Flow frame for an electrochemical cell

Abstract

Flow frame (10) for an electrochemical cell, in particular for a cell of a redox flow battery, wherein the flow frame (10) defines at least one electrode space (14) for receiving an electrode, comprising: - at least one supply channel system (16, 16-1, 16-2) for supplying electrolyte into the electrode space (14), wherein the supply channel system (16, 16-1, 16-2) comprises a fluid connection (20, 20-1, 20-2) which is fluidically connected to the electrode space (14) via supply channel structures (22, 22-1, 22-2); - at least one return channel system (18, 18-1, 18-2) for returning electrolyte from the electrode chamber (14), wherein the return channel system (18, 18-1, 18-2) comprises a fluid connection (24, 24-1, 24-2) which is fluidically connected to the electrode chamber (14) via return channel structures (26, 26-1, 26-2); wherein the supply channel structures (16, 16-1, 16-2) and / or the return channel structures (18, 18-1, 18-2) comprise a plurality of secondary channels (32) which branch off at separate positions of the respective fluid connection (20, 24) and open into the electrode space (14) via inflow regions (34) wherein the secondary channels (32) each have a plurality of sub-channels (38), wherein the secondary channels (32) each comprise a plurality of secondary channel segments (46-1, 46-2, 46-3, 46-4), which each have a plurality of sub-channels (38) and which are arranged one behind the other along the extension of the respective secondary channel (32) from the fluid connection (20, 24) to the electrode space (14), wherein at least one secondary channel segment (46-3) of at least one secondary channel (32) has a smaller number of sub-channels (38) than a secondary channel segment (46-2) located upstream of this secondary channel segment (46-3) along the extension of this secondary channel (32) from the fluid connection (20, 24) to the inflow region (34).

Description

[0001] The invention relates to a flow frame for an electrochemical cell, in particular for a redox flow battery stack. The invention also relates to an electrochemical cell, in particular a redox flow battery cell.

[0002] Redox flow batteries are electrochemical energy storage devices with flowable, particularly liquid, storage media in which a redox-active material or substance is dissolved in a liquid electrolyte. The electrolytes (called anolyte or catholyte depending on their polarity) are provided separately, e.g. stored in separate tanks, and fed as needed to an electrochemical energy conversion unit (the so-called cell of the redox flow battery) for the charging or discharging process. During the charging or discharging process, the redox-active materials in the cell are oxidized or reduced in separate half-cells. During the discharging process, chemical energy is converted into electrical energy, and during the charging process, electrical energy is converted back into chemical energy.A particular advantage of redox flow batteries is that power (number and size of electrochemical energy converters / cells) and capacity (electrolyte volume, size and number of tanks) can be adjusted independently of each other, so that centralized and decentralized storage systems can be realized on a scale of a few kilowatts to megawatts.

[0003] A redox flow battery typically comprises a plurality of identical cells connected fluidically in parallel and electrically in series. The cells are assembled into a stack, the so-called cell stack, and pressed together using a bracing system and, if necessary, clamped using tie rods. The bracing system typically comprises end plates made of plastic and / or non-ferrous metals such as aluminum, between which the individual cells are arranged. Additionally, the bracing system can include insulating plates to separate the current-carrying individual cells from the end plates, current collectors with electrical connections for conducting or supplying the charging or discharging current, and media connections for supplying and discharging the electrolyte (anolyte / catholyte).

[0004] To electrically connect the individual cells, a so-called bipolar plate, e.g., made of a graphite-plastic composite material, is usually placed between two individual cells. Each individual cell, in turn, is composed of two half-cells separated by an ion-conducting membrane.

[0005] The half-cells, in turn, each comprise a flow frame and an electrode, which is usually arranged in a frame opening of the flow frame. The frame opening thus forms an electrode chamber for accommodating an electrode and defines the actual active space or active area of ​​the half-cell, i.e., the active region in which the electrochemical processes take place. In addition, the known flow frames usually comprise an integrated supply channel system for supplying electrolyte into the electrode chamber and a return channel system for returning electrolyte from the electrode chamber. These channel systems usually comprise a fluid connection (primary channel), e.g., in the form of a through-hole in the flow frame, from which a single channel (secondary channel) branches off, which ultimately opens into the electrode chamber via fan-shaped or comb-shaped distributor structures.Such a flow frame is known, for example, from US 2018 / 0062188 A1 and CN 2 04 596 879 U.

[0006] Further flow frames with feed and return channel systems are known from US 5 851 694 A, US 2017 / 0 229 715 A1 and CN 2 14 152 946 U.

