Method for assembling a water electrolysis stack, bipolar plate configured for use in an electrolytic cell stack, and use of the bipolar plate

Abstract

A bipolar plate (1) adapted for use in an electrolytic cell stack (4), each plate including a plate intermediate plane (2), whereby the plate (1) includes uniform spacers (7) arranged at intervals extending in opposite directions from the intermediate plane (2). All spacers (7) are arranged along concentric circles (8) on the intermediate plane (2), the spacers (7) projecting alternately in opposite directions with respect to the intermediate plane (2) along each concentric circle (8), and an even number of spacers (7) being provided on each circumferential circle (8) except for the innermost circle (9) which includes a single spacer (7).

Description

Technical Field

[0001] The present invention relates to a method for assembling a water electrolysis stack. Further, the present invention relates to a bipolar plate configured for use in an electrolytic cell stack. Still further, the present invention relates to the use of the bipolar plate.

Background Art

[0002] In a bipolar plate used in an electrolytic cell for electrolysis of water such as a pressurized water electrolytic cell, electrodes (cathode and anode) are disposed on both sides of the plate and are generally welded to bumps, which may also be called protrusions. These protrusions are orthogonal to the intermediate plane of the bipolar plate and extend in opposite directions away from the plate. The protrusions ensure a distance between the bipolar plate and the electrodes, allowing the electrolyte to flow and be continuously exchanged during use of the electrolytic cell. Between any two consecutive bipolar plates of the above type of electrolytic cell, there is a sandwich including an electrode - diaphragm - electrode (also called an EDE sandwich), and the two electrodes are always a cathode and an anode. It is important that there is no gap between the electrode and the diaphragm. Surprisingly, it has been found that protrusions aligned opposite each other on both sides of the EDE sandwich can result in an undesired zero - gap relationship between the diaphragm and the electrodes. In particular, in the region near the outer periphery of the bipolar plate, this problem can become prominent, especially when the protrusions are not uniformly distributed along the outer periphery of the bipolar plate. When a slight pressure difference occurs on both sides of the diaphragm, the electrode material may permanently deform if it is somewhat flexible, thus creating a permanent space between the electrode material and the diaphragm, which is highly undesirable. Also, for some types of electrodes, it is important that the electrodes are correctly oriented according to the dominant flow direction in the electrolytic cell chambers surrounding both sides of each bipolar plate in the electrolytic cell. Therefore, there is a need for a bipolar plate that can use an improved assembly method different from the plates of the prior art and can further assemble an improved stack.

Summary of the Invention

Means for Solving the Problems

[0003] In a first aspect of the present invention, the object is a bipolar plate configured for use in an electrolytic cell stack, each bipolar plate including two opposite surfaces and spacers arranged at intervals extending outward from the surfaces of the bipolar plate, the spacers being arranged along concentric circles, the spacers protruding alternately in opposite directions from the opposite surfaces of the bipolar plate (1) and with respect to the intermediate plane (2) along each concentric circle (8), and an even number of spacers (7) being provided on each circumferential circle (8), which can be achieved by the bipolar plate.

[0004] The present invention also relates to a bipolar plate configured for use in an electrolytic cell stack, each plate including a plate intermediate plane, whereby the plate includes uniform spacers arranged at intervals extending in opposite directions from the intermediate plane. Further, according to the present invention, all the spacers are arranged along concentric circles, the spacers protruding alternately in opposite directions with respect to the intermediate plane along each concentric circle, whereby an even number of spacers are provided on each circumferential circle.

[0005] When the spacers are arranged along concentric circles that are concentric with the center of the circular bipolar plate, there are concentric circles of the outermost spacers, and they project in each of two directions, intermittently away from the plate, so that an even distribution of the spacers along the outer periphery of the bipolar plate is achieved. If all the spacers are identically mapped on all the plates regardless of which direction they project, it becomes even easier to rotate any bipolar plate around the central axis of the plate and place it at a predetermined angular position during assembly, and in particular, it becomes easy to rotate it to the same angular position as the angular position of the plate below. When this is done for the entire stack, all the spacers will necessarily align along an axis parallel to the length axis of the stack, and if the plates are not inverted relative to each other, all the spacers will align along an axis parallel to the central axis of the stack, and all the spacers aligned along such an axis project in the same direction.

[0006] The manufacture of plates containing spacers usually involves deep drawing operations in one or more steps. The spacers may be manufactured one by one on a numerically controlled deep drawing machine, or all the spacers projecting in one direction, or all the spacers projecting in both directions, may be manufactured by rolling or other known methods in operations such as deep drawing operations.

[0007] In some embodiments, the spacers are formed as protrusions (or bumps) from the plate.

[0008] In a further embodiment, the spacers are formed as essentially hemispherical protrusions projecting from the plate.

[0009] In a further embodiment, the protrusions forming the spacers each include a flat top.

[0010] In a further embodiment of the present invention, the bipolar plate is fabricated such that the nominal thickness of the EDE, including the electrodes, the separator, and the further electrodes, exceeds the distance between two adjacent virtual planes having a predetermined dimension, the virtual planes being inscribed by the flat tops of the spacers.

[0011] Here, the cell is defined as being composed of the following - a bipolar plate, - its spacer extending into the first half cell (anode-containing or cathode-containing) and contacting the first electrode, - the first electrode, - the separator, - the next electrode, - the next half cell (anode-containing or cathode-containing), - the spacer extending into this half cell from the next bipolar plate.

