Frame for a half-cell of a redox flow battery
Patent Information
- Application Number
- EP2024776856
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-11-03
- Filing Date
- 2024-09-20
- Publication Date
- 2026-09-09
AI Technical Summary
Existing redox flow batteries face challenges in maintaining internal tightness within half-cells and between neighboring cells, leading to potential leakage paths for electrolyte fluids, which can result in self-discharge and damage to components.
The proposed frame design for half-cells includes a bridge that connects two flow channels, ensuring they are open on opposite sides of the frame, with one end connected to the electrolyte fluid channel and the other to the recess. This design supports a continuous sealing surface and reduces the risk of deformation, thereby enhancing internal tightness.
The improved frame design significantly reduces the risk of leakage and mixing of electrolyte liquids, enhances the internal tightness of half-cells and between neighboring cells, and lowers the tolerance requirements for electrode plates, resulting in cost savings and improved performance of the redox flow battery.
Smart Images
Figure EP2024076454_08052025_PF_FP_ABST
Abstract
Description
[0001] Frame for a half-cell of a redox flow battery
[0002] The present invention relates to a frame for a half-cell of a redox flow battery, wherein the frame has two opposite end faces, wherein a central recess is provided in the frame which connects the two end faces to each other and in a first of the end faces of the frame a flow channel is provided which is at least partially open towards this first end face for supplying or discharging electrolyte fluid, and the flow channel is connected to an electrolyte fluid channel on the frame which passes through the frame,At least one further flow channel is provided on the frame for draining or supplying the electrolyte fluid, and in the second end face of the frame, opposite the end face with the flow channel, a depression is provided around the circumference of the recess, extending from the second end face and toward the first end face, and the depression is delimited by a continuous circumferential surface, the circumferential surface connecting a base of the depression to the second end face, and the base of the depression forming a sealing surface. The invention also relates to a single cell of a cell stack of a redox flow battery and a cell stack of a redox flow battery with a plurality of single cells.
[0003] A redox flow battery is a well-known electrochemical energy storage device and typically consists of storage tanks for storing differently charged electrolyte fluids, such as positive and negative ones, as well as pumps and lines for circulating the electrolyte fluids (electrolytes) through one or more cell stacks, each containing a number of individual electrochemical cells. The individual cells of the cell stack are each formed by a positive half-cell and a negative half-cell arranged side by side, with the positive and negative half-cells of an individual cell separated from each other by a semipermeable membrane, typically an ion exchange membrane. The semipermeable membrane is, for example, a cation and / or anion exchange membrane, e.g., Nation®.The positive half-cell contains a positive electrode located in a frame through which the positive electrolyte flows. The negative half-cell contains a negative electrode located in a frame through which the negative electrolyte flows. The positive and negative electrolytes are circulated separately through the half-cells. The positive and negative electrodes are usually made of porous graphite felts through which the respective electrolyte flows. The half-cell frames are arranged next to one another and the resulting individual cells are connected to one another to form a cell stack, with negative and positive half-cells alternating. Electrically conductive electrode plates, for example bipolar plates, are arranged as current collectors between adjacent individual cells of the cell stack. These plates are usually made of a composite material made of carbon and plastic.On the axial outer sides of the axially outer individual cells of the cell stack, there are current collectors on the electrode plates. An electrical contact is made via these collectors to the outside in order to tap an electrical voltage across the entire cell stack (discharging the redox flow battery) or to apply an electrical voltage to the cell stack (charging the redox flow battery). The cell stack is closed off on each axial outer side by an end plate, which holds the cell stack together. Bolts are usually inserted through the end plates, and the end plates are pressed together onto the bolts by nuts. The nuts on at least one side are usually preloaded by a spring to compensate for any settlement of the half-cell frames.
[0004] In a vanadium-based redox flow battery, the positive electrolyte fluid in the charged state consists of a redox pair in the form of vanadium with the oxidation number +4 (also known as V lv or V 4+ referred to) and vanadium with the oxidation number +5 (also known as V v or V 5+ The negative electrolyte fluid in the charged state consists of a redox pair in the form of vanadium with the oxidation number +2 (also known as V" or V 2+ referred to) and vanadium with the oxidation number +3 (also known as V 111 or V 3+(referred to as "redox flow batteries"), meaning that the negative electrolyte fluid has a more negative electrochemical potential than the positive electrolyte fluid. Redox flow batteries based on other redox pairs, for example, those based on the chemical elements Br, S, Fe, Ti, Mn, Cr, or organic compounds such as ferricyanide or quinone, are also known, all of which operate essentially according to the same principle.
[0005] A redox flow battery typically consists of several such cell stacks that are electrically connected to each other. The electrolyte fluids for all cell stacks are also usually supplied from the same storage tanks.
[0006] This structure and function of a redox flow battery is well known, for example from AT 501 902 B1 or AT 510 723 B1.
[0007] An important aspect in the operation of a redox flow battery is the tightness between the two electrolytes. This is because leaks, i.e. cross-flows between the two half-cells of a single cell or between two adjacent single cells, or external leaks, lead to mixing of the two electrolytes, which causes the redox flow battery to self-discharge. Furthermore, parts of the redox flow battery that should not come into contact with an electrolyte can be damaged by the electrolyte. This can lead to a loss of function, performance, or efficiency in the redox flow battery. Equally critical can be the leakage of an electrolyte from the cell stack, as the electrolyte is often aggressive and can attack or damage other components of the redox flow battery. If it leaks into the environment, it can cause environmental damage.The seal between the two half-cells of a single cell or between two adjacent single cells is critical in terms of tightness.
