An integrated bipolar liquid flow battery electrode frame and its all-vanadium liquid flow battery

Abstract

The present invention discloses an integrated bipolar flow battery electrode frame and an all-vanadium flow battery thereof, wherein the upper and lower surfaces of the electrode frame body serve as the positive electrode side and the negative electrode side respectively, and the middle of the upper and lower surfaces of the electrode frame body are provided with an electrode cavity, wherein the electrode cavity on one side is provided with an annular groove; the upper and lower surfaces of the electrode frame body are provided with a secondary flow channel, and a comb groove is provided between the secondary flow channel and the electrode cavity, and the width of the comb groove on one side of the groove is 1 / 3-2 / 3 of the width of the comb groove on the other side; the bipolar plate is annular, and the bipolar plate coated with a sealing gasket is embedded in the groove; the fixing ring is annular, matching the shape of the bipolar plate, and the fixing ring is installed on the side of the bipolar plate coated with the sealing gasket away from the groove. After being pressed, the fixing ring and the surface of the electrode frame body are flush. The present invention reduces the use of bipolar plates, has good sealing effect, better flow field uniformity, and significantly improves the battery stack assembly efficiency, operation stability and service life.

Description

Technical Field

[0001] The present invention relates to the technical field of redox flow batteries, and in particular to an integrated bipolar flow battery electrode frame and an all-vanadium flow battery thereof. Background Art

[0002] In recent years, the rapid consumption of fossil fuels and increased greenhouse gas emissions have led to a growing demand for renewable energy. However, renewable energy sources, such as wind and solar power, are unstable and discontinuous, requiring large-scale energy storage systems for their grid connection. Among the available energy storage options, electrochemical energy storage technology is considered the most economical and practical. Among these electrochemical energy storage technologies, all-vanadium redox flow batteries have garnered widespread attention due to their high safety, separation of energy and power, long cycle life, and deep charge and discharge capabilities.

[0003] All-vanadium liquid flow batteries are applied on a large scale using a battery stack, which contains multiple battery cells connected to an external liquid storage tank via a circulating pump. Currently, the flow field structure, sealing issues, and assembly costs of the battery stack have always been obstacles to the commercialization of vanadium batteries. In the existing technology, each battery cell in the battery stack contains positive and negative electrode frames, positive and negative electrodes, diaphragms, and related components. The assembly process is very tedious and complicated. In order to increase the sealing, welding is often used to connect the various components. However, there is still a high risk of leakage in long-term operation. At the same time, the effective utilization rate of diaphragms and bipolar plates is also relatively low, which leads to increased assembly costs.

[0004] Patent CN 111370730 A designs an integrated bipolar plate and battery cell frame, combining the positive and negative electrode frames into a single, sealed frame, into which multiple bipolar plate materials are embedded. This technology theoretically simplifies battery stack sealing and reduces the number of bipolar plates used. However, in practice, bipolar plate embedding is difficult, and the combination of multiple bipolar plate materials increases the risk of leakage through gaps, making it impractical.

[0005] Patent CN 114520345 A discloses an integrated electrode frame with bipolar plates. This laser-welds the bipolar plates and the positive and negative electrode frames into one, improving the sealing reliability of the battery stack and possessing certain practical significance. However, the current application of welding technology in flow battery stacks still carries some risks, and the cost of welding equipment and materials increases during the battery stack production process.

[0006] Patent CN 215933654 U discloses an all-vanadium liquid flow battery stack structure, which also adopts an integrated electrode frame structure. However, it uses a mortise and tenon structure to connect the electrode frame, which has high requirements on the mechanical properties and processing accuracy of the material, and increases the assembly cost and labor cost of the battery stack.

[0007] This shows that the design concept of the integrated electrode frame is excellent and has development prospects, but there are currently certain technical difficulties. At the same time, the integrated bipolar flow battery electrode frame has higher requirements for the flow field structure and needs to ensure the uniformity of the flow. Otherwise, it will lead to the formation of reaction "blind spots" on the electrodes, reducing the battery energy efficiency and performance. In addition, the bipolar plates commonly used in battery stacks are flexible graphite plates with low pressure resistance. During the assembly of the battery stack, the electrodes are compressed, and greater pressure is generated on both sides of the bipolar plates in the electrode frame. Cracks are easily formed under compression, causing the battery to short-circuit, reduce efficiency, and shorten lifespan.

[0008] Therefore, designing a new integrated bipolar flow battery electrode frame to reduce leakage risk and assembly costs is of great significance to the commercial development of vanadium batteries. Summary of the Invention

[0009] In order to solve the above problems, the present invention provides an integrated bipolar liquid flow battery electrode frame, which reduces the use of bipolar plates, has good sealing effect, better flow field uniformity, and significantly improves the battery stack assembly efficiency, operation stability and service life.

