Electrochemical system unit with a sealing element

Abstract

The present invention describes an electrochemical system unit having a plurality of layered electrochemical cells arranged successively one behind the other, each of the electrochemical cells having an anode plate, a cathode plate, and a sealing element, wherein the sealing element is arranged to seal the space between the anode plate and the cathode plate; and at least two of the electrochemical cells of the electrochemical system unit have different manufacturing types of the sealing element.

Description

Technical Field

[0001] The present invention relates to an electrochemical system unit with a sealing element for an electrochemical cell stack. Background Art

[0002] Electrochemical devices can have electrochemical cells for converting electrical energy into chemical energy or for converting chemical energy into electrical energy.

[0003] Examples of electrochemical devices are polymer electrolyte membrane (PEM) fuel cells, solid oxide fuel cells (SOFC), also generally high-temperature or low-temperature fuel cells, and electrolyzers or redox flow batteries.

[0004] As an example of an electrochemical device, a fuel cell or a battery pack is typically used as a current source for powering an electric motor or machine or for a stationary decentralized energy system. Here, electric drive devices are increasingly part of the vehicle drive device for electric bicycles, electric vehicles, hybrid vehicles or other vehicles. Such systems allow for efficient energy supply and have the advantage of environmental protection.

[0005] A fuel cell converts a pair of chemical reactions, i.e., a fuel and an oxidant, into reaction products in an electrode reaction, wherein electrical energy is provided. A fuel cell typically uses an electrolyte that is arranged between two electrodes, i.e., a cathode and an anode. Catalysts typically facilitate the desired electrochemical reactions at the electrodes.

[0006] Since a single fuel cell does not generate much energy and only generates a small voltage (e.g., about 0.7 - 0.9 volts), multiple fuel cells can be arranged together in a stack in order to generate sufficient electrical energy for the operation of a motor vehicle or in order to stably generate electrical energy.

[0007] Fuel cells, such as proton exchange membrane (PEM-) fuel cells, typically comprise a membrane electrode assembly (MEA) that is formed by a membrane sheet coated with a catalyst, the membrane sheet being arranged between a pair of gas diffusion layers. The membrane sheet coated with a catalyst itself typically has an electrolyte membrane sheet that is arranged between a pair of catalyst layers. Summary of the Invention

[0008] Generally, an electrochemical cell is sealed by a seal in order to prevent leakage of pressurized gases and liquids. In order to ensure that pressurized gases and liquids do not bypass the electrolyte membrane sheet, the seal is typically formed around the periphery of the electrochemical cell.

[0009] The sealing element causes a sealing effect by means of extrusion pressure, which must be considered when sealing a fuel cell stack with the aid of the sealing element. When the membrane electrode assembly (MEA) arranged inside the electrochemical cell is strongly compressed, the anode layer and the cathode layer come into contact through the corresponding electrolyte membrane, which results in an electrical short circuit. Correspondingly, too weak compression results in the fuel cell not being sealed by means of the sealing element.

[0010] A fuel cell stack or an electrochemical cell stack is typically manufactured by repeatedly laminating hundreds of fuel cells or electrochemical cells. Each of these electrochemical cells is provided with a seal in order to seal the reaction gas and the cooling water relative to each other inside the electrochemical cell.

[0011] Since hundreds of electrochemical cells are stacked under the action of a predetermined pressure load, each seal remains in a compressed state, for example, for 80,000 hours during the service life of the electrochemical cell or the fuel cell stack.

[0012] A fuel cell stack or an electrochemical cell stack typically operates under different conditions of temperature, pressure, and relative humidity. During the service life of the fuel cell stack, each individual fuel cell must ensure tightness, especially with respect to the fuel gas and the corresponding oxidizing gas.

[0013] The present invention discloses an electrochemical system unit according to the features of the independent claims. Advantageous configurations are the subject matter of the dependent claims and the following description.

[0014] The present invention relates to the recognition that the use of a uniform sealing element having irregularities in certain partial regions of the sealing element determined by manufacturing may be disadvantageous for the sealing effect, since these correspondingly arranged irregularities of the sealing element can act together such that leak tightness is produced.

[0015] Aspects of the present invention relate to an electrochemical system unit having a plurality of electrochemcial cells arranged one above the other in layers, each of the electrochemical cells having an anode plate, a cathode plate, and a sealing element. Here, the sealing element is arranged to seal the space between the anode plate and the cathode plate. In this electrochemical system unit, at least two electrochemical cells have different manufacturing types of sealing elements.

