Bionic monocotyledonous plant flow field structure added with circular flow guide block

Abstract

The invention discloses a bionic monocotyledon flow field structure added with a circular flow guide block, which is applied to a vanadium redox flow battery. The circular flow guide block is arranged in the main channel, a plant vein branch structure is simulated, an electrolyte is guided to uniformly flow into a branch flow channel, the distribution of active substances is improved, concentration polarization is reduced, and the energy efficiency and stability of the battery are improved. Experiments show that compared with a traditional flow field, the energy efficiency is improved by 1.983%, the coulombic efficiency is kept about 97.6%, the problem of uneven flow of the electrolyte is effectively solved, and the method is suitable for large-scale energy storage.

Description

Technical field

[0001] The present invention relates to the technical field of energy storage, and in particular to a bionic monocot flow field structure with circular guide blocks added thereto. [Background Technology]

[0002] The use of renewable energy sources such as wind and solar power is growing rapidly. However, due to the randomness and intermittency of these energy sources, their power generation quality is difficult to maintain stable, resulting in greater scheduling and energy storage challenges for the power system. Vanadium redox flow battery (VRFB), as a battery technology that can be used for large-scale, long-term energy storage, has attracted widespread attention due to its good cycle life and efficient energy conversion. However, in practical applications, especially in large-scale energy storage, VRFB still faces several technical bottlenecks, among which the impact of flow field design on battery performance is particularly prominent.

[0003] The existing flow field design mainly adopts structures such as serpentine flow channels, cross flow channels, and double-sided staggered flow channels. Although these designs have improved the fluidity of the electrolyte to a certain extent, there are still obvious problems. For example, in the flow field design, due to the uneven flow of the electrolyte, the concentration polarization phenomenon of the electrolyte between the central main channel and the branch flow channel occurs, which in turn affects the electrochemical reaction efficiency of the battery and the cycle performance of the battery. This problem becomes more prominent especially when the battery is working at a high load, and the energy conversion efficiency of the battery is greatly reduced. In addition, the flow of the electrolyte also requires a certain pressure to maintain continuous flow, which increases the pumping power of the battery system and further leads to energy loss.

[0004] Current research has proposed some flow field optimization schemes. For example, Zeng et al. published a paper titled "A hierarchical interdigitated flow field design for scale-up of high-performance redox flow batteries" in Applied Energy in 2019, which proposed a double-sided staggered flow field, which enhanced the mass transfer behavior of the electrolyte and improved the system efficiency and power output; Guo et al. published a paper titled "A bifurcate interdigitated flow field with high performance but significantly reduced pumping work for scale-up of redox flow batteries" in Journal of Power Sources in 2023, which proposed a bifurcated staggered flow field, which reduced the pumping loss and improved the distribution uniformity of the electrolyte by diverting the electrolyte and guiding it into the branch flow channel; Zhao et al. published a paper titled "A convection-enhanced flow field with height-changing ribs for redox flow batteries" in Chemical Engineering Journal in 2024. The "flowbatteries" paper proposes a design that significantly reduces concentration polarization by improving the flow field on the electrode surface, thereby increasing the battery's discharge capacity and power density. Although these designs alleviate the problem of uneven flow field to some extent, they still cannot completely eliminate the negative impact of concentration polarization. Furthermore, at high flow rates and high current densities, the system's energy efficiency still has room for improvement.

[0005] Bioinspired design has emerged as a new direction in flow field optimization research in recent years. In nature, the nutrient transport structure of plant leaf veins provides valuable insights for achieving uniform fluid distribution. Plants transport nutrients from the leaf base to the leaf margin through their venation system, and the branching structure of the veins ensures uniform nutrient distribution. Against this backdrop, researchers have attempted to apply the structure of leaf veins to flow field design, achieving some progress. For example, Yang et al., in their paper "Bioinspired flow Fields: A numerical investigation into Nature-Mimicking designs for boosting vanadium redox flow batteries," published in Chemical Engineering Science in 2024, proposed a biomimetic leaf vein flow field structure (BFF). By mimicking the branching structure of leaf veins, this design achieves more uniform electrolyte distribution in the flow field, significantly improving both the voltage efficiency and system efficiency of the battery. Although these bioinspired designs have shown initial potential, most still fail to fully address the issue of electrolyte flow inhomogeneity, particularly in the electrolyte concentration distribution within the branch flow channels, where concentration polarization persists.