[0008] To improve sealing, AT 501 902 B1 or AT 510 723 B1 propose frames made of an elastomer that form individual cells. Sealing surfaces are provided on one end face of the frame. Two adjacent frames rest against each other along these sealing surfaces and are pressed together in a cell stack. The elastomer material of the frames and the compression ensure a good seal at the end faces. Nevertheless, this design of a frame for an individual cell in a redox flow battery also has disadvantages.
[0009] On the end of the frame facing the electrode plate, channels are provided for the supply and removal of an electrolyte fluid. These channels open into distribution channels in the frame that are connected to a recess in which the electrode of the individual cell is arranged. A recess in the frame is provided around the recess, into which an electrode plate is arranged. Due to tolerances in the electrode plate, sealing fingers are arranged in the area of this recess. These sealing fingers interact with bevelled peripheral surfaces on the edge of the electrode plate to prevent the formation of leakage channels. The electrode plates are therefore complex to manufacture due to the double-bevelled peripheral surfaces and the high tolerance requirements. In addition, the channels interrupt the sealing surface for sealing the electrode plate at the base of the recess.At this point, there is a risk of a bypass for electrolyte fluid forming around the electrode plate, which can lead to leakage and mixing of the electrolyte fluids in neighboring individual cells.
[0010] In the area of the channels and distribution channels in the frame, the electrode plate comes into contact with the electrolyte fluid only over a small surface area, whereas in the area of the electrode, the electrode and the electrode plate come into contact with the electrolyte fluid over a large surface area. This means that in areas where the electrode plate only comes into contact with the electrolyte fluid, a high electrical overvoltage can occur, which can locally overload the electrode plate and irreversibly damage the electrode plate. This can lead to swelling of the electrode plate, which can block fluid paths. However, it can also cause the electrode plate to become permeable, creating leakage paths for electrolyte fluid.To reliably prevent this, the edge areas of the electrode plate, i.e. the areas that could come into contact with the electrolyte, were taped off with adhesive tape. However, the adhesive points of such an adhesive tape are potential weak points that could lead to electrolyte leaks. For example, the electrolyte can penetrate the adhesive surface between the adhesive tape and the electrode plate, which can open up a continuous leak path between the adhesive tape and the electrode plate. Apart from that, because the edges of the electrode plate are taped all around, there would be overlapping adhesive strips in the corners of the electrode plate. This can also lead to a leak path for electrolyte. Due to the overlap, the taped electrode plate is also thicker at the corners than in between, which in turn can compromise the tightness of the seal of the electrode plate.
[0011] Although the frames known from AT 501 902 B1 or AT 510 723 B1 can be used to manufacture reliable cell stacks of redox flow batteries, there is still a need, in particular, to improve the internal tightness in the half-cells of a single cell and between adjacent single cells and to reduce the possibilities for potential leakage paths of electrolyte fluids and, at the same time, to reduce the manufacturing effort for a single cell and a cell stack of a redox flow battery.
[0012] This is achieved according to the invention with a frame as described at the outset in that a web is provided which divides the at least one flow channel into two flow channel branches, that each of the flow channel branches separated by the web is connected to an opening passing through the frame and the web is arranged in the region of the openings, wherein a first end of each opening is connected to the respective flow channel branch of the at least one flow channel on the first end face and the opposite second end of each opening on the frame opens in the direction of the recess at a distance from the circumferential surface of the depression and is connected to the recess in the frame, and the web on the first end face extends at least between the region of the openings and the circumferential surface of the depression.The web can at least reduce any possible deformation of the frame in the cell stack, preventing a narrowing or blockage of the flow channel. In addition, the sealing surface in the region of the flow channel is supported by the web. Both of these factors help to improve the internal tightness in the half-cells of a single cell and between adjacent single cells. According to the invention, the flow channel and the inflow of the electrolyte fluid into the recess are provided on different, opposite sides of the frame. The inventive positioning of the openings at a distance from the circumferential surface of the recess ensures that a continuous sealing surface is formed around the recess through the base of the recess.The interaction of the continuous sealing surface with an electrode plate arranged in the recess when the frame is used in a cell stack can reduce the risk of a leakage path forming around the electrode plate. Thus, with a frame according to the invention, the internal tightness in the half-cells of a single cell and between adjacent single cells of a cell stack can be improved. Due to the continuous sealing surface, the tolerance requirements for the electrode plate are also lower, which significantly reduces the costs of the cell stack. Last but not least, the continuous sealing surface can also simplify any taping of an edge of the electrode plate, which also reduces the costs of the cell stack.
[0013] Preferably, the opening is positioned at a distance of between 25%, preferably 33%, 50%, or 75%, and less than 100% of the width of the recess in the region of the opening's mouth from the peripheral surface of the recess. Thus, the opening opens in the region of the sealing surface of the recess. The greater the distance, the wider the sealing surface in the region of the opening, and the better and more reliable the seal.
