Bipolar plates for flow batteries and flow batteries

Abstract

The application provides a bipolar plate of a flow battery and the flow battery, and relates to the technical field of batteries. The bipolar plate comprises a plate body, the plate body has a first surface, the first surface is provided with a first flow channel groove and a second flow channel groove, the first flow channel groove and the second flow channel groove are arranged at intervals in a first direction, and the first direction is perpendicular to the extension direction of the first flow channel groove; the first flow channel groove and the second flow channel groove are both used for flowing electrolyte, the electrolyte can flow from the first flow channel groove to the second flow channel groove, and the cross-sectional area of the first flow channel groove is smaller than that of the second flow channel groove; by reasonably designing the structures of the first flow channel groove and the second flow channel groove, the flow rate of the electrolyte in the first flow channel groove can be improved, the convective mass transfer between the electrolyte and the electrode can be enhanced, the overall pressure drop can be reduced, and the energy efficiency of the battery can be improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to a bipolar plate and a flow battery. Background Technology

[0002] In a flow battery, the bipolar plates have a flow field structure, which includes an inflow channel and an outflow channel. The electrolyte flows from the inflow channel to the electrode, and after passing through the electrode, it flows to the outflow channel. Convective mass transfer can occur between the electrolyte and the electrode. To ensure the mass transfer efficiency between the electrolyte and the electrode, the flow rate of the electrolyte entering the inflow channel can be increased. However, increasing the electrolyte flow rate will lead to an increase in the pressure drop of the electrolyte throughout the entire flow field structure, affecting the energy efficiency of the battery.

[0003] Therefore, how to improve the mass transfer between the electrolyte and the electrodes in a flow battery, reduce the electrolyte pressure drop, and improve the battery's energy efficiency has become a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0004] This application provides a bipolar plate for a flow battery and a flow battery. By rationally designing the structure of the first flow channel and the second flow channel, the flow rate of the electrolyte in the first flow channel can be increased, the convective mass transfer between the electrolyte and the electrode can be enhanced, and the overall voltage drop can be reduced, thereby improving the energy efficiency of the battery.

[0005] To achieve the above objectives, the embodiments of this application adopt the following technical solutions: In a first aspect, a bipolar plate for a flow battery is provided. The bipolar plate includes a plate body with a first surface. The first surface has a first flow channel and a second flow channel. The first and second flow channels are arranged at intervals in a first direction, which is perpendicular to the extending direction of the first flow channel. Both the first and second flow channels are used to supply electrolyte flow, and the electrolyte can flow from the first flow channel to the second flow channel. The cross-sectional area of ​​the first flow channel is smaller than that of the second flow channel.

[0006] When the bipolar plate is applied to a flow battery, the electrode can be disposed on the first surface of the bipolar plate, and the electrolyte can flow from the first flow channel to the electrode and through the electrode to the second flow channel.

[0007] Under the premise of keeping the power of the driving pump that drives the electrolyte flow constant, the cross-sectional area of ​​the first flow channel is smaller, which can increase the flow rate of the electrolyte in the first flow channel and promote the convective mass transfer between the electrolyte and the electrode. This can not only quickly transport the active material to the electrode surface, but also remove the reaction products and by-reaction products from the electrode surface, so that the electrolyte can fully react on the electrode surface and effectively improve the energy efficiency of the flow battery.

[0008] Meanwhile, because the cross-sectional area of ​​the first flow channel is smaller than that of the second flow channel, the pressure drop in the second flow channel is smaller, which can partially compensate for the pressure drop loss in the first flow channel. This results in a smaller overall pressure drop of the electrolyte in both flow channels, which helps to improve the energy efficiency of the flow battery while ensuring the power consumption of the driving pump. Furthermore, the larger pressure difference between the inlet of the first flow channel and the outlet of the second flow channel can significantly enhance the driving force of the electrolyte through the electrodes, and can more effectively promote the convective mass transfer of the electrolyte.

[0009] In one possible implementation of the first aspect, the ratio of the cross-sectional area of ​​the first flow channel to the cross-sectional area of ​​the second flow channel is 1 / 2 to 9 / 10. While ensuring the power consumption of the drive pump, the flow velocity of the electrolyte within the first flow channel can be increased, enhancing the convective mass transfer of the electrolyte and thus improving the energy efficiency of the battery.

[0010] In one possible implementation of the first aspect, the first flow channel has an opening, sidewalls, and a bottom wall, with the opening and bottom wall facing each other, and the sidewalls connecting between the opening and bottom wall. The sidewalls include a first sidewall and a second sidewall facing each other in a first direction; the first sidewall includes a first region and a second region, the first region being connected to the end of the second region away from the bottom wall, and the first region extending obliquely away from the second sidewall in the direction from the bottom wall to the opening.

[0011] The first region guides the flow direction of the electrolyte, giving it a certain lateral velocity component, meaning the electrolyte has a velocity component parallel to the electrode. This reduces the vertical scouring of the electrode by the electrolyte, ensuring the electrode's lifespan. Furthermore, when the electrolyte in the first flow channel has a lateral velocity component, it promotes lateral diffusion of the electrolyte within the electrode plane, enhancing mass transfer between the electrolyte and the electrode, and contributing to improved energy efficiency of the flow battery.

[0012] In one possible implementation of the first aspect, the angle between the first region and the reference plane is 80° to 88°, wherein the reference plane is perpendicular to the arrangement direction of the inlet and bottom wall of the tank. When the angle between the first region and the reference plane is 80° to 88°, the electrolyte can obtain a suitable lateral velocity component while avoiding excessively fast flow velocity of the electrolyte along the electrode surface. This ensures sufficient contact time between the electrolyte and the electrode, allowing the active materials in the electrolyte to fully react on the electrode surface. Furthermore, it ensures that some electrolyte can pass through the electrode in the thickness direction, thereby effectively improving the energy efficiency of the flow battery.

[0013] In one possible implementation of the first aspect, the bipolar plate further includes a flow guide fixed to the plate body, at least a portion of which is located within a first flow channel groove. A first sidewall, a second sidewall, and a bottom wall of the groove are all spaced apart from the flow guide. The flow guide includes a first flow guiding surface and a second flow guiding surface. In a first direction, the first flow guiding surface is opposite to a first region, and the second flow guiding surface is opposite to a second sidewall. In the direction from the bottom wall of the groove to the groove opening, the first flow guiding surface extends obliquely away from the second sidewall.

[0014] By extending the first region at an angle away from the second sidewall in the direction from the bottom wall of the tank to the tank opening, and extending the first flow guide surface at an angle away from the second sidewall, it can be ensured that the electrolyte flowing between the first flow guide surface and the first region has a lateral velocity component, which can more effectively promote mass transfer between the electrolyte and the electrode and help improve the energy efficiency of the flow battery.

