Method for producing an electrochemical cell unit
Patent Information
- Application Number
- PCT/EP2026/057536
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-26
- Filing Date
- 2026-03-18
- Publication Date
- 2026-10-01
Smart Images
Figure EP2026057536_01102026_PF_FP_ABST
Abstract
Description
[0001] R. 417808
[0002] - 1 -
[0003] Description
[0004] title
[0005] Method for manufacturing an electrochemical cell unit
[0006] The present invention relates to a method for producing an electrochemical cell unit according to the preamble of claim 1 and an electrochemical cell system according to the preamble of claim 15.
[0007] State of the art
[0008] Fuel cell units, as galvanic cells, convert continuously supplied fuel and oxidizing agent into electrical energy and water via redox reactions at an anode and cathode.
[0009] Fuel cells are used in a wide variety of stationary and mobile applications, for example in homes without a connection to the power grid, in motor vehicles, rail transport, aviation, space travel, and shipping. Fuel cell units consist of multiple fuel cells arranged in a stack.
[0010] 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 oxidizer, that is, a flow space for the passage of an oxidizer, such as ambient air containing oxygen. This gas space for the oxidizer is formed by channels on the bipolar plate and a gas diffusion layer for the cathode. The channels are thus formed by a corresponding channel structure on the bipolar plate, and the oxidizer, namely oxygen, reaches the cathode of the fuel cells through the gas diffusion layer.
[0011] Similarly, a gas space for fuel is formed at an anode. R. 417808
[0012] - 2 -
[0013] 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.
[0014] Fuel cell units and electrolysis cell units form electrochemical cell units. Fuel cells and electrolysis cells form electrochemical cells.
[0015] Within the fuel cell stack, channels for fuel, oxidizer, and coolant are formed. Furthermore, electrical current is conducted within the fuel cell stack, particularly by the bipolar plates. To ensure sufficient channel tightness and adequate electrical conductivity of the fuel cell stack components, it is necessary to prestress the fuel cell stack with a compressive force. For this purpose, an upper clamping element, in the form of a clamping plate, rests on the uppermost fuel cell, and a lower clamping element, also in the form of a clamping plate, rests on the lowermost fuel cell. Outside the fuel cell stack, connecting devices such as tie rods, bolts, or tension bands are typically arranged and subjected to a tensile force.Due to the direct or indirect attachment of the tie rods or the tension band to the upper and lower clamping element, this tensile force is transferred to the clamping plates, so that the upper clamping plate exerts a compressive force on the upper fuel cell and the lower clamping plate exerts a compressive force on the lower fuel cell.
[0016] The connecting devices, whether a tension band or a tension rod, are subjected to a tensile force during the pre-tensioning of the cell stack. Therefore, after assembly and the application of a compressive force to the cell stack, and thus a tensile force to the connecting devices, plastic deformation of the connecting devices occurs, particularly over time during and / or after the conditioning and commissioning of the cell stack. This adversely reduces the pre-tension of the cell stack under compressive force. This can adversely affect R. 417808.
[0017] - 3 -
[0018] This can lead to leaks in the process fluids and an increase in electrical resistance within the cell stack between the electrochemical cell units. After stacking the electrochemical cells, manufacturing inaccuracies result in cell stacks with varying heights. Therefore, it is necessary to manufacture connecting devices of different lengths separately, in a complex and expensive process, to accommodate these varying cell stack heights.
[0019] DE 102019215888 A1 discloses a fuel cell unit as a fuel cell stack for the electrochemical generation of electrical energy, comprising fuel cells arranged one above the other, an upper clamping element for applying a compressive force to an upper fuel cell, a lower clamping element for applying a compressive force to a lower fuel cell, at least one connecting device subjected to a tensile force, which is in mechanical operative connection with the upper and lower clamping elements, such that, due to the tensile force in the at least one connecting device, a compressive force can be applied from the upper clamping element to the upper fuel cell and a compressive force can be applied from the lower clamping element to the lower fuel cell, wherein the at least one connecting device is arranged within the fuel cell stack.
[0020] DE 102022205729 A1 discloses 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 stacked electrochemical cells as a cell stack, a first clamping element for applying a compressive force to a first electrochemical cell, a second clamping element for applying a compressive force to a last electrochemical cell, and at least one connecting device subjected to a tensile force, which is in mechanical operative connection with the first and second clamping elements, such that, due to the tensile force in the at least one connecting device, a compressive force can be applied from the first clamping element to the first electrochemical cell and a compressive force from the second clamping element to the last electrochemical cell. R. 417808
[0021] - 4 -
[0022] is applicable, where the number of connecting devices is greater than eight.