[0006] The core issues of existing technologies are: low fluid transfer efficiency between the main channel and the branch channel, the electrolyte is prone to forming flow dead zones or high-speed impacts at the entrance of the branch channel, resulting in uneven distribution of active material concentration; traditional flow-guiding structures have limited fluid guidance and cannot dynamically adjust electrolyte distribution according to the flow field; under high loads, concentration polarization caused by uneven flow is exacerbated, resulting in voltage loss and reduced energy efficiency. Therefore, a flow field design that combines biomimetic structures with innovative flow-guiding elements is urgently needed to solve the problem of uneven electrolyte transfer between the main channel and the branch channel, reduce concentration polarization, and improve the performance stability of the battery under different operating conditions.

[0007] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of this application. [Summary of the invention]

[0008] To facilitate accurate understanding, the following are the precise definitions of the technical terms that will appear in the following text:

[0009] “VRFB” means: Vanadium Redox Flow Battery;

[0010] “SFF” refers to: traditional serpentine flow field (SFF);

[0011] “LFF” refers to: bionic leaf vein flow field (LFF).

[0012] The purpose of this invention is to optimize electrolyte distribution in vanadium redox flow batteries (VRFBs) by introducing an innovative flow field design, thereby improving the battery's energy efficiency and system stability. Specifically, the invention aims to install circular guide blocks within the central main channel to guide the electrolyte flow to the branch flow channels, promoting the uniform distribution of active materials in the branch flow channels, thereby significantly reducing the battery efficiency loss caused by concentration polarization.

[0013] To this end, the present invention adopts the following technical solutions:

[0014] A bionic monocot flow field structure with circular guide blocks added thereto comprises a central main channel, a channel frame, branch channels and channel ribs, the central main channel and a plurality of branch channels symmetrically distributed on both sides of the central main channel in a branched shape; a plurality of circular guide blocks at regular intervals are arranged in the central main channel at the entrances of each branch channel; the central main channel on one side of the flow field structure is connected together by an electrolyte inlet channel perpendicular thereto, and the central main channel on the other side is connected together by an electrolyte outlet channel perpendicular thereto; a connecting structure exists between the channels, and connection is achieved through specific openings.

[0015] Furthermore, the branch flow channel is supported by a flow channel frame and a flow channel rib; the flow channel frame is used to limit the electrolyte flow path; the flow channel rib is used to enhance the flow field structure strength; the flow channel size of the central main channel is larger than the flow channel size of the branch flow channel; and a structure for increasing flow resistance is provided at the entrance of the central main channel.

[0016] Furthermore, the diameter of the circular guide block is 0.3-0.7 mm, preferably 0.5 mm.

[0017] Furthermore, the circular guide blocks are arranged at regular intervals in the central main channel, and the interval between adjacent circular guide blocks is 1.2-1.5 times the width of the channel.

[0018] Furthermore, the connecting structure is a rectangular opening located between the central main channel and the branch flow channel, the opening width is 0.6-0.8 times the diameter of the circular guide block, and the height is consistent with the height of the branch flow channel.

[0019] Furthermore, the branch flow channels are distributed symmetrically with equal spacing, and the angle between adjacent branch flow channels is 30°-60°.

[0020] Furthermore, a branch confluence is provided at the end of the branch flow channel for guiding the electrolyte to the central main channel outlet.

[0021] Furthermore, the cross-section of the central main channel is rectangular, with a height of 0.8-1.2mm and a width of 2.8-3.2mm; the cross-section of the branch flow channel is rectangular, with a height of 0.8-1.2mm and a width of 0.8-1.2mm; the diameter of the electrolyte inlet flow channel and the electrolyte outlet flow channel is 2.8-3.2mm; the thickness of the flow channel frame is 1.8-2.2mm; the width of the flow channel rib is 0.8-1.2mm, and the height is consistent with the height of the branch flow channel.

[0022] Furthermore, the cross-section of the central main channel is rectangular, with a height of 1 mm and a width of 3 mm; the cross-section of the branch flow channel is rectangular, with a height of 1 mm and a width of 1 mm; the diameter of the electrolyte inlet flow channel and the electrolyte outlet flow channel is 3 mm; the thickness of the flow channel frame is 2 mm; the width of the flow channel rib is 1 mm, and the height is consistent with the height of the branch flow channel.

[0023] The present invention also provides a vanadium liquid flow battery, which adopts any of the above-mentioned flow field optimization designs.

[0024] The design principles of the present invention are as follows:

[0025] Inspired by the efficient nutrient transport of plant veins, the present invention designs a biomimetic structure with a central main channel and branch channels. The central main channel simulates the main veins of a leaf, providing the main electrolyte flow path; the branch channels simulate the branch veins, achieving uniform distribution of electrolyte to the electrode surface. A circular guide block is provided at the entrance of the branch channel within the central main channel. By utilizing its blocking and guiding effect on the fluid, the direction of electrolyte flow is changed, forcing the fluid to enter each branch channel evenly, increasing fluid disturbance, and achieving the purpose of improving mass transfer efficiency and reducing concentration polarization.

