Flow batteries and flow battery stacks

Abstract

This invention provides a flow battery and a flow battery stack, belonging to the field of energy storage technology. The flow battery includes a first electrode frame stacked sequentially, a first positive electrode and a first negative electrode stacked through a first sealing layer, a separator, a second negative electrode and a second positive electrode stacked through a second sealing layer, and a second electrode frame. The stacking order of the two electrodes is reversed. The first electrode frame is provided with a first flow channel and a second flow channel. The first flow channel allows positive electrolyte to flow into the first positive electrode, and the second flow channel allows negative electrolyte to flow into the first negative electrode. The second electrode frame is provided with a third flow channel and a fourth flow channel. The third flow channel allows positive electrolyte to flow into the second positive electrode, and the fourth flow channel allows negative electrolyte to flow into the second negative electrode. Compared with related flow battery stacks, the output voltage of the flow battery stack formed using the above-described flow battery can be increased by up to two times.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and more specifically to a flow battery and a flow battery stack. Background Technology

[0002] Energy storage, as a key technology for improving energy efficiency, is used in grid connection of renewable energy, peak shaving and valley filling, and peak and frequency regulation, thereby improving the utilization rate of renewable energy and enhancing grid stability. Flow batteries, due to their long lifespan, safety, reliability, and the ability to be individually designed for power and capacity, have become one of the main technologies for large-scale energy storage.

[0003] A flow battery typically consists of power units and capacity units. The electrolyte, acting as a capacity unit, stores and releases energy through changes in the valence states of its active substances. During operation, the electrolyte flows through the stack, which acts as the power unit, converting electrical energy into chemical energy, thus enabling power input and output.

[0004] Currently, flow batteries generally have low voltage levels, partly due to the influence of bypass current and partly because stacking more batteries would cause manufacturing difficulties. Summary of the Invention

[0005] The purpose of this invention is to provide a flow battery and a flow battery stack to solve the technical problem of the generally low voltage level of flow batteries.

[0006] To achieve the above objectives, embodiments of the present invention provide a flow battery, comprising a first electrode frame stacked sequentially, a first positive electrode and a first negative electrode stacked through a first sealing layer, a separator, a second negative electrode and a second positive electrode stacked through a second sealing layer, and a second electrode frame. The stacking order of the first positive electrode and the first negative electrode is reversed compared to the stacking order of the second negative electrode and the second positive electrode, thereby enabling the flow battery to include two sub-flow batteries stacked in opposite directions. The first electrode frame is provided with a first flow channel and a second flow channel. The first flow channel is used to allow positive electrolyte to flow into the first positive electrode, and the second flow channel is used to allow negative electrode electrolyte to flow into the first negative electrode. The second electrode frame is provided with a third flow channel and a fourth flow channel. The third flow channel is used to allow positive electrolyte to flow into the second positive electrode, and the fourth flow channel is used to allow negative electrode electrolyte to flow into the second negative electrode.

[0007] Optionally, the first positive electrode, the first negative electrode, the second negative electrode, and the second positive electrode are all the same size.

[0008] Optionally, the dimensions of the first positive electrode, the first negative electrode, the second negative electrode, and the second positive electrode are 100 cm.2 -5000cm 2 100cm is preferred. 2 -2000cm 2 .

[0009] Optionally, the first sealing layer and / or the second sealing layer are made of one or more of the following materials: PP, PE, neoprene rubber, EPDM, and fluororubber.

[0010] Accordingly, embodiments of the present invention also provide a flow battery stack, including: the flow battery described above; and a positive current output plate and a negative current output plate disposed at one end of the flow battery stack and superimposed by a first insulating layer, wherein the positive current output plate is used to output the positive current of the flow battery stack, and the negative current output plate is used to output the negative current of the flow battery stack.

[0011] Optionally, the flow battery stack includes one flow battery as described above, and the two sub-flow batteries are connected in series.

[0012] Optionally, the flow battery stack further includes a monopole plate disposed at the other end of the flow battery stack, and the two sub-flow batteries are connected in series through the monopole plate.

