Plate assembly for an electrochemical cell

Abstract

An electrochemical cell (1), in particular a plate assembly (2) for a fuel cell, comprising a grid formed as expanded metal (3) provided for sandwich-like arrangement between a first plate (5) located in a base plane and a second plate (4) parallel to the first plate (5), the grid having a plurality of nodules (6) and webs (10, 11) connecting the nodules (6), wherein nodule rows (KR1, KR2) defining a longitudinal direction (LR) are formed, which extend parallel to each other in a plan view of the grid (3) from above, and all nodules (6) have a planar, bent shape with a fold line oriented transversely to the longitudinal direction (LR) separating two nodule sections (7, 8) from each other. A plate assembly (2) wherein in at least a subset of the nodules (6), each one of the nodule sections (7) is arranged at least substantially parallel to the above-mentioned plates (4, 5).

Description

Technical Field

[0001] The present invention relates to a plate assembly including a grid formed as expanded metal, which is defined for use in an electrochemical cell, particularly a fuel cell, as described in the preamble of claim 1.

Background Art

[0002] Such a plate assembly of an electrochemical cell is known, for example, from German Patent Invention No. 112009004658. This known plate assembly is defined for use in a fuel cell and includes a so-called gas passage forming element, which exists in the form of an expanded metal grid. The connecting sections of the expanded metal, i.e., the nodes, have distinguishable sections, and these sections are inclined in different forms with respect to a plate, particularly in the form of a separator, into which the expanded metal is inserted. An acute angle may be formed particularly between the node section and the plate. The angle formed between one section of the node and the separator is smaller than the angle formed between another section of the node and the gas diffusion layer. German Patent Invention No. 112009004658 defines the production of expanded metal from titanium.

[0003] DE11200700017T5 is directed to a method for forming a gas diffusion layer for a fuel cell. Within the framework of this method, a metal grid processing device for processing a special steel thin plate is used. The special steel thin plate can be supplied to a holding mechanism using supply rollers. Similarly, through holes are formed in a lattice-like offset arrangement by a cutting tool belonging to the metal grid processing device. These through holes have a hexagonal shape and provide a free cross-section when the grid is incorporated into the fuel cell.

[0004] The separator for a fuel cell described in U.S. Patent No. 8,206,865 is in contact connection by a current collector formed from a metal lattice. The possibility of laminating a number of metal lattices to form the current collector is also mentioned. It is desirable that the contact area between the current collector and the electrode layer be equal to or greater than the contact area between the current collector and the separator body.

[0005] Another element forming a gas flow path within a fuel cell battery is disclosed in U.S. Patent No. 9,160,026. Also in this case, the element forming the gas flow path is provided in the form of a metal lattice structure. The above-described element has a plurality of annular sections forming through openings.

[0006] U.S. Patent No. 9,450,253 describes possible geometric details of a cell structure of a fuel cell formed from expanded metal. Also in this case, the mesh of the expanded metal exhibits a hexagonal or other polygonal shape. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0007] The problem underlying the present invention is to improve elements for electrochemical cells, in particular fuel cells, with respect to the above prior art, particularly from the viewpoints of flow technology and manufacturing technology, and in particular to aim for a robust structure suitable also for mobile applications of end products in the form of fuel cell stacks, i.e., fuel cell systems or other electrochemical systems. MEANS FOR SOLVING THE PROBLEM

[0008] According to the present invention, this problem is solved by a plate assembly suitable for use in an electrochemical cell having the features described in claim 1. The plate assembly is suitable for forming a stack of electrochemical cells described in claim 10.

[0009] The plate assembly, based on a known basic concept, includes a lattice formed as expanded metal, which is provided to be arranged in a sandwich-like manner between a first plate located in a base plane and a second plate parallel to the first plate. The lattice has a plurality of nodes and webs connecting the nodes, and in a plan view of the lattice seen from above, a row of nodes defining a longitudinal direction is formed, which extends parallel to each other. All the nodes have a planar bent shape with a fold line oriented transversely to the longitudinal direction, which separates two node segments of each node from each other.

