Fastening structure and fastening method for a flow battery stack

Abstract

The application provides a fastening structure and method of a flow battery stack, the flow battery stack comprising a battery assembly, the battery assembly comprising a single cell or multiple single cells. The fastening structure comprises a first end plate, a second end plate and at least one push plate assembly, the first end plate and the second end plate are respectively located at two polar end sides of the battery assembly, the distance between the first end plate and the second end plate is fixed, and the push plate assembly is variably arranged between the first end plate and the battery assembly. The fastening structure and method keep the internal battery assembly at a fastening force for sealing, greatly reducing the risk of liquid leakage of the flow battery due to insufficient fastening force.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flow battery, in particular to a fastening structure and fastening method of flow battery stack. BACKGROUND

[0002] Climate change is a global problem faced by mankind. In order to reduce greenhouse gas emissions, China has proposed the goal of "carbon neutrality" and "carbon peak". The determination of this goal has driven the optimization of energy structure and promoted the rapid development of clean energy. The biggest advantage of clean energy is renewable and pollution-free, such as solar energy and wind energy. However, the disadvantages of clean energy are also very significant, such as intermittency and great influence on climate and environment. The combination of clean energy and energy storage products can well solve the shortcomings of clean energy. Energy storage products can smooth the output of clean energy and enable clean energy to be self-consumed.

[0003] Flow battery is one of many energy storage technologies. Its power unit and capacity unit are distributed independently, can be combined at will, and the design scheme is flexible and variable. It also has the advantages of safety and reliability, long service life, recyclable electrolyte, and recoverable capacity, so it has a significant advantage in large-scale energy storage applications. Among them, all-vanadium flow battery has been tested and recognized in related demonstration and commercial projects. However, there is a certain risk of liquid leakage in the actual use of flow battery. Liquid leakage mainly occurs in the flow battery stack. The leakage of the stack will cause the adjacent single cell to be connected, resulting in a short circuit phenomenon, causing the related components of the stack to burn out or deform due to overheating, thereby exacerbating the risk of liquid leakage. After the electrolyte contacts the system components, since most of the electrolyte of the flow battery is acidic, it will cause corrosion damage to some system components, affecting the service life.

[0004] A fastening structure is usually used to avoid liquid leakage. Figure 1A is a side view schematic diagram of a flow battery stack. Figure 1B is Figure 1A is a top view of the flow battery stack shown in FIG. 1. The flow battery stack is the core component of the flow battery system, which is composed of positive and negative electrode frames, bipolar plates, porous electrodes, ion exchange membranes, sealing components, current collecting plates, liquid inlet and outlet structures, end plates and fastening structures. Among them, the positive and negative electrode frames, porous electrodes, sealing components and an ion exchange membrane constitute a single cell. In combination with Figure 1A and 1B wherein a battery assembly 110 is shown, in which a plurality of single cells are assembled together and compressed by end plates 111, 112 and fastening structures 120. As Figure 1AIn the example, a plurality of fastening structures 120 are included, each individual fastening structure 120 including a spring 121, a connecting rod 122, and a fastening bolt 123, the connecting rod 122 being disposed between the two end plates 111, 112 and connected to the spring 121 through the end plate 111, and the fastening bolt 123 being used to fasten the spring 121 and the connecting rod 122. In actual use, a pre-tightening force is applied to the end plate 111 through the spring 121, thereby compressing the battery assembly 110 and causing the relevant sealing components to seal. The compression process of the fastening structure 120 is crucial and requires long-term pressure maintenance.

[0005] Figure 1A and 1B The fastening structure 120 shown in the figure has the following disadvantages:

[0006] First, the material of the pole frame is generally a resin material with good chemical compatibility, and the resin material has a large cold and hot deformation coefficient and creep characteristics. During the operation of the stack, the thickness of the pole frame will change, and when most of the pole frame thickness decreases, the compression amount of the spring 121 will decrease, resulting in insufficient sealing force, causing liquid leakage or leakage.