[0014] If a distribution channel is provided on the frame, which is connected to the recess in the frame and which extends at least partially along an edge of the recess, wherein the second end of the at least one opening is connected to the recess in the frame via the distribution channel, the opening is advantageously positioned at a distance of at least 100% of the width of the recess in the region of the opening's mouth from the peripheral surface of the recess. The opening opens in the region of the distribution channel. This allows the entire width of the recess to be utilized for the sealing surface, maximizing the sealing effect.
[0015] Preferably, two flow channels according to the invention are provided on a frame. This allows the advantage of the invention to be utilized for each flow channel, further improving the frame's tightness.
[0016] The present invention will be explained in more detail below with reference to Figures 1 to 12, which show exemplary, schematic, and non-limiting advantageous embodiments of the invention. Figure 1 shows the basic functional principle of a redox flow battery.
[0017] Fig.2 a redox flow battery with a cell stack,
[0018] Fig.3 shows the structure of a cell stack of a redox flow battery,
[0019] Fig.4 and 5 a frame of a half cell of a single cell of a cell stack of a redox flow battery from two different sides, Fig.6 a detailed view of the frame
[0020] Fig.7 an electrode plate with taped edge in the frame,
[0021] Fig. 8 and 9 show a frame according to the invention of a half-cell of a single cell of a cell stack of a redox flow battery from two different sides, Fig. 10 shows a detailed view of a single cell in the area of the opening,
[0022] Fig.11 is a detailed view of two adjacent individual cells with electrode plates and Fig.12 is an electrode plate with taped edges in a frame according to the invention.
[0023] Fig. 1 shows a schematic structure of a redox flow battery 1 using a single cell 2 of a cell stack 10 to explain the well-known functional principle of a redox flow battery 1. For better explanation and illustration, only a single cell 2 of a cell stack 10 of a redox flow battery 1 is shown in Fig. 1, whereby a cell stack 10 will generally have a plurality of single cells 2.
[0024] A single cell 2 consists of two half-cells 2a, 2b, which form a positive reaction chamber 3a and a negative reaction chamber 3b. The two half-cells 2a, 2b, or the positive reaction chamber 3a and the negative reaction chamber 3b, are separated by a semipermeable, in particular ion-selective, membrane 4. The reaction chambers 3a, 3b are formed, for example, in recesses 6a, 6b of frames 5a, 5b. An electrode 7a, 7b is arranged in each of the reaction chambers 3a, 3b and in the recesses 6a, 6b. Electrolyte fluids 15a, 15b with different electrical charges (positive and negative electrolyte fluids) flow through the recesses 6a, 6b and the electrodes 7a, 7b arranged therein of a single cell 2. Each of the electrolyte liquids 15a, 15b contains a redox pair with specific, time-varying concentrations (depending on the state of charge) of redox elements.The semipermeable, particularly ion-selective, membrane 4 can be made, for example, from sulfonate-modified polytetrafluoroethylene (PTFE), with the trade name Nation™, and enables ions to achieve charge equalization between the positive reaction chamber 3a and the negative reaction chamber 3b (or between the electrolyte liquids 15a, 15b contained therein). The individual cell 2 is closed off on both sides by an electrode plate 8. A redox flow battery 1 also includes power connections 11, 12 for tapping an electrical cell stack voltage Vz applied to the cell stack 10 via a consumer 14 (discharging the redox flow battery 1) or for applying an electrical cell stack voltage Vz to the cell stack 10 (charging the redox flow battery 1).
[0025] An electrical load 14 can take any form. Based on the electrical voltage, current, or power requirements of the electrical load 14, a cell stack 10 can be configured in a redox flow battery 1 to provide the necessary electrical voltage and / or the necessary electrical current. Redox flow batteries 1 are often used as stationary energy storage devices, for example, to serve as emergency power systems for industrial plants, storage systems for renewable energy (photovoltaics, wind power), and the like. Consequently, depending on the application, a person skilled in the art can design or select a cell stack 10, or a parallel and / or serial connection of multiple cell stacks, and redox pairs in a redox flow battery 1.
[0026] The electrolyte fluids 15a, 15b are stored in storage tanks 13a, 13b and are circulated from there through the cell stack 10 by means of circulation pumps 9a, 9b, specifically through a half-cell 2a, 2b of a single cell 2 of the cell stack 10. For this purpose, a supply line 16a, 16b and a discharge line 17a, 17b are provided for each electrolyte fluid 15a, 15b, which are connected via electrolyte fluid connections 22a, 22b, 23a, 23b to corresponding electrolyte fluid channels 18a, 18b, 19a, 19b (see Fig. 3) in the cell stack 10.
[0027] In a cell stack 10 with several adjacent individual cells 2, an electrode plate 8, such as a bipolar plate, is arranged between each two adjacent individual cells 2. At the outer ends of the cell stack 10, a power connection 11, 12 can be located on the outer electrode plates 8 or on the outer half-cells 2a, 2b (or electrodes 7a, 7b) of the cell stack 10, which can be electrically contacted from the outside.
[0028] The typical structure of a cell stack 10 of a redox flow battery 1 is explained in more detail with reference to Figs.2 and 3.