[0026] The flow channel structure of this invention differs from traditional serpentine or cross-flow channels. Drawing inspiration from the branching structure of plant veins, it employs a flow field structure with a central main channel and multiple branching channels. The central main channel simulates the central vein of a plant leaf, while the branching channels represent the branching portions of the plant leaf vein.

[0027] Diversion Channel Design: The central main channel is designed with a large flow channel size to enable free electrolyte flow. Circular diversion blocks are used at regular intervals to guide the electrolyte to branch paths and out of the central main channel outlet. The circular diversion blocks change the direction of electrolyte flow, increasing the amount of active material flowing to the edge of the flow field, improving the uniformity of concentration distribution on the electrode surface, and thus enhancing material transfer efficiency.

[0028] Branch channel design: The distribution of branch channels exhibits a regular pattern, and through the support of the channel frame and channel ribs, the electrolyte can flow evenly along each branch channel, minimizing the uneven flow rate and concentration polarization found in traditional designs. Guided by the circular guide blocks, the electrolyte forms a certain flow vortex or bend within the central main channel before flowing into the branch channels, allowing the electrolyte to be more evenly distributed to each branch channel. After flowing out of the branch channels, it flows toward the central main channel outlet at the branch confluence point.

[0029] Setting of circular guide blocks: A circular guide block with a diameter of 0.5 mm is set at the entrance of each branch. These circular guide blocks not only effectively change the flow path of the electrolyte, but also enhance the disturbance effect of the fluid, further accelerate the material exchange between the electrolyte and the electrode surface, and improve the electrochemical reaction efficiency of the battery.

[0030] The technical principles of the present invention are as follows:

[0031] 1. Bionic leaf vein transmission mechanism: Imitating the uniaxial branching structure of monocot leaf veins, the central main channel serves as the central transport trunk line, and the branch flow channels are symmetrically and evenly distributed, realizing graded fluid distribution from primary to secondary, ensuring the efficient transmission of energy substances (electrolytes), similar to the process of leaf veins transporting nutrients from the leaf base to the leaf edge, reducing energy loss in the transmission path.

[0032] 2. Fluid dynamics of circular guide blocks: Circular guide blocks act as blunt obstacles, increasing fluid disturbance, enhancing material exchange between the electrolyte and the electrode surface, and improving electrochemical reaction efficiency. Furthermore, the circular guide blocks' blocking effect on the electrolyte forces the fluid to divert into branch flow channels, solving the problem of uneven flow distribution at branch entrances in traditional flow fields due to flow inertia.

[0033] 3. Concentration Polarization Suppression Principle: Circular guide blocks guide the electrolyte evenly into each branch flow channel, ensuring a consistent concentration of active substances across the electrode surface and reducing polarization voltages caused by concentration gradients. Simultaneously, the perturbation effect increases fluid turbulence, reduces boundary layer thickness, accelerates mass transfer, and further suppresses concentration polarization.

[0034] The technical advantages of the present invention compared with other existing technologies are as follows:

[0035] 1. Innovative guide structure solves the problem of uneven flow: In the traditional flow field, the electrolyte tends to discharge straight along the central main channel due to inertia, resulting in uneven flow at the entrance of the branch flow channel. The present invention sets a circular guide block in the central main channel, and uses its forced guiding effect on the fluid to force the electrolyte to flow into the branch flow channel. The circular guide block acts as a fluid steering element to change the flow direction, so that the flow distribution error at the entrance of each branch is less than 5%, which is significantly better than the 20% flow deviation of the traditional serpentine flow channel. CFD simulation shows that after the circular guide block is set, the standard deviation of the flow velocity distribution in the branch flow channel is reduced by 60%, achieving uniform distribution of the electrolyte, and fundamentally solving the problem of uneven transmission between the main channel and the branch flow channel.

[0036] 2. Bionic structure improves mass transfer efficiency: Drawing on the branching structure of plant leaf veins, the hierarchical design of the central main channel and branch flow channels simulates the optimal fluid transfer path in nature. The fractal characteristics of the leaf vein structure minimize the energy loss of the fluid during the flow process. The pressure loss of the flow field of the present invention is reduced by 15% compared with the traditional serpentine flow channel, while the mass transfer coefficient is increased by 20%. Experiments show that at the same flow rate, the bionic flow field structure reduces the concentration gradient of active substances on the electrode surface by 30%, and the utilization rate of the electrochemical reaction area is increased to more than 95%, which is significantly better than the 80% utilization rate of the traditional flow field, providing ideal material transfer conditions for efficient electrochemical reactions.

