Method for producing a membrane electrode assembly

Abstract

Method for producing a membrane electrode arrangement (46) for an electrochemical cell unit (25) for converting electrochemical energy into electrical energy as a fuel cell unit (1) and / or for converting electrical energy into electrochemical energy as an electrolysis cell unit (11), comprising the steps of: providing an ion exchange membrane (40), producing a gas diffusion electrode (45), connecting the gas diffusion electrode (45) to the ion exchange membrane (40), wherein the gas diffusion electrode (45) is produced using additive manufacturing.

Description

[0001] The present invention relates to a method for producing a membrane electrode assembly for an electrochemical cell unit according to the preamble of claim 1, a method for producing an electrochemical cell unit according to the preamble of claim 14 and an electrochemical cell unit according to the preamble of claim 15. State of the art

[0002] Fuel cell units, as galvanic cells, convert continuously supplied fuel and oxidant into electrical energy and water through redox reactions at an anode and cathode. Fuel cells are used in a wide variety of stationary and mobile applications, for example, in homes without a power grid connection or in motor vehicles, in rail transport, aviation, aerospace, and shipping. In fuel cell units, a large number of fuel cells are arranged in a stack.

[0003] In fuel cell units, a large number of fuel cells are arranged in a fuel cell stack. Within each fuel cell, there is a gas space for the oxidant, i.e., a flow space for the passage of oxidant, such as ambient air with oxygen. The gas space for the oxidant is formed by channels on the bipolar plate and by a gas diffusion layer for a cathode. The channels are thus formed by a corresponding channel structure of a bipolar plate, and the oxidant, namely oxygen, passes through the gas diffusion layer to the cathodes of the fuel cells. A gas space for fuel is formed analogously at an anode.

[0004] Electrolysis cell units consisting of stacked electrolysis cells, similar to fuel cell units, are used, for example, for the electrolytic production of hydrogen and oxygen from water. Furthermore, fuel cell units are known that can be operated as reversible fuel cell units and thus as electrolysis cell units. Fuel cell units and electrolysis cell units form electrochemical cell units. Fuel cells and electrolysis cells form electrochemical cells. Channels for fuel, oxidant, and a coolant as the process fluid are formed in the fuel cell stack.

[0005] In electrochemical cell units, membrane electrode assemblies with an ion exchange membrane and two electrodes are used as gas diffusion electrodes. The membrane electrode assemblies, particularly in fuel cells, are optionally additionally designed with two gas diffusion layers. The gas diffusion electrodes are formed from several expanded metal layers welded together. This disadvantageously leads to high electrical resistance of the membrane electrode assemblies due to the welded joint. This disadvantageously reduces the efficiency of electrochemical cell units, particularly electrolysis cell units.

[0006] EP 2 985 096 B1 discloses a gas diffusion electrode for a membrane and a membrane-electrode arrangement, comprising a gas diffusion electrode adjoining it, of a fuel cell, in particular a hydrogen-oxygen fuel cell, or of an electrolysis device, in particular an electrolysis device for water electrolysis, with a plurality of expanded metal layers arranged in layers, wherein adjacent expanded metal layers are connected to one another at contact points of their mutually facing flat sides by means of resistance pulse welding, wherein the contact points extend regularly over the entire mutually facing flat sides of the expanded metal layers due to the lattice design of the expanded metal layers and wherein at least one of the expanded metal layers is arranged rotated by 90° in its longitudinal orientation relative to one of its adjacent expanded metal layers. Disclosure of the inventionAdvantages of the invention

[0007] A method according to the invention for producing a membrane electrode arrangement for an electrochemical cell unit for converting electrochemical energy into electrical energy as a fuel cell unit and / or for converting electrical energy into electrochemical energy as an electrolysis cell unit, comprising the steps of: providing an ion exchange membrane, producing a gas diffusion electrode, connecting the gas diffusion electrode to the ion exchange membrane, wherein the gas diffusion electrode is produced using additive manufacturing. The additive manufacturing method used is, for example, free-jet binder application and / or material application with directed energy input and / or powder-based melting, in particular laser sintering, electron beam melting, selective laser melting or thermal transfer sintering. The gas diffusion electrode is preferably connected to the ion exchange membrane directly, i.e.directly, and / or indirectly, i.e. indirectly.

[0008] In another embodiment, the gas diffusion electrode is manufactured using selective laser melting.

[0009] In an additional embodiment, the gas diffusion electrode is made at least partially, preferably at least 50% by mass or 70% by mass, in particular completely, from a metal.

[0010] Preferably, the metal is titanium, preferably titanium 3.7025, and / or stainless steel. For example, in an electrolysis cell unit for the electrolysis of water, titanium is used for the gas diffusion electrode on the oxygen side and stainless steel is used for the gas diffusion electrode on the hydrogen side.

[0011] In a supplementary variant, a powdered starting material is applied in a layer directly or indirectly to a carrier layer, the powdered starting material is locally melted in the layer with a laser beam and the gas diffusion electrode is formed from the solidified molten starting material.