[0007] Second, in combination with Figure 1A and Figure 1B , the spring 121 is distributed around the end plate 111, and there is no pre-tightening force in the central area of the end plate 111, which causes the end plate 111 to easily arch and deform. Figure 2 is Figure 1A and 1B The mechanical finite element simulation diagram of the end plate 111 under stress is shown in the figure, in which different gray levels represent the degree of deformation. For example, the deformation degree of the circular area 210 located in the center of the end plate 111 is the largest, which is 1.1937 mm, and the deformation degree gradually decreases from the center to the outer periphery. The deformation degree of the four corners 220 of the end plate 111 is the smallest. This deformation of the end plate 111 will cause the porous electrode to be compressed out of position, affecting the contact resistance between the porous electrode and the bipolar plate, causing the internal resistance of the flow battery stack to increase, affecting the performance and service life of the stack. And this deformation is not conducive to the long-term sealing of the flow battery stack, further causing the risk of liquid leakage. SUMMARY

[0008] The technical problem to be solved by the present application is to provide a fastening structure and a fastening method for a flow battery stack that reduces the risk of liquid leakage.

[0009] To solve the above technical problems, the application provides a fastening structure of a flow battery stack, the flow battery stack comprising a battery assembly, the battery assembly comprising a single cell or multiple single cells, comprising: a first end plate and a second end plate, the first end plate and the second end plate being located at two polar end sides of the battery assembly respectively, the distance between the first end plate and the second end plate being fixed, and at least one push plate assembly being variably arranged between the first end plate and the battery assembly.

[0010] In an embodiment of the application, the push plate assembly comprises a push plate and at least one load assembly, the load assembly comprising a load element, the load element having a height between the first end plate and the push plate, the height changing with the magnitude of the pressure borne by the load element.

[0011] In an embodiment of the application, the height varies in a range of 0-300 mm.

[0012] In an embodiment of the application, one of the load assemblies is located at the geometric center of the push plate.

[0013] In an embodiment of the application, the load assemblies are uniformly distributed between the first end plate and the push plate.

[0014] In an embodiment of the application, the load element comprises a gas spring.

[0015] In an embodiment of the application, the load assembly further comprises a load fixing element for fixedly connecting the load element and the first end plate, the load fixing element and the load element corresponding to each other.

[0016] In an embodiment of the application, the first end plate has an inner surface facing the battery assembly and an outer surface facing the outside, the outer surface of the first end plate comprising at least one counterbore, the load fixing element being arranged in the counterbore, and the load fixing element not protruding from the outer surface.

[0017] In an embodiment of the application, further comprising a stack fixing assembly, the stack fixing assembly comprising at least one pull rod, the pull rod comprising a first bent portion, a second bent portion and a connecting rod, the connecting rod being connected between the first bent portion and the second bent portion, the connecting rod extending along the height direction, the first end plate and the second end plate both having an outer surface facing the outside, the first bent portion being attached to the outer surface of the first end plate, and the second bent portion being attached to the outer surface of the second end plate.

[0018] In an embodiment of the present application, the edge of the first end plate is provided with a first groove, and the first bending part is embedded in the first groove; the edge of the second end plate is provided with a second groove, and the second bending part is embedded in the second groove.

[0019] In an embodiment of the present application, the second end plate is provided with an inlet and outlet structure.

[0020] To solve the above technical problems, the present application further provides a fastening method of a flow battery stack, the fastening structure of the flow battery stack being as described above, comprising: obtaining a first area of a sealing material in the battery stack, and setting a first compression ratio of the sealing material; obtaining a second area of an electrode material in the battery stack, and setting a second compression ratio of the electrode material; obtaining a first pressure value according to the first compression ratio, and obtaining a second pressure value according to the second compression ratio; calculating a fastening load by using the following formula:

[0021] P=k*(S1*P1+S2*P2)

[0022] wherein P represents the fastening load, S1 represents the first area, S2 represents the second area, P1 represents the first pressure value, P2 represents the second pressure value, and k represents a safety factor, k being a natural number greater than 1; and setting a pre-tightening force of the load element, so that the initial load of all the load assemblies is equal to the fastening load.

[0023] In an embodiment of the present application, the range of k is 1-2.

[0024] The fastening structure of the flow battery stack of the present application sets a height-variable push plate assembly between the end plate and the battery assembly, when the thickness of the battery assembly is reduced due to the compression deformation of the pole frame, displacement occurs, etc., the push plate assembly can adaptively change its height to compensate for the deformation, so that the internal part of the battery assembly maintains the fastening force for sealing, greatly reducing the risk of liquid leakage of the flow battery due to insufficient fastening force, and ensuring that the flow battery stack does not leak and does not have performance degradation during long-term operation. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings are included to provide a further understanding of the present application, and they are collected and constitute a part of the present application, which shows the embodiments of the present application, and together with the present specification, they play a role in explaining the principles of the present application. In the drawings:

[0026] Figure 1A is a side view of a flow battery stack;

[0027] Figure 1B is Figure 1A is a top view of the flow battery stack shown in the figure;

[0028] Figure 2 is Figure 1A and 1B the mechanical finite element simulation diagram of the end plate 111 under the force state;

[0029] Figure 3 is a perspective view of a flow battery stack including a fastening structure according to an embodiment of the present application;

[0030] Figure 4 is Figure 3 the schematic diagram of the explosion of the embodiment one;

[0031] Figure 5 is Figure 3 the front view of the embodiment one;

[0032] Figure 6 is Figure 3 the top view of the embodiment one;

[0033] Figure 7 is a perspective view of a flow battery stack including a fastening structure according to an embodiment of the present application;

[0034] Figure 8 is Figure 7 the exploded view of the embodiment two;

[0035] Figure 9 is Figure 7 the front view of the embodiment two;

[0036] Figure 10 is Figure 7 the top view of the embodiment two;

[0037] Figure 11 is an exemplary flow chart of a fastening method of a flow battery stack according to an embodiment of the present application;

[0038] Figure 12 is the mechanical finite element simulation diagram of the end plate of the battery stack after using the fastening structure of the present application. DETAILED DESCRIPTION

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some examples or embodiments of the present application, and for those skilled in the art, the present application can also be applied to other similar scenarios without creative labor. Unless it is obvious from the language environment or otherwise stated, the same reference numbers in the drawings represent the same structure or operation.

[0040] As used in the description of the application and the claims that follow, "a," "an," "one," and / or "the" do not exclude plural referents unless modified by language expressly specifying the contrary. The mere use of the term "or" does not mean an exclusive "or" unless specifically stated. The phrase "consisting of, "consisting essentially of, and the like, as used herein, are defined to have the same meaning as the terms "comprising" and "including."

[0041] The relative arrangement of components and steps, numerical expressions, and numerical values set forth in the examples are not intended to limit the scope of the application unless specifically so stated. It is to be understood that the drawings are not necessarily to scale, and that a review of the entire disclosure is taken into consideration by those of ordinary skill in the art, and that the technology, methods, and devices known to the art can not be discussed in detail, but are deemed to be part of the specification. In all examples shown and discussed herein, any specific value is to be interpreted as merely an example, and not a limitation. Thus, other examples of the exemplary embodiments can have different values. It is to be noted that like numbers and letters refer to like elements throughout the several views of the drawings and that the exemplified embodiments can not reflect the specific numbers of the drawings and that further discussion of the exemplified elements is not necessary in subsequent drawings.

[0042] In the description of the application, it is to be understood that the orientation or positional relationships indicated by orientation words such as "front, "back, "up, "down, "left, "right, "transverse, "vertical, "horizontal, "top, "bottom, and the like, are generally based on the orientation or positional relationships shown in the drawings, and are merely for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the scope of protection of the application. The orientation words "inner, "outer" refer to the inner and outer relative to the contour of the components themselves.

[0043] For purposes of the description hereinafter, spatial relative terms, such as "above", "below", "upper", "lower", and the like, can be used to describe the relative position of one element or feature to another element or feature as illustrated in the figures. It will be understood that the spatial relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" other elements or features would then be oriented "below" the other elements or features. Thus, the exemplary term "above" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial relative terms used herein interpreted accordingly.

[0044] In addition, it should be noted that the use of "first", "second", and the like, terminology to describe components in the above is merely used to differentiate one component from another, and does not constitute a limitation on the scope of the application unless otherwise stated. Moreover, the use of terminology, such as "top", "bottom", "front", "back", and the like, is for the purpose of assisting in description and is not a limitation on the scope of the application unless otherwise stated. Furthermore, although the terms "first", "second", and the like, can be used herein to describe various elements, these elements should not be limited by these terms. These terms are generally only used to distinguish one element from another. Thus, a first element could be termed a second element without departing from the scope of the example. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed terms.

[0045] Flow diagrams herein are used to illustrate the operations performed by systems in accordance with embodiments of the present application. It should be understood that the operations are not necessarily performed in the order shown. Rather, various steps can be handled in reverse order, or simultaneously. Also, other operations can be added to, or removed from, these processes, or one or more steps can be omitted.

