A structure type of a spiral electrode for a liquid flow battery

Abstract

The application provides a structure type of a spiral electrode for a liquid flow battery, and belongs to the technical field of liquid flow batteries.The structure type of the spiral electrode for the liquid flow battery comprises a polar plate, a spiral flow channel is arranged on the polar plate, the spiral flow channel takes the center of the polar plate as an inlet area, extends to the periphery along a streamlined spiral path, and forms an outlet at the edge area of the polar plate; after electrolyte is pumped into the center of the polar plate, the electrolyte uniformly diffuses and flows outward along the spiral flow channel; by adopting the design of the spiral flow channel cooperating with the center liquid inlet and the periphery liquid outlet, remarkable beneficial effects are achieved in reducing flow resistance and pressure drop and improving mass transfer efficiency; the spiral flow channel adopts a streamlined geometric structure, the sudden turning and stopping phenomenon of a traditional snakelike flow channel is avoided, the electrolyte flows smoothly in the polar plate, and therefore the overall energy efficiency of the liquid flow battery system is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, and specifically relates to a structural type of spiral electrode for flow batteries. Background Technology

[0002] Flow batteries are a novel large-scale electrochemical energy storage technology. Their core characteristic lies in the fact that the electroactive materials are stored as a liquid electrolyte in an external tank, rather than within traditional solid electrodes. During charging and discharging, the electrolyte flows through the stack via a pump, where a redox reaction occurs on the electrode surface, converting electrical energy into chemical energy. Because power and energy can be independently designed, and the electrolyte is non-flammable, long-lasting, and has a fast response time, flow batteries are particularly suitable for large-scale, long-term energy storage scenarios involving grid-connected renewable energy sources such as wind and solar power. Among these, the vanadium redox flow battery is currently the most technologically mature and commercially widely used flow battery system.

[0003] Currently, most vanadium redox flow batteries employ traditional single-serpentine, double-serpentine, parallel-connected, or hollow electrode flow channels. While single-serpentine channels enhance local convection mass transfer, the long-distance electrolyte backflow along the channel results in significantly large inlet and outlet pressure drops, often exceeding kilopascals, leading to high pumping power consumption and the potential for localized high-speed and low-speed stagnation zones at bends. Double-serpentine channels balance the inlet and outlet positions to some extent, but still suffer from high pressure drops and uneven flow velocities at the edges. Parallel-connected channels have smaller pressure drops, but uneven flow distribution between channels means the electrolyte mainly diffuses into the porous electrode, resulting in weak convection under the fins and a tendency for weak mass transfer zones to form in the center of the electrode. Hollow structures, lacking proper electrolyte distribution, are prone to creating significant dead zones and backflow dead zones within the active region.

[0004] During charging and discharging, uneven flow rate distribution can prevent active ions in the electrolyte from being replenished evenly and promptly to the surface of the carbon fiber electrodes, exacerbating concentration polarization and reducing voltage efficiency. Excessive voltage drop significantly increases pumping power loss, reducing the overall energy efficiency of the system. Backflow dead zones or mass transfer dead zones prevent some electrode areas from receiving fresh electrolyte for the reaction, resulting in low electrode utilization and, with long-term operation, the deposition of by-reaction products. Therefore, optimizing the flow field distribution, reducing voltage drop, and eliminating dead zones through optimized flow guiding structures have become important technical directions for improving the performance of flow batteries.

[0005] Therefore, in order to solve the above problems, it is necessary to provide a structural form of a spiral electrode for flow batteries. Summary of the Invention

[0006] The purpose of this invention is to provide a spiral electrode structure for flow batteries, which aims to solve the problems of large pressure drop, high flow resistance, uneven flow velocity distribution, severe concentration polarization caused by backflow dead zone, and low energy efficiency in existing flow battery electrode flow channels.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A spiral electrode structure for a flow battery includes an electrode plate with a spiral flow channel. The spiral flow channel has an inlet area at the center of the electrode plate and extends outward along a streamlined spiral path, forming an outlet at the edge of the electrode plate. After being pumped in from the center of the electrode plate, the electrolyte diffuses outward uniformly along the spiral flow channel.

[0009] Preferably, the spiral flow channel has a spiral structure, and the inlet width of the spiral flow channel gradually narrows from the center of the electrode to the edge, which can make the flow velocity of the electrolyte in the flow channel uniform.