[0012] The next bipolar plate itself is counted as part of the next entire cell. Each such cell is provided with a self-frame of the bipolar plate and a self-frame of the separator. When the cell stack is assembled, the pull rod causes the entire stack of self-frames to be pressed against each other between the end plates, and the soft components (such as the separator and / or the electrodes) deform into the total thickness of the two self-frames, at least while the self-frames are biased against each other. When the separator is quite soft, flexible, sheet-like, somewhat elastic and elastically stretchable material, and both the electrodes on both sides are also made of a flexible material like the EDE sandwich shown, and further, when the spacer has little flexibility in the direction perpendicular to the bipolar plate, when pressure is applied by the spacers displaced from both sides, the EDE sandwich bends and takes a wavy shape. That is, when viewed from the first side, there is a shallow valley around the spacer that pushes down the first side, and there is a flat "hill" around the area where the spacer pushes down the sandwich from the opposite side. In this slightly wavy state, the separator is slightly stretched, and due to the combined effect of the stretching and the waviness, the zero-gap relationship between the separator and the electrodes on both sides thereof is maintained.

[0013] This undulation is defined as the dimension between the top of the mound and the valley in the direction perpendicular to the bipolar plate.

[0014] It is desirable that the total nominal thickness of the EDE elements is greater by a predetermined dimension than the distance between adjacent virtual planes.

[0015] When the spacers from the opposing bipolar plates in the half-cell that protrude towards the half-cell are aligned, in this case, since pressure is applied to both sides of the EDE in this case by the opposing spacers, undulation does not occur, and also, an EDE sandwich thicker than the distance between the opposing virtual planes will not occur without damaging the diaphragm and / or the electrodes.

[0016] The distance v between the virtual planes may be zero, in which case, for any EDE sandwich, undulation corresponding to its thickness occurs. v may also be a negative value, in which case, the undulation includes the sum of the thickness of the EDE and the distance v (having a positive sign).

[0017] In one embodiment, it is preferable that the distance v is negative. The distance v is preferably from -0.1 mm to -1.0 mm.

[0018] In one embodiment, the EDE sandwich includes a diaphragm having a thickness between 0.1 mm and 0.5 mm and electrodes each having a thickness between 0.1 mm and 0.3 mm. The thinnest EDE sandwich possible under these constraints is thus 0.3 mm, and the thickest is 1.1 mm.

[0019] The upper limit of the undulation is defined by the height h of the spacer because the value obtained by subtracting v corresponding to the undulation from the thickness of the EDE sandwich does not exceed the height h. In a preferred embodiment, v is -0.3 mm, the EDE sandwich is 1.1 mm, and h is 4.90 mm. Thus, the headspace above the mound is as follows: 4.90 mm - (1.1 mm - (-0.30 mm)) = 4.90 mm - 1.40 mm = 3.50 mm.

[0020] In one embodiment, each bipolar plate has at least one orientation tab and / or indentation, and the orientation tab and / or indentation is provided radially outside the radius of the outermost circle of the spacer in each bipolar plate, whereby the orientation tab and / or indentation is arranged at the same position relative to the spacer in all plates, and as a result, any spacer is mapped in the same way to at least one tab and / or indentation in all plates.

[0021] The orientation tabs and / or indentations provided on the rim of each bipolar plate serve to align the plates with each other. In particular, when corresponding tabs / indentations are provided on each self-frame as in this example, the bipolar plates can be arranged within the cell according to the orientation features of the self-frame and the bipolar plates. This is achievable because the self-frames used for the bipolar plates are stacked in the same way with respect to each other throughout one cell stack.

[0022] In one embodiment, in a bipolar plate, each spacer includes a conical shoulder rising from the intermediate surface, a flat circular top, a rounded interface between the intermediate surface and the shoulder, and a similarly rounded interface between the shoulder and the flat top.

[0023] The flat top can function as a welding surface to which the electrode is fixed, and the shoulder, together with the rounded interface, ensures a smooth flow around any spacer and helps to ensure that the spacer is pushed or stretched from the sheet material of the bipolar plate in a well-known manufacturing process. Since the electrode is made of a stretchable material such as stretch metal or the like, the electrode can deviate from the planar shape between the spacers as may be required when the stack is assembled.

[0024] In one embodiment, the flat top of the spacer protruding from the bipolar plate is inscribed in a virtual plane, which is parallel to the middle plane of the plate from which the spacer protrudes. Further, when the distance between the virtual plane and the middle plane is h and the diameter of the outermost concentric circle is D, the size relationship of D / h is 100 or more and 135 or less, preferably between 115 and 125.

[0025] The fact that the flat top of the spacer is inscribed in the virtual plane is mathematically interpreted such that the sum of the distances between the flat top and the virtual plane is minimized under the condition that the virtual plane extends parallel to the middle plane of the bipolar plate. The size relationship of D / h is selected such that an appropriate flow within the cell can be reliably achieved without the pump capacity becoming excessively large. Also, this relationship helps to ensure undulation and can be unified when considering the materials used for EDE and when larger plates or somewhat smaller plates are desired. In one embodiment, the value of D / h is equal to 122.

[0026] In one embodiment, in the bipolar plate, the number of concentric circles is 7 or more.