[0029] A cell stack 10 of a redox flow battery 1 comprises at least one individual cell 2, generally a plurality of individual cells 2, which in turn are each formed from two frames 5a, 5b of half-cells 2a, 2b. A frame 5a, 5b is preferably made of a plastic, such as an elastomer, such as a polyolefinic thermoplastic elastomer (TPE or TPO), such as Santoprene®, or a thermoplastic vulcanate (TPV), in particular using an injection molding process. In the stack direction R (in the direction in which the individual cells 2a, 2b are arranged next to one another), between two frames 5a, 5b of an individual cell 2 in the cell stack 10, a semipermeable membrane 4, typically an ion exchange membrane (either a cation or anion exchange membrane, e.g. Nation®), is arranged.The membrane 4 separates the reaction spaces 3a, 3b, recesses 6a, 6b of the half-cells 2a, 2b of a single cell 2, the electrodes 7a, 7b arranged therein, and the electrolyte liquids 15a, 15b located therein. Between each two individual cells 2 adjacent in the stack direction R, an electrode plate 8, e.g., a bipolar plate, is arranged in the cell stack 10. The electrode plate 8 is, as shown in Fig. 3, inserted into mutually facing recesses 40 in the frames 5a, 5b. The frames 5a, 5b have central recesses 6a, 6b that run through in the stack direction R, each forming a reaction space 3a, 3b and in which electrodes 7a, 7b, e.g., mats made of carbon fiber, are arranged, as shown in Fig. 3.
[0030] The differently charged electrolyte fluids 15a, 15b are pumped through the recesses 6a, 6b in the frames 5a, 5b through the individual cells 2, with an electrolyte fluid 15a, 15b with a different electrical charge flowing through the electrode 7a, 7b of each half-cell 2a, 2b of an individual cell 2. The electrolyte fluids 15a, 15b are supplied and discharged from the outside via electrolyte fluid connections 22a, 22b, 23a, 23b and are then distributed internally via an electrolyte fluid channel system provided in the frames 5a, 5b with electrolyte fluid channels 18a, 18b, 19a, 19b, as explained in more detail below. The electrolyte fluid connections 22a, 22b, 23a, 23b are provided, for example, on an end plate 24 of the cell stack 10, as shown in Fig.3, although other arrangements of the electrolyte fluid connections 22a, 22b, 23a, 23b, for example on an end frame 20, are also possible.
[0031] The cell stack 10 can be closed off in the stacking direction R by an end frame 20 at each of its two axial ends. An electrically conductive current collector 21 is arranged in the end frame 20, e.g., in a recess on one end face of the end frame 20, and is connected to an externally routed electrical power connection 11, 12. In the illustrated embodiment, the current collector 21 rests against the last electrode plate 8 of the last individual cell 2 to establish electrical contact. However, the current collector 21 or a power connection 11, 12 could also be designed differently. Likewise, the end frame 20 could be omitted from the cell stack 10.
[0032] In the illustrated embodiment, the cell stack 10 is arranged between two rigid end plates 24 and pressed together by clamping means 25. The clamping means 25 are designed, for example, with through-reaching bolts 26, nuts 27, washers 28, and springs 29, as shown in Fig. 2. However, the cell stack 10 can also be held together in other ways; in particular, the clamping means 25 can be designed differently. The two end plates 24 can also be arranged between two pressure plates 30, which are pressed together by the clamping means 25, as shown in Fig. 2. To prevent the frames 5a, 5b from settling due to the contact pressure of the clamping means 25, a spacer 31 can also be provided between the end plates 24.
[0033] To prevent the electrolyte fluids 15a, 15b from mixing, a seal must be provided between adjacent half-cells 2a, 2b and between adjacent individual cells 2, preventing a leakage path for one of the electrolyte fluids 15a, 15b. The seal is intended to prevent an electrolyte fluid 15a, 15b from flowing via another flow path, such as in particular around an electrode plate 8, in addition to the intended flow through the recesses 6a, 6b and the electrodes 7a, 7b arranged therein. In the prior art, the electrode plates 8 are located in recesses 40 on the frames 5a, 5b. The base of the recess 40 forms a sealing surface 41 against which the electrode plate 8 rests. By pressing the frames 5a, 5b together in the cell stack 10, the seal between the electrode plate 8 and the respective frame 5a, 5b is achieved. This is illustrated in Fig.4 to 7, which illustrate a frame 5a, 5b according to the prior art, as described, for example, in AT 501 902 B1. The known frame 5a, 5b will be discussed below only to the extent necessary for explaining the invention.