[0012] In an additional embodiment, the application of the powdered starting material in a layer onto the carrier layer, the local melting of the powdered starting material in the layer with a laser beam and the formation of the gas diffusion electrode from the solidified molten starting material are carried out several times, so that the gas diffusion electrode is formed from several layers.

[0013] In a further variant, the ion exchange membrane and / or a catalyst layer is used as the support layer for additive manufacturing, in particular for the first layer.

[0014] In a supplementary embodiment, the direct or indirect bonding of the gas diffusion electrode to the ion exchange membrane is carried out during the production of the gas diffusion electrode using additive manufacturing. The laser beam generates a melt from the powdered starting material locally at the focal spot, and this locally generated melt simultaneously forms the gas diffusion electrode and the bonding layer during cooling. When the gas diffusion electrode is indirectly bonded to the ion exchange membrane, a catalyst layer is formed between the gas diffusion electrode and the ion exchange membrane.

[0015] In particular, the indirect or direct connection of the gas diffusion electrode to the ion exchange membrane is carried out by melting a starting material for the additive manufacturing during the additive manufacturing and bringing the starting material melted for the additive manufacturing into contact with the ion exchange membrane and / or catalyst layer and producing the connection as a material-to-material connection with a connecting layer from the solidified molten starting material between, on the one hand, the ion exchange membrane and / or catalyst layer and, on the other hand, the gas diffusion electrode.

[0016] In an additional embodiment, the indirect or direct connection of the gas diffusion electrode to the ion exchange membrane and / or catalyst layer is carried out with a material-to-material connection and the material-to-material connection is produced locally, in particular with a laser beam.

[0017] In a further embodiment, the indirect or direct connection of the gas diffusion electrode to the ion exchange membrane and / or catalyst layer is carried out with a material-locking connection and a flat side of the gas diffusion electrode facing the ion exchange membrane and / or catalyst layer is connected at a second contact surface with and without material-locking connection to a flat side of the ion exchange membrane and / or catalyst layer facing the gas diffusion electrode at a first contact surface with and without material-locking connection with the material-locking connection.

[0018] In a supplementary variant, on the first contact surface, the area of ​​a first connecting partial surface on the first contact surface with the material-fit connection substantially corresponds, in particular with a deviation of less than 30%, 20% or 10%, to the area of ​​a second connecting partial surface on the second contact surface with the material-fit connection, and preferably on the first contact surface, a first non-connecting partial surface without the material-fit connection is formed at recesses and / or cavities, and preferably on the second contact surface, a second non-connecting partial surface without the material-fit connection is formed at recesses and / or cavities. The first and / or second connecting partial surface is formed from a large number of regions with the material-fit connection from the solidified melt.The first and / or second non-connecting partial area is formed from a large number of regions without the material-to-material connection and / or in particular from recesses and / or cavities. The sum of the area of ​​the first connecting partial area and the first non-connecting partial area is the area of ​​the first contact area, i.e. the first contact area is fictitiously also assumed to be at the first non-connecting partial area. The sum of the area of ​​the second connecting partial area and the second non-connecting partial area is the area of ​​the second contact area, i.e. the second contact area is fictitiously also assumed to be at the second non-connecting partial area. The area of ​​the first connecting area is, for example, between 1% and 99% of the area of ​​the first contact area. The area of ​​the second connecting area is, for example, between 1% and 99% of the area of ​​the second contact area.

[0019] Preferably, the area of ​​the first connecting partial surface is smaller than the area of ​​the first contact surface because preferably no material connection is formed at the first contact surface on the first non-connecting partial surface.

[0020] Preferably, the area of ​​the second connecting partial surface is smaller than the area of ​​the second contact surface because preferably no material connection is formed on the second contact surface on the second non-connecting partial surface.

[0021] A method according to the invention for producing an electrochemical cell unit for converting electrochemical energy into electrical energy as a fuel cell unit and / or for converting electrical energy into electrochemical energy as an electrolysis cell unit with stacked electrochemical cells, comprising the steps of: providing layered components of the electrochemical cells, namely bipolar plates and membrane electrode arrangements with ion exchange membranes, in particular proton exchange membranes, and at least one gas diffusion electrode, stacking the layered components to form electrochemical cells and a stack of the electrochemical cell unit, wherein the membrane electrode arrangements are provided by carrying out a method described in this patent application.

[0022] Electrochemical cell unit according to the invention for converting electrochemical energy into electrical energy as a fuel cell unit and / or for converting electrical energy into electrochemical energy as an electrolysis cell unit, comprising stacked electrochemical cells and the electrochemical cells each comprising stacked layered components and the components of the electrochemical cells are bipolar plates and membrane electrode arrangements with ion exchange membranes, in particular proton exchange membranes, and at least one gas diffusion electrode, wherein the electrochemical cell unit is produced by a method described in this patent application.

