Electrolyte flow channel structure of all-vanadium redox flow battery

Abstract

This invention provides an electrolyte flow channel structure for a vanadium redox flow battery, including electrolyte channels etched onto bipolar plates. The electrolyte flow channels include a first main channel, a last main channel, and multiple S-shaped channels. The first and last main channels are cuboid structures located on opposite sides of the bipolar plates and arranged parallel to each other. The multiple S-shaped channels are evenly spaced along the length of the bipolar plates, with each S-shaped channel connected to both the first and last main channels at its two ends. The etching depth of the first main channel, the last main channel, and all the S-shaped channels is the same. The first main channel has an inlet, and the last main channel has an outlet, located diagonally opposite to the bipolar plates. One technical advantage of this invention is that it promotes effective electrolyte transfer on the electrodes, ensures uniform electrolyte distribution on the electrode surface, reduces electrolyte concentration differences on the electrodes, lowers overpotential, and thus improves battery performance.

Description

Technical Field

[0001] This invention belongs to the field of vanadium redox flow battery technology, specifically relating to an electrolyte flow channel structure for a vanadium redox flow battery. Background Technology

[0002] With rapid economic development, energy demand is growing exponentially. Traditional fossil fuels face depletion due to their non-renewability and environmental pollution, necessitating the search for sustainable alternatives. While renewable energy sources such as solar, wind, and tidal power offer advantages in terms of cleanliness and low carbon emissions, their output is constrained by natural conditions, exhibiting inherent defects such as intermittency and volatility, leading to unstable power quality and failing to meet the continuity and reliability requirements of modern power grids. Against this backdrop, the development of efficient, safe, and large-scale energy storage technologies has become imperative. Among these, vanadium redox flow batteries, as a novel energy storage technology, have attracted widespread attention due to their ability to individually design power and capacity, high safety factor, stable and reliable performance, and long lifespan.

[0003] A typical vanadium redox flow battery consists of porous electrodes, bipolar plates, an ion exchange membrane, end plates, current collectors, a reservoir, a pump, a load, and delivery tubing. The following reactions occur at the positive and negative electrodes: Positive electrode: VO2+ + H2O - e- - = VO2 + + 2H + Negative electrode: V 3+ + e - = V 2+ Compared to other flow batteries, the all-vanadium redox flow battery uses vanadium ions in different valence states as the active materials of the positive and negative electrode electrolytes, which greatly reduces the self-discharge problem caused by cross-contamination. At the same time, only the valence state of vanadium ions changes during charging and discharging, thus having a longer service life and more reliable operational stability.

[0004] Despite the many advantages of vanadium redox flow batteries, improving the uniform distribution of electrolyte on porous electrodes remains a significant challenge in enhancing their performance. Uneven electrolyte distribution can lead to concentration differences of active materials on the electrode surface, exacerbating concentration polarization, resulting in excessively high electrode overpotentials, ultimately reducing battery efficiency and accelerating capacity decay.

[0005] In traditional parallel flow channels, the electrolyte flows in a single direction, which can easily lead to differences in the concentration gradient of the electrolyte on the electrode due to speed differences during long-distance transport, resulting in a decrease in battery performance. Therefore, there is an urgent need for a reasonable flow channel to make the electrolyte more evenly distributed on the porous electrode. Summary of the Invention

[0006] The present invention aims to at least solve one of the technical problems existing in the prior art, and to provide a new technical solution for the electrolyte flow channel structure of a full vanadium redox flow battery.

[0007] According to a first aspect of the present invention, an electrolyte flow channel structure for a vanadium redox flow battery is provided, comprising electrolyte flow channels etched on a bipolar plate; the electrolyte flow channels include a first main flow channel, a last main flow channel, and multiple S-shaped flow channels, wherein the first and last main flow channels are both cuboid structures and are located on both sides of the bipolar plate and arranged in parallel, and the multiple S-shaped flow channels are distributed at equal intervals along the length of the bipolar plate, and the two ends of each S-shaped flow channel are respectively connected to the first and last main flow channels; the first main flow channel, the last main flow channel, and all S-shaped flow channels have the same etching depth, and ribs are formed between adjacent S-shaped flow channels; an inlet is provided on the first main flow channel, and an outlet is provided on the last main flow channel, wherein the inlet and outlet are located at opposite corners of the bipolar plate.

[0008] Furthermore, the planar curve shape of the S-shaped flow channel is a sine function curve, a Bezier curve, or a polynomial function curve.

[0009] Furthermore, the number of S-shaped flow channels is greater than or equal to three.