[0034] Figs. 4 and 5 show the frame 5a, 5b from different directions. Fig. 4 shows the end face 42, where the electrode plate 8 is arranged in the cell stack 10, and Fig. 5 shows the opposite end face 43, where the membrane 4 is arranged in the cell stack 10. The recess 6a, 6b is arranged in the central area of the frame 5a, 5b and connects the two end faces 42, 43. The recess 6a, 6b thus extends through the frame 5a, 5b in the stack direction R. The electrolyte fluid channels 18a, 18b, 19a, 19b are provided in the frame 5a, 5b, which also connect the two end faces 42, 43 with each other and thus pass through the frames 5a, 5b, and in the cell stack 10 through the individual cells 2 of the cell stack 10, in the stack direction R.One electrolyte fluid channel 18a serves to supply a first electrolyte fluid 15a into a first half-cell 2a of the single cell 2, and the other electrolyte fluid channel 18b serves to remove the first electrolyte fluid 15a from the first half-cell 2a. The other electrolyte fluid channels 19a, 19b serve to supply and remove the second electrolyte fluid 15b into or from the second half-cell 2b. Advantageously, the frame 5a, 5b is designed so that it can be used for both half-cells 2a, 2b by turning it over. In a frame 5a, 5b, the electrolyte liquid channel 18a, 19a serving for supply is connected to the recess 6a, 6b via a flow channel 44a in an end face 42, and the electrolyte liquid channel 18b, 19b serving for discharge is connected to the recess 6a, 6b via a flow channel 44b in the end face 42.In the illustrated embodiment, the supply channel 44a and the discharge channel 44b are each connected to the recess 6a, 6b via a distribution channel 45 extending at least partially along the edge of the recess 6a, 6b. The supply channel 44a and the discharge channel 44b, as well as the distribution channels 45, are open toward the end face 42. In the known frame 5a, 5b, all channels are provided in one end face 42. In the cell stack 10, these open channels are sealed by the adjacent frame 5a, 5b and / or an electrode plate 8.
[0035] To at least partially accommodate the electrode plate 8, a recess 40 is provided on the end face 42 around the central recess 6a, 6b, into which the electrode plate 8 is inserted at least partially, preferably half the height of the electrode plate 8 in the stack direction R. The base of the recess 40 thus forms a sealing surface 41, which, in cooperation with the electrode plate 8, forms a seal in the cell stack 10. In Fig. 4 and Fig. 6, sealing fingers 46 can also be seen in the region of the recess 40, which rest against the electrode plate 8 for improved sealing in the cell stack 10.
[0036] It can be seen in Fig. 4 and Fig. 6 that the sealing surface 41 is interrupted by the respective flow channel 44a, 44b in the region of the transition to the flow channel 44a, 44b, which is shown in detail in Fig. 6. In the region of the interrupted sealing surface 41, a leakage path for an electrolyte liquid 15a, 15b can therefore easily form. The electrode plate 8 was therefore subject to high tolerance requirements in order to reduce the probability of a leakage path forming. It can also be seen that an electrode plate 8 arranged in the recess 40 is subjected to flow on the circumference of the electrode plate 8 in the region of the transition to the flow channel 44a, 44b. This is also unfavorable with regard to the formation of a possible leakage path, particularly if the electrode plate 8 is provided with an adhesive bond 47 at the edge, as shown in Fig. 7, and the adhesive bond 47 can be passed behind by the flow. Fig.7 shows a frame 5a, 5b with an electrode plate 8 inserted in the recess 40 with adhesives 47 along the edges of the electrode plate 8.
[0037] With reference to Figures 8 to 12, a frame 5a, 5b according to the invention for a half-cell 2a, 2b of a single cell 2 of a cell stack 10 of a redox flow battery 1 is described below, with which the sealing in the cell stack 10 can be improved. In particular, the risk of a leakage path for an electrolyte liquid 15a, 15b in the cell stack 10 can be reduced with the frame 5a, 5b according to the invention. Furthermore, the tolerance requirement for the electrode plate 8 can be reduced with the frame 5a, 5b according to the invention. Last but not least, any adhesive bonding can be at least partially eliminated. This can result in considerable cost savings for a cell stack 10. Figures 8 and 9 show a frame 5a, 5b of a half-cell 2a, 2b of a single cell 2 of a redox flow battery 1 in an embodiment according to the invention.The frame 5a, 5b again has a central recess 6a, 6b, which connects the two opposite end faces 42, 43 of the frame 5a, 5b. The recess 6a, 6b extends through the frame 5a, 5b in the stack direction R. When the frame 5a, 5b is used in the cell stack 10, an electrode 7a, 7b is again arranged in the recess 6a, 6b. On an end face 42, the recess 40 is arranged around the recess 6a, 6b, emanating from this end face 42 and extending towards the opposite end face 43 (opposite the end face 42) of the frame 5a, 5b. The recess 40, of course, does not extend through the frame 5a, 5b. The base of the recess 40 again forms a sealing surface 41. The recess 40 is delimited by a continuous circumferential surface 48, wherein the circumferential surface 48 connects the bottom of the recess 40 with the end face 42 in which the recess 40 is arranged.When using the frame 5a, 5b in the cell stack 10, an electrode plate 8 is arranged in the recess 40 as usual. When using the frame 5a, 5b in the cell stack 10, a membrane 4 is arranged on the side of the end face 43 opposite the recess 40 as usual.
[0038] At least one flow channel 44a, 44b is arranged on the end face 43 opposite the recess 40. The at least one flow channel 44a, 44b is connected at a first end to an electrolyte fluid channel 18a, 18b, 19a, 19b in the frame 5a, 5b. When the frame 5a, 5b is used in a cell stack 10, an electrolyte fluid 15a, 15b can be supplied to or discharged from the flow channel 44a, 44b via the connected electrolyte fluid channel 18a, 18b, 19a, 19b. The flow channel 44a, 44b is at least partially open to the end face 43 on which it is arranged. In a single cell 2, the frames 5a, 5b abut one another at least partially at the end faces 43, thereby closing and sealing the at least partially open flow channels 44a, 44b. The end faces 43 thus serve at least partially as sealing surfaces in the cell stack 10.