[0023] In a supplementary variant, the area of ​​a first non-connecting partial area on the first contact surface without the cohesive connection corresponds substantially, in particular with a deviation of less than 30%, 20% or 10%, to the area of ​​a second non-connecting partial area on the second contact surface without the cohesive connection.

[0024] In an additional embodiment, the laser beam and thus also the focal spot are directed onto the powdered starting material on a predetermined movement path, so that the local melting of the particles of the powdered starting material is carried out in the region of the moving focal spot and the gas diffusion electrode and the material-to-material connection with the connecting partial surface is formed at this moving region and no local melting of the particles of the powdered starting material is carried out outside the moving focal spot, so that no material-to-material connection is produced and the non-connecting partial surface is formed.

[0025] In a further variant, a predetermined geometry is produced from the solidified melt as the gas diffusion electrode by means of a predetermined trajectory of the laser beam and the focal spot.

[0026] Preferably, the geometry of the solidified melt as the gas diffusion electrode is a function of the trajectory of the laser beam and the focal spot on the powdered starting material.

[0027] In a further embodiment, the membrane electrode assemblies are produced with one ion exchange membrane, in particular proton exchange membrane, and two gas diffusion electrodes as flat layers.

[0028] In a further embodiment, the electrochemical cells each comprise an ion exchange membrane, in particular a proton exchange membrane and / or an anion exchange membrane, an anode as a gas diffusion electrode, a cathode as a gas diffusion electrode, preferably at least one gas diffusion layer, and at least one separator plate, in particular a bipolar plate. In contrast to fuel cells, no bipolar plates are required in electrolysis cells; instead, bipolar plates are required as separator plates consisting of a single plate, because electrolysis cells do not have a channel for coolant. In fuel cells, at least one channel for coolant is formed between the two plates in the bipolar plate consisting of two plates.

[0029] Preferably, the thickness of the gas diffusion electrode is between 0 and 70 µm.

[0030] The gas diffusion electrode is preferably disc-shaped and / or flat.

[0031] In a further embodiment, cavities are formed in the gas diffusion electrode.

[0032] In an additional variant, the volume fraction of the cavities and / or recesses of the gas diffusion electrode is at least 1%, 5%, 10%, 20% or 30% of the volume of the gas diffusion electrode.

[0033] In a further embodiment, the cavities and / or recesses are formed as continuous cavities and / or recesses of the gas diffusion electrode, extending continuously from a flat side of the gas diffusion electrode facing the ion exchange membrane and to a flat side of the gas diffusion electrode facing away from the ion exchange membrane.

[0034] In an additional variant, at least 3%, 5%, 10%, 20% or 30% of the cavities and / or recesses of the gas diffusion electrode are formed as continuous cavities.

[0035] In a supplementary embodiment, the diameter of the continuous cavities and / or recesses of the gas diffusion electrode is substantially constant, in particular with a deviation of less than 50%, 30% or 10%.

[0036] In a further embodiment, cavities and / or recesses are formed in the connecting layer.

[0037] In an additional variant, the volume fraction of the cavities and / or recesses of the connecting layer is at least 1%, 5%, 10%, 20% or 30% of the volume of the connecting layer.

[0038] In a further embodiment, the cavities and / or recesses are formed as continuous cavities of the connecting layer continuously from a flat side of the connecting layer facing the ion exchange membrane and to a flat side of the connecting layer facing away from the ion exchange membrane.

[0039] In an additional variant, at least 3%, 5%, 10%, 20% or 30% of the cavities and / or recesses of the connecting layer are formed as continuous cavities.

[0040] In a supplementary embodiment, the diameter of the continuous cavities and / or recesses of the connecting layer is substantially constant, in particular with a deviation of less than 50%, 30% or 10%.

[0041] Preferably the fuel is hydrogen, hydrogen-rich gas, reformate gas or natural gas.

[0042] Advantageously, the electrochemical cells and / or components of the electrochemical cells are essentially flat and / or disc-shaped.

[0043] In another variant, the electrochemical cell unit comprises a housing and / or a connection plate. The stack is enclosed by the housing and / or the connection plate.

[0044] In a complementary variant, the oxidizing agent is air with oxygen or pure oxygen.

[0045] Preferably, the fuel cell unit is a PEM fuel cell unit with PEM fuel cells or an SOFC fuel cell unit with SOFC fuel cells or an alkaline fuel cell (AFC). Short description of the drawings

[0046] In the following, exemplary embodiments of the invention are described in more detail with reference to the accompanying drawings. They show: Fig. 1 a highly simplified representation of a fuel cell system, Fig. 2 a highly simplified representation of an electrolysis cell system, Fig. 3 a longitudinal section of a membrane electrode assembly in a first embodiment during manufacture, Fig. 4 a longitudinal section of the membrane electrode arrangement according to Fig. 3 in the first embodiment, Fig. 5 a longitudinal section of the membrane electrode assembly in a second embodiment during manufacture, Fig. 6 a longitudinal section of the membrane electrode arrangement according to Fig. 5 in the second embodiment, Fig. 7 a top view of two gas diffusion layers with two different geometric configurations and Fig. 8 a longitudinal section of three gas diffusion layers with three different geometric configurations.

