Flow battery

Abstract

The application provides a flow battery, and relates to the technical field of batteries. A specific technical scheme is as follows: the flow battery comprises a first electrolyte, a first bipolar plate and a first electrode, the first bipolar plate is in contact with the first electrolyte, the first electrode is in contact with the first electrolyte, the first electrode is fixed to the first bipolar plate, and the first electrolyte can undergo an oxidation-reduction reaction on the first electrode; the first bipolar plate is provided with a first electrode layer, and the first electrolyte can undergo an oxidation-reduction reaction on the first electrode layer; the scheme can improve the electrochemical active area of the electrode in the flow battery, provide more active sites for the active substances in the first electrolyte to undergo oxidation-reduction reactions, and is beneficial to reducing the internal resistance of the flow battery and improving the power and energy efficiency of the flow battery.

Description

Technical Field

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

[0002] In flow batteries, the electrodes, as the sites of redox reactions in the electrolyte, have an electrochemically active surface area that determines the current density, thus affecting the battery's power and energy efficiency. Related technologies typically increase the electrode thickness to enhance the electrochemically active surface area. However, at the same compression ratio, excessively thick electrodes have a high areal density, making it difficult for the electrolyte to penetrate the electrode. This results in greater mass transfer polarization, hindering the improvement of the flow battery's current density and instead increasing its resistance, thereby reducing its energy efficiency. Summary of the Invention

[0003] This application provides a flow battery that can increase the electrochemical active area of ​​the electrodes, providing more active sites for the active materials in the first electrolyte to undergo redox reactions, which is beneficial to reducing the internal resistance of the flow battery and improving its power and energy efficiency.

[0004] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0005] In a first aspect, a flow battery is provided, comprising a first electrolyte, a first bipolar plate, and a first electrode. The first bipolar plate is in contact with the first electrolyte, and the first electrode is in contact with the first electrolyte. The first electrode is fixed to the first bipolar plate, and the first electrolyte can undergo a redox reaction on the first electrode. A first electrode layer is provided on the first bipolar plate, and the first electrolyte can undergo a redox reaction on the first electrode layer.

[0006] It is understandable that the first electrolyte can undergo redox reactions not only at the first electrode but also on the first electrode layer. This increases the number of active sites for redox reactions in the first electrolyte, compared to the first electrolyte only undergoing redox reactions at the first electrode. This is equivalent to increasing the electrochemical active area of ​​the electrodes in the flow battery, which is beneficial for increasing the power and energy efficiency of the flow battery. Furthermore, the first bipolar plate with the first electrode layer not only conducts current but also provides a site for redox reactions.

[0007] Furthermore, in this case, the first electrode does not need to be made too thick. Under the same compression ratio, the areal density of the first electrode will not be too high. The first electrolyte can effectively penetrate the first electrode and flow to the surface of the first electrode near the first bipolar plate to carry out oxidation-reduction reaction. This helps to reduce the internal resistance of the flow battery and can effectively increase the current density of the flow battery, thereby further increasing the power and energy efficiency of the flow battery.

[0008] In one possible implementation of the first aspect, the first bipolar plate has a flow channel for the flow of a first electrolyte, thus enabling the first bipolar plate to conduct the first electrolyte in addition to conducting current. The flow channel has an opening, a bottom wall, and side walls, with the opening and bottom wall facing each other. A first electrode layer is provided on the bottom wall; alternatively, a first electrode layer is provided on the side walls; or, both the bottom wall and side walls are provided with first electrode layers. This increases the electrochemical active area of ​​the first electrode layer, which is more conducive to increasing the power and energy efficiency of the flow battery.

[0009] In one possible implementation of the first aspect, the first electrode has a first surface with a flow channel groove, the first electrode is fixed to the first surface, and the first electrode covers the groove opening. In this way, the first electrolyte flowing within the flow channel groove can undergo redox reactions not only on the first electrode layer on the inner wall of the flow channel groove, but also on the first electrode itself, resulting in a more complete reaction.

[0010] In one possible implementation of the first aspect, the cross-sectional area of ​​the channel gradually decreases along the flow direction of the first electrolyte.

[0011] It is understandable that during the flow of the first electrolyte in the flow channel, the concentration of active material in the first electrolyte will gradually decrease due to the consumption of the reaction. This can easily lead to uneven concentration of the first electrolyte in the flow direction, and the amount of active material flowing through a specific position per unit time will be different. Therefore, the current generated when the first electrolyte undergoes oxidation-reduction reaction at different positions in the flow channel will be different, which will naturally affect the power and energy efficiency of the flow battery.

[0012] By gradually reducing the cross-sectional area of ​​the flow channel along the flow direction of the first electrolyte, the flow rate of the first electrolyte can be gradually increased. Although the concentration of active material in the first electrolyte naturally decreases due to reaction consumption during the flow process, the gradual increase in the flow rate of the first electrolyte ensures that the total amount of active material contained in the first electrolyte flowing through each location per unit time is not significantly different. This can offset the effect of the decrease in the concentration of active material in the first electrolyte and help increase the power and energy density of the flow battery.

[0013] In addition, the faster flow rate of the first electrolyte makes it easier for the first electrolyte to penetrate the first electrode, allowing the active substances in the first electrolyte to react fully.

[0014] In one possible implementation of the first aspect, the bottom wall of the tank extends at an angle toward the opening of the tank in the direction of flow of the first electrolyte. This allows the cross-sectional area of ​​the flow channel to gradually decrease along the direction of flow of the first electrolyte, thereby ensuring the power and energy density of the flow battery.

[0015] In one possible implementation of the first aspect, the bottom wall of the tank and the first reference surface have a first included angle, the first reference surface being perpendicular to the arrangement direction of the bottom wall of the tank and the opening of the tank, and the first included angle being 1.5°~2°.

[0016] It should be noted that when the first included angle is too large, i.e., the angle at which the bottom wall of the tank tilts towards the tank opening is too large, it may cause a sharp increase in the flow velocity of the first electrolyte in the flow channel and flow instability. This can lead to a rapid increase in flow velocity over a short distance, resulting in excessive pressure drop and consequently unstable flow rate. Furthermore, in areas with excessively high flow velocities, the residence time of the first electrolyte may be too short, causing the active material to be discharged before it has fully reacted. Moreover, excessively high flow velocities exacerbate the erosion of the inner wall of the flow channel, the first electrode layer, and the first electrode, making the flow channel more susceptible to damage and shortening the lifespan of the first electrode layer and the first electrode.

[0017] When the first included angle is too small, meaning the angle at which the bottom wall of the tank tilts towards the tank opening is too small, insufficient flow rate compensation occurs. The flow rate of the first electrolyte increases slowly and cannot effectively offset the decrease in the concentration of the active material along the flow path, resulting in an excessively low concentration of the active material in the later section of the flow channel. An excessively low flow rate of the first electrolyte may also cause it to stagnate at the end of the flow channel, leading to significant concentration polarization and a decrease in the voltage efficiency of the flow battery.

[0018] Therefore, by controlling the first included angle between 1.5° and 2°, on the one hand, the instability of the first electrolyte flow and the aggravation of the scouring of the flow channel caused by the first included angle being too large can be avoided; on the other hand, the insufficient concentration compensation caused by the first included angle being too small can be avoided, the reaction uniformity of the active material is comprehensively improved, concentration polarization is effectively reduced, and it is also helpful to achieve long service life of flow batteries and improve operational reliability.

[0019] In one possible implementation of the first aspect, the size of the flow channel is 0.1 mm to 0.2 mm in the direction of arrangement of the bottom wall and the opening of the channel.

[0020] It should be understood that the dimensions of the flow channel in the direction of its arrangement on the bottom wall and at the opening refer to the depth of the flow channel. When the depth of the flow channel is too small, it will cause difficulty in the flow of the first electrolyte within the flow channel; when the depth of the flow channel is too large, it is easy for the flow channel to penetrate the opposite surfaces of the first bipolar plate, making it difficult to ensure the normal function of the flow channel and affecting the structural strength of the first bipolar plate.