[0039] At least one opening 49a, 49b is provided on the frame 5a, 5b, extending through the frame 5a, 5b in the stacking direction R, wherein a first end of the at least one opening 49a, 49b is connected to the at least one flow channel 44a, 44b on the end face 43 in which the flow channel 44a, 44b is provided. The opposite second end of the opening 49a, 49b opens on the side of the frame 5a, 5b opposite the end face 43 in the direction of the recess 6a, 6b, spaced from the peripheral surface 48 of the depression 40, and is connected to the recess 6a, 6b in the frame 5a, 5b. The flow channel 44a, 44b and the recess 40, including the sealing surface 41 of the recess 40, are thus arranged on opposite end faces 42, 43 of the frame 5a, 5b.
[0040] If the depression 40 between the peripheral surface 48 and the recess 6a, 6b in the frame 5a, 5b in the region of the mouth of the opening 49a, 49b has a width B, then the opposite second end of the opening 49a, 49b opens on the side of the frame 5a, 5b opposite the end face 43 in the direction of the recess 6a, 6b at a distance A from the peripheral surface 48 of the depression 40. The distance A is preferably at least 25% of the width B of the depression 40 in order to have a sufficient sealing surface 41 between the peripheral surface 48 and the opening 49a, 49b. The opposite second end of the opening 49a, 49b thus opens on the side of the frame 5a, 5b opposite the end face 43 in the region of the sealing surface 41 of the recess 40. The sealing effect can be improved the larger the distance A becomes. The distance A is therefore particularly advantageous at least 33% or 50% or 75% of the width B. The distance A can also be 100% of the width B, or more.A distance A of 100%, or more, of the width B would result in the opposite second end of the opening 49a, 49b no longer opening on the side of the frame 5a, 5b opposite the end face 43 in the region of the sealing surface 41 of the recess 40. This is possible, for example, if a distribution channel 45 is provided on the frame 5a, 5b and the opening 49a, 49b opens into the distribution channel 45. Such an embodiment is shown in Fig. 10, in which the distance A is equal to the width B and the distance A is therefore 100% of the width B. If the opening of the opening 49a, 49b is moved even further into the distribution channel 45, the distance A can also be greater than 100% of the width B.
[0041] When the frame 5a, 5b is used in the cell stack 10, an electrolyte fluid 15a, 15b is supplied to or discharged from the flow channel 44a, 44b on the end face 43 via an electrolyte fluid channel 18a, 18b, 19a, 19b. Via the flow channel 44a, 44b and the opening 49a, 49b, the electrolyte fluid 15a, 15b flows from the flow channel 44a, 44b to the opposite side of the frame 5a, 5b and into the recess 6a, 6b on the opposite side, or is discharged from the recess 6a, 6b.
[0042] In a cell stack 10, electrolyte fluid channels 18a, 18b, 19a, 19b of the frames 5a, 5b are aligned to conduct an electrolyte fluid 15a, 15b through the entire cell stack 10.
[0043] In the embodiment according to Fig.8, the mouth of the opening 49a, 49b is connected to the recess 6a, 6b via a distribution channel 45 which extends at least partially along the peripheral edge of the recess 6a, 6b, but could also open directly into the recess 6a, 6b.
[0044] A further flow channel 44a, 44b on the frame 5a, 5b can be designed as in the prior art, i.e. arranged on the same side as the recess 40. However, a further flow channel 44a, 44b in the frame 5a, 5b is also advantageous according to the invention and designed as described above, i.e. with recess 40 and flow channel 44a, 44b on opposite end surfaces 42, 43, as also shown in Fig.8 and Fig.9.
[0045] Typically, at least two flow channels 44a, 44b are provided on a frame 5a, 5b, one serving to supply an electrolyte liquid 15a, 15b and the other serving to remove the electrolyte liquid 15a, 15b.
[0046] In the embodiments of the frames 5a, 5b shown in Fig. 8 and Fig. 9, a flow channel 44a, 44b splits in the region of the opening 49a, 49b, so that a web 50 remains in the flow channel 44a, 44b in this region. In this embodiment, two openings 49a, 49b can also be provided, with each opening 49a, 49b being connected to one of the branches of the flow channel 44a, 44b (as in Fig. 8 and Fig. 9). However, both branches of the flow channel 44a, 44b could also be connected to an opening 49a, 49b each. The web 50 can at least reduce any possible deformation of the frame 5a, 5b in the cell stack 10 in order to prevent a narrowing or blockage of the flow channel 44a, 44b. In addition, the sealing surface 41 is supported by the web 50 in the area of the flow channel 44a, 44b.If several flow channels 44a, 44b arranged according to the invention are provided on the frame 5a, 5b, then preferably at least one of the flow channels 44a, 44b has such a web 50, particularly advantageously each of the flow channels 44a, 44b. In any case, each of the openings 49a, 49b opens, as described above, in the direction of the recess 6a, 6b at a distance from the peripheral surface 48 so as not to interrupt the sealing surface 41 in the region of the peripheral surface 48.
