WO2022263363A1

WO2022263363A1 - Method for producing an electrochemical cell unit

Info

Publication number: WO2022263363A1
Application number: PCT/EP2022/066005
Authority: WO
Inventors: Andreas RINGK; Anton Ringel
Original assignee: Robert Bosch Gmbh
Priority date: 2021-06-14
Filing date: 2022-06-13
Publication date: 2022-12-22
Also published as: DE102021205989A1

Abstract

The invention relates to a method 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 electrolytic cell unit with stacked electrochemical cells, comprising the steps of: providing lamellar components (6, 10) of the electrochemical cells, namely preferably proton-exchange membranes, anodes, cathodes, preferably membrane electrode assemblies (6), preferably gas diffusion layers and flow field plates (10); applying seals (11) made of a primary seal material (73) to the lamellar components (6, 10) in order to seal channels (12) for conduction for at least one process fluid; stacking the lamellar components (6, 10) to form electrochemical cells and to form a stack of the electrochemical cell unit; wherein, after the seals (11) made of the primary seal material (73) have been applied to the lamellar components (6, 10), the seals (11) are physically and/or chemically treated such that, after the physical and/or chemical treatment, the primary seal material (73) of the seals (11) is at least partly converted into a secondary seal material (75), the secondary seal material (75) having a lesser diffusion coefficient than the primary seal material (73).

Description

description

title

Method of making an electrochemical cell unit

The present invention relates to a method for manufacturing an electrochemical cell unit according to the preamble of claim 1 and an electrochemical cell unit according to the preamble of claim 12.

State of the art

Fuel cell units as galvanic cells convert continuously supplied fuel and oxidizing agent into electrical energy and water by means of redox reactions at an anode and cathode. Fuel cells are used in a wide variety of stationary and mobile applications, for example in houses without a connection to a power grid or in motor vehicles, in rail transport, in aviation, in space travel and in shipping. In fuel cell units, a multiplicity of fuel cells are arranged in a stack as a stack.

In fuel cell units, a large number of fuel cells are arranged in a fuel cell stack. Inside each fuel cell there is a gas space for oxidizing agent, ie a flow space for conducting oxidizing agent, such as air from the environment with oxygen, through. The oxidant gas space 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 oxidizing agent, namely oxygen, reaches the cathode of the fuel cells through the gas diffusion layer. A gas space for fuel is present in an analogous manner. Electrolytic cell units made up of stacked electrolytic cells, analogous to fuel cell units, are used, for example, for the electrolytic production of hydrogen and oxygen from water. Furthermore, fuel cell units are known which can be operated as reversible fuel cell units and thus as electrolytic cell units. Fuel cell units and electrolytic cell units form electrochemical cell units. Fuel cells and electrolytic cells form electrochemical cells.

Fuel cells thus have channels for the process fluids fuel and oxidant. Electrolytic cells have channels for the process fluids, electrolytes. These channels of the electrochemical cells are sealed with gaskets. In this case, the seals are generally arranged between two layered components of the electrochemical cells. These seals made from a primary sealant, such as silicone, have a large diffusion coefficient. Due to the large diffusion coefficient, there is considerable diffusion of the process fluids through the seals into the environment. Disadvantageously, there is a considerable loss of process fluids into the environment during operation of the electrochemical cells or the electrochemical cell unit. This disadvantageously reduces the efficiency of the electrochemical cell unit and, in addition, results in environmental pollution. Additional measures are therefore often necessary to catch the leakage of the process fluid after it has diffused through the seals, for example in a collection container for electrolytes. This causes additional costs and increases the maintenance effort for the electrochemical cell unit.

US Pat. No. 5,176,966 shows a fuel cell unit with a silicone seal. The sealant as the silicone is arranged in a seal groove, for example.

Disclosure of Invention

Advantages of the Invention 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 electrolytic cell unit with stacked electrochemical cells, with the steps: providing layered components of the electrochemical cells, namely preferably proton exchange membranes, Anodes, cathodes, preferably membrane electrode assemblies, preferably gas diffusion layers and bipolar plates, applying seals made of a primary sealant to the layered components to seal channels for conducting at least one process fluid, stacking the layered components to form electrochemical cells and into a stack of the electrochemical cell unit, wherein after application of the gaskets of the primary gasket material to the layered components, the gasket en are treated physically and / or chemically, so that after the physical and / or chemical treatment of the primary sealant of the seals is at least partially converted into a secondary sealant and the secondary sealant has a smaller diffusion coefficient than the primary sealant. Preferably the diffusion coefficient of the secondary sealant is less than 1%, 5%, 10%, 20%, 30%, 50% or 70% of the diffusion coefficient of the primary sealant. The diffusion coefficient of the sealing material of the seal can thus be reduced during the production of the electrochemical cell unit, so that there is advantageously a significantly reduced diffusion through the seals of process fluids from the channels into the environment. Normally, this results in a technically essentially negligible diffusion of the process fluids through the seals from the channels into the environment, so that the electrochemical cell unit has an increased efficiency and, moreover, no measures are necessary to collect the process fluids that have diffused through the seals and/or to collect.

In a further embodiment, the physical and/or chemical treatment causes the primary sealing material to oxidize to form an oxide primary sealant and/or an oxide of an element or compound in the primary sealant and the oxide forms the secondary sealant. The chemical treatment thus causes chemical oxidation. The oxide as the secondary sealant advantageously has a much smaller diffusion coefficient than the primary sealant so that diffusion through the seals can be significantly reduced.

In a supplementary variant, the physical and/or chemical treatment of the seals is carried out after the layered components have been stacked to form electrochemical cells and to form the stack of the electrochemical cell unit. Expediently, the layered components are first completely stacked to form the electrochemical cell unit and then the physical and/or chemical treatment of the seals is carried out.

In a further variant, after the layered components have been stacked into electrochemical cells and into the stack of the electrochemical cell unit, the seals partially delimit an outside of the stack. The seals are thus formed on an outer edge area of the stack of the electrochemical cell unit.

In an additional configuration, the seals are arranged between the layered components in a direction perpendicular to imaginary planes spanned by the layered components and electrochemical cells.

