Redox-Flusszelle

Abstract

A redox flow cell (10) comprising at least two electrode modules (1, 1') and at least one polymeric ion exchange membrane (9) arranged between the two electrode modules (1, 1'), wherein each electrode module (1, 1') comprises a metallic electrode plate (2) and an electrically insulating frame (3) encompassing the electrode plate (2), wherein the frame (3) has a constant frame thickness (RD) and extends between a top (5) and a bottom (6) of the frame (3), wherein the frame (3) has an outer circumference (3a) and at least one flow opening (3b), wherein the frame (3) has frame edges (3c) on the outer circumference (3a) and in the region of the flow openings (3b) which are covered by a sealing structure (4) and are each provided with the sealing structure (4) made of an elastically deformable plastic, wherein the sealing structure (4) is annular and is positively and releasably attached to the frame (3),In cross-section, it forms a U-shaped clip-on or insert sealing element.

Description

[0001] The invention relates to a redox flow cell comprising at least two electrode modules and at least one polymeric ion exchange membrane arranged between the two electrode modules, wherein each electrode module comprises a metallic electrode plate and an electrically insulating frame comprising the electrode plate, the frame having an outer circumference and at least one flow opening, each of which is provided with a sealing structure made of an elastically deformable plastic.

[0002] Electrode modules of this type for use in redox flow cells, as well as the construction of redox flow cells, are already known.

[0003] A redox flow cell uses chemically stored energy to generate electrical energy through redox reactions, with electrolyte solutions, used for energy storage, flowing through the cell. The electrolytes flowing through each half-cell of the redox flow cell are also called catholyte and anolyte. Depending on the design of the redox flow cell, the catholyte (also called prosolyte) and the anolyte (also called negolyte) can be interconverted. In principle, a redox flow battery can be constructed from a large number of redox flow cells, much like a rechargeable battery.A fundamental advantage of a redox flow battery compared to a rechargeable battery is that the capacity and electrical power of a redox flow battery can be scaled independently of each other, since the electrolyte solutions in the case of a redox flow battery are kept in tanks whose size is independent of the geometry and number of redox flow cells.

[0004] A common feature of electrochemical cells, such as those used in batteries, and redox flow cells is a membrane or ion exchange membrane, which is permeable to specific ions or molecules in a defined manner, but impermeable to electrons. Ions or molecules that pass through the membrane of a redox flow cell, that is, migrate from one half-cell to the other, can donate or accept electrons at electrodes located in the half-cells, representing oxidation or reduction, respectively. The electrodes can, in particular, form the walls of the half-cells.

[0005] DE 10 2020 133 090 A1 describes an electrode plate in the form of a three-dimensionally structured electrode sheet. The electrode sheet is part of a flux plate with an electrically insulating frame that has openings and seals. These openings allow an electrolyte solution to flow through the plate.

[0006] Applying sealing material to the frame and allowing it to harden into a seal that is bonded to the frame is time-consuming and leads to long lead times in the production of a flow plate, also called an electrode module.

[0007] JP 2004-103 296 A describes a solid electrolyte fuel cell with a current collector plate that includes a distributor opening. A ring-shaped sealing element with a U-shaped cross-section is located in the area of ​​the distributor opening for corrosion protection.

[0008] WO 03 / 094 264 A2 discloses a fuel cell in which U-shaped sealing elements, open towards the interior of the fuel cell, laterally surround and seal the current collector of the anode or cathode.

[0009] US 2013 / 0307227A1 describes an annular sealing element with a sealing body and forked, elongated sealing extensions arranged on one side of the sealing body, which is used for sealing between two thin plate elements. The plate elements can be components used in a secondary battery, such as a redox flow battery.

[0010] The object of the invention is to provide a redox flow cell with an alternative sealing structure that enables faster manufacturing of the electrode module.

[0011] The problem is solved for the redox flow cell with the features according to claim 1. The redox flow cell comprises at least two electrode modules and at least one polymeric ion exchange membrane arranged between the two electrode modules, each electrode module having a metallic electrode plate and an electrically insulating frame encompassing the electrode plate, the frame having a constant thickness and extending between a top and a bottom surface. The frame has an outer circumference and at least one flow opening, the frame having edges on the outer circumference and in the region of the flow openings, which are covered by a sealing structure and each provided with the sealing structure made of an elastically deformable plastic.The sealing structure is ring-shaped and forms a U-shaped clip-on or insert sealing element that is positively and releasably attached to the frame in cross-section.

