Structure of a zinc-bromine flow battery electrode

Abstract

This invention belongs to the field of flow battery energy storage technology, and specifically relates to a zinc-bromine flow battery structure. The electrode is a carbon felt electrode, and the electrode has grooves parallel to the electrolyte flow direction. The cross-section of the grooves perpendicular to the electrolyte flow direction is trapezoidal or inverted T-shaped, and the groove depth is 50%-80% of the electrode thickness. The grooves on the porous carbon felt negative electrode provide more ample deposition space for the zinc negative electrode, and the bottom of the flow channel grooves remains on the carbon felt substrate, ensuring electron conduction. This effectively increases the deposition capacity of the battery stack without reducing its polarization.

Description

Technical Field

[0001] This utility model belongs to the field of flow battery energy storage technology, and specifically relates to a zinc-bromine flow battery structure. Background Technology

[0002] Zinc-bromine flow batteries are a low-cost, high-safety, and high-energy-density flow battery energy storage technology. The negative electrode involves the deposition and dissolution reaction of zinc. During charging, zinc ions are converted into elemental zinc and deposited on the electrode; during discharging, elemental zinc is converted back into zinc ions and released into the electrolyte. Because zinc-bromine flow batteries are deposition-based batteries, the deposition capacity of zinc at the negative electrode limits the battery's performance and cycle stability. Excessive zinc deposition can lead to zinc dendrites, which can puncture the separator, causing a short circuit and battery failure. Therefore, improving the deposition capacity of zinc-bromine flow batteries is crucial for their technological development. Utility Model Content

[0003] To address the aforementioned technical problems, the purpose of this invention is to provide an electrode structure for a zinc-bromine flow battery.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A zinc-bromine flow battery electrode structure is disclosed, wherein the electrode is a carbon felt electrode, and the electrode is provided with a groove parallel to the electrolyte flow direction. The cross-section of the groove perpendicular to the electrolyte flow direction is trapezoidal or inverted T-shaped, and the groove depth is 50%-80% of the electrode thickness. When the cross-section of the groove perpendicular to the electrolyte flow direction is trapezoidal, the width of the upper bottom edge of the groove cross-section is 10mm-20mm (preferably 13mm-17mm), the width of the lower bottom edge of the groove cross-section is 15mm-40mm (preferably 25mm-30mm), and the distance between the lower bottom edges of adjacent groove cross-sections is 50mm-150mm (preferably 90mm-110mm); or, when the cross-section of the groove perpendicular to the electrolyte flow direction is inverted T-shaped, the groove cross-section is composed of connected upper and lower rectangles, the width of the upper rectangle is 10mm-20mm (preferably 13mm-17mm), and the height is 20-30% (preferably 23%-27%) of the electrode thickness, the width of the lower rectangle is 15mm-40mm (preferably 25mm-30mm), and the height is 30%-40% (preferably 33%-37%) of the electrode thickness; the distance between the lower rectangles of adjacent groove cross-sections is 50mm-150mm (preferably 90mm-110mm). The electrode is a porous carbon felt with a thickness of 4mm-6mm (preferably 4.5mm-5.5mm, more preferably 4.8mm-5.2mm). Multiple grooves parallel to the electrolyte flow direction are formed on the electrode. The distance between the bottom edge or lower rectangle of the groove cross-section near the two edges of the electrode and the adjacent two edges of the electrode is 50mm-150mm (preferably 90mm-110mm). When assembled into a zinc-bromine flow battery, the grooved side of the negative electrode faces the separator. The carbon felt negative electrode is rectangular, and its length and width match the hollow area inside the annular electrode frame; that is, the surface shape and size of the carbon felt electrode are the same as the hollow area inside the annular electrode frame. This electrode structure is only used at the negative electrode of the battery stack; the positive electrode still uses a traditional flat carbon felt electrode, without increasing the internal resistance of the battery stack and maintaining its performance.