In another embodiment, the gaskets are positioned between bipolar plates and membrane electrode assemblies to seal fuel and/or electrolyte channels and/or to seal oxidant and/or electrolyte channels.

In an additional variant, the outside of the stack is treated physically and/or chemically, so that the primary sealing material of the seals is converted into the secondary sealing material in an area facing the outside. In an additional embodiment, the primary sealant of the seals is converted into the secondary sealant on a secondary sub-area and no conversion of the primary sealant into the secondary sealant is carried out on a primary sub-area, so that hybrid seals with one primary sub-area and one secondary each Section are made.

The physical and/or chemical treatment is preferably carried out for a period of 5 s to 60 min, in particular 1 min to 30 min.

In an additional embodiment, the primary sealant includes silicon and the secondary sealant includes silicon oxide.

In an additional embodiment, the physical and/or chemical treatment is carried out with a treatment fluid, in particular ozone and/or plasma, so that during the physical and/or chemical treatment the primary sealant is treated with the treatment fluid, in particular ozone and/or the plasma. is contacted.

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 electrochemical cells arranged stacked and the electrochemical cells each comprising layered components arranged stacked, the components of the electrochemical cells preferably proton exchange membranes, anodes , Cathodes, preferably membrane electrode arrangements, preferably gas diffusion layers and bipolar plates, channels for the passage of process fluids, seals for sealing the channels for the process fluids, wherein the electrochemical cell unit is produced using a method described in this property right application and/or the seals are designed as hybrid seals each with a primary sealant on a primary portion and each with a secondary sealant at a secondary sub-area and the secondary Sealant has a lower diffusion coefficient than the primary sealant.

In a further embodiment, the primary portions of the seals delimit the channels for the process fluids and the secondary portions of the seals partially form an outside of the stack.

In an additional variant, seals are arranged between bipolar plates and membrane electrode arrangements, in particular subgaskets of membrane electrode arrangements.

The secondary sealing material expediently has a greater hardness, in particular greater Brinell hardness, than the primary sealing material. The hardness, in particular Brinell hardness, of the secondary sealing material is preferably 1.2 times, 1.5 times, 2 times, 3 times or 5 times greater than the hardness, in particular Brinell hardness, of the primary sealing material.

In a further embodiment, the seals are used to seal channels for coolants, in particular the seals are arranged between two sheets of a bipolar plate.

In a further embodiment, there are no areas of the seals on the seals with the secondary sealing material through which the process fluid can diffuse from the channels through the seal without penetrating the secondary sealing material.

The method is preferably carried out so that on the seals with the secondary sealant there are no areas of the seals through which the process fluid can diffuse from the channels through the seal without penetrating the secondary sealant.

In a supplementary embodiment, the seals are designed and/or are produced in such a way that the secondary sealing material is completely formed in a section perpendicular to a diffusion direction of the process fluid through the seal. In a supplementary embodiment, the seals are formed circumferentially, in particular completely circumferentially, on the outside of the stack of the electrochemical cell unit.

In an additional configuration, the secondary partial area has a thickness of between 0.1 nm and 2 mm, preferably between 10 nm and 1 mm, in particular between 10 μm and 0.1 mm.

In a supplementary embodiment, the physical and/or chemical treatment with the treatment fluid is carried out by the treatment fluid being applied to the fuel cell unit with at least one nozzle and/or the electrochemical cell unit being arranged in a treatment chamber with the treatment fluid.

In an additional variant, the physical and/or chemical treatment with the treatment fluid is carried out by passing the treatment fluid through the channels for the process fluid, in particular the channels for the process fluid fuel and/or electrolyte and/or the channels for the process fluid oxidant and/or Electrolyte is passed. In passing the treatment fluid through the channels for the process fluid, the formation of the secondary sealing material is thus carried out on a side of the seal which faces the channel.

In an additional embodiment, before and/or during the physical and/or chemical treatment of the seals, the stack of the electrochemical cell unit is preloaded with a compressive force. Preferably, the compressive force with which the stack is prestressed during the physical and/or chemical treatment is essentially, in particular with a deviation of less than 10%, 20% or 30%, the final compressive force of the stack of the electrochemical cell unit for the operation of the electrochemical cell unit. The final compressive force of the stack preload is necessary to ensure sufficient tightness and low electrical resistance between the electrochemical cells. After the production of the secondary sealing material, there is preferably essentially no change, in particular with a deviation of less than 10%, 20% or 30%, in the prestressing of the stack electrochemical cell unit performed with the compressive force. A larger change in the preload of the stack with the compressive force after the production of the secondary sealant could lead to cracks in the seal at the secondary sealant, so that the seal as a whole would not have a substantially lower sealing coefficient because the process fluids between the cracks or at can penetrate the cracks.

In an additional embodiment, the treatment fluid is a liquid and/or a gas.

The treatment fluid is preferably an oxidizing agent, in particular hydrogen peroxide and/or fluorine and/or bromate and/or oxygen difluoride.

In a supplementary embodiment, the seal made from the primary sealant is applied to the layered components by dispensing and/or screen printing and/or stencil printing and/or injection molding and/or extrusion.

The membrane electrode arrangements are preferably formed by one proton exchange membrane each, at least one subgasket each, one anode each and one cathode each, in particular as a CCM (catalyst coated membrane) with catalyst material in the anodes and cathodes.

In a further variant, an electrochemical cell unit described in this patent application is produced using the method described in this patent application.

In a supplementary embodiment, the method is carried out with a robot, in particular at least one nozzle and/or the stack is moved with the robot during production.

The invention also includes a computer program with program code means, which are stored on a computer-readable data carrier, in order to carry out a method described in this property right application, if the Computer program is carried out on a computer or a corresponding computing unit.

The invention also includes a computer program product with program code means that are stored on a computer-readable data carrier in order to carry out a method described in this property right application when the computer program is carried out on a computer or a corresponding processing unit.

In an additional embodiment, the electrochemical cell unit is a fuel cell unit as a fuel cell stack for converting electrochemical energy into electrical energy and/or an electrolytic cell unit for converting electrical energy into electrochemical energy.

