other in such a way that the cooling fluid flow fields are facing each other, and the reactant fluid flow fields face the sandwiching membrane electrode assemblies. The electric current is produced by the membrane electrode assemblies during operation of the fuel cell stack in the electricity generating subassemblies. The electricity generating subassembly of a membrane electrode assembly comprise an ion-conducting membrane, and two electro catalyst layers being arranged at either side of the membrane serving as anode and cathode. During operation of the fuel cell stack, fuel, particularly hydrogen is provided at the anode, while an oxidant, usually oxygen or air is provided at the cathode. At the anode, the electro catalyst, usually a platinum catalyst, causes the hydrogen to split into positive hydrogen ions (protons) and negatively charged electrons. The ion conducting membrane, e.g. the polymer electrolyte membrane (PEM) allows only the positively charged ions to pass through it to the cathode. At the cathode, the electrons and positively charged hydrogen ions combine with oxygen to form water, which flows out of the cell. Since the ion conducting membrane allows only the positively charged ions to pass to the cathode, a voltage potential difference is created on both sides of the membrane electrode assembly and therefore between the bipolar plate assemblies. During the operation of the electric cell stack, the voltage produced by the stacked cells needs to be monitored for determining whether the stack is operating within its intended operation parameters. For that, it is known that the bipolar plates are equipped with voltage monitoring units, which are fixed to the bipolar plates and are provided with wires for connecting the voltage monitoring units to an external voltage monitoring controller, which monitors and controls the operation of the stack. Thereby, it is known to attach the wires, e.g. by soldering or welding, directly at the bipolar plate. It is also known to use pin connections, where the pins are inserted between the plates of the bipolar plates, where they are fixed by friction force or press-fit. However, placing and fixing the wires and pins into the fuel cell stack is cumbersome and time-consuming, which makes the stacking process inefficient and slow. Additionally, the known fixation methods are also prone to failure as the wires and pins may come loose from the plates or the wires and pins are misplaced so that they cause failures in the stack. Additionally, due to the usually tight stacking of the bipolar plates and associated membrane electrode assemblies, the fuel cell stack lacks the space to fit voltage monitoring interface elements, which might be easier to mount. It is also known to arrange and fix an electrical conductor on a foil, which can be arranged between a gas diffusion layer and an adjacent electrode of the membrane electrode assembly so that the electrical conductor is in electric contact with the respective electrode. The electrical conductor extends over the membrane electrode assembly so that the electrical conductor can be connected to a voltage monitoring unit. Disadvantageously, the electrical conductor is easily damaged during assembling of the fuel cell stack and also hinders correct alignment of the membrane electrode assemblies and bipolar plates during the stacking process. It is therefore object of the present invention, to provide solution for the voltage monitoring of the fuel cell stack, which is easily and reliably mounted, without being prone to damage or hindering alignment of the elements. This object is solved by a membrane electrode assembly according to claim 1 as well as a fuel cell stack according to claim 13. In the following a membrane electrode assembly for a fuel cell stack is disclosed which comprises at least an electricity genera