[0010] Furthermore, the width of the S-shaped flow channel is 2mm, and the spacing between adjacent S-shaped flow channels is 1~4mm.

[0011] Furthermore, the etching process of the electrolyte channel is selected according to the electrolyte flow rate requirement. Under low flow rate conditions, wet etching is used to process the electrolyte channel, and the surface roughness of the electrolyte channel is controlled between 5 and 10 μm. Under high flow rate conditions, ultraviolet laser etching or step-by-step dry etching is used to process the electrolyte channel, and the surface roughness of the electrolyte channel is controlled between 1 and 5 μm.

[0012] Furthermore, the electrolyte flow rate under the low flow condition is 60 ml / min, and the electrolyte flow rate under the high flow condition is 120 ml / min.

[0013] Furthermore, the width of the first and last main channels is 5mm, the length is 495mm, and the etching depth of all channels is 2mm.

[0014] Furthermore, the bipolar plate is made of graphite, metal, or carbon-plastic composite material.

[0015] Furthermore, it also includes an ion exchange membrane, and the bipolar plate includes a positive electrode side bipolar plate and a negative electrode side bipolar plate; the ion exchange membrane isolates the electrolyte flow channel into a positive electrode region near the positive electrode side bipolar plate and a negative electrode region near the negative electrode side bipolar plate, wherein a porous positive electrode is provided in the positive electrode region and a porous negative electrode is provided in the negative electrode region.

[0016] Furthermore, the positive and negative electrode regions are symmetrically distributed.

[0017] One technical advantage of this invention is that: In this embodiment, the electrolyte flow channel structure of the all-vanadium redox flow battery is formed by etching a flow channel structure consisting of a first main channel, a last main channel, and multiple S-shaped channels on the bipolar plate. The continuous curved surfaces in the S-shaped channels constantly change the flow direction of the electrolyte, promoting mixing between fluids, enhancing mass transfer, effectively interfering with the development of the near-wall boundary layer, reducing dead zones, and improving the uniformity of electrolyte distribution on the electrodes, thereby reducing overpotential and improving battery performance. Moreover, the continuous curved surfaces increase the length of the fluid flow path, effectively increasing the contact area with the electrodes, promoting the transfer of reactants and products on the electrode surface, accelerating the reaction rate, and improving the energy efficiency of the battery. Furthermore, the arrangement of the inlet and outlet at diagonal positions on the bipolar plate ensures that the electrolyte flow path covers the entire surface of the bipolar plate, further improving the uniformity of electrolyte distribution. In addition, by rationally selecting the etching process and roughness parameters according to the flow conditions, the optimal matching between the surface characteristics of the flow channel and the flow conditions is achieved, resulting in lower overpotential and higher energy efficiency under different flow conditions. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the electrolyte flow channel structure of an all-vanadium redox flow battery according to an embodiment of the present invention; Figure 2 for Figure 1 Sectional view of section AA; In the diagram: 1. Liquid inlet; 2. Bipolar plate on the positive electrode side; 3. Positive electrode region; 4. Liquid outlet; 5. Ion exchange membrane; 6. Negative electrode region; 7. Bipolar plate on the negative electrode side; 8. First main flow channel; 9. S-shaped flow channel; 10. Rib; 11. Tail main flow channel. Detailed Implementation

[0019] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0020] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0022] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0023] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0024] like Figures 1-2 As shown, this application provides an electrolyte flow channel structure for a vanadium redox flow battery, which promotes the effective transfer of electrolyte on the electrodes, ensures the uniform distribution of electrolyte on the electrode surface, reduces the concentration difference of electrolyte on the electrodes, reduces overpotential, and thus improves battery performance.

[0025] Specifically, the electrolyte flow channel structure of this vanadium redox flow battery includes electrolyte channels etched onto the bipolar plates. The electrolyte flow channels include a first main channel 8, a last main channel 11, and multiple S-shaped channels 9. The first main channel 8 and the last main channel 11 are both cuboid structures, located on opposite sides of the bipolar plates and arranged parallel to each other. The multiple S-shaped channels 9 are evenly spaced along the length of the bipolar plates, with each S-shaped channel 9 connected to both the first main channel 8 and the last main channel 11 at both ends. The etching depth of the first main channel 8, the last main channel 11, and all S-shaped channels 9 is the same, and ribs 10 are formed between adjacent S-shaped channels 9. The first main channel 8 has an inlet 1, and the last main channel 11 has an outlet 4, with the inlet 1 and outlet 4 located diagonally opposite each other on the bipolar plates.

