A flow cell structure unit and flow cell stack

Abstract

The application discloses a kind of liquid flow single cell structure unit and liquid flow battery stack, liquid flow single cell structure unit includes first carbon felt, first flow field frame, ion conducting film, second carbon felt, second flow field frame and bipolar plate in turn, wherein, ion conducting film is fixedly connected with first flow field frame, bipolar plate is fixedly connected with second flow field frame;First flow field frame and second flow field frame structure are same, and are rectangular frame body with rectangular hole in middle, and four corners are respectively provided with through hole;Two long side frames of the side adjacent to first carbon felt or second carbon felt are provided with recessed groove type flow guide channel, and two recessed groove type flow guide channels are respectively communicated with two through holes of the same end, one through hole is used as electrolyte inlet, and the other through hole is used as electrolyte outlet;Second flow field frame and first flow field frame are 180° horizontal overturn setting each other.The application can improve the performance of single battery and stack;Reduce the space requirement of energy storage system, also can improve unit volume electrolyte power.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical energy storage, and particularly relates to a flow cell structure unit and a flow cell stack. BACKGROUND

[0002] With the popularization and application of renewable energy, its proportion in the energy supply structure is gradually increasing, and it is gradually transformed from an auxiliary energy into a leading energy to support the sustainable development of human society. However, the instability and discontinuity of renewable energy represented by wind energy and solar energy have a serious impact on the power grid. Large-scale and efficient energy storage technology is a key technology for realizing large-scale utilization of renewable energy generation, and is also a bottleneck technology for building smart grids and improving the power grid's ability to accept discontinuous and unstable renewable energy generation. It is a major demand for the country to achieve energy security and economic sustainable development.

[0003] Among many energy storage technologies, electrochemical energy storage technology is developing rapidly due to its high efficiency and environmental friendliness. As a typical device of electrochemical energy storage technology, flow batteries have outstanding advantages such as high efficiency, long cycle life, independent design of capacity and power, fast response, high safety, and high cost performance in the life cycle, and are particularly suitable for large-scale energy storage. At present, several countries have successively built kW-MW level flow battery demonstration systems, which are matched with renewable energy generation systems such as solar energy and wind energy to smooth output, track planned generation, balance load, and cut peak and fill valley.

[0004] With the rapid decline in cost in recent years and the gradual maturity of commercial application, the advantages of flow batteries are becoming more and more obvious, and they are gradually becoming the mainstream of new energy storage installations. There is still a lot of room for cost reduction in the future, and the development prospect is broad. Therefore, strengthening the research on the structure of single cells in flow battery energy storage systems is particularly important for improving the overall efficiency of the battery and reducing the cost of the energy storage system.

[0005] The structure of a traditional flow single cell is shown in Figure 1 The battery is centered on a separator 600 and symmetrically distributed, with gaskets 300, electrodes 500, electrode frames 400, gaskets 300, bipolar plates 200, and cell end plates 100 on both sides. The electrolyte flow channel is usually processed on the surface of the bipolar plate or separately embedded in a flow channel frame in the flow field frame. Both of these methods have certain defects: the bipolar plate is easily affected by the strong acid and strong base of the battery flow to cause chemical and electrochemical corrosion, which in turn affects the performance of the battery; and the method of separately embedding a flow channel frame in the flow field frame has a complex installation process and also increases the material cost, and the installation and sealing of the flow field frame and the flow channel frame are also prone to problems. SUMMARY

[0006] In order to solve the above problems existing in the prior art, the application provides a liquid flow single cell structure unit and a liquid flow battery stack.

[0007] The application provides a liquid flow single cell structure unit, which comprises a first carbon felt, a first flow field frame, an ion conductive film, a second carbon felt, a second flow field frame and a bipolar plate in sequence, wherein,

[0008] The ion conductive film is fixedly connected with the first flow field frame, and the bipolar plate is fixedly connected with the second flow field frame.