[0016] Such an electrochemical system unit can be used to convert electrical energy into chemical energy or to convert chemical energy into electrical energy. Examples of such conversions are fuel cells, redox flow batteries, or electrolytic cells.

[0017] With such an electrochemical system unit, a fuel cell stack, also referred to as a fuel cell stack-up, can be constructed, for example. A plurality of electrochemically cells arranged successively in layers can include a small number of cells, for example two or three cells, and the plurality can also include 100 cells, or a larger number of electrochemically cells can be arranged close to each other, for example to form a fuel cell stack.

[0018] When different manufacturing types of sealing elements are used in such a successive arrangement with each other, these manufacturing types can interact in such a way that irregularities caused, for example, by the manufacturing of the sealing elements are either compensated for or at least do not accumulate, for example, in partial regions of the sealing elements. Such accumulation occurs when sealing elements of the same manufacture of individual fuel cells or electrochemically cells, having irregularities in corresponding partial regions, are arranged successively with each other and a compressive force is applied. Leakage occurs when sealing elements of the same manufacture with irregularities in corresponding partial regions are arranged successively with each other.

[0019] Such irregularities can occur in different partial regions of the sealing element and are, for example, related to the width of the seal, the compressibility, hardness, crosslink density, residual pressure deformation or other mechanical properties, in particular, of the sealing element in this partial region.

[0020] The different manufacturing types of the sealing elements basically relate to different manufacturing methods of sealing elements that are as identical in shape as possible in terms of geometric and mechanical properties. However, depending on the manufacturing method, local differences determined by the manufacturing, i.e., differences in the sealing element in different partial regions, are usually inevitable.

[0021] In particular, the number of different manufacturing types is also significantly greater than two, which occurs especially in the following cases: for example, when the elasticity of the sealing elements of adjacent fuel cells is not sufficient to compensate for local non-uniformities or irregularities, but more sealing elements of adjacent fuel cells are required to compensate for such irregularities.

[0022] In addition, the manufacturing-determined irregularities can be arranged locally on partial regions of the sealing element on which external forces act, for example, in the form of clips of the fuel cell stack, in order to reduce or avoid leakage due to such local irregularities of the sealing element. Since this pressure acts on the individual fuel cells via the end plates of the fuel cell stack and the end plates are deformable, different mechanical pressures act through different partial regions of the sealing element.

[0023] The successively arranged electrochemically cells can have a membrane electrode assembly between their cathode and anode plates, at which the actual electrochemical reaction takes place.

[0024] The sealing element can undertake different sealing tasks in different spatial regions between the cathode plate and the anode plate. On the one hand, the sealing element can separate the cathode chamber from the anode chamber so that the fuel and the oxidant can only meet in the region of the catalyst. On the other hand, the sealing element can be used to seal the corresponding reaction chambers of the cathode and the anode relative to the cooling circuit and also undertake additional tasks for gas distribution inside the electrode chambers.

[0025] According to another aspect, the anode plate and the cathode plate of at least one electrochemical cell are each configured as a bipolar plate. In this case, the bipolar plate is used as the anode plate, for example, on one side of the arrangement of at least two electrochemical cells and as the cathode plate on the other side. The thus configured anode plate or cathode plate can also relate to multiple fuel cells or can relate to all fuel cells, configured as bipolar plates, except for the respective outer fuel cells, end plates.

[0026] When the fuel cell or the electrochemical cell is configured with a bipolar plate, the entire fuel cell stack can be manufactured smaller with the same number of fuel cells.

[0027] According to another aspect, different manufacturing types of the sealing element are applied to the electrode plates of the electrochemical cell by means of an injection molding method or a dispensing method.

[0028] In this injection molding method for manufacturing the sealing element, the corresponding anode plate or cathode plate is introduced into the injection mold so that a very small change in the density of the sealing element can be achieved during manufacturing.

[0029] The advantage of the dispensing method is that the cost for manufacturing the corresponding injection mold is eliminated.

[0030] Here, the sealing element can be applied to one of the two electrode plates, i.e., the cathode plate or the anode plate, or also to both electrode plates.

[0031] For manufacturing the sealing element, for example, thermoplastics (PET, PP, PE, EPDM), thermoplastic elastomers (TPA - A, TPE - E, TPE - O, TPS, TPU, TPV), elastomers and thermosetting plastics (silicone resin, epoxide, urethane, fluororubber, acrylate) can be used for the injection molding method. For the dispensing method, for example, silicone resin, acrylate, epoxide, urethane can be used, and the corresponding materials are used for insertion.

