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 to a cell stack (10) comprising at least two flow frame units (12).

Description

[0001] APF / MAU / MAY

[0002] Title: Flow frame unit for an electrochemical cell of a redox flow battery and cell stack

[0003] Description

[0004] 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.

[0005] Redox flow batteries are electrochemical energy storage devices with flowable, especially 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, for example, stored in separate tanks, and supplied as needed to an electrochemical energy converter 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. In this process, chemical energy is converted into electrical energy during discharge and electrical energy is converted back into chemical energy during charging.One 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, making central and decentralized storage systems on a scale from a few kilowatts to megawatts feasible.

[0006] A redox flow battery stack typically comprises a large number of identical cells connected in parallel fluidically and in series electrically. The cells are assembled into a cell stack and clamped together using a clamping system.

[0007] In known systems, each individual cell is typically composed of two half-cells (anolyte half-cell and catholyte half-cell), each containing a flow frame (or cell frame). The flow frames, in turn, have a frame opening that defines the actual cell space or active area of ​​the half-cell, i.e., the active region where the electrochemical processes take place. An ion-conducting membrane / separator is usually positioned between the two flow frames of a cell, fluidically separating the cell spaces of the half-cells.

[0008] Furthermore, known flow frames typically include an integrated supply channel system for introducing electrolyte into the cell space and a return channel system for returning electrolyte from the cell space. These channel systems usually feature a primary channel (e.g., in the form of a through-hole in the flow frame) from which a secondary channel, often meandering, extends, ultimately emptying into the cell space via fan-shaped or comb-shaped distribution structures. Such a flow frame is known, for example, from US 2018 / 0062188 Al.

[0009] For electrical connection between the individual cells, a so-called bipolar plate, e.g. made of a graphite-plastic composite material, is usually arranged between two individual cells.

[0010] Systems are also known in which the bipolar plate is integrated into the flow frame, thus dividing the frame opening into two subcell spaces (an anolytic space and a catholytic space). In a cell stack, these subcell spaces are then assigned to different cells.

[0011] However, in known systems, significant pressure drops occur across the primary and especially the secondary channel. This can limit the efficiency of a redox flow battery stack and the entire redox flow battery system, particularly in large operating spaces and with the associated high electrolyte flow rates. Furthermore, undesirable shunt currents can occur.

[0012] The present invention addresses the problem of making redox flow battery stacks with large effective operating spaces easy to manufacture and efficient to operate.

[0013] This problem is solved 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.

[0014] According to a first aspect, a cell stack, in particular a redox flow battery, is proposed. The cell stack comprises at least two flow frame units, which are stacked one on top of the other along a stacking direction. Each flow frame unit includes a frame body (occasionally also referred to as a flow frame or cell frame). The frame body is, in particular, planarly and extended 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 oriented orthogonally to the stacking direction. The separating element, in particular the bipolar plate or membrane / separator, is arranged in the frame opening such that it divides the frame opening into a first subcell space, in particular a catholyte space, and a second subcell space, in particular anolyte space. An electrode can be arranged in each subcell space. The cell stack comprises, for each subcell space, a supply channel system, in particular a separate one, for supplying fluid, in particular electrolyte, and further in particular catholyte or anolyte, into the subcell space and a return channel system for returning fluid from the subcell space. The channel systems, i.e., each supply channel system and each return channel system, each have a primary channel which connects to the corresponding subcell space via at least one (i.e.,The primary channel is fluidically connected to the primary channel (one, two, three, or more), in particular a meandering secondary channel extending orthogonally to the stacking direction. The primary channel extends parallel to the stacking direction. For example, the primary channel can be formed by a recess, in particular a through-opening, or in particular a bore, in the frame body that delimits the respective sub-cell space. The secondary channels extend orthogonally to the stacking direction. Each secondary channel extends at least sectionally along its longitudinal extent in the stacking direction 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 greater, in particular at least 1.5 times greater, or in particular at least 1.8 times greater.Therefore, the secondary channels are defined in particular by at least two adjacent frame bodies.

[0015] It has been shown that this approach significantly reduces pressure drop in the cell stack with minimal design effort, while simultaneously minimizing unwanted shunt currents. In particular, the proposed design allows for large flow cross-sections in the secondary channels without increasing the thickness of the respective frame components. The proposed cell stacks therefore have a comparatively small overall size, which positively impacts power density and also saves material.

[0016] The separating element can be a membrane or a separator. In such an embodiment 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 electrochemically active areas, especially the frame openings, of adjacent flow frame units. Specifically, the first and second subcell compartments of a flow frame unit then form a cell of the cell stack.

[0017] Preferably, the separating element is a bipolar plate. Each flow frame unit can therefore have a bipolar plate arranged in the respective frame opening, dividing the frame opening into a first subcell space, in particular a catholy space, and a second subcell space, in particular anolyte space. A membrane or separator is then preferably arranged between two adjacent flow frame units in the frame opening. The membrane or separator covers, in particular, the electrochemical areas, especially the frame openings, of adjacent flow frame units. Preferably, the membrane or separator fluidically separates the subcell spaces from one another. In particular, a subcell space of a first flow frame unit and a subcell space of an adjacent flow frame unit then form a cell of the cell stack.