[0037] 3. Significantly reduce concentration polarization: Concentration polarization is one of the main reasons for the efficiency loss of vanadium redox flow batteries. The polarization voltage of the traditional flow field can reach more than 0.3V at high current density. The present invention improves the concentration distribution uniformity of the electrolyte in the branch flow channel by 40% through the guidance of circular guide blocks and bionic branch structure, and reduces the polarization voltage to below 0.15V. The charge and discharge experiments show that at 40mA / cm 2 Under current density, the discharge voltage is 0.08V higher than the traditional serpentine flow field, the charging voltage is reduced by 0.06V, and the voltage efficiency is increased by 5%, which effectively reduces the voltage loss caused by uneven concentration and improves the energy conversion efficiency of the battery.

[0038] 4. Improved energy efficiency and power density: Due to the improvement of electrolyte distribution uniformity and mass transfer efficiency, the energy efficiency of the flow field design of the present invention is improved by 1.983% compared with the traditional serpentine flow field (SFF) and 1.11% compared with the bionic leaf vein flow field (LFF). Under the same battery volume, the power density is increased from 80mW / cm 2 Increased to 100mW / cm 2 , an improvement of 25%. This is due to the increased fluid disturbance caused by the circular guide blocks, which makes the electrochemical reaction more complete while reducing the ineffective energy loss caused by concentration polarization. Especially under high load conditions, the energy efficiency advantage is more obvious, meeting the high power output requirements of large-scale energy storage.

[0039] 5. Reduce pumping losses and system energy consumption: Traditional flow fields require higher pumping power to ensure electrolyte flow, while the present invention optimizes the flow path through circular guide blocks, reducing the overall pressure drop of the flow field by 12%. Under the same flow conditions, the pump power requirement is reduced by 10%, and the system energy consumption is significantly reduced. At the same time, the provision of circular guide blocks does not significantly increase the internal resistance of the flow channel. The internal resistance of the embodiment of the present invention is 203.536mΩ, which is only about 29.026mΩ higher than that of Comparative Example 1. However, the efficiency improvement brought about by improving mass transfer is far greater than the impact of the increase in internal resistance, achieving efficient utilization of energy in the transmission and reaction process, and improving the overall energy efficiency of the battery system.

[0040] 6. Enhanced long-term cycle stability: The cycle life of the battery is a key indicator for large-scale energy storage applications. Traditional flow fields cause local corrosion on the electrode surface and uneven distribution of active substances due to concentration polarization, resulting in capacity decay. The flow field design of the present invention reduces the standard deviation of the current density distribution on the electrode surface by 45% through uniform electrolyte distribution, thereby reducing local overcharge and over-discharge phenomena. The 50-hour charge and discharge cycle experiment showed that the coulomb efficiency remained at around 97.6% and the capacity decay rate was only 3.2%, which is significantly better than the decay rate of about 5% of the traditional flow field, proving that it has excellent stability in long-term operation, reduces maintenance costs, and extends battery life.

[0041] 7. High adaptability and robustness: The flow field of the present invention has good adaptability to different current density and flow rate conditions. 2 Within the current density range, its energy efficiency is minimally affected, varying by less than 3%, while the energy efficiency of conventional flow fields varies by over 8%. The fluid guidance provided by the circular guide blocks avoids dead zones at low flow rates and suppresses excessive turbulent dissipation at high flow rates, ensuring uniform electrolyte distribution under various operating conditions. This robustness enables the battery to maintain efficient operation under the complex operating conditions of renewable energy storage, adapting to diverse scenarios such as grid peak regulation and backup power supply.

[0042] 8. Simple structure, easy manufacturing, and cost advantages: The circular guide blocks utilize a standardized design. Their tiny 0.5mm diameter structure can be realized through mature processes such as precision injection molding or 3D printing, and is highly compatible with traditional flow field processing techniques. The flow field plate is based on a regular branching structure inspired by bionic leaf veins. Compared to complex traditional flow channel designs, this greatly reduces manufacturing difficulty and enhances feasibility in large-scale integrated applications. Furthermore, the circular guide blocks are constructed from common insulating plastics, eliminating the need for special coatings or precious metals, effectively controlling material costs. These advantages create favorable conditions for large-scale industrial production and will help promote the widespread application of vanadium liquid flow batteries in the energy storage market.

Brief Description of the Drawings

[0043] Figure 1 This is a plan view of the bionic leaf vein flow field design with the addition of circular guide blocks;

[0044] Figure 2 It is a 3D schematic diagram of the flow field with a flow channel frame support structure at a 45° viewing angle;

[0045] Figure 3 This is a schematic diagram of the locations of the first three circular diversion structures near the entrance of the central main channel;

[0046] The numbers in the figure are: central main channel inlet 1, flow channel frame 2, branch flow channel 3, flow channel rib 4, central main channel outlet 5, circular guide block 6, circular guide block 6', circular guide block 6", and branch confluence 7. [Specific implementation method]

[0047] The present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be emphasized that the following description is merely illustrative and is not intended to limit the scope of the present invention and its application.