[0012] The sealing structure is designed for automated positioning on the frame and for attaching it to the frame's circumferential edges or inserting it into existing flow openings. This simplifies the assembly process for the sealing structures and accelerates the production of an electrode module. Robots capable of simultaneously attaching sealing structures to multiple positions on the frame can be used for automated assembly.

[0013] The sealing structure is ring-shaped, and in particular, the ring is closed. In such a case, the dimensions of the sealing structure are adapted to the circumference of an opening in the frame or to the circumference of the frame itself, into which it is to be inserted or to which it is to be attached. Due to the elastic deformability of the sealing structure, it can be easily mounted on the frame by compressing or stretching it, whereby the sealing structure springs back to its original shape after the deformation force is removed.

[0014] The electrically insulating frame is preferably made of a plastic in the form of polypropylene (PP). Alternatively or additionally, the sealing structure is made of an elastically deformable plastic in the form of a thermoplastic elastomer (TPE). In particular, thermoplastic products have proven suitable for this purpose. ® K of the Kraiburg company has proven itself.

[0015] The electrically insulating frame has a thickness of 0.5 to 3 mm perpendicular to the electrode plate. This allows for the reliable automated application of a sealing structure to the frame. If the frame is too thick, the sealing structure is difficult to mount. If the frame is too thin, it lacks sufficient mechanical stability to allow for automated mounting of the sealing structure without damage or distortion of the frame.

[0016] The frame forms a frame edge on its outer circumference and in the area of ​​the at least one flow opening, which is preferably covered by the sealing structure. More precisely, the connection between the two legs of a U-shaped snap-on or push-in sealing element rests against this frame edge.

[0017] The sealing structure has a thickness of 0.1 to 0.5 mm in the area of ​​each frame edge. This ensures sufficient stability of the sealing structure during automated assembly on the frame.

[0018] An annular area adjacent to the frame edge on both the top and bottom of the frame is preferably covered by the sealing structure. More precisely, the two legs of a U-shaped snap-on or insert sealing element rest against this top and bottom surface. On the top or bottom of the frame, an annular sealing area with a width of 0.5 to 2 mm is particularly visible. During installation, this area snaps over the frame edge, locking the sealing structure into place within a flow opening. This locking mechanism makes it difficult to remove the sealing structure from the flow opening, even when removed in the opposite direction of installation.

[0019] The sealing structure has a thickness of 0.1 mm to 0.5 mm on both the top and bottom surfaces of the frame. This allows for good deformability of the sealing structure when inserting a push-in sealing element into a flow opening and precise positioning on the frame, as no folded or creased areas can form on the sealing structure. This dimensioning has also proven effective for a push-on sealing element, enabling the legs of the U-shaped push-on sealing element to be slid over the circumference of the frame.

[0020] In the case of a U-shaped snap-on sealing element, the fixing to the frame is achieved by the fact that the inner sides of the legs lie tightly against the top and bottom of the frame and the friction between the components counteracts any displacement.

[0021] The sealing structure is preferably injection-molded or extruded. This ensures cost-effective production of the sealing structure in large quantities.

[0022] The Fig. Figures 1 to 3 are intended to illustrate an electrode module and a redox flow cell constructed with it. This demonstrates: Fig. 1 an electrode module in a top view of the top of the frame, Fig. 2 a section II - II through the electrode module according to Fig. 1, and Fig. 3 A redox flow cell in a schematic representation.

