A flow battery stack structure, sealing method and application

Abstract

The present invention discloses a flow battery stack structure, sealing method, and application. The stack structure is composed of multiple battery cells, with adjacent battery cells connected by bipolar plates. Multiple through-flow holes are set at the same position on each electrode frame and bipolar plate. After multiple identical electrode frames are stacked, the flow holes form a main channel for liquid inlet or outlet. The electrode frames are provided with liquid inlet secondary flow channels and liquid outlet secondary flow channels, and the main channel is connected to the corresponding secondary flow channels. End plates are installed at both ends of the electrode frames. Liquid inlet comb grooves and liquid outlet comb grooves are set at the connection between the electrode area and the corresponding secondary flow channels, and are neatly arranged at the edges of the secondary flow channels. The present invention has a better sealing effect, more uniform and easy-to-wash liquid flow, reduces the problems of electrolyte dendrites, deposition, and blockage, thereby improving the reliability of the battery stack and enhancing applicability.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid flow batteries and relates to a liquid flow battery stack structure, a sealing method and an application thereof. Background Art

[0002] Liquid flow battery is a new type of large-scale energy storage technology with the advantages of energy and power separation, long life, high safety, and green environmental protection. It has broad application space in energy storage fields such as new energy power generation grid connection, peak and frequency regulation, and smart grid.

[0003] Commercial flow batteries generally utilize a battery stack, stacking and pressing multiple battery cells into a single unit. An external circulation pump supplies electrolyte to all cells through a flow channel structure, achieving electrolyte circulation. Currently, the technical difficulties of battery stacks primarily lie in sealing the stack and ensuring uniform electrolyte flow. Existing technologies often use sealing gaskets for external sealing, but due to the incompressibility of rubber materials, the rubber deforms under pressure, potentially wrinkling and causing leakage. This phenomenon is particularly prone to occur when the pressure is uneven. Furthermore, to ensure a tight seal, existing flow channel structures often utilize a single main flow channel, with the electrolyte flowing from bottom to top and from left to right (or right to left at the other electrode). This flow pattern can lead to uneven solution flow when the electrode area is large, resulting in "blind spots" during charge and discharge, increased local potential differences, and reduced battery life.

[0004] As researchers continue to deepen their research in the field of flow batteries, numerous new flow battery systems have emerged, following the development of iron-chromium and all-vanadium flow batteries. These systems, such as vanadium-titanium flow batteries, iron-sulfur flow batteries, zinc-based flow batteries, and organic aqueous flow batteries, exhibit diverse advantages and are expected to compete with the high-cost all-vanadium flow batteries in the market. However, current battery stack architectures are primarily designed for all-vanadium flow batteries and are less suitable for flow batteries of other systems, particularly those containing solid electrolytes. Directly switching to electrolytes that contain solids during operation, such as zinc-based and neutral iron-sulfur flow battery electrolytes, can lead to uneven solid deposition, resulting in dendrite formation, or solid accumulation in the flow channels, leading to blockage and damage to the stack. Furthermore, some systems are highly corrosive and require enhanced sealing. Therefore, a more adaptable battery stack architecture is needed to advance the development of large-scale flow battery energy storage technology. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a liquid flow battery stack structure with better sealing effect, stronger stability, more uniform liquid flow and easy flushing, reducing the problems of dendrites, deposition and blockage of the electrolyte, thereby improving the reliability of the battery stack, making it more applicable, and solving the problems existing in the prior art.

[0006] Another object of the present invention is to provide a method for sealing a flow battery stack structure.

[0007] The third object of the present invention is to provide an application of a flow battery stack structure.

[0008] The technical solution adopted by the present invention is a liquid flow battery stack structure composed of multiple battery cells, wherein two adjacent battery cells are connected by bipolar plates, and each battery cell contains two electrode frames, two electrodes, and a diaphragm; multiple through-flow holes are set at the same position on each electrode frame and bipolar plate. After multiple identical electrode frames are stacked, the flow holes form a main channel for liquid inlet or outlet, and the electrode frames are provided with liquid inlet secondary flow channels and liquid outlet secondary flow channels, and the main channel is connected to the corresponding secondary flow channels;

[0009] End plates, which are installed at both ends of the electrode frame, and the liquid inlet and outlet main channels are connected to the liquid storage tank through the end plates and pipelines;

[0010] Liquid inlet comb grooves, the liquid inlet comb grooves are provided at the connection between the electrode area and the liquid inlet secondary flow channel, and are neatly arranged at the edge of the liquid inlet secondary flow channel;

[0011] The liquid outlet comb tooth grooves are arranged at the connection between the electrode area and the liquid outlet secondary flow channel, and are neatly arranged at the edge of the liquid outlet secondary flow channel.