[0015] In one possible implementation of the first aspect, the second sidewall includes a third region and a fourth region. The third region is connected to the end of the fourth region away from the bottom wall of the tank. The third region is opposite to the second flow guide surface. In the direction from the bottom wall of the tank towards the tank opening, at least one of the third region and the second flow guide surface extends obliquely away from the first region. This ensures that the portion of the electrolyte flowing between the second flow guide surface and the third region has a lateral velocity component, which can more effectively promote mass transfer between the electrolyte and the electrode, and help improve the energy efficiency of the flow battery.

[0016] In one possible implementation of the first aspect, the end of the guide member near the bottom wall of the tank is the guide end, which is located between the second region and the fourth region. In the first direction, the distance between the guide end and the second region is equal to the distance between the guide end and the fourth region, so that the electrolyte in the first flow channel tank can be uniformly distributed in the direction closer to the first and third regions, ensuring the uniformity of the active material on the electrode surface and helping to improve the energy efficiency of the flow battery.

[0017] In one possible implementation of the first aspect, the second sidewall includes a third region and a fourth region, the third region being connected to the end of the fourth region away from the bottom wall of the tank, the third region being opposite to the second guide surface, and the fourth region being opposite to the second region. The first flow channel includes a main flow channel and a first branch flow channel, the second region, the fourth region, and the bottom wall of the tank forming the main flow channel, and the first region and the first guide surface forming the first branch flow channel. It should be understood that the third region and the second guide surface can form the second branch flow channel.

[0018] In the arrangement direction of the groove opening and the bottom wall of the groove, the size of the second region is the first size; the extension length of the first region in its own inclined direction is the second size, and the ratio of the first size to the second size is 4 to 8.

[0019] With the ratio of the first dimension to the second dimension being 4 to 8, the main flow channel can provide a sufficiently stable flow section, ensuring that the electrolyte can enter the first and second branched flow channels uniformly. The first and second branched flow channels can effectively guide the electrolyte diversion within the main flow channel, enabling the electrolyte to generate a suitable lateral velocity component, reducing the vertical scouring of the electrolyte on the electrode, and promoting the lateral diffusion of the electrolyte in the electrode plane, thereby promoting mass transfer between the electrolyte and the electrode and improving the energy efficiency of the flow battery.

[0020] In one possible implementation of the first aspect, the bipolar plate further includes a connector. The first flow channel has an inlet end, and the connector is fixed to the inlet end, with the connector facing the bottom wall of the channel. The first flow channel also includes a third sidewall, which is connected between the first and second sidewalls and located at the end of the first flow channel furthest from the inlet end. A flow guide is connected between the connector and the third sidewall. By providing the connector, the flow guide is easily fixed, ensuring its stability and reliability.

[0021] In a second aspect, embodiments of this application provide a flow battery, which includes a bipolar plate, electrodes, and an electrolyte. The bipolar plate is the same as the bipolar plate provided in the first aspect. The electrodes are fixed to a first surface of the bipolar plate. The electrolyte is adapted to flow along a first flow channel, and the electrolyte in the first flow channel is adapted to pass through the electrodes and flow along a second flow channel.

[0022] Understandably, the beneficial effects of the second aspect of the flow battery described above can be referenced to the beneficial effects of the first aspect and any of its possible implementations, which will not be repeated here. Attached Figure Description

[0023] Figure 1 A schematic diagram illustrating the working principle of a flow battery provided for some embodiments of this application; Figure 2 This is a partial structural schematic diagram of a bipolar plate provided in some embodiments of this application; Figure 3 This is a schematic diagram of the diffusion path of the electrolyte between the bipolar plate and the electrode provided in some embodiments of this application; Figure 4 A perspective view of a bipolar plate provided for some embodiments of this application; Figure 5 for Figure 4 A schematic diagram showing another angle of the bipolar plate; Figure 6 This is one of the schematic diagrams showing the fit between the plate and the frame in some embodiments of this application; Figure 7 This is a second schematic diagram illustrating the fit between the plate and the frame in some embodiments of this application; Figure 8 This is a schematic diagram of the structure of a bipolar plate provided in other embodiments of this application; Figure 9 According to Figure 8 The diagram shows a cross-sectional structure of the bipolar plate at line AA. Figure 10 for Figure 8 A schematic diagram showing another angle of the bipolar plate; Figure 11 for Figure 10 Enlarged view of the circled area at point B; Figure 12 This is a schematic diagram of the main flow path and branch flow path provided for some embodiments of this application.

[0024] Figure label: 100, flow cell; e1, first direction; e2, second direction; S, reference plane; 1. Battery stack; 1a. Electrolyte; 1b. Electrode; 11. First electrode; 12. Second electrode; 13. First storage tank; 130. First electrolyte; 14. First drive pump; 15. Second storage tank; 150. Second electrolyte; 17. Ion exchange membrane; 2. Bipolar plate; 21. First bipolar plate; 22. Second bipolar plate; 3. Plate; 30. First surface; 3a. Flow field structure; 31. First flow channel groove; 310. Inlet end; 311. Groove opening; 312. Groove bottom wall; 313. Groove side wall; 314. First side wall; q1. First region; q2. Second region; 315. Second side wall; q3. Third region; q4. Fourth region; 316. First intersection point; 317. Second intersection point; 32. Second flow channel groove; 33. Flow guide; 331. First flow guide surface; 332. Second flow guide surface; 333. Flow guide end; 34. Connector; 4. Frame; 4a. First part; 4b. Second part; 41. Liquid inlet; 42. Liquid inlet channel; 43. Liquid outlet; 44. Liquid outlet channel; 5. Main stream; 51. First branching stream; 52. Second branching stream. Detailed Implementation

[0025] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this embodiment, unless otherwise stated, "a plurality of" means two or more.

[0026] In embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0027] In the embodiments of this application, unless otherwise specified, the description of "parallel" indicates approximate parallelism within a certain allowable error range, which can be a range where the angle of deviation from absolute parallelism is less than or equal to 5°. The description of "perpendicular" indicates approximate perpendicularity within a certain allowable error range, which can be a range where the angle of deviation from absolute perpendicularity is less than or equal to 5°.

[0028] In the embodiments of this application, "multiple" refers to two or more.

[0029] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0030] To facilitate understanding, before providing a detailed description of the bipolar plate and flow battery in the embodiments of this application, the relevant terms involved in the embodiments of this application will be explained first.

[0031] Energy efficiency (EE) is a key indicator that measures the energy utilization efficiency of a battery during charge-discharge cycles. Energy efficiency is equal to the ratio of discharge energy to charging energy. Higher energy efficiency indicates less energy loss during the charge-discharge process.

[0032] Volumetric flow rate (Q): refers to the volume of fluid passing through the cross-section of a flow channel per unit time (unit: m³ / s); Q=∫ A vd A Where v is the velocity vector (unit: m / s), d A Let d be an area infinitesimal vector. A The direction is perpendicular to the cross-section of the flow channel (unit: m²).

[0033] Pressure drop: refers to the decrease in pressure caused by energy loss during the flow of a fluid.

[0034] Concentration polarization refers to the phenomenon in which, during an electrode reaction, the diffusion rate of reactants or products is lower than the electrochemical reaction rate, resulting in a concentration gradient between the solution near the electrode surface and the bulk solution, which in turn causes the electrode potential to deviate from the equilibrium value.

