Electrolyser cell having frame made of polymeric material

Abstract

An electrolyser cell is disclosed, which comprises: a frame (10) with a central opening (30) arranged to act as active chamber of the electrolyser, and a bipolar plate (12) of metallic material arranged to be assembled to the frame (10) so as to close the central opening (30). The frame (10) is made of polymeric material without reinforcing fibres or reinforcing mineral charge, or having an amount of reinforcing fibres or reinforcing mineral charge not exceeding 10%, and the bipolar plate (12) is configured to comprise a flat base element (12') and at least one coupling element (12") protruding towards the frame (10) from said flat base element (12') and engaging with the frame (10) so as to act as a reinforcing element for the frame (10).

Description

[0001] ELECTROLYSER CELL HAVING FRAME MADE OF POLYMERIC MATERIAL

[0002] Technical field of the invention

[0003] The present invention relates generally to the field of electrolysers for the production of hydrogen and oxygen by water electrolysis process. More specifically, the present invention relates to an electrolyser cell intended to be assembled with other identical cells according to a side-by-side arrangement to form a so-called cell stack

[0004] State of the art

[0005] An electrolyser cell typically includes a frame with a structural function, which is made of an electrically nonconductive material, usually plastic, and a bipolar plate, made of an electrically conductive material, usually metal, as well as, of course, a number of other components such as a cathode plate, an anode plate, a membrane (where provided), a number of gaskets, etc.

[0006] In order for it to properly perform its structural function, the frame of an electrolyser cell is typically made by injection moulding process of thermoplastic polymer, for example mPPO, PSU, PPS, PPE, loaded with reinforcing fibres, especially glass fibres, in a percentage generally between 30% and 60%. However, the construction of a frame for an electrolyser cell in such a material involves high production costs, as the addition of reinforcing fibres leads to higher costs both in terms of material procurement and in terms of the manufacturing process (due in particular to increased wear of the mould and thus the need to overhaul or replace the mould more frequently). Furthermore, the addition of reinforcing fibres to the material of the polymeric frame results in an increase in the weight of that component.

[0007] An electrolyser cell having the features defined in the preamble of the attached independent claim 1 is known from WO 2023 / 193057 A1. According to that document, a bipolar plate of metallic material is coupled to a frame of polymeric material to compress a gasket interposed between the bipolar plate and the frame and thus ensure a seal between these two components of the cell.

[0008] Summary of the invention

[0009] It is an object of the present invention to provide an electrolyser cell that is able to overcome the drawbacks of the prior art discussed above. More particularly, it is an object of the present invention to provide an electrolyser cell that can be manufactured at a lower cost than the prior art.

[0010] It is a further object of the present invention to provide an electrolyser cell that exhibits a lower weight than the prior art, or rather, in which the assembly formed by the frame and the bipolar plate exhibits a lower weight than the prior art.

[0011] These and other objects are fully achieved according to the present invention by an electrolyser cell as defined in the attached independent claim 1 .

[0012] Additional advantageous aspects of the electrolyser cell according to the present invention are defined in the dependent claims, the subject-matter of which is to be intended as forming an integral part of the following description.

[0013] In summary, the invention is based on the idea of using for the cell frame a polymeric material without reinforcing fibres or mineral charge, or at most with a low content (not greater than 10%) of reinforcing fibres or mineral charge, and of configuring the bipolar plate so as to engage with the frame to act, at least during operation of the cell (i.e., when the active chamber of the cell is subject to the pressure of the fluid present within it), as a reinforcing element for the frame itself. More specifically, the bipolar plate is configured so as to include a flat base element and at least one coupling element that protrudes toward the frame relative to the base element and engages with the frame.