[0012] A method for sealing a flow battery stack structure, comprising the following steps:

[0013] Install an I-shaped sealing gasket in the flow channel hole on the bipolar plate, assemble the positive electrode frame, negative electrode frame and bipolar plate, and tightly press the sealing gasket and bipolar plate together with the positive electrode frame and negative electrode frame. The sealing gasket separates the main flow channel from the bipolar plate, thus cutting off the generation of branch current.

[0014] A channel cover is installed on the top of each liquid inlet secondary channel and liquid outlet secondary channel, and the channel cover is flush with the surface of the electrode frame;

[0015] Place the gasket protrusion into the sealing groove to complete the assembly of the electrode frame;

[0016] The assembled components are stacked one by one to form a battery stack.

[0017] A liquid flow battery stack structure is used in a liquid flow battery system.

[0018] The beneficial effects of the present invention are:

[0019] 1. In the embodiment of the present invention, multiple main channels make the electrolyte distribution more uniform and the flow rate more consistent at all parts of the electrode, effectively avoiding the phenomenon of excessive local potential difference caused by reaction blind spots, gas generation, or uneven solid deposition leading to the formation of dendrites.

[0020] 2. The sealing gasket at the flow channel hole in the embodiment of the present invention has both sealing and insulating effects, which can effectively prevent the occurrence of short circuits and self-discharge caused by leakage; the specifically shaped support blocks and teardrop-shaped protrusions designed on the electrode frame can not only support the flow channel cover and assist in sealing, but also prevent blockage, guide solids, and uniform the flow field. This design can effectively reduce internal damage to the liquid flow battery and extend its service life.

[0021] 3. In the embodiment of the present invention, a sealing structure with protrusions is used at the edge of the electrode frame, wherein the protrusions can effectively avoid gaps caused by uneven pressure on the sealing gasket, and the gasket base can effectively block corrosion from the electrolyte and reduce corrosion at the protrusions.

[0022] 4. The flow battery stack of the embodiment of the present invention can be applied to more flow battery systems, including but not limited to all-vanadium flow batteries, vanadium-titanium flow batteries, zinc-iron flow batteries, iron-sulfur flow batteries and other systems, and has high compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 It is a schematic diagram of the electrode frame and a partial enlarged diagram of the comb grooves according to an embodiment of the present invention.

[0025] Figure 2 3D is a three-view drawing of a sealing gasket at a flow channel hole according to an embodiment of the present invention.

[0026] Figure 3 It is a partial assembly cross-sectional view of the sealing gasket at the flow channel hole of an embodiment of the present invention.

[0027] Figure 4 This is a cross-sectional view of the sealing ring at the edge of the electrode frame according to an embodiment of the present invention.

[0028] Figure 5a It is a schematic structural diagram of a single-layer protrusion of a gasket base layer according to an embodiment of the present invention.

[0029] Figure 5b It is a schematic structural diagram of the five-layer protrusion of the gasket base layer according to an embodiment of the present invention.

[0030] Figure 6 This is an efficiency diagram of the battery stack according to an embodiment of the present invention using the electrolyte of the all-vanadium liquid flow battery system.

[0031] Figure 7 This is an efficiency diagram of the battery stack according to an embodiment of the present invention using the electrolyte of the vanadium-titanium liquid flow battery system.

[0032] Figure 8 This is a diagram showing the efficiency and capacity retention rate of a neutral iron-sulfur liquid flow battery system electrolyte used in a fuel cell stack according to an embodiment of the present invention.

[0033] Figure 9 This is a diagram showing the efficiency and capacity retention rate of the alkaline iron-sulfur liquid flow battery system electrolyte used in the battery stack of an embodiment of the present invention.

[0034] Figure 10 This is a diagram showing the efficiency and capacity retention rate of the zinc-iron liquid flow battery system electrolyte used in the battery stack of an embodiment of the present invention.

[0035] Figure 11 This is a diagram showing the efficiency and capacity retention rate of the zinc-iodine flow battery system electrolyte used in the battery stack of an embodiment of the present invention.

[0036] Figure 12 This is a diagram showing the efficiency and capacity retention rate of the zinc-bromine flow battery system electrolyte used in the battery stack of an embodiment of the present invention.

[0037] Figure 13 This is a diagram showing the efficiency and capacity retention rate of the iron-chromium liquid flow battery system electrolyte used in the battery stack of an embodiment of the present invention.

[0038] Figure 14 This is a diagram showing the efficiency and capacity retention rate of the aqueous organic liquid flow battery system electrolyte used in the battery stack of an embodiment of the present invention.

[0039] In the figure: 1. Liquid inlet hole; 2. Liquid outlet hole; 3. Liquid inlet secondary flow channel; 4. Liquid outlet secondary flow channel; 5. Electrode area; 6. Sealing groove; 7. Gasket base; 8. Gasket protrusion; 9. Liquid inlet comb groove; 10. Cylindrical support block; 11. Liquid outlet comb groove; 12. Main channel; 13. Bipolar plate; 14. Sealing gasket; 15. Electrode frame; 16. Teardrop-shaped protrusion; 17. Teardrop-shaped support block. DETAILED DESCRIPTION

[0040] 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.