[0007] However, existing systems regularly experience high pressure drops across the primary and secondary channels, which can limit the efficiency of the redox flow battery stack and the entire redox flow battery system, especially at high electrolyte flow rates. Furthermore, existing systems often exhibit uneven electrolyte distribution within the active chamber, which can also negatively impact battery performance.

[0008] The present invention addresses the problem of improving electrolyte flow in a redox flow battery. In particular, high electrolyte volume flows should be able to be efficiently and homogeneously conducted through the active spaces of a redox flow battery cell. Furthermore, flexible scaling of the redox flow battery is desirable.

[0009] This object is achieved by a flow frame having the features of claim 1. The flow frame is designed for use in an electrochemical cell, in particular for use in a cell of a redox flow battery.

[0010] The flow frame defines a frame opening for accommodating an electrode. The frame opening thus forms an electrode space for accommodating the electrode. In particular, the electrode space defines the actual effective space of a half-cell comprising such a flow frame.

[0011] The flow frame comprises at least one supply channel system formed in the flow frame for supplying electrolyte to the electrode chamber. The supply channel system comprises a fluid connection (primary channel) through which electrolyte can be supplied to the flow frame. The fluid connection is fluidically connected to the electrode chamber via supply channel structures. The supply channel structures thus open into the electrode chamber.

[0012] The flow frame also includes at least one return channel system formed in the flow frame for returning electrolyte from the electrode chamber. The return channel system also includes a fluid connection (primary channel) through which electrolyte can be drained from the flow frame.

[0013] The fluid connection is fluidically connected to the electrode chamber via return channel structures.

[0014] The fluid connections are connected to the electrode chamber, in particular via the channel structures (supply channel structures or return channel structures), in such a way that electrolyte can be supplied to and removed from the electrode chamber, in particular to an electrode arranged therein, via the channel systems. In particular, the fluid connections can be designed in the form of through-holes in the flow frame.

[0015] The supply channel structures and / or the return channel structures comprise a plurality of secondary channels (fluid channels) that branch off from different and separate positions of the respective fluid connection. Viewed the other way around, the secondary channels open into the respective fluid connection at different positions and separately from one another. At their other end, the secondary channels open into the electrode chamber or the frame opening via inflow regions, in particular comprising distributor structures for distributing fluid. The secondary channels therefore extend, in particular, from the respective fluid connection to the respective inflow region.

[0016] In the proposed flow frame, not only a single channel branches off from a fluid connection, which then branches out, e.g., in a tree-like manner. Instead, a plurality of fluid channels (secondary channels) are provided, which branch off from the fluid connection at different positions and are thus fluidically connected in parallel. In particular, the secondary channels themselves do not have any branches. In such a flow frame, the overall pressure drop between the fluid connection and the electrode space is reduced, since a total electrolyte volume flow is distributed across a plurality of secondary channels (segmented fluid flow). This can reduce the peripheral energy demand of a redox flow battery system, since, for example, lower pump pressures are required, which has a positive effect on the energy consumption of the peripheral units and the overall system efficiency. In addition, such a flow frame enables high electrolyte volume flows, e.g.to realize high electrical current densities [> 200 A / cm. 2 ] through a redox flow stack without significant performance degradation and / or uneven distribution of the electrolyte in the electrode space of the individual cells in the stack. A design with multiple secondary channels also promotes a compact design of the supply and return channel structures and thus a compact design of the entire flow frame (material cost savings).

[0017] The flow frame can be manufactured, for example, using an injection molding process. Advantageous materials for the flow frame include polypropylene, polyethylene, or polyamide.

[0018] The fluid connections can in particular be formed in the form of through-holes in the flow frame. In this respect, the secondary channels can branch off radially from the through-hole at different positions. The flow frames can in particular be stacked on top of one another in a stack such that the through-holes of the flow frames are aligned with one another, thus forming an electrolyte line penetrating the stack. The supply channel structures and the return channel structures are preferably formed in the flow frame, for example in the form of local recesses on the surface of the flow frame. The channel structures and / or the through-holes can already be created during the primary shaping of the flow frame (for example in an injection molding process). However, it is also conceivable for the channel structures and / or the through-holes to be created in a frame surface of the flow frame by material-removing methods, e.g. drilling, punching, or milling.

[0019] For a homogeneous fluid distribution in the electrode chamber, it may be advantageous if the supply channel system and the return channel system are configured such that the supply channel structures and the return channel structures open into the electrode chamber on opposite sides of the latter. Furthermore, it may be advantageous if the number of secondary channels of the supply channel structures and the number of secondary channels of the return channel structures are the same. In particular, the supply channel structures and the return channel structures can be arranged point-symmetrically to a center point of the electrode chamber.