[0026] In this embodiment, an electrolyte flow channel structure consisting of a first main channel 8, a last main channel 11, and multiple S-shaped channels 9 is etched onto the bipolar plate. The continuous curved surfaces in the S-shaped channels 9 constantly change the flow direction of the electrolyte, promoting mixing between fluids and enhancing mass transfer. Compared with traditional parallel channels, this effectively interferes with the development of the near-wall boundary layer, encouraging more fluid to participate in the main flow, reducing dead zones, and improving the uniformity of electrolyte distribution on the electrode. The first main channel 8 and the last main channel 11 are located on both sides of the bipolar plate and arranged in parallel. Combined with multiple equally spaced S-shaped channels 9, this achieves uniform distribution of electrolyte from one main channel to the other via the S-shaped channels 9. The design of having the same etching depth in all channels ensures consistent flow resistance of the electrolyte in each channel. The arrangement of the inlet 1 and outlet 4 at diagonal positions on the bipolar plate ensures that the flow path of the electrolyte in the channels covers the entire surface of the bipolar plate, further improving the uniformity of electrolyte distribution.

[0027] Optionally, the planar curve shape of the S-shaped flow channel 9 is a sine function curve, a Bézier curve, or a polynomial function curve. A sine function curve has the characteristics of good periodicity and uniform curvature change, which is beneficial for the smooth flow and uniform distribution of the electrolyte within the flow channel; a Bézier curve has the advantage of smooth curvature transition, which can effectively reduce the flow resistance of the electrolyte at bends and reduce pressure loss; a polynomial function curve has high design flexibility and can be parametrically adjusted according to specific battery structures and flow requirements.

[0028] Optionally, the number of S-shaped flow channels 9 is greater than or equal to 3, which ensures sufficient coverage of the bipolar plate surface and allows the electrolyte to be evenly distributed to various areas of the electrode through multiple parallel flow channels, avoiding the problems of insufficient local coverage and uneven electrolyte distribution caused by too few flow channels.

[0029] Optionally, the width of the S-shaped flow channel 9 is 2 mm, and the spacing between adjacent S-shaped flow channels 9 is 1~4 mm. While ensuring sufficient cross-sectional area for electrolyte flow, it also ensures sufficient contact area between the flow channel and the electrode; the spacing is controlled within the range of 1~4 mm, taking into account both the flow channel distribution density and the width of the ribs, which ensures both uniform coverage of the electrolyte on the electrode surface and maintains the structural strength of the bipolar plate.

[0030] Optionally, the etching process for the electrolyte flow channel is selected based on the electrolyte flow rate requirements. Under low flow rate conditions, wet etching is used to process the flow channel, with the surface roughness controlled between 5 and 10 μm. This lower surface roughness results in more uniform electrolyte flow, which is beneficial for electrolyte mass transfer, thereby reducing overpotential and improving energy efficiency. Under high flow rate conditions, ultraviolet laser etching or stepwise dry etching is used to process the flow channel, with the surface roughness controlled between 1 and 5 μm. This higher surface roughness leads to turbulent electrolyte flow, breaking the flow boundary layer, enhancing turbulent mixing, reducing concentration polarization, thereby reducing overpotential and improving energy efficiency.

[0031] Optionally, the electrolyte flow rate under the low flow condition is 60 ml / min, and the electrolyte flow rate under the high flow condition is 120 ml / min.

[0032] In the above embodiments, the specific flow parameters for low flow and high flow conditions are clearly defined, providing a clear basis for the selection of etching processes. This facilitates the selection of the corresponding etching process based on the specific flow range in actual production, ensuring the matching of the flow channel surface roughness with the flow conditions.

[0033] Optionally, the width of the first mainstream channel 8 and the length of the last mainstream channel 11 are both 5 mm and 495 mm, respectively, and the etching depth of all channels is 2 mm. The width of the first mainstream channel 8 and the last mainstream channel 11 is designed to be 5 mm to ensure that the mainstream channel has a sufficient flow cross-section to uniformly distribute the electrolyte to multiple S-shaped channels 9 simultaneously; the length is designed to be 495 mm to ensure that the mainstream channel covers the effective area of ​​the bipolar plate.

[0034] Optionally, the bipolar plate is made of graphite, metal, or carbon-plastic composite material. The bipolar plate can simultaneously meet the multiple performance requirements of vanadium redox flow batteries for high conductivity, corrosion resistance, and high mechanical strength: graphite materials possess excellent conductivity and chemical stability, metal materials provide high mechanical strength and good electrical and thermal conductivity, while carbon-plastic composite materials balance conductivity, corrosion resistance, and processability.