[0010] According to claim 1, in at least a subset of the nodes, one node segment of each of the two node segments is arranged at least substantially parallel to the above-mentioned plate. In this case, the substantially parallel arrangement means that the corresponding node segment forms an angle of 15° or less with the adjacent plate of the electrochemical system. In particular, the corresponding node segment may be flatly placed on the above-mentioned plate formed by the membrane electrode assembly.

[0011] Due to this shape of the expanded metal, multiple functions of the plate assembly are equally fulfilled. On the one hand, a large-sized contact area as a whole is provided by a large number of node segments of the expanded metal that are at least substantially parallel to the plate. This contact area receives the force in the plate stack with an appropriate surface pressure and conducts an electric current. On the other hand, the inclined plate segments, together with the lattice, i.e., the webs of the expanded metal, provide an intentional flow guiding effect, and the medium flowing between the plates obtains a flow component perpendicular to the plate.

[0012] Each node section that is arranged parallel to the plate or is merely slightly inclined with respect to the plate, i.e., at an angle of less than 15°, is connected via two webs to a node section that is inclined to a large extent with respect to the plate defining the base plane, i.e., forms a larger angle with the plate, unless this node section is arranged at the edge of the grid. This means that the webs themselves are twisted. This contributes to both the flow guide and the mechanical stability of the expanded metal.

[0013] According to a possible configuration, in some nodes of the expanded metal, particularly in nodes arranged in a specific row, while a first node section is planar-ly placed on a base plane that may be generated by a membrane electrode assembly, in another node typically arranged in a row in a similar manner, there is a gap between the node and the above-mentioned plane, and the first node section is arranged in a plane parallel to the base plane. In this configuration, indeed, compared to an embodiment where the first node section of each node is in contact connection with the base plane, a generally smaller contact area occurs between the node and one of the plates applied to the expanded metal. However, precisely based on the node section lifted from the base plane, there is an expanded free cross-section for the medium flowing through the plate assembly.

[0014] The nodes placed on the base plane and the nodes lifted from the base plane may be alternately arranged in one node row extending in the longitudinal direction of the expanded metal. Similarly, for example, a variant of the expanded metal can also be realized where two rows of nodes always arranged side by side are placed on the base plane and a third row of nodes is lifted from the base plane.

[0015] When manufacturing expanded metal from a thin metal sheet that initially has no openings, it is possible to work using a variable feed of the thin metal sheet, and this feed is reflected in the finished product, i.e., the expanded metal, in that there are nodule sections of various lengths. The length can be measured in the feed direction. The feed direction forms a right angle with the broken line that forms the boundary line between both nodule sections. In each nodule section, its length is measured on the surface of each nodule section. That is, it is not measured in the projection view of the nodule on the base plane.

[0016] Due to the variable feed that the thin metal sheet to be processed into expanded metal undergoes, four different types of nodules can be formed in a single manufacturing process within one and the same lattice existing in the form of expanded metal. That is, in the first nodule row, there are nodules formed from two long nodule sections, and one of the two nodule sections can be placed flat on the base plane. Between each two such so-called large nodules, there are nodules formed from two relatively short nodule sections, called small nodules, and in this case, both nodule sections are arranged inclined with respect to the base plane. In the second nodule row that is completely lifted from the base plane, there are various variations of medium-sized nodules. Each one of the nodule sections of the nodule sections is spaced apart from the base plane and from the second plate, for example, spaced apart in parallel, while the second nodule section that is tilted as a single section or more strongly tilted makes a linear contact connection with the second plate.

[0017] The first variation of the node part is formed by a short node part section, one of the two lengths, particularly parallel to the plate, and a long second node part section. In the second variation, the reverse situation exists. In this case, a short inclined node part section reaching the second plate is connected to the long node part section parallel to the plate. The webs connecting the node parts extend from one long node part section to another long node part section or between two short node part sections, and thus each web has a certain width by itself.

[0018] Furthermore, due to another variation in the feed length during manufacturing, an expanded metal lattice with three or more different node part rows, for example, three or four different node part rows, can also be realized. It is also conceivable that the various types of node part rows are each composed only of nodes where the adjacent sections have different lengths in each individual case.