[0010] Another object of the present invention is to provide an all-vanadium liquid flow battery, comprising the above-mentioned integrated bipolar liquid flow battery electrode frame.

[0011] The technical solution adopted by the present invention is to provide an integrated bipolar liquid flow battery electrode frame, comprising:

[0012] An electrode frame body, wherein the upper and lower surfaces of the electrode frame body serve as the positive electrode side and the negative electrode side, respectively, and the positive and negative electrode sides are interchangeable; an electrode cavity is provided in the middle area of ​​the upper and lower surfaces of the electrode frame body, and an annular groove is provided around the electrode cavity on one side; a secondary flow channel is provided on the upper and lower surfaces of the electrode frame body, and a comb groove is provided between the secondary flow channel and the electrode cavity, and the width of the comb groove on the side with the groove is 1 / 3-2 / 3 of the width of the comb groove on the other side;

[0013] The bipolar plate is annular and matches the shape of the groove. The outer side and upper and lower edges of the bipolar plate are covered with sealing gaskets. The bipolar plate covered with the sealing gasket is embedded in the groove.

[0014] The fixing ring is annular and matches the shape of the bipolar plate. The fixing ring is installed on the side of the bipolar plate covered with the sealing gasket away from the groove. After being pressed, the fixing ring is flush with the surface of the electrode frame body.

[0015] An all-vanadium liquid flow battery comprises the above-mentioned integrated bipolar liquid flow battery electrode frame.

[0016] The beneficial effects of the present invention are:

[0017] 1. In the embodiments of the present invention, the usage amount of bipolar plates is significantly reduced compared with the prior art, the utilization rate of bipolar plates is increased, the assembly cost of the stack is effectively reduced, the usage amount of sealing materials is effectively reduced, and the sealing risk is reduced; the combined integrated bipolar flow battery electrode frame is equivalent to the positive electrode frame, negative electrode frame, bipolar plates and related seals in the traditional technology, so the assembly difficulty is reduced and the assembly efficiency is improved.

[0018] 2. The sealing gasket in the embodiments of the present invention adopts a "C"-shaped cross-section design, which has better sealing effect and can buffer the pressure received by the bipolar plates at the same time; the convex strips of the sealing gasket can achieve multi-stage sealing and enhance the sealing performance. The trapezoidal cross-section of the convex strips can increase the sealing area, the stress area of the bipolar plates is increased, the risk of fracture due to shear force is reduced, and the cycle life is increased.

[0019] 3. The support frame on the fixing ring in the embodiments of the present invention can support the electrode and prevent the bipolar plates from being fractured. The secondary flow channels on the electrode frame have a flow splitting structure and can supply liquid to each electrode area; it can be used in a flow battery system similar to the electrolyte properties of a vanadium redox flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a front view schematic diagram of the integrated bipolar flow battery electrode frame in the embodiments of the present invention.

[0022] Figure 2 It is a back view schematic diagram of the integrated bipolar flow battery electrode frame in the embodiments of the present invention.

[0023] Figure 3 It is a structural schematic diagram of the fixing ring in the embodiments of the present invention.

[0024] Figure 4 It is a cross-sectional schematic diagram of the sealing gasket in the embodiments of the present invention.

[0025] Figure 5 It is a test performance diagram of the vanadium redox flow battery stack in Example 1.

[0026] Figure 6 It is a test performance diagram of the vanadium redox flow battery stack in Example 2.

[0027] Figure 7 It is a test performance diagram of the vanadium redox flow battery stack in Example 3.

[0028] Figure 8 This is a performance diagram of the all-vanadium liquid flow battery stack test in Example 4.

[0029] Figure 9 This is a photo of the bipolar plate after testing in Example 4.

[0030] Figure 10 Schematic diagram of the cross section of the bipolar plate sealing gasket of Example 5.

[0031] Figure 11 This is a performance diagram of the all-vanadium liquid flow battery stack test in Example 5.

[0032] Figure 12 It is a schematic cross-sectional view of the bipolar plate sealing gasket of Example 6.

[0033] Figure 13 This is a performance diagram of the all-vanadium liquid flow battery stack test in Example 6.

[0034] Figure 14 This is a schematic cross-sectional view of the bipolar plate sealing gasket of Example 7.

[0035] Figure 15 This is a performance diagram of the all-vanadium liquid flow battery stack test of Example 7.

[0036] Figure 16 It is a schematic cross-sectional view of the bipolar plate sealing gasket of Example 8.