[0010] Preferably, the groove width of the spiral flow channel is 2mm to 4mm and the groove depth is 1.5mm to 3mm.

[0011] Preferably, it also includes a porous graphite felt electrode, which is attached to the flow channel surface of the electrode plate. The electrolyte in the spiral flow channel penetrates into the interior of the porous graphite felt electrode through the flow channel wall and can undergo an electrochemical reaction with the surface of the graphite felt fiber.

[0012] Preferably, the porous graphite felt electrode has a porosity of 85% to 95% and a thickness of 5 mm to 12 mm.

[0013] Preferably, the battery also includes a battery frame and a sealing gasket, wherein the electrode plate is embedded in the battery frame and the sealing gasket is disposed between the electrode plate and the battery frame to prevent electrolyte leakage and maintain a sealed pressure environment within the flow channel.

[0014] Preferably, the battery frame has an electrolyte inlet channel and an electrolyte outlet channel corresponding to the spiral flow channel inlet and outlet. The electrolyte inlet channel is located in the central region of the electrode plate, and the electrolyte outlet channel is located in the edge region of the electrode plate.

[0015] Preferably, the surface of the spiral flow channel is hydrophobically modified, and its surface contact angle is greater than 90 degrees, in order to reduce the adhesion and residue of electrolyte on the flow channel wall.

[0016] Preferably, the electrode plate is made of high-purity graphite or carbon composite material, and the spiral flow channel is integrally processed onto the surface of the electrode plate by a molding process, and the surface roughness Ra of the inner wall of the spiral flow channel is less than 3.2 μm.

[0017] Preferably, the spiral channel has 2 to 6 spiral turns, and the ratio of the flow distance of the electrolyte from the inlet to the outlet along the spiral path to the side length of the electrode plate is between 1.5:1 and 3:1.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. This invention, through the use of a spiral flow channel with a central inlet and peripheral outlet design, achieves significant benefits in reducing flow resistance and pressure drop, and improving mass transfer efficiency. The spiral flow channel employs a streamlined geometry, avoiding the abrupt turns and stops of traditional serpentine flow channels, ensuring smooth electrolyte flow within the electrode plates. Compared to traditional serpentine, parallel, and hollow flow channels, the pressure drop along the electrode flow channel of this invention is significantly reduced, both locally and in terms of pressure drop. This reduction in pressure drop directly lowers the pumping power loss of the circulating pump, reduces parasitic energy consumption in the battery system, and thus effectively improves the overall energy efficiency of the flow battery system. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0022] Figure 2 This is a schematic diagram of the electrode plate of the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of a single parallel flow channel of the present invention;

[0024] Figure 4 This is a schematic diagram of the structure of the double serpentine loop flow channel of the present invention;

[0025] Figure 5 This is a schematic diagram of the single serpentine flow channel of the present invention;

[0026] Figure 6 This is a schematic diagram of the hollow flow channel in this invention;

[0027] Figure 7 The figure shows the experimental results of the single serpentine flow channel of the present invention;

[0028] Figure 8 The figure shows the experimental results of the double serpentine loop flow channel of the present invention;

[0029] Figure 9 The figure shows the experimental results of the parallel flow channels of the present invention;

[0030] Figure 10The diagram shows the experimental results of the spiral flow channel of this invention.

[0031] Figure 11 The figure shows the experimental results of the hollow flow channel in this invention;

[0032] Figure 12 Table 1 shows the experimental data from this invention.

[0033] Figure 13 Table 2 shows the experimental data from this invention.

[0034] In the diagram: 1. Electrode plate; 2. Spiral flow channel; 3. Porous graphite felt electrode; 4. Battery frame; 41. Electrolyte inlet channel; 42. Electrolyte outlet channel; 5. Sealing gasket. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Please see Figure 1 and Figure 2 The present invention provides the following technical solution: a spiral flow channel 2 is provided on the electrode plate 1. The spiral flow channel 2 takes the center of the electrode plate 1 as the inlet area and extends outward along the streamlined spiral path, forming an outlet in the edge area of ​​the electrode plate 1. After the electrolyte is pumped in from the center of the electrode plate 1, it diffuses and flows outward evenly along the spiral flow channel 2.

[0037] The spiral flow channel 2 has a spiral structure. The inlet width of the spiral flow channel 2 gradually narrows from the center of the electrode to the edge, which can make the flow velocity of the electrolyte in the flow channel uniform.