[0041] Example 1:

[0042] A flow battery stack structure consists of multiple battery cells, with adjacent cells connected by bipolar plates 13. Each cell contains two electrode frames 15 (a positive electrode frame and a negative electrode frame), two electrodes, and a diaphragm. The electrodes are mounted within the electrode frames 15, which sandwich a diaphragm. For each cell, the positive and negative electrode frames and the bipolar plates on either side are symmetrical about the diaphragm.

[0043] like Figure 1 As shown, a plurality of through flow channel holes are provided at the same position on each electrode frame 15 and the bipolar plate 13. When a plurality of identical electrode frames 15 are stacked, a main flow channel 12 for liquid inlet or outlet is formed at the flow channel hole. A liquid inlet secondary flow channel 3 and a liquid outlet secondary flow channel 4 are provided inside the electrode frame 15. The main flow channel 12 is connected to the corresponding secondary flow channel; all corners of the liquid inlet secondary flow channel 3 and the liquid outlet secondary flow channel 4 are arc transitions without right angles, which are used to prevent the deposition of small solid particles and play a role in preventing blockage;

[0044] End plates are mounted on both ends of the electrode frame 15, and the main channel 12 for liquid inlet or outlet is connected to the liquid storage tank through the end plates and pipes;

[0045] The liquid inlet comb grooves 9 are provided at the connection between the electrode area 5 and the liquid inlet secondary flow channel 3 and are neatly arranged at the edge of the liquid inlet secondary flow channel 3;

[0046] The liquid outlet comb grooves 11 are provided at the connection between the electrode area 5 and the liquid outlet secondary flow channel 4 , and are neatly arranged at the edge of the liquid outlet secondary flow channel 4 .

[0047] A channel cover plate is provided on the top of the liquid inlet secondary flow channel 3 and the liquid outlet secondary flow channel 4. The flow channel cover plate is sealed and connected to the electrode frame 15 on the corresponding side. The flow channel cover plate is flush with the surface of the electrode frame 15. The thickness of the flow channel cover plate is 1-3 mm. Through holes are provided on the flow channel cover plate at positions corresponding to the flow channel holes (i.e., the liquid inlet hole 1 or the liquid outlet hole 2). The main flow channel 12 and the secondary flow channel are smoothly connected without causing internal leakage and short circuit.

[0048] There is a liquid flow space under the flow channel cover plate, which can meet the connection of the liquid in the secondary flow channel and the flow channel hole. A support block is provided under the flow channel cover plate. The support block is located in the liquid inlet secondary flow channel 3 or the liquid outlet secondary flow channel 4. In the middle of the secondary flow channel area, the flow channel groove area is large to prevent the flow channel cover plate from collapsing downward. The required support block area is large. The support block located 3 cm outside the edge of the liquid inlet hole 1 or the liquid outlet hole 2 is a cylindrical support block 10. The diameter of the cylindrical support block 10 is 3~5mm, and the layout spacing is 8mm~10mm to prevent the flow channel cover plate from collapsing downward and causing leakage problems. Care must be taken to prevent clogging of the inlet 1 or outlet 2 with large solid particles. Therefore, the support blocks are reduced in size. The support blocks located within 3 cm of the edge of the inlet 1 or outlet 2 are teardrop-shaped support blocks 17 or cylindrical (3-5 mm diameter). The teardrop-shaped support blocks 17 have a maximum width of 3-5 mm and are spaced 5-8 mm apart. If the support blocks are too small, they will be ineffective and extremely difficult to manufacture. If the spacing is too large, the flow channel cover plate will lack support, resulting in a slight collapse in the middle, which may cause solids to accumulate. If the spacing is too small, solids will be difficult to flow. The original height of the space under the flow channel cover plate is about 2 mm. If the flow channel cover plate deforms downward under pressure, the remaining height is about 1.5 mm.

[0049] Each of the liquid inlet comb grooves 9 and the liquid outlet comb grooves 11 is formed by a plurality of evenly arranged cylindrical or teardrop-shaped protrusions 16. The cylindrical protrusions have a diameter of 4 to 7 mm and a spacing of 8 to 12 mm. The teardrop-shaped protrusions 16 have a maximum width of 4 to 7 mm and a spacing of 8 to 15 mm, with the arc portion of the teardrop-shaped protrusions away from the electrode area 5. If the width of the teardrop-shaped protrusions 16 exceeds this range, the frictional force on the solids when the solution scours the solids will increase, hindering the scouring. If the spacing exceeds this range, the flow channel cover plate will lack support and deform downward, reducing the space for liquid flow and hindering the flow.