[0037] Figure 17 This is a performance diagram of the all-vanadium liquid flow battery stack test of Example 8.

[0038] Figure 18 It is a schematic diagram of the existing sealing structure in Example 9.

[0039] Figure 19 This is a performance diagram of the all-vanadium liquid flow battery stack test of Example 9.

[0040] Figure 20 Schematic diagram of the structure of the sealing gasket in Example 10.

[0041] Figure 21 This is a test performance diagram of the all-vanadium liquid flow battery stack of Example 10.

[0042] Figure 22 This is a performance diagram of the all-vanadium liquid flow battery stack test of Example 11.

[0043] In the figure: 1. Negative electrode liquid inlet; 2. Liquid inlet secondary flow channel; 3. Negative electrode liquid outlet; 4. Liquid outlet secondary flow channel; 5. Electrode cavity; 6. Groove; 7. Fixing ring; 8. Comb groove; 9. Support frame; 10. Outer ring; 11. Upper flat pad; 12. Upper slope; 13. Lower flat pad; 14. Lower slope; 15. Bipolar plate; 16. Raised strip, 17. Fixing ring comb groove, 18. Positive electrode liquid inlet, 19. Positive electrode liquid outlet, 20. Sealing round bar. DETAILED DESCRIPTION

[0044] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] Example 1:

[0046] Integrated bipolar flow battery electrode frame, such as Figure 1 、 Figure 2 As shown, it includes an electrode frame body with a secondary flow channel, a bipolar plate 15, a fixing ring 7, and a sealing gasket. The upper and lower surfaces of the electrode frame body serve as the positive electrode side and the negative electrode side respectively, and the two sides are interchangeable.

[0047] The positive electrode side is provided with a positive electrode liquid inlet hole 18, a positive electrode liquid outlet hole 19, a negative electrode liquid inlet hole 1, and a negative electrode liquid outlet hole 3. The positive electrode liquid inlet hole 18 is connected to the positive electrode liquid inlet secondary flow channel, and the positive electrode liquid outlet hole 19 is connected to the positive electrode liquid outlet secondary flow channel. The negative electrode side is also provided with a positive electrode liquid inlet hole 18, a positive electrode liquid outlet hole 19, a negative electrode liquid inlet hole 1, and a negative electrode liquid outlet hole 3. The inlet and outlet holes are all through holes, that is, four holes are punched through an electrode frame body, two holes on each side are connected to the electrode frame body, and multiple electrode frame bodies are stacked, and the through holes in the same position form the main flow channel. There are four main flow channels: the positive electrode liquid inlet main flow channel, the positive electrode liquid outlet main flow channel, the negative electrode liquid inlet main flow channel, and the negative electrode liquid outlet main flow channel. Since the positive and negative electrode electrolytes need to be separated and cannot contact, only the positive electrode's liquid inlet and outlet holes on the positive electrode side are connected to the secondary flow channel. The negative electrode electrolyte only passes through this plane and does not flow out. The negative electrode side is the same as the positive electrode side.

[0048] The negative electrode inlet hole connects to the negative electrode inlet secondary channel, and the negative electrode outlet hole connects to the negative electrode outlet secondary channel. All secondary channels (including the positive electrode inlet secondary channel, positive electrode outlet secondary channel, negative electrode inlet secondary channel, and negative electrode outlet secondary channel) have the same structure, and the inlet and outlet secondary channels are centrally symmetrical about the center point of the electrode frame. The secondary channels are equipped with a diversion structure, which diverts the electrolyte from the channel hole and is buffered by the secondary channels before reaching different electrode areas.

[0049] An electrode cavity 5 is provided in the middle of the upper and lower surfaces of the electrode frame body, and an annular groove 6 is provided around the electrode cavity 5 on one side; secondary flow channels (including a liquid inlet secondary flow channel 2 and a liquid outlet secondary flow channel 4) are provided on the upper and lower surfaces of the electrode frame body, and a comb-tooth groove 8 is provided between the secondary flow channel and the electrode cavity 5, and the width of the comb-tooth groove 8 on the side with the groove 6 is 1 / 3-2 / 3 of the width of the comb-tooth groove 8 on the other side.

[0050] Groove 6 houses the bipolar plates 15, sealing gaskets, and retaining rings 7. The length of the positive and negative secondary channels is the same. Each stage of the battery stack has positive and negative electrode inlet and outlet secondary channels, inlet and outlet ports, and electrode cavities. Groove 6's top and bottom depth is the same as its left and right width, ranging from 10-15mm. Any depth or width outside this range is redundant, taking up space and wasting materials, while any width below this range can compromise sealing performance.