[0020] A particularly homogeneous distribution of electrolyte in the electrode space can also be promoted by having each secondary channel open into the electrode space via its own inflow area. Therefore, a number of secondary channels and inflow areas are preferably identical. The inflow areas of the secondary channels are preferably spatially separated from one another. The secondary channels therefore preferably open into the electrode space at separate locations. This can reduce high local shunt currents when the electrolyte enters the electrode space.

[0021] Furthermore, it may be advantageous if the secondary channels are fluidically and electrically insulated from one another along their entire course from the fluid connection to the electrode chamber. In particular, the secondary channels can be fluidically and electrically insulated from one another along their course from the fluid connection to the electrode chamber by material sections of the flow frame, in particular in the form of webs.

[0022] The secondary channels, in turn, each have a plurality of sub-channels, in particular those running parallel. Such an additional subdivision into sub-channels further reduces the overall pressure drop. In addition, with such a configuration, the channel width per channel (sub-channel) is smaller than the channel width of an individual channel with a comparable overall flow cross-section to the sum of the sub-channels of a secondary channel. This makes it possible to easily seal the secondary channels or sub-channels using soft sealing materials, in particular flat gaskets, since the narrow channel width prevents the sealing materials from sinking into the channels, for example during pressing in the stack, or at least reduces this to an acceptable level. In this context, it can be advantageous if the channel width of the sub-channels is between 1 and 6 mm, preferably between 2 and 4 mm, and / or if the channel depth (orheight) of the subchannels is between 0.3 and 4 mm, preferably between 0.5 and 2 mm.

[0023] The subchannels can generally have the same flow cross-section, in particular the same channel width and / or channel depth. It is also conceivable for a subset of the subchannels of a flow channel to have a different flow cross-section. It is also conceivable for a subchannel to have a varying channel width and / or channel depth along its course within a secondary channel segment.

[0024] The subchannels, in turn, preferably open into the respective fluid connection at different positions, in particular separately from one another. In other words, the subchannels branch off, in particular, at different positions of the fluid connection.

[0025] The subchannels can extend along the entire length of a respective secondary channel. In particular, the subchannels can be fluidically and electrically insulated from one another along their entire length from the fluid connection to the electrode chamber. For example, the subchannels can be separated from one another at least in sections by webs. The webs can be formed by material sections of the flow frame. The webs can serve as support surfaces for optional sealing elements such as flat gaskets.

[0026] However, to enable compensation of any pressure differences between the subchannels, it may be advantageous if at least a subset of the subchannels of at least a subset of the secondary channels are connected to one another via at least one transverse channel. This can be achieved, for example, by interrupting the webs separating adjacent subchannels at least in sections. It is also conceivable to provide transverse channels of different widths.

[0027] The secondary channels comprise a plurality of secondary channel segments arranged one behind the other along the extension of the secondary channel from the fluid connection to the electrode space. In other words, each secondary channel is divided along its length into several sections, which together form the secondary channel. The secondary channels are designed such that they pass through various segments along their extension from the fluid connection to the electrode space.

[0028] At least one secondary channel segment of a secondary channel has a smaller number of subchannels than a secondary channel segment located upstream of this secondary channel segment along the extension of the secondary channel from the fluid connection to the inflow area. This can promote homogenization of the fluid flow through the secondary channel.

[0029] The secondary channel segments can be configured such that at least a subset of the secondary channel segments of a secondary channel has a different orientation. In this respect, adjacent secondary channel segments can be arranged at an angle to one another, for example, they can run orthogonally to one another.

[0030] Homogenization of the fluid flow in the secondary channels can be further promoted by fluidically connecting the subchannels to one another via a grid-like channel network at a connection point, in particular a deflection point, between two adjacent secondary channel segments of a secondary channel. For example, the webs described above between adjacent subchannels can be interrupted in sections to form a grid-like channel network. Such a configuration also enables pressure differences between the subchannels to be compensated.

[0031] Within the scope of an advantageous embodiment, the at least one supply channel system and / or the at least one return channel system, in particular the secondary channels, can be designed such that a pressure difference between the fluid connection and the respective inflow area of ​​the secondary channels into the electrode space is between 0 and 10%, in particular between 0.1 and 1.0%.

[0032] In order to achieve the most homogeneous pressure drop possible across all secondary channels from their branching off from the fluid connection to the entry into the electrode chamber, it may also be advantageous if the at least one supply channel system and / or the at least one return channel system, in particular the secondary channels, further in particular a configuration of the sub-channels, are designed such that a difference between the partial volume flows through the secondary channels is less than 10%, preferably less than 1%, in particular between 0.1 and 0.8%.