The bipolar plates are expediently designed as separator plates and an electrical insulation layer, in particular a proton exchange membrane, is arranged between each anode and each cathode, and preferably the electrolysis cells each include a third channel for the separate passage of a cooling fluid as the third process fluid.

In an additional variant, the electrolytic cell unit is additionally designed as a fuel cell unit, in particular a fuel cell unit described in this patent application, so that the electrolytic cell unit forms a reversible fuel cell unit.

In a further variant, the first substance is oxygen and the second substance is hydrogen.

In a further variant, the electrolytic cells of the electrolytic cell unit are fuel cells.

In a further variant, the electrochemical cell unit comprises a housing and/or a connection plate. The stack is enclosed by the housing and/or the connection board. Fuel cell system according to the invention, in particular for a motor vehicle, comprising a fuel cell unit as a fuel cell stack with fuel cells, a compressed gas store for storing gaseous fuel, a gas delivery device for delivering a gaseous oxidizing agent to the cathodes of the fuel cells, the fuel cell unit being a fuel cell unit described in this patent application and/or Electrolytic cell unit is formed.

Electrolysis system and/or fuel cell system according to the invention, comprising an electrolysis cell unit as an electrolysis cell stack with electrolysis cells, preferably a pressurized gas store for storing gaseous fuel, preferably a gas delivery device for delivering a gaseous oxidizing agent to the cathodes of the fuel cells, a storage container for liquid electrolyte, a pump for delivering the liquid Electrolytes, wherein the electrolytic cell unit is designed as an electrolytic cell unit and/or fuel cell unit described in this patent application.

In a further embodiment, the fuel cell unit described in this patent application also forms an electrolytic cell unit and preferably vice versa.

In a further variant, the electrochemical cell unit, in particular the fuel cell unit and/or the electrolytic cell unit, comprises at least one connecting device, in particular several connecting devices, and tensioning elements.

Components for electrochemical cells, in particular fuel cells and/or electrolytic cells, preferably insulation layers, in particular proton exchange membranes, preferably membrane electrode arrangements, anodes, cathodes, preferably gas diffusion layers and bipolar plates, in particular separator plates, are expedient.

In a further embodiment, the electrochemical cells, in particular fuel cells and/or electrolytic cells, each preferably comprise an insulating layer, in particular a proton exchange membrane, an anode, a cathode, preferably membrane electrode arrangements, preferably at least one gas diffusion layer and at least one bipolar plate, in particular at least one separator plate.

In a further embodiment, the connecting device is designed as a bolt and/or is rod-shaped and/or is designed as a tension belt.

The clamping elements are expediently designed as clamping plates.

In a further variant, the gas conveying device is designed as a blower and/or a compressor and/or a pressure vessel with oxidizing agent.

In particular, the electrochemical cell unit, in particular a fuel cell unit and/or an electrolytic cell unit, comprises at least 3, 4, 5 or 6 connecting devices.

In a further embodiment, the tensioning elements are plate-shaped and/or disc-shaped and/or flat and/or designed as a lattice.

Preferably the fuel is hydrogen, hydrogen rich gas, reformate gas or natural gas.

The fuel cells and/or electrolytic cells are expediently designed to be essentially flat and/or disc-shaped.

In a supplementary variant, the oxidizing agent is air with oxygen or pure oxygen.

Preferably, the fuel cell unit is a PEM fuel cell unit with PEM fuel cells, or a SOFC fuel cell unit with SOFC fuel cells, or an alkaline fuel cell (AFC).

Brief description of the drawings The following are exemplary embodiments of the invention

Described in more detail with reference to the accompanying drawings. It shows:

1 shows a greatly simplified exploded view of an electrochemical cell system as a fuel cell system and electrolytic cell system with components of an electrochemical cell as a fuel cell and electrolytic cell,

2 is a perspective view of part of a fuel cell and electrolytic cell,

3 shows a longitudinal section through electrochemical cells as a fuel cell and electrolytic cell,

4 shows a perspective view of an electrochemical cell unit as a fuel cell unit and electrolysis cell unit as a fuel cell stack and electrolysis cell stack,

5 shows a side view of the electrochemical cell unit as a fuel cell unit and electrolytic cell unit as a fuel cell stack and electrolytic cell stack,

6 shows a perspective view of a bipolar plate,

7 is a perspective view of a membrane electrode assembly,

8 is a side view of a robot,

9 shows a longitudinal section of a seal between a bipolar plate and a subgasket of the membrane electrode arrangement from the physical and/or chemical treatment of the seal,

10 shows a longitudinal section of the seal between the bipolar plate and the subgasket of the membrane electrode assembly according to FIG. 9 after the physical and/or chemical treatment of the seal, so that a primary and secondary partial area of the seal is formed, Fig. 11 is a perspective view of the stack of electrochemical

cell unit during the application of a treatment fluid to an outside of the stack with a nozzle,

Fig. 12 is a perspective view of the stack of electrochemical

cell unit during the application of a treatment fluid to an outside of the stack with multiple nozzles,

13 shows a perspective view of the stack of the electrochemical cell unit during the arrangement of the stack in a treatment chamber.

14 shows a diagram of the thickness d of a secondary partial region plotted on the ordinate as a function of the treatment time t and plotted on the abscissa

Figure 15 is a flow chart of the steps in manufacturing the electrochemical cell unit.

1 to 3 show the basic structure of a fuel cell 2 as a PEM fuel cell 3 (polymer electrolyte fuel cell 3). The principle of fuel cells 2 is that electrical energy or electrical current is generated by means of an electrochemical reaction. Hydrogen H2 is passed as a gaseous fuel to an anode 7 and the anode 7 forms the negative pole. A gaseous oxidizing agent, namely air with oxygen, is fed to a cathode 8, i. H. the oxygen in the air provides the necessary gaseous oxidant. A reduction (acceptance of electrons) takes place at the cathode 8 . The oxidation as electron release is carried out at the anode 7 .