[0019] Generally, the node part section is also called a half node. When the node part section is arranged parallel to the base plane, it is simply called a horizontal node part section regardless of the actual orientation of the plate assembly in space. In various forms of expanded metal, an angle, for example, at least 90° and at most 150°, may be formed between the two node part sections of one node.

[0020] The plate generally called the second plate is particularly a bipolar plate. As is known per se, the bipolar plate may be composed of two half metal sheets, and a passage for a coolant is formed between these two half metal sheets. A configuration of the second plate as a monopolar plate is also possible. In the case of both the bipolar plate and the monopolar plate, the name separator is also used for the second plate.

[0021] A first plate-like assembly, hereinafter referred to as the first plate for short, which defines a base plane, includes in particular a proton-permeable polymer electrolyte membrane (PEM). In a typical configuration, a porous anode catalyst layer, a cathode catalyst layer, and a porous gas diffusion layer, which should likewise belong to the first plate, are adjacent to the PEM. Thus, in a plate stack including a plurality of plate assemblies of the same type, there are contacts between various gas diffusion layers and the expanded metal lattice. Regardless of the geometric configuration of the expanded metal, the expanded metal lattice forms a flow region for the operating medium of the electrochemical system in any case.

[0022] In the previously described configuration in which expanded metal manufactured by variable feed is used, the row of nodules lifted from the base plane may be spaced apart by a distance that, for example, corresponds to at least 30% and at most 60% of the thickness of the expanded metal lattice, i.e., the distance between the two plates, measured from the base plane.

[0023] According to another possible embodiment, the nodules of the first type of nodule row contact and connect exclusively to the first plate of the plate assembly, while the nodules of the second type of nodule row contact and connect exclusively to the second plate. In this case, the nodule segments of all nodules may have a uniform length, and - when viewed in the lateral direction of the expanded metal - the first type and the second type of nodule rows are arranged alternately. Assuming that the plate assembly is arranged horizontally, the nodules of the various nodule rows are located at different heights from each other, which can be regarded as a waveform in the lateral direction of the expanded metal. This waveform opens a particularly large flow cross-section within the plate assembly. In this case, all webs have a uniform width defined by the feed during the manufacturing process.

[0024] In an improved embodiment, the variable feed that appears in the nodular section of non-uniform width is combined with the wave formation of the expanded metal. Also in this case, as in the configuration already described in detail, there are various nodular section rows, and in one nodular section row, long nodular sections and short nodular sections are alternately arranged in sequence, while in the second nodular section row, nodular sections of various intermediate lengths exist. Different from the configuration already described, this improved embodiment may be particularly excellent in that the nodular sections of intermediate length are lifted particularly greatly from the first plate. By the horizontal nodular section distance of these nodular sections from the first plate within a range of, for example, 50% ± 10%, particularly 50% ± 5% of the distance between the plates, a plurality of flow passages are formed that extend longitudinally through the plate assembly and are dimensioned particularly large, and these flow passages may extend from the inlet to the outlet of the flow region.

[0025] Hereinafter, four embodiments of the present invention will be described in detail with reference to the drawings.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0027] The following description applies to all embodiments unless otherwise specified. Parts or outlines of parts that correspond to each other or act equivalently in principle are denoted by the same reference numerals in all the drawings.

[0028] The electrochemical cell, generally designated by the numeral 1, is a fuel cell in this embodiment, and this fuel cell includes a plurality of stacked plate assemblies 2 of the same type. For the principle structure and function of the stack of the electrochemical cell 1, reference may be made to the prior art cited at the beginning.

[0029] The plate assembly 2 may include an expanded metal lattice 3, which is also referred to simply as expanded metal or lattice. Further, the plate assembly 2 includes a membrane electrode assembly including a first plate-like assembly 5, also simply referred to as the first plate, which is a gas diffusion layer. Further, the plate assembly 2 may include a second plate 4 which is part of a bipolar plate.