[0033] For a homogeneous distribution of electrolyte fluid in the electrode space, it can also be advantageous if a segmented fluid guide also takes place at the level of the primary channels, i.e. at the level of the fluid connections. For this purpose, the flow frame can, within the scope of an advantageous development, have a plurality of supply channel systems described above and a plurality of return channel systems described above. In this respect, the flow frame can comprise a plurality of fluid connections for supplying electrolyte into the flow frame and a plurality of fluid connections for returning electrolyte from the flow frame. For example, it is conceivable for the flow frame to comprise at least two fluid connections which are connected to the electrode space by means of the supply channel structures described above, and at least two fluid connections which are connected to the electrode space by means of the return channel structures described above.Such a segmented fluid supply and fluid return further reduces the pressure drop, so that even high electrolyte volume flows can be efficiently passed through the electrode chamber.

[0034] Advantageously, the flow frame can comprise a plurality of flow frame segments, each having a supply channel system and a return channel system. The flow frame segments can be arranged adjacent to one another, in particular, along a frame axis. In particular, the flow frame segments each define an electrode space segment, wherein the electrode space segments as a whole form the electrode space.

[0035] The flow frame segments can be configured such that the electrode space segments of the flow frame segments, as a whole, form a continuous electrode space. For example, it is conceivable that the electrode space segments are open on one or both sides when viewed along the frame axis, so that the size of the electrode space can be variably changed by combining several flow frame segments. When the flow frame is used as intended, a single electrode can then be provided, for example, which fills the electrode space, in particular completely.

[0036] It is also conceivable for the electrode space segments to be fluidically separated from one another. In this respect, the flow frame segments can be designed such that they delimit a respective electrode space segment to the outside. For example, the flow frame can enclose a plurality of separate frame openings, with each frame opening forming an electrode space segment. Each electrode space segment is then assigned, in particular, a supply channel system and a return channel system in order to be able to supply electrolyte to or remove it from the electrode space segment. When the flow frame is used as intended, an electrode can then be arranged in each electrode space segment.

[0037] The flux frame can fundamentally be formed in one piece. In this respect, the flux frame segments can be formed by sections of the flux frame. However, it is also possible for the flux frame to be modularly assembled from the flux frame segments. In particular, the flux frame segments can be formed by separately provided frame elements which are connected to one another in a fluid-tight manner to form the flux frame. The frame elements can then in particular each enclose or at least partially delimit at least one frame opening which forms an electrode space segment. The frame elements can, for example, be connected to one another in a materially bonded manner, e.g. by welding and / or gluing. It is also conceivable for the frame elements to be connected in a fluid-tight manner by means of sealing elements.Such a modular design makes it possible to easily increase the electrode space and thus the effective area of ​​a half-cell and still achieve a low overall pressure drop.

[0038] In an advantageous embodiment, the flow frame segments can be designed identically to one another. Such a flow frame can be provided relatively cost-effectively, since the large number of identical parts allows for economies of scale in production (only one tool, mass production of identical parts).

[0039] Depending on the orientation of the flow frame segments in the flow frame, the relative arrangement of the fluid connections can then be changed. For example, it is conceivable for the flow frame segments to be arranged next to one another in the same orientation along the frame axis. Then, for example, the relative arrangement of the fluid connections can be identical for adjacent flow frame segments, i.e., those located next to one another along the frame axis. In this respect, the flow frame segments can, in particular, be designed and arranged such that a fluid connection of a flow frame segment that is fluidically connected to the electrode space is arranged next to a fluid connection of an adjacent flow frame that is fluidically separated from the electrode space.In particular, fluid connections which are fluidically connected to the electrode space and fluid connections which are fluidically separated from the electrode space segment can alternate along the frame axis.

[0040] It is also conceivable for adjacent flow frame segments to be rotated by 180° relative to one another around an axis of rotation. The axis of rotation can correspond to the frame axis. The axis of rotation can also run orthogonal to a frame plane spanned by the flow frame. The axis of rotation can also run orthogonal to the frame axis and lie in the frame plane. For example, it is conceivable for adjacent flow frame segments to be arranged in such a way that the relative arrangement of the fluid connections is reversed for adjacent flow frame segments, i.e. flow frame segments lying next to one another along the frame axis. In this respect, the flow frame segments can in particular be designed and arranged in such a way that, for adjacent flow frame segments, fluid connections of the same category (fluid connections fluidically connected to the electrode space or fluid connections fluidically separated from the electrode space) lie next to one another along the frame axis.This enables a particularly simple and space-saving fluid distribution to the fluid connections, since supply or return fluid connections are then preferably located next to each other.