The redox equations of the electrochemical processes are:

Cathode:

0 ₂ + 4 H ⁺ + 4 e- ~ » 2 H ₂ 0 Anode:

2 H ₂ -> 4 H ⁺ + 4 e-

Summation reaction equation of cathode and anode: 2 H ₂ + 0 ₂ -> 2 H ₂ 0

The difference between the normal potentials of the pairs of electrodes under standard conditions as a reversible fuel cell voltage or no-load voltage of the unloaded fuel cell 2 is 1.23 V. This theoretical voltage of 1.23 V is not reached in practice. In the idle state and with small currents, voltages of over 1.0 V can be reached and when operating with larger currents, voltages between 0.5 V and 1.0 V are reached. The series connection of several fuel cells 2, in particular a fuel cell unit 1 as a fuel cell stack 1 of several stacked fuel cells 2, has a higher voltage, which corresponds to the number of fuel cells 2 multiplied by the individual voltage of each fuel cell 2.

The fuel cell 2 also includes a proton exchange membrane 5 (proton exchange membrane, PEM), which is arranged between the anode 7 and the cathode 8 . The anode 7 and cathode 8 are in the form of layers or discs. The PEM 5 acts as an electrolyte, catalyst support and separator for the reaction gases. The PEM 5 also acts as an electrical insulator and prevents an electrical short circuit between the anode 7 and cathode 8. In general, 12 μm to 150 μm thick, proton-conducting foils made from perfluorinated and sulfonated polymers are used. The PEM 5 conducts the H ⁺ protons and essentially blocks ions other than H ⁺ protons, so that the charge transport can take place due to the permeability of the PEM 5 for the H ⁺ protons. The PEM 5 is essentially impermeable to the reaction gases oxygen O ₂ and hydrogen H ₂ , ie blocks the flow of oxygen O ₂ and hydrogen H ₂ between a gas space 31 at the anode 7 with fuel hydrogen H ₂ and the gas space 32 at the cathode 8 with air or oxygen 0 ₂ as the oxidizing agent. The proton conductivity of the PEM 5 increases with increasing temperature and increasing water content. The electrodes 7 , 8 as the anode 7 and cathode 8 lie on the two sides of the PEM 5 , each facing towards the gas chambers 31 , 32 . A unit made up of the PEM 5 and the electrodes 7, 8 is referred to as a membrane electrode assembly 6 (membrane electrode assembly, MEA). The electrodes 7, 8 are pressed with the PEM 5. The electrodes 7, 8 are platinum-containing carbon particles bonded to PTFE (polytetrafluoroethylene), FEP (fluorinated ethylene-propylene copolymer), PFA (perfluoroalkoxy), PVDF (polyvinylidene fluoride) and/or PVA (polyvinyl alcohol) and embedded in microporous carbon fiber, Glass fiber or plastic mats are hot-pressed. A catalyst layer 30 (not shown) is normally applied to each of the electrodes 7, 8 on the side facing the gas chambers 31, 32. The catalyst layer 30 on the gas space 31 with fuel on the anode 7 comprises nanodisperse platinum-ruthenium on graphitized soot particles which are bound to a binder. The catalyst layer 30 on the gas space 32 with oxidizing agent on the cathode 8 analogously comprises nanodispersed platinum. Examples of binders used are Nafion®, a PTFE emulsion or polyvinyl alcohol.

Deviating from this, the electrodes 7, 8 are constructed from an ionomer, for example Nafion®, platinum-containing carbon particles and additives. These electrodes 7, 8 with the ionomer are electrically conductive due to the carbon particles and also conduct the protons H ⁺ and also function as a catalyst layer 30 due to the platinum-containing carbon particles. Membrane electrode assemblies 6 with these electrodes 7, 8 comprising the ionomer form membrane electrode assemblies 6 as a CCM (catalyst coated membrane).

On the anode 7 and the cathode 8 there is a gas diffusion layer 9 (gas diffusion layer, GDL). The gas diffusion layer 9 on the anode 7 distributes the fuel from fuel channels 12 evenly onto the catalyst layer 30 on the anode 7. The gas diffusion layer 9 on the cathode 8 distributes the oxidant from oxidant channels 13 evenly onto the catalyst layer 30 on the cathode 8. The GDL 9 also draws off reaction water in the reverse direction to the direction of flow of the reaction gases, ie in one direction each from the catalyst layer 30 to the channels 12, 13. Furthermore, the GDL 9 keeps the PEM 5 wet and conducts the current. The GDL 9 is constructed, for example, from hydrophobic carbon paper as the carrier and substrate layer and a bonded carbon powder layer as the microporous layer.

A bipolar plate 10 rests on the GDL 9 . The electrically conductive bipolar plate 10 serves as a current collector, for water drainage and for conducting the reaction gases as process fluids through the channel structures 29 and/or flow fields 29 and for dissipating the waste heat, which occurs in particular during the exothermic electrochemical reaction at the cathode 8. In order to dissipate the waste heat, channels 14 are incorporated into the bipolar plate 10 as a channel structure 29 for conducting a liquid or gaseous coolant as the process fluid. The channel structure 29 in the gas space 31 for fuel is formed by channels 12 . The channel structure 29 in the gas space 32 for the oxidizing agent is formed by channels 13 . Metal, conductive plastics and composite materials and/or graphite, for example, are used as the material for the bipolar plates 10 .

In a fuel cell unit 1 and/or a fuel cell stack 1 and/or a fuel cell stack 1, a plurality of fuel cells 2 are arranged stacked in alignment (FIGS. 4 and 5). 1 shows an exploded view of two fuel cells 2 arranged in a stacked alignment. Seals 11 seal the gas chambers 31, 32 or channels 12, 13 in a fluid-tight manner. Hydrogen H2 is stored as fuel at a pressure of, for example, 350 bar to 700 bar in a compressed gas store 21 (FIG. 1). From the compressed gas reservoir 21, the fuel is passed through a high-pressure line 18 to a pressure reducer 20 to reduce the pressure of the fuel in a medium-pressure line 17 from approximately 10 bar to 20 bar. The fuel is routed to an injector 19 from the medium-pressure line 17 . At the injector 19, the pressure of the fuel is reduced to an injection pressure of between 1 bar and 3 bar. From the injector 19 the fuel is supplied to a fuel supply line 16 (FIG. 1) and from the supply line 16 to the fuel channels 12 which form the channel structure 29 for fuel. As a result, the fuel flows through the gas space 31 for the fuel. The gas space 31 for the fuel is formed by the channels 12 and the GDL 9 on the anode 7 . After flowing through the channels 12 is not consumed in the redox reaction at the anode 7 fuel and if necessary, water from a controlled humidification of the anode 7 is discharged from the fuel cells 2 through a discharge line 15 .