[0013] Optionally, the flow battery stack includes M flow batteries according to the above claims, and the flow battery stack further includes: a first bipolar plate and a second bipolar plate disposed between two adjacent flow batteries and superimposed by a second insulating layer, so that the flow battery stack includes two sets of sub-flow batteries stacked in opposite directions, each set of sub-flow batteries including M sub-flow batteries, wherein the two sets of sub-flow batteries are connected in series, and M is a positive integer greater than 1.

[0014] Optionally, the flow battery stack further includes a monopole plate disposed at the other end of the flow battery stack, and the two sets of sub-flow batteries are connected in series through the monopole plate.

[0015] Optionally, the first insulating layer and the second insulating layer are formed by sealing or welding.

[0016] The flow battery provided in this embodiment of the invention includes a first electrode frame stacked sequentially, a first positive electrode and a first negative electrode stacked through a first sealing layer, a separator, a second negative electrode and a second positive electrode stacked through a second sealing layer, and a second electrode frame. This is equivalent to a single flow battery being formed by stacking two sub-flow batteries in reverse. The flow battery has the following technical advantages:

[0017] (1) Compared with a flow battery stack formed by the same number of flow batteries in related technologies, the output voltage of a flow battery stack formed by using the flow batteries provided in the embodiments of the present invention can be increased by up to two times.

[0018] (2) The increase in the output voltage of the flow battery stack can promote the implementation of inverter and boost, reduce the difficulty of system integration, and make the flow battery stack more flexible in various scenarios.

[0019] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0021] Figure 1 A schematic diagram of a flow battery according to an embodiment of the present invention is shown;

[0022] Figure 2 A schematic diagram of a flow battery stack according to an embodiment of the present invention is shown; and

[0023] Figure 3 It shows Figure 2 The discharge polarization curves of the shown flow battery stack are compared with those of flow battery stacks in related technologies. Detailed Implementation

[0024] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0025] Figure 1 A schematic diagram of a flow battery according to an embodiment of the present invention is shown. Figure 1As shown, this embodiment of the invention provides a flow battery, including a first electrode frame 11 stacked sequentially, a first positive electrode 12 and a first negative electrode 18 stacked through a first sealing layer 16, a separator 13, a second negative electrode 14 and a second positive electrode 19 stacked through a second sealing layer 17, and a second electrode frame 15. The stacking order of the first positive electrode 12 and the first negative electrode 18 is reversed compared to the stacking order of the second negative electrode 14 and the second positive electrode 19, thereby making the flow battery include two sub-flow batteries stacked in opposite directions. The first electrode frame 11 is provided with a first flow channel and a second flow channel. The first flow channel is used to allow positive electrolyte to flow into the first positive electrode 12, and the second flow channel is used to allow negative electrolyte to flow into the first negative electrode 18. The second electrode frame 15 is provided with a third flow channel and a fourth flow channel. The third flow channel is used to allow positive electrolyte to flow into the second positive electrode 19, and the fourth flow channel is used to allow negative electrolyte to flow into the second negative electrode 14.

[0026] Each sub-flow battery can be considered to be formed by sequentially stacking a first electrode frame 11, a sub-positive electrode, a separator 13, a sub-negative electrode aligned in position with the sub-positive electrode, and a second electrode frame 15. In any embodiment of the present invention, the direction of "stacking" is perpendicular to the direction of "layering". For example... Figure 1 As shown, the direction of "layering" is horizontal, and the direction of "overlay" is vertical. "Reverse overlay order" means that the first positive electrode 12 and the second negative electrode 14 are aligned in the overlay direction, and the first negative electrode 18 and the second positive electrode 19 are aligned. "Reverse overlay" means that the positive electrode of the first sub-flow battery and the negative electrode of the second sub-flow battery are overlaid in the two sub-flow batteries.

[0027] The flow battery may also include sealing components located around the positive and negative electrodes to prevent electrolyte from seeping to the outside of the flow battery and corroding it.