[0051] The bipolar plate 15 is annular and matches the shape of the groove 6 . The outer side and upper and lower edges of the bipolar plate 15 are covered with sealing gaskets. The bipolar plate 15 covered with the sealing gaskets is embedded in the groove 6 .

[0052] The structure of the fixing ring 7 is as follows Figure 3 As shown, the fixing ring 7 is annular and matches the shape of the bipolar plate 15. The fixing ring 7 is installed on the side of the bipolar plate 15 covered with a sealing gasket away from the groove 6. After being pressed, the fixing ring 7 is flush with the surface of the electrode frame body. A secondary flow channel and a fixing ring comb groove 17 are provided on the side of the fixing ring 7 away from the groove 6. The secondary flow channel on the fixing ring 7 is connected to the secondary flow channel on the electrode frame body. After the fixing ring comb groove 17 is spliced ​​with the shorter comb groove 8, it has the same structure and size as the comb groove 8 on the other side of the electrode frame body. In the embodiment, the width of the shorter comb groove 8 is 10-15 mm. If it is too wide, the width of the fixing ring comb groove 17 will be too small. If the width of the fixing ring comb groove 17 is too large, the sealing performance will be reduced.

[0053] A cross-shaped support frame 9 is located in the center of the retaining ring 7. The thickness of the support frame 9 is 1 / 3-2 / 3 of the thickness of the retaining ring 7 and is flush with the bottom of the retaining ring 7. It supports the bipolar plates 15, reducing the pressure on the bipolar plates 15 and preventing them from cracking. It also supports the retaining ring 7 and prevents it from deforming toward the center. If the thickness of the retaining ring 7 is less than this range, it is too thin to withstand pressure and is prone to bending and breaking. If the thickness exceeds this range, it will block the flow of electrolyte, requiring the addition of comb grooves on the support frame, which increases processing difficulty and wastes material.

[0054] The electrode chamber 5 is divided into four rectangles by a cross-shaped support frame 9. There are four positive electrodes, which are respectively installed in the four rectangular electrode chambers 5 and have the same size as the four electrode chambers 5. The negative electrode is a single piece and has the same size as the negative electrode chamber. When the battery stack operates, the solution flows into the inlet secondary flow channel from the inlet hole. After being split by the secondary flow channel, it enters the electrodes in different regions, and then converges at the outlet hole after passing through the outlet secondary flow channel.

[0055] The support frame 9 divides the electrode chamber 5 inside the fixing ring 7 into multiple electrode regions. Each electrode region has a length or width of 12 - 25 cm. The secondary flow channel is provided with a splitting structure, and the number of splits is the same as the number of columns of the divided electrode regions. The inlet secondary flow channels and outlet secondary flow channels of the positive and negative electrodes of the electrode frame body have the same structure and are centrosymmetric about the center point of the electrode frame body. The electrolyte is split from the flow channel hole and evenly reaches different electrode regions after being buffered by the secondary flow channel. If the electrode region is too small, it will waste materials and occupy space. If it is too large, the supporting force will decrease and the risk of bipolar plate fracture will increase. In some embodiments, the support frame 9 is any one of a grid shape, two vertical and one horizontal, three vertical and two horizontal, or three vertical and one horizontal.

[0056] The structure of the sealing gasket is as Figure 4 shown. The cross-section of the sealing gasket is in a "匚" shape and is integrally formed, wrapping around the outer side and the upper and lower edges of the bipolar plate 15. The manufacturing process is injection molding, which can prevent cracks from occurring in the middle of the gasket. If it is separated and composed of several components, cracks will appear at the combination interface under pressure, resulting in liquid leakage and short circuit.

[0057] The sealing gasket includes an outer ring (part a) 10, an upper flat gasket (part b) 11, an upper slope (part c) 12, a lower flat gasket (part d) 13, a lower slope (part e) 14 and a ridge (part f) 16. The outer ring 10 is tightly attached to the outer wall of the bipolar plate 15. The upper flat gasket 11 and the upper slope 12 are both located on the upper part of the bipolar plate 15 (away from the side of the groove 6). The longitudinal section of the upper flat gasket 11 is rectangular, and the longitudinal section of the upper slope 12 is triangular. The longitudinal sections of the upper flat gasket 11 and the upper slope 12 are combined into a right-angled trapezoid. The two right-angled sides of the right-angled trapezoid are flush with the edge of the outer ring 10. The right-angled side where the upper flat gasket 11 and the upper slope 12 are joined is Parallel to the upper surface of the bipolar plate 15, the right-angled trapezoidal inclined surface is located on the inner ring side of the bipolar plate 15, and gradually tilts away from the bipolar plate 15 along the direction from the inner ring to the outer ring of the bipolar plate 15; the lower flat pad 13 and the lower slope 14 are located at the lower part of the bipolar plate 15, and the lower flat pad 13 and the lower slope 14 have the same structure as the upper flat pad 11 and the upper slope 12, respectively, and are symmetrically arranged on the bipolar plate 15; a ridge 16 is provided between the bipolar plate 15 and the upper flat pad 11 and the upper slope 12, and the ridge 16 is in close contact with the bipolar plate 15. The ridge 16 is trapezoidal in shape, narrow at the top and wide at the bottom; the thickness of the outer ring 10 is the sum of the thicknesses of the upper flat pad 11, the lower flat pad 13, the bipolar plate 15 and the ridge 16.