A gas conveying device 22, embodied for example as a fan 23 or a compressor 24, conveys air from the environment as oxidizing agent into a supply line 25 for oxidizing agent. The air is supplied from the supply line 25 to the channels 13 for oxidizing agent, which form a channel structure 29 on the bipolar plates 10 for oxidizing agent, so that the oxidizing agent flows through the gas space 32 for the oxidizing agent. The gas space 32 for the oxidizing agent is formed by the channels 13 and the GDL 9 on the cathode 8 . After the oxidizing agent 32 has flowed through the channels 13 or the gas space 32, the oxidizing agent not consumed at the cathode 8 and the water of reaction formed at the cathode 8 due to the electrochemical redox reaction are discharged from the fuel cells 2 through a discharge line 26. A supply line 27 is used to supply coolant into the channels 14 for coolant and a discharge line 28 is used to discharge the coolant conducted through the channels 14 . The supply and discharge lines 15, 16, 25, 26, 27, 28 are shown in FIG. 1 as separate lines for reasons of simplification. At the end area near the channels 12, 13, 14, aligned fluid openings 41 are formed in the stack as a stack of the fuel cell unit 1 on sealing plates 39 as an extension on the end area 40 of the bipolar plates 10 (FIG. 6) and membrane electrode arrangements 6 (FIG. 7) lying one on top of the other . The fuel cells 2 and the components of the fuel cells 2 are disk-shaped and span imaginary planes 59 aligned essentially parallel to one another. The aligned fluid openings 41 and seals (not shown) in a direction perpendicular to the notional planes 59 between the fluid openings 41 thus form an oxidant supply duct 42, an oxidant discharge duct 43, a fuel supply duct 44, a fuel discharge duct 45, a Supply channel 46 for coolant and a discharge channel 47 for coolant. The supply and discharge lines 15, 16, 25, 26, 27, 28 outside the stack of the fuel cell unit 1 are designed as process fluid lines. The supply and discharge lines 15, 16, 25, 26, 27, 28 outside the stack of the fuel cell unit 1 open into the supply and discharge channels 42, 43, 44, 45, 46, 47 within the stack of the fuel cell unit 1. The Fuel cell stack 1 together with the compressed gas storage device 21 and the gas delivery device 22 forms a fuel cell system 4.

The fuel cells 2 are arranged as clamping plates 34 between two clamping elements 33 in the fuel cell unit 1 . A first clamping plate 35 lies on the first fuel cell 2 and a second clamping plate 36 lies on the last fuel cell 2 . The fuel cell unit 1 comprises approximately 200 to 400 fuel cells 2, not all of which are shown in FIGS. 4 and 5 for reasons of drawing. The clamping members 33 apply a compressive force to the fuel cells 2, i. H. the first clamping plate 35 rests on the first fuel cell 2 with a pressing force, and the second clamping plate 36 rests on the last fuel cell 2 with a pressing force. The fuel cell stack 2 is thus braced in order to ensure tightness for the fuel, the oxidizing agent and the coolant, in particular due to the elastic seals 11, and also to keep the electrical contact resistance within the fuel cell stack 1 as small as possible. To brace the fuel cells 2 with the tensioning elements 33, four connecting devices 37 are designed as bolts 38 on the fuel cell unit 1, which are subjected to tensile stress. The four bolts 38 are connected to the chipboards 34 .

In Fig. 6, the bipolar plate 10 of the fuel cell 2 is shown. The bipolar plate 10 includes the channels 12, 13 and 14 as three separate channel structures 29. The channels 12, 13 and 14 are not shown separately in FIG Bipolar plates 10 (FIG. 6) and membrane electrode arrangements 6 (FIG. 7) are arranged stacked in alignment within the fuel cell unit 1, so that feed and discharge channels 42, 43, 44, 45, 46, 47 are formed. Seals (not shown) are arranged between the sealing plates 39 for fluid-tight sealing of the supply and discharge channels 42, 43, 44, 45, 46, 47 formed by the fluid openings 41.

Since the bipolar plate 10 also separates the gas chamber 31 for fuel from the gas chamber 32 for oxidizing agent in a fluid-tight manner and also seals the channel 14 for coolant in a fluid-tight manner, the term separator plate 51 can also be used for the bipolar plate 10 for fluid-tight separation or separation of process fluids can be selected. The term separator plate 51 is thus also subsumed under the term bipolar plate 10 and vice versa. The channels 12 for fuel, the channels 13 for oxidant and the channels 14 for coolant of the fuel cell 2 are also formed on the electrochemical cell 52, but with a different function.

The fuel cell unit 1 can also be used and operated as an electrolytic cell unit 49, ie forms a reversible fuel cell unit 1. A number of features that allow the fuel cell unit 1 to be operated as an electrolytic cell unit 49 are described below. A liquid electrolyte, namely highly diluted sulfuric acid with a concentration of approximately c(H2SO4) = 1 mol/l, is used for the electrolysis. A sufficient concentration of oxonium ions H ₃ 0 ⁺ in the liquid electrolyte is necessary for the electrolysis.