[0023] Disclosure of the invention
[0024] Advantages of the invention
[0025] A method according to the invention for manufacturing 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 electrochemical cells, providing a first clamping element for applying a compressive force to a first electrochemical cell, providing a second clamping element for applying a compressive force to a last electrochemical cell, providing at least one connecting device, stacking the electrochemical cells to form a cell stack, the first clamping element being arranged directly or indirectly on the first electrochemical cell of the cell stack, and the second clamping element being arranged directly or indirectly on the last electrochemical cell of the cell stack.Assembly of the at least one connecting device by bringing the at least one connecting device into direct or indirect mechanical operative connection with the first and second clamping elements and by subjecting the at least one connecting device to a tensile force, such that, due to the tensile force in the at least one connecting device, a compressive force is applied from the first clamping element to the first electrochemical cell and a compressive force is applied from the second clamping element to the last electrochemical cell, and thus the cell stack is pre-tensioned with a compressive force, wherein the at least one connecting device is provided by providing at least one raw connecting device before the assembly of the at least one connecting device and subjecting the at least one raw connecting device to a tensile force for cold working.so that plastic deformation is carried out as a permanent increase in the length of at least one pipe joining device and the R. 417808,
[0026] - 5 -
[0027] At least one connecting device with a permanent increase in length forms the at least one connecting device. Advantageously, this significantly reduces the plastic strain, i.e., the increase in length of the at least one connecting device, during the preloading of the electrochemical cell stack with the at least one connecting device, so that there is essentially no reduction in the preload of the electrochemical cell stack due to plastic strain of the at least one connecting device.
[0028] In another embodiment, several connecting devices, in particular four connecting devices for one electrochemical cell each, are provided and assembled.
[0029] In a supplementary embodiment, the elongation of at least one pipe joining device for cold working is carried out by between 0.1% and 10%, in particular between 0.2% and 6%. The elongation is the ratio of the change in length to the original length. With an elongation of less than 10%, as uniform elongation, essentially no necking occurs, i.e., essentially no reduction in diameter of the pipe joining device, preferably with a deviation of less than 30%, 20%, 10%, 5%, 3%, 2%, or 1%.
[0030] In an additional embodiment, the elongation of at least one pipe connection device for cold working is implemented to be less than 20%. This essentially eliminates the risk of a stainless steel pipe connection device breaking with an elongation at break of 25%.
[0031] In a supplementary embodiment, several connecting devices of different lengths are provided for mounting on cell stacks with different heights due to manufacturing inaccuracies of the cell stacks.
[0032] Preferably, the multiple connecting devices are provided with different lengths by different R. 417808
[0033] - 6 -
[0034] Plastic expansions are implemented as an increase in the length of the pipe joining devices.
[0035] In a further embodiment, the different plastic strains are implemented as an increase in the length of the raw joining devices, with raw joining devices having essentially identical lengths, particularly with a deviation of less than 10%, 5%, 3%, 1%, or 0.1%, so that joining devices of different lengths are provided. The raw joining devices thus preferably differ only in manufacturing inaccuracies; that is, large quantities of identical raw joining devices can be produced and provided, and the different lengths are achieved solely through the plastic strain of the raw joining devices.
[0036] In a supplementary variant, several connecting devices with at least two classes of different lengths are provided, in particular connecting devices between two and eight classes are provided.
[0037] Advantageously, connecting devices of the same class have essentially identical lengths, in particular with a deviation of less than 30%, 20%, 10%, 5%, 3%, 1% or 0.1%.
[0038] In an additional embodiment, connecting devices of the same class are mounted on each cell stack, depending on the height of the cell stack. The greater the height of the cell stack, the longer the connecting devices, particularly those from only one class, are mounted on the cell stack.
[0039] Preferably, the at least one connecting device is designed as a pull strap and / or a pull rod.
[0040] In a further embodiment, the at least one connecting device is equipped with a positive-locking connecting element with the R. 417808
[0041] - 7 -
[0042] first and / or second clamping element brought into indirect or direct mechanical connection, in particular by forming a loop on each tension band, arranging a bolt in the loop and by means of a screw shaft attached to the bolt, each tension band is indirectly or directly attached to the first and / or second clamping element in a form-fitting manner.
[0043] In a supplementary variant, at least one connecting device is brought into indirect or direct mechanical connection with the first and / or second clamping element by inserting one screw shaft with an external thread into a bore of a clamping element and then screwing a nut onto the screw shaft so that the nut applies the compressive force to the clamping element.
[0044] In a further embodiment, for the plastic elongation as an increase in the length of the at least one pipe connection device in each pipe connection device, the at least one positive-locking connecting element on each pipe connection device is also subjected to a force, in particular a tensile force, so that a deformation, in particular bending and / or elongation, of the at least one positive-locking connecting element on each pipe connection device is also carried out, preferably as plastic bending and / or plastic elongation of the connecting element and / or simultaneously the plastic elongation as an increase in the length of the at least one pipe connection device and the subjection of the force to the at least one connecting element is carried out.