[0041] The object stated at the outset is also achieved by an electrochemical cell according to claim 15. In particular, the electrochemical cell is a cell of a redox flow battery. The cell comprises a first and a second half-cell. The cell also comprises a membrane which is arranged between the first and the second half-cell. The membrane is in particular designed to be ion-permeable at least in sections. Each half-cell comprises a flow frame as described above and an electrode arranged in the electrode space of this flow frame. The electrode preferably completely fills the electrode space. The electrode can, for example, be a felt electrode, e.g. made of a carbon material.

[0042] In an advantageous embodiment, the flow frame of the first half-cell and the flow frame of the second half-cell are identical to one another, wherein the flow frame of the second half-cell is folded by 180° around one of its outer edges relative to the flow frame of the first half-cell.

[0043] For use in a redox flow battery, it may also be advantageous if a plurality of the cells described above are stacked to form a cell stack. To achieve this objective, a cell stack comprising a plurality of the cells described above is also proposed. The cells are stacked one on top of the other, in particular, along a stacking direction orthogonal to the frame plane spanned by the flow frame. A bipolar plate is arranged between each adjacent cell. A bipolar plate is thus assigned to each two adjacent half-cells.

[0044] The invention is explained in more detail below with reference to the figures.

[0045] They show: Fig. 1 simplified schematic representation of a design of a flow frame in a plan view and enlarged sections to explain an exemplary design of the channel structures; Fig. 2 simplified schematic representation to explain an exemplary design of a secondary channel; Fig. 3 simplified schematic representation to explain a connection between two secondary channel segments; Fig. 4 simplified schematic representation of a further embodiment of a flow frame; Fig. 5 simplified schematic representation of a further embodiment of a flow frame; Fig. 6 simplified schematic representation of a design of a flow frame constructed modularly from several frame elements; and Fig. 7 simplified schematic representation of a further embodiment of a flow frame constructed modularly from several frame elements.

[0046] In the following description and in the figures, the same reference symbols are used for identical or corresponding features.

[0047] The Fig. 1 shows a simplified schematic representation of an embodiment of a flow frame, which is designated overall by the reference numeral 10. The flow frame 10 is intended for use in a cell of a redox flow battery (not shown) already mentioned above, in particular in a redox flow battery stack.

[0048] The flow frame 10 defines a frame opening 12, which is central in the example. The frame opening serves to accommodate an electrode (not shown) and thus forms an electrode space 14 of the flow frame 10. The electrode space 14 forms the actual active space of the flow frame 10, i.e. the area in which the electrochemical processes take place.

[0049] The flow frame 10 also comprises a supply channel system 16 for supplying electrolyte into the electrode chamber 14 and a return channel system 18 for returning electrolyte from the electrode chamber 14.

[0050] The supply channel system 16 comprises a fluid connection 20 for supplying electrolyte fluid into the flow frame 10. The supply channel system 16 also comprises supply channel structures 22, via which the fluid connection 20 is fluidically connected to the electrode chamber 14 (explained in more detail below). Similarly, the return channel system 18 comprises a fluid connection 24 for discharging electrolyte fluid from the flow frame 10, as well as return channel structures 26, via which the fluid connection 24 is fluidically connected to the electrode chamber 14.

[0051] By way of example and preferably, the fluid connection 20 of the supply channel system 16 and the fluid connection 24 of the return channel system 18 are located diagonally opposite one another with respect to the electrode space 14 (cf. Fig. 1). Supply channel structures 22 and return channel structures 26 thus open into the electrode chamber 14 on opposite sides. Advantageously, the supply channel system 16 and the return channel system 18 can be arranged point-symmetrically to a center point of the electrode chamber 14.

[0052] In the illustrated example, the flow frame 10 also comprises two additional fluid connections 28, 30, which are not connected to the electrode chamber 14 via channel structures. The additional fluid connections 28, 30 are also arranged diagonally opposite one another, by way of example and preferably.

[0053] By way of example and preferably, the fluid connections 20, 24, 28, 30 are formed in the form of through holes in the flow frame 10. The flow frame 10 can be made, in particular, of polypropylene, polyethylene, or polyamide, for example by injection molding.