[0058] During installation, the bipolar plate 15 is placed between the ridges 16 and the lower flat pad 13 and the lower slope 14, so that the upper and lower edges of the bipolar plate 15 are covered with sealing gaskets, that is, the upper edge of the bipolar plate 15 is close to the lower part of the ridges 16, and the lower edge of the bipolar plate 15 is close to the lower flat pad 13 and the lower slope 14. The upper slope 12 and the lower slope 14 provide deformation space. While ensuring the sealing effect, the three ridges of the ridges 16 will increase the force-bearing area, which not only increases the sealing effect, but also reduces the risk of fracture of the bipolar plate 15. The bipolar plate 15 and the sealing gasket are fixed in the middle of the electrode frame body by using the fixing ring 7, thereby separating the front and back sides of the electrode frame body, and the positive and negative electrodes can be placed at the same time to realize an integrated bipolar.

[0059] The integrated bipolar liquid flow battery electrode frame (i.e., integrated bipolar electrode frame) can be assembled before the battery stack is assembled. It includes the electrode frame body, bipolar plate 15, fixing ring 7, and electrode. When the battery stack is assembled, after the pressure plate and end plate are placed, the electrode frame body and diaphragm can be placed in order.

[0060] The combination of the sealing gasket, bipolar plate 15, and retaining ring 7, with their unique structural features, enhances sealing and ensures uniform fluid flow, resulting in stable operation and low long-term fluctuations. The battery stack of the present invention exhibits superior sealing performance, and the bipolar plates, a key component, are resistant to fracture and damage, ensuring long-term use and extending cycle life.

[0061] Figure 5 Figure 2 shows the test performance of an all-vanadium redox flow battery stack, shown in an embodiment of the present invention. The stack utilizes the integrated bipolar electrode frame described in Example 1, with carbon felt as the electrode material. The stack achieved a coulombic efficiency of 97.6%, an energy efficiency of 81.5%, and a voltage efficiency of 83.5%. The stack operated smoothly, exhibiting no leakage, and the bipolar plates 15 remained intact and free of cracks. Testing has demonstrated that the integrated bipolar electrode frame can be effectively applied to all-vanadium redox flow batteries, reducing the manufacturing cost of the stack.

[0062] Example 2:

[0063] The difference from Example 1 is that Example 2 has a larger bipolar plate area, with specific dimensions of 55 cm wide and 65 cm long. The simple cross-shaped support frame 9 is not enough to provide more support, so the support frame 9 is arranged in a well shape, and the length, width and thickness of each support bar are the same as those in Example 1, dividing the electrode cavity into 9 parts on average, and each part has the same size. The change in the secondary flow channel structure corresponds to the structure of the support frame 9, that is, there are three branch flow channels at the liquid inlet and outlet, which divide the solution into 3 parts and lead to each column of electrode areas. When the stack is running, the solution flows into the liquid inlet secondary flow channel from the liquid inlet, and is divided into 3 parts through the secondary flow channel, respectively entering the 3 columns of electrode areas, and then passing through the liquid outlet secondary flow channel and converging at the liquid outlet.

[0064] Figure 6 The graph shows the test performance of the all-vanadium redox flow battery stack used in this example. The stack uses an integrated bipolar electrode frame and carbon felt as the electrode material. The stack achieved a coulombic efficiency of 97.0%, an energy efficiency of 81.0%, and a voltage efficiency of 83.5%. The stack operated smoothly, without leakage, and the bipolar plates remained intact and free of cracks.

[0065] Example 3:

[0066] The difference from Example 1 is that the electrode cavity of this embodiment is relatively narrow and long (12 cm wide × 60 cm long), and its support frame 9 is in the shape of a fence. No support bars are required in the width direction, but its length is relatively large, and three support bars need to be added in the length direction for support. The electrode cavity is divided into 4 areas on average, each with the same size. The changes in the structure of the liquid inlet secondary flow channel and the liquid outlet secondary flow channel correspond to the structure of the support frame 9, that is, there are 4 branch flow channels at the liquid inlet and outlet holes, which divide the solution into 4 parts and lead to each electrode area. When the battery stack is running, the solution flows into the liquid inlet secondary flow channel from the liquid inlet, is divided into 4 parts through the liquid inlet secondary flow channel, enters the 4 electrode areas respectively, and then merges at the liquid outlet after passing through the liquid outlet secondary flow channel, and finally returns to the liquid storage tank.