[0028] Figure 1 The example shown illustrates a flow battery comprising an integral first electrode frame 11 and an integral second electrode frame 15. In an optional embodiment, the first electrode frame 11 may be divided into a first positive electrode frame and a first negative electrode frame stacked together by a sealing layer. The first positive electrode frame is provided with a flow channel for the positive electrolyte to flow into the first positive electrode 12, and the first negative electrode frame is provided with a flow channel for the negative electrode electrolyte to flow into the first negative electrode 18. Correspondingly, the second electrode frame 15 may be divided into a second negative electrode frame and a second positive electrode frame stacked together by a sealing layer. The second negative electrode frame is provided with a flow channel for the negative electrode electrolyte to flow into the second negative electrode 14, and the second positive electrode frame is provided with a flow channel for the positive electrolyte to flow into the second positive electrode 19.

[0029] The first positive electrode 12, the first negative electrode 18, the second negative electrode 14, and the second positive electrode 19 are preferably identical, for example, they are identical in size and material. The dimensions of the first positive electrode 12, the first negative electrode 18, the second negative electrode 14, and the second positive electrode 19 are 100 cm². 2 -5000cm 2 100cm is preferred. 2 -2000cm 2 .

[0030] The first sealing layer 16 is used to ensure that there is no electrical connection, short circuit or leakage between the stacked first positive electrode 12 and the first negative electrode 18. The second sealing layer 17 is used to ensure that there is no electrical connection, short circuit or leakage between the stacked second negative electrode 14 and the second positive electrode 19.

[0031] The first sealing layer 16 and the second sealing layer 17 can be made of any suitable material, and they can be made of the same or different materials, preferably of the same material. The materials used to make the first sealing layer 16 and the second sealing layer 17 may include one or more of the following: PP, PE, PVC, EPDM, neoprene rubber, nitrile rubber, fluororubber, etc.

[0032] Although the embodiments of this invention describe a flow battery comprising two counter-stacked sub-flow batteries, it is understood that in extended embodiments, the flow battery may also comprise more than two counter-stacked sub-flow batteries, the structure of which can be derived from the structure of the flow battery comprising two counter-stacked sub-flow batteries described above, and will not be repeated here.

[0033] In a further embodiment of the present invention, a flow battery stack is provided, comprising: a flow battery according to any embodiment of the present invention; and a positive current output plate and a negative current output plate disposed at one end of the flow battery stack and superimposed by a first insulating layer, wherein the positive current output plate is used to output the positive current of the flow battery stack, and the negative current output plate is used to output the negative current of the flow battery stack.

[0034] The first insulating layer ensures that there is no electrical connection, short circuit, or leakage between the stacked positive and negative current-conducting plates. The first insulating layer can be made of any suitable insulating material.

[0035] At the other end of the flow battery stack, the positive and negative electrodes are connected in series, which enables the output voltage of the flow battery stack provided in this embodiment of the invention to be increased by up to two times compared to a flow battery stack formed by the same number of flow batteries in related technologies.

[0036] In an alternative embodiment, the flow battery stack may include a flow battery according to any embodiment of the present invention.

[0037] Optionally, in this embodiment, the flow battery stack may further include a single plate disposed at the other end of the flow battery stack. The single plate is used to connect the positive electrode and the negative electrode at the other end of the flow battery stack in series, thereby realizing the series connection of two sub-flow batteries of the flow battery. However, the embodiments of the present invention are not limited thereto. For example, the flow battery stack may include a first single plate and a second single plate disposed at the other end of the flow battery stack and superimposed by an insulating layer. Furthermore, the first single plate and the second single plate may be connected in series by an external circuit.

[0038] A first polymer plate can be further disposed on the outer side of the superimposed positive and negative current-delivering plates. This first polymer plate has a flow channel interface, through which the positive electrolyte can be supplied to the first and second electrode frames, for example. A second polymer plate can be further disposed on the outer side of the single-electrode plate. This second polymer plate also has a flow channel interface, through which the negative electrolyte can be supplied to the first and second electrode frames, for example. The components of the flow battery stack can be fastened or fixed by bolts or welding. The first and second polymer plates are made of polymer materials.

[0039] The output voltage of the flow battery stack provided in this embodiment of the invention is twice that of a flow battery stack including a single flow battery in the related art.