[0014] By virtue of such a solution, the frame is less expensive to manufacture and less heavy than the prior art because it is deprived of reinforcing fibres or reinforcing mineral charge or at least contains a significantly lower percentage of reinforcing fibres or reinforcing mineral charge than the prior art. The reduction in the manufacturing costs of the frame is greater than the increase in the manufacturing costs of the bipolar plate, which, compared with the prior art, requires at least one additional operation (i.e., the one required to obtain the at least one coupling element) and thus involves higher costs, so that the overall cost of the cell is still lower than in the prior art. Similarly, the reduction in the weight of the frame is greater than the increase in the weight of the bipolar plate, which, compared with the prior art, includes, in addition to the flat base element, one or more protruding coupling elements, and thus has a greater amount of material. As a result, the overall weight of the cell is also lower than in the prior art. In particular, the reduction in the weight of the frame is due both to the lower density of the material (due to the reduction in the amount of reinforcing fibres or reinforcing mineral charge) and to the fact that the frame can have a smaller volume since it does not have to perform the function of resisting pressure by itself. In addition, using for the frame a polymeric material without reinforcing fibres or reinforcing mineral charge, or at least with a low amount of reinforcing fibres or reinforcing mineral charge (i.e. , as mentioned above, not greater than 10%) also makes it possible to improve the quality of the frame itself, in particular to obtain a frame with tighter geometric tolerances (particularly flatness tolerances) and dimensional tolerances and with a lower surface roughness. In addition, it is possible in this way to make a frame with a lower thickness than the prior art, which further helps to reduce the cost and weight of the frame itself, and thus of the cell as a whole.

[0015] Brief description of the drawings

[0016] Further features and advantages of the present invention will become more apparent from the following description, given purely by way of non-limiting example with reference to the accompanying drawings, in which:

[0017] - Figure 1 is an exploded view of an electrolyser cell according to an embodiment of the present invention;

[0018] - Figure 2 is a front view of the assembly formed by the frame and the bipolar plate of the cell of Figure 1 ;

[0019] - Figure 3 is a sectional view of the assembly of Figure 2, through the sectional plane indicated by line Ill-Ill in that figure;

[0020] - Figure 4 shows on an enlarged scale the detail A of Figure 3;

[0021] - Figure 5 is a front view of the assembly formed by the frame and the bipolar plate of an electrolyser cell according to a further embodiment of the present invention;

[0022] - Figure 6 is an exploded view of the assembly of Figure 5;

[0023] - Figure 7 is a front view of the assembly formed by the frame and the bipolar plate of an electrolyser cell according to yet another embodiment of the present invention;

[0024] - Figure 8 is a sectional view of the assembly of Figure 8, through the sectional plane indicated by line VI I l-VI 11 in that figure; and

[0025] - Figure 9 shows on an enlarged scale the detail B of Figure 8.

[0026] Detailed description

[0027] With reference first to Figure 1 , an electrolyser cell according to an embodiment of the present invention is generally shown in exploded view. The electrolyser cell according to the present invention is a cell suitable for use in electrolysers operating at low temperatures, particularly electrolysers of the types known by the acronyms AEMWE (Anion Exchange Membrane Water Electrolyser), PEMWE (Proton Exchange Membrane Water Electrolyser) and AWE (Alkaline Water Electrolyser).

[0028] As shown in Figure 1 , the electrolyser cell basically comprises a frame 10, a bipolar plate 12, a membrane 14 (or a diaphragm, depending on the electrolyser technology used), a cathode electrode 16, an anode electrode 18, one or more cathode current collectors 20, one or more anode current collectors 22, and a plurality of gaskets 24, 26 and 28 of various shapes and / or types.

[0029] As regards the membrane (or diaphragm) 14, the cathode electrode 16, the anode electrode 18, the cathode current collectors 20, the anode current collectors 22, and the gaskets 24, 26 and 28, these are per-se-known components, whose features are not relevant for the purposes of the present invention. Therefore, these components will not be described in detail here.

