Flow frame unit for an electrochemical cell of a redox flow battery and cell stack

Abstract

The invention relates to a flow frame unit (12) for a redox flow battery and a cell stack (10) comprising at least two flow frame units (12).

Description

[0001] The invention relates to a flow frame unit for an electrochemical cell of a redox flow battery and to a cell stack comprising several such flow frame units.

[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 on a scale from a few kilowatts to megawatts can be realized.

[0003] A redox flow battery stack typically comprises a large number of identical cells connected fluidically in parallel and electrically in series. The cells are assembled into a cell stack (also called a cell stack) and pressed together using a clamping system.

[0004] In known systems, each individual cell is typically composed of two half-cells (anolyte half-cell and catholyte half-cell), each of which has a flow frame (also called a cell frame). The flow frames, in turn, have a frame opening that defines the actual cell space or active space of the half-cell, i.e., the active area in which the electrochemical processes take place. An ion-conducting membrane / separator is typically arranged between the two flow frames of a cell, fluidically separating the cell spaces of the half-cells.

[0005] In addition, the known flow frames typically include an integrated supply channel system for supplying electrolyte to the cell space and a return channel system for returning electrolyte from the cell space. These channel systems, in turn, typically have a primary channel (e.g., in the form of a through-hole in the flow frame), from which an often meandering secondary channel branches off, which ultimately flows into the cell space via fan-shaped or comb-shaped distribution structures. Such a flow frame is known, for example, from US 2018 / 0062188 A1.

[0006] To electrically connect the individual cells to each other, a so-called bipolar plate, e.g. made of a graphite-plastic composite material, is usually arranged between two individual cells.

[0007] Systems are also known in which the bipolar plate is integrated into the flow frame, thus dividing the frame opening into two sub-cell compartments (an anolyte compartment and a catholyte compartment). In a cell stack, these sub-cell compartments are then assigned to different cells.

[0008] From DE 20 2017 106 988 U1, for example, a cell stack of a redox flow battery is known, wherein the cell stack has a plurality of cell frames, wherein the cell frames each have a bipolar plate and a frame body, wherein an electrode is arranged in a respective frame opening of the frame body.

[0009] From CN 1 03 647 099 B, a flow battery is also known which comprises an electrode, an ion exchange membrane and a liquid flow frame arrangement, wherein the electrode and the liquid flow frame arrangement are arranged in contact with the ion exchange membrane, wherein the flow frame arrangement comprises a first body and a second body, wherein a flow channel is formed between the first body and the second body. In the known systems, however, high pressure drops occur across the primary and in particular across the secondary channel, which can limit the efficiency of a redox flow battery stack and the entire redox flow battery system, particularly in the case of large active spaces and the associated high electrolyte volume flows. In addition, undesirable shunt currents can occur.

[0010] The present invention addresses the problem of designing redox flow battery stacks with large effective working spaces that are easy to manufacture and efficiently operable.

[0011] This object is achieved by a cell stack having the features of claim 1, a flow frame unit having the features of claim 4, and a cell stack having the features of claim 18.

[0012] According to a first aspect, a cell stack, in particular a redox flow battery, is proposed. The cell stack has at least two flow frame units which are stacked on top of one another along a stacking direction. Each flow frame unit comprises a frame body (occasionally also referred to as flow frame or cell frame). The frame body extends flatly, in particular in a direction orthogonal to the stacking direction. The frame body has a frame opening, in particular a central one. The frame opening defines in particular a cell space (also called an active space) of the flow frame unit, i.e. an active region in which electrochemical reactions take place. Each flow frame unit also has a separating element, in particular a bipolar plate or membrane (or separator), preferably a bipolar plate, which is arranged in the respective frame opening.The separating element, in particular the bipolar plate or membrane / separator, is in particular aligned orthogonally to the stacking direction. The separating element, in particular the bipolar plate or membrane / separator, is arranged in the frame opening in such a way that it divides the frame opening into a first partial cell space, in particular catholyte space, and a second partial cell space, in particular anolyte space. An electrode can be arranged in each partial cell space. The cell stack comprises, for each partial cell space, a supply channel system, in particular a separate one, for supplying fluid, in particular electrolyte, further in particular catholyte or anolyte, into the partial cell space and a return channel system for returning fluid from the partial cell space. The channel systems, ie each supply channel system and each return channel system, each have a primary channel, which is connected to the corresponding partial cell space via at least one (ieone, two, three or more), in particular meander-shaped, further in particular extending orthogonally to the stacking direction, secondary channel. The primary channel extends in particular parallel to the stacking direction. For example, the primary channel can be formed by a recess, in particular a through-opening, further in particular a bore, in the frame body delimiting the respective partial cell space. The secondary channels extend in particular in a direction orthogonal to the stacking direction. The secondary channels each extend in the stacking direction at least in sections along their longitudinal extent over at least two adjacent frame bodies, in particular such that a diameter (height) of the secondary channel in the stacking direction is greater than a thickness of a frame body in the stacking direction, in particular at least 1.2 times as large, further in particular at least 1.5 times as large, further in particular at least 1.8 times as large.In this respect, the secondary channels are defined in particular by at least two adjacent frame bodies.

[0013] It has been shown that this approach can significantly reduce pressure drop in the cell stack with minimal design effort, while simultaneously reducing unwanted shunt currents. In particular, the proposed design allows for large flow cross-sections of the secondary channels without having to increase the thickness of the respective frame bodies. The proposed cell stacks therefore have a comparatively small overall dimension, which has a positive effect on power density and also saves material.

[0014] The separating element can be a membrane or a separator. In such a configuration with a membrane or separator in the frame opening, a bipolar plate is preferably arranged between two adjacent flow frame units. The bipolar plate covers, in particular, the electrochemical active areas, in particular the frame openings, of adjacent flow frame units. In particular, the first sub-cell space and the second sub-cell space of a flow frame unit then form one cell of the cell stack.

[0015] The separating element is preferably a bipolar plate. In this respect, each flow frame unit can have a bipolar plate, which is arranged in the respective frame opening and divides the frame opening into a first partial cell space, in particular a catholyte space, and a second partial cell space, in particular anolyte space. A membrane or a separator is then preferably arranged in the frame opening between two adjacent flow frame units. The membrane or separator covers in particular the electrochemical active regions, in particular the frame openings, of adjacent flow frame units. The membrane or separator preferably fluidically separates the partial cell spaces from one another. In particular, a partial cell space of a first flow frame unit and a partial cell space of an adjacent flow frame unit then form a cell of the cell stack.