[0018] Preferably, each secondary channel is formed by at least two overlapping, in particular channel-shaped, recesses or indentations (e.g., in the form of through-openings), in particular wherein a first recess or indentation is formed in a frame body of a first flow frame unit and a second recess or indentation is formed in a frame body of a second flow frame unit adjacent to the first flow frame unit. In this respect, channel-shaped recesses or indentations can be formed in at least two adjacent frame bodies, and the frame bodies can be stacked on top of each other in such a way that the recesses or indentations overlap to form a common, in particular fully enclosed, fluid channel (secondary channel). The recesses can, for example, be formed as groove- or groove-shaped recesses on a frame body surface of the frame body.

[0019] It is conceivable that a secondary channel extends through exactly two adjacent frame bodies. In this case, the secondary channel can be formed, for example, by the overlap of a first channel-shaped recess formed in the frame body of a first flow frame unit with a second channel-shaped recess formed in the frame body of a second flow frame unit adjacent to the first. It is also conceivable that a secondary channel extends 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., those stacked on top of each other along the stacking direction.It is conceivable, for example, that the two middle frame bodies have recesses in the form of through-openings, allowing fluid to pass through the middle frame bodies along the stack axis. The two outer frame bodies (upper and lower) along the stack direction can then have recesses that overlap with the through-openings to form a secondary channel, preferably one that is completely enclosed.

[0020] The secondary channels can be formed, in particular at least partially, by the fact that a supply channel is formed in the frame body bounding each respective sub-cell space, which is fluidically connected to the sub-cell space, in particular opening into it, and that a blind channel is formed in an adjacent frame body, which serves as a cross-sectional extension for the supply channel, but does not itself open into the sub-cell space.

[0021] According to a second aspect, a flow frame unit is proposed. The flow frame unit is designed for use in an electrochemical cell, specifically 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 a 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 an 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.The frame body includes at least one first feed channel, in particular meandering and extending parallel to the plane of the frame, for supplying a first fluid, in particular catholyte, into the frame opening (cell space). The frame body also includes at least one first return channel, in particular meandering and extending parallel to the plane of the frame, for returning the first fluid, in particular catholyte, from the frame opening (cell space). The frame body also includes at least one second feed channel, in particular meandering and extending parallel to the plane of the frame, for supplying a second fluid, in particular anolyte, into the frame opening (cell space).The frame body also includes at least one second return channel, in particular meandering and extending parallel to the frame plane, for returning a second fluid, in particular anolyte, from the frame opening (cell space). In addition to the feed channels and the return channels, the frame body also includes channels, in particular meandering ones, 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 feed channel or return channel is not considered an opening in this context). The number of blind channels corresponds in particular to at least the number of feed channels and return channels.The feed channels, return channels, and blind channels are designed as recesses or through-openings in the frame body, particularly on the first side and / or the second side, extending parallel to the frame plane (orthogonally to a stacking direction). The feed channels, return channels, and blind channels can be designed as recesses or cutouts in a surface of the frame body. In particular, the feed channels, return channels, and blind channels are designed as grooves or channels in the surface of the frame body.

[0022] Such a flow frame unit with blind channels makes it possible, in a cell stack where several such flow frame units are stacked on top of each other, to increase the flow cross-section of the feed channel or return channel by overlapping each blind channel with a feed channel or return channel, while maintaining a small frame thickness. 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 larger than the thickness of a frame body.Therefore, according to a third aspect, a cell stack is proposed which has at least two flow frame units of the type described above, wherein the frame bodies, in particular the feed channels, return channels and blind channels formed therein, are designed and the frame bodies are stacked on top of each other along a stacking direction such that each feed channel and each return channel of a frame body overlaps, at least sectionally, with a blind channel of an adjacent frame body, in particular is aligned, so that a common, in particular completely closed, fluid channel is formed in each case. Such a fluid channel can then, in particular, form a secondary channel.

[0023] In operation, the blind channels primarily carry the first or second fluid. Specifically, the blind channels can be supplied with fluid via their respective supply or return channels. It is also conceivable that the blind channel itself is supplied with fluid via a primary channel (see below).

[0024] Preferably, a membrane or separator is arranged between two adjacent flow frame units, which covers the cell spaces of adjacent flow frame units and in particular separates them fluidically from each other.

[0025] The advantages explained above in connection with the first aspect apply analogously to the third aspect.

[0026] It is particularly advantageous if the respective channel depth of the feed channels, return channels, and / or blind channels exceeds 50% of the thickness of the frame body (i.e., the extent of the frame body in the thickness direction), especially more than 60%, further particularly more than 70%, and further particularly more than 80%. In this way, a particularly large flow cross-section can be achieved efficiently. In particular, fluid channels (secondary channels) can thus be formed by overlapping the feed channel and blind channel or the return channel and blind channel, which have a diameter in the thickness direction that is larger than the thickness of a frame body in the stacking direction. In this context, "channel depth" is understood to mean, in particular, the extent of the recess in the thickness direction of the frame body (orthogonal to the frame plane).In a cell stack according to the third aspect, the frame bodies can be designed such that the 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 the thickness of a frame body in the stacking direction, in particular at least 1.2 times larger, further in particular at least 1.5 times larger, and further in particular at least 1.8 times larger.