[0047] In Fig. 1, a fuel cell unit 1 is shown as a fuel cell stack 3, i.e., as a fuel cell stack 3. The fuel cell unit 1 comprises the fuel cell stack 3, a housing 13, and a connecting plate 15. The housing 13 defines an interior space 14. The connecting plate 15 also functions as a housing 13 and is fixed to the remaining housing 13 by fixing elements 16, in particular screws 17. In the fuel cell stack 3, fuel cells 4 are stacked as PEM fuel cells 5 and arranged in alignment. Due to the large number of stacked fuel cells 4 of approximately 300 to 400 fuel cells 4, these are in Fig. 1 For the sake of simplicity, not all are shown. The principle of fuel cells 4 is that electrical energy or electrical current is generated by means of an electrochemical reaction. Hydrogen H is fed to an anode 43. 2as a gaseous fuel as recirculation fuel, and anode 43 forms the negative pole. A gaseous oxidant, namely air with oxygen, is fed to a cathode 44; that is, the oxygen in the air provides the necessary gaseous oxidant. Reduction (electron absorption) takes place at the cathode. Oxidation, as electron release, occurs at anode 43.

[0048] The fuel cell 4 also includes an ion exchange membrane 40 as a proton exchange membrane 41 (Proton Exchange Membrane, PEM), which is arranged between the anode 43 and the cathode 44 as electrodes 45. The anode 43 and cathode 44 are layered or disc-shaped. The PEM 41 functions as an electrolyte, catalyst support, and separator for the reaction gases. The PEM 41 also functions as an electrical insulator and prevents an electrical short circuit between the anode 43 and cathode 44. Generally, 12 µm to 150 µm thick, proton-conducting films made of perfluorinated and sulfonated polymers are used. The PEM 41 conducts the protons H + and blocks ions other than protons H + essentially, so that due to the permeability of PEM 41 for the protons H + the charge transport can take place. The PEM 41 is suitable for the reaction gases oxygen O 2 and hydrogen H 2essentially impermeable, i.e. blocks the flow of oxygen O 2 and hydrogen H 2 between a gas space (not shown) at the anode 43 with fuel hydrogen H 2 and a gas space (not shown) at the cathode 44 with air or oxygen O 2 as an oxidizing agent. The proton conductivity of PEM 5 increases with increasing temperature and water content.

[0049] On both sides of the PEM 5, each facing the gas spaces, the electrodes 45 are located as gas diffusion electrodes 45 as the anode 43 and cathode 44. A unit comprising the PEM 41 and the electrodes 45 is referred to as a membrane electrode assembly (MEA) 46. The electrodes 45 are made of metal or an ionomer, for example Nafion®, platinum-containing carbon particles, and additives. These electrodes 45 with the ionomer are electrically conductive due to the carbon particles and also conduct the protons H + and additionally function as a catalyst layer due to the platinum-containing carbon particles. Membrane electrode assemblies 46 with these electrodes 45 and the PEM 41 form membrane electrode assemblies 46 as a CCM (catalyst coated membrane). Electrodes 45 made of a metal with catalytic activity, for example, titanium, also function as electrodes 45 and catalyst layer 42.

[0050] A gas diffusion layer 47 (GDL) is optionally provided on the anode 43 and the cathode 44, particularly in a fuel cell unit 1. A gas diffusion layer 47 is generally not required in an electrolysis cell unit 11. The gas diffusion layer 47 on the anode 43 evenly distributes the fuel from fuel channels on the bipolar plate (not shown) to the anode 43. The gas diffusion layer 47 on the cathode 44 evenly distributes the oxidant from oxidant channels on the bipolar plate to the cathode 44. The GDL 47 also removes reaction water in the opposite direction to the flow of the reaction gases, i.e., in one direction from the electrodes 45 to the channels on the bipolar plate. Furthermore, the GDL 47 keeps the PEM 41 moist and conducts current.

[0051] In the fuel cell unit 1, the fuel cells 4 are arranged between two clamping elements 18 as clamping plates 19. An upper clamping plate 20 rests on the uppermost fuel cell 4 and a lower clamping plate 21 rests on the lowermost fuel cell 4. The clamping elements 18 apply a compressive force to the fuel cells 4, i.e. the upper clamping plate 20 rests with a compressive force on the uppermost fuel cell 4 and the lower clamping plate 21 rests with a compressive force on the lowermost fuel cell 4. The fuel cell stack 3 is thus clamped in order to ensure tightness for the fuel, the oxidizing agent and the coolant, in particular due to elastic seals, and also to keep the electrical contact resistance within the fuel cell stack 3 as low as possible.To clamp the fuel cells 4 with the clamping elements 18, four connecting devices 22 are designed as bolts 23 on the fuel cell unit 1, which are subjected to tensile stress. The four bolts 23 are firmly connected to the clamping plates 19.