[0067] Figure 7The graph shows the test performance of the all-vanadium redox flow battery stack used in this example. The stack uses an integrated bipolar electrode frame and carbon felt as the electrode material. The stack achieved a coulombic efficiency of 97.5%, an energy efficiency of 80.5%, and a voltage efficiency of 82.6%. The stack operated smoothly, without leakage, and the bipolar plates remained intact and free of cracks.

[0068] Example 4:

[0069] Unlike Example 1, the retaining ring 7 used in this embodiment does not utilize a support frame, but rather an outer frame structure. In this case, the positive and negative electrodes within the integrated bipolar electrode frame severely squeeze the bipolar plates, causing fractures after a period of use. The fractures gradually expand under the constant erosion of the solution, causing the battery to rapidly fail if a bipolar plate fractures at a certain location.

[0070] Figure 8 This is a performance graph of an all-vanadium redox flow battery stack using the structure of this embodiment. The stack uses an integrated bipolar electrode frame and carbon felt as the electrode material. The stack achieved a coulombic efficiency of 93.5%, an energy efficiency of 78.8%, and a voltage efficiency of 84.2%. After a short period of testing, some bipolar plates in the stack fractured, causing rapid degradation of the stack's charge and discharge performance and battery failure.

[0071] Figure 9 This is a photo of the bipolar plate 15 after testing using this embodiment. It can be seen that the bipolar plate 15 is broken at the inner edge of the fixing ring 7, and then a large range of holes appear under the flushing of the electrolyte. The positive and negative electrolytes flow here, and the entire battery stack is damaged.

[0072] Example 5:

[0073] The difference from Example 1 is that the number of trapezoidal ridges of the ridges 16 in this embodiment is 2, as shown in FIG. Figure 10 As shown in Figure 2, the sealing effect is weakened, and the solution can more easily enter the other electrode through the gap in the sealing strip, causing a short circuit and increased self-discharge. Correspondingly, the coulombic efficiency of the battery using this structure is reduced, and the battery performance is degraded.

[0074] Figure 11 This is a performance graph of an all-vanadium redox flow battery stack using the structure of this embodiment. The stack uses an integrated bipolar electrode frame and carbon felt as the electrode material. The stack achieved a coulombic efficiency of 96.4%, an energy efficiency of 81.4%, and a voltage efficiency of 84.5%. After the stack test, the bipolar plates remained intact, with no cracks.

[0075] Example 6:

[0076] The difference from Example 1 is that the number of trapezoidal ridges in this embodiment is one. Figure 12As shown in Figure 2, the sealing effect is weakened, and the solution can more easily enter the other electrode through the gap in the sealing strip, causing a short circuit and increased self-discharge. Correspondingly, the coulombic efficiency of the battery using this structure is reduced, and the battery performance is degraded.

[0077] Figure 13 This is a performance graph of an all-vanadium redox flow battery stack using the structure of this embodiment. The stack uses an integrated bipolar electrode frame and carbon felt as the electrode material. The stack achieved a coulombic efficiency of 94.5%, an energy efficiency of 75.9%, and a voltage efficiency of 80.4%. After the stack test, the bipolar plates remained intact, with no cracks.

[0078] Example 7:

[0079] The difference from Example 1 is that the sealing gasket used in this embodiment is not provided with ridges 16. The ridges 16 are a part of the specific sealing gasket of the present invention. If the ridges 16 are not provided, as shown in FIG. Figure 14 As shown, the upper flat cushion layer 11 and upper slope 12 may deform under pressure, creating a tiny channel extending directly to the edge of the bipolar plate. This makes it easier for solution to enter the other electrode through the gap in the sealing strip, causing a cross-current short circuit and increased self-discharge. Consequently, batteries using this structure experience a relatively significant decrease in coulombic efficiency, severely degrading battery performance.

[0080] Figure 15 This is a performance graph of an all-vanadium redox flow battery stack using the structure of this embodiment. The stack uses an integrated bipolar electrode frame and carbon felt as the electrode material. The stack achieved a Coulombic efficiency of 92.7%, an energy efficiency of 73.7%, and a voltage efficiency of 79.5%. After the stack test, the bipolar plates remained intact, with no cracks.