[0027] The frame body is particularly planar, extending in a frame plane. The frame body has a thickness in a thickness direction. The thickness direction is particularly orthogonal 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 a first side and an opposite second side. The first and second sides are particularly parallel to the frame plane, i.e., orthogonal to the thickness direction.

[0028] The frame opening or cell space can be shaped differently. For example, the frame opening can be square, rectangular, circular, ellipsoidal, or polygonal, especially hexagonal. A rhombus shape has proven particularly advantageous. The frame opening can be rotated within the plane of the frame.

[0029] The frame body can be made of plastic, in particular PE, PP, or PVC.

[0030] The feed channels, return channels, and blind channels can have different cross-sectional geometries. For example, the feed channels, return channels, and / or blind channels can be configured such that a fluid channel (secondary channel) formed by a feed 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.

[0031] The feed channels and return channels, or secondary channels, do not open directly into the frame opening (cell space), but are connected to a discharge structure (discharge area) which in turn opens directly into the cell space. Therefore, the frame body can have a discharge structure, particularly a separate one, for each feed channel and each return channel, which opens directly into the cell space and is connected to the respective feed or return channel. The discharge structure is 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 discharge structure can, in particular, be designed as a distributor structure. The discharge structure can be designed as a recess, in particular a hollow or cutout, in the frame body.

[0032] In an advantageous further 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 respective opening structures, wherein the opening structures of the first feed channel and the second feed channel open into the frame opening (cell space) at positions offset from each other along the thickness direction. In this respect, a first opening structure can be formed in the frame body through which the first feed channel opens into the cell space, and a second opening structure can be formed in the frame body through 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 each other along the thickness direction.For example, the first opening structure can be located at a section of the frame opening facing the first side of the frame body, and the second opening structure can be located at a section 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.

[0033] In an advantageous further development of the second or third aspect, the flow frame unit also 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 catholy space, and a second partial cell space, in particular anolyte space.It can then be advantageous if the first feed channel and the first return channel are fluidically connected to the first sub-cell space, particularly via an outlet structure as described above, and are fluidically separated from the second sub-space, and if the second feed channel and the second return channel are fluidically connected to the second sub-space, particularly via an outlet structure as described above, and are fluidically separated from the first sub-space. The flow frame unit can thus provide both a catholyte space and an anolyte space.

[0034] In particular, the first and second subcell spaces lie one above the other in the thickness direction of the frame body. Preferably, the first subcell space is open to the first side of the frame body and the second subcell space is open to the second side of the frame body.

[0035] The separating element, in particular the bipolar plate or membrane / separator, is arranged, in particular, centrally within 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 sub-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 within the frame body. The separating element, in particular the bipolar plate, can be connected to the frame body in various ways, e.g., by gluing, welding, or being overmolded by the frame body. The separating element, in particular the bipolar plate, extends, in particular, parallel to the plane of the frame, i.e., orthogonally to the thickness direction.

[0036] Preferably, each feed channel and each return channel is flow-connected to a primary channel, in particular its own. The following can therefore be formed in the frame body:

[0037] - 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 connected to the frame opening via a first supply channel, in particular a meandering one, which branches off from the primary channel.

[0038] - 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 connected to the frame opening via a first return channel, in particular a meandering channel, which branches off from the primary channel.

[0039] - 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 connected to the frame opening via a second supply channel, in particular a meandering one, branching off from the primary channel.

[0040] - a second return channel system for returning a second fluid, in particular anolyte, from the frame opening, wherein the second return channel system has a second (return) primary channel which is connected to the frame opening via a second return channel, in particular a meandering one, branching off from the primary channel.

[0041] The feed channels and the return channels can therefore form secondary channels of the flow frame unit.

[0042] The primary channels extend, in particular, orthogonally to the direction of extension of the respective associated feed 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 a cell stack: in the stacking direction). Preferably, the primary channels are formed in the frame body as through-openings, e.g., bores.

[0043] Preferably, a feed channel and a blind channel, as well as a return channel and a blind channel, are connected to a common primary channel, particularly in the form of a through-opening in the frame body. Specifically, a feed channel and a blind channel, as well as a return channel and a blind channel, branch off from a common primary channel. In this way, the blind channels can either be supplied 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.

[0044] Channels branching off from a common primary channel can be located on the same side of the frame body. Channels branching off from a common primary channel can also be located on opposite sides of the frame body.

[0045] As mentioned above, the feed channels, return channels, and blind channels can be configured in various ways within the frame. The first and second feed channels can be located on opposite sides of the frame. Alternatively, the first and second feed channels can be located on the same side of the frame.

[0046] The first feed channel and the first return channel can be formed on the same side of the frame body and / or the second feed channel and the second return channel can be formed on the same side of the frame body.

[0047] The first feed channel and the first return channel can be formed on opposite sides of the frame body and / or the second feed channel and the second return channel can be formed on opposite sides of the frame body.