[0021] The depth of the flow channel is 0.1mm~0.2mm, which can ensure the normal flow of the first electrolyte in the flow channel and also ensure the structural strength of the first bipolar plate.

[0022] In one possible implementation of the first aspect, the tank sidewall includes a first sidewall and a second sidewall, which are opposite to each other in a first direction; in the flow direction of the first electrolyte, the first sidewall extends obliquely toward the direction close to the second sidewall. This also allows the cross-sectional area of ​​the flow channel to gradually decrease along the flow direction of the first electrolyte, thereby ensuring the power and energy density of the flow battery.

[0023] In one possible implementation of the first aspect, the first sidewall and the second reference surface have a second included angle of 1.5° to 2°, and the second reference surface is perpendicular to the first direction.

[0024] It is understandable that when the second included angle is too large or too small, the effects on the first electrolyte, flow channel, first electrode layer, and first electrode can be referenced to the effects caused by the first included angle being too large or too small, as described above, and will not be repeated here. Therefore, by setting the second included angle to 1.5°~2°, on the one hand, the instability of the first electrolyte flow and the aggravated scouring of the flow channel caused by the second included angle being too large can be avoided; on the other hand, insufficient concentration compensation caused by the second included angle being too small can be avoided, the reaction uniformity of the active material is comprehensively improved, concentration polarization is effectively reduced, and it is also helpful to achieve a longer lifespan and improved operational reliability of the flow battery.

[0025] In one possible implementation of the first aspect, the second sidewall extends toward the direction close to the first sidewall in the flow direction of the first electrolyte. This also allows the cross-sectional area of ​​the flow channel to gradually decrease along the flow direction of the first electrolyte, thereby ensuring the power and energy density of the flow battery.

[0026] In one possible implementation of the first aspect, the second sidewall and the second reference plane have a third included angle of 1.5° to 2°.

[0027] When the third included angle is too large or too small, the effects on the first electrolyte, flow channel, first electrode layer, and first electrode can be referenced from the effects caused by the first included angle being too large or too small, as described above, and will not be repeated here. Therefore, by setting the third included angle to 1.5°~2°, on the one hand, the instability of the first electrolyte flow and the aggravated scouring of the flow channel caused by the third included angle being too large can be avoided; on the other hand, insufficient concentration compensation caused by the third included angle being too small can be avoided, the reaction uniformity of the active material is comprehensively improved, concentration polarization is effectively reduced, and it is also helpful to achieve a longer lifespan and improved operational reliability of the flow battery.

[0028] In one possible implementation of the first aspect, a baffle is provided in the flow channel, and the baffle is located on the bottom wall of the channel. The baffle has a first guiding surface and a second guiding surface, which are arranged sequentially in the flow direction of the first electrolyte. In the direction from the first guiding surface to the second guiding surface, the first guiding surface extends obliquely towards the direction close to the channel opening, and the second guiding surface extends obliquely towards the direction close to the bottom wall of the channel.

[0029] It should be understood that when fluid flows within a channel, the flow velocity is highest in the central region, while the velocity near the channel walls is extremely low due to viscosity. Therefore, when the first electrolyte flows within the channel, its velocity is higher in the central region and very low near the bottom and side walls, creating a velocity gradient. The first electrolyte undergoes mass transfer only through diffusion between the first electrode and the first electrode layer, resulting in a slow mass transfer rate and high mass transfer polarization. The lower concentration of the first electrolyte near the bottom and side walls affects the efficiency of the redox reactions of the active substances in the first electrolyte on the first electrode and the first electrode layer.

[0030] On the one hand, the first and second guide surfaces guide the flow direction of the first electrolyte within the flow channel. On the other hand, the first guide surface can act as the upstream surface, and the second guide surface as the downstream surface. The upstream surface forces the fluid to accelerate around obstacles (i.e., baffles), while the downstream surface, due to the adverse pressure gradient, forms flow separation and generates vortices. These vortices change the mainstream direction, causing local flow directions to deviate from their original paths, transforming laminar flow into turbulent flow. In particular, the enhanced turbulence on the side of the second guide surface away from the first guide surface promotes mixing of the first electrolyte in the central region of the flow channel and near the bottom and side walls of the tank. This results in a uniform concentration of active substances in the mixed first electrolyte, thereby increasing convective mass transfer and enhancing the mass transfer of the first electrolyte.

[0031] In one possible implementation of the first aspect, the cross-sectional shape of the baffle is triangular, and the baffle can be a triangular prism. When the first electrolyte flows to the first guide surface, the edges of the triangular prism away from the bottom wall of the tank can force the fluid to separate instantaneously, forcing the first electrolyte to generate strong acceleration to form a low-pressure core. The low-pressure core will entrain the fluid behind, forming a high-intensity vortex, which will entrain the first electrolyte in the middle area to the wall of the flow channel, and throw the first electrolyte near the wall of the flow channel away from the surface of the first electrode, further increasing the convective mass transfer, thereby enhancing the mass transfer of the first electrolyte.

[0032] In one possible implementation of the first aspect, the included angle between the first guide surface and the second guide surface is 30° to 40°.

[0033] It should be noted that when the angle between the first and second guide surfaces is too large, the resulting vortex is too weak. Conversely, when the angle between the first and second guide surfaces is too small, it may cause the first electrolyte to stratify, and a backflow dead zone to form on the side of the second guide surface opposite to the first guide surface. Within the backflow dead zone, the concentration of active substances in the first electrolyte is low, resulting in low efficiency of redox reactions on the first electrode and the first electrode layer. Furthermore, the first electrolyte consumes a large amount of energy and experiences significant pressure drop when passing through the baffle column.

[0034] By setting the angle between the first and second guide surfaces to 30°~40°, the first electrolyte can form a high vortex in the flow channel, which promotes uniform mixing of active materials and avoids the formation of backflow dead zones in the flow channel, reducing the energy consumed by the first electrolyte when passing through the baffle and reducing pressure drop loss.

[0035] In one possible implementation of the first aspect, the size of the baffle protruding from the bottom wall of the channel is 100μm to 150μm. It should be understood that if the size of the baffle protruding from the bottom wall of the channel is too small, the disturbance will be limited to the vicinity of the baffle, and the vortex intensity will be insufficient; while if the size of the baffle protruding from the bottom wall of the channel is too large, it will easily block the flow channel, increase the pressure drop, and cause a large energy loss.

[0036] Therefore, by having the baffle protruding from the bottom wall of the tank by 100μm~150μm, a high vortex is formed in the flow channel, which promotes uniform mixing of active materials. At the same time, the baffle can also avoid blocking the flow channel, reduce the energy consumed by the first electrolyte when passing through the baffle, and reduce the voltage drop loss.

[0037] In one possible implementation of the first aspect, the extension length of the baffle is 300 μm to 750 μm. It should be understood that if the extension length of the baffle is too small, the scale of the vortex generated by the first electrolyte in the flow channel is small, and the vortex coverage is insufficient; if the side length is too large, it will cause the flow separation zone to expand, forming a backflow dead zone on the side of the second guide surface opposite to the first guide surface, and causing a sharp increase in pressure drop and a large power consumption of the first drive pump.

[0038] By controlling the extension length of the baffle column within the range of 300μm to 750μm, a large vortex is formed in the flow channel groove to promote uniform mixing of active materials. At the same time, a backflow dead zone is avoided on the side of the second guide surface opposite to the first guide surface, reducing pressure drop and lowering the power consumption of the first drive pump.