[0038] The groove width of the spiral flow channel 2 is 2mm to 4mm, and the groove depth is 1.5mm to 3mm.

[0039] It also includes a porous graphite felt electrode 3, which is attached to the flow channel surface of the electrode plate 1. The electrolyte in the spiral flow channel 2 penetrates into the interior of the porous graphite felt electrode 3 through the flow channel wall and can undergo an electrochemical reaction with the surface of the graphite felt fiber.

[0040] The porous graphite felt electrode 3 has a porosity of 85% to 95% and a thickness of 5 mm to 12 mm.

[0041] It also includes a battery frame 4 and a sealing gasket 5. The electrode plate 1 is embedded in the battery frame 4, and the sealing gasket 5 is disposed between the electrode plate 1 and the battery frame 4 to prevent electrolyte leakage and maintain a sealed pressure environment in the flow channel.

[0042] The battery frame 4 has an electrolyte inlet channel 41 and an electrolyte outlet channel 42 corresponding to the inlet and outlet of the spiral flow channel 2. The electrolyte inlet channel 41 is located in the central region of the electrode plate 1, and the electrolyte outlet channel 42 is located in the edge region of the electrode plate 1.

[0043] The surface of the spiral flow channel 2 is hydrophobically modified, and its surface contact angle is greater than 90 degrees, which is used to reduce the adhesion and residue of electrolyte on the flow channel wall.

[0044] Hydrophobic modification treatments, such as fluorosilane coatings and plasma treatments, are existing technologies and will not be elaborated further.

[0045] The electrode plate 1 is made of high-purity graphite or carbon composite material, and the spiral flow channel 2 is integrally processed onto the surface of the electrode plate 1 through a molding process. The surface roughness Ra of the inner wall of the spiral flow channel 2 is less than 3.2 μm.

[0046] The spiral channel 2 has 2 to 6 spiral turns, and the ratio of the flow distance of the electrolyte from the inlet to the outlet along the spiral path to the side length of the electrode plate 1 is between 1.5:1 and 3:1.

[0047] The smooth, streamlined design of the spiral flow channel 2, combined with the hydrophobically modified channel walls, significantly reduces frictional resistance and wall adhesion during electrolyte flow. Its flow resistance is far lower than traditional flow channel structures. This low flow resistance allows the electrolyte to flow more smoothly, reducing energy dissipation caused by excessive flow resistance and improving electrolyte delivery efficiency. This facilitates the rapid and uniform penetration of the electrolyte into the porous graphite felt electrode 3 for reaction. The spiral flow channel 2, through its optimized inlet width gradually narrowing from the center to the edge, combined with 2 to 6 spiral turns, ensures that the electrolyte flows at a uniform speed throughout the channel, completely eliminating the low-speed stagnation zone and high-speed impact zone that occur at bends in traditional flow channels. This improved flow uniformity effectively reduces concentration polarization, allowing active ions in the electrolyte to diffuse promptly and fully to the graphite felt fiber surface to participate in electrochemical reactions, thereby significantly improving the battery's voltage efficiency and energy conversion efficiency.

[0048] like Figures 3 to 11 As shown, it should be noted that, in order to verify the superiority of the spiral flow channel 2 of the present invention over the traditional flow channel, a comparative analysis was conducted on the traditional single serpentine, double serpentine loop, parallel connection, hollow shape and the spiral flow channel of the present invention through fluid simulation experiments.

[0049] like Figure 7The figure shows the experimental results for a single serpentine flow channel. Figure 7 (a) Velocity contour map and Figure 7 (c) The velocity vector diagram shows that the electrolyte distribution within the single serpentine channel is relatively uniform, but there are obvious right-angle turns at the channel bends, resulting in localized low flow velocities and the formation of dead flow areas; from Figure 7 (d) As can be seen from the particle trajectory diagram, the electrolyte ion flux is extremely low at the right-angle bends. Figure 7 (b) The pressure cloud map shows that the pressure distribution is extremely uneven, with the highest pressure in the inlet region, gradually decreasing along the flow direction, and significant pressure loss in the bend connection region. This uneven pressure distribution leads to a large concentration gradient inside the electrode, exacerbating concentration polarization and reducing the energy efficiency of the battery.