[0045] An 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 arranged as a cell stack, a first clamping element for applying a compressive force to a first electrochemical cell, a second clamping element for applying a compressive force to a last electrochemical cell, and at least one connecting device subjected to a tensile force, as described in R. 417808.
[0046] - 8 -
[0047] The at least one connecting device is indirect or direct mechanical connection with the first and second clamping elements, such that, due to the tensile force in the connecting device, a compressive force can be applied from the first clamping element to the first electrochemical cell and from the second clamping element to the last electrochemical cell, and the cell stack is prestressed with the compressive force. The at least one connecting device is manufactured using a method described in this patent application. Cold working and plastic deformation cause a demonstrable change in the structure of the material of the connecting device; for example, atomic planes in crystals are displaced and / or linear lattice defects occur and / or, in the case of step substitutions, lattice lines terminate abnormally within the lattice structure, which is therefore distorted and / or the lattice planes are displaced.The structural changes in the material of the connecting device can be detected using the methods and procedures of materials science, for example with FE scanning electron microscopy, ion preparation of cross-sections, metallographic preparation techniques and light microscopy, energy-dispersive spectrometry of X-rays, optical glow discharge spectrometry, atomic force microscopy, profilometry, spectroscopic ellipsometry, UV / VIS / NIR spectroscopy, light scattering, hardness and elastic modulus, layer stresses, adhesion strength by scratch test and / or abrasion resistance.
[0048] In another embodiment, the electrochemical cells are provided by providing layered components of the electrochemical cells and stacking the layered components on top of each other to form electrochemical cells.
[0049] In a supplementary variant, at least one clamping element is designed as a clamping plate and / or a clamping grid and / or a clamping frame.
[0050] In a supplementary embodiment, the at least one connecting device, in particular including connecting means, is made at least partially, preferably to at least 80% by mass, 90% by mass or 95% by mass, in particular completely, of metal, in particular stainless steel and / or chromium-nickel steel, preferably 1.4301. R. 417808
[0051] - 9 -
[0052] In a further embodiment, the at least one connecting device is mechanically connected to a clamping element, in particular a second clamping element, and an additional plate is arranged between the clamping element and the cell stack, and elastic elements, in particular coil springs, are arranged between the additional plate and the clamping element, so that in the event of a reduction in the height or the extent of the cell stack due to the preload and temperature, the preload and the compressive forces in the cell stack are only slightly reduced due to the elastic properties of the coil springs and vice versa.
[0053] Preferably, the components of the electrochemical cells and / or the electrochemical cells are formed in layers and span fictitious planes.
[0054] In a further embodiment, a fuel cell system comprises a fuel supply system with a pressure vessel for fuel as a process fluid and an oxidant supply system with a gas conveying device for oxidant as a process fluid and / or at least one discharge opening for discharging at least one process fluid into the environment.
[0055] In a further embodiment, an electrolysis cell system comprises an electrolysis cell unit, an electrolyte supply system with a storage container for electrolyte and a pump for electrolyte and preferably a separator for hydrogen and / or a separator for oxygen.
[0056] In a complementary variant, the fuel cell system comprises a fuel cell unit, a cooling system, an oxidant supply system, and a fuel supply system.
[0057] In a further embodiment, the electrochemical cells each comprise as components an ion exchange membrane, in particular a proton exchange membrane and / or anion exchange membrane, an anode, a cathode, preferably at least one gas diffusion layer. 417808
[0058] - 10 -
[0059] and / or at least one separator plate, in particular a bipolar plate. In contrast to fuel cells, electrolysis cells do not require bipolar plates; instead, bipolar plates consisting of only one plate are used as separators because electrolysis cells lack a coolant channel. In fuel cells, the bipolar plate, which consists of two plates, has at least one coolant channel between the two plates.
[0060] Preferably, the fuel is hydrogen, hydrogen-rich gas, reformate gas or natural gas.
[0061] The electrochemical cells and / or components of the electrochemical cells are expediently designed to be essentially flat and / or disc-shaped.
[0062] 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.
[0063] Preferably, the connection plate has at least one inlet opening and / or at least one outlet opening.
[0064] In a complementary variant, the oxidizing agent is air with oxygen or pure oxygen.
[0065] 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).
[0066] Brief description of the drawings
[0067] Exemplary embodiments of the invention are described in more detail below with reference to the accompanying drawings. These show:
[0068] Fig. 1 shows a highly simplified representation of a fuel cell system, R. 417808
[0069] - 11 -
[0070] Fig. 2 shows a highly simplified representation of an electrolysis cell system and
[0071] Fig. 3 shows a perspective view of an electrochemical cell unit,
[0072] Fig. 4 shows a view of a positive-locking connecting element of a tension band as a connecting device,
[0073] Fig. 5 shows a side view of a device for the plastic expansion of a pipe joining device and the pipe joining device itself.