[0032] According to one aspect, different manufacturing types of a sealing element are inserted into an electrochemical cell. Here, the different manufacturing types of the sealing element are manufactured in different types outside the electrochemical cell, i.e., without being applied to one of the two electrode plates, and then inserted between the electrode plates in order to seal the corresponding fuel cell in the assembled state of the fuel cell stack.

[0033] According to another aspect, different manufacturing types of the sealing element are molded between the cathode plate and the anode plate by means of an injection molding method or a dispensing method. In this method, it must be ensured that during the molding of the sealing element, the two electrodes of a fuel cell have a defined distance relative to each other. In this method, the adhesion to the two electrodes of the corresponding fuel cell can improve the sealing performance.

[0034] According to one aspect, at least two different manufacturing types of the sealing element have manufacturing-determined irregularities in different partial regions of the sealing element.

[0035] This avoids that, through the correspondingly arranged irregularities of the same sealing element, the irregularities can act together in such a way that a leak-tightness is thereby produced.

[0036] According to one aspect, the sealing element has manufacturing-determined irregularities at the initial partial region and / or the end partial region of the manufacturing of the respective sealing element. For example, in the manufacturing method of the sealing element by means of an injection molding method, injection points are generated at the locations where the material of the sealing element is pressed into the mold. In addition, this location or this partial region of the sealing element is exposed to a higher heat load during the manufacturing method, which can cause inhomogeneous properties of the material of the sealing element at this location. Since this location must be identified, for example, the injection points can be changed by means of a corresponding casting tool, which either has different injection points accordingly or can be realized by means of so-called "Moving Inserts". Here, the sealing element can also be manufactured with multiple injection points, because in this case the injection points can also be arranged in different partial regions of the sealing element. In this case, the multiple injection points correspondingly correspond to multiple irregularities of the sealing element at multiple partial regions.

[0037] According to one aspect, different manufacturing types of the sealing element have the initial partial region and / or the end partial region of the manufacturing of the sealing element in different spatial regions of the sealing element.

[0038] This means for the dispensing of the sealing element, for example, that the initial point and / or the end point of the application of the material for the sealing element changes with respect to the spatial arrangement of the sealing element, thereby producing different sealing elements in this way, which are arranged, for example, offset relative to each other in fuel cells arranged side by side, in order to ensure better sealing.

[0039] According to one aspect, it is proposed that the at least two different production types of the sealing element have production-determined irregularities in different spatial regions of the sealing element by virtue of at least two different positions of the injection point of the injection molding method with respect to the configuration of the sealing element.

[0040] According to a further aspect, it is proposed that the at least two different production types of the sealing element have production-determined irregularities in different spatial regions of the sealing element by virtue of at least two different positions of the starting point of the dispensing method with respect to the configuration of the sealing element.

[0041] According to one aspect, it is proposed that the at least two different production types of the sealing element are arranged in an electrochemical system unit and act together in such a way that the production-determined irregularities are compensated. Here, by means of an offset arrangement with respect to the orientation in the fuel cell stack, for example, it can be achieved that the seals of successively arranged fuel cells can, for example, compensate for the inhomogeneities or irregularities of adjacent seals by virtue of their inherent elasticity, or at least prevent these irregularities from interacting with each other in such a way that a lack of sealing results due to the corresponding arrangement of the irregularities.

[0042] When using more than two different sealing elements, which each have production-determined irregularities in a further partial region of the sealing element, the effect of such irregularities can be evenly distributed over the partial regions of the sealing element by means of a suitably offset arrangement, in order to minimize the adverse effects on the sealing.

[0043] According to one aspect, it is proposed that the at least two different production types of the sealing element are arranged inside the electrochemical system unit in the electrochemical system unit in such a way that the production-determined irregularities of the sealing element are spatially offset relative to each other.

[0044] According to a further aspect, it is proposed to select the production types of the sealing elements of at least two adjacent electrochemical cells at the lower end in the system unit in such a way that the irregularities of the sealing elements do not correspond spatially. This reduces the interaction of the correspondingly arranged irregularities and results in better sealing of the sealing element.

[0045] According to one aspect, a sealing element is provided between the outside of at least one first electrochemical cell and a second electrochemical cell arranged adjacent in a system unit for sealing the space between two electrochemical cells having a sealing element according to claims 3 to 12.

[0046] When a bipolar plate is not used between the electrochemical cells, this intermediate space is typically used for cooling the electrochemical cells. Here, the sealing of this intermediate space can also be improved by using the described sealing element and arranging the irregularities of the sealing element there such that the sealing element does not correspond to the sealing element of another cooling intermediate space. In particular, the irregularities of the sealing element of the cooling intermediate space can also be jointly assigned to partial regions of the sealing element together with the irregularities of the sealing element of the electrochemical cell, such that overall an optimized sealing is caused.