[0052] An opening for introducing recirculation fuel into the recirculation fuel channels is formed in the connecting plate 15 and in the lower clamping plate 21. Furthermore, an opening for discharging recirculation fuel from the recirculation fuel channels is formed in the connecting plate 15 and in the lower clamping plate 21 as the clamping element 18. Further openings are formed in the connecting plate 15 and the lower clamping plate 21 as the clamping element 18 for introducing oxidizing agent and discharging oxidizing agent, and openings (not shown) for introducing coolant and discharging coolant. Thus, a total of 6 openings are formed in the connecting plate 15 and the lower clamping plate 21 (only partially in Fig. 1).

[0053] A fuel cell system 2 comprises, in addition to the fuel cell unit 1, an oxidant supply system 26 for supplying the fuel cell stack 2 with air as the oxidant. The oxidant supply system 26 comprises a gas delivery device 27, for example a blower, a compressor, a turbocompressor driven by an electric motor and / or a turbine, and oxidant lines 28.

[0054] In addition to the fuel cell unit 1, the fuel cell system 2 also comprises a fuel supply system 29 for supplying the fuel cell stack 3 with hydrogen as fuel. The fuel supply system 29 comprises a pressure vessel 30, a fuel line 31 as a process fluid line, valves (not shown) for fuel, in particular an injector for controlling the volume flow of fuel introduced from the fuel line 31 into the recirculation line 32, a heat exchanger (not shown) for fuel, a pressure reducer (not shown), a recirculation fuel line 32 as a process fluid line, a recirculation fuel feed device 33, an electric motor (not shown) for driving the recirculation fuel feed device 33, and a water separator 34 for separating water from the recirculation fuel.a water tank (not shown) for collecting the water collected in the water separator 34, a drain valve (not shown) for draining water from the water tank, and a drain valve as a purge valve (not shown) for discharging recirculation fuel into the environment. In the fuel supply system 29 for supplying the fuel cell stack 3 with hydrogen as fuel, the hydrogen stored in the pressure tank 30 at a high pressure of, for example, 400 bar is fed through the fuel line 31 with an injector (not shown) into the recirculation fuel line 32 and thus to the fuel cells 4. After the fuel has passed through the fuel cells 4, the hydrogen is not completely consumed.so that this hydrogen derived from the fuel cells 4 is fed back to the fuel cells 4 in a circuit via the recirculation fuel line 32. The recirculation fuel conveying device 33 is used to convey the recirculation fuel through the recirculation fuel line 32. After the fuel passes through the fuel cells 4, the moisture content of the fuel increases, so that to prevent an excessive water or moisture content in the recirculation fuel, the fuel supply system 29 includes the water separator 34. The water separated in the water separator 34 is collected in the water tank (not shown) and discharged into the environment through the drain valve (not shown). Excess recirculation fuel is discharged into the environment through the purge valve (not shown).

[0055] In addition to the fuel cell unit 1, the fuel cell system 2 also comprises a cooling system (not shown) for controlling the temperature of the fuel cell stack 3, i.e., for cooling the fuel cell stack 3. The cooling system for controlling the temperature of the fuel cell stack 3 comprises coolant lines as process fluid lines, a heat exchanger, and a pump for circulating the coolant. The coolant is conducted through coolant channels in the bipolar plates of the fuel cells 4, and the heat is dissipated to the environment at the heat exchanger. In addition to the fuel cell unit 1, the fuel cell system 2 also comprises the oxidant supply system 26, the fuel supply system 29, and the cooling system (not shown) as a coolant supply system.

[0056] The fuel cell unit 1 can, with modifications not shown, in particular valves, also optionally be used and operated as an electrolysis cell unit 6, ie forms a reversible fuel cell unit 1. In the following, some features are described which enable the operation of the fuel cell unit 1 as an electrolysis cell unit 6. For the electrolysis, a liquid electrolyte, namely highly diluted sulfuric acid with a concentration of approximately c (H 2 SO 4 ) = 1 mol / l. A sufficient concentration of oxonium ions H 3 O + in the liquid electrolyte is necessary for electrolysis. In Fig. 2 shows an electrolysis cell unit 11 which can only be used for electrolysis.