[0050] Traditional battery stacks use a direct current flow channel, a rectangular trough with a width of 5-8 mm and a length of 10-20 mm, evenly spaced above and below the electrodes. This direct current flow channel structure causes the solution in the secondary inlet flow channel to flow upward in a straight line, while the solution flow near the electrode directly above the comb teeth is slow, resulting in a large number of small reaction "blind spots" (blind spots do not mean that no solution flows at all, but rather that less solution flows through at a slower rate, which cannot meet the battery reaction requirements and thus cause overcharging). To eliminate blind spots during assembly, the electrode area must be reduced, resulting in waste of materials such as the electrode frame, separator, and bipolar plate.

[0051] In the embodiment of the present invention, the liquid inlet comb groove 9 and the liquid outlet comb groove 11 need to be arranged at the edge of the secondary flow channel, close to the electrode area. According to the principle of the "Coanda effect", the embodiment of the present invention designs the support block into a circular or teardrop shape, allowing the liquid to flow along the curve without accumulation; in addition, the liquid inlet comb groove 9 and the liquid outlet comb groove 11 need to be neatly arranged at the edge of the secondary flow channel, and the teardrop-shaped structure of the liquid inlet comb groove 9 and the liquid outlet comb groove 11 allows the solution to cover the entire cross-section when it rushes out, and then rise as a whole, without a reaction blind spot at the comb teeth, which is very helpful for the uniform flow of the solution in the electrode.

[0052] After the electrode frame 15 is assembled with the flow channel cover plate, the overall thickness needs to be kept consistent. The height of the cylindrical support block 10 and the liquid outlet comb groove 11 plus the thickness of the flow channel cover plate need to be the same as the depth of the secondary flow channel groove. If there is an error, it can be filled by adding silicone glue. The flow channel hole is located in the inlet and outlet secondary flow channel, with the liquid inlet hole 1 close to the bottom and the liquid outlet hole 2 close to the top. When the flow channel cover plate covers the entire secondary flow channel area, the flow channel hole edges can be placed in the same plane.

[0053] like Figures 2 and 3 As shown, a sealing gasket 14 is provided in the flow channel hole between the positive electrode frame and the negative electrode frame. The sealing gaskets 14 at both ends of the flow channel hole sandwich the bipolar plate 13 in the middle. The positive electrode frame and the negative electrode frame tightly press the sealing gasket 14 and the bipolar plate 13 together. The sealing gasket 14 separates the main channel 12 from the bipolar plate 13, thus cutting off the generation of branch current. The spacing between the upper and lower sealing gaskets 14 is consistent with the thickness of the bipolar plate 13, and the bipolar plate 13 can be sandwiched in the middle for sealing. This method can effectively reduce the possibility of leakage at the flow channel hole, while separating the bipolar plate 13 from the electrolyte, reducing self-discharge, and improving the efficiency of the battery stack. The embodiment of the present invention isolates the influence of the branch current, so the serpentine flow channel can be eliminated, and the cylindrical support block 10 facilitates the flushing of solid particles, taking into account the technical effects of uniformity and easy flushing, thereby improving the universality of the embodiment of the present invention.

[0054] The sealing gaskets 14 at both ends of the flow channel hole are a unified whole with an I-shaped cross-section. When the sealing gasket 14 is assembled, the middle circular hole of the sealing gasket 14 is located in the flow channel hole, so the inner hole diameter of the sealing gasket 14 is smaller than the flow channel hole diameter of the bipolar plate 13. The thickness of the sealing gasket 14 is 1-2 mm, and the inner hole diameter of the sealing gasket 14 is 12-25 mm. The material of the sealing gasket 14 is corrosion-resistant EPDM rubber or fluororubber, and its hardness range is 60-70HA.

[0055] like Figure 4 、 5aAs shown, at least one annular sealing groove 6 is provided around the outer periphery of the electrode frame 15. An annular gasket base layer 7 is provided around the outer periphery of the adjacent electrode frame 15. The gasket base layer 7 has at least one annular gasket protrusion 8. The gasket protrusion 8 corresponds to the position of the sealing groove 6. The width of the sealing groove 6 is 0.5-2 mm larger than the width of the gasket protrusion 8. When subjected to pressure, the gasket protrusion 8 is pressed into the sealing groove 6. The gasket base layer 7 seals the diaphragm, effectively preventing leakage caused by uneven pressure or corrosion of the gasket base layer 7 near the electrode area 5. The gasket base layer 7 has a thickness of 0.3-1 mm and is flattened under pressure during assembly. It cooperates with the protrusion layer to achieve a seal between the electrode frame 15 and the diaphragm. The gasket base layer 7 increases the sealing area, reduces the risk of leakage, and also prevents the diaphragm from being cracked by the sealing strip. The gasket base layer 7 and the gasket protrusion 8 are integrally formed and are injection molded from corrosion-resistant EPDM rubber or fluororubber.

