Redox flow converter
By designing the frame structure of the redox flow core, using the frame width to provide a large channel cross-section, the conflict between the redox flow converter between fluid technology and electronic technology requirements is solved, and efficient electrolyte solution flow is achieved and Compact construction.
Patent Information
- Application Number
- CN202380041074.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-07-26
- Filing Date
- 2023-06-20
- Publication Date
- 2024-12-27
AI Technical Summary
The existing redox flow converters have a target conflict between fluid technology and electronic technology requirements, making it difficult to achieve a compact construction and efficient electrolyte solution flow simultaneously.
Multiple redox flow cells in the form of a cell stack are designed, each cell is formed by two half-cells separated by a membrane, the height of the shunt channel formed in the frame exceeds the height of the half-cell, the winding channel or The height of the shunt channel in other shapes is smaller than the cell height, and a large channel cross-section is provided by the frame width, and the channel height is maintained at the semi-cell height, forming a channel through opening and curved section through the difference in frame height to extend the electrolyte flow path.
The conflict between fluid technology and electronic technology requirements is reduced, the flow efficiency of electrolyte solution is improved, and the compact and manufacturing-friendly structure is achieved, the channel cross-sectional area is large, the fluid technology is more favorable, and the electronic technology is relatively balanced.
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Figure CN119213589A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a redox flow converter configured in stacked form according to the preamble of claim 1 . Background Art
[0002] Such a redox flow converter is known, for example, from EP 3 545 566 B1. The frame of the porous electrode of the known redox flow converter has a channel for an electrochemical fluid. The channel exists in the form of a supply channel and an output channel and leads to the side of the electrode respectively. The frame of the device according to EP 3 545 566 B1 is constructed in a multi-piece manner, i.e., it is constructed by an upper frame and a lower frame, wherein each of the two frames accommodates an electrode and the electrodes are separated from each other by a membrane. The supply channel and the output channel are formed not only by the upper frame but also by the lower frame. In addition, not only the upper frame but also the lower frame provide space for accommodating a seal, which is in contact with the membrane.
[0003] DE 10 2021 111 054 B3 describes a redox flow battery cell and a method for assembling a redox flow battery. The redox flow battery cell belongs to an electrode module, which has an electrode frame, and the electrode frame has a circumferential seal arranged on the inner circumference of the electrode frame. The seal in turn has a retaining frame, on which a snap-in protrusion for accommodating an electrode is formed. A membrane module is connected to the electrode module of the redox flow battery cell according to DE 10 2021 111 054 B3, and the membrane module includes a membrane frame and a membrane.
[0004] Redox flow cells are generally different from conventional batteries in that an electrolyte flows through them. The electrolytes can be provided in separate tanks, which provides the possibility of scaling performance and capacity independently of one another. In this way, redox flow systems can be designed in particular as large-scale energy storage devices. A redox flow converter is understood to be an arrangement of electrochemical cells, i.e. redox flow cells, which is typically constructed as a cell stack and is a core component of a redox flow battery.
[0005] In the design of redox flow systems, not only fluid technology aspects must be taken into account, but also electronic technology and electrochemistry aspects. From the perspective of fluid technology, short, straight flow channels for the electrolyte solution are preferred. On the other hand, in the battery cell stack, due to the given voltage difference, an electric current is generated in the electrolyte solution, the so-called shunt current, which reduces the efficiency of the redox flow converter as a parasitic current. Therefore, a long path through which the electrolyte solution flows will be advantageous. Therefore, in general, there is a conflict of objectives between optimization in fluid technology on the one hand and optimization in electronic technology on the other hand.
[0006] In principle, targeted extension of channels, in particular in frame-shaped components, is known as a means of simultaneously taking into account different, partly contradictory requirements placed on redox flow converters. For example, in this context, reference is made to US 2020 / 0220194 A1, US 9,653,746 B2, EP 1 119 880 B1 and WO 2021 / 090976 A1. Summary of the invention
[0007] The object of the present invention is to further improve a redox flow converter which can be operated, for example, with an organic electrolyte compared to the prior art with regard to the conflict of objectives between fluid technology and electronics technology, while at the same time providing a compact, production-friendly design of the redox flow converter.