[0047] Thus, a frame 5a, 5b for a half-cell 2a, 2b of a cell stack 10 of a redox flow battery 1 is provided with a web 50 that divides the at least one flow channel 44a, 44b into two flow channel branches. Each of the flow channel branches separated by the web 50 is connected to an opening 49a, 49b extending through the frame 5a, 5b, and the web 50 is arranged in the region of the openings 49a, 49b. A first end of each opening 49a, 49b is connected to the respective flow channel branch of the at least one flow channel 44a, 44b at the first end face 43, and the opposite second end of each opening 49a, 49b opens at the frame 5a, 5b in the direction of the recess 6a, 6b, spaced from the peripheral surface 48 of the depression 40, and is connected to the recess 6a, 6b in the frame 5a, 5b. The web 50 extends on the first end face 43 at least between the region of the openings 49a, 49b and the peripheral surface 48 of the depression 40.
[0048] It can be seen in Fig. 8 that, due to the inventive design of a flow channel 44a, 44b on the end face 43 opposite the recess 40, the sealing surface 41 at the base of the recess 40 is not interrupted by the flow channel 44a, 44b. A continuous sealing surface 41 is formed around the circumference of the recess 6a, 6b. Thus, the sealing in the cell stack 10 can be improved with a frame 5a, 5b according to the invention. Sealing fingers 46 are therefore no longer required, which simplifies the frame 5a, 5b. Likewise, the tolerance requirements for the electrode plate 8 can be reduced.
[0049] Fig. 10 shows a section through a single cell 2 with two half-cells 2a, 2b formed by frames 5a, 5b, the section being made in the region of an opening 49b. The recesses 6a, 6b and the electrodes 7a, 7b in the recesses 6a, 6b are not visible in this view. Electrode plates 8 are arranged in the depressions 40 on both sides of the single cell 2 in an arrangement of the single cell 2 in a cell stack 10, as shown in Fig. 11. Fig. 11 also shows that the electrolyte fluid 15a, 15b is not applied to the outer circumferential surface 51 of the electrode plate 8, but rather in the region of an end face 52 of the electrode plate 8, which also improves sealing. The arrows in Fig.10 and Fig.11 each indicate the flow direction of the supplied electrolyte liquid 15a, 15b, whereby the flow direction for the discharge of the electrolyte liquid 15a, 15b can also be reversed.
[0050] In a single cell 2, the two end faces 43, in which the at least one flow channel 44a, 44b is provided, face each other and at least partially form a sealing surface in the cell stack 10. The end face 42 with the recess 40 is located on the outside of a single cell 2 in the stack direction R and also at least partially forms a sealing surface in the cell stack 10. In a cell stack 10, several single cells 2 are arranged next to each other in the stack direction R, whereby the recesses 40 of two adjacent frames 5a, 5b of two single cells 2 are arranged facing each other and the end faces 42 of the adjacent single cells 2 at least partially abut each other in the stack direction R. An electrode plate 8 is arranged in the mutually facing recesses 40. The electrode plate 8 thus separates the recesses 6a, 6b of two adjacent frames 5a, 5b of two single cells 2.
[0051] Due to the improved seal between the electrode plate 8 and the frame 5a, 5b due to the continuous sealing surface 41, any intended taping 47 of the electrode plate 8 can also be simplified. Such a taping 47 can be made in an area of the electrode plate 8 where the electrode plate 8 comes into direct contact with the electrolyte liquid 15a, 15b. This is possible, for example, in a design of the frame 5a, 5b with a distribution channel 45 in the area of the distribution channel 45. The taping 47 can therefore be limited to this area in any case. This can also improve the seal because there is less taping 47 behind which electrolyte liquid 15a, 15b can flow if a leakage path is formed. The area in the corners of the electrode plate 8 with double taping (as in Fig. 7) is also eliminated, which also helps to improve the seal.
Claims
Patent claims 1 . A frame for a half-cell (2a, 2b) of a cell stack (10) of a redox flow battery (1), wherein the frame (5a, 5b) has two opposite end faces (42, 43), wherein a central recess (6a, 6b) is provided in the frame (5a, 5b) which connects the two end faces (42, 43) to one another, and wherein a flow channel (44a, 44b) is provided in a first end face (43) of the end faces (42, 43) of the frame (5a, 5b), which is at least partially open towards this first end face (43), for supplying or removing electrolyte fluid (15a, 15b), and the flow channel (44a, 44b) is connected to an electrolyte fluid channel (18a, 18b, 19a, 19b) passing through the frame (5a, 5b). on the frame (5a, 5b), wherein at least one further flow channel (44a, 44b) for discharging or supplying the electrolyte liquid (15a, 15b) is provided on the frame (5a, 5b), wherein in the first end face (43) with the flow channel (44a,44b) opposite the second end face (42) of the frame (5a, 5b), around the circumference of the recess (6a, 6b), a depression (40) is provided, starting from the second end face (42) and extending in the direction of the first end face (43), and the depression (40) is delimited by a continuous circumferential surface (48), wherein the circumferential surface (48) connects a base of the depression (40) to the second end face (42), and the base of the depression (40) forms a sealing surface (41), characterized in that a web (50) is provided which divides the at least one flow channel (44a, 44b) into two flow channel branches, that each of the flow channel branches separated by the web (50) is connected to an opening (49a, 49b) passing through the frame (5a, 5b), and that the web (50) in the region of the openings (49a, 49b), wherein a first end of each opening (49a,49b) is connected to the respective flow channel branch of the at least one flow channel (44a, 44b) on the first end face (43), and the opposite second end of each opening (49a, 49b) on the frame (5a, 5b) opens in the direction of the recess (6a, 6b) at a distance from the peripheral surface (48) of the depression (40) and is connected to the recess (6a, 6b) in the frame (5a, 5b), and that the web (50) on the first end face (43) extends at least between the region of the openings (49a, 49b) and the peripheral surface (48) of the depression (40).