[0039] In one possible implementation of the first aspect, multiple baffles are spaced apart along the flow direction of the first electrolyte, with a spacing of 1 mm to 2 mm between adjacent baffles. It should be understood that if the spacing between adjacent baffles is too small, resulting in overly dense placement of the baffles within the flow channel, adjacent vortices will interfere with each other, leading to energy dissipation. Conversely, if the spacing between adjacent baffles is too large, the spacing between adjacent vortices will be too large, interrupting mass transfer enhancement. Once the vortex decays, the inner wall of the flow channel reverts to a low-velocity boundary layer, failing to enhance convective mass transfer.

[0040] Therefore, by setting the spacing between two adjacent baffles to 1mm~2mm, it is possible to avoid the baffles being set too densely in the flow channel, thereby reducing the possibility of mutual interference and energy loss between two adjacent vortices. Moreover, it is possible to avoid the interruption of mass transfer enhancement caused by a large spacing between two adjacent vortices, thereby enhancing convective mass transfer and increasing the energy efficiency of the flow battery.

[0041] In one possible implementation of the first aspect, the thickness of the first electrode layer is 200 μm to 250 μm. It should be understood that when the first electrode layer is too thick, the resistance of the first bipolar plate will increase, which in turn will increase the internal resistance of the flow battery; while when the thickness of the first electrode layer is too thin, the electrochemical active area of ​​the first electrode layer will be too small, making it difficult to effectively improve the battery power.

[0042] Therefore, by using a first electrode layer with a thickness of 200μm~250μm, the resistance of the first bipolar plate is not too high, thus preventing the internal resistance of the flow battery from becoming too high. Furthermore, the electrochemical active area of ​​the first electrode layer can be increased, thereby effectively improving the power of the flow battery.

[0043] In one possible implementation of the first aspect, the first electrode layer includes a first electrode material, the first electrode includes a second electrode material, and both the first electrode material and the second electrode material are carbon-containing materials. Carbon-containing materials possess excellent electrical conductivity, and their abundant defect sites and unsaturated carbon atoms provide more active sites, significantly improving the efficiency of redox reactions of the active substances in the first electrolyte; furthermore, carbon-containing materials have lower costs. Attached Figure Description

[0044] Figure 1 A schematic diagram illustrating the working principle of a flow battery provided for some embodiments of this application;

[0045] Figure 2 This application provides a cross-sectional schematic diagram of a portion of the structure in a flow battery, as shown in some embodiments.

[0046] Figure 3 A schematic diagram of a partial structure of a first bipolar plate provided in some embodiments of this application;

[0047] Figure 4 According to Figure 3 The cross-sectional view of the first bipolar plate shown at the BB line;

[0048] Figure 5 A schematic diagram of a partial structure of a flow channel provided in some embodiments of this application;

[0049] Figure 6 This application provides a schematic diagram of the structure of a retaining post according to some embodiments;

[0050] Figure 7 According to Figure 5 The diagram shows a cross-sectional view of the flow channel at line AA.

[0051] Figure label:

[0052] 100. Flow battery;

[0053] 1. Battery stack; 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;

[0054] 2a. First bipolar plate; 20. First surface; 21. First electrode layer; 22. Flow channel; 221. Channel opening; 222. Channel bottom wall; 223. Channel side wall; 224. First side wall; 225. Second side wall; 23. Baffle; 231. First guide surface; 232. Second guide surface; 2b. Second bipolar plate;

[0055] 30. Flow field structure; 35. First flow channel groove; 36. Second flow channel groove. Detailed Implementation

[0056] 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.

[0057] 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.

[0058] To facilitate understanding, before providing a detailed description of the flow battery in the embodiments of this application, the relevant terms involved in the embodiments of this application will be explained first.

[0059] Electrochemical active area: This is an important parameter for measuring the effective surface area of ​​an electrode material that actually participates in an electrochemical reaction, rather than the geometric or physical surface area of ​​the electrode. The entire surface of an electrode (especially a catalyst) may not be able to participate in the electrochemical reaction.

[0060] Energy efficiency: This is a key indicator that measures the energy utilization efficiency of a battery during charge and discharge cycles. It is determined by both coulombic efficiency and voltage efficiency.

[0061] Power density: This includes mass power density and volume power density. In this application, power density mainly refers to volume power density, which represents the power output capability of a battery per unit volume.

[0062] 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.

[0063] Pressure drop loss: refers to the decrease in pressure caused by energy loss during fluid flow.

[0064] With economic development, the demand for energy is increasing, and the environmental problems caused by the massive consumption of fossil fuels are becoming increasingly prominent. Large-scale utilization of renewable energy and achieving energy diversification have become important strategies for energy security and sustainable development for countries worldwide. However, the discontinuity and instability of renewable energy sources such as wind and solar power make direct utilization difficult. Therefore, utilizing energy storage technology to achieve a continuous supply of renewable energy is key to solving these problems. Flow batteries, due to their flexible design, high safety, and long design life, have become one of the most promising technologies in the large-scale, long-term energy storage market. Flow batteries are not only used for energy storage in renewable energy generation from wind and solar power, but also for emergency power systems, backup power stations, and peak shaving and valley filling in power systems.

[0065] Reference 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. A flow battery typically includes an electrolyte and a battery stack 1. The battery stack 1 converts electrical energy into chemical energy, which is stored in the electrolyte. When needed, the chemical energy in the electrolyte is 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.

[0066] A single battery cell may include an electrode and an ion exchange membrane 17. The electrode can serve as a site for redox reactions of active substances (such as iron ions, chromium ions, vanadium ions, etc.) in the electrolyte. For example, the electrode includes an electrode material containing a catalyst, which can promote the redox reactions of the active substances on the electrode.

[0067] In some embodiments, the electrolyte includes a first electrolyte 130 and a second electrolyte 150, with a first electrode 11 in contact with the first electrolyte 130 and a second electrode 12 in contact with the second electrolyte 150. The electrodes 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.

[0068] 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.

[0069] 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, while the ion exchange membrane 17 can block other ions in the first electrolyte 130 from passing through.

[0070] 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.

[0071] For example, the flow battery 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.

[0072] 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 the 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 to transform into Cr. 2+ When the flow battery 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+ .

[0073] The individual cells of a flow battery may also include bipolar plates, which are typically bonded tightly to the electrodes using a thermo-pressing process. As a key component in a flow battery, the primary purpose of the bipolar plate is to conduct current. Electrons generated by the redox reactions of the active materials on the electrodes 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. Therefore, efficient current collection and conduction are crucial for reducing the internal resistance of the flow battery and improving its energy efficiency and power density. The bipolar plate provides a large-area, highly conductive surface that effectively collects and conducts the current generated at various active sites on the electrodes. For example, the bipolar plate can conduct current to adjacent cells or ultimately to the end plates at both ends of the battery stack.

[0074] Because of the resistance between the bipolar plates and the electrodes, excessive resistance reduces the energy efficiency of flow batteries. Therefore, current optimizations of bipolar plates involve fixing the electrodes to the bipolar plates in the flow battery, reducing the resistance between the electrodes and the bipolar plates, and thus improving the battery's energy efficiency. However, this results in a relatively small electrochemical active area for the electrodes. The electrochemical active area is the effective surface area on the electrode that actually participates in electrochemical redox reactions. The electrochemical active area of ​​the electrode determines the current density of the flow battery, thus affecting its power and energy efficiency.

[0075] In related technologies, increasing the electrode thickness can improve the electrochemical active area of ​​the electrode. However, at the same compression ratio, for an excessively thick electrode, its surface density is high, making it difficult for the electrolyte to penetrate the electrode. This results in greater mass transfer polarization of the electrode, making it difficult to effectively improve the current density of the flow battery. Instead, it increases the resistance of the flow battery, thereby reducing its energy efficiency.

[0076] To solve the above-mentioned technical problems, refer to Figure 1 and Figure 2 , Figure 2 This is a cross-sectional schematic diagram of a partial structure of a flow battery provided in some embodiments of this application. This application proposes a flow battery including a first electrolyte 130 and a first electrode 11. The first electrolyte 130 and the first electrode 11 can be designed with reference to the first electrolyte 130 and the first electrode 11 described above. The flow battery may include a first bipolar plate 2a, which is in contact with the first electrolyte 130. The first electrode 11 is fixed to the first bipolar plate 2a, and the first electrolyte 130 can undergo a redox reaction on the first electrode 11. A first electrode layer 21 is provided on the first bipolar plate 2a, and the first electrolyte 130 can undergo a redox reaction on the first electrode layer 21.