[0016] Preferably, each secondary channel is formed by at least two overlapping, in particular channel-shaped, depressions or recesses (e.g. in the form of through-openings), in particular wherein a first depression or recess is formed in a frame body of a first flow frame unit and a second depression or recess is formed in a frame body of a second flow frame unit adjacent to the first flow frame unit. In this respect, channel-shaped depressions or recesses can be formed in at least two adjacent frame bodies and the frame bodies can be stacked on top of one another in such a way that the depressions or recesses overlap in order to form a common, in particular circumferentially closed fluid channel (secondary channel). The depressions can be formed, for example, as groove- or channel-shaped recesses on a frame body surface of the frame body.

[0017] It is conceivable for a secondary channel to extend through exactly two adjacent frame bodies. The secondary channel can then be formed, for example, by overlapping a first channel-shaped depression formed in the frame body of a first flow frame unit with a second channel-shaped depression formed in the frame body of a second flow frame unit adjacent to the first flow frame unit. It is also conceivable for a secondary channel to extend over more than two frame bodies. In this way, it is possible to realize secondary channels with diameters (heights) that exceed twice the thickness of a frame body. For example, a secondary channel can extend over four adjacent frame bodies, i.e. frame bodies stacked on top of one another along the stacking direction.Then, for example, it is conceivable for the two middle frame bodies to have recesses in the form of through-openings, allowing fluid to flow through the middle frame bodies along the stacking axis. The two outer frame bodies (upper and lower) along the stacking direction can then have recesses that overlap with the through-openings to form a secondary channel, preferably one that is closed around its circumference.

[0018] The secondary channels can in particular be formed at least in sections in that a supply channel is formed in the frame body delimiting a respective partial cell space, which is fluidically connected to the partial cell space, in particular opens into it, and in that a blind channel is formed in an adjacent frame body, which serves as a cross-sectional widening for the supply channel, but does not itself open into the partial cell space.

[0019] According to a second aspect, a flow frame unit is proposed. The flow frame unit is designed for use in an electrochemical cell, in particular for use in a cell of a redox flow battery. In particular, the flow frame unit is designed for use in the cell stack according to the first aspect. The flow frame unit comprises a frame body (occasionally also referred to as flow frame or cell frame). The frame body has a frame opening, in particular a central one. The frame opening defines in particular a cell space (also called active space) of the flow frame unit, i.e. an active region in which electrochemical reactions take place. In particular, one or more electrodes are arranged in the cell space.At least one first, in particular meander-shaped, furthermore in particular extending parallel to the frame plane, supply channel for supplying a first fluid, in particular catholyte, into the frame opening (cell space) is formed in the frame body. Furthermore, at least one first, in particular meander-shaped, furthermore in particular extending parallel to the frame plane, return channel for returning the first fluid, in particular catholyte, from the frame opening (cell space) is formed in the frame body. Furthermore, at least one second, in particular meander-shaped, furthermore in particular extending parallel to the frame plane, supply channel for supplying a second fluid, in particular anolyte, into the frame opening (cell space) is formed in the frame body.Furthermore, at least one second, in particular meander-shaped, furthermore in particular extending parallel to the frame plane, return channel for returning a second fluid, in particular anolyte, from the frame opening (cell space) is formed in the frame body. In addition to the supply channels and the return channels, in particular meander-shaped channels are formed in the frame body, which are closed at least at one end, in particular at an axial end (blind channels). In particular, the blind channels do not open into the frame opening (cell space) (an indirect flow connection of such a blind channel to the frame opening via a supply channel or return channel is not understood as opening in the present case). The number of blind channels corresponds in particular to at least the number of supply channels and return channels.The feed channels, the return channels, and the blind channels are formed as recesses or through-openings in the frame body, in particular on the first side and / or the second side, in particular channel-shaped recesses or through-openings, which extend parallel to the frame plane (orthogonal to a stacking direction). The feed channels, the return channels, and the blind channels can be formed as recesses or cutouts in a frame body surface of the frame body. In particular, the feed channels, the return channels, and the blind channels are formed as grooves or flutes in the frame body surface.

[0020] Such a flow frame unit with blind channels makes it possible, in a cell stack in which several such flow frame units are stacked on top of one another, to increase the flow cross-section of the feed channel or the return channel by overlapping each blind channel with a feed channel or a return channel, while maintaining a low thickness of the frame bodies. Cell stacks comprising such flow frame units can therefore be designed to be particularly space-saving, which is advantageous for high power density and also saves material. In particular, the proposed design of the flow frame units makes it possible to provide secondary channels with a total cross-section that is greater than the thickness of a frame body.

[0021] In this respect, according to a third aspect, a cell stack is proposed which comprises at least two flow frame units of the type described above, wherein the frame bodies, in particular the supply channels, return channels, and blind channels formed therein, are designed in such a way, and the frame bodies are stacked one on top of the other along a stacking direction, such that each supply channel and each return channel of a frame body overlaps, in particular is aligned, with a blind channel of an adjacent frame body at least in sections, so that a common, in particular circumferentially closed, fluid channel is formed in each case. Such a fluid channel can then, in particular, form a secondary channel.

[0022] During operation, the blind channels carry either the first or second fluid. In particular, the blind channels can be fed with fluid via the respective supply or return channel. It is also conceivable for the blind channel itself to be fed with fluid via a primary channel (see below).

[0023] Preferably, a membrane or a separator is arranged between two adjacent flow frame units, which membrane or separator covers the cell spaces of adjacent flow frame units and in particular fluidically separates them from each other.

[0024] The advantages explained above in connection with the first aspect apply analogously to the third aspect.

[0025] It is particularly advantageous if a respective channel depth of the feed channels, the return channels and / or the blind channels is more than 50% of a thickness of the frame body (i.e. an extension of the frame body in the thickness direction), in particular more than 60%, further in particular more than 70%, further in particular more than 80%. In this way, a particularly large flow cross-section can be achieved in an efficient manner. In particular, by overlapping the feed channel and blind channel or the return channel and blind channel, fluid channels (secondary channels) can be formed which have a diameter in the thickness direction that is greater than a thickness of a frame body in the stacking direction. In the present case, “channel depth” is understood to mean in particular an extension of the recess in the thickness direction of the frame body (orthogonal to the frame plane).

[0026] In a cell stack according to the third aspect, the frame bodies can be designed such that a diameter of a fluid channel formed by two overlapping channels (feed channel + blind channel or return channel + blind channel) in the stacking direction is larger than a thickness of a frame body in the stacking direction, in particular at least 1.2 times as large, further in particular at least 1.5 times as large, and further in particular at least 1.8 times as large.

[0027] The frame body extends flatly, in particular, in a frame plane. The frame body has a thickness in a thickness direction. The thickness direction is oriented orthogonally to the frame plane. In a cell stack, the thickness direction corresponds in particular to a stacking direction along which the flow frame units are stacked. The frame body has, in particular, a first side and an opposite second side.