[0027] Furthermore, the concentric circles may be arranged at equal intervals, and as a result, in the cross-section passing through the center of the concentric circles of the spacer, the radial distance from one concentric circle to the next concentric circle is the same throughout the bipolar plate.

[0028] The fact that the concentric circles are arranged at the same distance helps to ensure that the spacers are evenly distributed on the plate. It is possible to arrange the spacers exactly uniformly along each concentric circle, but due to geometric and numerical constraints, there will be a small variation in the distance between the individual circles with respect to the distance between the spacers. However, this is hardly or not a problem at all as long as the spacers are evenly distributed as a whole, thereby leaving a larger area of the bipolar plate without spacers.

[0029] In a further embodiment, a single spacer may be further provided at the center of the concentric circles.

[0030] In another aspect, the object of the present invention is achieved by using a bipolar plate as defined in any one of the embodiments of the first aspect of the present invention. During use, the plates are stacked such that an EDE sandwich is pressurized between the spacers of the individual plates. Further, all bipolar plates have at least one alignment tab / dimple aligned in the rotational direction with each other within the stack. Further, all spacers of the plates within the cell stack aligned along one length axis direction of the stack are reversed so as to protrude in only one predetermined direction. Using the bipolar plate in this way can ensure that the EDE sandwich is pressurized from two opposing sides without generating concentrated stress. The stress is more evenly distributed. As a result, in two assembled adjacent half-cells, a structure having a nominal thickness of the EDE sandwich exceeding the distance between the virtual planes of the spacer surface functions and is further advantageous. In such an assembly, the desired zero gap between the diaphragm and the adjacent electrode is improved. Since the stress is distributed to the diaphragm and the adjacent electrode, a higher pressure difference between both sides of the membrane can be accepted before the entire electrode is permanently damaged.

[0031] In a third aspect, the present invention relates in particular to a method of assembling a water electrolysis stack that holds the range of the same bipolar plate, having an array of spacers extending away from an intermediate plane in two opposite directions. According to this aspect, for the bipolar plates throughout the stack, during assembly, all spacers within the range of the plates are aligned along an axis parallel to the length axis of the stack, and further, all spacers along any one alignment axis are arranged to protrude in the same direction.

[0032] As long as the problem spacers are aligned along the same alignment axis parallel to the stack central axis, they project in only one direction. Desirably, the spacer arrangement includes spacers arranged in concentric circles, with the spacers projecting alternately in each direction along each circle. This spacer arrangement ensures that spacers projecting towards the same EDE sandwich from each side are never aligned, resulting in a much more even distribution of stress in the EDE.

[0033] In one embodiment of the assembly method, during assembly, if the nominal height dimension of the EDE element of the cell exceeds the distance between the virtual planes including the flat tops of the spacers of the opposing bipolar plates, such that when the stack elements are pressed against each other, the EDE elements between the spacers will tend to undulate between the two arrays of spacers of the opposing bipolar plates.

[0034] This assembly method ensures a very stable zero-gap distance between the diaphragm and the electrodes on both sides thereof, even if the pressure difference between both sides of the EDE is not always within the specified range.

[0035] According to one embodiment of this assembly method, at least one orientation tab and / or indentation provided along the edge of the usually circular bipolar plate is aligned with the corresponding tab and / or indentation of the cell frame to which the bipolar plate is attached during assembly.

[0036] In this way, all the plates are aligned in the same way within the stack, and all the other cell frames are stacked in exactly the same rotational position, and thus receive bipolar plates oriented according to the bipolar plates arranged above or below in the stack. All the cell frames arranged between the two cell frames carrying the bipolar plates are provided with diaphragms to form an EDE sandwich.

[0037] In yet another embodiment of the assembly method, before adding the bipolar plate to the self-frame, each spacer protruding from the first side of the bipolar plate is welded to the electrode, and each spacer protruding from the second side of the bipolar plate is welded to a further electrode, whereby the electrodes before the welding operation are rotated so that the orientation markers on the electrodes are oriented in a predefined manner with respect to the orientation features of the corresponding bipolar plate.

[0038] Due to this predefined orientation of the electrodes with respect to the bipolar plate, the orientation of all the electrodes in the stack is homogenized. Such an orientation may be important for certain types of electrodes that are sensitive to the direction of the flow within the cell. For these electrodes, the electrolyte needs to always flow in a predefined main direction with respect to the mechanical structure. Therefore, they need to be oriented according to the inlets and outlets of each half-cell. Such inlets and outlets are not marked on the bipolar plate, but when the bipolar plate is placed within the self-frame as described above, the inlets and outlets are defined, and the electrodes are correctly oriented with respect to the bipolar plate and can receive the flow of the electrolyte from the preferred direction when attached to the self-frame that defines the inlets and outlets.

[0039] In a further embodiment of the assembly method, during assembly, all the bipolar plates are rotated and / or reversed so that the cathode electrode faces the end plate with inlets and outlets for the electrolysis process of the assembled stack, or all the bipolar plates are rotated and / or reversed so that the cathode electrode faces away from the end plate with an inlet.