[0009] The first flow field frame and the second flow field frame are identical in structure and are both rectangular frame bodies provided with rectangular holes in the middle, and the four corners of the frame bodies are respectively provided with through holes; two long side frames on one side adjacent to the first carbon felt or the second carbon felt are provided with recessed groove type flow guide channels, and the two recessed groove type flow guide channels are respectively communicated with two through holes at the same end, one through hole serving as an inlet of electrolyte and the other through hole serving as an outlet of electrolyte; the second flow field frame and the first flow field frame are arranged in a 180° horizontal flip manner.

[0010] The electrolyte is injected into the inlet, flows through the first carbon felt or the second carbon felt through the communicated recessed groove type flow guide channels, enters the recessed groove type flow guide channels on the opposite side and flows back to the outlet, so that the electrolyte completes one cycle in the single cell.

[0011] In an embodiment of the application, the length-width ratios of the first flow field frame and the second flow field frame are both 2.5:1-5:1.

[0012] In an embodiment of the application, the length-width ratio of the rectangular hole is 5.5:1-7:1.

[0013] In an embodiment of the application, the recessed groove type flow guide channel comprises a plurality of first-level flow guide channels, a plurality of second-level flow guide channels and a plurality of third-level flow guide channels, wherein,

[0014] One end of each first-level flow guide channel is communicated with one liquid flow through hole, and the other end is communicated with a second-level flow guide channel, and the second-level flow guide channels are equidistantly distributed along the inner edge of the flow field frame;

[0015] The plurality of third-level flow guide channels are uniformly arranged in the inner edges of the two long sides adjacent to the rectangular hole of the flow field frame and communicated with the second-level flow guide channels.

[0016] In an embodiment of the application, the plurality of first-level flow guide channels are different in shape, same in length and same in volume.

[0017] In one embodiment of the present application, the secondary flow guide channel comprises a plurality of interval parts and flow channels on both sides of the interval parts, and the interval parts are odd in number, and a obtuse triangle-shaped protruding buffer device is arranged on the middle position of the upper surface of the middle interval part to face the primary flow guide channel, so as to make the electrolyte passing through the primary flow guide channel evenly pass through the flow channels on both sides of the interval parts of the secondary flow guide channel and enter the tertiary flow guide channel.

[0018] In one embodiment of the present application, the rectangular hole is single-layer step-shaped recessed platform around the side opposite to the side provided with the groove-shaped flow guide channel, and the depth of the recessed platform is the same as the thickness of the bipolar plate and the ion-conducting film.

[0019] In one embodiment of the present application, the ion-conducting film is fixedly connected with the first flow field frame by bonding, and the bipolar plate is fixedly connected with the second flow field frame by welding.

[0020] In one embodiment of the present application, the welding is laser welding, the laser power is 20W-30W, and the wavelength is 980nm.

[0021] The present application also provides a flow battery stack comprising a plurality of the flow battery cell structure units according to any one of the above.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] The flow battery cell structure unit and the flow battery stack of the embodiments of the present application optimize the shape and length-width ratio of the flow field frame and the rectangular hole, and combine the special design and reasonable layout of the groove-shaped flow guide channel on the flow field frame, so that when the electrolyte passes through the groove-shaped flow guide channel to reach the electrode area, the flow rate is uniform, the pressure is stable, the electrolyte ion is fully reacted, and the performance of the single battery and the stack is improved. In addition, the structure of the flow field frame and the fixing mode thereof with the bipolar plate and the ion-conducting film reduce the thickness of the flow battery structure unit and the entire flow battery stack, which can not only reduce the space requirement of the energy storage system, but also increase the electrolyte power per unit volume, thereby improving the performance of the stack. The flow battery structure unit no longer needs to be sealed by interlayer sealing gaskets, and the flow field frames are tightly connected with each other, and the external sides are hot melt welded when the flow battery stack is formed, so that a better sealing effect can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a structural schematic diagram of a traditional flow battery cell;

[0025] Figure 2 is a structural schematic diagram of each component of a flow battery cell structure unit provided by the embodiments of the present application;

[0026] Figure 3 is a structural schematic diagram of a flow field frame and bipolar plate and ion conductive membrane fixed after the structure unit of the flow cell of the embodiment of the present application;

[0027] Figure 4 is a back structure schematic diagram of the flow field frame of the embodiment of the present application;

[0028] Figure 5 is a structure schematic diagram of the flow field frame of the embodiment of the present application;

[0029] Figure 6 is a partial structure schematic diagram of the flow field frame of the embodiment of the present application.