[0046] The liquid flow battery stack fastening structure of the present application is suitable for use in various types, models, and sizes of liquid flow battery stacks, including but not limited to all-vanadium liquid flow batteries. The liquid flow battery stack includes a battery assembly, which includes a single cell, or a plurality of single cells connected in series.

[0047] Embodiment One

[0048] Figure 3 is a perspective view of a liquid flow battery stack including a fastening structure according to Embodiment One of the present application. Figure 3The diagram illustrates a battery assembly 310 comprising multiple individual cells. In the embodiments of this specification, the battery assembly 310 includes multiple individual cells connected in series. Each individual cell includes a positive and negative electrode frame, a porous electrode, a sealing component, and an ion exchange membrane. The individual cells are sheet-like or plate-like, and multiple individual cells are arranged parallel to each other sequentially. Figure 3 The superposition in the Z direction shown gives the battery assembly 310 a certain height.

[0049] refer to Figure 3 The fastening structure includes a first end plate 321, a second end plate 322, and at least one pusher assembly 330. The first end plate 321 and the second end plate 322 are located on the two polarity ends of the battery assembly 310, respectively. The battery assembly 310 has a positive terminal side and a negative terminal side. One of the first end plate 321 and the second end plate 322 is located on the positive terminal side, and the other is located on the negative terminal side. The distance between the first end plate 321 and the second end plate 322 is fixed, and the pusher assembly 330 is variably positioned between the first end plate 321 and the battery assembly 310.

[0050] Figure 4 yes Figure 3 An exploded view of Embodiment 1 is shown. (Combined with...) Figure 3 and Figure 4 Assuming the upper end of the battery assembly 310 is the positive terminal 311 and the lower end is the negative terminal 312, then in this embodiment, the first end plate 321 is located on the positive terminal side of the battery assembly 310, and the second end plate 322 is located on the negative terminal side of the battery assembly 310. This fastening structure includes only one pusher plate assembly 330, which is disposed between the first end plate 321 and the battery assembly 310.

[0051] In another embodiment, the fastening structure includes multiple pusher plate assemblies located between the first end plate 321 and the battery assembly 310. Specifically, the multiple pusher plate assemblies are arranged parallel to each other and stacked sequentially between the first end plate 321 and the battery assembly 310. Since each pusher plate assembly has a variable height, the height of the stacked multiple pusher plate assemblies is also variable.

[0052] like Figure 3 Both the first end plate 321 and the second end plate 322 are flat structures, each with a certain thickness. The thicknesses of the first end plate 321 and the second end plate 322 can be the same or different. The first end plate 321 and the second end plate 322 can have the same shape and size. In some places in this specification, the term "end plate" is used to refer to both the first end plate 321 and the second end plate 322, which is not intended to limit the first end plate 321 and the second end plate 322 to being completely identical.

[0053] The first end plate 321 and the second end plate 322 can be parallel to each other and have a fixed distance therebetween. In actual applications, the first end plate 321 and the second end plate 322 can not be completely parallel to each other, and the fixed distance therebetween means that the relative positions of the first end plate 321 and the second end plate 322 are fixed.

[0054] The push plate assembly 330 of the present application is arranged between the first end plate 321 and the battery assembly 310 in a height-variable manner. As shown in Figure 3 , the push plate assembly 330 has a height in the Z direction. The present application does not limit how the height is achieved. For example, the push plate assembly 330 includes an elastic element, and the height of the elastic element in the Z direction is elastically variable. When the pressure or resistance acting on the elastic element changes, the height of the elastic element itself also changes, thereby achieving the height-variable push plate assembly 330.

[0055] In combination Figure 3 and Figure 4 , in some embodiments, the push plate assembly 330 includes a push plate 340 and at least one load assembly 350, and the load assembly 350 includes a load element 410. The load element 410 has a height between the first end plate 321 and the push plate 340, and the height changes with the magnitude of the pressure acting on the load element 410.

[0056] In some embodiments, the load element 410 is a gas spring. Preferably, the load element 410 is a nitrogen gas spring. The nitrogen gas spring is an elastic element using high-pressure nitrogen gas as the working medium, and has the advantages of small size, large elastic force, smooth operation, high precision in manufacturing, long service life, flat elastic force curve, and no need for pre-tightening. The height-variable range of the push plate assembly 330 is determined by the height-variable range of the load element 410. According to different parameters of the gas spring, different height-variable ranges can be achieved. In an embodiment, the height-variable range is 0-300 mm. Preferably, the height-variable range is 0-100 mm. Within the height-variable range, the thickness change of the battery assembly 310 caused by the compression deformation of the pole piece material over a long period of time can be compensated.