[0030] With reference also to Figure 2, the frame 10 is a plate element that may have various shapes. In the example of Figures 1 and 2, as well as in the example of Figure 7, the frame 10 is rectangular in shape with rounded corners, but as shown in Figures 5 and 6 it may have ear-shaped formations at the four corners. The frame 10 has a central opening 30 defining the active chamber of the cell. In the example proposed herein, the central opening 30 is rectangular in shape, but it might have, however, a different shape. The frame 10 also has a plurality of holes for the inlet and outlet of the electrolyte solution, namely, a first hole 32 positioned near one of the corners of the frame 10 (bottom left corner, according to point of view of a person looking at Figure 2), a second hole 34 positioned near the corner of the frame 10 opposite to that of the first hole 32 (top right corner, according to point of view of a person looking at Figure 2), a third hole 36 positioned near one of the other two corners of the frame 10 (bottom right corner, according to point of view of a person looking at Figure 2), and a fourth hole 38 positioned near the corner of the frame 10 opposite to that of the third hole 36 (top left corner, according to point of view of a person looking at Figure 2). The first hole 32 and the second hole 34 are in fluid communication with the central opening 30 via a plurality of first channels 40 and a plurality of second channels 42, respectively, which are made on one side of the frame 10, in the present case on the anode side (i.e., on the side facing the anode side of the cell). The gaskets 24, three in number, are arranged on the anode side of the frame 10, the first one around the first hole 32, the second hole 34 and the central opening 30 so as to hydraulically isolate those holes and that opening, together with the relating first channels 40 and second channels 42, from the outside, the second one around the third hole 36 so as to hydraulically isolate that hole from the outside, and the third one around the fourth hole 38 so as to hydraulically isolate that hole from the outside.

[0031] Likewise, the third hole 36 and the fourth hole 38 are in fluid communication with the central opening 30 via a plurality of third channels (not shown) and a plurality of fourth channels (also not shown), respectively, which are made on the opposite side of the frame 10, thus in the present case on the cathode side (i.e. , on the side facing the cathode side of the cell). The gaskets 28, three in number, are arranged on the cathodic side of the frame 10, the first one around the third hole 36, the fourth hole 38 and the central opening 30 so as to hydraulically isolate those holes and that opening, together with the relating third channels and fourth channels, from the outside, the second one around the first hole 32 so as to hydraulically isolate that hole from the outside, and the third one around the second hole 34 so as to hydraulically isolate that hole from the outside.

[0032] In the example proposed herein, the first channels, the second channels, the third channels and the fourth channels are straight channels, but they might have a different geometry, for example at least partially curvilinear and / or with one or more changes of direction.

[0033] The frame 10 is made of a non-reinforced polymeric material, i.e. a polymeric material without reinforcing fibres or reinforcing mineral charge, or alternatively with a low amount of reinforcing fibres or reinforcing mineral charge, specifically with a percentage of reinforcing fibres and / or reinforcing mineral charge not exceeding 10%. In this way, the frame 10 is less expensive to manufacture, as well as less heavy, than a frame made of reinforced polymeric material according to the prior art. Specifically, thermoplastic polymers, such as PSU, PPS, PPE or combinations thereof, or even mPPO (modified polyphenylene oxide), i.e., a mixture of PPO and other resins, such as PS or PA, or rubbers (such as EPDM) can be used as materials for the frame 10. The polymeric material of the frame 10 may possibly also contain additives of various kinds, but with no reinforcing function.

[0034] The bipolar plate 12 is made of a metallic material, specifically of any one of the metallic materials typically used for this component, for example stainless steel, nickel-plated carbon steel, nickel, titanium, etc., and has a thickness between, for example, 0.1 mm and 1 mm. To overcome the lower mechanical strength of the material of the frame 10, and hence the lower ability of the frame 10 to act as a structural element for the cell, the bipolar plate 12 is appropriately configured and coupled to the frame 10 so as to act as a reinforcing element for the latter. In this way, the assembly formed by the frame 10 and the bipolar plate 12 acts as a structural element in a manner similar to a frame made of fibre-reinforced polymeric material according to the prior art, but with lower production costs and weight than the prior art.