[0077] For example, a portion of the outer surface of the first bipolar plate 2a may be provided with a first electrode layer 21; or, the entire outer surface of the first bipolar plate 2a may be provided with a first electrode layer 21.

[0078] It is understandable that the first electrolyte 130 can undergo redox reactions not only on the first electrode 11 but also on the first electrode layer 21. This increases the number of active sites for redox reactions in the first electrolyte 130 compared to when the redox reaction only occurs on the first electrode 11. This is equivalent to increasing the electrochemical active area of ​​the electrodes in the flow battery, which is beneficial for increasing the power and energy efficiency of the flow battery. Furthermore, the first bipolar plate 2a, with the first electrode layer 21, not only conducts current but also provides a site for redox reactions.

[0079] Furthermore, in this case, the first electrode 11 does not need to be made too thick. Under the same compression ratio, the areal density of the first electrode 11 will not be too high. The first electrolyte 130 can effectively penetrate the first electrode 11, and the first electrolyte 130 can flow to the surface of the first electrode 11 near the first bipolar plate 2a to carry out oxidation-reduction reaction. This is beneficial to reduce the internal resistance of the flow battery and can effectively increase the current density of the flow battery, so as to further increase the power and energy efficiency of the flow battery.

[0080] In some embodiments, the first electrode layer 21 includes a first electrode material, and the first electrode 11 includes a second electrode material. Both the first electrode material and the second electrode material are carbon-containing materials. The first electrode material and the second electrode material can be the same or different. Carbon-containing materials have excellent conductivity, and their abundant defect sites and unsaturated carbon atoms can provide more active sites, significantly improving the efficiency of the redox reaction of active substances in the first electrolyte. Furthermore, carbon-containing materials have lower costs.

[0081] For example, the first electrode material may include at least one of graphite powder, graphite fiber, graphite foil, graphite paper, graphite cloth, carbon felt, carbon cloth, and carbon paper; the second electrode material may include at least one of graphite powder, graphite fiber, graphite foil, graphite paper, graphite cloth, carbon felt, carbon cloth, and carbon paper. Methods for depositing the first electrode layer 21 on the first bipolar plate 2a include, but are not limited to, vapor deposition, liquid deposition, or graphite conductive adhesive bonding.

[0082] In some embodiments, the first bipolar plate 2a may be made of graphite-metal composite material.

[0083] It should be understood, and referenced Figure 1 and Figure 2The flow battery also includes a second electrolyte 150, a second electrode 12, and a second bipolar plate 2b. The second bipolar plate 2b can be designed with reference to the first bipolar plate 2a described above. The relationship between the second electrolyte 150, the second electrode 12, and the second bipolar plate 2b can be referred to the relationship between the first electrolyte 130, the first electrode 11, and the first bipolar plate 2a described above, and will not be repeated here.

[0084] In some embodiments, the thickness D of the first electrode layer 21 is 200 μm to 250 μm, and the thickness D of the first electrode layer 21 can be 200 μm, 210 μm, 215 μm, 225 μm, 230 μm, 235 μm, 240 μm, 245 μm, or 250 μm. It should be understood that when the first electrode layer 21 is too thick, the resistance of the first bipolar plate 2a will increase, which in turn will increase the internal resistance of the flow battery; while when the thickness of the first electrode layer 21 is too thin, the electrochemical active area of ​​the first electrode layer 21 will be too small, making it difficult to effectively improve the battery power.

[0085] Therefore, by having a thickness D of 200μm~250μm for the first electrode layer 21, the resistance of the first bipolar plate 2a is not too high, which in turn prevents the internal resistance of the flow battery from becoming too high. Furthermore, the electrochemical active area of ​​the first electrode layer 21 can be increased, thereby effectively improving the power of the flow battery.

[0086] An electrochemical test experiment can be conducted on the flow battery to verify the effect of setting a first electrode layer 21 of different thicknesses on the power and energy efficiency of the flow battery.

[0087] In some embodiments, the flow battery being tested is an iron-chromium flow battery, and is a single cell; the ion exchange membrane 17 is a perfluorosulfonic acid proton exchange membrane (Nafion™ NR212); the second electrode material is carbon felt, and the first electrode material is carbon paper; the electrolyte includes ferrous chloride (FeCl₂) with a molar concentration of 1 mol / L. 2 ), chromium trichloride (CrCl) with a molar concentration of 1 mol / L 3 The test parameters included: a test temperature of 65℃ and an electrode area of ​​7.1 × 7.1 cm². The test also included dilute hydrochloric acid (HCl) with a molar concentration of 3 mol / L. 2 The charging and discharging current density is 100 mA / cm². 2 The charge / discharge cutoff voltage is 0.8V~1.2V.

[0088] Electrochemical testing experiment one can include multiple embodiments. In these embodiments, the arrangement of the first electrode layer 21 on the first bipolar plate 2a differs, as does the thickness of the first electrode layer 21, which is typically within the range of 200 μm to 250 μm. Electrochemical testing experiment one can also include multiple comparative examples. In these comparative examples, the arrangement of the first electrode layer 21 on the first bipolar plate 2a differs, as does the thickness of the first electrode layer 21, which is typically not within the range of 200 μm to 250 μm.

[0089] The parameters of the first bipolar plate 2a in multiple embodiments and comparative examples are shown in Table 1.1, and the test results of the battery performance in multiple embodiments and comparative examples are shown in Table 1.2.

[0090] Table 1.1 Parameters of the first bipolar plate

[0091]

[0092] Table 1.2 Electrochemical test results of flow batteries

[0093]

[0094] As can be seen from Tables 1.1 and 1.2, in Comparative Example 1, the first bipolar plate 2a does not have a first electrode layer 21, and the flow battery of Comparative Example 1 has a power of 3.45W and an energy efficiency of 78.06%. Compared to Comparative Example 1, the flow batteries of Examples 1 to 5 all have a power greater than 3.6W and an energy efficiency greater than 78.4%, which are significantly higher than the power and energy efficiency of the flow battery of Comparative Example 1. This is because the first bipolar plate 2a of Examples 1 to 5 has a first electrode layer 21, resulting in a larger electrochemical active area within the flow battery, thus leading to higher power and energy efficiency.

[0095] Although Comparative Example 2 has a first electrode layer 21 on the bipolar plate, the thickness of the first electrode layer 21 is only 150 μm. The electrochemical active area provided by the first electrode layer 21 is limited, which has a limited effect on improving the power and energy efficiency of the flow battery. Its power is only 3.50 W and its energy efficiency is 78.05%. In Comparative Example 3, the thickness of the first electrode layer 21 is 270 μm, which ensures that it can provide sufficient electrochemical active area. However, the thickness of the first electrode layer 21 is too thick, and the first electrolyte 130 has difficulty penetrating the first electrode layer 21. This results in fewer sites on the surface of the first electrode layer 21 near the first bipolar plate 2a where redox reactions can occur, leading to increased mass transfer polarization in the flow battery. Ultimately, this leads to a decrease in the power and energy efficiency of the flow battery, with a power of only 3.62 W and an energy efficiency of 77.01%.

[0096] Therefore, in summary, when multiple battery cells have the same volume, the battery cell with the first electrode layer 21 disposed on the first bipolar plate 2a exhibits a significantly increased electrochemical active area and a significantly increased battery power, with the area of ​​the first electrode 11 being 7.1 × 7.1 cm². 2 In this case, compared to a battery cell that does not have a first electrode layer 21 on the first bipolar plate 2a, the power of a battery cell with a first electrode layer 21 on the first bipolar plate 2a can be increased by 5% to 10%.

