WO2022128738A1

WO2022128738A1 - Cell element for a redox-flow battery, and membrane layer

Info

Publication number: WO2022128738A1
Application number: PCT/EP2021/085022
Authority: WO
Inventors: Udo Martin; Andreas Schiegl; Lars KÜHNLE; Christian Teufel
Original assignee: J.Schmalz Gmbh
Priority date: 2020-12-18
Filing date: 2021-12-09
Publication date: 2022-06-23
Also published as: DE102020134183A1

Abstract

The invention relates to a cell element (10) for a redox-flow battery, comprising a cell frame (14) which defines a frame opening (16), an electrode (18) which is arranged within the frame opening and provides an active surface (22) of the cell element, and a membrane layer (24) which is designed and arranged relative to the cell frame so as to cover the frame opening, wherein the membrane layer has at least one ion-conductive region (30) and at least one non-ion-conductive region (32). The invention additionally relates to a membrane layer (24) for use in a cell element.

Description

Title: Cell element for a redox flow battery as well

membrane layer

description

The invention relates to a cell element for a redox flow battery according to the preamble of claim 1 and a membrane layer for use in such a cell element.

Redox flow batteries are electrochemical energy stores with free-flowing, in particular liquid, storage media in which a redox-active material or a redox-active substance is dissolved in a liquid electrolyte. The electrolytes (anolyte or catholyte, depending on polarity) are provided separately, eg stored in separate tanks and, if necessary, an electrochemical one Energy converter unit (the so-called. Cell of the redox flow battery) supplied for the charging or discharging process. When loading or During the discharging process, the redox-active materials in the cell are oxidized in separate half-cells or reduced . Here, chemical energy is converted into electrical energy during the discharging process and electrical energy is converted back into chemical energy during the charging process. In particular, one advantage of redox flow batteries is that the power (number and size of the electrochemical energy converters/cells) and capacity (electrolyte volume, size and number of tanks) can be adjusted independently of one another, enabling centralized and decentralized storage systems on a few kilowatt scale up to megawatts are easily realizable .

A redox flow battery usually includes a large number of identical cells, which are connected hydraulically and fluidly in parallel and electrically in series. The cells are usually arranged in a stack called a Cell stack, assembled and pressed using a bracing system. The bracing system can include, for example, end plates made of plastic and/or non-ferrous metals such as aluminum, between which the individual cells are arranged and braced using tension elements. In addition, the cell stack can include a media plate for connecting media inlet and outlet lines and electrical connection lines.

Each individual cell is made up of two half-cells, which are separated from one another by a membrane. the For their part, half-cells generally comprise a cell frame and an electrode, which provides the actual active surface of the respective half-cell, ie the active area in which the electrochemical processes take place. For the electrical connection of the individual cells in a cell stack, it is known to provide electrically conductive bipolar plates between the individual cells. In a cell stack, the individual components are stacked between the end plates in the following order: bipolar plate, cell frame with electrode, membrane, cell frame with electrode, bipolar plate, cell frame with electrode, etc. Such a structure of a cell stack is described for example in US 2017/0324108A1.

In each cell, the membrane has the task of sealing the active surfaces of the adjoining half-cells from one another, of insulating them electrically and at the same time enabling an exchange of ions between the active surfaces. For this purpose, it is known to use ion-conducting membrane foils and to cut and arrange them in such a way that the membrane foil covers the active surfaces of the two adjacent half-cells and also partially overlaps with the cell frames. In the cell stack, the membrane foil is then clamped between the cell frames and thus sealed. In this case, an overlap between the cell frame and the membrane is generally kept as small as possible in order to save costs for the comparatively expensive ion-conducting material. In practice, however, this regularly leads to difficulties in positioning the membrane foil, which usually Maneuvered by hand or with a grip. In addition, it can happen that the surface of the comparatively sensitive membrane film becomes contaminated or damaged during assembly or operation of the cell stack.

The present invention deals with the task of enabling a simple, reliable and cost-effective construction of a cell stack of a redox flow battery.