[0074] Fig. 6 shows a cross-section of a tension band as a connecting device and
[0075] Fig. 7 shows a stress-strain diagram of a connecting device.
[0076] Figure 1 shows a fuel cell unit 1 as a fuel cell stack 3. The fuel cell unit 1 comprises the fuel cell stack 3, a housing 13, and a connection plate 15. The housing 13 defines an interior space 14. The connection plate 15 also functions as a housing 13 and is fixed to the rest of the housing 13 by fixing elements 16, in particular screws 17. Fuel cells 4, specifically PEM fuel cells 5, are stacked and aligned within the fuel cell stack 3. Due to the large number of stacked fuel cells 4, approximately 300 to 400, not all of them are shown in Figure 1 for the sake of simplicity. The principle of fuel cells 4 is that electrical energy, or electric current, is generated by means of an electrochemical reaction.Hydrogen (H₂) is fed to an anode (not shown) as a gaseous fuel for recirculation, and the anode forms the negative terminal. A gaseous oxidizing agent, namely air with oxygen, is fed to a cathode (not shown); that is, the oxygen in the air provides the necessary gaseous oxidizing agent. Reduction (electron uptake) takes place at the cathode. Oxidation (electron release) occurs at the anode. The fuel cells 4 also include an ion exchange membrane, specifically a proton exchange membrane (PEM), which is positioned between the anode and the cathode. On both sides of the PEM, facing the gas spaces, are the R. 417808.
[0077] - 12 -
[0078] Electrodes are arranged as the anode and cathode (not shown). A unit consisting of the PEM and anode and cathode is called a membrane electrode assembly (MEA) (not shown). A gas diffusion layer (GDL) lies on top of the anode and cathode. A bipolar plate (not shown) rests on the GDL. The electrically conductive bipolar plate serves as a current collector, for water drainage, and for conducting the reaction gases.
[0079] In the fuel cell unit 1, the fuel cells 4 are arranged between two clamping elements 18, which act as clamping plates 19. An upper clamping plate 20 rests directly or indirectly on the uppermost fuel cell 4, and a lower clamping plate 21 rests directly or indirectly on the lowermost fuel cell 4. The clamping elements 18 exert a compressive force on the fuel cells 4; that is, the upper clamping plate 20 exerts a compressive force on the uppermost fuel cell 4, and the lower clamping plate 21 exerts a compressive force on the lowermost fuel cell 4. This clamps the fuel cell stack 3 to ensure a tight seal for the fuel, oxidizer, and coolant, particularly due to elastic seals, and also to minimize the electrical contact resistance within the fuel cell stack 3.For clamping the fuel cells 4 with the clamping elements 18, four connecting devices 22 are formed on the fuel cell unit 1 in the form of bolts 23 or tie rods 23, which are subjected to tensile stress. The four bolts 23 are rigidly connected to the clamping plates 19.
[0080] The connection plate 15 and the lower clamping plate 21 each have an opening for introducing recirculating fuel into the recirculating fuel channels. They also each have an opening for discharging recirculating fuel from the recirculating fuel channels. The connection plate 15 and the lower clamping plate 21, as clamping elements 18, have further openings for introducing and discharging oxidizers, and openings (not shown) for introducing and discharging coolant. Thus, the connection plate 15 and the lower clamping plate 21 have a total of six openings (only partially shown in Fig. 1). R. 417808
[0081] - 13 -
[0082] 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 3 with air as the oxidant. The oxidant supply system 26 comprises a gas conveying device 27, for example a blower, a compressor, a turbo compressor, which is driven by an electric motor and / or a turbine, and oxidant lines 28.
[0083] The fuel cell system 2 comprises, in addition to the fuel cell unit 1, 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 a recirculation fuel line 32, a heat exchanger (not shown) for fuel, a pressure reducer (not shown), the recirculation fuel line 32 as a process fluid line, a recirculation fuel conveying device 33, an electric motor (not shown) for driving the recirculation fuel conveying 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 purge valve (not shown) for releasing recirculated 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 vessel 30 at a high pressure of, for example, 400 bar, is fed through the fuel line 31 to the recirculated 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 this hydrogen drawn from the fuel cells 4 is fed back to the fuel cells 4 in a cycle through the recirculated fuel line 32. To convey the recirculated fuel through the R. 417808,
[0084] - 14 -
[0085] The recirculation fuel supply device 33 is used in the recirculation fuel line 32. After the fuel passes through the fuel cells 4, its moisture content increases. To prevent excessive water or moisture content in the recirculation fuel, the fuel supply system 29 includes a water separator 34. The water separated in the water separator 34 is collected in the water tank (not shown) and discharged into the environment via the drain valve (not shown). Excess recirculation fuel is discharged into the environment via the purge valve (not shown).
