Frame for use in an electrochemical system, and electrochemical system, particularly electrolyser

Abstract

The invention relates to an electrically insulating, planar frame (1) having a main frame body (1a) with an upper face (1b) and a lower face (1c), for use in an electrochemical system (10) which is constructed in a stacked manner, having - a plurality of frame openings comprising a central opening (1') and a plurality of media passage openings (2) arranged around a circumference of the central opening (1'), - at least one annular seal (8, 9) on each of the upper face (1b) and the lower face (1c) of the main frame body (1a), wherein each seal (8, 9) runs around at least one of the frame openings, wherein - the main frame body (1a) is formed from a non-metallic semi-finished fibre matrix product (3) which is at least partially embedded in an overmoulding (4) made of plastic, wherein individual surface regions of the semi-finished fibre matrix product (3) are arranged in at least two different layer planes (S1, S2, S3) of the frame main body (1a), said layer planes being spaced apart from one another in parallel, and wherein the frame main body (1a) forms a step (ST) between the upper face (1b) and the lower face (1c) adjacent to the central opening (1a).

Description

[0001] Frame for use in an electrochemical system, as well as electrochemical system, in particular electrolyzer

[0002] The invention relates to an electrically insulating, plate-shaped frame comprising a frame base with a top and a bottom, intended for use in a stacked electrochemical system. The invention further relates to a stacked electrochemical system, in particular an electrolyzer, especially for the production of hydrogen, with at least one such frame.

[0003] WO 2015 / 126746 A1 discloses an arrangement of electrochemical cells comprising a plurality of membrane electrode assemblies, each arranged between two cell separator plates. The cell arrangement according to WO 2015 / 126746 A1 further comprises frame elements and porous elements, which are made, for example, of carbon fiber paper or a woven carbon fiber nonwoven fabric.

[0004] US patent 8,349,151 B2 discloses an electrolyzer designed for water electrolysis, comprising frames on the anode and cathode sides. The frames feature structures for fluid flow and are equipped with seals.

[0005] EP 1 956669 B1 relates to a membrane electrode assembly for a solid polymer fuel cell. The device according to EP 1 956669 B1 comprises a polymer electrolyte membrane, a fuel electrode layer, and an air electrode layer, each located on a surface of the membrane. Furthermore, the membrane electrode assembly includes a fiber-reinforced reinforcement frame made of a thermoset plastic, which is located on a portion of the polymer electrolyte membrane. The invention aims to further develop mechanically stressed components of electrochemical systems compared to the prior art, both with regard to manufacturing technology and operational properties.

[0006] This problem is solved according to the invention by a frame having the features of claim 1 for use in a stacked electrochemical system, in particular an electrochemical cell or an electrochemical cell stack, such as an electrolysis stack, preferably for the electrolysis of water, a fuel cell stack or a redox flow cell stack.

[0007] According to claim 9, an electrochemical system, in particular designed as an electrolyzer, may comprise at least one frame designed according to claim 1.

[0008] The electrically insulating, plate-shaped frame according to the invention has a frame base body with a top and a bottom, for use in a stacked electrochemical system.

[0009] The terms "top" or "bottom" do not imply any statement about the actual orientation of the frame in a three-dimensional space.

[0010] Furthermore, the frame has several openings comprising a central opening and several media passage openings arranged around the circumference of the central opening. These media passage openings allow fluid media, such as coolants or operating fluids, to pass through the frame body perpendicularly to the top or bottom surface.

[0011] Furthermore, the frame includes at least one ring-shaped seal on the top and bottom of the frame base body, with each seal surrounding at least one of the frame openings.

[0012] The frame body is formed from a non-metallic fiber-matrix semi-finished product (3), which is at least partially embedded in a plastic overmolding, wherein individual surface areas of the fiber-matrix semi-finished product are arranged in at least two different, parallel, spaced-apart layer planes of the frame body. Furthermore, the frame body forms a step between the top and bottom surfaces adjacent to the central opening.

[0013] Parts of the fiber-matrix semi-finished product can be located on the surface of the frame. This is advantageous, for example, to allow surface areas of the fiber-matrix semi-finished product to contact the mold used during an injection molding process and thus be used for positioning. In various configurations, the proportion of the fiber-matrix semi-finished product's surface not covered by overmolding is less than 25%, and in particular less than 10%.