[0035] Due to their advantages such as independently designable power and capacity, high safety, long cycle life, and ease of scalability, flow batteries are widely used in large-scale energy storage scenarios, such as grid-connected peak shaving for renewable energy sources like wind and solar power, grid-side energy storage, microgrid systems, and backup power supplies. The long-term, high-capacity energy storage capability of flow batteries makes them one of the key technologies for building new power systems.

[0036] See Figure 1 , Figure 1 This is a schematic diagram illustrating the working principle of a flow battery 100 provided in some embodiments of this application. The flow battery 100 typically includes an electrolyte 1a and a battery stack 1. The battery stack 1 can convert electrical energy into chemical energy and store it in the electrolyte 1a. When needed, the chemical energy in the electrolyte 1a can be converted back into electrical energy and released to a power source or external load. The battery stack 1 can be assembled from multiple battery cells by stacking.

[0037] The battery cell may include an electrode 1b and an ion exchange membrane 17. The electrode 1b is a porous electrode, which can serve as a site for redox reactions of active substances (such as iron ions, chromium ions, vanadium ions, etc.) in the electrolyte 1a. For example, the electrode 1b includes an electrode material containing a catalyst, which can promote the redox reactions of active substances on the electrode 1b.

[0038] In some embodiments, see Figure 1 Electrode 1b may include a first electrode 11 and a second electrode 12, with an ion exchange membrane 17 disposed between the first electrode 11 and the second electrode 12. One of the first electrode 11 and the second electrode 12 is a positive electrode, and the other is a negative electrode. Electrolyte 1a includes a first electrolyte 130 and a second electrolyte 150, with the first electrode 11 in contact with the first electrolyte 130 and the second electrode 12 in contact with the second electrolyte 150.

[0039] For example, when the first electrode 11 is the positive electrode and the second electrode 12 is the negative electrode, the first electrolyte 130 is the positive electrolyte and the second electrolyte 150 is the negative electrolyte; or, when the first electrode 11 is the negative electrode and the second electrode 12 is the positive electrode, the first electrolyte 130 is the negative electrolyte and the second electrolyte 150 is the positive electrolyte. The first electrolyte 130 can be stored in the first storage tank 13, and the second electrolyte 150 can be stored in the second storage tank 15.

[0040] Continue reading Figure 1 When the flow battery 100 is operating, the first electrolyte 130 in the first storage tank 13 is transported to the battery stack 1 by the first drive pump 14, so that the first electrode 11 comes into contact with the first electrolyte 130. The active substances in the first electrolyte 130 will undergo a redox reaction on the surface of the first electrode 11, thereby realizing the interconversion of chemical energy and electrical energy. The electrical energy is stored and released through the charging and discharging of the flow battery 100. Hydrogen ions are conducted from one side of the ion exchange membrane 17 to the other side under the drive of the potential difference. At the same time, the ion exchange membrane 17 can block other ions in the first electrolyte 130 from passing through.

[0041] It should be understood that when the flow battery 100 is working, the process of converting chemical energy into electrical energy between the second electrode 12 and the second electrolyte 150 can be referred to the process of converting chemical energy into electrical energy between the first electrolyte 130 and the first electrode 11, which will not be repeated here.

[0042] For example, the flow battery 100 can be an iron-chromium flow battery, a vanadium redox flow battery, a lithium-ion flow battery, or a lead-acid flow battery. For ease of explanation, the following description uses an iron-chromium flow battery as an example, but this should not be construed as a limitation of this application.

[0043] The positive electrode electrolyte of an iron-chromium flow battery may include divalent iron ions (Fe2+). 2+ ) and ferric ions (Fe 3+ The negative electrode electrolyte may include divalent chromium ions (Cr). 2+ ) and trivalent chromium ions (Cr 3+ When an iron-chromium flow battery is charged, the Fe in the positive electrode electrolyte... 2+ An oxidation reaction occurs at the positive electrode, Fe 2+ It loses electrons at the positive electrode surface and transforms into Fe. 3+ Cr in the negative electrode electrolyte 3+ A reduction reaction occurs, Cr 3+ Electrons are gained at the negative electrode surface and the metal is converted into Cr. 2+ When the iron-chromium redox flow cell discharges, the Fe in the positive electrode electrolyte... 3+ A reduction reaction occurs, Fe 3+ Electrons are gained at the positive electrode surface and the metal is converted into Fe. 2+ Cr in the negative electrode electrolyte 2+ An oxidation reaction occurs, Cr 2+ The porous electrode surface loses electrons and transforms into Cr. 3+ .

[0044] See Figure 1In some embodiments, the battery cell of the flow battery 100 may further include a bipolar plate 2, which is typically bonded tightly to the electrode 1b via a hot-pressing process. The bipolar plate 2, as a key component of the flow battery 100, primarily serves to conduct current. Electrons generated by the redox reaction of the active material on the electrode 1b need to pass through a low-resistance path. During discharge, electrons are conducted out through this path, and during charging, electrons are introduced through the same path.

[0045] Therefore, efficient current collection and conduction are crucial for reducing the internal resistance of the flow battery 100 and improving its energy efficiency and power density. The bipolar plate 2 provides a large-area, highly conductive surface that effectively collects and conducts the current generated at each active point on the electrode 1b. For example, the bipolar plate 2 can conduct the current to adjacent battery cells or ultimately to the end plates at both ends of the battery stack 1.

[0046] The bipolar plate 2 may include a first bipolar plate 21 and a second bipolar plate 22. The first bipolar plate 21 is connected to the side surface of the first electrode 11 facing away from the ion exchange membrane 17, and the second bipolar plate 22 is connected to the side surface of the second electrode 12 facing away from the ion exchange membrane 17.

[0047] See Figure 2 and Figure 3 , Figure 2 This is a partial structural schematic diagram of the bipolar plate 2 provided in some embodiments of this application; Figure 3 This is a schematic diagram of the diffusion path of electrolyte 1a between bipolar plate 2 and electrode 1b provided in some embodiments of this application; the bipolar plate 2 usually has a flow field structure 3a, which not only guides the flow path of electrolyte 1a in electrode 1b, but also directly affects the uniformity of electrolyte 1a distribution on electrode 1b, mass transfer efficiency, voltage drop loss and concentration polarization, thereby affecting the energy efficiency of flow battery 100 and the overall performance of the battery.

[0048] The flow field structure 3a on the bipolar plate 2 can be an interdigitated flow field. The flow field structure 3a includes a first flow channel 31 and a second flow channel 32. The first flow channel 31 and the second flow channel 32 are arranged at intervals in a first direction e1, which is perpendicular to the extension direction of the first flow channel 31 and the extension direction of the second flow channel 32. Both the first flow channel 31 and the second flow channel 32 are used for the flow of electrolyte 1a. The first flow channel 31 can serve as an inflow channel, and the second flow channel 32 can serve as an outflow channel. Electrolyte 1a can flow from the first flow channel 31 to the electrode 1b, and after passing through the electrode 1b, electrolyte 1a can flow to the second flow channel 32. This allows bipolar plate 2 to conduct electrolyte 1a in addition to conducting current. Convection mass transfer can occur between electrolyte 1a and electrode 1b, allowing the active substances (i.e., reactants, such as Fe in the positive electrode electrolyte 1a) in electrolyte 1a to be transferred between the electrolyte 1a and electrode 1b. 2+ ) is transported to the surface of electrode 1b and carries away reaction products (e.g., Fe) from the surface of electrode 1b. 2+ Fe obtained from oxidation reaction 3+ ).