[0086] Fuel cell system 2 comprises, in addition to fuel cell unit 1, a cooling system (not shown) for temperature control of the fuel cell stack 3. This cooling system includes coolant lines for process fluids, a heat exchanger, and a pump for circulating the coolant. The coolant is routed through coolant channels in the bipolar plates of the fuel cells 4, and the heat is dissipated to the environment via the heat exchanger. Fuel cell system 2 also includes, in addition to fuel cell unit 1, the oxidizer supply system 26, the fuel supply system 29, and the cooling system (not shown) as a coolant supply system.
[0087] The fuel cell unit 1 can optionally be used and operated as an electrolysis cell unit 6 with modifications not shown, particularly valves; that is, it forms a reversible fuel cell unit 1 or is designed to be operable only as an electrolysis cell unit 6. Some features that enable the operation of the fuel cell unit 1 as an electrolysis cell unit 6 are described below. A liquid electrolyte, namely highly diluted sulfuric acid with a concentration of approximately c(H₂SO₄) = 1 mol / L, is used for electrolysis. A sufficient concentration of hydronium ions (H₃C) in the liquid electrolyte is necessary for electrolysis. Figure 2 shows an electrolysis cell unit 6 that can only be used for electrolysis. R. 417808
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[0089] The polarity of the electrodes during electrolysis is reversed (not shown) when operating as electrolysis cell unit 6 compared to operation as fuel cell unit 1. This means that hydrogen (H₂) is formed at the cathodes in the fuel channels through which the liquid electrolyte is passed. The hydrogen (H₂) is then absorbed by the liquid electrolyte and transported along in solution. Similarly, the liquid electrolyte is passed through the oxidant channels, and oxygen (O₂) is formed at the anodes or in the oxidant channels. When operating as electrolysis cell unit 6, the fuel cells 2 of fuel cell unit 1 function as electrolysis cells 9. Fuel cells 2 and electrolysis cells 9 thus form electrochemical cells 24. The oxygen (O₂) produced is absorbed by the liquid electrolyte and transported along in solution.The hydrogen H₂ produced is absorbed by the liquid electrolyte and transported in solution. The liquid electrolyte is stored in a storage container 35 and is pumped by a pump 37 through electrolyte lines 36 and 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 located on the recirculation fuel line 32 and the oxidizer line 28 and are switched during operation as an electrolysis cell unit 6, so that instead of recirculation fuel and oxidizer, the liquid electrolyte is introduced by the pump 37 from the storage container 35 into the recirculation fuel line 32 and the oxidizer line 28 as electrolyte line 36. A hydrogen separator 38 separates the hydrogen obtained from the electrolyte during electrolysis.An oxygen separator 39 separates the oxygen obtained from electrolysis from the electrolyte. The electrolyte is circulated through the electrolysis cell unit 6, and sulfuric acid is added according to consumption by a device not shown. The electrolysis cell system 6 comprises, in addition to the electrolysis cell unit 6 with the electrolysis cell stack 8, an electrolyte supply system 12. The electrolyte supply system 12 includes the storage tank 35, the electrolyte lines 36, the pump 37, the hydrogen separator 38, and the oxygen separator 39. A fuel cell unit 1 and an electrolysis cell unit 6 form an electrochemical cell unit 25. A fuel cell system 2 and / or an electrolysis cell system 7 form an electrochemical cell system 11.R. 417808.
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[0091] In the electrochemical cell unit 25 (Figs. 1 and 2), the cell stack 3, 8 is supplied with or discharged from electrical energy by two current plates 43 (Fig. 3, not shown in Figs. 1 and 2). An electrical potential is thus present between the two current plates 43. Insulating plates 42 (Fig. 3, not shown in Figs. 1 and 2) serve to electrically insulate the current plates 43 and the electrochemical cells 24 from the end plates, which are the clamping elements 18, and from the surroundings, in order to prevent an electrical short circuit within the cell stack 3, 8.
[0092] Figure 3 shows a second embodiment of an electrochemical cell unit 25. To supply the electrochemical cell stack 3, 8, it is necessary to introduce and remove process fluids through inlet and outlet channels. These inlet and outlet channels open into nozzles, which are shown at the bottom of the electrochemical cell stack 3, 8 in Figure 3. For this purpose, inlet and outlet openings (not shown) are provided in the second lower clamping plate 18, 21, the insulating plate 42, and the current plate 43.