[0030] Legend:

[0031] 1-first carbon felt; 2-first flow field frame; 3-ion conductive membrane; 4-second carbon felt; 5-second flow field frame; 6-bipolar plate; 7-recessed table; 8-primary flow guide channel; 9-secondary flow guide channel; 10-tertiary flow guide channel; 11-spacing part; 12-protruding buffer device; 13-flow channel; 100-battery end plate; 200-bipolar plate; 300-sealing gasket; 400-electrode frame; 500-electrode; 600-battery with diaphragm. DETAILED DESCRIPTION

[0032] The present application will be further described in detail below with specific embodiments, but the embodiments of the present application are not limited thereto.

[0033] Please refer to Figure 2 and Figure 3 , Figure 2 is a structural schematic diagram of each component of the structure unit of the flow cell of the embodiment of the present application, Figure 3 is a structural schematic diagram of a flow field frame and bipolar plate and ion conductive membrane fixed after the structure unit of the flow cell of the embodiment of the present application.

[0034] It should be noted that the structure unit of the flow cell of the embodiment of the present application is one of a plurality of repeatedly stacked single cell structure units in the flow cell stack.

[0035] The single cell structure unit of the embodiment of the present application sequentially includes, from one side to the other side: first carbon felt 1, first flow field frame 2, ion conductive membrane 3, second carbon felt 4, second flow field frame 5 and bipolar plate 6. Figure 2 In the embodiment of the present application, the second flow field frame 5 and the bipolar plate 6 on the leftmost side are the same in structure and function as the second flow field frame 5 and the bipolar plate 6 on the rightmost side in the present single cell structure unit, and serve as part of the single cell structure unit on the left side of the single cell structure unit of the embodiment of the present application.

[0036] The ion-conducting membrane 3 is fixedly connected with the first flow field frame 2, and the bipolar plate 6 is fixedly connected with the second flow field frame 5 in the single cell structure unit of the embodiment of the application.

[0037] The first flow field frame 2 and the second flow field frame 5 are identical in structure, and are both rectangular frame bodies provided with rectangular holes in the middle, and provided with through holes at four corners; two long side frames on one side adjacent to the first carbon felt 1 or the second carbon felt 4 are provided with recessed groove type flow guide channels, and the two recessed groove type flow guide channels are respectively communicated with two through holes at the same end, one through hole serving as an inlet of electrolyte, and the other through hole serving as an outlet of electrolyte. The second flow field frame 5 and the first flow field frame 2 are horizontally flipped by 180 degrees, that is, the flow field frame for fixing the ion-conducting membrane 3 and the flow field frame for fixing the bipolar plate 6 are completely identical in structure, and only need to be horizontally rotated by 180 degrees in use, so as to be used as positive flow field frames and negative flow field frames respectively. This design reduces the mold design cost, simplifies the incoming material processing and acceptance link, improves the assembly line efficiency, and is convenient for injection and outflow of positive electrolyte and negative electrolyte.

[0038] The electrolyte is injected into the inlet of each flow field frame, and after flowing through the first carbon felt 1 or the second carbon felt 4 through the communicated recessed groove type flow guide channels, the electrolyte enters the recessed groove type flow guide channels on the opposite side and flows back to the outlet, so as to complete one cycle of the electrolyte in the single cell.