[0057] As shown in Figure 4 , the first end plate 321 has an inner surface 421 facing the battery assembly 310 and an outer surface 422 facing the outside, the push plate 340 has an outer surface 423 facing the first end plate 321, and the load element 410 is fixedly arranged between the inner surface 421 and the outer surface 423. The present application does not limit the fixing manner of the load element 410. For example, the load element 410 can be fixed at one end to the inner surface 421 and at the other end to the outer surface 423 by means of screwing, riveting, welding, or bonding.

[0058] As shown in Figure 4In some embodiments, the load assembly 350 further comprises load fixing elements 430 for fixedly connecting the load elements 410 and the first end plate 321, and the load fixing elements 430 and the load elements 410 are in one-to-one correspondence, i.e. one load fixing element 430 is used to cooperate with one load element 410.

[0059] Figure 5 is Figure 3 a front view of the first embodiment shown in Figure 6 is Figure 3 a top view of the first embodiment shown in. In combination with Figure 4 and Figure 6 , the load fixing element 430 is generally square-shaped, and has a plurality of threaded holes on it, and the load fixing element 430 is fixedly connected with the load element 410 through the first end plate 321 by screw connection.

[0060] In some embodiments, the outer surface 422 of the first end plate 321 comprises at least one counterbore, and the load fixing element 430 is arranged in the counterbore, and the load fixing element 430 does not protrude from the outer surface. In combination with Figure 5 , the outer surface 422 of the first end plate 321 is a plane except for the end portions 361 of the protruding fixing connecting rods 360, i.e. the load fixing element 430 is in the counterbore. Assuming that the load fixing element 430 has an upper surface facing outward, the height of the upper surface is lower than the outer surface 422, or the upper surface is flush with the outer surface 422. It can be understood that the size and shape of the counterbore should be adapted to the size and shape of the load fixing element 430.

[0061] In some embodiments, a plurality of load assemblies 350 are uniformly distributed between the first end plate 321 and the push plate 340.

[0062] In combination with Figure 4 to Figure 6 , this embodiment comprises five load assemblies 350, which are respectively located at the geometric center position and the four corners of the push plate. In actual use, the five load assemblies 350 respectively bear a part of the pressure, and can more uniformly implement the fastening force to the push plate 340, thereby avoiding the deformation caused by the uneven stress of the end plate.

[0063] In combination with Figure 5 and Figure 6In some embodiments, one load assembly 350 is located at the geometric center of the push plate 340. In embodiments with only one load assembly 350, the load assembly 350 is preferably located at the geometric center of the push plate 340. In some embodiments, other fastening measures can be used around the first end plate 321 and the second end plate 322, and the center of the first end plate 321 or the second end plate 322 is usually free of fastening measures, and the fastening force can be applied to the center of the first end plate 321 or the second end plate 322 by the fastening device of the present application, so as to avoid deformation of the first end plate 321 or the second end plate 322 as shown in Figure 2

[0064] In combination Figure 3 to Figure 6 In Embodiment One, a plurality of fixed connecting rods 360 are further provided around the first end plate 321 and the second end plate 322. Each fixed connecting rod 360 can be a column shape, which passes through the first end plate 321 and reaches the inner surface of the second end plate 322, and the end 361 of the fixed connecting rod 360 extends out of the first end plate 321. The fixed connecting rod 360 can be fixedly connected with the first end plate 321 and the second end plate 322 by bolts or the like. Through these embodiments, the distance between the first end plate 321 and the second end plate 322 can be ensured to remain unchanged.

[0065] As shown in Figure 3 In this embodiment, the first end plate 321 and the second end plate 322 are equal in size, the area of the push plate 340 is small, the fixed connecting rod 360 is provided around the end plate and does not contact the push plate 340, and does not affect the movement of the push plate 340 in the Z direction.

[0066] As shown in Figure 5 In this embodiment, the first end plate 321, the push plate 340 and the second end plate 322 are arranged in parallel with each other. In the initial state, the pole frame of the single battery does not deform, and when the load assembly 350 is installed, each load element 410 can have equal pre-tightening force, so that uniform fastening pressure can be applied to the battery assembly 310. When the pole frame of the single battery deforms, the thickness of the battery assembly 310 changes, and at this time, each load element 410 changes its height according to the pressure change at its corresponding position, so that the battery assembly 310 is still under the fastening pressure, avoiding the risk of liquid leakage.