[0035] Optionally, the flow channel structure further includes an ion exchange membrane 5, and the bipolar plates include a positive-side bipolar plate 2 and a negative-side bipolar plate 7. The ion exchange membrane 5 isolates the electrolyte flow channel into a positive electrode region 3 near the positive-side bipolar plate 2 and a negative electrode region 6 near the negative-side bipolar plate 7. The positive electrode region 3 contains a porous positive electrode, and the negative electrode region 6 contains a porous negative electrode. The ion exchange membrane 5 enables independent circulation of the positive and negative electrode electrolytes, preventing cross-mixing. The porous electrode provides a three-phase interface for the electrochemical reaction, and together with the uniform distribution effect of the S-shaped flow channel 9, ensures that the electrolyte is fully distributed on the surface of the porous electrode.

[0036] For example, the ion exchange membrane 5 must have high proton conductivity, good chemical stability, low vanadium ion permeability, and high mechanical strength and structural stability, including but not limited to zwitterionic exchange membranes, cation exchange membranes, anion exchange membranes, etc.

[0037] Optionally, the positive electrode region 3 and the negative electrode region 6 are symmetrically distributed and are completely identical in terms of material and size parameters. The symmetrical distribution of the positive electrode region 3 and the negative electrode region 6 ensures that both sides of the positive and negative electrodes have the same flow channel structure, electrode area and flow characteristics, so that the electrochemical reaction conditions on both sides of the positive and negative electrodes are consistent, avoiding performance differences caused by structural asymmetry.

[0038] The present invention will now be demonstrated by simulating three specific embodiments and one comparative example using COMSOL simulation software to verify the beneficial effects of the present invention.

[0039] Example 1: In this example, the battery size is 500mm × 500mm, the bipolar plate thickness is 4mm, and the channel etching depth is 2mm. The width of the first main channel 8 and the tail main channel 11 are both 5mm, and the length is 495mm. The width of the S-shaped channel 9 is 2mm, and the spacing between adjacent S-shaped channels 9 is 1mm, for a total of 163 S-shaped channels 9.

[0040] Example 2: In this example, the battery size is 500mm × 500mm, the bipolar plate thickness is 4mm, and the channel etching depth is 2mm. The width of the first main channel 8 and the tail main channel 11 are both 5mm, and the length is 495mm. The width of the S-shaped channel 9 is 2mm, and the spacing between adjacent S-shaped channels 9 is 2mm, for a total of 122 S-shaped channels 9.

[0041] Example 3: In this example, the battery size is 500mm × 500mm, the bipolar plate thickness is 4mm, and the channel etching depth is 2mm. The width of the first main channel 8 and the tail main channel 11 are both 5mm, and the length is 495mm. The width of the S-shaped channel 9 is 2mm, and the spacing between adjacent S-shaped channels 9 is 4mm, for a total of 81 S-shaped channels 9.

[0042] Comparative example: The battery size is 500mm×500mm, the bipolar plate thickness is 4mm, there is no channel etching on the bipolar plate, and the electrolyte enters directly from one side of the electrode.

[0043] The simulation conditions for the vanadium redox flow battery are as follows: the bipolar plate material is graphite, the porous electrode material is graphite felt, and the ion exchange membrane is Nafion 117. The total vanadium ion concentration in the electrolyte is 1500 mol / m³, and the H ion concentration is 3000 mol / m³. The vanadium redox flow battery is simulated for charge and discharge at a current density of 1000 A / m². The above examples and comparative examples were simulated under low and high flow rate conditions, respectively. Under low flow rate conditions, the electrolyte flow rate was 60 ml / min, and under high flow rate conditions, the electrolyte flow rate was 120 ml / min. Simulations were also conducted under low roughness of 3 μm and high roughness of 8 μm, respectively.

[0044] Table 1 shows the performance parameters of the examples and comparative examples regarding overpotential and energy efficiency at an electrolyte flow rate of 60 ml / min and a surface roughness of 3 μm.

[0045] Table 1 Performance parameters under low flow rate and low roughness conditions

[0046] Table 2 shows the performance parameters of the examples and comparative examples regarding overpotential and energy efficiency at an electrolyte flow rate of 60 ml / min and a surface roughness of 8 μm.

[0047] Table 2 Performance parameters under low flow rate and high roughness conditions

[0048] Table 3 shows the performance parameters of the examples and comparative examples regarding overpotential and energy efficiency at an electrolyte flow rate of 120 ml / min and a surface roughness of 3 μm.