[0006] The beneficial effects of this utility model are as follows:

[0007] Grooves are incorporated into the porous carbon felt electrode for the negative electrode, providing ample deposition space for the zinc negative electrode. Furthermore, the bottom of the grooves remains on the carbon felt substrate, ensuring electron conduction and effectively increasing the deposition capacity of the fuel cell without reducing its polarization. In addition, this electrode structure is only used in the negative electrode; the positive electrode still uses a traditional flat carbon felt electrode, thus not increasing the internal resistance of the fuel cell and maintaining its performance. Attached Figure Description

[0008] To more clearly illustrate the embodiments of this utility model, the accompanying drawings related to the embodiments will be briefly described below.

[0009] Figure 1 This is a schematic diagram of the zinc-bromine flow battery electrode of this utility model.

[0010] Figure 2 This is a schematic diagram of the trapezoidal cross-section of the zinc-bromine flow battery electrode of this utility model.

[0011] Figure 3 This is a schematic diagram of the inverted T-shaped cross-section of the zinc-bromine flow battery electrode of this utility model. Detailed Implementation

[0012] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0013] This utility model embodiment is a composite electrode structure for a zinc-bromine flow battery. The electrode is provided with a groove parallel to the electrolyte flow direction. The cross-section of the groove perpendicular to the electrolyte flow direction is trapezoidal or inverted T-shaped, and the groove depth is 50%-80% of the electrode thickness. When the cross-section of the groove perpendicular to the electrolyte flow direction is trapezoidal, the width of the upper bottom edge of the groove cross-section is 10mm-20mm (preferably 13mm-17mm), the width of the lower bottom edge of the groove cross-section is 15mm-40mm (preferably 25mm-30mm), and the distance between the lower bottom edges of adjacent groove cross-sections is 50mm-150mm (preferably 90mm-110mm); or, when the cross-section of the groove perpendicular to the electrolyte flow direction is inverted T-shaped, the groove cross-section is composed of connected upper and lower rectangles, the width of the upper rectangle is 10mm-20mm (preferably 13mm-17mm), and the height is 20-30% (preferably 23%-27%) of the electrode thickness, the width of the lower rectangle is 15mm-40mm (preferably 25mm-30mm), and the height is 30%-40% (preferably 33%-37%) of the electrode thickness; the distance between the lower rectangles of adjacent groove cross-sections is 50mm-150mm (preferably 90mm-110mm). The electrode is a porous carbon felt with a thickness of 4mm-6mm (preferably 4.5mm-5.5mm, more preferably 4.8mm-5.2mm). Multiple grooves parallel to the electrolyte flow direction are formed on the electrode. The distance between the bottom edge or lower rectangle of the groove cross-section near the two edges of the electrode and the adjacent two edges of the electrode is 50mm-150mm (preferably 90mm-110mm). When assembled into a zinc-bromine flow battery, the grooved side of the negative electrode faces the separator. The carbon felt negative electrode is rectangular, and its length and width match the hollow area inside the annular electrode frame; that is, the surface shape and size of the carbon felt electrode are the same as the hollow area inside the annular electrode frame. This electrode structure is only used at the negative electrode of the battery stack; the positive electrode still uses a traditional flat carbon felt electrode, without increasing the internal resistance of the battery stack and maintaining its performance.

[0014] The embodiments and comparative examples of this utility model were tested under the following conditions:

[0015] The electrolyte is an aqueous solution of 2 mol / L zinc bromide, 3 mol / L potassium chloride, and 0.4 mol / L MEP (chemical name: 1-methyl-1-ethylpyrrolidine bromide) complexing agent. The diaphragm is a commercially available Daramic porous membrane; the negative and positive carbon felt electrode areas are 800 cm². 2 .

[0016] Comparative Example 1

[0017] Comparative Example 1 uses a conventional electrode structure as the negative electrode to assemble a zinc-bromine flow battery. The electrodes (positive and negative electrodes) are composed of flat carbon felt. The electrodes are placed in the central cavity of the annular electrode frame of the battery. The length and width of the carbon felt electrodes are matched (the same or equivalent) to the length and width of the central cavity region inside the annular electrode frame. Inlet and outlet channels are respectively set on two opposite sides of the electrode frame. The electrolyte flows into the electrode in the central cavity from the inlet channel and then flows out of the electrode frame through the outlet channel.