[0039] The flow field frame of the application is obviously different from the traditional flow field frame, and is a rectangle, and the hole on each flow field frame is also a rectangle. Preferably, the length-width ratio of the first flow field frame 2 and the second flow field frame 5 is 2.5:1-5:1, and the length-width ratio of the rectangular hole is 5.5:1-7:1. In actual manufacturing, the length of the flow field frame is 500mm-1000mm, and the width is 200mm-400mm. Further, the thickness of the flow field frame is 1.5mm-3.5mm, and the thickness of the first carbon felt 1 and the second carbon felt 4 is 2.5mm-3.5mm. The first carbon felt 1 and the second carbon felt 4 form electrode areas respectively with the rectangular holes on the first flow field frame 2 and the second flow field frame 5 adjacent thereto.

[0040] The hole on the flow field frame of the application is a rectangle. In the process of flowing through the electrode area, the distance and time of flow movement are shorter than those of a square hole with the same area, the concentration difference generated in the movement process is reduced, the distribution of the electrolyte when flowing out of the electrode area is relatively uniform, the concentration polarization loss is reduced, the surface reaction activity of the battery is improved, the activation polarization loss is reduced, the internal resistance of the single cell and the stack is reduced, and the ohmic polarization loss is reduced.

[0041] In addition, the traditional liquid flow single cell and the stack adopt an external externally added bolt and nut fastening mode to realize overall sealing, and this mode needs to ensure that the overall stress of the stack is uniform, so a square shape or a shape with a length-width ratio close to 1 is often used for the design of the liquid flow single cell to facilitate the uniform arrangement of the bolts and nuts arranged on the outermost end plate of the external connection, and then the best effect of fastening and sealing is realized. The design of the rectangular flow field frame of the present application not only facilitates the setting of the required groove type flow guide channel, but also facilitates the assembly of the stack and the external packaging. When packaging, it can be directly packaged by heat melting welding of the external several surfaces, and no longer needs to be packaged by the bolt and nut fastening mode, and the sealing effect is better.

[0042] Please refer to Figure 4 , Figure 4 is a back surface structure schematic diagram of a flow field frame provided by an embodiment of the present application. As an implementation manner, the back surface (the side without the groove type flow guide channel, such as the right side in Figure 3 ) of each flow field frame is provided with a single-layer stepped recess 7. Specifically, the recess 7 is arranged around the side opposite to the side provided with the groove type flow guide channel of the rectangular hole, and the depth of the recess 7 is the same as the thickness of the bipolar plate 6 and the ion conductive film 3. In this way, after the flow field frame is bonded with the bipolar plate 6 or the ion conductive film 3, the back surface of the flow field frame forms a protrusion, which further affects the assembly and sealing of the overall system of the stack.

[0043] The ion conductive film 3 of the embodiment of the present application is fixedly connected with the first flow field frame 2 in a bonding mode. Specifically, PP glue sealing bonding can be used. The bipolar plate 6 is fixedly connected with the second flow field frame 5 in a welding mode, and laser welding is preferably used, the laser power is 20W-30W, and the wavelength is 980nm. The connection between the flow field frame and the bipolar plate 6 of the present application is the connection between the conductive and non-conductive polypropylene materials. Other methods such as hot melting and carbon dioxide welding cannot effectively connect, but laser welding can realize reliable connection between the two. And by using the laser with the specific power and the specific wavelength, the two welding materials can be tightly connected, avoiding the defects such as air bubbles, incomplete welding, incomplete welding and the like on the welding surface. At the same time, this tight welding mode can not only save cost and reduce the thickness of the battery by omitting the use of sealing pads, but also is beneficial to the overall external sealing of the battery stack composed of the single cell structure unit of the present application.