[0014] Regardless of the surface area of ​​the fiber-matrix semi-finished product not covered by the plastic overmolding, the planar fiber-matrix semi-finished product, insofar as it has injection-molded plastic applied to it, can be arranged in a single layer within the overmolding. In any case, different surface areas of the fiber-matrix semi-finished product lie in different, parallel, and spaced-apart layer planes of the frame. The term "layer plane" is to be understood here purely geometrically. In particular, the layer planes do not define any boundaries between demountable individual parts of the frame.

[0015] A first surface area of ​​the fiber-matrix semi-finished product, located in a first layer plane, can be integrally connected to a second surface area of ​​the fiber-matrix semi-finished product, located in a further layer plane, by an intermediate section of the fiber-matrix semi-finished product that runs obliquely to the layers. Likewise, configurations are possible in which sections of the fiber-matrix semi-finished product, separated from one another in the normal direction of the layer planes, are located in different surface areas.

[0016] It is also possible to join flat sections of the fiber-matrix semi-finished product using separate connecting elements made of the same fiber-matrix material or of another material. Likewise, the fiber-matrix semi-finished product can be arranged in multiple layers in one, several, or all surface sections. In the case of a multi-layer arrangement, the individual layers can have a uniform thickness or vary in thickness.

[0017] Within the electrochemical system, the frame's primary function is to define an active zone—that is, the area where electrochemical reactions take place—and, if applicable, a cooling layer. The frame may incorporate structures for positioning and securing at least one seal, which are typically integrated into the frame body as sealing grooves. These seals define a space for the operating medium or cooling medium of the electrochemical system. In this context, the term "cooling medium" refers to any medium that can regulate temperature, including any medium that can introduce heat into the electrochemical system.

[0018] Fluorocarbon rubber (FKM) or ethylene propylene diene monomer rubber (EPDM) have proven particularly effective as sealing materials for the formation of seals.

[0019] Furthermore, the frame absorbs forces during operation of the electrochemical system, particularly those acting in the stacking direction of the electrochemical cells. These include forces acting on the seals. The frame is constructed entirely of plastic. Both thermosetting and thermoplastic materials are suitable for overmolding the fiber-matrix semi-finished product. Suitable plastics for overmolding include thermoplastics such as polyamides (PA), polyetherimides (PEI), polyetheretherketones (PEEK), polyetherketoneketones (PEKK), polypropylenes (PP), polyethylenes (PE), etc. Thermosetting plastics, such as epoxides, etc., can also be used.

[0020] Likewise, a wide variety of starting materials, particularly organic or inorganic fibers, exist for the production of the fiber-matrix semi-finished product. The fiber-matrix semi-finished product is preferably made of a non-metallic material. It ideally comprises at least one fiber material from the group consisting of glass fibers, carbon fibers, basalt fibers, and aramid fibers.

[0021] In particular, the fiber-matrix semi-finished product can be a so-called organosheet. DE 102010 053381 A1 serves as an example in this context. Generally, an organosheet is understood to be a continuous fiber-reinforced composite material comprising a woven fabric, for example, in the form of a carbon fiber or glass fiber fabric, embedded in a polymer matrix, especially a thermoplastic matrix. A thermoset matrix can also be used instead of a thermoplastic matrix. Regardless of the matrix material, a non-woven fabric can also be used instead of a woven fabric.

[0022] In comparison to unstressed plastic parts in which fiber segments are uniformly or unevenly distributed, the frame according to the invention is characterized, among other things, by the fact that the absence of fibers on the workpiece surface allows for a very high surface quality. This benefits the sealing properties and minimizes the probability of particles, such as fiber segments, entering the active area of ​​the electrochemical system. A single frame or multiple frames can be present per cell, particularly an electrolysis cell, of the electrochemical system.