[0018] The specific parameters of the fuel cell stack are as follows:

[0019] Electrode area: 800 cm² 2 ;

[0020] Before compression, the thickness of the positive and negative carbon felt is 5mm. When assembling the battery, the thickness of the electrode is 120% of the thickness of the electrode frame. After assembling the battery, the electrode is compressed to be consistent with the thickness of the electrode frame.

[0021] Number of fuel cell stack sections: 10;

[0022] Current density: 40 mA / cm 2 Charging time: 3 hours; Discharge cut-off voltage: 8V.

[0023] Battery cycle performance: Coulombic efficiency 87.4%, voltage efficiency 83.2%, energy efficiency 72.7%; Comparative Example 1 has lower performance, which is due to zinc deposition on the carbon felt surface, zinc dendrites gradually accumulate, and after multiple cycles, the zinc deposition sites gradually decrease, resulting in a decline in battery performance.

[0024] Comparative Example 2

[0025] Comparative Example 2 uses grooved carbon felt as the negative electrode in a zinc-bromine flow battery assembly. Flat carbon felt is used for both the positive and negative electrodes. The electrodes are placed in the central cavity of the annular electrode frame. The length and width of the carbon felt electrodes match (are the same or equivalent) the length and width of the central cavity region within the annular electrode frame. Inlet and outlet channels are provided on opposite sides of the electrode frame. The electrolyte flows into the electrode in the central cavity from the inlet channel and then flows out of the electrode frame through the outlet channel. Multiple grooves parallel to the electrolyte flow direction are provided on the surface of the negative electrode facing the separator. The cross-section of the grooves perpendicular to the electrolyte flow direction is trapezoidal. The groove depth is 90% of the electrode thickness. The width of the upper bottom edge of the groove cross-section is 10 mm, the width of the lower bottom edge is 15 mm, and the distance between the lower bottom edges of adjacent grooves is 50 mm. The electrode is a porous carbon felt with a thickness of 5 mm.

[0026] The specific parameters of the fuel cell stack are as follows:

[0027] Electrode area: 800 cm² 2 ;

[0028] Before compression, the thickness of the positive and negative carbon felt is 5mm. When assembling the battery, the thickness of the electrode is 120% of the thickness of the electrode frame. After assembling the battery, the electrode is compressed to be consistent with the thickness of the electrode frame.

[0029] Number of fuel cell stack sections: 10;

[0030] Current density: 40 mA / cm 2 Charging time: 3 hours; Discharge cut-off voltage: 8V.

[0031] Battery cycle performance: Coulombic efficiency 86.2%, voltage efficiency 78.5%, energy efficiency 67.6%; Comparative Example 2 has lower performance, which is due to the grooves set in the negative electrode carbon felt, and the grooves are too deep, which increases the mass transfer resistance of ions on the electrode, resulting in excessive battery polarization and lower performance.

[0032] Comparative Example 3

[0033] Comparative Example 3 uses grooved carbon felt as the negative electrode in a zinc-bromine flow battery assembly. The positive and negative electrodes are still made of flat carbon felt. The electrodes are placed in the central cavity of the annular electrode frame. The length and width of the carbon felt electrodes match (are the same or equivalent) the length and width of the central cavity region inside the annular electrode frame. Inlet and outlet channels are provided on opposite sides of the electrode frame. The electrolyte flows into the electrode in the central cavity from the inlet channel and then flows out of the electrode frame through the outlet channel. Multiple grooves parallel to the electrolyte flow direction are provided on the surface of the negative electrode facing the separator. The groove cross-section is trapezoidal, the groove depth is 50% of the electrode thickness, the upper edge width is 25 mm, the lower edge width is 30 mm, and the cross-sectional distance between adjacent grooves is 50 mm. The electrode is a porous carbon felt with a thickness of 5 mm.

[0034] The specific parameters of the fuel cell stack are as follows:

[0035] Electrode area: 800 cm² 2 ;

[0036] Before compression, the thickness of the positive and negative carbon felt is 5mm. When assembling the battery, the thickness of the electrode is 120% of the thickness of the electrode frame. After assembling the battery, the electrode is compressed to be consistent with the thickness of the electrode frame.