[0081] Example 8:

[0082] The difference from Example 1 is that the ridges 16 of the sealing gasket used in this embodiment are rectangular. Figure 16 As shown, its stress-bearing area is reduced, the risk of fracture under pressure increases, cracks are prone to occur, resulting in solution penetration, a slight short circuit between the positive and negative electrodes, aggravated self-discharge during battery stack operation, and reduced charge and discharge performance.

[0083] Figure 17 This is a performance graph of an all-vanadium redox flow battery stack using the structure of this embodiment. The stack uses an integrated bipolar electrode frame and carbon felt as the electrode material. The stack achieved a coulombic efficiency of 96.3%, an energy efficiency of 77.0%, and a voltage efficiency of 79.9%. After the stack test, cracks and gaps were found in some bipolar plates.

[0084] Example 9:

[0085] The difference from Example 1 is that this embodiment adopts the existing sealing structure, which has only three layers of sealing round strips 20. Figure 18 As shown, the three-layer sealing round bar 20 is located on the upper or lower surface of the bipolar plate 15. This sealing structure causes uneven stress on the upper and lower surfaces of the bipolar plate 15, making the edges susceptible to fracture. A broken bipolar plate 15 loses its sealing effectiveness, allowing electrolyte to flow freely between the positive and negative electrodes, leading to battery failure. Furthermore, this structure reduces the stress-bearing area, increasing the risk of fracture under pressure. Cracks can easily form, leading to solution leakage and a slight short circuit between the positive and negative electrodes. This can exacerbate self-discharge during battery stack operation and reduce charge and discharge performance.

[0086] Figure 19 This is a performance graph of an all-vanadium redox flow battery stack using the structure of this embodiment. The stack uses an integrated bipolar electrode frame and carbon felt as the electrode material. The stack achieved a coulombic efficiency of 89.8%, an energy efficiency of 71.6%, and a voltage efficiency of 79.7%. After the stack test, cracks and gaps were found in some bipolar plates.

[0087] Example 10:

[0088] The difference from Example 1 is that the structure of the sealing gasket used in this embodiment is as follows: Figure 20 As shown, the outer side of the outer ring 10 is sloped. In this case, the force-bearing area of ​​the sealing gasket is reduced, and the force on the outer ring is significantly reduced, resulting in almost no deformation. In this case, the sidewalls of the bipolar plate 15 are almost completely sealed, and the risk of leakage is serious.

[0089] Figure 21 This is a performance graph of an all-vanadium redox flow battery stack using the structure of this embodiment. The stack uses an integrated bipolar electrode frame and carbon felt as the electrode material. The stack achieved an energy efficiency of 77.3%, a coulombic efficiency of 94.0%, and a voltage efficiency of 82.2%. After the stack test, cracks and gaps were found in some bipolar plates.

[0090] Example 11:

[0091] The difference from Example 1 is that the integrated bipolar electrode frame used in this embodiment does not use a secondary flow channel with a shunt structure, which causes the electrolyte to not flow evenly to each column of electrode areas. In the electrode cavity, due to the obstruction of the vertical support frame 9, the solution flow in different columns of electrode areas is poor, resulting in reaction blind spots in the electrode areas with less liquid flow, reduced battery energy efficiency, and decreased performance.

[0092] Figure 22 The performance diagram of the all-vanadium liquid flow battery stack test using the structure of this embodiment is shown. The battery stack uses an integrated bipolar electrode frame, its secondary flow channel does not have a shunt structure, the electrode material is carbon felt, the stack coulomb efficiency is 97.4%, the energy efficiency is 73.4%, and the voltage efficiency is 75.4%.

[0093] The use of traditional flow channels will be similar to that of Example 11, where the flow of liquid in one or several rows of electrodes is slow, resulting in a reaction "blind zone" during battery operation, causing overcharge or overdischarge.