[0023] At the same time, the frame's rigidity is drastically increased compared to all-plastic frames. Regarding manufacturability, even significant variations in wall thickness can be produced with minimal distortion – again, compared to all-plastic frames. Generally, a single reinforcing insert in the form of a fiber-matrix semi-finished product within the frame is sufficient. Frame designs are also possible in which multiple inserts, either flat or shaped, i.e., segments, reinforce the frame. The individual segments can be shaped, for example, by stamping or cutting and then joined together by forming and / or a compression molding and injection molding process, which will be discussed in more detail later. The process by which the fiber-matrix semi-finished product is formed into its final shape can include machining in a transfer press or compression mold.Final post-processing, such as deburring, can be carried out as required.

[0024] According to various possible configurations, more than two layer levels exist, for example, a total of three layer levels, each containing a surface area of ​​the fiber-matrix semi-finished product. Regardless of the number of layer levels, a media guidance structure can be formed by overmolding the fiber-matrix semi-finished product. Such a structure comprises, for example, at least one rib, and in particular, a plurality of ribs. Specifically, the overmolding creates a media guidance structure comprising at least one rib adjacent to each media passage opening, either on the top or bottom surface of the frame base.

[0025] Preferably, interlocking contours for stacking several identical frames are formed on the top and bottom surfaces of the frame body. A rib-shaped interlocking contour running around the edge of the frame on the top surface and a groove running around the bottom surface, into which the rib-shaped interlocking contour can engage, have proven particularly effective. However, differently shaped protrusions and recesses suitable for engagement by the protrusions are also suitable as interlocking contours.

[0026] In particular, in a section formed perpendicular to the surface through the frame base body, a surface area of ​​the fiber matrix semi-finished product is arranged sandwich-like between the top and bottom of the frame base body and between a plurality of mutually parallel ribs and at least one seal oriented orthogonally to the ribs.

[0027] In the case of an actively cooled electrochemical system, the frame preferably includes its own cooling level with cooling channels through which a coolant can be circulated. The frame can have one or more annular seals on the top and bottom of the frame body. For example, a seal provided by the frame has an elongated shape, oriented orthogonally to at least one of the aforementioned ribs designed to guide a fluid. A surface area of ​​the fiber-matrix semi-finished product can be sandwiched between a plurality of parallel ribs and the seal.

[0028] These seals can be injection-molded and therefore integrally bonded to the frame body. Alternatively, the seals can be designed as O-rings, for example. Sealing grooves can be provided in the frame body to facilitate injection molding or insertion of the seals. Injection-molded seals can be single- or multi-lip. In particular, several single-lip seals are provided on the frame, or alternatively, several single-lip seals are provided in combination with a multi-lip seal located on the underside of the frame body. Specifically, a seal pointing in the direction of the ribs is arranged on the step.

[0029] To manufacture a frame for a stacked electrochemical system, it is generally provided that a planar fiber-matrix semi-finished product, which has different surface areas that are offset from each other in the stacking direction of the electrochemical system, is overmolded with plastic, which is a thermoplastic or a thermosetting material.

[0030] In efficient process control, the same tool used for producing the plastic overmolding can be used to generate the offset between different surface areas of the fiber-matrix semi-finished product that is present in the final product, i.e., the finished frame.

[0031] The electrochemical system according to the invention, in particular an electrolyzer, comprises at least one frame according to the invention, at least one fluid-permeable, electrically conductive, open-porous first layer which is arranged to fill the central opening, at least one polymer electrolyte membrane or membrane electrode arrangement which is arranged on the stage and covering the first layer, at least one fluid-permeable, electrically conductive, open-porous second layer which is arranged congruently with the first on the polymer electrolyte membrane or membrane electrode arrangement, and two electrically conductive, flat electrode plates which are arranged to cover the top and bottom of the frame body. The electrode plates are preferably made of metal.

[0032] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows:

[0033] Fig. 1 a three-dimensional view of a frame (top side),

[0034] Fig. 2 shows another three-dimensional view of the frame (underside)

[0035] as shown in Figure 1 ,

[0036] Fig. 3 shows a section of the frame according to Figures 1 and 2 in a sectional view.

[0037] Fig. 4 shows a section of another frame in a sectional view, Fig. 5 shows a schematic representation of a tool usable for manufacturing a frame base body including a fiber matrix semi-finished product to be formed,

[0038] Fig. 6 shows the tool according to Figure 5 including the formed fiber matrix semi-finished product, and

[0039] Fig. 7 shows a section of an electrochemical system comprising several frames according to Figures 1 to 3.