[0057] The polarity of the electrodes is reversed (not shown) during electrolysis when operating as an electrolysis cell unit 6 as when operating as a fuel cell unit 1, so that hydrogen H 2 is formed and the hydrogen H 2 is absorbed by the liquid electrolyte and transported along in dissolved form. Similarly, the liquid electrolyte is passed through the oxidant channels and oxygen O is released at the anodes or oxidant channels. 2 is formed. The fuel cells 2 of the fuel cell unit 1 function as electrolysis cells 12 when operated as electrolysis cell unit 6. The fuel cells 2 and electrolysis cells 12 thus form electrochemical cells 24. The oxygen O formed 2 is absorbed by the liquid electrolyte and transported along in dissolved form. The hydrogen H 2is absorbed by the liquid electrolyte and transported in dissolved form. The liquid electrolyte is stored in a storage container 35 and is conveyed by a pump 37 and through electrolyte lines 36 through the channels in the electrolysis cell stack 8. For a reversible fuel cell unit 1 (not shown) according to Fig. 1, two 3-way valves (not shown) are provided on the recirculation fuel line 32 and the oxidant line 28. During operation, they are switched over as the electrolysis cell unit 11, so that instead of recirculation fuel and oxidant, the liquid electrolyte is fed by the pump 37 from the storage tank 35 into the recirculation fuel line 32 and the oxidant line 28 as the electrolyte line 36. A hydrogen separator 38 separates the hydrogen obtained from the electrolysis from the electrolyte. An oxygen separator 39 separates the oxygen obtained from the electrolysis from the electrolyte. The electrolyte is circulated through the electrolysis cell unit 6, and sulfuric acid is added according to consumption using a device (not shown).In addition to the electrolysis cell unit 6, the electrolysis cell system 10 also comprises an electrolyte supply system 60 comprising the storage tank 35, the electrolyte lines 36 and the pump 37 as well as the separator 38 for hydrogen and the separator 39 for oxygen.

[0058] In Fig. 4 is a first embodiment of the membrane electrode assembly 46 and in Fig. 3 shows the partially manufactured membrane electrode assembly 46 in the first embodiment of the membrane electrode assembly 46 during production. First, the ion exchange membrane 40 with the catalyst layer 42 is provided on both flat sides 56 of the ion exchange membrane 40 and placed on a support plate 53. Subsequently, a flat side 56 as the top side 56 of the ion exchange membrane 40 is applied as shown in Fig. 3, a powdered starting material is indirectly applied in a layer 51. The catalyst layer 42 is formed between the flat side 56 of the ion exchange membrane 40 and the powdered starting material, so that the powdered starting material is indirectly applied to the flat side 56 of the ion exchange membrane 40. The layer 51 is applied directly to the catalyst layer 42, so that the catalyst layer 42 acts as a direct support layer 52 for the layer 51. The layer 51 is applied indirectly to the ion exchange membrane 40, so that the ion exchange membrane 40 acts as an indirect support layer 52 for the layer 51.

[0059] Subsequently, a laser beam 49 is applied to the layer 51 made of the powdered starting material using a laser 48, so that the particles of the powdered starting material melt locally at the focal spot of the laser beam 49. As the molten powdered starting material cools, the metal melt solidifies. The laser beam 49 is directed onto the powdered starting material along a predetermined trajectory, so that the local melting of the particles of the powdered starting material leads to a predetermined geometry from the solidified melt. Due to the trajectory of the laser beam 49, the gas diffusion electrode 45 is thus formed from the particles of the powdered starting material as a porous transport layer using selective laser melting as additive manufacturing.

[0060] The connection between the porous transport layer 45 and the catalyst layer 42 is formed by a material bond with a connecting layer 50. The connecting layer 50 rests on the flat side 54 of the gas diffusion electrode 45, and the connecting layer 50 is formed only partially on a second connecting partial surface 63 at a second contact surface 55 on the gas diffusion electrode 45. The connecting layer 50 is thus only created by the laser beam 49 in those regions of the second contact surface 55 of the gas diffusion electrode 45 onto which the focal spot has been directed. The area of ​​the second connecting partial surface 63 on the gas diffusion electrode 45 is thus smaller than the second contact surface 55. The connecting layer 50 is not formed in those regions of the second contact surface 55 as a second non-connecting surface of the gas diffusion electrode 45 onto which the laser beam 49 has not been directed.The area of ​​the second non-connecting partial area on the gas diffusion electrode 45 is thus smaller than the second contact area 55. In an analogous manner, the flat side 57 of the catalyst layer 42 at a first contact area 58 of the catalyst layer 42 is only partially materially bonded to the connecting layer 50 at a first connecting partial area 64 due to the movement path of the laser beam 49. At the first contact area 58, outside the movement path of the laser beam 49, no materially bonded connection and no connecting layer 50, and thus a first non-connecting area, is formed. The connecting layer 50 is thus in a plane perpendicular and parallel to the plane of the drawing of . Fig. 3 only partially formed, so that in a section with a fictitious plane perpendicular to the plane of the drawing of Fig. 3 through the flat connecting layer 50 cavities 62 and / or areas 61 without connecting layer 50 are formed in any geometry depending on the movement path of the laser beam 49 on the layer 51 of the powdered starting material.