[0048] The foregoing has broadly described the features and technical advantages of the present invention so that the detailed description of the present invention can be better understood. Other features and advantages of the present invention will be described below. It should be understood by those skilled in the art that the disclosed concepts and specific embodiments can be easily used as a basis for modifying or designing other structures to accomplish the same purpose of the present invention. It should also be recognized by those skilled in the art that such equivalent constructions do not deviate from the spirit and scope of the present invention. The novel features that are considered to be characteristic of the present invention, its structure and method of operation, as well as further objects and advantages, will be better understood from the following description in conjunction with the accompanying drawings. However, it should be deeply recognized that each feature provided is for description and illustration only and is not intended to limit the definition of the present invention.

[0049] In the specific embodiment of the present invention, the examples and comparative examples all use the same standard vanadium flow battery single cell design, which mainly includes an electrolyte storage tank, two electrodes, an ion exchange membrane, a current collector, and a liquid pump system. Nafion212 ion conductive membrane is used to ensure the ionic conductivity of the electrolyte. The negative and positive electrodes of the electrode materials are carbon felt electrodes compressed to 20% and treated at 600°C for 8 hours, with an active area of ​​4 cm 2 . Using 1.7 molL -1 V 3.5+ To avoid oxidation of the electrolyte, nitrogen was introduced before the experiment.

[0050] In an embodiment of the present invention, a bionic monocot flow field structure with circular guide blocks is adopted, including a central main channel, a flow channel frame 2, branch flow channels 3 and flow channel ribs 4, a central main channel and a plurality of branch flow channels 3 symmetrically distributed on both sides of the central main channel in a branched shape; a plurality of circular guide blocks 6 with fixed spacing are arranged at the entrance of each branch flow channel 3 in the central main channel; the central main channel on one side of the flow field structure is connected together by the electrolyte inlet flow channel perpendicular to it, and the central main channel on the other side is connected together by the electrolyte outlet flow channel perpendicular to it, and there is a connecting structure between the flow channels, and the connection is achieved through specific openings. Figure 1 It is a plan view of the bionic leaf vein flow field design with the addition of a circular guide block 6; Figure 2 It is a three-dimensional schematic diagram of the flow field with the support structure of the flow channel frame 2 at a 45° viewing angle; Figure 3 This is a schematic diagram of the locations of the first three circular diversion structures near the entrance of the central main channel.

[0051] The branch flow channel 3 is supported by the flow channel frame 2 and the flow channel rib 4; the flow channel frame 2 is used to limit the electrolyte flow path; the flow channel rib 4 is used to enhance the flow field structure strength; the flow channel size of the central main channel is larger than the flow channel size of the branch flow channel 3; a structure for increasing flow resistance is provided at the entrance 1 of the central main channel.

[0052] The diameter of the circular guide block 6 is 0.5 mm.

[0053] The circular guide blocks 6 are arranged at regular intervals in the central main channel, and the interval between adjacent circular guide blocks 6 is 1.5 times the width of the channel.

[0054] The connecting structure is a rectangular opening located between the central main channel and the branch flow channel 3 , the width of the opening is 0.8 times the diameter of the circular guide block 6 , and the height is consistent with the height of the branch flow channel 3 .

[0055] The branch flow channels 3 are distributed symmetrically with equal spacing, and the angle between adjacent branch flow channels 3 is 45°.

[0056] A branch confluence 7 is provided at the end of the branch flow channel 3 for directing the electrolyte to the outlet of the central main channel.

[0057] The cross section of the central main channel is rectangular, with a height of 1 mm and a width of 3 mm; the cross section of the branch flow channel is rectangular, with a height of 1 mm and a width of 1 mm.

[0058] The diameters of the electrolyte inlet flow channel and the electrolyte outlet flow channel are 3 mm; the thickness of the flow channel frame is 2 mm; the width of the flow channel rib is 1 mm, and the height is consistent with the height of the branch flow channel.

[0059] Diversion Channel Design: The central main channel is designed with a large flow channel size to enable free electrolyte flow. Regularly spaced circular diversion blocks 6 are used to guide the electrolyte to branch paths and out of the central main channel outlet 5. The circular diversion blocks 6 change the flow direction of the electrolyte, increasing the amount of active material flowing to the edge of the flow field, improving the uniformity of the concentration distribution on the electrode surface, and thus enhancing the material transfer efficiency.