[0093] In the second embodiment shown in Fig. 3, the connecting devices 22 are designed as a pull strap 10 and a tension strap 10. The pull strap 10 has a total length of 1200 mm. In cross-section, the pull strap 10 is rectangular (Fig. 6) with a width 40 of 25 mm and a thickness 41 of 1 mm. The cross-sectional area of the pull strap 10 is therefore 25 mm². 2At each end of the drawstring 10, a loop 46 is formed by bending an end section of the drawstring 10 so that the drawstring 10 overlaps at an overlap area 56, and three weld points 55 are formed at this overlap area 56 (Figs. 3 and 4). The weld points 55 thus connect the overlap area 56 to each other in a material-bonded manner, forming the loop 46. An opening 47 is present in the loop 46. This is achieved during manufacturing by punching a corresponding slot in the loop 46 before bending the end sections of the drawstring 10. A slot is thus punched into both end sections of the drawstring 10 as an elongated hole before bending. The two loops 46 of the drawstring 10 are formed as a single R. 417808
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[0095] A bolt 48 is arranged in the pipe connection device 44. A screw shaft 49 with an external thread is attached to the bolt 48 perpendicular to a central longitudinal axis of the bolt 48. The screw shaft 49 projects through the opening 47 of the loop 46, and a nut 50 is screwed onto one end of the screw shaft 49. The loop 46 with the opening 47, as well as the bolt 48 with the screw shaft 49 and the nut 50, form a connecting element 45 for the positive locking or fastening of the tension band 10 to a clamping element 18, namely, in the second embodiment according to Fig. 3, the second lower clamping plate 21.
[0096] To pre-tension the cell stack 3, 8 with a compressive force, the screw shank 49 is inserted into bores (not shown) in the lower clamping plate 21, and the tension band 10 is placed around the cell stack 3, 8 so that the U-shaped tension band 10 rests on the first upper clamping plate 20, and both screw shanks 49 of each tension band 10 are arranged in the bore (not shown) of the lower second clamping plate 21. For pre-tensioning, the nut 50 is screwed onto the screw shank 49 so that the nut 50 rests on the second lower clamping plate 21, and the diameter of the nut 50 is larger than the diameter of the bores in the second lower clamping plate 21 into which a screw shank 49 has been inserted. Tightening the nut 50 pre-tensions the cell stack 3, 8.
[0097] The tension band 10 is made of stainless steel 1.4301. Figure 7 shows a stress-strain diagram of the tension band 10. The strain c is plotted on the abscissa and the stress o on the ordinate. In the first section up to the first circle, the line in the diagram is a straight line, i.e., ideally, only elastic strain occurs, in which the material returns to its original shape, i.e., its original length, after unloading as a reversible change in length.
[0098] Between the first circle and the second circle, plastic deformation occurs up to a uniform elongation A. g of approximately 10% at a stress of approximately 500-750 N / mm 2With further elongation (increase in length) of the tension band 10, the tension band 10 breaks at the breaking elongation A of approximately 25%. In practice, however, it has been shown that even at the beginning of the elongation up to the first loop, a slight plastic deformation occurs, so that after the tension band 10 is released, it does not break down to the breaking elongation A. R. 417808
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[0100] The material does not return to its original length, but exhibits a slightly greater length. For metallic materials, the range of strain with purely elastic deformation is very difficult to determine, so the range with purely or substantially elastic deformation of a metallic active material, such as a tensile band, is defined as 10 times a 0.2% yield strength or elastic limit R. P In technical practice, a simplification of 0.2 is assumed.
[0101] The cell stack 3, 8 shown in Fig. 3 comprises approximately 450 electrochemical cells 24. After stacking the electrochemical cells 24, different cell stacks 3, 8 exhibit a height difference of approximately + / - 12 mm due to manufacturing inaccuracies. Therefore, four different classes of tension bands 10 are manufactured or provided for pre-tensioning the cell stack 3, 8. This ensures that the appropriate tension bands 10 from a suitable class are used to pre-tension each cell stack 3, 8, adapted to its actual height. The plastic deformation of identical pipe connection devices 44 is carried out until the intended length for each class is reached. The difference in length between the classes with the longest tension band 10 and the class with the shortest tension band 10 is 40 mm.During operation of the cell stack 3, 8, it is prestressed with a compressive force of approximately 50 kN between the clamping elements 18, so that a tensile force of 50 kN / 8 = 6.25 kN occurs in the tension bands 10 on each side between the upper clamping plate and the lower clamping plate.
[0102] For the manufacture or provision of the tension bands 10 as the connecting devices 22, a raw connecting device 44 is first provided as a raw tension band 44 as shown in Fig. 5 with the two connecting means 45 at the ends of the raw tension band 44. The raw tension band 44 has not yet been subjected to any elastic or plastic deformation. For the provision or manufacture of the tension band 10, the raw tension band 44 is subjected to plastic deformation in a device 51. The device 51 comprises two compression bars 52, the ends of which are arranged and fastened in a motion and force measuring device 54. At the ends of the R. 417808
[0103] - 19 -
[0104] Opposite the ends of the compression rods 52 in the motion and force measuring device 54, locking elements 53 are attached by means of a slot or elongated hole. A nut 50 of the tensile cord 44 is fixed in each locking element 53. The distance between the locking elements 53 can be increased or decreased by means of the motion and force measuring device 54, and thus the tensile cord 44 can be stretched. For this purpose, an electric or hydraulic actuator is installed in the motion and force measuring device 54, as well as sensors for detecting the compressive force in a compression rod 52 and for detecting the change in the distance between the two locking elements 53. With a compressive force of 10 kN in the compression rod 52, an identical tensile force of 10 kN occurs in the tensile cord 44. Due to the cross-sectional area of the tensile cord 44 of 25 mm² 2 This results in a stress of 400 N / mm². 2and an elongation of approximately 4%. The elongation of 4% is the ratio between the length of the raw tension band 44 during or after the application of the tensile force to the raw tension band 44 and the original length of the raw tension band 44 before the application of the tensile force to the raw tension band 44 in the device 51. After the plastic elongation of the raw tension band 44 in the device 51, the tensile force in the raw tension band 44 is reduced back to zero and removed from the device 51, so that the tension band 10 is thereby produced and made available as the tension band 10. Due to the plastic elongation of the raw tension band 44 in the device 51, the tension band 10 produced or made available in this way has a greater length than the raw tension band 44 as the raw joining device 44.