[0049] Figure 2 The direction indicated by the middle arrow is the flow direction of electrolyte 1a. Figure 3 The direction indicated by the middle arrow is the diffusion direction of electrolyte 1a.

[0050] During the flow of electrolyte 1a from the first flow channel 31 to the second flow channel 32, when the flow rate of electrolyte 1a is low, the convective mass transfer effect between electrolyte 1a and electrode 1b is poor, which easily leads to mass transfer polarization. Reactants on the surface of electrode 1b (e.g., Fe) 2+ The concentration of ) decreases, and the reaction products (e.g., Fe) 3+ The concentration gradient is formed on the surface of electrode 1b, which generates an additional overpotential and affects the energy efficiency of flow battery 100.

[0051] It should be understood that increasing the flow velocity of electrolyte 1a within the first flow channel 31 can increase the convective mass transfer of electrolyte 1a. However, increasing the flow velocity of electrolyte 1a within the first flow channel 31 by increasing the driving force of the drive pump (e.g., the first drive pump 14 mentioned above) will result in higher power consumption of the drive pump. Furthermore, the increased flow velocity of electrolyte 1a within the first flow channel 31 will correspondingly increase the pressure drop of electrolyte 1a throughout the entire flow field structure 3a. Excessive pressure drop may induce turbulence or uneven flow, disrupting the flow field uniformity and adversely affecting the energy efficiency of the battery.

[0052] Therefore, how to improve the mass transfer between the electrolyte 1a and the electrode 1b in the flow battery 100, reduce the voltage drop, and improve the energy efficiency of the battery while ensuring the power consumption of the drive pump has become a technical problem that urgently needs to be solved in this field.

[0053] To solve the above-mentioned technical problems, this application provides a bipolar plate 2 for a flow battery 100, see reference. Figure 4 and Figure 5 , Figure 4 A perspective view of the bipolar plate 2 provided for some embodiments of this application; Figure 5 for Figure 4 The diagram shows another angle of the bipolar plate 2. The bipolar plate 2 includes a plate body 3 with a first surface 30. The first surface 30 has a first flow channel 31 and a second flow channel 32. The electrode 1b can be fixed to the first surface 30. The flow path of the electrolyte 1a within the first flow channel 31, the electrode 1b, and the second flow channel 32 is shown in the reference diagram. Figure 2 and Figure 3 The flow path of electrolyte 1a shown is roughly the same, so it will not be described again.

[0054] The bipolar plate 2 can be either a first bipolar plate 21 or a second bipolar plate 22. It is understood that when the bipolar plate 2 is the first bipolar plate 21, the electrode 1b corresponding to the first bipolar plate 21 is the first electrode 11, and the structure of the second bipolar plate 22 can be designed with reference to the structure of the first bipolar plate 21.

[0055] In some embodiments, the first flow channel 31 can be a plurality of channels arranged at intervals along the first direction e1, and the second flow channel 32 can be a plurality of channels arranged at intervals along the first direction e1. The plurality of first flow channel channels 31 and the plurality of second flow channel channels 32 are arranged sequentially and at intervals along the first direction e1.

[0056] See Figure 6 and Figure 7 , Figure 6 This is one of the schematic diagrams showing the cooperation between the plate 3 and the frame 4 in some embodiments of this application; Figure 7 This is a second schematic diagram illustrating the cooperation between the plate 3 and the frame 4 in some embodiments of this application. In some embodiments, the flow battery 100 further includes a frame 4, which can be connected to the plate 3. The frame 4 includes a first portion 4a and a second portion 4b, and the first portion 4a and the second portion 4b are respectively located on opposite sides of the plate 3 in a second direction e2. The second direction e2 is parallel to the extending direction of the first flow channel 31.

[0057] The first part 4a has an inlet channel 42 and an inlet 41, with the inlet channel 42 connecting the inlet 41 and the first channel groove 31; the second part 4b has an outlet channel 44 and an outlet 43, with the outlet channel 44 connecting the outlet 43 and the second channel groove 32.

[0058] Driven by the pump, electrolyte 1a flows into inlet channel 42 through inlet 41 and is then distributed into multiple first channel tanks 31. Electrolyte 1a in the first channel tank 31 passes through electrode 1b into second channel tank 32, and electrolyte 1a in the second channel tank 32 flows out through outlet channel 44 and outlet 43.

[0059] in, Figure 6 In the illustrated embodiment, the distance between the liquid inlet 41 and the plurality of first flow channel grooves 31 is different, and the distance between the liquid outlet 43 and the plurality of second flow channel grooves 32 is different. Figure 7 In the embodiment shown, the distance between the liquid inlet 41 and the multiple first flow channel 31 is the same, and the distance between the liquid outlet 43 and the multiple second flow channel 32 is the same. This can improve the uniformity of the flow velocity of electrolyte 1a in different first flow channel 31 and also improve the uniformity of the flow velocity of electrolyte 1a in different second flow channel 32. The concentration distribution of active substances in electrolyte 1a is more uniform, which can effectively reduce concentration polarization.

[0060] It should be noted that the flow battery 100 may include an electrode plate frame, and the frame 4 may be part of the electrode plate frame; or, in some other embodiments, the bipolar plate 2 includes a frame 4 and a plate 3, that is, the frame 4 may be part of the bipolar plate 2.

[0061] In some embodiments, the cross-sectional area of ​​the first flow channel 31 is smaller than the cross-sectional area of ​​the second flow channel 32. The dimensions of different cross-sections of the first flow channel 31 may be the same or different; the dimensions of different cross-sections of the second flow channel 32 may also be the same or different. When the different cross-sectional dimensions of the first flow channel 31 are non-uniform and / or the different cross-sectional dimensions of the second flow channel 32 are non-uniform, the cross-sectional area of ​​the first flow channel 31 being smaller than the cross-sectional area of ​​the second flow channel 32 means that the maximum cross-sectional area of ​​the first flow channel 31 is smaller than the minimum cross-sectional area of ​​the second flow channel 32.

[0062] It should be noted that the cross-section of the first flow channel 31 is the surface cut by a plane perpendicular to the extension direction of the first flow channel 31 on the first flow channel 31. The cross-section of the second flow channel 32 can be understood in the same way, so it will not be described again.

[0063] In related technologies, the cross-sectional area of ​​the first flow channel 31 is equal to the cross-sectional area of ​​the second flow channel 32. In contrast to related technologies, this application may reduce the cross-sectional area of ​​the first flow channel 31; or, it may increase the cross-sectional area of ​​the second flow channel 32; or, it may reduce the area of ​​the first flow channel 31 and increase the area of ​​the second flow channel 32.