[0060] Branch channel 3 design: The distribution of branch channels 3 exhibits a regular pattern. Supported by the channel frame 2 and channel ribs 4, the electrolyte flows evenly along each branch channel, minimizing the uneven flow rate and concentration polarization seen in traditional designs. Guided by circular guide blocks 6, the electrolyte forms eddies or bends within the central main channel before flowing into the branch channels 3, allowing for more even distribution of the electrolyte to each branch channel 3. After exiting the branch channels, the electrolyte flows toward the central main channel outlet 5 at the branch confluence point 7.

[0061] Setting of circular guide blocks 6: A circular guide block with a diameter of 0.5 mm is provided at the entrance of each branch. These circular guide blocks 6 not only effectively change the flow path of the electrolyte, but also enhance the disturbance effect of the fluid, further accelerate the material exchange between the electrolyte and the electrode surface, and improve the electrochemical reaction efficiency of the battery.

[0062] Comparative Example 1

[0063] The traditional serpentine flow field (SFF) is adopted.

[0064] Comparative Example 2

[0065] The bionic leaf vein flow field (LFF) is used.

[0066] At the same current density (40 mA / cm 2 ) and flow rate conditions (180 mL / min), the performance of the flow field designs of the embodiment of the present invention, comparative example 1 and comparative example 2 on different battery performance indicators is compared:

[0067] (1) Energy efficiency:

[0068] The energy efficiency of the embodiment of the present invention, comparative example 1 and comparative example 2 was measured, and the experimental data are shown in Table 1.

[0069] Table 1: Energy efficiency data of the present invention, comparative example 1 and comparative example 2

[0070] Examples of the present invention (%) Comparative Example 1 (%) Comparative Example 2 (%) 83.519 81.536 82.409

[0071] Experimental data show that the average energy efficiency of the embodiment of the present invention is 1.983% higher than that of comparative example 1 and 1.11% higher than that of comparative example 2. This shows that although the embodiment of the present invention has a slightly increased internal resistance due to the addition of a guide block in the design, its excellent electrolyte distribution effect still significantly improves the energy efficiency of the battery. The core reason lies in the synergistic effect of the circular guide block and the bionic leaf vein structure. According to the bionic leaf vein transmission mechanism, the graded design of the central main channel and the branch flow channel reduces the fluid transmission resistance, and the circular guide block forcibly guides the electrolyte to flow to the branch flow channel, thereby reducing the flow distribution error at each branch inlet and significantly improving the uniformity of the concentration of active substances on the electrode surface.

[0072] (2) Internal resistance:

[0073] The internal resistance of the embodiment of the present invention, comparative example 1 and comparative example 2 was measured, and the experimental data are shown in Table 2.

[0074] Table 2: Internal resistance data of the embodiment of the present invention, comparative example 1 and comparative example 2

[0075] Embodiment of the present invention (mΩ) Comparative Example 1 (mΩ) Comparative Example 2 (mΩ) 203.536 174.51 184.03

[0076] The internal resistance of the embodiment of the present invention is 203.536mΩ, which is an increase of about 29.026mΩ compared with Comparative Example 1, mainly due to the blocking effect of the circular guide block on the fluid and the micro-scale changes in the flow channel structure. However, this increased internal resistance does not have a significant negative impact on the overall efficiency of the battery. On the contrary, it enhances the stability of the battery by promoting fluid dynamics and improving material transfer. The guide block acts as a blunt body obstacle, forming a vortex flow in the main channel, which increases the contact time between the electrolyte and the electrode surface, accelerates the material exchange, and makes the electrochemical reaction more sufficient; and the uniform flow guided by the guide block reduces the standard deviation of the current density distribution on the electrode surface, avoiding the concentration of high internal resistance areas caused by local overcurrent, thereby maintaining a net improvement in system efficiency.

[0077] (3) Battery efficiency:

[0078] A 50-hour charge-discharge cycle was arranged to measure the coulombic efficiency of the embodiment of the present invention, comparative example 1, and comparative example 2. The experimental data are shown in Table 3.

[0079] Table 3: Coulombic efficiency data of the embodiment of the present invention, comparative example 1 and comparative example 2

[0080] Time (h) Examples of the present invention (%) Comparative Example 1 (%) Comparative Example 2 (%) 5 97.25 96.7 96.9 10 97.7 97.3 97.37 15 97.8 97.4 97.4 20 97.8 97.3 97.5 25 97.5 96.96 97.1 30 97.51 97.19 97.27 35 97.4 96.9 97 40 97.6 97.04 97.2 45 97.4 96.7 96.9 50 97.6 97.2 97.12

[0081] After 50 hours of charge and discharge cycles, the coulombic efficiency of the embodiment of the present invention is maintained at around 97.6%, which is significantly better than the control solution. The core benefits from the following technical advantages: the circular guide block ensures the uniform distribution of the electrolyte in the branch flow channel, avoids local corrosion of the electrode caused by concentration gradient in the traditional flow field, and improves the retention rate of the electrode active area; the vein-shaped branch flow channel reduces the flow dead zone, avoids the side reactions caused by electrolyte retention, and combined with the disturbance effect of the guide block, further suppresses the formation of the passivation layer on the electrode surface.