[0049] Table 3 Performance parameters under high flow rate and low roughness conditions

[0050] Table 4 shows the performance parameters of the examples and comparative examples regarding overpotential and energy efficiency at an electrolyte flow rate of 120 ml / min and a surface roughness of 8 μm.

[0051] Table 4 Performance parameters under high flow rate and high roughness conditions

[0052] Comparing the data in each table reveals that under low flow rate conditions, low roughness results in lower overpotential and higher energy efficiency. This is because lower roughness promotes more uniform electrolyte flow, which is beneficial for electrolyte mass transfer, thereby reducing overpotential and improving energy efficiency. Conversely, higher roughness hinders electrolyte flow, leading to increased concentration polarization in localized areas. Under high flow rate conditions, high roughness results in lower overpotential and higher energy efficiency. This is because higher roughness induces turbulent electrolyte flow, breaking the flow boundary layer, enhancing turbulent mixing, and reducing concentration polarization. Under low roughness conditions, it is difficult to induce turbulent disturbances, which may not effectively disrupt the laminar boundary layer, leading to reduced electrolyte mixing efficiency. All embodiments exhibit significantly lower overpotential and higher energy efficiency compared to the comparative examples, verifying the beneficial effects of the S-shaped flow channel structure design of this invention.

[0053] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. An electrolyte flow channel structure for an all-vanadium redox flow battery, characterized in that, Including the electrolyte flow channels etched on the bipolar plate; The electrolyte flow channel includes a first main flow channel, a last main flow channel, and multiple S-shaped flow channels. The first and last main flow channels are both cuboid structures and are located on both sides of the bipolar plate and arranged in parallel. The multiple S-shaped flow channels are distributed at equal intervals along the length of the bipolar plate, and the two ends of each S-shaped flow channel are connected to the first and last main flow channels, respectively. The first main flow channel, the last main flow channel, and all S-shaped flow channels have the same etching depth, and ribs are formed between adjacent S-shaped flow channels. The first section of the main channel is provided with an inlet, and the last section of the main channel is provided with an outlet. The inlet and outlet are located at opposite corners of the bipolar plate.

2. The electrolyte flow channel structure of the all-vanadium redox flow battery according to claim 1, characterized in that, The planar curve shape of the S-shaped flow channel is a sine function curve, a Bezier curve, or a polynomial function curve.

3. The electrolyte flow channel structure of the all-vanadium redox flow battery according to claim 1, characterized in that, The number of S-shaped flow channels is greater than or equal to 3.

4. The electrolyte flow channel structure of the all-vanadium redox flow battery according to claim 1, characterized in that, The width of the S-shaped flow channel is 2mm, and the spacing between adjacent S-shaped flow channels is 1~4mm.

5. The electrolyte flow channel structure of the all-vanadium redox flow battery according to claim 1, characterized in that, The etching process for the electrolyte flow channel is selected according to the electrolyte flow rate requirement. Under low flow rate conditions, wet etching is used to process the electrolyte flow channel, and the surface roughness of the electrolyte flow channel is controlled between 5 and 10 μm. Under high flow rate conditions, ultraviolet laser etching or step-by-step dry etching is used to process the electrolyte flow channel, and the surface roughness of the electrolyte flow channel is controlled between 1 and 5 μm.

6. The electrolyte flow channel structure of the all-vanadium redox flow battery according to claim 5, characterized in that, The electrolyte flow rate is 60 ml / min under low flow conditions and 120 ml / min under high flow conditions.

7. The electrolyte flow channel structure of the all-vanadium redox flow battery according to claim 1, characterized in that, The width of the first and last main channels is 5mm, the length is 495mm, and the etching depth of all channels is 2mm.

8. The electrolyte flow channel structure of the all-vanadium redox flow battery according to claim 1, characterized in that, The bipolar plate is made of graphite, metal, or carbon-plastic composite material.

9. The electrolyte flow channel structure of the all-vanadium redox flow battery according to claim 1, characterized in that, It also includes an ion exchange membrane, and the bipolar plate includes a positive electrode side bipolar plate and a negative electrode side bipolar plate; The ion exchange membrane isolates the electrolyte flow channel into a positive electrode region near the positive electrode side bipolar plate and a negative electrode region near the negative electrode side bipolar plate. The positive electrode region is provided with a porous positive electrode, and the negative electrode region is provided with a porous negative electrode.

10. The electrolyte flow channel structure of the all-vanadium redox flow battery according to claim 9, characterized in that, The positive and negative electrode regions are symmetrically distributed.

Images