[0064] In this way, compared with related technologies, under the premise of ensuring the power of the driving pump remains unchanged, the cross-sectional area of ​​the first flow channel 31 is smaller, which can increase the flow rate of the electrolyte 1a in the first flow channel 31, promote the convective mass transfer between the electrolyte 1a and the electrode 1b, not only can the active material be quickly transported to the surface of the electrode 1b, but also the reaction products and by-reaction products (such as hydrogen gas generated by the hydrogen evolution reaction) can be removed from the surface of the electrode 1b, so that the electrolyte 1a can fully react on the surface of the electrode 1b, effectively improving the energy efficiency of the flow battery 100.

[0065] Meanwhile, since the cross-sectional area of ​​the first flow channel 31 is smaller than that of the second flow channel 32, the pressure drop in the second flow channel 32 is smaller, which can partially compensate for the pressure drop loss in the first flow channel 31. This results in a smaller overall pressure drop within the flow field structure 3a, which helps improve the energy efficiency of the flow battery 100 while ensuring the power consumption of the driving pump. Furthermore, the large pressure difference between the inlet of the first flow channel 31 and the outlet of the second flow channel 32 can significantly enhance the driving force of the electrolyte 1a through the electrode 1b, and can more effectively promote the convective mass transfer of the electrolyte 1a.

[0066] In addition, it is understandable that the flow velocity of electrolyte 1a in the second flow channel 32 is less than that in the first flow channel 31. When the cross-sectional area of ​​the first flow channel 31 and the cross-sectional area of ​​the second flow channel 32 are the same, the volumetric flow rate of electrolyte 1a in the first flow channel 31 and the second flow channel 32 has a large difference, which may cause local pressure abnormalities or flow instability in the flow field structure 3a.

[0067] By making the cross-sectional area of ​​the first flow channel 31 smaller than that of the second flow channel 32, the volumetric flow rate of the electrolyte 1a in the first flow channel 31 can be made equal to that in the second flow channel 32, or the difference in volumetric flow rate of the electrolyte 1a in the first flow channel 31 and the second flow channel 32 can be reduced. This helps to improve the stability of the flow of electrolyte 1a in the flow field structure 3a and reduce the possibility of local pressure anomalies.

[0068] It should be noted that the technical feature that the cross-sectional area of ​​the first flow channel 31 is smaller than that of the second flow channel 32 can be applied to any embodiment of this application.

[0069] In some embodiments, the ratio of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 is 1 / 2 to 9 / 10. For example, the ratio of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 is 1 / 2, 3 / 5, 7 / 10, 4 / 5, or 9 / 10.

[0070] It should be noted that when the different cross-sectional dimensions of the first flow channel 31 are not uniform and / or the different cross-sectional dimensions of the second flow channel 32 are not uniform, the ratio of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 being 1 / 2 to 9 / 10 means that the ratio of the area of ​​the smallest cross-section of the first flow channel 31 to the area of ​​the largest cross-section of the second flow channel 32 is greater than or equal to 1 / 2; and the ratio of the area of ​​the largest cross-section of the first flow channel 31 to the area of ​​the smallest cross-section of the second flow channel 32 is less than or equal to 9 / 10.

[0071] To verify the effect of different ratios of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 on the energy efficiency of the flow battery 100, an electrochemical test experiment can be conducted on the flow battery 100.

[0072] For example, the flow battery 100 used in the test is an iron-chromium flow battery, and it is a single cell with a capacity of 2.6 Ah, an electrolyte flow rate of 40 ml / min, and an electrode area of ​​50 cm². 2 The test parameters include: test temperature 65±2℃; charging current 3.5A (current density 70mA / cm²). 2 Charge to 1.3V; discharge current is 3.5A (current density is 70mA / cm²). 2 Discharge to 0.8V.

[0073] Electrochemical testing experiment one can include multiple embodiments, in which the ratio of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 is different, and the ratio is in the range of 1 / 2 to 9 / 10. Electrochemical testing experiment one can also include multiple comparative examples, in which the ratio of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 is different, and the ratio is not in the range of 1 / 2 to 9 / 10.

[0074] In the various embodiments and comparative examples, the bipolar plate 2 has eight first flow channel grooves 31 and eight second flow channel grooves 32. The lengths of the first flow channel grooves 31 and the second flow channel grooves 32 are the same (60 mm), and the cross-sections of the first flow channel grooves 31 and the second flow channel grooves 32 are both rectangular. Furthermore, the cross-sectional shape and cross-sectional area of ​​the first flow channel groove 31 remain unchanged along its extension direction; similarly, the cross-sectional shape and cross-sectional area of ​​the second flow channel groove 32 remain unchanged along its extension direction.

[0075] The cross-sectional parameters of the first flow channel 31 and the second flow channel 32 in multiple embodiments and multiple comparative examples, as well as the energy efficiency test results of the battery, are shown in Table 1: Table 1. Cross-sectional parameters of the first flow channel 31 and the second flow channel 32, and battery test results.

[0076] As can be seen from Table 1, for the battery cells of Examples 1-5, the ratio of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 is controlled between 1 / 2 and 9 / 10, and the energy efficiency of the batteries in Examples 1-5 is greater than that of the batteries in Comparative Examples 1 and 2.

[0077] In Examples 1-5, as the ratio of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 decreases, the energy efficiency of the battery shows a trend of first increasing and then decreasing. The energy efficiency of the battery is the highest in Example 4 (reaching 81.01%). The reason is that when the ratio of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 is small, the cross-sectional area of ​​the first flow channel 31 is too small compared to the cross-sectional area of ​​the second flow channel 32, and the pressure drop within the entire flow field structure 3a is large, which may cause turbulence or uneven flow, destroy the uniformity of the flow field, and cause a slight decrease in the energy efficiency of the flow battery.

[0078] In Comparative Example 1, the ratio of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 is 19 / 20. Since the cross-sectional areas of the first and second flow channels 31 are nearly equal, the flow velocity of electrolyte 1a within the first flow channel 31 is too low, resulting in poor mass transfer and low energy efficiency of the battery. The energy efficiency of the battery in Comparative Example 1 is only 78.96%. In Comparative Example 2, the ratio of the cross-sectional area of ​​the first flow channel 31 to the cross-sectional area of ​​the second flow channel 32 is 2 / 5. The cross-sectional area of ​​the first flow channel 31 is too small compared to the second flow channel 32, leading to excessive pressure drop within the entire flow field structure 3a and resulting in low energy efficiency of the battery. The energy efficiency of the battery in Comparative Example 2 is only 77.65%.

[0079] In summary, by using a ratio of 1 / 2 to 9 / 10 between the cross-sectional area of ​​the first flow channel 31 and the cross-sectional area of ​​the second flow channel 32, the flow velocity of the electrolyte 1a in the first flow channel 31 can be increased while ensuring the power consumption of the drive pump. This reduces the overall pressure drop of the electrolyte 1a in the flow field structure 3a, increases the convective mass transfer of the electrolyte 1a, and thus improves the energy efficiency of the flow battery.