[0040] In a known electrolytic cell configuration, two stacks are electrically interconnected such that as a result, an electrical high potential (such as an electrical positive potential) is supplied to a far end of one stack and an electrical connection to a proximal end of the next stack is established at a near or proximal end of the stack opposite. Further, this next stack has a high potential supplied to its far or distal end but with a sign opposite to that supplied to the far end of the first stack, which in this case is an electrical negative potential. At the proximal ends of the two stacks, there will be a potential of approximately zero under the condition that the two stacks achieve equal potential losses, which is the normal case. At the zero potential ends of these stacks, connections for the supply and extraction of the electrolyte are typically arranged. In such an arrangement, the bipolar plates with electrodes will face in opposite directions with respect to the zero potential or the proximal end of the stack in order to achieve the correct potential in both stacks. For this purpose, it is advantageous to be able to rotate (invert) the bipolar plate about its diameter axis so that the cathode or anode portion of the electrodes attached to the bipolar plate faces either the proximal or distal end of the stack.

[0041] Various exemplary and non - limiting embodiments regarding both structure and method of operation will be best understood from the following description of specific exemplary and non - limiting embodiments when read in conjunction with the accompanying drawings, together with additional objects and advantages.

[0042] As used herein, the verbs “comprise” and “comprising” are used as open limitations that do not exclude the presence of features not recited and also do not require them. The features recited in the dependent claims can be freely combined with each other unless otherwise explicitly stated. Further, it should be understood that even when the singular form “a” or “an” is used throughout this specification, the plural form is not excluded.

[0043] As used herein, the terms "comprising", "including", and "consisting of" are to be construed as specifying the presence of the stated features, integers, steps, or components, but not precluding the presence or addition of one or more other features, integers, steps, components, or groups thereof.

[0044] Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the accompanying drawings. It should be emphasized here that the embodiments shown are for illustrative purposes only and should not be used to limit the scope of the present invention.

Brief Description of the Drawings

[0045]

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Mode for Carrying Out the Invention

[0046] Figures 1A and 1B show two embodiments of a set including two bipolar plates 1. In each embodiment, each bipolar plate 1 includes two opposite surfaces 1', 1'', namely, the first or upward surface 1' and the second or downward surface 1'', and a plurality of spaced-apart spacers 7, each of these spacers 7 extending outwardly from either the first surface 1' of the bipolar plate 1 or the second surface 1'' of the bipolar plate 1. In each embodiment, both bipolar plates 1 (or simply plates 1) have electrodes 17 formed on the plate 1 and welded to the spacers 7 extending outwardly from the plate 1. In the illustrated embodiment, the spacers 7 are provided as protrusions formed, for example, as recesses deeply drawn in the plate 1. Each protruding spacer 7 has a flat top 13. In the embodiments shown in Figures 1A and 1B, the flat top 13 of the spacer 7 is a circular flat top 13. The electrode 17 is welded to the flat circular top 13 of the spacer 7 or the protrusion. In each of the embodiments shown in Figures 1A and 1B respectively, the uppermost bipolar plate 1 shows the electrode 17 on its lower side, and the lowermost plate 1 shows the electrode 17 on its upper side. A separator 19 is provided between the electrodes 17, and it is desired that the electrodes 17 on both sides of it always maintain a zero-gap configuration with the separator 19 at any point of the separator 19. In a cell stack configuration, the electrodes 17 must be welded to both sides of all bipolar plates 1.

[0047] In Figure 1A, it is shown that the spacers 7 of the upper plate and the lower plate are aligned and in the same orientation. Thus, the upward spacers of the lower plate are located directly below the upward spacers of the upper plate in the figure. As a result, at no point do the sets of spacers protruding towards the EDE on both sides of the EDE align with each other.

[0048] Figure 1A further shows the intermediate plane 2 of the uppermost bipolar plate 1. It can also be considered that the spacers 7 extend in opposite directions from the intermediate plane 2. It will be understood that each bipolar plate 1 has an intermediate plane 2.

[0049] In some embodiments, as shown, for example, in FIG. 1A, spacer 7 is formed as a protrusion (or bump) extending from bipolar plate 1 (plate 1).

[0050] In some embodiments, as shown, for example, in FIG. 1A, spacer 7 is formed as an essentially hemispherical protrusion protruding from bipolar plate 1.

[0051] In further embodiments, the protrusions forming spacer 7 each include a flat top 13.

[0052] FIG. 1B is a possible prior art configuration of the elements shown in FIG. 1A. Here, the downward spacer 7 of the upper bipolar plate 1 is aligned with the upward spacer 7 of the lower plate of the two bipolar plates 1 shown. Thus, EDE sandwich 20 appears to be sandwiched between the aligned spacers. In particular, when the pressure difference between the cathode side and the anode side of the diaphragm in the stack increases, EDE sandwich 20 may be damaged, the electrodes may be permanently deformed, and a gap may occur between the diaphragm and the electrodes, which is undesirable. Further, in this prior art structure, if the size of the EDE is too large, inevitably, the diaphragm, the electrodes, or both will be overly sandwiched between the spacers, or if the size of the EDE is too small, due to the gap between the diaphragm and the electrodes, the efficiency of the electrolytic cell stack is likely to be impaired, so it is not easy to accept manufacturing tolerances.

[0053] The cell stack 4 includes a number of electrolytic cells 3 provided in a horizontal row. The cell frame 5 is pressed against each other between two end plates 6 and 23 on opposite sides, and alternately forms a catalytic process chamber and an analysis process chamber separated from each other by a diaphragm 19. The electrolytic cell 3 includes stack members in the order of a bipolar plate, an electrode (cathode or anode), a diaphragm, and an electrode (cathode or anode). In this way, a bipolar plate and the electrodes on both sides thereof are provided to every other cell frame, and a diaphragm is provided to every other cell frame. When the first electrode is an anode, the electrode following the diaphragm becomes a cathode, and vice versa.