[0028] The first and second sides extend in particular parallel to the frame plane, ie orthogonal to the thickness direction.

[0029] The frame opening or the cell space can have different shapes. For example, the frame opening can be square, rectangular, circular, ellipsoidal, or polygonal, especially hexagonal. A diamond shape has proven particularly advantageous. The frame opening can be rotated within the frame plane.

[0030] The frame body can be made in particular of plastic, more particularly of PE, PP, or PVC.

[0031] The supply channels, the return channels, and the blind channels can have different cross-sectional geometries. For example, the supply channels, the return channels, and / or the blind channels can be designed such that a fluid channel (secondary channel) formed by a supply channel and a blind channel or by a return channel and a blind channel has an oval, angular, polygonal, or star-shaped cross-section. A round shape has proven particularly advantageous.

[0032] The supply channels and the return channels or the secondary channels in particular do not open directly into the frame opening (cell space), but are flow-connected to an opening structure (opening region), which in turn opens directly into the cell space. In this respect, a separate opening structure, in particular a separate one, can be formed in the frame body for each supply channel and each return channel, which opens directly into the cell space and is flow-connected to the respectively assigned supply or return channel. The opening structure is in particular not part of the respective channel and can therefore differ in its design (e.g. shape, depth, cross-sectional shape) from the advantageous designs described in connection with the channels. The opening structure can in particular be designed as a distributor structure. The opening structure can be designed as a depression, in particular a recess or cutout, in the frame body.

[0033] Within the scope of an advantageous development, the first feed channel (and the first return channel) and the second feed channel (and the second return channel) can open into the cell space via a respective opening structure, wherein the opening structure of the first feed channel and the opening structure of the second feed channel open into the frame opening (cell space) at positions offset from one another along the thickness direction. In this respect, a first opening structure can be formed in the frame body, via which the first feed channel opens into the cell space, and wherein a second opening structure is formed in the frame body, via which the second feed channel opens into the cell space, wherein the first opening structure and the second opening structure open into the cell space at positions offset from one another along the thickness direction.For example, the first orifice structure can open into a portion of the frame opening facing the first side of the frame body, and the second orifice structure can open into a portion of the frame opening facing the second side of the frame body. This allows the first fluid and the second fluid to flow into the cell space at different positions along the thickness direction.

[0034] Within the scope of an advantageous development of the second or third aspect, the flow frame unit further comprises a separating element, in particular a bipolar plate or membrane (or separator), preferably a bipolar plate. The separating element, in particular the bipolar plate or membrane / separator, is preferably arranged in the frame opening (cell space) such that the separating element divides the frame opening, in particular along the thickness direction, into a first partial cell space, in particular a catholyte space, and a second partial cell space, in particular anolyte space.It may then be advantageous if the first supply channel and the first return channel are fluidically connected to the first sub-cell space, in particular via a mouth structure as described above, and in particular are fluidically separated from the second sub-space, and if the second supply channel and the second return channel are fluidically connected to the second sub-space, in particular via a mouth structure as described above, and in particular are fluidically separated from the first sub-space. The flow frame unit can thus provide both a catholyte space and an anolyte space.

[0035] In particular, the first partial cell space and the second partial cell space lie one above the other in a thickness direction of the frame body. Preferably, the first partial cell space is open toward the first side of the frame body, and the second partial cell space is open toward the second side of the frame body.

[0036] The separating element, in particular the bipolar plate or membrane / separator, is arranged in particular centrally in the frame opening with respect to a thickness of the frame body. In this respect, the separating element can divide the frame opening into two equally sized partial cell spaces. The frame body is arranged in particular around the circumference of the separating element, in particular the bipolar plate or membrane / separator. The separating element can be arranged in a corresponding receptacle in the frame body. The separating element, in particular the bipolar plate, can be connected to the frame body in different ways, for example glued, welded or overmolded by the frame body. The separating element, in particular the bipolar plate, extends in particular parallel to the frame plane, i.e. orthogonal to the thickness direction.

[0037] Preferably, each supply channel and each return channel is fluidly connected to a primary channel, in particular a separate one. In this respect, the frame body can be formed with: - a first supply channel system for supplying first fluid, in particular catholyte, into the frame opening (cell space), wherein the first supply channel system has a first (supply) primary channel which is fluidly connected to the frame opening via a first supply channel, in particular leading from the primary channel and further in particular meandering. - a first return channel system for returning first fluid, in particular catholyte, from the frame opening, wherein the first return channel system has a first (return) primary channel which is fluidly connected to the frame opening via a first return channel, in particular leading from the primary channel and further in particular meandering. - a second supply channel system for supplying a second fluid, in particular anolyte, into the frame opening, wherein the second supply channel system has a second (supply) primary channel which is fluidly connected to the frame opening via a second supply channel, in particular leading from the primary channel and further in particular meandering. - a second return channel system for returning second fluid, in particular anolyte, from the frame opening, wherein the second return channel system has a second (return) primary channel which is fluidly connected to the frame opening via a second return channel, in particular leading from the primary channel and further in particular meandering.

[0038] The supply channels and the return channels can therefore form secondary channels of the flow frame unit.

[0039] The primary channels extend, in particular, orthogonally to an extension direction of the respectively associated supply channel or return channel. The primary channels extend, in particular, parallel to the thickness direction of the frame body, i.e., orthogonally to a frame plane (in the cell stack: in the stacking direction). The primary channels are preferably formed in the form of through-openings, e.g., bores, in the frame body.

[0040] Preferably, one supply channel and one blind channel, as well as one return channel and one blind channel, are each fluidly connected to a common primary channel, in particular in the form of a through-opening in the frame body. In particular, one supply channel and one blind channel, as well as one return channel and one blind channel, each branch off from a common primary channel. Thus, the blind channels can either be fed with fluid via a primary channel, or fluid can be discharged from the blind channels into the primary channel. In such a configuration with a primary channel, the "closed end" of a blind channel described above can be the end facing away from the primary channel.

[0041] The channels leading from a common primary channel can be formed on the same side of the frame body. The channels leading from a common primary channel can also be formed on opposite sides of the frame body.

[0042] As mentioned above, the supply channels, return channels, and blind channels can be formed in various configurations in the frame body. The first supply channel and the second supply channel can be formed on opposite sides of the frame body. The first supply channel and the second supply channel can be formed on the same side of the frame body.

[0043] The first supply channel and the first return channel may be formed on the same side of the frame body and / or the second supply channel and the second return channel may be formed on the same side of the frame body.

[0044] The first supply channel and the first return channel may be formed on opposite sides of the frame body and / or the second supply channel and the second return channel may be formed on opposite sides of the frame body.