[0044] The application can realize that the thickness of the flow field frame with the installed bipolar plate 6 or ion conductive film 3 is the same as the thickness of the flow field frame itself by arranging a single-layer stepped recess 7 on the back of the flow field frame, and the depth of the recess 7 is the same as the thickness of the bipolar plate 6 and the ion conductive film 3. In addition, the thickness of the flow field frame is smaller than the thickness of the flow field frame of the traditional flow cell, and compared with the traditional flow cell composed of the bipolar plate, the sealing gasket, the flow field frame, the ion conductive film and other components, the thickness is reduced by 2-2.5 times, the product volume is reduced, and the product cost is saved. In addition, the energy efficiency of the flow battery is related to the contact area of the electrolyte solution and the bipolar plate, the larger the contact area, the more sufficient the energy efficiency of the flow battery. The thickness of the flow field frame is thin, and the thickness of the assembled battery is also thin, so the volume of the electrolyte solution contained in the electrode area is also small. At this time, the same volume of electrolyte solution can be used for more flow batteries while ensuring the efficiency of the battery. Therefore, the thinner design of the flow battery structure of the application can reduce the space requirement of the energy storage system, and can reduce the demand for electrolyte solution while maintaining the efficiency, thereby reducing the product cost, or realizing the effect of increasing the power per unit volume of electrolyte.

[0045] It should be noted that the polarity of the electrode area formed by the first carbon felt 1 and the second carbon felt 4 in the embodiment of the application is opposite, which is determined according to the polarity of the electrolyte flowing through the adjacent flow field frame. The first carbon felt 1 and the second carbon felt 4 are preferably polypropylene carbon felt, which has excellent electrical conductivity and a pore structure in the carbon felt that is conducive to improving the catalytic activity of the flow battery electrode, thereby increasing the supply of electrolyte in the single cell during the operation of the flow battery, and further improving the overall performance of the flow battery.

[0046] Please refer to Figure 5 , Figure 5 is a structural schematic diagram of a flow field frame provided by the embodiment of the application, and the specific structure of the flow field frame of the application will be described in detail below.

[0047] The two long edges of the face adjacent to the electrode of each flow field frame are provided with recessed flow guide channels, and the recessed flow guide channels include a plurality of first-level flow guide channels 8, a plurality of second-level flow guide channels 9 and a plurality of third-level flow guide channels 10. One end of each first-level flow guide channel 8 is communicated with a liquid flow hole, and the other end is communicated with a second-level flow guide channel 9, and the second-level flow guide channels 9 are equidistantly distributed on the inner edge of the flow field frame. A plurality of third-level flow guide channels 10 are uniformly arranged on the inner edges of the two long edges adjacent to the rectangular hole of the flow field frame, and are communicated with the second-level flow guide channels 9.

[0048] It should be noted that, due to the different distances of the positions on the frame from the inlet and outlet, in order to ensure that the electrolyte can be uniformly and simultaneously distributed to any position on the side of the electrode area, under the condition that the frame area of the flow field frame is limited, the present application achieves efficient and uniform distribution of the electrolyte solution in each single battery, reduces the concentration polarization loss, thereby improving the battery surface reaction activity and reducing the effect of activation polarization loss, by specifically designing the structures and shapes of the first-level flow guide channels 8, the second-level flow guide channels 9 and the third-level flow guide channels 10.

[0049] The shapes of the plurality of first-level flow guide channels 8 of the embodiment of the present application are different, the lengths are the same, and the volumes are the same. Figure 4 As shown in the figure, since the plurality of first-level flow guide channels 8 are all communicated with the same inlet or outlet, the first-level flow guide channel 8 communicated with the second-level flow guide channel 9 farthest from the inlet or outlet can be arranged at the outermost side of the frame, and the first-level flow guide channel 8 communicated with the second-level flow guide channel 9 farthest from the inlet or outlet can be arranged at the innermost side of the frame. Since the lengths of the first-level flow guide channels 8 are the same, and the volumes are the same, the electrolyte will be uniformly distributed by the first-level flow guide channels 8, and the time of flowing through each first-level flow guide channel 8 is the same, and the electrolyte enters each second-level flow guide channel 9 equally and simultaneously.