[0030] The surface of the plate 5 that makes contact connection with the expanded metal 3 defines the base plane of the plate assembly 2. There are significant differences in mechanical load resistance between the two plates 4 and 5. Both plates 4 and 5 are intended to guide current, and the current flows particularly through the contact connection regions between the lattice 3 and the various plates 4 and 5. The expanded metal 3 is also given an important function regarding the guidance of liquid and / or gaseous media, i.e., the operating media of the electrochemical cell 1.

[0031] The grid 3 has a plurality of nodular parts 6, and each of these nodular parts 6 has a first nodular part section 7 and a nodular part section 8 inclined with respect to the first nodular part section 7, and can be confirmed in a partially simplified form in the drawing. The first nodular part section 7 is arranged parallel to the plates 4 and 5 in this embodiment. The nodular part sections 7 and 8 are adjacent to each other with a broken line. The angle between the nodular part sections 7 and 8 is represented by α.

[0032] The nodular parts 6 of the grid 3 are connected to each other by webs 10 and 11, whereby an opening 9 having a rhombic basic shape is formed. The flow passage formed between the plates 4 and 5 by the grid 3 is generally indicated by reference numeral 12. The medium flowing through the plate assembly 2 generally flows in the longitudinal direction of the plate assembly 2 indicated by LR. In the longitudinal direction LR, the mesh dimension SWD (short-side center-to-center distance) of the grid 3 can be measured. The dimension LWD (long-side center-to-center distance) can likewise be measured in a conventional manner in a direction transverse to the longitudinal direction LR. KB indicates the nodular part width, that is, the coinciding width of the nodular part sections 7 and 8. SH indicates the expanded metal height, that is, the distance between the plates 4 and 5. The substantially uniform wall thickness to be measured in the horizontal section 7 of the grid 3 is indicated by WS. The nodular parts 6 are arranged in nodular part rows KR1 and KR2 extending in the longitudinal direction LR.

[0033] In the embodiments shown in FIGS. 1 to 5, unlike the embodiments shown in FIGS. 6 to 14 and FIGS. 20 to 26, all the nodule rows KR1, KR2 are formed in the same manner. Here, all the nodule sections 7 are flatly placed on the first plate 5, that is, on the membrane electrode assembly. In contrast, in this embodiment, the flat second plate 4 in the illustrated region is in contact connection only by the edge of the second nodule section 8, which is acceptable based on the given current capacity and mechanical load capacity of the second plate 4. In the flow direction, that is, the longitudinal direction LR, each nodule 6 of the expanded metal 3 shown in FIG. 1 forms an obstacle filling the space between the plates 4, 5, and the inclination of the section 8 contributes to deflecting the medium in the direction of the adjacent webs 10, 11 passing through the nodule 6. Each web 10, 11 connects the horizontal nodule section 7 to the inclined nodule section 8. This means that the webs 10, 11 themselves are twisted. Such twisting of the webs 10, 11 is also provided in all other embodiments and contributes to the flowing medium obtaining a movement component perpendicular to the plates 4, 5. Furthermore, the twisting of the webs 10, 11, together with the bent shape of the nodules 6, enhances the stability of the entire expanded metal 3.

[0034] The embodiments shown in FIGS. 6 to 12 are clearly different from the embodiments according to FIGS. 1 to 5 in that different lengths are given to the adjacent sections 7, 8 of the nodules 6. This is achieved by the variable feed of the metal sheet from which the expanded metal 3 is manufactured.

[0035] As can be particularly seen from FIG. 12, in the expanded metal lattice 3 shown in FIG. 6, all the nodules 6 of the first nodule row KR1 are lifted from the membrane electrode assembly 5. In contrast, as can be seen from FIG. 11, the nodules 6 of the second nodule row KR2 are applied to the thin film electrode assembly 5 in a planar or linear manner. In the latter case, the nodule row KR2 is formed by alternately arranged long nodules 6 and short nodules 6. The length of the first nodule section 7 of the long nodule 6 among the long and short nodules is indicated by L1. The inclined nodule section 8 connected to the long nodule section 7 has a length L2, and the length L2 coincides with the length L1 in the illustrated case. The adjacent nodules 6 in the nodule row KR2 are short nodules, and in this case, the two nodule sections 7 and 8 are inclined with respect to the plates 4 and 5 in different manners. Each of the nodule sections 7 and 8 has a length L3 that is shorter than the length L1. By inclining the short nodules 6 more significantly compared to the long nodules 6, the short nodules 6 also extend from the surface of the bipolar plate 4 to the surface of the first plate 5. Therefore, all the nodules 6 of the nodule row KR2 of the lattice 3 shown in FIG. 6 extend over the entire expanded metal height SH.