[0097] By using a first electrode layer 21 with a thickness ranging from 200 μm to 250 μm, the flow battery can maintain high energy efficiency while increasing battery power. Furthermore, as can be seen from Embodiments 1 to 5, the arrangement of the first electrode layer 21 on the first bipolar plate 2a has no significant impact on the power and energy efficiency of the flow battery.

[0098] Reference Figure 3 and Figure 4 , Figure 3 A schematic diagram of a partial structure of a first bipolar plate provided in some embodiments of this application; Figure 4 According to Figure 3 The diagram shows a cross-sectional view of the first bipolar plate at the BB line. In some embodiments, the first bipolar plate 2a is provided with a flow field structure 30, which may include a flow channel 22 for supplying the first electrolyte 130 for flow. This allows the first bipolar plate 2a to conduct electrolyte in addition to conducting current. The flow channel 22 has a channel opening 221, a bottom wall 222, and a side wall 223, with the channel opening 221 and the bottom wall 222 facing each other. The bottom wall 222 is provided with a first electrode layer 21; or, the side wall 223 is provided with a first electrode layer 21; or, both the bottom wall 222 and the side wall 223 are provided with a first electrode layer 21. This increases the electrochemical active area of ​​the first electrode layer 21, which is more conducive to increasing the power and energy efficiency of the flow battery.

[0099] The first bipolar plate 2a has a first surface 20, and a flow channel 22 can be disposed on the first surface 20. The first electrode 11 is fixed on the first surface and covers the opening 221 of the channel. In this way, the first electrolyte 130 flowing in the flow channel 22 can not only undergo an oxidation-reduction reaction on the first electrode layer 21 on the inner wall of the flow channel 22, but also undergo an oxidation-reduction reaction on the first electrode 11, making the reaction more complete.

[0100] The flow field structure 30 may include at least one of the following: a through-flow field, a parallel flow field, a serpentine flow field, and an interdigitated flow field. For ease of explanation, the following description uses an interdigitated flow field as an example of the flow field structure 30, but this should not be construed as a limitation of this application.

[0101] Reference Figure 3 and Figure 4 In some embodiments, the flow field structure 30 includes an inflow channel, an outflow channel, an inlet, and an outlet. The inflow channel is connected to the inlet, and the outflow channel is connected to the outlet. The inflow channel may include a plurality of first flow channel grooves 35 arranged at intervals along a first direction, and the outflow channel may include a plurality of second flow channel grooves 36 arranged at intervals along the first direction S1. The plurality of first flow channel grooves 35 and the plurality of second flow channel grooves 36 are arranged alternately along the first direction S1, and the flow directions of the first electrolyte in the first flow channel grooves 35 and the second flow channel grooves 36 are different. The aforementioned flow channel groove 22 includes the first flow channel groove 35 and the second flow channel groove 36.

[0102] When the flow battery is working, the first electrolyte 130 can enter the inflow channel from the inlet, and the first electrolyte 130 in the inflow channel can pass through the first electrode 11 and enter the outflow channel, and then flow out through the outlet.

[0103] In other words, the interdigitated flow channel forces the first electrolyte 130 to penetrate the first electrode 11 along its thickness direction, significantly overcoming the high flow resistance problem caused by relying solely on self-permeability. This enhances the mass transfer between the first electrolyte 130 and the first electrode 11, allowing the first electrolyte 130 to react fully on the first electrode 11, thus improving the power and energy efficiency of the flow battery. Furthermore, it also enhances the mass transfer between the first electrolyte 130 and the first electrode layer 21, further improving the power and energy efficiency of the flow battery.

[0104] It is understandable that during the flow of the first electrolyte 130 in the flow channel 22, the concentration of active material in the first electrolyte 130 will gradually decrease due to the consumption of the reaction. This can easily lead to uneven concentration of the first electrolyte 130 in the flow direction, and the amount of active material flowing through a specific position per unit time will be different. Therefore, the current generated when the first electrolyte 130 undergoes oxidation-reduction reaction at different positions in the flow channel 22 will be different, which will naturally affect the power and energy efficiency of the flow battery.

[0105] Reference Figure 1 and Figure 2 In some embodiments, the cross-sectional area of ​​the flow channel 22 gradually decreases along the flow direction of the first electrolyte 130, which allows the flow rate of the first electrolyte 130 to gradually increase. Although the concentration of active material in the first electrolyte 130 naturally decreases due to reaction consumption during the flow process, the gradual increase in the flow rate of the first electrolyte 130 ensures that the total amount of active material contained in the first electrolyte 130 flowing through each location per unit time is not significantly different. This can offset the effect of the decrease in the concentration of active material in the first electrolyte 130, and help increase the power and energy density of the flow battery.

[0106] In addition, the faster flow rate of the first electrolyte 130 makes it easier for the first electrolyte 130 to penetrate the first electrode 11, allowing the active materials in the first electrolyte 130 to react fully. Furthermore, in the interdigitated flow field, the first electrolyte 130 flowing into the channel can enter the outflow channel after penetrating the first electrode 11, which increases the flow rate of the first electrolyte 130 in the outflow channel, further enhancing the power and energy density of the flow battery.

[0107] It should be noted that the cross-section of the flow channel 22 refers to the surface cut by a plane perpendicular to the length direction of the flow channel 22 on the flow channel 22.

[0108] Reference Figure 3 and Figure 4 In some embodiments, the bottom wall 222 of the tank extends at an angle toward the opening 221 in the flow direction of the first electrolyte 130. This allows the cross-sectional area of ​​the flow channel 22 to gradually decrease along the flow direction of the first electrolyte 130, thereby ensuring the power and energy density of the flow battery.

[0109] A plane perpendicular to the arrangement direction of the bottom wall 222 and the opening 221 of the groove can be defined as a first reference plane. The bottom wall 222 and the first reference plane have a first included angle, which is 1.5° to 2°. For example, the first included angle can be 1.5°, 1.6°, 1.7°, 1.8°, 1.9° or 2°.

[0110] It should be noted that when the first included angle is too large, i.e., the angle at which the bottom wall 222 of the tank tilts too much towards the tank opening 221, it may cause a sharp increase in the flow velocity of the first electrolyte 130 in the flow channel 22 and flow instability. This can lead to a rapid increase in flow velocity over a short distance, resulting in excessive pressure drop and consequently unstable flow rate. Furthermore, in areas with excessively high flow velocities, the residence time of the first electrolyte 130 may be too short, causing the active material to be discharged before it has fully reacted. Moreover, excessively high flow velocities exacerbate the erosion of the inner wall of the flow channel 22, the first electrode layer 21, and the first electrode 11, making the flow channel 22 more susceptible to damage and shortening the lifespan of the first electrode layer 21 and the first electrode 11.

[0111] When the first included angle is too small, that is, the angle at which the bottom wall 222 of the tank tilts towards the tank opening 221 is too small, the flow rate compensation is insufficient. The flow rate of the first electrolyte 130 increases slowly and cannot effectively offset the decrease in the concentration of the active material along the flow path, resulting in an excessively low concentration of the active material in the later section of the flow channel 22. The excessively low flow rate of the first electrolyte 130 may also cause the first electrolyte 130 to stagnate at the end of the flow channel 22, resulting in significant concentration polarization and a decrease in the voltage efficiency of the flow battery.

[0112] Therefore, by controlling the first included angle between 1.5° and 2°, on the one hand, the instability of the first electrolyte 130 caused by an excessively large first included angle and the aggravation of the scouring of the flow channel 22 can be avoided; on the other hand, the insufficient concentration compensation caused by an excessively small first included angle can be avoided, the reaction uniformity of the active material is comprehensively improved, concentration polarization is effectively reduced, and it helps to achieve a longer lifespan and improve the operational reliability of the flow battery.