[0040] Fig. 1 shows a three-dimensional view of an electrically insulating, plate-shaped frame 1 comprising a frame base 1a from the top side 1b. Fig. 2 shows another three-dimensional view of the frame 1 according to Fig. 1 comprising the frame base 1a from the bottom side 1c. Fig. 3 shows a partial sectional view of the frame according to Fig. 1 III-III. Identical reference numerals in Figs. 1 to 3 denote identical elements. The frame 1 can be used in a stacked electrochemical system 10, in particular an electrolyzer (see Fig. 7).

[0041] The frame 1 has several frame openings comprising a central opening 1' and several media passage openings 2 arranged around the circumference of the central opening 1'. Ring-shaped seals 8 are provided on the top 1b and bottom 1c of the frame body 1a, each seal 8 encircling at least one of the frame openings.

[0042] The terms "top" or "bottom" refer exclusively to the figures and do not imply any statement about the actual orientation of the frames 1 in space. In particular, a vertical orientation of the parallel frames 1 is possible.

[0043] Thus, four seals 8 are provided on the upper surface 1b of the frame body 1a. Two of the four seals 8 each surround four media passage openings 2. Another seal 8 surrounds the central opening 1' on a step ST, on which a polymer electrolyte membrane or a membrane-electrode assembly 17 can be placed in the electrochemical system 10. The fourth seal 8 surrounds the central opening 1', the seal 8 arranged around it, and six media passage openings 2, arranged in two groups of three. As can be seen in Figure 3, the frame body 1a is formed from a fiber-matrix semi-finished product 3, which is embedded in an overmolding 4 made of plastic. Individual surface areas of the fiber-matrix semi-finished product 3 are arranged in at least two different, parallel layer planes S1, S2, S3 of the frame body 1a.

[0044] In the present case, the frame 1 is therefore reinforced by the planar fiber-matrix semi-finished product 3, which is also referred to as a reinforcing insert. In the sketched embodiment, the fiber-matrix semi-finished product 3 is completely embedded in the overmolding 4 made of plastic. Alternatively, embodiments are also possible in which the overmolding 4 only partially covers the fiber-matrix semi-finished product 3, with the degree of coverage exceeding 75%, and in particular exceeding 90%.

[0045] The frame 1 has, among other things, a fluid-conducting function. For this purpose, it has a plurality of ribs 5, with channels formed between individual ribs 5 for conveying a fluid, i.e., a service fluid or coolant. In the sectional view according to Figure 3, a fluid can flow from the media passage opening 2, also called port 2, to the right through the channels in the direction of the central opening 1'. Similarly, a fluid can be discharged from the central opening 1' through the channels formed between the ribs 5 into port 2.

[0046] The frame 1 has several seals 8. These can be injection-molded and therefore integrally connected to the frame body 1a, or they can be attached in other ways, for example as O-rings, in sealing grooves 1d provided for the seals 8 in the frame body 1a. In the exemplary embodiment of the frame 1 according to Figures 1 to 3, only single-lipped seals 8 are present.

[0047] Figure 4 shows a section of another frame 1 in a sectional view similar to Figure 3. The same reference numerals as in Figure 3 denote identical elements. Here too, the frame 1 has several single-lipped seals 8 and a double-lipped seal 9 on the underside 1c, which are fitted into sealing grooves 1d provided in the frame body 1a. The double-lipped seal 9 is located in the same area of ​​the frame 1 below the reinforcing insert 3, where the ribs 5 extending from port 2 are located above the reinforcing insert 3. This means that a section of the reinforcing insert 3 is sandwiched between the ribs 5 and the double-lipped seal 9. The seal 9 has an elongated shape, which is oriented orthogonally to the ribs 5.The double-lipped seal 9 according to Figure 4 combines two single-lipped seals 8, which, according to Figure 3, are arranged on the underside 1c of the frame 1 in two separate sealing grooves 1d, into one in a space-saving manner. In order to be able to stack identical frames 1 on top of each other in a form-fitting manner during the formation of a stacked electrochemical system 10, a form-fitting contour 6 in the form of a circumferential rib is formed on the upper side 1b of the frame 1 according to Figure 4, and a corresponding form-fitting contour 7 in the form of a groove is formed on the underside 1c, into which the form-fitting contour 6 can engage.