[0054] Figure 2 shows spacers 7 of a prior art plate protruding in one direction from the plate plane, visualizing how they are aligned along straight vertical and horizontal lines in a two-dimensional array. Four adjacent spacers like this all form the corners of a rectangle. It is also shown that there are some fairly large patches without spacers near the edges of the plate. This increases the risk that some parts of the rim area of the diaphragm will remain unsupported. Although it is possible to add spacers, it is inevitable that the spacers approach closer than average on the plate, which may lead to the spacers providing undesirable obstacles to the uniform flow of the electrolyte in the space between the spacers and the diaphragm along the plane of the plate. Also, even if spacers are added to the prior art plate, there is no reasonable way to make them protrude in the same direction on adjacent plates while adding support for the EDE.

[0055] FIG. 3 discloses a plan view of the plate 1 according to the present invention, showing both the spacers 7 that point towards the viewer and the spacers 7 that point away from the viewer. All the spacers 7 are arranged along concentric circles 8, and along each circle, the spacers 7 project alternately in each direction with respect to the intermediate plane 2 of the plate 1. In FIG. 5, only the spacers 7 that project in one direction are disclosed, but here it is clear that the spacers are evenly distributed along the outer periphery of the circular plate. As can be seen in the same way in FIGS. 3 and 5, there are seven concentric circles 8 and the innermost circle 9, which contain only one spacer. The one spacer 7 provided on the innermost circle 9 can also be considered to be formed at the center of the concentric circles. The radial distance from one circle to the next is all the same. Mathematically speaking, the plate includes an intermediate plane 2 defined by a normal vector (not shown), and the spacers project along this normal and its opposite direction. However, the plate has to be manufactured with the spacers with the normal tolerances of a metal plate having a thickness of about 0.5 mm.

[0056] In FIG. 1A, the height of the cell indicated by reference numeral 3 corresponds to the combined height of two cell frames (the frame 5 for the bipolar plate 1 and the frame 5 for attaching the separator 19) in the stack direction. These two frames are identical, and the combined height thereof corresponds to the combined height of the EDE sandwich 20 and the bipolar plate 1 including the spacers on both sides thereof. When this is ensured, ideally, when the stack is assembled, the separator contacts the electrodes on both sides thereof. However, due to manufacturing tolerances, a slight gap may occur between the separator and the electrodes, and if an undesirable pressure difference occurs between the cathode side and the anode side of the separator, the electrodes may be damaged, and as mentioned, this can be particularly problematic in prior art stack assemblies where the spacers can be aligned on both sides of the separator. The displacement of the spacer 7 directed towards the EDE sandwich according to the present invention as shown in FIG. 1A allows the sum of the heights of the EDE sandwich 20 and the bipolar plate to exceed the actual height or the nominal height of the parts. Therefore, the inside of the cell is assumed to have a combined height that nominally exceeds the height of the two cell frames that constitute the height of the cell when assembled. This makes it possible because the displaced spacer supporting the EDE sandwich 20 allows the sandwich to be slightly wavy and make way for the spacer. It should be mentioned that the separator of the inner rim of the cell is maintained and fixed to the cell frame over the entire circumference of the inner periphery of the cell frame. However, since the separator is usually an element with a certain degree of elasticity, a certain amount of elongation of the material is allowed, and this elongation also contributes to reliably maintaining the zero-gap relationship between the separator and the electrodes.

[0057] The plane that inscribes the flat top 13 of the spacer 7 is called the virtual plane 16, and the distance between two such adjacent planes 16 is for accommodating the EDE sandwich. Let this distance be v. When the distance v between the virtual planes 16 is zero, the flat top of the spacer from a certain plate aligns with the flat top of the spacer on the next plate within the half cell. As shown in FIGS. 13 and 14, if the distance between the virtual planes is negative, the flat top of the downward spacer of the upper plate is located below the top of the upward spacer of the lower plate. In this case, even for an infinitely thin EDE sandwich, as shown in FIG. 13, it must be curved so as to exist between the upward spacer and the downward spacer.

[0058] In the embodiment as shown in FIG. 13, the distance v between the virtual planes is -0.3 mm, and the EDE has a combined thickness t of 1.1 mm. The separator is 0.5 mm, and the two electrodes each have a nominal thickness of 0.3 mm. Thereby, the height of the curvature is t - v = 1.1 mm - (-0.3 mm) = 1.4 mm, and as a result, the nominal difference between the top of the mound and the depth of the valley is 1.4 mm.

[0059] If the distance from the top of the mound thus named to the intermediate surface 2 of the bipolar plate arranged opposite is called the head space, as is clear from FIG. 13, the head space is calculated as adding the distance v (with indication mark) to the result of subtracting the thickness t of the EDE from the height h of the spacer. In the above example, since the height h of the spacer is 4.90 mm, the thickness t of the EDE is 1.10 mm, and v is -0.30 mm, a head space of 4.90 - 1.1 - 0.3 mm = 3.50 mm is obtained. It is desirable that the head space is not below zero. When the head space exceeds the height h of the spacer, the EDE sandwich does not contact the spacer and the zero gap cannot be maintained. The thickness of the bipolar plate is ignored in this calculation, but it is easy to include and will not change the result significantly.