[0008] According to the invention, the object is achieved by a redox flow converter having the features of claim 1. The redox flow converter according to the present application comprises, in a basic design known per se, a plurality of redox flow cells arranged in the form of a cell stack, wherein each redox flow cell is formed by two half-cells separated from each other by a membrane, so that the height of each redox flow cell is given by the height of the half-cell of the redox flow cell, wherein there is a frame surrounding the membrane, and wherein a shunt channel connected to the active area of the half-cell is formed in the frame. According to the present application, the height of the shunt channel, which is also generally referred to as a frame channel, exceeds the height of the individual half-cells. At the same time, the height of the meandering channel or other shunt channels is less than the height of each redox flow cell, that is, less than the sum of the heights of the two half-cells.
[0009] In particular, the aforementioned conflict of objectives between fluidic and electronic requirements is thereby reduced, so that in the case of a flat channel, an increase in height is more advantageous in terms of fluidic technology than disadvantageous in terms of electronics. In contrast, in variants of other channel dimensions (length, width), it tends to be desirable to compensate for fluidic advantages and electronic disadvantages.
[0010] The present invention is based on the consideration that, due to the plate-like construction of the individual cells of the redox flow converter, a large width is typically provided for unobstructed passages, whereas narrower boundaries are provided in the direction of the cell height. Here, the cell height is measured in the stacking direction of the cell stack, i.e. in the vertical direction in horizontally oriented, essentially planar cells. Based on the considerations described, the channel cross section of the electrolyte can be increased in practically any way, in such a way that a large part of the width of the frame is fully utilized. Thus, a large channel cross section is obtained even in the case of a small frame height. Here, the channel height can be kept limited to half the cell height.
[0011] The solution according to the present application deliberately moves away from approaches that break up the average half-cell height by the channel height, by limiting the channel height to the entire cell height while maintaining a compact and production-friendly design.
[0012] The redox flow converter can be operated in particular with vanadium electrolytes known per se. Independently of the type of electrolyte solution, a channel cross section with a favorable height / width ratio can be achieved by utilizing approximately the entire cell height of the channel formed in the frame for the electrolyte input or output. For example, the width of the shunt channel can correspond to at least 80% and a maximum of 400% of the height of the shunt channel, including square channel cross sections. If the channel is to have a variable width and / or height over its length, the values relate to a channel cross section that is present in the middle of the channel, that is, at the same distance from the beginning of the channel and the end of the channel. At this height, the shunt channel extends, for example, at a height corresponding to at least 70% and a maximum of 95% of the height of the electrochemical cell.
[0013] According to different possible designs, the shunt channel is formed by a region of increased frame height, wherein within the cell stack, the region of increased frame height is adjacent to a region of decreased frame height of an adjacent frame. This includes a structural form in which the frame height is zero in the region of decreased frame height, i.e., there is a hole or a constricted outer contour in the frame.
[0014] In the region of the increased frame height, a channel through-opening can be formed which is oriented orthogonally to the plane in which the frame is located. In this case, the entirety of the channel through-openings aligned with one another is a main channel as a supply channel or purge channel, via which all redox flow cells can be supplied with electrolyte solution or which serves to discharge electrolyte solution from all redox flow cells.
[0015] Likewise, in the region of increased frame height, curved sections of the shunt channels can be connected to the channel through-openings, wherein the curved sections are selected from a number of channel shapes, including channels in a meandering shape, a sawtooth shape, and a spiral shape. Channel shapes in rectangular, circular, or elliptical patterns are also conceivable. In all cases, the shunt channels arranged on the positive electrolyte side and the negative electrolyte side are preferably designed so that the shunt channels do not overlap in a top view of the frame.
[0016] A plurality of distribution channels that are located outside the region of increased frame height and that lead into the active region are connected to the curved section. The distribution channels can here fan out toward the active region, wherein, unlike the flow diversion channels located in the region of increased frame height, each distribution channel can have a straight section or an overall straight shape.
[0017] In particular, electrically insulating plastics are suitable as materials for producing the frame. The frame channels are not in contact with the electrodes of the redox flow cell, thereby preventing electrical short circuits between the frame channels and the electrodes or between the beginning and the end of the frame channels. The electrodes can be, for example, so-called battery felts, structured graphite electrodes or metal electrodes, in particular electrodes consisting of three-dimensionally structured metal sheets. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The following is a detailed description of several embodiments of the present invention based on the accompanying drawings. The accompanying drawings show:
[0019] Figure 1 shows a frame of a cell stack for a redox flow converter,
[0020] Figure 2 The exploded diagram shows Figure 1 Parts of multiple frames,
[0021] Figure 3 Show according to Figure 1 Details of the framework,
[0022] Figure 4 The cross-sectional view shows Figure 2 Part of the device,
[0023] Figure 5 Shown including according to Figures 1 to 4 Details of multiple frames of redox flow converters,
[0024] Figure 6 An alternative embodiment of a frame for a redox flow converter is shown.