[0054] In a redox flow stack (not shown), the flow frames 10 are stacked in particular such that the fluid connections 20, 24, 28, 30 of adjacent flow frames 10 are aligned with one another, thus forming an electrolyte line running through the stack. As already mentioned, two flow frames 10 are preferably provided in a cell, which are arranged in a mirror-inverted manner. In this respect, the fluid connections 28, 30 without channel structures of one flow frame 10 can be fluidically connected, in particular aligned, to the fluid connections 20, 24 with channel structures 22, 26 of the second flow frame 10 of a cell.

[0055] In an exemplary application of the flow frame 10 in a redox flow battery, the fluid connection 20 can serve to supply one of the two electrolytes used in the redox flow battery (e.g., the catholyte) into the electrode chamber 14 (catholyte supply), and the fluid connection 24 can serve to return this electrolyte from the electrode chamber 14. The two other fluid connections 28, 30 (without channel structures) can then serve, in particular, to forward the other electrolyte (e.g., the anolyte) to the adjacent flow frame 10 of the cell.

[0056] As from Fig. 1, the feed channel structures 22 and the return channel structures 26 each comprise a plurality of, in the example shown four, secondary channels 32, which branch off from the respective fluid connection 20, 24 at different and separate positions (cf. section I in Fig. 1). The secondary channels 32 can thus discharge fluid from the fluid connection 20 (supply channel system) or supply fluid to the fluid connection 24 (return channel system) in parallel.

[0057] The secondary channels 32 open into the electrode chamber 14 via separate, spatially separated inflow regions 34. The inflow regions 34 may comprise distributor structures for distributing electrolyte fluid into the electrode chamber 14.

[0058] The secondary channels 32 are fluidically and electrically insulated from one another along their entire course from the fluid connection 20, 24 to the inflow regions 34, for example and preferably by material sections 36 of the flow frame 10.

[0059] The secondary channels 32 in turn each comprise a plurality of sub-channels 38, in particular running parallel to one another (cf. section II in Fig. 1). The sub-channels 38 themselves open into the fluid connection 20, 24 at different and separate positions (see section II in Fig. 1). The subchannels 38 are separated from each other at least in sections by material sections 40 of the flow frame 10 (webs 42).

[0060] Specifically, the subchannels 38 can be formed, at least in sections, by local recesses in a frame surface of the flow frame 10. For example, it is conceivable that the flow frame 10 with the channel structures 22, 26 is manufactured in an injection molding process.

[0061] As in Fig. As shown in Figure 1, Section II, the webs 42 can be interrupted in sections. The subchannels 38 can thus be fluidically connected to one another by transverse channels 44. It is also conceivable, in principle, for the subchannels 38 to be fluidically and electrically insulated from one another along their entire length.

[0062] The Fig. 2 shows a simplified schematic representation of an exemplary course of a secondary channel 32, wherein the subchannels 38 are represented in a simplified manner by arrow lines. The secondary channel 32 comprises a plurality of, for example four, secondary channel segments 46-1, 46-2, 46-3, 46-4, each of which has a plurality of subchannels 38. In the specific example, the first secondary channel segment 46-1 comprises two subchannels 38, the second secondary channel segment 46-2 comprises three subchannels 38, the third secondary channel segment 46-3 comprises two subchannels 38, and the fourth secondary channel segment 46-4 comprises four subchannels 38. In this respect, the number of subchannels 38 can vary along a course of the secondary channel 32 from the fluid connection 20, 24 to the inflow region 34.As illustrated in the transition from the second secondary channel segment 46-2 to the third secondary channel segment 46-3, the number of subchannels 38 along the path from the fluid connection 20, 24 to the electrode space 14 can in particular also decrease, further in particular and then increase again.

[0063] As in Fig. 2, the secondary channel segments 46-1, 46-2, 46-3, 46-4 can be arranged at an angle to one another, for example, they can run orthogonally to one another. Advantageously, at connection points 48 of two secondary channel segments 46, in particular at deflection points of two secondary channel segments 46, the subchannels 38 can be fluidically connected to one another by a grid-like channel network 50 (cf. Fig. 3). For example, the webs 42 can be interrupted in sections such that a grid-like channel network 50 is formed.

[0064] In the example shown, the subchannels 38 each have the same channel width. In embodiments not shown, however, it is also possible for the subchannels 38 to have different channel widths and / or channel depths. It is also possible for a channel width of a subchannel 38 to change during the transition from one secondary channel segment 46 to another secondary channel segment 46. It is also conceivable for a subchannel 38 to have a varying channel width along its course within a secondary channel segment 46.

[0065] By way of example and preferably, a channel width of the sub-channels 38 is between 1 and 6 mm, preferably between 2 and 4 mm and / or a channel depth (or height) of the sub-channels 38 is between 0.3 and 4 mm, preferably between 0.5 and 2 mm.