[0035] More specifically, as shown in Figures 3 and 4, the bipolar plate 12 is configured to include a flat base element 12' of such a shape (in the present case, rectangular shape) and size as to completely enclose the central opening 30 of the frame 10, and to further include at least one coupling element 12" that protrudes towards the frame 10 relative to the flat base element 12' and engages with the frame 10 so as to act as a reinforcement for the frame 10. Preferably, the flat base element 12' and the coupling element(s) 12" of the bipolar plate 12 are made in one piece.

[0036] As regards the type of coupling element(s) 12" used, several solutions may be envisaged.

[0037] For example, according to the solution shown in Figures 3 and 4, a single coupling element 12" is provided, which comprises an inner edge 12a that extends substantially at right angle to the flat base element 12' so as to encircle the frame 10 along its perimeter. According to this solution, the coupling element 12" further comprises an outer edge 12b extending outwardly from the free end of the inner edge 12a, parallel to the flat base element 12', and an even more outer edge 12c extending outwardly from the free end of the outer edge 12b, inclined at a certain angle to the latter, so that the coupling element 12" has, in cross-section, a substantially rectangular trapezoidal shape.

[0038] However, the coupling element 12" may have a configuration different from the one shown in Figure 4.

[0039] The coupling element 12" can be easily made by cold plastic deformation process using a press with a suitably shaped punch.

[0040] As can be seen in Figure 4, the inner edge 12a of the coupling element 12" has no protrusions facing the frame 10, so that the bipolar plate 12 can be disassembled from the frame 10 without the need to deform the inner edge 12a to disengage the coupling element 12" from the frame 10. This allows the bipolar plate 12 to be disassembled from the frame 10, for example in the case of maintenance or repair work, easily as well as safely (i.e. , without the risk of causing damage to the frame during disassembly). The coupling element 12" may be sized so that the inner edge 12a engages with the frame 10 with some interference or, on the contrary, with some clearance. In the latter case, however, the clearance between the inner edge 12a and the frame 10 will be defined in such a way that, during operation of the cell, the expansion of the frame 10 due to the pressure of the fluid in the active chamber urges the frame 10 against the inner edge 12a, thereby putting that edge under tension.

[0041] As can be seen from Figure 4, the coupling element 12" of the bipolar plate 12 is shaped so that it does not protrude beyond the thickness of the frame 10, or, more generally, so that it does not protrude from the frame 10 to such an extent that it contacts, once the cell is assembled with other identical cells, the bipolar plate of the adjacent cell. In fact, any contact between the bipolar plates of adjacent cells would generate an unwanted electrical by-pass. In order to avoid contact between the bipolar plates of adjacent cells, a special gasket interposed between the facing portions of the bipolar plates that protrude laterally from the perimeter of the frame 10 can also be provided.

[0042] Instead of a single coupling element that in the assembled condition encircles the frame along its entire perimeter, several coupling elements protruding from the base element of the bipolar plate might be provided. For example, one or more pairs of coupling elements, each cooperating with a pair of opposite edges of the frame, might be provided.

[0043] Figures 5 and 6, in which parts and elements identical or corresponding to those of Figures 1 to 4 are indicated with the same reference numbers, show a cell in which the frame 10, and consequently also the bipolar plate 12, has a different shape than the rectangular one with rounded corners of the solution shown in Figures 1 to 4, namely a rectangular shape with ear-shaped formations at the four corners of the rectangle. What has been stated above with reference to the embodiment of Figures 1 to 4 applies otherwise, particularly with regard to the configuration of the coupling element of the bipolar plate.

[0044] Finally, Figures 7 to 9, in which parts and elements identical or corresponding to those of Figures 1 through 4 are indicated with the same reference numbers, show a cell in which the coupling element 12" of the bipolar plate 12 is a folded edge that extends substantially at right angle to the flat base element 12' and engages in a corresponding groove 44 provided on an outer side 10a of the frame 10.