This problem is solved by a cell element with the features of claim 1 .

The cell element is designed for use in a redox flow battery, in particular for use in a cell stack of a redox flow battery.

The cell element comprises a cell frame which encloses a frame opening. The cell element also includes an electrode located within the frame opening. The electrode is preferably supported by the cell frame. In particular, the electrode can be designed as a felt-electrode, for example. be made of a graphite felt z. The electrode provides an active surface of the cell element. To this extent, the electrode defines in particular the active area of the cell element in which the electrochemical processes take place. In particular, the effective area corresponds to the surface area of the electrode within the frame opening. The electrode preferably completely fills the frame opening. Then the Effective area in particular a dimension of the frame opening. In particular, the electrode has the same surface area as the frame opening.

The cell element also includes a membrane layer, in particular in the form of a material layer that can be distinguished from the electrode. The cell element thus forms in particular a half-cell membrane unit of a cell. The membrane layer extends over an area and is arranged relative to the cell frame in such a way that it covers the frame opening, in particular completely, when viewed in a direction orthogonal to a frame plane spanned by the cell frame. In this respect, the membrane layer also covers the effective area of the electrode that is delimited by the frame opening. The membrane layer is preferably in contact with the electrode.

The membrane layer has at least one ion-conducting area and at least one non-ion-conducting area. In this respect, the membrane layer is designed in particular in such a way that it has at least one surface section in which ion conduction through the membrane layer is possible and that it has at least one surface section in which no ion conduction through the membrane layer is possible.

Such an embodiment facilitates the construction of a cell stack, since the membrane layer can be gripped and positioned in a simple manner over the at least one non-ion-conducting area without the sensitive area having to touch ionically conductive areas. In this way, in particular, material waste as a result of damage to or contamination of the membrane surface can also be reduced. With such a cell element, the proportion of comparatively expensive ion-conducting material can also be reduced, thus promoting a cost-effective construction of a cell stack. For this purpose, the cell element can advantageously be designed in such a way that the at least one ion-conducting area of the membrane layer is limited in its surface area to the effective area and the membrane layer bears exclusively with the at least non-ion-conducting area on the cell frame.

Membrane layer, cell frame and electrode are preferably connected to one another in a fluid-tight manner. In particular, it is possible for the cell frame and/or membrane layer and/or electrode to be connected to one another with a material fit, for example by gluing, laminating and/or welding. In principle, however, it is also possible for the cell frame and membrane layer to be initially loosely joined together and only connected to one another in a fluid-tight manner by pressing in the cell stack. In order to increase a sealing effect and/or to reduce compression forces, the membrane layer and/or the cell frame can be provided with sealing elements, for example in the form of sealing rings surrounding the frame opening.

In particular, the membrane layer is designed and arranged in such a way that it is connected to the at least one ion-conducting area covers the active surface at least in sections. In order to ensure efficient ion exchange over the entire surface area of the active surface, it can be advantageous if the membrane layer is designed and arranged in such a way that the at least one ion-conducting region completely covers the active surface, in particular the electrode, when viewed orthogonally to the frame plane , in particular having the same surface area as the active surface. The membrane layer preferably lies flush with the at least one ion-conducting area on the active surface. In this respect, the membrane layer is designed in particular in such a way that the at least one ion-conducting area exclusively covers the active surface. Such a cell element is constructed in a particularly cost-effective manner, since comparatively expensive ion-conducting material is only used where ion conduction is required for the function of the cell element.

In order to protect the at least one ion-conducting area from mechanical influences from the cell frame, it can also be advantageous if the surface area of the at least one ion-conducting area is slightly smaller than the surface area of the active surface, so that an edge area of the active surface adjoining the cell frame is protected from the at least an ionically conductive area is not covered. In other words, the membrane layer can be designed and arranged in such a way that the at least one ion-conducting area in particular the frame opening, completely covered except for a peripheral edge area. A width of the edge area, in particular a distance between an outer edge of the at least one ion-conducting area and the cell frame, is preferably less than 5 mm, more preferably less than 2 mm, more preferably less than 1 mm.