[0060] In FIG. 3, three orientation tabs 10 can be seen along the outer periphery or rim 32 of the bipolar plate 1. The spacers 7 of all the plates produced must be mapped to the tabs 10. Usually, the self-frame 5, which is an injection-molded annular flat polymer element, is provided with similarly arranged recesses 11 so that the plate fits the self-frame 5 only at one rotational position with respect to the self-frame 5. As shown in FIG. 3, there are three such tabs 10, which are symmetrically arranged with respect to the diameter line 20, whereby the plate 1 can fit within the self-frame even if it is reversed or inverted (rotated about the axis running through the intermediate surface 2). This is necessary to ensure that all the plates 1 have aligned spacers, as disclosed in FIG. 1A.

[0061] FIG. 4 is a top view showing details of the bipolar plate 1 similar to the bipolar plate 1 shown in FIG. 3. In FIG. 4, a recess 10 is disclosed, and adding this recess 10 to the outer rim 32 of the bipolar plate 1 functions similarly to the tab 10 in FIG. 3, and corresponding changes to the self-frame 5 may be made.

[0062] FIG. 5 shows all the spacers 7 extending in one direction from the bipolar plate 1 according to the present invention. As can be seen, along the outer periphery, the spacers 7 are equally spaced from each other and follow the locus of the circle 8. As is clear from FIG. 3, the outermost circle of the spacers of the plate 1 is concentric with the circular outer shape of the plate 1. As can be seen from FIG. 3, along each circle, the spacers alternately project with respect to the intermediate surface of the plate, and to achieve this, an even number of spacers must be provided on each circle. Also, due to this constraint, it is impossible to make the distance between the spacers exactly the same along each circle, but the slight difference in the distance between the spacers from one circle to another does not prevent the achieved effect of evenly distributing the stress of the EDE.

[0063] In FIG. 6A, an example of an electrode is disclosed in a photograph and is disposed at a predetermined position with respect to the bipolar plate 1. In the enlarged view of the square segment, one feature of the electrode 17, namely the outer shape of the orifice of the electrode material, is shown. The orifice has an outer shape similar to the cross-sectional shape of a brilliant 22 (diamond cut), and the domed side faces are opposed to an angle facing away from the domed shape. In use, the fluid flow of the electrolyte is arranged to flow between the spacers from the inlet to the oppositely disposed outlet in the space between the bipolar plate 1 and the diaphragm 19. For certain electrodes 17 such as those shown in FIG. 6, it is preferred that this electrolyte flow has a predetermined direction with respect to the brilliant trace 22 of the orifice. For this purpose, the electrode 17 is also desirably oriented in a predetermined manner with respect to the bipolar plate 1 prior to the welding process that fixes the electrode 17 on the flat top 13 of each spacer 7 on one side of the plate 1. FIG. 6B shows, in sketch form, a line drawing of the photographic representation of FIG. 6A. In the sketch of FIG. 6B, the brilliant shape is represented in a simpler geometric representation, but it should be of a shape such as the brilliant 22, and it will be understood that its standard shape (side view) is represented in FIG. 6C.

[0064] In FIGS. 7 and 3, it is shown that the bipolar plate 1 has an electrode orientation feature 18, which is to correspond to an orientation marker 21 of a similar shape of the electrode 17. As seen in FIG. 7, when the electrode orientation feature 18 of the bipolar plate is aligned with the orientation marker 21 of the electrode 17, the electrode 17 can be rotated with respect to the bipolar plate 1 in a predetermined manner, and the two can be welded in this mutual rotational relationship. When disposed in the self-frame 5 with the orientation tab 10 disposed in the corresponding tab and / or recess 11 of the self-frame 5, it is ensured that the inlet and outlet are automatically disposed in the self-frame to ensure a general flow direction corresponding to the orientation of the brilliant trace 22 of the electrode 17. Therefore, the inlets and outlets (not shown) to the electrolytic chambers on both sides of the self-frame and the bipolar plate must also be mapped with respect to the orientation tab and / or recess 11 of the self-frame 5.

[0065] In FIG. 8, a schematic view of a part of the bipolar plate 1 to which the electrode 17 is welded on both sides thereof is disclosed. In the enlarged portion on the left side of FIG. 8, the flat top 13 of the spacer 7 can be clearly seen.

[0066] In FIG. 9, a cross-sectional view of an embodiment of the spacer 7 is disclosed. In this embodiment, the spacer 7 is formed as a protrusion (or bump) extending from the plate. In this embodiment, each spacer 7 includes a conical shoulder 12 rising from the surfaces 1', 1'' of the bipolar plate 1 and a flat circular top 13. The shoulder can also be considered to rise from the intermediate surface 2. A rounded interface 14 is provided between the surfaces 1', 1'' of the bipolar plate 1 and the shoulder 12. Similarly, a rounded interface 15 is provided between the shoulder 12 and the flat top 13. Here, φ1 is the diameter of the flat top 13 of the spacer, and R1 and R2 are the rounded diameters at the intersection of the intermediate surface 2 and the shoulder 14 and at the intersection of the shoulder 12 and the flat top 13. h is the distance between the virtual plane 16 where the flat top 13 exists and the intermediate surface 2. t is the thickness of the bipolar plate 1. φ2 is the diameter of the spacer 7 starting from the beginning of the rounded interface 14 at the intermediate surface 2. When D is the diameter of the outermost circle of the spacer 7 projected onto the intermediate surface 2, it is preferable that the quotient of D / h is between 100 and 135, preferably between 115 and 119. In the most preferred embodiment, the quotient of D / h is between 116 and 118.