[0045] Within the scope of a first advantageous embodiment of a flow frame unit, the supply channels, the return channels, and the blind channels can be formed on the same side of the frame body. In this respect, the supply channels, the return channels, and the blind channels can all be formed on the first side or the second side of the frame body. In particular, the supply channels, the return channels, the blind channels, and the first orifice structure(s) are formed on the first side, and the second orifice structure(s) are formed on the second side of the frame body. In a cell stack comprising at least two such flow frame units, the flow frame units can then be stacked on top of one another such that the sides containing the channels face one another.

[0046] In the first embodiment, the frame body can be designed in particular point-symmetrically with respect to a center point of the frame opening.

[0047] Within the scope of a second advantageous implementation of a flow frame unit, the first supply channel and the second supply channel can be formed on opposite sides of the frame body, wherein the first supply channel and the first return channel are formed on the same side of the frame body, wherein the second supply channel and the second return channel are formed on the same side of the frame body, and wherein the channels leading from a common primary channel (blind channel + supply channel or blind channel + return channel) are formed on the same side of the frame body. For example, the second supply channel and the second return channel can be formed on the first side of the frame body, and the first supply channel and the first return channel can be formed on the second side of the frame body.In the second embodiment, it may further be advantageous if the mouth structure associated with a respective supply or return channel and the associated supply or return channel are formed on opposite sides of the frame body.

[0048] The second embodiment makes it possible, in particular, to arrange the flow frame units in a cell stack in such a way that the same fluid, in particular the first fluid (catholyte) or the second fluid (anolyte), is exchanged between two adjacent flow frame units, preferably exclusively. In a cell stack, the flow frame units of the second embodiment can, in particular, be arranged in such a way that the supply channel and the associated return channel (i.e. the first supply channel and the first return channel or the second supply channel and the second return channel) each overlap with a blind channel of the same adjacent flow frame unit to form a fluid channel (secondary channel), but in particular the first channels (first supply channel and first return channel) and the second channels (second supply channel and second return channel) overlap with blind channels of different flow frame units (e.g.the first supply channel and the first return channel with blind channels of a flow frame unit located above in the cell stack, and the second supply channel and the second return channel with blind channels of a flow frame unit located below in the cell stack).

[0049] Within the scope of a third advantageous embodiment of a flow frame unit, the first supply channel and the second supply channel can be formed on opposite sides of the frame body, wherein the first supply channel and the first return channel are formed on the same side of the frame body, and wherein the second supply channel and the second return channel are formed on the same side of the frame body, wherein the channels leading from a common primary channel (blind channel + supply channel or blind channel + return channel) are formed on opposite sides of the frame body. In the third embodiment, it can also be advantageous if the mouth structure assigned to a respective supply or return channel and the assigned supply or return channel are formed on the same side of the frame body.

[0050] An embodiment according to the third embodiment enables, in particular, an arrangement of the flow frame units in a cell stack such that both the first fluid (catholyte) and the second fluid (anolyte) can be exchanged between two adjacent flow frame units. In particular, the flow frame units of the third embodiment can be arranged in a cell stack such that the first supply channel and the second supply channel (and analogously the first return channel and the second return channel) overlap with blind channels of different flow frame units (e.g. the first supply channel with a blind channel of a flow frame unit located above in the cell stack and the second supply channel with a blind channel of a flow frame unit located below in the cell stack), but in particular the supply channel and the associated return channel (iethe first supply channel and the first return channel or the second supply channel and the second return channel) each overlap with a blind channel of the same adjacent flow frame unit.

[0051] Within the scope of a fourth advantageous implementation of a flow frame unit, the first supply channel and the first return channel can be formed on opposite sides of the frame body, the second supply channel and the second return channel can be formed on opposite sides of the frame body, and the first supply channel and the second supply channel can be formed on opposite sides of the frame body. In particular, the first supply channel and the second return channel can be formed on the first side of the frame body, and the second supply channel and the first return channel can be formed on the second side of the frame body.

[0052] In the fourth embodiment, it can be particularly advantageous if the channels leading from a common primary channel are formed on opposite sides of the frame body. Furthermore, it can be advantageous if the orifice structure associated with a respective feed channel and the associated feed channel are formed on the same side of the frame body, but in particular, an orifice structure associated with a respective return channel and the associated return channel are formed on opposite sides of the frame body.

[0053] An embodiment according to the fourth embodiment enables, in particular, an arrangement of the flow frame units in a cell stack such that both the first fluid (catholyte) and the second fluid (anolyte) can be exchanged between two adjacent flow frame units. In a cell stack, the flow frame units of the fourth embodiment can, in particular, be arranged such that the first supply channel and the second supply channel (and analogously the first return channel and the second return channel) overlap with blind channels of different flow frame units (e.g., the first supply channel with a blind channel of a flow frame unit located above in the cell stack and the second supply channel with a blind channel of a flow frame unit located below in the cell stack), in particular the supply channel and the associated return channel (i.e.the first supply channel and the first return channel or the second supply channel and the second return channel) but each overlap with a blind channel of the same adjacent flow frame unit.

[0054] The invention is explained in more detail below with reference to the figures. They show: Fig. 1 a simplified schematic representation of a cell stack to explain a basic principle of the invention; Fig. 2 a simplified schematic representation of a flow frame unit of the cell stack according to Fig. 1 in a plan view; Fig. 3 a simplified schematic representation of a flow frame unit according to a first embodiment in a plan view; Fig. 4 the flow frame unit according to Fig. 3 in a sectional view along the Fig. 3 marked section line IV-IV; Fig. 5 the flow frame unit according to Fig. 3 in a sectional view along the Fig. 3 marked section line VV; Fig. 6 a sectional view through a cell stack of two flow frame units according to Fig. 3 along the Fig. 3 marked section line VV; Fig. 7 a sectional view through a cell stack of two flow frame units according to Fig. 3 along the Fig. 3 marked section line IV-IV; Fig. 8 simplified schematic representation to explain a structure of a cell stack from several flow frame units according to Fig. 3; Fig. 9 a simplified schematic representation of a flow frame unit according to a second embodiment in a plan view; Fig. 10 the flow frame unit according to Fig. 9 in a sectional view along the Fig. 9 drawn section line XX; Fig. 11 the flow frame unit according to Fig. 9 in a sectional view along the Fig. 9 marked section line XI-XI; Fig. 12 a sectional view through a cell stack of two flow frame units according to Fig. 9 along the Fig. 9 marked section line XI-XI; Fig. 13 simplified schematic representation to explain a structure of a cell stack from several flow frame units according to Fig. 9; Fig. 14 is a simplified schematic representation of a flow frame unit according to a third embodiment in a plan view; Fig. 15 the flow frame unit according to Fig. 14 in a sectional view along the Fig. 14 marked section line XV-XV; Fig. 16 the flow frame unit according to Fig. 14 in a sectional view along the Fig. 14 marked section line XVI-XVI; Fig. 17 a sectional view through a cell stack of two flow frame units according to Fig. 14 along the Fig. 14 marked section line XVI-XVI; Fig. 18 simplified schematic representation to explain a structure of a cell stack from several flow frame units according to Fig. 14; Fig. 19 is a simplified schematic representation of a flow frame unit according to a fourth embodiment in a plan view; Fig. 20 the flow frame unit according to Fig. 19 in a sectional view along the Fig. 19 marked section line XX-XX; Fig. 21 the flow frame unit according to Fig. 19 in a sectional view along the Fig. 19 marked section line XXI-XXI; Fig. 22 a sectional view through a cell stack of two flow frame units according to Fig. 19 along the Fig. 19 marked section line XXI-XXI; and Fig. 23 simplified schematic representation to explain a structure of a cell stack from several flow frame units according to Fig. 19.