As part of an advantageous development, the membrane layer can be designed in such a way that the at least one non-ion-conducting area surrounds the at least one ion-conducting area viewed in the area. In particular, the at least one non-ionically conductive area frames the at least one ionically conductive area. The ionically conductive area on the inside is then protected from damage by the non-ionically conductive area on the outside. Such a membrane layer can also be gripped at the edge in a simple manner without having to touch the comparatively sensitive ion-conducting area, which promotes easy handling of the membrane layer when assembling the cell element.

The membrane layer preferably rests, in particular exclusively, with the at least one non-ion-conducting region on the cell frame, in particular on a parallel to the effective surface or to the frame plane oriented cell frame surface. It when the at least one non-ionically conductive area is dimensioned such that it is parallel to the is particularly advantageous Frame level oriented cell frame surface completely covered, in particular corresponds to a dimension of the cell frame surface. This achieves a particularly good seal between the membrane layer and the cell frame. In particular, no additional components or sealing elements are required for sealing channel structures optionally provided in the cell frame in such a configuration.

Furthermore, it can be advantageous if the membrane layer has the same external dimensions as the cell frame when viewed orthogonally to the frame plane. In this respect, the membrane layer is in particular designed and arranged in such a way that the membrane layer and cell frame terminate flush with one another at their respective outer contour. Such a cell element can be assembled in a particularly simple manner, since the membrane layer and cell frame can be easily and reliably positioned relative to one another and then connected due to the same external dimensions.

To supply the electrode with electrolytes, the cell frame can include channel structures for supplying and removing fluid into the frame opening. In addition or as an alternative, it is also possible for the membrane layer to have channel structures in the at least one non-ion-conducting region for supplying and discharging electrolyte liquid into the frame opening. In an advantageous embodiment, the cell frame can at least one side towards the Have membrane layer of fene channel structure for supplying and / or discharging fluid in the frame opening. The channel structure can then be covered in particular by the non-ion-conducting area of the membrane layer. It can also be advantageous if the membrane layer, in particular in the at least one non-ion-conducting region, has at least one corresponding counter-channel structure open on one side in the direction of the cell frame. The channel structure of the cell frame and the counter-channel structure of the membrane layer are then preferably configured relative to one another and the cell frame and the membrane layer are arranged relative to one another in such a way that the channel structure and the counter-channel structure are aligned with one another and thus form a common, in particular closed, fluid channel. In such an embodiment, the cross section of the channel structure, in particular the electrolyte-carrying channel structure, in the cell frame can be enlarged and the pressure drop of the electrolyte as it flows through the channel structure can thus be reduced.

In principle, the membrane layer can be constructed in one or more parts. Within the scope of a possible configuration, the membrane layer can comprise a plastic film which is designed to be ion-conducting in some areas and non-ion-conducting in some areas. In particular, the plastic film can consist and/or be produced in some areas from an ion-conducting material and in some areas from a non-ion-conducting material. Preferably, the membrane layer consists of a single one plastic film. A one-piece membrane layer can be maneuvered and positioned particularly easily when assembling the cell element. In addition, such a membrane layer promotes effective sealing of the active surface, since boundary surfaces are reduced.