[0056] The structure of the positive electrode frame and the negative electrode frame is a centrally symmetrical structure, and graphite felt and carbon felt are used as the electrode materials of the liquid flow battery stack. When the liquid flow battery stack is in operation, the electrolyte flows out of the liquid storage tank under the driving force of the circulation pump, flows into the end plate through the circulation pump, and flows into each liquid inlet main channel 12 at the end plate, enters the liquid inlet secondary channel 3 through the liquid inlet hole 1, and then flows evenly through the liquid inlet comb groove 9, the electrode area 5, and the liquid outlet comb groove 11, enters the liquid outlet secondary channel 4, and finally enters each liquid outlet main channel 12 from the liquid outlet hole 2 and returns to the circulation pump.

[0057] For each electrode frame 15, four holes are required, namely the positive electrode liquid inlet hole, the positive electrode liquid outlet hole, the negative electrode liquid inlet hole, and the negative electrode liquid outlet hole. In order to ensure uniform flow field and liquid flow, the number of flow channel holes in the embodiment of the present invention is a multiple of 4, and in the embodiment, there are 8 to 20, forming 2 to 5 main channels 12; all liquid inlet flow channel holes are located on the same horizontal line, and all liquid outlet flow channel holes are located on the same horizontal line. Multiple flow channel holes will form multiple main channels 12, which helps to make the flow field uniform and avoid reaction blind spots. In the embodiment, the positive and negative electrodes of the battery stack use two main liquid inlet and outlet channels, that is, 8 flow channel holes are set on each electrode frame 15, the flow channel hole diameter range is 15 to 30 mm, and the layout spacing is 8 to 12 cm.

[0058] Due to the increase in the number of flow channel holes, the electrolyte flow rate in each area is balanced, the reaction "blind zone" caused by different electrolyte flow rates is avoided, and the stability and safety of the battery stack are effectively improved. At the same time, the liquid inlet comb groove 9, the liquid outlet comb groove 11 and the support block can effectively avoid the deposition of solids in the flow channel, and can ensure the normal circulation of the electrolyte containing small solid particles. In the secondary flow channel of the traditional zinc battery stack, there are some places (such as corners) where the flow is slow. For the all-vanadium system electrolyte, this is not a big problem, but for the electrolyte containing small solid particles, the small particles will gather into large particles in the area where the flow is slow, causing the battery stack to gradually become blocked. The battery stack of the present invention eliminates the right-angle structure and uses a circular structure based on the principle of the Coanda effect, so that the water flow can flow evenly, making full use of the impact of the water flow to flush out the solid particles.

[0059] Figure 6 The figure shows a battery stack operating with all-vanadium liquid flow battery electrolyte, with a coulombic efficiency of 96.5%, an energy efficiency of 83.0%, and a voltage efficiency of 86.1%. The operation is stable without large fluctuations or leakage.

[0060] Example 2:

[0061] The difference from Example 1 is that Example 2 uses a larger electrode area (60×80 cm). To further ensure a stable electrolyte flow rate, the number of positive and negative electrode inlet and outlet main channels 12 will be increased to 3~4. This method can effectively solve the problem of uneven liquid flow in longer electrodes and enhance the stability of the battery stack during operation.

[0062] Example 3:

[0063] The difference from Example 1 is that the electrode frame used in Example 3 is larger in size (82×95 cm), and a highly corrosive iodine-containing electrolyte is used, which has a higher risk of leakage and requires enhanced sealing effect. Therefore, the number of protrusion layers is increased. In the embodiment of the present invention, the sealing gasket 14 is an injection molded part, and its structure is similar to combining a thin flat gasket with a sealing strip. A layer of protrusion is a layer of sealing strip, and a multi-layer protrusion is similar to a multi-layer sealing strip structure. 1-5 layers of gasket protrusions 8 and sealing grooves 6 can be designed according to needs, such as Figure 5b As shown, the five-layer gasket protrusion 8 forms a ring-shaped seal electrode frame 15, and the gasket base layer 7 is flush with the electrode frame 15 under pressure to ensure the sealing effect.

[0064] Example 4:

[0065] This example differs from Example 1 in that the electrolyte system used in this example is a vanadium-titanium flow battery system. The positive electrode is a vanadium solution, the negative electrode active material is titanium ions or a titanium-containing ion, and the electrolyte is a strongly acidic electrolyte. The electrolyte in a vanadium-titanium flow battery system is acidic and highly corrosive. The different active materials in the positive and negative electrode electrolytes require enhanced sealing and corrosion protection during operation. At high temperatures, a small amount of crystallization may form on one side of the vanadium solution.

[0066] Figure 7 The figure shows the efficiency of the vanadium-titanium stack, with a coulombic efficiency of 96.9%, an energy efficiency of 79.7%, and a voltage efficiency of 82.3%. The stack operates smoothly without significant fluctuations, demonstrating that the stack designed in this invention is suitable for vanadium-titanium flow battery systems. When crystalline particles appear, the water flow flushes them out, preventing obstruction to the flow path. This can address issues such as corrosion and leakage of sealing gaskets and crystal blockage caused by acidic conditions.