[0037] Number of fuel cell stack sections: 10;

[0038] Current density: 40 mA / cm 2 Charging time: 3 hours; Discharge cut-off voltage: 8V.

[0039] Battery cycle performance: coulombic efficiency 88.1%, voltage efficiency 80.2%, energy efficiency 70.6%;

[0040] The battery performance of Comparative Example 3 is improved compared to Comparative Example 2, but it is still not ideal. Although the depth of the groove is controlled within a reasonable range, the groove width is large, which reduces the contact area between the carbon felt and the separator. The battery polarization is still large, and the performance does not meet expectations.

[0041] Comparative Example 4

[0042] Comparative Example 4 uses grooved carbon felt as the negative electrode in a zinc-bromine flow battery assembly. The positive and negative electrodes are still made of flat carbon felt. The electrodes are placed in the central cavity of the annular electrode frame. The length and width of the carbon felt electrodes match (are the same or equivalent) the length and width of the central cavity region inside the annular electrode frame. Inlet and outlet channels are provided on opposite sides of the electrode frame. The electrolyte flows into the electrode in the central cavity from the inlet channel and then flows out of the electrode frame through the outlet channel. Multiple grooves parallel to the electrolyte flow direction are provided on the surface of the negative electrode facing the separator. The groove cross-section is trapezoidal, the groove depth is 50% of the electrode thickness, the upper bottom edge width is 20 mm, the lower bottom edge width is 15 mm, and the distance between the lower bottom edges of adjacent grooves is 50 mm. The electrode is a porous carbon felt with a thickness of 5 mm.

[0043] The specific parameters of the fuel cell stack are as follows:

[0044] Electrode area: 800 cm² 2 ;

[0045] Before compression, the thickness of the positive and negative carbon felt is 5mm. When assembling the battery, the thickness of the electrode is 120% of the thickness of the electrode frame. After assembling the battery, the electrode is compressed to be consistent with the thickness of the electrode frame.

[0046] Number of fuel cell stack sections: 10;

[0047] Current density: 40 mA / cm 2 Charging time: 3 hours; Discharge cut-off voltage: 8V.

[0048] Battery cycle performance: Coulombic efficiency 89.5%, voltage efficiency 77.2%, energy efficiency 69.1%;

[0049] Comparative Example 4 sets the groove to be wider at the top and narrower at the bottom. It can be seen that the voltage efficiency of the battery is lower than that of Comparative Example 3. This is mainly because the upper surface of the carbon felt groove is wider, the contact area with the separator is reduced, the battery polarization increases, and the battery voltage efficiency decreases.

[0050] Comparative Example 5

[0051] Comparative Example 5 uses a conventional electrode structure as the negative electrode to assemble a zinc-bromine flow battery. The electrodes (positive and negative electrodes) are composed of flat carbon felt. The electrodes are placed in the central cavity of the annular electrode frame of the battery. The length and width of the carbon felt electrodes are matched (the same or equivalent) to the length and width of the central cavity region inside the annular electrode frame. Inlet and outlet channels are respectively set on two opposite sides of the electrode frame. The electrolyte flows into the electrode in the central cavity from the inlet channel and then flows out of the electrode frame through the outlet channel.

[0052] The specific parameters of the fuel cell stack are as follows:

[0053] Electrode area: 800 cm² 2 ;

[0054] Before compression, the thickness of the positive and negative carbon felt is 5mm. When assembling the battery, the thickness of the electrode is 120% of the thickness of the electrode frame. After assembling the battery, the electrode is compressed to be consistent with the thickness of the electrode frame.

[0055] Number of fuel cell stack sections: 10;

[0056] Current density: 40 mA / cm 2 Charging time: 5 hours; Discharge cut-off voltage: 8V.