It is also possible for the membrane layer to comprise a base film which is made of an ion-conducting material over its entire surface, with the base film--to form the at least one non-ion-conducting area--in some areas having a surface modification such that ion conduction is prevented in these areas. The membrane layer can preferably consist of such a base film. The surface change can in particular be a surface treatment or an application of material. In particular, the base film can have a surface coating that prevents ion conduction in certain areas. Such a membrane layer can be produced in a particularly simple and cost-effective manner. It is conceivable, for example, that a surface layer made of a non-ion-conducting silicone or epoxy resin is applied in certain areas to the base film, for example by means of screen printing processes. It is also conceivable that chemical substances are applied to areas of the base film (eg via a spraying process) which inactivate the functional groups of the ion-conducting material of the base film that cause ion conduction and thus prevent ion conduction through the base film. The membrane layer can also be made in several parts. In particular, the membrane layer can comprise at least one ion-conducting film, preferably made from an ion-conducting material, and a non-ion-conducting edge layer, preferably made from a non-ion-conducting material. In such a configuration, the at least one ion-conducting area is then provided by the at least one ion-conducting film and the at least one non-ion-conducting area is provided by the non-ion-conducting edge layer. Such a multi-part structure makes it possible to individually adapt the membrane layer to different requirements in a simple manner. For example, it is conceivable that the at least one ion-conducting film is selected as required depending on an electrolyte used. An advantageous configuration can consist in particular in that the non-ion-conducting edge layer is designed in the shape of a frame and delimits a central opening. The at least one ion-conducting film can then be arranged in particular within the opening, preferably completely filling the opening.

The non-ionically conductive edge layer can consist of a single non-ionically conductive plastic film. It is also possible for the non-ion-conducting edge layer to have a multi-layer structure, in particular to be formed by a plurality of plastic films stacked on top of one another. Preferably, the plastic films are formed separately, insofar as the plastic films for producing the Membrane layer are provided as separate elements and then assembled to form the membrane layer.

In principle, it is conceivable that the at least one ion-conducting film and the edge layer or the at least one non-ion-conducting plastic film, are only loosely joined together and are only pressed together in a fluid-tight manner when used in the cell stack. However, in order to achieve a good seal, it can be advantageous if the films are connected to one another in a fluid-tight manner, in particular in a material-locking manner. For this purpose, it can be advantageous if the at least one ion-conducting film and the edge layer, or the at least one non-ion-conducting plastic film is made of materials that can be connected to one another, preferably in an electrolyte-tight manner, e.g. by plastic welding with heating element, ultrasonic or laser welding, thermal joining, sealing, gluing and/or laminating.

In order to increase the mechanical stability of such a multilayer membrane layer, it can be advantageous if a dimensionally stable layer is introduced between at least two of the non-ion-conducting plastic films of the edge layer, for example in the form of a metal insert or a mat made of fiber-reinforced plastic. The dimensionally stable layer is preferably arranged in such a way that it is completely surrounded by the plastic films and is therefore separated from the electrolyte. In the case of a multi-part construction of the membrane layer from separately formed foils, it is particularly easy to select individually advantageous materials for the different functions of the at least one ion-conducting area and the at least one non-ion-conducting area and to combine their properties with one another in the membrane layer. For example, it is possible to combine materials with high ion conductivity for the ion-conducting area with robust, inexpensive materials that provide a good sealing effect for the non-ion-conducting area.

As part of an advantageous embodiment, the at least one non-ion-conducting area, in particular the non-ion-conducting edge layer, more particularly the at least one non-ion-conducting plastic film, made of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyphenylene sulphide (PPS) or polytetrafluoroethylene (PTFE) or be made from combinations of the materials mentioned.

In order to achieve a good seal between the membrane layer and the cell frame, it can also be advantageous if the at least one non-ion-conducting area, in particular the non-ion-conducting edge layer, more particularly the at least one non-ion-conducting plastic film, is a non-ion-conducting elastomer includes, in particular consists of. In particular, the non-ion-conductive surface layer made of a thermoplastic Elastomer ( TPE ) or from a pure elastomer, such as e.g. B. Ethylene-propylene-diene rubber (EPDM), fluorine rubber (FKM), silicone rubber or a combination of the materials mentioned. If such a material is used, an electrolyte-tight connection between the membrane layer and an adjacent cell frame can be made in a simple manner by pressing in the cell stack. In particular, the cell frame can then be designed without additional sealing elements, which promotes cost-effective production and simple assembly of the cell element.

The at least one ion-conducting region of the membrane layer can be made, in particular, from a selectively anion-conducting material or from a selectively cation-conducting material. For example, it is conceivable that the at least one ion-conducting area of the membrane layer, in particular the base film or the at least one ion-conducting film is made from a halogenated polymer, in particular from a fluorinated polymer, more in particular from a polymer containing perfluorosulfonic acid (PFSA), more in particular from a PFSA/polytetrafluoroethylene copolymer (e.g. a Nafion™ membrane ) . It is also conceivable, for example, for the at least one ion-conducting region to be made from a porous material.