[0036] Unlike the nodules 6 of the nodule row KR2, all the nodules 6 of the first nodule row KR1 do indeed contact and connect to the second plate 4, but do not contact and connect to the first plate 5. In the case of the first nodule row KR1, at each nodule 6, a combination 7, 8 of a short nodule section and a long nodule section is provided. When the first nodule section 7 is formed as a short nodule section having a length L3, the inclined second nodule section 8 is a long nodule section having a length L2. In contrast, the adjacent nodules 6 in the nodule row KR1 are given the reverse length situation, that is, the first horizontally oriented nodule section 7 is formed as a long nodule section having a length L1. Subsequently, the inclined nodule section 8 is a short section having a length L3. The distance d is less than half of the expandable metal height SH in the embodiments shown in FIGS. 6 to 12. Depending on the relationship between the distance d and the expandable metal height SH and the flexibility of the first plate 5, the first plate 5 may also be applied to the nodules 6 of the first nodule row KR1. In other respects, as can be seen from FIG. 12, a free space that may belong to the flow passage 12 is formed between the nodules 6 of the first nodule row KR1 and the plate 5.

[0037] Also in the embodiments shown in FIGS. 13 to 19, the nodules 6 of the nodule row KR1 are lifted from the first plate 5, as can be seen from FIG. 18. At the same time, these nodules 6 are also in contact connection with the bipolar plate 4, as can be seen from FIG. 18. The reverse is true for the nodules 6 of the second nodule row KR2. In this case, all the nodule sections 7 are placed on the first plate 5, while the inclined nodule sections 8 are spaced apart from the bipolar plate 4. In cross-section, all the nodules 6 of the nodule rows KR1, KR2 have a uniform cross-sectional shape, as can be seen from a comparison of FIGS. 18 and 19. The lengths of the nodule sections 7, 8 are both L1. Overall, in the embodiments shown in FIGS. 13 to 19, there is an expandable metal 3 with a corrugated shape.

[0038] In the embodiments shown in FIGS. 24 to 26, the features of the embodiments shown in FIGS. 13 to 19 are combined with the features of the embodiments shown in FIGS. 6 to 12. Therefore, in the case of FIGS. 20 to 26, there is an expanded metal 3 of a waveform manufactured using a variable feed. FIG. 25 shows the cross-sectional shape of the nodule 6 in the second nodule row KR2. The common point with the configuration shown in FIG. 11 is that, alternately in the longitudinal direction LR, the nodule 6 formed from two long nodule sections 7 and 8 and the nodule 6 formed from two short nodule sections 7 and 8 each having a length L3 are arranged in a row with each other while maintaining the interval existing as the opening 9. However, unlike the configuration shown in FIG. 11, in the case of FIG. 25, all the nodules 6 in the nodule row KR2 are separated from the bipolar plate 4. Regarding the first nodule row KR1, the cross-sectional configuration understood from FIG. 26 is basically analogous to the cross-sectional configuration shown in FIG. 12. This means that all the inclined nodule sections 8 are in contact connection with the bipolar plate 4, while the horizontal nodule section 7 is lifted from the first plate 5. The interval d between the horizontal nodule section 7 and the first plate 5 corresponds to approximately half of the expanded metal height SH in the case of FIG. 26. In this case, the long nodule section 7 each having a length L1 is somewhat farther away from the first plate-shaped assembly 5 than the short nodule section 7 each having a length L3. Overall, in the embodiments shown in FIGS. 20 to 26, a particularly wide open cross-section of the flow passage 12 is provided, and at the same time, there is a planar and material-non-damaging attachment of the expanded metal 3 in the first plate-shaped assembly 5.