[0050] Please refer to Figure 6 , Figure 6 which is a partial structure schematic diagram of a flow field frame provided by the embodiment of the present application, Figure 6 It can be seen from the figure that the second-level flow guide channel 9 of the embodiment of the present application includes a plurality of interval parts 11 and flow channels 13 on both sides of the interval parts 11, and the interval parts 11 are odd, and a obtuse triangle-shaped protruding buffer device 12 facing the first-level flow guide channel 8 is arranged at the middle position of the upper surface of the middle interval part 11, so as to uniformly pass the electrolyte through the flow channels 13 on both sides of the interval parts 11 of the second-level flow guide channel 9 into the third-level flow guide channel 10.

[0051] The second-level flow guide channel 9 of the embodiment of the present application can buffer the electrolyte entering the second-level flow guide channel 9 by arranging the interval parts 11 as odd, and arranging the obtuse triangle-shaped protruding buffer device 12 facing the first-level flow guide channel 8 at the middle position of the upper surface of the middle interval part 11, and can improve the uniformity of the distribution of the electrolyte in the second-level flow guide channel 9, so as to stably and uniformly enter the third-level flow guide channel 10.

[0052] Combined with Figure 1 and Figure 5The working principle of the liquid flow single cell structure unit provided by the embodiment of the present application is described. The positive electrolyte / negative electrolyte is injected from the inlet A at the upper end of the second flow field frame 5, enters the primary flow guide channel 8, and is evenly distributed into three parts. The positive electrolyte / negative electrolyte flows through the primary flow guide channel 8 and is also evenly and equally distributed into the secondary flow guide channel 9. The positive electrolyte / negative electrolyte is evenly distributed into four parts again in the secondary flow guide channel 9 and then smoothly and evenly enters the plurality of tertiary flow guide channels 10. The positive electrolyte / negative electrolyte flowing through the tertiary flow guide channels 10 is evenly distributed into a plurality of streams and enters the electrode area formed by the electrodes laid in the middle holes. The positive electrolyte / negative electrolyte flowing through the electrode area enters the plurality of tertiary flow guide channels 10 at the lower end of the second flow field frame 5, is evenly collected through the three secondary flow guide channels 9, and then enters the three primary flow guide channels 8, respectively, and finally flows out from the outlet B, completing a cycle of the positive electrolyte / negative electrolyte in the liquid flow single cell structure unit. Correspondingly, the negative electrolyte / positive electrolyte is injected from the inlet C at the upper end of the first flow field frame 2, flows through the groove-shaped flow guide channel, and then flows out from the outlet D at the lower end of the first flow field frame 2, completing a cycle of the negative electrolyte / positive electrolyte in the liquid flow single cell structure unit. In this process, the ions in the positive and negative electrolytes pass through the ion-conducting membrane 3 and are collected by the bipolar plate 6, completing the charging / discharging process in the single cell.

[0053] The embodiment of the present application also provides a liquid flow battery stack, which is stacked by a plurality of liquid flow single cell structure units described above. Since the specific structure and effects of the liquid flow single cell structure unit have been described in detail above, they will not be described here again.

[0054] The current density, coulombic efficiency, voltage efficiency and energy efficiency of the liquid flow battery stack provided by the embodiment of the present application and the conventional stack are compared and tested, and the results are shown in Table 1.

[0055] Table 1 Performance comparison of the liquid flow battery stack of the present application and the conventional stack

[0056] Stack Current density mA / cm 2 ]] Coulombic efficiency % Voltage efficiency % Energy efficiency % Conventional structured battery series stack 70 96.1 82 72 Flow battery stack of the invention 100 97.9 89.2 80.1

[0057] It can be seen that the liquid flow battery stack composed of the liquid flow single cell structure unit of the present application has a significantly improved current density, and the coulombic efficiency, voltage efficiency and energy efficiency are also improved to different degrees compared with the conventional liquid flow battery stack.

[0058] The liquid flow single cell structure unit and the liquid flow battery stack of the embodiment of the present application optimize the shape and length-width ratio of the flow field frame and the rectangular hole, and combine the special design and reasonable layout of the groove type flow guide channel on the flow field frame, so that when the electrolyte passes through the groove type flow guide channel to reach the electrode area, the flow rate is uniform, the pressure is stable, the electrolyte ion reaction is fully promoted, and the performance of the single cell and the stack is improved. In addition, the structure of the flow field frame and the fixing method thereof with the bipolar plate and the ion conductive film reduce the thickness of the liquid flow battery structure unit and the entire liquid flow battery stack, which can not only reduce the space requirement of the energy storage system, but also increase the electrolyte power per unit volume, thereby improving the performance of the stack.