Depending on a selected thickness of the membrane layer, when pressed in a cell stack on the Electrodes acting forces can be adjusted specifically, especially regardless of a thickness of the cell frame. A comparatively small thickness of the membrane layer, in particular in the at least one ion-conducting area, is advantageous for good ion conduction. On the other hand, as the thickness increases, the mechanical stability of the membrane layer is improved. It has proven to be advantageous if the membrane layer has a thickness in the range from 0.005 to 5.0 mm, in particular from 0.01 to 0.1 mm, more particularly from 0.03 to 1.0 mm. It is particularly advantageous if the membrane layer has a thickness in the range from 0.005 to 0.2 mm in the at least one ion-conducting region.

The object stated at the outset is also achieved by a membrane layer which is designed to be used in a cell element described above, or by using such a membrane layer in the manner mentioned. The advantages and features described above in relation to the cell element can be used to design the membrane layer.

The invention is explained in more detail below with reference to the figures. Show it:

FIG. 1: Sketched representation of an embodiment of a cell element in a plan view; FIG. 2: Sketched representation of the cell element according to FIG. 1 in a sectional view along the sectional plane II-II shown in FIG. 1;

Figures 3a and 3b: simplified schematic representation of a

Design of a membrane layer in a plan view (view a) and in a sectional view along the sectional plane IIIb-IIIb (view b) shown in view a;

FIGS. 4 to 6: simplified schematic representations of further configurations of a membrane layer in a sectional view along a sectional plane corresponding to the sectional plane IIIb-IIIb shown in FIG. 3a; and

Figure 7: Outlined representation of a cell of a

redox flow battery .

In the following description and in the figures, the same reference symbols are used for identical or corresponding features.

Figures 1 and 2 show an outline of an embodiment of a cell element, which overall with the reference numeral 10 is denoted. The cell element 10 is designed in particular for use in a redox flow cell 12, described in detail below and illustrated in FIG.

The cell element 10 comprises a cell frame 14 which delimits a central frame opening 16 . In the example shown, both the cell frame 14 and the frame opening 16 have a rectangular basic shape. In the case of configurations that are not shown, the cell frame 14 and/or frame opening 16 can also have other geometries.

The cell element 10 also includes an electrode 18 which is arranged within the frame opening 16 and preferably fills it completely. As can be seen from FIG. 2, the electrode 18 in the example shown lies flush against the inner edges 20 of the cell frame 14 facing the frame opening 16 and is held there. The electrode 18 can, for example, be designed as a felt electrode.

The electrode 18 provides an active surface 22 of the cell element 10, on which the electrochemical processes take place when the cell element 10 is used as intended in a redox flow battery. In the example shown, the active surface 22 corresponds to the entire surface area of the electrode 18 . In this respect, the active surface 22 has, for example, the same surface area as the frame opening 16 (cf. FIG. 1). The cell element 10 also comprises a membrane layer 24, which is arranged on an outer side 26 of the cell frame 14 and rests there on the cell frame surface 28 oriented parallel to a frame plane spanned by the cell frame 14 (parallel to the drawing plane in Figure 1) (cf. Figure 2 ) . In the example shown, the membrane layer 24 has the same external dimensions as the cell frame 14 when viewed orthogonally to the plane of the frame (cf. FIG. 1). In this respect, the membrane layer 24 completely covers both the frame opening 16 and the cell frame surface 28 .

FIG. 3a schematically shows such a membrane layer 24 in a plan view. The membrane layer 24 has an ion-conducting region 30 (shown shaded gray in FIGS. 2 and 3) and a non-ion-conducting region 32 (shown without shading in FIGS. 2 and 3). By way of example and preferably, the non-ionically conductive region 32 surrounds the ionically conductive region 30 in the form of a frame (cf. FIG. 3a).