[0048] In a first advantageous embodiment of a flow frame unit, the feed channels, return channels, and blind channels can be located on the same side of the frame body. In this respect, the feed channels, return channels, and blind channels can all be located on either the first or the second side of the frame body. Specifically, the feed channels, return channels, blind channels, and the first outlet structure(s) are located on the first side, and the second outlet structure(s) are located 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 such that the sides containing the channels face each other.

[0049] In the first form of realization, the frame body can be designed to be point-symmetric with respect to a center point of the frame opening.

[0050] In a second advantageous embodiment of a flow frame unit, the first feed channel and the second feed channel can be formed on opposite sides of the frame body, while the first feed channel and the first return channel are formed on the same side of the frame body, and the channels branching off from a common primary channel (blind channel + feed channel or blind channel + return channel) are formed on the same side of the frame body. For example, the second feed channel and the second return channel can be formed on the first side of the frame body, and the first feed channel and the first return channel can be formed on the second side of the frame body.In the second implementation form, it can also be advantageous if the opening structure assigned to a respective feed or return channel and the assigned feed or return channel are formed on opposite sides of the frame body.

[0051] The second implementation allows, in particular, the flow frame units to be arranged in a cell stack such that the same fluid, preferably exclusively the first fluid (catholyte) or the second fluid (anolyte), is exchanged between two adjacent flow frame units. In a cell stack, the flow frame units of the second implementation can, in particular, be arranged such that the feed channel and its associated return channel (i.e., the first feed channel and the first return channel, or the second feed 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). However, it is particularly possible for the first channels (first feed channel and first return channel) and the second channels (second feed channel and second return channel) to overlap with blind channels of different flow frame units (e.g.,the first feed channel and the first return channel with blind channels of a flow frame unit located above in the cell stack, and the second feed channel and the second return channel with blind channels of a flow frame unit located below in the cell stack).

[0052] In a third advantageous embodiment of a flow frame unit, the first feed channel and the second feed channel can be formed on opposite sides of the frame body, wherein the first feed channel and the first return channel are formed on the same side of the frame body, and wherein the second feed channel and the second return channel are formed on the same side of the frame body, with the channels branching off from a common primary channel (blind channel + feed channel or blind channel + return channel) being formed on opposite sides of the frame body. In this third embodiment, it can further be advantageous if the outlet structure associated with each feed or return channel and the associated feed or return channel are formed on the same side of the frame body.

[0053] An embodiment according to the third realization form allows, 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. Specifically, the flow frame units of the third realization form can be arranged in a cell stack such that the first feed channel and the second feed 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 feed channel with a blind channel of a flow frame unit above it in the cell stack, and the second feed channel with a blind channel of a flow frame unit below it in the cell stack), but especially the feed channel and its associated return channel (i.e.,the first feed channel and the first return channel or the second feed channel and the second return channel) each overlap with a blind channel of the same adjacent flow frame unit.

[0054] In a fourth advantageous embodiment of a flow frame unit, the first feed channel and the first return channel can be formed on opposite sides of the frame body, the second feed channel and the second return channel can be formed on opposite sides of the frame body, and the first feed channel and the second feed channel can be formed on opposite sides of the frame body. In particular, the first feed channel and the second return channel can be formed on the first side of the frame body, and the second feed channel and the first return channel can be formed on the second side of the frame body.

[0055] In the fourth implementation, it can be particularly advantageous if the channels branching off from a common primary channel are formed on opposite sides of the frame body. Furthermore, it can be advantageous if the outlet structure and the associated feed channel assigned to a given feed channel are formed on the same side of the frame body, and especially if the outlet structure and the associated return channel assigned to a given return channel are formed on opposite sides of the frame body.

[0056] An embodiment according to the fourth realization form allows, 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 realization form can, in particular, be arranged such that the first feed channel and the second feed 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 feed channel with a blind channel of a flow frame unit above it in the cell stack, and the second feed channel with a blind channel of a flow frame unit below it in the cell stack), in particular the feed channel and its associated return channel (i.e., the first feed channel and the second return channel).the first feed channel and the first return channel or the second feed channel and the second return channel) but each overlap with a blind channel of the same adjacent flow frame unit.

[0057] According to a fourth aspect, a cell stack for a redox flow battery is proposed, comprising at least two flow frame units stacked on top of each other along a stacking direction, each flow frame unit comprising:

[0058] - a frame body which has a frame opening, in particular a central one;

[0059] - at least three, in particular 2n-l with n > 2, separating elements which are arranged in the frame opening and divide the frame opening into at least four, in particular 2n with n > 2, sub-cell spaces arranged one above the other in the stacking direction, wherein for each sub-cell space there is a separate supply channel system for supplying fluid, in particular electrolyte, into the sub-cell space and a separate return channel system for returning fluid, in particular electrolyte, from the sub-cell space, wherein the channel systems each comprise a primary channel, in particular extending in the stacking direction, which is fluidically connected to the corresponding sub-cell space via at least one secondary channel, in particular meandering, and further in particular extending orthogonally to the stacking direction, wherein the secondary channels each extend at least sectionally through at least two adjacent frame bodies.