[0055] In the following description and in the figures, the same reference symbols are used for identical or corresponding features.

[0056] The Fig. 1 and Fig. 2 show simplified schematic representations of an exemplary embodiment of a cell stack 10 to explain a basic principle of the invention. Possible concrete implementations are described below with reference to Fig. 3 ff.

[0057] The cell stack 10 comprises two flow frame units 12, 12', which are stacked one on top of the other along a stacking direction 14. Each flow frame unit 12 has a frame body 16. The frame body 16 extends flatly in a frame plane orthogonal to the stacking direction 14 (see FIG. Fig. 2). The frame body 16 has in a thickness direction 18 (in Fig. 1 corresponding to the stacking direction 14) has a thickness of 20.

[0058] The frame body 16 has a frame opening 22, in the example, centrally located. The frame opening 22 defines a cell space 24 (or active space) of the flow frame unit 12, in which the electrochemical processes take place.

[0059] As from Fig. As can be seen in Figure 1, each flow frame unit 12 also includes a bipolar plate 26. The bipolar plate 26 is arranged in the respective frame opening 22, so that the frame opening 22 is divided by the bipolar plate 26 into a first sub-cell space 28-1 and a second sub-cell space 28-2. The bipolar plate 26 thus forms a separating element of the flow frame unit 12. An electrode can be arranged in each sub-cell space 28-1, 28-2.

[0060] In the example, the first sub-cell space 28-1 forms a catholyte space and the second sub-cell space 28-2 forms an anolyte space.

[0061] Between the two flow frame units 12, a membrane / separator 30 is arranged, which covers the frame openings 22 and thus fluidically separates the cell spaces 24 of the flow frame units 12 from each other. The membrane / separator 30 is designed to be particularly permeable to ions. In the specific example, the membrane 30 / separator separates the second subspace 28-2 of the first (in Fig. 1 upper) flow frame unit 12 and the first subspace 28-1 of the second (in Fig. 1 lower) flow frame unit 12. The second subspace 28-2 of the first flow frame unit 12 and the first subspace 28-1 of the second flow frame unit 12 thus form a cell of the cell stack 10.

[0062] In embodiments not shown, the membrane / separator 30 and bipolar plate 26 can be interchanged in their relative arrangement. In this respect, a membrane / separator 30 (analogous to the position of the bipolar plate 26 shown in the figures) can be arranged in the frame opening 22 of a respective flow frame unit 12, and a bipolar plate 26 (analogous to the position of the membrane 30 / separator shown in the figures) can then be arranged between two adjacent flow frame units 12.

[0063] As in the Fig. 1 and Fig. 2, for each partial cell space 28-1, 28-2 there is a supply channel system 32-1, 32-2 for supplying fluid, in particular electrolyte, into the partial cell space 28-1, 28-2 and a return channel system 34-2 for returning fluid, in particular electrolyte, from the partial cell space 28-1, 28-2.

[0064] For clarity, the assignment of the channel systems or individual channels to the sub-cell spaces 28-1, 28-2 is illustrated in the figures by different hatching. However, the hatching does not imply that different fluids flow in the sub-cell spaces 28-1, 28-2 or in the channel systems during operation. Thus, in the example, all first sub-cell spaces 28-1 (oblique hatching and vertical hatching) are fed with catholyte, and all second sub-cell spaces 28-2 (dotted hatching and no hatching) are fed with anolyte.

[0065] In the example, each supply channel system 32-1, 32-2 has a (supply) primary channel 36-1, 36-2 (e.g., formed in the form of a through-opening in the frame body 16), which is fluidly connected to the respective sub-cell space 28-1, 28-2 via a, in particular meander-shaped, (supply) secondary channel 38-1, 38-2. Similarly, each return channel system 34-1, 34-2 in the example has a (return) primary channel 40-1, 40-2, which is fluidly connected to the respective sub-cell space 28-1, 28-2 via a, in particular meander-shaped, (return) secondary channel 42-1, 42-2.

[0066] The secondary channels 38-1, 38-2, 42-1, 42-2 can in turn open into the respective sub-cell space 28-1, 28-2 via respective orifice structures 44 (explained in more detail below).

[0067] By way of example and preferably, the (supply) primary channel 36-1, 36-2 and the associated (return) primary channel 40-1, 40-2 are arranged diagonally opposite one another with respect to the frame opening 22.

[0068] As from Fig. 1, the secondary channels 38-1, 38-2, 42-1, 42-2 each extend over two adjacent frame bodies 16, in particular such that a diameter 46 of the secondary channels 38-1, 38-2, 42-1, 42-2 along the stacking direction 14 (thickness direction 18) is greater than the thickness 20 of a respective frame body 16.

[0069] In the example shown, each secondary channel 38-1, 38-2, 42-1, 42-2 is formed by two overlapping channel-shaped recesses in the adjacent frame bodies 16. One of these two channel-shaped recesses is designed as a supply channel 48-1, 48-2 or return channel 50-1, 50-2, which is fluidly connected to the respective sub-cell space 28-1, 28-2 via the aforementioned orifice structure 44. The other of the two channel-shaped recesses forming a respective secondary channel is designed as a blind channel 52, which serves as a cross-sectional extension of the supply or return channel 48-1, 48-2, 50-1, 50-2, but does not itself open into the respective sub-cell space 28-1, 28-2 via an orifice structure 44.

[0070] The Fig. Figure 1 shows the supply and return channels 48-1, 48-2, 50-1, 50-2 only schematically to explain the basic concept of the invention. Exemplary embodiments are described in more detail below with reference to Fig. 3 ff. This explains features that have already been discussed in connection with the Fig. 1 and Fig. 2 and are identical or equivalent in function, will not be described again unless it is relevant for the specific design.

[0071] The Fig. 3 shows a simplified schematic representation of an embodiment of a flow frame unit 12 according to a first embodiment.