[0025] Figure 7 and Figure 8 shows a modified embodiment of a frame for a cell stack of a redox flow converter,
[0026] Fig. 9 and Fig.10 shows a further embodiment of a frame for a redox flow converter,
[0027] Fig.11 The schematic cross-sectional view shows the structure of an electrochemical cell, namely a redox flow cell, and a frame in a redox flow converter.
[0028] Fig.12 and Fig.13 The geometry of the channels running through the frame of the cell stack is shown. DETAILED DESCRIPTION
[0029] Unless otherwise specified, the following description applies to all embodiments. Components that correspond to one another or have essentially the same function are denoted by the same reference numerals in all figures.
[0030] The redox flow converter, which is generally indicated by the reference numeral 1, is constructed from a plurality of electrochemical cells 3, which are present as a cell stack 2. Each cell 3 comprises two half cells 4, 5, which are separated from each other by a proton-permeable membrane 7. The electrochemical cells 3, i.e. the redox flow cells, are delimited by planar electrodes 8, which are designed as bipolar plates. The cell stack 2 comprises a plurality of frames 6, whose narrow sides are indicated by 9 and whose long sides are indicated by 10. The frames 6 surround an active area 11 inside the redox flow converter 1, in which the desired electrochemical reaction takes place. A distribution area for the input and output of the electrolyte solution is indicated by 12. For sealing, a surrounding seal 13 is provided in particular.
[0031] In the embodiment, each electrochemical cell 3 uses H 3 The height indicated is evenly divided into the height H of half cells 4 and 5 4 , H 5 Each frame 6 has a frame area 14 of medium height, wherein the cell height H 3 Essentially corresponds to twice the median height. In addition to the median height frame region 14, the frame 6 forms a region 15 with increased frame height and a region 16 with reduced frame height. In the exemplary embodiment, the region 16 with reduced frame height is recessed into a recess, i.e. a frame region with zero height. In a top view of the frame 6, the outer contour of each region 15 with increased frame height corresponds to the contour of the associated recess 16. It is thereby possible to stack a plurality of identically shaped frames 6 alternately on top of one another in a first orientation and in an orientation rotated 180° or mirrored relative to the first orientation.
[0032] In each of the regions 15 where the frame height is increased, a frame channel 19 is formed, which is also referred to as a shunt channel and which starts at a channel through-opening 18 which passes through all frames 6. The path through which the electrolyte must flow is purposefully extended by means of the frame channels 19 in order to minimize electrical losses. The frame channels 19 include curved channel sections 20 which can have a meandering shape ( Figures 1 to 5 , Figure 7 , Figure 8 , Fig.12). A plurality of distribution channels 21 are connected to the channel section 20, which are generally fan-shaped and belong to the frame area 14 of medium height. Unlike the frame channels 19, the distribution channels 21 are already located in the distribution area 12. As a result, the height of the distribution channels 21 is limited to the height H of the half cells 4, 5. 4 , H 5 superior.
[0033] Especially from Fig.11 It is found that the above-mentioned restrictions do not apply to the height H of the frame channel 19 . Rather, in all exemplary embodiments, the height H of the frame channel 19 exceeds the height H of the individual half cells 4 , 5 . 4 , H 5 The length of the frame channel 19 is indicated overall by L. The upper limit of the height H is only determined by the total height H of each electrochemical cell 3. 3 Given. Maximum available height H 3 The height H of the frame channel 19 is utilized up to approximately 90%, for example. 4 , H 5 Compared to the conceivable channels in the frame, a significantly more favorable height / width ratio H / B of the frame channel 19 can be achieved. For example, the width B of the frame channel 19 is at least 80% and at most 400% of the height H of the same frame channel 19. Fig.12 and Fig.13 The channel shape is for example in accordance with Fig. 9 and Fig.10 An embodiment is given in which the channel section 20 is only substantially visible.
[0034] In accordance with Figure 4 and Figure 5 In the arrangement of the embodiment of the invention, the surface of the zone 15 of the increased frame height, which is structured by the channel section 20, contacts the back side of the zone 15 of the next frame 6 inside the cell stack 2, which extends from the frame region 14 of the middle height of the same frame 6 and does not limit the upper side of the zone 15 generally referred to as the relevant zone 15. The rubber layer 17 on the zone 15 as a seal follows the shape of the curved channel section 20.