Description of Reference Numerals

[0039] 1 Electrochemical cell, fuel cell 2 Plate assembly 3 Expanded metal, grid 4 Second plate, bipolar plate 5 First plate-shaped assembly, MEA 6 Nodule 7 First nodule section 8 Inclined second nodule section 9 Opening 10 Web 11 Web 12 Flow Path α Angle d Distance KB Knot Width KR1, KR2 Knot Rows L1 Length L2 Length L3 Length LR Longitudinal Direction LWD Lateral Width SH Expanded Metal Height SWD Short Direction Center Distance WS Wall Thickness

Claims

Claim 1 A plate assembly (2) for an electrochemical cell (1), comprising a grid formed as expanded metal (3) provided for being arranged in a sandwich-like manner between a first plate (5) located in a base plane and a second plate (4) parallel to the first plate (5), the grid having a plurality of nodes (6) and webs (10, 11) connecting the nodes (6) to each other, and in a plan view of the grid (3) from above, node rows (KR1, KR2) defining a longitudinal direction (LR) are formed and extend parallel to each other, and all nodes (6) have a planar bent shape with a fold line oriented transversely to the longitudinal direction (LR) separating two node sections (7, 8) from each other. In the plate assembly (2), the plate assembly (2), characterized in that in at least a subset of the nodes (6), each one of the node sections (7) of the node sections is arranged at least substantially parallel to the plates (4, 5). Claim 2 The plate assembly (2) according to claim 1, characterized in that in at least some of the nodes (6) belonging to the subset, the first node section (7) forms an angle of less than 15 degrees with the base plane and is in particular placed flat on the base plane. Claim 3 The plate assembly (2) according to claim 2, characterized in that there are additional nodes (6) each having one node section (7) belonging to the subset and spaced apart from the base plane. Claim 4 The plate assembly (2) according to any one of claims 1 to 3, characterized in that there are nodes (6) having the same length (L1, L2) of the node sections (7, 8). Claim 5 The plate assembly (2) according to any one of claims 1 to 4, characterized in that the length (L1, L3) of the first node section (7) is different from the length (L3, L1) of the second node section (8) in at least some of the nodes (6). Claim 6 In one of the nodular part rows (KR2) of the nodular part rows, only the nodular part (6) having two nodular part sections (7, 8) of the same length is arranged, and the nodular part (6) having two long nodular part sections (7, 8) alternates with the nodular part (6) formed from two short nodular part sections (7, 8). In another nodular part row (KR1), only the nodular part (6) having nodular part sections (7, 8) of non-uniform length is arranged. In this case, one nodular part (6) having a long section (7) and a shorter and more strongly inclined short section (8) that are at least substantially parallel to the plates (4, 5), and a nodular part (6) having a short section (7) and a relatively strongly inclined long section (8) that are at least substantially parallel to the plates (4, 5) are arranged alternately in sequence. The plate assembly (2) according to claim 5, which cites claim 4, is characterized in that.

7. The nodular part section (7) of the nodular part row (KR2) formed from nodular parts (6) having nodular part sections (7, 8) of the same length and being at least substantially parallel to the plates (4, 5) is in contact with the base plane, while the nodular part section (7) of another nodular part row (KR1) that is at least substantially parallel to the base plane is lifted from the base plane by a distance (d) that corresponds to at least 30% to a maximum of 60% of the distance (SH) between both of the plates (4, 5), that is, the thickness of the grid (3). The plate assembly (2) according to claim 6 is characterized in that.

8. An angle (α) of at least 90° to a maximum of 150° is formed between the two nodular part sections (7, 8) of one nodular part (6). The plate assembly (2) according to any one of claims 1 to 7 is characterized in that.

9. Use of the plate assembly (2) according to claim 1 in a fuel cell (1).

10. A stack of electrochemical cells (1) including a plurality of the plate assemblies (2) according to claim 1, wherein the plate assembly (2) has a grid formed as an expanded metal (3) and two plates (4, 5) that are in contact connection with the grid (3), that is, a membrane electrode assembly (5) as the first plate and a bipolar plate (4) as the second plate. A stack.

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