[0059] In addition, in the traditional liquid flow single cell structure, the bipolar plate and the flow field frame are independent individuals, and a sealing gasket is used in the middle to realize the connection and sealing of the bipolar plate and the flow field frame under the fastening action of the external bolt and nut. The ion conductive film and the flow field frame are also connected by relying on the fastening force of the external bolt and nut of the battery. This sealing method has the problem that the sealing gasket is prone to aging over time and causes liquid leakage. The liquid flow battery structure unit of the present application no longer needs to realize sealing by arranging a sealing gasket between layers, and the flow field frames can be connected in close contact through reasonable involvement. When the liquid flow battery stack is formed, the stack can be better sealed through hot melting welding of each side surface.

[0060] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0061] In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0062] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0063] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0064] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0065] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A flow cell structural unit, characterized in that, It sequentially includes a first carbon felt (1), a first flow field frame (2), an ion-conducting membrane (3), a second carbon felt (4), a second flow field frame (5), and a bipolar plate (6), wherein, The ion-conducting membrane (3) is fixedly connected to the first flow field frame (2) by PP glue, and the bipolar plate (6) is fixedly connected to the second flow field frame (5) by laser welding. The first flow field frame (2) and the second flow field frame (5) have the same structure. They are both rectangular frames with a rectangular hole in the middle and through holes at the four corners. The two long frames on the side adjacent to the first carbon felt (1) or the second carbon felt (4) are provided with grooved flow channels. The two grooved flow channels are respectively connected to two through holes at the same end. One through hole serves as the inlet of the electrolyte and the other through hole serves as the outlet of the electrolyte. The second flow field frame (5) and the first flow field frame (2) are horizontally rotated 180° to each other. The aspect ratio of the first flow field frame (2) and the second flow field frame (5) is 2.5:1-5:1; the aspect ratio of the rectangular hole is 5.5:1-7:1; the rectangular hole has a single-layer stepped recessed platform (7) on the side opposite to the grooved flow channel, and the depth of the recessed platform (7) is the same as the thickness of the bipolar plate (6) and the ion conduction membrane (3); The groove-shaped flow channel includes multiple primary flow channels (8), multiple secondary flow channels (9), and multiple tertiary flow channels (10). Each primary flow channel (8) has a liquid flow hole at one end and a secondary flow channel (9) at the other end. The secondary flow channels (9) are equidistantly distributed along the inner edge of the flow field frame. The multiple tertiary flow channels (10) are uniformly arranged along the inner edge of the two long sides of the flow field frame adjacent to the rectangular hole and are connected to the secondary flow channels (9). The multiple primary flow channels (8) have different shapes but the same length and volume. The secondary flow channel (9) includes multiple intervals (11) and flow channels (13) on both sides of the intervals (11). The number of intervals (11) is odd. The middle of the upper surface of the middle interval (11) is provided with an obtuse triangular protrusion buffer device (12) facing the primary flow channel (8) so as to uniformly guide the electrolyte passing through the primary flow channel (8) through the flow channels (13) on both sides of the intervals (11) of the secondary flow channel (9) into the tertiary flow channel (10). Electrolyte is injected into the inlet. The electrolyte flows through the first carbon felt (1) or the second carbon felt (4) via the connected groove-shaped guide channel, and then flows back to the outlet through the groove-shaped guide channel on the opposite side, completing one cycle of the electrolyte inside the single cell.

2. The flow cell structure unit according to claim 1, characterized in that, The welding is laser welding, with a laser power of 20W-30W and a wavelength of 980nm.

3. A flow battery stack, characterized in that, It includes multiple flow single-cell structural units as described in any one of claims 1-2.

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