[0047] According to a further aspect, a membrane electrode assembly is arranged in the space between the cathode plate and the anode plate of the electrochemical cell.

[0048] According to a further aspect, two successively arranged electrochemical cells have sealing elements manufactured differently.

[0049] According to a further aspect, such a number of different sealing elements are manufactured, in which manufacturing-determined irregularities are arranged in different partial regions of the sealing element respectively, and these irregularities are necessary in order to minimize the influence on the sealing of the electrochemical cell stack by the joint action of successively arranged electrochemical cells having such sealing elements.

[0050] According to a further aspect, the irregularities are distributed on the periphery of the sealing element of the electrochemical cell such that the irregularities are arranged below the clips causing the clamping force of the electrochemical cell stack. That is, the influence of the irregularities on the sealing of the electrochemical cell can be further reduced by arranging the irregularities in a region with increased pressure.

[0051] According to a further aspect, the irregularities are distributed on the periphery of the sealing element of the electrochemical cell as there are a plurality of different manufacturing types of the sealing element.

[0052] A method for manufacturing an electrochemical system unit as described above is proposed, wherein the at least two manufacturing types of the sealing element are caused by a change in the starting point of the manufacturing of the sealing element.

[0053] The application of the electrochemical system unit as described above for the energy supply of a mobile platform is proposed.

[0054] A mobile platform can be understood as an at least partially automated and mobile system and / or driver assistance system. Examples can be an at least partially automated vehicle or a vehicle with a driver assistance system. That is, an at least partially automated system in this regard includes a mobile platform with respect to the functionality of at least partial automation, but the mobile platform also includes vehicles and other mobile machines, including driver assistance systems. Further examples for mobile platforms can be driver assistance systems with multiple sensors, mobile multi-sensor robots such as robotic vacuum cleaners or lawn mowers, multi-sensor monitoring systems, manufacturing machines, personal assistants or access control systems. Each of these systems can be a fully or partially automated system. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Embodiments of the present invention are shown in the attached Figures 1 to 4 drawings and are explained in detail below and are used to better understand the present invention.

[0056] The drawings show:

[0057] Figure 1 Sealing elements with different injection points;

[0058] Figure 2 Pouring tools with four different injection points;

[0059] Figure 3 Cross-sections of fuel cells with a bounded cooling chamber; and

[0060] Figure 4 Exploded views of electrodes of an electrochemical cell with a sealing element.

[0061] In the drawings, identical or similar components are marked with identical or similar reference numerals, where in individual cases the repeated description of these components is dispensed with. DETAILED DESCRIPTION

[0062] Figure 1 Schematically shows four different manufacturing types 10a to 10d of a sealing element 38, where in these examples the irregularities 12 of the sealing element 38 are present in the form of injection points 12, and these four different manufacturing types 10a to 10d of the sealing element 38 have this irregularity at four corresponding different partial regions of the sealing element 38.

[0063] In one manufacturing type 10a for the sealing element 38 Figure 1The injection gland (Anspritzdrüse) 14 is depicted, which creates injection points 12 during the production of the sealing element 38 of type 10a. Here, the irregularities 12 of this production type 10a of the sealing element 38 can go beyond a mere magnification of the sealing surface in this area and be attributed, for example, to a material change of the sealing elements 10a, 38 caused by a greater energy input at this location.

[0064] Figure 2 Schematically shown is a casting tool 20, in which, for example, there are recesses 24 for the production of the sealing element 38. For the production of four different production types 10a to 10d of the sealing element 38, the casting tool 20 has, for example, four different injection glands 22a to 22d. When using these casting tools 20 for the production of different production types 10a to 10d of the sealing element 38, a larger number of injection glands 22a to 22d can also be used, which are correspondingly arranged in different partial regions of the sealing element 38. In Figure 2 the example of the casting tool 20, for example, two different production types of the sealing element can be correspondingly produced when using two of each of the nozzles 22a, 22b, 22c, or 22d.

[0065] Figure 3 Schematically shown is a cross-section of an electrochemical cell 30, which has a bounded cooling chamber 35, which has an anode plate 32, a cathode plate 36, a membrane electrode assembly 34, an anode chamber 31, a cathode chamber 33, and a sealing element 38. By an externally acting force, the assembled fuel cell stack applies this force to the electrode plates 32, 36 of such a formed fuel cell or electrochemical cell 30, causing the sealing element 38 to be in close contact with the membrane electrode assembly 34 and the corresponding opposing electrodes 32, 36, and causing the sealing effect of the sealing element 38 by this force.