[0035] In the manner described, the framework 6 is based on Figures 7 to 10 The cells can also be stacked one on top of the other within the cell stack 2. The groove for inserting the seal is indicated by 22. Fig.10 In the case of , there is no delimitation of the recess 16 , so that the outer rectangular shape of the frame 6 is modified by the recess 16 which is open to the outside.
[0036] About Fig.13The channel cross section shown in or other feasible channel cross sections do not take into account the given height-to-width ratio for the resistance, only the cross section is decisive. However, for the resistance based on fluid viscosity in flow technology, the height-to-width ratio is important under the same area. Therefore, the wide and flat channel cross section shown - caused by the limitation of the small frame height - is more disadvantageous than a square or approximately square channel with the same cross section in terms of the sum of characteristics, but is advantageous compared to a flatter, wider channel cross section. In short, the design of the frame channel 19 is a compromise considering the electronic technology aspects as well as the fluid technology aspects and the structural space limitations.
[0037] Reference numerals list
[0038] 1 Redox flow converter
[0039] 2 Cell stack
[0040] 3 Electrochemical cells
[0041] 4 Half Cells
[0042] 5 Half Cell
[0043] 6 Framework
[0044] 7 Membrane
[0045] 8 Electrodes
[0046] 9 Narrow side of the frame
[0047] 10 Long side of frame
[0048] 11 Active area
[0049] 12 Allocation Area
[0050] 13 Seal, surrounding
[0051] 14 Medium height frame area
[0052] 15 Areas with increased frame height
[0053] 16 Area where the frame height is reduced, leaving a blank space
[0054] 17 Seal, rubber layer
[0055] 18-channel through opening
[0056] 19 frame channel, diversion channel
[0057] 20 curved channel sections, meanders, spirals
[0058] 21 Distribution Channels
[0059] 22 slots
[0060] B Width
[0061] H Channel height
[0062] H 3 Height of electrochemical cell
[0063] H 4 , H 5 Half cell height
[0064] L length
Claims
1. A redox flow converter (1) comprising a plurality of redox flow cells (3) arranged in the form of a cell stack (2), wherein each redox flow cell (3) is formed by two half cells (4, 5) separated from each other by a membrane (7), so that the height (H3) of each redox flow cell (3) is given by the height (H4, H5) of the half cells (4, 5) of the redox flow cell, wherein there is a frame (6) surrounding the membrane (7), and wherein a shunt channel (19) connected to the active area (11) and the electrode (8) of the half cells (4, 5) is formed in the frame (6), characterized in that The height (H) of the branch channel (19) exceeds the height (H4, H5) of each half-cell, but is less than the height (H3) of each redox flow cell (3).
2. The redox flow converter (1) according to claim 1, characterized in that The branch flow channels (19) are formed by regions (15) of increased frame height, wherein within the cell stack (2) the regions (15) of increased frame height are respectively adjacent to regions (16) of reduced frame height of adjacent frames (6).
3. The redox flow converter (1) according to claim 2, characterized in that In the region (16) where the frame height is reduced, the frame height is zero.
4. The redox flow converter (1) according to claim 2 or 3, characterized in that In the region (15) where the frame height is increased, a channel through-opening (18) is formed which is oriented at least approximately in a normal direction to the plane in which the frame (6) is located, so that a channel is formed which passes through the entire cell stack (2).
5. The redox flow converter (1) according to any one of claims 2 to 4, characterized in that In the region (15) where the frame height is increased, a curved section (20) of the branch channel (19) is connected to the channel through-opening (18), wherein the curved section (20) is selected from a number of channel shapes, including channels in a meandering shape, a zigzag shape, and a spiral shape.
6. The redox flow converter (1) according to claim 5, characterized in that A plurality of distribution channels (21) located outside the region (15) of increased frame height and opening out into the active region (11) in a fan-shaped manner are connected to the curved section (20).
7. The redox flow converter (1) according to any one of claims 2 to 6, characterized in that The planar electrodes (8) of the cell stack (2) extend neither into the region (15) in which the frame height is increased nor into the region (16) in which the frame height is reduced.
8. The redox flow converter (1) according to any one of claims 1 to 7, characterized in that The branch channel (19) extends over a height (H) which corresponds to at least 70% and at most 95% of the height (H3) of the electrochemical cell (3).
9. The redox flow converter (1) according to any one of claims 1 to 8, characterized in that The width (B) of the branch channel corresponds to at least 80% and at most 400% of the height (H) of the branch channel.
10. The redox flow converter (1) according to any one of claims 1 to 9, characterized in that The frames (6) stacked one above the other are identically shaped and are stacked one on top of the other in an orientation rotated 180° relative to one another.