[0057] Battery cycle performance: Coulombic efficiency 74.5%, voltage efficiency 71.2%, energy efficiency 53.0%;

[0058] Comparative Example 5 increases the battery's charging surface capacity to 200mAh / cm². 2 As can be seen, the coulombic efficiency and voltage efficiency of the battery have decreased significantly. At this point, the battery separator has been pierced by zinc dendrites, and the battery has failed due to a short circuit.

[0059] Example 1

[0060] Example 1 uses the electrode structure provided by this invention as the negative electrode to assemble a zinc-bromine flow battery. Both the positive and negative electrodes are made of flat carbon felt. The electrodes are placed in the central cavity of the annular electrode frame. The length and width of the carbon felt electrodes match (are the same or equivalent to) the length and width of the central cavity region inside the annular electrode frame. Inlet and outlet channels are respectively provided on opposite sides of the electrode frame. The electrolyte flows into the electrode in the central cavity from the inlet channel and then flows out of the electrode frame through the outlet channel. Multiple grooves parallel to the electrolyte flow direction are provided on the surface of the negative electrode facing the separator. The cross-section of the grooves perpendicular to the electrolyte flow direction is trapezoidal. The groove depth is 50% of the electrode thickness. The width of the upper bottom edge of the groove cross-section is 15 mm, the width of the lower bottom edge of the groove cross-section is 25 mm, and the distance between the lower bottom edges of adjacent grooves is 100 mm. The electrode is a porous carbon felt with a thickness of 5 mm.

[0061] The specific parameters of the fuel cell stack are as follows:

[0062] Electrode area: 800 cm² 2 ;

[0063] Before compression, the thickness of the positive and negative carbon felt is 5mm. When assembling the battery, the thickness of the electrode is 120% of the thickness of the electrode frame. After assembling the battery, the electrode is compressed to be consistent with the thickness of the electrode frame.

[0064] Number of fuel cell stack sections: 10;

[0065] Current density: 40 mA / cm 2 Charging time: 3 hours; Discharge cut-off voltage: 8V.

[0066] Battery cycle performance: Coulombic efficiency 93.8%, voltage efficiency 85.1%, energy efficiency 79.8%;

[0067] Example 1 uses the electrode structure provided by this utility model as the negative electrode of the battery. Since the electrode has grooves, it provides sufficient deposition sites for the deposition of zinc negative electrode. Therefore, as the battery is cycled, the battery performance does not decrease due to the gradual accumulation of zinc. Furthermore, since the width, depth and spacing of the grooves are within the range of the specific implementation of this utility model, the battery polarization can also be controlled, and the battery performance can be maintained at a high level.

[0068] Example 2

[0069] Example 2 uses the electrode structure provided by this invention as the negative electrode to assemble a zinc-bromine flow battery. The positive and negative electrodes are both made of flat carbon felt. The electrodes are placed in the central cavity of the battery's annular electrode frame. The length and width of the carbon felt electrodes match (are the same or equivalent) the length and width of the central cavity region inside the annular electrode frame. Inlet and outlet channels are respectively provided on opposite sides of the electrode frame. The electrolyte flows into the electrode in the central cavity from the inlet channel and then flows out of the electrode frame through the outlet channel. Multiple grooves parallel to the electrolyte flow direction are provided on the surface of the negative electrode facing the separator. The cross-section of the grooves perpendicular to the electrolyte flow direction is trapezoidal. The groove depth is 80% of the electrode thickness. The width of the upper bottom edge of the groove cross-section is 15mm, the width of the lower bottom edge of the groove cross-section is 25mm, and the distance between the lower bottom edges of adjacent grooves is 100mm. The electrode is a porous carbon felt with a thickness of 5mm. The specific parameters of the battery stack are as follows:

[0070] Electrode area: 800 cm² 2 ;

[0071] Before compression, the thickness of the positive and negative carbon felt is 5mm. When assembling the battery, the thickness of the electrode is 120% of the thickness of the electrode frame. After assembling the battery, the electrode is compressed to be consistent with the thickness of the electrode frame.

[0072] Number of fuel cell stack sections: 10;

[0073] Current density: 40 mA / cm 2 Charging time: 3 hours; Discharge cut-off voltage: 8V.