[0023] Fig. Figure 1 shows an electrode module 1 for a redox flow cell 10 in a top view of the upper surface 5 of an electrically insulating frame 3 made of plastic. The electrode module 1 comprises a metallic electrode plate 2 with a three-dimensional embossed structure 2a and the frame 3 enclosing the electrode plate 2. The frame 3 has an outer circumference 3a (compare Figure 1). Fig. 2) and four flow openings 3b, each provided with a sealing structure 4, 4' made of an elastically deformable plastic. The sealing structure 4, 4' forms a U-shaped, in cross-section, snap-on or insert sealing element, positively and detachably attached to the frame 3, as shown in section II - II according to Fig. 2. The frame thickness is indicated by RD and extends between the top 5 and the bottom 6 of the frame 3. In the area of ​​the flow openings 3b, the frame 3 has frame edges 3c, which are covered by the respective sealing structure 4 in the form of a U-shaped insert sealing element. These are inserted into the flow openings 3b and locked in place due to their U-shape. In the area of ​​the outer diameter 3a of the frame 3, there is also a frame edge 3c, which is covered by a circumferential sealing structure 4' in the form of a U-shaped snap-on sealing element.

[0024] Fig. Figure 3 shows a schematic representation of a redox flow cell 10 or a redox flow battery with a redox flow cell 10. The redox flow cell 10 comprises two electrode modules 1, 1', shown only schematically (for details, see Figure 3). Fig. 1 and Fig. 2) a first reaction chamber 90a and a second reaction chamber 90b, each reaction chamber 90a, 90b being in contact with one of the electrode modules 1, 1'. The reaction chambers 90a, 90b are separated from each other by a polymeric ion exchange membrane 9. A liquid anolyte 91a is pumped from a tank 93a via a pump 92a into the first reaction chamber 90a and passed between the electrode module 1 and the membrane 9. A liquid catholyte 91b is pumped from a tank 93b via a pump 92b into the second reaction chamber 90b and passed between the electrode module 1' and the membrane 9. Ion exchange takes place across the membrane 9, with the redox reaction occurring at the electrode plates 2 (compare Fig. 1) electrical energy is released from the electrode modules 1, 1'.

[0025] The Fig.Figure 3 is intended to schematically illustrate the operation of a redox flow cell 10 with a membrane 9. However, setups with at least 10 or more membranes 9 are possible. Reference symbol list 1, 1' Electrode module 2 Electrode plate 2a Embossing structure 3 frames 3a External circumference 3b Flow opening 3c frame edge 4, 4' sealing structure 5 Top 6 Underside 9 polymeric ion exchange membrane 10 Redox flow cell 90a, 90b reaction chamber 91a Anolyte 91b Catholic 92a, 92b pump 93a,93b Tank RD frame thickness

Claims

[1] Redox flow cell (10) comprising at least two electrode modules (1, 1') and at least one polymeric ion exchange membrane (9) arranged between the two electrode modules (1, 1'), wherein each electrode module (1, 1') comprises a metallic electrode plate (2) and an electrically insulating frame (3) encompassing the electrode plate (2), wherein the frame (3) has a constant frame thickness (RD) and extends between a top (5) and a bottom (6) of the frame (3), wherein the frame (3) has an outer circumference (3a) and at least one flow opening (3b), wherein the frame (3) has frame edges (3c) on the outer circumference (3a) and in the region of the flow openings (3b) which are covered by a sealing structure (4) and are each provided with the sealing structure (4) made of an elastically deformable plastic, wherein the sealing structure (4) is annular and is positively and releasably attached to the frame (3). fastened,In cross-section, it forms a U-shaped clip-on or insert sealing element. [2] Redox flow cell (10) according to claim 1, wherein the frame is made of a plastic in the form of polypropylene (PP) and / or the sealing structure is made of the elastically deformable plastic in the form of a thermoplastic elastomer (TPE). [3] Redox flow cell (10) according to one of the preceding claims, wherein the frame (3) has a constant frame thickness (RD) perpendicular to the electrode plate (2) in the range of 0.5 to 3.0 mm. [4] Redox flow cell (10) according to one of claims 1 to 3, wherein the sealing structure (4) in the area of ​​each frame edge (3c) has a thickness in the range of 0.1 to 0.5 mm. [5] Redox flow cell (10) according to one of claims 1 to 4, wherein an annular area adjacent to the frame edge (3c) on the top (5) and the bottom (6) of the frame (3) is covered by the sealing structure (4). [6] Redox flow cell (10) according to claim 5, wherein the sealing structure (4) in the area of ​​the top (5) and the bottom (6) of the frame (3) each has a thickness in the range of 0.1 to 0.5 mm. [7] Redox flow cell (10) according to one of the preceding claims, wherein the sealing structure (4) is injection molded or extruded.

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