[0113] Reference Figure 4 In some embodiments, the size of the flow channel 22 is 0.1mm to 0.2mm in the arrangement direction of the bottom wall 222 and the opening 221. For example, the size of the flow channel 22 can be 0.1mm, 0.12mm, 0.14mm, 0.16mm, 0.18mm or 0.2mm.

[0114] It should be understood that the dimension of the flow channel 22 in the direction of its arrangement with the bottom wall 222 and the opening 221 refers to the depth of the flow channel 22. When the depth of the flow channel 22 is too small, it will cause the first electrolyte 130 to have difficulty flowing in the flow channel 22; when the depth of the flow channel 22 is too large, it is easy for the flow channel 22 to penetrate the opposite two sides of the first bipolar plate 2a, making it difficult to ensure the normal function of the flow channel 22, and affecting the structural strength of the first bipolar plate 2a.

[0115] The depth of the flow channel 22 is 0.1mm~0.2mm, which can ensure the normal flow of the first electrolyte 130 in the flow channel 22 and also ensure the structural strength of the first bipolar plate 2a.

[0116] Reference Figure 5 , Figure 5 This is a schematic diagram of a partial structure of a flow channel provided in some embodiments of this application; in some embodiments, the channel sidewall 223 includes a first sidewall 224 and a second sidewall 225, which are opposite to each other in a first direction S1; in the flow direction of the first electrolyte 130, the first sidewall 224 extends obliquely toward the direction close to the second sidewall 225, so that the cross-sectional area of ​​the flow channel 22 gradually decreases along the flow direction of the first electrolyte 130, thereby ensuring the power and energy density of the flow battery.

[0117] The plane perpendicular to the first direction S1 is defined as the second reference plane. The first sidewall 224 and the second reference plane have a second included angle, which is 1.5° to 2°. For example, the second included angle can be 1.5°, 1.6°, 1.7°, 1.8°, 1.9° or 2°.

[0118] In the flow direction of the first electrolyte 130, the second sidewall 225 extends toward the direction close to the first sidewall 224. This also allows the cross-sectional area of ​​the flow channel 22 to gradually decrease along the flow direction of the first electrolyte 130, thereby ensuring the power and energy density of the flow battery.

[0119] The second sidewall 225 has a third included angle with the second reference surface, which is 1.5° to 2°. For example, the third included angle can be 1.5°, 1.6°, 1.7°, 1.8°, 1.9° or 2°.

[0120] It is understandable that when the second angle is too large or too small, the effects on the first electrolyte 130, the flow channel 22, the first electrode layer 21, and the first electrode 11 can be referenced to the effects caused by the first angle being too large or too small, as described above, and will not be repeated here. Therefore, by setting the second angle to 1.5°~2°, on the one hand, the flow instability of the first electrolyte 130 and the aggravated scouring of the flow channel 22 caused by the second angle being too large can be avoided; on the other hand, insufficient concentration compensation caused by the second angle being too small can be avoided, the reaction uniformity of the active material can be comprehensively improved, concentration polarization can be effectively reduced, and it can help to achieve a longer lifespan and improve the operational reliability of the flow battery.

[0121] When the third included angle is too large or too small, the effects on the first electrolyte 130, the flow channel 22, the first electrode layer 21, and the first electrode 11 can be referenced to the effects caused by the first included angle being too large or too small, as described above, and will not be repeated here. Therefore, by setting the third included angle to 1.5°~2°, on the one hand, the flow instability of the first electrolyte 130 and the aggravated scouring of the flow channel 22 caused by the third included angle being too large can be avoided; on the other hand, insufficient concentration compensation caused by the third included angle being too small can be avoided, the reaction uniformity of the active material can be comprehensively improved, concentration polarization can be effectively reduced, and it can help to achieve a longer lifespan and improve the operational reliability of the flow battery.

[0122] In summary, by controlling at least one of the first included angle, the second included angle, and the third included angle within the range of 1.5° to 2°, the cross-sectional area of ​​the flow channel 22 can be gradually reduced along the flow direction of the first electrolyte 130, which helps to increase the power density and energy efficiency of the flow battery.

[0123] For example, the cross-sectional shape of the flow channel 22 can be rectangular, making the flow channel 22 easier to manufacture. Of course, in other embodiments, the cross-sectional shape of the flow channel 22 can also be trapezoidal, circular, or other shapes, and this application does not limit this.

[0124] Electrochemical test experiment two can be conducted on the flow battery to verify the effects of the first, second, and third included angles on the power and energy efficiency of the flow battery. The test method and parameters for electrochemical test experiment two can be designed with reference to electrochemical test experiment one for the flow battery in the above embodiments.

[0125] The test experiment can set up multiple embodiments and multiple comparative examples. In all embodiments and comparative examples, the first bipolar plate 2a is the same as the first bipolar plate 2a in Embodiment 1. The angles of the first included angle, the second included angle, and the third included angle are shown in Table 2.1. The test results of the battery performance in the multiple embodiments and multiple comparative examples are shown in Table 2.2.

[0126] Table 2.1 Angles of the first, second, and third included angles

[0127]

[0128] Table 2.2 Electrochemical test results of flow batteries

[0129]

[0130] As can be seen from Examples 6, 7 and 8 in Tables 2.1 and 2.2, when the first included angle, the second included angle and the third included angle are all between 1.5° and 2.0°, the total amount of active material flowing through each position of the flow channel 22 per unit time can be increased, thereby offsetting the effect of concentration decrease, and thus making the energy efficiency of the flow battery greater than or equal to 80%.

[0131] Because the flow channel 22 of the first bipolar plate 2a in Comparative Example 4 was not sloped (the first, second, and third included angles were all 0), the flow battery may have severe concentration polarization. Therefore, the flow battery had the lowest energy efficiency, only 78.1%. In Comparative Example 5, the first, second, and third included angles were smaller, and the velocity increase of the first electrolyte 130 in the flow channel 22 along the flow direction was smaller. Therefore, some concentration polarization still existed.

[0132] In Comparative Example 6, the excessively large first, second, and third included angles led to a surge in flow velocity and flow instability, causing a sharp increase in the flow velocity of the first electrolyte 130. This negatively impacted the battery's power and energy efficiency, resulting in lower energy efficiency compared to Examples 6 to 8. In Comparative Examples 7 and 8, although the first included angle was 1.50°, the excessively large second and third included angles (2.9°) caused the first electrolyte 130 to counteract within the flow channel 22, resulting in a loss of mass transfer energy and increased battery voltage drop. Under the premise that the power of the first drive pump 14 remained unchanged, the performance of the battery cell decreased. In Comparative Example 8, the excessively small second and third included angles resulted in insufficient increase in the flow velocity of the first electrolyte 130, failing to achieve a relatively uniform distribution of the total amount of active material. Consequently, the performance improvement of the battery cell was minimal, resulting in lower battery power and energy efficiency.

[0133] Similarly, although the second and third included angles of Comparative Examples 9 and 10 are 1.5°, the first included angle of Comparative Example 9 is too small, resulting in a dead zone for mass transfer of the first electrolyte 130 inside the flow channel 22. The pressure of the first electrolyte 130 entering the first electrode 11 on the bottom wall is relatively small, resulting in a small improvement in the performance of the battery cell. The first included angle of Comparative Example 10 is too large, causing the bottom wall of the tank to impede the flow of the first electrolyte 130 to a certain extent, increasing the scouring of the first electrode layer 21 by the first electrolyte 130, increasing the pressure drop of the battery cell, and under the premise that the power of the first drive pump 14 remains unchanged, the performance of the battery cell decreases, that is, the battery power and energy efficiency are low.

[0134] As can be seen from Comparative Examples 7 to 10, there is a synergistic relationship between the first included angle, the second included angle, and the third included angle. When all three are within 1.5° to 2.0°, it can increase the electrolytic pressure difference between adjacent flow channel 22, make the reactive substances evenly distributed, increase the convective mass transfer of the electrolyte, and achieve excellent energy efficiency with a small pressure drop.