[0094] In this embodiment of the present invention, the secondary flow channel cooperates with the retaining ring 7. Due to the placement of the support frame 9 on the retaining ring 7, the left-right flow of the solution is somewhat hindered. To eliminate this, a diversion structure is used to divert the solution at the inlet, ensuring that solution enters each row of electrode areas. Under the mechanical force of the circulating pump, the solution flows upward through the electrode areas, enters the secondary flow channel, and merges at the outlet, achieving more uniform flow field.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. An integrated bipolar liquid flow battery electrode frame, characterized in that: Comprising: An electrode frame body, the upper and lower surfaces of the electrode frame body are respectively the positive electrode side and the negative electrode side, and the positive electrode side and the negative electrode side are interchangeable; electrode cavities (5) are provided in the middle regions of the upper and lower surfaces of the electrode frame body, and an annular groove (6) is provided around the electrode cavity (5) on one surface; secondary flow channels are provided on the upper and lower surfaces of the electrode frame body, and a comb tooth groove (8) is provided between the secondary flow channel and the electrode cavity (5), and the width of the comb tooth groove (8) on the surface with the groove (6) is 1 / 3 - 2 / 3 of the width of the comb tooth groove (8) on the other surface; A bipolar plate (15), the bipolar plate (15) is annular and matches the shape of the groove (6), and sealing gaskets are coated on the outer side, upper and lower edges of the bipolar plate (15), and the bipolar plate (15) coated with the sealing gaskets is embedded in the groove (6); A fixing ring (7), the fixing ring (7) is annular and matches the shape of the bipolar plate (15), and the fixing ring (7) is installed on the side of the bipolar plate (15) coated with the sealing gasket away from the groove (6), and after pressing, the surface of the fixing ring (7) is flush with the surface of the electrode frame body; A support frame (9) is provided in the middle of the fixing ring (7), and the support frame (9) divides the electrode cavity (5) inside the fixing ring (7) into multiple electrode regions, the length or width of each electrode region is 12 - 25 cm, and a flow splitting structure is provided in the corresponding secondary flow channel, and the number of flow splits is the same as the number of columns of the divided electrode regions; The cross-section of the sealing gasket is "匚”-shaped and is integrally formed, and wraps around the outer side and upper and lower edges of the bipolar plate (15); The sealing gasket includes an outer ring (10), an upper flat cushion layer (11), an upper slope (12), a lower flat cushion layer (13), a lower slope (14) and a convex strip (16). The outer ring (10) is closely attached to the outer side wall of the bipolar plate (15). The upper flat cushion layer (11) and the upper slope (12) are both located on the upper part of the bipolar plate (15). The longitudinal section of the upper flat cushion layer (11) is rectangular, and the longitudinal section of the upper slope (12) is triangular. The longitudinal sections of the upper flat cushion layer (11) and the upper slope (12) are combined into a right trapezoid. The two right sides of the right trapezoid are flush with the edge of the outer ring (10). The right side where the upper flat cushion layer (11) and the upper slope (12) are spliced is parallel to the upper surface of the bipolar plate (15). The inclined surface of the right trapezoid is located in the inner ring of the bipolar plate (15) and gradually inclines away from the bipolar plate (15) along the direction from the inner ring to the outer ring of the bipolar plate (15). The lower flat cushion layer (13) and the lower slope (14) are located on the lower part of the bipolar plate (15). The lower flat cushion layer (13) and the lower slope (14) are respectively the same as the upper flat cushion layer (11) and the upper slope (12) in structure and are symmetrically arranged with respect to the bipolar plate (15). A convex strip (16) is provided between the bipolar plate (15) and the upper flat cushion layer (11) and the upper slope (12). The convex strip (16) is closely attached to the bipolar plate (15), and the thickness of the outer ring (10) is the sum of the thicknesses of the upper flat cushion layer (11), the lower flat cushion layer (13), the bipolar plate (15) and the convex strip (16).

2. The integrated bipolar liquid flow battery electrode frame according to claim 1, characterized in that: A secondary flow channel and a fixed ring comb groove (17) are provided on a side of the fixed ring (7) away from the groove (6); the secondary flow channel on the fixed ring (7) is connected to the secondary flow channel on the electrode frame body; and after the fixed ring comb groove (17) is spliced ​​with the shorter comb groove (8), the structure and size of the comb groove (8) on the other side of the electrode frame body are the same.

3. The integrated bipolar liquid flow battery electrode frame according to claim 1, characterized in that: The support frame (9) is in any one of a cross shape, a well shape, two vertical and one horizontal shape, three vertical and two horizontal shapes, or three vertical and one horizontal shape.

4. The integrated bipolar liquid flow battery electrode frame according to claim 1, characterized in that: The convex strip (16) is in a trapezoidal or rectangular shape, narrow at the top and wide at the bottom. The convex strip (16) is provided with multiple layers to achieve multi-level sealing.

5. The integrated bipolar liquid flow battery electrode frame according to claim 1, characterized in that: The groove (6) has the same upper and lower depths and left and right widths, and the depth or width is 10-15 mm.

6. The integrated bipolar liquid flow battery electrode frame according to claim 1, characterized in that: The thickness of the support frame (9) is 1 / 3-2 / 3 of the thickness of the fixing ring (7) and is flush with the bottom of the fixing ring (7).

7. An all-vanadium redox flow battery, characterized in that: It comprises an integrated bipolar liquid flow battery electrode frame as described in any one of claims 1 to 6.

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