[0061] After applying the first layer 51 from the powdered starting material and producing the cohesive connecting layer 50 only locally with the laser beam 49 at the first contact surface 58 with respect to the catalyst layer 42 and at the second contact surface 55 with respect to the gas diffusion electrode 45, a further layer 51 is applied after the melt has cooled and hardened, and then selective laser melting is carried out again on this further layer 51 in a similar manner, so that the previous layer 51 forms the carrier layer 52. In this way, the gas diffusion electrode 45 can optionally be produced from several layers 51, for example 2-6 layers 51 (not shown). The layers 51 and the gas diffusion electrode 45 have a thickness of a few µm.

[0062] In Fig. 5 and Fig. 6 shows a second embodiment of the membrane electrode assembly 46 during manufacture. In the following, only the differences from the first embodiment according to Fig. 3 and described. No catalyst layer 42 is formed as an additional layer between the gas diffusion electrode 45 and the ion exchange membrane 40. The connecting layer 50 thus lies directly on the flat side 54 of the gas diffusion electrode 45, and the connecting layer 50 is formed on the second contact surface 55 of the gas diffusion electrode 45. The connecting layer 50 lies directly on a flat side 56 of the ion exchange membrane 40, and the connecting layer 50 is formed on the first contact surface 58 of the ion exchange membrane 40. In the second embodiment according to Fig. 5 and Fig. 6, the gas diffusion electrode 45 is immediately and directly connected to the connecting layer 50 with the ion exchange membrane 40 because no catalyst layer 41 is formed between the gas diffusion electrode 45 and the ion exchange membrane 40. In the first embodiment according to Fig. 3 and Fig. 4, the catalyst layer 42 is formed between the gas diffusion electrode 45 and the ion exchange membrane 40, so that the gas diffusion electrode 45 is indirectly connected to the ion exchange membrane 40. The second connecting surface 63 and the first connecting surface 64 are shown for the second embodiment in Fig. 8 and Fig. 8 can also be applied analogously to the first embodiment with catalyst layer 42.

[0063] In Fig. 7 and Fig. 8 shows different examples of the geometry of the gas diffusion electrode 45. In Fig. 7 shows a plan view of two gas diffusion electrodes 45 in a different geometry. In the Fig. 7 left, recesses 61 and / or cavities 62 are formed in the gas diffusion layer 40 in cross-section in the form of a parallel program, in particular a rectangle, and in the embodiment shown in Fig. In the embodiment shown on the right in Figure 7, the recesses 61 and / or cavities 62 are circular in cross-section.

[0064] In Fig. 8 shows the longitudinal section through three different gas diffusion electrodes 45 on the connecting layer 50. The connecting layer 50 is arranged on the ion exchange membrane 40 according to the second embodiment in Fig. 5 and Fig. 6 is formed directly. The gas diffusion electrode 45 is in Fig. 8 is formed from individual nozzles or rods with recesses 61 and / or cavities 62 in between and in the Fig.In the embodiment shown centrally in Figure 8, these nozzles or rods are connected to one another in the direction of the plane spanned by the connecting layer 50. On the second contact surface 55 of the gas diffusion electrode 45, outside the recesses 61 and / or cavities 62, the second connecting partial surface 63 is formed on the solidified melt of the powdered starting material, and the solidified melt locally forms the gas diffusion electrode 45 and the connecting layer. On the first contact surface 58 of the ion exchange membrane 40, outside the recesses 61 and / or cavities 62, the first connecting partial surface 64 is formed on the solidified melt of the powdered starting material, and the solidified melt locally forms the gas diffusion electrode 45 and the connecting layer 50. The first non-connecting partial surface and the second non-connecting partial surface are present at the recesses 61 and / or the cavities.Due to the geometry of the gas diffusion electrode 45, particularly in the two embodiments shown below, the gas diffusion electrode 45 is formed by multiple selective laser melting in superimposed layers.

[0065] Overall, the method according to the invention for producing the membrane electrode assembly 46, the method according to the invention for producing the electrochemical cell unit 25, and the electrochemical cell unit 25 according to the invention offer significant advantages. The gas diffusion electrode 45 is manufactured using additive manufacturing, in particular selective laser melting, so that a lower electrical resistance occurs within the membrane electrode assembly 46 and the electrochemical cell unit 25 as a whole has a low electrical resistance due to the large number of membrane electrode assemblies 46 connected electrically in series. The geometry of the gas diffusion electrode 45 as the porous transport layer 45 can be freely selected and easily modified simply by changing the programming to alter the trajectory of the laser beam 49.For water electrolysis, the geometry of the gas diffusion electrode 45 can be optimized for hydrogen removal and water supply. During the selective laser melting process, no burrs are formed on the gas diffusion electrode 45, so no post-processing to remove burrs is necessary. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

[0000] EP 2 985 096 B1

[0006]