[0066] As already mentioned, the segmented fluid guidance described above at the level of the secondary channels 32 can optionally also be continued at the level of the primary channels (fluid connections 20, 24, 28, 30). An exemplary embodiment of such a further development with segmented fluid supply and fluid return is shown in the Fig. 4 to 7 shown.

[0067] At the Fig. 4, the flow frame 10 comprises, by way of example, two supply channel systems 16-1, 16-2 explained above and two return channel systems 18-1, 18-2 explained above. In this respect, two separate supply channel systems 16-1, 16-2 are provided for the electrode chamber 14 in order to be able to supply electrolyte fluid to the electrode chamber 14, as well as two separate return channel systems 18-1, 18-2 in order to be able to discharge electrolyte fluid from the electrode chamber 14. The corresponding supply channel structures 22-1, 22-2 and the return channel structures 26-1, 26-2 are shown in the Fig. 4-7 are shown simplified as a single line, but in particular comprise the plurality of secondary channels 32 and sub-channels 38 described above.

[0068] In the Fig. 4 and Fig. 5, the flow frame 10 comprises two flow frame segments 52-1, 52-2, which are arranged along a frame axis 54 (cf. double arrow 54 in Fig. 4) are arranged side by side. Each of these flow frame segments 52-1, 52-2 comprises one of the above-described supply channel systems 16-1, 16-2 and one of the return channel systems 18-1, 18-2. In the example, each flow frame segment 52-1, 52-2 also comprises the two previously mentioned fluid connections 28-1, 28-2, 30-1, 30-2 without channel structures. As explained above, the fluid connections 28-1, 28-2, 30-1, 30-2 are preferably designed in the form of through holes in the flow frame 10 and thus form fluid passages.

[0069] The flow frame 10 can basically be formed in one piece. In this respect, the flow frame segments 52-1, 52-2 can be formed by sections of the flow frame 10. However, the flow frame segments 52-1, 52-2 can advantageously be formed by separately provided frame elements 56-1, 56-2, which are connected to one another in a fluid-tight manner to form the flow frame 10 (in Fig. 4 and Fig. 5 by the dash-dotted central axis 57). For example, the frame elements 56-1, 56-2 can be connected to one another in a materially bonded manner, e.g., by welding and / or gluing. It is also possible for the frame elements 56-1, 56-2 to be connected to one another in a fluid-tight manner via corresponding sealing elements.

[0070] As from Fig. 4, each flow frame segment 52-1, 52-2 or each frame element 56-1, 56-2 delimits an electrode space segment 58-1, 58-2, wherein the electrode space segments 58-1, 58-2 in their entirety form the electrode space 14.

[0071] The Fig. 4 shows an exemplary embodiment in which the relative arrangement of the fluid connections 20, 24, 28, 30 is identical for both flow frame segments 52-1, 52-2. When used as intended, for example, the fluid connections 20-1, 20-2 can serve as the catholyte supply and the fluid connections 24-1, 24-2 can serve as the catholyte return. Then, the fluid connections 28-1, 28-2 can serve as the anolyte supply and the fluid connections 30-1, 30-2 can serve as the anolyte return. Of course, it is also possible for the catholyte and anolyte to be interchanged.

[0072] The Fig. Figure 5 shows a further embodiment in which the relative arrangement of the fluid connections 20, 24, 28, 30 in the two flow frame segments 52-1, 52-2 is reversed. In such an embodiment, the return fluid connections 24-1, 24-2 are arranged side by side, allowing for easy fluid removal.

[0073] For example, the flow frame can be Fig. 4 may be formed by two mutually identical frame elements 56-1, 56-2, wherein the frame element 56-2, which is the Fig. 4 right flow frame segment 52-2, compared to the frame element 56-1, which forms the Fig. 4 left flow frame segment 52-1, by 180° to a frame plane orthogonal to a frame plane spanned by the flow frame 10 (in Fig. 1 corresponding to the plane of the drawing).

[0074] The Fig. 6 and Fig. 7 show further embodiments of a flow frame 10 constructed modularly from several frame elements 56-1, 56-2. In the Fig. 6, the frame elements 56-1, 56-2 each define an electrode space segment 58-1, 58-2 that is open on one or both sides, so that in effect a continuous electrode space 14 is formed. Such a modular structure makes it possible to add optional additional frame elements (in Fig. 6, exemplified by the frame element 56-3' shown in dashed lines) to flexibly enlarge the electrode space 14.