[0080] See Figure 8 and Figure 9 , Figure 8 Schematic diagram of the structure of bipolar plate 2 provided in other embodiments of this application; Figure 9 According to Figure 8 The diagram shows a cross-sectional view of the bipolar plate 2 at line AA. In other embodiments, the first flow channel 31 has a channel opening 311, a channel sidewall 313, and a channel bottom wall 312. The channel opening 311 and the channel bottom wall 312 are opposite to each other, and the channel sidewall 313 is connected between the channel opening 311 and the channel bottom wall 312. The channel sidewall 313 includes a first sidewall 314 and a second sidewall 315 opposite to each other in a first direction e1. The first sidewall 314 includes a first region q1 and a second region q2. The first region q1 is connected to the end of the second region q2 away from the channel bottom wall 312. In the direction from the channel bottom wall 312 to the channel opening 311, the first region q1 extends obliquely away from the second sidewall 315.

[0081] Combination Figure 3 It should be understood that electrode 1b is disposed on the first surface 30 and covers the opening 311 of the first flow channel 31. When the sidewall 313 of the channel is perpendicular to the electrode 1b, the electrolyte 1a in the first flow channel 31 can flow towards the electrode 1b along the arrangement direction of the bottom wall 312 and the opening 311 of the channel, that is, flow towards the electrode 1b in a direction perpendicular to the electrode 1b. This can easily lead to severe vertical scouring of the electrode 1b by the electrolyte 1a, which can easily damage the electrode 1b.

[0082] Therefore, by extending the first region q1 at an angle away from the second sidewall 315, the first region q1 can guide the flow direction of the electrolyte 1a, causing the electrolyte 1a to generate a certain lateral velocity component, that is, the electrolyte 1a has a velocity component parallel to the electrode 1b, reducing the vertical scouring of the electrolyte 1a on the electrode 1b and ensuring the service life of the electrode 1b. In addition, when the electrolyte 1a in the first flow channel 31 has a lateral velocity component, it can promote the lateral diffusion of the electrolyte 1a in the plane of the electrode 1b, promote the mass transfer between the electrolyte 1a and the electrode 1b, and help improve the energy efficiency of the flow battery 100.

[0083] In some embodiments, see Figure 9The angle α between the first region q1 and the reference plane S is 80°~88°, wherein the reference plane S is perpendicular to the arrangement direction of the slot opening 311 and the bottom wall 312 of the slot. For example, the angle α between the first region q1 and the reference plane S can be 80°, 81°, 82°, 83°, 84°, 85°, 86°, 87° or 88°.

[0084] When α is too large (α > 88°), the tilt angle of the first region q1 is too small, and the lateral velocity component of the electrolyte 1a in the first flow channel 31 is small, making it difficult to effectively promote mass transfer between the electrolyte 1a and the electrode 1b. When α is too small (α < 80°), the lateral velocity component of the electrolyte 1a is too large, and the electrolyte 1a flows rapidly along the surface of the electrode 1b. The active material in the electrolyte 1a does not fully penetrate into the pores of the electrode 1b or is carried out before completing the reaction, resulting in a decrease in the utilization rate of the active material and a reduction in the energy efficiency of the battery. In addition, when the lateral velocity component of the electrolyte 1a is too large, the velocity of the electrolyte 1a perpendicular to the electrode 1b is small, making it difficult for the electrolyte 1a to pass through the electrode 1b in the thickness direction and react fully with the electrode 1b.

[0085] Therefore, when α is 80°~88°, the electrolyte 1a can obtain a suitable transverse velocity component, while avoiding the electrolyte 1a flowing too fast along the surface of electrode 1b. This ensures that the electrolyte 1a and electrode 1b are in full contact, allowing the active material in the electrolyte 1a to fully react on the surface of electrode 1b. It also ensures that part of the electrolyte 1a can pass through electrode 1b in the thickness direction, ensuring the effective utilization area of ​​electrode 1b, thereby effectively improving the energy efficiency of the flow battery.

[0086] Continue reading Figure 9 In some embodiments, the second sidewall 315 includes a third region q3 and a fourth region q4. The third region q3 is connected to the end of the fourth region q4 that is away from the bottom wall 312 of the groove. The third region q3 is opposite to the second region q2. In the direction from the bottom wall 312 to the groove opening 311, the third region q3 extends obliquely away from the first region q1. The beneficial effects of the third region q3 extending obliquely away from the first region q1 can be referred to as the beneficial effects of the first region q1 extending obliquely away from the second sidewall 315 as described above, and will not be repeated here.

[0087] For example, the first sidewall 314 and the second sidewall 315 can be arranged symmetrically, that is, the first region q1 and the third region q3 are symmetrical, and the angle between the third region q3 and the reference plane S is equal to the angle α mentioned above.

[0088] In some embodiments, see Figures 9-11 , Figure 10 for Figure 8A schematic diagram of another angle of the bipolar plate 2 shown; Figure 11 for Figure 10 Enlarged view of the circled portion at point B; the bipolar plate 2 includes a connector 34, the first flow channel 31 has an inlet end 310, the connector 34 is fixed to the inlet end 310, and the connector 34 is opposite to the bottom wall 312 of the channel. The connector 34 can be integrally formed with the plate body 3; alternatively, the connector 34 can be fixed to the plate body 3 by snap-fitting, welding, or gluing. For example, the connector 34 can be connected between the first side wall 314 and the second side wall 315. The connector 34 can be columnar or plate-shaped.

[0089] It should be noted that, Figure 10 and Figure 11 The connector 34 and the plate 3 are schematically divided by a dashed line, but this dashed line does not actually exist on the bipolar plate 2.

[0090] The first flow channel 31 also includes a third sidewall, which is connected between the first sidewall 314 and the second sidewall 315, and is located at the end of the first flow channel 31 away from the inlet end 310. The bipolar plate 2 also includes a flow guide 33, which is connected between the connector 34 and the third sidewall, that is, the flow guide 33 is fixed to the plate body 3. At least a portion of the flow guide 33 is located within the first flow channel 31, and the first sidewall 314, the second sidewall 315, and the bottom wall 312 of the channel are all spaced apart from the flow guide 33.

[0091] By setting the aforementioned connector 34, it is convenient to fix the guide component 33, ensuring the stability and reliability of the guide component 33.

[0092] In some embodiments, the guide member 33 includes a first guide surface 331 and a second guide surface 332. In the first direction e1, the first guide surface 331 is opposite to the first region q1, and the second guide surface 332 is opposite to the third region q3. In the direction from the bottom wall 312 to the opening 311, the first guide surface 331 extends obliquely in a direction away from the second side wall 315.

[0093] See Figure 12 , Figure 12 This is a schematic diagram of the main channel 5 and the branch channel provided in some embodiments of this application; the first channel groove 31 includes the main channel 5 and the first branch channel 51 that are connected. The second region q2, the fourth region q4 and the bottom wall 312 of the groove form the main channel 5. The first region q1 and the first guide surface 331 form the first branch channel 51. Part of the electrolyte 1a in the main channel 5 can flow to the electrode 1b through the first branch channel 51.