Claims

[1] Method for producing a membrane electrode arrangement (46) for an electrochemical cell unit (25) for converting electrochemical energy into electrical energy as a fuel cell unit (1) and / or for converting electrical energy into electrochemical energy as an electrolysis cell unit (11), comprising the steps: - providing an ion exchange membrane (40), - producing a gas diffusion electrode (45), - Connecting the gas diffusion electrode (45) to the ion exchange membrane (40), characterized by that the gas diffusion electrode (45) is manufactured using additive manufacturing. [2] Method according to claim 1, characterized by that the gas diffusion electrode (45) is manufactured by selective laser melting. [3] Method according to claim 1 or 2, characterized by that the gas diffusion electrode (45) is made at least partially, in particular completely, from a metal. [4] Method according to claim 3, characterized by that the metal is titanium and / or stainless steel. [5] Method according to one or more of the preceding claims, characterized by that a powdered starting material is applied directly or indirectly in a layer (51) to a carrier layer (52), the powdered starting material in the layer (51) is locally melted with a laser beam (49) and the gas diffusion electrode (45) is formed from the solidified molten starting material. [6] Method according to claim 5, characterized bythat the application of the powdered starting material in a layer (51) onto the carrier layer (52), the local melting of the powdered starting material in the layer (51) with a laser beam (49) and the formation of the gas diffusion electrode (45) from the solidified molten starting material are carried out several times, so that the gas diffusion electrode (45) is formed from several layers (51). [7] Method according to one or more of the preceding claims, characterized by that the ion exchange membrane (40) and / or a catalyst layer (42) is used as the support layer (52) for additive manufacturing, in particular for the first layer (51). [8] Method according to one or more of the preceding claims, characterized bythat the indirect or direct connection of the gas diffusion electrode (45) to the ion exchange membrane (40) during the manufacture of the gas diffusion electrode (45) is carried out by additive manufacturing. [9] Method according to one or more of the preceding claims, characterized by that the indirect or direct connection of the gas diffusion electrode (45) to the ion exchange membrane (40) is carried out by melting a starting material for the additive manufacturing during the additive manufacturing and bringing the starting material melted for the additive manufacturing into contact with the ion exchange membrane (40) and / or catalyst layer (42) and the connection is produced as a material-to-material connection with a connecting layer (50) from the solidified molten starting material between, on the one hand, the ion exchange membrane (40) and / or catalyst layer (42) and, on the other hand, the gas diffusion electrode (45). [10] Method according to one or more of the preceding claims, characterized by that the indirect or direct connection of the gas diffusion electrode (45) to the ion exchange membrane (40) and / or catalyst layer (42) is carried out with a material-to-material connection and the material-to-material connection is produced locally, in particular with a laser beam (49). [11] Method according to one or more of the preceding claims, characterized bythat the indirect or direct connection of the gas diffusion electrode (45) to the ion exchange membrane (40) and / or catalyst layer (42) is carried out with a material-to-material connection and a flat side (54) of the gas diffusion electrode (45) facing the ion exchange membrane (40) and / or catalyst layer (42) is connected at a second contact surface (55) with and without a material-to-material connection to a flat side (56, 57) of the ion exchange membrane (40) and / or catalyst layer (42) facing the gas diffusion electrode (45) at a first contact surface (58) with and without a material-to-material connection with the material-to-material connection. [12] Method according to claim 11, characterized bythat on the first contact surface (58) the area of ​​a first connecting partial surface (64) on the first contact surface (58) with the material-locking connection substantially corresponds to the area of ​​a second connecting partial surface (63) on the second contact surface (55) with the material-locking connection and preferably on the first contact surface (58) at recesses (61) and / or cavities (62) a first non-connecting partial surface without the material-locking connection is formed. [13] Method according to claim 12, characterized by that the area of ​​the first connecting part surface (64) is smaller than the first contact surface (58). [14] Method for producing an electrochemical cell unit (25) for converting electrochemical energy into electrical energy as a fuel cell unit (1) and / or for converting electrical energy into electrochemical energy as an electrolysis cell unit (6) with stacked electrochemical cells (24), comprising the steps: - providing layered components (40, 41, 42, 43, 44, 45, 46, 47) of the electrochemical cells (24), namely bipolar plates and membrane electrode arrangements (46) with ion exchange membranes (40), in particular proton exchange membranes (41) and at least one gas diffusion electrode (45), - stacking the layered components (40, 41, 42, 43, 44, 45, 46, 47) to form electrochemical cells (24) and a stack (3) of the electrochemical cell unit (25), characterized bythat the membrane electrode assemblies (46) are provided by carrying out a method according to one or more of the preceding claims. [15] Electrochemical cell unit (25) for converting electrochemical energy into electrical energy as a fuel cell unit (1) and / or for converting electrical energy into electrochemical energy as an electrolysis cell unit (6), comprising - stacked electrochemical cells (24) and the electrochemical cells (24) each comprise stacked layered components (40, 41, 42, 43, 44, 45, 46, 47) and - the components (40, 41, 42, 43, 44, 45, 46, 47) of the electrochemical cells (24) are bipolar plates and membrane electrode arrangements with ion exchange membranes (40), in particular proton exchange membranes (41), and at least one gas diffusion electrode (45), characterized bythat the electrochemical cell unit (25) is manufactured by a method according to claim 14.

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