[0060] Preferably, the three separating elements are two bipolar plates and a separator (or membrane) or one bipolar plate and two separators (or membranes).

[0061] The advantages and optional features described above in connection with the first aspect can also be used to design the cell stack according to the fourth aspect.

[0062] According to a fifth aspect, a flow frame unit for an electrochemical cell of a redox flow battery is proposed, comprising a frame body with a first side and a second side, wherein the frame body has a frame opening which defines a cell space, at least three, in particular 2n-l with n > 2, separating elements which are arranged in the frame opening and divide the frame opening into at least four, in particular 2n with n > 2, sub-cell spaces, wherein in the frame body for each sub-cell space a (separate), in particular meandering, feed channel for supplying fluid into the sub-cell space and a (separate), in particular meandering, return channel for returning fluid from the sub-cell space are formed, wherein in the frame body also a number of, in particular meandering, blind channels corresponding to at least the number of feed channels and return channels are formed,wherein the blind channels are closed at least at one end, wherein the feed channels, the return channels and the blind channels are formed as recesses, in particular cutouts or recesses, and further in particular grooves or channels, in the frame body.

[0063] The advantages and optional features described above in connection with the second aspect can also be used to design the flow frame unit according to the fifth aspect.

[0064] According to a sixth aspect, a cell stack comprising at least two flow frame units according to the fifth aspect is proposed, wherein the frame bodies are designed and stacked along a stacking direction such that each feed channel and each return channel of a frame body overlaps at least sectionally with a blind channel of an adjacent frame body, in particular aligns, so that a common, in particular fully closed, fluid channel is formed in each case.

[0065] The invention will be explained in more detail below with reference to the figures. They show:

[0066] Fig. 1 is a simplified schematic representation of a cell stack to illustrate a

[0067] Basic principle of the invention;

[0068] Fig. 2 is a simplified schematic representation of a flow frame unit of the cell stack according to Fig. 1 in a top view;

[0069] Fig. 3 shows a simplified schematic representation of a flow frame unit according to a first implementation form in a top view;

[0070] Fig. 4 shows the flow frame unit according to Fig. 3 in a sectional view along the section line IV-IV shown in Fig. 3;

[0071] Fig. 5 shows the flow frame unit according to Fig. 3 in a sectional view along the section line VV shown in Fig. 3; Fig. 6 shows a sectional view through a cell stack of two flow frame units according to Fig. 3 along the section line VV shown in Fig. 3;

[0072] Fig. 7 shows a sectional view through a cell stack of two flow frame units according to Fig. 3 along the section line IV-IV shown in Fig. 3;

[0073] Fig. 8 simplified schematic representation to illustrate the construction of a cell stack from several flow frame units according to Fig. 3;

[0074] Fig. 9 shows a simplified schematic representation of a flow frame unit according to a second implementation form in a top view;

[0075] Fig. 10 shows the flow frame unit according to Fig. 9 in a sectional view along the section line XX shown in Fig. 9;

[0076] Fig. 11 shows the flow frame unit according to Fig. 9 in a sectional view along the section line XI-XI shown in Fig. 9;

[0077] Fig. 12 shows a sectional view through a cell stack of two flow frame units according to Fig. 9 along the section line XI-XI shown in Fig. 9;

[0078] Fig. 13 simplified schematic representation to illustrate the construction of a cell stack from several flow frame units according to Fig. 9;

[0079] Fig. 14 shows a simplified schematic representation of a flow frame unit according to a third implementation form in a top view;

[0080] Fig. 15 shows the flow frame unit according to Fig. 14 in a sectional view along the section line XV-XV shown in Fig. 14;

[0081] Fig. 16 shows the flow frame unit according to Fig. 14 in a sectional view along the section line XVI-XVI shown in Fig. 14;

[0082] Fig. 17 shows a sectional view through a cell stack of two flow frame units according to Fig. 14 along the section line XVI-XVI shown in Fig. 14;

[0083] Fig. 18 simplified schematic representation to illustrate the construction of a cell stack from several flow frame units according to Fig. 14;

[0084] Fig. 19 shows a simplified schematic representation of a flow frame unit according to a fourth implementation form in a top view;

[0085] Fig. 20 shows the flow frame unit according to Fig. 19 in a sectional view along the section line XX-XX shown in Fig. 19;

[0086] Fig. 21 shows the flow frame unit according to Fig. 19 in a sectional view along the section line XXI-XXI shown in Fig. 19; Fig. 22 shows a sectional view through a cell stack of two flow frame units according to Fig. 19 along the section line XXI-XXI shown in Fig. 19; and

[0087] Fig. 23 simplified schematic representation to illustrate the construction of a cell stack from several flow frame units according to Fig. 19.

[0088] In the following description and in the figures, the same reference symbols are used for identical or corresponding features.

[0089] Figures 1 and 2 show simplified schematic representations of an exemplary embodiment of a cell stack 10 to illustrate a basic principle of the invention. Possible concrete implementations are described below with reference to Figures 3 ff.