[0074] Battery cycle performance: Coulombic efficiency 94.1%, voltage efficiency 83.3%, energy efficiency 78.4%;

[0075] Example 2 uses the electrode structure provided by this utility model as the negative electrode of the battery. Compared with Example 1, this example further deepens the depth of the carbon felt groove, but still within the range required by this utility model. Due to the increased groove depth, the zinc monomass that the groove can accommodate is further increased, the cycle stability of the battery is improved, and the coulombic efficiency of the stack is improved. However, the polarization also increases at the same time, and the voltage efficiency of the battery is reduced.

[0076] Example 3

[0077] Example 3 uses the electrode structure provided by this invention as the negative electrode to assemble a zinc-bromine flow battery. Both the positive and negative electrodes are made of flat carbon felt. The electrodes are placed in the central cavity of the annular electrode frame. The length and width of the carbon felt electrodes match (are the same or equivalent) the length and width of the central cavity region inside the annular electrode frame. Inlet and outlet channels are respectively provided on opposite sides of the electrode frame. The electrolyte flows into the electrode in the central cavity from the inlet channel and then flows out of the electrode frame through the outlet channel. Multiple grooves parallel to the electrolyte flow direction are provided on the surface of the negative electrode facing the separator. The cross-section of the grooves perpendicular to the electrolyte flow direction is trapezoidal. The groove depth is 50% of the electrode thickness. The width of the upper bottom edge of the groove cross-section is 15 mm, the width of the lower bottom edge of the groove cross-section is 25 mm, and the distance between the lower bottom edges of adjacent grooves is 100 mm. The electrode is a porous carbon felt with a thickness of 5 mm.

[0078] The specific parameters of the fuel cell stack are as follows:

[0079] Electrode area: 800 cm² 2 ;

[0080] Before compression, the thickness of the positive and negative electrode carbon felt is 5 mm.

[0081] Number of fuel cell stack sections: 10;

[0082] Current density: 40 mA / cm 2 Charging time: 5 hours; Discharge cut-off voltage: 8V.

[0083] Battery cycle performance: Coulombic efficiency 92.8%, voltage efficiency 83.6%, energy efficiency 77.6%;

[0084] Example 3 increases the battery charging surface capacity to 200mAh / cm². 2 As can be seen, the coulombic efficiency and voltage efficiency of the battery remain at a high level, indicating that the electrode structure provided by this utility model can effectively improve the battery's surface capacity while maintaining high performance.

[0085] Example 4

[0086] Example 4 uses the electrode structure provided by this invention as the negative electrode to assemble a zinc-bromine flow battery. Both the positive and negative electrodes are made of flat carbon felt. The electrodes are placed in the central cavity of the annular electrode frame. The length and width of the carbon felt electrodes match (are the same or equivalent) the length and width of the central cavity region inside the annular electrode frame. Inlet and outlet channels are respectively provided on opposite sides of the electrode frame. The electrolyte flows into the electrode in the central cavity from the inlet channel and then flows out of the electrode frame through the outlet channel. Multiple grooves parallel to the electrolyte flow direction are provided on the surface of the negative electrode facing the separator. The cross-section of the groove perpendicular to the electrolyte flow direction is inverted T-shaped. The cross-section of the groove consists of connected upper and lower rectangles. The upper rectangle is 15mm wide and 25% of the electrode thickness in height, while the lower rectangle is 25mm wide and 35% of the electrode thickness in height. The distance between the lower rectangles of adjacent grooves is 100mm. The electrode is a porous carbon felt with a thickness of 5mm.

[0087] The specific parameters of the fuel cell stack are as follows:

[0088] Electrode area: 800 cm² 2 ;

[0089] Before compression, the thickness of the positive and negative electrode carbon felt is 5 mm.

[0090] Number of fuel cell stack sections: 10;

[0091] Current density: 40 mA / cm 2 Charging time: 3 hours; Discharge cut-off voltage: 8V.