[0135] Reference Figure 6 and Figure 7 , Figure 6 This application provides a schematic diagram of the structure of a retaining post according to some embodiments; Figure 7 According to Figure 5 The diagram shows a cross-sectional view of the flow channel 22 at line AA. In some embodiments, a baffle 23 is provided inside the flow channel 22, and the baffle 23 is located on the bottom wall 222 of the channel. The extending direction of the baffle 23 forms a fourth angle with the flow direction of the first electrolyte 130, and the fourth angle is 5° to 90°. For example, the fourth angle can be 5°, 30°, 35°, 45°, 50°, 60°, 70°, 80°, or 90°.

[0136] The baffle 23 may be spaced apart from at least one of the first sidewall and the second sidewall, and the baffle 23 may also be in contact with the first sidewall and the second sidewall. The baffle 23 is spaced apart from the first electrode 11 to allow the first electrolyte 130 to flow between the baffle 23 and the first electrode 11.

[0137] It should be understood that when fluid flows within a channel, the flow velocity is highest in the central region of the channel, while the flow velocity near the channel wall is extremely low due to fluid viscosity. Therefore, when the first electrolyte 130 flows within the channel tank 22, the flow velocity of the first electrolyte in the central region of the channel tank 22 is higher, while the flow velocity of the first electrolyte near the bottom wall 222 and the side wall 223 is very low, forming a velocity gradient. The first electrolyte 130 only undergoes mass transfer through diffusion between the first electrode 11 and the first electrode layer 21, resulting in a slow mass transfer rate and high mass transfer polarization. The concentration of the first electrolyte 130 near the bottom wall 222 and the side wall 223 is lower, affecting the efficiency of the redox reaction of the active substances in the first electrolyte 130 on the first electrode 11 and the first electrode layer 21.

[0138] It should be noted that the central region of the flow channel refers to the area far from the flow channel wall.

[0139] Reference Figure 6 and Figure 7 In some embodiments, the baffle 23 has a first guide surface 231 and a second guide surface 232, which are arranged sequentially in the flow direction of the first electrolyte 130. In the direction from the first guide surface 231 to the second guide surface 232, the first guide surface 231 extends obliquely toward the direction close to the tank opening, and the second guide surface 232 extends obliquely toward the direction close to the bottom wall 222 of the tank.

[0140] On the one hand, the first guide surface 231 and the second guide surface 232 guide the flow direction of the first electrolyte 130 within the flow channel 22. On the other hand, the first guide surface 231 can act as a frontal surface, and the second guide surface 232 can act as a backal surface. The frontal surface forces the fluid to accelerate around the obstacle (i.e., the baffle 23), while the backal surface forms flow separation due to the adverse pressure gradient, generating vortices. These vortices change the mainstream direction, causing the local flow direction to deviate from its original path, thus changing laminar flow to turbulent flow. In particular, the enhanced turbulence on the side of the second guide surface 232 away from the first guide surface 231 promotes the mixing of the first electrolyte 130 in the central region of the flow channel and near the bottom wall 222 and side wall 223 of the channel. This results in a uniform concentration of active substances in the mixed first electrolyte 130, thereby increasing convective mass transfer and enhancing the mass transfer of the first electrolyte 130.

[0141] For example, the angle between the extension direction of the baffle 23 and the arrangement direction of the first guide surface 231 and the second guide surface 232 is 5° to 90° (e.g., 5°, 15°, 30°, 45°, 50°, 60°, 80° or 90°).

[0142] Reference Figure 6 and Figure 7 In some embodiments, the cross-sectional shape of the baffle 23 can be triangular, or the baffle 23 can be a triangular prism. For example, the cross-sectional shape of the baffle 23 can be an isosceles triangle, with the base of the isosceles triangle parallel to the flow direction of the first electrolyte 130. In other embodiments, the cross-sectional shape of the baffle 23 can also be trapezoidal.

[0143] When the first electrolyte 130 flows to the first guide surface 231, the edges of the triangular prism away from the bottom wall 222 of the tank can force the fluid to separate instantly, causing the first electrolyte 130 to generate strong acceleration to form a low-pressure core. The low-pressure core will entrain the fluid behind it, forming a high-intensity vortex, which will entrain the first electrolyte 130 in the middle area of ​​the flow channel 22 to the wall of the flow channel 22 and the surface of the first electrode, and throw the first electrolyte 130 near the wall of the flow channel 22 away from the surface of the first electrode layer, and also throw the first electrolyte near the first electrode away from the surface of the first electrode, further increasing the convective mass transfer, thereby strengthening the mass transfer of the first electrolyte 130.

[0144] It should be noted that in the embodiments of this application, "front" or "rear" refers to the direction of flow of the first electrolyte.

[0145] Reference Figure 7 In some embodiments, the included angle α between the first guide surface 231 and the second guide surface 232 is 30°~40°. For example, the included angle α between the first guide surface 231 and the second guide surface 232 can be 30°, 31°, 32°, 33°, 34°, 35°, 36°, 37°, 38°, 39° or 40°.

[0146] For example, when the cross-sectional shape of the stop post 23 is an isosceles triangle, the vertex angle α of the isosceles triangle is 30°~40°.

[0147] It should be noted that when the angle α between the first guide surface 231 and the second guide surface 232 is too large, the resulting vortex is too weak. Conversely, when the angle between the first guide surface 231 and the second guide surface 232 is too small, it may cause the first electrolyte 130 to flow in stratification, and a backflow dead zone to form on the side of the second guide surface 232 facing away from the first guide surface 231. The concentration of active material in the first electrolyte 130 is low in the backflow dead zone, resulting in low efficiency of redox reactions on the first electrode 11 and the first electrode layer 21. Furthermore, when the first electrolyte 130 passes through the baffle 23, it consumes a large amount of energy, resulting in a significant pressure drop.

[0148] By setting the angle between the first guide surface 231 and the second guide surface 232 to 30°~40°, it can be ensured that the first electrolyte 130 forms a high vortex in the flow channel 22, which promotes the uniform mixing of active materials and avoids the formation of backflow dead zone in the flow channel 22, reducing the energy consumed by the first electrolyte 130 when passing through the baffle 23 and reducing pressure drop loss.

[0149] Reference Figure 6 and Figure 7 In some embodiments, the dimension H of the baffle 23 protruding from the bottom wall 222 of the channel is 100μm to 150μm. For example, the dimension H of the baffle 23 protruding from the bottom wall 222 of the channel can be 100μm, 110μm, 120μm, 125μm, 130μm, 140μm, or 150μm. If the dimension of the baffle 23 protruding from the bottom wall 222 of the channel is too small, the disturbance will be limited to the vicinity of the baffle 23, and the vortex intensity will be insufficient; while if the dimension H of the baffle 23 protruding from the bottom wall 222 of the channel is too large, it will easily block the flow channel, increase the pressure drop, and cause a large energy loss.

[0150] Therefore, by having the baffle 23 protrude from the bottom wall 222 of the tank with a size H of 100μm~150μm, a high vortex is formed in the flow channel 22, which promotes uniform mixing of active materials. At the same time, the baffle 23 can also prevent the flow channel from being blocked, reduce the energy consumed by the first electrolyte 130 when passing through the baffle 23, and reduce the pressure drop loss.

[0151] In some embodiments, the extension length L of the baffle 23 can be 3 to 5 times the dimension H of the baffle 23 protruding from the bottom wall 222 of the groove, that is, the extension length L of the baffle 23 is 300μm to 750μm. For example, the extension length L of the baffle 23 can be 300μm, 350μm, 400μm, 500μm, 520μm, 600μm, 700μm or 750μm.

[0152] It should be noted that if the extension length of the baffle 23 is too small, the scale of the vortex generated by the first electrolyte 130 in the flow channel 22 is small and the vortex coverage is insufficient; if the side length is too large, it will cause the flow separation zone to expand, forming a backflow dead zone on the side of the second guide surface 232 opposite to the first guide surface 231, and causing the pressure drop to increase sharply and the power consumption of the first drive pump 14 to be large.