[0105] The plastic strain, as a plastic deformation of the tension band 10 in the device 51, as work hardening, causes the tension band 10 to exhibit no or substantially no plastic strain during the prestressing of the cell stack 3, 8. This advantageously prevents any or substantially no reduction in the prestress of the cell stack 3, 8 due to plastic strain of the tension band 10. The four different length classes of the tension band 10 can be easily produced by using a type of raw joining device 44 as the raw tension band 10 with substantially identical lengths, differing only by manufacturing inaccuracies. R. 417808
[0106] - 20 -
[0107] Different length classes of the tension bands 10 can be produced in the device 51 by means of different plastic strains. Only strains in the range between 2% and 5% are necessary for the production of the different length classes of the tension bands 10, i.e., significantly smaller than the uniform strain A. g of approximately 10% to avoid constriction, i.e., a reduction in the width 40 of the tension band 10. Furthermore, the necessary elongation is significantly less than the elongation at break A of approximately 25%, so there is no risk of breakage during the stretching and elongation of the pipe joining device 44.
[0108] In the device 51, the entire tension band 10, including the connecting element 45, in particular the loop 46, the bolt 48 and the screw shaft 49, is subjected to tensile and bending stress, so that essentially no plastic elongation of the connecting element 45 occurs during the prestressing of the cell stack 3, 8 with the connecting device 22.
[0109] Overall, the inventive method for manufacturing the electrochemical cell unit 25 and the inventive electrochemical cell unit 25 offer significant advantages. The plastic deformation of the raw connection device 44 prior to assembly on the cell stack 3, 8 causes work hardening of the stainless steel material of the connection devices 22, so that during pre-tensioning of the cell stack 3, 8, essentially no plastic deformation occurs as an increase in the length of the tension band 10. A resulting reduction in the pre-tension of the cell stack 3, 8 can be avoided.In addition, the costs for manufacturing different classes of connecting devices 22 with different lengths can be reduced because initially only one type or genus of raw connecting device 44 needs to be available or manufactured in large quantities, and the different classes of connecting devices 22 with corresponding lengths can be produced from this raw connecting device 44 with plastic deformation. The plastic deformation of the connecting devices 22 also has the advantage that waves or unevenness on the outside of the connecting devices 22 due to R. 417808.
[0110] - 21 -
[0111] inaccurate manufacturing geometry can be reduced by plastic deformation.
Claims
R. 417808 - 22 - Claims 1. Method for manufacturing an electrochemical cell unit (1 , 6, 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 the steps: - providing electrochemical cells (4, 5, 9, 24), - providing a first clamping element (18, 19, 20) for applying a pressure force to a first electrochemical cell (4, 5, 9, 24), - providing a second clamping element (18, 19, 21) for applying a compressive force to a final electrochemical cell (4, 5, 9, 24), - provide at least one connecting device (10, 22, 23), - Stacking the electrochemical cells (4, 5, 9, 24) to form a cell stack (3, 8), - the first clamping element (18, 19, 20) is arranged directly or indirectly on the first electrochemical cell (4, 5, 9, 24) of the cell stack (3, 8), - the second clamping element (18, 19, 21) is arranged directly or indirectly on the last electrochemical cell (4, 5, 9, 24) of the cell stack (3, 8), - Assembly of the at least one connecting device (10, 22, 23) by bringing the at least one connecting device (10, 22, 23) into mechanical operative connection with the first and second clamping elements (18, 19, 20, 21) and subjecting the at least one connecting device (10, 22, 23) to a tensile force, such that, due to the tensile force in the at least one connecting device (10, 22, 23), a compressive force is applied from the first clamping element (18, 19, 20) to the first electrochemical cell (4, 5, 9, 24) and from the second clamping element (18, R. 417808 - 23 - 19, 21) a pressure force is applied to the last electrochemical cell (4, 5, 9, 24) and thus the cell stack (3, 8) is prestressed with a pressure force, characterized by the fact that at least one connecting device (10, 22, 3) is provided by providing at least one pipe connecting device (44) before the assembly of the at least one connecting device (10, 22, 23) and subjecting the at least one pipe connecting device (44) to a tensile force for cold working, so that plastic elongation is carried out as a permanent increase in the length of the at least one pipe connecting device (44) and the at least one pipe connecting device (44) with the permanent increase in length forms the at least one connecting device (10, 22, 23).