[0075] At the Fig. 7, the frame elements 56-1, 56-2 each define an electrode space segment 58-1, 58-2, so that the flow frame 10 ultimately comprises a plurality of fluidically separated electrode space segments 58-1, 58-2, which in their entirety then form the electrode space 14. Also in the embodiment shown in Fig.7, the effective electrode space 14 can be enlarged overall by adding optional additional frame elements 56-3' and thus additional electrode space segments 58-3'.

Claims

[1] Flow frame (10) for an electrochemical cell, in particular for a cell of a redox flow battery, wherein the flow frame (10) defines at least one electrode space (14) for receiving an electrode, comprising: - at least one supply channel system (16, 16-1, 16-2) for supplying electrolyte into the electrode space (14), wherein the supply channel system (16, 16-1, 16-2) comprises a fluid connection (20, 20-1, 20-2) which is fluidically connected to the electrode space (14) via supply channel structures (22, 22-1, 22-2); - at least one return channel system (18, 18-1, 18-2) for returning electrolyte from the electrode chamber (14), wherein the return channel system (18, 18-1, 18-2) comprises a fluid connection (24, 24-1, 24-2) which is fluidically connected to the electrode chamber (14) via return channel structures (26, 26-1, 26-2); wherein the supply channel structures (16, 16-1, 16-2) and / or the return channel structures (18, 18-1, 18-2) comprise a plurality of secondary channels (32) which branch off at separate positions of the respective fluid connection (20, 24) and open into the electrode space (14) via inflow regions (34) wherein the secondary channels (32) each have a plurality of sub-channels (38), wherein the secondary channels (32) each comprise a plurality of secondary channel segments (46-1, 46-2, 46-3, 46-4), which each have a plurality of sub-channels (38) and which are arranged one behind the other along the extension of the respective secondary channel (32) from the fluid connection (20, 24) to the electrode space (14), wherein at least one secondary channel segment (46-3) of at least one secondary channel (32) has a smaller number of sub-channels (38) than a secondary channel segment (46-2) located upstream of this secondary channel segment (46-3) along the extension of this secondary channel (32) from the fluid connection (20, 24) to the inflow region (34). [2] Flow frame (10) according to claim 1, wherein each secondary channel (32) opens into the electrode space (14) via its own inflow region (34), in particular wherein the inflow regions (34) of the secondary channels (32) are spatially separated from one another. [3] Flow frame (10) according to one of the preceding claims, wherein the secondary channels (32) are fluidically and electrically insulated from one another along their course from the fluid connection (20, 24) to the electrode space (14). [4] Flow frame (10) according to one of the preceding claims, wherein the sub-channels (38) of a respective secondary channel (32) run parallel to one another. [5] Flow frame (10) according to one of the preceding claims, wherein the sub-channels (38) branch off at separate positions of the respective fluid connection (20, 24) and / or wherein the sub-channels (38) of a secondary channel (32) are separated from one another at least in sections along their longitudinal extent by webs (42). [6] Flow frame (10) according to one of the preceding claims, wherein the sub-channels (38) of at least a subset of the secondary channels (32) are interconnected via at least one transverse channel (44). [7] Flow frame (10) according to one of the preceding claims, wherein at least a subset of the secondary channel segments (46-1, 46-2, 46-3, 46-4) of a secondary channel (32) has a different orientation. [8] Flow frame (10) according to one of the preceding claims, wherein at a connection point (48), in particular a deflection point, of two secondary channel segments (46-1, 46-2, 46-3, 46-4) of a secondary channel (32), the sub-channels (38) are connected to one another via a grid-like channel network (50). [9] Flux frame (10) according to one of the preceding claims, wherein the flow frame (10) comprises at least two flow frame segments (52-1, 52-2) which are arranged next to one another along a frame axis (54), wherein each of these flow frame segments (52-1, 52-2) defines an electrode space segment (58-1, 58-2), wherein the electrode space segments (58-1, 58-2) in their entirety form the electrode space (14), and wherein each of these flow frame segments (52-1, 52-2) comprises a supply channel system (16) and a return channel system (18). [10] Flow frame (10) according to the preceding claim, wherein the electrode space segments (58-1, 58-2) form a continuous electrode space (14) or wherein the electrode space segments (58-1, 58-2) are fluidically separated from one another. [11] Electrochemical cell, in particular for a redox flow battery, comprising a first and a second half-cell, wherein a membrane is arranged between the first and the second half-cell, wherein each half-cell comprises a flow frame (10) according to one of the preceding claims and an electrode arranged in the electrode space (14) of this flow frame (10).

Images