[0050] like Figure 8 As shown, the experimental results of the double serpentine loop flow channel are as follows. Compared with the single serpentine flow channel, although the double serpentine loop balances the inlet and outlet positions, the overall pressure drop actually increases due to the increased flow channel. Figure 8 (a) Velocity contour map and Figure 8 (d) The particle trace plot shows that there are many dead zones where the electrolyte does not flow within the electrode channel, especially at right-angle bends where significant turbulent and vortex flows occur, leading to dead flow zones. Although the velocity distribution improves at high flow rates, Figure 8 (c) The velocity vector diagram shows that the internal pressure drop and flow resistance of the electrode are still relatively large.

[0051] like Figure 9 The figure shows the experimental results of parallel flow channels. Figure 9 (c) The velocity vector diagram shows that the electrolyte flow velocity is mainly concentrated in the vertical main channel, while the flow velocity in the intermediate transverse branch channels far from the pump inlet is extremely slow, or even non-existent. Figure 9 (d) The particle trace plot further confirms that approximately two transverse channels have almost no ion distribution, resulting in low electrode utilization. Figure 9 (b) The pressure cloud map shows a relatively uniform pressure distribution, but Figure 9 (a) The velocity contour plot reveals a serious problem of uneven flow rate, which can easily lead to a phenomenon where the reaction is fast on both sides and slow in the middle, resulting in a serious concentration overpotential.

[0052] like Figure 11 The image shows the experimental results for the hollow flow channel. This structure lacks effective flow guidance design. Figure 11 (a) Velocity contour map and Figure 11 (c) The velocity vector diagram shows that the electrolyte flow velocity decreases from the inlet to the opposite side, with the flow velocity in the middle region approaching zero, indicating a large area of ​​backflow dead zone. Figure 11 (b) The pressure cloud map shows an overly flat pressure distribution, lacking driving force. Figure 11(d) The particle trace diagram shows that the ions are mainly concentrated in the four corners, with very few distributed in the middle area, which cannot meet the requirements of uniform reaction.

[0053] In comparison, such as Figure 10 The figure shows the experimental results of the spiral flow channel 2. By moving the pump inlet from the corner to the center of the electrode plate (1) and adopting a streamlined spiral path design, the flow resistance caused by the right-angle bend is eliminated. Figure 10 (a) The velocity distribution diagram shows that the electrolyte flows at a uniform velocity throughout the flow channel, with the velocity distribution ranging from [missing information]. And there are no regions of abrupt changes in flow velocity. Figure 10 (b) The pressure cloud diagram shows that, except for the significant pressure change at the inlet, the overall pressure drop within the flow channel is minimal. Figure 10 (c) Velocity vector diagram and Figure 10 (d) The particle trace diagram shows that electrolyte ions fill the entire flow channel, with no backflow dead zone and smooth flow trajectory. This indicates that the present invention effectively reduces flow resistance by optimizing the flow channel geometry, ensuring uniform distribution of electrolyte in the porous graphite felt electrode 3, thereby improving the electrochemical reaction rate and battery efficiency.

[0054] In summary, this invention, through the use of a spiral flow channel 2 combined with a central inlet and peripheral outlet design, achieves significant benefits in reducing flow resistance and pressure drop, and improving mass transfer efficiency. The spiral flow channel 2, with its streamlined geometry, avoids the abrupt turns and stops of traditional serpentine flow channels, ensuring smooth electrolyte flow within the electrode plate 1. Compared to traditional serpentine flow channels, parallel flow channels, and hollow flow channels, the pressure drop along the electrode and the local pressure drop within the electrode flow channel of this invention are significantly reduced. This reduction in pressure drop directly lowers the pumping power loss of the circulating pump, reduces parasitic energy consumption of the battery system, and thus effectively improves the overall energy efficiency of the flow battery system.

[0055] Please see Figure 12 and Figure 13 In the simulation experiment, a laminar flow module was used, with the electrolyte inlet set as a velocity boundary condition and the outlet as a pressure boundary condition. The electrolyte physical properties were set with reference to the standard vanadium electrolyte, as shown in Table 1. The pressure drop generated in the five structural channels under varying flow rates was calculated. The electrolyte flow velocities inside the corresponding electrode channels under four flow conditions (60 mL / min, 90 mL / min, 120 mL / min, and 150 mL / min) were input into a 36-inch area... The simulation model of the single-cell flow channel electrode was used to configure the relevant flow parameters. The pressure drop of the spiral flow channel 2 was 25.326 Pa, 51.289 Pa, 85.431 Pa and 128.470 Pa, respectively, with the smallest pressure drop.