[0067] Figure 10 shows two cell stacks 4 in cross section. The interior of stack 4, which includes bipolar plates, separators, and electrodes, is not part of the figure. The stacks are each enclosed between end plates 6, 23, and a set of pull rods 24 and nuts 29 are provided outside the self-frame between the two end plates 6, 23. In this way, the self-frame 5 is biased together between the two end plates 23 by the pull rods 24 and the corresponding nuts 29, so that the interior of the self-frame 5 can maintain an internal high pressure. Fluid connection means 27 are provided on one of the end plates, namely the proximal end plate 6 of each cell stack 4. In one embodiment, the positive and negative electrodes of the current supply are connected to a distal current injection plate 30 provided at the far end or distal end (proximal side of the distal end plate 23) of the two stacks shown in Figure 10, while the proximal current injection plate 31 provided at the proximal end of the stack is short-circuited so that current passes through one cell stack and enters the opposing stack in Figure 10. At the proximal end plate 6, a zero potential is maintained, and in some cases, it is also assisted by an electrically grounded lead (not shown), so it is convenient to provide all of the fluid connection means 27 for the two stacks 4 on the proximal end plate 6. In such an embodiment, all of the bipolar plates in the first stack have one side, for example the cathode side, facing the proximal end plate 6, while all of the bipolar plates in the other stack have the cathode side of all of the bipolar plates facing the distal end plate 23 of this stack. This arrangement can be provided without further complication by allowing the bipolar plates to be reversed so that their cathodes face either the proximal end plate or the distal end plate throughout the stack when the bipolar plates are assembled into the self-frame.

[0068] Figure 12 shows a portion of the same self-frame 5, with the inner rims of the self-frame shown on the left and right sides. On the right side, an orientation indentation 11 is shown, along with two similar orientation indentations 11 on the left side. As can be seen in Figure 12, a diameter line 28 passing through the center of the orientation indentation 11 on the right side is drawn, and when extended through the center 25 of the circular structure of the inner rim of the self-frame 5, this diameter line is assumed to be equidistant from the two left-side indentations 11. The right-side and left-side indentations are hardly visible in Figure 12 and are therefore shown enlarged in Figure 11. If the orientation indentations and / or tabs 11, 10 in the self-frame 5 and the bipolar plate 1 are provided symmetrically with respect to the diameter line 28 in the plane of the self-frame 5, the bipolar plate 1 can be inverted or rotated 180 degrees with respect to the self-frame around such a diameter line 28 in the intermediate plane 2 and still be able to fit with the tabs / indentations in the self-frame 5. As can be seen in Figure 3, the bipolar plate 1 has three orientation tabs 10, and thus this plate 1 must fit with the self-frame disclosed in Figure 11 when inverted around the diameter line 28 as disclosed in Figure 3 or passing through the tab 10 shown on the left side of Figure 3. Reversing around any axis in the intermediate plane of the bipolar plate serves the purpose, but if an axis different from the diameter line 28 is selected, fitting with the self-frame requires further translation and / or rotation of the plate to align it with the features of the self-frame after the reversal or inversion operation.

[0069] Note that each figure and the above description simply and schematically illustrate exemplary embodiments. Many specific mechanical details are not shown as they would be familiar to those skilled in the art and would only make this description unnecessarily complex.

Description of Reference Numerals

[0070] 1 Bipolar plate (plate) 1’ Surface of the bipolar plate formed on one side of the bipolar plate / First surface of the bipolar plate The surface of the bipolar plate formed on the other side of the 1’’ bipolar plate / The second surface of the bipolar plate 2 The intermediate surface of the bipolar plate 3 Electrolytic cell 4 Cell stack 5 Cell frame 6 Proximal end plate 7 Spacer (may be a depression formed in the plate, resulting in a protrusion extending from the surface / side of the plate) 8 Concentric circles 9 Center of the concentric circles 10 Orientation tab and / or indentation 11 Corresponding tab and / or indentation of the cell frame 12 Conical shoulder 13 Flat circular top 14 Rounded interface between the intermediate surface and the shoulder 15 Rounded interface between the shoulder and the circular flat top 16 Virtual plane 17 Electrode 18 Electrode orientation feature of the bipolar plate 19 Diaphragm 20 EDE i.e. electrode - diaphragm - electrode sandwich 21 Orientation marker of the electrode 22 Brilliant trace (orifice) 23 Distal end plate 24 Pull rod 25 Center of the inner circular rim of the cell frame 26 Longitudinal axis of the stack 27 Fluid connection means 28 Cell frame or bipolar plate diameter line 29 Nut 30 Distal current injection plate 31 Proximal current injection plate 32 Rim of the bipolar plate h Height of the spacer from the intermediate surface to the virtual plane D Diameter of the outermost ring of the spacer on the plate v Distance between adjacent virtual planes within the half cell Thickness of the t EDE sandwich

Claims

1. A bipolar plate (1) configured for use in an electrolytic cell stack (4), wherein each bipolar plate (1) includes two opposite surfaces (1', 1'') and spaced spacers (7) extending outward from the surfaces (1', 1'') of the bipolar plate (1), wherein the spacers (7) are arranged along concentric circles (8), and the spacers (7) alternately protrude in opposite directions relative to the intermediate surface (2) of the bipolar plate (1) along each concentric circle (8), and an even number of spacers (7) are provided in each circumferential circle (8).