[0040] In an optional embodiment, the flow battery stack may include M flow batteries according to any embodiment of the present invention, where M is a positive integer greater than 1. Accordingly, the flow battery stack provided in the embodiments of the present invention may further include a first bipolar plate and a second bipolar plate disposed between two adjacent flow batteries and stacked together by a second insulating layer, thereby the flow battery stack includes two sets of sub-flow batteries stacked in opposite directions, each set of sub-flow batteries including M sub-flow batteries. The number of bipolar plates is the number of flow batteries minus one. Each bipolar plate has a positive electrode and a negative electrode adjacent to its two sides, respectively. Each bipolar plate can be used to connect two adjacent sub-flow batteries in series in the stacking direction.

[0041] Optionally, in this embodiment, the flow battery stack may further include a single plate disposed at the other end of the flow battery stack. The single plate is used to connect the positive electrode and the negative electrode at the other end of the flow battery stack in series, thereby realizing the series connection of two sets of sub-flow batteries. However, the embodiments of the present invention are not limited thereto. For example, the flow battery stack may include a first single plate and a second single plate disposed at the other end of the flow battery stack and superimposed by an insulating layer. Furthermore, the first single plate and the second single plate may be connected in series by an external circuit.

[0042] A first polymer plate can be further disposed on the outer side of the superimposed positive and negative current-delivering plates. This first polymer plate has a flow channel interface, through which positive electrolyte can be supplied to the first and second electrode frames of each flow battery, for example. A second polymer plate can be further disposed on the outer side of each single-electrode plate. This second polymer plate also has a flow channel interface, through which negative electrolyte can be supplied to the first and second electrode frames of each flow battery, for example. The components of the flow battery stack can be fastened or fixed by bolts or welding. The first and second polymer plates are made of polymer materials.

[0043] The second insulating layer ensures that there is no electrical connection, short circuit, or leakage between the stacked first and second bipolar plates. The first insulating layer can be made of any suitable insulating material. The second insulating layer can be made of the same or different materials as the first insulating layer.

[0044] The first bipolar plate, the second bipolar plate, the positive current conduction plate, the negative current conduction plate, and the monopolar plate can all be made of the same conductive material, such as graphite. The dimensions of the first bipolar plate, the second bipolar plate, the positive current conduction plate, the negative current conduction plate, and the monopolar plate can be adjusted according to the dimensions of the positive and negative electrodes.

[0045] In this embodiment, the two sets of sub-flow batteries are connected in series. Since the sub-flow batteries in each set are also connected in series, it is equivalent to each sub-flow battery being connected in series with the others.

[0046] Furthermore, the external structure and dimensions of the flow battery stack provided in this embodiment of the invention can be kept the same as those of the flow battery stack in the related art, thereby facilitating the replacement of the flow battery stack in the related art. Additionally, the flow battery stack provided in this embodiment of the invention can also be considered as a division of components within the flow battery stack, wherein the electrodes, bipolar plates, and one-end monopolar plates are uniformly divided into two pieces. The division direction of each component is consistent, and the division positions can be on the same horizontal line. The electrode frame is not divided, but its flow channels are altered, so that the two divided electrodes are respectively fed with positive and negative electrolytes, and that the diagonal sides of adjacent electrodes are fed with the same type of electrolyte, thereby making the flow battery stack comprise two sets of counter-stacking flow batteries. The gaps between the divided electrodes are filled with a sealing layer, and the gaps between the divided bipolar plates and one-end monopolar plates are filled with an insulating layer. The separation or non-separation of other components in the flow battery stack will not affect the high voltage output of the flow battery stack. Therefore, it is preferable not to separate these other components, such as the diaphragm and the monopole plate at the other end.

[0047] The segmentation is equivalent to forming two small battery stacks in the stacking direction of the flow battery stack. The monopole plate at the other end, which is not segmented, is used to connect these two small battery stacks in series. The terminal voltage output of the flow battery stack will be twice that of an unsegmented flow battery stack of the same type. It is understood that the "segmentation" here is merely an analogy. In actual applications, the flow battery stack provided in this embodiment is not formed using a "segmentation" method. During initial design or actual production, the "segmented" components are preferably formed using the "stacked" method described above. Furthermore, in this embodiment, Figure 1 The "segmentation" or "overlay" directions shown are for illustrative purposes only and can be expanded to apply to individual components in relation to each other. Figure 1 The "segmentation" or "overlay" direction shown is perpendicular to the direction of "segmentation" or "overlay".