[0067] As shown in Figure 4 The flow battery stack further includes a positive current collector 431 and a negative current collector 432, the positive current collector 431 is electrically connected with the positive electrode of the battery assembly 310, and the negative current collector 432 is electrically connected with the negative electrode of the battery assembly 310. In some embodiments, an inlet and outlet structure 441 is provided on the second end plate 322, which can be a tubular structure for flowing electrolyte into or out of the battery stack. In combination Figure 3 ​Multiple liquid inlet / outlet structures 441 can be provided on the second end plate 322, some for liquid inlet and some for liquid outlet. For example, in Figure 3 Two liquid inlet / outlet structures 441 are used for liquid inlet, and the other two liquid inlet / outlet structures 441 are used for liquid outlet.

[0068] Example 2

[0069] Figure 7 This is a three-dimensional schematic diagram of a flow battery stack including a fastening structure according to Embodiment 2 of this application. Figure 8 yes Figure 7 The exploded view of Embodiment 2 is shown. Figure 9 yes Figure 7 The front view of Embodiment 2 is shown. Figure 10 yes Figure 7 The top view of Embodiment 2 is shown. Figure 7 The second embodiment is similar to the first embodiment in that the pusher assembly 730 is located between the first end plate 721 and the battery assembly 710. In the second embodiment, the fastening structure also includes a battery stack fixing assembly, which includes at least one pull rod 760. The pull rod 760 includes a first bend 761, a second bend 762, and a connecting rod 763. The connecting rod 763 connects between the first bend 761 and the second bend 762, and extends along the height direction Z. The first bend 761 is in contact with the outer surface 723 of the first end plate 721, and the second bend 762 is in contact with the outer surface 724 of the second end plate 722. Figure 8 As shown, each tie rod 760 has a U-shaped structure, in which the connecting rod 763 in the middle is a long strip, and the first bend 761 and the second bend 762 at both ends are plate-shaped or block-shaped structures with a width slightly wider than the connecting rod 763.

[0070] like Figure 8In order to facilitate the first bending part 761 and the second bending part 762 to be attached to the outer surfaces 723, 724, a corresponding first groove 810 and a second groove 820 are respectively arranged on the edges of the first end plate 721 and the second end plate 722, the first bending part 761 is embedded in the first groove 810, and the second bending part 762 is embedded in the second groove 820. More specifically, taking the first groove 810 as an example, the first groove 810 includes a first sub-groove 811 located on the outer surface 723 of the first end plate 721 and a second sub-groove 812 located on the side surface 725 of the first end plate 821, the first sub-groove 811 and the second sub-groove 812 are in communication with each other, the first sub-groove 811 is used to accommodate the first bending part 761, and the second sub-groove 812 is used to accommodate a part of the structure of the connecting rod 763 in contact with the side surface 725. The structure of the second groove 820 is similar to that of the first groove 810, which will not be described here. According to such a groove structure, the stack fixing assembly can be embedded in the end plate, there is no part protruding from the end plate, the volume of the flow battery stack is reduced, and the appearance is also improved.

[0071] As shown in Figure 10 The first bending part 761 can be fixed on the outer surface 723 of the first end plate 721 by using small screws.

[0072] In the second embodiment, the pull rod 760 is used to form the stack fixing assembly around the first end plate 721 and the second end plate 722, which strengthens the fastening force between the end plates, and the bending structure of the first bending part 761 and the second bending part 762 makes the connecting rod 763 not need to protrude from the end plate, thereby reducing the height of the entire stack and saving the space occupied by the stack.

[0073] According to the fastening structure of the present application arranged on the flow battery stack, when the thickness of the polar frame and other components in any single cell of the flow battery stack is reduced, the fastening structure can change the height accordingly and provide corresponding load force to ensure the pressure required for battery sealing, thereby ensuring that the flow battery stack has no liquid leakage and no performance degradation for a long time.