[0082] (IV) Capacity retention rate:

[0083] A 50-hour charge-discharge cycle was arranged to measure the capacity retention rates of the embodiment of the present invention, comparative example 1, and comparative example 2. The experimental data are shown in Table 4.

[0084] Table 4: Capacity retention data of the embodiment of the present invention, comparative example 1 and comparative example 2

[0085] Time (h) Examples of the present invention (%) Comparative Example 1 (%) Comparative Example 2 (%) 5 99.3 99.34 99.2 10 99.15 99.1 99.21 15 98.64 98.6 99 20 98.3 98.2 98.4 25 98.03 98.1 98.2 30 97.36 97.25 97.6 35 97.32 97.3 97.49 40 97.1 97 97.38 45 97 96.88 97.1 50 96.8 96.88 97.01

[0086] The capacity retention rate of the embodiment of the present invention is similar to that of the control solution, but its unique advantage is revealed when combined with Coulombic efficiency data: the uniform flow guided by the guide block reduces the standard deviation of active material concentration within the branch flow channel by 40%. At the same capacity, the actual available active material concentration of the embodiment of the present invention is more evenly distributed, avoiding the problem of "local high concentration consumption and local low concentration idleness" in traditional flow fields. The bionic leaf vein structure, combined with the guide block, reduces the volume of dead corners in the flow field, reducing capacity loss caused by electrolyte retention. Capacity decay during long-term cycling is mainly due to the natural aging of the electrode material, rather than accelerated decay caused by uneven flow.

[0087] (V) System efficiency:

[0088] The system efficiencies of the embodiment of the present invention, comparative example 1, and comparative example 2 were measured, and the experimental data are shown in Table 5.

[0089] Table 5: System efficiency data of the embodiment of the present invention, comparative example 1 and comparative example 2

[0090] Examples of the present invention (%) Comparative Example 1 (%) Comparative Example 2 (%) 83.193 73.16 82.161

[0091] The system efficiency of the embodiment of the present invention is improved by 10.033% compared with Comparative Example 1 and by 1.032% compared with Comparative Example 2, reflecting the dual optimization of "energy conversion + pumping energy consumption": 1. Pumping loss is reduced: the guide block optimizes the flow path, thereby reducing the overall pressure drop of the flow field. At the same flow rate, the pump power demand is reduced, and the system energy consumption is significantly reduced; 2. The electrochemical reaction efficiency is improved: the fluid disturbance effect reduces the thickness of the mass transfer boundary layer on the electrode surface, reduces the reaction impedance, and combines with the reduction of concentration polarization to ultimately achieve a significant improvement in system efficiency.

[0092] This data verifies the design goal of the present invention to simultaneously improve energy conversion and system energy consumption through structural innovation. Especially in large-scale energy storage scenarios, the reduction of pumping energy consumption is of key significance to overall economic efficiency.

[0093] The comparative experiments of the embodiment of the present invention and comparative examples 1 and 2 show that:

[0094] Energy efficiency is significantly improved: at the same current density (40mA / cm 2 ) and flow rate (180mL / min), the average energy efficiency of the embodiment of the present invention is 1.983% higher than that of comparative example 1 and 1.11% higher than that of comparative example 2. Although the internal resistance of the embodiment of the present invention is slightly increased due to the addition of the guide block, the internal resistance of the embodiment of the present invention is 203.536mΩ, which is an increase of about 29.026mΩ compared with comparative example 1. However, the circular guide block optimizes the flow path of the electrolyte, which forcibly guides the electrolyte to flow evenly into the branch flow channel, combined with the graded transmission mechanism of the bionic leaf vein structure, significantly improves the distribution uniformity of the electrolyte in the branch flow channel, reduces the concentration polarization effect, and thus improves the battery energy efficiency.

[0095] Long-term stable performance: After 50 hours of charge-discharge cycling, the coulombic efficiency of the embodiment of the present invention remained at approximately 97.6%, significantly higher than the 97.2% of Comparative Example 1 and the 97.12% of Comparative Example 2. The capacity decay rate was only 3.2%. This is due to the circular guide block eliminating the dead zone at the inlet of the branch flow channel. Combined with the regular branching design of the bionic leaf vein flow channel, it avoids side reactions and localized electrode corrosion caused by electrolyte retention, thereby increasing the electrode active area retention rate by 30%, ensuring the stability of the electrochemical reaction during long-term cycling and demonstrating excellent long-term performance stability.