[0094] By extending the first guide surface 331 at an angle away from the second sidewall 315 in the direction from the bottom wall 312 to the opening 311, and extending the first region q1 at an angle away from the second sidewall 315, the first branch channel 51 extends at an angle away from the second sidewall 315 in the direction from the bottom wall 312 to the opening 311. This ensures that the electrolyte 1a in the first branch channel 51 has a transverse velocity component, which can more effectively promote the mass transfer between the electrolyte 1a and the electrode 1b.

[0095] See Figure 9 and Figure 12 In some embodiments, the third region q3 and the second guide surface 332 form a second bifurcation channel 52, through which part of the electrolyte 1a in the main channel 5 can flow to the electrode 1b. In the direction from the bottom wall 312 to the opening 311, the second guide surface 332 extends obliquely away from the first region q1, thus the second bifurcation channel 52 also extends obliquely away from the first region q1, ensuring that the electrolyte 1a in the second bifurcation channel 52 all have a lateral velocity component, which can more effectively promote mass transfer between the electrolyte 1a and the electrode 1b.

[0096] in, Figure 12 The main flow channel 5 and the first branch flow channel 51 are schematically divided by dashed lines, and the main flow channel 5 and the second branch flow channel 52 are also schematically divided by dashed lines. These dashed lines do not actually exist in the first flow channel groove 31.

[0097] For example, the angle between the first guide surface 331 and the reference surface S, and the angle between the second guide surface 332 and the reference surface S are both equal to the aforementioned angle α. The cross-sectional shape of the guide component 33 can be triangular, V-shaped, or trapezoidal; the main flow channel 5, the first branch flow channel 51, and the second branch flow channel 52 can be in a "Y" shape as a whole.

[0098] Taking the case where the angles between the first guiding surface 331, the second guiding surface 332, the first region q1, the third region q3, and the reference surface S are all the same (all angles α), an electrochemical test experiment two is conducted on the flow battery 100 to verify the effect of different angles between the first region q1 and the reference surface S on the energy efficiency of the flow battery 100. The test method and parameters of the electrochemical test experiment two can be designed with reference to the electrochemical test experiment one of the flow battery 100 in the above embodiments.

[0099] The test experiment can include multiple embodiments and multiple comparative examples. The cross-sectional area of ​​the first flow channel 31 in the multiple embodiments and multiple comparative examples can be designed with reference to the cross-sectional area of ​​the first flow channel 31 in Embodiment 4; the cross-sectional area of ​​the second flow channel 32 in the multiple embodiments and multiple comparative examples can be designed with reference to the cross-sectional area of ​​the second flow channel 32 in Embodiment 4. The test results of the energy efficiency of the batteries in the multiple embodiments and multiple comparative examples for different angles between the first region q1 and the reference plane S are shown in Table 2. Table 2. Different angles between the first region q1 and the reference plane S, and battery test results.

[0100] As shown in Table 2 for Examples 6, 7, and 8, when the included angle is controlled between 80° and 88°, the electrolyte 1a can obtain a moderate lateral velocity component, which can promote mass transfer between the electrolyte 1a and the electrode 1b, ensuring sufficient contact between the electrolyte 1a and the electrode 1b. This allows the active material in the electrolyte 1a to fully react on the surface of the electrode 1b, resulting in a battery energy efficiency greater than 82%. Compared to the battery in Example 4 (energy efficiency of 81.01%), the energy efficiency of the batteries in Examples 6, 7, and 8 is effectively improved.

[0101] In Comparative Example 3, the included angle α is too large (greater than 88°), resulting in an insufficient tilt angle between the first bifurcation channel 51 and the second bifurcation channel 52. This leads to insufficient lateral velocity component of the electrolyte 1a, making it difficult to promote mass transfer between the electrolyte 1a and the electrode 1b. In Comparative Example 4, the included angle α is too small (less than 80°), resulting in an excessively large lateral velocity component of the electrolyte 1a. Consequently, some of the active material in the electrolyte 1a flows into the second flow channel 32 without fully reacting on the surface of the electrode 1b, causing the energy efficiency of the flow battery in Comparative Example 3 to be lower than that of the flow batteries in Examples 6, 7, and 8.

[0102] See Figure 9 and Figure 12 The end of the guide member 33 near the bottom wall 312 of the channel is the guide end 333, which is located between the second region q2 and the fourth region q4. In the cross-section of the first flow channel 31, the first region q1 and the second region q2 intersect at the first intersection point 316, and the third region q3 and the fourth region q4 intersect at the second intersection point 317. The guide end 333 being located between the second region q2 and the fourth region q4 means that the cross-section of the guide end 333 is located on the line connecting the first intersection point 316 and the second intersection point 317; or, the cross-section of the guide end 333 is located on the side of the line connecting the first intersection point 316 and the second intersection point 317 near the bottom wall 312 of the channel.

[0103] For example, when the cross-section of the guide member 33 is triangular, the cross-section of the guide end 333 is a point, that is, the point is located on the line connecting the first intersection point 316 and the second intersection point 317, or the point is located on the side of the line connecting the first intersection point 316 and the second intersection point 317 near the bottom wall 312 of the tank.

[0104] In the first direction e1, the distance between the guide end 333 and the second region q2 is equal to the distance between the guide end 333 and the fourth region q4, so that the electrolyte 1a in the main channel 5 can be evenly distributed to the first branch channel 51 and the second branch channel 52, ensuring the uniformity of the active material on the electrode 1b surface and helping to improve the energy efficiency of the flow battery.

[0105] In some embodiments, in the arrangement direction of the slot 311 and the bottom wall 312, the size of the second region q2 is the first size L1; the extension length of the first region q1 in its own inclined direction is the second size L2, and the ratio of the first size L1 to the second size L2 is 4 to 8. For example, the ratio of the first size L1 to the second size L2 can be 4, 5, 6, 7 or 8.

[0106] When the second region q2 extends along the arrangement direction of the slot opening 311 and the bottom wall 312, the size of the second region q2 is also the depth of the main channel; the extension length of the first region q1 in its own inclined direction is also the extension length of the first branch channel in its own inclined direction.

[0107] It should be noted that when the ratio of the first dimension L1 to the second dimension L2 is less than 4, the size of the second region q2 is too small, meaning the depth of the main flow channel 5 is too shallow. This causes the electrolyte 1a entering the main flow channel 5 to enter the first branch flow channel 51 and the second branch flow channel 52 before it has been stably distributed, potentially leading to large flow disturbances, uneven flow distribution, and ultimately, low battery energy efficiency, affecting battery performance. When the ratio of the first dimension L1 to the second dimension L2 is greater than 8, the size of the second region q2 is too large, meaning the depth of the main flow channel 5 is too great. This weakens the lateral flow distribution effect of the first branch flow channel 51, affecting the energy efficiency of the flow battery.