2. The bipolar plate (1) according to claim 1, wherein the spacer (7) is formed as a protrusion from the bipolar plate (1).

3. The bipolar plate (1) according to claim 2, wherein the spacer (7) is formed as an essentially hemispherical projection from the bipolar plate (1).

4. The bipolar plate (1) according to claim 2, wherein each of the protrusions forming the spacer (7) includes a flat top (13).

5. The bipolar plate (1) according to claim 1, wherein the nominal thickness of the electrode-diaphragm-electrode (EDE) (20), which includes an electrode (17), a diaphragm (19), and a further electrode (17), exceeds the distance between two adjacent virtual planes (16) by a predetermined dimension, and the virtual planes inscribe the flat tops (13) of projections (7) that project in one direction from the bipolar plate (1).

6. The bipolar plate (1) according to claim 1, characterized in that at least one orientation tab and / or recess (10) is provided in each bipolar plate (1) radially outward of the outermost circle of the spacer (7), so that the orientation tab and / or recess (10) is positioned in the same location relative to the spacer (7) in all plates, and as a result, each spacer (7) is mapped in the same manner to at least one tab and / or recess (10) in all plates (1).

7. The bipolar plate (1) according to claim 1, wherein each spacer (7) includes a conical shoulder (12) rising from the surface (1', 1'') of the bipolar plate (1), a flat circular apex (13), a rounded interface (14) between the surface (1', 1'') of the bipolar plate (1) and the shoulder (12), and a similarly rounded interface (15) between the shoulder (12) and the flat apex (13).

8. The bipolar plate (1) according to claim 7, wherein the flat top (13) of the spacer (7) protruding from the bipolar plate (1) is inscribed in the virtual plane (16), the virtual plane (16) is parallel to the intermediate surface (2) of the plate (1) from which the spacer (7) protrudes, the distance between the virtual plane (16) and the intermediate surface (2) is denoted as h, and the diameter of the outermost concentric circle is denoted as D, the size relationship D / h is 100 or more and 135 or less, preferably between 115 and 125.

9. The bipolar plate (1) according to claim 1, wherein the number of concentric circles (8) is 7 or more.

10. The bipolar plate (1) according to claim 1, wherein the concentric circles (8) are arranged at equal intervals, and as a result, in a cross-section of the spacer (7) passing through the center of the concentric circles, the radial distance from one concentric circle (8) to the next concentric circle (8) is the same throughout the bipolar plate (1).

11. The bipolar plate (1) according to claim 1, wherein a single spacer (7) is further provided at the center of the concentric circles (8).

12. A use of the bipolar plate (1) according to any one of claims 1 to 11, characterized in that, during use, the bipolar plates (1) are arranged in a stack (4) such that the EDE sandwich (20) is pressed between the spacers (7) of the individual bipolar plates (1), all bipolar plates (1) have at least one orientation tab / recess (10) aligned with each other in the longitudinal direction (26) of the stack (4), and are further rotated around the cell frame diameter line (28) on the intermediate surface (2) such that all spacers (7) in the plate (1) within the cell stack (4) aligned along the longitudinal axis direction (26) of the stack (4) protrude in only one predetermined direction.

13. A method for assembling a water electrolysis stack (4) having a range of identical bipolar plates (1) having an array of uniformly distributed spacers (7) extending in two opposite directions perpendicularly away from the opposite surfaces (1', 1'') and intermediate surfaces (2) of each plate (1), characterized in that, during assembly, the bipolar plates (1) throughout the stack (4) are arranged such that all spacers (7) within the range of the plate are aligned along an axis parallel to the length axis (26) of the stack (4), and all spacers (7) along any one of the alignment axes protrude in the same direction.

14. The assembly method according to claim 13, wherein during assembly, the nominal height dimension of the EDE element (20) of the cell (3) exceeds the distance between the virtual planes (16) including the flat tops (13) of the spacers (7) of the opposing bipolar plate (1), and as a result the stacked elements are pressed against each other, the EDE element (20) between the spacers (7) undulates between the two arrays of spacers (7) of the opposing bipolar plate (1).

15. The assembly method according to claim 13, wherein at least one orientation tab and / or recess (10) along the edge of a normally circular bipolar plate is aligned with a corresponding tab and / or recess (11) of a cell frame (5) to which the bipolar plate (1) is attached.

16. The assembly method according to claim 13, characterized in that, before adding the bipolar plate (1) to the cell frame (5), each spacer (7) protruding from the first side of the bipolar plate (1) is welded to an electrode (17), and each spacer (7) protruding from the second side of the bipolar plate (1) is welded to a further electrode (17), thereby rotating the electrode (17) before welding so that the orientation marker (21) on the electrode (17) is oriented in a predetermined manner with respect to the orientation feature portion (18) of the corresponding bipolar plate (1).

17. The assembly method according to any one of claims 13 to 15, wherein the bipolar plate (1) is rotated so that the cathode electrode faces an end plate (6) which has an inlet and outlet for the electrolytic process of the stack (4), also called a proximal end plate (6), or the bipolar plate (1) is rotated so that the cathode electrode faces away from the proximal end plate (6).

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