[0045] Preferably, the folded edge forming the coupling element 12" extends along the entire perimeter of the bipolar plate 12. Furthermore, the folded edge forming the coupling element 12" has preferably no protrusions, both on its side facing the central opening 30 of the frame 10 and on its opposite side, so as to allow the bipolar plate 12 to be disassembled from the frame 10 without the need to deform the folded edge to disengage the coupling element 12" from the frame 10.

[0046] The coupling element 12" can be sized to mate with an inner side 44a of the groove 44 (i.e. , with a side of the groove facing the central opening 30 of the frame 10) with some interference or with some clearance. In the latter case, however, the clearance will be defined so that, during operation of the cell, the expansion of the frame 10 due to the pressure of the fluid in the active chamber urges the side 44a of the groove 44 of the frame 10 against the folded edge forming the coupling element 12", thereby putting that edge under tension.

[0047] What has been explained above with reference to the embodiment of Figures 1 to 4 apply otherwise.

[0048] The present invention has been described so far with reference to preferred embodiments thereof, but it is clear that other embodiments may be envisaged which share with those described herein the same inventive core, as defined by the appended claims.

Claims

CLAIMS1. Electrolyser cell including:- a frame (10) made of polymeric material with a central opening (30) arranged to act as active chamber of the electrolyser, and- a bipolar plate (12) of metallic material arranged to be assembled to the frame (10) so as to close said central opening (30), wherein the bipolar plate (12) comprises a flat base element (12') and at least one coupling element (12") that protrudes towards the frame (10) from said flat base element (12') and engages with the frame (10), characterized in that the polymeric material of the frame (10) has no reinforcing fibres or reinforcing mineral charge or contains an amount of reinforcing fibres or reinforcing mineral charge equal at most to 10%.

2. Electrolyser cell according to claim 1 , wherein the polymeric material of the frame (10) is a thermoplastic polymer, particularly PSU, PPS, PPE or combinations thereof, or mPPO, or a rubber, particularly EPDM.

3. Electrolyser cell according to claim 1 or claim 2, wherein the bipolar plate (12) is made of stainless steel, nickel-plated carbon steel, nickel or titanium.

4. Electrolyser cell according to any one of the preceding claims, wherein said at least one coupling element (12") of the bipolar plate (12) comprises an inner edge (12a) extending substantially at right angle to the flat base member (12') so as to encircle the frame (10) along its perimeter.

5. Electrolyser cell according to claim 4, wherein said inner edge (12a) has no protrusions facing the frame (10).

6. Electrolyser cell according to claim 4 or claim 5, wherein said at least one coupling element (12") of the bipolar plate (12) further comprises an outer edge (12b) extending outwardly, from the free end of the inner edge (12a), parallel to the flat base element (12'), and an even more outer edge (12c) extending outwardly from the free end of the outer edge (12b), inclined at an angle to the outer edge (12b), in such a way that said at least one coupling element (12') has in crosssection a substantially rectangular trapezoidal shape.

7. Electrolyser cell according to any one of claims 1 to 3, wherein said at least one coupling element (12") of the bipolar plate (12) is a folded edge extending substantially at right angle to the flat base element (12') and engaging in a corresponding groove (44) provided on an outer side (10a) of the frame (10).

8. Electrolyser cell according to claim 7, wherein the folded edge forming said at least one coupling element (12") extends around the entire perimeter of the bipolar plate (12).

9. Electrolyser cell according to claim 7 or claim 8, wherein the folded edge forming said at least one coupling element (12") has no protrusions, either on its side facing said central opening (30) of the frame (10) or on its opposite side.

10. Electrolyser for producing hydrogen and oxygen by water electrolysis process, comprising a plurality of cells according to any one of the preceding claims, arranged one next to the other.

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