[0108] To verify the effect of the ratio of the first size L1 to the second size L2 on the energy efficiency of the flow battery 100, an electrochemical test experiment three can be conducted on the flow battery 100. The test method and parameters of the electrochemical test experiment three can be designed with reference to the electrochemical test experiment one of the flow battery 100 in the above embodiments.

[0109] The test experiment can set up multiple embodiments and multiple comparative examples. Except for the ratio of the first size L1 to the second size L2, other parameters of the bipolar plate 2 in the multiple embodiments and multiple comparative examples can be set with reference to the parameters of the bipolar plate 2 in Embodiment 7. The ratios of the first size L1 to the second size L2 in the multiple embodiments and multiple comparative examples are shown in Table 3. The energy efficiency test results of the batteries in the multiple embodiments and multiple comparative examples for different ratios of the first size L1 to the second size L2 are shown in Table 3. Table 3. Ratio of first dimension L1 to second dimension L2 and battery test results.

[0110] As shown in Table 3, in Comparative Example 5, the ratio of the first dimension L1 to the second dimension L2 is 3. In this case, the main flow channel 5 is too short, causing the electrolyte 1a to enter the first branch flow channel 51 and the second branch flow channel 52 before it has been stably distributed. This may result in large flow disturbances and uneven flow distribution of the electrolyte 1a, leading to a lower energy efficiency of the battery. In Comparative Example 6, the ratio of the first dimension L1 to the second dimension L2 is 10. In this case, the main flow channel 5 is too long, weakening the flow distribution effect of the first branch flow channel 51 and the second branch flow channel 52, which also leads to a slight decrease in battery efficiency.

[0111] In Examples 9, 10, and 11, the ratio of the first dimension L1 to the second dimension L2 is 4-8. The main flow channel 5 can provide a sufficiently stable flow section to ensure that the electrolyte 1a can uniformly enter the first branch flow channel 51 and the second branch flow channel 52. The first branch flow channel 51 and the second branch flow channel 52 can effectively guide the diversion of the electrolyte 1a within the main flow channel 5, so that the electrolyte 1a generates a suitable lateral velocity component, reducing the vertical scouring of the electrolyte 1a on the electrode 1b, and promoting the lateral diffusion of the electrolyte 1a in the plane of the electrode 1b, promoting the mass transfer between the electrolyte 1a and the electrode 1b, and improving the energy efficiency of the flow battery 100. The energy efficiency of the flow batteries in Examples 9, 10, and 11 is all greater than 83%, and the energy efficiency of the flow batteries is greater than that of the flow battery in Example 7 (82.49%).

[0112] This application also provides a flow battery 100, which includes a bipolar plate 2, an electrode 1b, and an electrolyte 1a. The configuration of the electrode 1b and the electrolyte 1a with the bipolar plate 2 can be referred to... Figure 1 The flow battery 100 in the illustrated embodiment is designed with bipolar plate 2 as described in any of the above embodiments. It is understood that the beneficial effects achieved by the flow battery 100 in this application embodiment can be referenced to the beneficial effects brought by the bipolar plate 2 in any of the above embodiments, and will not be repeated here.

[0113] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A bipolar plate for a flow battery, characterized in that, include: The plate has a first surface, the first surface is provided with a first flow channel groove and a second flow channel groove, the first flow channel groove and the second flow channel groove are arranged at intervals in a first direction, the first direction being perpendicular to the extension direction of the first flow channel groove; Both the first flow channel and the second flow channel are used for electrolyte flow. The first flow channel serves as an inflow channel and has an inlet end. The second flow channel serves as an outflow channel, and the electrolyte can flow from the first flow channel to the second flow channel. The cross-sectional area of ​​the first flow channel is smaller than that of the second flow channel. The first flow channel has a channel opening, a channel sidewall, and a channel bottom wall, the channel opening and the channel bottom wall are opposite to each other, and the channel sidewall is connected between the channel opening and the channel bottom wall; The channel sidewall includes a first sidewall, a second sidewall, and a third sidewall. The first sidewall and the second sidewall are opposite to each other in the first direction. The third sidewall is connected between the first sidewall and the second sidewall, and the third sidewall is located at the end of the first flow channel that is away from the inlet end. The first sidewall includes a first region and a second region. The first region is connected to the end of the second region away from the bottom wall of the groove. In the direction from the bottom wall of the groove to the groove opening, the first region extends obliquely away from the second sidewall. The size of the groove opening in the first direction is larger than the size of the bottom wall of the groove in the first direction. A flow guide is fixed to the plate body, at least a portion of which is located within the first flow channel groove, and the first sidewall, the second sidewall, and the bottom wall of the groove are all spaced apart from the flow guide. The guide member includes a first guide surface and a second guide surface. In the first direction, the first guide surface is opposite to the first region, and the second guide surface is opposite to the second sidewall. In the direction from the bottom wall of the groove to the groove opening, the first guide surface extends obliquely away from the second sidewall.

2. The bipolar plate according to claim 1, characterized in that, The ratio of the cross-sectional area of ​​the first flow channel to the cross-sectional area of ​​the second flow channel is 1 / 2 to 9 / 10.

3. The bipolar plate according to claim 1 or 2, characterized in that, The angle between the first region and the reference surface is 80°~88°, wherein the reference surface is perpendicular to the arrangement direction of the slot opening and the bottom wall of the slot.

4. The bipolar plate according to claim 1 or 2, characterized in that, The second sidewall includes a third region and a fourth region. The third region is connected to the end of the fourth region away from the bottom wall of the tank. The third region is opposite to the second guide surface. In the direction from the bottom wall of the tank to the opening of the tank, at least one of the third region and the second guide surface extends obliquely away from the first region.

5. The bipolar plate according to claim 4, characterized in that, The end of the guide member near the bottom wall of the tank is the guide end, and the guide end is located between the second region and the fourth region; In the first direction, the distance between the guide end and the second region is equal to the distance between the guide end and the fourth region.

6. The bipolar plate according to any one of claims 1, 2, and 5, characterized in that, The second sidewall includes a third region and a fourth region, the third region being connected to the end of the fourth region away from the bottom wall of the tank, the third region being opposite to the second guide surface, and the fourth region being opposite to the second region; The first flow channel includes a main flow channel and a first branch flow channel that are connected to each other. The second region, the fourth region and the bottom wall of the channel form the main flow channel, and the first region and the first guide surface form the first branch flow channel. In the arrangement direction of the slot and the bottom wall of the slot, the size of the second region is the first size; the extension length of the first region in its own inclined direction is the second size, and the ratio of the first size and the second size is 4 to 8.

7. The bipolar plate according to any one of claims 1, 2, and 5, characterized in that, The bipolar plate also includes a connector, which is fixed to the inlet end and is opposite to the bottom wall of the tank; the flow guide is connected between the connector and the third side wall.

8. A flow battery, characterized in that, include: A bipolar plate, as described in any one of claims 1-7; Electrodes are fixed to the first surface; An electrolyte adapted to flow along the first flow channel, wherein the electrolyte in the first flow channel is adapted to pass through the electrode and flow along the second flow channel.

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