[0072] As above to Fig. 1, is also the case for the flow frame unit 12 according to Fig. 3 in the frame opening 22 a bipolar plate 26 (in Fig. 3 not shown) which divides the frame opening 22 into a first (upper in the thickness direction 18) partial cell space 28-1 and a second (lower in the thickness direction 18) partial cell space 28-2 (cf. Fig. 4).

[0073] For better understanding, the top views according to Fig. 3, Fig. 9, Fig. 14, and Fig. 19 Elements, in particular supply channels, return channels and blind channels, which are below the drawing plane, are shown in dashed lines.

[0074] As from Fig. 3, a first supply channel system 32-1 for supplying first fluid, in particular catholyte, into the first partial cell space 28-1 and a first return channel system 34-1 for returning first fluid from the first partial cell space 28-1 are formed in the frame body 16.

[0075] The first supply channel system 32-2 comprises a first primary channel 36-1, a supply channel 48-1 branching off from the primary channel 36-1, which is meander-shaped in the example, and a first orifice structure 44-1, via which the supply channel 48-1 opens into the first sub-cell space 28-1. Similarly, the first return channel system 34-1 comprises a (return) primary channel 40-1, a return channel 50-1 branching off from (or opening into) the primary channel 40-1, which is meander-shaped in the example, and an orifice structure 44-1, via which fluid can be discharged from the first sub-cell space 28-1.

[0076] In an analogous manner, a second supply channel system 32-2 (comprising primary channel 36-2, supply channel 48-2 and second mouth structure 44-2) for supplying second fluid into the second partial cell space 28-2 (in Fig. 3 not visible) and a second return channel system 34-2 (comprising primary channel 40-2, return channel 50-2 and mouth structure 44-2) for returning second fluid from the second partial cell space 28-2.

[0077] As from Fig. 4, the first and second mouth structures 44-1, 44-2 open into the frame opening 22 (cell space) at positions offset from one another along the thickness direction 18.

[0078] As from Fig. 3, a previously mentioned blind channel 52 also branches off from each primary channel 36-1, 36-2, 40-1, 40-2, which in the example is also designed in a meandering shape. The blind channels 52 are closed at their end facing away from the associated primary channel 36-1, 36-2, 40-1, 40-2 and thus do not open directly into the frame opening 22 (a flow connection of the blind channel 52 to the frame opening 22 via the supply or return channel 48, 50 branching off from the same primary channel 36-1, 36-2, 40-1, 40-2 is not referred to as "opening" in the context of this application).

[0079] As from Fig. 5, the channels (supply channels 48-1, 48-2, return channels 50-1, 50-2, and blind channels 52) are formed as depressions, for example in the form of groove-shaped recesses or cutouts in the frame body 16. In the first embodiment, all supply channels 48-1, 48-2, return channels 50-1, 50-2, and blind channels 52 are formed on the same side, in the example a first side 54-1, of the frame body 16. As explained in more detail below, the channels or a subset of the channels can also be formed on the opposite second side 54-2 of the frame body 16.

[0080] For example, a respective channel depth 55 in the thickness direction 18 is more than 50% of a thickness 20 of the frame body 16.

[0081] If two such flow frame units 12 are now stacked on top of each other in such a way that the first sides 54-1 face each other, in the concrete example in which one flow frame unit 12 is offset from the other by the Fig. 3, a feed channel 48-1, 48-2 and a blind channel 52 or a return channel 50-1, 50-2 and a blind channel 52 overlap with each other, so that a circumferentially closed fluid channel is formed, which forms a secondary channel 38-1, 38-2, 42-1, 42-2 of the respective channel system as described above (in Fig. 6 shown as an example for a Fig. 5 corresponding sectional view).

[0082] As mentioned above, a membrane 30 or separator is arranged between two adjacent flow frame units 12, which membrane covers the frame openings 22 and thus fluidically separates the adjacent sub-cell spaces 28-1, 28-2 of adjacent flow frame units 12 from each other.

[0083] For better understanding, Fig. 8 one of the Fig. 1 corresponding view of a four flow frame units 12 according to Fig. 3 existing cell stack 10 is shown in exploded view, wherein in the example two flow frame units 12 are facing each other with the first sides 54-1. A flow connection between the channels, which are only shown schematically, is shown in Fig. 8 (and analogously in the following Fig. 13, Fig. 18 and Fig. 23) shown by dashed lines).

[0084] In such a structure, three cells 56-1, 56-1, 56-3 are formed, each of which is formed by a (catholyte) partial cell space 28-1 of a flow frame unit 12, an (anolyte) partial cell space 28-2 of an adjacent flow frame unit 12, and a membrane 30 / separator arranged therebetween.

[0085] The Fig. 9 shows a further exemplary embodiment of a flow frame unit 12 according to a second implementation, which differs from the flow frame unit 12 according to the first implementation by the relative arrangement of the channels.

[0086] In the example according to Fig. 9 the first feed channel 48-1 and the second feed channel 48-2 - and analogously the first return channel 50-1 and the second return channel 50-2 - are formed on opposite sides 54-1, 54-2 of the frame body 16 (cf. Fig. 11). The feed channel 48-1, 48-2 and the return channel 50-1, 50-2 of the same feed system 32-1, 32-2, 34-1, 34-2 are arranged on the same side 54-1, 54-2 of the frame body 16.

[0087] A further difference results from the fact that the feed channel 48-1, 48-2 and return channel 50-1, 50-2 assigned to a respective partial cell space 28-1, 28-2 are formed on the side 54-1, 54-2 of the frame body 16 opposite the partial cell space 28-1, 28-2 (cf. Fig. 9 and Fig. 10). In this respect, the respective feed channel 48-1, 48-2 or return channel 50-1, 50-2 and the respectively associated orifice structure 44-1, 44-2 are formed on opposite sides 54-1, 54-2 of the frame body 16.

[0088] As from Fig. 9, the channels leading from a common primary channel 32-1, 32-2, 34-1, 34-2 (feed channel 48-1, 48-2 and blind channel 52 or return channel 50-1, 50-2 and blind channel 52) are formed on the same side 54-1, 54-2 of the frame body 16.

[0089] Such a configuration enables an arrangement of the flow frame units 12 in a cell stack 10 such that the supply and return channels 48-1, 50-1 assigned to the first partial cell space 28-1 and the supply and return channels 48-2, 50-2 assigned to the second partial cell space 28-2 overlap with blind channels 52 of different flow frame units 12 (cf. Fig. 13). When considering the Fig. 13 second flow frame unit 12' from below, for example, the first feed channel 48-1' is fluidly connected to a blind channel 52 of the overlying flow frame unit 12, while the second feed channel 48-2' interacts with a blind channel 52 of the underlying flow frame unit 12.