[0067] Example 5:

[0068] The difference from Example 1 is that the electrolyte system used in this embodiment is a neutral iron-sulfur liquid flow battery system, the electrolyte is a neutral electrolyte with low corrosiveness, the negative electrode active material is sulfide or polysulfide, the negative electrode polysulfide is prone to solid crystallization, and the positive electrode active material is iron ions or iron-containing ions.

[0069] Figure 8 The figure shows the efficiency and capacity retention of a neutral iron-sulfur stack, showing a coulombic efficiency of 98.5%, an energy efficiency of 76.6%, a voltage efficiency of 77.8%, and a capacity retention of 89.2% after 450 cycles. The stack operated smoothly without significant fluctuations, demonstrating that the stack designed in this invention is suitable for neutral iron-sulfur flow battery systems, resolving the crystallization clogging problem that can occur during long-term operation.

[0070] Example 6:

[0071] The difference from Example 1 is that this embodiment uses an alkaline iron-sulfur liquid flow battery system as the electrolyte system, the electrolyte is an alkaline solution, the positive electrode active material is iron ions or iron-containing ions, and the negative electrode active material is sulfide or polysulfide. Polysulfide has crystallization problems.

[0072] Figure 9 The figure shows the efficiency and capacity retention of an alkaline iron-sulfur stack, showing a coulombic efficiency of 99.1%, an energy efficiency of 65.9%, a voltage efficiency of 66.5%, and a capacity retention of 90.5% after 500 cycles. The stack operated smoothly without significant fluctuations, demonstrating that the stack designed in this invention is suitable for alkaline iron-sulfur flow battery systems and can flush out solids that form during long-term battery operation, preventing clogging and damage.

[0073] Example 7:

[0074] This embodiment differs from Example 1 in that the electrolyte system used in this embodiment is a zinc-iron flow battery system, the positive electrode active material is iron ions or iron-containing ions, and the negative electrode active material is zinc ions or zinc-containing ions or zinc-containing compounds. During long-term operation of a zinc-iron flow battery, zinc dendrites may form at the negative electrode. If these dendrites are not removed in a timely manner, they can cause battery blockage.

[0075] Figure 10 The figure shows the efficiency and capacity retention of the zinc-iron stack, with a coulombic efficiency of 98.8%, an energy efficiency of 84.6%, and a voltage efficiency of 85.6%. After 630 cycles, the capacity retention rate was 91.6%. The stack operated smoothly without significant fluctuations, demonstrating that the stack designed in the present invention is suitable for zinc-iron flow battery systems. Its flow channel structure allows the electrolyte to promptly expel zinc dendrite solids, extending the battery life. Zinc dendrite solids first accumulate as small particles in areas with slow flow, gradually forming larger particles that block the flow channel. In conventional battery stacks, slow flow occurs in some areas of the secondary flow channel (such as corners), causing the stack to gradually clog. However, the stack in the present invention eliminates these right-angle structures and uses a circular structure based on the principle of the Coanda effect, allowing the water flow to flow evenly and flushing solid particles out of the flow channel. Without the aggregation of zinc dendrite particles, battery life is naturally extended.

[0076] Example 8:

[0077] This embodiment differs from Example 1 in that the electrolyte system used in this embodiment is a zinc-iodine flow battery system, the positive electrode active material is iodine ions or iodine-containing compounds, and the negative electrode active material is zinc ions or zinc-containing ions or zinc-containing compounds. During long-term operation, the positive electrode is prone to producing elemental iodine, which is corrosive and toxic; the negative electrode can produce zinc dendrites.

[0078] Figure 11 The graph shows the efficiency and capacity retention of a zinc-iodine flow battery stack. The coulombic efficiency is 98.7%, the energy efficiency is 81.5%, the voltage efficiency is 82.6%, and the capacity retention is 87.3% after 900 cycles. The stack is stable during operation, with no significant fluctuations, demonstrating that the stack designed in this invention is suitable for zinc-iodine flow battery systems. The sealing structure effectively isolates corrosive substances, and the flow channel structure allows the electrolyte to promptly expel zinc dendrite solids, ensuring long-term stable battery operation.

[0079] Example 9:

[0080] This embodiment differs from Example 1 in that the electrolyte system used in this embodiment is a zinc-bromine flow battery system, the positive electrode active material is bromide ions or bromine-containing compounds, and the negative electrode active material is zinc ions or zinc-containing ions or zinc-containing compounds. Bromine in the positive electrode electrolyte is corrosive and volatile, and zinc dendrites are prone to forming during operation at the negative electrode.

[0081] Figure 12 The figure shows the efficiency and capacity retention of a zinc-bromine stack, with a coulombic efficiency of 99.1%, an energy efficiency of 80.9%, a voltage efficiency of 81.7%, and a capacity retention of 90.5% after 600 cycles. The stack operates smoothly without significant fluctuations, demonstrating that the stack designed in this invention is suitable for zinc-bromine flow battery systems. The 3-5 layers of gasket protrusions 8 effectively seal the stack, preventing bromine from damaging the sealing structure. The support blocks and comb teeth do not hinder the removal of solid particles, allowing the electrolyte to promptly expel solids, ensuring long-term stable operation of the zinc-bromine flow battery.