As shown in FIG. 2, the ion-conducting region 30 is, for example and preferably, dimensioned such that, when viewed orthogonally to the plane of the frame, it has the same surface area as the electrode 18 and thus as the active surface 22 . In the example shown, the ion-conducting area 30 has the same surface area as the frame opening 16 . The membrane layer 24 preferably lies flush with the ion-conducting region 30 on the electrode 18 . In the case of configurations that are not shown, the ion-conducting area 30 can also be dimensioned in such a way that it completely covers the electrode 18 except for an edge area adjoining the cell frame 14, i.e. an edge area of the electrode 18 not by the ion-conducting area 30 but by the non-ion-conducting area Area 32 is covered.

As can be seen from FIG. 2, the membrane layer 24 in the example shown is in contact with the cell frame 14 exclusively with the non-ion-conducting region 32 . By way of example and preferably, the non-ion-conducting region 32 is dimensioned in such a way that it has the same surface area as the corresponding cell frame surface 28 .

In order to supply the electrode 18 with electrolyte liquid, the cell frame 14 in the example shown comprises a plurality of channel structures 34 for supplying and removing electrolyte liquid into the frame opening 16 (cf. FIG. 1). The channel structures 34 are, for example and preferably, formed by corresponding recesses 36 on the cell frame surface 28 of the cell frame 14 (cf. FIG. 2). As can be seen from FIG. 2, the recesses 36 are covered by the non-ion-conducting region 32 of the membrane layer 24 and are thus sealed. In order to feed the channel structures 34 with electrolyte liquid, the cell frame 14 in the example shown in FIG can be formed, for example, by circular recesses in the cell frame 14 .

In configurations that are not shown, it is possible for the membrane layer 24 to have counter-channel structures in the non-ion-conducting region 32, which are designed to correspond to the channel structures 34 of the cell frame 14 and are arranged in such a way that, when the membrane layer 24 and the cell frame 14 are in the assembled state, they are aligned with the channel structures 34 of the cell frame 14 and thus form a closed fluid channel.

FIG. 2 also shows optional sealing elements 40 which are arranged between membrane layer 24 and cell frame 14 . The sealing elements 40 are designed, for example, in the form of sealing rings, which are arranged in corresponding grooves 42 on the cell frame surface 28 of the cell frame 14 . Advantageously, the sealing elements 40 and the grooves 42 completely surround the frame opening 16 .

The membrane layer 24 shown schematically in FIG. 2 can in principle take on different configurations, in particular it can be designed in one piece or in multiple pieces (cf. FIGS. 3a to 6).

As shown schematically in FIGS. 3a and 3b, the membrane layer 24 can be provided, for example, by a plastic film 44, which in some areas consists of an ion-conducting material (Ionically conductive area 30) and is made in some areas from a non-ionically conductive material (non-ionically conductive area 32) (highlighted in FIGS. 3a and 3b by the different shades).

Figures 4 to 6 show further exemplary configurations of the membrane layer 24, each in a sectional view analogous to Figure 3b, with a basic shape of the respective membrane layer 24, in particular the surface area and relative arrangement of the ion-conducting area 30 and the non-ion-conducting area 32, the corresponds to the configuration shown in FIG. 3a.

In an embodiment shown in FIG. 4, the membrane layer 24 comprises a base film 46 which is made of an ion-conducting material over its entire surface (for example a PFSA membrane). The base film 46 has a surface coating 48 in certain areas, which prevents ion conduction. In the example shown, the surface coating 48 is provided on both sides in an edge region 49 of the base film 46, analogously to the non-ionically conductive region 32 shown in FIG. 3a. The edge area 49 of the base film 46 with the surface coating 48 forms the non-ionically conductive area 32 in this respect. In the case of configurations that are not shown, the surface coating 48 can also be provided on only one side of the base film 46 .