[0048] Optionally, the flow battery stack provided in the embodiments of the present invention can be an all-vanadium redox flow battery stack, a flow battery stack of other systems, or a single flow battery stack.

[0049] In related technologies, the components in flow batteries or flow battery stacks are not "segmented" or "stacked". Compared to flow battery stacks formed by the same number of flow batteries in related technologies, the output voltage of flow battery stacks formed using the flow batteries provided in this invention can be increased by two times, while maintaining the external structure and size unchanged.

[0050] The beneficial effects of the flow battery stack provided in the embodiments of the present invention will be further described below through some specific examples. In these examples, the flow battery stack is an all-vanadium redox flow battery stack.

[0051] Example 1

[0052] like Figure 2 As shown, in this embodiment, the flow battery stack consists of three flow batteries. Each flow battery includes: a first electrode frame stacked sequentially, a first positive electrode and a first negative electrode stacked through a first sealing layer, a separator, a second negative electrode and a second positive electrode stacked through a second sealing layer, and a second electrode frame. A first bipolar plate and a second bipolar plate stacked through a second insulating layer are disposed between two adjacent flow batteries. A stacked positive current-conducting plate and a stacked negative current-conducting plate are disposed at one end of the flow battery stack. A single electrode plate is disposed at one end of the flow battery stack. A first polymer plate may be further disposed on the outer side of the stacked positive current-conducting plate and the negative current-conducting plate, and a second polymer plate may be further disposed on the outer side of the single electrode plate. The flow battery stack is equivalent to being formed by stacking two sets of sub-flow batteries, each set of sub-flow batteries including three sub-flow batteries.

[0053] The positive current of the flow battery stack is extracted through the positive current extraction plate, and the negative current of the flow battery stack is extracted through the negative current extraction plate.

[0054] In this embodiment, the total area of ​​the positive and negative electrodes is 200 cm². 2 The corresponding areas of the first positive electrode, the first negative electrode, the second negative electrode, and the second positive electrode are all 100 cm². 2 .

[0055] The initial concentration of the positive electrode electrolyte in the flow battery stack is 0.8 mol L. -1 V(IV) + 0.8 mol L -1 V(IV) + 3mol L -1 H2SO4, negative electrode electrolyte concentration is 0.8 mol / L -1 V(II) + 0.8 mol L -1 V(III) + 3mol L -1 H2SO4.

[0056] Because the sub-flow cells are connected in series, the potential at the positive electrode of each sub-flow cell increases progressively. For example... Figure 2 As shown, starting from the negative electrode, the potentials at the positive electrodes of the sequentially connected sub-flow batteries are 1*OCP, 2*OCP, 3*OCP, 4*OCP, 5*OCP, and 6*OCP, respectively. Therefore, in this embodiment, the flow battery stack can output a voltage of 6*OCP, where OCP represents the open-circuit potential.

[0057] Comparative Example 1

[0058] This embodiment describes a flow battery stack in the related art. In this embodiment, N=1, and the flow battery stack consists of three flow batteries. Each flow battery includes: a positive electrode frame, a positive electrode, a separator, a negative electrode, and a negative electrode frame stacked sequentially. A bipolar plate is disposed between two adjacent flow batteries. A positive end plate and a negative end plate are disposed at both ends of the flow battery. The positive end plate includes a positive current discharge plate and a first polymer plate, and the negative end plate includes a negative current discharge plate and a second polymer plate.

[0059] In this embodiment, the total area of ​​the positive and negative electrodes is 200 cm². 2 The discharge polarization performance of a flow battery stack can be measured using a potentiostat.

[0060] The initial concentration of the positive electrode electrolyte in the flow battery stack is 0.8 mol L. -1 V(IV) + 0.8 mol L -1 V(IV) + 3mol L -1 H2SO4, negative electrode electrolyte concentration is 0.8 mol / L -1 V(II) + 0.8 mol L -1 V(III) + 3mol L -1 H2SO4.