[0082] Example 10:

[0083] The difference from Example 1 is that this example uses an iron-chromium flow battery system as the electrolyte system, the positive electrode active material is iron ions or iron-containing ions, and the negative electrode active material is chromium ions or chromium-containing compounds. The positive and negative electrode electrolytes are different, and the generation of branch currents must be prevented.

[0084] Figure 13 The figure shows the efficiency and capacity retention of an iron-chromium liquid flow battery stack. The coulombic efficiency is 97.85%, the energy efficiency is 81.9%, the voltage efficiency is 83.7%, and the capacity retention is 92.0% after 550 cycles. The stack operates smoothly without significant fluctuations, demonstrating that the stack designed in this invention is suitable for liquid flow battery systems. Its excellent sealing performance completely isolates the positive and negative electrolytes, preventing internal leakage and the generation of branch currents.

[0085] Example 11:

[0086] This embodiment differs from Example 1 in that the electrolyte system used in this embodiment is an aqueous organic flow battery system, and its active substances include ferrocene, viologen derivatives, five-membered ring pyrrole nitroxide derivatives, six-membered ring nitroxide active substances, etc. Some organic substances are toxic and require proper sealing to prevent vapor escape. Some organic substances are prone to reaction with oxygen, requiring the battery stack to be isolated from the outside air.

[0087] Figure 14The graph shows the efficiency and capacity retention of an aqueous organic flow battery stack. The coulombic efficiency is 96.7%, the energy efficiency is 78.6%, the voltage efficiency is 81.3%, and the capacity retention is 92.1% after 430 cycles. The stack operates smoothly without significant fluctuations, demonstrating that the stack designed in this invention is suitable for aqueous organic flow battery systems.

[0088] The present invention can be applied to aqueous organic liquid flow batteries. It has high sealing performance, can isolate the inside of the battery stack from the outside, prevent internal gas from escaping and external oxygen from entering, and enable the battery stack to operate stably for a long time.

[0089] The battery stack of the embodiment of the present invention can be applied to all liquid flow battery systems, including but not limited to all-vanadium liquid flow batteries, vanadium-titanium liquid flow batteries, zinc-iron liquid flow batteries, iron-sulfur liquid flow batteries and other systems, and has high compatibility; currently, all-vanadium liquid flow batteries are the most mature system among all liquid flow batteries, so almost all battery stacks are designed around all-vanadium liquid flow batteries, ignoring the differences between other systems and all-vanadium liquid flow batteries. This phenomenon further hinders the maturity of other systems. The embodiment of the present invention develops a universal battery stack based on the characteristics of electrolytes of different systems, which solves the problem that current battery stacks are incompatible with electrolytes of liquid flow batteries of non-all-vanadium systems.

[0090] Example 12,

[0091] A method for sealing a flow battery stack structure, comprising the following steps:

[0092] Install the sealing gasket 14 with an I-shaped cross section into the flow channel hole on the bipolar plate 13, assemble the positive electrode frame, the negative electrode frame and the bipolar plate 13, and tightly press the sealing gasket 14 and the bipolar plate 13 together with the positive electrode frame and the negative electrode frame. The sealing gasket 14 separates the main flow channel 12 from the bipolar plate 13, thus cutting off the generation of branch current;

[0093] A channel cover is installed on the top of each liquid inlet secondary channel 3 and liquid outlet secondary channel 4, and the channel cover is flush with the surface of the electrode frame 15;

[0094] Place the gasket protrusion 8 into the sealing groove 6 to complete the assembly of the electrode frame;

[0095] The assembled components are stacked one by one to form a battery stack.

[0096] Traditional battery stacks require each component to be assembled one by one, which is not only cumbersome but also prone to problems and cannot be checked later. This application separates the tedious steps, allowing small details to be assembled in advance. After inspection, the components can be simply stacked and pressed together, effectively reducing the possibility of errors during assembly.

[0097] An embodiment of the present invention provides an application of a flow battery stack structure in a flow battery system to form an energy storage system. The system can be assembled into a large energy storage system as a system unit.