[0153] By controlling the extension length of the baffle 23 within the range of 300μm to 750μm, a large vortex is formed in the flow channel 22 to promote uniform mixing of active materials. At the same time, a backflow dead zone is avoided on the side of the second guide surface 232 facing away from the first guide surface 231, reducing pressure drop and lowering the power consumption of the first drive pump 14.

[0154] In some embodiments, the baffles 23 are a plurality of baffles spaced apart along the flow direction of the first electrolyte 130. It should be noted that "a plurality of baffles" in the embodiments of this application refers to two or more.

[0155] The spacing between two adjacent stop posts 23 is 1mm to 2mm. For example, the spacing between two adjacent stop posts 23 can be 1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm or 2mm.

[0156] It should be understood that if the distance between two adjacent baffles 23 is too small, the baffles 23 will be too densely packed in the flow channel 22, which will cause adjacent vortices to interfere with each other and consume energy. If the distance between two adjacent baffles 23 is too large, the distance between two adjacent vortices will be too large, the mass transfer enhancement will be interrupted, and when the vortex decays, the inner wall of the flow channel 22 will return to the low-speed boundary layer and will not be able to enhance the convective mass transfer.

[0157] Therefore, by setting the distance between two adjacent baffles 23 to 1mm~2mm, it is possible to avoid the baffles 23 being set too densely in the flow channel 22, thereby reducing the possibility of mutual interference and energy loss between two adjacent vortices; and it is also possible to avoid the interruption of mass transfer enhancement caused by a large distance between two adjacent vortices, thereby enhancing convective mass transfer.

[0158] Electrochemical test experiment three can be performed on the flow battery to verify the influence of the parameters of the baffle 23 on the power and energy efficiency of the flow battery. The test method and parameters of electrochemical test experiment three can be designed with reference to electrochemical test experiment one of the flow battery in the above embodiments.

[0159] Electrochemical test experiment three can set up multiple embodiments and multiple comparative examples. In multiple embodiments and multiple comparative examples, the first bipolar plate 2a is the first bipolar plate 2a in embodiment six. In multiple embodiments and multiple comparative examples, the cross-sectional shape of the baffle 23 is an isosceles triangle. Then, the included angle between the first guide surface 231 and the second guide surface 232 is equal to the vertex angle of the isosceles triangle. The size of the baffle 23 protruding from the bottom wall 222 of the tank is equal to the height of the isosceles triangle.

[0160] The specific parameters of the baffle 23 are shown in Table 3.1, and the test results of the battery performance in multiple embodiments and comparative examples are shown in Table 3.2.

[0161] Table 3.1 Parameters of the retaining column

[0162]

[0163] Table 3.2 Electrochemical test results of flow batteries

[0164]

[0165] Referring to Examples 9 to 12 in Tables 3.1 and 3.2, it can be seen that by setting baffles 23 in the flow channel 22, and the baffles 23 simultaneously satisfying the following conditions: the included angle between the first guide surface 231 and the second guide surface 232 is 30°~40°; the size of the baffles 23 protruding from the bottom wall 222 of the channel is 100μm~150μm; the extension length of the baffles 23 is 300μm~750μm; and the distance between two adjacent baffles 23 is 1mm~2mm. This can enhance the mass transfer between the first electrolyte 130 and the first electrode 11, thereby further improving the energy efficiency of the flow battery, and the energy efficiency of the flow battery is greater than or equal to 81%.

[0166] In Comparative Example 11, the baffle 23 has an excessively large angle between the first guide surface 231 and the second guide surface 232, resulting in a weak vortex. Additionally, the baffle 23 protruding too small from the bottom wall 222 of the tank also results in a weak vortex. The combination of these two factors leads to weak mass transfer between the first electrolyte 130 and the first electrode layer 21. Therefore, the energy efficiency of the flow battery in Comparative Example 11 is only 80.7%.

[0167] In Comparative Example 12, the baffle 23 causes flow stratification due to the small angle between the first guide surface 231 and the second guide surface 232, resulting in a backflow dead zone on the side of the second guide surface 232 facing away from the first guide surface 231. Furthermore, the baffle 23 protrudes too much from the bottom wall 222 of the tank, causing the baffle 23 to block the flow channel. Both of these factors significantly increase the pressure drop of the first electrolyte 130, affecting the energy efficiency of the flow battery, which is only 79.2%.

[0168] In Comparative Example 13, the size of the baffle 23 protruding from the bottom wall 222 of the tank is too small, resulting in insufficient vortex strength. Furthermore, the distance between two adjacent baffles 23 in Comparative Example 13 is too large, which fails to enhance the mass transfer between the first electrolyte 130 and the first electrode 11 and the first electrode layer 21. Both of these factors lead to a low energy efficiency of the flow battery, with an energy efficiency of only 79.5%.

[0169] 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.

[0170] 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 flow battery, characterized in that, include: First electrolyte; The first bipolar plate is in contact with the first electrolyte. The first bipolar plate is provided with a first electrode layer. The first electrolyte can undergo an oxidation-reduction reaction on the first electrode layer. The first bipolar plate has a first surface, and the first surface is provided with a flow channel groove for the first electrolyte to flow through; the flow channel groove has a groove opening, a groove bottom wall and a groove side wall, the groove opening and the groove bottom wall are opposite to each other, and the groove bottom wall and / or the groove side wall are provided with the first electrode layer; The first electrode is in contact with the first electrolyte, and the first electrolyte can undergo an oxidation-reduction reaction on the first electrode; the first electrode is fixed to the first surface and covers the groove opening; The flow channel is provided with baffles, and the baffles are located on the bottom wall of the channel; The baffle has a first guide surface and a second guide surface, which are arranged sequentially in the flow direction of the first electrolyte. In the direction from the first guide surface to the second guide surface, the first guide surface extends obliquely toward the direction close to the opening of the tank, and the second guide surface extends obliquely toward the direction close to the bottom wall of the tank.

2. The flow battery according to claim 1, characterized in that, Along the flow direction of the first electrolyte, the cross-sectional area of ​​the flow channel gradually decreases.

3. The flow battery according to claim 2, characterized in that, In the flow direction of the first electrolyte, the bottom wall of the tank extends at an angle toward the tank opening.

4. The flow battery according to claim 3, characterized in that, The bottom wall of the groove has a first included angle with the first reference surface, the first reference surface is perpendicular to the arrangement direction of the bottom wall of the groove and the groove opening, and the first included angle is 1.5°~2°; and / or, in the arrangement direction of the bottom wall of the groove and the groove opening, the size of the flow channel groove is 0.1mm~0.2mm.

5. The flow battery according to any one of claims 2-4, characterized in that, The groove sidewall includes a first sidewall and a second sidewall, which are opposite to each other in a first direction; In the flow direction of the first electrolyte, the first sidewall extends obliquely toward the direction close to the second sidewall; and / or, in the flow direction of the first electrolyte, the second sidewall extends toward the direction close to the first sidewall.

6. The flow battery according to any one of claims 1-4, characterized in that, The stop post satisfies at least one of the following conditions: (1) The cross-sectional shape of the retaining post is triangular; (2) The included angle between the first guide surface and the second guide surface is 30°~40°; (3) The size of the baffle protruding from the bottom wall of the groove is 100μm~150μm; (4) The extension length of the stop post is 300μm~750μm; (5) The baffles are a plurality of them arranged at intervals along the flow direction of the first electrolyte, and the distance between two adjacent baffles is 1mm to 2mm.

7. The flow battery according to claim 1, characterized in that, The thickness of the first electrode layer is 200μm~250μm; and / or, the first electrode layer includes a first electrode material, the first electrode includes a second electrode material, and both the first electrode material and the second electrode material are carbon-containing materials.

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