The following redox reactions take place during electrolysis:

Cathode:

4 H ₃ 0 ⁺ + 4 e- ~» 2 H ₂ + 4 H ₂ 0

Anode:

6 H ₂ 0 --» 0 ₂ + 4 H ₃ 0 ⁺ + 4 e-

Summation reaction equation of cathode and anode:

_2H20 --» _2H2 + 0 ₂

The polarity of the electrodes 7, 8 with electrolysis when operating as an electrolytic cell unit 49 is reversed (not shown) as when operating as a fuel cell unit 1, so that in the channels 12 for fuel, through which the liquid electrolyte is conducted, at the cathodes Hydrogen H ₂ is formed as a second substance and the hydrogen H ₂ is taken up by the liquid electrolyte and transported in dissolved form. Analogously, the liquid electrolyte is conducted through the channels 13 for the oxidizing agent and oxygen O ₂ is formed as the first substance at the anodes in or on the channels 13 for the oxidizing agent. During operation, the fuel cells 2 of the fuel cell unit 1 act as a Electrolytic cell unit 49 as electrolytic cells 50. The fuel cells 2 and electrolytic cells 50 thus form electrochemical cells 52. The oxygen O2 formed is absorbed by the liquid electrolyte and transported in dissolved form. The liquid electrolyte is stored in a storage tank 54 . In order to simplify the drawing, two storage containers 54 of the fuel cell system 4 are shown in FIG. 1, which also functions as an electrolytic cell system 48 . The 3-way valve 55 on the fuel supply line 16 is switched over during operation as an electrolytic cell unit 49, so that the liquid electrolyte is introduced into the fuel supply line 16 from the storage tank 54 with a pump 56 and not fuel from the compressed gas storage tank 21 . A 3-way valve 55 on the supply line 25 for oxidant is switched over during operation as an electrolytic cell unit 49, so that the liquid electrolyte with the pump 56 from the storage tank 54 is fed into the supply line 25 for oxidant rather than oxidant as air from the gas delivery device 22 is initiated. The fuel cell unit 1, which also functions as an electrolytic cell unit 49, has optional modifications to the electrodes 7, 8 and the gas diffusion layer 9 compared to a fuel cell unit 1 that can only be operated as a fuel cell unit 1: for example, the gas diffusion layer 9 is not absorbent, so that the liquid electrolyte easily drains completely or the gas diffusion layer 9 is not formed or the gas diffusion layer 9 is a structure on the bipolar plate 10. The electrolytic cell unit 49 with the storage tank 54, the pump 56 and the separators 57, 58 and preferably the 3-way valve 55 forms a electrochemical cell system 60.

A separator 57 for hydrogen is arranged on the discharge line 15 for fuel. The separator 57 separates the hydrogen from the electrolyte with hydrogen and the separated hydrogen is introduced into the compressed gas reservoir 21 with a compressor (not shown). The electrolyte discharged from the hydrogen separator 57 is then returned to the electrolyte storage tank 54 through a pipe. A separator 58 for oxygen is arranged on the discharge line 26 for fuel. The separator 58 separates the oxygen from the electrolyte with oxygen and the separated oxygen is with a compressor not shown in a compressed gas storage for oxygen, not shown initiated. The oxygen in the compressed gas reservoir for oxygen, not shown, can optionally be used to operate the fuel cell unit 1 by using a line, not shown, to slide the oxygen into the supply line 25 for oxidizing agent when operating as a fuel cell unit 1. The electrolyte derived from the separator 58 for oxygen is then fed back to the storage tank 54 for the electrolyte with a line. The channels 12, 13 and the discharge and supply lines 15, 16, 25, 26 are designed in such a way that after use as an electrolytic cell unit 49 and the pump 56 has been switched off, the liquid electrolyte runs back completely into the storage container 54 due to gravity. Optionally, after use as an electrolytic cell unit 49 and before use as a fuel cell unit 1, an inert gas is passed through the channels 12, 13 and the discharge and supply lines 15, 16, 25, 26 for the complete removal of the liquid electrolyte before the passage of gaseous fuel and oxidizing agent. The fuel cells 2 and the electrolytic cells 2 thus form electrochemical cells 52. The fuel cell unit 1 and the electrolytic cell unit 49 thus form an electrochemical cell unit 53. The channels 12 for fuel and the channels for oxidizing agent thus form channels 12, 13 for the passage of the liquid electrolyte during operation as an electrolytic cell unit 49 and this applies analogously to the supply and discharge lines 15, 16, 25, 26. An electrolytic cell unit 49 does not normally require any channels 14 for the passage of coolant for process-related reasons. In an electrochemical cell unit 49, the channels 12 for fuel also form channels 12 for passing fuel and/or electrolyte and the channels 13 for oxidant also form channels 13 for passing fuel and/or electrolyte.

In a further exemplary embodiment, which is not shown, the fuel cell unit 1 is designed as an alkaline fuel cell unit 1 . Potassium hydroxide solution is used as a mobile electrolyte. The fuel cells 2 are stacked. A monopolar cell structure or a bipolar cell structure can be formed. The potassium hydroxide solution circulates between an anode and cathode and transports water of reaction, heat and impurities (carbonates, dissolved gases). The fuel cell unit 1 can also be operated as a reversible fuel cell unit 1, ie as an electrolytic cell unit 49.

A robot 61 for manufacturing the electrochemical cell unit 53 is shown in FIG. The robot 61 includes robot arms 62 and robot joints 63. At an end portion of a last robot arm 62, a process unit 65 as a mechanical gripper 66 and a camera 64 are attached. The gripper 66 is attached to the last robot arm 62 with a motorized movable ball joint (not shown). A computer 67 with a processor and a data memory controls the robot 61. The camera 64 optically captures the stack 70 and image processing software in the computer 67 captures the actual position of the stack 70 relative to the robot 48. The movement of robot 61 is thus controlled as a function of the intended position data stored in the data memory and/or the data on the actual position of stack 70 relative to robot 48 determined by the image processing software.

For the production of an electrochemical cell unit 53, the layered components 5, 6, 7, 8, 9, 10, 30, 51 of electrochemical cells 52 are first made available 79. The layered components 5, 6, 7,

8, 9, 10, 30, 51 are, for example, in a fuel cell unit 1, a proton exchange membrane 5, an anode 7, a cathode 8, a gas diffusion layer 9 and a bipolar plate 10. The anode 7, the cathode 8 and the proton exchange membrane 5 form a membrane electrode arrangement 6 with subgasket 69 as a sealing layer 68 (FIG. 7) in which the anode 7 and the cathode 8 are additionally provided with a catalyst material as a CCM (catalyst coated membrane), so that the anode 7 and the cathode 8 also form a catalyst layer 30. The layered components 5, 6, 7, 8, 9, 10, 30, 51 of the fuel cells 2 are stacked as a stack 70 to form a stack 70, shown for example in FIGS.