2. Method according to claim 1, characterized by the fact that several connecting devices (10, 22, 23), in particular four connecting devices (10, 22, 23) for which one electrochemical cell unit (1, 6, 25) is provided and mounted.
3. Method according to one or more of the preceding claims, characterized by the fact that an elongation of the at least one pipe joining device (44) for cold working is carried out between 0.1% and 10%, in particular between 0.2% and 6%.
4. Method according to one or more of the preceding claims, characterized by the fact that R. 417808 - 24 - an elongation of the at least one pipe joining device (44) for cold working is less than 20%.
5. Method according to one or more of the preceding claims, characterized by the fact that Several connecting devices (10, 22, 23) of different lengths are provided for mounting on cell stacks (3, 8) of different heights due to manufacturing inaccuracies of the cell stacks (3, 8).
6. Method according to one or more of the preceding claims, characterized by the fact that the multiple connecting devices (10, 22, 23) of different lengths are provided by implementing different plastic strains as an increase in the length of the raw connecting devices (44).
7. Method according to claim 6, characterized by the fact that the different plastic strains as an increase in the lengths of the pipe connection devices (44) are implemented with pipe connection devices (44) with an essentially identical length of the pipe connection devices (44) in such a way that connection devices (10, 22, 23) with different lengths are provided.
8. Method according to one or more of claims 5 to 7, characterized by the fact that R. 417808 - 25 - Several connecting devices (10, 22, 23) with at least two classes of different lengths are provided.
9. Method according to claim 8, characterized by the fact that the connecting devices (10, 22, 23) of the same class have essentially identical lengths.
10. Method according to claim 8 or 9, characterized by the fact that Connecting devices (10, 22, 23) of the same class are mounted on each cell stack (3, 8) depending on the height of the cell stack (3, 8).
11. Method according to one or more of the preceding claims, characterized by the fact that the at least one connecting device (10, 22, 23) is designed as a pull strap (10) and / or a pull rod (23).
12. Method according to one or more of the preceding claims, characterized by the fact that at least one connecting device (10, 22, 23) with a positive-locking connecting means (45) is brought into direct or indirect mechanical connection with the first and / or second clamping element (18, 19, 20, 21), in particular by forming a loop (46) on each of the tension bands (10), a bolt (48) being arranged in the loop (46) and connected to the bolt (48). R. 417808 - 26 - attached screw shaft (49) to which each tension band (10) is attached directly or indirectly to the first and / or second clamping element (18, 19, 20, 21) in a form-fitting manner.
13. Method according to claim 12, characterized by the fact that the at least one connecting device (10, 22, 23) with a positive-locking connecting means (45) is brought into indirect or direct mechanical connection with the first and / or second clamping element (18, 19, 20, 21) by inserting one screw shaft (49) with an external thread into a bore of a clamping element (18, 19, 20, 21) and then screwing a nut (50) onto the screw shaft (49) so that the nut (50) applies the compressive force to the clamping element (18, 19, 20, 21).
14. Method according to claim 12 or 13, characterized by the fact that For plastic elongation as an increase in the length of the at least one pipe connection device (44) in each pipe connection device (44), the at least one positive-locking connecting element (45) on each pipe connection device (44) is also subjected to a force, in particular tensile force, so that a deformation, in particular bending and / or elongation, of the at least one positive-locking connecting element (45) on each pipe connection device (44) is also carried out.
15. Electrochemical cell unit (1, 6, 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 R. 417808 - 27 - - stacked electrochemical cells (4, 5, 9, 24) arranged as a cell stack (3, 8), - a first clamping element (18, 19, 20) for applying a compressive force to a first electrochemical cell (4, 5, 9, 24), - a second clamping element (18, 19, 21) for applying a compressive force to a last electrochemical cell (4, 5, 9, 24), - at least one connecting device (10, 22, 23) subjected to a tensile force, which is in direct or indirect mechanical connection with the first and second clamping elements (18, 19, 20, 21), such that, due to the tensile force in the at least one connecting device (10, 22, 23), a compressive force can be applied from the first clamping element (18, 19, 20) to the first electrochemical cell (4, 5, 9, 24) and from the second clamping element to the last electrochemical cell (4, 5, 9, 24). is applicable and the cell stack (3, 8) is prestressed with a compressive force. characterized by the fact that which produces at least one connecting device (10, 22, 23) using a method according to one or more of the preceding claims.