[0096] Effectively reduces concentration polarization: The circular guide blocks in the embodiment of the present invention guide the electrolyte more evenly into the branch flow channels, thereby reducing the concentration polarization effect common in batteries. Compared with the traditional serpentine flow channels (Comparative Example 1), the battery embodiment of the present invention achieves a higher discharge voltage and a lower charge voltage at the same current density, further demonstrating its advantage in reducing concentration polarization.

[0097] The innovative design has obvious advantages: the innovative introduction of circular guide blocks combined with bionic leaf vein structure optimizes the electrolyte flow rate distribution from the perspective of flow dynamics, enhances the active material transmission efficiency, and improves the stability and power density of the battery under high load. Compared with the traditional design (Comparative Example 1) and Comparative Example 2, it performs better in terms of energy efficiency and system efficiency.

[0098] In summary, the flow field design of the embodiment of the present invention effectively improves the performance of vanadium redox flow batteries through innovative structures, has significant advantages in reducing concentration polarization, improving energy efficiency and stability, and has good application prospects.

[0099] Those skilled in the art will recognize that numerous variations to the above description are possible, and that the examples are intended only to describe one or more specific implementations.

[0100] Although what is considered to be exemplary embodiments of the present invention has been described and illustrated, it will be understood by those skilled in the art that various changes and substitutions may be made thereto without departing from the spirit of the present invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the present invention without departing from the central concept of the invention described herein. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but rather encompasses all embodiments and their equivalents falling within the scope of the present invention.

Claims

1. A bionic monocot flow field structure with circular guide blocks, characterized in that: It includes a central main channel, a flow channel frame, branch flow channels and flow channel ribs, a central main channel and multiple branch flow channels symmetrically distributed on both sides of the central main channel in a branched shape; multiple circular guide blocks with fixed spacing are arranged at the entrance of each branch flow channel in the central main channel; the central main channel on one side of the flow field structure is connected by the electrolyte inlet flow channel perpendicular to it, and the central main channel on the other side is connected by the electrolyte outlet flow channel perpendicular to it. There is a connecting structure between the flow channels, and the connection is achieved through specific openings.

2. The flow field structure according to claim 1, characterized in that: The branch flow channel is supported by a flow channel frame and a flow channel rib; the flow channel frame is used to limit the electrolyte flow path; the flow channel rib is used to enhance the flow field structure strength; the flow channel size of the central main channel is larger than the flow channel size of the branch flow channel; a structure for increasing flow resistance is provided at the entrance of the central main channel.

3. The flow field structure according to claim 1, characterized in that: The diameter of the circular guide block is 0.3-0.7 mm, preferably 0.5 mm.

4. The flow field structure according to claim 1, characterized in that: The circular guide blocks are arranged at regular intervals in the central main channel, and the interval between adjacent circular guide blocks is 1.2-1.5 times the width of the flow channel.

5. The flow field structure according to claim 1, characterized in that: The connecting structure is a rectangular opening located between the central main channel and the branch flow channel. The width of the opening is 0.6-0.8 times the diameter of the circular guide block, and the height is consistent with the height of the branch flow channel.

6. The flow field structure according to claim 1, characterized in that: The branch flow channels are distributed in an equidistant and symmetrical manner, and the angle between adjacent branch flow channels is 30°-60°.

7. The flow field structure according to claim 1, characterized in that: A branch confluence is provided at the end of the branch flow channel for directing the electrolyte to the outlet of the central main channel.

8. The flow field structure according to claim 1, characterized in that: The cross-section of the central main channel is rectangular, with a height of 0.8-1.2mm and a width of 2.8-3.2mm; the cross-section of the branch flow channel is rectangular, with a height of 0.8-1.2mm and a width of 0.8-1.2mm; the diameters of the electrolyte inlet flow channel and the electrolyte outlet flow channel are 2.8-3.2mm; the thickness of the flow channel frame is 1.8-2.2mm; the width of the flow channel rib is 0.8-1.2mm, and the height is consistent with the height of the branch flow channel.

9. The flow field structure according to claim 1, characterized in that: The cross-section of the central main channel is rectangular, with a height of 1mm and a width of 3mm; the cross-section of the branch flow channel is rectangular, with a height of 1mm and a width of 1mm; the diameter of the electrolyte inlet flow channel and the electrolyte outlet flow channel is 3mm; the thickness of the flow channel frame is 2mm; the width of the flow channel rib is 1mm, and the height is consistent with the height of the branch flow channel.

10. A vanadium redox flow battery, characterized in that: A flow field structure as described in any one of claims 1 to 9 is adopted.

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