After providing 79 the layered components 5, 6, 7, 8,

9, 10, 30, 51, a stacking 81 of the layered components 5, 6, 7, 8, 9,

10, 30, 51 and applying 80 seals 11 to the bipolar plates 10 and/or the subgaskets 69 of the membrane electrode assemblies 6. The application 80 is carried out, for example, by means of extrusion or dispensing. After stacking 81 the gaskets 11 are placed between the bipolar plates 10 and membrane electrode assemblies 6 . The seals 11 are formed completely circumferentially on an outer side 71 of the stack 70 and are used to seal the channels 12 for fuel between the bipolar plates 10 and the subgasket 69 of FIG

Membrane electrode assemblies 6. The seals 11 also function analogously to seal off the channels 13 (not shown). After being applied to the layered components 5, 6, 7, 8, 9, 10, 30, 51, the seals 11 are formed entirely from a primary sealing material, essentially silicone. In general, the layered components 5, 6, 7, 8, 9, 10, 30, 51 are stacked 81 one after the other and the seals 11 are applied 80 to the layered components 5, 6, 7, 8, 9, 10, 30 , 51 executed. After the stacking 81 of all layered components 5, 6, 7, 8, 9, 10, 30, 51 of the electrochemical cell unit 53 as the fuel cell unit 1, the stack 70 with the two clamping elements 33 is prestressed with the final compressive force for the operation of the fuel cell unit 1 , i.e. H. a biasing 82 of the stack 70 is performed.

The physical and/or chemical treatment 83 of the seals 11 is then carried out with a treatment fluid, for example ozone (O3) or plasma, so that the production 84 of a secondary sealant 75 from the primary sealant 73 is carried out as a result of physical and/or chemical processes ( 9 and 10). During the treatment 83, oxidation of the silicon to silicon oxide (S1O2) as the secondary sealant 75 is carried out. In FIG. 9 the section through the seal 71 before the treatment 83 is shown and in FIG. 10 the section through the seals 11 after the treatment 83 is shown. After the treatment 83, a hybrid seal 11 is present, i.e. primary partial areas 74 with the unmodified and applied primary sealant 73 and the secondary partial area 76 with the secondary sealant 75. The treatment 83 is carried out with a treatment fluid which is applied to an outer side 71 of the Stacks 70 is applied, thereby partially oxidizing the primary sealing material 73 on the secondary portion 76 facing the outside 71 . The primary sealing material 73 thus becomes a by means of oxidation Making 84 of the secondary sealant 75 performed. The secondary sealant 75 made of silicon oxide has a much lower diffusion coefficient than the primary sealant 73. Since the secondary sealant 75 is and/or is formed on the entire outside 71 of the seal 21, the process fluid needs fuel to exit the channel 12 in pass through the environment through the secondary partial area 76, so that advantageously due to the small diffusion coefficient of the secondary sealing material 75 essentially no diffusion of the fuel into the environment occurs.

In Fig. 11 a first embodiment for the treatment 83 of the seals 11 is shown. The treatment fluid, namely ozone or a plasma, is applied uniformly to the entire outside 71 of the stack 70 using a nozzle 77 . The nozzle 77 is thereby moved by the gripper 66 of the robot 66 . The nozzle 77 is thus moved around the entire stack 70 around.

A second exemplary embodiment for the treatment 83 of the seals 11 is shown in FIG. In the following, essentially only the differences from the first exemplary embodiment according to FIG. 11 are described. Not one nozzle 77 is used for the treatment 83, but several nozzles 77, which are arranged on a connecting means (not shown), for example a connecting rod. The nozzles 77 fastened to the connecting means are moved around the entire stack 70 of the electrochemical cell unit 53 by the gripper 66 of the robot 61, analogously to the first exemplary embodiment.

In Fig. 13 a third embodiment for the treatment 83 of the seals 11 is shown. The stack 70 is arranged in a treatment chamber 78 during the treatment 83. The treatment chamber 78 can be opened at a cover wall not shown separately and then the stack 70 is inserted into the opened treatment chamber 71 with the gripper 66 of the robot 61. The treatment chamber 78 is then closed with the top wall and the treatment fluid is then introduced into the treatment chamber 78 . During the placement of the stack 70 in the processing chamber 78, the openings are of the channels 12, 13, 14 in the vicinity of the stack 70 is closed, so that the treatment fluid does not penetrate into the channels 12, 13 and 14.

In Fig. 14, the treatment time t of the treatment 83 with the treatment fluid is plotted in minutes (min) on the abscissa and the thickness letter d of the secondary partial region 76 after the treatment 83 is plotted in nanometers (nm) on the ordinate. The thickness d is thus a function of the treatment time t and the longer the treatment time t, the greater the thickness d. The treatment time t can be controlled, for example, via the dwell time of the stack 70 in the treatment chamber 78 or via the speed at which the nozzles 77 move around the stack 70 . Depending on the treatment fluid used and/or the primary sealing material 73, it is also possible to produce significantly greater thicknesses d than, for example, 2 or 3 nm, for example thicknesses of 1 mm or 100 μm.

In a further exemplary embodiment, not shown, the treatment 83 with the treatment fluid takes place in that the treatment fluid is passed through the channels 12, 13 for fuel and/or oxidizing agent, so that the secondary partial area 76 made of the secondary sealing material 75 is attached to one of the channels 12, 13 side facing from the primary sealant 73 is formed. On a side of the seals 11 facing away from the channels 12,13, i. H. On the side of the seals 11 , which partially also form the outside 71 of the stack 70 , no secondary sealing material 75 according to this exemplary embodiment, which is not shown, is formed during the treatment 83 .

Considered overall, there are significant advantages associated with the method according to the invention for producing the electrochemical cell unit 53 and the electrochemical cell unit 53 according to the invention. During the treatment 83 of the seals 11 with the ozone (O3) or the plasma, the secondary sealant 75 is formed from the primary sealant 73 with the significantly lower diffusion coefficient and thus also with the greater sealing effect, because the secondary sealant 75 has an essentially negligible diffusion occurs. The formation of the secondary sealing material 75 is thereby on the entire outside 71 of Seal 11 is formed so that there are no areas of seal 11 through which the process fluid can diffuse through seal 11 without penetrating the secondary sealant 75. The secondary sealant 75 can be produced inexpensively with little technical effort, so that the electrochemical cell unit 53 at im

Essentially the same manufacturing costs has significant advantages. The efficiency of the electrochemical cell unit 53 is significantly greater because there are essentially no losses of process fluids to the environment. In addition, no complex and expensive devices are required for collecting process fluids that have diffused through the seals 11 .