[0098] 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. A flow battery stack structure, characterized in that: The invention is composed of a plurality of battery cells, wherein two adjacent battery cells are connected by a bipolar plate (13), and each battery cell contains two electrode frames (15), two electrodes, and a diaphragm; a plurality of through-flow holes are provided at the same position on each of the electrode frames (15) and the bipolar plate (13); after a plurality of identical electrode frames (15) are stacked, a main flow channel (12) for liquid inlet or outlet is formed at the flow channel hole; a liquid inlet secondary flow channel (3) and a liquid outlet secondary flow channel (4) are provided inside the electrode frame (15); and the main flow channel (12) is communicated with the corresponding secondary flow channel; End plates, the end plates being mounted on both ends of the electrode frame (15), and the liquid inlet and liquid outlet main channels being connected to the liquid storage tank via the end plates and pipelines; Liquid inlet comb grooves (9), the liquid inlet comb grooves (9) are provided at the connection between the electrode area (5) and the liquid inlet secondary flow channel (3), and are neatly arranged at the edge of the liquid inlet secondary flow channel (3); Liquid outlet comb grooves (11), the liquid outlet comb grooves (11) are provided at the connection between the electrode area (5) and the liquid outlet secondary flow channel (4), and are neatly arranged at the edge of the liquid outlet secondary flow channel (4); A sealing gasket (14) having an I-shaped cross section is installed in the flow channel hole between the positive electrode frame and the negative electrode frame. The central circular hole of the sealing gasket (14) is located in the flow channel hole. The inner hole diameter of the sealing gasket (14) is smaller than the flow channel hole diameter of the bipolar plate (13). The portion of the sealing gasket (14) extending out of the flow channel hole sandwiches the bipolar plate (13) in the middle. The positive electrode frame and the negative electrode frame tightly press the sealing gasket (14) and the bipolar plate (13) together. The sealing gasket (14) separates the main flow channel (12) from the bipolar plate (13), thereby cutting off the generation of branch current. At least one layer of annular sealing groove (6) is provided around the outer side of the electrode frame (15), and an annular gasket base layer (7) is provided at the corresponding position of the adjacent electrode frame (15), and at least one layer of annular gasket protrusion (8) is provided on the gasket base layer (7), and the gasket protrusion (8) corresponds to the position of the sealing groove (6), and the width of the sealing groove (6) is 0.5-2 mm larger than the width of the gasket protrusion (8); when subjected to pressure, the gasket protrusion (8) is pressed into the sealing groove (6), isolating the gasket base layers (7) on both sides.

2. A flow battery stack structure according to claim 1, characterized in that: A flow channel cover plate is provided on the top of the liquid inlet secondary flow channel (3) and the liquid outlet secondary flow channel (4), and the flow channel cover plate is sealed to the electrode frame (15) on the corresponding side. A support block is provided below the flow channel cover plate, and the support block is located in the liquid inlet secondary flow channel (3) or the liquid outlet secondary flow channel (4).

3. A flow battery stack structure according to claim 2, characterized in that: The thickness of the flow channel cover plate is 1-3 mm. The support block located 3 cm outside the edge of the flow channel hole is a cylindrical support block (10) with a diameter of 3-5 mm and a layout spacing of 8 mm-10 mm. The support block located within 3 cm of the edge of the flow channel hole is teardrop-shaped or cylindrical. The maximum width of the teardrop-shaped support block is 3-5 mm and the layout spacing is 5 mm-8 mm.

4. The flow battery stack structure according to claim 1, characterized in that: The liquid inlet comb groove (9) or the liquid outlet comb groove (11) is formed by a plurality of cylindrical protrusions or teardrop-shaped protrusions (16) arranged evenly, the diameter of the cylindrical protrusion is 4-7 mm, and the spacing is 8-12 mm; the maximum width of the teardrop-shaped protrusion (16) is 4-7 mm, and the spacing is 8-15 mm, and the teardrop-shaped arc portion is away from the electrode area (5).

5. The flow battery stack structure according to claim 1, characterized in that: The number of flow channel holes provided on each electrode frame (15) is a multiple of 4, forming a plurality of main channels (12), all the liquid inlet flow channel holes are located on the same horizontal line, and all the liquid outlet flow channel holes are located on the same horizontal line.

6. A flow battery stack structure according to claim 1, characterized in that: It is applicable to all-vanadium liquid flow batteries, vanadium-titanium liquid flow batteries, zinc-iron liquid flow batteries, iron-sulfur liquid flow battery systems, zinc-iodine liquid flow battery systems, zinc-bromine liquid flow battery systems, iron-chromium liquid flow battery systems or aqueous organic liquid flow battery systems.

7. The method for sealing a flow battery stack structure according to claim 1, wherein: The following steps are involved: A sealing gasket (14) having an I-shaped cross section is installed in the flow channel hole on the bipolar plate (13), and the positive electrode frame, the negative electrode frame and the bipolar plate (13) are assembled. The positive electrode frame and the negative electrode frame tightly press the sealing gasket (14) and the bipolar plate (13) together. The sealing gasket (14) separates the main flow channel (12) from the bipolar plate (13), thereby cutting off the generation of branch current. A flow channel cover plate is installed on the top of each liquid inlet secondary flow channel (3) and liquid outlet secondary flow channel (4), and the flow channel cover plate is flush with the surface of the electrode frame (15); Place the gasket protrusion (8) into the sealing groove (6) to complete the assembly of the electrode frame; The assembled components are stacked one by one to form a battery stack.

8. Application of a liquid flow battery stack structure as claimed in any one of claims 1 to 6 in a liquid flow battery system.

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