[0090] In this respect, only the first fluid (catholyte) or the second fluid (anolyte) is exchanged with an adjacent flow frame unit 12.

[0091] The Fig. 14 shows a further exemplary embodiment of a flow frame unit 12 according to a third embodiment, which differs from the second embodiment in that the channels branching off from a common primary channel 32-1, 32-2, 34-1, 34-2 (supply channel 48-1, 48-2 and blind channel 52 or return channel 50-1, 50-2 and blind channel 52) are formed on opposite sides 54-1, 54-2 of the frame body 16. Furthermore, the supply and return channels 48-1, 48-2, 50-1, 50-2 are formed on the same side as their respective associated orifice structure 44-1, 44-2. In this respect, the supply and return channels 48-1, 48-2, 50-1, 50-2 assigned to a respective partial cell space 28-1, 28-2 are formed on the same side 54-1, 54-2 as the partial cell space 28-1, 28-2.

[0092] As from Fig. As can be seen from Figure 18, such a configuration enables an arrangement of the flow frame units 12 in a cell stack 10 such that both the first fluid (catholyte) and the second fluid (anolyte) are exchanged between two adjacent flow frame units 12. For example, the supply and return channels 48-1, 50-1 assigned to the first sub-cell space 28-1 and the supply and return channels 48-2, 50-2 assigned to the second sub-cell space 28-2 overlap with blind channels 52 of different flow frame units 12 (cf. Fig. 18). When considering the Fig. 18 second lowest flow frame unit 12, for example, the first feed channel 48-1 is fluidly connected to a blind channel 52 of the overlying flow frame unit 12', while the second feed channel 48-2 interacts with a blind channel 52 of the underlying flow frame unit 12'.

[0093] The Fig. 19 shows a further exemplary embodiment of a flow frame unit 12 according to a fourth embodiment, which differs from the third embodiment by the arrangement of the return channels 50-1, 50-2 and the blind channels 52 connected to them. As can be seen from Fig. 19, the supply channel systems 32-1, 32-2 are designed identically to the third embodiment, but the return channels 50-1, 50-2 and the blind channels 52 connected to them in terms of flow are swapped in their side assignment compared to the third embodiment (first return channel 50-1 on the second side 54-2 and second return channel 50-2 on the first side 54-1 of the frame body 16). In this respect, the first feed channel 48-1 and the first return channel 50-1 are formed on opposite sides 54-1, 54-2 of the frame body 16, the second feed channel 48-2 and the second return channel 50-2 are formed on opposite sides 54-1, 54-2 of the frame body 16, and the first feed channel 48-1 and the second feed channel 48-2 are formed on opposite sides 54-1, 54-2 of the frame body 16.The channels leading from a common primary channel 32-1, 32-2, 34-1, 34-2 (feed channel 48-1, 48-2 and blind channel 52 or return channel 50-1, 50-2 and blind channel 52) are formed on opposite sides 54-1, 54-2 of the frame body 16.

[0094] In contrast to the third embodiment, in the fourth embodiment, the return channels 50-1, 50-2 and their respective associated orifice structures 44-1, 44-2 are arranged on opposite sides 54-1, 54-2 of the frame body 16. In the specific example, the first return channel 50-1 is passed through the frame body 16 from the second side 54-2 to the first side 54-1, and the second return channel 50-2 is passed through the frame body 16 from the first side 54-1 to the second side 54-2.

[0095] As from Fig. 23, such a configuration allows an arrangement of the flow frame units 12 in a cell stack 10 such that between two adjacent flow frame units 12 both the first fluid (catholyte) and the second fluid (anolyte) are exchanged, with the supply and return of the same fluid taking place via different flow frame units 12. For example, in the case of the Fig. 23 second lowest flow frame unit 12 first fluid (catholyte) is supplied to the first sub-cell space 28-1 by interaction of the first supply channel 48-1 of this flow frame unit 12 with a blind channel 52' of the overlying flow frame unit 12, but is removed from the first sub-cell space 28-1 by interaction of the first return channel 50-1 of this flow frame unit 12 with a blind channel 52' of the underlying flow frame unit 12.

[0096] The cell stacks 10 shown are merely examples. In particular, more or fewer flow frame units 12 can be provided. Furthermore, the cell stacks 10 can comprise further elements in a known manner, for example, end plates, electrical contact plates, and / or a housing.