[0048] Figures 5 and 6 illustrate the steps for manufacturing a frame 1. A multi-part tool 11 is used both for forming the fiber-matrix semi-finished product 3 and for injection molding the overmolding 4. In the arrangement shown in Figure 5, the tool 11, whose tool parts are labeled 12 and 13, is open. The fiber-matrix semi-finished product 3, which is still undeformed at this stage, is placed into the cavity of the tool 11 labeled 14. By closing the tool 11, an inclined transition area 15 is formed between flat areas of the fiber-matrix semi-finished product 3. This inclined transition area is retained throughout the further manufacturing process and is also visible in the sectional views shown in Figure 3 or 4. After the fiber-matrix semi-finished product 3 has been formed, the distance between the tool parts 12 and 13 is increased again until the configuration shown in Figure 3 or 4 is achieved.In this setting, the fiber-matrix semi-finished product 3 is overmolded with plastic, i.e., the overmolding 4 is produced. In contrast to the process illustrated in Figures 5 and 6, process variants are also possible in which the fiber-matrix semi-finished product 3 is formed in at least one separate tool and, if necessary, cut to size before being overmolded in another tool. During the cutting process, recesses can also be created that expose the central opening 1' and the media passage openings 2 in the finished frame 1.

[0049] Regarding the arrangement of the formed reinforcement insert 3 in the frame 1, reference is again made to Figure 3 or 4. According to these figures, various planar areas of the fiber-matrix semi-finished product 3 are located in different, parallel layer planes S1, S2, S3. The areas of the fiber-matrix semi-finished product 3 located in the different layer planes S1, S2, S3 are connected to each other via the transition areas 15 already mentioned. In the exemplary embodiment, the reinforcement insert 3 approaches the underside 1c of the frame 1 from the outside inwards, i.e., in the direction of the central opening 1, in a stepped manner. Below the ribs 5 provided for fluid routing, the reinforcement insert 3 is located in the middle layer plane S2. The reinforcement insert 3 extends over the step ST in the frame base body 1a towards the central opening 1' and reinforces the thinnest area of ​​the frame 1 particularly effectively there.

[0050] The virtually complete coverage of the reinforcement insert 3, regardless of which layer level S1, S2, or S3 it is located in, results in a particularly high surface quality of the overmolding 4. This is especially relevant in surface areas of the overmolding 4 where it makes sealing contact with another frame 1 or another component of the electrochemical system 10.

[0051] The electrochemical system designated 10 in Figure 7 is, in the exemplary embodiment, designed as an electrolyzer for producing hydrogen from water. An electrochemical system 10 comprises at least one frame 1 according to Figures 1 to 3, at least one fluid-permeable, electrically conductive, open-porous first layer 16a, which is arranged to fill the central opening 1' of the frame 1, at least one polymer electrolyte membrane or membrane electrode assembly 17, which is arranged on the ST stage (compare Figures 3 and 4) and covering the first layer 16a, at least one fluid-permeable, electrically conductive, open-porous second layer 16b, which is arranged congruently with the first layer on the polymer electrolyte membrane or membrane electrode assembly 17, and two electrically conductive, flat electrode plates 18, which are arranged to cover the top 1b and the bottom 1c of the frame body 1a.The electrode plates 18 are preferably made of metal.

[0052] Furthermore, a stacked electrochemical system 10, in particular an electrolyzer, can comprise a plurality of stacked frames 1 according to Figures 1 to 4, wherein the frames 1 contain ports 2 for supplying and discharging operating and cooling media. Within the frames 1, in the region of the central openings 1', lie the active fields of the electrochemical system 10 (not shown), i.e., the areas in which the desired electrochemical reactions take place.