Claims

Expectations

1. A method for producing an electrochemical cell unit (1, 49, 53) for converting electrochemical energy into electrical energy as a fuel cell unit (1) and/or for converting electrical energy into electrochemical energy as an electrolytic cell unit (49) with stacked electrochemical cells (2, 50 , 52) with the steps: providing layered components (5, 6, 7, 8, 9, 10, 30, 51) of the electrochemical cells (2, 50, 52), namely preferably proton exchange membranes (5), anodes ( 7), cathodes (8), preferably membrane electrode assemblies (6), preferably gas diffusion layers (9) and bipolar plates (10), application of seals (11) made of a primary sealing material (73) to the layered components (5, 6, 7, 8 , 9, 10, 30, 51) for sealing channels (12, 13, 14) for the passage of at least one process fluid,

Stacking the layered components (5, 6, 7, 8, 9, 10, 30, 51) into electrochemical cells (2, 50, 52) and into a stack (70) of the electrochemical cell unit (1, 49, 53), thereby characterized in that after the application of the seals (11) from the primary sealant (73) to the layered components (5, 6, 7, 8, 9,

10, 30, 51) the seals (11) are treated physically and/or chemically so that after the physical and/or chemical treatment the primary sealant (73) of the seals (11) is at least partially converted into a secondary sealant (75). and the secondary sealant (75) has a smaller diffusion coefficient than the primary sealant (73).

2. The method according to claim 1, characterized in that the physical and/or chemical treatment causes oxidation of the primary sealant (73) to an oxide of the primary sealant (73) and/or to an oxide of an element or compound in the primary sealant (73) and the oxide forms the secondary sealant (75).

3. The method according to claim 1 or 2, characterized in that the physical and/or chemical treatment of the seals (11) after the stacking of the layered components (5, 6, 7, 8, 9, 10,

30, 51) to electrochemical cells (2, 50, 52) and to the stack (70) of the electrochemical cell unit (1, 49, 53).

4. The method according to one or more of the preceding claims, characterized in that the seals (11) after the stacking of the layered components (5, 6, 7, 8, 9, 10, 30, 51) to form electrochemical cells (2, 50 , 52) and to the stack (70) of the electrochemical cell unit (1, 49, 53) partially delimit an outside (71) of the stack (70).

5. The method according to one or more of the preceding claims, characterized in that the seals (11) in a direction perpendicular to notional planes (59) spanned by the layered components (5, 6, 7, 8, 9, 10, 30 , 51) and electrochemical cells (2, 50, 52), between the layered components (5, 6, 7, 8, 9, 10, 30, 51) are arranged.

6. The method according to claim 5, characterized in that the seals (11) between the bipolar plates (10) and membrane electrode assemblies (6) for sealing channels (12) for fuel and / or electrolyte and / or for sealing channels (13) for Oxidizing agent and / or electrolyte are arranged.

7. The method according to one or more of claims 4 to 6, characterized in that the outside (71) of the stack (70) is treated physically and / or chemically, so that the primary sealing material (73) of the seals (11) on one the area facing the outside (71) is converted into the secondary sealant (75).

8. The method according to one or more of the preceding claims, characterized in that the primary sealing material (73) of the seals (11) is converted into the secondary sealing material (75) at a secondary partial area (76) and at a primary partial area (74 ) no conversion of the primary sealing material (73) into the secondary sealing material (73) is carried out, so that hybrid seals (11) each having a primary section (74) and a secondary section (76) are produced.

9. The method according to one or more of the preceding claims, characterized in that the physical and/or chemical treatment is carried out for a period of 5 s to 60 min, in particular 1 min to 30 min will.

10. The method according to one or more of the preceding claims, characterized in that the primary sealant (73) comprises silicone and the secondary sealant (75) comprises silicon oxide.

11. The method according to one or more of the preceding claims, characterized in that the physical and/or chemical treatment is carried out with a treatment fluid, in particular ozone and/or plasma, so that the primary sealing material ( 73) is contacted with the treatment fluid, in particular ozone and/or the plasma.

12. Electrochemical cell unit (1, 49, 53) for converting electrochemical energy into electrical energy as a fuel cell unit (1) and/or for converting electrical energy into electrochemical energy as an electrolytic cell unit (49).

- Electrochemical cells (2, 50, 52) arranged in a stack and the electrochemical cells (52) each comprise layered components (5, 6, 7, 8, 9, 10, 30, 51) arranged in a stack,

- The components (5, 6, 7, 8, 9, 10, 30, 51) of the electrochemical cells (2, 50, 52) preferably proton exchange membranes (5), anodes (7), cathodes (8), preferably membrane electrode assemblies (6 ), preferably gas diffusion layers (9) and bipolar plates (10),

- channels (12, 13, 14) for the passage of process fluids,

- Gaskets (11) for sealing the channels (12, 13, 14) for the process fluids, characterized in that the electrochemical cell unit (1, 49, 53)) is produced using a method according to one or more of the preceding claims and/or the seals (11) are designed as hybrid seals (11), each with a primary sealant (73) on a primary Section (74) and one secondary sealing material (75) each on a secondary section (75) and the secondary sealing material (75) has a smaller diffusion coefficient than the primary sealing material (73).

13. Electrochemical cell unit according to claim 12, characterized in that the primary partial areas (74) of the seals (11) the channels (12, 13,

14) for the process fluids and the secondary partial areas (76) of the seals (11) partially form an outside (71) of the stack (70).

14. Electrochemical cell unit according to claim 12 or 13, characterized in that

Seals (11) are arranged between bipolar plates (10) and membrane electrode assemblies (6), in particular subgaskets (69) of membrane electrode assemblies (6).

15. Electrochemical cell unit according to one or more of claims 12 to 14, characterized in that the secondary sealing material (75) has a greater hardness, in particular greater Brinell hardness, than the primary sealing material (73).