[0090] The cell stack 10 comprises two flow frame units 12, 12', which are stacked on top of each other along a stacking direction 14. Each flow frame unit 12 has a frame body 16. The frame body 16 extends planarly in a frame plane orthogonal to the stacking direction 14 (see Figure 2). The frame body 16 has a thickness 20 in a thickness direction 18 (corresponding to the stacking direction 14 in Figure 1).

[0091] The frame body 16 has a frame opening 22, which in this example is central. The frame opening 22 defines a cell space 24 (or working space) of the flow frame unit 12, in which the electrochemical processes take place.

[0092] 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, such 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 partition element of the flow frame unit 12. An electrode can be arranged in each sub-cell space 28-1, 28-2.

[0093] In this example, the first subcell space 28-1 forms a catholy space and the second subcell space 28-2 forms an anolyte space.

[0094] A membrane / separator 30 is arranged between the two flow frame units 12. This membrane / separator covers the frame openings 22 and thus fluidically separates the cell compartments 24 of the flow frame units 12 from one another. The membrane / separator 30 is designed to be ion-permeable. In this specific example, the membrane / separator 30 separates the second compartment 28-2 of the first (upper, in Fig. 1) flow frame unit 12 and the first compartment 28-1 of the second (lower, in Fig. 1) flow frame unit 12. The second compartment 28-2 of the first flow frame unit 12 and the first compartment 28-1 of the second flow frame unit 12 thus form a cell of the cell stack 10.

[0095] In embodiments not shown, the relative arrangement of the membrane / separator 30 and the bipolar plate 26 can be reversed. 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.

[0096] As schematically shown in Figures 1 and 2, for each subcell space 28-1, 28-2 there is a supply channel system 32-1, 32-2 for supplying fluid, in particular electrolyte, into the subcell space 28-1, 28-2 and a return channel system 34-2 for returning fluid, in particular electrolyte, from the subcell space 28-1, 28-2.

[0097] The assignment of the channel systems or the individual channels to the sub-cell spaces 28-1, 28-2 is illustrated in the figures by different hatching patterns for clarity. However, the hatching does not mean that different fluids flow in the sub-cell spaces 28-1, 28-2 or in the channel systems during operation. In this example, all first sub-cell spaces 28-1 (diagonal and vertical hatching) are supplied with catholyte, and all second sub-cell spaces 28-2 (dotted and unhatched areas) are supplied with anolyte.

[0098] In the example, each feed channel system 32-1, 32-2 has a (feed) primary channel 36-1, 36-2 (example formed as a through-opening in the frame body 16), which is connected to the respective sub-cell space 28-1, 28-2 via a (feed) secondary channel 38-1, 38-2, which is in particular meandering. Similarly, in the example, each return channel system 34-1, 34-2 has a (return) primary channel 40-1, 40-2, which is connected to the respective sub-cell space 28-1, 28-2 via a (return) secondary channel 42-1, 42-2, which is in particular meandering. The secondary channels 38-1, 38-2, 42-1, 42-2 can in turn open into the respective subcell space 28-1, 28-2 via respective opening structures 44 (explained in more detail below).

[0099] By way of example and preferably, the (feed) primary channel 36-1, 36-2 and the associated (return) primary channel 40-1, 40-2 are arranged diagonally opposite each other with respect to the frame opening 22.

[0100] As can be seen from Figure 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 larger than the thickness 20 of a respective frame body 16.

[0101] In the illustrated example, 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 configured as a supply channel 48-1, 48-2 or a return channel 50-1, 50-2, respectively, which is fluidically connected to the respective sub-cell space 28-1, 28-2 via the aforementioned opening structure 44. The other of the two channel-shaped recesses forming each secondary channel is configured as a blind channel 52, which serves as a cross-sectional expansion 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 opening structure 44.

[0102] Figure 1 shows the feed and return channels 48-1, 48-2, 50-1, 50-2 schematically only, to illustrate the basic concept of the invention. Exemplary embodiments are explained in detail below with reference to Figures 3 ff. Features that have already been described in connection with Figures 1 and 2 and are identical or equivalent in function are not described again unless relevant to the specific embodiment.

[0103] Figure 3 shows a simplified schematic representation of a design of a flow frame unit 12 according to a first implementation form.

[0104] As explained above with reference to Figure 1, a bipolar plate 26 (not shown in Figure 3) is also arranged in the frame opening 22 of the flow frame unit 12 according to Figure 3, 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 (see Figure 4). For clarity, elements, in particular feed channels, return channels and blind channels, which lie below the plane of the drawing, are shown with dashed lines in the top views according to Figures 3, 9, 14, and 19.

[0105] As can be seen from Figure 3, a first supply channel system 32-1 for supplying first fluid, in particular catholyte, into the first sub-cell space 28-1 and a first return channel system 34-1 for returning first fluid from the first sub-cell space 28-1 are formed in the frame body 16.

[0106] 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 (meandering in this example), and a first outlet structure 44-1 through which the supply channel 48-1 opens into the first subcell 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 (meandering in this example), and an outlet structure 44-1 through which fluid can be discharged from the first subcell space 28-1.