[0053] Regarding the basic function and structure of stacked electrolysis systems, reference is also made to the prior art cited at the beginning. List of reference symbols

[0054] 1 frame

[0055] 1a Frame base

[0056] 1b Top

[0057] 1c Underside

[0058] 1d Sealing groove

[0059] central opening

[0060] 2 Media penetration opening, Port

[0061] 3 Fiber matrix semi-finished product, reinforcement insert

[0062] 4. Overmolding

[0063] 5th rib

[0064] 6. Form-fitting contour, here in the form of a rib

[0065] 7. Form-fit contour, here in the form of a groove

[0066] 8 Single-lipped seal

[0067] 9. Multi-lipped seal

[0068] 10 electrochemical system, electrolyzer

[0069] 11 tools

[0070] 12 Tool part

[0071] 13 Tool part

[0072] 14 Cavity

[0073] 15 Transition area

[0074] 16a, 16b open-porous layer

[0075] 17 Polymer electrolyte membrane, membrane electrode assembly 18 Electrode plate

[0076] S1, S2, S3 layer levels

[0077] ST level

Claims

Patent claims 1. Electrically insulating, plate-shaped frame (1) comprising a frame base body (1a) with a top (1b) and a bottom (1c), for use in a stacked electrochemical system (10), comprising - several frame openings comprising a central opening (1') and several media passage openings (2) arranged around a circumference of the central opening (1'), - at least one annular seal (8, 9) on the top (1b) and bottom (1c) of the frame base body (1a), wherein each seal (8, 9) surrounds at least one of the frame openings, wherein - the frame base body (1a) is formed from a non-metallic fiber matrix semi-finished product (3), which is at least partially embedded in an overmolding (4) made of plastic, wherein individual surface areas of the fiber matrix semi-finished product (3) are arranged in at least two different layer planes (S1, S2, S3) of the frame base body (1a) that are spaced apart from each other, and wherein the frame base body (1a) forms a step (ST) between the top (1b) and the bottom (1c) adjacent to the central opening (1a).

2. Frame (1) according to claim 1, characterized in that the surface area of ​​the fiber matrix semi-finished product (3) not covered by overmolding (4) is less than 25% and more than two layer planes (S1 , S2, S3) exist, in each of which a surface area of ​​the fiber matrix semi-finished product (3) is located.

3. Frame (1) according to claim 1 or 2, characterized by form-fitting contours (6, 7) formed on its upper surface (1b) and lower surface (1c) for stacking several similar frames (1).

4. Frame (1) according to one of claims 1 to 3, characterized in that by overmolding (4) a structure comprising at least one rib (5) for media guidance is formed adjacent to each media passage opening (2) either on the top (1b) or on the bottom (1c) of the frame base body (1a). is.

5. Frame (1) according to claim 4, characterized in that, in a section formed perpendicular to the surface (1b) through the frame base body (1a), a surface area of ​​the fiber matrix semi-finished product (3) is arranged sandwich-like between the top (1b) and the bottom (1c) of the frame base body (1a) and between a plurality of mutually parallel ribs (5) and at least one seal (8, 9) oriented orthogonally to the ribs (5).

6. Frame (1) according to one of claims 1 to 5, characterized by at least one multi-lipped seal (9) arranged on the underside (1c) of the frame base body (1a).

7. Frame (1) according to one of claims 1 to 6, characterized in that each seal (8, 9) is arranged in a sealing groove (1d) in the frame base body (1a).

8. Frame (1) according to one of claims 4 to 7, characterized in that a seal (8) pointing in the direction of the ribs (5) is arranged on the step (ST).

9. Electrochemical system (10), in particular electrolyzer, comprising at least one frame (1) according to one of claims 1 to 8, at least one fluid-permeable, electrically conductive, open-porous first layer (16a) which is arranged to fill the central opening (1'), at least one polymer electrolyte membrane (17) which is arranged on the step (ST) and covering the first layer (16a), at least one fluid-permeable, electrically conductive, open-porous second layer (16b) which is arranged congruently with the first layer on the polymer electrolyte membrane (17), and two electrically conductive, flat electrode plates (18) which are arranged to cover the top (1b) and the bottom (1c) of the frame base body (1a).

10. Electrochemical system (10) according to claim 9, wherein the electrode plates (18) are metallic.

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