[0092] Battery cycle performance: Coulombic efficiency 95.5%, voltage efficiency 85.2%, energy efficiency 81.4%; In Example 4, the groove cross-section is set as an inverted T-shape. Compared with the trapezoidal cross-section groove, the cavity volume of the inverted T-shaped flow channel is larger, which can provide more sufficient deposition space. In addition, the effective contact area between the carbon felt surface and the separator is the same as that of the trapezoidal groove, which can ensure that the stack has a higher voltage efficiency. Therefore, the stack has better performance by adopting the groove structure with an inverted T-shaped cross-section.

Claims

1. A zinc-bromine flow battery electrode structure, wherein the electrode is a carbon felt electrode, characterized in that: The electrode is provided with a groove parallel to the electrolyte flow direction. The cross-section of the groove perpendicular to the electrolyte flow direction is trapezoidal or inverted T-shaped, and the groove depth is 50%-80% of the electrode thickness.

2. The electrode structure according to claim 1, characterized in that: When the cross-section of the groove perpendicular to the direction of electrolyte flow is trapezoidal, the width of the upper bottom edge of the groove cross-section is 10mm-20mm, the width of the lower bottom edge of the groove cross-section is 15mm-40mm, and the distance between the lower bottom edges of adjacent groove cross-sections is 50mm-150mm. Alternatively, when the cross-section of the groove perpendicular to the electrolyte flow direction is an inverted T-shape, the groove cross-section is composed of a connected upper rectangle and a lower rectangle. The width of the upper rectangle is 10mm-20mm and the height is 20-30% of the electrode thickness. The width of the lower rectangle is 15mm-40mm and the height is 30%-40% of the electrode thickness. The distance between the lower rectangles of adjacent groove cross-sections is 50mm-150mm.

3. The electrode structure according to claim 1, characterized in that: When the cross-section of the groove perpendicular to the direction of electrolyte flow is trapezoidal, the width of the upper bottom edge of the groove cross-section is 13mm-17mm, the width of the lower bottom edge of the groove cross-section is 25mm-30mm, and the distance between the lower bottom edges of adjacent groove cross-sections is 90mm-110mm. Alternatively, when the cross-section of the groove perpendicular to the electrolyte flow direction is an inverted T-shape, the groove cross-section is composed of a connected upper rectangle and a lower rectangle. The width of the upper rectangle is 13mm-17mm and the height is 23%-27% of the electrode thickness. The width of the lower rectangle is 25mm-30mm and the height is 33%-37% of the electrode thickness. The distance between the lower rectangles of adjacent groove cross-sections is 90mm-110mm.

4. The electrode structure according to claim 1 or 2, characterized in that: The electrode is a porous carbon felt with a thickness of 4mm-6mm.

5. The electrode structure according to claim 1 or 2, characterized in that: The electrode is a porous carbon felt with a thickness of 4.5mm-5.5mm.

6. The electrode structure according to claim 1 or 2, characterized in that: The electrode is a porous carbon felt with a thickness of 4.8 mm to 5.2 mm.

7. The electrode structure according to claim 1 or 2, characterized in that: The electrode is provided with multiple grooves parallel to the electrolyte flow direction. The distance between the bottom edge or lower rectangle of the groove cross-section near the two edges of the electrode and the two edges of the electrode near it is 50mm-150mm.

8. The electrode structure according to claim 1 or 2, characterized in that: The electrode is provided with multiple grooves parallel to the electrolyte flow direction. The distance between the bottom edge or lower rectangle of the groove cross-section near the two edges of the electrode and the two edges of the electrode near it is 90mm-110mm.

9. The electrode structure according to claim 1, 2, or 3, characterized in that: When assembling a zinc-bromine flow battery, the side of the negative electrode with the groove faces the separator; The carbon felt negative electrode used is rectangular, and the length and width of the carbon felt electrode match the hollow area inside the annular electrode frame. That is, the surface shape and size of the carbon felt electrode are the same as the hollow area inside the annular electrode frame.

10. The electrode structure according to claim 1, 2, or 3, characterized in that: This electrode structure is only used at the negative electrode of the fuel cell stack, while the positive electrode still uses the traditional flat carbon felt electrode, which does not increase the internal resistance of the fuel cell stack and maintains the performance of the fuel cell stack.

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