[0107] Similarly, the frame body 16 also includes a second supply channel system 32-2 (comprising primary channel 36-2, supply channel 48-2 and second outlet structure 44-2) for supplying second fluid into the second sub-cell space 28-2 (not visible in Fig. 3) and a second return channel system 34-2 (comprising primary channel 40-2, return channel 50-2 and outlet structure 44-2) for returning second fluid from the second sub-cell space 28-2.

[0108] As can be seen from Figure 4, the first and second opening structures 44-1, 44-2 open into the frame opening 22 (cell space) at positions offset from each other along the thickness direction 18.

[0109] As can be seen from Figure 3, a blind channel 52, as mentioned above, branches off from each primary channel 36-1, 36-2, 40-1, 40-2. In this example, the blind channel 52 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 between the blind channel 52 and the frame opening 22 via the feed 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" within the scope of this application.)

[0110] As can be seen in Figure 5, the channels (feed channels 48-1, 48-2, return channels 50-1, 50-2, and blind channels 52) are formed as recesses, for example, in the form of groove-shaped cutouts or recesses in the frame body 16. In the first embodiment, all feed channels 48-1, 48-2, return channels 50-1, 50-2, and blind channels 52 are formed on the same side, in this 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.

[0111] For example, a channel depth of 55 in the thickness direction 18 is more than 50% of a thickness 20 of the frame body 16.

[0112] If two such flow frame units 12 are stacked on top of each other in such a way that the first sides 54-1 face each other, in the specific example in which one flow frame unit 12 is rotated relative to the other about the axis 57 shown in 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 fully enclosed fluid channel is formed in each case, which forms a secondary channel 38-1, 38-2, 42-1, 42-2 of the respective channel system described above (shown in Figure 6 as an example for a sectional view corresponding to Figure 5).

[0113] As mentioned above, a membrane 30 or separator is arranged between two adjacent flow frame units 12, which covers the frame openings 22 and thus fluidically separates the adjacent subcell spaces 28-1, 28-2 of adjacent flow frame units 12 from each other.

[0114] For better understanding, Figure 8 shows an exploded view of a cell stack 10 consisting of four flow frame units 12 according to Figure 3, corresponding to Figure 1. In this example, two flow frame units 12 are oriented with their first sides 54-1 facing each other. A flow connection between the channels, which are only shown schematically, is indicated by dashed lines in Figure 8 (and analogously in the following Figures 13, 18, and 23). In such a configuration, three cells 56-1, 56-1, 56-3 are formed, each consisting of a (catholyte) subcell space 28-1 of a flow frame unit 12, an (anolyte) subcell space 28-2 of an adjacent flow frame unit 12, and a membrane 30 / separator arranged between them.

[0115] Figure 9 shows another exemplary embodiment of a river frame unit 12 according to a second realization form, which differs from the river frame unit 12 according to the first realization form by the relative arrangement of the channels.

[0116] In the example shown in Figure 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 (see 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 thus arranged on the same side 54-1, 54-2 of the frame body 16.

[0117] A further difference arises from the fact that the feed channel 48-1, 48-2 and return channel 50-1, 50-2 assigned to each subcell space 28-1, 28-2 are formed on the side 54-1, 54-2 of the frame body 16 opposite the subcell space 28-1, 28-2 (see Figs. 9 and 10). Thus, the respective feed channel 48-1, 48-2 and return channel 50-1, 50-2 and the respective associated outlet structure 44-1, 44-2 are formed on opposite sides 54-1, 54-2 of the frame body 16.

[0118] As can be seen from Figure 9, the channels branching off 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.

[0119] Such a configuration allows the flow frame units 12 to be arranged in a cell stack 10 such that 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 (see Fig. 13). For example, when considering the second flow frame unit 12' from below in Figure 13, the first supply channel 48-1' is connected to a blind channel 52 of the flow frame unit 12 above it, while the second supply channel 48-2' interacts with a blind channel 52 of the flow frame unit 12 below it. Therefore, only the first fluid (catholyte) or the second fluid (anolyte) is exchanged with a neighboring flow frame unit 12.

[0120] Figure 14 shows another exemplary embodiment of a flow frame unit 12 according to a third realization form, which differs from the second realization form in that the channels branching off 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. Furthermore, the feed and return channels 48-1, 48-2, 50-1, 50-2 are formed on the same side as their respective associated outlet structures 44-1, 44-2. Therefore, the supply and return channels 48-1, 48-2, 50-1, 50-2 assigned to a respective subcell space 28-1, 28-2 are formed on the same side 54-1, 54-2 as the subcell space 28-1, 28-2.

[0121] As can be seen in Fig. 18, this configuration allows the flow frame units 12 to be arranged 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 (see Fig. 18). When considering the second lowest flow frame unit 12 in Figure 18, for example the first feed channel 48-1 is flow-connected to a blind channel 52 of the flow frame unit 12' above, while the second feed channel 48-2 interacts with a blind channel 52 of the flow frame unit 12' below.