[0056] As shown in Table 2, the friction resistance increases with the length of the flow path. Therefore, a design that gradually narrows the inlet width maintains the uniformity of the flow velocity within the channel, such as a spiral channel. Due to its streamlined geometry, the spiral channel reduces the pressure drop and flow resistance inside the electrode, allowing the electrolyte to fully contact the graphite felt and participate in the subsequent electrochemical reaction. The flow resistance experienced by the electrolyte under varying flow rates in the five channel structures is calculated using the velocity resistance formula (existing technology, not elaborated here). The velocity resistance in the spiral channel region is... , , and The pressure drop is minimal.

[0057] Therefore, this invention, through the spiral flow channel 2, eliminates the backflow dead zones and flow dead angles commonly found in hollow flow channels and parallel flow channels. Combined with a porous graphite felt electrode 3 with a porosity of 85% to 95%, it ensures coverage of the electrode active area. This not only improves the utilization rate of the electrode material but also avoids the deposition of localized by-reaction products, extending the battery's lifespan.

[0058] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A structural type of spiral electrode for a flow battery, comprising an electrode plate (1), characterized in that: The electrode plate (1) is provided with a spiral flow channel (2). The spiral flow channel (2) takes the center of the electrode plate (1) as the inlet area and extends outward along the streamlined spiral path. An outlet is formed in the edge area of ​​the electrode plate (1). After the electrolyte is pumped in from the center of the electrode plate (1), it diffuses outward evenly along the spiral flow channel (2).

2. The structural form of the spiral electrode for a flow battery according to claim 1, characterized in that: The spiral flow channel (2) has a spiral structure. The inlet width of the spiral flow channel (2) gradually narrows from the center of the electrode plate to the edge, which can make the flow velocity of the electrolyte in the flow channel uniform.

3. The structural form of the spiral electrode for a flow battery according to claim 1, characterized in that: The spiral channel (2) has a groove width of 2 mm to 4 mm and a groove depth of 1.5 mm to 3 mm.

4. The structural form of the spiral electrode for a flow battery according to claim 1, characterized in that: It also includes a porous graphite felt electrode (3), which is attached to the flow channel surface of the electrode plate (1). The electrolyte in the spiral flow channel (2) penetrates into the interior of the porous graphite felt electrode (3) through the flow channel wall and can undergo an electrochemical reaction with the surface of the graphite felt fiber.

5. The structural form of the spiral electrode for a flow battery according to claim 4, characterized in that: The porous graphite felt electrode (3) has a porosity of 85% to 95% and a thickness of 5 mm to 12 mm.

6. The structural form of the spiral electrode for a flow battery according to claim 1, characterized in that: It also includes a battery frame (4) and a sealing gasket (5), wherein the electrode plate (1) is embedded in the battery frame (4) and the sealing gasket (5) is disposed between the electrode plate (1) and the battery frame (4) to prevent electrolyte leakage and maintain a sealed pressure environment in the flow channel.

7. The structural form of the spiral electrode for a flow battery according to claim 6, characterized in that: The battery frame (4) is provided with an electrolyte inlet channel (41) and an electrolyte outlet channel (42) corresponding to the inlet and outlet of the spiral flow channel (2). The electrolyte inlet channel (41) is located in the central region of the electrode plate (1), and the electrolyte outlet channel (42) is located in the edge region of the electrode plate (1).

8. The structural form of the spiral electrode for a flow battery according to claim 7, characterized in that: The surface of the spiral channel (2) is hydrophobically modified, and its surface contact angle is greater than 90 degrees, which is used to reduce the adhesion and residue of electrolyte on the channel wall.

9. The structural form of the spiral electrode for a flow battery according to claim 8, characterized in that: The electrode plate (1) is made of high-purity graphite or carbon composite material. The spiral flow channel (2) is integrally processed on the surface of the electrode plate (1) by molding process. The surface roughness Ra of the inner wall of the spiral flow channel (2) is less than 3.2 μm.

10. The structural form of the spiral electrode for a flow battery according to claim 9, characterized in that: The spiral channel (2) has 2 to 6 spiral turns, and the ratio of the flow distance of the electrolyte from the inlet to the outlet along the spiral path to the side length of the electrode plate (1) is between 1.5:1 and 3:1.

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