[0061] Based on a similar principle to Example 1, in this example, the flow battery stack can output a voltage of 6*OCP. It is readily apparent that, compared to the comparative example, the output voltage of the flow battery stack in Example 1 is increased by two times.

[0062] Figure 3 It shows Figure 2 The discharge polarization curves of the shown flow battery stack are compared with those of flow battery stacks in related technologies. From Figure 3 As can be seen from the figure, the working voltage of the fuel cell stack in the embodiment is twice that of the working voltage of the fuel cell stack in the comparative example, which verifies that the fuel cell stack using the structure of the embodiment of the present invention can double the working voltage of the fuel cell stack of the same scale as the comparative example structure.

[0063] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0064] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0065] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0066] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A flow battery, characterized in that, It includes a first electrode frame stacked sequentially, a first positive electrode and a first negative electrode stacked through a first sealing layer, a diaphragm, a second negative electrode and a second positive electrode stacked through a second sealing layer, and a second electrode frame. The stacking order of the first positive electrode and the first negative electrode is the reverse of the stacking order of the second negative electrode and the second positive electrode, thereby making the flow battery include two sub-flow batteries stacked in reverse order. The first electrode frame is provided with a first flow channel and a second flow channel. The first flow channel is used to allow the positive electrolyte to flow into the first positive electrode, and the second flow channel is used to allow the negative electrode electrolyte to flow into the first negative electrode. The second electrode frame is provided with a third flow channel and a fourth flow channel. The third flow channel is used to allow the positive electrode electrolyte to flow into the second positive electrode, and the fourth flow channel is used to allow the negative electrode electrolyte to flow into the second negative electrode.

2. The flow battery according to claim 1, characterized in that, The first positive electrode, the first negative electrode, the second negative electrode, and the second positive electrode are all the same size.

3. The flow battery according to claim 2, characterized in that, The dimensions of the first positive electrode, the first negative electrode, the second negative electrode, and the second positive electrode are all 100 cm. 2 -5000cm 2 .

4. The flow battery according to claim 2, characterized in that, The dimensions of the first positive electrode, the first negative electrode, the second negative electrode, and the second positive electrode are all 100 cm. 2 -2000cm 2 .

5. The flow battery according to claim 1, characterized in that, The first sealing layer and / or the second sealing layer are made of one or more of the following materials: PP, PE, neoprene rubber, EPDM, and fluororubber.

6. A flow battery stack, characterized in that, include: The flow battery according to any one of claims 1 to 5; as well as A positive current extraction plate and a negative current extraction plate are disposed at one end of the flow battery stack and superimposed through a first insulating layer. The positive current extraction plate is used to extract the positive current of the flow battery stack, and the negative current extraction plate is used to extract the negative current of the flow battery stack.

7. The flow battery stack according to claim 6, characterized in that, The flow battery stack includes a flow battery according to any one of claims 1 to 5, wherein the two sub-flow batteries are connected in series.

8. The flow battery stack according to claim 7, characterized in that, The flow battery stack also includes a monopole plate disposed at the other end of the flow battery stack, and the two sub-flow batteries are connected in series through the monopole plate.

9. The flow battery stack according to claim 6, characterized in that, The flow battery stack comprises M flow batteries according to any one of claims 1 to 5, and the flow battery stack further comprises: A first bipolar plate and a second bipolar plate are disposed between two adjacent flow batteries and stacked together by a second insulating layer, thereby the flow battery stack includes two sets of sub-flow batteries stacked in opposite directions, each set of flow batteries including M sub-flow batteries. The two sets of sub-flow batteries are connected in series. Where M is a positive integer greater than 1.

10. The flow battery stack according to claim 9, characterized in that, The flow battery stack also includes a monopole plate disposed at the other end of the flow battery stack, and the two sets of sub-flow batteries are connected in series through the monopole plate.

11. The flow battery stack according to claim 9, characterized in that, The first insulating layer and the second insulating layer are formed by sealing or welding.

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