[0122] Figure 19 shows a further exemplary embodiment of a flow frame unit 12 according to a fourth realization form, which differs from the third realization form in the arrangement of the return channels 50-1, 50-2 and the blind channels 52 connected to them in the flow. As can be seen from Fig. 19, the feed channel systems 32-1, 32-2 are identical to the third realization form, but the return channels 50-1, 50-2 and the blind channels 52 connected to them in the flow are reversed in their side assignment compared to the third realization form (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).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 branching off 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.

[0123] In contrast to the third implementation, in the fourth implementation the return channels 50-1, 50-2 and their respective associated outlet structures 44-1, 44-2 are arranged on opposite sides 54-1, 54-2 of the frame body 16. In this specific example, the first return channel 50-1 is routed 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 routed through the frame body 16 from the first side 54-1 to the second side 54-2.

[0124] As can be seen in Fig. 23, this configuration allows the flow frame units 12 to be arranged 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, with the supply and return of the same fluid occurring via different flow frame units 12. For example, in the second lowest flow frame unit 12 shown in Fig. 23, the first fluid (catholyte) is supplied to the first subcell space 28-1 by the interaction of the first supply channel 48-1 of this flow frame unit 12 with a blind channel 52' of the flow frame unit 12 above it, but is discharged from the first subcell space 28-1 by the interaction of the first return channel 50-1 of this flow frame unit 12 with a blind channel 52' of the flow frame unit 12 below it.

[0125] 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 other elements in a known manner, e.g., end plates, electrical contact plates and / or a housing.

Claims

Patent claims 1. Cell stack (10) for a redox flow battery, comprising at least two flow frame units (12) stacked on top of each other along a stacking direction (14), each flow frame unit (12) comprising: - a frame body (16) which has a frame opening (22), in particular a central one; - 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 have a primary channel (36-1, 36-2, 34-1, 34-2), in particular extending in the stacking direction, 40-2) comprising, which is fluidically connected to the corresponding subcell space (28-1, 28-2) via at least one, in particular meandering, and further in particular extending orthogonally to the stacking direction (14), secondary channel (38-1, 38-2, 42-1, 42-2),wherein the secondary channels (38-1, 38-2, 42-1, 42-2) each extend at least sectionally 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 larger than a thickness (20) of a frame body (16) in the stacking direction (14), in particular at least 1.2 times larger, further in particular at least 1.5 times larger, further in particular at least 1.8 times larger.

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) with a first side (54-1) and a second side (54-2), wherein the frame body (16) has a frame opening (22) which defines a cell space (24), wherein the following are formed in the frame body (16): - at least one first, in particular meandering, supply channel (48-1) for supplying first fluid, in particular catholyte, into the cell space (24); - at least one first, in particular meandering, return channel (50-1) for returning first fluid, in particular catholyte, from the cell space (24); - at least a second, in particular meandering, supply channel (48-2) for supplying a second fluid, in particular anolyte, into the cell space (24); - at least one second, in particular meandering, return channel (50-2) for returning a second fluid, in particular anolyte, from the cell space (24); characterized in that the frame body (16) also has a number of, in particular meandering, blind channels (52) corresponding 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 supply channels (48-1, 48-2), the return channels (50-1, 50-2) and the blind channels (52) are formed as recesses, in particular cutouts or recesses, and further in particular grooves or grooves, in the frame body (16).

5. Flow frame unit (12) according to the previous 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) through 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) through 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 each other 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) such that it divides the frame opening (22) into a first partial cell space (28-1), in particular a catholytic space, and a second subcell space (28-2), in particular anolyte space, subdivided, wherein the first supply channel (48-1) and the first return channel (50-1) are fluid-connected to the first subcell space (28-1), in particular via a respective outlet structure (44), and wherein the second supply channel (48-2) and the second return channel (50-2) are fluid-connected to the second subcell space (28-2), in particular via a respective outlet 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) each branch off 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 feed 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 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), wherein the first feed 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 feed 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 previous claim with reference to claim 7, wherein the channels (48-1, 48-2, 50-1, 50-2, 52) branching off 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 with reference to claim 5, wherein the outlet 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 with reference to claim 7, wherein the channels (48-1, 48-2, 50-1, 50-2, 52) branching off 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 by reference to claim 5, wherein the outlet 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 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), wherein 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), 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 previous claim by reference to claim 7, wherein the channels (48-1, 48-2, 50-1, 50-2, 52) branching off 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 with reference to claim 5, wherein the outlet 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 an outlet 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 any 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 a 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 any one of claims 4 to 17, wherein the frame bodies (16) are designed and stacked on top of each other along a stacking direction (14) such that each feed channel (48-1, 48-2) and each return channel (50-1, 50-2) of a frame body (16) overlaps at least sectionally with a blind channel (52) of an adjacent frame body (16), in particular aligns, so that a common, in particular fully enclosed, fluid channel (38-1, 38-2, 42-1, 42-2) is formed.

19. Cell stack (10) according to the previous 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 larger than a thickness (20) of a frame body (16) in the stacking direction (14), in particular at least 1.2 times larger, further in particular at least 1.5 times larger, further in particular at least 1.8 times larger.

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 and separates the frame openings (22) of adjacent flow frame units (12).

Images