In a further configuration shown in FIG. 5, the membrane layer 24 has a multi-part design. In which illustrated example, the membrane layer 24 comprises an ion-conducting film 50 which provides the ion-conducting region 30 . For example, the ionically conductive foil 50 can be made of a PFSA membrane. The membrane layer 24 also includes a non-ionically conductive edge layer 51 which provides the non-ionically conductive region 32 . As can be seen from FIG. 5, the edge layer 51 in the example shown is formed from two non-ion-conducting plastic films 52-1, 52-2. The non-ion-conducting plastic films 52-1, 52-2 are, for example and preferably, designed in the shape of a frame and delimit a central opening 54 in which the ion-conducting film 50 is arranged. By way of example and preferably, the central opening 54 has the same surface area as the active surface 22 . As can be seen from FIG. 5, the two non-ion-conducting plastic films 52-1, 52-2 are stacked on top of one another, with the ion-conducting film 50 being arranged between the two non-ion-conducting plastic films 52-1, 52-2.

The ion-conducting film 50 and the non-ion-conducting plastic films 52-1, 52-2 can in particular be connected to one another with a material fit, for example by means of gluing, welding and/or laminating. In the case of configurations that are not shown, only one or more than two non-ion-conducting films 52-1, 52-2 can also be provided.

The non-ion-conducting plastic films 52-1, 52-2 can be made of polyethylene (PE), polypropylene (PP), Polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE) or combinations of the materials mentioned. It is also possible for the non-ion-conducting plastic films 52-1, 52-2 to be made from a thermoplastic elastomer (TPE) or from a pure elastomer, such as an ethylene-propylene-diene rubber (EPDM), fluororubber or silicone rubber are.

Optionally, a dimensionally stable layer 56 can be inserted between the non-ion-conducting plastic films 52-1, 52-2, for example in the form of a metallic film or a fiber-reinforced plastic mat. As shown by way of example in FIG. 6, the dimensionally stable layer 56 is preferably completely enclosed by the non-ion-conducting plastic films 52-1, 52-2, so that the dimensionally stable layer 56 is electrically insulated from the electrode 16. By way of example and preferably, the dimensionally stable layer 56 completely surrounds the opening 54 .

As already mentioned, a cell element 10 described above is used in particular for use in a redox flow cell 12 (cf. FIG. 7). Such a cell 12 basically comprises two half cells 58 - 1 , 58 - 2 which are separated from one another by a membrane layer 24 . Each half-cell 58-1, 58-2 in turn comprises a cell frame 14-1, 14-2 and an electrode 18-1, 18-2, the electrode 18-1, 18-2 being exemplarily and preferably in a frame opening 16-1 , 16-2 of the respective cell frame 14-1, 14-2 is arranged. The cell 12 shown in FIG. 7 comprises in this respect a cell element 10 described above (cell frame 14-1, electrode 18-1 and membrane layer 24) and a further cell frame 14-2 with electrode 18-2. In other words, a cell element 10 described above provides a half-cell 58 - 1 and the membrane layer 24 of the cell 12 .

As can be seen from FIG. 7, the cell frames 14-1, 14-2 are, by way of example and preferably, of identical design, but are folded relative to one another by 180° about the plane of the membrane.

The membrane layer 24 bears against both cell frames 14-1, 14-2 in an analogous manner. For the further configuration of the cell frames 14-1, 14-2, the electrodes 18-1, 18-2 and the membrane layer 24 and their relative arrangement, reference is made to the configurations described above in relation to the cell element 10.

In a redox flow battery, a plurality of such cells 12 can be stacked on top of one another in a stacking direction 60 to form a cell stack (not shown) and by a

Verspannsystem (not shown) be pressed against each other. A bipolar plate 62 can be arranged in such a cell stack between the individual cells 12 for the electrical connection of adjacent cells 12 . FIG. 7 shows two such bipolar plates 62-1, 62-2, which are each arranged on that cell frame surface 64-1, 64-2 of the corresponding cell frame 14 which is opposite the cell frame surface 28 on which the membrane layer 24 rests. Preferably, the bipolar plates cover 62-1, 62-2 also the frame opening 16 and thus the active surface 22 completely. To seal off the bipolar plates 62-1, 62-2 from the cell frame 14, optional sealing elements 66 can be provided, which can be configured and arranged analogously to the sealing elements 40 described above between the cell frame 14 and the membrane layer 24.