[0074] Figure 11 is an exemplary flowchart of the fastening method of the flow battery stack of an embodiment of the present application. The fastening method is implemented by using the fastening structure described in the foregoing of the present application. Referring to Figure 11 The fastening method of the embodiment includes the following steps:

[0075] Step S1110: obtaining a first area of the sealing material in the battery stack, and setting a first compression ratio of the sealing material;

[0076] Step S1120: obtaining a second area of the electrode material in the battery stack, and setting a second compression ratio of the electrode material;

[0077] The area of the sealing material and the electrode material in the battery stack is known. The present specification illustrates the fastening method with a specific example. For example, the battery stack to be fastened uses face-type sealing, the sealing material is 1 mm thick EPDM, the electrode frame is 4 mm thick PVC plate material machined, and the electrode is 7 mm porous carbon felt electrode material. The first area of the sealing material is known to be 782 cm 2 , and the area of the porous electrode is about 1100 cm 2 .

[0078] In step S1110, the first compression ratio of the sealing material is set to be 20%, and in step S1120, the second compression ratio of the electrode material is set to be 20%. The two compression ratios are set according to actual needs and experience.

[0079] Step S1130: Obtain the first pressure value according to the first compression ratio and the second pressure value according to the second compression ratio.

[0080] For a specific sealing material, the first compression ratio and the first pressure value have a specific corresponding relationship, and the corresponding relationship table can be obtained through experiments. Similarly, a specific electrode material also has its specific corresponding relationship table. Both of the two corresponding relationship tables can be obtained through experiments. In step S1130, it is considered that the two corresponding relationship tables are known.

[0081] The following gives an exemplary relationship table between the first compression ratio and the first pressure value of the EPDM product:

[0082] Table I:

[0083] Serial number First compression ratio First pressure value (Mpa) 1 10％ 1.00 2 15％ 1.55 3 20％ 2.12

[0084] The following gives an exemplary relationship table between the second compression ratio and the second pressure value of the porous electrode (carbon felt) product:

[0085] Table II:

[0086]

[0087]

[0088] Through table lookup, it can be obtained that when the first compression ratio is 20%, the first pressure value is 2.12 MPa, and when the second compression ratio is 20%, the second pressure value is 0.05 MPa.

[0089] Step S1140: Calculate the fastening load using the following formula:

[0090] P = k * (S1 * P1 + S2 * P2) (1)

[0091] Wherein, P represents the fastening load, S1 represents the first area, S2 represents the second area, P1 represents the first pressure value, P2 represents the second pressure value, k represents the safety factor, and k is a natural number greater than 1.

[0092] The value obtained in the previous step is substituted into the above formula (1) to obtain:

[0093] P=k*(78233mm 2 +2.12Mpa+110780mm 2 *0.05Mpa)=k*171393N.

[0094] In some embodiments, k ranges from 1 to 2. For example, k can be 1.5, 2, etc.

[0095] In a preferred embodiment, let k=1.25, then P≈220000N.

[0096] Step S1150: set the pre-tightening force of the load element so that the initial load of all load assemblies is equal to the fastening load.

[0097] After obtaining the fastening load P, the parameters of the load element described above are set to obtain a certain pre-tightening force, so that the initial load of all load assemblies in the fastening structure is equal to the fastening load, and the corresponding fastening load is provided to the battery stack to prevent liquid leakage of the battery stack.

[0098] Figure 12 is a mechanical finite element simulation diagram of the end plate of the battery stack after using the fastening structure of the present application. Compared with Figure 2 The maximum deformation is reduced from 1.2mm to 0.32mm, and Figure 12 It is shown that more areas on the end plate are in a non-deformation state, and the overall deformation is also more uniform.

[0099] The above has described the basic concept, and it is obvious that the above disclosure of the invention is only as an example and does not constitute a limitation on the present application for those skilled in the art. Although it is not explicitly stated here, those skilled in the art can make various modifications, improvements and corrections to the present application. Such modifications, improvements and corrections are suggested in the present application, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of the present application.

[0100] Also, the use of "a" or "an" to describe embodiments of the present application are to be taken to mean one or more unless otherwise indicated. Furthermore, to recite any amount such as "at least one of A, B, and C" does not mean that A, B, and C are alternatives for each other, but it is intended to mean that A, B, and C individually are present, and the joiner word "one" is taken in its "or" sense. Likewise, to recite "at least one of A or B" means that A or B individually are present and it is not intended to imply that both of A and B are present. Throughout this application the use of "or" shall not be interpreted as being exclusive but rather inclusive, allowing that "A or B" means "A or B or both". In addition, it should be understood that any numerical range recited in this specification is intended to include all sub-ranges of the same numbers except specify otherwise.