[0066] Figure 4 Schematically shown is the electrode 36 of the electrochemical cell 30, which has penetrations 36a, 36b at the upper or lower ends of the electrodes 32, 36, which form channels for the supply and discharge of fuel, oxidant, and coolant when the electrochemical cells 30, such as fuel cells, are stacked on top of each other, and are separated from each other by means of sealing elements 38a, 38b, which can be arranged either on the upper side or the lower side of the electrodes 32, 36.

[0067] In Figure 4 two different production types 38a, 38b of the sealing element 38 are used, which have production-determined irregularities 40a or 40b in corresponding different partial regions of the sealing elements 38a, 38b.

Claims

1. An electrochemical system unit having a plurality of layered electrochemical cells (30) arranged successively one above the other, each of the electrochemical cells having an anode plate (32), a cathode plate (36) and a sealing element (38), wherein, the sealing element (38) is arranged between the anode plate (32) and the cathode plate (36); and at least two of the electrochemical cells (30) of the electrochemical system unit have different manufacturing types (10a, 10b, 10c, 10d, 38a, 38b) of the sealing element (38), wherein at least two different manufacturing types (10a, 10b, 10c, 10d, 38a, 38b) of the sealing element (38) have manufacturing-determined irregularities (12, 40a, 40b) in different partial regions of the sealing element (38), wherein the sealing element (38) has the manufacturing-determined irregularities (12, 40a, 40b) at an initial partial region and / or an end partial region of the manufacturing of the respective sealing element (38), wherein at least two different manufacturing types (10a, 10b, 10c, 10d, 38a, 38b) of the sealing element (38) are arranged in the electrochemical system unit such that the manufacturing-determined irregularities (12, 40a, 40b) of the sealing element (38) are offset relative to one another in a projection onto the plane in which the layered electrochemical cells (30) are located, wherein at least two different manufacturing types (10a, 10b, 10c, 10d, 38a, 38b) of the sealing element (38) are arranged in the electrochemical system unit and they cooperate such that the manufacturing-determined irregularities (12, 40a, 40b) are compensated for.

2. The electrochemical system unit according to claim 1, wherein, the anode plate (32) and the cathode plate (36) of at least one electrochemical cell (30) are each configured as bipolar plates.

3. The electrochemical system unit according to claim 1 or 2, wherein, the different manufacturing types (10a, 10b, 10c, 10d, 38a, 38b) of the sealing element (38) are applied to the electrode plates (32, 36) of the electrochemical cell (30) by means of an injection molding method or a dispensing method.

4. The electrochemical system unit according to claim 1 or 2, wherein, the different manufacturing types (10a, 10b, 10c, 10d, 38a, 38b) of the sealing element (38) are inserted into the electrochemical cell (30).

5. The electrochemical system unit according to claim 1 or 2, wherein, the different manufacturing types (10a, 10b, 10c, 10d, 38a, 38b) of the sealing element (38) are molded between the cathode plate (36) and the anode plate (32) by means of an injection molding method or a dispensing method.

6. The electrochemical system unit according to claim 1 or 2, wherein, At least two different manufacturing types (10a, 10b, 10c, 10d, 38a, 38b) of the sealing element (38) have the manufacturing-determined irregularities (12, 40a, 40b) in different spatial regions of the sealing element (38) at at least two different positions of the injection points of the injection molding method with respect to the configuration of the sealing element (38).

7. The electrochemical system unit according to claim 1 or 2, wherein, At least two different manufacturing types (10a, 10b, 10c, 10d, 38a, 38b) of the sealing element (38) have the manufacturing-determined irregularities (12, 40a, 40b) in different spatial regions of the sealing element (38) at at least two different positions of the starting point of the dispensing method with respect to the configuration of the sealing element (38).

8. The electrochemical system unit according to claim 1 or 2, wherein, A membrane electrode unit (34) is arranged in the space between the cathode plate (36) and the anode plate (32) of the electrochemical cell (30).

9. A method for manufacturing the electrochemical system unit according to any one of claims 1 to 8, wherein, At least two different manufacturing types (10a, 10b, 10c, 10d, 38a, 38b) of the sealing element (38) are caused by changing the starting point of the manufacturing of the sealing element (38).

10. Use of the electrochemical system unit according to any one of claims 1 to 8 for the energy supply of a mobile platform.

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