Claims

27

Claims Cell element (10) for a redox flow battery, comprising

- A cell frame (14) defining a frame opening (16);

- An electrode (18), which is arranged within the frame opening (16) and provides an active surface (22) of the cell element (10);

- a membrane layer (24), which is designed and arranged relative to the cell frame (14) in such a way that it covers the frame opening (16), characterized in that the membrane layer (24) has at least one ion-conducting region (30) and at least one non-ion-conducting region -Ionically conductive region (32). Cell element (10) according to claim 1, wherein the at least one ion-conducting area (30) of the membrane layer (24) has almost the same surface area as the active area (22), in particular completely covering the active area except for an edge area. Cell element (10) according to one of the preceding claims, wherein the at least one non-ion-conducting area (32) surrounds the at least one ion-conducting area (30), in particular the membrane layer (24) with the at least one non-ion-conducting area (32). the cell frame (14) rests. Cell element (10) according to any one of the preceding claims, wherein the membrane layer (24) has the same external dimensions as the cell frame (14). Cell element (10) according to any one of the preceding claims, wherein the cell frame (14) comprises a channel structure (34) open in the direction of the membrane layer (24) for supplying and/or discharging fluids into the frame opening (16), the membrane layer (24), in particular in the at least one non-ion-conducting region (32), has a corresponding counter-channel structure which is open in the direction of the cell frame (14) and the cell frame (14) and the membrane layer (24) are arranged relative to one another in this way, that the channel structure (34) and the counter-channel structure form a common fluid channel. Cell element (10) according to one of the preceding claims, wherein the membrane layer (24) comprises a plastic film (44), in particular consists of a single plastic film (44) which is partially ion-conductive and partially non-ion-conductive. Cell element (10) according to any one of the preceding claims, wherein the membrane layer (24) comprises a base film (46) which is made of an ionically conductive material, wherein the base film (46) - for

forming the at least one non-ionically conductive

Area (32) - one by area Has a surface change such that ion conduction is prevented, in particular wherein the base film (46) has a surface coating (48) that prevents ion conduction in some areas.

8. Cell element (10) according to one of claims 1 to 5, wherein the membrane layer (24) comprises at least one ion-conducting film (50) and a non-ion-conducting edge layer (51), in particular wherein the at least one ion-conducting film (50) and the non-ion-conducting edge layer (51) fluid-tight, in particular cohesively, are connected to each other.

9. cell element (10) according to claim 8, wherein the non-ion-conductive edge layer (51) comprises a plurality of stacked plastic films (52-1, 52-2).

10. Cell element (10) according to claim 9, wherein a dimensionally stable layer (56) is introduced between at least two plastic films (52-1, 52-2).

11. Cell element (10) according to any one of claims 8 to 10, wherein the non-ion-conducting edge layer (51) made of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyphenylene sulfide (PPS) or Polytetrafluoroethylene (PTFE) or combinations of the materials mentioned is made. 12. Cell element (10) according to one of claims 8 to 10, wherein the non-ion-conducting edge layer (51) consists of a non-ion-conducting elastomer, in particular a thermoplastic elastomer (TPE) or an ethylene-propylene-diene rubber (EPDM ) , a fluorine rubber (FKM), a silicone rubber or a combination of the materials mentioned.

13. Cell element (10) according to one of the preceding claims, wherein the at least one ion-conducting region (30) of the membrane layer (24) is made of a selectively anion-conducting material or of a selectively cation-conducting material or of a porous material.

14. Cell element (10) according to any one of the preceding claims, wherein the membrane layer (24) has a thickness between 0.005 and 5.0 mm, in particular between 0.01 and 0.1 mm, further in particular between 0.03 and 1.0 mm.

15 membrane layer (24) for use in a cell element (10) according to any one of the preceding claims.