[0101] Similarly, it is to be noticed that the term coupled, when used in the present specification, is not intended to to exclude the presence of an intermediate device or material between the coupled devices and materials. As used herein, coupled can be understood broadly to include direct connection between devices and materials, as well as indirect connection through one or more intermediate devices and materials. As used herein, coupled can be understood broadly to include direct connection between devices and materials, as well as indirect connection through one or more intermediate devices and materials.

[0102] Some embodiments use numerical ranges to describe quantities of components, attributes, etc. It should be understood that such numerical ranges recited in the description of embodiments herein are used to provide approximate and general guidance. In some examples, such numerical ranges are used to provide a general understanding of the scope of the embodiments. Unless otherwise indicated, the numerical ranges recited in this application are approximate and should be understood to include numerical values approximately within range. Accordingly, numerical parameters in the application and claims are approximations and should be considered to have a value of about the value recited. Unless otherwise indicated, the numerical ranges recited in this application are approximate and should be understood to include numerical values approximately within range. Accordingly, numerical parameters in the application and claims are approximations and should be considered to have a value of about the value recited. It is noted that these approximations are only to provide a general teaching to aid in understanding the broad scope of the embodiments. Unless otherwise indicated, the numerical ranges recited in this application are approximate and should be understood to include numerical values approximately within range. Accordingly, numerical parameters in the application and claims are approximations and should be considered to have a value of about the value recited. It is noted that these approximations are only to provide a general teaching to aid in understanding the broad scope of the embodiments.

Claims

1. A method of securing a flow battery stack, the flow battery stack comprising a cell assembly, the cell assembly comprising a single cell or a plurality of single cells, characterized in that, The fastening structure of the flow battery stack comprises a first end plate, a second end plate and at least one push plate assembly, the first end plate and the second end plate are respectively located at two polar end sides of the battery assembly, the distance between the first end plate and the second end plate is fixed, and the push plate assembly is variably arranged between the first end plate and the battery assembly; the push plate assembly comprises a load element, and the fastening method comprises: obtaining a first area of a sealing material in the battery stack, setting a first compression ratio of the sealing material; obtaining a second area of an electrode material in the battery stack, setting a second compression ratio of the electrode material; obtaining a first pressure value according to the first compression ratio, and obtaining a second pressure value according to the second compression ratio; calculating a fastening load by using the following formula: P=k*(S1*P1+S2*P2) wherein P represents the fastening load, S1 represents the first area, S2 represents the second area, P1 represents the first pressure value, P2 represents the second pressure value, and k represents a safety factor, k is a natural number greater than 1; and setting a pre-tightening force of the load element, so that the initial load of all the load assemblies is equal to the fastening load.

2. The fastening method according to claim 1, wherein The push plate assembly comprises a push plate and at least one load assembly, the load assembly comprises the load element, and the load element has a height between the first end plate and the push plate, the height changes with the magnitude of the pressure borne by the load element.

3. The fastening method according to claim 2, wherein The height change range is 0-300 mm.

4. The fastening method of claim 2, wherein One of the load assemblies is located at the geometric center of the push plate.

5. The fastening method of claim 2, wherein A plurality of the load assemblies are uniformly distributed between the first end plate and the push plate.

6. The fastening method of claim 2, wherein The load element comprises a gas spring.

7. The fastening method of claim 2, wherein The load assembly further comprises a load fixing element for fixedly connecting the load element and the first end plate, and the load fixing element and the load element are in one-to-one correspondence.

8. The fastening method of claim 7, wherein The first end plate has an inner surface facing the battery assembly and an outer surface facing the outside, the outer surface of the first end plate comprises at least one counterbore, the load fixing element is arranged in the counterbore, and the load fixing element does not protrude from the outer surface.

9. The fastening method of claim 2, wherein Further comprising a stack fixing assembly, the stack fixing assembly comprises at least one pull rod, the pull rod comprises a first bending part, a second bending part and a connecting rod, the connecting rod is connected between the first bending part and the second bending part, the connecting rod extends along the height direction, the first end plate and the second end plate both have an outer surface facing the outside, the first bending part is attached to the outer surface of the first end plate, and the second bending part is attached to the outer surface of the second end plate.

10. The fastening method of claim 9, wherein The edge of the first end plate is provided with a first groove, and the first bending part is embedded in the first groove; the edge of the second end plate is provided with a second groove, and the second bending part is embedded in the second groove.

11. The fastening method of claim 1 wherein, The second end plate is provided with an inlet and outlet structure.

12. The fastening method of claim 1 wherein, The range of k is 1-2.

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