2. Frame according to claim 1, characterized in that the openings (49a, 49b) open at a distance (A) between 25%, preferably 33% or 50% or 75%, and less than 100% of a width (B) of the recess (40) in the region of the mouths of the respective second end of the openings (49a, 49b) spaced from the peripheral surface (48) of the recess (40) in the region of the sealing surface (41) of the recess (40).
3. Frame according to claim 1 or 2, characterized in that a distribution channel (45) is provided on the frame (5a, 5b), which is connected to the recess (6a, 6b) on the frame (5a, 5b) and which extends at least partially along an edge of the recess (6a, 6b), wherein the respective second end of the openings (49a, 49b) is connected via the distribution channel (45) to the recess (6a, 6b) in the frame (5a, 5b).
4. Frame according to claim 1, characterized in that a distribution channel (45) is provided on the frame (5a, 5b), which is connected to the recess (6a, 6b) on the frame (5a, 5b) and which extends at least partially along an edge of the recess (6a, 6b), wherein the second end of the openings (49a, 49b) is connected to the recess (6a, 6b) in the frame (5a, 5b) via the distribution channel (45) and that the openings (49a, 49b) open at a distance (A) of at least 100% of a width (B) of the recess (40) in the region of the mouths of the openings (49a, 49b) from the peripheral surface (48) of the recess (40) in the region of the distribution channel (45).
5. Frame according to one of claims 1 to 4, characterized in that in the first end face (43) of the frame (5a, 5b) there is provided a further flow channel (44a, 44b) which is at least partially open towards the first end face (43) for supplying or discharging electrolyte liquid (15a, 15b), and the flow channel (44a, 44b) is connected to a further electrolyte liquid channel (18a, 18b, 19a, 19b) on the frame (5a, 5b) which passes through the frame (5a, 5b), that a further web (50) is provided which divides the further flow channel (44a, 44b) into two flow channel branches, that each of the flow channel branches of the further flow channel (44a, 44b) separated by the web (50) is each provided with a through the frame (5a, 5b) through further opening (49a, 49b) and the further web (50) is arranged in the region of the further openings (49a, 49b), wherein a first end of each further opening (49a,49b) is connected to the respective flow channel branch of the at least one further flow channel (44a, 44b) on the first end face (43), and the opposite second end of each further opening (49a, 49b) on the frame (5a, 5b) opens in the direction of the recess (6a, 6b) at a distance from the peripheral surface (48) of the depression (40) and is connected to the recess (6a, 6b) in the frame (5a, 5b), and that the further web (50) on the first end face (43) extends at least between the region of the further openings (49a, 49b) and the peripheral surface (48) of the depression (40).
6. Frame according to claim 5, characterized in that the further openings (49a, 49b) open at a distance (A) between 25%, preferably 33% or 50% or 75%, and less than 100% of a width (B) of the recess (40) in the region of the mouths of the respective second end of the further openings (49a, 49b) spaced from the peripheral surface (48) of the recess (40) in the region of the sealing surface (41) of the recess (40).
7. Frame according to claim 5 or 6, characterized in that a further distribution channel (45) is provided on the frame (5a, 5b), which is connected to the recess (6a, 6b) on the frame (5a, 5b) and which extends at least partially along an edge of the recess (6a, 6b), wherein the respective second end of the further openings (49a, 49b) is connected to the recess (6a, 6b) in the frame (5a, 5b) via the further distribution channel (45).
8. Frame according to claim 5, characterized in that a further distribution channel (45) is provided on the frame (5a, 5b), which is connected to the recess (6a, 6b) on the frame (5a, 5b) and which extends at least partially along an edge of the recess (6a, 6b), wherein the respective second end of the further openings is connected to the recess (6a, 6b) in the frame (5a, 5b) via the further distribution channel (45) and that the further openings (49a, 49b) open at a distance (A) of at least 100% of a width (B) of the recess (40) in the region of the respective mouth of the further openings (49a, 49b) from the peripheral surface (48) of the recess (40) in the region of the distribution channel (45).
9. Single cell (2) of a cell stack (10) of a redox flow battery (1) consisting of two adjacent half-cells (2a, 2b), each half-cell (2a, 2b) comprising a frame (5a, 5b) according to one of claims 1 to 8, the frames (5a, 5b) adjoining one another at the first end faces (43) with the at least one flow channel (44a, 44b) and the recesses (6a, 6b) of the frames (5a, 5b) being separated from one another by a membrane (4), and an electrode (7a, 7b) being arranged in each of the recesses (6a, 6b).
10. Cell stack (10) of a redox flow battery (1) with a plurality of individual cells (2) according to claim 9, wherein the individual cells (2) are arranged next to one another in a stack direction (R) and the recesses (6a, 6b) of adjacent frames (5a, 5b) of individual cells (2) are separated by an electrode plate (8), wherein the electrode plate (8) is arranged in mutually facing recesses (40) of the adjacent frames (5a, 5b).