Claims

[1] Cell stack (10) for a redox flow battery, comprising at least two flow frame units (12) which are stacked one on top of the other along a stacking direction (14), wherein each flow frame unit (12) comprises: - a frame body (16) which has a, in particular central, frame opening (22); - a separating element, in particular a bipolar plate (26), arranged in the frame opening (22), which divides the frame opening (22) into a first partial cell space (28-1), in particular a catholyte space, and a second partial cell space (28-2), in particular anolyte space, wherein for each partial cell space (28-1, 28-1) there is a separate supply channel system (32-1, 32-2) for supplying fluid, in particular electrolyte, into the partial cell space (28-1, 28-2) and a separate return channel system (34-1, 34-2) for returning fluid, in particular electrolyte, from the partial cell space (28-1, 28-2), wherein the channel systems (32-1, 32-2, 34-1, 34-2) each comprise a primary channel (36-1, 36-2, 40-1, 40-2), which extends in particular in the stacking direction and which is connected to the corresponding partial cell space (28-1, 28-2) via at least one secondary channel (38-1, 38-2, 42-1, 42-2) is fluidically connected, wherein the secondary channels (38-1, 38-2, 42-1, 42-2) each extend at least partially through at least two adjacent frame bodies (16). [2] Cell stack (10) according to claim 1, wherein the secondary channels (38-1, 38-2, 42-1, 42-2) extend through at least two adjacent frame bodies (16) such that a respective diameter (46) of the secondary channels (38-1, 38-2, 42-1, 42-2) in the stacking direction (14) is greater than a thickness (20) of a frame body (16) in the stacking direction (14), in particular at least 1.2 times as large, further in particular at least 1.5 times as large, further in particular at least 1.8 times as large. [3] Cell stack (10) according to claim 1 or 2, wherein each secondary channel (38-1, 38-2, 42-1, 42) is formed by overlapping channel-shaped depressions or recesses in at least two adjacent frame bodies (16). [4] Flow frame unit (12) for an electrochemical cell of a redox flow battery, in particular for use in a cell stack (10) according to one of the preceding claims, comprising a frame body (16) having a first side (54-1) and a second side (54-2), the frame body (16) having a frame opening (22) defining a cell space (24), wherein the frame body (16) is formed with: - at least one first, in particular meander-shaped, supply channel (48-1) for supplying first fluid, in particular catholyte, into the cell space (24); - at least one first, in particular meander-shaped, return channel (50-1) for returning first fluid, in particular catholyte, from the cell space (24); - at least one second, in particular meander-shaped, supply channel (48-2) for supplying a second fluid, in particular anolyte, into the cell space (24); - at least one second, in particular meander-shaped, return channel (50-2) for returning second fluid, in particular anolyte, from the cell space (24); characterized by , that in the frame body (16) there is also formed a number of, in particular meander-shaped, blind channels (52) corresponding at least to the number of supply channels (48-1, 48-2) and return channels (50-1, 50-2), wherein the blind channels (52) are closed at least at one end, wherein the feed channels (48-1, 48-2), the return channels (50-1, 50-2) and the blind channels (52) are formed as depressions, in particular cutouts or recesses, further in particular grooves or channels, in the frame body (16). [5] Flow frame unit (12) according to the preceding claim, wherein the frame body (16) has a thickness (20) in a thickness direction (18), in particular corresponding to a stacking direction 14, wherein a first opening structure (44-1) is formed in the frame body (16), via which the first feed channel (48-1) opens into the cell space (24), and wherein a second opening structure (44-2) is formed in the frame body (16), via which the second feed channel (48-2) opens into the cell space (24), wherein the first opening structure (44-1) and the second opening structure (44-2) open into the cell space (24) at positions offset from one another along the thickness direction (18). [6] Flow frame unit (12) according to claim 4 or 5, further comprising a separating element, in particular a bipolar plate (26), which is arranged in the frame opening (22) in such a way that it divides the frame opening (22) into a first partial cell space (28-1), in particular a catholyte space, and a second partial cell space (28-2), in particular anolyte space, wherein the first feed channel (48-1) and the first return channel (50-1) are fluidically connected to the first partial cell space (28-1), in particular via a respective orifice structure (44), and wherein the second feed channel (48-2) and the second return channel (50-2) are fluidically connected to the second partial cell space (28-2), in particular via a respective orifice structure (44). [7] Flow frame unit (12) according to one of claims 4 to 6, wherein a feed channel (48-1, 48-2) and a blind channel (52) as well as a return channel (50-1, 50-2) and a blind channel (52) lead from a common primary channel (36-1, 36-1, 40-1, 40-2), in particular in the form of a through opening in the frame body (16). [8] Flow frame unit (12) according to one of claims 4 to 7, wherein the supply channels (48-1, 48-2), the return channels (50-1, 50-2) and the blind channels (52) are formed on the same side (54-1) of the frame body (16). [9] Flow frame unit (12) according to one of claims 4 to 7, wherein the first supply channel (48-1) and the second supply channel (48-2) are formed on opposite sides (54-1, 54-2) of the frame body (16), wherein the first supply channel (48-1) and the first return channel (50-1) are formed on the same side (54-2) of the frame body (16), and wherein the second supply channel (48-2) and the second return channel (50-2) are formed on the same side (54-1) of the frame body (16). [10] Flow frame unit (12) according to the preceding claim when referring back to claim 7, wherein the channels (48-1, 48-2, 50-1, 50-2, 52) leading from a common primary channel (36-1, 36-1, 40-1, 40-2) are formed on the same side (54-1, 54-2) of the frame body (16). [11] Flow frame unit (12) according to claim 9 or 10 when referring back to claim 5, wherein the mouth structure (44-1, 44-2) associated with a respective feed channel (48-1, 48-2) and the feed channel (48-1, 48-2) are formed on opposite sides of the frame body (16). [12] Flow frame unit (12) according to claim 9 when referring back to claim 7, wherein the channels (48-1, 48-2, 50-1, 50-2, 52) leading from a common primary channel (36-1, 36-1, 40-1, 40-2) are formed on opposite sides (54-1, 54-2) of the frame body (16). [13] Flow frame unit (12) according to claim 9 or 12 when referring back to claim 5, wherein the mouth structure (44-1, 44-2) associated with a respective feed channel (48-1, 48-2) and the feed channel (48-1, 48-2) are formed on the same side (54-1, 54-2) of the frame body (16). [14] Flow frame unit (12) according to one of claims 4 to 7, wherein the first supply channel (48-1) and the first return channel (50-1) are formed on opposite sides (54-1, 54-2) of the frame body (16), wherein the second supply channel (48-2) and the second return channel (50-2) are formed on opposite sides (54-1, 54-2) of the frame body (16), wherein the first feed channel (48-1) and the second feed channel (48-2) are formed on opposite sides (54-1, 54-2) of the frame body (16). [15] Flow frame unit (12) according to the preceding claim when referring back to claim 7, wherein the channels (48-1, 48-2, 50-1, 50-2, 52) leading from a common primary channel (36-1, 36-1, 40-1, 40-2) are formed on opposite sides (54-1, 54-2) of the frame body (16). [16] Flow frame unit (12) according to claim 14 or 15 when referring back to claim 5, wherein the mouth structure (44-1, 44-2) associated with a respective feed channel (48-1, 48-2) and the feed channel (48-1, 48-2) are formed on the same side (54-1, 54-2) of the frame body (16), in particular wherein a mouth structure (44-1, 44-2) associated with a respective return channel (48-1, 48-2) and the return channel (48-1, 48-2) are formed on opposite sides (54-1, 54-2) of the frame body (16). [17] Flow frame unit (12) according to one of claims 4 to 16, wherein a respective channel depth (55) of the feed channels (48-1, 48-2), the return channels (50-1, 50-2) and / or the blind channels (52) in a thickness direction (18) of the frame body (16) is more than 50% of a thickness (20) of the frame body (16) in the thickness direction (18), in particular more than 60%, further in particular more than 70%, further in particular more than 80%. [18] Cell stack (10) comprising at least two flow frame units (12) according to one of claims 4 to 17, wherein the frame bodies (16) are designed and stacked on top of one another along a stacking direction (14) in such a way that each supply channel (48-1, 48-2) and each return channel (50-1, 50-2) of a frame body (16) overlaps, in particular is aligned, with a blind channel (52) of an adjacent frame body (16) at least in sections, so that in each case a common, in particular circumferentially closed, fluid channel (38-1, 38-2, 42-1, 42-2) is formed. [19] Cell stack (10) according to the preceding claim, wherein the frame bodies (16) are designed such that a diameter (46) of the fluid channel (38-1, 38-2, 42-1, 42-2) in the stacking direction (14) is greater than a thickness (20) of a frame body (16) in the stacking direction (14), in particular at least 1.2 times as large, further in particular at least 1.5 times as large, further in particular at least 1.8 times as large. [20] Cell stack (10) according to claim 18 or 19, wherein a membrane / separator (30) or a bipolar plate (26) is arranged between two adjacent flow frame units (12), which covers the frame openings (22) of adjacent flow frame units (12) and separates them from one another.

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